Detailed OPEX comparison of modern copper smelting technologies using HSC-SIM

Since there are major differences between the technologies, we decided to model each process flowsheet using the Outotec HSC-SIM process modeling tool to see how they would perform against each other in terms of OPEX when simulated in the same way. The configurations we chose to include in the comparison were:

1. Outotec Flash Smelting (FSF) – Outotec-Kennecott Flash Converting (FCF)
2. Outotec Flash Smelting (FSF) – Peirce-Smith Converting (PSC)
3. Outotec Ausmelt TSL Smelting (ASF) – Peirce-Smith Converting (PSC)
4. Outotec Ausmelt TSL Smelting (ASF) – Outotec Ausmelt TSL Converting (ACF)
5. Mitsubishi Smelting Process (MIT)
6. Bottom Blowing Reactor (BBR) – Bottom Blowing Continuous Converting (BCC)
7. Side Blowing Furnace (SBF) – Top Blowing Converting (TBC)

Methodology and base parameters

All seven smelting routes were tasked to produce blister copper from clean copper concentrate, with an annual treatment capacity of 1.2 million tonnes. Fire refining of the blister copper to anodes was not included due to the relatively similar blister quality between processes when impurities are missing. In addition, evaluation was limited to the ID fan outlets of the smelter off-gases, meaning no wet gas cleaning and acid plant subprocesses either.

For simplicity, the number of concentrate components was limited and impurity elements were excluded. The concentrate grade used together with its analysis is presented in Table 1. The term “Others” in the table and calculations describes the proportion of additional impurity elements in the concentrate with no effect on the main component concentrations. The initial moisture of the concentrate was set to a typical 8%.

All furnace units were dimensioned to obtain to appropriate refractory amounts, annual availability hours, heat loss values, and electricity consumption for the given process. The refractory mass was basically a function of residence time versus the required melt and gas volume flow multiplied by the brick thickness on each surface. Annual operation times were full campaign years with major and minor shutdowns and standby situations deducted. Heat losses were estimated based on surface area and whether they were water or air cooled. Electricity consumption calculations relied on the earlier published work of one of the authors.

Generally, all results were cross-checked against real-life references and literature. Where data was reliable, the authors used the information as such. Where there was a conflict, for example when a parameter applied to a process model produced an impossible outcome (like with the BBR slag flotation), a deviation to the reported data point was made with considerable care.

Results and discussion

The results of the HSC-SIM simulations are shown in Table 2 and the same information has been translated into US dollar values in Figure 2. Overall, the results clearly indicate that the total operational cost appears to be strongly dependent on the copper smelting technology used in the smelting process. In this study, the FSF-FCF, FSF-PSC, ASF-ACF, and SBF-TBC processes achieved the lowest costs with the applied parameters and unit costs. This is mostly explained by their being balanced processes without any apparent downsides such as excessive electricity use or poor copper recovery.

Naturally this study only reflects a snapshot of the true picture; more work is required to simulate the processes with full smelter scope, a CAPEX element, and sensibility analysis included.

by Ali Bunjaku, Hannu Johto, Lauri Pesonen

This article is a shortened version of the Copper 2019 conference paper published in August 2019. For more detailed information about the results or methodology, please see the article or contact the authors.