EP0077852B1 - Gas cooler for a synthesis gas generator - Google Patents

Description

The invention relates to a gas cooler connected to a synthesis gas generator according to the preamble of claim 1. Such a gas cooler is known from DE-OS 2611 949. It cannot be avoided that water from the water bath evaporates or evaporates, whereby heat of a relatively high temperature drops to a lower level. This is not only associated with thermodynamic losses, but also the calorific value of the synthesis gas is reduced. This phenomenon is particularly aggravated when, for cleaning the chute, water is injected into the chute under high pressure by means of specially provided nozzles, which should cause the slag adhering to the chute wall to peel off.

It is an object of the invention to substantially reduce the thermodynamic losses associated with the evaporation of the water.

According to the invention, this object is achieved by the features of the characterizing part of claim 1. This ensures that a circulation movement occurs in the water bath which is directed in the vessel and in the subsequent insert from top to bottom and in the annular space between the insert and the wall surrounding it. As a result, the water temperature at the bath surface becomes approximately equal to the inlet temperature of the water supplied via the heat exchanger, and it then rises to a maximum value on the way to the water withdrawal point. Not only is the evaporation of the water largely reduced and the evaporation greatly reduced, but the circulating water is also brought to a relatively high temperature so that its heat content can be used - all without condensation on the parts of the gas cooler covered with synthesis gas occurs. Arranging the slag breaker at the lower end of the insert means that the slag particles release most of their thermal energy in the water bath and then largely settle, which means that the water used for thermal use can be drawn out of the bath in a fairly clean manner.

In steam generators with liquid slag removal, it is known to provide a water bath. However, this bath is kept at such a low temperature that little steam is formed when the slag is quenched. The temperature of the water remains so low that it is not worth using the thermal energy inside. Condensation of smoke gases is not avoided.

The design according to claim 3 prevents slag particles from being deposited in the heat exchanger, which would result in an increase in the temperature difference on the heat transfer surfaces and consequently thermodynamic losses.

Claim 4 shows a way to use the heat obtained from the water bath as useful as possible.

With the water supply according to claim 5, the water level in the water bath is always kept at an optimal level.

With the damper according to claim 6 can be prevented that heavy slag particles get too quickly and only superficially quenched in the slag crusher. The slag crusher can therefore not be smeared with sticky slag and thus become inoperable.

The water drainage device according to claim 7 prevents a stable layer of slag particles from forming on the water surface, which would prevent the immersion of heavier particles.

• Fig. 1 einen Vertikalschnitt, stark schematisiert, durch einen Gaskühler nach der Erfindung.
• Fig. 2 den unteren, das Wasserbad enthaltenden Teil des Gaskühlers, in grösserem Massstab als in Fig. 1 und
• Fig. 3 einen Vertikalschnitt durch ein abgewandeltes Detail des Gaskühlers.

An embodiment of the invention will now be explained in more detail with reference to the drawing. Show it:

• Fig. 1 is a vertical section, highly schematic, through a gas cooler according to the invention.
• Fig. 2 shows the lower part of the gas cooler containing the water bath, on a larger scale than in Fig. 1 and
• Fig. 3 shows a vertical section through a modified detail of the gas cooler.

1, the gas cooler 1 has a pressure vessel 2, in which a coaxial chute 6 is arranged, which is formed from tubes 5, which start from a ring distributor 3 and are connected gastight to a cylindrical tube wall 4. The tube wall 4 is drawn in at its upper end to form a neck 7 which is surrounded by a ring collector 8 into which the tubes 5 open. At the end face of the neck 7 there is a tightly connected connector 10 which has thermal insulation and which penetrates an upper flange 11 of the pressure vessel 2 and is part of a coal gasification reactor (not shown). A part of the tubes 5 is bent outwards in a lower zone 14 of the tube wall 4 to form passage openings. In the annular space between the tube wall 4 and the wall of the pressure vessel 2 there is a tube wall 15, also formed from vertical tubes, the tubes of which are welded tightly to one another via connecting webs and form dense conical surfaces 16 and 17 at the top and bottom. The tubes of the tube wall 15, like the tubes 5, are connected to the ring distributor 3 and the ring collector 8. The tube wall 15 is then provided in its upper region with a radial gas outlet connection 20 which penetrates the wall of the pressure vessel 2.

The tubes of the tube wall 15 originating from the cone 17 form a flange 9 with their connecting webs in the central plane of the ring distributor 3 (FIG. 2). A horizontal flange of an annular bellows 21 is screwed tightly to this flange via an unrecognizable seal. The lower end of the bellows 21 is welded to the outer wall 22 of a cylindrical hollow wall vessel 24. The lower end of the inner wall 25 of the cavity wall vessel 24 adjoins a cone 26, the outside of which is connected to the lower end of the outer wall via an annular plate 27 22 is tightly welded. The annular space of the cavity wall vessel 24 is supplied with water near its lower end via a line 28 having a closure member 29, which - ascending through the annular space - passes into the central space of the cavity wall vessel via several water outlet openings 30 arranged in the region of the upper edge of the inner wall 25 . Approximately in the upper third of the cavity wall vessel 24, its outer wall 22 and inner wall 25 are penetrated by water injection lances 32. These lances are constricted like a nozzle at the front and connected to a ring distributor 34 at the back, which is supplied with heated water via a water supply line 35. The line 28 is connected to the water supply line 35 outside the pressure vessel 2.

A discharge funnel 40 is arranged eccentrically in the cavity wall vessel 24, from which a discharge line 41 is led to the outside, which passes through the inner wall 25, the outer wall 22 and the wall of the pressure vessel 2 and has a closing element (not shown). The cavity wall vessel 24 stands with its ring plate 27 on a frame 44 made of I-beams, which is fastened to the wall of the pressure vessel 2 by means of tabs 45.

The cone 26 opens with its tapered end into a vertical, rectangular cross-section channel 50, at the lower end of which a similar cross-section channel 51 is fastened with screws 52. At the lower end of this channel 51, a channel end piece 53 is connected via a flange connection 54, the four walls of which two opposing walls are inclined to one another. Two racket rollers 55 of a slag crusher 56 are arranged near the narrowest point at the lower end of the channel end piece 53. Each of the two racket rollers is driven by a motor, which is also not shown, via a shaft (not shown) having universal joints which extends through the wall of a pot 70 surrounding the channel 51 and the channel end piece 53.

The pressure vessel 2 is provided with a base 57, which has a central connecting piece 58 with flange 59 and two connecting pieces 60 with bellows 61. At the lower end of the bellows 61, a water supply pipe 62 is welded tight, which extends through the nozzle 60 and leads to the ring distributor 3. In the connecting piece 58 there is a sleeve 63 with a lower flange 64. The upper end of the sleeve 63 is detachably fastened via a bellows 65 with a flange 66 tightly connected to the cone 26. The above-mentioned pot 70 is clamped together with an upper flange 71 with the flanges 59 and 64 and has a conical bottom 72 at its lower end. The bottom 72 of the pot 70 has a central outlet connection 73 which, as can be seen in FIG. 1, is connected to the one leg 76 ′ of a Y-shaped branch piece 76 via a closing member 75. On the other leg 76 ″ of the branch 76 is a lock chamber 77 with a vent valve 78. The lower connection 80 of the branch 76 is provided with a closing element 82 and ends above a sludge collecting trough 83.

In the water-filled annular space 67 between the upper channel 50 and the sleeve 63, a suction basket 68 is arranged, from which a water pipe 69 extends, which penetrates the pot 70 and leads via a separating element 100 and a circulation pump 101 to a heat exchanger 102, which is on the outlet side is connected to the water supply line 35. The separating element 100, in which impurities contained in the water are to be separated out, can be a filter or a separator. The heat exchanger 102 is connected on the secondary side as feed water preheater of a steam generator. A bypass line 103 branches off between the circulation pump 101 and the heat exchanger 102 and opens into the water supply line 35 via an actuator 104. A temperature measuring element 105 is connected to the water supply line 35 below this mouth, which gives signals corresponding to the respective water temperature in the line 35 to a controller 106. The controller 106 compares the temperature signal with a setpoint signal. The controller 106 is operatively connected to the actuator 104, which thus adjusts the amount of water to be conducted past the heat exchanger 102 via the bypass line 103 as a function of the deviation between the measured temperature and the target temperature determined in the controller 106.

As can be seen from FIG. 2, the depth of the water bath extends from the water level in the hollow wall vessel 24 to the entry of the water into the Schlakkenbrecher 56. This depth is a multiple of the horizontal extent of the water bath, which corresponds to the inner diameter of the inner wall 25 of the hollow wall vessel 24.

The gas cooler 1 described works as follows: The reaction products (synthesis gas with liquid slag particles), which are more than 900 ° C., flow from the coal gasification reactor (not shown) through the nozzle 10 into the chute 6, which can be 30 m long, for example. In this shaft, the reaction products give off heat to the tube wall 4, preferably by radiation, whereby most of the slag particles - at least superficially - solidify. When the gas is deflected in the zone 14 of the chute 6, the slag particles are more or less deflected from their fall line by the gas forces and thrown into the water bath or onto the cone 17. The conical surface is so steep that the slag particles falling on it slide or roll into the water bath. The synthesis gas which has been roughly cleaned in this way now flows through the annular space between the tube walls 4 and 15 upwards and via the connection piece 20 directly - or via a separator - into a convection cooler, in which heat is further extracted from the synthesis gas.

The ejected slag particles sink in a water bath, taking them to their core Larger slag particles are crushed in the slag crusher 56 before they settle on the conical bottom 72 and sediment there. The sediments are periodically drawn off from the bottom 72 by opening the closing member 75, so that - when the closing member 82 is closed - water and sediments are driven under high pressure into the lock chamber 77, which is initially filled with air at atmospheric pressure. The air in the lock chamber 77 is temporarily compressed in the upper chamber section. After the pressure has been equalized, the closing element 75 is closed and the vent valve 78 is opened, so that the air escapes and the pressure in the sluice chamber 77 is relieved. Now the closing member 82 is opened so that water and sediments pour out of the lock chamber 77 into the sludge collecting trough 83. If necessary, the lock chamber 77 is rinsed with water, for example. The closure member 82 and the vent valve 78 are closed, whereby the discharge device is ready for the next discharge operation.

In order to prevent air from rising into the water bath when discharging, branch piece 76 can be filled with water, for which purpose leg 76 ′ leading to closing element 75 can be designed to be ventable.

During the operation of the gas cooler, water is continuously circulated through the water bath by means of the pump 101. This water is introduced via line 35 with the aid of the control means 103 to 106 into the water bath at a temperature which is kept between the dew point of the synthesis gas as the lower limit and the water evaporation point at the pressure of the synthesis gas as the upper limit, preferably in the lower third of this Temperature interval. The water to be introduced into the water bath enters the annular space of the cavity wall vessel 24 via the line 28, rises therein and runs through the water outlet openings 30 and the inner wall 25 to the surface of the water bath. On the other hand, water from the supply line 35 reaches the surface of the water bath via the ring distributor 34 and the water injection lances 32, agitating the bath and larger, not yet fully solidified particles that dance on the bath surface as a result of the Leidenfrost phenomenon cools down. The water in the bath then circulates downward, being further heated by the entrained particles. The pressure drop caused by the circulating pump 101 and the drag force of the sinking particles mean that the water inside the channels 50 and 51 - although it is warmer in the lower region of the bath than in the upper region - moves down over the entire cross section without that inversion currents occur.

Larger slag particles and occasionally slag pieces falling in the form of a cone are comminuted in the slag crusher 56. The depth of the water bath is dimensioned such that even larger slag structures solidify to their core before they enter the slag crusher 56, so that there is no danger that the slag crusher will be smeared by still sticky slag and thus become inoperable. From the outlet of the slag crusher 56, the water rises in the annular space 67, while a substantial fraction of the slag particles settles on the conical bottom 72. It is then returned to the supply line 35 by means of the pump 101 via the suction basket 68, the line 69, the separating member 100, and the heat exchanger 102.

It can happen that porous slag particles that are lighter than water accumulate on the surface of the bath or float thereon due to the appropriate surface tension. Such particles can be drawn off via the discharge funnel 40.

The water losses in the bath caused by the removal of particles floating on the surface, the removal of sediments with water and the inevitable evaporation or evaporation in the area of the water surface are replaced by the addition of fresh water. For this purpose, a device, not shown, is provided which - as long as the water level in the bath falls below a certain setpoint - feeds fresh water into the supply line 35. This device is expediently influenced by a water level sensor, which can be designed as a pressure difference measuring device which is connected below and above the water surface.

During operation, water is fed into the tubes of the tube walls 4 and 15 via the water supply tubes 62 and the ring distributor 3. The water is partially evaporated in these walls. The water vapor mixture is discharged via the ring collector 8 and pipes, not shown, for example into a steam drum of a steam generator. The tubes of the two tube walls 4 and 15 can - as is known from steam generator construction - be switched in natural circulation, in forced circulation or in forced passage; it is also possible to change the switching types as required or to overlap one another.

The above-mentioned limitation of the temperature of the water supplied to the water bath ensures that no surface parts inside the gas cooler have a lower temperature than the dew point of the synthesis gas. This prevents the synthesis gas from depositing on such surfaces or condensing gas fractions. This is particularly important if the space between the tube wall 15 and the wall of the pressure vessel 2 is filled with stagnant synthesis gas for reasons of pressure equalization.

The temperature of the water supplied to the gas cooler via the supply line 35 is selected as close as possible to the dew point temperature, but with sufficient certainty above it, so that as little water as possible in the region of the The surface of the water bath evaporates or evaporates.

In order to prevent large, not completely solidified slag chunks or cones from getting into the slag crusher 56, means can be provided to delay the sinking of the slag parts. Such a means exists according to FIG. 3 in the form of baffles 87. On the two longer rectangular sides of the channel 51 there is provided an outwardly curved groove 85, in which a shaft 86 is arranged parallel to the adjacent wall. On each of these shafts 86, secured against rotation, a stowage flap 87 is inserted. The two shafts 86 penetrate the shorter rectangular sides of the channel 51, and levers 90 are attached in a rotationally fixed manner to the projecting shaft ends, at the free ends of which a spring 91 engages, which is anchored to the channel wall via a tab 92. Stops 93 determine the closed position of the baffle flaps 87. If a lump of slag falls onto the baffle flaps 87, the force of the springs 91 and the inertia of the baffle flaps 87 must first be overcome until the flaps open and let the slag lump fall further. The energy of the fall of the boulder is largely consumed by the flaps 87. Since the flaps 87 have to displace a lot of water when opened, they can only move relatively slowly. Additional dampers can also be provided to limit the opening speed of the flaps.

The gas cooler has the advantage that - when it is out of operation and emptied - it can be inspected, cleaned and repaired relatively easily. For this purpose, the pot 70 is removed after the water has been drained, with the line 69 and the suction basket 68 also being removed. Then the annular space 67 can be climbed to release the connection on the flange 66, whereupon the sleeve 63 can be removed downwards.

The interior of the cavity wall vessel 24 is accessible via the upper channel 50. The annular space between the outer wall 22 of the cavity wall vessel 24 and the wall of the pressure vessel 2 is also easily accessible after the sleeve 63 has been removed.

The ring distributor 3 is easily accessible if the connection of the annular bellows 21 to the flange 9 is released from the last-mentioned annular space and the connections of the tube 28 and the water injection lances 32 are separated, so that after moving the I-beam of the frame 44 the whole Cavity wall vessel 24 can be lowered.

The invention is in no way limited to the exemplary embodiment shown; For example, the sleeve 63 can be cylindrically extended up to the cone 26 and welded tightly to it in an annular seam. The cone 26 is conveniently divided close below this ring seam and the two parts connected by a detachable screw. Such an embodiment has the advantage that after removal of the pot 70 and the lower channel 51 when removing the lower part of the cone 26, a larger access opening to the chute 6 is available. The scaffold 44 could also be dispensed with and the pressure vessel 2 shortened below. The annular space between the cavity wall vessel 24 and the wall of the pressure vessel 2 would expediently be made accessible by at least one manhole connection in the wall of the pressure vessel 2.

It may also be desirable to make the slag crusher 56, which is subject to wear, laterally removable. This can be achieved in that the channel end piece 53 is firmly connected to the pot 70 via two parallel pipe pieces which run coaxially to the beater rollers 55. The beater rollers are in this case firmly connected to the shafts of the drive motors, which are screwed tightly to the wall of the pot 70 via a flange on the outside. If you want to avoid two separate motors for driving the two racket rollers 55, the rollers can also be driven by a single motor with the interposition of gear wheels.

Claims (7)

1. A gas cooler (1) connected to a synthesis gas generator and having: a pressure vessel (2) in which a fall shaft (6) bounded by radiation-cooling walls (4) is disposed; a cylindrical vessel (24) into which the fall shaft (6) merges at its bottom end and which has a funnel-like narrowing (26) and which is adapted to receive a water bath; a number of exit orifices for the cooled synthesis gas, such orifices being disposed in the cooling walls (4) just above the water bath; and a closable sludge removal opening (73) disposed at the lowest part of the water bath, the depth thereof being a multiple of its horizontal dimension, characterised in that the funnel-like narrowing (26) of the vessel (24) merges sealingly into a downwardly extending element (50, 51) having a clinker breaker (56) disposed near its bottom end; a water removal station (68) is disposed in an annular chamber (67) between the element (50, 51) and a cylindrical wall (70) bounding the water bath and communicating with the pressure vessel (2); and such station (68) communicates, by way of a line (69, 35) comprising a pump (101) and a heat exchanger (102), with the top end of the water bath.

2. A gas cooler according to claim 1, characterised in that means (103-106) for controlling the temperature of the water supplied to the top end of the water bath through the line (35) are provided.

3. A gas cooler according to claim 1 or 2, characterised in that a separating element (100) for particles differing from water in density and/or in the aggregate state is provided in the line (69) between the station (68) and the pump (101).

4. A gas cooler according to any of claims 1-3, the walls (4) of the fall shaft (6) being cooled by the working medium of a vapour generator, characterised in that the heat exchanger (102) is connected on the secondary side in the feed water flow of the vapour generator.

5. A gas cooler according to any of claims 1-4, characterised in that the water bath is connected to a water supply controlled by a sensor responding to the water level in the water bath.

6. A gas cooler according to any of claims 1-5, characterised in that at least one clinker-delaying flap (87) is provided in the water bath, preferably above the clinker breaker (56).

7. A gas cooler according to any of claims 1-6, characterised in that water removal means (40, 41) connected to a closure element are disposed just below the surface of the water in the water bath and are adapted to remove periodically or continuously, as required, a surface layer of water containing floating particles.

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