CN111187016B - System and process for preparing high-strength alpha-semi-hydrated gypsum from desulfurized gypsum and product thereof - Google Patents
System and process for preparing high-strength alpha-semi-hydrated gypsum from desulfurized gypsum and product thereof Download PDFInfo
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- CN111187016B CN111187016B CN202010043588.4A CN202010043588A CN111187016B CN 111187016 B CN111187016 B CN 111187016B CN 202010043588 A CN202010043588 A CN 202010043588A CN 111187016 B CN111187016 B CN 111187016B
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- 239000010440 gypsum Substances 0.000 title claims abstract description 77
- 229910052602 gypsum Inorganic materials 0.000 title claims abstract description 76
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 9
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 64
- 239000000706 filtrate Substances 0.000 claims abstract description 50
- 238000006243 chemical reaction Methods 0.000 claims abstract description 42
- 238000005406 washing Methods 0.000 claims abstract description 41
- UXVMQQNJUSDDNG-UHFFFAOYSA-L Calcium chloride Chemical compound [Cl-].[Cl-].[Ca+2] UXVMQQNJUSDDNG-UHFFFAOYSA-L 0.000 claims abstract description 38
- 238000006477 desulfuration reaction Methods 0.000 claims abstract description 36
- 230000023556 desulfurization Effects 0.000 claims abstract description 36
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims abstract description 25
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 claims abstract description 25
- 239000011575 calcium Substances 0.000 claims abstract description 25
- 229910052791 calcium Inorganic materials 0.000 claims abstract description 25
- 239000003546 flue gas Substances 0.000 claims abstract description 25
- 239000002002 slurry Substances 0.000 claims abstract description 25
- 239000012066 reaction slurry Substances 0.000 claims abstract description 22
- 238000000034 method Methods 0.000 claims abstract description 20
- 238000003860 storage Methods 0.000 claims abstract description 20
- 238000001035 drying Methods 0.000 claims abstract description 17
- 238000011010 flushing procedure Methods 0.000 claims abstract description 16
- 239000012043 crude product Substances 0.000 claims abstract description 14
- 230000008569 process Effects 0.000 claims abstract description 12
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 claims abstract description 10
- 239000007788 liquid Substances 0.000 claims abstract description 6
- 238000002156 mixing Methods 0.000 claims abstract description 6
- 238000000926 separation method Methods 0.000 claims abstract description 5
- 239000007789 gas Substances 0.000 claims description 17
- 239000012266 salt solution Substances 0.000 claims description 16
- 239000001110 calcium chloride Substances 0.000 claims description 13
- 229910001628 calcium chloride Inorganic materials 0.000 claims description 13
- 239000000463 material Substances 0.000 claims description 12
- 239000007787 solid Substances 0.000 claims description 10
- 239000007921 spray Substances 0.000 claims description 6
- 150000004683 dihydrates Chemical class 0.000 claims description 5
- 230000035484 reaction time Effects 0.000 claims description 3
- 238000004891 communication Methods 0.000 claims description 2
- 239000000047 product Substances 0.000 abstract description 6
- 150000003839 salts Chemical class 0.000 description 6
- 239000002912 waste gas Substances 0.000 description 5
- 239000000428 dust Substances 0.000 description 4
- 238000003756 stirring Methods 0.000 description 4
- BHPQYMZQTOCNFJ-UHFFFAOYSA-N Calcium cation Chemical compound [Ca+2] BHPQYMZQTOCNFJ-UHFFFAOYSA-N 0.000 description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 3
- 229910001424 calcium ion Inorganic materials 0.000 description 3
- 238000010924 continuous production Methods 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 238000000746 purification Methods 0.000 description 3
- 238000004064 recycling Methods 0.000 description 3
- KIUKXJAPPMFGSW-DNGZLQJQSA-N (2S,3S,4S,5R,6R)-6-[(2S,3R,4R,5S,6R)-3-Acetamido-2-[(2S,3S,4R,5R,6R)-6-[(2R,3R,4R,5S,6R)-3-acetamido-2,5-dihydroxy-6-(hydroxymethyl)oxan-4-yl]oxy-2-carboxy-4,5-dihydroxyoxan-3-yl]oxy-5-hydroxy-6-(hydroxymethyl)oxan-4-yl]oxy-3,4,5-trihydroxyoxane-2-carboxylic acid Chemical compound CC(=O)N[C@H]1[C@H](O)O[C@H](CO)[C@@H](O)[C@@H]1O[C@H]1[C@H](O)[C@@H](O)[C@H](O[C@H]2[C@@H]([C@@H](O[C@H]3[C@@H]([C@@H](O)[C@H](O)[C@H](O3)C(O)=O)O)[C@H](O)[C@@H](CO)O2)NC(C)=O)[C@@H](C(O)=O)O1 KIUKXJAPPMFGSW-DNGZLQJQSA-N 0.000 description 2
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 230000018044 dehydration Effects 0.000 description 2
- 238000006297 dehydration reaction Methods 0.000 description 2
- 238000005265 energy consumption Methods 0.000 description 2
- 238000001914 filtration Methods 0.000 description 2
- 150000004676 glycans Chemical class 0.000 description 2
- 229920002674 hyaluronan Polymers 0.000 description 2
- 229960003160 hyaluronic acid Drugs 0.000 description 2
- 230000014759 maintenance of location Effects 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 229920001282 polysaccharide Polymers 0.000 description 2
- 239000005017 polysaccharide Substances 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 230000001502 supplementing effect Effects 0.000 description 2
- 239000002351 wastewater Substances 0.000 description 2
- 229920001285 xanthan gum Polymers 0.000 description 2
- 239000000230 xanthan gum Substances 0.000 description 2
- 229940082509 xanthan gum Drugs 0.000 description 2
- 235000010493 xanthan gum Nutrition 0.000 description 2
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 1
- KDYFGRWQOYBRFD-UHFFFAOYSA-N Succinic acid Natural products OC(=O)CCC(O)=O KDYFGRWQOYBRFD-UHFFFAOYSA-N 0.000 description 1
- 230000002159 abnormal effect Effects 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- DIZPMCHEQGEION-UHFFFAOYSA-H aluminium sulfate (anhydrous) Chemical compound [Al+3].[Al+3].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O DIZPMCHEQGEION-UHFFFAOYSA-H 0.000 description 1
- -1 aluminum ions Chemical class 0.000 description 1
- 229910052925 anhydrite Inorganic materials 0.000 description 1
- KDYFGRWQOYBRFD-NUQCWPJISA-N butanedioic acid Chemical compound O[14C](=O)CC[14C](O)=O KDYFGRWQOYBRFD-NUQCWPJISA-N 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 229910000019 calcium carbonate Inorganic materials 0.000 description 1
- OSGAYBCDTDRGGQ-UHFFFAOYSA-L calcium sulfate Chemical compound [Ca+2].[O-]S([O-])(=O)=O OSGAYBCDTDRGGQ-UHFFFAOYSA-L 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
- 239000000460 chlorine Substances 0.000 description 1
- 229910052801 chlorine Inorganic materials 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 239000002440 industrial waste Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 239000003607 modifier Substances 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 229910001414 potassium ion Inorganic materials 0.000 description 1
- OTYBMLCTZGSZBG-UHFFFAOYSA-L potassium sulfate Chemical compound [K+].[K+].[O-]S([O-])(=O)=O OTYBMLCTZGSZBG-UHFFFAOYSA-L 0.000 description 1
- 229910052939 potassium sulfate Inorganic materials 0.000 description 1
- 235000011151 potassium sulphates Nutrition 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 238000011165 process development Methods 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 238000010992 reflux Methods 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- 239000002910 solid waste Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
Images
Classifications
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B11/00—Calcium sulfate cements
- C04B11/26—Calcium sulfate cements strating from chemical gypsum; starting from phosphogypsum or from waste, e.g. purification products of smoke
- C04B11/262—Calcium sulfate cements strating from chemical gypsum; starting from phosphogypsum or from waste, e.g. purification products of smoke waste gypsum other than phosphogypsum
- C04B11/264—Gypsum from the desulfurisation of flue gases
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Ceramic Engineering (AREA)
- Materials Engineering (AREA)
- Structural Engineering (AREA)
- Organic Chemistry (AREA)
- Treating Waste Gases (AREA)
- Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
Abstract
The invention discloses a system and a process for preparing high-strength alpha-semi-hydrated gypsum from desulfurized gypsum and a product thereof. The process comprises the following steps: mixing and reacting cyclone underflow slurry of a calcium-based wet flue gas desulfurization system and a calcium chloride solution in a reaction kettle, carrying out solid-liquid separation and two-stage flushing on the reaction slurry through a vacuum belt conveyor after the reaction is finished to obtain an alpha-semi-hydrated gypsum crude product, a reaction slurry filtrate, a first-stage flushing water filtrate and a second-stage flushing water filtrate, and drying the alpha-semi-hydrated gypsum crude product to obtain high-strength alpha-semi-hydrated gypsum; and recovering reaction slurry filtrate and first-stage washing water filtrate for preparing a calcium chloride solution, and recovering second-stage washing water filtrate for a calcium-based wet flue gas desulfurization system. The system comprises a coal-fired boiler, a desulfurization system containing a cyclone, a saline solution storage tank with a first temperature control device, a reaction kettle with a second temperature control device, a vacuum belt conveyor and a dryer.
Description
Technical Field
The invention relates to the technical field of industrial waste recycling, in particular to a system and a process for preparing high-strength alpha-semi-hydrated gypsum from desulfurized gypsum and a product thereof.
Background
In recent decades, calcium-based wet flue gas desulfurization has become the largest flue gas desulfurization process in China, so that a large amount of desulfurization byproducts, mainly desulfurization gypsum, are produced. If the desulfurized gypsum is not properly disposed and comprehensively utilized, the desulfurized gypsum is bound to become solid waste, possibly causes secondary pollution to the environment, and can restrict the development of the calcium-based wet flue gas desulfurization process. Therefore, SO can be fundamentally solved only by realizing effective resource utilization of the desulfurized gypsum2The method has the advantages of increasing the selection space of the flue gas desulfurization method, improving the technical level of wet flue gas desulfurization, expanding the environmental capacity of process development, realizing the conversion from 'resource-product-waste discharge and tail end treatment' to 'resource-product-renewable resource and recycling' mode, and promoting the credit-worthwhile circulation of the desulfurization industry.
The method for preparing the high-strength alpha-semi-hydrated gypsum by utilizing the desulfurized gypsum is a resource utilization way with high added value, the process for preparing the alpha-semi-hydrated gypsum by utilizing the desulfurized gypsum is still in the beginning stage at present, and few cases for realizing engineering application are provided. Patent specification CN 107572571A discloses a preparation method of high-strength flaky alpha-semi-hydrated gypsum, which comprises the steps of mixing desulfurized gypsum, water, sulfate (potassium sulfate or aluminum sulfate) and biomacromolecule polysaccharide crystal-converting agent (hyaluronic acid or xanthan gum), stirring and refluxing for 2-4 h in a reactor under the conditions of normal pressure, 93-97 ℃ and pH value of 4.5-7.5, and finally dehydrating, washing and drying to obtain the alpha-semi-hydrated gypsum. The technology can not be matched with calcium-based wet desulphurization to realize continuous production, and potassium ions, aluminum ions, hyaluronic acid, xanthan gum and other substances in a desulphurization system can be increased by adding sulfate and a biomacromolecule polysaccharide crystal transformation agent in the reaction process, so that the desulphurization system can not normally run.
The patent specification with publication number CN 107399755A discloses a method for preparing high-whiteness short-column alpha-semi-hydrated gypsum from desulfurized gypsum, which comprises the steps of mixing concentrated hydrochloric acid, water, calcium chloride and desulfurized gypsum, heating to 95-100 ℃ for reaction, aging after the reaction is finished, filtering, washing to be neutral, and drying; mixing the slurry with water, NaCl and succinic acid, and adjusting the pH of the slurry to 7-12; and placing the mixture in a crystallization kettle for reaction, filtering and drying to obtain the high-whiteness short columnar alpha-semi-hydrated gypsum. The technical method is complex, the reaction time is long, and the reagents required by the reaction cannot be recycled, so that the operation cost is overhigh.
The patent specification with the publication number of CN 100345788C discloses a preparation method of alpha-type high-strength gypsum, which comprises the steps of adding 0.1-1% of a habit modifier and 10-15% of water into desulfurized gypsum, uniformly stirring, mechanically pressing into a spherical or blocky shape, placing into an autoclave, autoclaving at the temperature of 135-160 ℃ for 1-3 hours under the saturated steam condition, preserving heat at the temperature of 80-100 ℃, finally drying and crushing to obtain the alpha-type high-strength gypsum. The technology needs to react at high temperature and high pressure, the required energy consumption is high, and the technology cannot be matched with calcium-based wet desulphurization to realize continuous production.
Disclosure of Invention
Aiming at the defects in the field, the invention provides a process for preparing high-strength alpha-semi-hydrated gypsum from desulfurized gypsum, which takes underflow slurry of a cyclone of a coal-fired flue gas calcium-based wet desulphurization system as a raw material and prepares the high-strength alpha-semi-hydrated gypsum by a normal-pressure salt solution method.
A process for preparing high-strength alpha-hemihydrate gypsum from desulfurized gypsum comprises the following steps: mixing and reacting cyclone underflow slurry of a calcium-based wet flue gas desulfurization system and a calcium chloride solution in a reaction kettle, carrying out solid-liquid separation and two-stage flushing on the reaction slurry through a vacuum belt conveyor after the reaction is finished to obtain an alpha-semi-hydrated gypsum crude product, a reaction slurry filtrate, a first-stage flushing water filtrate and a second-stage flushing water filtrate, and drying the alpha-semi-hydrated gypsum crude product to obtain the high-strength alpha-semi-hydrated gypsum;
and recovering the reaction slurry filtrate and the first-stage washing water filtrate to prepare the calcium chloride solution, and recovering the second-stage washing water filtrate to use the calcium-based wet flue gas desulfurization system.
The invention changes the coal-fired flue gas calcium-based wet desulphurization gypsum production process, the slurry of the cyclone underflow does not directly enter a vacuum belt conveyor, but enters a reaction kettle first, and then enters the vacuum belt conveyor after generating a high-strength alpha-semi-hydrated gypsum crude product under the action of a calcium chloride solution, so that the one-time dehydration and washing process can be saved, the investment and operation cost can be reduced, the water balance of the whole system can be ensured, and no new wastewater is generated.
Secondly, the reaction slurry filtrate and the first-stage flushing water filtrate of the vacuum belt conveyor are collected and then conveyed back to a salt solution storage tank to be used as a calcium chloride solution for standby. Chlorine-containing gas such as HCl is usually present in coal-fired flue gas and is absorbed by desulfurization slurry after calcium-based wet flue gas desulfurization, and the main components of the desulfurization slurry are calcium sulfate dihydrate and calcium carbonate, so that the cyclone sub-underflow slurry often contains a large amount of chloride ions and calcium ions, and the calcium chloride carried away by the alpha-hemihydrate gypsum and the secondary washing water can be supplemented by the chloride ions and the calcium ions in the cyclone sub-underflow slurry, so that the balance of the salt solution concentration of the whole system is realized, new calcium chloride does not need to be supplemented, and the operation cost can be reduced.
Preferably, the solid content of the cyclone underflow slurry is 40-60%, and the purity of the dihydrate gypsum in the solid matter is more than 85%.
In order to prevent the calcium chloride solution from crystallizing out, the temperature of the calcium chloride solution is preferably 25-40 ℃, and the mass fraction of the calcium chloride is preferably 40-50%.
Preferably, the volume ratio of the cyclone underflow slurry to the calcium chloride solution is 1: 0.8-3.
Preferably, the reaction temperature is 90-98 ℃, and the reaction time is 2-5 h.
Preferably, in the two-stage washing, the volume ratio of the first-stage washing water to the reaction slurry is 1: 6-40, and the volume ratio of the second-stage washing water to the reaction slurry is 1: 0.5-1.5. The secondary washing water filtrate is recycled and used for the calcium-based wet flue gas desulfurization system, and can be used for specifically using as water for slurrying, washing of a demister of a desulfurization tower and the like, so that on one hand, not only is the water required for slurrying and washing of the demister of the desulfurization tower originally saved, but also the water balance of the whole system can be ensured, no new waste water is generated, on the other hand, the secondary washing water filtrate finally enters the cyclone to become a part of the cyclone underflow slurry, circulation is formed, and the cost is reduced.
Preferably, the alpha-hemihydrate gypsum crude product has an attached water content of 5% to 30%.
Preferably, the drying temperature is 100-150 ℃. Too high a drying temperature can result in dehydration of the alpha-hemihydrate to form anhydrite.
The invention also provides the high-strength alpha-semi-hydrated gypsum prepared by the process, the attached water content of the high-strength alpha-semi-hydrated gypsum is less than 3%, the whiteness is greater than 70, and the flexural strength is greater than 25 MPa.
The invention also provides a system for preparing high-strength alpha-semi-hydrated gypsum from desulfurized gypsum, which comprises a coal-fired boiler and a calcium-based wet flue gas desulfurization system, wherein the calcium-based wet flue gas desulfurization system comprises a cyclone, and the process is adopted, and the system also comprises:
the saline solution storage tank is provided with a first temperature control device and is used for preparing and storing the calcium chloride solution;
the top of the reaction kettle is communicated with the cyclone underflow pipe and the salt solution storage tank, and the bottom of the reaction kettle is provided with a discharge port;
a material inlet is communicated with the discharge port, a first section of washing water spray head and a second section of washing water spray head are sequentially arranged above a belt of the vacuum belt along the material advancing direction, a front section of filtrate collecting tank and a rear section of filtrate collecting tank are arranged at the bottom of the vacuum belt, the front section of filtrate collecting tank is communicated with the saline solution storage tank and is used for recovering the reaction slurry filtrate and the first section of washing water filtrate, and the rear section of filtrate collecting tank is connected with the calcium-based wet flue gas desulfurization system and is used for recovering the second section of washing water filtrate;
and the dryer is used for drying the alpha-semi-hydrated gypsum crude product, the top of the dryer is provided with a gas outlet and a feed inlet communicated with the material outlet of the vacuum belt conveyor, and the bottom of the dryer is provided with a discharge outlet and a gas inlet for high-temperature drying gas to enter.
Preferably, the gas outlet is in communication with a main flue of the coal-fired boiler. The waste gas of the dryer enters a main flue of the coal-fired boiler through a gas outlet, and is discharged after being treated by purification equipment (such as a dust remover and the like).
Compared with the prior art, the invention has the main advantages that:
1. the normal-pressure salt solution method is adopted as a reaction mode, so that the investment is low, the energy consumption is low, high-pressure equipment is not required, and the method is safe and stable.
2. The invention can be seamlessly butted with the existing coal-fired flue gas calcium-based wet desulphurization, and continuous production operation is realized.
3. The underflow slurry of the cyclone is used as a raw material to prepare the high-strength alpha-hemihydrate gypsum, so that the processes of dewatering and washing at one time can be saved, the investment and operation cost can be reduced, and the water balance of the whole system can be ensured.
4. By recycling the filtrate and supplementing the calcium chloride brought away by the alpha-hemihydrate gypsum and the secondary washing water by using the chloride ions and the calcium ions in the cyclone underflow slurry, the salt solution concentration of the whole system is balanced without supplementing new calcium chloride, and the operation cost is reduced.
5. The waste gas at the outlet of the dryer is directly introduced into the flue of the main boiler body, so that subsequent waste gas purification equipment can be omitted, and the investment and the operation cost are saved.
Drawings
FIG. 1 is a schematic view of a system for producing high strength alpha-hemihydrate gypsum from desulfurized gypsum according to an embodiment;
in the figure: the system comprises a desulfurization system 1, a cyclone 2, a salt solution storage tank 3, a salt bin 4, a reaction kettle 5, a vacuum belt conveyor 6, reaction slurry filtrate, first-stage flushing water filtrate 7, second-stage flushing water filtrate 8, a dryer 9, high-temperature drying gas 10, a main flue 11 and an alpha-hemihydrate gypsum bin 12.
Detailed Description
The invention is further described with reference to the following drawings and specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. The following examples are conducted under conditions not specified, usually according to conventional conditions, or according to conditions recommended by the manufacturer.
As shown in fig. 1, the system for preparing high-strength alpha-semi-hydrated gypsum from desulfurized gypsum of this embodiment includes a coal-fired boiler and a corresponding calcium-based wet flue gas desulfurization system (desulfurization system for short) 1, the coal-fired boiler has a main flue 11, and the calcium-based wet flue gas desulfurization system 1 includes a cyclone 2. The system also comprises a salt solution storage tank 3, a salt bin 4, a reaction kettle 5, a vacuum belt conveyor 6, a dryer 9 and an alpha-semi-hydrated gypsum bin 12.
Salt storehouse 4 is used for storing and supplying with calcium chloride, and the bottom is equipped with the electric control valve who takes metering function, the feed rate of steerable calcium chloride, and 4 bottom calcium chloride exports in salt storehouse are located 3 tops of salt solution storage tank, and pass through the tube coupling with 3 tops of salt solution storage tank. The salt bin 4 conveys calcium chloride to the salt solution storage tank 3 when the first reaction and the system operation are abnormal, and the concentration of the calcium chloride in the salt solution storage tank 3 is ensured to be within a reasonable range.
The salt solution storage tank 3 is used for preparing and storing calcium chloride solution, is provided with a first temperature control device and is used for controlling the temperature of the calcium chloride solution in the tank. The saline solution storage tank 3 is connected with the top of the reaction kettle 5 through a pipeline.
The cyclone 2 receives the slurry from the desulfurization system 1, and the underflow outlet is positioned above the reaction kettle 5 and is connected with the top of the reaction kettle 5 through a pipeline.
The reaction kettle 5 is used as a reaction vessel for preparing the high-strength alpha-semi-hydrated gypsum from the desulfurized gypsum and is provided with a second temperature control device for controlling the reaction temperature. A stirring device is also arranged in the reaction kettle 5. The bottom of the reaction kettle 5 is connected with a discharge pump, and the other end of the discharge pump is connected with a material inlet of the vacuum belt conveyor 6.
A first section of washing water spray head and a second section of washing water spray head are sequentially arranged above the belt of the vacuum belt conveyor 6 along the advancing direction of the material. The bottom of the vacuum belt conveyor 6 is provided with a front filtrate collecting tank and a rear filtrate collecting tank, the front filtrate collecting tank is connected with the saline solution storage tank 3 through a pipeline and is mainly used for recovering reaction slurry filtrate and a section of washing water filtrate 7; the rear section filtrate collecting tank is connected with the desulfurization system 1 through a pipeline and is mainly used for recovering the filtrate 8 of the second-section washing water. The material outlet of the vacuum belt conveyor 6 is connected with the material inlet at the top of the dryer 9.
The dryer 9 is used for drying the alpha-semi-hydrated gypsum crude product, and the bottom of the dryer is provided with a discharge hole connected with an alpha-semi-hydrated gypsum bin 12. The gas in the dryer 9 flows from bottom to top, the bottom gas inlet is connected with the pipeline of the high-temperature dry gas 10, and the top gas outlet is connected with the boiler main body flue 11 in front of the purification equipment such as a dust remover. The waste gas discharged from the gas outlet of the dryer 9 enters the main flue 11 of the coal-fired boiler, and is discharged after being treated by a purifying device (such as a dust remover).
The system of the embodiment is adopted to prepare the high-strength alpha-semi-hydrated gypsum from the desulfurized gypsum, and the process flow is as follows:
slurry of the desulfurization system 1 is conveyed to the cyclone 2 through a pipeline, and after cyclone layering, underflow slurry with the solid content of 40-60% (the purity of dihydrate gypsum in solid matter is more than 85%) enters a reaction kettle 5 through a pipeline; the salt bin 4 conveys calcium chloride to the salt solution storage tank 3, and the mass fraction of the calcium chloride solution in the tank is kept to be 40-50%; the temperature of the salt solution storage tank 3 is controlled to be 25-40 ℃, and the flow rate is controlled by an electric valve, so that the volume ratio of the calcium chloride solution entering the reaction kettle 5 to the underflow slurry of the cyclone 2 is controlled to be 0.8-3: 1; after the underflow slurry of the cyclone 2 and the calcium chloride solution enter the reaction kettle 5, the mixture is stirred and mixed uniformly by a stirring device arranged in the reaction kettle 5.
The reaction temperature of the reaction kettle 5 is controlled to be 90-98 ℃, and the reaction residence time is controlled to be 2-5 hours. After the reaction is finished, the obtained reaction slurry is conveyed to a vacuum belt conveyor 6 through a pipeline for solid-liquid separation.
Washing the solid-liquid separated alpha-semi-hydrated gypsum in two sections by a washing water nozzle arranged above the vacuum belt conveyor 6, wherein the volume ratio of the first section of washing water to the reaction slurry is 1: 6-40, and the volume ratio of the second section of washing water to the reaction slurry is 1: 0.5-1.5; reaction slurry filtrate obtained by solid-liquid separation and first-stage washing water filtrate 7 are collected and then conveyed back to the saline solution storage tank 3 to be used as a calcium chloride solution for standby, and second-stage washing water filtrate 8 is collected and then conveyed back to the desulfurization system 1 to be used as water for slurrying and washing a demister of a desulfurization tower.
The content of the attached water of the washed alpha-semi-hydrated gypsum at the outlet of the vacuum belt conveyor 6 is 5-30%, the alpha-semi-hydrated gypsum is conveyed to a dryer 9 through a belt, the temperature of the dryer 9 is controlled to be 100-150 ℃, and a heat source is provided by high-temperature drying gas 10; the dried high-strength alpha-semi-hydrated gypsum enters an alpha-semi-hydrated gypsum bin 12, and the obtained high-strength alpha-semi-hydrated gypsum finished product has the attached water content of less than 3 percent, the whiteness of more than 70 percent and the flexural strength of more than 25 MPa. The dried waste gas enters a boiler main body flue 11 in front of the dust remover and is discharged after being purified.
Application example 1
The calcium-based wet desulphurization system of a 35t/h coal-fired boiler in a self-contained power plant adopts the process and the system for preparing the high-strength alpha-semi-hydrated gypsum from the desulfurized gypsum of the embodiment, and the flow rate of the slurry of the cyclone sub-bottom flow is 1.05m3The solid content is 50 percent, the purity of the dihydrate gypsum in the solid matter is 92 percent, the attached water content of the high-strength alpha-hemihydrate gypsum finished product is 2.3 percent, the whiteness is 70, and the flexural strength is 26 MPa.
The temperature of the reaction kettle is controlled at 96 ℃, the retention time is controlled at 4 hours, and the mass fraction of the calcium chloride solution is45 percent, and the flow rate of the calcium chloride solution is 2.05m3Per h, first stage flushing water flow of 0.30m3The flow rate of the second-stage flushing water is 2.90m3And h, the attached water content of the alpha-hemihydrate gypsum crude product at the material outlet of the vacuum belt conveyor is 14 percent.
Application example 2
The calcium-based wet desulphurization system of a 75t/h coal-fired boiler in a self-contained power plant adopts the process and the system for preparing the high-strength alpha-semi-hydrated gypsum from the desulfurized gypsum of the embodiment, and the flow rate of the slurry of the cyclone sub-bottom flow is 2.03m3The solid content is 50 percent, the purity of the dihydrate gypsum in the solid matter is 90.5 percent, the attached water content of the high-strength alpha-hemihydrate gypsum finished product is 2.5 percent, the whiteness is 75 percent, and the flexural strength is 25 MPa.
The temperature of the reaction kettle is controlled at 97 ℃, the retention time is controlled at 3.5 hours, the mass fraction of the calcium chloride solution is 50 percent, and the flow rate of the calcium chloride solution is 3.95m3Per h, first stage flushing water flow rate of 0.58m3H, the flow rate of the second-stage flushing water is 6.00m3And h, the attached water content of the alpha-hemihydrate gypsum crude product at the material outlet of the vacuum belt conveyor is 16 percent.
Furthermore, it should be understood that various changes and modifications can be made by one skilled in the art after reading the above description of the present invention, and equivalents also fall within the scope of the invention as defined by the appended claims.
Claims (4)
1. A process for preparing high-strength alpha-semi-hydrated gypsum from desulfurized gypsum is characterized by comprising the following steps: mixing and reacting cyclone underflow slurry of a calcium-based wet flue gas desulfurization system and a calcium chloride solution in a reaction kettle, carrying out solid-liquid separation and two-stage flushing on the reaction slurry through a vacuum belt conveyor after the reaction is finished to obtain an alpha-semi-hydrated gypsum crude product, a reaction slurry filtrate, a first-stage flushing water filtrate and a second-stage flushing water filtrate, and drying the alpha-semi-hydrated gypsum crude product to obtain the high-strength alpha-semi-hydrated gypsum;
recovering the reaction slurry filtrate and the first-stage washing water filtrate to prepare the calcium chloride solution, and recovering the second-stage washing water filtrate to the calcium-based wet flue gas desulfurization system;
the solid content of the cyclone underflow slurry is 40-60%, and the purity of dihydrate gypsum in the solid matter is more than 85%;
the temperature of the calcium chloride solution is 25-40 ℃, and the mass fraction of calcium chloride is 40-50%;
the volume ratio of the cyclone underflow slurry to the calcium chloride solution is 1: 0.8-3;
the reaction temperature is 90-98 ℃, and the reaction time is 2-5 h;
in the two-stage washing, the volume ratio of first-stage washing water to the reaction slurry is 1: 6-40, and the volume ratio of second-stage washing water to the reaction slurry is 1: 0.5-1.5;
the attached water content of the alpha-hemihydrate gypsum crude product is 5% -30%;
the drying temperature is 100-150 ℃;
the high-strength alpha-semi-hydrated gypsum has the attached water content of less than 3 percent, the whiteness of more than 70 percent and the flexural strength of more than 25 MPa.
2. The process of claim 1, wherein the system for preparing high-strength alpha-hemihydrate gypsum from desulfurized gypsum comprises a coal-fired boiler and a calcium-based wet flue gas desulfurization system, the calcium-based wet flue gas desulfurization system comprises a cyclone, and the system for preparing high-strength alpha-hemihydrate gypsum from desulfurized gypsum further comprises:
the saline solution storage tank is provided with a first temperature control device and is used for preparing and storing the calcium chloride solution;
the top of the reaction kettle with a second temperature control device is communicated with the cyclone underflow pipe and the salt solution storage tank, and the bottom of the reaction kettle is provided with a discharge port;
a material inlet is communicated with the discharge port, a first section of washing water spray head and a second section of washing water spray head are sequentially arranged above a belt of the vacuum belt along the material advancing direction, a front section of filtrate collecting tank and a rear section of filtrate collecting tank are arranged at the bottom of the vacuum belt, the front section of filtrate collecting tank is communicated with the saline solution storage tank and is used for recovering the reaction slurry filtrate and the first section of washing water filtrate, and the rear section of filtrate collecting tank is connected with the calcium-based wet flue gas desulfurization system and is used for recovering the second section of washing water filtrate;
and the dryer is used for drying the alpha-semi-hydrated gypsum crude product, the top of the dryer is provided with a gas outlet and a feed inlet communicated with the material outlet of the vacuum belt conveyor, and the bottom of the dryer is provided with a discharge outlet and a gas inlet for high-temperature drying gas to enter.
3. The process of claim 2, wherein the gas outlet is in communication with a main flue of the coal-fired boiler.
4. High strength alpha-hemihydrate gypsum prepared by the process of any one of claims 1 to 3.
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|---|---|---|---|---|
| CN1513766A (en) * | 2003-06-06 | 2004-07-21 | 浙江大学 | Techlogogy for making alpha semi-water desulfur gypsum using normal pressure salt solution method |
| CN2813074Y (en) * | 2005-08-16 | 2006-09-06 | 孙克勤 | Gypsum slurry dewatering device in wet-process flue gas desulfurizing system |
| CN101182150A (en) * | 2007-11-09 | 2008-05-21 | 浙江大学 | Industrial crystallization technique for preparing alpha-semi-hydrated gypsum directly by desulfurized gypsum slurry |
| CN101302029A (en) * | 2008-06-26 | 2008-11-12 | 武汉科技大学 | Method for preparing alpha-hemihydrate gypsum with desulfurated gypsum |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1513766A (en) * | 2003-06-06 | 2004-07-21 | 浙江大学 | Techlogogy for making alpha semi-water desulfur gypsum using normal pressure salt solution method |
| CN2813074Y (en) * | 2005-08-16 | 2006-09-06 | 孙克勤 | Gypsum slurry dewatering device in wet-process flue gas desulfurizing system |
| CN101182150A (en) * | 2007-11-09 | 2008-05-21 | 浙江大学 | Industrial crystallization technique for preparing alpha-semi-hydrated gypsum directly by desulfurized gypsum slurry |
| CN101302029A (en) * | 2008-06-26 | 2008-11-12 | 武汉科技大学 | Method for preparing alpha-hemihydrate gypsum with desulfurated gypsum |
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Application publication date: 20200522 Assignee: ZHEJIANG TIANLAN ENVIRONMENTAL PROTECTION ENGINEERING CO.,LTD. Assignor: ZHEJIANG TIANLAN ENVIRONMENTAL PROTECTION TECHNOLOGY Co.,Ltd. Contract record no.: X2023330000964 Denomination of invention: Preparation of high-strength desulfurization gypsum a- The system, process, and products of hemihydrate gypsum Granted publication date: 20220429 License type: Common License Record date: 20231227 |