Abstract：
Produced water (PW) is the largest by-product that comes out of the oil wells during oil and gas (O&G) field exploration. PW contains high-salt concentration along with other organic and inorganic components; therefore, PW must be treated before disposal. Electrocoagulation (EC) is an effective treatment method to remove pollutants from PW which has been the focus of many experimental studies; however, a mathematical model specifically for PW treatment by EC has not been developed yet. In this work, a comprehensive mathematical model has been developed to elucidate the role of EC operating parameters on the PW treatment performance and determine the mechanism for COD (Chemical Oxygen Demand) removal. The present model considers and identifies the dominant Al-hydroxy complex species and their contribution to the COD removal from synthetic PW samples by estimating their rate constants and comparing their magnitudes and investigates multi-scale modelling of the EC reactor. The influence of working parameters such as current density, initial pH, interelectrode distance, mixing speed and solution volume of PW on Al coagulant production and COD removal was investigated and modelled. The study estimates the rate constants of the reactions taking place for COD removal by EC process and by comparing their magnitudes identifies the dominant reactions and coagulant species involved in the process. The mathematical model prediction of COD removal fits well with the experimental data at 10 mA cm-2, 15 mA cm-2 and 20 mA cm-2 current density with R2 value of 0.96, 0.97 and 0.92, respectively and for dissolved Al concentration R2 value of 0.96, 0.99, and 0.97, respectively. The simulated results reproduced a good fit at initial pH of 6.1, 7.3 and 8.6 with R2 value of 0.92, 0.96 and 0.98, respectively for COD removal. The mathematical model and the experimental results showed the role of dominant Al-hydroxy complex species such as Al OH 2 + , Al OH 2 + , Al OH 3 , Al 2 OH 2 + 4 and Al OH 4 - in controlling the COD removal process. Under different operating conditions considered in the study, the model also predicted the COD removal performance of the EC reactors at different reactor volumes with R2 value of 0.96 for higher solution volume and larger reactor. The model presented and rate constants determined in the study will provide a theoretical basis for designing, scaling up and operating the EC reactor for oil-field PW treatment.
摘要：
产出水（PW）是石油和天然气（O＆G）现场勘探过程中从油井中流出的最大副产品。PW含有高盐浓度以及其他有机和无机成分；因此，PW必须在处置前进行处理。电凝法(EC)是一种有效去除PW中污染物的方法,已成为许多实验研究的重点,专门用于EC治疗PW的数学模型尚未开发。在这项工作中,一个全面的数学模型已经开发出来，以阐明EC操作参数对PW处理性能的作用，并确定COD（化学需氧量）去除机制。本模型通过估算其速率常数并比较其大小，并研究了EC反应器的多尺度建模，从而考虑并确定了主要的Al-羟基络合物种类及其对合成PW样品中COD去除的贡献。电流密度等工作参数的影响，初始pH值,极间距离,研究并模拟了PW的混合速度和溶液体积对Al混凝剂生产和COD去除的影响。该研究估算了EC工艺去除COD所发生的反应的速率常数，并通过比较它们的大小来确定该过程中涉及的主要反应和促凝剂种类。COD去除的数学模型预测与10mAcm-2，15mAcm-2和20mAcm-2电流密度下的实验数据吻合良好，R2值分别为0.96，0.97和0.92，溶解铝浓度R2值分别为0.96，0.99和0.97。模拟结果再现了在初始pH为6.1、7.3和8.6时的良好拟合，COD去除的R2值分别为0.92、0.96和0.98。数学模型和实验结果表明了占主导地位的Al-羟基配合物的作用，如[公式：见正文]，[公式:见正文],[公式:见正文],控制COD去除过程中的[公式：见正文]和[公式：见正文]。在研究中考虑的不同操作条件下，该模型还预测了不同反应器体积下EC反应器的COD去除性能，对于较高的溶液体积和较大的反应器，R2值为0.96。研究中提出的模型和确定的速率常数将为设计提供理论依据，扩大和操作用于油田PW处理的EC反应器。
