Gross calorific value

Gross calorific value (gross heat of combustion at constant volume) heat produced by combustion of a unit quantity of a solid or liquid fuel when burned at constant volume in an oxygen bomb calorimeter under specified conditions, with the resulting water condensed to a liquid not applied to gaseous fuels and applies to a volatile liquid fuel only if it is suitably contained during the measurement closely related to the internal energy of combustion for the same reaction at constant standard temperature and pressure. 

Fig. 5 Comparison of the calorific value (gross - GCV and net - NCV) of waste wood...

Combustion in the enclosed heat exchanger causes the instrument s response to be to the total calorific value (gross, higher). The water vapor formed during combustion is condensed and the latent heat of vaporization is included in the BTU measurement All products of combustion are returned to the initial temperature. 

One aspect of energy calculations that causes many problems in interpretation is the conversion factor used to convert fuel mass to energy. The conversion factor is called the calorific value of the fuel and represents the quantity of energy that can be derived from unit mass of fuel. There are, however, two types of calorific value—gross and net. 

Gross calorific values are high, being about 100000 kJ/m ... 

Table 1. International Classification of Coals having a Gross Calorific Value below 23.8 MJ/kg — ...

Coals having 69% or more fixed carbon on the dry, mineral -m a tter-free basis are classified according to fixed carbon, regardless of gross calorific value. 

Ha.rd Coa.1, The amount of coal in international commerce since ca 1945 necessitated an international system of coal classification and in 1956 the Coal Committee of the European Economic Community agreed on a system designated the International Classification of Hard Coal by Type (3). Volatile matter and gross calorific value on a moist, ash-free basis are among the parameters considered. Table 4 shows the various classes of the international system and gives the corresponding national names used for these coals. 

Calorific value The measure of the heating capacity of a fuel, usually expressed as the available heat resulting from the complete combustion of that fuel in kj kg or kj nr Gross calorific value includes the heat of condensation of the water vapor in a hydrogen fuel net calorific value excludes this. 

The high hydrogen/carbon ratio of gas means that the quantity of water vapor in the products of combustion is greater than most other fossil fuels. The latent heat of this cannot be released in conventional appliances leading to a low net/gross ratio of calorific value of 90 per cent. (It is normal practice to quote gross CV in Europe net CV is often used. If net CV is quoted, efficiencies of over 190 per cent are possible.)... 

The calorific value is constantly monitored, and it is a condition of the Gas (Declaration of Calorific Value) Regulations 1972 that alterations in the declared calorific value (CV) are publicly made known. It is customary to quote the gross (upper) CV rather than the net (lower) CV. The difference between the two represents the heat contained in the latent heat of vaporization of the water vapor in the products of combustion that can only be recovered in condensing appliances. 

Table 20.3 Typical gross calorific values of fuel gases...

The basic price of coal at the pit is based on the coal gross calorific value, with allowances then made for the ash, sulfur and chlorine contents. The haulage charges depend on the distance from the pit to the site and on the method of delivery. Tipper-vehicle deliveries are cheaper than conveyor vehicles which, in turn, are cheaper than the pneumatic (blower) vehicles. The method of delivery will obviously be decided by a combination of space and cleanliness factors. In the case of certain customers, special agreements may be available at special rates where the annual coal consumption is large and the supplier wishes to retain the market. 

Condensing boilers are now available for both gas- and oil-fired plant, the advantage of these being that the flue gases are further cooled down to below 100°C so that the latent heat available in the flue gas water vapor is recovered. The condensate has to be removed and the boiler capital cost is higher than for conventional plant. However, the boiler plant efficiency is increased to the order of 90 per cent, based upon the fuel gross calorific value. Where the flue gas exit temperatures are in excess of 200° C a further economy can be obtained by the provision of a spray recuperator in the case of gas and flue gas economizers for oil and coal. 

Fuels, especially coals, are ranked according to limits on fixed carbon, volatile matter, and calorific value. Typical gross heating values of some common fuels (based on approximately 80% fuel to steam efficiency) are listed here ... 

The reactor is a pipe reactor heated with fuel gas, gross calorific value 33.5 MJ/m3. Estimate the quantity of fuel gas required. 

Fixed carbon limits (dry, mineral-matter-free basis), % Volatile matter limits (dry, mineral-matter-free basis), % Gross calorific value limits (moist, mineral-matter-free basis) ... 

The heating value, or calorific value, expressed as kj/kg (Btu/lb), is the heat produced at constant volume bv the complete combustion of a unit quantity of coal in an oxygen-bomt calorimeter under specified conditions (ASTM D 5865-04, ASTM International, op.cit.). The result includes the latent heat of vaporization of the water in the combustion products and is called the gross heating or high heating value (HHV) Qh- And Qh in Btu/lb (x 2.326 = kJ/kjy on a dry basis can be approximated by a formula developed by the Institute of Gas Technology ... 

Gross calorific value.BTU/scf. Pressure.psig./inch WG. 

DI989 Standard Test Method for Gross Calorific Value of Coal and Coke by Microprocessor Controlled Isoperihol Calorimeters,... 

The actual gross calorific values of gas from each source were taken into consideration. 

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. 

Proximate analysis, determination of moisture content of the general analysis sample of coke Proximate analysis, determination of volatile matter content Proximate analysis, determination of ash content Determination of gross calorific value Ultimate analysis of coal and coke, determination of carbon and hydrogen content, high temperature combustion method Liebig method... 

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) ... 

Gross calorific value on a moist, ash-free basis (30°C, 96% relative humidity, Btu/lb). 

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