1. MODELING OF BARK BOILERS a valuable tool in the design and operation of power boilers
Process Simulations Limited
March 12th, 2001
Cincinnati, Ohio

2. PRESENTATION Mathematical modelling in the pulp and paper industry
Mathematical modelling of boilers
Examples of modelling of bark boilers
Process simulators in operations, training and safety

3. PROCESS MODELING GROUP

4. PROCESS MODELLING

5. STAGES OF ANALYSIS INITIAL STAGE IN PROGRESS INDUSTRIAL APPLICATION
PROCESS
SIMULATORS
Literature review
Mill interaction
Industrial innovators
Process knowledge
Commitment of industry
Physical model
Numerical model
Model development
Model validation
Industrial testing
Industrial application
Parametric studies
Solve problems
Model proposed retrofits
Improve operations
Reduce costs
Envelope calculations
Interpolation
Operational simulator
Training& safety
Interacts with control system
Technology transfer

6. MODELLING EXAMPLES
Jet engines
Weather
Computer
Harrier jet
Automotive

7. CFD PROCESS MODELLING IN OUT OUT Principle of conservation Mass
Momentum
Energy
…….
IN = OUT
OUT
OUT

8. EFFECTIVE 3-D PROCESS MODELING REQUIRES
Detailed knowledge of the process
Sound understanding of the physics involved
Expertise in computational methods
Ability to collect information from operators and process engineers that have an understanding of the operation of the equipment

9. MODELING STATEGY
Use modeling as measurements resolution is low and environment severe
Can evaluate “what if” scenarios
Supplements operator equipment knowledge
Assists mills to make informed decisions regarding upgrades to reduce risk
Provide comprehensive information and 3-D view of equipment

10. USAGE OF PROCESS MODELING
Project Engineering
reduce capital investment risks
testing of design before committing funds
train operators beforehand
Process Engineering
determine and solve immediate problems
training of operators & reduce variations
avoid customers being beta test site for equipment or retrofits

11. WHY RECOVERY BOILER 3-D PROCESS MODELING
Recovery boiler environment is too severe for measurement
Model provides comprehensive information throughout the entire boiler at relatively low cost
Can evaluate “what if” scenarios to improve operation and design
Supplements steam chief and operator knowledge of recovery boiler operations
Assists mill managers in making informed decisions regarding boiler refits and replacements

12. DETAILS OF BOILER MODEL
Advanced and verified solution algorithm
Black liquor combustion model
Drying
Pyrolysis CO, CO2, CH4, H2, H2O
Char gasification
Gas phase combustion model
Advanced radiation model
Convective section model
Char bed model
After this slide show:
Convergence slide from Dan
Segmentation slide from Dan
Droplet combustion slide from Mike
A slide on the convective section
A Slide of the bed.

13. ISSUES ADDRESSED Improve flow and heat distribution High excess air
Emissions: CO, CO2, TRS, NOx,
Mechanical carryover & plugging
Superheater and waterwall tube thermal stress failures
Boiler stability & capacity increase

14. MODEL PREDICTIONS Gas species distributions Gas flow velocity fields
H2, O2, N2, CO, CO2, H2O, CH4, NOx
Gas flow velocity fields
Temperature distributions and heat transfer to wall surfaces
Liquor spray combustion and droplet trajectories
Carryover characteristics

15. MODEL VALIDATION Isothermal flow validation Water model measurements
Full scale measurements
CE Boiler Model
Hot flow validation
Temperature measurements at bullnose
Carryover prediction trends
CO emission trends
Velocity measurements
B&W Boiler Model
Different aspects of model results have been validated against data from operating boilers

16. RETROFIT EXAMPLE Issue Objective High plugging rates
High gas temperature at superheater
Bed growth control
Objective
Recommend modifications to air system

17. Secondary Air Ports (30%)
RETROFIT EXAMPLE
Test Case Geometries
Tertiary Air Ports (20%)
Secondary Air Ports (30%)
Primary Air Ports (50%)
Base Case
Modified Air System

18. RETROFIT EXAMPLE Base Case Modified Air System
SECONDARY AIR SYSTEM: PROBLEM AND SOLUTION
Jets collide
Carryover
Core forms
Secondary jets
Liquor guns
Jets Interlace
Uniform flow
Base Case
Modified Air System

19. RETROFIT EXAMPLE
Velocity Profiles

20. Fuel Particle Trajectories
RETROFIT EXAMPLE
Fuel Particle Trajectories
Base Case
Modified Air System

21. RETROFIT EXAMPLE
Carryover Mass Flux

22. RETROFIT EXAMPLE Larger air ports provides better jet penetration
Increases gas mixing
Breaks up the vertical air core
Significantly reduces plugging rates
Reduces gas temperatures at superheater

23. PROBLEM SOLUTION

24. FUEL AND GAS FLOW

25. DESIGN MODIFICATIONS
Current
Modified

26. MANUFACTURE DESIGN VS REALITY
Intended Interlace of Secondary Jets
Actual Interlace of Secondary Jets
FRONT WALL
REAR WALL
LEFT SIDE WALL
RIGHT SIDE WALL

27. EXAMPLE OF BENEFITS OBTAINED
Improve jet penetration
Increase gas mixing
Breaks up the vertical air core
Significantly reduce plugging rates
Reduces gas temperatures at superheater
Helps mill managers make informed decisions regarding boiler refits/replacements
Reduce capital expenditure risks

28. BARK BOILERS ISSUES ADDRESSED BY MODEL High excess air Emissions
Mechanical carryover & plugging
Bed Issues
Air flow distribution optimization
Tubes thermal stress failures
Boiler stability and capacity

29. MODELING BENEFITS Reduce your operational costs Optimize air system
Increase the range of operational conditions
Improve controllability of the boiler
Increase the capacity of the boiler
Optimize air system
Lower excess air necessary for complete combustion
Improve overall thermal efficiency

30. MODELING BENEFITS Increase the efficiency of boiler
Analyse the existing air and fuel system
Improve gas mixing and combustion effectiveness
Optimise firing strategies for different loads/fuels
Minimise danger of blackouts
Analyse the possibility of air/fuel system upgrade
Lessen the environmental impact
Minimise particulate carryover, unburned char
Minimise emission of CO2, CO, Nox

31. BARK BOILERS Upward gas velocity in a bark boiler (1) base case
(2) interlaced overfire air system
Base Case
Interlaced Case

32. BARK BOILERS
Examples of carryover particulate trajectories in different combustion stages
Base Case
Interlaced Case

33. BARK BOILER

34. POWER BOILERS
Developed tools to predict with high resolution complex processes occurring in power boiler
Model air system, fuel injection, fuel/air interaction, coal combustion, particle flight trajectories, convection sections, emissions, chemical species

35. WHAT MODEL CAN DO FOR YOU
Increase the load and efficiency of boiler
Reduce operational costs
Significantly reduce decision making risks for retrofits
Minimise pollutants emissions
Provide valuable information for operator training
Minimize flue gas emissions
Address fuel variability (ash, heating value)

36. PROCESS MODELING ADDRESSES
Low combustion efficiency
Unstable combustion process (especially at lower load and for lower grade coal)
Slagging on furnace walls and fouling on heater surfaces
Local overheating
High pollutants (NOx, SOx) emissions
High temperature corrosion issues
Optimisation of air and fuel delivery system

37. HOW IT MAKES A DIFFERENCE
Improve combustion efficiency by optimising air and fuel system
Improve combustion stability through retrofitting of burner structure and adjusting of air and fuel system
Lighten slagging through retrofitting of burner structure and adjusting of air and fuel system
Predict optimal operation systems for different kinds of coal
Reduce Pollutants emissions by introducing advanced combustion techniques

38. POWER BOILERS EXAMPLE
Solve high temperature corrosion at wall

39. POWER BOILERS

40. BOILER PROCESS MODELING
Recovery Boilers
Bark Boilers
Power Boiler

41. PROCESS SIMULATORS Simulator Core Operational Simulators Training
Operator
experience
Process
knowledge
Operational
Simulators
Training
Simulators
Simulator
Core
Measurements
Safety
Simulators j i S x u = ÷ ø ö ç è æ G - f r
Process Model
Virtual
Cameras
Physical
Model

42. PROCESS SIMULATORS

43. PROCESSCAM 1000’s of cameras inside the equipment
Ability to predict equipment behavior for any configuration
Scientific method for process design and optimization
A simulator can assist with operational decisions based on some predetermined values
Almost real time access
Show a 2 minute video of recovery boiler and lime kiln before slide 3

44. PROCESSCAM TECHNOLOGY

45. PROCESSCAM TECHNOLOGY
Highly scalable and modular
Provide process engineers, project engineers and operators more information for analyzing equipment operations
Displays detailed 3-D results of a process in almost real time
Application: training, simulator, control

46. SIMULATOR BENEFITS Simplified technology transfer to mills
Reduce equipment operating costs
Provide more rapid solutions to operating problems
Improve operator training and safety
Modelling available in “real time”
Supporting a “What If” mode of operator interaction
Reduce variability in operations

47. VIRTUAL CAMERA 3-D view of process occurring inside recovery boiler
For selected inputs
immediate and easy to see variations
effect on flow, temperatures, chemical species, liquor combustion
Compliments, enhances, and challenges ways to view process

48. TRAINING TOOL
Operators can understand why some modes of operation are better than others
Provide insight that would be impossible to obtain with traditional methods
Enable realistic training outside the envelope of parameters characterizing normal operation
New training scenarios can be programmed remotely
Tool can significantly shorten startups

49. SAFTEY TOOL Simulate various accident scenarios
Display interactively in a class room setting effects of various accident conditions and impact
Identify ways to prevent accidents before they occur

50. INPUT CONTROLS & 3D VIEWER

51. ADVANCED ANALYSIS

52. EASY ANIMATION OF FLOW & FUEL

53. COMPARISON STATES WITH SYNOPSIS

54. PROCESS MODELLING Questions Comments Feedback Safety issues T ( F ) 21 5 9 8 6 O 7 4 3
Questions
Comments
Feedback
Safety issues