Investigation of pirina combustion in a test boiler for energy production
Tez Türü: Yüksek Lisans
Tezin Yürütüldüğü Kurum: Dokuz Eylül Üniversitesi, Fen Bilimleri Enstitüsü, Çevre Teknolojisi (Yl) (Tezli), Türkiye
Tez Danışmanı: Abdurrahman Bayram
Tezin Onay Tarihi: 2003
Tezin Dili: İngilizce
Özet:
As the resources of the fossil fuels are
exhausted and air pollution due to usage of these fuels is a major problem,
alternative energy resources are considered seriously. Biomass usage is common
among different alternative energy resources. Olive oil production waste,
pirina, is a good example of biomass in Mediterranean countries because of its
high availability. In this study, fuel characteristics of pirina were
determined and appropriate combustion conditions to obtain low emissions were
investigated.
Pirina’s oil, water and solid contents
vary depending on the olive oil production processes. The average values were
found as 4-8% oil, 20-60% water and 40-70% olive stone and pulp. Proximate
analyses were conducted on raw pirina and de-oiled pirina samples in order to
identify fuel characteristics of pirina. Result were 25.8-69.3% moisture,
2.5-3.1 %ash, 67.9-70.6% volatile matter, 25.8-28.7% fixed carbon,
18,225-20,413 kj/kg higher heating value for raw pirina and 6.3-16.7% moisture,
2.7-7.1 %ash, 57.5-68.2% volatile matter, 22.1-28.6% fixed carbon,
19,196-19,860 kj/kg higher heating value for de-oiled pirina. Raw pirina should
not be used directly as fuel due to its high moisture and oil content.
Therefore, the usage of de-oiled pirina as a fuel was investigated. Pirina has
high volatile matter content. Gasification of volatile matters at low
temperatures and their release through stack without complete combustion is an
important negative factor for pirina combustion.
Combustion tests were conducted using a
laboratory scale boiler. The fuel feeding rate was established using the screw
type feeder having a capacity of 40 g/sec. Combustion tests were made in
different feeding rates while feeding and stop times ranged between 1-3 seconds
and 30-60 seconds, respectively. According to elementary analyses of pirina,
stoichiometric oxygen requirement for combustion varied between 4.15 to 4.5 Nm3/kg.
Low carbon monoxide (CO) emissions were obtained for excess air ratios between
2.0 to 2.2 during combustion tests.
The combustion tests were repeated for
different fuel feeding rates and fluctuations of CO emissions were observed
throughout the experiments. Average fuel flow rate was 7.5 kg/h for Run 1 and
Run 2, and 10 kg/h for Run 3 and Run 4. Average CO emissions in these Runs were
1451, 1341, 1664, 1723 mg/Nm3, respectively. Average excess air
ratios were 2.6, 2.7, 2.2, 2.2, respectively. According to results of
combustion experiments, CO emissions of the test boiler were generally above
the emission limits (460 mg/Nm3, based on 6% O2).
The biggest problem encountered during the
experiments of this study was the exact adjustment of air to fuel ratio. This
problem originated from combustion air feeding system of the furnace. And this
resulted in incomplete combustion. CO emissions measured during combustion for
different excess air ratios (λ) were compared and it was found that CO
emissions increased as the excess air ratio increased. This was due to the
decrease of temperature in combustion zone (650-800 ºC) with increasing λ.
As a result of the experiments to achieve
low CO emissions, it was concluded that fuel feeding must be done automatically
and continuously and the combustion system should have secondary air feeding.
The furnace must be designed to increase the retention time of volatile matter
at high temperatures. In line with the results obtained, it was suggested that
combustion system should be improved and experiments should be continued.
In line with these results obtained,
combustion systems should be improved and experiments should be continued.