IMPROVING THE BOILER EFFICIENCY BY OPTIMIZING THE COMBUSTION AIR R.Pachaiyappan 1, a* , J. Dasa Prakash 2, b 1 Assistant professor, 2 M.E. Final year (Thermal Engineering) 1,2 Department of Mechanical Engineering, Adhiparasakthi Engineering College, Melmaruvathur-603319, Tamil Nadu, India. a rp00212@gmail.com, b dasaprakash3@gmail.com Keywords: Air Preheater, Heat Exchangers, Economizer, Seal Leakages, Heat Conductivity, Flue Gas, Optimum Air. Abstract. Air pre-heater and economizer are heat transfer surfaces in which air temperature and water temperature are raised by transferring heat from other media such as flue gas. Hot air is nec- essary for rapid combustion in the furnace and also for drying coal in milling plants. So an essential boiler accessory which serves this purpose is air pre-heater. The air pre-heater is not essential for operation of steam generator, but they are used where a study of cost indicates that money can be saved or efficient combustion can be obtained by their use. The decision for its adoption can be made when the financial advantages is weighed against the capital cost of heater. The efficiency of the boiler increases with the increase in the temperature of the combustion air used in the furnace. This is achieved by the increased temperature of the flue gas in the air preheater and economizer zone. This paper deals with the different ways to obtain the maximum heat from the flue gas travel- ling through the air preheater and the economizer zone to improve the boiler efficiency. Introduction Air is a primary component in furnaces and boilers. In each of these equipments, the ambi- ent air needs to be heated up to high temperatures. Preheating the incoming air largely improves the thermal efficiency of the system, thereby increasing the energy savings of the industry and results in lower operating costs. In fact, every 22 0 C rise in combustion air temperature increases the boiler efficiency by nearly 1%. Heat exchangers can be used to recover the heat from various processes to preheat the air. However, the heat transfer coefficient of air is low and hence, fins or extended sur- faces are used to enhance the heat transfer [1]. It is a common industrial practice to utilize the heat of exhaust gases or flue gases and process steam to preheat ambient air. Air pre-heater is the most common equipment responsible for deterioration in boiler efficiency and increase in auxiliary pow- er consumption in ID (Induced draft), FD (Forced draft), and PA (Primary air) fans. In this paper different aspects of air pre-heater performance has been discussed such as, the parameters to be monitored, causes and effects of poor performance of the air pre-heater and how the air pre-heater performance affects the boiler efficiency. Some suggestions to improve the air pre-heater perfor- mance are also discussed in this paper. Specification of air preheater Type: 27-VI-72 (T) 74 Where, 27 is the nominal diameter of rotor in feet VI stands for vertically erected down flow air pre-heater 72 is the height of rotor in inches 74 is the height of casing in inches Applied Mechanics and Materials Vol. 787 (2015) pp 238-242 Submitted: 2015-02-05 © (2015) Trans Tech Publications, Switzerland Revised: 2015-03-23 doi:10.4028/www.scientific.net/AMM.787.238 Accepted: 2015-04-22 All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, www.ttp.net. (ID: 106.208.18.68-24/06/15,13:26:36)