JOM • July 2005 52 Copper and Nickel Production Overview A cost model for the operation of copper converters is developed in this study, allowing an evaluation of the economic impact of changes to operating procedures and/or injection technolo- gies. The model uses material and enthalpy balances for the slag and copper blows in a Peirce-Smith converter. The length of the converting cycle is calcu- lated from the capacity of the blowers and the required blast along with the times required for other operations such as charging and skimming and idle time. Downtime, labor, and materials for converter lining repair as well as other costs such as oxygen enrichment are also considered in the cost calculations. The model is formulated in a spreadsheet using common programming language and is easily extended to examine the costs of alternative operating strategies or injection technologies such as high- pressure, shrouded injection. Example calculations showing the cost benefits of changing operating procedures and technology are presented. INTRODUCTION Due to intense competition among manufacturing businesses, R&D activi- ties must continuously respond to the dynamics of the market. When new technology is considered, a decision on its implementation is made in the context of foreseeable profitability, or in other words, in terms of the rate of return on the investment. To facilitate decision making in material-processing indus- tries, Szekely et al. 1 proposed a “techni- cal cost modeling” methodology that combines physical and mathematical modeling with cost modeling to the mutual benefit of the managerial decision makers and the R&D community. For the copper pyrometallurgical production industry, there is one study Modeling Peirce-Smith Converter Operating Costs Ka Wing Ng, Joël P.T. Kapusta, Ralph Harris, Albert E. Wraith, and Roberto Parra addressing the capital costs of Peirce- Smith converting (PSC) and the returns on the associated capital investment. 2 However, to the knowledge of the authors, there are no published studies on the day-to-day operating costs for PSC. In this paper, a technical cost model reflecting Szekely et al.’s methodology is developed for PSC in order to examine operating costs under various operating conditions. The resulting model also provides a tool to study the impact of new injection technology such as high- pressure shrouded injection (HPSI) on the process operating cost. Peirce-Smith converting technology has been in place since 1910 and sub- stantial developments related to its operation have been achieved. Those developments include improvements in the ancillary operations, increases in reactor size, and decreases in fugitive gases. The vast majority of the world’s copper smelting capacity, today more than 90%, involves the use of Peirce- Smith converters to transform copper matte into blister copper. The batch-wise nature of PSC, which is sandwiched between a continuous or semi-continu- ous smelting process and a batch fire- refining process, poses a significant challenge to the scheduling of matte, slag, and blister copper transfers to and from the converting aisle. Attempts have been made to replace the batch Peirce-Smith converter by a continuous converting process, but tech- nical difficulties still need to be resolved before there is full-scale movement away from PSC. Today, only the Mitsubishi process is truly a continuous converting operation. Thus, it is foreseeable that PSC will be the dominant converting technology employed in pyrometallurgi- cal copper production for some time. Despite the advancements in opera- tions, PSC has remained essentially the same batch-wise operation with subsonic blast injection via tuyeres with nozzle gas velocities of about 150 m/s and tuyere submergence of about 0.5 m to 0.8 m. Developments in gas injection tech- nologies have resulted in alternative blast injection approaches for the converting process (i.e., HPSI and concentrate injec- tion). In view of the successful applica- tion of the HPSI technology, also known as Air Liquide Shrouded Injector Tech- nology, in copper converting 3,4 and nickel converting, 4–6 the model was used here to both demonstrate the operating cost implications of applying HPSI to copper converting and as an example of the potential of technical cost modeling to assist managerial decision making regarding the deployment of new tech- nology. Note that the present model is not meant to elaborate on the process kinetics, but provides a means for exam- ining the effect of changing operating conditions and blast injection technology on the overall operating costs of PSC. COST OF CONVERTING The present model examines costs relevant only to the day-to-day converter operations (see the Model Formulation sidebar for details). It does not consider issues such as capital investment, plant depreciation, and the like. Moreover, due to the variation in the operating practice of individual converters in different smelters, it was unrealistic to attempt to develop a universal detailed model suit- able for all converting processes from various smelters. However, to remain useful, the present model considers costs applicable to a typical converting operation. Each category of costs is considered and the simplifying assump- tions that have been used to formulate some example costs are discussed.