[Water Activity at High Temperature]

Is it possible to model water in the gas phase (ie steam) or is water always modeled as a liquid in the GWB software?

 

Can water pressure or fugacity be used as a variable in GWB calculations?

 

Thanks,

 

David

[Water Activity at High Temperature]

Thanks Brian,

 

Appreciate your help. Will look at your suggestions

 

Best,

 

David

[Water Activity at High Temperature]

I uploaded the incorrect file (only difference is system pressure).

 

Please find the correct one attached

Act2_output.txt

[Water Activity at High Temperature]

Hi Tom,

 

I understand the water activity is not the same as the fugacity. My problem is that I have never heard of a water "activity" when in the gas and I am trying to understand what it means physically in terms of something such as pressure or fugacity which are more prevalent for reporting gas phase data.

 

I have attached the Act2 file output.

 

Thanks,

 

David

Act2_output.txt

[Water Activity at High Temperature]

Hi Tom,

 

I really appreciate your help. I have attached an output example of the type of diagram i am trying to generate.

 

My problem is that the x-axis is specified as water activity and I cannot seem to change it to fugacity although it should be fugacity since at the given conditions (200C, 1bar) water is in the gas phase.

 

Basically, my question is what does this water activity in the gas phase mean? is it the same as water fugacity?

 

The output file reports this data for water but does not say whether its activity or fugacity. Since the plot says activity I assumed this is what is output, although I do not know what this activity means in the gas phase

 

Thanks again,

 

David

[Water Activity at High Temperature]

Hi David:

 

GWB calculates water vapor fugacity as well- you can see this under the 'gas fugacities' section in the text output, or under the Gtplot plotting variables.

 

Hope that helps,

 

Tom Meuzelaar

RockWare, Inc.

 

 

Hi Tom,

 

Thanks for your reply, much appreciated.

 

Specifically, I am trying to plot phase diagrams using Act2 where all my phases are solid minerals in the presence of Co2 and water gases.

The output file does not seem to specify whether the water data is activity or fugacity. However, the output plot has water activity on the x axis.

 

When i generate similar phase diagrams manually, they are somewhat comparable to Act2 results other than the fugacity/activity issue.

 

I hope I am not being too confusing.

 

David

[Water Activity at High Temperature]

I am interested in understanding magnesium mineral species equilibrium at high temperatures in the presence of (and as a function of) CO2 and water.

 

At these conditions, the co2 and water are both present in the gas phase. Whilst the co2 data is given as fugacity, the water is given in terms of activity even though it is in the vapor phase at my reaction conditions, ie steam.

 

How can i convert/relate this water activity to a water fugacity of partial pressure?

 

Thank you,

 

David