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PNEUMATIC CONVEYING SYSTEM DESIGN AND A PROVEN APPROACH TO SOLUTION DEVELOPMENT

 

Thursday, February 28, 2019


Pneumatic conveying system design is the process of developing solutions that use air streams to transport powders, granules, pellets or flakes through a pipeline according to a set of operational requirements.

Pneumatic conveying system design has many complexities, and requires expertise in advanced and specialised engineering. The complexities arise from the numerous types of powders and granular materials and the large variation of operational situations to which this conveying method can be applied.

Pneuvay has developed a proven approach to solution development for pneumatic conveying system design. It is based on industrial best practice, and our vast industrial experience from mining and chemicals to food processing and pharmaceuticals. Read on for an overview of what problems we avoid and the requirements we take into account in our approach to pneumatic conveying system design and solution development.

Why expert pneumatic conveying system design is so important

An improperly designed pneumatic conveying system can result in several major operational problems that seriously reduce its performance and maintainability. Further, troubleshooting these problems and diagnosing issues may be difficult and can consume much time and effort.

Many of these problems are likely to impact the overall performance of the processing plant within which the system is embedded. This is because pneumatic conveying plays a central role within processing plant. They are used to transfer bulk materials from one location to another for some form of processing. Any reduction in conveying performance will greatly affect the processing plant output.

To rectify problems when a pneumatic conveying system is operational is often a complex process and costly to implement. Remediation work often requires detailed planning and skilful execution to minimise downtime for the processing plant.

There are several types of major operational problems that can arise from poor pneumatic conveying system design.

Buildup and plugging

Accumulation and buildup of powder or granular material can lead to plugging and blockages within a pneumatic conveying system. These deposits may result in increased energy usage or reduced throughput.

Restricted throughput

Unsuitable pipeline layout and obstructions within the pipe work from poorly integrated components can reduce the pneumatic conveying capacity rate. Also, pneumatic conveying capacity may be reduced if excessive air speed is used to transport within the pipeline (this effect is not intuitive).

Line or elbow wear

Excessive conveying speed applied to hard powder or granular materials will greatly increase the abrasive wear of elbows and sweeps along the pipework. This can result in a greater need for maintenance and increase downtime as these sections will require more frequent replacement or more robust construction.

Particle attrition

Excessive conveying speed applied to certain powder or granular materials will result in the particles chipping or shattering into smaller particles. Fines are dust that results from these smaller particles travelling at excessive speed and continuing to break apart through contact with rough internal surfaces within the conveying system. This can result in significant damage to the bulk material being transported and can seriously affect output quality.





Problems from improper pneumatic conveying system design or operation
Problems from improper pneumatic conveying system design or operation

Proven approach to pneumatic conveying system design

The determination of several pneumatic conveying characteristics are needed when designing a best-fit solution for a new system or optimising an existing system. These pneumatic conveying characteristics include:
  • Minimum and optimal conveying air flow rates
  • Optimal pipeline diameters
  • Solids to air ratio along the pipeline
  • Pressure gradient along the pipeline
These characteristics provide most of the information required to develop an optimal pneumatic conveying system design that:
  • Minimises energy use
  • Minimises pipeline wear
  • Utilises optimal feeding and receiving mechanisms
  • Utilises optimal air-particle separation systems

Know your bulk material pneumatic conveying characteristics

The key to avoiding pneumatic conveying system design problems is to know the conveying characteristics of the bulk materials to be transported. These are largely dependent on the size, distribution and density of the conveyed bulk material. It is vital to know how the powder or granular material will behave when pneumatic conveyed. This will allow for accurate determination of conveying mode (dense or lean phase), air flow, and air mover type (fan, blower or compressor) to be used within the system.

Bulk materials that have a low melting point can be vulnerable to streamers, snakeskins, angel hair and fluff. Streamers and snakeskins are long, ribbon-like particles formed by frictional heat through extended contact with smooth internal surfaces such as a long sweeping bend. Angel hair and fluff are hair-like particles formed by frictional heat through brief contact with internal surfaces.

A number of operating parameters are determined from these bulk material characteristics. One such parameter is the minimum transport speed required to lift and convey the bulk material. This speed depends on bulk material characteristics such as density, bulk density and flow mode. These are determined with testing on:

  • Fluidisation and permeability
  • Air-retention and deaeration
  • Vertical and horizontal minimum transport.

Understand the pneumatic conveying system requirements

There are several requirements of a pneumatic conveying system that need to be understood when designing a best-fit solution.

Meeting your needs

In general, to meet your needs requires design of a pneumatic conveying system within a processing plant for delivery to a specific:
  • Capacity rate of system
  • Distance to be transport

Powder properties

The powder or granular material conveying characteristics are necessary to determine the conveying mode to be used. Lean phase systems are dominated by characteristics such as lift, drag and particle collisions. Dense phase systems are dominated by air particle interactions characteristics that are much more complex than in lean systems.

Operating conditions

Various constraints and parameters need to be calculated and verified as acceptable, including:
  • Air speeds and capacity rates
  • Pressure drops and energy losses
  • Ratio of solids to air within system

Pipeline size and layout

How the pneumatic conveying system will fit with minimal length into the processing plant needs to be determined. Wear minimisation and maintenance requirements for pipeline and bends need to be checked against what impact is expected from the air flow rates of the transported bulk materials. These factors need to be balanced to determine the pipeline layout and diameters, including:
  • Minimum acceleration zone lengths
  • Type of elbows and sweeps in pipeline
  • Components such as diverters
  • Replacement times for pipeline and components

Air movement

Determination of the air flow rates required throughout the pneumatic conveying system will allow for the optimal specification of any required fans, blowers, or compressors.

Special features

Determine if specialised components are required to prevent or reduce the impact of effects such as:
  • Abrasive pipeline wear
  • Particle attrition, dust and fines
  • Material accumulation and build up
  • Streamers, snakeskins and angel hair

Delivering pneumatic conveying system design results

Using our combination of industrial experience and best practice to a thoroughly investigate our specific set of requirements has proven to deliver superior pneumatic conveying system design and avoid major problems.



Proven approach to pneumatic conveying system design
Proven approach to pneumatic conveying system design

Contact us for assistance on pneumatic conveying system design

Pneuvay is a leading provider of pneumatic conveying system design. We have a focus on food processing plants, cover the Asia-Pacific and Middle East regions, and are expanding into the Australian industry. We service many large food producers and provide best fit and turnkey solutions for food processing plants looking to:
  • Install new powder material systems
  • Expand production capacity;
  • Upgrade existing powder material systems

If you have any questions in relation to powder material systems for a specific food processing, feel free to call on 1300721458 or contact us.

 
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