Emissions & Flares: 2018 #50

Problem 50: Which of the following statements concerning flaring is most FALSE? 

(A) All hydrocarbons with a C-to-H ratio of greater than 0.33 tend to soot. 
(B) Combustion efficiency of 98% is equivalent to a destruction efficiency of 96.5%. 
(C) Combustion efficiency is the % of HC in flare vent gas completely converted to CO2 & H2O. 
(D) Petro refinery flare: NHV of gas in flare combustion zone is >= 270 Btu/ft3 for 98% destruction.

This answer are easily found on 8 FAC 9. On (B), the 96.5% & 98% are merely reversed.

Emissions: 2018 #49

Problem 49. Flare 4.9 MSCF/D sour gas 4% H2S. SO2 emissions TPY? (A) 5.5; (B) 6;(C) 6.5; (D) 7?

Solved using 8 FAC 9 of the 2018 V2 Guidebook. Note emission calculations are rarely found in PE textbooks (they aren't in any of mine). But they are pretty much just dimensional analysis. However, it isn't the thing one can do without knowing the lingo.

Steps:
1. Convert lbs of NG to SCF w/Ideal Gas conversion: 379.3 SCF/lb-mole SO2 Emissions (lb/hr).
2. Flare gas vol.(scf/hr)*(1/379 scf/lb-mole)(64 lb/lb-mole)(%H2S).
3. (4,900 scf/d)(1 d/24 hr)(1/379/scf/lb-mole)(64 lb/lb-mole)(4/100) = 1.38 lb/hr SO2.
4. Emissions (TPY) = (1.38 lb/hr SO2)(8,760 hr/yr)(1 ton/2,000 lb) = 6.04 TPY SO2.

Note the Guidebook walks you through this type of calculation step-by-step so the process is second nature under time pressure.