CERCHAR : Combustion of pulverised Coal in Cerchar's furnace (duplicated, see TestCase056)

_Authors: _

Type: Numerical

Status: stargold stargold



Flow Parameters

Reference Publications



This case aims at testing pulverised coal and radiation component's of Code_Saturne. It simulates Cerchar's furnace which is located in the hall of Mazingarbe's rigi : it is a cylindrical and horizontal device. Main lengths of this element are given herein : axis located above the floor, inside diameter of 1.5m and overall length of 7.7m. It is made of a frontal plate designed to connect all kinds of burners, of a water cooled combustion chamber, of a 0.9m converging part long and a carneau of 0.9m long inside diameter : details are presented in Figure 1.
Figure 1 : 3MW furnace of Mazingarbe
The nominal power of the furnace is 3MW but the whole experimental facility was built to cover a range going from 1.5MW to 6MW (global incoming thermal flow).
Secondary equipments are showed in Figure 2 ; it consists of an air supplying system for combustion, of an air heater, of an pulverised coal supplying system, of an smoke cooler and of a control room.
The multi-staged Cerchar's combustor is represented in Figure 3 and has the following main elements :
  • A central tube able to receive a gas inlet cylinder if a multi fuel combustion is wanted.
  • around the tube which contains the main flow, secondary air flow is injected and swirls by the mean of the vent's generator of Cerchar (Rotation intensity or swirl number are adjustable)
  • a divergent part which collects the primary and secondary flows
  • a containment room which provides a coaxial space around the latter divergent part which allows the tertiary air to flow.

The principle of the multi staged combustor is to reduce primary and secondary air flows (the overall flow is significantly smaller than the stoichiometric air flow). This way, we can get an higher flame temperature in the divergent part where the coal combustion must stabilize.
The furnace geometry near divergent part and the locations of various air and combustible inlet are given in Figure 4.
The available experimental data include radial profiles of the temperature measured by the mean of suction pyrometer. The data include the concentration of CO2, CO, O2, NO by measured sampling and IR paramagnetical and chemiluminescence analysis. It includes also thermal fluxes measured by calorimetric loops and velocity profiles obtained by a Phase Doppler Anemometer.
More details of this test case can be found in [77],[78],[79].
Figure 2 : Scheme of Cerchar system

figure 3 : Multi-staged burner

figure 4 : Divergent part details

Flow Parameters

Flame settings parameters

Flame settings parameters are given in Table 1. The characteristic swirl number $C_{swirl}$ gives the direction of the velocity $e=(e_{u}, e_{v}, e_{w})$ (the norm of velocity is calculated from the imposed flow.
Pulverised coal flow $450 kg.h^{-1}$
Primary air flow $700 kg.h^{-1}$
Secondary air flow $2300 kg.h^{-1}$
Tertiary air flow $2100 kg.h^{-1}$
Temperature of CP AP, AS and AT 37C
Swirl number 1

Table 1 : inlet flow characteristics

Fluid Physical Properties :

  • Reference velocity : $uref =5m.s^{-1}$
  • Type of Fluid : Air
  • Reference density : $\rho_{0}=1.17kg.m^{-3}$ (cold)
and $\rho_{0}=0.235 kg.m^{-3}$ (warm)
  • Dynamic viscosity : $\mu=0.2\times10^{-4} kg.m^{-1}.s^{-1}$
The dynamic viscosity was calculated with the Table software at a temperature of 37C.

Fuel Physical and Chemical properties

The fuel used is a Freyming Blazing coal which characteristics are given in Tables 2 and 3
Immediate Analysis Mass percentage
Humidity 1.25
Volatile materials (on dry coal) 34.84
Carbon (on dry coal) 58.95
Ash (on dry coal) 6.21

Table 2 : characteristics deduced from immediate analysis

Elementary Analysis % on dry coal % on pur coal
Carbon 76.65 81.72
Hydrogen 5.16 5.50
Oxygen 9.90 10.56
Sulphur 0.80 0.85
Nitrogen 1.28 1.36

Table 3 : characteristics deduced from elements analysis

Low calorific value on dry coal is $30 MJ.kg^{-1}$. We will assume that during the injection, the mean diameter of coal is 25 micrometer and that the specific heat capacity (at constant pressure) is constant and equals to $1800 J.kg^{-1}.K^{-1}$ . The initial density of dry coal is taken equal to $1200 kg.m^{-3}$.

Parameters for devolatilisation and heterogeneous combustion models

Kinetic constant of reaction k1, k2, and kc involved in the devolatilisation model defined with two competitive reactions, and in the heterogeneous combustion model, are written under the formulation of Arrhenius (defined by energy activation E1, E2, and Ec and peudo constant of reaction speed A1, A2 and Ac). They are given in table 4. We also give stoichiometric coefficients Y1 and Y2 of devolatilisation model (Kobayashi).

Parameter Value
A1 $3.7\times10^{5}s^{-1}$
E1 $7.4\times10^{4} J.mol^{-1}$
A2 $1.3\times10^{13}s^{-1}$
E2 $2.5\times10^{5} J.mol^{-1}$
Ac $1.79\times10^{-4}kg.m^{-2}.s^{-1}.Pa^{-1}$
Ec $1.3\times10^{13} J.mol^{-1}$
Y1 $0.37$
Y2 $0.74$

Table 4 : Parameters for devolatilisation and heterogeneous combustion models
Note : In the file named dp_FCP used for thermochemistry, we give the values of stoichiometric coefficient Y1 and Y2 and we precise that they are not automatically recalculated. These values are imposed to the file through GUI (graphical user interface).

Reference Publications


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Topic attachments
I Attachment Action Size Date Who Comment
pngpng fig131_cerchar.png manage 50.5 K 2009-10-09 - 14:18 MickaelHassanaly 3 MW furnace of Mazingarbe
pngpng fig132_cercharmod2.png manage 47.0 K 2009-10-07 - 08:13 MickaelHassanaly Scheme of Cerchar system
pngpng fig133_cercharmod.png manage 41.2 K 2009-10-07 - 08:16 MickaelHassanaly Multi-staged burner
pngpng fig134_cercharmod.png manage 11.9 K 2009-10-07 - 08:21 MickaelHassanaly Divergent part details
Topic revision: r12 - 2011-08-31 - 14:19:28 - DavidMonfort

Computational Fluid Dynamics and Turbulence Mechanics
@ the University of Manchester
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