Pilot Plant Reactor Research Articles

Modeling a Silicon CVD Spouted Bed Pilot Plant Reactor

This study reports a comprehensive multiphase gas-solid dynamic mathematical model that successfully describes the batch growth of silicon particles in a CVD submerged spouted bed reactor. This multiphase reactor model takes into account the hydrodynamics and interphase mass exchange between the different fluidized bed regions (spout or grid zone, bubbles and emulsion phase) and uses applicable kinetic rate models to describe both heterogeneous and homogeneous reactions. The model also incorporates a population balance equation representing particle growth and agglomeration.The CVD submerged spouted bed reactor operation is simulated by means of a sequential modular procedure, which involves the solution of the reactor model and the population balance equation.It is shown that the proposed CVD multiphase reactor model successfully simulates experimental data obtained from batch operation in a pilot scale reactor at REC Silicon Inc. The modeling of experiments obtained for different operating conditions allows correlating the scavenging factor as a function of the silane concentration for short- and long-term operations.

Eliminating non-renewable CO2 emissions from sewage treatment: An anaerobic migrating bed reactor pilot plant study

The aim of this work was to demonstrate at pilot scale a high level of energy recovery from sewage utilising a primary Anaerobic Migrating Bed Reactor (AMBR) operating at ambient temperature to convert COD to methane. The focus is the reduction in non-renewable CO(2) emissions resulting from reduced energy requirements for sewage treatment. A pilot AMBR was operated on screened sewage over the period June 2003 to September 2004. The study was divided into two experimental phases. In Phase 1 the process operated at a feed rate of 10 L/h (HRT 50 h), SRT 63 days, average temperature 28 degrees C and mixing time fraction 0.05. In Phase 2 the operating parameters were 20 L/h, 26 days, 16 degrees C and 0.025. Methane production was 66% of total sewage COD in Phase 1 and 23% in Phase 2. Gas mixing of the reactor provided micro-aeration which suppressed sulphide production. Intermittent gas mixing at a useful power input of 6 W/m(3) provided satisfactory process performance in both phases. Energy consumption for mixing was about 1.5% of the energy conversion to methane in both operating phases. Comparative analysis with previously published data confirmed that methane supersaturation resulted in significant losses of methane in the effluent of anaerobic treatment systems. No cases have been reported where methane was considered to be supersaturated in the effluent. We have shown that methane supersaturation is likely to be significant and that methane losses in the effluent are likely to have been greater than previously predicted. Dissolved methane concentrations were measured at up to 2.2 times the saturation concentration relative to the mixing gas composition. However, this study has also demonstrated that despite methane supersaturation occurring, micro-aeration can result in significantly lower losses of methane in the effluent (<11% in this study), and has demonstrated that anaerobic sewage treatment can genuinely provide energy recovery. The goal of demonstrating a high level of energy recovery in an ambient anaerobic bioreactor was achieved. An AMBR operating at ambient temperature can achieve up to 70% conversion of sewage COD to methane, depending on SRT and temperature.

Application of genetic algorithm for optimization of vegetable oil hydrogenation process

Finding optimal reaction conditions leading to minimal total trans isomer and maximal cis-oleic acid formation during vegetable oil hydrogenation is very crucial. An Artificial Neural Network was developed and used to predict the amount of total trans isomer and cis-oleic acid during the hydrogenation process. Using a large number of experimental data from a pilot plant reactor, the Neural Network was trained and then validated with a validation subset. Having a reasonably accurate Neural Network model of the hydrogenation process, Genetic Algorithm was then used to search for a combination of process variables resulting in minimal total trans isomer and maximal cis-oleic acid formation during the hydrogenation process. The outputs of Genetic Algorithm (i.e. predicted process variables) were used in actual settings of the hydrogenation process to evaluate the effectiveness of the scheme. The results indicated that the scheme could be effectively used to identify the optimal hydrogenation conditions resulting in minimal trans isomer and maximal cis-oleic acid formation during vegetable oil hydrogenation process.

Combined Effects of Cadmium and Zinc on both Sequencing Batch Reactor and Continuous Activated Sludge

This study aims to investigate the performance and treatment capability of sequencing batch reactor and activated sludge systems under heavy metals shock loads. The combined effects of cadmium and zinc on both systems were studied. Two pilot plant units, one for each system were used to study the effect of gradually increasing both cadmium and zinc on the treatment process. Batch tests were also performed to study the effect of both cadmium and zinc shock loads on the acclimated sludge that collected from each pilot plant. The results of the pilot plant units showed that the efficiency of COD removal decreases under the gradual increase of heavy metals and that this efficiency was higher in the sequencing batch reactor pilot plant than the activated sludge pilot plant. Results of batch tests showed that the efficiency of COD removal of acclimated sludge collected from each pilot plant was higher than the normal sludge collected from both systems before adding metals. Similarly this efficiency was higher in the sequencing batch reactor pilot plant than the activated sludge pilot plant operated under the same conditions.

Estimation of trickle-to-pulse flow regime transition and pressure drop in high-pressure trickle bed reactors with organic liquids

Flow regime boundaries and pressure drop in trickle bed reactors are crucial for design, scale-up and operation of such reactors. The flow map experiments are performed in a pilot plant reactor of 0.051 m diameter and 1.2 m height, with cumene–hydrogen system. A new technique – the acoustic signal measurement – is used for distinguishing between trickle and pulse flow regimes. The effect of operating pressure was investigated in the pressure range of 0.14–2.0 MPa. For higher operating pressures, the trickle-to-pulse transition boundary moves towards higher flow rates of both liquid and gas phases. The pressure drop over the reactor bed is increasing with increasing operating pressure and gas/liquid throughputs. The pressure drop results obtained with hydrogen at higher operation pressures match reasonably well the results obtained with air–water at atmospheric pressure. This comparison is made using a new developed pressure drop correlation and illustrates the influence of increased gas density (high operating pressure effect). The Trickle Bed Simulator of University Laval [F. Larachi, B. Grandjean, I. Iliuta, Z. Bensetiti, A. André, G. Wild, M. Chen, Excel Worksheet Simulator for Trickle-Bed Reactors, http://www.gch.ulaval.ca/bgrandjean/pbrsimul/pbrsimul.html, 1999] was found to match reasonably well our pilot plant measured values for low and high operating pressures.

Fuzzy control of dissolved oxygen in a sequencing batch reactor pilot plant

The present work is part of a global development of reliable real-time control and supervision tools applied to wastewater pollution removal processes. In these processes, oxygen is a key substrate in animal cell metabolism and its consumption is thus a parameter of great interest for the monitoring. In this paper, are presented and discussed the results of the dissolved oxygen (DO) control in a SBR pilot plant based on a predefined 8 h step-feed cycle. As first approach, the application of classical methods (on/off and PID) was considered. Due to the non-linear character of the process, the PID parameter adjusting was very difficult and the obtained results showed a beating phenomenon around the setpoint. This phenomenon was more and less amplified according to the step of the cycle and the water pollution level. The second approach to achieve more stable DO control was based on a fuzzy logic strategy, taking into account the step and the difference between the measured DO and the setpoint. In this case, control action performances were highly improved. It is also shown that, using the fuzzy controller, the pH profile made it possible to clearly detect the ammonia valley during the aerobic phases. Thus, fuzzy logic proved to be a robust and effective DO control tool, easy to integrate in a global monitoring system for cost managing.

Scale-up and Modeling of Fixed-Bed Reactors for Catalytic Phenol Oxidation over Adsorptive Active Carbon

The wet air oxidation of phenol over a commercial active carbon catalyst has been studied in laboratory-scale and pilot-plant fixed-bed reactors at mild temperatures and oxygen partial pressures of 120−160 °C and 0.05−0.2 MPa, respectively. The performances of the fixed-bed reactors have been assessed and compared to each other for both up- and downflow operation mode. Depending on the flow mode and reactor scale, distinct phenol destruction rates have been observed in the experiments. A series of batch experiments are carried out to obtain phenol removal kinetics, which are subsequently implemented in the modeling of the pilot-plant fixed-bed reactor. A one-dimensional, nonisothermal piston dispersion model is developed to describe in detail the interplay of reaction kinetics, gas−liquid hydrodynamics, and heat and mass transfer in both flow directions. The model predicts reasonably well the experimental data, thus allowing for a thorough explanation of the observed pilot-plant reactor performance.

Optimizing the solar photo-Fenton process in the treatment of contaminated water. Determination of intrinsic kinetic constants for scale-up

The elimination of aromatic compounds present in surface water by photo-Fenton with sunlight as the source of radiation was studied. The concentrations of Fe 3+ and H 2O 2 are key factors for this process. A solar simulator and a prototype parabolic collector were used as laboratory-scale reactors to find the parameters of those key factors to be used in the CPC (compound parabolic collector) pilot plant reactor. The initial mineralization rate constant ( k obs) was determined and evaluated at different Fe 3+ and H 2O 2 concentrations to find the best values for maximum efficiency. In all the experiments the mineralization of an aqueous phenol solution was described by assuming a pseudo-first-order reaction. The intrinsic kinetic constants not dependent on the lighting conditions were also estimated for scale-up.

Two Severity Indices for Scale-Up of Steam Cracking Coils

A direct experimental scale-up method is presented for steam cracking of hydrocarbon feedstocks. It is based on the “severity” concept but uses two severity indices instead of one to unambiguously characterize the product yields for a given feedstock. Reaction path analysis suggests that the combination of the ethylene/ethane yield ratio and the methane yield characterizes the complete product spectrum. Simulation results for n-butane cracking in a pilot plant reactor, a Lummus SRT-1 reactor, and a 4-2-1 split coil reactor confirm that the same product spectrum is obtained for identical values of both indices in the different reactor geometries although the process conditions differ strongly. The soundness of the approach is further corroborated by experimental results obtained from a pilot plant reactor and a small scale Uno-Quattro coil. This approach is only valid when similar feedstocks are used. A rule of thumb is that the highest PIONA weight fraction for a feedstock cannot deviate by more than 5% of the corresponding value for the reference feedstock. Stronger deviations in feedstock composition lead to larger differences between the product spectra.

Safety Improvement of a Grignard Reaction Using On-Line NIR Monitoring

A quantitative on-line NIR (near-infrared) method for the monitoring of the formation of a Grignard reagent was developed on laboratory scale using chemometrics and tested in a 630 L pilot plant reactor. Good accuracy of the model was obtained, and feasibility of the on-line measurement was demonstrated. The concentrations of the added reagent (and thus its degree of accumulation) and of the formed Grignard reagent (indication of the reaction initiation) can be determined in real time. Therefore, the safety of the highly exothermic process and its robustness are significantly improved. Furthermore, the method is applicable to monitoring concentrations during the following cross-coupling reaction so that it can be used to determine in real time the reaction yield. By using on-line spectroscopy, the product quality and performance can be guaranteed on an industrial scale. Moreover, the cycle times are reduced due to the elimination of waiting times caused by traditional analysis.

A MULTI-MODEL APPROACH FOR THE MONITORING OF CARBON AND NITROGEN CONCENTRATIONS DURING THE AEROBIC PHASE OF A BIOLOGICAL SEQUENCING BATCH REACTOR

This paper presents i) an extension of a simple model describing the dynamical behavior of important variables during the aerobic phase of a biological wastewater treatment plant and ii) a simple asymptotic observer based on this extended model for online estimating both soluble biodegradable carbon and nitrate+nitrite nitrogen concentrations. The proposed model is identified and the observer is validated with real data acquired on a real biological Sequencing Batch Reactor pilot plant.

Modeling a continuous multistage liquid phase cyclohexane oxidation reactor network

A model is presented for a continuous multistage liquid phase cyclohexane oxidation reactors-in-series network, which uses, unlike previous efforts, a closed form rate model derived on the basis of the well-known free-radical kinetic mechanism of the oxidation reaction leading to a more generalized representation of the oxygen dependence of the rate. The model calculates the required transport and hydrodynamic parameters by one of the best available set of correlations shown earlier to be successfully used in cyclohexane oxidation in a well-designed laboratory reactor. Process sensitivities with regard to variables such as air rate, residence time, head pressure, inlet air composition and sparger configuration have been predicted. Some of these trends compared very well with the limited published experimental data in a three (35 l) agitated and sparged tank-in-series reactor system, thus partially validating the model. The model has highlighted a fairly generalized way of correlating performance data from a given reactor, namely in terms of a yield–conversion characteristic which can change depending on the mass transfer efficiency and the effective kinetics. Hence, it can aid in plant monitoring and optimization. It has also been shown how to use the same as an aid in preliminary scale-up studies based on laboratory or pilot plant reactor performance data.

Runaway Detection in a Pilot-Plant Facility

The divergence criterion allows detection in advance runaway initiation. When divergence (div) is greater than zero, this indicates that the reactor is moving to a dangerous state. In this work, a series of experiments have been carried out in a pilot-plant reactor, using the esterification reaction between 2-propanol and propionic anhydride, in order to assess the performances of a developed algorithm to calculate div online using temperature or pressure data. Furthermore, the model developed for this process allows a comparison between simulated and experimentally reconstructed divergences. The results show that a good agreement is obtained for the runaway experiments, whereas for near-runaway conditions, the presence of “noise” in the data shows the necessity to establish a limit value for the divergence, i.e., div > lim. In any case, we show that this methodology can be applied online to detect anomalous behavior in chemical reactors.

Pilot-plant treatment of olive mill wastewater (OMW) by solar TiO 2 photocatalysis and solar photo-Fenton

Olive mill wastewater (OMW), a highly polluted wastewater from the olive oil industry, was treated by solar photocatalysis and solar photo-Fenton. Among the tested systems the application of titanium dioxide alone was not successful. The addition of peroxydisulphate as an electron acceptor had only limited effect on degradation performance and led to high salt concentrations (30 g/l sulphate generated) and a pH value near zero. The photo-Fenton method successfully removed up to 85% COD and up to 100% of phenol index of OMW with different initial concentrations and from different sources. Two solar photocatalytic pilot-plant reactors were used; one of conventional CPC type and an open non-concentrating Falling Film Reactor. The latter, newly designed reactor worked properly and yielded comparable results to the CPC in terms of degradation rate referred to incident UV radiation energy per solution volume. The suspended solids in the OMW hinder light from entering the reactor. Therefore, flocculation induced by a commercial flocculation agent was successfully applied to remove suspended solids. Application of this pre-treatment led to considerable increase of degradation rates and decrease of hydrogen peroxide consumption.

Induced pulse operation of high-pressure trickle bed reactors with organic liquids: hydrodynamics and reaction study

Trickle-bed reactors (TBR) are often applied in chemical and petrochemical industry. The performance of these reactors can be improved substantially by periodic operation of the liquid feed and/or operation in the natural pulsing flow regime. The aim of this pilot plant study is to present a flow map for the cumene–hydrogen system at elevated pressures, and to evaluate the reactor performance improvement obtained by periodic operation of a trickle-bed reactor. The experiments presented in this work are performed in a pilot plant reactor of 0.051 m diameter and 1.2 m length. The transition from trickle to pulsing flow depends on fluid physical properties, operating conditions, and geometrical parameters. Although many industrial trickle-bed reactors using organic liquids are operated at high pressure, the transition map for these systems is scarcely reported in literature. In this study, the effect of operating pressure on transition from trickle to pulse flow has been investigated in the pressure range of 0.14–2.0 MPa. The boundary between trickle and pulse flow shifts towards higher superficial liquid velocity when the operating pressure increases. The hydrogenation of α-methyl styrene (AMS) over 2 wt.% Pd/C catalyst was selected as test reaction. The reaction is performed at a liquid inlet temperature of 40 °C and at an operating pressure of 0.2 MPa. The cyclic operation mode is compared with the trickle operation mode. It is found that periodic operation results in a significant improvement in reaction rate.

Calorimetric estimation for a batch-loop emulsion polymerisation reactor

To facilitate the online monitoring and control of a pilot-scale polymerisation reactor, state estimation techniques are investigated. Specifically, a batch-loop reactor is employed for the emulsion polymerisation of methyl methacrylate. The reactor consists of jacketed tubular sections fitted with in-line static mixers, thus providing mixing homogeneity and improved temperature control. A direct estimation of the reaction rate is attained through measurements of process and jacket side temperatures, and thus a calorimetric method of estimation. This is compared with a Kalman filter based calorimetric approach, in which there is compensation for model uncertainties and measurement noise. For both estimation methods, no knowledge of the kinetic model for polymerisation is needed. Experimental results indicate that with an accurate model of the process energy balance, in which, for example, the recycle pump energy input is described, the Kalman filter approach is found to provide excellent prediction of conversion, for both high and low conversions, for this pilot-plant reactor system. The approach does not require any (approximate) kinetic knowledge, and is thus considerably easier in implementation than the extended Kalman filter approaches.

Complete study of the pyrolysis and gasification of scrap tires in a pilot plant reactor.

The pyrolysis and gasification of tires was studied in a pilot plant reactor provided with a system for condensation of semivolatile matter. The study comprises experiments at 450, 750, and 1000 degrees C both in nitrogen and 10% oxygen atmospheres. Analysis of all the products obtained (gases, liquids, char, and soot) are presented. In the gas phase only methane and benzene yields increase with temperature until 1000 degrees C. In the liquids the main components are styrene, limonene, and isoprene. The solid fraction (including soot) increases with temperature. Zinc content of the char decreases with increasing temperature.

Electrochemical removal of arsenic from technical grade phosphoric acid

The electrolytic de-arsenication of technical grade phosphoric acid 85 wt % by cathodic deposition in order to produce chemically pure phosphoric acid was examined. Polarization curves using Cu, Pb, 316L stainless steel and graphite as cathodic rotating discs were determined. The best results were achieved for copper where the arsenic deposition takes place in a range of potentials without hydrogen evolution. Long term experiments in a laboratory batch reactor with a rotating cylinder cathode of copper showed that the electrodeposited arsenic was a non-conductor, poorly adherent and can be detached from the electrode by means of an ultrasonic cleaner. Experimental results with a pilot plant reactor with a three-dimensional cathode of copper nets showed a high degree of scatter. However, typical values of the figures of merit are: fractional conversion per pass 24%, specific energy consumption 250 kWh kg−1 As for a volumetric flow rate of 1.5 dm3 min−1 at 60 A and 3.4 V of cell voltage.

New Formulations for Syndiotactic Polystyrene

The formation of syndiotactic polystyrene in the presence of catalysts was investigated. The yield of syndiotactic polystyrene obtained in a 240 dcm3 pilot plant reactor was 7 - 15 kg/charge. The weight-average molecular weight was about 200 000 g/mol and the syndiotacticity was about 96%. Composites based on the syndiotactic polystyrene have also been obtained. The polymer was granulated with the stabiliser (Irganox 1076) and modifiers in a twin-screw extruder with double degassing. It was then reinforced by glass fibre or talc. Syndiotactic polystyrene was also modified with polyoxyphenylene and linear polyethylene. The structure and physical and mechanical properties of the composites were investigated.

Calorimetric Estimation of Viscosity and Acid Number in Alkyd Reactors

In the industrial operation of batch alkyd polymerization reactors, the process evolution is monitored by measuring the acidity and the viscosity of samples withdrawn from the reactor. The synthesis is stopped at the maximum yield allowed by the gelation point of the cold product. In this work, a software sensor that estimates the C(cold)viscosity and the conversion of acid groups on the basis of the continuous measurement of the heat exchange rate between a continuous stirred vessel appended to the reactor and a cooling coil is designed and experimentally tested. The identification of the underlying timevarying observability property yields the designs of the heat exchange devise and of the corresponding robust nonlinear geometric observer. The resulting software sensor is experimentally tested in a pilot plant reactor