Reducing Manufacturing Energy Costs With Flue Gas Economisers

Best practice dictates that businesses should be constantly looking into ways to improve operating efficiency. Despite becoming popular over 100 years ago the humble boiler is still a major energy consumer in many factories and other types of business.

The number of companies that use flue gas economisers effectively; to reduce energy costs and improve efficiency, however is far fewer. UK supplier ThermTech believes this is due mostly to lack of detailed awareness, rather than any unwillingness to embrace the technology.

An economiser can reduce gas usage for the same boiler output, and can typically offer businesses fuel savings of between 4% and 6% with a return on investment between 6 to 18 months. In fact, a recent pair of economisers installed by ThermTech at a hospital in Liverpool has already saved £100,000 per annum.

How do economisers work?

Installed between the boiler and chimney, economisers operate on the principle of heat exchange, salvaging the boiler flue gases to pre-heat the boiler feed water. This reduces the amount of energy that is required to heat the boiler feed water to operating temperature.

Usually constructed from carbon steel, the economiser design incorporates finned tubes, containing the boiler feed water, that run perpendicular to the flow of hot gas. These finned tubes transfer heat from the flue gases into the water flow. This process lowers the flue gas temperature while the feed water temperature is increased.

The extent to which the economiser pre-heats the feed water will depend on the specific economiser design and boiler parameters. The key to an efficient heat transfer rate is the design of the finned surface, which needs to be in complete thermal contact with the water tubes.

Since every application is different, each economiser should be purpose built to suit the specific boiler design and the way in which it operates. More traditional designs are based on boilers that operate continuously at maximum flow rates, but these can lose efficiency when used in applications that operate with variable flow rates.

Improving costs and sustainability

Neil English, Managing Director at ThermTech comments: “Over the past 25 years we have designed, manufactured and installed over 350 boiler flue gas economisers. Our economisers are an ideal way to maximise the boiler’s efficiency by shortening the time required for steam production and also aid longevity, as the problem of thermal strain within the boiler is greatly reduced.

“Whilst many would consider the advantages of a system as purely economical to increase plant efficiency and reduce fuel consumption, another key advantage is a reduction in CO2 emissions. In fact, over the past 20 years we have saved companies in the chemical and process industries over £8,000,000 on fuel bills, which is equivalent to a reduction of 500,000 tonnes of CO2 emissions.”

ThermTech’s boiler flue gas economisers can be installed for boilers which use gas, sulphur-free oil and digester gas fuel types. They can be installed on steam boilers, hot water boilers, waste heat boilers, process plant, thermal oil heaters, CHP engines and plant turbines. They are ideal for the chemical, pharmaceutical, processing, industrial and manufacturing sectors.