Sandlerchemeq

Chemical equilibrium calculation utilities based on Sandler's 5th ed.

Sandlerchemeq implements computational tools for chemical equilibrium calculations based on Chemical, Biochemical, and Engineering Thermodynamics (5th edition) by Stan Sandler (Wiley, USA). It should be used for educational purposes only.

Installation

Sandlerchemeq is available via pip:

pip install sandlerchemeq

Usage

Command-line

The general structure of a sandlerchemeq command is

$ sandlerchemeq [<global-options>] <tool> [<tool-options>]

Currently available tool(s) is/are

• solve: Solve a chemical equilibrium system

$ sandlerchemeq --help
usage: sandlerchemeq [-h] [-b | --banner | --no-banner] [--logging-level {None,info,debug,warning}] [-l LOG] <command> ...

Chemical equilibrium calculations via Gibbs energy minimization

options:
  -h, --help            show this help message and exit
  -b, --banner, --no-banner
                        toggle banner message
  --logging-level {None,info,debug,warning}
                        Logging level for messages written to diagnostic log
  -l LOG, --log LOG     File to which diagnostic log messages are written

subcommands:
  <command>
    solve               Solve chemical equilibrium

sandlertools solve

Below are examples of using sandlerchemeq solve to solve chemical equilibrium systems.

The first set uses the Lagrange multiplier method to determine equilibrium compositions; hence, there is no concept of "reactions" here.

$ sandlerchemeq solve --components hydrogen nitrogen ammonia -T 400 -P 100 -n0 3. 1. 0.
N_{H2}=0.1113 y_{H2}=0.0536
N_{N2}=0.0371 y_{N2}=0.0179
N_{NH3}=1.9258 y_{NH3}=0.9285
$ sandlerchemeq solve --components hydrogen nitrogen ammonia -T 600 -P 100 -n0 3. 1. 0.
N_{H2}=1.2110 y_{H2}=0.4314
N_{N2}=0.4037 y_{N2}=0.1438
N_{NH3}=1.1926 y_{NH3}=0.4248
$ sandlerchemeq solve --components hydrogen nitrogen ammonia -T 600 -P 50 -n0 3. 1. 0.
N_{H2}=1.5881 y_{H2}=0.5192
N_{N2}=0.5294 y_{N2}=0.1731
N_{NH3}=0.9412 y_{NH3}=0.3077

The second set explicitly declares the reaction by the ordered list of compounds:

$ sandlerchemeq solve --reactions hydrogen,nitrogen,ammonia -T 400 -P 100 -n0 3. 1. 0. -xinit 0.95
Reaction    I:  3 H2  +  1 N2   <->   2 NH3  |  Ka(400.00 K)=3.12266e+01 => Xeq=9.62910e-01
N_{H2}=0.1113 y_{H2}=0.0536
N_{N2}=0.0371 y_{N2}=0.0179
N_{NH3}=1.9258 y_{NH3}=0.9285
$ sandlerchemeq solve --reactions hydrogen,nitrogen,ammonia -T 600 -P 100 -n0 3. 1. 0. -xinit 0.8
Reaction    I:  3 H2  +  1 N2   <->   2 NH3  |  Ka(600.00 K)=1.56354e-03 => Xeq=5.96321e-01
N_{H2}=1.2110 y_{H2}=0.4314
N_{N2}=0.4037 y_{N2}=0.1438
N_{NH3}=1.1926 y_{NH3}=0.4248
$ sandlerchemeq solve --reactions hydrogen,nitrogen,ammonia -T 600 -P 50 -n0 3. 1. 0. -xinit 0.3
Reaction    I:  3 H2  +  1 N2   <->   2 NH3  |  Ka(600.00 K)=1.56354e-03 => Xeq=4.70618e-01
N_{H2}=1.5881 y_{H2}=0.5192
N_{N2}=0.5294 y_{N2}=0.1731
N_{NH3}=0.9412 y_{NH3}=0.3077

When specifying --reactions you have to also specify -xinit for each reaction. These have to be pretty good guesses to arrive at the right answer.

sandlerchemeq can handle systems of multiple reactions, but as long as you have an exhaustive list of the compounds you expect, the Lagrange method is much more robust.

API

sandlerchemeq exposes several classes, objects, and functions from its component packages:

Component

Component is a class that inherits from the Compound class of sandlerprops, and it has some additional attributes. If you set a component's temperature you can query its standard-state Gibbs energy of formation at that temperature:

>>> from sandlerchemeq.component import Component 
>>> from sandlerprops.properties import get_database
>>> d = get_database()
>>> ammonia = Component.from_compound(d.get_compound('ammonia'), T=500) 
>>> ammonia.dGf
-16160.0
>>> ammonia.dGf_T
1732.1145064099328

Reaction

Reaction is a class for handling reaction stoichiometries. For example, initializing a Reaction object with an ordered list of components, one can determine the reaction stoichiometry (via the stoichiometric coefficients) and the property-changes upon reaction (including enthalpy of formation, Gibbs energy of formation, and ideal-gas heat capacity).

>>> from sandlerchemeq.reaction import Reaction
>>> from sandlerchemeq.component import Component 
>>> from sandlerprops.properties import get_database
>>> ammonia = Component.from_compound(d.get_compound('ammonia'), T=298.15, P=1.0)                 
>>> hydrogen = Component.from_compound(d.get_compound('hydrogen (equilib)'), T=298.15, P=1.0)               
>>> nitrogen = Component.from_compound(d.get_compound('nitrogen'), T=298.15, P=1.0)               
>>> rxn = Reaction(components=[ammonia, nitrogen, hydrogen])
>>> rxn.nu
array([-2.,  1.,  3.])
>>> rxn.stoProps
{'dGf': np.float64(32320.0), 'dHf': np.float64(91460.0), 'Cp': array([ 5.7950e+01, -3.3408e-02, -4.8770e-05,  3.4955e-08])}

ChemEqSystem

ChemEqSystem is a class for handling chemical equilibria. Initializing with an ordered list of components and initial molar amounts, it uses the Lagrange multiplier method to determine equilibrium amounts of all components:

>>> from sandlerchemeq.reaction import Reaction
>>> from sandlerchemeq.component import Component 
>>> from sandlerprops.properties import get_database
>>> ammonia = Component.from_compound(d.get_compound('ammonia'), T=298.15, P=1.0)                 
>>> hydrogen = Component.from_compound(d.get_compound('hydrogen (equilib)'), T=298.15, P=1.0)               
>>> nitrogen = Component.from_compound(d.get_compound('nitrogen'), T=298.15, P=1.0)
>>> system = ChemEqSystem(Components=[ammonia, nitrogen, hydrogen], N0=np.array([0.0, 1.0, 3.0]),
                              T=500.0, P=100.0)
>>> system.solve_lagrange()
>>> print(system.report())
N_{NH3}=1.6828 y_{NH3}=0.7262
N_{N2}=0.1586 y_{N2}=0.0684
N_{H2}=0.4757 y_{H2}=0.2053

Alternatively, initializing with one or more reactions and initial guesses for extents of reaction results in the use of equilibrium constants to solve for the equilibrium compositions:

>>> rxn = Reaction(components=[nitrogen, hydrogen, ammonia])
>>> system = ChemEqSystem(Components=[nitrogen, hydrogen, ammonia],
                              Reactions=[rxn],
                              N0=np.array([1.0, 3.0, 0.0]),
                              T=500.0,
                              P=100.0)   
>>> system.solve_implicit(Xinit=[0.76])
>>> print(system.report())
Reaction    I:  1 N2  +  3 H2   <->   2 NH3  |  Ka(500.00 K)=8.90496e-02 => Xeq=8.41419e-01
N_{N2}=0.1586 y_{N2}=0.0684
N_{H2}=0.4757 y_{H2}=0.2053
N_{NH3}=1.6828 y_{NH3}=0.7262

Release History

• 0.2.1
  • included roman dependency
• 0.2.0
  • Full van't Hoff option available via abbreviated=False argument to ChemEqSystem
• 0.1.0
  • Initial release

Meta

Cameron F. Abrams – cfa22@drexel.edu

Distributed under the MIT license. See LICENSE for more information.

https://github.com/cameronabrams

Contributing

1. Fork it (https://github.com/cameronabrams/sandlerchemeq/fork)
2. Create your feature branch (git checkout -b feature/fooBar)
3. Commit your changes (git commit -am 'Add some fooBar')
4. Push to the branch (git push origin feature/fooBar)
5. Create a new Pull Request