Background
A cement plant in northern Turkey was facing regulatory pressure over dust emissions from its raw meal conveyor β a 380-meter conveyor transferring ground raw meal from the vertical roller mill to the preheater tower feed bin. Raw meal is an extremely fine powder (80β90% passing 90 microns) that becomes airborne at the slightest air movement.
The existing flat belt conveyor ran in an enclosed gallery with belt covers, but fine raw meal escaped at the loading point, at the head discharge, and through gaps in the gallery panels. Dust filters on the gallery were struggling to handle the volume. The plant was receiving enforcement notices from the provincial environmental authority.
Three options were evaluated: 1. Improve the enclosure and dust extraction on the existing flat belt 2. Replace with a bucket elevator 3. Replace with a pipe conveyor belt
Option Evaluation
Improved flat belt enclosure: Engineers estimated this would reduce but not eliminate dust emissions. Raw meal at this fineness passes through very small gaps. Maintaining a fully sealed flat belt enclosure long-term is difficult β covers get damaged, gaps open at wear points, and maintenance access creates reclosure challenges. Estimated effectiveness: 60β70% dust reduction. Not sufficient for compliance.
Bucket elevator: A bucket elevator would fully enclose the material and eliminate horizontal conveying emissions. However, the 380-meter horizontal run with a 45-meter lift made a single bucket elevator impractical β it would require a very large elevator housing or an intermediate transfer. The layout did not favor this option.
Pipe conveyor: A pipe conveyor with 200mm pipe diameter could handle the raw meal capacity (180 t/h) on the same routing as the existing conveyor, with the material fully enclosed in the pipe-shaped belt throughout the run. Loading and discharge points are the only emission sources β both manageable with standard dust extraction hoods.
Pipe Conveyor Implementation
The existing flat belt conveyor was decommissioned. A pipe conveyor was installed on the same structural support framework with modifications.
Specification: - 200mm pipe diameter (from 500mm flat belt width) - EP200 belt construction (adequate for 380m length and 45m lift) - Capacity: 180 t/h at 1.2 m/s - Standard hexagonal idler frames β six rolls per set - Transition sections at loading (flat to pipe) and discharge (pipe to flat)
The loading chute was redesigned with a dust extraction hood and negative pressure maintained inside the chute housing. The head discharge was enclosed with a small collection hood and connected to the plant's existing bag filter system.
Outcome
Following commissioning, dust emissions from the raw meal conveying system were reduced by approximately 95% compared to the previous flat belt arrangement. Visible dust escape from the conveyor during operation was eliminated in normal conditions.
The environmental authority inspection conducted 3 months after commissioning found emissions within permitted limits. The enforcement notices were closed.
Operational considerations noted: - Pipe conveyor maintenance requires access to the hexagonal idler frames, which is more involved than standard troughed idler sets - The transition sections at loading and discharge require inspection every 3 months to check that the belt is forming the pipe shape correctly - Belt tracking in the pipe section is essentially self-correcting β the pipe shape keeps the belt centered
Key Points
Pipe conveyors are specifically suited to fine, dusty materials. Raw meal, cement, coal fines, potash, and similar materials are the core application for pipe conveyors. For these materials, the dust containment benefit justifies the additional capital cost.
Flat belt enclosures struggle with very fine materials. Maintaining a truly sealed flat belt enclosure long-term is difficult. A pipe conveyor eliminates the sealing challenge by enclosing material within the belt itself.
Horizontal curves are an additional benefit not needed here but worth noting. This installation was a straight run, so the pipe conveyor's curve-navigation ability was not utilized. In some plants, the ability to navigate horizontal curves eliminates additional transfer points β an additional benefit.
Elephant Rubber supplied the pipe conveyor belt for this project.