Optimization of boiler efficiency through stack gas heat recovery using an economizer. at Century Bottling Company (Mbarara branch)

Abstract

This report contains an overview of designing a heat exchanger used as an economizer used to recover heat from hot flue gas to pre-heat boiler feed water at Century Bottling Company, Mbarara. In order to achieve a good heat transfer, a tubular heat exchanger was selected for the application. Among the different types of tubular heat exchangers, a fixed tube type shell and tube heat exchanger was taken into consideration due accompanying pros such as availability, cost and design convenience. Two heat exchangers were designed for comparison purposes and Kern’s method was used to size both. Heat Exchanger 1 is 2m with an overall heat transfer coefficient of 10.8 W/m2oC, surface area of 13.6 m2 and a tube bundle containing 16 tubes. Heat Exchanger 2 is 3m with overall heat transfer coefficient 9.4 W/m2oC, surface area of 18m2 and a tube bundle containing 12 tubes. Material of construction used is stainless steel 18/8 due to its corrosive resistant properties since flue gas is corrosive. Finally heat exchanger 1 was recommended for installation following the discussion.