| The steel industry is a high-water-consuming industry.It’s necessary to improve the water utilization from it and reduce efflux to achieve “zero emissions”.The Ezhou Iron and Steel Plant continuous casting equipment of the net circulating cooling water system has large amount of fresh water replenishment with high cost and the part of continuous casting turbid circulation water is discharged directly without reuse.On the one hand,this kind of measure wastes water resources,on the other hand,it needs to pay environmental protection tax.In order to reduce the turbid circulation drainage volume and the fresh water replenishment volume of the net circulating cooling water system,this study proposes an energy-saving and emission-reducing plan to supplement the net circulating cooling water system after the turbid circulation water treatment meets the standard.Therefore,this study optimizes the current turbid circulating water treatment process,and the treatment effect,process parameters of each process and economic cost are analyzed and discussed.Through the flocculation and sedimentation experiment,the treatment effect of each flocculant was analyzed,the best dosage was clarified,the current mechanical flocculation and sedimentation process of Ezhou Steelmaking Plant was optimized,and the chemicals and dosage suitable for continuous casting turbidity circulation treatment was selected.The results showed that: the effluent of 4.00 mg/L PAC and 0.15 mg/L PAM was optimal.Using inorganic flocculant treatment,the effect of PAC treatment was better than that PFS.After added PAM,the quality of the effluent treated with PAC+PAM was significantly improved,but the all of them didn’t get rid of the hardness.When added Na2CO3 and Ca(OH)2,the removal rate of hardness and Fe was high,but the turbidity and p H increased significantly.Through the filtration test,this study selected the appropriate filter material,and clarify the optimal filtration speed,and obtain the operating conditions of the filtration treatment.The filtration experiments suggested that using activated zeolite as filter material with the filtration rate was 5 m / h,the effluent quality was the best.The removal effect of COD and turbidity was better than that of natural zeolite and activated zeolite with quartz sand as filter material,but there was no removal effect on hardness.After activated zeolite as filter material,the removal effect of hardness was obvious,and the removal rate of Fe by three kinds of filter materials was slightly different.Through flocculation precipitation filtration experiment,a complete set of operating plans with definite operating conditions was obtained.Besides,this study compares the cost with the current continuous casting turbidity cycle processing process of Ezhou Steelmaking Plant.The results showed that added 4.00 mg/L PAC +0.15 mg/L PAM in flocculation process,precipitation 30 min;using activated zeolite as filter material with the filtration rate was 5 m/h in filtration process,the turbidity,hardness,COD and Fe removal rate of filtration effluent increased by 71.86%,51.90%,16.58% and 63.68% respectively compared with the original process.The effluent quality of the optimized process was significantly improved and the economic effect was remarkable,the effluent could be reused in continuous casting net circulation system after p H adjustment.Through the above optimization treatment,the water quality of the turbid circulation treatment is improved and the cost of fresh water replenishment is reduced.The production goal of the “zero discharge” in the Ezhou Iron and Steel Plant is achieved,which also meet the national energy-saving and emission-reduction production requirements. |
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