Displacement Reactor Research Articles

Optimization of technological parameters of the methane tri-reforming process based on the phenomenon of conservatively perturbed equilibrium

course under the condition of the phenomenon of conservative perturbed equilibrium (CPE) are considered. It is shown that the onset of the CPE point - an extremum of the over-equilibrium concentration - occurs at a certain point in time. Therefore, one of the tasks of optimal control is to calculate the time of occurrence of this point and determine the effect of temperature and pressure on its position. The modeling of the TRM process is performed for an ideal displacement reactor. The DWSIM software product was used to model the TRM process. The kinetic equations were programmed in the form of scripts. The position of the over-equilibrium concentration point was also investigated depending on the initial composition of the mixture. According to the modeling results, it was concluded that the position of the CPE point for product H₂ is constant, and depends only on pressure and temperature and does not depend on the initial composition of the mixture. This allows us to conclude that the control can ensure that the product yield with the maximum concentration is achieved. The problem of optimizing the initial composition of the mixture for the methane tri-reforming process using CPE is formulated: the objective function and constraints are defined, and the solution method is chosen. The optimization problem is to maximize the target product of methane tri-reforming, H2. The solution to the problem is the composition of the mixture (concentrations of CH4, H2O, CO2). As for the constraints, the pressure and temperature are limited by the physicochemical properties of the process and the design features of the reactor, the elemental balance must be maintained, the key component at the input must have an equilibrium concentration at a given pressure and temperature, and the concentrations of other components must be deviated from their equilibrium values. A software implementation of the optimization problem based on the Optimization Toolbox Matlab was performed. The research results indicate an increase in the efficiency of the process (increase in the output of the target component) and the possibility of implementing optimal solutions in real time, which opens up prospects for implementation in existing control systems and development of decision-making systems.

Development of a laboratory unit and a solid fuel gasification reactor

The paper investigates the process of gasification of pyrolysis coal and other coal-containing materials A schematic diagram of the installation of the gasification process of pyrolysis coal and other coal-containing materials was developed, the design of the reactor for coal gasification and the methodology for conducting experiments and analysing the gasification process of pyrolysis coal and other coal-containing materials were developed. Research methods - modelling of the coal gasification process using the results of theoretical studies. A detailed analysis of the experimental and theoretical data concerning the feasibility of the pyrolysis coal gasification process was carried out, a schematic diagram of the laboratory installation and the design of the gasification reactor were developed. The main goal is to develop a method of gasification of solid pulverised fuel that will simplify the process control and ensure its stability due to the unity of the drying and gasification processes of pyrolysis coal, which are linked by means of a gasification reactor. Additionally, this method provides for the neutralisation of harmful impurities generated during the coal gasification process. As a result of theoretical studies of the solid fuel gasification process, a design of a coal gasification reactor was proposed, which is an ideal displacement reactor. The length-diameter ratio for the working part of the reactor should be at least 10:1. It is proposed to use a heat-resistant molybdenum steel tube (operating temperature up to 1600 0C) with a diameter of two inches to manufacture the reactor. Also, to study the gasification process of pyrolysis coal and other coal-containing materials, a laboratory installation for gasification of solid crushed fuel is proposed, in which a gas mixture of carbon dioxide and oxygen is fed into the reactor and serves as an activator of the gasification process. The prospects of coal processing by gasification to produce a mixture of combustible gases (H2, CO, CH4) are investigated. It is analysed that coal gasification allows obtaining valuable gas that can be used not only as an energy fuel, but also as a technological raw material for the production of methanol, dimethyl ether, hydrogen production, and use as a reducing agent in metallurgical processes.

Polymer properties of softwood organosolv lignins produced in two different reactor systems.

Lignin, the second most abundant biopolymer on earth and with a predominantly aromatic structure, has the potential to be a raw material for valuable chemicals and other bio-based chemicals. In industry, lignin is underutilized by being used mostly as a fuel for producing thermal energy. Valorization of lignin requires knowledge of the structure and different linkages in the isolated lignin, making the study of structure of lignin important. In this article, lignin samples isolated from two types of reactors (autoclave reactor and displacement reactor) were analyzed by FT-IR, size exclusion chromatography, thermogravimetric analysis (TGA), and Py-GC-MS. The average molecular mass of the organosolv lignins isolated from the autoclave reactor decreased at higher severities, and FT-IR showed an increase in free phenolic content with increasing severity. Except for molecular mass and molecular mass dispersity, there were only minor differences between lignins isolated from the autoclave reactor and lignins isolated from the displacement reactor. Carbohydrate analysis, Py-GC-MS and TGA showed that the lignin isolated using either of the reactor systems is of high purity, suggesting that organosolv lignin is a good candidate for valorization.

Morphology of lignin structures on fiber surfaces after organosolv pretreatment.

The redeposition of lignin to the fiber surface after organosolv pretreatment was studied using two different reactor types. Results from the conventional autoclave reactor suggest that redeposition occurs during the cooling down stage. Redeposited particles appeared to be spherical in shape. The size and population density of the particles depends on the concentration of organosolv lignin in the cooking liquor, which is consistent with the hypothesis that reprecipitation of lignin occurs when the system is cooled down. The use of a displacement reactor showed that displacing the spent cooking liquor with fresh cooking liquor helps in reducing the redeposition and the inclusion of a washing stage with fresh cooking liquor reduced the reprecipitation of lignin, particularly on the outer fiber surfaces. Redeposition of lignin was still observed on regions that were less accessible to washing liquid, such as fiber lumens, suggesting that complete prevention of redeposition was not achieved.

STUDY OF THE PROCESS OF HYDRATION OF MESITYL OXIDE IN THE PRESENCE OF NANOCATALYZERS

The process of mesityl oxide hydrogenation in the presence of a nickel catalyst prepared by impregnating a support with an aqueous solution of the corresponding salt in a displacement reactor in a gas-liquid-solid catalyst system has been studied. It has been established that the use of the catalyst used in the work makes it possible to selectively obtain methyl isobutyl ketone with complete conversion of mesityl oxide in the temperature range 70-100 ºС.

The phenomenon of conservative-perturbed equilibrium in conditions different reactors

Finding the optimal mode is a conceptual problem. The most important indicator that reflects the perfection of a chemical reactor is the intensity of the process in it.
 The phenomenon of conservatively perturbed-equilibrium (CPE) in the conditions of different types of reactors (in acyclic and cyclic systems) was studied: the ideal displacement reactor ("steady-state plug flow reactor, PFR") and the ideal mixing reactor ("steady-state continuous stirred tank reactor, CSTR").
 For the acyclic reaction, the time of extremum onset was less in CSTR by ≈2.1%, but the concentration of substance B in the extremum in PFR was greater by ≈17.2% than in CSTR. For the cyclic reaction, the time of extremum onset was less in CSTR by ≈5.6%, but the concentration of substance B in the extremum in PFR was greater by ≈11.6% than in CSTR. For the acyclic and cyclic reaction in PFR, the time of occurrence of the extremum of the cyclic reaction was lower by ≈44.2% than in the acyclic, but the concentration of substance B in the extremum of the acyclic reaction was greater by ≈24.8% than in the cyclic reaction. For the acyclic and cyclic reaction in CSTR, the time of occurrence of the extremum of the cyclic reaction was lower by ≈46.2% than in the acyclic, but the concentration of substance B in the extremum in the acyclic reaction was greater by ≈18.9% than in the cyclic reaction. The cyclic system showed a shorter time for the onset of the extremum, but the acyclic reaction system showed a higher concentration of substance B at the extremum in PFR and CSTR. Although the time of extremum onset was the lowest in CSTR in the cyclic system, the concentration of substance B in the extremum was highest in the PFR in the acyclic system. Therefore (from our systems and reactors) the acyclic system in PFR shows the best characteristics. 
 The extremum in transient modes is always observed for acyclic and cyclic complex reactions in both reactors, both in PFR and in CSTR. The phenomenon of conservatively perturbed-equilibrium is manifested in both PFR and CSTR. With the same rate constants, the acyclic system in PFR is characterized by higher values of "over equilibrium" conversion than the acyclic system in CSTR. Similarly, with the same rate constants, the cyclic system in PFR is characterized by higher values of "over equilibrium" conversion than the cyclic system in CSTR.
 The time of extremum onset is less in CSTR. This is true for acyclic and cyclic systems.
 The greater the difference between the initial concentrations of the two substances, the greater the "over equilibrium" concentration of the third substance, the initial concentration of which was equilibrium. 
 At our values of kinetic parameters, the sensitivity of the time of occurrence of the extremum of the same reaction in different reactors (PFR and CSTR) is small (up to ≈5.6%), and at different reactions (acyclic and cyclic), but in one type of reactor (PFR or CSTR) - significant, reaching ≈46.2%.

Quasi-Invariants of Chemical Reactions in the Ideal Displacement Reactor

Mathematical models of nonequilibrium processes in distributed systems are described by partial differential equations with given boundary conditions and, as a rule, cannot be solved analytically. The absence of exact solutions of such models does not allow one to find exact invariants; i.e., functions are strictly constant on these solutions. This article has developed a method for determining the approximate spatiotemporal kinetic invariants (quasi-invariants) of chemical reactions that do not take into account diffusion in an ideal displacement reactor. Spacetime quasi-invariants are explicit algebraic expressions that relate the nonequilibrium values of the concentrations of the reagents and/or temperatures measured in two or more experiments with various specially selected initial and input conditions (multiexperiments). The selection of suitable initial conditions makes it possible to find such functions of solutions that weakly depend on the time and length of the reactor, i.e., remain almost constant throughout the reaction in the entire reactor volume. It is shown that the number of quasi-invariants is determined by the number of independent model variables (reagent concentrations and temperature). The application of the method is illustrated by the example of a one-stage reaction occurring in a reactor of ideal displacement. The quasi-invariant 3D surfaces found for this reaction are compared with 3D plots of concentration and temperature changes during the reaction. It is shown that quasi-invariants vary in a smaller range (along the ordinate axis) than the corresponding concentrations and temperatures in different experiments, i.e., are spacetime approximate invariants. Quasi-invariants of this kind can be observed on the dependences of the model variables (concentrations and temperatures) on the time and length of the reactor in the form of various flattened three-dimensional structures (“lying” waves). The method expands the tools for analyzing the unsteady kinetics of chemical reactions in distributed systems of ideal displacement.

THE INVESTIGATION OF FURAN DERIVATIVES HYDROGENATION PROCESS IN PRESENCE OF COPPER AND COBALT CATALYSTS, SUPPORTED ON MGO

The hydrogenation of furfural during catalysis by copper nanoparticles deposited on MgO in a gas phase displacement reactor or in a gas-liquid-solid catalyst system proceeds at atmospheric pressure of hydrogen.

RESEARCH OF THE CHEMICAL REACTION OPTIMALITY CRITERION FOR TECHNOLOGICAL PROCESS REALIZATION

The optimality criterion of the chemical reaction by the Euler method was investigated in the search for the most suitable reactor design for the realization of the technological process. The optimality criterion corre- sponds to the minimum of the surface of the compared apparatus of a particular chemical reaction with the calculation of a number of reactors, which allows to achieve a minimum investment in the construction in proportion to the material capacity of the apparatus. A system of simple differential equations reflecting the formal model of the chemical reac- tion kinetics was solved by a first-order method. The Euler method scans the time axis with steps, using the recurrence relation to calculate the concentration of the component in the step from the results of calculating the concentration of this component in the previous step. In PascalABC. NET with the ability to determine the necessary duration of the reaction and the output of intermediate values of the concentrations of the reaction components at the reference points, a calculation was made with the ini- tial concentration of the component. The values of the most suitable design of ideal displacement reagents and ideal mixing were determined for this process. The models of ideal mixing of periodic and flowing action, as well as an ideal displacement reactor, are analyzed. Mathematical models were for- mulated and kinetic calculation results were obtained with reaction time values and apparatus volumes at which the yield of the target product was the highest. In the course of the examination, as optimality criterion of the surface of reactor construction was found and, in comparison with these devices, the efficiency of the ideal intermixing model of batch action was noted.

Effect of feed composition of co-pyrolysis of corncobs–polypropylene plastic on mass interaction between biomass particles and plastics

Polypropylene plastic (PP), which has higher hydrogen content compared to that in biomass, is potential to be used as a cheap hydrogen source for pyrolysis of biomass, such as corncobs, to remove part of oxygen content in the biomass pyrolysis oil. By charging these two materials, synergistic effects will appear that improve quality and quantity of bio-oil produced. The aim of the present work is to investigate possible mass interaction between biomass and plastic materials leading to the synergistic effects using slow co-pyrolysis. The experiment was performed in a displacement reactor. Feed composition was varied at 12.5%, 25%, 37.5%, 50%, 62.5%, 75%, and 87.5% weight of PP. This phenomenon was observed through expansion-contraction of the reactor prior to large mass decomposition of the reactor feed. In experiment involving biomass-dominated feeds, i.e. PP contents < 50% (regime 1), there was reactor bed contraction due to slight biomass decomposition followed by no-displacement of reactor piston. During the contraction, it is estimated, there was low velocity ejection of biomass volatile matter, while during no-displacement stage, there was a phase change of plastic granules to plastic melt. In experiment with plastic-dominated feeds, i.e. PP ≥ 50% (regime 2), the reactor bed underwent contraction due to phase change of plastic granules which reduced the bed volume, followed by bed expansion due to the swelling of biomass particles estimated in the presence of hydrogen bonding in the phenolic environment in biomass material. The last stage of co-pyrolysis in regime 2 was the bed contraction and it is predicted that there was high velocity gas ejection through the small pores which intensified interaction of biomass-plastic radicals in hydrogen-rich environment favourable for exerting synergistic effect.

Life Tests and Kinetic Experiment in a Displacement Reactor with a Fixed Catalyst Bed

Alternative designs of a pilot reactor for long-term testing of heterogeneous fixed bed catalysts were discussed with liquid-phase hydrogenation of methylphenylketone to 1-phenylethanol as an example. The discussion is exemplified with the calculation of a reactor unit for hydrogenation over catalyst NTK-11. It was demonstrated that a cascade of three adiabatic reactors with a 4,5 m high catalyst bed in each of them is needed to provide the residual concentration of the reactant less than 1 wt.%.

Analysis of Parameters of High-Purity Hydrogen Production from Methane in a Laboratory-Scale Membrane Reformer with an Ultrathin Palladium Membrane

The key characteristics of a laboratory-scale membrane reformer for high-purity hydrogen production from methane with a 4- $$ \mu $$ m-thick palladium membrane are described quantitatively using a mathematical model for an ideal displacement reactor that takes account of the hydrogen mass flux through the membrane and chemical reaction in the gas phase. Application of model representations for calculating the basic technological and design parameters of a high-efficiency membrane reformer with a 41.8 m 3 H 2 /h production capacity for feeding a 50 kW battery of proton exchange membrane fuel cells (PEMFC) with hydrogen is illustrated on a project example.

Temperature profile in a displacement reactor

Results of a mathematical simulation of the heat and mass exchange in the displacement reactor are presented.

Two-zone structure of the filtration combustion front in the presence of an inert gaseous admixture

The structure of the filtration combustion front with two reaction zones separated by an inert gas layer, whose concentration in the front is conditioned by specific features of the front structure, is studied. The process of initiation of the filtration combustion front with this structure is demonstrated, and its quasi-steady dynamics is considered. The possibility of using this front structure in a displacement reactor with a porous medium moving with the combustion velocity is examined. An approximate analytical description of the fields of temperature, pressure, and species concentrations in a steady operation mode of the reactor is given. Possibilities of using this reactor in high-temperature synthesis processes are discussed.

Temperature profile in the displacement reactor with laminar movement of the medium

Temperature profile in the displacement reactor with laminar movement of the medium

Determination of the main geometric parameters of a displacement reactor for laminar flow of the medium

The throughput of chemical reactors for exothermal processes complicated by heat and mass exchange often depends on the possibility of heat transfer from the reaction mass to the surface of heat exchangers, e.g., built into a tank-type reactor or forming a displacement reactor. It is of practical interest, therefore, to assess that possibility, which requires that the main geometric parameters of the hea-exchange elements be determined

Mathematical modeling of the process of isothermalortho-para conversion

Production of liquid hydrogen includes a stage of ortho-para conversion (i.e., obtaining the para form equilibrated to the saturation temperature), without which prolonged storage of liquid hydrogen is not possible. Obviously, it is economically expedient to withdraw some of the heat of the ortho-para transition at the highest temperature level using the liquid nitrogen cooling loop traditionally used in hydrogen equipment. According to current terminology, equipment for carrying out ortho-para conversion with cooling by a boiling cryogenic agent are called isothermal converters. This does not reflect the essence of the process since it actually occurs at a variable temperature, despite the fact that the initial and final temperatures of the process are equal in some cases. Characteristics of the process of isothermal ortho-para conversion have been studied for the following assumptions: the reaction occurs in the kinetic region, the rate constant for the chemical reaction does not depend on temperature, the catalyst is a homogeneous irregulate structure, the apparatus is an ideal displacement reactor, the thermal resistance of the walls of the reactor tubes is negligibly small, and there is no economizer zone.

Towards a theory of bubble reactor combustion (displacement reactor)

We examine the thermal regime of a displacement reactor in which a monodisperse bubble medium is reacting. We propose a model of the thermal processes taking place in the reactor which differs significantly from the known models of homogeneous single-temperature reactors. Classification of the operating regimes of a reactor is based on the dynamic balance method, which consists of comparing the local values of the combustion wave velocity u(x) computed along the channel length in a quasisteady approximation, with characteristic velocity uo. We determine the regions of steady solutions in the parameter plane and classify the stable and unstable states on the basis of the solution to a system of equations. This system connects the values of the combustion wave propagation velocity, the position of the front in the reactor channel, the initial and final temperatures of the phases, and a measure of the completeness of combustion.

Calculation of combustion regimes for a twisted gas flow in a tubular ideal displacement reactor

Using the equations of the hydrodynamics of a twisted flow, we have employed a numerical method to construct the temperature and concentration fields of an exothermically reactive gas. We have analyzed the regimes of combustion and the mechanism involved in the ignition of the flow at various values of the twist parameter.

Laws governing processes in a displacement reactor taking account of longitudinal transfer and lateral heat losses

Laws governing processes in a displacement reactor taking account of longitudinal transfer and lateral heat losses