Status Phosphorus recovery

Transcription

1 Status Phosphorus recovery Dipl.-Ing. Fatah Naji University of Stuttgart, Germany RecoPhos Demonstration Event Leoben, February 24th 2015 Tel.: Fax.: Dipl.-Ing. Fatah Naji Universität Stuttgart, ISWA

2 Quality and Solid Waste Management Oldest and largest institute for environmental sciences in Europe Teaching in 2 German and 4 international master courses; 2 PhD programmes 2 4 professors, 47 academic employees, 48 technical and administrative staff Interdisciplinary: civil, process and environmental engineers, biologists, chemists, geo-scientists Research, development and consulting for public bodies and industry Large laboratory equipment for solid and liquid analyses Own fully operational sewage treatment plant for education and research ( PE)

3 Outline Observation Sewage Sludge Ash Experiments - RecoPhos bench scale plant 3

4 Observation Sewage Sludge Ash Sewage Sludge in Germany 1,85 Mio. T DM/a Thermal treatment in Germany 55 % 20 municipal incineration plants 6 industrial incineration plants T SSA/a (KRÜGER 2014) 4 WWTP / Sewage Sludge incineration Stuttgart

5 Observation Sewage Sludge Ash Sampling Standard Ash 5

6 6 Observation Sewage Sludge Ash Composition and Basicity of Standard ash Composition analysis (ICP-OES) Main components (DIN 51729) Wt% Al 2 O BaO CaO 13.3 Fe 2 O K 2 O 1.71 MgO 3.37 MnO Na 2 O P 2 O SO SiO SrO TiO Total % Phase analysis (XRD) Phase Wt% SiO 2 30 Ca 9 AlP 7 O Fe 2 O 3 13 Al 2 O 3 11 FePO 4 7 Rest 10 Total 100% Flowability of molten SSA is mainly influenced by the basicity B1. B1 = CaO/SiO 2 = 0.41 Acidic

7 Outline Observation Sewage Sludge Ash Experiments - RecoPhos bench scale plant 7

8 Experiments RecoPhos bench scale plant bench-scale plant 8 Design

9 Experiments RecoPhos bench scale plant >1600 C 9 Heating up: ~ 4 h Feeding: ~ 5 h Cooling: ~ over night

10 Experiments RecoPhos bench scale plant side top bottom Sample fragments Fragment 10 P removal efficiency analysed

11 Experiments RecoPhos bench scale plant P recovery mechanism First experiments confirmed our basic assumptions CO as main reduction agent for phosphates! Slag stalagmite (simplified image) Efficient P removal from SSA melt starts once a sufficiently high CO content is generated! Slag in equilibrium operation Very low P content 11 Slag after several minutes of operation Slag from beginning of trial Medium P content High P content

12 Experiments RecoPhos bench scale plant P removal mechanism Influence of basicity on Phosphorus removal Basicity 0.4 Phosphorus removal rate from slag: < 10 % Basicity 0.8 Phosphorus removal rate from slag: % 12 Experiments with basicity in planning!

13 Experiments RecoPhos bench scale plant P removal mechanism P removal rate from slag >90% What about the P content in the metal phase? Slag immediately solidifies when it leaves the reactor vessel Metal rich fractions/ droplets are found within slag Operating under nonequilibrium conditions, allows us to improve P recovery compared to calculations 13

14 Challenges in current lab setup Challenge Consequence Solution for Pilot Plant Slag freezing in reactor outlet Built up of a slag pond within furnace Geometrical changes, higher throughput Carry-over of SSA melt into gas outlet Continuous readjustment of suction pressure Geometrical changes in interface between reactor and gas exhaust tube P2O5 condensation in tubing after combustion Mass balance not possible Higher throughput 14

15 Summary/ Outlook Summary: > 90 % Phosphorus removal from slag Formation of iron phosphorus lower than expected Outlook: Find optimal Basicity for P recovery Analyse P recovery rate for different ash compositions Different carbon sources/ susceptor materials Separation of metal alloy 15

16 Thank you! Contact Dipl.-Ing. Fatah Naji / Dipl.-Ing. Matthias Rapf University of Stuttgart, ISWA, Stuttgart, Germany Tel.: