Hazardous waste reduction from mixed acid titanium etching

This paper presents the findings of a technical study performed by the New York State Pollution Prevention Institute at Rochester Institute of Technology to evaluate process modifications that would reduce hazardous waste generated from the manufacture of titanium alloy turbine blades. This study focused on the acid etch process step in which titanium alloy turbine blades are immersed in a mixed nitric and hydrofluoric acid solution to chemically mill the blades; which is one of a sequence of finishing steps. The spent acid is a hazardous waste that is sent off-site for disposal. A pollution prevention approach identified several process and operational improvements that would significantly reduce the amount of hazardous acid waste generated. Implementation of process improvements identified in this study resulted in reducing the quantity of hazardous waste generated from 502 tons/year in the Baseline year to less than 210 tons/year in Year 2, thereby resulting in a cost savings of nearly 43% per year. Full implementation of the study recommendations are expected to reduce the hazardous waste quantity to 71 tons/year, thereby achieving a cost savings of nearly 70% due to an 86% reduction in waste generation and a 66% reduction of total acid purchase and disposal costs.