Costly Hazardous Waste Reduction in Heat Treating Operation

RESULTS
The hazardous waste minimization alternatives identified by NYSP2I confirmed that using heated water to increase solubility will reduce the amount of water necessary for the cleaning process. This water reduction has the potential for reducing the hazardous waste generated by approximately 13% and reducing the cleaning costs by over 14%. Furthermore, cleaning process time (and associated labor) can be reduced by approximately 77%.

In addition to using less water for cleaning, utilizing a Salt Recovery Unit to recover quench salts from the liquid waste brine creates the best opportunity for hazardous waste reduction and cost savings. NYSP2I was able to test the salts recovered from the Salt Recovery Unit and confirm that the salts could be reused in the salt bath quench tank operation. This results in direct cost avoidance (savings) by reducing the amount of replacement salt required for the operation and the associated cost. The impact of using the Salt Recovery Unit would yield an 84% reduction in hazardous waste and up to a 97% cost savings per cleaning (Cleaning costs include waste management costs, fees, labor, and new salts added to the bath).

COMPANY
A global leader in the design and manufacture of automotive chain systems and components has a facility located in New York State.

SITUATION
The company utilizes salt bath quench tanks to heat-treat parts for their automotive assemblies. Periodically, the quench tanks need to be cleaned which requires the reusable salts to be removed from the tank temporarily. Water is then used for cleaning the remaining salts left in the tank. This generates a liquid waste brine that is pumped into totes for disposal as a costly hazardous waste. The company requested assistance from AM&T’s partner New York State Pollution Prevention Institute (NYSP2I) to identify practical options to reduce the hazardous waste generated from the salt bath quench tank cleaning activities.

SOLUTION
NYSP2I identified hazardous waste minimization alternatives, designed a cleaning process that will optimize the amount of water needed during cleaning, and validated solubility through testing the remaining salts. NYSP2I also tested the liquid waste brine to determine if the salt can be recovered and reused in the salt bath quench tank operation.

NYSP2I identified potential alternative methods for reducing and reusing waste solids and liquids generated during tank cleaning:

  • Minimize Waste Water Produced: Use temperature and solubility principles to optimize the amount of water used to dissolve salt and contaminants in the quench tank cleaning
  • Process Liquid Waste Brine Through Salt Recovery Unit: Removal of nitrate and nitrite salts from liquid waste brine to remove hazardous characteristic while capturing salts for reuse
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