Inherently Safer Acids: A Case Study on the Application of Polyelectrolytes

摘要

Strong acids, such as aqueous hydrochloric acid (HCl), are commonly used in thechemical process industry to purify streams or remove particulates from raw material,product, and waste streams. The benefits of HCl are its’ low cost, large dissociationconstant, and stability over time. However, the hazards associated with handling andprocessing HCl must be seriously considered when designing plants and specifyingmaterials of construction and personal protective equipment. This typically results inhigher capital, maintenance, and replacement costs to minimize the potential forpersonnel injury, equipment damage, and associated business interruption. This paperexamines one such facility where aqueous HCl had been in use for many years. A numberof inherently safer process design (ISPD) principles were evaluated against the existingoperation, in order to identify opportunities for risk reduction. As a result, the inherentsafety of the process was enhanced by converting an HCl system for dissolving inorganicparticulates to a sequestration process utilizing polyelectrolytes. Application of thisinherently safer process reduces maintenance costs, capital replacement costs, and mostimportantly, the potential for employee exposure. A review of the process chemistry andexamples of process technologies that ultimately led to this inherently safer design areprovided.