Tuesday 24 September 2013

Feed purification features

It is imperative to remove impurities like sulphur and chlorine efficiently from the hydrocarbon feed in order to prevent poisoning of catalysts in the downstream (tubular) steam reformer.

Topsoe's range of feed purification catalysts provides an effective and economical removal of sulphur and chlorine compounds from hydrocarbon feedstocks ranging from natural gas to naphtha.

Purification steps

The purification section includes a number of steps:

Hydrogenation
Hydrogenation converts organic compounds into hydrogen sulphide and hydrogen chloride, as the organic compounds are not easily absorbed on downstream absorbents. The hydrogenation process is also applicable for feedstock containing olefins and di-olefins.

Topsoe’s extensive R&D activities within the hydrotreating area have resulted in the development of superior catalysts. Catalysts offered for this application are TK-250 (CoMo type) and TK-261 (NiMo type).

AbsorptionAfter hydrogenation the feed contains hydrogen sulphide and hydrogen chlorine, which are absorbed on a zinc oxide and a chlorine guard respectively. The concentration of these components at the outlet of the absorber is practically nil. The sulphur is removed to very low concentrations (ppb level).

The Topsoe chlorine guard - HTG-1 - offers high chlorine absorbtion capacity at a wide range of temperatures. The range of zinc oxide absorbents, the HTZ series, provides very efficient sulphur removal for all applications.

Final purification
Large variations in the sulphur content in the feed, low operating temperatures, high carbon dioxide or water content may require a final purification step. A solution is to install Topsoe's sulphur guard catalyst ST-101 where a high Cu surface area will remove any remaining hydrogen sulphide as well as organic sulphur in the bottom of the zinc oxide reactor.