GB2032595A

GB2032595A - Simultaneously cooling gas and granulating slag discharged from a gasification reactor

Info

Publication number: GB2032595A
Application number: GB7933118A
Authority: GB
Original assignee: Brennstoffinstitut Freiberg
Current assignee: Brennstoffinstitut Freiberg
Priority date: 1978-09-28
Filing date: 1979-09-25
Publication date: 1980-05-08
Also published as: TR20835A; DE2935991C2; DD145025A3; ATA604079A; PL117637B1; HU180685B; GB2032595B; AT369718B; AU5114479A; FR2437438A1; FR2437438B1; DE2935991A1; CS235908B1; AU527799B2; PL218607A1; GR65681B; YU40236B; YU235779A; IN152257B

Abstract

A method and apparatus for simultaneously cooling gas and granulating slag discharged from a gasification reactor, in which a liquid slag surrounded on all sides by hot crude gas is passed downwardly through a double wall or jacketed tube 2, 12 the inside surface of which is coated with a downwardly flowing film of water 5. The lower end of the tube dips into a water bath 3. The film water is supplied by water flowing upwardly through the jacket space of the tube. Cooled gas is discharged from above the water bath through an outlet 10. <IMAGE>

Description

SPECIFICATION Method and apparatus for simultaneously cooling gas and granulating slag.

This invention relates to a method and apparatus for simultaneously cooling gas and granulating slag at the discharge point of reactors in which at high pressure CO- and H2-containing bases are produced autothermally from ballast containing solid and liquid fuels suspended in gas.

In the gasification of ballast-containing solid pulverulent and liquid fuels suspended in gas it is necessary when considering the high reaction temperatures required, to convert the ballast materials (ash) into the liquid state in order to prevent sintering and thus narrowing of the flow passages or the reaction chamber. The discharge of the liquid ballast materials which contact the contours of the reaction chamber can be carried out independently of the reaction gas discharge or in common with the reaction gas. The discharging liquid ballast materials are cooled by being contacted with water and granulated. This results in a detrimental water evaporation.

In DEA 2723601 it is stated that the evaporation has a considerable cooling effect which leads to increased viscosity in the slag and thus to an increase in blockages of slag discharge openings.

These difficulties are tackled by various methods, such as for example by feeding the gas and slag in the same stream from the reaction chamber. The hot gas prevents the cold water vapour from reaching the discharge opening and the dripping slag is kept at the necessary temperature.

The further use of the gases produced makes it necessary to cool the slag as well as the gas to a suitable temperature. The cooling of the liquid slag, which takes place without a gas stream from the reaction chamber in a free stream, is suitable effected by dripping into a water bath whereby the surrounding wall of the free stream is sprinkled with water to prevent caking.

The surrounding wall is designed in the form of a tube which for shutting off the gas to the reactor is dipped into a water bath for cooling the slag, according to DEA 2723601. In this form the arrangement is not suited for granulating the slag and at the same time to discharge the gases produced.

An object of this invention is to prevent blockages in the discharge passages of reactors during the production of CO- and H2 containing gases under pressure and to prevent overheating of parts through incompletely cooled gases, and to provide a suitable method and a device which will make it possible during cooling of the CO- and H2 containing crude gas produced by the pressure gasification of ballast-rich solid or liquid fuels suspended in gas at the same time to granulate the slag thus produced. The advantageous effect of the hot gas stream on the slag discharge is thus utilised.

According to this invention there is provided a method for simultaneously cooling gas and granulating slag by contacting with water at the discharge point in reactors in which at elevated pressures CO- and H2 containing gases are produced autothermally from ballast containing solid and liquid fuels suspended in gas, in which method a compact stream of liquid slag is removed from the reactor in such a way that it is surrounded on all sides by a crude gas stream flowing in the same direction and passed through a down tube, the velocity of the gas being between 8 and 1 Om/sec, and water being passed through the annular space formed by a double pipe from the bottom to the top for evenly wetting the inner surface of the down tube and for indirectly cooling the tube, the slag and crude gas being cooled by the water bath at the- lower end of the double pipe immersed in the water bath causing the liquid slag to granulate and form a sediment, the discharging crude gas dispersing at the lower end of the down tube, rising up in the water bath and finely dispersed by the gas distributor means is subjected to a residual cooling, coilected above the water bath in the upper part of the container and discharged through a socket for cooled gas.

This two-phase stream is surrounded by a double pipe comprising an inner down pipe and an outer jacketed tube which on the inside is completeiy covered with a film of water. The double pipe dips into a water bath in which the slag stream is cooled and through which the crude gas stream must also pass at the same time.

It has been found that when the gas velocity in the down tube is too high, the compact slag stream atomises and despite the water film, caking of the slag on the rigid pipe wall cannot be avoided. On the other hand when the gas velocities are too low, the flow back of cold water vapour into the double pipe up to the discharge device of the reactor cannot be avoided, whereby at this point the slag may solidify and construct the through passage. The dimensions of the down tube are therefore adapted to those of the volume of the gas stream. According to the invention the gas velocites in the down tube range between 8 and 1.0 m/sec.

Under these conditions the cooling effect of the down tube is insufficient to adequately cool the gas and slag. For both media the residual cooling takes place after entering the water bath, whereupon on contact with water the slag solidifies and forms sediment in the water, while in an additional device the rising gas is cooled to the temperature of the water bath.

Through undetected deviations in the operation of the plant (caused by pressure changes which cause changes in the gas volume or changes in the water volume being supplied) it may happen that in the down tube locally a water film may rupture and the tube be overheated and destroyed by the hot gas stream. In such an event uncooled gas, because the immersion is omitted, would flow into the parts of the plant designed for low operating temperatures and cause damage there.

According to the invention this is avoided in that the down tube is adapted to be in the form of a double pipe through the annular chamber of which the water for spraying the wall is passed from the bottom to the top. This ensures an indirect water cooling of the down tube even though there is insifficient water for providing an uninterrupted film of water spray.

An embodiment by way of example is described in conjunction with the accompanying drawing showing an apparatus schematically in section.

A stream of crude gas mixture at a flow rate of 12000 m3/h a temperature of 1 3000C and a pressure of 25 bar flows from a pressure reactor into upper opening of the down tube 2. Parallel to the stream of crude gas a compact stream of slag in a quantity of 2000 kg/h likwise without touching the walls enters the upper opening 1.

The down tube 2 has an internal diameter of 640 mm; this results in an effective flow velocity of the gas of approximately 10 m/sec. Under these conditions the slag stream is not ruptured. The tube 2 extends approximately 1200 mm into a water bath 3. The gas stream displaces the water from the tube 2 and at the end of the tube disperses about the circumference and enters the water bath 3 where it is finely dispersed for further cooling by special distributor means for gas 4.

Parallel to the gas stream and slag stream a water film 5 sprinkles evenly over the circumference of the tube 2 and downwards and cools the tube 2, thereby preventing the caking of solid slag.

Through the water inlet 6 and the double pipe 7 a quantity of water of approximately 80000 kg/h at a temperature of approximately 1 500 is added to the water film. The water rising up in the annular chamber 11 of the double pipe 7 protects the tube from overheating if the water film should become ruptured.

After falling through the tube 2 the slag stream, only slightly cooled, enters the water bath 3 and is granulated there. The slag granules are removed from the container 9 through the socket 8.

The gas flowing through the water bath 3 is now cooled almost to the temperature of the water and collects in the gas chamber of the container 9 from where, through the socket for cooling gas 10, it is passed on for further processing. At the boiling pressure of water the gas hereby becomes saturated with steam. This water steam content of the gas may be utilised in further processes.

Claims

1. Method for simultaneously cooling gas and granulating slag by contacting with water at the discharge point in reactors in which at elevated pressures CO- and H2 containing gases are produced autothermally from ballast containing solid and liquid fuels suspended in gas, in with method a compact stream of liquid slag is removed from the reactor in such a way that it is surrounded on all sides by a crude gas stream flowing in the same direction and pased through a down tube, the velocity of the gas being between 8 and 10 m/sec, and water being passed through the annular space formed by a double pipe from the bottom to the top for evenly wetting the inner surfaces of the down tube and for indirectly cooling the tube, the slag and crude gas being cooled by the water bath at the lower end of the double pipe immersed in the water bath causing the liquid slag to granulate and form a sediment, the discharging crude gas dispersing at the lower end of the down tube, rising up in the water bath and finely dispersed by the gas distributor means is subjected to a residual cooling, collected above the water bath in the upper part of the container and discharged through a socket for cooled gas.

2. Apparatus for carrying out the method according to Claim 1, comprising a double walled pipe for receiving a cohesive stream of liquid slag contained within a crude gas stream and arranged in the centre of a vessel, the pipe comprising a down tube and jacket with the inner surface of the down tube wetted with a film of water, the annular space formed between the jacket and the down tube being connected to a water inlet with the double pipe dipping into a water bath within the vessel and a discharge socket for the cooled gas being arranged above the water bath.

3. A method substantially as herein described and exemplified.

4. An apparatus for the purposes herein described and substantially as described and shown in the accompanying drawing.