Recycling drum using a counterflow process with a hot gas generator.

The hot gas generator
from BENNINGHOVEN

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

Providing asphalt in the required quality and quantity at the right time is already a challenging task that requires perfectly coordinated plant components. When maximum recycling 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 a counterflow process with a hot gas generator

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

While direct firing would tend to “burn” the RAP material coated with bitumen or at least impair its properties, the hot gas generator simply heats it indirectly and therefore raises it gently to the optimum processing temperature.

This process also cuts emissions by ensuring the total carbon content in the exhaust gas flow is largely combusted at the same time.

The RAP material is heated to the optimum processing temperature of 160 °C. Emissions are kept within the standard range and the bitumen contained in the material is not combusted.

Hot gas generator technology means that fresh asphaltic mixture can be made from up to 100% reclaimed asphalt.

The result – crucial advantages:
  • RAP proportion of up to 100%
  • TC emissions <50 mg/m³
  • Optimized plant energy balance
  • Lower strain on the filter unit
  • Reduced bitumen costs
  • More economical asphalt production
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Systematic structure
Hot feed system

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

> RAP chute (self-cleaning)
> Recycling drum
> Burner
> Hot-gas generator
> Extraction hood
> Transitions/knife valves are heated, preventing adhesion 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 input rates with low emissions can only be achieved by means of the counterflow process 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. Degasification of bitumen is therefore minimized. Any TC concentrations generated are mostly returned to the hot gas generator with the circulating air and burned there.

Recycling drum

> RAP material flows against the heat flow
> Longer active dwell time of the RAP material in the drum and gentle indirect heating
> Better heat transfer with optimized material veil (100% closed material curtain) in the drum
> Homogeneous heating of the drum with new (patented) generation of internal drum parts
> Less material accumulation/adhesion 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)

Optimized for Users
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 air flow on the plant: emissions from the mixer and the skip track can be added to the hot recycling system and burned.

Optimized energy balance

> The mineral does not have to be overheated
> Gentle on the material
> Gentle on the plant (no hydraulic shocks)
> Energy-optimized – e.g. with a frequency-controlled, closed system for circulating air and exhaust air
> Lower load on the dust collection system (filter bags) due to lower fine content from the recycling process
> Adjustable exhaust gas temperature level, just above the dew point
> Reduced emissions, which degasify 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 with high RAP content
> Production does not have to be interrupted for changing the RAP input rate
> No recipe change necessary
> Continuous asphalt quality

Easy maintenance and accessibility

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

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 help to cut energy consumption and emissions, and enable the operation of asphalt mixing plants with high rates of RAP usage – which also ensures the long-term future of the mixing plant site.

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BENNINGHOVEN technologies

Asphalt production, recycling systems, combustion technology, control systems, and bitumen technologies – thanks to BENNINGHOVEN’s technologies, each of our customers can find the right solution for their specific site that fully complies with requirements and conditions.

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