WO2001094497A1

WO2001094497A1 - Method and apparatus for separating solids from pyrolysis liquid

Info

Publication number: WO2001094497A1
Application number: PCT/FI2001/000536
Authority: WO
Inventors: Yrjö SOLANTAUSTA; Anja Oasmaa
Original assignee: VTT Technical Research Centre of Finland Ltd
Current assignee: VTT Technical Research Centre of Finland Ltd
Priority date: 2000-06-08
Filing date: 2001-06-06
Publication date: 2001-12-13
Anticipated expiration: 2002-12-08
Also published as: FI20001371A0; AU2001274126A1; FI108462B

Abstract

The invention relates to a method for separating solid matter from a pyrolysis liquid produced from solid raw material via flash pyrolysis by condensing the pyrolysis steam obtained into a pyrolysis liquid. According to the invention, most of the solid matter contained in the pyrolysis liquid obtained from the pyrolysis process is separated from it in a separating device after a suitable delay, by separating from the surface of the pyrolysis liquid a desired surface fraction having a high solid matter content. The apparatus of the invention comprises at least one separating device (3) for the separation of solid matter and at least one control device (9) for setting a suitable delay and/or controlling the separation of a desired surface fraction, and the apparatus is disposed substantially in conjunction with a flash pyrolysis apparatus (1, 2).

Description

METHOD AND APPARATUS FOR SEPARATING SOLIDS FROM PYROLYSIS LIQUID

The present invention relates to a method as defined in the preamble of claim 1 and to an apparatus as defined in the preamble of claim 9 for the separation of solid matter from a pyrolysis liquid produced by flash pyrolysis of solid raw material by condensing the pyrolysis steam generated, .producing a pyrolysis liquid. The solid raw material used in the pyrolysis process may consist of e.g. wood, bark, forest waste chips or a mixture of these, or peat or other solid biomass .

The pyrolysis steam and liquid produced con- ventionally contain solid matter, e.g. carbonization residue, sand and/or impurities or the like. Some of the solid matter can be removed during the flash pyrolysis process by using e.g. filters and cyclones, as described e.g. in patent applications FI 19992080 and FI 19992181. However, some of the solid matter may remain in the pyrolysis liquid product. This solid matter causes problems in the storage and use of the pyrolysis liquid product, e.g. when the pyrolysis liquid is used as a fuel in boilers and power plants. The solid matter tends to block filters and atomizers in such apparatus and it may also cause erosion. In addition, sediments accumulate on the bottom of containers during storage. Such sediments cannot be easily removed and they are difficult to treat using conven- tional fuel treatment apparatus. Moreover, solid matter in the fuel increases particle emissions from the combustion process.

In prior art, several methods for separating solid matter from a pyrolysis liquid using a filter or equivalent are known. However, a filter is apt to get blocked by the solid matter, or the cake accumulated on the surface of the filter material will soon become almost impermeable.

Previously known are also methods for separating solid matter from a pyrolysis liquid by using a separate solvent, which is an expensive method for separating solid matter, due to the use of a solvent.

The object of the invention is to eliminate the above-mentioned problems and to disclose a new and practicable method for separating solid matter from a pyrolysis liquid that is more effective than previously known methods. A further object of the invention is to disclose a method that is easy to implement while allowing easy elimination of the problems caused by solid matter in connection with the use of pyroly- sis liquid.

The method of the invention is characterized by what is presented in the claims.

The invention is based on separating solid matter from a pyrolysis liquid obtained via pyrolysis. Most of the solid matter contained in the pyrolysis liquid is separated from it in a separating device after a suitable delay by removing from the surface of the pyrolysis liquid a desired surface fraction having a high solid matter content. The pyrolysis liquid is produced from solid raw material by generating pyrolysis steam via flash pyrolysis and condensing the steam into a liquid.

In an embodiment of the invention, the surface fraction is separated from the pyrolysis liquid after condensation performed in a condenser, wh-ere the gas and liquid phases are effectively intermixed. In the condenser, a gas, e.g. pyrolysis vapor, combines with the pyrolysis liquid in a dissolved form. After the condenser, as the liquid-gas mixture is cooling down, the gas is released and rises as gas bubbles toward the surface of the pyrolysis liquid. Solid matter particles adhere to the surface of the gas bubbles, rising with the bubbles to the surface portion of the pyrolysis liquid. In this way, a surface fraction having a high solid matter content is. formed. With time, however, the solid matter begins to settle back to the bottom.

In an embodiment of the invention, the surface fraction separated constitutes 1 - 30 vol-%, preferably 1- 20 vol-% of the pyrolysis liquid. In an embodiment, the surface fraction is a substantially separate surface phase. The formation of a separate surface phase depends on the raw material used and the processing conditions; phase separation does not always occur in the pyrolysis liquid. A separate surface phase may also be formed in a situation where e.g. a scrubbing liquid in the condenser forms a multiphase oil with the pyrolysis liquid.

In an embodiment of the invention, a suitable delay is 1 - 720 min, preferably 1 - 60 min. In an embodiment, the surface fraction is separated after a delay period, preferably within 1 h - 5 days, by which time possible phase separation from the pyrolysis liquid will substantially have taken place. In an alternative embodiment, the surface fraction containing solid matter may be first separated from the pyrolysis liquid within a delay of 1 - 720 min, whereupon the separate surface phase is separated after phase separation has occurred. The phase separation may take place considerably more slowly than the rising of solid matter into the surface fraction of the pyroly- sis liquid.

The delay may be dependent on the condenser, e.g. a scrubber, on the velocity and/or volume of gas flow in it and the efficiency of the liquid-gas contact. Moreover, the delay may depend on circumstances like design of the solids separation device, the raw material, its particle size, the reaction conditions, the number of phases in the pyrolysis liquid and other physical properties of the solid matter and liquid. An appropriate selection of the delay can have a decisive effect on the efficiency of separation of solid matter. In an embodiment of the invention, solid matter is substantially removed from the surface fraction separated.

In an embodiment of the invention, at least part of the surface fraction separated is passed to an energy production stage in the pyrolysis process, e.g. into a combustion boiler. The solid matter removed from the surface fraction may also be taken into a combustion boiler.

The apparatus of the invention comprises at least one separating device for separating solid matter from the pyrolysis liquid obtained from a pyrolysis process by separating a desired surface fraction having a high solid matter content from the surface of the pyrolysis liquid, and at least one control device for setting a suitable delay and/or controlling the separation of a desired surface fraction. The device is disposed substantially in conjunction with a flash pyrolysis apparatus comprising a pyrolyzer for generating pyrolysis steam and a condenser for condensing the pyrolysis steam into pyrolysis liquid.

In an embodiment of the invention, the device is disposed in conjunction with the condenser, preferably a scrubber. In an embodiment, the device is disposed after the condenser. When a scrubber is used as a condenser, the scrubbing fluid used may consist of any scrubbing fluid known in the art, e.g. the pyrolysis liquid or an external scrubbing fluid.

The method of the invention makes it possible to improve the quality of the pyrolysis liquid/oil produced in a pyrolysis process by reducing its solid matter content. A lower solid matter content facilitates the storage and processing of the pyrolysis liq- uid while making the pyrolysis liquid more usable as a fuel in boilers and power plants.

By the method of the invention, the separation of solid matter from pyrolysis liquid can be per- formed more effectively than by prior-art methods.

The method and apparatus of the invention have the advantages of being easy and economical to use. Further, the apparatus of the invention can be easily combined with existing equipment and the method can be easily implemented in prior-art apparatus even after small investments.

In addition, the method and apparatus of the invention can be advantageously combined with the methods and apparatus presented in patent applications FI 19992080 and FI 19992081, the result being an effective pyrolysis process and a very good pyrolysis liquid product regarding its quality, e.g. stability.

In the following, the invention will be described by the aid of detailed examples of its embodi- ments with reference to the attached drawings, wherein

Fig. 1 presents a diagram representing an embodiment of the apparatus of the invention, and

Fig. 2 - 5 illustrate the effect of the delay on the separation of solid matter and the distribution of solid matter particles between the surface fraction and the pyrolysis oil- Fig. 1 presents an apparatus according to the invention for the separation of solid matter, in conjunction with a flash pyrolysis apparatus also pre- sented in the figure.

The flash pyrolysis apparatus in Fig. 1 comprises a pyrolyzer 1 for generating pyrolysis steam and a condenser 2, in the present embodiment a scrubber, for condensing the pyrolysis steam into a pyroly- sis liquid. The flash pyrolysis apparatus may be any type of pyrolysis apparatus known in the art and it will not be described here in detail . In the embodiment presented in Fig. 1, the apparatus of the invention comprises one separating device 3 for separating a surface fraction 6 containing solid matter from the surface of the pyrolysis liquid obtained from the pyrolysis process. Further, the apparatus comprises a control device 9 for setting a suitable delay and controlling the separation of a desired surface fraction and surface phase. The control device may be a manually or automatically oper- ated device.

The separating device 3 used may be a simple separating device, such as a sedimentation basin, flotation apparatus or the like. In the embodiment in Fig. 1, the separating device is a sedimentation basin 3. The embodiment in Fig. 1 further comprises an extraction pipe 8 for bringing the pyrolysis liquid product, i.e. pyrolysis oil, out of the separating device 3. The pyrolysis oil is passed via the extraction pipe 8 preferably into a product container 4. In addition, the apparatus in Fig. 1 comprises an extraction pipe 10 for bringing the separated surface fraction 6 out of the separating device 3. Via this extraction pipe 10, the surface fraction can be passed into a separator device 5, in the pres- ent embodiment a filter 5, or to a direct utilization stage 12, e.g. an energy production device, such as a combustion boiler, for the pyrolysis process. In the filter 5, solid matter 7 is separated from the surface fraction 6, producing a surface fraction 11 with a low solid matter content. The solid matter fraction 7 and/or the surface fraction 11 may be passed e.g. into a combustion boiler.

In the embodiment in Fig. 1, the apparatus of the invention is disposed after the scrubber 2, the separation of solid matter being performed upon the lapse of a certain delay after the condensation 2. The scrubber 2 used is a device in which the gas and liquid phases intermingle effectively, in other words, the gas and liquid phases have a good liquid-gas contact surface with respect to each other. In the scrubber, the pyrolysis liquid is used as a scrubbing fluid. In an alternative embodiment, the apparatus of the invention may be disposed in conjunction with a scrubber 2 for separating solid matter from the condensed pyrolysis liquid after a certain delay.

In the embodiment of the apparatus in Fig . 1 , the gas 13 released from the separation 3 of solid matter is passed back into the pyrolysis reactor 1 or into a combustion boiler used in the pyrolysis process while any scrubbing fluid 14 that may be separated is taken back into the scrubber 2. In the embodiment of the apparatus in Fig. 1, it is possible to use any types of known separating devices, control devices, extraction pipes and separator devices, which will not be described here in detail.

In an alternative embodiment of the appara- tus, the apparatus comprises two separating devices 3. In this case, a first separating device is arranged to separate a surface fraction containing solid matter from the surface of the pyrolysis liquid after a short delay, 1 - 720 min. A second separating device is ar- ranged to separate after a longer delay, 1 h - 5 days, the entire surface phase that may have been formed in the surface portion of the pyrolysis liquid. The apparatus may also comprise one or more control devices. In this embodiment, the pyrolysis liquid is preferably produced from a raw material which is pyrolyzed to produce a multiphase liquid.

Example 1

An experiment was carried out to test the separation of solid matter from a substantially homogeneous pyrolysis liquid. The pyrolysis liquid was produced by condensing pyrolysis steam in a scrubber in which the gas and liquid phases intermingled effectively.

From the surface of the pyrolysis liquid, an amount of 1 - 20 vol-% of the pyrolysis liquid was separated within a delay of 1 - 60 min.

The separated surface fraction containing solid matter was passed into a combustion boiler disposed in conjunction with a flash pyrolysis apparatus, where it was burned to produce energy.

Example 2

An experiment was carried out to test the separation of solid matter from a multiphase pyrolysis liquid consisting of two phases.

Substantially the entire separate surface phase was separated from the surface of the pyrolysis liquid after a period during which phase separation had occurred in the pyrolysis liquid. The period was 1 h - 5 days .

From the separated surface phase, solid matter was substantially removed using a filter. The solid matter was taken into a combustion boiler and the rest of the surface phase was recovered for later utilization, e.g. in the production of a chemical. Alternatively, the surface phase can be utilized or burned as such without removal of solid matter.

Example 3

An experiment was carried out to test the separation of solid matter and a surface phase from a pyrolysis liquid when the separation occurs in two stages.

First, a surface fraction containing solid matter was separated from the surface of the pyrolysis liquid after a short delay, 1 - 60 min. After this, phase separation was allowed to take place in the pyrolysis liquid, about 1 h - 5 days. After the phase separation, the entire surface phase was separated from the pyrolysis liquid. The surface phase contained only small amounts of solid matter.

Example 4

The separation of solid matter was performed in a separating device at a low temperature, below 50 °C. The surface phase was in a solid state while the oil at the bottom, i.e. the pyrolysis product, was in a fluid state. The oil was removed from the separating device via a drain valve.

Example 5

An experiment was carried out to test the separation of solid matter from a single-phase pyrolysis liquid produced from pinewood sawdust and to establish a suitable delay in connection with the separation.

From the surface of the pyrolysis liquid, a surface fraction constituting 10 vol-% of the pyrolysis liquid was separated.

Fig. 2 shows the quantity of solid matter in the surface fraction and in the oil at the bottom, i.e. in the pyrolysis oil product, as a function of the delay in the separation of solid matter. Fig. 3 illustrates the distribution of the total amount of solid matter in the pyrolysis liquid between the surface fraction and the bottom oil as a function of the delay. From Fig. 2 - 3, it can be seen that an advantageous delay for the separation of solid matter from a single-phase pyrolysis liquid is in the range of 10 min - 60 min, when the criterion is minimization of solid matter content in the bottom oil. Fig. 3 further shows that, within the range of advantageous delay, 70 - 95 w-% of the total amount of solid matter originally contained in the pyrolysis liquid can be removed.

Example 6

An experiment was carried out to test the separation of solid matter from a multiphase pyrolysis liquid produced from forest waste chips and to establish a suitable delay in connection with the separation. A separate surface phase was separated from the pyrolysis liquid.

Fig. 4 shows the amount of solid matter in the surface phase and in the bottom oil, i.e. in the pyrolysis oil product, as a function of the delay in the separation of solid matter. Fig. 5 shows the distribution of the total amount of solid matter in the pyrolysis liquid between the surface phase and the bottom oil as a function of the delay.

From Fig. 4 - 5, it can be seen that an ad- vantageous delay for the separation of a surface phase containing solid matter from a multiphase pyrolysis liquid is in the range of 30 min - 6000 min when the criterion is minimization of solid matter content in the bottom oil. Fig. 5 further shows that, within the range of advantageous delay, 70 - 90 w-% of the total amount of solid matter originally contained in the pyrolysis liquid can be removed.

It was established in the experiment that separating a surface phase containing solid matter at room temperature requires a longer time than the separation of a mere surface fraction containing solid matter. Example 7

An experiment was carried out to test the separation of solid matter from a pyrolysis liquid produced from peat .

A pyrolysis liquid produced from peat is a multiphase liquid, so the entire separate surface phase was separated. From the separated surface phase, solid matter was further separated, whereupon the surface phase was fit to be used e.g. for the production of a lubricant, because the surface phase of a pyrolysis liquid produced from peat has a lower resin content than the surface phase of a pyrolysis liquid pro- duced from e.g. forest waste.

The method and apparatus of the invention in its various embodiments are applicable for the separation of any kind of solid matter from any kind of py- rolysis liquid.

The embodiments of the invention are not restricted to the examples described above; instead, they may be varied within the scope of the following claims .

Claims

1. Method for separating solid matter from a pyrolysis liquid produced from solid raw material via flash pyrolysis by condensing the pyrolysis steam ob- tained into a pyrolysis liquid, characteri zed in that, from the pyrolysis liquid obtained from the pyrolysis process, most of the solid matter contained in it is separated in a separating device after a suitable delay, by separating from the surface of the pyrolysis liquid a desired surface fraction having a high solid matter content.

2. Method as defined in claim 1, characterized in that the surface fraction is separated from the pyrolysis liquid after condensation in a con- denser in which the gas and liquid phases intermingle effectively.

3. Method as defined in claim 1 or 2, characterized in that the separated surface fraction constitutes 1 - 30 vol-%, preferably 1 - 20 vol-%, of the pyrolysis liquid.

4. Method as defined in any one claims 1 - 3 , characterized in that the surface fraction is a separate surface phase.

5. Method as defined in any one claims 1 - 4, characterized in that a suitable delay is 1 -

720 min, preferably 1 - 60 min.

6. Method as defined in any one claims 1 - 5, characterized in that the surface fraction is separated after a delay period during which phase separation has substantially taken place in the pyrolysis liquid, preferably within 1 h - 5 days.

7. Method as defined in any one claims 1 - 6, characterized in that solid matter is substantially removed from the surface fraction sepa- rated.

8 . Method as defined in any one claims 1 - 7 , c h a r a c t e r i z e d in that at least part of the surface fraction separated is passed into an energy production stage in the pyrolysis process.

9. Apparatus for separating solid matter from a pyrolysis liquid produced in a flash pyrolysis appa- ratus comprising a pyrolyzer (1) for producing pyrolysis steam and a condenser (2) for condensing the pyrolysis steam into a pyrolysis liquid, c h a r a c - terized in that the apparatus comprises at least one separating device (3) for separating solid matter from the pyrolysis liquid obtained from the pyrolysis process by separating a desired surface fraction (6) having a high solid matter content from the surface of the pyrolysis liquid, and at least one control device

(9) for setting a suitable delay and/or controlling the separation of the desired surface fraction, and the apparatus is disposed substantially in conjunction with the flash pyrolysis apparatus.

10. Apparatus as defined in claim 9, characterized in that the apparatus is disposed in conjunction with the condenser (2) , in which the gas and liquid phases intermingle effectively.

11. Apparatus as defined in claim 9, characterized in that the apparatus is disposed after the condenser (2) , in which the gas and liquid phases intermingle effectively.

12. Apparatus as defined in any one of claims 9 - 11, characterized in that the apparatus comprises at least two separating devices (3) .

13. Apparatus as defined in any one of claims 9 - 12, characterized in that the separating device (3) is a sedimentation device, a flotation device or a similar device.

14. Apparatus as defined in any one of claims 9 - 13, characterized in that the apparatus comprises a separator device (5) for the removal of solid matter from the surface fraction (6) separated.

15. Apparatus as defined in any one of claims

9 - 14, characterized in that the apparatus comprises at least one means (5,10,12) for passing the separated surface fraction (6) into an energy production stage in the pyrolysis process.