Zinc oxide desulphurisation

The H2S formed in the hydro-desulphurisation process can be removed from the product stream in a variety of ways. Commonly used methods are chemical reaction with, for example, zinc oxide or iron oxide, caustic scrubbing and absorption processes. For the H2S decomposition processes treated in this chapter, only the absorption/desorption methods are of importance. Most used are absorber/stripper combination units with an alkanolamine as absorbing compound [2],... 

A zinc-oxide mass containing copper may take care of traces of sulphur passing through the zinc oxide by establishing the chemisorption equilibrium over copper, which is independent of the presence of water (Table 1.18). The prereformer catalyst establishes the H2S/Ni chemisorption equilibrium at a much lower value than H2S/CU (refer to Section 5.4). However, it is expensive to use the prereformer catalyst as a desulphurisation mass. 

Group VIII metals are susceptible to sulphur poisoning [39] and sulphur must be removed from the feed stream. Natural gas may be cleaned over active carbon, but normally all hydrocarbon feedstocks are treated by hydro-desulphurisation over CoMo (or Ni/Mo) catalyst followed by sulphur absorption on a zinc-oxide absorption mass (refer to Section 1.5.1). 

Arsenic may come from the feed, impurities and some zinc-oxide masses for desulphurisation, or from the C02-removal system (Vetro-coke). In contrast, calcium and zinc transferred from the zinc-oxide vessel has no deactivating effect on the reforming catalyst. 

The methods involving phen or 2,2 -bipyridyl were used in the determination of Fe, for example, in natural waters [17,28,29,145-148], in zinc and cadmium [31], in silicate minerals [149,150], in bauxites, soil, and clay [151], in aluminium oxide [152], in glass [19,153], and in the alkaline method for coal desulphurising [154]. Iron was also determined by the FIA technique with the use of 1,10-phenanthroline [108,155,156]. 

The feed consisting of zinc and lead sulphidic concentrates, oxidic materials and fluxes is desulphurised and agglomerated. 

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