Study On Technology Of Oil Recovery From Oily-Sludge Of Tank Bottom

Sludge, which is discharged from the process of oil crude production and transport, can not be free settled because of its sufficient emulsification. It can get the environment polluted, and also be a waste of crude oil resource while the oily sludge is discharged directly without any disposal. Study focuses on treating oily sludge of tank bottom which is harmful, oily, valuable and difficult to dispose. Freeze/thaw method and thermochemical cleaning method are considered to be the valuable methods that studied to treat the oily sludge and recycle oil.Controling the growth of ice crystal and choosing the right reagent are the core factors in these two methods.(1) The sample is taken from oil tank bottom of Liao River Oil field, new test approaches are attempted on the base analyse of nature and chemical compositions of the sample. Water content, oil conten, sand content and the residual oil rate in solid are 50.62%, 39.3%, 9.98% and 22.7%, respectively. Boiling points of hydrocarbon in oil are between 300-400℃, the heating value of the sludge is 15347.2 kJ/kg.(2) The study observes the performances of freeze/thaw method and thermochemical cleaning method on oily sludge treatment without using reagent and determines the best initial parameters: for freeze/thaw method, the best water content, freezing temperature, freezing time and thawing temperature are 70%, -16±0.5℃, 8 h and 20-25°C, respectively. The best residual oil rate in solid could reach 2.6%, 0.5% could be reached while using the second level of freeze/thaw method; For thermochemical cleaning method, the best water content is 65%, washing temperature is 60°C, washing time is 30 min, agitation speed is 200 r/min and the residual oil rate in solid could reach 4.4%.(3) Under the best technologcial conditions, LAS:Na₂CO₃=1:2(mass ratio) are selected. The residual oil rates reduced to 1.7% when LAS:Na₂CO₃=1:2 and to 0.19% while using the second level washing. The heating value is 39186.3 kJ/kg which closes to the average heating value of oil.(4) In the flocculation experiment of the thawing water and waste water, Zeta electric potential and COD were measured to select the optimum inorganic flocculate solution and organic macromolecule. PFS and CPAM are chosen in freeze/thaw method and the COD could reach 177 when they were combined. PAC and CPAM are chosen in thermochemical cleaning method and the COD could reach 149 when they were combined. (5) Based on freeze/thaw principle and basal experiments, an oily sludge floating freeze/thaw treatment equipment which is high performance, low cost and convenient to operate are designed.