A method for treating calcium chloride brine discharged from an epichlorohydrin production process

Abstract

The present application relates to a kind of by epichlorohydrin production process discharging calcium chloride wastewater treatment method, the preparation method includes calcium chloride wastewater pretreatment, filtrate heating, high-temperature heterogeneous fenton and deep purification etc.Steps.Adopt coagulation sedimentation to remove the particulate matter and part of organic matter in brine;Adopt heat exchange and steam combination mode to improve brine temperature, recover heat;Use multiple bed layer solid catalyst to carry out high-temperature heterogeneous fenton, oxidize most of organic matter;Residual hydrogen peroxide and ozone combination is used to organic matter oxidation to tail water again, using reducing agent eliminates water body oxidizing species, finally filter recovery catalyst, discharge clear brine.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology. More specifically, this invention relates to a method for treating calcium chloride wastewater discharged from the epichlorohydrin production process. Background Technology

[0002] Epichlorohydrin is an important basic chemical raw material, and its production process generates a large amount of CaCl2 brine during the cyclization stage. This wastewater is characterized by high salinity and high organic matter content. Currently, the main treatment methods are to concentrate the wastewater into concentrated CaCl2 water for sale using MVR (Multi-Effect Vapor Reduction) equipment, or to obtain CaCl2 salt using multi-effect evaporation methods; however, these methods are energy-intensive. For example, Xiao Ming, in his article "Research Progress on Epichlorohydrin Wastewater Treatment Technology in my country," published in the journal "Fine and Specialty Chemicals" (online first edition March 13, 2026), pages 1-6, explains that advanced oxidation methods are a promising development direction for treating calcium chloride brine discharged from epichlorohydrin production processes. Wet catalytic oxidation can remove a large amount of organic matter from the brine, but it is limited by high temperature and pressure conditions and carries significant risks; see CN120943472A, invention title "A Method for Treating Wastewater Generated from the Glycerol Method for Epichlorohydrin Preparation"; traditional Fe... 2+ Homogeneous Fenton reactions have a fast reaction rate and low reaction temperature, but they produce a large amount of iron sludge. Ordinary low-temperature heterogeneous Fenton reactions can avoid iron sludge production, but they suffer from slow reaction rates and low hydrogen peroxide utilization. See the literature: Xu Licong, "Research Progress on Wide pH Degradation of Organic Pollutants by Iron-Based Heterogeneous Fenton Oxidation Technology," Journal "Environmental Engineering," Vol. 43, No. 8, pp. 14-27. Directly using ozone catalytic oxidation results in high organic matter concentration, high ozone consumption, and high cost. See CN215327579U, Utility Model Name "Epoxychloropropane Wastewater Treatment System."

[0003] In order to overcome the technical defects of the existing technology, the inventors conducted extensive experimental research and analysis, and finally completed this invention. Summary of the Invention Technical problems to be solved

[0004] The purpose of this invention is to provide a method for treating calcium chloride brine discharged from the epichlorohydrin production process. Technical solution

[0005] The present invention is achieved through the following technical solution.

[0006] This invention relates to a method for treating calcium chloride wastewater discharged from the epichlorohydrin production process.

[0007] The processing steps of this method are as follows:

[0008] A. Pretreatment of calcium chloride wastewater

[0009] The calcium chloride wastewater is sent to equalization tank 1, where its pH is neutralized to 6.0-8.0 using an acid solution. It is then sent to coagulation tank 2, where a coagulant is added and the mixture is stirred for 30-60 minutes. The resulting mixture is then piped to plate and frame filter 3 for filtration. The resulting filtrate is adjusted to pH 3-5 using an acid solution before being sent to subsequent processing steps. The resulting filter cake is discharged outside the facility for solid waste treatment.

[0010] B. Heating the filtrate

[0011] The filtrate from step A is sent to the bottom of heat exchanger 4 and exchanges heat with brine (pH adjusted to 6-9 by an alkaline solution) discharged from the top of heterogeneous Fenton reactor 6 as oxidation tail water, raising its temperature to 80-120°C. Then, it enters steam heater 5 to exchange heat with high-temperature steam, heating the filtrate to 120-150°C. The filtrate then enters the heterogeneous Fenton reactor 6 through a pipe at the bottom. The oxidation tail water, with its temperature reduced to 30-70°C, is sent from the bottom of heat exchanger 4 to the bottom of fluidized bed reactor 7 through a pipe.

[0012] C. High-temperature heterogeneous Fenton reaction

[0013] In the heterogeneous Fenton reaction tower 6, the pH of the heated filtrate from step B is adjusted to 3-5 with an alkaline solution. Then, the heated filtrate is reacted with a hydrogen peroxide solution with a concentration of 27.5%-30.0% by volume at a volume ratio of 1:0.005-0.04, a temperature of 130-160℃, and a pressure of 0.5-0.8MPa in the presence of a catalyst to carry out a high-temperature heterogeneous Fenton reaction for 10-60 min.

[0014] D. Deep Purification

[0015] In the fluidized bed reactor 7, ozone, catalyst slurry and heat exchange oxidation tailwater from step B are reacted with the heat exchange oxidation tailwater at a volume ratio of 0.5-5.0:0.001-0.05:1.0, with a solid content of 1-20% by weight of catalyst slurry, for 30-120 minutes. After the reaction is completed, the oxidation tailwater is discharged from the top of the tower. A small amount of reducing agent is then added to remove residual oxidizing particles in the oxidation tailwater. The catalyst is then recovered through a bag filter 8, and the clarified oxidation tailwater is discharged.

[0016] According to a preferred embodiment of the present invention, in step A, the calcium chloride wastewater discharged from the epichlorohydrin production process contains 14-18% CaCl2, 0.01-0.20% glycerol, 0.01-0.30% chloropropanol and 800-4000 mg / L of organic matter TOC, and has a pH value of 12.0-13.0 by weight.

[0017] According to another preferred embodiment of the present invention, the acid solution is a hydrochloric acid solution with a concentration of 5-30% by weight; the alkaline solution is a sodium hydroxide solution with a concentration of 30-50% by weight.

[0018] According to another preferred embodiment of the present invention, in step A, the coagulant is one or more coagulants selected from polyferric aluminum sulfate, polyferric chloride, polyaluminum chloride or polyacrylamide; the concentration of the coagulant is 0.1 to 1.0% by weight, and its dosage is 0.1 to 3.0% of the volume of calcium chloride wastewater.

[0019] According to another preferred embodiment of the present invention, in step B, the heat exchanger 4 is a plate heat exchanger, a shell-and-tube heat exchanger, a spiral plate heat exchanger, or a coaxial heat exchanger, and the steam heater 5 is a Venturi jet mixer, a shell-and-tube heat exchanger, a plate steam heat exchanger, or a steam coil heat exchanger.

[0020] According to another preferred embodiment of the present invention, in step C, the heterogeneous Fenton reaction tower 6 is a vertical cylindrical reaction tower with a uniform water distribution zone, a fixed packing zone and an outlet water zone. Two to four catalyst beds are provided in the heterogeneous Fenton reaction tower 6, with each layer spaced 0.5 to 1.5 meters apart. Except for the bottom catalyst bed, the remaining beds are provided with hydrogen peroxide and alkali feeders and arrangers at the wastewater inlet end.

[0021] According to another preferred embodiment of the present invention, in step C, the catalyst is a particulate, honeycomb, or corrugated catalyst in which active components of Mn, Ce, Pt, and Ru oxides are supported on ceramic, cordierite, or corundum.

[0022] According to another preferred embodiment of the present invention, in step D, the fluidized bed reactor 7 is a vertical hollow cylindrical reactor with a uniformly distributed water and gas distribution structure.

[0023] According to another preferred embodiment of the present invention, in step D, the catalyst slurry is one or more catalyst slurries selected from FeOOH, Fe2O3, Fe3O4, MgFe2O4, CaFe2O4, MgO or CaOH2.

[0024] According to another preferred embodiment of the present invention, in step D, the reducing agent is one or more reducing agents selected from ferrous chloride, ferrous sulfate, sulfurous acid, sodium sulfite or ammonium sulfite.

[0025] According to another preferred embodiment of the present invention, in step D, the bag filter 8 is a filter bag with a mesh size of 200 mesh, 400 mesh, or 1000 mesh, made of polyphenylene sulfide (PPS), polyimide P84, polytetrafluoroethylene (PTFE), or aramid material.

[0026] According to another preferred embodiment of the present invention, in step D, the discharged clarified oxidation tailwater contains less than 18% CaCl2, less than 0.001% glycerol, less than 0.001% chloropropanol and less than 20 mg / L of organic matter TOC by weight, and has a pH value of 6 to 9.

[0027] The invention will now be described in more detail.

[0028] This invention relates to a method for treating calcium chloride wastewater discharged from the epichlorohydrin production process; the specific process flow is shown in the appendix. Figure 1 For details of the implementation process, please refer to Example 1.

[0029] The processing steps of this method are as follows:

[0030] A. Pretreatment of calcium chloride wastewater

[0031] The calcium chloride wastewater is sent to equalization tank 1, where its pH is neutralized to 6.0-8.0 using an acid solution. It is then sent to coagulation tank 2, where a coagulant is added and the mixture is stirred for 30-60 minutes. The resulting mixture is then piped to plate and frame filter 3 for filtration. The resulting filtrate is adjusted to pH 3-5 using an acid solution before being sent to subsequent processing steps. The resulting filter cake is discharged outside the facility for solid waste treatment.

[0032] In this patent application, the discharge of calcium chloride wastewater from the epichlorohydrin production process is equivalent to calcium chloride wastewater, and will not be further explained in the following sections.

[0033] According to the present invention, the main purpose of the calcium chloride wastewater pretreatment step is to remove suspended particulate matter present in the calcium chloride wastewater, and at the same time remove the organic matter it carries.

[0034] According to the analytical methods specified in GB / T 23941-2025 "Analytical Method for Industrial Calcium Chloride", GB / T 13216-2008 "Test Method for Glycerol", GB / T 21936-2008 "Determination of Chloropropanol in Water Quality" and HJ 501-2009 "Determination of Total Organic Carbon in Water Quality", the calcium chloride wastewater discharged from the epichlorohydrin production process used in this invention contains, by weight, 14-18% CaCl2, 0.01-0.20% glycerol, 0.01-0.30% chloropropanol, and 800-4000 mg / L of total organic carbon (TOC), with a pH value of 12.0-13.0. Specifically, the calcium chloride wastewater used in this invention is provided by Ningbo Huanyang New Materials Co., Ltd.

[0035] In this step, an acid solution is used in equalization tank 1 to neutralize the pH of the calcium chloride wastewater to 6.0-8.0. Its main function is to promote the flocculation and precipitation of calcium chloride contained in the calcium chloride wastewater.

[0036] The acid solution used in this invention is a hydrochloric acid aqueous solution with a concentration of 5-30% by weight. If the concentration of the hydrochloric acid aqueous solution is less than 5%, the amount of acid solution used is too large; if the concentration of the hydrochloric acid aqueous solution is higher than 30%, the concentration of the acid solution is too high, and the operation risk is too great. Therefore, a hydrochloric acid aqueous solution concentration of 5-30% is reasonable, preferably 8-26%, and more preferably 10-22%.

[0037] The acid solutions used subsequently are all hydrochloric acid aqueous solutions of the above concentration, so they will not be described again below.

[0038] In this step, if the pH of the neutralized calcium chloride wastewater is below 6.0, the coagulation and sedimentation effect will be poor because the strong acidity inhibits the hydrolysis of the coagulant, destroying the charge neutralization and trapping effects; if the pH of the neutralized calcium chloride wastewater is above 8.0, the coagulation and sedimentation effect will be worse because the strong alkali dissolves the flocs, destroying the charge neutralization and trapping effects. Therefore, it is appropriate to neutralize the pH of the calcium chloride wastewater to 6.0-8.0, preferably 6.4-7.6, and more preferably 6.6-7.2.

[0039] Next, the neutralized calcium chloride wastewater is mixed with a coagulant in coagulation tank 2 for 30-60 minutes. The concentration of the coagulant is 0.1-1.0% by weight, and its dosage is 0.1-3.0% of the volume of the calcium chloride wastewater.

[0040] The main purpose of adding coagulants to neutralized calcium chloride wastewater is to promote the aggregation and sedimentation of colloidal particles and suspended solids present in the wastewater.

[0041] The coagulant used in this invention is one or more coagulants selected from polyferric aluminum sulfate, polyferric chloride, polyaluminum chloride, or polyacrylamide. These are all products currently sold on the market, such as polyferric aluminum sulfate sold by Gongyi Tenglong Water Treatment Materials Co., Ltd. under the trade name polyferric aluminum sulfate, polyferric chloride sold by Gongyi Tenglong Water Treatment Materials Co., Ltd. under the trade name polyferric chloride, and polyacrylamide sold by Gongyi Tenglong Water Treatment Materials Co., Ltd. under the trade name polyacrylamide.

[0042] In this step, the concentration of the coagulant solution is 0.1-1.0% by weight, and its dosage is 0.1-3.0% of the volume of calcium chloride wastewater. When the dosage of the coagulant is within the aforementioned range, if the concentration is below 0.1%, the dosage of the coagulant solution is too large, affecting its coagulation effect; if the concentration is above 1.0%, the coagulant solution is too thick, affecting the aggregation effect of colloidal particles and suspended solids. Therefore, a coagulant concentration of 0.1-1.0% is reasonable, preferably 0.2-0.8%, and more preferably 0.4-0.6%. When the concentration of the coagulant is within the aforementioned range, if the dosage is below 0.1%, the aggregation effect of colloidal particles and suspended solids is poor; if the dosage is above 3.0%, the cost of this treatment method will be too high. Therefore, a coagulant dosage of 0.1-3.0% is appropriate, preferably 0.6-2.4%, and more preferably 1.0-1.8%.

[0043] After adding the coagulant, the mixture needs to be stirred for 30 to 60 minutes. If the stirring time is less than 30 minutes, the coagulation time will be insufficient and the coagulation effect will be poor; if the stirring time is more than 60 minutes, the coagulation efficiency will decrease. Therefore, a stirring time of 30 to 60 minutes is appropriate, preferably 36 to 54 minutes, and more preferably 40 to 50 minutes.

[0044] The resulting mixture was filtered using a plate and frame filter 3, and the pH of the filtrate was adjusted to 3.0–5.0 with an acid solution.

[0045] The main purpose of adjusting the pH of the filtrate to 3.0–5.0 using an acid solution is to ensure the stability of the hydrogen peroxide added in subsequent steps. If the pH of the filtrate is adjusted below 3.0, a large amount of acid solution will be needed, which will aggravate the corrosion of pipes, equipment, and catalysts; if the pH of the filtrate is adjusted above 5.0, the stability of the hydrogen peroxide added in subsequent steps will be reduced. Therefore, adjusting the pH of the filtrate to 3.0–5.0 is preferable, preferably 3.4–4.6, and more preferably 3.6–4.4.

[0046] The equalization tank 1 and coagulation tank 2 used in this step are reaction vessels with agitators currently sold on the market. For example, equalization tank 1 is a product sold by Zhejiang Deqiang Technology Co., Ltd. under the trade name equalization tank; coagulation tank 2 is a product sold by Zhejiang Deqiang Technology Co., Ltd. under the trade name coagulation tank.

[0047] The plate and frame filter 3 used in this step is a filtration device commonly used in the chemical technology field and currently sold on the market, such as the product sold by Jiangsu Keyue Filtration Equipment Co., Ltd. under the trade name Stainless Steel Plate and Frame Filter.

[0048] B. Heating the filtrate

[0049] The filtrate from step A is sent to the bottom of heat exchanger 4 and exchanges heat with brine (pH adjusted to 6-9) discharged from the top of heterogeneous Fenton reactor 6 as oxidation tail water, raising its temperature to 80-120°C. Then, it enters steam heater 5 to exchange heat with high-temperature steam, heating the filtrate to 120-150°C. The filtrate then enters the heterogeneous Fenton reactor 6 through a pipe at the bottom. The oxidation tail water, with its temperature reduced to 30-70°C, is sent from the bottom of heat exchanger 4 to the bottom of fluidized bed reactor 7 through a pipe.

[0050] In this step, the brine discharged from the top of the heterogeneous Fenton reaction tower 6 needs to have its pH adjusted to 6-9 using an alkaline solution. The purpose is to neutralize the acidic substances in the brine and reduce their corrosion of the treatment equipment. If the pH of the brine is adjusted below 6, the treatment equipment will be severely corroded; if the pH is adjusted above 9, the amount of alkaline solution used will increase, raising the treatment cost. Therefore, a pH of 6-9 is desirable, preferably 6.5-8.5, and more preferably 6.8-8.0.

[0051] The alkaline solution mentioned is a sodium hydroxide solution with a concentration of 30-50% by weight. Subsequent alkaline solutions used will all be aqueous sodium hydroxide solutions of the above concentration, and therefore will not be described further below.

[0052] According to the present invention, two heating methods are used in step B, filtrate heating. One heating method uses brine discharged from the top of the heterogeneous Fenton reaction tower 6 as a heat exchange medium to raise the temperature of the filtrate from step A to 80-120°C. In this heating method, the filtrate from step A is heated and its temperature is accurately controlled within the range of 80-120°C through heat exchange. The other heating method uses high-temperature steam from the steam heater 5 as a heat exchange medium to raise the temperature of the filtrate to 120-150°C. In this heating method, the filtrate at 80-120°C is heated and its temperature is accurately controlled within the range of 120-150°C through heat exchange or thermal radiation.

[0053] The heat exchanger 4 used in this invention is a plate heat exchanger, shell-and-tube heat exchanger, spiral plate heat exchanger, or coaxial heat exchanger. These are all products currently sold on the market, such as plate heat exchangers sold by Jiangsu Ruiyi Co., Ltd. under the trade name "plate heat exchanger," shell-and-tube heat exchangers sold by Jiangsu Ruiyi Co., Ltd. under the trade name "shell-and-tube heat exchanger," spiral plate heat exchangers sold by Jiangsu Ruiyi Co., Ltd. under the trade name "spiral plate heat exchanger," and coaxial heat exchangers sold by Jiangsu Ruiyi Co., Ltd. under the trade name "coaxial heat exchanger."

[0054] The steam heater 5 used in this invention is a Venturi jet mixer, a shell-and-tube heat exchanger, a plate steam heat exchanger, or a steam coil heat exchanger. These are all products currently sold on the market. For example, the Venturi jet mixer sold by Yutai Environmental Protection Co., Ltd. under the trade name Venturi jet mixer, the shell-and-tube heat exchanger sold by Jiangsu Ruiyi Co., Ltd. under the trade name shell-and-tube heat exchanger, the plate steam heat exchanger sold by Jiangsu Ruiyi Co., Ltd. under the trade name plate steam heat exchanger, and the steam coil heat exchanger sold by Jiangsu Ruiyi Co., Ltd. under the trade name steam coil heat exchanger.

[0055] The heterogeneous Fenton reactor 6 is a vertical cylindrical reactor with a uniform water distribution zone, a fixed packing zone, and an outlet zone. The uniform water distribution zone is located between the bottom of the tower and the catalyst bed, and its structure is a six-claw flange lower water distributor. The fixed packing zone consists of 2 to 4 layers of catalyst bed, with each layer spaced 0.5 to 1.5 meters apart. Except for the bottom catalyst bed, the remaining beds are equipped with hydrogen peroxide and alkali feeders and distributors at the wastewater inlet. The feeders have a built-in static mixer inlet, and the distributors have a six-claw side-mounted lower water distributor structure. The outlet zone is located at the top of the tower and its structure consists of a shut-off valve and a gas-liquid separator.

[0056] The heterogeneous Fenton reaction tower 6 used in this invention is a product currently sold on the market, such as the heterogeneous Fenton reaction tower sold by Zhejiang Deqiang Technology Co., Ltd.

[0057] C. High-temperature heterogeneous Fenton reaction

[0058] In the heterogeneous Fenton reaction tower 6, the pH of the heated filtrate from step B is adjusted to 3-5 with an alkaline solution. Then, the heated filtrate is reacted with a hydrogen peroxide solution with a concentration of 27.5%-30.0% by volume at a volume ratio of 1:0.005-0.04, a temperature of 130-160℃, and a pressure of 0.5-0.8MPa in the presence of a catalyst to carry out a high-temperature heterogeneous Fenton reaction for 10-60 min.

[0059] According to the present invention, the high-temperature heterogeneous Fenton reaction should be understood as a combination of direct oxidation of hydrogen peroxide and indirect oxidation of hydrogen peroxide via hydroxyl radicals, and the specific chemical reaction formula is as follows:

[0060] C x H y O z + H2O2 → CO2 + H2O

[0061] H2O2 →·OH

[0062] C x H y O z + ·OH → CO2 + H2O

[0063] H2O2 → H2O + O2

[0064] In this step, the catalyst is a granular, honeycomb, or corrugated catalyst in which Mn, Ce, Pt, and Ru oxide active components are supported on ceramics, cordierite, or corundum. The catalysts used in this invention are all commercially available products, such as the precious metal-supported granular catalyst sold by Jiangxi Huihua Technology Co., Ltd. under the trade name "Precious Metal Ceramic Ball Particles," the precious metal-supported honeycomb catalyst sold by Jiangxi Huihua Technology Co., Ltd. under the trade name "Precious Metal Honeycomb Catalyst," and the precious metal-supported corrugated catalyst sold by Jiangxi Huihua Technology Co., Ltd. under the trade name "Precious Metal Corrugated Catalyst."

[0065] In the heterogeneous Fenton reaction tower 6, the alkaline solution adjusts the pH of the heated filtrate from step B to 3-5. If the pH of the heated filtrate is adjusted below 3, it will aggravate the corrosion of the equipment and is not conducive to the stability of hydrogen peroxide; if the pH of the heated filtrate is adjusted above 5, the stability of hydrogen peroxide will decrease and self-decomposition will be accelerated. Therefore, adjusting the pH of the heated filtrate to 3-5 is appropriate, preferably 3.4-4.6, and more preferably 3.6-4.2.

[0066] The concentration of hydrogen peroxide solution used in high-temperature heterogeneous Fenton reactions is 27.5%–30.0% by volume. Exceeding this concentration range is unacceptable, as this is the standard concentration for commercially available products. A 50% concentration of hydrogen peroxide solution poses a danger in use and storage; an 8% concentration results in large quantities of hydrogen peroxide required and high investment costs for treatment equipment.

[0067] In the high-temperature heterogeneous Fenton reaction of the present invention, when the temperature, pressure and time of the high-temperature heterogeneous Fenton reaction are within the specified range, if the volume ratio of the heated filtrate to the hydrogen peroxide solution is higher than 1:0.005, the hydrogen peroxide feed is too low, and its oxidation effect is insufficient; if the volume ratio of the heated filtrate to the hydrogen peroxide solution is less than 1:0.04, the hydrogen peroxide feed concentration is high, self-decomposition is aggravated, and utilization efficiency is reduced; therefore, a volume ratio of 1:0.005 to 0.04 for the heated filtrate to the hydrogen peroxide solution is reasonable, preferably 1:0.008 to 0.035, and more preferably 1:0.012 to 0.030.

[0068] Similarly, when the volume ratio of the heated filtrate to the hydrogen peroxide solution, the pressure, and the time are within the aforementioned range, if the high-temperature heterogeneous Fenton reaction temperature is below 130°C, the oxidation effect is poor; if the high-temperature heterogeneous Fenton reaction temperature is above 160°C, the self-decomposition of hydrogen peroxide intensifies, and the utilization rate decreases; therefore, a high-temperature heterogeneous Fenton reaction temperature of 130–160°C is appropriate, preferably 135–155°C, and more preferably 140–152°C.

[0069] When the volume ratio of the heated filtrate to the hydrogen peroxide solution, the temperature, and the time are within the aforementioned ranges, if the high-temperature heterogeneous Fenton reaction pressure is below 0.5 MPa, the inhibitory effect on the self-decomposition of hydrogen peroxide decreases; if the high-temperature heterogeneous Fenton reaction pressure is above 0.8 MPa, the requirements for the equipment become higher, and the safety risks increase. Therefore, a high-temperature heterogeneous Fenton reaction pressure of 0.5~0.8 MPa is suitable, preferably 0.56~0.75 MPa, and more preferably 0.60~0.70 MPa.

[0070] When the volume ratio of the heated filtrate to the hydrogen peroxide solution, the temperature, and the pressure are within the aforementioned ranges, if the high-temperature heterogeneous Fenton reaction time is less than 10 min, the heterogeneous Fenton reaction will be incomplete and the oxidation effect will be poor; if the high-temperature heterogeneous Fenton reaction time is longer than 60 min, the heterogeneous Fenton reaction efficiency will be low and the equipment investment will increase. Therefore, a high-temperature heterogeneous Fenton reaction time of 10–60 min is appropriate, preferably 18–52 min, and more preferably 24–46 min.

[0071] Preferably, the heated filtrate and hydrogen peroxide solution are subjected to a high-temperature heterogeneous Fenton reaction for 18 to 52 minutes at a volume ratio of 1:0.008 to 0.035, a temperature of 135 to 155°C, and a pressure of 0.56 to 0.75 MPa.

[0072] More preferably, the heated filtrate and hydrogen peroxide solution are subjected to a high-temperature heterogeneous Fenton reaction for 24 to 46 minutes at a volume ratio of 1:0.012 to 0.030, a temperature of 140 to 152°C, and a pressure of 0.60 to 0.70 MPa.

[0073] D. Deep Purification

[0074] In the fluidized bed reactor 7, ozone, catalyst slurry and heat exchange oxidation tailwater from step B are reacted with the heat exchange oxidation tailwater at a volume ratio of 0.5-5.0:0.001-0.05:1.0, with a solid content of 1-20% by weight of catalyst slurry, for 30-120 minutes. After the reaction is completed, the oxidation tailwater is discharged from the top of the tower. A small amount of reducing agent is then added to remove residual oxidizing particles in the oxidation tailwater. The catalyst is then recovered through a bag filter 8, and the clarified oxidation tailwater is discharged.

[0075] In this step, ozone, catalyst slurry, and heat exchange oxidation tailwater react in the presence of catalyst slurry at a volume ratio of 0.5–5.0:0.001–0.05:1.0 for 30–120 min.

[0076] The ozone concentration is 80~300 mg / L. If the ozone concentration is below 80 mg / L, the ozone oxidation effect is poor; if the ozone concentration is above 300 mg / L, the ozone load increases, and the equipment investment cost is high. Therefore, an ozone concentration of 80~300 mg / L is suitable, preferably 120~260 mg / L, and more preferably 145~230 mg / L.

[0077] The catalyst slurry is one or more catalyst slurries selected from FeOOH, Fe2O3, Fe3O4, MgFe2O4, CaFe2O4, MgO, or CaOH2, and the solid content of the catalyst slurry is 1-20% by weight. The FeOOH, Fe2O3, Fe3O4, MgFe2O4, CaFe2O4, MgO, or CaOH2 used in this invention are all commercially available products, such as FeOOH sold by Zhejiang Deqiang Technology Co., Ltd. under the trade name "ferric hydroxide," Fe3O4 sold by Zhejiang Deqiang Technology Co., Ltd. under the trade name "iron oxide spinel," MgFe2O4 sold by Zhejiang Deqiang Technology Co., Ltd. under the trade name "magnesium iron spinel," CaFe2O4 sold by Zhejiang Deqiang Technology Co., Ltd. under the trade name "calcium iron spinel," and MgO sold by Zhejiang Deqiang Technology Co., Ltd. under the trade name "magnesium oxide."

[0078] In this step, when the amounts of catalyst slurry, heat exchange oxidation tailwater, and reaction time are within the specified range, if the ozone dosage is less than 0.5, the ozone feed will be insufficient, resulting in inadequate oxidation; if the ozone dosage is greater than 5.0, the ozone feed will be excessive, increasing treatment costs. Therefore, an ozone dosage of 0.5 to 5.0 is reasonable, preferably 1.2 to 4.2, and more preferably 1.8 to 3.6.

[0079] When the dosage of ozone and the amount of heat exchange oxidation tailwater are within the range described, and the reaction time is within the range described, if the amount of catalyst slurry is less than 0.001, the amount of catalyst added will increase, and the equipment investment will increase; if the amount of catalyst slurry is more than 0.05, the slurry will be difficult to transport and the dispersibility will be poor. Therefore, the amount of catalyst slurry is appropriate to be 0.001 to 0.05, preferably 0.006 to 0.045, and more preferably 0.010 to 0.040.

[0080] When the ozone, catalyst slurry, and heat exchange oxidation tailwater are within the aforementioned range, if the reaction time is less than 30 min, the reaction is insufficient and the oxidation effect is poor; if the reaction time is longer than 120 min, the oxidation time is long and the efficiency is reduced. Therefore, a reaction time of 30 to 120 min is suitable, preferably 45 to 100 min, and more preferably 55 to 92 min.

[0081] After the reaction is complete, the oxidation tailwater is discharged from the top of the fluidized bed reactor 7. A small amount of reducing agent is then added to remove any remaining oxidizing particles in the tailwater. The reducing agent is one or more selected from ferrous chloride, ferrous sulfate, sulfurous acid, sodium sulfite, or ammonium sulfite. These are all commercially available products, such as ferrous chloride sold by Zhejiang Deqiang Technology Co., Ltd. under the trade name ferrous chloride, and sodium sulfite sold by Zhejiang Deqiang Technology Co., Ltd. under the trade name sodium sulfite.

[0082] Next, the oxidation tailwater, after removing oxidizing particles, is filtered through bag filter 8 to recover the catalyst, and then the clarified oxidation tailwater is discharged.

[0083] The fluidized bed reactor 7 is a vertical cylindrical reactor with a uniform water and gas distribution structure. The fluidized bed reactor 7 used in this invention is a product currently sold on the market, such as the product sold by Zhejiang Deqiang Technology Co., Ltd. under the trade name Fluidized Bed Reactor.

[0084] The bag filter 8 is a filter bag made of polyphenylene sulfide (PPS), polyimide P84, polytetrafluoroethylene (PTFE), or aramid material with mesh sizes of 200 mesh, 400 mesh, and 1000 mesh. The bag filter 8 used in this invention is a product currently sold on the market, such as PPS (polyphenylene sulfide) sold by Hebei Baize Environmental Protection Equipment Co., Ltd. under the trade name PPS chlorination, P84 (polyimide P84) sold by Hebei Baize Environmental Protection Equipment Co., Ltd. under the trade name P84 filter bag, PTFE (polytetrafluoroethylene) sold by Hebei Baize Environmental Protection Equipment Co., Ltd. under the trade name PTFE filter bag, and aramid material filters sold by Hebei Baize Environmental Protection Equipment Co., Ltd. under the trade name aramid filter bag.

[0085] According to the standard analytical method described above, the discharged clarified oxidation tailwater contains less than 18% CaCl2, less than 0.001% glycerol, less than 0.001% chloropropanol and less than 20 mg / L of organic matter (TOC) by weight, and the pH value is 6-9.

[0086] [Beneficial Effects]

[0087] The beneficial technical effects of this invention are as follows: Hydrogen peroxide is stabilized and its self-decomposition is reduced by increasing the oxygen partial pressure in the reaction tower and adjusting the pH of the brine; the reaction rate is increased by conducting the reaction at a higher temperature. A heat exchange system is used to recover heat from the oxidation tailwater, reducing energy consumption for heating the influent. After the high-temperature heterogeneous Fenton reaction, residual hydrogen peroxide in the water is further catalytically oxidized in a weakly alkaline environment by supplementing ozone, decomposing the residual hydrogen peroxide and further reducing organic matter in the brine. Finally, a reducing agent is added to eliminate residual oxidizing species in the water, and the catalyst from the secondary reaction tower is recovered using a filter. This method can rapidly and efficiently oxidize organic matter in brine, improving the utilization efficiency of hydrogen peroxide, and is a novel treatment method for epichlorohydrin calcium chloride brine. Attached Figure Description

[0088] Appendix Figure 1 This is a schematic diagram of the process for treating calcium chloride wastewater discharged from the epichlorohydrin production process according to the present invention.

[0089] In the picture:

[0090] 1-Equalization tank, 11-Wastewater inlet, 12-Acid solution inlet, 13-Wastewater outlet; 2-Coagulation tank, 21-Acid-equalized wastewater inlet, 22-Coagulant inlet, 23-Mixed mixture outlet; 3-Plate and frame filter, 31-Mixed wastewater inlet, 32-Filter cake outlet, 33-Filtrate outlet; 4-Heat exchanger, 41-Pipeline mixer, 42-Filtrate inlet, 43-Heated filtrate outlet, 44-Equalized brine inlet, 45-Heat exchange oxidation tailwater outlet; 5-Steam heater, 51-Heated filtrate inlet, 5 2-Steam inlet, 53-Reheated filtrate outlet; 6-Heterogeneous Fenton reactor, 61-Reheated filtrate inlet, 62-Hydrogen peroxide inlet, 63-Compressed air inlet, 64-Alkali outlet, 65-Brine outlet; 7-Fluorescent bed reactor, 71-Heat exchange oxidation tailwater inlet, 72-Ozone inlet, 73-Catalyst inlet, 74-Reaction oxidation tailwater outlet; 8-Bag filter, 81-Reaction oxidation tailwater inlet, 82-Reducing agent inlet, 83-Clarified oxidation tailwater outlet, 84-Catalyst outlet. Detailed Implementation

[0091] The invention will be better understood through the following examples.

[0092] Example 1: Treatment of calcium chloride wastewater discharged from epichlorohydrin production process

[0093] The processing steps of this method are as follows:

[0094] A. Pretreatment of calcium chloride wastewater

[0095] The epichlorohydrin production process used in this embodiment discharges calcium chloride wastewater containing 16% CaCl2, 0.08% glycerol, 0.30% chloropropanol and 2900 mg / L of organic matter (TOC) by weight, with a pH of 13.0.

[0096] The calcium chloride wastewater is fed to wastewater inlet 11 located on the wall of equalization tank 1. Simultaneously, a 22% (by weight) hydrochloric acid aqueous solution is fed to acid solution inlet 12 located at the top of equalization tank 1. This hydrochloric acid aqueous solution neutralizes the pH of the calcium chloride wastewater to 8.0. The wastewater is then fed to acid-balanced wastewater inlet 21 located on the wall of coagulation tank 2. Simultaneously, a 0.4% (by weight) polyferric aluminum sulfate coagulant solution is fed to coagulant inlet 22 located at the top of coagulation tank 2. The amount of coagulant solution used is equal to the amount of calcium chloride wastewater. 2.0% by volume; In coagulation tank 2, calcium chloride wastewater and coagulant are stirred and mixed for 50 minutes. The resulting mixture is discharged from mixture outlet 23 and then sent through a pipeline to mixture inlet 31 located in the middle of the side wall of plate and frame filter 3 for filtration. The resulting filtrate is discharged from filtrate outlet 33 and adjusted to pH 3.0 in pipeline mixer 41 with hydrochloric acid aqueous solution with a concentration of 22% by weight. It is then sent to subsequent processing steps. The resulting filter cake is discharged outside the boundary from filter cake outlet 32 ​​for solid waste treatment.

[0097] B. Heating the filtrate

[0098] The filtrate from step A is fed into the plate heat exchanger 4 through the filtrate inlet 42 at the bottom of the plate heat exchanger 4. The brine discharged from the brine outlet 65 at the top of the heterogeneous Fenton reaction tower 6 has its pH adjusted to 8.0 by a 50% sodium hydroxide alkaline solution from the alkaline outlet 64. This adjusted brine is then sent as oxidation tailwater to the adjusted brine inlet 44 at the top of the heat exchanger 4, where it exchanges heat with the filtrate, raising its temperature to 106°C. The heated filtrate is then sent from the heated filtrate outlet 43 at the top of the heat exchanger 4 to the heated filtrate inlet 51 at the top of the Venturi jet mixer steam heater 5. The filtrate is reheated to 150°C by exchanging heat with high-temperature steam in steam heater 5. It is then discharged from reheated filtrate outlet 53 at the bottom of steam heater 5 and enters the heterogeneous Fenton reactor 6 through reheated filtrate inlet 61 at the bottom of the reactor. At the same time, a portion of hydrogen peroxide enters the heterogeneous Fenton reactor 6 through hydrogen peroxide inlet 62 at the middle of the reactor, and the remaining portion enters the reactor through reheated filtrate inlet 61. The heat exchange oxidation tailwater, which has dropped to 56°C, is sent through a pipeline from heat exchange oxidation tailwater outlet 45 at the bottom of heat exchanger 4 to heat exchange oxidation tailwater inlet 71 at the bottom of fluidized bed reactor 7.

[0099] C. High-temperature heterogeneous Fenton reaction

[0100] In the heterogeneous Fenton reaction tower 6, the pH of the reheated filtrate from step B was adjusted to 5.0 by weight using a 50% sodium hydroxide alkaline solution. The reheated filtrate was then reacted with a 28.4% hydrogen peroxide aqueous solution at a volume ratio of 1:0.040, a temperature of 140°C, and a pressure of 0.7 MPa in the presence of a particulate catalyst with Mn oxide active components supported on a ceramic substrate for 60 min.

[0101] D. Deep Purification

[0102] In the fluidized bed reactor 7, ozone, catalyst slurry, and heat exchange oxidation tailwater from step B are reacted with the heat exchange oxidation tailwater at a volume ratio of 3.5:0.034:1.0, with the catalyst slurry containing 8% FeOOH solids by weight. The reaction is carried out for 90 minutes. After the reaction is completed, the reaction oxidation tailwater is discharged from the reaction oxidation tailwater outlet 74 located at the top of the fluidized bed reactor 7 and sent to the reaction oxidation tailwater inlet 81 of the bag filter 8 made of polyphenylene sulfide (PPS) with a filter bag mesh of 200 mesh. At the same time, a small amount of ferrous chloride reducing agent is added through the reducing agent inlet 82 to remove residual oxidizing particles in the reaction oxidation tailwater. Then, the catalyst is recovered through the catalyst outlet 84 of the bag filter 8, and the clarified oxidation tailwater is discharged through the clarified oxidation tailwater outlet 83.

[0103] According to the standard analytical method described in this application, the discharged clarified oxidation effluent contains 16.4% CaCl2, 0.0005% glycerol, 0.0002% chloropropanol and 18 mg / L of organic matter (TOC) by weight, and has a pH of 8.2.

[0104] Example 2: Treatment of calcium chloride wastewater discharged from epichlorohydrin production process

[0105] The processing steps of this method are as follows:

[0106] A. Pretreatment of calcium chloride wastewater

[0107] According to the standard analytical method described in this application, the calcium chloride wastewater discharged from the epichlorohydrin production process used in this embodiment contains 18% CaCl2, 0.01% glycerol, 0.01% chloropropanol and 1800 mg / L of organic matter TOC by weight, and the pH value is 12.0.

[0108] The calcium chloride wastewater is fed to wastewater inlet 11 located on the wall of equalization tank 1. Simultaneously, a 5% (by weight) hydrochloric acid aqueous solution is fed to acid solution inlet 12 located at the top of equalization tank 1. This hydrochloric acid aqueous solution neutralizes the pH of the calcium chloride wastewater to 6.0. The wastewater is then fed to acid-balanced wastewater inlet 21 located on the wall of coagulation tank 2. Simultaneously, a 0.1% (by weight) polyferric chloride coagulant solution is fed to coagulant inlet 22 located at the top of coagulation tank 2. The amount of coagulant solution used is equal to the volume of calcium chloride wastewater. The volume is 3.0%; in coagulation tank 2, calcium chloride wastewater and coagulant are stirred and mixed for 30 minutes. The resulting mixture is discharged from the mixture outlet 23 and then sent through a pipeline to the mixture inlet 31 located in the middle of the side wall of plate and frame filter 3 for filtration. The resulting filtrate is discharged from the filtrate outlet 33 and adjusted to pH 3.6 in the pipeline mixer 41 with a 5% hydrochloric acid aqueous solution by weight before being sent to the subsequent processing steps. The resulting filter cake is discharged outside the boundary from the filter cake outlet 32 ​​for solid waste treatment.

[0109] B. Heating the filtrate

[0110] The filtrate from step A is sent to the filtrate inlet 42 at the bottom of the shell-and-tube heat exchanger 4. The brine discharged from the brine outlet 65 at the top of the heterogeneous Fenton reaction tower 6 has its pH adjusted to 6.0 by a 30% sodium hydroxide alkaline solution from the alkaline outlet 64. The adjusted brine is then sent as oxidation tailwater to the adjusted brine inlet 44 at the top of the heat exchanger 4, where it exchanges heat with the filtrate to raise its temperature to 80°C. The heated filtrate is then sent from the heated filtrate outlet 43 at the top of the heat exchanger 4 to the heated filtrate inlet 51 at the top of the steam heater 5 of the shell-and-tube heat exchanger. The filtrate is reheated to 120°C by heat exchange with high-temperature steam in steam heater 5. It is then discharged from reheated filtrate outlet 53 at the bottom of steam heater 5 and enters the heterogeneous Fenton reactor 6 through reheated filtrate inlet 62 at the bottom of the reactor. At the same time, a portion of hydrogen peroxide enters the heterogeneous Fenton reactor 6 through hydrogen peroxide inlet 61 at the middle of the reactor. The remaining portion of hydrogen peroxide enters the reactor through reheated filtrate inlet 61. The heat exchange oxidation tailwater, which has dropped to 30°C, is sent through a pipeline from heat exchange oxidation tailwater outlet 45 at the bottom of heat exchanger 4 to heat exchange oxidation tailwater inlet 71 at the bottom of fluidized bed reactor 7.

[0111] C. High-temperature heterogeneous Fenton reaction

[0112] In the heterogeneous Fenton reaction tower 6, the pH of the reheated filtrate from step B was adjusted to 3.0 by weight using a 30% sodium hydroxide alkaline solution. The reheated filtrate was then reacted with a 29.2% hydrogen peroxide aqueous solution at a volume ratio of 1:0.016, a temperature of 130°C, and a pressure of 0.5 MPa in the presence of a honeycomb catalyst with Ce oxide active components supported on cordierite for 10 min.

[0113] D. Deep Purification

[0114] In the fluidized bed reactor 7, ozone, catalyst slurry, and heat exchange oxidation tailwater from step B are reacted with the heat exchange oxidation tailwater at a volume ratio of 0.5:0.001:1.0, with the catalyst slurry containing 14% Fe3O4 solids by weight. The reaction is carried out for 60 minutes. After the reaction is completed, the reaction oxidation tailwater is discharged from the reaction oxidation tailwater outlet 74 located at the top of the fluidized bed reactor 7 and sent to the reaction oxidation tailwater inlet 81 of the bag filter 8 made of polyimide P84 material with a filter bag mesh of 400 mesh. At the same time, a small amount of ferrous sulfate reducing agent is added through the reducing agent inlet 82 to remove residual oxidizing particles in the reaction oxidation tailwater. Then, the catalyst is recovered through the catalyst outlet 84 of the bag filter 8, and the clarified oxidation tailwater is discharged through the clarified oxidation tailwater outlet 83.

[0115] According to the standard analytical method described in this application, the discharged clarified oxidation effluent contains 18.2% CaCl2, 0.0010% glycerol, 0.0008% chloropropanol and 20 mg / L of organic matter (TOC) by weight, and has a pH of 6.0.

[0116] Example 3: Treatment of calcium chloride wastewater discharged from epichlorohydrin production process

[0117] The processing steps of this method are as follows:

[0118] A. Pretreatment of calcium chloride wastewater

[0119] According to the standard analytical method described in this application, the calcium chloride wastewater discharged from the epichlorohydrin production process used in this embodiment contains 17% CaCl2, 0.14% glycerol, 0.10% chloropropanol and 4000 mg / L of organic matter TOC by weight, and the pH value is 12.4.

[0120] The calcium chloride wastewater is fed to wastewater inlet 11 located on the wall of equalization tank 1. Simultaneously, a 14% (by weight) hydrochloric acid aqueous solution is fed to acid solution inlet 12 located at the top of equalization tank 1. This hydrochloric acid aqueous solution neutralizes the pH of the calcium chloride wastewater to 6.6. The wastewater is then fed to acid-balanced wastewater inlet 21 located on the wall of coagulation tank 2. Simultaneously, a 0.7% (by weight) polyaluminum chloride coagulant solution is fed to coagulant inlet 22 located at the top of coagulation tank 2. The amount of coagulant solution used is equal to the volume of calcium chloride wastewater. 1.0% of the volume; In coagulation tank 2, calcium chloride wastewater and coagulant are stirred and mixed for 40 minutes. The resulting mixture is discharged from the mixture outlet 23 and then sent through a pipeline to the mixture inlet 31 located in the middle of the side wall of the plate and frame filter 3 for filtration. The resulting filtrate is discharged from the filtrate outlet 33 and adjusted to pH 4.2 in the pipeline mixer 41 with a hydrochloric acid aqueous solution with a concentration of 14% by weight before being sent to the subsequent processing steps. The resulting filter cake is discharged outside the boundary from the filter cake outlet 32 ​​for solid waste treatment.

[0121] B. Heating the filtrate

[0122] The filtrate from step A is fed into the spiral plate heat exchanger 4 through the filtrate inlet 42 at the bottom of the spiral plate heat exchanger 4. The brine discharged from the brine outlet 65 at the top of the heterogeneous Fenton reaction tower 6 has its pH adjusted to 9.0 by a 36% (by weight) sodium hydroxide alkaline solution from the alkaline outlet 64. This adjusted brine is then sent as oxidation tailwater to the adjusted brine inlet 44 at the top of the heat exchanger 4, where it exchanges heat with the filtrate, raising its temperature to 94°C. The heated filtrate is then sent from the heated filtrate outlet 43 at the top of the heat exchanger 4 to the heated filtrate inlet 5 at the top of the plate steam heat exchanger steam heater 5. 1. The filtrate is reheated to 140°C by heat exchange with high-temperature steam in steam heater 5. It is then discharged from reheated filtrate outlet 53 at the bottom of steam heater 5 and enters the heterogeneous Fenton reactor 6 through reheated filtrate inlet 62 at the bottom of the reactor. At the same time, a portion of hydrogen peroxide enters the heterogeneous Fenton reactor 6 through hydrogen peroxide inlet 61 in the middle of the reactor. The remaining portion of hydrogen peroxide enters the reactor through reheated filtrate inlet 61. The heat exchange oxidation tailwater with a temperature reduced to 44°C is sent to heat exchange oxidation tailwater inlet 71 at the bottom of fluidized bed reactor 7 through a pipeline from heat exchange oxidation tailwater outlet 45 at the bottom of heat exchanger 4.

[0123] C. High-temperature heterogeneous Fenton reaction

[0124] In the heterogeneous Fenton reaction tower 6, the pH of the reheated filtrate from step B was adjusted to 3.6 by weight with a sodium hydroxide alkaline solution of 36% by weight. The reheated filtrate and hydrogen peroxide solution of 27.5% by volume were then subjected to a high-temperature heterogeneous Fenton reaction for 26 min in the presence of a corrugated catalyst with Pt oxide active components supported on corundum at a volume ratio of 1:0.005, a temperature of 150°C and a pressure of 0.6 MPa.

[0125] D. Deep Purification

[0126] In the fluidized bed reactor 7, ozone, catalyst slurry, and heat exchange oxidation tailwater from step B are reacted with the heat exchange oxidation tailwater at a volume ratio of 5.0:0.050:1.0, with the catalyst slurry containing 20% ​​MgFe2O4 solids by weight, for 30 minutes. After the reaction, the reaction oxidation tailwater is discharged from the reaction oxidation tailwater outlet 74 located at the top of the fluidized bed reactor 7 and sent to the reaction oxidation tailwater inlet 81 of a 1000-mesh bag filter made of polytetrafluoroethylene (PTFE). At the same time, a small amount of sodium sulfite reducing agent is added through the reducing agent inlet 82 to remove residual oxidizing particles in the reaction oxidation tailwater. Then, the catalyst is recovered through the catalyst outlet 84 of the bag filter 8, and the clarified oxidation tailwater is discharged through the clarified oxidation tailwater outlet 83.

[0127] According to the standard analytical method described in this application, the discharged clarified oxidation effluent contains 17.6% CaCl2, 0.0008% glycerol, 0.0006% chloropropanol and 15 mg / L of organic matter (TOC) by weight, and has a pH of 7.2.

[0128] Example 4: Treatment of calcium chloride wastewater discharged from epichlorohydrin production process

[0129] The processing steps of this method are as follows:

[0130] A. Pretreatment of calcium chloride wastewater

[0131] According to the standard analytical method described in this application, the calcium chloride wastewater discharged from the epichlorohydrin production process used in this embodiment contains 15% CaCl2, 0.20% glycerol, 0.20% chloropropanol and 800 mg / L of organic matter TOC by weight, and the pH value is 12.6.

[0132] The calcium chloride wastewater is fed to wastewater inlet 11 located on the wall of equalization tank 1. Simultaneously, a 30% (by weight) hydrochloric acid aqueous solution is fed to acid solution inlet 12 located at the top of equalization tank 1. This hydrochloric acid aqueous solution neutralizes the pH of the calcium chloride wastewater to 7.4. The wastewater is then fed to acid-balanced wastewater inlet 21 located on the wall of coagulation tank 2. Simultaneously, a 1.0% (by weight) polyacrylamide coagulant solution is fed to coagulant inlet 22 located at the top of coagulation tank 2. The amount of coagulant solution used is equal to the volume of calcium chloride wastewater. 0.1% of the volume; In coagulation tank 2, calcium chloride wastewater and coagulant are stirred and mixed for 60 minutes. The resulting mixture is discharged from the mixture outlet 23 and then sent through a pipeline to the mixture inlet 31 located in the middle of the side wall of the plate and frame filter 3 for filtration. The resulting filtrate is discharged from the filtrate outlet 33 and adjusted to pH 5.0 in the pipeline mixer 41 with a 30% hydrochloric acid aqueous solution by weight before being sent to subsequent processing steps. The resulting filter cake is discharged outside the boundary from the filter cake outlet 32 ​​for solid waste treatment.

[0133] B. Heating the filtrate

[0134] The filtrate from step A enters the shell-and-tube heat exchanger 4 through the filtrate inlet 42 at the bottom. The brine discharged from the brine outlet 65 at the top of the heterogeneous Fenton reaction tower 6 has its pH adjusted to 7.0 by a 44% (by weight) sodium hydroxide alkaline solution from the alkaline outlet 64. This adjusted brine, as oxidation tailwater, is then sent to the adjusted brine inlet 44 at the top of the heat exchanger 4. It exchanges heat with the filtrate in the heat exchanger 4, raising its temperature to 120°C. The heated filtrate is then sent from the heated filtrate outlet 43 at the top of the heat exchanger 4 to the heated filtrate inlet 51 at the top of the steam heater 5 of the steam coil heat exchanger. The filtrate is reheated to 130°C by exchanging heat with high-temperature steam in steam heater 5. It is then discharged from reheated filtrate outlet 53 at the bottom of steam heater 5 and enters the heterogeneous Fenton reactor 6 through pipeline via reheated filtrate inlet 61 at the bottom of the reactor. At the same time, a portion of hydrogen peroxide enters the heterogeneous Fenton reactor 6 through hydrogen peroxide inlet 61 at the middle of the reactor, and the remaining portion enters the reactor through reheated filtrate inlet 61. The heat exchange oxidation tailwater, which has dropped to 70°C, is sent through pipeline from heat exchange oxidation tailwater outlet 45 at the bottom of heat exchanger 4 to heat exchange oxidation tailwater inlet 71 at the bottom of fluidized bed reactor 7.

[0135] C. High-temperature heterogeneous Fenton reaction

[0136] In the heterogeneous Fenton reaction tower 6, the pH of the reheated filtrate from step B was adjusted to 4.4 with a sodium hydroxide alkaline solution of 44% by weight. The reheated filtrate and hydrogen peroxide solution of 30.0% by volume were then subjected to a high-temperature heterogeneous Fenton reaction for 44 min in the presence of a particulate catalyst with Ru oxide active component supported on ceramic at a volume ratio of 1:0.028, a temperature of 160°C and a pressure of 0.8 MPa.

[0137] D. Deep Purification

[0138] In the fluidized bed reactor 7, ozone, catalyst slurry, and heat exchange oxidation tailwater from step B are reacted with the heat exchange oxidation tailwater at a volume ratio of 2.0:0.016:1.0, with the presence of catalyst slurry containing 1% CaFe2O4 solids by weight, for 120 minutes. After the reaction, the reaction oxidation tailwater is discharged from the reaction oxidation tailwater outlet 74 located at the top of the fluidized bed reactor 7 and sent to the reaction oxidation tailwater inlet 81 of a 200-mesh bag filter made of aramid material. At the same time, a small amount of ammonium sulfite reducing agent is added through the reducing agent inlet 82 to remove residual oxidizing particles in the reaction oxidation tailwater. Then, the catalyst is recovered through the catalyst outlet 84 of the bag filter 8, and the clarified oxidation tailwater is discharged through the clarified oxidation tailwater outlet 83.

[0139] According to the standard analytical method described in this application, the discharged clarified oxidation effluent contains 15.8% CaCl2, 0.0003% glycerol, 0.0010% chloropropanol and 12 mg / L of organic matter (TOC) by weight, and has a pH of 9.0.

Claims

1. A method for treating calcium chloride wastewater discharged from the epichlorohydrin production process, characterized in that... The processing steps of this method are as follows: A. Pretreatment of calcium chloride wastewater The calcium chloride wastewater is sent to the equalization tank (1), where the pH of the wastewater is neutralized to 6.0-8.0 using an acid solution. Then it is sent to the coagulation tank (2), where a coagulant is added and the mixture is stirred for 30-60 minutes. The resulting mixture is then sent through a pipeline to a plate and frame filter (3) for filtration. The pH of the resulting filtrate is adjusted to 3-5 using an acid solution before being sent to subsequent processing steps. The resulting filter cake is discharged outside the site for solid waste treatment. B. Heating the filtrate The filtrate from step A is sent to the bottom of the heat exchanger (4) and exchanged with the brine with pH adjusted to 6-9 by an alkaline solution discharged from the top of the heterogeneous Fenton reaction tower (6) as oxidation tail water. The temperature of the filtrate is raised to 80-120°C. Then it enters the steam heater (5) to exchange with high-temperature steam, thereby heating the filtrate to 120-150°C. Then it enters the heterogeneous Fenton reaction tower (6) through a pipe. The heat exchange oxidation tail water with the temperature dropped to 30-70°C is sent from the bottom of the heat exchanger (4) to the bottom of the fluidized bed reaction tower (7) through a pipe. C. High-temperature heterogeneous Fenton reaction In the heterogeneous Fenton reaction tower (6), the pH of the heated filtrate from step B is adjusted to 3-5 by alkaline solution. Then, the heated filtrate and a hydrogen peroxide solution with a concentration of 27.5%-30.0% by volume are reacted in the presence of a catalyst at a volume ratio of 1:0.005-0.04, a temperature of 130-160℃ and a pressure of 0.5-0.8MPa for 10-60 min. D. Deep Purification In the fluidized bed reactor (7), ozone, catalyst slurry and heat exchange oxidation tailwater from step B are reacted with the heat exchange oxidation tailwater at a volume ratio of 0.5-5.0:0.001-0.05:1.0, with a solid content of 1-20% by weight of catalyst slurry, for 30-120 min. After the reaction is completed, the oxidation tailwater is discharged from the top of the tower. A small amount of reducing agent is added to remove residual oxidizing particles in the oxidation tailwater. Then, the catalyst is recovered through a bag filter (8) and the clarified oxidation tailwater is discharged.

2. The processing method according to claim 1, characterized in that... In step A, the calcium chloride wastewater discharged from the epichlorohydrin production process contains 14-18% CaCl2, 0.01-0.20% glycerol, 0.01-0.30% chloropropanol and 800-4000 mg / L of organic matter TOC by weight, and has a pH value of 12.0-13.

0.

3. The processing method according to claim 1, characterized in that... The acid solution is a hydrochloric acid solution with a concentration of 5-30% by weight; the alkaline solution is a sodium hydroxide solution with a concentration of 30-50% by weight.

4. The processing method according to claim 1, characterized in that... In step A, the coagulant is one or more coagulants selected from polyferric aluminum sulfate, polyferric chloride, polyaluminum chloride or polyacrylamide; the concentration of the coagulant is 0.1 to 1.0% by weight, and its dosage is 0.1 to 3.0% of the volume of calcium chloride wastewater.

5. The processing method according to claim 1, characterized in that... In step B, the heat exchanger (4) is a plate heat exchanger, shell and tube heat exchanger, spiral plate heat exchanger or coaxial heat exchanger, and the steam heater (5) is a Venturi jet mixer, shell and tube heat exchanger, plate steam heat exchanger or steam coil heat exchanger.

6. The processing method according to claim 1, characterized in that... In step C, the heterogeneous Fenton reaction tower (6) is a vertical cylindrical reaction tower with a uniform water distribution zone, a fixed packing zone and an outlet zone. Two to four catalyst beds are set in the heterogeneous Fenton reaction tower (6), with each bed spaced 0.5 to 1.5 meters apart. Except for the bottom catalyst bed, the other beds are equipped with hydrogen peroxide and alkali feeders and arrangers at the wastewater inlet end.

7. The processing method according to claim 1, characterized in that... In step C, the catalyst is a particulate, honeycomb, or corrugated catalyst in which active components of Mn, Ce, Pt, and Ru oxides are supported on ceramic, cordierite, or corundum.

8. The processing method according to claim 1, characterized in that... In step D, the fluidized bed reactor (7) is a vertical hollow cylindrical reactor with a uniform water and gas distribution structure.

9. The processing method according to claim 1, characterized in that... In step D, the catalyst slurry is one or more catalyst slurries selected from FeOOH, Fe2O3, Fe3O4, MgFe2O4, CaFe2O4, MgO or Ca(OH)2.

10. The processing method according to claim 1, characterized in that... In step D, the reducing agent is one or more reducing agents selected from ferrous chloride, ferrous sulfate, sulfurous acid, sodium sulfite or ammonium sulfite.

11. The processing method according to claim 1, characterized in that... In step D, the bag filter (8) is a filter bag made of polyphenylene sulfide (PPS), polyimide P84, polytetrafluoroethylene (PTFE), or aramid material with a mesh size of 200 mesh, 400 mesh, or 1000 mesh.

12. The processing method according to claim 1, characterized in that... In step D, the discharged clarified oxidation tailwater contains less than 18% CaCl2, less than 0.001% glycerol, less than 0.001% chloropropanol and less than 20 mg / L of organic matter TOC by weight, and its pH value is 6 to 9.

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