rus
Issue #2/2023
D.M.Bamatov, I.M.Bamatov, H.H.Sapaev
CHEMICAL REACTOR DESIGN. THE CONFIGURATION OF PARTS FOR A MULTI-STAGE CHEMICAL REACTOR FOR CONTINUOUS LIQUID MIXING
CHEMICAL REACTOR DESIGN. THE CONFIGURATION OF PARTS FOR A MULTI-STAGE CHEMICAL REACTOR FOR CONTINUOUS LIQUID MIXING
DOI: https://doi.org/10.22184/1993-8578.2023.16.2.144.151
The purpose of this work was to propose a configuration of the elements of a model of a continuous chemical reactor that would meet the criteria for the ideality of the operation of chemical reactors. A technique has been proposed for modeling a chemical reactor. The 7-step method for designing reactors makes it possible to select materials for the reactor according to pre-calculated parameters, and makes it possible to carry out a preliminary design of the reactor with the necessary weight and size characteristics. This allowed us to propose the configuration of elements for a multi-stage chemical reactor for continuous mixing of liquids. A six stage reactor configuration has been proposed. In which each stage is an isolated mixing volume. Mixing is achieved by means of an oscillatory element in the form of the base of the reactor. Mixing volumes are designed in such a way that each volume equals 1 liter. All six volumes are interconnected in series, which is achieved due to the correct design of the covers of the mixing volume. One more configuration element of the reactor proposed is a system for monitoring the temperature regime inside the reactor mixing volume. A design like this will allow the construction of a multifunctional chemical reactor for continuous liquid mixing with an output capacity of 6 liters per a working cycle.
The purpose of this work was to propose a configuration of the elements of a model of a continuous chemical reactor that would meet the criteria for the ideality of the operation of chemical reactors. A technique has been proposed for modeling a chemical reactor. The 7-step method for designing reactors makes it possible to select materials for the reactor according to pre-calculated parameters, and makes it possible to carry out a preliminary design of the reactor with the necessary weight and size characteristics. This allowed us to propose the configuration of elements for a multi-stage chemical reactor for continuous mixing of liquids. A six stage reactor configuration has been proposed. In which each stage is an isolated mixing volume. Mixing is achieved by means of an oscillatory element in the form of the base of the reactor. Mixing volumes are designed in such a way that each volume equals 1 liter. All six volumes are interconnected in series, which is achieved due to the correct design of the covers of the mixing volume. One more configuration element of the reactor proposed is a system for monitoring the temperature regime inside the reactor mixing volume. A design like this will allow the construction of a multifunctional chemical reactor for continuous liquid mixing with an output capacity of 6 liters per a working cycle.
Теги: carbon fiber chemical reactor continuous mixing element configuration reactor base reactor design thermosensor беспрерывное смешивание конфигурация элементов моделирование реактора основание реактора термосенсоры углеродное волокно химический реактор
INTRODUCTION
Russia finds itself in an unprecedented sanctions environment in 2022. The issue of domestic industrial and chemical technologies has become particularly acute. The development of new methods for developing chemical technologies as well as production of apparatuses for chemical technologies are the most important tasks of the scientific and industrial complex. One of the most sought-after apparatuses in almost all industrial enterprises are chemical reactors.
MODELLING OF CHEMICAL REACTORS
The development of chemical reactor strategy will allow to design these devices individually, depending on the required functionality, at different levels of complexity and configuration.
A chemical reactor is a structure that isolates interacting chemicals from the outside environment and allows energy generated inside the reactor to be added or absorbed. The reactor technology was developed for Chemical Reaction Engineering (CRI) research [1].
Two types of ideal reactors are used to describe and evaluate performance of a chemical reactor: the Ideal Displacement Reactor (IDR) and the Ideal Stirred Continuous Reactor (ICDR) [2, 3].
Basically, a flow in tube reactors is directed in one dimension, let’s say in the z direction. Then the main gradients (flow velocity, pressure, convection) will also be pointed in this direction. If convective transport completely dominates over diffusive transport, then diffusive transport can be ignored. Derivation of the equations resulting from this assumption and their solution led to the development of the RIV model. In the case of homogeneous concentration and temperature due to large dispersion coefficients (i.e. mean squares of deviations) one can completely neglect gradients in all directions and integrate all equations globally in all directions (assuming convective flows at boundaries), then the RIF model is obtained.
Idealised reactor models give a good representation of what is going on inside the reactor, provided there are no unintended reactants in the reactor. This makes it possible to assess the performance of a reactor based on certain criteria. Such criteria could be, for example, a comparison of performance and control complexity. Of course, the use of idealised reactors is not practical, as such technology is expensive and, therefore, the industry mainly uses either simplified chemical reactors or averaged modified copies of ideal reactors:
. (1)
This relationship is called the ideal displacement reactor model [4]. In this formula MWs is the molecular mass of the flow at the outer boundaries of the tube, ρs is the density of the mixture inside the reactor, A is the cross sectional area, Vs is the average mixture flow rate, Fs is the force acting on the mixture particles to create the flow, rs is the reaction rate.
Equation (2) is called the ideal continuous stirred reactor model (IFRM):
Fs | out – Fs | in = RsV, (2)
where Fs | out is mixing force on the mixture particles when leaving the reactor, Fs | in in is the mixing force acting on the mixture particles when entering the reactor, Rs is the energy expended on mixing and V is the reactor volume [5].
The design of a chemical reactor is usually done on the basis of a specific task – to handle certain reagents and to achieve a specific end goal. According to Tavler and Sinnolt, the modelling of a reactor must be based on the chemical processes that will take place inside the reactor. This has a major impact on the final cost and complexity of controlling the reactor parts [6].
We propose a seven-step methodology for the design of chemical reactors:
the first step is to collect data regarding the chemical processes for which a given reactor will be produced, such as reaction enthalpy, phase equilibrium constants, mass and heat transfer coefficients, and reaction rate constants;
the second step is to select the initial reaction conditions for reactor operation. Conditions such as type of reaction, use of catalysts, temperature range of reactor operation, pressure inside the reactor and solvents are considered;
the third step is to select the chemical reactor construction materials depending on the above mentioned initial conditions of reactor operation;
the fourth step is to determine the critical reaction rate and critical reactor size parameters;
the fifth step is preliminary determination of the reactor’s dimensions, component layout and cost;
sixth step – experimental verification of reactor operation;
seventh step – optimisation and refinement of the reactor based on the data obtained throughout the previous six steps.
Also, one of the important aspects of modelling is reactor safety. One of the main safety concerns is possibility of a thermal chain reaction inside the reactor. For example, if the cooling system cannot cope with increasing temperature of exothermic reactions, and temperature rise increases the reaction rate, a vicious cycle of negative feedback is created. This can lead to an uncontrolled, avalanche-like temperature increase in the reactor, which can be dangerous and lead to fatal consequences [7, 8].
The most common cause of such chain reactions is an incorrect ratio of reagents, poor temperature control or heating and cooling system.
Following the reactor design methodology, a component configuration for an integrated RIV and IRBDM model for continuous fluid mixing was developed. The model is to be a flow-through six-stage reactor where the main mixing element is the reactor base instead of the agitator. This should allow a high degree of displacement to be maintained while maintaining a high degree of mixing in the reactor [9, 10].
The control system of the sample multistage continuously mixing reactor should allow continuous mixing of liquid chemical reagents in 6 cylindrical volumes of the reactor at once, while allowing the uninterrupted introduction of additional reagents during mixing in progress and allowing the heating of some reactor tubes and cooling of others. The first four tubes should be provided with a tubular heating system and the last two should be provided with a cooling system. Each mixing volume is connected to the next by means of flexible hydrocarbon fibre tubing.
The mixing of reagents must be ensured, in other words, even when a new reagent is added to the liquid mixture in the reactor, the mixing process must be continued if necessary. For this purpose, the reactor is configured with a reagent tap system in the reactor tube. Two taps are placed at the end of each tube, one to connect to the other tubes and the other to pour in the reagents. This results in a staggered tube arrangement where the tube connects on one side to the other previous tube and on the other side to the next tube along with the reagent pour tap.
The thermosensor system is designed as follows. At the inlet of the tube, next to the hydrocarbon connection hose to the preceding reactor tube, space was provided for placing thermosensors in the tube. The sensors send information to an information processing receiver at a selected time interval set by the operator. The receiver stores this information for a specified period of time, which by default is set to one hour, and can be changed by the operator. The layout of the thermosensors in the reactor tube is shown in Fig.3.
During the reactor configuration development the problem of cleaning the reactor from residual liquid after operation had to be solved. In order to solve this problem, screw-in and screw-out taps on the reactor tubes were proposed. Figure 4 shows these covers as well as the necessary threads on the reactor tubes to ensure a tight connection between the covers and tubes.
Thus, the proposed configuration of the elements of the multi-stage chemical reactor is as follows (Fig.5). It shows sequential connection of all stages of reactor operation. On each stirring volume there should be a thermal sensor, which will monitor the temperature regime inside the reactor tube. The length of the mixing volume is 280 mm and its diameter is 70 mm. This is done to ensure that the actual volume of the cylinder is 1 litre. A thread is also provided for tight fitting of the stirring volume covers with a length of 10 mm. The wall thickness of the cylinder is 3 mm so that threads can be made for the covers. The mixing process will mainly be achieved by the moving base of the reactor. The base must oscillate right and left of the reactor user at a controlled frequency.
In Fig.5 a is the thermosensor inlet of the platform tube for temperature monitoring, b is the reactor base vessel, c is the oscillating reactor platform, d is the copper line of the heating/cooling system, e is the clamp of the mixing volumes to the reactor base, f is the reactor base oscillation control bar, g is the on/off button of the reactor, h is the reactor tubes with the developed reactor cover design, i is the carbon fibre hose for connecting reactor tubes together which creates six stages of mixing in the reactor.
CONCLUSIONS
To summarise the above, the design of a chemical reactor begins long before configuring components of the chemical reactor is designed. The chemical reactor is designed for a specific task on the basis of which type of the reactor is designed. This sets the initial, intermediate and final conditions of the reactor, based on reactor materials are selected, the critical values of parameters such as pressure, enthalpy, etc. are calculated, and the reactor is designed based on these data. The reactor is then tested and optimized. If the reactor has necessary functionality to perform the required task, the reactor can be used, but if the reactor does not, this process of reactor improvement is repeated. Based on this methodology, configuration of the components of a chemical reactor for continuous mixing of liquids has been worked out, namely:
external mixing source (reactor base) which will not interfere with the displacement process;
heating and cooling system that allows exo- and endothermic reactions;
reactor staging and how to achieve it;
temperature control inside the reactor;
reactor cleaning process.
ACKNOWLEDGMENTS
The authors thank Djabrail Musaevich Bamatov, a senior researcher of the Research and Development Centre for Nanotechnologies and Nanomaterials, for his help and support in this work. The Russian Science Foundation, grant No. 22-16-00092, supported this study.
PEER REVIEW INFO
Editorial board thanks the anonymous reviewer(s) for their contribution to the peer review of this work. It is also grateful for their consent to publish papers on the journal’s website and SEL eLibrary eLIBRARY.RU.
Declaration of Competing Interest. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Russia finds itself in an unprecedented sanctions environment in 2022. The issue of domestic industrial and chemical technologies has become particularly acute. The development of new methods for developing chemical technologies as well as production of apparatuses for chemical technologies are the most important tasks of the scientific and industrial complex. One of the most sought-after apparatuses in almost all industrial enterprises are chemical reactors.
MODELLING OF CHEMICAL REACTORS
The development of chemical reactor strategy will allow to design these devices individually, depending on the required functionality, at different levels of complexity and configuration.
A chemical reactor is a structure that isolates interacting chemicals from the outside environment and allows energy generated inside the reactor to be added or absorbed. The reactor technology was developed for Chemical Reaction Engineering (CRI) research [1].
Two types of ideal reactors are used to describe and evaluate performance of a chemical reactor: the Ideal Displacement Reactor (IDR) and the Ideal Stirred Continuous Reactor (ICDR) [2, 3].
Basically, a flow in tube reactors is directed in one dimension, let’s say in the z direction. Then the main gradients (flow velocity, pressure, convection) will also be pointed in this direction. If convective transport completely dominates over diffusive transport, then diffusive transport can be ignored. Derivation of the equations resulting from this assumption and their solution led to the development of the RIV model. In the case of homogeneous concentration and temperature due to large dispersion coefficients (i.e. mean squares of deviations) one can completely neglect gradients in all directions and integrate all equations globally in all directions (assuming convective flows at boundaries), then the RIF model is obtained.
Idealised reactor models give a good representation of what is going on inside the reactor, provided there are no unintended reactants in the reactor. This makes it possible to assess the performance of a reactor based on certain criteria. Such criteria could be, for example, a comparison of performance and control complexity. Of course, the use of idealised reactors is not practical, as such technology is expensive and, therefore, the industry mainly uses either simplified chemical reactors or averaged modified copies of ideal reactors:
. (1)
This relationship is called the ideal displacement reactor model [4]. In this formula MWs is the molecular mass of the flow at the outer boundaries of the tube, ρs is the density of the mixture inside the reactor, A is the cross sectional area, Vs is the average mixture flow rate, Fs is the force acting on the mixture particles to create the flow, rs is the reaction rate.
Equation (2) is called the ideal continuous stirred reactor model (IFRM):
Fs | out – Fs | in = RsV, (2)
where Fs | out is mixing force on the mixture particles when leaving the reactor, Fs | in in is the mixing force acting on the mixture particles when entering the reactor, Rs is the energy expended on mixing and V is the reactor volume [5].
The design of a chemical reactor is usually done on the basis of a specific task – to handle certain reagents and to achieve a specific end goal. According to Tavler and Sinnolt, the modelling of a reactor must be based on the chemical processes that will take place inside the reactor. This has a major impact on the final cost and complexity of controlling the reactor parts [6].
We propose a seven-step methodology for the design of chemical reactors:
the first step is to collect data regarding the chemical processes for which a given reactor will be produced, such as reaction enthalpy, phase equilibrium constants, mass and heat transfer coefficients, and reaction rate constants;
the second step is to select the initial reaction conditions for reactor operation. Conditions such as type of reaction, use of catalysts, temperature range of reactor operation, pressure inside the reactor and solvents are considered;
the third step is to select the chemical reactor construction materials depending on the above mentioned initial conditions of reactor operation;
the fourth step is to determine the critical reaction rate and critical reactor size parameters;
the fifth step is preliminary determination of the reactor’s dimensions, component layout and cost;
sixth step – experimental verification of reactor operation;
seventh step – optimisation and refinement of the reactor based on the data obtained throughout the previous six steps.
Also, one of the important aspects of modelling is reactor safety. One of the main safety concerns is possibility of a thermal chain reaction inside the reactor. For example, if the cooling system cannot cope with increasing temperature of exothermic reactions, and temperature rise increases the reaction rate, a vicious cycle of negative feedback is created. This can lead to an uncontrolled, avalanche-like temperature increase in the reactor, which can be dangerous and lead to fatal consequences [7, 8].
The most common cause of such chain reactions is an incorrect ratio of reagents, poor temperature control or heating and cooling system.
Following the reactor design methodology, a component configuration for an integrated RIV and IRBDM model for continuous fluid mixing was developed. The model is to be a flow-through six-stage reactor where the main mixing element is the reactor base instead of the agitator. This should allow a high degree of displacement to be maintained while maintaining a high degree of mixing in the reactor [9, 10].
The control system of the sample multistage continuously mixing reactor should allow continuous mixing of liquid chemical reagents in 6 cylindrical volumes of the reactor at once, while allowing the uninterrupted introduction of additional reagents during mixing in progress and allowing the heating of some reactor tubes and cooling of others. The first four tubes should be provided with a tubular heating system and the last two should be provided with a cooling system. Each mixing volume is connected to the next by means of flexible hydrocarbon fibre tubing.
The mixing of reagents must be ensured, in other words, even when a new reagent is added to the liquid mixture in the reactor, the mixing process must be continued if necessary. For this purpose, the reactor is configured with a reagent tap system in the reactor tube. Two taps are placed at the end of each tube, one to connect to the other tubes and the other to pour in the reagents. This results in a staggered tube arrangement where the tube connects on one side to the other previous tube and on the other side to the next tube along with the reagent pour tap.
The thermosensor system is designed as follows. At the inlet of the tube, next to the hydrocarbon connection hose to the preceding reactor tube, space was provided for placing thermosensors in the tube. The sensors send information to an information processing receiver at a selected time interval set by the operator. The receiver stores this information for a specified period of time, which by default is set to one hour, and can be changed by the operator. The layout of the thermosensors in the reactor tube is shown in Fig.3.
During the reactor configuration development the problem of cleaning the reactor from residual liquid after operation had to be solved. In order to solve this problem, screw-in and screw-out taps on the reactor tubes were proposed. Figure 4 shows these covers as well as the necessary threads on the reactor tubes to ensure a tight connection between the covers and tubes.
Thus, the proposed configuration of the elements of the multi-stage chemical reactor is as follows (Fig.5). It shows sequential connection of all stages of reactor operation. On each stirring volume there should be a thermal sensor, which will monitor the temperature regime inside the reactor tube. The length of the mixing volume is 280 mm and its diameter is 70 mm. This is done to ensure that the actual volume of the cylinder is 1 litre. A thread is also provided for tight fitting of the stirring volume covers with a length of 10 mm. The wall thickness of the cylinder is 3 mm so that threads can be made for the covers. The mixing process will mainly be achieved by the moving base of the reactor. The base must oscillate right and left of the reactor user at a controlled frequency.
In Fig.5 a is the thermosensor inlet of the platform tube for temperature monitoring, b is the reactor base vessel, c is the oscillating reactor platform, d is the copper line of the heating/cooling system, e is the clamp of the mixing volumes to the reactor base, f is the reactor base oscillation control bar, g is the on/off button of the reactor, h is the reactor tubes with the developed reactor cover design, i is the carbon fibre hose for connecting reactor tubes together which creates six stages of mixing in the reactor.
CONCLUSIONS
To summarise the above, the design of a chemical reactor begins long before configuring components of the chemical reactor is designed. The chemical reactor is designed for a specific task on the basis of which type of the reactor is designed. This sets the initial, intermediate and final conditions of the reactor, based on reactor materials are selected, the critical values of parameters such as pressure, enthalpy, etc. are calculated, and the reactor is designed based on these data. The reactor is then tested and optimized. If the reactor has necessary functionality to perform the required task, the reactor can be used, but if the reactor does not, this process of reactor improvement is repeated. Based on this methodology, configuration of the components of a chemical reactor for continuous mixing of liquids has been worked out, namely:
external mixing source (reactor base) which will not interfere with the displacement process;
heating and cooling system that allows exo- and endothermic reactions;
reactor staging and how to achieve it;
temperature control inside the reactor;
reactor cleaning process.
ACKNOWLEDGMENTS
The authors thank Djabrail Musaevich Bamatov, a senior researcher of the Research and Development Centre for Nanotechnologies and Nanomaterials, for his help and support in this work. The Russian Science Foundation, grant No. 22-16-00092, supported this study.
PEER REVIEW INFO
Editorial board thanks the anonymous reviewer(s) for their contribution to the peer review of this work. It is also grateful for their consent to publish papers on the journal’s website and SEL eLibrary eLIBRARY.RU.
Declaration of Competing Interest. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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