CN110182838B - Modification process system and method for flue gas desulfurization ash - Google Patents
Modification process system and method for flue gas desulfurization ash Download PDFInfo
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- CN110182838B CN110182838B CN201910555301.3A CN201910555301A CN110182838B CN 110182838 B CN110182838 B CN 110182838B CN 201910555301 A CN201910555301 A CN 201910555301A CN 110182838 B CN110182838 B CN 110182838B
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F11/00—Compounds of calcium, strontium, or barium
- C01F11/46—Sulfates
- C01F11/464—Sulfates of Ca from gases containing sulfur oxides
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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
- C04B11/02—Methods and apparatus for dehydrating gypsum
- C04B11/028—Devices therefor characterised by the type of calcining devices used therefor or by the type of hemihydrate obtained
- C04B11/032—Devices therefor characterised by the type of calcining devices used therefor or by the type of hemihydrate obtained for the wet process, e.g. dehydrating in solution or under saturated vapour conditions, i.e. to obtain alpha-hemihydrate
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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
- C04B11/02—Methods and apparatus for dehydrating gypsum
- C04B11/028—Devices therefor characterised by the type of calcining devices used therefor or by the type of hemihydrate obtained
- C04B11/036—Devices therefor characterised by the type of calcining devices used therefor or by the type of hemihydrate obtained for the dry process, e.g. dehydrating in a fluidised bed or in a rotary kiln, i.e. to obtain beta-hemihydrate
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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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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/91—Use of waste materials as fillers for mortars or concrete
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Abstract
The invention discloses a modification process system and method for flue gas desulfurization ash. The modification process system comprises an ash bin, an acid tank, a slurry pump, a forced flow state reactor, a slurry tank, a solid-liquid separator, a dehydration reactor, a first fan and a second fan. The method disclosed by the invention is mainly based on a conventional aeration oxidation technology, and adopts multiple strengthening measures to break down a hard shell layer and an air film barrier wrapped on the surface of the desulfurization ash, so that calcium sulfite and lime in the desulfurization ash are completely exposed and dispersed, high-efficiency conversion and stabilization are ensured, and meanwhile, doping and cladding impurities are removed, so that the product grade is effectively improved. Different from the conventional oxidation or modification method, the desulfurized fly ash can be directly obtained into various phase gypsum products with high purity after being modified by the system and the method, and can be respectively used for downstream medium-high grade building material products, self-leveling materials, cementing materials, mould products and the like, thereby ensuring that all the desulfurized fly ash can be recycled.
Description
Technical Field
The invention belongs to the technical field of environmental protection and inorganic mineral material preparation, and particularly relates to a modification process system and a modification process method for modifying and converting a calcium-based dry or semi-dry flue gas desulfurization byproduct into various high-purity gypsum powder products and realizing resource utilization of flue gas desulfurization ash.
Background
Sulfur dioxide in flue gas discharged from coal-fired thermal power plants, steel, smelting and industrial kilns is an important component causing pollution of acid rain, sulfuric acid smoke and atmospheric dust haze, and an effective control method is to comprehensively implement flue gas desulfurization. Among numerous flue gas desulfurization processes, the semi-dry or dry flue gas desulfurization process has the advantages of short flow, less equipment, small occupied area, no process wastewater and the like, and is particularly suitable for being applied to flue gas desulfurization engineering in water-deficient areas. The calcium-based semi-dry method or dry method flue gas desulfurization process using lime as an absorbent has a large market proportion because of low cost. However, the economical and reasonable disposal of desulfurization byproducts becomes a great difficulty in the popularization and application of the process.
The main component of the calcium-based dry or semi-dry desulfurization ash is calcium sulfite, and contains CaO or Ca (OH) which is partially and completely unreacted 2 In addition, there are impurities such as calcium carbonate and fly ash. The particle size of the desulfurization ash is very small and is generally 3-20 mu m, and the desulfurization ash produced in many desulfurization projects is mainly particles with the size of less than 10 mu m. There have been many experimental studies showing that oxidation of homogeneous sulphites is easier to achieve, but that the dry desulphurized ash is much more difficult to handle. The direct dry oxidation with air generally needs to control the temperature to 400-700 ℃ and takes 4-6 hours until the oxidation rate reaches more than 80%, and the product is anhydrous calcium sulfate with more impurities. The gas-liquid-solid three-phase wet oxidation generally needs long-time aeration to convert the desulfurized fly ash into a product mainly comprising calcium sulfate dihydrate, and the excessive aeration energy consumption is quite large. There are studies on the adoption of strong oxidants such as hydrogen peroxide, ozone and the like to assist in oxidation or the adoption of an additional catalyst to promote the oxidation process, but the cost is too high and the application is limited. Therefore, the conventional desulfurization ash modification process method converts desulfurization ash into dihydrate gypsum or anhydrous gypsum with more impurities, and basically solves the problem of stability, but has higher cost, only obtains low-value mixed products, and has great difficulty in comprehensive utilization of the desulfurization ash and poor economic benefit.
Research shows that the calcium-based desulfurized fly ash is SO in lime powder and flue gas 2 Products subjected to a gas-liquid-solid three-phase reaction (semi-dry process) or a gas-solid two-phase reaction (dry process): in a very short time, SO in the flue gas 2 Reacts with lime to generate calcium sulfite crystals, and simultaneously, the moisture on the surface of the absorbent particles quickly evaporates to form a compact product layer which is wrapped on the surface of fresh lime powder particles. This product layer outer shell prevents further gas-solid desulfurization reactions, so that the fresh lime inside is not exposed and participates in the reaction to be consumed, and thus the residual amount is large. Meanwhile, other coal ash components are mixed in the desulfurization ash with extremely fine grain size, and the desulfurization ash presents irregular morphology and microstructure. Through intensive research, the outer surface of the dry fine particles is further coated by a layer of air film, and the air film has strong compactness, so that the desulfurized fly ash particles are difficult to wet and dissolve during slurry preparationThe reaction resistance increases and the reaction rate is limited. Therefore, it is difficult to obtain a high-efficiency oxidation effect only by conventional aeration, and impurities cannot be removed and the purity of the product cannot be improved effectively. Starting from the double obstacle of effectively breaking the gas film wrapped outside the particles and the hard product shell, a plurality of cooperative strengthening measures are adopted to stabilize the high-efficiency reaction of the desulfurized fly ash, remove various impurities of the product to improve the purity, and further integrate a dehydration modification unit, thereby obtaining various gypsum products with higher value on one process production line.
Disclosure of Invention
The invention aims at providing a modification process system of flue gas desulfurization ash, aiming at the problems of high energy consumption and cost, low multiple added values of product impurities and difficult utilization of the conventional desulfurization ash modification process method.
The first object of the invention is achieved by the following technical scheme: the modification process system of the flue gas desulfurization ash comprises an ash bin, an acid tank, a slurry pump, a forced flow state reactor, a slurry tank, a solid-liquid separator, a dehydration reactor, a first fan and a second fan; the outlets of the ash bin and the acid tank are communicated with a slurry tank through a pipeline, and a stirrer is arranged in the slurry tank; the forced flow state reactor is positioned above the slurry pool, and the outlet at the bottom of the forced flow state reactor is communicated with the slurry pool through a pipeline or directly; the slurry tank outlet and the slurry tank bottom reflux outlet are communicated with the liquid phase inlet of the forced fluidization reactor through a slurry pump and a pipeline; the bottoms of the slurry tank and the slurry tank are respectively connected with a first fan through a pipeline to be aerated by air; the outlet of the slurry tank is connected with the inlet of the solid-liquid separator through a pipeline, the solid outlet of the solid-liquid separator is communicated with the material inlet of the dehydration reactor through a conveyor belt or a screw conveyor, the liquid phase outlet of the solid-liquid separator is communicated with the slurry tank through a pipeline, and the top of the solid-liquid separator is provided with a washing water inlet; the top of the dehydration reactor is provided with an exhaust port, the exhaust port is communicated with the air inlet of the forced flow state reactor through a second fan and a pipeline, the dehydration reactor is connected with a pipeline for introducing air or water vapor, and the bottom of the dehydration reactor is provided with a solid material outlet; valves are arranged on the pipelines.
Specifically, the dehydration reactors are reactors with heating and constant temperature functions, the number of the dehydration reactors is 1-24, and when the number of the dehydration reactors is more than 2, the dehydration reactors are arranged in a series or parallel mode.
Specifically, the forced fluidization reactor comprises a necking section, namely a venturi section and a filler section, wherein a liquid phase inlet and an air inlet are formed in the necking section, and a plurality of movable spherical, ellipsoidal or cylindrical fillers are arranged in the filler section.
Specifically, the solid-liquid separator adopts one of a vacuum belt filter, a vacuum rotary drum or centrifugal separation equipment.
The second object of the invention is to provide a flue gas desulfurization ash modification process method based on the flue gas desulfurization ash modification process system, which comprises the following steps:
(1) Mixing the flue gas desulfurization ash in the ash bin with reuse water at a liquid phase outlet of the solid-liquid separator in a slurry tank to prepare slurry with the solid content of 12-50%, and regulating the pH value of the slurry to 3.5-7.5 by sulfuric acid or hydrochloric acid in an acid tank;
(2) Introducing air into a slurry tank and slurry in the slurry tank through a fan to aerate for 10-100 min, pumping the slurry in the slurry tank into a forced fluidization reactor through a slurry pump, enabling the slurry to fully contact with air flow sent by a fan II, and then entering the slurry tank;
(3) Reflux-pumping part of the slurry in the slurry tank into a forced fluidization reactor through a slurry pump, removing scum on the surface of the slurry in the slurry tank, transferring the slurry in the slurry tank to a solid-liquid separator for filtration, and washing with water simultaneously;
(4) The filtrate and washing water in the solid-liquid separator are returned to the slurry tank for slurry preparation through a liquid phase outlet and a pipeline of the solid-liquid separator, and the separated solids are transferred into a dehydration reactor;
(5) Introducing air or water vapor into the dehydration reactor, controlling the temperature to be 60-300 ℃ for dehydration treatment, controlling the solid materials to stay in the dehydration reactor for 2-300 min, and exhausting through a second fan;
(6) And cooling the dehydration reactor, and discharging the solid materials in the dehydration reactor through a solid material outlet, so as to obtain the high-purity gypsum powder with stable quality.
Specifically, in the slurry tank and slurry tank aeration process, the total aeration intensity is 1-30L/m 2 S, controlling the diameter of the bubble to be 0.1 μm to 10mm.
Specifically, the gas velocity of the necking section of the forced flow state reactor is controlled to be 30-120 m/s, and the liquid-gas ratio is controlled to be 10-300L/m 3 Within a range of (2). Under the actions of impact, shearing, pressure shock and the like of high-speed air flow, the air film on the surface of the desulfurized ash and the shell layer of a desulfurized product are destroyed, the exposed internal materials are wetted, and the desulfurized ash is further ground and dispersed by strong turbulence, mutual friction and collision formed by the suspension fluidization of the built-in filler and desulfurized ash particles, so that gas-liquid-solid three-phase close contact is caused, and mass transfer and heat transfer are efficiently carried out.
Specifically, the specific control method and conditions of the dehydration reactor during operation are as follows:
when a gypsum product of two aqueous phases is to be produced: introducing air and controlling the temperature in the reactor to be 60-120 ℃ and the residence time of the solid phase material to be 2-60 min; when a beta-gypsum containing half the water of crystallization, i.e. an architectural gypsum product, is to be produced: introducing air and controlling the temperature in the reactor to be 121-250 ℃ and the residence time of the solid phase material to be 5-120 min; when alpha-gypsum, i.e., a high strength gypsum product, is to be produced: adding a crystal form control agent commonly used in the field into the solid-phase material, introducing saturated water vapor or generating the saturated water vapor by heating the water carried by the material, and controlling the temperature in the reactor to be 124-250 ℃ and the residence time of the solid-phase material to be 20-300 min; when an anhydrous gypsum product is to be produced: introducing air and controlling the temperature at 251-400 ℃ and the solid phase material residence time at 30-150 min.
The desulfurization ash modification process disclosed by the invention is based on a conventional aeration oxidation technology, and adopts multiple strengthening measures to break down a hard shell layer and a gas film barrier wrapped on the surface of the desulfurization ash, so that calcium sulfite and lime in the desulfurization ash are completely exposed and dispersed, high-efficiency conversion and stabilization are ensured, and meanwhile, blending and cladding impurities are removed, so that the product grade is effectively improved. Different from the conventional oxidation or modification method, the desulfurized fly ash can be directly obtained into various phase gypsum products with high purity after being modified by the system and the method, and can be respectively used for downstream medium-high grade building material products, self-leveling materials, cementing materials, mould products and the like, thereby ensuring that all the desulfurized fly ash can be recycled. In addition, the process system of the invention can also be used for modifying calcium-based byproducts (such as desulfurization slag with more impurities) of a wet desulfurization system. The whole modification process is compact and efficient, flexible in regulation and control, energy-saving and environment-friendly, and strong in market demand adaptability.
The outstanding effects of the present invention are expressed as follows:
(1) The desulfurization ash modification process equipment is compact and efficient, the process water is recycled completely, and the modification process is energy-saving and environment-friendly.
(2) The method integrates and utilizes multiple strengthening measures such as gas-liquid-solid three-phase full mixing aeration, high-strength pneumatic shearing crust breaking, multi-medium fluidization grinding dispersion, wet thermal oxidation and the like to ensure that the desulfurized fly ash is fully converted into a stable product, and simultaneously, the impurities contained in the desulfurized fly ash are effectively removed to effectively improve the mineral grade, and the desulfurized fly ash can obtain a high-purity gypsum raw material after being modified by the method.
(3) The gypsum powder capable of flexibly controlling the production of dihydrate, hemihydrate and anhydrous phase on one modification process production line can realize the full coverage of gypsum products in various phases, so that the properties and added values of the products can flexibly adapt to the change of market demands, and the desulfurization ash or desulfurization slag can be fully utilized by recycling.
Drawings
FIG. 1 is a schematic flow diagram of a modification process system for flue gas desulfurization ash according to the present invention.
FIG. 2 is a schematic view of the structure of the forced fluidized reactor in FIG. 1.
Detailed Description
The invention is further described below with reference to the drawings and examples.
Example 1:
referring to fig. 1, the modification process system of flue gas desulfurization ash in this embodiment includes an ash bin 1, an acid tank 2, a slurry tank 3, a slurry pump 4, a forced flow reactor 5, a slurry tank 6, a solid-liquid separator 7, a dehydration reactor 8, a first fan 9, and a second fan 10. As can be seen from fig. 1, the outlets of the ash bin 1 and the acid tank 2 are communicated with the slurry tank 3 through pipelines, and a stirrer 11 is arranged in the slurry tank 3; wherein, ash bin 1 passes through the pipeline and carries desulfurization ash to thick liquid groove 3, and acid tank 2 is linked together through liquid pipeline and thick liquid groove 3 and through the measuring pump (not shown in the figure) with acidizing fluid ration to add thick liquid groove 3. The forced flow state reactor 5 is positioned above the slurry pond 6 and is communicated with the slurry pond 6; the slurry pump 4 is respectively communicated with the outlet of the slurry tank 3, the liquid phase inlet of the forced fluidization reactor 5 and the reflux outlet of the slurry tank 6 through pipelines. The outlet of the first fan 9 is communicated with a gas distribution pipe and an aeration element (not shown) at the bottoms of the slurry tank 3 and the slurry tank 6 through pipelines. The outlet of the slurry tank 6 is connected with the inlet of the solid-liquid separator 7 through a pipeline, the solid outlet of the solid-liquid separator 7 is communicated with the material inlet of the dehydration reactor 8 through a conveyor belt or a screw conveyer, and the liquid phase outlet of the solid-liquid separator 7 is communicated with the slurry tank 3 through a pipeline, so that the liquid phases separated by the solid-liquid separator 7 are collected and then sent back to the slurry tank 3 through a pipeline; the top of the solid-liquid separator is provided with a washing water inlet. The top of the dehydration reactor 8 is provided with an exhaust port, the exhaust port is communicated with the air inlet of the forced flow state reactor 5 through a second fan 10 and a pipeline, the dehydration reactor 8 is connected with a pipeline for introducing air or water vapor, and the bottom of the dehydration reactor 8 is provided with a solid material outlet. Valves (not shown) are arranged on the pipelines in the system for controlling the opening and closing of the pipelines. Referring to fig. 2, a necking section 501 and a packing section 502 are connected in series on the gas passage of the forced flow reactor 5, 15-40 movable spherical plastic packing are arranged in the packing section 502, and a liquid phase inlet 503 and a gas inlet 504 are arranged on the forced flow reactor 5. In this embodiment, 2 dehydration reactors 8 with temperature adjusting function are arranged in parallel, and semi-continuous production is realized through alternate operation.
In order to improve the automation degree, the periphery of the flue gas desulfurization ash modification process system can be provided with a measuring and monitoring system which comprises a slurry pH value and temperature, gas and slurry flow, a dehydration reactor temperature and pressure monitoring and displaying instrument and a corresponding feedback control component; wherein, the slurry tank 3 and the slurry tank 6 can be provided with pH value and temperature monitoring instruments and corresponding feedback control mechanisms, the gas pipeline is provided with gas speed and gas quantity monitoring instruments and corresponding control executing mechanisms, and the dehydration reactor can be provided with temperature and pressure monitoring instruments and corresponding control executing mechanisms and the like. Because this part of the equipment and technology is the existing mature technology, according to the technological requirements of this technical scheme, the skilled person in the art or related fields can design and implement this technology, and this will not be described in detail here.
The following is an engineering example of a flue gas desulfurization ash modification process method based on the flue gas desulfurization ash modification process system.
The semi-dry desulfurization ash produced by a certain enterprise has the main components of 31 percent of calcium sulfite, 24 percent of calcium sulfate, 26 percent of calcium hydroxide, 15 percent of calcium carbonate and about 4 percent of other impurities through analysis.
The method for modifying the desulfurization ash by using the flue gas desulfurization ash modification process system comprises the following steps: 1/2 volume of filtered water returned from the solid-liquid separator 7 is injected into the slurry tank 3, flue gas desulfurization ash (about 1/10 slurry tank volume) in the ash bin 1 is injected into the slurry tank 3, and the slurry is stirred and mixed to prepare suspended slurry with the mass solid content of about 30%, sulfuric acid solution in the acid tank 2 is uniformly injected into the suspended slurry, and the pH value of the slurry is controlled to be 4.0-5.0. Then the first fan 9 is started, air is introduced into the slurry in the slurry tank 3, and the aeration intensity in the slurry tank is regulated to be 2L/m 2 S and aeration is continued for 30min. The slurry pump 4 is started to pump the slurry in the slurry tank 3 into the forced flow state reactor 5, and meanwhile, the second fan 10 is started to enable the slurry to enter the slurry tank 6 together after being fully contacted with the air flow sent by the second fan 10, and the air is emptied from the slurry tank 6 (the slurry tank is open). Periodically pumping part of the slurry in the slurry tank 6 into the forced flow state reactor 5 again, simultaneously introducing air into the slurry tank 6 through a first fan 9, and adjusting the aeration intensity in the slurry tank to 15L/m 2 S, aeration time is about 60min, and scum on the surface of the slurry in the tank is removed. The slurry was then sent to a solid-liquid separator 7 (using a vacuum belt filter) for filtration and simultaneous water washing. Wherein the filtrate and the washing water are returned to the slurry tank 3 for supply after being collectedThe slurry is prepared, and the separated solid material is transferred to a dehydration reactor 8 for further treatment. Introducing air with the temperature of about 200 ℃ into the dehydration reactor 8 for treatment, keeping the temperature constant and controlling the solid materials to stay in the dehydration reactor 8 for 5-10 min, then exhausting the air through a second fan 10 and a pipeline connected with the dehydration reactor 8, and introducing the exhausted air into the forced flow state reactor 5. Discharging the solid material after cooling to 60 ℃ to obtain the building gypsum with the purity of more than 90 percent, and directly selling or further processing the building gypsum into gypsum powder products with other specifications for selling. The two dehydration reactors 8 are used for feeding and discharging in turn, and a dust collector can be arranged at a discharging hole to avoid dust emission.
Example 2:
the properties of the desulfurization ash of this example are the same as those of example 1, and the flue gas desulfurization ash modification process system used in this example is the same as that of example 1, except for the operation method and the properties of the modified product when the modification of the desulfurization ash is performed by using this system.
The method for modifying the desulfurization ash by using the flue gas desulfurization ash modification process system comprises the following steps: 1/2 volume of filtered water returned from the solid-liquid separator 7 is injected into the slurry tank 3, flue gas desulfurization ash (about 1/10 slurry tank volume) in the ash bin 1 is injected into the slurry tank 3, and the slurry is stirred and mixed to prepare suspended slurry with the mass solid content of about 30%, sulfuric acid solution in the acid tank 2 is uniformly injected into the suspended slurry, and the pH value of the slurry is controlled to be 4.0-5.0. Then the first fan 9 is started, air is introduced into the slurry in the slurry tank 3, and the aeration intensity in the tank is adjusted to be 5L/m 2 S and aeration is continued for 30min. And (3) starting a slurry pump to pump the slurry in the slurry tank 3 into the forced flow state reactor 5, and simultaneously starting a second fan 10 to ensure that the slurry and the air flow sent by the second fan 10 are fully contacted and then enter the slurry tank 6, and the air is emptied from the slurry tank 6. Periodically re-pumping part of the slurry in the slurry tank 6 into the forced flow state reactor 5, simultaneously introducing air into the slurry tank 6 through a first fan 9, and adjusting the aeration intensity in the tank to 20L/m 2 S, aeration time is about 60min, and scum on the surface of the slurry in the tank is removed. The slurry was then sent to a solid-liquid separator 7 (using a vacuum belt filter) for filtration and simultaneous water washing. Wherein the filtrate and the washing water are returned after being collectedThe slurry tank 3 is used for preparing slurry, and the separated solid material is mixed with a crystal form control agent (sodium tartrate or malic acid) with the total mass of about 0.3 percent and then is transferred into a dehydration reactor 8 for further treatment. Introducing water vapor with the temperature of about 180 ℃ into the dehydration reactor 8 for treatment, controlling the solid materials to stay in the dehydration reactor 8 for 150min for constant temperature reaction, then exhausting the gas through a second fan 10 and a pipeline connected with the dehydration reactor 8, and introducing the exhausted gas into the forced flow state reactor 5. And discharging the solid material after the temperature is reduced to 60 ℃ to obtain the alpha-gypsum with the purity of more than 90%. The two dehydration reactors 8 are used for carrying out feeding reaction and discharging in turn, and a dust collector can be arranged at a discharging hole in order to avoid dust emission. Can be directly sold or further processed into high-strength gypsum powder products with other specifications for sale.
Example 3:
the semi-dry desulfurization ash produced by a certain enterprise has the main components of 26% of calcium sulfite, 28% of calcium sulfate, 21% of calcium hydroxide, 18% of calcium carbonate and about 7% of other impurities through analysis. The modification process system flow and the constitution are basically the same as those of the embodiment 1, and the difference is that: the reflux outlet of the slurry tank 6 in the system is connected with the liquid phase inlet 503 of the forced fluidization reactor 5 through a new pump and pipeline, and the dehydration reactor 8 in the system is provided with only 1. The method for modifying the desulfurization ash by using the system comprises the following steps: 1/2 volume of filtered water returned from the solid-liquid separator 7 is injected into the slurry tank 3, flue gas desulfurization ash (about 1/8 slurry tank volume) in the ash bin 1 is injected into the slurry tank 3, and the slurry is stirred and mixed to prepare suspended slurry with the mass solid content of about 35%, hydrochloric acid solution in the acid tank 2 is uniformly injected into the suspended slurry, and the pH value of the slurry is controlled to be 5.5-6.5. Then the first blower 9 is started, air is introduced into the slurry in the slurry tank 3, and the aeration intensity in the tank is regulated to be 10L/m 2 S and aeration is continued for 20min. And (3) starting a slurry pump to pump the slurry in the slurry tank 3 into the forced flow state reactor 5, and simultaneously starting a second fan 10 to ensure that the slurry and the air flow sent by the second fan 10 are fully contacted and then enter the slurry tank 6, and the air is emptied from the slurry tank 6. Part of the slurry in the slurry pool 6 is re-pumped into the forced flow state reactor 5 every half an hour, and simultaneously the slurry pool is conveyed to the slurry pool through a fan 96, introducing air, and regulating the aeration intensity in the pool to be 12L/m 2 S, aeration is performed for about 30 minutes, and scum on the surface of the slurry in the tank is removed. The slurry was then sent to a solid-liquid separator 7 (using a vacuum belt filter) for filtration and simultaneous water washing. Wherein, the filtrate and the washing water are collected and returned to the slurry tank 3 for slurry preparation, and the separated solid materials are transferred to a dehydration reactor 8 for further treatment. Introducing air with the temperature of 60-80 ℃ into the dehydration reactor 8 for dehydration treatment, controlling the solid material to stay in the dehydration reactor 8 for about 60min, exhausting the solid material through a second fan 10 and a pipeline connected with the dehydration reactor 8, and introducing the exhausted material into the forced flow state reactor 5. After the dehydration reaction is completed, the solid material is discharged after the temperature is slightly reduced, so that the dihydrate gypsum powder with the purity of about 95 percent is obtained, and can be directly sold as a raw material of a downstream gypsum product or further processed into other gypsum powder products for sale.
The above are only examples of embodiments of the invention and should not be used to limit the scope of the claims. Those skilled in the art, after having understood the innovative and principle of the present invention, can make several modifications in the combination of operating steps and reaction conditions, or add several links well known in the art, which should also be considered as not exceeding the scope of protection of the invention.
Claims (6)
1. A modification process system of flue gas desulfurization ash is characterized in that: the device comprises an ash bin, an acid tank, a slurry pump, a forced flow state reactor, a slurry tank, a solid-liquid separator, a dehydration reactor, a first fan and a second fan; the outlets of the ash bin and the acid tank are communicated with a slurry tank through a pipeline, and a stirrer is arranged in the slurry tank; the forced flow state reactor is positioned above the slurry pool, and the outlet at the bottom of the forced flow state reactor is communicated with the slurry pool through a pipeline or directly; the slurry tank outlet and the slurry tank bottom reflux outlet are communicated with the liquid phase inlet of the forced fluidization reactor through a slurry pump and a pipeline; the bottoms of the slurry tank and the slurry tank are respectively connected with a first fan through a pipeline to be aerated by air; the outlet of the slurry tank is connected with the inlet of the solid-liquid separator through a pipeline, the solid outlet of the solid-liquid separator is communicated with the material inlet of the dehydration reactor through a conveyor belt or a screw conveyor, the liquid phase outlet of the solid-liquid separator is communicated with the slurry tank through a pipeline, and the top of the solid-liquid separator is provided with a washing water inlet; the top of the dehydration reactor is provided with an exhaust port, the exhaust port is communicated with the air inlet of the forced flow state reactor through a second fan and a pipeline, the dehydration reactor is connected with a pipeline for introducing air or water vapor, and the bottom of the dehydration reactor is provided with a solid material outlet; valves are arranged on the pipelines;
the forced flow state reactor comprises a necking section, namely a Venturi section and a filling section, wherein a liquid phase inlet and an air inlet are arranged on the necking section, and a plurality of movable spherical, ellipsoidal or cylindrical filling materials are arranged in the filling section.
2. The flue gas desulfurization ash modification process system according to claim 1, wherein: the dehydration reactors are reactors with heating and constant temperature functions, the number of the dehydration reactors is 1-24, and when the number of the dehydration reactors is more than 2, the dehydration reactors are arranged in a series or parallel mode.
3. The flue gas desulfurization ash modification process system according to claim 1, wherein: the solid-liquid separator adopts one of a vacuum belt filter, a vacuum rotary drum or centrifugal separation equipment.
4. A flue gas desulfurization ash modification process method based on the flue gas desulfurization ash modification process system of claim 1, characterized by comprising the following steps:
(1) Mixing the flue gas desulfurization ash in the ash bin with reuse water at a liquid phase outlet of the solid-liquid separator in a slurry tank to prepare slurry with the solid content of 12-50%, and regulating the pH value of the slurry to 3.5-7.5 by sulfuric acid or hydrochloric acid in an acid tank;
(2) Introducing air into the slurry tank and slurry in the slurry tank by a fan for aeration for 10-100 min, pumping the slurry in the slurry tank into a forced fluidization reactor by a slurry pump, enabling the slurry to fully contact with air flow sent by a fan II, and then carrying out aerationEntering a slurry pond; the gas speed of the necking section of the forced flow state reactor is controlled to be 30-120 m/s, and the liquid-gas ratio is controlled to be 10-300L/m 3 Is within the range of (2);
(3) Reflux-pumping part of the slurry in the slurry tank into a forced fluidization reactor through a slurry pump, removing scum on the surface of the slurry in the slurry tank, transferring the slurry in the slurry tank to a solid-liquid separator for filtration, and washing with water simultaneously;
(4) The filtrate and washing water in the solid-liquid separator are returned to the slurry tank for slurry preparation through a liquid phase outlet and a pipeline of the solid-liquid separator, and the separated solids are transferred into a dehydration reactor;
(5) Introducing air or water vapor into the dehydration reactor, controlling the temperature to be 60-300 ℃ for dehydration treatment, controlling the solid materials to stay in the dehydration reactor for 2-300 min, and exhausting through a second fan;
(6) And cooling the dehydration reactor, and discharging the solid materials in the dehydration reactor through a solid material outlet, so as to obtain the high-purity gypsum powder with stable quality.
5. The modification process method for flue gas desulfurization ash of the modification process system for flue gas desulfurization ash according to claim 4, wherein: the aeration process of the slurry tank and the slurry pool has the total aeration intensity of 1-30L/m 2 S, controlling the diameter of the bubble to be 0.1 μm to 10mm.
6. The modification process method for flue gas desulfurization ash of the modification process system for flue gas desulfurization ash according to claim 4, wherein: the specific control method and conditions during the operation of the dehydration reactor are as follows:
when a gypsum product of two aqueous phases is to be produced: introducing air and controlling the temperature in the reactor to be 60-120 ℃ and the residence time of the solid phase material to be 2-60 min; when a beta-gypsum containing half the water of crystallization, i.e. an architectural gypsum product, is to be produced: introducing air and controlling the temperature in the reactor to be 121-250 ℃ and the residence time of the solid phase material to be 5-120 min; when alpha-gypsum, i.e., a high strength gypsum product, is to be produced: adding a crystal form control agent commonly used in the field into the solid-phase material, introducing saturated water vapor or generating the saturated water vapor by heating the water carried by the material, and controlling the temperature in the reactor to be 124-250 ℃ and the residence time of the solid-phase material to be 20-300 min; when an anhydrous gypsum product is to be produced: introducing air and controlling the temperature at 251-400 ℃ and the solid phase material residence time at 30-150 min.
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