Elimination of carbon deposits in heat exchanger, e.g. for hydrotreatment installation, involves purging with inert gas, preheating and controlled oxidation

摘要

The heat exchanger is purged with an inert gas to eliminate the hydrocarbons, preheated and then it undergoes at least one controlled oxidation at 400-500 degreesC for at least 4 hours using an oxidizing fluid, which is preferably an inert gas with a small proportion of oxygen. The fluids entering or leaving the exchanger stay below 520 degreesC throughout, and the hot inlet to the exchanger stays below 120 degreesC The heat exchanger operates with a maximum service temperature less than 540 degreesC. The fluids entering or leaving the exchanger stay below 500 degreesC throughout, and the hot inlet to the exchanger stays below 100 degreesC. The temperature of at least one of the fluids entering the exchanger, or the proportion of oxygen in the oxidizing fluid is reduced if during the oxidation the temperature of one of the fluids entering or leaving the exchanger reaches or passes a limit temperature of 490 degreesC, or the hot inlet to the exchanger reaches or passes 90 degreesC. The proportion of oxygen in the oxidizing fluid is less than or equal to 2.5%, preferably 2% by mole, or is such that the temperature differential in total adiabatic combustion is less than 100 degreesC. The oxidation is carried out in situ. At least two controlled oxidation stages are carried out with an oxidizing fluid containing 0.4-1.5% oxygen at a temperature of 420-490 degreesC for at least four hours in the first stage, and a higher oxygen concentration of 1.3-2.0% at a temperature of 420-490 degreesC for at least two hours in the second stage.