JPH03502547A - Method for dry separation of harmful substances from flue gases and equipment for carrying out this method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Method for dry separation of harmful substances from flue gases and equipment for carrying out this method The present invention is characterized by the fact that an absorbent is added to the flue gas stream and this absorbent reacts with the harmful substances and smokes the smoke. Flue gas separated in a filter along with solids carried by the flue gas Combustion boilers, converters, rotors, etc. that produce exhaust gases from or containing corresponding hazardous substances. - Simultaneous dry separation of solid or gaseous substances from equipment such as tally kilns, etc. Concerning how to. The invention further provides a combustion boiler or a converter or a rotary - A flue gas duct or exhaust gas duct extends from the kiln, etc. the filter is equipped with a device for adding an absorbent and at least one filter; It relates to an apparatus for carrying out the method.

The simultaneous dry separation of solid and gaseous substances from flue gases is known. this In some cases, absorbents, such as lime or lime products, are added to the flue gas stream.

Absorbents remove gases such as sulfur, fluorine, chlorine, etc. that are carried along with the flue gas. Reacts with toxic substances in the form of gas. Reaction products in the form of lumps or dust should be removed with a filter element. separated by a filter. This filter element can be made of wool, synthetic resin or glass. It is made of woven fibers. Such filter elements can be heated to temperatures of approximately 220"C. Therefore, the flue gas stream must be kept at a suitably low temperature before entering the filter. It needs to be cooled to a certain degree.

This is especially true for the subsequent use of purified flue gas, e.g. to operate gas turbines. and when it has to be reheated, it requires costly measures.

The problem of the present invention is to remove harmful substances from exhaust gases (process gases), especially flue gases. It is the dry separation of gaseous substances and solid substances (dust) at the same time.

The challenge is that the absorbent is added to the flue gas stream at temperatures above 250°C and With filters made of ceramic fibers or porous metal films, along with solids. Solved by separation. Separation is carried out at 250-900°C, especially at 300-6 00”C, and in specified cases 450-500°C. Wear.

Filter elements made of ceramic fibers or porous metal films are I can endure it.

As a result, there is no need to cool the hot flue gas to a temperature below 220°C. dry Heating of the flue gas after dry separation is also no longer necessary. In addition, absorbents and flue gas Reactions with harmful substances carried along with the product occur quickly.

Other preferred embodiments of the method according to the invention are apparent from claims 5 to 7. It is. This embodiment allows quick or complete dry separation of hazardous substances and filters The separated solids are returned to the process, reducing the amount of waste material or Can be recycled into plaster after other treatments.

The equipment for carrying out the process is usually a combustion boiler or a converter or a rotary kiln. from which a flue gas duct or exhaust gas duct extends; is equipped with a device for adding absorbent and at least one filter.

The device according to the invention is characterized in that the filter is made of ceramic fibers and/or porous material. Particularly manufactured, characterized in that it has a filter element consisting of a metal film of The safety of the filter element against pressure loads such as those occurring as a result of burst combustion in the case of mesh converters. The quality can be improved by reinforcement. This reinforcement can be made of steel, aluminum , synthetic resin, etc.

When the filter element consists of a metal film, the pores are between 3 and 200 μm, especially 10-100 μm fog.

The size of the pores can be determined depending on the size of the particles present in each case.

Such filter elements consisting of ceramic fibers or metal films are particularly suitable for When gaseous ammonia NFIx is added to the flue gas as is known, and Ceramic fibers or metal films coated with catalytically active materials Sometimes it can be used to separate nitrogen oxides NOx.

The coating layer is made of titanium oxide, vanadium oxide, chromium oxide, iron oxide, or the like.

Due to the action of the catalyst material, nitrogen oxides NOx, ammonia NH3 and oxygen 0. between The reaction is carried out as known.

Next, an embodiment of the present invention shown in the figures will be described.

Figure 1 shows the simultaneous drying of gaseous and solid harmful substances from the flue gas of a converter for steel manufacturing. a diagram schematically showing an apparatus for separating; Figure 2 shows the simultaneous drying of gaseous and solid harmful substances from the flue gas of a furnace boiler. FIG. 3 shows a device for separating.

FIG. 1 shows a converter 1 for producing steel or non-ferrous metals. This converter A flue gas duct 2 extends from there. During steel manufacturing, raw steel is refined in converter 1. It will be done. In particular, high carbon contents are reduced to useful values for the desired steel quality. . The flue gas duct 2 first moves vertically upwards and then vertically downwards again in a U-shape. I am being guided. There is a normal waste heat boiler in both U-shaped corners of the flue gas duct 2. La 3 and 4 are housed. Inside this waste heat boiler, the flue gas has a temperature of approximately 500°C. cooled down to A waste heat boiler is essentially multiple pipes (not shown) through which water flows. It is becoming more and more. In this case, the water receives heat from the hot flue gases and generates electricity, for example. It is generally heated up to a steam stage for later heat recovery for purposes. vertically downward An impingement plate 5 is provided at the end of the section of the flue gas duct guided to. child In the impingement plate of the , coarse-grained solids, which are carried along with them by the flue gases, are collected.

This coarse-grained solid and possibly fine-grained solid is removed by a discharge device 6. It is discharged from the flue gas duct 2 and collected in the silo 7. Is this solid silo 7? and solidified by, for example, brick-forming or pellet-forming (pressing device 18). After that, it is supplied to the converter 1 again. This is because this solid contains iron. It is. If this solid contains hazardous substances, it is also fed to the converter. Why , because harmful substances react with the process slag and become virtually harmless. It is.

The flue gas stream is supplemented with an absorbent, e.g. finely divided lime, in its further passages. It will be done. This lime includes caustic lime (Cab), lime-rich hydrate (Ca(O)l )x), in some cases limestone (CaCO,) can be used The particle diameter ranges from 2μ to 200μ, preferably 20μ. Contains 50% or more of particles.

The absorbent is in a container 8 and added to the flue gas stream via a placement device 9 and a nozzle 10 etc. be done. FIG. 1 shows the area of the nozzle 10 for separating nitrogen oxide NOx. In particular, other equipment for adding ammonia NH3 is provided, but not shown. An example of such a device is shown in FIG. 2 (nozzle 26).

The flue gas duct 2 extends to a filter device 11 .

In the embodiment shown, this filtration device has four filters connected in parallel to each other. To which filter 12 belongs.

The flue gas duct 2 and the filtration device 11 are arranged so that the gas velocity in the flue gas duct is approximately 16-2 0 m/s, and the gas velocity within the filter is approximately 0.5-8 m/s. There is.

Each filter 12 is made of ceramic fiber and/or porous metal film. A zero-grain-fiber-ceramic filter with a filter element 13 of Today, there are products on the market that can withstand temperatures up to about 1000°C. filter For example, a rigid matrix of micropores made of silicon carbide particles is coated with mineral fibers. It seems that the clusters are bound together with ceramics so that they do not unravel and are movable. It can be formed into This filter is partly formed as a so-called surface filter. ing. In the case of this surface filter, the porosity with large pores of the filter element The matrix is made of silicon carbide. This matrix has little pressure loss exclusively as a rigid and self-supporting body for the surface membrane. The function of The membrane consists of mineral fibers and silicon carbide particles. The membrane does not come loose & J Such a fibre, which is connected to the support in a manner similar to The router elements are easily cleanable and can withstand temperature changes.

For example, a thin film made of chromium-nickel steel can be used as a metal filter. can be used.

The number of pores (openings) in this film is approximately 10 to 100, depending on the size of the dust particles generated. It has a diameter in the range of μ.

This hole can be drilled, for example, with a laser beam.

Titanium oxide, vanadium oxide as catalytic materials for removing harmful substances chromium oxide, iron oxide, etc., as well as mixtures thereof.

These catalytic oxidizing materials enter the flue in the form of fine particles before the filter 12. Can be introduced into gas ducts. However, in particular and/or additionally, Filter element 13 is coated with the catalytic material described above. The oxidizing substances to be applied are e.g. It can be manufactured by the following method. Finely ground titanium oxide is first dissolved in sulfuric acid. , and this sulfuric acid is evaporated. Then, the melted titanium oxide acts as a catalyst ( Oxidized by other oxides (such as vanadium oxide, tungsten oxide etc.) Processed into a paste-like substance by stirring something with aqueous ammonia . This paste-like substance is usually applied to the surface of the metal filter 13 using, for example, a spatula. clothed. After drying, the applied catalyst layer can withstand temperatures up to approximately 500°C. can.

Under the action of this catalyst material, the nitrogen oxides NOx carried along with the flue gas are Reacts with atomized gaseous ammonia NHs and oxygen to form nitrogen and water.

The absorbent added to the flue gas stream is added to the flue gas stream between the addition and the filter element 13. It reacts with the harmful substances carried along with the gas and is further formed in the filter element 13. It also reacts in the area of the filter cake. The coating layer of the filter element 13 and the shape The resulting filter cake protects the metal film from possible glow combustion. Protect.

The solids dried and separated in the range of the filter 12 are removed from the filter after cleaning the filter 12. from time to time through the gate valve 14 and transported to the silo 16 by the conveyor 15. Ru. Solids are discharged from the silo 16 via another gate valve 17, and the solids are discharged from the silo 16 through another gate valve 17. When released, it is fed to a waste disposal site or is likewise solidified in a press 18. It is returned to the furnace 1 (gate valve 37).

The purified flue gas leaving the filtration device 11 passes through a fan 19 to a switching device 20. reach. The purified flue gas is passed from the switching device to the gas cooler 21 and then to the gas station. The gas is supplied to the tank 22 from which it passes through the gas distribution stage town 23. A gas supply pipe 36 reaches each consumption part (gas pipe 35) from the gas tank 22. can be mixed with gases of lower caloric value, e.g. furnace gas. It means something. Unneeded flue gas is transferred from the switching device 20 to the chimney 2. 4 and can be disposed of by burning. In this case, some of the hydrocarbons present are removed. be removed.

In the case of the device shown in FIG. 2, like reference numbers indicate like parts. Figure 2 A combustion boiler 25 belongs to the device shown in FIG. This combustion boiler has a waste heat boiler. A flue gas duct 2 with an irra 3 (economizer) is connected. combustion boiler is used in power plants to generate electricity. At that time, fuels such as coal and oil The resulting heat energy is used to generate steam, which is used to generate electricity. to drive steam turbines for

The introduction of absorbents, in particular lime products, into the flue gas stream takes place via parts 8, 9.10. , the ammonia gas is introduced via a nozzle 26. In the filtration device 11, the acid NOx, sulfur-containing flue gas components, and are carried together by the flue gas stream. The loose solids are separated.

The injection of Nus into the flue gas stream and the dry separation in the filtration device 11 is carried out at 300-45 It is carried out at temperatures between 0°C.

The dry purified gas stream first passes through an air preheater 28. From this air preheater, Preheated air (tube 31) is fed to the boiler in the usual manner. This method is easy The gas emitted from the 1st 24 (not shown) can be disposed of by burning. Hydrocarbons carried along with the water are also removed. discharged from the filter 12 Solids, especially calcium sulfate, are suspended in a watery suspension with injected oxygen in the stirring device 32. liquefied, international search report international search report DE 89f10331

Claims (13)

[Claims] 1. An absorbent is added to the flue gas stream and this absorbent reacts with the harmful substances, causing the flue gas to The flue gas is separated by a filter (11) together with the solids carried along by the flue gas. combustion boilers, converters, which produce exhaust gases from gas or containing corresponding hazardous substances; Simultaneously drying solid or gaseous substances from equipment such as rotary kilns. In the method for separating, the absorbent is added to the flue gas stream at a temperature above 250°C. At this temperature, along with solids, materials such as ceramic fibers or porous metal films are formed. A method characterized in that the separation is performed by a filter (11). 2. Claims characterized in that the separation is carried out in the temperature range from 250 to 900 °C The method described in box 1. 3. Claims characterized in that the separation is carried out in the temperature range from 300 to 600 °C The method according to item 1 or 2. 4. Claims characterized in that the separation is carried out in a temperature range of 450-500 °C The method described in any one of items 1 to 3. 5. Before the filter, titanium oxide, vanadium oxide, chromium oxide, iron oxide, etc. catalytic oxidizing particles are introduced into the flue gas stream. The method according to at least one of items 1 to 4. 6. The solids separated by the filter are returned to the process producing flue gas or flue gas. At least one of claims 1 to 5, characterized in that Method described. 7. A watery suspension is created from the solids obtained when cleaning the filter, and this A claim characterized in that enzymes are injected into the suspended liquid and gypsum is produced after dehydration. The method according to at least one of items 1 to 6. 8. It is equipped with a combustion boiler (25), a converter (1), a rotary kiln, etc. A flue gas duct or flue gas duct (2) extends from this, which carries the absorbent. comprising a device for adding (10; 26) and at least one filter (12); carrying out the method described in any one of claims 1 to 7, In the device for characterized in that it is equipped with a filter element (13) made of a transparent metal film. Device. 9. Claim characterized in that the filter element (13) is provided with a reinforcement. Apparatus according to clause 8. 10. The reinforcing material is made of synthetic resin and/or metal material. 10. The apparatus according to claim 9. 11. The metal film has pores of 3 to 200 μm, especially 10 to 100 μm. 11. Device according to claim 8, 9 or 10, characterized in that: 12. Ceramic fibers or metal films coated with catalytic materials Claims 8 to 11, characterized in that: equipment. 13. The coating layer may consist of titanium oxide, vanadium oxide, chromium oxide, iron oxide, etc. 13. Device according to claim 12, characterized in that: