What are the typical levels of H2S and SO2 at the inlet of the exhaust gas hydrogenation unit? What is the SO2 content at the outlet of the low-temperature exhaust hydrogenation catalyst?
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As the title suggests, what are the typical levels of H2S and SO2 at the inlet of the exhaust gas hydrogenation unit? What is the optimal control range? Some manufacturers recommend the range of 2 to 5 – is that correct? Additionally, manufacturers generally claim that the exhaust gas from the hydrogenation unit contains no SO2, but it’s impossible for there to be absolutely no SO2 during operation. What are the approximate ranges for SO2 content in the exhaust gas at the beginning, middle, and end of operation?
1. H2S:SO2 ratio at the exhaust gas hydrogenation inlet – theoretical value: 2:1; actual value: slightly less than 2:1. 2. The exhaust gas at the exit of the hydrogenation process should not contain oil or SO2 under normal operating conditions. 3. As long as the hydrogenation catalyst remains active, there is sufficient hydrogen and the reaction temperature is appropriate, then there will be no SO2 in the exhaust gas at any stage – initial, intermediate, or final –; otherwise, corrosion in the subsequent quench tower will be severe
The 2:1 ratio is intended to take into account the conversion rate of the upstream Claus unit. I would like to ask whether this ratio has a significant impact on the hydrogenation conversion rate for the hydrogenation unit Additionally, during analysis in the workshop, H2S and SO2 generally cannot be analyzed simultaneously; some manufacturers use rapid gas quantification tubes to analyze SO2, but the accuracy of this method is relatively low. Are there any data available for trace analysis (≤10mg/m3)? Manufacturers generally do not pay attention to the analysis of trace sulfur; are there any data from relevant laboratories? Thank you so much!
The 2:1 ratio has a significant impact on the hydrogenation load and conversion rate; the higher this ratio, the less sulfur dioxide enters the hydrogenation reactor, and vice versa； Generally, workshops do not analyze the process gas before hydrogenation, but a ratio analyzer used before hydrogenation can simultaneously measure hydrogen sulfide and sulfur dioxide; otherwise, how can the air-fuel ratio be controlled? The sulfur dioxide concentration at the inlet of the hydrogenation reactor is generally between 0.3% and 1.5% (v/v), while there is virtually no sulfur dioxide at the outlet of the hydrogenation reactor ； If there is no analysis data, you can approximately determine the sulfur dioxide content before the hydrogenation reactor by subtracting the hydrogen sulfide analysis value before the reactor from the hydrogen sulfide analysis value after the reactor.
Okay, I’ve learned it, thank you so much! However, due to blockages at the on-site sampling points, there seems to be a deficiency in sampling and the analysis of hydrogenation exhaust gases, especially regarding the analysis of trace amounts of organic sulfur compounds such as SO2, COS, CS2, thiols, and thioethers in the exhaust gases.
There is generally no sulfur dioxide at the outlet of the exhaust gas hydrogenation reduction process, as the acid gas test parameters in the sulfur recovery unit show that the hydrogen content is 1%-2%, ensuring that all sulfur oxides present in the elemental sulfur entering the hydrogenation reducer are reduced to hydrogen sulfide.
If the hydrogen analyzer at the top of the quench tower shows no readings and the pH level in the quench tower drops sharply, it indicates that too much air is being supplied, resulting in an excess of sulfur dioxide. In the hydrogenation reactor, hydrogen supplementation is not timely. Apart from this situation, it is rare for there to be an excess of sulfur dioxide behind the quench tower. The exhaust gas you mentioned could be due to the absorption tower not being able to absorb all of the hydrogen sulfide, which leads to its combustion in the incinerator and thus an excess of sulfur dioxide. In your case, a comprehensive analysis should be conducted, taking various factors into consideration
I’ve learned it, thank you so much! We conduct research on exhaust gas hydrogenation catalysts in order to delve deeper into the subject.