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Diesterol: The Future Fuel for IC Engines

by P. Kannadasan, 1st yr B.E. (Mechanical Engg.)

Abstract

Diesterol is a new specific term which denotes a mixture of fossil diesel fuel,

vegetable oil methyl ester called biodiesel and plant derived ethanol. This refers specifically

the combination of diesel fuel, bioethanol and methyl ester produced through

transesterification. The mixture of these, i.e. diesterol, was patented under the Iranian patent

No. 39407, dated 12-3-2007. The main aim of using diesterol was to reduce engine exhaust

NOx, CO, HC and smoke emissions due to application of biofuel and the increase of fuel

oxygen content. It was needed to prepare suitable low cost and renewable additives. Theoptimum ratio of bioethanol and biodiesel for diestserol was 40/60 considering fuel oxygen

content, fuel price and mixture properties. Bioethanol was added to enhance the oxygenated

component in the fuel, while the methyl ester was added to maintain the fuel stability at low

temperatures.

Introduction

Energy demand is increasing continuously due to rapid growth in population and

industrialization development. The development of energy sources is not keeping pace with

spiraling consumption. Even developed countries are not able to compensate even after

increasing the energy production multifold. The major energy demand is provided from the

conventional energy sources such as coal, oil, natural gas, etc. Two major problems, which

every country is facing with these conventional fuels, are depletion of fossil fuels and

deterioration of environment.

The biofuels can be obtained from biomass which can be obtained from various

sources like wastes (agro industries, corp residues), standing forests and energy crops (edibleand nonedible crops). The amount of biofuel that a plant can produce depends on how much

sunlight the plant receives and the amount it can store as carbohydrates.

Demand for both bioethanol and biodiesel is forecast to rise sharply. Biodiesel output

by the firm is expected to reach 600 M l/y by 2012 when the Brazilian biodiesel market

should total 2.5 bn l. In Australia, BP plans to use hydrogenation technology to produce 2 bn

l/y of diesel containing 5% biodiesel by 2008. Ethanol production by the firm is expected to

reach 80 M tonne/y, with biofuels from BP providing over 50% of the 350 M l required in

Australia in 2008.

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Due to depletion of fossil fuels the demand for biofuels has been increasing for years

back. Although biodiesel and bioethanol were studied for more than a decade ago, its

application has been limited due to its high emissions. Now a new kind of biomass, Diesterol

was emerging as the future fuel for IC engines. The following section will focus on some of

the factors which need to be taken care for efficient use ofDiesterol.

Performance parameters for Diesterol

1. Selection of fuel blend ratio

The ultimate aim was to get a suitable blend of bioethanol, biodiesel and diesel fuel which

was then called Diesterol. Another idea of developing a suitable blend was to can overcome

the problem of solubility of bioethanol in diesel fuel and maintaining the stability of the blend

at low temperatures as well.

2. Fuel stability

One of the main advantages of using fuel blends in diesel engines is to keep the engine

modification minimal. A solution is a single-phase liquid system, homogeneous at the

molecular level. Some e-diesel formulations may be a solution of bioethanol, plus additives

in diesel fuel. Some materials such as emulsifier, cosolvent, isopropanol were added to the

mixtures to satisfy homogeneity and to prevent phase separation. Presence of water in

bioethanol or diesel fuel can critically reduce solubility. Blending of up to 45% bioethanolcan place no additional temperature restrictions on these fuels (if no water is present). Thus,

diesel fuel chemical properties can have a large effect on bioethanol solubility. Methyl ester

can be added to increase miscibility of bioethanol. At low temperature close to diesel fuel

pour point, adding 8% biodiesel to the blend increases fuel stability without phase separation.

3. Fuel oxygen content

The oxygenated fuel is the most common additive that improves fuel combustion and reduces

the engine emission level. Several oxygenated compounds were used for this purpose but the

most common ones are biodiesels, alcohols, and ethers. Ethers that are octane enhancer

increase fuel oxygen content but their use is limited because of the cancer risk probability and

none renewability. On the other hand, bioethanol is an aliphatic alcohol which is produced

from plants and agricultural wastes and is more suitable in comparison to the other alcohols.

4. Fuel blend properties

Several fuel blends were prepared and tested; four of them are Diesterols. Four different

dieselbiodiesel blend ratios were prepared. Diesterol is a fuel mixture that contains diesel

fuel, bioethanol and biodiesel regardless of their quantity.

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5. Cetane number

Using 12% bioethanol to diesel fuel can reduce the fuel blends cetane number to 40. But

addition of methyl ester will improve bioethanoldiesel cetane number due to higher cetane

number of methyl ester. This cetane number could be regarded as a suitable one to be used in

diesel engines.

6. Other fuel properties

The fuel blends could resist low temperature and it can be more suitable for cold climate.

During winter, the diesel fuel blends with small amount of kerosene or low temperature flow

improving additives so phase separation or fuel gelling can be avoided. The solubility of

bioethanol in diesel fuel is low especially in low temperatures. Phase separation occurs when

bioethanoldiesel blend temperature is reduced. Adding methyl ester to bioethanoldiesel can

help to solve the phase separation problem at lower temperatures. By adding 1020% of

methyl ester and bioethanol to the diesel fuel, the pour point was reduced from 2 C to 7 C

making the new mixture suitable for cold climate.

Conclusion

Biomass has always been a major source of energy for mankind from ancient times.

Presently, it contributes around 1014% of the worlds energy supply. Biomass can be

converted into three main types of products: 1. electrical/heat energy, 2. fuel for transport

sector and 3. feedstock for chemicals. Diesterolwhich is blend derived from biomass can be

utilized as a suitable alternative for fossil fuels considering of the following advantages:

Bioethanol addition to diesel fuel can significantly reduce fuel blend cetane number.

Bioethanol and methyl ester (sunflower) can improve low temperature flow properties

due to very low freezing point of bioethanol and low pour point of methyl ester,

consequently diesterol is more suitable for cold climate compared with diesel fuel.

Adding only 3% bioethanol to diesel and methyl ester reduces the flash point of the

fuel blend very much lower than ASTM standard limits which cause a problem in storage

and transportation of diesterol.

Sulfur content of diesterol was low when oxygenated compounds are high.

The CO and HC emission concentration of diesterol is low compared to the

conventional diesel fuel and even dieselbiodiesel blends.

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