Structure and Working Principle

The pulse jet bag filter consists of several key components:

• Cleaning system
• Sealed dust chamber
• Main frame
• Dust hopper
• Electrical control system for operation

Role of the Dust Collector Filter Bag

In the operation of the pulse jet bag filter, dusty gas flows through the dust collector filter bag. The gaps between the filter fibers trap particles larger than the gap diameter. Dust sticks to the filter surface during this process. This method is called screening.

Initially, new filter bags have larger gaps between the fibers. This results in less effective dust removal. After some time, a significant layer of dust builds up on the bag surface. This enhances the screening effect. After the dust cleaning process, some residual dust remains on the surface and inside the filter bag. This allows the filter to maintain good dust removal efficiency. Materials like needle-punched felt or plush filter fabric create a dense, porous layer. This optimizes the screening effect without relying only on the dust layer.

Dust Cleaning Process

The dust cleaning of the filter bags is achieved through compressed air. The cleaning system consists of an air reservoir, blowing pipes, and electromagnetic pulse control valves. Each row of filter bags is equipped with a blowing pipe at the top, aligned with a nozzle that faces the center of the filter bag. Each blowing pipe has a pulse valve connected to the compressed air reservoir.

During the dust cleaning process, the electromagnetic valve opens the pulse valve. This allows compressed air to flow through the nozzle toward the filter bag. The air, along with surrounding gas, enters the filter bag. This causes the bag to vibrate and creates reverse airflow from the inside out. As a result, dust is effectively removed from the outer surface of the bag.

The pulse jet cleaning method generates the most energy for dust removal. It is a typical external cleaning approach. This method provides strong cleaning power and leaves minimal residual dust within the filter bag fibers. The filter bag is usually made from felt or needle-punched fabric. The pulse jet action causes significant deformation of the filter bag, generating substantial stress. Therefore, the filter material must have high tensile strength. Additionally, the frequent friction between the filter bag and its support frame requires durable materials, such as wear-resistant or woven filter bags.

Types of Cleaning Methods

Bag filters can be classified into three types based on their cleaning methods:

1.Mechanical Vibration Type

• The mechanical vibration type features a simple structure and reliable operation; however, its cleaning effect is relatively weak and prone to damaging the filter bags. Consequently, this cleaning method is becoming less common.

2.Reverse Jet Type

• The reverse jet type can be further divided into chamber reverse jet and nozzle reverse jet.

• Chamber Reverse Jet: This design employs a chamber structure to introduce clean gas from the atmosphere or the dust collection system into different bag chambers for cleaning. However, its cleaning efficiency is low, and the investment cost is relatively high.

• Nozzle Reverse Jet: This type uses a high-pressure fan or compressor to provide reverse airflow, cleaning through a moving nozzle. While it offers strong cleaning capabilities, it is complex and costly, with a high risk of damaging the filter bags.

3.Pulse Jet Type

• The pulse jet type can be categorized based on the pressure of the blowing air into low-pressure (below 0.25 MPa), medium-pressure (0.25 MPa to 0.5 MPa), and high-pressure (above 0.5 MPa) categories. Additionally, it can be divided into rotating pulse jet and inline pulse jet types.

• Rotating Pulse Jet Type: This type features a modular structure, allowing for online or offline cleaning. It has fewer pulse valves and operates reliably, but its complexity requires strict installation and maintenance.

• Inline Pulse Jet Type: Also known as pipe jet pulse filters, these have the blowing pipes fixed within the upper casing of the dust collector. Each pulse valve's blowing pipe typically has multiple nozzles aimed at the filter bags below, allowing for efficient pulse jet cleaning. Its advantages include a simple structure, fewer moving parts, low failure rates, and reliable operation. It allows flexible design of filter bag distribution based on process requirements, with low operating costs. It also utilizes compressed air to ensure sufficient cleaning pressure at the bottom of the filter bags. The overall cost is low, with compartmentalized bag filters enabling online maintenance. However, this type requires a larger number of pulse valves.

Factors Affecting Efficiency

Several factors influence the efficiency of the pulse jet bag filter:

• Dust Characteristics: The size and density of particles affect filtration performance.

• Filter Material Quality: The quality of the materials directly impacts overall performance.

• Airflow Velocity: Proper settings can significantly enhance capture rates.

• Design: A well-planned layout for inlets and outlets helps avoid inefficiencies.

• Cleaning Method: Effective cleaning is crucial for maintaining filter bag performance.

Importance of Maintenance

Regular inspections are essential for achieving optimal operation of the pulse jet bag filter. Maintaining the dust chamber, tightening screws to prevent leaks, and periodically replacing worn seals all contribute to extending the equipment's lifespan.