This article takes an in-depth look at jet dust collectors.
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The efficiency of pulse jet dust collectors has made them the most widely used type of dust collection system. They require little maintenance, can clean high-density dust-filled air, and have excellent filtration systems. The uses for pulse jet dust collectors include product recovery, dust capturing, filtering explosive media, metalworking chip capturing, central vacuum cleaning systems, and pneumatic conveying.
Pulse jet dust collectors are a special type of baghouse dust collecting system. The term pulse jet dust collector refers to the method that the dust collector uses to clean its filters, which is a reverse jet of air that forces the dust off the fabric of the dust-caked filters. With some types of pulse jet dust collectors, the determination of when to clean the filters is triggered by the differential pressure between the clean and dirty sides of the filters, which is registered by a differential pressure sensor.
Maintaining a clean and contaminant-free air environment is crucial for workplace safety. Pulse jet dust collectors are highly effective for this purpose, capable of capturing particles as tiny as two microns (µ).
Cylindrical pulse jet dust collectors are built to withstand both internal and external static pressures, making them well-suited for explosion protection. They filter various types of dust, including sander dust, fine lint, grain, and cellulose. These collectors can process air media at speeds reaching up to 20 feet per minute (FPM) or 6 meters per minute. The design features a tangential inlet that functions as a cyclone, spinning the air to direct heavier particles towards the wall and into a collection bag.
One distinct type of pulse jet dust collector is the offline system, where the system’s inlets and outlets are sealed to halt the flow of contaminated air. Once sealed, a pulse valve releases compressed air into blowpipes positioned above the vertical bags. Additionally, a pneumatic damper system is employed at both the inlet and outlet to prevent air flow.
The pulses of air are released at 0.1-second intervals to supply a burst of air to clean the filter bags. The complete process takes approximately 30 seconds, after which the pneumatic dampers reopen. The offline cleaning system is used for coal-fired boilers and municipal waste incinerators. It allows for thorough and continuous cleaning of the bag filters to achieve low emissions.
Modular pulse jet dust collectors offer flexibility by allowing the addition or connection of multiple units to expand filtering capacity as needed. They feature a hopper inlet equipped with a deflector plate or baffle to capture heavier particles, which then fall directly into a hopper or bag. This design minimizes the dust's contact with the filter bags, reducing abrasion, lowering pressure drop, and extending the lifespan of the filter bags.
Air box pulse jet dust collectors are a common type of baghouse dust collector that draws air into the system, where a baffle at the inlet captures larger particles. One method for cleaning filters is backflushing, which employs air, chemicals, or water. Some air box pulse jet dust collectors integrate both backflushing and pulse jet cleaning methods to enhance the efficiency of filter cleaning.
The integration of backflushing and pulse jet cleaning methods boosts the dust collector's effectiveness and extends the lifespan of the filter bags. Air box pulse jet dust collectors are highly reliable and can be customized to meet the requirements of various dust and gas characteristics.
Cartridge pulse jet dust collectors feature a horizontal design that offers a smaller footprint and compact form. These collectors provide exceptional filtration performance, capable of capturing particles as small as 0.5 microns with 99.99% efficiency. The filters are cleaned with pulses while the system remains operational. Cartridge systems are ideal for handling dry, free-flowing powders, dust, and fumes.
In a bin vent pulse jet dust collector, dust-laden air is introduced from the bottom, where it collects on the surface of bag filters. A burst of air from a Venturi tube dislodges the accumulated dust, which then falls through the open bottom. These collectors maintain a constant pressure regulated by an electronic timer and can handle grain loads up to 100 grains per cubic foot.
Bin vent pulse jet dust collectors require minimal maintenance due to their few moving parts. When bulk materials are discharged into a silo, heavier particles settle at the bottom, while finer dust particles rise towards the bin's vent. To comply with Environmental Protection Agency (EPA) standards, these dust particles must be removed before the air is released.
A fume pulse jet dust collector is a cartridge-style system designed with the fume inlet located at the bottom. It is specifically engineered to manage fine and light dust applications. The particulate matter captured by these collectors is sub-micrometer in size, often measured in nanometers (1/1000th of a micrometer). This precision allows fume pulse jet dust collectors to effectively remove even the smallest particulate matter from gas streams.
Due to their function, fume pulse jet dust collectors must be equipped with a spark baffle to ensure safe operation.
The filter in a pulse jet dust collector is crucial for completing the dust collection process. Filters are constructed from various materials depending on the type of mechanism and the media being filtered. As dust comes into contact with the filter, it accumulates on the outside of the bag while air passes through.
The cleaning process for pulse jet dust collector filters can occur online while the filtration mechanism is still operating or offline during a pause in the filtering process. Filter bags for pulse jet dust collectors may be made of paper or fabric.
Cartridge systems in pulse jet dust collectors feature round, pleated filters designed to maximize surface area within a compact space. These filters are usually crafted from paper materials such as cellulose, polyester, or a blend of these fibers.
Bag filters are a prevalent choice for pulse jet dust collectors. These filters operate by accumulating dust on their outer surface. Periodic bursts of compressed air are used to dislodge the collected dust, which then falls into a collection hopper. The timing of these air pulses can be controlled either by a preset timer or in response to pressure drops.
The pressure drop system activates only when the dust layer reaches a specific thickness that creates enough resistance to trigger the controller. Additionally, the compressed air pulse generates a shockwave and ripple effect on the filter bag's surface, enhancing the cleaning efficiency by the pulse jet mechanism.
Filters for high-temperature pulse jet dust collectors are designed to handle environments where temperatures can reach up to 400°F (204°C). These filters are essential in industries dealing with extremely hot dust. Typically, high-temperature applications require cooling the dust before it enters the collector. However, using high-temperature filters eliminates the need for this cooling step, streamlining the dust collection process.
The choice of filter material is based on the characteristics of the media being filtered, as different materials are suited to various types of air streams. Additionally, filters may be either woven or non-woven, which also influences the selection criteria.
Fiberglass pulse jet bag filters are suitable for environments with corrosive gases or high temperatures up to 500 °F (260 °C). They offer outstanding resistance to a wide range of chemicals. These filters are non-absorbent, non-combustible, and maintain excellent dimensional stability.
PTFE filters are capable of withstanding temperatures as high as 500 °F (260 °C). They offer exceptional resistance to oxidation, chemicals, UV rays, and mildew. However, a significant drawback of PTFE filters is their high cost.
PPS felt is known for its high-temperature filtration capabilities and excels in alkaline environments with excellent chemical resistance. This durable, abrasion-resistant material is suitable for use in temperatures up to 374 °F (190 °C). PPS filters are commonly utilized in various industrial applications, including coal-fired boilers, waste incinerators, fluidized bed reactors, cement production facilities, and metal smelting operations.
Aramid fibers are ideal for high-temperature settings because of their abrasion resistance and capability to withstand temperatures up to 400 °F (205 °C). They offer excellent flame resistance and thermal stability. Aramid is available in both felted and woven forms, and can be produced as either filament or staple fibers.
The main quality of polypropylene that makes it ideal for pulse jet dust collectors is its smooth surface that easily releases caked dust. The material is resistant to abrasion and static buildup but has a low operating temperature of 194 °F (90 °C).
Polyester filters operate effectively within a temperature range of 266 °F to 302 °F (130-150 °C). They offer good resistance to oxidation but have limited tolerance to acids and alkalis. While polyester filters excel in resisting solvents, they are prone to degradation from water and acids such as nitric, sulfuric, and carbonic. Hydrolysis at elevated temperatures can also affect their performance.
Homopolymer acrylic filter bags are constructed from needle-felt acrylic, offering robust abrasion resistance, energy absorption, and moisture-related heat hydrolysis properties within a temperature range of 260 °F to 275 °F (127 °C to 135 °C). To extend their lifespan, these filters may be treated with a coating of calcium carbonate or a thin Teflon layer. They are primarily used for filtering processes involving both ferrous and nonferrous metals.
Filter bags are supported by wire cages featuring 10, 12, or 20 vertical wires. These cages are available in both top-loading and bottom-loading configurations. The collar on the cage ensures the bag is held firmly. Cages typically have diameters ranging from 4 inches to 7 inches, with wire thicknesses between 9 gauge and 11 gauge. Bottom-loading cages have split collars and share the same diameter and metal gauge specifications as their top-loading counterparts.
The core components of a pulse jet baghouse dust collection system include the filter bag assembly, blow pipe, and hopper. These systems are designed to separate dust particles from the air, ensuring that the air is purified and cleansed.
As dust accumulates on the outside of the filters in a filtration system, it forms a layer that needs to be removed to maintain optimal performance. Pulse jet dust collectors address this by using bursts of compressed air to blow off the accumulated dust, allowing the filtration system to continue functioning efficiently.
Dust-laden air is introduced into the dust collector through the inlet, located on the left side of the diagram below. As the air flows into the collector, its velocity is reduced due to the increased volume. This decrease in velocity allows larger particles to settle and drop into the hopper positioned beneath the dust collector. In certain pulse jet dust collectors, a baffle plate within the inlet directs the larger particles into the hopper, enhancing the separation process.
Once the larger particles are removed, the remaining dust-laden air passes through the filter bags, which trap the particulate matter on their surfaces.
As the dust-laden air ascends through the filters, dust particles are collected on the exterior of the filter bags, allowing clean air to be released. The grey section in the diagram below illustrates the filter bags within the filtration system.
As the air moves upward, the bag filters capture the finer dust particles, allowing only clean air to pass through. Ultimately, the purified air is expelled through the outlet of the dust collector.
Pulse jet valves are indirect solenoid valves that are energized when air is trapped in their diaphragm, causing a pressure difference that forces the diaphragm to suddenly open. When air passes back into the chamber, the new air pressure balance de-energizes and closes the valve. The opening and closing of the diaphragm happen in quick pulses during bag filter cleaning.
Differential pressure is a key metric used to monitor the performance of a pulse jet dust collector. As dust accumulates on the filter surfaces, it increases resistance to airflow. To assess this resistance, a differential pressure reading is taken between the dirty and clean sides of the filter; typically, the pressure is lower on the dirty side.
When the pressure reaches a high threshold, compressed air is discharged through the Venturi valve to clean the filters. In automated systems, a differential pressure sensor notifies operators of any issues with the cleaning process.
As dust-laden air passes through the filter bags, a significant buildup of dust accumulates on the outside, increasing resistance and reducing efficiency. To maintain the filter’s performance and extend its lifespan, regular cleaning of the clogged filters is necessary.
One common method for cleaning bag filters is using compressed air jets. This can be triggered manually, by a pressure sensor, or by a timer. In all cases, a solenoid valve and compressed air header release short bursts of air, creating shock waves that dislodge the accumulated dust. These pulses, lasting only a few seconds, move in the opposite direction of the airflow, causing the dust to fall into the hopper.
The air bursts are delivered through a Venturi valve, a cone-shaped device positioned at the top of the tubular filters. The Venturi creates a negative pressure at its top, which helps pull additional air into the filter walls during the pulsing process.
The diagram below shows how the Venturi valve inside the bag cage expels air pulses to remove the dust particles adhering to the filters.
With increasing regulations on air quality, growing manufacturer concerns, and a heightened focus on environmental issues, pulse jet dust collectors have become more popular and widely used. Their most notable advantage is their ability to maintain continuous operation while the filter bags are being cleaned.
Pulse jet dust collectors now account for about 50% of all dust collectors in use. Effective filter cleaning is crucial for maintaining good air quality and optimizing collector performance, and the pulse jet system's precise cleaning capabilities make it one of the most efficient methods available.
The streamlined design of a pulse jet dust collector enhances performance, reduces maintenance needs, and extends equipment life. Rapid valve actuation ensures effective cleaning of bag filters while minimizing compressed air consumption. Some valves are capable of enduring up to one million cycles.
Maintaining a clean and hazard-free work environment is crucial for a company's success. It ensures worker safety and promotes good health. The pulse jet dust collector's efficient air purification process helps keep the work area free from contaminants, safeguarding both employees and equipment.
A clean and organized workspace is essential for efficient project completion. Dust and debris can impede production, spread rapidly, and infiltrate machinery, potentially causing malfunctions. Pulse jet dust collectors address these issues by continuously removing dust and ensuring a steady flow of clean air, thereby enhancing productivity and equipment reliability.
Manufacturing processes often produce air pollutants that must be controlled according to guidelines set by the Environmental Protection Agency (EPA), which has identified five major air pollutants for regulation.
Pulse jet dust collectors are engineered to capture and eliminate pollutants from the air in manufacturing and production environments.
The chart below illustrates air quality using a numerical index ranging from 0 to 500. Higher index values indicate greater health risks, with an index of 300 or above denoting hazardous air quality.
| Air Quality Index for Ozone Levels and Particulate Pollution | |||
|---|---|---|---|
| Daily AQI Color | Level of Concern | Values of Index | Description of Air Quality |
| Green | Good | 0 to 50 | Air quality is satisfactory, and air pollution poses little or no risk. |
| Yellow | Moderate | 51 to 100 | Air quality is acceptable. However, there may be a risk for some people, particularly those who are unusually sensitive to air pollution. |
| Orange | Unhealthy for Sensitive Groups | 100 to 150 | Members of sensitive groups may experience health effects. The general public is less likely to be affected. Some members of the general public may experience health affects; members of sensitive groups may experience more serious health effects. |
| Red | Unhealthy | 151 to 200 | Some members of the general public may experience health affects; members of sensitive groups may experience more serious health effects. |
| Purple | Very Unhealthy | 201 to 300 | Health alert: The risk of health effects is increased for everyone. |
| Maroon | Hazardous | 301 and higher | Health warning of emergency conditions: everyone is more likely to be affected. |
Manufacturers of pulse jet dust collectors are well-versed in air quality regulations and continually enhance, design, and adapt their products to comply with EPA standards.
Dust poses significant challenges not only to employees and machinery but also to the quality of products, particularly in sensitive areas like electronics and technical devices. Maintaining high air quality standards is crucial for enhancing product quality and ensuring that the final output meets the manufacturer's specifications.
Pulse jet dust collectors and filters can be tailored to meet the specific needs of different manufacturing environments. Each production facility has unique requirements based on its location, the type of dust generated, and local regulations. The adaptability of pulse jet dust collectors ensures they can be customized to address any particular conditions.
Some systems may need fire suppression features, while others might prioritize handling high air volumes. Regardless of the specific requirements, pulse jet dust collectors can be adjusted and configured to meet various demands.
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