To prove the claim that dense phase conveying can be done with ultra-low conveying velocities down to 0.5m/s or slower for extremely abrasive products, Techmatic recently upgraded their full-scale test rig to showcase the technology to a skeptical customer.

The resultant test runs proved that extremely gentle conveying is possible – below the speeds generally associated with dense phase conveying. During the test, it was possible for the testing team to walk next to the pipe and follow the material slugs in the pipeline at walking speed as they made their way down the pipeline.

The technology developed by Techmatic in conjunction with a third-party partner is based on injecting air along pre-determined points along the pipeline to prevent blockages due to material settling at the very low velocities. Air injection is normally done using solenoid valves and pressure transmitters to control the duration and timing of the pulses. This results in long cable runs for instrumentation and solenoid valves together with the cost of the instruments and PLC programming.

The technology that Techmatic employs is a purely mechanical sensing and injection system that requires no control logic programming, electronic sensors or solenoids.

That makes the system super robust and at the same time allows the system to be safely shut down during a power failure or an emergency plant shutdown. Material discharge valves and the compressed air supply valves are closed at the infeed end of the conveyor, and the product is allowed to settle in the pipeline as the compressed air supply loses pressure.

Once the product in the pipeline has settled after a power outage or emergency stop, the system is able to restart fully automatically as soon as air pressure is applied again to the injection pipeline and the conveying vessels. This includes clearing vertical sections of pipeline where product tends to drop to the bottom of the pipeline when the system is shut down mid-conveying cycle.

One of the challenges that Techmatic is now faced with is that at these ultra-low conveying speeds, the pipeline diameters have to be increased to achieve the necessary feed rate throughput that has been specified.

Pneumatic conveying is the technology of conveying dry powders and granular material in a pipeline using air or an inert gas as the carrier medium. The technology is classified according to the material-to-air ratio. The higher the air-to-material ratio, the more material is conveyed per kg of carrier gas. For products that are abrasive or fragile, dense phase conveying technology with a material-to-air ratio of up to 50 or higher is the preferred method of conveying.

Techmatic also has the record for an ultra-long distance dense phase conveying system to convey cement to an underground cement batch plant at a gold mine in South Africa. The total distance of the conveyor is 3000m with 1500m vertically down and 1500m at a light incline downwards to the batch plant. 600kg/hr is achieved in an 80NB pipeline.

Techmatic has just commissioned a 70t/hr retrofitted dense phase conveying system to replace the original 15t/hr lean phase conveying system at a mine in the DRC. This system also conveys cement for a backfill paste plant.

With over 40 years of engineering experience, Techmatic Engineering supports clients in designing, troubleshooting, and optimising bulk material handling systems. Need technical assistance with conveying, storage, or process performance challenges? Contact our team at salesjhb@techmatic.co.za or fill in the form below.