IE41818L - Sampling gas for analysis - Google Patents

Abstract

1500508 Sampling gases BRITISH STEEL CORP 28 Oct 1975 [28 Oct 1974] 46432/74 Heading G1B A method for the rapid transfer of gas from a sampling probe at a source of the gas to a gas analyzer remote from the gas source, comprises passing the gas from the probe along a first gas sampling duct intercommunicating with a second gas sampling duct which transfers a gas sample to the gas analyzer, the first gas sampling duct being relatively long compared with the second gas sampling duct and the gas being transferred along the first duct at a high gas transfer rate relative to the transfer rate along the second duct, a proportion of the gas in the second gas sampling duct being vented to the atmosphere immediately prior to the analysis of the remaining gas. In an example a steelmaking vessel 10 is shown with a hood 11 and an oxygen lance 12. The hood draws the hod exhaust gases into a waste gas duct 14. Waste gas sampled through the probe 15 passes at about 56 litres per minute along a first sampling duct 16 through filter 17 and cooler 18 to vacuum pump 19. In the filter fume particles are removed, and in the cooler the gas temperature is reduced to ambient temperature. Beyond the pump 19 the sampled gas continues along the duct 16 at a positive pressure until the duct leads into an analysis room 20. The duct 16 passes through the analysis room and the bulk of the sampled gas is exhausted to atmosphere at 24. A second sampling duct 25 branches from the first duct 16 within the analysis room and part of the sampled gas is drawn along the second duct 25 and through a further filter 26 at about 5 litres per minute by pump 27. From pump 27 the second sampling duct leads through a further cooler 28, to remove any residual moisture in the gas, to three gas analysers e.g. a paramagnetic oxygen analyzer 31 and infrared analyzers 32 and 33 for carbon monoxide and carbon dioxide respectively. From these analyzers the gas is exhausted through a duct 35. The analyzers 31, 32 and 33 require a gas supply rate of about one litre per minute. A bleed line 36 is provided in the second gas sampling duct 25 prior to the analyzers to vent excess gas to the atmosphere. It is possible to operate the steelmaking process with a time lag of as little as 10 to 15 seconds between sampling the waste gas and obtaining an analysis of its oxygen, carbon monoxide and carbon dioxide content. Pump 19 transfers gas at about 56 litres per minute along duct 16 at a pressure of about 22mm. mercury gauge. Duct 16 is unrestricted and of 12À7mm. internal diameter. The second gas sampling duct 25 is of 6À3 mm. internal diameter and is provided with gas from pump 27 at a pressure of approximately 60 mm. mercury gauge. [GB1500508A]