Showing papers on "Substitute natural gas published in 2016"

Storing renewables in the gas network: modelling of power-to-gas seasonal storage flexibility in low-carbon power systems

Abstract: The power-to-gas (P2G) process, whereby excess renewable electrical energy is used to form hydrogen and/or synthetic natural gas (NG) that are injected, transported, and stored in the gas network, has the prospect to become an important flexibility option for the seasonal storage of low-carbon electricity. This study is the first to model and assess the potential of P2G when combined with gas seasonal storage operation accounting for the two networks' characteristics and constraints (including the amount of hydrogen that can be blended with NG under different gas network conditions). Power system operation with P2G is analysed via a two-stage optimisation based on DC power flow to assess the gas production from otherwise curtailed renewables, also considering impact of P2G on short-term and long-term gas prices. Additionally, impact of P2G on gas network operation and its potentially required re-dispatch are evaluated with a steady-state gas flow model. Case studies conducted on the Great Britain gas and electrical transmission networks quantify benefits and limitations of the integrated usage of P2G with seasonal gas storage under different scenarios. The proposed model thus sets the fundamentals for further development of this emerging technology as a seasonal storage option in low-carbon power systems.

Chemical Methanation of CO2: A Review

Abstract: The chemical methanation of CO2 may become a ubiquitous process for the production of renewable substitute natural gas from any CO2 source coupled with renewable hydrogen. The produced gas can be fed into the natural gas pipeline or used as fuel. Over the past few years, great efforts have been made in developing the process of CO2 methanation. In this paper, the chemical methanation, which is the most common process, is reviewed. The purpose is to present a comprehensive updated review of the process. The CO2 methanation, covering the process mechanisms, thermodynamics, catalysts, kinetics, and reactors are discussed with the aim to outline the pathways for the future development of the methanation process.

The BioSCWG Project: Understanding the Trade-Offs in the Process and Thermal Design of Hydrogen and Synthetic Natural Gas Production

Abstract: This article presents a summary of the main findings from a collaborative research project between Aalto University in Finland and partner universities. A comparative process synthesis, modelling and thermal assessment was conducted for the production of Bio-synthetic natural gas (SNG) and hydrogen from supercritical water refining of a lipid extracted algae feedstock integrated with onsite heat and power generation. The developed reactor models for product gas composition, yield and thermal demand were validated and showed conformity with reported experimental results, and the balance of plant units were designed based on established technologies or state-of-the-art pilot operations. The poly-generative cases illustrated the thermo-chemical constraints and design trade-offs presented by key process parameters such as plant organic throughput, supercritical water refining temperature, nature of desirable coproducts, downstream indirect production and heat recovery scenarios. The evaluated cases favoring hydrogen production at 5 wt. % solid content and 600 °C conversion temperature allowed higher gross syngas and CHP production. However, mainly due to the higher utility demands the net syngas production remained lower compared to the cases favoring BioSNG production. The latter case, at 450 °C reactor temperature, 18 wt. % solid content and presence of downstream indirect production recorded 66.5%, 66.2% and 57.2% energetic, fuel-equivalent and exergetic efficiencies respectively.

Life Cycle Assessment of Power-to-Gas: Syngas vs Methane

Abstract: Power-to-Gas enables the integration of renewable electricity and carbon into the chemical industry. The electricity is used to produce hydrogen, which is subsequently converted with CO2 as the renewable carbon source. The resulting products can be used as feedstock for the chemical industry replacing current fossil-based feedstock. Because the integration of renewable electricity and carbon into the chemical industry is mainly environmentally motivated, we identify the conditions under which Power-to-Gas pathways are environmentally beneficial. The conditions are expressed as environmental threshold values for electricity supply. The threshold values are derived by a comparative life cycle assessment (LCA) of Power-to-Gas pathways to fossil-based processes. We analyze Power-to-Gas pathways to synthetic natural gas (Power-to-SNG) and to syngas (Power-to-Syngas). SNG is produced by the Sabatier reaction; syngas by reverse water gas shift (rWGS) and dry reforming of methane (DRM). The threshold values for e...

CO2 methanation over a Ni based ordered mesoporous catalyst for the production of synthetic natural gas

Abstract: Ni based catalysts have been considered as ideal candidates for the CO2 methanation reaction to generate synthetic natural gas owing to its high activity and low cost. In the present manuscript, we described a kind of ordered mesoporous NiO–Al2O3 composite metal oxide, fabricated by a one-step evaporation induced self-assembly (EISA) strategy, which was utilized as the catalyst for CO2 methanation. The obtained material was characterized by XRD, N2 adsorption–desorption, TEM-EDS, H2-TPR, and XPS techniques. The mesoporous catalyst with a large specific surface area (232.8 m2 g−1), big pore volume (0.43 cm3 g−1), tunable pore diameter (9.5 nm), strong metal–mesoporous framework interaction, and outstanding thermal stability (up to 800 °C) had a better catalytic performance than traditional non-mesoporous and supported reference catalysts. The ordered interconnected mesoporous network was beneficial to the mass diffusion of the gaseous reactants and enhanced the catalytic performance by providing sufficient accessible metallic active centers for the gaseous reactants. Besides, the Ni metallic nanoparticles could be stabilized via the space confinement effect of the mesoporous framework, finally reinforcing the catalytic stability. Generally, the presently reported ordered mesoporous NiO–Al2O3 composite oxide promises to be a potential catalyst candidate for CO2 methanation.

Metal-foam-structured Ni–Al2O3 catalysts: Wet chemical etching preparation and syngas methanation performance

Abstract: Production of substitute natural gas (SNG) by methanation of syngas generated from various carbon sources provides a promising route towards coal clean utilization and sustainable energy future. Monolithic Ni (or Cu, NiCu-alloy)-foam-structured Ni–Al2O3 catalysts were developed by a facile modified wet chemical etching method. The as-prepared catalysts were characterized by X-ray diffraction, scanning electron microscopy, inductively coupled plasma atomic emission spectrometry and H2-temperature programmed reduction. Among these catalysts, Ni–Al2O3/Ni-foam has the most surface active Ni atoms and exhibits the best catalytic methanation performance, achieving 99.9% CO conversion with 90.0% methane selectivity and being stable for at least 1000 h for a feed gas of H2/CO (3/1) at 330 °C and gas hourly space velocity (GHSV) of 5000 h−1. Effects of reaction temperature, reaction pressure and GHSV are also investigated on the catalytic performance of Ni–Al2O3/Ni-foam for CO methanation. Computational fluid dynamics calculation and experimental measurement consistently show that such monolithic Ni–Al2O3/Ni-foam can dramatically reduce the “hotspot” temperature due to its high thermal conductivity. Moreover, the feasibility of our Ni–Al2O3/Ni-foam catalyst for co-methanation of a simulated feed gas from coal gasification is studied as well as CO2 methanation in the presence of high CH4 concentration. We anticipate that our present work might stimulate commercial exploitation of the new-generation structured catalyst and reactor technology for the strongly exothermic syngas methanation toward energy-efficient process for SNG production.

Kinetic studies of CO2 methanation over a Ni/γ-Al2O3 catalyst.

Abstract: The production of methane by reacting CO2 with H2 (CO2 methanation) has the potential for producing synthetic natural gas, which could be exported using the existing infrastructure for the distribution of natural gas. The methanation of CO2 was investigated over a wide range of partial pressures of products and reactants using (i) a gradientless, spinning-basket reactor operated in batch mode and (ii) a laboratory-scale packed bed reactor operated continuously. The rate and selectivity of CO2 methanation, using a 12 wt% Ni/γ-Al2O3 catalyst, were explored at temperatures 445–497 K and pressures up to 20 bar. Research with the batch reactor showed that the rate increased with increasing partial pressures of H2 and CO2 when the partial pressures of these reactants were low; however, the rate of reaction was found to be insensitive to changes in the partial pressures of H2 and CO2 when their partial pressures were high. A convenient method of determining the effect of H2O on the rate of reaction was also developed using the batch reactor and the inhibitory effect of H2O on CO2 methanation was quantified. The kinetic measurements were compared with a mathematical model of the reactor, in which different kinetic expressions were explored. The kinetics of the reaction were found to be consistent with a mechanism in which adsorbed CO2 dissociated to adsorbed CO and O on the surface of the catalyst with the rate-limiting step being the subsequent dissociation of adsorbed CO. The ability of the kinetic expressions to predict the results from the continuous, packed-bed reactor was explored, with some discrepancies discussed.

Synthetic Natural Gas from Coal, Dry Biomass, and Power-to-Gas Applications

Abstract: Due to the increasing integration of stochastic renewable sources like photovoltaics and wind energy into the electricity generation, the demand for balancing the electricity supply and the demand over spatial and temporal distances is increasing. For the future, even the seasonal storage of electricity may be necessary. Here, the production of Synthetic Natural Gas (SNG) from domestic resources such as biomass and coal can play an important role. Moreover, in times where the electricity production from renewables exceeds the actual demand in the electricity grid (a situation that today occasionally is observed in Central Europe and is expected to be more common in future), producing SNG could utilise the excess electricity instead of curtailing photovoltaics or wind turbines.

Slurry phase methanation of carbon monoxide over nanosized Ni–Al2O3 catalysts prepared by microwave-assisted solution combustion

Abstract: The clean transformation of coal into natural gas is an interesting topic in green chemistry, as well as a promising process for the production of natural gas. In the present work, the methanation of CO was performed in a slurry-bed reactor with a series of nanosized Ni–Al2O3 catalysts prepared by microwave-assisted solution combustion with different fuels (urea, glycine, ethylene glycol and citric acid). As compared with other fuels, a majority of urea and nitrates simultaneously decompose and occur in extensive overlapped temperature ranges during heating, which is conducive to the formation of a moderate and sustained combustion reaction. In addition, the thermodynamic calculation and thermogravimetric analysis indicate that the amount of heat generated during combustion is the minimum when urea was used as fuel. By the formation of a stable combustion and a relative low combustion temperature, the NiAl-U catalyst exhibits the largest BET area and metal surface area, the smallest Ni particle size and more dispersive Ni species, as evidenced by XRD, TEM, N2 adsorption–desorption, H2-TPR and H2 pulse chemisorption characterizations. In the slurry methanation of CO, the conversion of CO and selectivity for CH4 over NiAl-U catalyst reach up to 95.7% and 96.2% at 300 °C, 1.0 MPa and 3000 mL/gcat h, respectively, which are superior to those of other combustion-synthesized catalysts and commercial catalyst. In addition, The NiAl-U catalyst exhibits significant improvement in anti-sintering during 200 h lifetime test, mainly because of smaller Ni particle size, high dispersity of Ni active species on support and high stability of support. The findings presented here are expected to provide new approaches for rational design of nanosized Ni–Al2O3 catalysts for CO methanation reactions in slurry phase.

A novel salt separator for the supercritical water gasification of biomass

Abstract: The production of synthetic natural gas (SNG) via supercritical water (or hydrothermal) gasification (SCWG or HTG) offers the possibility to exploit the energetic content of biomass with a high water content. Separation and recovery of inorganic constituents present in the feed stream is crucial, as these constituents can lead to blocking of the plant, and to fouling and poisoning of the gasification catalyst. In addition, the recovery of salts offers the potential of producing a fertilizer as a valuable by-product. A new salt separator design for the SCWG process was tested with two different setups using model solutions with water/2-propanol/Na2SO4/K2SO4. The separation and recovery efficiency proved to be superior compared to the previously used salt separator. The sulfur recovery increased by a factor of 3.5–7 and the sulfur accumulation decreased by a factor of 2–10 using the novel design.

Flexible Operation of Fixed-Bed Reactors for a Catalytic Fuel Synthesis—CO2 Hydrogenation as Example Reaction

Abstract: It may become attractive in the future to operate fuel-related chemical reactions, with H2 as reactant, under flexible load conditions when H2 is produced through H2O electrolysis using fluctuating renewable energy. In this way, the size of the H2 storage device connected to the electrolysis cell can be reduced and, consequently, its investment costs. The design of a flexible reactor depends on the characteristics of the catalyst and the chemical reaction. CO2 hydrogenation over Fe catalysts to short-chain hydrocarbons, which can be used to adjust the heating value of substitute natural gas, is investigated as example reaction. A specific reactor design for flexible operation with gas recycling is a consequence of the constraints resulting from product partial pressures and reaction temperature. The experimental and mathematical methods developed can be applied to other fuel-synthesis processes.

Advances in the biological treatment of coal for synthetic natural gas and chemicals

Abstract: Coal, the most primitive fossil fuel, has been exploited for ages, and reserves dictate the economies of many countries. Presently, most energy is generated by direct combustion, raising concerns over global warming. Biological pretreatment of fossil resources and generation of alternative green energy can address the environmental issues associated with global coal utilization. Biological coal treatment can produce industrially important chemicals and bio-methane by employing microorganisms able to depolymerize/degrade coal. This review discusses current advances in microbial coal conversion, such as the efforts made to comprehend microbial processes, significant outputs of coal conversion, principle components responsible for coal conversion, and factors affecting the biological processes to convert coal. Development of these biological processes can be a stepping stone for greener coal; however, integration of multidisciplinary technologies is needed to increase the efficiency of economic coal utilization and production of economically and industrially feasible biomethane.

Method and device for producing synthetic natural gas

Abstract: The invention provides a method and device for producing synthetic natural gas The method comprises the continuous technological process that coal or a biomass gasification product is taken as raw materials to produce methane-rich gas containing methane with the mole percent of 94% or above, and the specific technological process comprises the following steps that feed gas (or synthetic gas) is divided into two streams after being preheated, wherein the first-stream feed gas is mixed with recycle gas, and then the mixed gas enters a first methanation reactor segment to be subjected to a reaction to prepare first-segment product gas; the second-stream feed gas is mixed with the cooled first-segment product gas, and then the mixed gas enters a second methanation reactor segment to be subjected to a reaction to prepare second-segment product gas; the prepared second-segment product gas is divided into two streams after being cooled, the first-stream second-segment product gas serves as the recycle gas and then enters the first methanation reactor segment after being pressurized through a recycle compressor, and the second-stream second-segment product gas enters a third methanation reactor segment to be subjected to a reaction to prepare third-segment product gas; the product gas is obtained after gas-liquid separation is performed on the third-segment product gas

V-promoted Ni/Al2O3 catalyst for synthetic natural gas (SNG) production: Catalyst preparation methodologies

Abstract: The effect of preparation method on the catalytic performance of V-promoted Ni/Al2O3 catalysts for synthetic natural gas (SNG) production via CO methanation has been investigated. The Ni-V/Al2O3 catalysts were prepared by co-impregnation (CI) method, deposition precipitation (DP) method as well as two sequential impregnation (SI) methods with different impregnation sequence. Among the prepared catalysts, the one prepared by CI method exhibited the best catalytic performance due to its largest H2 uptake and highest metallic Ni dispersion. In a 91h-lifetime test, this catalyst showed high stability at high temperature and weight hourly space velocity. This work demonstrates that the catalytic performance of the V-promoted Ni/Al2O3 catalysts can be improved by carefully controlling the preparation method/conditions.

Production of Synthetic Natural Gas from Refuse-Derived Fuel Gasification for Use in a Polygeneration District Heating and Cooling System

Abstract: Nowadays conventional district heating and cooling (DHC) systems face the challenge of reducing fossil fuel dependency while maintaining profitability. To address these issues, this study examines ...