DE2759286A1 - Purificn. and heat recovery from exhaust gases - using injection of volatile liq., e.g. water, under pressure to recover heat by driving turbine with subsequent recycle of liq. - Google Patents

Abstract

Exhaust gases, esp. from combustion processes before discharge to atmosphere, can have heat recovered from them and be purified by filtering the gases, injecting a volatile material (e.g. water or refrigerant) into the gases under pressure, and passing the resulting vapour stream through a turbine. The exhaust vapours from this are cooled to condense out the liquid which is then recycled. The gases can be further compressed and processed to remove contaminants, esp. acidic vapours. Used for purifying exhaust gas stream before discharging to atmosphere. The process uses direct heat transfer by use of injected liquid instead of surface heat exchange.

Description

J3e writing

The invention relates to a method for treating flue gases od. Like. Combustion exhaust gases prior to being discharged into the atmosphere, consisting of Dust removal, cooling down to below the dew point of the water vapor through heat exchange with a cooling medium, separation of the condensate and separation of gaseous pollutants by precipitation on large surfaces over which the smoke gases are conducted, where the cooling medium is initially a liquid one and when exchanging heat with the flue gases used evaporating working medium and this is circulated in which which are generated during the cooling of the gases Taken walls by work performance is withdrawn again under relaxation, and the separation; the gaseous Pollutants from freezing to deep-frozen to below their probe temperature Generator flea takes place, according to patent (P 26 56 866 Such, the subject of the Lauptpatentes forming process enables a complete separation of all Pollutants from the flue gases before they are released into the atmosphere, so only completely clean and cool gas is released into the atmosphere. Through this chimneys and the like can be completely saved, and moreover can partially consider the separated pollutants as suitable for further processing pure gases can be obtained. That which is otherwise lost in chimneys which can be felt and latent heat of the flue gases can largely be converted into work and thereby can also be used.

The process described in the main patent is in the cooling stage an indirect heat exchange between the flue gases and the circulated one Working medium provided. The work that can be gained is limited due to the relatively small volume of the working medium.

The object of the invention is the method according to the main patent to improve so that the energy gained during the cooling of the flue gases is still can be better converted into work performance.

This is achieved according to the invention in that the working medium is injected directly into the previously compressed flue gases and evaporated in the process and that the steam-flue gas mixture gektihlt by relaxation under work performance and the working medium condenses, separated from the cooled flue gases and recirculated is returned.

In this process, the expansion machine, in particular, performs a turbine, not only the mass of the evaporated working medium, but also the total wetness of the flue gases. This allows a much more extensive Conversion of the heat content of the flue gases into usable energy can be achieved.

In a simpler embodiment of the method, the working medium Water can be used, which has the advantage that when separating the condensate also the proportion of water vapor contained in the flue gases together with the working medium can be deducted.

According to a preferred embodiment of the invention, however as the working medium an organic liquid with a temperature of the accruing smoke gases and the conditions of the R * nkSne-Kreielauf to go through adapted boiling behavior used. In particular, halogenated hydrocarbons are used, e.g. octafluoroyclobutane in question. From the Mollier diagram of this connection a particularly favorable behavior can be seen in the intended working cycle.

The inventive method in which together with the working medium the smoke gases themselves should also do relaxation work, presupposes a previous one Compression of the flue gases ahead. This can be particularly advantageous take place in that the combustion process itself which generates the flue gases Printing is carried out. This means that there is no need for downstream compressors.

Further advantageous features of the invention emerge from the Subclaims.

The combustion gases from the combustion chamber are shown as indicated by arrows 15, 16, 17, passed through a series of dust collectors 20, 21, 22, in which solid parts are held back. The separator 20 is preferably a cyclone, wherein particles up to 50 µm are deposited as indicated by arrow 24. the Separators 21 and 22 are e.g. bag filters that separate even smaller particles (see arrows 25, 26). The separators 20, 21, 22 should be insulated to prevent heat losses largely to be avoided.

The flue gases that have been freed of dust particles and are still under pressure now get into an evaporation vessel 30, in which via a line 31 and a Shower 32 or the like. Injection device under a liquid cooling and working medium corresponding pressure is injected, which during heat exchange with the e.g. 200 up to 300 C evaporates hot flue gases. The working medium is in is injected in such an amount that it is as rich as possible, preferably almost saturated Vapor of the working medium is formed, but if possible no non-evaporated liquid Working medium remains. Any liquid working medium that still occurs can collect in a sump 33 and enter the circuit via a line 34 to be led back.

Water can be used as the working medium. Preferably will but one of the known organic working fluids suitable for a Rankine cycle is used, especially a halogenated hydrocarbon such as octafluorocyclobutane C4P8, as marketed by Hoechst AG under the brand name Frigen C 318 will. This working medium has a sufficient temperature range in the relevant temperature range Stability and a subsequent relaxation-condensation cycle particularly well adapted boiling behavior (Mollier diagram).

The still pressurized vapor / breath gas mixture from the Evaporation vessel 30 is then fed to an expansion turbine 91 in which it relaxes and cools down while doing work. The work that becomes free can be converted into electrical energy by a generator 99 driven by the turbine 91 implemented. Due to the large amount of moisture in the steam / gas mixture passed through the turbine 91 high work output can be gained.

The relaxed and cooled steam-gas mixture then enters a by a condenser 35 indirectly cooled by a coolant 39, in which the condensate, both the working medium and the condensed The water content of the smoke gases is separated off. The condensed working medium is Via the line 95 and the pump 93 again in the circuit to the supply line 31 returned. If the working medium is water, the condensed water vapor fraction can also be used the smoke gases are drawn off via line 95 and circulated, excess water being removed from the circuit at a suitable point can. If, as mentioned above, an organic working medium is preferably used, it is easy to dispose of the immiscible water with the working medium via a separate Take off line (not shown) from the condenser 35.

Those freed from the condensate, relaxed and, for example, at ambient temperature (10 - 400 C), cooled gases are drawn off from the condenser 35 via the line 38, again compressed to approx. 3 atmospheres by a compressor 45 and via line 49, optionally an aftercooler 50 and the line 53 into the cleaning and separation system 58 passed to separate the gaseous pollutants. With only incomplete relaxation of the flue gases in the turbine 91 can possibly be the downstream compressor 45 also omitted.

Notwithstanding the embodiment shown, instead of the indirect The cooled capacitor 35 is also a directly duro-injected one water cooled condenser and stripper vessel can be provided in which the working medium and the water vapor is condensed and separated by directly injected water so that two immiscible liquid layers are in the bottom of the vessel the Arbeitsiediums and the water form, connected to the drainage pipes are.

The separation system 58 consists of at least three identical regenerators 59, 61, 63. Each of these regenerators 59, 61, 63 contain loose solids like 8.3. Keraiik balls, quartz stones, steel balls or other bodies that have large surfaces and serve as a heat transfer medium and do not corrode. He is at least thermally insulated in its lower part. Automatic switching valves 64a, 64b, 64c, and 65a, 65b and 65c are at both ends of each of the regenerators 59, 61, 63 via pipe connections 67, 68 connected. The supply line 53 leads to the valves 64a. A discharge line £ - " 70 for acid gas goes out from the valves 64b, while the cleaned gas goes through line 71 is withdrawn from valves 64c. Is on the valves 65a and 65c An expansion turbine 75 is connected via lines 73, 74, which has an electric generator 76 drives.

The acid gas, i.e. the pollutants, are released by a vacuum pump 79 is sucked out of the discharge line 70 and reaches the compressor via a line 80 81, who kosprimiert it as far as necessary and via line 82 to Further processing, especially for neutralization gas scrubbing, brings.

The flue gases are processed cyclically in the regenerator system 58. In each period, each of the regenerators 9, 61, 63 works in a different work phase. While a xegenerator cools the inflowing gas and the filling compound a little is heated in the second regenerator, which is switched off from the gas supply the separated heavier components sucked off by vacuum and in the third Regenerator by supplying the pure gas, which has been further cooled by relaxation the first regenerator recently cooled down the filling compound. The first period is initiated by opening valves 64a, 65a at the top and bottom the regenerator 59 and the valves 64c, 65c at the top and bottom of the regenerator 63. Gas flows through canister 59, drives turbine 67, and is through the canister 63 returned. The expanding gases in the turbine 67 are thereby cooled and release the cold in the regenerator 63. Of course, it is assumed that the plant has already been pre-cooled and the regenerators at the cold end the corresponding Maintain temperature. During the charging of the regenerators with the flue gas the less volatile components frozen out. Every 6 to 10 minutes the Regenerators switched. A sufficient one is important for the function of the system Pressure ratio between the inlet and outlet of the expansion turbine 67. This pressure ratio must be large enough to accommodate the recirculated clean gas and thus the regenerator 63 accordingly to cool off. The less volatile components of the gas when cooling in the regenerator 59 condenses or sublimates, while the clean gas " is reheated to ambient temperature via the regenerator 63. The connections or switching valves 65b are not required here, but can be useful, if e.g.

a fourth regenerator is to be connected.

Another phase that coincides with the loading of the first and cooling of the third regenerator is running, the evaporation of the frozen Components in the second regenerator 61. This step is carried out by the valves 65a, 65b and 65c are closed and the warm end of the regenerator 61 is connected to the pump 79 and the compressor 81 through the valve 64b. the Vacuum pump works at a pressure ratio of ls10. At this pressure ratio the frozen components are evaporated again and taken out in the form of acid gas the generator 61 deducted. The gas sucked off in this way is compressed in the compressor 81 and pressed into the pipeline 81. The acid gas will usually consist of CO2 with relatively small amounts of H2S, SO2, SO3, HCN, NOx and other pollutants. Depending on how low the temperature at the lower end of the regenerators 59, 61, 63 is set, unburned Hydrocarbons such as s.B. C2H4 and C2E6 as well as C3 and Cq fractions recorded will. The pollutants in the farm gas are neutralized in a lye wash, whereby the water which is discharged from the exchanger 35 was left, Can be used. The hydrocarbons mentioned can then be reused be separated.

The successive phases as just described are then shifted so that the regenerator 63 through line 53 and valve 64 is charged, the harmful components in turn being excreted while the clean gas, after being expanded in turbine 72, through regenerator 61 is returned. At the same time, the sublimated resp. frozen components that were held in the regenerator 59. The next Switching phase is similar to the previous one, with the gas flowing through the pipe 53 is fed into the regenerator 61 and the regenerator 59 is cooled by pure gas and from the regenerator 63 the acid gas is sucked off by pump 79 and in the compressor 81 is brought to pressure. The purified gases are released into the atmosphere at 71 delivered without the need for a chimney. Because these exhaust gases are dry they can possibly be used in an evaporative cooler.

The gas that is sent through line 82 to a neutralization plant is, goes through a lye wash, including the water from exchanger 35 for Reprocessing is used.

Pollutants from chemical processes, i.e. not from combustion originate at 10 can be treated with the gases in line 53. The admixture of solitary gases is indicated by the arrow 90 in the process diagram.

A drainage system similar to a sewer system 101 can do this be provided to clean exhaust gases of all kinds.

A corresponding compression can be provided in line 101 be in order to give up the collected gases in the line 53 can. If also more valuable Components such as hydrogen or hydrocarbons get into the collection system 101, they can be separated beforehand and recycled.

L e r s e i t e

Claims (10)

Process and device for the treatment of flue gases according to patent ... e 26 56 563.3 P a t e n t a n s p r ü c h e 1. Process for treating flue gases or the like. Combustion exhaust gases before being discharged into the atmosphere, consisting of dedusting, Cooling down to below the dew point of the water vapor by exchanging heat with a Cooling medium, separation of the condensate, and separation of gaseous pollutants through Precipitation on large surfaces over which the smoke gases are directed, whereby as a cooling medium an initially liquid and heat exchange with the flue gases used evaporating working medium and this is circulated in which the heat absorbed during the cooling of the gases through work performed under relaxation is withdrawn again, and the Separation of the gaseous pollutants by freezing out on generator surfaces that are frozen below their condensation temperature takes place, according to patent ... (P 2 @ 5 @ @@ 8.3), thus g e -k e n n z e i c h n e t, that the working medium is injected directly into the previously compressed breath gases and it is vaporized @@@ e: the steam permanent gas mixture @@@ through relaxation under work performance cooled and the working medium condensed, separated from the cooled breath gases and is returned to the cycle. 2. The method according to A of claim 1, characterized in that g e 1; e n n z e i c h -n e t that water is used as the working medium. 3. The method according to claim 1, characterized in that g e k e n n z e i c h -n e t that the working medium is an organic liquid, especially a halogenated one Hydrocarbon is used. 4. The method according to claim 3, characterized in that g e k e n n z e i c h -n e t that octafluorocyclobutane C4F8 is used as the working medium. 5 The method according to any one of claims 1 to 4, characterized g e -k e n It is noted that the compression of the flue gases is at least partially thereby takes place that the combustion producing the flue gases in the combustion chamber is under pressure he follows. t. Method according to claim 3 or 4, d u r c h e k e n nz e i c h n e t that the water condensed during cooling is separate from the condensed water Working medium separated and withdrawn and used as a neutralizing liquid in the used to neutralize the pollutants drawn off from the regenerator cooling surfaces will. 7. The method according to claim 1, characterized in that g e k e n n z e i c h -n e t, that the amount of the injected working medium is calculated so that almost one Saturated steam is formed. . Device for carrying out the method according to one of the claims 1 to 7 with a dedusting stage, a cooling stage provided with a heat exchanger and a separation stage for gaseous pollutants with a neutralizing device for the pollutants, by noting that the cooling stage is an evaporation vessel with feed line (31) for the flue gases, injection device (32) for the working medium, and a relaxation work machine connected to the evaporation vessel (30) (91). 9. Eiprichtung according to claim 8, d a d u r c h g e k e n n z e i c hnet that to the relaxation machine (91) a capacitor for the hbtennunb of the condensed working medium is connected, from which a discharge line (95) for the condensed working medium via a pump (93) in the circuit back to Injection device (32) is carried. 10. Device according to claim 8 or 9, characterized in that g e -k e n n z e i c h n e t that the evaporation vessel (30) has a pool (33) for excess liquid Has working medium which is connected to the pump (93) via a line (34) is.