# Simulation of multiple char reactions for coal combustion

### Introduction

Thepurposeofthistutorialistoprovideguidelinesandrecommendationstosetupandsolve multiple char reactions for coal combustion or gasiﬁcation using ﬁnite-rate/eddy-dissipation model. This tutorial demonstrates how to do the following:

• Use discrete phase model to set up and solve multiple char reactions for coal combustion.
• Activate and set up the ﬁnite-rate/eddy-dissipation model for the reactions occurring during combustion.
• Solve the case using appropriate solver settings.
• Postprocess the resulting data.
• Include the radiation model and study its eﬀect on reaction temperature.

### Prerequisites

This tutorial is written with the assumption that you have completed Tutorial 1 from ANSYS FLUENT 14.5 Tutorial Guide, and that you are familiar with the ANSYS FLUENT navigation pane and menu structure. Some steps in the setup and solution procedure will not be shown explicitly. In this tutorial, you will use turbulence and combustion models, so you should have some experience with them. This tutorial will focus on the application of these models in coal combustion and will not cover the mechanics of using these models

### Problem Description

The coal combustion system considered in this tutorial is a simple 10 m × 1 m two-dimensional duct as shown in Figure 1. Only half of the domain width is modeled because of symmetry. The inlet of the 2D duct is split into two streams. A high-speed stream near the center of the duct enters at 50 m/s and spans 0.125 m. The other stream enters at 15 m/s and spans 0.375 m. Both streams are air at 1500 K. Coal particles enter the furnace near the center of the high-speed stream with a mass ﬂow rate of 0.1 kg/s (total ﬂow rate in the furnace is 0.2 kg/s). The duct wall has a constant temperature of 1200 K. The Reynolds number, based on the inlet dimension and the average inlet velocity is approximately 100,000. Thus, the ﬂow is turbulent.

### Result

In this tutorial, an injection group is introduced at the inlet. The coal-mv particles travel a distance before they start releasing volatiles. The reaction starts at this point and the temperature increases. The radiation model lowers the peak temperature by taking the heat away from the reaction zone. In ﬁnite-rate/eddy-dissipation coal combustion, coal particles release volatiles that react with oxygen and produce combustion products. The stoichiometric coeﬃcients can be calculated once chemical composition of coal volatiles is known. For information on determining coal volatile composition, see tutorial, Using the Non-Premixed Combustion Model in the ANSYS FLUENT 14.5 Tutorial Guide.

### Summary

Application of multiple char reactions and ﬁnite-rate/eddy-dissipation model in a coal combustion case has been demonstrated.