Construction World June 2021

EQUIPMENT

ASPHALTMIXING PLANTMEETS REQUIREMENTS FORMAXIMUMRECYCLING Producing asphalt in the right quality and quantity at the right time is in itself a challenge that requires perfectly aligned plant engineering. In case of high recycling rates needing to be achieved while still keeping emissions low, hot-gas generator technology from BENNINGHOVEN is virtually indispensable. This enables operators to turn reclaimed asphalt fully into new asphaltic mixture while complying with Germany’s new TA-Luft standard. This was adapted in line with the latest technological developments and approved by the German Federal Cabinet on 16 December 2020 following a consultation process lasting several years.

plant,” explains Managing Director, Nicolas Knäble, a member of the fourth generation of the founding family. Another benefit of this approach was that the company did not lose a single day of production. The 'old' TBA 3000 kept on making the necessary asphaltic mixture until the BENNINGHOVEN technicians gave the green light to switch over to the BA RPP 4000 after installing and checking it. Higher mixing capacity, greater energy efficiency In order to integrate the sustainable recycling technology throughout, Knäble wanted a higher mixing capacity of 320 metric tons per hour instead of the previous level of 240 as well as a more user- friendly technology. At the end the decision was made for a new BA RPP 4000. The plant also includes two EVO JET 3 burners, one each for the virgin mineral dryer drum and recycling drum. Besides oil and coal dust, these burners can also burn natural gas very efficiently. In the future, this will allow Knäble to respond flexibly to price fluctuations on the energy

T he hot-gas generator technology means that fresh asphaltic mixture can be made up of 90 + X% re-used asphalt – more than with any other recycling system on the market. BENNINGHOVEN can also integrate the hot feed system into existing asphalt mixing plants as a retrofit solution. However, an example from southern Germany shows in impressive fashion why investing in an entirely new asphalt mixing plant can pay off. Investing in new technology rather than opting for a retrofit From the topmost platform 43 metres off the ground, the Kinzigtal valley in the Black Forest looks truly resplendent. The new BA RPP 4000 is a total of 55 metres tall and makes a majestic impression, even when viewed from the ground. The new asphalt mixing plant owned by Knäble GmbH Straßenbau, a medium-sized company from Biberach (Baden), is remarkable in many respects. One of the things that makes it unique is the fact that the BA RPP 4000 is replacing a BENNINGHOVEN TBA 3000 plant, which replaced the asphaltic mixture for Knäble’s two asphalt crews reliably for ten years. This is not a long time for an asphalt mixing plant, as most BENNINGHOVEN plants have a service life of 30 to 40 years. So why did the road construction company with its rich tradition invest in new technology rather than in a retrofit solution, for instance? “As it happens, our planning did start with a retrofit. Ultimately, it was mainly the market environment and our requirements in terms of the technology and its capacity that swayed us toward a brand-new

market and always use the cheapest fuel. All in all, Knäble is making a genuine investment in the future with its new asphalt mixing plant. The family-owned company from the central Black Forest region enjoys a rich tradition and employs around 150 staff. Two own asphalt crews mostly produce asphaltic mixtures on local road construction sites using VÖGELE feeders and finishers and HAMM rollers. A KLEEMANN screening plant and WIRTGEN milling machines also form part of the machinery fleet. Hot-gas generator sets the standard in recycling technology Achieving high recycling rates and low emissions at the same time is only possible by using the counter flow principle combined with a hot-gas generator. Why? Since the old asphalt is heated up, the virgin mineral that is added does not need to be overheated when it is put into the mixing process in order to reach the necessary temperature, which is between 140°C and 180°C for warm mix asphalt. The method thus saves a lot of energy as well as emissions. It is the use of the BENNINGHOVEN hot-gas generator that makes the process possible: Whilst direct firing would 'burn' the RAP with its bitumen content, the hot-gas generator only heats it indirectly, bringing it gently to its ideal application temperature. The technique also pushes emissions down below the limit stipulated by the TA-Luft, not least because most of the hydrocarbons contained in the exhaust gas stream are burned off at the same time. Continuous emisssion measurements onKnäble’s plants prove, that limit values can

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