TPi March 2018

A more useful alternative technology is to apply a boiler economiser. Spent heated gases from the outlet or flue of the boiler burner are returned to the inlet of the boiler to pre-warm the in-feed water, thus providing a higher inlet temperature to the boiler. This results in less fuel demand to reach a usable water heat. This technique is often used in modern domestic boilers but is not common for industry. Many industrial boiler systems are often older installations, and awareness of this energy-efficient technique as a retrofit option is not always known, therefore energy savings are looked for elsewhere. How do economisers work? Installed between the boiler outlet and the flue or chimney, economisers operate on the principle of heat exchange, salvaging boiler gases to pre-heat the boiler in-feed water. This reduces the energy 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 running perpendicular to the flow of hot outlet gases. By heat transfer, the flue gas temperature reduces as it increases the feed water temperature. The extent to which the economiser pre-heats the feed water depends on the design of the economiser and existing boiler parameters. The key to efficient heat transfer rate, however, is the design of the finned tube surface, which needs to maximise total thermal contact with the hot gas. Off-the-shelf or custom-built economisers Since every application is different, each economiser should be purpose-built to achieve the best transfer efficiency for the boiler design and the way it operates. This may include minor changes to an existing design, which is common for some more traditional designs based on boilers that operate continuously at maximum flow rates. More modern designs with variable flow rates, however, will usually require something more specifically suited to the application. ThermTech has been providing industry advice on heat recovery for over 25 years and is accredited by CHAS, ISO 9001, Achilles and ASME Boiler and Pressure Vessel Code Certification. The objective of the company’s engineers is to help assess the quantity and quality of available heat and match it to the most effective re-use cycle, using the most cost-effective and practically suitable forms of heat recovery equipment.

About ThermTech ThermTech designs, manufactures and installs bespoke industrial waste heat recovery systems and flue gas filter systems, with technical excellence, through a highly skilled workforce. In business for over 25 years, it has a track record in innovation and quality in the construction of conventional and condensing economisers, plus activated carbon filter systems. Its systems are designed to offer energy-saving and sustainability solutions to businesses predominantly across the UK, Ireland, Europe, the Middle East and North America. Based in Manchester, UK, but operating in many export markets, ThermTech works with consultants, contractors and end-users across the chemical, processing, power, industrial and manufacturing sectors. ThermTech remains at the forefront of heat recovery, keeping boiler performance at the optimum efficiency levels whilst at the same time reducing energy bills, reducing emissions and managing the carbon footprint of businesses.

ThermTech – UK info@thermtech.co.uk www.thermtech.co.uk

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TUBE PRODUCTS INTERNATIONAL March 2018

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