Showing papers on "Substitute natural gas published in 2014"

A bridge to nowhere: methane emissions and the greenhouse gas footprint of natural gas

Abstract: In April 2011, we published the first peer-reviewed analysis of the greenhouse gas footprint (GHG) of shale gas, concluding that the climate impact of shale gas may be worse than that of other fossil fuels such as coal and oil because of methane emissions. We noted the poor quality of publicly available data to support our analysis and called for further research. Our paper spurred a large increase in research and analysis, including several new studies that have better measured methane emissions from natural gas systems. Here, I review this new research in the context of our 2011 paper and the fifth assessment from the Intergovernmental Panel on Climate Change released in 2013. The best data available now indicate that our estimates of methane emission from both shale gas and conventional natural gas were relatively robust. Using these new, best available data and a 20-year time period for comparing the warming potential of methane to carbon dioxide, the conclusion stands that both shale gas and conventional natural gas have a larger GHG than do coal or oil, for any possible use of natural gas and particularly for the primary uses of residential and commercial heating. The 20-year time period is appropriate because of the urgent need to reduce methane emissions over the coming 15–35 years.

Methanation of CO2 - storage of renewable energy in a gas distribution system

Abstract: This article presents some crucial findings of the joint research project entitled «Storage of electric energy from renewable sources in the natural gas grid-water electrolysis and synthesis of gas components». The project was funded by BMBF and aimed at developing viable concepts for the storage of excess electrical energy from wind and solar power plants. The concept presented in this article suggests the conversion of CO2-containing gases into methane in a pressurized reactor using hydrogen produced via electrolysis. The produced gas can be upgraded to synthetic natural gas (SNG) and fed into the well-developed German natural gas grid. This concept benefits from the high storage capacity of the German gas grid and does not require any extensions of the current gas or power grid. The reaction heat released by the exothermic methanation reaction leads to a temperature rise of the gas in the fixed bed catalyst of the reactor. The conversion of carbon dioxide is limited in accordance to the chemical equilibrium which depends strongly on temperature and pressure. For maximum carbon dioxide conversion, it is convenient to split the methanation into several stages adding cooling sections in between. This article focuses on the methanation process and its transfer onto an industrial scale evaluating the different plant capacities and feedstock mixtures used. The methanation takes place in a staged fixed bed reactor. This staged reactor concept is an in-house development based on know-how from the sulfuric acid production technology.

Biomass gasification for synthesis gas production and applications of the syngas

Abstract: Synthesis gas from biomass can be produced and utilized in different ways. Conversion of biomass to synthesis gas can be done either in fluidized bed or entrained flow reactors. As gasification agent oxygen, steam, or mixtures are used. The most common use of biomass gasification in the last decades has been for heat and/or power production. Nowadays, the importance of transportation fuels from renewables is increased due to environmental aspects and growing fossil fuels prices. That is why the production of Fischer‐Tropsch (FT) liquids, methanol, mixedalcohols,substitutenaturalgas(SNG),andhydrogenfrombiomassisnowin focus of view. The most innovative and interesting ways of synthesis gas utilization andprojects,BioTfueLorGoBiGas,BioLiq,Choren,etc.arediscussedhere.Further the microchannel technology by Oxford Catalysts and distributed production of SNG in decentral small scale are presented. The synthesis platform in G¨ ussing, Austria is also presented. The FT liquids, hydrogen production, mixed alcohols, and BioSNG, these are the projects associated with the FICFB gasification plant in G¨ ussing. Also the principle and examples of sorption-enhanced reforming to adjust H2/CO ratio in product gas during the gasification is described. Finally, in the conclusion also an outlook for the thermochemical pathway to transportation fuels is given. © 2013 John Wiley & Sons, Ltd.

Catalytic and adsorption studies for the hydrogenation of CO2 to methane

Abstract: CO2 methanation has been evaluated as a means of storing intermittent renewable energy in the form of synthetic natural gas. A range of process parameters suitable for the target application (4720 h−1 to 84,000 h−1 and from 160 °C to 320 °C) have been investigated at 1 bar and H2/CO2 = 4 over a 10% Ru/γ-Al2O3 catalyst. Thermodynamic equilibrium was reached at T ≈ 280 °C at a GHSV of 4720 h−1. Cyclic and thermal stability tests specific to a renewable energy storage application have also been conducted. The catalyst showed no sign of deactivation after 8 start-up/shut-down cycles (from 217 °C to RT) and for total time on stream of 72 h, respectively. In addition, TGA-DSC was employed to investigate adsorption of reactants and suggest implications on the mechanism of reaction. Cyclic TGA-DSC studies at 265 °C in CO2 and H2, being introduced consecutively, suggest a high degree of short term stability of the Ru catalyst, although it was found that CO2 chemisorption and hydrogenation activity was lowered by a magnitude of 40% after the first cycle. Stable performance was achieved for the following 19 cycles. The CO2 uptake after the first cycle was mostly restored when using a H2-pre-treatment at 320 °C between each cycle, which indicated that the previous drop in performance was not linked to an irreversible form of deactivation (sintering, permanent poisoning, etc.). CO chemisorption on powder Ru/γ-Al2O3 was used to identify metal sintering as a mechanism of deactivation at temperatures higher than 320 °C. A 10% Ru/γ-Al2O3//monolith has been investigated as a model for the design of a catalytic heat exchanger. Excellent selectivity to methane and CO2 conversions under low space-velocity conditions were achieved at low hydrogenation temperatures (T = 240 °C). The use of monoliths demonstrates the possibility for new reactor designs using wash-coated heat exchangers to manage the exotherm and prevent deactivation due to high temperatures.

Process Design and Integration of Shale Gas to Methanol

Abstract: The substantial discoveries of shale gas present many opportunities for the chemical, petrochemical, and fuel industries. As in conventional natural gas, shale gas contains primarily methane, but some formations contain significant amounts of higher molecular weight hydrocarbons and inorganic gases such as nitrogen and carbon dioxide. These differences present several technical challenges to incorporating shale gas with the current infrastructure designed to be used with natural gas. This paper is aimed at process synthesis, analysis, and integration of the production of methanol from shale gas. The composition of the shale gas feedstock is assumed to come from the Barnett Shale play located near Fort Worth, Texas, which is currently the most active shale gas play in the United States. Process simulation using ASPEN Plus along with published data were used to construct a base-case scenario. Key performance indicators were assessed. These include overall process targets for mass and energy and economic per...

Impact of choice of CO2 separation technology on thermo-economic performance of Bio-SNG production processes

Abstract: Three different CO2 separation technologies for production of synthetic natural gas (SNG) from biomass gasification – amine-based absorption, membrane-based separation and pressure swing adsorption – are investigated for their thermo-economic performance against the background of different possible future energy market scenarios. The studied scale of the SNG plant is a thermal input of 100 MWth,LHV to the gasifier at a moisture content of 20 wt-% with a preceding drying step reducing the biomass' natural moisture content of 50 wt-%. Preparation of the CO2-rich stream for carbon capture and storage is investigated for the amine-based absorption and the membrane-based separation technology alternatives. The resulting cold gas efficiency ηcg for the investigated process alternatives ranges between 0.65 and 0.695. The overall system efficiency ηsys ranges from 0.744 to 0.793, depending on both the separation technology and the background energy system. Amine-based absorption gives the highest cold gas efficiency whereas the potential for cogeneration of electricity from the process' excess heat is higher for membrane-based separation and pressure swing adsorption. The estimated specific production costs for SNG cSNG for a process input of 90.3 MWth,LHV at 50 wt-% moisture vary between 103–127 €2010/MWhSNG. The corresponding production subsidy level csubsidy needed to achieve end-user purchase price-parity with fossil natural gas is in the range of 56–78 €2010/MWhSNG depending on both the energy market scenario and the CO2 separation technology. Sensitivity analysis on the influence of changes in the total capital cost for the SNG plant on the production cost indicates a decrease of about 12% assuming a 30% reduction in total capital investment. Capture and storage of biogenic CO2 – if included in the emission trading system – only becomes an option at higher CO2 charges. This is due to increased investment costs but, in particular, due to the rather high costs for CO2 transport and storage that have been assumed in this study.

Sorption-enhanced synthetic natural gas (SNG) production from syngas: A novel process combining CO methanation, water-gas shift, and CO2 capture

Abstract: Synthetic natural gas (SNG) production from syngas is under investigation again due to the desire for less dependency from imports and the opportunity for increasing coal utilization and reducing greenhouse gas emission. CO methanation is highly exothermic and substantial heat is liberated which can lead to process thermal imbalance and deactivation of the catalyst. As a result, conversion per pass is limited and substantial syngas recycle is employed in conventional processes. Furthermore, the conversion of syngas to SNG is typically performed at moderate temperatures (275–325 °C) to ensure high CH4 yields since this reaction is thermodynamically limited. In this study, the effectiveness of a novel integrated process for the SNG production from syngas at high temperature (i.e. 600 °C) was investigated. This integrated process consists of combining a CO methanation nickel-based catalyst with a high temperature CO2 capture sorbent in a single reactor. Integration with CO2 separation eliminates the reverse-water-gas shift and the requirement for a separate water-gas shift (WGS) unit. Easing of thermodynamic constraint offers the opportunity of enhancing yield to CH4 at higher operating temperature (500–700 °C) which also favors methanation kinetics and improves the overall process efficiency due to exploitation of reaction heat at higher temperatures. Furthermore, simultaneous CO2 capture eliminates greenhouse gas emission. In this work, sorption-enhanced CO methanation was demonstrated using a mixture of a 68% CaO/32% MgAl2O4 sorbent and a CO methanation catalyst (Ni/Al2O3, Ni/MgAl2O4, or Ni/SiC) utilizing a syngas ratio (H2/CO) of 1, gas-hour-space velocity (GHSV) of 22,000 h−1, pressure of 1 bar and a temperature of 600 °C. These conditions resulted in ∼90% yield to methane, which was maintained until the sorbent became saturated with CO2. By contrast, without the use of sorbent, equilibrium yield to methane is only 22%. Cyclic stability of the methanation catalyst and durability of the sorbent were also studied in the multiple carbonation–decarbonation cycle studies proving the potential of this integrated process in a practical application.

CFD Simulation of Hydrodynamics and Methanation Reactions in a Fluidized-Bed Reactor for the Production of Synthetic Natural Gas

Abstract: Numerical investigations of hydrodynamics and kinetic reactions in a fluidized bed methanation reactor are carried out by coupling methanation kinetics with the two-fluid flow model. The gas–solid reacting flow models are implemented within OpenFOAM software. The grid resolution is investigated using two-dimensional and three-dimensional (2D and 3D) meshes. The bed height is reasonably predicted with the Gidaspow and Syamlal models. Simulated results are compared against experimental data in the literature. The simulated axial species concentrations agree well with the measured results at the end of the bed. The effects of different operating parameters are evaluated using the established models. The increase in the gas inlet velocity results in more dilute solid concentration and larger bed expansion. The weak bed expansion results from the methanation reaction with gas volume reduction. The methane concentration is increased when increasing catalyst inventory in the reactor. The addition of water into t...

The sintering of Ni/Al2O3 methanation catalyst for substitute natural gas production

Abstract: The sintering behavior of a co-precipitated Ni/Al2O3 methanation catalyst is studied by investigating the effect of treating time, temperature and atmosphere. Fresh and sintered samples are characterized by N2 physisorption, H2 chemisorption, temperature programmed reduction, X-ray diffraction and transmission electron microscopy. A reduction both in total and nickel surface area has been observed, the extent depending on the experimental conditions. Sintering of the studied catalyst, reflected by a significant decrease of nickel surface area, is a combined effect of primary encapsulation of metallic nickel due to the collapse of the support structure and sporadic agglomeration of nickel crystallites. The formation of a Ni2+ doped alumina phase, induced by steam ambience, further accelerates loss of surface nickel atoms. It is found that the sintering rate obeys a simple power law expression, with the apparent activation energy value of 118 kJ/mol. The sintered methanation catalyst suffers considerable decay of CO hydrogenation activity in a simulated industrial atmosphere, which suggests that extraordinarily high temperatures should be avoided as much as possible in the practical operation.

Thermochemical Equilibrium Model of Synthetic Natural Gas Production from Coal Gasification Using Aspen Plus

Abstract: The production of synthetic or substitute natural gas (SNG) from coal is a process of interest in Colombia where the reserves-to-production ratio (R/P) for natural gas is expected to be between 7 and 10 years, while the R/P for coal is forecasted to be around 90 years. In this work, the process to produce SNG by means of coal-entrained flow gasifiers is modeled under thermochemical equilibrium with the Gibbs free energy approach. The model was developed using a complete and comprehensive Aspen Plus model. Two typical technologies used in entrained flow gasifiers such as coal dry and coal slurry are modeled and simulated. Emphasis is put on interactions between the fuel feeding technology and selected energy output parameters of coal-SNG process, that is, energy efficiencies, power, and SNG quality. It was found that coal rank does not significantly affect energy indicators such as cold gas, process, and global efficiencies. However, feeding technology clearly has an effect on the process due to the gasifying agent. Simulations results are compared against available technical data with good accuracy. Thus, the proposed model is considered as a versatile and useful computational tool to study and optimize the coal to SNG process.

Design, control and comparison of fixed-bed methanation reactor systems for the production of substitute natural gas

Abstract: The design and control of processes for the methanation of synthesis gas to produce substitute natural gas (SNG) using fixed-bed reactors is investigated. Three different strategies for controlling the reactor temperature rise are considered: recycle of a portion of the reactor effluent, introduction of additional water into the reactor feed, and non-adiabatic reactor operation with catalyst dilution. The results show that the process with a non-adiabatic reactor has the lowest cost and produces the greatest amount of high-pressure steam. However the efficacy of catalyst dilution for preventing reaction run-away has not been tested experimentally. Among the remaining options, partial recycle of reactor effluent is preferred because it can produce a greater amount of high-pressure steam than the process with additional water. Control studies indicate that all processes can be controlled and can tolerate production rate changes, however none can tolerate a large change in the feed composition due to inherent stoichiometric limitations.

Surface Structure and Catalytic Performance of Ni-Fe Catalyst for Low-Temperature CO Hydrogenation

Abstract: Catalysts 16NiFe/Al2O3 ( is 0, 1, 2, 4, 6, 8) were prepared by incipient wetness impregnation method and the catalytic performance for the production of synthetic natural gas (SNG) from CO hydrogenation in slurry-bed reactor were studied. The catalysts were characterized by BET, XRD, UV-Vis DRS, H2-TPR, CO-TPD, and XPS, and the results showed that the introduction of iron improved the dispersion of Ni species, weakened the interaction between Ni species and support and decreased the reduction temperature and that catalyst formed Ni-Fe alloy when the content of iron exceeded 2%. Experimental results revealed that the addition of iron to the catalyst can effectively improve the catalytic performance of low-temperature CO methanation. Catalyst 16Ni4Fe/Al2O3 with the iron content of 4% exhibited the best catalytic performance, the conversion of CO and the yield of CH4 reached 97.2% and 84.9%, respectively, and the high catalytic performance of Ni-Fe catalyst was related to the property of formed Ni-Fe alloy. Further increase of iron content led to enhancing the water gas shift reaction.

CO2 Reduction to Substitute Natural Gas: Toward a Global Low Carbon Energy System

Abstract: Methane has proven to be an outstanding energy carrier and is the main component of natural gas and substitute natural gas (SNG). SNG may be synthesized from the CO2 and hydrogen available from various sources and may be introduced into the existing infrastructure used by the natural gas sector for transport and distribution to power plants, industry, and households. Renewable SNG may be generated when H2 is produced from renewable energy sources, such as solar, wind, and hydro. In parallel, the use of CO2-containing feed streams from fossil origin or preferably, from biomass, permits the avoidance of CO2 emissions. In particular, the biomass-to-SNG conversion, combined with the use of renewable H2 obtained by electrolysis, appears a promising way to reduce CO2 emissions considerably, while avoiding energy intensive CO2 separation from the bio feed streams. The existing technologies for the production of SNG are described in this short review, along with the need for renewed research and development efforts to improve the energy efficiency of the renewables-to-SNG conversion chain. Innovative technologies aiming at a more efficient management of the heat delivered in the exothermic methanation process are therefore highly desirable. The production of renewable SNG through the Sabatier process is a key process to the transition towards a global sustainable energy system, and is complementary to other renewable energy carriers such as methanol, dimethyl ether, formic acid, and Fischer-Tropsch fuels.

Design and Control of the Cryogenic Distillation Process for Purification of Synthetic Natural Gas from Methanation of Coke Oven Gas

Abstract: A cryogenic distillation process for the upgrade of synthetic natural gas (SNG) from methanation of coke oven gas (COG) is designed and controlled using a method of gradually reducing independent variables. Freedom analysis is performed to decide independent variables of the cryogenic distillation column. Based on the equilibrium stage model and Peng–Robinson–Boston–Mathias (PR-BM) thermodynamics method, parameters sensitivity analysis is implemented to obtain the optimal operation conditions using Aspen Plus software. After supplying the physical dimensions and control variables (reflux flow rate and reflux ratio) of the distillation column, three control structures that involve fixed reflux flow rate, fixed reflux ratio and dual-composition controllers are developed to control the cryogenic distillation process. Under the significant disturbances of feed flow rate and feed composition, evaluation results show that the dual-composition control system displays the best effect for maintaining the mole perc...

Influence of Operating Conditions on Carbon Deposition Over a Ni Catalyst for the Production of Synthetic Natural Gas (SNG) from Coal

Abstract: Carbon deposition over a Ni/Al2O3 methanation catalyst was studied emphasizing the effects of operating conditions. A method to quantify the deposited carbon was developed from TG analysis, and samples were also characterized by TPO and TEM. Carbon formation boundaries were presented in a CHO ternary diagram based on thermodynamic calculations. In the carbon-forming region, it is found that both the temperature and H2/CO ratio are significantly influential factors for the morphology and amount of carbon deposits. The amount of generated carbon varies with reaction time nonlinearly, meanwhile carbon laydown is favored by low pressure and space velocity. Consequently, it provides guidance for the optimization of operating conditions. .

Continuous Hydrothermal Gasification of Glycerol Mixtures: Autothermal Operation, Simultaneous Salt Recovery, and the Effect of K3PO4 on the Catalytic Gasification

Abstract: We have developed a continuous process for the catalytic hydrothermal gasification of wet biomass to synthetic natural gas (SNG). Salts contained in the biomass and released during the liquefaction step are continuously withdrawn in the supercritical salt separation step upstream of the catalytic reactor. The catalytic reactor is operated at temperatures of 400–450 °C and pressures of 25–35 MPa. In this article we provide a detailed description of the process and demonstrate the proof of concept as well as the process operation characteristics, based on a systematic study of the continuous gasification of aqueous solutions of glycerol with and without K3PO4 with simultaneous salt recovery. Glycerol was gasified efficiently to a methane-rich gas without the formation of tars or char. The gas composition corresponded to the thermodynamic equilibrium. The process could be operated in an autothermal mode, although the large surface-to-volume ratio and the imperfect insulation of the laboratory-scale reactor w...