Tuesday, August 7, 2007
“Within the United States, the Environment Protection Agency (EPA, www.epa.gov) has enforced emission levels of NOx (Nitrous Oxides) and highly reactive volatile organic compounds (HRVOC) through individual states with allocations and fines. In Texas, California, and New Jersey the ozone depletion has led to stricter total emissions and monitoring of HRVOCs.. In Texas, the Texas Commission of Environmental Quality (TCEQ, www.tceq.state.tx.us) Chapter 115 Regulation has set the levels for each flare stack. The new regulations require a flare gas flowmeter to be specified to have +/- 5 percent inaccuracy at 30, 60, and 90 percent of range under its installed condition”
Calculating flare gas has gone into history. One of the biggest challenges of measuring flare gas is large TURNDOWN. Flare gas flow can ranged from low fuel gas purge during normal operation to large flow during emergency relief and/or total plant blowdown.
Common flowmeter type such as differential-pressure, vortex-shedding, and insertion thermal mass meters, etc are unable to meet such low turndown requirement. Ultra-sonic flowmeter is generally used in flare gas measurement & recording. See some features and benefits of an Ultra-Sonic Flowmeter HERE and HERE
Apart from large turndown capability (from 0.03 m/s to 85 m/s), ULTRA-SONIC flowmeter also has the following advantages in flare gas application :
- Extremely low pressure drop (virtual zero pressure drop)
- No internal, insertion and moving parts which potential create partial blockage of flare line
- Tolerate some condensed liquid
- Can take higher operating temperature (upto 260 degC)
- No affected by gas composition
- No maintenance
Thus, stringent authority requirements on flare gas measurement, ULTRA-SONIC flowmeter would be one of the best offers.