Are Ni/and Ni5Fe1/biochar catalysts suitable for synthetic natural gas production?A comparison with g-Al2O3 supported catalysts

Among challenges implicit in the transition to the post-fossil fuel energetic model,the finite amount of resources available for the technological implementation of CO_(2) revalorizing processes arises as a central issue.The development of fully renewable catalytic systems with easier metal recovery strategies would promote the viability and sustainability of synthetic natural gas production circular routes.Taking Ni and NiFe catalysts supported over g-Al_(2)O_(3) oxide as reference materials,this work evaluates the potentiality of Ni and NiFe supported biochar catalysts for CO_(2) methanation.The development of competitive biochar catalysts was found dependent on the creation of basic sites on the catalyst surface.Displaying lower Turn Over Frequencies than Ni/Al catalyst,the absence of basic sites achieved over Ni/C catalyst was related to the depleted catalyst performances.For NiFe catalysts,analogous Ni_(5)Fe_(1) alloys were constituted over both alumina and biochar supports.The highest specific activity of the catalyst series,exhibited by the NiFe/C catalyst,was related to the development of surface basic sites along with weaker NiFe-C interactions,which resulted in increased Ni0:NiO surface populations under reaction conditions.In summary,the present work establishes biochar supports as a competitive material to consider within the future low-carbon energetic panorama.

Energy Efficiency of a Simulated Synthetic Natural Gas Combined Cycle (SNGCC)

The objective of this investigation is to analyze the impact of the flue gas recirculation (FGR) ratio on the different energy inputs and outputs of a SNGCC power plant as well as its overall efficiency. Simulation results indicate that increasing flue gas recirculation increases the energy consumed by the recirculation compressor and the energy produced by the gas turbine. On the other hand, it decreases the production of energy of the steam turbine and the energy consumed by the pump of the steam cycle. The overall energy efficiency of the SNGCC power plant is highest (41.09%) at a value of 0.20 of the flue gas recirculation. However, the flue gas composition with a FGR ratio of 0.37 is more suitable for effective absorption of carbon dioxide by amine solutions. Based on the low heating value (LHV) of hydrogen, the corresponding overall efficiency of the power plant is 39.18% and the net power output of the plant is 1273 kW for consumption of 97.5 kg/hr. of hydrogen.

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

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 carb on yield, and enhance the CO2 con tent. 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.

Simulation and energy performance assessment of CO_2 removal from crude synthetic natural gas via physical absorption process

The paper presents an energy performance assessment of CO2 removal for crude synthetic natural gas （SNG） upgrade by Selexol absorption process. A simplified process simulation of the Selexol process concerning power requirement and separation performance was developed. The assessment indicates that less pressure difference between crude SNG and absorption pressure favors the energy performance of CO2 removal process. When both crude SNG and absorption pressures are 20 bar, CO2 removal process has the best energy performance. The optimal specific power consumption of the CO2 removal process is 566 kJ/kgCO2. The sensitivity analysis shows that the CO2 removal efficiency would significantly influence the total power consumption of the removal process, as well as higher heating value （HHV） and CO2 content in SNG. However, the specific power consumption excluding crude SNG and SNG compressions changes little with the variance of CO2 removal efficiency. If by-product CO2 is compressed for CO2 capture, the process would turn into a CO2-sink for the atmosphere. Correspondingly, an increase of 281 kJ/kgCO2 in specific power consumption is required for compressing the separated CO2.

Experimental Study of Natural Gas Storage in Hydrates

Hydrate formation rate plays an important role in the making of hydrates for natural gas storage. The effect of sodium dodecyl sulfate (SDS), alkyl polysaccharide glycoside (APG) and cyclopentane (CP) on natural gas hydrate formation rate, induction time and storage capacity was studied. Micellar surfactant solutions were found to increase hydrate formation rate in a quiescent system and improve hydrate formation rate and natural gas storage capacity. The process of hydrate formation includes two stages with surfactant presence. Hydrate forms quickly in the first stage, and then the formation rate is slowed down. Surfactants (SDS or APG) reduce the induction time of hydrate formation. The effect of an anionic surfactant (SDS) on gas storage in hydrates is more pronounced compared to a nonionic surfactant (APG). CP also reduces the induction time of hydrate formation, but can not improve the natural gas storage capacity in hydrates.

Technical assessment of synthetic natural gas (SNG) production from agriculture residuals

This paper presents thermodynamic evaluations of the agriculture residual-to-SNG process by thermochemical conversion, which mainly consists of the interconnected fluidized beds, hot gas cleaning, fluidized bed methanation reactor and Selexol absorption unit. The process was modeled using Aspen Plus soft-ware. The process performances, i.e., CH4 content in SNG~ higher heating value and yield of SNGexergy efficiencies with and without heat recovery, unit power consumption, were evaluated firstly. The results indicate that when the other parameters remain unchanged, the steam-to-biomass ratio at carbon boundary point is the optimal value for the process. Im proving the preheating temperatures of air and gasifying agent is beneficial for the SNG yield and exergy effi ciencies. Due to the effects of COz removal efficiency, there are two optimization objectives for the SNG produc tion process： （I） to maximize CH4 content in SNC or （II） to maximize SNG yield. Further, the comparison among different feedstocks indicates that the decreasing order of SNG yield is： corn stalk 〉 wheat straw 〉 rice straw. The evaluation on the potential of agriculture-based SNG shows that the potential annual production of agriculture re sidual-based SNG could be between 555 108 - 611 108 m3 with utilization of 100% of the available unexplored resources. The agriculture residual-based SNG could play a significant role on solving the big shortfall of China＇s natural gas supply in future.

焦炉煤气制合成天然气(SNG)分析

焦炉煤气的利用途径主要包括作为燃料气直接利用、发电、合成甲醇、合成氨或尿素、制氢、合成天然气等,通过对焦炉煤气不同利用途径的技术和经济可行性分析,提出了焦炉煤气制合成天然气,配套建设焦炉煤气合成甲醇或LNG方案。焦炉煤气的统一合理利用,符合大力深化转型综改的政策要求,满足发展循环经济、提高资源综合利用率的要求。既能够填补天然气供应的缺口,又能够起到一定的储气调峰作用,在促进焦化行业健康发展的同时,还能带来一定的经济效益、环境效益和社会效益。

合成天然气(SNG)产品中氢气含量控制手段的研究

煤制天然气的合成天然气(SNG)产品与常规天然气最大的不同在于其H_2含量高,可能对燃气电厂等用户有较大影响,需要在设计阶段做好控制方案。控制SNG中H_2含量的工艺手段主要有调节氢碳比、调整反应温度和调节分水量等。采用ASPEN PLUS对国内某煤制天然气项目甲烷化工艺流程进行模拟,分析几种工艺调节手段对H_2含量控制的敏感性,结果显示氢碳比和第二辅甲烷化(最后一级甲烷化)入口温度对SNG中H_2含量和产品品质影响较大,适合作为H_2含量控制的主要调控手段。

Simulation of a NGCC Power Generation Plant for the Production of Electricity from CO2 Emissions Part II: SNGCC Power Plant

The objective of the first part of the investigation was to use Aspen Plus software and the Redlich-Kwong-Soave equation of state in order to simulate an adiabatic methanation reactor for the production of synthetic natural methane (SNG) using 1 kg/hr of carbon dioxide. In this paper, we define the Synthetic Natural Gas Combined Cycle (SNGCC) as a combined cycle power plant where the fuel is synthetic natural gas (SNG) produced by a methanation reactor. The feed of the methanation reactor is the recycled stream of carbon dioxide of a CO2 capture unit treating the flue gas of the SNGCC power plant. The objective of the second part of the investigation is the utilization of Aspen plus software with SRK equation of state for the simulation of the SNGCC power plant. The metallurgical limitation of the gas turbine was fixed at 1300°C in this investigation. For effective absorption by amine solutions, the molar percentage of CO2 in the flue gas should be higher than 10%. Moreover, in order to reduce technical problems linked to oxidative degradation of amine in the CO2 capture plant, the percentage of O2 in the flue gas should also be lower than 5%. To reach this goal, the primary air for combustion has 10% excess air (compared to stoichiometric air) and 37% of the flue gas leaving the SNGCC is recirculated as the secondary air for cooling the turbine. As a result, the concentration of CO2 and O2 of the flue gas entering the CO2 capture unit were respectively equal to 10.2% and 2.01%. The simulation results of the SNGCC power plant indicate that 6.6 MJ of electricity are produced for each kg of carbon dioxide recycled from the CO2 capture unit of the power plant. In other terms, the production of the 24.88 kg/hr of synthetic natural gas (SNG) consumes 62.36 kg/hr of recycled carbon dioxide and 16.4 kg/hr of hydrogen. The SNG produced by the methanation reactor of the power plant generates 114 kW of electricity. It is assumed in this paper that the hydrogen needed for the methanation of carbon dioxide is a product of a catalytic reforming plant that produces gasoline from heavy naphta fraction of an atmospheric distillation unit of crude oil.

从市场供需看我国煤制天然气发展前景

煤制天然气已成为国内投资和研究的热点,但该行业发展不能一哄而上,而需要统筹规划、合理布局,做好总量控制。为此,从分析我国天然气市场中远期需求量入手,综合考虑国产、进口等各类资源因素,预测了我国煤制天然气的市场空间;在剖析煤制天然气项目的特点、能耗、水耗和综合能源利用效率的基础上,结合煤炭资源保有量及其分布对我国煤制天然气产业的发展前景作出分析。结论认为:我国可实现的天然气消费需求量2020年约为3 800×108 m3,2030年有望达到5 200×108 m3;根据各类资源规划和合同签订情况,并考虑勘探开发的不确定性,初步判断我国煤制天然气合理规模2020年约为300×108 m3、2030年约为500×108 m3,峰值达到800×108 m3。最后建议:1国家支持研发和示范,环境上严格准入;2结合我国的国情因地制宜,适度发展;3煤制天然气利用方向上应定位于城市燃气和工业燃料;4煤制天然气项目发展应统筹规划布局。

煤制天然气液化流程初步研究

鉴于煤炭清洁利用的必要性以及国内天然气供不应求的格局,煤制天然气(SNG)具有了一定的发展空间。以液化的方式储运煤制天然气是应对我国特殊的天然气市场结构的较好选择。而由于煤制天然气与常规天然气不同的组成,特别是氢气的存在,需要为其设计专门的液化流程。为了给流程的设计提供参考,在HYSYS软件上模拟分析了常规天然气液化流程(氮气膨胀流程和混合制冷剂流程)用于液化煤制天然气的可行性及其特点,发现常规天然气液化流程可以用于液化煤制天然气,只是流程的单位能耗稍有增加。另外,还通过模拟分析了精馏分离氢气对液化流程所产生的影响。

均温甲烷化技术用于煤制天然气探讨

在成功进行了采用水冷换热甲烷化反应器的焦炉煤气均温甲烷化技术制合成天然气的工业试验的基础上,讨论了该技术用于煤制合成天然气的可行性。结果表明,该技术具有能量效率高(>60%),CO、CO2转化率高,催化剂寿命长、价格低,流程短、设备少和投资省等优势,具有较高的吸引力。

煤制合成天然气过程经济性分析

煤制合成天然气与其他煤化工技术(煤制油,煤制烯烃等)相比具有流程短、能量利用效率高、水耗相对较少、投资相对较少等特点,已呈现大规模工业化的趋势。基于鲁奇煤气化工艺及自制的甲烷化催化剂,以锡林浩特煤为原料,年产10×108 m3(标准)天然气项目为目标,对煤制合成天然气过程进行经济性分析。

焦炉尾气耦合生物沼气制取天然气的工艺集成研究

为研究焦炉尾气耦合生物沼气进行工艺集成制取天然气的可行性,通过系统阐述焦炉尾气制天然气技术与生物沼气制天然气技术,进而分析二者技术方案存在的问题及共性,提出了初步的工艺集成方案设想,同时运用Aspen Plus软件进行集成工艺的模拟研究。由结果可知,生物沼气净化提纯与焦炉尾气补碳工艺是目前较为现实、经济的制取天然气的路径,而生物沼气可作为焦炉尾气补碳工艺的碳源,二者可初步实现工艺耦合集成,能够提高企业产能和效益,具有较好的参考意义和实际应用价值。

焦炉煤气制天然气产业的发展探讨

分析了目前国内焦炉煤气利用现状,指出焦炉煤气制天然气是焦炉煤气高效利用的新途径。探讨了焦炉煤气制天然气产业的宏观市场环境,提出该产业的发展不但可以解决焦化企业焦炉煤气过剩的问题,而且有利于缓解国内天然气短缺的矛盾,对加快传统焦化产业升级和煤基产业链延伸等均具有重要的意义,焦炉煤气制天然气产业在我国具有很好的发展前景。着重分析了山西省发展焦炉煤气制天然气产业的意义。

甲烷化技术国产化研究进展

甲烷化是焦炉气制天然气、煤制天然气生产流程的关键步骤,为打破国外技术垄断,国内研究机构积极进行技术开发。系统梳理了甲烷化技术的国产化研究进展,分析了焦炉气甲烷化技术的应用现状,探讨煤制天然气甲烷化技术的应用前景,并就降低首次工程应用风险提出几点建议。国内甲烷化技术已经实现广泛开发,焦炉气甲烷化技术成功实现工业化应用,其国内市场占有率高于国外技术。煤制天然气甲烷化技术已成功开发,工业化应用前景广阔,首次工程应用时应注重经验借鉴、安全分析及设备选型等。

煤制天然气碳排放全生命周期分析及横向比较

在中国天然气市场需求旺盛、供需缺口快速扩大的大背景下,煤制天然气(SNG)迎来了大规模的投资与发展热潮。然而,随着"低碳经济"发展模式的转变预期,SNG又面临着"低碳"与否的争议。为此,采用全生命周期(LCA)评价方法对SNG项目从原煤开采到转化为煤制天然气、直至进入终端消费全过程的直接和间接二氧化碳排放及其温室气体排放进行了清单分析。同时,对SNG与煤层气、液化天然气、管输天然气的全生命周期二氧化碳排放清单进行了横向比较,将相关产业链划分为国外和国内两个环节并进行分析,结果认为LNG在国际贸易中具有明显的碳减排优势。结合美国大平原SNG工厂碳减排对我国的启示,提出中国发展SNG的"低碳"途径与选择,并呼吁应从多方面谨慎对待具体SNG项目的前期规划和研究。

中国东南沿海发展煤制天然气的可行性

随着近年来煤制天然气(SNG)技术的发展,国内呈现出积极开发SNG项目的热潮,但输送距离成为坑口建厂模式与天然气市场之间的巨大沟壑。通过在西部煤矿坑口建厂与在东南沿海地区建设SNG工厂的技术与经济可行性分析,认为沿海SNG工厂在价格和风险承受等方面更富竞争力,同时对于东南沿海地区掌握自主气源的意义重大。尤其对于国内石油公司而言,SNG相比在沿海建设的液化天然气项目,是一种更为可靠的资源和价格对冲工具,而且沿海SNG项目在获取煤炭资源方式上有更多的灵活性。在提高经济性方面,资源与运输费用的长期锁定、褐煤的坑口提质处理都是必要的,但在污染物排放、废水处理及废渣利用方面,应进行审慎的风险评估和措施论证,确保其成为受欢迎的新型能源项目。

煤制天然气废水的水解酸化法处理工艺

采用厌氧间歇式反应器,以煤制天然气(SNG)废水为处理对象,研究了在中温条件下水解酸化处理SNG废水后有机污染物的降解情况。以某柠檬酸生产厂废水厌氧反应器中的颗粒污泥为接种污泥进行4个月的驯化,形成处理SNG废水的稳定体系。试验结果表明运行温度为(35±1)℃,水解酸化时间为48 h,进水CODCr、总酚和挥发酚分别为1 100、220和110 mg/L的条件下,COD、总酚和挥发酚的去除率分别为45%、50%和99%左右,三者的降解均符合一级动力学特征。该体系主要停留在水解酸化阶段,甲烷产率为0.002 5 kg CH4/kg COD removal,去除的TOC中有77%左右的有机碳用于污泥增殖,污泥增长率为0.3 kg SS/kg COD removal。

煤制天然气技术路线的全生命周期分析

采用Well to Wheel评价了从煤炭出发利用不同技术路线满足天然气下游需求的全生命周期能耗情况,并以北京、上海为例探讨了煤制天然气及其替代技术路线的整体影响。研究结果表明,煤制天然气能够解决清洁用能以及终端污染的问题,但是这是以较高的全生命周期能耗为代价的,以北京为例,存在比煤制天然气节省煤炭消耗33%的更加合理的利用途径。因此中国远期煤制天然气项目须谨慎规划和研究。