Air pollution control

Transcription

1 Absorption ACFM Aerosol Aeration Aerosol Photometer Aerosol Spectrometer Agglomeration Air Change Air Filter Air to Cloth Ratio Ambient Air Arrestance ASHRAE Atmospheric Pressure Bag Cup Baghouse The process by which a liquid or gas is taken into the filter media substance and held there Actual Cubic Feet per Minute adjusted for operational parameters. (Actual CFM required in the application at elevation and temperature) An assemblage of small particles, solid or liquid, suspended in air. The diameter of the particles may vary from 100 microns down to 0.01 microns. Examples: dust, smoke, and fog. The action of introducing air (or gas) to a bulk material by any means. May cause the material to become fluidized or agitated. A light-scattering mass concentration indicator. A device for measuring particle size distribution in air. The formation of a larger airborne particle by the collision of two or more small particles. Agglomeration takes place when the attractive forces between the particles is greater than the kinetic energy of collision. A measure of the amount of air moving into and out of a space because of leakage or mechanical ventilation. One air change is a volumetric flow of air equal to the cubic content of the space. Example: If a space has a cubic content of 10,000 cubic feet and the ventilation rate is 1000 cfm, 0.1 (1000/10,000) air change is occurring every minute, or 6 (60x0.1) air changes are occurring per hour. A device for removing particulate material from an airstream. A measurement of the relationship between the amount of air in the system to the amount of filtration media in the dust collector. Air : Cloth Ratio = (ACFM of air / Sq. Ft. of cloth) Example: 3800 ACFM / Sq. Ft. = 2.4:1 (This number is within the acceptable range. Most reverse pulse-jet baghouses should be in the 2.0:1 to 6.0:1 range. A lower ratio is better. Increase the number of bags, increase the bag length, or reduce the airflow to reduce the ratio.) Air which surrounds the occupant or process in a space. A measure of the ability of an air filtration device to remove a synthetic dust from the air. ASHRAE arrestance is a measure of the ability of a device to remove ASHRAE dust from test air. American Society of Heating, Refrigerating, and Air-Conditioning Engineers The pressure exerted upon the earth s surface by the weight of the atmosphere above it. Measure at 14.7 psi at sea level. ( x105 newtons per sq. meter) Also known as a thimble. The spun or cast piece that the filter bag and cage assembly clamps on. Only on bottom load units. These typically have a venturi attached to them. A style 3 unit. This includes a clean air plenum, tubesheet, dirty air housing, and hopper. It may or may not include legs. It is commonly used as a high airflow, low product loading, low pressure and low vacuum system unit. The bottom of the collector discharges into a barrel, airlock, screw conveyor, or other mechanical device to move the collected product to another area of the plant. This type of unit is square or rectangular. Typical pressure and vacuum ratings to +/- 20 water column. Typically there is a cyclone ahead of this unit in a system to remove heavy product load if being used on a conveying system. This type of unit frequently has a fan that is used to move the air through the unit in either a pressure or vacuum application.

2 Binvent Blow Pipe Blower Bottom Load Brownian movement Cage Can Velocity Cartridge Filter CFM Clean Air Plenum Cloth Area CV Dead Load Delta P Diaphragm Valve Differential Pressure A style 2 unit. This includes a clean air plenum, tubesheet, and dirty air housing. It is commonly used to vent a silo or bin where there is low product loading and relatively low airflow, generally for displaced air coming into the silo. The bottom of the collector discharges any product collected directly into the silo it is mounted on. It may or may not have a fan attached for air removal from the silo. Typically this unit is square or rectangular but may be manufactured as round. The pipe inside the clean air plenum that dispenses the compressed cleaning air into each of the filter bags. This pipe is attached to the discharge side of the diaphragm valve. A fan used to move air under pressure. When the filter bag and cage assemblies are installed from the bottom side of the tubesheet. This would be from the dirty air or product side of the tubesheet. The continuous zig-zag motion of particles (aerosols) in suspension. The motion is caused by the impact of the molecules of the fluid (air) upon the particles. The welded wire support that holds the filter bag open during operation. Can be top load or bottom load. Top load typically has a venturi welded in the top. Upward velocity (FPM) in the dust collector if there were no filter bags. (the lower the number the better the product will drop off the bags., improving separation.) (CV) = ACFM of air / (Side L (in.) x Side W (in.) 144sq. in. / sq. ft. Example: 3800 ACFM / 88 x 88 = FPM 144 A cartridge filter is generally tubular and is made of cellulose paper or a blend of cellulose and synthetic paper. Pleats are very tightly packed; cartridges must be operated at extremely low air to cloth ratios (less than 2.00 to 1) and will not operate reliably in heavy inlet grain loading, nor sticky, tacky dust applications. Cubic Feet per Minute. The section of the dust collector that is downstream from the filter media. This is the area above the tubesheet after the air has passed through the filter media and had the particulate removed. Also referred to as a style 1 unit. Amount of filtration media in the dust collector. (Square Feet of Cloth) Square Feet of Cloth = Bag Dia. (in.) x x length of cage callout (in.) x No. of bags 144 sq. in. / sq. ft. Example: (6.20 x x 96 ) / (144 sq. in / sq. ft) x 121 bags = Sq. Ft. of cloth Can Velocity Operational weight (Lb.) of dust collector when set up for normal operation. Includes weight of bags, cages, platform, ladder, etc. under normal operation after start up. See pressure drop. Delta is the Greek symbol for change. The primary reverse pulse valve that blows a charge of compressed air down the blow-pipe. See pressure drop.

3 Din The German Institute for Standardization (Deutsches Institut fur Normung e.v.). This institute establishes standards for testing and classifying air filters. Dirty Air Plenum The section of the collector immediately below the tubesheet in the product contact side of the air stream. This is on the unfiltered air side of the tubesheet. This piece along with a clean air plenum makes up a style 2 unit or binvent. Dop DSCF Dioctlyphthalate (diethylhexylphosphate), an oily liquid used in an aerosol form as a challenge for efficiency and leak testing HEPA filters. Dunnage Blocks and braces used to support a piece of equipment during freight transport. Includes items such as blocks, pallets, boxes, packaging materials, and support braces that are to be removed for operation. Dust Spot Efficiency See efficiency. Dust An aerosol of particles of any solid material, usually with particle size less than 100 microns. Efficiency The ability of a device to remove particulate or gaseous material from an air stream by measuring the concentration of the material upstream and downstream of the device. In the ASHRAE 52.1 Standard test method, it is a measure of the ability of a filter to remove the staining portion of atmospheric dust from the test air. This is officially termed Atmospheric Dust Spot Efficiency. Emission Standard Emissions through the fabric filter are measured in grams per dry standard cubic feet: Typical standard for non-hazardous dusts: 0.02 grs/dscf; Hazardous Dusts: 0.01 grs/dscf. This emission may be converted into pounds per hour of emission. Emission Testing Generally the EPA requires a compliance test to determine the emissions. A isokinetic test is the standard procedure required to test emissions. Face Area The area of an air filter or other air treatment device normal to the flow of air through it. Filter Bag The filter media used in a dust collector. This is typically a tubular style bag. A filter bag needs a support cage inside it to keep it open during operation. Filter Media Material that makes up the filter element. Glass fibers and polyester fibers are examples of filter media. ( Media is the plural of medium. Common practice allows it to be used as the singular form and medias as the plural.) Filter Receiver A style 3 unit that is round. This includes a clean air plenum, tubesheet, dirty air housing, and hopper. It may or may not include legs. It is commonly used in medium to high airflow systems with high product loading. This unit is frequently used to replace a cyclone and baghouse combination. This unit is also used in high pressure and high vacuum applications typical of those used in pneumatic conveying systems (14.9 PSI max. pressure or 17 Hg max. vacuum.) The bottom of the collector discharges into a barrel, airlock, screw conveyor, or other mechanical device to move the collected product to another area of the plant. This type of unit frequently has a positive displacement blower that is used to move air through the unit in either a pressure or vacuum application. Fog An aerosol of fine water droplets in a gas. FPM Feet Per Minute Fume An aerosol of fine particles formed by the condensation of vapors of solid materials. Gasket (Filter) Material used to prevent air leakage between filter media surface and its holding device.

4 HEPA Housing Impingement Inches of Water Gauge (in. w.g.) Inertia Interception Interstitial Velocity IV Laser Particle Counter Live Load Magnehelic Media area Median Efficiency Micron Outlet Velocity High Efficiency Particulate Air (filter). Device used to hold filter. The process in which particles are removed from an airstream because of their inertia. As air containing a particle flows toward a filter fiber or other collecting surface, the particle does not follow the air streamlines because of its inertia. Instead it moves in a straight line colliding with the filter fiber or surface to which it may become attached. A unit used in measuring pressures. The equivalent measurement in SI is Pascal s, 1 in, w.g. = Pascals (Pa). ( Also referred to as inches of water column, W.C.) The tendency of a body in motion to move in the same straight line unless acted upon by some external force. The process in which a particle is removed from an air stream as it follows the streamlines around a fiber. The particle comes in contact with a fiber and stays attached to it. Upward velocity (FPM) between the filter bags. (Max. 300 FPM) Acceptable ranges depend entirely upon the density of the product. The lower the density the lower the acceptable velocity. ACFM of air / (Side L (in.) x Side W (in.) - ((Bag Dia.(in.)/2)Squared) x x # bags) 144sq. in. / sq. ft. 144sq. in. / sq. ft ACFM / 88 x 88 - ((6.2 /2)Sq.) x x 121 = FPM This number will range from 100 FPM to 250 FPM. The acceptable level depends on the product handled. A light fluffy material that will catch a lot of air like cotton balls or whole soybean hulls needs to have a very low number 125 FPM or below. Products such as sand can tolerate the higher velocities. If the velocity is too high for a given product, the collector can be plug filled from the top down because the material cannot drop out from between the bags. Interstitial Velocity A device for measuring the size and quantity of aerosols in the air stream. It depends on the measurement of the amount of light reflected by individual particles. The strength and the coherent nature of light emitted by a laser result in more light being reflected by particles and so allow for the accurate sizing of very small particles. Product weight (Lb.) at the worst case if the dust collector filled to the tubesheet with product. (Do not include unit weight in this number.) Registered trade name for a diaphragm-activated dial gauge for measuring resistance. (Differential Pressure) Gross: The total area of media used in the production of a filter. Net effective: The measure of usable media in a filter. In a series of efficiency tests, the median efficiency is the one which has an equal number of test results higher and lower than it. One millionth of a meter. A micron is more correctly known as a micrometre (m). The velocity of the air in the outlet of the clean air plenum of the dust collector. Air Outlet Velocity (FPM) = (ACFM of air / Sq. Ft. of cross sectional area of outlet) Example: 3800 SCFM / ((8 x 30 ) / (144 sq. in / sq. ft)) = 2280 FPM This number should be maintained below 3250 Feet per Minute.

5 Particle Counter A device for measuring the number and size distribution of particles in a fluid. Penetration A measure, in percent, of the material passing through a filter. Mathematically penetration is 100- Efficiency (percent). If a filter is 98% efficient, its penetration is 2% (100 98). Penetration is used to measure the performance of very high efficiency filters. Photometer A device which measures the mass concentration of an aerosol by the amount of light the aerosol scatters. Pitot Tube A device used to measure the velocity pressure of an air stream by simultaneously measuring its static and total pressures. Velocity pressure is the total pressure minus the static pressure. Velocity of air at standard conditions can be calculated by using the formula V (fpm) 4005 VP (in. w.g.) where: V = velocity of air and VP = velocity pressure from pitot tube readings. Pleated Element Another type of filter media used in a dust collector. Similar to a cartridge type with multiple pleats. Length can be varied to attain wide ranges of air to cloth ratios. Installs in the same manner as a top or bottom load bag and cage assembly. Plenum Chamber An air compartment maintained under positive or negative pressure and connected to one or more distributing ducts. PPM Parts Per Million. Pressure Drop The resistance of a device to the flow of a fluid through it. The pressure drop of a filter is a measure of its resistance to airflow through it. Resistance is measured in inches w.g. in the Inch-Pound system of measurement. It is measured in Pascals in the SI system. ( The higher the number, the more the resistance to flow. A high number could indicate a dirty or plugged filter media.) Pyramidal Hopper A hopper that has a square discharge and relatively equal sides, thus looking like a pyramid when turned upside down. Rated Filter Capacity The specific quantity of air recommended by a filter manufacturer to be handled by a filter. Resistance See pressure drop. SCFM Standard Cubic Feet per Minute (CFM required if at sea level, 70 deg. F., 14.7 PSI) Shipping Weight Dead load less bags and cages, but including dunnage. (Lb.) Side Load See bottom load. Solenoid Valve An electrically actuated valve that controls the compressed air release to open a diaphragm valve in a dust collection application. Square Feet of Cloth See Cloth Area Static Pressure The potential pressure exerted in all directions by a fluid. For a fluid in motion it is measured in the direction normal to the direction of flow. It has the potential to either burst or collapse a duct or other enclosure. Style 1 A dust collector consisting of a clean air plenum, air header, diaphragm valves, blow pipes, solenoid valves, timer box, tubesheet, filter bags (or elements) and cages. This unit can be round, square, or rectangular. Style 2 A style 1 unit with a housing added on the dirty air side of the tubesheet. This unit can be round or square or rectangular. It is commonly referred to as a binvent.

6 Style 3 Tackifier Top Load Trough Hopper Tubesheet Van Der Waals Forces Velocity Venturi A style 2 unit with a hopper added below the dirty air housing section. The hopper can be any shape. It may or may not include legs. This is commonly referred to as a baghouse if it is square or rectangular. Also referred to as a filter receiver if it is round. A substance applied to filter media to increase the retention of dust. It can be applied to the surface of media or throughout its depth. It may be an oil, a pressure-sensitive resin, or a solvent which imparts a tacky surface to the media. When the filter bag and cage assemblies are installed from the top side of the tubesheet. This would be on the clean air side. A hopper on a baghouse that is designed to accept a screw conveyor and has a long, narrow opening for the material discharge. Sometimes referred to as a chisel hopper. The sheet of metal that separates the clean air plenum from the dirty air plenum. This piece has the filter bags and cages or the pleated elements attached to it. The forces of attraction between molecules. The distance traveled in a given time. Air velocity is measured in feet per minute (fpm) or meters per second (m/s) A short tube with a constricted throat that is used under the blow pipe to increase the air volume and energy imparted into the filter media to improve cleaning APCDEF001 I Industrial Accessories Company 4800 Lamar Avenue Mission, KS Sales: Fax: iaccorp@iac-intl.com