![Page 1: S&C Thermofluids Ltd CFD modelling of adsorption in carbon filters E Neininger*, MW Smith** & K Taylor* * S&C Thermofluids Ltd ** Dstl, Porton Down](https://reader033.vdocument.in/reader033/viewer/2022051314/5515e149550346dd6f8b4d29/html5/thumbnails/1.jpg)
S&C Thermofluids Ltd
CFD modelling of adsorption in carbon filters
E Neininger*, MW Smith** & K Taylor*
* S&C Thermofluids Ltd
** Dstl, Porton Down
![Page 2: S&C Thermofluids Ltd CFD modelling of adsorption in carbon filters E Neininger*, MW Smith** & K Taylor* * S&C Thermofluids Ltd ** Dstl, Porton Down](https://reader033.vdocument.in/reader033/viewer/2022051314/5515e149550346dd6f8b4d29/html5/thumbnails/2.jpg)
Overview
• Background to filter model development• Physics of adsorption modelling• Validation• Implementation in PHOENICS• Future developments
![Page 3: S&C Thermofluids Ltd CFD modelling of adsorption in carbon filters E Neininger*, MW Smith** & K Taylor* * S&C Thermofluids Ltd ** Dstl, Porton Down](https://reader033.vdocument.in/reader033/viewer/2022051314/5515e149550346dd6f8b4d29/html5/thumbnails/3.jpg)
Typical filter application
Air Flow
Impregnated granularactivated carbon
Glass FibreFilter
Canister filter for respirator
![Page 4: S&C Thermofluids Ltd CFD modelling of adsorption in carbon filters E Neininger*, MW Smith** & K Taylor* * S&C Thermofluids Ltd ** Dstl, Porton Down](https://reader033.vdocument.in/reader033/viewer/2022051314/5515e149550346dd6f8b4d29/html5/thumbnails/4.jpg)
Modelling Requirements
• Pressure drop
• Contaminant breakthrough time
![Page 5: S&C Thermofluids Ltd CFD modelling of adsorption in carbon filters E Neininger*, MW Smith** & K Taylor* * S&C Thermofluids Ltd ** Dstl, Porton Down](https://reader033.vdocument.in/reader033/viewer/2022051314/5515e149550346dd6f8b4d29/html5/thumbnails/5.jpg)
Other filter geometries
Small scale filter test bed
- 2 cm diameter carbon bed
Carbon monolith filter - Courtesy of MAST
![Page 6: S&C Thermofluids Ltd CFD modelling of adsorption in carbon filters E Neininger*, MW Smith** & K Taylor* * S&C Thermofluids Ltd ** Dstl, Porton Down](https://reader033.vdocument.in/reader033/viewer/2022051314/5515e149550346dd6f8b4d29/html5/thumbnails/6.jpg)
Flow through filter bed
![Page 7: S&C Thermofluids Ltd CFD modelling of adsorption in carbon filters E Neininger*, MW Smith** & K Taylor* * S&C Thermofluids Ltd ** Dstl, Porton Down](https://reader033.vdocument.in/reader033/viewer/2022051314/5515e149550346dd6f8b4d29/html5/thumbnails/7.jpg)
Flow through packed bed
• Pressure drop- local voidage distribution coupled to Ergun equation for pressure loss through bed:
p/L = 5 So2(1-)2U/3 + 0.29 So(1-)U2/3
viscous loss turbulent loss
- earlier work using this equation given good agreement with experimental data for pressure drop.
• Voidage distribution- Mueller model good for uniform spherical particles- uniform voidage gives better comparison with measured breakthrough times for granular carbon
![Page 8: S&C Thermofluids Ltd CFD modelling of adsorption in carbon filters E Neininger*, MW Smith** & K Taylor* * S&C Thermofluids Ltd ** Dstl, Porton Down](https://reader033.vdocument.in/reader033/viewer/2022051314/5515e149550346dd6f8b4d29/html5/thumbnails/8.jpg)
Adsorption rate• Two scalar equations solved
- one for transport of contaminant vapour- one for rate of ‘uptake’ of adsorbed phase
• A linear driving force approach is used for the adsorption rate, whereby this is proportional to the amount of remaining capacity
-C/t = 1/ So km (C - Ci)
• Equilibrium uptake determined by adsorption isotherm = f(C,T)
![Page 9: S&C Thermofluids Ltd CFD modelling of adsorption in carbon filters E Neininger*, MW Smith** & K Taylor* * S&C Thermofluids Ltd ** Dstl, Porton Down](https://reader033.vdocument.in/reader033/viewer/2022051314/5515e149550346dd6f8b4d29/html5/thumbnails/9.jpg)
Adsorption isotherm
• Pentane adsorption isotherm on BPL carbon at 295K
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.00.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
p/p0
Up
take
(g
/g)
X – experimental data
__ - Dual Dubinin-Astakhov equation
![Page 10: S&C Thermofluids Ltd CFD modelling of adsorption in carbon filters E Neininger*, MW Smith** & K Taylor* * S&C Thermofluids Ltd ** Dstl, Porton Down](https://reader033.vdocument.in/reader033/viewer/2022051314/5515e149550346dd6f8b4d29/html5/thumbnails/10.jpg)
Validation
Breakthrough of pentane (3lpm flow, 295K, various bed depths)
![Page 11: S&C Thermofluids Ltd CFD modelling of adsorption in carbon filters E Neininger*, MW Smith** & K Taylor* * S&C Thermofluids Ltd ** Dstl, Porton Down](https://reader033.vdocument.in/reader033/viewer/2022051314/5515e149550346dd6f8b4d29/html5/thumbnails/11.jpg)
Validation
Breakthrough of pentane (3lpm flow, 1cm bed depth, 295K)
![Page 12: S&C Thermofluids Ltd CFD modelling of adsorption in carbon filters E Neininger*, MW Smith** & K Taylor* * S&C Thermofluids Ltd ** Dstl, Porton Down](https://reader033.vdocument.in/reader033/viewer/2022051314/5515e149550346dd6f8b4d29/html5/thumbnails/12.jpg)
Saturation of filter bed
![Page 13: S&C Thermofluids Ltd CFD modelling of adsorption in carbon filters E Neininger*, MW Smith** & K Taylor* * S&C Thermofluids Ltd ** Dstl, Porton Down](https://reader033.vdocument.in/reader033/viewer/2022051314/5515e149550346dd6f8b4d29/html5/thumbnails/13.jpg)
Variable inlet concentration
Outflow concentration from pulsed inflow
With no filter
0.5cm filter – experimental
1cm filter – experimental
0.5 filter – CFD
1cm filter - CFD
![Page 14: S&C Thermofluids Ltd CFD modelling of adsorption in carbon filters E Neininger*, MW Smith** & K Taylor* * S&C Thermofluids Ltd ** Dstl, Porton Down](https://reader033.vdocument.in/reader033/viewer/2022051314/5515e149550346dd6f8b4d29/html5/thumbnails/14.jpg)
Pentane concentration at outlet
0
500
1000
1500
2000
2500
3000
3500
4000
4500
0.00 20.00 40.00 60.00 80.00 100.00 120.00 140.00
Time (mins)
Co
nc
entr
ati
on
(m
g/m
3)
dry air inlet RH 80% bed + inlet RH 80%
Adsorption in wet air
-C/t = 1/ So km (C - Ci)
but Ci for pentane limited so that
uptake </= total pore volume - water uptake
Water on Carbon Adsorption Isotherm
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
p/p0
Up
take
(g
/g)
DDA
![Page 15: S&C Thermofluids Ltd CFD modelling of adsorption in carbon filters E Neininger*, MW Smith** & K Taylor* * S&C Thermofluids Ltd ** Dstl, Porton Down](https://reader033.vdocument.in/reader033/viewer/2022051314/5515e149550346dd6f8b4d29/html5/thumbnails/15.jpg)
Implementation in PHOENICS
• Pre-processor• User interface allows rapid input of geometry and
property data• Writes Q1 file and runs FEMGEN to create mesh
• Run steady-state to establish flowfield then transient to model adsorption
• Run full transient if inlet flowrate varies with time
![Page 16: S&C Thermofluids Ltd CFD modelling of adsorption in carbon filters E Neininger*, MW Smith** & K Taylor* * S&C Thermofluids Ltd ** Dstl, Porton Down](https://reader033.vdocument.in/reader033/viewer/2022051314/5515e149550346dd6f8b4d29/html5/thumbnails/16.jpg)
Implementation in PHOENICS
• Pre-processor• User interface allows rapid input of geometry and
property data• Writes Q1 file and runs FEMGEN to create mesh
• Run steady-state to establish flowfield then transient to model adsorption
• Run full transient if inlet flowrate varies with time
![Page 17: S&C Thermofluids Ltd CFD modelling of adsorption in carbon filters E Neininger*, MW Smith** & K Taylor* * S&C Thermofluids Ltd ** Dstl, Porton Down](https://reader033.vdocument.in/reader033/viewer/2022051314/5515e149550346dd6f8b4d29/html5/thumbnails/17.jpg)
Implementation in PHOENICS
• Pre-processor• User interface allows rapid input of geometry and
property data• Writes Q1 file and runs FEMGEN to create mesh
• Run steady-state to establish flowfield then transient to model adsorption
• Run full transient if inlet flowrate varies with time
![Page 18: S&C Thermofluids Ltd CFD modelling of adsorption in carbon filters E Neininger*, MW Smith** & K Taylor* * S&C Thermofluids Ltd ** Dstl, Porton Down](https://reader033.vdocument.in/reader033/viewer/2022051314/5515e149550346dd6f8b4d29/html5/thumbnails/18.jpg)
Implementation in PHOENICS
• Customised GROUND Coding• Pressure drop and adsorption source terms • Outlet contaminant concentration can be
monitored as run progresses
• Modelling issues• Cell blockages
![Page 19: S&C Thermofluids Ltd CFD modelling of adsorption in carbon filters E Neininger*, MW Smith** & K Taylor* * S&C Thermofluids Ltd ** Dstl, Porton Down](https://reader033.vdocument.in/reader033/viewer/2022051314/5515e149550346dd6f8b4d29/html5/thumbnails/19.jpg)
Monolith filter model
• Activated carbon monolith
• Low pressure drop
• Single channel model• detailed model of one
flow path
• contaminant diffuses into porous monolith
• can model several monoliths in series
![Page 20: S&C Thermofluids Ltd CFD modelling of adsorption in carbon filters E Neininger*, MW Smith** & K Taylor* * S&C Thermofluids Ltd ** Dstl, Porton Down](https://reader033.vdocument.in/reader033/viewer/2022051314/5515e149550346dd6f8b4d29/html5/thumbnails/20.jpg)
Monolith – vapour concentration
Hexane breakthrough
0
1000
2000
3000
4000
5000
6000
0 20 40 60 80 100 120
Time (min)
Co
nce
ntr
atio
n (m
g/m
3)
vapour concentration after 6 mins
outlet vapour concentration vs time
![Page 21: S&C Thermofluids Ltd CFD modelling of adsorption in carbon filters E Neininger*, MW Smith** & K Taylor* * S&C Thermofluids Ltd ** Dstl, Porton Down](https://reader033.vdocument.in/reader033/viewer/2022051314/5515e149550346dd6f8b4d29/html5/thumbnails/21.jpg)
Future development of model
• Multiple adsorbents• Non-linear driving force for adsorption• Property database/GUI• Heat of adsorption source terms• Improved solver speed
- optimisation of GROUND coding
- parallel processing
![Page 22: S&C Thermofluids Ltd CFD modelling of adsorption in carbon filters E Neininger*, MW Smith** & K Taylor* * S&C Thermofluids Ltd ** Dstl, Porton Down](https://reader033.vdocument.in/reader033/viewer/2022051314/5515e149550346dd6f8b4d29/html5/thumbnails/22.jpg)
Conclusions
• Requirement for CFD modelling of filters• CFD model of adsorption process
developed• Validation of packed bed model
promising• Monolith model requires validation• Customised user interface• Ongoing developments