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Science Research Technology

BHS-Sonthofen: Mixers from Bavaria on the roof of the world

Mixing hydro dram concrete: Twin-shaft batch mixers deployed 3,700 m above sea level

BHS-Sonthofen: Mixers from Bavaria on the roof of the world

The six BHS-Sonthofen mixers are located in the building holding the batcher that feeds aggregates

Six twin-shaft batch mixers of type DKX 6.0 delivered by BHS-Sonthofen are producing the concrete needed to build the main embankment of the Dagu hydro dam undergoing construction near the Tibetan city of Zangmu. The construction site is located 3,700 m above sea level, making this the most elevated site ever for employing mixers from BHS. BHS-Sonthofen specially modified the mixers to meet the challenges they are facing at this extreme altitude.

The first two mixers of type DKX 6.0 started producing the first batches of concrete on 12 July 2017. Two months later, Sinohydro No. 9 Engineering Company commissioned four more units. The mixers will produce approximately three million tons of roller compacted concrete (RCC) over the course of the dam“s construction, which is scheduled for completion in 2019. The complete facility, which comprises six mixers, is dimensioned to produce 160,000 m³ of hardened concrete per month.

The mixers are equipped with a coarse-grain mixing unit for processing grain sizes up to 160 mm, as is typical in hydro dam construction. This mixer type has proven its worth in numerous installations across the globe.

About 6 m³ of hardened concrete are discharged per batch at a rate of up to 48 cycles per hour, resulting in a total yield of up to 288 m³ of hardened concrete in one hour. The cycle times are short due to the intensive mixing of the concrete and the extra-large rotary valves at the underside of the mixing trough, which significantly speed up the discharge process.

Given the vast amount of concrete that needs to be processed, BHS-Sonthofen reinforced the mixing troughs with a tougher version of its 28-mm „Optilong“ wear tiles. The service life of these tiles is nearly twice as long as the diamond-shaped tiles commonly used in construction projects. The variable hardness of the individual tile rows ensures uniform abrasion across all wear zones.

BHS-Sonthofen even accounted for the remote location of the construction site: In order to prepare the machines for a potentially unstable grid, the company used special motor couplings. The hydrodynamic turbo couplings reduce mechanical as well as electrical load peaks. Thanks to this property, they have proven ideal for use in locations with critical grid fluctuations.

Also, since high-altitude air does not extract as much heat from the electric motors, BHS-Sonthofen equipped the mixers with special motors that feature type „H“ insulation.

The sheer remoteness of the construction site posed yet another challenge. The construction site in Tibet is nearly 4,000 km from Tianjin near Beijing, which is where BHS-Sonthofen“s Chinese subsidiary is situated. It took 20 days to transport the mixers across this distance.

The project:

Once completed, the Dagu dam will be 126 m tall with a dam crest measuring 385 m. The power plant will generate 640 MW of hydro energy.

The dam is part of a major project undertaken by the Chinese government to provide the eastern parts of the Tibetan Autonomous Region with electricity, all the way to remote villages. Multiple hydro dams are damming up the Yarlung Tsangpo, the Earth“s highest river. It crosses Tibet from west to east and continues through India, where it is called Brahmaputra.

About BHS-Sonthofen GmbH

BHS-Sonthofen GmbH is an owner-operated group of companies in the field of machinery and plant engineering based in Sonthofen, Germany. The company offers technical solutions for mechanical process technology, concentrating primarily on mixing, crushing, recycling and filtration. BHS-Sonthofen has a global presence, with more than 350 employees and several subsidiaries.

The Mixing Technology division produces batch and continuous mixers and offers the full range of process technology services for mixing applications. The twin-shaft batch mixer, which is considered a global benchmark in the concrete industry, is a key product.

Building companies use the mixers first and foremost to produce transport, precast, high-performance and hydro dam concrete or concrete paving blocks. BHS mixers are also highly suited for mixing dry mortar, cement and sand-lime products or for processing clay-and-rock mixtures.

They are widely used for processing mineral mixes, landfill substances, fly ash, dusts or other bulk materials, or for the conditioning of sludges and the production of suspensions. The latter is often done in the context of backfilling mines or depositing mineral waste.

For further information, please visit: www.bhs-sonthofen.de

BHS-Sonthofen GmbH
Roland Schmid
An der Eisenschmelze 47
D-87527 Sonthofen, Germany
Phone: +49 8321 6099-231
E-Mail: press@bhs-sonthofen.de
Url: http://www.bhs-sonthofen.de

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Regina Reinhardt
Dennewartstr. 25-27
52068 Aachen, Germany
Phone: +49.241.89468-24
Fax: +49.241.89468-44
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Science Research Technology

bauma premiere: Mixing high-abrasive material with minimum abrasion

Mixer for the sand-lime brick industry: New twin-shaft batch mixer with rubber provides low-cost mixing.

bauma premiere: Mixing high-abrasive material with minimum abrasion

The first twin-shaft batch mixer in the new DKXK variant for producing sand-lime bricks.

At bauma 2016, BHS-Sonthofen is introducing a new generation of twin-shaft batch mixers of type DKXK that features a rubber trough specially designed for producing sand-lime bricks. This new type of batch mixer features particularly low wear to the trough – an important factor when processing abrasive mixtures such as sand-lime bricks.

The new DKXK version that BHS has developed for the proven twin-shaft batch mixer is optimally adapted for producing sand-lime bricks. This new innovation allows this industry to take advantage of BHS-Sonthofen twin-shaft mixing technology. The results are homogeneous mixing, short mixing times and low wear. The intensive mixing process also utilizes a high percentage of the lime used in each mixture, which in turn produces a very dense packing mixture.

The first mixer in this new generation – which has a 2,300-liter capacity – will start operations in February 2016 in Baden-Baden (Germany) as the main mixer upstream of the reactor. Since 1971, the client has been operating a BHS-manufactured twin-shaft batch mixer of similar design that they are now replacing with a more powerful state-of-the-art unit.

Sand-lime bricks are made of sand mixtures containing a high silicate, quicklime and water content. This material is highly abrasive. Considerable wear occurs in previously used conventional mixing systems such as intensive mixers. The reason so much wear occurs is because the fine sand acts like sandpaper on the mixing tools and on the mixer’s trough wall.

BHS has therefore specifically developed the DKXK type of mixer for producing lime mixtures as an alternative version to the world’s proven DKX type of twin-shaft batch mixer. Instead of a steel trough with a lining made of wear tiles, BHS builds their sand-lime brick mixer with a rubber mixing trough that pulsates when mixing, thus effectively preventing sticky mixing material from caking. This reduces blade and trough lining wear as well as reduces the engine’s power consumption.

This solution has long proved itself as one of BHS’s very reliable single-shaft continuous mixers. DKXK can optionally equip the mixing blades with Widia (tungsten-carbide) plates, which significantly increases service life.

The new DKXK mixer variant offers several advantages when compared with the intensive mixers that have been used in the sand-lime brick industry until now: In contrast to the circular motion of other mixing systems, the three-dimensional mixing principle of the twin-shaft batch mixer produces a more intensive exchange of material. This results in shorter mixing cycles with the effect of a lower energy consumption. In addition, the mixer requires less maintenance because wear parts are easy to replace.

This is another reason why the twin-shaft batch mixer by BHS-Sonthofen is an economical alternative for producing sand-lime brick mixtures.

In the future, BHS-Sonthofen will offer the DKXK twin-shaft batch mixer for the sand-lime brick industry with a filling volume ranging from 1,000 to 6,500 liters.

Background: Twin-shaft batch mixers of the DKX series

The twin-shaft batch mixers from BHS-Sonthofen have a mixing mechanism whose arms, which are in the form of an interrupted spiral, are arranged on two counter-rotating mixing shafts. They generate a circular, three-dimensional movement with intense material exchange in the turbulent overlap area of the two mixing circuits. Counter paddles on the shaft ends redirect the entire material, so that it is repeatedly returned to the mixing process.

They achieve a higher mixing effect than comparable single-shaft or intensive mixers as all the material is constantly in movement even at low speeds – and at significantly lower energy consumption.
In contrast to other mixer systems, twin-shaft batch mixers can be filled to a much higher level, so that they are more compact with the same throughput. Thus in new-build plants the mixers score points with their small dimensions. Moreover in case of retrofit and plant modifications in existing installations a more powerful mixer can be installed.

About BHS-Sonthofen

BHS-Sonthofen is an owner-operated group of companies in the machinery and plant engineering field, based in Sonthofen, Germany. The company offers technical solutions for mechanical process engineering, concentrating primarily on mixing, crushing, recycling and filtration. With more than 350 employees and several subsidiaries, BHS-Sonthofen has a global presence.

The Mixing Technology division produces batch and continuous mixers with single and twin-shaft technology and offers a full range of process technology for mixing. The spectrum extends from conventional applications in the concrete industry for transport, precast, dam or high-performance concrete and the mixing of dry mortar, cement, mineral mixes, landfill construction materials or other bulk materials to the conditioning of sludges, the production of suspensions or applications in mining.

For more information, see www.bhs-sonthofen.de.

BHS-Sonthofen GmbH
Roland Schmid
An der Eisenschmelze 47
D-87527 Sonthofen, Germany
+49 8321 6099-231

VIP Kommunikation
Regina Reinhardt
Dennewartstr. 25-27
52068 Aachen, Germany