GB1056540A - Method of and apparatus for measurement of calorific values - Google Patents

Abstract

1,056,540. Measuring thermal efficiency electrically. VYZKUMNEY USTAV ENERGETICKY OF PRAHA. Oct. 26, 1963, No.42311/63. Heading G1N. The calorific value of fuel supplied per unit time to a furnace 7 Fig. 1 (not shown), is measured in terms of the air required to burn it, the rate of air input to the furnace being measured by a flowmeter 3, 4 the output signal from which is combined with a signal representing the proportion of unburned air in the furnace exhaust gases, thus providing an indication of the amount of air actually burned. A sample of the gases and combustible remnants extracted at 9, from the furnace, is mixed in a constant ratio with a further air input, regulated by a valve 11 either manually or automatically, then fed to a heat exchanger 12, and completely burned in an oven 14. The exhaust from this oven 14 passes through a cyclone ash separator, 15 and is blown back into the furnace, a sample being taken via a junction 17 to an oxygen analyzer 18 which measures a quantity "α" defined as the ratio of the amount of air introduced into the furnace 7 to the actual amount of air required for complete burning of the fuel. The analyzer may be in the form of an oxygen sensitive inductor Z m , Fig.2 (not shown) with a centre-tapped iron-cored choke T, and a variable inductance Z o which sets the zero value for calibration purposes. If K is a constant representing the heat developed by a given fuel per unit weight of consumed air when the fuel is completely burned, and V is the flowmeter reading (3, 4), then the required calorific value, Q, is given by Q = K Î 1/α x V. The factor K is introduced at 20, and the signal representing V is delayed in unit 22 to allow for the time of passage of a sample from extractor 9 around the system to the analyzer 18, the output from the unit 19 then representing V Î 1/α. The unit 5 (Fig. 1) compensates the flowmeter reading for any temperature variations in the input conditions to the furnace. The furnace may burn liquid, pulverized, or gaseous fuel.