Integrated reagent for treating circulating wastewater from coal-fired power plants and method for recycling wastewater

Abstract

The present invention discloses an integrated agent for treating circulating sewage from a coal-fired power plant and a method for recycling circulating sewage from a coal-fired power plant. The integrated agent comprises lime, a desulfurizing agent, a coagulant, a flocculant and a sensitizer. The method for recycling circulating sewage from a coal-fired power plant comprises the following steps: (1) mixing the circulating sewage from the coal-fired power plant with the integrated agent, stirring for 0.5 to 1 hour and then letting it stand, stratifying to form a supernatant and a precipitate, and treating the precipitate as solid waste; (2) filtering the supernatant through a nanofiltration membrane or a reverse osmosis membrane, and using the obtained water containing monovalent ions as circulating water replenishment, introducing the flue gas generated by the coal-fired power plant into the obtained water containing a high concentration of divalent ions, and adding limestone powder to the water to prepare a limestone slurry, which is used as a desulfurization slurry. The method has good operability and economy, and can be replicated and used in different power plants.

Description

Technical Field

[0001] The present invention relates to sewage treatment, and more specifically, to an integrated agent for treating circulating sewage from a coal-fired power plant and a method for recycling circulating sewage from a coal-fired power plant. Background Art

[0002] There are currently two main approaches to treating circulating wastewater from coal-fired power plants: one is to meet discharge standards, that is, to directly discharge the wastewater after reducing impurities such as phosphate and ammonia nitrogen to below the emission standards through certain chemical treatment methods; the other is effective reuse, that is, to treat the circulating wastewater into high-quality produced water that meets the requirements of reuse within the plant through a variety of treatment processes. The concentrated water generated during the treatment process is deeply treated or mixed with desulfurization wastewater for treatment as terminal concentrated water.

[0003] The former treatment method causes extreme waste of water resources, and with the gradual tightening of environmental protection policies, wastewater discharge restrictions will become increasingly strict, and this method will no longer be applicable. The latter is the development trend of circulating sewage treatment. At present, the reuse channels of circulating sewage from coal-fired power plants vary greatly, and the treatment effects are uneven. There is still room for improvement in process optimization, cost savings, and increasing the reuse rate. Effective treatment processes and reuse methods have not yet been formed.

[0004] For example, patent application number CN202210089426.3 (invention name: A method and system for recycling circulating water wastewater for desulfurization process water) discloses a method and system for recycling circulating water wastewater for desulfurization process water, the system comprising a pretreatment tank, a classification treatment tank and a neutralization tank arranged in sequence along the direction of the sewage treatment process. The application pretreats the circulating water wastewater to obtain pretreated sewage, and divides the pretreated sewage into multiple parts according to the water category of the desulfurization system, and respectively passes them into the corresponding treatment tanks for treatment to obtain classified treatment sewage, so that it can be classified and treated according to different types of desulfurization water in the desulfurization system. When the desulfurization system is in use, the desulfurization system is replenished with the missing water in a timely manner, so that the circulating water wastewater is recycled, which avoids the waste of water resources and reduces the water cost of the desulfurization system.

[0005] Patent application number CN202111464383.4 (invention name: A method for treating circulating water and sewage from a power plant) discloses a method for treating circulating water and sewage from a power plant, which can be summarized as: softening + desalination + concentration + crystallization. The treatment steps of the softening treatment system are: the sewage first enters the interior of the reaction box, and after treatment, it enters the interior of the clarification tank for clarification treatment to obtain softened water. The softened water obtained is transported to the pre-desalting treatment system: the softened water enters the self-cleaning filter, enters the ultrafiltration after filtration, and the filtered water enters the ultrafiltration water tank, and then enters the primary reverse osmosis module for treatment to obtain clean water and concentrated water. The obtained clean water is transported to the make-up water tank, and then the obtained concentrated water is transported to the concentration treatment system for treatment; the obtained clean water is transported to the make-up water tank, and then the obtained concentrated water is crystallized. In this system, the reverse osmosis produced water is recycled to the circulating water replenishment, and the concentrated water is crystallized into salt after treatment, thereby realizing the treatment of circulating water and sewage from the power plant. See the specific process. Figure 1 .

[0006] "Application of Recycling Cooling Wastewater for Circulating Water System in Dalian Power Plant" (Wang Bohui, Fang Zheng, Qu Dalei, Cui Hao, Li Xin, Cao Shijian, Contemporary Chemical Research, 2022(18): 80-82) proposed a reuse scheme for circulating cooling wastewater, specifically: the circulating cooling wastewater is treated with lime after ultrafiltration, reverse osmosis, and desalination, and the product water is mixed with the circulating cooling wastewater to be used as circulating water replenishment. The concentrated water is used as process water for the desulfurization system, and the sludge from the clarifier is transported to the pulping unit of the desulfurization system for use as gypsum. See the specific process for details. Figure 2 .

[0007] "Deep Treatment and Reuse of Circulating Cooling Wastewater from Yantai Power Plant" (Song Rongjie, Wang Yueguang, Industrial Water Treatment, 2006(08):70-72) proposed a deep treatment system for circulating cooling wastewater, which consists of pretreatment, pre-desalting, primary desalting, deep desalting and other parts. It uses the circulating wastewater from coal-fired power plants as a water source to produce desalted water, which is then supplied to the first station of the Yantai heating network and the boiler water of the power plant together with the desalted water from the original water treatment workshop. For the specific process, see Figure 3 .

[0008] The existing technology for treating circulating wastewater from coal-fired power plants has the following disadvantages:

[0009] 1. Complex process: The existing circulating wastewater treatment technology of coal-fired power plants, regardless of whether the treatment target is reuse or zero emission, is equipped with many equipment and reactors, with complex treatment processes, complicated processes, and heavy operation and maintenance workload.

[0010] 2. There are many types of chemical treatment agents: In the pretreatment stage, in order to remove the impurity ions, the existing technology adopts the treatment method of adding chemical agents, but there are generally problems such as a wide variety of added agents and inaccurate control of the added amount.

[0011] 3. High cost: The investment cost and operating cost of the existing process are both high. The high investment cost is mainly due to the large number of treatment modules, which increases the equipment investment cost; the high operating cost is mainly due to the high energy consumption of the membrane system during operation, and the large amount of dosing also requires the operation and maintenance of multiple dosing systems. Summary of the invention

[0012] In view of the defects of the existing methods for treating circulating wastewater from coal-fired power plants, the present invention proposes an integrated agent for treating circulating wastewater from coal-fired power plants and a method for recycling circulating wastewater from coal-fired power plants. The method has good operability and economy and can be replicated and used in different power plants. To achieve the purpose of the present invention, the present invention adopts the following scheme:

[0013] An integrated agent for treating circulating sewage from a coal-fired power plant, wherein the integrated agent comprises the following components in 100 parts by weight:

[0014]

[0015] The sensitizer is a mixture containing modified activated carbon and modified sepiolite, wherein the mass ratio of the modified activated carbon to the modified sepiolite is 1:0.4-0.7.

[0016] The modified activated carbon is activated carbon that has been oxidized by an oxidant and ultrasonically treated.

[0017] The modified sepiolite is sepiolite that has been sequentially treated with acid immersion, metal ion solution immersion and calcination.

[0018] In some specific embodiments of the present invention, the content of lime is 30-40 parts.

[0019] In some specific embodiments of the present invention, the content of the desulfurizing agent is 5 to 7 parts.

[0020] In some specific embodiments of the present invention, the content of the coagulant is 5 to 10 parts.

[0021] In some specific embodiments of the present invention, the content of the flocculant is 2 to 3 parts.

[0022] In some specific embodiments of the present invention, the content of the sensitizer is 40 to 55 parts.

[0023] The preparation method of the modified activated carbon comprises the following steps:

[0024] (1) Ultrasonic oxidation: Grind the activated carbon, pass it through a 100-200 mesh sieve, then add it to a potassium dichromate solution and soak it for 3-5 hours, and finally ultrasonically treat it for 10-30 minutes;

[0025] (2) Drying: The suspension obtained in step (1) is filtered and the obtained oxidized activated carbon is dried at 80-120°C.

[0026] The preparation method of the modified sepiolite comprises the following steps:

[0027] (1) Acid leaching: Soak the sepiolite in nitric acid for 18 to 30 hours;

[0028] (2) Grinding: Clean the acid-leached sepiolite and grind it to 100-200 mesh;

[0029] (3) taking the sieved sepiolite, adding it to a metal ion solution and soaking it for 5 to 10 hours, and stirring it at 60 to 100° C. for 4 to 8 hours, wherein the metal ion solution contains zinc chloride and nickel chloride;

[0030] (4) Filter the suspension obtained in step (3), wash the obtained precipitate, and calcine it at 400-600° C. for 1-2 h.

[0031] In some specific embodiments of the present invention, the desulfurizing agent is selected from aluminum salts. In some specific embodiments of the present invention, the aluminum salt is selected from sodium aluminate, aluminum chloride, or a combination thereof. In some specific embodiments of the present invention, the aluminum salt is selected from sodium aluminate.

[0032] In some specific embodiments of the present invention, the coagulant is selected from polyaluminum coagulants. In some specific embodiments of the present invention, the polyaluminum coagulant is selected from polyaluminum chloride, polyaluminum ferric chloride, or a combination thereof. In some specific embodiments of the present invention, the polyaluminum coagulant is selected from polyaluminum chloride.

[0033] In some specific embodiments of the present invention, the flocculant is selected from polyacrylamide polymer flocculants.

[0034] In some specific embodiments of the present invention, the polyacrylamide polymer flocculant is selected from cationic polyacrylamide, anionic polyacrylamide, nonionic polyacrylamide, amphoteric polyacrylamide, or a combination thereof. In some specific embodiments of the present invention, the polyacrylamide polymer flocculant is selected from cationic polyacrylamide.

[0035] Another aspect of the present invention provides a method for recycling circulating wastewater from a coal-fired power plant, the method comprising the following steps:

[0036] (1) Mix the circulating sewage from the coal-fired power plant with the above-mentioned integrated reagent, stir for 0.5 to 1 hour, let it stand, separate into layers, and form a supernatant and a precipitate, and treat the precipitate as solid waste;

[0037] (2) The supernatant is filtered through a nanofiltration membrane or a reverse osmosis membrane, and the water containing monovalent ions obtained by filtration is used as circulating water for coal-fired power plants. Flue gas generated by the coal-fired power plants is introduced into the water containing high concentrations of divalent ions obtained by filtration, so that the calcium ions therein react with CO2 in the flue gas to generate calcium carbonate. At the same time, limestone powder is added to the water with high ion concentration to prepare limestone slurry, which is used as desulfurization slurry.

[0038] In some specific embodiments of the present invention, the flue gas removes dust, NOx and SO2, and the main component is CO2.

[0039] In some specific embodiments of the present invention, the mass volume ratio of the integrated agent to the circulating sewage from the coal-fired power plant is 0.5 to 2 g / L.

[0040] In some specific embodiments of the present invention, step (1) and step (2) of the recycling method are both performed at room temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 The present invention is a process flow chart of a method for treating circulating water and sewage in a power plant in the prior art.

[0042] Figure 2 The invention is a circulating cooling wastewater reuse system in the prior art.

[0043] Figure 3 The invention is a circulating cooling wastewater deep treatment system in the prior art.

[0044] Figure 4 This is the method for reusing circulating sewage from a coal-fired power plant of the present invention. The dashed box contains a special device for the method of the present invention, and the equipment or devices outside the dashed box are the equipment or devices of the coal-fired power plant itself. DETAILED DESCRIPTION

[0045] After long-term and extensive research, the inventor of this application has discovered an integrated agent for treating circulating sewage from coal-fired power plants, which can effectively remove impurities such as sulfate, phosphorus, and heavy metals in circulating sewage from coal-fired power plants, and effectively reduce the COD value. The supernatant treated with the integrated agent is filtered through a nanofiltration membrane or a reverse osmosis membrane, and the obtained water containing a high concentration of divalent ions is used to absorb flue gas whose main component is CO2, and limestone powder is added thereto to prepare a desulfurization slurry, and the filtered water containing monovalent ions is used as circulating water for coal-fired power plants. The present invention was completed on this basis.

[0046] The integrated agent for treating circulating sewage from a coal-fired power plant of the present invention comprises the following components in 100 parts by weight: 20 to 50 parts of lime, 4 to 10 parts of desulfurizer, 4 to 15 parts of coagulant, 1 to 5 parts of flocculant, and 30 to 66 parts of sensitizer, wherein the sensitizer is a mixture of modified activated carbon and modified sepiolite, wherein the mass ratio of the modified activated carbon to the modified sepiolite is 1:0.4 to 0.7, the modified activated carbon is activated carbon oxidized by an oxidant and ultrasonically treated, and the modified sepiolite is sepiolite sequentially treated by acid immersion, metal ion solution immersion, and calcination.

[0047] In the integrated agent for treating circulating sewage from coal-fired power plants of the present invention, the role of lime is to increase the pH value, so that metal ions such as magnesium in the wastewater form hydroxide precipitation, promote phosphate to form composite salt precipitation, and supplement calcium ions required for subsequent treatment.

[0048] In the integrated agent for treating circulating wastewater from a coal-fired power plant of the present invention, the desulfurizer is used to remove sulfate radicals in the wastewater. The desulfurizer that can be used in the present invention includes but is not limited to aluminum salts. The aluminum salts include but are not limited to sodium aluminate and aluminum chloride.

[0049] In the integrated agent for treating circulating wastewater from a coal-fired power plant of the present invention, the function of the coagulant is to remove suspended matter in the wastewater and further remove impurity ions. The coagulant that can be used in the present invention includes but is not limited to polyaluminum coagulants. The polyaluminum coagulants include but are not limited to polyaluminum chloride and polyaluminum ferric chloride.

[0050] In the integrated agent for treating circulating sewage from coal-fired power plants of the present invention, the flocculant functions to enhance the treatment effect of the coagulant, increase the particle size of the alum flocs, and increase the sedimentation rate. The flocculants that can be used in the present invention include but are not limited to polyacrylamide polymer flocculants. The polyacrylamide polymer flocculants include but are not limited to cationic polyacrylamide, anionic polyacrylamide, nonionic polyacrylamide, and amphoteric polyacrylamide.

[0051] In the integrated agent for treating circulating sewage from coal-fired power plants of the present invention, the sensitizer functions to reduce the COD value of the wastewater and adsorb impurity ions such as heavy metals. The sensitizer that can be used in the present invention includes but is not limited to a mixture of modified activated carbon and the modified sepiolite.

[0052] Preparation of modified activated carbon:

[0053] The preparation method of modified activated carbon of the present invention comprises the following steps: (1) ultrasonic oxidation: grinding the activated carbon, passing through a 100-200 mesh sieve, then adding it into a potassium dichromate solution and soaking it for 3-5 hours, and finally ultrasonic treatment for 10-30 minutes; (2) drying: filtering the suspension obtained in step (1), and drying the obtained oxidized activated carbon at 80-120° C. The mass concentration of the potassium dichromate solution used is 5%-15%, and the ultrasonic power is 200-600W. In a specific embodiment of the present invention, the sieve used is 150 mesh.

[0054] Preparation of modified sepiolite

[0055] The preparation method of the modified sepiolite of the present invention comprises the following steps: (1) acid leaching: soaking the sepiolite in nitric acid for 18 to 30 hours; (2) grinding: cleaning the sepiolite after acid leaching and then grinding it to pass through a 100 to 200 mesh sieve; (3) taking the sieved sepiolite, adding it into a metal ion solution and soaking it for 5 to 10 hours, and stirring it at 60 to 100° C. for 4 to 8 hours, wherein the metal ion solution contains zinc chloride and nickel chloride; and (4) filtering the suspension obtained in step (3), washing the obtained precipitate, and calcining it at 400 to 600° C. for 1 to 2 hours.

[0056] The concentration of nitric acid used is 2% to 8%. Acid leaching can be carried out at room temperature. The purpose of acid leaching is to remove impurities in sepiolite while providing an acidic environment. The concentrations of zinc chloride and nickel chloride used are 5% to 20% and 2% to 10% respectively. The purpose of immersing with a mixed solution of metal ions is to create metal points on the sepiolite and enhance the effect of the activated carbon after ultrasonic treatment. The solvent used to wash the obtained precipitate can be water.

[0057] The method for recycling circulating sewage from a coal-fired power plant of the present invention comprises the following steps: (1) mixing the circulating sewage from the coal-fired power plant with the above-mentioned integrated agent, stirring for 0.5 to 1 hour and then letting it stand, stratifying to form a supernatant and a precipitate, and treating the precipitate as solid waste; (2) filtering the supernatant through a nanofiltration membrane or a reverse osmosis membrane, using the water containing monovalent ions obtained by filtration as circulating water for the coal-fired power plant, introducing the flue gas generated by the coal-fired power plant into the water containing a high concentration of divalent ions obtained by filtration, so that the calcium ions therein react with CO2 in the flue gas to generate calcium carbonate, and adding limestone powder to the water with a high ion concentration to prepare a limestone slurry, which is used as a desulfurization slurry. In a specific embodiment of the present invention, the flue gas removes dust, NOx and SO2, and the main component is CO2.

[0058] In a specific embodiment of the present invention, step (1) is carried out in an integrated reaction tank. Specifically, the circulating sewage of the coal-fired power plant is introduced into the integrated reaction tank, and an integrated agent is added to the integrated reaction tank. After chemical reaction, impurities such as sulfate, phosphorus, and heavy metals in the circulating sewage of the coal-fired power plant are removed, and its COD value is effectively reduced. Compared with the traditional softening precipitation, this step makes full use of the original components of the circulating sewage of the coal-fired power plant, deliberately retains the calcium ions therein, and adds a certain amount of calcium therein through the integrated agent. In the integrated reaction tank, impurity ions such as sulfate, magnesium, and phosphate are removed by forming precipitation with the integrated agent, and the calcium content therein increases. The precipitate generated by the reaction is deposited at the bottom of the pool due to its high density, and is discharged regularly after being treated by a scraper. The collected sludge mainly contains magnesium hydroxide, calcium sulfonate, activated carbon, etc., which can be treated together with the solid waste in the plant area.

[0059] In a specific embodiment of the present invention, step (2) is carried out in a nanofiltration device or a reverse osmosis device, and the reaction with the flue gas is carried out in a carbon pool. Specifically, the effluent of the integrated reaction pool enters the nanofiltration device or the reverse osmosis device, and the filtration recovery rate is set to 45% to 50%, and the monovalent and divalent ions are effectively separated by filtration. The monovalent ions are mainly Na + , Cl - , K + Plasma, water containing monovalent ions (i.e. Figure 4 The produced water can be used as circulating water replenishment in coal-fired power plants and reused in the circulating water system. The main divalent ions are Ca 2+ Scaling ions such as divalent ions, water containing high concentrations of divalent ions (i.e. Figure 4 The concentrated water in the flue gas is led to the carbon pool, and the flue gas with dust, NOx and SO2 removed is introduced to make the two fully contact, and the heat of the flue gas is transferred to the water containing high concentration of divalent ions, so that the temperature of the water is appropriately increased, further improving the reaction rate, and at the same time, the calcium ions in the water fully react with the CO2 in the flue gas to generate CaCO3. The turbid liquid containing CaCO3 is further prepared into limestone slurry as slurry for the desulfurization tower.

[0060] The method for recycling circulating sewage from a coal-fired power plant of the present invention fully utilizes calcium ions in water containing high-concentration divalent ions, reduces the amount of limestone powder used, and reduces the carbon emission of flue gas.

[0061] In the recycling method of circulating wastewater from a coal-fired power plant of the present invention, the main pollution indicators of the circulating wastewater are removed in the integrated reaction tank, and mainly rely on the chemical reaction of the integrated reagent with the impurity ions. The treatment effect of the integrated reaction tank is the fundamental and basis for guaranteeing the subsequent process.

[0062] The present invention has the following beneficial effects:

[0063] (1) Integrated reagents are used to replace many reagents in the existing process. While ensuring the water quality of the effluent, the dosing system is streamlined and the dosing method is optimized, so that the dosage can be accurately adjusted and the workload of operating and maintaining the circulating sewage treatment system of the coal-fired power plant can be reduced.

[0064] (2) Based on the water quality characteristics of circulating wastewater from coal-fired power plants, the traditional approach of removing all impurity ions was abandoned. Instead, some of the impurity ions (for example, calcium ions) were processed into desulfurization agents necessary for the desulfurization system, achieving deep utilization of wastewater, fully developing the value of wastewater, further simplifying the process, increasing the in-plant reuse rate of wastewater, and reducing water extraction costs.

[0065] (3) This technical solution has low cost, and the main cost is the cost of purchasing medicines.

[0066] In the description of the present invention, normal temperature refers to 0-40°C, such as 10-30°C, 15-25°C, etc.

[0067] In the description of the present invention, an integrated reaction pool refers to multiple chemical reactions being carried out in coordination in the same pool.

[0068] In the description of the present invention, the integrated agent refers to a composite agent that integrates multiple treatment effects and has a synergistic removal effect of impurity ions.

[0069] The present invention will be further described below in conjunction with specific examples. Specific examples are implemented under the premise of technical solutions of the present invention, and detailed implementation methods and operating procedures are provided. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. The experimental methods for which specific conditions are not specified in the following examples are usually carried out under normal conditions. Unless otherwise indicated, ratios and percentages are by weight.

[0070] In the following examples, the desulfurizer used is sodium aluminate (Chinese medicine, analytical grade), the coagulant is polyaluminium chloride (Aladdin, chemically pure), and the flocculant is cationic polyacrylamide (Aladdin, chemically pure).

[0071] In the following examples, the manufacturer of the nanofiltration device used is GE's DK4040F30 spiral membrane; the manufacturer of the reverse osmosis device used is Dow's SW30-4040 spiral membrane.

[0072] In the following examples, the sensitizer is a mixture of modified activated carbon and modified sepiolite mixed in a mass ratio of 6:4.

[0073] The preparation method of the modified activated carbon comprises the following steps:

[0074] (1) Ultrasonic oxidation: Grind the activated carbon, pass it through a 150-mesh sieve, and then soak it in potassium dichromate solution for 4 h, and finally ultrasonically treat it for 20 min;

[0075] (2) Drying: The activated carbon obtained in step (1) is filtered and placed in an oven at 103° C. for 1 h to obtain modified activated carbon.

[0076] The preparation method of the modified sepiolite comprises the following steps:

[0077] (1) Acid leaching: Soak the sepiolite in 1 mol / L nitric acid for 24 h;

[0078] (2) Grinding: The acid-leached sepiolite is cleaned and ground, and passed through a 150-mesh sieve;

[0079] (3) taking the sieved sepiolite, adding it to a metal ion solution and soaking it for 8 hours. The metal ion solution is zinc chloride (mass concentration is 10%) and nickel chloride (mass concentration is 5%), and stirring it at 80° C. for 6 hours;

[0080] (4) Filter the suspension obtained in step (3), wash the obtained precipitate with water, and calcine at 500° C. for 2 h to obtain modified sepiolite.

[0081] Example 1

[0082] 1.1 The integrated pharmaceutical composition used in this embodiment is composed of the following components in parts by weight:

[0083]

[0084] 1.2 Preparation method of integrated medicine:

[0085] The various components are fully mixed according to corresponding proportions to obtain the integrated medicine.

[0086] 1.3 The method for recycling circulating wastewater from coal-fired power plants includes the following steps:

[0087] (1) Coal-fired power plant circulating sewage with a conductivity of 1843 μS / cm, a pH of 8.57, a turbidity of 9.49 NTU, a calcium content of 324 mg / L, a magnesium content of 110 mg / L, a phosphate content of 4.32 mg / L, and a sulfate content of 582 mg / L was introduced into an integrated reaction pool, and then the integrated agent prepared in this embodiment was added to the pool (wherein the amount of the integrated agent was: 80 g of the integrated agent was added to 100 L of coal-fired power plant circulating sewage), and the mixture was fully stirred for 30 min at room temperature to obtain a supernatant. The effluent quality is shown in Table 1;

[0088] Table 1 Treatment effect of integrated reagents on circulating wastewater from coal-fired power plants

[0089] Magnesium content Sulfate content Calcium content Phosphate content 5.2mg / L 87mg / L 1205mg / L 0.19mg / L

[0090] In the integrated reaction pool, impurity ions such as sulfate, magnesium, and phosphate all precipitate with the integrated reagents. The calcium in the supernatant increases from 324 mg / L to 1205 mg / L. The precipitate generated by the reaction is deposited at the bottom of the pool due to its high density. It is discharged regularly after being treated by a scraper. The collected sludge mainly contains magnesium hydroxide, calcium sulfoxide, activated carbon, etc., which can be treated together with the solid waste in the plant area.

[0091] (2) The upper clear liquid of the integrated reaction pool is pressurized by a pump and then enters the nanofiltration device. The operating pressure of the nanofiltration membrane is about 0.5 MPa. The water containing monovalent ions obtained by nanofiltration is used in the circulating water system of the coal-fired power plant. The water containing high concentration of divalent cations obtained by nanofiltration is introduced into the carbon pool. Flue gas whose main component is CO2 is introduced into the carbon pool (the flue gas is clean flue gas after desulfurization, and the dust, NOx and SO2 in the flue gas are effectively removed in various environmental protection systems required by the power plant). At the same time, limestone powder is added to the carbon pool under continuous stirring to prepare limestone slurry. After the density of the limestone slurry reaches the requirement, it is pumped to the desulfurization tower, thereby achieving full reuse of the water containing high concentration of divalent cations.

[0092] In this embodiment, the desalination rate of nanofiltration can reach 48%, the conductivity of the produced water is 603μS / cm, which is equal to the conductivity of the circulating water intake, and the sulfate removal rate is 98%, and the hardness removal rate is about 70%, which meets the water quality requirements for recycling the circulating water system. The water containing high concentrations of divalent cations obtained by nanofiltration collects sulfate, chlorine, calcium and other ions and is weakly alkaline. Therefore, the introduction of carbon dioxide is conducive to the fixation and absorption of carbon, and promotes the combination of calcium ions in the solution to form calcium carbonate. The carbon pool is a can-shaped container equipped with a stirrer, with a cover on the top but not sealed. The clean flue gas enters from the bottom of the carbon pool through the induced draft fan, and flows out from the top layer after sufficient contact. At the same time, limestone powder is added to the tank body under continuous stirring to prepare limestone slurry. Therefore, the carbon pool also plays the role of desulfurization slurry preparation, integrating decarbonization and slurry preparation.

[0093] Example 2

[0094] 2.1 The integrated pharmaceutical composition used in this embodiment is composed of the following components in parts by weight:

[0095]

[0096] 2.2 Preparation method of integrated medicine:

[0097] The various components are fully mixed according to corresponding proportions to obtain the integrated medicine.

[0098] 2.3 The method for recycling circulating wastewater from coal-fired power plants includes the following steps:

[0099] (1) Coal-fired power plant circulating sewage with a conductivity of 1601 μS / cm, a calcium content of 348 mg / L, a magnesium content of 73.6 mg / L, a phosphate content of 3.36 mg / L, and a sulfate content of 603 mg / L was introduced into an integrated reaction pool, and then the integrated agent prepared in this embodiment was added to the pool (wherein, the amount of the integrated agent was: 100 g of the integrated agent was added to 100 L of coal-fired power plant circulating sewage), and the mixture was fully stirred for 30 min at room temperature to obtain a supernatant. The effluent water quality is shown in Table 1;

[0100] Table 2 Treatment effect of integrated reagents on circulating sewage

[0101] Magnesium content Sulfate content Calcium content Phosphate content 0.9mg / L 108mg / L 1412mg / L 0.22mg / L

[0102] In the integrated reaction tank, impurity ions such as sulfate, magnesium, and phosphate all form precipitation with the integrated reagents. The calcium in the supernatant increases from 348 mg / L to 1412 mg / L. The precipitation generated by the reaction is deposited at the bottom of the tank due to its high density. It is discharged regularly after being treated by a scraper. The collected sludge mainly contains magnesium hydroxide, calcium sulfoxide, activated carbon, etc., which can be treated together with the solid waste in the plant area.

[0103] (2) The upper clear liquid of the integrated reaction pool is pressurized by a pump and then enters the nanofiltration device. The operating pressure of the nanofiltration membrane is about 0.6 MPa. The water containing monovalent ions obtained by nanofiltration is used in the circulating water system. The water containing high concentration of divalent cations obtained by nanofiltration is introduced into the carbon pool. Flue gas mainly containing CO2 is introduced into the carbon pool (the flue gas is clean flue gas after desulfurization, and the dust, NOx and SO2 in the flue gas are effectively removed in various environmental protection systems required by the power plant). At the same time, limestone powder is added to the carbon pool under continuous stirring to prepare limestone slurry. After the density of the limestone slurry reaches the requirement, it is transported to the desulfurization tower by a pump, so as to achieve full reuse of the water containing high concentration of divalent cations.

[0104] In this embodiment, the nanofiltration desalination rate is 53%, the produced water conductivity is 699μS / cm, which is equal to the circulating water intake conductivity, and the sulfate removal rate is 98%, and the hardness removal rate is about 65%, which meets the water quality requirements for reuse in the circulating water system.

[0105] Example 3

[0106] 3.1 The integrated pharmaceutical composition used in this embodiment is composed of the following components in parts by weight:

[0107]

[0108]

[0109] 3.2 Preparation method of integrated medicine:

[0110] The various components are fully mixed according to corresponding proportions to obtain the integrated medicine.

[0111] 3.3 The method for recycling circulating wastewater from coal-fired power plants includes the following steps:

[0112] (1) Coal-fired power plant circulating sewage with a conductivity of 2540 μS / cm, a calcium content of 280 mg / L, a magnesium content of 156 mg / L, a phosphate content of 5.43 mg / L, and a sulfate content of 324 mg / L was introduced into an integrated reaction pool, and then the integrated agent prepared in this embodiment was added to the pool (wherein, the amount of the integrated agent was: 120 g of the integrated agent was added to 100 L of coal-fired power plant circulating sewage), and the mixture was fully stirred for 30 min at room temperature to obtain a supernatant. The effluent quality is shown in Table 3;

[0113] Table 3 Treatment effect of integrated reagents on circulating sewage

[0114] Magnesium content Sulfate content Calcium content Phosphate content 2.1mg / L 109mg / L 1211mg / L 0.21mg / L

[0115] In the integrated reaction pool, impurity ions such as sulfate, magnesium, and phosphate all precipitate with the integrated reagents. The calcium in the supernatant increases from 280 mg / L to 1211 mg / L. The precipitate generated by the reaction is deposited at the bottom of the pool due to its high density. It is treated by a scraper and discharged regularly. The collected sludge mainly contains magnesium hydroxide, calcium sulfoxide, activated carbon, etc., which can be treated together with the solid waste in the plant area.

[0116] (2) The upper clear liquid of the integrated reaction pool is pressurized by a pump and then enters the nanofiltration device. The operating pressure of the nanofiltration membrane is about 0.5 MPa. The water containing monovalent ions obtained by nanofiltration is used in the circulating water system. The water containing high concentration of divalent cations obtained by nanofiltration is introduced into the carbon pool. Flue gas mainly containing CO2 is introduced into the carbon pool (the flue gas is clean flue gas after desulfurization, and the dust, NOx and SO2 in the flue gas are effectively removed in various environmental protection systems required by the power plant). At the same time, limestone powder is added to the carbon pool under continuous stirring to prepare limestone slurry. After the density of the limestone slurry reaches the requirement, it is pumped to the desulfurization tower, so as to achieve full reuse of the water containing high concentration of divalent cations.

[0117] In this embodiment, the nanofiltration desalination rate can reach 47%, the produced water conductivity is 672μS / cm, which is equal to the circulating water intake conductivity, and the sulfate removal rate is 95%, and the hardness removal rate is about 70%, which meets the water quality requirements for reuse in the circulating water system.

[0118] Example 4

[0119] The nanofiltration device in Example 1 was replaced with a reverse osmosis device. The integrated reagents used and other operating conditions and steps were the same as those in Example 1, and finally the effective reuse of circulating wastewater from a coal-fired power plant was achieved.

[0120] Compared with reverse osmosis devices, nanofiltration devices have lower inlet pressure of nanofiltration membranes, so the additional energy required is also smaller. The water quality of reverse osmosis devices is better than that of nanofiltration devices, but from the perspective of reuse, the water produced by nanofiltration devices has fully met the subsequent requirements, and considering that the reverse osmosis membrane of reverse osmosis devices has a relatively high scaling risk, nanofiltration is given priority.

[0121] All documents mentioned in the present invention are cited as references in this application, just as each document is cited as reference individually. In addition, it should be understood that after reading the above teachings of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

Claims

1. An integrated agent for treating circulating sewage from coal-fired power plants, characterized in that: Based on 100 parts by weight, the integrated medicament includes the following components: 20~50 parts of lime, 4~10 parts of desulfurizer, 4~15 parts of coagulant, 1~5 parts of flocculant, 30~66 parts of sensitizer, The sensitizer is a mixture containing modified activated carbon and modified sepiolite, wherein the mass ratio of the modified activated carbon to the modified sepiolite is 1:0.4-0.

7. The modified activated carbon is activated carbon that has been oxidized by an oxidant and ultrasonically treated, and the preparation method thereof comprises the following steps: (1) Ultrasonic oxidation: Grind the activated carbon, pass it through a 100-200 mesh sieve, then add it to a potassium dichromate solution and soak it for 3-5 hours, and finally ultrasonically treat it for 10-30 minutes; (2) Drying: The suspension obtained in step (1) is filtered and the obtained oxidized activated carbon is dried at 80-120°C; The modified sepiolite is sepiolite that has been treated with acid immersion, metal ion solution immersion and calcination in sequence, and the preparation method thereof comprises the following steps: (1) Acid leaching: Soak the sepiolite in nitric acid for 18 to 30 hours; (2) Grinding: After cleaning the acid-leached sepiolite, grind it and pass it through a 100-200 mesh sieve; (3) Soaking in a metal ion solution: taking the sieved sepiolite, adding it to a metal ion solution and soaking it for 5 to 10 hours, stirring it at 60 to 100° C. for 4 to 8 hours, wherein the metal ion solution contains zinc chloride and nickel chloride; (4) Calcination: Filter the suspension obtained in step (3), wash the obtained precipitate, and calcine at 400-600° C. for 1-2 h.

2. The integrated reagent for treating circulating wastewater from a coal-fired power plant according to claim 1, characterized in that: The content of lime is 30-40 parts, and / or The content of the desulfurizer is 5 to 7 parts, and / or The content of the coagulant is 5 to 10 parts, and / or The content of the flocculant is 2 to 3 parts, and / or The content of the sensitizer is 40 to 55 parts.

3. The integrated reagent for treating circulating sewage from a coal-fired power plant according to claim 1, characterized in that: The desulfurizing agent is selected from aluminum salts, The aluminum salt is selected from sodium metaaluminate, aluminum chloride, or a combination thereof.

4. The integrated reagent for treating circulating sewage from a coal-fired power plant according to claim 3, characterized in that: The aluminum salt is sodium metaaluminate.

5. The integrated reagent for treating circulating wastewater from a coal-fired power plant according to claim 1, characterized in that: The coagulant is selected from polyaluminium coagulants, The polyaluminium coagulant is selected from polyaluminium chloride, polyaluminium ferric chloride, or a combination thereof.

6. The integrated reagent for treating circulating sewage from a coal-fired power plant according to claim 5, characterized in that: The polyaluminium coagulant is polyaluminium chloride.

7. The integrated reagent for treating circulating wastewater from a coal-fired power plant according to claim 1, characterized in that: The flocculant is selected from polyacrylamide polymer flocculants. The polyacrylamide polymer flocculant is selected from cationic polyacrylamide, anionic polyacrylamide, nonionic polyacrylamide, amphoteric polyacrylamide, or a combination thereof.

8. The integrated reagent for treating circulating wastewater from a coal-fired power plant according to claim 7, characterized in that: The polyacrylamide polymer flocculant is cationic polyacrylamide.

9. A method for recycling circulating wastewater from a coal-fired power plant, characterized in that: The recycling method comprises the following steps: (1) Mixing the circulating sewage from a coal-fired power plant with the integrated reagent according to any one of claims 1 to 8, stirring for 0.5 to 1 hour and then letting it stand to separate into layers to form a supernatant and a precipitate, and treating the precipitate as solid waste; (2) The supernatant is filtered through a nanofiltration membrane or a reverse osmosis membrane, and the water containing monovalent ions obtained by filtration is used as circulating water for coal-fired power plants. Flue gas generated by the coal-fired power plants is introduced into the water containing a high concentration of divalent ions obtained by filtration, so that the calcium ions therein react with CO2 in the flue gas to form calcium carbonate. At the same time, limestone powder is added to the water containing a high concentration of divalent ions to prepare a limestone slurry, which is used as a desulfurization slurry.

10. The method for recycling circulating wastewater from a coal-fired power plant according to claim 9, characterized in that: The flue gas removes dust, NOx and SO2, and the main component is CO2, and / or The mass volume ratio of the integrated agent to the circulating sewage from the coal-fired power plant is 0.5-2 g / L.

11. The method for recycling circulating wastewater from a coal-fired power plant according to claim 9, characterized in that: The steps (1) and (2) of the recycling method are both performed at room temperature.

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