DE3511669A1 - Process for removing gaseous pollutants from flue gases, and apparatus for carrying out the process - Google Patents

Abstract

A process for removing gaseous pollutants from the flue gases of furnace plants is described, in which the pollutants are reacted in aqueous solution with suitable chemical substances and/or the flue gases are discharged via a stack or the like. In this case, the hot flue gases are cooled essentially as far as the dew point, the cooled gases together with the condensing water are conducted over solid substrates, which are composed of at least partially the suitable chemical substances, so that the condensate together with the pollutants dissolved therein forms the aqueous solution, and finally the purified flue gases are discharged.

Description

The invention relates to a method of removal

of gaseous pollutants from the flue gases of combustion systems, taking the pollutants in aqueous solution with suitable chemical substances can react and discharges the flue gases through a chimney or the like, as well an apparatus for performing this method.

Fossil fuel firing systems are known to contain Large amounts of sulfur oxides in their flue gases, which are a major contributor to environmental pollution with their known harmful consequences.

The large combustion systems, which are being rebuilt today, provide one in general with desulphurisation plants, already existing plants will be partly retrofitted or shut down.

The desulphurisation systems in use today, those in large combustion systems They mostly work with the lime washing process - wet desulphurisation -, whereby the flue gas after Abt filtering the dust contained in it with lime water is sprayed. The lime reacts with the sulfur dioxide to gypsum, which then follows Drying is stopped. In a similar process, ammonia water is used instead of lime water used, in which case the end product is ammonium sulfate, which is used as an artificial fertilizer in the Agriculture can be used.

This well-known principle is also used in a simplified form for smaller ones Combustion systems are used, but with a minimum heat output of 200 kW for reasons of profitability are required. For reasons of cost, small systems are for single and smaller Apartment buildings out of the question for combustion systems up to 50 kW.

In a known method for smaller combustion plants the flue gases are cooled by blowing in tap water, after which the condensate is passed through neutralizing media and fed into the sewer. at However, this method involves, on the one hand, high water consumption or

a high amount of wastewater, on the other hand, this process only use in connection with new systems, as new boilers are in connection with suitable chimneys to be newly constructed are required.

Another known method is by means of so-called fixed bed catalysis in temperature ranges of over 3000 C carbon monoxide and hydrocarbons to carbon dioxide and water, but with sufficient amounts of oxygen in the flue gas to be processed required are. Sulfur oxides cannot be removed with this process.

In another known method, the flue gases are via a Layer of lattice bricks passed, contaminated with absorbent substances are. A heat exchanger is arranged within these lattice bricks. However, since the stone masses store the heat to a high degree, the proportions of the im Fixed bed arranged heat exchanger uncontrollable, so that the systems only It is extremely difficult to regulate and also the discontinuous, with smaller combustion systems Usual operation is not possible when high efficiencies in removing the Pollutants are to be reached.

Based on the aforementioned prior art, it is therefore an object of the present invention for smaller, possibly already existing heating systems to show a method according to the preamble of the main claim, which is a cost-effective and yet allows effective removal of pollutants from the flue gases, as well to provide an apparatus for performing this method.

This task is achieved with a method according to the preamble of the main claim solved by cooling the hot flue gases essentially to the dew point, the cooled gases together with the condensing water over solid substrates which at least partially consist of the appropriate chemical substances, so that the condensate together with the pollutants dissolved in it the aqueous Solution forms, and discharges the so purified smoke gases.

By having the water required for the chemical reaction Removes flue gases, there is no additional fresh water supply, so that the operating costs can be reduced significantly. Furthermore, the flue gas during the cooling Heat withdrawn for another purpose, e.g. domestic water heating are supplied so that the efficiency of the combustion system increases considerably, which in turn significantly shortens the payback periods.

In a preferred embodiment of the method according to the invention the flue gases are led from the surrounding area before they are discharged into the chimney to and increases the pressure of the resulting mixture.

This ensures that the initially water-saturated Smoke gases after leaving the decontamination substrate in a lower relative ~ air11 moisture are transferred, so that it does not occur with further cooling in the chimney Dreaded condensation can occur there.

Furthermore, the train of the system is guaranteed by the pressure increase.

Preference is given to passing excess condensate to further suitable ones Substances in which this is detoxified or neutralized.

For safety reasons, it is particularly advantageous if the pressure difference of the flue gases over the solid substrates so between entry and the exit of the smoke gases to the substrates and, if the measured value is too high, the indicates a blockage, bypassing the fumes on the solid substrates. on In this way it is guaranteed that the combustion system does not resist excessively high flow resistance have to work.

A device is suitable for carrying out the method described which has a heat exchanger connected to the combustion system and a coolant circuit is connected in such a way that the flue gases discharged from the combustion system Heat is withdrawn. Furthermore, a reaction container is arranged in the device, the one with a flue gas inlet at the outlet of the heat exchanger, with a flue gas outlet connected to the chimney.

A gas-permeable first substrate bed is gas-tight in the container arranged between the flue gas inlet and the flue gas outlet. Through this series connection The heat exchanger and reaction vessel ensure that the reaction is rapid on changed conditions z. B. can be done when switching the system on and off, so that the reaction vessel operated at essentially constant conditions can be, which in turn significantly increases its efficiency in detoxification. A relaxation space is advantageously located between the substrate bed and the flue gas inlet arranged for the flue gases. The gas coming from the heat exchanger is therefore in this Room initiated first. From there it flows through the substrate bed in the direction of the flue gas outlet and from there to the fireplace.

The substrate bed can or else consist of a homogeneous layer also made up of several layers separated by relaxation rooms for the flue gases are.

The substrate layer here advantageously consists of a neutralizing acting granules or powder, or from solids, which preferably have pores and are shaped accordingly to create a large surface area (e.g. B. are rolled up like corrugated cardboard) and with the corresponding neutralizing Substances are contaminated. The amount of substance should be measured so that at least A sufficiently high neutralization capacity is ensured over a whole year is.

Advantageously, calcium carbonate, Barium oxide, ammonium bicarbonate, caustic soda, milk of lime or the like are used.

In addition, activated carbon, sintered glass or the like can be used in the substrate beds be arranged for further detoxification.

Advantageously, there is an inlet opening for air in the flue gas outlet provided from the surrounding space, after the inlet port pressure increasing means, such as z. B. a fan or the like, which the resulting gas mixture to the fireplace respectively.

In this way it is ensured that the exhausted smoke gases a have low relative humidity, so that it is the next, in the chimney following Cooling does not result in falling below the dew point.

In a preferred embodiment of the device is a second Substrate bed spatially below the first gas-permeable substrate bed in the reaction vessel arranged, and also provided an overflow nozzle, which relative to the second Substrate bed is arranged so that the amount of water from the second substrate bed can no longer be collected via this overflow nozzle into the sewer can be discharged. The excess amount of water preferably flows here through the second substrate bed and is neutralized there.

In order to ensure that the However, it is advantageous to ensure the combustion system is located between the flue gas inlet and the flue gas outlet a Syasleitun is provided in which valve means, e.g. Legs Smoke damper, for locking or releasing are arranged. With the valve means is a flifferenzdruckmeßorgan in operative connection, which the differential pressure in the direction of flow measured before and after the gas-permeable first substrate bed seen. When exceeded a presettable differential pressure level then opens the differential pressure measuring element the valve means so that the smoke gases no longer pass through the substrate bed but go directly into the chimney.

The differential pressure measuring element is advantageously at the same time Valve means in the coolant circuit in operative connection, so that when exceeded the presettable differential pressure level, the coolant circuit is also closed will. In addition, the pressure increasing means are also advantageously at Exceeding the differential pressure level switched off. In this way it is guaranteed that in the event of malfunctions in the reaction vessel, the combustion system works in a conventional manner works so that the flue gases are at their original temperature as they come out come from the combustion system, get into the chimney and flow off freely there.

The heat exchanger preferably consists of individual elements that have Clamping devices for units of any length in gas- or liquid-tight connection are packable together. With this embodiment of the heat exchanger it can be ensured that the smoke gases are on the for the detoxification process necessary temperature can be cooled with exact adjustment, as the heat exchanger be dimensioned larger or smaller depending on the thermal output of the combustion system can. So you don't have to control the coolant circuit, as has been the case up to now, but can determine the capacity of the heat exchanger itself.

The individual elements advantageously consist of pieces of inner pipe with ribs protruding radially outward and parallel to the pipe axis, which are closely enclosed by outer pipe elements, the inner pipe pieces preferably as Castings are formed. The water flow takes place in countercurrent to the flue gas in the central pipe, while the flue gases flow through the central pipe outside. The ribbing is a good one Heat transfer guaranteed.

The heat transfer elements arranged on the central tube, d. H. the Ribs are advantageously arranged and designed so that the of several Heat exchangers composed of individual segments are easily removed from residues (e.g. soot, Flying coke, tarry components) can be cleaned. This is due to the star-shaped Reached rib arrangement, which is streamlined in the axial direction. In general, simple cleaning can be achieved by z. B. with a special cleaning brush each between a pair of ribs on the whole Heat exchanger length passes through.

The outer pipe elements can be firmly connected to the inner pipe pieces be (e.g. by casting on). However, separate outer tubular elements can also be used be arranged around the inner pipe pieces. The outer tube elements can be used as one inside the other be designed slidable pipe pieces, or as pipe half-shells can also be built up by segment.

In both preferred embodiments, there is simple disclosure of the heat exchanger possible, so that the above-mentioned cleaning can be done easily can.

The number of individual segments required in each individual case is determined by two lids attached at both ends closed, which in turn have a continuous Central rod to be connected to each other. The individual elements are preferably braced via thread and associated nuts.

Of course, the individual elements are manufactured in this way or by Seals connected to one another in such a way that the interior is tightly sealed off from the exterior so that no cooling medium can escape.

The cooling medium is fed into the central tube through the Lid or a single segment at the entrance of the heat exchanger, e.g. B. in the way, that the feed pipe passed through the cover to the end of the heat exchanger where then the cooling medium enters the interior of the inner pipe section and flows back against the direction of flow of the flue gases.

There is also a supply of the medium directly through the lid or possible through a single segment at the end of the heat exchanger. Preferably im Corresponding turbulence elements attached to the interior of the inner pipe pieces ensure that over the entire cross-section of the inner pipe section a uniform Heat distribution in the cooling medium is given.

The heat exchanger can advantageously also consist of groups of individual elements exist, the z. B. are connected to each other via 900 or 1800 manifolds.

In this way, the system can be particularly suitable for the given space can be easily adjusted.

This can be achieved, for example, in that the inner pipe pieces In the crinkling area from cover to cover, connecting pipes for the flow and return of the cooling medium. It is also possible to use compact parts to reduce the area of curvature to bridge, which essentially correspond to the normal axial individual elements. The outer pipe elements for guiding and limiting the outside of the flue gases can be in the area of curvature be replaced by a corresponding pipe elbow. With compact individual elbow segments (with molded outer pipe elements ) this is also possible.

The individual elements are advantageously cast from aluminum and, if required, can be given a surface coating in the flue gas duct Protection against the acidic components in the flue gases. Plastics are suitable for this or enamel. The same applies of course to other individual parts, which are exposed to the smoke gases, whereby one can also use resistant stainless steels can use.

Due to the construction of the heat exchangers described in segment design it is achieved that not only the desired flue gas temperature can be reached exactly can, but also only those costs that are absolutely necessary are.

Furthermore, it is due to the preferred embodiment of the heat exchanger possible the annual energy costs (for gas, oil or coal) by up to 15% lower, resulting in a short-term amortization of the cost given is.

The invention results in a reduction in sulfur oxides in the annual mean uin.ca. 909G achieved, whereby the necessary investment costs extremely are low. In particular, it should be noted that no additional Costs such as B.

The chimney or the other parts of the furnace are converted. The cleaning and maintenance of the entire system is easy to accomplish, the neutralized Condensates can be drained into the public sewer system.

The following are preferred embodiments of the invention Device based on exemplary embodiments explained in more detail, which are shown in figures. 1A shows a cross section through an inner tube length of the heat exchanger along the line A-A of Fig. 1B; Figure 1B a longitudinal section through an inner pipe piece according to Figure 1A along the line B-B; 2 shows a longitudinal section through a complete heat exchanger; 3A, B manifold elements a heat exchanger according to FIG. 2; 4 shows a schematic diagram of a system with Heat exchanger, reaction vessel, bypass and chimney; Fig. 5 is a schematic diagram of the Arrangement of a complete system, and FIGS. 6A-C various spatial arrangement forms of the system.

According to Fig. 1, the inner pipe pieces 20 consist of pipe sections, which are provided with ribs 21 protruding outward in a star shape, between which the room 31 for the flue gases takes place. The inner pipe pieces are advantageous here designed as castings, the ribs 21 the flue gas flowing through the Withdraw heat and give it off to the cooling medium in the interior 32 of the inner pipe sections 20. The additional formation of ribs and / or turbulence elements is also a matter of course possible inside the inner pipe section.

In Fig. 2, a complete heat exchanger is shown, which consists of Inner pipe pieces 20 according to FIG. 1, which are placed on top of one another with end pieces 15A and 15B are completed.

The end pieces 15A and 15B are provided with central bores, through which is guided by a tie rod 13 which has threaded projections at both ends. In a departure from the embodiment shown, the inner pipe pieces can also be different Have length.

On the thread lugs sit nuts over which the inner pipe pieces 20 can be clamped together.

The coolant inlet 12 and the coolant outlet open into one cover 15A 10, the coolant inlet 12 via an extension pipe up to the vicinity of the second cover 15B is performed. In this way it is ensured that the cooling medium from one end of the inner tube back to the other end and there to the coolant outlet 10 flows.

Opposite the opening of the coolant inlet 12 is a valve cone 5 arranged, which sits on an actuating rod, the liquid-tight through the second cover 15B is guided to the outside.

With this arrangement, the coolant circuit can be interrupted.

In Figs. 3A and 3B two bends are shown which are used to build the heat exchanger from groups of individual segments in any shape. Here, the outer pipe elements 24 are connected via a curved outer pipe element 24B or 24C, while the inner pipe elements are connected via elbows 15C and 15D, respectively are.

The heat exchanger according to the invention is operated as follows: Through the coolant inlet 12, water z. B. from the heating return of a central heating system passed into the interior 32 of the inner pipe pieces 20 and flows there to the return 10 back.

The flue gas is through the outer space 31 between inner pipe pieces 20 and outer tube elements 24 out against the coolant flow. Over the ribs 21 the heat exchange takes place from the flue gas to the coolant.

With this energy recovery, the heating operator can, depending on the Saving proportions of up to 15% of heating costs. At the exit of the heat exchanger the flue gases are cooled to a temperature of about 1000 C, so that the condensation begins.

The complete system is described below with reference to FIG. The flue gases passed through the heat exchanger enter a flue gas inlet 210, which leads into the interior of a reaction container 200. The flue gas inlet 210 leads into a relaxation room 212, above which a substrate bed 214 is arranged. That Substrate bed consists either directly of the suitable substances or of one Solid contaminated with the appropriate substances. Here is the substrate bed so loosely built that the flue gases flow through with only a slight loss of pressure can. Characterized in that the flue gas by the heat extraction in the heat exchanger 2 on a If the temperature is relatively low, the water condenses in the flue gas. The resulting fine droplets adhere to the solid interfaces in the substrate bed at. Further condensation takes place at the interfaces, with the liquid penetrates further into the interior of the solid. The pollutants dissolve in the liquid, especially the sulfur oxides eager, so that now the pollutants in aqueous Solution available. In this aqueous solution they react with the active one Material of the substrate bed, with a catalytic oxidation at the same time from SO2 to SO3 and from sulfite to sulfate takes place. Part of the water will z. B. bound in the production of gypsum, the balance residue drips down.

After the flue gas has flowed through the substrate bed 214, it arrives it into a space 218 above the substrate bed and from there into a flue gas outlet 220. There are openings 222 in the flue gas outlet 220. At the end of the flue gas outlet 220 a fan wheel 110 is attached, which has an external electric motor 113 is driven.

This arrangement ensures that the smoke gases do not come out the openings 222 can escape, but rather ambient air the flue gases is admixed.

The gases emerging from the fan wheel 110 then pass through a Line 240 into chimney 100.

Between the flue gas inlet 210 and the flue gas outlet 220 or the Line 240 to chimney 100, a pipe section 230 is provided as a bypass. This piece of pipe 230 is normally closed by a flap 117. In room 218 above the Substrate bed 214 protrudes a differential pressure mechanism 114, which with its other End communicates with the flue gas inlet 210, so that it is with the differential pressure is acted upon above the bed of solids 214.

The flap 117 is via a lever connection with the operating rod of the valve cone 5 connected in such a way that when the flap 117 is opened, the valve cone 5 is pressed onto the opening of the coolant inlet 12.

Furthermore, the flap 117 is connected to a connecting means 107 Switch 116 in connection, which turns the motor 113 on and off. This connection 107 is such that when the flap 117 is opened (counterclockwise) the switch 116 is opened, so that the electric motor 113 is put out of operation will.

The differential pressure measuring element 114 acts in such a way that with an increased differential pressure the flap117 is released so that it is positioned in the direction of flow and releases the bypass. In this way it is guaranteed that if the substrate bed is clogged 214 on the one hand, the flue gases pass directly from the heat exchanger 2 into the chimney 100, on the other hand, the heat exchanger is out of operation by switching off the coolant circuit is set so that the flue gases are now at the usual high temperature in the chimney 100 can flow.

As soon as the system is switched off, the flap 117 closes again, so that when the furnace is started up again, the differential pressure is measured again and thus the permeability of the substrate layer 214 is checked again, after which the bypass 230 is opened again if necessary.

A second substrate bed 216 is arranged under the substrate bed 214, drips into the excess water from the first substrate bed 214 and neutralized there will. After neutralization, excess condensate flows through an overflow nozzle 224 into sewers (not shown).

Fig. 5 shows a complete system in a schematic arrangement. The system is connected between a boiler 1 and a chimney 100. Of the Functionally necessary heat exchanger 2 is arranged in front of the reaction vessel 200. If the coolant inlet 76 in the heat exchanger 2 is shut down, the direct inflow 78 comes into effect. In addition is the heat exchanger provided with a safety valve 77.

6A-6C are various forms of arrangement of the invention Device shown by the special shape variability of the Heat exchanger 2 can be made possible, so that you can connect the system to any existing room can customize.

Claims (11)

Process for removing gaseous pollutants from flue gases, and device for carrying out the method PATENT CLAIMS 1. Method for Removal of gaseous pollutants from the flue gases of combustion systems, taking the pollutants in aqueous solution with suitable chemical substances lets react and discharges the flue gases through a chimney or the like, thereby It is not noted that - the hot smoke gases are essentially up to cools to the dew point, - the cooled gases together with the condensing Water carries over solid substrates, at least partly from the appropriate chemical Substances exist, so that the condensate together with the pollutants dissolved in it forms the aqueous solution, and - removes the thus cleaned flue gases. 2. The method according to claim 1, characterized in that g e k e n nz e i c h n e t, that this air is supplied from the surrounding space before the exhaust gases are discharged and increases the pressure of the resulting mixture. 3. The method according to any one of claims 1 or 2, characterized g e k e n It is not noted that excess condensate can be added to other suitable substances and the pollutants dissolved therein chemically and / or physically binds. 4. The method according to any one of claims 1 to 3, characterized g e k e n n z e i c h n e t that one can determine the pressure difference of the smoke gases over the solid substrates measures and, if the measured value is too high, directs the flue gases past the solid substrates. 5. Apparatus for performing the method according to claim 1, g e k e n n n z e i n e t by - a heat exchanger (2) connected to the combustion system (1) and a coolant circuit (10, 12) is connected in such a way that the heat is extracted from the flue gases removed from the combustion system (1); - a reaction vessel (200) with a flue gas inlet (210) to the outlet of the heat exchanger (2) and connected to a flue gas outlet (220) to the chimney (100) is, and - a gas-permeable first substrate bed (214), which is in gas-tight connection with the reaction vessel (200) between the flue gas inlet (210) and the flue gas outlet (220) is arranged. 6. Apparatus according to claim 5, for performing the method according to one of claims 1 or 2, g e k e n n n z e i c h n e t through - an inlet opening (222) in the flue gas outlet (220) and - pressure increasing means (110/113) between the flue gas outlet (220) and fireplace (100). 7. Device according to one of claims 5 or 6 for implementation of the method according to claim 3, g e k e n n n z e i c h n e t through - a second Substrate bed (216) which is spatially below the gas-permeable first substrate bed is arranged in the reaction vessel (200), and - an overflow nozzle (224), the is arranged relative to the second substrate bed (216) so that the amount of water 1 which can no longer be collected by the second substrate bed (216), via the Overflow nozzle (224), preferably after flowing through the second Substrate bed (216) can run off. 8. Device according to one of claims 5 to 7 for performing the Method according to claim 4, g e k e n n z e i c h n e t by - a BY, Jass line (230) between the flue gas inlet (210) and the flue gas outlet (220), valve means (117) for locking or releasing the bypass line (230), and - a differential pressure measuring element (114), its first measuring point in front of and its second as seen in the direction of flow The measuring point is arranged behind the gas-permeable first substrate bed (214) and which is in operative connection with the valve means (117) in such a way that when exceeded a presettable differential pressure level, the valve means (117) are opened and if necessary the pressure increasing means (110, 113) deactivated via switching means (116) will. 9. Apparatus according to claim 8, characterized in that g e -k e n n z e i c h n e t that the differential pressure measuring element (114) continues with valve means (5) in such a way is in operative connection that when the presettable differential pressure level is exceeded the coolant circuit (10, 12) is closed. 10. Device according to one of claims 5 to 9, characterized g e k e n n z e i c h n e t that the heat exchanger (2) consists of individual elements (20, 21; 24) consists of clamping devices (13) to form units of any length in gas- or liquid-tight Connection can be packed together. 11. The device according to claim 10, characterized in that g e -k e n n z e i c h n e t that the individual elements from inner pipe pieces (20) with radially outwardly protruding and ribs (21) running parallel to the pipe axis, which are formed by outer pipe elements (24) are essentially tightly enclosed, the inner tube pieces (20) preferably are designed as cast parts.