How to model an incremental serie of batch

[tneron]

Hello everyone.

I have a question maybe already answered by the forum and if it's the case sorry for that.

The aim of my script is to precipitate calcite. I have already a script which is operational. I have a solution with calcium, in equilibrium ( equilibrium_phases) with CO2 and a kinetics defined as follow :

Code: [Select]

RATES
Ore1
   -start
30 sr_cc = SR("Calcite")
40 IF (M <= 0  and si_cc < 0) THEN GOTO 200
50 k1 = 8.15355E-06
90 IF M0 > 0 THEN area = PARM(1)*M0*(M/M0)^PARM(2)
110 rate =-k1*area*(sr_cc-1)
150 moles =rate *TIME
160 PUT(rate,1)
170 PUT(sr_cc,1,2)
180 PUT(area,1,3)
190 PUT(LA("Ca+2"),1,4)
200 SAVE moles
-end


KINETICS 1
Ore1
    -formula    CaCO3
-tol   1e-8
-m0    0.005
-m     0.005
-parms 70 0.667 # m^2/mol calcite, exp factor
-steps       1 in 100 steps # seconds
-step_divide 1
-runge_kutta 3

My wish is to change this batch reaction and compare it with a script matlab in which I add carbon in solution (so I remove equilibrium_phases).
To sum up:
I have a Calcium intially in my solution.
I add a small amount of Carbone, to precipitate calcite.
I recover the output solution + quantity of solid precipitate.
And I add again small amount of carbone.

What I've read in the guide is that I must use, incremental_reactions true and maybe combine this with REACTION.
Am I right ?

Thanks a lot for your time
Sincerely
Thomas

[dlparkhurst]

Yes, I think you want to use REACTION. However, if your reactant is CO2, adding a bit of CO2 to a solution in equilibrium with calcite will tend to dissolve calcite; removing CO2 will tend to precipitate calcite. Also, if you just want to see equilibrium with calcite, you can use EQUILIBRIUM_PHASES instead of KINETICS. With KINETICS, you will achieve some saturation index for calcite, which may or may not be equilibrium, depending on the time step.

If you do not use INCREMENTAL_REACTIONS, the mole transfers are calculated as the difference between the initial condition and the current reaction step. If you use INCREMENTAL_REACTIONS, the mole transfers are between the last step and the current step.

The following would remove 1 mmol of CO2 incrementally; using +1 would add CO2:

Code: [Select]

REACTION 1
CO2 -1
0.001