Agriculture Reference
In-Depth Information
is reduced by around 20% in comparison to coal only firing, over the range of the
operating conditions tested. This aspect can be used to enhance the throughput of such
energy conversion systems.
Because of the presence of high amounts potassium in pressed pulp, which could
cause agglomeration during combustion in fluidized beds, longer term tests were carried
out with 50/50 blend of coal and pulp. Scanning Electron Microscopy (SEM) analyses of
bed samples taken at the end of every day have shown the up to 1% accumulation of
potassium in the bed. For comparison purposes tests were also carried out by co-firing
coal with raffinate and vinasse. Post experiment SEM analysis confirmed the
accumulation of potassium in the bed which was found to be around 8% for raffinate and
around 10% for the vinasse experiment. It was observed that vinasse and raffinate, due to
very high potassium content, require the introduction of alkali getters for successful
energy recovery.
The study has a broad application and can be beneficial in utilizing relatively cheap,
poor quality, unprepared biomass materials. The results of this study can be helpful in
devising systems to deal with wastes or by-products from different industries in co-
combustion with a fuel of higher calorific value such as coal. Thus the study will have
dual impact on the industry; addressing waste management issues on one hand and
producing useful energy on the other. This may contribute towards meeting the targets of
Kyoto Protocol by reducing emissions of carbon dioxide (CO
2
) as biomass is thought to
be CO
2
neutral.
1.
I
NTRODUCTION
Greenhouse gas (GHG) emissions are on the rise despite investment in energy intensive
technologies as well as efficiency improvements. The emissions increased by 1.6% per year
on average, over the last three decades. Carbon dioxide emissions resulting from the
combustion of fossil fuels are increasing at a rate of 1.9% [Rogner, et al. 2007]. According to
the fourth assessment report of the IPCC, in 2030 more than 80% of the global energy mix
will be from fossil fuels with consequent GHG emission implications if energy policies are
not substantially changed. The energy related CO
2
emissions are projected to be 40 - 110%
higher in 2030 as compared to 2000.
Humankind has a long history of using biomass for cooking and heating purposes. The
use of wood is thought to be much older than civilisation. In third world countries where the
majority of the population lives in villages with no access to natural gas, wood is still the
primary source of their energy source and to fulfil their everyday needs. Biomass is
considered to be CO
2
neutral as during its growth it uses the equivalent amount of CO
2
that is
then emitted during its combustion. Of course there is an energy penalty associated with its
harvesting and transportation etc and somebody can argue on the CO
2
neutrality of biomass.
Nevertheless, using biomass for power production can significantly reduce GHG emissions.
The combustion of biomass is widely recognised to be a means of reducing carbon
dioxide emissions from heating processes. However one of the main barriers to the more
widespread application of the technology has been the difficulty of burning relatively cheap,
poor quality, unprepared biomass materials. These unprepared potential fuels can be variable
in composition and fuel properties and often have relatively low calorific values and high
moisture content so that the stability and efficiency of the combustion process can be
adversely affected unless they are co-fired with a hydrocarbon support fuel. By-products of
