A method of cleaning an evaporator that includes at least one heat transfer element for the evaporation of water, comprising forming a sacrificial layer of a first material on a surface of the heat transfer element (1); evaporating water that includes a second material to deposit the second material on top of the sacrificial layer (2, 3); and cleaning the evaporator by removing both the sacrificial layer formed on the heat transfer element and the second layer formed on top of the sacrificial layer; wherein the first material is more easily removed from the heat transfer element than the second material (4).

A catalyst regeneration gas loop is operated in a heat exchanger decoking mode. A regeneration gas is diverted away from a burn zone of the catalyst regeneration gas loop and to a heat exchanger, where coke deposits are disposed on a surface of the heat exchanger. The regeneration gas is prevented from flowing to an oxychlorination/calcination zone of the catalyst regeneration gas loop. Within the heat exchanger, the coke deposits are combusted with oxygen of the regeneration gas, thereby removing the coke deposits from the surface of the heat exchanger and producing carbon dioxide. Oxygen is replenished to the regeneration gas. The regeneration gas is recycled to the heat exchanger.