The issue of injecting methanol into the cold zone of the ethylene plant
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KBR technology for ethylene plants, pre-depropanization pre-hydrogenation process. Methanol is injected at many injection points starting from the high-pressure depropanization tower. What is the purpose of injecting methanol at these different points? Are there any other impacts in the process, such as reactors or reboilers? How are these injected methanol molecules ultimately removed?
The location of the methanol injection point is primarily for thawing, and it can only be used in the intercooler area. The freezing point of methanol is around -98°C; therefore, it is not possible to use methanol in cryogenic environments with temperatures below -98°C. It is mainly discharged from the lowest end of the injection system. The specific steps to follow depend on the system.
The design of different injection points is determined based on the various locations that could cause freezing blockages. Injection into the high-pressure tower is intended to prevent freezing and blockage in that tower, while the injection point in the ethylene tower is used to prevent freezing and blockage in that tower as well. After injecting alcohol to prevent freezing blockages, it is generally necessary to use the nearest torch discharge line for discharge. For example, after filling the high-pressure tower, discharge can be carried out through the bottom discharge line of the tower; after filling the ethylene tower, discharge can be done through the ethane discharge line, and so on.