Incorporating ash removal unit in local rice parboiling industries for flue gas cleaning and heat recovery

Abstract

Local rice parboiling industries of Bangladesh are burdened with heavy emission. Despite recent modification in the rice-parboiling boiler, the amount of stack emission (especially particulate matter) from local rice parboiling industry is still considerably high to jeopardize public health and environmental sustainability. There is no provision of flue gas cleaning in these industries since flue gas cleaning often requires significant investment, complicated installation and heavy-maintenance. Therefore, a modified flue gas cleaning system, namely Ash removal unit (ARU) was designed for simultaneously and synergistically removing particulate matter (PM), SO2, NOx, CO2 and heat from flue gas of local rice parboiling industries. In this study, ARU was incorporated in a local rice parboiling industry in order to evaluate the co-removal efficiency achieved by the ARU. Installation of ARU eliminated PM from flue gas by 91.8%, while it removed 78.5% SO2, 78.3% NOx and 23.9% CO2 respectively from the emitting stack. Other than flue gas cleaning , ARU also facilitates heat exchange between flue gas and boiler feed water. Hence, flue gas temperature was dropped by 42.1%, while boiler feed water temperature was raised by 36% in 30 min. Moreover, adopting ARU also improved the ambient air quality surrounding the industrial area, since it reduced SO2, NOx, SPM, PM2.5 and PM10 level in ambient air by 81.7%, 78.2%, 21.1%, 22.9% and 43.1% respectively.