Hidrometalurgia

COPPER SX CIRCUIT DESIGN AND OPERATION CURRENT ADVANCES AND FUTURE POSSIBILITIES

by

Gary Kordosky Cognis Corporation

CONTENTS
ABSTRACT 1. INTRODUCTION 2. PLANT STAGING AND COPPER RECOVERY 3. COPPER RECOVERY AND CONCENTRATRION OF SULFURIC ACID IN THE STRIP ELECTROLYTE 4. THE TREND TO LOWER ACID CONCENTRATION IN THE STIPPING ELECTROLYTE 5. NITRATE CONTAINING LEACH SOLUTIONS 6. LEACHSOLUTIONS AT ELEVATED TEMPERATRUES 7. CONCLUSIONS 8. REFERENCES 1 1 2 4 5 6 8 9 9

ABSTRACT Copper solvent extraction is a well known, proven process that has been in commercial practice since 1968. Advances in this technology continue to be made as the copper industry strives to lower the cost to produce copper while at the same time improving the quality of the copper cathode produced. Optimizingreagent formulations, 90% verses 95% copper recovery across solvent extraction, the most efficient staging, the treatment of nitrate containing leach solutions that at one time would have been considered untreatable and changing conditions in electrowinning are discussed in the context of lowering costs and improving copper quality. The importance of reagent stability when treating hightemperature leach solutions is also briefly mentioned. INTRODUCTION The title of this paper was suggested by Alan Taylor. After agreeing to write and present this paper both the author and Dr. Taylor compiled a list of the topics to be discussed. The topics discussed in this paper were selected from the combined list because of their importance with respect to “current advances and future possibilities”.Some of the topics have been discussed previously to the point that one wonders what new information or idea on the topic can be considered as applying to current advances or future possibilities. Plant staging and copper recovery is one of these. Others are relatively new and little has been previously published about them for example nitrate containing leach solutions. Then there are topics thatinvolve several trends that in a sense are opposed to one another, for example the trend toward lower acid in the strip system along with the trend to higher recovery across the solvent extraction plant. The importance of certain topics to the plant operator is based on the simple premise that plant design and operation should be directed at maximizing the revenue and minimizing the total cost ofthe operation for the life of the operation. Maximizing revenue is achieved by producing as much copper of the highest quality as possible. Minimizing the total cost includes minimizing the capital cost as well as minimizing the operating cost. Maximizing revenue and minimizing total cost forces the plant designers to make economic decisions during the design and construction of the plant and itforces operators to make economic decisions while running the plant. In many cases these economic decisions can be and are made on solid numbers and as such these decisions are relatively easy to make. For example, there is a trade off between the staging in a plant and the reagent consumption at some fixed copper recovery. Experimental work can accurately determine the relationship between reagentconcentration and staging. In addition, the capital cost of a stage as well as the cost and loss rate of reagent can be predicted fairly accurately. Therefore the decision on plant staging can be made on hard numbers and as such should be a relatively easy decision to make. Now consider the decision a plant operator must make with respect to the copper and sulfuric acid content of the barren andpregnant strip solutions. In most cases the plant operator needs to produce Class A copper in order to maximize revenue therefore the copper and sulfuric acid content of the electrolyte must be in a range such that class A copper can be produced on a consistent basis. However, within the range there are some choices that cannot be made on hard numbers. For example, the plant operator can choose...