Mocca.jl

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Processes and validation ​

Mocca's library holds processes from published studies, set up at the papers' operating conditions. Read one by name with read_process, change a setting and run it:

julia
using Mocca
library_processes()
process = read_process("krishnamurthy_2014_lpp_vsa")

This page compares Mocca's results for each of them with the paper's, and says where they differ and why, as far as it is known.

How Mocca compares ​

Mocca's results against the published ones. A point on the diagonal is an exact match; the dotted lines are ±10%.

ProcessPurityRecoveryPump energyProductivity
Four-step VSApaper88.7%35.8%
Mocca79.5%36.7%
Wet flue gas, LPPpaper78.8% (95.2% dry)88.6%188.8 kWh/t1.73 t/(m³·day)
Mocca82.6% (97.5% dry)79.2%185 kWh/t1.56 t/(m³·day)
Wet flue gas, dual adsorbentpaper95%90%177 kWh/t1.82 t/(m³·day)
Mocca95.6%85.6%192 kWh/t1.74 t/(m³·day)

The energy counts the vacuum pumps only, as the papers do; performance also counts the feed compressor. Productivity is per m³ of 13X. Purities with water count the water in the CO₂ product.

What is known about the differences:

  • Four-step VSA. Mocca's purity is about 9 points below the paper's at the same recovery, and the difference does not change with the grid, the time step or the heat model. Its cause has not been found yet.

  • Wet flue gas, LPP. Water builds up in the bed over hundreds of cycles, and after the 300 cycles of the example the CO₂ balance is still 0.7% open. Mocca pressurises with nitrogen where the paper uses stored light product. Recovery is 9 points below the paper's.

  • Wet flue gas, dual adsorbent. The CO₂ balance closes after 131 cycles, but the silica gel is still filling with water, and in Mocca a few hundred ppm of water reach the 13X bed, against 20 ppm in the paper. Recovery is 4 points lower and the energy 8% higher.

Four-step VSA ​

Haghpanah et al. (2013): dry flue gas, one bed of zeolite 13X. Library name "haghpanah_2013_four_stage_vsa".

13XV_productlight product, N₂V_feedfeed, 15% CO₂V_vacuumCO₂ product
Bedpressurisation, 15 sadsorption, 15 sblowdown, 30 sevacuation, 40 s0255075100time in the cycle [s]pressurisationadsorptionblowdownevacuation
The flowsheet and one cycle, to scale. Valve names are those of the process.
SettingValue
Feed15% CO₂ in N₂, 25 °C, 1 bar, interstitial velocity 1 m/s
Column1 m long, 0.289 m inner diameter, with the steel wall
Pressures1 bar adsorption, 0.2 bar blowdown, 0.1 bar evacuation
Stepspressurisation 15 s, adsorption 15 s, blowdown 30 s, evacuation 40 s

The Getting started example runs it, and How a VSA cycle works follows it through one cycle.

Two-bed VSA ​

Built in Mocca from the beds of Haghpanah et al. (2013), to show a multi-bed cycle; it has no published counterpart. Make it with two_bed_vsa_process().

ABV_product_AV_product_BV_eqV_feed_AfeedV_feed_BfeedV_vacuum_AV_vacuum_BCO₂ product
Apressurisation, 15 sadsorption, 15 sequalisation, 10 sevacuation, 30 sequalisation, 10 sBevacuation, 30 sequalisation, 10 spressurisation, 15 sadsorption, 15 sequalisation, 10 s0255075time in the cycle [s]pressurisationadsorptionequalisationevacuation
The beds run half a cycle apart and pass gas through the link between their tops.

Evacuating to 0.1 bar, it gives 57.4% purity, 60.6% recovery and 93.4 kWh/t, pumps and compressor together. The Two-bed VSA with pressure equalisation example builds it step by step and shows what the equalisation is worth.

Wet flue gas, light product pressurisation ​

Section 3 of Krishnamurthy et al. (2014): wet flue gas, one bed of zeolite 13X. Library name "krishnamurthy_2014_lpp_vsa".

13XV_productlight product, N₂V_lppN₂ in (LPP)V_feedfeed, 15% CO₂, 3% H₂OV_vacuumCO₂ product
BedLPP, 20 sadsorption, 78.4 sblowdown, 37.9 sevacuation, 111.6 s050100150200time in the cycle [s]LPPadsorptionblowdownevacuation
Light product pressurisation fills the bed from the top with nitrogen before the feed starts.
SettingValue
Feed15% CO₂, 82% N₂, 3% H₂O, 25 °C, 1.013 bar, interstitial velocity 0.45 m/s
Column1 m long, 0.3 m inner diameter
Pressures1.013 bar adsorption, 0.08 bar blowdown, 0.03 bar evacuation
StepsLPP 20 s, adsorption 78.4 s, blowdown 37.9 s, evacuation 111.6 s

The Wet flue gas: single-bed VSA with light product pressurisation example runs it and compares its bed profiles with the paper's.

Wet flue gas, dual adsorbent ​

Section 4 of Krishnamurthy et al. (2014): a silica gel bed takes the water out of the wet flue gas before a 13X bed captures the CO₂. Library name "krishnamurthy_2014_dual_adsorbent_vsa".

silica gel13XV_linkV_feedwet feedV_wastewasteV_vacuumCO₂ productV_productlight productV_lppN₂ in
SGpressurisation, 20 sadsorption, 46.2 sblowdown, 42.21 sevacuation, 46.02 sidle, 69.27 s13XLPP, 20 sadsorption, 46.2 sblowdown, 56.3 sevacuation, 101.2 s050100150200time in the cycle [s]pressurisationadsorptionblowdownevacuationidleLPP
The silica gel bed takes the wet feed and passes dry gas to the 13X bed during adsorption; it then waits, closed, until the 13X bed finishes its cycle.
SettingValue
Feed15% CO₂, 82% N₂, 3% H₂O, 25 °C, 1.013 bar, interstitial velocity 0.7 m/s
Columnssilica gel 0.41 m long, 13X 1 m long, both 0.3 m inner diameter
Pressuressilica gel down to 0.48 bar and then 0.3 bar through its bottom; 13X down to 0.07 bar through its top and then 0.03 bar through its bottom
Stepssilica gel 154 s and then closed until the 13X bed finishes its 224 s

The Wet flue gas: dual-adsorbent, two-bed VSA example runs it and follows the water into the 13X bed.