kajthomsen_phosphorus1298

8/11/2019 KajThomsen_Phosphorus1298

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Recovery of Phosphorus forRecyclingKaj Thomsen

CERE, Center for Energy Ressources Engineering

DTU, Technical University of DenmarkLyngby, Denmark


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June 27, 2012Recovery of Phosphorus for Recycling2 DTU Chemical Engineering,

Technical University of Denmark

Importance of phosphorus

Phosphorus is found in every cell of all living beings(ADP/ATP, DNA, bone)

Phosphorus can not be replaced by another compound, itis a non-renewable resource

Phosphorus is one of the most abundant elements in theearths crust

The known reserves of high concentration phosphate rockare being depleted

Lack of phosphorus will cause increase in food prices,food shortages, geopolitical rifts

Phosphorus has been designated as a strategic mineralresource by many countries


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Peak phosphorus

Hubbert curve by Dana Cordell and Stuart White, Sustainability,3(2011)2027-2049


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Phosphorus as a waste product

Straw and other organic material is increasingly being used for

power and heat generation

Gasification and combustion processes

Much of the phosphorus in the straw ends up in the fly ash

from the combustion Up to 90% of the fly ash is soluble, inorganic salts

The fly ash cant be deposited in land fills in the European

Union due to its solubility

The fly ash cant be used as a fertilizer due to its content ofcadmium and other heavy metals

This project was started in cooperation with the Danish

company Kommunekemi in order ot solve this waste problem


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Soluble salts in fly-ash

Flyash from straw combustion

30 mass % K2SO4 50 mass % KCl

5-10 mass % P2O5 10-15 mass % insoluble

Flyash from sewage sludge or manure combustion

Rich in P2O5

Both contain various metals and other impurities besidesfertilizer material

Fluoride Aluminum

Iron(III)

Copper(II)

Cadmium (10-15 ppm)


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Benefits of recycling phosphorus

The rate of consumption of the limited sources of

phosphate rock in the world can be reduced

The environment benefits from reduced eutrophication

Money and energy is saved on the mining and import of

phosphate products

Indepedence from geopolitical tensions

Thermodynamic modeling of the relevant aqueous salt

systems is required in order to design appropriate

processes for recycling phosphorus

Process simulation

Process design


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Previous modeling of similar

systems Wang et al., Modeling phase equilibria and speciation in mixed-

solvent electrolyte systems, Fluid Phase Equilibria, 222-223(2004)11-17

System: K+, Na+, H2PO4-, HPO4

2-, H3PO4 OLI mixed solvent electrolyte model

Christensen and Thomsen, Modeling of Vapor-Liquid-SolidEquilibria in Acidic Aqueous Solutions, Ind. Eng. Chem. Res.,42(2003)4260-4268

System: K+, Na+, NH4+, Ca2+, Cl-, H2PO4

-, HPO42-, H3PO4

Extended UNIQUAC modeling did not include high pH range

Weber et al., A Solubility Model for Aqueous SolutionsContaining Sodium, Fluoride, and Phosphate Ions, Ind. Eng.Chem. Res., 39(2000)518-526

System: Na3PO4, Na2HPO4, NaF, NaOH

Pitzer model to describe phase equilibria up to 100C


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Extended UNIQUAC model

Not a new model but new parameters

Thermodynamic model for solutions containing

electrolytes

Debye-Hckel term for electrostatic interactions

UNIQUAC term for short range interactions

Soave-Redlich-Kwong term for gas phase fugacities

The model is used for calculation of

Speciation equilibrium

Solid-liquid equilibrium

Vapor liquid equilibrium

Liquid-liquid equilibrium

Thermal properties


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Extended UNIQUAC modelex ex ex ex

Combinatorial Residual Extended Debye-Hckel = + +G G G G

ln - ln2

exCombinatorial i i

i ii

i i ii

zG x xq

RT x

ln

ex

Residualji i ji

i j

G = x qRT

expji ii

ji

u u

= - T

;i i i i

i i

j j j j

j j

x r x q

x r x q

2

3

4ln 1

2

EExtended Debye-Hckel

w w

Ba IAG= x M BaI BaI +

RT Ba

3/2

21/2

0

0

2 ; 1.54

A

r

eA N d Ba

kT


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Extended UNIQUAC model

Relative permittivity for pure water is used for all

solutions

The effect of other species on the chemical potentials in the

solution is accounted for by interaction parameters

The hydrogen ion is given fixed parameters, includinginteraction parameters with all other species

The hydrogen ion is considered an anchor for the parameters

The properties of all other species are determined relative to

those of the hydrogen ion The temperature dependence of chemical potentials is

determined by the Gibbs-Helmholtz equation: 0 0

2

/lnat constant pressure

d G RT d K H

dT dT RT


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Model parameters and standard

state properties H2O, CO2, HF, HCl, HNO3, H3PO4

H+, Na+, K+, Ca2+, Cu2+, Cd2+, Fe3+, Al3+

F-, Cl-, SO42-, HSO4

-, NO3-, OH-, CO3

2-, HCO3-, PO4

3-, HPO42-, H2PO4

-,

AlO2-

Adjustable model parameters UNIQUAC surface area and volume parameters

Interaction parameters for each pair of species

Standard state properties

Aqueous species properties were taken from NIST/NBS tables

Temperature dependent heat capacities of aqueous speciesgiven by three-parameter expression

Pure salt properties were adjusted to the experimental data

Heat capacities of pure salts were determined by Kopps rule


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Experimental data

Over 150,000 experimental data on electronic form

More than 350 solute species

Types of data include:

Activity/osmotic coefficient

Enthalpy of mixing

Heat capacity

Degree of dissociation

Gas solubility

Enthalpy of absorption/evaporation

Density

Salt solubility (Solid-liquid equilibrium)

Liquid-liquid equilibrium

Vapor-liquid equilibrium

The databank can be browsed at http://www.cere.dtu.dk/Expertise/

Electrolyte data bank will be presented in the poster session


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Determination of parameters

The adjustable parameters were determined using a modifiedMarquard routine from Harwell subroutine library and aNelder-Mead simplex routine

Sequence of parameter determination:1. Core system consisting of H+, Li+,Na+, K+, Mg2+, Ca2+, OH-, Cl-, HCl,

NO3-

, HNO3, SO42-

, HSO4-

based on ca. 27000 experimental datapoints. 23 binary and 87 ternary systems.

2. Carbonate species based on ca. 7000 experimental data

3. Phosphate species based on ca. 5000 experimental data

4. Fluorides species based on ca. 2000 experimental data

5. Aluminum species based on ca 1100 experimental data

6. Copper (II) based on ca 1500 experimental data7. Iron (III) based on ca 1900 experimental data

8. Cadmium based on ca 1000 experimental data

About 200 model parameters and 360 standard stateproperties of salts were adjusted based on these data.


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0

10

20

30

40

50

60

70

80

90

100

100

90

80

70

60

50

40

30

20

10

0

0 10 20 30 40 50 60 70 80 90 100

P2O5

Na2O

H2O

H3PO4

NaOH

NaH2PO4

NaOH3H2O

NaOHH2O

NaH2PO42H2O

NaH2PO4H2O

NaH2PO4H3PO4

Na2HPO42NaH2PO42H2O

Na2HPO4NaH2PO4

Na2HPO4

Na3PO4

Na3PO4H2O

Na3PO48H2O

Na3PO46H2O

Na3PO412H2O

Na2HPO412H2O

Na2HPO47H2O

H3PO4H2O

4(Na3PO412H2O)H2O

2H3PO4 = 3H2O + P2O52H3PO4H2O = 4H2O + P2O52Na3PO4 = 3Na2O + P2O52Na2HPO412H2O = 2Na2O + P2O5 + 25H2O

Large number of phosphates

24 solids can form inthe H3PO4NaOH

H2O system


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0

5

10

15

20

25

30

35

40

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

molH2O/molsalt

mol Na2O/(mol Na2O + mol P2O5)

ExperimentalExtended UNIQUACTie linesSolids composition

NaH2PO4H3PO4

NaH2PO4H2O

Na2HPO42

NaH2PO42H

2O

Na3PO412

H2O

Na2

HPO42H2

O

(4Na3PO412H2O)NaOH

Na3PO4H2O

40 C

Na2HPO4NaH2PO4

Na2HPO47H2O

NaH2PO4

NaH2PO4 Na2HPO4 Na3PO4

H3PO4


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0

10

20

30

40

50

60

70

80

90

100

100

90

80

70

60

50

40

30

20

10

0

0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00 100.00

Experimental

Extended UNIQUAC

P2O5

Na2O

H2O

H3PO4

NaH2PO4

NaOH3H2O

NaH2PO42H2O

NaH2PO4H2O

NaH2PO4H3PO4 Na2HPO42NaH2PO42H2O

Na3PO412H2O

Na2HPO412H2O

H3PO4H2O

4(Na3PO412H2O)NaOH

25C


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0

10

20

30

40

50

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

molH2O/molsalt

mol K2O/(mol K2O + mol P2O5)

Experimental

Extended UNIQUAC

Tie linesSolids composition

0 C

H3PO4H2OKH2PO4H3PO4

KH2PO4

K2HPO

46H

2O

K3PO47H2O

KOH2H2O

K3PO4KH2PO4 K2HPO4


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0

10

20

30

40

50

60

70

80

90

100

100

90

80

70

60

50

40

30

20

10

0

0 10 20 30 40 50 60 70 80 90 100

Ravich and Popova, 1942Platford, 1974Beremzhanov et al., 1978Makin, 1957Bel Madani et al., 1999Ravich, 1938Selva, 1947Extended UNIQUAC, this work

T= 25.0C

NaKHPO45H2O

Na2HPO47H2O

K2HPO43H2O

Na2HPO412H2O

K2HPO

Na2HP

H2O


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-2

0

2

4

6

8

10

12

14

0

10000

20000

30000

40000

50000

60000

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

pH

molH2O/(molCa

O+molP2O5)

mol CaO/(mol CaO + mol P2O5)

Experimental

Extended UNIQUACTie lines

pH

25C

Ca3(PO4)2

CaHPO42H2O

Ca(H2PO4)2H2O


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-2

0

2

4

6

8

10

12

14

0

5

10

15

20

25

30

35

40

45

50

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45

pH

molH2O/(molCa

O+molP2O5)

mol CaO/(mol CaO + mol P2O5)

Experimental

Extended UNIQUACTie linespH

25C

Ca(H2PO4)2H2O

CaHPO42H2O

3 0E+09


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0.0E+00

5.0E+08

1.0E+09

1.5E+09

2.0E+09

2.5E+09

3.0E+09

0 0.2 0.4 0.6 0.8 1

molH2O/molsalt

mol Fe2O3/(mol Fe2O3+ Mol P2O5)

Experimental

Extended UNIQUAC model, this work

25C

FePO42H2O

Fe2(HPO4)3H3PO46H2O

Fe(H2PO4)32H2O

0

100

200

300

400

500

600

0 0.05 0.1 0.15 0.2 0.25

molH2O/molsalt

mol Fe2O3/(mol Fe2O3+ Mol P2O5)

ExperimentalExtended UNIQUAC

25C

FePO42H2O

Fe2(HPO4)3H3PO46H2O

Fe(H2PO4)32H2O

FePO42H2O

Solubility: Ca3

(PO4

)2

> Cu3

(PO4

)2

>

AlPO4> FePO4


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0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

NaFmass%

Na3PO4, mass %

Extended UNIQUAC

Guiot (1967)

Nagorskaya and Novoselova (1935)

Morozova and Rzhechitskii (1977)

Tananaev (1941)

Morrison and Jache (1959)

Payne (1937)

Na3PO412H2O

2Na3PO4NaF19H2O

NaF0 C

Systems with data of

questionable quality


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0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

0 2 4 6 8 10 12 14

NaF

mass%

Na3PO4, mass %

Extended UNIQUAC

Roslyakova et al. (1979)

Foote and Schairer (1930)

Herting (1996)

Clark (1919)

Carter (1928)

Na3PO412H2O

2Na3PO4NaF19H2O

NaF

25 C


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0.0000

0.0005

0.0010

0.0015

0.0020

0.0025

0.0030

0.0035

0.0040

0.0045

0 10 20 30 40 50 60 70 80

Mass

%CaF2

Temperature C

Extended UNIQUAC

Experimental

CaF2


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Potassium salts with low

solubility

0

5

10

15

20

25

30

0 2 4 6 8

Wt%A

l2(SO4)3

Wt % K2SO4

Extended UNIQUAC this work

Ts'ai et al., 1936

0C

KAl(SO4)212H2O


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0

5

10

15

20

25

30

35

0 10 20 30 40 50 60 70

Wt%

Al(OH)3

wt % KOH

Extended UNIQUAC, this work

Du et al., 200540C

2KOHAl2O32H2O

Al(OH)3

Aluminate ion, AlO2-

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

8.5 9 9.5 10 10.5 11

A

lO2-fraction

pH

Al3+

AlO2-

Al3++4OH-AlO2-+2H2O

Standard state properties for AlO2-

fG, kJ/mol fH, kJ/mol

NIST -830.9 -930.9

This work -734.0 -923.0


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Salting in of CaSO4by AlCl3

0

5

10

15

20

25

30

35

0 0.2 0.4 0.6 0.8 1 1.2 1.4

Wt%A

lCl3

Wt % CaSO4

Extended UNIQUAC, this work

Li and Demopoulos, 2006

50C

AlCl36H2O

CaSO4

CaSO42H2O


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0

200

400

600

800

1000

1200

0 0.2 0.4 0.6 0.8 1

Vaporpressure,kPa

HF mol fraction

Pxy diagram for HF-H2O at 100C

Extended UNIQUAC

Experimental

50

60

70

80

90

100

110

120

0 0.2 0.4 0.6 0.8 1

Vaporpress

ure,kPa

HF mol fraction

Pxy diagram for HF-H2O at 100C

Extended UNIQUAC

Experimental


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Model implementation

The model is implemented in a dynamic link library (DLL-

file)

Multi-phase flash algorithm

The program can be called from programs that have a Visual Basic

interface such as Microsoft Excel Simulations can be carried out directly in Excel

The excel sheet can be used as an interface to Aspen Plus

The model can be implemented as a user model in Aspen Plus


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Conclusion

Phosphate is essential to life on earth no substitutes

Recycling of phosphate is extremely important due to limitedressources.

Thermodynamic modeling of phase behaviour in systemscontaining phosphate enable us to design processes for

producing food grade phosphate from waste such as sewagesludge

Modelling with current activity coefficient models only possible withthe use of good quality experimental data

Experimental data for solubility in many systems representingphosphate and its impurities are of low quality

New experimental measurements of solubility and otherproperties of these systems are required to improve themodeling


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Acknowledgment

This project was supported by a grant from ForskEL

projekt nr. 2008-1-0111 Working up phosphate from

ashes

The project was carried out in cooperation with

Kommunekemi as, Denmark


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Thank you for your attention


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0

0.05

0.1

0.15

0.2

0 10 20 30 40 50 60

CaSO4solubili

ty,mol/kgwater

H3PO4 mol/kg water

Experimental, CaSO4

Experimental, CaSO4H2O

Experimental, CaSO42H2O

Extended UNIQUAC

80 C

CaSO4

CaSO4H2O

CaSO42H2O


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-60

-40

-20

0

20

40

0 20 40 60 80 100

Tem

peratureC

Mass % H3PO4

Experimental

Extended UNIQUAC

H3PO4H2O

H3PO4

Ice


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0

1

2

3

4

5

6

0 10 20 30 40 50 60

FeF3

KF

T= 25.0C

Weight%

FeF33H2O

FeF32KFH2O

KF2H2OFeF33KF3H2O


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June 27 2012Recovery of Phosphorus for Recycling36 DTU Chemical Engineering

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 10 20 30 40 50 60 70 80 90 100 110 120

saltfraction

Calculated

Experimental

Temperature, CCuSO4

Na2SO4

CuSO4Na2SO42H2O

CuSO45H2O

Na2SO410H2O

Na2SO4

CuSO43H2O

kajthomsen_phosphorus1298

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