Biomass gas

Fig. 6.12 Integrated biomass gas turbine/steam eombined-cycle power plant...

DC Dirccl Combustion of Biomass Gas if GasiticjMion for power generation s-fluesM... 

V, Hacker, G. Faleschini, H. Fuchs, R. Fankhauser, G, Simader, M. Ghaemi, B. Spreitz, K. Friedrich (1998) Usage of Biomass Gas for Fuel Cell by the SIR Process. Journal of Power Sources, 71, pp. 226-30... 

We have measured many important gasification and combustion properties of biomass gas made in the Turbo Stove and believe that this stove could solve many problems in world cooking. We present here a single model for sizing other stoves. 

Biomass gas producers can generate liquid, gaseous and solid end products. The desired end product of this unit is gas. Gas temperature is maintained high enough to inhibit condensation of low boiling point distillates. 

Based on the MCFC, the German companies MTU and Daimler-Benz have developed the Hot Module concept of a decentralized power plant, which can be fueled with natural gas, coke furnace gas, or biomass gas. Efficiencies of up to 65 % are expected to be achievable. A demonstration plant in Dorsten, Germany, with an electric power of 300 kW working with pipeline natural gas is being connected to the electricity grid since August 1997 [37]. In addition, process heat at a temperature of 400 - 450 °C can be utilized the efficiency is about 50 %. 

Several studies have been published describing results from the flash pyrolysis of biomass. Most of these studies were carried out at higher temperatures and were intended to promote biomass gas production. However, the work of Roy and Chornet [4] reported high liquid yields from biomass pyrolysis under vacuum conditions. More recently, Roy et al. [5] have described a vacuum pyrolysis system for the production of liquids from biomass, based on a multiple hearth type of reactor. Knight et al. [6] have developed an upward flow entrained pyrolyzer for the production of liquids from the thermal pyrolysis of biomass. 

Naphthalene is a key component of tars present in biomass gas. Its absorption efficiency in oily liquids can be ranked as follows diesel fuel > vegetable oil > biodiesel fuel > engine oil (Table 11.3). Diesel fuel however is expensive from an economic viewpoint, vegetable oil becomes the best option for biomass tar removal. 

For example, biomass and RDF (refuse-derived-fuels) can be integrated into a fuel cell system as long as the gas product is processed to meet the requirements of the fuel cell. The resulting systems would be very similar to the coal gas system with appropriate gasifying and cleanup systems. However, because biomass gas products can be very low in sulfur, the acid cleanup systems may simply consist of large sulfur polishers. 

Singh D, Hemandez-Pacheco E, Hutton PN, Patel N, Mann MD (2005) Carbon deposition in an SOFC fueled by tar-laden biomass gas a thermodynamic analysis. J Power Sources 142 194-199... 

Biomass ---------Gas-phase isoprene----------------- liquid-phase Isoprene... 

Alternative feedstocks for petrochemicals have been the subject of much research and study over the past several decades, but have not yet become economically attractive. Chemical producers are expected to continue to use fossil fuels for energy and feedstock needs for the next 75 years. The most promising sources which have received the most attention include coal, tar sands, oil shale, and biomass. Near-term advances ia coal-gasification technology offer the greatest potential to replace oil- and gas-based feedstocks ia selected appHcations (10) (see Feedstocks, coal chemicals). 

Because oil and gas ate not renewable resources, at some point in time alternative feedstocks will become attractive however, this point appears to be fat in the future. Of the alternatives, only biomass is a renewable resource (see Fuels frombiomass). The only chemical produced from biomass in commercial quantities at the present time is ethanol by fermentation. The cost of ethanol from biomass is not yet competitive with synthetically produced ethanol from ethylene. Ethanol (qv) can be converted into a number of petrochemical derivatives and could become a significant source. 

Renewable carbon resources is a misnomer the earth s carbon is in a perpetual state of flux. Carbon is not consumed such that it is no longer available in any form. Reversible and irreversible chemical reactions occur in such a manner that the carbon cycle makes all forms of carbon, including fossil resources, renewable. It is simply a matter of time that makes one carbon from more renewable than another. If it is presumed that replacement does in fact occur, natural processes eventually will replenish depleted petroleum or natural gas deposits in several million years. Eixed carbon-containing materials that renew themselves often enough to make them continuously available in large quantities are needed to maintain and supplement energy suppHes biomass is a principal source of such carbon. 

With all components in the ideal gas state, the standard enthalpy of the process is exothermic by —165 kJ (—39.4 kcal) per mole of methane formed. Biomass can serve as the original source of hydrogen, which then effectively acts as an energy carrier from the biomass to carbon dioxide, to produce substitute (or synthetic) natural gas (SNG) (see Euels, synthetic). 

Table 2. Potential Substitute Natural Gas in United States from Biomass at Different Crop Yields...

The market penetration of synthetic fuels from biomass and wastes in the United States depends on several basic factors, eg, demand, price, performance, competitive feedstock uses, government incentives, whether estabUshed fuel is replaced by a chemically identical fuel or a different product, and cost and availabiUty of other fuels such as oil and natural gas. Detailed analyses have been performed to predict the market penetration of biomass energy well into the twenty-first century. A range of from 3 to about 21 EJ seems to characterize the results of most of these studies. 

Steam also is blended with air in some gasification units to promote the overall process via the endothermic steam—carbon reaction to form carbon monoxide and hydrogen. This was common practice at the turn of the nineteenth century, when so-called producer gasifiers were employed to manufacture LHV gas from different types of biomass and wastes. The producer gas from biomass and wastes had heating values around 5.9 MJ /mr at... 

Another hydrogenation process utilizes internally generated hydrogen for hydroconversion in a single-stage, noncatalytic, fluidized-bed reactor (41). Biomass is converted in the reactor, which is operated at about 2.1 kPa, 800°C, and residence times of a few minutes with steam-oxygen injection. About 95% carbon conversion is anticipated to produce a medium heat value (MHV) gas which is subjected to the shift reaction, scmbbing, and methanation to form SNG. The cold gas thermal efficiencies are estimated to be about 60%. 

Chemicals have long been manufactured from biomass, especially wood (sHvichemicals), by many different fermentation and thermochemical methods. For example, continuous pyrolysis of wood was used by the Ford Motor Co. in 1929 for the manufacture of various chemicals (Table 20) (47). Wood alcohol (methanol) was manufactured on a large scale by destmctive distillation of wood for many years until the 1930s and early 1940s, when the economics became more favorable for methanol manufacture from fossil fuel-derived synthesis gas. 

There are many different routes to organic chemicals from biomass because of its high polysaccharide content and reactivity. The practical value of the conversion processes selected for commercial use with biomass will depend strongly on the availabiUty and price of the same chemicals produced from petroleum and natural gas. 

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