Solutions to challenges in hydrotreating sour fuel gas
Fuel gases in refineries are almost by definition low-value gases composed of off-gases from a variety of sources within the refinery. Plant operators are naturally interested in utilizing these gases in a way that will maximize their earnings, and they may be required to treat them in order to minimize environmentally harmful emissions, particularly of sulfur compounds. This can be rather challenging. Off gases are often loaded with unwanted components, and their composition and rate of production are highly variable.
A number of methods are applied in order to recover the most valuable constituents of these gases such as hydrogen, olefins, and LPG (propane/butane). What is left is often a light, methane rich gas, which may still contain significant amounts of olefins and diolefins. A high content of sulfur compounds is usual, including 1 to 15% of H2S and hundreds of ppm of organic sulfur species such as mercaptans and thiophenes. Amine washing can remove the H2S, but as environmental regulations become stricter, more of the sulfur needs to be removed, and the possibility of hydro-desulfurizing the fuel gas is gaining interest amongst refiners.
Haldor Topsoe A/S has developed a commercially proven solution for hydrotreating fuel gases containing very high levels of H2S as well as percentage levels of alkenes and CO/CO2 and substantial amounts of organic sulfur species.
Examples will be presented of the substantial challenges related to the chemistry and analysis of sulfur compounds that were encountered in the development and validation of this process. It will be demonstrated how crucial the selection of a COS hydrolysis catalyst is in order to avoid recombination, when ppm-levels of olefins are present along with a high concentration of H2S.
The Haldor Topsoe fuel gas hydrotreating technology converts virtually all sulfur species to H2S and reduces the slip of organic sulfur to the low ppm range, enabling effective sulfur removal in a single downstream amine wash.
Changes in refinery feedstock may generate excess fuel gas, and this technology provides an opportunity for purifying the fuel gas to such an extent that, the methane-rich gas can be used as a feedstock in the production of syngas or hydrogen.
This is profitable and adds to the operational flexibility of the plant.
See more of this Group/Topical: Topical 6: 16th Topical Conference on Gas Utilization