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Turn-key projects

Economisers and condensate treatment system ECONERG

The economiser – free additional heat and the removal of solid particles from the flue gas.

The stainless steel economiser is a shell and tube type heat exchanger. According to the nature of thermal energy, economisers are divided into condensing and non-condensing types. When using stainless steel economisers, heat production can be substantially increased with the combustion of the same amount of fuel in the boiler. Due to deep cooling of the flue gas and the condensation of water vapour the economiser produces additional heat amounting up to 20-30 percent. The high performance indicators of the economiser are achieved due to the fact that high moisture content wood is combusted in the biofuel boilers, and a large portion of the combustion heat is used to evaporate moisture from the fuel. In the condensing economiser, contrary to the boiler, this heat is recovered and reused.


The condensate formed in the condensing economiser is collected in a container where it constantly accumulates. In such a way, there is a condensate excess, which needs to be removed; however, removal is not available due to the contamination of the condensate. Solid particles in the flue gas get into the condensate, thus affecting the quality of the water. In order to remove the excessive condensate, it must first be neutralised and cleaned. Therefore, the excessive condensate is added to the condensate cleaning system, where, first of all, its pH level is neutralised to achieve a pH= 6.5 – 6.8, which is necessary before disposing of the condensate in the sewage system. In order to achieve this, acid or alkaline solutions are added to the condensate. After this neutralisation, the condensate has to be prepared for filtration, which is achieved using a Laminar flow filter “Lamella”. The coagulation of small particles in the condensate into larger ones can be ensured by the use of a coagulant agent. The coagulated particles are then flocculated using a flocculent agent. After this chemical and mechanical treatment of the condensate, the mechanical filters designed by the professionals at Enerstena are used, and only then is the condensate suitable for disposal as sewage. To maintain the uninterrupted operation of the condensing system, and to increase the heat transfer efficiency, the remaining treated and filtered condensate is recirculated in the system. No additional cold water is used in the condensate treatment system.

Enerstena Group offers its clients not only economisers manufactured as heat generating equipment, but also a fully complementary and automated system at a very low cost. The available condensing economisers can be employed in biofuel boilers with a capacity of up to 150 MW.


• Low hydraulic and aerodynamic resistance with low electricity consumption.
• Efficient heat exchange in the economiser.
• Condensing economisers are easily adjustable to all types of boilers.
• District heating water is heated without an transitional heat exchanger.
• Additional capacity of up to 30% may be reached from the nominal boiler capacity.
• Effective condensate cleaning system.