System and method for preparing calcium acetate crystal and gypsum by using semi-dry desulfurization ash

Abstract

The invention discloses a system and a method for preparing calcium acetate crystals and gypsum by using semi-dry desulfurization ash. The system comprises a semi-dry desulfurization ash storage and transportation unit, a dissolution oxidation unit, a magnetic separation unit, an acetic acid reaction unit, a gypsum dehydration unit, an impurity removal unit, a solid-liquid separation unit, a purification unit, a crystallization dehydration unit and a dust removal unit. The method comprises the following steps: dissolving and oxidizing the semi-dry desulfurization ash, performing magnetic separation, performing acetic acid reaction, dehydrating, performing quick lime reaction, performing solid-liquid separation, performing acetic acid reaction again and crystallizing to obtain calcium acetate crystals and gypsum. According to the method, calcium oxide, calcium hydroxide, calcium carbonate, calcium sulfite and the like in the semi-dry desulfurization ash can be fully utilized, and multiple products can be produced at the same time.

Description

Technical Field

[0001] The invention relates to a system and a method for preparing calcium acetate crystals and gypsum by utilizing semi-dry desulfurization ash, and belongs to the technical field of solid waste treatment. Background Art

[0002] The desulfurization of sintering flue gas in steel enterprises includes a variety of desulfurization processes such as wet, semi-dry and dry. Since the semi-dry desulfurization process has the advantages of less water consumption, no corrosion to equipment, dry by-products, no wastewater generation, and less moisture content in the flue gas after desulfurization, it can well overcome some problems and shortcomings of the wet desulfurization process. The semi-dry desulfurization process has gradually become the dominant direction of sintering flue gas desulfurization. With the promotion of the semi-dry flue gas desulfurization process, the problems exposed by it are becoming increasingly prominent. Among them, the by-product of the semi-dry desulfurization process, desulfurization ash, is produced in the flue gas desulfurization process with calcium oxide and calcium hydroxide as desulfurizers. Its main components include calcium oxide, calcium hydroxide, calcium carbonate, calcium sulfate and calcium sulfite, etc., and contain a certain proportion of ash and impurity ions. The composition of semi-dry desulfurization ash is complex and difficult to use; however, if it is piled or landfilled, the desulfurization ash will seep into the soil after rain, causing serious pollution to the soil and groundwater.

[0003] At present, most of the semi-dry desulfurization ash is used for backfilling and stacking. The main reason is that the composition of desulfurization ash is complex and changeable, and the chemical properties are unstable. Since it contains calcium sulfite, calcium oxide and calcium hydroxide, the former is prone to oxidation reaction, and the latter is prone to react with carbon dioxide, making the chemical composition and properties of desulfurization ash unstable. When used as building materials, the calcium sulfite in it has the possibility of oxidation and will generate crystalline calcium sulfate, causing micro-expansion of building materials, affecting the safety performance of building materials. Therefore, how to modify semi-dry desulfurization ash is the key to the resource treatment of desulfurization ash.

[0004] CN110436506A discloses a method for oxidation treatment of semi-dry desulfurization ash using industrial waste sulfuric acid, wherein the semi-dry desulfurization ash and water are made into slurry, industrial waste sulfuric acid solution is added, and stirred, and the slurry is allowed to stand after the reaction is completed, the upper layer of water is removed, and the product is repeatedly rinsed and allowed to stand until the upper clear liquid is transparent and colorless, thus obtaining the product after oxidation treatment of semi-dry desulfurization ash. Although this method can effectively utilize calcium oxide and convert it into calcium sulfate, it will produce harmful sulfur dioxide gas, which is easy to cause secondary pollution, and sulfuric acid is highly corrosive, and has high requirements on equipment. In the end, only a single calcium sulfate product can be obtained, and its application is limited.

[0005] "Oxidation modification of semi-dry sintering flue gas desulfurization ash" (Yao Lu, Liu Qingcai, Fang Shihui, etc. Oxidation modification of semi-dry sintering flue gas desulfurization ash [J]. Journal of Environmental Engineering, 2016, 10 (6): 5.) The semi-dry desulfurization ash was treated by low-temperature static catalytic oxidation and high-temperature dynamic roasting oxidation. The former is to add a powdered catalyst to the desulfurization ash at a dosage of 1.5%, and oxidize it at a lower temperature; the latter is to roast and oxidize the desulfurization ash at a temperature of about 450 ° C. Although this method can realize the conversion of calcium sulfite in the desulfurization ash, the calcium oxide resource with a high content is not separated and utilized, and the calcium oxide in it will affect the resource utilization of the subsequent modified desulfurization ash to a certain extent.

[0006] Therefore, the current method for treating semi-dry desulfurization ash still has the problem that the calcium oxide, calcium hydroxide, calcium carbonate, calcium sulfite, etc. therein are not fully utilized, and there is also the problem that the product is still a mixture that cannot be separated. Summary of the invention

[0007] In order to solve at least one of the above technical problems, the object of the present invention is to provide a system and method for preparing calcium acetate crystals and gypsum using semi-dry desulfurization ash. The present invention can make full use of calcium oxide, calcium hydroxide, calcium carbonate and calcium sulfite in semi-dry desulfurization ash and produce multiple products at the same time.

[0008] In order to achieve the above-mentioned object, the first aspect of the present invention provides a system for preparing calcium acetate crystals and gypsum using semi-dry desulfurization ash, which comprises: a semi-dry desulfurization ash storage and transportation unit, a dissolution oxidation unit, a magnetic separation unit, an acetic acid reaction unit, a gypsum dehydration unit, an impurity removal unit, a solid-liquid separation unit, a purification unit, a crystallization dehydration unit and a dust removal unit;

[0009] The dissolution oxidation unit is at least provided with a semi-dry desulfurization ash inlet, an air inlet, a dust gas outlet and a slurry outlet; the magnetic separation unit is at least provided with a slurry inlet, a magnetic separation slag outlet and a slurry outlet; the acetic acid reaction unit is at least provided with a slurry inlet, an acetic acid inlet and a slurry outlet; the gypsum dehydration unit is at least provided with a slurry inlet, a gypsum outlet and a slurry outlet; the impurity removal unit is at least provided with a slurry inlet, a quicklime inlet and a slurry outlet; the solid-liquid separation unit is at least provided with a slurry inlet, a residue outlet and a clear liquid outlet; the purification unit is at least provided with a clear liquid inlet, an acetic acid inlet and a calcium acetate solution outlet; the crystallization dehydration unit is at least provided with a calcium acetate solution inlet, a mother liquor and condensed water outlet and a calcium acetate crystal outlet;

[0010] The semi-dry desulfurization ash storage and transportation unit is connected to the semi-dry desulfurization ash inlet of the dissolution oxidation unit; the slurry outlet of the dissolution oxidation unit is connected to the slurry inlet of the magnetic separation unit; the slurry outlet of the magnetic separation unit is connected to the slurry inlet of the acetic acid reaction unit; the slurry outlet of the acetic acid reaction unit is connected to the slurry inlet of the gypsum dehydration unit; the slurry outlet of the gypsum dehydration unit is connected to the slurry inlet of the impurity removal unit; the slurry outlet of the impurity removal unit is connected to the slurry inlet of the solid-liquid separation unit; the clear liquid outlet of the solid-liquid separation unit is connected to the clear liquid inlet of the purification unit; the calcium acetate solution outlet of the purification unit is connected to the calcium acetate solution inlet of the crystallization dehydration unit; the dust gas outlet of the dissolution oxidation unit and the mother liquor and condensed water outlet of the crystallization dehydration unit are respectively connected to the dust removal unit; gypsum is produced from the gypsum outlet of the gypsum dehydration unit, and calcium acetate crystals are produced from the calcium acetate crystal outlet of the crystallization dehydration unit.

[0011] According to a specific embodiment of the present invention, preferably, the semi-dry desulfurization ash storage and transportation unit includes a semi-dry desulfurization ash storage bin, an ash unloading pipeline and an ash unloading valve, and the semi-dry desulfurization ash storage bin is connected to the semi-dry desulfurization ash inlet of the dissolution oxidation unit through the ash unloading pipeline and the ash unloading valve.

[0012] According to a specific embodiment of the present invention, preferably, the dissolution oxidation unit includes a dissolution oxidation tank, water is injected into the dissolution oxidation tank, an air distribution pipe is arranged at the bottom of the dissolution oxidation tank, and an agitator is arranged in the dissolution oxidation tank; the air distribution pipe is connected to an air inlet, and the air inlet is connected to a Roots blower for conveying air into the air distribution pipe.

[0013] According to a specific embodiment of the present invention, preferably, the acetic acid reaction unit comprises an acetic acid reaction tank, and the acetic acid reaction tank is provided with an agitator and a heating device. More preferably, the heating device comprises one or more of a steam coil, an electric heater, a hot water coil, etc.

[0014] According to a specific embodiment of the present invention, preferably, the gypsum dehydration unit includes one or more of a vacuum belt dehydrator, a centrifugal dehydrator, a plate and frame filter press, and the like.

[0015] According to a specific embodiment of the present invention, preferably, the impurity removal unit comprises an impurity removal box, and an agitator is arranged in the impurity removal box.

[0016] According to a specific embodiment of the present invention, preferably, the solid-liquid separation unit comprises a centrifuge and a filter connected in sequence, the centrifuge is used to perform a primary separation on the slurry obtained by the impurity removal unit to obtain a first residue and a supernatant; the filter is used to perform a secondary separation on the supernatant to obtain a second residue and a filtrate; the first residue and the second residue are discharged from the residue outlet of the solid-liquid separation unit, and the filtrate is discharged from the clear liquid outlet of the solid-liquid separation unit; or, the solid-liquid separation unit comprises an inclined plate sedimentation tank.

[0017] According to a specific embodiment of the present invention, preferably, the purification unit comprises a purification box, and an agitator is arranged in the purification box.

[0018] According to a specific embodiment of the present invention, preferably, the crystallization and dehydration unit includes a multiple-effect evaporation crystallizer or an MVR evaporation crystallizer, etc.

[0019] According to a specific embodiment of the present invention, preferably, the dust removal unit includes a wet dust collector, and the wet dust collector is provided with at least a dust gas inlet, a recovery water inlet and a dust-containing wastewater outlet; the dust gas inlet of the wet dust collector is connected to the dust gas outlet of the dissolution oxidation unit; the recovery water inlet of the wet dust collector is connected to the mother liquor and condensed water outlet of the crystallization dehydration unit, for using the mother liquor and condensed water of the crystallization dehydration unit as part or all of the water source; the dust-containing wastewater outlet of the wet dust collector is connected to the dissolution oxidation unit, for recycling the dust-containing wastewater. More preferably, the wet dust collector is further provided with a new water inlet, for replenishing new water as part of the water source.

[0020] It can be understood by those skilled in the art that the above-mentioned system for preparing calcium acetate crystals and gypsum using semi-dry desulfurization ash also includes conventional equipment such as pipelines and pumps. The present invention does not impose any special restrictions on it, and it can be routinely adjusted by those skilled in the art.

[0021] The second aspect of the present invention provides a method for preparing calcium acetate crystals and gypsum using semi-dry desulfurization ash, the method adopts the above-mentioned system for preparing calcium acetate crystals and gypsum using semi-dry desulfurization ash, and the method comprises the following steps:

[0022] (1) allowing the semi-dry desulfurization ash to be unloaded into a dissolution and oxidation unit through a semi-dry desulfurization ash storage and transportation unit, wherein the semi-dry desulfurization ash is mixed with water and brought into contact with air for dissolution and oxidation to obtain a first slurry and dust gas; and allowing the dust gas to enter a dust removal unit for dust removal;

[0023] (2) allowing the first slurry to enter a magnetic separation unit for magnetic separation to obtain a second slurry and magnetic separation slag;

[0024] (3) allowing the second slurry to enter an acetic acid reaction unit to react with an acetic acid solution to obtain a third slurry;

[0025] (4) allowing the third slurry to enter a gypsum dehydration unit for dehydration to obtain a fourth slurry and gypsum;

[0026] (5) allowing the fourth slurry to enter an impurity removal unit to react with quicklime to obtain a fifth slurry;

[0027] (6) allowing the fifth slurry to enter a solid-liquid separation unit for separation to obtain a clear liquid and a residue;

[0028] (7) allowing the clear liquid to enter a purification unit to react with an acetic acid solution to obtain a calcium acetate solution;

[0029] (8) allowing the calcium acetate solution to enter a crystallization and dehydration unit for crystallization to obtain a mother liquor, condensed water, and calcium acetate crystals; allowing the mother liquor and condensed water to enter a dust removal unit as part or all of the water source.

[0030] According to a specific embodiment of the present invention, preferably, in step (1), in the dissolution oxidation unit, the mixing ratio of the semi-dry desulfurization ash and the water is controlled so that the mass concentration of the first slurry is 20% to 35%, and the amount of air introduced is such that the O in the air is 2 and S (i.e. O 2 / S) has a molar ratio of ≥ 3. More preferably, the mixing of the semi-dry desulfurization ash and water and the contact with air are carried out under stirring conditions, and the stirring speed is 30 to 180 revolutions per minute.

[0031] According to a specific embodiment of the present invention, preferably, in step (2), in the magnetic separation unit, the magnetic field strength of the magnetic separation is above 1000 mT. More preferably, step (2) further comprises: recovering iron from the magnetic separation slag.

[0032] According to a specific embodiment of the present invention, preferably, in step (3), in the acetic acid reaction unit, the concentration of the acetic acid solution added is 2 to 4 mol / L, and the mass ratio of the semi-dry desulfurization ash to the acetic acid solution is 1:(1.5 to 2.5).

[0033] According to a specific embodiment of the present invention, preferably, in step (3), in the acetic acid reaction unit, the reaction temperature is 45 to 60° C. and the reaction time is 0.5 to 2 hours. More preferably, the reaction is carried out under stirring conditions at a stirring speed of 400 to 600 rpm.

[0034] According to a specific embodiment of the present invention, preferably, in step (5), in the impurity removal unit, the reaction temperature is room temperature (i.e., 20 to 30° C.), the time is 5 to 20 minutes, and the amount of quicklime added is controlled so that the pH value of the fifth slurry is 10 to 11. More preferably, the reaction is carried out under stirring conditions, and the stirring speed is 10 to 30 rpm.

[0035] According to a specific embodiment of the present invention, preferably, in step (6), in the solid-liquid separation unit, when the solid-liquid separation unit includes a centrifuge and a filter connected in sequence, the fifth slurry is first separated by a centrifuge at a rotation speed of 5000 to 15000 rpm to obtain a first residue and a supernatant; the supernatant is then separated by a filter at a filtration pressure of 0.2 to 0.4 MPa and a filtration speed of 10 to 20 m / h to obtain a second residue and a filtrate; the first residue and the second residue are combined into the residue, and the filtrate is the clear liquid.

[0036] According to a specific embodiment of the present invention, preferably, in step (7), in the purification unit, the concentration of the acetic acid solution added is 2 to 4 mol / L, the amount of the acetic acid solution added is controlled so that the pH value of the system after the addition of the acetic acid solution is 6.0 to 8.0, the reaction temperature is room temperature (i.e., 20 to 30° C.), and the reaction time is 5 to 10 minutes. More preferably, the reaction is carried out under stirring conditions, and the stirring speed is 30 to 180 rpm.

[0037] According to a specific embodiment of the present invention, preferably, the method further comprises: allowing the dust-containing wastewater in the dust removal unit to enter the dissolution oxidation unit for recycling.

[0038] According to a specific embodiment of the present invention, preferably, the method further comprises: adding new water to the dust removal unit as part of the water source.

[0039] The present invention has at least the following beneficial effects:

[0040] The present invention first converts calcium sulfite into calcium sulfate through a specific system and process flow, and then uses acetic acid to react with calcium oxide, calcium hydroxide and calcium carbonate in semi-dry desulfurization ash to separate it from calcium sulfate, and removes impurity components such as iron, heavy metals, magnesium, etc. in the overall process, thereby obtaining a gypsum product and a calcium acetate crystal product with high utilization value. The present invention uses semi-dry desulfurization ash and acetic acid to react to prepare calcium acetate, effectively utilizing the residual calcium oxide, calcium hydroxide and calcium carbonate in the desulfurization ash, and further controlling the reaction conditions within the scope of the present invention so that calcium oxide, calcium hydroxide and calcium carbonate are fully converted. The calcium acetate crystals obtained by the present invention can be used in various industries, thereby realizing the high-value utilization of semi-dry desulfurization ash. At the same time, after removing calcium sulfite, calcium oxide, calcium hydroxide and calcium carbonate from the desulfurization ash, the gypsum product obtained by the present invention is pure calcium sulfate, and its utilization value is significantly improved. In addition, the present invention can also recycle iron elements. Therefore, the present invention can make the semi-dry desulfurization ash with complex components and no effective utilization path be separated, high-quality and fully utilized, fully converting the calcium oxide, calcium hydroxide, calcium carbonate and calcium sulfite therein, and can obtain a variety of products at the same time, including the Fe element recovered from the magnetic separation slag, high-purity gypsum products and high-purity calcium acetate crystal products. Moreover, the present invention uses acetic acid to treat the semi-dry desulfurization ash, and no harmful gases such as sulfur dioxide will be produced, and the corrosion to the equipment is also small. In addition, the present invention recycles the waste water (mother liquor and condensed water) generated in the process, and the waste gas (dust gas) generated is also managed. Only a small amount of waste slag (residue) containing magnesium and heavy metals is produced in the overall process, realizing the resource utilization and reduction of solid waste. The present invention provides a new direction for the treatment of the semi-dry desulfurization by-products, which is a stubborn disease in the solid waste management industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 and Figure 2 They are schematic diagrams of the structures of a system for preparing calcium acetate crystals and gypsum using semi-dry desulfurization ash in a specific embodiment of the present invention.

[0042] Description of Figure Numbers:

[0043] 1-semi-dry desulfurization ash storage and transportation unit; 2-dissolution oxidation unit; 3-magnetic separation unit; 4-acetic acid reaction unit; 5-gypsum dehydration unit; 6-impurity removal unit; 7-solid-liquid separation unit; 8-purification unit; 9-crystallization dehydration unit; 10-dust removal unit; 11-suction and discharge tank truck;

[0044] 101-semi-dry desulfurization ash storage bin; 102-ash unloading pipeline; 103-ash unloading valve 103;

[0045] 201-air distribution pipe; 202-first agitator; 203-Roots blower;

[0046] 401-second stirrer; 402-heating device;

[0047] 601- the third agitator;

[0048] 701-centrifuge; 702-filter; 703-inclined plate sedimentation tank;

[0049] 801-Fourth agitator. DETAILED DESCRIPTION

[0050] In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the present invention is now described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0051] It should be noted that, unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs.

[0052] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0053] It should be understood that the terms "comprises," "comprising" and / or "containing" when used herein specify the presence of stated features, integers, steps, components or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, components or combinations thereof.

[0054] In the present invention, it should be noted that the terms "upper", "lower", "top / bottom" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0055] In the present invention, it should be noted that, unless otherwise clearly stipulated and limited, the terms "installed", "provided with", "mounted / connected", "connected", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection. It can be a mechanical connection or an electrical connection. It can be a direct connection or an indirect connection through an intermediate medium. It can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0056] In the present invention, the endpoints and any values ​​of the disclosed ranges are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in the present invention.

[0057] According to a specific embodiment of the first aspect of the present invention, the present invention provides a system for preparing calcium acetate crystals and gypsum using semi-dry desulfurization ash, such as Figure 1 and Figure 2 As shown, it includes: a semi-dry desulfurization ash storage and transportation unit 1, a dissolution oxidation unit 2, a magnetic separation unit 3, an acetic acid reaction unit 4, a gypsum dehydration unit 5, an impurity removal unit 6, a solid-liquid separation unit 7, a purification unit 8, a crystallization dehydration unit 9 and a dust removal unit 10;

[0058] The dissolving oxidation unit 2 is at least provided with a semi-dry desulfurization ash inlet, an air inlet, a dust gas outlet and a slurry outlet; the magnetic separation unit 3 is at least provided with a slurry inlet, a magnetic separation slag outlet and a slurry outlet; the acetic acid reaction unit 4 is at least provided with a slurry inlet, an acetic acid inlet and a slurry outlet; the gypsum dehydration unit 5 is at least provided with a slurry inlet, a gypsum outlet and a slurry outlet; the impurity removal unit 6 is at least provided with a slurry inlet, a quicklime inlet and a slurry outlet; the solid-liquid separation unit 7 is at least provided with a slurry inlet, a residue outlet and a clear liquid outlet; the purification unit 8 is at least provided with a clear liquid inlet, an acetic acid inlet and a calcium acetate solution outlet; the crystallization dehydration unit 9 is at least provided with a calcium acetate solution inlet, a mother liquor and condensed water outlet and a calcium acetate crystal outlet;

[0059] The semi-dry desulfurization ash storage and transportation unit 1 is connected to the semi-dry desulfurization ash inlet of the dissolution oxidation unit 2; the slurry outlet of the dissolution oxidation unit 2 is connected to the slurry inlet of the magnetic separation unit 3; the slurry outlet of the magnetic separation unit 3 is connected to the slurry inlet of the acetic acid reaction unit 4; the slurry outlet of the acetic acid reaction unit 4 is connected to the slurry inlet of the gypsum dehydration unit 5; the slurry outlet of the gypsum dehydration unit 5 is connected to the slurry inlet of the impurity removal unit 6; the slurry outlet of the impurity removal unit 6 is connected to the slurry inlet of the solid-liquid separation unit 7; the clear liquid outlet of the solid-liquid separation unit 7 is connected to the clear liquid inlet of the purification unit 8; the calcium acetate solution outlet of the purification unit 8 is connected to the calcium acetate solution inlet of the crystallization dehydration unit 9; the dust gas outlet of the dissolution oxidation unit 2 and the mother liquor and condensed water outlet of the crystallization dehydration unit 9 are respectively connected to the dust removal unit 10; gypsum is produced from the gypsum outlet of the gypsum dehydration unit 5, and calcium acetate crystals are produced from the calcium acetate crystal outlet of the crystallization dehydration unit 9.

[0060] In some embodiments, the semi-dry desulfurization ash storage and transportation unit 1 includes a semi-dry desulfurization ash storage bin 101, an ash unloading pipeline 102 and an ash unloading valve 103. The semi-dry desulfurization ash storage bin 101 is connected to the semi-dry desulfurization ash inlet of the dissolution oxidation unit 2 through the ash unloading pipeline 102 and the ash unloading valve 103.

[0061] also, Figure 1 Also shown is a suction tanker 11, which is connected to the semi-dry desulfurization ash storage bin 101 through a pneumatic ash conveying pipeline.

[0062] In some embodiments, the dissolution oxidation unit 2 includes a dissolution oxidation tank, water is injected into the dissolution oxidation tank, an air distribution pipe 201 is arranged at the bottom of the dissolution oxidation tank, and a first agitator 202 is arranged in the dissolution oxidation tank; the air distribution pipe 201 is connected to the air inlet, and the air inlet is connected to a Roots blower 203 for conveying air into the air distribution pipe 201.

[0063] In some embodiments, a delivery pump is provided on the pipeline connecting the slurry outlet of the dissolution oxidation unit 2 and the inlet of the magnetic separation unit 3 .

[0064] In some embodiments, the magnetic separation unit 3 comprises a magnetic separator.

[0065] In some embodiments, the acetic acid reaction unit 4 includes an acetic acid reaction tank, in which a second agitator 401 and a heating device 402 are provided. Preferably, the heating device 402 includes one or more of a steam coil, an electric heater, and a hot water coil.

[0066] In some embodiments, a delivery pump is provided on the pipeline connecting the slurry outlet of the acetic acid reaction unit 4 and the slurry inlet of the gypsum dehydration unit 5 .

[0067] In some embodiments, the gypsum dehydration unit 5 includes one or more of a vacuum belt dehydrator, a centrifugal dehydrator, a plate and frame filter press, and the like.

[0068] In some embodiments, the impurity removal unit 6 includes an impurity removal box in which a third agitator 601 is disposed.

[0069] In some embodiments, a delivery pump is provided on the pipeline connecting the slurry outlet of the impurity removal unit 6 and the slurry inlet of the solid-liquid separation unit 7 .

[0070] In some embodiments, Figure 1As shown, the solid-liquid separation unit 7 includes a centrifuge 701 and a filter 702 connected in sequence, the centrifuge 701 is used to perform a primary separation on the slurry obtained by the impurity removal unit 6 to obtain a first residue and a supernatant; the filter 702 is used to perform a secondary separation on the supernatant to obtain a second residue and a filtrate; the first residue and the second residue are discharged from the residue outlet of the solid-liquid separation unit 7, and the filtrate is discharged from the clear liquid outlet of the solid-liquid separation unit 7. In other embodiments, such as Figure 2 As shown, the solid-liquid separation unit 7 includes an inclined plate sedimentation tank 703 .

[0071] In some embodiments, the purification unit 8 includes a purification box in which a fourth agitator 801 is disposed.

[0072] In some embodiments, a delivery pump is provided on the pipeline connecting the calcium acetate solution outlet of the purification unit 8 and the calcium acetate solution inlet of the crystallization and dehydration unit 9 .

[0073] In some embodiments, the crystallization and dehydration unit 9 includes a multiple-effect evaporation crystallizer or an MVR evaporation crystallizer, etc.

[0074] In some embodiments, the dust removal unit 10 includes a wet dust collector, which is provided with at least a dust gas inlet, a recovery water inlet and a dust-containing waste water outlet; the dust gas inlet of the wet dust collector is connected to the dust gas outlet of the dissolution oxidation unit 2; the recovery water inlet of the wet dust collector is connected to the mother liquor and condensed water outlet of the crystallization dehydration unit 9, for using the mother liquor and condensed water of the crystallization dehydration unit 9 as part or all of the water source; the dust-containing waste water outlet of the wet dust collector is connected to the dissolution oxidation unit 2, for recycling the dust-containing waste water. Preferably, the wet dust collector is further provided with a new water inlet, for replenishing new water as part of the water source.

[0075] According to a specific embodiment of the second aspect of the present invention, the present invention provides a method for preparing calcium acetate crystals and gypsum using semi-dry desulfurization ash, the method adopts the above-mentioned system for preparing calcium acetate crystals and gypsum using semi-dry desulfurization ash, and the method comprises the following steps:

[0076] (1) allowing the semi-dry desulfurization ash to be unloaded into the dissolution oxidation unit 2 through the semi-dry desulfurization ash storage and transportation unit 1, wherein the semi-dry desulfurization ash is mixed with water and contacted with air to be dissolved and oxidized to obtain a first slurry and dust gas; and the dust gas is allowed to enter the dust removal unit 10 for dust removal;

[0077] (2) allowing the first slurry to enter the magnetic separation unit 3 for magnetic separation to obtain a second slurry and magnetic separation slag;

[0078] (3) allowing the second slurry to enter the acetic acid reaction unit 4 to react with the acetic acid solution to obtain a third slurry;

[0079] (4) allowing the third slurry to enter the gypsum dehydration unit 5 for dehydration to obtain a fourth slurry and gypsum;

[0080] (5) allowing the fourth slurry to enter the impurity removal unit 6 to react with quicklime to obtain a fifth slurry;

[0081] (6) allowing the fifth slurry to enter the solid-liquid separation unit 7 for separation to obtain a clear liquid and a residue;

[0082] (7) allowing the clear liquid to enter the purification unit 8 to react with the acetic acid solution to obtain a calcium acetate solution;

[0083] (8) The calcium acetate solution is allowed to enter the crystallization and dehydration unit 9 for crystallization to obtain mother liquor, condensed water and calcium acetate crystals; the mother liquor and condensed water are allowed to enter the dust removal unit 10 as part or all of the water source.

[0084] In some embodiments, in step (1), in the dissolution oxidation unit 2, the mixing ratio of the semi-dry desulfurization ash and the water is controlled so that the mass concentration of the first slurry is 20% to 35% (calculated by the mass of the semi-dry desulfurization ash ÷ (the mass of the semi-dry desulfurization ash + the mass of the water) × 100%), and the amount of air introduced is such that the O in the air is 2 and S (i.e. O 2 / S) has a molar ratio of ≥3. Preferably, the mixing of the semi-dry desulfurization ash with water and the contact with air are carried out under stirring conditions, and the stirring speed is 30 to 180 rpm. The present invention controls the dissolution and oxidation conditions within the above range to ensure the full dissolution and oxidation of the semi-dry desulfurization ash, so that the calcium sulfite therein is oxidized into calcium sulfate.

[0085] In some embodiments, in step (2), in the magnetic separation unit 3, the magnetic field strength of the magnetic separation is above 1000 mT. Preferably, step (2) further comprises: recovering iron from the magnetic separation slag. Specifically, the magnetic separation slag can be sent to the ironmaking and steelmaking process to recover iron.

[0086] In some embodiments, in step (3), in the acetic acid reaction unit 4, the concentration of the added acetic acid solution is 2 to 4 mol / L, and the mass ratio of the semi-dry desulfurization ash to the acetic acid solution is 1:(1.5 to 2.5). In the acetic acid reaction unit 4, the reaction temperature is 45 to 60°C and the reaction time is 0.5 to 2 hours. Preferably, the reaction is carried out under stirring conditions at a stirring speed of 400 to 600 rpm. The present invention controls the reaction conditions in step (3) within the above range so that the calcium oxide, calcium hydroxide and calcium carbonate in the second slurry fully react with the acetic acid and are effectively recovered.

[0087] In some embodiments, in step (5), in the impurity removal unit 6, the reaction temperature is room temperature (i.e., 20-30° C.), the reaction time is 5-20 minutes, and the amount of quicklime added is controlled so that the pH value of the fifth slurry is 10-11. Preferably, the reaction is carried out under stirring conditions, and the stirring speed is 10-30 rpm. The present invention controls the pH value of the fifth slurry within the above range so that the Mg in the fourth slurry is 2+ , heavy metal ions are fully precipitated and removed.

[0088] In some embodiments, in step (6), in the solid-liquid separation unit 7, when the solid-liquid separation unit 7 includes a centrifuge and a filter connected in sequence, the fifth slurry is first separated by a centrifuge 701, and the rotation speed of the centrifuge 701 is 5000 to 15000 rpm to obtain a first residue and a supernatant; then the supernatant is subjected to a secondary separation by a filter 702, and the filtration pressure of the filter 702 is 0.2 to 0.4 MPa, and the filtration speed is 10 to 20 m / h to obtain a second residue and a filtrate; the first residue and the second residue are combined into the residue, and the filtrate is the clear liquid.

[0089] In some embodiments, in step (7), in the purification unit 8, the concentration of the acetic acid solution added is 2-4 mol / L, the amount of the acetic acid solution added is controlled so that the pH value of the system after the addition of the acetic acid solution is 6.0-8.0, the reaction temperature is room temperature (i.e., 20-30° C.), and the reaction time is 5-10 minutes. Preferably, the reaction is carried out under stirring conditions, and the stirring speed is 30-180 rpm.

[0090] In some embodiments, the method further includes: allowing the dust-containing wastewater in the dust removal unit 10 to enter the dissolution oxidation unit 2 for recycling.

[0091] In some embodiments, the method further includes: adding new water to the dust removal unit 10 as part of the water source.

[0092] The process of using the system and method of the present invention to treat semi-dry desulfurization ash is to first dissolve and oxidize the semi-dry desulfurization ash to convert calcium sulfite into calcium sulfate; then perform magnetic separation; then react with acetic acid solution, acetic acid reacts with calcium oxide, calcium hydroxide and calcium carbonate in the desulfurization ash to generate water-soluble calcium acetate, while calcium sulfate remains in an insoluble solid form; then dehydrate gypsum to obtain a gypsum product; then react the slurry obtained after dehydrating the gypsum with quicklime to remove magnesium ions and heavy metal ions, and perform solid-liquid separation; then react with acetic acid solution again to generate calcium acetate, and after crystallization and dehydration, obtain a calcium acetate crystal product.

[0093] Specifically, the calcium-based semi-dry desulfurization ash is transported to the system of the present invention through a suction tanker 11, and then transported to the semi-dry desulfurization ash storage bin 101 through an aeration ash conveying pipeline. Then, the amount of the semi-dry desulfurization ash is controlled by an ash discharge pipeline 102 and an ash discharge valve 103 under the bin and discharged into the dissolution oxidation unit 2 under the bin. Under the stirring action of the first agitator 202, part of the semi-dry desulfurization ash is dissolved by water to form a slurry. At the same time, the CaSO 3 It contacts with the air blown by the Roots blower 203 through the air distribution pipe 201 and is oxidized into CaSO 4 The stirring action of the first agitator 202 accelerates the oxidation process; in the process of adding semi-dry desulfurization ash and blowing air into the dissolving oxidation unit 2, the generated dust-containing gas is discharged through the top dust gas outlet to the dust removal unit 10 for wet dust removal.

[0094] Among them, CaSO 3 Oxidized to CaSO 4 The reaction equation is shown in the following formula (1):

[0095] CaSO 3 +2H 2 O+1 / 2O 2 = CaSO 4 ·2H 2 O formula (1)

[0096] The first slurry obtained after full dissolution and oxidation is lifted by a delivery pump and sent to the magnetic separation unit 3; the magnetic separation unit 3 separates the iron components contained in the desulfurization ash to obtain the second slurry and magnetic separation slag, which can be sent to the ironmaking and steelmaking process to recover the iron element, and the second slurry flows into the acetic acid reaction unit 4 by gravity; acetic acid solution is added to the acetic acid reaction unit 4, and acetic acid reacts with calcium oxide, calcium hydroxide and calcium carbonate in the desulfurization ash to generate water-soluble calcium acetate, and CaSO 4 The acetic acid solution and the second slurry are mixed evenly by the stirring action of the second stirrer 401 , and the reaction proceeds fully; and the reaction temperature is automatically controlled by the heating device 402 .

[0097] The reaction equations of acetic acid with calcium oxide, calcium hydroxide and calcium carbonate are shown in the following equations (2), (3) and (4):

[0098] CaO+2CH 3 COOH(aq)= H 2 O+Ca(CH 3 COO 2 (aq) Formula (2)

[0099] Ca(OH) 2 +2CH 3COOH(aq)=2H 2 O+Ca(CH 3 COO 2 (aq) Formula (3)

[0100] CaCO 3 +2CH 3 COOH(aq)=CO 2 (g)+H 2 O+Ca(CH 3 COO 2 (aq) Formula (4)

[0101] The third slurry is treated with acetic acid, and then lifted by a delivery pump and sent to the gypsum dehydration unit 5. The CaSO 4 ·2H 2 O dehydration separation to obtain a high-purity gypsum product; the fourth slurry obtained after removing the gypsum flows into the impurity removal unit 6 by gravity. Quicklime is added to the impurity removal unit 6, and under the stirring action of the third stirrer 601, the quicklime and the Mg in the fourth slurry are mixed. 2+ 、Heavy metal ions (in M + Then, the solid-liquid separation unit 7 is lifted by a delivery pump, and solid-liquid separation is performed by a centrifuge 701 and a filter 702, or a sloping plate sedimentation tank 703 is used for solid-liquid separation to obtain a clear liquid and a residue.

[0102] Among them, quicklime and Mg in the fourth slurry 2+ 、Heavy metal ions (in M + The reaction equations are shown in (5), (6) and (7):

[0103] Under normal temperature conditions, K sp [Ca(OH) 2 ](solubility product constant)=5.6×10 -6 ; K sp [Mg(OH) 2 ]=1.8×10 -11

[0104] CaO+H 2 O= Ca(OH) 2 Formula (5)

[0105] Ca(OH) 2 +Mg 2+ →Mg(OH) 2 ↓+Ca 2+ K = 3.11 × 10 5 Formula (6)

[0106] Ca(OH)2 +2M + →2MOH↓+Ca 2+ Formula (7)

[0107] Due to the addition of excessive quicklime, the Mg 2+ 、M + It is fully precipitated to be removed, so the clear liquid obtained by the solid-liquid separation unit 7 is alkaline; then, the clear liquid obtained by the solid-liquid separation unit 7 flows into the purification unit 8 by gravity, and acetic acid solution needs to be added to the purification unit 8. Under the stirring action of the fourth agitator 801, the excess quicklime is also converted into calcium acetate.

[0108] The purified calcium acetate solution is lifted by a delivery pump and sent to the crystallization and dehydration unit 9 for crystallization, thereby obtaining a high-purity calcium acetate crystal product. The mother liquor and condensed water separated by the crystallization and dehydration unit 9 are reused as part of the water source for the dust removal unit 10. At the same time, in order to ensure the water balance of the system, new water is added to the dust removal unit 10. The dust-containing wastewater in the dust removal unit 10 flows into the dissolution oxidation unit 2 by gravity for recycling without external discharge.

[0109] The technical solutions of the present invention are specifically described below by way of examples, but the present invention is not limited to these examples and can of course be implemented in various modifications within the scope of the gist of the present invention.

[0110] Example 1

[0111] This embodiment provides a system for preparing calcium acetate crystals and gypsum using semi-dry desulfurization ash, such as Figure 1 As shown, it includes: a semi-dry desulfurization ash storage and transportation unit 1, a dissolution oxidation unit 2, a magnetic separation unit 3, an acetic acid reaction unit 4, a gypsum dehydration unit 5, an impurity removal unit 6, a solid-liquid separation unit 7, a purification unit 8, a crystallization dehydration unit 9 and a dust removal unit 10;

[0112] The dissolving oxidation unit 2 is at least provided with a semi-dry desulfurization ash inlet, an air inlet, a dust gas outlet and a slurry outlet; the magnetic separation unit 3 is at least provided with a slurry inlet, a magnetic separation slag outlet and a slurry outlet; the acetic acid reaction unit 4 is at least provided with a slurry inlet, an acetic acid inlet and a slurry outlet; the gypsum dehydration unit 5 is at least provided with a slurry inlet, a gypsum outlet and a slurry outlet; the impurity removal unit 6 is at least provided with a slurry inlet, a quicklime inlet and a slurry outlet; the solid-liquid separation unit 7 is at least provided with a slurry inlet, a residue outlet and a clear liquid outlet; the purification unit 8 is at least provided with a clear liquid inlet, an acetic acid inlet and a calcium acetate solution outlet; the crystallization dehydration unit 9 is at least provided with a calcium acetate solution inlet, a mother liquor and condensed water outlet and a calcium acetate crystal outlet;

[0113] The semi-dry desulfurization ash storage and transportation unit 1 is connected to the semi-dry desulfurization ash inlet of the dissolution oxidation unit 2; the slurry outlet of the dissolution oxidation unit 2 is connected to the slurry inlet of the magnetic separation unit 3; the slurry outlet of the magnetic separation unit 3 is connected to the slurry inlet of the acetic acid reaction unit 4; the slurry outlet of the acetic acid reaction unit 4 is connected to the slurry inlet of the gypsum dehydration unit 5; the slurry outlet of the gypsum dehydration unit 5 is connected to the slurry inlet of the impurity removal unit 6; the slurry outlet of the impurity removal unit 6 is connected to the slurry inlet of the solid-liquid separation unit 7; the clear liquid outlet of the solid-liquid separation unit 7 is connected to the clear liquid inlet of the purification unit 8; the calcium acetate solution outlet of the purification unit 8 is connected to the calcium acetate solution inlet of the crystallization dehydration unit 9; the dust gas outlet of the dissolution oxidation unit 2 and the mother liquor and condensed water outlet of the crystallization dehydration unit 9 are respectively connected to the dust removal unit 10; gypsum is produced from the gypsum outlet of the gypsum dehydration unit 5, and calcium acetate crystals are produced from the calcium acetate crystal outlet of the crystallization dehydration unit 9.

[0114] In this embodiment, the semi-dry desulfurization ash storage and transportation unit 1 includes a semi-dry desulfurization ash storage bin 101, an ash unloading pipeline 102 and an ash unloading valve 103. The semi-dry desulfurization ash storage bin 101 is connected to the semi-dry desulfurization ash inlet of the dissolution oxidation unit 2 through the ash unloading pipeline 102 and the ash unloading valve 103.

[0115] The dissolution oxidation unit 2 includes a dissolution oxidation tank, water is injected into the dissolution oxidation tank, an air distribution pipe 201 is arranged at the bottom of the dissolution oxidation tank, and a first agitator 202 is arranged in the dissolution oxidation tank; the air distribution pipe 201 is connected to the air inlet, and the air inlet is connected to a Roots blower 203 for conveying air to the air distribution pipe 201.

[0116] A delivery pump is provided on the pipeline connecting the slurry outlet of the dissolution oxidation unit 2 and the inlet of the magnetic separation unit 3 .

[0117] The magnetic separation unit 3 includes a magnetic separator.

[0118] The acetic acid reaction unit 4 comprises an acetic acid reaction tank, in which a second agitator 401 and a heating device 402 are arranged. The heating device 402 is a hot water coil.

[0119] A delivery pump is provided on the pipeline connecting the slurry outlet of the acetic acid reaction unit 4 and the slurry inlet of the gypsum dehydration unit 5 .

[0120] The gypsum dehydration unit 5 includes a vacuum belt dehydrator.

[0121] The impurity removal unit 6 comprises an impurity removal box, in which a third agitator 601 is arranged.

[0122] A delivery pump is provided on the pipeline connecting the slurry outlet of the impurity removal unit 6 and the slurry inlet of the solid-liquid separation unit 7 .

[0123] The solid-liquid separation unit 7 includes a centrifuge 701 and a filter 702 connected in sequence. The centrifuge 701 is used to perform a primary separation on the slurry obtained by the impurity removal unit 6 to obtain a first residue and a supernatant; the filter 702 is used to perform a secondary separation on the supernatant to obtain a second residue and a filtrate; the first residue and the second residue are discharged from the residue outlet of the solid-liquid separation unit 7, and the filtrate is discharged from the clear liquid outlet of the solid-liquid separation unit 7.

[0124] The purification unit 8 comprises a purification box in which a fourth agitator 801 is arranged.

[0125] A delivery pump is provided on the pipeline connecting the calcium acetate solution outlet of the purification unit 8 and the calcium acetate solution inlet of the crystallization and dehydration unit 9.

[0126] The crystallization and dehydration unit 9 comprises a triple-effect evaporation crystallizer.

[0127] The dust removal unit 10 includes a wet dust collector, which is at least provided with a dust gas inlet, a recovery water inlet and a dust-containing waste water outlet; the dust gas inlet of the wet dust collector is connected to the dust gas outlet of the dissolution oxidation unit 2; the recovery water inlet of the wet dust collector is connected to the mother liquor and condensed water outlet of the crystallization dehydration unit 9, for using the mother liquor and condensed water of the crystallization dehydration unit 9 as part of the water source; the dust-containing waste water outlet of the wet dust collector is connected to the dissolution oxidation unit 2, for recycling the dust-containing waste water. The wet dust collector is further provided with a new water inlet, for replenishing new water as another part of the water source.

[0128] Example 2

[0129] This embodiment provides a method for preparing calcium acetate crystals and gypsum using semi-dry desulfurization ash. The method is carried out using the system for preparing calcium acetate crystals and gypsum using semi-dry desulfurization ash of Example 1. The method comprises the following steps:

[0130] (1) The semi-dry desulfurization ash is unloaded into the dissolution oxidation unit 2 through the semi-dry desulfurization ash storage and transportation unit 1. In the dissolution oxidation unit 2, the semi-dry desulfurization ash is mixed with water under stirring conditions and contacted with air to dissolve and oxidize to obtain a first slurry and dust gas. The stirring speed is 120 rpm. The mixing ratio of the semi-dry desulfurization ash and water is controlled so that the mass concentration of the first slurry is 30%. The amount of air introduced is such that the O in the air is 2.5 2 and S (i.e. O 2 / S) is 4.5, thereby ensuring the full dissolution and oxidation of the semi-dry desulfurization ash, so that the calcium sulfite therein is oxidized into calcium sulfate; the dust gas enters the dust removal unit 10 for dust removal;

[0131] (2) the first slurry is introduced into the magnetic separation unit 3 for magnetic separation, and the magnetic field strength is 1500 mT to obtain a second slurry and magnetic separation slag; the magnetic separation slag is sent to the sintering batch or cold pressing process of the ironmaking and steelmaking process, and is used as a coolant and slag-making agent for the converter, thereby recovering the iron element;

[0132] (3) adding an acetic acid solution accounting for 20% of the volume of the acetic acid reaction tank to the acetic acid reaction unit 4, the concentration of the acetic acid solution is 3 mol / L, and heating is performed by a heating device 402, the heating device 402 is a hot water coil, and the temperature in the tank is gradually increased to 45° C., and stirring is performed at a stirring speed of 400 rpm; the second slurry is allowed to enter the acetic acid reaction unit 4, and the mass ratio of the semi-dry desulfurization ash and the acetic acid solution is 1:1.5 by controlling the amount of the second slurry entering the acetic acid reaction unit 4, and the temperature is maintained at 45° C., and stirring is continued. The reaction is performed for 0.5 h, and the acetic acid reacts with the calcium oxide, calcium hydroxide and calcium carbonate in the desulfurization ash to generate water-soluble calcium acetate, thereby obtaining a third slurry;

[0133] (4) allowing the third slurry to enter the gypsum dehydration unit 5 for dehydration to obtain a fourth slurry and gypsum;

[0134] (5) The fourth slurry is allowed to enter the impurity removal unit 6 to react with quicklime under stirring conditions. The stirring speed is 30 rpm, the reaction temperature is room temperature, and the reaction time is 15 minutes. After the quicklime is hydrated, it reacts with the Mg in the fourth slurry. 2+ 、M + The reaction is performed to generate a precipitate to obtain a fifth slurry, and the amount of quicklime added is controlled so that the pH value of the fifth slurry is 10 to 11;

[0135] (6) The fifth slurry enters the solid-liquid separation unit 7, and the fifth slurry is first separated by a centrifuge 701, the rotation speed of the centrifuge 701 is 10000 rpm, and a first residue and a supernatant are obtained; the supernatant is then subjected to a secondary separation by a filter 702, the filtration pressure of the filter 702 is 0.2 MPa, and the filtration speed is 13 m / h, to obtain a second residue and a filtrate; the first residue and the second residue are combined into a residue, and the filtrate is a clear liquid;

[0136] (7) allowing the clear liquid to enter the purification unit 8 to react with the acetic acid solution under stirring conditions, the stirring speed is 120 rpm, the concentration of the acetic acid solution is 4 mol / L, the amount of acetic acid solution added is controlled so that the pH value of the system after the addition of the acetic acid solution is 6.0-8.0, the reaction temperature is room temperature, the reaction time is 5 minutes, and the remaining calcium hydroxide reacts with acetic acid to generate calcium acetate, thereby obtaining a calcium acetate solution;

[0137] (8) allowing the calcium acetate solution to enter the crystallization and dehydration unit 9 for crystallization. In a triple-effect evaporation crystallizer, the calcium acetate solution is evaporated, concentrated, crystallized, and centrifuged to obtain a mother liquor, condensed water, and calcium acetate crystals; allowing the mother liquor and condensed water to enter the dust removal unit 10 as part of the water source;

[0138] (9) In the dust removal unit 10, the mother liquor and condensed water from the crystallization dehydration unit 9 are used as part of the water source, and industrial new water is added as another part of the water source, thereby removing dust from the dust gas from the dissolution oxidation unit 2. The dust-containing wastewater flows back to the dissolution oxidation unit 2 by gravity for recycling and is not discharged.

[0139] The purity of the calcium acetate crystals in this embodiment was 99.5% as detected by high performance liquid chromatography, and the purity of the gypsum in this embodiment was 97% as detected by barium sulfate weighing method.

[0140] Example 3

[0141] This embodiment provides a method for preparing calcium acetate crystals and gypsum using semi-dry desulfurization ash, which is basically the same as that of embodiment 2, except that: (3) an acetic acid solution accounting for 20% of the volume of the acetic acid reaction tank is added to the acetic acid reaction unit 4, the concentration of the acetic acid solution is 4 mol / L, and the heating device 402 is used to heat the tank, the heating device 402 is a steam coil, and the temperature in the tank is gradually increased to 45°C, and stirring is performed at a stirring speed of 400 rpm; the second slurry is allowed to enter the acetic acid reaction unit 4, and the mass ratio of the semi-dry desulfurization ash and the acetic acid solution is 1:1.75 by controlling the amount of the second slurry entering the acetic acid reaction unit 4, and the temperature is maintained at 45°C, and stirring is continued. The reaction is carried out for 1 hour, and the acetic acid reacts with the calcium oxide, calcium hydroxide and calcium carbonate in the desulfurization ash to generate water-soluble calcium acetate to obtain the third slurry. The remaining steps are the same as those of embodiment 2.

[0142] The purity of the calcium acetate crystals in this embodiment is 99.6%, and the purity of the gypsum is 98%. The detection method is the same as that in Example 2.

[0143] Example 4

[0144] This embodiment provides a method for preparing calcium acetate crystals and gypsum using semi-dry desulfurization ash, which is basically the same as that of embodiment 2, except that: (3) an acetic acid solution accounting for 20% of the volume of the acetic acid reaction tank is added to the acetic acid reaction unit 4, the concentration of the acetic acid solution is 3 mol / L, and the heating device 402 is used to heat the tank, the heating device 402 is a steam coil, and the temperature in the tank is gradually increased to 50°C, and stirring is performed at a stirring speed of 500 rpm; the second slurry is allowed to enter the acetic acid reaction unit 4, and the mass ratio of the semi-dry desulfurization ash and the acetic acid solution is 1:2 by controlling the amount of the second slurry entering the acetic acid reaction unit 4, and the temperature is maintained at 50°C, and stirring is continued, and the reaction is performed for 0.75 hours, and the acetic acid reacts with the calcium oxide, calcium hydroxide and calcium carbonate in the desulfurization ash to generate water-soluble calcium acetate to obtain the third slurry. The remaining steps are the same as those of embodiment 2.

[0145] The purity of the calcium acetate crystals in this embodiment is 99.6%, and the purity of the gypsum is 98%. The detection method is the same as that in Example 2.

[0146] Example 5

[0147] This embodiment provides a system for preparing calcium acetate crystals and gypsum using semi-dry desulfurization ash, which is basically the same as Embodiment 1, except that: the solid-liquid separation unit 7 includes an inclined plate sedimentation tank 703, such as Figure 2 The rest of the structure is the same as that of Example 1.

[0148] This embodiment also provides a method for preparing calcium acetate crystals and gypsum using semi-dry desulfurization ash, which is carried out using the system for preparing calcium acetate crystals and gypsum using semi-dry desulfurization ash of this embodiment, and is basically the same as that of Example 2, except that: in step (6), the fifth slurry enters the solid-liquid separation unit 7, and is separated using an inclined plate sedimentation tank 703 to obtain a clear liquid and a residue. The remaining steps are the same as those of Example 2.

[0149] The purity of the calcium acetate crystals in this embodiment is 95%, and the purity of the gypsum is 98%. The detection method is the same as that in Example 2.

[0150] Comparative Example 1

[0151] This comparative example provides a method for preparing calcium acetate crystals and gypsum using semi-dry desulfurization ash, which is basically the same as Example 2, except that the magnetic separation unit 3 is arranged after the acetic acid reaction unit 4.

[0152] The specific steps include:

[0153] (1) The semi-dry desulfurization ash is unloaded into the dissolution oxidation unit 2 through the semi-dry desulfurization ash storage and transportation unit 1. In the dissolution oxidation unit 2, the semi-dry desulfurization ash is mixed with water under stirring conditions and contacted with air to dissolve and oxidize to obtain a first slurry and dust gas. The stirring speed is 120 rpm. The mixing ratio of the semi-dry desulfurization ash and water is controlled so that the mass concentration of the first slurry is 30%. The amount of air introduced is such that the O in the air is 2.5 2 and S (i.e. O 2 / S) is 4.5, thereby ensuring the full dissolution and oxidation of the semi-dry desulfurization ash, so that the calcium sulfite therein is oxidized into calcium sulfate; the dust gas enters the dust removal unit 10 for dust removal;

[0154] (2) adding an acetic acid solution accounting for 20% of the volume of the acetic acid reaction tank to the acetic acid reaction unit 4, the concentration of the acetic acid solution being 3 mol / L, heating the solution by means of a heating device 402, the heating device 402 being a hot water coil, gradually raising the temperature in the tank to 45° C., stirring the solution at a stirring speed of 400 rpm; allowing the first slurry to enter the acetic acid reaction unit 4, controlling the amount of the first slurry entering the acetic acid reaction unit 4, so that the mass ratio of the semi-dry desulfurization ash to the acetic acid solution is 1:1.5, maintaining the temperature at 45° C., and continuing stirring the solution for 0.5 h, wherein the acetic acid reacts with the calcium oxide, calcium hydroxide and calcium carbonate in the desulfurization ash to generate water-soluble calcium acetate, thereby obtaining a second slurry;

[0155] (3) the second slurry is introduced into the magnetic separation unit 3 for magnetic separation, and the magnetic field strength is 1500 mT to obtain a third slurry and magnetic separation slag; the magnetic separation slag is sent to the sintering batch or cold pressing process of the ironmaking and steelmaking process, and is used as a coolant and slag-making agent for the converter, thereby recovering the iron element;

[0156] (4) allowing the third slurry to enter the gypsum dehydration unit 5 for dehydration to obtain a fourth slurry and gypsum;

[0157] (5) The fourth slurry is allowed to enter the impurity removal unit 6 to react with quicklime under stirring conditions. The stirring speed is 30 rpm, the reaction temperature is room temperature, and the reaction time is 15 minutes. After the quicklime is hydrated, it reacts with the Mg in the fourth slurry. 2+ 、M + The reaction is performed to generate a precipitate to obtain a fifth slurry, and the amount of quicklime added is controlled so that the pH value of the fifth slurry is 10 to 11;

[0158] (6) The fifth slurry enters the solid-liquid separation unit 7, and the fifth slurry is first separated by a centrifuge 701, the rotation speed of the centrifuge 701 is 15000 rpm, and a first residue and a supernatant are obtained; the supernatant is then subjected to a secondary separation by a filter 702, the filtration pressure of the filter 702 is 0.2 MPa, and the filtration speed is 13 m / h, to obtain a second residue and a filtrate; the first residue and the second residue are combined into a residue, and the filtrate is a clear liquid;

[0159] (7) allowing the clear liquid to enter the purification unit 8 to react with the acetic acid solution under stirring conditions, the stirring speed is 120 rpm, the concentration of the acetic acid solution is 4 mol / L, the amount of acetic acid solution added is controlled so that the pH value of the system after the addition of the acetic acid solution is 6.0-8.0, the reaction temperature is room temperature, the reaction time is 5 minutes, and the remaining calcium hydroxide reacts with acetic acid to generate calcium acetate, thereby obtaining a calcium acetate solution;

[0160] (8) allowing the calcium acetate solution to enter the crystallization and dehydration unit 9 for crystallization. In a triple-effect evaporation crystallizer, the calcium acetate solution is evaporated, concentrated, crystallized, and centrifuged to obtain a mother liquor, condensed water, and calcium acetate crystals; allowing the mother liquor and condensed water to enter the dust removal unit 10 as part of the water source;

[0161] (9) In the dust removal unit 10, the mother liquor and condensed water from the crystallization dehydration unit 9 are used as part of the water source, and industrial new water is added as another part of the water source, thereby removing dust from the dust gas from the dissolution oxidation unit 2. The dust-containing wastewater flows back to the dissolution oxidation unit 2 by gravity for recycling and is not discharged.

[0162] The purity of the calcium acetate crystals in this comparative example is 95.8%, and the color is yellow; the purity of the gypsum is 97%. The detection method is the same as that of Example 2.

[0163] Comparative Example 2

[0164] This comparative example provides a method for preparing calcium acetate crystals and gypsum using semi-dry desulfurization ash, which is basically the same as Example 2, except that: the impurity removal unit 6, the solid-liquid separation unit 7 and the purification unit 8 are not provided.

[0165] The specific steps include:

[0166] (1) The semi-dry desulfurization ash is unloaded into the dissolution oxidation unit 2 through the semi-dry desulfurization ash storage and transportation unit 1. In the dissolution oxidation unit 2, the semi-dry desulfurization ash is mixed with water under stirring conditions and contacted with air to dissolve and oxidize to obtain a first slurry and dust gas. The stirring speed is 120 rpm. The mixing ratio of the semi-dry desulfurization ash and water is controlled so that the mass concentration of the first slurry is 30%. The amount of air introduced is such that the O in the air is 2.5 2 and S (i.e. O2 / S) is 4.5, thereby ensuring the full dissolution and oxidation of the semi-dry desulfurization ash, so that the calcium sulfite therein is oxidized into calcium sulfate; the dust gas enters the dust removal unit 10 for dust removal;

[0167] (2) the first slurry is introduced into the magnetic separation unit 3 for magnetic separation, and the magnetic field strength is 1500 mT to obtain a second slurry and magnetic separation slag; the magnetic separation slag is sent to the sintering batch or cold pressing process of the ironmaking and steelmaking process, and is used as a coolant and slag-making agent for the converter, thereby recovering the iron element;

[0168] (3) adding an acetic acid solution accounting for 20% of the volume of the acetic acid reaction tank to the acetic acid reaction unit 4, the concentration of the acetic acid solution is 3 mol / L, and heating is performed by a heating device 402, the heating device 402 is a hot water coil, and the temperature in the tank is gradually increased to 45° C., and stirring is performed at a stirring speed of 400 rpm; the second slurry is allowed to enter the acetic acid reaction unit 4, and the mass ratio of the semi-dry desulfurization ash and the acetic acid solution is 1:1.5 by controlling the amount of the second slurry entering the acetic acid reaction unit 4, and the temperature is maintained at 45° C., and stirring is continued. The reaction is performed for 0.5 h, and the acetic acid reacts with the calcium oxide, calcium hydroxide and calcium carbonate in the desulfurization ash to generate water-soluble calcium acetate, thereby obtaining a third slurry;

[0169] (4) allowing the third slurry to enter the gypsum dehydration unit 5 for dehydration to obtain a fourth slurry and gypsum;

[0170] (5) allowing the fourth slurry to enter the crystallization and dehydration unit 9 for crystallization, and in the triple-effect evaporation crystallizer, the calcium acetate solution is evaporated, concentrated, crystallized, and centrifuged to obtain a mother liquor, condensed water, and calcium acetate crystals; allowing the mother liquor and condensed water to enter the dust removal unit 10 as part of the water source;

[0171] (6) In the dust removal unit 10, the mother liquor and condensed water from the crystallization dehydration unit 9 are used as part of the water source, and industrial new water is added as another part of the water source, thereby removing dust from the dust gas from the dissolution oxidation unit 2. The dust-containing wastewater flows back to the dissolution oxidation unit 2 by gravity for recycling and is not discharged.

[0172] The purity of the calcium acetate crystals in this comparative example is 91.3%, and the purity of the gypsum is 96%. The detection method is the same as that in Example 2.

[0173] Comparative Example 3

[0174] This comparative example provides a method for preparing calcium acetate crystals and gypsum using semi-dry desulfurization ash, which is basically the same as Example 2, except that: (3) an acetic acid solution accounting for 20% of the volume of the acetic acid reaction tank is added to the acetic acid reaction unit 4, the concentration of the acetic acid solution is 2 mol / L, and the heating device 402 is used for heating, and the heating device 402 is a hot water coil, and the temperature in the tank is gradually increased to 30°C, and stirring is performed at a stirring speed of 400 rpm; the second slurry is allowed to enter the acetic acid reaction unit 4, and the mass ratio of the semi-dry desulfurization ash and the acetic acid solution is 1:2 by controlling the amount of the second slurry entering the acetic acid reaction unit 4, and the temperature is maintained at 30°C, and stirring is continued, and the reaction is performed for 0.5h, and the acetic acid reacts with the calcium oxide, calcium hydroxide and calcium carbonate in the desulfurization ash to generate water-soluble calcium acetate to obtain the third slurry. The remaining steps are the same as Example 2.

[0175] The purity of the calcium acetate crystals in this comparative example is 81.6%, and the purity of the gypsum is 95%. The detection method is the same as that in Example 2.

[0176] Comparative Example 4

[0177] This comparative example provides a method for preparing calcium acetate crystals and gypsum using semi-dry desulfurization ash, which is basically the same as Example 2, except that: (6) the fifth slurry enters the solid-liquid separation unit 7, and the fifth slurry is separated by a centrifuge 701, the rotation speed of the centrifuge 701 is 10000 rpm, and a residue and a clear liquid are obtained. The remaining steps are the same as Example 2.

[0178] The purity of the calcium acetate crystals in this comparative example is 74.5%, and the purity of the gypsum is 95%. The detection method is the same as that in Example 2.

[0179] Comparative Example 5

[0180] This comparative example provides a method for preparing calcium acetate crystals and gypsum using semi-dry desulfurization ash, which is basically the same as Example 2, except that: (6) the fifth slurry enters the solid-liquid separation unit 7, and the fifth slurry is separated by a filter 702, the filtration pressure of the filter 702 is 0.2 MPa, and the filtration speed is 13 m / h, to obtain residue and clear liquid. The remaining steps are the same as Example 2.

[0181] The purity of the calcium acetate crystals in this comparative example is 77.9%, and the purity of the gypsum is 95%. The detection method is the same as that in Example 2.

Claims

1. A system for preparing calcium acetate crystals and gypsum using semi-dry desulfurization ash, comprising: Semi-dry desulfurization ash storage and transportation unit, dissolution oxidation unit, magnetic separation unit, acetic acid reaction unit, gypsum dehydration unit, impurity removal unit, solid-liquid separation unit, purification unit, crystallization dehydration unit and dust removal unit; The dissolution oxidation unit is at least provided with a semi-dry desulfurization ash inlet, an air inlet, a dust gas outlet and a slurry outlet; the magnetic separation unit is at least provided with a slurry inlet, a magnetic separation slag outlet and a slurry outlet; the acetic acid reaction unit is at least provided with a slurry inlet, an acetic acid inlet and a slurry outlet; the gypsum dehydration unit is at least provided with a slurry inlet, a gypsum outlet and a slurry outlet; the impurity removal unit is at least provided with a slurry inlet, a quicklime inlet and a slurry outlet; the solid-liquid separation unit is at least provided with a slurry inlet, a residue outlet and a clear liquid outlet; the purification unit is at least provided with a clear liquid inlet, an acetic acid inlet and a calcium acetate solution outlet; the crystallization dehydration unit is at least provided with a calcium acetate solution inlet, a mother liquor and condensed water outlet and a calcium acetate crystal outlet; The semi-dry desulfurization ash storage and transportation unit is connected to the semi-dry desulfurization ash inlet of the dissolution oxidation unit; the slurry outlet of the dissolution oxidation unit is connected to the slurry inlet of the magnetic separation unit; the slurry outlet of the magnetic separation unit is connected to the slurry inlet of the acetic acid reaction unit; the slurry outlet of the acetic acid reaction unit is connected to the slurry inlet of the gypsum dehydration unit; the slurry outlet of the gypsum dehydration unit is connected to the slurry inlet of the impurity removal unit; the slurry outlet of the impurity removal unit is connected to the slurry inlet of the solid-liquid separation unit; the clear liquid outlet of the solid-liquid separation unit is connected to the clear liquid inlet of the purification unit; the calcium acetate solution outlet of the purification unit is connected to the calcium acetate solution inlet of the crystallization dehydration unit; the dust gas outlet of the dissolution oxidation unit and the mother liquor and condensed water outlet of the crystallization dehydration unit are respectively connected to the dust removal unit; gypsum is produced from the gypsum outlet of the gypsum dehydration unit, and calcium acetate crystals are produced from the calcium acetate crystal outlet of the crystallization dehydration unit.

2. The system for preparing calcium acetate crystals and gypsum using semi-dry desulfurization ash according to claim 1, wherein: The semi-dry desulfurization ash storage and transportation unit includes a semi-dry desulfurization ash storage bin, an ash unloading pipeline and an ash unloading valve. The semi-dry desulfurization ash storage bin is connected to the semi-dry desulfurization ash inlet of the dissolution oxidation unit through the ash unloading pipeline and the ash unloading valve.

3. The system for preparing calcium acetate crystals and gypsum using semi-dry desulfurization ash according to claim 1, wherein: The dissolution oxidation unit includes a dissolution oxidation tank, water is injected into the dissolution oxidation tank, an air distribution pipe is arranged at the bottom of the dissolution oxidation tank, and an agitator is arranged in the dissolution oxidation tank; the air distribution pipe is connected to an air inlet, and the air inlet is connected to a Roots blower for conveying air into the air distribution pipe.

4. The system for preparing calcium acetate crystals and gypsum using semi-dry desulfurization ash according to claim 1, wherein: The acetic acid reaction unit comprises an acetic acid reaction tank, in which an agitator and a heating device are arranged; Preferably, the heating device comprises one or more of a steam coil, an electric heater and a hot water coil.

5. The system for preparing calcium acetate crystals and gypsum using semi-dry desulfurization ash according to claim 1, wherein: The gypsum dehydration unit comprises one or more of a vacuum belt dehydrator, a centrifugal dehydrator and a plate and frame filter press.

6. The system for preparing calcium acetate crystals and gypsum using semi-dry desulfurization ash according to claim 1, wherein: The impurity removal unit comprises an impurity removal box, and an agitator is arranged in the impurity removal box.

7. The system for preparing calcium acetate crystals and gypsum using semi-dry desulfurization ash according to claim 1, wherein: The solid-liquid separation unit comprises a centrifuge and a filter connected in sequence, wherein the centrifuge is used to perform a primary separation on the slurry obtained by the impurity removal unit to obtain a first residue and a supernatant; the filter is used to perform a secondary separation on the supernatant to obtain a second residue and a filtrate; the first residue and the second residue are discharged from the residue outlet of the solid-liquid separation unit, and the filtrate is discharged from the clear liquid outlet of the solid-liquid separation unit; Alternatively, the solid-liquid separation unit comprises an inclined plate sedimentation tank.

8. The system for preparing calcium acetate crystals and gypsum using semi-dry desulfurization ash according to claim 1, wherein: The purification unit comprises a purification box, in which a stirrer is arranged.

9. The system for preparing calcium acetate crystals and gypsum using semi-dry desulfurization ash according to claim 1, wherein: The crystallization and dehydration unit comprises a multiple-effect evaporation crystallizer or an MVR evaporation crystallizer.

10. The system for preparing calcium acetate crystals and gypsum using semi-dry desulfurization ash according to claim 1, wherein: The dust removal unit includes a wet dust collector, which is at least provided with a dust gas inlet, a recovery water inlet and a dust-containing wastewater outlet; the dust gas inlet of the wet dust collector is connected to the dust gas outlet of the dissolution oxidation unit; the recovery water inlet of the wet dust collector is connected to the mother liquor and condensed water outlet of the crystallization dehydration unit, and is used to use the mother liquor and condensed water of the crystallization dehydration unit as part or all of the water source; the dust-containing wastewater outlet of the wet dust collector is connected to the dissolution oxidation unit, and is used to recycle the dust-containing wastewater; Preferably, the wet dust collector is further provided with a new water inlet for replenishing new water as part of the water source.

11. A method for preparing calcium acetate crystals and gypsum using semi-dry desulfurization ash, the method being carried out using the system for preparing calcium acetate crystals and gypsum using semi-dry desulfurization ash according to any one of claims 1 to 10, the method comprising the following steps: (1) allowing the semi-dry desulfurization ash to be unloaded into a dissolution and oxidation unit through a semi-dry desulfurization ash storage and transportation unit, wherein the semi-dry desulfurization ash is mixed with water and brought into contact with air for dissolution and oxidation to obtain a first slurry and dust gas; and allowing the dust gas to enter a dust removal unit for dust removal; (2) allowing the first slurry to enter a magnetic separation unit for magnetic separation to obtain a second slurry and magnetic separation slag; (3) allowing the second slurry to enter an acetic acid reaction unit to react with an acetic acid solution to obtain a third slurry; (4) allowing the third slurry to enter a gypsum dehydration unit for dehydration to obtain a fourth slurry and gypsum; (5) allowing the fourth slurry to enter an impurity removal unit to react with quicklime to obtain a fifth slurry; (6) allowing the fifth slurry to enter a solid-liquid separation unit for separation to obtain a clear liquid and a residue; (7) allowing the clear liquid to enter a purification unit to react with an acetic acid solution to obtain a calcium acetate solution; (8) allowing the calcium acetate solution to enter a crystallization and dehydration unit for crystallization to obtain a mother liquor, condensed water, and calcium acetate crystals; allowing the mother liquor and condensed water to enter a dust removal unit as part or all of the water source.

12. The method for preparing calcium acetate crystals and gypsum using semi-dry desulfurization ash according to claim 11, wherein: In step (1), in the dissolution oxidation unit, the mixing ratio of the semi-dry desulfurization ash and the water is controlled so that the mass concentration of the first slurry is 20% to 35%, and the amount of air introduced is such that the molar ratio of O2 in the air to S in the semi-dry desulfurization ash is ≥3; preferably, the mixing of the semi-dry desulfurization ash and water and the contact with the air are carried out under stirring conditions, and the stirring speed is 30 to 180 rpm; Preferably, in step (2), in the magnetic separation unit, the magnetic field strength of the magnetic separation is above 1000 mT; more preferably, step (2) further comprises: recovering iron from the magnetic separation slag.

13. The method for preparing calcium acetate crystals and gypsum using semi-dry desulfurization ash according to claim 11, wherein: In step (3), in the acetic acid reaction unit, the concentration of the added acetic acid solution is 2-4 mol / L, and the mass ratio of the semi-dry desulfurization ash to the acetic acid solution is 1:(1.5-2.5); Preferably, in step (3), in the acetic acid reaction unit, the reaction temperature is 45 to 60° C. and the reaction time is 0.5 to 2 hours; more preferably, the reaction is carried out under stirring conditions at a stirring speed of 400 to 600 rpm.

14. The method for preparing calcium acetate crystals and gypsum using semi-dry desulfurization ash according to claim 11, wherein: In step (5), in the impurity removal unit, the reaction temperature is room temperature, the reaction time is 5 to 20 minutes, and the amount of quicklime added is controlled so that the pH value of the fifth slurry is 10 to 11; preferably, the reaction is carried out under stirring conditions, and the stirring speed is 10 to 30 rpm; Preferably, in step (6), in the solid-liquid separation unit, when the solid-liquid separation unit comprises a centrifuge and a filter connected in sequence, the fifth slurry is first separated by a centrifuge at a speed of 5000 to 15000 rpm to obtain a first residue and a supernatant; the supernatant is then separated by a filter at a filtration pressure of 0.2 to 0.4 MPa and a filtration speed of 10 to 20 m / h to obtain a second residue and a filtrate; the first residue and the second residue are combined into the residue, and the filtrate is the clear liquid; Preferably, in step (7), in the purification unit, the concentration of the acetic acid solution added is 2 to 4 mol / L, the amount of the acetic acid solution added is controlled so that the pH value of the system after the addition of the acetic acid solution is between 6.0 and 8.0, the reaction temperature is room temperature, and the reaction time is 5 to 10 minutes; more preferably, the reaction is carried out under stirring conditions, and the stirring speed is 30 to 180 rpm.

15. The method for preparing calcium acetate crystals and gypsum using semi-dry desulfurization ash according to claim 11, wherein: The method further comprises: allowing the dust-containing wastewater in the dust removal unit to enter the dissolution oxidation unit for recycling; Preferably, the method further comprises: adding new water to the dust removal unit as part of the water source.

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