(48ij) Compliance with EPA Boiler MACT standards: Mercury-In-Fuel Gas

Compliance with the fuel gas mercury specification described in 40 CFR Part 63 Subpart DDDDD (Boiler MACT) requires ethylene plants to measure the mercury content of gaseous fuels classified as a Gas 2 fuel.  The primary objective is to verify and “establish a mercury fuel specification through which gas-fired boilers that use a fuel other than natural gas or refinery gas may be considered Gas 1 unit” as identified in 40 CFR Part 63.7521.(f).

It is critical that data be of “compliance quality”, which is obtained by employing:

• Sorbent Trap Breakthrough Bed: Minimum of two sorbent beds in series to verify that no breakthrough occurred from the leading bed.

• Duplicate Samples: Parallel trains used to verify precision in the sample collection process.

• NIST Traceable Spike: Sorbent traps with a third bed (downstream) spiked with a NIST traceable spiked mass of mercury serves as a matrix spike and provides a means of verifying that components in the matrix (the fuel gas) are not affecting trapping efficiency of sorbent traps.

Sampling and analysis must address critical issues specific to mercury in gaseous hydrocarbon streams: 

1. Plant Process Unit Safety Requirements

2. Sample Point Location and Design

3. Representative Sampling

4. Sampling Methods and Procedures

5. Analytical Methods and Procedures

6. Fuel Gas Quality