| Author | Kitipong Jaojaruek |
| Call Number | AIT Diss. no.ET-11-01 |
| Subject(s) | Biomass gasification
|
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Engineering in Energy, School of Environment, Resources and Development |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. ET-11-01 |
| Abstract | Biomass has become one of the promising al ternative fuels and a sustainable energy source. It has been promoted to be used extensively to reduce reliance on fossils fuels which are seen as finite energy source. On e method of generating gas fuel from solid biomass is the downdraft gasification process. Downdraft gasifiers have many advantages and can be used for thermal applications, el ectricity generation and internal combustion engine applications. However, the major issues with gasification are the tar and heating value of the producer gas. To improve the pr oducer gas qualities, namely, tar content and heating value, this study designed an auto -thermal two-stage single reactor downdraft gasifier using wood chip as fuel and air as gasification agent. Theoretical and experimental studies were carried out to model the pyrol ysis and the gasifica tion process, and to experimentally validate the model developed, besides showing the generation of high quality producer gas. The research involved experime ntal studies and mathematical model development. This study also explored supplying primary air into th e reactor at the combustion nozzle and return producer gas to mix with the secondary air supplied at the pyrolysis nozzle. The returned producer gas helped the process reac h higher temperatures in the pyrolysis zone, which also increases the temperature in the combustion zone. This makes the zone of high temperature (the location around combustion zone) become wider, which is good for thermal cracking of tar. Experi mental results show that gas generation rate increased up to 30% (for the same condition) when compar ed to the original two-stage method (no returned gas). The producer gas high heating value improved from 4.50 MJ/Nm 3 to 6.19 MJ/Nm 3 . The reactor generated high percentage of combustible gas (up to 41%) and high generation of H 2 (20.5%). The tar was reduced to around 80 mg/m 3 . A model to simulate the pyrolysis process wa s developed using the pr inciples of thermo- chemical kinetics and heat transfer. It was ab le to predict the temperature profile, volatile gas fraction and feedstock consumption rate in the pyrolysis zone . The model simulation results fitted well with the experimental data. The maximum temperature deviation was within 44 o C (at the temperature of more than 800 o C). The feedstock consumption rate was also validated. It had a maximum deviation of less than 1 kg/h. The minimization of Gibbs free energy principle was adopted for gasificatio n model to predict th e percentage of gas component in the producer gas. The model resu lts fitted well with experiment data for CO, CO 2 and H 2 and deviations were within 3%. However, the CH 4 percentage from the model was very low and methane contributes only 2% or less while the total combustible gas percentage is around 40%. Over all, the gasification model ca n be applied to reasonably predict the gas component percentage. |
| Year | 2011 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. ET-11-01 |
| Type | Dissertation |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Energy and Climate Change (Former title: Department of Energy, Environment, and Climate Change (DEECC)) |
| Academic Program/FoS | Energy Technology (ET) |
| Chairperson(s) | Kumar, S.; |
| Examination Committee(s) | Salam, P. Abdul ;Oanh, Nguyen Thi Kim; |
| Scholarship Donor(s) | Kasetsart Univers ity Kamphaengsaen, Thailand ;Asian Institute of Technology Fellowship; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2011 |