07 Alternative energy sources (bioconversion energy)

99lo3091 Rapid pyrolysis of straw at high temperature Zanzi, R. et al. Dev. Thermochem. Biomass Comers., 1997, 1, 61-66. Edited by A free-fall

Bridgwater, A. V. and Boocock, D. G. B., Blackie, London, UK. reactor was implemented in the study of the rapid pyrolysis of

biomass, which in this case was untreated straw and straw pellets. Subsequently, the results were compared with those previously obtained in wood pyrolysis. Before pyrolysis the straw is milled, sieved, and wind classified to obtain fractions of uniform particle size. The free-fall reactor has a heated length of 2.9 m and an inner diameter of 0.04 m. The char from the rapid pyrolysis is further pyrolysed in nitrogen atmosphere in a thermobalance with a slow heating rate (ZO”C/min) up to 850°C in order to obtain complete pyrolysis. This work focuses on the effect of the treatment conditions on the product distribution, gas composition and properties of the char obtained in pyrolysis. The product distribution in rapid pyrolysis of wood, untreated straw, and pelletized straw was revealed to be similar. A little less char is produced by wood than straw. The higher treatment temperature has led to lower yields of tar and higher yields of gaseous products. At higher temperature, the heat flux and the heating rate are higher. The higher heating rate favours also the decrease of char yield.

99103092 Relationship between gasification reactivity of straw char and water soluble compounds present in this material Henriksen, U. el al. Dev. Thermochem. Biomass Comers., 1997, 2, 881- 891. Edited by Bridgwater, A. V. and Boocock, D. G. B., Blackie, London, UK. The content of water soluble compounds in the straw determines the reactivity in the gasification of straw char. Water solubles were extracted and reabsorbed into a previously washed sample. Washing significantly reduced the reactivity and the original high reactivity could be re- established by absorption of the water soluble compounds back in the sample. This effect was observed to be caused by the presence of water solubles during the gasification, while their presence during pyrolysis had no measurable effect on the gasification reactivity. A linear correlation between the reactivity and the concentration of the water solubles was found.

99103093 Removal of residual char fines from pyrolysis vapors by hot gas filtration Scahill, J. et al. Dev. Thermochem. Biomass Cowers., 1997, 1, 253-266. Edited by Bridgwater, A. V. and Boocock, D. G. B., Blackie, London, UK. Hot gas filtration of biomass pyrolysis vapours has been studied in an NREL-designed vortex reactor fast pyrolysis process development unit (PDU). Most of the experimental work employed a conventional baghouse type of filter that used NEXTEL ceramic cloth filter bags as the filter medium. A series of experimental runs demonstrated that hot gas filtered bio-crude oils having less than 10 ppm of total alkali could be reproducibly made. Char cake removal from the filter elements proved to be a difficult problem; the char appears to become progressively more sintered to itself and the filter as a function of the cumulative biomass process. This dense char can be removed from the filters with dense filtration, but this leaves residual ash on the filter cloth fibres. This ash may in turn cause subsequent biomass pyrolysis vapours that pass through the filter to produce additional char (coke) in the interstices of the filter cloth. Data suggest this char formation may contribute to a more rapid rate of filter blinding as measured by the increase in recovered filter pressure drop.

98/03094 A review of the chemical composition of fast- pyrolysis oils from biomass Milne, T. et al. Dev. Thermochem. Biomass Cowers., 1997, 1, 409-424. Edited by Bridgwater, A. V. and Boocock, D. G. B., Blackie, London, UK. Literature available on the detailed chemical composition of fast or flash pyrolysis oils produced from biomass under conditions that minimize secondary cracking are reviewed. The findings, including a list of compounds reported and their quantities, are summarized here. Where quantitative yields are available, an attempt has been made to relate yields to feedstocks and conditions of pyrolysis.

98103095 Role of forest sector and bioenergy in limiting the carbon emissions of Finland Pingoud, K. and Lehtilti, A. Biomass and Bioenergy, 1997,13, (6), 413-420. The paper discusses the greenhouse impacts of the Finnish forest sector. The main carbon storages and flows are estimated and the greenhouse gas balance are presented both totally and on national level. The history of the greenhouse impact is also estimated and two future scenarios of the forest sector are compared. Also reviewed are the present use and potential for additional use of bioenergy and the impact of expanded bioenergy use on the national CO2 emissions is illustrated with scenario examples.

98103096 RTP biocrude: a combustion/emissions review Huffman, D. R. and Freel, B. A. Dev. Thermochem. Biomass Comers., 1997, 1, 489-494. Edited by Bridgwater, A. V. and Boocock, D. G. B., Blackie. London. UK.

(Canada), SANDIA (USA), ENEL (Italy), NESTE (Finland) and ARSTA (Sweden). Using mechanical, air and steam atomization nozzles, data on flame temperatures, heat release profiles and emissions have been collected for systems. These tests have conclusively established that biocrudes can be burned with steady-state self-sustaining flames that closely resemble those from petroleum-based fuel oils. Results have confirmed that conversion to a liquid permits better combustion control resulting in significantly lower emission levels than those typically obtained by direct combustion of the solid biomass wastes. It is expected that existing combustion systems for fuel oils can be modified to burn biocrudes with emission levels that will allow permitting in normal situations.

9aio3097 Simultaneous heat, mass and momentum transfer during biomass drying Di Blasi, C. Dev. Thermochem. Biomass Comers., 1997, 1, 117-131. Edited by Bridgwater, A. V. and Boocock, D. G. B., Blackie, London, UK. Transport phenomena and moisture evaporation of biofuels exposed to radiative/convective heating are represented in a mathematical model. The medium is considered as a three-phase mixture: virgin solid with bound water to the FSP, capillary water that partially fills the pores and bubbles containing inert gas and water vapour. Transport phenomena account for convection of capillary water, convection and diffusion of water vapour, surface diffusion of bound water, heat convection and conduction, liquid and gas phase pressure and velocity variations. The partial pressure of vapour is equal to its equilibrium value, which is a function of both temperature and moisture content. The high-temperature drying of I x lo- m thick particles, with an initial moisture content of 50% on dry basis, has been simulated by varying the external heat transfer coefficient and the permeabilities to liquid and gas flow. The findings are applied to understand thermal drying dynamics and to assess the validity limits of simplified theories of moisture evaporation, usually introduced in the mathematical description of moist particle pyrolysis and gasification.

90lO3098 Towards a standard methodology for greenhouse gas balances of bioenergy systems in comparison with fossil energy systems Schlamadinger, B. et al. Biomass and Bioenergy, 1997, 13, (6), 359-375. As part of IEA Bioenergy Task XV, this work outlines a standard methodology for comparing the greenhouse gas balances of bioenergy systems with those of fossil energy systems. Emphasis is on a careful definition of system boundaries. Recommendations are given on how analyses of greenhouse gas balances should be performed. In some cases we also point out alternative ways of doing the greenhouse gas accounting. The paper finally gives some recommendations on how bioenergy systems should be optimized from a greenhouse-gas emissions point of view.

98/03099 Usage of biomass gas for fuel cells by the SIR process Hacker, V. et al. J. Power Sources, 1998, 71, (l/2), 226-130. A cost-efficient production and supply of hydrogen (Hz) and carbon monoxide (CO) are essential for the successful application of fuel cells in our future energy system. The process cycle iron oxide/iron/hydrogen offers a simple possibility to store the energy of synthesis gases in the form of sponge iron and at the same time to reform and condition these synthesis gases. As ‘product’ of this energy storage system one receives pure hydrogen. The advantages offered by the ‘Sponge Iron Reaction’ (SIR) process over conventional gas cleaning and conversion processes include: (i) low-cost hydrogen by using cheap sponge iron materials; (ii) high-quality hydrogen from low-BTU gases by a two-step operation; (iii) high efficiency compared with competitive technologies and (iv) system versatility and ease of siting.

98/03100 Wood gasification in the fluidized bed Ising, M. et al. Brennst.-Waerme-Krafi, 1998, 50, (l/2), 59-62. (In German) At the Fraunhofer Umsicht in Oberhausen, Germany, a pilot plant for combined heat and power generation from wood and biomass was designed and constructed. Wood chips were gasified in a circulation fluidized bed and the generated gas was used in a gas engine to produce electricity. The plant was received a feed of 80-100 kg/h wood and reached a electric performance of 25-28%. The low ash content in the fuel in comparison with coal, meant it was necessary to stabilize the fluidized bed by adding sand. The pilot plant was operated under different conditions and the gas composition, gas production rate and performance were measured. Finally the economical application of this technology was discussed due to dimensioning of the plant, availability and costs of the fuel.

90lo3101 Yields of oil products from thermochemical bio- mass conversion processes

A number of research, pilot plant and commercial systems produce Demirbas, A. et al. Energy Comers. Manage., 1998, 39, (7), 685-690. sufficient quantities of liquid fuels from solid biomass waste for applied In order to obtain the maximum fuels from biomass, thermochemical combustion tests, firmly establishing this thermochemical conversion via biomass conversion processes were applied non-catalytically and catalyti- fast pyrolysis. Biocrudes produced with Ensyn’s RTP technology have tally. Different solvents and their mixtures were used in simple and undergone characterization and combustion tests in flame tunnels,’ furnaces, combustors and boilers, including work at MIT (USA), ERL

supercritical extractions. Basic catalysts were used in the catalytic conversion experiments and they were performed at 498-820 K.

206 Fuel and Energy Absttacts July 1996