Study On Petroleum Microbial Dewaxing By High Gravity Technique

Petroleum microbial dewaxing technique is a deep dewaxing method using microbial fermentation, which is usually adopted in refining petroleum process. The culture solution consists of oil and water in microbial dewaxing process, which has poor emulsification and solubility of oil in water and oil content in water is also very high. Thus the emulsified state and oxygen content in culture solution become the key factors in microbial dewaxing process.High gravity technique is a novel process intensification technique, whose core reactor is a rotating packed bed. The rotating packed bed utilizes centrifugal acceleration to intensify the mixing and mass-transfer processes previously conducted in columns. In view of the characteristics of high gravity technique, the petroleum microbial dewaxing by high gravity technique was proposed in this paper, and the mixing and emulsified states of oil and water was supposed to be improved and mass-transfer process in petroleum microbial dewaxing can be intensified by high gravity technique. Thus the oxygen content in culture solution can be increased; the higher productivity and shorter dewaxing duration with better quality of product were obtained.The feasibility of petroleum microbial dewaxing by high gravity technique was investigated by comparison with the conventional bubbling dewaxing process. And then, the effects of operational parameters on petroleum microbial dewaxing process were studied, and the better operational parameters fitted to petroleum microbial dewaxing by high gravity technique were screened by orthogonal tests. The mechanism of microbial dewaxing by high gravity technique was investigated by analyzing the dewaxing process and oil droplets morphology. The results were as follows:(1) The investigation of feasibility of petroleum microbial dewaxing by high gravity technique shown that the packed mesh is not easily clogged. Compared with the conventional bubbled dewaxing technique, the high gravity technique has advantages in lower oil consumpation, shorter time demand and more bacteria in cultivating seeds. In the same gas flowrate, the pour point of dewaxed oil was lower 14℃than that parepared by bubbled dewaxing technique. The demanded dewaxing time using high gravity technique was less 30 hours than that using bubbled dewaxing technique when the same pour point of the dewaxed oil was reached. The matrix oil was saved 10%, gas consumpation was decreased 50% and cost of fermentation reduced 50%.(2) The pour point of MVI150 can reach -43℃in 60 hours by high gravity technique, which can be completed in 120 hours by conventional bubbled dewaxing. The pour point of MVI150 can not be reduced -43℃by conventional bubbled dewaxing, which can be completed in 150 hours by high gravity technique. The pour point of MVI400(V4073.34 mm2/s)can be reduced for -9℃to -21℃, and that of HVI200(V4044.96 mm2/s) can be reduced from-12℃to -17℃.(3) The effects of rotating speed, gas and liquid flowrate on dewaxing process of high gravity technique were studied, and the better operational parameters fitted to petroleum microbial dewaxing by high gravity technique were screened by orthogonal tests, which were gas flowrate 2 m3/h, liquid flowrate 1m3/hand rotating speed 1180 rpm (20Hz).(4) The mechanism of microbial dewaxing by high gravity technique was investigated by analyzing the dewaxing process and oil droplets morphology. The diameter of oil droplets is less 4 micrometer, which is in favor of mass-transfer of dewaxing process.