No / In this work, a reverse osmosis (RO) desalination process operating under batch mode is considered experimentally. The effect of operating parameters, such as pressure and feed salinity on the permeate quantity and salinity is evaluated. In addition, the water permeability constant, Kw, which is one of the main parameters that affect the optimal design and operation of RO processes is evaluated as a function of changing feed salinity and pressure using the experimental data and two literature models. A strong pressure dependence of the water permeability constant is observed in line with earlier observations. Interestingly, a strong concentration dependence of the water permeability constant is also observed which has always been neglected or ignored in the literature. Finally, for a given pressure, concentration dependent correlations for Kw are developed and are used in the full process model (described by a system of ordinary differential and algebraic equations) for further simulation studies and to validate the experimental results.

Yes / This work investigates how batch reactors can be optimized to increase the yield of a desired product coupling two appealing techniques for process control and optimization: the nonlinear model predictive control (NMPC) and the dynamic real-time optimization (D-RTO). The overall optimization problem is formulated and applied to calculate the optimal operating parameters of a selected case study and the numerical results are compared to the traditional control/optimization techniques. It has been demonstrated in our previous work (Pahija et al, Selecting the best control methodology to improve the efficiency of discontinuous reactors, Computer Aided Chemical Engineering, 32, 805-810, 2013) that the control strategy can significantly affect optimization results and that the appropriate selection of the control methodology is crucial to obtain the real operational optimum (with some percent of improved yield). In this context, coupling NMPC and D-RTO seems to be the ideal way to improve the process yield. The results presented in this work have been obtained by using gPROMS® and MS C++ with algorithms of BzzMath library.

Yes / Synthesis of methyl palmitate (MP) has not been considered in the past using a reactive distillation process (continuous or batch) due to the challenge of keeping the reactants palmitic acid (PA) and methanol (MeOH) together in the reactive zone. MeOH, being the lightest in the reaction mixture, travels up the distillation column as distillation proceeds and will be removed from the system via the distillate in a conventional batch reactive distillation (CBRD) column and thus will limit the conversion of PA. Therefore, in this work semi-batch reactive distillation (SBRD) column is proposed where additional methanol will be fed at the bottom of the column in a continuous mode allowing the chemical reaction to continue. However, as water (H2O) is one of the reaction products and is the second lightest component in the mixture, it will travel up the column next and will be removed in the distillate tank. Also due to wide difference in the boiling points of the reaction products and due to diminishing amount of water in the reboiler, the backward reaction will not be a dominating factor and therefore ignored in this work. With this backdrop, optimal performance of the SBRD column is evaluated in terms of conversion of PA to MP and energy consumption via minimization of the operating batch time for a wide range on MP purity.

Batch distillation with chemical reaction when takes place in the same unit is referred to as batch reactive distillation process. The combination reduces the capital and operating costs considerably. Among many different types of batch reactive distillation column configurations, (a) conventional (b) inverted (c) semi-batch columns are considered here. Three reaction schemes such as (a) esterification of methanol (b) esterification of ethanol (c) hydrolysis of methyl lactate are studied here. Four different types of dynamic optimisation problems such as (a) maximum conversion (b) maximum productivity (c) maximum profit and (d) minimum time are formulated in this work. Optimal design and or operation policies are obtained for all the reaction schemes. A detailed rigorous dynamic model consisting of mass, energy balances, chemical reaction and thermodynamic properties is considered for the process. The model was incorporated within the dynamic optimisation problems. Control Vector Parameterisation (CVP) technique was used to convert the dynamic optimisation problem into a nonlinear programming problem which was solved using efficient SQP (Successive Quadratic Programming) method available within the gPROMS (general PROcess Modelling System) software. It is observed that multi-reflux ratio or linear reflux operation always led to better performance in terms of conversion, productivity for all reaction schemes compared to that obtained using single reflux operation. Feed dilution (in the case of ethanol esterification) led to more profit even though productivity was found to be lower. This was due to reduction in feed price because of feed dilution. Semi-batch reactive distillation opertation (for ethanol esterification) led to better conversion compared to conventional batch distillation, however, the total amount of acetic acid (reactant) was greater in semi-batch operation. Optimisation of design and operation (for ethanol esterification) clearly showed that a single cloumn will not lead to profitable operation for all possible product demand profile. Also change in feed and /or product price may lead to adjust the production target to maximise the profitability. In batch distillation, total reflux operation is recommended or observed at the begining of the operation (as is the case for methnaol or ethanol esterification). However, in the case of hydrolysis, total reflux operation was obseved at the end of the operation. This was due to lactic acid (being the heaviest) was withrawn as the final bottom product. / Libyan Petroleum Institute

<p> This dissertation examines the influence of the process variables, organic carbon concentration, nitrate concentration, pH, organism concentration, and temperature, on the rate of denitrification of dominant batch cultures of Pseudomonas denitrificans. The aim of the work was to determine which of the first four variables were important in controlling rate, and whether significant interactions existed between variables. As well, the ability of these typical bacterial denitrifiers to operate at low temperature conditions was to be ascertained. </p> <p> The experimental procedure indicated that pH and carbon concentration are the major influences on the unit denitrification rate a well as the overriding factor temperature which profoundly influences any bacterial process. Organic carbon concentration controls the rate up to the point where the stoichiometric requirements for nitrate reduction and the carbon needs for new cell growth are satisfied. A broad pH optimum within the normal range experienced in most wastewater treatment conditions was demonstrated. The temperature dependancy of the unit denitrification rate was shown to follow an Arrhenius relationship between 3ºC and 27ºC. As well, for the simplified system investigated the unit rate was independent of nitrate concentration. </p> <p> The dominant culture was related to mixed cultures of activated sludge to provide an estimate of the denitrifying rate of activated sludge on a similar simple batch system. </p> / Thesis / Doctor of Philosophy (PhD)

<p> The transient behaviour of a batch stirred-tank reactor (BSTR) for free radical polymerization of styrene in toluene has been studied experimentally and theoretically. A kinetic model applicable to high conversions was developed using data from measurements of monomer conversion and molecular weight distribution (MWD). Significant improvement over the conventional kinetic model is obtained when the viscosity or gel effect is accounted for. The termination rate constant and catalyst efficiency are allowed to vary with viscosity. The findings agree with the general theory of diffusion-controlled reaction which predicts that viscosity is the most important parameter.</p> / Thesis / Master of Engineering (MEngr)

<p> The free radical polymerization of styrene in benzene using azo-bisisobutyronitrile as a catalyst has been studied both theoretically and experimentally. The molecular-weight distribution and conversion are predicted on the basis of a simplified kinetic mechanism, neglecting a number of minor side reactions. The steady-state assumption is investigated and is shown to be applicable in the case of styrene polymerization, a pseudo-steady-state being reached in less than one second. Using the steady-state approach a relatively simple kinetic model is obtained, suitable for computer simulation. The prime variables consist of the ordinary reaction conditions such as monomer concentration, solvent concentration, catalyst concentration, reaction temperature and reaction time.</p> <p> The polymerization was carried out isothermally in a stirred batch reactor from which samples were abstracted at various time intervals. Conversion was determined by precipitating the polymer with methanol, filtering, and weighing, and the molecular-weight distribution has been obtained by gel-permeation chromatography. A computer program was written to interpret the variation of refractive index with respect to the elution volume trace from the chromatograph, giving a readout of molecular chain length in monomer units versus weight fraction.</p> <p> The experimentally obtained conversion and distribution curves are compared with those obtained from the mathematical model. Except for bulk polymerization agreement between the two is good. Good agreement for conversion is obtained for all cases if the catalyst initiation efficiency is adjusted according to the monomer or solvent concentration. However, the same considerations do not give good agreement for molecular-weight distribution. Rather it appears that the rate constants instead of the catalyst efficiency are monomer or solvent concentration dependent, which would explain the discrepancies.</p> / Thesis / Master of Engineering (MEngr)

Batch reactors are often used to produce high quality products because any batch that does not meet quality speci cations can be easily discarded. However, for high-value products, even a few wasted batches constitute substantial economic loss. Fortunately, databases of historical data that can be exploited to improve operation are often readily available. Motivated by these considerations, this thesis addresses the problem of direct, data-based quality control for batch processes. Speci cally, two novel datadriven modeling and control strategies are proposed. The rst approach addresses the quality modeling problem in two steps. To begin, a partial least squares (PLS) model is developed to relate complete batch trajectories to resulting batch qualities. Next, the so called missing-data problem, encountered when using PLS models partway through a batch, is addressed using a data-driven, multiple-model dynamic modeling approach relating candidate input trajectories to future output behavior. The resulting overall model provides a causal link between inputs and quality and is used in a model predictive control scheme for direct quality control. Simulation results for two di erent polymerization reactors are presented that demonstrate the e cacy of the approach. The second strategy presented in this thesis is a state-space motivated, timeinvariant quality modeling and control approach. In this work, subspace identi cation methods are adapted for use with transient batch data allowing state-space dynamic models to be identifi ed from historical data. Next, the identifi ed states are related through an additional model to batch quality. The result is a causal, time-independent model that relates inputs to product quality. This model is applied in a shrinking horizon model predictive control scheme. Signi cantly, inclusion of batch duration as a control decision variable is permitted because of the time-invariant model. Simulation results for a polymerization reactor demonstrate the superior capability and performance of the proposed approach. / Thesis / Doctor of Philosophy (PhD) / High-end chemical products, ranging from pharmaceuticals to specialty plastics, are key to improving quality of life. For these products, production quality is more important than quantity. To produce high quality products, industries use a piece of equipment called a batch reactor. These reactors are favorable over alternatives because if any single batch fails to meet a quality specifi cation, it can be easily discarded. However, given the high-value nature of these products, even a small number of discarded batches is costly. This motivates the current work which addresses the complex topic of batch quality control. This task is achieved in two steps: first methods are developed to model prior reactor behavior. These models can be applied to predict how the reactor will behave under future operating policies. Next, these models are used to make informed decisions that drive the reaction to the desired end product, eliminating o -spec batches.

<p> Polymerization of styrene was carried out in continuous and batch reactors using azobisis obutyronitrile as initiator and benzene as solvent. Monomer conversion, molecular weight distribution (MWD) and viscosity were measured.</p> <p> Corrections to the conventional kinetic mechanism using results from the continuous reactor were determined. These corrections were applied to the batch reactor kinetic model and the conversion and MWD thus predicted were compared to experimental results. It was found that the corrections applied to the batch system were not adequate to give accurate predictions of conversion and MWD.</p> <p> A short computer study of the effect of oscillating monomer flow and temperature, as opposed to steady flow, on a transient continuous reactor was also carried out. It was found from this study that at low conversions oscillations in monomer flow will not affect the time average conversion and molecular weight. Oscillations in temperature caused an increase in time average conversion and a decrease in time average molecular weight as compared to results obtained when the reactor was operated at a steady temperature which was the average of the oscillating temperatures.</p> / Thesis / Master of Engineering (MEngr)

Stronger and higher strength steels are continuously being demanded by industry. A stronger steel enables less material to be used to meet structural requirements, allowing for both cost and weight savings. Through collaboration with Stelco, CanmetMATERIALS, and McMaster University, this project focused on the development of a Grade 80 (550MPa YS and 600MPa UTS) steel with elongation at fracture of 16%. The design space for the creation of the steel was limited to high-strength low-alloy and low-carbon steels that are compatible with batch-annealing processes. To achieve this goal, two main strengthening methods were explored. The first method employed the use of precipitation hardening through microalloying additions of Mo, Nb, Ti, and V to form various metal carbide precipitates. The second method was based upon dislocation strengthening using recovery annealing and Ti to delay recrystallization. Multi-scale characterization was used to quantify the strengthening mechanisms and to explain how the microstructural changes, features, and evolution affected the properties of the steel. Uniaxial tensile testing was performed to determine key mechanical properties, namely the yield strength, tensile strength, and elongation at fracture. Optical microscopy, scanning electron microscopy, energy-dispersive x-ray spectroscopy, electron backscatter diffraction, transmission electron microscopy, and atom probe tomography were utilized extensively for microstructural analysis to further quantify the steels. The precipitation hardened steel reached a yield strength of 605MPa with 15.4% elongation at fracture for a 50mm gauge length. This was achieved using a cold rolling reduction of 66% followed by a heat treatment at 670°C for 24 hours. The recovery-annealed steel obtained even better properties. It achieved a yield strength of 610MPa with a 19.6% elongation at fracture for a 25.4mm gauge length. A cold rolling reduction of 60% was used followed by a heat treatment at 550°C for 36 hours. The strengthening mechanism for this steel is novel, and involves the slowing of recrystallization without Zener pinning nor solute decoration of dislocations. This thesis will hopefully bring upon new research into this mechanism. Furthermore, the properties of this recovery-annealed steel shows great promise for use in industry due to its high strength, good elongation, and low materials cost. Consequently, this steel could be the subject of substantial research in the near future. / Thesis / Master of Applied Science (MASc)