Chemical reactions in Comsol ?

26 July 2023 1 9K Report

Hello !!

I'm trying to simulate oxy-fuel combustion of solid waste in vertical type incinerator using Comsol multi-physics.

I got my geometries for stoker type and vertical type incinerators which I'll attach. My main approach is modelling the waste bed as porous medium, And then figure out a way to couple gas phase reactions with the heterogeneous waste bed reactions in Comsol if it's possible.

- First I plan to model the reactions under N2/O2 combustion conditions and then under CO2/O2.

my reaction mechanism is 1) Waste=> Dry waste+H2O(vapor) , 2) Dry Waste => volatiles + char.

My 2nd reaction formula is: C40H65O25N => 25CO + 15CH4 + 3H2 + NH3 "not including char"

I got the formula for CHON product representing solid waste from ultimate analysis results. I'm wondering how to apply this reaction in Comsol. I used reaction engineering module and got the attached graph. I know I need more kinetic information to represent chemical reactions for drying and combustion domains. So, I got TGA results for the waste sample and planning to do DSC to determine the heat of each reaction.

Now I'm wondering how to apply the data I have in Comsol.

I tried looking online but there is a severe shortage in chemical modelling tutorial and if found the examples are way simple.

* I can model the physical phenomenon's like the flow and heat transfer in free and porous media domains successfully but I'm struggling with chemical part of the study.

I appreciate any thoughts and comments on how to approach my project, especially on the point on how to couple solid phase and gas phase reactions. Also would appreciate any knowledge about the combustion reactions under oxy-fuel conditions.

Best Regards,

AHMED ESAA

Samsul Islam

COMSOL Multiphysics is a powerful simulation software that allows users to model and simulate various physical processes, including chemical reactions. Within COMSOL, you can set up and solve chemical reaction problems using the Reaction Engineering interface, which provides tools and features specifically designed for simulating chemical reactions.

Here's an overview of how chemical reactions can be modeled in COMSOL:

Define the Chemistry: In the Reaction Engineering interface, you can define the chemical reactions you want to simulate. This includes specifying the reactants, products, stoichiometry, reaction rates, and other relevant parameters.

Set up the Geometry: Create the geometry of your chemical reactor or domain using COMSOL's geometry modeling tools. Define the regions where the reactions will take place.

Specify Initial and Boundary Conditions: Set up the initial concentrations of the reactants and any boundary conditions that affect the chemical reactions, such as inlet concentrations, temperature, and pressure.

Define Reaction Kinetics: Choose the appropriate reaction kinetics model for your chemical system. COMSOL supports various reaction kinetics models, including rate expressions, mass action kinetics, and Arrhenius kinetics.

Select Transport Mechanisms: In addition to reaction kinetics, you need to consider the transport mechanisms that play a role in the reactions. These may include diffusion, convection, and other mass transport phenomena.

Solve the System: Once you have set up the chemistry, geometry, and boundary conditions, you can solve the system using the appropriate solver in COMSOL. The software will simulate the chemical reactions and their interactions with other physics, such as heat transfer and fluid flow, depending on your specific application.

Analyze Results: After solving the system, COMSOL provides various post-processing tools to analyze and visualize the results of the chemical reactions, including concentrations of species over time, reaction rates, and temperature profiles.

COMSOL's Reaction Engineering interface is well-suited for simulating complex chemical reactions in various engineering and scientific applications, such as chemical reactors, catalysis, combustion, and more. The software's flexibility and user-friendly interface make it a valuable tool for researchers and engineers involved in chemical reaction studies and design.

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