$ TREATMENT OF PRODUCT WATER $

Experimental Study on Treatment of Produced Water :-

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    A new research in chemical engineering has been submitted on " study on treatment of produced water , by the industries " by Khalid M Mousa - and Sheikhah Arafat A Department of Chemical Engineering, College of Engineering, Nahrain University, Iraq, Baghdad.

Abstract:-
                   The oil drilling operations create large quantities of contaminated water known as “Produced Water”. The present study aims to treatment of produced water of the North Rumaila and Zubair oil fields (Iraq), using stainless steel autoclave. A series of experiments were carried out, firstly pretreatment to remove solid particles using sedimentation with and without flocculation, secondly study the effect of pH, pressure, temperature, salinity, operation time, outlet time and RPM. The ranges of salinity, pH, pressure and temperature were selected according to the PW conditions which out from dehydrator and desalter as follow: 80000 ppm, 6,3 bar and 60°C respectively, finally sorbents (polypropylene, polyethylene, used plastic and sawdust) were used. The results showed a great improvement in the oil recovery percent (all the oil was recovered) when using sorbents.

Introduction:-
                           Large quantities of water produced during oil and gas extraction, called produced water, are generated in drought prone locations that are also experiencing an increase in population. Produced water is a waste byproduct of the oil and gas industry; however, with appropriate treatment and application to beneficial use, produced water can serve as a new water supply [1]. Additional water is often injected into the reservoirs in order to achieve maximum oil recovery. Both the formation water and the injected water are eventually produced along with the oil and therefore as the field becomes depleted the produced water content of the oil increases [2]. As long as the oil production nonstop for next years the produced water continual. According subsequent data in South Iraq oil fields supplied by petroleum development & research center and South Oil Company the Production rate of produced water at 2003 for Basra oil fields/main pay was found 107,621 bbl/d [3]. The Production rate expected of produced water at 2025 for North Rumaila/Main Pay reach to 500,000 bbl/d [4]. In Iraq the current water oil ratio is 1:5 [3], while in USA the current water oil ratio is 10:1, for an annual total of about 3 billion tons, this is by some estimates the largest single waste stream in the USA [5]. Reinjection for enhanced recovery or disposal accounts for as much as 95% of this water [6]. The remaining fraction is still considerable. Reinjection is not always feasible because of geographic and cost considerations [7]. The terrible huge quantities of produced water take off the consideration. Thus the most petroleum researcher's focus to solve this problem of this pollute water. George et al. [8] carry out chain experiments on filter. The separation mechanism involves capture of small droplets of the immiscible phase, coalescence of the small droplets into larger droplets as the immiscible liquid flows through the fiber filter, and release of the large immiscible droplets from the filter. Scott [9] studied three commercial membranes for the pretreatment of produced water. Fraser [10] compared filter of Twenty-five polymeric (organic) and eight inorganic membrane. Huishu Li [11] connected the relation between pH and TDS with ground layer depth. Abouther [12] investigated the effect of salinity on percent oil removal. Fraser [10] checked influence of high temperatures ranges 65°C to 80°C on both types of inorganic and polymeric membranes; the tests didn’t mention a significant temperature impact so the effect was neglected. Rafique et al. [13] invent that raise of pH in produce water treatment will increase silica solubility in PW and breaks emulsions of oil in water. Mareth [14] state that the Reducing of pH decreases silica solubility but increases Ca(CO)3 solubility. Jixiang et al. [15] added four kinds of agents (SL-2, 1227, PAC and HEDP), the investigation results showed that increasing of SL2 and 1227 decreased interfacial tension of oil-water emulsion means they were higher interfacial activity then others. Abdolhamid et al. [16] applied ultra filtration on produced water treatment with two filters types a poly sulfone and a poly acrylonitrile effects. Sonia [17] studied the efficacy of using organoclay to remove oil by measuring its adsorption capacity to remove the oil. Jing Zhong et al. [18] treated the PW using Micro-filtration method with flocculation. The aim of this work is Pretreatment study to remove solid particles using sedimentation with and without flocculation, study the effect of pH, pressure, temperature, salinity, operation time, outlet time and RPM on the recovery of oil percent to find the optimum conditions, finally Study the effect of addition of polypropylene, polyethylene, used plastic and sawdust as a sorbents.

Results and Discussion :-

Settling with and without flocculation:-
                                                                   The effect of sedimentation time on the percent of sediment removed. Its clear that after about one hour a 65% of solid particle was removed. There are three forces effected the process of sedimentation, namely, electrostatic forces, van der waals forces and Brownian motion. If van der waals forces and Brownian motion are gretar than electrostatic forces the settling rate was increases and this agree with Nicholas [19]. During the first hour, the heavy particles settle to the bottom after that the settling rate was practically closed to a straight line. The curves started to inclinedbecause rate of sedimentation slightly decrease as a result of heavy particles settle in the bottom and light particles take time to fall down depending on gravity force. Flocculants were added to increase the settling velocity, in order to enhance settling rate. The effects of fluc douseg on the percent of sediment removed. One can see that the rate of settling increases with the increase in the dose of flocculant. The 400 part per million (ppm) of PAA reduce the settling time to a half, while 500 ppm give 100% of settling in the 45 minute due to configeration among the close relation with flocculation conditions, such as, dosage of flocculant, stirring time, holding time after stirring, flocculation temperature, on the other hand the better performance of polymer flocculants is due to its long chain bridged between and/or absorbed the particles and emulsified oil in wastewater, then increase their sedimentation rate (Jing Zhong [18]).

Effect of time on removed oil:-
                                                        The percent of oil removed increases during the first 5-10 min, the maximum oil recovery occur at 15 min with and without flocculent, then the behavior was declined, the reason is that the oil droplets until 15 minute were coalesce, when residence time increase the dispersed started again because droplets were lose the attraction between each other, that’s led to a decrease in the oil recovery. The outlet waiting time was fixed at fifth minutes on next experiments.

Effect of salinity on removal oil:-
                                                            The effect of salinity on oil removal percentag. Its clear that the removal percent increases with increasing the salinity. This attrebuted to the reduction in surface tension of the solution.

 

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