MDI Emissions Reporting Guidelines for the ... - Polyurethanes

21.0 Water Heaters
MDI Emissions Reporting Guidelines for the Polyurethanes Industry
M W = 250.26
K MDI = .60
C f = 3.9%
359 = the molar volume of an ideal gas in ft 3 /lb-mole @ 0 o
C and 1-atmosphere
VP MDI = 0.00005071 mm
C mdi = (0.00005071/760) x 10 6 = 0.6672 ppmv
L = (V air /359) * (273.15/T sp ) * 60 * (C mdi /1000000) * M W * k MDI * C f
L = (8400/359)*(273.15/333.2)*(.6672/1000000)*(250.26)*(.60)*(.039)*(60)
L = .0045 lbs/hr
L = .0045 lbs/hr x 8760 hrs/yr
L = 40 lbs/yr
A water heater assembly facility that produces water heaters insulated with MDI-based rigid
foam uses a total of 6,000,000 pounds of feedstocks that comprise a rigid foam “system.”
The “system” includes an MDI/PMDI-containing component and a polyol/catalyst/blowing
agent component. The MDI/PMDI component is purchased in bulk and stored indoors in a
60,000-gallon tank. The tanks are filled 65 times each year. The temperature of the MDI
storage tank does not exceed 25 o
C and only drops 20 o
on an average a day. MDI is
transferred to 400 pound day tank as needed. The day tanks are stored indoors and
temperature is maintained at 25 o
C. The MDI is pumped directly from the day tanks to the
foam mixer head. The density of the foam is 1.9 pounds/ft3 . It may be difficult to
estimate the cavity size of each water heater that is filled with rigid foam insulation. MDI
releases can instead be estimated from the target foam density for the water heater
insulation and the total quantity of foam feedstocks that are used in the year.
Calculating Stack Emissions
To estimate emissions from enclosed processes when the volume of the mold is not known
or when a large number of different cavity or mold sizes are filled each year can be
determined from the following:
1. The density of the cured foam.
2. The total weight of the MDI-based component in the foam.
3. The temperature of the foam at the tack-free time during the curing process.
5-49