Syngas production via plasma photocatalytic reforming of methane with carbon dioxide

Anthropogenic emission of CH₄ and CO₂ contributes for most of global warming. Hence, simultaneous conversion of CH₄ and CO₂ into syngas (dry reforming of methane) can be a promising way to alleviate climate change. In this work, we developed a series of perovskite-type photocatalysts, based on LaFeO₃ with various calcination temperatures to combine with a spark discharge reactor to form a hybrid plasma photocatalysis reactor. The hybrid reactor is applied for dry reforming of methane to investigate the syngas generation rate and to reveal possible interactions between plasma and photocatalyst. Results show that LFO600-packed bed has the best CH₄ and CO₂ conversions and syngas generation efficiency of 53.6%, 40.0% and 18.4 mol/kWh, respectively. The enhancement of syngas generation rate can be attributed to synergies between LFO and plasma. Furthermore, changing calcination temperature of photocatalyst also leads to variable characteristics of photocatalyst and hence plasma photocatalysis performance for syngas production.     

Efficient recovery of syngas from dry methane reforming product by a dual pressure swing adsorption process

In recent years, there has been growing interest in the dry reforming of methane (using CO₂ instead of H₂O) to obtain syngas, due to its economic and environmental advantages. In this reaction, to achieve conversions close to 100%, it is necessary to work at temperatures higher than 1000 °C. However, to attenuate the catalyst deactivation by sintering is convenient to work at lower temperatures, so that normally the syngas (mixture CO + H₂) is obtained mixed with unreacted CO₂ and CH₄. In this work a process has been simulated to recover the syngas from the product of a dry reforming reaction of methane at 700 °C by means of a Dual PSA (Dual Pressure Swing Adsorption) process with heavy reflux using BPL activated carbon as an adsorbent, operating at 25 °C. The process can recover syngas with purity and recovery higher than 99%. Unreacted CO₂ and CH₄ can be recycled to the reactor, leading to effective CO₂ and CH₄ conversions close to 100%. The process specific energy input (SEI) is 4.7 thermal kJ per L (STP) of syngas. The process can also be used to recover the syngas contained in the tail gas of a H₂ purification PSA from SMR-off gas.     

Novel quasi-autothermal hydrogen production process in a fixed-bed using a chemical looping approach: A numerical study

This paper presents a novel quasi-autothermal hydrogen production process. The proposed layout couples a Chemical Looping Combustion (CLC) section and a Steam Methane Reforming (SMR) one. In CLC section, four packed-beds are operated using Ni as oxygen carrier and CH₄ as fuel to continuously produce a hot gaseous mixture of H₂O and CO₂. In SMR section, two fixed-beds filled with Ni-based catalyst convert CH₄ and H₂O into a H₂-rich syngas. Four heat exchangers were employed to recover residual heat content of all the exhaust gas currents. By means of a previously developed 1D numerical model, a dynamic simulation study was carried out to evaluate feasibility of the proposed system in terms of methane conversion (100% circa), hydrogen yield (about 0.65 mol_H2/mol_CH4) and selectivity (about 70%), and syngas ratio (about 2.3 mol_H2/mol_CO). Energetic and environmental analyses of the system performed with respect to conventional steam methane reforming, highlights an energy saving of about 98% and avoided CO₂ emission of about 99%.     

CO2 reforming of methane combined with steam reforming or partial oxidation of methane to syngas over NdCoO3 perovskite-type mixed metal-oxide catalyst

CO₂ reforming with simultaneous steam reforming or partial oxidation of methane to syngas over NdCoO₃ perovskite-type mixed metal oxide catalyst (prereduced by H₂) at different process conditions has been investigated. In the simultaneous CO₂ and steam reforming, the conversion of methane and H₂O and also the H₂/CO product ratio are strongly influenced by the CO₂/H₂O feed-ratio. In the simultaneous CO₂ reforming and partial oxidation of methane, the conversion of methane and CO₂, H₂ selectivity and the net heat of reaction are strongly influenced by the process parameters (viz. temperature, space velocity and relative concentration of O₂ in the feed). In both cases, no carbon deposition on the catalyst was observed. The reduced NdCoO₃ perovskite-type mixed-oxide catalyst (Co dispersed on Nd₂O₃) is a highly promising catalyst for carbon-free CO₂ reforming combined with steam reforming or partial oxidation of methane to syngas.     

Technoeconomic analysis of a methanol plant based on gasification of biomass and electrolysis of water

Methanol production process configurations based on renewable energy sources have been designed. The processes were analyzed in the thermodynamic process simulation tool DNA. The syngas used for the catalytic methanol production was produced by gasification of biomass, electrolysis of water, CO₂ from post-combustion capture and autothermal reforming of natural gas or biogas. Underground gas storage of hydrogen and oxygen was used in connection with the electrolysis to enable the electrolyser to follow the variations in the power produced by renewables. Six plant configurations, each with a different syngas production method, were compared. The plants achieve methanol exergy efficiencies of 59–72%, the best from a configuration incorporating autothermal reforming of biogas and electrolysis of water for syngas production. The different processes in the plants are highly heat integrated, and the low-temperature waste heat is used for district heat production. This results in high total energy efficiencies (∼90%) for the plants. The specific methanol costs for the six plants are in the range 11.8–25.3 €/GJ_exergy. The lowest cost is obtained by a plant using electrolysis of water, gasification of biomass and autothermal reforming of natural gas for syngas production.     

Forging furnace with thermochemical waste-heat recuperation by natural gas reforming: Fuel saving and heat balance

This paper considers thermochemical recuperation (TCR) of waste-heat using natural gas reforming by steam and combustion products. Combustion products contain steam (H₂O), carbon dioxide (CO₂), and ballast nitrogen (N₂). Because endothermic chemical reactions take place, methane steam-dry reforming creates new synthetic fuel that contains valuable combustion components: hydrogen (H₂), carbon monoxide (CO), and unreformed methane (CH₄). There are several advantages to performing TCR in the industrial furnaces: high energy efficiency, high regeneration rate (rate of waste-heat recovery), and low emission of greenhouse gases (CO₂, NO_x). As will be shown, the use of TCR is significantly increasing the efficiency of industrial furnaces – it has been observed that TCR is capable of reducing fuel consumption by nearly 25%. Additionally, increased energy efficiency has a beneficial effect on the environment as it leads to a reduction in greenhouse gas emissions.     

Process design and techno-economic analysis of dual hydrogen and methanol production from plastics using energy integrated system

This study has been dedicated towards the conversion of plastics to methanol and hydrogen. The base design (case 1) represents the conventional design for producing syngas via steam gasification of waste plastics followed by CO₂ and H₂S removal. The syngas then processed in the methanol synthesis reactor to produce methanol, whereas, the remaining unconverted gases are processed in water gas shift reactors to produce hydrogen. On the other hand, an alternative design (case 2) has been also developed with an aim to increase the H₂ and methanol production, which integrates the plastic gasification and the methane reforming units to utilize the high energy stream from gasification unit to heat up the feed stream of reforming unit. Both the cases have been techno-economically compared to evaluate the process feasibility. The comparative analysis revealed that case 2 outperforms the case 1 in terms of both process efficiency and economics.     

Thermodynamic analysis of solar energy use for reforming fuels to hydrogen

In this paper, a method is proposed for reforming fuels to hydrogen using solar energy at distributed locations (industrial sites, residential and commercial buildings fed with natural gas, remote settlements supplied by propane etc). In order to harness solar energy a solar concentrator is used to generate high temperature heat to reform fuels to hydrogen. A typical fuel such as natural gas, propane, methanol, or an atypical fuel such as ammonia or urea can be transported to distributed locations via gas networks or other means. The thermodynamic analysis of the process shows the general reformation reactions for NH₃, CH₄ and C₃H₈ as the input fuel by comparison through operational fuel cost and CO₂ mitigation indices. Through a cost analysis, cost reduction indices show fuel-usage cost reductions of 10.5%, 22.1%, and 22.2% respectively for the reformation of ammonia, methane, and propane. CO₂ mitigation indices show fuel-usage CO₂ mitigations of 22.1% and 22.3% for methane and propane respectively, where ammonia reformation eliminates CO₂ emission at the fuel-usage stage. The option of reforming ammonia is examined in further detail as proposed cycles for solar energy capture are considered. A mismatch of specific heats from the solar dish is observed between incoming and outgoing streams, allowing a power production system to be included for a more complete energy capture. Further investigation revealed the most advantageous system with a direct expansion turbine being considered rather than an external power cycle such as Brayton or Rankine type cycles. Also, an energy efficiency of approximately 93% is achievable within the reformation cycle.     

Hydrogen production and carbon sequestration by steam methane reforming and fracking with carbon dioxide

An opportunity to sequester large amounts of carbon dioxide (CO₂) is made possible because hydraulic fracturing is used to produce most of America's natural gas. CO₂ could be extracted from natural gas and water using steam methane reforming, pressurized to its supercritical phase, and used instead of water to fracture additional hydrocarbon-bearing rock. The useful energy carrier that remains is hydrogen, with carbon returned to the ground. Research on the use of supercritical CO₂ is reviewed, with proppant entrainment identified as the major area where technical advances may be needed. The large potential for greenhouse-gas reduction through sequestration of CO₂ and avoidance of methane leakage from the natural gas system is quantified.     

IR spectroscopic measurement of hydrogen production kinetics in methane dry reforming

Dry reforming of methane (DRM) is a reaction that converts two greenhouse gases, CH₄ and CO₂, to syngas (H₂ + CO). Gas chromatography (GC) is almost exclusively used to evaluate catalyst performance. In order to measure the hydrogen production rate with GC, an inert gas with a constant flow rate is usually fed into the system as an internal standard. In this work, an IR spectroscopy-based method is used to achieve the same technical goal with much higher time resolution and much smaller measurement errors. IR measures the molar fractions of CH₄, CO₂, CO and H₂O in the reaction effluent. By applying general mass balance principle and the relevant reaction stoichiometries, H₂ production rate is successfully measured without an internal standard. The results are quite close to those obtained by GC with much higher time resolution, making it possible to observe fast reaction kinetics.     

Biomass Derived low concentration CO2 mixed Gas Combined Steam to Reform Methane through Ni based volcanic rock catalyst

The utilization of CO₂ has attracted lots of attentions, while the conversion and utilization of common low concentration carbon dioxide has not been widely concerned. Herein, oxygen-free low concentration(<40%) CO₂ mixed gas has been explore in the utilization of methane reforming. the low concentration CO₂ mixed gas, which derived from biomass gasification, combined steam reforming methane route has been proposed and explored in the study. The effect of each key parameters, including CO₂ mixed gas addition, reaction temperature, S/C and WHSV, on the syngas yield were investigated.In the proper condition, an product with H₂/CO ratio around 2 and 97% syngas purity was obtained. Furthermore, since the Ni-modified volcanic rock catalyst showed excellent activity in the reforming reaction, its stability was further confirmed via life test, meanwhile, the other characterizations were observed via XRD, SEM,TEM and BET. the results showed that the catalyst was stable after 24h life experiment with less than 0.15% carbon deposited. Moreover, TEM results revealed that Na and Fe existed in the volcanic rock would gradually migrated to the Ni particle during the reaction, which should be the main mechanism for the improvement of activities and stability of the catalysts. The study provide a new way to utilized the low concentration CO₂ mixed gas.     

Thermodynamic analysis of hydrogen production via sorption-enhanced steam methane reforming in a new class of variable volume batch-membrane reactor

Combined reaction–separation processes are a widely explored method to produce hydrogen from endothermic steam reforming of hydrocarbon feedstock at a reduced reaction temperature and with fewer unit operation steps, both of which are key requirements for energy efficient, distributed hydrogen production. This work introduces a new class of variable volume batch reactors for production of hydrogen from catalytic steam reforming of methane that operates in a cycle similar to that of an internal combustion engine. It incorporates a CO₂ adsorbent and a selectively permeable hydrogen membrane for in situ removal of the two major products of the reversible steam methane reforming reaction. Thermodynamic analysis is employed to define an envelope of ideal reactor performance and to explore the tradeoff between thermal efficiency and hydrogen yield density with respect to critical operating parameters, including sorbent mass, steam to methane ratio and fraction of product gas recycled. Particular attention is paid to contrasting the variable volume batch-membrane reactor approach to a conventional fixed bed reaction–separation approach. The results indicates that the proposed reactor is a viable option for low temperature distributed production of hydrogen from methane, the primary component of natural gas feedstock, motivating a detailed study of reaction/adsorption kinetics and heat/mass transfer effects.     

A novel approach for treatment of CO2 from fossil fired power plants,Part A: The integrated systems ITRPP

The environmental issues, due to the global warming caused by the rising concentration of greenhouse gases in the atmosphere, require new strategies aimed to increase power plants efficiencies and to reduce CO₂ emissions.This two-paper work focuses on a different approach for capture and reduction of CO₂ from flue gases of fossil fired power plant, with respect to conventional post-combustion technologies. This approach consists of flue gases utilization as co-reactants in a catalytic process, the tri-reforming process, to generate a synthesis gas suitable in chemical and energy industries (methanol, DME, etc.). In fact, the further conversion of syngas to a transportation fuel, such as methanol, is an attractive solution to introduce near zero-emission technologies (i.e. fuel cells) in vehicular applications.In this Part A, integrated systems for co-generation of electrical power and synthesis gas useful for methanol production have been defined and their performance has been investigated considering different flue gases compositions. In Part B, in order to verify the environmental advantages and energy suitability of these systems, their comparison with conventional technology for methanol production is carried out.The integrated systems (ITRPP, Integrated Tri-Reforming Power Plant) consist of a power island, based on a thermal power plant, and a methane tri-reforming island in which the power plants' exhausts react with methane to produce a synthesis gas used for methanol synthesis. As power island, a steam turbine power plant fuelled with coal and a gas turbine combined cycle fuelled with natural gas have been considered.The energy and environmental analysis of ITRPP systems (ITRPP-SC and ITRPP-CC) has been carried out by using thermochemical and thermodynamic models which have allowed to calculate the syngas composition, to define the energy and mass balances and to estimate the CO₂ emissions for each ITRPP configuration.The repowering of the base power plants (steam turbine power plant and gas turbine combine cycle) is very high because of the large amount of steam produced in the tri-reforming island (in the ITRPP-SC is about of 64%, while in the ITRPP-CC is about of 105%).The reduction in the CO₂ emissions has been estimated in 83% (15.4 vs. 93.4 kg/GJ_Fuelinput) and 84% (8.9 vs. 56.2 kg/GJ_Fuelinput) for the ITRPP-SC and ITRPP-CC respectively.     

Performance improvement of the proton-conducting solid oxide electrolysis cell coupled with dry methane reforming

The proton-conducting solid oxide electrolysis cell (H-SOEC) is a clean technology for syngas production from H₂O and CO₂ through electrochemical and chemical reactions. However, it provides a low CO₂ conversion and produces a syngas product with a high H₂O content. To improve the H-SOEC for syngas production, H-SOEC coupled with a dry methane reforming process (H-SOEC/DMR) was proposed in this work. The process flowsheet of the H-SOEC/DMR was developed and further used to evaluate the performance of the H-SOEC/DMR process. From the performance analysis of the H-SOEC/DMR process, it was found that the CO₂ and CH₄ conversions were higher than 90% and 80%, respectively, when the process was operated in the temperature range of 1073–1273 K. In addition, the result showed that a syngas product with a low H₂O content could be obtained. Energy efficiency was then considered and the results indicated that the highest energy efficiency of 72.80% could be achieved when the H-SOEC/DMR process was operated at a temperature of 1123 K, pressure of 1 atm, and current density of 2500 A m^?2. Based on a pinch analysis, a heat exchanger network was applied to the H-SOEC/DMR process that improved the energy efficiency to 81.46%. Finally, an exergy analysis was performed and showed that the H-SOEC/DMR unit had the lowest exergy efficiency as a high-temperature exhaust gas was released.     

A review on coke management during dry reforming of methane

The dry (CO₂) reforming of methane is a great promising technology, particularly because of its dual advantages of natural gas valorization and mitigating global warming via carbon dioxide sequestration. However, coke management is the most difficult problem in commercialization of the process. We have therefore examined in this paper the various catalytic systems being evaluated for the dry reforming with emphasis on operating parameters, activity, and coke deposition. Other factors such as the catalyst promoter, the reactor system, and the periodical regeneration were also critically reviewed. The benefits of utilizing methane from natural gas and other sources, where carbon dioxide is considered as an impurity component, are emphasized. Structured basic catalysts, with periodic regeneration certainties, are strong candidates for industrial applications. Therefore, efforts to build commercial scales for the benefit of global energy industries were highlighted. Copyright © 2015 John Wiley & Sons, Ltd.     

Study on hydrogen-rich syngas production by dry autothermal reforming from biomass derived gas

In this study, the H₂-rich syngas (H₂ + CO) production from biomass derived gas (BDG) by dry autothermal reforming (DATR) is investigated. Methane and carbon dioxide is the major composition of biomass derived gas. DATR reaction combined benefits of partial oxidation (POX) and dry reforming (DR) reaction was carried out in this study. The reforming parameters on the conversion of methane and syngas selectivity were explored. The reforming parameters included the fuel feeding rate, CO₂/CH₄ and O₂/CH₄ molar ratios. The experimental results demonstrated that it not only supplied the energy required for self-sustained reaction, but also avoided the coke formation by dry autothermal reforming. It has a wide operation region to maintain the moderate production of the syngas. During the reforming process, the reformate gas temperature was between 650 and 900 °C, and energy loss percentage in reforming process was between 15 and 30%. Further, high CO₂ concentration in the reactant had a considerable influence on the heat release of oxidation, and thereby decreased the reformate gas temperature. It caused the reduction of synthesis gas concentration and assisting/impeding combustion composition (A/I) ratio. However, it was favorable to CO selectivity because of the reverse water-gas shifting reaction. The H₂/CO molar ratio between 1 and 2 was achieved by varying CO₂/CH₄ molar ratio. However, the syngas concentrations were affected by CO₂/CH₄ and O₂/CH₄ molar ratio.     

Gas Switching Reforming for syngas production with iron-based oxygen carrier-the performance under pressurized conditions

A four-stage Gas Switching Reforming for syngas production with integrated CO₂ capture using an iron-based oxygen carrier was investigated in this study. The oxygen carrier was first reduced using dry methane, where high methane conversion rate was achieved producing CO₂ and steam. Following the reduction stage is a transition to syngas production in an intermediate stage that begins with partial oxidation of methane while methane cracking dominates the rest of the stage. This results in substantial carbon deposition that gasifies in a subsequent reforming stage by cofeeding steam and methane, contributing to more syngas yield. Some of the deposited carbon that could not gasify during the reforming stage slip to the oxidation stage and get combusted by oxygen in the air feed to release CO₂, thereby reducing the CO₂ capture efficiency of the process. It is in this oxidation stage that heat is being generated for the whole cycle given the high exothermicity nature of this reaction. Methane conversion was found to drop substantially in the reforming stage as the pressure increases driven by the negative effect of pressure on both carbon gasification by steam and on the steam methane reforming. The intermediate stage (after reduction) was found less sensitive to the pressure in terms of methane conversion, but the mechanism of carbon deposition tends to change from methane cracking in the POX stage to Boudouard reaction in the reforming stage. However, methane cracking shows a tendency to reduce substantially at higher pressures. This is could be a promising result indicating that high-pressure operation would remove the need for the reforming stage with steam as no carbon would have been deposited in the POX stage.     

Microwave-enhanced methane cracking for clean hydrogen production in shale rocks

Steam methane reforming (SMR) generates about 95% of hydrogen (H₂) in the U.S. using natural gas as a main feedstock. However, this technology also generates a large amount of carbon dioxide (CO₂), a major greenhouse gas causing global warming. Carbon capture and storage (CCS) technique is required, but the cost and safety of storing CO₂ underground are a concern. Here we propose a new approach using microwave/electromagnetic irradiation to produce clean hydrogen from unrecovered hydrocarbons within petroleum reservoirs. Solid carbon or CO₂ produced during this process will be simultaneously sequestrated underground without involving CCS. In this paper, we perform a series of experiments to investigate the in-situ hydrogen production from shale gas (methane) conversion by passing a methane stream through a packed shale rock sample heated by microwave. We found that methane conversion was significantly enhanced in the presence of Fe and Fe₃O₄ particles as catalysts, with a conversion of 40.5% and 100% at reaction temperature of 500 °C and 600 °C, respectively. Methane conversion is promoted at a lower reaction temperature by the catalytic effect of minerals in shale. Additionally, the influences of catalysts, shale rock, and methane flow rate are characterized.     

The integration of hybrid hydrogen networks for refinery and synthetic plant of chemicals

Hydrogen is the core source to both refinery and synthetic plant of chemicals. Refinery consumes high purity hydrogen while synthetic plant of chemicals needs syngas consists of hydrogen and carbon oxides. As main hydrogen production technologies, industrial coal gasification and steam methane reforming based pathways generate H₂, CO and CO₂, which is actually the mixture of hydrogen and carbon oxides. Hence, the gases demand of refinery and synthetic plant of chemicals and their supply from hydrogen production can form hybrid hydrogen networks. On the basis of complementary reuse, this paper firstly proposes integration of hybrid hydrogen network for refinery and synthetic plant of chemicals. Superstructures of individual and hybrid hydrogen networks are employed as problem illustration and corresponding linear programming (LP) mathematical models are formulated. Practical refinery and synthetic plant of chemicals cases are employed to demonstrate its application. Compared with individual networks, the natural gas conservation case can recover 8660.4 Nm³·h^-1 hydrogen in purge gas, reduce 1386.6 Nm³·h^-1 CO₂ emission, equaling to reduction of 278.11 kmol·h^-1 natural gas feedstock and 14.8% of total gas production load; the coal conservation case can even waive the total coal consumption and extra 104.1 kmol·h^-1 natural gas, recover 8660.4 Nm³·h^-1 hydrogen in purge gas, reduce 5255.8 Nm³·h^-1 of CO₂ emission and decrease 21.2% of the total gas production load. Furthermore, economic evaluation is also placed to account for the economic advantage of hybrid network.