Study of Phosphoric Acid Production Lines Using Radiotracers

Transcription

1 Study of Phosphoric Acid Production Lines Using Rachad ALAMI 1 st International Conference on Applications of Radiation Science & Technology ICARST IAEA, Vienna - April 24 th 28 th 217

2 Study of Phosphoric Acid Production Lines Using 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). Khouribga site: three mines currently operating opening of two more in 217.

3 Study of Phosphoric Acid Production Lines Using Office Chérifien des Phosphates (OCP Group): world s leading producer and exporter of phosphates and its derivatives, including phosphorous and agricultural fertilizers. 187 km Minéroduc = Phosphate pulpe pipe or Slurry pipe 38 km Drainage of phosphate rock from the mines to Jorf Lasfar chemical site which was done up to 215 by train, Is now carried out by slurry pipe

4 Study of Phosphoric Acid Production Lines Using Phosphoric acid (H 3 PO 4 ) prepared in most cases by adding sulfuric acid to tricalcium phosphate rock: Ca 5 (PO 4 )3X + 5 H 2 SO H 2 O 3 H 3 PO CaSO4 2 H 2 O + HX where X may include OH, F, Cl, and Br. 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, Fe 2 O 3 (rust) to ferric phosphate, FePO 4. - 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.

5 Study of Phosphoric Acid Production Lines Using Détecteur S1 Détecteur S3 Détecteur S4 Détecteur S7 Case study 1: Line X of XXX Unit: 2 digestors D1,D2 (2x 95 m 3 ) 4 crystallizers C1-C4 (4x7 m 3 ) Détecteur S Détecteur S2 Détecteur S5 Détecteur S6 Study concerned mainly the digestors and the cristalizers. Overall activities injected in the form of liquid Na 131 I: - 1st injection : 1,8 GBq (3 mci) at the inlet of digestor D1-2 nd injection :18 GBq (5 mci) at the inlet of crystallizer C1 Detectors location: 8 detectors (S to S7) placed along the line as shown

6 Study of Phosphoric Acid Production Lines Using Détecteur S1 Détecteur S3 Détecteur S4 Détecteur S7 Case Study 1-1 st injection: Dirac signal registered at the entry of D1 Détecteur S Détecteur S2 Détecteur S5 Détecteur S D D C C2 C3 C4

7 Study of Phosphoric Acid Production Lines Using D1 Case Study 1-1 st injection: Flow regime in the digester D1 conforms to the model of a perfect mixer Mean residence time ṫ D1 in the digester: 23.5mn. ṫ D1-th = 23.45mn No process anomaly detected Deconvolution of the response curves obtained at the output of digesters D1 and D2. D2 ṫ D2 = 25.75mn ṫ D2-th = 23.45mn Response curve obtained at the output of digesters D1+D2 considered as a unique reservoir: ṫ D1+D2 = 49.42mn ṫ D2 = ṫ D1+D2 - ṫ D1 = 25.88mn ṫ D2-th = 23.45mn No process anomaly is detected at the digester D2

8 Study of Phosphoric Acid Production Lines Using Case Study 1-1 st injection: Deconvolution from the response curve at the output of the digester D2 used as an input pulse of the crystallizer C1. C1 Flow regime in crystallizer C1 is assimilated to the model of a perfect mixer. ṫ C1 = 1.47h ṫ C1-th = 1.59h 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: ṫ D1+D2+C1 = 2.14 h ṫ C1 = ṫ D1+D2+C1 - ṫ D1+D2 = 1.32h

9 Study of Phosphoric Acid Production Lines Using Case Study 1-1 st injection: C2 C3 C4 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. Tracer Arrival Times Production Line Component Tracer Arrival Time (s) Tracer Arrival Time (mn) Digestor D1 12,2 Digestor D2 6 1 Crystallizer C1 3 5 Crystallizer C ,67 Crystallizer C ,33 Crystallizer C4 9 15

10 Study of Phosphoric Acid Production Lines Using Détecteur S1 Détecteur S3 Détecteur S4 Détecteur S7 Case Sudy 1-2 nd injection: Dirac signal registered at the entry of C1 Détecteur S Détecteur S2 Détecteur S5 Détecteur S6 1 C C C C

11 Study of Phosphoric Acid Production Lines Using Case Study 1-2 nd injection: Flow regime in crystallizer C1 is assimilated to the model of a perfect mixer. ṫ C1 = 1. 74h ṫ C1-th = 1.59h C1 Case Study 1 C1 crystallizer - 1 st injection compared to 2 nd injection: 1 st injection: 2 nd injection: 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. ṫ C1 = 1.47h ṫ C1-th = 1.59h Response curve at the output of C1 to a Dirac pulse at the entry of C1: flow regime in crystallizer C1 is assimilated to the model of a perfect mixer. ṫ C1 = 1. 74h

12 Study of Phosphoric Acid Production Lines Using Case Study 1-2 nd injection: deconvolution from the response curve at the output of crystallizer C1 used as an input pulse of crystallizer C2 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 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 ṫ C1+C2+C3 = 5.39 h 3 perfect mixers in series

13 Study of Phosphoric Acid Production Lines Using Case Study 1 - Estimation of radiotracer Activity: A = C max.v.[2 1/2 / P e 1/2 ] (axial dispersion flow) A = C max.v.{[(j-1)!]/ J J }. e J (tanks in series flow model) m 3 /mn Maximum tracer velocity Versus Specific Activity C1 D1 C2 D2 C1 C3 C2 C4 C3 C4 MBq/m 3

14 Study of Phosphoric Acid Production Lines Using Case Study 2 D D4 D3 D2, D2 D1, D1 D5 Study concerned mainly two tanks (R63 and R631) where the attack of crude phosphate by sulfuric acid (H 2 SO 4 ) takes place. Other detectors were also placed at the output of: - the passage tank, - the digester, - the large filter, on the return line to tank R63. Tracer activity :13.32 GBq (36 mci) of 131 I (in the form of liquid Na 131 I).

15 Cps(s) Cps(s) Study of Phosphoric Acid Production Lines Using Cps(s) Cps(s) (s) Case Study R63 Temps(s) A B C R631 Temps(s) 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 H 2 SO 4 (from 42m 3 /h to 12m 3 /h) Passage Tank Temps(s) Digestor Temps(s) Filter

16 Study of Phosphoric Acid Production Lines Using Case Study 2 R63 perfect mixer ṫ R63 = 11s ṫ R63-th = 18s Dead volume: 38% R631 perfect mixer with recycling. ṫ R631 = 2.86h ṫ R631-th = 3.1h Dead volume: 1% Tracer Arrival Times Elément de l unité PP2 Temps d arrivée (s) Entrée cuve d attaque Entrée cuve de passage 2 Entrée digesteur 11 Entrée filtre 46 Recyclage d acide vers la cuve 5 63

17 Incomplete info Study of Phosphoric Acid Production Lines Using Cases 1 and 2 - Estimation of radiotracer Activity: m 3 /mn Loss of info MBq/m 3

18 Study of Phosphoric Acid Production Lines Using Conclusion Thank You 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