Industrial/commercial-scale biological applications including cell therapy, drug testing and regenerative medicine, require the production of a large number of cells. A suspension culture method has been extensively used to generate sufficiently large quantities of high-quality cells in a defined form. In this study, we carried out the present numerical simulation to first characterize the performance of two different shaking methodologies in an orbitally shaken bioreactor, namely, one direction rotation (ODR) and periodic alternate rotation (PAR). Cell distribution, suspension level and shear stress at varying shaking conditions are obtained, indicating that the PAR method is superior to another one, as it could generate upward fluid motion to suspend adequate cells. Additionally, the parametric study of the PAR method is further explored to capture an optimum culture condition concerning cells quality and energy consumption. It is concluded that our simulation results give a new insight for bioreactor design and would be beneficial to the shaking techniques for cell cultivation in suspension culture.

The aeration performance of inverted umbrella aerator is optimized through response surface methodology. The Box-Behnken design (BBD) method is used to design the experimental scheme, and three variables (blade number, plate tilt angle and plate gap opening) are selected to optimize the structure of the inverted umbrella aerator impeller and improve the aeration performance. The corresponding response value is obtained by experiments through the established scheme. The regression model is fitted through the response value, and the variance analysis is performed on the regression model to test the significance of the model. The results show that the P-value is less than 0.05. Therefore, the model is significant and fits well in the regression area. The effect of the blade number and the plate tilt angle on the target is significant, while plate gap opening is not significant. The inverted umbrella aerator has the best aeration performance when the number of the blades is 6, the plate tilt angle is 65° and the plate gap opening is 16.07%. The aeration performance and flow field before and after optimization are compared. It shows that the standard oxygen mass transfer coefficient after optimization increases by 1.59%, and the standard aeration efficiency increases by 4.78%. The flow becomes more intense after optimization. The oxygen mass transfer process is further strengthened, and the aeration performance of inverted umbrella aerator is optimized.

Interaction of silica sand or bentonite particles with alkaline components contained in ash of empty fruits bunches (EFB) was investigated by observation of agglomeration and defluidization behaviors in a bubbling fluidized bed process at conventional gasification temperatures. In this study, agglomeration and defluidization formation along with EFB ash addition were evaluated by differential pressure change of the fluidized bed, and sticky level of agglomerates estimated by elemental analysis of particles in bed residue and discharged line. Fluidization operation at 750°C showed that number of coarse agglomerates formed after at more than 0.12 wt% of EFB ash addition with high sticky level on silica sand particles while bentonite kept running in normal fluidization until 4.66 wt% addition. Bubbling fluidization at 800°C has a higher tendency to form bigger and stickier agglomeration on both particles. In the silica sand bed, hard and sticky agglomerates were built up to form extensive bulk agglomerates at more than 1.55 wt% ash addition. On the other hand, bentonite also produced huge agglomerates, but a part of the bed was still fluidized because of the formation of weak agglomerates. The difference was caused by the structure of the agglomerates. Application of bentonite in fluidized bed gasifiers is, therefore, more promising to maintain fluidization state than silica sand.

Numerical simulations of seeded batch cooling crystallization were performed to investigate the effect of stochastic nucleation on crystal quality parameters. In a typical deterministic mathematical model for crystallization, which contains population and mass balance equations, primary and secondary nucleation are regarded as Poisson processes in order to derive a stochastic model. In this study, these stochastic model equations were repeatedly solved to achieve a stochastic simulation, and statistical analysis of the results revealed differences in product quality when the simulations were run under certain conditions. In particular, the statistics, such as the mean and the coefficient of variation, of the product crystal size distribution were found to fluctuate as a result of stochastic primary and secondary nucleation. Further, stochastic primary nucleation was also found to be the source of the differences between the statistics obtained using the deterministic and stochastic simulations when the seed-loading ratio was very low. This difference was attributed to the growth of crystals when the total number of crystals was less than one, as well as the accompanying secondary nucleation, in the standard deterministic simulation. Thus, a novel deterministic model in which secondary nucleation does not occur until the total number of crystals reaches one was used, and the results and statistics were found to agree with those obtained using the stochastic numerical simulation. In addition, a stochastic model ignoring stochastic secondary nucleation omitted to predict the significant statistical fluctuations under certain conditions. Finally, the statistical fluctuations were predicted for several crystallizer scales, and crystallizer scale-up was found to reduce the fluctuations caused by stochastic primary and secondary nucleation.

This work presents the development of membrane reactors to generate hydrogen by biogas steam reforming. The reactors consisted of Rh/Al₂O₃ catalysts and hydrogen-selective amorphous silica membranes that were prepared by the chemical vapor deposition of dimethoxydimethylsilane (DMDMS) with oxygen. Silica membrane application to such membrane reactors for the steam reforming of methane in biogas is novel. In the membrane reactors, hydrogen that is generated at the catalytic bed is expected to be extracted through the hydrogen-selective DMDMS-derived membranes immediately. This process intensification was effective, and the methane conversions always exceeded that using packed-bed reactors in which no hydrogen extraction occurred, even when the flow rate, the reaction temperature, and the model biogas composition varied. This behavior was due to hydrogen extraction through the DMDMS-derived membranes. We tested the membrane reactor stability by changing the composition of the model biogas every 6 h, and demonstrated that it showed excellent performance against the fluctuation of the feed composition from 50% methane with 50% carbon dioxide to 70% methane with 30% carbon dioxide. These results indicate that the developed membrane reactors are applicable for hydrogen production from biogas that is generated through the anaerobic digestion of organic matter.

Inferential control facilitates the direct feedback control of a variable that is difficult to measure in real time and achieves more efficient plant operation. However, when an inferential control system is introduced into the existing plant, the difficult-to-measure variable cannot be estimated accurately because operating conditions during data acquisition differ from those during inferential control operation. Thus, the control performance of the difficult-to-measure variable is poor. The contribution of this research is to propose a method to obtain an inferential control system that has high control performance and robustness against estimation error. In the proposed method, the degree of change in the operating conditions is limited by setting constraints on the inferential control system. Restrictions are relaxed in a step-by-step manner when the model is updated with the newly acquired data under the inferential control operation. The usefulness of the proposed method was evaluated through simulation case studies. In the case studies, control simulations of a vinyl acetate monomer (VAM) plant were performed. The bottom water concentration of the distillation column of the VAM plant was controlled. Four control methods including the proposed method were compared. The results of the case study showed that using the proposed method enhances both control performance and robustness against estimation error.

Coal-fired power plants are the main sources of atmospheric Pb. The mineral composition of coal is an important factor of the trace element distribution. The Pb volatilization characteristics of the anthracite, lignite and bitumite were examined in the horizontal tube furnace. SiO₂, Al₂O₃, CaO and Fe₂O₃ were chosen as the mineral compositions and PbO was chosen as Pb source to investigate the effect of minerals on Pb volatilization during coal combustion. The results indicated that the occurrence modes of Pb and mineral composition were major factors in Pb volatilization and the coal containing more silicon and aluminum had the lower Pb volatilization rate. The intrinsic minerals in coal immobilized the released Pb through both physisorption and chemisorption. The combustion and thermogravimetric investigation showed that the Pb capture efficiency of the four minerals ranked as SiO₂>Al₂O₃>CaO>Fe₂O₃. The formation of the non-volatile materials such as PbSiO₃, Ca₂PbO₄ and PbFe₁₂O₁₉ accounted for the capture mechanisms of SiO₂, CaO and Fe₂O₃, while Al₂O₃ stabilized Pb via the physisorption. The synergy of SiO₂ and Al₂O₃ exhibited the most superior capture efficiency on Pb, which provided references to the preparation of oriented Pb removal adsorbent.