Cooling and scrubbing of a crude gas from entrained flow gasification

Abstract

An apparatus for a three-stage cooling and scrubbing system for the treatment of hot crude gases and liquid slag downstream of an entrained flow gasification. Crude gas and slag are firstly cooled and prescrubbed in a first stage by injection of water from ring and/or wall nozzles into a free quench space. Crude gas and slag are then fed together with excess water into a waterbath as a second stage before intensive spraying is once again carried out as a third cooling and scrubbing stage in an annular space.

Claims

1. An apparatus for treating hot crude gases and liquid slag having temperatures of 1200-1800 C. and pressures of up to 10 MPa in an entrained flow gasification of fuel dust, the apparatus comprising a gasification reactor, a quencher, a crude gas and slug outlet, a crude gas outlet, a funnel, first nozzles, and second nozzles, wherein the quencher is arranged downstream of the gasification reactor, and the quencher and the gasification reactor are surrounded by a pressure wall; the crude gas and slag outlet connects the gasification reactor to the quencher; the quencher has an inner wall spaced inward of the pressure wall; a waterbath is located in a lower part of the quencher; a free space quench is located in the quencher in flow succession after the crude gas and slag outlet, the free space quench having the first nozzles located and configured for injecting cooling and scrubbing water into the free space quench; the funnel is located in the quencher inside the inner wall and downstream of the free-space quench; the funnel has an upper end in contact with the inner wall of the quencher and has an open lower end dipping into the waterbath; an annular space is formed between the funnel, a surface of the waterbath, and the inner wall of the quencher; the crude gas outlet is connected to the annular space for the flow of crude gas that has passed downward through the funnel, downward through the waterbath, upward through the waterbath, and upward through the annular space, the flow of crude gas flowing through the crude gas outlet outside of the pressure wall; the second nozzles are configured and located above the surface of the waterbath for injecting cooling and scrubbing water, the second nozzles being arranged inside the annular space; and the inner wall bounds the free space quench in the radial direction with respect to the central longitudinal axis of the quencher.

2. The apparatus as claimed in claim 1, further comprising a water wall is located between the pressure wall and the inner wall and below the funnel upper end where it is in contact with the inner wall.

3. The apparatus as claimed in claim 1, wherein the first nozzles are arranged on the inner wall of the quencher and have outlets inward of the inner wall.

4. The apparatus as claimed in claim 3, wherein the first nozzles are supported directly on the pressure wall.

5. The apparatus as claimed in claim 1, further comprising third nozzles located and configured for injecting cooling and scrubbing water in the free space quench and wherein the third nozzles tightly surround the crude gas and slag outlet.

6. The apparatus as claimed in claim 5, wherein the third nozzles are arranged in a nozzle ring arranged directly at the crude gas and slag outlet in the free-space quench.

7. The apparatus as claimed in claim 1, further comprising an inner tube having a lower end that dips into the waterbath and wherein the inner tube is arranged below the second nozzles.

8. The apparatus as claimed in claim 1, further comprising a cooling shield delimiting the gasification reactor of the apparatus.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 a cooling and scrubbing system according to the invention, with the figure being depicted as a section through a rotationally symmetric system, and

(2) FIG. 2 a cooling and scrubbing system having an additional guide device 17 for the bubble column stage 2.

DESCRIPTION OF EMBODIMENTS

(3) In the Figures, identical reference numerals denote identical elements.

(4) In a gasification reactor 1 as per FIG. 1, in a reaction space delimited by a cooling shield 12, 68 t/h of coal dust are converted, at a net power output of 500 MW, with addition of an oxygen-containing gasification agent and of steam, into crude gas and liquid slag by autothermal partial oxidation at an operating pressure of 4.2 MPa. The amount of moist crude gas produced of 145 000 m.sup.3 (STP)/h and the 4.7 Mg/h of liquid slag 11 formed from the fuel ash flow together at temperatures of 1400-1800 C. through the gas and slag outlet 16 into the first stage configured as free-space quencher 2 of the cooling and scrubbing system. Cooling and scrubbing water is injected into the crude gas and slag stream 11 directly downstream of the gas and slag outlet 16 via a nozzle ring 13 in order to cool the crude gas to the saturation temperature determined by the pressure and ensure wetting of the subsequent components. In addition to the nozzle ring 13, further cooling and scrubbing water can be introduced through nozzles 15 passed through the pressure wall 3. The inlets 13 and 15 can be operated either alone or together. Precooled crude gas, slag and excess water are conveyed through the funnel 9 into the waterbath 7 in which the slag settles out and is removed in a downward direction via the outlet 8. The funnel 9 dips into the waterbath 7, and guides the crude gas into the waterbath 7 so as to form an ascending gas-scrubbing water suspension, in a manner similar to a bubble column having a good scrubbing effect as second scrubbing stage of the cooling and scrubbing process. After leaving the waterbath 7, the crude gas is treated further with scrubbing water in a superposed free space via a nozzle ring 5 as third scrubbing stage in order to remove further dust particles from the crude gas. The cooled and scrubbed crude gas leaves the three-stage cooling and scrubbing system via the gas outlet 6 at a pressure of 4.1 MPa and a temperature of 225 C. and is passed for further treatment. To protect the pressure wall 3, a water wall 10 which is supplied with pure water via the inlet 14 is formed on the inner wall 4 and at the upper end 18 of the inner wall 4 flows over into the free-space quencher 2.

(5) In a particular embodiment in FIG. 2, the bubble column in the water bath 7 can be configured by means of an inner ring 17 in such a way that the crude gas has to complete another change in direction before the nozzle ring 5.

(6) The apparatus of the invention also makes it possible to perform a process in which the crude gas which has a temperature of 1200-1800 C. and is under a pressure of up to 10 MPa is conveyed together with the liquid slag from a gasification reactor 1 delimited by a cooling shield 12 via a crude gas and slag outlet 16 into a three-stage cooling and scrubbing apparatus, cooling and scrubbing water are injected into a free-space quench 2 as a first cooling and scrubbing stage, the precooled crude gas and the slag from the free-space quench 2 are conveyed via a funnel 9 into a waterbath as a second cooling and scrubbing stage in which the ascending crude gas forms a gas-water suspension with the waterbath 7 in a manner similar to a bubble column, after leaving the bubble column, the crude gas is subjected in a superposed free space as a third cooling and scrubbing stage to another intensive free-space scrub by means of a nozzle ring 5 and the temperature of water vapor saturation determined by the process pressure is attained and the cooled and scrubbed crude gas is passed via the gas outlet 6 to further treatment stages in order to produce a pure gas.

(7) In an apparatus in which an inner wall 4 is arranged in the quencher, the annular gap 10 between the pressure wall 3 and the inner wall 4 is, in an inventive embodiment of the invention, continuously flushed with water.

(8) In an apparatus in which an inner wall 4 is arranged in the quencher and in which the annular gap 10 between the pressure wall 3 and the inner wall 4 is continuously flushed with water, the water leaving the annular gap 4 as a water wall runs down as a water film on the inside of the inner wall 4.

(9) In an apparatus in which an inner ring 17 is arranged in the free space, the bubble column in the waterbath 7 is, in an inventive embodiment of the process, kept away from the inner wall 4 by the inner ring 17, with the crude gas experiencing another change in direction at the upper end of the inner ring 17.

LIST OF REFERENCE NUMERALS

(10) 1 Gasification reactor 2 Free-space quench 3 Pressure wall 4 Inner wall 5 Nozzle ring 6 Gas outlet 7 Waterbath 8 Slag outlet 9 Funnel 10 Annular gap as water wall 11 Crude gas, slag 12 Cooling shield 13 Nozzle ring 14 Pure water inlet 15 Nozzles on pressure wall 16 Gas and slag outlet 17 Inner ring, inner tube, guide device, 18 Upper end of the inner wall