Adiabatic Bed Research Articles

Effect of an axial-radial plate reactor modifications on a mega methanol plant production

Abstract Axial-radial flow plate reactors have been recently considered as efficient and practical types of reactors for methanol synthesis. Generally, an axial–radial reactor (AR) consists of two main parts namely the axial section and the radial section and the vast majority of the feed enters the radial section. Moreover, the structure of AR has a space above the axial part, which can add an adiabatic bed in the system. In this study, the performance of two novels AR configurations is investigated to improve the effectiveness of the axial–radial plate reactor. In the first configuration, the optimum length of the adiabatic bed is calculated and the adiabatic bed is located above the axial section inside the AR and is named IAAR. Therefore, in IAAR the feed of the axial section just enters the adiabatic bed and warms up. On the other configuration, the adiabatic bed with the optimum length is placed outside the reactor and is named OAAR. Therefore, in OAAR the total feed passes through the adiabatic bed, highly warms up, then cools to the optimum temperature in a heat exchanger, and finally enters AR. Two-dimensional mathematical modeling via orthogonal collocation on the finite element method is developed to compare the performance of two configurations. The results show that the maximum proportion of methanol produces in IAAR, which is approximately 3.8% higher than that produced in conventional AR due to utilizing an adiabatic bed inside the AR and superior gas distribution in the process. Momentum, mass, and heat equations are calculated and molar flow rates, mole fractions and temperatures are depicted along the radius and the length of the three configurations.

Introducing a novel process to enhance the syngas conversion to methanol over Cu/ZnO/Al2O3 catalyst

In this study, a novel configuration, Adiabatic and Plate Water-cooled Reactors, which called APW is introduced as an alternative for a two stage conventional methanol process consisting of gas-cooled and water-cooled reactors. In the APW configuration, the gas-cooled reactor is replaced with two adiabatic reactors with the optimized basic design. A water-cooled reactor is like a plate heat exchanger with three sections by the different number of plates. The gas flow rate through each section is optimized, so that pressure and temperature changes along these sections are almost identical. Mathematical modeling indicates that, temperature rise within the adiabatic reactor precludes gas condensate formation, consequently improves the catalyst durability. Moreover, the small length to cross section ratio of the adiabatic bed results in low pressure drop. Also, high average temperature and low pressure drop along the adiabatic beds enhance methanol production. The proposed configuration, provides different advantages than the conventional process, e.g. low pressure drop, high cooling efficiency of the water-cooled reactor and higher H2 and CO2 conversions. The APW configuration enhances the methanol production rate 12.2% in comparison with conventional configuration. Other advantages in this configuration are, eliminating condensate formation, preventing greenhouse gas emissions and improving catalyst durability.

The Simulation of an Industrial Fixed Bed Reactor for Methanol Dehydration to Dimethyl Ether

Compared to methane and methanol, dimethyl ether seems to be a superior candidate for high quality diesel fuel in the near future. To meet the continuously increasing global requirements, a larger scale reactor is needed to produce more dimethyl ether. A heterogeneous one-dimensional model was developed to simulate a staged adiabatic fixed bed reactor for the catalytic dehydration of methanol to dimethyl ether. To verify the proposed model, the simulated catalyst bed temperature has been compared to available data from an industrial reactor. A good agreement has been found between the simulation and plant data. Also, the effects of some operational parameters, such as feed flow rates, the inlet temperatures of methanol, pressure, and catalyst particle diameter on reactor behavior were investigated. The simulated results show that this model is reasonable and reliable.

MODELING AND APPLICATION OF RESPONSE SURFACE METHODOLOGY IN OPTIMIZATION OF A COMMERCIAL CONTINUOUS CATALYTIC REFORMING PROCESS

A kinetic model based on five groups of 26 lumped pseudo-components, including C6 to C9 carbon atoms in categories of paraffins, isoparaffins, cyclohexanes, cyclopenthanes, and aromatics was developed for modeling and optimization of a commercial continuous catalytic naphtha reformer in Bandar Abbas Refinery. The reaction network consisted dehydrogenation, hydrogenation, ring expansion, paraffin and isoparaffin cracking, naphthene cracking, paraffin isomerization, and hydrodealkylation of aromatics as well as coke formation. The product compositions, temperature profile, pressure drop, and coking profiles were determined in the four radial-flow moving bed reactors. The kinetic parameters were derived from the literature and used without tuning the parameters in the CCR model. The outlet temperature, reformate yield, and research octane number (RON) were compared and validated with the outlet results of the commercial CCR. Optimization of operational conditions was carried out using the CCR model and response surface methodology (RSM) based on the statistical analysis. The influence of inlet feed temperature, bed pressure, inlet hydrogen to feed ratio, and the number of adiabatic beds was analyzed simultaneously on the yield and research octane number of the reformate product, and the optimal results were calculated and discussed to approach to the highest RON and reformate yield.

Updraft fixed bed gasification of mesquite and juniper wood samples

Biomass gasification is being considered as one of the most promising technologies for converting biomass into gaseous fuel. Here we present results of gasification, using an adiabatic bed gasifier with air as gasification medium, of mesquite (Prosopis glandulosa) and redberry juniper (Juniperus pinchotii), two woody species that dominate uncultivated lands in the Southern Great Plains, U.S.A., that may have potential for bioenergy utilization. The effects of equivalence ratio (ER), particle size, and moisture content on the temperature profile, gas composition (CO, CO2, H2, N2, CH4, and C2H6), and higher heating value (HHV) were investigated. As ER decreased from 4.2 to 2.7, the mole composition of the end product gas for mesquite contained: 13–21% CO, 1.6–3% H2, 1–1.5% CH4, 0.4–0.6% C2H6, 60–64% N2, 11–25% CO2, and 1–2% O2. The mole composition of the end product gas for juniper consisted of 21–25% CO, 2.5–3.5% H2, 1.5–1.8% CH4, 0.3–0.5% C2H6, 58–61% N2, 9–12% CO2, and 1–2% O2. The H2 and CO mole percentages decreased with increasing ER while the CO2 and N2 mole percentage increased. After removing N2, the HHV of the end-product gas for mesquite and juniper reached 26 and 27.5% of natural gas HHV, respectively, when ER ≈ 2.7.

Catalytic flue gas conditioning in electrostatic precipitators of coal-fired power plants

The paper is dedicated to development of the catalytic process for controlled SO 3 production for conditioning of flue gases from coal-fired power plants. On the basis of comparative technological analysis performed for different variants of the process arrangement, it was shown that optimal technological decision is catalytic sulfur dioxide oxidation in synthetic SO 2-containing stream in a separate reactor with two adiabatic beds of catalyst with following introduction of SO 3-containing flow into the main coal boiler gas duct. Undoubted benefits of this process are: complete independence of the process from the flue gases properties; possibility to control SO 3 concentration in the flue gases in the wide range; possibility to process gases with high SO 2 concentration, providing low gas flow rate and low catalyst loading; absence of limitations for the pressure drop of the catalyst bed. Among catalysts on the basis of fiber–glass support the best catalytic performance was observed for platinum-containing catalyst on support modified with zirconium dioxide. It was demonstrated that optimal catalyst solution is combination of conventional granular vanadia and platinum woven fiber–glass catalysts, providing high activity both at high and low temperatures.

140 g H 2/kg biomass d.a.f. by a CO-shift reactor downstream from a FB biomass gasifier and a catalytic steam reformer

The effect of adding a CO-shift reactor downstream from a fluidized bed biomass gasifier and a steam reforming catalytic reactor is studied in this paper. The upstream gasifier was of small pilot plant scale, 10 kg biomass/h. Therefore, the downstream catalytic reactors, steam reformer and CO-shift, operated under a real gasification gas. The gasifying agent used was H 2 O – O 2 mixtures. The CO-shift catalytic reactor used had one high (HT) and one low temperature (LT) adiabatic beds. Two commercial catalysts were used throughout the process. CO-conversions (eliminations) were higher than 90% and a H 2 -content as high as 73 vol%, dry basis, were obtained by the CO-shift system. This H 2 content is equivalent to a yield of 140 g H 2 / kg biomass d.a.f. The CO conversion and the increase (up to 14 vol%) of the H 2 content, correlate well with the molar steam/CO ratio in the gasification gas at the inlet of the HT bed.

Scaleable, microstructured plant for steam reforming of methane

We report results obtained in a demonstration plant for hydrogen production at 5 Nm 3 h −1 in a microchannel system constructed using techniques proven in Heatric printed-circuit heat exchangers (PCHE). The manufacturing technique allows great complexity in the design to be achieved with little incremental cost and our plant takes advantage of this to carry out the combustion and reforming reactions in highly integrated multiple adiabatic beds (MAB). The PCHE manufacturing technique is scaleable and the results from this small-scale plant demonstrate not only a practical miniplant for distributed manufacture of hydrogen but also provide the design basis for much larger plant (for example for transport fuelling and industrial applications) based on replication of the plate structures. The system operated at 2 bar to produce hydrogen for a notional PEM fuel cell, with essentially complete conversion of natural gas in the reformer to equilibrium yields of CO, CO2 and H2 (∼80%). The plant showed excellent turn-down characteristics to 30% of design capacity. © 2007 Elsevier B.V. All rights reserved.

Application of heat interchange systems to enhance the performance of ammonia reactors

A rigorous heterogeneous model for adiabatic ammonia reactors is used to explore the application of internal heat exchange theory to cross the adiabatic reaction equilibrium values and to improve the conversion in ammonia reactors. The mathematical model is developed for adiabatic ammonia converters and the resulting two-point boundary value differential equation for the catalyst particles is solved using the orthogonal collocation method. Two simple configurations of reactors with heat interchangers are implemented. An industrial ammonia reactor having three adiabatic beds with Montecatini Edison catalyst and interstage cooling is used as the basis for comparison. The comparison shows that an increase of 13.37% of the overall ammonia conversion is possible. The results presented in this study reveal the potential application of energy optimization and integration in the ammonia industry.

Non-adiabatic radial-flow reactor for styrene production

A non-adiabatic radial reactor is proposed to carry out the dehydrogenation of ethylbenzene to styrene. Radial flow and continuous heating (using superheated steam) are the main features of the new design. Steam used as heating medium flows through tubes, which are radially installed in the catalyst bed. By means of steady-state simulations, this new design has been compared with two adiabatic beds with radial flow and reheating between stages (similar to those used in industry). For equal steam consumption, the proposed design leads to higher selectivity to styrene than the industrial adiabatic design. This enhancement in selectivity (which is observed for different conversion levels) would significantly improve the economics of the styrene production process.

Characteristic investigation on unsteady heat transfer between gas and solids

A series of experimental researches on unsteady heat transfer between gas and solids have been made in an adiabatic bed, used in a new plant of cryogenic recycling of tired tyre. The gas-solids temperature profiles with different bed length levels and a wide range of Reynold's numbers are presented, and from which a Nu-Re correlation is obtained Based on the results, a new mathematical model is proposed. It would be clear that the model as well as the experimental results are useful for both theoretical research on unsteady heat transfer and design of cryogenic recycling plant.

Dynamics of pressurization and blowdown of an adiabatic adsorption bed: 4. Intraparticle diffusion/convection models

Abstract The importance of intraparticle mass transfer during pressurization and blowdown steps of PSA processes in an adiabatic adsorption bed was assessed by comparing intraparticle diffusion/ convection and intraparticle diffusion models. Film mass/heat transfer resistances are also considered in the model. The film heat transfer resistance is more important than the heat transfer resistance inside the particle; it can be assumed to be negligible in PSA processes when the temperature variation is not very large, otherwise it leads to serious errors when the adsorption capacity of adsorbents is high and the heat capacity of the system is not high. Intraparticle convection improves the mass transfer inside the particle and leads to faster heat releases into and out of the adsorbents.

Dynamics of pressurization and blowdown of an adiabatic bed: III

The importance of heat effects in an adiabatic bed during the pressurization and blowdown steps of pressure swing adsorption (PSA) processes is assessed. The compression energy is included in the energy balance. The effect of the temperature fluctuations on the separation results is much more important than the effect of the adsorption capacity. It is very important and useful to improve the bed dynamics by using high-heat-capacity adsorbent particles or heat exchange in order to reduce the temperature fluctuations in PSA processes as suggested by R.T. Yang and P. Cen ( Ind Eng Chem Des Dev (1986) 25 54–59) 1 .

A computer software package for the simulation and optimization of an industrial ammonia converter based on a rigorous heterogeneous model

A computer package for the modelling, simulation and optimization of an ammonia reactor is developed for use on personal computers. The package is easy to use with user friendly interface utilizing the graphical capabilities of the personal computer. The model used in the package is a heterogeneous model, which has been checked against an industrial reactor having three adiabatic beds with interstage cooling, and gave excellent agreement with the industrial data. The two-point boundary value differential equation for the catalyst particles is solved using the orthogonal collocation method and three internal collocation points are necessary to obtain accurate results. The model is used to investigate the optimal behavior of the reactor.

Desiccant Cooling System Performance: A Simple Approach

A simple algebraic model of wave motion arising in the adiabatic fixed-desiccant bed dehumidification of an air stream is applied to the prediction of the performance potential of a desiccant air conditioning system. The model is used to explain the increase in cooling system performance that has been realized through the use of mixed inert-desiccant material adsorption beds. The response of cooling system performance to changes in external process conditions is examined and conclusions are drawn relative to optimization of system characteristics.

Catalyst poisoning and fixed bed reactor dynamics part III: Start-up and quasi-steady state profiles in fresh and deactivated adiabatic beds

Previous studies of the dynamic behavior of adiabatic fixed bed reactors under conditions of catalyst poisoning have been extended to investigation of the start-up of both fresh and partially deactivated beds. In addition, bed thermal conductivity and heat capacity have been varied by a factor of about two via the addition of inert diluents in order to investigate the effect of these thermal factors on reactor transients. The quasi-steady state behavior under poisoning conditions has also been determined and is compared for the different thermal properties of the beds and at different levels of poison concentration. Reactor behavior was simulated using a one-dimensional pseudo-homogeneous model incorporating the effects of mass and heat dispersion. As in previous work, the parameters required in the simulation were, as far as possible, determined via separate experiments or literature correlation. In general, the simulation of quasi-steady deactivation behavior was quite good; however, start-up (ignition) conditions provide a very severe test of the simulation, particularly for those cases of high bed thermal conductivity.

Heat Transfer in Gas-Solid Packed Bed Systems. 3. Overall Heat Transfer Rates in Adiabatic Beds

Heat Transfer in Gas-Solid Packed Bed Systems. 3. Overall Heat Transfer Rates in Adiabatic Beds

Optimal control policies for tubular reactors experiencing catalyst decay: II. Multiple‐bed semiregenerative reactors

AbstractThe optimal control problem for multiple beds is formulated and a distributed maximum principle derived. Gradient methods are then used to synthesize the optimal control policies for some examples in three‐bed isothermal and adiabatic reactors. Finally, examples are worked to illustrate the computational algorithm in adiabatic beds when optimal catalyst loading is to be determined, and when it is desired to distribute the feed in an optimal fashion between the beds. Reasonably good convergence was obtained in all the examples, so that the method appears quite feasible for determining optimal control policies in multiple reactors subject to catalyst decay.

Optimal Adiabatic Bed Reactor with Cold Sheet Cooling (7th Episode)

Optimal Adiabatic Bed Reactor with Cold Sheet Cooling (7th Episode)

Control of Cold Shot Adiabatic Bed Reactor with Decaying Catalyst

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTControl of Cold Shot Adiabatic Bed Reactor with Decaying CatalystKung-You Lee and Rutherford ArisCite this: Ind. Eng. Chem. Process Des. Dev. 1963, 2, 4, 306–309Publication Date (Print):October 1, 1963Publication History Published online1 May 2002Published inissue 1 October 1963https://doi.org/10.1021/i260008a010RIGHTS & PERMISSIONSArticle Views62Altmetric-Citations9LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (357 KB) Get e-Alerts