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Www.psl.bc.ca Recovery Boiler Modeling Process Simulation Ltd.

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Presentation on theme: "Www.psl.bc.ca Recovery Boiler Modeling Process Simulation Ltd."— Presentation transcript:

1 Recovery Boiler Modeling Process Simulation Ltd.

2 Develop modeling tools to improve existing designs and operating procedures, and to lower carry over and environmental impact Analyse performance of different air systems and liquor firing strategies Objectives

3 Introduction Process and equipment design was, until recently, based on experience Advances in numerical methods and computer speed and memory –increased possibility of using more scientific methods, called mathematical modeling, for process design and optimization

4 Mathematical Modeling Applications in Other Industries Computer Jet engines Weather Automotive Harrier jet

5 Equipment Modeling Capabilities: MatureDevelopingPreliminary Time Bark Boiler BFB Bark Boiler Hydrocyclone Head box Digester Lime kiln Gasifier Recovery Boiler We have active projects on this equipment >

6 Client List Weyerhaeuser USA Weyerhaeuser Canada Canfor Kvaerner Scott Paper Anthony Ross Weldwood

7 Why Use Modeling? Recovery Boiler environment is too severe for measurement The model provides comprehensive information throughout the entire boiler at relatively low cost Can evaluate what if scenarios to improve operation/design Supplements steam chief and operator knowledge of recovery boiler operations Assists mill managers in making informed decisions regarding boiler refits/replacements

8 Details of the Recovery Boiler Model Liquor Combustion Model Advanced and verified solution algorithm Black liquor combustion model Drying Pyrolysis CO, CO 2, CH 4, H 2, H 2 O Char gasification Gas phase combustion model Advanced radiation model Convective section model Char bed model

9 Issues Addressed by the Model High excess air CO, CO 2, and other emissions Mechanical carryover & plugging Bed blackouts Superheater and waterwall tube thermal stress failures Boiler stability and capacity

10 Input Data Required Boiler geometry Bed shape Convective section layout Air temperature and flow rate at each port Liquor characteristics

11 Model Predictions Gas species (e.g. H 2,O 2,N 2,CO,CO 2,H 2 O,CH 4 ) distributions Gas flow velocity fields Temperature distributions and heat transfer to wall surfaces Liquor spray combustion and droplet trajectories. Carryover characteristics

12 Model Validation Water Model Measurements Full Scale Measurements Isothermal flow validation Hot flow validation Temperature measurements at bullnose Carryover prediction trends CO emission trends Velocity measurements CE Boiler Model B&W Boiler Model Different aspects of model results have been validated against data from operating boilers

13 Recovery Boiler Refit Example High plugging rates High gas temperature at superheater Bed growth control The Issue: The Objective: To recommend modifications to air system

14 Tertiary Air Ports (20%) Secondary Air Ports (30%) Primary Air Ports (50%) Base Case Modified Air System Test Case Geometries

15 Secondary Air System Problem and Solution Jets collide Carryover Core forms Secondary jets Liquor guns Jets Interlace Uniform flow Secondary jets Base Case Modified Air System

16 Primary V = 30 m/s 50% Air T = 423 K M = 46 kg/s z = 1.2 m Liquor Guns HV=15000 kJ/kg T = 400 K M = 18 kg/s z = 7 m Base Case Secondary V = 85 m/s 30% Air T = 423 K M = 27.6 kg/s z = 3 m Tertiary 20% Air V = 50 m/s T = 423 K M = 18.4 kg/s z = 10 m Modified Air System Tertiary 20% Air V = 50 m/s T = 423 K M = 18.4 kg/s z = 10 m Secondary V = 85 m/s 30% Air T = 423 K M = 27.6 kg/s z = 3 m Common Air/Liquor System Data in Plan View

17 Temperature Profiles

18 Velocity Profiles

19 Fuel Particle Trajectories Base Case Modified Air System

20 Carryover Mass Flux

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24 Conclusions The modified air system: –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 In general, modeling: –Provides detailed data to facilitate efficient operation of Recovery Boilers. –Helps mill managers make informed decisions regarding boiler refits/replacements


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