Agglomeration and fouling in three industrial petroleum coke-fired CFBC boilers due to carbonation and sulfation

Petroleum coke is quickly becoming the fuel of choice for many FBC boiler o perators, due to its low cost, high availability and high heating value. Ho wever, these inherent benefits come with a price, as the high sulfur conten t of coke requires limestone use as a sorbent fbr sulfur capture. In some c ases, operational problems associated with limestone use have arisen, Fouli ng, in terms of solid deposits in such boilers are normally thought to occu r as a result of interaction with various fuel-ash-derived species within t he system. However, detailed examination of the solid deposits demonstrated that the fouling was, most generally, associated with an agglomeration mec hanism we have called extended sulfation, i.e., sulfation to near quantitat ive levels of the limestone sorbent. Carbonation and hydration have also be en found to play a role in the agglomeration process at lower temperatures. This paper describes the fouling mechanisms in three circulating fluidized bed boilers firing petroleum coke as the only fuel.