CFD Simulation And Optimization Of Coenzyme Q10 Fermentation

Coenzyme Q10 is widely used in cosmetics,food additives and clinical treatment due to its important role in human body.Fermentation is one of the main methods for the commercial production of coenzyme Q10.As a typical multiphase process and involves complex biochemical reactions,scale-up effect inevitably exists in the process from laboratory fermentation to commercial production,which requires corresponding optimization and adjustment of the production process.At present,most optimization studies are carried out through empirical methods with long optimization cycle and heavy workload.In this thesis,commercial computational fluid dynamics software Fluent was used to study the gas-liquid dispersion and liquid-liquid mixing behavior of coenzyme Q10 fermenter.The two-fluid model and k-? model were used to describe the interphase interaction between air and fermentation liquid,while the PBM model(Population Balance Model)was used to describe the breakage and coalesce of bubbles.The actual fermentation system was simplified into ternary system of glycerol,water and NaCl and the mass transfer process between nutrient matrix and fermentation broth during feeding was simulated by component transport model and realizable k-? model.The results showed that with the increase of ventilation,the gas holdup increases and the power consumption decreases.When the rotating speed increases,the gas holdup increases,the bubble diameter decreases,and the liquid-liquid mixing efficiency increases.When the ventilation rate and gas velocity are constant,the ring diameter and aperture of the air distributor have no significant effect on the overall gas-liquid dispersion in the fermenter.When the input power is constant,the influence of the diameter of the agitator on the gas holdup in the fermenter is not significant,but too small diameter of the agitator is not conducive to liquid-liquid mixing.The diameter of the agitator should be at least 0.45 times of that of the fermenter.The amount of liquid loaded in the fermenter should not be too large.In the case of the upper axial flow agitator,the distance between the upper agitator and the liquid level should be reduced as far as possible.Based on the ternary system of glycerol,water and NaCl and component transport model,the optimal feeding position was explored,and a four-equivalent point rotation feeding pattern was proposed.The simulation results showed that the mixing dead zone is not easy to appear in the fermenter at the early feeding stage,and the overall effect of liquid-liquid mixing is far better than that of other static feeding ports.A deformed turbine impeller was designed based on the gas-liquid two-phase flow calculation model.The simulation results showed that the power number of the impeller decreass by 18.8%while the gas hold up increass by 17.96%.as the bottom impeller,this impeller is helpful to reduce the enrichment degree of gas phase at the flow circulation center at the bottom of the fermenter,and gas-liquid distribution in the fermenter is more uniform.