Calcium carbonate production from surf clam and ocean quahog shells: Process development and techno-economic analysis

The conversion of surf clam shells (SCS) and ocean quahog shells (QS) into three different grades of CaCO₃ products using water and lower-temperature processing was investigated. Coarsely ground shells were boiled in water for 2 h and then washed and dried, followed by fine grinding and heating. To produce the highest quality of CaCO₃, the washed ground shells were processed at 300 °C for 2 h. Process modeling and economic analysis were performed on these three products using SuperPro Designer. For a processing plant with an annual capacity of 10,886 MT of waste shells, the highest grade CaCO₃ product had the highest predicted economic performance with a net present value of $4.3 M, an internal rate of return of 12.7 %, and payback period of 5.6 years. The sensitivity analysis showed plant capacity and selling price were the predominant variables that affected production economic feasibility.