| Author | Siddiki, Md. Mahbube Khoda |
| Call Number | AIT Thesis no.ET-06-17 |
| Subject(s) | Fluidized-bed furnances
|
| Note | A thesis submitted in partial fulfillment of the requirements for the
degree of Master of Engineering, School of Environment, Resources and Development
|
| Publisher | Asian Institute of Technology |
| Abstract | The fluidized bed (FB) has two major advantages as a furnace for combustion of solid fuels compared to suspension burners and fixed bed combustors. First it enable combustion with low emissions of nitric and sulfur oxides without flue gas treatment, second a fluidized bed is fuel flexible, and several fuel can be burnt in the same furnace. A distributor system is a key component of a FB combustor that support material and ensure a uniform distribution of flow. At present, higher pressure distributors are used to prevent backflow of solids and to have a uniform distribution. This requires a higher auxiliary power consumption compared to other types of combustors. To address this issue the present study was undertaken for developing a low pressure air distributor system that could prevent backflow of solids. A nozzle type distributor was selected for the study. Experimental investigations were carried out on a number of nozzles namely: double opening arrow head nozzle, single opening arrow head nozzle and inverse U- shape nozzle. Parameters varied were percentage of opening, bed materials, bed height and superficial velocities. The performance measures include, material backflow, uniformity of gas flow and distributor to bed pressure drop (dPd /4P,) ratio. A ratio of maximum flow rate through a nozzle distributor to average flow rate through all nozzle distributors (Q IQ,,,) is used as the indicator for uniform flow distribution. The result of the investigation revealed the followings. Material back flow found in multi opening arrow head nozzle. Single opening arrow head nozzle was also unable to overcome this problem, whereas inverse U-shape nozzle successfully prevented it. The result revealed that geometric shape of the nozzle should be considered most importantly while designing a new distributor system to prevent back flow of solids. Two different sizes of sand of Geldart particle B, used as bed materials, showed no effect in preventing material backflow or assuring uniform fluidization. Windbox design has shown significant role in uniform flow distribution for low as well as high pressure drop distributor. The inverse U-shape nozzle was selected considering the criteria of preventing backflow of solids. This nozzle was further modified to ensure a uniform fluidization by changing the percentage of opening. Result also shows that a pressure drop ratio(JPd /AP,) of 0.5, a maximum flow ratio of 20% is obtained, which could be used as a preliminary guideline for a inverse U-Shape distributor design. A further study is recommended to develop a correlation between (d Pd /4P,) and (Q1712T/Q~~) |
| Year | 2006 |
| Type | Thesis |
| 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) | Dutta, Animesh; |
| Examination Committee(s) | Kumar, Sivanappan ;Surapong Chirarattananon; |
| Scholarship Donor(s) | The Government of France
AIT Institute Fellowship ; |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 2006 |