PFAS Volatility Study in Medical Waste Treated by Pyrolysis
Montrose Environmental was hired by Monarch Waste Technologies (MWT) located in Santa Fe, New Mexico to provide consulting expertise for a per- and polyfluoroalkyl substance (PFAS) volatility study of typical medical waste treated by the MWT pyrolysis facility during its project initiation phase.
Montrose provided consulting services by selecting the PFAS compounds (a range of volatile and semi-volatile compounds) to spike and test, and the range of temperatures. Objectives of the study were to measure the temperatures that various PFAS compounds volatilized from the waste and determine if pyrolysis was a viable treatment technology.
Real-time measurements were performed by government laboratory personnel downstream of a large glass tube furnace containing the waste while the furnace temperature was incrementally increased and any compounds that volatilized were swept downstream at a MWT-representative flow rate using inert argon gas to pass through several high-resolution gas analyzers including gas chromatographs and mass spectrometers. MWT requested that Montrose consult on the study due to our knowledge of PFAS and the MWT pyrolysis process where Montrose was currently performing comprehensive testing (non-PFAS) and Title V permitting.
Montrose personnel worked in partnership with MWT and government facilities in Albuquerque, New Mexico to develop the testing methodology and parameters. The MWT medical waste pyrolysis process is conducted during three principal stages:
- Pyrotube where decomposition of waste is initiated. Temperature 750-1000 °C, residence time of waste ~ 5-25 mins. Waste gas is exhausted.
- Gasifier where pyrolysis conditions are maintained with waste gas. Temperature 700-850 °C, residence time on order of several seconds.
- Once waste gas is dispatched from the gasifier, air is injected, and it passes through an oxidizer at 1100-1300 °C. Residence time approx. 2 seconds. The heat from the oxidizer is sent to the pyrotube jacket to maintain the pyrotube temperature.
The leading challenge of the study was to determine the temperatures that various PFAS compounds would volatilize and if the MWT pyrolysis process temperatures and residence times were sufficient to treat and destroy PFAS without the use of additional emissions controls.
Testing was performed in accordance with project specifications and real-time measurements were collected by government personnel.
- Volatile PFAS compounds (<4 carbon chains) were measured downstream at the 300-400 oC range
- >99% of all PFAS compounds volatilized at 1000 oC
- The material balance of the spiked PFAS compounds was acceptable at >70%
Due to the relatively low volatilization temperatures, the MWT pyrolysis process was not deemed a viable PFAS treatment technology without installing downstream emissions capture controls (i.e. condensers, carbon canisters).