Clean-Air Technology

Recycling plant for industrial goods with asbestos-containing components

In order to decompose asbestos-containing electrical storage units a stationary disassembly plant was established. More than 90 % of the materials contained in the devices can be cleaned from adhering asbestos fibers and recirculated into the economic cycle. Asbestos-containing remaining materials are disposed of according to regulation. The disassembly and treatment of the residual substances are accomplished in the black range, which is constantly kept under negative pressure by suction systems with filters. The plant is constantly supervised by electronic control and particle measurement in the exhaust air. 



A plant was established for the dismantling of asbestos-containing electrical storage units with the goal of the material recycling of the contained materials. The asbestos-containing electrical storage units are disposed of such that a material utilization of 90 to 95 per cent of the materials contained in the devices takes place. The dismantling of the devices is accomplished in a stationary plant, which is divided in a black range (dismantling of the devices and treatment of the residual substances) and a white range (equipment and product storage). 

The black range, in which protective suits and respiratory protection are worn, is held under low negative pressure in order to avoid a release of asbestos fiber emissions into the breathing air. Here the asbestos fibers and other adherences are separated by blowing during cutting and subsequent air classification. Accumulator stones are cleaned by brushing and blowing in a particularly designed cleaning machine and supplied to recycling e.g. for flints. Fans are cleaned in an industrial washing machine, which is loaded in the black range and unloaded in the white range. The instrument panels are cleaned in a drum by a combined blowing-suction procedure, dismantled externally and reusable parts are supplied to recycling. A particularly developed equipment controls the cleaning performance. After the shredding asbestos-containing materials, e.g. insulating materials, are compressed in a high-pressure press, welded into PE foil, and after removing from the black range casted into foil strands and deposited. The concrete blocks are used in mines to secure underground digging areas in the context of the misalignment economy. The intended operation of the plant is constantly supervised by electronic control and particle measurement in the exhaust air.

The results of the asbestos measurements showed that related to a load within the black range of up to 65.000 fibers/m3 air no asbestos fibers could be proven both for persons as well as for the exhaust air of the plant.


1. Starting situation and setting of tasks

In the Federal Republic approximately 4 to 5 millions thermal storage heaters (TSH) and many industrial and household products contain asbestos.

The classification of asbestos in the dangerous material class 1, highly carcinogenic, requires an environmentally-fair processing of asbestos-containing components in a stationary plant. In this plant the dismantling of the asbestos-containing industrial goods can take place safely concerning humans and environment. For this purpose an all-side enclosed production and storage hall with the necessary disassembly and filtering units was established and approved and operated according to the Federal Immission Control Law.


2. Structure of the disassembly plant

The delivery of the TSH takes place in the ground floor, with an unloading zone for trucks. The TSH are sorted there and nontiltingly packed with a band on pallets.

  • The storage area is intended for a capacity of approx. 3,300 TSH. The TSH fastened on pallets are stored there sorted in shelves.
  • The disassembly area (black range) is located on the level at + 6.0 m above the sorting and social area. The disassembly area is constantly kept under negative pressure by suction systems with filters.
  • The sorting area for electrical parts, sheet metals, stones etc. as well as the social area are located on the level +/- 0 m.
  • The aeration and ventilation units with the energy center are located on the level of + 6.0 m.
  • In the storage hall the won secondary resources are stored in temporary storage facilities.


Further this building serves as additional store for TSH.

The plant is designed for a disassembly capacity of 15,000 thermal storage heaters per year in the one-shift operation. The pure work time within the black range with breathing mask amounts to 2 hours, afterwards there is a break of at least 0.5 hours. In the disassembly plant approx. 6 persons are employed in the black range and approx. 6 other persons in the adjoining area.

Access to the black range is possible only via the personnel locks with decontamination mechanism in the ground floor. Large goods are supplied and removed via the large-goods lock with the dimensions B = 4m, H = 4 m, L = 5 m. The water which accumulates there and within the black range is filtered and only then discharged to the general sewage system.


3. Runoff of disassembly

The TSH are taken out of the storage shelves with a control device and transported to the disassembly area on + 6.0 m.

The pallet with the devices is placed on the conveyor for disassembly. At the conveyor end the devices are individually taken from the pallet by means of a lifting apparatus and put with the back on a conveyor for TSH. Via the material lock for TSH the devices are supplied to the disassembly area.

In the section 1:

  • the tapes
  • the cover plates in front and on top
  • the heat damming mats

are removed. 

In the section 2:

  • the accumulator stones
  • the heat damming panels
  • the heating rods
  • the heat damming mats

are removed. 

In the section 3:

  • the fans and engines
  • the mounting panel for electrical components
  • the electrical cables
  • the remaining sheet metals and metals are removed.


4. Air supply and exhaust air system

The disassembly is accomplished in the black range. The black range is constantly kept under negative pressure, which amounts to approx. 20 Pa. The negative pressure is maintained by suction systems, which are doubly redundantly arranged.

The sucked off air from the disassembly area is cleaned by means of three-stage filtering units and discharged to the environment. Additionally a second particulate matter filter (police filter) was used. This filter is not necessary for the normal air cleaning. The supply air necessary for the pressure balance is conditioned in supply air devices and supplied draught-free to the areas by suitable blowing out systems. The supply and exhaust air systems are located on the level + 6.0 m. Thus the filter change at the exhaust air system can take place via the black range.


5. Control and monitoring

The plant is supervised and controlled by a central control stand on the ground floor. The control and monitoring function is divided into 3 ranges.

  1. Storage-programmable logic controller (SPLC) and monitoring
  2. video monitoring
  3. intercom system

The plant can generally have two operating conditions: disassembly operation and standstill preselectable by function switches.

The following functional ranges are constantly supervised and controlled by the SPLC:

  • The gates and doors of the large-item TSH and the lock for persons as well as air-locks and escape doors are automatically secured and supervised regarding correct locking and unauthorized opening.
  • Amount of air and negative pressure within the black range and in the air-locks
  • Malfunctions at the cleaning and disassembly machines, as well as the
  • The ready status of the following installations is registered:
    • machine exhaust air
    • high pressure suction
    • waste water filtration
    • exhaust and supply air in the area.

The failure and/or malfunction of the safety-relevant components and/or equipment is recorded and processed in the process computer control. The process engineering data of the plant are recorded by printers and writers and saved in an environmental manual.

Depending upon plant failure the reserve plant is automatically activated and/or the disassembly operation automatically stopped. For the elimination of malfunctions and/or for test purposes individual components can be switched from mechanical to manual operation.

The disassembly area on the ground floor and the first floor is supervised by means of video camera and visualized in the central control stand.

In the exhaust air a particle measuring system is installed, which registers all particles in the exhaust air, processes and saves them in the computer, as well as visualizes them on a monitor.

By means of this system with simple measurement of the entire exhaust air particles the intended operation of the exhaust air system can be constantly proven.


6. Process-related runoff and utilization of the residual substances

6.1 Sorting, cleaning and utilization of the heat accumulator stones

In a continuous blasting plant heat accumulator stones are blasted with steel balls from all sides, blown off with air and thus cleaned from adhering asbestos fibers. The heat accumulator stones are sorted in three different quality classes:

  • class 1: magnesite
  • class 2: magnesite/chrome
  • class 3: forsterite

and as valuable raw material re-supplied into the economic cycle by the fireproof enterprises.

A deposit of the accumulator stones on domestic refuse and building debris dumps should be omitted due to the high chrome VI load of the stones.


6.2 Sheet metals

Sheet metals are cut into parts of approx. 9 cm2 in special, slowly running machines. In repeated runs possible adherences are mechanically solved and filtered by blowing.


6.3 Mineral wool and asbestos-containing damming materials

The mineral wool is compressed in the insulating material cutting-up and compression plant. Thus a volume reduction in the relationship 1:15 takes place.

After this procedure the mineral wool has a spec. weight of 1,000 kg/m3. The disposal of the mineral wool takes place in Big Bags on the dump.

The asbestos-containing damming materials are separated from the mineral wool and compressed and concreted in concrete containers lined with PE foil.


6.4 Cleaning of the TSH fans

The fans of the TSH are heavily contaminated with asbestos fibers and house dust. In a hollow belt blasting plant the fans are metallically brightly blasted with steel balls.


6.5 Cleaning and disassembly of the electrical instrument panels and heating rods

Die Schalttafeln und Heizstäbe werden in speziellen Transportwagen gelagert. In der Großgeräteschleuse werden diese Produkte mit einem Hochdruck-strahler mit Wasser von anhaftenden Fasern gereinigt. Die 2 bis 4 Regier-kapillare pro Schalttafel mit ca. 2 g PCB werden manuell demontiert und speziell entsorgt.


6.6 Disassembly of other products

On the ground floor of the black range other asbestos-containing products such as fire protection flaps, fire doors, heat and annealing furnaces can be manually dismantled on a disassembly surface of approx. 40 m2.

The residual substances are cleaned in the large-item lock and duly disposed of.


7. Operational experience

At the start-up of the plant the high mechanization degree of the plant as well as the mechanical cleaning of the components led to some malfunctions which could be eliminated in the meantime.

The resulting dust at the TSH disassembly is considerable and was underestimated during disassembly planning.

Special problems and malfunctions at the plants arose for the following reasons:

  • mineral material mats destroyed by thermal effect
  • destroyed accumulator stones partially caused by inappropriate equipment disassembly
  • wet devices with mineral wool sticking to the stones of (inappropriate storage)
  • house dust in the devices due to 20 to 30 years of operation.

In the meantime the disassembly performance achieved the planned values of 60 TSH per shift.

The accomplished asbestos fiber measurements did not show limit value excesses.

For the documentation of the intended operation an environmental manual is recorded, in which all process engineering data are specified.


8. Consideration of economic feasibility

Disassembly performance

In the 1st half-year 1994 altogether approx. 9470 thermal storage heaters were dismantled. This disassembly performance was essentially achieved in January and February in the one-shift operation, from March to July in the two-shift operation.

The total costs for the disassembly of a thermal storage heater amount to 152 DM/device (78 €/device).


Price and proceeds situation

At the planning of the plant the calculated prices for the recycling of thermal storage heaters amounted to 320 DM/device (164 €/device) resp. in the most unfavorable case to 240 DM/device (123 €/device).

Since the prices calculated at the time of the planning for the recycling of storage units could not be obtained, the operation was stopped in the year 1998 because of lacking profitability.

Project Participants

Implementing Institution

Rethmann Elektrorecycling GmbH, NL Wieler + Durian Umwelttechnik

More Project Information

Project title: Wiederverwertungsanlage für Industriegüter mit asbesthaltigen Bauteilen

Project number: 6018

Reference number: FKZ: 30441-1/12

Project period: 1993 - 1994

Project region: Germany (Baden-Württemberg)

Project contact:

Frau Fischer

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+49 (340) 2103 3067

+49 (340) 2104 3067

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Source: Environmental library of the Federal Environment Agency (UBA)