Scale-up and thermal stability analysis of fluidized bed reactors for ethylene polymerization

A set of hydrodynamic similarity laws is applied to the scale-up of ethylene polymerization fluidized bed reactors(FBRs)under the condensed mode operation.The thermal stability of open-loop controlled FBRs is investigated by the homotopy continuation method.And the Hopf bifurcation point is selected as an index of the thermal stability similarity.The simulation results show the similarity in state variables,operation parameters,the space-time yield(STY),and the thermal stability of FBRs with different scales.Furthermore,the thermal stability behaviors and similarity of the closed-loop controlled FBRs with different scales are analyzed.The observed similar trend of Hopf bifurcation curves reveals the similarity in the thermal stability of closed-loop controlled FBRs with different scaling ratios.In general,the results of the thermal stability similarity confirm that the hydrodynamics scaling laws proposed in the work are applicable to the scale-up of FBRs under the condensed mode operation.

Electrochemical Removal of Chlorophenol Pollutants by Reactive Electrode Membranes: Scale-Up Strategy for Engineered Applications

Chlorophenols(CPs)are significant refractory pollutants that are highly toxic to humans and other organ-isms.Reactive electrode membranes(REMs)show considerable potential in the electrochemical removal of refractory pollutants by allowing flow-through operations with convection-enhanced mass transfer.However,relevant studies are commonly performed on the laboratory scale,and there is no straightfor-ward method that guarantees success in scaling up engineered REM reactors.In this study,we demon-strated that a tubular concentric electrode(TCE)configuration with a titanium suboxide ceramic anode and a stainless-steel cathode is suitable for large-scale CPs removal.Both theoretical and experi-mental results showed that the TCE configuration not only allows the electrode surface to be orthogonal to electric field lines everywhere,but also has an ohmic resistance that is inversely proportional to the length of the electrode.In addition,the TCE configuration can be operated in either the anode-to-cathode(AC)or the cathode-to-anode(CA)mode based on the flow direction,creating adjustable condi-tions for selective degradation of CPs.This was confirmed by 98%removal of 2,4-dichlorophenol(2,4-DCP)and 72.5%removal of chemical oxygen demand(COD)in the CA mode,in which the kinetic constant was one order of magnitude higher than that for the AC mode under flow-through single-pass operations.This can be explained by the lower activation energy and free energy in the CA mode,as revealed by the-oretical calculations and experimental measurements.The TCE configuration is also suitable for a numbering-up strategy to scale up the electrochemical reactor without increasing the ohmic resistance or decreasing the specific electrode area,achieving 99.4%removal of 2,4-DCP with an energy consump-tion of 1.5 kW·h·m^(-3) when three TCE modules were employed.This study presents a suitable electrode design configuration for the REM reactor,offering effective strategies to bridge the“Valley of Death”encountered when scaling up the electrochemical removal of CP pollutants.

Effect of impeller type and scale-up on spatial distribution of shear rate in a stirred tank

The main spatial distribution features of shear rate in a stirred tank operated with five different radial and axial flow impellers were presented with particle image velocimetry(PIV)experiments.Not only the average shear rate in the whole tank but also the local value in the vicinity of impeller increases linearly with impeller speed.Furthermore,the shear coefficient(Ks,imp)at the impeller outlet is linearly related to the impeller flow number(Nq)and decreases with the increase of Nq in general at the constant power consumption per unit volume(Pv).During scale-up based on the constant Pv and geometric similarity,CFD results show that the volume-averaged shear rate(cavg)for RDT decreases faster than that of other impellers with the impeller tip velocity(Utip).The novel multi-blade combined(MBC)impeller with the increased height-to-diameter ratio of the stirred tank is able to more effectively improve the distribution uniformity of shear rate at the same Pv after scale-up.These studies provide a data basis for selecting the impeller types and improving the shear rate environment in the large-scale stirred tank.

Scale-Up Synthesis of Hydrogen Peroxide from H_2/O_2 with Multiple Parallel DBD Tubes

The scale-up synthesis of H2O2 from H2/O2 via a dielectric barrier discharge （DBD） under ambient conditions was studied. A plasma reactor consisting of multiple parallel DBD tubes was designed to scale up the H2O2 synthesis. The number of tubes had no significant effect on the discharge mode, and no decay occurred in H2O2 selectivity during the scale-up process. These advantages made this technology more stable and efficient. The reactor＇s energy efficiency increased with the number of tubes and reached 136 g H2O2/kWh in the four-tube reaction. The total energy efficiency was limited by the extremely low energy transfer efficiency of power supply, and might be enhanced by optimizing the impedance matching between the power supply and the reactor load. As a result, an assembly of multiple DBD tubes may provide a viable route for the scale-up synthesis of H2O2 by a non-equilibrium plasma.

Understanding the scale-up of fermentation processes from the viewpoint of the flow field in bioreactors and the physiological response of strains

The production capability of a fermentation process is predominately determined by individual strains,which ultimately affected ultimately by interactions between the scale-dependent flow field developed within bioreactors and the physiological response of these strains.Interpreting these complicated interactions is key for better understanding the scale-up of the fermentation process.We review these two aspects and address progress in strategies for scaling up fermentation processes.A perspective on how to incorporate the multiomics big data into the scale-up strategy is presented to improve the design and operation of industrial fermentation processes.

美国SCALE-UP教学方法及其应用与探讨

SCALE-UP教学方法已经应用在美国300多所大学和高等院校,尤其是在工科教学过程中。本文介绍了SCALE-UP教学方法以及其在美国基础代数课程中的应用;并将SCALE-UP教学方法与国内教学方式进行了对比和分析,为国内工程类课程教学改革提供参考。

Experimental and numerical investigations of scale-up effects on the hydrodynamics of slurry bubble columns

Experiments and simulations were conducted for bubble columns with diameter of 0.2 m(180 mm i.d.), 0.5 m(476 mm i.d.) and 0.8 m(760 mm i.d.) at high superficial gas velocities(0.12–0.62 m·s-1) and high solid concentrations(0–30 vol%). Radial profiles of time-averaged gas holdup, axial liquid velocity, and turbulent kinetic energy were measured by using in-house developed conductivity probes and Pavlov tubes. Effects of column diameter, superficial gas velocity, and solid concentration were investigated in a wide range of operating conditions. Experimental results indicated that the average gas holdup remarkably increases with superficial gas velocity, and the radial profiles of investigated flow properties become steeper at high superficial gas velocities. The axial liquid velocities significantly increase with the growth of the column size, whereas the gas holdup was slightly affected. The presence of solid in bubble columns would inhibit the breakage of bubbles, which results in an increase in bubble rise velocity and a decrease in gas holdup, but time-averaged axial liquid velocities remain almost the same as that of the hollow column. Furthermore, a 2-D axisymmetric k–ε model was used to simulate heterogeneous bubbly flow using commercial code FLUENT 6.2. The lateral lift force and the turbulent diffusion force were introduced for the determination of gas holdup profiles and the effects of solid concentration were considered as the variation of average bubble diameter in the model. Results predicted by the CFD simulation showed good agreement with experimental data.

Comparison between the new mechanistic and the chaos scale-up methods for gas-solid fluidized beds

The chaotic scale-up approach by matching the Kolmogorov entropy(E_K) proposed by Schouten et al.(1996) was assessed in two geometrically similar gas–solid fluidized bed columns of 0.14 and 0.44 m diameter.We used four conditions of our validated new mechanistic scale-up method based on matching the radial profiles of gas holdup where the local dimensionless hydrodynamic parameters were similar as measured by advanced measurement techniques.These experimental conditions were used to evaluate the validity of the chaotic scale-up method,which were selected based on our new mechanistic scale-up methodology.Pressure gauge transducer measurements at the wall and inside the bed at various local radial locations and at three axial heights were used to estimate KE.It was found that the experimental conditions with similar or close radial profiles of the Kolmogorov entropy and with similar or close radial profiles of the gas holdup achieve the similarity in local dimensionless hydrodynamic parameters,and vice versa.

Scale-up of biomass conversion using 1-ethyl-3-methylimidazolium acetate as the solvent

This scale-up study demonstrated the feasibility of an ionic liquid(IL)pretreatment process at 40 kg scale,using the IL 1-ethyl-3-methylimidazolium acetate([C2C1Im][OAc])as the solvent.The pretreatment was followed by enzymatic hydrolysis through which the process efficiency for biomass conversion to monomeric sugars was determined.The results show that 43 wt%of switchgrass was dissolved in IL after 2 h of pretreatment at 160℃ with 15 wt%solid loading.A 120 h enzymatic hydrolysis of the pretreated switchgrass results in 96%glucan and 98%xylan conversion.[C2C1Im][OAc]pretreatment has been successfully scaled up to 40 kg with improved sugar titers and yields relative to bench scale(6 kg).The mass flow of the overall process was established and the major scale-up challenges of the process were identified.

Simulation and Scale-up of Barium Sulphate Precipitation Process Using CFD Modeling

Some empirical mixing models were used to describe the imperfect mixing in precipitation process.However, the models can not, in general, reflect the details of interactions between mixing and crystallization in a vessel. In this study, CFD (computational fluid dynamics) technique were developed by simulating the precipitation of barium sulphate in stirred tanks by integration of population balance equations with a CFD solver. Two typical impellers, Rushton and pitched blade turbines, were employed for agitation. The influence of feed concentration and position on crystal product properties was investigated by CFD simulation. The scale-up of these precipitators was systematically studied. Significant effect on the crystal properties was found for the scale-up under some conditions.Keywords simulation, scale up, precipitation, CFD(computational fluid dynamics)

STUDY ON THE SCALE-UP EFFECT OF CYCLONES

The scale-up effect, which is a key factor controlling the performance of industrial cyclones, is conventionally estimated through grade efficienty curves. A new principle based on the centrifugal separation factor (CSF) is proposed to improve the scale-up procedure in designing industrial cyclones.

Scale-up of rifamycin B fermentation with Amycolatoposis mediterranei

Study of the effect of dissolved oxygen and shear stress on rifamycin B fermentation with A. mediterranei XC 9-25 showed that rifamycin B fermentation with Amycolatoposis mediterranei XC 9-25 needs high dissolved oxygen and is not very sensitive to shearing stress. The scale-up ofrifamycin B fermentation withA, mediterranei XC 9-25 from a shaking flask to a 15 L fermentor was realized by controlling the dissolved oxygen to above 25% of saturation in the fermentation process, and the potency of rifamycin B fermentation in the 15 L fermentor reached 10 g/L after 6-day batch fermentation. By continuously feeding glucose and ammonia in the fermentation process, the potency of rifamycin B fermentaion in the 15 L fermentor reached 18.67 g/L, which was 86.65% higher than that of batch fermentation. Based on the scale-up principle of constantly aerated agitation power per unit volume, the scale-up of rifamycin B fed-batch fermentation with continuous feed from a 15 L fermentor to a 7 m^3 fermentor and further to a 60 m^3 fermentor was realized successfully. The potency of rifamycin B fermentation in the 7 m^3 fermentor and in the 60 m^3 fermentor reached 17.25 g/L and 19.11 g/L, respectively.

Scale-up Efficient Synthesis of α-Poly(L-lysine)

α-Poly(_(L)-lysine)(α-PLL)is a water-soluble cationic biopolymer containing the monomeric unitα-_(L)-lysine,which not only possesses excellent intrinsic properties but also can be modified via facile reactions between the side amine groups and many other functional moieties.Ring-opening polymerization(ROP)is the most prevalently used technique for the synthesis of PL_(L)-based polypeptides,which involves initial conversion of theε-primary amine-protectedα-_(L)-lysine to the _(L)-lysine NCA monomer.However,obtaining N-carboxyanhydrides(NCAs)in high purity has been a formidable challenge for over 50 years,let alone the large-scale synthesis.Herein,we show an unprecedented scale-up synthesis of _(L)-Cbz-LysNCA monomer and its polymers,generating linearα-poly(_(L)-lysine)with molecular weight(MW)up to 13.4 kDa.This easy operated scale-up strategy will lay the foundations for the industrial preparation of _(L)-Cbz-LysNCA and its polymers,and further extend the realm of existing applications,offering a paradigm for scale-up synthesis of other polypeptides.

二氧化碳捕集技术研究和工程示范进展

捕集、封存(CCS)/捕集、利用和封存(CCUS)技术是缓解日趋严重气候问题的有效措施,其中CO_(2)捕集是CCS/CCUS技术中的关键环节。经过多年发展,以乙醇胺为代表以及在此基础上发展起来的多氨基胺、位阻胺、离子液体等化学胺吸收碳捕集技术逐渐成熟,此类技术已开展或正在进行大型试验或工业示范。科研机构已经完成了技术评审(TR)的关键节点验证,积累了丰富的经验。本文结合具体案例简要介绍了包括燃烧前、富氧燃烧、化学链燃烧和燃烧后捕集技术的进展情况,分析了各类技术目前存在的主要问题,并提出了影响CO_(2)捕集技术大范围推广的关键因素。捕集能耗高、设备投资和维护成本高、产生的废弃物量大是影响捕集成本的主要因素。此外,捕集的CO_(2)主要还是用于驱油和埋存,尚不成熟的CO_(2)化工转化技术生产的产品竞争力比较弱。

中药饮片产业发展现状及供给侧问题与对策

分析了中药饮片产业及市场规模现状,相关法律、法规、政策等,从供给侧剖析产业发展瓶颈,解析中药饮片生产标准化、规模化程度低,技术及产品创新不足,缺少协调供需平衡的宏观统筹问题,提出加强炮制理论基础研究、提高中药饮片生产标准化水平的对策措施,包括提高中药炮制技术的标准化水平、完善质量控制标准、建立等级标准等,倡导提高产业规模化水平、实施大品种战略、鼓励科技创新、组建创新联合体,加快中药饮片数字化、智能化生产管理研发及新产品研发,并从调控供需平衡角度提出了推进中药饮片区域化生产与流通的措施等,以期构建以高品质中药饮片为核心的创新型产业发展格局,探寻振兴中药饮片产业高质量发展之路。

粉煤灰基陶瓷膜支撑体的制备与尺寸放大试验

选取固体废物粉煤灰作为支撑体骨料,TiO_(2)为烧结助剂,羧甲基纤维素(CMC)为黏结剂,木炭粉为造孔剂,采用固态粒子烧结法制得初始陶瓷膜支撑体样品,并对其进行等比尺寸(直径)放大制备。探究支撑体尺寸放大制备中烧结温度、造孔剂添加量、尺寸(直径)放大倍数等因素对支撑体性能的影响,对物质组成、微观形貌、抗折强度、纯水通量、酸碱腐蚀率及孔径分布等性能进行表征。结果表明:最高烧结温度为1 050℃,造孔剂木炭粉添加量为15%(质量分数),放大到原尺寸(直径)的2倍时,所制得支撑体性能最佳,其内部孔隙均匀,颈型结构明显,纯水通量为4 728.26 L/(m^(2)·h·MPa),抗折强度为25.15 MPa,中值孔径为3.06μm,孔隙率为38.56%,酸、碱质量损失率分别为0.33%、0.25%。

螺杆挤出机相似放大理论的研究进展

总结了近些年来国内外提出的螺杆挤出机相似放大准则,并对比分析了常用的放大系数和适用范围,同时,介绍了相似放大理论在螺杆挤出机中的优化挤出机的结构参数、工艺条件的实际应用,最后指出了螺杆挤出机相似放大理论进一步探索和优化,为螺杆挤出机行业的可持续发展提供更加有效的理论支持。

Hydrodynamic analysis of carbon nanotube clusters in distributor-less conical fluidized beds with step-by-step scaling

As a high-performance material with great application potential,the application of carbon nanotubes has been limited by their production volume.A distributor-less conical fluidized bed is the main equipment used in the industrial production of carbon nanotubes.To improve the production volume and product quality of carbon nanotubes,the study of fluidized-bed-diameter scaling is important.Three different diameters of distributor-less conical fluidized beds were established,and then the particle behavior and bubble characteristics of carbon nanotube clusters at these bed diameters were investigated.Time-series and wavelet analysis methods were used to analyze the pressure-fluctuation signals inside the fluidized beds.Results showed that the distributor-less design caused the airflow to break through the middle of the bed,which did not change with the change in bed diameter.The powder-bridging phenomenon of carbon nanotube clusters in a 100-mm-diameter fluidized bed was related to the special microstructure of carbon nanotube clusters.The frequency of pressure fluctuations in the bed decreased nonlinearly with increasing bed diameter.This study can guide the design and scale-up of distributor-less conical fluidized beds,especially for the scale-up of carbon nanotube production equipment,which can contribute to the improvement of carbon nanotubes’capacity and quality in industrial production.

企业数字化转型对劳动力需求的影响:创造抑或破坏?

稳就业是维持经济高质量发展的关键。数字经济的快速发展带来的就业不确定性引发社会的广泛担忧。利用文本分析法构建企业数字化转型的特征指标并运用2011—2020年沪深A股上市企业样本,考察企业数字化转型对劳动力需求的影响。研究发现:企业数字化转型最终会对劳动力需求产生正向作用;机制检验结果表明,企业数字化转型通过规模扩张效应增加了高、低学历劳动力需求,通过技术升级效应增加了高学历劳动力需求,降低了低学历劳动力需求,在规模扩张效应和技术升级效应共同作用下导致企业会同时增加高学历和低学历劳动力需求;在非国有企业和高新技术企业中,企业数字化转型对劳动力需求的正向作用更明显;进一步研究表明,从员工岗位结构来看,企业数字化转型会增加技术人员和其他人员需求,而减少生产人员需求;从员工薪酬结构来看,企业数字化转型会提高管理层和普通员工薪酬,但对管理层薪酬的促进作用更强。