CN114504929A - Ammonia recovery method for flue gas denitration - Google Patents
Ammonia recovery method for flue gas denitration Download PDFInfo
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- CN114504929A CN114504929A CN202011279544.8A CN202011279544A CN114504929A CN 114504929 A CN114504929 A CN 114504929A CN 202011279544 A CN202011279544 A CN 202011279544A CN 114504929 A CN114504929 A CN 114504929A
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- flue gas
- liquid
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- denitration
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- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 title claims abstract description 353
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 title claims abstract description 167
- 239000003546 flue gas Substances 0.000 title claims abstract description 167
- 229910021529 ammonia Inorganic materials 0.000 title claims abstract description 166
- 238000011084 recovery Methods 0.000 title claims abstract description 95
- 238000000034 method Methods 0.000 title claims abstract description 46
- 239000007788 liquid Substances 0.000 claims abstract description 143
- 238000010521 absorption reaction Methods 0.000 claims abstract description 95
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims abstract description 38
- 235000011114 ammonium hydroxide Nutrition 0.000 claims abstract description 38
- 230000005587 bubbling Effects 0.000 claims abstract description 38
- 238000006477 desulfuration reaction Methods 0.000 claims abstract description 28
- 230000023556 desulfurization Effects 0.000 claims abstract description 28
- 238000005192 partition Methods 0.000 claims description 26
- 239000007789 gas Substances 0.000 claims description 24
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 20
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonium chloride Substances [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 claims description 19
- 239000003085 diluting agent Substances 0.000 claims description 13
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 claims description 11
- 239000004202 carbamide Substances 0.000 claims description 11
- 238000001914 filtration Methods 0.000 claims description 9
- 239000000126 substance Substances 0.000 claims description 8
- 239000003795 chemical substances by application Substances 0.000 claims description 7
- 238000005507 spraying Methods 0.000 claims description 6
- 230000003247 decreasing effect Effects 0.000 claims description 4
- 230000007613 environmental effect Effects 0.000 abstract description 5
- 239000000243 solution Substances 0.000 description 17
- 239000011882 ultra-fine particle Substances 0.000 description 15
- 230000008569 process Effects 0.000 description 12
- 238000010586 diagram Methods 0.000 description 6
- 230000008901 benefit Effects 0.000 description 5
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 description 5
- 230000003749 cleanliness Effects 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- 238000004064 recycling Methods 0.000 description 3
- 241000197194 Bulla Species 0.000 description 2
- 208000002352 blister Diseases 0.000 description 2
- 238000010531 catalytic reduction reaction Methods 0.000 description 2
- 239000000428 dust Substances 0.000 description 2
- 239000005696 Diammonium phosphate Substances 0.000 description 1
- 229920000877 Melamine resin Polymers 0.000 description 1
- 239000003929 acidic solution Substances 0.000 description 1
- LFVGISIMTYGQHF-UHFFFAOYSA-N ammonium dihydrogen phosphate Chemical compound [NH4+].OP(O)([O-])=O LFVGISIMTYGQHF-UHFFFAOYSA-N 0.000 description 1
- 229910000387 ammonium dihydrogen phosphate Inorganic materials 0.000 description 1
- BFNBIHQBYMNNAN-UHFFFAOYSA-N ammonium sulfate Chemical compound N.N.OS(O)(=O)=O BFNBIHQBYMNNAN-UHFFFAOYSA-N 0.000 description 1
- 229910052921 ammonium sulfate Inorganic materials 0.000 description 1
- 235000011130 ammonium sulphate Nutrition 0.000 description 1
- 239000004568 cement Substances 0.000 description 1
- MNNHAPBLZZVQHP-UHFFFAOYSA-N diammonium hydrogen phosphate Chemical compound [NH4+].[NH4+].OP([O-])([O-])=O MNNHAPBLZZVQHP-UHFFFAOYSA-N 0.000 description 1
- 229910000388 diammonium phosphate Inorganic materials 0.000 description 1
- 235000019838 diammonium phosphate Nutrition 0.000 description 1
- 239000006260 foam Substances 0.000 description 1
- 230000036541 health Effects 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- JDSHMPZPIAZGSV-UHFFFAOYSA-N melamine Chemical compound NC1=NC(N)=NC(N)=N1 JDSHMPZPIAZGSV-UHFFFAOYSA-N 0.000 description 1
- 239000011259 mixed solution Substances 0.000 description 1
- 235000019837 monoammonium phosphate Nutrition 0.000 description 1
- 239000006012 monoammonium phosphate Substances 0.000 description 1
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 239000000779 smoke Substances 0.000 description 1
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-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2257/00—Components to be removed
- B01D2257/40—Nitrogen compounds
- B01D2257/406—Ammonia
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Analytical Chemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Treating Waste Gases (AREA)
Abstract
The invention provides an ammonia recovery method for flue gas denitration, which comprises the following steps: enabling the denitrated flue gas to pass through a liquid pool formed by absorption liquid in a bubbling mode to absorb ammonia gas in the flue gas, so as to obtain ammonia recovery liquid; and treating the ammonia recovery liquid and returning the treated ammonia recovery liquid to a flue gas denitration and/or desulfurization system for reuse. The scheme of the invention ensures the full contact of the flue gas and the absorption liquid in a bubbling mode, thereby effectively absorbing the escaped ammonia in the flue gas, ensuring the removal efficiency of the escaped ammonia in the flue gas and ensuring that the flue gas emission meets the requirement of the environmental protection standard. And moreover, the ammonia recovery liquid is treated to meet the reuse requirement and then returned to the flue gas denitration and/or desulfurization system for reuse, so that the consumption of the ammonia water is reduced, the utilization rate of the ammonia water is improved, and the flue gas treatment cost is saved.
Description
Technical Field
The invention relates to the technical field of gas treatment, in particular to an ammonia recovery method for flue gas denitration.
Background
With increasingly stringent environmental requirements, emission limits for nitrogen oxides (NOx) are becoming lower. In order to meet the requirement of emission limit, when the pollution gas (such as flue gas and the like) is denitrated, the spraying amount of the denitrating agent (such as ammonia water, urea, melamine and other nitrogen-containing substances) is increased, so that the problem of ammonia escape is also increased. The escape of ammonia can not only pollute the atmosphere and influence the health of human bodies, but also increase the consumption of the denitration agent and increase the cost. In the prior art, no scheme for effectively recycling ammonia escaping from the flue gas denitration process exists.
Disclosure of Invention
In view of the above problems, the present invention has been made in order to provide a method for ammonia recovery for denitration of flue gas that overcomes or at least partially solves the above problems.
One object of the present invention is to provide an ammonia recovery method for flue gas denitration, which can effectively recover and reuse ammonia escaping from a flue gas denitration process.
A further object of the present invention is to further improve the efficiency of removal of escaped ammonia by absorbing ammonia in flue gas with one or two or more stages of bubbling.
According to an aspect of the embodiments of the present invention, there is provided an ammonia recovery method for flue gas denitration, including:
enabling the denitrated flue gas to pass through a liquid pool formed by absorption liquid in a bubbling mode to absorb ammonia gas in the flue gas, so as to obtain ammonia recovery liquid;
and treating the ammonia recovery liquid and returning the treated ammonia recovery liquid to a flue gas denitration and/or desulfurization system for reuse.
Optionally, the bubbling the denitrated flue gas through a liquid pool formed by an absorption liquid includes:
continuously spraying the absorption liquid from bottom to top in an absorption chamber, so that the sprayed absorption liquid reaches the upper part of a partition plate arranged in the absorption chamber through a through hole on the partition plate and forms a liquid pool on the partition plate;
and enabling the denitrated flue gas to flow from bottom to top in the absorption chamber, and forming bubbles through the through holes in the partition plate to enter and pass through the liquid pool.
Optionally, the diameter of the through hole is 0.2-5 mm.
Optionally, the step of passing the denitrated flue gas through a liquid pool formed by an absorption liquid in a bubbling manner to absorb ammonia gas in the flue gas comprises at least two-stage bubbling; and is
And the ammonia concentration of the ammonia recovery liquid obtained after each stage of bubbling passes through a liquid pool formed by the absorption liquid is decreased progressively.
Optionally, the absorption liquid is water.
Optionally, the liquid-gas ratio of the absorption liquid to the denitrated flue gas is (1-10) L:1m3。
Optionally, the concentration of ammonia in the denitrated flue gas is 10-300mg/m3The ammonia concentration in the flue gas after the ammonia gas is absorbed is less than or equal to 10mg/m3(ii) a And is
The temperature of the denitrated flue gas is 50-300 ℃.
Optionally, the treating the ammonia recovery liquid includes:
and filtering the ammonia recovery liquid.
Optionally, the processing the ammonia recovery liquid further includes:
and mixing the filtered ammonia recovery solution with the required amount of diluent and concentrated ammonia water or urea according to the ammonia concentration of the ammonia recovery solution and the specified concentration of the ammonia solution required by flue gas denitration and/or desulfurization to obtain the ammonia solution with the specified concentration.
Optionally, the processing the ammonia recovery liquid further includes:
adding an alkaline substance into the filtered ammonia recovery liquid to separate out ammonia, and directly taking the separated out ammonia as a denitration agent returned to a flue gas denitration and/or desulfurization system; or
Adding an alkaline substance into the filtered ammonia recovery liquid to separate out ammonia;
and mixing the precipitated ammonia with the required amount of diluent and concentrated ammonia water or urea according to the specified concentration of the ammonia solution required by the denitration and/or desulfurization of the flue gas to obtain the ammonia solution with the specified concentration.
In the ammonia recovery method for flue gas denitration provided by the embodiment of the invention, the denitrated flue gas passes through the liquid pool formed by the absorption liquid in a bubbling manner to absorb ammonia gas in the flue gas, so as to obtain the ammonia recovery liquid, and the ammonia recovery liquid is treated and then returned to a flue gas denitration and/or desulfurization system for reuse. The scheme of the invention ensures the full contact of the flue gas and the absorption liquid in a bubbling mode, thereby effectively absorbing the escaped ammonia in the flue gas, ensuring the removal efficiency of the escaped ammonia in the flue gas and ensuring that the flue gas emission meets the requirement of the environmental protection standard. And moreover, the ammonia recovery liquid is treated to meet the reuse requirement and then returned to the flue gas denitration and/or desulfurization system for reuse, so that the consumption of the ammonia water is reduced, the utilization rate of the ammonia water is improved, and the flue gas treatment cost is saved.
Further, in the ammonia recovery method for flue gas denitration according to the embodiment of the invention, ammonia in the flue gas is absorbed by bubbling in one stage or two or more stages, so that the removal efficiency of escaped ammonia is further improved.
The foregoing description is only an overview of the technical solutions of the present invention, and the embodiments of the present invention are described below in order to make the technical means of the present invention more clearly understood and to make the above and other objects, features, and advantages of the present invention more clearly understandable.
The above and other objects, advantages and features of the present invention will become more apparent to those skilled in the art from the following detailed description of specific embodiments thereof, taken in conjunction with the accompanying drawings.
Drawings
Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Also, like reference numerals are used to refer to like parts throughout the drawings. In the drawings:
FIG. 1 shows a schematic flow diagram of an ammonia recovery method for flue gas denitration according to an embodiment of the invention;
FIG. 2 shows a schematic flow diagram of an ammonia recovery method for denitration of flue gas according to another embodiment of the present invention;
FIG. 3 shows a system block diagram of an ammonia recovery method for denitration of flue gas according to an embodiment of the invention.
Detailed Description
Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
In order to solve the technical problem, the invention provides an ammonia recovery method for flue gas denitration. The flue gas denitration related in the invention can comprise Selective Catalytic Reduction (SCR) denitration, Selective Non-Catalytic Reduction (SNCR) denitration, or SNCR-SCR combined denitration and the like.
Fig. 1 shows a schematic flow diagram of an ammonia recovery method for flue gas denitration according to an embodiment of the present invention. Referring to fig. 1, the method for recovering ammonia through denitration of flue gas according to the present invention may include at least the following steps S102 to S104.
And S102, enabling the denitrated flue gas to pass through a liquid pool formed by the absorption liquid in a bubbling mode to absorb ammonia gas in the flue gas, so as to obtain ammonia recovery liquid.
In some embodiments, in order to make the absorption of ammonia in the flue gas more sufficient, the liquid-gas ratio of the absorption liquid to the denitrated flue gas may be set at (1-10) L:1m in step S1023Preferably (3-5) L:1m3. The flow of the denitrated flue gas can be set according to the treatment capacity requirement of practical application, for example, the flow can be set at 7000-14000m3In the range of/h.
And step S104, treating the ammonia recovery liquid, and returning the treated ammonia recovery liquid to a flue gas denitration and/or desulfurization system for reuse.
In this step, the flue gas denitration and desulfurization system may refer to a system in which a flue gas denitration device and a desulfurization device (such as a denitration tower and a desulfurization tower) are integrated.
In the ammonia recovery method for flue gas denitration provided by the embodiment of the invention, the flue gas is ensured to be fully contacted with the absorption liquid in a bubbling manner, so that escaped ammonia in the flue gas is effectively absorbed, the removal efficiency of the escaped ammonia in the flue gas is ensured, and the emission of the flue gas is ensured to meet the requirement of an environmental standard. And moreover, the ammonia recovery liquid is treated to meet the reuse requirement and then returned to the flue gas denitration and/or desulfurization system for reuse, so that the consumption of the ammonia water is reduced, the utilization rate of the ammonia water is improved, and the flue gas treatment cost is saved.
In one embodiment of the present invention, the process of bubbling flue gas in step S102 above may be performed in an absorption chamber. Specifically, in step S102, the denitration flue gas is bubbled through a liquid pool formed by the absorption liquid, which may be implemented as follows: and continuously spraying the absorption liquid from bottom to top in the absorption chamber, so that the sprayed absorption liquid reaches the upper part of the partition plate through a through hole on the partition plate arranged in the absorption chamber and forms a liquid pool on the partition plate. Simultaneously, the flue gas after denitration flows from bottom to top in the absorption chamber, and the bubbles are formed through the through holes on the partition plate to enter and pass through the liquid pool. The bubbling absorption mode can further promote the full contact of the flue gas and the absorption liquid, and is simple to operate and easy to implement.
Specifically, the absorption chamber may be a flat cavity (specifically, a square cavity), and the lower portion and the upper portion (e.g., the top portion) of the absorption chamber are respectively provided with a gas inlet and a gas outlet, the bottom portion is provided with a liquid outlet, and the side surface is provided with a liquid inlet. The liquid inlet may comprise a nozzle extending into the interior of the process chamber for spraying the absorption liquid. A baffle plate is arranged in the absorption chamber, is positioned above the nozzle and is provided with a plurality of through holes (also called foam rising holes). The partition plate may be horizontally disposed in the absorption chamber, and thus, the partition plate may partition the absorption chamber into a first region communicating with the gas inlet and a second region communicating with the gas outlet. The nozzle is located in the first region, and the absorption liquid is sprayed toward the partition plate through the nozzle. The absorption liquid sprayed by the nozzle can reach the upper part of the partition plate through the through hole, and the absorption liquid falls onto the partition plate and then is accumulated to form a liquid pool. The flue gas entering the absorption chamber from the gas inlet flows upwards, bubbles are generated through the through holes and enter the liquid pool, and therefore ammonia in the flue gas is absorbed through the absorption liquid. The absorption liquid above the partition also seeps downward through the through holes and finally flows down to the bottom of the absorption chamber. By controlling the jet flow rate and the downward seepage flow rate of the absorption liquid, a liquid pool with relatively stable depth can be maintained on the partition plate.
In a preferred embodiment, the diameter of the through-hole may be set in the range of 0.2-5 mm. The aperture of the through hole is set within the range of 0.2-5mm, so that the flue gas can form more tiny and uniform bubbles in the process of passing through the liquid pool, the contact between the flue gas and the absorption liquid is enhanced, and the absorption efficiency of ammonia in the flue gas is improved.
In some embodiments, a wire mesh with a mesh size of micrometer scale may be used as the partition plate, and the through holes of the wire mesh constitute the through holes of the partition plate. Therefore, the flue gas can generate micron-sized bubbles through the meshes of the wire mesh to enter the liquid pool, and the contact and mixing efficiency of the flue gas and the absorption liquid is greatly improved.
In an embodiment of the present invention, only one stage of bubbling may be included in the above step of passing the denitrated flue gas through the liquid pool formed by the absorption liquid in a bubbling manner to absorb ammonia gas in the flue gas.
In another embodiment of the present invention, the step of bubbling the denitrated flue gas through the liquid pool formed by the absorption liquid to absorb ammonia gas in the flue gas may include at least two-stage bubbling, that is, ammonia in the flue gas may be absorbed by two or more stages of bubbling in step S102, and the ammonia concentration of the ammonia recovery liquid obtained after each stage of bubbling through the liquid pool formed by the absorption liquid is gradually decreased (for example, gradually decreased). The ammonia in the flue gas is absorbed by adopting two or more bubbling stages, so that the removal efficiency of escaped ammonia is further improved.
Specifically, in one mode, at least two absorption chambers may be connected in series, the gas outlet of the preceding absorption chamber being connected to the gas inlet of the succeeding absorption chamber, and only one partition plate and corresponding nozzle being provided in each absorption chamber. So, carry out the one-level tympanic bulla in every absorption chamber, the flue gas carries out the ammonia absorption back through the liquid pond on the baffle, flows out from the gas outlet and gets into next absorption chamber and carry out the next-level tympanic bulla. And the flue gas in the last absorption chamber is discharged from the gas outlet to a subsequent process (such as desulfurization, dust removal and the like) or directly discharged to the atmosphere.
In another mode, at least two layers of partition plates can be arranged in the same absorption chamber, and corresponding nozzles are arranged below each layer of partition plate. Therefore, the flue gas is subjected to first-stage bubbling and absorption when passing through the liquid pool above each layer of partition plate, and finally flows out from the gas outlet.
In the embodiment of the invention, the absorption liquid can be one or more of water, an acidic solution, an ammonium sulfate solution, a monoammonium phosphate solution, a diammonium phosphate solution and other ammonia absorption substances. Preferably, the absorption liquid is water.
In addition, the temperature of the flue gas after denitration can be in the range of 50-300 ℃, for example, 80-140 ℃. Therefore, the ammonia recovery method can be suitable for treating the denitrated flue gas under various working conditions (including severe working conditions under the condition that the cement kiln is stopped to grind).
In some embodiments, the ammonia concentration in the denitrated flue gas may be in the range of 10-300mg/m3In the range, for example, from 31 to 72mg/m3. After the ammonia is treated by the ammonia recovery method, the ammonia concentration in the flue gas after the ammonia gas is absorbed can be reduced to be less than or equal to 10mg/m3For example, in the range of 0.73 to 2.1mg/m3Within the range. The removal efficiency of escaping ammonia in the flue gas can reach more than 96 percent.
In addition, the denitrated flue gas usually contains ultrafine particles (smoke dust) and water vapor with higher concentration, and the ammonia recovery method can also effectively remove the ultrafine particles and the water vapor in the flue gas in the process of bubbling the flue gas through the absorption liquid pool, ensure the cleanliness of the treated flue gas and prevent the ultrafine particles in the flue gas from polluting the atmosphere and preventing the equipment from being corroded and damaged by the water vapor in the flue gas.
In an embodiment of the present invention, the processing of the ammonia recovery liquid in the step S104 may specifically include filtering the ammonia recovery liquid. In the foregoing, the flue gas after denitration usually contains ultrafine particles, and the ultrafine particles are intercepted by the absorption liquid in the bubbling absorption process and then enter the ammonia recovery liquid, so that the ultrafine particles in the ammonia recovery liquid can be removed by filtering the ammonia recovery liquid, and the cleanliness of the ammonia recovery liquid meets the requirement of recovery and reuse. In practical application, the ammonia recovery liquid can be filtered by a filtering device. As shown in the system block diagram of fig. 3, the flue gas denitrated by the denitrating apparatus (such as SNCR and/or SCR denitrating apparatus) is introduced into the absorption chamber for bubbling absorption, and then the flue gas is discharged through the flue gas outlet, and the ammonia recovery liquid enters the filtering apparatus for filtering.
Further, after the ammonia recovery liquid is filtered, the ammonia recovery liquid can be reused in a plurality of different ways.
In the first mode, after the ammonia recovery liquid is filtered, the filtered ammonia recovery liquid may be mixed with a required amount of a diluent (specifically, water) and concentrated ammonia water or urea according to the ammonia concentration of the ammonia recovery liquid and a specified concentration of the ammonia solution required for flue gas denitration and/or desulfurization, so as to obtain an ammonia solution with a specified concentration. Specifically, the amount of the absorbing solution and the concentrated aqueous ammonia required for mixing can be determined by calculation, and a person skilled in the art can understand a specific calculation manner, which is not described in detail herein. Then, the ammonia solution with the specified concentration is used as a denitration agent and returned to a flue gas denitration and/or desulfurization system for reuse.
In this case, referring to fig. 2, step S104 may be embodied as the following steps:
in step S204, the ammonia recovery solution is filtered.
And S206, mixing the filtered ammonia recovery solution with the required amount of diluent and concentrated ammonia water or urea according to the ammonia concentration of the ammonia recovery solution and the required concentration of the ammonia solution required by the denitration and/or desulfurization of the flue gas to obtain the ammonia solution with the required concentration.
And step S208, returning the ammonia solution with the specified concentration to the flue gas denitration and/or desulfurization system for reuse.
In practical applications, as shown in the system block diagram of fig. 3, the ammonia recycling liquid may be stored in a liquid storage device (e.g., a liquid storage tank) after entering the filtering device for filtering. When needed, according to the ammonia injection flow and the specified concentration (such as 10%) required by the flue gas denitration and/or desulfurization process, the ammonia recovery liquid, the concentrated ammonia water or the urea and the diluent (such as water) are added into the mixing device to be mixed, so as to obtain the ammonia solution with the specified concentration. The concentrated ammonia and the diluent can be stored in an ammonia tank and a diluent tank respectively, and water in the diluent tank is used as the diluent of the concentrated ammonia. And finally, the ammonia solution with the specified concentration is sent back to the denitration device again, so that the denitration cost is saved.
In the second mode, after the ammonia recovery solution is filtered, an alkaline substance is added into the filtered ammonia recovery solution to precipitate ammonia, and the precipitated ammonia (namely ammonia gas) is directly used as a denitration agent and returned to a flue gas denitration and/or desulfurization system for reuse.
In the third mode, after the ammonia-recovering solution is filtered, an alkaline substance is added to the filtered ammonia-recovering solution to precipitate ammonia. Then, according to the specified concentration of the ammonia solution required for denitration and/or desulfurization of the flue gas, the precipitated ammonia (i.e. ammonia gas) is mixed with the required amount of diluent (such as water) and concentrated ammonia water or urea to obtain the ammonia solution with the specified concentration. And finally, returning the ammonia solution with the specified concentration as a denitration agent to a flue gas denitration and/or desulfurization system for reuse.
The three recycling modes can be selected according to actual application requirements.
The following description is provided for the purpose of illustrating the embodiments of the present invention by way of example, and it is therefore intended that the present invention not be limited to the embodiments disclosed herein. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.
Example 1
In this example, ammonia was recovered by using the system shown in FIG. 3, and the absorption liquid was water. The specific process conditions are as follows:
the SNCR denitration flue gas passes through a liquid pool formed by absorption liquid in an absorption chamber in a one-stage bubbling mode to absorb ammonia gas in the flue gas, wherein the flow rate of the flue gas is 7000m3The liquid-gas ratio of the absorption liquid to the denitrated flue gas is 3L to 1m3The temperature of the denitrated flue gas (i.e. the gas inlet temperature of the absorption chamber) was 80 ℃, and the ammonia concentration in the denitrated flue gas was 31mg/m3The content of ultrafine particles is 8.8mg/Nm3The water vapor content (absolute moisture content) was 9.1%. The ammonia concentration of the flue gas (i.e. the gas outlet of the absorption chamber) after the absorption of ammonia gas is 1.4mg/m3The content of ultrafine particles is 2.6mg/Nm3The water vapor content (absolute moisture content) was 7.7%.
The ammonia recovery liquid is filtered and then stored in a liquid storage device. And when needed, adding the ammonia recovery solution, urea and water serving as a diluent into a mixing device for mixing according to the ammonia spraying flow required by the SNCR denitration process to obtain a mixed solution of the ammonia water recovery solution and the urea. And (4) returning the solution to the SNCR denitration process for flue gas denitration.
In this embodiment, the removal efficiency (also referred to as recovery efficiency) of escaped ammonia in flue gas reaches 95.5%, and the removal efficiency of ultrafine particles reaches 70%.
Example 2
The basic operation of this example is similar to example 1, except that:
the flue gas flow is 10000m3The liquid-gas ratio of the absorption liquid to the denitrated flue gas is 4L:1m3The temperature of the denitrated flue gas (i.e. the gas inlet temperature of the absorption chamber) was 100 ℃, and the ammonia concentration in the denitrated flue gas was 72mg/m3The content of ultrafine particles is 8.6mg/Nm3The water vapor content (absolute moisture content) was 11.4%. The ammonia concentration of the flue gas (i.e. the gas outlet of the absorption chamber) after the absorption of ammonia gas was 2.1mg/m3The content of ultrafine particles is 2.4mg/Nm3The water vapor content (absolute moisture content) was 2.5%.
In this embodiment, the removal efficiency (also referred to as recovery efficiency) of escaped ammonia in flue gas reaches 97%, and the removal efficiency of ultrafine particles reaches 72%.
Example 3
The present embodiment is different from embodiment 1 in that:
the SNCR denitration flue gas passes through a liquid pool formed by absorption liquid in an absorption chamber in a two-stage bubbling mode to absorb ammonia gas in the flue gas, wherein the flow rate of the flue gas is 14000m3The liquid-gas ratio of the total absorption liquid to the denitrated flue gas is 5L to 1m3The temperature of the denitrated flue gas (i.e. the gas inlet temperature of the absorption chamber) was 140 ℃, and the ammonia concentration in the denitrated flue gas was 33.5mg/m3The content of ultrafine particles is 8.0mg/Nm3The water vapor content (absolute moisture content) was 18.8%. The ammonia concentration of the flue gas (i.e. the gas outlet of the absorption chamber) after the absorption of ammonia gas is 0.73mg/m3The content of ultrafine particles is 2.3mg/Nm3The water vapor content (absolute moisture content) was 10.8%. The ammonia concentration of the obtained primary ammonia recovery liquid (i.e. the ammonia recovery liquid obtained after the primary bubbling) is 3%, and the ammonia concentration of the secondary ammonia recovery liquid (i.e. the ammonia recovery liquid obtained after the secondary bubbling) is 1%.
In this embodiment, the removal efficiency (also referred to as recovery efficiency) of escaped ammonia in flue gas reaches 98%, and the removal efficiency of ultrafine particles reaches 71%.
The test data of the embodiment show that the ammonia recovery method for flue gas denitration provided by the embodiment of the invention can effectively recycle escaped ammonia in flue gas, remove ultrafine particulate matters and water vapor in the flue gas, ensure the cleanliness of the treated flue gas, prevent the flue gas from polluting the atmosphere and save the flue gas treatment cost.
According to any one or a combination of multiple optional embodiments, the embodiment of the present invention can achieve the following advantages:
in the ammonia recovery method for flue gas denitration provided by the embodiment of the invention, the denitrated flue gas passes through the liquid pool formed by the absorption liquid in a bubbling manner to absorb ammonia gas in the flue gas, so as to obtain the ammonia recovery liquid, and the ammonia recovery liquid is treated and then returned to a flue gas denitration and/or desulfurization system for reuse. The scheme of the invention ensures the full contact of the flue gas and the absorption liquid in a bubbling mode, thereby effectively absorbing the escaped ammonia in the flue gas, ensuring the removal efficiency of the escaped ammonia in the flue gas and ensuring that the flue gas emission meets the requirement of the environmental protection standard. And moreover, the ammonia recovery liquid is treated to meet the reuse requirement and then returned to the flue gas denitration and/or desulfurization system for reuse, so that the consumption of the ammonia water is reduced, the utilization rate of the ammonia water is improved, and the flue gas treatment cost is saved.
Further, in the ammonia recovery method for flue gas denitration according to the embodiment of the invention, ammonia in the flue gas is absorbed by bubbling in one stage or two or more stages, so that the removal efficiency of escaped ammonia is further improved.
In the description provided herein, numerous specific details are set forth. It is understood, however, that embodiments of the invention may be practiced without these specific details. In some instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.
Thus, it should be appreciated by those skilled in the art that while a number of exemplary embodiments of the invention have been illustrated and described in detail herein, many other variations or modifications consistent with the principles of the invention may be directly determined or derived from the disclosure of the present invention without departing from the spirit and scope of the invention. Accordingly, the scope of the invention should be understood and interpreted to cover all such other variations or modifications.
Claims (10)
1. An ammonia recovery method for flue gas denitration is characterized by comprising the following steps:
enabling the denitrated flue gas to pass through a liquid pool formed by absorption liquid in a bubbling mode to absorb ammonia gas in the flue gas, so as to obtain ammonia recovery liquid;
and treating the ammonia recovery liquid and returning the treated ammonia recovery liquid to a flue gas denitration and/or desulfurization system for reuse.
2. The method for recovering ammonia according to claim 1, wherein the bubbling of the denitrated flue gas through a liquid pool formed by an absorption liquid comprises:
continuously spraying the absorption liquid from bottom to top in an absorption chamber, so that the sprayed absorption liquid reaches the upper part of a partition plate arranged in the absorption chamber through a through hole on the partition plate and forms a liquid pool on the partition plate;
and enabling the denitrated flue gas to flow from bottom to top in the absorption chamber, and forming bubbles through the through holes in the partition plate to enter and pass through the liquid pool.
3. The ammonia recovery method according to claim 2, wherein the diameter of the through-hole is 0.2-5 mm.
4. The ammonia recovery method according to claim 1, wherein the step of bubbling the denitrated flue gas through a liquid pool formed by an absorption liquid to absorb the ammonia gas in the flue gas comprises at least two-stage bubbling; and is
And the ammonia concentration of the ammonia recovery liquid obtained after each stage of bubbling passes through a liquid pool formed by the absorption liquid is decreased progressively.
5. The method according to claim 1, wherein the absorbing liquid is water.
6. The ammonia recovery method according to claim 1, wherein a liquid-gas ratio of the absorption liquid to the denitrated flue gas is (1-10) L:1m3。
7. The ammonia recovery method according to claim 1, wherein the concentration of ammonia in the denitrated flue gas is 10 to 300mg/m3The ammonia concentration in the flue gas after the ammonia gas is absorbed is less than or equal to 10mg/m3(ii) a And is
The temperature of the denitrated flue gas is 50-300 ℃.
8. The method of claim 1, wherein the treating the ammonia recovery liquid comprises:
and filtering the ammonia recovery liquid.
9. The method for recovering ammonia according to claim 8, wherein the treating the ammonia recovery liquid further comprises:
and mixing the filtered ammonia recovery solution with the required amount of diluent and concentrated ammonia water or urea according to the ammonia concentration of the ammonia recovery solution and the specified concentration of the ammonia solution required by flue gas denitration and/or desulfurization to obtain the ammonia solution with the specified concentration.
10. The method for recovering ammonia according to claim 8, wherein the treating the ammonia recovery liquid further comprises:
adding an alkaline substance into the filtered ammonia recovery liquid to separate out ammonia, and directly taking the separated out ammonia as a denitration agent returned to a flue gas denitration and/or desulfurization system; or
Adding an alkaline substance into the filtered ammonia recovery liquid to separate out ammonia;
and mixing the precipitated ammonia with the required amount of diluent and concentrated ammonia water or urea according to the specified concentration of the ammonia solution required by the denitration and/or desulfurization of the flue gas to obtain the ammonia solution with the specified concentration.
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