Boiler using Biomass as Fuel

Transcription

1 Boiler using Biomass as Fuel International Conference The Future of ASEAN S Energy Journey E mobility Smart Grid Smart City 6 June 2018, BITEC, Bangkok, Thailand Suthum PATUMSAWAD Department of Mechanical Engineering Faculty of Engineering King Mongkut s University of Technology North Bangkok (KMUTNB) Director of Renewable Energy and New Energy Technologies Program National Science and Technology Development Agency (NSTDA) 6 June 2018, BITEC, Bangkok, Thailand Bio Energy: Pretreatment, Combustion and Pyrolysis of Biomass 1

2 Outlines of Presentation General Description of Boilers Biomass Fuel Opportunity Technical Barriers Choosing the right Fuel? The need of Biomass Characterisation Concluding Remarks 2

3 General Description of Boilers A boiler (or steam generator) consists of a fossil fuels or biomass burner and a heat-transfer system to boil water and generate steam. Steam generators also include systems and components for pressure control, heat recovery, steam delivery and distribution, condensate drainage, and separation of oxygen and non-condensable gases. 3

4 Use of Boilers o o o o o o Electrical generation Chemical industry Petroleum industry Pulp & paper industry Food industry Etc. 4

5 Biomass Fuel Opportunity Biomass fuel is : Regenerative Energy Plants continue to grow as long as existence of sun light, water and soil. Efficient use of biomass energy is applauded as fossil fuels become depleted. Agro-forestry wastes previously disposed of are recovered as fuel energy. This forms a recycling type community with reduced waste generation and efficient energy use Earth-friendly Energy Plants absorb CO2 in the growing process. Rich, green forests thus help prevent global warming. o Addresses key energy, economic, environmental and social problems at the local and global scale 5

6 Biomass Fuel Opportunity Power generation from biomass can be achieved with a wide range of feedstock which have different properties. 6

7 Biomass Characteristics Lower density Higher moisture content, often up to 50% Lower calorific value Broader size distribution, unless pre-conditioned by screening, crushing or pelletising The variability of the material as a fuel will be greater 7

8 Biomass differs from conventional fossil fuels Physical structure Chemical structure Technical barriers Moisture content Therefore it must be burnt differently. Effect of Moisture Decreases combustion temperature Leads to incomplete combustion higher CO and Carbon in Ash Decreases boiler efficiency Leads to more fuel use, higher energy costs and increased air pollutants 8

9 Biomass Fuel - Volatiles 70 80% of dry biomass is volatile hydrocarbons. Released from the biomass structure at relatively low temperatures. Volatiles burn in suspension way from the biomass particles. Balance is fixed carbon or char. 9

10 Biomass Fuel - Ash 10

11 Biomass Fuel - Ash Combines with alumina and silica lowers melting point Slagging on grate and boiler tubes Ash accumulation Airflow problems High draft losses Reduced heat transfer Boiler shutdowns 11

12 Biomass Fuel - Ash Agglomeration and Sintering problems Fouling and Slagging problems Corrosion and Erosion problems 12

13 Choosing the right fuel? Prior to design combustion system, answers to the following questions must be known: Is the biomass which will be used apt for combustion system? What are the optimal conditions for the combustion of the specific biomass? What is the range of biomass which may be used in the specific combustion system? 13

14 The need ofbiomass Characterisation Quality of biomass fuel is the most important point for the reliability of the plant Avoid Contaminants Control moisture content Chemical analysis is critical to understanding of performance The lack of sufficient information concerning biomass feeding as well as the combustion and emission characteristics of biomass. This information is important for the design and efficient operation of combustion systems 14

15 The need of Biomass Characterisation Biomass characterization Identifies the fuel value Provides an estimate of ash handling requirement Describes something of the burning characteristics Indicative of problems arising during combustion Useful important for the design and efficient operation of combustion systems 15

16 Some outputs: Fuel property analyses 11 fuel samples: 2 coals, 8 biomasses and 1 wastewater sludge Table 1. Fuel sample used in this study Fuel Properties Testing method Fuel sample Source 1. Lignite Coal (Lig) Thai lignite company, Lampang 2. Sub-bituminous Coal (SB) Asia Green company 3. Rice husk (RH) Rice field in Nakornphatom 4. Rice straw (RS) Rice field in Nakornphatom 5. Giant Leuceana Wood (LW) Mitr Phol Group, Suphanburi 6. Eucalyptus Wood (EW) Asia charcoal company 7. Napier Grass (NP) Farm in Kanchanaburi 8. Palm empty fruit bunch (EFB) 9. Sugarcane Top and Leaf (CT/L) Suksomboon oil plam company, Chonburi Mitr Phol Group, Suphanburi 10. Sugarcane Leave (CL) Mitr Phol Group, Suphanburi 11. Wastewater sludge (Slud) Samutsakorn Industrial estate Table 2. Fuel properties and testing method 1. Proximate analysis - Volatile matter - Fixed carbon - Ash (at 900 O C) 2. Ultimate analysis C, H, N, S, O ASTM D 5142 by TGA Organic elemental analyzer (OEA) 3. Moisture content (%ar) ASTM D Gross Heating Value Bomb Calorimeter 5. Ash content ASTM E1755 at 575 O C 6. Chemical structure - Hemicellulose - Cellulose - Lignin TAPPI T203om-88 TAPPI T204 om-88 TAPPI T222 om-88 TAPPI T223 cm-01 (biomass only) 7. Ash composition XRF, XRD 8. Ash Fusion Temperature (AFT) for coal only Oxidation by air, Reduction by CO/CO 2 60/40 (v/v) 16

17 Some outputs: Fuel property analyses 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Proximate analysis (dry basis, wt%) Table 3. Moisture content and HHV Fuel Moisture (wt%, ar) HHV (MJ/kg dry) 1. Lig SB RH RS LW EW NP EFB Fixed carbon VM ash Figure 1. Proximate analysis of the fuel samples 9. CT/L CL Slud

18 Some outputs: Fuel property analyses Table 4. Ash composition of fuel sample by XRF (%wt dry ash) Sample SiO 2 Al 2 O 3 SO 3 CaO Fe 2 O 3 MgO K 2 O Na 2 O MnO P 2 O 5 Cl BaO TiO 2 SrO Rb 2 O ZnO CuO Cr 2 O 3 SnO 2 Sludge Lignite SB NP LW CT/L EW EFB RS RH The major elements in both coals were Si, Al, Ca, Fe and also high in SO 3 - NP, CT/L, RS, and EFB were high in both K and Cl and therefore likely to have ash related problems - Slud was high in Al, Ca and also high in Si and SO 3 18

19 Some outputs: Fuel property analyses Table 5. Chemical structure of biomass samples Biomass Chemical Structure (%wt, dry biomass) Cellulose a Lignin b Hemicellulose c Extractives d Rice husk (RH) Rice straw (RS) Leuceana Wood (LW) Eucalyptus Wood (EW) Napier Grass (NP) Empty fruit bunch (EFB) Cane Top and Leave (CT/L) a TAPPI T203 om-88 (1992). Alpha, beta, gramma cellulose in pulp, b TAPPI T222 om-88 (1988). Acid-insoluble lignin in wood and pulp c TAPPI T223 cm-01 (2001). Pentosans in wood and pulp, d TAPPI T204 om-88 (1997). Solvent extractives of wood and pulp 19

20 Some outputs: Fuel property analyses Coal Lignite SB coal Atmosphere Initial Deformation Temperature ( O C) Spherical Temperature Hemispherical Temperature Flow Temperature Reduction 1,190 1,210 1,230 1,230 (CO/CO 2, 60/40 %v/v) Oxidation (Air) 1,250 1,260 1,280 1,290 Reduction 1,130 1,160 1,190 1,220 (CO/CO 2, 60/40 %v/v) Oxidation (Air) 1,190 1,220 1,230 1,250 Coals had relatively low IDT, especially under reducing atmosphere 20

21 Some outputs: Combustion characteristic of fuel Combustion characteristic of Single Fuels (example curves) Figure 2. TG and DTG curve of single fuel combustion Coal exhibited a one-step combustion, two-step combustion (devolatilization followed by char combustion) was clearly observed for biomass (incl. sludge). Decomposition of biomass started at lower temperature than coal was due to the higher VM content. 21

22 Some outputs: Combustion characteristic of fuel Combustion characteristic of blend Fuels Example 1: Lig/RS blends Pure Lig Pure RS Pure Lig Pure RS Figure 3. TG curves of combustion of Lig/RS blends Figure 4. DTG curves of combustion of Lig/RS blends Combustion behavior of the blends clearly presents the behaviour of individual components that is the prior decomposition of biomass followed by that of coal. 22

23 Some outputs: Fouling tendency of fuel combustion 23

24 Some outputs: Fouling tendency of fuel combustion Morphology of deposit (1000X) Pure SB Pure RS SB/RS (1:1) SB/EFB (1:1) Pure NP SB/NP (1:1) Pure CTL Pure EFB Deposit Bottom ash SB/CTL (1:1) Morphology of deposit from co-combustion was drastically changed into the melted surfaces, in particular SB/RS and SB/NP 24

25 Some outputs: Simulation of fuel combustion 25

26 Concluding Remarks Although combustion technologies can already be considered as proven, there is a continuous demand for equipment with: Lower investment and operational cost Increased fuel flexibility Lower emissions Increased reliability and efficiency 26

27 Thank You National Science and Technology Development Agency (NSTDA) 111Thailand Science Park Phahonyothin Road Klong Nueng, Klong Luang Pathum Thani Thailand 27

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