Lower heating value of fuels

Lower Heating Value of Anode Fuel(s) Produced Lower Heating Value of Fuel Used... 

In most cases, Qf ei is calculated based on the lower heating value of fuel. G,- is quantified in different units according to specifications in the marketplace, namely, Btu/h for fuel, Ib/h for steam, and kWh for power. Thus, specific FE factors can be developed as follows based on this general definition of fuel equivalent. Energy are required for making boiler feed water (BFW), condensate and cooling water. The FE factors for these utilities will be discussed in Chapter 3. 

Energy efficiency = total fuel cell system effidency/fiiel cell stack efficiency or lower heating value of hydrogenxO.95/lower heating value of fuel. 

Methanol 5500 Based on lower heating value of fuel... 

The energy consumption (lower heating value of the feedstock plus fuel) of the low pressure process has successively improved from over 38.3 GJ/1 when it was first introduced to 29.0—30.3 GJ/thy the mid-1990s. Natural gas-based reforming plants have advanced to the point where the scope for stiU further gains in efficiency is small and the gains costiy to obtain. 

If the substitute fuel is of the same general type, eg, propane for methane, the problem reduces to control of the primary equivalence ratio. For nonaspiring burners, ie, those in which the air and fuel suppHes are essentially independent, it is further reduced to control of the fuel dow, since the air dow usually constitutes most of the mass dow and this is fixed. For a given fuel supply pressure and fixed dow resistance of the feed system, the volume dow rate of the fuel is inversely proportional to. ypJ. The same total heat input rate or enthalpy dow to the dame simply requires satisfactory reproduction of the product of the lower heating value of the fuel and its dow rate, so that WI = l- / remains the same. WI is the Wobbe Index of the fuel gas, and... 

The calculation of the turbine firing temperature (Ttit) is based firstly on the fuel injected into the turbine and the fuel s lower heating value (LHV). The lower heating value of the gas is one in which the Fl20 in the products has not condensed. The lower heating value is equal to the higher heating value minus the latent heat of the condensed water vapor. 

Heat Value of Fuel Lower heating value... 

A fuel cell system for automobile application is shown in Figure 1.5 [41]. At the rated power, the PEMFC stack operates at 2.5 atm. and 80°C to yield an overall system efficiency of 50% (based on lower heating value of hydrogen). Compressed hydrogen and air are humidified to 90% relative humidity at the stack temperature using process water and heat from the stack coolant. A lower system pressure is at part load and is determined by the operating map of the compressor-expander module. Process water is recovered from spent air in an inertial separator just downstream of the stack in a condenser and a demister at the turbine exhaust. 

Given a 2.0 MWac fuel cell cycle operating on 700 Ib/hr of methane, what is (a) the HHV thermal input of the methane gas, (b) the LHV thermal input, (c) the HHV electric efficiency, (d) the LHV electric efficiency, and (e) the HHV Heat Rate Assume the higher and lower heating value of methane as 23,881 and 21,526 Btu/lb respectively. 

Boiler Thermal Efficiency Traditionally, boiler thermal efficiency is calculated pour/pm, where in is the LHV (lower heating value) of the fuel. A rule of thumb for economizers is that boiler efficiency increases by 1 percent for every 22°C (40°F) drop in temperature of the dry flue gas. These two statements do not reveal the considerable quantity of additional heat, available to be recovered through condensation of the water vapor in the flue gas, which is lost to atmosphere with hot flue gas. Based on fuel HHV (higher heating value), the total latent heat loss can be substantial an additional 9.6 percent (natural gas), 8.0 percent (propane), 6.5 percent (heating ou). 

Table 2.3.1 Lower heating value of some fuels. LHV analyzed for fuels studied at Abo Akademi University unless noted otherwise. Higher heating values from a[2], b[3], and c[4] were converted to LHV using the concentration of hydrogen.

A blend of 15% methanol with gasoline (M15 blend) is the most practical initial approach because it requires only minor adjustments to engine fuel systems and is interchangeable with gasoline. It also provides a 3% improvement in energy efficiency, which largely offsets the lower heating value of methanol. 

Formulation of the left-hand side of Eq. (5-180) requires representative thermodynamic data and information on the combustion stoichiometry. In particular, the former includes the lower heating value of the fuel, the temperature-dependent molal heat capacity of the inlet and outlet streams, and the air preheat temperature T . It proves especially convenient now to introduce the definition of a pseudoadiabatic flame temperature Tt, which is not the true adiabatic flame temperature, but rather is an adiabatic flame temperature based on the average heat capacity of the combustion products over the temperature interval T < T < 7), The calculation of Tf does not allow for dissociation of chemical species and is a surrogate for the total enthalpy content of the input fuel-air mixture. It also proves to be an especially convenient system reference temperature. Details for the calculation of 7 are illustrated in Example 13. 

To calculate a lower heating value of a fuel from a higher heating value or vice versa, you must determine the moles of water produced when one mole of the fuel is burned. If this quantity is designated n, then... 

Figure 4.10. Average energy flows during a bus driving cycle for a SCANIA hybrid fuel cell bus (based on lower heating value of hydrogen). (From A. Folkesson, C. Andersson, P. Alvfors, M. Alakula, L. Overgaard (2003). Real life testing of a hybrid PEM fuel cell bus. J. Power Sources 118,349-357. Used by permission from Elsevier.)...

The oxygen inlet concentration was varied between 1 and 21 v-% at a constant air-to-fijel ratio by varying also the fuel load. With the lower heating value of the volatiles (composition refer to Table 1) of 426 kJ/mol the variation of the 0 concentration between 1 and 21 v-% is equal to a variation of the fuel load from 45 to 954 kj/m. In Figure 7 the emissions of HCN, NH3, NO, NO , and N 0 versus the oxygen concentration are given,... 

The gas turbine was started with diesel oil. Then followed a change over of the fuel through the main nozzle from diesel oil to bio-oil. Due to the lower heating value of the bio-oil it was only possible to operate the gas turbine at part load in the dual-fuel-mode. With the mass flows in Fig. 3 the following power levels are calculated and shown in Table 2. 

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