RD of Small-Scale Municipal Solid Waste Gasification for Power by dfq22970


									      R&D of Small-Scale Municipal Solid Waste Gasification for Power Generation
                     Somrat Kerdsuwan*, Suthum Patumsawad* and Kunio YOSHIKAWA**

                               The Waste Incineration Research Centre (WIRC)
                                   Department of Mechanical Engineering
                                           Faculty of Engineering
                            King Mongkut’s Institute of Technology North Bangkok
                                          Bangkok, Thailand 10800
                               Email : srk@kmitnb.ac.th, somrat_k@yahoo.com

                      **Interdisciplinary Graduate School of Science and Engineering,
                            Department of Environmental Science and Technology
                 Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama, Japan


Municipal Solid Waste (MSW) is considered as a discard matter which needs a special disposal method. At
present, landfill is the most common treatment method of MSW in Thailand. This is due to its lowest net
treatment cost when comparing with the other methods, i.e. thermal treatment and composting. However, it is
quite clear that the landfill method is not an ultimate and sustainable way for the MSW treatment. In deed, it
works in such a way that the waste would be transferred into land and waiting for final disposal process in the
future, causing a large land usage and long-term treatment. In order to solve this dilemma, the thermal treatment
method has been considered as an efficient alternative approach in which the MSW can be transformed
effectively into ash and its mass and volume can be reduced up to 70 to 90%. Moreover, the energy recovery
from this process can be utilized for electricity power generation and heat generation. This can result in the
income of the plant when selling such energy to the industry or, at least, the lower operating cost of the plant
from its own energy subsidy. In addition, according to the energy crisis nowadays in Thailand due to the high
petroleum price, the Ministry of Energy has developed a plan to treat the MSW effectively and, at the same time,
benefit from the energy produced from the waste. It is expected that the Waste-to-Energy plant will be installed
in Thailand by the year 2011, where the 100-MW electricity can be generated from the energy recovery.
However, in order to achieve the goal of the Ministry plan, the technology for the Waste-to-Energy plant has to
be imported from aboard, resulting in the lost of international currency. To avoid this situation, the research and
development of Waste-To-Energy technology is therefore very crucial for Thailand. This R&D project covers 3
important steps in three years, namely; i) the experiments in laboratory scale, ii) the prototype machine build-up
and iii) the technology transfer to industry for commercialization.

In the first year of project, an intensive investigation has been carried out using a lab-scale downdraft gasifier
constructed for this study. The gasifier was initially run on a batch mode and has a designed capacity of about 30
kg feed per batch. In the preliminary tests, wood blocks were used. The temperatures and gas compositions along
the height of the gasifier have been measured. Despite the temperature fluctuation, some observation could be
made. At high percentage of theoretical air, i.e. 40-47 %, the combustion did not occur where air blast was
injected, but shifted to the lower position. The temperatures in the shifted combustion zone were also very high,
which also raised the temperature in the vicinity, including the temperature in the reduction zone. At low
percentage of theoretical air, i.e. ~20 %, the combustion zone existed at position as expected. However, the
overall temperatures were found to be lowest among the three study cases. The temperatures investigated in the
combustion zone were around 800°C, which is considered to be too low for volatile combustion and therefore
likely that a large amount of tar could form. From the analysis results, the gas sampled at the exit consists of
12.97 %CO2, 1.88 %O2, 47.9 % N2, 2.80 % CH4, 18.83 % CO and 15.62 % H2. The calculated heating value was
5.68 MJ/m3. The gas compositions at different heights are also reported in this study. Further work on the
composition analysis of gas in each reaction zone and the tar measurement will help on explaining the reaction

It is noteworthy to conclude that this R&D project for MSW can contribute a number of benefits to Thailand in
variety aspects. At the end of the project, it is expected that not only the imported know-how, technologies and
equipments concerning the waste treatment can be reduced for Thailand; but the intellectual properties can also
be produced

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