Ash Handling in Power Plants

1. Business Problem Identification
• Discussed with OS and NETRA about the current/pressing
problems faced.
MAJOR ISSUES
Ash-Handling related
problems
Coal-Blending related
problems

2. Mr. A K Tripathi
(AGM, Senior
Faculty)
Mr. Sujoy Karmakar
(AGM)
Mr. Kumar Swadhin
(AGM)
Mr. Dilip Kumar
(AGM & HOD,
Boiler)
Mr. A K Samaiyar
(AGM, Boiler)
Mr. Anjan Sinha
(AGM)
Mr. Sneh Banerjee
(AGM, EEMG)
Mr. Himanshu
Chaturwedi (AGM,
EEMG)
Discussions for Problem Identification
PMI NETRA OS
EEMG
(STATIONS)

3. Discussions for Problem Identification
• Coal-Blending problem was chosen for study
• Coal related problems more wide spread.
• Challenges with Ash-Handling:
 Very plant specific.
 More difficult to analyze (Two phase flow).
 Work requires lots of site’s operational data.

4. Why Coal-Blending
• Coal-fired power plants are designed to burn coal with
defined characteristics.
• Over time, the accessibility of coals change and coals may
become less available.
• To meet the shortfalls different types of coals may be
required to be blended
 Imported Coal Blended with Indigenous Coal.
 Blending of indigenous coals may also be required.

5. Possible advantages of coal-blending for the power plants are:
1. Reducing fuel costs.
2. Controlling emission limits.
3. Enhancing fuel flexibility and extending the range of acceptable
coals.
4. Providing a uniform product from coal of varying quality.
5. Solving existing problems such as poor carbon burnout, slagging
and fouling, and improving boiler performance.
Coal-Blending Advantages

6. Coal Blending Issues
Unpredictability in Boiler Performance
• Coal-Blending brings unpredictability in Boiler Performance.
• Blended coals performance may not be “interpolated
linearly” from that of the parent coals.
• Coal-Blends have two kinds of properties:
 Additive - Properties remain additive after blending, such as
calorific value, volatile matter and ash content.
 Synergistic (non-additive) – Properties cannot be predicted by the
additivity, such as ignition behaviour, burnout, unburned carbon,
slagging, fouling and NOx emissions.

7. Coal Blending Issues
Prediction of Parameters is Important
• It is necessary to predict, as much as possible, the physical and
economic challenges that will arise when switching coals.
• Power plant operators must decide which parameters are most
important in each plant.
• Optimizing blending and boiler operations increase plant power
output while reducing negative effects on the plant (such as
corrosion and fouling) and potentially reducing emissions.

8. What We are exactly going to Study
1. Effect of coal-blending on performance, temperature profile and
NOx formation in boiler.
2. Understand the cause of temperature imbalance in crossover pass.
3. Understand the cause of high temperature at SH and at flue gas exit
(FEGT) for a particular mill combination.
4. Understand the cause of unburnt carbon in boiler.

9. Computational Modelling to Understand the
Effect of Blending
• Possible to use CFD models to understand and simulate the
combustion behavior of blends.
• CFD model allows the operating engineers to gain better
understanding of underlying process and to carry out virtual
experiments to evaluate new ideas.
• A priori predictions of process performance with just the knowledge of
geometry and operating parameters.
• More efficient, economical and helps in understanding the relative
contributions of each individual process.

10. Other Benefits of Computational Modelling
• CFD model is useful in evaluating the influence of
hardware configurations such as:
 Location and tilt of burners
 Swirl at burners.
 Location and configuration of internal heat exchangers.
 Air ingress.
 Heat transfer effectiveness.
 Imbalance in temperatures.

11. Computational Modelling
Package being used for this project
• Modelling and Analysis being done in (ANSYS-15.0):
 For modelling : is to be used.
 For analysis and post processing : is to be used.
• Geometrical configuration of boiler & furnace is modelled in
ANSYS-ICEM.
• Actual physical processes and corresponding mathematical
equations are modelled and solved in ANSYS-FLUENT.
ANSYS-FLUENT
ANSYS-ICEM

12. ANSYS Pre Requisites
• The above software requires high computing speed.
• High performance computing resources are available at IIT-
Delhi and NETRA.
• NETRA has 64-Core processer computing facility.
• Working in collaboration with Professors at IIT-Delhi.
• Reference book : “Computational Modeling of Pulverized
Coal Fired Boilers” (Issued from IIT-Delhi library)

13. Selection of NTPC Unit for Study
• Discussed with OS, NETRA and EEMG to select the units.
• Selected units are:
1. UNCHAHAAR UNIT- 1 (210MW)- Selected for initial trials
2. VINDHYACHAL UNIT-7 (500MW)- Selected for actual detailed
study
• 210MW units are slowly getting obsolete.
• Many plants have 500MW units, which are facing
problems due to blending

14. Various Problems Mentioned at EEMG Workshop
PLANT PROBLEMS FACED
TANDA Part load, Steam pressure, Unburnt carbon.
VINDHYACHAL MW shortfall, Condenser vacuum, High FEGT, Clinkering, Pressure fluctuations.
KORBA Clinkering, Unburned carbon.
BARH Vacuum loss, High make-up water requirement.
SIMADHARI Air ingress problem.
KEHALGAON High APC.
UNCHAHAAR High APC, Cooling tower performance, Slagging at full load.
SIPAT Safety valve problem, Cooling tower performance.
FARAKHHA Clinkering problem, BFP performance.
MOUDA Cooling tower performance, Condenser loss, APH performance.
RAMAGUNDAM Unburnt carbon.

15. Geometrical Modelling Done till date in this
project - in ANSYS-ICEM
ICEM MODEL : UNCHAHAAR UNIT-1
Furnace Dimensions:
D X W = 10.592m X 13.868m
Boiler Height: 43.129m

16. ICEM MODEL : VINDHYACHAL UNIT-7
Geometrical Modelling Done in ANSYS-ICEM
Furnace Dimensions:
D X W = 15.797m X 19.177m
Boiler Height: 62.313m

17. The Modelling Process in ANSYS-ICEM
• Need to divide the boiler into number of
small volumes (grid/mesh generation).
• Smaller the unit volume size more the
accuracy of predicted results, but
require more computation time.
• Approximately 1 million computational
cells are required for simulation of a
typical 500MW plant.

18. The Next Process – Analysis in ANSYS-FLUENT
• FVM (Finite Volume Method) is used to calculate the physical
properties at each point in space.
• Physical processes such as coal combustion, radiation exchange,
volatile release etc. are modelled using various mathematical
models.
• Boundary conditions such as fuel flow rate, pressure and
temperature are put at all the inlets and outlets.
• Grid independence is ensured.

19. TYPICAL EXPECTED RESULTS
(Influence of Coal Blends on Temperature Distribution)

20. TYPICAL EXPECTED RESULTS
(Influence of Coal Blends on Temperature Distribution)

21. TYPICAL EXPECTED RESULTS
(Flow Distribution)

22. TYPICAL EXPECTED RESULTS
(Coal Particles’ Tracking)

23. TYPICAL EXPECTED RESULTS
(Influence of Burner Tilt on Temperature)

24. Project Timeline - Gantt Chart
FEBRUARY 16 MARCH 16 APRIL 16 MAY 16 JUNE 16
W1 W2 W3 W4 W1 W2 W3 W4 W1 W2 W3 W4 W1 W2 W3 W4 W1 W2 W3 W4
ICEM Modelling and Coarse Meshing
Vindhyachal Visit and Site Data Collection
Fine Meshing of the Model
Second Presentation on Project Progress
General Validation of Model with Actual Site
Results
Report Writing and Final Presentation
Implementation of Any Suggestions/ Trail

25. References
1. Modelling of a wall fired furnace for different operating conditions using FLUENT (2006) – VUTHALURU
2. Modeling of thermal characteristics for a furnace of a 500 MW boiler fired with high-ash coal (2001) – KOUPRIANOV
3. Modeling of a Coal-Fired Natural Circulation Boiler (2007) – BHAMBARE
4. Three-dimensional furnace computer modelling-BOYD
5. Modelling and prediction of NOx emission in a coal-fired power generation plant-LI
6. Modeling-of-a-front-wall-fired-utility-boiler-for-different-operating-conditions (2001)- XU
7. A-computational-fluid-dynamics-based-study-of-the-combustion-characteristics-of-coal-blends-in-pulverised-coal-fired-
furnace_2004_Fuel-SHENG
8. Boilers and Burners-Design and Theory-Prabir_Basu
9. Computational Modeling of Pulverized Coal Fired Boilers- RANADE
10. 3D CFD modelling of 500MW tangentially fired tower type boiler - PRABODH 2002
11. CFD Modeling of Vindhyachal Stage II 500MWe Boiler- SWADHIN 2009
12. Effect of heating on char structure and fragmentation of high ash indian coal- KARMAKAR 2009
13. 3D CFD modelling of NOX and temperature imbalance in 500MW boiler-JENA 2007

26. Thank You