Sorption-enhanced reaction process with reactive regeneration

Steam and Pressure Management for the Conversion of Steelworks Arising Gases to H2 with CO2 Capture by Stepwise Technology

Steel production is a main source of CO2 emissions globally. These emissions must be drastically reduced to meet climate change mitigation goals. STEPWISE is a Sorption Enhanced Reactive Process (SERP) technology that converts steel works arising gases to H2 with simultaneous CO2 capture. The main energy requirements of the process are the high- and low-pressure steam quantities that are needed to rinse and regenerate the adsorbent. In this simulation study, the separation performance of STEPWISE is evaluated over a range of steam and feed pressure inputs by searching those design points where CO2 recovery and purity percentages are equalized. This method is used to facilitate the comparison of different operating regimes. Results highlight the importance of the rinse to purge ratio (R/P) as a design variable. A higher R/P ratio is demonstrated to maintain CO2 recovery and purity of ~95.5%, while total steam consumption and feed carbon loading are reduced by 27% and 20%, respectively. This is achieved without changing other parameters, like cycle time. Additionally, it is demonstrated that the CO2 capture performance can be maintained for varying feed pressure values by tuning the feed carbon loading. Future studies are recommended to focus on the expected role of the feed gas steam content on these findings.

Numerical Investigation of Process Enhancement Using a Bifunctional Catalyst in a Dual Fluidized-Bed Reactor

The paper outlines the concept of process intensification and integration, with a particular focus on sorption-enhanced, solid-catalyzed chemical processes. An alternative and attractive solution to a system of parallel fixed-bed apparatuses is evaluated, which utilizes the solids’ circulation in a dual fluidized-bed reactor–regenerator system. This allows for continuous mode operation and greatly simplifies the control procedures. To illustrate some aspects related to the steady-state operation of such a dual system, a simplified mathematical model of two interconnected fluidized beds operating in the bubbling regime was developed. A generic reversible chemical reaction of the overall second-order, catalyzed by bifunctional pellets, integrating catalytic active sites and adsorption sites, was considered as a test case. The model was used to study the effects of the bed hydrodynamics, as well as of the chemical reaction and physical adsorption equilibrium constants. It was shown how the superposition of various chemical, physical and hydrodynamical phenomena affects the performance of the system.

Multiphase carbon mineralization for the reactive separation of CO2 and directed synthesis of H2

There is a need to capture, convert and store CO₂ by atom-efficient and energy-efficient pathways that use as few process configurations as possible. This need has motivated studies into multiphase reaction chemistries and this Review describes two such approaches in the context of carbon mineralization. The first approach uses aqueous alkaline solutions containing amine nucleophiles that capture CO₂ and eventually convert it into calcium and magnesium carbonates, thereby regenerating the nucleophiles. Gas-liquid-solid and liquid-solid configurations of these reactions are explored. The second approach combines silicates such as CaSiO₃ or Mg₂SiO₄ with CO and H₂O from the water-gas shift reaction to give H₂ and calcium or magnesium carbonates. Coupling carbonate formation to the water-gas shift reaction shifts the latter equilibrium to afford more H₂ as part of a single-step catalytic approach to carbon mineralization. These pathways exploit the vast abundance of alkaline resources, including naturally occurring silicates and alkaline industrial residues. However, simple stoichiometries belie the complex, multiphase nature of the reactions, predictive control of which presents a scientific opportunity and challenge. This Review describes this multiphase chemistry and the knowledge gaps that need to be addressed to achieve 'step-change' advancements in the reactive separation of CO₂ by carbon mineralization.

Theoretical Analysis of Forced Segmented Temperature Gradients in Liquid Chromatography

An equilibrium model is applied to study the effect of forced temperature gradients introduced through heat exchange via specific segments of the wall of a chromatographic column operating with a liquid mobile phase. For illustration of the principle, the column is divided into two segments in such a manner that the first segment is kept at a fixed reference temperature, while the temperature of the second segment can be changed stepwise through fixed heating or cooling over the column wall to modulate the migration speeds of the solute concentration profiles. The method of characteristics is used to obtain the solution trajectories analytically. It is demonstrated that appropriate heating or cooling in the second segment can accelerate or decelerate the specific concentration profiles in order to improve certain performance criteria. The results obtained verify that the proposed analysis is well suited to evaluate the application of forced segmented temperature gradients. The suggested gradient procedure provides the potential to reduce the cycle time and, thus, improving the production rate of the chromatographic separation process compared to conventional isothermal (isocratic) operation.

Modeling and Comparison a Thermally Coupled Reactor of Methane Tri – Reforming and Dehydrogenation of Cyclohexane Reactions for Syngas Production in Both Co- & Counter-Current Modes

The aim of this work is a comparison of different inlets (Co- and Counter-current modes) to feed a thermally coupled reactor (TCR) in producing syngas as a valuable chemical. The novel thermally coupled reactor has been designed as a double pipe reactor where tri-reforming of methane for syngas production has been considered in the exothermic side of fixed bed plug reactor, and dehydrogenation of cyclohexane reaction occur in the endothermic side. The heat generated in the exothermic part by the walls of the tube side is transferred to the endothermic section. A steady-state homogeneous one-dimensional model predicts the performance of this reactor for simultaneous production of synthesis gas and benzene in an economical approach for both co- and counter-current modes of operation. The reversed flow of cyclohexane has been considered for the counter-current flow regime. The simulation results of co- and counter-current modes of TCR and also an optimized tri-reforming of methane (OTRM) single reactor are investigated and compared with each other. The results showed that methane conversion, hydrogen yield and ${H_2}/Co$ ratio in the exothermic side of TCR reached to 91.1 %, 1.82 and 2.1 in co-current mode and 87.8 %, 1.77 and 2.3 in counter-current mode, respectively. Additionally, the results showed that cyclohexane conversion at the endothermic side of the reactor in co- and counter-current modes achieved to 98.6 % and 99.9 %, respectively. So, the results for counter-current mode showed superior performance in hydrogen and benzene production in the endothermic side of TCR. Also, Changes in various operating parameters during the reactor have been studied.

Mathematical Modeling and Optimization of Syngas Production Process: A Novel Axial Flow Spherical Packed Bed Tri-Reformer

A recently proposed approach for the production of syngas is Tri-reforming process. Significant preferences of tri-reforming over conventional reformers are high methane conversion in a single unit, in situ heat generation, carbon dioxide consumption and adjustable outlet H2/CO ratio. In this work, a one dimensional mathematical model was developed for a novel axial-flow spherical packed bed tri-reformer. The results of reforming model were compared with the process data obtained from conventional Lurgi-steam reformer (CSR). Effects of feed flow rate, inlet temperature and length per radius (L/R) of the reactor on outlet hydrogen yield, methane conversion and H2/CO ratio were also studied. To maximize the outlet hydrogen yield, operation conditions and L/R ratio of the reactor were optimized applying differential evolution (DE) method. Obtained results were then compared with non-optimized condition. High methane conversion (99.68 %), high hydrogen yield (1.896) and much lower pressure drop were the superiorities of the presented reactor to the previous configurations.

Factorial design analysis of parameters for the sorption-enhanced steam reforming of ethanol in a circulating fluidized bed riser using CFD

The sorption-enhanced steam reforming of ethanol (SESRE) has recently been reported as a novel process for hydrogen (H₂) production.

Progress on sorption-enhanced reaction process for hydrogen production

Concerns about the environment and fossil fuel depletion led to the concept of “hydrogen economy”, where hydrogen is used as an energy carrier. Nowadays, hydrogen is mostly produced from fossil fuel resources by natural gas reforming, coal gasification, as well as the water-gas-shift (WGS) reaction involved in these processes. Alternatively, bioethanol, glucose, glycerol, bio-oil, and other renewable biomass-derived feedstocks can also be employed for hydrogen production via steam reforming process. The combination of steam reforming and/or WGS reaction with

Modelling of the Membrane Permeability Effect on the H2 Production Using CFD Method

Autothermal reforming of CH4 in a membrane catalytic microreactor for the production of hydrogen at different temperatures over supported Ni catalysts has been studied. A three-dimensional mathematical model was developed using a computational fluid dynamics (CFD) technique. The effect of using different membranes on the performance of the micro-reactor was analysed. The amounts of hydrogen produced and separated in each case, under the same operating conditions, were compared. It was proven that using the porous membrane (Ni–Al2O3) could be an economic solution for the production and separation of hydrogen in membrane reactors.