Shaft kiln designing kiln simulation and modelling with CFD ansys fluent simulations heat transfer in Kiln Combustion in kiln

1. Design of Shaft Kiln
Presented By:
Mohsin Ajmal 201228
Ans Bilal Cheema 201556
Muhammad Irfan Aslam 199056
Presented to: Date:
Prof. Dr.-Ing. Eckehard Specht 23.06.2015
Supervisors:
M.Sc. G. Sandaka
M.Sc. B. Hallak

2. Lime Calcination in Shaft Kiln
Given parameters:
lime production= 200 tons of lime per day
Impurities= 5%
Diameter of particle= 60mm to 80mm
Fuel= lignite gas
Internal diameter of kiln= 2.5m
Problem statement:
1. Design of the kiln (diameter, length of preheating, reaction and cooling zone).
2. Arrangement of burner for homogeneous fuel distribution in the cross section.
3. Fuel consumption (spec. energy demand).
4. Pressure drop.
5. Amount and concentration of the flue gas.

3. Schematic diagram
Preheating zone
Reaction zone
Cooling zone

4. Design of the kiln
To Calculate the Value of the the Preheating Zone and Cooling zone we use this
Equation.
The dimensionless temperature for the cooling zone can be calculated by the
following relation
Where
𝑇𝑠𝐿 =80 C
𝑇𝑠0 =1200 C
𝑇𝑔𝐿 =20 C
For pre-heating zone
Where
𝑇𝑠𝐿 =910 C
𝑇𝑠0 =20 C
𝑇𝑔0 = 300 C
=0.95
=1.46

5. where
Ṁg =
Ṁs =
cpg=
cp𝑠=
ṁg=
Ṁg
𝐴
A= area of cross section of the kiln
u = overall heat transfer coefficient=
O =
6
d
d = particle diameter
Ψ = porosity = 0.4
=1.62
6.83kg/s
4.11kg/s
1.12kj/s
1.15kg/s
=1.4kg/s/m2
80W/m2.K
=85.7m‾1 =70mm

6. The length of the reaction zone can be calculated through the time of reaction
where
Resistances: Form Functions for spherical particles:
=210
=79
=0.9
=0.55

7. Material velocity inside the kiln can be calculated from the
throughput of lime
ML = ρ . u . A
Kc= concentration of carbon dioxide in lime tone = 1190 kg/m3
∆hr= specific reaction enthalpy = 3820 KJ/kg
TA = 1200 C
TF= 900 C
α = heat transfer coefficient
λ = thermal conductivity
𝑟𝑠= radius of sphere
b = shape factor
X = conversion
= 0.49 m/hr

8. Length of Zones inside the kiln
Cooling zone Reaction zone Pre heating zone
1.3m 2m 1.3m

9. Energy Balance
Equation for Fuel Consumption
E=

10. yCO2
= 0.44kgCO2 / kg limestone
Tg = 300C
Teq = 910 C
λ = excess air number = 1.2
L = air demand = 7.3 kgair / kg fuel
Qw= heat loss through wall
The fuel consumption thus calculated to be 4.5 MJ/kg lime
By using this Equations the flow rates of various species can be
calculated
= 4.5 kg/s
= 6.8 kg/s
= 4.11 kg/s

11. Compositions of Flue Gases
lignite C H N L
(kgair/kg fuel
λ
Excess air
number
70% 5% 25% 7.3 1.2
Composition of lignite and parameters for stiociometric calculations
Flue gas
composition
𝐶𝑂2 𝑂2 𝐻2O
54% 10% 36%

12. Pressure Drop
By Ergun Equation we can calculate the Pressure Drop:
Pressure drop in cooling zone= ΔP = 6.86 mbar
Pressure drop in reaction zone= ΔP = 792 mbar
Pressure drop in preheating zone= ΔP =435 mbar

13. Arrangement of burner for homogeneous fuel distribution in the cross section
• Increase of penetration depth depends upon the depth of the nozzle inside the
kiln
• 3-D shape with 45° angel, being divided by 360°, there are 8 nozzles which are
averagely distributed around the kiln.
• Placement of burner signify the end of the reaction zone and start of cooling
zone therefore placement of burners should be done according to calculations
of fore mentioned zone lengths

14. Thanks