S.C. Code Regs. § ch. 61, 61-62, 61-62.5, STANDARD NO. 3.1, app 61-62.5.3.1.B
The review of all incinerators shall include verification of the residence time stated on the application. This guidance shall be followed to assure that these calculations are handled in a uniform manner.
STEP 1. Estimate the total heat input to the system:
Total system heat input (BTU/hr) = [Maximum waste firing rate (lbs/hr) x Maximum heating value (BTU/lb)] +" Average primary burner heat input +" Average secondary burner input.
NOTE: Use the average burner inputs required after the onset of waste burning.
Use a waste heating value of 8,500 BTU/lb.
STEP 2. Estimate the system heat loss (prior to heat recovery):
System heat loss = Shell loss +" sensible heat in ash +" sensible heat in unburned carbon +" latent heat.
The heat loss may be assumed to be 20% of total heat input.
STEP 3. Calculate the net heat available (Q) to raise the temperature of the products of combustion:
Q (BTU/hr) = (Total system heat input) - (system heat loss).
STEP 4. Calculate the weight of product of combustion (M)
M = Q/ {Cp x (To - Ti)}
Cp = average specific heat (BTU/lb F), assume a value of 0.28
To = exit temperature (°F), use the design temperature of 2000° F as To.
Ti = ambient air temperature (°F), assume the ambient temperature to be 70° F.
STEP 5. Calculate the volume of product of combustion (F):
F (scfs) = M / d x 60 x 60
d (lb/cu. ft.) = density of exhaust gases at 70° F, use a value of 0.075.
Fl (acfs) = F x (To + 460) / 530
Fl design temperature = F x 2460 / 530
STEP 6. Calculate the volume of secondary chamber.
STEP 7. Residence time = chamber volume / Fl
For a minimum 1 sec secondary chamber residence time and design temperature 2000° F.
secondary chamber volume m = > 1 / Fl
S.C. Code Regs. ch. 61, 61-62, 61-62.5, STANDARD NO. 3.1, app 61-62.5.3.1.B