电脱盐废水稳定性分析及破乳技术

doi:10.16085/j.issn.1000-6613.2021-2425

摘要/Abstract

摘要：

石油炼制行业电脱盐废水乳化严重、破乳难，影响后续深度处理，已成为企业污染防治的重要难题。本研究针对典型炼化企业电脱盐废水的排放与处理需求，实时跟踪电脱盐废水的水质波动。基于电脱盐废水的污染组成特点，分析其稳定性，并首次利用管式电絮凝处理电脱盐废水。结果表明，该企业电脱盐反冲洗时，电脱盐废水中石油类浓度>400mg/L，最高时可达1700mg/L，显著高于设计值。其化学需氧量（COD）平均为4484mg/L，与原油性质密切相关，其中溶解性COD约765mg/L，主要来源于电脱盐注水。反冲洗废水中胶质、沥青质重质组分占总油比例28%，高于正常排水。电脱盐废水具有一定的自发破乳性，但时间较长；曝气预处理30min后COD可降至原水的26.2%；电絮凝可进一步大幅降低COD与溶解性COD，且在初始电流1.0A、反应时间15min时，COD和溶解性COD的平均去除率分别达到80%和50%，降解过程符合准一级动力学模型，此时直接运行成本约0.92CNY/m³废水。

关键词: 电脱盐废水, 乳化, 破乳, 化学需氧量, 电絮凝

Abstract:

The serious emulsion of petroleum refinery desalter effluent is hard to break and presents difficult operating challenges for wastewater treatment, which is a major problem for pollution prevention and control in refineries. In this study, the fluctuation of desalter effluent quality was investigated in a typical refinery according to its discharge and treatment requirements. Based on the characteristics of desalter effluent, the stability was studied and tube electrocoagulation was used for the first time to treat the actual desalter effluent. When the desalter unit was backwashed, oil in the desalter effluent was higher than 400mg/L with the highest concentration of 1700mg/L, which was significantly beyond the design value. The average COD was about 4484mg/L and closely related to the properties of crude oil. Average dissolved COD was about 765mg/L, which mainly arose from desalter feed water. Resin and asphaltene in backwashed wastewater accounted for 28% of total oil, which was higher than that of normal desalter effluent. Spontaneous demulsification could occur in desalter effluent but it took a long time. Pretreatment by aeration for 30min reduced the COD of desalter effluent to be 26.2% of raw water, and electrocoagulation further decreased its COD and dissolved COD significantly. Under the operating conditions of initial current of 1.0A and reaction time of 15min, the average removal efficiencies of COD and dissolved COD were 80% and 50%, respectively. The pseudo first order kinetic model was more suitable to describe the removal of COD and dissolved COD from desalter effluent. Under the optimum conditions, 0.92CNY/m³ of total operation cost was obtained.

Key words: desalter effluent, emulsion, demulsification, chemical oxygen demand (COD), electrocoagulation

中图分类号:

TQ085.4

张华, 刘光全, 张晓飞, 罗臻. 电脱盐废水稳定性分析及破乳技术[J]. 化工进展, 2022, 41(9): 5047-5054.

ZHANG Hua, LIU Guangquan, ZHANG Xiaofei, LUO Zhen. Stability analysis and demulsification treatment for desalter effluent[J]. Chemical Industry and Engineering Progress, 2022, 41(9): 5047-5054.

图/表 10

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名称	平均pH	平均电导率 /mS·cm^-1	平均COD /mg·L^-1	平均溶解性COD /mg·L^-1
原油罐底水	6.93	7.83	385	433
电脱盐注水	8.43	0.24	832.5	834
电脱盐废水	7.88	0.87	4484.2	765

名称	平均pH	平均电导率 /mS·cm^-1	平均COD /mg·L^-1	平均溶解性COD /mg·L^-1
原油罐底水	6.93	7.83	385	433
电脱盐注水	8.43	0.24	832.5	834
电脱盐废水	7.88	0.87	4484.2	765

项目	原水	两周后
pH	6.86	7.34
氧化还原电位/mV	-78.8	-63.6
COD/mg·L^-1	2140	1277
粒径中值/μm	18.513	14.538
ζ电位/mV	-7.93	-16.73

项目	原水	两周后
pH	6.86	7.34
氧化还原电位/mV	-78.8	-63.6
COD/mg·L^-1	2140	1277
粒径中值/μm	18.513	14.538
ζ电位/mV	-7.93	-16.73

项目	电流/A	一级动力学模型		二级动力学模型		准一级动力学模型
项目	电流/A	k₁/min^-1	R²	k₂/L⋅mg^-1⋅min^-1	R²	k^app/min^-1	C_e/mg∙L^-1	R²
COD	0.5	0.142	0.98	0.00037	0.94	0.164	43.65	0.97
	1.0	0.186	0.88	0.00056	0.98	0.388	155.4	0.99
	1.5	0.146	0.93	0.00045	0.99	0.303	139.8	0.98
溶解性COD	0.5	0.060	0.66	0.00045	0.83	0.346	102.0	0.98
	1.0	0.064	0.87	0.00048	0.95	0.205	86.6	0.98
	1.5	0.061	0.82	0.00046	0.92	0.308	95.2	0.97