Design and testing of a new isothermal flow gas calorimeter: the Hart Field-deployable natural gas energy meter

Abstract

The design and testing of a new isothermal flow gas calorimeter is described. The calorimeter achieves complete combustion of the natural gas at temperatures from 400 to 500°C using a bed packed with a proprietary catalyst. The catalyst is 100% efficient for mixtures containing all of the typical natural gas components (C 1-C 6). The calorimeter assembly consists of a flow reactor that is suspended in a high temperature air bath. The temperature sensors for both reactor and shield temperature measurement or control are Pt RTDs. The gas is delivered by a cycling sample loop with constant volume and a lean gas/air mixture is supplied to the reactor. The gas sample net heating value (NHV) is determined from the gas flow rate required to maintain a constant reactor temperature. The water content in the exhaust is measured to obtain the gross heating value (GHV). All operations of the calorimeter including periodic calibration and reporting of heating values, specific gravity, and compressibility data are automated. The calorimeter makes energy measurements with an accuracy of ±1 BTU ft −3 and a precision of 0.5 BTU ft −3 for gas samples having gross heating values ranging from 800 to 1200 BTU ft −3. The calorimeter measures both the net and gross heating values. The mol. percent inerts, specific gravity, and compressibility are calculated by use of empirical correlation equations relating these properties to the net and gross heating values. The gas calorimeter has been packaged for field operation and operation in areas with potentially combustible atmospheres. The field performance of the gas calorimeter is compared with both an on-line gas Chromatograph and a Cutler-Hammer calorimeter.