What are the H2S content requirements for fully low-temperature imported materials?
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For a fully low-variation process, what is the required level of hydrogen sulfide content? No matter how high the hydrogen sulfide content is after desulfurization earlier on? Some say it’s 80–100 mg/Nm3, while others say it’s 90–120 mg/Nm3; all these figures refer to the hydrogen sulfide concentration at the inlet of the converter. Is this value on the low side? Can it meet the requirements for using fully low-volatility catalysts? I hope fellow sailors will not hesitate to share their insights!
The minimum hydrogen sulfide content required for the desulfurization of fully reduced transformation catalysts is related to the catalyst’s hot spot temperature and the water vapor ratio. For fully low-variation processes, an imported hydrogen sulfide concentration of 80 mg/m3 is generally sufficient to meet the requirements of the catalyst. In our operation, since gas coke is used for gas production, its sulfur content is extremely low; thus, even when the hydrogen sulfide concentration at the inlet of the shift converter is 60 mg/m3, no desulfurization reaction occurs
What will happen if the H2S level is high? For example, 200mg/Nm3?
A high hydrogen sulfide level has no effect on sulfur-resistant shift catalysts; it merely increases the burden on the desulfurization process for the shifted gas!
The full low-variation requirement stipulates that the H2S content in the inlet gas must be higher than that in the medium-low-low category; it is generally kept between 150–200 mg/Nm3, and sometimes below 300 mg/Nm3. In our case, there is no separation step – the gas goes directly to the pressure swing adsorption carbon removal unit. The adsorption towers can remove some of the H2S, and after thorough desulfurization, virtually no sulfur is detected in the gas.
Isn’t it necessary to desulfurize first before going into the low-voltage transformer? ? ? ? How can there still be such a high level of hydrogen sulfide?
Catalyst manufacturers state that retro-sulfidation will not occur when the total sulfur content of fully low-volatility imported catalysts reaches 80–100 mg/Nm3
Our company deals with ammonium carbonate; there is no desulfurization before or after the conversion process. Before the conversion, 700 milligrams are used, while after the conversion carbonation and pressure swing adsorption are employed
You can calculate the minimum sulfur content requirement under your current operating conditions based on the components and the equilibrium constant for desulfurization; this requirement is primarily related to the water vapor concentration, and the values vary depending on the operating conditions.
The sulfur content in coal used these days is increasing, and the composition of sulfur is becoming more complex. Given the characteristics of this industry, it is appropriate to use the H2S content at the exit of the conversion process as an indicator. Through this conversion process, 85–90% of the organic sulfur is converted into inorganic sulfur. Under normal circumstances, as long as the H2S content at the exit of the conversion process is not less than 120 mg/m3, it will not lead to desulfurization of the low-temperature conversion catalyst.
For the full low-temperature conversion process, we keep the level at around 120–150 mg/Nm3. The design requirement is that the H2S level at the exit of this process should be no less than 100 mg/Nm3; it can be higher, but not lower...