Energy Audit on Two 22-TPH Coal-fired Boilers of a Pineapple Processing Plant

Abstract

The price of coal used by a pineapple processing plant has increased from 3.90 Php/kg in 2018 to 8.60 Php/kg in 2022, thus increasing steam generation costs. This study conducted an energy audit on the two 22-TPH coal-fired boilers of the pineapple processing plant to determine boiler efficiency, quantify sources of heat loss, identify energy conservation measures, and calculate energy and coal savings. The coal-fired boilers investigated were fluidized bed combustion boilers with a reverse osmosis feedwater system. The boiler efficiency was calculated using an indirect method, considering energy losses from sensible heat in refuse and blowdown water. Of the three performance tests conducted, the average boiler efficiency is at 80.655%. The top five sources of heat loss were dry flue gas, hydrogen in coal, moisture in coal, surface radiation and convection, and boiler blowdown. These sources account for 18.322% of the energy input. The identified energy conservation measures include the installation of an automatic oxygen trim control, the installation of an economizer, the installation of a caustic injection system, and the insulation of uninsulated surfaces. These measures have a total potential energy savings of 52,494,974 MJ/yr and coal savings of 2,594,579 kg/yr. While a caustic injection system is not yet installed, setting blowdown TDS to 2,090 ppm can reduce energy consumption by 1,656,496 MJ/yr and coal consumption by 81,873 kg/yr. Using coal with lower hydrogen and moisture content can also reduce energy loss by 6,096,810 MJ/yr per 0.5% reduction in hydrogen content and 6,816,813 MJ/yr per 5% reduction in moisture content.