Hardwood heating value

The fuel properties of wood can be summarized by ultimate and proximate analyses and deterrnination of heating value. The analytical procedures are the same as those for coal, but with some modifications. Analytical results generally vary about as much within a species as they do between species, except that softwood species generally have a higher carbon content and higher heating values than hardwood species because of the presence of more lignin and resinous materials in softwood species (see Fuels from waste). 

The cost of transporting wood chips by truck and by pipeline as a water slurry was determined. In a practical application of field delivery by truck of biomass to a pipeline inlet, the pipeline will only be economical at large capacity (>0.5 million dry t/yr for a one-way pipeline, and >1.25 million dry t/yr for a two-way pipeline that returns the carrier fluid to the pipeline inlet), and at medium to long distances (>75 km [one-way] and >470 km [two-way] at a capacity of 2 million dry t/yr). Mixed hardwood and softwood chips in western Canada rise in moisture level from about 50% to 67% when transported in water the loss in lower heating value (LHV) would preclude the use of water slurry pipelines for direct combustion applications. The same chips, when transported in a heavy gas oil, take up as much as 50% oil by weight and result in a fuel that is >30% oil on mass basis and is about two-thirds oil on a thermal basis. Uptake of water by straw during slurry transport is so extreme that it has effectively no LHV. Pipeline-delivered biomass could be used in processes that do not produce contained water as a vapor, such as supercritical water gasification. 

Wood, a renewable source, is not an important industrial fuel today. However, its use continues in some mral areas where it is often supplemented with liquid propane. In some underdeveloped countries, wood is still the principal source of energy. Dry wood contains from 1% to 12% moisture whereas green wood contains from 26% to 50% water. The resinous woods, like pine or cedar, yield about 18.5 MJ/kg of air-dried wood or, allowing for the moisture content, about 21 MJ/kg on a dry weight basis. Hardwoods have a heating value of about 19.4 MJ/kg. The energy available in present forest stocks is estimated to be equivalent to about 270 x 10 t of coal or about 2/3 of the equivalent oil reserves. 

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