FI62554B - FARING EQUIPMENT FOR ORGANIZATION OF FAST KOLHALTIGT MATERIAL - Google Patents

Description

1 '6? 554

Method and apparatus for gasifying solid carbonaceous material - Förfarande och anordning för förgasning av fast kolhaltigt material

The present invention relates to a method and apparatus for gasifying solid carbonaceous material in a fluidized bed reactor, in which solid particles contained in the gases leaving the upper end of the reactor are separated and returned to the bottom of the reactor.

The object of the invention is to provide a method and an apparatus for gasifying a solid carbonaceous material, in which case the free oxygen of the oxygen-containing gas is used in the carburettor primarily for the oxidative gasification of the solid particle formed as a result of pyrolysis.

The main problem of gasification of solid materials is the reduction of CO 2 S and H 2 O from the oxidation stage by means of solid carbon through the kinetically slow reactions CO 2 + C (sj -> 2CO and H 2 O + e-4 CO + H 2. The earliest types of gasifiers in which the gasification material was fed from above the solid gasification material layer and the oxidant below said layer In these so-called fixed bed gasifiers, as the material travels downwards, it first pyrolyzed in a low-temperature reducing environment.

The temperature of the lower layer is -1000 ° C and the reducing carbon surface area / volume is abundant, thus providing an effective reduction of the gas phase. Known disadvantages of these types of carburetors are the tar compounds in the product gas and the transport of small particles with the product gases.

In a downstream gasifier, both the gasification material and the oxidant are introduced to the beginning of the reactor, whereby a significant portion of the pyrolysis gases are oxidized to CO2 and H2O. The remaining solid carbon must be gasified through the slow reduction reactions described above. As a result, the problems with conventional 2,62554 30 downstream carburetors are either high CCL and H 2 O concentrations in the product gas or significant carbon losses.

In the 2-reactor gasifiers, an attempt has been made to avoid the disadvantages of the above-mentioned carburetor types by dividing the gasification event into two different reactors so that the material to be gasified is first pyrolyzed. The solid material remaining from the pyrolysis is gasified in a separate reactor, the flue gases of which are introduced into the pyrolysis reactor. Thus, gasification takes place in two downstream reactors. The disadvantages of 2-reactor carburetors are flow technical problems and high investment costs.

U.S. Patent 4,154,581 discloses a two-stage gasification process that takes place in a fluidized bed reactor. Here, the fluidized bed is divided by a spacer into two parts, the lower temperature of which is considered suitable for combustion or gasification 45 and the upper temperature is adjusted in the most advantageous manner in terms of sulfur absorption. The fuel or gasifiable material is fed to the lower part of the fluidized bed with free oxygen remaining. In this case, the primarily pyrolyzable hydrocarbons are oxidized to form CO2 and H2O, resulting in 50 abundant carbon residues which must be gasified with the products of combustion of the hydrocarbons.

The present invention relates to a solution in which the operation described above in connection with 2-reactor gasifiers is carried out in one reactor as follows. The gasification material supply point 55 is suitably raised above the air nozzles (3 to 6 m) in an area where the free oxygen content is low. In this case, the pyrolysis gases generated in the vicinity of the feed point i do not oxidize, but thermally decompose into short-chain hydrocarbons, which further react with the CO 2 60 and H 2 O rising from the bottom of the reactor. These so-called the reduction reactions take place at the top of the gasification reactor, where the gas delay time (2 to 20 s) and temperature (£ 900¾) are selected so that the product gases end up close to thermodynamic equilibrium. Reduction reaction! - The energy required for 3 62554 den is obtained from 65 mainly carbon oxidation reactions at the bottom of the reactor. To avoid excessively high temperatures, the temperature differences in the reduction and oxidation zones are compensated by circulating carbon and a chemically inert material, e.g., sand, through both reactors. Since the oxidation and reduction zones are physically composed of a single reactor, recycling can be readily accomplished by selecting the particle size and amount of inert material so that a suitable proportion of the total material is in the gas flow rate range used in pneumatic conveying. In this case, the solid material separated in the gas purifier, which is returned to the bottom of the oxidation reactor, first passes through the hot oxidation zone and then cools as it passes through the reduction reactor. The mass flow of the inert circuit is controlled by adjusting the amount of circulating material so that, depending on the sintering temperature of the ash to be gasified, the highest temperature is 80 ° C in the oxidation zone and lower in the reduction zone after 70-120 ° C. '

In order to keep the temperature differences between the oxidizing and reducing zones within the above limits, the solid material must be recycled so that the reactor gas contains 85,500 to 1,000 g / mol of solids. Thus, a large mass flow of fine sand (10 μm <dp <400 μm) as well as unreacted carbon must be returned from the separator to the bottom of the reactor.

The invention will now be described with reference to the accompanying drawing, which schematically shows a device applying the method 90 according to the invention in a vertical sectional view.

In Fig. 1, reference numeral 1 denotes a fluidized bed gasification reactor, 2 cyclone separators in which solids are separated from the gases leaving the upper end of the reactor in a manner known per se and 3 solids return pipes. 95 At the lower end of the reactor there is a distribution plate 4 with openings, through which an oxygen-containing gas, e.g. air, is led to the lower part of the reactor. At the upper end of the reactor there is a degassing opening 5, through which the gases are led tangentially to the chamber 4 of the separator 2 & The material to be gasified is lifted into a feed tank 100 7, from where it is fed to the reactor by means of a screw feeder 8 To start the process, the reactor is equipped with a starter burner 10.

An axial degassing tube 11 is arranged in the vortex chamber of the separator, through which the gases from which the solid particles 105 have been separated are removed from the chamber upwards. The heat contained in the gases is used to preheat the air supplied to the reactor and the preheated gas is led to an air cabinet 12 under the distribution plate.

The solid particles settle in the funnel-shaped lower part 110 of the separator, from where they are returned to the lower part of the reactor by means of a pipe 3 through the opening 14.

The location of the feed point for the material to be gasified is chosen so that it is located above the distribution plate at a height where there is no longer a significant amount of oxygen.

115 Example:

Peat was gasified in a gasification reactor with a diameter of 600 mm, a height of 11 m from the manifold to the degassing opening and a height of 4 feed from the manifold under the following conditions:

Dry peat flow 100 g / s water flow 25 g / s air flow 210 g / s oxidation zone <

maximum temperature 990 C

post-separator ggg o temperature

The composition of the gas after the cyclone was:

Compound molar proportion of CO 0.245 CO- 0.051 9 * 5 62554

Compound molar fraction H 2 O 0.092 CH 4 0.018 H2 0.163 N2 0.412 H2S 0.0004

The molar flow of the gas is 14.2 mol / s

Circulation material flow 7.8 kg / s (sand)

Claims (3)

62554 A method for gasifying solid carbonaceous material in a fluidized bed reactor, wherein the solid particles contained in the gases leaving the upper end of the reactor are separated and returned to the lower part of the reactor, characterized in that oxygen-containing gas is introduced into the lower part substantially oxygen-free zone, and that the carbonaceous material is pyrolyzed and reduced by hot gases and particles rising from the bottom of the reactor. An apparatus for gasifying solid carbonaceous material, comprising a fluidized bed reactor (1) having an outlet (5) at the top connected to a separator (2) in which solid particles contained in the reactor effluent are separated and an inlet (14) at the bottom to return the separated particles to the reactor and a distribution plate (4) for supplying oxygen-containing gas to the reactor, characterized in that it comprises a supply device (8, 9) arranged to supply the gasifiable material to the reactor (1) in a zone above the distribution plate (4) at a significantly oxygen-free zone . Device according to Claim 2, characterized in that the feed point (9) is at least 3 m higher than the distribution plate (4), preferably 4 to 6 m.