Petroleum refining and chemical emulsified acidic water treatment process
Highly emulsified acidic water is a relatively difficult wastewater to treat in refining and chemical industry, and its sources mainly include the following aspects:
- Atmospheric and vacuum distillation unit: During the atmospheric and vacuum distillation process, acidic water mainly comes from the atmospheric tower top reflux tank and the vacuum tower top water seal tank. The amount of acidic water in the atmospheric tower top reflux tank depends on the amount of stripping steam at the bottom of the tower, the amount of stripping steam on the side line, and the amount of water injected at the top of the tower.
- Catalytic cracking unit: The acidic water of the catalytic cracking unit comes from the fractionation tower top reflux tank, the compressor outlet oil-gas separator, the compressor intermediate condensate tank, and the stabilization tower top reflux tank.
- Coking unit: During the coking process, sulfur-containing and nitrogen-containing compounds generate toxic and harmful gases such as H2S and NH3 through high-temperature cracking, catalytic cracking and other reactions. These gases are absorbed by water in the subsequent processing technology and become sulfur-containing and ammonia-containing wastewater, that is, acidic water.
- Hydrotreating unit and hydrocracking unit: In these units, sulfur-containing and nitrogen-containing compounds also generate acidic gases through high-temperature cracking, catalytic cracking and other reactions, and then form acidic water.
The treatment difficulties of acidic water include:
- Severe emulsification: Acidic water contains a large amount of emulsified oil and suspended solids, which affect the stripping effect and liquid ammonia quality, and easily cause blockage of the stripping tower. In severe cases, it may lead to unplanned shutdown.
- Complex composition and large fluctuation in content: Acidic water contains irritating substances such as sulfide and ammonia nitrogen, which are difficult to treat.
- Limited effect of traditional treatment methods: Such as gravity sedimentation method, cyclone oil and coke powder removal process, etc. Although they have a certain treatment effect, the separation effect is not obvious, and there are problems such as equipment blockage and high operation cost.
New process for treating acidic water in refining and chemical industry:
The new process for treating highly emulsified acidic water in refining and chemical industry overcomes the defects of traditional processes and better solves the problem of treating this wastewater.
To light sewage oil tank, sewage oil, sewage oil receiving tank, to low flare liquid separation tank, to coke pit, nitrogen/methane, light sewage oil, waste gas, light sewage oil, acidic water, coalescing oil-water separator, effluent (cyclone dissolved air flotation) CDFU, effluent, filter A/B, effluent, coalescing oil remover, KHC, effluent, into stripping unit, backwash water, backwash water, backwash water.
Process flow chart of acidic water treatment in refining and chemical industry.
- Pretreatment stage: Acidic wastewater first enters the CDFU device, and through the combined action of cyclone and micro-nano bubbles, the suspended solids, sewage oil and emulsified oil in the water are quickly removed.
- Fine filtration stage: The treated water is further filtered through a fine filter to ensure the quality of the effluent.
- Final treatment stage: Finally, the oil-water separation is carried out through the KHC high-efficiency coalescing separator to ensure the quality of the effluent, which can directly enter the stripping unit for recycling.
CDFU (Cyclone Dissolved Air Flotation): CDFU is a high-efficiency compact cyclone flotation device. Through the combination of ultra-fine bubble generation, cyclone centrifugal separation technology and dissolved air flotation separation technology, it can greatly improve the flotation effect and efficiently remove the suspended solids, sewage oil and emulsified oil in the water. This technology has the advantages of pure physical demulsification, no chemical agent, low energy consumption and high degree of automation. The effluent quality is good and can directly enter the stripping unit for recycling.
Fine filter: Used for further filtering the treated water to ensure the quality of the effluent. This filter has high filtration accuracy and stability and can effectively remove the residual suspended solids and oil droplets.
KHC high-efficiency coalescing separator: The KHC high-efficiency coalescing separator efficiently separates through the density difference of oil-gas-water three phases and can remove the suspended solids, sewage oil and emulsified oil in the water. This technology has the characteristics of pure physical demulsification, no secondary pollution, stable and reliable operation, and is suitable for treating acidic water with high oil content and severe emulsification.
Case of an acidic water treatment project in a petrochemical plant in Henan.
Technical characteristics and application effects: - Pure physical demulsification: No chemical agent is required, avoiding secondary pollution. - High-efficiency separation: It can efficiently remove the suspended solids, sewage oil and emulsified oil in the water in a short time. - Stable operation: The equipment has a compact structure, small floor area, high degree of automation and stable and reliable operation. - High effluent quality: The treated effluent can be directly recycled or enter the stripping unit for recycling, meeting the environmental protection requirements.
