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DGE-Thermolysis plant MIDI

Scrap Tire Recycling

Safety at pyrolysis plants
Presentation: DGE-Thermolysis of scrap tires
Massflow and emissions
Economic of DGE-scrap tire-thermolysis
Information about scrap tires
Information about thermolysis condensate

Technical Details
Infos zum BImSchG
Dirk Gerlach Engineer

Massbalance sample of a MIDI-Quad project

Sankey-Diagram for MIDI-Quad scrap tire thermolysis


To get a first impression of emisssions the following categories are interesting:

Fine dust

limit value for this plant
according to
measurement (LUA Bayern)
MPA Burgau
limit value for
pellet heating
limit value for
10 mg/m³ 1,3 mg/m³ 60 mg/m³ 150 mg/m3


Matured scrap tires which can not be exported due to age reasons contain significantly less smelling softeners than new tires.
The scrap tire granulate is almost odorless.
The combustion air is being deducted from the open storage dump to install (another) safety to reduce odor.


The gas which is led through ex.g. THIOPAQ® and the active coal filters contains mainly methane, carbondioxide, hydrogen, carbon monoxide. There are also small amounts of ethane, propane and butane (propane and butane are the two components of autogas).
The gas will be converted into electricity by means of a gas engine. The off-gas then contains carbon dioxide and water.
So, in a norminal case (i.e. 600 kg/h input) there will be emissions of approx. 600 - 800 Nm³/h Abgase.


The processing of scrap tires to rubber granulate is done in a housed granulator.

Condensate oil

The condensate oil is kept in a completely closed system and does not exit the system!
In case of a pipe line break there are sumps for hazardous goods integrated in the plant. If the sensor technology detects a break the broken pipe line is automatically shut down. Afterwards the plant goes into a secure operational state (i.e. the input material is discharged from the rotary kiln).
The oil is being stored in a certified tank and is collected four times a week (each approx. 30m3).

Solid 'coke'

The product received contains up to 83% elementary carbon and the filling material of the tires, mostly silicium.
According to process parameters there may be up to 2% of sulphur in the coke.
The removal/collection of the certified carbon dust silo with filter is done 8 times a week.
The carbon green corresponds to a large extent to the specification of active coal N660.


According to process parameters the sulphur remains as elementary sulphur in the solid or it goes as sulphur compound into the condensate or ideally as hydrogen sulphide into the gas phase.
With the THIOPAQ®process the hydrogen sulphide is separated from the permanent gas and will be separated as elementary by means of a biological treatment.
During nominal operation there will be maximal 280 kg/d of elementary sulphur generated. According to safety data sheet sulphur does not fulfill the PTB-criterias (persistent/bioaccumulative/toxic).

Theoretically maximal incidence emissions

In a worst-case scenario (i.e. sudden blackout of gas treatment/condensation) the temperature in the reactor is lowered beneath 300°C within 15 minutes. Theorectically the plant could achieve 25% of the hourly output.
Steady variations are detected by the system itself (e.g. presssure measurements) and the plant goes automatically into a secure operational state.
Substance critical temperature
transfer into gas phase
bagatelle mass flow
according to TA-Luft
tire analysis incident mass flow  
Arsenic 613 °C 0,0025 kg/h 10 mg/kg
Benzo(a)pyren °C 0,0025 kg/h      
Benzene °C 0,05 kg/h      
Cadmium 767 °C 0,0025 kg/h 10 mg/kg 0,003 kg/h  
Mercury 356 °C 0,0025 kg/h 0,17 ppm 0,00005 kg/h  
Sulphur oxide - 20 kg/h 1% 4 kg/h  
Dust - 1 kg/h      
For this kind of incidence an emergency flare is installed to burn all carbon hydrides safely.
The possible short-term heavy metal pollution on the contrary is within bagatelle mass flow limits for continuous operation. For the approval process one has to take a closer look at this.

Dipl.-Ing.(FH) Dirk Gerlach   •   Passion for Innovation

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