International Ship Insurance Companies advise alertness at heavy fuel oil bunkering

By Peter Pospiech at January 17, 2013 05:59
Filed Under: drive systems, Fuels & Lubes, General

Fuel impurities are an ongoing problem in ship operations. In spite of quality and delivery standards again and again poor heavy fuel oil is offered worldwide in many ports. This leads to severe engine damages and extremely high costs for the shipping owner. But what are the main impurities? And what can the ships crew do to be warned? 


In the case of impurities these are mainly cat fines, asphaltenes, water and dirt. Asphaltenes, water and dirt can be removed by the use of good separation devices, like separators. What are cat fines and can they be separated? 

In order to make petrol or other fuels out of crude oil, refineries work with the catalyst cracking process. So-called “cat fines” (including aluminum and silicon compounds) are used as catalysts and these are then found in the fuel. Cat fines are extremely damaging to engines. Cat fines are substances like silicon and aluminum compounds which are required as catalysts in the refining process known as catalytic cracking (“cat cracking”). This method of crude oil treatment splits large, high-boiling hydrocarbon molecules into lots of smaller, lowboiling molecules. It is only this conversion which creates fuels like diesel, petrol or kerosene from crude oil. This process takes place in special cracking towers at a temperature of around 500 °C. After the conversion, there is then a large quantity of cat fines in both the residues of the cracking towers and the distilled crude oil products. These cat fines have a negative impact on the end products, as silicon and aluminum compounds are extremely abrasive. If they get into an engine, this can rapidly lead to the destruction of sensitive components and thus to total failure. The separator manufacturer developed equipments which allow cat fines to be removed reliably from the oil residues. This system combines clarifiers and decanters with one another. In the first stage, the job of the clarifier is to remove the fine solids from the heavy fuel oil sludge. Once treated in this way, the heavy fuel oil can have a cat fines content of less than 100 ppm. The sludge which leaves the separator is treated by a decanter in the second separation stage. 

Recovery of cat fines from oil residues

On-board crews should take immediately during each bunkering fuel samples and pay lots of attention during the following engine operation. Particular factors like abnormal exhaust temperatures or changes in sludge production give precise warning sizes for activities. 

Image: PPM archiv, graph: courtesy of Westfalia Separators




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