Project Description

The objective of the BioFoulControl project is to develop an ozone based bio-fouling prevention system for heat exchangers in maritime seawater coolers. The system will be cost-effective, user-friendly, safe to handle, environmentally acceptable and flexible compared to existing methods. Laboratory studies have shown that ozonation technology has very promising potential for control of bio-fouling in seawater cooling systems of vessels.

The BioFoulControl project addresses the challenges in the maritime sector regarding bio-fouling of heat exchangers that has high economic and environmental implications. Bio-fouling costs tens of billions of euros each year worldwide in the form of work associated with cleaning fouled components and failures related to biofouling. Bio-fouling is caused by the attachment of the larvae of marine organisms to surfaces in contact with seawater and then rapidly growing to adult fouling organisms. Subsequently, the surface will be colonised by seaweeds and the marine invertebrate. Efficient operation of seawater-based cooling systems on vessels is thus hampered by the settlement of plant and animal life and accumulation and excessive growth of organisms on the surface of heat exchangers and pipes. Efficient operation of seawater-based cooling systems on vessels is thus hampered by the settlement of plant and animal life and accumulation and excessive growth of organisms on the surface of heat exchangers and pipes.

Bio-fouling reduces the heat transfer in heat exchangers due to slime and biofilm formation, it reduces the water circulation in condenser tubes and accelerates the bio-corrosion of metallic surfaces in cooling systems as a result of extra-cellular polymeric substances and acids released by colonies of the accumulated organisms, and salt formation on the walls of the cooling systems. In many cases, heat exchanger tubing may become blocked and can only be rectified by extensive and costly cleaning operations. The principal solution for marine fouling has been overhaul and maintenance procedures during which the heat exchanger is disassembled and the tubes are physically cleaned, as by ramming cleaning rods through the tubes.

Heat exchangers placed in sea chests as a cooling system (box coolers) are in constant contact with seawater stream used for receiving heat from the cooling medium. As a result, they are exposed to bio-fouling and consequently to reduced heat transfer rate, increased working temperature of engine and other heated appliances and possible shorter life time or failure unless effective control measure is established. In addition, intake piping systems could be clogged with marine organisms propagating along with cooling seawater that reduce the capacity of the cooling system and compromising the safety of the vessel.

To develop a system, such as BioFoulControl, for effective control of bio-fouling in marine environment with the application of ozonation technique, the main challenge is associated with attaining adequate dispersion and content of ozone the water stream. Therefore, the project will focus on the development of an ozone injection and dispersion unit and a real time sensor-based Process Control Unit for control of the ozone injection and dispersion process.

The ozone injection and dispersion unit will ensure a high rate of mass transfer, a substantial degree of contact between ozone and water in order to raise the seawater/ozone inter-reaction, and to maintain high concentrations of dissolved ozone required to effect desirable inactivation of organisms that would potentially accumulate on the surfaces of the cooling system.

The real time Process Control Unit (PCU) will be set up to monitor and control the flow rate and critical water parameters that impact on ozonation with the help of water proof sensors and through a state-of-the-art water resistant sensor to regulate the injection and dispersion of ozone with the application of sensors with high accuracy.