DEQ-CFW_00087892

Butacite Extrusion Process - Line 4
Point Source Emission Determination
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40 Point Source Emission Determination - Line 4 Extrusion Process
Triethylene glycol di-2-ethylhexanoate CAS No. 94-28-0
(3GO)
Emission Estimation Approach:
Emissions from the Butacite® extruders are calculated using amass balance approach. Based
on the vapor pressure exerted by organic material in the extruder and the flow rate out of the
extruder, material flowrates throughout the entire extruder process are calculated. There are a
total of 3 extruders in the Line 4 extruder operation.
The extruder process consists of the extruder unit followed by a knock -out pot, and the steam
jet vacuum system. Material flowrates into and out of each of these process steps are
calculated below.
General Steps for Quantifying Emissions:
The primary purpose of the extruders is to remove water from the extruder feed material.
This is accomplished by heating the feed material and operating the extruders under vacuum
conditions. A vacuum is pulled on each extruder via a 2-stage steam jet vacuum system. The
vacuum jet system consists of a 1st condenser followed by the 1st vacuum jet, 2nd
condenser, 2nd vacuum jet, and lastly a final condenser. The purpose of the first condenser is
to remove condensable substances so as to maximize efficiency of the steam jet. The purpose
of the 2nd condenser is to condense steam injected into the 1st vacuum jet in order to
maximize efficiency of the 2nd vacuum jet. The purpose of the final condenser is to
condense the steam that is injected into the 2nd vacuum jet. The general steps for quantifying
emissions are as follows:
STEP 1: Estimate the VOC's vented from the extruder unit based on the water and
noncondensables that are vented, the total system pressure, and the approximate vapor
pressure of organics.
STEP 2: Calculate the amount of VOC that passes through the first condenser based on the
temperature out of the first condenser, the noncondensable flow, and the system pressure.
STEP 3: Calculate the amount of VOC that passes through the second condenser based on
the temperature of the second condenser, the noncondensable flow, and the system pressure.
STEP 4: Calculate the amount of VOC that passes through the final condenser based on the
temperature of the final condenser, the noncondensable flow, and the atmospheric pressure.
For Steps 1 and 2, the VOC flowrates are calculated on a per extruder basis. For Steps 3 and
4, the VOC flowrates are calculated per extruder and for all three extruders combined.
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Butacite Extrusion Process - Line 4
Point Source Emission Determination
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Moles of VOC emitted from the extruder are determined by subtracting the non -organic
moles in the off -gas ( 10.46 lb-mole/hr/extruder ) from the total moles in the off -gas
( 10.85 lb-mole/hr/extruder).
10.85 lb -mole _ 10.46 lb -mole _ 0.39 lb -mole VOC
hr - extruder hr - extruder hr - extruder
The mass of VOC emitted from each extruder is determined by number of moles emitted
from an extruder per hour ( 0.39 lb -mole VOC ) by the molecular weight of the organic,
which is assumed to be 3GO with a molecular weight of 402.6 lb / lb -mole.
0.39 lb -mole VOC
hr - extruder
402.6 lb
x =
lb -mole
STEP 2: VOC's passing through the first condenser:
156.3 lb VOC
hr - extruder
Note: Much of the VOC in the extruder off -gas is expected to be captured in the knock -out
pot. However, for the purposes of these calculations, it is assumed that all of the VOC enters
into the 1 st condenser.
All of the noncondensables pass through the first condenser. Most of the water and most of
the VOC are condensed. The vapor pressure of water and VOC at the condenser outlet are
used to calculate their overall mole fraction. Based on this and the known moles of
noncondensables passing through the condenser, the mass of VOC and water passing
through the condenser is calculated.
Mole fraction of Water
Calculated as the vapor pressure of water ( 42.2 mmHg at 35 deg. C) divided by
the system pressure ( 90 mmHg).
42.2 mmHg = 46.9% water
90 mmHg
Mole fraction of VOC
Calculated as the vapor pressure of the VOC ( 0.26 mmHg at 35 deg. C ) divided by
the system pressure ( 90 mmHg).
0.26 mmHg = 0.29% VOC as 3GO
90 mmHg
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Butacite Extrusion Process - Line 4
Mole fraction of noncondensables
Point Source Emission Determination
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Calculated as 100% minus the mole fraction of the water and VOC.
100% minus 46.9% water minus 0.29% VOC = 52.8% noncondensable gases
Total Moles
Calculated as the lb -moles of noncondensables (0.71 lb -moles per hour per extruder)
divided by the noncondensable mole fraction (52.8% noncondensables).
0.71 lb -moles per hour per extruder 1.352 lb -moles
52.8% hour - extruder
Mass of VOC in condenser outlet
Calculated as the mole fraction of VOC ( 0.29% ) times the total moles of gas
( 1.352 lb -moles per hour per extruder ) times the VOC molecular weight o: 402.6 .
1.352 lb -moles x 0.29% VOC x 402.6 lb = 1.57 lb VOC
hour - extruder lb -mole hour - extruder
STEP 3: VOC's passing through the second condenser:
In general the same approach used in Step 2 is applied here with the only difference being
that the system pressure is slightly higher which results in a slightly lower VOC mole
fraction.
Mole fraction of Water
Calculated as the vapor pressure of water ( 42.2 mmHg at 35 deg. C) divided by
the system pressure( 225 mmHg).
42.2 mmHg = 18.8% water
225 mmHg
Mole fraction of VOC
Calculated as the vapor pressure of the VOC ( 0.26 mmHg at 35 deg. C ) divided by
the system pressure ( 225 mmHg ).
03 mmHg = 0.12% VOC as 3GO
225 mmHg
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Butacite Extrusion Process - Line 4
Mole fraction of noncondensables
Calculated as 100% minus mole fraction of water and VOC
Point Source Emission Determination
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100% minus 18.8% water minus 0.12% VOC = 81.1% noncondensable gases
Total Moles
Calculated as the lb -mole of noncondensables ( 0.71 lb -moles per hour per extruder)
divided by the noncondensable mole fraction ( 8 1. 1 % noncondensables ).
0.71 lb -moles per hour per extruder 0.88 lb -moles
81.1 % hour - extruder
Mass of VOC in condenser outlet
Calculated as the mole fraction of VOC ( 0.12% ) times the total moles of gas
( 0.88 lb -moles per hour per extruder) times the VOC molecular weight of 402.6 .
0.88 lb -moles x 0.12% VOC x 402.6 lb = 0.41 lb VOC
hour - extruder lb -mole hour - extruder
Total Potential Emissions before the final condenser
Calculated by using the VOC emission rate of 0.41 lb. VOC per hour per extruder
multiplied by 3 extruders and multiplied by 8,760 hours per year.
0.41
lb VOC x 3 extruders x 8,760 hours 10,764 lb VOC
=
hour - extruder year year
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Butacite Extrusion Process - Line 4 Point Source Emission Determination
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STEP 4: VOC's passing through the final condenser:
In general the same approach used in Steps 2 and 3 is applied here with the only difference
being that the system pressure is atmospheric at the condenser outlet which results in a lower
VOC mole fraction.
Mole fraction of Water
Calculated as the vapor pressure of water ( 42.2 mmHg at 35 deg. C ) divided by
condenser's atmospheric pressure ( 760 mmHg).
42.2 mmHg _ o
760 mmHg — 5.6 /o water
Mole fraction of VOC
Calculated as the vapor pressure of the VOC ( 0.26 mmHg at 35 deg. C ) divided by
the system pressure ( 760 mmHg).
0.26 mmHg = 0.03% VOC as 3GO
760 mmHg
Mole fraction of noncondensables
Calculated as 100% minus the mole fractions of water and VOC
100% minus 5.6% water minus 0.03% VOC = 94.4% noncondensable
Total Moles
Calculated as the lb -mole of noncondensables ( 0.71 lb -moles per hour per extruder )
divided by the noncondensable mole fraction ( 94.4% noncondensables ).
0.71 lb -moles per hour per extruder 0.76 lb -moles
94.4% hour - extruder
DEQ-CFW 00087896