Please, experts, answer two questions
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1. Nowadays, high requirements are placed on hydrogenation refining products, with standards corresponding to National V; the sulfur content must be kept below 10. Is the flow rate higher or lower in those areas of the reactor where the temperature is higher? 2. The flow of crude oil in the reactor is driven by circulating hydrogen; increasing the amount of circulating hydrogen will it increase or decrease the degree of reaction?
1. The flow velocity is slower in areas with higher temperature within the same bed layer. 2. Increasing the amount of recycled hydrogen reduces the reaction depth.
Reactions are more intense in areas with higher temperatures; at greater depths, the flow rate is likely to be slower. Increasing the amount of circulating hydrogen, while keeping the temperature constant, facilitates the hydrogenation reaction
In areas where the flow rate is low, the fluid stays for a longer time; as a result, the heat of reaction is not removed in time, leading to higher temperatures； An increase in the amount of recycled hydrogen leads to an increase in the hydrogen-to-oil ratio; at a constant reaction temperature, this facilitates an increase in the degree of reaction. However, if the amount of recycled hydrogen is too high and the hydrogen-to-oil ratio exceeds the designed range, the degree of reaction will be low.
In the first case, it’s possible that there is a deviation in flow within the catalyst bed, that part of the catalyst may coking, or that the thermocouples are faulty (this situation is less common)! In the second case, as the circulating hydrogen amount increases and the hydrogen-to-oil ratio rises, the corresponding hydrogen partial pressure also increases, thereby increasing the degree of reaction – provided that all other operating conditions remain unchanged! However, an excessively high hydrogen-to-oil ratio wastes energy; it not only fails to increase the degree of reaction but actually reduces it. Everything should be done in moderation!
The space velocity for the diesel heavy fractions is low, and the hydrogenation depth is high.
1. Catalyst coking may occur in areas with higher temperatures within the same bed layer. 2. Increasing the flow rate of recycled hydrogen raises the hydrogen-to-oil ratio and enhances the degree of hydrogenation; however, if the recycled hydrogen flow is increased too much, the reaction pressure rises, preventing the components in the feed oil from being decomposed in the reactor, and as a result the degree of hydrogenation actually decreases. It's just my personal opinion; please feel free to correct me.
1. The flow velocity is low in areas with high temperatures and high in areas with low temperatures. 2. With this issue, it’s important to find the right balance; going too far has the opposite effect