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COMFLEX® - High Efficient and Flexible Comminution System

Siegfried Strasser; Dr. Stefan Seemann

Humboldt Wedag GmbH, Grinding Technology

1. Summary

Energy saving is one of the multinational targets of the 21st century. Grinding consumes more than 65 % of the energy in the cement manufacturing process and is therefore an ecological and economical important process. The cement industry as an outrider in terms of developing of energy saving production methods accepted the challenge to enhance this status. The introduction of the roller press in the 80th was a milestone in the cement production history. During the last decades the roller press became one of the mayor grinding machines in the cement and minerals world. More than 50 % energy saving are possible compared with traditional grinding systems like ball mills and up to 20 % can be saved against vertical roller mills. And this is only one advantage.

KHD Humboldt Wedag as one of the founders of the roller press started in 2007 an energy saving and very flexible comminution system containing of a Roller Press as the key equipment for grinding and an efficient and flexible separation system. The name of this system is COMFLEX®. Continuous development steps resulted in the present benchmark in the cement grinding world. This paper will explain the process and the ideas behind COMFLEX® and its features.

2. Road of development

End of the 70th a German professor discovered the advantages of the pressure comminution. Enormous energy saving were possible and therewith environmental protection and also cost savings. KHD Humboldt Wedag as a pioneer of roller press grinding put the very first Roller Press in 1984 in operation. Since more than 25 years KHD Humboldt Wedag is developing the machinery and process steps which are necessary to clear the way for successful using of the Roller Press in the cement industry. A breakthrough for Roller Press grinding was the V-Separator for deglomeration, drying and separation. With the V-Separator, different versions of the SEPMASTER and the continuous further developed Roller Press the direction of evolution for the market were given. COMFLEX® reflects the current evolution stage of Roller Press grinding. It combines the approved machinery with intelligent process solutions.

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3. Arrangement of the single machinery

Besides Roller Press, efficient circuits contain of the static V-Separator, usually a dynamic separator and a material circuit. The V-Separator is the origin of the static separators and developed as well as applied by KHD. The separator is used for Roller Press grinding and is well proven in the cement industry worldwide. Several dynamic separators are available on the market to do the final separation of the product. KHD’s SEPMASTER excels in efficiency, service friendly handling and space requirements and is therefore a bestseller. The Roller Press appeals of high reliability and low maintenance cost with superior wear protection like Stud-lining.

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But the machines itself are only one part of the success story. The understanding of the process and the optimized utilization of the machinery are another important part. Operating experience of plants helped to understand and enhance the system.

The placement of the VS, above or below RP is a very important subject. Following findings were made in older RP installations:

• Discharge material of the Roller Press contain a high portion of fines asking for special design of conveying equipment against dust, spillage and moisture

• Moist material and heated separator rejects in raw mill circuits create dust and vapors after being ground by the RP, resulting in blockage of chutes and venting equipments.

• When grinding blast furnace slag with fresh feed moisture of 6 to 18%, additionally to the formation of fines and vapors, the product becomes highly reactive when leaving the RP. Even with external heating and insulation of venting equipment, material handling requires high maintenance.

The best solution to avoid above shortcomings is to place the V-Separator below Roller Press which has following features:

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• Fines are removed from the external conveying circuit by the VS-air stream. Only coarse, nearly dust-free material is conveyed. Dust and spillage is avoided.

• Moist material is dried in the VS by introducing hot gas, avoiding coating in chutes and venting equipment.

• Ground moist slag is dried in the VS right after leaving the RP and fines are removed, avoiding dust, clogging and reaction of slag – resulting in improved ground slag quality.

• The feed distribution across the width of the VS is ideal since Roller Press gap and VS inlet are parallel. (figure 2)

• With the RP above VS deglomeration is improved. Material impact at VS-inlet is supported by the roller speed.

Figure 2

Additionally for the new COMFLEX® the proven V separator was developed further. The new designed VS (longer step grate and a slightly flatter shape) decrease also the floor level of the RP which it is now around 10 m. This helps accessorily to save civil cost.

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With the VS and RP being on the right place, the final cut for cement or slag meal is done by a dynamic separator. Typical layouts of grinding plants operating in Europe and Asia are shown in figure 3. In both cases the V-Separator is placed below Roller Press. On the left hand side, the SEPMASTER takes care of the finish product

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fineness, while on the right hand side a VSK-Separator is used, which combines VS and SKS to one compact unit. The dynamic separator is placed on the same level as the Roller Press or even below. Rejected coarse material of the separator cage is lifted by the bucket elevator together with the coarse material of the VS.

From this point the layout has been improved further. To avoid mechanical lifting of the rejects of the SEPMASTER which are below 2 mm in top grain size, but containing considerable portion of fines below 200 µm, the SEPMASTER is placed above the Roller Press. The rejects are fed to the RP by gravity chute. In this case the air required for the separating process is fully used for pneumatically lifting of fine material from the VS. The bucket elevator can be designed smaller, reducing investment cost. For larger plants a second bucket elevator can be avoided. If high drying capacity is required, e.g. for raw mills, gas flows for drying can be higher than for separating. The higher gas flow can be fully used for conveying without increasing

the energy consumption of the overall system.

To avoid segregation in large bins on top of the Roller Press, feed chute with level measurement is used in COMFLEX®. Instead, a “circuit bin” placed parallel to the Roller Press takes the material during plant-stop. To avoid a horizontal belt conveyor, a specially designed aerated chute enables trouble-free and dust-tight conveying of large material capacities from the bucket elevator to the Roller Press.

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In summary, COMFLEX® is a contribution of the cement world to save energy and natural resources. The state of the art combination of static and dynamic separators as well as modern Roller Press technology reduces operation cost and also overall investment cost. With intelligent design KHD Humboldt Wedag provides environmentally friendly and customer focused solutions for the future.

You can download the paper and the presentation:

www.khd.com/aucbm2010