TKK, Energy Engineering and Environmental Protection in ChemCom

Transcription

1 HELSINKI UNIVERSITY OF TECHNOLOGY TKK, Energy Engineering and Environmental Protection in ChemCom Mika Järvinen, Ari Kankkunen, Pasi Miikkulainen and Carl-Johan Fogelholm Helsinki University of Technology Anders Brink, Christian Mueller and Mikko Hupa Åbo Akademi University

2 Contents 1. Black Liquor Spray Study in the Furnace - Objectives - Droplet measurements in the furnace - First results 2. Development of the comprehensive DPM model for black liquor - Detailed droplet model, Järvinen et al. (2002) - Description of the new simplified comprehensive droplet model - Sample results

3 Black Liquor Spray Study in the Furnace

4 Introduction TKK, Laboratory of energy engineering and environmental protection has long traditions in black liquor spray research since 1990, Liekki I Small scale nozzles and substitute liquids Full scale nozzles in spray chamber Full scale nozzles in furnace (velocity, sheet break-up mechanisms, spray appearance) Droplet size and shape in furnace 2006! Spraying results currently effectively utilized in furnace conditions with ÅA

5 Objective Spray droplets properties in the furnace Droplet size and other spray properties was measured in a test chamber earlier. Are results applicable to a furnace? Droplet size and shape was documented inside a furnace for the first time Are droplets spherical inside the furnace? - What is the relevant droplet size? - What is the velocity of the droplets? - What is the shape of the spray?

6 Furnace Spray Spray Spray Splashplate nozzle Splashplate nozzle Splashplate nozzle Furnace wall 2 m 2 m

7 Conditions around spray Spray was directed along furnace wall The spray slightly hit the furnace wall in some test cases Furnace temperature was 1100 C Downwards gas flow was detected near the furnace wall Occasionally, burning particle flocks hit the spray

8 Spray at varying locations ( 4 m, 4 l/s) above center line below

9 Development of the comprehensive DPM model for black liquor

10 Introduction Droplet combustion modeling work was initiated 1996, furnace studies Development of the detailed single droplet model , Järvinen (2002), TEKES/CODE Simplification of the detailed model on physical basis (Post-Doc, Academy of Finland ) Development of the simplified comprehensive DiscreteParticeModel model (ChemCom)

11 Detailed droplet model Järvinen et al. 2002

12 Detailed droplet model - Internal profiles R i (mol/m 3 s) Dry Pyro Temperature ( C) Temperature and reaction profiles during pyrolysis R i, mol/m 3 s H 2 O + C O 2 + C CO 2 + C R i r Radial coordinate (r/r s ) Radial coordinate, r/r s R i (mol/m 3 s) H 2 O + C CO 2 + C O 2 + C CO + H 2 O Temperature ( C) Temperature and reaction profiles during char combustion R i (mol/m 3 s) O 2 + Na 2 S M 2 CO C M 2 SO C Radial coordinate (r/r s ) Radial coordinate (r/r s )

13 Important observations from the detailed model Overlapping drying and devolatilization stages in thin cores with characteristic temperatures: T b ~ 150 C, T p ~ C Intraparticle thermal radiation is important a R ~ 850 1/m During drying and devolatilization, temperature profile approaches quasi-steady state profile Char conversion occurs simultaneously with drying and devolatilization During pure char combustion stage particle is almost isothermal No single dominating char reaction

14 The simplified comprehensive droplet model T b = const T p = const H 2 O(l) C(s) + DS N(s) DS MCl(s) M 2 S(s) M 2 SO 4 (s) M 2 CO 3 (s) T s (t) T g -only T s (t) + 8 tracked species m i (t) solved - const. T b, T p -Na + K => M

15 Reactions in the simplified model Drying, shrinking core heat transfer model Pyrolysis, shrinking core heat transfer model Overlapping char and sulfide oxidation -C(s) + 0.5O 2 CO Smith M 2 S(s) + 2 O 2 M 2 SO 4 (s) - - Char gasification -C(s) + H 2 O CO + H 2 Li et al C(s) + CO 2 2 CO Inorganic reactions -M 2 CO 3 (s) + 2 C(s) 2 M + 3 CO Li et al M 2 SO 4 (s) + 2 C(s) Ma 2 S(s) + 2 CO 2 Wåg et al., 1995

16 Towards a sub-model for CFD Developed C-source code of the stand-alone droplet model delivered to ÅA by TKK Conversion of source code to Fluent UDF and implementation into Fluent at ÅA Fluent UDF in use at ÅA and TKK, common test case Sensitivity analysis, comparison and application of all single droplet/particle models developed at TKK and ÅA at well defined conditions

17 First application of the sub model Droplet data from measurents u = 12 m/s X = 7.44 mm (RR) q = 2.5

18 First application of the sub model Solids content Surface temperature

19 First application of the sub model Initial results for computational Demand, CPU-time [s] 10 droplets from one liquor gun, 50 stochastic tries 500 droplet trajectories ÅA Furnace Model: 9 s Comprehensive SDM: 109 s Increase in computational time per DPM iteration: ~ factor 12 This factor has decreased after further development and simplification

20 Summary A new comprehensive single black liquor droplet combustion sub-model has been implemented into FLUENT software and is currently in use at TKK and ÅA Simplified model is based on the experimentally validated detailed model, using the most essential physical and chemical mechanisms observed by simulations and experiments Close co-operation between Helsinki University of Technology and Åbo Akademi University has been essential for effectively combining the knowledge on detailed model development, combustion experiments and CFD model implementation The project has been definitely a Win- Win deal for both sides

21 Acknowledgement TEKES Andritz Oy Kvaerner Power Oy Foster Wheeler Energy Oy Vattenfall Utveckling AB Metsä-Botnia Oy International Paper Mill Personel