Reactor Temperature Profile Research Articles

Application of Fiber‐Optic Measurement Technology for Minimally‐Invasive Measurements of Temperature Profiles in Reactors

AbstractDie Temperatur ist eine wichtige Messgröße in technischen Prozessen, da nahezu alle mechanischen, elektrischen, magnetischen und optischen Stoffeigenschaften sowie die Selektivität in chemischen Reaktoren temperaturabhängig sind. Die faseroptische Messtechnik ermöglicht eine gering‐invasive, gleichzeitige Temperaturerfassung an zahlreichen Messstellen entlang einer Sensorfaser und wird zur Aufnahme von Temperatur‐ und Dehnungsprofilen eingesetzt. In diesem Beitrag wird stellvertretend ihre Anwendung bei der heterogenen Gasphasenkatalyse in Festbettreaktoren diskutiert.

Optimization of Thermal and Mechanical Properties of Unsaturated Polyester Resin as a Binder in Polymer Concrete for Manufacturing Precision Tool Machine Bases

This study investigates the effect of unsaturated polyester resin chemical composition on the coefficient of thermal expansion, damping properties, flexural strength, tensile strength and hardness. The resin is used as binder in polymer concrete for manufacturing the bases of precision tool machines in previous work published by the authors. Resins of various ratios of styrene-ARAPOL and methyl methacrylate (MMA)-ARAPOL were made and their curing kinetics was studied using viscosity measurements and exothermic reaction temperature profiles. The resins were studied using dynamic mechanical analysis and in-house thermal expansion measuring devices. It was found that ARAPOL–MMA (60:40) has the highest damping factor of 5.46%, and the thermal expansion coefficient of 7.98 × 10- 5/°C. This composition also has the optimum flexural and tensile strengths at 128 MPa and 58.6 MPa

Impact of inter- and intra-molecular movements on thermoset polymerization reactions

The large increase in viscosity during thermoset reactions leads to reduced frequencies of reacting moiety collisions with respective reduced reaction rates. Molecular diffusion substantially ends after the gel point; however, reactions continue after the gel point through mechanisms involving local movement (and reacting moiety contact) of polymer sections/branches which is referred to as intra-molecular movement. The impact of inter- and intra-molecular movements was simulated for polyurethane reactions to better understand the impact of mass transfer on polymerization reactions.Inter-molecular reaction mechanisms are dominant prior to the gel point, and intra-molecular mechanisms are dominant after the gel point. Representing the Arrhenius pre-exponential factor as a sum of a viscosity-dependent term and a viscosity-independent term was identified as the most efficient method to model this phenomenon. Good agreement of simulation results for reaction temperature, foam height, and viscosity profile with the experimental data were obtained.

Effect of initiator concentration to low-density polyethylene production in a tubular reactor

Low-density polyethylene (LDPE) is one of the most widely used polymers in the world, which is produced in high-capacity tubular and autoclave reactors. As the LDPE industry turn into more competitive and its market profit margins become tighter, manufacturers have to develop solutions to debottleneck the reactor output while abiding to the stringent product specification. A single polyolefin plant producing ten to forty grades of LDPE with various melt flow index (MFI), therefore understanding the reaction mechanism, the operating conditions as well as the dynamic behavior of tubular reactor is essential before any improvement can take place. In the present work, a steady state mathematical model representing a tubular reactor for the production of LDPE is simulated using MATLAB R2015a®. The model developed is a function of feed inlet, reactor jacket, single initiator injector and outlet stream. Analysis on the effect of initiator concentration (CI) shows sudden declining trend of initiator's concentration which indicates that all of the initiators are exhausted after polymerization reaction and no further reaction occur from this point onwards. Furthermore, the results demonstrate that the concentration of initiator gives significant impact on reactor temperature's profile and monomer conversion rate, since higher initiator concentration promotes greater polymerization rate, and therefore leads to higher monomer conversion throughput.

Reactor temperature profiles of non-thermal plasma reactor using fiber Bragg grating sensor

The temperature profile of atmospheric pressure non-thermal plasma packed-bed reactor was monitored using a single 1550nm fiber Bragg Grating (FBG) sensor with sensitivity of 10.8pm/°C. The FBG was embedded at the midpoint of the reactor which was packed with barium titanate (BaTiO3) pellets. Four types of carrier gas for plasma generation were manipulated with different applied voltages for each gas in order to investigate the behaviour of the temperature profiles of non-thermal plasma (NTP). Results showed that using air and nitrogen, plasma produced higher average reactor temperature, which is approximately 207°C and 202°C respectively, in a 30-min interval with the maximum applied voltage of 16kV. The reactor temperature for helium carrier gas revealed the lowest, approximately 77°C. Reactor temperature profiles for each type of gas is different due to the gas composition and breakdown voltage behaviour. From the reactor temperature profiles, we were able to examine the appropriate carrier gases and optimum applied voltage operating range in order to enhance plasma process for treating pollutants in future work since higher temperature affect the rate of chemical reaction.

Interactive Matching between the Temperature Profile and Secondary Reactions of Oil Shale Pyrolysis

This article investigates the effect of the reactor temperature profile on the distribution and characteristics of the products from fixed-bed pyrolysis of oil shale. Experiments were performed in a one-stage fixed-bed reactor and in a two-stage fixed-bed reactor. In the one-stage reactor, the shale oil yield reached 7.40 wt % with a reactor temperature profile from 900 to 550 °C and decreased to 2.23 wt % with the reverse temperature profile. The effect of the temperature profile was investigated further in the two-stage fixed-bed reactor combining a pyrolysis stage operating at 550 °C and a shale char bed operating at different temperatures. At low temperatures ( 550 °C), severe crac...

Simulation and control of water-gas shift packed bed reactor with inter-stage cooling

Water-Gas Shift Reaction (WGSR) has become one of the well-known pathways for H2 production in industries. The issue with WGSR is that it is kinetically favored at high temperatures but thermodynamically favored at low temperatures, thus requiring careful consideration in the control design in order to ensure that the temperature used does not deactivate the catalyst. This paper studies the effect of a reactor arrangement with an inter-stage cooling implemented in the packed bed reactor to look at its effect on outlet temperature. A mathematical model is developed based on one-dimensional heat and mass transfers which incorporate the intra-particle effects. It is shown that the placement of the inter-stage cooling and the outlet temperature exiting the inter-stage cooling have strong influence on the reaction conversion. Several control strategies are explored for the process. It is shown that a feedback- feedforward control strategy using Multi-scale Control (MSC) is effective to regulate the reactor temperature profile which is critical to maintaining the catalysts activity.

Simulation Studies of Low-density Polyethylene Production in a Tubular Reactor

This paper deals with the model based of an industrial low-density polyethylene (LDPE) tubular reactor. As the LDPE industry becomes more competitive, manufacturers have to come out with solutions to debottleneck the reactor output while abiding to the stringent product specification. In other words, they have to deal with maximization of the production (maximization of the monomer conversion for a given feed flow rate) and minimization of unwanted product (ethyl, butyl, vinyl and vinylidene groups), while maintaining the polymer product quality with regards to its molecular weight distribution (MWD). To achieve these goals, understanding the effects of operating variables manipulation as well as the dynamic behavior of tubular reactor is essential to develop high performance tubular reactor. In this study, the dynamic model of a tubular reactor for the production of low-density polyethylene (LDPE) is simulated using MATLAB R2015a® in order to predict the temperature profile and monomer conversion percentage along the tubular reactor. The model consists of feed stream, reactor jacket, initiator injector and outlet stream. Several operating variables are involved, notably the feed flow rates, the inlet pressure and temperature with varying parameters to analyze the effect on the reactor productivity. Plots of reactor temperature profile and monomer conversion percentage are presented and from the result, it can be concluded that feed temperature gives significant impact as it effects monomer conversion rate.

Modeling and Simulation Study of an Industrial Radial Moving Bed Reactor for Propane Dehydrogenation Process

Abstract An accurate model is required to optimize the propane dehydrogenation reaction carried out in the radial moving bed reactors (RMBR). The present study modeled the RMBR using a plug flow reactor model incorporated with kinetic models expressed in simple power-law model. Catalyst activity and coke formation were also considered. The model was solved numerically by discretizing the RMBR in axial and radial directions. The optimized kinetic parameters were then used to predict the trends of propane conversion, temperature, catalyst activity and coke content in the RMBR along axial and radial directions. It was found that the predicted activation energies of the propane dehydrogenation, propane cracking and ethylene hydrogenation were in reasonable agreement with the experimental values reported in the literature. The model developed has accurately predicted the reaction temperature profile, conversion profile and catalyst coke content. The deviations of these simulated results from the plant data were less than 5%.

Predicting optimal temperature profiles in single-stage fixed-bed reactors for CO2-methanation

The catalytic conversion of carbon dioxide into methane, known as Sabatier process, is a promising option for chemical storage of excess renewable energy and greenhouse gas emission control. Typically externally cooled fixed-bed reactors (FBR) using supported nickel or ruthenium catalyst are applied. The Sabatier process, however, is strongly exothermic and leads to substantial hot spots within the reactor at stoichiometric feed ratios. Although high temperatures increase the reaction rate in general, they thermodynamically limit the achievable methane-yield in the Sabatier process. Here, we present an easy-to-use method based on a Semenov number optimization (SNO) to compute optimal axial temperature profiles in single-stage fixed-bed reactors that account for kinetic and thermodynamic limitations simultaneously, and thus result in maximized yield for a fixed reactor length. In a case study on CO2-methanation, these temperature profiles result in a twofold improvement of the methane-yield compared to isothermal and adiabatic operation, and thus demonstrate the high potential of thermal optimization that lies in the Sabatier process. The SNO-method provides a valuable tool to compute optimal temperature profiles, and allows intuitive insight into the key parameters for thermal process intensification. Further, it can readily be transferred to other processes that suffer from the dilemma between kinetic and thermodynamic limitations. Our findings illustrate the attractiveness of the SNO-method to compute optimal temperature profiles in fixed-bed reactors, and the need for catalyst supports with enhanced and tailorable heat transport properties.

Towards MEMS Pellistor Spectrometers

We report on an innovative use of high-temperature MEMS heater platforms as micro pellistor spectrometers. MEMS heater elements, initially designed for use as thermal infrared emitters, were fitted with thin-film noble metal layers to enable catalytic combustion processes on the hotplate surface. The modified heater platforms were operated in a range of combustible gas ambients while applying saw-tooth-like heater waveforms. Measurements of this kind revealed the heat of reaction vs. hotplate temperature profiles for each individual gas. We find that different families of gases yield distinctly different heat of reaction vs. temperature profiles and that these profiles allow the different families, and members inside some of these families, to be distinguished.

Acid-catalyzed production of biodiesel over arenesulfonic SBA-15: Insights into the role of water in the reaction network

This work presents a systematic approach to understand the effect of the presence of water in highly acidic crude palm oil–typical conditions of low-grade oleaginous feedstock on the performance of arene-SO3H-SBA-15 catalyst in the batch-production of biodiesel. The addition of small amounts of water (1 wt%) to the reaction medium led to a clear reduction of the observed yield to fatty acid methyl esters (FAME), being this decay usually attributed to the highly hydrophilic nature of arenesulfonic acid groups, and the associated difficulties of hydrophobic substrates to access these catalytic acid sites. However, the addition of larger amounts of water –up to 10 wt%– did not cause a proportional decay in the yield to FAME, but a higher production of free fatty acids (FFA). This is attributed to the promotion of acid-catalyzed hydrolysis of both starting triglycerides and formed FAME. The net result is not only a significant reduction of the final FAME yield, but also the appearance of high acid values, i.e. FFA contents, in the final biodiesel. Consequently, the overall process is simultaneously affected by transesterification, esterification and hydrolysis reactions, all of them catalyzed by Brønsted acid sites and dependent on the reaction conditions –temperature and water concentration– to different extents. Several strategies devoted to manage such behavior of sulfonic acid-modified SBA-15 catalysts in presence of water, aiming to maximize FAME yield while minimizing FFA content, have been explored: (1) minimization of the water content in the reacting media by pre-drying of feedstock and catalyst; (2) addition of molecular sieves to the reacting media as water scavengers, (3) hydrophobization of the catalyst surface to minimize the water uptake by the catalyst; and (4) use of a decreasing reaction temperature profile in order to first promote transesterification at high temperature and then reduce the temperature to keep at a minimum the hydrolysis of formed FAME. All these strategies resulted in an improvement of the catalytic performance, especially the use of a decreasing temperature profile. The results showed by the latter strategy open new possibilities and reaction pathways in which readily available, low-grade, cheap oleaginous feedstock with high water and FFA contents can be efficiently converted into biodiesel.

Mathematical modelling of a hydrocracking reactor for triglyceride conversion to biofuel: model establishment and validation

In the study, a 2D, non-isothermal, heterogeneous model of a triglyceride hydrocracking reactor is investigated. The internal heat and mass transfer within the phases in the reactor were considered using the film theory. The conservation equations for energy and mass were solved simultaneously using appropriate numerical techniques whose reliability was assessed by comparison of the results with previously reported experimental data. The modelling was performed with consideration of two proposed hydrocracking kinetic models. The model predictions showed reasonable correlation with published experimental data and conversion rates. The calculations indicated that at feed temperature of 380 °C, liquid hourly space velocity of 8 h−1 and hydrogen : feed ratio of 1500:1, the total triglyceride conversion was 82.54% for four major classes of hydrocarbons (light, middle, heavy and oligomerised). In addition, the concentration distribution and temperature profile along the reactor were investigated. The product concentrations along the reactor show that higher rates of production at the beginning of the reactor were achieved because of high concentration of triglyceride due to the exothermic hydrocracking reactions and counter-current flow modes of triglyceride and hydrogen; a jump of 90 °C was shown at the beginning of the reactor temperature profile. Copyright © 2014 John Wiley & Sons, Ltd.

Modeling and Simulation of a Multibed Industrial Hydrotreater with Vapor–Liquid Equilibrium

Dealing with vapor–liquid equilibrium (VLE) in hydrotreating reactors is a major obstacle to realistic process simulation. The present study focused on the modeling and simulation of a commercial light-cycle-oil (LCO) hydrotreater with rigorous vapor–liquid equilibrium (VLE) calculations. The hydrotreater was represented as a one-dimensional plug-flow adiabatic reactor with interbed gas quenching. The model accounted for the hydrodesulfurization (HDS) and hydrodearomatization (HDA) reactions. VLE calculations were performed in situ with a calibrated flash calculation program developed in-house specifically for hydrogen–petroleum systems. Significant differences in reactor temperature profiles, hydrotreating conversions, fluid rates, and phase compositions were observed between the simulations with and without VLE. Analysis of the effect of temperature indicated that reactor performance depends heavily on the axial temperature distribution, which is established based on the catalyst bed layout and the sele...

An investigation of a stratified catalyst bed for small-scale hydrogen production from methanol autothermal reforming

This research project explored a methanol reforming system using a stratified catalyst bed. Commercially available catalysts were used within a single reactor and the system was run autothermally (fuel, steam and oxidizer). The investigation explored the fuel conversion and reactor temperature profile at various O2/CH3OH ratios. The experiments showed that the stratified system had fairly high conversions at low O2/CH3OH ratios. Additionally, it showed high selectivity towards hydrogen, and low selectivity for carbon monoxide. The experimental results gathered show a promising use of stratified catalyst beds for small-scale reforming systems.

Efficient Superionic Conductor Catalyst for Solid in Solution-Solid-Solid Growth of Heteronanowires.

How efficient could a superionic conductor catalyst be? Beyond the traditionally used molecular precursors when the solution dispersed solid nanomaterials of variable size, shape and phase are introduced under certain reaction condition; the catalyst is found to digest all these structures in minutes irrespective of their phase and morphology, resulting unique heteronanowires. This has been inspected here by employing different ZnSe nanostructures as precursor for Ag2Se nanocrystal catalyst in its superionic conductor phase to obtain the Ag2Se-ZnSe heteronanowires. This dissolution and formation process of these nanostructures is correlated with the change in the reaction temperature profile, the phase of the catalyst, the shape/phase and surface ligands of the source nanostructures, and the possible mechanism of the unique heteronanowires growth has been investigated.

Reaction modeling of urethane polyols using fraction primary secondary and hindered‐secondary hydroxyl content

AbstractThe effect of primary, secondary, and hindered‐secondary hydroxyl groups on reactions and temperature profiles of polyurethane gels was investigated and modeled using a computer simulation that simultaneously solves over a dozen differential equations. Using urethane gel reaction temperature profiles of the reference compounds 1‐pentanol, 2‐pentanol, and Voranol 360 reactivity parameters were determined for reference primary, secondary, and hindered‐secondary hydroxyl moieties. The reaction parameters, including Arrhenius constants and heats of reaction, were consistent with previous values reported in literature. The approach of using fractions primary, secondary, and hindered‐secondary hydroxyl content to characterize reactivity sets the basis for a powerful approach to simulating/predicting urethane reaction performance with limited data on new polyols and catalysts. This code can be used for all polyols, as the kinetic parameters are based on the fraction primary, secondary, and hindered‐secondary alcohol moieties, not the type of the polyol. Kinetic parameters are also specific to catalysts where at least one parameter specific to each catalyst is necessary to simulate the impact of that catalyst. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40388.

Effect of process variables on the preparation of artificial bone cements

The present work concerns the preparation of bone cements based on poly(methyl methacrylate) (PMMA), used mainly for prosthesis fixation and cavity filling for correction of human bone failures. A typical bone cement recipe contains methyl methacrylate, which polymerizes in situ during cement application. An inherent problem of this reaction is the large amount of heat released during the cement preparation, which may lead to irreparable damage of living tissues. Optimization of PMMA-based bone cement recipes is thus an important step towards safe and reliable clinical usage of these materials. Important process variables related to the reaction temperature profile and the mixing of the recipe constituents were studied in order to allow for the adequate production of bone cements. It is shown that the average molar mass and size of the PMMA particles used in the production of the bone cement, as well as incorporation of radiopaque contrast, co-monomers and fillers into the bone recipe play fundamental roles in the course of the polymerization reaction. Furthermore, the injection vessel geometry may interfere dramatically with the temperature profile and the time for its occurrence. Finally, it has been observed that the morphology of the PMMA particles strongly affects the mixing of the bone cement components.

Fischer–Tropsch synthesis in a bench-scale two-stage multitubular fixed-bed reactor: Simulation and enhancement in conversion and diesel selectivity

A process based on a two-stage multitubular fixed-bed reactor is presented to enhance in conversion and diesel selectivity for the Fischer–Tropsch synthesis (FTS) process, which is characterized by the condensation and separation of liquid products and water from the outlet of the first-stage reactor. A two-dimensional pseudohomogeneous reactor model is proposed to simulate the temperature profile and CO conversion of the two-stage fixed-bed process. Model calculations indicate that the condensation and separation of liquid products and water between the two stages of the multitubular fixed-bed reactor plays an important role by changing temperature profile and synthesis gas partial pressure of the second-stage reactor. The model validation has been verified on the basis of the bench-scale test data in a single-stage and two-stage fixed-bed reactor, respectively, which demonstrates the understandable products distribution shift toward diesel-range hydrocarbon. The combined action of higher temperature, syngas/H2 partial pressure and readsorption of olefins at the two-stage fixed-bed reactor make CO conversion and C5+ selectivity increase, while CH4 and CO2 selectivity keep decreasing trends. Compared with the single-stage fixed-bed reactor process, the total CO conversion increases from 79% to 89% in the two-stage fixed-bed reactor process. The high valuable diesel range (C12–C22) increases significantly from 67% to 78%, while the gasoline range (C5–C11) decreases from 27% to 18%. The catalysts exhibit more stability and less deactivation rate over the two-stage fixed-bed process. The results are helpful to obtain more valuable diesel products and effective utilization of the syngas by the multi-stage fixed-bed process without tail gas recycling, which provides a practical case for multi-stage short reactor rather than one long reactor for FTS to improve products distribution.

Numerical evaluation of the gas–liquid interfacial heat transfer in the trickle flow regime of packed beds at the micro and meso-scale

In the present work, two different models (micro-scale and meso-scale) were developed to investigate the heat transfer between the gas and liquid phases in the trickle flow regime of a packed bed reactor. In the micro-scale model, a simplified description of bed geometry, known as the double-slit model, was implemented to study the effects of different operating parameters, in terms of gas and liquid Reynolds, Prandtl and Eötvös numbers, on the interfacial Nusselt number. In the meso-scale model, the Volume-of-Fluid (VOF) approach was used to simulate trilobe, cylindrical and spherical catalyst shapes and accurately predict the effects of interface morphology and bed geometry on interfacial heat transfer. To validate the implemented methods, a simple packed bed reactor with spherical catalysts was developed to experimentally investigate the interfacial heat transfer of co-current, downward gas–liquid film flows. The results obtained from CFD simulations and experimental data were in agreement and accurately predicted bed reactor temperature profiles with a mean relative error of 2.15%. In both the micro- and meso-scale models, an increase in the Reynolds and Prandtl numbers increased the interfacial Nusselt number; whereas, an increase in dimensionless groups of the liquid phase or the Eötvös number caused the opposite effect. Finally, a new correlation was proposed that evaluated the gas–liquid Nusselt number in the trickle flow regime with a standard deviation of 7.19% compared to results acquired using the micro-scale model.