Hydrogenation unit processing load
Thread Content
1. What determines the minimum load of the hydrorefining unit? 2. In the event of a shortage of some raw materials or hydrogen, reducing the operation to its minimum load and switching to a partial diesel cycle will certainly result in a decrease in the reaction temperature; how can product quality be maintained?
1. Hydrogenation units generally have a designed minimum load, which is primarily related to the space velocity. For fixed-bed reactors, the amount of catalyst used remains constant; therefore, when the load is reduced, the space velocity also decreases. An excessively low space velocity is very harmful to the catalyst, as it can cause the flow of materials within the catalyst bed to become uneven or channelized. Hot spots may form in the bed, and if these hot spots are not eliminated over time, the catalyst will sinter. This not only makes operation more difficult but also increases the risk of temperature spikes. From an economic perspective, too low a load is also not cost-effective. 2. In the situation you described, there is no need to strive excessively for a low temperature rise. Since the amount of fresh raw material has decreased significantly, the amount of heat released during the reaction also decreases. Moreover, by adding diesel that has already been reacted, the remaining fresh raw material is diluted, which inevitably leads to a lower temperature rise. In such cases, it is sufficient to increase the temperature at the reaction inlet slightly to ensure that the temperature of the bed does not drop too low. Under normal circumstances, the inlet temperature must be increased by at least 10°C, and the total temperature rise of the bed layer will be more than 50°C lower than under normal conditions.
1. The minimum load should be specified in the design specifications. 2. If the operation time is long, the product quality cannot be guaranteed; however, it should be fine for short periods of time
What was said on the first floor is very comprehensive. What I would like to add is that in cases of interruptions in feed or fresh hydrogen supply, the plant operates in an abnormal state, which constitutes an accident or incident. In such situations, product quality is not the top priority; the main focus should be on bringing the plant back to a stable state, protecting the catalysts and equipment, and preventing overheating, overpressure, or pressure surges