Wet desulfurization (PDS + tannin) is used for gas purification; how to ensure that the hydrogen sulfide content in the gas after desulfurization meets the specified standards
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Our company uses a wet desulfurization (PDS + tannin) process for gas purification. Among them: the hydrogen sulfide content at the inlet of the desulfurization tower is 4–6 g/L ； Liquid-to-gas ratio 20 L/m3 ； The temperature of the gas entering the desulfurization tower is 32–35°C, with a pressure of 13 Kpa ； Temperature of desulfurization liquid entering the desulfurization tower: 34-36℃ ； In the composition of the desulfurization solution: the content of double salts is high, exceeding 300 g/L; PDS levels are 30–50 ppm; suspended sulfur is less than 1.5 g/L; free ammonia exceeds 6 g/L; the pH of the solution is 8.5–9.3; and the resistance in the desulfurization tower is 3 KPa ； The average long-term hydrogen sulfide content in the exported gas is 330 mg/m3, while the average organic sulfur content is 550 mg/m3 – these levels remain quite high. I’m not sure how other companies handle this issue; let’s discuss it.
The temperature is a bit high; this is a common issue in coking plants during summer. The ammonia concentration would be better if it’s above 10 g
PDS is combined with tannin; it has the effect of reducing resistance in the tower and also enhances the solution’s ability to remove organic sulfur. 4-6 g/L of hydrogen sulfide is quite high; it is not effective to remove it using ammonia water.
There are two reasons: one is the high temperature of the desulfurization solution, and the other is the high content of by-products. Especially in summer, when the temperature is high, the ammonia content in the desulfurization solution decreases significantly. This is the main reason why the hydrogen sulfide level remains high after desulfurization. It is possible to cool the desulfurization solution further. If concentrated ammonia solution obtained through ammonia evaporation is used for replenishment, it is essential to ensure that the ammonia evaporation process operates steadily and properly; the free ammonia content in the desulfurization solution should be at least 9 g/l in order to maintain an effective desulfurization effect. We use high-sulfur coke, and the hydrogen sulfide level before desulfurization is above 8 g/L, while after desulfurization it can be reduced to below 20 mg/L； Another issue is the high level of by-products; they must be discharged in fixed amounts on a regular basis. It’s similar to human metabolism – if waste products are not removed continuously, it will definitely lead to problems.
High levels of by-products are a significant factor affecting desulfurization efficiency
At the desulfurization inlet, the concentration is 4–6 g/l, while at the outlet it is 330 mg/m3; the desulfurization effect is quite good, with an efficiency of 93.4%.
1. The content of double salts is relatively high, at >300 g/L, which is considered high in the ammonia-based desulfurization process; an analysis of the by-products can help determine how well the system is functioning. 2. The free ammonia level is >6 g/L; according to the equilibrium principles, a level higher than 10 would be better. The hydrogen sulfide level was high earlier on. You haven’t provided details regarding the gas flow rate and the overall conditions of the system; providing such information will make it possible to find specific ways to reduce the hydrogen sulfide level. WeChat ID: 1123267744
Hello, teacher. I work in desulfurization and purification. Could you please share your contact information? I hope we can communicate