Patent ID: 8283635

Claim:
Method for determining the gas quality of a sample gas mixed at least in part with biogas or processed biogas, having the main components CH 4 , CO 2 , N 2 , O 2 , and H 2 , proceeding from a spectrum of the sample gas determined via at least one infrared-spectroscopy device, under operating conditions, from which the mole ratios of the sample gas are determined via a correlation calculation performed by a computer, and converted via the computer to characteristic variables of the gas quality, wherein the spectrum comprises an optical absorption of methane CH 4 and carbon dioxide CO 2 of the sample gas, and, if liquid gas LPG is mixed in, the optical absorption of the LPG, and the heat conductivity λ is measured, wherein the mole ratio xCH 4 is determined via the computer from the absorption of the CH 4 , the mole ratio xCO 2 is determined via the computer from the absorption of the CO 2 , and, if liquid gas LPG is mixed in, the mole ratio xLPG is determined via the computer from the absorption of the LPG, wherein the mole ratios of nitrogen xN 2 , of oxygen xO 2 and of hydrogen xH 2 that are not detected optically are determined from the mole ratios xCH 4 , xCO 2 and the heat conductivity λ, and, if liquid gas LPG is mixed in, from the mole ratio xLPG, via the correlation calculation performed by the computer, the correlation calculation comprising λ=F(xCH 4 ,xCO 2 ,xN 2 ,xO 2 ,xH 2 ) or λ=F(xCH 4 ,xCO 2 ,xN 2 ,xO 2 ,xH 2 ,xLPG), and wherein characteristic parameters of the sample gas are calculated from the mole ratios obtained in this way, under the prerequisites that: all the mole ratios together amount to 100% of the sample gas, and the mole ratios xN 2 of N 2 and xO 2 of O 2 are determined as a sum.