Ralph P. Overend

Biomass and renewable fuels

Abstract Biomass is an important contributor to the world economy. Agriculture and forest products industries provide food, feed, fiber, and a wide range of necessary products like shelter, packaging, clothing, and communications. However, biomass is also a source of a large variety of chemicals and materials, and of electricity and fuels. About 60% of the needed process energy in pulp, paper, and forest products is provided by biomass combustion. These processes could be improved to the point of energy self-sufficiency of these industries. Todays corn refinery industry produces a wide range of products including starch-based ethanol fuels for transportation. The biomass industry can produce additional ethanol by fermenting some by-product sugar streams. Lignocellulosic biomass is a potential source for ethanol that is not directly linked to food production. Also, through gasification biomass can lead to methanol, mixed alcohols, and Fischer–Tropsch liquids. The life science revolution we are witnessing has the potential to radically change the green plants and products we obtain from them. Green plants developed to produce desired products and energy could be possible in the future. Biological systems can already be tailored to produce fuels such as hydrogen. Policy drivers for increased use of biomass for energy and biobased products are reviewed for their potential contributions for a carbon constrained world.

Catalytic conditioning of synthesis gas produced by biomass gasification

The catalytic steam reforming of aromatic hydrocarbons in a background of synthesis gas was investigated for two catalysts. A proprietary non-nickel based catalyst, designated DN-34, and a commercial nickel steam reforming catalyst ICI 46-1 were tested. Statistically designed experiments were used to examine the effects of temperature, space velocity and percent of steam in the feed on catalyst performance. All experiments were performed in a plug-flow micro-reactor interfaced with a molecular beam mass spectrometer. The catalyst DN-34 was also tested in slip-stream fluidized bed reactors attached to a 9 tonne day−1 indirectly heated biomass gasifier at Battelle Columbus Laboratory. DN-34 was found to be effective for destroying a variety of aromatic hydrocarbons found in biomass gasifier tar in both the micro-reactor and gasifier-scale experiments. DN-34 also exhibited significant water-gas shift activity but was unsatisfactory for methane destruction. ICI 46-1 exhibited excellent methane steam reforming activity. A process is suggested that uses DN-34 to steam reform tar and perform the water-gas shift, followed by a second reactor with ICI 46-1 to reform methane. Differences and similarities with other dual-bed processes described in the literature are discussed.

The cleavage of the arylOCH3 bond using anisole as a model compound

Abstract The thermal decomposition of anisole as a prototype of the aryl-methyl-ether linkage of lignin and coals has been studied under supercritical conditions using tetralin as hydrogen donor solvent. The effect of homogenous Lewis acid catalysts have also been studied under the same conditions. The main reaction products are phenol, benzene, toluene and cresols. At high tetralin to anisole ratios the selectivity to phenol is almost 80% with little or no cresol production. This selective conversion can be carried out rapidly and cleanly at high temperature (> 450 °C). Kinetic studies were undertaken using pyrolytic, donor solvent hydrogenolytic and Lewis acid catalysed regimes in the temperature range 400–500 °C. The kinetics of anisole decomposition in a large excess of tetralin have been found to be in good agreement with those published in the literature. The Lewis acid catalysts lower the activation energy relative to the pyrolytic and hydrogenolytic cases. The kinetic studies and their mechanistic interpretation lead to a mechanism involving surprisingly few radical species: methyl, phenoxy, phenoxymethyl and phenyl radicals. In the presence of FeCl3, the selectivity towards phenols and cresols is enhanced, though a side reaction leads to polymerization at low (400–420 °C) temperatures. It is concluded that the aryl-O-methyl ether linkage in anisole can easily be broken at high temperatures, 450–500 °C, in supercritical hydrogen donor solvent to give phenol in high yield and selectivity.

The aryl ether bond reactions with H-donor solvents : guaiacol and tetralin in the presence of catalysts

Abstract The effect of homogeneous catalysis, Fe and Ru, on the conversion of guaiacol in tetralin to catechol and phenol has been investigated as a model for the behaviour of the aryl-oxy linkage that is found in wood, peat and younger coals. In the absence of catalyst and at low ratios of guaiacol to tetralin, the primary product is catechol. Kinetic analysis has confirmed that the rate constant for this primary and rate determining step is given by an Arrhenius pre-exponential factor of 10 13.8 s −1 with an activation energy of 215 kJ mol −1 . The activation energy found is in good agreement with those of other investigators and lies between the values proposed for homolytic fission (>240 kJ mol −1 ) and for a concerted or pericyclic reaction (188 kJ mol −1 ). In the presence of catalysts the rate is not changed; however, the yield of a secondary product phenol is increased with both Fe and Ru. Separate experiments confirmed that the selectivity of catechol to phenol conversion was markedly increased in the presence of these catalysts. There is strong evidence for the formation of catecholato-iron complexes and this suggests that in pyrolysis and liquefaction of biomass and young coals there may well be a role for homogeneous catalysts in directing the product slate towards useful intermediate chemicals such as phenols.

Status of the IEA Voluntary Standards Activity — Round Robins on Whole Wood and Lignins

The International Energy Agency -- Bioenergy Agreement — Biomass Conversion Annex VII -- Standardized Analytical Methods Activity has been ongoing for the past three years. Participating countries are Canada, Finland, the Netherlands, New Zealand, Norway, Sweden, and the United States. The goal is to provide researchers and technology developers with information on reliable methods in use, or proposed, for characterizing feedstocks, process intermediates, and end products from biomass conversion to fuels, energy-intensive chemicals, and electric power. Accurate compositional analyses of biomass feedstocks and lignins are important for the commercialization of these technologies. This international activity provided and tested selected analytical methods for use in the characterization of a wide range of biomass feedstocks and lignins. Two round robins were conducted, one on the analysis of whole biomass feedstocks and the other on analysis of lignins.

Thermogravimetric analysis of glycol lignin fractions obtained by sequential solvent extraction

Abstract Data are presented on the thermal behaviour of a solvolytic lignin and its fractions during combustion and devolatilization in a thermal analyser.

Chapter 3 – Heat, Power and Combined Heat and Power

Publisher Summary Biomass combustion such as burning fuel wood to provide heat, power, or combined heat and power (CHP) is a link in the energy chain from producing renewable biomass resources to providing sustainable services in the form of heat (or refrigeration), shaft power and electricity. Combustion is in fact the most common application of biomass energy with the heat produced in a combustor or furnace being used in a manufacturing process, or to raise steam in a boiler which can be expanded through a steam turbine in the so called Rankine cycle. Other prime movers include the Brayton cycle of gas turbines, Stirling engines, as well as thermo-electric and thermo-volatic possibilities. Shaft power from these cycles can be used directly to drive a mill or other machine, or to turn an alternator to produce electricity. In combined heat and power the most common variant is when the electricity is generated first and the heat is taken from the exhaust of the electricity cycle (topping cycle). The benefits of combustion are unfortunately accompanied by a number of environmental costs which require innovation and significant investment for their mitigation. These costs include both direct human health impacts as well as environmental damage to the Earths productive ecosystems. However, biomass has one clear advantage over fossil fuels in that the emissions of carbon dioxide derived from biomass combustion to the atmosphere are essentially in equilibrium with the uptake of carbon dioxide by the biosphere through photosynthesis.

Thermochemical Conversion Research in the U.S. Department of Energy Biofuels and Power Programs

With proper resource management and through the development of efficient conversion processes, biomass could contribute as much as 20% of current U.S. energy consumption by 2030; i.e. 4 to 5 times today’s 3.8 quads, as estimated for the National Energy Strategy. This can only be obtained through the conversion of biomass into efficient secondary energy forms such as electricity and liquid fuels (ethanol, methanol, and oxygenates). Methanol, oxygenates, and electricity are produced through thermochemical conversion processes such as gasification, liquefaction, and combustion. Biomass already constitutes a significant resource for producing electricity. In 1989, biomass-and municipal-solid-waste-powered facilities provided a generation capacity of almost 8.4 GWe.

Biomass Gasification — Commercialization and Development: The Combined Heat and Power (CHP) Option

World-wide, biomass is the most used nonfossil fuel and is expanding from its traditional thermal applications to more usage for liquid fuels and electricity. More than 9 gigawatts of biomass electrical generation capacity have been installed in the United States, primarily by forest products industries, since the Public Utilities Regulatory Policy Act (PURPA) was passed. Combined heat and power (CHP) technologies promise to improve power-to-heat efficiencies to strengthen the economic viability of these electrical generating methods. These technologies, which are now being tested and demonstrated, employ industrial and aeroderivative gas turbines; use a variety of feedstocks including agricultural wastes, residues, and dedicated energy crops; and range in size from 8 MW to 75 MW. Specific demonstrations with the U.S. Department of Energy Biomass Power Program and partners in Vermont and Hawaii are discussed.© 1997 ASME