Screw pyrolysis technology for sewage sludge treatment.

Area of Science:

• Environmental Engineering
• Chemical Engineering
• Waste Management

Background:

• Growing sewage sludge volumes necessitate advanced treatment and recycling solutions.
• Current methods like incineration have limitations, driving interest in alternative technologies.
• Decentralized treatment and nutrient recovery are key challenges for smaller wastewater plants.

Purpose of the Study:

• To evaluate the potential of screw reactor pyrolysis for sewage sludge conversion.
• To investigate the influence of temperature on product yields and composition.
• To assess the feasibility of decentralized energy and nutrient recovery.

Main Methods:

• Pyrolysis of approximately 100kg of dried sewage sludge in the STYX Reactor at KIT.
• Experiments conducted at temperatures ranging from 350°C to 500°C.
• Analysis of char, pyrolysis oil, and gas yields, including elemental composition and energy content.

Main Results:

• Char yield decreased from 66.7wt.% to 53.0wt.% with increasing temperature.
• Maximum pyrolysis oil yield of 13.4wt.% achieved at 500°C.
• Metals and minerals were retained in char; nitrogen and sulfur migrated to condensate/gas.
• A concept for decentralized cogeneration achieved up to 40% efficiency.

Conclusions:

• Screw reactor pyrolysis is a viable technology for sewage sludge conversion, recovery, and recycling.
• The process allows for decentralized production of char, heat, and power.
• Nutrient recovery and energy generation are key benefits for small-scale wastewater treatment.