Issues related to the trip of the air separation expander! !
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I hope the scheduling team can help and resolve my doubts! ! I’m a new dispatcher, and I would like to seek advice from those with more experience: Our company operates a system for producing 300,000 tons of synthetic ammonia. The gasification process uses SHELL technology, the air separation unit is from Linde, and the expanders are made by ACD. If the expanders stop working during normal operation, does it mean that the gasification process must be stopped immediately? As a dispatcher, what should I do??? Thank you! !
Excessively high oil temperature can cause the bearing temperature to rise, leading to a shutdown as a result. k
1. The shutdown of the expander does not mean that the air separation unit cannot operate normally; it is related to the cooling capacity of the main cooler. In some cases, the air separation unit can continue to function properly for 1–2 days after the expander shuts down, while in other cases it can only operate for less than an hour; this is especially true for air separation units that produce liquids. II. As for the air separation situations you described, it is unclear; in many cases, multiple units are used to supply customers, and these units can be adjusted as needed. In particular, there are buffer systems as well as comprehensive and robust backup supply systems to prevent supply disruptions. Therefore, the decision on whether to stop gasification depends on whether air separation can ensure supply, how much supply can be provided, and for how long it can be maintained ； And it is also necessary to take into account the safe production issues related to oneself and gasification.
1. In fact, you yourself are the one who knows the situation best, but from the questions you’ve asked, it’s clear that you’re not familiar with the system’s utility conditions. The shift supervisor is responsible for 8 hours of work; you need to work hard, otherwise a single wrong instruction could have life-threatening consequences! 2. The first principle of scheduling is to act according to pre-established plans in case of emergencies – what to do if the expander stops working, if the air separation unit shuts down, or what to do in cases of gasification issues. If your company doesn’t even have such plans, you need to start developing them right away and conduct drills! I’ve worked in production; there have been power outages, water shortages, gas supply interruptions, as well as shutdowns of various processes – it’s all part of actual drills. All positions! In such a situation, here, your instruction is simple: use code 03 to exit the vehicle and follow Plan 3. 3. The following opinions are for reference only: First of all, I can conclude that you do not have a backup expander! The air separation unit is a single unit with a capacity of 28,000–32,000 units. 3.1 Since it is unknown whether there are backup liquid oxygen storage tanks or oxygen buffer tanks, in any case, supply cannot be provided if the gasification unit is under high load. Therefore, gasification must be stopped; however, if there are backup storage tanks, an immediate shutdown is not necessary. Reduce load immediately upon coal gasification, carry out a normal shutdown; maintain a heat cycle in the steam system, reduce the load on the coal grinding system, and continue coal powder circulation. Purge with nitrogen as required for parking! Other units shut down (not an emergency stop! ) 3.2 Do not drain the liquid from the air separation cold box for now; disconnect the expander from the system, and inform the control, instrumentation, and mechanical teams to identify the cause from their respective fields. 3.3 Protect the operation records! 3.4 You cannot notify of a trial start until the cause of the fault has been identified! (Safe parking is your responsibility; other matters are not related to you.) 3.5 The most likely reason for getting out of the vehicle is excessive vibration caused by too sudden a load increase; it’s not necessarily a fault. Conclusions will be drawn later. 3.6 Stop the boiler operation and reduce load (the air separation unit is shut down, resulting in less steam consumption). However, the furnace must not be shut down. After maintaining it for 3.7 hours, it will be possible to determine the severity of the situation. Well, it can be done by parking or driving. 4. Most importantly, report to your superiors as soon as possible, no matter how good or bad your relationship with them is! Get to know the specific configurations of utility systems better; scheduling requires thinking from a higher perspective. Wishing you success in your work!
Gasification does not need to be stopped; immediately activate the backup expander, and adjusting the nitrogen purity is key.
The issue should be checked in the DCS; it’s not possible to perform an emergency stop right away in such a situation.
There is no need to stop the gasification process, but it is necessary to activate the backup expansion turbine or the emergency expansion turbine as soon as possible. During this time, the volume of gasification can be reduced appropriately, and the load on the air separation unit producing oxygen can also be decreased slightly, in order to maintain the level of the main cooling liquid as well as the purity of oxygen and nitrogen.
Thank you for your reply! ! Wish you success in your work and good health! ! Our air separation capacity is 52,000 NM3/H. There are two liquid nitrogen storage tanks with a capacity of 50 M3 each, and two oxygen buffer tanks with a capacity of 50 M3 each. There is only one expander. The entire system has only one air separation unit. This post was last edited by sgwwood on 2009-3-22 21:47]
Yes, I’m also someone who has just started learning about this. But as far as I know, it’s possible to use a backup expansion machine; in other words, it’s still possible to maintain operations without reducing the load on the air-cooling tower in a short period of time