FTIR transmission emission spectroscopy of gases at high temperatures: Experimental set-up and analytical procedures

An experimental laboratory set-up for high-temperature gas analysis is presented. The set-up, which comprises an FTIR instrument with an internal detector, an external blackbody source and a heated gas cell, can be used to measure the transmissive and emissive properties of gases at elevated temperatures. The stainless-steel cell designed for this work was heated to temperatures ranging from 294 to 1273 K. Measurements of the spectral transmittance and radiance (4 cm(-1)) of heated carbon dioxide (CO2) in various concentrations (0.5, 10, 100 vol%) were performed to test the experimental set-up. A solution to the problem is given of how to express analytically both the transmitted and especially the emitted radiation of a heated gas sample enclosed in a gas cell. In order to measure the gas radiation, it is necessary to measure the wave-number-dependent thermal radiation from the heated sapphire gas cell windows. It is shown that the gas temperature can be determined at low temperatures (473 K), if the measured thermal radiation of the gas is corrected for the thermal radiation emitted by the FTIR instrument. (C) 1998 Elsevier Science Ltd. All rights reserved.