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The benefits of aerating the silo floor

Jason Heiser discusses how the Ful-Floor™ Pneumatic Reclaim System works, and the advantages of fluidisation over other discharge methods.

2nd Dec 2024

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Ful-Floor reclaim system
Pneumatic conveying

90% reclaim vs 99% reclaim

“Imagine a silo full of 50 000 tonnes of cement. That’s around US$7 million worth of material. But if your silo reclaim system is only enabling you to discharge 90% of that material, you’re instantly losing US$700 000. What operation can accept those kinds of losses?” asks Jason Heiser, Head of Sales and Support for FLSmidth Cement’s Pneumatic Transport Product Line. “That’s the number one reason why it’s worth getting the discharge system right – and why we’re proud to be able to offer 99% reclaim.”

The Ful-Floor™ Pneumatic Reclaim System is an aeration-based dome and silo reclaim system that uses air, gravity and very little energy to reclaim at least 99% of the customer’s product – significantly more than the other aeration-based systems on the market, which have only achieved 90% – 95% reclaim.

“Un-reclaimed material is a real problem,” says Jason. “On top of the financial losses, there is the cost of digging out the leftover material, the damage that might be done to your equipment in the process, and simply the safety risk of sending your people into the silo.

“Meanwhile, emptying a silo is very hard work. Even if your system has managed to achieve 90% withdrawal, in a 50,000-ton silo that still leaves you with 5000 tonnes of material to clean up – and often that material has compacted and is difficult to remove. In the extreme, once hardened, the customer must jack-hammer what they can get to, then get in a vacuum truck to suck up what can be reached, but ultimately, they have to send people in there to clean it out by hand. The Ful-Floor® was designed to make the whole process much simpler, much safer, and much more efficient.”

How fluidisation works

The Ful-Floor™ Pneumatic Reclaim System lives up to its name – it’s a system that covers almost the entire floor of the dome or silo. It uses aeration and a comprehensive understanding of the behaviour of dry bulk materials to achieve high reclaim rates with minimal effort.

Mike Heenan, Senior Project Engineer, Pneumatic Conveying, explains: “All materials have a natural angle of repose – an angle at which they can be piled up without slumping and the material on the slope face is on the verge of sliding. We combine our knowledge of material behaviour with some very gentle aeration to get powdery materials to flow like liquid. We design the floor to direct the materials towards the discharge points and it’s all very smooth, very energy efficient, and very easy. It works for any fine dry bulk material and is most commonly used for things like cement and fly ash, but we’re open to exploring all applications.”

Angle of repose

The Ful-Floor is embedded into the dome or silo floor, so it’s flush with the top of the poured concrete and there are no gaps or voids between the aerated sections where material could get stuck and over time become un-reclaimed The floor is made up of sections, each covered with Airslide® fabric, which is designed to allow compressed air to pass through, aerating the material and causing a systematic reclaim in a sequence determined by FLSmidth Cement’s proprietary control system.

Low energy

Typical systems require three blowers (125hp to 150hp each) to be able to aerate and clean out the entire floor, though this all depends on the diameter, arrangement of the discharge and the rate requirements.

This low energy requirement is one of the big advantages of the system, especially given the ambition for industry to reduce energy consumption. The Ful-Floor designs enable the customer to reclaim the first 60% or more of their material using just one blower, nearly 85% with two blowers and ultimately 99% using all three blowers.

This is the second Ful-Floor Dome I have worked with, and I am very pleased with the reclaim abilities of this design. Having emptied the domes multiple times I have seen visually that it more or less completely reclaims all product.

Seth Underwood, Terminal Manager, Titan Cement.

Fluidisation testing

One of the reasons for the success of the Ful-Floor is the attention to detail throughout the process.

“We ask a lot of questions before we even begin,” says Jason. “In order to make sure the Ful-Floor is the right solution for the application, we need a complete understanding of the project, the materials and the environment. Even things like site elevation have an impact of the equipment and function of the system.


“We have a state-of-the-art materials testing laboratory where we can study your specific materials to ensure we have optimised the design of the Ful-Floor® to ensure that our product and solution will operate as expected.”

The laboratory has been in operation for decades and holds countless data about a materials behaviour and its properties.

“We test fluidisation, the angle of the floor, pack set, the compressed air requirements – basically everything that’s required to determine the parameters of operation,” says Jason. “This ensures that when you invest in a Ful-Floor there are no surprises.”

State-of-the-art materials testing laboratory

Low maintenance

Mechanical silo discharge systems rely on maintenance-heavy conveyor systems, often using screw conveyors to withdraw dry bulk materials from the silo. Another mechanical alternative is a vibratory floor, which uses motor-driven vibrating plates to move material around and onto a conveyor. With so many moving parts, the burden is on maintenance teams to keep the mechanics in optimal condition to maximise availability. The last thing they want is to have to clear the silo to carry out maintenance.
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The part of the Ful-Floor that’s subject to the most wear is the Airslide fabric, but this has proved to be very wear resistant.

“We’ve seen customers achieve 20 years’ service life without having to replace the Airslide fabric,” says Jason. “If it does need replacing – which is more likely to happen because of accidental damage rather than wear – it’s easy to replace sections of the fabric, and we usually leave customers with a little extra fabric in case they need to make any repairs. The system is designed to be manageable – we want all maintenance to be as simple as possible.”

Flexible layout

The flexibility of the Ful-Floor™ Pneumatic Reclaim System is another of its strengths. The layout can be tailored precisely to the needs of the application. Larger operations might want two or more discharge points. Smaller areas might only need one. The valve arrangement is also flexible.

“We have been involved with installations where our control valves and piping are installed in a tunnel under the dome, so it’s really easy for maintenance teams to access when needed. This keeps them and the valves out of the elements. In other installations, the control valves have been put in a ring around the perimeter of the dome. Either way works, so long as there is access when it’s needed,” says Jason. “It’s a very flexible system. We can manage small or large diameters, in a wide range of arrangements. The Ful-Floor has designs for dual discharges, single side discharges and center discharges, giving the customer multiple options regarding where their product is dispersed.”

From this point there is a good bit of flexibility. The customer can feed a completely pneumatic system or just an FK Pump or Feeder to a mechanical conveyor. It’s a solution that suits both new projects and retrofits.

Control valves and piping are installed in a tunnel under the dome

Happy customers

The Ful-Floor reclaim system has been installed all over the world discharging millions of tonnes of product.

“This is the second Ful-Floor Dome I have worked with, and I am very pleased with the reclaim abilities of this design. Having emptied the domes multiple times I have seen visually that it more or less completely reclaims all product,” says Seth Underwood, Terminal Manager, Titan Cement.

“FLSmidth Cement’s Ful-Floor™ was integrated seamlessly into our newly constructed dome workflow and performing smoothly. We successfully emptied the dome last year and verified there was hardly any residual amount just as promised by FLSmidth Cement. We have moved 113 000 tons with Ful-Floor™ and have experienced zero operational issues thus far. The Ful-Floor™ performance and experience has exceeded our expectations with its reclaim ability, ease-of-use, and knowledgeable support from our FLSmidth Cement colleagues,” says Michael Trujillo, Assistant Terminal Manager, Titan America.

A customer in the United States has replaced more than twenty of their current silo reclaim systems with the Ful-Floor and they are extremely happy with the speed of installation, the reliability and ultimately the better than 99% reclaim they are getting now.