Institute of Energy Process Engineering and Chemical Engineering Chair EVT Kinetic study on gasification of chars from co-pyrolysis of German brown coal and wheat straw Zhou, L. , Schurz, M., Reichel, D., Zhang, G. 6th International Freiberg Conference on IGCC & XtL Technologies – IFC2014 19th – 22nd May 2014 – Dresden/Radebeul, Germany Session 12-3 –Gasification kinetics
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Institute of Energy Process Engineering and Chemical Engineering
Chair EVT
Kinetic study on gasification of chars from co-pyrolysis of German brown coal and wheat straw
Zhou, L., Schurz, M., Reichel, D., Zhang, G.
6th International Freiberg Conference on IGCC & XtL Technologies – IFC2014
19th – 22nd May 2014 – Dresden/Radebeul, Germany
Session 12-3 –Gasification kinetics
1 Introduction
2
Advantage of thermal co-processing
For kinetics study § Better understand the process and design coal gasifiers
§ The gasification of char with CO↓2 Fundamentally to study the char reactivity Easily adopted in the laboratory scale
Economics Efficiency
Environment Flexibility
Thermal co-processing of coal
and biomass
2 Materials and methods 2.1 Sample list
3
Experiment plan and conditions § Samples: Wheat straw (WS), Rhenish brown coal (WS), co-pyrolysis chars (Mix) § WS ratios: 10, 50 and 90 wt.% based on raw WS § Pyrolysis temperatures (P): 750 and 1000 ̊C § Gasification temperatures (G): 750, 800, 850, 900 and 1000 ̊C
Example for experiments list § WS/P750/G750, HKN/P750/G750 § MIX10%/P750/G750, MIX50%/P750/G750
2 Materials and methods 2.2 Sample characteristics
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Proximate analysis of wheat straw and Rhenish brown coal Ultimate analysis of wheat straw and Rhenish brown coal Index of basicity [1] of Rhenish brown coal and wheat straw The value are 0.03 for wheat straw and 0.28 for Rhenish brown coal.
Index of basicity =w(A)∗Fe↓2 O↓3 +CaO+MgO+ Na↓2 O+ K↓2 O/SiO↓2 + Al↓2 O↓3 (2.1)
3 Results and discussion 3.1 Gasification of co-pyrolysis char samples
(a) (b) (c)
Comparison with experimental and calculated gasification of MIX/P1000 chars at 800 °C
Comparison with experimental and calculated co-pyrolysis of WS and HKN
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200 400 600 800 10000.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
200 400 600 800 10000.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
Temperature (°C)
Mas
s lo
ss (T
G)
Cal, 10 wt% Cal, 50 wt% Cal, 90 wt%
Exp, 10 wt% Exp, 50 wt% Exp, 90 wt%
3 Results and discussion 3.1 Gasification of co-pyrolysis char samples Ø Characteristics of blend chars and comparison with calculated values Ultimate analysis of MIX/P1000 chars pyrolyzed at 1000 °C Index of basicity (B) of MIX/P1000 chars pyrolyzed at 1000 °C
3 Results and discussion 3.2 Synergy effect on kinetics parameters Apparent activation energy E for single and MIX/P1000 chars, comparison of experimental and calculated values High T: § E(Exp) < E(Cal) High reactivity Not agree with experimental behavior § E(High T) < 1/2 E(Low T), Film diffusion at around 975 °C (E(975−1000)≈0) Ash sintering can not be reflected More diffusion compared to single char
Pre-exponential factors A for single and MIX/P1000 chars, comparison of experimental and calculated values
A(Exp) < A(Cal) Low reactivity Agree with experimental behavior § Low A values are caused by pore blocking and ash sintering
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E (kJ/mol) WS HKN Cal, 10wt.% E1CP
Cal, 50wt.% E5CP
Low T 217.29 171.22 173.90 168.16 187.66 188.24 High T 125.07 90.73 92.73 78.06 102.99 79.35
≈ ≈ > >
A (1/h) WS HKN Cal, 10wt.% E1CP
Cal, 50wt.% E5CP
Low T 9.31*109 6.40*107 6.01*108 3.44*107 3.36*109 2.64*108 High T 2.89*105 1.12*104 2.70*104 2.73*103 1.10*105 3.02*103
>>
>>
4 Conclusions
Experimental behavior Lower reactivity for E1CP and E5CP § Synergy effects in co-pyrolysis process(The loss of Oxygen, Hydrogen and catalytic
Diffusion controlled zone: E↓Exp < E↓Cal , A↓Exp < A↓Cal Low reactivity § Pre-exponential factor A: Agree with experimental behavior in both zones Low A values are caused by pore blocking and ash sintering
15 TU Bergakademie Freiberg · Institute of Energy Process Engineering and Chemical Engineering · Chair of Energy Process Engineering and Thermal Waste Treatment · Reiche Zeche · Fuchsmuehlenweg 9 · 09599 Freiberg, Germany · Phone: +49 3731 39-4511 · Fax: +49 3731 39-4555 · www.iec.tu-freiberg.de
Reference
[1] M. Sakawa, Y. Sakurai. Influence of coal characteristics on CO2 gasification. Fuel, 61(8) (1982), 717-720. [2] Higman, Chris. Gasification / Chris Higman and Maarten van der Burgt.—2nd ed. [3] G.Q. Lu, D.D. Do. Comparison of structural models for high-ash char gasification. Carbon, 32 (1994), 247-263. [4] M. Ishida, C.Y. Wen. Comparison of zone-reaction model and unreacted-core shrinking model in solid-gas reactions. I. Isothermal analysis, Chem. Eng. Sci., 26 (1971), 1031-1041. [5] J. Szekely, J.W. Evans, A structural model for gas-solid reactions with a moving boundary, Chem. Eng. Sci., 25 (1970), 1091-1107. [6] Bhatia S. K., Perlmutter D. D. A Random Pore Model for Fluid-Solid Reactions: I. Isothermal, Kinetic Control. AIChE J., 26 (1980), 379. [7] Dong Kyun Seo, Sun Ki Lee, Min Woong Kang. Gasification reactivity of biomass chars with CO2. Biomass and bioenergy, 34(2010), 1946-1953.
16 TU Bergakademie Freiberg · Institute of Energy Process Engineering and Chemical Engineering · Chair of Energy Process Engineering and Thermal Waste Treatment · Reiche Zeche · Fuchsmuehlenweg 9 · 09599 Freiberg, Germany · Phone: +49 3731 39-4511 · Fax: +49 3731 39-4555 · www.iec.tu-freiberg.de
IEC – TU Bergakademie Freiberg
Acknowledgement
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Thanks to: German Federal Ministry of Education and Research
RWE AG, Vattenfall Europe AG, MIBRAG mbH and Romonta AG