Showing papers on "Chemical reactor published in 2018"

Modelling of Blast Furnace with Respective Chemical Reactions in Coke and Ore Burden Layers

Abstract: The ironmaking blast furnace (BF) is an efficient chemical reactor for producing liquid iron from solid iron ore, where the solids of coke and iron ore are charged in alternative layers and different chemical reactions occur in the two solid layers as they descend. Such respective reacting burden layers have not been considered explicitly in the previous BF models. In this article, a mathematical model based on multi-fluid theory is developed for describing the multiphase reacting flows considering the respective reacting burden layers. Then, this model is applied to a BF, covering the area from the burden surface at the furnace top to the liquid surface above the hearth, to describe the inner states of a BF in terms of the multiphase flows, temperature distribution and reduction process. The results show that some key important features in the layered burden with respective chemical reactions are captured, including fluctuating iso-lines in terms of gas flow and thermochemical behaviours; particularly the latter cannot be well captured in the previous BF models. The temperature difference between gas–solid phases is found to be larger near the raceway, at the cohesive zone and at the furnace top, and the thermal reserved zone can be identified near the shaft. Three chemical reserve zones of hematite, magnetite and wustite can also be observed near the stockline, in the shaft near the wall and near centre, respectively. Inside each reserve zone, the corresponding ferrous oxides stay constantly high in alternative layers; the overall performance indicators including gas utilization efficiency and reduction degree also stay stable in an alternative-layered structure. This model provides a cost-effective tool to investigate the BF in-furnace process and optimize BF operation.

A hierarchical approach to chemical reactor engineering: an application to micro packed bed reactors

Abstract: Hierarchical modeling is applied for the investigation of micro packed bed reactors. This method allows for the use of Computational Fluid Dynamics (CFD) simulations in the analysis of representative complex geometries, where a full-scale CFD simulation of the entire reactor is not possible. Detailed and computationally demanding analyses are used to study a selected number of conditions and phenomena. Then, lumped parameters are derived from CFD results by means of engineering correlations. These parameters are incorporated in simplified reactor models based on macroscopic conservation equations. We provide evidence for the potential of the approach by using as a show-case a micro packed bed reactor in the context of highly exothermic selective oxidation processes. This reactor configuration consists of catalytic particles packed in the channels of a honeycomb matrix, which is expected to strongly enhance the radial heat transfer. In particular, we first focus on the analysis of energy transfer mechanisms by CFD and their interpretation via a 1D model and we provide an assessment of existing correlations with respect to the unconventional configuration (2 mm channel equivalent diameter and 0.8 mm sphere diameter). These correlations are then implemented in a pseudo-continuous (i.e. macroscopic) 2D model to allow for a systematic investigation of the capabilities of the micro packed bed reactor in dealing with the selective oxidation of o-xylene to phthalic anhydride. We found that due to the enhanced radial heat transfer micro packed bed reactors allow for quasi-isothermal operations, thus extending the range of operating conditions possible without occurring in adverse thermal behavior of the reactor. On a more general basis, we prove that the hierarchical approach to chemical reactor engineering is an effective tool to bring the application of fundamental modeling at a level of complexity relevant to full-scale applications, otherwise not possible because of the impractical computational costs.

Improved Kinetic Data Acquisition Using An Optically Accessible Catalytic Plate Reactor with Spatially-Resolved Measurement Techniques. Case of Study: CO2 Methanation

Abstract: Modelling and optimization of chemical reactors require a good understanding of the reactions mechanism with the corresponding kinetic description. Therefore, high quality kinetic data are needed, which can be challenging to obtain, especially for fast and highly exothermic reactions such as the CO2 methanation. Traditionally, kinetic studies rely on measuring the exit gas composition (1 data point per species and experiment) using differential reactors with diluted catalyst beds and reactants to avoid temperature change. Therefore, an optically accessible catalytic channel reactor was designed, which allowed for the chance to gather spatially-resolved information on axial gas composition and catalyst surface temperature, specifically by means of a movable sampling capillary and shortwave infrared-thermography (SWIR), respectively. A catalyst coated plate was placed at the bottom of the channel, while a set of two quartz glass plates covers the top. In the current study 35 data points per gas species were collect for 1 experiment conducted under laminar flow conditions at 425 °C. Catalyst surface temperature determined via a SWIR camera was not influenced by polyatomic molecules partaking in the reaction and thus did not falsify the kinetic data. The catalyst mass distribution along the reactor axis was determined, enabling the development of a correct reactor model for kinetic parameter estimation and model discrimination.

Modelling of heating of plasma-chemical reactor in Comsol Multiphysics.

Abstract: For the thermophysical calculation of the reactor, a mathematical model was developed in Comsol Multiphysics, describing physical processes in the plasma-chemical reactor at a stationary mode. To simplify the calculation at this stage, it was carried out for an air plasma torch. The model includes two processes: fluid dynamic and heat transfer ones. As a result of the mathematical modelling the following parameters were obtained: temperature distribution in the reactor at steady state, average mass temperature in the reaction volume, velocity field and others.

Fast synthesis of optimal chemical reactor networks based on a universal system representation

Abstract: We propose a new approach for the synthesis of optimal chemical reactor networks based on the concept of elementary process functions [1] and dynamic optimization. This approach is capable of incorporating process intensification options at an early design stage. Only one single differential equation is required to describe the mass balance of the whole reactor system along the reaction route. This equation contains terms describing mass fluxes from outside the reactor system and mass fluxes which flow between different positions of the reaction route. We demonstrate that different reactor types and different reactor connections can be represented by such a formulation. After solving an optimization problem using such a model, optimal profiles of state variables and fluxes are obtained. Based on these profiles, the optimal reactor system is determined. After the presentation of the theoretical background and the derivation of the new approach, it is illustrated in case studies and validated by comparison with literature results. The advantages of this new approach presented in our contribution are its simplicity in description and implementation, universality in representing different reactor types and networks, and the potential to consider different intensification and integration options at an early design stage.

Entropy generation minimization of steam methane reforming reactor with linear phenomenological heat transfer law

Abstract: This paper investigates a class of tubular plug flow steam methane reforming reactor coupling among heat exchange, fluid flow and chemical reaction, in which the heat transfer between the heat reservoir outside the conversion tube and the reactants inside the tube is assumed to obey the linear phenomenological heat transfer law [ q ∝ Δ ( T − 1 ) ]. Under the condition that all of the hydrogen production rate, the inlet pressure, the total inlet molar flow rate, the inert gas (N2) molar flow rate are given, and the reservoir temperature is assumed to be controllable completely, both the minimum entropy generation rate of the process and the corresponding optimal reservoir temperature profile are obtained for minimizing the total entropy generation due to heat transfer, fluid flow and chemical reaction and by applying the theory and method of finite time thermodynamics with the help of nonlinear programming method. The obtained results are also compared with other two classes of reference reactors under the heat transfer strategies of constant and linear reservoir temperature operations and the optimization results for the minimum entropy generation of the case with Newtonian heat transfer law [ q ∝ Δ ( T ) ]. The results show that compared to the two classes of the reference reactors, optimizing the reservoir temperature profiles could reduce the entropy generation by more than 58%, which is mainly due to the decrease in the entropy generation caused by heat transfer; a shorter reactor may perform equally well, and the optimal path shows immediate regions of either a constant thermal force or a constant chemical force; heat transfer laws have significant effects on the optimal temperature configurations of both the heat reservoir and the reaction mixture for the minimum entropy generation of the chemical reactor.

Fast nonlinear model predictive control of a chemical reactor: a random shooting approach

Abstract: Abstract This paper presents a fast way of implementing nonlinear model predictive control (NMPC) using the random shooting approach. Instead of calculating the optimal control sequence by solving the NMPC problem as a nonlinear programming (NLP) problem, which is time consuming, a sub-optimal, but feasible, sequence of control inputs is determined randomly. To minimize the induced sub-optimality, numerous random control sequences are selected and the one that yields the smallest cost is selected. By means of a motivating case study we demonstrate that the random shooting-based approach is superior, from a computational point of view, to state-of-the-art NLP solvers, and features a low level of sub-optimality. The case study involves a continuous stirred tank reactor where a fast multi-component chemical reaction takes place.

Cuboid Packed-Beds as Chemical Reactors?

Abstract: Columns are widely used as packed-bed or fixed-bed reactors in the chemical process industry. Packed columns are also used for carrying out chemical separation techniques such as adsorption, distillation, extraction and chromatography. A combination of the variability in flow path lengths, and the variability of velocity along these flow paths results in significant broadening in solute residence time distribution within columns, particularly in those having low bed height to diameter ratios. Therefore, wide packed-column reactors operate at low efficiencies. Also, for a column of a particular bed height, the ratio of heat transfer surface area to reactor volume varies inversely as the radius. Therefore, with wide columns, the available heat transfer area could become a limiting factor. In recent papers, box-shaped or cuboid packed-bed devices have been proposed as efficient alternatives to packed columns for carrying out chromatographic separations. In this paper, the use of cuboid packed-beds as reactors for carrying out chemical and biochemical reactions has been proposed. This proposition is primarily supported in terms of advantages resulting from superior system hydraulics and narrower residence time distributions. Other potential advantages, such as better heat transfer attributes, are speculated based on geometric considerations.

Design trade-offs in a column with side-reactor configuration for improving selectivity in multiple reaction systems

Abstract: The configuration of columns with side-reactors (SRC) can effectively enhance the performance of reaction–separation processes, particularly where the operational limitations of conventional multifunctional reactors, such as reactive distillation systems, negate the overall benefits. Industrial manufacturing processes often use multiple reaction schemes that result in both desired and undesired products. The selectivity and yield of the desired product are usually improved by using large reaction vessels or high recycle flow rates of excess reactant. Therefore, in multiunit chemical processes, the foremost design trade-off is between the reaction vessel volume and the recycle flow rate. In this study, we investigate the competition of these parameters in SRC configurations in achieving specific conversion or yield criteria. Two real chemical processes involving side-reactors of non-reactive distillation columns and recycle streams are considered and their optimal design configurations are detailed. The results affirm the importance of this trade-off and its quantitative analysis to obtain the optimal SRC configuration.

The chemical energy unit partial oxidation reactor operation simulation modeling

Abstract: The chemical energy unit scheme for synthesis gas, electric and heat energy production which is possible to be used both for the chemical industry on-site facilities and under field conditions is represented in the paper. The partial oxidation reactor gasification process mathematical model is described and reaction products composition and temperature determining algorithm flow diagram is shown. The developed software product verification showed good convergence of the experimental values and calculations according to the other programmes: the temperature determining relative discrepancy amounted from 4 to 5 %, while the absolute composition discrepancy ranged from 1 to 3%. The synthesis gas composition was found out practically not to depend on the supplied into the partial oxidation reactor (POR) water vapour enthalpy and compressor air pressure increase ratio. Moreover, air consumption coefficient α increase from 0.7 to 0.9 was found out to decrease synthesis gas target components (carbon and hydrogen oxides) specific yield by nearly 2 times and synthesis gas target components required ratio was revealed to be seen in the water vapour specific consumption area (from 5 to 6 kg/kg of fuel).

Design and validation of an advanced entrained flow reactor system for studies of rapid solid biomass fuel particle conversion and ash formation reactions.

Abstract: The design and validation of a newly commissioned entrained flow reactor is described in the present paper. The reactor was designed for advanced studies of fuel conversion and ash formation in powder flames, and the capabilities of the reactor were experimentally validated using two different solid biomass fuels. The drop tube geometry was equipped with a flat flame burner to heat and support the powder flame, optical access ports, a particle image velocimetry (PIV) system for in situ conversion monitoring, and probes for extraction of gases and particulate matter. A detailed description of the system is provided based on simulations and measurements, establishing the detailed temperature distribution and gas flow profiles. Mass balance closures of approximately 98% were achieved by combining gas analysis and particle extraction. Biomass fuel particles were successfully tracked using shadow imaging PIV, and the resulting data were used to determine the size, shape, velocity, and residence time of converting particles. Successful extractive sampling of coarse and fine particles during combustion while retaining their morphology was demonstrated, and it opens up for detailed time resolved studies of rapid ash transformation reactions; in the validation experiments, clear and systematic fractionation trends for K, Cl, S, and Si were observed for the two fuels tested. The combination of in situ access, accurate residence time estimations, and precise particle sampling for subsequent chemical analysis allows for a wide range of future studies, with implications and possibilities discussed in the paper.

Even feeding type chemical reactor of intermittent type formula

Abstract: The utility model relates to a chemical reactor especially relates to an even feeding type chemical reactor of intermittent type formula. The to -be -solved technical problem of the utility model is to provide an even feeding type chemical reactor of intermittent type formula. In order to solve the technical problem, the utility model provides a such even feeding type chemical reactor of intermittent type formula is including first barrel etc. Even feed arrangement's top is provided with feed arrangement at intermittence, and the feeder hopper is located feed arrangement's at intermittence top, the feeder hopper with intermittence feed arrangement be connected, the middle part of upper end bottom first barrel of discharging pipe is passed through welded connection's mode and is connected,installs the valve on the discharging pipe. The utility model provides an even feeding type chemical reactor of intermittent type formula, have even feed arrangement and intermittence feed arrangement, when adding the industrial chemicals, even stirring can also be carried out to the industrial chemicals to the emergence that can avoid blockking up the problem, is favorable to improving the quality simple structure, convenient operation.

Unsteady State Heat Transfer in Packed-Bed Elliptic Cylindrical Reactor: Theory, Advanced Modeling and Applications

Abstract: Transport phenomena through porous media has been of continuing interest for scientists, researchers and engineers due to the wide range of industrial applications. This chapter presents information about unsteady-state heat transfer and fluid flow inside of packed-bed reactors. The topics covered are related to fundamentals of porous media, chemical reactors, including mathematical modeling and applications. Emphasis is placed on packed-bed elliptic-cylindrical reactor. Based on the concept of local thermal equilibrium, a general mathematical formulation for a pseudo-homogeneous heat transfer model written in elliptic-cylindrical coordinates along with the numerical solution of the governing equation has been presented. Herein, an overview of currently-used models and the pertinent transient conductive transport processes inside the reactor were explored. A numerical example of heat transfer and fluid flow in a multiphase system (elliptic-cylindrical reactor filled with particles) was performed, and results of the temperature distribution inside the equipment at different instant of process are presented and discussed.

Chemical reactor inherent safety index at preliminary design stage

Abstract: The design inadequacy of chemical reactor has caused many major accidents in process industries. The absence of safety analysis for chemical reactor especially in the early design stage is one of the reasons for faulty designs. Inherent safety can be used to perform the safety analysis at preliminary design phases. However, the literature is deficient in reporting inherent safety assessment method for chemical reactors. Therefore, this paper introduces a new indexing method for inherently safety assessment of chemical reactors at the preliminary design stage. Chemical Reactors Inherent Safety Index (CRISI) is based on three sub-indices; chemical index, process index and reaction index. These sub-indices are estimated through scores of numerous parameters in each dimension. For the unacceptable score, the process conditions are changed according to the favorable reaction conditions. CRISI is estimated for all combination of process conditions and lowest CRISI value indicates the inherently safer design of the reactor.

Chemical reactor with waste gas treatment device and using method of chemical reactor

Abstract: The invention discloses a chemical reactor with a waste gas treatment device in the technical field of chemical equipment The chemical reactor comprises a reactor body; the bottom of the reactor bodyis provided with a supporting seat; the bottom of the supporting seat is provided with a motor; an output shaft of the motor is provided with a stirring shaft; the outer wall of the stirring shaft issequentially provided with a semispherical stirring head, a first stirring blade, a rhombic stirring blade and a second stirring blade from bottom to top; the center of the top of the reactor body isprovided with a feeding funnel; the top of the feeding funnel is provided with a quantifying device; an exhaust vent is formed in the right side of the top of the reactor body and is connected with afilter box by an exhaust pipe; the right side of the filter box is provided with a collecting hood; the collecting hood is connected with a purification box by a guide pipe; due to the arrangement ofthe quantifying device at the top of the reactor body, the equivalent feeding of a material can be realized, the material in the reactor body can be more sufficiently stirred, and no materials are wasted The waste gas treatment device is low in cost and high in purification efficiency; and waste gases exhausted into the air after being subjected to multilayer filtration are pollution-free and odorless

Effect of the Calorific Intensity of Combustion Chamber on Production of Synthesis Gas in Partial Oxidation of Methane–Oxygen Mixtures in the Combustion Mode

Abstract: Optimal design of a flow-through chemical reactor with increased calorific intensity was experimentally sought for in partial oxidation of natural gas by oxygen at oxidant excess factors in the range 0.27 < α < 0.4. It was shown that this reactor with a chamber for additional turbulent mixing of the starting components, turbulizer, and supercritical pressure difference at the outlet from the combustion chamber can provide a combustion mode close to the process in the plug-flow reactor. The increase in the calorific intensity of the combustion chamber of the reactor as a result of a decrease in its volume leads to full conversion of the starting reagents and to lower carbon-black formation.

Method for generating energy and energy generation device, in particular for mobile applications

Abstract: The invention relates to a method for generating energy, wherein hydrogen is produced by at least partially dehydrogenating a hydrogenated liquid organic hydrogen carrier (LOHC) in a chemical reactor (3) and wherein, from the produced hydrogen, electricity and water are generated in at least one fuel cell (4) and heat for the chemical reactor (3) is generated in a heating device (8), wherein, according to the invention, the hydrogen produced by the chemical reactor (3) is first conducted through the at least one fuel cell (4) and then supplied to the heating device (8). The at least one fuel cell (4) can therefore be operated under partial load and thus with better efficiency than if the hydrogen for the heating device (8) is branched off before the fuel cell (4). The invention is preferably used in mobile applications, in particular of water vehicles.

Robust concentration control of target product in chemical reactor

Abstract: A liquid-phase continuous stirred tank reactor equipped with a mechanical stirrer and cooling jacket is considered as a control object. The reactor operates in the polytropic mode. The multistep series-parallel exothermic process is carried out in the reactor. The objective of chemical reactor operation is to obtain the key product of specified concentration. The paper deals with analytical synthesis of automatic concentration control system of target product which provides invariance, covariance to the given actions, asymptotic stability and robustness under the action of uncontrollable parametric and signal disturbances. The astatic control law obtained using the synergetic control theory is proposed. Using the method of analytical design of aggregated regulators (ADAR) for a given invariant manifold, a non-linear control algorithm with an integral part was synthesized which solves the problem of stabilization of the concentration of target component on the exit of the reactor at the given value under the action of disturbances on the object. Algorithmic synthesis of the control law is carried out using a non-linear mathematical model of the object without the use of the linearization procedure. As a result of simulation it was found that the closed-loop control system has no static control error under the action of uncontrollable parametric and signal disturbances on the object, changes in the set points and initial deviation of the state variables from the static values. Consequently, the proposed non-linear concentration control algorithm has the property of robustness. The obtained results indicate the effectiveness of the ADAR method and the prospects of the synergetic control theory for solving problems of algorithmic synthesis of control systems of non-linear, multi-dimensional and multi-connected technological objects. The integration of the synthesized control law of chemical reactor at the design stage will allow implementing flexible cybernetically organized chemical-technological systems.

Fault Detection in the Green Chemical Process: Application to an Exothermic Reaction

Abstract: The chemical industry’s activities are often controversial due to the high risks that they represent. Over the past decades, serious industrial events affecting lives, facilities and environment have heightened society's awareness of the negative effects of technology. Among the most hateful events in the chemical industries are the phenomena of thermal runaway that often result in operator errors. Predicting and controlling them is essential to the processes design and safe operation. The objective of this work is to develop a method for early detection of malfunctions in a chemical reactor based on a reference model, before resulting in a critical event. For this, the reaction of perhydrolysis of formic acid to peroxyformic acid by hydrogen peroxide is used as a test case to simulate the reaction in abnormal operating mode. This exothermic reaction is composed of several secondary decomposition steps. The kinetic model of the reaction was determined in order to simulate the reaction in an abnormal mode with defects related to operator error. The detection method has been validated by simulation data. A performance analysis of the proposed detection method was carried out showing the robustness and the efficiency of this method, in presence of various errors due to the operator. The proposed method can contribute to the safety of chemical reactors in the chemical industry.

Model-Based Approach for Combustion Monitoring Using Real-Time Chemical Reactor Network

Abstract: Flame stability and pollution control are significant problems in the design and operation of any combustion system. Real-time monitoring and analysis of these phenomena require sophisticated equipment and are often incompatible with practical applications. This work explores the feasibility of model-based combustion monitoring and real-time evaluation of proximity to lean blowout (LBO). The approach uses temperature measurements, coupled with Chemical Reactor Network (CRN) model to interpret the data in real-time. The objective is to provide a computationally fast means of interpreting measurements regarding proximity to LBO. The CRN-predicted free radical concentrations and their trends and ratios are studied in each combustion zone. Flame stability and a blowout of an atmospheric pressure laboratory combustor are investigated experimentally and via a phenomenological real-time Chemical Reactor Network (CRN). The reactor is operated on low heating value fuel stream, i.e., methane diluted with nitrogen with N2/CH4 volume ratios of 2.25 and 3.0. The data show a stable flame-zone carbon monoxide (CO) level over the entire range of the fuel-air equivalence ratio (Φ), and a significant increase in hydrocarbon emissions approaching blowout. The CRN trends agree with the data: the calculated concentrations of hydroxide (OH), O-atom, and H-atom monotonically decrease with the reduction of Φ. The flame OH blowout threshold is 0.025% by volume for both fuel mixtures. The real-time CRN allows for augmentation of combustion temperature measurements with modeled free radical concentrations and monitoring of unmeasurable combustion characteristics such as pollution formation rates, combustion efficiency, and proximity to blowout. This model-based approach for process monitoring can be useful in applications where the combustion measurements are limited to temperature and optical methods, or continuous gas sampling is not practical.