RU2371239C2 - Complex method and device for cleaning and recovery of smoke fumes with receiving of methane - Google Patents

Abstract

FIELD: heating.

SUBSTANCE: invention relates to heat and power engineering and can be used during the cleaning and recovery process of smoke fumes of heat and power installations for protection of ozone screen and reduction of greenhouse effect of ambient air. Cleaning method includes cooling of smoke fumes up to temperature lower the dew point, condensation of water vapor, release of carbon dioxide by absorption and withdrawal of cleaned smoke fumes into the atmosphere. Cleaning of smoke fumes includes absorption of nitric oxides, sulphur oxides, carbon dioxides, drips and water vapors by nontreated sludge of waste water with its simultaneous heating in absorption tower up to fermentation temperature 30-50°C, washing of waste and cooled gas against remains of nontreated sludge by raw water in flushing tower, separation of received mud mixture by means of sedimentation to muddy water and saturated raw sludge in settling tank, withdrawal of muddy water to irrigated fields, mixing of saturated heated raw sludge from absorption tower with sediment from settling tank, fermentation of saturated heated raw sludge in anaerobic digester with receiving of methane and digested sludge. Device for method implementation contains transit gas pipeline 1, heat exchanger 6, stripping 7 and flushing 15 towers, herewith transit gas pipeline 1 is branched to reserve gas pipeline 2 with slide valve 3, connected to smokestack and actuation gas pipeline 4 with slide valve 5, connected successively to heat exchanger 6, absorbing tower 7, inside which downright there are located transversal inclined interlocking partition 8 with aperture 9 in the form of segment in its bottom part, direction of inclination of which is in turn changes in opposing sides, herewith absorbing tower 7 in its top part is outfitted by feeding branch of raw sludge 10, located on inlet into the first from above interlocking partition 8 and build into in top cover by branch pipe of inlet of treated gas 11, connected to reverse actuation gas pipeline 12, and in its bottom part is outfitted by feeding branches of initial gas 13 and saturated raw sludge, agreeably. Reserve actuation gas pipeline 12 is connected also to flushing tower 15, in top part of which it is placed liquid 16, connected to pipeline of raw water 17, herewith its bottom part is connected by pipeline 18 to settling tank 19, top part of which is connected to pipeline of muddy water 20, and bottom part- to pipeline of raw sludge 21, which, in turn, is connected to anaerobic digester 22.

EFFECT: increasing ecological and cost-effectiveness of cleaning process of smoke fumes of heat and power intallation.

2 cl, 2 dwg

Description

The present invention relates to a power system and can be used in the cleaning and utilization of flue gases from thermal power plants of thermal power plants to protect the ozone shield and reduce the greenhouse effect of the surrounding atmosphere.

A comprehensive method for cleaning and utilizing flue gases is known, including cooling the flue gases in the 1st stage heat exchanger to a temperature below the dew point, condensing water vapor, mixing the flue gases with an ozone-air mixture, oxidizing and absorbing nitrogen oxides and sulfur oxides obtained by the condensate, followed by cooling in the heat exchanger of the 2nd stage and the interaction of CO ₂ with calcium hydroxide to form calcium nitrite and calcium nitrate (Ca (NO) ₂ and Ca (NO) _3, respectively. The device in which the method is implemented consists of a box, in The plate heat exchangers of the 1st and 2nd stages, cooled by blast air, and perforated cassettes coated with a layer of calcium hydroxide are placed by a otor [1].

The disadvantages of the known method and device include a short duty cycle and a limited absorption capacity for carbon dioxide cassettes coated with calcium hydroxide, the frequency of operation and low productivity of the device.

Closer in technical essence to the present invention relates to a method for the release of carbon dioxide, which also consists in cooling the flue gas to a temperature below the dew point with the formation of condensate of water vapor and the subsequent release of carbon dioxide from them due to the difference in the density of carbon dioxide and nitrogen and absorption (absorption ) carbon dioxide obtained condensate of water vapor, implemented in a device containing a transit gas duct, in the bottom of which there is a window connected to a vertical cor whisker, inside which there are shell-and-tube heat exchanger, an absorption (absorption) and desorption cooling section, a suction hood connected to a fan and a drying agent, and the housing bottom is connected via a circulating pump with liquid distributor pipes [2].

The disadvantages of the known method and device include a small amount of trapped nitrogen oxides and carbon dioxide, due to their limited solubility in water, the inability to use trapped carbon dioxide to reduce fuel consumption, which reduces the economic and environmental efficiency of flue gas cleaning.

The technical result of the invention is to increase the environmental and economic efficiency of the process of cleaning flue gases from thermal power plants.

The technical result is achieved in an integrated method for purification and utilization of flue gases to produce methane, which includes cooling the flue gas to a temperature below the dew point, condensation of water vapor, absorption of nitrogen oxides, sulfur oxides, carbon dioxide, condensate droplets and water vapor with a crude sewage sludge with by simultaneously heating it in the absorption tower to the optimum fermentation temperature due to the heat of the flue gases, washing the treated gases from the residues of the raw sludge with raw water in the washing tower and removing flue gases to the atmosphere, separation of the resulting mud mixture by settling on dirty water and saturated crude sludge in the sump, drainage of dirty water to irrigation fields, mixing of saturated heated sludge from an absorption tower with sludge from a sump, fermentation of saturated heated sludge in a digester with obtaining methane and fermented sludge.

The method is implemented in a device containing a transit gas duct branched into a reserve gas duct with a gate connected to a chimney, and a working gas duct with a gate connected in series with a heat exchanger and an absorption tower, inside of which inclined grating partitions are arranged from top to bottom with an opening in the form of a segment in its the lower part, the direction of the slope of which alternately changes in opposite directions, and the absorption tower in its upper part is equipped with a raw sediment supply pipe located at the input de to the first inclined grating partition from the top and a processed gas outlet pipe integrated in the upper cover connected to the return working gas duct, and in its lower part equipped with nozzles for supplying the source gas and saturated crude sediment, respectively, while the return working gas duct is also connected to the washing tower, in the upper part of which is placed a liquid distributor connected to the raw water pipeline, and its lower part is connected by a pipeline to a sump, the upper part of which communicates with the piping vodom dirty water, and the lower part is connected to the conduit saturated crude precipitate which, in turn, connected to the digester.

The basis of the work of the proposed method and device is: features of the composition of the flue gases of heat power units, the main components of which on the basis of experimental data and calculation of the composition of the products of combustion, are nitrogen (76-82) vol.%, Carbon dioxide (7-14) vol.% water vapor (5-17) vol.%, the concentration of which depends on the type of fuel and method of combustion [3, p.15]; a significant excess of the solubility of carbon dioxide in the raw sewage sludge due to the presence of proteins, fats and other organic compounds in it over its solubility in pure water [4, p. 490] and the possibility of methane production by fermentation of the raw sewage sludge [5, p. 263].

A device for cleaning and utilizing flue gases with the conversion of carbon dioxide to methane is shown in figures 1, 2.

The device comprises a transit gas duct 1 branched into a reserve gas duct 2 with a gate 3 connected to a chimney (not shown in FIG. 1), a working gas duct 4 with a gate 5 connected in series with a heat exchanger 6 and an absorption tower 7 inside of which are arranged from top to bottom transverse inclined lattice partitions 8 with an opening 9 in the form of a segment in its lower part, the direction of the slope of which changes alternately. The absorption tower 7 in its upper part is equipped with a raw sediment supply pipe 10 located at the inlet of the first trellised partition 8 and a processed gas outlet pipe 11 connected to the return working gas duct 12, and in its lower part is equipped with a source gas supply pipe 13 and output saturated crude sediment 14, respectively. The washing tower 15 is connected by a return working gas duct 12 to the absorption tower 7, with a liquid distributor 16 connected to the raw water pipe 17 at the top of it and the lower part connected by a pipe 18 to a sump 19, which is connected from above to the dirty water pipe 20, and bottom with a pipeline of saturated crude sediment 21, which, in turn, is connected to a digester 22.

Cleaning and disposal of flue gases with the production of methane is carried out in the proposed device as follows.

Flue gases from the boiler unit, the amount of which is due to the performance of the device, as a result of the pressure created by the smoke exhauster (not shown in Fig. 1), from the transit flue 1 through the working flue 4 with the open gate 5, enter the heat exchanger 6, cooled, for example, by blow air or feed water, where they are cooled to a temperature of (60-70) ° С with the formation of condensate that mixes with flue gases, which through the pipe 13 enter the absorption tower 7. In the tower 7, flue gases move from bottom to top, contact comfort in countercurrent with raw sludge from urban wastewater entering through pipe 10 and sliding from one partition 8 to another under the influence of gravity and inclination (the inclination of partitions 8 is equal to the angle of repose of the raw sludge and is determined experimentally for a specific type of sludge), passing through cracks in the partitions 8. As a result of repeated contact of flue gases and crude sediment particles, the gases are cooled and released from nitrogen oxides, sulfur oxides, carbon dioxide, drops of condensate and water vapor, after which the post Payuta through the return gas duct work 12 to a wash tower 15, while crude precipitate is saturated with these elements as a result of absorption, adsorption and chemisorption, which occur while the components of sludge (water, particles of proteins, fats, sand, and clay. d.), is heated to the optimum fermentation temperature of 30-50 ° C due to the heat of the flue gases and is discharged through the pipe 14 and the saturated sludge pipe 21 to the digester 22. In the washing tower 15, the cleaned and cooled flue gases are in countercurrent contact with raw water entering from the liquid distributor 16, the amount of which is determined from the condition of ensuring the necessary density of irrigation, while being cleaned of particles of crude sediment and other impurities carried away from the absorption tower 7, and are released into the atmosphere, and the mud mixture is enriched It also flows with nitrogen, sulfur, and carbon oxides and flows through gravity pipe 18 to sump 19. In sump 19, as a result of settling, the mud mixture is divided into saturated crude sediment that settles to the bottom and dirty water that accumulates in the upper zone, which is fed through pipeline 20 to irrigation fields, where it, due to the increased content of carbon dioxide, intensifies the photosynthesis process [6, p. 210], and the sediment from the lower zone enters the pipeline 21, where it is mixed with saturated sediment from the absorption tower 7, from where the resulting mixture fed to digester 22. In digester 22, neutralization of saturated raw sludge by anaerobic digestion occurs, which is the main method of neutralizing urban wastewater. Moreover, as a result of the decomposition of organic matter of the precipitate and the interaction of the decomposition products with carbon dioxide, methane is obtained as the main products.

Methane is formed as a result of reduction of CO ₂ or methyl group of acetic acid

where AH ₂ is an organic substance that serves for methane-forming bacteria as a hydrogen donor (fatty acids, except acetic, and alcohols, except methyl);

In addition, many types of methane-forming bacteria oxidize the molecular hydrogen formed in the acid phase by reaction

Microorganisms using acetic acid and methyl alcohol carry out reactions

In this case, in this case, the reaction rate (1), (2) due to the presence of free CO ₂ in the precipitate increases, and (3), (4) decreases, which increases the methane fraction in the produced gas.

Periodically, the absorption tower 7 is washed with raw water in order to prevent overgrowth of the sediment (washing frequency and flow rate of raw water are determined from operating experience). After washing, the dirty water is sent to the sump 19, where it is mixed with dirty water from the washing tower 15 and is clarified with it.

In case of refusal or repair of the cleaning installation, the backup gas duct 2 is opened, opening the gate 3, and the working gas duct 4 is turned off by closing the gate 5.

The methane obtained can be used as an additive to the fuel of the main boiler units or to provide auxiliary heat generator with fuel, thus increasing the fuel utilization coefficient, and the fermented sludge is used as a highly effective fertilizer for agriculture.

The use of the proposed method and installation for cleaning and disposal is possible when placing heat generators on the territory of treatment facilities, in close proximity to them or while transporting raw sludge to the territory of the thermal power plant.

Thus, the proposed integrated method and device for cleaning and utilizing flue gases to produce methane provides a high degree of absorption of nitrogen oxides, sulfur oxides, carbon dioxide, water vapor, heat recovery, obtaining additional fuel, intensifying the operation of treatment facilities, while reducing the threat of the greenhouse effect and destruction of the ozone shield of the surrounding atmosphere, which increases the environmental and economic efficiency of the flue gas cleaning process.

Literature

1. RF patent No. 2254161, MKL B01D 53/60, 53/14, 2005.

2. RF patent №2217221, MKl. B01D 53/14, 53/62, 2003.

3. KF Roddatis et al. Handbook of low-capacity boiler plants. - M .: Energy, 1975, 370 p.

4. K. Nenitsesku. General chemistry. - M .: Mir, 1968, 816 p.

5. S.V. Yakovlev and others. Sewerage. - M.: Gosstroyizd. 1976, 632 p.

6. Komov V.P., Shvedova V.N. Biochemistry. - M.: Bustard, 2004, 640 p.

Claims (2)

1. An integrated method of purification and utilization of flue gases to produce methane, comprising cooling the flue gas to a temperature below the dew point, condensing water vapor, emitting carbon dioxide by absorbing, and discharging the purified flue gas to the atmosphere, characterized in that the flue gas purification comprises absorption of nitrogen oxides sulfur oxides, carbon dioxide, drops of condensate and water vapor by raw sewage sludge with its simultaneous heating in an absorption tower to a fermentation temperature of 30-50 ° C, washing the treated and cooling gases from residues of raw sludge with raw water in a wash tower, separation of the resulting mud mixture by settling into dirty water and saturated wet sludge in a sump, discharge of dirty water into irrigation fields, mixing of saturated heated sludge from an absorption tower with sludge from a sump, fermentation of saturated heated crude sediment in a digester with methane and fermented sediment. 2. The device for implementing the method according to claim 1, comprising a transit gas duct, a heat exchanger, an absorption and washing tower, characterized in that the transit gas duct is branched into a reserve gas duct with a gate connected to the chimney, and a working gas duct with a gate connected in series with the heat exchanger , an absorption tower, inside of which transverse oblique lattice partitions are placed from top to bottom with an opening in the form of a segment in its lower part, the direction of the slope of which alternately changes to the opposite hundred they are, moreover, the absorption tower in its upper part is equipped with a raw sludge supply pipe located at the entrance to the first trellised partition and a processed gas outlet pipe integrated in the upper cover connected to the return working gas duct, and in its lower part is equipped with feed gas pipes and saturated raw sludge, respectively, while the return working flue is also connected to the washing tower, in the upper part of which is placed a liquid distributor connected to the crude water pipe s, while its lower part is connected to a sump duct, the upper part of which is connected to the dirty water pipe while the lower part - with the conduit crude precipitate which, in turn, connected to the digester.

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