How to use inherent reactions
In How to setup simple chemistry, we showed an example of setting up a thermo_config and reaction_config and put all reactions in that reaction_config. However, it is possible to place reactions into the thermo_config itself using Inherent Reactions. This guide will perform the same walk through and setup from How to setup simple chemistry, but will place reactions into the thermo_config itself.
Inherent Reaction vs Other Reactions
The Inherent Reactions are reactions that will be common to all unit processes within a flowsheet. Thus, it is convenient to put those common reactions into the thermo_config as inherent. Then, the non-inherent reactions in the reaction_config will be unique to a specific unit process.
Note
It is possible to mix inherent reactions and non-inherent reactions within the same unit process. However, user’s need to take care and make sure that if a reaction is in the thermo_config as inherent, then it SHOULD NOT also show up in the reaction_config. This would create a degeneracy in the model.
Example thermo_config
In this example, we will define a simple thermo-properties configuration dictionary for a chemical system that contains only water. The water dissociation reaction will be declared as inherent and, thus, be a part of this configuration dictionary.
# Importing the object for units from pyomo
from pyomo.environ import units as pyunits
# Imports from idaes core
from idaes.core import AqueousPhase
from idaes.core.base.components import Solvent, Cation, Anion
# Imports from idaes generic models
import idaes.models.properties.modular_properties.pure.Perrys as Perrys
from idaes.models.properties.modular_properties.pure.ConstantProperties import Constant
from idaes.models.properties.modular_properties.state_definitions import FTPx
from idaes.models.properties.modular_properties.eos.ideal import Ideal
# Importing the object for units from pyomo
from pyomo.environ import units as pyunits
# Import the object/function for heat of reaction
from idaes.models.properties.modular_properties.reactions.dh_rxn import constant_dh_rxn
# Import built-in Gibb's Energy function
from idaes.models.properties.modular_properties.reactions.equilibrium_constant import van_t_hoff
# Import safe log power law equation
from idaes.models.properties.modular_properties.reactions.equilibrium_forms import log_power_law_equil
# Importing the enum for concentration unit basis used in the 'get_concentration_term' function
from idaes.models.properties.modular_properties.base.generic_reaction import ConcentrationForm
# Configuration dictionary
thermo_config = {
"components": {
'H2O': {"type": Solvent,
# Define the methods used to calculate the following properties
"dens_mol_liq_comp": Perrys,
"enth_mol_liq_comp": Perrys,
"cp_mol_liq_comp": Perrys,
"entr_mol_liq_comp": Perrys,
# Parameter data is always associated with the methods defined above
"parameter_data": {
"mw": (18.0153, pyunits.g/pyunits.mol),
# Parameters here come from Perry's Handbook: p. 2-98
"dens_mol_liq_comp_coeff": {
'eqn_type': 1,
'1': (5.459, pyunits.kmol*pyunits.m**-3),
'2': (0.30542, pyunits.dimensionless),
'3': (647.13, pyunits.K),
'4': (0.081, pyunits.dimensionless)},
"enth_mol_form_liq_comp_ref": (-285.830, pyunits.kJ/pyunits.mol),
"enth_mol_form_vap_comp_ref": (0, pyunits.kJ/pyunits.mol),
# Parameters here come Perry's Handbook: p. 2-174
"cp_mol_liq_comp_coeff": {
'1': (2.7637E5, pyunits.J/pyunits.kmol/pyunits.K),
'2': (-2.0901E3, pyunits.J/pyunits.kmol/pyunits.K**2),
'3': (8.125, pyunits.J/pyunits.kmol/pyunits.K**3),
'4': (-1.4116E-2, pyunits.J/pyunits.kmol/pyunits.K**4),
'5': (9.3701E-6, pyunits.J/pyunits.kmol/pyunits.K**5)},
"cp_mol_ig_comp_coeff": {
'A': (30.09200, pyunits.J/pyunits.mol/pyunits.K),
'B': (6.832514, pyunits.J*pyunits.mol**-1*pyunits.K**-1*pyunits.kiloK**-1),
'C': (6.793435, pyunits.J*pyunits.mol**-1*pyunits.K**-1*pyunits.kiloK**-2),
'D': (-2.534480, pyunits.J*pyunits.mol**-1*pyunits.K**-1*pyunits.kiloK**-3),
'E': (0.082139, pyunits.J*pyunits.mol**-1*pyunits.K**-1*pyunits.kiloK**2),
'F': (-250.8810, pyunits.kJ/pyunits.mol),
'G': (223.3967, pyunits.J/pyunits.mol/pyunits.K),
'H': (0, pyunits.kJ/pyunits.mol)},
"entr_mol_form_liq_comp_ref": (69.95, pyunits.J/pyunits.K/pyunits.mol)
# End parameter_data
}},
'H_+': {"type": Cation, "charge": 1,
# Define the methods used to calculate the following properties
"dens_mol_liq_comp": Constant,
"enth_mol_liq_comp": Constant,
"cp_mol_liq_comp": Constant,
"entr_mol_liq_comp": Constant,
# Parameter data is always associated with the methods defined above
"parameter_data": {
"mw": (1.00784, pyunits.g/pyunits.mol),
"dens_mol_liq_comp_coeff": (55, pyunits.kmol*pyunits.m**-3),
"enth_mol_form_liq_comp_ref": (0, pyunits.kJ/pyunits.mol),
"cp_mol_liq_comp_coeff": (75000, pyunits.J/pyunits.kmol/pyunits.K),
"entr_mol_form_liq_comp_ref": (0, pyunits.J/pyunits.K/pyunits.mol)
},
# End parameter_data
},
'OH_-': {"type": Anion, "charge": -1,
# Define the methods used to calculate the following properties
"dens_mol_liq_comp": Constant,
"enth_mol_liq_comp": Constant,
"cp_mol_liq_comp": Constant,
"entr_mol_liq_comp": Constant,
# Parameter data is always associated with the methods defined above
"parameter_data": {
"mw": (17.008, pyunits.g/pyunits.mol),
"dens_mol_liq_comp_coeff": (55, pyunits.kmol*pyunits.m**-3),
"enth_mol_form_liq_comp_ref": (-230.000, pyunits.kJ/pyunits.mol),
"cp_mol_liq_comp_coeff": (75000, pyunits.J/pyunits.kmol/pyunits.K),
"entr_mol_form_liq_comp_ref": (-10.75, pyunits.J/pyunits.K/pyunits.mol)
},
# End parameter_data
}
},
# End Component list
"phases": {'Liq': {"type": AqueousPhase,
"equation_of_state": Ideal},
},
"state_definition": FTPx,
# This is an optional dictionary to setup bounds on
# the state variables. Names below MUST correspond
# to the 'FTPx' type state definition
"state_bounds": {"flow_mol": (0, 50, 100),
"temperature": (273.15, 300, 650),
"pressure": (5e4, 1e5, 1e6)
},
# These are generally optional parameters, however, because we
# are using the Perry's model to calculate temperature dependent
# properties, we MUST provide these here.
"pressure_ref": 1e5,
"temperature_ref": 300,
# Our dictionary for base units MUST define the following
"base_units": {"time": pyunits.s,
"length": pyunits.m,
"mass": pyunits.kg,
"amount": pyunits.mol,
"temperature": pyunits.K},
# Inherent reactions
# These are added just like any other equilibrium reaction
# would be defined in a reaction config
"inherent_reactions": {
"H2O_Kw": {
"stoichiometry": {("Liq", "H2O"): -1,
("Liq", "H_+"): 1,
("Liq", "OH_-"): 1},
"heat_of_reaction": constant_dh_rxn,
"equilibrium_constant": van_t_hoff,
"equilibrium_form": log_power_law_equil,
"concentration_form": ConcentrationForm.moleFraction,
"parameter_data": {
"dh_rxn_ref": (55.830, pyunits.J/pyunits.mol),
"k_eq_ref": (10**-14/55.2/55.2, pyunits.dimensionless),
"T_eq_ref": (298, pyunits.K),
# By default, reaction orders follow stoichiometry
# manually set reaction order here to override
"reaction_order": {("Liq", "H2O"): 0,
("Liq", "H_+"): 1,
("Liq", "OH_-"): 1}
}
# End parameter_data
}
}
# End inherent reactions
}
# End thermo_config definition
For a detailed analysis of everything from above, see How to setup simple chemistry.
Note
Even if your system only involves inherent reactions, you may still be required to provide a reaction configuration dictionary to construct certain unit models (such as EquilibriumReactor). However, your reaction configuration may be a blank or a dummy config (see below)
Example of a dummy reaction_config
# Importing the object for units from pyomo
from pyomo.environ import units as pyunits
# Import safe log power law equation
from idaes.models.properties.modular_properties.reactions.equilibrium_forms import log_power_law_equil
# This config is REQUIRED to use EquilibriumReactor even if we have no equilibrium reactions
reaction_config = {
"base_units": {"time": pyunits.s,
"length": pyunits.m,
"mass": pyunits.kg,
"amount": pyunits.mol,
"temperature": pyunits.K},
"equilibrium_reactions": {
"dummy": {
"stoichiometry": {},
"equilibrium_form": log_power_law_equil,
}
# End reaction
}
# End equilibrium_reactions
}
# End reaction_config definition
Example: Using our configuration dictionaries in an EquilibriumReactor
Recall, we had named our configuration dictionaries as thermo_config and
reaction_config. We will reference those dictionary names in the example
code below.
# Import specific pyomo objects
from pyomo.environ import ConcreteModel
# Import the core idaes objects for Flowsheets and types of balances
from idaes.core import FlowsheetBlock
# Import the idaes objects for Generic Properties and Reactions
from idaes.models.properties.modular_properties.base.generic_property import GenericParameterBlock
from idaes.models.properties.modular_properties.base.generic_reaction import GenericReactionParameterBlock
# Import the idaes object for the EquilibriumReactor unit model
from idaes.models.unit_models.equilibrium_reactor import EquilibriumReactor
# Create an instance of a pyomo model
model = ConcreteModel()
# Add an IDAES flowsheet to that model
model.fs = FlowsheetBlock(dynamic=False)
# Add a thermo parameter block to that flowsheet
# Here, we are passing our 'thermo_config' dictionary we created earlier
model.fs.thermo_params = GenericParameterBlock(**thermo_config)
# Add a reaction parameter block to that flowsheet
# Here, we are passing our thermo block created above as the property package
# and then giving our 'reaction_config' as the instructions for how the
# reactions will be constructed from the thermo package.
model.fs.rxn_params = GenericReactionParameterBlock(property_package=model.fs.thermo_params, **reaction_config)
# Add an EquilibriumReactor object as the unit model
# Here, we pass both the thermo package and reaction package, as well
# as a number of other arguments to help define how this unit process
# will behave.
#
# NOTE: What is different here is now we state that there are no
# equilibrium reactions in this unit model because we defined
# those reactions as inherent.
model.fs.unit = EquilibriumReactor(property_package=model.fs.thermo_params,
reaction_package=model.fs.rxn_params,
has_rate_reactions=False,
has_equilibrium_reactions=False,
has_heat_transfer=False,
has_heat_of_reaction=False,
has_pressure_change=False)
# At this point, you can 'fix' your inlet/outlet state conditions,
# setup scaling factors, initialize the model, then solve the model
# just as you would with any other IDAES flowsheet