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Category: Refining
Question: Can flaring of light hydrocarbons (up to C4) be avoided in FCC startup?
Keywords: fluidized,catalystic,cracker,flare,start,up
Answer: In general, you must be able to start up the Wet Gas Compressor with your internal fuel gas. There must be sufficient molecular weight, supply pressure and a large enough line to provide enough suction flow to avoid surging the WGC as it comes up to speed. This will vary depending on whether you have a motor or turbine driver. If you can get the WGC running on total recycle without surge, then you are in good shape. Depending on the type of anti-sruge control, it may be possible to run the WGC in automatic. When feed is charged, the gas production will increase the the compressor will automatically increase in speed or suction butterfly opening and pump the gas into the Vapor Recovery. All your operators have to do is close the vent to flare as the gas make increase to prevent the flaring. This can still be accomplished in manual control but it requires a little more operator attention and control. The key is really to keep the flare vent as closed as possible without surging the WGC as the gas make increases. You nmust balance the increases in feed rate to match the control or operator response to minimize flaring. It's not all that difficult once you've done it the first time but the important point is really operator attention to keep the flare valve closed without surging.


Keep your down stream system ready to receive material from wet gas compressor. At a same time you must have sufficient provision to store the off spec lighter material. 

This will help you to reduce the flaring.