Separation process modelling. B. Dinh, M. Montuir, C. Sorel, X. Héres. Département de RadioChimie et Procédés CEA 10 AVRIL 2012 PAGE 1

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1 Separation process modelling B. Dinh, M. Montuir, C. Sorel, X. Héres Département de RadioChimie et Procédés CEA 10 AVRIL 2012 PAGE 1

2 MODELING FOR PROCESS DEVELOPMENT A qualified code for process simulation is a valuable tool as it allows The design and optimisation of flowsheet The realization of safety analysis prior to plant operation - Process parameter margin evaluation - Process state parameter to monitor in order to detect a mal operation - Dynamic behaviour of the process during malfunction Develop tools for plant operation aid as - Automatic flowsheet calculation - Simulators for plant operators training - Diagnosis tools PAGE 2

3 THE PAREX CODE Designed initially for PUREX process simulation Calculate concentration profiles of relevant species in the different operations of the PUREX process In steady or transient states Taking into account different types of contactors (mixer-settlers, pulsed columns or centrifugal contactors) Has been successfully used for the design of the purification cycles of the La Hague plant 15 AVRIL 2014 PAGE 3

4 THE MODELLING APPROACH Phenomena analysis Elementary models Numerical solving Model qualification APPLICATIONS 15 AVRIL 2014 PAGE 4

5 U/PU SPLITTING OPERATION IN PULSED COLUMN Distribution of relevant species in both phases Redox reactions Transfer efficiency of pulsed column mass transfer kinetics axial mixing 15 AVRIL 2014 PAGE 5

6 REDOX REACTIONS Functional reaction : Pu(IV) reduction by U(IV) Interferent reaction : Pu(III) oxidation catalyzed by nitrous acid Stabilizing reaction : nitrous acid scavenging by hydrazine nitrate Side-Inteferent reactions : Hydrazin catalytic destruction by technetium 15 AVRIL 2014 PAGE 6

7 TRANSFER EFFICIENCY IN PULSED COLUMNS Axial mixing decreases the driving force Plug flow with axial mixing model for the phases characterized by a dispersion coefficient Mass transfer kinetics : Film theory scheme F = K x (x - x * ) =k x (x - x i ) = k e (x i - x i* ) = k y (y i -y) 15 AVRIL 2014 PAGE 7

8 REDOX REACTIONS MASS TRANSFER EFFICIENCY INTER ACTION Organic phase Pu(IV) + U(IV) Pu(III) + HNO 2 Hydrazine HNO 2 HN 3 Aqueous phase Poor mass transfer efficiency affects nitrous acid elimination, and thus Pu(III) and U(IV) oxidation 15 AVRIL 2014 PAGE 8

9 EXPERIMENTATION OF U/PU SPLITTING IN PULSED COLUMNS Pilot of pulsed columns of 4m height Continuous organic phase mode chosen to minimize plutonium hold-up in the column Progressive experimentation nitric acid transfer flowsheet uranium (IV) transfer flowsheet uranium, plutonium splitting flowsheet Inactive tests in industrial scale columns nitric acid transfer flowsheet uranium (IV) transfer flowsheet 15 AVRIL 2014 PAGE 9

10 NITRIC ACID TRANSFER IN PILOT COLUMNS U profiles permit to be sure of U solvent loading HNO 3 profiles give overall mass transfer efficiency of the column 15 AVRIL 2014 PAGE 10

11 U(IV) TRANSFER FLOWSHEET The mass transfer efficiency parameters permit a good simulation of uranium (IV) concentration profiles in the column 15 AVRIL 2014 PAGE 11

12 U/PU SPLITTING FLOWSHEET 15 AVRIL 2014 PAGE 12

13 U/PU SPLITTING PLUTONIUM, NITRIC ACID PROFILES Mass transfer efficiency could be reduced to simulate plutonium leak in the solvent (not necessary with very efficient mass transfer obtained with intense pulsation conditions) Could be due to side effects related to the small size of the column and wettability Characteristics in columns interns. PAGE 13

14 U/PU SPLITING U(IV), HYDRAZINE PROFILES Good agreement between simulated and measured profiles for other relevant species PAGE 14

15 INACTIVE TESTS AT INDUSTRIAL SCALE COLUMNS Similar flowsheet performed in industrial scale columns Mass transfer efficiency obtained were greater than in pilot columns Good plutonium back extraction performance expected for industrial column (verified at plant operation) PAGE 15

16 EN RESUME Perfectible kinetics model for redox reaction for U/Pu May be get around by mass transfer efficiency has to be adjust to simulate plutonium leak in solvent outlet in some case) Design of U/Pu splitting flowsheet gave excellent results Pu leak in solvent outlet was less than 50 µg/l The PAREX code can be useful for performance analysis of the U/Pu splitting column In case of mass transfer decrease with aging of the column interns The PAREX can be used to design new plant TBP as the extractant molecule like COEX for example. PAGE 16

17 FLOWSHEETING PAGE 17

18 TRAINING SIMULATOR PAGE 18

19 DIAGNOSIS Process Perturbation space Data monitoring Model Measures from process Responses space Treatment algorithm Learning algorithm Diagnosis ASSOCIATIVE MEMORIES OPERATOR PAGE 19

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