Presentation on theme: "An Introduction to Isokinetic Source Sampling presented by: Apex Instruments Inc. Manufacturer of Quality Sampling Equipment Since 1988 204 Technology."— Presentation transcript:
An Introduction to Isokinetic Source Sampling presented by: Apex Instruments Inc. Manufacturer of Quality Sampling Equipment Since Technology Park Lane Fuquay Varina, North Carolina tel: fax: web:
Apex Instruments Inc. designs, manufactures, and markets equipment used for the collection of air samples from smoke stacks, chimneys, industrial ducts, and other process air streams.
Emission Data can be used: Government To provide data for determining appropriate emission limits. To provide data for determining compliance. To provide data for health risk assessments. To provide data for dispersion modeling.
Emission Data can be used: Industry (continued) To evaluate air pollution control equipment. To provide information for design of new process and control equipment. To provide information on process operations.
Isokinetic Measurement of Source Emissions: Particulate emissions from a source are sampled isokinetically using a US EPA Method 5 sampling train. The collected sample is analyzed to determine the pollutant concentrations.
ISOKINETIC ISO = EQUAL+ KINETIC = MOTION Isokinetic Sampling is an equal or uniform sampling of particles and gases in motion within the air stream.
Basic Terminology Pmr s = C s Q s CONCENTRATION (C s ) Quantity of pollutant per volume of effluent gas grams / cubic meter STACK GAS FLOW RATE (Q s ) Volume of effluent gas per length of time cubic meters / hour POLLUTANT MASS RATE EQUATION (Pmr s ) Volume of pollutant gas per length of time grams / hour
Isokinetic Sampling is the application of five sampling methods developed by the USEPA plus the applicable method: Method 1 - Sample and Velocity Traverses from Stationary Sources Method 2 - Determination of Stack Gas Velocity and Volumetric Flow Rate Method 3 - Gas Analysis for Carbon Dioxide, Oxygen, Excess Air, and Dry Molecular Weight Method 4 - Determination of Moisture Content in Stack Gases Method 5 - Determination of Particulate Emissions from Stationary Sources
Method 8Sulfuric Acid Mist & SO 2 Method 12Inorganic Lead Method 13AFluorides Method 17 Particulate Emissions (in stack filter) Method 23Dioxin / Furans Method 26AHydrogen Chloride Method 29Multi Metals Method 201A Determination of PM 10 Particulate Method 0010Semi Volatile Compounds Partial Listing of US EPA Isokinetic Sampling Methods:
Method 1 Sample and Velocity Traverses from Stationary Sources
Method 1 is used to: 1.Select an appropriate sampling location 2.Determine the required number of particulate sampling points 3.Calculate the location of the sampling points within the duct.
Ideal site should be at least 8 duct diameters downstream & 2 duct diameters upstream from any flow disturbance. Minimum distances are 2 duct diameters downstream and ½ duct diameters upstream from any flow disturbance.
The number of sample points is dependent on the distance from any flow disturbance (measured in duct diameter). The following table is used for determining the required number of sampling points.
The cross section is divided into the desired number of equal areas. Isokinetic sampling is conducted at discrete points in the cross- section of the duct. The following table is used for determining the location of sampling points.
Location of Traverse Points in Circular Stacks
The probe is marked to correspond to the appropriate sampling point using the table from Method 1.
Method 2 Determination of Stack Gas Velocity and Volumetric Flow Rate
Velocity Traverses are conducted by measuring the stack gas velocity pressure ( p) and stack temperature at each of the sample points determined by the Method 1 calculations. Method 2 is used to: Conduct a pre-test velocity traverse Determine the effluent gas velocity
Pressure Components in Gas Streams a) Stagnation Pressure b) Static Pressure c) Velocity Pressure, ( P)
Type S (Stausscheibe) Pitot Tube Most commonly used in conjunction with Method 5 because of its: Compact size - fits in small ports Durability in design Plugging resistance in heavy particulate Sensitivity at low velocities
Velocity measurements are conducted simultaneously during the sample period for the setting of the isokinetic sampling rate. Volumetric flows are adjusted for temperature, pressure, and gas molecular weight.
Stack Gas Analysis for Carbon Dioxide, Oxygen, Excess Air, and Dry Molecular Weight Method 3
Method 3 is applicable for determining Dry Molecular Weight and excess air correction factors from fossil fuel combustion sources.
Orsat Analyzer A gas sample is collected in a tedlar bag and analyzed for CO 2, O 2 and sometimes CO.
Dry molecular weight (Md) is calculated from the gas analysis results Md = (0.44 % CO 2 ) (% O 2 ) (% CO + % N 2 )
Determination of Moisture Content in Stack Gases Method 4
Moisture Content Procedure The water vapor is condensed in the impingers. The net gain is measured and the percent moisture is calculated. * Approximation methods are used to estimate percent moisture for setting isokinetic sampling rates.
Determination of Particulate Emissions from Stationary Sources Method 5
Method 5 Principle Particulate matter is withdrawn isokinetically from the source and collected on a glass fiber filter maintained at a temperature in the range of o C. The particulate mass is determined gravimetrically after removal of uncombined water.
Components: Probe Assembly Heated Filter Compartment (Hot Box) Condenser Unit (Cold Box) Umbilical Cable Metering Console with Pump Method 5 System
To obtain a representative sample of particulate matter from an air stream the velocity at the nozzle opening should be equal to the velocity of the approaching gas stream.
100% I sokinetic 100% isokinetic means that the velocity at the tip of the nozzle is equal to stack velocity. The true particulate concentration will therefore be obtained.
Under I sokinetic When the nozzle velocity is less than the stack velocity the results will be biased high due to the inertia of the large particles.
Over I sokinetic When the nozzle velocity is greater than the stack velocity the results will biased low since the larger particles break through the air stream and bypass the nozzle.
Tools available for solving isokinetic rate equations include: Slide Rule Computer Program Calculator
PRETEST PREPARATIONS A tared filter is placed in the filter holder A known amount of water and silica gel is placed in the impingers A preliminary velocity determination is made to select the proper size nozzle Sampling train is leak checked
Method 5 Components
Particulate Train Operation A compliance test will require at least three Method 5 sample runs. Each run must be for a minimum of 1 hour and 30 scf or other specified minimum time and sample volume. Sample train placed at first point and sample pump is started
Particulate Train Operation (cont.) Sample rate is adjusted to isokinetic after moving to each new sample point and any time the velocity pressure reading changes by more than 20%. The isokinetic rate setting is determined with a calculator or nomograph and established with a flowrate meter called an orifice meter. The sampling train is only shut down to move from port to port and at the end of the sample run.
Post Test Operation Upon completion of testing the sampling train must pass a leak test. The sample train is removed to a cleanup area that is free of dust and wind. The filter is removed from the container and placed in a sample container. Sample is removed from the sample exposed portions of the nozzle, probe liner and filter holder with acetone and placed in a sample container.
Analysis Filter is desiccated for a minimum of 24 hours and then weighed to a constant weight. Acetone sample rinse and an acetone blank are evaporated to dryness and weighed to a constant weight. The sample residue is weighed to a constant weight and the residue weight of the acetone is subtracted from the evaporated sample to yield the weight of the sample. Sum of the weight of the sample on the filter and in the acetone rinse is used to calculate the particulate emissions.
Alternative Sampling Trains for Particulates Flexible Method 5 Compact Method 5 Method 17 Method 201A
Flexible Method 5 Uses flexible line between filter unit and condenser * Heated line may be required for some methods
Compact Method 5 Includes: Heated Stainless Steel Filter Unit Stainless Steel Liner Flexible Sample Line extension Cut-back Umbilical Cable
Method 17 In-stack Filter Applicability In sources where particulate matter concentration is independent of temperature.
Schematic of the EPA Method 17 Flex Sampling Train
The PM 10 Cyclone is built to EPA specifications for Method 201A testing and is designed for in-stack measurement of particulate matter equal to or less than 10 microns. The cyclone and in-stack filter assembly adapts easily to Method 5 probe assembly. PM 10 Kit