Operation of Boilers in Port
Boilers form a major part of ship-board energy consumption in ports in particular for certain types of ships such as oil tankers. Although boilers emit less harmful emissions than diesel engines (e.g. less NOx), nevertheless the control of their energy use will be beneficial for the port area emissions. This is the case as the ship auxiliary boilers mostly operate at low loads while in port. At low loads, the energy efficiency reduces and emissions factors increase that is not helpful.
The following shipboard measures could potentially reduce the usage of boilers in ports:
- Use of parallel operation of two boilers should be avoided. This not only improves the efficiency of the working boiler but also gets rid of electrical requirements for the second auxiliary boiler.
- Planning and optimization of cargo discharge operation is another area if it relies on steam driven cargo pumps, the steam condenser of cargo pumps should be worked under vacuum pressure (e.g. larger oil tankers). In some of the ships, there may be provisions for a mix of electric and steam driven pumps. Proper planning could be done to avoid excessive use of boilers.
- Plan and optimize ballast operation if it relies on steam driven ballast pumps. In many ships, the ballast pumps are now electric driven or a mix of steam and electric drives are used for this purpose.
- All aspects covered in relation to steam system maintenance on reducing the ship-board steam demand will also help the port operation. In other words, steam users need to be investigated and their operations decided based on port requirements.
In some ships such as oil tankers, auxiliary boilers may be used for inert gas generation (IGG). The whole process of generating inert gas and its use can be part of optimization; as for inner gas generation, the boiler would normally run at very low load (normally a dedicated IGG system is used to avoid use of large boilers) (MariEMS 2017).