Short-process reverse osmosis pretreatment method for high-salinity and high-hardness mine water

Abstract

The invention discloses a short-process reverse osmosis pretreatment method for high-salinity and high-hardness mine water. The method comprises the following steps: sequentially adding an alkaline agent and a silicon removal agent into the high-salinity and high-hardness mine water for reaction; the preparation method of the silicon removal agent comprises the following steps: placing porous magnesium oxide in a polyferric chloride solution for vacuum impregnation, separation and gradient drying, then placing the porous magnesium oxide in an AlCl3 solution for impregnation, separation and drying, and calcining to obtain the silicon removal agent. Effluent enters a concentration tank; the outlet water of the concentration tank enters a tubular micro-filtration membrane device to be filtered, and the outlet water is pretreated mine water; sludge discharged by the tubular microfiltration membrane device is dehydrated by the stacked screw machine and then is subjected to low-temperature sludge drying by using non-condensable gas in the evaporative crystallization heating chamber. Magnesium oxide is modified to serve as a silicon removal agent, and a tubular membrane device is used for filtering, so that the hardness and silicon removal effect can be effectively improved, the dosage is reduced, and the technological process is shortened; meanwhile, the sludge is dewatered by adopting a stacked screw machine and a low-temperature drying process, so that the sludge can be greatly reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, in particular to a short-process reverse osmosis pretreatment method for high-salt and high-hardness mine water. Background Art

[0002] Coal mines are widely distributed in my country, and the quality of the mine water produced during coal production varies widely. Mine water in the Huaibei and Huainan regions has a low salt content and low hardness, often allowing it to enter reverse osmosis equipment after sedimentation and filtration. However, mine water in the Yulin region of Shaanxi Province is characterized by high salt content and high hardness, requiring hardness removal before entering reverse osmosis equipment.

[0003] In the prior art, chemical precipitation plus membrane treatment processes are generally used to perform reverse osmosis pretreatment on high-salt, high-hardness wastewater. For example, patent CN116444106B discloses a short-process zero-discharge treatment method and device for high-hardness, high-sulfate coal mine water. The method first performs coagulation and clarification to remove substances such as coal powder and colloids. Chemical softening is then used to remove calcium, magnesium, and silicon. The effluent is further filtered and the pH value is adjusted to 7.8-8.3. Ultrafiltration, weak acid cation exchange, carbon dioxide removal, reverse osmosis desalination, disc-tube nanofiltration with simultaneous salt separation and concentration, and evaporation crystallization are then performed in sequence to achieve zero discharge of high-hardness, high-sulfate coal mine water.

[0004] However, the existing process has limited effect in removing hardness and silicon, and produces a large amount of sludge; it also occupies a large area, which is not suitable for renovation projects or projects with compact plant areas. Summary of the Invention

[0005] The present invention aims to overcome the above-mentioned problems existing in the reverse osmosis pretreatment method of high-salt and high-hardness wastewater in the prior art, and provides a short-process reverse osmosis pretreatment method for high-salt and high-hardness mine water. Magnesium oxide is modified as a desiliconizing agent, and a tubular membrane device is used for filtration, which can effectively improve the hardness and silicon removal effect, reduce the amount of added drugs, and shorten the process flow; at the same time, the present invention adopts a spiral stacking machine + low-temperature drying process to dehydrate the sludge, which can achieve great sludge reduction.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: A short-process reverse osmosis pretreatment method for high-salt and high-hardness mine water, comprising the following steps: (1) High-salt and high-hardness mine water enters the first reaction tank and is added with an alkali agent and a desiliconizer for reaction; the preparation method of the desiliconizer is as follows: porous magnesium oxide is placed in a polyferric chloride solution for vacuum impregnation, separated, gradient dried, and then placed in an AlCl3 solution for impregnation, separated, dried, and then calcined to obtain the desiliconizer; (2) The effluent from the first reaction tank enters the second reaction tank and an alkali agent is added to adjust the pH to 10.5-11.5; (3) The effluent from the second reaction tank is precipitated in the concentration tank and then enters the tubular microfiltration membrane device for filtration. The effluent is pretreated mine water; (4) The sludge discharged from the tubular microfiltration membrane device is dehydrated by the screw stacker and then dried at low temperature using the non-condensable gas in the evaporation crystallization heating chamber.

[0007] The present invention first adds an alkaline agent in step (1) to remove calcium and magnesium ions in mine water, and then adds a silicon remover in step (2) to remove silicon in the water. After precipitation in a concentration tank, the water enters a tubular membrane system for filtration to further remove suspended matter, colloids, calcium, magnesium, and silicon hardness in the water. The effluent can directly enter a reverse osmosis device for subsequent treatment.

[0008] The present invention is to pyrolyze porous magnesium oxide after being immersed in polyferric chloride and aluminum chloride solution successively as desiliconizing agent, magnesium oxide and silicic acid reaction generate magnesium silicate precipitation, and polyferric chloride is as inorganic polymer flocculant, can pass through electric neutralization and adsorption bridging effect, make fine precipitation particles condense into larger flocs, promote magnesium silicate sedimentation velocity. The present invention is to load polyferric chloride in the pore of magnesium oxide by vacuum impregnation in combination with gradient drying, can increase the contact site of flocculant and silicate, accelerate magnesium silicate precipitation generation rate, significantly improve desiliconization effect. Moreover, polyferric chloride is loaded in the pore of magnesium oxide and can be fixed polyferric chloride by physical confinement effect, avoid the dispersion loss of the medicament caused by hydraulic scouring, extend action time, reduce medicament consumption; The rigid pore of magnesium oxide can also provide support for polyferric chloride, prevent it from causing structural collapse due to flocculation expansion during the reaction, improve the density of precipitate, make it easier to dehydrate. At the same time, the present invention loads aluminum chloride on the surface of magnesium oxide after loading polyferric chloride, and the aluminum ions are hydrolyzed to generate aluminum hydroxide colloid, which can form more highly active adsorption sites, effectively adsorb silicate in wastewater, and further improve the removal efficiency of silicon; the synergistic effect of magnesium oxide and aluminum chloride can reduce the total dosage of the reagent and reduce the treatment cost; at the same time, loading aluminum chloride on the surface of magnesium oxide can reduce the residual aluminum ion amount after the reaction, and will not cause scaling risk to subsequent membrane treatment or evaporation crystallization system. The present invention can simultaneously remove suspended matter, colloids and hardness in mine water through a tubular membrane device after chemical precipitation. The effluent can directly enter the reverse osmosis device, which can shorten the reverse osmosis pretreatment process and reduce the floor space. In addition, the present invention optimizes the desiliconization agent, which can improve the desiliconization efficiency, reduce the agent dosage, and reduce the sludge output. At the same time, the present invention uses a spiral stacking machine + low-temperature drying process to dehydrate the sludge, which can achieve great sludge reduction.

[0009] Preferably, the alkaline agent in steps (1) and (2) is selected from one or more of lime, sodium hydroxide and sodium carbonate.

[0010] Preferably, the pH value in the first reaction tank after adding the alkaline agent in step (1) is 9.5 to 10.5.

[0011] Preferably, when preparing the desiliconizer, the concentration of the polyferric chloride solution is 5 to 10 g / L, and hydrochloric acid is added to adjust its pH to 5.0 to 7.5. The mass volume ratio of the porous magnesium oxide to the polyferric chloride solution is 1 g:20 to 50 mL. The vacuum degree during vacuum impregnation is 0.05 to 0.1 MPa, and the impregnation time is 30 to 60 minutes. The present invention uses vacuum impregnation of the polyferric chloride solution, and the pressure difference can drive the solution into the pores, reducing surface residue.

[0012] Preferably, when preparing the desiliconizer, the concentration of the AlCl3 solution is 0.1 to 0.3 mol / L, the mass volume ratio of the porous magnesium oxide to the AlCl3 solution is 1 g:20 to 50 mL; and the immersion time of the porous magnesium oxide in the AlCl3 solution is 30 to 60 min.

[0013] Preferably, when preparing a desiliconizer, the gradient drying method after vacuum impregnation in a polyferric chloride solution is: first drying at 50-60°C for 1-3 hours, then heating to 80-100°C and drying for 3-5 hours. The gradient drying method employed after impregnation with the polyferric chloride solution in the present invention prevents rapid evaporation of the solution from the surface, thereby promoting the migration of the polyferric chloride into the pores as the solvent evaporates. Preferably, when preparing the desiliconizer, the calcination temperature is 250-350°C, and the calcination time is 1-2 hours.

[0014] Preferably, the dosage of the desiliconizer in step (1) is 3 to 6 times the silicon concentration in the mine water.

[0015] Preferably, stirring and aeration are performed in the concentration tank in step (3) to alleviate the sludge accumulation in the tank.

[0016] Preferably, the salt content of the high-salt and high-hardness mine water in step (1) is ≥5000 mg / L; the calcium hardness is ≥400 mg / L; the magnesium hardness is ≥200 mg / L; and the silicon content is ≥60 mg / L.

[0017] Preferably, the calcium and magnesium hardness of the pretreated mine water obtained in step (3) are both ≤20 mg / L, and the silicon content is ≤10 mg / L.

[0018] Therefore, the present invention has the following beneficial effects: (1) After chemical precipitation, the tubular membrane device can simultaneously remove suspended matter, colloids, and hardness from the mine water. The effluent can directly enter the reverse osmosis device, which can shorten the reverse osmosis pretreatment process and reduce the floor space. (2) Optimizing the desiliconization agent can improve the desiliconization efficiency, reduce the dosage of the agent, and reduce the sludge production; (3) Using a screw stacker + low-temperature drying process to dehydrate the sludge can achieve significant sludge reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0020] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0021] In the present invention, unless otherwise specified, all equipment and raw materials can be purchased from the market or are commonly used in the industry. The methods in the following embodiments, unless otherwise specified, are all conventional methods in the art.

[0022] Overall embodiment: A short-process reverse osmosis pretreatment method for high-salt and high-hardness mine water, the process flow is as follows Figure 1 As shown in , the steps include: (1) High-salt and high-hardness mine water enters the first reaction tank and is added with an alkali agent and a desiliconizer for reaction; the preparation method of the desiliconizer is as follows: porous magnesium oxide is placed in a polyferric chloride solution for vacuum impregnation, separated, gradient dried, and then placed in an AlCl3 solution for impregnation, separated, dried, and then calcined to obtain the desiliconizer; (2) The effluent from the first reaction tank enters the second reaction tank and an alkali agent is added to adjust the pH to 10.5-11.5; (3) The effluent from the second reaction tank is precipitated in the concentration tank and then enters the tubular microfiltration membrane device for filtration. The effluent is pretreated mine water; (4) The sludge discharged from the tubular microfiltration membrane device is dehydrated by the screw stacker and then dried at low temperature using the non-condensable gas in the evaporation crystallization heating chamber.

[0023] As a specific embodiment, the alkaline agent in step (1) is selected from one or more of lime, sodium hydroxide, and sodium carbonate.

[0024] As a specific embodiment, after adding the alkaline agent in steps (1) and (2), the pH value in the first reaction tank is 9.5 to 10.5.

[0025] As a specific embodiment, when preparing a silicon remover, the concentration of the polyferric chloride solution is 5 to 10 g / L, and hydrochloric acid is added to adjust its pH to 5.0 to 7.5. The mass volume ratio of porous magnesium oxide to the polyferric chloride solution is 1 g: 20 to 50 mL. The vacuum degree during vacuum impregnation is 0.05 to 0.1 MPa, and the impregnation time is 30 to 60 minutes. The present invention uses vacuum impregnation of the polyferric chloride solution, utilizing a pressure differential to drive the solution into the pores, reducing surface residue.

[0026] As a specific embodiment, when preparing the desiliconizer, the concentration of the AlCl3 solution is 0.1-0.3 mol / L, the mass volume ratio of the porous magnesium oxide to the AlCl3 solution is 1 g:20-50 mL; and the immersion time of the porous magnesium oxide in the AlCl3 solution is 30-60 min.

[0027] As a specific embodiment, when preparing a silicon remover, a gradient drying method is used after vacuum impregnation in a polyferric chloride solution: first drying at 50-60°C for 1-3 hours, then heating to 80-100°C for 3-5 hours. The gradient drying method used in the present invention after impregnation with the polyferric chloride solution prevents rapid evaporation of the solution from the surface, thereby promoting the migration of the polyferric chloride into the pores as the solvent evaporates. As a specific embodiment, when preparing the silicon remover, the calcination temperature is 250-350° C. and the calcination time is 1-2 hours.

[0028] As a specific embodiment, the dosage of the desiliconizer in step (1) is 3 to 6 times the silicon concentration in the mine water.

[0029] As a specific implementation method, stirring and aeration are performed in the concentration tank in step (3).

[0030] As a specific embodiment, the aeration rate in the concentration tank in step (3) is 0.5 to 1.0 m 3 Air / m 3 Chi Rong·h.

[0031] As a specific implementation method, the salt content of the high-salt and high-hardness mine water in step (1) is ≥5000 mg / L; the calcium hardness is ≥400 mg / L; the magnesium hardness is ≥200 mg / L; and the silicon content is ≥60 mg / L.

[0032] As a specific embodiment, the calcium and magnesium hardness of the pretreated mine water obtained in step (4) are both ≤20 mg / L, and the silicon content is ≤10 mg / L.

[0033] Example 1: A short-process reverse osmosis pretreatment method for high-salt and high-hardness mine water, comprising the following steps: (1) High-salt and high-hardness mine water (salt content 6000 mg / L, calcium hardness 420 mg / L, magnesium hardness 200 mg / L, silicon content 60 mg / L, bicarbonate 700 mg / L, water volume 200m 3 / h) into the first reaction tank and add an alkali agent and a silicon remover for reaction; the alkali agent includes a sodium hydroxide solution and strong calcium oxide; the sodium hydroxide solution concentration is 30wt%, the addition amount is 600mg / L; the addition amount of calcium hydroxide is 100mg / L, and the pH in the first reaction tank is maintained at 10.5; The dosage of the desiliconizer is 200 mg / L. The preparation method of the desiliconizer is as follows: porous magnesium oxide (specific surface area 120 m 2 / g, pore volume 0.3cm 3 / g) is placed in a polyferric chloride solution for vacuum impregnation, the concentration of the polyferric chloride solution is 8 g / L, the pH value is adjusted to 6.0 with hydrochloric acid, and the mass volume ratio of the porous magnesium oxide to the polyferric chloride solution is 1 g: 30 mL; the vacuum degree during vacuum impregnation is 0.08 MPa, and the impregnation time is 45 min; the porous magnesium oxide is filtered and gradient dried, and the gradient drying method is as follows: first drying at 55 ° C for 2 h, then heating to 90 ° C and drying for 4 h; then the dried porous magnesium oxide is placed in an AlCl3 solution with a concentration of 0.2 mol / L and immersed for 45 min, and the mass volume ratio of the porous magnesium oxide to the AlCl3 solution is 1 g: 30 mL; after filtering the porous magnesium oxide, it is dried at 90 ° C for 2 h and then calcined at 300 ° C for 2 h to obtain a desiliconizer; (2) The effluent from the first reaction tank enters the second reaction tank, where 30 wt% sodium hydroxide solution is added to adjust the pH to 10.8 for deep hardness removal; (3) The effluent from the second reaction tank enters the concentration tank; the concentration tank is stirred and aerated through the perforated aeration device at the bottom of the tank; the stirring speed is 45 rpm; the aeration volume is 0.6 m 3 Air / m 3 Tank capacity·h; The concentration tank is equipped with an automatic mud discharge device, which automatically discharges mud regularly according to the mud accumulation in the concentration tank; (4) The effluent from the concentration tank enters the tubular microfiltration membrane device for filtration. The effluent is pre-treated mine water and can directly enter the reverse osmosis device. The operating pressure of the tubular microfiltration membrane device is 0.3 MPa, and the turbidity of the produced water is 0.9 NTU. (5) The sludge discharged from the tubular microfiltration membrane device is dehydrated by the screw stacker and then dried at low temperature using the non-condensable gas in the evaporation crystallization heating chamber to reduce the sludge moisture content to 15%.

[0034] Example 2: A short-process reverse osmosis pretreatment method for high-salt and high-hardness mine water, comprising the following steps: (1) High-salt and high-hardness mine water (salt content 12400 mg / L, calcium hardness 280 mg / L, magnesium hardness 190 mg / L, silicon content 46 mg / L, bicarbonate 450 mg / L, water volume 250m 3 / h) into the first reaction tank and add an alkali agent and a silicon remover for reaction; the alkali agent includes a sodium hydroxide solution and strong calcium oxide; the sodium hydroxide solution concentration is 30wt%, the addition amount is 500mg / L; the addition amount of calcium hydroxide is 100mg / L, and the pH in the first reaction tank is maintained at 10.4; The dosage of the desiliconizer is 140 mg / L. The preparation method of the desiliconizer is as follows: porous magnesium oxide (specific surface area 120 m2 / g, pore volume 0.3cm 3 / g) is placed in a polyferric chloride solution for vacuum impregnation, the concentration of the polyferric chloride solution is 5g / L, the pH value is adjusted to 7.5 with hydrochloric acid, and the mass volume ratio of the porous magnesium oxide to the polyferric chloride solution is 1g:50mL; the vacuum degree during vacuum impregnation is 0.05MPa, and the impregnation time is 30min; the porous magnesium oxide is filtered and gradient dried, and the gradient drying method is as follows: first drying at 50°C for 3h, then heating to 80°C and drying for 5h; then the dried porous magnesium oxide is placed in an AlCl3 solution with a concentration of 0.1mol / L and immersed for 60min, and the mass volume ratio of the porous magnesium oxide to the AlCl3 solution is 1g:50mL; after filtering the porous magnesium oxide, it is dried at 80°C for 3h and then calcined at 250°C for 2h to obtain a desiliconizer; (2) The effluent from the first reaction tank enters the second reaction tank, where 30 wt% sodium hydroxide solution is added to adjust the pH to 10.5 for deep hardness removal; (3) The effluent from the second reaction tank enters the concentration tank; the concentration tank is stirred and aerated through the perforated aeration device at the bottom of the tank; the stirring speed is 42 rpm; the aeration volume is 0.6 m 3 Air / m 3 Tank capacity·h; The concentration tank is equipped with an automatic mud discharge device, which automatically discharges mud regularly according to the mud accumulation in the concentration tank; (4) The effluent from the concentration tank enters the tubular microfiltration membrane device for filtration. The effluent is pre-treated mine water and can directly enter the reverse osmosis device. The operating pressure of the tubular microfiltration membrane device is 0.3 MPa, and the turbidity of the produced water is 0.8 NTU. (5) The sludge discharged from the tubular microfiltration membrane device is dehydrated by the screw stacker and then dried at low temperature using the non-condensable gas in the evaporation crystallization heating chamber to reduce the sludge moisture content to 12%.

[0035] Example 3: A short-process reverse osmosis pretreatment method for high-salt and high-hardness mine water, comprising the following steps: (1) High-salt and high-hardness mine water (salt content 6000 mg / L, calcium hardness 420 mg / L, magnesium hardness 200 mg / L, bicarbonate 450 mg / L, silicon content 60 mg / L, water volume 200m 3 / h) enters the first reaction tank and adds sodium hydroxide solution and silicon remover to react; The concentration of sodium hydroxide solution is 30wt%, the dosage is 450mg / L, and the pH in the first reaction tank is maintained at 10.4; The dosage of the desiliconizer is 185 mg / L. The preparation method of the desiliconizer is as follows: porous magnesium oxide (specific surface area 120 m 2 / g, pore volume 0.3cm 3 / g) is placed in a polyferric chloride solution for vacuum impregnation, the concentration of the polyferric chloride solution is 10 g / L, the pH value is adjusted to 5.5 with hydrochloric acid, and the mass volume ratio of the porous magnesium oxide to the polyferric chloride solution is 1 g: 20 mL; the vacuum degree during vacuum impregnation is 0.1 MPa, and the impregnation time is 60 min; the porous magnesium oxide is filtered and gradient dried, and the gradient drying method is as follows: first drying at 60 ° C for 1 hour, then heating to 100 ° C and drying for 3 hours; then the dried porous magnesium oxide is placed in an AlCl3 solution with a concentration of 0.3 mol / L and immersed for 30 minutes, and the mass volume ratio of the porous magnesium oxide to the AlCl3 solution is 1 g: 20 mL; after filtering the porous magnesium oxide, it is dried at 100 ° C for 3 hours and then calcined at 350 ° C for 1 hour to obtain a desiliconizer; (2) The effluent from the first reaction tank enters the second reaction tank, where an alkali agent is added to adjust the pH to 10.5 for deep hardness removal; the alkali agent includes sodium hydroxide solution and sodium carbonate; the concentration of the sodium hydroxide solution is 30 wt%, and the dosage is 200 mg / L; the dosage of the sodium carbonate is 300 mg / L; (3) The effluent from the second reaction tank enters the concentration tank; the concentration tank is stirred and aerated through the perforated aeration device at the bottom of the tank; the stirring speed is 42 rpm; the aeration volume is 0.6 m 3 Air / m 3 Tank capacity·h; The concentration tank is equipped with an automatic mud discharge device, which automatically discharges mud regularly according to the mud accumulation in the concentration tank; (4) The effluent from the concentration tank enters the tubular microfiltration membrane device for filtration. The effluent is pre-treated mine water and can directly enter the reverse osmosis device. The operating pressure of the tubular microfiltration membrane device is 0.3 MPa, and the turbidity of the produced water is 1 NTU. (5) The sludge discharged from the tubular microfiltration membrane device is dehydrated by the screw stacker and then dried at low temperature using the non-condensable gas in the evaporation crystallization heating chamber to reduce the sludge moisture content to 15%.

[0036] Comparative Example 1 (magnesium oxide is not modified): A short-process reverse osmosis pretreatment method for high-salt and high-hardness mine water, comprising the following steps: (1) High-salt and high-hardness mine water (salt content 6000 mg / L, calcium hardness 420 mg / L, magnesium hardness 200 mg / L, silicon content 60 mg / L, bicarbonate 700 mg / L, water volume 200m 3 / h) into the first reaction tank and add an alkali agent and a silicon remover for reaction; the alkali agent includes a sodium hydroxide solution and strong calcium oxide; the sodium hydroxide solution concentration is 30wt%, the addition amount is 600mg / L; the addition amount of calcium hydroxide is 100mg / L, and the pH in the first reaction tank is maintained at 10.5; The silicon remover is porous magnesium oxide (specific surface area 120m 2 / g, pore volume 0.3cm 3 / g), the dosage of silicon remover is 200mg / L; (2) The effluent from the first reaction tank enters the second reaction tank, where 30 wt% sodium hydroxide solution is added to adjust the pH to 10.8 for deep hardness removal; (3) The effluent from the second reaction tank enters the concentration tank; the concentration tank is stirred and aerated through the perforated aeration device at the bottom of the tank; the stirring speed is 45 rpm; the aeration volume is 0.6 m 3 Air / m 3 Tank capacity·h; The concentration tank is equipped with an automatic mud discharge device, which automatically discharges mud regularly according to the mud accumulation in the concentration tank; (4) The effluent from the concentration tank enters the tubular microfiltration membrane device for filtration. The effluent is pre-treated mine water and can directly enter the reverse osmosis device. The operating pressure of the tubular microfiltration membrane device is 0.3 MPa, and the turbidity of the produced water is 0.9 NTU. (5) The sludge discharged from the tubular microfiltration membrane device is dehydrated by the screw stacker and then dried at low temperature using the non-condensable gas in the evaporation crystallization heating chamber to reduce the sludge moisture content to 16%.

[0037] Comparative Example 2 (no polyferric chloride loaded in the desiliconizing agent): A short-process reverse osmosis pretreatment method for high-salt and high-hardness mine water, comprising the following steps: (1) High-salt and high-hardness mine water (salt content 6000 mg / L, calcium hardness 420 mg / L, magnesium hardness 200 mg / L, silicon content 60 mg / L, bicarbonate 700 mg / L, water volume 200m 3 / h) into the first reaction tank and add an alkali agent and a silicon remover for reaction; the alkali agent includes a sodium hydroxide solution and strong calcium oxide; the sodium hydroxide solution concentration is 30wt%, the addition amount is 600mg / L; the addition amount of calcium hydroxide is 100mg / L, and the pH in the first reaction tank is maintained at 10.5; The dosage of the desiliconizer is 200 mg / L. The preparation method of the desiliconizer is as follows: the preparation method of the desiliconizer is as follows: porous magnesium oxide (specific surface area 120m 2 / g, pore volume 0.3cm 3 / g) was immersed in a 0.2 mol / L AlCl3 solution for 45 min, with the mass volume ratio of porous magnesium oxide to AlCl3 solution being 1 g:30 mL; the porous magnesium oxide was filtered and dried at 90°C for 2 h, and then calcined at 300°C for 2 h to obtain a desiliconizer; (2) The effluent from the first reaction tank enters the second reaction tank, where 30 wt% sodium hydroxide solution is added to adjust the pH to 10.8 for deep hardness removal; (3) The effluent from the second reaction tank enters the concentration tank; the concentration tank is stirred and aerated through the perforated aeration device at the bottom of the tank; the stirring speed is 45 rpm; the aeration volume is 0.6 m 3 Air / m 3Tank capacity·h; The concentration tank is equipped with an automatic mud discharge device, which automatically discharges mud regularly according to the mud accumulation in the concentration tank; (4) The effluent from the concentration tank enters the tubular microfiltration membrane device for filtration. The effluent is pre-treated mine water and can directly enter the reverse osmosis device. The operating pressure of the tubular microfiltration membrane device is 0.3 MPa, and the turbidity of the produced water is 0.9 NTU. (5) The sludge discharged from the tubular microfiltration membrane device is dehydrated by the screw stacker and then dried at low temperature using the non-condensable gas in the evaporation crystallization heating chamber to reduce the sludge moisture content to 15%.

[0038] Comparative Example 3 (the surface of the silicon remover does not carry AlCl3): A short-process reverse osmosis pretreatment method for high-salt and high-hardness mine water, comprising the following steps: (1) High-salt and high-hardness mine water (salt content 6000 mg / L, calcium hardness 420 mg / L, magnesium hardness 200 mg / L, silicon content 60 mg / L, bicarbonate 700 mg / L, water volume 200m 3 / h) into the first reaction tank and add an alkali agent and a silicon remover for reaction; the alkali agent includes a sodium hydroxide solution and strong calcium oxide; the sodium hydroxide solution concentration is 30wt%, the addition amount is 600mg / L; the addition amount of calcium hydroxide is 100mg / L, and the pH in the first reaction tank is maintained at 10.5; The dosage of the desiliconizer is 200 mg / L. The preparation method of the desiliconizer is as follows: porous magnesium oxide (specific surface area 120 m 2 / g, pore volume 0.3cm 3 / g) was placed in a polyferric chloride solution for vacuum impregnation, wherein the concentration of the polyferric chloride solution was 8g / L, the pH value was adjusted to 6.0 with hydrochloric acid, and the mass volume ratio of the porous magnesium oxide to the polyferric chloride solution was 1g:30mL; the vacuum degree during vacuum impregnation was 0.08MPa, and the impregnation time was 45min; the porous magnesium oxide was filtered and then gradient dried, the gradient drying method being: first drying at 55°C for 2h, then heating to 90°C and drying for 4h; and then calcining at 300°C for 2h to obtain a desiliconizer; (2) The effluent from the first reaction tank enters the second reaction tank, where 30 wt% sodium hydroxide solution is added to adjust the pH to 10.8 for deep hardness removal; (3) The effluent from the second reaction tank enters the concentration tank; the concentration tank is stirred and aerated through the perforated aeration device at the bottom of the tank; the stirring speed is 45 rpm; the aeration volume is 0.6 m 3 Air / m 3 Tank capacity·h; The concentration tank is equipped with an automatic mud discharge device, which automatically discharges mud regularly according to the mud accumulation in the concentration tank; (4) The effluent from the concentration tank enters the tubular microfiltration membrane device for filtration. The effluent is pre-treated mine water and can directly enter the reverse osmosis device. The operating pressure of the tubular microfiltration membrane device is 0.3 MPa, and the turbidity of the produced water is 0.9 NTU. (5) The sludge discharged from the tubular microfiltration membrane device is dehydrated by the screw stacker and then dried at low temperature using the non-condensable gas in the evaporation crystallization heating chamber to reduce the sludge moisture content to 15%.

[0039] Comparative Example 4 (changing the impregnation order of porous magnesium oxide): A short-process reverse osmosis pretreatment method for high-salt and high-hardness mine water, comprising the following steps: (1) High-salt and high-hardness mine water (salt content 6000 mg / L, calcium hardness 420 mg / L, magnesium hardness 200 mg / L, silicon content 60 mg / L, bicarbonate 700 mg / L, water volume 200m 3 / h) into the first reaction tank and add an alkali agent and a silicon remover for reaction; the alkali agent includes a sodium hydroxide solution and strong calcium oxide; the sodium hydroxide solution concentration is 30wt%, the addition amount is 600mg / L; the addition amount of calcium hydroxide is 100mg / L, and the pH in the first reaction tank is maintained at 10.5; The dosage of the desiliconizer is 200 mg / L. The preparation method of the desiliconizer is as follows: porous magnesium oxide (specific surface area 120 m 2 / g, pore volume 0.3cm 3 / g) was placed in a 0.2 mol / L AlCl3 solution for vacuum impregnation, the vacuum degree during vacuum impregnation was 0.08 MPa, and the impregnation time was 45 min; the mass volume ratio of porous magnesium oxide to AlCl3 solution was 1 g: 30 mL; the porous magnesium oxide was filtered and gradient dried, the gradient drying method was: first dried at 55 ° C for 2 h, then heated to 90 ° C and dried for 4 h; then the dried porous magnesium oxide was placed in a polyferric chloride solution for 45 min, the concentration of the polyferric chloride solution was 8 g / L, and the pH value was adjusted to 6.0 with hydrochloric acid, the mass volume ratio of porous magnesium oxide to polyferric chloride solution was 1 g: 30 mL; the porous magnesium oxide was filtered and dried at 90 ° C for 2 h; and then calcined at 300 ° C for 2 h to obtain a desiliconizer; (2) The effluent from the first reaction tank enters the second reaction tank, where 30 wt% sodium hydroxide solution is added to adjust the pH to 10.8 for deep hardness removal; (3) The effluent from the second reaction tank enters the concentration tank; the concentration tank is stirred and aerated through the perforated aeration device at the bottom of the tank; the stirring speed is 45 rpm; the aeration volume is 0.6 m 3 Air / m 3 Tank capacity·h; The concentration tank is equipped with an automatic mud discharge device, which automatically discharges mud regularly according to the mud accumulation in the concentration tank; (4) The effluent from the concentration tank enters the tubular microfiltration membrane device for filtration. The effluent is pre-treated mine water and can directly enter the reverse osmosis device. The operating pressure of the tubular microfiltration membrane device is 0.3 MPa, and the turbidity of the produced water is 0.9 NTU. (5) The sludge discharged from the tubular microfiltration membrane device is dehydrated by the screw stacker and then dried at low temperature using the non-condensable gas in the evaporation crystallization heating chamber to reduce the sludge moisture content to 15%.

[0040] Comparative Example 5 (without vacuum impregnation and gradient drying): A short-process reverse osmosis pretreatment method for high-salt and high-hardness mine water, comprising the following steps: (1) High-salt and high-hardness mine water (salt content 6000 mg / L, calcium hardness 420 mg / L, magnesium hardness 200 mg / L, silicon content 60 mg / L, bicarbonate 700 mg / L, water volume 200m 3 / h) into the first reaction tank and add an alkali agent and a silicon remover for reaction; the alkali agent includes a sodium hydroxide solution and strong calcium oxide; the sodium hydroxide solution concentration is 30wt%, the addition amount is 600mg / L; the addition amount of calcium hydroxide is 100mg / L, and the pH in the first reaction tank is maintained at 10.5; The dosage of the desiliconizer is 200 mg / L. The preparation method of the desiliconizer is as follows: porous magnesium oxide (specific surface area 120 m 2 / g, pore volume 0.3cm 3 / g) is placed in a polyferric chloride solution for impregnation, the concentration of the polyferric chloride solution is 8g / L, the pH value is adjusted to 6.0 with hydrochloric acid, and the mass volume ratio of the porous magnesium oxide to the polyferric chloride solution is 1g:30mL; the porous magnesium oxide is filtered and dried at 90°C for 6h; then the dried porous magnesium oxide is placed in a 0.2mol / L AlCl3 solution and immersed for 45min, the mass volume ratio of the porous magnesium oxide to the AlCl3 solution is 1g:30mL; the porous magnesium oxide is filtered and dried at 90°C for 2h, and then calcined at 300°C for 2h to obtain a desiliconizer; (2) The effluent from the first reaction tank enters the second reaction tank, where 30 wt% sodium hydroxide solution is added to adjust the pH to 10.8 for deep hardness removal; (3) The effluent from the second reaction tank enters the concentration tank; the concentration tank is stirred and aerated through the perforated aeration device at the bottom of the tank; the stirring speed is 45 rpm; the aeration volume is 0.6 m 3 Air / m 3 Tank capacity·h; The concentration tank is equipped with an automatic mud discharge device, which automatically discharges mud regularly according to the mud accumulation in the concentration tank; (4) The effluent from the concentration tank enters the tubular microfiltration membrane device for filtration. The effluent is pre-treated mine water and can directly enter the reverse osmosis device. The operating pressure of the tubular microfiltration membrane device is 0.3 MPa, and the turbidity of the produced water is 0.9 NTU. (5) The sludge discharged from the tubular microfiltration membrane device is dehydrated by the screw stacker and then dried at low temperature using the non-condensable gas in the evaporation crystallization heating chamber to reduce the sludge moisture content to 15%.

[0041] Comparative Example 6 (polyferric chloride and AlCl3 are directly blended with magnesium oxide): A short-process reverse osmosis pretreatment method for high-salt and high-hardness mine water, comprising the following steps: (1) High-salt and high-hardness mine water (salt content 6000 mg / L, calcium hardness 420 mg / L, magnesium hardness 200 mg / L, silicon content 60 mg / L, bicarbonate 700 mg / L, water volume 200m 3 / h) into the first reaction tank and add an alkali agent and a silicon remover for reaction; the alkali agent includes a sodium hydroxide solution and strong calcium oxide; the sodium hydroxide solution concentration is 30wt%, the addition amount is 600mg / L; the addition amount of calcium hydroxide is 100mg / L, and the pH in the first reaction tank is maintained at 10.5; The dosage of desiliconizer is 200mg / L; the desiliconizer is porous magnesium oxide (specific surface area 120m 2 / g, pore volume 0.3cm 3 / g), a mixture of polyferric chloride and AlCl3 in a mass ratio of 1:0.24:0.8; (2) The effluent from the first reaction tank enters the second reaction tank, where 30 wt% sodium hydroxide solution is added to adjust the pH to 10.8 for deep hardness removal; (3) The effluent from the second reaction tank enters the concentration tank; the concentration tank is stirred and aerated through the perforated aeration device at the bottom of the tank; the stirring speed is 45 rpm; the aeration volume is 0.6 m 3 Air / m 3 Tank capacity·h; The concentration tank is equipped with an automatic mud discharge device, which automatically discharges mud regularly according to the mud accumulation in the concentration tank; (4) The effluent from the concentration tank enters the tubular microfiltration membrane device for filtration. The effluent is pre-treated mine water and can directly enter the reverse osmosis device. The operating pressure of the tubular microfiltration membrane device is 0.3 MPa, and the turbidity of the produced water is 0.9 NTU. (5) The sludge discharged from the tubular microfiltration membrane device is dehydrated by the screw stacker and then dried at low temperature using the non-condensable gas in the evaporation crystallization heating chamber to reduce the sludge moisture content to 15%.

[0042] The calcium and magnesium hardness and silicon content in the effluent of the tubular microfiltration membrane in step (4) of the above embodiment and comparative example were tested; and the effluent in each embodiment and comparative example was fed into a reverse osmosis device for reverse osmosis treatment, and the inlet flow rate of the reverse osmosis device was 200m 3 / h; the reverse osmosis recovery rate was calculated, and the results are shown in Table 1.

[0043] Table 1: Test results of calcium, magnesium hardness and silicon content of produced water. Test items Calcium hardness (mg / L) Magnesium hardness (mg / L) Silicon content (mg / L) Reverse osmosis recovery rate (%) Example 1 20 18 10 92 Example 2 19 19 9.5 91 Example 3 21 20 9.5 91 Comparative Example 1 22 20 25 85 Comparative Example 2 20 23 18 90 Comparative Example 3 20 22 17 88 Comparative Example 4 22 21 14 89 Comparative Example 5 21 22 15 90 Comparative Example 6 22 20 17 85

[0044] As can be seen from Table 1, the pretreatment method of the present invention used in Examples 1 to 3 can effectively remove calcium, magnesium and silicon hardness in the mine in a short process, and the reverse osmosis recovery rate can reach 90%.

[0045] And comparative example 1 adopts unmodified polyferric chloride and AlCl3modified porous magnesium oxide as desiliconizing agent in the second reaction tank, lacks the flocculation effect of polyferric chloride and AlCl3synergistic effect, desiliconization efficiency significantly decreases compared with Example 1, and the silicon content in pretreatment water is significantly improved compared with the embodiment. In the desiliconizing agent of comparative example 2, polyferric chloride is not loaded, and the desiliconizing agent surface of comparative example 3 is not loaded with AlCl3, lacks the flocculation effect of polyferric chloride or AlCl3synergistic effect, desiliconization efficiency and Example 1 are all decreased. In comparative example 4, polyferric chloride and AlCl3impregnation order are changed, and the desiliconization efficiency in the first reaction tank is also decreased compared with Example 1, which may be due to AlCl3solution after first impregnation.AlCl3will enter the pores of porous magnesium oxide, and the subsequent impregnation load polyferric chloride will block the pores, and silicate cannot diffuse into the pores and contact with Al (OH)3. The polyferric chloride covered on the surface also affects the contact area of ​​magnesia with wastewater, resulting in a decrease in desiliconization effect. In comparative example 5, vacuum impregnation is not carried out when dipping polyferric chloride solution, and gradient drying is not carried out after dipping, and polyferric chloride cannot effectively enter the duct inside of porous magnesium oxide, but is present on its surface, the contact area of ​​porous magnesium oxide and waste water can be affected, and silicon removal effect is decreased compared with embodiment. In comparative example 6, polyferric chloride and AlCl are not by load on porous magnesium oxide, but directly by three being blended, and silicon removal efficiency is also decreased compared with embodiment, and this may be due to after polyferric chloride is loaded on magnesium oxide, magnesium oxide surface alkaline environment can accelerate the hydrolysis and charge neutralization of polyferric chloride, forms the hydroxy complex of high charge density, strengthens the adsorption and coprecipitation effect to silicate ion;And polyferric chloride and magnesium oxide, AlCl after loadThe flocs formed by joint action are more dense, and sedimentation velocity is faster, and flocs anti-shearing ability strengthens, and is not easily broken in flowing process, avoids secondary release silicate, thus can promote silicon removal efficiency;AlCl is added separately simultaneouslyCan cause aluminum ion to remain, can increase the scaling risk of subsequent reverse osmosis treatment, cause reverse osmosis recovery rate to decline.

Claims

1. A short-process reverse osmosis pretreatment method for high-salt and high-hardness mine water, characterized in that the steps include: (1) High-salt and high-hardness mine water enters the first reaction tank and is added with alkali agent and silicon remover for reaction; The preparation method of the silicon remover comprises the following steps: placing porous magnesium oxide in a polyferric chloride solution for vacuum impregnation, separating and gradient drying the porous magnesium oxide, then impregnating the porous magnesium oxide in an AlCl3 solution, separating and drying the porous magnesium oxide, and calcining the porous magnesium oxide to obtain the silicon remover; (2) The effluent from the first reaction tank enters the second reaction tank and an alkali agent is added to adjust the pH to 10.5-11.5; (3) The effluent from the second reaction tank is precipitated in the concentration tank and then enters the tubular microfiltration membrane device for filtration. The effluent is pretreated mine water; (4) The sludge discharged from the tubular microfiltration membrane device is dehydrated by the screw stacker and then dried at low temperature using the non-condensable gas in the evaporation crystallization heating chamber.

2. The short-process reverse osmosis pretreatment method for high-salt and high-hardness mine water according to claim 1 is characterized in that: The alkaline agent in steps (1) and (2) is selected from one or more of lime, sodium hydroxide and sodium carbonate.

3. The short-process reverse osmosis pretreatment method for high-salt and high-hardness mine water according to claim 1 or 2, characterized in that: After the alkaline agent is added in step (1), the pH value in the first reaction tank is 9.5-10.

5.

4. The short-process reverse osmosis pretreatment method for high-salt and high-hardness mine water according to claim 1 is characterized in that: When preparing the desiliconizer, the concentration of the polyferric chloride solution is 5-10 g / L, and hydrochloric acid is added to adjust its pH value to 5.0-7.5; the mass volume ratio of porous magnesium oxide to the polyferric chloride solution is 1 g:20-50 mL; the vacuum degree during vacuum impregnation is 0.05-0.1 MPa, and the impregnation time is 30-60 minutes.

5. The short-process reverse osmosis pretreatment method for high-salt and high-hardness mine water according to claim 1 or 4, characterized in that: When preparing the desiliconizer, the concentration of the AlCl3 solution is 0.1~0.3 mol / L, the mass volume ratio of the porous magnesium oxide to the AlCl3 solution is 1g:20~50mL; and the immersion time of the porous magnesium oxide in the AlCl3 solution is 30~60min.

6. The short-process reverse osmosis pretreatment method for high-salt and high-hardness mine water according to claim 1 or 4, characterized in that: When preparing the silicon remover, the gradient drying method after vacuum impregnation in the polyferric chloride solution is: first drying at 50-60°C for 1-3 hours, then heating to 80-100°C and drying for 3-5 hours.

7. The short-process reverse osmosis pretreatment method for high-salt and high-hardness mine water according to claim 1 is characterized in that: When preparing the desiliconizer, the calcination temperature is 250~350℃ and the calcination time is 1~2h.

8. The short-process reverse osmosis pretreatment method for high-salt and high-hardness mine water according to claim 1 is characterized in that: The dosage of the desiliconizer in step (1) is 3 to 6 times the silicon concentration in the mine water.

9. The short-process reverse osmosis pretreatment method for high-salt and high-hardness mine water according to claim 1, characterized in that: In step (3), stirring and aeration are performed in the concentration tank.

10. The short-process reverse osmosis pretreatment method for high-salt and high-hardness mine water according to claim 1, characterized in that: Step (1) The salt content of the high-salt and high-hardness mine water is ≥5000 mg / L; the calcium hardness is ≥400 mg / L; the magnesium hardness is ≥200 mg / L; and the silicon content is ≥60 mg / L; The calcium and magnesium hardness of the pretreated mine water obtained in step (3) are both ≤20 mg / L, and the silicon content is ≤10 mg / L.

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