Cartridge Dust Collector : Key Points for Selection, Design, and Fabrication

Part 1: Design Principles and Core Components

01 Working Principle

A cartridge dust collector works mainly by filtration and separation.

First, dusty gas enters the collector housing through the inlet.

Then, for pre-separation, some large particles fall into the hopper due to gravity or inertia when the airflow changes direction.

Next, the gas passes through the filter cartridges. The filter media traps dust particles on its surface or within its depth.

• For new cartridges, deep bed filtration occurs inside the fiber matrix.

• After a dust cake forms, surface filtration begins. This dust layer acts as a highly efficient filter. Alternatively, membrane-coated filter media provides direct surface filtration.

After filtering, the clean air flows upward through the cartridge’s inner channel. It then moves into the clean air plenum and exits through the outlet.

Later, when the pressure drop reaches a set value, the cleaning system activates. Pulse-jet cleaning is the most common method.

• The pulse valve releases compressed air instantly.

• This air travels through a venturi tube, which induces surrounding clean air into the cartridge.

• Inside the cartridge, the air expands rapidly, creating shock waves and vibration.

• Consequently, these shock waves dislodge the dust cake from the cartridge’s outside surface. The dust then falls into the hopper.

Finally, the collected dust is discharged regularly or continuously by a rotary valve, screw conveyor, or other discharge device.

02 Core Components

• Housing: We fabricate the housing from steel plates. It includes the dirty air chamber, clean air plenum, and hopper. The structure must be strong, sealed well, and corrosion-resistant.

• Filter Cartridges: These are the core components.

  • Filter Media: Common materials are polyester, polypropylene, PPS, or PTFE. A PTFE membrane coating provides high efficiency and easy cleaning.

  • Structure: They have a pleated design for a large surface area. Key parts are the inner and outer support cages, end caps, and sealing gaskets.

  • Dimensions: Standard diameters are 324mm or 350mm. Common lengths are 600mm, 660mm, 750mm, 1000mm, and 1200mm.

• Tube Sheet: This thick steel plate separates the dirty and clean air chambers. Cartridges seal tightly into the tube sheet holes using gaskets. It must be flat and precise.

• Cleaning System:

  • Pulse Valves control compressed air release.

  • The Air Receiver Tank stores air to ensure strong pulse pressure.

  • The Blowpipe is in the clean air plenum. It has nozzles aligned with each cartridge, often with venturis.

  • Venturi Tubes increase induced air for better cleaning.

  • The Control Cabinet manages the pulse sequence, interval, and duration.

• Compressed Air System: This system provides cleaning power. It includes an air compressor, dryer/filter, pipes, and pressure regulator.

• Hopper and Discharge Device: The hopper collects dust. A discharge device, like a rotary valve or screw conveyor, removes it.

• Inlet and Outlet: We design these with baffles for even airflow. This protects the cartridges.

• Differential Pressure Gauge: This instrument monitors pressure drop across the cartridges. It shows when cleaning is needed.

• Safety Devices: These include explosion vents, access doors, and safety platforms.

Part 2: Design Key Points

First, determine the air volume (Q). This is the foundation for selection. Calculate the total air volume from all dust sources. Remember to add 10%-15% for air leakage.

Next, select the filtration velocity (Vf). This speed greatly affects size, cost, and filter life.

• Choose a lower velocity for fine, sticky, or moist dust.

• Choose a slightly higher velocity for coarse, dry, and free-flowing dust.

• Typically, keep Vf between 0.6 and 1.0 m/min for most applications. A conservative choice extends cartridge life.

Then, calculate the required filtration area (A). Use the formula: A = Q / (60 × Vf).

• Find the number of cartridges (N) by dividing the total area (A) by the area of one cartridge (A₁).

• Round up this number for the final count.

After that, determine the model and size.

• Design the housing based on cartridge count, length, and spacing.

• Ensure the hopper has enough capacity and a steep slope (≥60°).

• Design the inlet with baffles for even airflow and to prevent direct dust impact on cartridges.

Now, design the cleaning system.

• Set the pulse pressure between 0.4 and 0.6 MPa.

• Set the pulse duration between 0.1 and 0.2 seconds.

• Adjust the pulse interval to balance pressure drop and energy use.

• Select pulse valves based on the number of cartridges per valve.

• Ensure the air receiver tank is large enough to maintain stable pressure during pulses.

Also, calculate the system resistance. Estimate the pressure drop for fan selection.

Furthermore, select appropriate materials.

• For the housing/hopper: Use carbon steel with coating, stainless steel for corrosion, or PP/FRP for strong acids.

• For filter media: Select material based on temperature, humidity, and chemical resistance.

Finally, consider safety design. For explosive dusts, include explosion vents, anti-static filter media, grounded construction, and flame arresters. Follow ATEX/NFPA standards.

Part 3: Fabrication Key Points

For cutting and forming, cut steel plates with high precision using laser or plasma. Ensure bending is accurate.

For welding,

• Certified welders must perform all welding.

• Use full, continuous welds for strength and seal.

• Control distortion to keep the housing square and the tube sheet flat.

• Remove all slag and spatter after welding.

For tube sheet machining, ensure high precision for hole location and diameter. Maintain flatness within tolerance (e.g., ≤ 3mm/m).

During assembly,

• Follow the drawings strictly.

• Ensure all housing parts connect tightly. Use seals between flanges.

• Install the tube sheet level and secure it firmly.

For sealing,

• Seal all access doors, flange connections, and the tube sheet-housing joint. Use proper gaskets and sealant.

• Perform a leak test before shipping.

For anti-corrosion treatment,

• Clean surfaces by blasting to Sa2.5 grade.

• Apply coating evenly to the specified thickness (e.g., ≥120µm).

• Use heavy-duty coatings or linings for harsh environments.

For internal installation,

• Install blowpipes accurately. Nozzles must align with cartridge centers.

• Install venturis correctly.

• Install filter cartridges carefully. Ensure they are vertical and the gaskets seal tightly against the tube sheet. Check for leaks after installation.

For electrical and control systems, wire according to diagrams. Ensure secure connections and proper grounding. Test the control program for proper operation.

Finally, perform factory inspection. Check appearance, dimensions, sealing, pulse cleaning function, and electrical systems.

Summary

Designing and building a cartridge dust collector requires both theory and practice. The key is to understand the operating conditions accurately. Then, choose the filtration velocity and filter media wisely. Also, design the airflow and cleaning system carefully. Finally, ensure high fabrication quality and excellent sealing.

Working closely with experienced manufacturers and engineers is crucial. It ensures the equipment runs efficiently, reliably, and for a long time. Remember: A conservative choice in filtration velocity often leads to more reliable long-term operation.