Refining Sour Wastewater Treatment Process: Efficiently Breaking the Bottleneck in Emulsified Oil and Suspended Solids Separation

Wastewater discharged from the various unit operations and processes of petroleum processing can be roughly divided into four streams:

1. Desalter wastewater (desalting wastewater)

2. Sour wastewater (atmospheric and vacuum distillation, fluid catalytic cracking, stripping

column, hydrotreating, etc.)

3. Spent caustic wastewater (Merox process, alkylation, ethylene, viscosity breaker, etc.)

4. Oily wastewater (crude oil and waste oil tanks)

Among them, sour wastewater cannot be discharged directly into the wastewater treatment system because it contains high concentrations of hydrogen sulphide, ammonia, mercaptans, phenols, hydrocarbons and suspended solids, and usually needs to be purified by a stripping process. However, the coke fines and emulsified oil contained in this wastewater easily cause scaling and plugging of the stripper trays and lead to the failure of some instrument controls, seriously affecting the smooth operation and long-cycle operating performance of the stripping unit.

To ensure the stability and efficiency of the stripping process, effective de-oiling and solid-phase separation must be completed before the sour water enters the stripper. The conventional “double-tank” process relies only on gravity settling to separate floating oil, requires a long residence time and has almost no removal effect on emulsified oil; although cyclone de-oilers and coke-fines removal equipment achieve oil–solid separation by centrifugal force, their high-speed rotation easily causes secondary emulsification of oil droplets, which is instead unfavourable for thorough removal of emulsified oil; adding a sand filter can only intercept larger coke fines above 0.15 mm and has limited capability for finer particles; although the coagulation–flotation process performs relatively well in de-oiling and solids removal, it requires chemical dosing and carries the risk of secondary pollution; and precision treatment methods such as membrane filtration face the problems of easy clogging and short service life.

Developing new wastewater treatment processes and equipment, researching fine filtration materials and integrating the advantages of multiple technologies to build an efficient, integrated and stable compliant treatment system has therefore become an urgent need in the field of refining oily wastewater treatment.

To solve this problem, SINOKLE has, through years of technology accumulation and engineering practice, successfully developed a coking sour wastewater treatment unit centred on “cyclonic dissolved gas flotation (CDFU) – fine filtration – KHC high-efficiency coalescing de-oiling”.

SINOKLE coking wastewater treatment process

Several major advantages of SINOKLE technology:

1. No chemical reagents required.

2. Stable demulsification performance, effectively separating emulsified oil and suspended solids in the wastewater.

3. Recovered waste oil of good quality with low water content.

4. Fully automatic, closed and pressurised operation of the unit.

5. Small equipment footprint and low operating cost.

Application cases:

Coking sour wastewater treatment site of a petrochemical enterprise in Luoyang

Effluent performance of the coking sour wastewater treatment unit