EFFICIENT AND FLEXIBLE BIOGAS PRODUCTION

Transcription

1 EFFICIENT AND FLEXIBLE BIOGAS PRODUCTION Barbara Waelkens, M. Sc. and Dr. -Ing. Werner Sternad Verona,

2 Overview: Waste sources for the production of biogas Semi-Solids Municipal organic solid waste Industrial organic solid residue Agriculture waste Liquids Municipal wastewater WWTP sludge Industrial wastewater

3 Overview: Biogas production and quality by substrate Biogas Production Methane Content CO 2 content Material Source l gas /kg VS [%] [%] Carbohydrates Proteins Fats Organic MSW Energy Crops (Source: Weiland, 2003) What can be done if the substrate quality changes? How can a plant be more flexible?

4 Overview: Anaerobic digestion for sludge and waste management Pre- Treatment Biogas use (CH 4 + CO 2 ) Reduce odor Reduce the mass of organic material Improve digestate quality Decrease organic material disposal cost Produce and use biogas Sludge/Waste

5 Flexibility on Biogas Plants Variables and Flexibilization of the anaerobic digestion process Feedstock quantity and quality Feedstock preparation Operational temperature Digester Operation The digestion system can be optimized to the demands The digestion system can be more flexible

6 Project Flexible Anaerobic Digester in Edenkoben

7 Project Edenkoben The WWTP in Edenkoben was built in the mid 1980ies and equipped with an aerobic sludge stabilization. Within the context of the Neutral Energy Costs WWTP Edenkoben several measures were undertaken. Adaptation of the aerobic sludge stabilization to an anaerobic sludge stabilization to reduce energy consumption was undertaken. One major challenge was the variable feedstock.

8 Average COD Inflow [kg/d] Project Edenkoben: Average COD Inflow Mittlere CSB-Zulauffracht in kg/d Month Monat

9 Project Edenkoben: Decision process - Conventional Anaerobic Digester vs. High Load Digester Conventional Digesters in Germany are designed according to the DWA M 368: Mesophilic at about 20 days HRT Recommended Organic Loading Rates from 1 to 4 kg/(m 3 *d) Typically below 1 kg/(m 3 *d) High Load Digesters: Mesophilic at about 7-10 days HRT Recommended Organic Loading Rates starting at 2,5 kg/(m 3 *d) Typically between 4 and 8 kg/(m 3 *d)

10 Organic Loading Rate [kg/(m 3 *d)] Project Edenkoben: Decision process - Conventional Anaerobic Digester vs. High Load Digester High Load Digesters Conventional Digesters Underloaded Digesters Hydraulic Retention Time [d] High Load Digester Regular Digesters Underloaded Digesters

11 Project Edenkoben: Decision process - Conventional Anaerobic Digester vs. High Load Digester Typical european digesters: Cylindrical with conic top and bottom or egg shaped

12 Project Edenkoben: Decision process - Conventional Anaerobic Digester vs. High Load Digester The high load anaerobic digester (HLAD) on WWTPs is operated under high organic loading rates reaching up to 8 kg TVS/(m 3 *d). It is essential to guarantee the removal of the biogas from the reactor for operational stability. Mixing of the HLAD reactor is based on the gas lift principle. It requires low mixing energy and produces a large volumetric flow. The complete reactor volume is mixed homogeneously without large shear forces. Microorganisms receive more food and grow faster. This allows shorter hydraulic retention times of about 7 days on WWTPs. (Source: Blenke, 1984)

13 Project Edenkoben: Mixing in the gas lift reactor

14 Project Edenkoben: Process Flow Diagram

15 Project Edenkoben: Raw Sludge Flow

16 Project Edenkoben: Parallel to Serial Operation

17 Project Edenkoben: Serial to Parallel Operation

18 Project Edenkoben: Organic Loading Rate

19 Project Edenkoben: Biogas per TVS Added

20 Project Edenkoben: Biogas per Reactor Volume

21 Project Edenkoben: Dewatered Sludge Volume

22 Project Edenkoben: Machine hall and Foundations

23 Project Edenkoben: Construction of the Digesters

24 Project Edenkoben: Construction of the Digesters

25 Project Edenkoben: Machine Hall and CHP

26 Conclusion It is possible to attend the demands of waste disposal Reduce odor Reduce the mass of organic material Improve digestate quality Decrease organic material disposal cost Produce and use biogas Feedstock quantity and quality can be variable, it is possible to tackle this challenge.

27 Acknowledgements Dr. -Ing. Werner Sternad (Fraunhofer IGB) Martin Hanke (VG Edenkoben) Werner Staudt (VG Edenkoben)

28 GRAZIE PER LA TUA ATTENZIONE! DANKE!