Stoichiometric Reactor Costing Method

Currently, the costing method is implemented for lime and soda ash softening and acidification which only include the capital cost of building the reactor. The capital cost of lime and soda ash is a function of total reagent mass being added to the softening process and is only constructed when both precipitant and reagents are provided. While acid addition capital cost is only constructed if reagents are provided but precipitants are not. Acid addition costing is based on volume flow of acid per day. (Please refer to the stoichiometric reactor documentation for details on dissolution and precipitation reaction configurations).

Costing Method Parameters

The following parameters are constructed for the unit on the FlowsheetCostingBlock (e.g., m.fs.costing.stoichiometric_reactor) when applying the cost_stoichiometric_reactor costing method in the watertap_costing_package:

Description	Symbol	Parameter Name	Default Value	Units
Softening capital cost	\(C_{softening}\)	`capital_cost_softening`	374.9	\(\text{USD/(lb/day)}\)
Acid addition capital cost	\(C_{acid}\)	`capital_cost_acid_addition`	127.8	\(\text{USD/(gallon/day)}\)

Costing Method Variables

There are not unique costing variables constructed for the stoichiometric reactor.

Capital Cost Calculations

If user only includes reagents, refer to stoichiometric reactor documentation

\[ \begin{align}\begin{aligned}CC_{softening}=C_{softening}*\sum{M_{reagent}}\\CC_{acidification}=C_{acid}*\sum{Q_{reagent}}\end{aligned}\end{align} \]

where \(M_{reagent}\) is mass flow all reagent added in softening processes, and \(Q_{reagent}\) is flow volume of chemical added.

Operating Cost Calculations

There are no operational costs provided, user needs to manually cost the reagent addition per mass/flow of reagent as done in the example below for softening operation with soda ash and lime addition.

# build the unit model
 reagents = {
      "Na2CO3": {
            "mw": 105.99 * pyunits.g / pyunits.mol,
            "dissolution_stoichiometric": {"Na_+": 2, "HCO3_-": 1},
      },
      "CaO": {
            "mw": 56.0774 * pyunits.g / pyunits.mol,
            "dissolution_stoichiometric": {"Ca_2+": 1, "H2O": 1},
      },
   }
 m.fs.chemical_addition = StoichiometricReactor(
      property_package=m.fs.properties,
      reagent=reagents,
   )
 # The user must the specify how much reagent to add
 m.fs.chemical_addition.reagent_dose["Na2CO3"].fix(1e-3)
 m.fs.chemical_addition.reagent_dose["CaO"].fix(1e-3)

 # specify the costs for lime (CaO)
 blk.lime_cost = Param(
     initialize=0.13,
     units=m.fs.costing.base_currency / pyunits.kg,
     mutable=True,
 )
 # specify the costs for soda ash (Na2CO3)
 blk.soda_ash_cost = Param(
     initialize=0.13,
     units=m.fs.costing.base_currency / pyunits.kg,
     mutable=True,
 )
 # Register the cost for each chemical being added
 m.fs.costing.register_flow_type("lime_cost", blk.lime_cost )
 m.fs.costing.register_flow_type("soda_ash_cost", blk.soda_ash_cost )

 # Register the mass or volume flow for each chemical being added
 m.fs.costing.cost_flow(
     blk.chemical_precipitator.flow_mass_reagent["CaO"],
     "lime_cost",
 )
 m.fs.costing.cost_flow(
     blk.chemical_precipitator.flow_mass_reagent["Na2CO3"],
     "soda_ash_cost",
 )

Code Documentation

watertap.costing.unit_models.stoichiometric_reactor

References

Amusat, A. Atia, A. Dudchenko, T. Bartholomew, “Modeling Framework for Cost Optimization of Process-Scale Desalination Systems with Mineral Scaling and Precipitation”, ACS ES&T Engr, (2024)