Process and system for directly producing solid polyferric sulfate by ball milling and mixing reaction in one step

Abstract

The invention discloses a process and system for directly producing solid polyferric sulfate in a one-step ball milling mixed reaction. Ferrous sulfate containing crystal water and grinding balls are added to a horizontal ball milling reaction equipment cylinder. 30-45 DEG C of hot air are conveyed in the cylinder. The cylinder rotates and drives the grinding balls to slide back and forth. The crystal water-containing ferrous sulfate crystal particles are ball milled and crushed. After the conditioning agent is conveyed in the cylinder and mixed, the chlorate oxidant solid particles are continuously and evenly conveyed into the cylinder for oxidation reaction. The material color gradually turns yellow-brown. More than 98wt% of concentrated sulfuric acid is evenly sprayed into the surface of the material in the cylinder in an atomized form. It is regulated that the hot air temperature entering the cylinder is 45-60 DEG C. The material is further oxidized, hydrolyzed and polymerized under the mechanical force of ball milling mixing and collision to obtain brown solid powdered polyferric sulfate. The crystal water removed containing ferrous sulfate containing crystal water and the water vapor and gaseous by-products produced by the reaction are extracted from the cylinder by negative pressure.

Description

Technical Field

[0001] The invention relates to the technical field of solid polyferric sulfate production, and in particular to a process and system for directly producing solid polyferric sulfate through a ball milling mixing reaction in one step. Background Art

[0002] Coagulation and sedimentation process is the most widely used process unit in water treatment. Coagulants are widely used in water treatment and have a large demand. Common coagulants include aluminum coagulants and iron coagulants. Aluminum salt coagulants have a large amount of sludge and residual Al 3+ It has a certain degree of toxicity. Among iron-based coagulants, polyferric sulfate is the most widely used. It is mainly used in coagulation units for industrial wastewater treatment and municipal sewage treatment such as papermaking and printing and dyeing, as well as a conditioner for sludge dewatering. Iron-based coagulants include polyferric sulfate, and the preparation process of polyferric sulfate usually adopts catalytic oxidation and direct oxidation methods. The catalytic oxidation method generally uses NaNO2 catalyst, and uses oxygen or air to oxidize ferrous ions to produce trivalent iron to prepare liquid polyferric sulfate. This method is carried out between gas and liquid phases, resulting in a large amount of catalyst input and a long oxidation reaction time. In addition, the nitrogen oxides discharged during the reaction will pollute the environment, and the exhaust gas needs to be further purified.

[0003] At present, the production process of polyferric sulfate generally adopts the direct oxidation method, which usually uses ferrous sulfate, a by-product of titanium dioxide production, as raw material. A certain amount of water and sulfuric acid are added to the reactor to dissolve the ferrous sulfate. Then, an oxidant such as H2O2, KCIO3 or HNO3 is added to oxidize the ferrous sulfate into ferric sulfate. By controlling the addition ratio of sulfuric acid, basic ferric sulfate is generated. The basic ferric sulfate is mixed and stirred under heating conditions to undergo hydrolysis and polymerization reaction to generate a reddish-brown liquid polyferric sulfate.

[0004] Liquid PFS is difficult to transport, expensive to transport over long distances, and prone to turbidity or precipitation over long storage periods, making it inconvenient to transport and use. Typically, solid PFS is produced by evaporating, concentrating, drying, or spray-drying the liquid. This process is complex, has low thermal efficiency, high energy consumption, and high production costs.

[0005] In view of the shortcomings of the two-step method of preparing solid polyferric sulfate after evaporation or drying of liquid polyferric sulfate, which has a long process flow and high energy consumption, a large number of explorations and studies on the one-step method for preparing solid polyferric sulfate have been carried out in recent years.

[0006] The invention patent application with application number CN201210191010.9 discloses a method for producing solid polyferric sulfate. The method comprises placing industrial ferrous sulfate heptahydrate into an acid-resistant reactor, heating the mixture to 80-130°C, and electrically stirring the mixture until it becomes a slurry. 98wt% concentrated sulfuric acid and 50% hydrogen peroxide are then added by spraying, respectively. After stirring for 1-4 hours, industrial-grade ammonium salt is added and stirred evenly. The product is then transferred to a condensation tank and cooled and allowed to stand for 8-36 hours to obtain powdered solid polyferric sulfate.

[0007] The invention patent application with application number CN201510912769.5 discloses a method for producing polyferric sulfate by anhydrous reaction. Industrial ferrous sulfate and concentrated sulfuric acid are added to a professional stainless steel reaction device. The mass ratio of ferrous sulfate to concentrated sulfuric acid is 10:1. Sodium nitrite or dilute nitric acid catalyst is added under near vacuum state, and the oxygen pressure is maintained at 0.02-0.04MPa. The material dissolution and reaction are carried out in the same device. The reaction is carried out at about 100°C for 3 to 10 hours. The viscous liquid polyferric sulfate material is pumped into a spray drying tower for drying to obtain solid polyferric sulfate. The tail gas is sent to an alkali absorption tower for treatment. After the alkali solution is saturated, it is returned to be recycled as a catalyst.

[0008] The invention patent application with application number CN201510154057.1 discloses a method for preparing a solid polyferric zinc sulfate flocculant. First, solid ferrous sulfate heptahydrate is acidified with concentrated sulfuric acid, and then sodium chlorate is added and slowly stirred to form a brown-yellow uniform liquid. Then, solid powdered zinc sulfate is added and slowly stirred to completely dissolve it. Then, a carbon oxide material is added to accelerate the curing speed of the flocculant. The flocculant is dry-heated with an electric heating jacket and matured at room temperature to obtain a light yellow solid polyferric zinc sulfate flocculant.

[0009] The above patented technology improves the existing two-step process in the production of solid polyferric sulfate, simplifies the process flow, and reduces energy consumption. However, the entire production process still involves first generating liquid polyferric sulfate and then obtaining solid polyferric sulfate through concentration and drying or spray drying. It has not yet been achieved that solid polyferric sulfate can be directly produced in one reaction equipment. Summary of the Invention

[0010] In response to the problems of long process, long reaction time and high energy consumption in the above-mentioned production of solid polyferric sulfate, in order to accelerate the efficiency of the reaction between ferrous sulfate and a solid oxidant in the solid-liquid phase, the present invention provides a process and system for directly producing solid polyferric sulfate in a one-step ball milling mixing reaction, thereby simplifying the solid polyferric sulfate production process, reducing energy consumption, shortening the reaction time, reducing production costs and improving production efficiency.

[0011] The specific technical solutions are as follows:

[0012] A process for directly producing solid polyferric sulfate by ball milling and mixing reaction in one step, comprising the steps of:

[0013] S1, adding ferrous sulfate containing crystal water and grinding balls into the cylinder of a horizontal ball mill reaction equipment, supplying hot air at 30-45°C into the cylinder, and rotating the cylinder, driving the grinding balls to slide back and forth, thereby grinding the ferrous sulfate containing crystal water crystal particles into fine particles;

[0014] S2, a conditioning agent is fed into the cylinder. During the sliding process of the grinding balls, the conditioning agent is mixed with the ferrous sulfate powder containing crystal water. Then, solid particles of chlorate oxidant are continuously and evenly fed into the cylinder for oxidation reaction. The color of the material changes from yellow-green to light yellow, and then gradually changes from light yellow to yellow-brown.

[0015] The conditioning agent is at least one of calcium carbonate, sodium carbonate, ammonium sulfate, and ammonium bicarbonate;

[0016] S3, spraying concentrated sulfuric acid with a mass concentration of more than 98% evenly onto the surface of the material in the cylinder in an atomized form, adjusting the temperature of the hot air entering the cylinder to 45-60°C, and the material further undergoes oxidation, hydrolysis and polymerization reactions under the mechanical force of ball milling mixing and collision;

[0017] The crystal water removed from ferrous sulfate containing crystal water and the water vapor and gas by-products generated by the reaction are extracted from the cylinder through negative pressure. During the ball milling reaction, the material is gradually dehydrated and dried through its own oxidation heat release, ball milling heat, and external hot air heat conduction. Under the mechanical force of the sliding grinding balls, it is gradually transformed into fine-grained uniform powder material, and brown-yellow solid powdered polyferric sulfate is directly produced in one step.

[0018] Existing polyferric sulfate production typically involves dissolving ferrous sulfate containing crystal water by adding a certain amount of water and sulfuric acid. An oxidant (oxygen, hydrogen peroxide, or chlorate, etc.) is then used in the solution to oxidize the ferrous ions to ferric ions. While the ferric ions are being hydrolyzed, the sulfate ion concentration in the solution is controlled to be insufficient to polymerize and form a viscous liquid polyferric sulfate. To produce solid polyferric sulfate, a liquid film is formed during evaporation, concentration, and drying, which consumes significant energy and takes a long time.

[0019] The present invention provides a process for directly producing solid polyferric sulfate by ball milling and mixing solid materials in one step. The process adopts a horizontal ball milling reaction device. The rotating cylinder of the device can drive the relative sliding of the grinding balls and the material to generate a mechanochemical effect, which can induce a chemical reaction and induce changes in the structural properties of the material. The process can not only crush the granular material, but also strengthen the mixed mass transfer of the solid material, improve the probability of mixed contact of the materials, and reduce the activation energy of the reaction. Ferrous sulfate containing seven crystal waters can be oxidized into ferric sulfate by a solid chlorate oxidant in a non-solution system. The addition of a conditioning agent can "lock" the crystal water removed from the ferrous sulfate, and the material is in a semi-fluid state, avoiding the occurrence of a viscous liquid in the oxidation stage. The process not only ensures effective mass transfer and chemical reaction of the material in the ball milling mixing process, but also enables the reaction to be oxidized in a non-solution state. The heat released during the oxidation of the material and the heat energy converted from mechanical energy during the ball milling process can be fully utilized to synchronously dry the reaction product, saving a large amount of energy consumption required in the drying and dehydration process of the liquid polyferric sulfate. The process achieves the production of solid polyferric sulfate in one device, simplifies the production process flow, and improves production efficiency.

[0020] In addition, the present invention adopts a direct oxidation method, and the entire production process is carried out in a closed device. Sodium nitrite or dilute nitric acid is not used as a catalyst. No highly polluting waste gas such as nitrogen oxides is generated during the production process. A very small amount of by-product chlorine or hydrogen chloride gas generated by the oxidation of ferrous sulfate by chlorate is extracted from the equipment cylinder through negative pressure and can be collected in a specific storage tank, without causing air pollution to the environment.

[0021] In step S1, the ferrous sulfate containing crystal water may be ferrous sulfate heptahydrate and / or ferrous sulfate pentahydrate.

[0022] In step S1, the grinding balls may be at least one of glass balls, ceramic balls, and zircon balls.

[0023] In step S1, the weight ratio of the grinding balls to the ferrous sulfate containing crystal water can be 2.5-3.5:1.

[0024] In step S1, the drum rotation speed may be 25-40 rpm.

[0025] In step S1, the ball milling time may be 20-30 minutes.

[0026] In step S2, the weight ratio of the conditioning agent to the ferrous sulfate containing crystal water can be 5-10:100.

[0027] In step S2, the chlorate oxidant may be sodium chlorate and / or potassium chlorate.

[0028] In step S2, the weight ratio of the chlorate oxidant solid particles to the ferrous sulfate containing crystal water can be 5-8:100.

[0029] In step S2, the oxidation reaction time may be 30-50 minutes.

[0030] In step S3, the weight ratio of the concentrated sulfuric acid to the ferrous sulfate containing crystal water can be 7-10:100.

[0031] In step S3, the reaction time may be 40-90 minutes.

[0032] A system for directly producing solid polyferric sulfate in one step by ball milling and mixing reaction, comprising:

[0033] A horizontal ball mill reaction device comprises a rotatable horizontal cylinder, the cylinder being provided with an opening which can be used as a feeding port or a discharging port, and a sealing cover plate and a grid cover plate which are adapted to the opening and can be detachably replaced with each other;

[0034] Hot air delivery equipment for delivering hot air into the cylinder;

[0035] Solid material pneumatic diaphragm pump dosing equipment for delivering solid particles of conditioning agent and chlorate oxidant into the cylinder;

[0036] Acid liquid high-pressure pump atomizing dosing equipment used to spray concentrated sulfuric acid with a mass concentration of more than 98% evenly into the cylinder in an atomized form;

[0037] The water vapor vacuum filtration equipment is used to remove the crystal water of ferrous sulfate containing crystal water and the water vapor and gas by-products generated by the reaction from the cylinder through negative pressure.

[0038] In one embodiment, in the system for directly producing solid polyferric sulfate by ball milling mixing reaction in one step, the cylinder is connected to a variable frequency reduction motor and can be driven to rotate by the variable frequency reduction motor.

[0039] In one embodiment, in the system for directly producing solid polyferric sulfate by ball milling and mixing reaction in one step, the hot air conveying equipment and the solid material pneumatic diaphragm pump feeding equipment are both connected to the cylinder through the hollow first support shaft.

[0040] In one embodiment, in the system for directly producing solid polyferric sulfate by ball milling and mixing reaction in one step, the acid liquid high-pressure pump atomization dosing device is connected to the cylinder through the hollow second support shaft.

[0041] In one embodiment, in the system for directly producing solid polyferric sulfate by ball milling and mixing reaction in one step, the water vapor vacuum filtration equipment includes an alkali solution absorption tank, which is connected to the cylinder through a vacuum pump and a dust filter.

[0042] In one embodiment, the system for directly producing solid polyferric sulfate by ball milling mixing reaction in one step, the horizontal ball milling reaction equipment further includes a closed cover arranged outside the cylinder, and the closed cover is provided with a loading port.

[0043] The system of the present invention for directly producing solid polyferric sulfate in one step by ball milling and mixing reaction can be used to implement the process of directly producing solid polyferric sulfate in one step by ball milling and mixing reaction.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] The present invention truly realizes the one-step direct production of solid polyferric sulfate using solid ferrous sulfate containing crystal water as a raw material, and has the characteristics of a short production process, low equipment energy consumption, and convenient production operation and management. The production efficiency of the solid polyferric sulfate is greatly improved. Compared with the method of producing solid polyferric sulfate by oxidizing a ferrous sulfate solution to generate ferric sulfate and then drying it, the production cost can be saved by about 30%.

[0046] The powdered solid polyferric sulfate directly produced by the ball milling mixing step of the present invention can reach the particle size and solubility of the solid polyferric sulfate after spray drying of the liquid polyferric sulfate on the market.

[0047] 100 parts by weight of the solid polyferric sulfate prepared by the present invention is added to 60-90 parts of tap water, and the mixture is fully stirred and dissolved to obtain a liquid polyferric sulfate product, which can be directly used in a coagulation and dosing system using a liquid storage tank in an existing coagulation and sedimentation project.

[0048] The solid polyferric sulfate directly produced in one step can be used for treating wastewater from enterprises that need to be transported over long distances. The agent is first prepared into a concentration of about 10% in a drug dissolving tank and then added using a metering pump. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 This is a schematic structural diagram of the system for directly producing solid polyferric sulfate in one step through ball milling mixing reaction according to the present invention. DETAILED DESCRIPTION

[0050] The present invention will be further described below with reference to specific examples. It should be understood that these examples are only intended to illustrate the present invention and are not intended to limit the scope of the present invention.

[0051] In the following examples, the operating methods without specifying specific conditions are generally carried out under conventional conditions or conditions recommended by the manufacturer.

[0052] See also Figure 1A system for directly producing solid polyferric sulfate through a one-step ball milling and mixing reaction comprises a horizontal ball milling reaction apparatus with a cylinder 1, a hot air conveying apparatus 2, an acid liquid atomizing pump 3, a solid material pneumatic diaphragm pump 4, a water vapor vacuum filtration apparatus 5, and a solid powder unloading apparatus 6. The cylinder 1 is horizontal and fixed to a bracket. It can be rotated by a variable frequency reduction motor at a speed of 25-40 rpm. The cylinder 1 is provided with an opening that can serve as a feeding port or a discharge port, as well as a sealing cover and a grille cover that are compatible with the opening and are removable and interchangeable. The hot air conveying apparatus 2 comprises a heating furnace, an air compressor, and a gas dryer. Hot air is conveyed into the cylinder 1 via a pipeline through a first hollow support shaft on one side of the cylinder 1. The hot air temperature can be controlled to 30-45°C or 45-60°C using a heating furnace thermocouple. The acid liquid high-pressure pump atomizing device 3 consists of a high-pressure metering pump and an atomizing nozzle. It sprays concentrated sulfuric acid in atomized form evenly onto the surface of the material from a second hollow support shaft on the other side of the cylinder 1. The solid material pneumatic diaphragm pump dosing device 4 primarily consists of a storage barrel and a pneumatic diaphragm pump. After being lifted by the pneumatic diaphragm pump, these solid materials, such as the conditioning agent and chlorate oxidant solid particles, are transported into the cylinder 1 from a first hollow support shaft on one side of the cylinder 1. The transport flow rate of the solid material can be adjusted by air pressure. The water vapor vacuum filtration device 5 primarily consists of a vacuum pump, an alkali solution absorption tank, and a dust filter. It can draw the removed crystal water, water vapor generated by the reaction, and a small amount of by-product waste gas into the alkali solution absorption tank along with the exhaust air. The solid powder unloading equipment 6 is mainly composed of a closed cover outside the cylinder 1 and a grille cover of the cylinder 1. After the reaction is completed, the sealing cover of the feeding port of the cylinder 1 is replaced with a grille cover. The cylinder 1 can be rotated to transfer the brown-yellow powdered solid polyferric sulfate to the closed cover. After unloading and packaging, the solid coagulant agent product is directly obtained.

[0053] Example 1

[0054] Using the above Figure 1The ball milling mixing reaction shown is a system for directly producing solid polyferric sulfate in one step. 100 parts by weight of industrial-grade ferrous sulfate heptahydrate is weighed and added into the feeding port of the cylinder 1 of the horizontal ball mill reaction equipment, and then 300 parts by weight of glass balls are added. After the feeding port of the cylinder 1 is sealed with a sealing cover, the speed of the cylinder 1 is controlled to 35 rpm by the variable frequency reduction motor. The temperature of the dry hot air entering the cylinder 1 is controlled to 30°C by the heating furnace thermocouple, and the water vapor vacuum filtration equipment 5 is turned on. After 30 minutes, the ferrous sulfate heptahydrate crystals are ground into fine particles. 8 parts by weight of solid ammonium sulfate powder are evenly transported into the cylinder 1 from the hollow first support shaft at one end of the cylinder 1 through the pneumatic diaphragm pump feeding equipment 4. After 10 minutes, the solid ammonium sulfate and powdered ferrous sulfate heptahydrate can be fully mixed during the sliding process of the glass balls in the cylinder 1. Then the pneumatic diaphragm pump feeding equipment is used to feed the solid ammonium sulfate and powdered ferrous sulfate heptahydrate. 4. 7 parts by weight of sodium chlorate crystals are uniformly conveyed into the cylinder 1 over 10 minutes. After 40 minutes of oxidation reaction, the color of the material gradually changes from light yellow to yellow-brown. At this time, most of the ferrous sulfate has been oxidized to ferric hydroxysulfate. Then, 8 parts by weight of 98wt% concentrated sulfuric acid are evenly sprayed onto the surface of the material in an atomized form through the second hollow support shaft on the other side of the cylinder 1 using a high-pressure pump atomization and dosing system 3. After the material further oxidizes, hydrolyzes, and polymerizes for 30 minutes, the temperature of the hot air entering the cylinder 1 is increased to 50°C by adjusting the thermocouple of the heating furnace of the hot air conveying device 2. The material is gradually dehydrated and dried under the action of ball mill mixing and hot air drying. After 30 minutes, the material is ground and pulverized into a brown solid powder. After the reaction is completed, the material is discharged, and a solid polyferric sulfate coagulant is directly produced in one step.

[0055] Example 2

[0056] Using the above Figure 1The ball milling mixing reaction shown is a system for directly producing solid polyferric sulfate in one step. 100 parts by weight of industrial-grade ferrous sulfate pentahydrate is weighed and added into the feeding port of the cylinder 1 of the horizontal ball mill reaction equipment, and then 300 parts by weight of zircon balls are added. After the feeding port of the cylinder 1 is sealed with a sealing cover, the speed of the cylinder 1 is controlled to 30 rpm by the variable frequency reduction motor. The temperature of the dry hot air entering the cylinder 1 is controlled to 35°C by the heating furnace thermocouple, and the water vapor vacuum filtration equipment 5 is turned on. After 20 minutes, the ferrous sulfate pentahydrate crystals are ground into fine particles. 5 parts by weight of solid calcium carbonate powder are evenly transported into the cylinder 1 from the hollow first support shaft at one end of the cylinder 1 through the pneumatic diaphragm pump feeding equipment 4. After 5 minutes, the solid calcium carbonate and powdered ferrous sulfate pentahydrate can be fully mixed during the sliding process of the glass balls in the cylinder 1, and then the pneumatic diaphragm pump feeding equipment 4 is used. 8 parts by weight of sodium chlorate crystals are evenly conveyed into the cylinder 1 within 10 minutes. After 30 minutes of oxidation reaction, the color of the material gradually changes from light yellow to yellow-brown. At this time, most of the ferrous sulfate has been oxidized to ferric hydroxysulfate. Then, 10 parts by weight of 98wt% concentrated sulfuric acid are evenly sprayed onto the surface of the material in an atomized form through the second hollow support shaft on the other side of the cylinder 1 using a high-pressure pump atomization and dosing device 3. After the material is further oxidized, hydrolyzed and polymerized for 20 minutes, the heating furnace thermocouple of the hot air conveying device 2 is adjusted to increase the temperature of the hot air entering the cylinder 1 to 60°C. The material is gradually dehydrated and dried under the action of ball milling mixing and hot air drying. After 20 minutes, the material is ground and pulverized into a brown solid powder. After the reaction is completed, the material is discharged, and a solid polyferric sulfate coagulant is directly produced in one step.

[0057] In addition, it should be understood that after reading the above description of the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

Claims

1. A process for directly producing solid polyferric sulfate by ball milling and mixing reaction in one step, characterized in that: Including steps: S1, adding ferrous sulfate containing crystal water and grinding balls into the cylinder of a horizontal ball mill reaction equipment, supplying hot air at 30-45°C into the cylinder, and rotating the cylinder, driving the grinding balls to slide back and forth, thereby grinding the ferrous sulfate containing crystal water crystal particles into fine particles; S2, a conditioning agent is fed into the cylinder. During the sliding process of the grinding balls, the conditioning agent is mixed with the ferrous sulfate powder containing crystal water. Then, solid particles of chlorate oxidant are continuously and evenly fed into the cylinder for oxidation reaction. The color of the material changes from yellow-green to light yellow, and then gradually changes from light yellow to yellow-brown. The conditioning agent is at least one of calcium carbonate, sodium carbonate, ammonium sulfate, and ammonium bicarbonate; The weight ratio of the conditioning agent to the ferrous sulfate containing crystal water is 5-10:100; S3, spraying concentrated sulfuric acid with a mass concentration of more than 98% evenly onto the surface of the material in the cylinder in an atomized form, adjusting the temperature of the hot air entering the cylinder to 45-60°C, and the material further undergoes oxidation, hydrolysis and polymerization reactions under the mechanical force of ball milling mixing and collision; The crystal water removed from ferrous sulfate containing crystal water and the water vapor and gas by-products generated by the reaction are extracted from the cylinder through negative pressure. During the ball milling reaction, the material is gradually dehydrated and dried through its own oxidation heat release, ball milling heat, and external hot air heat conduction. Under the mechanical force of the sliding grinding balls, it is gradually transformed into fine-grained uniform powder material, and brown-yellow solid powdered polyferric sulfate is directly produced in one step.

2. The process according to claim 1, characterized in that In step S1: The ferrous sulfate containing crystal water is ferrous sulfate heptahydrate and / or ferrous sulfate pentahydrate; The grinding balls are at least one of glass balls, ceramic balls, and zircon balls; The weight ratio of the grinding balls to the ferrous sulfate containing crystal water is 2.5-3.5:

1.

3. The process according to claim 1, characterized in that In step S1: The cylinder speed is 25-40 rpm; The ball milling time is 20-30 minutes.

4. The process according to claim 1, characterized in that In step S2: The chlorate oxidant is sodium chlorate and / or potassium chlorate; The weight ratio of the chlorate oxidant solid particles to the ferrous sulfate containing crystal water is 5-8:

100.

5. The process according to claim 1, characterized in that In step S2, the oxidation reaction time is 30-50 minutes.

6. The process according to claim 1, characterized in that In step S3, the weight ratio of the concentrated sulfuric acid to the ferrous sulfate containing crystal water is 7-10:

100.

7. The process according to claim 1, characterized in that In step S3, the reaction time is 40-90 minutes.

8. The process according to claim 1, characterized in that The process adopts a system for directly producing solid polyferric sulfate in one step by ball milling and mixing reaction. The system for directly producing solid polyferric sulfate in one step by ball milling and mixing reaction comprises: A horizontal ball mill reaction device comprises a rotatable horizontal cylinder, the cylinder being provided with an opening which can be used as a feeding port or a discharging port, and a sealing cover plate and a grid cover plate which are adapted to the opening and can be detachably replaced with each other; Hot air delivery equipment for delivering hot air into the cylinder; Solid material pneumatic diaphragm pump dosing equipment for delivering solid particles of conditioning agent and chlorate oxidant into the cylinder; Acid liquid high-pressure pump atomizing dosing equipment used to spray concentrated sulfuric acid with a mass concentration of more than 98% evenly into the cylinder in an atomized form; The water vapor vacuum filtration equipment is used to remove the crystal water of ferrous sulfate containing crystal water and the water vapor and gas by-products generated by the reaction from the cylinder through negative pressure.

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