From Earth to Earth Some Metals Also - University of Calabar

UNIVERSITY OF CALABAR, CALABAR.
42 nd INAUGURAL LECTURE
FROM EARTH TO EARTH:
Some Metals Also
Udofot Jack Ekpe
Professor of Applied Physical Chemistry
25th Ju ne 2008

1.0 INTRODUCTION
FROM EARTH TO EARTH: SOME METALS ALSO
At the interment of departed Christians, the priest often quotes these sobering words
By the sweat of your brow you will eat your food until you return to the
ground, since from it you were taken; for dust you are and to dust you must
return. Gen. 3:19 (NIV)
The above expression informs us that our bodies are products of the earth, and at death we return to it.
Most metals occur in the form of ores in the earth’s crust. The ores are mined from the earth. ‘As mined
metallic ores’ are unsuitable for the reduction process so they are beneficiated or concentrated into
suitable form for the next process. This is followed by reduction to impure metals. We observe that the
metals in their interaction with the immediate environment “seek” to return to the combined state (ore)
from which they were initially obtained. It is this cycle of mining, beneficiation, reduction, refining to
metals and their eventual corrosion to form metallic compounds and so return to the earth that I am
referring to as ‘Earth to Earth’. In short, this INAUGURAL LECTURE is all about the LIFE CYCLE OF METALS.
(Fig. I)
Interaction with
METALLIC
ORE
environment Beneficiation
PURE
METAL
Refining
Fig. I. THE LIFE CYCLE OF A METAL
IMPURE
METAL
Smelting or
Reduction
ORE
CONCENTRATE
In retrospect I observed that most of my research has had some connection with metals. The topic of my
Bachelor of Science project was ‘The Stability Constants of Organtin Halides’ while my Master of
Philosophy in Physical Chemistry topic was ‘Viscosities of Molten Lead and Zinc Carboxylates’. My Doctor of
Philosophy work was on ‘Reduction Characteristics of Iron Ore for uses of in Nigerian Steel Industry’. This

was a study on the extractive metallurgy of Itakpe iron ores of Nigeria, as compared to Nimba ore (of
Guinea), which was being used at that time in Delta Steel Midrex process at Aladja, Warri. The major aim of
the work was to establish the suitability of Itakpe iron ore as a replacement for imported Nimba iron ores.
In the last twenty years I have worked with my colleagues and students on corrosion inhibition processes.
My Chairman, permit me to acknowledge three of my former students who are now my colleagues in the
Department of Chemistry. They are Dr. Eno Ebenso, Dr. Benedict Ita, and Dr. Peter Okafor. The first two are
senior lecturers with at least 45 publications each. They are waiting to have enough post graduate
supervision to apply for professorship. The third colleague, Dr. Peter Okafor is a lecturer II with about 20
publications. He is currently on a post-doctoral programme in China’s Institute of Metals. These are a few
of my academic ambassadors.
1.1 AIMS AND OBJECTIVES
An Inaugural lecture is an address at the inauguration of a Professor at which he outlines his research work
to the Gown and Town. In the course of doing this, Mr. Chairman, I wish also to highlight my fascination for
applied chemistry and to demonstrate its character building capabilities.
1.2 HOW DO METALS OCCUR?
Metals occur as minerals in the earth’s crust in the following chemical states: oxides, sulphides oxysalts,
and to a lesser extent in ‘native’ form. A mineral from which the metal of interest can be extracted at a
profit is called an ore. Chemically, an ore may contain three classes of minerals namely:
. Value Minerals: This is the past of the ore consisting of the metals bearing mineral i.e. the
metal of interest – the metal which is being sought, or which is of primary importance;
. Secondary Value: this consists of compounds associated metals which may be of secondary
importance; and
. Gangue Minerals: These are unwanted minerals or earthly impurities accompanying the value
mineral during the mining process.
1.3 ORE PREPARATION
Ore preparation is a two-part process consisting of (ore dressing) beneficiation and agglomeration. Ore
dressing involves the separation of the valuable metal leaving part of the ore by a series of mainly physical
and chemical processes such processes select the physical or chemical characteristic of the ore which is
absent in the gangue for the separation of the ore.
1.3.1 BENEFICIATION OF ORES
This involves the separation of valuable mineral from the gangue.
For example, iron ore (iron oxide) is magnetic, but the gangue (sand) has little or no magnetic property.
The ore may therefore be separated from the gangue by magnetic separation techniques. Wettability
differences between the ore (e.g. iron sulphide) and gangue is used in the froth flotation process. The ore
is churned up with oil and water to form a froth. The oil wets the ore and floats in the soapy water
provided. A blast of compressed air enables the floating ore to be moved to the surface and can be
skimmed off while the sand (gangue) settles at the bottom of the tank. Where the ore (gold ore) is denser
than the siliceous gangue both may be separated by washing.
Roasting and calcining are considered as beneficiation processes, probably because they have been used
mainly in the iron industry to effect preliminary concentration of the ore. At the same time, the ore may
also be made more permeable and hence more reactive to a gaseous reductant. The main chemical
method applied in beneficiation of ores is selective dissolution of the ore in a solvent, and leaving the
indissoluble gangue behind. This principle is generally described as leaching.

1.3.2 Agglomeration of ores
This is the process of re-forming fine particles into larger lumps of appropriate size and strength.
Agglomeration becomes necessary:
- The ore particles are too fine to be added directly to the furnace
- The beneficiated ore is too dense to be efficiently reduced due to low porosity and the
consequent poor reducing gas – solid ore contact. Agglomeration improves the efficiency of
the subsequent smelting process.
The main methods of agglomeration are sintering nodulising, pelletising and briquetting [Chemical Pilet. J.J.
Moore (1981)]
1.3.2.1 Sintering
In sintering ore fines of less than or equal to 6mm diameter are thoroughly mixed with 5-6% coal dust and
about 10-12% water, and fed into a grate of sintertr and heated.
heated
Ore fines + Coal dust + water sinter
The sinters are formed in two stages:
i. Initial calcinations during which decomposition and drying take place. Water, carbon (II)
oxide and any volatile metals e.g. cadmium, and arsenic are removed.
ii. Incipient fusion during which partial melting of the surface of the ore fines and the resultant
liquid is drawn into the interstices between the ore fines by capillary action. The strength of
the sinter is due to the filling of the interstices by the molten liquid.
Ore fines of less than 0.2mm are unsuitable for sintering due to the danger of complete fusion. The process
must be conducted below the melting point, but involves important chemical reactions resulting in
crystallization, which provides the main mechanism for the formation of bridges between particles. A good
sinter should be strong but capable of being crushed to its required size without generating large
quantities of fines. It should also be chemically reactive, porous to gases and of large specific surfaces.
1.3.2.2 Pelletising
Pellets are made from ore ground to - 50μm. These ore fines are thoroughly washed with water (about
10%) to improve permeability, and a binder such as bentonite, lime, salts or organic material and fed into
an inclined rotating drum or disc. The initial rotation action produces a number of nuclei in which the
particles are bonded together by the water and hinder moving into the crevices between the particles due
to capillary attraction. On further rotation, each neucleus grows into a pellet by collecting more fines. The
final pellet size is controlled by the residence fine in the drum. Other factors in turn control the residence
time. These factors include:
- The rate of rotation of the drum or disc
- Length or diameter of the drum or disc
- The angle of inclination of the drum or disc
- The applied pressure
The optimum size of the pellet is determined by reduction process envisaged, but it requires a compromise
between high permeability (large pellets) and high surface area (small pellets).
The green pellets thus produced from the drum would be too soft to withstand the load of the charge.
Therefore they require firing in a kiln. They must be handled carefully until they are strong. The firing
temperature ranges from 1,100 0 C to 1300 0 C. Finished pellets should be strong without having been
vitrified and should not exhibit too large an expansion when heated up in a reducing gas resulting in the
breakdown of the furnace. That is to say that prepared pellets should be strong enough to resist

mechanical damage due to either fracture or abrasion during their movement down the reduction furnace.
Water content of the green pellet is very critical in the preparation of pellets. A moisture content sufficient
to fill the veidage completely would appear to offer the greatest strength in a given material but even a
small excess would confer mobility and rapidly reduce strength. A small deficiency in water content below
what is required to fill the pores is preferred.
1.3.2.2 Nodulising and Briquetting
In nodulising, ore fines and process fines, coal dust and moisture are thoroughly mixed and fed into a
rotating drum at an elevated temperature. At this high temperature some of the components begin to
melt resulting in the formation of nodules. The lower melting point constituents of the concentrate tend to
fuse, resulting in irregular shaped nodules of low porosity. Consequently nodulising is used only for
agglomeration of metallic fines produced from smelting, polishing and machining operations in the
production of secondary metals.
In briquetting, ore fines are mixed with a binder and tempered with water and mechanically pressed or
extruded at room temperature into briquets. The process may be subsequently hardened in a tunnel kiln.
Hot briquetting is also used in a limited sense in processing metal bearing particles from flue dust.
Briquetting is an expensive process owing to the excessive wear and tear of the press.
The choice of the type of agglomerate for a particular smelting process depends on the composition of the
ore, the permeability of the agglomerate and the total processing cost. Generally pellets and sinters are
preferred agglomerates for the blast furnace process.
Pellets offer better reducibility than sinter during reduction smelting because of its higher porosity.
Sintering provides favourable chemical effects such as elimination of CO2 and sulphur as SO2. However
sinter has a very low thermal efficiency.
PRINCIPLES OF METAL EXTRACTION
One of the outstanding properties of a metal is its tendency to ionize (ease of ionization to form positive
ions). This tendency is measured by means of electrode potentials. If the metals are arranged in a
decreasing order of their electropositivities (reactivities) we have an activity or electrochemical series. In
this arrangements the metals may be subdivided into three categories namely most electropositive,
moderately electropositive and least electropositive. Very reactive elements exist mainly in form of
chloride, trioxo-carbonate (IV) and oxide ores. Moderately electropositive metal ores exist in the form of
oxides, tetraoxocarbonate (IV) and sulphides while ores of least electropositive metals exist in the form of
sulphides and native (free) elements.
It is observed that the method of extraction (reduction) of a particular metal depends on its
electropositivity or its position in the electrochemical series. Most electropositive metals are extracted by
electrolysis of molten ores (electrometallurgy) while moderately are obtained by reduction of the oxides
(pyrometallurgy).
Ores of least electropositive metals are extracted by thermal or chemical methods (hydrometallurgy).
Table I below outlines the activity series of metals, the ores and method of extraction.
In electrolytic reduction, the electrolyte must be in molten form because aqueous form will introduce
competition between the metal of interest and hydrogen ions and hydrogen instead of the metal will be
preferentially discharged. At the cathode, the metal ion is discharged by the supply. The chemical methods
involve the use of a reducing agent (e.g. carbon or carbon (II) oxide for example.
Fe2O3 + 3CO 2Fe 3CO2
2Fe2O3 + 3C 4Fe 3CO2

1.4 IRON MAKING PROCESS
The reduction of the iron ore into metal is referred to iron making. There are two distinct routes for iron
making, namely Blast Furnace and Direct Reduction.
1.4.1. THE BLAST FURNACE ROUTE
The blast furnace route consists essentially of a shaft furnace made up of two inverted funnels. (Fig. 2)
Around the rim joining the two funnels are equidistantly placed tuyeres through which blasts of hot air
enter the furnace. The blast furnace charges are:
1. Iron ore (source of iron) in form of pellets and or sinters
2. Limestone (fluxing agent)
3. Metallurgical coke (source of reductant) and
4. Blasts of hot air
The furnace is a giant heat exchanger and reactor which operates as counter current process – the solid
charge moves downward while the reducing gas moves upwards. Japanese research teams [Shikawa
(1976), Kanlora et al (1977), Sasaki et al (1977)], were the first to study a quenched and dissected furnace.
They discovered that the furnace is divided into five zones namely: Granular, Cohesive, Active,
Raceway/Combustion and Hearth zones. (fig. … ..)
Various physical and chemical interactions in the zones together account for the overall changes in the
zone and the final reduction of iron ore to pig iron collected in the hearth. These physio-chemical changes
make interesting reading, and are outlined below.
The granular or the preparatory zone consists of alternate layers of (i) coke and (ii) solid gangue and flux
oxides arising from the original charging sequence. The chemical reactions in this zone include:
1. Decomposition of hydrates and carbonates;
2. Reduction of higher iron oxides by CO forming CO2 and wustite;
3. Generation of more CO by the Bouduaurd reaction.
Reactions (2) and (3) lead to a series of cyclic reactions involving the use and regeneration of carbon
monoxide. In the lowest part of this zone, the temperature changes remain relatively constant, hence this
portion constitutes thermal and chemical pinch-points.
Within the cohesive or softening-melting zone, wustite is reduced to iron mainly by carbon and the slag
and metal ore fused. The zone consists of alternate layers of permeable coke and a viscous semifused slag
and iron. The coke slits assists in the radial distribution of the reducing gas across the furnace and the gas
pressure below this inverted u-shaped zone tends to support the furnace burden. Iron is melted exclusively
in the inner and lower surface of this zone, and the molten liquid globules descend to the hearth through
the active coke zone.
In the active coke zone, the reduction of silica, MnO phosphates, and aluminium occur, and silicon,
manganese and phosphorus dissolve in the liquid iron. The Silicon content of the pig iron is regarded as the
barometer of pig iron quality and the thermal state of the hearth. Because of this silica reduction and
subsequent transfer of silicon will be singled out for discussion.
It was always thought that the reduction of silica and silica transfer between carbon-saturated iron and
blast furnace slag occurred according to the reaction
SiO2 + 2C Si + 2CO (g)

(in slag) (in Fe) (in iron)
It was later shown by Tokuda et al (1970) and Tsuchiya (1976) that the silicon content of iron in the
industrial blast furnace product is inconsistent with silicon transfer by slag-metal reaction because of its
slow rate and oxygen potential. A new mechanism aimed at accounting for the low silicon content of iron
has been proposed. The proposal suggests that silicon transfer occurs via gaseous silicon monoxide and for
silicon sulphide (SiS).
(1) Formation of SiO and SiS in the combustion zone
(i) SiO2 + C(s) SiO (g) + CO (g)
in coke ash
or
(ii) SiO2 + CO(g) SiO (g) + CO2 (g)
(coke ash)
(iii) CO2 (g) + C (s) 2CO
And a combination of (ii) and (iii) gives (i).
(iv) CaS + SiO (g) SiS + CaO
(in coke ash)
(2) Transfer of silicon and sulphur to metal and slag in the bosh as SiO and SiS ascend the furnace.
(v) SiO (g) + Fe Si + FeO
In Fe
(vi) FeO + CO Fe + CO
(vii) C + CO2 2CO
A combination of equation (v) to (vii) gives an overall reaction
(viii) SiO (g) + C Si + CO
In Fe in Fe
(3) The oxidation of Si and iron and manganese oxides in the slag as the iron droplets pass through the
slag layer.
(ix) 2FeO + Si SiO2 + 2Fe
(in iron)
2MnO + Si 2Mn + SiO2
(in Fe) (in Fe)
(4) The resulphurisation of metal droplets as they pass through the slag layer.
CaO +
1
/2Si + S CaS +
(in Fe) (in Fe)
1 /2SiO2
The raceway zone which may extend 1 or 2metres into the furnace is formed by the blast clearing a
pathway of gas and rapidly hurtling coke in front of the tuyere. The roof of the raceway in contrast with
other boundaries is formed by loosely packed lumped coke brought about by the rapid ascent of raceway
gas between the pieces. Within the raceway there is the combustion zone consisting of an inner reduction
zone and an outer oxidizing sub-zones. The combustion within these sub-zones leads to the oxidation of
metallic or slag iron in the oxygen rich oxidation zone and the reduction of carbon dioxide by coke in the
reducing sub-zone. Beyond the reduction sub-zone (i.e. after the raceway boundary) there in a central
column of coke known as the dead man’s zone. This column in the hearth region allow slag-metal reactions
which lead to the oxidation of Mn and Si in iron and the removal of sulphur dissolved in iron.
1.4.1.1 DEVELOPMENT OF THE BLAST FURNACE IRONMAKING

Although the basic principle of reducing iron oxide using a carbonaceous reductant has not changed, blast
furnace technology has developed quite rapidly. This development is particularly obvious in terms of the
furnace size, operational techniques and fuel efficiency. Between 1860 and 1960 the diameter of the
furnace increased from smaller than 1 meter to 9 metres, and production increased from 25-150 THM per
day to 1500 – 2,000 THM per day. 10 The working volume has increased from 63m 3 in 1860 to 5,000m 3 in
1975, Biswas (1981). The factors that have led to these developments include:
1. Improved raw material preparation and distribution
2. Blast modifications
3. Application of high top pressure
4. Better understanding of the physical and chemical processes within the furnace
5. Extensive use of computers for process control.
Improved burden preparation has meant the increased use of agglomerated (with or without fluxes) and
closely sized ores and other materials. The use of closely sized burden coupled with the use of better
charging techniques has improved furnace productivity. The charging system has changed from the
double-bell. Through double-bell-fitted devices to movable throat armour. High top pressure improves the
combustion of carbon, since it allows for more oxygen and a smoother furnace operation due to increased
permeability. Various research projects into the physical and chemical reactions within the furnace assisted
by the study of quenched experimental blast furnace, and the use of sensors have led to a better
understanding of blast furnace reactions. This, coupled with the use of Reichardt – Rist diagrams have
made the mathematical modeling of the blast furnace
DISADVANTAGES OF THE BLAST FURNACE RONT
However, despite this remarkable progress in blast furnace operations in recent times, the process suffers
from a number of disadvantages:
1. High capital cost of construction of the furnace and supporting facilities made even higher by an
increasing emphasis on environmental pollution control;
2. Greater demand for high quality metallurgical coke by the large furnaces;
3. A longer commissioning time (about five years) for a Blast Furnace/Basic oxygen Furnace Steel plant
as compared with two to three years for a DR/EAF plant.
These and many other reasons may have prompted the search for an alternative route for iron making of
which the Direct Reduction appears to be the answer.
1.4.2 THE DIRECT REDUCTION (DR) ROUTE
The Direct Reduction (DR) process is defined as any process in which iron is produced by the reduction of
iron ore or any other oxide below the melting point of any of the materials involved. The product of the DR
process is called Direct Reduced Iron (DRI). A large number of DR processes have been proposed, but only
some of these (54) Metals Society (1979, 1980) have been developed to at least the experimental stage,
and only a small percentage of these (about 17) (Stephenson and Smaller, 1980) are of great industrial
significance. Some of the commercial processes may be classified in terms of the reductant into four
groups (Davies et al, 1982) namely:
1. Reformed Natural Gas Processes
2. Coal-based DR processes
3. Second generation coal based processes, and
4. Coke oven gas (COG) – DRI processes.

A classification of DR processes according to the above scheme is given in Table I. Only a few DR processes
will be described here but a detailed description of DR processes may be found elsewhere (Metals Society,
1979; Stephenson and Smaller, 1980; Davies et al, 1982).
TABLE I SOME DR PROCESSES
DR PROCESSES FURNACE TYPE MATERIAL
P=PELET, S=SINTER,
1.REFORMED
NATURAL GAS
PROCESSES
a) Midrex
b) Armco
c) Purofer
d) HYL
e) Fior
f) HIB
2. COAL-BASED SOLID
REDUCTANTS
PROCESSES
a) SL/RN
b) Krupp (Codir)
(c) DRC
d) Kawasaki
e) SDR
3. 2 ND GENERATION
COAL BASED
PROCESSES
a) ACCAR
b)Hot-gas
desulphurization
c)Improved SL/RN
d) SALEM
e) SPM
4. COKE OVEN GAS
DRI
HYL
Midrex
Shaft
Shaft
Shaft
Static bed
Fuidised bed
Fuidised bed
Rotary kiln
‘’
‘’
‘’
‘’
Rotary kiln
Shaft
Rotary kiln
Rotary kiln
Rotary kiln
As in 1 (d)
As in (a)
L=LUMP
P & L
P, L & S
P, L & S
‘’
‘’
S
P & L
“
“
P of waste dust &
residue from Steel
plant.
P
P or L
P or L
P or L
P
1.4.2.1 REFORMED NATURAL GAS DR PROCESSES
-
OPERATION
BATCH/CONTINUOUS
Continuous
Continuous
Continuous
Batch
Continuous
Continuous
Continuous
Continuous
Continuous
Continuous
Continuous
Continuous
Continuous
Continuous
Continuous
Continuous
Batch
-
DR processes using reformed natural gas as fuel and reductant have been particularly successful. There are
at least five such processes using three furnace types between them. Of these, the HYL and the Midrex
processes are popular, and will be discussed below.

1.4.2.2 THE HYL PROCESS
The HYL process was developed in Mexico by and named for Hojalata Y Lamina, S. A., and its first plant
commissioned in 1957. The process is a cyclic-batch operation involving a unique system of 4 reactors each
of which contains ore in a stationary bed, and operates in a cycle of four stages. The basic equipment
consists of a gas reforming unit, a reduction unit of 4 reactors and ancillary equipment. The flowsheet for
the process is given in figure 3.
The process uses properly sized lump and/or pellets of iron oxide (pellets 9.5 – 16mm, lump ore 13-15mm).
The reducing gas generated by nickel-based catalytic reforming of desulphurised natural gas consists of
75% H2, 14 0 , CO, 8% CO2 and 3% CH4. The reducing gas system is connected to the 4 reactors by an intricate
system of pipes and valves which permits the reactor at a particular process stage to be linked with the
relevant process gas. Each of the reactors is operated in a staged sequence as follows:
(1) Charging/discharging stage
(2) Preheating/initial reduction stage
(3) Main reduction stage and
(4) Cooling stage.
Each stage takes 3 hours to run, and the entire operation takes 12 hours. The sequence of stages that each
reactor undergoes is shown in Table 2.
TABLE 2
The circulation of the reducing gas through the reactors is a unique process. The fresh reducing gas from
the reformer is first used for cooling in a reactor at the cooling stage before it is used for reduction in the
reactor in the main reduction reactor stage. The spent gas from the main reduction reactor is then used in
the reactor at the preheating, initial reduction stage. Following passage through each reactor the reducing
gas is stripped of water vapour, and then reheated before use in the next stage. The reducing gas is used
on a once-through basis, and the energy available in the spent gas is used to provide fuel for the reformer
and the gas reacting furnaces.
HYL processes consist of the following:
1. The reactors are arranged in a single tower to allow for the use of a single charging bin and
discharge hopper thereby, improving material handling and reducing pipe network;
2. Combining the gas reforming and process gas heating furnace into a single unit and using high
temperature alloy tubes to enable continuous heating above 950 o C.
3. Transportation of reducing gas from heaters to reactors by hot-transfer lines.
1.4.2 THE MIDREX PROCESS
The Midrex process was developed by the Midland-Ross Corporation, and the first commercial plant was
commissioned in 1969. Since then, the process has attracted many developing countries with untapped
natural gas reserves, and has registered an impressive growth.
The process is based on the principle of counter-current flow in which the iron oxide charge descends
through a shaft furnace where it is heated and reduced by a stream of hot reducing gases. The main
components of the process are the gas-reforming unit, the reduction shaft and the cooling gas unit. The
shaft is divided into an upper refractory lined reduction zone and an unlined lower cooling zone separated
by a transition zone. The reducing gas is generated by catalytic reforming of desulphurised natural gas
stock mixed with the process off-gas; and consists of about 95% H2 and CO the H2/CO ratio being 1.50 to

1.60. The reducing gas is introduced through empty pots spaced around the furnace about 1 /3 of the
distance from the bottom of the reduction zone. The process flowsheet for the standard process is shown
in Figure 4.
The charge, consisting of fluxed ore pellets, briquetted fines and lump ores, is charged through the top of
the furnace. The reduction of the charge takes place in the reduction zone according to reactions (1) to (4)
above at about 760 0 C to 927 0 C. The retention time for the solids in the reduction zone is about 6.5 hours.
A large portion of the spent gas containing about 70% (CO + H2) is scrubbed, cooled, compressed, enriched
with natural gas and reformed after which it is recycled. The other portion of the spent gas provides fuel
for the reformer burners. The hot flue gas from the burner is used in the heat recuperators for the
reformer burner and process gas.
The cooling gas is mainly an inert gas mixed with a controlled amount of fresh natural gas and process gas.
By this arrangement, reforming reaction occurs within the cooling zone, and being endothermic, helps to
cool the DRI. The spent cooling gas is reprocessed in a demister and recycled in the cooling zone.
The most desirable raw materials are those of low gangue content with a sulphur content below 0.01%. For
systems using natural gas with high sulphur content, the alternative flow sheet is used. In this flow sheet,
the tail gas used in the reformer is first used as the cooling gas so that the DRI absorbs the sulphur in the
gas and prevents catalyst poisoning in the reformer.
TABLE II: HYL CYCLE
TIME (HRS) REACTOR I REACTOR II REACTOR III REACTOR IV
0-3 Discharging/ Preheating/ Main reduction Cooling
Recharging Initial reduction
3-6 Preheating/ Main reduction Cooling Discharging/
Initial reduction
Recharging
6-9 Main reduction Cooling Discharging/ Preheating/
Recharging Initial reduction
9-12 Cooling Discharging/ Preheating/ Main reduction
Recharging Initial reduction
1.5 THE NIGERIAN STEEL INDUSTRY– HISTORICAL DEVELOPMENT

Planning for the Nigerian Steel Industry started around 1958 just about the time oil exploration started. As
expected, during the colonial days the industry was not encouraged because iron ore deposits with total Fe
content more than 40% had not been found. In any case, Colby iron ores (in UK) was in existence and the
need for expansion of the steel industries to Colonies had not arisen. After independence in 1960,
feasibility studies for a steel plant were commissioned by the Federal Ministry of Industries. In 1971 an
extra-ministerial agency, Nigerian Steel Development Agency (ASDA) was established by Decree 9 to
galvanise the efforts to actualize an integrated steel plant.
In 1972 Itakpe iron ores with total iron content of about 46% were discovered by the Soviet magnetic
survey team, and by 1975 a contract for the first phase of an integrated steel plant construction was signed
with a Soviet State owned firm Trajpromexport(TPE). The first was scheduled to be completed by 1981. In
the same year owing to pressure from the Nigerian Metallurgical Association and elsewhere, the Federal
Government signed a contract for the construction of a Direct Reduction plant (Midrex) in Aladja Warri.
The company with a German-Austrian Consortium. The Delta Steel plant was completed and commissioned
in 1981. Unfortunately, the Ajaokuta Steel project has not seen the light of day 33 years after the contract
was awarded.
NIGERIAN STEEL INDUSTRY – HISTORY AND DEVELOPMENT
INRODUCTION
Planning for the Nigerian Steel Industry started around 1958. Many international organizations and
consulting firms had been commissioned at various times to study the feasibility of steel plants under the
aegis of the Federal Ministry of Industries. Parallel efforts were also made to identify and analyse the
principal raw materials needed for the steel industry. In 1971 an extra-ministerial agency was established
by Decree to focalize efforts required to actualize a steel plant. That Agency was called “Nigerian Steel
Development Authority” (NSDA).
Under the NSDA, organized efforts were intensified in market survey of the steel market in Nigeria; on indepth
geological investigation of local raw materials, on aeromagnetic survey for alternative sources of
iron-ore etc. The discovery of the Itakpe iron ore deposit in 1972 by the Soviet aero-magnetic survey team
catalyzed the formal signing of a contract in 1975 with the Soviet state-owned firm Tiajpromexport(TPE)
for the construction of an integrated steel plant to be carried out in phases. The first phase will produce 1.3
million tones of flat products. The second phase will produce 2.6 million tones of flat products while the
third phase will raise the annual production to 5.2 million tones. The first phase was to be completed in
1981. The plant was to be based on the traditional Blast Furnace/Basic Oxygen Furnace Technology of steel
production.
After the Soviet’s established the viability of a steel industry in Nigeria in the seventies, (in the height of
Nigeria’s new found economic wealth – oil), European countries which hitherto had advised Nigeria to
concentrate on Agriculture rather than venture into the high-tech steel business, began to flood the
Federal government with proposals on alternative technologies for new-breed steel plants based on the
“Direct Reduction (DR) Process”. Secondly, there was pressure from within from the newly formed
Nigerian Metallurgical Association requesting for the construction of a DR process. In 1975 the Federal
Government signed a “Turn-Key” contract with a German-Australian Consortium for a DR plant to be
located in Aladja, Warri (DELTA STEEL COMPANY). It was financed from a guaranteed loan from Deutche
Bank.
Thus, in the 1970/1980 periods Nigeria embarked on two integrated steel development programmes.
Unfortunately the Federal Government dissolved the NSDA; the only viable agency that could have

scientifically managed the situation. Their functions were returned to the non-technical bureaucrats of a
new Ministry of Steel. A lot of activities were then haphazardly embarked upon.
In 1981, due largely to the tidy “Turn-Key” contract with the German-Australian Consortium, and the even
tidier financing arrangement, the Delta Steel plant was completed and commissioned on schedule. On the
contrary the Ajaokuta Plant had become more complicated by sheer Ministerial mishandling than anything
else. Subsidiary contracts outside the main contract were awarded faster than total national fund could
sustain. In consequence the principal contract of the steel plant received lesser and lesser attention. The
Federal Government was continually defaulting on the payment to the Soviet Company and other
European civil engineering contractors who were the main steel plant contractors. To worsen issues the
national economy dipped in the mid-eighties and worse still the so called Structural Adjustment
Programme (SAP) and its consequences on on-going government projects spelt doom to Nigeria’s hope for
industrialization. Thus, Ajaokuta plant that was programmed to last five/six years lingered, limped, and
repeatedly got grounded over the period.
BACK GROUND TO THE NIGERIAN STEEL INDUSTRY
Planning for the Nigerian Steel Industry started around 1958 as earlier stated. The starting point was the
search for appropriate local inputs, the characteristics of which determined the particular technologies
that would be adopted. Iron ore was located at Agbaja, Itakpa and Udi; suitable Limestone at Jakura,
Mfamosin and other parts of the country. Coal deposits were always there at Enugu while potential cokeable
coal was struck at Lafia.
Market surveys were commissioned and the construction of the Kainji Hydro-electric Dam promised an
abundant source of electrical energy. Between 1961 and 1965 many firms from the industrialized nations
of the West submitted proposals for the construction of an integrated Steel Plant in Nigeria. The view,
then, was that the available raw materials could not be used in vonventional Iron and Steel making
technologies. The “Strategic Udy Process”, a Direct Reduction (DR) process still in the pilot plant stage in
the USA, was then considered by Nigeria. The idea was accepted and a joint venture company, the Nigerian
Steel Associates was formed with Westinghouse and Koppers as the foreign Partners. This programme
failed because it did not prove capable of meeting commercial scale requirements.
In 1967 a UNIDO survey identified Nigeria as a potential steel Market. This led to the signing of a bilateral
agreement between the defunct Soviet Union and Nigeria, and, the arrival of Soviet steel experts in Nigeria
to conduct a feasibility study. The experts recommended the Blast Furnace/Basic Oxygen Furnace (BF/BOF)
process of 570,000 tonnes per annum capacity of rolled products. They also confirmed the availability of
raw materials and recommended further geological surveys. In 1970 a contract was awarded to
TiajPromoExport (TPE) of defunct USSR to conduct a study to identify sources of feedstock, quality and
quantity of materials for the proposed integrated iron and steel plant. By this time the second National
Development Plant (1970 – 1975) had envisaged the construction of a 750,000 tonnes per year capacity
Plant.
Apart from Government Ventures there were a few private initiatives in the lesser capital-intensive steel
industry of rolling mills coming up.
THE NIGERIAN STEEL DEVELOPMENT AUTHORITY
In April 1971, the Nigerian Steel Development Authority (NSDA) was established by a Military Decree (No. 9
of April 14). Thus, the first formal body to be charged with the supervision of the steel programme in
Nigeria was born. NSDA was charged with the following:
1. Planning, construction and operation of Steel Plants.

2. Carrying out geological surveys, market survey/studies and metallurgical research and training.
The Authority was to examine various routes including natural gas-based direct reduction processes that
would require high-grade iron ores, which were not available in Nigeria. In 1973, the presence of good
grade ore (though not of high-grade quality) was confirmed at Itakpe leading to having the NSDA
commissioning TPE to prepare a preliminary scrutinized and finally accepted in 1975. With the source of
iron ore confirmed, it was proposed that coking coal would be imported and blended appropriately with
local coals. A three-phased development programme (the first phase was to produce 1.3 million tonnes,
which would be expanded to 2.6 million tonnes incorporating the flat sheet production in the second
phase, and the third phase to increase capacity to 5.2 million tonnes) was accepted.
The initial product mix proposal suggested 50% long products and 50% flat products. This was based on the
product demand profile revealed by market surveys. The Government decided that Ajaokuta Steel Plant
should produce only long products in the first stage of 1.3 million tones per year, and flat products in the
2.6 million tones expansion which was planned to overlap with the first phase completion and this is to be
followed by a third phase of 5.2 million tones per annum. This decision was advised by the need to take
advantage of economy of scale since flat-product mills of capacity below 1 million tones were considered
uneconomical. An additional consideration was to use the relatively simpler technology of long-products
rolling to rain up an otherwise virgin and inexperienced Nigerian Workforce of the time.
The NSDA was dissolved by the Federal Government in 1979 and this metamorphosed in to several
organizations, thus:
i. Ajaokuta Steel Project, Ajaokuta
ii. The Delta Steel Company, Ovwian – Aladja
iii. Jos Steel Rolling Company, Jos
iv. Katsina Steel Rolling Company, Katsina
v. Oshogbo Steel Rolling Company, Oshogbo
vi. National Iron Ore Mining Company, Itakpe
vii. National Steel Raw Materials Exploration Agency, Kaduna
viii. National Metallurgical Development Centre, Jos
ix. Metallurgical Training Institute, Onitsha.
The last three establishments, vii, viii, ix are to be fully funded by the Government, through the Ministry.
The organizations i, to vi, are supposed to be companies that should be self funding, because at one time
or the other, they had been incorporated as limited liability companies. The current status of these
companies and organizations is deplorable. Ajaokuta Steel Project is yet to be commissioned twenty nine
years after the installation began. Delta Steel Company started to decline in 1994 and has now (2008)
stopped production. The three Rolling Mills are now for sale.
2.0 METALS AND CORROSION
2.1 WHAT ARE METALS?
Metals are opaque, lustrous elements that are good conductors and most are malleable and ductile. In
Chemistry, metals may be defined as elements that readily form cations (positive ions) and form metallic
bonds with other metal atoms and ionic bonds with non-metals.
Metals may also be described as a lattice of positive ions surrounded by a cloud of localized electrons. The
metallurgist consider metals as elements that have overlapping conduction bands and valence bands in
their electronic structure. They react with oxygen in the air to form basic oxides. Metals constitute over
80% of the elements in the periodic table. They are about 86 metallic elements.

2.1.1 USES OF METALS
Metals are widely used in:
• Construction – farming tools, bridges, household conveniences, building, communication
• Transportation – Cars, buses, trucks, ships, airplanes
• Electric power generation and distribution
• Biomedical application
• Ornaments
Metals historical timeline (fig. ) further outlines the uses of metals and how metal use is a historical
indicator of the development of human society.
2.1.2 WHAT IS CORROSION?
Corrosion may be described as the deterioration of a material, (usually metals) and their properties arising
from its interaction with its environment. Corrosion may be defined as a chemical or electrochemical
reaction between a material and its environment which produces a deterioration of the material and its
properties. The environment consists of the immediate surrounding in contact with the material. Its
features include:
- Physical state – solid, liquid and gas;
- Chemical composition – constituents and concentration
- Temperature among others (fig……… .)
Fig… ..: Influencing factors that causes corrosion
2.1.3 HOW DOES CORROSION OCCUR?
The electrochemical reaction that causes corrosion consists of 4 factors namely:
i. Anode
ii. Cathode
iii. Electrolyte and
iv. Electronic circuit
Corrosion involves the release of electrons at the anode (a more easily oxidized region) and a simultaneous
acceptance of the released electrons by the cathode (a less easily oxidized region) by either forming
negative ions or by neutralizing positive ions. For example, in the atmospheric corrosion of a metal,
corrosion proceeds by balancing anodic and cathodic reactions in the presence of a thin film of
electrolytes. (fig… ..)
Anode reaction: 2M 2M 2+ + 4e
Cathode reaction: O2 + 2H2O 4OH -
Anodic reaction is an oxidation reaction involving the dissolution of the electrolyte while the cathodic
reaction is often assumed to be the Oxygen reduction reaction. Under thin film corrosion conditions.
Oxygen from the atmosphere is readily supplied to the electrolyte.
Fig…… : Corrosion, an electrochemical process

2.1.4 TYPES OF CORROSION
There are various forms of corrosion (about 15 in number) which can be divided into three categories
namely:
Group I - Those which can be observed by the naked eye (general, localized and galvanic
corrosion)
Group II - Those which can be recognized with the assistance of certain means of examination
(velocity – related intergranular, dealloying corrosion)
Group III - Those which can only be identified by using microscopes (cracking high temperature
and microbial corrosion).
The forms of corrosion are shown in Fig… .. and their inter-relationship is shown in the corrosion wheel
diagram (Fig… ..)
Fig… ..: Corrosion wheel diagram
2.1.5 WHY DOES CORROSION OCCUR?
Corrosion is a natural process driven by energy considerations. The process of extraction of the metal from
the ore stores up vast quantities of energy in the metal. Corrosion is therefore a means of releasing this
stored up-energy. The metal, because of its high energy is in a state of high energy. The corrosion process
permits the metal to go to a lower energy state (the combined state).
2.1.6 EFFECTS AND ECONOMIC IMPACT OF CORROSION
The effects of corrosion in our daily lives are both direct and indirect. The direct effects involves a decrease
of the usefulness of our possessions which are affected by corrosion. The indirect effects are experienced
in the high cost of materials arising from the building in of corrosion prevention and corrosion control
products, as well as maintenance, repair, and prematerial replacement. The ultimate cost is the loss of lives
in accidents resulting from structural failure of buildings, bridges and industrial plants due to corrosion. A
case in point is the sudden collapse of Silver Bridge over Ohio River in 1967, resulting in the loss of 46 lives.
Perhaps most dangerous of all is observed in major industrial plants, such as electrical power plants
(including nuclear plants) or chemical processing plants. Notable examples is corrosion induced leak in an
oil pipeline with a resulting loss of the product and environmental pollution.
According to a landmark study by the National Institute of Science Technology USA on the Economic Effects
of Metallic Corrosion in the United States,the annual costs of corrosion were estimated to be about 4.2% of
the GNP, which when projected to current values is about N350 billion annually. By this study, the
industrial sectors identified with the highest corrosion costs in decreasing importance were:
• Oil and gas extraction
• Petroleum refining
• Chemical processing
• Pulp and paper
• Public utilities (electric, gas and water)

• Transportation (auto, train, air)
• Metals production
• Civil infrastructure
And the economic costs of corrosion come in the following forms:
• Replacement of corroded equipment
• Overdesign to allow for corrosion
• Preventive maintenance
• Shutdown of equipments
• Contamination of products
• Loss of valuable products, e.g. from a container that has corroded through
• Loss of efficiency – such as when overdesign and corrosion of products decrease the heat transfer
rate in heat exchangers.
• Inability to use otherwise desirable materials
• Damage of equipment adjustment to that which corrosion failure occurs.
Other effects of corrosion are social, involving:
• Depletion of natural resources
• Danger to human life through sudden failure which can result in, explosion, fire, release of toxic
products and construction collapse.
• Health problems arising from pollution due directly or indirectly to corrosion.
• Appearance – Loss of aesthetics (http.www.asminternational.org, 2000)
In the light of the economic and social consequences of corrosion, available corrosion control procedures
should be followed strictly.
2.1.7 CORROSION INHIBITION
An inhibitor is a substance that slows down or retards a chemical reaction. A corrosion inhibitor is a
substance which when added to an environment, reduces the rate of attack by the environment. The use
of corrosion inhibitors has become one of the foremost methods of combating corrosion. To use them
effectively, three issues must be considered, namely:
• Identification of corrosion problems
• The economics of the inhibition process. It should be established whether or not the loss due to
corrosion exceeds the cost of the inhibitor and maintenance and operation of the attendant
injection system.
• The compatibility of the inhibitor with the process being used: This must be ensured in order to
avoid adverse effects. Inhibitors must be applied under conditions which produce maximum effect.
(NACE, 1984)
Generally three of the four components of a corrosion cell (anode, cathode, electrolyte and electronic
conductor) may be affected by corrosion inhibitor in order to reduce corrosion. The inhibitor may cause:
• Anodic inhibition by increasing the polarization of the anode.
• Cathodic inhibition by increasing the polarization of the cathode.
• Resistance inhibition by increasing the electrical resistance of the circuit while forming a thick
deposit on the surface of the metal
• Diffusion restriction by restricting the diffusion of depolarisers (e.g. dissolved oxygen) to the surface
of the metal. By so doing they play a dual role.

There are six classes of inhibitors namely; Passivating (anodic), Cathodic, Ohmnic, Vapour phase and
Organic. For the purpose of this lecture I will highlight the specific type of inhibitor I studied: organic
inhibitors.
2.1.8 ORGANIC INHIBITORS
There are six classes of inhibitors namely; Passivating (anodic), Cathodic, Ohmnic, Vapour phase and
Organic. For the purpose of this lecture I will highlight the specific type of inhibitor I studied: organic
inhibitors.
Organic compounds constitute a large class of corrosion inhibitors which as a general rule affect the entire
surface of a corroding metal when present in sufficient concentration. Organic compounds containing
elements of groups Vb, VIb or functional groups of the Type – NH2, > Co and CHO are effective inhibitors
(Ma Krides).
The principal mechanism suggested for corrosion inhibitors is adsorption. The inhibitor is adsorbed in the
entire surface of the corroding metal and by so doing prevents attack from the corrodent. Organic
inhibitors are adsorbed according to the ionic charge of the inhibitor on the metals surface. Cationic
inhibitors e.g. amines (positively charged, +) or anionic inhibitors (negatively charged, -) e.g. sulphonates
will be adsorbed preferentially, depending on whether the metal is charged negatively or positively.
Therefore, a combination of cathodic protection on an inhibitor which is adsorbed more strongly at
negative potentials gives greater inhibition than either cathodic protection or an inhibitor when used
alone.
Inhibitors may be considered as two fundamental types (Moore, 1981):
TYPE A
Those which form a protective barrier film on anodes or cathodes by reaction between the metal and
the environment. Type (a) Inhibitors function in neutral or in some cases , alkaline solution in which the
main cathodic reactions is oxygen reduction reaction and a corroding metal surface is covered by a film
oxide or hydroxide. Type (a) inhibitors tends to produce a protective film or stabilize an already existing
one.
TYPE B
Those which are initially adsorbed directly onto the metal surface by interaction between surface
charges and ionic and/or molecular dipole charges. This division of inhibitor types results principally
from the pH of the solution where they operate.
Inhibitors must be present in a minimum concentration for them to be fully effective. When the inhibitor
falls below a specified minimum, the cover it provides is inadequate and the exposed area becomes a
centre of more active corrosion. This is very common with anodic inhibitors. It has been observed that at
certain concentrations, inhibitors loose their efficiency and become corrosion promoters (Ateya, El-
Anadouli and El-Nizamy, 1981)
SYNERGISM WITH HALOGEN IONS
The efficiency of organic inhibitors is improved in the presence of certain halogen ions. Halogen ions alone
are known to inhibit corrosion to some extent in acid solutions. The efficiency of inhibition is in the order І -
> Br - >Cl. Flouride does not show inhibition characteristics. One explanation for the Synergism of halogen
ions is that the metal adsorbs halogen ions whose charge shifts the surface in a negative direction, thereby
increasing adsorption of the cationic organic inhibitor.

4.0 MY CONTRIBUTION
As mentioned earlier, my research work is centred around metals – their extraction, corrosion and
corrosion inhibition. In the first part of this section, I will focus on conversion of iron ore samples to
metallic iron. In the second part, I will discuss corrosion and corrosion inhibition in metals.
4.1 METAL EXTRACTION STUDIES
4.1.1 EVALUATION OF ITAKPE AND NIMBA IRON ORE PELLETS FOR DR (EKPE AND WALKER, 1989)
The DR characteristics namely Reducibility, clustering behavior or sticking tendency and fine generation
were investigated.
Properties of Nimba and Itakpe ores
The Chemical analysis of concentrates of Nimba and Itakpe are listed in Table 4.1 while their physical
properties are presented in Table 4.2.
We observe that porosity, and tumbler test (fines generation) show that Nimba is better than Itakpe in
terms of porosity while Itakpe is better in terms of fines generation.
Reducibility
This is related to the rate of reaction. Usually the rate at 40% reduction is commonly used for determining
the rate Figure 4.1 and 4.2. Reduction of the ores followed typical reduction curves and table 4.3 show R40
at the 3 temperatures.
Table 4.3 Instantaneous rate of reduction (R40) for Nimba and Itakpe Iron ore pellets reduced at
750 0 c, 850, and 950 0 c with 3:1 H2O CO Mixtures
Samples 750 0 c 850 0 c 950 0 c
Nimba 4.72 9.10 11.26
Itakpe 2.30 4.57 5.39
From Table 4.3 we observe that the rate of reduction of Nimba nearly doubled that of Itakpe. This may be
attributed to the higher porosity of Nimba pellets. The siliceous constant of Itakpe may also play part in
lowering its reducibility.
The clustering behavior was determined by using a Tensometer type-E electronic tensile machine. The
Shrinkage curves shown in Fig. 4.3 indicate that the strength of Itakpe pellets under reduction was higher
than that of Nimba. Maximum Shrinkage ratio for Nimba ws 20% and 8.20% for Itakpe. Using Hendrickson
and Sandoval (1980) specifications namely:
• Metallisation > 90%
• No clustering
• Abrasive resistance (0-0.5mm) < 5%
• Strength index (+6.4mm) > 80%

Nimba pellets quality in all but one. It forms cluster at 950 0 c but not at 850 0 c. A lower reduction
temperature is recommended. Itakpe pellets qualify in all. No cluster was formed at 950 0 c therefore
reduction temperature of 950 0 c is recommended.
4.1.2 INVESTIGATION OF EFFECTS OF SLAKED LIME ADDITIONS ON CLUSTERING BEHAVIOUR OF NIMBA
PELLETS. (EKPE, IBOK, Walker 1989)
Calculated amounts of Ca(OH)2 was added to Nimba to produce basicity ratios 0.25 to 2.0:
Lime addition on shrinkage ration and clustering behavior are shown in fig. 4.4 and fig. 4.5 respectively.
Figure 4.5 clearly shows that the acid pellets (Basicity Ratios 0.25, and 0.5) form clusters, but the basic
pellets do not. A clearer picture was obtained from Table 4.4 where the factor affecting reducibility are
outline.
TABLE 4.4 EFFECT OF SLAKED LIME ON CLUSTERING FACTORS AT 950 0 C
Basicity ratio 0.25 0.50 0.75 1.00 1.50
Cluster strength 0.92 0.72 0.00 0.10 0.16
Max % Shrinkage 20.00 18.62 10.62 12.86 14.46
% Metallisation 97.03 96.00 93.01 95.82 94.62
From table 4.4 cluster strength decreased as the basicity increased. However, lowest cluster strength was
obtained at basicity ratio of 0.25. hence reduction of Nimba pellets at 950 0 c with basicity ratio of 0.75 was
recommended.
4.1.3 Effect of slaked addition on reducibility and fines generation of Nimba and Itakpe fire compacts
were studies at 750 0 c, 850 0 c and 950 0 c (Ekpe and Walker 1989)
Instaneous rate curves obtained at various basicity ratios are shown in Fig. 4.6. From the curves obtained
the variation of reducibility is highest at the lowest basicity. The trend with the two extremes are irregular
for Nimba pacts. Itakpe compacts show a better trend, howbeit the variation within the limits are not
linear.
Metallographic examination of fired compacts showed some interesting results. Examination of the
fracture surfaces of unreduced compacts in the scanning electron microscope revealed a tendency for the
grain size to increase in proportion to basicity. (Fig. 4.7). This may be taken as an evidence of reduction in
the internal surface area which should adversely affect reducibility.
Optical micrographs of both unreduced compacts reveal the presence of a slag phase at the hematile grain
boundaries and silica and various ferrite were detected (fig. 4.8 and 4.9). Attempts to determine
composition using spot analysis and X-ray mapping only gave quantitative results.
In conclusion
• Fired compacts of Nimba at basicity ratio of 0.75 showed
a. minimum reducibility
b. maximum contraction during reduction under load and
c. maximum abrasion resistance at 750 0 C
• Nimba iron ore is quite suitable for gaseous DR process while Itakpe iron ore in this study appears
to be appropriate for blast furnace smelting. Now that it has been reported that itakpe has been
beneficiated to 68% (NSSA, 2008) it is believed that it may well be useful for gaseous DR process.
4.4 Optimum Calcinations for Some Nigerian Limestones (Ibok, Ekpe and Uwah, 1990)

Limestones from Mfamosing in Cross River, Okpella from Edo State and Jakura from Kogi State were
clacined at temperatures between 750 0 c to 1050 0 c at different durations. This project was aimed at
determining the most suitable limestone for the Nigerian Steel Industry.
The optimum conditions were determined by means of chemical reactivities of the calcined products
chemical reactivities of the calcined products. Chemical reactivities were determined in terms of degree
rise in temperature after 60 seconds of the slaking time of products (Slatter 1975).
The variation of chemical reactivity of the limestone samples at vatious duration shown in fig. 4.10.
The following chemical reactivity results were obtained.
• At 950 0 c Mfamosing > Okpella>Jakura
• At 850 0 c Mfamosing>Okpella>Jakura
• At 150 0 c Okpella>Jakura>Mfamosing
4.1.5 Kinetics of Reduction of Slaked Lime Fluxed Itrakpe and Nimba Iron Ore Compacts
Slaked-lime fluxed Itakpe and Nimba iron ore fired compacts with basicities ranging from 0.04 to 1.50 have
reduced at temperatures ranging from 750 0 c to 950 0 c using 75%/25% H2/CO mixture. Micrographs of
pellets reduced at various levels fig. 4.7 and fig 4.8 for Nimba and Itakpe respectively.
These figures show that 20% reduction even at 750 0 c thin layer of iron is formed and that as % reduction
increases the layer of iron become thicker enclosing a shrinking wustite core. In fig 4.7 the absence of a
sharp interface between iron and wustite suggest that some degree of non-topochemical reduction. At
intermediate stages of reduction the iron layer is thicker suggesting that the reaction may be controlled by
the diffusion across the product layer. In contrast, figure 4.8 shows partially reduced Itakpe compacts with
sharper iron-wustite interface suggesting a greater control by product layer diffusion. Therefore Itakpe
mainly in a topochemical fashion.
The following conclusions are obtained from this study:
• Lime addition changes mode of reduction from non-topochemical at low basicity to topochemical
at high basicity.
• A change in mechanism is observed during the course of reduction from chemical control to a pore
diffusion control. Therefore the kinetics of the process may be described in terms of mixed control.
• Nimba iron ore reduction was by a non-topochemical process while Itakpe iron ore was controlled
by topochemical reaction
• Addition of lime increased the regime of pore diffusion control.
• Pre-heating temperature influences the range of diffusion control regime of direct reduced iron
4.1.6 Studies on non-metals
Some of our studies on non-ferrous metals include pyrometallurgy of tin oxides and cementation tin on
aluminium from stamous chloride solutions.
4.1.6 (a) Mechanism of Gaseous reduction of tine oxides
The mechanism of pure synthetic stannic oxide and naturally occurring cassiterite was investigated by
reducing these materials with reducing gas mixture of H2, Co and CH4. The following conclusions were
obtained:
• The mechanism for the reduction of SnO2 by the reducing gas mixture was considered to be
sequencial via the SnO intermediate below 400 0 c when the disproportionation of SnO is slow.
Removal of Oxygen occurs at gas/oxides interface as follows:
H2 + SnO2 SnO + H2O
H2 + SnO Sn + H2O

The overall reaction is given by
2H2 + SnO2 Sn + 2H2O
• The reduction of SnO2 to Sn at temperatures below thermal decomposition of SnO was classified as
topotactic and reconstructive.
4.1.6 (b) Cementation of tin
The rate controlling factors in the cementation of tin on aluminium metal surface was investigated by using
acidified stannous chloride.
The following conclusions were drawn from the study:
• The rate of cementation increases with stirring speed but there is a critical stirring speed above
which cementation rate remains constant.
• Within the range of initial tin cementation investigated the rate of cementation increased
significantly with increasing initial tin concentration.
• The reaction rate decreases with increasing pH.
4.2 Corrosion and Corrosion Inhibition
The study of corrosion and corrosion inhibition in our department was fortuitous. At the Nigeria Christian
Graduate Conference held in Ibadan in 1992 a farmer shared his experience with us. He mentioned that he
observed that his Cassava crops planted near the boundary of his farm lined with Azardicta Indica trees
were not affected by the devastating cassava leaf disease known as.
The rest of the farm was reflected. I cannot now tell why I thought that the leave…… of said should be
investigated as a corrosion inhibitor.
4.2.1 Inhibition Action of Azadirachta leaves Extract (Ekpe, Ebenso and Ibok, 1994)
The corrosion of mild steel in tetraoxosulphate (IV) acid at different concentrations using weight loss
methods. Azadirachta indica leaves acid extracts were used as inhibitor for mild steel in ).5M H2SO4 at 30 0 c
and 40 0 c. Different concentration of inhibitor was used from 2.50 x 10 -4 gdm -3 to 1.25 x 10 -3 gdm -3 . The value
of percentage inhibitor efficiency (p… ) which is defined by the equation.
PorI = Wu - Wi
Wu
Where Wu and Wi are the weight losses of the mild steel in unhibited and inhibited solution (Talati
and Modi 1986).
The following conclusions were drawn:
• Azadiracta indica leaves extracts inhibit acid corrosion of mild steel at 30 0 c and 40 0 c.
• Maximum inhibition efficiency of 75.75% was obtained at the highest concentration of 1.25 x 10 -
3 gdm -3
• Azadiracta indica extract may have been physically adsorbed on the mild steel surface. Evidence is
hereby provided.
4.2.2 Investigation of Inhibition Property of Carica Papaya (paw paw) leaves extract (Ekpe, Ita and
Bassey)

The success in the investigation of corrosion inhibition by Azadiracta indica leaves spurred us to have a
look at Carica papaya leaves extract. This time we used Al-Mn Alloy instead of mild Steel and alkaline
medium instead of acid. We used both weight loss and gas e solution techniques and the inhibitor
concentration varied from 1.0 to 5.0g in increment of 1.0g. The observation and conclusion made were as
follows:
• Maximum inhibition efficiency was 91.44% from weight loss technique while 93.30% inhibition
efficiency was obtained from hydrogen evolution technique.
• Physical adsorption mechanism was proposed for the inhibition process
• A first order type of reaction was proposed.
4.2.3 Comparism of inhibition Properties of Acid Extracts of Azadiracta Indica and Carica Papaya Leaves
(Ebenso, Ekpe)
Carica papaya and Azadiracta indica leaves extracts were separately used as inhibitors for the corrosion of
mild steel in 0.5M H2SO4 at 30 0 c and 40 0 c.
It was found that:
• % inhibition efficiency increased with increase in inhibitor concentration for both inhibitors. For
Carica papaya, the % inhibition efficiency varied from 72.8% to 87.5% at concentration of 2.50 x 10 -4
to 1.25 x 10 -3 g/dm -3 at 30 0 c and for Azadiracta indica 60.13% to 75.75% at similar concentration
range.
• Increase in temperature reduced the % inhibition efficiencies of both inhibitors
• Carica papaya leaves extract is a better inhibitor than that of Azadiracta indica.
• For both inhibitors physical adsorption was the proposed mechanism of inhibition
The general problem in leaves extract studied was being able to identify the particular compound involved
in the inhibition. We know that many organic compounds have been identified e.g:
• Nimbocinone [Siddiqui et al, 1986]
This inadequately made us look for other inhibitor whose molecular formular and structure was
known. We turned our attention to thiosemicarbazons which were being synthesized in our
departments.
• 2 1 ,3 1 -dehydrosalanal (a tetranortriterpenoid) (Garg and Bhakuni 1985)
• Nunonol (G. Suresh, N.S. Narasimhan and Palani, 1996)
• 6d-O-acetyl-7-deacetylnimocinol and meliacinol [Saddrqui Afshan, Ghiasuddin, Faizi, Naqui and
Tariq 2000)
4.3 Lessons from Chemistry
Mr. Chairman let me here support the Registrars of all university using chemical concepts. At convocation
Registrars announce that the graduands have been found worthy in learning and character. I had been
wondered how the character aspect is acquired until I discovered in chemistry and I think every discipline
has character trait that her students can discover and use.
4.3.1 The Politics and Sociology of Chemical Systems
In fig 4, we see the Periodic Table of Elelments which can be called the Nation of Chemical Elements. Her
current (2008) population is 112 consisting of 86 solids (metals) 3 liquids, 11 gases and 22 artificially
prepared, 17 non-metals in fig. 4. We see the Nation divided into four states namely:
S, Pee, Dee and F-States. The distribution of the local government areas and clans are as follows:

S state – 6 LGAs and 2 clans
Pee State - 6 LGAs and 6 clans
Dee State - 2 LGAs and 2 clans
F-state - 2 LGAs and 2 clans
The periods represent the local government areas while the groups represent the clans.
State characteristics: In S state intra marriage is not allowed. In Pee state intra and intermarriage and it is
supposed that intramarriage allows them to produce giants (giant molecules). The D state is nicknamed
peacock state because of the variety of colours while F state is nicknamed Radical state because of their
spontaneous reactions.
Their form of government is ‘Modified Monarchy’ – modified in the sense that Monarchy is in a group – the
six noble gases. Mr. Chairman, I am attracted to this nation because of their order and organization. There
is no ethnicity-remember the noble which rule all the states are in the Pee state. They do not go on strike,
delay results or be paid for being employed and not for the job they do. All these are attributed to the
nature of their rulership. There is a structure attributed to royalty – the possession of octet state that is
having 2 or eight electrons on the outermost state. All the elements acquire this noble state when they
react. All are encourage to marry (react) so there is no promiscuity. And the elements with one accord are
saying to the rulers ‘may you rule for ever since you do not make royalty your reserved characteristic. Their
diplomacy is beautiful – where there are disagreements the catalysts are there as roving diplomats
The lesson the offer to married homo-sapiens is wonderful. They marry in three ways covalently,
electrovalently and dative-ly. Electrovalent bonds and covalent bonds are strong because of the sacrifice
each contributes to the relationship. Take sodium and chlorine for example, they are each poisonous on
the individual status. But when they react, sodium gives out its precious valence electron while chlorine is
willing to carry the burden of an extra electron. As a result they form NaCl which if far less poisonous than
their parents. Take the diamond example in which each carbon atom donates one electron each for the
formation of strong covalent bonds. However in the dative bonding a very weak bond is produced when
one of the partner provides all the electron required for the bonding. One learns the lesson that in
marriage equal sacrifice towards the relationship will strengthen the marriage. But if all the burden of
sacrifice for the relationship is carried by only one member there is no strength to withstand the stress and
strains of marriage. No wonder that a little heat will break up the relationship.
The chairman, ladies and gentlemen it is appropriate at this time to thank you for listening and to say:
Go to the elements learn their ways and be wise.
Acknowledgements
My wife and children Dr. (Mrs.) Stella I. Ekpe, thank you for choosing to sacrifice and make our
electrovalent bonding strong. Ediomo, Ukeme, Ifiok and Utibeima, you know I will always be proud of you.
My parents, late Mr. and Mrs Jack Ekpe, I wish to thank them for the care and even though I cannot
remember my father’s face because he died when I was too young to capture his image in my brain but I
have since come to know the foundation of integrity and service to God he laid for me. As for my mother
an embodiment of integrity, thank you for being a good model for me. My siblings – Being the last of all of
you, I appreciate your love, care and sacrifice for me. They are Chief A.J. Ekpe (called to the Bar at 70 years
of age), late Chief U.O. Ekpe, Late Mrs Nko Elijah Udo, Mr. A.P. Ekpe, Mr. U.J. Ekpe and Mr. U.P. Ekpe.
My colleagues in the department and entire University of Calabar. Thank you for your friendship.Someone
has said that friendship is the rent we pay for our room on earth. My students, both post graduates and

undergraduates and especially my project students with whom we related as a family. Thank you for your
support.
My Christian friends, my Pastors (Bishop Adeleye and Rev. F. Ajoku) Together with you we have been made
joint heirs with Jesus. Thank you for your support and prayer.
Prof. and Mrs. Ivara Isu. I thank you for fishing me out and giving me the opportunity to join you to make a
difference on this campus.
TO GOD ALMIGHTY, WHO proved to me that He is the father of the fatherless and that with Him even
beyond the sky is not a limit. I thank you with my life.