Economisers and waste heat recovery systems

Green’s is a world leader in the design and manufacture of bespoke waste heat recovery systems that often include our patented economisers. We help the energy industry reduce emissions, improve efficiency and cut costs.  Alongside our engineering and production capabilities, we provide inspection, repairs, spares and maintenance services for virtually all makes of boilers and related equipment.

Waste heat recovery explained

A waste heat recovery unit, or heat exchanger, recovers heat from hot streams that would otherwise go unused into the atmosphere usually taking exit gases from boilers.

The diagram show waste heat recovery using an economiser application, technology that was first developed by Green’s in the 1800s.

The technology

The main equipment includes:

  1. Economiser – waste heat in the exhaust gas leaving the boiler is passed over the economiser’s heating surface, which often includes finned tubes heating the feedwater that passes through the tubes before it enters the boiler, which increases boiler efficiency. Economisers also enable boilers to react more readily to loads by using heated feedwater, protecting them from thermal stresses caused by relatively cold water entering which helps to prolong boiler service life too.
  2. Waste heat boilers (WHB) or exhaust gas boilers (EGB) can be used to create steam without needing a separate boiler. This steam can be used in other processes and, if superheated, drive a steam turbine to generate electricity.
  3. Flue gas coolers cool down flue gas from boilers and utilise waste heat to heat up water which is then used in the plant.
  4. Air preheaters preheat combustion air and also for drying fuel. It can be applied at the very end of boiler exhaust systems as a flue gas and air heat exchanger.

Using the recovered waste heat

Common uses include:

  • pre-heating combustion air for boilers and furnaces
  • pre-heating fresh air used to ventilate the building
  • hot water generation including pre-heating boiler feed water
  • direct steam generation for power generation
  • space heating
  • drying fuel

Clearly this is a very brief summary of how waste heat recovery systems that include our patented economisers operate. We integrate other technologies and work with our clients to design, manufacture and install bespoke solutions that achieve their objectives. To find out more and discuss your requirements please contact us.