study of phosphoric acid production lines cnesten using ... · rachad alami 1st international...

Rachad ALAMI

1st International Conference on Applications of Radiation Science & Technology

ICARST

IAEA, Vienna - April 24th – 28th 2017

Study of Phosphoric Acid Production Lines

Using RadiotracersCNESTEN

CNESTEN

Morocco’s phosphate rock reserves are the largest

reserve base in the world, accounting for nearly 75%

of the world’s reserves,

(U.S. Geological Survey: USGS).


Using Radiotracers

Khouribga site:

• three mines currently operating

• opening of two more in 2017.

CNESTEN

Drainage of phosphate rock from the mines to Jorf Lasfar chemical site …

…which was done up to 2015 by train,

…Is now carried out by slurry pipe


Using Radiotracers

187 km

38 kmMinéroduc =

Phosphate pulpe pipe or ‘‘Slurry pipe’’

“Office Chérifien des

Phosphates” (OCP Group):

world’s leading producer

and exporter of phosphates

and its derivatives, including

phosphorous and

agricultural fertilizers.

In addition to being a chemical reagent, phosphoric acid has a wide variety

of uses as:

- rust inhibitor (direct application to rusted iron, steel tools, or other

surfaces changes the reddish-brown iron (III) oxide, Fe2O3 (rust) to

ferric phosphate, FePO4.

- food additive (to acidify various colas and jams, as leavening agent…)

- Dental, orthopedic and industrial etchant (to clean and roughen the

surfaces of teeth where dental appliances or fillings will be placed)

- ingredient in over-the-counter anti-nausea medications

- fertilizer feedstock,

- dispersing agent and component of home cleaning products

- Phosphoric acids are also important in biology.


Using Radiotracers

CNESTEN

Phosphoric acid (H3PO4)prepared in most cases by adding sulfuric acid to tricalcium phosphate rock:

Ca5(PO4)3X + 5 H2SO4 + 10 H2O → 3 H3PO4 + 5 CaSO4·2 H2O + HX

where X may include OH, F, Cl, and Br.

Détecteur S0

Détecteur S1

Détecteur S2

Détecteur S3 Détecteur S4


Détecteur S7

Détecteur S0

Détecteur S1

Détecteur S2



Détecteur S7

Line X of XXX Unit:

2 digestors D1,D2 (2x 95 m3)

4 crystallizers C1-C4 (4x700 m3)

Case study 1:


Using Radiotracers

• Detectors location: 8 detectors (S0 to S7) placed along the line as shown

CNESTEN

- 1st injection : 10,80 GBq (300 mCi) at the inlet of digestor D1

- 2nd injection :18 GBq (500 mCi) at the inlet of crystallizer C1

• Study concerned mainly the digestors and the cristalizers.

• Overall activities injected in the form of liquid Na131I:

Study of Phosphoric Acid Production Lines Using

Radiotracers

Case Study 1 - 1st injection:

Détecteur S0

Détecteur S1

Détecteur S2



Détecteur S7

Détecteur S0

Détecteur S1

Détecteur S2



Détecteur S7

Dirac signal registered at the entry of D1

CNESTEN

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cp

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C1D1 D2

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C2 C3 C4

Response curve obtained at the output of digesters

D1+D2 considered as a unique reservoir:

ṫD1+D2 = 49.42mn → ṫD2 = ṫD1+D2 - ṫD1 = 25.88mn

ṫD2-th = 23.45mn


Radiotracers


Flow regime in the digester D1 conforms to the

model of a perfect mixer

Mean residence time ṫD1 in the digester: 23.5mn.

ṫD1-th = 23.45mn

No process anomaly detected

D1

Deconvolution of the response curves

obtained at the output of digesters D1 and D2.

ṫD2 = 25.75mn

ṫD2-th = 23.45mnD2

No process anomaly is detected at the digester D2

CNESTEN


Radiotracers


Considering the assembly of the two digesters and the crystallizer C1 as a

single reactor having as input the Dirac signal at the input of digester D1:

ṫD1+D2+C1 = 2.14 h → ṫC1 = ṫD1+D2+C1 - ṫD1+D2 = 1.32h

Deconvolution from the response curve at the

output of the digester D2 used as an input

pulse of the crystallizer C1.

Flow regime in crystallizer C1 is assimilated to

the model of a perfect mixer.

ṫC1 = 1.47h

ṫC1-th = 1.59h

C1

CNESTEN


Radiotracers


Production Line

Component

Tracer Arrival Time

(s)

Tracer Arrival Time

(mn)

Digestor D1 12 0,2

Digestor D2 60 1

Crystallizer C1 300 5

Crystallizer C2 1300 21,67

Crystallizer C3 3500 58,33

Crystallizer C4 9000 150

Tracer Arrival Times

CNESTEN

C2, C3 and C3 crystallizers

Output of crystallizer C2 is separated from Dirac pulse at the input of digester D1 by 4 reactors,

This has the effect of obtaining a response curve at the output of C2 which is totally degraded (magnitude

of background noise).

Consequently, no results can be obtained for this reactor.

The above remark is even more true for the crystallizers C3 and C4.

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C2 C3 C4


Radiotracers

Case Sudy 1 - 2nd injection:

Détecteur S0

Détecteur S1

Détecteur S2



Détecteur S7

Détecteur S0

Détecteur S1

Détecteur S2



Détecteur S7

CNESTEN

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Dirac signal registered at the entry of C1

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C1 C2

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C3 C4


Radiotracers

Deconvolution from the response curve at the

output of the digester D2 used as an input

pulse of the crystallizer C1:

flow regime in crystallizer C1 is assimilated to


ṫC1 = 1.47h

Response curve at the output of C1 to a Dirac

pulse at the entry of C1:

flow regime in crystallizer C1 is assimilated to


ṫC1 = 1. 74h

1st injection: 2nd injection:

ṫC1-th = 1.59h

Case Study 1 – C1 crystallizer - 1st injection compared to 2nd injection:

Case Study 1 - 2nd injection:CNESTEN

Flow regime in crystallizer C1 is assimilated to


ṫC1 = 1. 74h

ṫC1-th = 1.59h

C1


Radiotracers

Case Study 1 - 2nd injection:

deconvolution from the response curve

at the output of crystallizer C1 used as

an input pulse of crystallizer C2

considering the assembly of the two

crystallizers C1 and C2 as a single

reactor having as input pulse the Dirac

signal at the input of the crystallizer C1

C2

C3

set of 3 crystallizers C1, C2 and C3

considered as a single reactor having

as input the Dirac signal at the input of

the crystallizer C1

ṫC1+C2+C3 = 5.39 h

3 perfect mixers in series

CNESTEN

A = Cmax.V.[21/2 / Pe1/2] (axial dispersion flow)

A = Cmax.V.{[(J-1)!]/ JJ }. eJ (tanks in series flow model)


Radiotracers

Case Study 1 - Estimation of radiotracer Activity:

D1

D2 C1C2 C3 C4

C1

C2

C3C4

MBq/m3

m3/mn

Maximum tracer velocity Versus Specific Activity

CNESTEN


Radiotracers

Case Study 2

D0

D1, D1’D2, D2’D3

D4

D5

CNESTEN

• Other detectors were also placed at the output of:

- the passage tank,

- the digester,

- the large filter, on the return line to tank R6300.

• Tracer activity :13.32 GBq (360 mCi) of 131I (in the form of liquid Na131I).

• Study concerned mainly two tanks (R6300 and R6301) where the attack

of crude phosphate by sulfuric acid (H2SO4) takes place.


Radiotracers

Case Study 2CNESTEN

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Passage Tank Digestor Filter

• A: 4mn stop of the phosphate and sulfuric acid feed;

• B: variation over a period of 2mn of the phosphate feed rate (from

95 t/h to 42 t/h);

• C: variation of supply over 5mn in H2SO4 (from 42m3/h to 12m3/h)


Radiotracers

Case Study 2

Elément de l’unité PP2 Temps d’arrivée

(s)

Entrée cuve d’attaque 6301 10

Entrée cuve de passage 20

Entrée digesteur 110

Entrée filtre 460

Recyclage d’acide vers la cuve

6300

500

Tracer Arrival Times

CNESTEN

perfect mixer

ṫR6300 = 110s

ṫR6300-th = 180s

Dead volume: 38%

R6300

perfect mixer with recycling.

ṫR6301 = 2.86h

ṫR6301-th = 3.1h

Dead volume: 10%

R6301


Radiotracers

Cases 1 and 2 - Estimation of radiotracer Activity:

MBq/m3

m3/mn

CNESTEN

Loss of info

Incom

ple

tein

fo

CNESTEN

Conclusion


Radiotracers

• Residence Time Distributions for Phosphoric

Acid Production Lines can be accurately

established using radiotracer techniques

• Process anomalies can be detected

• Radiotracer Activity needed: ≥ 12MBq x

Overall volume of reservoirs to be inspected

Thank You

study of phosphoric acid production lines cnesten using ... · rachad alami 1st international...

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