Feasibility Study of Co-Firing of Torrefied Empty Fruit Bunch and Coal through Boiler Simulation
Abstract
:1. Introduction
2. Torrefaction-Based Co-Firing System
3. Experimental Section
3.1. Material Properties
3.2. Experimental Studies on TG and DTG and Kinetics Tests of T-EFB Biomass
4. Description of Methodology
4.1. Boiler Information
4.2. Numerical Simulation
4.3. Boundary Conditions and Simulation Scenarios
5. Results and Discussion
5.1. Comparison of R-EFB and T-EFB Combustion Characteristics with TG/DTG
5.2. Grid Independence and Validation of the CFD Simulation
5.3. Effects of T-EFB Co-Firing Substitutions on the Combustion Characteristics
5.4. Effects of T-EFB Co-Firing Substitutions on the Heat Flux Distribution
5.5. Effects of T-EFB Co-Firing Substitutions on Gas Emission (NOX, SO2)
6. Conclusions
Author Contributions
Funding
Conflicts of Interest
Abbreviations
CFD | computational fluid dynamics |
CO2 | carbon dioxide |
CO | carbon monoxide |
DTG | derivative thermogravimetric |
DTF | drop tube furnace |
ECO | economizer |
EFB | empty fruit bunch |
HHV | higher heating value |
HT-EFB | hydrothermal empty fruit bunch |
HT | hydrothermal |
KIER | Korea institute of energy research |
OFA | overfire air |
NOX | oxides of nitrogen |
O2 | oxygen |
PKS | palm kernel shells |
PM | pollution minimum |
R-EFB | raw empty fruit bunch |
RH | reheaters |
SO2 | sulfur dioxide |
SH | superheaters |
T-EFB | torrefied empty fruit bunch |
TGA | thermogravimetric analysis |
UBC | unburned carbon |
TG | weight loss curves |
FEGT | furnace exit gas temperature |
PA | primary air |
SA | secondary air |
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Fuel Samples | Coal | R-EFB | T-EFB |
---|---|---|---|
Proximate analysis (as-received basis, wt%) | |||
Moisture | 14.20 | 60.00 | 2.99 |
Volatile matter | 39.70 | 34.84 | 65.19 |
Fixed Carbon | 40.90 | 3.71 | 19.00 |
Ash | 5.20 | 1.46 | 12.82 |
Ultimate analysis (dry ash-free basis, wt%) | |||
Carbon (C) | 81.80 | 46.62 | 59.45 |
Hydrogen (H) | 5.40 | 6.45 | 5.36 |
Nitrogen (N) | 2.20 | 1.21 | 1.06 |
Sulfur (S) | 0.40 | 0.035 | 0.15 |
Oxygen (O) | 10.20 | 45.66 | 24.16 |
Calorific value (as-received basis, MJ/Kg) | |||
HHV | 30.18 | 17.02 | 20.9 |
Parameter | Coal a | T-EFB b |
---|---|---|
Devolatilization kinetics | ||
A (s−1) | 3.12 × 105 | 1.1 × 104 |
E (kJ/mol) | 7.4 × 104 | 8.87 × 104 |
Char oxidation kinetics | ||
A (s−1) | 0.0043 | 6.4 |
E (kJ/mol) | 83.7 | 110 |
Item | Operation Boiler | Simulation Cases | ||||
---|---|---|---|---|---|---|
Case | Case 1 | Case 2 | Case 3 | Case 4 | Case 5 | Case 6 |
Combustion type | Pure coal | Co-firing | ||||
T-EFB bleeding ratio (%, thermal basis) | 0 | 10 | 20 | 30 | 40 | 50 |
Fuel mills in service (burn zone) | A B C D E | |||||
Coal feed rates (kg/s) | 51.3 | 46.2 | 41.1 | 35.9 | 30.8 | 25.7 |
Biomass feed rates (kg/s) | - | 6.2 | 12.5 | 18.7 | 24.9 | 31.1 |
PA a flow rate (kg/s) | 109.8 | 110.7 | 111.6 | 112.4 | 113.2 | 113.8 |
SA a flow rate (kg/s) | 276.9 | 279.3 | 281.4 | 283.5 | 285.4 | 287.1 |
OFA a flow rate (kg/s) | 90.7 | 91.5 | 92.2 | 92.9 | 93.5 | 94.0 |
Temperature of PA (°C) | 58.5 | |||||
Temperature of SA (°C) | 303.5 | |||||
Temperature of OFA (°C) | 303.5 | |||||
Burner zone stoichiometry ratio | 0.91 |
Case Type | Case 1 | Case 2 | Case 3 | Case 4 | Case 5 | Case 6 | |
---|---|---|---|---|---|---|---|
Pure Coal | T-EFB 10% Co-Firing | T-EFB 20% Co-Firing | T-EFB 30% Co-Firing | T-EFB 40% Co-Firing | T-EFB 50% Co-Firing | ||
Method | Experimental | Simulation | Simulation | Simulation | Simulation | Simulation | Simulation |
Furnace peak temperature (°C) | - | 1484.5 | 1480.2 | 1476.5 | 1470.3 | 1465.1 | 1459.4 |
Furnace exit gas temperature (°C) | 1257 | 1258.8 | 1266 | 1268 | 1268.8 | 1269.4 | 1270.2 |
Gas temperature at boiler exit (°C) | 333.5 | 353.5 | 360.4 | 361.2 | 362.1 | 362.9 | 363.6 |
O2 content at boiler exit (vol%) | 2.2 | 2.2 | 2.3 | 2.36 | 2.41 | 2.46 | 2.54 |
CO content at boiler exit (vol%) | - | 8.8 × 10−11 | 4.9 × 10−11 | 6.64 × 10−9 | 8.02 × 10−9 | 9.9 × 10−9 | 1.29 × 10−8 |
CO2 content at boiler exit (vol%) | - | 14.60 | 14.84 | 14.65 | 14.65 | 14.65 | 14.62 |
SO2 content at boiler exit (ppm, at 6% O2) | 474.2 | 476.1 | 441.4 | 402.4 | 363.1 | 331.7 | 292.5 |
Discrepancies a (%) | - | 0.4 | 7.3 | 15.5 | 23.7 | 30.3 | 38.6 |
NOX emission at boiler exit (ppm, at 6% O2) | 159.2 | 170 | 152.2 | 133.9 | 122 | 110.1 | 97.8 |
Discrepancies a (%) | - | 6.8 | 10.5 | 21.2 | 28.2 | 35.2 | 42.5 |
Average residence time of fuel particles (s) | - | 20.24 | 20.19 | 20.13 | 19.85 | 19.6 | 19.5 |
Unburned carbon content (wt%) | 3.48 | 3.21 | 3.12 | 3.02 | 2.91 | 3.5 | 4.2 |
Economizer heat absorption (MW) | 64.3 | 61.7 | 57.5 | 58.2 | 58.8 | 59.4 | 59.9 |
Reheater heat absorption (MW) | 224 | 205.5 | 207.1 | 209.5 | 211.6 | 213 | 213.9 |
Superheater heat absorption (MW) | 317 | 312 | 314.9 | 317.5 | 319.1 | 319.4 | 319.5 |
Water wall heat absorption (MW) | 482.1 | 488 | 472.2 | 465.2 | 457.8 | 451.8 | 440.1 |
Total heat absorption (MW) | 1087 | 1067.2 | 1051.7 | 1050.4 | 1047.3 | 1043.6 | 1033.4 |
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Jiang, Y.; Park, K.-H.; Jeon, C.-H. Feasibility Study of Co-Firing of Torrefied Empty Fruit Bunch and Coal through Boiler Simulation. Energies 2020, 13, 3051. https://doi.org/10.3390/en13123051
Jiang Y, Park K-H, Jeon C-H. Feasibility Study of Co-Firing of Torrefied Empty Fruit Bunch and Coal through Boiler Simulation. Energies. 2020; 13(12):3051. https://doi.org/10.3390/en13123051
Chicago/Turabian StyleJiang, Yu, Kyeong-Hoon Park, and Chung-Hwan Jeon. 2020. "Feasibility Study of Co-Firing of Torrefied Empty Fruit Bunch and Coal through Boiler Simulation" Energies 13, no. 12: 3051. https://doi.org/10.3390/en13123051