Hydrocyclones, produced water

In Hydrocyclones A Solution to Produced Water Treatment, Meldrum presents the basic design principle of a dc-oilmg hydrocy leone. System design, early operational experiences, and test results on a full-scale application in the North Sea are discussed. Oil-removal efficiency was seen to rise with increasing reject ratio up to around 1%, producing acceptable outlet concentrations Early field test results on a tension leg platform in the North Sea are discussed. Preliminary data on a pumped system are also given. 

MF or UF or their combined solutions are suitable technologies to separate oils from water. Bilstad and EspedaF" compared MF and UF membranes in a pilot trial to treat the North Sea oil field-produced water. By UF membrane treatment, the total hydrocarbon concentration can be reduced to 2 from 50 mg/L (96% removal). Benzene, toluene, and xylene (BTX) were reduced by 54%, and some heavy metals like Cu and Zn were removed to the extent of 95%. Lee and Frankiewicz of NATCO group tested a hydrophilic UF membrane to treat oil field-produced water, placing the membrane units after a hydrocyclone used to desand and deoil the wastewater. At the end of the process, the oil and gas concentration was reduced to less than 2 mg/L. 

Subsea gas-liquid separation of multiphase well flow, produced-water reinjection and multiphase one-way transportation of gas and crude oil can be achieved by Subsea gas-liquid hydrocyclone separator systems during the prophase subsea separation and processing. The gas-liquid hydrocyclone separator is the key equipment of the separation system, which can reahze gas and Uquid hydrocyclone separating based on the principle of density difference of the gas and liquid (Zhao Guoqing, 2003). 

Some years after Professor Waldie s work, the idea of using hydrocyclones to effect hquid-fiquid separation down hole was examined. The development was motivated by the need to deal effectively with produced water - that arising from oil and gas wells and contaminated with these products. If the water can be extracted from the oil or... 

Liu, S., Zhao, X., Dong, X., Miao, B., and Du, W. 2005. Treatment of Produced Water From Polymer Flooding Process Using a New Type of Air Sparged Hydrocyclone. Paper SPE 95343 presented at the SPE Asia Pacific Health, Safety and Environment Conference and Exhibition, Kuala Lumpur, 19-21 September. DPI 10.2118/95343-MS. 

The emulsions in produced water will become oil in the form of dispersed droplets after the emulsion film is broken. The droplets will coalesce to yield an oily film that can be separated from the produced water using gravity settling devices such as skim vessels, coalescers, and plate separators. However, small droplets require excessive gravity settling time, so flotation cells or acceleration enhanced methods such as hydrocyclones and centrifuges are used. Equipment selection is based on the inlet oil s droplet diameter and concentration. 

Since the early 1980s, hydrocyclones have been used in produced water treatment to de-oil the water prior to discharge. Hydrocyclones used to de-oil the water are referred to as "hquid-liquid de-oiling" hydrocyclones. Liquid-liquid hydrocyclones are further classified as static or dynamic hydrocyclones. 

A promising technique currently under development is downhole separation whereby a device similar to a hydrocyclone separates oil and water in the well bore. The water is subsequently compressed into a zone beneath the producing interval and only the oil is produced to surface. 

Slurry is drawn from the sump of the absorber and passed through hydrocyclones, which concentrate gypsum crystals that have grown to the required size. The gypsum slurry is fed to filters, which remove the liquor and rinse the solids. The gypsum so produced contains about 10 % of water. 

Hydrocyclone a cyclone which creates a vortex in water to produce a size separation. 

The potential for membrane technologies to treat PW has been already assessed in various studies and field trails . One of these works demonstrated that, with proper pretreatment (hydrocyclone), a UF process can treat PW and generate a water stream with oil concentrations continuously below 2 ppm. In another study with PW from an oilfield in Montana (US), the combination of UF + RO, after some preliminary pretreatment, was able to reduce the TDS, Turbidity and Chemical Oxygen Demand (COD) by more than 99% and produce clean water to be reused for irrigation. 

Recent developments in the last category show that hydrocyclones can separate oil from water, dewater light oils and produce highly concentrated samples of a lighter dispersed phase. 

Water-washed day - Water-washed kaolin has been slurried in water and centrifuged or hydrocycloned to remove impmities and produce specific particle size fractions. The refined slurry is either dewatered (to reduce soluble impurities) and dried, or concentrated to 70% solids and sold in slurry form. Water-washed clays are often treated to improve brightness. This includes chemical bleaching and/or high-intensity magnetic separation to remove iron and titanium impurities. 

In any solids removal system, there is a need for equipment to handle the bulk solids or sludge removed from the water and a procedure for removal of these solids. For many common water injection systems, the amount of bulk solids to be removed can be rather large. If the solids are free of oil, they may be disposed of in slurry piped to pits onshore or overboard offshore. If coated with oil, they may require treating prior to disposal. Treating oil from solids is beyond the scope of this chapter. Oil is normally separated from produced solids by abrasion in hydrocyclones or by washing with detergents or solvents. 

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