Meeting Report

exhibited their new instruments in 1400 booths. Of the 900 papers presented at the conference, the following from the symposium on 'Process analysers' dealt with automated stream analysis for process control. Gibbon and Hackett [1] described the use of automated research-quality gas chromatographs to analyse the effluents from bench-scale coal gasification or liquefaction equipment. The high specificity of process-control chromatographs is a disadvantage if the process gas stream being monitored is undergoing rapid and wide changes in chemical composition; this happens during process development. For example the gas composition, during an experimental run of a bench-scale coal liquefaction or gasification process development unit, may include pure nitrogen during the initial purge, unreacted feed-gas during start-up, and a variety of product compositions during the reaction phase of the experiment. Another common approach to monitoring these gases is taking 'grab' gas samples for subsequent laboratory analysis. Such an approach is labour intensive, and it is slow relative to the time scale of an on-line analysis. An alternative to this 'grab'-sampling approach is the attachment of automated research-quality gas chromatographs directly to the coal gasification or liquefaction equipment. The degree of automation of these chromatographs is defined by the analyst and may include a fully automated system that requires virtually no operator attention during routine operation. This eliminates sampling errors, eases manpower needs and time delays. Gibbon and Hackett describe the use of Hewlett Packard 5730 gas chromatograph, with dual thermal conductivity cells, to handle routine gas analysis. Five gases, hydrogen, nitrogen, methane, carbon monoxide and carbon dioxide, can be analysed, as well as hydrocarbons (up to four carbons), hydrogen sulphide and water vapour. The columns used are (a) a 60/80 mesh 5A molecular sieve, 1/8 in. OD by 10 ft. stainless steel with argon as carrier gas; (b) an 80/100 mesh Porapak 'R', 1/8 in. OD by 12 ft. stainless steel with helium as the carrier gas. The columns and detectors are operated at 100C, bridge currents are 120mA (argon carrier) and 250 mA (helium carrier) and the carrier gas flow rate is 20cc/min. Samples are injected using an air-activated Valco six-port gas-sampling valve; a 'flow type' sampling system, which is capable of sampling more than one stream. The chromatograph is calibrated daily using three quantitative standard mixtures. Response factors, based on peak areas, for each gas are adjusted every day to yield the known volume percentage concentration for each species in …