Method and device for removal of oxides of nitrogen and oxides of sulfur

 

(57) Abstract:

The invention relates to a power system and can be used in the purification of flue gases of thermal power plants from oxides of nitrogen and oxides of sulfur. The use of this invention provides a more effective process for cleaning the flue gases from nitrogen oxides and sulfur oxides with simultaneous utilization of their heat and the design of the device. The method consists in the fact that the flue gases are mixed with ozonopause mixture desorbed from the recirculation of the condensate is cooled to a temperature below the dew point temperature, in contact with the recirculation of the condensate is saturated with ozone, oxygen and acid components in the absorption section, which has absorbed from the flue gases oxides of nitrogen and oxides of sulfur with simultaneous oxidation and the formation of acidic condensate, much of which is mixed with fresh condensate from the coil and through the hydraulic gravity fed to the recirculation in the case of air, mixed with ozonopause mixture, forming a gas-liquid emulsion, rises with the simultaneous absorption of ozone and oxygen and their chemical wsimages emulsion is separated and desorbed part ozonopause mixture, and recirculating the condensate is saturated with ozone, oxygen and acid components by gravity to the distribution grid, where irrigates the absorption section. The device comprises a treatment zone in the flue holds heat exchanger and absorber sections are installed over the treatment area on the ceiling flue desorbtion distribution section, in which there is arranged in the ceiling flue distributive lattice, the threshold, the inlet pipe with a perforated nozzle, the mouth of the riser pipe of the airlift housing which is connected to the bottom of the flue trap. 2 S. p. f-crystals, 1 Il.

The present invention relates to a power system and can be used in the purification of flue gases of thermal power plants from oxides of nitrogen and oxides of sulfur.

The known method and device for cleaning the flue gases from acidic impurities, which consists in the fact that the flue gas stream is passed through a cooling zone, where the gases are cooled through the tubular wall of the refrigerator to a temperature below the dew point. On the wall surface of the refrigerator is formed condensate containing acidic components, which is in contact with ohlo way device is the low efficiency of flue gases from nitrogen oxides, due to a weak oxidation of nitrogen and sulfur oxides oxygen and insufficient quantity of absorbent acid condensate.

More closest to the technical essence of the present invention is a method of removing sulfur oxides (SOxand oxides of nitrogen NOxof gaseous products, which consists in the fact that the flow of the gaseous combustion products are passed through a treatment zone where it is cooled through the wall of the tube refrigerator in which the cooling fluid to a temperature below the dew point, resulting in the surface of the tube refrigerator condensation containing acidic components. At the time of lowering the temperature of the gas stream to the dew point in the treatment area introducing gaseous ammonia to neutralize the acid condensate components on the surface of the tubes of the refrigerator, after which the purified gas is removed into the atmosphere, and the acidic condensate is removed from the treatment area. A device that implements this method, represents the portion of the flue (treatment area), in which is placed a tubular refrigerator for cooling the gas and the absorption of ammonia gas (heat transfer and absorption sections, the pipe with perforin smeshannyi in the bottom of the duct [2].

The main disadvantages of this method is the low technological and economic efficiency, increased environmental hazard due to insufficient quantity of absorbent acid condensate, low rate of mass transfer between the contacting phases, the use of ammonia in the process and the possibility of leakage into the atmosphere.

The main disadvantage of the known device is the low efficiency of its work, due to the impossibility of increasing the flow of absorbent acid condensate and increase the surface contact between the phases.

The technical task to be solved by the invention, is to improve the efficiency and environmental safety of the process flue gases from nitrogen oxides and sulfur with simultaneous utilization of their heat and the design of the device.

The technical result is achieved by the fact that the proposed method includes the supply of flue gases into the treatment area, placed in the duct, where they are mixed with ozonopause mixture discharged from the recirculation of the condensate, then do the annulus of the tubular Teploobmennik the flue gases and condensation in them steams then go in the absorption section, where contact with the recirculation of the condensate is saturated with ozone, oxygen and acid components flowing through cracks distributive lattice on the surface of the nozzle and absorbing oxides of nitrogen and sulfur, on the bottom of the absorption section, where the acidic condensate is removed from the treatment area, and the purified flue gases in the flue output into the atmosphere; formed in the heat exchanger fresh condensate flows down the outer surface of the pipe in contact with the mixture of flue gases, ozone and air, on the bottom of the duct where it mixes with a large part of the acidic condensate, representing a mixture of dilute nitric and sulfuric acid, the mixture is acidic and fresh condensate by gravity through the hydraulic flow to the recirculation in the lower part of the housing of the airlift, which also comes osvobozdeniya mixture, which, passing through the holes in the mixer airlift forms when a gas-liquid emulsion rising due to its small weight lifting up the airlift pipe with simultaneous absorption of ozone and oxygen from the air and their chemical interaction with oxides of nitrogen, sulfur and water; saturated recircle separated and desorbed part ozonopause mixture, which then mixes with the combustion gases and recirculating the condensate is saturated with ozone, oxygen and acid components by gravity to the distribution grid, where irrigates the absorption section.

The method is implemented in the device shown in the drawing.

The device comprises a treatment zone consisting of a section of the duct 1, in which is placed a pipe with a perforated nozzle 2, the lifting pipe airlift 3, the heat exchange section 4, the absorption section 5 which is located above the treatment area on the ceiling flue desorbtion distribution section 6, in which there is arranged in the ceiling of the duct 1 distribution grid 7, the threshold is 8, the inlet pipe with a perforated nozzle 2, the mouth of the riser pipe of the air pump 3, is placed in the bottom of the flue 1 fitting 9, the hydraulic lock 10, which connects the bottom of the duct 1 to the housing of the air pump 11, where the lifting pipe 3 with a mixer 12 and duct 13 through the duct 1 and opening his mouth in desorbtion distribution section 6.

The proposed method of removal of nitrogen and sulfur oxides from flue gases is carried out in the proposed device, as follows. Smoke g is Noah mixture, released from the saturated condensate recirculation in desorbtion distribution sections 6 and entering the flue 1 due to the higher pressure in sections 6 through a pipe perforated with nozzle 2, after which the gas mixture is directed into the annulus heat transfer section 4, the pipes which circulates a refrigerant (for example, feed water or blowing air), where it is cooled to a temperature below the temperature of the dew and equal (80-90)oC, the value of which is taken to ensure complete condensation of all water vapour in the flue gases, and the possibility of carrying out the oxidation of insoluble nitrogen monoxide (NO) and dioxide (NO2), the balance of which is moved to the right at a temperature below 100oC, and flows entirely in the direction of education NO2[3, S. 347]; the lower limit of cooling is limited to the necessary value of temperature pressure. Along with the cooling in the annular space section 4 is the interfacial contact downstream of the condensate from the gas mixture, the chemical interaction of the oxides in the flue gases, ozone, oxygen, water between the gas and liquid phases, the absorption of the formed nitrogen dioxide (NO2) and sulfur dioxide the new mixture greatly increases the reaction rate of oxidation [4, C. 180]. The resulting fresh condensate flows down the outer surface of the pipe on the bottom of the duct 1, which is mixed with the acidic condensate and cooled flue gases with ozonopause mixture arrives in the absorption section 5, filled with nozzle (which it is desirable to use a nozzle with a large living section and a low hydraulic resistance), on which surface through cracks distributive lattice 7 flows circulating condensate saturated with ozone, oxygen and acid components, which is in contact with a gas mixture with a simultaneous process of absorption of nitrogen and sulfur oxides, and chemical reactions similar to reactions held in the annular space of the heat exchange section 4 with the formation of nitric and sulphuric acids, but with higher speed, due to the larger surface mass transfer, high density, irrigation, carrying out oxidation reactions mainly in the liquid phase, which greatly increases its speed, and the presence of condensate dissolved ozone and acids, which are the catalysts of nitrogen and sulfur oxides [5, S. 10, 14], resulting from flue gases is removed a significant portion of the nitrogen oxides and senasica acidic condensate, representing a mixture of dilute nitric and sulphuric acid flows down to the bottom of the absorption section 5, where a portion of it equal to the amount of water vapor in the flue gases are removed from the treatment area through the nozzle 9, and a large part is mixed with fresh condensate and through the water seal 10, the height hris determined by the pressure above the surface of the condensate in the housing of the air pump 11 and which serves to prevent breakthrough of air from the housing of the air pump 11 in the absorption section 5, enters the body of the air pump 11, which is also the duct 13 serves Ozonesondes mixture, which, passing through the holes of the mixer 12, is mixed with the acidic condensate, forming a gas-liquid emulsion with the developed interfacial surface that provides a high rate of mass transfer between the gas and liquid phases and respectively intensive absorption of ozone and oxygen condensate [6, S. 483], high speed chemical interaction between the components of the mixture; the resulting gas-liquid emulsion due to the small specific gravity rises by lifting the pipe airlift 3 [7, s 8], which has a height (H-h) is determined by the height of the flue 1, flows out of the mouth of the pipe 3 in desorbtion distribution section 6, where from the high pressure coming into the flue gas duct 1 and is mixed with the combustion gases, and the rest of intense recirculation of the condensate by gravity to the distribution grid 7 (screening area which is chosen such that the layer of condensate on the lattice 7 created hydraulic resistance sufficient to prevent leakage ozonopause mixture through her slit and then by the absorption nozzle section 5, after which the process is repeated. The rate of circulation of the condensate is determined by the amount of water vapor in the flue gas and the flow rate of the absorbent (condensate), necessary for the absorption of oxidant (ozone and oxygen), sufficient for complete oxidation of oxides of nitrogen and oxides of sulfur.

In turn, the air flow to the process is determined by the flow rate of the oxidizer and equal to 2-3% of the flow of flue gases.

Thus, the proposed method and device provide significant improvements in efficiency and environmental safety of the process flue gases from nitrogen oxides and sulfur oxides with simultaneous heat recovery.

Bibliography

1. Application France N 2592812, Ál.4B 01 D 53/34, 1986.

2. U.S. patent N 4753784, Ál.4B 01 D 53/34, 1986.

3. Kutepov, A. M. and other General chemical those who P CLASS="ptx2">

5. Kuznetsov, I. C. New methods of gas purification from nitrogen oxides. - K.: RBM, NINTI, 1971, 45 S.

6. Kafarov centuries fundamentals of mass transfer. - M.: Higher school, 1972, S. 493

7. Paralo L. C. air / gas lifts liquid. - M.: Mashinostroenie, 1969, 160 C.

1. Method of removing nitrogen oxides and sulfur oxides from flue gas, comprising cooling the flue gases to a temperature below the dew point, condensation of water vapor in a tubular heat exchanger, mixing the flue gas with a gaseous reagent, removing the cleaned flue gases and part of the acidic condensate from the treatment area, wherein the flue gases before cooling, is mixed with ozonopause mixture desorbed from the recirculation of the condensate after cooling contact with the recirculation of the condensate is saturated with ozone, oxygen and acid components in the absorption section, which has absorbed from the flue gases oxides of nitrogen and oxides of sulfur with simultaneous oxidation and the formation of acidic condensate, much of which is mixed with fresh condensate from the coil and through the hydraulic gravity fed to the recirculation in the case of air, mixed with Ozonesondes is Suha and their chemical interaction with the components of the condensate by lifting the pipe airlift in desorbtion distribution section, where the emulsion is separated and desorbed part ozonopause mixture, and recirculating the condensate is saturated with ozone, oxygen and acid components by gravity to the distribution grid, where irrigates the absorption section.

2. A device for removing nitrogen oxides and sulfur oxides from flue gases, comprising a treatment zone in the flue holds heat exchanger and absorber sections, a pipe with a perforated nozzle, characterized in that above the treatment area on the ceiling duct placed desorbtion distribution section, in which there is arranged in the ceiling flue distributive lattice, the threshold, the inlet pipe with a perforated nozzle, the mouth of the riser pipe of the airlift housing which is connected to the bottom of the flue trap.

 

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