The oil industry produces large quantities of solid and semi-solid wastes called oily sludge. Oily sludge usually contains water, sand, oil, grease, organic compounds and metals. Due to the diversity of crude oil quality, the differences arising from the different processes used in the oil-water separation process, the leakage in the industrial process, and the mixing with a variety of other existing oily sludge, the composition of the oily sludge has a variety of difference.
These oily sludge can be produced in several steps of oil production and refining, for example in oil-water separation and settling at the tank bottom..
The high stability of the oily sludge is due to the oil adsorbed on the solid particles, resulting in the formation of the protective layer. The stability is enhanced by the presence of polar fractions in the oil, especially resins and asphaltene, which also contribute to the high viscosity of these sludge. In addition, the protective layer is conducive to the production of microorganisms, but also for the diversity of microbial communities to provide a breeding cover, thereby causing environmental corrosion, which is reflected in each use of storage tanks, the storage tank will be corroded. Oily remnants accumulate in the petroleum industry and cause serious environmental problems.
This type of sludge is considered hazardous waste in many countries because it contains high concentrations of toxic components and therefore requires proper management. Recycling of the waste crude oil in such oily sludge is an ideal treatment because it not only recovers valuable energy, but also minimizes the concentration and total amount of hazardous waste. We benefit from the recovered oil and at the same time reduce the cost for the residual further disposal treatment.
There are various ways to recycle the waste crude oil. The cost and production efficiency mainly become the points when user choose their own. However, the combination of chemical additives, heating, and physical separation has undoubtedly become a mainstream choice in current processing methods, because of its mature technology, the equipment used is simple and easy to operate. Through different temperature configurations, chemical additives, core equipment, and even fine-tuning of the entire process, make it can adapt to different area of various sludge oil recovery.
Step 1: Pretreatment
In the waste treatment process, whether it is reduction, recycling or harmless treatment, after the initial experimental analysis of waste, in order to meet the next stage of the entire process requirements, will be pre-treatment of materials. Such pretreatment methods can be dilution, sedimentation, sieving, heating, demulsification, gel breaking, viscosity reduction and so on. Of course, in the treatment of certain special oily sludge, such as some heavy crude oil sludge , aging sludge, adding a certain proportion of light crude oil for dilution, in order to make it easier for the next separation, will achieve surprising results . In the initial classification of the waste sludge, according to the size of oil particles inside the sludge and the proportion of the solids, mechanical vibrating screen or roller screen to be chosen. According to the oil content of the sludge, sludge viscosity, different crude oil condensate point , we will choose different chemical additives to broken gel, breaking, and set the different heating temperature. As the entire process using pipeline transport, the main purpose of the pretreatment is to ensure the viscosity of oil sludge and liquidity suitable for the pumping process.
Step 2: Separation
After pretreatment, centrifugal separation is the most important part of the process. Due to the different density of the different physical phase, the different components will go through a specific orbit attribute to the centrifugal force. In general, the oily sludge components are divided into oil, water, solid. Separation equipment selection in the process should be based on the actual proportion of material components, and reduce the cost point of view , such as two-phase decanter centrifuge, three-phase decanter centrifuge, Disc separator and oil-water separator.
Step 3: Filtration
Taking the recovered crude oil quality into consideration, a filter system may be put into the process after the separation part. Or it’s even better to send the recovered oil to refinery plant for further purification process.
ZK separation is an experienced solution and equipment provider on oilfield waste management. The company has been dealing with oily waste including cured oil, cooking oil, engine oil, lubrication oil for more than 16 years. The valuable practice on projects enhance the production performance for various working condition and different types of oily waste.