Experimental studies on parametric sensitivity of a batch reactor

Runaway behaviour of exothermic reactions in a batch reactor has been studied experimentally on the example of acetic anhydride hydrolysis catalyzed by sulphuric acid, in a 700 ml batch reactor. High parametric senstivities of peak reactor temperature with respect to initial reactor temperature and catalyst concentration were obtained.     

Studies on parametric sensitivity and safe operation criteria of batch processes

Heat accumulation in batch reactors may eventually lead to a temperature runaway. Critical values of process parameters were used to investigate process safety. Parameter sensitivity is discussed for a wide range of operating conditions. Two criteria for safe operation are presented, based on critical values of process parameters.     

Experimental studies on semibatch reactor parametric sensitivity

Runaway behaviour of an exothermic reaction in a semibatch reactor was studied experimentally on the example of hydrolysis of acetic anhydride catalyzed by sulphuric acid, in a 700 cm³ thinwalled stainless steel stirred reactor, 10.2 cm in diameter and 13.0 cm high. The reactor was partially immersed, to a depth of 2.1 cm, in a thermostatic bath, in order to obtain sufficiently rapid cooling of its contents. A reaction run was performed by first introducing water, acetic acid and sulphuric acid into the reactor. After the contents attained bath temperature, acetic anhydride at room temperature was fed to the reactor for a fixed time period, at a constant flow rate. When water was present in excess of the stoichiometric requirement and addition of acetic anhydride completed before the reactor attained peak temperature, the system showed sensitivity to coolant temperature and sulphuric acid concentration. When the reactants were present in stoichiometric quantities and addition of acetic anhydride was completed after the reactor attained peak temperature, the system did not exhibit any significant parametric sensitivity.     

A new approach to batch process optimization using experimental design

Empirical and mechanistic experimental design methods are combined to construct partial models, which are, thus, used to design a process. The grid algorithm restricts the next experimental point to potential process optima, according to the confidence intervals around the optimal points, and works with any experimental design algorithm such as D‐optimal. Two case studies show the advantages of implementing the grid algorithm. On average the improvement due to the grid algorithm was 15–20% in the first case study. The second case study is based on thin film growth using four potential models, with the most probable model used for experimental design. The grid algorithm balances the trade‐off between two extremes: D‐optimal designs and sampling at the predicted optimal point. The methodology presented shows that the experimenter does not have to decide ahead of time on purely empirical or mechanistic experimental design methods, since both may be useful. © 2008 American Institute of Chemical Engineers AIChE J, 2009     

人工免疫系统在间歇化工过程故障诊断中的应用

故障诊断是保证化工过程稳定性和安全性的重要技术。本文结合动态时间规整算法提出了一个基于人工免疫系统的间歇化工过程故障诊断方法,并成功应用于青霉素发酵仿真过程的故障诊断。诊断结果显示,该方法可以满足间歇过程的在线动态故障诊断要求,并且通过自学习可以对未知故障进行诊断。     

An experimental reactor for kinetic studies: continuously-fed batch reactor

The use of a continuously-fed batch reacter (CFBR) as an experimental tool for the kinetic studies is presented for liquid- and gas-phase reactions, and noncatalytic gas-solid reactions. An experimental CFBR run is demonstrated using the reaction involving sucrose conversion to substantiate the theoretical results. The concept used for the CFBR is the fact that at an extremum of concentration the rate of concentration change is zero. For the liquid- and gas-phase reactions, the CFBR can be used as an alternative to the CSTR. For slow reactions, the rate determined from a CFBR run is more accurate than the rate determined from a CSTR run. Determination of the rates over the entire conversion range is made easy for fast reactions with the use of the CFBR. Results are extended to noncatalytic gas-solid reactions. It is shown that the fractional change of reacting surface area of the solid reactant can be obtained using the CFBR under the limiting condition of negligible effect of mass transfer.     

Theoretical and experimental studies of chiral polyurethanes

The theoretical and experimental design strategies of chiral polyurethanes with good second harmonic generation efficiencies are discussed. The noncentrosymmetry of the polymers was broken by means of chiral and chemical poling. Different varieties of main chain chiral polymers are obtained by varying the composition of chiral and amido diol monomers using DBTDL catalyst. The designed chiral polymer architecture gives rise to high molecular weight polymers by the polyaddition polymerization with good thermal stability, linear and nonlinear optical activity. The polymer with isomannide as chiral moiety and CED (obtained by the aminolysis of ε-Caprolactone with 1, 2 diamino ethane) as amido diol monomer is found to possess high second harmonic generation efficiency. Both theoretical and experimental studies based on second order nonlinearity indicated that the designed chiral polyurethanes are useful for various nonlinear optical applications.     

Theoretical and experimental studies of multiple nucleation

The theory of the potentiostatic current transient for three-dimensional multiple nucleation with diffusion controlled growth is discussed. Reliable values of nuclear number densities and nucleation rates are obtained from the analysis of the current maximum, and good agreement is obtained with experimental data for nucleation in several electrochemical systems. The termination of the nucleation process by the expansion of diffusion fields is considered, as well as the deviations from randomness observed in the distribution of nuclei on the electrode surface.     

Application of parametric control concepts to decoupler design and heating control design for a batch reactor

Parametric control involves expressing the manipulated variables of a process in terms of a new set of variables, called parametric variables. The control engineer can choose the functional relationships between the two sets of variables to provide added flexibility in control loop design. The design of a static decoupler and the linearization of a batch reactor heating system are provided as examples.     

Theoretical and experimental studies of confined vortex flow

A study of the air flow characteristics is reported for a vortex chamber 122 cm in diameter consisting of an upper cylindrical section 61 cm high and of a lower conical section 108 cm high. Measurements were made with a five-channel pressure probe of the radial profiles of tangential and axial velocities, with varying inlet air velocity and axial distance from the top of the chamber. Measurements of the static pressure profiles were made simultaneously. Finally, the angle of flow of the air entering through the single tangential inlet could be adjusted, and its effects on the flow recorded. From these results and from a theoretical analysis, generalized expressions for the tangential velocity profiles were obtained for the two regions of flow, forced-vortex and quasi-free vortex, which prevail in a confined vortex chamber, as a function of the entrance air velocity and of the radius at the point considered only. The angle of entering air was found to have no effect on the tangential velocity and only a minor effect on the static pressure distribution. The outlet diameter of the chamber was found to have a large effect on the profile of the axial velocities, reflecting the influence of the chamber static pressure on the latter.     

Dynamic response and safety assessment of a batch process on cooling breakdown

Cooling breakdown in highly exothermic reaction processes may lead to runaway. The sensitivity and the safety assessment of a batch process on cooling breakdown are studied. The dependence of the minimum cooling time and the maximum allowable time of cooling breakdown for safe operation on the process parameters is investigated.     

Theoretical and experimental studies of confined vortex flow

A study of the air flow characteristics is reported for a vortex chamber 122 cm in diameter consisting of an upper cylindrical section 61 cm high and of a lower conical section 108 cm high. Measurements were made with a five-channel pressure probe of the radial profiles of tangential and axial velocities, with varying inlet air velocity and axial distance from the top of the chamber. Measurements of the static pressure profiles were made simultaneously. Finally, the angle of flow of the air entering through the single tangential inlet could be adjusted, and its effects on the flow recorded. From these results and from a theoretical analysis, generalized expressions for the tangential velocity profiles were obtained for the two regions of flow, forced-vortex and quasi-free vortex, which prevail in a confined vortex chamber, as a function of the entrance air velocity and of the radius at the point considered only. The angle of entering air was found to have no effect on the tangential velocity and only a minor effect on the static pressure distribution. The outlet diameter of the chamber was found to have a large effect on the profile of the axial velocities, reflecting the influence of the chamber static pressure on the later.     

Theoretical and experimental studies of network formation and properties

A survey of recent work on pre-gel intramolecular reaction and gelation in oxypropylene-triol and tetrol-based polyester and polyurethane network-forming systems is presented, and relationships between the properties of the networks formed at complete reaction and the product of extents of reaction at gelation (α_c) are discussed. In contrast to that in corresponding linear reaction systems, the amount of pre-gel intramolecular reaction in the triol-based polyurethanes is never negligible, even in bulk. Kilb's model of RA₂ + RB_f type gelling systems has been reanalysed and a more accurate condition for gelation evaluated. The shear moduli and T_gs of dry networks are found to increase as α_c increases, indicating that these properties are strongly dependent on the amount of pre-gel loop formation. Extrapolated values of the shear moduli indicate that perfect, affine rather than phantom networks would be formed by reaction systems having the ideal gel point [α_c = (f ? 1)^?1].     

Flamespreading during Base Ignition of Propellant Charge: Theoretical and experimental studies

In the paper theoretical modeling of flamespreading through granular propellant charge during base ignition is given. The theoretical model includes the balance equations for the gas and solid phase, as well as necessary constitutive laws. The stable convergent numerical procedure for solution of the system of equations is developed. This procedure is included in computational program FSPC (Flame-spreading through Propellant Charge). The program FSPC enables investigations of influence of ignition material, physical and chemical characteristics of propellant and propellant charge loading density on the flamespreading process. The experimental investigations by an especially designed apparatus are performed. The verification of the theoretical-numerical access through the comparison with the experimental data (pressure vs. time and locations, flamespreading velocity, propellant grains displacements) is carried out. The entire access makes possible more successful solutions of many interior ballistics problems.     

Cadmium adsorption on modified chitosan‐coated bentonite: batch experimental studies

BACKGROUND: Several researchers have investigated the use of chitosan as an adsorbent for removal of heavy metals from aqueous streams. Chitosan flake or powder swells and crumbles making it unsuitable for use in an adsorption column. Chitosan also has a tendency to agglomerate or form a gel in aqueous media. The adsorption capacity can be enhanced by spreading chitosan on physical supports that can increase the accessibility of the metal binding sites. Although several attempts have been made to enhance the adsorption capacity of chitosan, using various chemicals, the sorption capacity for metal ions decreased after cross‐linking of chitosan. RESULTS: Bentonite was coated with chitosan (Chi) and its derivative, 3,4‐dimethoxy‐benzaldehyde (Chi/DMB). The product was then used as adsorbent for the removal of Cd²⁺ from aqueous solutions. The presence of imine groups resulting from chemical modification was confirmed using IR, DRS and SEM. The adsorption followed the Langmuir isotherm and could be described by pseudo‐second order kinetics. CONCLUSION: Chi/DMB coated on bentonite increased the accessibility of metal binding sites. The Chi/DMB/bentonite showed no significant pH dependence in the pH range 2–9, but bentonite coated with chitosan revealed very intensive pH dependence, which had a considerable effect on cadmium removal. As expected adsorption of Cd²⁺ by Chi/bentonite and Chi/DMB/bentonite is dependent on contact time and adsorbent dose. In addition, an EDTA solution is suitable for desorption of cadmium ions, and the reusability of Chi/DMB/bentonite is quite good. © 2012 Society of Chemical Industry     

新型双醚催化剂在间歇本体聚丙烯装置的应用

本文详述了新型双醚催化剂在间歇小本体聚丙烯装置的工业应用情况,并与CS-1型高效催化剂进行了比较。该催化剂对丙烯中杂质的适应性强,操作温度及压力较CS-1催化剂低。聚丙烯产品指标满足用户需要的同时,原料消耗大大低于使用CS-1型催化剂;在使用时不需要加DDS(二苯基二甲氧基硅烷)组分,大大降低了生产成本。反应终期可杜绝聚丙烯产品因粉料温度过高而发生降解现象,可提高产品质量。     

In process monitoring of polymer batch to batch variation in injection moulding

Abstract

Injection moulding studies are reported, during which in process measurements have been used to monitor batch to batch variation of several production grade polymers. Three materials were studied: a polyamide 6, a polyacetal, and a flexible poly(vinyl chloride), all of which were commercial injection moulding polymers supplied by industrial collaborators. Instrumented high precision electric and servohydraulic moulding machines were used to mould parts in house from a number of different material batches. Moulding conditions were kept constant throughout and several process variables were monitored during injection, including melt pressure, melt temperature, and viscosity index –a specific pressure integral calculated from primary injection. Part weights were measured to provide an indication of part quality. Results showed that in each case, variations between batches produced a measurable effect on part quality. These variations were detected by in process measurements, particularly by viscosity index, which tracked significant changes in part weight. Several ‘problem’batches not identified by the compounder's internal quality checks were detected, and the influence of regrind and a development compound were also clearly identified. No simple relationship between viscosity index and part quality was observed for the limited processing range covered. Overall, the studies show the potential of in process measurements to provide a real time, sensitive indication of process variation.     

Transesterification of Jatropha curcas oil glycerides: Theoretical and experimental studies of biodiesel reaction

Vegetal oil, also known as triglycerides, is a mixture of fatty acid triesters of glycerol. In the triglycerides alkyl chains of Jatropha curcas oil, predominate the palmitic, oleic and linoleic fatty acids. The process usually used to convert these triglycerides to biodiesel is called transesterification. The overall process is a sequence of three equivalent, consecutive and reversible reactions, in which di- and monoglycerides are formed as intermediates. Semi-empirical AM1 molecular orbital calculations were used to investigate the reaction pathways of base-catalyzed transesterification of glycerides of palmitic, oleic and linoleic acid. The most probable pathway and the rate determining-step of the reactions were estimated from the molecular orbital calculations. Our results suggest the formation of only one tetrahedral intermediate, which in a subsequent step rearranges to form the products. The rate determining-step is the break of this tetrahedral intermediate.     

Eye gaze movement studies of control room operators: A novel approach to improve process safety

Process industries continue to suffer from accidents despite significant regulatory intervention since the mid-1980s. Human error is widely considered to be the major cause for most accidents today. Detailed analysis of various incidents indicates that reduced staffing levels in control rooms and inadequate operator training with complex automation strategies as common reasons for human errors. Therefore, there is a need to develop deeper understanding of human errors as well as strategies to prevent them. However, similar to hardware failures, traditionally human error has been quantified using likelihood approaches; this viewpoint abnegates the role of the cognitive abilities of the operators. Recent studies in other safety critical domains (aviation, health-care) show that operator's level of situation awareness as inferred by eye tracking is a good online indicator of human error. In this work, a novel attempt is made to understand the behavior of the operator in a typical chemical plant control room using the information obtained from eye tracker. Experimental studies conducted on 72 participants reveal that fixation patterns contain signatures about the operators learning and awareness at various situations. Implications of these findings on human error in process plant operations them are discussed.