C2 hydrogenation start-up (pre-hydrogenation)
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First, the general sequence for pressurizing the reactor when starting up is low-pressure nitrogen, CO, high-pressure nitrogen, and cracking gas, followed by starting up the process. Many sources state that it is not necessary to use ethylene gas for this purpose. There are two reasons for this: 1) It takes 10 minutes for the temperature to rise to the reaction temperature using ethylene, during which time all of the ethylene is wasted as flue gas; 2) A large amount of ethylene gas in the reactor can inhibit the normal hydrogenation of acetylene to ethylene, causing instead hydrogenation to ethane. So what is the purpose of using ethylene gas then?
Second, if the hydrogenation reactor overheats, it must wait until the bed temperature drops below 80 before it can be used again. What is the reason for this? The documentation states that high temperatures cause propylene to crack; what does this cracking produce, and what are the consequences? Seek answers from experts
The hydrogenation reaction is an exothermic reaction, and the higher the temperature, the faster the reaction proceeds. If the temperature in the reactor rises too much and does not drop, it can lead to overheating and damage to the catalyst.
Ethylene gas is mainly used for pressurization, while propylene is used for cooling, I guess