响应面法优化冷冻-空气解冻预处理切削液废水

Optimization of freeze-air thawing process for cutting fluid wastewater pretreatment with response surface methodology

采用冷冻-空气解冻法对切削液废水进行预处理,使用单因素实验和响应面法探究了解冻时间、冷冻时间和冷冻-空气解冻总次数对解冻后挥发到空气中的有机碳质量及烧杯中上层浮沫、中层废水、下层废水各部分的有机碳质量占原切削液废水总有机碳质量的百分比(η挥、η上、η中、η下)的影响,且考察了3个影响因素的交互作用和优化了最佳操作条件。结果表明:各影响因素对预处理后待后续处理的出水(即中层水)η中′的影响大小顺序为冷冻-空气解冻总次数>冷冻时间>解冻时间;在冷冻时间为19.84 h、解冻时间为6.94 h、冷冻-空气解冻总次数为3次时,响应面法模拟得到的η中′的最低响应值为25.26%,3次平行验证实验得到η中实测值为26.60%。经冷冻-空气解冻预处理后废水中油滴平均粒径较原切削液废水明显增大,浮沫层中油滴成串或者成片存在。

The cutting fluid wastewater was pretreated by a freezing-air thawing method.Using single factor experiment and response surface methodology,the influences of the thawing time,freeze time and the cycle times of freezing-air thawing on TOC which was evaporated into the air and TOC percentages in the original cutting fluid wastewater TOC(ηvol、ηup、ηmid、ηlow)which remained at the upper-layer froth,middle-layer wastewater and lower-ayer wastewater were studied.Meanwhile the interactions of the above three factors and the optimal operating conditions were studied.The experimental results showed that the order of the influence factors for the pretreatment effluent(i.e.middle wastewater)was:the cycle times of freezing-air thawing>freezing time>thawing time.The optimization experimental results showed that when the freezing time was19.84 h,thawing time was 6.94 h,and the cycle times of freeze-air thawing was 3 times,the lowest response valueηmid′simulated by response surface method was 25.26%,and the actual measured valueηmid was 26.60%through three parallel validation experiments.After freezing-air thawing pretreatment,the average particle size of the oil droplets in the wastewater was significantly larger than that in the original cutting fluid wastewater,and the oil droplets in the froth layer existed in series or pieces.