Modeling of biomass-based hydrogen production via catalytic sorption-enhanced reformer integrated with a gasifier

The sorption enhanced reformer concept breaks the thermodynamic limits of steam methane reforming and water-gas shift reactions with selective CO₂ removal to produce more H₂. In this paper, we propose a dynamic kinetic model for sorption-enhanced steam reformers (SERs) integrated with biomass gasifiers. An analysis of operating conditions was conducted to examine high purity hydrogen production. The kinetic model was validated with published literature results at different reactor pressures (5-20 bar), steam/carbon ratios (2-5), and reactor temperatures (673K–1023K). This study shows that biomass gasifiers can be integrated with SER reactors to produce high purity H₂.     

A two dimensional Euler–Lagrangian model of wood gasification in a charcoal bed—Part II: Parameter influence and comparison

A Euler–Lagrangian simulation was employed for a comprehensive parameter study of wood gasification in a fluidized charcoal bed. The parameters that were varied include the initial bed temperature, fuel mass flow rate, inert tar fraction, and kinetic energy losses caused by particle–particle and particle–wall collisions. The results of each parameter variation are compared with a base scenario, previously described in detail in Part I of this study (Gerber & Oevermann, 2014). The results are interpreted by comparing the reactor outlet temperature, averaged particle temperature, overall wood mass, overall charcoal mass, concentrations of several gaseous species, and axial barycenter data for particles obtained with different sets of parameters. The inert tar fraction and fuel mass flow rate are the most sensitive parameter, while the particle–particle and particle–wall contact parameters have only a small impact on the results. Increasing the reactive tar components by 19% almost doubled the amount of reactive tars at the reactor outlet, while decreasing the restitution coefficients of the particle collisions by 0.2 results in higher overall gas production but almost no change in bed height. Herein, our numerical results are discussed in detail while assessing the model restrictions.     

Gasification characteristics of woody biomass in the packed bed reactor

Gasification technology is recognized as one of the possibilities for utilizing biomass effectively. This study focused on woody biomass gasification fundamentals, using a bench-scale packed-bed reactor. In this experiment, pellets of black pine were gasified, using air as the oxidizing agent. Gasification tests were carried out under both updraft and downdraft conditions. Temperature distributions and compositions of syngas inside the gasifier were continuously monitored during gasification experiments at several ports on the wall of the reactor. The syngas at the exit of the gasifier was also sampled to estimate the amount of tar. Lower heating values of the syngas under updraft and downdraft conditions were 4.8 and 3.8 MJ/m³N, respectively. It was easier to control the height of the packed bed under the downdraft condition than under the updraft condition. Under the updraft condition, a bridging phenomenon occurred. Tar generation under the downdraft condition was lower than that under the updraft condition. This is because tar passes through a partial combustion zone or higher temperature zone in the downdraft gasifier.     

基于三种气化炉的整体煤气化湿化燃气轮机循环热力性能分析

将燃料湿化和空气湿化应用到整体煤气化燃气轮机循环中,以降低NOx排放并有效利用系统低品位热。基于水煤浆、干煤粉及输运床三种气化炉,构建了多种整体煤气化湿化燃气轮机循环,分析了其热力性能并给出了湿化方式建议。研究表明：燃料湿化循环系统效率较高;空气湿化循环燃气轮机比功较大;整体煤气化湿化燃气轮机循环具有利用系统外部中低品...     

An economic and environmental comparison of a biochemical and a thermochemical lignocellulosic ethanol conversion processes

With the world’s focus on rapidly deploying second generation biofuels technologies, there exists today a good deal of interest in how yields, economics, and environmental impacts of the various conversion processes of lignocellulosic biomass to transportation fuels compare. Although there is a good deal of information regarding these conversion processes, this information is typically very difficult to use on a comparison basis because different underlying assumptions, such as feedstock costs, plant size, co-product credits or assumed state of technology, have been utilized. In this study, a rigorous comparison of different biomass to transportation fuels conversion processes was performed with standard underlying economic and environmental assumptions so that exact comparisons can be made. This study looked at promising second-generation conversion processes utilizing biochemical and thermochemical gasification technologies on both a current and an achievable state of technology in 2012. The fundamental finding of this study is that although the biochemical and thermochemical processes to ethanol analyzed have their individual strengths and weaknesses, the two processes have very comparable yields, economics, and environmental impacts. Hence, this study concludes that based on this analysis there is not a distinct economic or environmental impact difference between biochemical and thermochemical gasification processes for second generation ethanol production.     

Development of plasma pyrolysis/gasification systems for energy efficient and environmentally sound waste disposal

As more efficient and reliable torches for thermal plasma generation have become available in recent years, the use of thermal plasma as an energy source for pyrolysis/gasification has attracted much interest, and special attention has been paid to waste treatment for resource and energy recovery. Plasma pyrolysis/gasification systems have unique features such as the extremely high reaction temperature and ultra-fast reaction velocity compared to traditional pyrolysis/gasification systems. Plasma pyrolysis/gasification is therefore acknowledged as a novel pyrolysis/gasification technology with great potential in solid waste disposal. This paper gives a comprehensive review on the development of fundamental researches on plasma pyrolysis/gasification systems including direct current (DC) arc plasma system and radio frequency (RF) plasma system with an emphasis on reactor design such as plasma fixed/moving bed reactor system, plasma entrained-flow bed reactor system and plasma spout-fluid bed reactor system.     

Determination of the heats of gasification of polymers using differential scanning calorimetry

The amount of heat that is required to gasify unit mass of material is one of the key properties that define its ignition resistance and fire response. Knowledge of this property is necessary to assess a material's fire hazard in a particular fire scenario. Nevertheless, even for the most common polymers the values of this property are not well established. Here we present a method for determining the heat of gasification using differential scanning calorimetry and apply this method to a set of ten common plastics and engineering polymers.     

生物质洁净能源研究中的流化床动力学模型

分别对最小流化床、鼓泡流化床和腾涌流化床及相应的全混模型、鼓泡模型、气泡汇集模型等加以综述 ,分析其优缺点 ,并在此基础上提出动力学模拟研究的新思路 .根据流化床内在的本质———流化态的不同 ,将流化床分为最小流化床、鼓泡流化床和腾涌流化床三种 .总结了前人针对各种流化床提出的全混模型、鼓泡模型、气泡汇集模型等思想 ,建议今后可以在以下几个方面进行深入研究 :⑴使得模型更有普适性 .⑵由于气泡有效直径尚不能在理论上求得 ,可以在理想气泡直径变化公式的基础上 ,加入非线性化学的计算 .⑶确定不同情况下的参数 ,使得工作更有延续性 ,也使得模型更加具有生命力 .⑷从高压的角度去进行模型的计算 ,并得到相应的试验数据支持 .     

Analysis of the product gas from biomass gasification by means of laser spectroscopy

The use of biomass and waste for decentralised combined heat and power production (CHP) requires highly efficient gasification processes. In the Technische Universität München (TUM), an innovative gasification technology has been developed. This allothermal gasifier is producing a hydrogen- rich, high-calorific gas, that can be further used in a microturbine or a fuel cell producing energy. For the operation of such a system, the online analysis of the composition of the product gas is of high importance, since the efficient working of the machines is linked with the gas quality. For this purpose an optical measurement system based on laser spectroscopy has been applied. This system can measure not only the basic components of the product gas (H₂, CH₄, CO, CO₂, H₂O), but it also gives information concerning the content of high hydrocarbons, the so-called tars, in the product gas.     

The rate of gasification by CO2 of chars from waste

Three chars and an activated carbon were gasified by reaction with CO₂ in a fluidised bed of sand, at 800–1050 °C. The chars were produced from (i) dried sewage sludge, (ii) car tyres, and (iii) a bituminous coal. For the conditions used, the rate of CO₂ + C → 2CO was largely determined by chemical kinetics; there was a small effect from mass transfer for the most reactive char, derived from sewage sludge. The rate of CO formation, r, differed greatly for these chars, but was well described by:

The reactivity of a char depends on: (i) its pore structure, (ii) catalytic activity of the associated ash, and (iii) the activity of the char’s carbon. The sewage sludge char was the most reactive, on the basis of either BET area or mass by 2 orders of magnitude. The activated carbon had the lowest reactivity per unit BET surface area, indicating that the area in its micropores is comparatively unreactive.