A critical analysis of emission quantification methods in the ferrochrome industry

Abstract

Ferrochrome (FeCr) furnaces are significant CO2 emitters due to the large amounts of carboncontaining materials being used. FeCr industries will therefore become liable for carbon tax (CT), which is set for implementation in 2019. To estimate the CT liability of a certain entity, the CO2 emissions must be determined as accurately as possible. However, the prescribed way to quantify these emissions is overly generic and the implementation thereof still uncertain. This study was therefore conducted to critically assess the CO2 emission quantification methods available to the FeCr industry. Unfortunately, the initial research showed that there are no detailed analyses or practical examples available. The lack of detail and case studies limits insights available on the practical and operational reality and how it can affect the results produced by the prescribed methods. It was therefore necessary to perform a critical literature analysis of the emission quantification methods to determine the associated risks for the ferrochrome industry. This comprehensive analysis, using a significant amount of literature references, aimed to identify the main focus areas of the study. The focus areas identified are (1) practical application of prescribed methods, (2) refinement of the prescribed methods and (3) comparison of the different methods. Three separate chapters are dedicated to develop and verify methodologies for each focus area. The verifications were done using practical case studies from 17 different FeCr furnaces, all situated in South Africa. Focus area 1: Although there are prescribed methods (tier 1, 2 and 3) to perform the emission calculation of a FeCr furnace, there was a lack of literature studying the practical application, as well as the implications associated with these methods. The three prescribed calculation methods were therefore evaluated and applied to 17 case studies. It was found that one is likely to obtain results with errors ranging from 8.9% - 18.8% when performing the prescribed calculations.

Focus area 2: The prescribed calculation methods are relatively simple to apply but produce results with varying levels of accuracy. The need was therefore established to refine these prescribed methods to improve the accuracy of the results. The developed methodology delivered a systematic approach to refine the prescribed tier 3 mass balance approach. The case studies proved that by constructing an advanced mass balance, a much smaller error (2.4%) will be achieved, adding to the reliability of the final results. Focus area 3: The study presented six quantification methods (three prescribed and three developed methods) and applied all the methods to 17 case studies. A comparison of the generated results shows a variance of 13-33% on the calculated CO2 emission result. This translates to a variance of R75 million – R185 million per year in carbon tax liability. An evaluation of the associated accuracies also shows a wide range of variance from tier 1 (25%-50% error) to tier 3 (<5% error). The complexity of the different methods increases significantly between the prescribed methods and the refined mass balances. It was found, however, that with a little extra “complexity” a much higher accuracy can be accomplished. Based on the method developed throughout this study, and based on the case studies performed, the advanced mass balance gives an average error of 2.4%. A significant contribution of the approach is realised by improved CT liability estimation. The monetary value for the entire FeCr industry in SA has decreased throughout the course of this study. From an initial estimation of R562 million per annum with a 50% uncertainty (purely based on literature assumptions) to a value of R448 million with a 2.4% uncertainty (based on the use of methods developed within this study). The developed approach is therefore confirmed to make a critical contribution to the emission quantification methods for FeCr furnaces.