Experimental and numerical evaluation of napier grass gasification in an auto-thermal fluidized bed reactor
Biomass gasification is a promising renewable energy generation technology as alternative to fossil based fuels for cleaner and sustainable future. At site auto-thermal gasifier built in affordable economic scale can overcome the high costs of grid lining, supplementary resources and the deliv...
Saved in:
| 主要作者: | |
|---|---|
| 格式: | Thesis |
| 語言: | English |
| 出版: |
2018
|
| 主題: | |
| 在線閱讀: | http://psasir.upm.edu.my/id/eprint/71457/1/FK%202018%20107%20IR.pdf |
| 標簽: |
添加標簽
沒有標簽, 成為第一個標記此記錄!
|
| id |
my-upm-ir.71457 |
|---|---|
| record_format |
uketd_dc |
| institution |
Universiti Putra Malaysia |
| collection |
PSAS Institutional Repository |
| language |
English |
| topic |
Renewable energy sources Biomass energy |
| spellingShingle |
Renewable energy sources Biomass energy Khezri, Ramin Experimental and numerical evaluation of napier grass gasification in an auto-thermal fluidized bed reactor |
| description |
Biomass gasification is a promising renewable energy generation technology
as alternative to fossil based fuels for cleaner and sustainable future. At site
auto-thermal gasifier built in affordable economic scale can overcome the
high costs of grid lining, supplementary resources and the delivery of
feedstock as main target for this study. A biomass gasification system with
Napier grass as feedstock was investigated with the target of the producer
gas to be used in direct combustion for power generation. The study consists
of two main parts of experimental evaluations and numerical models.
Experiments carried out to study the effect of three different operating
parameters namely, temperature, equivalence ratio (ER) and static bed
height (SBH) on the gasification of Napier grass in an auto-thermal bubbling
fluidized bed gasifier. The results showed that the temperature has the most
significant effect on the production of syngas as well as the composition of
combustible species. The highest yield of syngas, with highest compositions
of hydrogen and carbon monoxide and lowest yield of residues (i.e. biochar,
tar and ash) were achieved at maximum temperature of 824°C. ER on the
other hand has more complex effects on responses. The increase in ER up
to 0.33 favored the yields of syngas, H2 and CO however the inverse effect
was observed for ER above 0.33. SBH was found an important factor to
effect on the production of H2 and CO and the maximum yields of each
obtained at temperature of 824°C, ER of 0.33 and SBH of 0.105m. Common
challenges encountered in performing the experiments were related to the
complexity and instability of the process and the difficulties to maintain the
temperature at a constant level due to the auto-thermal characteristics.
Difficulties are expected to be diminished once achieved a steady-state
operating condition through process improvement and optimization to which
the process become adaptable to any imposed variations such as different
feedstock types.An integrated numerical simulation were developed to study over
hydrodynamics and thermodynamics of the gasification process.
Hydrodynamics of solid particles fluidization were modelled to study on the
effect of superficial velocity, viscous and drag models on the expansion of
fluidizing bed, formation and distribution of bubbles inside the gasifier. The
effect of air distributor plate with different pore diameters was modelled
individually to determine the initial condition of the fluid as entered the
gasifier. The results showed that the turbulent model of RNG K-Ɛ describes
the actual process more accurately than other fluid regimes. Laminar and
turbulent models although resulted in similar bed expansion level, the
turbulent model showed higher distribution of solid particles and their related
interactions as the result. Thermodynamic studies were conducted to
simulate the heat distribution and to determine the temperature profile of the
reactor at any time step of the operation. The temperature values at steady
operation were verified by experimental records. The conduction heat
transfer from gasifier media into the center of a single particles with different
diameters were studied individually to calculate the particle degradation
period. It was found from the results that fully degradation of a particle to
solid biochar as entered the gasifier at constant temperature takes place
after 0.66, 1.1 and 1.55 seconds for particles with 300,500 and 700 μm
diameters respectively. The effect of particle size and initial reactor
temperature on heat distribution were evaluated as well. Using the model
eases the monitoring of system behavior while functions under various
operating conditions.
The findings from empirical optimization while integrated with numerical
models provides an in-depth understanding over the gasification process
and facilitates the scale-up determinations so that the technology in the
future can be utilized in larger scales to provide power from biomass
particularly in form of electricity in rural area. |
| format |
Thesis |
| qualification_level |
Doctorate |
| author |
Khezri, Ramin |
| author_facet |
Khezri, Ramin |
| author_sort |
Khezri, Ramin |
| title |
Experimental and numerical evaluation of napier grass gasification in an auto-thermal fluidized bed reactor |
| title_short |
Experimental and numerical evaluation of napier grass gasification in an auto-thermal fluidized bed reactor |
| title_full |
Experimental and numerical evaluation of napier grass gasification in an auto-thermal fluidized bed reactor |
| title_fullStr |
Experimental and numerical evaluation of napier grass gasification in an auto-thermal fluidized bed reactor |
| title_full_unstemmed |
Experimental and numerical evaluation of napier grass gasification in an auto-thermal fluidized bed reactor |
| title_sort |
experimental and numerical evaluation of napier grass gasification in an auto-thermal fluidized bed reactor |
| granting_institution |
Universiti Putra Malaysia |
| publishDate |
2018 |
| url |
http://psasir.upm.edu.my/id/eprint/71457/1/FK%202018%20107%20IR.pdf |
| _version_ |
1747813005991608320 |
| spelling |
my-upm-ir.714572019-11-13T06:43:21Z Experimental and numerical evaluation of napier grass gasification in an auto-thermal fluidized bed reactor 2018-05 Khezri, Ramin Biomass gasification is a promising renewable energy generation technology as alternative to fossil based fuels for cleaner and sustainable future. At site auto-thermal gasifier built in affordable economic scale can overcome the high costs of grid lining, supplementary resources and the delivery of feedstock as main target for this study. A biomass gasification system with Napier grass as feedstock was investigated with the target of the producer gas to be used in direct combustion for power generation. The study consists of two main parts of experimental evaluations and numerical models. Experiments carried out to study the effect of three different operating parameters namely, temperature, equivalence ratio (ER) and static bed height (SBH) on the gasification of Napier grass in an auto-thermal bubbling fluidized bed gasifier. The results showed that the temperature has the most significant effect on the production of syngas as well as the composition of combustible species. The highest yield of syngas, with highest compositions of hydrogen and carbon monoxide and lowest yield of residues (i.e. biochar, tar and ash) were achieved at maximum temperature of 824°C. ER on the other hand has more complex effects on responses. The increase in ER up to 0.33 favored the yields of syngas, H2 and CO however the inverse effect was observed for ER above 0.33. SBH was found an important factor to effect on the production of H2 and CO and the maximum yields of each obtained at temperature of 824°C, ER of 0.33 and SBH of 0.105m. Common challenges encountered in performing the experiments were related to the complexity and instability of the process and the difficulties to maintain the temperature at a constant level due to the auto-thermal characteristics. Difficulties are expected to be diminished once achieved a steady-state operating condition through process improvement and optimization to which the process become adaptable to any imposed variations such as different feedstock types.An integrated numerical simulation were developed to study over hydrodynamics and thermodynamics of the gasification process. Hydrodynamics of solid particles fluidization were modelled to study on the effect of superficial velocity, viscous and drag models on the expansion of fluidizing bed, formation and distribution of bubbles inside the gasifier. The effect of air distributor plate with different pore diameters was modelled individually to determine the initial condition of the fluid as entered the gasifier. The results showed that the turbulent model of RNG K-Ɛ describes the actual process more accurately than other fluid regimes. Laminar and turbulent models although resulted in similar bed expansion level, the turbulent model showed higher distribution of solid particles and their related interactions as the result. Thermodynamic studies were conducted to simulate the heat distribution and to determine the temperature profile of the reactor at any time step of the operation. The temperature values at steady operation were verified by experimental records. The conduction heat transfer from gasifier media into the center of a single particles with different diameters were studied individually to calculate the particle degradation period. It was found from the results that fully degradation of a particle to solid biochar as entered the gasifier at constant temperature takes place after 0.66, 1.1 and 1.55 seconds for particles with 300,500 and 700 μm diameters respectively. The effect of particle size and initial reactor temperature on heat distribution were evaluated as well. Using the model eases the monitoring of system behavior while functions under various operating conditions. The findings from empirical optimization while integrated with numerical models provides an in-depth understanding over the gasification process and facilitates the scale-up determinations so that the technology in the future can be utilized in larger scales to provide power from biomass particularly in form of electricity in rural area. Renewable energy sources Biomass energy 2018-05 Thesis http://psasir.upm.edu.my/id/eprint/71457/ http://psasir.upm.edu.my/id/eprint/71457/1/FK%202018%20107%20IR.pdf text en public doctoral Universiti Putra Malaysia Renewable energy sources Biomass energy |