The design of your pneumatic conveying system should be properly calibrated based on the type of bulk material that your system will convey. As well as this, different types of bulk materials have different fluid dynamics. You should be aware of these so that you can install the proper components and adjust things like the air speed, ensuring that your pneumatic system is optimized for the type of bulk material it’s conveying. This article will run through some of the important things that you should know about bulk materials...but first, what is a bulk material?
What Is Meant By ‘Bulk Material’?
Bulk materials refer to dry solid substances that are typically found in powder, granular or lumpy forms. With a bulk material, the particle components are too small to be counted individually and these materials are typically stored in heaps or within silos. When flowing, bulk materials behave as a fluid, which is why they’re often put through pneumatic conveying systems.
Some examples of bulk materials are:
- Sand
- Gravel
- Cement
- Minerals
- Coal
- Plastic pellets
- Dry pet food
- Grains
- Coffee beans
- Sugar
- Salt
- Flour
Bulk materials cannot be easily transported without proper containers. This is especially true for fine grains or powders. These materials are usually transported in closed or sealed containers to prevent spillage and contamination. However, the most efficient way to transport powdery bulk materials within a factory for processing is through a pneumatic conveying system.
The handling of bulk materials in a factory setting is a very important component of many industrial processes. Industries that process bulk ingredients for food grade products and beverages need efficient, sanitary, and safe systems for conveying bulk materials.
Similarly, industries that process other dry products, such as plastic, rubber, textiles, and paper, have specific designs for their respective bulk material conveying systems and processing machines.
4 Things You Need To Know About Bulk Materials In Pneumatic Conveying
1. Bulk materials are present in many industrial processes
Bulk materials are present almost everywhere, especially when it comes to industrial processes. Approximately 70% of all industrial processes, from mining to dog food manufacturing, involve bulk materials that need to be properly handled. Powdery and light bulk materials are commonly conveyed by pneumatic systems.
Here’s a list of some of the industry sectors that handle bulk materials:
- Agriculture
- Mining
- Construction
- Food processing
- Pharmaceuticals
- Plastic manufacturing
- Paper manufacturing
2. Bulk materials require various types of conveying systems
Different types of conveying systems are used to handle different types of bulk materials. For example, food processing and medicine manufacturing require highly hygienic conveying systems that are free from pathogens and impurities. Meanwhile, the conveying systems for materials like coal typically don’t need to be hygienic or free from impurities.
Depending on the size of the bulk material particles, conveying systems vary in design and components. For instance, conveyor belts are used in ore mining, and the systems themselves are designed to be robust so that they can carry heavy loads and withstand impacts.
While the designs and types of conveying systems are varied, the basic components of bulk material conveying systems are the following:
- Motors: These provide the mechanical drive that conveyors need to move the bulk materials. Motors can either be electric, gas powered, or internal combustion engines. In some designs, the mechanical power is provided by turbines driven by water flow or wind.
- Gears, rollers, or pulleys: These components provide the mechanical advantage that can increase the speed and strength of the conveying system.
- Conveyors: These are what carry the bulk materials. They include large rubber or metal belts, screw conveyors for vertical conveyance of materials, tubular conveyors, moving floors, and pneumatic conveyors.
3. Bulk materials cause wear and tear in pneumatic systems
Bulk materials cause wear and tear on various components in pneumatic conveying systems as they slide down tubes, and especially when they change direction round bends and come into greater contact with the walls of the tubes.
This can lead to impact damage, friction, and abrasive wear. Over time, this causes the pneumatic conveying system to deteriorate as a result of its components sustaining regular damage.
Abrasive bulk materials, such as plastic pellets and powdered minerals, can even cause damage in the pipeline of pneumatic systems. If the bulk material is being conveyed at high speed or air velocity, it can also generate heat, which can impact your system in the following ways:
- Electrostatic buildup
- Cracking and bursting of gaskets
- Deformation and misalignment
- Metal expansion and contraction
You can protect your system against wear by installing abrasion-resistant components. Unlike bare components, where the part itself is in direct contact with the particles being conveyed, abrasion-resistant components are usually encased in a jacket or coating. By doing this, the jacket or coating takes on the brunt of the damage while the component stays safe inside. One of the most common coatings or linings used in conveying systems are ceramic.
4. Two phases in pneumatic conveying
Pneumatic conveying systems can be designed or calibrated based on the type of bulk material. Doing this will optimize your system and safeguard it against certain risks. There are two phases that pneumatic conveying systems can be calibrated to dense phase or for dilute phase.
- Dense phase: This involves conveying tightly packed bulk material particles, such as dog kibble and plastic pellets. With dense phase conveying, the product isn’t suspended in the air because it’s too heavy. Instead, the velocity of the air current is kept at 100kPa or higher so that the product travels in ‘waves’, which causes less abrasion.
- Dilute phase: Here, the bulk material particles are suspended in the air. Dilute phase conveying systems handle lighter and less abrasive materials, such as flour or creamer. These types of bulk materials can be conveyed at higher velocity and pressure because the particles are less abrasive.
