Chemical water production acidic and alkaline water recycling system and recycling method

Abstract

The present invention relates to the technical field of wastewater treatment, and the disclosed chemical water production acidic and alkaline water recycling system comprises: a water treatment workshop acid and alkaline wastewater drainage channel, which is provided with an inlet filter valve of the drainage channel acid and alkaline wastewater suction pump; a group of waste acid tanks, one of which is pumped to an external discharge pool, and the other is pumped to a triple-box reaction pool; a group of waste alkali tanks, one of which is pumped to a triple-box neutralization pool, and the other is pumped to a stripping pool. The present invention replaces the raw hydrochloric acid of the Fenton reaction in the original desulfurization and denitrification wastewater treatment COD degradation process with chemical water production acidic water, thereby reducing the purchase cost of hydrochloric acid and the corresponding hydrochloric acid neutralization alkali consumption of chemical water wastewater.

Description

Technical Field

[0001] The present invention belongs to the technical field of wastewater treatment, and particularly relates to a chemical water production acid-base medium water recycling system and a recycling method. Background Art

[0002] More than 90% of coal-fired power plants in China adopt limestone-gypsum wet flue gas desulfurization. In the wet flue gas desulfurization process, in order to maintain the material balance of the slurry circulation system, prevent the chloride ion concentration from exceeding the standard, and ensure the quality of gypsum, a certain amount of waste liquid, namely the tail-end desulfurization wastewater, must be discharged regularly from the desulfurization tower.

[0003] According to the differences in fuels, desulfurization devices, coal types, etc. used in coal-fired power plants, the water quality of the discharged desulfurization wastewater also varies greatly. By comprehensively comparing the desulfurization wastewater of each power plant, it mainly has the following characteristics:

[0004] 1. The wastewater is acidic: the pH is generally 4-6;

[0005] 2. The SS content is high: mainly gypsum particles, silicon dioxide, and hydroxides of iron and aluminum, etc.;

[0006] 3. Cations: mainly hardness ions such as calcium and magnesium, the contents of iron and aluminum are also relatively high, and there are also a small amount of heavy metal ions (such as Hg, As, Cr, Ni, Pb), etc.;

[0007] 4. Anions: The wastewater contains a large amount of anions such as F-, Cl, and SO4 2- and so on;

[0008] 5. NH formed by the absorption of escaped ammonia gas in the flue gas ammonia denitration by the desulfurization slurry 3 .H 2 O.

[0009] Traditional desulfurization wastewater treatment mainly adopts the chemical precipitation method. Through processes such as oxidation, neutralization, flocculation, and precipitation (i.e., the traditional "triple box"), heavy metals and suspended solids in the desulfurization wastewater are removed. For power plants using ammonia denitration, the escaped ammonia gas will be absorbed and dissolved in the desulfurization slurry, resulting in the ammonia nitrogen in the desulfurization wastewater exceeding the standard, and an additional ammonia nitrogen removal process for desulfurization wastewater is required. Since the chloride ion concentration still cannot be reduced after treatment, the waste liquid has strong corrosiveness and cannot be reused in other systems.

[0010] With the continuous improvement of environmental protection requirements, power plants are required to achieve zero discharge of desulfurization wastewater. However, the investment and operating costs of zero-discharge projects are not low. Taking a 2×600MW unit coal-fired boiler as an example, the desulfurization wastewater generation rate is about 20-30 m³ / h. According to the traditional zero-discharge treatment mode, the project investment is about 40-50 million yuan, and the operating cost is often as high as 100 yuan / m³.

[0011] Therefore, how to find an efficient and low-consumption desulfurized wastewater treatment technology is an issue that has drawn close attention in the current renovation of desulfurized wastewater treatment in coal-fired power plants. Summary of the Invention

[0012] To solve the above technical problems, the objective of the present invention is to provide a chemical water production acid-base intermediate water recycling system and a recycling method to solve the technical defect of the existing technology on how to achieve an efficient and low-consumption desulfurized wastewater treatment technology, which is an issue that has drawn close attention in the current renovation of desulfurized wastewater treatment in coal-fired power plants.

[0013] To achieve the above objective, the present invention provides the following technical solution: A chemical water production acid-base intermediate water recycling system, including:

[0014] The acid and alkaline wastewater drainage channels in the chemical water treatment workshop are internally provided with inlet filter valves for the acid and alkaline wastewater suction pumps in the drainage channels.

[0015] A group of waste acid tanks, where one waste acid tank is pumped to the external drainage pool and the other waste acid tank is pumped to the triple-box reaction tank.

[0016] A group of waste alkali tanks, where one waste alkali tank is pumped to the triple-box neutralization tank and the other waste alkali tank is pumped to the stripping tank.

[0017] As a further solution of the present invention, an inlet valve for the suction pump is provided above the acid and alkaline wastewater drainage channels in the chemical water treatment workshop. One side of the inlet valve for the suction pump is provided with a suction pump, and one side of the suction pump is provided with a check valve and an isolation valve at the outlet of the suction pump.

[0018] The inlet filter valves for the acid and alkaline wastewater suction pumps in the drainage channels are sequentially connected through pipelines to the inlet valve for the suction pump, the suction pump, the check valve and the isolation valve at the outlet of the suction pump, a pressure gauge, and an acid and alkali wastewater flowmeter.

[0019] As a further preferred solution of the present invention, a waste acidic water inlet acid tank valve is provided on the pipeline between the group of waste acid tanks and the acid and alkali wastewater flowmeter.

[0020] As a further preferred solution of the present invention, a waste alkaline water inlet alkali tank valve is provided on the pipeline between the group of waste alkali tanks and the acid and alkali wastewater flowmeter.

[0021] As a further preferred solution of the present invention, a new sluice gate is provided on one side of the acid and alkaline wastewater drainage channels in the chemical water treatment workshop at the inlet filter valves for the acid and alkaline wastewater suction pumps in the drainage channels. One side channel part of the acid and alkaline wastewater drainage channels in the chemical water treatment workshop is communicated with the acid and alkaline drainage pipelines for the regeneration and backwashing of the anion and cation beds in the chemical water treatment workshop.

[0022] As a further preferred solution of the present invention, the suction pump is a pump with a head of 45 meters and a flow rate of 10 tons per hour.

[0023] As a preferred embodiment of the present invention, the acid and alkali waste water flow meters are connected to the incoming water pipe from the outlet of the original drainage pump in the chemical water neutralization tank after the check valve and the isolation valve at the outlet of the water suction pump.

[0024] To achieve the above object, the present invention also provides a method for recovering acid and alkaline intermediate water in chemical water production, including the following steps:

[0025] Step 1, recovery of acid and alkaline intermediate water:

[0026] When the cation resin is regenerated, acid is introduced for displacement, and the corresponding acidic intermediate water is discharged into the drainage channel. Since in the initial water inlet stage of the resin, the resin regeneration absorbs a large amount of H + and the H + content in the effluent is low. As the resin displacement rate gradually increases, the pH of the effluent will gradually decrease, and the H + content increases. When the pH of the effluent reaches below 2 and the H + concentration is greater than 0.01 mol / l, the valve of the drainage channel is closed to store water, and the recovery water pump is turned on to recover the acidic intermediate water to the storage tank in the desulfurization waste water workshop. When the pH exceeds 2, the operation stops.

[0027] Similarly, when the anion resin is regenerated, alkali is introduced for displacement, and the corresponding alkaline intermediate water is discharged into the drainage channel. Since in the initial water inlet stage of the resin, the resin regeneration absorbs a large amount of OH - and the OH - content in the effluent is low. As the resin displacement rate gradually increases, the pH of the effluent will gradually increase, and the OH - content increases. When the pH of the effluent reaches above 12 and the OH - concentration is greater than 0.01 mol / l, the valve of the drainage channel is closed to store water, and the recovery water pump is turned on to recover the alkaline intermediate water to the storage tank in the desulfurization waste water workshop. When the pH is below 12, the operation stops, and the recoverable intermediate water is fully recovered.

[0028] Step 2, replacing the hydrochloric acid solution used in the Fenton reaction in the triple box with acidic intermediate water:

[0029] The acidic intermediate water is pumped from the storage tank to the reaction tank of the triple box by a metering pump, and the pH is adjusted to 3 - 4 to cause a Fenton reaction in the adjustment tank, reducing the COD of the waste water. The acidic intermediate water is used to replace the hydrochloric acid solution used in the Fenton reaction in the triple box.

[0030] Step 3, replacing the process of adjusting the alkalinity by adding the original lime solution with alkaline intermediate water:

[0031] The alkaline intermediate water is pumped from the storage tank to the neutralization tank of the triple box by a metering pump. After neutralizing the acidic effluent from the reaction tank of the triple box, the pH of the neutralization tank is adjusted to 8 - 9 to be slightly alkaline at the same time. The effluent overflows to the coagulation tank of the triple box, and PAM and heavy metal scavengers are added to cause a flocculation precipitation complex reaction. The process of adjusting the alkalinity by adding the original lime solution is replaced with alkaline intermediate water.

[0032] Step 4: Use alkaline water to replace the alkali solution used in the desulfurization wastewater ammonia nitrogen removal stripping process:

[0033] Pump the alkaline water from the storage tank with a metering pump to the stripping tank for removing ammonia nitrogen from desulfurization wastewater, adjust the pH to 10-11, and heat it to 40-50℃ to promote the free stripping of dissolved ammonia in the water into the biochemical ammonia absorption tank to achieve the purpose of reducing ammonia nitrogen in wastewater, and use chemical alkaline water to replace the original process of adding sodium hydroxide solution.

[0034] Step 5: Use acidic water to replace the acid used for neutralization of the effluent from the desulfurization wastewater ammonia nitrogen stripping process:

[0035] Pump the acidic water from the storage tank to the neutralization tank behind the desulfurization wastewater stripping tank with a metering pump, and adjust the effluent to 6-9 to meet the sewage discharge standard.

[0036] Step 6, as a further solution of the present invention, utilizes the reaction mechanism of dissolving ammonium ions in water under alkaline conditions of about pH 10 to generate ammonia gas NH 4 + +OH - NH 3 ↑+H 2 0, blow off ammonia and reduce nitrogen under continuous aeration conditions at 40-50℃.

[0037] Compared with the prior art, the chemical water production acid-base water recycling system and recycling method provided by the present invention has the following beneficial effects:

[0038] 1. The present invention uses chemically produced acidic water to replace the raw hydrochloric acid used in the Fenton reaction of the traditional desulfurization and denitrification wastewater treatment COD degradation process, which can reduce the cost of purchasing hydrochloric acid and the alkali consumption of the corresponding hydrochloric acid neutralization of chemical wastewater.

[0039] 2. The present invention uses chemically produced alkaline water to replace the raw material limestone slurry in the treatment of desulfurization and denitrification wastewater, reducing the cost of purchasing limestone powder.

[0040] At the same time, the concentration of calcium and magnesium ions in alkaline water is extremely low, and it contains more SO 4 2- 、CO 3 2- , conducive to the formation of CaSO 4 、CaCO 3 Sedimentation, the removal of sediment into the filter press system is beneficial to reduce the hardness of the effluent and reduce the impact on subsequent processes.

[0041] 3. The present invention uses chemical water-making alkaline water to replace the process of adding sodium hydroxide solution in the denitrification process of desulfurization and denitrification wastewater, thereby reducing the cost of purchasing sodium hydroxide solution.

[0042] ​​​4. After the denitrification process using acidic intermediate water from chemical water production in the present invention replaces the desulfurization and denitrification wastewater, the pH of the drained water decreases from 10 - 11 to 6 - 9, neutralizing the reaction raw material hydrochloric acid solution and reducing the purchase cost of hydrochloric acid.

[0043] 5. In the present invention, the COD and ammonia nitrogen in the acidic and alkaline intermediate water from chemical water production are significantly lower than the emission standards themselves. When recycled into the desulfurization and denitrification wastewater, it also has a dilution effect, reducing the consumption cost of COD and ammonia nitrogen removal materials under the condition that the total wastewater volume remains unchanged.

[0044] 6. In the present invention, pumping the acidic and alkaline intermediate water from chemical water production to the desulfurization and denitrification wastewater treatment system for recycling also reduces the consumption cost of acid and alkali materials used for self - neutralization in the chemical water production system.

[0045] 7. The present invention effectively utilizes the volume of the acid - base storage tanks and intermediate water tanks in the chemical water production workshop, reducing the investment in acid - base storage and release equipment in the desulfurization and denitrification wastewater treatment process system and the management risk of hazardous chemicals.

[0046] 8. The present invention reduces the addition of new acid and new alkali, reduces the amount of raw water added for drug dissolution, reducing both the cost of new water and the wastewater discharge. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only individual cases of the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0048] Figure 1 It is the process schematic diagram of the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0049] In order to make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the following further details the embodiments of the present invention in conjunction with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0050] In the description of the embodiments of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "upper", "lower", "front", "rear", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings. It is only for the convenience of describing the embodiments of the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the embodiments of the present invention.

[0051] In the description of the embodiments of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "installation", "connection", and "coupling" should be understood in a broad sense. For example, it can be a fixed connection, an integral connection, or a detachable connection; it can be the communication inside two components; it can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific situations.

[0052] See Figure 1 , the water recycling system for the acidity and alkalinity of chemically produced water in the embodiments of the present invention includes: the acid and alkaline wastewater drainage channels in the water treatment workshop, in which inlet filter valves for the acid and alkaline wastewater suction pumps in the drainage channels are provided; a group of waste acid tanks, one of which is pumped to the external drainage pool and the other is pumped to the triple-box reaction tank; a group of waste alkali tanks, one of which is pumped to the triple-box neutralization tank and the other is pumped to the stripping tank.

[0053] An inlet valve for the suction pump is provided above the acid and alkaline wastewater drainage channels in the water treatment workshop. One side of the inlet valve for the suction pump is provided with a suction pump, and one side of the suction pump is provided with a check valve and an isolation valve at the outlet of the suction pump.

[0054] The inlet filter valve for the acid and alkaline wastewater suction pump in the drainage channel, the inlet valve for the suction pump, the suction pump, the check valve and the isolation valve at the outlet of the suction pump, the pressure gauge, and the acid and alkali wastewater flow meters are connected in sequence through pipelines.

[0055] A new sluice gate is provided on one side of the inlet filter valve for the acid and alkaline wastewater suction pump in the acid and alkaline wastewater drainage channels in the water treatment workshop. On one side of the acid and alkaline wastewater drainage channels in the water treatment workshop within the workshop, there are drainage pipelines for the anion and cation beds in the water treatment, which are the drainage pipelines for the middle water during the regeneration of the anion and cation beds with acid and alkali.

[0056] On the pipeline between a group of waste acid tanks and the acid and alkali wastewater flow meters, an inlet valve for waste acidic water into the acid tank is provided; on the pipeline between a group of waste alkali tanks and the acid and alkali wastewater flow meters, an inlet valve for waste alkaline water into the alkali tank is provided.

[0057] The suction pump has a head of 45 meters and a flow rate of 10 tons per hour.

[0058] One side of the acid and alkali wastewater reuse flow meter is connected to the water supply pipe from the outlet of the original drainage pump in the water treatment neutralization tank.

[0059] Process description before the technical solution of the present invention:

[0060] 1. Chemical water production process and middle water generation.

[0061] The make-up water for the power plant boiler is deionized water (conductivity ≤ 0.3 μs / cm) produced by the ion exchange method. The ion exchange process is as follows:

[0062] Industrial water → water purifier (removing suspended solids) → activated carbon filter (adsorbing and filtering to remove organic matter and suspended solids) → cation exchanger (replacing and removing cations in water) → carbon remover (removing dissolved CO2 in water) → anion exchanger (replacing and removing anions in water) → mixed cation and anion exchanger (further replacing to reduce cations and anions in water) → qualified demineralized water.

[0063] After the resin in the ion exchanger is saturated in replacement, it is regenerated and restored to performance by soaking in running water diluted with strong acid and strong base to about 5% concentration. The process of the regeneration replacement reaction is as follows:

[0064] Cation resin: R(SO 3 ) 2 Mg (Ca, Na and other cationic ions) + 2HCl R(SO 3 H) 2 + MgCl 2 (CaCl 2 etc.)

[0065] Anion resin: R(≡N) 2 SO 4 + 2NaOH R(≡NOH) 2 + Na 2 SO 4

[0066] R≡NCl + NaOH R≡NOH + NaCl

[0067] R≡NHCO 3 + NaOH R≡NOH + NaHCO 3

[0068] R≡NHSiO 3 + NaOH R≡NOH + NaHSiO 3

[0069] During the regeneration process, medium salinity water with 1% - 3% concentration of acidity and alkalinity is discharged.

[0070] For the medium salinity water in chemical water production, the indexes of COD ≤ 50mg / l, suspended solids ≤ 50mg / l, and ammonia nitrogen ≤ 5mg / l are all relatively good and are much lower than the environmental protection discharge standards. It only needs to adjust the PH to 6 - 9 with acid and alkali before discharging.

[0071] 2. Process of desulfurization and denitrification wastewater treatment system.

[0072] In the environmental protection removal process of sulfur dioxide and nitrogen oxides in the flue gas of power plant boilers, the SNCR non-catalytic reduction process of ammonia injection is used for denitrification and nitrogen removal, and the limestone-gypsum large wet desulfurization will produce a large amount of high-hardness and high-ammonia-nitrogen acidic process wastewater for desulfurization and denitrification.

[0073] The effluent indexes of desulfurization and denitrification wastewater are: solids 10%-20%, COD 1000-2000 mg / l, ammonia nitrogen 1000-2000 mg / l, PH 5-6. It must be treated qualified before being discharged to the sewage treatment plant.

[0074] The desulfurization and denitrification wastewater treatment process flow first passes through the desulfurization waste triple-tank treatment process to control COD ≤ 400 mg / l and suspended solids ≤ 300 mg / l. Then the wastewater enters the denitrification process to control ammonia nitrogen ≤ 35 mg / l, and after PH 6-9, it is discharged qualified.

[0075] The process is as follows: wastewater from the desulfurization and denitrification system → sewage tank → triple-tank Fenton reaction tank (adding hydrogen peroxide, iron salt, hydrochloric acid to adjust PH 3-4 to degrade COD) → neutralization tank (adding lime milk to control PH 8-9) → flocculation tank (adding PAM to coagulate and solidify solids, adding heavy metal capturer to capture heavy metals) → sedimentation tank (sedimenting solids for dehydration and pressing for recovery) → denitrification stripping tank (adding alkali to adjust PH 10-11 to make dissolved ammonia free and stripped into the biochemical denitrification system for absorption and decomposition into nitrogen gas) → chlorine addition tank (continuing breakpoint chlorination of low-nitrogen water to convert it into nitrogen gas to control the discharge of low-ammonia-nitrogen wastewater) → neutralization tank (adjusting PH back to 6-9) → discharging qualified to the sewage treatment plant.

[0076] The production system is equipped with two coherent systems of triple-tank wastewater treatment and wastewater denitrification process. Acid and alkali solutions need to be added in multiple links. Strong acids and alkalis are purchased during production and stored in the storage tanks in the wastewater treatment workshop for use. In the process of reducing wastewater COD, hydrochloric acid is added to adjust PH to 3-4 to reduce the wastewater COD index by using the "Fenton" chemical reaction. Limestone slurry is used to weakly increase PH to 8-9 to complex and precipitate heavy metal ions with heavy metal capturer and flocculate and precipitate solids with PAM. The effluent from the triple-tank enters the denitrification stripping tank, and alkali is added to adjust PH to 10-11 to make dissolved ammonia free and stripped into the biochemical system for absorption. The wastewater continues to enter the chlorine addition tank to add sodium hypochlorite for breakpoint chlorination to further reduce the ammonia nitrogen in the wastewater to reach the discharge standard, and then hydrochloric acid is used for neutralization to adjust PH to drop to 6-9. After the wastewater treatment is qualified, it is discharged externally.

[0077] The qualified discharge standard for wastewater into the pipe is: COD ≤ 400 mg / l, suspended solids ≤ 300 mg / l, ammonia nitrogen ≤ 35 mg / l, PH 6-9, and the color and luster are clear.

[0078] The present invention provides a recovery method for a chemical water-making acid-base intermediate water recycling system, including the following steps:

[0079] Step 1, acid-base intermediate water recovery:

[0080] During the regeneration of cation resin, acid is introduced for displacement, and the corresponding acidic intermediate water is discharged into the drainage channel. Since in the initial stage of resin water intake, the resin absorbs a large amount of H + and the H + content in the effluent is low. As the resin displacement rate gradually increases, the pH of the effluent gradually decreases while the H + content increases. When the pH of the effluent reaches below 2 and the H + concentration is greater than 0.01 mol / l, the valve of the drainage channel is closed to store water, and the recycling water pump is turned on to recycle the acidic intermediate water to the storage tank in the desulfurization wastewater workshop. The process stops when the pH exceeds 2.

[0081] During the regeneration of anion resin, alkali is introduced for displacement, and the corresponding alkaline intermediate water is discharged into the drainage channel. Since in the initial stage of resin water intake, the resin absorbs a large amount of OH - and the OH - content in the effluent is low. As the resin displacement rate gradually increases, the pH of the effluent gradually increases while the OH - content increases. When the pH of the effluent reaches above 12 and the OH - concentration is greater than 0.01 mol / l, the valve of the drainage channel is closed to store water, and the recycling water pump is turned on to recycle the alkaline intermediate water to the storage tank in the desulfurization wastewater workshop. The process stops when the pH is below 12.

[0082] Step 2: Replace the hydrochloric acid solution used in the Fenton reaction in the triple box with acidic intermediate water:

[0083] Pump the acidic intermediate water from the storage tank to the reaction tank of the triple box using a metering pump. When the pH is adjusted to 3 - 4, the Fenton reaction occurs in the adjustment tank to reduce the COD of the wastewater, and the acidic intermediate water is used to replace the hydrochloric acid solution used in the Fenton reaction in the triple box.

[0084] Step 3: Replace the process of adjusting alkalinity by adding lime solution with alkaline intermediate water:

[0085] Pump the alkaline intermediate water from the storage tank to the neutralization tank of the triple box using a metering pump. After neutralizing the acidic effluent from the reaction tank of the triple box, the pH of the neutralization tank is adjusted to 8 - 9 to be slightly alkaline, and the effluent overflows to the coagulation tank of the triple box. PAM and heavy metal scavengers are added to carry out flocculation precipitation complexation reactions, and the process of adjusting alkalinity by adding lime solution is replaced with alkaline intermediate water.

[0086] Step 4: Replace the alkali solution used in the ammonia stripping process for removing ammonia nitrogen from desulfurization wastewater with alkaline intermediate water:

[0087] Pump the alkaline intermediate water from the storage tank to the stripping tank for ammonia nitrogen removal from desulfurization wastewater using a metering pump. Adjust the pH to 10 - 11, and under the condition of heating to 40 - 50 °C, promote the free stripping of dissolved ammonia in the water into the biochemical ammonia absorption tank, and replace the process of adding sodium hydroxide solution with the alkaline intermediate water from demineralized water.

[0088] Step 5: Replace the acid solution used for neutralization in the ammonia nitrogen stripping process of desulfurized wastewater with acidic intermediate water:

[0089] Pump the acidic intermediate water from the storage tank to the neutralization tank after the desulfurized wastewater stripping tank using a metering pump, and adjust the pH of the effluent to 6 - 9 to meet the sewage discharge standard.

[0090] Step 6: Under the alkaline condition of pH 10, the reaction mechanism of dissolved ammonia ions in water to generate ammonia gas is NH 4 + + OH - NH 3 ↑ + H 2 0. Under the condition of continuous aeration with heating to 40 - 50 °C, strip away ammonia gas to reduce nitrogen.

[0091] Principle of the technical solution of the present invention:

[0092] During the production process, the amount of chemically treated water with high acidity, alkalinity, and high salinity is relatively large, with an annual discharge of more than 120,000 tons. The amount of desulfurized and denitrified wastewater is about 6,000 tons, and the requirements for the acid - base concentration in the desulfurized and denitrified wastewater treatment process are lower than the pH of the chemically treated water with high acidity and alkalinity. Considering reusing the chemically treated water with high acidity, alkalinity, and high salinity as the acid - base raw materials in the desulfurized and denitrified wastewater treatment, the process is experimentally improved to solve the problems existing in the use of chemically treated high - acid - base wastewater in the desulfurized and denitrified wastewater treatment system and ensure that the effluent meets the wastewater discharge standard.

[0093] Chemically treated acidic intermediate water contains a large amount of Na + , Ca 2+ , Mg 2+ , Al 3+ , H + and other cations replaced from the raw water through cation exchange resin. Alkaline intermediate water contains a large amount of SO 4 2- , SiO 3 2- , CO 3 2- , OH - , Cl - and other anions.

[0094] Replace hydrochloric acid in the Fenton reaction with acidic intermediate water. The other cations in the acidic intermediate water are similar to the cation components of desulfurized and denitrified wastewater, which does not affect the relevant reaction results and does not produce new reactants.

[0095] In the triple - box heavy - metal capture, flocculation, precipitation, and complexation reaction stage, replace the original process of adding lime solution to adjust the alkalinity with alkaline intermediate water, which can reduce the new Ca 2+ brought by lime milk. The SO 42- , CO 3 2- For the high-Ca 2+ wastewater in the limestone desulfurization process, it has a good effect of removing by chemical reaction precipitation. The precipitate enters the sludge pressing and recycling system for separation and is recycled as building materials raw materials.

[0096] In the wastewater denitrification system, the alkaline intermediate water in the demineralized water is used to replace the original process of adding sodium hydroxide solution, and the pH is adjusted to about 10 - 11. Utilize the reaction mechanism that ammonia ions dissolved in water generate ammonia gas under alkaline conditions NH 4 + + OH - NH 3 ↑ + H 2 0. Under the condition of continuous aeration while heating to 40 - 50 °C, the ammonia gas is stripped and the nitrogen is reduced. Due to the influence of adding limestone solution in the flue gas desulfurization reaction, there are still a large number of soluble calcium ions in the effluent wastewater of the triple-box sedimentation tank. Under the alkaline condition of about pH 10 and after appropriate heating, the reaction occurs: Ca 2+ + 2OH - Ca(OH) 2 ↓, and the solubility of calcium hydroxide decreases with the increase of temperature and precipitates in the pool water to produce a milky white precipitate. After the denitrification is completed, the denitrified wastewater containing the milky white precipitate overflows into the neutralization tank after aeration and stirring, and acidic intermediate water is added for neutralization adjustment, reducing the pH from about 10 to 6 - 9. At the same time, under the action of the acidic wastewater,

[0097] Ca(OH) 2 + 2H + === Ca 2+ + H 2 0, the precipitate dissolves to form a colorless solution, which better solves the problem of excessive suspended solids and unclear color caused by the milky white precipitate, and makes the wastewater clarified and up to the standard for discharge.

[0098] The above shows and describes the basic principle of the present invention. The above is only the preferred embodiment of the present invention and is not used to limit the present invention. The descriptions in the above embodiments and the specification only illustrate the principle of the present invention. Without departing from the scope of the present invention, any modifications, equivalent replacements, and improvements made within the spirit and scope of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for recovering acidic and alkaline water from chemical water production, characterized in that: The following steps are involved: Step 1: Acid and alkali water recovery: When the cationic resin is regenerated, acid is introduced to displace the corresponding acidic water and discharge it to the drainage ditch. During the initial water inlet stage of the resin, the resin regeneration absorbs H + More, water outlet H + The content is small, and the pH of the effluent gradually decreases when the resin replacement rate gradually increases. + The content increases, and when the effluent pH reaches below 2 + When the concentration is greater than 0.01 mol / l, close the drain valve to store water and open the recovery water pump to recover the acidic water to the desulfurization wastewater workshop storage tank. Stop when the pH exceeds 2; When the anion resin is regenerated, alkali is introduced to replace the corresponding alkaline water and discharged to the drainage ditch. Since the resin absorbs OH in the initial water inlet stage, the resin regeneration - More, water OH - The content is small, and the pH of the effluent gradually increases when the resin replacement rate gradually increases. - Increase the content and control the PH value of the effluent to above 12 OH - When the concentration is greater than 0.01 mol / l, close the drain valve to store water and open the recovery water pump to recover the alkaline water to the desulfurization wastewater workshop storage tank. Stop when the pH is lower than 12; Step 2: Replace the hydrochloric acid solution used in the triple-tank Fenton reaction with acidic water: The acidic water is pumped from the storage tank to the reaction tank of the triple tank by a metering pump. When the pH is adjusted to 3-4, the Fenton reaction occurs in the regulating tank to reduce the COD of the wastewater. The acidic water replaces the hydrochloric acid solution used for the Fenton reaction in the triple tank. Step 3: Use alkaline water to replace the original lime solution to adjust the alkalinity process: The alkaline water is pumped from the storage tank to the neutralization tank of the triple tank by a metering pump. After neutralizing the acidic effluent of the triple tank reaction tank, the pH of the neutralization tank is adjusted to 8-9, which is slightly alkaline. The effluent overflows to the triple tank coagulation tank, and PAM and heavy metal capture agent are added to cause flocculation precipitation complex reaction. The alkaline water is used to replace the original lime solution to adjust the alkalinity process; Step 4: Use alkaline water to replace the alkali solution used in the stripping process of removing ammonia nitrogen from desulfurization wastewater: The alkaline water is pumped from the storage tank to the stripping tank for removing ammonia nitrogen from desulfurization wastewater by a metering pump, the pH is adjusted to 10-11, and the dissolved ammonia in the water is blown off at 40-50℃ to enter the biochemical ammonia absorption tank, and the original process of adding sodium hydroxide solution is replaced by the alkaline water. Step 5: Use acidic water to replace the acid used for neutralization of the effluent from the desulfurization wastewater ammonia nitrogen stripping process: The acidic neutral water is pumped from the storage tank to the neutralization tank behind the desulfurization wastewater stripping tank by a metering pump, and the effluent pH is adjusted to 6-9 to meet the sewage discharge standard.

2. The method for recovering acidic and alkaline water from chemical water production according to claim 1, characterized in that: The following steps are also included: Step 6: Under alkaline conditions of pH 10-11, the reaction mechanism of dissolving ammonium ions in water to generate ammonia gas NH4 + +OH - NH3↑+H20, blow off ammonia and reduce nitrogen under continuous aeration conditions while heating to 40-50℃.

3. A system for recycling acidic and alkaline water from chemical water production using the method for recycling acidic and alkaline water from chemical water production according to any one of claims 1 to 2, characterized in that ,include: The acid and alkaline wastewater drainage channel of the chemical water workshop is equipped with an inlet filter valve for the acid and alkaline wastewater suction pump of the drainage channel; A group of waste acid tanks, one of which is pumped to an external discharge tank, and the other is pumped to a triple tank reaction tank; A group of waste alkali tanks, one of which is pumped to the triple-box neutralization tank, and the other is pumped to the stripping tank.

4. The chemical water production acid-base water recycling system according to claim 3 is characterized by: A water suction pump inlet valve is arranged above the acid and alkaline wastewater drainage channel of the water treatment workshop, a water suction pump is arranged on one side of the water suction pump inlet valve, and a water suction pump outlet check valve and an isolation valve are arranged on one side of the water suction pump; The drainage channel acid and alkaline wastewater suction pump inlet filter valve is sequentially connected to the suction pump inlet valve, suction pump, suction pump outlet check valve and isolation valve, pressure gauge, acid and alkaline wastewater flow meter through pipelines.

5. The chemical water production acid-base water recycling system according to claim 4 is characterized by: A waste acid water inlet valve is arranged on the pipeline between the group of waste acid tanks and the acid and alkali waste water flowmeters.

6. The chemical water production acid-base water recycling system according to claim 5 is characterized by: A waste alkaline water inlet valve for the alkali tank is arranged on the pipeline between the group of waste alkali tanks and the acid and alkali waste water flowmeter.

7. The chemical water production acid-base water recycling system according to claim 6 is characterized by: The acid and alkaline wastewater drainage channel of the chemical water workshop is provided with a new gate plate on one side of the inlet filter valve of the acid and alkaline wastewater suction pump of the drainage channel, and the channel part on one side of the acid and alkaline wastewater drainage channel of the chemical water workshop is connected with the acid and alkaline drainage pipes for regeneration backwashing of chemical water anion and cation beds.

8. The chemical water production acid-base water recycling system according to claim 7 is characterized by: The water suction pump has a head of 45 meters and a flow rate of 10 tons / hour.

9. The chemical water production acid-base water recycling system according to claim 8, characterized in that: The acid and alkali wastewater flowmeter is connected to the original drainage pump outlet water pipe of the chemical water neutralization tank after the check valve and isolation valve at the water suction pump outlet.

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