Air Preheaters

Power boiler applications require highly efficient and reliable air preheaters to ensure optimum boiler performance. Howden has more than 80 years experience of supplying high quality air preheaters for customers worldwide.

In 1923 the Howden company and Fredrick Ljungstrom co-operated to develop the rotary regenerative air preheater for boiler applications.

The core of the preheater, the heat exchange surface, is composed of multiple metal plates known as elements. As the preheater slowly rotates, at around 1-2rpm, the elements collect heat in the hot gas stream and then transfer it to the cold air stream. Because both surfaces of the element plate are used for heat transfer simultaneously this type of heat exchanger is the most efficient and compact.  It is particularly suited to handling large quantities of hot gas and cold air.

The heat transfer elements comprise thin steel plates formed by rolling. We supply a wide range of profiles to best match various fuels and applications; combining minimum pressure drop, high efficiency, compact depth and ease of cleaning.

It is important to keep air to gas leakage as low as possible as leakage leads to increased fan power. We provide a range of sealing systems, including the advanced Howden “VN” sealing system. This fixed sealing system includes full depth rotor double sealing that keeps leakage constantly low for extended periods between outages. In addition to fixed sector plates, we supply a range of actuated control systems should the application require them.

The main drive is located at the upper end of the shaft rather than on the periphery of the rotor. This removes the drive components from the corrosive and erosive gas stream and also allows the axial seals run the full length of the rotor.

We supply a range of on-line cleaning options that use combinations of air, water or steam, in semi or fully retractable configurations.

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