Charles University Prague, Department of Analytical Chemistry

Albertov 2030, CZ-128 40 Prague 2, Czech republic

A new principle has been developed for continuous determination of the heat of combustion of a broad range of gases and vapors such as natural gas, biogas, process gases and their mixtures.

The principle is based on pseudo-calorimetric method involving direct measurement of the heat of combustion by means of a newly developed sensor. The sensor, international patent pending WO 2004/048954 A1, from June 10^th, 2004, is small, it weighs less then 10 grams and allows fast and sensitive measurement of combustion heat changes in various gas streams, even those with high contents of water vapor and carbon dioxide, such as biogas.

The developed pseudo-calorimetric method employs the principle of additivity of partial energy sources (one source is the burning gas and the other source is electrical heating) to determine the actual temperature of the sensor. Thus when maintaining the sensor temperature constant, any change in the combustion heat content of the gas under investigation will be compensated by the reciprocal change of the power of the electrical heating. The developed pseudo-calorimetric method thus responds to all combustible components in the gas stream in terms of energy, continuously and without delay (the signal is processed within 0.5 sec intervals), the overall precision of measurement is better then 0.6% (temperature sensing is 200 ± 0.01 degree C, electrical heating regulation is 5± 0.0125W). The instrument is connected to a pressure-regulated bypass line of the gas stream.

Unlike the conventional methods (gas chromatography, ultrasonic measurement correlation procedures, etc.) the new principle allows a straightforward determination of the heat of combustion, the measured value coresponds to the true value of the heat of combustion of the controlled gas and is free of any kind of numerical corrections.

The new method of determination of the heat of combustion represents superior approach to the quality and process control of natural gas mining, transportation, distribution networks and end-users. The special attention has been paid to a process of mixing of gas streams of a different heat of combustion. Fast and on-line measurement enables regulation of mixed gas streams in such a way that a constant heat of combustion of gas mixture output is provided.

The system has been developed in cooperation with the natural gas processing company RWE Transgas, a.s., Czech republic, and is subject of international patent applications (US Appl. No. 10/533,171).