Mixing water, NaOH, and CO2 yields many more than three components in the system. Is this a student project? The sparse details you gave are not sufficient for me to understand what you are trying to do. Are you trying to model an existing commercial design or trying to invent some new scheme?

Hello Pilesar!

Many thanks for your reply!

It is the project for my thesis. I have to design, using Aspen Plus, a complete CO2 capture system from the flue gas of an industrial plant, including cooling of the flue gas and compression of the CO2 captured.

For now, I am focusing on the flue gas cooling system, composed of a "quench tower". The "quench tower" is normally used to bring the flow gas to the absorber working temperature, around 40 C.

Characteristics of the flue gas to be treated are:

Flow: 6112 kg/h (130 C and 1,2 bar)

Composition: CO2 = 838 kg/h, H2O = 540 kg/h, O2 = 711 kg/h and N2 = 4023 kg/h.

The scheme that I want to use to model the "quench tower" is:

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From the literature, I found:

In Aspen plus, the "quench tower" is modelled using a packed, RadFrac column and using a rate-based approach.

The steps involved in the design are:

1. Characterization of the flue gas and the liquid solvent (except for the flowrate) and definition of the target performance (temperature of the flue gas output from the "quench tower")

2. Infinite packing height column

- Definition of the minimum number of cooling units to respect the constraint on the maximum value of the diameter;

- Evaluation of the minimum solvent flow rate by means of sensitivity analysis;

3. Effective column

- Simulation of the "quench tower" for different multiples of the minimum solvent flow rate and evaluation of the corresponding column dimensions (packing height and diameter);

- Identification of the extremes of the L/V ratio where isothermal packing zones are avoided;

4. Choice of the effective solvent flow rate and effective packing height by means of an optimization problem.

My goal is to design the "quench tower", determining the diameter, height and quantity of water to be used to reduce the temperature of flue gas from 130 C to 40 C.

I hope it's clearer now! Many thanks!

p.s. To model the CO2 capture system on Aspen Plus, I am using a guide found in literature: CO2 Capture by Reactive Absorption-Stripping, Modeling, Analysis and Design. C. Madeddu, M. Errico and R. Baratti, 2019. However, the reference does not include the "quench tower" and there isn't much on it in the literature.

Any comment on the reference used and on the other, it's appreciated.