Abstract
The aim of the present study was to obtain effective and economical chemical agents for treatment of oily water from N oilfield. Component characterization of crude oil from N oilfield was carried out with gas chromatography–mass spectrometry. Optimization of non-ionic surfactants combined with dissolved air flotation (DAF) for oil removal was investigated. The results show that the crude oil consisted of nine major components which counted for 96.4% of the total composition, and the first four compounds made up 50% of the total composition. For the first four compounds, the density difference between water and each individual compound is smaller than the difference between water and normal alkanes with the same number of carbon atoms, while the solubility of these four compounds in water is greater than that of normal alkanes with the same number of carbon atoms. The characteristic of both density and solubility of the crude oil increased the oil water separation difficulty in DAF progress. The oil content in oily water from N oilfield without any treatment was 5285.95 mg/L. The oil content after treatment of DAF without any chemicals was 895.53 mg/L. Non-ionic surfactants NIS1, NIS2 and NIS3 all were effective for removing emulsified oil in oily water in DAF progress. 1200 mg/L NIS1 combined with DAF was the optimized formulation by the view of efficiency and economy. The formulation could be successfully used as a commercial product in N oilfield.
Highlights
Water is produced in the petroleum industry process, such as drilling, oil recovery, oil gathering and transportation and oil refining
The Gas chromatography–mass spectrometry (GC–MS) analysis result showed the crude oil consisted of nine major components which counted for 96.4% of the total composition: toluene, 2-methylnaphthalene, naphthalene, trimethylbenzene, 1,4-xylene, 1-methylnaphthalene, Fig. 1 The GC–MC spectrometry of crude oil
With the increase in NIS1 concentration from 400 to 1200 monthly average limits of emulsified oil Concentration (mg/L), the residual emulsified oil content was decreased significantly from 70 to 9.6 mg/L, the latter of which can meet the requirement prescribed by People’s Republic of China (PRC) similar to the previous results (Lv et al 2017)
Summary
Water is produced in the petroleum industry process, such as drilling, oil recovery, oil gathering and transportation and oil refining. Since unqualified oily water generates pollution to surface and underground, discharging oily water is getting more and more attention (Abdol et al 2008). Water is a special liquid-in-liquid colloidal dispersions classified as O/W emulsions (Raya et al 2020). The dispersion, aggregation (Mozaffari et al 2015) and the adsorption (Darjani et al 2017) phenomenon are the main aspects which related the colloidal kinetic stability. Non-ionic surfactants were often used in oily wastewater treatment (Abedi and Nekouei 2011; Zhang et al 2014; Souza et al 2017), especially for removal of emulsified oil from gas condensate oil–water emulsion (Al-Sabagh et al 2015). Certain characteristic properties of non-ionic surfactants for instance, its non-volatility, temperature and environment-friendly surfactant (Sarmah et al 2020) and stable at high salinity (Lawson 1978) make it more efficient and feasible for field application
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