EP0358923B1 - Process and apparatus for purifying a raw gas originating from the gasification of solids - Google Patents

Abstract

In a process and apparatus for purifying raw gas from solids gasification, containing granular and dusty solids particles, a solution is to be found, by means of which solids particles of any size are largely removed from the raw gas before entry to downstream cooling devices. This is achieved when the raw gas is passed in a first purification stage from the gasification zone in a straight line in the direction of a gas-holding space, whereby the granular solids particles are precipitated at the bottom of the gas-holding space and then, in a second purification stage, the partially purified raw gas is laterally deflected from the gas-holding space and undergoes a change to a velocity reduced by a factor of at least 3 and, after a further gas deflection, is passed substantially in the vertical direction through a solids filter, where the dusty solids particles are removed from the raw gas. <IMAGE>

Description

The invention relates to a method and a device for cleaning raw gas from a solid gasification with contents of granular and dusty solid particles. Solid gasification means in particular the gasification of hard coal or lignite. The coal can be used both as coal dust and as a slurry together with the oxidizing agent, e.g. Air or oxygen-enriched air are fed into the gasification reactor. The hot crude gas obtained can either be passed through the applied coal layer or can be freely discharged in the opposite direction from the gasification reactor. The invention does not relate to the purification of raw gas which is discharged through the abandoned coal layer, but only from that which is discharged freely.

It is advantageous to solidify the liquid slag portions only by known measures in the latter gas conduction, since solid slag parts can be removed from the gas stream more easily.

Raw gas from solid gasification described above is not free of solids, but must be subjected to a separation of the solid parts before further processing. It is necessary to remove the solids before any further treatment of the raw gas, e.g. Cooling, to separate from this. So far, this demand could not be met or only in an inadequate form.

According to DE-PS 32 23 702 a process for the production of synthesis gas is known in which coal dust in a reactor and oxidizing gas are introduced. The coarse ash is collected and drawn off in the lower part of the reactor, while synthesis gas together with the fly ash in the form of dust is fed via a line into a heat exchanger which is also a fly ash separator. Because of the widely differing gas velocities and the long gas path to a cyclone after the heat exchanger, undesirable dust deposits are inevitable, essentially in the heat exchanger. This severely limits the efficiency of the heat exchanger or requires periodic cleaning at short intervals.

According to EP-PS 0 077 851, a gas cooler arrangement for cooling the reaction products of a coal gasification reactor is known. The new gas cooler arrangement is intended to separate small ash particles on the pipes of the convective gas cooler. This is achieved in that the convective gas cooler comprises at least one ascent for the gas to be cooled. In order to remove contamination on the gas cooler surfaces, special pipe cleaning agents, e.g. Sootblower to be installed.

FR-E-55 473 discloses a gas generator for motor vehicles, but also for other types of use. It consists of a gasification reactor with a raw gas outlet arranged at the bottom, an ash collecting chamber, a fixed bed filter and a filter inflow chamber which connects peripherally to the raw gas outlet. Such a device is unsuitable for cleaning gases which contain sticky or liquid ash particles. Because these particles bake on the surface and in the interior of the filter, form solid layers and trigger blockages that reduce the cleaning effect of the filter and ultimately bring it to a standstill.

The invention is based, to remove the solid particles of any size occurring in the gasification of solids largely before entering cooling devices from the raw gas.

The object is achieved according to the invention by the features of the characterizing part of claim 1.

According to one embodiment of the invention, the method is carried out in a device which is characterized in that the gasification reactor has a gas outlet in the lower part, to which the filter inflow space connects peripherally, which is arranged above the fixed bed filter, the surface of the fixed bed facing the filter inflow space at least is three times larger than the circular area of the gas outlet pipe from the gasification reactor, the fixed bed is inclined and the top filter layer after covering the filter surface with dust is brought back into the ash collecting space by means of the gas backflushing by means of the nozzles.

The advantages achieved by the invention consist in particular in that, in terms of process engineering, the coarse and fine cleaning of the crude gas from granular and dusty solid particles takes place immediately one after the other, without interposing sensitive gas path sections or further containers. Because of the continued direct consequence of the strong gas speed reduction after the change in gas direction, there is an even flow through the following filter surface. This is also achieved according to the invention in that the crude gas, which is still free of the granular solid particles and still contains dust, flows through an area which is at least 3 times larger than the circular area of the gas outlet pipe from the gasification reactor.

In addition, it is ensured that caking layers covering the filter surface slide on the inclined filter during backwashing and break open in the process. This means that the entire surface of the fixed bed filter is always available for gas cleaning.

The invention is described in more detail using the exemplary embodiment.

Fig. 1:

Prinzipskizze des Verfahrens

Fig. 2:

Vorrichtung mit einem Festbettfilter

Nach Fig. 1 strömt aus dem nicht vollständig dargestellten Vergasungsreaktor 1, frei-wählbarer Bauart,das Rohgas über den trichterförmigen Rohgasauslaß 2 am Boden des Reaktors ab. Unterhalb des trichterförmigen Rohgasauslasses 2 befindet sich der Gasstauraum 3. Von hier aus muß das Gas radial seitlich und nach oben in den Filterzuströmraum 4 entweichen. Die im Rohgas enthaltenen körnigen Festpartikel werden von der Gasumlenkung nicht mitgerissen, sondern infolge ihrer Flieh- oder Schwerkraft in den Aschesammelraum 5 am Boden des Gasstauraumes geschleudert. Von hier aus werden sie taktweise über eine Schleuse 6 bekannter Bauart abgezogen. Aus dem Filterzuströmraum 4 tritt das noch mit Staubpartikeln von 0 bis 200 µm verschmutzte Rohgas in das Festbettfilter 7 ein, durchströmt dieses und sammelt sich im Abströmraum 8 um von hier über einen Auslaß 9 einer weiteren Wärmerückgewinnung zugeführt zu werden. Die Temperatur des gereinigten Rohgases liegt noch oberhalb 500 °C.The invention is described in more detail with reference to the drawings. Show it:

Fig. 1:

Outline of the procedure

Fig. 2:

Device with a fixed bed filter

According to FIG. 1, the raw gas flows out of the gasification reactor 1, of a freely selectable type, which is not shown completely, via the funnel-shaped raw gas outlet 2 at the bottom of the reactor. The gas storage space 3 is located below the funnel-shaped raw gas outlet 2. From here, the gas must escape radially laterally and upwards into the filter inflow space 4. The granular solid particles contained in the raw gas are not entrained by the gas deflection, but rather are thrown into the ash collecting space 5 at the bottom of the gas storage space due to their centrifugal or gravitational force. From here they are withdrawn in cycles over a lock 6 of known design. From the filter inflow chamber 4, the raw gas still contaminated with dust particles of 0 to 200 μm enters the fixed-bed filter 7, flows through it and collects in the outflow chamber 8 to be fed from here via an outlet 9 to further heat recovery. The temperature of the cleaned raw gas is still above 500 ° C.

According to FIG. 2, a radiation cooler 10 is installed in the lower part of the gasification reactor 1 in order to reduce the temperature of the raw gas to 500-700 ° C. The raw gas flows through the radiation cooler without any noticeable deposition of solid particles on the heat exchanger surfaces. The ash collecting space 5 can also be designed as a water bath. The fixed bed filter 7, designed as an annular surface, advantageously consists of a plurality of ring sectors which are individually filled with the material for the solid filter via feed lines 11. After the filter surface has been covered with dust, the uppermost filter layer is brought back into the ash collecting space 5 by gas backwashing by means of the nozzles 12. The cleaned gas flowing through the filter 7 enters the manifold 13 and is withdrawn from the device. The refilling of fresh filter sand is carried out in a known manner from sand storage 14 via the feed lines 11.

Claims (4)

1. A two-stage process for cleaning raw gas containing granular and dust-like solid particles from a solids gasification plant, whereby the raw gas is passed in the first cleaning stage from the gasification zone in a straight line in the direction of a gas build-up chamber (3), the granular solid particles being deposited on the bottom of the gas build-up chamber, the partially cleaned raw gas being diverted sideways away from the gas build-up chamber (3), characterised in that the velocity of raw gases which are partially cleaned and diverted sideways away from the gas build-up chamber (3) is reduced by at least a factor of 3 and, after the gas has again been diverted, substantially in the vertical direction, it is passed in the second cleaning stage through a fixed-bed filter whose area is at least three times larger than the circular area of the gas outlet pipe from the gasification reactor, the fixed bed is inclined and, once the surface of the filter is covered with dust, the top filter layer is caused to slide into the ash collection chamber (5) by gas backflushing with the nozzles (12) .
2. A process according to claim 1, characterised in that the fixed-bed filter is a free-flowing sand bed filter.
3. A process according to claims 1 and 2, characterised in that the second cleaning stage is performed at a temperature of over 500°C.
4. A device for performing the process according to one or more of claims 1 to 3 mainly comprising a gasification reactor with a vertical cooling zone having a bottom raw gas outlet (2) and an ash collection chamber (5) as well as a downstream fixed-bed filter, characterised in that the filter inflow chamber (4) is located around the side of the raw gas outlet (2), said chamber being arranged above the fixed-bed filter (7), the surface of the fixed-bed filter facing the filter inflow chamber (4) is at least three times larger than the circular area of the gas outlet pipe from the gasification reactor, the fixed bed is inclined and, once the surface of the filter is covered with dust, the top filter layer is caused to slide into the ash collection chamber (5) by gas backflushing with the nozzles (12) .

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