Gas Transport

[nickvz]

I posted the a question a while back on using the shrinking core model to fit leach data observed from tailing storage facilities. I understand from the PHREEQC manual that oxygen can only be transported if it is dissolved. Is it possible to do a gas phase transport in a transport block?. Otherwise the following PDE needs to be solved with every time step to calculate gas phase oxygen at every node to calculate pore gas phase oxygen concentration.

∂C/∂t=D_1 *(∂^2 C)/(∂Z^2 )-S ( C is the oxygen gas phase concentration)

Where is is a oxygen sink (pyrite oxidizing and consuming oxygen), driving the mass transfer down the column.

[dlparkhurst]

Sorry, there is no gas-transport capability in TRANSPORT. A 1D multiphase UZ model has been on my list for quite a while, but I probably will not do it, and I haven't gotten anybody else interested. Other codes have the capability to model multiphase flow, including MIN3P and TOUGH-REACT. HP1 (Hydrus) and (PHT3D) consider UZ flow, but I do not think handle transport in the gas phase.

[nickvz]

Hi

Thank you for the reply. I am using the PYROX code to model Oxygen ingress into a tailings heap at this stage. Will it be possible to use a series of rates blocks to solve the oxygen mass transport equation and then the shrinking core model for every time step, using this to calculate pore gas concentrations for every cell in a transport block. 

[dlparkhurst]

Maybe, but I don't really see it. You could do some scripting with Python, Visual Basic or Matlab. Seems like the sequence would be to start from a GAS_PHASE initial condition for each cell. Run reactions with TRANSPORT for a step. Take the gas-phase compositions from PHREEQC and transport each component with a gas transport code for a time step. Then use GAS_PHASE_MODIFY to set the composition of the gas phases after transport and repeat the sequence. You would need to take small time steps because the gas transport/diffusion is rapid.