Calculating dehydration emissions

Emission Group 5: Dehydration

Identify the Substances of Concern

The only substances of concern released this group are Part 4 substances (i.e. CACs) substances.

Identify the Method of Calculating Emissions

Table 11 identifies the specific emission sources included in the Dehydration grouping for this facility. This table presents one possible emission estimation technique and the amount of natural gas consumed by each source, if applicable.

Table 11: Possible Methods of Estimation for the Dehydration Emissions and Consumption Data
Emission Source Suggested Estimation Method(s) Consumption Data
Natural Gas Burning Reciprocating Engine1 (SCC 20200254) Mass Balance, Emission Factor Natural Gas: 160,000 m3/yr (6,176 GJ/yr)2
Leaks from operating valve(s) (4 valves)3 (SCC 30600811) Emission Factors N/A

Notes:
1 Considering internal combustion, four-stroke lean burn reciprocating engines, fueled by natural gas and operating at 90-105% load.
2 Natural gas in cubic metres can be changed to gigajoules using the conversion factor 0.0386 GJ/m3.
3 These emission sources will most likely only emit VOCs. However diligence must be exercised if it is expected that other CACs are being emitted from the source.

calculate Emissions

For the sources in Group 5, published emission factors will be used to estimate the emissions for these sources. The applicable emission factors can be found in the Table 12, shown below. In this case study, the emission factors from WebFIRE (based on the SCC identified in Table 11) were utilized with the appropriate conversions applied (i.e. imperial to metric conversions).

Table 12: Emission Factors
  NOx SO2 CO VOC TPM PM10 PM2.5
Natural Gas Burning Reciprocating Engine(kg/GJ) 1.754 2.528E-4 0.239 0.051 3.315E-5 3.315E-5 3.315E-5
Leaks (kg/leak per year) N/A N/A N/A 234.417 N/A N/A N/A

N/A -- Not applicable.

Example Calculation

The equation for calculating releases from internal combustion engines using emission factors is:

Emission [kg/year]=natural gas consumed [GJ/year] x EF [kg/GJ]

From Tables 11 and 12:

Natural gas consumed = 6176 GJ
SO2 emission factor = 2.528E-4 kg/GJ

Using the above equation and the known values:

VOC Emission = (6176 GJ) (2.528x10-4 kg/GJ)

VOC Emission = 1.559 kg

VOC Emission = 0.002 tonnes

The same method is utilized to calculate the emissions for the remaining sources using the consumption data in Table 11 and emission factors presented in Table 12. Table 13 shows uncontrolled emissions from the sources in the Dehydration group.

Table 13: Uncontrolled Annual CAC Releases for Group 5 Sources
Source NOx SO2 CO VOC TPM PM10 PM2.5
Natural Gas Burning Reciprocating Engine 10.833 1.561E-3 1.476 0.313 2.047E-4 2.047E-4 2.047E-4
Leaks N/A N/A N/A 0.938 N/A N/A N/A
Total 10.833 1.561E-3 1.476 1.251 2.047E-4 2.047E-4 2.047E-4

N/A -- Not applicable.

Emission Group 6: Condensate Recovery System

Identify the Substances of Concern

The only substances of concern released this group are Part 4 substances (i.e. CACs) substances.

Identify the Method of Calculating Emissions

Table 11 identifies the specific emission sources included in the Dehydration grouping for this facility. This table also presents the suggested emission estimation techniques and the amount of natural gas consumed by each source, if applicable.

Table 14: Possible Methods of Estimation for the Condensate Recovery System Emissions and Consumption Data
Emission Source Suggested Estimation Method(s) Consumption Data
Natural Gas Burning Reciprocating Engine1 (SCC 20200254) Mass Balance, Emission Factor Natural Gas: 160,000 m3/yr (6,176 GJ/yr)2
Leaks from operating
valve(s) (8 valves)3(SCC 30600811)
Emission Factors N/A

N/A -- Not applicable.

Notes:
1 Considering internal combustion, four-stroke lean burn reciprocating engines, fueled by natural gas and operating at 90-105% load.
2 Natural gas in cubic metres can be changed to gigajoules using the conversion factor 0.0386 GJ/m3.
3 These emission sources will most likely only emit VOCs. However diligence must be exercised if it is expected that other CACs are being emitted from the source.

calculate Emissions

For the sources in Group 6, published emission factors will be used to estimate the emissions for these sources. The applicable emission factors can be found in the Table 15, shown below. In this case study, the emission factors from FIRE 6.25 (based on the SCC identified in Table 14) were utilized with the appropriate conversions applied (i.e. imperial to metric conversions).

Table 15: Emission Factors
Source NOx SO2 CO VOC TPM PM10 PM2.5
Natural Gas Burning Reciprocating Engine(kg/GJ) 1.754 2.528E-4 0.239 0.051 3.315E-5 3.315E-5 3.315E-5
Leaks (kg/leak per year) N/A N/A N/A 234.417 N/A N/A N/A

N/A -- Not applicable.

Example Calculation

The equation for calculating releases from internal combustion engines using emission factors is:

Emission [kg/year]=natural gas consumed [GJ/year] x EF [kg/GJ]

From Tables 14 and 15:

Natural gas consumed = 6176 GJ
NOx emission factor = 1.754 kg/GJ

Using the above equation and the known values:

NOx Emission = (6176 GJ) x (1.754 kg/GJ)

NOx Emission = 10833.223 kg

NOx Emission = 10.833 tonnes

The same method is utilized to calculate the emissions for the remaining sources using the consumption data in Table 14 and emission factors presented in Table 15. Table 16 shows uncontrolled emissions from the sources in the Condensate Recovery group.

Table 16: Uncontrolled Annual CAC Releases for Group 6 Sources
Source NOx SO2 CO VOC TPM PM10 PM2.5
Natural Gas Burning Reciprocating Engine 10.883 1.561E-3 1.476 0.313 2.047E-4 2.047E-4 2.047E-4
Leaks N/A N/A N/A 1.875 N/A N/A N/A
Total 10.883 1.561E-3 1.476 2.187 2.047E-4 2.047E-4 2.047E-4

N/A -- Not applicable.

Emission Group 7: Gas Recompression

Identify the Substances of Concern

The only substances of concern released this group are Part 4 substances (i.e. CACs) substances.

Identify the Method of Calculating Emissions

Table 17 identifies the specific emission sources included in the Gas Recompression grouping for this facility. This table also presents the suggested emission estimation techniques and the amount of natural gas consumed by each source, if applicable.

Table 17: Possible Methods of Estimation for the Gas Recompression System Emissions and Consumption Data
Emission Source Suggested Estimation Method(s) Consumption Data
Gas Cooler1 (SCC 30600702) Emission Factors Natural Gas: 1,368,270 m3
Natural Gas Turbine (SCC 20100201) Emission Factors Natural Gas: 130,000 m3/year (5018 GJ)2
Leaks from operating
valve(s) (10 valves)1(SCC 30600811)
Emission Factors N/A

N/A -- Not applicable.

Notes:
1 These emission sources will most likely only emit VOCs. However diligence must be exercised if it is expected that other CACs are being emitted from the source.
2 Natural gas in cubic metres can be changed to gigajoules using the conversion factor 0.0386 GJ/m3.

calculate Emissions

For the sources in Group 7, published emission factors will be used to estimate the emissions for these sources. The applicable emission factors can be found in the Table 18, shown below. In this case study, the emission factors from WebFIRE (based on the SCC identified in Table 17) were utilized with the appropriate conversions applied (i.e. imperial to metric conversions).

Table 18: Emission Factors
Source NOx SO2 CO VOC TPM PM10 PM2.5
Gas Cooler (kg/m3 feed gas) N/A N/A N/A 0.029 N/A N/A N/A
Natural Gas Turbine (kg/GJ) 0.137 4.041 0.035 9.028E-4 8.169E-42 8.169E-42 8.169E-42
Leaks (kg/leak per year) N/A N/A N/A 234.417 N/A N/A N/A

N/A -- Not applicable

Notes:
1 Assumes the sulphur content of the natural gas is 10%. If the natural gas has different sulphur content the emission factor can be found using the following formula: 0.4041 x S kg per GJ Fuel Input, where S is equal to the percent of sulphur present in the natural gas. (For this example the sulphur content in the natural gas was assumed to be 10%, i.e.; S = 10)
2 Emission factors are based on combustion turbines using water-steam injection.

Example Calculation

The equation for calculating releases from the gas cooler using emission factors is:

Emission [kg/year]=natural gas consumed [m3/year] x EF [kg/m3]

From Tables 17 and 18:

Natural gas consumed = 1,368,270 m3
VOC emission factor = 0.029 kg/m3

Using the above equation and the known values:

VOC Emission = (1,368,270 m3) x (0.029 kg/m3)

VOC Emission = 39036.883 kg

VOC Emission = 39.037 tonnes

The same method is utilized to calculate the emissions for the remaining sources using the consumption data in Table 17 and emission factors presented in Table 18. Table 19 shows uncontrolled emissions from the sources in the Gas Recompression group.

Table 19: Uncontrolled Annual CAC Releases for Group 7 Sources (tonnes)
Source NOx SO2 CO VOC TPM PM10 PM2.5
Gas Cooler N/A N/A N/A 39.037 N/A N/A N/A
Natural Gas Turbine 0.690 0.203 0.177 4.530E-3 4.099E-3 4.099E-3 4.099E-3
Leaks N/A N/A N/A 2.344 N/A N/A N/A
Total 0.690 5527.811 0.177 41.386 4.099E-3 4.099E-3 4.099E-3

N/A -- Not applicable

Emission Group 8: Painting of Process Equipment

Identify the Substances of Concern

During the paint drying process VOCs are released to the atmosphere. The MSDS for the paint used on the tanks and process equipment is below:

Sample MSDS for "Paint ABC"

Material Safety Data Sheet

SECTION 1 - CHEMICAL PRODUCT AND COMPANY IDENTIFICATION
PRODUCT NAME : PAINT ABC
SUPPLIER : ABC INC
Specific Gravity: 1.03

SECTION 2 - COMPOSITION / INFORMATION ON INGREDIENTS
CHEMICAL NAME CAS# PERCENT BY WEIGHT
Methyl Ethyl Ketone 78-93-3 30%
Xylene 1330-20-7 20%
Ethylbenzene 100-41-4 15%
n-Butyl Alcohol 71-36-3 25%
Carbon Black 133-86-4 <3%
Other   balance
SECTION 3 - PHYSICAL AND CHEMICAL PROPERTIES
Chemical Name Specific Gravity Percent Volatile
Methyl Ethyl Ketone 0.805 100%
Ethyl Benzene 0.867 100%
Xylene 0.867 100%
N-Butyl Alcohol 0.810 100%

Part 1A: The Paint ABC contains Part 1A substances such as: Methly Ethyl Ketone, Xylene, Ethyl Benzene, and n-butyl Alcohol in a concentration greater than 1%. According to the reporting requirements these substances are reportable when in a concentration of 1% or greater, as is the case.

Part 1B: The paint contains no Part 1B substances.

Part 2: The paint contains no Part 2 substances.

Part 3 - Painting is not one of the 17specified activities that require the reporting of Part 3 substances.

Part 4 - All the substances listed under Part 1A are also considered VOC and need to be added together to determine the amount of total VOCs are released due to the paint activities. Total VOCs are the only Part 4 substance of concern for painting processes.

Part 5 - Based on the MSDS of this particular paint, a substance report for Ethyl Benzene is require if a facility report for Part VOC is required and if amount of Ethyl Benzene released is 1 tonne or more.

Identify the Method of Calculating Emissions

Last year approximately 2,500 L of Paint ABC was used to paint the two storage tanks and process equipment.

Part 1A Substances: Since there are no emission factors available for this type of operation the appropriate estimation method is to use a mass balance.

The general mass balance equation is:
Me = Mi - Mo - Ma - Mr

Where:
Me = Mass of coating compound emitted
Mi = Mass of coating compound in input stream. In this case Mi is the mass of the substance in the coating being applied.
Mo = Mass of coating compound in the output stream in the finished product. For this scenario, the amount of the substance in the finished product is zero, due to the 100% volatility.
Ma = Mass of coating compound accumulated in the system. Due to the nature of the activity there is no accumulation of the substance so Ma is zero.
Mr = Mass of coating compound captured for recovery or disposal. This term would be required, if for example the coating was conducted in a sealed environment, where some or all of the substances released were captured for recovery or disposal - this is not the case for this scenario so it is also zero.

For the given scenario, the general mass balance equation reduces too:

Me = Mi

calculate Emissions

To apply the mass balance the substance content in the coating compound must be determined. In many instances, the MSDS for that compound will indicate percent weight content of the predominate substances. The annual consumption of the compound could be obtained from the facilities operation log or sales slips.

It is assumed that all VOC substances in "PAINT ABC" were released into the atmosphere. The following equation will be used to determine the amount of each of the Part 1A substances released to air and is based on the specific gravity and percent volatiles.

Example Calculation

The following equation will be used to determine the amount the substances released:

Me = Mi = Q x D x c

Where:
Me = Total uncontrolled emission, kg
Q = Total annual consumption of coating material, litres = 2500 litres
D = Density of coating material, kg/litre from MSDS. Note that the specific gravity (SG) of substances are usually supplied in Section 3: Physical and Chemical Properties of the MSDS. To convert the SG to density, into units of  kg/litre, multiply the SG by the density of water, 1 kg/litre.
c = Percent by weight of substance in coating, (from MSDS)

Me MethylEthylKetone = (2500 litres) x (1.03 kg/litres) x (30 kg/100 kg)

Me MethylEthylKetone = 772.5 kg

Me MethylEthylKetone = 0.773 tonnes

Me Xylene = (2500 litres) x (1.03 kg/litres) x (20 kg/100 kg)

Me Xylene = 515 kg

Me Xylene = 0.515 tonnes

Me EthyBenzene = (2500 litres) x (1.03 kg/litres) x (15 kg/100 kg)

Me EthyBenzene = 386.3 kg

Me EthyBenzene = 0.386 tonnes

Men-ButylAlcohol = (2500 litres) x (1.03 kg/litres) x (25 kg/100 kg)

Men-ButylAlcohol = 643.75 kg

Men-ButylAlcohol = 0.644 tonnes

Part 4 Substances: The individual releases of each of the Part 1A VOCs released due to the painting process can be added together to calculate the total VOCs released due to the painting activities.

Example Calculation

Total VOCs = Methyl Ethyl Ketone + Xylene + Ethylbenzene + n - Butyl Alcohol
Total VOCs = (0.733 + 0.515 + 0.386 + 0.644) tonnes
Total VOCs = 2.318 tonnes

Table 20, summarizes the releases from the painting activities.

Table 20: Uncontrolled Releases from Group 8
Substance Category Substance Name Release Amount (tonnes)
Part 1A Methyl Ethyl Ketone 0.733
Xylene 0.515
Ethylbenzene 0.386
n-Butyl Alcohol 0.644
Part 4 VOCs 2.318
Part 5 Ethyl Benzene 0.386

Step 4 - Add Emissions From All Groups

After calculating emissions from each source at the facility, the next step is to add emissions from each group and calculate the total emissions from the facility to determine if the NPRI thresholds were met.

Total facility Part 1 - 3 emissions

Based on the threshold calculations no reports are required for Parts 1 - 3 substances. Recall that the only group with Part 1 substances was Group 8 ( Painting of Process Equipment). Even though these substances met the concentration threshold, the mass balance calculation for this activity showed that none of the four substances met the 10 tonnes reporting threshold, therefore a substance report is not required.

Recall, that at this particular facility, no Part 2 substances were incidentally manufactured, thus no substance reports are required.

Finally, substance reports for Part 3 substances are not require since the activity triggers were not met.

Total facility Part 4 emissions (CAC emissions)

Table 21 summarizes the emissions from all of the assigned groups.

Table 21: Total Facility Emissions based on Assigned Groups
NPRI Substance Releases (tonnes)
Group NOx SO2 CO VOCs TPM PM10 PM2.5
1 - Utilities 8.4179 0.00156 1.025 0.321 0.105 0.105 0.105
2 - Sulphur Flare Stack N/A 13.723 N/A N/A N/A N/A N/A
3 - Horizontal Separator 0.301 1.448E-3 0.371 0.248 4.632E-3 4.632E-3 4.632E-3
4 - Gas Sweetening (Amine Treatment) 88.317 1.41E-2 12.364 3.065 6.30E-03 6.30E-03 6.30E-03
5 - Dehydration 10.833 1.561E-3 0.842 1.251 2.047E-4 2.047E-4 2.047E-4
6 - Condensate Recovery System 10.833 1.561E-3 0.842 2.187 2.047E-4 2.047E-4 2.047E-4
7 - Gas Recompression 0.690 5527.811 0.177 41.386 4.099E-3 4.099E-3 4.099E-3
8 - Painting of Process Equipment N/A N/A N/A 2.318 N/A N/A N/A
TOTAL 119.392 5541.544 15.621 50.776 0.120 0.120 0.120

N/A -- Not applicable

NPRI Reporting Determination for CACs

Table 22 compares the substances releases to the NPRI reporting thresholds and lists which substances require a report.

Table 22: Comparison of Annual Emissions to the NPRI Reporting Thresholds
NPRI Substance Total Emission (tonnes/year) NPRI Facility Threshold (tonnes/year) NPRI Threshold Exceeded (?) Rationale
NOx 119.392 20 Yes Facility emission is > than NPRI threshold
SO2 5541.546 20 Yes Facility emission is > than NPRI threshold
CO 15.621 20 No Facility emission is < than NPRI threshold
VOC 50.776 10 Yes Facility emission is > than NPRI threshold
TPM 0.120 20 No Facility emission is < than NPRI threshold
PM10 0.120 0.5 No Facility emission is < than NPRI threshold
PM2.5 0.120 0.3 No Facility emission is < than NPRI threshold

Conclusion

For each CAC where the total facility release exceeded the NPRI release threshold, a report is required. A report is not required for those CACs where the release is less than the release threshold. Reporting for one CAC does not trigger reporting for another CAC.

Step 5 - How to Report Facility Emissions

Substance information is entered in the reporting form of the 2003 NPRI Reporting Software, starting at the "Substance Identification" screen (section B1.0). Report all air releases of the NPRI substance to be reported and the basis of estimate. Air releases for each substance are entered in section B12.0 for Stacks or Point Sources and Fugitive releases and will be reported as shown below.

B12.1.a Stack or point releases - Total releases from stack or point sources. This will include, for this case study:

  • Emergency Flares
  • Space Heaters
  • Boilers
  • Reciprocating Engines
  • H2S Flare
  • Cooling Tower
  • Gas Cooler
  • Turbine

B12.1.cFugitive releases - Air releases that are not released through stacks or points. This will include, for this case study:

  • Valve leaks
  • Painting of process equipment

A summary of the reported emissions for this facility are shown in Table 23.

Table 23 - Summary of Substances Release to the Air
NPRI Substance Total Point Source Emission (tonnes) Enter Releases in Field Number Basis of Estimate Code Total Fugitive Emission (tonnes) Enter Releases in Field Number Basis of Estimate Code
NOx 119.3919 B12.1.a E2 0 N/A N/A
VOC 41.426 B12.1.a E2 9.350 B12.1.c E2

N/A -- Not applicable

The reporting software has a pick-list for choosing the "Basis of Estimate" codes. Select the letter code identifying the method that applies to the largest portion of the estimated releases or transfers (you can choose only one code). In this case study, the basis of estimates are E2 (published emission factor). Select the basis of estimate which provides the majority of the total emission for each CAC from the facility.

Note that if the substance was released through a stack greater than or equal to a height of 50m, a stack profile must be created and the quantity of the substance released assigned to the stack. More information on stack reporting can be found in the Guide for Reporting to the National Pollutant Release Inventory (NPRI).

Step 6 - Speciated VOC Calculations

Since the Part 4 VOC emissions exceeded the NPRI threshold speciated VOC calculations are required. A report is required for each of the speciated VOC that is released in a quantity of 1 tonne or greater. VOC profiles can be used to determine the breakdown of the total VOC reported in Part 4. These profiles can be found on the NPRI's Toolbox website along with instructions on how to use the profiles.

Step 7 - Calculate the Monthly Breakdown of Annual Releases to Air by Percentage

Detailed emission estimates show that the facility is required to report to the NPRI. Additional reporting such as monthly breakdown of emissions by percentage for each pollutant must be reported. The general equation and methodologies for estimation monthly emissions is the same as the annual emissions for each source.

Example Calculation

Usage of natural gas, water and paint for each month is obtained from facility records. You can calculate emissions for each month and add the total to determine the annual emissions. Using the annual total, calculate the monthly emission percentage using the following equation:

January emission percentage = (January emission / Total annual emissions) x 100%

For example, add the VOC emission from each source for the month of January. As in this case study, the emissions of VOCs from the eight groups is 12.157  tonnes, the January percentage VOC emission is:

January emission percentage = (12.157 tonnes / 50.776 tonnes) x 100%

January emission percentage = 23.94%

Enter the information (calculated percentage emission) for each substance in field B13.1 of the reporting form. The percentage for months must total 100%.

Step 8 - Reasons for Change in Quantities Released from Previous Year

In section B14.0 of the reporting software you are required to select all applicable reasons for changes in substance releases from the previous reporting year (check the applicable boxes from B14.1a through B14.1i).

Step 9 - Anticipated Releases to Air

Users are required to estimate anticipated releases for each substance released to the air from the facility for the years 2004 - 2006. Reporting anticipated releases for the years 2007 and 2008 are optional. Enter the information for each substance in field B15.1 of the reporting form.

Step 10 - Pollution Prevention (P2) Activities

If the facility has employed P2 activities, it should be noted in section B30.0 of the reporting form (check the applicable boxes from B30.1a through B30.1g).

References

US EPA AP-42: compilation of Air Pollution Emission Factors, AP-42, Fifth Edition, Volume 1: Stationary Point Area Sources, 2004

US EPA Factor Information Retrieval (WebFIRE), December 2005

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