Conditions for the sustainability of biomass based fuel use

Sustainability of biomass based fuel use requires that in biomass production erosion and water usage do not exceed addition to stocks of soil and water and that levels of nutrients and organic matter in soils do not decrease. Levels of volatile carbon compounds and N₂O in the atmosphere should remain unaffected. To maintain ecosystems services of nature useful to mankind, restriction of biomass production to degraded and currently fallow land is to be preferred. Also sustainability of biomass-for-energy use requires a high efficiency recycling of nutrients present in ashes and low emissions of persistent organics, acidifying compounds and heavy metals due to biomass combustion. Meeting such conditions requires major efforts.     

生物质热裂解制取液体燃料技术的发展

对生物质热裂解技术进行了系统的研究,阐述了其基本技术要求和发展现状,并将现有的生物质热裂解反应器进行分类,分析了相应的优势与不足。最后评估了生物质热裂解制取液体燃料技术的经济和社会效益,结果表明它具有广泛的应用前景。     

Experimental study on oxygen-enriched combustion of biomass micro fuel

The oxygen-enriched combustion of biomass micro fuel (BMF) was carried out respectively in the thermogravimetric analyzer and cyclone furnace to evaluate the effects of oxygen concentration on combustion performance. The experimental results show that with the increasing oxygen concentration, the volatile releasing temperature, ignition temperature and burnout temperature were decreasing. Oxygen-enriched atmosphere subtracts burning time and improves combustion activity of biomass micro fuel. Oxygen-enriched atmosphere improves the combustion temperature of BMF in cyclone furnace; while the improvement is weaken as oxygen concentration is above 40%.     

Assessment of the fuel wood of India: A case study based on fuel characteristics of some indigenous species of Arunachal Pradesh

Biomass in the form of fuelwood has been a source of energy for many centuries all over the world. In rural India, fuelwood remains the first choice of energy source. Arunachal Pradesh is home to many different tree species; so far most of the fuelwoods of Arunachal Pradesh have never been studied for their fuel characteristics. This study is carried out with the following objectives: (i) Identification and selection of indigenous fuelwood species, which are widely distributed throughout Arunachal Pradesh, North East India; (ii) quantitative and qualitative analysis of these fuelwoods; and (iii) to rank these fuelwoods according to their fuel value index.     

The introduction and expansion of biomass use in Swedish district heating systems

District heating satisfies about 60% of the heat demand in Swedish buildings. Today, more than two thirds of the heat supply to the district heating systems is based on biomass and waste, and biomass alone accounts for about half of the heat supply. The purpose of this paper is to present the Swedish experiences of introducing and expanding the use of biomass in the district heating systems and to identify the main drivers behind this development. Our five research questions and the corresponding conclusions consider the driving forces from energy policy tools and local initiatives, the biomass prices, the established infrastructures in forestry and district heating, the technology paths for biomass conversion, and finally the future challenge of competing uses of biomass.     

Effect of gasification agent on the performance of solid oxide fuel cell and biomass gasification systems

In this paper, an integrated solid oxide fuel cell (SOFC) and biomass gasification system is modeled to study the effect of gasification agent (air, enriched oxygen and steam) on its performance. In the present modeling, a heat transfer model for SOFC and thermodynamic models for the rest of the components are used. In addition, exergy balances are written for the system components. The results show that using steam as the gasification agent yields the highest electrical efficiency (41.8%), power-to-heat ratio (4.649), and exergetic efficiency (39.1%), but the lowest fuel utilization efficiency (50.8%). In addition, the exergy destruction is found to be the highest at the gasifier for the air and enriched oxygen gasification cases and the heat exchanger that supplies heat to the air entering the SOFC for the steam gasification case.     

Industrial processes for biomass drying and their effects on the quality properties of wood pellets

This paper contributes to the discussion of how different kinds of industrial scale dryers for biomass influence the quality properties of wood pellets. It also discusses how the drying technique can affect the environment. The most common biomass drying processes in use, i.e., convection dryers are discussed. The discussion of drying techniques is based on advantages and disadvantages with a focus on the drying medium, temperature and residence time. The choice of drying technique is particularly important if the end-user’s choice of pellets is made due to the specific requirements for the heating system used. Some specific parameters were tested in order to investigate how the choice of drying technique affects the pellet quality. The parameters tested were moisture content and the emissions of volatile hydrocarbons. Pellets available on the market were chosen for the tests. The amount of volatile hydrocarbons left in sawdust after drying vary with drying technique, as emissions of terpenes are larger in dryers with long residence times. Low emissions of volatile hydrocarbons would improve the energy content of the sawdust, and by decreasing air pollution improve the work environment and the environment in the surroundings of the dryers.     

A study on torrefaction of various biomass materials and its impact on lignocellulosic structure simulated by a thermogravimetry

Torrefaction processes of four kinds of biomass materials, including bamboo, willow, coconut shell and wood (Ficus benjamina L.), were investigated using the thermogravimetric analysis (TGA). Particular emphasis is placed on the impact of torrefaction on hemicellulose, cellulose and lignin contained in the biomass. Two different torrefaction processes, consisting of a light torrefaction process at 240 °C and a severe torrefaction process at 275 °C, were considered. From the torrefaction processes, the biomass could be divided into two groups; one was the relatively active biomass such as bamboo and willow, and the other was the relatively inactive biomass composed of coconut shell and wood. When the light torrefaction was performed, the results indicated that the hemicellulose contained in the biomass was destroyed in a significant way, whereas cellulose and lignin were affected only slightly. Once the severe torrefaction was carried out, it further had a noticeable effect on cellulose, especially in the bamboo and willow. The light torrefaction and severe torrefaction were followed by a chemically frozen zone, regardless of what the biomass was. From the viewpoint of torrefaction application, the investigated biomass torrefied in less than 1 h with light torrefaction is an appropriate operation for producing fuels with higher energy density.     

Plate reactor as an analysis tool for rapid pyrolysis of biomass

This work presents a study of the performance of the modified plate reactor by rapid pyrolysis experiments with different biomass samples (MDF, bark pine and Avicel cellulose). The use of the plate instead of a grid allowed us to achieve a more homogeneous temperature distribution across the plate and, therefore, biomass sample. The mass yields of the major pyrolysis products CO, CO₂, C₂H₂, CH₄, C₂H₄ and C₂H₆ are measured as a function of the holding time (from 0 to 50 s) for a number of the final temperatures (from 435 to 1100 C) using the novel approach to quantitative FTIR analysis of biomass pyrolysis spectra. Special care was taken to demonstrate the influence of the secondary tar cracking on the yields of the permanent gases. Yields of major permanent gases plotted versus each other on a logarithmic scale show two distinctive regions reflecting primary and secondary kinetic processes. The experiments show that the modified plate reactor can be used for studying the kinetics of the primary decomposition of the biomass at temperatures ≤600 C.     

Investigation of forestry wastes: Torrefaction and their thermal properties for use in energy recovery schemes

Three biomasses like Eucalyptus, Azadirachata, and Ficus religiosa were torrefied to investigate the effect of temperature and residence time was investigated on torrefied biomasses for yield, volatile matter, fixed carbon, ash, and Gross calorific value (GCV). Thermogravimetric analysis and Hardgrove grindability index (HGI) of three torrefied samples were studied at optimum conditions of temperature and residence time. According to the results, an optimum temperature was found to be 260°C at 45 min residence time. A maximum GCV of torrefied biomasses of Eucalyptus, Azadirachata, and F. religiosa were found to be 4,301, 3,190, and 3,278 kcal/kg, respectively. According to thermogravimetric analyzer results, the Azadirachata has shown higher weight loss compared to Eucalyptus and F. religiosa during thermogravimetirc study. The weight loss rate for Azadirachata was maximum to nearly 12.8%/min compared to 6.11 and 5.12%/min for Eucalyptus and F. religiosa, respectively. The order of reactivity based on mean reactivity and combustion characterization factor was found to be Azadirachata indica > Eucalyptus > F. religiosa. According to HGI results, Eucalyptus, Azadirachata, and F. religiosa have shown HGI values of 71, 60.7, and 81.7, respectively. The results of this study could be useful for the energy recovery schemes in the country.     

Influence of temperature and residence time in the pyrolysis of woody biomass waste in a continuous screw reactor

The aim of this paper is to study the influence of temperature and residence time in the quality of the charcoal obtained in the pyrolysis of biomass waste, in order to be used as a reducing agent in metallurgical applications. Woody biomass waste (pinus pinaster) coming from forest activities carried out in the north of Spain has been pyrolyzed in a laboratory scale screw continuous reactor connected to a second reactor where the pyrolysis vapors have been thermally treated to promote further cracking, with the aim of diminishing tars and improving the composition of the gas phase.Both the peak temperature and the exposition time at peak temperature have an impact in the pyrolysis fractions yields and composition, however it is at 1173 K where the bigger changes occur both in pyrolysis products yield and composition. In all cases the solids obtained (charcoal) fulfill the requirements to perform as metallurgical reducers. The higher the peak temperature the greater the charcoal quality but the lower the pyrolysis solid yield since secondary pyrolysis reactions consume charcoal. The pyrolysis gases obtained are valuable products rich in CO (22–35 vol%) and hydrogen (35–50 vol%); on the contrary, the pyrolysis liquids obtained are mainly worthless products composed of water and some aromatic compounds (e.g. naphthalene, fluorene & antrhacene).     

Investigating the effects of methanol-water vapor mixture on a PBI-based high temperature PEM fuel cell

This paper investigates the effects of methanol and water vapor on the performance of a high temperature proton exchange membrane fuel cell (HT-PEMFC). A H₃PO₄-doped polybenzimidazole (PBI) membrane electrode assembly (MEA), Celtec P2100 of 45 cm² of active surface area from BASF was employed. A long-term durability test of around 1250 h was performed, in which the concentrations of methanol-water vapor mixture in the anode feed gas were varied. The fuel cell showed a continuous performance decay in the presence of vapor mixtures of methanol and water of 5% and 8% by volume in anode feed. Impedance measurements followed by equivalent circuit fitting revealed that the effects were most significant for intermediate-high frequency resistances, implying that charge transfer losses were the most significant losses. Vapor mixture of 3% in feed, however, when introduced after operation at 8%, showed positive or no effect on the cell's performance in these tests.     

Cogeneration of power and substitute of natural gas using electrolytic hydrogen,biomass and high temperature fuel cells

Energy storage from renewable sources is one of the main current goals for the energy sector, and the production of a substitute of natural gas could be a good solution to solve the problem in the short term, helping the transition to hydrogen in the long term.Renewable energy sources usually generate variable electric power or medium/low energy content gas. This paper proposes a way to upgrade these products through the use of electrolytic hydrogen. By using electrolytic oxygen as an oxidant for biomass partial oxidation and for high temperature fuel cells, the exhaust gas after post-combustion is an almost pure mixture of water and carbon dioxide. Once such a gas is dehydrated, the carbon dioxide can be mixed with electrolytic hydrogen to obtain methane through the Sabatier process.Four layouts based on molten carbonate fuel cells and solid oxide fuel cells has been investigated. The results obtained are very similar: the conversion efficiency is close to 60% and the mix of energy output consist of fuel for about 75% and electric power for about 25%.     

Thermodynamic evaluation of small-scale systems with biomass gasifiers, solid oxide fuel cells with Ni/GDC anodes and gas turbines

Thermodynamic calculations were carried out to evaluate the performance of small-scale gasifier–SOFC–GT systems of the order of 100 kW. Solid Oxide Fuel Cells (SOFCs) with Nickel/Gadolinia Doped Ceria (Ni/GDC) anodes were considered. High system electrical efficiencies above 50% are achievable with these systems. The results obtained indicate that when gas cleaning is carried out at temperatures lower than gasification temperature, additional steam may have to be added to biosyngas in order to avoid carbon deposition. To analyze the influence of gas cleaning at lower temperatures and steam addition on system efficiency, additional system calculations were carried out. It is observed that steam addition does not have significant impact on system electrical efficiency. However, generation of additional steam using heat from gas turbine outlet decreases the thermal energy and exergy available at the system outlet thereby decreasing total system efficiency. With the gas cleaning at atmospheric temperature, there is a decrease in the electrical efficiency of the order of 4–5% when compared to the efficiency of the systems working with intermediate to high gas-cleaning temperatures.     

Ultrasonic vibration-assisted pelleting of cellulosic biomass for ethanol manufacturing: An investigation on pelleting temperature

Ethanol made from cellulosic biomass is an alternative to petroleum-based liquid transportation fuels. However, large-scale manufacturing of cellulosic ethanol is hindered by the low density of cellulosic biomass. Experiments have shown that ultrasonic vibration-assisted (UV-A) pelleting could compress low-density raw biomass into high-density pellets, and pelleting temperature increased during pelleting process. However, pelleting temperature was not fully investigated. This paper reports an investigation on pelleting temperature in UV-A pelleting of wheat straw. The precision of temperature measurement was first evaluated. Relationships between pelleting temperature and pelleting time were then investigated. Also, the pattern of pelleting temperature distribution was evaluated by ranking the pelleting temperatures at six different locations in a pellet. Finally, effects of three input variables (ultrasonic power, pelleting pressure, and pellet weight) on pelleting temperature were discussed. Results reported in this paper are the foundation of a follow-up paper reporting relationship between pelleting temperature and pellet quality (density, durability, and sugar yield).     

Influence of biomass addition on electricity harvesting from solid phase microbial fuel cells

In this study, two types of biomass (Acorus calamus leaves and wheat straw) were added to a matrix of sediment and soil inside the anode of solid phase microbial fuel cells (SMFCs) in order to increase their output power. SMFC containing 3% leaves in their sediment had a maximum power density of 195 mW m⁻² in contrast to 4.6 mW m⁻² of that SMFC without leaves. Similarly, SMFC containing 1% wheat straw in their soil environment had a maximum power density of 167 mW m⁻². It suggests that the addition of biomass in appropriate proportions increases contact opportunities between the matrix, the anode and the added biomass, increases organic matter content, and enhances cellulase activity, thus serving as an important method for enhancing output power in SMFCs.     

Optimal temperature control of solar heating systems

Temperature control systems based on solar and wind energy differ in two important ways from existing fossil fuel systems. One is that solar systems, at least active solar systems, all have some kind of energy storage, the other is that the source of energy in a solar and wind energy system is variable and uncontrollable. Because of these added complications and the high capital investment required for solar and wind energy systems, considerably more sophisticated techniques are required for the design of those systems. In this study, a new technique is applied to the optimal control problem of solar heating systems.     

高温移动床废轮胎与生物质直接热解制气性能研究

对以不同比例组成的废轮胎与生物质均匀混合物在移动床内高温直接热解的制气性能进行了研究,考察了温度和废轮胎含量对产物产率、气体组分以及热值等影响。结果表明,温度对直接热解气产率和热值影响较大,温度越高,气体产率越大而热值越小;混合物中废轮胎含量增大,热解气中碳氢气体含量增多而含氧气体减少,气体产率逐渐减小而热值增大。温度升高,合成气(H2+CO)含量和H2/CO比值均增大;废轮胎含量增大,合成气(H2+CO)含量和H2/CO比值先增大后减小。当热解温度为1 000℃,废轮胎含量为35%时,热解产物中(H2+CO)含量最高为61%,且H2/CO的比值达到最大值为1.53,有利于作为工业合成气原料。同一温度下,混合物直接热解气热值远远高于生物质单独热解,说明废轮胎的掺入有助于优化热解气组成,提升燃气品质。     

Study on prediction models of biomass ash softening temperature based on ash composition

As a characterization constant of fuel's ash fusibility, ash melting point of fuel plays an important role in the performance of boiler burning. The properties of the ash melting point of fuel have been proved to have close relationships with the contents of oxides in the ash. This paper focuses on finding out general laws to predict the ash melting point of biomass based on the classification of biomass and the analysis of oxides contents. The results of testing and verifying have shown that, the method of biomass ash melting point prediction is effective.