11-08-2012, 01:05 PM
EXPERIMENTAL ANALYSIS OF VEGETABLE OIL BLENDS IN A COMPRESSION IGNITION (CI) ENGINE
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ABSTRACT
Vegetable oils have been used as possible substitute to diesel in CI engines with
the possibility of also reducing harmful exhaust gas emissions. Various blends
have been reported by researches in this area as the optimum, giving higher or
comparable engine performance. This research considered three locally available
but marginally utilized vegetable oils and their respective blends with diesel in CI
engines. Physical properties relevant to the fuel industry were determined for the
three pure vegetable oils and their respective blends with diesel. A four stroke
single cylinder, fixed throttle CI engine was run on blends containing 1, 2, 3, 4, 5,
10, 50 and 100% of the three vegetable oils and diesel to measure their
performance characteristics. In terms of cetane index, calorific value and density,
jatropha oil came close to diesel than coconut and palm kernel oils. Combustion
characteristics and viscosity were higher for jatropha than coconut or palm kernel
oil. Even though all three vegetable oils can replace diesel in a CI engine, the
performance characteristics of the blends were generally lower than those for
diesel. Up to 5% substitution of diesel with coconut or palm kernel oil resulted in
Brake Specific Fuel Consumption (BSFC),
INTRODUCTION
PROJECT OVERVIEW
In the face of escalating oil prices and depleting oil reserves, the search for
alternative sources of fuels has been intensified more than ever before in the
history of mankind. Aside energy security concerns, issues of climate change as a
result of the emission of carbon dioxide (CO2) and carbon monoxide (CO) and
other harmful compounds associated with the use of fossil fuel have also been one
of the driving forces in the search for alternative sources which are
environmentally friendly and sustainable.
The use of vegetable oil in diesel engines dates back to 1892 when Rudolf Diesel
demonstrated his new invention (diesel engine) using peanut (groundnut) oil as
the fuel. Aside economies of scale (Gerpen et al, 2007) which favoured petroleum
derived fuels subsequently, other factors have also hampered the use of vegetable
oils in diesel engines. Of great concern are the relatively high viscosities and the
low volatilities of most of the vegetable oils and carbon deposits on the piston
during the running of the engine. All these factors have been observed to have a
negative impact on the performance of the engine. A possible remedy proposed by
many authors is the blending of the vegetable oil and diesel in some proportions
(Cloin, 2007). This is expected to cut down on cost, improve the fuel properties to
make it suitable for use in engines and also reduce the quantity of greenhouse
gases being emitted into the atmosphere.
THE PETROLEUM SECTOR IN GHANA
The economy of Ghana is heavily reliant on imported crude oil. At the moment
Ghana imports about 99% of her crude oil needs from abroad specifically through
bilateral agreement with Nigeria and also from the international market through
competitive bidding (Energy Commission, 2006). Ghana utilized more than
1,900,000,000 liters of petroleum products incurring a total expenditure of about
$520 million constituting nearly 19% of all imports (MOEn, 2006) in the year
2000. With an average annual growth rate of about 3% as shown in figure 1.1
below, the expenditure on oil rose to about $1,304.5million in 2006 (MOFEP,
2006). This can largely be attributed to the price hikes and partly to the exchange
rate of the Ghanaian Cedi against the United States Dollar. As observed by the
then Minister of Energy, Michael Oquaye in 2006, the price of crude oil is not
likely to fall below the $60/barrel rather it is expected to rise further
GHANA’s BIOFUEL POLICY
Fuels from renewable sources such as vegetable oils have been identified by
government to play a key role in the socio-economic development of the country.
This has led the government to set a target of 10% penetration of liquid fuels by
renewables by 2015 rising to 20% by 2020 (Energy Commission, 2006). This
target is to be achieved by introducing renewable energy fuels such as biodiesel
and gasohol into the supply mix of the country. The document goes further to
propose a road map for the introduction of biofuels into the petroleum sub sector.
In 2008 B52 is expected to be introduced into the supply chain, though marketing
companies will not be mandated to sell it. However, by 2020, it is expected that
all fuel stations will be mandated by law to sell both B5 and B10 and other
renewable sources of fuel. In promoting biofuels, the Strategic National Energy
Policy (SNEP) fails to point out in which direction the policy will take; either
transesterified vegetable oil blends with diesel or straight vegetable oil blends
with diesel. One may argue then that this has been left to technocrats and
researchers to figure it out. Though this is refreshing, studies on the sources of
biodiesel and their properties as a substitute for diesel have been limited to
Jatropha oil and to some extent coconut oil even though the document (Energy
Commission, 2006) did not promote jatropha or any other vegetable oil source.
RELEVANCE OF PROJECT TO NATIONAL DEVELOPMENT
Diesel/Gas oil is one of the derivatives of fossil fuel used in the transportation
sector. In Ghana, diesel fuel consumption constitutes about 41% (MoEn, 2006) of
the petroleum products utilized in the country. Consumption has been growing
steadily at an annual rate of about 5%. Diesel can thus be seen as an important
derivate of fossil fuel to the economy. Aside the transportation sector, the mining
sector is also heavily reliant on diesel accounting for about 10% of the total
consumption in the country. Replacing petroleum derived diesel with alternative
sources will have a huge positive impact on the quantity of fossil fuels imported
into the country and thus conserve the nation’s foreign currency reserves. Aside
this, an added advantage of pursing a biofuel policy is its ability to create and
sustain jobs especially in the agriculture sector of the economy.
ENERGY OR FOOD SECURITY
Ever since vegetable oil and other sources of biomass were proposed as possible
substitute for fossil derived fuels a lot of concerns have been raised most
especially on the impact biofuels will have on food security domestically and
globally. These concerns seems genuine especially when sharp increases in the
price of wheat which is a global commodity has been attributed to climate change
and more especially conversion of agricultural lands to grow energy crops like
corn (BBC, 2007).
The Food and Agricultural Organisation (FAO) defines food security as all people
at all times having access to sufficient, safe and nutritious food to meet their
dietary needs and food preferences for an active and healthy life. Intrinsically in
this definition lies energy security especially when most foodstuffs must be
cooked to render it eatable.