What are the components of sulfur content in hydrogen produced from dry gas, and how can it be controlled?
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The main raw material for the dry gas hydrogen production unit in our plant is coking dry gas. The hydrogen sulfide content in the raw gas before it enters the unit is zero; however, after sampling and analysis in the adiabatic hydrogenation reactor, the hydrogen sulfide content is around 100. I believe that the dry gas contains thioethers and thiols – but what else might be present? And how to get guidance from experts?
Coking dry gas contains some organic sulfides, the main components of which are compounds such as thiols and thioethers; the ultimate component is thiophene. After desulfurization of coking dry gas, only hydrogen sulfide and low-molecular-weight thiols can be removed, while thioethers and thiophene cannot be eliminated. Therefore, it is normal for the hydrogen sulfide level to be above 100 ppm after hydrogenation.
Sulfur in hydrogen production dry gas exists mainly in the forms of H2S, elemental S, thiolles, sulfides, disulfides, and thiophenic sulfur... These forms can be divided into three categories: the first category consists of acidic sulfides that readily react with metals at room temperature and are highly corrosive; the main components of this category are sulfur, hydrogen sulfide, and low-molecular-weight thiolles. Thiols are insoluble in water, have weak acidity, and can react directly with iron to form ferrous thiol. Thus, they corrode metal equipment. Thiol compounds decompose into alkenes and hydrogen sulfide when heated. The second category mainly includes thioethers (RSR’) and disulfides (RSSSR’); these are neutral at room temperature but can decompose upon heating to produce corrosive sulfides. The third category consists of thiophenes and their derivatives, which are thermally stable.
That’s right; inert sulfides such as thioethers are not corrosive in themselves, but they decompose when heated
The sulfur content in the dry gas must be kept below 50 ppm, otherwise it causes significant damage to the conversion catalyst.
The sulfur content before the dry gas enters the converter (at the outlet of the desulfurization reactor) should be below 0.5 ppm, right? Isn’t 50ppm too high?
It is normal for the organic sulfur contained in it to be converted into inorganic sulfur after passing through the hydrogenation reactor; it will be removed in the desulfurization step, as long as its level remains below 0.5 ppm after desulfurization