Showing papers on "Substitute natural gas published in 2018"

Biofuels production by biomass gasification: A review

Abstract: The production of biofuels from renewable sources is a major challenge in research. Methanol, ethanol, dimethyl ether (DME), synthetic natural gas (SNG), and hydrogen can be produced from syngas which is the result of the gasification of biomasses. Syngas composition varies according to the gasification technology used (such as fixed bed reactors, fluidized bed reactors, entrained flow reactors), the feedstock characteristics, and the operating parameters. This paper presents a review of the predominant biomass gasification technologies and biofuels obtained from syngas by biomass gasification.

Steam gasification of biomass in dual fluidized bed gasifiers: A review

Abstract: Indirect or allothermal gasification of biomass in dual fluidized bed (DFB) gasifiers such as the Gussing gasifier or the biomass heatpipe reformer becomes particularly attractive for the conversion of biomass into hydrogen or any second generation fuel such as substitute natural gas (SNG), methanol or Fischer-Tropsch diesel fuel. Interconnected and indirectly heated DFB gasifiers produce syngas with H2/CO ratios of 2–3 and hydrogen concentrations even above 50 vol%(dry basis). Fluidized bed particles, the operating pressure, solids circulation rate and heat transfer coefficients determine the layout of these gasifiers. This article summarizes the state of the art with respect to layout and dimensioning of DFB gasifiers and reviews the impact of the steam equivalence ratio, fuel and bed material properties, char conversion, and combustion efficiency on cold gas efficiency and syngas quality of DFB gasifiers.

Optimal Day-Ahead Scheduling of Power-to-Gas Energy Storage and Gas Load Management in Wholesale Electricity and Gas Markets

Abstract: Power-to-gas (PtG) energy storage converts electricity to hydrogen or synthetic natural gas. The gas produced is stored and converted back to electricity at a later time; or it is directly used to supply a gas load and/or sell in the gas market. In the first case, due to double energy conversion in a relatively less efficient process, a large portion of the energy is wasted. The latter case is examined in this paper, where PtG storage is optimally scheduled to convert waste/inexpensive electricity to synthetic natural gas for some useful operations at appropriate time periods. To that end, a new model is proposed for optimal day-ahead scheduling of PtG storage and gas load management in electricity and gas markets to minimize the cost of gas consumption for the gas load. A gas demand forecasting algorithm is integrated into the scheduling model. Reserve provision is formulated as part of the optimization problem to optimally manage the gas load in case of an outage in the gas grid. The application of the proposed model to a test case is examined, and the results are studied.

Power-to-Gas through High Temperature Electrolysis and Carbon Dioxide Methanation: Reactor Design and Process Modeling

Abstract: This work deals with the coupling between high temperature steam electrolysis using solid oxide cells (SOEC) and carbon dioxide methanation to produce a synthetic natural gas (SNG) directly injecta...

Parametric, cyclic aging and characterization studies for CO2 capture from flue gas and catalytic conversion to synthetic natural gas using a dual functional material (DFM)

Abstract: Solid sorbents have attracted extensive research attention for enhanced adsorption of effluent CO2. A Dual Functional Material (DFM), composed of a CO2 adsorbent (“Na2O” derived from hydrogenated Na2CO3) in combination with Ru both supported on the same Al2O3, overcome limitations of traditional sorbent technology. It captures CO2 from a simulated flue gas and catalytically converts it to synthetic natural gas (CH4) in the same reactor and temperature utilizing H2 generated from renewable sources. The methane produced is recycled to the plant inlet for repeated combustion maintaining a closed carbon loop. The process is envisioned to operate with parallel reactors, containing DFM, where one captures CO2 and the other methanates and vis versa for continuous operation. We report parametric, cyclic aging and characterization studies in a simulated natural gas power plant flue gas using 10 g of 5 mm × 5 mm tablet DFM. This material shows stable CO2 capture and conversion to CH4 performance for over 50 adsorption and conversion aging cycles (equivalent to 80 h of operation) with no loss in BET surface area, CO2 capture capacity nor Ru dispersion.

Start-up Time and Load Range for the Methanation of Carbon Dioxide in a Fixed-Bed Recycle Reactor

Abstract: Fluctuating wind and solar energy can be used to produce hydrogen by water electrolysis and subsequently for the synthetic natural gas production via methanation in the power-to-gas process. This p...

Scale-Up of Innovative Honeycomb Reactors for Power-to-Gas Applications – The Project Store&Go

Abstract: The German ‘‘Energiewende’’ is heavily based on electric power and, therefore, requests solutions to serve non-electric energy uses and to store electric energy in large scale Synthetic natural gas (SNG) produced with hydrogen from water electrolysis and with CO2 from mainly renewable sources is one approach For the catalytic SNG production efficient removal and utilization of the reaction heat is the main issue A metallic honeycomb-like carrier-based reactor proved in laboratory scale to match this challenge This type of reactor shows good heat conductivity and enables optimized operation In the EU-funded project Store&Go the honeycomb methanation is scaled up to MW-scale For this, heat transfer and kinetic data were determined experimentally and used in CFD calculations for the reactor design Finally a SNG plant with 1MW feed-in will be built and fully integrated operation will be shown

CO2 conversion to synthetic natural gas: Reactor design over Ni–Ce/Al2O3 catalyst

Abstract: Within the Power-to-Gas concept, the catalytic conversion of renewable hydrogen and carbon dioxide to methane for injection to the gas grid has recently attracted much attention. In the present work, the implementation of a nickel–ceria–alumina catalyst on a multitubular reactor for CO2 methanation was studied. The reaction kinetics were experimentally obtained and considered for a CFD model by means of Ansys® Fluent software, to evaluate the behaviour of a multitubular heat-exchange reactor. The simulations showed that most reaction occurs at the beginning of the reactor tube and the temperature raises rapidly. At the kinetic regime zone, a proper control of the temperature is required to avoid excessive hot-spots. In contrast, the final reactor volume is mainly controlled by the reaction thermodynamics. In this zone, the reaction is shifted toward products by using a cooling medium at low temperature. The effect of several design variables on the final methane yield and on the temperature profile was carried out, and finally, a reactor able to convert the CO2 present in the biogas to synthetic natural gas is proposed. The modelling showed that the proposed reactor tube (di = 9 mm and L = 250 mm) should be able to obtain a high methane content (>95%), at high GHSV (14,400 h−1), and keeping the hot-spots at minimum (Δ100 K). Within this reactor design approach, almost 1000 of tubes are necessary for the methanation of a medium-size biogas plant.

Equilibrium and kinetic aspects for catalytic methanation focusing on CO2 derived Substitute Natural Gas (SNG)

Abstract: The production of Substitute Natural Gas (SNG) can be a key component of indigenous energy supply towards a low carbon future. In the present work, state of the art catalytic processes for SNG production based on CO and CO2 methanation are presented. Equilibrium based simulations are performed for both CO and CO2 methanation in order to define the optimum process parameters. A special focus is given on SNG derived from CO2 and hydrogen via power to gas process, which combines energy storage, Carbon Capture and Utilisation (CCU) with SNG production. Three kinetic models for CO2 methanation at 10 atm, 17 atm and 20 atm from the literature are compared. The quality of SNG produced is evaluated depending on the different operating pressure and temperature of CO2 derived SNG process. Low pressure bulk methanation (

An Al2O3-Coated SiC-Supported Ni Catalyst with Enhanced Activity and Improved Stability for Production of Synthetic Natural Gas

Abstract: An Al2O3-coated SiC, Al2O3@SiC, was designed via the evaporation-induced self-assembly method to serve as a composite support for Ni catalysts in synthetic natural gas (SNG) production through carbon monoxide (CO) methanation. Scanning electron microscopy images of the Al2O3@SiC composite showed that the SiC surface was coated by an Al2O3 layer homogeneously. The Ni/Al2O3@SiC catalyst exhibited excellent initial activity and superior long-term stability in CO methanation. The structural characterizations revealed that the high activity of the Ni/Al2O3@SiC catalyst was mainly due to the small size of Ni nanoparticles and the mesoporous structure of Al2O3 layers coated on SiC surface. The superior stability of the Ni/Al2O3@SiC catalyst was rationalized by the enhanced anticoke and antisintering properties. The present work will provide guidelines in the synthesis of highly efficient composite catalysts for SNG production.

CO hydrogenation combined with water-gas-shift reaction for synthetic natural gas production: a thermodynamic and experimental study

Abstract: The hydrogenation of CO to synthetic natural gas (SNG) needs a high molar ratio of H2/CO (usually large than 3.0 in industry), which consumes a large abundant of hydrogen. The reverse dry reforming reaction (RDR, 2H2 + 2CO ↔ CH4 + CO2), combining CO methanation with water-gas-shift reaction, can significantly decrease the H2/CO molar ratio to 1 for SNG production. A detailed thermodynamic analysis of RDR reaction was carried out based on the Gibbs free energy minimization method. The effect of temperature, pressure, H2/CO ratio and the addition of H2O, CH4, CO2, O2 and C2H4 into the feed gas on CO conversion, CH4 and CO2 selectivity, as well as CH4 and carbon yield, are discussed. Experimental results obtained on homemade impregnated Ni/Al2O3 catalyst are compared with the calculations. The results demonstrate that low temperature (200–500 °C), high pressure (1–5 MPa) and high H2/CO ratio (at least 1) promote CO conversion and CH4 selectivity and decrease carbon yield. Steam and CO2 in the feed gas decrease the CH4 selectivity and carbon yield, and enhance the CO2 content. Extra CH4 elevates the CH4 content in the products, but leads to more carbon formation at high temperatures. O2 significantly decreases the CH4 selectivity and C2H4 results in the generation of carbon.

Relative Greenhouse Gas Abatement Cost Competitiveness of Biofuels in Germany

Abstract: Transport biofuels derived from biogenic material are used for substituting fossil fuels, thereby abating greenhouse gas (GHG) emissions. Numerous competing conversion options exist to produce biofuels, with differing GHG emissions and costs. In this paper, the analysis and modeling of the long-term development of GHG abatement and relative GHG abatement cost competitiveness between crop-based biofuels in Germany are carried out. Presently dominant conventional biofuels and advanced liquid biofuels were found not to be competitive compared to the substantially higher yielding options available: sugar beet-based ethanol for the short- to medium-term least-cost option and substitute natural gas (SNG) for the medium to long term. The competitiveness of SNG was found to depend highly on the emissions development of the power mix. Silage maize-based biomethane was found competitive on a land area basis, but not on an energetic basis. Due to land limitations, as well as cost and GHG uncertainty, a stronger focus on the land use of crop-based biofuels should be laid out in policy.

Simultaneous Tar Reforming and Syngas Methanation for Bio-Substitute Natural Gas

Abstract: Biomass steam gasification in a free-fall reactor followed by the as-produced biogenous syngas upgrading over Ni/olivine and Ni/olivine+CaO in a countercurrent moving bed reactor was performed in this study. In the newly developed moving bed configuration, the tar in the syngas was steam reformed and simultaneously the syngas was methanated. As a preliminary part of this research, the influences of tar on syngas methanation at different temperatures and H2O contents were studied as well in a fixed-bed reactor with toluene as a model tar compound. It was found that the carbon deposition behavior was greatly affected by the reaction conditions. During raw biogenous syngas upgrading over Ni/olivine in the countercurrent moving bed upgrading reactor, both CH4-rich gas production and tar elimination with good resistance toward carbon deposition were achieved. With the introduction of CO2 sorbent into the upgrading reactor further, CH4/H2 mixture was achieved.

Upscaling Effects on Char Conversion in Dual Fluidized Bed Gasification

Abstract: Dual fluidized bed gasification (DFBG) is an emerging technology that can be employed as a first step in the transformation of lignocellulosic materials into transportation fuels such as substitute natural gas, dimethyl ether, methanol, and Fischer-Tropsch diesel. The present work aims at (i) identifying challenges that arise in the upscaling of DFBG plants, (ii) determining whether the increased fuel residence time that results from the upscaling is sufficient for process optimization, and (iii) evaluating the impact of measures to mechanically control the fuel residence time. The investigations use a semiempirical 1-dimensional model, which is validated with industrial-scale measurements. The scope includes both DFBG units delivering gas as the main product and those in which the product gas is a byproduct in a heat and power plant. Moreover, both new designs and retrofit cases of existing CFB combustion plants (i.e., adding a gasifier to the return leg) are considered. Modeling results show that although there is an initial increase in the fuel residence time as the size of the gasifier increases, further upscaling eventually leads to a decrease in the degree of char gasification due to (i) a decrease in the fuel residence time, as there is a transition in lateral fuel mixing from the dispersion-dominant regime to the convection-dominant regime; and (ii) a decrease in the char gasification rate due to an increased bed material velocity, which increases the probability that pyrolysis occurs on the bed surface (leading to a less reactive char as the heat transfer is lower there compared to inside the dense bed). For DFBG units of around 100 MW, proper combinations of operational conditions (e.g., the solids circulation, the steam-fuel ratio, and the temperature of the circulating solids) result in an optimized process when heat and power is the main product, with gas as a byproduct. However, when gas is the sole targeted product, it is likely that baffles are also necessary to achieve sufficient fuel conversion for process optimization.

Exploring the integration of the power to gas technologies and the sustainable transport

Abstract: The de-carbonization of the transport sector is a particularly complex challenge as greenhouse gases are delocalized and diffused. Therefore, the problem has to be tackled from the source of the emissions, and efforts in the scientific and technological field must seek out new energy vectors of high density, neutral in CO2 and based on renewable energy that meet the sector demands and requisites. This could be the case of the synthetic natural gas which can be produced through the Power to Gas process (PtG). This process, originally developed by the German institutes ZSW and IWES, converts electricity into synthetic natural gas (SNG) via the methanation of CO2 together with H2 from water electrolysis. The energy content of the produced methane comes from the primary source for power generation (optimally renewable electricity) and it is possible to produce a CO2 neutral fuel by capturing the carbon emissions from an existing source. In addition, the PtG process can be seen as a new concept of renewable energy and CO2 hybrid storage. This paper identifies the possibilities that the Power to Gas technology offers for the production of sustainable methane and the existing potential for the symbiosis of industrial sectors through optimization of their waste streams of matter and energy. In particular power and transport sectors are considered and the outline of a small facility for the generation of synthetic natural gas from renewable electricity and its consumption in the vehicles of a road freight company is presented as a case study. Not only the technical feasibility but the economic viability of the process and the environmental improvements resulting from the use of a renewable fuel free of CO2 emissions in terms of carbon footprint are evaluated.