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Turbidity and Oil Removal from Oilfield Produced Water, by Coagulation

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Turbidity and Oil Removal from Oilfield Produced Water, by Coagulation The Eighth Jordan International Chemical Engineering Conference (JIChEC 2017) November 7-9, 2017 Turbidity and Oil Removal from Oilfield Produced Water, by Coagulation - Flocculation Technique Thamer J.Mohammed1, Esraa R. Abbas 2 AbstractProduced water is one of huge 2Chemical Engineering Department, University of Technology, effluents in petroleum industry,the estimated Iraq, [email protected] quantities of produced water by Middle Oil studied effect of adding coagulants for Company of Iraqi Petroleum Companies are removing oil content from produced water. The (217100-275600) bb1/d via reported in 2014- best oil content removal when using of 15 mg/l 2015.The aim of this study is conducting to of ferric chloride as coagulant with different remove oil content and suspended solidsfrom concentrations of PE (0.5, 1, 1.5 mg/l) decrease produced water obtained from Middle Oil the oil content from 46.6 mg/l to 4.7, 4.5 , and Company by used chemical precipitation, 4.3 mg/l ,respectively. And also the effect of coagulation-flocculation for reinjection natural coagulant (plantago ovate seeds) was application and for environmental aspects. studied and it was found that it has high Different parameters related to the specific effective in reducing turbidity. This technology were studied; pH, type and seedcharacterized with a high molecular weight concentration of coagulant. The efficiency of and helps to accelerate the process and an turbidity removal was studied via four different increase sedimentation rate.The best results coagulants (poly aluminum–chloride, ferric were get it when 10mg/L oftheFeCl .6H Owas chloride , and polyelectrolyte and 3 2 added to1.5 mg/L ofseedsextracted and it is plantago.ovata seed). used individually and found that R= (99.2%) (0.89 NTU residual combined to decrease the turbidity of produced turbidity). This technique provide the possibility water. The obtained jar test results during the of reuse the water and can be injected in oil experiments proved that the optimal wells. concentrations of PAC, ferric chloride, PE(polyelectrolyte) and (Plantago.ovata seed) were 75, 20, 1, and 1 mg/l respectively when Keywords: Oilfields; Produced water; coagulation- these chemicals were used individually. Where flocculation; plantago ovata ; Oil Content, combined PAC-PE, ferric chloride – PE, the efficiency of turbidity removal was increased 1INTRODUCTION higher than individually coagulant dose. The Produced water is water trapped in underground best turbidity efficient removing was 99.6% reservoir rocks and is brought to surface along with when the concentrations of coagulant ferric crude oil and gas. Besides elevated concentration of chloride and PE were 20 and 1 mg/l, heavy metals such as Barium, Uranium, Cadmium, respectively.And the best turbidity efficient Chromium, Strontium and Lead, produced water contains dispersed oil droplets, dissolved organic removing was 99.2% when the concentrations compounds and significant amount of anion, such as of ferric chloride and PE were 10 mg/L and 1.5 Carbonate, Bromide and Sulfate. The largest volume mg/L , respectively. And also it has been of waste in the upstream petroleum industry is 1Corresponding Author, Engineering Department, University of produced water. The total volume of produced water Technology, Iraq, [email protected] in the United States is roughly 21 billion/year [1]. 1 The Eighth Jordan International Chemical Engineering Conference (JIChEC 2017) November 7-9, 2017 Sources of this water may include flow from above or below or within the hydrocarbon zone, or flow Oilfield produced water used in the present study from injected fluids and additives resulting from was kindly provided by Petroleum Research and production activities [2]. Produced water is usually Development Center staff from Middle Oil Company very salty and may contain suspended and dissolved .Its chemical and physical characteristics include pH solids, residual hydrocarbons, numerous organic was around (7), EC(144300μs/cm), Turbidity (120 species, heavy metals, naturally occurring NTU), oil content (46.6 mg/l), TDS (133477mg/l) radioactive and chemicals used in hydrocarbon and TSS (90mg/l). extraction [3]. Coagulation-Flocculation in general, is a two phase process aimed at removing stable particles by forming larger aggregates that can be 2.2MATERIAL AND METHOD separated from the aqueous phase by a subsequent A Series of experiments were conducted with separation step. The preliminary phase is the different chemical and different dosages using a coagulation phase in which destabilization is bench-scale jar test (Flocculator/JT-M6) show in induced, either by the reduction of repulsive forces Fig.1, coagulation/ flocculation with different between particles or by the enmeshment in dosages of ; poly-aluminum chloride, ferric chloride, precipitates[4].Flocculation is the second stage of the and cationic polyelectrolyte and plantago ovata seeds combined process and consists of the aggregation of as a coagulant aid to achieve maximum removal of coagulated particles and/or precipitate precursors in turbidity and oil content. All the chemical coagulants flocs. Coagulation and flocculation occur in used in this study were provided by al-Dura refinery successive steps intended to overcome the forces (Iraq).except plantago ovatawas purchased stabilizing the suspended particles, allowing particle frompharmacyAL-hadr in Baghdad. collision and growth of floc. Coagulation has been defined as the addition of a positively charged ion of metal salt or catalytic polyelectrolyte that results in particle destabilization and charge neutralization [5].It is found thatmost researchers [6,7]have studiedthe process ofcoagulation and flocculation, particularlythey suggested that the coagulation/ flocculation can decrease the oil content and turbidity value of oily wastewater by using different coagulant. Coagulation-flocculation followed sedimentation technology process is one of the important ways and the most popular process to deal with oily wastewater treatment to remove suspended particular, COD and oil with addition natural or synthetic coagulants flocculants , this technique Fig. 1: Jar test were investigated by many researchers [8-13]. The researches were investigated the optimization of multi variables effect on coagulation-flocculation via Coagulant dosing was added to produce water and experiments jar-test and response surface mixed 1 min under rapid mixing condition “flash methodology. mix” (150 rpm). Reduce the speed as necessary to the minimum required (50 rpm G=52 sec-1) to keep The aim of the study is to remove suspended solid floc particles uniformly suspended throughout the and oil from produced water by coagulation- “slow mix” period of 20 min. suspended solid and flocculation.In the research, oil field produced water oil content of supernatant liquor was measured and treated by the coagulation- flocculation treatment other required analyses after settling for 20 min.oil process before the produced water reinjection to the content was determined by oil content analyzer reservoir (oil well) with allowable limit (HORIBA/OCMA-350).And The turbid meter that concentrations parameter.Where access to the was used in the measurements of the samples conditions required. turbidities during the experiments was Lovibond TurbDirect.And also measured the percentage of 2 EXPERIMENT removal R% for each of the turbidity and oil content through the following equation:- 2.1 CHARACTERISTICS OF OILFIELD (1) PRODUCED WATER 2 The Eighth Jordan International Chemical Engineering Conference (JIChEC 2017) November 7-9, 2017 Where Co initial concentration, C residual Fig 3: Turbidity removal by using Fecl36H2O concentration in ppm dose. 3 RESULTS and DISCUSSION Also it is seen that combining 25 mg/l PAC when with (1.5 mg/L) PE is mostly effective in reducing 3.1 TURBIDITY REMOVAL BY the turbidity and providing higher removal efficiency COAGULATION-FLOCCULATION PROCESS which is increased up to more than 99.3 % residual Different coagulants doses were used in coagulation- turbidity (0.8 NTU) as show in Fig. 4.This flocculation experiment under Jar-Test with initial improving in results because the added aid coagulant turbidity of (120NTU). Figures 2 and 3 show as PE caused increase positive electric charge and coagulants used alone.The removal efficiency of reacts relatively quickly with colloid particles in turbidity (7.7NTU) up to approximately 93.5% when pollutant water to cause neutralization of the surface the best dose value of PAC was (75 mg/L) as shown charge and reduce Zeta potential. The particle then in Fig.2.and the results of optimum coagulant dose coagulate to form primary microfloccule. During the ofFeCl3.6H2Oas a primary coagulant, this flocculation process, micro-floccules continue Fig.4indicates that the removal efficiency of increasing in size to form flocs with large size and turbidity increases with increasing ferric chloride density [11]. dose until the R% reaches the maximum value (95.5%) residual turbidity (5.3 NTU) at dose 20 PE DOSE = 0.5 mg/l mg/l. PE DOSE =1 mg/l PE DOSE =1.5 mg/l R% % turbidity NTU turbidity REMOVAL y = 0 R² = #N/A Residual PAC DOSE mg/l PAC DOSE mg/l Fig4:Turbidity removal by using combining PAC dose with the different Fig 2: Turbidity removal by using PAC dose. doses of PE Also, results of optimum doses of ferric chloride as R% primary coagulant combined with polyelectrolyte Residual… (PE) as a coagulant aid in different doses of (0.5, 1,and 1.5 mg/l). Ferric chloride
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