Calorific value, calculation

Feedstock Characteristics. Feedstock characteristics are presented in Table I. Results of the metal analysis will be considered in Phase II of the project. Calorific values were approximated using Dulong s formula and not actually measured. The oat straw had a lower ash content than the stover and a correspondingly higher calorific value. Calorific values, calculated on a dry basis and including the latent heat of water vapour in the products of combustion (high heat value), were 17.9 MJ/kg for the straw and 16.0 MJ/kg for the stover. 

The basis for the two ASTM criteria (the fixed-carbon content and the calorific value calculated on a moist, mineral-matter-free basis) are shown in Fig.6.13 for over 300 typical coals of the United States. The classes and groups of Table 6.4 are indicated in Fig. 6.13. For the anthracitic and low- and medium-volatile bituminous coals, the moist, mineral-matter-free calorific value changes very little hence the fixed-carbon criterion is used. Conversely, in the case of the high-volatile bituminous, subbituminous, and lignitic coals, the moist, mineral-matter-free calorific value is used, since the fixed-carbon value is almost the same for aU classifications. 

Natural gas analysis has considerable economic importance. In fact, commercial contracts increasingly specify not just volume but the calorific or heating value as well. Today the calorific value of a natural gas calculated from its composition obtained by chromatography is recognized as valid. There is therefore a large research effort devoted to increasing the precision of this analysis. 

The analyst now has available the complete details of the chemical composition of a gasoline all components are identified and quantified. From these analyses, the sample s physical properties can be calculated by using linear or non-linear models density, vapor pressure, calorific value, octane numbers, carbon and hydrogen content. 

ISO, Natural Gas—Calculation of Calorific Value, Density and Relative Density International Organization for Standardization ISO 6976-1983(E). 

The economic value of natural gas is primarily determined by the thermal energy it contains, which is expressed in British thermal units (Btu) or calorific value (CV). Other important physical properties comprise the liquid content, the burning characteristics, the dew point and the compressibility. In order to enable the calculation of these properties from its composition, a natural gas analysis should contain a detailed determination of all of the individual components, even in the low-concentration range. 

Eor (1), MSWIs, the maximum bonus is limited by the calorific value of the plastics waste (about 40 MJ/kg). Eurthermore, the energy recovery is relatively low due to technical limitations in comparison to normal power plants. Normally, at best some 20% electrical energy is recovered (or some 50%-70% calculated as primary energy). 

The calorific value of a gas can be calculated from the heats of combustion of its constituents the method is illustrated in Example 3.14. 

Worked Example 3.11 The wood mentioned in our title question is a complicated mixture of organic chemicals so, for simplicity, we update the scene. Rather than prehistoric men sitting around a fire, we consider the calorific value of methane in a modem central-heating system. Calculate the value of A Hc for methane at 25 °C using molar enthalpies of formation AH. ... 

Natural Gas—Calculation of Calorific Values, Density, Relative Density and Wobbe Index from Composition. ISO 6976 1995(E). 

The most important of these are the Wobbe index [or Wobbe number = calorific value/(specific gravity)] and the flame speed, usually expressed as a factor or an arbitrary scale on which that of hydrogen is 100. This factor can be calculated from the gas analysis. In fact, calorific value and specific gravity can be calculated from compositional analysis (ASTM D3588). 

Compositional analysis can be used to calculate calorific value, specific gravity, and compressibility factor (ASTM D3588). 

Effective Calculated Calorific Values of Propellants. If it is assumed that for a certain muzzle velocity and a given projectile, the product of the charge weight and calorific value of a propint is constant, then by knowing the calorific value and wt of one propint, it is possible to calculate the calorific value of a second proplnr of a similar nature (if its chge wt had been previously deed experi men tally). For example, if for one propint the values were 820kcalAg and wt 4.3kg and for a 2nd propint Xkcal and 6.2kg, respectively, then... 

In calculating the life of a gun barrel, it was considered in Germany to relate to the "effective calorific value , more than to the values obed in a calorific bomh (See also under " Energy Content of a Propellant Charge" and under "Erosion of the Bore")... 

See also Effective Calculated Calorific Values of Propellants)... 

Effective calculated calorific values of propints 5E13... 

Gross Calorific Value factor (GCV factor) is calculated to convert between nominations that are done in energy units, and bookings that are done in volume units. 

Such data are necessary for calculation of parameters in the classification of coal by rank dry, mineral-matter-free volatile matter (or fixed carbon) as well as moist, mineral-matter-free gross calorific value. For volatile matter and fixed-carbon data, it is also necessary to assume that 50% by weight of the sulfur is volatilized in the volatile matter test and therefore should not be included as part of the organic volatile matter (nor should the loss from clays and carbonate minerals) ... 

Thus, to classify coal, the calorific value and a proximate analysis (moisture, ash, volatile matter, and fixed carbon by difference) are needed. For lower-rank coals, the equilibrium moisture must also be determined. To calculate these values to a mineral-matter-free basis, the Parr formulas are used (ASTM D-388). 

Thus (Table 1.7), coal with a fixed carbon value in excess of 69% w/w or more, as calculated on a dry, mineral-matter-free basis, are classified according to the fixed-carbon value. Coal with a calorific value below 14,000 Btu/lb, as calculated on a moist, mineral-matter-free basis, is classified according to calorific value on a moist, mineral-matter-free basis, provided that the dry, mineral-matter-free fixed carbon is less than 69%. The agglomerating character is considered for coal... 

Inherent or equilibrium moisture is used for calculating moist, mineral-matter-free calorific values for the rank classification of high-volatile bituminous coals. It is also used for estimating free or surface moisture, since total moisture is equal to the sum of the inherent moisture and the free moisture and is considered the inherent moisture of the coal as it occurs in the unexposed seam, where the relative humidity is probably near 100%. However, due to physical limitations, equilibrium moisture determinations are made at 96 to 97% relative humidity and used as inherent moisture values. 

The classification of coal (ASTM D-388) depends on calculation of the volatile matter yield and fixed carbon values on a dmmf basis. Calorific values are calculated on a moist, mineral-matter-free basis. The Parr formula is used in the classification system to calculate the mineral matter from ash and sulfur data. 

An adiabatic calorimeter is a calorimeter that has a jacket temperature adjusted to follow the calorimeter temperature so as to maintain zero thermal head, and the test method (ASTM D-2015, ISO 1928) consists of burning the coal sample in the calorimeter, and the jacket temperature is adjusted during the burning so that it is essentially the same as the calorimeter water temperature. The calorific value is calculated from observations made before and after the combustion. In the isothermal method (ASTM D-3286 ISO 1928), the calorific value is determined by burning a weighed sample of coal in oxygen under controlled conditions, and the calorific value is computed from temperature observations made before, during, and after combustion with appropriate allowances made for the heat contributed by other processes. The value computed for the calorific value of coal... 

In either form of measurement (ASTM D-2015 ASTM D-3286), the calorific value recorded is the gross calorific value. The net calorific value is calculated from the gross calorific value [at 20°C (68°F)] by making a suitable subtraction (= 1030 Btu/lb = 572 cal/g = 2.395 MJ/g) to allow for the water originally present as moisture as well as the moisture formed from the coal during the combustion. The deduction, however, is not equal to the latent heat of vaporization of water [1055 Btu/lb (2.4 MJ/g) at 20°C (68°F)] because the calculation is made to reduce from the gross value at constant volume to a net value at constant pressure for which the appropriate factor under these conditions is 1030 Btu/lb (2.395 MJ/g). 

---