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We are going to carry out steam air decoking in VDU during shutdown in our refinery for the first time. Before that only spalling has been done. I am a fresh Chemical Engineer. So I would like to know what are the problems those are generally faced while air burning process and what are the possible solutions to avoid these problems?
 
Answers
24/03/2015 A: Sudhakara Babu Marpudi, Oman Refineries and Petroleum Industries Company, m_sudhakarababu@yahoo.com
One must be careful with two main issues. The air is injected into the system to burn of the residual coke deposits inside the tubes. Continuous burning can lead to tube burn outs / bowing and so air is to be injected in short bursts followed by a quick steam burst (so that the coke id kept under controlled burning and the loosened coke is blown off by the following steam bursts). If the steam is not dry, the condensate inside the pipe can cause water hammer and dislodge the pipe off its supports. Vertical tube heaters often experience such tube jumping out of the anchor supports.