Even with the recent spectacular drop in the price of oil, bunkers still constitute a very high proportion of voyage costs. Because of this, Aalborg Industries is recommending that owners and operators should look closely at the efficient recovery of waste heat from main and auxiliary diesel engines. In a recent issue of its house magazine, Aalborg claims that efficient recovery of waste heat can contribute substantially to the operating economy of a ship and at the same time save fuel for the benefit of the environment.
In this respect, the company points out that efficient exhaust gas economisers are worthwhile examining. Utilising fuel consumption to its full potential is not just about lowering an engine’s fuel consumption, or even installing an advanced oil/gas burner on the boiler; it is also about ensuring maximum waste heat recovery by installing a new unit or upgrading to the most efficient economiser.
It is not unusual for a substantial amount of thermal energy to be wasted as exhaust gas. Aalborg recommends replacing less efficient economisers with the most efficient type available today. These are likely to pay for themselves in a comparatively short time scale, which, Aalborg claims, can be as little as four or five years.
The company believes that this is often particularly relevant when a vessel changes trades and is used for a purpose for which it was not originally built and where more steam or power is required. Once collected, waste heat can then be used for a number of purposes including preheating combustion air or for heating cargo or water.
Aalborg’s most efficient exhaust gas economiser at present is the Mission XW, which is designed with double gilled tubes. This design is said to be especially suited to the ever increasing power versus weight requirements of today’s modern tonnage, since it is an extremely compact and has a very large surface area providing a high level of heat recovery.
When a vessel reaches port it normally shuts down its main engines but usually continues to run auxiliaries. By installing waste heat recovery units in the exhaust lines of these ever-larger pieces of machinery, considerable amounts of thermal heat can be saved and utilised for other purposes, again increasing efficiency and reducing fuel consumption.
In some cases, instead of firing the main boiler in port it would be far more economical to install economisers on auxiliary engines and run these during port operations, believes Aalborg. This would not only save fuel, but would also save on maintenance of the main boiler.
At the same time, Aalborg claims that ship operators often fail to put proper maintenance procedures in place. Matters such as soot blowing and water washing can help keep an economiser in good condition and help maintain its thermal efficiency. Regular maintenance can also avoid the accumulation of soot, which can be a safety hazard since it can cause fires that can melt down the economiser. Further, poor quality heavy fuel means that economisers can be rapidly contaminated. Aalborg recommends regular, or even daily, monitoring.
If the worst comes to the worst and an economiser fails, Aalborg also offers a tube replacement service at sea. This is done by installing a by-pass duct for the flue gases that allows for easy replacement of the tubes and returns the economiser to its original operating efficiency. MP
With high quality products and considerate service, we will work together with you to enhance your business and improve the efficiency. Please don't hesitate to contact us to get more details of Waste Heat Recovery Boiler.