Determination of effluent reduction and capital cost targets through pinchtechnology

This paper demonstrates how new techniques developed for the design of mass exchange networks may be applied to the reduction of waste in existing sys tems where pollutants are removed using processes such as absorption, strip ping, adsorption, ion exchange, or solvent extraction. The paper applies re cently developed Pinch Technology techniques for the design of systems to r emove species from rich streams using mass exchange with lean streams (mass separating agents). These techniques are demonstrated by application to th e retrofit of a gold solvent extraction process to reduce the effluent disc harge by 40%. The result is an impact diagram that shows how much capital i s required for a particular reduction in effluent. This is a significant di agram that shows the point of diminishing return on investment as well as t he thermodynamic limit for effluent reduction (43% in this case). A design is presented that achieves the targeted effluent reduction at a capital cos t within 6% of the target. The impact diagram developed is a significant ne w tool that may be used to determine the effluent reduction potential of ex isting processes as well as to evaluate alternative technologies for efflue nt reduction in both new and existing processes.