| Biodegradation of oily sludge involves complex multiphase fluid dynamics and biochemical processes,and this method has become a research focus and main method in the treatment of oil pollution.However,due to the complex physical and chemical characteristics of petroleum waste and the shallow understanding of the fluid dynamics and reaction mechanism of each phase in the biological reactor,the biodegradation of oil sludge is still in the laboratory stage,and there is no efficient degradation equipment and treatment method that can be applied to the actual production of oil fields and enterprises.Taking the oily sludge produced in Changqing Oilfield as the research object,based on the degradation process in the multifunctional bioreactor,the scientific problems such as its working parameters,flow fieldbiological field coupling model,degradation efficiency and how to realize accurate control were studied.Finally,a high-efficiency and low-cost biodegradation treatment method of oily sludge was proposed.The main research achievements of this paper are as follows:(1)Study on working parameters of bioreactorFirstly,according to the characteristics and degradation process of oily sludge,a multifunctional bioreactor with adjustable speed and aeration rate and controllable temperature was designed.The preliminary experiments showed that the biodegradation of oily sludge by bioreactor is innovative and feasible.Secondly,the gas-liquid-solid three-phase flow field dynamic model in the biodegradation system was established,and the flow field of the reaction system was simulated by computational fluid dynamics software Fluent.The results showed that the above flow field model could well reveal the flow state of each phase in the bioreactor.Finally,the optimal working parameters of the process were solved respectively,and the main conclusions were as follows:(1)The optimal off-bottom suspension speed was 150 r/min;(2)The relationship curve of dissolved oxygen concentration with aeration volume and time was obtained.(3)The optimum culture conditions were as follows:the inoculation amount was 15.23%,the ambient temperature was 32.56℃ and the p H was8.3.(2)Coupled solution of flow field-biological field and experimental verificationFirstly,the reaction kinetics models of oxygen,petroleum hydrocarbon and NY3 bacteria were established,and coupled with the three-phase flow field kinetics model,the multiphase turbulent reaction kinetics model of oil-bearing sludge degradation process was obtained.Secondly,the solution program was developed by UDF,and the three-dimensional flow field and water concentration field of gas,liquid and solid components in the bioreactor were simultaneously simulated.Finally,the degradation experiment of oily sludge was carried out under the condition that the simulation parameters were consistent with the experimental parameters,and the experimental results were relatively consistent with the simulation results,and the degradation efficiency error was only 3.72%,indicating that the established coupling model can provide a reliable theoretical basis for adjusting process parameters,calculating and predicting degradation efficiency.(3)Effects of different reactor structures on degradation efficiencyFirstly,the multiphase flow model and population balance model(PBM)model in the bioreactor were established.Based on the CFD method,the effects of different aeration modes and different agitation modes on the degradation efficiency were studied,the simulation results were basically consistent with the experimental results.And the optimized new biological reactor can effectively solve the traditional biological reactor encountered in the experimental process of oily sludge caking,sticking to the wall,low aeration efficiency.Secondly,the stirring period of the reactor was optimized to solve the serious heating problem in the stirring process of the reactor.Finally,the experimental results showed that the degradation efficiency of the new bioreactor was improved by 6.62% and the energy consumption was reduced by 32% compared with the traditional bioreactor.(4)Study on control system of bioreactorFirstly,according to the characteristics of oily sludge degradation system in bioreactor:complex and changeable,multi domain integration,difficult to establish accurate mathematical model,time delay and nonlinearity,combined with the advantages of Takagi-Sugeno(T-S)fuzzy reasoning and generalized predictive control(GPC)algorithm,a generalized fuzzy predictive control model was obtained.The model is suitable for the parameter control and regulation of any different kinds of oily sludge.Secondly,the temperature control and dissolved oxygen concentration control system models of bioreactor were established and analyzed based on the above model.Finally,through simulation verification,it was found that compared with the traditional PID control method,the generalized fuzzy predictive control model has good stability,strong anti-interference ability,and sensitive response.It can always keep the working parameters running according to the track of the set optimal value,which provides an important guarantee for improving the degradation efficiency.In summary,theoretical and relevant experimental studies showed that bioreactor degradation of oily sludge has the advantages of low cost,high efficiency,easy adjustment and control,and can be degraded to different degrees according to the disposal methods and requirements of final waste,and providing an effective and reliable new way to treat oily sludge. |
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