Landfill Gas Flare Capacity and Destruction
Sizes an enclosed flare from the peak gas flow and a design margin.
Example
You enter
- Peak landfill gas flow (cfm) 1712
- Methane fraction (%) 50
- Design margin (%) 25
- Flare turndown ratio 10
- Methane heating value (Btu/cu ft) 911
- Destruction efficiency (%) 98
- Methane global warming potential 28
- Reduced methane fraction to check (%) 20
- Methane density (lb/cu ft) 0.04226
You get
- Methane (CFM) 856
- Rated flare capacity 2,140 scfm for a 1,712 cfm peak
- Heat release at the peak 46.8 MMBtu/h from 856 cfm of methane
- Minimum stable flow 214 scfm -- the peak is 8.0x above it
- Heat content of the gas 456 Btu/cu ft at the design methane fraction
- At the reduced methane fraction 182.2
- Methane lb per year 19013300
- Methane destroyed 9,317 short tons a year
- Carbon dioxide equivalent credit 260863
No published worked example is on file for this calculation. It is checked against a hand-worked derivation of its method and an independent reference test.
Details, formula, and sources
ScopeWith the minimum stable flow from its turndown and the methane destruction credit. The worked flare reaches its turndown only after decades, but a well field pulled too hard takes the gas to 182 Btu/cu ft and trips it in a week.
Formula or tablerated capacity = peak flow x (1 + design margin); minimum stable flow = rated / turndown ratio; heat release = methane flow x heating value; credit = methane mass destroyed x its global warming potential.
Source and editionFlare sizing against the manufacturer's rated capacity and turndown. A flare needs roughly 20% methane to hold a flame. The site's gas analysis and the applicable air permit govern.
Free accessPublic arithmetic; the turndown and rated capacity come from the flare manufacturer.
What governsEstimate. AHJ and licensed professional govern.
API field namespeak_lfg_cfm, methane_fraction_pct, design_margin_pct, turndown_ratio, methane_heating_value_btu_per_cf, destruction_efficiency_pct, global_warming_potential, reduced_methane_fraction_pct, methane_density_lb_per_cf, methane_cfm, rated_capacity_scfm, heat_release_mmbtu_per_hr, minimum_stable_scfm, design_btu_per_cf, reduced_btu_per_cf, methane_lb_per_year, methane_destroyed_tons, co2e_tons
- Biogenic carbon dioxide the flare's own CO2 is biogenic and is not charged against the creditgreenhouse gas accounting convention
- Destruction efficiency entered; it is a permit and manufacturer figure, not a calculated oneair permit / manufacturer