Wet biofuel

Heat fluxes (grate loadings) on 1500 kW/m can be obtained by cocurrent combustion, but for wet biofuels the heat fluxes are only 500 kW/m. Wood chips with a moisture content of 40% are very hard to bum in a cocurrent configuration. On the other hand, if a countercurrent configuration is used between fuel feed and primary air flow it is possible to bum very wet fuels upto 55-60%. Heat fluxes on 1 500 kW/m can be attained for wood chips with a moisture content of 40%, if the air flow velocity is 0.1 m/s. 

The simulation calculations were verified by field measurements in the test plant at Nakkila Works and in the demonstration plant at Pori Forest Institute. The calculation results seemed to be accurate enough for practical dimensioning and designing purposes. The most essential benefit of the system is the possibility to use both dry and wet biofuel without lower limitation in nominal heat output. 

Thunman, H, Leckner, B. (2000) Ignition and propagation of a reaction front in cross-current bed combustion of wet biofuels. Fuel (in press). 

Both biomethane production paths complement one another in an ideal way. While the thermo-chemical route focuses on solid biofuels e.g. wood, straw) the bio-chemical route uses wet biomass e.g. animal manure, maize silage). The latter will be realized with plant capacities in the one-digit thermal MW-scale and the former in the two- to three-digit MW-scale. The provided product is basically similar and can be used together with natural gas in any mixture. The erection of the biogas and Bio-SNG conversion plants can be planned directly at the established gas grid. 

Rather few papers deal with the kinetics of biofuel drying and most designs seem to be experience-based. Bagasse is reported to be easily dewatered with exit temperatures for commercial rotary dryers approaching the wet bulb temperature [7]. A study of drying rates of milled peats [21] in a fluid-bed bench-scale dryer showed no influence on the origin of the peat. On the other hand, different size fractions of the same peat gave quite different results. The intraparticular resistance is pronounced and, of course, controlled by the particle size. 

Ramirez EC, Johnston DB, McAloon AJ, Shigh V. Enzymatic com wet milling engineering process and cost model. Biotechnol Biofuels 2009 2 2. 

Figure 4A.10 Internal structure of a corn kernel and analysis of a corn grain. (Adapted from http //bio web-sungrantorg/Technical/Biofuels/rechnologies/Ethanol+Production/Ethanol+Wet+Grind+Processes/ Default.htm)...

Canada presented a bioethanol capacity of 1800 million liters in 2014, with 15 operative refineries operating at 95%, under production incentives administrated by the Federal Department of Natural Resources. Canadian bioethanol industry, based on com and wheat, produced 1.1 MMT of DDGs, 6.5 MMT of WDG (wet dry grains), and 6000 metric tons of com oil that could be valorized for second-generation biofuel production. This fact represents a major concern for older small factories, with weak co-product production lines, that need to compete with low-cost US ethanol. As an example, the 25-million-liter-capacity wheat-based plant settled in Saskatchewan (from the American company Bioenergy Crop) shut down in 2015 with low possibilities of reopening (Dessureault, 2015). 

Libra, J.A., et al., 2011. Hydrothermal carbonization of biomass residuals a comparative review of the chemistry, processes and applications of wet and dry pyrolysis. Biofuels 2 (1), 71-106. 

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