Hello How to control the evolution of reactor temperature during FCC start-up and what are the consequences of a sudden rise in reactor temperature on the refractory lining.
Mar 12, 2017 02:03 pm
Joshua:Slow and steady. Slow and steady. Introducing feed and increasing at rates slowly and steadily so...MoreSlow and steady. Slow and steady. Introducing feed and increasing at rates slowly and steadily so that exotherms can be managed with the heat balance of your unit. Temperature runaway can always cause damage to any portion of any unit due to uneven heating, fast rates of metal expansion, or excessive temperatures. Refractory lining can slough off.Less
Mar 12, 2017 02:04 pm
Michael Edwards:You mention refractory. There are two different rates of heat-up. After a turnaround with...MoreYou mention refractory. There are two different rates of heat-up. After a turnaround with extensive refractory repair of Reactor / Regen & piping, or the initial startup for that matter, heat-up rate must be controlled per the recommendations of the refractory advisers (the refrac company, the refrac installers, third-party mech advisers, and/or your own in-house experts). X degrees per hour max, hold at Y temperature min for Z hours min, repeat until oil-in temperature is achieved. But if only minor repairs, or a brief shutdown for other reasons, a faster rate will be allowed, normally subject to expansion issues and lining-up the rest of the unit (Main Column and Gas Plant, tankage, etc). Reactor reactions are net endothermic. Regen combustion is of course exothermic. So careful control of the Regen cat temperature (air fired heater, then adding torch oil) and circulation rate to reactor are vital to avoid sudden jumps on Reactor side. If for example, too much torch oil (or feed, after oil-in) is permitted without compensating increase in Regen air rate, the coke on Regen cat will build up. A panicked response of quickly boosting air rate guarantees very rapid Regen cat temperature, and even reduced cat circulation may not prevent damage to Reactor (and Regen, and piping) refractory.Less