国际可再生能源新闻

综合类 太阳能驱动生物质气化生产合成燃料 近日,挪威科技大学(NTNU)研究人员提出了利用太阳能作为主要能源从生物质气化途径生产合成燃料的新工艺.用于生物质气化的高温热量可从太阳能聚热塔中的熔融盐系统获得.     

生物质费托合成制取液体燃料的仿真及分析

以生物质费托合成制取液体燃料工艺为基础,利用Aspen Plus软件建立其流程的仿真模型,研究各单元操作参数变化对航空煤油产量的影响,并在最优工况下对系统进行能量分析.结果表明:生物质气化单元对航油产量的影响主要来自产物合成气中H2与CO物质的量之比(H2/CO),最优操作条件为T=750℃,P=0.1 MPa,进口水...     

生物质气化费托合成航空煤油的模拟和火用分析

基于Aspen Plus软件对生物质串行流化床气化费托(FT)合成加氢裂化制取航空煤油进行模拟和热力学分析,研究操作参数变化和副产品蜡循环利用对系统性能的影响。结果表明:系统损失主要在气化子系统中,而合成气提质子系统损较小,过程不可逆损是系统损的主要来源,内部损率为88.3%,生物质大分子结构改变是造成不可逆损的主要原因。所有操作参数中水蒸气与生物质质量配比(S/B)对系统效率影响最大,气化合成气H_2与CO物质的量之比(H_2/CO)在1.95～2.00为宜,增大合成温度和压力可提高系统航空煤油产率和效率。对于玉米秆气化FT加氢裂化制取航空煤油系统,推荐的操作参数:气化温度和压力750℃,0.1～0.2 MPa,S/B为0.4～0.5,合成温度240℃,合成压力1.5～2.0 MPa。此时,航空煤油产率最大可达85.3 kg/t,系统效率为54.3%。副产品蜡进行循环利用,可提高航空煤油产率3.9%,并降低最佳S/B为0.3～0.4。     

生物质化学链气化联合燃气轮机发电系统模拟

使用Aspen Plus软件对以Fe_2O_3为载氧体的生物质化学链气化系统进行模拟,分析温度、压力、载氧体与生物质摩尔比、水蒸气与生物质摩尔比等因素对合成气制备的影响;对不同生物质的气化条件进行优化;将气化制得的合成气通入M701F燃气轮机中发电,考察系统的发电效率。结果表明:常压下,不同生物质气化的优化温度均在740℃左右,此时制备的合成气冷煤气效率较高;提高反应压力有利于系统热量自平衡,但合成气的冷煤气效率降低;载氧体与生物质摩尔比的优化值与生物质中氧碳摩尔比呈负相关,且达到优化值时,气化环境中氧碳摩尔比在1.25左右;水蒸气通入气化系统后冷煤气效率可提高15.00%～20.00%,主要原因为H_2的产量显著增加,通入水蒸气后的气化环境的氧碳比在1.4左右时,制备合成气的冷煤气效率较高;系统的发电效率在30.00%～37.00%,高于生物质发电效率。     

生物质化学链气化多联产工艺热力学分析

为提高生物质的利用效率,提出了生物质化学链气化氢-电-甲醇多联产工艺,采用CaO吸附强化Fe_2O_3生物质化学链气化过程,生产高纯度氢气和适用于甲醇合成的高氢碳比合成气。选用木屑作为生物质,利用Aspen Plus软件进行过程模拟和热力学分析,以合成气的氢碳比(H/C)、系统氢气效率、净电效率、甲醇效率和总效率作为评价指标,讨论了水蒸气与生物质质量比(S/B)、氧载体与生物质质量比(M_(Ca)/B、M_(Fe)/B)和气化压力(p_(CLG))对系统性能的影响。结果表明:在S/B=0.4、M_(Ca)/B=1、M_(Fe)/B=0.5和p_(CLG)=0.8 MPa时,系统性能最优,合成气的H/C为2.09,甲醇效率为41.28%,总效率为59.34%。     

生物质气流床气化制取合成气的试验研究

利用一套小型生物质层流气流床气化系统,研究了稻壳、红松、水曲柳和樟木松4种生物质在不同反应温度、氧气/生物质比率(O/B)、水蒸汽/生物质比率(S/B)以及停留时间下对合成气成分、碳转化率、H2/CO以及CO/CO2比率的影响.研究表明4种生物质在常压气流床气化生成合成气最佳O/B范围为0.2～0.3(气化温度.1300℃),高温气化时合成气中CH4含量很低,停留时间为1.6s时其气化反应基本完毕.加大水蒸汽含量可增加H2/CO比率,在S/B为0.8时H2/CO比率都在1以上,但水蒸汽的过多引入会影响煤气产率.气化温度是生物质气流床气化最重要的影响因素之一.     

我国生物燃料技术开发成果

正我国生物燃料产业经过十几年的发展,已经形成十几条技术转化路线,生物质气化-合成油、生物质裂解提质油、EL类生物燃油、生物MTG油、CBGTL油、藻类油/燃气、生物质气化-合成天然气等各种新型生物燃料有望在今后几年商业化。用生物质原料制合成气,目前已开发出多系列达到示范工厂和商业应用规模的气化炉。采用气化-合成工艺生产生物天然气,可用木质类和干秸秆类原料,突破了微生物发酵法对原料的严格限制。     

生物质加压气化技术的研究与应用现状

生物质气化气可以替代化石燃料用于发电、供热和用于生产合成反应的化工原料,解决日益严重的能源短缺和环境污染等问题.加压气化具有生产能力大、效率高,可降低单位投资成本,减少焦油的产生,有利于后续发电及合成工艺等诸多优点.文章介绍了压力对气化的影响,加压气化存在的主要问题,加压在生物质和劣质煤等联合气化、定向气化制备合成气、IGCC上应用的研究和应用现状.     

木屑水蒸气气化热重分析及合成气释放特性

试验研究了木屑在水蒸气气氛下的热失重行为及气化过程中合成气释放特性。首先采用TG-DTA对木屑样品进行了水蒸气气氛下的热重行为分析,结果表明,木屑气化过程可以分为挥发分释放和半焦气化两个阶段,分别可由二级反应动力学和三维扩散Ginstling-Broushtein方程描述,对应的表观活化能分别为87.014kJ/mol和103.35 kJ/mol。此外,在自制的固定床气化反应装置上,研究了生物质气化过程中挥发分释放和半焦气化阶段合成气释放特性。另外,半焦水蒸气气化阶段对气体中合成气含量和H2/CO起到决定性作用,通过合理调控半焦气化阶段反应条件,可以得到合适化学当量比的生物质合成气。     

双流化床生物质气化及CO2捕获的模拟

用Aspen Plus建立了双流化床气化和燃烧模型,对生物质在双流化床中气化及CaO吸收合成气中的CO2过程进行了模拟研究;探讨不同反应条件:气化温度、蒸汽与生物质的质量配比(S/B)以及CaO循环量与生物质的质量配比(Ca/B)对合成气成分的影响,为该类型工业反应器的研发提供了理论依据.模拟分析结果表明:气化温度低于700℃时,CaO能很好地吸收气化过程中产生的CO2并促进平衡反应向产氢方向进行;在温度为650℃及CaO作用下,S/B在0.6～1.7内对合成气成分的影响不大;CaO的加入能够有效地改善合成气的组成,合成气中氢气浓度能达到95％以上,氢气产量达到52 mol/kg.     

Decentralized generation of electricity with solid oxide fuel cells from centrally converted biomass

A thermodynamic evaluation of different energy conversion chains based on centralized biomass gasification and decentralized heat and power production by a solid oxide fuel cell (SOFC) has been performed. Three different chains have been evaluated, the main difference between the chains is the secondary fuel produced via biomass gasification. The secondary fuels considered are hydrogen, synthetic natural gas (SNG) and syngas. These fuels are assumed to be distributed through a transport and distribution grid to the micro-combined heat and power (μ-CHP) systems based on a SOFC and a heat pump.     

Small‐scale production of synthetic natural gas by allothermal biomass gasification

The gasification of biomass can be coupled to a downstream methanation process that produces synthetic natural gas (SNG). This enables the distribution of bioenergy in the existing natural gas grid. A process model is developed for the small‐scale production of SNG with the use of the software package Aspen Plus (Aspen Technology, Inc., Burlington, MA, USA). The gasification is based on an indirect gasifier with a thermal input of 500 kW. The gasification system consists of a fluidized bed reformer and a fluidized bed combustor that are interconnected via heat pipes. The subsequent methanation is modeled by a fluidized bed reactor. Different stages of process integration between the endothermic gasification and exothermic combustion and methanation are considered. With increasing process integration, the conversion efficiency from biomass to SNG increases. A conversion efficiency from biomass to SNG of 73.9% on a lower heating value basis is feasible with the best integrated system. The SNG produced in the simulation meets the quality requirements for injection into the natural gas grid. Copyright © 2012 John Wiley & Sons, Ltd.     

Thermodynamic analysis and techno-economic assessment of synthetic natural gas production via ash agglomerating fluidized bed gasification using coal as fuel

Implementing coal to synthetic natural gas (SNG) is a key way to deal with the conflict between supply and demand of natural gas in China. For the coal to SNG process, gasification is a crucial unit, which determines the syngas composition and influences cost of coal to SNG system. In this current study, a coal to SNG system using ash agglomerating fluidized bed gasification is designed and modeled. According to the above results, the thermal performance and technoeconomic assessment of the coal to SNG system are performed. The research demonstrates that exergy efficiency and energy efficiency of the whole system are 55.37% and 61.50%, respectively. Additionally, the results of the economic evaluation show that the SNG production cost is 1.87 CNY/Nm³ with a coal price of 250 CNY/t and an electricity price of 0.65 CNY/kWh. Sensitivities to variables such as water price, electricity price, total equipment cost and coal price are performed. Coal price represents the most important sensitivity, but the sensitivity to water price is relatively small.     

Simulation of a new biomass integrated gasification combined cycle (BIGCC) power generation system using Aspen Plus: Performance analysis and energetic assessment

A new biomass integrated gasification combined cycle (BIGCC), which featured an innovative two-stage enriched air gasification system coupling a fluidized bed with a swirl-melting furnace, was proposed and built for clean and efficient biomass utilization. The performance of biomass gasification and power generation under various operating conditions was assessed using a comprehensive Aspen Plus model for system optimization. The model was validated by pilot-scale experimental data and gas turbine regulations, showing good agreement. Parameters including oxygen percentage of enriched air (OP), gasification temperature, excess air ratio and compressor pressure ratio were studied for BIGCC optimization. Results showed that increase OP could effectively improve syngas quality and two-stage gasification efficiency, enhancing the gas turbine inlet and outlet temperature. The maximum BIGCC fuel utilization efficiency could be obtained at OP of 40%. Increasing gasification temperature showed a negative effect on the two-stage gasification performance. For efficient BIGCC operation, the excess air ratio should be below 3.5 to maintain a designed gas turbine inlet temperature. Modest increase of compressor pressure ratio favored the power generation. Finally, the BIGCC energy analysis further proved the rationality of system design and sufficient utilization of biomass energy.     

Thermal conversion efficiency of producing hydrogen enriched syngas from biomass steam gasification

This paper presents the results from an experimental study on the energy conversion efficiency of producing hydrogen enriched syngas through uncatalyzed steam biomass gasification. Wood pellets were gasified using a 100 kW_th fluidized bed gasifier at temperatures up to 850 °C. The syngas hydrogen concentration and cold gas efficiency were found to increase with both bed temperature and steam to biomass weight ratio, reaching a maximum of 51% and 124% respectively. The overall energy conversion to syngas (based on heating value) also increased with bed temperature but was inversely proportional to the steam to biomass ratio. The maximum energy conversion to syngas was found to be 68%. The conversion of energy to hydrogen (by heating value) increased with gasifier temperature and gas residence time, but was found to be independent of the S/B ratio. The maximum conversion of all energy sources to hydrogen was found to be 25%.     

Thermodynamic analysis of a multigeneration system using solid oxide cells for renewable power-to-X conversion

A hybrid renewable-based integrated energy system for power-to-X conversion is designed and analyzed. The system produces several valuable commodities: Hydrogen, electricity, heat, ammonia, urea, and synthetic natural gas (SNG). Hydrogen is produced and stored for power generation from solar energy by utilizing solid oxide electrolyzers and fuel cells. Ammonia, urea, and synthetic natural gas are produced to mitigate hydrogen transportation and storage complexities and act as energy carriers or valuable chemical products. The system is analyzed from a thermodynamic perspective, the exergy destruction rates are compared, and the effects of different parameters are evaluated. The overall system's energy efficiency is 56%, while the exergy efficiency is 14%. The highest exergy destruction occurs in the Rankine cycle with 48 MW. The mass flow rates of the produced chemicals are 0.064, 0.088, and 0.048 kg/s for ammonia, urea, and SNG, respectively.     

Exergy analysis of biomass-to-synthetic natural gas (SNG) process via indirect gasification of various biomass feedstock

This paper presents an exergy analysis of SNG production via indirect gasification of various biomass feedstock, including virgin (woody) biomass as well as waste biomass (municipal solid waste and sludge). In indirect gasification heat needed for endothermic gasification reactions is produced by burning char in a separate combustion section of the gasifier and subsequently the heat is transferred to the gasification section. The advantages of indirect gasification are no syngas dilution with nitrogen and no external heat source required. The production process involves several process units, including biomass gasification, syngas cooler, cleaning and compression, methanation reactors and SNG conditioning. The process is simulated with a computer model using the flow-sheeting program Aspen Plus. The exergy analysis is performed for various operating conditions such as gasifier pressure, methanation pressure and temperature. The largest internal exergy losses occur in the gasifier followed by methanation and SNG conditioning. It is shown that exergetic efficiency of biomass-to-SNG process for woody biomass is higher than that for waste biomass. The exergetic efficiency for all biomass feedstock increases with gasification pressure, whereas the effects of methanation pressure and temperature are opposite for treated wood and waste biomass.     

Effect of the blend ratio on the co-gasification of biomass and coal in a bubbling fluidized bed with CFD-DEM

Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) is employed to describe the co-gasification of biomass and coal in bubbling fluidized bed coupled with chemical reaction kinetic model. Six sets of simulations are set up to study the effect of blend ratio on the amount of gasification products compared with experiments. The calorific value of syngas, carbon conversion efficiency, hydrogen conversion efficiency and cold gas efficiency are calculated. Compared with the separate gasification, the hydrogen efficiency and cold gas efficiency in the co-gasification are enhanced. When biomass accounts for 75%, the contents of CO gas and CO₂ gas are the lowest, while the contents of H₂ gas and CH₄ gas are the highest. The high calorific value, carbon conversion efficiency and hydrogen conversion efficiency reach the maximum under this blend ratio. The cold gas efficiency is not obviously affected by the blend ratio, and reaches the maximum when the biomass content is 50%.     

The production of synthetic natural gas (SNG): A comparison of three wood gasification systems for energy balance and overall efficiency

The production of Synthetic Natural Gas from biomass (Bio-SNG) by gasification and upgrading of the gas is an attractive option to reduce CO₂ emissions and replace declining fossil natural gas reserves. Production of energy from biomass is approximately CO₂ neutral. Production of Bio-SNG can even be CO₂ negative, since in the final upgrading step, part of the biomass carbon is removed as CO₂, which can be stored. The use of biomass for CO₂ reduction will increase the biomass demand and therefore will increase the price of biomass. Consequently, a high overall efficiency is a prerequisite for any biomass conversion process. Various biomass gasification technologies are suitable to produce SNG. The present article contains an analysis of the Bio-SNG process efficiency that can be obtained using three different gasification technologies and associated gas cleaning and methanation equipment. These technologies are: 1) Entrained Flow, 2) Circulating Fluidized Bed and 3) Allothermal or Indirect gasification. The aim of this work is to identify the gasification route with the highest process efficiency from biomass to SNG and to quantify the differences in overall efficiency. Aspen Plus^® was used as modeling tool. The heat and mass balances are based on experimental data from literature and our own experience.Overall efficiency to SNG is highest for Allothermal gasification. The net overall efficiencies on LHV basis, including electricity consumption and pre-treatment but excluding transport of biomass are 54% for Entrained Flow, 58% for CFB and 67% for Allothermal gasification. Because of the significantly higher efficiency to SNG for the route via Allothermal gasification, ECN is working on the further development of Allothermal gasification. ECN has built and tested a 30 kW_th lab scale gasifier connected to a gas cleaning test rig and methanation unit and presently is building a 0.8 MWth pilot plant, called Milena, which will be connected to the existing pilot scale gas cleaning.