Online cleaning and coking removal using heat transfer oil

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This post was last edited by dongjiang1001 on 2011-9-17 at 15:26. Analysis of the mechanism behind coking in heat transfer oil. As an excellent heat transfer medium, heat transfer oil (organic heat carrier) features heat transfer under high temperature and low pressure conditions; it offers high thermal efficiency, uniform heat distribution, accurate temperature control, and significant energy-saving benefits. However, whether it is synthetic or mineral-based, heat transfer oil is an organic substance – namely alkanes, cycloalkanes, aromatics, and their derivatives. They will undergo cracking when operating for long periods in hot oil furnaces at high temperatures. The carbonization and coking reaction is a typical chain reaction (as shown in the figure above). Its common feature is that as the temperature rises and the reaction time increases, hydrogen is continuously released; the hydrogen content in the residue (tar) gradually decreases, while the hydrocarbon ratio (RC/h), molecular weight, and density increase. In other words, the feed hydrocarbons undergo gradual dehydrogenation and condensation, with monocyclic or low-ring-number aromatic compounds transforming into polycyclic aromatics, and further into condensed polycyclic aromatics. The liquid tar then turns into asphaltenes, which are mainly crystalline condensed polycyclic aromatic compounds whose chemical structure remains unclear. It then transforms into carbaphene (which is a condensed polycyclic aromatic hydrocarbon with a higher molecular weight and lower hydrogen content), and further transforms into high-molecular-weight coke. Technical features of online coking removal for heat transfer oil furnaces: (1) It is possible to remove the carbon deposits accumulated inside the heat transfer oil furnace system and the end-use heating equipment without shutting down the furnace ； (2) The heat transfer oil furnace does not need to have its operating conditions changed; it is sufficient to inject the additive into the system using a backup pump or from a high-level tank ； (3) The heat transfer oil can be used continuedly; it will not be affected ； (4) Extending the lifespan of the heat transfer oil allows the overall overhaul period of the heat transfer oil furnace to be postponed to a time when conditions permit. Working principle and efficacy: The online coking inhibitor for heat transfer oil possesses strong reducing properties and cleaning capabilities; it cleans existing coke deposits and prevents their formation. The working principle is as follows: (1) The additive can capture the coke-forming groups that arise from aromatic hydrocarbons, hydrocarbon chain dehydrogenation, cracking, and condensation reactions, thereby preventing the degradation and coking of heat transfer oil ； (2) The additive components help to clean and disperse the coking and heavy polycyclic aromatic compounds resulting from dehydrogenation within the system, enabling them to be liquefied and removed from the metal surface. Construction process: 1. Inject it into the system at a rate of 1% of the volume of the heat transfer oil, ensuring that the cleaning agent reaches all parts of the piping. If the system is not fully filled, top it up with used heat transfer oil (be careful not to introduce water remaining in the low-level tank into the system). 2. During operation, monitor the pressure indicated by the pressure gauge; if the pressure rises significantly, open the forced exhaust valve. If the pressure drops markedly, clean the filter screen immediately.