GB2086257A

GB2086257A - Fluidised gasification reactor

Info

Publication number: GB2086257A
Application number: GB8131615A
Authority: GB
Original assignee: Mannesmann AG
Current assignee: Vodafone GmbH
Priority date: 1980-11-03
Filing date: 1981-10-20
Publication date: 1982-05-12
Also published as: CS224630B2; FR2493334A1; PL130056B1; PL233662A1; AU546742B2; GB2086257B; AU7692181A; FR2493334B1; ZA817444B; DE3042142C2; DE3042142A1; JPS57105487A

Abstract

A fluidized bed reactor for the gasification of coal dust with super- heated water under pressure comprises a reactor vessel (1) having an inlet for water vapour (3) in its base, an inlet (5) and an outlet (6) for maintaining a bed of coal dust, an outlet (11) for product gas, a heating tube coil (10) extending into the bed, and at least one wall (13) located in the bed (14) to impede direct flow of material from the inlet (5) to the outlet (6); the material is thus forced to follow a tortuous route, e.g. as shown by the arrows (15). The wall may be spiral in form. <IMAGE>

Description

SPECIFICATION Fluidized bed gasification reactor The invention relates to a fluidized bed reactor for the production of gas from coal dust and water vapour under pressure. More particularly, it relates to such a reactor in which a fluidized bed is maintained within a reactor vessel, and heated by a heating coil while being supplied with water vapour.

Gasification of coal takes place at increased temperatures and the requisite heat can be provided either by the partial combustion of the coal feedstock (autothermal process) or by the addition of heat from an external source (allothermal process). In allothermal gasification the coal used can be utilized entirely for the conversion into gas, whereas in the autothermal processes a not inconsiderable portion of it must be burned to generate heat, and consequently is no longer available for the production of gas.

Allothermal gasification thus has the advantage that the requisite heat can be extracted from any external sources, such as high-temperature nuclear reactors as discussed in Err61 and Kohle Erdgas-Petrochemie vereinigt mit Brennstoff Chemie (Petroleum and Coal-Natural Gas Petrochemistry combined with Fuel Chemistry) (32 (1 979) Pages 17 to 23). To carry out the process effectively the supply of heat must cause the coal to heat up and cover the reaction heat requirement at temperatures preferably in excess of 8000C. Further, it must be practicable for large throughputs of coal. This is not possible in known proposais, according to which, for example, solid substances are added to the coal as heat carriers, or the reactor vessel is heated from the outside.

For this reason it has been proposed to use nuclear energy for the generation of gas, in which the heat is drawn out of the nuclear reactor by a gas as heat carrier and is supplied to the coal through a pipe system immersing into the fluidized bed in the reactor vessel, again as discussed in Erdöl und Kohle-Erdgas-Petrochemie vereinigt mit Brennstoff-Chemie (1973, Page 701 to 703).

For autothermal coal gasification it is known to use vertical fluidized bed reactors, generally of circular cross-section. These reactors are not also readily suitable for aliothermal gasification, which generally operates at lower temperatures and requires a longer dwell time for the coal in the reaction chamber. The maximum reaction temperature arises through the temperature stability of the materials for the heat exchange elements. As noted above though, on longer dwell times for the coal a mixture of fresh coal with particles of ash would take place, and a not inconsiderable proportion of unconverted or not completely converted coal would be discharged with the ash.

The present invention seeks to design a vertical fluidized bed generator, which in itself is known, in which coal dust can be gasified while minimizing admixture between fresh or unreacted coal and ash (so-called "Backmixing") and hence reducing coal wastage. To this end, the invention provides a fluidized bed reactor for the gasification of coal dust with superheated water vapour under pressure, comprising a reactor vessel having an inlet for water vapour to the base thereof, inlet and outlet connections for maintaining a bed of material comprising coal dust within the vessel; a heating tube coil for extending into a said bed within the tank; at least one wall for impeding the direct flow of a said material between the inlet and outlet connections through said bed; and a gas discharge connection for the discharge of product gas generated in said bed.

A plurality of walls may be used to define one or more tortuous paths for the reacting material to follow. Typically these walls are planar, and at least some of the walls will normally extend directly from the walls of the vessel. Curved walls can also be used and in one embodiment, the or at least one of the walls forms a spiral in plan view, forcing the material to circulate in the vessel before discharging after gasification on the axis of the spiral. Particularly in this latter embodiment, a plurality of inlet connectors are preferably included to replenish the bed material.

The depth of the bed in the vessel will be Xprmally controlled, and the height of the wall or walls is preferably such as to extend above the surface of the bed to avoid overflow of unreacted fuel. Thus, all the bed material is forced to follow the path or paths defined by the wall or walls.

Embodiments of the invention will now be described by way of example and with reference to the accompanying drawings wherein: Figure 1 shows a longitudinal cross-section through a first reactor according to the invention; Figure 2 shows a vertical cross-section, through the reactor of Figure 1; Figure 3 shows a vertical cross-section similar to that of Figure 2 but showing an alternative wall arrangement; Figure 4 shows a vertical cross-section through a third embodiment of the invention; and Figure 5 shows a longitudinal cross-section through the reactor of Figure 4.

As shown in Figures 1 and 2, the pressure vessel 1 has in its lower base 2 a connection 3 for the supply of superheated water vapour, and in the vertical wall 4 is the connection 5 for the introduction of the coal dust and, diametrically opposite, the connections 6 for the discharge of the gasification residues. At the upper end 7 of the pressure vessel 1 the connections 8 and 9 are arranged for the admission or discharge of the heating medium, which are connected to the heating tube coils 10. The discharge connection 11 for the discharge of product gas is located at the top of the vessel, and communicates with an upper gas collecting chamber 1 2 over the fluidized bed 14.Vertical flow-guiding walls 1 3 are incorporated in the interior of the pressure tank to subdivide the fluidized bed 14 and extend into the gas collecting chamber 12. Their surfaces are arranged at right angles to the inlet 5 and the outlet 6, so that the horizontal flow of the fluidized bed 14 is turned around and runs as indicated by arrows 1 5 (Figure 2). As shown, the heating coils 10 extend around and between the walls 13.

As shown in Figure 2, there is only one flow path for the material in the bed 14. An alternative arrangement is shown in Figure 3 where the path divides and converges alternately.

In the embodiment of Figures 4 and 5, the flowguiding walls of the earlier embodiments are replaced by a single shaped element in the form of a spiral 16, for example of heat resistant tin sheeting or a fireproof material. Several connections 5 for the introduction of the coal dust are disposed at intervals around the vertical container wall 4. The outlet 6 for the gasification residues is in this case expediently situated in the centre of the lower base 2. The flow of the fluidized bed 14 is indicated by arrows 1 7. This embodiment is of particular advantage if apparatus is to be used which blasts in the coal.

These only have a limited capacity per unit and are to be arranged at certain minimum intervals, in order to prevent caking of the insufflated particles.

It will be appreciated that a plurality of spiral walls may be included in a single reactor vessel if desired.

The heat transmission elements 10 for the supply of the process heat can be passed from above or from below into the channels 18, formed by the flow-guiding walls, in all embodiments shown.

Claims

1. A fluidized bed reactor for the gasification of coal dust with superheated water vapour under pressure, comprising a reactor vessel having an inlet for water vapour to the base thereof, inlet and outlet connections for maintaining a bed of material comprising coal dust within the vessel; a heating tube coil for extending into a said bed within the tank; at least one wall for impeding the direct flow of a said material between the inlet and outlet connections through said bed; and a gas discharge connection for the discharge of product gas generated in said bed.

2. A reactor according to Claim 1 including a plurality of said walls spaced from one another to define one or more tortuous paths for a said material passing through the reactor.

3. A reactor according to Claim 2 wherein at least some of the walls extend from the wall of the vessel.

4. A reactor according to Claim 2 or Claim 3 wherein the walls are planar and disposed perpendicular to a straight line between the inlet and outlet connections.

5. A reactor according to any preceding Claim wherein the inlet and outlet connections are located diametrically opposite each other in the wall of the vessel.

6. A reactor according to any of Claims 1 to 3 wherein at least one outlet connection is located at the base of the vessel.

7. A reactor according to Claim 6 having a plurality of inlet connections for a said material disposed around the wall of the vessel.

8. A reactor according to Claim 6 or Claim 7 wherein said at least one wall comprises a substantially spiral wall extending around a substantially vertical axis in the vessel.

9. A reactor according to Claim 8 including a single substantially spiral wall extending around a central vertical axis of the vessel, and wherein a single outlet connection is located on said axis.

10. A reactor according to any preceding Claim wherein the connections for a said material are controllable to maintain a said bed at a predetermined level in the vessel, and wherein said at least one wall extends above said predetermined level.

.11. A fluidized bed reactor substantially as described herein with reference to Figures 1 and 2; Figure 3; or Figures 4 and 5 of the accompanying drawings.