【Q&A Question 097】2016.07.26
Thread Content
【Q&A Question 097】July 26, 2016: The impact of temperature on desulfurization. The answer key can be seen after responding; scoring is based on identifying the key points. The hydrogenation reaction is an exothermic reaction; therefore, from a thermodynamic perspective, increasing the temperature is unfavorable for such reactions. However, from a kinetic perspective, raising the temperature can accelerate the reaction rate. Since the hydrodesulfurization and hydrodenitration of sulfur and nitrogen compounds are irreversible reactions at the normal operating temperatures of hydrorefining, not governed by thermodynamic equilibrium, the reaction rate increases as the temperature rises; therefore, raising the reaction temperature can accelerate the hydrogenation reaction, increase its depth, and reduce the impurities in the resulting oil. However, if the temperature is too high, excessive cracking reactions occur, leading to increased carbon deposition on the catalyst, a decrease in the liquid yield of the product, and even an increase in the olefin content in the product. The reaction temperature in hydrorefining is directly related to the energy consumption of the plant and the amount of hydrogen used; the optimal reaction temperature is the lowest temperature at which the properties of the product meet the required standards.
To prevent dew formation, the gas temperature must be above the dew point
Raising the temperature has a significant effect on desulfurization, and it also significantly improves nitrogen removal under higher pressure.
For more details, please refer to the response: The hydrogenation reaction is an exothermic reaction. Therefore, from a thermodynamic perspective, increasing the temperature is unfavorable for exothermic reactions. However, from a kinetic perspective, raising the temperature can accelerate the reaction rate. Since the hydrodesulfurization and hydrodenitration of sulfur and nitrogen compounds are irreversible reactions at the normal operating temperatures of hydrorefining, not governed by thermodynamic equilibrium, the reaction rate increases as the temperature rises; therefore, raising the reaction temperature can accelerate the hydrogenation reaction, increase its depth, and reduce the impurities in the resulting oil. However, if the temperature is too high, excessive cracking reactions occur, leading to increased carbon deposition on the catalyst, a decrease in the liquid yield of the product, and even an increase in the olefin content in the product. The reaction temperature in hydrorefining is directly related to the energy consumption of the plant and the amount of hydrogen used; the optimal reaction temperature is the lowest temperature at which the properties of the product meet the required standards.
1. The high flue gas temperature results in a higher specific resistance in the electrostatic precipitator field under the same conditions, leading to a relatively lower dust removal efficiency. This increases the ash content in the flue gas and reduces the desulfurization efficiency. 2. The equipment in the flue ducts may be affected by high flue gas temperatures, such as the dynamically controlled booster fans installed at the inlet of the absorption tower, as well as equipment like flue gas analyzers. 3. The solubility of sulfur dioxide decreases at high temperatures, resulting in a reduced desulfurization efficiency. 4. The water evaporation in the absorption tower increases, raising the humidity of the exhaust gas; this can lead to ash buildup in the GGH. In the absence of a GGH, gypsum rain may occur.
Impact: The hydrogenation reaction is an exothermic reaction; therefore, from a thermodynamic perspective, increasing the temperature is unfavorable for such reactions. However, from a kinetic perspective, raising the temperature can accelerate the reaction rate. Since the hydrodesulfurization and hydrodenitration of sulfur and nitrogen compounds are irreversible reactions at the normal operating temperatures of hydrorefining, not governed by thermodynamic equilibrium, the reaction rate increases as the temperature rises; therefore, raising the reaction temperature can accelerate the hydrogenation reaction, increase its depth, and reduce the impurities in the resulting oil. However, if the temperature is too high, excessive cracking reactions occur, leading to increased carbon deposition on the catalyst, a decrease in the liquid yield of the product, and even an increase in the olefin content in the product. The reaction temperature in hydrorefining is directly related to the energy consumption of the plant and the amount of hydrogen used; the optimal reaction temperature is the lowest temperature at which the properties of the product meet the required standards.
1. The high flue gas temperature results in a higher specific resistance in the electrostatic precipitator field under the same conditions, leading to a relatively lower dust removal efficiency. This increases the ash content in the flue gas and reduces the desulfurization efficiency. 2. The equipment in the flue ducts may be affected by high flue gas temperatures, such as the dynamically controlled booster fans installed at the inlet of the absorption tower, as well as equipment like flue gas analyzers. 3. The solubility of sulfur dioxide decreases at high temperatures, resulting in a reduced desulfurization efficiency.
With the feed rate, hydrogen-to-oil ratio, pressure, etc. remaining constant, the higher the temperature, the better the desulfurization effect