Granular Activated Carbon
Introduction
The simple granular activated carbon (GAC) flowsheet can be simulated to predict the performance of a GAC system to treat residual organics. This flowsheet can be useful to expedite the set-up, usage, and costing of a GAC system for conventional water treatment applications using the constant pattern homogeneous surface diffusion model (CPHSDM) model.
Implementation
Only consisting of a single unit operation, the assumptions for the flowsheet are aligned with those detailed in the GAC unit model documentation. The code-based naming of modeling objects for the inlets, outlets, units, and streams are shown in Figure 1.
Figure 1. GAC flowsheet
The following modeling components are used within the flowsheet:
- Documentation for property models:
- Documentation for unit models:
- Documentation for unit models from IDAES:
- Documentation for costing models:
Degrees of Freedom
The degrees of freedom for the flowsheet can change depending on the configuration options specified during the build. Excluding those variables which are only necessary for specific configuration options, the following variables are initially fixed for simulating the GAC flowsheet (i.e., degrees of freedom = 0):
feed conditions (component flows, temperature, pressure)
Freundlich isotherm parameters \(k\) and \(\frac{1}{n}\)
liquid phase film transfer coefficient
surface diffusion coefficient
particle apparent density
particle diameter
empty bed contact time
bed voidage
bed length
effluent to inlet concentration ratio at operational time
CPHSDM empirical parameters
Flowsheet Specifications
Description |
Value |
Units |
|---|---|---|
feed molar flowrate of water |
2433.81215 |
\(\text{mol}/\text{s}\) |
feed molar flowrate of the solute |
0.05476625 |
\(\text{mol}/\text{s}\) |
feed temperature |
298.15 |
\(\text{K}\) |
feed pressure |
101325 |
\(\text{Pa}\) |
Freundlich isotherm k parameter |
10 |
\(\left(\text{m}^3\text{/kg}\right)^\left( \frac{1}{n} \right)\) |
Freundlich isotherm 1/n parameter |
0.9 |
\(\text{dimensionless}\) |
liquid phase film transfer coefficient |
5e-5 |
\(\text{m/s}\) |
surface diffusion coefficient |
2e-13 |
\(\text{m}^2\text{/s}\) |
gac apparent density |
750 |
\(\text{kg/}\text{m}^3\) |
gac particle diameter |
0.001 |
\(\text{m}\) |
empty bed contact time |
600 |
\(\text{s}\) |
bed void fraction |
0.4 |
\(\text{dimensionless}\) |
bed length |
6 |
\(\text{m}\) |
effluent to inlet concentration ratio at operational time |
0.50 |
\(\text{dimensionless}\) |
Stanton equation parameter 0 |
3.68421 |
\(\text{dimensionless}\) |
Stanton equation parameter 1 |
13.1579 |
\(\text{dimensionless}\) |
throughput equation parameter 0 |
0.784576 |
\(\text{dimensionless}\) |
throughput equation parameter 1 |
0.239663 |
\(\text{dimensionless}\) |
throughput equation parameter 2 |
0.484422 |
\(\text{dimensionless}\) |
throughput equation parameter 3 |
0.003206 |
\(\text{dimensionless}\) |
throughput equation parameter 4 |
0.134987 |
\(\text{dimensionless}\) |
Future Refinements
The following modifications to the GAC flowsheet are planned for development:
Add surrogate models to lessen the need for numerous empirical parameters
Improve auto-scaling of model for ease of use
Code Documentation
watertap.examples.flowsheets.gac
References
Hand, D. W., Crittenden, J. C., & Thacker, W. E. (1984). Simplified models for design of fixed-bed adsorption systems. Journal of Environmental Engineering, 110(2), 440-456.
Crittenden, J., Rhodes, R., Hand, D., Howe, K., & Tchobanoglous, G. (2012). MWHs Water Treatment. Principles and Design. John Wiley & Sons.
United States Environmental Protection Agency. (2021). Work Breakdown Structure-Based Cost Model for Granular Activated Carbon Drinking Water Treatment.