【Q&A Question 152】2016.09.19
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【Q&A Question 152】September 19, 2016: What is the impact of temperature on the operation of a liquefied gas desulfurization tower? The answer key will be available after responding; scoring is based on answering the key points. Low temperatures are favorable for the desulfurization effect of the amine-poor solution, but excessively low temperatures can cause light hydrocarbons in the liquefied gas to condense, leading to foaming of the amine solution and affecting the absorption efficiency. Therefore, the temperature at the top of the control tower is kept around 38°C, with the temperature of the lean amine solution being slightly higher than that of the liquefied gas.
The absorption operation temperature has a significant impact; the lower the temperature, the better the absorption effect
High temperatures are favorable for desulfurization, but excessively high temperatures can lead to the formation of foam entrainment, which results in liquid present at the inlet of the hydrogen circulation pump; high inlet temperatures are not conducive to safe operation
Excessively high temperatures can cause vaporization, leading to large pressure fluctuations that affect operation; the accumulation of high-boiling substances in the liquid phase increases, reducing the absorption efficiency of the liquid phase. Lower temperatures are favorable for operation.
At constant pressure and with unchanged compositions of the absorbent and the gas, an increase in temperature reduces the solubility of the target gas in the absorbent; therefore, to maintain the same absorption efficiency, it is necessary to increase the amount of absorbent used or raise the pressure in the absorption system. As the absorbed dose increases, the concentration of the solute in the absorbent decreases, which increases the load on the desorption tower, creating a vicious cycle. Therefore, choosing a lower temperature is more favorable for absorption; however, if the temperature is too low and causes the viscosity of the absorbent to increase excessively, it will affect the fluidity of the absorbent as well as its contact with the gas, thereby reducing the absorption efficiency.
Impact: Lower temperatures are beneficial for the desulfurization effect of the amine-poor solution; however, if the temperature is too low, light hydrocarbons in the liquefied gas may condense, causing the amine solution to foam and thereby affecting the absorption efficiency. Therefore, the temperature at the top of the control tower is kept around 38°C, with the temperature of the lean amine solution being slightly higher than that of the liquefied gas.
Excessively high temperatures affect the solvent’s ability to absorb H2S and CO2
Low temperature and high pressure are favorable for absorption; at high temperatures, the absorption efficiency is poor, and the sulfur content in liquefied gas increases
Low temperatures are favorable for absorption, while high temperatures may lead to the loss of the desulfurizing agent
Both excessively high and low temperatures can affect the desulfurization efficiency; too high a temperature causes the amine solution to foam, while too low a temperature prevents effective desulfurization. Generally, the temperature should be maintained around 45-50 degrees