I would appreciate your advice on several issues regarding the reformation of pre-hydrogenation chains!
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1. The pre-hydrogenation feed pump is a high-pressure pump equipped with a return line (minimum flow line). Then why, among all the interlocks, is it only when the circulation hydrogen flow is low that the feed pump is shut down? Why, in cases of low feed pressure or low fuel gas pressure, are only the furnace and the feed stopped, rather than the feed pump as well? ? I don’t think it’s necessary to shut down the feed pump just because the circulating hydrogen level is low! 2. Why is it that when the pressure in the main fuel gas line is low, only the fuel gas supply is cut off while the pilot light remains intact, whereas when the pressure of the pilot light is low, both the main line and the pilot light line are shut off?
First, understand the role of circulating hydrogen: it acts as a heat carrier and prevents coking during the reaction. The first issue is obvious: when the circulating hydrogen level is very low, the reaction must be stopped to prevent coking. When the feed rate is low and the fuel gas level is low, it is sufficient to shut down the furnace to lower its temperature
2. The permanent light inside the furnace must be burning, so that no explosion testing is required when restarting the furnace.
1. If the hydrogen flow rate here is very low, the hydrogen supply machine will trigger an interlock, and both the feed system and the furnace will also experience interlocks. The pump stops immediately, and the feed UV valve is shut off right away. Prevent oil and gas from entering the bed and causing coking. 2. The pilot light is kept to facilitate re-ignition of the furnace. The temperature of the eternal light in the furnace is limited, so it will not damage the furnace tubes
The hydrogen circulation pump will surge if the pressure is too low. If the hydrogen circulation pump is a centrifugal pump, in an emergency, the main burner should be shut down to prevent excessive temperatures; otherwise, the pilot light interlock system will not function, which makes it difficult to restart the system. In cases such as burnout of the furnace tubes, both the main burner and the pilot light must activate through the interlock system! It depends on the situation!
Thank you to everyone above. There are still 2 points I don’t understand: 1. Why does the feed pump need to be shut down when the circulating hydrogen level is very low (with a minimum flow line installed at the pump outlet)? The reactor feed has been cut off. Is it still necessary to cut the pump? 2. Why must the main fuel gas be cut off when the pressure of the permanent light is very low?
When the pressure of the permanent light is low, the burner is prone to going out; if fuel supply is not cut off, an excessive amount of fuel entering the furnace can lead to a flash explosion, so the gas valve should be turned off when the pressure is low. After the feed is cut off, the pump has a low-flow protection feature; if the system can recover, there’s no need to shut down the pump. If recovery is not possible, then the pump can be shut down. Should the pump be switched off? I don’t understand its function
1 Do you mean that if the pilot light, which is used to prevent flash explosions, goes out, there is a risk of a flash explosion? So, when the pilot light goes out, the main fuel gas must also be turned off, right? 2. I don’t understand it either; it’s actually about whether the feed pump still needs to be stopped after the low-low interlock for recycled hydrogen triggers automatic feed shutdown! Of course, the feed pump has minimum flow protection! When the main fuel gas level is at a low-low level, only the furnace and the feed are shut down; why is it that when the circulating hydrogen level is at a low-low level, the pumps are also shut down? Are you afraid of leakage from the XCV valve when cutting the feed? If you’re worried about leaks, you should cut the feed pump too when cutting the furnace! I don’t understand!
Yes, when the pressure of the perpetual flame is low, it’s easy for the flame to go out as well. When fuel gas enters the furnace and the temperature of the furnace has not yet dropped, a flash explosion can occur very easily. Pre-hydrogenation circulators are equipped with standby units; when the flow rate of circulating hydrogen drops, switching to the standby unit quickly can restore normal operation, so there is no need to stop the pump. Once the hydrogen flow rate is restored, feeding should be resumed immediately to restart the furnace – otherwise, the value of such equipment is lost. If the flow rate of circulating hydrogen is low, only the feed isolation valve should be closed; the pump should not be stopped.
Mm-hmm, thanks bro! I’ll need to ask for advice again in the future; thank you in advance!
All the feed UV valves are closed; then what’s the point of keeping the feed pump running? Of course, it should also be shut down. Moreover, under normal operating conditions, the minimum flow line is not turned on. In an emergency, the operator may not have time to turn on that line, which could result in damage to the pump. Speaking of, it’s not a hassle to get a pump.