Preparation process for producing polyaluminum chloride

Abstract

The invention relates to the technical field of polyaluminum chloride, and discloses a preparation process for polyaluminum chloride production, which comprises the following steps: step 1, preparation and pretreatment of raw materials: selecting 80-150kg of bauxite and 200-300kg of hydrochloric acid as main raw materials, and preparing 0.7-1.0 kg of biomass charcoal-based catalyst, 30-40kg of composite modifier and 30-40kg of coal gangue as auxiliary materials; 2, acid dissolution reaction: adding the mixed raw material and hydrochloric acid into a reaction kettle according to a mass ratio of 1: (2.2-2.5), and adding a biomass charcoal-based catalyst accounting for 0.5-1% of the total mass of the raw material at the same time; 3, preliminary filtration: after the reaction in the reaction kettle is finished, the reaction liquid is filtered through a ceramic membrane filter, according to the preparation technology for producing the polyaluminum chloride, the biomass charcoal-based catalyst is added in the acid dissolution stage through the biomass charcoal-based catalyst synergistic acid dissolution technology, aluminum ions are adsorbed through a porous structure and surface acid groups of the biomass charcoal-based catalyst, and the reaction liquid is filtered through a ceramic membrane filter; the acid dissolution reaction rate is accelerated, so that the aluminum dissolution rate is increased to 95% or above, and meanwhile, the reaction temperature is reduced by 10-20 DEG C.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of polyaluminum chloride, in particular to a preparation process for polyaluminum chloride production. BACKGROUND

[0002] Polyaluminum chloride is a widely used in water treatment field of efficient inorganic polymer coagulant, its production process has calcium hot method, acid method, alkali method, spray drying method, green catalytic synthesis method and so on nine kinds, process flow generally includes raw material preparation, reaction process, curing, drying and packaging storage and other process links.

[0003] The traditional preparation process of polyaluminum chloride has low utilization rate of aluminum source, difficult product base degree control, high energy consumption and secondary pollution and other problems. For example, bauxite acid dissolution method needs high temperature and high pressure conditions, and impurities such as iron and silicon affect the product quality; in the process of recycling of industrial waste, the dissolution rate of aluminum chloride is relatively low, and most of the dissolution rate is about 80%, and the reaction temperature is high, and the processing time is prolonged, so a preparation process with high production efficiency of polyaluminum chloride is needed. SUMMARY

[0004] (I) Technical problems to be solved In view of the shortcomings of the prior art, the present application provides a preparation process for polyaluminum chloride production, which solves the problem of low production efficiency of polyaluminum chloride.

[0005] (II) Technical scheme In order to achieve the above purpose, the present application provides the following technical scheme: a preparation process for polyaluminum chloride production, comprising the following steps: Step 1: preparation and pretreatment of raw materials: select bauxite 80-150 kg, hydrochloric acid 200-300 kg as main raw materials, prepare biomass charcoal catalyst 0.7-1.0 kg, composite modifier and coal gangue 30-40 kg, coal gangue is auxiliary material; Step 2: acid dissolution reaction: the mixed raw materials and hydrochloric acid are added into the reaction kettle according to the mass ratio of 1:2.2-2.5, and 0.5-1% of the total mass of the raw materials is added as biomass charcoal catalyst; Step 3: preliminary filtration: after the reaction of the reaction kettle is completed, the reaction liquid is filtered through a ceramic membrane filter, and the obtained solution is filtered through a ceramic membrane filter by cross flow filtration, the ceramic membrane pore size is 0.1-0.5um, the filtration area is 10-20 square meters, which is used for preliminary separation of insoluble impurities in the acid solution; Step 4: two-stage polymerization reaction: Fast reaction stage: the solution after preliminary filtration is transferred to the polymerization reactor, and 40% of the total mass of the composite modifier is added; Deep polymerization stage: cooling to 75-90℃, pressure drops to 0.15-0.3MPa, adding the remaining 60% composite modifier; Step five: dynamic impurity separation: during the polymerization reaction, using a multi-stage dynamic impurity separation device to separate impurities in real time; Step six: waste heat recovery: Using a plate heat exchanger to recover reaction heat, heat exchange between 85-95℃ reaction liquid and 20-30℃ raw material liquid, preheating the raw material liquid to 60-70℃, heat recovery rate ≥75%; Step seven: concentration and crystallization: Concentration and crystallization use a three-effect evaporation system to concentrate the solution to a density of 1.32-1.35g / cm 3 , crystallization at 25-35℃ for 12-24 hours; Step eight: solid-liquid separation: Using a horizontal screw centrifuge for solid-liquid separation, obtaining polyaluminum chloride solids and mother liquor; Step nine: drying and packaging: The solids are sent to a flash dryer and dried at an inlet air temperature of 180-220℃ and an outlet air temperature of 80-100℃ for 10-15 minutes, and packaged into finished products; Step ten: mother liquor recycling: Strengthening the recycling of mother liquor, adding an ion exchange resin treatment step, achieving zero wastewater discharge.

[0006] Preferably, the bauxite is crushed to a particle size of 100-200 mesh for standby use; the coal gangue is an auxiliary material, which is crushed to 100 mesh or less, calcined at 800-900℃, activated for 2 hours, and soaked in 20kg of waste hydrochloric acid for 30 minutes to remove surface impurities, then filtered and mixed with the bauxite at a mass ratio of 1:3.

[0007] Preferably, the mixed raw materials are reacted with hydrochloric acid at a temperature of 70-85℃ and a pressure of 0.15-0.3MPa for 1.5-2 hours, during which the mass transfer is strengthened by ultrasonic assistance, and when the membrane flux decreases by 15%-20%, backwashing combined with chemical cleaning is used for regeneration.

[0008] Preferably, the rapid reaction stage: control the temperature at 110-130℃ and the pressure at 0.5-0.7MPa, and react for 0.8-1.2 hours; Deep polymerization stage: react for 1.5-2.5 hours, during which ozone is introduced to oxidize ferrous ions.

[0009] Preferably, the device in step five includes: a primary cyclone separator, a secondary magnetic separator, and a tertiary nanofiltration membrane; The multi-stage dynamic impurity separation device is composed of a first-stage cyclone separator, a second-stage magnetic separator and a third-stage nanofiltration membrane, and realizes the graded removal of impurities.

[0010] Preferably, the plate heat exchanger in step six adopts stainless steel corrugated plates, and the heat exchange area is 30-50 square meters, which is used for preheating raw materials by recovering reaction heat. Method for use: the reaction liquid at 85-95 DEG C and the raw material liquid at 20-30 DEG C are respectively introduced into the two sides of the heat exchanger, the flow rate is controlled at 0.5-1 m / s, the outlet temperature of the raw material liquid is monitored by a temperature sensor, and when the preheating temperature does not reach 60-70 DEG C, the heat exchange time or flow rate is adjusted.

[0011] Preferably, the three-effect evaporation system is composed of three evaporators connected in series, adopts countercurrent operation, and has an evaporation capacity of 5-10 t / h, which is used for concentrating the polyaluminum chloride solution.

[0012] Preferably, the horizontal screw centrifuge has a drum diameter of 800-1000 mm and a rotating speed of 3500-4500 rpm, which is used for solid-liquid separation.

[0013] Preferably, the flash dryer has a drying chamber diameter of 1-1.5 m, a height of 3-5 m, a hot air inlet temperature of 180-220 DEG C, and an outlet temperature of 80-100 DEG C, which is used for rapidly drying the polyaluminum chloride solid.

[0014] (Three) beneficial effects Compared with the prior art, the polyaluminum chloride production preparation process provided by the application has the following beneficial effects: 1. The polyaluminum chloride production preparation process, the biomass carbon-based catalyst cooperates with the acid dissolution technology to add a biomass carbon-based catalyst in the acid dissolution stage, adsorbs aluminum ions through the porous structure and surface acidic groups, accelerates the acid dissolution reaction rate, increases the aluminum dissolution rate to more than 95%, and reduces the reaction temperature by 10-20 DEG C.

[0015] 2. The polyaluminum chloride production preparation process can use coal gangue, waste hydrochloric acid and other industrial wastes as auxiliary raw materials, remove harmful substances through pretreatment and impurity dynamic separation system, realize solid waste resource utilization and zero wastewater discharge, and reduce production cost by more than 20%. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 The figure is a schematic diagram of the polyaluminum chloride production preparation process of the application. DETAILED DESCRIPTION

[0017] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0018] See also Figure 1 The present invention provides a new technical solution: a preparation process for the production of polyaluminium chloride, comprising the following steps: Step 1: Preparation and pretreatment of raw materials: 80-150 kg of bauxite and 200-300 kg of hydrochloric acid are selected as the main raw materials, and the bauxite is crushed to a particle size of 100-200 mesh and set aside; At the same time, prepare 0.7-1.0 kg of biomass carbon-based catalyst (carbonized rice husk and loaded with SO4 2 -Preparation, specific surface area ≥800m 2 / g), composite modifier (sodium silicate 8-10kg: magnesium sulfate 2-3kg: graphene quantum dots 0.1-0.15kg = 8:2:0.1 mass ratio); 30-40kg of coal gangue, with coal gangue as auxiliary material, is crushed to below 100 mesh, calcined at 800-900℃, activated for 2 hours, soaked in 20kg of waste hydrochloric acid (HCl concentration ≥15%) for 30 minutes to remove surface impurities, filtered and mixed with bauxite at a mass ratio of 1:3; Step 2: Acid dissolution reaction: Add the mixed raw materials and hydrochloric acid into the reactor at a mass ratio of 1: (2.2-2.5), and add 0.5-1% of the total mass of the raw materials into the biomass carbon-based catalyst; The reaction was carried out at a temperature of 70-85°C and a pressure of 0.15-0.3 MPa for 1.5-2 hours, during which mass transfer was enhanced by ultrasound assistance (frequency 20-40 kHz); The reactor is made of glass-lined material and has heating, stirring and pressure control functions. It has a volume of 5-10 cubic meters and is suitable for acid dissolution and polymerization reactions. Usage: During the acid dissolution stage, add pretreated bauxite and coal gangue mixed raw materials and hydrochloric acid through the feed port, and then add the biomass carbon-based catalyst; start the agitator (speed 80-120rpm), turn on the electric heating device and pressure control system, raise the temperature to 70-85℃, maintain the pressure at 0.15-0.3MPa, and react for 1.5-2 hours; during the polymerization reaction, empty the reactor and transfer the acid-soluble filtrate, add the composite modifier in stages, adjust the temperature and pressure parameters, observe the solution state through the sight glass during the reaction, and obtain the reaction solution; Step three: preliminary filtration: after the reaction in the reactor is completed, the reaction solution is filtered through a ceramic membrane filter (pore size 0.1-0.5 μm) to remove insoluble impurities. The obtained solution is filtered through a ceramic membrane filter in a cross-flow filtration mode, with a ceramic membrane pore size of 0.1-0.5 μm and a filtration area of 10-20 square meters, to preliminarily separate insoluble impurities from the solution after acid dissolution; Method of use: after the acid dissolution reaction is completed, the solution is pumped into a ceramic membrane filter through a pipeline, with a feed pressure of 0.2-0.3 MPa and a flow rate of 1-2 m 3 / h. The filtered clear liquid flows into a storage tank. When the membrane flux decreases by 15%-20%, backwashing (pressure 0.4-0.5 MPa) combined with chemical cleaning (immersion in 0.5% sodium hydroxide solution for 2-3 hours) is used for regeneration; Step four: two-stage polymerization reaction: Fast reaction stage: the preliminarily filtered solution is transferred to a polymerization reactor, 40% of the total mass of the composite modifier is added, the temperature is controlled at 110-130°C, the pressure is controlled at 0.5-0.7 MPa, and the reaction is carried out for 0.8-1.2 hours; Deep polymerization stage: the temperature is lowered to 75-90°C, the pressure is lowered to 0.15-0.3 MPa, the remaining 60% of the composite modifier is added, and the reaction is carried out for 1.5-2.5 hours. During the reaction, ozone (concentration 5-10 mg / L) is introduced to oxidize ferrous ions; Step five: dynamic impurity separation: during the polymerization reaction, a multi-stage dynamic impurity separation device is used to separate impurities in real time. The device includes: A primary cyclone separator (to remove particles with a particle size >50 μm); A secondary magnetic separator (to remove ferromagnetic impurities); A tertiary nanofiltration membrane (to remove organic matter with a molecular weight >200 Da); The multi-stage dynamic impurity separation device is composed of a primary cyclone separator (to separate particles with a particle size >50 μm), a secondary magnetic separator (to remove ferromagnetic impurities), and a tertiary nanofiltration membrane (to remove organic matter with a molecular weight >200 Da), achieving the graded removal of impurities; Method of use: the polymerization reaction solution is sequentially introduced into each unit through a pipeline. The cyclone separator is controlled at an inlet pressure of 0.3-0.4 MPa, and the separated solid phase is discharged from the bottom. The magnetic separator is set at a magnetic field strength of 1-1.5 T, and the adsorbed ferromagnetic impurities are periodically cleaned. The nanofiltration membrane unit is controlled at an operating pressure of 0.8-1.2 MPa. The permeate is introduced into the next process, and the retentate is returned to the polymerization reactor for secondary treatment; Step six: waste heat recovery: The reaction heat is recovered using a plate heat exchanger to exchange heat between the 85-95°C reaction liquid and the 20-30°C raw material liquid, preheating the raw material liquid to 60-70°C, with a heat recovery rate of ≥75%. The plate heat exchanger uses stainless steel corrugated plates, and the heat exchange area is 30-50 square meters, which is used to recover reaction heat and preheat raw materials; Method for use: pass the reaction liquid at 85-95°C and the raw material liquid at 20-30°C into the two sides of the heat exchanger, control the flow rate at 0.5-1 m / s, monitor the outlet temperature of the raw material liquid through a temperature sensor, and adjust the heat exchange time or flow rate when the preheating temperature does not reach 60-70°C; Step seven: concentration and crystallization The concentration and crystallization use a three-effect evaporation system to concentrate the solution to a density of 1.32-1.35 g / cm 3 at 25-35°C for 12-24 hours; The three-effect evaporation system is composed of three evaporators connected in series and uses countercurrent operation, with an evaporation capacity of 5-10 t / h, which is used to concentrate the polyaluminum chloride solution; Method for use: send the filtered solution into the first-effect evaporator, control the heating steam pressure at 0.3-0.4 MPa and the temperature at 105-110°C; the secondary steam generated by the first-effect evaporator is used as the heat source for the second-effect evaporator, and so on; monitor the solution density during the concentration process, and when it reaches 1.32-1.35 g / cm 3 , deliver the concentrated solution to the crystallization kettle; Step eight: solid-liquid separation Use a horizontal screw centrifuge (rotating speed 3500-4500 rpm) for solid-liquid separation to obtain polyaluminum chloride solids and mother liquor; The horizontal screw centrifuge has a drum diameter of 800-1000 mm and a rotating speed of 3500-4500 rpm, which is used for solid-liquid separation; Method for use: send the material after concentration and crystallization into the centrifuge through the feeding pipe, start the equipment to reach the set rotating speed, the solids adhere to the inner wall of the drum under the action of centrifugal force, and the liquid is discharged through the filter screen on the drum; after the separation is completed, reduce the rotating speed to take out the solids, and collect the mother liquor into a storage tank; Step nine: drying and packaging Send the solids into a flash dryer, dry them for 10-15 minutes under the conditions of an air inlet temperature of 180-220°C and an air outlet temperature of 80-100°C, and package the finished product; The drying chamber of the flash dryer has a diameter of 1-1.5 m and a height of 3-5 m, the hot air inlet temperature is 180-220°C, and the outlet temperature is 80-100°C, which is used for rapid drying of polyaluminum chloride solids; Method for use: send the wet material after solid-liquid separation into the dryer through a screw conveyor, hot air enters from the bottom to fully contact with the material, and the material is rapidly dispersed and dried under the action of the high-speed rotating dispersing device; the dried product is collected through a cyclone separator and a bag-type dust collector, and is packaged through the discharge port; Step 10: Recycling of mother liquor: Strengthen the recycling of mother liquor, add ion exchange resin treatment steps, and achieve zero wastewater discharge.

[0019] Example 1: Raw materials preparation: Bauxite: Al2O3 content 60%, Fe2O3 content 2.5%, crushed to 180 mesh, 100kg; Gangue: Al2O3 content 20%, crushed to 80 mesh, calcined at 850℃ for 2 hours, 33kg; Hydrochloric acid: concentration 31%, 250kg; Biomass carbon-based catalyst: rice husk carbonized at 600℃ and loaded with 10% SO4 2- , specific surface area 850m 2 / g, 0.7kg; Composite modifier: sodium silicate (modulus 3.2) 8kg, magnesium sulfate (purity 98%) 2kg, graphene quantum dots (particle size 5-10nm) 0.1kg; Pretreatment process: Mix the gangue and bauxite, add 20kg of waste hydrochloric acid (concentration 18%) and soak for 30 minutes, filter and wash with water until the pH value reaches 6-7; Acid dissolution reaction: the raw materials were put into the reactor, the stirrer was started (speed 100 rpm), the temperature was raised to 75°C, the pressure was 0.2 MPa, and the ultrasonic device was turned on (frequency 30 kHz). The reaction was carried out for 1.8 hours. During this period, samples were taken every 30 minutes to test the aluminum dissolution rate. At the end of the reaction, the aluminum dissolution rate reached 94%; Preliminary filtration: After acid dissolution, the solution passes through a ceramic membrane filter with a feed pressure of 0.25 MPa. After filtration, the turbidity of the solution drops below 5 NTU; Two-stage polymerization reaction: Rapid reaction stage: the solution was transferred to a polymerization kettle, 4 kg of composite modifier was added, the temperature was raised to 120 ° C, the pressure was 0.6 MPa, and the reaction was carried out for 1 hour; Deep polymerization stage: cool to 85°C, pressure 0.2 MPa, add the remaining 6.1 kg of composite modifier, introduce ozone (concentration 8 mg / L), and react for 2 hours; Dynamic impurity separation: The solution passes through a cyclone separator (inlet pressure 0.35 MPa), a magnetic separator (magnetic field strength 1.2 T), and a nanofiltration membrane (operating pressure 1 MPa) in sequence. After treatment, the iron content of the solution is reduced to below 50 ppm. Waste heat recovery: The raw material liquid is preheated from 25°C to 68°C through a plate heat exchanger, with a heat recovery rate of 78%; Concentration and crystallization: In a three-effect evaporation system, the steam pressure of the first effect is 0.35 MPa, the temperature is 108°C, and the density of the concentrated solution is 1.33 g / cm 3crystallization at 30℃ for 18 hours; Solid-liquid separation: horizontal screw centrifuge at 4000 rpm for 15 minutes to obtain wet solid and mother liquor; Drying and packaging: flash dryer with inlet temperature of 200℃ and outlet temperature of 90℃ for 12 minutes, and then the product is packaged; Mother liquor treatment: the mother liquor is treated by strong acid cation exchange resin (type 001x7) and then returned to the acid dissolution process; Product testing: base value 87%, Al2O3 content 30.5%, after treating river water with turbidity 50 NTU and COD 150 mg / L, the residual turbidity is 0.4 NTU, and the COD removal rate is 86%.

[0020] Example Two: Raw material preparation: bauxite: Al2O3 content 58%, 80 kg, coal gangue: Al2O3 content 22%, 40 kg, hydrochloric acid: concentration 30%, 220 kg, biomass charcoal-based catalyst: 1.0 kg; The ratio of composite modifier is the same as in Example One; Pretreatment: coal gangue calcination at 900℃ for 2 hours; Acid dissolution reaction: temperature 80℃, pressure 0.25 MPa, ultrasonic frequency 35 kHz, reaction time 2 hours, aluminum dissolution rate 96%; Polymerization reaction: fast stage temperature 125℃, pressure 0.65 MPa; deep stage temperature 88℃, pressure 0.25 MPa, ozone concentration 10 mg / L; Dynamic impurity separation: through cyclone separator (inlet pressure 0.35 MPa), magnetic separator (magnetic field strength 1.2 T), and nanofiltration membrane (operating pressure 1 MPa) in sequence, the iron content of the treated solution is reduced to below 50 ppm; Waste heat recovery: through plate heat exchanger, the raw material liquid is preheated from 25℃ to 68℃, and the heat recovery rate is 78%; Concentration and crystallization: in a three-effect evaporation system, the first effect has a steam pressure of 0.35 MPa and a temperature of 108℃, and after concentration, the solution has a density of 1.33 g / cm 3 crystallization at 30℃ for 18 hours; Solid-liquid separation: horizontal screw centrifuge at 4000 rpm for 15 minutes to obtain wet solid and mother liquor; Drying and packaging: flash dryer with inlet temperature of 200℃ and outlet temperature of 90℃ for 12 minutes, and then the product is packaged; Mother liquor treatment: the mother liquor is treated by strong acid cation exchange resin (type 001x7) and then returned to the acid dissolution process; Product detection: basicity 89%, Al2O3 content 31.2%, raw material cost per ton of product reduced by 23% compared with traditional process, color removal rate of printing and dyeing wastewater after treatment 88%.

[0021] Example three: Raw material preparation: bauxite: Al2O3 content 62%, 120 kg; Coal gangue: 30 kg; Hydrochloric acid: 300 kg; Biomass charcoal-based catalyst: 0.8 kg; Composite modifier: sodium silicate 10 kg, magnesium sulfate 3 kg, graphene quantum dot 0.15 kg; Acid dissolution reaction: temperature 78℃, pressure 0.22MPa, reaction time 1.6 hours; Polymerization reaction: temperature 90℃ in deep polymerization stage, reaction time 2.5 hours, and intensive stirring (rotation speed 150rpm) to promote the dispersion of the modifier; Dynamic impurity separation: sequentially through cyclone separator (inlet pressure 0.35MPa), magnetic separator (magnetic field strength 1.2T), and nanofiltration membrane (operating pressure 1MPa), and the iron content of the treated solution is reduced to below 50ppm; Waste heat recovery: through plate heat exchanger, the raw material liquid is preheated from 25℃ to 68℃, and the heat recovery rate is 78%; Concentration and crystallization: in a three-effect evaporation system, the steam pressure in the first effect is 0.35MPa, and the temperature is 108℃, and after concentration, the solution density is 1.33g / cm 3 , and crystallization at 30℃ for 18 hours; Solid-liquid separation: horizontal screw centrifuge rotation speed 4000rpm, separation time 15 minutes, to obtain wet solid and mother liquor; Drying and packaging: flash dryer inlet air temperature 200℃, outlet air temperature 90℃, drying time 12 minutes, and product packaging; Mother liquor treatment: after treatment by strong acid cation exchange resin (type 001×7), the mother liquor is returned to the acid dissolution process; Product detection: basicity 90%, Al2O3 content 32%, after treatment of printing and dyeing wastewater with turbidity 1000NTU and SS 800mg / L, the residual turbidity is 15NTU, the SS removal rate is 95%, and the color removal rate is 92%.

[0022] In this process, the biomass charcoal-based catalyst cooperates with the acid dissolution technology to add biomass charcoal-based catalyst in the acid dissolution stage, adsorb aluminum ions through its porous structure and surface acidic groups, accelerate the acid dissolution reaction rate, and increase the aluminum dissolution rate to more than 95%, while reducing the reaction temperature by 10-20℃.

[0023] The process can use coal gangue, waste hydrochloric acid and other industrial wastes as auxiliary raw materials, remove harmful substances through pretreatment and impurity dynamic separation system, realize solid waste resource utilization and zero discharge of wastewater, and reduce production cost by more than 20%.

[0024] While embodiments of the application have been shown and described, it is to be understood that the embodiments described are merely divergences of the principles and spirit of the application and that numerous modifications, changes, substitutions, and alterations can be made thereto without departing from the spirit and scope of the application as defined by the appended claims and their equivalents.

Claims

1. A preparation process for the production of polyaluminium chloride, characterized in that: The following steps are involved: Step 1: Preparation and pretreatment of raw materials: Select 80-150kg of bauxite and 200-300kg of hydrochloric acid as the main raw materials, prepare 0.7-1.0kg of biomass carbon-based catalyst, 30-40kg of composite modifier and coal gangue, and use coal gangue as auxiliary material; Step 2: Acid dissolution reaction: Add the mixed raw materials and hydrochloric acid into the reactor at a mass ratio of 1:2.2-2.5, and add 0.5-1% of the total mass of the raw materials into the biomass carbon-based catalyst; Step 3: Preliminary filtration: After the reaction in the reactor is completed, the reaction liquid is filtered through a ceramic membrane filter to remove insoluble impurities. The resulting solution is filtered through a ceramic membrane filter in a cross-flow manner. The ceramic membrane has a pore size of 0.1-0.5 μm and a filtration area of ​​10-20 square meters, which is used to preliminarily separate insoluble impurities in the solution after acid dissolution; Step 4: Two-stage polymerization reaction: Rapid reaction stage: the solution after preliminary filtration is transferred to the polymerization reactor and 40% of the total mass of the composite modifier is added; Deep polymerization stage: cool down to 75-90℃, reduce pressure to 0.15-0.3MPa, and add the remaining 60% composite modifier; Step 5: Dynamic impurity separation: During the polymerization process, a multi-stage dynamic impurity separation device is used to separate impurities in real time; Step 6: Waste heat recovery: The plate heat exchanger is used to recover the reaction heat, and the reaction liquid at 85-95℃ is heat exchanged with the raw material liquid at 20-30℃, so that the raw material liquid is preheated to 60-70℃, and the heat recovery rate is ≥75%; Step 7: Concentration and crystallization: Concentrated crystallization uses a triple-effect evaporation system to concentrate the solution to a density of 1.32-1.35g / cm 3 , crystallize at 25-35°C for 12-24 hours; Step 8: Solid-liquid separation: Use a horizontal spiral centrifuge to perform solid-liquid separation to obtain polyaluminium chloride solid and mother liquor; Step 9: Dry packaging: The solid is sent to the flash dryer and dried for 10-15 minutes at an inlet air temperature of 180-220°C and an outlet air temperature of 80-100°C, and then packaged to obtain the finished product; Step 10: Recycling of mother liquor: Strengthen the recycling of mother liquor, add ion exchange resin treatment steps, and achieve zero wastewater discharge.

2. The process for producing polyaluminium chloride according to claim 1, wherein: The bauxite is crushed to a particle size of 100-200 mesh and set aside; coal gangue is used as an auxiliary material, the coal gangue is crushed to less than 100 mesh, calcined at 800-900° C., activated for 2 hours, soaked in 20 kg of waste hydrochloric acid for 30 minutes to remove surface impurities, filtered, and mixed with bauxite at a mass ratio of 1:

3.

3. The preparation process for producing polyaluminium chloride according to claim 2, wherein: The mixed raw material reacts with hydrochloric acid at a temperature of 70-85° C. and a pressure of 0.15-0.3 MPa for 1.5-2 hours, during which time ultrasound is used to enhance mass transfer. When the membrane flux decreases by 15%-20%, backwashing combined with chemical cleaning is used for regeneration.

4. The preparation process for producing polyaluminium chloride according to claim 3, wherein: The rapid reaction stage: controlling the temperature at 110-130°C and the pressure at 0.5-0.7 MPa, and reacting for 0.8-1.2 hours; Deep polymerization stage: The reaction lasts for 1.5-2.5 hours, during which ozone is introduced to oxidize ferrous ions.

5. The preparation process for producing polyaluminium chloride according to claim 4, wherein: The device in step 5 includes: a first-stage cyclone separator, a second-stage magnetic separator and a third-stage nanofiltration membrane; The multi-stage dynamic impurity separation device consists of a first-stage cyclone separator, a second-stage magnetic separator, and a third-stage nanofiltration membrane to achieve graded removal of impurities.

6. A preparation process for producing polyaluminium chloride according to claim 5, characterized in that: The plate heat exchanger in step 6 uses stainless steel corrugated plates with a heat exchange area of ​​30-50 square meters, which is used to recover reaction heat and preheat the raw materials; Usage: Pass the reaction liquid at 85-95℃ and the raw material liquid at 20-30℃ into the channels on both sides of the heat exchanger respectively, control the flow rate to 0.5-1m / s, monitor the outlet temperature of the raw material liquid through the temperature sensor, and adjust the heat exchange time or flow rate when the preheating temperature does not reach 60-70℃.

7. A preparation process for producing polyaluminium chloride according to claim 6, characterized in that: The triple-effect evaporation system consists of three evaporators connected in series, adopts countercurrent operation, has an evaporation capacity of 5-10 t / h, and is used to concentrate polyaluminium chloride solution.

8. A preparation process for producing polyaluminium chloride according to claim 7, characterized in that: The horizontal spiral centrifuge has a drum diameter of 800-1000 mm and a rotation speed of 3500-4500 rpm, and is used for solid-liquid separation.

9. A preparation process for producing polyaluminium chloride according to claim 8, characterized in that: The flash dryer has a drying chamber with a diameter of 1-1.5 m, a height of 3-5 m, a hot air inlet temperature of 180-220° C., and an outlet temperature of 80-100° C., and is used for rapidly drying polyaluminium chloride solid.

Images