SE1051371A1 - Two stage carburetors using high temperature preheated steam - Google Patents

Abstract

A carburettor is described which combines two reactors and which uses externally generated high temperature preheated steam which is injected into the first reactor, where the heating need for gasification is covered by sensible heat from the steam. The carburettor can produce synthesis gas with medium and high low calorific value ( LCV). The first reactor is a solid bed gasification section where coarse-grained raw material is gasified, and the second reactor is an entrained bed gasification section where liquid and fine-grained raw material is gasified. Solid-grained raw material is first freed from volatile components in the first fixed-bed reactor in the carburettor by means of high-temperature steam, and is then exposed in the second reactor to a higher temperature which is sufficient for cracking and destruction of tar and oils. Activated carbon can be produced as a simultaneous product. The carburettor can be used with various solid and surface raw materials. The carburettor has the ability to gasify these different raw materials simultaneously.

Description

2 The application of the technology of partial combustion of incoming carbonaceous materials is widespread. Using this technology, the non-combustible gas CO2 is obtained, and, since it is not removed, this leads to a dilute synthesis gas, and LCV (low caloric value, a measure of the calorific value of the dry gas mass) for the synthesis gas produced becomes limited. In addition, the presence of CO2 obtained as a result of partial combustion (oxidation) leads to a small partial pressure for the other gases, which is not favorable for other valuable gasification reactions, such as e.g. the water gas shift reaction. The hydrogen content of the synthesis gas will thus be negatively affected.

The idea of supplying most of the energy required for the gasification process using sensible heat has recently been investigated, and positive results have been shown. US 2004/0060236 A1 describes e.g. an economically small-scale gasification system for gasification of solid fuel to pyrolysis gas, whereby heated mixed gas of steam and air is introduced into a reformer together with pyrolysis gas which gives a reformed crude gas with a high temperature. The mixed gas of air and steam is preferably heated to at least 300 ° C, and more preferably at least 400 ° C. Any type of heat exchanger or heating device can be used as an air / steam heating device for heating the mixed gas of air and steam.

US 6,837,910 discloses an apparatus and method for gasifying fl liquid or solid fuel, wherein a heated mixed gas of steam and air is introduced into at least one of the thermal decomposition area of the solid or fl liquid fuel and the reforming area of the thermally decomposed gas . The mixed gas of air and steam is heated to a temperature of at least 700 ° C, and more preferably higher than 800 ° C.

Other known systems that use air / steam / oxygen with high temperature, as high as 1000 ° C, for a biomass / waste gasification process have also been used (Lucas C., Szewczyk D., Blasiak W., Mochida S., High Temperature Air and Steam Gasification of Densified Biofuels, Biomass and Bioenergy, Vol. 27, No. 6, December 2004, pp. 563-575). A hydrogen-rich gas free of char, where the process is carried out with steam only at a temperature of 1000 ° C and at a conventional pressure of about 1 atmosphere has been proposed by Ponzio Anna, Yang Weihong, Lucas C, Blaziak W, in Development of a Thermal Homogenous Gasifier System Using High Temperature Agent, CLEAN AIR - International Journal on Energy for a Clean Environment, vol. 7, No. 4, 2007.

US 2003/0233788 A1 describes a method for gasifying carbonaceous materials to fuel gases. It comprises the formation of a composition of ultra-superheated steam (USS) mainly containing water vapor, carbon dioxide and highly reactive free radicals thereof, at a high temperature of approx. 1316 ° C to about 2760 ° C. The USS composition, which comprises a high temperature fl breast, is contacted with a carbonaceous material for rapid gasification / reforming thereof. The USS is formed by the combustion of a substantially ash-free fuel with "artificial air" comprising enriched oxygen and water vapor, the "artificial air" constituting at least approx. 60 mol- percent. The ratio of oxygen fuel must be regulated so that soot is not formed. The use of enriched oxygen in the method will obviously increase the operating costs of the method.

According to US 2003/0233788 A1, gasification with steam only has been investigated and used commercially since 1950-1960. However, due to the limited heat in the steam, the problems associated with gas-only gasification include that only low reaction temperatures can be achieved, i.e. typically less than 8 1 5 ° C, where long residence times and high energy consumption prevail.

All known techniques mentioned above use only single-stage reactors, either a fixed bed carburettor or an id unidised bed.

It is known that the thermal conversion of biomass / waste / carbon can be understood as comprising two mainly highly endothermic steps: decomposition of volatile components and conversion of charred substance. As demonstrated in previous studies, 90% of the innehållcompatible content of the total weight of biomass will be released immediately if it were heated above 600 ° C. The second step is the conversion of char. To get ash free from charred substance, i.e. 100% conversion of char, a much higher temperature is required for the thermal conversion of char. Generally, this temperature should be higher than 1000 ° C, depending on the ash melting point.

Carburetors of the fixed bed type are widely used in small-scale energy production (<10 MWth) thanks to its very simple construction and operation. It has emerged that if the design of a fixed bed gasification reactor follows the above two steps, it would be more efficient from many points of view.

There are extensive studies on this approach for fixed bed carburetors. Secondary air injection into the carburettor is often used. For example, Pan et al. (YG Pan, X. Roca, E. Velo och L. Puigjaner, i Removal of tar by secondary air injection in fl uidized bed gasification of residual biomass and coal, Fuel 78 (1999) (14), s. 1703-1709) 88 , 7% by weight tar reduction by injecting seconds just above the point of biomass feed into the fl uidized bed at a temperature of 840-880 ° C.

Narv et al. (Biomass gasification With air in an atmospheric bubbling fl udized bed.

Effect of six operational variables on the quality of produced raw gas, Industrial and Engineering Chemistry Research 35 (1996) (7), pp. 2110-2120) performed secondary air injection in the freeboard of a carburetor with id uidised bed and observed a temperature increase of about 70 ° C which resulted in a tar reduction from 28 to 16 g / Nmß.

The Asian Institute of Technologist (AIT), Thailand modified a biomass gasifier which resulted in fuel gas with a tar formation of about 50 mg / Nm3, which is about 40 times smaller than a single-stage reactor under similar operating conditions (TA Milne and RJ Evans, Biomass Gasification "Tars ": Their Nature, Formation and Conversion. NREL, Golden, CO, USA, Report No. NREL / TP-570-25357 (1988). This concept involves a downstream carburetor (doWndraft) with air intakes in two levels. the tar in the biomass pyrolysis process passes through a high-temperature bed of residual char at the bottom and decomposes at the elevated temperature.

Bhattacharya et al. reported in A study on Wood gasification for low-tar gas production, Energy 24 (1999), pp. 285-296 a similar carburettor where charred substance formed inside the carburettor itself acted as a filter which further significantly reduced tar formation at 19 mg / Nmß higher CO and Hg concentration in the fuel gas.

Cao et al. reported in A novel biomass air gasi fi cation process for producing tar- free higher heating value fuel gas, Fuel Processing Technology 87 (2006) 343-353 a work concerning a reactor in two areas with id uidised bed. In this work, a supporting fuel gas and other air stream were injected into the upper region of the reactor to reduce the tar compositions. Experimental results showed a calorific value of about 5 MJ / Nmß.

US 6,960,234 describes a multifaceted carburettor and related methods. It is a carburettor that combines a section with fixed bed gasification and a section with entrained fl oW gasification. Activated carbon can be formed in the upper section with a fixed bed and in the section with gasification in flow.

US 6,647,903 discloses a method and apparatus for generating and using combustible gas using a carburetor comprising first and second reaction sections, wherein oxidizing gas is introduced into both sections. The invention works in a way which facilitates tar destruction and which at the same time gives the fuel gas products H2 and CO. In addition, a certain amount of methane can also be formed. In some ways, activated carbon can be formed.

JP 6256775 describes complete gasification of organic material in two steps for methanesynthesis, wherein organic material in a gasification process in a first step is gasified in the presence of steam and oxygen, and, in a gasification process in a second step, is gaseously unreacted material and tar gas are gasified at a higher temperature than in the gasification process in the first step. A carburetor comprising two steps is also described. To limit the passage of solid carbonaceous material from the gasification process in the first stage to the gasification process in the second stage, the passage between the two stages may be narrowed, or a filter may be located between the two stages.

The carburetor includes two inlets for oxygen and steam, one in the first stage and the other in the second stage. The purpose of secondary oxygen / air and / fuel injection in the above studies is to increase the temperature in the freeboard to decompose the tar, and to improve the vapor reforming reaction. However, the injection of secondary air not only increases the content of diluent components, especially nitrogen, but also reduces the combustible content generated by the gasification. This results in a reduction of low calorific value (LCV) for the gases produced. Injection of secondary air also makes it more difficult to regulate the composition of the product gas.

US 6,960,234 mentioned above also states that solid bed gasification requires coarse-grained fuels (typically 1A "to 2" in diameter) and that limiting technical features of solid bed gasification include: the transfer of tar and oil into the synthesis gas; difficulty in using granular coal / fuel as they tend to clog the voids between the coarse-grained fuels in the fixed bed; and difficulty in using liquid hydrocarbon feedstock.

In order to be able to produce combustible gases with medium and high low calorific value (LCV) and to be able to gasify both solid and f surface / fine-grained raw materials at the same time, and also to produce other valuable materials, such as activated carbon, a new fixed bed carburetor is proposed here. The carburettor is defined in claim 1. A method of gasifying a coarse-grained carbonaceous feedstock using a two-stage carburetor with two reactors to obtain synthesis gas, optionally together with activated carbon, where no oxygen is fed to the reactor in the first stage, but only preheated steam with a tem temperatures of at least 700 ° C are also described and specified in the claims. The method is stated in claim 4.

SUMMARY OF THE INVENTION For a prior art two-stage carburetor, as described in JP 6256775 and set out in the preamble of claim 1, comprising: a first reactor provided with an inlet for a coarse-grained carbonaceous feedstock, a first inlet for steam; and a second reactor provided with a second inlet for steam, optionally together with air or oxygen; and a synthesis gas outlet; wherein the first and second reactors are separated by a reduced cross-sectional area of narrowing to limit the passage of unreacted solid carbonaceous material from the first reactor to the second reactor, the first reactor being capable of being operated at a temperature of at least 600 ° C, and wherein the second reactor is capable of operating at a higher temperature, the above objects have been fulfilled by means of the technical features according to the characterizing part of said claim, according to which the second reactor is the lower reactor , the first reactor is the upper reactor, a grid arranged at the lower end of the first reactor, said first inlet for steam is located near the bottom of the first reactor, so that preheated steam with a temperature of at least 700 ° C can be fed to the first reactor from below under the grid via said inlet, said first reactor being provided with an outlet for synthesis gas, the second reactor being provided with a inlet for a fine-grained solid carbonaceous feedstock and / or a liquid carbonaceous feedstock, said second steam inlet being located near the bottom of the second reactor, so that preheated steam having a temperature of at least 700 ° C, optionally together with preheated air or oxygen with the same temperature, can be fed to the second reactor from below via inlet said inlet, and a second area of displacement with reduced cross-section is arranged at the bottom end of the second reactor.

According to one aspect, the invention therefore relates to a two-stage carburettor as above.

The carburettor according to the invention enables simultaneous gasification of solid coarse-grained material, on the one hand, and solid fine-grained and / or surface material, on the other hand.

Carbonaceous coarse-grained material is fed to the first reactor and carbonaceous (waste) liquid and / or carbonaceous non-granular solid material is fed to the second reactor.

In a further preferred embodiment of the two-stage carburettor, one or more, and preferably all inlets for steam, air, oxygen and carbonaceous (waste) liquid and / or carbonaceous fine-grained solid material lead into the carburettor tangentially in corresponding parts of the carburettor, which parts has internal circular cross-sections.

In a further preferred embodiment of the two-stage carburettor, the inlets for carbonaceous (waste) liquid and / or carbonaceous fine-grained solid material comprise at least two inlets separated by a maximum distance from each other along the circumference of the inner circular cross-section.

According to another aspect, the invention relates to a process for gasifying a coarse-grained carbonaceous feedstock, using a two-stage carburettor with two reactors, a first and a second, respectively, for the production of synthesis gas, optionally together with activated carbon. Such a process is set out in claim 4 and comprises the following steps: (a) a coarse-grained carbonaceous feedstock is fed to the reactor in the first stage of the gasifier; (b) the coarse-grained carbonaceous feedstock is subjected to steam in the first stage reactor at an operating temperature of at least 600 ° C in the reactor, to effect gasification of the carbonaceous feedstock, in which process no oxygen is fed to the first stage reactor, but only preheated steam with a temperature of at least 700 ° C, and which process further comprises a step (c), wherein any solid and / or surface carbonaceous materials obtained from step (b) are exposed to preheated steam, optionally together with air or oxygen, in the second stage reactor operating at a temperature of at least 700 ° C to obtain any combination of the following products: activated carbon; CO; CO 2; and combustion value- IT16.

According to a preferred embodiment, the process comprises an additional step (d), wherein a fi granular solid carbonaceous, and / or fl superficial carbonaceous raw material is simultaneously fed into the reactor of the second stage in the carburettor. Accordingly, in this embodiment, both a coarse-grained raw material and a fine-grained solid and / or liquid carbonaceous raw material can be fed into the carburettor at the same time.

According to another preferred embodiment of the process, externally generated preheated steam with a temperature of at least 700 ° C is also fed into the reactor in the second stage. With this embodiment, the internal combustion, also called partial combustion or oxidation, in the carburettor can be kept to a minimum, since the required energy is supplied from an external source. Consequently, the supply of air or oxygen for heat generation by internal combustion is not required in this embodiment.

When air or oxygen is not supplied to the reactor in the second stage, the yield of activated carbon can also be maximized. According to a further preferred embodiment of the process, air is supplied to the second reactor (i.e. in addition to the high temperature steam). With this embodiment, synthesis gas of particularly high quality can be obtained, since carbon is also converted to CO, and not only to activated carbon. In addition, depending on the steam / air ratio, internal combustion can still be avoided (i.e. formation of CO 2). At the same time, the CO: activated carbon ratio can also be regulated by regulating the steam / air ratio.

According to a further preferred embodiment of the process, pure oxygen (instead of air) is used. According to this embodiment, the method can be used for industrial purposes. The need for separation of by-products is also minimized, and undesired dilution of the gaseous product is kept to a minimum.

Additional embodiments and advantages will be apparent from the detailed description and claims.

The terms "internal combustion", "partial combustion" and "partial oxidation" have been used interchangeably to denote combustion taking place inside the carburettor.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a system fl destiny diagram which generally illustrates the inventive gasification process for biomass and solid waste.

Figure 2 shows a cross-sectional view of an embodiment of the carburettor 21.

Figure 3 is a plan view of the carburettor according to the invention showing the tangential injection of surface raw material via the inlets 19a and 19b.

DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS THEREFORE The carburetor of the invention combines two reactors utilizing the injection of externally generated preheated high temperature steam into the first reactor, where the heating need for gasification of gasification is met. The carburettor can produce a synthesis gas with medium and high LCV. The first reactor is a solid bed gasification section where the coarse-grained raw material is gasified, and the second reactor is a gasification section with an entrained bed where fl surface and fine-grained raw material are gasified. In the carburettor's first fixed bed reactor, volatile components are separated from the solid coarse-grained raw material by means of high-temperature steam, and then, in the second reactor, the solid coarse-grained raw material is exposed to a higher temperature sufficient for cracking and destruction of tar and oils.

Activated carbon can be formed as a parallel product. The carburetor can be used with various solid and liquid raw materials. The carburettor has the ability to gasify such different raw materials at the same time.

The underlying idea of the invention is that the carburettor 21 is separated into two stages: a first upper stage 3 for decomposition of volatile components, which first stage uses only externally generated preheated pure steam of high temperature (preferably 700 ° C-1000 ° C ), and a second lower step 4 for thermal conversion of charred substance, which uses a preheated mixture with high temperature (preferably 700-1600 ° C, more preferably 800-1200 ° C) of air and steam, oxygen and steam, or just steam, as shown in Figure 1. The reactor 3 comprises a fixed bed comprising grids 8.

In the first reactor 3, the energy used for decomposing volatile materials is supplied both from the sensible heat of the steam fed into the first reactor via inlet 7, and from the hot stream coming from the second reactor through the area 20 with displacement. The temperature in the first reactor is controlled to a level of at least 600 ° C by quantity of and temperature of the steam fed into said reactor.

In the first reactor 3, high-temperature steam is mixed with coarse-grained raw material (biomass) 1 which enters through inlet 2. When the biomass is heated by the high-temperature steam, the decomposition process of fl-rich material takes place according to: carbonaceous raw material heat from high-temperature steam C0, H2, C02, 02 etc.) + charred substance At the same time, due to the presence of steam, steam reacts with the volatile components: CmHn + H20 <-> CO + H2 (2) CO + Hg0-> CO 2 + H 2 (3) A small amount of oxygen released from the pyrolysis (which occurs in the first reactor, and also in the second reactor when a liquid and / or solid fine-grained raw material is injected) and from the second reactor 4 reacts as follows: cmHn + (m / z + n / 4) o2-> mco + n / 2H2o (4) co + ßog -> cog (s) H2 + wog -> H20 (6) co + H2o-> co2 + H2 (7) Since the reactor temperature in the first stage reactor 3 is regulated to a level of at least 600 ° C, and the residence time is regulated, and the gases in the first reactor If it is in an environment which to a very large extent lacks oxygen, any solid and / or liquid charred substance formed in the first reactor will not react with any oxidizing agents in said reactor. Consequently, any solid and / or liquid charred substance will instead fall into the second reactor 4 by gravity.

In the second reactor 4, the energy used for the process of conversion of char is preferably supplied from the sensible heat of the mixture of steam and air, and from partial oxidation of char. To achieve conversion free of char, the temperature in the second reactor should be higher than the ash melting point, to cause the ash to form slag. For wood biomass, the ash melting point can normally be 1300 ° C. The reactor 4 includes a bed in an fl (entrained bed) comprising grids 5. 12 The main reactions when there is no injection of other raw material (fl surface and fine-grained particles) are: Gasification: C + 02 => C02 -393.5 kJ / mol (8) C + H 2 O => CO + H 2 + 131.3 kJ / mol (9) C + 2H 2 O => CO 2 + H 2 +90.2 kJ / mol (10) - Partial oxidation: C + O, 502 => CO -110.5 kJ / mol (11) - Boudouard reaction: C + CO 2 => 2CO -172.4 kJ / mol (12) - Water gas shift: C0 + H 2 O => CO 2 + H 2 -41.1 kJ / mol (13) - Methanation: C0 + 3H2 => CH4 + H20 -206.1 kJ / mol (14) - Hydrogenation: C + 2H2 => CH4 -75 kJ / mol (15) When a second raw material (fl surface and fine-grained particles) are injected into the second reactor, all reactions from (1) to (15) will take place.

Many reactions occur simultaneously and it is difficult to control the process exactly as pointed out here. However, by carefully selecting the process parameters (temperature, residence time and oxygen / vapor ratios), according to the invention, it is possible to maximize certain desired products, such as activated carbon and synthesis gas.

In addition, the activated carbon can be treated as a co-preparation from thermal conversion of carbon-based materials by this invention. The production of activated carbon according to the prior art usually includes two steps: charring the raw material in the absence of oxygen at high temperature (500-1000 ° C) to eliminate maximum amounts of oxygen and hydrogen, and activating the charred product at a higher temperature in the presence of oxidizing gas such as water, carbon dioxide or both. Activation must be performed under well-controlled conditions to obtain the desired conversion. According to the invention, the raw material is first gasified by means of pure high-temperature steam (at a level of at least 600 ° C) in the first reactor 3, after which the carbon is preferably activated in the second reactor 4 by means of high-temperature steam.

According to the invention, as shown generally in Figure 1, high temperature steam, and optionally air or oxygen (above 700 ° C) is obtained, mainly by using a regenerative heat exchanger with honeycomb structure as explained in e.g. EP 0 607 921, or in the co-pending PCT / SE2009 / 050019, the contents of which in relevant parts are incorporated herein by reference.

Figure 2 illustrates a cross-sectional view of the carburetor 21. Carbonaceous feedstock 1 enters the reactor at the top, through a feed inlet 2, and continues downward as it moves through the first reactor 3, then passes the grid 8, then enters the second reactor 4, and passes then the grid 5 until it becomes a molten ash on the bottom 6. The raw material may include biomass, coal, municipal solid waste, or any combination thereof. The particle size of the coarse-grained carbonaceous raw material 1 is typically from 0.5 cm to 1.8 cm, and preferably from 0.5 to 1.2 cm.

In the first reactor 3, the raw material is heated by a combination of sensible heat caused by the high temperature steam (above 700 ° C), and sensible heat carried by the flue gases obtained by oxidation of char and gasification in the second reactor 4. High temperature steam as passed through the pipe 7 for gasification of the raw material in the first reactor enters an area with constriction or neck 20 through an opening (openings) l 1. The amount of high temperature steam supplied through the opening 7 is set so that the temperature at point 3 (first reactor) is kept between 600-900 ° C, and preferably above 700 ° C. At the point around 8 (grid), when air or oxygen is fed to the second reactor, a hot combustion flame may occur when excess oxygen burns with pyrolysis gases released from the raw material 1, and from any fl surface and / or solid fine-grained raw material fed into the other reactor.

The temperature in reactor 3 is regulated by the temperature and fl rate of fate of the steam injected from point 7, and the temperature and quantity of 14 excess oxygen from reactor 4. The residence time of the raw material 1 in reactor 3 is mainly controlled by the gap in the grid 8.

In order to achieve a good mixing between the gasifying agents (steam) with the raw material 1, a neck 20 is provided. The diameter of the neck is usually smaller than that of the core of the reactor 3. The inclination of the conical part 14 should preferably be around 45-60 °. The diameter of the steam injection opening 11 should preferably be 2-3 times smaller than that of the neck 20.

After volatile components have been separated from the coarse-grained carbonaceous feedstock by means of high-temperature steam in the first reactor 3, the remaining fixed carbon has become activated carbon, charred and solid ash material, which continues to move downward through the grid 8, then into a neck 20, then into the second reactor 4, where they are oxidized and gasified by means of a mixture of high-temperature air (or oxygen) and steam. When no air or oxygen is fed with the steam into the reactor 4, no oxidation takes place in reactor 4, only gasification. The temperature in the second reactor 4 is further increased to a temperature just above the softening point of the ash for the fuel in question at the grate 5. The pipe 9 carries the preheated high temperature steam or the mixture of high temperature air (or oxygen) and steam to the opening 10, which then enters in the other neck 18.

For wood pellets made from wood that has grown in Sweden, the ash softening point typically ranges from 1350-1400 ° C. If slag formation is to be avoided, the maximum peak temperature in reactor 4 is maintained during operation at a temperature of at least 50 ° C below the ash softening point, 100 ° C below being the normal and thus preferred maximum condition.

The temperature in reactor 4 is regulated by the preheating temperature, the rate of fate and the ratio of steam to carbon, and, when air or oxygen is also used together with the steam, the ratio of steam to oxygen in the mixture.

The diameter of the second region with constriction or neck 18 is usually smaller than the diameter of reactor 4, and preferably also smaller than that of the first region with constriction or first neck 20. The inclination of the conical region 17 should preferably be around 45-60 °. C. The diameter of the steam injection opening 10 should preferably be 3-5 times smaller than that of the neck 18.

The ash falls to the bottom 6 through the neck 18 and can be removed in batches from the reactor.

The synthesis gas flows out through the outlet pipe 12. Since the temperature in the first reactor 3 is sufficiently high, and steam is also present, most of the tar is destroyed and converted into synthesis gas. The main chemical constituents of the synthesis gas are hydrogen, carbon monoxide and methane as well as carbon dioxide.

The design of the carburettor according to the invention has the ability to advantageously regulate the ratio of hydrogen to carbon monoxide in the synthesis gas, since the carburettor enables control over the ratio of steam to oxygen in the carburettor within wide limits.

By controlling the temperature in the second reactor 4 to around 700 ° C, i.e. in one embodiment of the reactor mode, i.e. the same temperature as in the first reactor 3, and by only supplying steam to the second reactor, all the tar and oils of high temperature steam are consumed. This converts most of the fixed carbon to activated carbon in the carburetor. Therefore, the carburetor and the process described herein can also efficiently generate activated carbon. This approach is very efficient for the generation of activated carbon, and will also improve the quality of the activated carbon obtained. If, on the other hand, gasification is to be maximized, the second reactor should be operated at a higher temperature than the first reactor.

Accordingly, the invention can also be used to produce activated carbon. There are two methods by which activated carbon is formed in the carburetor. In the first, only the first reactor is used, i.e. only high temperature steam is injected through the pipe 7.

The high temperature mixture of steam and air from pipe 9 is closed. Another and more preferred method is to have both reactors running, but to inject only high-temperature steam from pipe 9. In this case, activated carbon is collected directly in the dry state.

The second method has surprisingly been found to have the ability to give higher quality activated carbon of the char. This is presumably due to the fact that the high-temperature steam injected from the pipe 9 causes the pores of the activated carbon to open in the second reactor 4. Activated carbon with larger pores than according to the prior art can thus be obtained by the method according to the invention. The size (diameter of the pores) can be controlled by means of the temperature of the steam in the reactor 4. Usually a higher temperature of the steam increases the number of pores in the activated carbon.

The invention is thus capable of producing two products (gas and activated carbon) from one and the same raw material 1. The desired proportion of the products can be determined according to the type of raw material available, the price of the products and so on.

The invention can also be used to treat both coarse-grained particles (diameter greater than 0.5 cm) of carbonaceous materials and fine-grained particles and / or liquid raw materials.

Figure 3 shows a cross-sectional view of the carburettor 21, showing the tangential injection of raw material of liquid / fine-grained particles. Two injection lances 19 (19a and 19b) are shown connected to the reactor 4. Liquid raw materials, such as liquid residues collected after a microwave pyrolysis process for Automotive Shredder Residue (ASR), and fine-grained or powdered raw materials can be injected into the reactor 4. The injected the raw material enters the reactor 4 tangentially and is mixed with high temperature air / steam coming from the grid 5. The tangential injection can increase the residence time of the liquid and / or fine-grained raw material. The entrained fl ow gases pass through the upper fixed bed grid 8, then enter the reactor 3 before leaving the carburettor at the outlet pipe 12. The injection port 19 should be located in the lower part of the core of the reactor 4 to increase the residence time. For a small-scale carburettor, the location of this injection opening (s) is usually 10 cm above the sloping wall 17.

The residence time can be regulated by the injection speed, and the angle of the injection lance relative to the carburettor.

In a preferred embodiment, the walls of the carburetor consist of two layers: an outer steel height, preferably 5.0 mm thick, and an inner casing of brittle ceramic insulation, preferably a high temperature resistant, high quality ceramic. The ceramic used at the walls 13 and 14 can preferably work with, ie. resist, a maximum temperature of 1400 ° C. A suitable material may be composed of AlgOg 45%, SiOg 36%, FegOg 0.9% and CaO 16%. The ceramic used for the walls, 16 and 17 is preferably adapted to withstand a higher temperature of 1400-1500 ° C. The maximum permissible operating temperature for this wall material is 1600 ° C.

A suitable material may have the following composition: AlgOg 61%, SiOg 26%, FegOg 0.5%, CaO 2.6%, ZrOg 2.95%, and BaO 3.3%. The ceramic materials are supported by a steel casing.

In a preferred embodiment, refractory ceramic tubes such as grids 8 and 5 are used.

The composition of these ceramic tubes can e.g. be 97% ZrO 3, and 3% MgO.

A high temperature mixture of steam, optionally together with air or oxygen, which is fed through the pipe 9 enters the throat 18 located below the grid 5.

This high temperature mixture of air and steam can keep the ash in a molten state in the throat 18, which ash finally falls to the bottom 6, and can be taken out in batches.

Example 1: 97 kg / h of wood pellets 1 with a diameter of around 8 mm are fed into the first reactor from the inlet 2 by gravity at room temperature (15 ° C). The properties of the wood pellets are shown in Table 1.

Table 1 Primary and elemental analysis of the raw materials used Primary analysis Wood pellets (WP) Total moisture content (SS 187170) 8% Ash content (SS-187171) 0.5-0.6% (dry) LHV (SS-ISO562) 17.76 MJ / kg (as obtained) Volatiles (SS-ISO) 84% (dry) Density 630-650 kg / mß Elemental analysis (dry compositions) Wood pellets 18 Sulfur (SS-l87177) S 0.01-0.02% Carbon ( Leco-600) C 50% Hydrogen (Leco-600) H 6.0-6.2% Nitrogen (Leco-600) N <0.1% Oxygen (calculated) O 43-44% Ash melt temperatures (oxidizing conditions) Wood pellets 1350 - 1,400 ° C 1450- 1,500 ° C 1500 ° C 1500- 1,550 ° C Initial deformation, IT Softening, ST Hemispheric, HT Temperature at liquid state, FT Example 2: 60 kg / h of waste-derived fuel (RDF), a pellet fuel made from paper fiber mixed with other substances such as textiles, wood chips and plastics, was used as a raw material, with a diameter of approx. 8 mm, and was fed into the first reactor 3 from the top 1 by its weight, i.e. by the action of gravity, at room temperature (15 ° C). The properties of the RDF pellets are shown in Table 2.

Table 2 Primary and elemental analysis of the RDF raw material used Primary analysis Waste-derived fuel (RDF) 2.9% 6.0% (dry) 26,704 MJ / kg (as obtained) 84.4% (dry) 472 kg / m3 Total moisture content (SS 187 170) Ash content (SS-187171) LHV (SS-ISO562) Volatiles (SS-ISO) Density Elemental analysis (dry compositions) RDF sulfur (ss-1s7177) s 0.09 0/0 K01 (Leco- øoo) c 63.3 0/0 19 Hydrogen (Leco-600) H 8.9% Nitrogen (Leco-600) N 0.3% Oxygen (Calculated) O 20.95% Ash melt temperatures (oxidizing conditions) RDF Initial deformation, IT 1210 ° C Softening, ST 1220 ° C Hemispherical, HT 1230 ° C Temperature at liquid state, FT 1240 ° C

Claims (9)

10 15 20 25 30 20 PATENT REQUIREMENTS A two-stage carburettor (21) for the production of synthesis gas, and optionally activated carbon, starting from a coarse-grained carbonaceous feedstock, the carburettor comprising: - a first reactor (3) provided with an inlet (2) for a coarse-grained carbonaceous feedstock ( 1), a first inlet (7) for steam; and - a second reactor (4) provided with a second inlet (9) for steam, optionally together with air or oxygen; - and an outlet (12) for synthesis gas; wherein the first and second reactors are separated by a displacement region (20) of reduced cross-section to limit the passage of solid carbonaceous unreacted substance from the first reactor to the second reactor, the first reactor being capable of being operated at a temperature of at least 600 ° C, and the second reactor is capable of operating at a higher temperature, characterized in that the second reactor (4) is the lower reactor, and the first reactor (3) is the upper reactor, a grid ( 8) is arranged at the bottom end of the first reactor, the inlet (7) is located near the bottom of the first reactor, so that preheated steam with a temperature of at least 700 ° C can be fed to the first reactor from below under grate (8) via the inlet (7), that the second reactor is provided with an inlet (19) for a granular solid carbonaceous raw material and / or a liquid carbonaceous raw material, that the inlet (9) is located near the bottom of the second reactor, so that preheated steam with a temperature of at least 700 ° C, optionally together with preheated air or oxygen of the same temperature, can be fed to the second reactor from below via inlet (9), and by a second area of constriction (18) with a reduced cross section being arranged at the bottom end of the second reactor (4). Two-stage carburettor according to claim 1, wherein one or fl are and preferably all of the inlets (7, 9, 19) open tangentially into the carburettor in corresponding parts (20, 18, 16) of the carburettor, which have internal circular cross-sections. A two-stage carburettor according to claim 1 or 2, wherein the inlet (19) comprises at least two inlets (19a, 19b) separated by a maximum distance from each other along the circumference of the circular cross-section. 10 15 20 25 30 21 A process for gasifying a coarse-grained carbonaceous feedstock using a two-stage carburettor with two reactors, a first and a second, respectively, for producing synthesis gas, optionally together with activated carbon, comprising the steps of: (a) feeding a coarse-grained carbonaceous feedstock; to the reactor in the first stage of the carburetor; (b) the coarse-grained carbonaceous feedstock is subjected to steam in the first stage reactor at an operating temperature of at least 600 ° C in the reactor, to effect gasification of the carbonaceous feedstock, characterized in that no oxygen is fed to the first stage reactor, but only preheated steam with a temperature of at least 700 ° C, and of a further step (c) where any solid and / or liquid carbonaceous materials obtained from step (b) are exposed to preheated steam, optionally together with air or oxygen, in the second the stage reactor operating at a temperature of at least 700 ° C to obtain any combination of the following products: activated carbon; CO; CO 2; and combustion heat. A method according to claim 4, comprising a further step (d) according to which a fine-grained solid carbonaceous, or fl liquid carbonaceous raw material is simultaneously fed to the reactor of the second stage in the carburettor. A process according to claim 4 or 5, wherein in step (c) the steam entering the second stage reactor is preheated to a temperature of 700-1600 ° C, and preferably 800-1200 ° C. A process according to any one of claims 4-6, wherein the ratio of steam / air or steam / oxygen used in step (c) is selected so that the internal combustion is minimized, and so that the yield of CO and / or activated carbon is maximized. A method according to any one of claims 4-7, wherein oxygen is used instead of air. 22 A method according to any one of claims 4-6, wherein no air or oxygen is supplied to the carburettor.