Wilhelmsen Ships Service advises vessel operators to wage war on soot. According to WSS, soot accumulation in a ship’s exhaust gas boiler (EGB) is a serious issue, leading to reduced EGB efficiency, significant cleaning costs, corrosion, and the risk of soot fires. However, a simple post-combustion fuel treatment can solve all these problems, at negligible cost.
Loss of Efficiency
Refined heavy marine fuels are full of contaminants, such as Vanadium, Sodium, Aluminium, Silica, and Potassium, which leave deposits when burnt. These particles, soot, pass through vessel exhaust valves and turbo chargers until they reach the EGB. As soot has insulating properties, heat transfer, and thus efficiency, is reduced.
Cleaning Every Two to Three Months
With typical EGBs, cleaning takes around five hours during port calls and has to be repeated every two to three months. In addition, un-burnt fuel and lubricants can also be deposited in the EGB. These lower the ignition temperature of soot, and increase the risk of soot fires.
Cold Corrosion
Another factor is cold corrosion. Sulphur in the fuel reacts with oxygen during combustion to form Sulphur Dioxide and Sulphur Trioxide. When the temperature drops below 135°C, which occurs in EGBs operating at low velocities, the Sulphur Trioxide reacts with the moisture in the air and forms sulphuric acid. This is very corrosive to tube surfaces, and affects metal in a similar way to rust.
Post-combustion Fuel Treatment
WSS says these problems can be mitigated by post-combustion fuel treatments. The company itself offers WSS’ Unitor’s FuelPower Soot Remover Liquid Plus, which dispenses a fine mist that condensates onto the soot and continues to oxidise it. The result is that almost no soot is deposited in the EGB. The solution is active from 180°C, making it suitable for the low exhaust gas temperatures associated with slow steaming.
Tested on Board
Unitor’s FuelPower Soot Remover Liquid Plus has been thoroughly tested over the course of the last year on board Wilh. Wilhelmsen’s 76,500 GT RoRo MV Tønsberg. Prior to its daily dosing, the vessel’s EGB required regular cleaning every two months.
However, after ten months of regular treatment, every six hours, the vessel, which has a busy trading pattern between Europe, the US and Japan, has yet to require EGB cleaning – saving time, money and a lot of work. The company further points out the Return on Investment is 'compelling'.
