Analysis of potential energy conservation and emissions reduction in ferrous foundries in the cities of Ekurhuleni and Johannesburg

Abstract

The challenge facing South African foundries today are compliance with the environmental legislations while maintaining a high production rate. The focus of this study is to assist foundries to comply with National Environment Management Air Quality Act 39 of 2004. The aim of the study is to achieve a foundry with high production rate with low energy consumption and low emissions, while complying with air quality legislation. Data was collected from foundries within the Cities of Ekurhuleni and Johannesburg. Foundries were requested to provide information such as the raw materials feed rate, and production rate, emission units, type of energy used and consumption rates. Seventeen foundries participated in this study. Data collected from these foundries assisted in determining the emissions rate generated during production process. Emissions were quantified from the foundries using emission factors. In this study electricity and natural gas were found to be the most preferred source of energy in the foundries. An energy intensity relationship exists, for both electricity and natural gas and its production rate. The results indicated efficiency of energy intensity of 0.25 to 6.37 GJ/Tonne in the foundries. Selection of furnace used by the facilities plays an important role on the energy saving and emission reduction. Foundries that need to reduce particulate matters on the melting should consider electric arc furnace because it generate less particulate matters than open hearth. Foundries that would like to reduce sulphur dioxide should consider electric arc furnace rather than open hearth. Foundries that have challenges on the NOx should consider open hearth furnace than electric arc. An installation of suitable abatement systems should also be considered for the reduction of other pollutants. Results indicated that installation of abatement system at 95% efficiency will decrease emission rates by twenty times. Study reveals that 3.93 kg is polluted to the atmosphere per tonne of production in a month for the foundries that do not have abatement system and installation of abatement system will decrease air pollution from 3.93 to 0.20 kg per tonne to the atmosphere