CH639290A5 - Apparatus for removing gaseous and solid pollutants and mists thereof from a waste gas - Google Patents

Description

The invention relates to a system for removing gaseous and solid pollutants and mist from an exhaust gas, which is designed for a gas throughput of at least 50,000 Nm3 / h, and the at least one saturator as the first washing stage and a downstream second washing stage in the gas flow direction and a Has blowers for conveying the exhaust gas through the system to a chimney.

Plants with the above-mentioned components are already known, but are only suitable for gas throughputs below 60,000 Nm3 / h. These known systems contain wash towers, which can be connected downstream of a saturator (Quentsche), and in which the gas entering the wash tower is usually first passed through at least one packed bed. In plants which are intended to be suitable for a throughput of larger gas volumes, the construction of such packing layers arranged horizontally in a washing tower is technically difficult and uneconomical. Even with a vertical arrangement, filler layers through which gas must be passed at a relatively low speed would become far too voluminous.

Despite the required high throughput rate, the entire plant should be kept as compact as possible. For this purpose, the vertical arrangement of several horizontal washing stages one above the other in a tower is not very suitable, since the gas should be routed through the shortest possible lines in the entire system and all the way to the chimney in view of the large pipe cross section required. However, towers are known to extend these lines.

In the known systems, the hydraulic delivery head for the washing liquid would be undesirably increased, which means increased energy consumption (pump).

The object of the invention is therefore to implement a system of the type described in the introduction, in which the entire system is kept compact, the gas lines are short, the hydraulic head is kept as small as possible, good accessibility to the apparatus parts of the system is permitted and whole plant despite high throughputs of z. B. 200 000 Nm3 / h and more can also be built up in a limited space.

Another object of the invention is to achieve a satisfactory separation effect with the lowest possible energy consumption despite the greatly increased throughput.

The object is achieved and the stated objectives are achieved in a system of the type described at the outset, which according to the invention is characterized in that the saturator is designed as a Venturi saturator, that between the first and the second washing stage there is an essentially vertical an2

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Ordered droplet separator is interposed, and that the second washing stage comprises one of the first facing arrangement of a number of packing-free washing gap elements, the gas flowing down from the saturator being introduced into the second washing stage with deflection in a substantially horizontal flow direction through the interposed droplet separator.

The washing gap elements can be designed as pressure jump separators, hereinafter referred to as X separators, which are accommodated in a wall arranged transversely to the gas flow.

However, the washing gap elements are preferably designed as annular gap units which are installed in a wall arranged in a step-like manner transversely to the gas flow.

According to a first embodiment, the ring-gap units with their inlet ends located towards the interposed droplet separator can be installed in wall parts which are inclined downwards at an incline and offset in a step-like manner and through which gas flows from bottom to top; lines are provided, each of which is connected to the inlet end of one of the annular gap units and via which each annular gap unit is acted upon individually with washing liquid.

With this arrangement, a particularly high degree of separation is achieved and particularly good spraying through of the space located behind the annular gap units in the gas flow direction is achieved. On the other hand, the installation of the lines, which are usually designed as hoses, can be critical as far as operational safety is concerned, because if such a hose breaks, the application of washing liquid to the affected annular gap unit is completely eliminated and the gas passes through this unit correspondingly worse cleaned in the next room. The inflow of washing liquid into the annular gap units must also be regulated in relation to the amount of gas flowing through in such a way that pulsation of this washing system with formation of a bubble layer over the diffusor ends of the annular gap units is avoided, since this stores the annular gap units in their walls are too stressed and can also damage the fan.

Therefore, an embodiment is particularly preferred even in the case of somewhat lower degrees of separation for solids, in which the annular gap units, in the position through which the gas flows from top to bottom, are installed with their inlet ends in wall sections rising from the interposed droplet separator, a spraying system for each wall section Spraying an entire wall section including the inlet openings of the annular gap units installed in it is provided with washing liquid.

The inlet opening of each annular gap unit can be provided with a circumferential overflow edge, which is preferably jagged, for uniform distribution of the portion of washing liquid not injected directly into the inlet opening over the wall of the confuser part of the annular gap unit, and at the inlet into the throat of the annular gap unit an annular rib is then provided projecting inwards, which, as a deflecting edge, directs the washing liquid flowing down the wall of the confuser part into the gas flow.

At the end of the second washing stage, an end droplet separator is preferably provided in the gas flow direction behind the washing gap elements. A packing layer can also be installed as a coarse droplet separator between the end droplet separator and the wall gap elements preceding it.

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The end droplet separator, with or without a packing layer upstream of it, is preferably built onto the wall carrying the washing gap elements so closely that a zone sprayed with washing liquid is formed between it and the wall, the surface of the end droplet separator or the packing layer facing the wall also being sprayed becomes. The washing liquid emerging from the diffuser ends of the washing gap elements can be collected underneath these and can be returned to the inlet ends of the same in the circuit. A device for adjusting the pH of the washing liquid is preferably connected to the circuit.

Further details of the invention are described below with reference to the accompanying drawings, in which

Figure 1 is a schematic representation of a first embodiment of the system according to the invention in elevation.

Figure 2 is a schematic representation of a second preferred embodiment of the system according to the invention in elevation.

Fig. 3 shows the same embodiment in plan, and

Fig. 4 shows a third embodiment of the system according to the invention.

FIG. 5 finally shows an axial section through an annular gap unit as it is installed in the system according to FIGS. 2 and 3.

In the following description, a saturator is used under Quentsche, a pressure surge separator according to e.g. DE-OS 2 729 092 and an annular gap washer or an annular gap unit according to e.g. DE-OS 2 851 176 understood. Saturators are also known as evaporative coolers.

The embodiment of the system according to the invention shown in FIG. 1 comprises a quench 1 as the first washing stage, which is seated on a quench lower chamber 2. The last is adjoined laterally by a chamber 3, in which a second washing stage is accommodated, which contains a wall 4 arranged transversely to the gas flow direction, in which ring jet units (annular gap washers) 5 are installed. A droplet separator 6 is arranged vertically between the wall 5 and the lower chamber 2.

In the gas flow direction, a vertically installed packing layer 7 is provided behind the wall 5, and an end drop separator 8 is provided behind this. An intensively sprayed wash chamber 9 is formed between wall 4 and the side of the packing layer 7 facing this, the two droplet separators 6 and 8 and transverse wall 5 preferably being installed in a common system housing 10.

At the bottom of the sub-chamber 2 and the chamber 3, washing liquid from the Quentsche 1 and from the droplet separator 6 collects in a first sump 11, from which part of the washing liquid is recirculated into the Quentsche through nozzles 14 via a line 12 with a pump 13 . Water losses can be replaced by fresh water (process water) via a feed line 15. Excess liquid can be removed from the sump 11 through an overflow 16, sediment through an outlet 17 with a valve (not shown).

The exhaust gas flowing into the Quentsche 1 from above, preferably pre-cleaned beforehand in an evaporative cooler and a cyclone, leaves the Quentsche 1 loaded with injected washing liquid downward and is deflected in the lower chamber 2 in a horizontal direction of flow through the droplet separator 6.

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In this sub-chamber and in the droplet separator, washing liquid is collected in the sump 11, which has primarily taken up hydrogen halides, such as HCl and H2F2, contained in the exhaust gas.

The ring jet units 5 are installed in three wall parts 20, 21 and 22 of the transverse wall 4 with their inlet ends 5a. These wall parts are arranged in a step-like manner with respect to one another, the uppermost step 20 being closer to the droplet separator 6, the lowest step 22 being farthest away from it, and each of the three wall parts is inclined somewhat obliquely downwards away from the droplet separator 6, so that they are on the top of the wall parts 20, 21 and 22 accumulating washing liquid flows off well and collects in a sump 19 at the bottom of the washing room 9, from which a part of the latter is recirculated via a mother line 23 and from this distributing hoses 24 into the diffusion ends 5b of the ring jet units 5 .

The inclined position of the wall parts 20, 21 and 22 also avoids the so-called spring arch effect, which would occur if the axes of the units 5 were vertical and worsens the degree of separation of this washing stage.

The circulating washing liquids have a pH in the acidic range in line 12, preferably below 4, e.g. from 1 to 3.5, while the pH of the washing liquid in line 23 is made less acidic, e.g. on 4 to 6.5. The adjustment of the pH value in this circuit can e.g. by adding sodium hydroxide solution via feed line 25 with metering pump 26, the motor M of which can be controlled for pH by a quality indicator control measuring device (QIC). The pump 27 causes the washing liquid to circulate from the sump 19 through line 23; Excess liquid is removed from the sump 19 by means of the overflow 28, sediment via outlet line 29 (with valve).

The blower 30 is provided in this system behind the outlet end 10a of the housing 10 and in front of the chimney 31 and sucks the exhaust gas from the Quentsche 1 through the system with a slight negative pressure. But it could also be attached in front of the Quentsche 1 and the exhaust gas through the system with a slight excess pressure, e.g. 0.1 to 0.3 bar.

The packing layer 7 is provided in order to act as a liquid brake and to prevent excessive amounts of water from being thrown onto the end droplet separator 8 with the exhaust gas. Rather, these are directed into the sump 19 beforehand.

In the preferred embodiment of the system according to the invention shown in FIGS. 2 and 3, the same components have the same reference numerals as in FIG. 1.

This embodiment differs from that of FIG. 1 by the arrangement of the washing gap elements 5 in the second washing stage. This comprises horizontally arranged wall parts 33, 34 and 35, in which the ring jet units 5 are installed with their inlet openings 5a pointing upwards and their outlet openings 5b pointing downwards.

Via branch lines 23a, 23b and 23c, washing liquid from the circulation line 23 is sprayed through the nozzles 36 onto the inlet openings 5a of the ring jet units 5 and the upper sides of the wall parts 33, 34 and 35 surrounding them. While in units 5 of the embodiment according to FIG. 1 the entire amount of liquid is introduced into unit 5 from the diffuser side 5b, in the system according to FIG. 2 only about a third of the sprayed washing liquid gets into the inlet opening 5a by directly spraying it the unit. Two thirds of the top, e.g. 33a of the wall part 33 sprayed liquid amount, however, flow through the incisions 51 (Fig. 5) in the upper peripheral edge 50 of the unit into the interior of the latter, first along the inner wall 52 of the confuser area 53, and then by means of an annular rib 54, the at the entrance to the throat 55 of the unit, is directed into the gas stream and is preferably finely distributed therein with the formation of fog in the diffuser area 56.

The arrows indicate the direction of gas flow.

In such a system, e.g. 120 to 150 Ringjet units can be used.

In the embodiment shown in FIG. 4, a so-called X separator 40 with X-shaped slots is installed instead of the ring jet units. Such X separators are relatively sensitive, especially to metal oxides as solid pollutants in the exhaust gas and should therefore only be used for exhaust gases that are free of this type of pollutant. The X separator 40 is sprayed with washing liquid by means of nozzles 41 via the circuit line 23.

Finally, if the exhaust gas is free of sulfur dioxide, the interposed drip catcher 6 may also be dispensed with.

Ringjet units are described in DE-OS 2 851 176 for use in systems according to FIG. 1 of a preferred embodiment.

The gas cleaning system with evaporative cooler and cyclone for pre-cleaning is known from DE-OS 2 849 607.

X-separators are available in various forms in the presentation of the Air Hygiene 1976 conference of the Association for the Promotion of Water and Air Hygiene on December 2 and 3, 1976 in Brugg-Windisch, Switzerland using FIGS. 2 and 3 of a special print from the report volume. Exhaust gas purification technology », filler body in the preferred hedgehog version described there with reference to FIG. 7.

If the gas inlet line into the Quentsche with a diameter of 2.5 m, the width of the confusor part of the Quentsche at the upper end with 3.5 m and the cross-sectional area of the interior of the housing 10 in the middle part with 25 m2 (5 x 5 m) , the fan can only work with portable energy consumption if hydraulic delivery heights are kept as low as possible. This is the case with the system according to the invention.

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Claims (10)

639 290 PATENT CLAIMS 1.System for removing gaseous and solid pollutants and mist from an exhaust gas, which is designed for a gas throughput of at least 50,000 Nm3 / h, and the at least one saturator (1) as the first washing stage and a second washing stage downstream of this in the gas flow direction and a blower for conveying the exhaust gas through the system to a chimney, characterized in that the saturator (1) is designed as a venturi tiger, that a substantially vertically arranged droplet separator (6) is interposed between the first and the second washing stage, and that the second washing stage comprises an arrangement facing the first of a number of packing gap-free washing gap elements (5; 40), the gas flowing down from the saturator (1) being deflected in a substantially horizontal flow direction through the interposed droplet separator (6) into the second washing stage is introduced. 2. Installation according to claim 1, characterized in that the washing gap elements are designed as pressure jump separators (40) and are accommodated in a wall (4) arranged transversely to the gas flow. 3. Plant according to claim 1, characterized in that the washing gap elements are designed as annular gap units (5) which are installed in a wall (4) arranged in a step-like manner transversely to the gas flow. 4. Plant according to claim 3, characterized in that the annular gap units (5) with their inlet ends (5a) to the interposed droplet separator (6) located in the inclined downward inclined, mutually stair-like offset wall parts (20-22) and through which the gas flows from bottom to top, and that lines (23, 24) are provided, each of which is connected to the inlet end (5a) of one of the annular gap units (5) and via which each annular gap unit individually with washing liquid. 5. Plant according to claim 3, characterized in that the annular gap units (5) in the gas flow from top to bottom position with their inlet ends in step-shaped from the interposed droplet separator (6) from rising wall parts (33-35) are installed, and that a spray system (36) is provided for each wall part for spraying the entire wall part including the inlet openings of the annular gap units (5) built into it with washing liquid. 6. Installation according to claim 5, characterized in that the inlet opening of each annular gap unit (5) with a preferably jagged peripheral overflow edge (50) for the uniform distribution of the portion of washing liquid not directly injected into the inlet opening over the wall of a confusion part (53 ) of the annular gap unit (5) and that an annular rib (54) at the entry into the throat (55) of the annular gap unit Inwardly projecting is provided which, as a deflecting edge, directs the washing liquid flowing down the wall of the confuser part (53) into the gas stream. 7. Plant according to one of claims 1 to 6, characterized in that an end droplet separator (8) is provided at the end of the second washing stage (4, 5) in the gas flow direction behind the washing gap elements. 8. Plant according to claim 7, characterized in that a packing layer (7) is installed as a coarse droplet separator between the final droplet separator (8) and the washing gap elements (5) preceding it. 9. Plant according to one of claims 7 and 8, characterized in that the final droplet separator (8) with or without the filler layer (7) connected upstream of it is so close to the wall (4) carrying the washing gap elements (5) that the latter is built onto the latter that between it and the wall a zone sprayed with washing liquid is formed, the surface of the end droplet separator (8) or the packing layer (7) facing the wall also being sprayed. 10. Plant according to one of claims 1 to 9, characterized in that the washing liquid emerging from the diffuser ends (5b) of the washing gap elements (5) is collected underneath these and is returned to the inlet ends (5a) of the same and that a device (QIC , M, 26, 27) is connected to the circuit for setting the pH value of the washing liquid.