De-Coking of Furnaces
The Regular De-Coking of Furnaces Has Numerous Benefits
Among the nation’s industries, there are countless instances in which heat is required to facilitate some essential process. In some cases, the heat provided by a boiler is quite sufficient for this purpose. However, there are also times when the requirement is for far higher temperatures, typically in excess of 400 °C. Frequently, these situations call for the use of furnaces and, with it, the need for regular de-coking.
In order to achieve the high temperatures required, air or even oxygen at high pressure is fed to the burning fuel and can generate temperatures of 2000-3000 °C or more. However, in the process of generating the necessary heat, the continuous flow of hot exhaust gasses from the combustion process also results in the formation of residual deposits of coke on the walls of reactor tubes. The effect is similar to the narrowing of the body’s arteries caused by the build-up of plaque. Likewise, while de-coking of furnaces is the industrial solution, this is quite similar to the procedure known as angioplasty used by a surgeon to widen those clogged-up arteries.
Just like those clogged arteries, when the reactor tubes become narrowed, they also tend to cause problems. In this case, however, it is the flow of hot air rather than of blood that becomes compromised. From an operational viewpoint, however, the possible long-term consequences of reduced flow can be just as serious. Firstly, for these devices to operate efficiently, the heat must be transferred from the reactor tubes to the process fluids as quickly and completely as possible. Because coke is a poor conductor, without regular de-coking of furnaces, the essential process of heat-transfer becomes increasingly inhibited. Paradoxically, in those regions of the tube where the deposit may be less pronounced, there is a tendency to form hotspots that can also interfere with the process or even cause physical damage.
Among those who are most dependent upon this type of process is the petrochemical industry. In order to break down the heavy hydrocarbons contained in crude oil, it must be subjected to intense heat, often under increased pressure. Consequently, unless de-coking of furnaces is carried out routinely, the necessary high temperatures cannot be maintained. The result is that the higher cost of producing light hydrocarbons such as petroleum could tend to render the process uneconomical, bearing in mind that its sale price is determined by supply and demand and not by its cost of production.
Unlike the predominantly manual procedures used to remove the clinker from industrial chimneys such as those that serve the nation’s coal-fired power stations, the de-coking of furnaces requires a more technical approach. To negotiate the narrow interior and bends that make up the heating elements or reaction tubes when de-coking furnaces requires a special device that is known to pipeline engineers as a “pig”. Inserted into the tubes, it is propelled along their length, scraping away the deposits and sweeping the tubes clean. The process is repeated, as necessary, until all traces of deposited coke have been cleared.
Expert “pigging” of reactor tubes is undertaken in South Africa by Oleum Process & Pipeline Services, who have the trained personnel, advanced equipment, and extensive experience required for efficient de-coking of industrial furnaces.