Lower heating value basis

The heat released from combustion of the fuel is transferred by radiation and convection to evaporate water and create superheated steam, which is then used to create electricity in a steam turbine. Steam temperatures in state-of-the-art coal-fired boilers are pushing close to 600°C (i.e. above the critical point of water) with net electricity production reaching 45% of the thermal energy of the burned fuel [43]. Modem subcritical boilers are closer to 39% net efficiency in electricity production, but older boilers can have efficiencies as low as 30% on a lower-heating-value basis. 

The DOE goal for electrolysis is a capital cost of 300/kW for a 250 kg/d plant (at 5000 pounds per square inch [psi] with 73 percent system efficiency, lower heating value basis [DOE, 2003b, p. 3-15]). Such a plant could be integrated with a renewable energy source to produce hydrogen at 2.50/kg by... 

Since photoelectrochemical hydrogen production is in an embryonic stage, a parallel effort to reduce the cost of electricity production from PV modules must be made. A substantial reduction in PV module cost (lower than 0.5/Wp) coupled with similar reductions in electrolyzer costs (about 125/kW at reasonable high efficiency of about 70 percent on a lower heating value basis) can provide hydrogen at reasonable cost. The potential research opportunities listed in the preceding subsection for PV solar cells along with electrolyzers must be actively explored. 

The key model outputs are overall efficiency (rf( the net electricity supplied to grid annually in MJ plus heat exported annually in MJ, all divided by the energy content of biomass delivered to plant annually in MJ on a lower heating value basis, expressed as... 

The exact conversion is 1 kg H2 = 0.96 gallons gasoline, on a lower heating value basis. 

This specific consumption figure is on an LHV (lower heating value) basis and is equivalent to approximately 31.5 MMBtu/t. This value is representative of the energy required not only to produce 2500 t/day of methanol plant but also to support all required off-sites, such as power generation, desalination of sea-water for boiler feedwater if required, and cooling water circulation. Battery limits energy consumption for a plant of this capacity would be about 2 MMBtu/1 less. 

Figure 27-11 gives the theoretical air requirements for a variety of combustible materials on the basis of fuel higher heating value (HHV). If only the fuel lower heating value is known, the HHVean be calculated from Eq. (27-6). If the ultimate analysis is known, Eq. (27-7) can be used to determine HHV. 

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. 

On an oven dry basis, the various biofuels contained similar C, H and O contents, but overall a much lower carbon content than coal, reflecting their lower heating values. Again typically biofuels had lower nitrogen and sulfur contents than that of coal. 

ABSTRACT The development of the HTU Process is now well under way. A pilot plant with an intake capacity of some 10 kg/h (dry basis) is in operation. Biomass is converted by treatment in liquid water at temperatures from 300 to 350"C and pressures from 100 to 180 bar. The product is Biocrude , a heavy organic liquid with a lower heating value of 30-35 M J/kg. 

Here Q is the sum of the endothermic enthalpies (heat inputs) and E is the sum of the work inputs, which are converted to heat inputs by dividing the work inputs by the efficiency for converting heat to electricity, Tj. This calculation is referred to as the lower heating value (LHV) basis. 

Bituminous coal generally has lower concentrations of pure carbon (46%-86%) and lower heat values (8,300-15,600 Btu/lb). Bituminous coals are often subdivided on the basis of their heat value, being classified as low, medium, and high volatile bituminous and subbituminous. 

If heating values (e.g., lower heating value [LHV] in MJ/kg) should be converted from one basis to another altering moisture, the changing in vaporization enthalpy of water at 25 °C must be incorporated (2.442 MJ/kg). 

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