Offshore oilfield wastewater treatment system

Offshore oilfield wastewater treatment system

Oily water offshore oil platforms handled in two ways: one is treated to meet emission standards back the sea; the other is the need to inject water reservoir development, oily wastewater treatment will reach after the injection of water quality, is injected into the formation. This paper mainly studied after oily wastewater treatment injected into the formation, as much as possible to reduce pollution of the marine environment . 1. Oily wastewater quality and separation principle 1.1 Quality of oily wastewater Oily water generally alkaline, low hardness, low iron, high salinity. Depending on the size of the oil particles, oil in water into four types: the first one is free of oil, oil particle diameter greater than 50 μm; the second is the dispersed oil, oil particle diameter between 20 ~ 50 μm, oil beads easy separated from the sewage out of this state of the oil accounts for 60% to 80% of the oil content of the sewage; third is emulsified oil, the oil particle diameter less than 20 μm, with water to form an emulsion, oil in water type belonging emulsion, This is difficult to remove part of the oil, then must be inverted before it can be removed by breaking, in an amount of 10% to 15% of the oil content of the sewage; fourth is dissolved oil, the oil was dissolved in a molecular state in water, the oil particle diameter is not measured , oil solubility in water is very small, is 5 ~ 15 mg / L, this part can not be removed, which accounted for 0.2% to 0.5% water content. 1.2 Oil-water separation principle Separation of oil from oily wastewater, depending on the oil particles of different diameters, there are three separate methods: The first method, for diameter greater than 50 μm oil particles by density difference between oil and water, oil particles in the buoyancy of water, float to the surface skimmer equipment, oil and water separation, oil particles floating rate Stoke's law can be used to calculate. According to Stoke's law formula can draw the following conclusions: The larger droplet size, the larger the diameter squared, and therefore the greater the increase in its speed, that is, the larger the size of the oil droplets rise to the surface of the collection the shorter the time required, so that oil and water separation becomes easy; the relative density difference between the oil droplets and the water phase, the greater the vertical rise velocity of oil droplets, the more light oil, water more easily handled; the higher the temperature , the lower the viscosity of water, the greater the vertical velocity of the droplets, so that at higher temperature conditions easier than treatment temperature is low. Often used as a platform inclined plate grease traps is to use this principle to oil-water separation. The second method for smaller particle size dispersed oil, because the oil particles smaller particle size, floating slowly, so the use of external force to separate oil particles from the water. Such as hydrocyclone, centrifugal force hydrocyclone is oil, water separation. The third method, filtration, oil is actually absorbed onto filter media. Such as walnut shell filter, it can be separated from the water dispersed oil and emulsified oil, in order to improve the efficiency of oil recovery, is still often the upstream device to the chemicals. 2. The processing of oily wastewater Oily wastewater treatment processes to confirm mainly based on the density and requirements of the oil after treatment : the density of light oil, water density difference between the large, easy to handle, less processing stages; for water demanding processing stages to more ʱ?? Water quality standards in accordance with the requirements of sewage treatment, waste water treatment in accordance with the peak amount, the nature of the formation water and sewage water treatment requirements, combined maritime space area to choose reasonable and economical sewage treatment equipment and processes

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