Benninghoven hot-gas generator defines the state of the art in recycling technology
High recycling rates with simultaneously low emissions can only be achieved using the counterflow principle combined with a hot-gas generator. Why? Since the reclaimed asphalt is heated up, added virgin mineral does not need to be overheated when it is put into the mixing process to reach the necessary temperature, which is between 140 °C and 180 °C for hot asphalt. Thus, the method saves a lot of energy as well as emissions.
Emissions reduced below the level stipulated by the TA Luft
The process is made possible by using the Benninghoven hot-gas generator: While the recycling material containing bitumen would “burn” with direct firing, the hot-gas generator only heats it indirectly, gently bringing it up to its optimum application temperature. At the same time, the process also pushes emissions down below the level stipulated by the TA Luft – for example, via thermal aftertreatment of most of the hydrocarbons contained in the exhaust gas stream. In the case of Knäble's plant, continuous emissions measurement at the plant's stack proves that the limit values are not exceeded at any time. “Compared to operating the old plant, our average recycling rate has increased from 25 % to 60 %”, Myriam Knäble, wife of the Managing Director, proudly reported. “And with the new technology, we’re saving 770 t of CO₂ per year compared to the old plant.”
Less CO₂ translates to cost savings
This is an enormous advantage, particularly considering the pricing of CO₂ in Germany, the market in which Knäble operates. This is because, as of recently, energy suppliers that bring fuels (with the exception of biofuels) to the market have to purchase emission allowances, better known as CO2₂ certificates. The costs incurred increase annually and are passed on to their customers. Companies with processes that are energy-efficient and therefore low-emission and environmentally friendly will therefore have an even greater advantage in the future.