1. 1
CHAPTER 1
INTRODUCTION
1.1 Background of Study
Over the years, more than 70% of used engine oil (commonly referred to as
condemned or spent oil) is most often disposed as waste in Nigeria after
automobile lubrication. This act brings about pollution of the environment.
However, it has been found to be a potential alternative raw material for ink
production. Its utilization in this area will minimize its wastage and reduce
pollution.
Waste engine oil is a highly hazardous pollutant that requires responsible
management. Waste engine oil may cause damage to the environment when
dumped into the ground or into water streams including sewers. This may
result in groundwater and soil contamination. Recycling of such contaminated
materials will be beneficial in reducing engine oil costs. In addition, it will have
a significant positive impact on the environment.
Used engine oil contains resin, organic acids and polymers. These substances
can be precipitated as varnish and asphaltic resin known as sludge. This can be
achieved by treating the oil with concentrated sulphuric acid, sodium
hydroxide and other additives to yield crude base oil and sludge as byproduct.
The sludge produced contains polymeric materials such as asphaltenes,
carboids, carbenes and petroleum resins which are responsible for the black
colour of engine oil.
Charcoal has been often used as fuel for cooking, the activated one is used in
air and water purification, treatment of sewage, as the filter unit in respirators
and gas masks, for the purification of gas and compressed air through filters
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such as in the life support in space suits. It is also used for the recovery of gold
from cyanide solutions, as a metal extraction method and for its use in the
cleanup of chemical spills. However, it can now be used as an alternative
material for ink production in place of carbon black which has since been used
in the production of black ink.
Printing of one form or another has been with us for centuries and whilst the
technologies of both the printing process and the ink formulations have
changed considerably, the main functions of decoration and information
remain. As new technologies are evolving, the printing industry undergoes
rapid development in the transmission of information within the society. It can
then be said that printing is an important tool for technology advancement
(Richard, 2008).
Ink is one of the most important materials used in the printing industry. There
are so many definitions of ink. To a layman, it can be defined as coloured
substance used for writing, printing and decoration purposes. But in a more
advanced context, ink is defined as a mixture of colouring matter dispersed in
a vehicle or carrier which forms a fluid or paste which can be imparted on a
substrate and dried.
Ink can be defined as a mixture of intimately ground pigment dispersed or
dissolved in a vehicle, which can be printed on a substrate and dried. Printing
ink contains colorants usually pigments which gives the image a contrast
against the background and the vehicle which binds the pigment to the
substrate and thus provides adhesion.
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1.2 Aims and Objectives
To produce a neutral and dehydrated sludge from used engine oil.
To determine the effect of temperature on sludge yield.
To use the sludge and generate a formulation for black printing ink.
To select the best formulation for black printing ink production.
1.3 Scope of Study
The project work covers the following areas:
Desludging of engine oil to yield resinous sludge and crude base oil.
Determination of the optimum temperature and development of the
sludge yield models.
Production of black printing Ink.
Quality test on the produced ink to ensure that it meets market
requirements.
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CHAPTER 2
LITERATURE REVIEW
2.1 Nature of Inks
Inks are coloured materials used for the purpose of writing, printing, and
decoration (Kirk, 1981). Ink is a liquid or a paste like (semi- liquid) material that
is used for drawing, writing, and printing either text or graphics (Lichtenberger,
2004). Ink is a colloidal system that is typically comprised of colorant, vehicle,
solvent, and additives (Lichtenberger, 2004). Ink can be defined as a mixture of
intimately ground pigment dispersed or dissolved in a vehicle, which can be
printed on a substrate and dried (Taylor 2007). They are materials designed to
have decorative, protective and communicative function (Othmer 1981). It is
applied on different surfaces ranging from aluminum cans and plastic bottles
through to paper (Taylor 2007).
According to Wansbrough (2007, p.1), printing inks are made of four basic
components:
Pigments: They colour the ink and make it opaque.
Resins: They bind the ink together into a film and bind it to the printed
surface.
Solvents: They make the ink flow so that it can be transferred to the
printing surface.
Additives: They alter the physical properties of the ink to suit different
situations.
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2.2 The History of Ink Production
Writing inks were first manufactured in both ancient Egypt and China in about
2500BC. These inks were composed of soot bound together with gums. This
paste was formed into rods and dried, then mixed with water immediately
before use (Wansbrough 2007).
Printing was invented by the Chinese about 3000 years later (Taylor, 2007).
They used a mixture of coloured earth, soot and plant matter for pigments,
again mixed with gums for a binder. By 1440, when Johannes Guttenberg
invented the first printing press with moveable type, ink was made of soot
bound with either linseed oil or varnish - similar materials to those used for
black inks today. Coloured inks were introduced in 1772 and drying agents
were first used in the nineteenth century.
Today's printing inks are composed of a pigment (one of which is carbon black,
which is not much different from the soot used in 2500BC), a binder (an oil,
resin or varnish of some kind), a solvent and various additives such as drying
and chelating agents. The exact recipe for a given ink depends on the type of
surface that it will be printing on and the printing method that will be used
(Taylor 2007). Inks have been designed to print on a wide range of surfaces
from metals, plastics and fabrics through to papers. The various printing
methods are all similar, in that the ink is applied to a plate / cylinder and this is
applied to the surface to be printed. (Wansbrough 2007) However, the plate /
cylinder can be made of metal or rubber, and the image can be raised up
above the surface of the plate, in the plane of the plate but chemically treated
to attract the ink, or etched into the plate and the excess ink scraped off.
Different inks are produced to suit these different conditions.
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2.3 Raw Materials and Components
As has already been stated, the raw materials for ink production are pigments,
binders, solvents and additives.
2.3.1 Pigments
The most obvious role of a pigment is to colour the ink. However, they can
also provide gloss, abrasiveness and resistance to attack by light, heat, solvents
etc. Pigments give the ink its characteristic colour and contribute to the opacity
and permanence of the ink. They are inorganic or organic in form (Bisset 1979)
e.g. Carbon black and charcoal (which is used for this work). Carbon black is the
pigment that has since been used for the manufacture of printing inks but in
this study, charcoal is identified as an alternative. Special pigments known as
extenders and opacifiers are also used. Extenders are transparent pigments
which make the colours of other pigments appear less intense, while opacifiers
are white pigments which make the paint opaque so that the surface below
the paint cannot be seen. The process of forming pigments all rely on the
thermal decomposition or incomplete combustion of hydrocarbons such has
fuel oil and natural gas. Pigment selection is based on their wettability and
dispersion characteristics in various solvent and resin (Taylor 2007). Some
common pigments used in the manufacture of printing inks are given in the
table below.
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Table 2.1 Pigments used in Ink Production
Source: Printing Ink Manual (Bisset 1979)
Fig 2.1 Structure of some pigments used in ink production
Class Examples
Inorganic white (opacifiers) Titanium dioxide, zinc oxide
Extenders Calcium Carbonate, Talc- mixed oxide of
aluminium,magnesium,silica and calcium
Inorganic Black Carbon Black
OrganIc red Lithol, Toluidine derivative
Organic orange Pyrazolone, Dinitroaniline
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2.3.2 Resins
Resin is a non-crystalline solid material or liquid of relatively high molecular
weight and viscosity. Resins are primarily binders - they bind the other
ingredients of the ink together so that it forms a film and they bind the ink to
the paper.(Domo-Spiff 2009) They also contribute to such properties as gloss,
hardness, adhesion, flexibility and resistance to heat, chemicals and water.
Resins are divided into the following categories.
Natural Resin: This includes those obtained from pine trees which can be
separated into turpentine oil or colophony. Another example is asphalt which
is a residue when crude oil or coal tar is distilled. They are dark and only be
used for black inks.
Semi Synthetic: This includes alkyd esters, polyesters made of phtalic acid
esters and glycerol which are modified with some fatty acid. It also includes
chemically modified cellulose such as nitrated cellulose, ethyl cellulose, and
sodium carboxyl methyl cellulose etc. (Nwanta 2005).
Synthetic Resin: They are virtually innumerable and include acrylic, polyvinyl
acetate polyvinyl alcohol, and polyamide resin. In this work only asphaltic resin
gotten from used engine oil is used.
Many different resins are used, and typically more than one resin is used in a
given ink. According to Taylor (2007, p.3), the most commonly used resins are
listed below:
Acrylics
Ketones
Alkyds
Maleics
Cellulose derivatives
Formaldehydes
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Rubber resins
Phenolics
2.3.3 Vehicle
This is the liquid ingredient in to which the pigment and other ingredient are
mixed. The vehicle acts as a carrier for the pigment and as binder to affix the
pigment to the printed surface and is also responsible for gloss and hardness of
the dried ink film.
To a great extent it determines the viscosity, consistency, and fluidity of the ink
(Domo-spiff 2009). Some of the popular examples are linseed oil, diesel oil,
resin oil, alcohol etc. Because every pigment-vehicle formulation behaves
differently, the addition of the ingredients is carefully considered.
2.3.4 Solvents
Solvents are used to keep the ink liquid from when it is applied to the printing
plate or cylinder until when it has been transferred to the surface to be
printed. At this point the solvent must separate from the body of the ink to
allow the image to dry and bind to the surface. Some printing processes (e.g.
the gravure and flexographic processes) require a solvent that evaporates
rapidly. These use volatile solvents (i.e. those with boiling points below 120°C)
such as methylated spirits, ethyl acetate, isopropanol, n-propyl acetate.
2.3.5 Additives
Many different types of additives are used to alter the final properties of the
ink. The most common types of additives and their respective functions are
listed below.
Plasticiser: It enhances the flexibility of the printed film. Eg dibutyl phthalate.
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Wax: It promotes rub resistance. E.g. Carnauba - an exudate from the leaves
of Copernicia prunifera. It consists of esters of hydroxylated unsaturated fatty
acids with at least twelve carbon atoms in the acid chain (Apps 1963).
Drier: Catalyses the oxidation reaction of inks which dry by oxidation. E.g. salts
or soaps of cobalt, manganese or zirconium.
Chelating agent: Increases the viscosity of the ink (aluminium chelate) and
promotes adhesion (titanium chelate)
Antioxidant: Delays the onset of oxidation polymerisation by reacting with free
radicals formed during the autooxidation thus preventing them from reacting
further. E.g. Eugenol.(Apps 1963)
Surfactants: Improves wetting of either the pigment or the substrate
Alkali: It controls the viscosity / solubility of acrylic resins in water based inks
e.g.HOCH2CH2NH2 (monoethanolamine).
Defoamer: It reduces the surface tension in water based inks, meaning that
stable bubbles cannot exit hydrocarbon emulsions.
2.4 The Manufacturing Process
Ink is manufactured in two stages: first varnish (a mixture of solvent, resins
and additives) is made and then pigments are mixed into it.
2.4.1 Varnish manufacture
Varnish is a clear liquid that solidifies as a thin film. It binds the pigment to the
printed surface, provides the printability of the ink and wets the pigment
particles. There are two main sorts of varnish: oleoresinous varnish (which
incorporates a drying oil such as linseed oil) and non-oleoresinous varnish.
Oleoresinous varnish is manufactured at much higher temperatures and in
much more rigorous conditions than non-oleoresinous varnish (Wansbrough
2007). The two manufacturing processes are discussed below.
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Oleoresinous Varnish Manufacture
These varnishes are typically manufactured in closed kettles where the oil and
solvent are heated to allow for rapid solutioning or transesterification
(Wansbrough 2007). The temperatures involved in the process will vary but
may range from 120°C to 260°C. Cooking times may range from a few minutes
to several hours. Temperature control is critical in the process. Rate of
temperature change, maximum temperature attained and cooking duration is
closely monitored. A condenser is usually used to prevent solvent loss.
Since these varnishes include a drying oil, atmospheric oxygen must be
excluded to prevent this from polymerising. For this reason cooks are often
done using a nitrogen blanket.
In the production of a typical oleoresinous ink varnish, drying oil, alkyd and
other solvents are added to the vessel under nitrogen prior to cooking. Hard
resins are then added when the correct temperature is attained. The cooking
process continues until the reactants are either totally consumed in the
transesterification process or achieve adequate solubility in the solvent (Taylor
2007). Additives such as the chelating agent are added after the batch cools
down. Finally, the varnish mixture is reheated to obtain targeted rheological
properties. The varnish produced is tested before sending to the storage tank.
Non-oleoresinous Varnish Manufacture
Varnishes of this type are usually simple resin solutions that do not require
high temperatures to effect a reaction. They are manufactured by breaking up
the resin particles and dissolving them in a solvent in either a cavitation or a
rotor / stator mixer. Cavitation mixers contain a saw tooth disc on a driven
shaft and are used to produce high viscosity resin solutions. They can operate
at variable speeds. Rotor / stator mixers operate at a fixed speed. Varnishes
produced in these mixers must be of lower viscosity than those produced in
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cavitation mixers because the agitation in the mixer is much less. Heat
sensitive resins cannot be used in a rotor / stator mixer because the high
friction within the mixer produces high temperatures (Bisset 1979).
2.4.2 Pigment Dispersal
Once the varnish (containing the solvent, resin and additives) has been
produced the pigment is mixed into it. At this point the pigment particles
clump together. These clumps must be broken up and the pigment dispersed
evenly through the resin. There are three main types of equipment used to do
this, and which is chosen depends on the tack (stickiness) and rheology of the
ink. The three equipment types are discussed below.(Wansbrough 2007)
Three Roll Mills
A three roll mill consists of a series of cambered rollers rotating in opposite
directions. The pigment particles are fed into a hopper above the two rear-
most rollers and are dispersed by the shear forces between the rollers. A
doctor blade is fitted to the front roller to remove the dispersed product. Roll
pressure, speed ratios and temperature must be carefully controlled to allow
reproducible dispersion. Each of the rolls is water cooled to reduce the
buildup of frictional heat.
Bead Mills
A bead mill consists of a cylindrical chamber filled with beads and surrounded
by a water jacket for cooling. Ink is pumped into the chamber and the beads
(known as the 'charge') set in motion by a series of spinning discs or pins
(Taylor 2007). The charge grinds the ink, breaking up the pigment clumps and
evenly dispersing the ink. The ink then flows out of the chamber through a
sieve and the charge remains behind to be re-used. According to Wansbrough
(2007 p.5) the bead size depends on the viscosity and rheology of the ink.
Typical bead sizes range from 1-2 mm for a high quality low viscosity product
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such as a gravure ink up to 4 mm for a medium viscosity paste or screen ink.
The beads can be made of zirconium oxide, glass or stainless steel. Certain
beads discolour certain inks, so it is important that each ink is tested with the
different beads before grinding to ensure that appropriate beads are used.
Cavitation Mixers
The use of cavitation mixers for the production of resin solutions has already
been discussed.
However, mixers of this type are also very efficient at dispersing certain
pigments, notably titanium dioxide, and allowing predispersion of a number of
others. In a highly viscous ink system a cavitation mixer may be insufficient to
ensure even dispersal and as a consequence an additional sweeper blade may
be added.
2.5 Engine Oil and Its Applications
Engine oil (sometimes called motor oil) is the oil used in lubricating various
internal combustion engines of road vehicles such as cars and motorcycles,
heavy duty vehicles such as buses, lorries, trailers, trucks and non road
vehicles such as go-carts, snow mobiles, boats, lawn mowers, large agricultural
and construction equipments, trains aircrafts and electrical generators. Its
main role is to clean, inhibit corrosion and cool the engine by carrying away
excessive heat generated by the moving parts of the engine (Domo-Spiff 2009).
In engines, the moving parts make contact with each other causing friction
which consumes the useful power by converting the energy to heat. This also
causes wears and tears in those parts and leads to lower efficiency and may in
some cases lead to total failure of the engine.
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Consequently, engine oil creates a separating film between the surfaces of the
adjacent moving parts to minimize direct contact between them, thereby
decreasing friction and production of excessive heat. One of the main
properties of the oil that enables it to be effective in lubrication is its viscosity.
This is the resistance to flow of the oil. It may be high enough to create a film
but low enough to flow around the engine parts satisfactorily.
2.5.1 Degradation of Engine Oil
The majority of motor oils is derived from petroleum and mostly consists of
hydrocarbons, organic compounds containing carbon and hydrogen. Most of
them are made from heavier petroleum base stock derived from crude oil, with
additives to improve certain properties.
During the operation of the engine, the oil breaks down and the major
properties of the oil change due to oxidation, deposits, thermal degradation,
corrosion, shearing and contamination. This reduces its ability to carry out its
primary function of reducing friction, heat dissipation, corrosion prevention
and cleaning.
Oxidation is the most important form of chemical breakdown of engine oil and
its additives. The chemicals in the motor oil are continuously reacting with
oxygen inside the engine. The byproducts of combustion produce very acidic
compounds inside the engine. These acidic compounds causes the corrosion of
the internal engine components, deposits and mainly changes in the oil
viscosity. Other substances like sludge, vanish and other insoluble combustion
products are solely responsible in the degradation of the engine over a period
of time due to oil break down. The products of combustion are less stable than
the original base hydrocarbon molecular structure and as they continue to be
stacked by these acidic compounds, vanish and sludge are produced.
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Fig 2.2 Processes in Hydrocarbon Oil Degradation
2.6 Chemical and Physical Properties of Engine Oil
Flash Point
The flash point of engine oil is the lowest temperature to which the oil must be
heated under specified conditions to give off sufficient vapor to form a mixture
with air that can be ignited spontaneously by a specified flame. The flash point
of engine oil is an indication of the oil’s contamination. A substantial indicator
of flash low flash point shows that the engine oil has been contaminated with
16. 16
gasoline. In the presence of 3.5% fuel or greater in used engine oils, the flash
point will potentially reduce to below 55 °C. The flash point is also an aid in
establishing the identity of a particular petroleum product. The flash point
increases with increasing molecular mass of the oil. Oxidation would result in
formation of volatile components which leads to decrease the flash point
(Lenoir 1975). For instance the flash point of the base oil (Ravenol, VSi SAE 5W-
40) is 232 °C because it is contains many different additives which contribute
to improving its flash point. (Hamawand et al 2013) In contrast, the flash point
of the measured used engine oil is 158 °C. This decrease in flash point is a
result of contamination with fuel and oxidation products (Lenoir 1975).
Kinematic Viscosity
Viscosity is a state function of temperature, pressure and density. There is an
inverse relationship between viscosity and temperature, when the
temperature of the engine oil decreases the viscosity increases and vice versa.
Viscosity testing can indicate the presence of contamination in used engine oil.
The oxidized and polymerized products dissolved and suspended in the oil may
cause an increase of the oil viscosity, while decreases in the viscosity of engine
oils indicate fuel contamination. (Diaz et al, 1996)
Specific Gravity
Specific gravity is the ratio of the mass of volume of substance to the mass of
the same volume of water and depends on two temperatures, at which the
mass of the sample and the water are measured. Specific gravity is influenced
by the chemical composition of the oil (Hamawand, Yusaf & Rafat, 2013). An
increase in the amount of aromatic compounds in the oil results in an increase
in the specific gravity, while an increase in the saturated compounds results in
a decrease in the specific gravity. An approximate correlation exists between
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the specific gravity, sulfur content, carbon residues, viscosity and nitrogen
content (Forsthoffer & Lube, 2011). Used engine oil’s specific gravity increases
with the presence of increasing amounts of solids in the used engine oil. One
percent of weight of solids in the sample can raise the specific gravity by 0.007
(Forsthoffer & Lube, 2011). Used engine oil is contaminated with oxidized and
condensed products rich in carbon. The high value of specific gravity of used
engine oil is due to the presence of oxidation products, metals and
contamination.
Refractive Index
Refractive index (RI) is the ratio of the light velocity in vacuum to the light
velocity in substances at a specific temperature. The measurement of the
refractive index is very simple, and requires small quantities of the samples.
The refractive index can be used to provide valuable information about the
composition of engine oils. Low values of refractive index indicate the presence
of paraffin material while high values indicate the presence of aromatic
compounds. It is also used to estimate other physical prosperities such as
molecular mass (Riazi & Roomi, 2001). This is due to the presence of additives
like polymers, polar organic compound, organic compound, different metals,
copolymers of olefins and hydrogenated diene styrene copolymers (Riazi &
Roomi, 2001). These components increase the molecular mass of the base oil
and consequently its refractive. The addition of acid reduces the RI.
Water and Sediments
Water is generally referred to as a chemical contamination when suspended in
engine oils. Water contamination of engine oil affects the oil quality, condition
and wear of engines in service. The water content in engine oil is governed by
the oil composition, physicochemical properties, production technology and
conditions of storage and use. Water created in engine oil is a result of:
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absorbing moisture directly from the air (oil is hygroscopic), condensation
(humid air entering oil compartments), heat exchanger (corroded or leaky heat
exchangers), combustion (fuel combustion forms water which may enter the
lubricant oil through worn rings), oxidation (chemical reaction) and
neutralization (when alkalinity improvers neutralize acids formed during
combustion), and free water entry (during oil changes). Water can prompt a
host of chemical reactions such as hydrolysis of compounds and atomic species
including oil additives base stock and suspended contaminants. In combination
with oxygen, heat and metal catalyst, water is known to promote the oxidation
and the formation of free radicals and peroxide compounds. Water attacks
additives such as oxidation inhibitors, rust inhibitor, viscosity improver and the
oil's base stock forming sludge. The water and sediment content of engine oil is
significant because it can cause corrosion of equipment and problems in
processing (Kishore, 2007).
Carbon Residue
The amount of carbonaceous residue remaining after thermal decomposition
of engine oil in a limited amount of air is also called coke or carbon forming
tendency. The test for carbon residue can be used at the same time to evaluate
the carbonaceous depositing characteristics of engine oils used in internal
combustion engines. The carbon residue value of engine oil is regarded as
indicative of the amount of carbonaceous deposits engine oil would form in
the combustion chamber of an engine. It is now considered to be of doubtful
significance due to the presence of additives in many oils. For example, an ash-
forming detergent additive can increase the carbon residue value of engine oil
yet will generally reduce its tendency to form deposits (Kishore, 2007). This
may be due to the complex reactions of the oil’s components with sulfuric acid
which may increase the sulfur content of the oil. A more precise relationship
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between carbon residue and hydrogen content, (H=C) atomic ratio, nitrogen
and sulfur content have been shown to exist.
Total Acid Number (TAN)
Total Acid number (TAN) is the weight (in milligrams) of potassium hydroxide
required to neutralize one gram of the materials in the oil that will react with
(KOH) under specific test conditions. The usual major components of such
materials are organic acids, soaps of heavy metals. As engine oils are subjected
to elevated temperatures, the process of oxidation occurs. Oxidation leads to
the formation of organic acids in the engine oil. Total acid number (TAN) has
been considered to be an important indicator for engine oil quality, specifically
in terms of defining oxidation states. The presence of oxygen, in most engine
oils environments, and hydrocarbons which make up the base oil lead to some
reactions. This reaction may lead to the formation of carbonyl-containing
products (primary oxidation products), subsequently these undergo further
oxidation to produce carboxylic acids (secondary products) which results in an
increase in the TAN value (Fox, Pawlak & Picken, 1991). In addition, with time
and elevated temperature, the oxidation products formed then polymerize
leading to precipitation of sludge which decreases the efficiency of engine oil
and causes excessive wear.
This is due to the presence of organic, inorganic, heavy metal salts, ammonia
slots, resin, water and corrosive materials which result from the oxidation
process that occurred at elevated temperatures in the engine.
Metallic Content
Metals are regarded as heteroatoms found in engine oil mixtures. The amounts
of metals are in range of a few hundred to thousands of ppm and their
amounts increase with an increase in the boiling points or decrease in the API
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gravity of the engine oil. Engine oils’ metallic constituents are associated with
heavy compounds and they mainly appear in the residues. Base and base
engine oils have very little metal content, which indicates their purity. Some
metals present in virgin oils in high concentrations are in the form of various
additives which improve the performance of the engine oil. Many others are
introduced in to the oils after using due to depletion of various additives,
engine bearings or bushings, and dilution of the engine oil with fuel containing
metal additives (Abou El Naga & Salem, 1984). According to Yusaf et al. (2013,
p.1035) Metals are found in used engine oil in two forms:
Metal Particulate Contamination
Metallic particulates enter the engine oil as a consequence of the breakdown
of oil-wetted surfaces due to ineffective lubrication, mechanical working,
abrasion erosion and/or corrosion. Metallic particles from deteriorating
component surfaces are generally hard and increase the wear rate as their
concentration in the oil increases.
Element (Metals)
Many oil constituents contain metallic elements that have been added to
enhance the oil’s efficiency. In general, metals in engine oils regarded as
contaminants that should be removed completely in order to produce suitable
base oil for producing new virgin oil Aucelio et al., 2007)
Copper (Cu) is introduced to engine oils after use from bearings, wearing and
valve guides. Engine oil coolers can also be contributing to copper content
along with some oil additives (Alder & West, 1972). Magnesium is normally
introduced into engine oil in an additive package.
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Magnesium is regarded as the most common wear metals in used engine oil
and is present in virgin oil in the form of magnesium phenates and magnesium
salicylates that behave as antioxidants at high temperatures (Hopp & Erdoel
Kohle, 1974).
Chromium presence in engine oil is normally associated with piston ring wear.
High levels can be caused by dirt coming through the air intake or broken rings.
Chromium may indicate excessive wear of chromed parts such as rings and
liners (Kahn, Peterson & Mannings, 1970).
The most common wear metal in a car's engine that is introduced into the
engine oil after a period of use is iron. Iron comes from many various places in
the engine such as liners, camshafts and crank shaft, pistons, gears, rings, and
oil pump. Iron concentration in engine oil depends on the bearing conditions
inside the engine. If a bearing fails, iron concentrations in used engine oil
increases. In the engine, the wear rises at a faster rate during the starting of
the engine.
Zinc is introduced to base oil in the form of additives package as anti-oxidant,
corrosion inhibitor, anti-wear, detergent and extreme pressure tolerance. Zinc
is introduced in to base oil as additives, such as:
Zinc diethyldithiophosphate (ZDDP), which functions as an oxidation
inhibitor that increases the oxidation resistance of the oil.
Zinc dithiophosphates, this is not only acts as an anti-oxidant, but also
acts as a wear inhibitor and protects the engine metals against
corrosion.
Zinc dialkyldithiocarbamates, this compound is mainly used as anti-
oxidants but it is also has extreme pressure activity.
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2.7 Oxidation Process in Internal Combustion Engines
Oxidation of engine oil inside the engine is related to the availability of oxygen
and in-cylinder pressure and temperature (Yusaf, 2011). It can be divided into
two types: oxidation at low and high temperatures. Oxidation of engine oil at
low temperatures leads to alkylhydroperoxides ROOH, dialkylperoxides ROOR,
alcohols ROH, aldehydes RCHO and ketones RR′C=O. In addition, cleavage of a
dihydroperoxide leads to diketones RCO(CH2)xCOR′, ketoaldehydes
RCO(CH2)xCHO, and hydroxyketones RCH(OH)–(CH2)xCOR′ (Owrang 2004). At
high temperatures (>120 °C) the engine oil oxidation process can be divided
into a primary and a secondary oxidation phase. In the primary oxidation phase
the initiation and propagation of the radical chain reaction are the same as
discussed under low-temperature conditions, but selectivity is reduced and
reaction rates increased. At high temperatures the cleavage of hydroperoxides
plays the most important role. Carboxylic acids (RCOOH) form, which
represents one of the principal products under these oxidation conditions. In a
subsequent step they can react with alcohols R′OH to form esters (RCOOR′).
The termination reaction proceeds through primary and secondary peroxy
radicals, but at temperatures above 120 °C these peroxy radicals also interact
in a non-terminating way to give primary and secondary alkoxy radicals
(Maduako 1996). The secondary oxidation phase happens at higher
temperatures where the viscosity of the bulk medium increases as a result of
the polycondensation of the difunctional oxygenated products formed in the
primary oxidation phase. Further polycondensation and polymerization
reactions of these high molecular weight intermediates lead to form sludge
(Owrang 2004). Reaction oxidation compounds in oil samples can be
determined qualitatively by obtaining their IR spectra in a Fourier Transform
Infrared Spectrometer (Thermo Scientific, Thermo Mattson Nicolet 300-FTIR).
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2.8 Charcoal and Industrial Applications
There are many uses of activated charcoal and these are found over a wide
range of industries. Several methods are used to activate the charcoal and
these all end with a similar result with the charcoal becoming very porous and
having a large surface area. This large surface area can be seen under a
microscope as something similar to multiple layers of holes, these act like a
sieve through which a various number of commodities that have impurities in
them are cleaned. These impurities may come from water, poisons, air, volatile
organic compounds, spill cleanups and numerous other things. This charcoal is
a product that is used in the process of filtration in many different industries
and everyday uses.
One of the many everyday uses of activated charcoal is in water purifiers. This
product helps to remove unwanted impurities from tap or drinking water with
the end result being clean water suitable for drinking and other household
uses. Activated charcoal is also used for the purification of air where it helps to
remove chemicals and volatile organic compounds through absorption. It is
generally used in association with other types of filter technology, especially
those of the HEPA kind. Other things that this charcoal is used for are in the
treatment of sewerage, as the filter unit in respirators and gas masks, for the
purification of gas and compressed air through filters such as in the life support
in space suits. It is also used for the recovery of gold from cyanide solutions, as
a metal extraction method and for its use in the cleanup of chemical spills.
Another one of the important uses of activated charcoal is in medicine. In the
medical field it is used for reducing the gas that occurs in the intestine, to help
with the treatment of cholestasis where bile flow from the liver is restricted
24. 24
during pregnancy and to help in certain cases with the lowering of cholesterol.
It is also used in medicine to treat acute overdoses and poisonings where it
appears to help prevent the absorption of poisons through the stomach or
intestine. There are many other conditions where activated charcoal is used
and this is especially so where any filtration or purification is needed.
25. 25
CHAPTER 3
METHODOLOGY
3.1 Apparatus
The following equipments were used in carrying out the project work.
Beaker
Weighing Balance
Separating Funnel
Measuring Cylinder
Stirrer
Water Bath
Retort Stand
Stop Watch
Test Tube
Litmus paper
PH Meter
Falling ball Viscometer
Proofing kit
OHAUS Weighing Balance
26. 26
3.2 Reagents
The following materials were used in performing the experiments.
Used Engine oil from petrol and diesel engines.
Charcoal solids
Distilled Water
Concentrated H2SO4
NaOH Pellets
Diesel oil
Ethanol
Universal Indicator
Anti-skinning agent
Wax
27. 27
3.3 Experimental Procedure
Used engine oil with an average SG of 0.925 (about 21.47 °API) at 25°C
obtained from petrol engine of an automobile workshop in Owerri metropolis,
was used to generate the asphaltic sludge as follows.
3.3.1 Production of Asphaltic/Resinous Sludge
150ml of used engine oil was mixed with 30ml of 2.0M H2SO4 in a beaker. The
mixture was placed on a water bath where it was heated and carefully stirred
for about 30mins to a temperature of 50°C.
The beaker was then transferred into cold water bath and was left to cool for
about 48 hours. Two distinct layers were observed- a mobile oil layer, on top of
a dense bottom layer (the asphaltic resin). The oil layer was afterwards
decanted, leaving the sludge. The PH of the layers was then measured.
The procedure was repeated at different acid volume (40 ml, 50ml, 60ml,
70ml, 80ml, 90ml and 100ml) and at different
temperatures(30°C,35°C,40°C,45°C,50°C,55°C, 60°C etc). The weights of sludge
produced in each case were measured and recorded.
3.3.2 Water Washing
The collected sludge was put in a beaker and 100ml of distilled water was
added. The resulting mixture was heated to 100°C and stirred continuously for
about 5 mins to ensure proper mixing.
Then the mixture was allowed to cool, settle and separate into the top dirty
water layer and the bottom layer (the purified sludge). The PH of the sludge
was measured afterwards.
28. 28
3.3.3 Alcohol Washing
The washed sludge was added into a separating funnel where 300g of ethanol
was added and the resulting mixture was stirred vigorously for about 30 mins.
The mixture was separated into two layers. The washing was repeated for the
second time. The bottom dense layer was then collected with a beaker.
3.3.4 Neutralisation of Sludge
This was then followed by neutralisation of the acidic sludge, which was
achieved by adding little quantity of NaOH at a time and testing with the
universal indicator. There was a violent release of fumes and the reacting
solution became hot. This was continued until the solution turned greenish
yellow by 30ml of NaOH, indicating a neutral solution.
3.3.5 Production of Printing Ink
20g of the extracted resinous sludge was added to a beaker containing 20g of
pulverised charcoal. The mixture was stirred with a glass rod and an
appropriate amount of diesel was added into the mixture. This is to help
disperse the black pigment in the mixture.
After the dispersion, additives were introduced in the medium and the
resulting mixture stirred for about 5 mins. This was to improve the physical
properties of the produced ink e.g. viscosity, adherence etc. and to avoid easy
fading.
The above steps were repeated for varying weight of sludge (30g, 40g etc.) to
determine the best formulation.
29. 29
3.3.6 Quality Tests
In order to ensure that the produced ink meets the required quality standard
in the market, the following quality assurance tests were carried out.
Viscosity Test
A sample of the ink was added in to the viscometer cup and channeled under
the viscometer. The viscosity of the ink was measured and recorded.
PH Test
The PH Meter was dipped in to a sample of the produced ink and the PH was
read and recorded.
Tackiness/Printability Test
This was performed using a proofing kit. Sample of the ink was dropped on the
smooth surface of the kit and the proofer was rolled on the drops. It was then
ran over newsprint and observed and the result was noted.
Drying Test
Sample of the ink was taken and printed on the substrate. It was timed from
when the ink was applied on the surface to when it dries using a stop watch.
The drying time was recorded
Adherence Test
A print of the sample of the ink was taken and allowed to dry. The print was
rubbed with hand to see if it will be wiped off.
Gloss Test
The ink was printed on a substrate and allowed to dry. The print was viewed at
a distance from oblique angle of 60°.
30. 30
CHAPTER 4
RESULTS AND DISCUSSION
4.1 RESULTS
The results obtained in the course of the experiments are recorded in the
following tables.
Table 4.1.1 Properties of Produced Sludge and Oil
Property Used Engine
Oil
Produced Sludge Regenerated Oil
PH 2.5 2.0 3.0
Kinematic Viscosity @ 30°C (cSt) 157 198 138
SG @ 30°C 0.925 0.945 0.8707
Flash Point(°C) 158 - 180
Pour Point -5 - -7
31. 31
Table 4.1.2 Quantities of Sludge and Oil Produced at Varying Acid Volume
N/B: Volume of used engine oil is constant at 120ml
Temperature is kept constant at 50°C.
Volume of
Acid(ml)
Weight of
Sludge(g)
Weight of
Regenerated Oil (g)
Acid volume required per g of
Sludge Produced (ml/g)
25.00 52.43 90.58 0.477
30.00 68.12 58.00 0.440
40.00 105.61 80.77 0.379
50.00 139.10 60.80 0.359
60.00 172.38 10.82 0.348
70.00 205.76 5.76 0.340
80.00 243.26 3.12 0.329
90.00 276.64 2.43 0.325
100.00 311.83 1.17 0.321
33. 33
Sludge Yield Prediction Models
From the data on the yield of sludge at different acid volume, the following
model was developed to assist in predicting the yield of sludge at higher
volumes of acid.
Two models were tested and the values calculated from these models are
shown below.
Model 1: Yprdt1 = 3.4574X – 34.3504
Model 2: Yprdt2 = 0.0003X2
+ 3.418X – 33.3362
Table 4.1.3 Model Calculations and Comparison
X Yprdt1 Yprdt2 Yexp (Yprdt1-Yexp)2
(Yprdt2-Yexp)2
25 52.0846 52.3013 52.43 0.11930116 0.01656369
30 69.3716 69.4738 68.12 1.56650256 1.83277444
40 103.9456 103.8638 105.61 2.77022736 3.04921444
50 138.5196 138.3138 139.10 0.33686416 0.61811044
60 173.0936 172.8238 172.38 0.50922496 0.19695844
70 207.6676 207.3938 205.76 3.63893776 2.66930244
80 242.2416 242.0238 243.26 1.03713856 1.52819044
90 276.8156 276.7138 276.64 0.03083536 0.00544644
100 311.3896 311.4638 311.83 0.19395216 0.13410244
∑ (Yprdt-Yexp) 2
10.20298404 10.0506632
SEEprdt1 = 1.207298285 SEEprdt2 =1.19825249
37. 37
Table 4.1.7 Formulation 3 (F3)
Table 4.1.8 Quality Test Results
Test F1 F2 F3
Viscosity(cP) 205 215 235
Drying Time(mins) 10 8 5
Gloss Good Very Good Excellent
Adherence Good Good Very Good
Tackiness Good Good Good
PH 7.24 7.35 7.44
Materials Weight (g) Weight %
Charcoal 20.0 21.16
Resinous Sludge 40.0 42.33
Diesel oil 20.0 21.16
Easigel 3.0 3.17
Anti-skinning agent 1.0 1.06
Wax 0.5 0.53
Black oil 10.0 10.58
Total 94.5 100
38. 38
4.2 DISCUSSION
There were three principal studies carried out, they include the effect of acid
volume and temperature on the yield of sludge and the selection of the best
ink formulation. As shown in Table 4.1, the produced sludge has a lower PH
due to the presence of acidic contaminants in the used engine oil. It can be
seen from Table 4.2 and Fig 4.1 that on increasing the acid volume, there was
higher sludge weight. This simply implies that for a larger yield of sludge, more
acid is required. Also it can be inferred that about 0.3-0.5 ml of the acid is
required to produce 1g of sludge. This range arose due to improper mixing,
residence time variation in the batch and systemic errors encountered in the
weighing balance.
From the SEE values calculated for the two models for effect of acid volume on
sludge weight, Model 2 has an SEE of 1.19825249 which is lower than that of
Model 1 (1.207298285). Thus, Model 2 is more accurate and best fit the
experimental data obtained.
The weight of sludge produced with a given volume of acid varies with
temperature as shown in Table 4.4 and Fig 4.3. It was also observed that as the
temperature rose from 30°C to 50°C, the sludge weight increased appreciably
from 55.12g to 66.81g. As the temperature was increased further above 50°C,
the sludge weight began to fall. This drop in the amount of sludge may be due
to the conversion of most of the hydrocarbons by sulphonation reaction of the
acid and the thermal cracking of the sludge formed. Consequently, the
desludging process was carried out at a temperature of 50°C to avoid the
adverse effect of high temperature. Also from the error functions (SEE and R2
)
calculated for the three models, it can be seen that 4th
degree model has the
least SEE and R2
values (1.33964517 and 0.93645197 respectively) when
39. 39
compared to the quadratic and cubic model with SEE values of 3.67828773 and
1.33978537 and R2
values of 0.8429389 and 0.93644576 respectively. Thus, the
4th
degree model is most accurate and can therefore be selected as the best
model.
As can be seen from the quality test carried out on the three ink formulations
(F1, F2 and F3) and recorded in Table 4.8, F3 has the highest viscosity of 235 cP
and takes the shortest time to dry. It also gave a very good gloss, adherence
and tackiness. The PH test shows that the three formulations are all neutral.
Thus, one can infer that the ink formulation with higher amount of sludge gives
a better result.
40. 40
CHAPTER 5
CONCLUSION AND RECOMMENDATION
5.1 CONCLUSION
Used engine oil is treated to remove most of the oxidation and degradation
products and consequently produce the resinous sludge as a binder for the
black ink. This was achieved with sulphuric acid which proved to be very
efficient because of its poly-functional nature. The amount of sludge produced
is dependent on the volume of the acid. Model 2 is the best for predicting the
effect of acid volume. The desludging process is temperature dependent and
as a result, the yield of sludge was lowered at temperatures above 52°C. The
4th
degree model is the best for determining the effect of temperature on
sludge weight. Also, the quality of the produced ink depends solely on the
amount of sludge added. The ink produced using F3 proved to have excellent
and desirable properties and therefore should be considered as the best
formulation for the production of high quality black ink.
4.2 RECOMMENDATION
The oil generated in the desludging process should be further refined using
solvent extraction and clay treatment to obtain base oil for other industrial
purposes. Further studies should be carried out using other acids like acetic
acid in order to know the most efficient acid. Also, efforts should be made in
designing a continuous system for large scale production. Comparative studies
should be carried out on charcoal to further justify its merits over carbon black.
41. 41
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44. 44
APPENDICES
APPENDIX 1
ERROR FUNCTION CALCULATIONS
STANDARD ERROR OF ESTIMATE
For Model 1
10.20298404
N = 9
SEE = [10.20298404/ (9-2)]1/2
= 1.207298285
For Model 2
10.0506632
SEE = [(10.0506632/ (9-2)]1/2
= 1.198252489
For Quadratic Model
= 33.1045896
N = 11
SEE = [33.1045896/ (11-2)]1/2
= 3.67828773
For Cubic Model
= 12.0580683
SEE = [12.0580683/ (11-2)]1/2
= 1.33978537
For 4th
Degree Model
= 12.0568065
SEE = [12.0568065/ (11-2)]1/2
= 1.33964517
45. 45
APPENDIX 2
CALCULATION OF THE COEFFICIENT OF DETERMINATION (R2
)
R2
=
For Quadratic Model
36.4993924
39.6139114
R2
= 36.4993924/39.6139114 = 0.8429389
For Cubic Model
= 36.5468612
= 36.6647161
R2
= 36.5468612/36.6647161 = 0.93644576
For 4th
Degree Model
= 36.4896167
= 36.61086
R2
= 36.4896167/36.61086 = 0.93645197
