| Zero discharge of high mineralized mine water is an inevitable requirement for the development of green environment.In this thesis,a new process of"pretreatment+membrane concentration+bipolar membrane hydrolysis and separation"was developed by using high mineralized mine water from a mine in Hebei Province as raw water.The new process has very important theoretical and practical significance for improving the treatment efficiency and utilization rate of high mineralized mine water and reducing the cost of resource utilization.It provides a feasible technical way for zero discharge of high mineralized mine water in practical engineering.The pretreatment process of"coagulation precipitation+ultrafiltration+reverse osmosis+reagent softening+ion exchange softening+blowing off"was adopted.Under the condition that the turbidity of raw water is 549 NTU and the conductivity is 6.82mS/cm,adding 120 mg/L PAC and 0.6 mg/L PAM,the turbidity of effluent water is 3.55NTU,and the turbidity removal rate is 99.35%.When the working pressure is 0.15 MPa and the membrane flux is 100 L/（m2·h）,the average turbidity value of ultrafiltration production level is 0.3 NTU.When the recovery of reverse osmosis is 50%,the average conductivity of reverse osmosis concentrated water is 12 mS/cm.After adding 550 mg/L Ca（OH）2 and 3500 mg/L Na2CO3 for 30 min,the total hardness decreased to 188 mg/L,and the hardness removal rate reached 93.29%.Using D402 resin,the flow rate is 15 m/h,effluent hardness is not detected,the removal rate is up to 100%;The silica content can be reduced to 1.61 mg/L and the removal rate can be up to 92.3%under the softening process of drug combined with ion exchange.In the blowout test,when the gas-liquid ratio is 5:1,the pH of mine water is neutral,and the total alkalinity drops below 100 mg/L.The membrane concentration test was carried out by electrodialysis process.Under the conditions of initial volume ratio of 3:1,operating voltage of 7 V and circulating flow rate of 20 L/h,one-stage electrodialysis was carried out for 270 min.The initial conductivity of the desalination chamber was diluted to 2.0 mS/cm,and the initial conductivity of the concentration chamber was concentrated to 36 mS/cm,with a relative concentration rate of about 173.1%.The energy consumption per unit volume of the concentrate was 6.30 kWh/m3.Multistage electrodialysis concentration was carried out under the optimal process conditions of first-stage and one-stage electrodialysis.The initial solution was concentrated into a high-salt solution with a conductivity of 156mS/cm after four-stage electrodialysis concentration.The relative energy consumption per unit volume of each stage was 6.30 kWh/m3,12.21 kWh/m3,20.03 kWh/m3 and 25.76kWh/m3,respectively.The bipolar membrane electrodialysis process was used for hydrolysis.When the current density of 30 m A/cm2 is constant rheological voltage,the water volume of salt chamber,acid chamber,alkali chamber and polar chamber is 4,1.5,1.5,2 L,respectively,the circulating flow rate is 30 L/h,and the electrolyte concentration of polar chamber is 2%,bipolar membrane electrodialysis has the best hydrolysis separation effect.After 120min of operation,the effect is ideal,and the expected concentration of acid and alkali is 5%,and the energy consumption is 1.66 k Wh/kg.The acid and base of bipolar membrane electrodialysis products can be reused in this process and downstream coal industry chain,which can not only solve the problem of high mineralized mine water discharge,but also improve the economic value of wastewater. |
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