Recycling drum using counterflow action with a hot gas generator.

The hot gas generator
from BENNINGHOVEN

The leading, patented RAP technology from BENNINGHOVEN allows plant owners to produce asphalt mixtures from 100% reclaimed asphalt. At the same time, the asphalt mixing plant meets the stringent regulatory limits for air quality control.

Providing asphalt in the required quality and quantity at the right time is a challenging task in itself that requires perfectly coordinated plant components. When maximum reclaimed asphalt pavement (RAP) content in asphalt production with minimum emissions are added to the equation, the BENNINGHOVEN hot gas generator becomes indispensable.

BENNINGHOVEN offers integration of the hot feed system for new plants as well as a Retrofit solution for existing asphalt mixing plants.

Clean performance

Recycling drum using counterflow action with a hot gas generator

Exhaust gas flow
RAP drum
Burner and hot gas generator
Further processing
Clever process solution

While the RAP material containing bitumen would “burn” with direct firing or undergo adverse changes to its properties, the hot gas generator heats it indirectly, gently bringing it to its optimum application temperature.

At the same time, the process lowers emissions, for example by burning most of the total carbon contained in the exhaust flow.

The RAP material is heated to the optimum processing temperature of 160 °C. All emissions are kept in the standard range and the contained bitumen does not burn.

The hot gas generator technology allows fresh asphalt mixtures to consist of 100% reclaimed asphalt.

The result – crucial benefits:
  • Up to 100% RAP content
  • TC emissions < 50 mg/m³
  • Optimised energy footprint of the plant
  • Lower strain on the filter unit
  • Reduced bitumen costs
  • More efficient asphalt production
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Systematic process
Hot feed system

The main components of the hot feed system are coordinated to optimise the process:

> RAP chute (self cleaning)
> Recycling drum
> Burner
> Hot-gas generator
> Extraction hood
> Transitions / knife gate valves are heated, preventing adhesions at transition areas

Hot gas generator

The hot gas generator essentially consists of a large cylindrical body. The opening for the burner on the face side is equipped with a pneumatically actuated heat protection door. A large maintenance access in combination with the key transfer system ensures maximum safety and ease of maintenance.

High RAP content with low emissions can only be achieved by means of counterflow action in the hot gas generator. Why? With the hot gas generator technology, only a small quantity of TC can be generated because the recycling material is heated to 160 °C with high efficiency and has no contact with the burner flame. This consequently minimises degasification of bitumen. Any generated TC concentrations are mostly returned to the hot gas generator with the circulating air and burned there.

RAP drum

> RAP material flows against the direction of the heat flow
> Longer active dwell time of the RAP material in the drum and gentle indirect heating
> Better heat transfer with an optimised material veil (100% continuous material curtain) in the drum
> Homogeneous heating of the drum with the new generation of internal drum parts (patented)
> Less material accumulation/adhesions and self cleaning effect

Extraction hood

> The extraction hood acts as a separator (fine particles)
> The exhaust flow can be calmed with the large extraction hood so that particles from the exhaust gas flow can settle.
> High level of separation so that fine particles cannot enter the exhaust gas channels but rather settle in the collection hull (no risk of the circulating air and exhaust air pipes clogging)

Ideal for users and for the environment
Low emissions

> Compliance with stringent legal emissions limits (e.g. in Germany: guaranteed compliance with the limits of the TA-Luft regulation in continuous operation with appropriate measurements)
> Clever airflow in the plant: Emissions from the mixer and the skip track can be added to the hot RAP system and burned.

Optimised energy balance

> The mineral does not have to be overheated.
> Gentle on the material
> Gentle on the plant (no hydraulic shocks)
> Energy-optimised, e.g. with a frequency-controlled, closed-loop system for circulating air and exhaust air
> Lower load on the dust collection system (filter bags) due to lower fine particle content from the recycling process
> Adjustable exhaust gas temperature level, just above the dew point
> Reduced emissions that degas at below 160 °C during heating of RAP material or aggregates

Recipe generator

> System-relevant software expansion for dynamic generation of recipes with variable RAP content
> Advantage when running a high RAP content
> No production interruption when changing the RAP feed rate
> No recipe change necessary
> Consistent asphalt quality

Easy maintenance and accessibility

> Large, ergonomic maintenance access points and service and inspection openings
> Movable burner – inspection of the burner head
> Partial replacement of RAP chute segments, including the ceramic coating
> Fixed slinging points for rope access
> Extraction hood with walk-on options
> Key transfer system for increased safety

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Benninghoven value

Using technology to work towards a more efficient use of energy and raw materials is the challenge of today and tomorrow. Solutions from Benninghoven can support the reduction of energy consumption and emissions while enabling asphalt mixing plants to run with a high reclaimed asphalt pavement (RAP) content to ensure the future of the facility.

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BENNINGHOVEN technologies

Asphalt production, recycling systems, combustion technology, control systems and bitumen technology – with BENNINGHOVEN technologies, every customer can find the right solution for their location, according to the specific requirements and conditions.

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