Key benefits

  • Solutions for difficult materials
  • High operating efficiency
  • Low power consumption
  • Flexibility

Pneumatic blending silos that stand out

80+ years experience – four great pneumatic blending systems We engineer our pneumatic blending silos to maximise the benefits of fluidisation and gravity technologies over mechanical blending. With 80+ years of experience worldwide, we have become the number one supplier of air gravity blenders. So, what pneumatic blending solutions are available?

Every pneumatic blending system begins with your application – what do you need? Are you blending fine, powdery materials? Or something more granular? Do you need storage and blending combined, or separate solutions? We have options for every dry bulk material covering a range of sizes, capacities and discharge options.


Central inverted cone blender – air assisted gravity blending


Multiple outlet gravity discharge combined with central cone construction gives advanced gravity blending and storage with a power consumption as low as 0.25 to 0.5 kWh/metric ton of cement raw meal. Air assisted gravity blending enables this solution to store capacities in excess of 6000 t, with discharge rates of 150 t/h+. Open Airslide® conveyor sections in the flat annulus ensure full clean-out when required. Other benefits include:


  • Controlled flow withdrawal
  • Reduced silo profile
  • Discharge equipment located under cone
  • Minimum dust collection
  • No segregation
  • Reduced foundation cost

 Material enters the central bin via multiple Airslide® conveyors, blending materials from different areas of the silo floor. An arrangement of air valves activates sequential discharge and provides a continuous blending of materials from the side of the silo through a funnel effect. Typically used in the cement industry for blending raw meal, this multiple-outlet gravity discharge blender offers super low power consumption.

Random Flow™ blender


The Random Flow system meets the cement industry’s demand for a more energy-efficient, cost-effective system. Designed for higher production at lower costs, the Random Flow system has proven its capabilities in new installations and retrofits worldwide.  The efficient process and simple design of the Random Flow system achieves accepted blending efficiencies for dry, pulverised and free-flowing particles, saving you both time and money. In retrofits, it can increase capacity up to 40% over fluidised systems while decreasing kiln fuel costs through a more uniform blend.


  • Reduced power consumption
  • Less maintenance
  • Less dust
  • Lower capital costs
  • Less kiln fuel consumption
  • Lower air flow

The Random Flow system is a cost-effective gravity blending and storage system that requires low power consumption but provides high blending efficiency. The system is well suited to converting existing fluid bed blenders and storage silos to gravity blenders.


The Random-Flow system minimises costly mechanical power requirements and maximises the free power of gravity for a variety of blending applications. In fact, the Random-Flow system can reduce power consumption from 2.0 kWh/metric ton of raw mix to as low as 0.07 kWh/metric ton.


In addition, the Random Flow system utilises oil-free dry air from equal-size, positive-displacement blowers, offering uniformity of parts, less component wear and minimal lubrication requirements.


The silo floor consists of six aeration zones. Each aeration zone has six collection points. Blending is achieved by systematically withdrawing layered material through a gathering slide from a total of thirty-six collection points. The material is withdrawn by low-pressure air in closed-type Airslide® gravity conveyors from the collection points to the central silo discharge point. A relatively small inverted cone, centrally positioned over the silo discharge point, prevents material from exiting without first flowing through a collection point.


The multiple collection points ensure uniform withdrawal of material about the entire floor area, closely resembling a mass flow discharge. This allows fluidisation from small zones to move material to the discharge point, resulting in material discharge using very low power and low air volumes.



Airmerge™ blending


Air blending is achieved by use of a porous membrane over the entire bin bottom, four air plenums and a simple flow control system enable. Together they change the density of material in the fluidised bed of material to generate a gentle folding action and a near perfect blend.  Because these pneumatic blenders just blend with air, it’s a very gentle blending action. That benefits your delicate materials, but it also makes this a very low maintenance option as there are no moving parts in contact with the material. It’s easy to operate, with no complicated controls, and it’s flexible – it can even be used in the food industry. Other benefits include:


  • Low pressure air
  • Steel flange connection
  • Batch or continuous working
  • Standard and FDA fabric option
  • Long life
  • Little dynamic loading
  • Complete cleanout
  • New or retrofit installations
  • System design flexibility

Airmerge™ pneumatic blenders can be designed for batch or continuous operation to meet your requirements. Porous fabric held with binding strips on top of removable grating panels in the air plenum allows access for fabric to be replaced in place. Higher air velocities in the blending quadrant lower the bulk density causing the denser material in the three fluidised quadrants to flow into it and be displaced upward in a continuously circulating bed. Air for fluidisation and blending can be supplied from common or separate blowers as required.


Column blender for difficult materials


A fully fluidised cone, an upper and lower air plenum and an open-ended central column allow the principle of air blending to be applied to even the most difficult materials. The ‘fountain-flow’ motion of the column blender gives a radial circulation capable of blending ultrafine powders, coarser sandy materials and products with a wide particle size distribution.


  • No moving parts
  • Gravity discharge 60° cone design
  • Simple operation
  • Robust design
  • Greater flexibility in particle size range

The fluidising air enters the cone beneath the column, reducing the density of the material within, which is displaced upward as the denser material from the annulus of the cone flows inward.


By dividing the central column into two or more separate pieces, the column blender can accommodate different volumetric batch sizes. In the smaller batches, material is lifted up in the same way but “fountain-flow” into the surrounding fluidised bed is via the spaces between the upper and lower column. For design purposes, batch volumes must be known in advance.


Stories from FLSmidth