Benzene NESHAP Regulations

Benzene emissions are produced when coal is heated, also known as coking, for use as a reducing agent in the production of iron, steel and ferro-alloys. The EPA regulates benzene emissions from coke byproduct recovery plants under 40 CFR Part 61, National Emission Standards for Hazardous Air Pollutants (NESHAP), Subpart L. The EPA also monitors benzene emissions from oil and natural gas production facilities under 40 CFR 63.772: test methods, compliance procedures, and compliance demonstrations to determine effectiveness of emission control equipment.

Closed System

• Recovery plants must be designed to recover or destroy benzene gas to acceptable atmospheric levels. EPA mandates that coke byproduct recovery plants must operate in a closed system, meaning all openings, including pressure valves, on process vessels, storage tanks and sumps must be sealed to prevent emission leaks. If parts of the sludge conveyor are open to the atmosphere, a water leg seal (a bundle of tubes that isolate and funnels vapors into an appropriate chamber) on the tar decanter roof must be implemented to limit air emissions.

Monitoring

• Oil and gas production facilities must monitor benzene emissions.

  At recovery plants, all seals and valve connections must be monitored using EPA Test Method 21, Determination of Volatile Organic Compound Leaks. Under this method, a portable instrument measures emissions from process equipment, displaying a meter reading for the measured compound. The equipment can be used to measure different compounds but must be calibrated specifically, using reference information on each compound, before measurements are taken. Benzene emissions must be monitored semi-annually, or anytime the system is repressurized, and visual inspections are required intermittently to identify any gaps and tears.

  For oil and gas facilities, monitoring equipment is installed directly onto process equipment, and flow rates are measured continually using EPA Method 18, (40 CFR Part 60, Appendix A). The flow rate provides emission values as kilograms per hour. Average results from three runs are used to determine annual emissions in kilograms per year by multiplying the mass rate times the number of hours the unit is operated per year.

NESHAP Standards

• For recovery plants, the NESHAP standard for benzene emissions is 500 parts per million (ppm) above background. Background levels are taken from atmospheric readings, in the vicinity of the process equipment using the same equipment as specified in EPA Method 21. The portable instrument is then calibrated with this background reference value before testing for leaks.

  For oil and gas production facilities, the NESHAP standard is revealed as the 120 day average benzene emission reduction equal to or greater than 90 percent, from before control equipment was implemented.