Hazardous Waste Treatment

Recycling of cooling lubricants by means of temperature-activated pressure hydrolysis (TPH)

With TPH, polluted cooling lubricants are hydrolytically split, condensed, and fermented. Biogas is produced in the process and the amount of heavy metals and hydrocarbons in the waste water can be reduced to under 100 mg/l. The oil phase is suitable for thermal recycling.



Cooling lubricants are indispensable in steal and iron manufacturing / processing because they cool materials and lengthen their service life through lubrication. Because of microbial decomposition processes, they have to be replaced after a certain time in operation. The used emulsions often contain heavy metals and organic as well as inorganic pollutants.


Because complete recycling of the used oil and water cannot be achieved using conventional processing techniques, the feasibility and economic efficiency of the so-called temperature-activated pressure hydrolysis (TPH) of cooling lubricants was examined in this project, meaning that the substrates were hydrolytically split at 200° C and approx. 30 bar, condensed, and fermented. Biogas was produced in the process.



  • For reliable and stable emulsion splitting, the pH-value has to lowered with acetic acid in addition to TPH. The acetic acid added and a large part of the organic burden can be removed by anaerobic aftertreatment of the water phase in a fermentation reactor.
  • Compared to the emulsion, the organic burden (TOC) of the waste water can be reduced to 10-40% and the hydrocarbons as well as the heavy metals to less than 100mg/l.
  • The oil phases produced (70-80% oil) are suitable for recycling.
  • In calculation, economic efficiency for plants in the size of 10m³/h and 1m³/h could be proven.

Project Participants

Implementing Institution

ATZ Entwicklungszentrum

Cooperation partner

Umweltschutz Nord GmbH & Co. KG

R. Scheuchl GmbH

Püschner Mikrowellen

Energietechnik GmbH

More Project Informations

Project title: Recycling of cooling lubricants by means of temperature-activated pressure hydrolysis (TPH)

Project number: 0330243

Project period: 1998 - 2001

Project region: Germany (Bavaria)

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Source: German National Library of Science and Technology Hannover (TIB)