Phosphorus Recovery from Incinerated Sewage Sludge Ash (ISSA) and - - PowerPoint PPT Presentation

The Hong Kong Polytechnic University

Phosphorus Recovery from Incinerated Sewage Sludge Ash (ISSA) and Turn into Phosphate Fertilizer

Student :Le FANG Supervisor: C. S. POON

• ---June. 2018

Contents

• Background and motivation
• Clarification of research key points
• Current results
• Conclusions

Contents

• Background and motivation
• Clarification of research key points
• Current results
• Conclusion

T‐Park

Incineration in Hong Kong - T-Park

Main Sewage Treatment Works Locations

• 1200 tons sewage sludge
• riginated from 11 wastewater

treatment plants in Hong Kong.

• Turn waste into energy. Thermal

energy in incineration process was collected and transferred into electricity.

• Volume reduction by 90%.

Decreased burden for landfill capacity.

• 2 s under 850C. Least formation
• f harmful organic pollutant.
• Incinerated sewage ash which was

present disposal by landfill.

ISSA

• 1200 tons sewage sludge
• riginated from 11 wastewater

treatment plants in Hong Kong.

• Turn waste into energy. Thermal

energy in incineration process was collected and transferred into electricity.

• Volume reduction by 90%.

Decreased burden on landfill capacity.

• 2 s under 850C. Minimal

formation of harmful organic pollutant.

• Incinerated sewage ash currently

disposal of at landfill. T‐Park

Incineration in Hong Kong - T-Park

Contents

• Background and motivation
• Clarification of research key points
• Current results
• On-going and plan to do…

HK ISSA P fertilizer

Characteristics: pH, specific gravity, LOI, XRF, XRD, SEM, BET

Purification P leaching

Practical applications of P fertilizer

Simplify the leaching process Potential application area Cost of the application process Design of reaction vessel Leaching by three kind of agents A two step leaching process Physical/chemic al characteristics High Fe ISSA Potential P resource sink Absorption. Fractional precipitation. Final recovery ratio Constituents analysis. Three kind fertilizers.

Research structure

Methods Results

Contents

• Background and motivation
• Clarification of research key points
• Current results
• Conclusion

Purification P leaching

HK ISSA

Characteristics of Hong Kong ISSA

Items Hong Kong ISSA US ISSA(Donatello and Cheeseman 2013) Physical properties Specific gravity 2.49 2.14-2.9 pH 8.45 7.6-8.8 Mean particle size (μm) 56.0 51.2-108.8 BET surface area (m2/g) 3.42 6.4-23.8 Loss on ignition (%) 0.99 0.9-2.1 Chemical composition (%) Na2O 2.21 0.01-6.8 MgO 1.54 0.02-23.4 Al2O3 11.56 4.4-34.2 SiO2 33.35 14.4-65.0 P2O5 9.16 0.3-26.7 Cl 0.28

—

SO3 4.04 0.01-12.4 K2O 3.50 0.1-3.1 CaO 9.54 1.1-40.1 TiO2 0.55 0.3-1.9 Cr2O3 0.09 — MnO 0.12 — Fe2O3 22.60 2.1-30 CuO 0.18

—

ZnO 0.69

—

20 40 60 80 500 1000 1500 2000 2500 3000

A Q F H Q Q F W F H H W Q F Q

Density (Counts) D egree (2Theta)

A A:A northite F:Feldspar H:H em atite Q:Q uartz W :W hitlockite

HK ISSA:

• Fine ash.
• Nearly no organic matter.
• High Fe ISSA.
• Contain significant P but co-

exist with Fe, Al, Ca.

0.01 0.1 1 10 100 1000 1 2 3 4 5 6

Volume (%) % (μm)

Suitable substitute for phosphorite deposit.

P leaching by three kind of extraction agents

Limited P leaching. Significant P was leached out by acids.

Inorganic acid

Chelatin g agents

Organic acid

Co-leaching of metal(loid)s

Inorganic acid

Chelatin g agents

Organic acid

Inorganic acid

Chelatin g agents

Organic acid Inorganic acid

Chelatin g agents

Organic acid

Co-leaching of metal(loid)s

Metal(loid)s were leached out with limited P leaching.

Two-step P extraction

• EDTA Pretreatment
• Metal(loid)s were leached out with limited P leaching.
• Optimized pretreatment conditions: 3 hour reaction at a pH of 1.3, at a

liquid-to-solid ratio of 20:1 and concentration of 0.02 mol/L.

• Sulphuric acid P extraction
• High efficiency in P extraction with relatively low metal(loid)s co-

dissolution.

• Optimized P extraction condition (94%)：2 hour reaction with 0.2 mol/L

at a liquid to solid ratio of 20:1.

Two-step leaching process with factional precipitation

Two-step extraction 1st step: EDTA pre-treatment 2nd step: sulphuric acid extraction 2-extract Filtrated and dried ISSA

P-extract P-free residue Ca(OH)2 NaOH pH=4 pH=4

2-Ca 2-Na ISSA Single-step extraction sulphuric acid extraction 1-extract

P-free residue P-extract NaOH pH=4

1-Ca 1-Na

Ca(OH)2

• 1. Two-step leaching decreased concentration of metal(loid)s, such as Cr (by

92%), Zn (by 58%), Mn (by 50%), Mg (by 49%), Cu (by 49%), Al (by 37%), Fe (by 23%), etc.

• 2. Subsequent pH adjusting by Ca(OH)2 would induce formation of Ca-P.

Purification of P-extract from two-step methods (to remove Al, Fe, Ca, Zn, etc.)

Activated carbon 732 cationic resin Low absorption efficiency in acids. High absorption efficiency in acids.

Purification-absorption

0.000 0.005 0.010 0.015 0.020 0.025 0.030 0.035 0.18 0.27

leachate 732 resin Extraction mass(mg/g)

Sb Se Ni As Cd Cr Mn Pb Cu

MAC

8 16 24

leachate 732 resin Extraction mass (mg/g) Mg Al Ca Fe Zn MAC

Obvious reduction of major metal(loid)s. MAC can remove metal(loid)s marginally.

Modified biochar for phosphorus absorption

Peanut shell (PS) Sugarcane bagasse (Sc)

• 1. Soaking with

MgCl2 solution Pyrolysis Mg-Ps Biochar Mg-Sc Biochar Ca-Ps Biochar Ca-Sc Biochar

• 2. Soaking with

CaCl2 solution

v

Biochar laden with phosphorus – a kind of fertilizer

Optimal biochar for phosphorus absorption

Ps700 PsM700 PsC450 PsC700 PsC850 Sc700 ScM450 ScM700 ScM850 ScC700

10 20 30 40 50 60 70 80 90 100

Phosphorus absorption efficiency(%) Biochars

Pristine biochars have low phosphorus removal capacity.

Optimal biochar for phosphorus absorption

Ps700 PsM700 PsC450 PsC700 PsC850 Sc700 ScM450 ScM700 ScM850 ScC700

10 20 30 40 50 60 70 80 90 100

Phosphorus absorption efficiency(%) Biochars

Pretreating of Ps & Sc with CaCl2 cannot significantly improve phosphorus removal capacity.

Optimal biochar for phosphorus absorption

Ps700 PsM700 PsC450 PsC700 PsC850 Sc700 ScM450 ScM700 ScM850 ScC700

10 20 30 40 50 60 70 80 90 100

Phosphorus absorption efficiency(%) Biochars

Pretreatment of Ps & Sc by MgCl2 can produce biochars with high phosphorus removal capacity.

Optimal pyrolysis temperature on phosphorus absorption

Ps700 PsM700 PsC450 PsC700 PsC850 Sc700 ScM450 ScM700 ScM850 ScC700

10 20 30 40 50 60 70 80 90 100

Phosphorus absorption efficiency(%) Biochars

Biomass pyrolysis at 700oC produced the highest P removal biochar.

Biochars laden with phosphorus

Before absorption After absorption PsM700 ScM700 Spectrum 1 Spectrum 2 Spectrum 1 Spectrum 2

Contents

• Background and motivation
• Clarification of research key points
• Current results
• Conclusions

Conclusions

• Two-step leaching method can not only decrease metal(loid)s in extraction but also increase

phosphorus-purity for the subsequent purification step.

• Precipitation of leachate from the two-step method by Ca(OH)2 pH adjustment induces

formation of Ca-P.

• 732 cationic resin is efficient in removing macro-metalloids like Al, Mg, Zn, Fe and Cu. The

purified leachate can be used for liquid phosphorus fertilizer.

• Both biomass of Ps and Sc have high phosphorus removal capacity after pretreatment by

MgCl2 and pyrolysis at 700oC. And ScM700 has advantages of higher phosphorus adsorption capacity, less adsorbed metal(loid)s and lower working pH over PsM700.

Thank you!