Bengal Tools

Regenerative Baskets

Quality Principals

Manufacturing

Air Preheaters

BENGAL TOOLS LTD
2, Jessore Road,
Dum Dum, Kolkata - 700 028. INDIA

Phone +9133-25502487
Fax +9133-25500249 / 25519953
Email: enquiry@shrachi.com

Regenerative Baskets

Regenerative Air Pre-Heater Baskets

Power generation industry always faces rigorous demands and Regenerative Rotary Heat Exchanger undoubtedly faces the toughest of them.

If optimum boiler performance is what one might rightly demand – highest quality of air pre-heater is a must. Design of Air Pre-heater Baskets with Elements has to take into account sulphur content of the fuel, erosion and fouling characteristics of the fly ash, soot blowing and periodic cold end temperatures as recommended and other sources of moisture. Thus Air Pre-Heaters are important components of Coal fired Power Stations. By Pre-heating the combustion air with hot flue gas leaving the boiler a gain in efficiency is obtained. Today’s call to RAPH manufacturers is to design for reduction of maintenance need and longer gap between overhauls.

Metal thinning due to corrosion by build up of deposits will eventually lead to reduction in service life of the Elements. Excessive corrosion will call for frequent overhauling / replacement. This will result in costs and reduction in unit efficiency. If on the other hand pressure drop across the heater increases, a higher capacity fan may have to be installed at a considerably higher price. With a large range of profiles at its command BTL can supply direct replacement of all elements. Many of BTL profiles have been individually tested. Elements can be supplied in a variety of baskets including BTL design, which has been developed to maximize rotor area and to reduce gas bypassing the elements. Various types of element surface profiles have been designed each with special properties for the many different type of application and operational conditions. The types are DU Element having a high heat transfer coefficient and at the same time a relatively low pressure drop factor. The parallel notches make the elements amenable to soot blowing. The CU element is a very efficient element in relation to heat transfer but has a relatively high pressure drop factor. This means a pre-heater but with more surface. The UNF element is especially easy to clean, which is used in cold end of Air Pre-Heater. There are also corrugated flat (CF) and notched flats (NF). The standard profiles are shown below:

Key considerations

While designing and manufacturing heating elements as per customer’s requirements, the following consideration are kept in the designer’s mind.

a)	Solid and Strong Structural formation
b)	Reduced pressure drop across the Heater
c)	Increased efficiency in Heat Transfer
d)	Trouble free assembly and disassembly
e)	Higher corrosion resistance
f)	Easy to clean
g)	Assured reliability
h)	Easy access while cleaning

The other major factors affecting design and operation of Air Pre-heaters are:

Corrosion

The use of cold elements of higher-grade steel or enamel coating will reduce the effect of corrosion.

Hot and fouling
With tough ash particles in the hot end elements, the profiles are such selected so as to reduce fouling and facilitate easier cleaning.

Cold End Fouling
Often due to inadequate ash in the flue gas not absorbing condensing acid. Answer could be closed profile elements.

Insufficient Heat Recovery
Heat recovery and boiler efficiency can be had by using higher efficiency elements and by use of unused space within the rotor.

BTL is a leading Indian supplier of regenerative Air and Gas Heater Replacement Baskets since 1967 in major Power Plants in India. BTL is equipped to supply all types and makes of RAPH.

Standard materials are:

	Carbon Steel
	Corten Steel
	Stainless Steel
	Enameled Coated Steel