As a system supplier, Beumer Group develops solutions perfectly adapted to meet cement plant requirements.
This includes conveying, loading and filling systems that are offered in different versions for various tasks, which are continuously optimised by our engineers in Beckum, Germany. Our goal is to make our customers' operations more efficient. Users have to face for example less maintenance, an increase in bucket elevator capacity and achieve more precise filling results. We provide innovative solutions to international cement companies who are looking for sustainable and cost-efficient ways to modernise their plants.
The conveying system has to meet high requirements to ensure safe and economic clinker transport in cement plants. The cement clinker leaves the clinker cooler of the kiln line at temperatures of up to 200 degrees Celsius, or up to 600 degrees Celsius if the coating collapses, and is temporarily stored in the clinker silo. To ensure a trouble-free transport of the clinker, the conveying system must withstand these high temperatures. This is where BEUMER apron conveyors are used. They are extremely robust and can navigate through complicated routings and considerable conveying heights. "We generally use the heavy-duty Beumer double sprocket chains as traction elements," explains Michael Brachthäuser, Director Business Unit Cement at Beumer Group. This makes it possible to handle inclinations of up to 60 degrees at a speed of 0.3 metres per second. "In order to increase performance we developed a version with the cells mounted to a belt instead of a chain," explains Michael Brachthäuser.
More compact and more powerful
The basis for this variant is our proven Beumer belt technology, which is also used in bucket elevators. The belt is reinforced with steel wires and can be designed in different widths. In the material feed area, special deflector plates protect the belt against hot coating that collapses when the kiln is not in continuous use. "With up to 1300 cubic metres of clinker per hour, belt apron conveyors achieve a higher conveying capacity than conventional apron conveyors," describes Michael Brachthäuser. This can be attributed to a higher running speed of up to 0.6 meter per second. Angles of inclination of up to 60 degrees are also possible. Wear and tear that occurs frequently on a chain can be practically eliminated when using a belt and lubricating the system is not necessary. The lighter and more compact design of this solution reduces the costs for the steel structure and the entire project. The entire belt lies with its surface on the drive and return pulley, thus, the unwanted polygon effect caused by the central chain is avoided. This ensures quiet running and low noise emission, and prevents additional exposure of the plant and adjacent buildings to load vibrations and noise.
The Beumer belt apron conveyor is an optimal choice for system modernisations. Thanks to faster conveying speeds, higher quantities of material can be transported while keeping the existing conveyor frames and steel bridges. "A concrete example: An apron conveyor with a chain of 1600 millimetres width and 131 metre centre distance weighs 128 tons," explains Michael Brachthäuser. The steel structure weighs about 80 t. An 800 x 131 metre belt apron conveyor capable of conveying the same capacity weighs only 90 t – that is 38 t less than the chain version. For the belt version, the net costs for the equipment are 25% lower, as the steel structure is approximately 30 t lighter and weighs only 50 t. A smaller drive unit can be used due to the reduced size, which further lowers the operational costs compared to conventional apron conveyors.
How to increase the capacity of belt bucket elevators
Modernisations are an important aspect to consider for bucket elevators. Cost-efficient production requires bucket elevators with low investment costs, a long service life and easy maintenance. The buckets are mounted either to a belt or a central chain. Belt bucket elevators are best suited for fine-grained bulk material, because coarse material could fall between the bucket and the belt and damage the belt. Central chain bucket elevators, however, are designed to transport all types of coarse, hot or abrasive bulk material. The fine dust of the material causes faster wear and tear on the chains as opposed to a belt. The user has to maintain the bucket elevators and replace the chains frequently. During repair, the operation has to stop. Additionally, replacement chains are very expensive. "That's why we have developed the innovative high-capacity belt bucket elevators type HD," says Michael Brachthäuser.
They are designed to eliminate the space between the individual buckets and the belt. This prevents coarse material from getting stuck during the scooping and filling process, which is often the case. This increases the service life of the belt considerably. The buckets are mounted firmly to the back of the belt with segments and bolts especially developed by Beumer Group. As with all belt bucket elevators by Beumer Group, Beumer belts with wire-free zones are also used on the high-capacity belt bucket elevators. Holes for the bucket mountings can be placed here without damaging or cutting the steel wires. The traction forces of the belt are maintained to the fullest extent. The current belt has a tensile load of 2500 N/mm; the new Beumer belt with wire-free zones has a tensile load of 3300 N/mm. The special Beumer bucket shape also allows for smoother running and therefore less noise generation. Depending on the material to be conveyed, Beumer Group offers special buckets or mounts a dynamic bottom into the bucket elevator boot. This prevents wet and sticky material in the bucket elevator boot. Belt bucket elevators with this equipment have a much longer service life when handling highly abrasive material than central chain bucket elevators.
These bucket elevators are already successfully used by many international cement manufacturers including Dyckerhoff, Yamama Cement, HeidelbergCement, LafargeHolcim. Beumer Group converted their existing bucket elevators into high-capacity belt bucket elevators type HD in a simple and cost-efficient way. This became necessary because the kiln systems had been modified, increasing their capacity. This meant that the bucket elevators to the raw mills had to increase their capacity as well.
"One of our German customers had the problem that coarse-grained material was falling between the bucket and the belt, damaging the belt," describes Michael Brachthäuser. Along with the modernisation of the plant, throughput as well as the running time of the bucket elevator per day increased, adding to this challenge. The belt started to get porous already after two years of use. Initially, it was planned to replace the old belt bucket elevator with a chain bucket elevator. But then the operator of the plant opted for the Beumer Group HD technology. The requirement was that the existing bucket elevator housing including the drive unit should remain for the retrofit.
This special Beumer bucket elevator technology is used for example for circulating bucket elevators in raw mills and cement mills for material with grain sizes of up to 120 millimetres and a humidity level of up to 6%. Conveying capacities of more than 1500 tph can be reached.
Read the article online at: https://www.worldcement.com/special-reports/08112016/solutions-that-you-can-build-on-part-one/