Autothermal Reforming Reactor Research Articles

Effect of pressure and CO2 dilution on soot formation in laminar inverse coflow flame at conditions close to autothermal reforming

Autothermal reforming (ATR) is an important technology for hydrogen production from natural gas, where soot formation deserves particular attention as it may cause catalyst poisoning. The typical configuration of ATR reactors is that of an inverse diffusion flame (IDF). In this study, soot formation near ATR conditions is investigated experimentally and numerically, focusing on the effects of pressure and CO2 dilution in IDFs with pressure reaching 5 bar. The fuel stream consists of methane diluted with CO2 or N2. The mole fraction of O2 in the oxidant stream is 70%. Polycyclic aromatic hydrocarbons (PAHs) and soot volume fraction are measured by the planar laser-induced fluorescence (PLIF) and planar laser-induced incandesce (PLII) methods. High-fidelity simulations with a detailed soot aerosol model are also performed, and an empirical reactive soot inception model is proposed. A comparison of the results shows that the soot behavior is well predicted by the empirical reactive inception model but not fully captured by the physical inception model based on irreversible dimerization, demonstrating the importance of radical involvement in the soot inception process. Both measurements and predictions show a linear relationship between peak soot volume fraction and pressure, which can be explained by the linear increase of PAH molar concentration with pressure. Simulation analysis indicates that the dimer adsorption and HACA mechanism have a similar quantitative contribution to the soot growth. The CO2 shows stronger suppression effects in soot formation at the investigated pressures compared to N2. The contributions of chemical and thermal effects to soot suppression are numerically analyzed and the results indicate that the chemical effect of CO2 is mainly due to the removal of H radicals through the reaction CO2 + H→CO + OH, providing a soot suppression contribution of two times larger compared to the thermal one.

Thermal Self-Sufficient Operation of Hydrogen Production from Used Vegetable Oil

This work aims to investigate the hydrogen production from used palm oil and used soybean oil through autothermal reforming (ATR). Thermodynamics analysis of this process was performed by using Aspen plus V9 simulation software. The gas compositions at equilibrium were calculated by using the Gibbs free energy minimization method. The hydrogen production process was composed of ATR reactor, high-temperature water gas shift (HT-WGS), low-temperature water gas shift (LT-WGS) and absorber. Considering the optimal conditions of each unit operation, it was found that the maximum hydrogen production can be provided when ATR reactor was operated at temperature of 580 °C, atmospheric pressure, steam to carbon (S/C) molar ratio of 10 and oxygen to carbon (O/C) molar ratio of 0.1. HT-WGS and LT-WGS reactors should be operated at temperature of 300 °C and 200 °C. For the absorber, the optimal conditions were at 40 atm with 6 kmol/h of MDEA solution at 35 °C. Under these operating conditions, hydrogen can be generated as 2.56 kmol/h or 99.7 mol%. Then, the hydrogen production under thermal self-sufficient operation was studied. The simulation result indicated that the ATR reactor should be operated at temperature of 580 °C and atmospheric pressure with S/C molar ratio of 4.5 and O/C molar ratio of 0.47 to achieve thermal self-sufficient operation. When the ATR reactor was operated under these operating conditions whereas the operating conditions of HT-WGS, LT-WGS and absorber were constant, it was found that hydrogen with molar flow rate of 1.71 kmol/h (99.7 mol%) can be provided.

Hydrogen production and temperature control for DME autothermal reforming process

This study focuses on the control of dimethyl ether (DME) autothermal reforming (ATR) process integrated with proton exchange membrane fuel cells to provide adequate external power for an on-board reformer hydrogen vehicle. ATR reaction was made over Pd–Zn/γ-Al2O3 catalyst, which provides higher selectivity to the hydrogen due to its good oxidation and reforming activities. Catalyst activity was tested experimentally by varying the temperature. The hydrogen volume fraction is close to 45% at the optimal temperature of 400 °C. The objective of the process control scheme was to control the ATR reactor's temperature and the hydrogen production rate. A combination of the feedforward control and the closed-loop control (based on PID control) was applied wherein the DME, and air flow rates were adjusted automatically, and steam was supplied excessively to promote reactions. Due to its good oxidation and reforming activity, it had a high selectivity to hydrogen. The experimental results showed that the volume fraction of hydrogen in the hydrogen-rich gas is close to 45% at the optimum temperature of 400 °C. The control strategy could ensure that the hydrogen production rate changed with the change of fuel cell load and did not affect the temperature of the autothermal reformer. In this way, the stable operation of the reformer was realized, and the fuel cell had a sufficient supply of hydrogen.

Numerical simulation of heat‐pipe and folded reformers for efficient hydrogen production through methane autothermal reforming

In order to intensify the methane autothermal reforming (ATR) process for efficient hydrogen production, novel heat-pipe and the folded reactors were designed and studied by numerical simulations. The reactor performance, such as methane conversion rate, hydrogen yield, and temperature difference between the reactor inlet and outlet, was computed and compared for both traditional tubular reactors and the novel reactors. Under the optimum operating parameters, compared with the tubular reactor, the heat pipe reactor and the folded reactor can help to increase methane conversion rate from 34% to 45% and 50%, while hydrogen productivity from 22.2% to 28.6% and 31.4%, respectively. The performance of the heat pipe reactor depends on the length and position of the heat pipe, while for the folded reactor, thicker intermediate plate with higher thermal conductivity material is more beneficial. Results were compared with previous experiments and could be used as a reference to guide new experimental and theoretical works toward the ultimate goal of designing and optimizing the ATR reactors for hydrogen production in the future.

Exergy analysis of a biomass-based multi-energy system

This paper focuses on a biofuel-based Multi-Energy System generating electricity, heat and hydrogen. The proposed system, that is conceived as refit option for an existing anaerobic digester plant in which the biomass is converted to biogas, consists of: i) a fuel processing unit, ii) a power production unit based on the SOFC (Solid Oxide Fuel Cell) technology, iii) a hydrogen separation, compression and storage unit. The aim of this study is to define the operating conditions that allow optimizing the plant performances by applying the exergy analysis that is an appropriate technique to assess and rank the irreversibility sources in energy processes. Thus, the exergy analysis has been performed for both the overall plant and main plant components and the main contributors to the overall losses have been evaluated. Moreover, the first principle efficiency and the second principle efficiency have been estimated. Results have highlighted that the fuel processor (the Auto-Thermal Reforming reactor) is the main contributor to the global exergy destruction (9.74% of the input biogas exergy). In terms of overall system performance the plant has an exergetic efficiency of 53.1% (it is equal to 37.7% for the H2 production).

Advances in autothermal reformer design

Together with the high-temperature polymer electrolyte fuel cell, the reactor for the autothermal reforming (ATR) of liquid hydrocarbons, such as diesel fuel or kerosene, is the key component of the Jülich fuel cell system in the 5kWe power class. This paper presents some of Jülich’s most recent development in the field of ATR reactors, specifically the ATR 12. ATR 12 is characterized by a new concept for the internal generation of superheated steam as one of the ATR reactants using concentric shells instead of coiled tubing and particularly by the integration of an electric heating wire to enable fast and autonomous start-up. Three different experimental procedures for heating up the ATR 12 are presented and discussed, the most suitable of which enables the start-up of the ATR 12 within approximately 15min. As a consequence, from the system perspective, the bulky start-up burner, which is also difficult to control, along with the corresponding heat exchanger unit, can be dispensed with. Additionally, comprehensive steady-state experiments identify suitable reaction conditions for the operation of the ATR 12.

Process Intensification in Fuel Cell CHP Systems, the ReforCELL Project

This paper reports the findings of a FP7/FCH JU project (ReforCELL) that developed materials (catalysts and membranes) and an advance autothermal membrane reformer for a micro Combined Heat and Power (CHP) system of 5 kWel based on a polymer electrolyte membrane fuel cell (PEMFC). In this project, an active, stable and selective catalyst was developed for the reactions of interest and its production was scaled up to kg scale (TRL5 (TRL: Technology Readiness Level)). Simultaneously, new membranes for gas separation were developed. In particular, dense supported thin palladium-based membranes were developed for hydrogen separation from reactive mixtures. These membranes were successfully scaled up to TRL4 and used in lab-scale reactors for fluidized bed steam methane reforming (SMR) and autothermal reforming (ATR) and in a prototype reactor for ATR. Suitable sealing techniques able to integrate the different membranes in lab-scale and prototype reactors were also developed. The project also addressed the design and optimization of the subcomponents (BoP) for the integration of the membrane reformer to the fuel cell system.

Internal Model Control Design for Autothermal Reforming System

This paper focuses on the control system design for a process of autothermal reforming (ATR) of ethanol. The targeted application is within an on-board fuel processor of ATR operating at the adiabatic reaction temperature for hydrogen production. An internal model control (IMC) method is designed for controlling the adiabatic reaction temperature of ATR reactor by manipulating the input air flow rate. Two strategies of controller design with and without the feed temperature control of the preheater unit are proposed in order to determine the suitable controller system as the surrounding temperature is a major disturbance for cold weather. Theoretical analysis demonstrates that IMC strategy can achieve desired performance. Two loops of control system of the ATR process combined with the feed temperature control can compensate the surrounding temperature better than without the feed temperature control.

Autothermal Reforming of Ethanol for Hydrogen Production: Modeling and Simulation

Autothermal reforming (ATR), which is the combination of endothermic steam reforming and exothermic partial oxidation, is an attractive process to produce hydrogen using for transportation fuel cell because of its moderate size. ATR is considered to be thermally self-sustaining that the external heat source is not required. In order to keep the adiabatic temperature of ATR reactor, the process control strategy needs in understanding the dynamic characteristics of the ATR system. Thus, the modeling and simulation of ATR process for hydrogen production fueled by ethanol is carried out in this work. The open loop responses of the feed and ATR temperatures are simulated by the dynamic models of ATR system. The simulation results showed the predominantly influence of the electrical power of preheater on the feed and ATR temperatures while the air flowrate has an inverse effect on the feed temperature and a direct effect on the ATR temperature. As a result, the match of control loop is very sensible for an effective control strategy in the development of control system design for maintaining the adiabatic temperature of ATR reactor for sustaining the effectiveness of hydrogen production.

Autothermal Reforming of Ethanol for Hydrogen Production: Thermodynamic Analysis

This work presents the autothermal reforming (ATR), or called oxidative steam reforming (OSR), of ethanol for hydrogen production. A thermodynamic analysis of product distribution for ATR from ethanol has been performed by using the method of Gibbs free energy minimization. The effect of steam-to-carbon (S:C) and air-to-carbon (A:C) molar ratios under adiabatic temperature of ATR reactor on chemical equilibrium composition of hydrogen rich stream is investigated. An increase of S:C ratio increases an efficiency of hydrogen production while carbon monoxide formation decreases but, however, more energy consumption for preheating reactants is also needed. An increase of A:C ratio in the range between 0 and 1.75 causes an increase of hydrogen yield but at greater A:C ratio, a decrease of hydrogen production and more water formation can be found. The results of the thermodynamic equilibrium show that the predicted hydrogen composition in the reaction of fuel-water-air system at constant temperature is higher than that obtained from experiment in both the absence and presence of catalysts in the OSR reaction when the temperature is fixed at 700 °C. The predicted carbon monoxide is lower than that obtained from the results of non-catalytic reaction but higher than that attained from the presence of catalyst in process.

Fuel cell feed system based on H2 production by a compact multi-fuel catalytic ATR reactor

Hydrogen fuel cells seem the most viable solution to the pollution reduction and the energy growing demand. Very compact and small size production plant for distribute H2 production may reduce hydrogen transport and storage difficulties. Due to the high reactor compactness and thermal self-sustainability, the auto-thermal reforming (ATR) reaction of gaseous and liquid hydrocarbons can be the optimal solution. Fossil hydrocarbons like methane, gasoline and diesel still remain the favourite feed for catalytic auto-thermal reformer, due to the widespread existing delivery pipelines and the high energy density. Unfortunately, due to the different characteristics of liquid and gaseous fuels, it's very difficult to realize a multi-fuel processor characterized by high performances in terms of thermal efficiency and hydrogen yield, and, up to now, very low number of papers dealing with multi-fuel reformers is present in the literature.In this work, a catalytic reactor for the auto-thermal reforming of gaseous and liquid hydrocarbons was developed. An high pressure feed system, based on the “common rail” technology, was adopted for liquid fuel, allowing the formation of micro-droplets, assuring a very quick liquid fuel vaporization, an uniform mixing with other reactants, avoiding the coke formation, and improving the hydrogen yield and thermal efficiency. A commercial monolith structured catalysts was used and the influence of catalyst configuration was analysed. In order to obtain a total self-sustainable process and a very compact system, a heat exchanger was integrated in the reactor to preheat water and air streams by exploiting the heat from exhaust stream. The process is monitored by following temperatures and compositions along the catalytic bed.Preliminary tests showed high thermal system efficiency, with a good hydrocarbon conversion at different operating conditions. The low start-up times make the system extremely versatile, and suitable for batch operations.

A microreactor modeling, analysis and optimization for methane autothermal reforming in fuel cell applications

Hydrogen production through autothermal reforming (ATR) of hydrocarbons, such as methane, is an attractive option for mobile applications of hydrogen fuel cells. In the present study, a numerical investigation of catalytic autothermal reforming of methane in a surface microreactor is presented. The microreactor is intended for use in a micro-fuel processor device for a low-power PEM fuel cell in a mobile application. A three-dimensional ATR reactor model is developed to simulate the flow and surface reactions in a microchannel of square cross-section. A four-reaction mechanism is implemented to simulate the surface reactions on a Ni/Al2O3 catalyst, and a global mechanism is used to model gas-phase methane oxidation. The governing equations in the model include conservations of mass, momentum, energy and chemical species. The simulation results reveal the dependency of hydrogen yield on space velocity (SV), air/fuel molar ratio (A/F), water/fuel molar ratio (W/F), and the feed gas temperature. The optimum conditions for the highest hydrogen yield were obtained in our simulations as: space velocity of 50,000h−1, A/F of 1.0, W/F of 3.0 and feed gas temperature of 600°C. The carbon monoxide production at these conditions is small enough to make the generated synthesis gas suitable for fuel cell applications after further treatment downstream of the ATR microreactor.

Novel Syngas Production Techniques for GTL-FT Synthesis of Gasoline Using Reverse Flow Catalytic Membrane Reactors

Syngas production plays a key role in gas-to-liquid (GTL) technology. In this feasibility study, existing and new syngas production techniques are compared. As the conventional autothermal reforming reactors (ATR) always consist of extensive heat exchange equipment and air separation units, alternatives are based on integrating these within the reactor design. Reverse flow catalytic membrane reactors (RFCMR) make it possible to perform heat integration within the reactor; integrated air separation is accomplished by incorporating O2 selective membranes. The alternatives show a higher economic potential than the conventional technique. The use of an O2 selective membrane still experiences reliability problems and was therefore not considered. The second part of the study consists of an extended conceptual design of both the conventional design as well as the reactor with integrated heat transfer. The design involved a GTL plant producing 100 000 bbl/day of gasoline. The feasibility of the reversed flow cat...

Numerical Analysis of the Heat and Mass Transfer Characteristics in an Autothermal Methane Reformer

This paper discusses a numerical analysis of the heat and mass transfer characteristics in an autothermal methane reformer. Assuming local thermal equilibrium between the bulk gas and the surface of the catalyst, a one-medium approach for the porous medium analysis was incorporated. Also, the mass transfer between the bulk gas and the catalyst’s surface was neglected due to the relatively low gas velocity. For the catalytic surface reaction, the Langmuir–Hinshelwood model was incorporated in which methane (CH4) is reformed to hydrogen-rich gases by the autothermal reforming (ATR) reaction. Full combustion, steam reforming, water-gas shift, and direct steam reforming reactions were included in the chemical reaction model. Mass, momentum, energy, and species balance equations were simultaneously calculated with the chemical reactions for the multiphysics analysis. By varying the four operating conditions (inlet temperature, oxygen to carbon ratio (OCR), steam to carbon ratio, and gas hourly space velocity (GHSV)), the performance of the ATR reactor was estimated by the numerical calculations. The SR reaction rate was improved by an increased inlet temperature. The reforming efficiency and the fuel conversion reached their maximum values at an OCR of 0.7. When the GHSV was increased, the reforming efficiency increased but the large pressure drop may decrease the system efficiency. From these results, we can estimate the optimal operating conditions for the production of large amounts of hydrogen from methane.

An experimental study of methanol autothermal reformation as a method of producing hydrogen for transportation applications

This study investigates autothermal reforming (ATR) of methanol as a method of producing fuel cell-grade hydrogen for transportation applications. From the previous works in autothermal reformation, it is known that while the steam-to-carbon ratio (S/C) may somewhat affect the efficiency of ATR, the oxygen-to-methanol ratio (O 2/CH 3OH) is a more significant parameter in ATR of higher hydrocarbons. Methanol differs from higher hydrocarbons in that it is reformed at relatively low temperatures and, therefore, may respond to O 2/CH 3OH differently from higher hydrocarbons. According to the past studies, the optimum O 2/CH 3OH for ATR of methanol is equal to 0.23. However, this conclusion is based on models which utilize assumptions that are not necessarily accurate, such as complete fuel conversion and ideal reaction products. This study presents experimental data that shows how the ATR reactor efficiency varies with O 2/CH 3OH. The results from this study may serve as a baseline for future research of autothermal reforming of hydrocarbon fuels as a method of producing hydrogen in transportation applications.

Experimental Investigation of a JP8 Fuel Processor: Autothermal Reformer and CO-Cleanup Train

This paper presents an experimental investigation of a fuel processor consisting of a JP-8 autothermal reforming (ATR) reactor and a surrogate-fed CO-cleanup train. The CO-cleanup train, comprising a water−gas shift (WGS) and two preferential oxidation (PROX) reactors, was tested as an integrated reactor train. A finned-wall ATR reactor was examined for light-off behavior and for steady-state product distribution, upon which the CO-cleanup train was designed. The thermal and chemical transient analysis during catalyst ignition indicated that the fuel undergoes deep oxidation to CO2 and H2O until 80% of the catalyst bed is ignited, followed by a significant rise in synthesis gas production. The WGS and PROX reactors were tested individually with the objective of identifying operating regimes for maximum CO removal. The PROX reactor train, consisting of two identical reactors connected in series, reduced the CO concentration from 1% to less than 6 ppm. The PROX-1 and PROX-2 reactors were compared in order t...

Self-sustained operation of a kWe-class kerosene-reforming processor for solid oxide fuel cells

Abstract In this paper, fuel-processing technologies are developed for application in residential power generation (RPG) in solid oxide fuel cells (SOFCs). Kerosene is selected as the fuel because of its high hydrogen density and because of the established infrastructure that already exists in South Korea. A kerosene fuel processor with two different reaction stages, autothermal reforming (ATR) and adsorptive desulfurization reactions, is developed for SOFC operations. ATR is suited to the reforming of liquid hydrocarbon fuels because oxygen-aided reactions can break the aromatics in the fuel and steam can suppress carbon deposition during the reforming reaction. ATR can also be implemented as a self-sustaining reactor due to the exothermicity of the reaction. The kW e self-sustained kerosene fuel processor, including the desulfurizer, operates for about 250 h in this study. This fuel processor does not require a heat exchanger between the ATR reactor and the desulfurizer or electric equipment for heat supply and fuel or water vaporization because a suitable temperature of the ATR reformate is reached for H 2 S adsorption on the ZnO catalyst beds in desulfurizer. Although the CH 4 concentration in the reformate gas of the fuel processor is higher due to the lower temperature of ATR tail gas, SOFCs can directly use CH 4 as a fuel with the addition of sufficient steam feeds (H 2 O/CH 4 ≥ 1.5), in contrast to low-temperature fuel cells. The reforming efficiency of the fuel processor is about 60%, and the desulfurizer removed H 2 S to a sufficient level to allow for the operation of SOFCs.

Optimization of bio-ethanol autothermal reforming and carbon monoxide removal processes

Experimental investigation of bio-ethanol autothermal reforming (ATR) and water-gas shift (WGS) processes for hydrogen production and regression analysis of the data is performed in the study. The main goal was to obtain regression relations between the most critical dependent variables such as hydrogen, carbon monoxide and methane content in the reformate gas and independent factors such as air-to-fuel ratio (λ), steam-to-carbon ratio (S/C), inlet temperature of reactants into reforming process (TATRin), pressure (p) and temperature (TATR) in the ATR reactor from the experimental data. Purpose of the regression models is to provide optimum values of the process factors that give the maximum amount of hydrogen. The experimental ATR system consisted of an evaporator, an ATR reactor and a one-stage WGS reactor. Empirical relations between hydrogen, carbon monoxide, methane content and the controlling parameters downstream of the ATR reactor are shown in the work. The optimization results show that within the considered range of the process factors the maximum hydrogen concentration of 42 dry vol. % and yield of 3.8 mol mol−1 of ethanol downstream of the ATR reactor can be achieved at S/C = 2.5, λ = 0.20–0.23, p = 0.4 bar, TATRin = 230 °C, TATR = 640 °C.

Equilibrium model validation through the experiments of methanol autothermal reformation

This study investigates autothermal reforming (ATR) of fuel cell-grade methanol as a method for producing hydrogen for transportation applications. From previous work in autothermal reformation, it is clear that while the steam-to-carbon ratio (S/C) may somewhat affect the efficiency of ATR, the oxygen-to-carbon ratio (O 2/CH 3OH) is a more significant parameter in ATR of higher hydrocarbons. According to past studies, the optimum O 2/CH 3OH for ATR of methanol is equal to 0.23. However, this conclusion is based on models which utilize assumptions that are not necessarily accurate. This study presents experimental data that shows how ATR reactor efficiency varies with O 2/CH 3OH. Reactor efficiency data is compared to equilibrium model outputs in order to quantify the effect of O 2/CH 3OH as well as validate the equilibrium model. The results from this study serve as a baseline for future research of autothermal reforming of hydrocarbon fuels as a method for producing hydrogen in real applications.

Multistage two-membrane ATR reactors to improve pure hydrogen production

A plate-type auto-thermal reforming (ATR) reactor with both hydrogen permeable and oxygen permeable membranes has unique characteristics of mass transfer and heat transfer, which have a big effect on the hydrogen production and hydrogen recovery. In order to study the special mass and heat transfer inside the two-membrane ATR reactor, a 2-D reactor model was developed, and a reactor simulation was carried out. In the single-stage two-membrane ATR reactor, the large gradients of temperature and hydrogen concentration indicate the limitation of mass transfer and heat transfer. To improve the mass and heat transfer, multistage reactors are suggested. The simulation results show that the multistage reactors have better mass and heat transfer, a lower rate of oxygen consumption, higher operating temperatures of the H 2 membrane, and a larger driving force for hydrogen permeation, and hence can produce more than three times the amount of pure hydrogen than the single-stage reactor.