Method and apparatus for gasifying raw material and gaseous product

Abstract

A method and apparatus for gasifying raw material. The method includes feeding the raw material into an upper part of a fixed-bed gasifier, introducing the raw material from the upper part of the gasifier to a pyrolysis zone of the gasifier to form the fixed-bed and pyrolyzing the raw material in the presence of pyrolysis air to form a pyrolysis product. Introducing the pyrolysis product from the pyrolysis zone to a lower part of the gasifier, introducing primary air countercurrently to the lower part, carrying out a final gasification in a lower part of the gasifier in order to form a gasified gas. Introducing the gasified gas to a catalytic oxidation part and through a catalyst layer of the catalytic oxidation part, and reforming the gasified gas by way of the catalytic oxidation in the presence of reforming air in the catalytic oxidation part, forming a gaseous product.

Claims

1. A method for gasifying raw material, wherein the raw material is fed to a gasifier, the raw material is treated in the gasifier having different zones and a gas from the gasifier is treated by way of a catalytic treatment, wherein the method comprises: providing a fixed-bed gasifier which is vertically inclined having an upper part forming a feed end, a lower part forming an output end, and a pyrolysis zone between the upper and lower parts, feeding the raw material and pyrolysis air into upper part of a fixed-bed gasifier, pressing the raw material to compact the bed; introducing the raw material and pyrolysis air from the upper part of the fixed-bed gasifier to the pyrolysis zone of the fixed-bed gasifier and pyrolyzing the raw material in the presence of the pyrolysis air in the pyrolysis zone to form pyrolysis products, agitating the fixed bed with a rotating grate, introducing the pyrolysis products from the pyrolysis zone to a lower part of the fixed-bed gasifier, beneath the pyrolysis zone, introducing primary air beneath the lower part of the fixed-bed gasifier upwardly countercurrently to the flow of pyrolysis products to carry out a final gasification in a gasifier to form a gasified gas pyrolysis product and ash, introducing reforming air into the gasified gas pyrolysis product before the catalytic oxidation zone, introducing the gasified gas pyrolysis product and reforming air into a catalytic oxidation zone and passing the gasified gas pyrolysis product and reforming air through a catalyst layer in the catalytic oxidation zone, and reforming the gasified gas pyrolysis product by way of catalytic oxidation in the presence of the reforming air in the catalytic oxidation zone, in order to form a final gaseous product.

2. The method according to claim 1, wherein the reforming air is introduced just before the catalytic oxidation zone.

3. The method according to, claim 1, wherein the raw material is selected from the group consisting of wood containing material, biomass based material, organic material and their combinations.

4. The method according to claim 1, wherein temperature of the catalyst layer is between 600 to 900 C.

5. The method according to claim 1, wherein temperature of the gasified gas pyrolysis product is between 400 to 600 C. before the catalytic oxidation part.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) FIGS. 1 presents the apparatuses according to the invention for gasifying raw material.

EXAMPLE 1

(2) The apparatus of FIG. 1 comprises a fixed-bed gasifier (1) which comprises an upper part (2), pyrolysis zone (3) in a middle part of the gasifier and lower part (4). Further, the apparatus comprises a catalytic oxidation part (5). The catalytic oxidation part (5) is arranged to surround the pyrolysis zone (3). Further, the apparatus comprises a feeding device (6) for feeding the raw material into the upper part (2) of the fixed-bed gasifier from which the raw material is introduced to the pyrolysis zone (3) to form the fixed-bed in the pyrolysis zone. The fixed-bed is arranged in the pyrolysis zone in which the raw material is pyrolyzed in the presence of pyrolysis air (7) for forming a pyrolysis product. The pyrolysis product is introduced to the lower part (4). Further, the apparatus comprises a first air feeding equipment for introducing the pyrolysis air (7) to the pyrolysis zone (3), a second air feeding equipment for introducing primary air (8) to the lower part (4) countercurrently, and gas introducing equipment for introducing a gasified gas (9) formed by a final gasification in the lower part (4) to the catalytic oxidation part (5). Further, the apparatus comprises a third air feeding equipment for introducing reforming air (10) for the catalytic oxidation just before the catalytic oxidation part (5), and a catalyst layer (11) in the catalytic oxidation part (5) through which the gasified gas (9) is led and in which the gasified gas is reformed by means of the catalytic oxidation and in the presence of reforming air (10) in order to form a gaseous product (12) with low-tar content.

(3) Further, the apparatus comprises a bed tightening device (13) which is piston type device for pressing and tightening the bed. A bottom ash (14) can be removed from the apparatus from the bottom of the apparatus.

(4) The devices used in this invention are known per se, and therefore they are not described in any more detail in this context.

EXAMPLE 2

(5) In this test, the catalytic oxidation and its efficiency were studied in laboratory scale. The wood gasification gas was introduced to the catalytic oxidation device in which the gasification gas was treated according to the invention. Compositions of the gasified gas before the catalytic oxidation and the gaseous product after the catalytic oxidation are represented in table 1.

(6) TABLE-US-00001 TABLE 1 Gaseous product Gasified gas prior after catalytic catalytic oxidation oxidation Gas components CO, vol-% 19.3 12.3 CO.sub.2, vol-% 7.8 13.6 H.sub.2, vol-% 8 13.7 CH.sub.4, vol-% 2.8 2.4 C.sub.2-C.sub.5, vol-% 2.5 1.5 H.sub.2O, vol-% 23.7 17 N.sub.2, vol-% 35.9 39.5 Higher hydrocarbon content, mg/m.sup.3n (dry gas) benzene 4690 2020 tars < naphthalene 2910 20 naphthalene 1080 50 tars > naphthalene 1065 <10

(7) It was observed that residue tars can be oxidated and decomposed during the catalytic oxidation.

(8) The method and apparatus according to the invention are suitable in different embodiments for gasifying different kinds of raw material. The method and apparatus according to the invention are suitable in different embodiments for forming different kinds of low-tar products.

(9) 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.