Trace Element Mass Flow Rates from U.S. Coal Fired Power Plants

Area of Science:

• Environmental Science
• Chemical Engineering
• Earth Science

Background:

• Coal-fired power plants (CFPPs) release trace elements (TEs) through solid, liquid, and gaseous waste.
• Accurate estimation of TE concentrations in waste streams is crucial for effective pollution control and emission reduction strategies.

Purpose of the Study:

• To introduce a generalizable mass balance model for estimating TE mass flow rates in CFPP waste streams.
• To evaluate the model's accuracy for the U.S. coal fleet under current data limitations.

Main Methods:

• A stochastic, bootstrapping approach was used to estimate plant-level mass flow rates for Hg, Se, As, and Cl in 2015.
• Combined publicly available data on coal TE concentrations with estimated TE partitioning in air pollution control processes.

Main Results:

• The model generally overestimates TE masses by 30-50% compared to measured data, with higher errors for mercury (Hg).
• Partitioning estimates showed consistency for Se, As, and Cl removal from flue gas.
• The model tended to underestimate mercury removal efficiency.

Conclusions:

• The developed model serves as a valuable tool for first-order estimates of TE mass flows from CFPPs.
• Future improvements require enhanced data collection on TE concentrations within the coal blend, which is currently a data quality weakness.