A method for treating formaldehyde-containing acidic wastewater

Abstract

The application discloses a treatment method of formaldehyde-containing acid wastewater and belongs to the wastewater treatment field. The formaldehyde wastewater is treated by adding the ilmenite and hydrogen peroxide together, so that the Femon oxidation reaction removes the formaldehyde in the wastewater, the ilmenite is decomposed to obtain calcium chloride, the acid in the wastewater can be recycled by subsequent vacuum rectification and concentration, and the calcium chloride snow melting agent product can be prepared. Because the concentration of the acid in the wastewater is high, the acid in the wastewater can be recycled by adopting the vacuum distillation method, the wastewater treatment process is added in the original aminotri(methylene) phosphonic acid (ATMP) process, a closed loop of clean production is formed, the environmental pollution is removed, the pollutants are converted into new products, and meanwhile, the process basically does not cause secondary pollution to the environment.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of sewage treatment, and relates to a treatment method of formaldehyde-containing acidic wastewater, in particular to a treatment method of formaldehyde-containing acidic wastewater generated in the production of aminotrimethylenephosphonic acid (ATMP). BACKGROUND

[0002] With the development of society, people's demand for water treatment agents is becoming larger and larger. A large amount of formaldehyde-containing acidic wastewater is generated in the industrial production of organic phosphorus water treatment agents, and the formaldehyde-containing wastewater seriously pollutes the environment. Therefore, certain production technology must be used in the production process to treat the acidic wastewater. Strengthening the prevention and control of soil pollution sources and developing new pollution control are advanced pollution prevention approaches and means.

[0003] Many existing water pollution purification processes are end-of-pipe control concepts. The end-of-pipe control concept of industrial pollution is only the removal of pollutants, and cannot effectively utilize resources, which is a huge waste of natural resources. Clean production as a new production mode has a creative idea. The upgrading of this concept is mainly from the past end-of-pipe pollution control to the whole process pollution control in industrial production. Clean production is a new technology and means to prevent and control pollution by striving to eliminate pollutants before they are generated.

[0004] In the past few decades, domestic and foreign researchers have conducted a large amount of research on the treatment of formaldehyde-containing wastewater and obtained many treatment technologies and methods. In the past treatment, wastewater is classified according to the presence or absence of phenol, mainly into two categories: phenol-containing formaldehyde wastewater and phenol-free formaldehyde wastewater. The phenol-containing formaldehyde wastewater is mainly treated by oxidation, condensation, coagulation, etc. The phenol-free formaldehyde wastewater is mainly treated by stripping, lime method, oxidation, condensation, etc. For formaldehyde-containing industrial wastewater, the relatively mature treatment process technologies include advanced oxidation process technology, stripping process technology, and biological method.

[0005] For acidic wastewater, the main treatment methods for different properties of acidic wastewater at home and abroad are neutralization precipitation, adsorption, ion exchange, wetland method, and microbial treatment method. The neutralization precipitation method mainly includes limestone neutralization method and sulfide precipitation method. The biggest advantage of the wetland method is low operating cost and easy management.

[0006] However, the current treatment technology and process research for formaldehyde-containing acid wastewater are still very few, and the production technology and process design for removing pollution by applying clean production concept to the production of organic phosphorus water treatment agent are still blank. Since the acid wastewater in the production process of aminotriisopropyl phosphonic acid contains a certain amount of formaldehyde, the wastewater contains formaldehyde and acid substances such as hydrochloric acid, and the simple removal of formaldehyde or acid neutralization technology cannot completely remove the pollution. Therefore, in the process design, the clean production technology is implemented, the formaldehyde and acid substances are combined, the formaldehyde pollution is removed, the resources are reused, the resource waste is not caused, and the clean production process technology is formed. SUMMARY

[0007] In order to solve the above technical problems, the present application provides a treatment method for formaldehyde-containing acid wastewater generated in the production of aminotriisopropyl phosphonic acid (ATMP), which utilizes ilmenite and hydrogen peroxide to be added into the formaldehyde wastewater, so that the Femon oxidation reaction removes the formaldehyde in the wastewater, the ilmenite is decomposed to obtain calcium chloride, and the acid in the wastewater can be recycled and used while the calcium chloride snow melting agent product can be prepared through subsequent vacuum distillation concentration.

[0008] Specifically, the present application provides a treatment method for formaldehyde-containing acid wastewater, which comprises the following steps:

[0009] (1) The formaldehyde-containing acid wastewater is introduced into a conditioning tank for flocculation;

[0010] (2) The wastewater is input into a reaction kettle, then ilmenite powder is added, and then hydrogen peroxide is added, so that the formaldehyde is subjected to Fenton reaction in the reaction kettle, calcium chloride dilute solution and titanium slag are obtained after the reaction, and the titanium slag precipitate is separated from the reaction kettle;

[0011] (3) The wastewater obtained in step (2) is transferred to a vacuum distillation column, the top temperature and pressure of the column are controlled, HCl gas is obtained at the top of the column, the gas is introduced into a spray tower, and HCl solution is obtained by washing with water at the top of the column; when no fraction is distilled at the top of the column, the wastewater solution at the bottom of the column is input into a neutralization reaction tank, weak base is added to adjust the pH value, acid-base neutralization reaction is carried out, and after the reaction is completed, the temperature is increased, the pressure is reduced, calcium chloride snow melting agent is prepared by evaporation, concentration, crystallization and dehydration.

[0012] In an embodiment of the present application, the formaldehyde-containing acid wastewater has a formaldehyde content of 4-4.5% by mass fraction and a hydrochloric acid concentration of 10-11 mol / L.

[0013] In an embodiment of the present application, in step (2), the amount of ilmenite powder added is 4-5 Kg / 100 L of wastewater.

[0014] In an embodiment of the present application, in step (2), the hydrogen peroxide is a 30% H2O2 solution, and the amount added is 18 g / L of the wastewater.

[0015] In an embodiment of the present application, in step (2), the formaldehyde in the wastewater can be removed sufficiently, and the obtained titanium residue can be used as a raw material for lithium iron phosphate batteries.

[0016] In an embodiment of the present application, in step (3), the control of the overhead temperature is 45-55°C, and the vacuum degree at the top of the column is 0.07-0.095 MPa.

[0017] In an embodiment of the present application, in step (3), the weak base is limestone or lime water. In an embodiment of the present application, in step (3), the pH value of the neutralization reaction is adjusted to 6-7.

[0018] In an embodiment of the present application, the specific steps taken for the purpose of recycling resources are as follows:

[0019] (1) At room temperature, ilmenite powder is added to a treatment kettle containing formaldehyde-containing acidic wastewater, and then 30% H2O2 is added while stirring, so that the concentration is maintained at 18 g / L, and the stirring reaction is carried out for 4 hours;

[0020] (2) After the Fenton reaction is completed, the solid-liquid phases are separated at room temperature to obtain a dilute calcium chloride solution containing hydrochloric acid and titanium residue;

[0021] (3) At room temperature, the liquid phase obtained in the previous step is pumped into a vacuum rectification column, and the dilute calcium chloride solution is concentrated by vacuum rectification, the overhead temperature is controlled to collect HCl gas, and the vacuum degree at the top of the column is 0.07-0.095 MPa, and the overhead temperature is 45-55°C; the gas is introduced into a spray tower, and a hydrochloric acid solution is obtained by washing with water from the top of the spray tower;

[0022] (4) At room temperature, liquid ammonia is pumped into a treatment kettle containing formaldehyde-containing acidic wastewater, and then limestone powder is added while stirring; when no fraction is distilled at the top, the solution at the bottom is pumped into a neutralization reaction tank; under stirring, limestone powder is added, and finally Ca(OH)2 is used to adjust the pH value of the solution to 6-7;

[0023] (5) The solution is concentrated by reducing the pressure and increasing the temperature to about 60-100°C to obtain a saturated calcium chloride solution containing a small amount of FeCl3;

[0024] (6) The saturated solution is pumped into a crystallization tank, and cooled and crystallized at room temperature; when the mass percentage concentration of calcium chloride in the treatment kettle is ≥30%, crystals begin to precipitate, the temperature is lowered, and aging is carried out, an anti-caking agent is added, centrifugal dehydration is carried out by a centrifuge, hot air drying is carried out, and the temperature of the crystallization is ≤35°C, the aging time of the crystals is 2-6 h, and a calcium chloride snow-melting agent is obtained.

[0025] The technical parameters of each device in the process flow are designed as follows:

[0026] (1) Adjusting pool: The adjusting pool is used to appropriately buffer the fluctuation of organic matter and reduce the peak flow rate in the physical and chemical treatment system. During the non-operation period of the factory, the water treatment unit is continuously supplied with water, and the flow fluctuation caused by seasonal changes is adjusted.

[0027] Design parameters: a. Hydraulic retention time T = 6h;

[0028] b. Design flow rate Q = 60m3·d -1 = 2.5m3·h -1 ;

[0029] c. Effective volume of adjusting pool: V = QT = 2.5x6 = 15m3;

[0030] e. Pool length L = 2.5m, pool width B = 2.5m, then the total size of the pool LxBxH = 2.5x2.5x3 = 18.75m3.

[0031] (2) Rectifying column: The operation is carried out under reduced pressure, and the substances are corrosive. The main equipment of the rectifying column is made of carbon steel with PTFE molded lining, and a packed column is selected. The packing has different types and materials. Because ceramic materials have strong corrosion resistance and low cost, they are easy to purchase and replace in large quantities. The design packing is CY700 type regular packing. The design parameters are as follows:

[0032] a. The determination of column diameter should be based on the liquid and gas treatment capacity to ensure that the column does not reach liquid flooding and has good mass transfer performance under operating conditions.

[0033] The roundness is 40mm.

[0034] b. The number of plates is 10, and HETP is 0.04m, then: the packing layer height obtained by process calculation is: Z = HETPxN T = 0.8m

[0035] The packing layer height Z' during design is (1.2-1.5)Z, taking a safety factor of 1.25, so the packing layer height during design is: Z' = 1.25xZ = 1.0m;

[0036] c. The internal components of the column mainly consist of the following components:

[0037] 1) Liquid distribution device: The function of the liquid distributor is to uniformly distribute or redistribute the liquid in the column, enhance the effect of heat and mass transfer, increase the contact between two phases, and improve the efficiency of the column.

[0038] The tower has small diameter and high corrosivity, and does not contain easily blocked substances, so the spray distributor is selected.

[0039] 2) The filler support device mainly promotes the uniform distribution and good contact of the gas and liquid in the tower.

[0040] In the wastewater treatment process, there is acid corrosion, and the temperature is 120 DEG C, so pure tetrafluoroethylene or stainless steel is selected as the support skeleton, and the outer layer is sprayed with a tetrafluoroethylene corrosion-resistant layer.

[0041] Compared with the prior art, the present application has the following advantages:

[0042] The present application has low cost and high economic feasibility, and the process involves fewer structures, one-stage adjustment, two-stage oxidation, three-stage recovery, and relatively simple process, so the cost is relatively low.

[0043] Effectively, because the acid concentration in the wastewater is high, the acid in the wastewater can be recovered and utilized by using the method of vacuum distillation, and the wastewater treatment process is added to the original aminotrimethylenephosphonic acid (ATMP) process to form a closed loop of clean production, which removes environmental pollution and converts pollutants into new products. At the same time, the process basically does not cause secondary pollution to the environment. BRIEF DESCRIPTION OF DRAWINGS

[0044] Figure 1 Process flow diagram. DETAILED DESCRIPTION

[0045] The following examples are further described in detail, and it should be understood that the examples are only used to explain the present application and do not include all the contents of the present application.

[0046] Example 1

[0047] (1) 50L of formaldehyde acid wastewater (hydrochloric acid concentration of 10.24mol / L) with a mass fraction of 4.24% produced in the production of aminotrimethylenephosphonic acid (ATMP) is pumped into the adjustment tank and then into the reaction kettle, 2kg of ilmenite powder and 900g of 30% H2O2 solution are added, and the mixture is stirred and reacted for 4h, and then the solid-liquid phase is separated to obtain titanium slag.

[0048] (2) The above-mentioned liquid phase solution is transferred to a vacuum rectification tower, the tower top temperature is controlled at 50 DEG C, the pressure is 20kPa, and vacuum rectification is carried out for 2h, HCl gas is collected at the tower top, water is continuously sprayed into the spray tower to obtain a hydrochloric acid solution, and calcium chloride solution is collected at the tower bottom until no distillation is analyzed.

[0049] (3) The calcium chloride solution is transported to the neutralization reaction tank, limestone is added, the reaction is stirred, and the pH value is adjusted. When the pH value reaches about 6, calcium hydroxide is added to adjust the pH to 6.8-7.

[0050] (3) The above solution is transported to a vacuum distillation reaction kettle, the temperature is controlled at 100 degrees Celsius, the pressure is controlled at 10 kPa, and vacuum distillation is continued for 1.5 hours. At this time, the water quality of the overhead fraction and the formaldehyde concentration in the calcium chloride solution below are detected to be 1.84 mg / L -1 .

[0051] (4) The concentrated ammonium chloride solution collected at the bottom is transported into a clean reactor, and calcium chloride crystals weighing 8.2 kg are obtained by crystallization. The crystallized solution is transported into a conditioning tank.

[0052] Example 2

[0053] (1) The formaldehyde acidic wastewater with a mass fraction of 4.12% generated in the process of producing aminotri (methylene) phosphonic acid (ATMP) with a concentration of 11.14 mol / L of hydrochloric acid is pumped into a conditioning tank and then into a reaction kettle, 3 kg of ilmenite powder and 1300 g of 30% H2O2 solution are added, the reaction is stirred for 4 hours, and the solid-liquid phase is separated to obtain solid titanium slag.

[0054] (2) The above liquid phase solution is transported to a vacuum rectifying column, the overhead temperature is controlled at 50 degrees Celsius, the pressure is controlled at 20 kPa, vacuum rectification is carried out for 2 hours, HCl gas is collected at the top of the column, is introduced into a spray tower, and water is continuously sprayed to obtain a hydrochloric acid solution, and a calcium chloride solution is collected at the bottom of the column until no distillation analysis is performed.

[0055] (3) The calcium chloride solution is transported to the neutralization reaction tank, limestone is added, the reaction is stirred, and the pH value is adjusted. When the pH value reaches about 6, calcium hydroxide is added to adjust the pH to 6.8-7.

[0056] (3) The above solution is transported to a vacuum distillation reaction kettle, the temperature is controlled at 100 degrees Celsius, the pressure is controlled at 10 kPa, and vacuum distillation is continued for 1.5 hours. At this time, the water quality of the overhead fraction and the formaldehyde concentration in the calcium chloride solution below are detected to be 1.82 mg / L -1 .

[0057] (4) The concentrated ammonium chloride solution collected at the bottom is transported into a clean reactor, and calcium chloride crystals weighing 12.12 kg are obtained by crystallization. The crystallized solution is transported into a conditioning tank.

[0058] Example 3

[0059] (1) 100L production of amino trimethylene phosphonic acid (ATMP) process in the mass fraction of 4.06% of formaldehyde acid wastewater (hydrochloric acid concentration of 10.54 mol / L) pump into the conditioning tank, pump into the reaction kettle, add 4 kg of ilmenite powder, 1800 g of 30% H2O2 solution, stirring reaction 4h, separation of solid-liquid phase, get solid titanium slag.

[0060] (2) The above liquid solution is transferred to a vacuum rectification column, the overhead temperature is controlled at 50 degrees Celsius, and the pressure is controlled at 20 kPa for vacuum rectification for 2h, the HCl gas is collected at the top of the column, introduced into the spray tower, and the water is continuously sprayed to obtain a hydrochloric acid solution, and the calcium chloride solution is collected at the bottom of the column until no distillation analysis.

[0061] (3) The calcium chloride solution is transported to a neutralization reaction tank, limestone is added, and stirring reaction is carried out to adjust the pH value, when the pH value reaches about 6, calcium hydroxide is added to adjust the pH value to 6.8-7.

[0062] (3) The above solution is transported to a vacuum distillation reaction kettle, the temperature is controlled at 100 degrees Celsius, and the pressure is controlled at 10 kPa, and vacuum distillation is continued for 1.5h, at this time the water quality of the overhead fraction and the formaldehyde concentration in the calcium chloride solution below are detected to be 1.76 mg / L -1 .

[0063] (4) The concentrated ammonium chloride solution collected at the bottom of the column is transported into a clean reactor, and calcium chloride crystals 16.31 kg are obtained by crystallization. The crystallized solution is transported into a conditioning tank.

[0064] Comparative Example 1

[0065] (1) 50L production of amino trimethylene phosphonic acid (ATMP) process in the mass fraction of 4.04% of formaldehyde acid wastewater (hydrochloric acid concentration of 10.12 mol / L) pump into the conditioning tank, pump into the reaction kettle, add 2 kg of ilmenite powder, 100 g of 30% H2O2 solution, stirring reaction 2h, separation of solid-liquid phase, get solid titanium slag.

[0066] (2) The above liquid solution is transferred to a vacuum rectification column, the overhead temperature is controlled at 50 degrees Celsius, and the pressure is controlled at 20 kPa for vacuum rectification for 2h, the HCl gas is collected at the top of the column, introduced into the spray tower, and the water is continuously sprayed to obtain a hydrochloric acid solution, and the calcium chloride solution is collected at the bottom of the column until no distillation analysis.

[0067] (3) The calcium chloride solution is transported to a neutralization reaction tank, limestone is added, and stirring reaction is carried out to adjust the pH value, when the pH value reaches about 6, calcium hydroxide is added to adjust the pH value to 6.8-7.

[0068] (3) The above solution is transported to a reduced pressure distillation reactor, the temperature is controlled at 100 degrees Celsius, the pressure is controlled at 10 kPa, and the reduced pressure distillation is continued for 1.5 hours. At this time, the water quality of the overhead distillate and the formaldehyde concentration in the calcium chloride solution below are detected to be 124.84 mg / L -1 .

[0069] (4) The concentrated ammonium chloride solution collected at the bottom is transported into a clean reactor, and calcium chloride crystals 3.2 kg are obtained by crystallization. The solution after crystallization is transported into a conditioning pool.

[0070] During the experiment, the concentration of hydrogen peroxide is low, and the reaction time is not enough, resulting in a low formaldehyde removal rate in the Fenton oxidation process.

[0071] Comparative Example 2

[0072] (1) The formaldehyde acidic wastewater (hydrochloric acid concentration is 10.36 mol / L) with a mass fraction of 4.18% generated in the process of producing aminotri (methylene) phosphonic acid (ATMP) in 50 L is pumped into a conditioning pool, then pumped into a reactor, 2 kg of ilmenite powder, 300 g of 30% H2O2 solution are added, and stirred for 2 hours. The solid-liquid phase is separated to obtain solid titanium slag.

[0073] (2) The above liquid phase solution is transported to a reduced pressure distillation column, the overhead temperature is controlled at 50 degrees Celsius, the pressure is controlled at 20 kPa, and the reduced pressure distillation is continued for 2 hours. HCl gas is collected at the top of the column and introduced into a spray tower. Water is continuously sprayed to obtain a hydrochloric acid solution. The calcium chloride solution is collected at the bottom of the column until no distillation is analyzed.

[0074] (3) The calcium chloride solution is transported to a neutralization reaction pool, limestone is added, and stirred for reaction. The pH value is adjusted. When the pH value reaches about 6, calcium hydroxide is added to adjust the pH value to 6.8-7.

[0075] (3) The above solution is transported to a reduced pressure distillation reactor, the temperature is controlled at 100 degrees Celsius, the pressure is controlled at 10 kPa, and the reduced pressure distillation is continued for 1.5 hours. At this time, the water quality of the overhead distillate and the formaldehyde concentration in the calcium chloride solution below are detected to be 124.84 mg / L -1 .

[0076] (4) The concentrated ammonium chloride solution collected at the bottom is transported into a clean reactor, and calcium chloride crystals 3.2 kg are obtained by crystallization. The solution after crystallization is transported into a conditioning pool.

[0077] During the experiment, the concentration of hydrogen peroxide is low, and the reaction time is not enough, resulting in a low formaldehyde removal rate in the Fenton oxidation process.

[0078] Comparative Example 3

[0079] (1) 50L production of amino trimethylene phosphonic acid (ATMP) process of mass fraction of 4.16% formaldehyde acid wastewater (hydrochloric acid concentration of 10.26 mol / L) pump into the conditioning tank, pump into the reaction kettle, add 2kg ilmenite powder, 100g of 30% H2O2 solution, stirring reaction 4h, separation of solid-liquid phase, get solid titanium slag.

[0080] (2) The above liquid phase solution is transported to the vacuum rectification column, the overhead temperature is controlled at 50 degrees Celsius, the pressure is 20kPa, and vacuum rectification is carried out for 2h, HCl gas is collected at the top of the column, and is introduced into the spray tower, water is continuously sprayed to obtain a hydrochloric acid solution, and calcium chloride solution is collected at the bottom of the column, and the distillation is analyzed until there is no distillation.

[0081] (3) The calcium chloride solution is transported to the neutralization reaction tank, limestone is added, stirring reaction, adjusting pH value, when the pH value reaches about 6, calcium hydroxide is added to adjust the pH to 6.8-7.

[0082] (3) The above solution is transported to the vacuum distillation reaction kettle, the temperature is controlled at 100 degrees Celsius, the pressure is 10kPa, and vacuum distillation is continued for 1.5h, at this time, the water quality of the overhead fraction and the formaldehyde concentration in the calcium chloride solution below are detected to be 112.36mg / L -1 .

[0083] (4) The concentrated ammonium chloride solution collected at the bottom of the column is transported into the clean reactor, and calcium chloride crystals 3.84kg are crystallized. The solution after crystallization is transported into the conditioning tank.

[0084] During the experiment, the concentration of hydrogen peroxide is low, which leads to the fact that the removal rate of formaldehyde in the Fenton oxidation process does not meet the requirements.

[0085] Although the content of the present application has been described in detail by the above preferred embodiments, it should be recognized that the above description should not be considered as a limitation of the present application. After reading the above content, various modifications and alternatives of the present application will be obvious to those skilled in the art. Therefore, the protection scope of the present application should be defined by the appended claims.

Claims

1. A method for treating formaldehyde-containing acidic wastewater generated during the production of aminotrimethylenephosphonic acid, characterized in that: The method comprises the following steps: (1) Passing formaldehyde-containing acidic wastewater into a regulating tank for flocculation; (2) The wastewater is fed into the reactor, and then ilmenite ore powder is added, and then hydrogen peroxide is added. Formaldehyde undergoes a Fenton reaction in the reactor. After the reaction is completed, a dilute calcium chloride solution and titanium slag are obtained. The titanium slag precipitate is separated from the reactor; (3) The wastewater obtained in step (2) is transferred to a vacuum distillation tower, and HCl gas is obtained at the top of the tower by controlling the temperature and pressure of the tower top. The gas is introduced into a spray tower, and the tower top is washed with water to obtain an HCl solution; when no fraction is distilled out from the top of the tower, the wastewater solution at the bottom of the tower is input into a neutralization reaction tank, a weak base is added to adjust the pH value, and an acid-base neutralization reaction is carried out. After the reaction is completed, the temperature is increased and the pressure is reduced, and then the calcium chloride de-icing agent is obtained by evaporation, concentration, crystallization, and dehydration; wherein the weak base is limestone or lime water; Wherein, step (2) fully removes formaldehyde in the wastewater, and the titanium slag obtained can be used as a raw material for lithium iron phosphate batteries.

2. The processing method according to claim 1, characterized in that The properties of the formaldehyde-containing acidic wastewater are as follows: the formaldehyde content is between 4 and 4.5% by mass, and the hydrochloric acid concentration is between 10 and 11 mol / L.

3. The processing method according to claim 1, characterized in that In step (2), the amount of ilmenite ore powder added is 4-5 kg / 100 L of wastewater.

4. The processing method according to claim 1, characterized in that In step (2), the hydrogen peroxide is a 30% H2O2 solution, and the added amount is 18g / L wastewater.

5. The processing method according to claim 1, characterized in that In step (3), the tower top temperature is controlled to be 45-55°C, and the tower top vacuum is controlled to be 0.07-0.095 MPa.

6. The processing method according to claim 1, characterized in that In step (3), the pH value of the neutralization reaction is adjusted to 6-7.

7. The processing method according to claim 1, characterized in that The method specifically comprises the following steps: (1) At room temperature, add ilmenite powder to a reactor containing formaldehyde acidic wastewater while stirring. Then add 30% H2O2 to the wastewater, maintaining its concentration at 18 g / L, and stir the reaction for 4 hours. (2) After the Fenton reaction is completed, the solid and liquid phases are separated at room temperature to obtain a dilute calcium chloride solution containing hydrochloric acid and titanium slag; (3) Under normal temperature conditions, the liquid phase obtained in the previous step is pumped into a vacuum distillation tower, and the dilute calcium chloride solution is concentrated by vacuum distillation. The temperature at the top of the tower is controlled to collect HCl gas. The vacuum degree at the top of the tower is 0.07~0.095 MPa, and the temperature at the top of the tower is 45~55℃; the gas is introduced into a spray tower, and the hydrochloric acid solution is obtained by eluting with water from the top of the spray tower; (4) When no fraction is distilled out from the top of the tower, the bottom solution is pumped into the neutralization reaction tank; limestone powder is added under stirring, and finally the pH of the solution is adjusted to 6~7 with Ca(OH)2; (5) The solution is decompressed and heated to about 60-100 degrees Celsius to concentrate the solution to obtain a saturated calcium chloride solution containing a small amount of FeCl3; (6) Pump the saturated calcium chloride solution into the crystallization pool and cool it at room temperature for crystallization. When the mass percentage concentration of calcium chloride in the crystallization pool is ≥30%, crystals begin to precipitate. Lower the temperature, age it, add an anti-caking agent, centrifuge it for dehydration, and dry it with hot air to obtain a calcium chloride snow melting agent.

8. The processing method according to claim 7, characterized in that: In step (6), the temperature of the cooling crystallization is ≤35°C, and the crystallization aging time is 2 to 6 h.

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