WO2022234180A1

WO2022234180A1 - A method and a system for producing a product fraction from biomass

Info

Publication number: WO2022234180A1
Application number: PCT/FI2022/050265
Authority: WO
Inventors: Tero Joronen
Original assignee: Valmet Technologies Oy
Current assignee: Valmet Technologies Oy
Priority date: 2021-05-06
Filing date: 2022-04-25
Publication date: 2022-11-10
Anticipated expiration: 2023-11-06
Also published as: FI20215538A1; FI131022B1; EP4334025A1; CN221638055U

Abstract

A method for producing a product fraction (PF) from feedstock that comprises water. The method comprises allowing the feedstock (FS) to react in a first reaction zone (Z1) of a conversion reactor (100) at a temperature of at least 350 °C in a pressure of at least 160 bar to form converted feedstock, separating at the temperature of at least 350 °C and in the pressure of at least 160 bar from the converted feedstock the product fraction (PF) and a fraction comprising a residue fraction (RF), letting out the product fraction (PF) from the first reaction zone (Z1 ). The method comprises letting out the residue fraction (RF) from the conversion reactor (100) through a first outlet (122), letting out fluid (FF, PF, WF) from the conversion reactor (100) through a second outlet (124), feeding the fluid (FF, PF, WF) that has been let out from the conversion reactor (100) in to the conversion reactor (100) through a nozzle arrangement (130) arranged inside the conversion reactor (100) and near a wall (102) of the conversion reactor (100), and flushing the wall (102) of the conversion reactor (100) with at least the fluid (FF, PF, WF). A conversion reactor (100) for performing the method.

Description

A method and a system for producing a product fraction from biomass Technical field

The invention relates to methods and devices for producing heat and/or a refined bio product. The refined bio product may be carbonized biomass, bio oil, or bio gas. The heat as well as the bio product may be produced from feedstock, e.g. feedstock that comprises biomass. The invention relates to a method and a device for producing bio oil or bio gas of high quality, the bio oil or gas being widely applicable, e.g. as a substitute for fossil fuel and/or as a feed for biochemical production.

Background

Bio based materials have received a lot of interest as a replacement of fossil based materials in fuels and chemical industry. Bio based oil or gas (hereinafter bio fluid) can be produced from biomass in processes known per se. Such processes include heat treatment of the biomass, possibly in the presence of water, steam, and/or a catalyst, and collection of the reaction products. Moreover, biomass can be utilized to produce heat by oxidation, thereby substituting fossil fuels in energy production. Finally, can be utilized to produce other bio based products than oil or gas, such as carbonized biomass (e.g. bio based carbon powder).

It has been found that these processes can be efficiently performed in supercritical conditions. It is known that biomass comprises salt or salts. However, salts do not dissolve into water in a supercritical or near supercritical condition well. This is because water loses its polarity at the supercritical condition, which causes rapid reduction in salt solubility. Thus, at least some of the salts may solidify. Oftentimes some of the salt or the salts tend to accumulate onto inner walls of the reactor. This causes malfunction and/or a need for maintaining the reactor.

The project leading to this application has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 884111 . Summary

It has now been found that accumulation of salt(s) onto inner walls of the reactor (i.e. fouling of the reactor) may be diminished by flushing the inner walls of the reactor. Moreover, it has been found that the walls can be flushed by a liquid that is recycled from the reactor. It has also been found that corrosion of the reactor can be reduced using similar principles.

The device is described in more detail in the independent claim 1. A corresponding method is described in more detail in the independent claim 12. The claims dependent on either of them and the description disclose preferable embodiments.

Brief description of the drawings

Fig. 1a shows a side view of a conversion reactor for producing a product fraction from biomass and a system comprising such a reactor,

Fig. 1 b shows the cross-sectional view lb-lb of Fig. 1 a,

Fig. 1 c shows the cross-sectional view lc-lc of Fig. 1 a,

Fig. 2a shows a side view of a conversion reactor for producing a product fraction from biomass and a system comprising such a reactor,

Fig. 2b shows the cross-sectional view llb-llb of Fig. 2a,

Fig. 2c shows the cross-sectional view llc-llc of Fig. 2a,

Fig. 2d shows a side view of a lower part of a conversion reactor,

Fig. 2e shows a side view of a conversion reactor,

Fig. 2f shows a cross-sectional view of a reactor in which the flow of the flushing fluid forms a circular cyclone,

Fig. 3 shows a side view of a conversion reactor, wherein flushing fluid forms a circular cyclone,

Fig. 4 shows a side view of a conversion reactor,

Fig. 5a shows a side view of a conversion reactor,

Fig. 5b shows the cross-sectional view Vb-Vb of Fig. 5a,

Fig. 6 shows a side view of system for producing a product fraction from biomass , the system comprising a conversion reactor and a chemical recovery boiler,

Fig. 7 shows a side view of a conversion reactor e.g. for supercritical water oxidation, Fig. 8a shows a side view of a conversion reactor e.g. for producing refined bio oil or bio gas,

Fig. 8b shows a side view of a conversion reactor e.g. for producing refined bio oil or bio gas,

Fig. 9a shows a side view of a conversion reactor comprising a heater for heating flushing fluid,

Fig. 9b shows a side view of a conversion reactor comprising a pump for circulating flushing fluid,

Fig. 9c shows a side view of a conversion reactor comprising an injector for circulating flushing fluid,

Fig. 9d shows a side view of a conversion reactor comprising a cooler for cooling flushing fluid,

Fig. 10a shows a side view of a conversion reactor having two circulations of flushing fluid,

Fig. 10b shows a side view of a conversion reactor having two circulations of flushing fluid,

Fig. 10c shows a side view of a conversion reactor having two circulations of flushing fluid,

Fig. 11 shows conversion reactor configured to re-dissolve and/or dilute contaminants, e.g. type two salts,

Fig. 12a shows a side view of a conversion reactor comprising an injector for circulating flushing fluid and for forming a cyclonic flow of the flushing fluid for separating the product fraction PF from other compounds, and Figs. 12b and 12c show side views of a conversion reactors comprising an injector for circulating flushing fluid and for forming a cyclonic flow of the flushing fluid for separating the product fraction PF from other compounds and a cyclone for separating a wash fraction WF and a residue fraction RF from the other compounds.

In the drawings, the directions Sx, Sy, and Sz are orthogonal to each other. In a typical use, Sz is vertical and reverse to gravitational force.

Detailed description

Figs. 1a and 2a describe a method and a device for producing a product fraction PF from feedstock FS, such as biomass. Concerning the embodiment of Fig. 1a, the product fraction PF may be a combusted effluent, in particular when the feedstock FS undergoes supercritical water oxidation (SCWO). In this process heat is also produced and may be recovered from the process, e.g. from the product fraction PF and/or by heat exchanger from the walls of the reactor 100. Concerning the embodiment of Fig. 2a, the product fraction PF may be a hydrocarbon rich fraction. The hydrocarbon rich fraction can be used to produce bio fluid, i.e. bio oil or bio gas. Other processes wherein the conversion reactor 100 can be used include hydrothermal carbonization and hydrothermal gasification. In any case, a residue fraction RF is also produced in the process and withdrawn from the process. Oftentimes the residue fraction RF contains some salt. Depending on the process and feedstock details, therein either the reactor with only one outlet for the residue fraction (e.g. Fig. 1a) or the reactor with at least two outlets, one the residue fraction RF and at least another for a wash fraction WF (e.g. Fig. 2a or 10a) can be used.

In the method, feedstock FS is provided to a first reaction zone Z1 of a conversion reactor 100. The first reaction zone Z1 is a space within the conversion reactor 100, in which conversion of the feedstock FS to chemically different compounds takes place. The feedstock FS comprises water. In a preferable embodiment, the feedstock FS comprises also biomass, which will be converted in the reactor 100. Typically the feedstock comprises a contaminant or contaminants, for instance, salts, metals, chemicals, minerals, or ash. Flerein the term contaminant is used to impress all possible contamination causing the problem. As for the problem, the problem may be e.g. corrosion or erosion of the reactor 100, or the reactor 100 becoming dirty as a result of fouling, carbonization, polymerization, or slagging of a compound within the reactor 100. Corrosion may be caused by a corrosion promoter, such as salt, e.g. type one salt. Erosion may be caused by hard particles, which may result from precipitation of salt or carbonization of feedstock. Fouling may be a result of a salt (e.g. type two salt) accumulating on the wall of the rector. Carbonization of the feedstock may result in the carbon accumulating of the wall. Flydrocarbons of the feedstock may polymerize to form larger molecules, which may accumulate in the reactor. Finally, some reaction product may solidify thereby causing slagging in the reactor 100. Thus, the contaminant may comprise salt (type one salt or type two salt), hard particles, carbon, hydrocarbon, or a compound causing slagging. In particular, the contaminant may be a salt. The salt may be responsible for corrosion and/or fouling and/or erosion. The term biomass covers materials that naturally comprise also some water. Thus, the water of the feedstock FS needs not be added water. However, oftentimes some water is added. A salt needs not be, but can be, added to a feedstock comprising water and biomass. For example, some salts may act as catalyst in the process.

The term “water” may refer also to steam. However, in the supercritical state, the term water is often preferred over steam. A water content of the feedstock may be at least 25 wt%. This has been found to be a sufficient content for the conversion reaction of the first reaction zone Z1. Thus, in an embodiment, a dry matter content of the feedstock FS is at most 75 wt%. A dry matter content of the feedstock FS may be from 20 wt% to 75 wt%, preferably from 30 wt% to 70 wt%.

The term “biomass” refers to material(s) of biological origin. Biomass may comprise virgin and waste materials of plant, animal and/or fish origin or microbiological origin, such as virgin wood, wood residues, forest residues, waste, municipal waste, industrial waste or by-products or effluents or wastewater, agricultural waste or by-products, residues or by-products of the wood-processing industry, waste or by-products of the food industry, solid or semi-solid organic residues of anaerobic or aerobic digestion, such as residues from bio-gas production from lignocellulosic and/or municipal waste material, residues from bio-ethanol production process, and any combinations thereof. Suitably said biomass comprises waste and by-products of the wood processing industry such as slash, urban wood waste, lumber waste, wood chips, wood waste, sawdust, straw, firewood, wood materials, paper, by products of the papermaking or timber processes, where the biomass (plant biomass) is composed of at least hemicellulose and lignin. The biomass may further comprise cellulose; however, cellulose fibres of wood may have been removed for other purposes, and the remaining biomass may constitute the biomass of the feedstock. In a preferable embodiment, the feedstock FS comprises at least on of cellulose, hemicellulose, and lignin.

The method is particularly suitable when a by-product, or by-products, of pulp or paper making industry, including black liquor of the Kraft process and brown liquor of the sulphite process, are used as the feedstock FS or at least a part thereof, since these by-products naturally comprise a lot of salts and also biomass, including lignin residues and hemicellulose. Moreover, if a purpose is to produce biofuel, the salts act as catalysts when converting the feedstock to bio oil or bio gas. Both the black liquor and the brown liquor are examples of a liquor that is a residue of a pulp process.

Typically, a dry matter content of such liquors is from 30 wt% to 40 wt%. In this way, in an embodiment, the biomass comprises at least one of lignin and hemicellulose. In an embodiment, the biomass comprises at least one of lignin and hemicellulose and a dry matter content of the feedstock FS is from 30 wt% to 40 wt%. Such by-products also comprise only a little cellulose. Thus, in an embodiment, the biomass comprises at least one of lignin and hemicellulose and comprises at most 10 wt% cellulose fibres on dry basis. In an embodiment, the biomass comprises at least one of lignin and hemicellulose and comprises at most 10 wt% cellulose fibres on dry basis, and a dry matter content of the feedstock FS is from 30 wt% to 40 wt%. As indicated above, because the salts are removed from the conversion reactor 100, it now has become possible to use also such a highly salt containing material as a feedstock for bio oil production and/or to use salts as catalysts for the conversion even without the salts accumulating on the walls of the reactor. Moreover, in such an embodiment, at least one of the salt rich fractions may be fed to a chemical recovery boiler 200 for recovering cooking chemicals from a salt rich fraction, as detailed below.

The term “contaminant” refers to a compound causing fouling or corrosion or other harmful issues; preferably, the “contaminant” refers to a compound causing fouling or corrosion. A salt may cause fouling or corrosion. Thus, the contaminant may be a salt or a combination of salts, or contaminant may comprise a salt or a combination of salts. The term “salt” refers to a chemical compound consisting of an assembly of cations and anions. Salts are composed of related numbers of cations (positively charged ions) and anions (negative ions) so that the product is electrically neutral (without a net charge).

In a biomass-to-liquid process (i.e. BTL process), the salt may be beneficial for catalysing reactions within the first process zone Z1 . In an SCWO process the salts in general are not beneficial. In any case, the presence of a contaminant, e.g. salts or other contamination pose the problem of salts or other materials solidifying on the walls of the reactor, resulting in fouling. Salts, or other contaminants, also accelerate corrosion. In an embodiment, a total content of salt(s) of the feedstock FS is at least 0.2 wt%, preferably from 0.2 wt% to 40 wt%. Preferably, a total content of salt(s) of the dry feedstock FS is at least 0.5 wt% (dry basis), preferably from 0.5 wt% to 60 wt% as measured on dry basis (i.e. from the dry matter of the feedstock FS). More preferably, the feedstock FS comprises at least 0.1 wt% ions of sodium or potassium. Even more preferably, the dry matter of the feedstock FS comprises at least 0.5 wt% (dry basis) sodium and/or potassium.

A feedstock comprising biomass may be a feedstock that can be converted as such following the principles indicated above. The feedstock, e.g. black liquor, may - as such - serve as the feedstock. In this way, salt (or water) needs not be added to the feedstock FS. In case of liquors, e.g. black liquor, some water may be removed by evaporation to obtain condensed black liquor. The condensed black liquor may serve as the feedstock FS.

In the first reaction zone Z1 , the convertible material, such as the biomass, of the feedstock FS may be converted by oxidation, e.g. in a SCWO process. Additional oxygen may be fed to the first reaction zone Z1 . In the alternative, in the first reaction zone Z1 , the convertible material, e.g. biomass, of the feedstock FS may be converted by reactions with water, catalysed by a salt, e.g. in a BTL process. The catalysing salt may be comprised by the feedstock FS, e.g. by the biomass thereof. The catalysing salt may be fed to the first reaction zone Z1 separately from the feedstock FS. For example, some of the catalysing salt may be fed with a flushing fluid FF. As a further alternative, in the first reaction zone Z1 , the convertible material, e.g. biomass, of the feedstock FS may be converted by reactions with water not catalysed by the salt, e.g. in a hydro carbonization process.

It has been found that these reactions are particularly efficient at supercritical or nearly supercritical process conditions. The term supercritical is used with respect to the critical point of water (i.e. temperature of 374 °C and pressure of 22 MPa, i.e. 220 bar). Therefore, in the method, the feedstock FS is allowed to react in the first reaction zone Z1 at a temperature T of at least 350 °C, e.g. from 350 °C to 450 °C, and in a pressure p of at least 160 bar. In an embodiment, the feedstock FS is allowed to react in this environment for a reaction time t of at least 5 minutes. Having a higher pressure does not prevent the conversion reaction from taking place. However, from point of view of manufacturing suitable conversion reactors 100, preferably the pressure p is from 160 bar to 350 bar. Moreover, having a longer reaction time does not normally worsen the properties of the conversion product. Moreover, the content of the product fraction PF may depend on reaction time. For example, reactions of a BTL process may take e.g. from 5 min to 30 min, while hydrothermal carbonization may require a longer reaction time. Therefore, in an embodiment, the feedstock FS is allowed to react in the first reaction zone Z1 at a temperature T of from 350 °C to 450 °C and in a pressure p of from 160 bar to 350 bar for a reaction time t of at least 5 minutes. Concerning the different aspects, in an embodiment, the feedstock FS is allowed to react in the first reaction zone Z1 at a temperature T of from 350 °C to 450 °C and in a pressure p of from 160 bar to 350 bar for a reaction time t of from 5 min to 30 min. In an embodiment, the feedstock FS is allowed to react in the first reaction zone Z1 at a temperature T of from 350 °C to 450 °C and in a pressure p of from 160 bar to 350 bar for a reaction time t of more than 30 min.

As a result of this process, the product fraction PF is obtained. In the context of a BTL process, the product fraction can be refined to produce bio oil or bio gas. As an alternative, the product fraction PF may be, as such, used as bio fluid or (after grinding and drying) as substitute for carbon. Herein the term bio fluid covers both bio oil, which is a liquid at STP environment, and bio gas, which is gas a gas at STP environment. STP environment refers to Standard Temperature and Pressure, i.e. 0 °C and 1 bar. In the context of a BTL process, the main product of the process is heat, but also a product fraction is produced.

Because of the reduced solubility of salts at supercritical conditions (see background), in these process conditions, it is possible to separate a residue fraction RF and the product fraction PF from the feedstock FS, i.e. the conversion product of the feedstock FS after the conversion. The separation may be done gravimetrically.

As for the product fraction PF this comprises a part of the materials of the process zone Z1 after the conversion reaction. As for the residue fraction RF, the residue fraction RF comprises the contaminant. The residue fraction RF need not comprise all the contaminant, but in general, because of the separation, a content of the contaminant is higher in the residue fraction RF than the content of the contaminant in the product fraction PF or a wash fraction WF. The product fraction PF or the wash fraction WF is receivable from a second outlet 124, as will be discussed below. Thus, the conversion reactor 100 is configured to separate the residue fraction RF from the converted feedstock such that a content of a contaminant is higher in the residue fraction RF than the content of the contaminant in a fluid receivable from a second outlet 124. Such separation is possible e.g. by using gravimetric means, since a density of the product fraction PF or a wash fraction WF (whichever is used for flushing), is often different from a density of the residue fraction RF. As usual, the term density refers to specific mass (in units of e.g. kg/m³) at the process conditions. Thus, a density of the fluid let out from the from the conversion reactor 100 through a second outlet 124 (i.e. the product fraction PF or the wash fraction WF) may be different from a density of the residue fraction RF. In a preferable embodiment, the density of the product fraction PF or the wash fraction WF (whichever is used for flushing, i.e. the fluid FF let out from the second outlet 124), is less than the density of the residue fraction RF. Flowever, it need not be, as detailed in the context of Fig. 12c. The gravimetric separation of the product fraction can be enhanced by a cyclonic flow of the flushing fluid, as depicted in Figs. 2f, 3, 12a, 12b, and 12c. Flowever, in some cases, separation of different fractions may be done by a filter, in which case the densities of different fractions need not be different.

In an embodiment, the residue fraction RF comprises first salt. The first salt may be in solid form, or, if diluted by subcritical water, the first salt dissolved in water. The first salt may be a salt generally called as type two salt. The solubility of type two salts decreases as function of increasing temperature near or at supercritical conditions more rapidly than the solubility of type one salts. In general, type one salts present a continuous solubility curve at supercritical temperature which does not cross the critical curve, whereas type two salts present an intersection between the solubility curve and the critical curve, leading to two critical endpoints in this domain. More information on these two different types of salts can be found from reference [1]. Therefore, type two salts tend to crystallize and/or form agglomerates at these process conditions, while type one salts tend to form brine. In this way, type one salts concentrate and type two salts crystallize at these conditions. Typically, type two salts form sticky precipitates that easily adhere on surfaces of the conversion reactor 100 and may cause blocking of the conversion reactor 100. Therefore, removal of such a residue fraction RF that comprises type two salts prevents blocking of the conversion reactor 100. Type two salts include MgCC>3, MgSC>4, CaCC>3, CaCC>4, Na2CC>3, Na2SC>4, Na3PC>4, KSO4 and S1O₂. In particular, type two salts involved in the process include MgC03, MgSC , CaCC>3, CaCC>4, Na2CC>3, Na2SC>4, and K2SO4. Moreover, removal of such a residue fraction RF that comprises other salts prevents corrosion of the conversion reactor 100, since salts accelerate corrosion. Finally, removal of other contaminants in the meaning discussed above with the residue fraction RF prevents fouling and/or corrosion and/or other harmful effects.

In an embodiment, the residue fraction RF comprises type two salt. By solidifying the type two salt(s) of the residue fraction RF, the aforementioned blocking problem can be reduced. Moreover separation of such a residue fraction RF is easy, since typically then a density of the residue fraction RF is substantially higher than a density of other fractions. As the type two salt is removed from the conversion reactor 100 with the residue fraction RF, it does not clog onto inner walls of the conversion reactor 100.

Thus, an embodiment comprises separating, at the temperature of from 350 °C to 450 °C and in the pressure of at least 160 bar, from the converted feedstock FS the the product fraction PF and a fraction comprising a residue fraction RF. The fraction comprising the residue fraction RF may consist of the residue fraction (as in e.g. the embodiments of Fig. 1a and 2a) or, as indicated in Figs. 12b and 12c, it may comprise the residue fraction RF and a wash fraction WF. The pressure in which the separation is done may be e.g. from 160 bar to 350 bar. The temperature and pressure in which the separation is done may be the same as in the conversion reaction 100.

To further reduce the problem of type contaminants accumulating on the walls of the reactor 100 or the contaminants corroding the walls of the reactor 100, the method comprises flushing a wall 102 of the conversion reactor 100 with a flushing fluid FF. To reduce the fouling and/or corrosion and/or other harmful effects, a content of the contaminant in the flushing fluid FF is less than a content of the contaminant in the residue fraction RF. As detailed above, the term “contaminant” refers to the compounds causing the fouling and/or corrosion and/or other harmful effects to the reactor 100. As for the content of the flushing fluid, some fluid is taken from the conversion reactor 100 and recycled back into the reactor 100, whereby the flushing fluid FF comprises fluid recycled from the reactor 100.

Referring to Fig. 1a, a part of the product fraction PF may be used as at least a part of the flushing fluid FF. Referring to Fig. 2a, a wash fraction WF may be used as at least part of the flushing fluid FF. The wash fraction is used for flushing the wall 102. The wash fraction WF may be brine or comprise brine. The tern “brine” refers to an aqueous solution comprising at least some salt. Flowever, the feedstock FS need not comprise salt.

Thus, a method for producing a product fraction PF from feedstock, such as biomass, comprises providing feedstock FS that comprises water to a first reaction zone Z1 of a conversion reactor 100. In the method, the feedstock FS is allowed to react in the first reaction zone Z1 at a temperature of at least 350 °C in a pressure of at least 160 bar to form converted feedstock. The method comprises separating at the temperature of at least 350 °C and in the pressure of at least 160 bar from the converted feedstock the residue fraction RF and the product fraction PF; letting out the product fraction PF from the first reaction zone Z1 ; and letting out the residue fraction RF from the conversion reactor 100. As detailed in connection with the conversion reactor 100, the residue fraction RF is let out through a first outlet 122.

In an embodiment of the method, the residue fraction RF comprises type two salt, such as at least one of MgCC>3, MgSC>4, CaCC>3, CaCC>4, Na2CC>3, Na2SC>4, Na3PC>4, KSO4 and S1O2.

Moreover, in order to flush the wall 102 of the reactor 100, the method comprises letting out flushing fluid FF from the conversion reactor 100; feeding at least some of the flushing fluid FF that has been let out from the conversion reactor 100 into the conversion reactor 100 through a nozzle arrangement 130 arranged inside the conversion reactor 100 and near the wall 102 of the conversion reactor 100; and flushing the wall 102 of the conversion reactor 100 with the flushing fluid FF. The flushing of the wall 102 is achieved by sufficient feeding of the flushing fluid FF through the nozzle arrangement 130. As indicated above, a part of the product fraction PF and/or a part of a wash fraction WF can be used as at least a part of the flushing fluid FF. In either case, the flushing fluid FF is let out through a second outlet 124 of the conversion reactor 100.

The wall 102 of the conversion reactor 100 is preferably flushed with the flushing fluid FF such that at least such a part of the wall 102 is flushed that the flushed part laterally encircles at least a part of the reaction zone Z1 . Thus, the nozzle arrangement is preferably configured to feed the flushing fluid FF into the reactor such that the flow of the flushing fluid laterally encircles at least part of the reaction zone Z1 . Preferably, the flow of the flushing fluid, or the flows of the circulations of the flushing fluids in case there are many, laterally encircle(s) the whole reaction zone Z1 .

As for the conversion reactor 100 itself, and with reference to Fig. 1a, an embodiment of a conversion reactor 100 is suitable for producing a product fraction PF from biomass at a temperature of at least 350 °C in a pressure of at least 160 bar. The conversion reactor 100 comprises a first inlet 112 for letting in the feedstock FS into the conversion reactor 100, a first outlet 122 for letting out the residue fraction RF from the conversion reactor 100, and a second outlet 124 for letting out fluid from the conversion reactor 100. Flerein the fluid refers to (at least a part of) the flushing fluid FF discussed in connection with the method, such as the product fraction PF and/or the wash fraction WF.

In order to flush the wall 102 of the reactor 100, the conversion reactor 100 comprises a second inlet 114 for letting in flushing fluid FF to the conversion reactor 100, and a nozzle arrangement 130 configured to feed the flushing fluid FF to flow along the wall 102 of the conversion reactor 100 so as to flush the wall 102 of the conversion reactor 100. The nozzle arrangement 130 is arranged inside the conversion reactor 100 and near a wall 102 of the conversion reactor 100. For example, an outlet of the nozzle arrangement 130 may be arranged e.g. at most 20 cm apart from the wall 102. In this way, the nozzle arrangement 130 is configured to flush a wall 102 of the conversion reactor 100. Naturally, an inner side of the wall 102 is configured to be flushed. In an embodiment, the residue fraction RF has a higher density than the product fraction PF. For example, the type two salts of the residue fraction RF have a higher density that other constituents within the conversion reactor 100. Therefore, the residue fraction RF would accumulate on a bottom of the conversion reactor 100 if not let out from the reactor 100. In order to properly let out the residue fraction RF, the second outlet 124 is configured to let out the fluid from a higher level than the first outlet 122. This ensures that not too much of the contaminants are circulated within the conversion reactor 100, since the contaminants are removed with the residue fraction RF through the first outlet 122, which is arranged at a lower level than the second outlet 124. The terms higher and lower relate to a vertical level of the outlets 122, 124; or more precisely, to vertical positions from which the outlets are configured to let out fluid. Anyway, the separation of the residue fraction RF, and also optionally a wash fraction WF, may also be arranged by cyclonic flow utilizing the centrifugal principle. As a result of either or both of these configurations, the conversion reactor 100 is configured to separate the residue fraction RF from the converted feedstock such that a content of a contaminant in the residue fraction RF is higher that a content of the contaminant in a fluid receivable from the second outlet 124. As indicated above, in such a case, a density of the residue fraction RF is different from the density of the fluid receivable from the second outlet 124.

For example, the second outlet 124 may be arranged at a higher level than the first outlet 122, as in Figs. 2a and 2d. Flowever, referring to Figs. 2a and 2d considering that an outlet could refer to an opening on an outer wall of the reactor 100, the location of such opening is immaterial. Instead, the reactor may comprise an inner wall, such as a wall of a tube, that defines the vertical level, from which the fluid is configured to be let out. Thus, with reference to Figs. 2a and 2d, from technical point of view it is immaterial, whether the pipe 140 is connected to the wall 124’ at a level that is above or below the outlet 122. What matters is that the second outlet 124 defined by a wall 124’ limiting the second outlet 124 is configured to let out the fluid from a higher level than the first outlet 122. For example in Figs. 2a and 2d an upper edge of the wall 124’ defines the level from which the second outlet 124 is configured to let out the fluid. As detailed above, the temperature within the reactor 100 is high. Thus, preferably, hot fluid is used as the flushing fluid FF. It has been found that hot fluid is available from the conversion reactor 100 itself. Flowever, since problems caused by the contaminant of the residue fraction RF, e.g. accumulation of the type two salts, are to be avoided, the residue fraction RF is not used as the flushing fluid FF. Instead, fluid obtainable from the second outlet 124 is used for flushing. Thus, the conversion reactor 100 comprises a pipeline 140 configured to convey at least some fluid from the second outlet 124 to the second inlet 114.

Naturally, some other fluid may be added to the recycled fluid. Thus, the flushing fluid FF comprises the fluid obtainable from the second outlet 124. Flowever, the flushing fluid FF may further comprise some other fluid, such as steam. Moreover, some of the fluid taken from the second outlet 124 may be used for other purposes than the flushing.

Referring to Figs. 2a to 2c, it has been found that the flushing fluid FF can, preferably, be taken from a location that is, in the vertical direction, in between the first outlet 122 and an outlet 126 from which product fraction PF. This has been found to be particularly feasible in the context of a BTL process, wherein the product fraction PF is a hydrocarbon rich fraction. In such a case it is feasible that a water and a salt contents of the product fraction PF remain low. This can be achieved by removing also a wash fraction WF from the reactor, which wash fraction WF can then be used for the flushing. In such a case, the flushing fluid FF, on one hand is reasonably aqueous for flushing purposes, as opposed to the product fraction PF. Moreover, as opposed to the residue fraction RF, the flushing fluid FF does not comprise much contaminants, e.g. type two salts. More precisely, the conversion reactor 100 is configured to separate the product fraction, wash fraction WF, and the residue fraction RF from the converted feedstock such that a content of a contaminant is higher in the residue fraction RF than the content of the contaminant in the wash fraction WF. Flowever, in such a case, the wash fraction WF typically comprises type one salts. Naturally, a content of a contaminant may higher in the residue fraction RF than in the product fraction PF.

Therefore, referring to Fig. 2a, in an embodiment the conversion reactor 100 comprises a third outlet 126. The third outlet 126 is configured to let out the product fraction PF from the conversion reactor 100. As detailed above, in this embodiment, the second outlet 124 is configured to let out the wash fraction WF from the conversion reactor 100. Moreover, as detailed above, from the second outlet 124, the fluid is recycled such that at least part of the fluid is used as at least a part of the flushing fluid FF.

In an embodiment, the residue fraction RF and the wash fraction WF have a higher density (as measured in kg/m³) than the product fraction PF. Thus, these fractions RF and WF may be separated from the converted feedstock FS for example by gravity and/or by utilizing a cyclonic effect of the flushing fluid FF. Preferably, a density of the wash fraction WF is between a density of the residue fraction RF and a density of the product fraction PF. In an embodiment, a density of the wash fraction WF is higher than a density of the residue fraction RF and lower than a density of the product fraction PF.

Therefore, in order to reduce the amount of hydrocarbons in the flushing fluid and in this way increasing their content in the product fraction to improve yield, preferably, the second outlet 124 is arranged at a lower level than the third outlet 126. Thus, the flushing fluid FF will be taken from a location that is, in the vertical direction, in between the first outlet 122 and the third outlet 126.

Preferably also the level to which the first inlet 112 is configured to let in the feedstock FS is arranged between the nozzle arrangement 130 and a level from which the second outlet 124 or a secondary second outlet 124b is configured to let out fluid. More preferably, the first inlet 112 is configured to let in the feedstock FS to the conversion reactor 100 at a higher level than a level of the second outlet 124 (or a secondary second outlet 124b, however, the numbering of outlets for letting out different parts of flushing fluid is not relevant). In the alternative, referring to Figs. 12b and 12c, in an embodiment, the conversion reactor 100 is configured to let out a fraction comprising the residue fraction RF from the process zone Z1 of the conversion reactor. Such fraction (WF+RF) is let out from the process zone from the outlet 129.

This has the effect that feedstock FS does not, as such, flow to the second outlet 124. Typically the feedstock comprises the solidifying type two salts, whereby the feedstock, if used as the flushing fluid FF, could cause salts accumulating on the wall 102. Flowever, when fed to a different level then from where the flushing fluid is taken, as detailed above, the feedstock FS has time to react, and the components thereof can be separated before the wash fraction WF is used as the flushing fluid. Flowever, similar effect can be achieved by forming a cyclonic flow of the flushing fluid FF and feeding the feedstock FS to a point that is encircled by the cyclonic flow of the flushing fluid FF. In any case, preferably, the first inlet 112 is configured to let in the feedstock FS to the conversion reactor 100 at a higher level than a level of an outlet (124, 129) from which a fraction (i.e. RF+WF or RF) comprising the residue fraction RF is let out from a process zone Z1 of the conversion reactor 100.

Thus, an embodiment of the method comprises letting out the residue fraction RF from the conversion reactor 100 through the first outlet 122 of the conversion reactor 100. The embodiment comprises separating at the temperature of at least 350 °C and in the pressure of at least 160 bar from the converted feedstock a wash fraction WF. In this embodiment, at least some of the wash fraction WF is used as at least a part of the flushing fluid FF. Therefore, the embodiment comprises letting out the wash fraction WF from the conversion reactor 100 through the second outlet 124 of the conversion reactor 100, and using at least some of the wash fraction WF for the flushing of the wall 102 of the conversion reactor 100. Flowever, as detailed below, the wash fraction WF can be separated in sub-critical conditions.

In an embodiment, the wash fraction WF comprises type one salt. In an embodiment, the wash fraction WF comprises at least one of NaCI, KCI, K2CO3, MgCl2, and CaCh.

In general, unlike type two salts, the type one salts tend to form brine in an aqueous solution. In brine, the type one salts are dissolved. In this way, type one salts concentrate in the brine. As detailed above, in contrast, the type two salts tend to solidify at the process conditions. Type one salts include NaCI, KCI, K2CO3, MgCl2, and CaC . In particular, type one salts involved in the process, when black liquor is used as the feedstock FS include NaCI, KCI, MgCl2, and CaC , and type two salts involved in the process include MgC03, MgS04, CaC03, CaC04, Na2C03, Na2S04, and K2SO4. Fig. 2d shows a lower part of a conversion reactor 100. The upper part is similar to the embodiment of Fig. 2a. As shown in Fig. 2d, an embodiment of the conversion reactor 100 comprises a fourth outlet 128 provided in the pipeline 140. The fourth outlet 128 is configured to let out some of the wash fraction WF. Thus, the wash fraction WF taken out through the fourth outlet 128 can be used for other purposes that flushing. In the alternative, the wash fraction WF taken out through the fourth outlet 128 can be treated in a waste water treatment plant.

In one arrangement, the wash fraction WF taken out through the fourth outlet 128 is exported form the circulation to avoid accumulation of chlorine and/or potassium into the circulation within the reactor 100, particularly when the reactor 100 is used for a BTL process. In one arrangement, the wash fraction WF taken out through the fourth outlet 128 is exported form the circulation to avoid accumulation of chlorine and/or potassium into a chemical circulation of a pulp process, particularly when the feedstock FS comprises black liquor BL. These options are not mutually exclusive. As detailed in Fig. 2d, the fourth outlet 128 is arranged between the second outlet 124 and the second inlet 114 in the direction of flow of the wash fraction WF within the pipeline 140.

When the system comprises multiple circulations for parts of the flushing fluid FF, as in the embodiments of Figs. 10a to 10c, the the fourth outlet 128 can be arranged in any one of the circulations of the flushing fluid. Moreover, outlets can be arranged in more than one of the circulations.

As detailed above, a pressure in the first reaction zone Z1 . Therefore, the feedstock FS is typically pumped to the first reaction zone Z1 of the conversion reactor 100. Thus, a system for producing a product fraction PF from biomass comprises the conversion reactor 100 as discussed above or below and a pump 180 configured to pump the feedstock FS through the first inlet 112 into the first reaction zone Z1 having the pressure of at least 160 bar (see Figs. 1a and 2a). Since the pressure is reasonably high, the pump 180 must be selected accordingly. When higher pressures are used, or at least can be used, the pump 180 is configured to pump the feedstock FS through the first inlet 112 to the first reaction zone Z1 having the pressure of at least 220 bar or at least 300 bar or 350 bar. In order to improve mixing of the compounds and to increase the residence time of the feedstock FS in the first process zone Z1 , preferably, the feeding of the feedstock FS and the flushing fluid FF is designed such that a vortex or vortices are generated into the first process zone Z1 . It has been found that this can be achieved, when an average direction of flow of the flushing fluid FF within the reactor 100 is reverse to the direction to which the feedstock FS is fed. This can be achieved by guiding the openings through which, on one hand the feedstock FS, and on the other hand, the flushing fluid FF, are fed. In addition or alternatively, vortices are more easily generated, when the level to which the feedstock FS is fed is arranged between (i) the level of the nozzle arrangement 130 and (ii) the level from which the flushing fluid FF is let out from the conversion reactor (i.e. the level from which the second outlet 124 is configured to let out the fluid, as discussed above). The flushing fluid flow can be directed to any direction compared to the normal of the wall 102. This direction might be useful in arranging a circular (i.e. cyclonic) flow inside the reactor 100. The feedstock FS can be directed on the average towards up or down in a cyclonic flow. The feedstock FS can be directed towards up or down without a circular component inf the flow. The feedstock FS can be directed on the average horizontally, be there a circular component or not. In the cyclonic flow, the flow of the flushing fluid FF has the circular component, and the flushing fluid FF therefore forms a cyclone in the reactor 100 near the reactor wall 102, as depicted in Fig. 2f. In case of a cyclonic flow, the average direction (as discussed above) of the flow is parallel to a longitudinal direction DL of the reactor.

Thus, to enhance the formation of vortices, in an embodiment, (i) the first inlet 112 is configured to let in the feedstock FS to the conversion reactor 100 at a higher level than a level from which the second outlet 124 is configured to let out the fluid and (ii) the nozzle arrangement 130 is arranged at a higher level than the level to which the first inlet 112 is configured to let in the feedstock FS.

Moreover, to enhance the formation of vortices, in the same or another embodiment, the feedstock FS and the flushing fluid FF are fed to the conversion reactor 100 such that an average direction of flow of the flushing fluid FF within the reactor 100 is reverse to the direction to which the feedstock FS is fed into the conversion reactor 100. The conversion reactor may be configured to feed the feedstock FS and the flushing fluid FF in this way. This applies at least when the nozzle arrangement 130 is configured to produce such a flow of the flushing fluid FF in the reactor 100 and near the wall 102 thereof that the flow is not cyclonic.

Flowever, when the nozzle arrangement 130 is configured to produce a cyclonic flow of the flushing fluid FF in the reactor 100 and near the wall 102 thereof, the first inlet 112 for the feedstock FS is preferably configured to feed the feedstock FS into the reactor 100 in a direction that is substantially the same as an average direction of the cyclonic flow of the flushing fluid FF. This facilitates flushing and prevents the feedstock FS from contacting the wall 102.

Figure 1c shows, as seen from top, a bottom part of the conversion reactor 100 of Fig. 1a. The first outlet 122 is shown in a center of the cross-section of the reactor 100. As evident, the first outlet 122 may be arranged at another part of a bottom of the reactor 100. Moreover, additional first outlets 122 for letting out the residue fraction RF may be provided.

Figure 2c shows, as seen from top, a bottom part of the conversion reactor 100 of Fig. 2a. The first outlet 122 is shown at a side of the cross-section of the reactor 100. As evident, the first outlet 122 may be arranged at another part of a bottom of the reactor 100. Moreover, additional first outlets 122 for letting out the residue fraction RF may be provided. Fig. 2c shows also the first inlet 112 through which the feedstock FS is fed to the reactor 100. Fig. 2c shows also the second outlet 124 through which the flushing fluid FF is let out from the reactor.

Concerning an embodiment of the nozzle arrangement 130, Figs. 1a, 1 b, 2a, and 2b show a preferable embodiment of a nozzle arrangement 130. As shown therein, the wall 102 of the reactor 100 in combination with a wall 132 of the nozzle arrangement 130 provides for a channel 134 for distributing the flushing fluid FF. Moreover, as detailed in Figs. 1 b and 2b, the channel 134 is provided with a slit 136 that forms a nozzle for distributing the flushing fluid FF to the wall 102. In this way, substantially the whole circumference of the wall 102 will be flushed. Alternatively, multiple nozzles supplying fluid at only one point can be used to cover the whole circumference of the reactor 100. Preferably, the nozzle arrangement 130 is configured to supply the flushing fluid to the whole perimeter of the first reaction zone Z1 . Herein the first reaction zone Z1 is the inner part of the reactor 100, wherein the reactions take place. The term perimeter refers the path that encompasses the first reaction zone Z1 .

More precisely, when the flushing fluid FF is configured to flow within the reactor 100 on the average in a longitudinal direction DL of the reactor, the term perimeter refers to the path that encompasses a cross section of the first reaction zone Z1 , wherein the cross section has a normal that is parallel to the longitudinal direction DL. The term on average is used here, since the nozzle arrangement 130 can be designed in such a manner that the direction of the flow of the flushing fluid FF has a circular component, i.e. a component that is parallel to the perimeter. E.g. the flow may be cyclonic. However, the flow of the flushing fluid FF need not be cyclonic. Instead, the flow of the flushing fluid FF may be parallel to the longitudinal direction DL.

The longitudinal direction DL may be substantially vertical and downwards as e.g. in Figs. 1a and 2a. The longitudinal direction DL may be substantially vertical and upwards as e.g. in Fig. 2e. However, the longitudinal direction DL need not be vertical. As an example, Fig. 3 shows an embodiment, wherein the longitudinal direction DL is horizontal. As depicted in Fig. 3, also therein, the flushing fluid FF is configured to flow, within the reactor 100, on the average in the longitudinal direction DL of the reactor 100. However, the longitudinal direction is horizontal. As depicted in Fig. 3, the flow of the flushing fluid FF has a circular component. Moreover, the first inlet 112 may be configured to feed the feedstock through an end of the reactor 100, the end having a normal that is substantially parallel to the longitudinal direction DL, as in Figs. 1a and 2a. However, the first inlet 112 may be configured to feed the feedstock through a wall 102 of the reactor 100, the wall 102 having a normal that is substantially perpendicular to the longitudinal direction DL, as in Figs. 2d, 10a, and 10b.

Figures 12a to 12c show possibilities for utilizing a cyclonic flow within the conversion reactor 100 or within a part of the conversion rector 100 for separating the fraction(s). Referring to Fig. 12a, the product fraction PF can be separated from the other fraction by using a cyclonic flow of the flushing fluid FF encircling the process zone Z1. Then the wash fraction and the residue fraction RF may be separated from each other e.g. using a tank, in which the residue fraction RF tends to settle to a bottom part.

Referring to Figs. 12b and 12c, instead of a tank, a cyclone 108 can be used to separate the wash fraction WF from the product residue fraction RF. A pump 160 can be used to provide for sufficient flow of the fraction(s) separated from the product fraction PF. These fractions are depicted in Fig. 12b by the reference “WF+RF”, and includes the compounds of both the wash fraction WF and the residue fraction RF, which are separated from the product fraction PF in the process zone Z1 and from each other in the cyclone 108. The cyclone 108 can be seen as a part of the conversion reactor 100. In the embodiment of Fig. 12b, the density of the residue fraction RF is higher than the density of the wash fraction WF, whereby the second outlet 124 of Fig. 12b is arranged higher than the first outlet 122. Flowever, the first outlet 122 may be arranged at a higher vertical level than the third outlet 126 for the product fraction PF.

Referring to Fig. 12c, it is also possible that the contaminant concentrates to a fraction that is not the most dense. In the embodiment of Fig. 12c, the product fraction PF is the lightest (least dense) and separated from both the fractions WF and BF as discussed above. Flowever, in the cyclone 108, the wash fraction WF and the residue fractions RF are separated from each other, and, as the wash fraction WF, the denser fraction is used. Thus, the second outlet 124 is arranged below the first outlet 122. As readable from Figs. 12a and 12b, it depends on the contaminant, the content of the product fraction PF, and the carrier liquid of the contaminant, how the separation of the different fraction is achieved. Flowever, preferably, the contaminant is accumulated in the most dense fraction and the product fraction is the lightest. Thus, preferably, a density of the residue fraction RF is higher than a density of the product fraction PF. More preferably, a density of the residue fraction RF is higher than a density of the wash fraction WF and the density of the wash fraction WF is higher than the density of the product fraction PF. In such a case e.g. the embodiments other than that of Fig. 12c are usable.

The clogging of the cyclone 108 by type two salts in the embodiments of Figs. 12b or 12c can be prevented e.g. by operating the cyclone 108 in sub-critical conditions. In such a case, a heater (not shown in Fig. 12b or 12b, but shown as 150 in Fig. 9a) may be applied to heat the flushing fluid FF flowing from the cyclone 108 to the second inlet 114. Moreover, in such a case, the wash fraction WF needs not be separated from the product fraction in the supercritical state. However, the fraction(s) comprising the residue fraction RF is separated in the supercritical state.

As an alternative to a cyclone 108, a filter may be used to separate the fractions WF, RF. This can be done even if the densities of the fractions are the same.

Concerning the method, the method comprises separating at the temperature of at least 350 °C and in the pressure of at least 160 bar from the converted feedstock the product fraction PF and a fraction comprising a residue fraction RF. The fraction comprising the residue fraction RF may consist of the residue fraction (as in e.g. the embodiments of Fig. 1a and 2a) or, as indicated in Figs. 12b and 12c, it may comprise the residue fraction RF and the wash fraction WF.

Even if now shown, a cyclone or a filter may be used to separate the product fraction PF from the wash fraction WF. E.g. in the context of Fig. 1a, a cyclone could be applied to separate the flushing fluid FF from the rest of the product fraction PF. Depending on the case, the flushing fluid FF may be denser or lighter than the rest of the product fraction PF.

As seen from Figs. 1a, 1 b, 2a, and 2b the shape of the reactor 100 may be cylindrical. However the shape may be selected according to needs. For example the reactor may be spherical, as depicted in 4. Moreover, the reactor may have a shape of a generalized cylinder, whereby its cross section that has a normal to the longitudinal direction DL need not be circular. Figs. 5a and 5b show an embodiment, wherein a cross section of the reactor 100, the cross section having a normal to the longitudinal direction DL, is quadrangular. Also other shapes are possible.

Referring to Fig. 6, preferably, the conversion reactor 100 is used in connection with a chemical recovery boiler 200. The term chemical recovery boiler refers to a boiler of a pulp process, the chemical recovery boiler 200 being configured to recover cooking chemicals by reducing the chemicals in a furnace and to produce heat by burning black liquor, which is a residue of the Kraft pulp process. In the alternative, a chemical recovery boiler 200 of a sulfite process is configured to recover chemicals by burning brown liquor. In Fig. 6, the feedstock FS comprises black liquor BL or brown liquor, preferably black liquor. In such an embodiment, the salt(s) of the residue fraction RF and/or the wash fraction WF comprise chemicals that can be utilized in the pulp process at least after reduced in the boiler. Thus, the salt(s) of the residue fraction RF and/or the wash fraction WF may be fed to the chemical recovery boiler 200 in order to recover cooking chemicals from these salts. The chemical recovery boiler 200 can be seen as a part of a chemical recovery cycle of a pulp process configured to recover cooking chemicals.

Thus, in an embodiment, the feedstock FS comprises black liquor BL or brown liquor, preferably black liquor. Herein the term “black liquor” refers to the by product from the Kraft process when digesting pulpwood into paper pulp by removing lignin, hemicelluloses and other extractives from the wood to free the cellulose fibers. Moreover, the embodiment comprises feeding at least some of the residue fraction RF and/or at least some of the wash fraction WF into chemical recovery cycle configured to recover cooking chemicals. Typically the residue fraction RF comprises chemicals that are important in the pulp process. Moreover, the wash fraction WF can be utilized for flushing. Therefore, preferably at least some of the residue fraction RF is fed into the chemical recover cycle to recover cooking chemicals, e.g. into a chemical recovery boiler 200 that is configured to burn black liquor.

Concerning the system of Fig. 6, a system for producing the product fraction PF from feedstock comprises the conversion reactor 100 as discussed above and as detailed below.

The system further comprises a chemical recovery boiler 200 configured to burn black liquor BL and a first pipeline 310 configured to convey black liquor BL to the first inlet 112. The system comprises a pipeline arrangement 330 configured to convey at least a part of the residue fraction RF and/or at least a part of the wash fraction WF to the chemical recovery boiler 200. For the reasons discussed above, preferably, the pipeline arrangement 330 is configured to convey at least a part of the residue fraction RF to the chemical recovery boiler 200. What has been said and will be said about feeding and processing black liquor BL applies to brown liquor mutatis mutandis. Preferably, a first part of the black liquor BL available from the pulp process is processed in the conversion reactor 100 and a second part is processed in the chemical recovery boiler 200. Thus, a preferable system comprises a second pipeline 320 configured to convey black liquor BL to the chemical recovery boiler 200. Moreover, the second pipeline 320 comprises a branch 322, such that a part of the black liquor BL is configured to be conveyed to the chemical recovery boiler 200 and a part of the black liquor BL configured to be conveyed to the first inlet 112 through the branch 322 and the first pipeline 310.

Moreover, as readable from the above, type one salts include salts comprising chlorine (Cl) and salts comprising potassium (K). When applying the process in combination with a chemical recovery boiler 200, such salts are preferably not recovered in the boiler 200, since the cooking phase of the Kraft process does not need such cooking chemicals. In contrast, most of the cooking chemicals to be recovered are in form of type two salts. Moreover the chlorine may pose corrosion problems to the equipment. Thus, in such a context, it is beneficial to feed only the type two salts (i.e. residue fraction RF) to a chemical recovery cycle configured to recover cooking chemicals, such as to a chemical recovery boiler 200, and use the type one salts (i.e. wash fraction WF) otherwise, e.g. by feeding at least part of them back to the process for flushing, as shown in Fig. 6. Optionally, another part of the wash fraction can be sent e.g. to a waste water treatment plant.

As detailed in Fig. 7, the conversion reactor 100 may be used in connection with a supercritical water oxidation (SCWO) process. In such a process, the biomass of the feedstock is oxidized in the supercritical conditions. To enhance oxidation, oxygen or oxygen containing gas may be fed to the conversion reactor. Thus, an embodiment of a conversion reactor 100 comprises a pipeline 184 for feeding oxygen containing gas, such as oxygen, to the conversion reactor 100. The oxygen containing gas is preferably fed to the first process zone Z1. An embodiment comprises feeding the oxygen containing gas, such as oxygen, to the conversion reactor 100, such as to the first process zone Z1 thereof. However, as indicated above, the conversion reactor may be used in context of a hydrothermal carbonization process or a hydrothermal gasification process or a BTL process, where oxygen needs not be fed. Moreover, even in the context of the embodiment where oxygen is fed, separate outlets for the wash fraction WF and the product fraction PF can be provided as shown in Fig. 2a. Thus, the embodiment having both the second and third outlets 124 and 126 (e.g. those of Fig. 2a and 2d) may be provided with the pipeline 184 for feeding oxygen.

The conversion reactor 100 may be used in connection with a biomass-to- liquid (BTL) process. In general a BTL process is a multi-step process that converts biomass to liquid (or gaseous) biofuels through thermochemical routes, in the present context, through a supercritical conversion process. The reactors of Figs. 1a and 2b are usable in this context. Flowever, since a biofuel in general should contain only a minor amount of salts, including the type one salts, preferably, the embodiments having separate outlets for the product fraction PF and the wash fraction WF are used in context of a BTL process.

In any case, a quality of the product obtainable from the conversion as such may not be sufficient for its use as a biofuel. Therefore, the conversion product can be refined e.g. catalytically. This applies at least in the context of the BTL process.

Referring to Figs. 8a and 8b, an embodiment comprises transferring the product fraction PF to a second reaction zone Z2 and allowing the product fraction PF to react in the presence of a solid catalyst CAT in the second reaction zone Z2 to refine the product fraction PF and to obtain refined product fraction (refined PF). Typically, the (unrefined) product fraction contains too much oxygen, which reduces the quality. Oxygen may be removed by deoxygenation. Thus, preferably such a such catalyst CAT is used that has at least a deoxygenating functionality.

As for the conversion reactor, an embodiment of the conversion reactor 100 comprises the first reaction zone Z1 and the second reaction zone Z2, and solid catalyst material CAT in the second reaction zone Z2. Moreover, the conversion reactor 100 is configured (i) to allow the feedstock FS to react in the first reaction zone Z1 at a temperature of at least 350 °C in a pressure of at least 160 bar to form converted feedstock, (ii) to allow the converted feedstock to flow to the second reaction zone Z2, and (iii) to allow the converted feedstock to react in the second reaction zone Z2 in the presence of the solid catalyst CAT. The first and second process zones Z1 and Z2 may be different parts of a vessel, the part being not separated from each other by a wall, as shown in Fig. 8a. However, the first and second process zones Z1 and Z2 may be separated from each other by a wall. The zones Z1 and Z2 may be provided in separate vessels combined with a pipeline for conveying the converted feedstock to flow to the second reaction zone Z2, as shown in Fig. 8b.

Hydrogen may be used with the catalyst CAT. Whether or not hydrogen is used may depend on the selected catalyst. Thus, an embodiment comprises a pipeline 182 for feeding hydrogen containing gas, such a hydrogen, to the second reaction zone Z2 of the conversion reactor 100. An embodiment comprises feeding hydrogen containing gas, such a hydrogen, to the second reaction zone Z2 of the conversion reactor 100. Even if the catalyst CAT is used for upgrading, feeding hydrogen, or the pipeline 182, is not mandatory.

The temperature in the first process zone Z1 is high, as detailed above. In the context of a SCWO process heat is produced by the oxidation. Therefore, when the reactor 100 is used for an SCWO process, excess heat is produced and may be recovered e.g. by a cooler 155. However, in the BTL process, heating of the feedstock and/or the circulated flushing fluid FF and/or the reactor 100 may be required. A heater 150 may be used.

For these reasons, referring to Fig. 9a, in an embodiment, the pipeline 140 is provided with a heater 150. The heater 150 may comprise or be a heat exchanger operating with a heat exchange medium, such as superheated or supercritical steam. A part of the pipeline 140 may serve as the heat exchanger and it may be provided in a heater, such as a furnace, a fluidized bed, or a flue gas channel. The heater 150 may comprise or be an electric heater.

Because the heater 150 heats the flushing fluid FF, natural circulation of the flushing fluid FF may provide for sufficient circulation of the flushing fluid FF. I.e. sufficient circulation of the flushing fluid FF may be achieved without a pump or an injector. Be there a pump or not, in any case, when the flushing fluid FF is heated, circulation of the flushing fluid FF inside the reactor in this case may be, on the average, upwards. In such a case, the natural tendency of the hot flushing fluid FF rising upwards will help the formation of the flow thereof. When the flushing fluid FF is heated with a heater 150 e.g. of Fig. 9a or Fig. 9c, the heater 150 may provide for sufficient heating also in the context of a BTL process. Thus, the reactor walls 102 need not be heated. In case the process zone Z1 was heated via the wall 102, the process conditions near the heated wall 102 would be even more supercritical than elsewhere causing the type two salts to stick on these hot spots. Thus, preferably, none of the walls of the reactor 100 is heated. Instead, a heater, if needed, may heat the flushing fluid FF.

Thus, an embodiment of the conversion reactor 100 comprises a heater 150. In an embodiment (e.g. Fig. 9a) the pipeline 140 is configured to convey at least some fluid from the second outlet 124 to heater 150 and from the heater 150 the second inlet 114.

Particularly in the context of the SCWO process, natural circulation of the flushing fluid FF is oftentimes not sufficient for purposes of flushing. As for sufficiency, preferably flow rates will be given below. Thus, the circulation of the flushing fluid FF can be enhanced with a pump 160 (see Fig. 9b). Even if the pump 160 of Fig. 9b is shown in the context of a reactor 100 with only two outlets (e.g. a reactor for a SCWO process), a pump 160 may be applied in the context of Fig. 9a (or any BTL process) as well. Thus, the pump 160 is configured to provide flow of the flushing fluid FF within the pipeline 140.

Thus, an embodiment of the conversion reactor 100 comprises a pump 160. In an embodiment (e.g. Fig. 9b), the pump 160 is configured to pump the fluid from the second outlet 124 to the second inlet 114.

Particularly in the context of the SCWO process, excess heat is produced. This heat may be removed by a cooler 155 (see Fig. 9d). The cooler 155 may comprise or be a heat exchanger operating with a heat exchange medium, such as water. A part of the pipeline 140 may serve as the heat exchanger and it may be provided in a cooler, such as a water bath.

One possibility to enhance the flow of the flushing fluid FF in the pipeline 140 is to use an ejector 170 (see Fig. 9c). The term injector is used interchangeably with the term ejector. As known, a primary flow driven to an inlet of the ejector 170 causes suction at another inlet of the ejector 170. Thus, a secondary flow can be sucked to the injector 170 and mixed with the primary flow. In Fig. 9c, the pump 160 is used to generate the primary flow for the injector 170, which flow is then heated by the heater 150. When the injector 170 receives the primary flow, the injector sucks the wash fraction WF from the second outlet 124 to the injector’s second inlet. As a result, the flushing fluid FF comprises at least some of the wash fraction WF and the fluid of the primary flow of the injector 170. The fluid of the primary flow may comprise e.g. water and/or steam (FI2O, as shown in Fig. 9c).

In the embodiment of Fig. 9c, the conversion reactor comprises a heater 150. Moreover, the pipeline 140, e.g. an injector 170 of the pipeline 140, is configured to mix fluid receivable from the second outlet 124 with fluid receivable from the heater 150.

When the process produces heat, the heater 150 can be replaced by a cooler 155 (see Fig. 9d). Naturally, a cooler 155 can be used together with a pump and an injector in a similar manner as the heater 150 is used in Fig. 9c. Thus, in an embodiment the conversion reactor comprises a cooler 155; and the pipeline 140, e.g. an injector 170 of the pipeline 140, is configured to mix fluid receivable from the second outlet 124 with fluid receivable from the cooler 155.

In the embodiment of Fig. 9c, the conversion reactor comprises a pump 160. The pump 160 is configured to drive an ejector 170 such that fluid is conveyed from the second outlet 124 to the second inlet 114.

If an ejector 170 is used, a pump 160 is not mandatory, provided that suitably high-pressure steam is available without a pump. If an ejector 170 is used, a heater 150 is not mandatory, provided that suitably high-temperature steam is available without a heater.

In order to properly prevent the type two salts from solidifying onto the wall 102, the flow rate of the flushing fluid FF should be sufficient. Preferably, the mass flow rate of the flushing fluid FF let in (i.e. fed) to conversion reactor 100 (i.e. to the nozzle arrangement 130 of the reactor) is at least two times the mass flow rate of the feedstock FS let in (i.e. fed) to the conversion reactor 100. The mass flow rate refers to the mass flow per unit time, e.g. in units of kg/s. Referring to Figs. 9a and 9b the mass flow rate of the flushing fluid FF fed to reactor 100 may be equal to the mass flow rate of the circulated part of the wash fraction WF (Fig. 9a) or the mass flow rate of the circulated part of the product fraction PF (Fig. 9b). Flowever, as detailed in Fig. 9a, some of the wash fraction WF may be let out through the fourth outlet 128, whereby the flow rate of the flushing fluid FF into the reactor may be less than the flow rate of the wash fraction WF taken out from the reactor. Moreover, as detailed in Fig. 9c, in addition, other fluid, such as water or steam, may be used as part of the flushing fluid FF. Thus the mass flow rate of the flushing fluid FF fed to reactor 100 may be greater than the mass flow rate of the circulated part of the wash fraction WF. More preferably, the mass flow rate of the flushing fluid FF fed to reactor 100 (i.e. to the nozzle arrangement 130 of the reactor) is at least five times the mass flow rate of the feedstock FS fed to the reactor 100.

There might be need to use different parts of the flushing fluid FF differently, for instance, to control the temperature of the reactor. For instance, it might be beneficial to have the upper part of the reactor in super-critical condition to enhance the separation of the contaminant (e.g. salt separation). The lower part of the reactor might be in sub-critical condition to flush the contaminants (e.g. to dissolve the separated salts). Thus, there might be a part of the flushing fluid FF with heating and/or another part of the flushing fluid FF (a) without heating or (b) with cooling. Moreover, one part of the flushing fluid FF could be cooled, while another part would not be cooled. Furthermore, the flushing fluid could be divided into more than two parts, e.g. such that one is heated, one is cooled, and one is neither cooler nor heated.

The flushing can be arranged by two or more than two separate circulations that together form the flushing effect. It has been also found that in some arrangements it would be beneficial to apply flows that are flowing to the opposite directions. This might be useful, for instance, for enhancing mixing within the reactor 100 or arranging separate flow patterns within the reactor 100.

Referring to Fig. 10a, in an embodiment, a first part of the flushing fluid FF is let out from the second outlet 124 and a second part of the flushing fluid FF is let out from a secondary second outlet 124b. Both the first part of the flushing fluid FF and the second part of the flushing fluid FF are guided (outside the reactor 100) to the second inlet 114. In Fig. 10a, the first part is circulated at a lower part of the reactor and the second part is circulated at an upper part of the reactor. The nozzle arrangement 130 is configured to divide the incoming flushing fluid to the said first part and second part. The first part of the flushing fluid FF flushes the part of the wall 102 that is between the nozzle arrangement 130 and the second outlet 124. The second part of the flushing fluid FF flushes the part of the wall 102 that is between the nozzle arrangement 130 and the secondary second outlet 124b.

In Fig. 10a, a heater 150 is configured to heat only the second part of the flushing fluid. A purpose of the heater 150 is to provide heat for the reactions within the process zone Z1 . Moreover, for reasons discussed above, within the reactor 100, the circulation of the second part of the flushing fluid is arranged such that the average direction of flow of the second part of the flushing fluid FF within the reactor 100 is substantially upwards. The flow of the second part may have, but need not have, a circular component as detailed above.

In Fig. 10a, no heater is configured to heat the first part of the flushing fluid. Thus, the lower part of the reactor 100 may be arranged to be in a subcritical state. To provide for further cooling, the system can be provided with a cooler (not shown) configured to cool the first part of the flushing fluid. Accordingly, the circulation of the first part of the flushing fluid is arranged such that the average direction of flow of the first part of the flushing fluid FF within the reactor 100 is substantially downwards. The flow of the first part may have, but need not have, a circular component as detailed above

A first pump (not shown) can be used to enhance circulation of the first part of the flushing fluid. In addition or alternatively, a second pump (not shown) can be used to enhance circulation of the second part of the flushing fluid. As detailed in connection with Fig. 9c, the first pump can be used to drive an injector that is configured to enhance the flow of the first part of the flushing fluid. This applies mutatis mutandis to the second pump.

As detailed in Fig. 10b, the directions of the flows of the first part of the flushing fluid FF and the second part of the flushing fluid FF can be reversed. In such a case, pumps may be needed to provide for sufficient circulation of the flushing fluid. Referring to Fig. 10b, in an embodiment, the system comprises the second inlet 114 for letting in the first part of the flushing fluid and a secondary second inlet 114b for letting in the second part of the flushing fluid. Moreover, the nozzle arrangement 130 is connected to the second inlet 114 and configured to flush a part of an inner side of a wall 102 of the conversion reactor 100 with the first part of the flushing fluid FF. Moreover, the system comprises a secondary nozzle arrangement 130b. The secondary nozzle arrangement 130b is connected to the secondary second inlet 114b and configured to flush a part of an inner side of a wall 102 of the conversion reactor 100 with the second part of the flushing fluid FF.

As detailed in Fig. 10c, the direction of the flow of only the first part can be reverse (relative to Fig. 10a). In such a case, a pump may be needed to provide for sufficient circulation of at least the first part of the flushing fluid. Referring to Fig. 10c, in an embodiment, the system comprises the second inlet 114 for letting in the first part of the flushing fluid and the second outlet 124 for letting out the first part of the flushing fluid. Moreover, the system comprises a secondary second inlet 114b for letting in the second part of the flushing fluid and a secondary second outlet 124b for letting out the second part of the flushing fluid. Moreover, the system comprises the nozzle arrangement 130 as discussed above and a secondary nozzle arrangement 130b. The secondary nozzle arrangement 130b is connected to the secondary second inlet 114b and configured to flush a part of an inner side of a wall 102 of the conversion reactor 100 with the second part of the flushing fluid FF.

In summary, in Figs. 10a to 10c, the system comprises (A) the secondary second inlet 114b and the secondary nozzle arrangement 130b and/or (B) a secondary second outlet 124b. These are, in combination, configured to form a first circulation of a first part of the flushing fluid FF and a second circulation of a second part of the flushing fluid FF. In Figs. 10a to 10c, the first circulation is arranged in a lower part of the reactor 100 and the second circulation is arranged above the first circulation. The numbering of the circulations is arbitrary, i.e. the first circulation can be arranged above the second circulation.

Flowever, as shown in Figs. 10a to 10c, when one of the circulations comprises a heater 150, preferably the circulation comprising the heater 150 is arranged above the other circulation(s). This helps to maintain supercritical conditions at least in the upper part of the reactor 100, while a lower part of the reactor may be in subcritical condition. It is noted that the cyclone 108 of the conversion reactor 100 shown in Figs. 12b and 12c can arranged directly in connection with the process zone Z1. Thus, one of the two circulations of the flushing fluid of the embodiments of Figs. 10a to 10c may form the cyclone 108 shown in Figs. 12b and 12b. The other circulation of the two circulations of the flushing fluid of the embodiments of Figs. 10a to 10c may encircle the process zone Z1 . Flowever, as readable from Figs. 12b and 12c, in those embodiments one of the circulations is configured to flush the wall 102 of the conversion reactor 100 and the other one of the circulations is configured to flush another wall of the conversion reactor 100.

As detailed above, the type two salts, which may be comprised by the residue fraction RF tend to solidify at supercritical conditions. Therefore, the salts may of this fraction typically are, at least at some point of time, in solid form. Flowever, the type two salts may be re-dissolved. The salts may be redissolved in the conversion reactor 100. Flowever, even the type two salts need not solidify, whereby they may be in a form a solution.

In the embodiment of Fig. 11 , the contaminants (e.g. type two salts) are separated and conveyed to a dissolving tank 105, which is provided as a part of the conversion reactor 100. The wash fraction WF is let out from the second outlet 124. A part of the wash fraction WF is used for flushing the wall 102 as indicated in the context of Figs. 9c and 10b. In Fig. 11 , another part of the wash fraction WF is used for dissolving and/or diluting the residue fraction RF that is arranged in the dissolving tank 105. A pump may be used to feed the part of the wash fraction WF to the dissolving tank 105. This part of the wash fraction WF may be cooled to a subcritical temperature, whereby the water regains is polarity. Thus, the subcritical wash fraction WF is capable of dissolving and/or diluting the type two salts within the dissolving tank. The aqueous solution comprising the contaminants (e.g. type two salts) dissolved and/or diluted in the wash fraction WF is then let out through the first outlet 122 and may be referred to as the residue fraction RF.

It may be possible that the dissolving tank 105 is not separated from other parts of the reactor 100 by an internal wall, whereby a lower part of the reactor 100 may be used to re-dissolve the type two salts. Such a solution would be more or less similar to the embodiment of Fig. 10a, 10b, or 10c. As for the composition of the solvent for solving the compounds entering the dissolving tank 105 or a lower part of the reactor 100, water and/or some other solvent can be used instead or in addition to the wash fraction WF (not shown). The residue fraction RF may be used as detailed above. E.g. it may be fed to a recovery boiler 200 to recover chemicals from the residue fraction RF.

Reference: [1] Thomas Voisin, Arnaud Erriguible, David Ballenghien, David Mateos, Andre

Kunegel, et al.. Solubility of inorganic salts in sub- and supercritical hydrothermal environment: Application to SCWO processes. Journal of Supercritical Fluids, Elsevier, 2017, 120, Part 1, pp.18-31.

10.1016/j.supflu.2016.09.020. hal-01417006

Claims

Claims:

1. A conversion reactor (100) for producing a product fraction (PF) from feedstock at a temperature of at least 350 °C in a pressure of at least 160 bar, the conversion reactor (100) comprising

- a first inlet (112) for letting in the feedstock (FS) into the conversion reactor

(100),

- a first outlet (122) for letting out a residue fraction (RF) from the conversion reactor (100), and

- a second outlet (124) for letting out fluid from the conversion reactor (100), characterized in that

- the conversion reactor (100) is configured to separate the residue fraction (RF) from the converted feedstock at the temperature of at least 350 °C and in the pressure of at least 160 bar, and in that the conversion reactor (100) comprises

- a second inlet (114) for letting in flushing fluid (FF) to the conversion reactor

(100),

- a nozzle arrangement (130) connected to the second inlet (114) and configured to flush an inner side of a wall (102) of the conversion reactor (100) with the flushing fluid (FF), and

- a pipeline (140) configured to convey at least some fluid from the second outlet (124) to the second inlet (114) for flushing.

2. The conversion reactor of claim 1 , wherein

- the second outlet (124) is configured to let out the fluid from a higher level than the first outlet (122), for the separating of the residue fraction (RF), and/or

- the nozzle arrangement (130) is configured to form a cyclonic flow of the flushing fluid (FF) within the conversion reactor (100), for separating a fraction comprising the residue fraction (RF).

3. The conversion reactor (100) of claim 1 or 2, comprising

- a third outlet (126) for letting out the product fraction (PF) from the conversion reactor (100), wherein

- the second outlet (124) is configured to let out a wash fraction (WF) from the conversion reactor (100), and

- the conversion reactor is configured to separate the wash fraction (WF) and the product fraction (PF) from the converted feedstock; preferably,

- the second outlet (124) is configured to let out the fluid from a lower level than the third outlet (126), and/or

- the nozzle arrangement (130) is configured to form a cyclonic flow of the flushing fluid (FF) within the conversion reactor (100) for separating the product fraction (PF).

4. The conversion reactor (100) of any of the claims 1 to 3, wherein

- the first inlet (112) is configured to let in the feedstock (FS) to the conversion reactor (100) at a higher level than a level of an outlet (124, 129) from which a fraction comprising the residue fraction (RF) is let out from a process zone (Z1 ) of the conversion reactor (100); preferably,

- the level to which the first inlet (112) is configured to let in the feedstock (FS) is arranged between the nozzle arrangement (130) and a level of an outlet (124, 129) from which a fraction comprising the residue fraction (RF) is let out from a process zone (Z1) of the conversion reactor (100); more preferably,

- the nozzle arrangement (130) is arranged at a higher level than the first inlet (112) is configured to let in the feedstock (FS) and/or

- the nozzle arrangement (130) is configured to form a cyclonic flow of the flushing fluid (FF) within the conversion reactor (100) and the first inlet (112) is configured to let in the feedstock (FS) to a point encircled by the cyclonic flow.

5. The conversion reactor (100) of any of the claims 1 to 4, wherein

- the feedstock (FS) and at least a first part or a second part of the flushing fluid (FF) are configured to be fed to the conversion reactor (100) such that an average direction of flow of the at least part of the flushing fluid (FF) within the reactor (100) at least in a reaction zone (Z1 ) is reverse to the direction to which the feedstock (FS) is fed into the conversion reactor (100).

6. The conversion reactor (100) of any of the claims 1 to 5, comprising

- [A] a secondary second inlet (114b) and a secondary nozzle arrangement (130b) and/or [B] a secondary second outlet (124b) that are, in combination, configured to form a first circulation of a first part of the flushing fluid (FF) and a second circulation of a second part of the flushing fluid (FF), wherein

- the first circulation is configured to flush at least a first part of the wall (102) and - the second circulation is configured to flush a second part of the wall (102) or another wall of the conversion reactor (100).

7. The conversion reactor (100) of any of the claims 1 to 6, comprising

- a heater (150), wherein

- the pipeline is configured to convey at least some fluid from the second outlet (124) or a secondary second outlet (124b) to the heater (150) and from the heater (150) the second inlet (114) or a secondary second inlet (114b), or

- the pipeline is configured to mix fluid receivable from the second outlet (124) or a secondary second outlet (124b) with fluid receivable from the heater (150).

8. The conversion reactor (100) of any of the claims 1 to 7, comprising

- a cooler (155), wherein

- the pipeline is configured to convey at least some fluid from the second outlet (124) or a secondary second outlet (124b) to the cooler (155) and from the cooler (155) the second inlet (114) or a secondary second inlet (114b), or

- the pipeline is configured to mix fluid receivable from the second outlet (124) a secondary second outlet (124b) with fluid receivable from the cooler (155).

9. The conversion reactor (100) of any of the claims 1 to 8, comprising

- a pump (160), wherein

- the pump (160) is configured to pump the fluid from the second outlet (124) or from a secondary second outlet (124b) to the second inlet (114) or to a secondary second inlet (114b); and/or

- the pump (160) or another pump is configured to drive an ejector (170) such that fluid is conveyed from the second outlet (124) or from a secondary second outlet (124b) to the second inlet (114) or to a secondary second inlet (114b).

10. A system for producing a product fraction (PF) from biomass, comprising

- the conversion reactor (100) of any of the claims 1 to 9,

- a chemical recovery boiler (200) configured to burn liquor that is a residue of a pulp process, such as black liquor (BL),

- a first pipeline configured to convey at least some of the liquor to the first inlet (112), and

- a pipeline arrangement configured to convey at least a part of the residue fraction (RF) and/or at least a part of the wash fraction (WF) to the chemical recovery boiler (200); preferably, - the pipeline arrangement is configured to convey at least a part of the residue fraction (RF) to the chemical recovery boiler (200); preferably the system comprises

- a second pipeline configured to convey a part of the liquor to the chemical recovery boiler (200), wherein

- the second pipeline comprises a branch, such that a part of the liquor is configured to be conveyed to the chemical recovery boiler (200) and a part of the liquor is configured to be conveyed to the first inlet (112) through the branch and the first pipeline; preferably the system comprises

- a pump (180) configured to pump the feedstock (FS) to the first reaction zone (Z1 ) having the pressure of at least 160 bar.

11 . A system for producing a product fraction (PF) from biomass, comprising

- the conversion reactor (100) of any of the claims 1 to 9, and

- a pump (180) configured to pump the feedstock (FS) to a first reaction zone (Z1 ) of the conversion reactor (100), the first reaction zone having the pressure of at least 160 bar.

12. A method for producing a product fraction (PF) from feedstock, the method comprising

- providing the feedstock (FS) that comprises water and convertible material to a first reaction zone (Z1 ) of a conversion reactor (100),

- allowing the feedstock (FS) to react in the first reaction zone (Z1 ) at a temperature of at least 350 °C in a pressure of at least 160 bar to form converted feedstock,

- separating at the temperature of at least 350 °C and in the pressure of at least 160 bar from the converted feedstock the product fraction (PF) and a fraction comprising a residue fraction (RF),

- letting out the product fraction (PF) from the first reaction zone (Z1 ), and

- letting out the residue fraction (RF) from the conversion reactor (100) through a first outlet (122), characterized by

- letting out fluid (FF, PF, WF) from the conversion reactor (100) through a second outlet (124),

- feeding the fluid (FF, PF, WF) that has been let out from the conversion reactor (100) in to the conversion reactor (100) through a nozzle arrangement (130) arranged inside the conversion reactor (100) and near a wall (102) of the conversion reactor (100), and

- flushing the wall (102) of the conversion reactor (100) with at least the fluid (FF, PF, WF).

13. The method of claim 12, wherein

- the feedstock (FS) comprises water, salt, and biomass, and

- the residue fraction (RF) comprises type two salt, such as at least one of MgCC>3, MgSC>4, CaCC>3, CaCC , Na₂CC>3, Na₂SC>4, Na3PC>4, KSO4 and Si0₂.

14. The method of claim 12 or13, wherein

- a mass flow rate of the flushing fluid (FF) let in to conversion reactor (100) is at least two times, preferably at least five times, a mass flow rate of the feedstock (FS) let in to conversion reactor (100).

15. The method of any of the claims 12 to14, wherein

- the feedstock (FS) comprises water and biomass, the method comprising

- separating a wash fraction (WF) from the converted feedstock or from the fraction comprising the residue fraction (RF),

- letting out the wash fraction (WF) from the conversion reactor (100) through the second outlet (124) of the conversion reactor (100),

- letting out the product fraction (PF) from the conversion reactor (100) through a third outlet (126), and

- using at least some of the wash fraction (WF) as at least a part of the flushing fluid (FF); preferably,

- a density of the wash fraction (WF) is different from the density of the residue fraction (RF) and the density of the wash fraction (WF) is different from a density of the product fraction (PF); preferably,

- the wash fraction (WF) comprises type one salt, such as at least one of NaCI, KCI, K2CO3, MgCI₂, and CaCI₂.

16. The method of any of the claims 12 to 15, wherein

- the feedstock (FS) comprises liquor that is a residue of a pulp process and the method comprises

- feeding at least some of the residue fraction (RF) and/or at least some of the wash fraction (WF) into a chemical recovery cycle of a pulp process configured to recover cooking chemicals; preferably, - at least some of the residue fraction (RF) is fed into the chemical recover cycle.