GB1286863A - Oxidizable hydrocarbon detecting apparatus - Google Patents

Abstract

1286863 Gas analysis W B INNES 19 Nov 1969 56621/69 Heading G1B A process for determining the quantity of oxidisable air polluting hydrocarbons in a gas sample comprises passing the sample and oxygen at a constant flow rate through a catalyst bed of supported or unsupported vanadia or chromia having a surface area of at least 5 m<SP>2</SP> /g, at least 5 per cent by weight of the catalyst being vanadia or chromia and the temperature of the bed being maintained between 200 and 500‹ C., and measuring the temperature rise of the catalyst due to oxidation of the hydrocarbons using a temperature sensor in the catalyst bed. In the apparatus shown in the figure the gas sample may be obtained from a flexible bag 8 using a pump 4, a flexible bag 26 using an aspirator device 24, from a chromatograph to separate the components in the sample before analysis, or by direct injection of a sample through a rubber plug 17<SP>1</SP> in the conduit 17 leading to the analyser A. The analyser A comprises an aluminum block heated by heaters 48, 49 and containing coils 19, 20 leading from the conduit 17 to a central chamber 33 in a bore 36 in the block. From the chamber 33 the gas flow divides to pass either through a bed of inert material 44 or a bed of the catalyst 45. A differential thermopile 46 has junctions disposed in the beds 44, 45 to generate a temperature difference signal which is indicated on a meter 47. In an alternative arrangement electric resistance temperature sensors are used in place of the thermopile 46. Optimum values for temperature, flow rate and catalyst bed dimensions and composition are given in the Specification.