Geochemist's Workbench Support Forum

# Script file for rate law

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Hi! I am very new to GWB, so forgive me if any of this seems rather simplistic.

I created a rate law script to try to fix a problem where certain parts of a chemical reaction are going to zero within a few years of a ten-year simulation, causing GWB to crash.

Reaction:

Methane(aq) + 8*Fe(OH)3 + 15*H+ -> 8*Fe++ +HCO3- + 21*H2O

To fix this, I think I want to set the rate equal to zero every time certain elements in a node dip below a threshold value, but running the simulation with my current script gives the following error message "Could not evaluate rate law script at line 2". I'm guessing I have not set up the indexing of my nodes or time step correctly, but am unsure how to proceed.

Here is the code as it stands now:

i = 1

begin_loop1: If (molality(Methane(aq)(i)) < 1e-20 or mass(Fe(OH)3(i)) < 100)

rate = 0;

return rate;

i = i+1

end_loop1

else

cat = 1.0

i = 1

begin_loop: If i > ncatal THEN GOTO end_loop

cat = cat* acatal(i)^pcatal(i)

i = i+1

GOTO begin_loop

end_loop: rate = Wmass*cat*rate_con*(1.0 - QoverK)

RETURN rate

I would appreciate any advice on how to adapt my script so that I am correctly indexing nodes at each time step.

Thanks!

Lauren

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Hi Lauren,

Can you please post the entire X1t input file so that I'm better able to take a look?

Thanks,

Brian Farrell

Aqueous Solutions LLC

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Here is my .x2t script. I was using the built in rate law before, and the only change now is substituting in a script for rate law. I cannot attach the document for some reason, but here is what I am using:

If (molality("Methane(aq)") < 1e-20 or mass("Fe(OH)3") < 100) THEN rate = 0 ELSE 40

RETURN rate

40: cat = 1.0

i = 1

begin_loop: If i > ncatal THEN GOTO end_loop

cat = cat* acatal(i)^pcatal(i)

i = i+1

GOTO begin_loop

end_loop: rate = Wmass*cat*rate_con*(1.0 - QoverK)

RETURN rate

At this point, I am not getting an error message, but the program is not running at all.

Thanks so much!

Lauren

methane react test-midscale.x2t

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