Fugitive Emissions

© Kerry Pritchard, 2015

Fugitive Emissions


Introduction

Emissions that are not released through a stack, vent, duct pipes or other confined air stream are termed as fugitive sources. These emissions include equipment leaks and area emissions. It is very difficult and expensive to estimate such emissions. It is advisable to calculate the fugitive emissions with the help of data available from direct measurement. Industries are free to use any method to estimate the fugitive emission. The emission factors given by the Synthetic Organic Chemical Manufacturing Industry (SOCMI) are widely used to perform the calculations.


Introduction

In 1986, Congress passed the Superfund Amendments and Reauthorization Act (SARA) which requires industries to quantify the levels of certain chemicals to waste as well as the loss of those chemicals to fugitive emissions. The plant are required to estimate fugitive emissions every six months to determine the facility's compliance with operating permits according to the Clean Air Act Amendment (CAAA) of 1990.


Sources of EmissionsProcess Equipment Leaks Valves Flanges Seals Sample connections Open-ended lines Pressure relief devices Screwed fittings Loading and unloading losses Evaporation from spills and retention ponds Uncaptured process emissions Waste treatment facilities


Determining LevelsFor uncaptured process emissions the data on air pollutant

concentration can provide a basis for determining fugitive emissions. Actual measurements taken to ensure compliance with standards should be used. In case of leaks from pipes, flanges, valves etc. emission factors are used to determine the releases.


Emissions Calculations

Widely used methods are given below: • use of "Average" SOCMI Emission Factors • use of Leak / No-Leak Emission Factors • use of Stratified Emission Factors • use of Screening concentration and Correlation Equations by USEPA • Bagging • New Process Specific Equations


"Average" SOCMI Emission Factors

Fugitive Emission Source Emission Factor (lb/hr)Pump Seals - Light Liquids 0.11 Pump Seals - Heavy Liquids 0.047 Valves ( in-line) - Gas 0.012 Valves ( in-line) - Light Liquid 0.016 Valves ( in-line) - Heavy Liquid 0.00051 Gas-Safety Relief Valves 0.23 Open-Ended Lines 0.0037 Flanges 0.0018 Sampling Connections 0.033


Leaking / Non-Leaking Emission Factors

More accurate method.Screening using the EPA Method 21 for VOC leaks.

• Components whose reading show above 10,000 ppmv are multiplied by a leaking emission factor and which are less are multiplied by a non-leaking emission factor. The equation for estimating fugitive emission is given by:

Total Emission = [(Number of Components)1 * (Emission Factor)1] + [(Number of Components)2* (Emission Factor)2]


Leaking / Non-Leaking Emission Factors

Fugitive Emission Source Leaking (>10000 ppm)Emission Factor

( lb / hr)

Non Leaking (<10000ppm)

Emission Factor(lb/hr)

Pump Seals - Light Liquids 0.96 0.026Pump Seals - Heavy Liquids 0.85 0.030Valves ( in-line) - Gas 0.099 0.0011Valves ( in-line) - Light Liquid 0.19 0.0038Valves ( in-line) - Heavy Liquid 0.00051 0.00051Gas-Safety Relief Valves 3.72 0.0098Open-Ended Lines 0.0263 0.0033Flanges 0.083 0.00013Sampling Connections - -Compressor Seals 3.54 0.20


Stratified Emissions Factors

This method is similar to the leak/non leak method. The components are tested for VOC leaks using the EPA Method 21. The components are put into three groups and thus offers a slightly more accurate method of calculating fugitive releases than the leak/non-leak method. The screening value ranges are • 0 - 1000 ppmv • 1001 - 10000 ppmv • Over 10000 ppmv


Stratified Emissions Factors

Fugitive Emission Source

Stratified Emission Factors

<1000 ppmv


1001 to 10,000 ppmv


> 10,000 ppmvPumps - LL 0.0044 0.0737 0.9614Pumps - HL 0.0084 0.2037 0.8547Valves - LL 0.0028 0.0212 0.1874Valves - GV 0.0003 0.0036 0.0992Valves - HL 0.0005 0.0005 0.0005Connections 0.00004 0.0193 0.0825PEVs 0.1167 0.6138 3.7202OELs 0.0003 0.0193 0.0263Compressers 0.0249 0.5808 3.5376


U.S. EPA Equations

The EPA conducted field tests to create curves which relate the Method 21 screenings to a mass emission rate. The equations are then derived from this data. The components are screened and the results are applied to the correlation curves to obtain mass emission rate.

The component / service categories are: • Valves in Light Liquid • Valves in Gas / Vapor Service • Pumps in light liquid Service The instruments used for screening are: • Bachrach TLV Sniffer • Century System OVA Instrument


U.S. EPA Equations

OVA = Instrument reading * Response Factor R.F. = ( Actual Concentration ) / (Observed Concentration from Detector )


Bagging

In this method the component is enclosed in a non-leaking material. Two openings are provided - one to let in fresh air and the other to test the exhaust air. The exhaust air is passed through an analyzer to measure VOC concentration which helps to obtain the mass emission rate. The flow rate of air is kept constant during bagging. The sampling of gas is done by:• Vacuum Method • Blow Through Technique • New Process Equations


Method 21The Method 21 was developed by the EPA as a standard to measure VOC components for leaks. Different components have to be screened differently in slightly different ways to get the best results. Some possible interferences while screening include:• Wind • Temperature fluctuations • Distance of component from screening Some of the possible discrepancies while screening include:• Open ended lines • Inaccurate components counts • Data entry errors • Missing plugs


Area Sources

If there are a number of small sources in a particular process then the whole process can be taken as an area and the fugitive emission can be estimated accordingly. Two software programs are available from EPA to measure the emissions from area sources. They are CHEMDAT7 and SIMS. Apart from this software there are other programs available in the market. There are several methods to estimate emission data from area sources, but they cannot be applied to all the sources or under all conditions.


ReferencesREFERENCES

Hazardous Waste Treatment, Storage and Disposal Facilities - Air Emission Models. ( U.S. EPA) Chemical Manufacturers Association - Fugitive Emission Database.


Documents

Fugitive Emissions