Method for treating heavy emulsified oil in waste water

Abstract

The invention relates to a method for treating heavy emulsified oil in wastewater. The method is characterized in that a treatment device is formed by a lower bubble section and an upper foam section, wherein the lower bubble section of the treatment device is an airlift inner-circulation reactor, and the upper foam section of the treatment device is an overflow box type gas-liquid separator; thepH value of the wastewater is regulated to 8-9, and the wastewater is introduced into the bubble section; air is introduced to a tower bottom, and flocculating agents and a surface active agent are added, wherein the amount of an inorganic flocculating agent is 0.02-0.1mmol/g COD (chemical oxygen demand), the amount of a polymer flocculating agent is 10-50mg/m<3> wastewater, and the amount of an anion surface active agent is 5-20mg/g COD and is not less than 15-20mg/m<3> wastewater; the emulsified oil is separated from the wastewater through collecting foam; the gas speed of an empty tower ismaintained at 0.5-1.5cm/s; the separation efficiency is high: the primary separation rate can reach above 90%; the process is simple: solid suspended matters in the wastewater are removed once; the energy consumption and the reagent consumption are low: the amount of the flocculating agents is low; and the process flow is short.

Description

technical field [0001] The invention relates to a method for removing heavy emulsified oil from crude oil processing wastewater. Background technique [0002] The processing of heavy crude oil, that is, heavy oil, will produce a large amount of wastewater containing heavy emulsified oil, including dehydration at the bottom of crude oil tanks, desalination and decalcification sewage, coking steam blowing condensate, etc. Compared with ordinary refinery wastewater and oilfield wastewater Its outstanding features are: ① High content of emulsified oil: In general, more than half of the oil in heavy crude oil processing wastewater exists in the form of emulsified oil. After removing slick oil and dispersed oil, more than 80% of COD is due to emulsified oil and Produced by colloidal suspended matter; ②Severe degree of emulsification and stable emulsion droplets: the diameter of emulsion droplets of heavy emulsified oil is usually only a few hundred nanometers to a few microns. Th...

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Problems solved by technology

[0004] Due to the high degree of emulsification, the emulsion droplets are very small and extremely stable, and the adsorption amount of stable oil droplets on the bubble interface is very small, so a large number of bubble interfaces are required to absorb emulsion droplets, and multi-stage air flotation is required to achieve the required separation effect. The energy consumption of air flotation separation is high and the separation efficiency is low. For example, CN101327966 discloses a jet dissolved air flotation process for heavy oil sewage, which includes a multi-stage separation technology including primary air flotation, jet dissolved air, and secondary air flotation.

[0005] In recent years, some new high-efficiency air flotation separation equipment and technologies have been reported, such as the cyclone flotation separation technology disclosed in US 2008 / 0006588, and the method and device for pressurized dissolved air flotation hydrocyclone oil-water separation disclosed in CN 1546196. The combination of air flotation deoiling and cyclone separation is used to deoil the oily wastewater feed liquid. None of the above documents have reported the separation effect on heavy emulsified oily wastewater.

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