Five Common Applications for Rotary Positive Displacement Blowers

Introduction

For many industries, rotary positive displacement (PD) blowers are considered critical equipment, helping to make processes safer, more efficient, and ultimately more productive.

Blowers work by moving air or gas from one place to another via the use of lobe impellers/rotors. As the blower spins, air or gas is drawn via the blower’s inlet and carried through the casing to the outlet. Rotary positive displacement blowers are significantly stronger than fans and are ideal for applications where steady and precise airflow is required, since they maintain airflow even during pressure changes.

You will find blowers across a wide range of industries and sectors, such as:

  • Power & Energy
  • Food & Beverage
  • Chemical
  • Plastics
  • Wastewater treatment

While they can serve many functions, five common applications for rotary positive displacement blowers are pneumatic conveying, dust collection, aeration, fluidization, and vapor recovery. 

Pneumatic Conveying

PD blowers can be used to move bulk materials through pipes. You can think of them as functioning like an air-based conveyor system, with the air pushing the materials from one end of the pipeline to the other. Common materials transported using pneumatic conveying include whole grains, flour, plastic pellets, and pet food.

In pneumatic conveying, the blower creates a pressure differential in the conveying line to provide the energy needed to move materials along the pipeline. The blower changes the air pressure, which can either create vacuum or pressure and allows the system to transfer materials successfully. 

The gas (typically air) velocity tends to increase along the pneumatic conveying lines as the pressure in the system decreases from the particle pickup point to the destination point. The increasing velocity is what keeps materials suspended and moving.

Rotary positive displacement blowers are excellent for pneumatic conveying because they help to efficiently transfer dry bulk materials at various vacuum levels and pressures. Pneumatic conveying systems rely on fewer mechanical parts and have fewer failures.

Dust Collection

PD blowers are commonly used for dust collection in pneumatic conveying systems. They create the necessary force to carry dust-laden air from the collection point to a dust filter unit. 

The main purpose of dust collection is to remove or collect dust from the air flow inside the conveying pipe in the pneumatic conveying system. This air carries products/ particles such as flour, plastic pellets, whole grains, or pet food. Effective dust collection helps to maintain the minimum air velocity that is required in order to keep the conveyed product/particles suspended and moving towards the dust filter unit and prevent them from settling in the conveyed pipe and clogging it. 

In pressure conveying systems, or push systems, blowers are placed before the dust collector, pushing the air and collected material through the piping to the dust collector or receiving bin.

In vacuum conveying systems, or pull systems, blowers are placed after the dust collector to generate the vacuum on the intake side, pulling air and collecting material through the system. The dust passes through the filter before reaching the blower, preventing abrasion and damage to the blower internals. 

Aeration

PD blowers also play a significant role in wastewater treatment. PD blowers are used by industrial wastewater facilities and municipal wastewater treatment plants for aeration, which is the process of adding oxygen to wastewater to help break down organic waste naturally.

When oxygen is added to wastewater, it encourages the development of aerobic microorganisms. This bacteria feeds on the fats, oils, human waste, and food residues found in wastewater. Aeration blowers help to increase the amount of oxygen in the water, stimulating bacterial growth. 

PD blowers are often the preferred method of treating wastewater because they provide better oxygen distribution and, due to the steady air flow, are considered to be easier to control. The consistency of the air flow also helps to keep the water’s oxygen levels high enough for the bacteria to grow and ultimately perform better. 

Fluidization 

PD blowers can also be used to improve the handling and processing of materials through a process called fluidization. Fluidization is the process by which solid materials temporarily take on fluid-like states by introducing air from below. 

PD blowers supply the consistent, high-volume, low-to-moderate pressure air (or gas) required to levitate and suspend a bed of solid particles, creating a fluidized bed. The PD blower is positioned upstream of the fluidized bed. It draws in ambient air, traps a fixed volume between its rotating lobes or screws, and then discharges this volume against the pressure resistance of the system.

The pressurized air then passes through a distribution plate at the bottom of the bed, creating the uniform upward velocity needed to suspend the solid particles. This process makes it easy to transport, handle, and manage materials, since materials that function as liquids are less likely to cause clogging, are easier to mix, and are easier to transport.

Fluidization is commonly used within the chemical manufacturing, food processing, and material handling industries.

Here are some examples of how fluidization is used:

  • Pneumatic conveying and material transfer: This helps fluidize bulk materials such as plastic pellets, cement, flour, and fly ash in bins or hoppers, ensuring the material flows easily and is consistently supplied to a pneumatic conveying system. 
  • Fluidized Bed Combustion (FBC): Blowers supply the air that fluidizes a bed of inert material like sand or limestone while burning fuel. The blower must maintain a uniform flow for efficient combustion and sulfur capture. 
  • Dry and coating: In fluidized bed dryers or coaters used in pharmaceutical or food industries, the blower supplies the heated process air that fluidizes the product, such as granules or tablets, while simultaneously drying or coating them. 

Vapor Recovery

Vapor recovery is important for both economic and environmental reasons. In some cases, excess gases produced during processes may be reused for other purposes. In other instances, those gases will be toxic and must be safely captured to prevent them from being released into the atmosphere.

PD blowers are used in vapor recovery applications to collect, transfer, and compress hydrocarbon vapors and other volatile organic compounds (VOCs) that would otherwise be vented into the atmosphere. This process is crucial for both environmental compliance and economic recovery of valuable gases.

PD blowers have three core functions in vapor recovery:

  • Vapor collection and suction: The blower draws vapors via vacuum out of low-pressure storage tanks, process vessels, rail cars, or marine loading terminals.
  • Vapor transfer and flow control: The blower moves the collected vapor stream to the processing section of the Vapory Recovery Unit (VRU), such as a scrubber, carbon bed, or compressor.
  • Process gas boosting: Once the vapors are collected, the blower increases their pressure so they can be reintroduced into a high-pressure stream, such as a natural gas pipeline or an industrial fuel gas system.

Due to the nature of the gases being handled, which are often flammable, toxic, or corrosive hydrocarbons, PD blowers can be configured with gas-tight seals, special materials, and ATEX safety certifications. 

PD Blower Options at Northwest Flow Technologies

At Northwest Flow Technologies, we provide quality PD blowers that are known for their performance and reliability. We proudly distribute the MD-Kinney brand of M-D Pneumatics® PD blowers. Across our product series, you’ll find PD blowers that come with standard and optional features that are suitable for a wide range of industries and applications.  

We offer PD blower repair services as well. From quick turnaround times to honest prices and quality work, we aim to maintain a high standard of service to help you keep your business running smoothly. 

To learn more about our products and services, get in touch with us today. 

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