Several issues regarding hydrogenation
Thread Content
In diesel hydrogenation units, reaction temperature serves as the primary means to achieve desulfurization. What I would like to ask is, in order to increase the desulfurization rate and the depth of the reaction, which part’s temperature is generally raised to do so? Is it the inlet temperature of the reactor? If so, then only the temperature of the upper bed layer should increase, while the lower layers, being controlled by cold hydrogen, should not see an increase in temperature. So, will raising only the reactor inlet temperature have a positive effect? In a reactor, there should be a temperature gradient from the first bed layer downward. So, how large should this gradient generally be?
The hydrogenation reaction is an exothermic reaction; without the injection of cold hydrogen, the temperature increases as it proceeds further. Therefore, if one wants to raise the temperature, it is possible to reduce the amount of cold hydrogen injected. Increasing the temperature means raising the reactor inlet temperature
The hydrogenation reaction is an exothermic reaction; without the injection of cold hydrogen, the temperature increases as it proceeds further. Therefore, if one wants to raise the temperature, it is possible to reduce the amount of cold hydrogen injected. Increasing the temperature means raising the reactor inlet temperature
Do you mean that increasing the reactor inlet temperature also requires raising the bed temperature?
The reaction temperature refers to the temperature at the highest point of the bed. Temperature control can be achieved most directly by increasing the temperature at the furnace outlet; after raising the temperature, sufficient time is required for the reaction to take place
I understand what you mean. My thought is that if the temperature at the reactor inlet is increased, what will happen to the temperatures of the other beds? Because the temperature of the lower bed layers should be controlled by cold hydrogen; if I only adjust the reactor outlet temperature, then the temperature of the first bed layer will undoubtedly rise, which will certainly enhance the desulfurization effect. But for the lower layers of beds, since the temperature of the cold hydrogen is controlled, the temperature should remain unchanged once it has stabilized. Does that mean these lower layers don’t serve any purpose at all? In other words, if I increase the temperature at the reactor inlet, it is the first layer that makes the most significant contribution, while the other layers still provide the same desulfurization effect as before?
Does your reactor require isothermal operation? If only desulfurization is used to increase the inlet temperature, the reaction temperature rises and cold hydrogen control is applied to the bed layer
What is increased is the reactor inlet temperature; quench hydrogen is used to regulate the temperature difference in the bed. Because of the exothermic reaction, quench hydrogen must be supplied
The temperature should be adjusted based on the sample and quality requirements of the product. Raising the inlet temperature is the most common control method; cold hydrogen is used only in cases of overheating. If the circulation rate is sufficient, overheating generally does not occur during hydroprocessing. Moreover, if there is no overheating, there is no need to adjust the cold hydrogen flow.
Do you really think that a reaction will occur as soon as the temperature is increased? There must be a reaction time. Besides, the temperature can’t be increased just by wishing it to; there are many other factors at play, such as the properties of the raw materials, the activity of the catalyst, the material used for the equipment. Of course, the quality of the product is also a very important factor.
I’m not sure if there’s something wrong with my way of expressing myself. What I mean is this: we increase the temperature mainly to deepen the reaction depth. During normal operation, it should be cold hydrogen that controls the bed temperature; it’s impossible for there to be no supply of cold hydrogen during normal operation. For example, the temperature of layer 1 is 330°C, layer 2 is 335°C, layer 3 is 340°C, and layer 4 is 345°C. Cold hydrogen is introduced between layer 1 and 2, between layer 2 and 3, and between layer 3 and 4 to maintain the temperature stable at the levels I mentioned above. Well, when I increase the temperature at the reactor inlet, the temperature of one bed layer will definitely rise. In that bed layer, as the temperature increases, the degree of reaction will certainly increase as well. However, the temperatures of the other bed layers remain controlled by the cold hydrogen. If I don’t change the set temperature for those bed layers, then the temperatures of bed layers 2 to 4 should remain unchanged; even if they increase temporarily, the cold hydrogen will bring them back to the set temperature. So my question is: when raising the temperature, if only the inlet temperature is increased, then only the temperature of one bed layer will rise, which will increase the reaction depth; however, the temperatures of the second to fourth bed layers remain unchanged. In that case, it shouldn’t have any effect, right? Then why is it said that increasing the reactor’s inlet temperature is a primary method for enhancing reaction depth?