Nimit Nipattummakul. Gasification of wastewater sludge from industrial estate in a downdraft gasifier for power generation. Doctoral Degree(Mechanical Engineering). King Mongkut's University of Technology North Bangkok. Central Library. : King Mongkut's University of Technology North Bangkok, 2010.
Gasification of wastewater sludge from industrial estate in a downdraft gasifier for power generation
Abstract:
Wastewater sludge from wastewater treatment plant typically consists of
organic, inorganic and toxic substance, heavy metal, and pathogenic or diseasecausing
microorganisms, which are harmful to the environment and all living
organisms. Therefore, appropriate technologies are necessary for safe and efficient
sludge disposal. Gasification technology is one of the most promising options for
wastewater sludge disposal as well as waste to energy conversion. This technology for
the thermal treatment can extract chemical energy from wastewater sludge and
simultaneously produce energy. The energy produced may can be used in the
wastewater treatment plant or for other purposes. It also stabilizes the harmful
substances in the residual char. Accordingly, this research is aimed at investigating
the potential of electricity generation from wastewater sludge gasification in a 50 kg/h
downdraft gasifier. The study includes the preparation (briquetting) and
characterization of the wastewater sludge, the analysis of the syngas properties, and
the estimation of gasification efficiency in order to find the optimum operational
conditions for the gasification system. The experiments were conducted at three
different air volumetric flow rates of 75, 100, and 125 m3
N/hr. At the optimum air
volumetric flow rate of 100 m3
N/hr, the syngas consisted of 14.95% CO, 1.13% CH4,
9.92% H2, 61.50% N2, 0.67% O2, and 11.83% CO2, and thus provided the higher
heating value (HHV) of 3.30 MJ/m3
N and the cold gas efficiency of 55.69%. The
results from the diesel engine tests fuelled dually with the syngas produced at the
optimum operation showed that the maximum diesel replacement rate was about
72.05% at 43.48% engine load (24 kWe), with specific energy consumption of about
14.48 MJ/kW-h. The electrical power generation could be run at optimum operation
without the air pollution control, while the overall efficiency was 11.22% at the
optimum operating condition with wastewater sludge consumption rate of 52.52 kg/h,
20.7 kg/h of char residual, and syngas flow rate of 132.2 m3
N/h. The results suggest
that wastewater sludge can be considered as renewable energy through downdraft
gasification.