Gas Processors Association Europe

Matthew Humphrys, Johnson Matthey PLC,U.K.

CNG an ideal fuel for road transport vehicles. It produces less green house gas, much lower levels of harmful chemicals and no particulates. Additionally, many city centres are better served with natural gas distribution systems than they are with gasoline and diesel. However, pipeline gas produced for the industrial and domestic fuel markets can contain high levels of sulphur and mercury.

Car exhausts rely on precious metal catalysts for the combustion of carbon monoxide and unburned hydrocarbons and for the destruction of NOx. These catalysts are remarkably effective but are poisoned by sulphur compounds and possibly also by heavy metals. Also, latest generation lightweight storage tanks on NGV vehicles are aluminium-lined, which can be corroded by mercury with catastrophic results.

Johnson Matthey has developed fixed bed absorbents for the removal of these impurities from natural gas. No byproducts are formed, the process is essentially "carbon free" during operation and the spent absorbents are completely reprocessed. This technology is being used for the removal of sulphur at CNG refuelling stations.

This paper shows the variation in the composition of natural gas and uses actual illustrations to demonstrate how this technology can be applied to the auto-gas industry.