Improving efficiency

Published:  15 November, 2017

Oil and gas-fired boilers have been providing the heating requirements for many industrial and commercial premises for over 100 years. In that time the energy efficiency of these installations has increased steadily, however there is a way to significantly reduce energy consumption that is still not universally applied and yet has a typical payback period of less than 18 months.

Boilers will always lose some degree of the heat generated through the chimney, but minimising this loss and making more efficient use of the energy conversion can reduce both costs and carbon emissions. One of the most cost effective solutions uses this waste heat to increase the temperature of the boiler feed water, thereby reducing the amount of energy required to bring the water up to operating temperature.

Flue gas economisers are positioned between the boiler and the chimney and transfer the heat of the exhaust gas to the boiler feed water which flows through finned tubes. The efficiency of this heat transfer depends on the design of the tubes and the flowrate of the water.

As businesses look to minimise overheads and also improve their environmental credentials, installing a retro-fit economiser on an existing boiler circuit can deliver a major step in the right direction. Furthermore, a system that has been correctly designed and installed can often recover the initial costs within 18 months.

Neil English, managing director at ThermTech, which specialises in tailor-made economisers, explains: “Every application is unique in some way, so it is very important to carefully assess the existing boiler system and then design the most suitable economiser that can be easily retro-fitted. Very often there will be multiple boilers involved and ideally the economisers should be installed without affecting the normal operation of the system.”

There are many examples of installations where the project costs have been recovered very quickly through savings in energy bills. Typically, savings of between 4% and 6% in fuel expenditure can be achieved while maintaining the same boiler output. For large businesses or facilities such as hospitals and factories, annual savings in excess of £100,000 are common.

In fact, as greater savings are being sought in the health sector, the investment in retro-fit economisers is proving to be a prudent one. Often built with multiple boilers, hospitals have found that the installation process can be achieved without affecting the heating services within the facility. Of course, this takes careful planning and execution of the project, but an experienced manufacturer and installer should be able to achieve this.

Once an economiser is installed, annual inspections should be carried out to check the efficiency of the process and to ensure continued reliability.

For further information please visit:

Sign up for the PWE newsletter

Latest issue

To view a digital copy of the latest issue of Plant & Works Engineering, click here.

View the past issue archive here.

To subscribe to the journal please click here.

To read the official BCAS Compressed Air & Vacuum Technology Guide 2018 click the image


"How is your manufacturing business preparing for a net Zero target?"