We have a recent application where the ductwork from a customer’s Cupola exploded. In our opinion the explosion was related to CO accumulation in the blast ductwork/bustle. We arrived at this conclusion since the Tuyere doors were not left cracked to allow a chimney effect draft of fresh air to rise in the Cupola.
Once the fresh coke was added to the coke bed after banking, the customer immediately had the three components of the Fire-Triangle. The Fire-Triangle is a combination of heat from the coke bed, fresh air from the blower inlet and the heavier CO laying in the low spots of the duct displacing the air. Once the fresh coke dropped everything mixed with the air wave of the falling coke, resulting in an explosion. Thankfully, no one was injured!
As a matter of process, at least every other Tuyere door should be cracked during banking. It actually would not hurt to crack all of the Tuyere doors during the process, with the idea to create a chimney effect to pull the CO up and out the stack of the combustion chamber with the cap open. Finally we would highly recommend Cupola Bustle Relief Ports to be installed on the existing Bustle.
At EC&S we have 40+ years of experience designing, building and installing melt system Cupolas. We are a Turn-Key supplier and will partner with you as a single source to solve your toughest applications.