Performance of Dust Removal Filter shared from filter sleeve manufacturer-INDRO FILTRATION

The performance of dust removal filter mainly involves filtration speed, dust removal efficiency, filtration resistance and dust removal methods.

Filtration speed is one of the main factors affecting the performance of filter dust collector. The filtration rate is calculated by the following formula:

v=Q/60×A

In formula:

V - Filtration speed, m/min

Q-Filtration Dust Collector Processing Gas Volume, m3/h

A-Filtration area of filter material for dust removal filter, m2

It is generally believed that the true velocity (Vp )of gas passing through the filter layer is as follows:Vp=v/εp

In formula:

Vp－Real speed of filtration through the filter layer, m/min

εp－The average voidage of dust layer is generally 0.8-0.95.

In the actual operation process, the filtration speed is determined by the type of filter material, the size of dust particle size, the physical and chemical properties and the way of ash removal. High filtration speed will increase the pressure difference between the two sides of the filter material, squeeze the fine dust which has been attached to the filter material, so that the filtration efficiency can not reach the prescribed discharge value or wear the single fiber of the filter material, especially accelerating the damage of the glass fiber filter material. If the filtration speed is small, the volume of the dust collector will be increased, thus the investment will be increased. Table 2-1 lists the filter speed design reference values of bag filter.

Table2-1 Design Reference Value of Filtration Speed of Bag Dust Collector (m/min)

Dust species	Dedusting method
	Combination of shaking and Adverse airflow	Pulse jet	Reverse air blow
Talc powder, coal, sand blasting cleaning dust, fly ash, ceramic firing dust, carbon black, pigments, kaolin, limestone, sand dust, tin ore, cement (from cooler), enamel firing	0.7～0.8	2.0～3.0	0.6～0.9
Sublimation of ferroalloy, cement discharged from casting dust, alumina, ball mill, sublimation of carburizing furnace, lime, corundum, powder and other fertilizer production, plastics, starch	0.5～0.75	1.5～2.5	0.45～0.55
Sublimates of carbon black, silicon oxide, tin and zinc, and other aerosols, cosmetic powder, detergent powder, milk powder, activated carbon and cement formed by condensation and chemical reaction in gases, etc.	0.45～0.5	0.8～2.0	0.33～0.45
Tobacco, Leather Powder, Mixed Feed, Dust from Wood Processing, Crude Vegetable Fiber (Casuarina, Jute, etc.)	0.9～2.0	2.56～0.6
Asbestos, fibre dust, gypsum, pearlite, rubber production dust, salt, flour, grinding process dust	0.3～1.1	2.5～4.5

Principle of filtration and dust removal shared from INDRO FILTRATION-filter bag manufacturer

The settling mechanism of dust particles, such as inertial collision, interception, diffusion, gravity and electrostatic force, is the theoretical basis for analyzing the mechanism of filter dust.

The filtration process of the filter is very complicated.

Generally speaking, the sedimentation of dust particles on the trap, i.e. separation and filtration, is not only the result of one sedimentation and filtration mechanism, but also the result of the combined action of various sedimentation and separation and filtration mechanisms.

According to the different mechanical characteristics of the movement of dust with different particle sizes in fluids, the mechanism of filtration and dust removal involves the following aspects:

1.1.1 Screening

The mesh of filter material is usually 5-50 micron. When the particle size of dust is larger than mesh or pore diameter or when the dust deposits in the inter space between the particles, the dust will be blocked.

For the new fabric filter material, because the pore size between the fibers is much larger than the particle size of the dust, the screening effect is very small, but when a large amount of dust deposits on the surface of the filter material to form a dust layer, the screening effect is significantly enhanced.

1.1.2 Inertial Collision

Generally, the dust with larger particle size is mainly trapped by inertial collision. When the dust-laden airflow approaches the filter material, the airflow will bypass the fiber, and the larger particles (larger than 1 micron) will deviate from the airflow line due to inertia, continue to move along the original direction of motion and impact on the fiber and be trapped.

All the large dust particles in the critical line of dust trajectory can reach the surface of the fiber and be trapped.

The inertial collision effect increases with the increase of particle size and airflow velocity.

Therefore, the inertial collision can be improved by increasing the flow rate through the filter material.

1.1.3 Interception

When the dust-laden airflow is close to the filter material fiber, the finer dust particles flow with the airflow. If the radius of the dust particles is larger than the distance between the center of the dust particles and the edge of the fiber, the dust particles will be intercepted because of the contact with the fiber.

1.1.4 Diffusion

For dust particles less than 1 micron, especially sub-micron particles less than 0.2 micron, they break away from streamline under the impact of gas molecules and make Brownian motion like gas molecules. If they are in contact with fibers during the movement, they can be separated from the airflow. This effect is called diffusion, which increases with the decrease of flow rate and the diameter of fibers and dust.

1.1.5 Electrostatic Action

Many fiber-woven filter materials, when air flows through, will produce static electricity due to friction, while dust will be charged due to friction and other reasons in the transport process, which will form a potential difference between the filter material and dust particles. When dust tends to filter material with air flow, due to the Coulomb force, dust and filter material fibers collide and enhance the adsorption of dust by the filter material. Force is captured to improve the efficiency of capture.

1.1.6 GRAVITY SETTLEMENT

When the slowly moving dust-laden airflow enters the dust collector, the dust particles with large particle size and density may naturally settle due to gravity (see follow Table1-1).

Table1-1

Particle size range of various trapping mechanisms

Serious No.	Mechanism	particle size range	Effect of Wind Speed Increase on Mechanism Efficiency
1	Interception	>1μm	reduce
2	Inertial collision	>1μm	improve
3	diffusion	<0.01～0.5μm	reduce
4	Electrostatic Action	<0.01～5μm	reduce
5	Screening	> Micro pore size of filter layer	reduce

Generally speaking, various dust removal mechanisms are not effective at the same time, but one or several combined functions.

Moreover, with the change of the void, airflow velocity, dust particle size and other reasons, the effects of various mechanisms on the filtration performance of different filters are also different.

In fact, when the new filter material starts to filter dust, the efficiency of dust removal is very low. After using for a period of time, the coarse dust will form a layer of dust on the surface of the filter cloth.

The effects of various mechanisms on the filtration performance of different filters are also different due to the changes of the voids, airflow velocity, dust particle size and other reasons. In fact, when the new filter material starts to filter dust, the efficiency of dust removal is very low. After using for a period of time, the coarse dust will form a layer of dust on the surface of the filter cloth. Because of the dust filtering effect of the initial layer of dust and the dust layer gradually accumulated on it, the filtering efficiency of the filter material is continuously improved, but the resistance is also correspondingly enhanced.

When cleaning ash, the primary layer should not be destroyed, otherwise the efficiency will decrease. The structure of dust initial layer plays a very important role in the efficiency, resistance and ash removal effect of bag filter.

PP pleated filter cartridge-size, materials, making process

PP pleated filter cartridge is constructed by 100% polypropylene media providing a wide range of chemical compatibility.

PP pleated cartridge made of 2-3 layers of membranes. The multi layer membrane structure enables graded filtration pore size and increase the dirt holding capacity of the cartridge.

With rigid outer cage and strengthened inner core, the pp pleated filter cartridge can hold higher operating pressure.

Polypropylene filter cartridges are precisely manufactured for use in critical filtration applications within food, pharmaceuticals, biotech, dairy, beverages, brewing, semiconductor, water treatment & other demanding process industries.

Technical Specification:

Size: 10”, 20”, 30”, 40”
Fitting: DOE/Code-7/Code-3
Micron Rating: 0.1,0.2,0.45,1,5,10,20,50
MOC: PP/PTFE/PES/PVDF
Gasket: Silicon, EPDM, Viton, Buna-N
Outer Diameter: 69mm(2.5”)
Inner Diameter: 28 mm

About production process of pp pleated filter cartridges:

-Making cartridge pleats: Using filter paper pleating machine to make filter cartridges pleats

-Length cutter/controller: Using filter cartridge length cutter to cut/trim off the pleats.

-Welding middle seam: Using middle seam welder to do middle seam thermal welding of filter cartridges paper

-Cartridge shaping: Putting filter membrane with correct length into the outer cage (plastic shell) with inner core inside of the membrane to keep pleated filter cartridge have initial shape.

-End cap welding: Using cap welder to welding cap onto both ends of filter cartridges

-Fitting end welding: using pleated filter cartridge fitting end welder to weld different types of fitting ends together with both ends of pleated cartridges and form one complete piece of pleated filter cartridges. The different ends types include: flat cover, fin, DOE215/220/222/226, M20/30 thread and other.

-Length jointing/connecting: for 20”/30”/40” long pleated filter cartridges, normally using pleated filter cartridge length connecting welder to weld  2/3/4 pieces of 10” pieces together to complete 20”/30”/40” long pleated filter cartridges.

Video list:

1.    making cartridge pleats

2.      cartridge pleats length cutting

3.      welding middle seam

4.      cartridge cap welding

5.      cartridge fitting end welding

6.      cartridge length connector welding

Fabric filters

Fabric filters

Commonly known as bag houses, fabric collectors use filtration to separate dust particulates from dusty gases. They are one of the most efficient and cost-effective types of dust collectors available, and can achieve a collection efficiency of more than 99% for very fine particulates.

Dust-laden gases enter the bag house and pass through fabric filter bags that act as filters. The filter bags can be of woven or felted cotton, synthetic, or glass-fiber material in either a tube or envelope shape.

Pre-coating

To ensure the filter bags have a long usage life they are commonly coated with a filter enhancer (pre-coat). The use of chemically inert limestone (calcium carbonate) is most common as it maximizes efficiency of dust collection (including fly ash) via formation of what is called a dust cake or coating on the surface of the filter media. This not only traps fine particulates but also provides protection for the filter bag itself from moisture, and oily or sticky particulates which can bind the filter media. Without a pre-coat the filter bag allows fine particulates to bleed through the bag filter system, especially during start-up, as the bag can only do part of the filtration leaving the finer parts to the filter enhancer dust cake.

Parts

Fabric filters generally have the parts of clean plenum, dusty plenum, filter bag, filter bag cage, venturi assembly, tube-plate, RAV/SCREW, compressed air header, blow pipe, housing and hoppe.

Types of bag cleaning

Bag houses are characterized by their cleaning method: shaking, reverse air, pulse jet and sonic bag filters.

Shaking bag filter (bag house)

A rod connecting to the filter bag is powered by a motor. This provides motion to remove caked-on particles. The speed and motion of the shaking depends on the design of the bag and composition of the particulate matter. Generally shaking is horizontal. The top of the filter bag is closed and the bottom is open. When shaken, the dust collected on the inside of the filter bag is freed. During the cleaning process, no dirty gas flows through a bag while the bag is being cleaned. This redirection of air flow illustrates why bag houses must be compartmentalized.

Reverse air bag filter (bag house)

Air flow gives the filter bag structure. Dirty air flows through the bag from the inside, allowing dust to collect on the interior surface. During cleaning, gas flow is restricted from a specific compartment. Without the flowing air, the bags relax. The cylindrical filter bag contains rings that prevent it from completely collapsing under the pressure of the air. A fan blows clean air in the reverse direction. The relaxation and reverse air flow cause the dust cake to crumble and release into the hopper. Upon the completion of the cleaning process, dirty air flow continues and the filter bag regains its shape.

Pulse jet bag filter (bag house)

This type of bag house cleaning (also known as pressure-jet cleaning) is the most common. A high pressure blast of air is used to remove dust from the filter bag. The blast enters the top of the filter bag tube, temporarily ceasing the flow of dirty air. The shock of air causes a wave of expansion to travel down the fabric. The flexing of the filter bag shatters and discharges the dust cake. The air burst is about 0.1 second and it takes about 0.5 seconds for the shock wave to travel down the length of the filter bag. Due to its rapid release, the blast of air does not interfere with contaminated gas flow. Therefore, pulse-jet bag houses can operate continuously and are not usually compartmentalized. The blast of compressed air must be powerful enough to ensure that the shock wave will travel the entire length of the filter bag and fracture the dust cake. The efficiency of the cleaning system allows the unit to have a much higher gas to cloth ratio (or volumetric throughput of gas per unit area of filter) than shaking and reverse air bag filters. This kind of filter thus requires a smaller area to admit the same volume of air.

Sonic bag filter (bag house)

The least common type of cleaning method is sonic. Shaking is achieved by sonic vibration. A sound generator produces a low frequency sound that causes the filter bags to vibrate. Sonic cleaning is commonly combined with another method of cleaning to ensure thorough cleaning.