GB2033563A

GB2033563A - Removing slag from a gasifier

Info

Publication number: GB2033563A
Application number: GB7933488A
Authority: GB
Original assignee: Brennstoffinstitut Freiberg
Current assignee: Brennstoffinstitut Freiberg
Priority date: 1978-09-28
Filing date: 1979-09-27
Publication date: 1980-05-21
Also published as: FR2437436A1; CS220582B1; ATA604279A; AU5114279A; DE2935752C2; HU181855B; YU235679A; AT376694B; DE2935752A1; FR2437436B1; GB2033563B; YU40235B; DD150313A3; AU529627B2

Abstract

Apparatus for gasification of fuels containing ash with a gasification medium containing oxygen is carried out in a reaction chamber 2 provided with water cooling coils 4. Molten slag accumulating in the bottom 7 of the chamber flows, over a weir defined by an annular cast iron insert assembly 9, into a cooling and granulating part 3 which contains water and which includes a water spray nozzle 13 acting on the falling slag. The annular assembly 9 includes a steel tube coil through which water flows to effect cooling of the gas and slag passing therethrough. <IMAGE>

Description

SPECIFICATION Apparatus for gasifying fuels containing ash This invention relates to an apparatus for gasifying fuels containing ash with a gasification medium containing free oxygen in fly dust and at temperatures above the melting point of the ash, preferably under elevated pressure.

In the technique of gas production, the gasification of coal in the form of dust with a mixture of oxygen and water vapour or carbon dioxide as a flame reaction in a fly dust has been used. With this technology, the gasification takes place at such - temperatures that the mineral components of the coal occur as molten slag. The same technology in principle is used for the gasification of liquid fuels rich in ash (tars, oil residues) and mixtures of suspensions of liquid and solid fuels containing ash.

Particularly when the gasification takes place at an elevated pressure the problem arises of constructing the reactor, serving for the gasification, so that the flow of slag can be controlled and the slag can be reliably removed from the system. Technical solutions are known wherein the molten slag is granulated and cooled in water inside the rector and removed from the pressure system as a granulate suspended in water. For the operational efficiency of such reactors, the combining of the molten slag outlet from the hot part of the reactor and the reaction chamber into the cooling and granulating part is necessary.

In DD Patent 119 266, a reactor for the gasification of coal dust under pressure is described with the reaction chamber comprising a tubular wall construction acted upon by water and protected by a layer of refractory tamping clay. For the molten slag to run out into the granulating part, a central aperture is provided in the bottom of the reaction chamber, the contours of which are formed by the correspondingly shaped tubular wall construction with a covering of clay. The bottom of the reaction chamber is slightly inclined in the direction of the slag outflow opening. The opening is provided with a sharp edge for the slag to drip off.

A similar solution in principle is known for a gasification plant operating at a little above atmospheric pressure, where the upper edge of the central slag outlet is raised like a dam so that the slag is guided towards the bottom of the reaction chamber and flows over the dam (Ullmann's Encyclopadie der technischen Chemie, 3rd edition, Vol. 10, page 416 1958). It is further known to transfer molten slag and hot gas through a bottom opening with a drip edge jointly into a cooling compartment, (Meunier, Vergasung fester Brennstoffe... Weinheim/Bergstrasse, 1962, page 453).

DE-OS 2 325 204 describes a reactor for the gasification of coal dust under pressure, wherein the hot gas and molten slag are removed jointly downwards through a central aperture in the bottom of the reaction chamber, a bed of slag being maintained at the bottom of the reaction chamber by a dam round the central aperture.

The stressing of the slag outflow opening by the action of the molten slag and the high temperatures in the reaction chamber is considerable. It is further increased if hot reaction gas is removed simul taneously from the reaction chamber through this slag outflow aperture. With a construction of ceramic material, infiltration of the molten slag into the material or loosening of the ceramic material or of part of the structural components of the ceramic material in the siag is inevitable. With a tubular construction with a covering of tamping clay, the clay is often removed locally for the same reasons and because of local differences in the heat removal from the layer of tamping clay into the cooling tubes.

Breaking away of the protective layer and local overheating of the tubular walls occurs. As a result the slag outflow opening becomes a wearing part which limits the life of the whole unit.

This invention seeks to provide an apparatus for the gasification of fuels containing ash, particularly coal dust with a gasificaton medium containing free oxygen as a flame reaction in fly dust, wherein high operational reliability and a long life are provided despite the occurrence of molten slag in the reaction chamber.

An object of the invention is the formation of a rector for the gasification of fuels containing ash, particularly coal dust with a gasification medium containing free oxygen as a flame reaction in a cloud of fly dust, consisting of a reaction chamber for the gasification reactions to take place at temperatures above the melting point of the ash and a cooling and granulating part below, wherein the reliable transfer of the molten slag formed in the reaction chamber possibily jointly with hot gas formed in the reaction chamber to a cooling and granulating part is assured and which is suitable for operation under elevated pressure.

According to this invention there is provided an apparatus for the gasification of fuels contaning ash with a gasifiction medium containing free oxygen as a flame reaction in fly dust at temperatures above the melting point of the ash, the molten slag preferably together with hot crude gas produced being transferred from a reaction chamber to a cooling and granulating part, wherein a slag outflow opening in the bottom of the reaction chamber consists of an annular cast-iron member in which a steel tube is cast and which is adapted to the shape of the cast-iron member, the tube being provided with a water feed pipe and a water discharge pipe.

The metal to metal contact between the turns of steel tube and the cast iron and the satisfactory heat conductivity of the cast iron guarantee an Intensive cooling of the slag outflow opening thus formed, a dense coating of the cast-iron member with a thin solidified layer of slag and the permanent retention of the outer contours of the slag outflow opening.

According to one embodiment of the invention, the upper edge of the annular cast-iron member projects in the manner of a dam above the surrounding bottom of the reaction chamber. With this embodiment, the molten slag at the bottom of the reaction chamber is dammed up so as to increase the staying time in the hot reaction chamber and to homogenize the composition and flow characteris tics of the slag.

The upper edge of the cast-iron member projecting like a dam above the surrouding bottom of the reaction chamber may extend horizontally, but according to the invention it may also be provided with one or more depressions at which the molten slag overflows like a jet and enters the cooling zone as a compact jet.

The reaction chamber is surrounded by a miltiplicity of water-cooled screens, of studded tubes coated with refractory tamping clay. In such a case, the construction according to the invention is characterised in that the supply and the offtake for the cooling water for cooling the annular cast-iron member is connected to the cooling water supply system of the cooling tube screen for the reaction chamber so that there is a uniform cooling system for cooling tube screen and slag outflow opening.

A mode of operation of reactors for the gasificaton of coal dust in fly dust is characterised in that the crude gas produced and the slag are cooled jointly by spraying in water and in the course of this the crude gas is saturated with water vapour. The content of water vapour is needed for the following gas conversion stages, particularly for the catalytic CO converting. A form of embodiment of the invention suiting this mode of operation is characterised in that the cooling water offtake of the slag outflow opening is connected to the water distributing device for the direct cooling and saturation of the crude gas. In this manner, the effect is achieved that the heat content of the water heated during the cooling of the slag outflow opening can be used to increase the saturation temperature of the crude gas and so to improve the CO converting.

The invention is described by way of example in conjunction with the accompanying drawings, wherein: Figure 1 shows diagrammatically a reactorforthe gasification of coal dust as a flame reaction in fly dust, and Figure 2 shows an enlarged detail of the slag outflow opening.

The reactorforthe gasification of coal dust under pressure consists of a reaction chamber 2 and a cooling and granulating part 3. The reaction chamber 2 is surrounded by a cooling tube screen 4 which is acted upon by water and which is coated with tamping clay 5 on the reaction chamber side.

Disposed at the head of the reaction chamber 2 is a burner 6 which serves for the supply of coal dust, oxygen and steam. At the base, the reaction chamber 2 is closed by a bottom 7 which results from an appropriate formation of the cooling tube screen.

Disposed in the centre of the bottom is the slag outflow opening 8which is formed by an annular cast-iron member 9 which in turn is held by a cooled supporting structure 12. During operation, such temperatures prevail in the reaction chamber that the ash contained in the coal dust becomes molten siag which is transferred to the cooling and granulating part 3 jointly with the crude gas formed through the slag outflow opening 8. A water distributing device 13 illustrated diagrammatically as a nozzle in Figure 1 serves for the direct cooling of crude gas and slag.

The cooling and granulating part 3 is further provided with a crude gas outlet socket 15 and a bottom opening 16. The bottom opening 16 serves for the joint removal of granulated slag and unevaporated sprayed water from the reactor, which collect in the lower half of the cooling and granulating part 3.

A Figure 2 further shows, a steel tube 17, which is connected to a water supply pipe 10 and a water discharge pipe 11, is cast into the annular cast-iron member 9 forming the slag outflow opening 9 in a plurality of turns and in the shape of the annular cast-iron member 9. The upper edge of the annular cast-iron member 9 projects above the level of the bottom 7 of the reaction chamber 2 so that the molten slag reaching the bottom 7 is there dammed up to form a flat bed of slag 18. The upper edge of the annular cast-iron member 9 is provided with a depression 19 at one side. Thus at this point the slag can flow as a compact jet 20 through the slag outflow opening 8 together with the crude gas into the cooling and granulating part 3. The water discharge pipe 11 is connected to the supply pipe 14 to the water distributing device 13. Thus the heat content of the cooling water flowing out of the annular cast-iron member 8 and heated there is used to increase the saturation temperature of the crude gas developing in the cooling and granulating part 3.

At the same time - except for the pressure drop of the flowing cooling water between entry into the annular cast-iron member 8 and water distributing device 13 - a pressure equalization is brought about between the pressure prevailing in the steel tube of the cast-iron member 9 and the pressure in the reaction chamber and the cooling and granulating part.

Claims

1. An apparatusforthe gasification of fuels containing ash with a gasification medium containing free oxygen as a flame reaction in fly dust at temperatures above the melting point of the ash, the molten slag preferably together with hot crude gas produced being transferred from a reaction chamber to a cooling and granulating part, wherein a slag outflow opening in the bottom of the reaction chamber consists of an annular cast-iron member in which a steel tube is cast and which is adapted to the shape of the cast-iron member, the tube being provided with a water feed pipe and a water discharge pipe.

2. An apparatus as claimed in Claim 1,wherein the upper edge of the annular cast-iron member projects to form a dam above the bottom of the reaction chamber.

3. An apparatus as claimed in Claim 2, wherein the upper edge of the annular cast-iron member is provided with one or more depressions.

4. An apparatus as claimed in Claims 1,2 or 3, wherein the water feed pipe and the water discharge pipe are connected to a cooling water supply to a cooling tube assembly for the reaction chamber.

5. An apparatus as claimed in Claims 1,2 or 3, wherein the water discharge pipe is connected to a water distributing device associated with the cooling and granulating part so that water heated in the annular cast-iron member and passing through the water discharge pipe can serve directly in the granulation of the slag and preferably also for the direct cooling of the crude gas.

6. An apparatus according to any preceding claim, wherein the steel tube is arranged within the cast iron member in a number of turns.

7. Apparatus substantially as herein described with reference to and as shown in the accompanying drawings.