Dual-stage Drying Process of Lignite Using Pilot Scale Coal Rotary Dryer

Transcription

1 Research Center for Coal and Minerals (tekmira) Ministry of Energy and Minerals Resources of Indonesia Dual-stage Drying Process of Lignite Using Pilot Scale Coal Rotary Dryer Energy and Mineral Resources for People s Welfare P. Phiciato and D.Yaskuri September 6 th 2016 ECCRIA 11 th University of Sheffield

2 Energy and Mineral Resources for People s Welfare

3 Outline Introduction Research Questions Materials & Methods Result & Discussion Conclusion Energy and Mineral Resources for People s Welfare

4 Introduction Indonesian Coal Issue Account for 44% electricity production Pulverized coal-fired boiler is still widely used 65% of resources is lignite Lignite high moisture low efficiency & high CO2 Rotary Dryer ing Evaporative Fluidized Bed Hot oil immersion Dryi Non Evaporative Microwave Rotary Dryer (top view) Energy and Mineral Resources for People s Welfare

5 Research Questions Optimum temperature = 180C (laboratory scale) Longer, bigger diameter, higher feed rate Temperature gradient along the axial length? Risk of condensation drying consistency? Maximum feed rate? Single stage pass through one step drying process Single stage is not effective to reduce inherent moisture Dual stage is vulnerable to spontaneous combustion Minimize risk of oxidation Energy and Mineral Resources for People s Welfare

6 Materials & Methods Sample : freshly-mined Lignite No. Parameters Unit Value 1 Total moisture %, arb wt.% 2 Inherent moisture %, adb 17 wt.% 900 km 3 Size 0 50 mm wt.% 4 Hard Groove Index HGI 63 5 Gross Calorific value Kcal/kg, arb Ttl Total sample weight iht : 25 tons Average temperature : 23 31⁰C Energy and Mineral Resources for People s Welfare 6

7 Materials & Methods (cont d) Dryer Specification Type t Residence Drum ength :8m Diameter Rotation Inclination Flue Gas Circulation : Direct contact : minutes : 0.8 m : 1.09 RPM : 3 Feeder Furnace Cyclone & Exhausting Fan Energy and Mineral Resources for People s Welfare Rotary Drum

8 Materials & Methods (cont d) Experiments Pulverized coal injection Thermocouples Conveyor Cyclone Furnace Hot flue gas Rotary Drum Furnace Intermediate chamber Energy and Mineral Resources for People s Welfare Rotary Drum Circulation of flue gas

9 Materials & Methods (cont d) Measures conveyor Hot flue gas rotary valve to exhausting fan Furnace Intermediate chamber Rotary Drum Material Cyclone Rotary Stockpile Preparation Furnace Drum Moisture Feed mass rate kg/hour Temperature Fuel consumption Temperature profile Oxygen level Moisture Variation i of moisture Particles Size Distribution Energy and Mineral Resources for People s Welfare 9

10 Results & Discussion Temperature gradient T = C exhausting fan TE MPERATURE E ( O C) Intermediate chamber Volumetric flow rate Air temperature Oxygen level 100 Furnace Intermediate chamber Section 1 Section 2 Section 3 section kg/hour 350 kg/hour 400 kg/hour 500 kg/hour Energy and Mineral Resources for People s Welfare 10

11 Results & Discussion (cont d) Temperature Gradient exhausting fan Temper rature (C) Section 1 Section 2 Section 3 section 4 Temperature gradient 325 kg/hour 350 kg/hour 400 kg/hour 500 kg/hour T = f (flue gas flow) T = f (thermal conductivity of bed) 1 k - lignite = 0.52 W/mK k - water = 0.6 W/mK Non uniform drying temperature 1 James M Herrin, D.D., Thermal Conductivity of U.S coals. Journal of Geophysical Research, (B11): p Energy and Mineral Resources for People s Welfare 11

12 Results & Discussion Oxygen Level Circulated flue gas More combustion in furnace Increase flue gas volume Less oxidative atmosphere Energy and Mineral Resources for People s Welfare 12

13 Results & Discussion (cont d) PSD of dried product PAR RTICLES SI IZE DISTR RIBUTION (%) kg/hour 350 kg/hour 400 kg/hour 500 kg/hour -9.5 mm (fine) - 19mm, +9.5mm (medium) +19mm (coarse) Cyclic internal pressure crack propagation thermal fragmentation 1 O.Senneca, M.U., R.Chirone, D.Cumbo, An experimental study of fragmentation of coals during fast pyrolysis at high temperature and pressure. FUEL, : p Energy and Mineral Resources for People s Welfare 13

14 Results & Discussion (cont d) Moisture Content Variation δ = 3.2 δ = 6.4 δ = δ = 3.6 δ = 3.2 δ = 2.3 Energy and Mineral Resources for People s Welfare 14

15 Results & Discussion (cont d) Moisture Content raw primary drying secondary drying Mois sture Cont tent (%) mm (fine) mm (medium) Particle Size +19mm (coarse) Mix Energy and Mineral Resources for People s Welfare 15

16 Conclusion Average moisture content of dried products are 24 %wt for single stage drying and 12 %wt for dual stage drying Dual stage is more effective than single stage drying Flue gas circulation reduces risk of spontaneous combustion during secondary drying Moisture content variation is reduced improve drying consistency Maximum feed rate is 500 kg/hours Future Works Storage of dried product? Implementation in minemouth coal-fired power plant Energy and Mineral Resources for People s Welfare

17 Contact : phiciato@tekmira.esdm.go.id i i id Energy and Mineral Resources for People s Welfare