TUGASAN

JANUARY 2014

HBSC3203

CHEMISTRY II

MATRICULATION NO : 830524085141001

IDENTITY CARD NO. : 830524085141

TELEPHONE NO. : 0199788779

E-MAIL : nurrania@oum.edu.my

LEARNING CENTRE : OPEN UNIVERSITY MALAYSIA PAHANG

INTRODUCTION

People discovered that a high temperature coal fire could be used for the extraction of

iron from iron ore. The discovery of electricity at the beginning of the nineteenth century

allowed the extraction of the more reactive metals. Aluminium has been extracted on a large

scale since about 1870. A solid element or compound which occurs naturally in the Earth's crust

is called a mineral. While an ore is a mineral from which metals can be extracted profitably is

called a metal ore. Profitable extraction means that the cost of getting the metal out of the ore is

sufficiently less than the amount of money made by selling the metal. So all ores are minerals but

all minerals are not ores. The most common metal ores are oxides and sulphides. Metals are

obtained from their ores by reduction.

Iron is very reactive and is found in nature in form of its oxides, carbonates and

sulphates. The main ores are; haematite (Fe2O3), magnetite (Fe3O4) and Iron Pyrites (FeS2).

The main iron ore is Haematite (iron (III) oxide - Fe2O3). The iron ore contains impurities,

mainly silica (silicon dioxide). Since iron is below carbon in the reactivity series, iron in the ore

is reduced to iron metal by heating with carbon (coke).

Iron is the cheapest, most abundant and most useful of all metals. It is used extensively

to construct tools, fasteners, machinery, vehicles, bridges, buildings, and appliances. Iron is

ductile, malleable, machinable, and takes a high polish. It can be melted and cast into forms and

it can weld when hot. Iron is used as a catalyst in the Haber process for making ammonia.

Steel is an alloy of iron, carbon, and small amounts of other elements to make it stronger than

iron. Like iron, steel also is of ancient, unknown origin and was used to make simple drilling,

digging and cutting tools in ancient Asian and North African cities. The famous Toledo and

Damascus sword blades of the Middle Ages were made of steel by hand, which made them very

expensive. Iron contains (usually) undesirable elements such as silicon, phosphorus, sulphur, and

manganese. In steel these impurities removed and replaced by more desirable elements, called

steel alloys to impart special properties for special uses.

The iron produced by extraction from iron ores in a blast furnace is called pig iron. It is

an alloy containing about 3% carbon and varying amounts of sulphur, silicon, manganese, and

phosphorus embedded in the ore along with the iron. It is hard and brittle, so it is usually

reworked to make other types of iron and steel with more desirable properties. Cast iron is

molten pig iron poured into a sand or clay mould of desired shape and allowed to harden to

produce such items as pots, skillets, weights, and cannons. Wrought iron contains only a few

tenths of one percent of carbon and slag, which gives its fibrous structure. It is tough, malleable,

less fusible than pig iron, and has a fibrous structure that is easily worked by hand tools.

Wrought iron is annealed to free it from stress and toughen it. Before steel became cheaper and

came into common use, wrought iron was used for bridges, aqueducts, buildings and other high-

load structures. When the slag is removed in the steel-making process, wrought iron becomes

low carbon steel.

PROCESS TO PRODUCE STEEL CUTLERY FROM IRON ORE

The basic materials for iron production are iron ore, coal and coke (also used as energy

input to the process) or alternative reducing agents, limestone and dolomite. The steelmaking

process starts with the processing of iron ore. Steel production requires iron, steel scrap and lime

(burnt limestone). The iron ore is smelted to produce an impure metal called "hot metal" when in

liquid phase or "pig iron" when in solid phase. In smelting, a reducing agent - usually coke - and

heat are used to remove oxygen from the metal ore. Carbon dioxide (CO2) and carbon monoxide

(CO) are produced during the reduction process. Limestone is used to remove impurities such as

slag. Blast Furnace, Midrex Direct Reduction Iron and steel production processes with CO2

emissions capture and storage (CCS) are still under development and testing.

Process of making steel cutlery from iron ore

Pure iron is not readily available since it easily oxidises in the presence of air and

moisture. The iron industry reduces iron oxides to obtain pure iron, i.e. metallic iron. Steel is an

alloy based on iron and carbon, with carbon concentration ranging from 0.2% to 2.14% in

weight. High carbon content results in higher hardness, tensile strength, and lower ductility. The

resulting steel is also more brittle. Steel alloys can be enriched with other materials to tune the

final material properties that also depend on production techniques and on the quality of the

basic materials.

Overall process of steel-making

There are three major commercial forms of Iron. They differ in their carbon content.

EXTRACTION OF IRON FROM IRON ORE

1. Concentration

The ore is crushed in crushers and is broken to small pieces. It is concentrated with gravity separation process in which it is washed with water to remove clay, sand,etc

2. Calcination

The ore is then heated in absence of air (calcined). This results in decomposition of carbonates into oxides and then ferrous oxide is converted into Ferric Oxide.

3: SmeltingThe concentrated ore is mixed with calculated quantity of coke, limestone and the mixture is put in the Blast Furnace from top.

Commercial Forms of Iron

Cast Iron (or Pig Iron)

It contains 2-5% Carbon along with traces of

other impurities like Sulphur, Phosphorus,

Manganese etc.

Wrought Iron

is the purest form of Iron and contains carbon to the extent of

0.25%

Steel

It contains 0.5 to 1.5 % of carbon

along with varying amount

of other elements.

FeCO3→FeO+CO2

4 FeO+O2→2Fe2 CO 3

What is Blast Furnance?It is a tall cylindrical furnace made of steel.It is lined inside with fire bricks.It is narrow at the top and has an arrangement for the introduction of ore and outlet for waste gases.Heated with help of Hot Gases.

Chemical Reactions Take Place in Blast Furnace

Function of Limestone

1. Formation of Carbon Monoxide

Near the bottom of the furnace, coke burns in air to form Carbon Dioxide and a lot of heat is produced. We get a temperature of about 1875 K.

This CO2 further reacts with more coke and is reduced to CO.

2. Reduction of Haematite to Iron

In the upper part of the furnace, the temperature is between 975K to 1075K. Here Haematite is reduced to Iron by CO. This molten Iron is collected at the bottom of the

furnace.

C+O2→CO2+HeatC+CO2→2 CO

Fe2 O3+3CO→2 Fe+3 CO2

Limestone

1. It acts as flux to remove sand from Haematite in form of liquid Slag. In the middle of the

furnace, the temperature is about 1075-1275 K. Here Limestone decomposes to produce

calcium oxide (CaO) and CO2.This CaO reacts with reacts with silica (sand) present in the

ore to form slag (CaSiO3).

2. Slag is lighter than molten iron so it floats over molten iron and protects it from

oxidising back into its oxides.

TRANSFORMATION TO STEEL

CaCO3+heat→CaO+CO2

CaO+SiO2→CaSiO3

The flow-chart of conversion from iron ore to steel

Transformation from iron ore to steel

ELECTROPLATING TO PRODUCE GOOD FINISHING CUTLERY

Ever since the First World War, electroplating methods have been used to build up and

restore damaged, worn and over-machined components. The practice persists, but with the

passage of time the methods employed have increasingly formed part of the initial design

concept for various engineering parts. The best combination of bulk and surface properties is

thus achieved, and deterioration due to wear and corrosion curbed. Every electroplating bath

contains electrically equivalent amounts of positively charged particles (cations) and negatively

charged particles (anions) dissolved in a solvent, usually water. There are several different kinds

of cation and anion in any single bath, together with unionized molecules of solvent and other

possible substances, such as addition agents.

Electroplating is performed by passing a direct electric current through the solution

between one or more anodes, connected to the positive terminal of the dc source, and one or

more cathodes (the work to be plated), and connected to the negative terminal. In the external

circuit, negatively charged electrons flow from anode to cathode via the power source. Within

the solution, all the cations migrate under the influence of the electric field towards the cathodes

and all the anions towards the anodes. Different types of ion move at different rates, depending

mainly on their size and the magnitude of their charge. The sum of their movements in both

directions produces a total flow of charge (i.e. current) equal to the external current.

Nickel and chromium are the main metals employed, on basis metals of carbon or alloy

steel, cast iron and aluminium alloys. Copper is used in certain circumstances. In engineering

applications, chromium plate is customarily described as hard chromium. Thickness up to 150μm

is generally recommended, although thicker coatings are possible. Except in regard to thickness,

hard chromium is not significantly different from a deposit applied for decorative purposes. It is

genuinely hard, 850 -1000 HV, it has a very high melting point, 1850°C, a low coefficient of

friction and high resistance to galling. Coatings thicker than 75 -100μm require grinding and

polishing to achieve the specified dimensions. By the use of special techniques a highly

reflecting surface can be obtained, with something approaching optical perfection.

How a fork looks after each operation is performed

Good finishing cutlery

Type of waste products from iron industry and

1. Acid tars and other tars

These wastes arise from coke oven plant during coke oven gas treatment. Coke oven gas includes

coke particles and tar, which are removed from coke gas by means of some physical operations.

This mixture of coke particles and tar are removed from decanter in sludge form.

2. Flue dust and stack gas treatment sludge

Blast furnace, basic oxygen furnace and sinter plant top gases contain large amounts of iron dust.

Iron dust can be removed from top gases either by dry methods (bag filter, electrostatic

precipitator) or by wet methods (scrubber). If gas treatment is by dry methods; collected dust

waste is coded as 100207. When wet methods are applied, the collected dust is in the form of a

sludge with the code of 100213. Collected dust or gas treatment sludge from sinter plants is

hazardous due to its high alkali content, and dusts and sludges from blast furnace and basic

oxygen furnace are hazardous due to their high heavy metal content.

The heavy metal that exists in these wastes at relatively high concentrations is zinc. In the

Literature, it is learned from the technical staff of the plant that the recirculation of sludge from

blast furnace and basic oxygen furnace gas treatment may be limited by its high zinc content.

3. Oily mill scale

During hot rolling, water is used to clean semi-finished product (slab or bloom) from mill scale

and to cool it. During these process, water is passed through the rolling machines thus gets

contaminated by oil and oily mill scale. Cooling water containing oily mill scale is treated by

chemical precipitation, its oil content is removed and then recirculated back to the process for

use in cooling towers. Oily mill scale sludge removed from water is a hazardous waste due to its

oil content and has the code of 100211. Its recirculation to the system may be limited due to its

high oil content.

Type of Pollution

1. Air pollution

Air pollution from iron- and steel-making operations has historically been an environmental

concern. This pollution includes gaseous substances such as oxides of sulphur, nitrogen dioxide

and carbon monoxide. In addition, particulates such as soot and dust, which may contain iron

oxides, have been the focus of controls. Emissions from coke ovens and from coke oven by-

product plants have been a concern, but the continuous improvements in the technology of steel-

making and of emissions control during the past two decades, coupled with more stringent

government regulations, have significantly reduced such emissions in North America, Western

Europe and Japan. Total pollution control costs, over half of which relate to air emissions, have

been estimated to range from 1 to 3% of total production costs; air- pollution control installations

have represented approximately 10 to 20% of total plant investments. Such costs create a barrier

to the global application of state-of-the-art controls in developing countries and for older,

economically marginal enterprises.

Air pollution vary with the particular process, the engineering and construction of the plant, the

raw materials employed, the sources and amounts of the energy required, the extent to which

waste products are recycled into the process and the efficiency of the pollution controls. For

example, the introduction of basic-oxygen steel making has permitted the collection and

recycling of waste gases in a controlled manner, reducing the amounts to be exhausted, while the

use of the continuous-casting process has reduced the consumption of energy, resulting in a

reduction of emissions. This has increased product yield and improved quality.

Air pollution from iron industry

2. Water Pollution

Steel works discharge large volumes of water to lakes, rivers and streams, with additional

volumes being vaporized while cooling coke or steel. Waste water retained in unsealed or

leaking holding ponds can seep through and may contaminate the local water table and

underground streams. These may also be contaminated by the leaching of rainwater through piles

of raw materials or accumulations of solid wastes. Contaminants include suspended solids, heavy

metals and oils and greases. Temperature changes in natural waters due to discharge of higher

temperature process water (70% of steel-making process water is used for cooling) may affect

the ecosystems of these waters. Consequently, cooling treatment prior to discharge is essential

and can be achieved through application of available technology.

Water pollution caused by iron industry

3. Soil Pollution

Much of the solid waste produced in steel making is reusable. The process of producing coke, for

example, gives rise to coal derivatives which are important raw materials for the chemical

industry. Many by-products (e.g., coke dust) can be fed back into the production processes. Slag

produced when the impurities present in coal and iron ore melt and combine with the lime used

as a flux in smelting can be used in a number of ways: land fill for reclamation projects, in road

building and as raw material for sintering plants that supply blast furnaces. Steel, regardless of

grade, size, use or length of time in service, is completely recyclable and can be recycled

repeatedly without any degradation of its mechanical, physical or metallurgical properties. The

recycling rate is estimated to be 90%.

Solid waste produced by iron industries

ACTION THAT SHOULD BE TAKEN BY THE GOVERNMENT TO

PREVENT/REDUCE POLLUTION FROM IRON INDUSTRY

1. Steel recycling

Steel cans and other steel recyclables are usually collected from the curbside or drop-off

programs, then hauled to a material recovery facility, where workers separate it from other

recyclables and crush it in to large bales. The bales are shipped to steel mills or foundries, where

they are combined with other steel scrap and melted in a furnace to make new steel. The steel

industry in North America has been recycling steel scrap for more than 150 years. The steel

industry needs scrap to produce new steel, which ensures that all steel products contain anywhere

from 25 percent up to 100 percent recycled content. It also is cheaper to recycle steel than it is to

mine virgin ore to manufacture new steel. New ore is still mined in order to supplement

production of steel and steel products. Recovering steel not only saves money, but also

dramatically reduces energy consumption, compared to making steel from virgin materials. In

turn, this reduces the amount of greenhouse gases released in to the air during processing and

manufacturing steel from virgin ore.

2. Source Reduction

Source reduction is the process of reducing the amount or toxicity of waste generated.

The steel industry has successfully been able to reduce the amount of material needed to make

the same products. According to data from AISI, over the past 25 years, the thickness of steel

containers has been reduced by 30 percent, from 0.20 millimeters (mm) to 0.14 mm.

Technological developments in gauge control are further reducing thicknesses to 0.12 mm.

Thickness will continue to be reduced through more advanced technology and higher-quality

steel. Steel for automobiles has also become more lightweight, especially given recent demand

for lighter, more fuel-efficient vehicles.

3. Energy Conversation

Energy conservation is desirable not only for economic reasons but also for reducing

pollution at energy-supply facilities such as electric utilities. The amount of energy consumed in

steel production varies widely with the processes used and the mix of scrap metal and iron ore in

the feed material. Increases in the cost of energy have stimulated development of energy- and

materials-saving technologies. Low-energy gases, such as by-product gases produced in the

blast-furnace and coke-oven processes, are recovered, cleaned and used as a fuel. Consumption

of coke and auxiliary fuel by the German steel industry, which averaged 830 kg/tonne in 1960,

was reduced to 510 kg/tonne in 1990. The Japanese steel industry was able to reduce its share of

total Japanese energy consumption from 20.5% in 1973 to about 7% in 1988. The United States

steel industry has made major investments in energy conservation. The average mill has reduced

energy consumption by 45% since 1975 through process modification, new technology and

restructuring (carbon dioxide emissions have fallen proportionately).

HOW TO EDUCATE PUPILS TO PREVENT/REDUCE POLLUTION RELATING TO

IRON INDUSTRY IN THE FUTURE?

Educate pupils to:

1. Reduce

Reduce the quantity of waste produced. For example, some products and packaging are designed

to use less material, to be recyclable or to contain fewer hazardous chemicals. We can produce

less waste through selective shopping. Also, we can encourage reduction by expressing our

views about products and packaging to retailers, industry and government.

2. Re-use

Bring own food container when buying foods at canteen. Re-use old clothes, stationeries many

more items can be reused.

3. Setting up recycling centre

Recycled paper can be made into newsprint, paper bags, house insulation, egg cartons, animal

bedding or cardboard. Glass and aluminum from beverage containers can be made into new

containers. Check with the local government or recycling center to find out which items are

recyclable in the school and how they should be sorted and prepared.

4. Preparing reading material

Provide resources for learning more about recycling, composting and waste reduction as a

starting point for resources to build and enhance education efforts focusing on recycling and

waste reduction.

(2929 words)

REFERENCES

Stubbles, John. “The Basic Oxygen Steelmaking Process.” American Iron and Steel Institute

Steelworks Learning Center. http://www.steel.org/learning/howmade/bos_process.htm

Joseph Edwards.(1983). Electroplating: A guide for designers and engineers. Retrieved 20th Feb,

2014 from, http://www.materialsfinishing.org/attach/Electroplating.pdf

U.S. Environmental Protection Agency. Waste and Recycling Educational Materials.

Washington, DCR. Retrieved 22th Feb, 2014 from

http://www.epa.gov/epawaste/education/index.html