Upon leaving the desalter, the crude oil will go to a crude processing unit where the first actual separations will take place. The feed charge will pass through the preheat bundles, generally on the shellside, where it will pick-up heat from an already processed stream. These bundles are where one type of refinery coke is formed. The temperatures are not high enough to form true carbon, but the deposit will still be extremely hard to remove chemically.
In previous discussions we have discussed this problem and also identified that technology has advanced so that very effective chemical cleaning of these “coke” (really asphaltene) deposits can be successfully accomplished in-place while off-line. Quite frankly, better outcomes are possible if operations would chemically clean these exchangers more often and not wait until the exchangers are nearly plugged solid.