Treatment of Daqing oily sludge by thermochemical cleaning method

The thermochemical cleaning method was used to treat the oily sludge produced from Daqing oilfield. Cleaning agents were screened innovatively by using interfacial tension (IFT) method. The mixture of sodium carbonate, fatty alcohol ethoxylate (AEO-9), and rhamnolipid with a ratio of 5:1:0.5 was found that had the lowest IFT. They were selected as the cleaning agents and when their mass fraction was 2 wt%, cleaning agents aqeous solution/sludge ratio was 3:1, cleaning time was 40 min and cleaning temperature was 50 degrees C, the oil content contained by solids after cleaning was reduced to less than 1 wt %, meeting the environmental protection requirement in China. In addition, the simulated adsorption experiment and the characterization of residue on the cleaned solids were done to provide insight into the cleaning process. The results revealed that the oil adsorbed onto the solids (clinoptilolite) mainly by the multilayer physisorption, most of them can be easily removed by the emulsification of cleaning agents, and the residue is mainly asphaltene.