CN117699840A - Method for desulfurizing gypsum in power plant - Google Patents
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- 239000010440 gypsum Substances 0.000 title claims abstract description 91
- 229910052602 gypsum Inorganic materials 0.000 title claims abstract description 91
- 238000000034 method Methods 0.000 title claims abstract description 60
- 230000003009 desulfurizing effect Effects 0.000 title claims description 4
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 claims abstract description 70
- 239000000047 product Substances 0.000 claims abstract description 67
- 238000006243 chemical reaction Methods 0.000 claims abstract description 63
- 239000007788 liquid Substances 0.000 claims abstract description 55
- 238000006477 desulfuration reaction Methods 0.000 claims abstract description 53
- 230000023556 desulfurization Effects 0.000 claims abstract description 53
- 239000012263 liquid product Substances 0.000 claims abstract description 50
- 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
- 229910000019 calcium carbonate Inorganic materials 0.000 claims abstract description 35
- 238000002425 crystallisation Methods 0.000 claims abstract description 35
- 230000008025 crystallization Effects 0.000 claims abstract description 35
- 239000007789 gas Substances 0.000 claims abstract description 30
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims abstract description 27
- 239000003546 flue gas Substances 0.000 claims abstract description 27
- 238000000926 separation method Methods 0.000 claims abstract description 24
- 239000002002 slurry Substances 0.000 claims abstract description 24
- 239000002699 waste material Substances 0.000 claims abstract description 24
- BFNBIHQBYMNNAN-UHFFFAOYSA-N ammonium sulfate Chemical compound N.N.OS(O)(=O)=O BFNBIHQBYMNNAN-UHFFFAOYSA-N 0.000 claims abstract description 20
- 229910052921 ammonium sulfate Inorganic materials 0.000 claims abstract description 20
- 235000011130 ammonium sulphate Nutrition 0.000 claims abstract description 20
- 238000001704 evaporation Methods 0.000 claims abstract description 18
- 230000008020 evaporation Effects 0.000 claims abstract description 18
- 238000010521 absorption reaction Methods 0.000 claims abstract description 14
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims description 28
- OSGAYBCDTDRGGQ-UHFFFAOYSA-L calcium sulfate Chemical compound [Ca+2].[O-]S([O-])(=O)=O OSGAYBCDTDRGGQ-UHFFFAOYSA-L 0.000 claims description 24
- 238000002156 mixing Methods 0.000 claims description 20
- 238000000746 purification Methods 0.000 claims description 17
- QGZKDVFQNNGYKY-UHFFFAOYSA-N ammonia Natural products N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims description 15
- 239000001569 carbon dioxide Substances 0.000 claims description 14
- 229910002092 carbon dioxide Inorganic materials 0.000 claims description 14
- 239000002250 absorbent Substances 0.000 claims description 13
- 230000002745 absorbent Effects 0.000 claims description 13
- ATRRKUHOCOJYRX-UHFFFAOYSA-N Ammonium bicarbonate Chemical compound [NH4+].OC([O-])=O ATRRKUHOCOJYRX-UHFFFAOYSA-N 0.000 claims description 11
- 239000001099 ammonium carbonate Substances 0.000 claims description 11
- 235000012501 ammonium carbonate Nutrition 0.000 claims description 10
- 238000003756 stirring Methods 0.000 claims description 10
- QAOWNCQODCNURD-UHFFFAOYSA-N sulfuric acid group Chemical group S(O)(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 8
- 239000002912 waste gas Substances 0.000 claims description 5
- 230000008901 benefit Effects 0.000 abstract description 6
- 230000000052 comparative effect Effects 0.000 description 8
- 230000008569 process Effects 0.000 description 8
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 6
- 238000004519 manufacturing process Methods 0.000 description 6
- 239000002245 particle Substances 0.000 description 6
- 239000002994 raw material Substances 0.000 description 5
- 229910021529 ammonia Inorganic materials 0.000 description 4
- 230000007613 environmental effect Effects 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 238000007873 sieving Methods 0.000 description 4
- 235000019738 Limestone Nutrition 0.000 description 3
- 239000006028 limestone Substances 0.000 description 3
- 229910052757 nitrogen Inorganic materials 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- 239000006096 absorbing agent Substances 0.000 description 2
- 239000004566 building material Substances 0.000 description 2
- 239000006227 byproduct Substances 0.000 description 2
- NKWPZUCBCARRDP-UHFFFAOYSA-L calcium bicarbonate Chemical compound [Ca+2].OC([O-])=O.OC([O-])=O NKWPZUCBCARRDP-UHFFFAOYSA-L 0.000 description 2
- 229910000020 calcium bicarbonate Inorganic materials 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 239000004568 cement Substances 0.000 description 2
- 239000003337 fertilizer Substances 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 238000004062 sedimentation Methods 0.000 description 2
- 239000002689 soil Substances 0.000 description 2
- 239000002910 solid waste Substances 0.000 description 2
- 229910000013 Ammonium bicarbonate Inorganic materials 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- 238000013019 agitation Methods 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 235000012538 ammonium bicarbonate Nutrition 0.000 description 1
- 238000000498 ball milling Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- PASHVRUKOFIRIK-UHFFFAOYSA-L calcium sulfate dihydrate Chemical compound O.O.[Ca+2].[O-]S([O-])(=O)=O PASHVRUKOFIRIK-UHFFFAOYSA-L 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 229910001385 heavy metal Inorganic materials 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Abstract
The present disclosure relates to a method for gypsum desulfurization in a power plant, the method comprising the steps of: s1, carrying out a first reaction on desulfurization flue gas and ammonia water in an absorption tower to obtain a first liquid product and a gas product; s2, enabling the desulfurized gypsum slurry and the first liquid product to enter a reaction device for a second reaction to obtain a second solid-liquid mixed product; s3, enabling the second solid-liquid mixed product to enter a solid-liquid separation device for solid-liquid separation treatment to obtain a calcium carbonate product and a third liquid product; s4, enabling the third liquid product to enter an evaporation crystallization device for evaporation crystallization treatment, and obtaining an ammonium sulfate product and ammonia water waste liquid. The reaction process of the method is easy to control, the conversion rate of the product is improved, the obtained calcium carbonate product and ammonia water waste liquid can be recycled, the cost of gypsum desulfurization treatment is reduced, and the ammonium sulfate product can be used as agricultural grade waste material, so that the method has good economic benefit.
Description
Technical Field
The disclosure relates to the technical field of desulfurization gypsum treatment, in particular to a gypsum desulfurization method for a power plant.
Background
The desulfurization gypsum is a solid byproduct obtained by desulfurizing and purifying the flue gas after the combustion of the sulfur-containing fuel by adopting a limestone-gypsum method. According to the report of environmental control of solid waste pollution in China, the year report of environmental control of solid waste in China, the year report of environmental control in China, the serious publication and investigation of the desulfurization gypsum production of industrial enterprises, is 1.3 hundred million tons, the same ratio is increased by 8.3%, the industry with the largest production is the power and thermal production supply industry, the production is 1.1 hundred million tons, and the ratio is 83.3%. At present, the comprehensive utilization rate of the desulfurization gypsum in China is only 71.3%, the desulfurization gypsum in China is mainly concentrated in the cement industry and the gypsum building material industry, the cement retarder is still the most main utilization channel of the desulfurization gypsum, the gypsum building material is produced, and meanwhile, the desulfurization gypsum is slightly applied to the improvement of saline-alkali soil in the agricultural field, and the large-scale and industrialized application in other fields is not achieved. In areas with underdeveloped economy, because the gypsum demand is small, the transportation distance is long, the raw material cost is high, the desulfurized gypsum is difficult to be effectively utilized, a large amount of land is occupied by long-term stacking, secondary pollution of soil and water sources can be caused, and the reasonable and effective disposal of the stacked desulfurized gypsum becomes one of the problems to be solved in the coal-fired power plants.
For partial power enterprises which cannot effectively digest the desulfurized gypsum, a large amount of gypsum serving as a byproduct becomes a heavy economic and environmental treatment burden of the enterprises, the carbon emission reduction pressure is relatively higher, and the sustainable high-quality healthy development of the enterprises is directly influenced.
Patent (CN 103910371 a) discloses a method for preparing calcium carbonate and co-producing ammonium sulfate by using flue gas desulfurization gypsum or desulfurization ash; patent (CN 102583443 a) discloses a method for producing ammonium sulfate using ammonium bicarbonate as a main raw material; patent (CN 110697731 a) discloses a process for preparing ammonium sulfate and calcium carbonate from desulfurized gypsum; in the above patent, the method adopts the desulfurized gypsum, phosphogypsum or desulfurized gypsum as raw materials to prepare the calcium carbonate and the ammonium sulfate, and although the method can solve the desulfurized gypsum treatment problem to a certain extent, the method is not combined with the existing limestone-gypsum flue gas desulfurization system and the whole process of the power plant, and the recycling utilization of the desulfurized gypsum is difficult to realize in a targeted manner.
Disclosure of Invention
The method has the advantages that the reaction process of the method is easy to control, the conversion rate of the product is improved, the obtained calcium carbonate product and ammonia water waste liquid can be recycled, the cost of gypsum desulfurization treatment is reduced, and the ammonium sulfate product can be used as agricultural grade waste, so that the method has good economic benefit.
In order to achieve the above object, the present disclosure provides a method of gypsum desulfurization, comprising the steps of:
s1, carrying out a first reaction on desulfurization flue gas and ammonia water in an absorption tower to obtain a first liquid product and a gas product;
s2, enabling the desulfurized gypsum slurry and the first liquid product to enter a reaction device for a second reaction to obtain a second solid-liquid mixed product;
s3, enabling the second solid-liquid mixed product to enter a solid-liquid separation device for solid-liquid separation treatment to obtain a calcium carbonate product and a third liquid product;
s4, enabling the third liquid product to enter an evaporation crystallization device for evaporation crystallization treatment, and obtaining an ammonium sulfate product and ammonia water waste liquid.
Optionally, in step S1, carbon dioxide in the desulfurized flue gas and NH in the aqueous ammonia 3 The molar ratio of (2) is 1:2-2.2; the concentration of the ammonia water is 10-25%; the conditions of the first reaction include: the temperature is 20-50deg.C, and the time is 30-90min.
Optionally, in step S2, the molar ratio of calcium sulfate in the desulfurized gypsum slurry to ammonium carbonate in the first liquid product is 1:1-1.1; the conditions of the second reaction include: the temperature is 20-70 ℃, the time is 30-120min, and the stirring speed is 60-600r/min.
Optionally, the method further comprises: and enabling the desulfurized gypsum from the gypsum desulfurization unit and the ammonia water waste liquid from the evaporation crystallization device to enter a mixing device for mixing treatment, so as to obtain the desulfurized gypsum slurry.
Optionally, the mass ratio of the desulfurized gypsum to the ammonia water waste liquid is 1:5-10; the conditions of the mixing treatment include: the temperature is 20-50 ℃, the time is 30-90min, and the stirring speed is 300-600r/min.
Optionally, in step S3, the solid-liquid separation device is selected from one or more of a precipitation device, a clarifier, a filter, a cyclone separator, and a filter press.
Optionally, the method further comprises: and returning the calcium carbonate product to a gypsum desulfurization unit for flue gas desulfurization treatment.
Optionally, the method further comprises: SS1, enabling the gas product from the absorption tower to enter a tail gas purification device to be in contact with an absorbent for tail gas purification treatment, so as to obtain a fourth liquid product and purified waste gas; SS2, making the fourth liquid product enter an evaporative crystallization device for evaporative crystallization treatment.
Optionally, the concentration of the absorbent is 1-10moL/L, preferably the absorbent is sulfuric acid.
Optionally, in the exhaust gas purification treatment, the contact time of the absorbent and the gas product is 20-60min; the conditions of the evaporative crystallization treatment include: the temperature is 80-110deg.C, and the time is 30-80min.
Through the technical scheme, the disclosure provides a gypsum desulfurization method, which has the following advantages:
(1) The two-step method is adopted to convert the desulfurized gypsum into the calcium carbonate product and the calcium sulfate product, the reaction process and the reaction condition of each step can be controlled independently, the reaction is more facilitated, the problem of incomplete reaction of converting the calcium carbonate into the calcium bicarbonate or the calcium sulfate due to excessive carbon dioxide is avoided, and the conversion rate of the product is improved.
(2) The method disclosed by the disclosure utilizes carbon dioxide in the desulfurization flue gas, reduces the cost of raw materials, and solves the problem of the going of desulfurization gypsum.
(3) The ammonium sulfate product can be used as agricultural grade waste, and has good economic benefit.
Additional features and advantages of the present disclosure will be set forth in the detailed description which follows.
Drawings
The accompanying drawings are included to provide a further understanding of the disclosure, and are incorporated in and constitute a part of this specification, illustrate the disclosure and together with the description serve to explain, but do not limit the disclosure. In the drawings:
FIG. 1 is a flow chart of a process for treating desulfurized gypsum in a gypsum desulfurization treatment process.
Description of the reference numerals
1. Mixing device 2 reaction device 3 absorption tower
4. Tail gas purifying device of solid-liquid separation device 5 evaporative crystallization device 6
Detailed Description
Specific embodiments of the present disclosure are described in detail below with reference to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating and illustrating the disclosure, are not intended to limit the disclosure.
The present disclosure provides a method of gypsum desulfurization, the method comprising the steps of:
s1, carrying out a first reaction on desulfurization flue gas and ammonia water in an absorption tower 3 to obtain a first liquid product and a gas product;
s2, enabling the desulfurized gypsum slurry and the first liquid product to enter a reaction device 2 for a second reaction to obtain a second solid-liquid mixed product;
s3, enabling the second solid-liquid mixed product to enter a solid-liquid separation device 4 for solid-liquid separation treatment to obtain a calcium carbonate product and a third liquid product;
s4, enabling the third liquid product to enter an evaporation crystallization device 5 for evaporation crystallization treatment, and obtaining an ammonium sulfate product and ammonia water waste liquid.
In the present disclosure, in a method of treating desulfurization gypsum in a power plant, the desulfurization gypsum is treated using a two-step process to convert the desulfurization gypsum into a calcium carbonate product and an ammonium sulfate product. The first step is to react carbon dioxide in the desulfurized flue gas with ammonia water to obtain a first liquid product containing ammonium carbonate, and the second step is to react ammonium carbonate in the first liquid product with calcium sulfate in the desulfurized gypsum slurry to obtain a second solid-liquid mixed product containing calcium carbonate and ammonium sulfate. The method can control the reaction process and the reaction condition of each step independently by a two-step method, is more beneficial to controlling the reaction, avoids the problem of incomplete reaction of converting calcium carbonate into calcium bicarbonate or calcium sulfate due to excessive carbon dioxide, and improves the conversion rate of products. The carbon dioxide adopted by the method comes from the desulfurization flue gas, so that partial carbon dioxide in partial desulfurization flue gas can be treated, and carbon emission is reduced. The nitrogen content in the ammonium sulfate product obtained in the method is more than or equal to 20.8%, meets the I-class standard of fertilizer grade ammonium sulfate (GB/T535-2020), has the heavy metal content lower than the limit requirement of harmful substances, and can be used as agricultural grade waste.
According to the disclosure, carbon dioxide in the desulfurized flue gas and NH in the ammonia water 3 The molar ratio of (c) may vary within a large range. In one embodiment of the present disclosure, in step S1, carbon dioxide in the desulfurized flue gas and NH in the aqueous ammonia 3 The molar ratio of (2) is 1:2-2.2. When the carbon dioxide in the desulfurization flue gas and NH in the ammonia water 3 When the molar ratio is within the range of the above embodiment, the first reaction proceeds more favorably. In a preferred embodiment of the present disclosure, the concentration of the aqueous ammonia is 10-25%.
The temperature and time of the first reaction may vary within a wide range according to the present disclosure. In one embodiment of the present disclosure, the conditions of the first reaction include: the temperature is 20-50deg.C, and the time is 30-90min. When the temperature and time of the first reaction may be within the ranges of the above embodiments, the progress of the first reaction may be further promoted.
According to the present disclosure, the molar ratio of calcium sulfate in the desulfurized gypsum slurry to ammonium carbonate in the first liquid product can vary over a wide range. In one embodiment of the present disclosure, in step S2, the molar ratio of calcium sulfate in the desulfurized gypsum slurry to ammonium carbonate in the first liquid product is 1:1-1.1. The second reaction is favored when the molar ratio of calcium sulfate in the gypsum slurry to ammonium carbonate in the first liquid product is within the scope of the above embodiments.
The temperature, time and agitation rate of the second reaction may vary over a wide range in accordance with the present disclosure. In one embodiment of the present disclosure, the conditions of the second reaction include: the temperature is 20-70 ℃, the time is 30-120min, and the stirring speed is 60-600r/min. When the temperature, time and stirring rate of the second reaction are within the ranges of the above embodiments, the progress of the second reaction can be further promoted.
In one embodiment of the present disclosure, in step S2, the method further comprises: the desulfurized gypsum from the gypsum desulfurization unit and the aqueous ammonia waste liquid from the evaporative crystallization device 5 are fed into the mixing device 1 to be mixed so as to obtain the desulfurized gypsum slurry. In the above embodiment, the mass ratio of the desulfurized gypsum to the aqueous ammonia waste liquid is 1:5-10; the conditions of the mixing treatment include: the temperature is 20-50 ℃, the time is 30-90min, and the stirring speed is 300-600r/min. In the present disclosure, the aqueous ammonia waste liquid can be returned to the mixing device to be mixed with the desulfurized gypsum to prepare gypsum slurry, thereby reducing the cost of desulfurized gypsum treatment.
In the present disclosure, the solid-liquid separation device may employ a separation device conventional in the art, as long as separation of the calcium carbonate product in the second solid-liquid mixed product can be achieved. In one embodiment of the present disclosure, in step S3, the solid-liquid separation device 4 is selected from one or more of a settling device, a clarifier, a filter, a cyclone separator, and a filter press.
In the present disclosure, by detecting the particle size and purity of the calcium carbonate product and then comparing with the particle size and purity requirements for the calcium carbonate product in the limestone/lime-gypsum wet flue gas desulfurization engineering general technical specification (HJ 179-2018), the inventors of the present disclosure found that the particle size range and purity of the calcium carbonate product separated by the solid-liquid separation device can satisfy the calcium carbonate content requirement of not less than 85% when the limestone-gypsum desulfurization system performs desulfurization, and the sieving rate of not less than 90% when sieving under the condition of not less than 250 mesh (65 μm).
In one embodiment of the present disclosure, the method further comprises: and returning the calcium carbonate product to a gypsum desulfurization unit for flue gas desulfurization treatment.
In the present disclosure, the calcium carbonate product can be returned to the gypsum desulfurization unit for flue gas desulfurization treatment, which not only reduces the ball milling system of limestone in the limestone-gypsum desulfurization system, but also reduces ore exploitation, simplifies the process flow, and reduces the cost of gypsum desulfurization.
In one embodiment of the present disclosure, the method further comprises:
SS1, making the gas product from the absorption tower 3 enter into the tail gas purifying device 6 to contact with the absorbent for tail gas purifying treatment, so as to obtain a fourth liquid product and purified waste gas;
SS2, the fourth liquid product is introduced into the evaporative crystallization device 5 to be subjected to evaporative crystallization treatment.
The concentration of the absorbent may vary over a wide range in accordance with the present disclosure. In one embodiment of the present disclosure, the absorbent is at a concentration of 1-10moL/L, preferably the absorbent is sulfuric acid. To absorb residual ammonia in the gaseous product. In the exhaust gas purification treatment, the contact time of the absorbent and the gas product is 20-60min.
In the present disclosure, a third liquid product obtained by performing separation treatment by a solid-liquid separation device and a fourth liquid product obtained by performing tail gas purification treatment by a tail gas purification device are both introduced into an evaporative crystallization device to perform evaporative crystallization treatment. According to the present disclosure, the temperature and time of the evaporative crystallization process may vary over a wide range. In one embodiment of the present disclosure, the conditions of the evaporative crystallization process include: the temperature is 80-110deg.C, and the time is 30-80min. The evaporative crystallization device may be a conventional device in the art, and is not described herein, and may be a multiple-effect evaporation system or a mechanical compression evaporation system, for example. The ammonia water waste liquid obtained by evaporation and crystallization treatment is circulated to a mixing device to be mixed with the desulfurized gypsum to prepare gypsum slurry, so that the cost of raw materials is reduced.
The gypsum desulfurization treatment is carried out by a gypsum desulfurization system of a power plant, which is adopted by the disclosure, and the system comprises a reaction unit and a purification unit;
the reaction unit comprises a mixing device 1, a reaction device 2 and an absorption tower 3, wherein the outlet of the mixing device 1 is communicated with the gypsum slurry inlet of the reaction device 2, and the first liquid product outlet of the absorption tower 3 is communicated with the first liquid product inlet of the reaction device 2;
the purification unit comprises a solid-liquid separation device 4 and an evaporation crystallization device 5, the outlet of the reaction device 2 is communicated with the inlet of the solid-liquid separation device 4, the outlet of the second liquid product of the solid-liquid separation device 4 is communicated with the inlet of the second liquid product of the evaporation crystallization device 5, and the outlet of the ammonia water waste liquid of the evaporation crystallization device 5 is communicated with the inlet of the ammonia water waste liquid of the mixing device 1.
The purification unit further comprises a tail gas purification device 6, a gas product outlet of the absorption tower 3 is communicated with an inlet of the tail gas purification device 6, and a third liquid product outlet of the tail gas purification device 6 is communicated with a third liquid product inlet of the evaporative crystallization device 5.
The invention is further illustrated by the following examples, which are not intended to be limiting in any way.
The chemical reagents used in the following examples and comparative examples are commercially available.
Example 1
The method for treating the desulfurization gypsum of the power plant by adopting the gypsum desulfurization system of the power plant comprises the following steps:
s1, enabling desulfurization flue gas and ammonia water (15%) to be in a molar ratio of carbon dioxide in the desulfurization flue gas to ammonia in the ammonia water of 1:2, and performing a first reaction for 60min at 30 ℃ to obtain a first liquid product and a gas product; the reaction equation for the first reaction is: CO 2 +2NH 3 ·H2O＝(NH 4 ) 2 CO 3 +H 2 O；
S2, mixing the desulfurized gypsum with the ammonia water waste liquid from the evaporative crystallization device 5 according to the ratio of 1:10, and mixing for 30min at 30deg.C and 300r/min to obtain gypsum slurry;
the desulfurized gypsum slurry and the first liquid product are reacted in a molar ratio of calcium sulfate in the desulfurized gypsum slurry to ammonium carbonate in the first liquid product of 1:1 into a reaction device 2, and carrying out a second reaction for 60min at the temperature of 30 ℃ and the stirring speed of 200r/min to obtain a second solid-liquid mixture; the reaction equation for the second reaction is: caSO (Caso-like conductor) 4 ·2H 2 O+(NH 4 ) 2 CO 3 ＝CaCO 3 +(NH 4 ) 2 SO 4 +2H 2 O；
S3, enabling the second solid-liquid mixture to sequentially enter a sedimentation tank and a filter press for solid-liquid separation treatment to obtain a calcium carbonate product and a third liquid product;
s4, enabling the gas product of the absorption tower 3 to enter a tail gas purification device 6, enabling the gas product to be in contact with sulfuric acid (1 moL/L) for 60min for tail gas purification treatment, obtaining a fourth liquid product and purified waste gas, and enabling the purified waste gas to be discharged into the atmosphere;
and enabling the third liquid product and the fourth liquid product to enter an evaporation crystallization device 5, and performing evaporation crystallization treatment for 60min at the temperature of 90 ℃ to obtain an ammonium sulfate product and ammonia water waste liquid.
Example 2
The same method as in example 1 was used, except that S1, the molar ratio of carbon dioxide in the desulfurized flue gas to ammonia in the ammonia water was 1:2.1 into an absorption tower 3;
s2, mixing the desulfurized gypsum with the ammonia water waste liquid from the evaporative crystallization device 5 according to the ratio of 1: a ratio of 8.5 into the mixing device 1;
the desulfurized gypsum slurry and the first liquid product of absorber 3 were reacted in a molar ratio of calcium sulfate in the gypsum slurry to ammonium carbonate in the first liquid product of 1: a ratio of 1.05 into the reaction device 2; carrying out a second reaction for 90min under the conditions of 50 ℃ and a stirring rate of 400 r/min;
s3, enabling the second solid-liquid mixture to sequentially enter a clarifier, a filter and a filter press for solid-liquid separation treatment, and obtaining a calcium carbonate product and a third liquid product.
Example 3
The same method as in example 1 was used, except that S1, the molar ratio of carbon dioxide in the desulfurized flue gas to ammonia in the ammonia water was 1:2.2 into the absorption tower 3;
s2, mixing the desulfurized gypsum with the ammonia water waste liquid from the evaporative crystallization device 5 according to the ratio of 1:5 into the mixing device 1;
the desulfurized gypsum slurry and the first liquid product of absorber 3 were reacted in a molar ratio of calcium sulfate in the gypsum slurry to ammonium carbonate in the first liquid product of 1:1.1 into the reaction device 2; carrying out a second reaction for 120min at 70 ℃ under the condition of stirring speed of 600 r/min;
s3, enabling the second solid-liquid mixture to sequentially enter a sedimentation tank, a filter and a filter press for solid-liquid separation treatment, and obtaining a calcium carbonate product and a third liquid product.
Comparative example 1
The same procedure as in example 1 was adopted except that the gypsum slurry, ammonia water and desulfurized flue gas were simultaneously fed into the reaction apparatus 2 for carrying out the reaction.
Test case
The ammonium sulfate obtained in examples 1 to 3 and comparative example 1 was tested according to GB/T535 to 2020.
The calcium carbonate obtained in examples 1 to 3 and comparative example 1 was examined, and the average particle diameter was examined using a laser particle size analyzer (Mastersizer 2000); purity was measured using a thermogravimetric analyzer (NETZSCH STA 449F 3). The results are shown in Table 1.
TABLE 1
As can be seen from Table 1, the ammonium sulfate products prepared in examples 1-3 have higher nitrogen content than comparative example 1, and it can be seen that the ammonium sulfate products obtained by the method of the present disclosure have nitrogen content of 20.8% or more, and meet the class I standard of fertilizer grade ammonium sulfate (GB/T535-2020).
The purity and conversion rate of the calcium carbonate product prepared in the examples 1-3 are higher than those of the calcium carbonate product prepared in the comparative example 1, the purity of the calcium carbonate product is more than or equal to 85 percent, and the sieving rate of the calcium carbonate product is more than 90 percent when sieving under the condition of not less than 250 meshes (65 mu m), which shows that the calcium carbonate product obtained by the method disclosed by the invention meets the requirements on the particle size range and the purity of the calcium carbonate product in the general technical specification (HJ 179-2018) of limestone/lime-gypsum wet flue gas desulfurization engineering.
As can be seen from a comparison of the data of example 1 and comparative example 1, the conversion of calcium carbonate in example 1 is much greater than that of comparative example 1, indicating that the two-step process of the present application can increase the conversion of calcium carbonate.
The preferred embodiments of the present disclosure have been described in detail above with reference to the accompanying drawings, but the present disclosure is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solutions of the present disclosure within the scope of the technical concept of the present disclosure, and all the simple modifications belong to the protection scope of the present disclosure.
In addition, the specific features described in the foregoing embodiments may be combined in any suitable manner, and in order to avoid unnecessary repetition, the present disclosure does not further describe various possible combinations.
Moreover, any combination between the various embodiments of the present disclosure is possible as long as it does not depart from the spirit of the present disclosure, which should also be construed as the disclosure of the present disclosure.
Claims (10)
1. A method for desulfurizing gypsum in a power plant, the method comprising the steps of:
s1, carrying out a first reaction on desulfurization flue gas and ammonia water in an absorption tower (3) to obtain a first liquid product and a gas product;
s2, enabling the desulfurized gypsum slurry and the first liquid product to enter a reaction device (2) for a second reaction to obtain a second solid-liquid mixed product;
s3, enabling the second solid-liquid mixed product to enter a solid-liquid separation device (4) for solid-liquid separation treatment to obtain a calcium carbonate product and a third liquid product;
s4, enabling the third liquid product to enter an evaporation crystallization device (5) for evaporation crystallization treatment, and obtaining an ammonium sulfate product and ammonia water waste liquid.
2. The method according to claim 1, characterized in that in step S1 the carbon dioxide in the desulphurised flue gas and the NH in the ammonia water 3 The molar ratio of (2) is 1:2-2.2;
the concentration of the ammonia water is 10-25%;
the conditions of the first reaction include: the temperature is 20-50deg.C, and the time is 30-90min.
3. The method of claim 1, wherein in step S2 the molar ratio of calcium sulfate in the desulfurized gypsum slurry to ammonium carbonate in the first liquid product is 1:1-1.1;
the conditions of the second reaction include: the temperature is 20-70 ℃, the time is 30-120min, and the stirring speed is 60-600r/min.
4. The method according to claim 1, characterized in that the method further comprises: and (3) enabling the desulfurized gypsum from the gypsum desulfurization unit and the ammonia water waste liquid from the evaporation crystallization device (5) to enter a mixing device (1) for mixing treatment, so as to obtain the desulfurized gypsum slurry.
5. The method according to claim 4, wherein the mass ratio of the desulfurized gypsum to the aqueous ammonia waste liquid is 1:5-10;
the conditions of the mixing treatment include: the temperature is 20-50 ℃, the time is 30-90min, and the stirring speed is 300-600r/min.
6. The method according to claim 1, characterized in that in step S3, the solid-liquid separation device (4) is selected from one or several of a settling device, a clarifier, a filter, a cyclone separator and a filter press.
7. The method according to claim 1, wherein the method further comprises: and returning the calcium carbonate product to a gypsum desulfurization unit for flue gas desulfurization treatment.
8. The method according to claim 1, characterized in that the method further comprises:
SS1, enabling the gas product from the absorption tower (3) to enter a tail gas purification device (6) to be in contact with an absorbent for tail gas purification treatment, so as to obtain a fourth liquid product and purified waste gas;
SS2, the fourth liquid product is put into an evaporative crystallization device (5) for evaporative crystallization treatment.
9. The method according to claim 8, wherein the absorbent is at a concentration of 1-10moL/L, preferably the absorbent is sulfuric acid.
10. The method according to claim 9, wherein in the exhaust gas purification treatment, the contact time of the absorbent with the gaseous product is 20 to 60min;
the conditions of the evaporative crystallization treatment include: the temperature is 80-110deg.C, and the time is 30-80min.
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