Method for producing a pyrolysis product

Abstract

The invention relates to a method and apparatus for producing a pyrolysis product, in which raw material are fed to the pyrolysis reactor and gaseous pyrolysis product fractions and by-product fractions are formed from raw material by pyrolysis in a pyrolysis reactor. According to the invention the method comprising steps: combusting at least one by-product fraction from the pyrolysis reactor in at least two combustors, and recovering energy formed in the combustor.

Claims

1. A method for producing a pyrolysis product, in which raw material is fed to a pyrolysis reactor and gaseous pyrolysis product fractions and by-product fractions are formed from raw material by pyrolysis in the pyrolysis reactor, and the gaseous pyrolysis product fractions are condensed to liquid pyrolysis product fractions, where the method comprises the steps of: combusting at least one by-product fraction comprising solid components from the pyrolysis reactor in at least two combustors so that the by-product fraction is partially combusted in a first combustor, solid components of the by-product fraction are recirculated back to the pyrolysis reactor, and the flue gases from the first combustor are supplied to a second combustor in which the flue gases are combusted to form energy; and recovering energy formed in the second combustor.

2. The method according to claim 1, characterized in that temperature is adjusted in the first combustor so that the temperature is below 700 C.

3. The method according to claim 1, characterized in that the energy recovered in the second combustor is supplied to at least one of feed water and a steam circuit of a boiler.

Description

LIST OF FIGURES

(1) In the following section, the invention will be described with the aid of detailed exemplary embodiments, referring to the accompanying FIGURE wherein

(2) FIG. 1 presents one embodiment of the apparatus according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

(3) FIG. 1 presents the apparatus according to the invention for producing pyrolysis products, the apparatus comprising a boiler 2, i.e. a fluidized bed boiler, for producing heat energy fractions 10 and 11, a fast pyrolysis reactor, i.e. a pyrolyzer, 1 for forming gaseous pyrolysis product 3 and by-product fractions 4 and 14, a condensing device 15 for condensing the gaseous pyrolysis product 3, and separate fuel feeding devices 5 and 6 for feeding raw material to the pyrolyzer 1 and the boiler 2. In addition, the apparatus comprises a cyclone 16 for separating the first by-product fraction 4, the second by-product fraction containing solids 14 and catalyst 13 from the gaseous pyrolysis product 3 after the pyrolyzer 1.

(4) Most of the fuel, e.g. biomass, carbon, peat, lignite or oil shale, is fed by the feeding device 6 to the fluidized bed boiler 2. Furthermore, the feeding device 6 is arranged so that amounts of forest chips or bark can be fed to the boiler 2 as well. Also air 22 is fed to the fluidized bed boiler 2. The feeding device 5 is arranged to feed e.g. wood-containing material, biomass, such as peat, saw dust or straw, or organic material to the pyrolyzer 1.

(5) In the pyrolyzer 1, gaseous pyrolysis product 3 is formed from the fuel to be pyrolyzed by fast pyrolysis at a temperature of 300 to 800 C. Further, by-product fractions 4 and 14 are generated in the pyrolysis. In this device embodiment, the pyrolyzer 1 is a circulating mass fluidization reactor. Heat transfer material 11, if used in the process, may be conducted from the fluidized bed boiler 2 to the pyrolyzer 1.

(6) The apparatus comprises a cyclone 16 after the pyrolyzer 1. The first by-products 4 and pyrolysis residue/solids/carbon matter 14, e.g. sand, coke and tar, and catalyst 13 are separated from the produced gaseous pyrolysis products 3 in the cyclone 16. Separated components or a part of separated components 4, 13 and/or 14 can be circulated to a combustor 7. Alternatively the separated solids and carbon matter 14 or a part of them can be directly conducted to the boiler 2 to be burned. Further, the heat transfer material 11, if used in the process, may be separated in the cyclone 16 and conducted to the boiler 2. Alternatively, the heat transfer material 11 may be conducted from the cyclone 16 together with catalyst flow 13 to the combustor 7 and from the combustor 7 to the boiler 2 and/or pyrolyzer 1. In the boiler 2, the heat transfer material 11 can be regenerated and heated.

(7) The apparatus comprises two combustors 7, 8 in which by-product fractions 4 and 14 from the pyrolysis reactor 1 is combusted. In the first combustor 7 the by-product fractions 4 and 14 containing also solids 14 and catalyst 13 are combusted partially to form flue gases 12. The flue gases 12 from the first combustor 7 are supplied to the second combustor 8. In the second combustor 8 the flue gases 12 are combusted completely to produce heat energy.

(8) The apparatus comprises separator for separating the remaining solids and catalyst 13 from the flue gases 12 in connection with the first combustor 7. Further, the apparatus comprises means for conducting the remaining solids and separated catalyst 13 back to the pyrolysis reactor 1 and/or the boiler 2. From the boiler 2 catalyst 13 can be conducted to the pyrolysis reactor 1. Further, the apparatus comprises means for feeding air 18 to the combustors 7 and 8.

(9) The apparatus comprises an adjusting device for adjusting temperature in the first combustor 7 so that the temperature is kept below 700 C.

(10) Further, the apparatus comprises a heat exchanger 9 in connection with the second combustor 8 for recovering heat energy formed in the second combustor 8. Boiler feed water 17 or alternatively steam can be heated by means of heat energy in the heat exchanger 9.

(11) From the cyclone 16, the gaseous pyrolysis product 3 is conducted to the condensing device 15, where the hot gaseous pyrolysis product 3 is condensed and fractionated in stages to a pyrolysis product liquid 20. Non-condensible gases, chemical compounds and/or aqueous solution 19 thereof can be conducted to the fluidized bed boiler 2 or pyrolyzer 1 or combustor 7 and/or 8 or to any other suitable process or device, e.g. gas turbine.

(12) In addition, the apparatus may comprise a filter for separating finer solids from the gaseous pyrolysis product 3.

(13) The apparatus may comprise a dryer for drying the raw material to be pyrolyzed. Either the combustion gas of the boiler or the heat transfer material conducted from the boiler may be utilized as the heat delivering agent in the dryer. Any dryer known per se, e.g. a mixing dryer, may be used as the dryer so it is not described in any more detail in this context.

(14) The chemical compounds separated from different parts of the apparatus can be recovered for possible subsequent utilization. The chemical compounds are utilized by means of processes known per se which are not described in any more detail in this context.

(15) By the apparatus according to the invention, the most valuable and suitable part of the raw material can be used as the material to be pyrolyzed, and the less suitable part in terms of the pyrolysis may be fed to the boiler. The raw material may be fractionated by processes known per se.

(16) The method and apparatus according to the invention is suitable in different embodiments for producing different kinds of pyrolysis products.

(17) The invention is not limited merely to the examples referred to above; instead many variations are possible within the scope of the inventive idea defined by the claims.