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NESC0886 EQ3/6.

EQ-3 EQ6, Thermodynamics Equilibrium for Aqueous Solution Mineral System

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1. NAME OR DESIGNATION OF PROGRAM:  EQ3/6.
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2. COMPUTERS
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Program name Package id Status Status date
EQ3/6 NESC0886/04 Tested 10-APR-1990

Machines used:

Package ID Orig. computer Test computer
NESC0886/04 DEC VAX series DEC VAX 8810
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3. DESCRIPTION OF PROBLEM OR FUNCTION

The EQ3/6 release 3230B soft- ware package is a set of computer programs and supporting data files, used in modeling aqueous geochemical systems. The two main programs are EQ3NR and EQ6. EQ3NR is a geochemical aqueous speciation-solubility program which models the thermodynamic state of an aqueous solution by calculating the distribution of aqueous species, such as simple ions, ion-pairs, and aqueous complexes. The EQ6 program, which must be initialized by an EQ3NR calculation, computes either reaction paths of reacting aqueous systems or heterogeneous equilibrium with fixed masses of chemical elements. Two auxiliary programs, MCRT and EQTL, are included in the package. MCRT is a database building program used to process thermo- dynamic input data files into a form suitable for the EQ3/6 thermo-  dynamic database and to perform temperature extrapolation of 25 degree C data. The primary data file that supports EQ3/6 contains thermodynamic data corresponding to the temperatures 0, 25, 60, 100, 150, 200, 250, and 300 degrees C, a pressure of 1.013 bar (1 atmosphere) up to 100 degrees C, the steam/liquid water equilibrium pressure at higher temperatures, and other necessary supporting data. EQTL, a database preprocessor, reads this primary data file, checks each reaction for mass and charge balance, fits interpolating polynomials to all data on temperature grids, and reformats the data into suitable form in three secondary data files  read directly by EQ3NR or EQ6.
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4. METHOD OF SOLUTION

EQ3NR uses a modified Newton-Raphson algorithm  to calculate the distribution of aqueous species. Input primarily consists of data derived from total analytical concentrations of dissolved components and can also include pH, alkalinity, electrical balance, phase equilibrium (solubility) constraints, and a default value for Eh, pe, or the logarithm of oxygen fugacity. The program evaluates the degree of disequilibrium for various reactions and computes either the saturation index or thermodynamic affinity for minerals. Individual values of Eh, pe, equilibrium oxygen fugacity,  and Ah (redox affinity) are computed for aqueous redox couples. EQ3NR can be used alone. It is required to initialize reaction-path  calculations performed by EQ6, its companion program.

EQ6 first checks that the input system is in homogeneous equilibrium If not, the system is "equilibrated" according to the specified mass balance constraints. This will yield a single Eh for  the solution and alter to some extent all the other solution parameters, including the pH. If there are any supersaturated phases, EQ6 then "precipitates" a set so that no supersaturations remain. This may result in still different values for the pH and other solution parameters. Any such initial precipitates may be retained in the system or deleted before the reaction progresses. Calculations may then be performed to model simple titration or irreversible reaction with "reactants" in systems that are either closed to solids or open (flow-through) systems. EQ6 solves at each  point of reaction progress the algebraic equations describing mass and charge balance, mass action, and non-ideality. Finite-difference expressions of high order are used to estimate derivatives with respect to reaction progress and predict the values of a basis set of unknowns at a subsequent point. The predicted values are then corrected by using the Newton-Raphson method. Convergence is aided by optimizing starting estimates and by under-relaxation techniques.
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5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

The temperature range of the thermodynamic data in the primary data file is 0 to 300 degrees C. The activity coefficient approximations for aqueous solutes are not dependable at ionic strengths of greater than roughly one molal.
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6. TYPICAL RUNNING TIME

On a CDC7600 the EQ3NR test cases requires about 2 seconds to run and the EQ6 test cases about 10 seconds.
NESC0886/04
NEADB executed the test cases included in this package  on a VAX 8810 computer. The following CPU times were required: EQPT(standard option): 47 secs; EQPT(pitzer option): 33 secs; EQ3NR(nacldot.3i data): 5 secs; EQ3NR(swpar1.3i data): 10 secs; EQ3NR(sylvite1.3i data): 4 secs; EQ6(pyrite1.6i data): 15 minutes; EQ6:( sylvite1.6i data): 8 secs.
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7. UNUSUAL FEATURES OF THE PROGRAM

The programs were developed for the FTN and CFT FORTRAN compiler language on the CDC7600 and CRAY1 computers with specific conventions adopted to facilitate transportability to UNIVAC, IBM, DEC VAX, and other systems.
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8. RELATED AND AUXILIARY PROGRAMS

Other well-known geochemical codes  for the EQ3 distribution-of-species problem are SOLSAT (Helgeson), SOLMNEQ (Kharaka and Barnes), the WATEQ series (Ruesdell, Plummer, Ball), REDEQL (Morel and Morgan), and MINEQL (Westall). Similar in modeling function to EQ6 are Helgeson's PATH1 and PATHCALC programs.
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9. STATUS
Package ID Status date Status
NESC0886/04 10-APR-1990 Tested restricted
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10. REFERENCES

- T.J. Wolery and L.J. Walters, Jr.,
  Calculation of Equilibrium Distributions of Chemical Species by
  Means of Monotone Sequences, Mathematical Geology, Vol. 7, pp.
  99-115, 1975.
- H.C. Helgeson,
  Evaluation of Irreversible Reactions in Geochemical Processes
  Involving Minerals and Aqueous Solutions-I.
Thermodynamic Relations, Geochimica et Cosmochimica Acta, Vol. 32,    pp. 853-877, 1968.
- T.J. Wolery and K.J. Jackson:
  Chapter 2: Activity Coefficients in Aqueous Salt Solutions -
  Hydration Theory Equations
  ACS Symposium Series 416; developed from a symposium sponsored by
  the Division of Geochemistry at the 196th National Meeting of the
American Chemical Society, Los Angeles, CA (September 25-30, 1988)  - U. Vuorinen and H. Leino-Forsman:
Solubility and Speciation Calculations (EQ3/6) for the Elements of    Importance in TVO-92
  YJT-92-11 (Auhust 1992).
NESC0886/04, included references:
- K.J. Jackson:
  Verification and Validation Studies of the Addition of Pitzer's
  Equations to the EQ3/6 Brine Model
  UCRL-53841 (July 20, 1988).
- S.A. Daveler and B. Bourcier:
  EQ3NR - Input File User's Guide
  LLNL (Version EQ3NR R114) (July 7, 1989).
- S.A. Daveler and B. Bourcier:
  EQ6 - Input File User's Guide
  LLNL (Version EQ6R104) (June 22, 1989).
- T.J. Wolery and S.A. Daveler:
  EQ6 A Computer Program for Reaction Path Modeling of Aqueous
  Geochemical Systems - User's Guide and Documentation
  LLNL (March 30, 1989).
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11. MACHINE REQUIREMENTS

About 136,000 (octal) words of SCM and 157,000 (octal) words of LCM are required on a CDC7600 for EQ3NR, about 124,000 (octal) words of SCM and 165,000 (octal) words of LCM  for EQ6. Three units in addition to the standard input/output units  used by EQ3NR, 11 units in addition to the standard I/O units by EQ6.
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12. PROGRAMMING LANGUAGE(S) USED
Package ID Computer language
NESC0886/04 FORTRAN-77
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13. OPERATING SYSTEM UNDER WHICH PROGRAM IS EXECUTED:  SCOPE 2.1.5 (CDC7600).
NESC0886/04
VMS V5.1-1 (VAX 8810) with compiler VAX FORTRAN V5.0-1.
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14. OTHER PROGRAMMING OR OPERATING INFORMATION OR RESTRICTIONS

The program is written in FORTRAN 66, but FORTRAN 77 compatible. Central memory must be preset to zero when running EQ6.
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15. NAME AND ESTABLISHMENT OF AUTHOR

   T.J. Wolery
   Earth Sciences Division
   Lawrence Livermore National Laboratory
   P.O. Box 808
   Livermore, California 94550
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16. MATERIAL AVAILABLE
NESC0886/04
File name File description Records
NESC0886_04.001 Information file 156
NESC0886_04.002 Data file data0; the eq3/6 data base 25704
NESC0886_04.003 Pitzer coefficient data file 4196
NESC0886_04.004 Harvie,Moller,Weare coefficient data file 3140
NESC0886_04.005 eq3nr include file 190
NESC0886_04.006 eq3nr source file 6763
NESC0886_04.007 eq6 include file 377
NESC0886_04.008 eq6 source file 15985
NESC0886_04.009 eqpt output file with pitzer data 695
NESC0886_04.010 second eqpt output file with pitzer data 737
NESC0886_04.011 eqpt short output file with pitzer data 179
NESC0886_04.012 eqpt output file with standard data 1546
NESC0886_04.013 eqpt short output file with standard data 569
NESC0886_04.014 eqpt include file 279
NESC0886_04.015 eqpt source file 4714
NESC0886_04.016 eqlib include file 625
NESC0886_04.017 eqlib source file 10368
NESC0886_04.018 the program to decompose *.inc file 73
NESC0886_04.019 eq3nr input file 37
NESC0886_04.020 eq3nr output file 481
NESC0886_04.021 eq6 input file 141
NESC0886_04.022 eq6 output file 5462
NESC0886_04.023 eq3nr input file 115
NESC0886_04.024 eq3nr output file 1099
NESC0886_04.025 eq3nr input file 50
NESC0886_04.026 eq3nr output file 542
NESC0886_04.027 eq6 input file 112
NESC0886_04.028 eq6 output file 2289
NESC0886_04.029 history file for eq3nr 417
NESC0886_04.030 history file for eq6 804
NESC0886_04.031 history file for eqpt 114
NESC0886_04.032 history file for eqlib 410
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17. CATEGORIES
  • R. Environmental and Earth Sciences

Keywords: aqueous solutions, chemical reactions, geochemistry, minerals, thermal equilibrium, thermodynamic properties.