The actual functions of the pre-lift dry gas and the pre-lift steam.
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In our plant, the media used for pre-lifting in the past have been dry gas and steam, both of which are employed to increase the linear velocity of the lift pipe. Some sources suggest that dry gas used for pre-lifting can act as a terminator, helping to reduce the generation of dry gas. What is the actual effect of this?
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The claim that dry gas can reduce the total amount of dry gas in the reaction is explained from the perspective of chemical equilibrium; in practice, however, there is not much difference. . . Because any principle must conform to axioms such as energy conservation and mass conservation. . . Under catalytic reaction conditions, regardless of the hydrocarbons fed into the riser—such as methane, ethane, propane, butane, pentane, gasoline, diesel, and so on—any substance will undergo decomposition and cracking as long as its activation energy for such decomposition is met. . . Adding dry gas can reduce its production; therefore, we often need to add gasoline as a terminator. Will this mean that our gasoline production will also decrease? Then how would we dare to use gasoline as a terminator? . . Gasoline is such an expensive thing. . . Haha. . . ^_^. . . I am merely mentioning this issue here; I have no intention of attacking those who support the theory of chemical equilibrium. . . Since I stopped attending university, these over twenty years of working in management roles within the oil refining industry have indeed given me some insights into the theories presented in books and the practical challenges encountered in reality. . . Haha. . . :lol
I feel the same way. Dry gas is used as a pre-lift medium, provided that there is sufficient capacity in the compressor; this approach helps to reduce the amount of acidic water, and it also allows for a varying degree of reduction in the condensation load at the top of the tower. Since a portion of the dry gas is circulated, it has not been specifically determined whether it is more energy-efficient than steam.
Dry gas can be used as a pre-lift medium at the bottom of the riser reactor; it not only mitigates the effect of heavy metals on the catalyst but also helps to increase the speed at which the catalyst is transported within the riser, thereby ensuring thorough mixing and contact between the catalyst and the feed materials, which aids in reducing coking.
The greatest advantage of using pre-heated dry gas is that it reduces the amount of acidic water.
Under normal circumstances, the volume of dry gas coming out of the reabsorption tower is quite large; after hydrogen sulfide removal, this gas is used as a pre-pressurization gas. The advantages of this approach include: denaturing heavy metals, preventing dehydrogenation, increasing the flow rate of the reaction gas, avoiding excessive reactions, reducing energy consumption, decreasing steam usage, and minimizing catalyst deactivation due to water. However, this also increases the load on the compressors and distillation towers.