Cement is a binding material used in construction to set, harden, and bind materials such as sand, gravel, and stones into concrete or mortar. It is one of the most widely used materials in construction and serves as the foundation for building infrastructure like roads, bridges, buildings, and dams.

3.4 Some manufacturing industries in Ethiopia.

3.4. 1 Glass manufacturing

Glass is an amorphous or non-crystalline solid material.
. It is inexpensive to make, easy to shape when it’s molten.
. It can be recycled any number of time.
. The main component of glass is silica.
Types of glass
Quartz glass– is made from pure silica, SiO₂, at a temperature of about 2300°C.
.It is of high strength, low thermal expansion and highly transparent.
Soda-lime glass- is ordinary glass.
. It is a mixture of sodium silicate and calcium silicate.
. It is made by heating a mixture of silica sand, sodium carbonate or sodium sulphate and limestone.
.The reactions that take place in forming soda-lime glass are:
Na₂CO₃+ SiO₂→ Na₂SiO₃ + CO₂
CaCO₃ + SiO₂→CaSiO₃ + CO₂
 Soda-lime glass accounts for about 90% of manufactured glass. Widely used for window panes, bottles, dishes etc.
 Boro silicate glass- is commonly known as Pyrex.
. It is manufactured using boron (III) oxide (B₂O₃).
.It has a very High resistance to chemical corrosion and temperature changes.
. It is widely used to make ovenware and laboratory equipment such as flasks, beakers, and test tubes.
 Colored glass is obtained by the addition of metallic oxides.
Example of Some substances and the color the impact to glass

Substance added	The color of the glass
Cobalt(II)oxide	Blue
Ferrous compounds	Green
Cadmium sulfide	Yellow
Chromium (III) oxide	Green

Steps in glass production

1. Batch preparation– the raw materials preparation.
    The raw materials are mixed in a proportion of 60% sand, 21% sodium carbonate and 19% limestone.
2. Glass melting– melting raw materials and recycled glass (according to their color) at 1600°C.
    The furnace operates continuously, producing glass 24 hours a day.
3. Glass forming-changing into a required shape.
4. Annealing– removal of internal stresses by reheating the glass followed by a controlled slow-cooling cycle.
5. Inspection- testing the quality of glass.
6. Packing and dispatching is the final stage before distribution

3.4.2 Ceramics

 Ceramic is an inorganic, non-metallic solid prepared by heating minerals to high temperature and then cooling.
 Traditional ceramics, such as porcelain, tiles, and pottery are formed from minerals such as clay, talc and feldspar.
 Modern ceramics are formed from extremely pure powders of specialty chemicals, such as silicon carbide,alumina, barium titanate, and titanium carbide.
Manufacturing of Ceramics
 The mineral used to make ceramics is first crushed and ground to a fine powder.
 Then it purified powder by mixing it in a solution and allowing a chemical to form precipitate (a uniform solid that forms within a solution).
 The precipitate is then separated from the solution and heated to drive off impurities including water.
The steps of manufacturing ceramics include:
A. Moulding
 The crushed fine powder, small amounts of wax is added to bind the ceramic powder and make it more workable.
 Plastics may also be added to the powder to give the desired pliability and softness.
 The powder can be shaped into different objects by various moulding processes.
B. Densification
 The ceramic object is heated in an electric furnace to temperatures between 1000 °C and 1700 °C.
 As the ceramic heats, the powder particles coalesce, much as water droplets join at room temperature.
 As the ceramic particles merge, the object becomes increasingly dense, shrinking by up to 20 percent of its original size.
 The goal of this heating process is to maximize the strength of ceramic by obtaining an internal structure that is compact and extremely dense.
 In general, most ceramics are hard and wear-resistant, brittle, refractory, thermal and electrical insulators, non-magnetic, oxidation-resistant, and chemically stable.
 Due to the wide range of properties of ceramic materials, are used for a multitude of applications.
Well-known uses of ceramics: – they are commonly found in art sculptures, dishes, platters, kitchenware, kitchen tiles and bath room structures.
Lesser-known uses for ceramics: – they are used as electrical insulators, computer parts, tools, dental replacements, engine parts, and tiles on space shuttles and to replace bones such as the bones in hips, knees, and shoulders.
Future uses of ceramics: – In the future, ceramics might be used to remove impurities from the drinking water and to replace diseased heart valves.

3.4.3 Cement

 The raw materials for the production of cement are limestone, clay, silica sand, gypsum, calcium silicate, calcium aluminate, iron (III) oxide, magnesium oxide and pumice.
 Cement mainly contains calcium silicate (CaSiO₃) and calcium aluminate (Ca (AlO₂)₂).
Manufacturing Process
 Cement is made by heating limestone (chalk), alumina (Al2O3) and silica-bearing materials such as clay to 1450 °C in a kiln. This process is known as calcination.
 Calcination results a hard substance called clinker. The clinker is then ground with a small amount of gypsum into a powder. The resulting cement is known as Ordinary Portland cement (OPC).
 Portland cement was first discovered in England.

When cement is mixed with water it forms a plastic mass that hardens after some time.
 Upper Part of the Kiln
Raw Material → complete elimination of moisture
 Middle Part of the Kiln
Limestone decomposes to calcium oxide ; CaCO₃ (s) → CaO(s) + CO₂ (g)
 Lower End of the Kiln

2CaO 2SiO₂ →2 CaOSiO₂

3CaO + 3 SiO₂ →3 CaOSiO₂

3CaO + 3 Al2 O₃ → 3 CaO .Al₂ O₃

4CaO + 4Al₂O₃ + 4 Fe₂ O₃ → 3 CaO .Al₂O₃. Fe₂O₃

MgO + SiO₂ → MgSiO₃

Setting of Cement
 When cement mixed with water, the cement first forms a plastic mass that hardens after sometime. This is due to the formation of three-dimensional cross-links between –Si–O–Si– and –Si–O– Al– chains.
 The first setting occurs within 24 hours, whereas the subsequent hardening requires about two weeks. In the hardening process of cement, the transition from plastic to solid state is called setting.

3.4.4 Sugar Manufacturing

 Sugar is prepared from sugar cane
The Steps in sugar production are:

1. Collecting the harvest – cutting matured cane and transport.
2. Cleaning and grinding – crushing the sugar cane.
    During grinding, hot water is sprayed onto the sugarcane to dissolve the remaining hard sugar.
3. Juicing- removing pulp or bagasse.
    Sugarcane travels on the conveyor belt through a series of heavy-duty rollers which extract juice from the pulp.
    The pulp that remains, or “bagasse”, is dried and used as a fuel.
4. Clarifying – removing non – sugar debris by adding CO₂
    Carbon dioxide and milk of lime are added to the liquid sugar mixture, which is heated until boiling.
    Carbon dioxide moves through the liquid, it forms calcium carbonate which attracts non-sugar debris (fats, gums and waxes) from the juice, and pulls them away from the sugar juice.
5. Evaporation – removal of water to form brown syrup.
6. Crystallization – removal of water from sugar syrup.
    The crystals are sent to a centrifuge that spins and dries them.
    The dried product is raw sugar, which is edible.
7. Refinery – purification and bleaching sugar
    Raw sugar is mixed with a solution of sugar and water to loosen the molasses from the outside of the raw sugar crystals, producing a thick matter known as “magma”.
    The crystals are promptly washed, dissolved and filtered to remove impurities.
    The golden syrup that is produced is then sent through filters, and SO2 is passed through it to remove the color and water and the process is known as bleaching.
8. Separation and packaging – final evaporation and drying process is done.

3.4.5 Paper and pulp

 Paper is not a chemical compound which can be expressed by a chemical formula.
 Paper is a mixture made from rags and wood pulp glued together with some additives, bleached and dried.
 Wood pulp is made from soft-wood trees, such as spruce, pine, fir, larch and hemlock, and from hard woods, such as eucalyptus, aspen and birch.
 Wood is composed of cellulose, lignin, oils and resins. Lignin is used to bind fibers of cellulose together.
 To provide wood pulp, the cellulose must be separated from the lignin.
Manufacturing of pulp and paper involves the following steps;
1. Harvesting: trees involve the cutting down of trees from their growing areas.
2. Preparation: for pulping is a step in which the bark of the tree is removed and then the wood is chipped and screened to provide uniform sized chips (pieces).

• 3. Pulping is a step used to make wood pulp from the chipped wood pieces.
•  This can be accomplished by either mechanical or chemical means depending on the strength and grade of paper to be manufactured.
• A. Mechanical pulping: It utilizes steam, pressure and high temperatures instead of chemicals to tear the fibers.
•  The fiber quality is greatly reduced because mechanical pulping creates short, weak fibers that still contain the lignin that bonds the fibers together.
•  Paper used for newspapers are a typical product of mechanical pulping.
• B. Chemical pulping: Chemical pulp is produced by combining wood chips and chemicals in large vessels called digesters.
•  Heat and the chemicals break down the lignin which binds the cellulose fibers together without seriously degrading the cellulose fibers.
•  Chemical pulp is manufactured using the Kraft process or the Sulphite Process.
• A. The Kraft Process is the dominant chemical pulping method.
•  It is the most widely used method for making pulp from all types of trees.
•  The process uses aqueous sodium hydroxide and sodium sulphide as a digestion solution.
• Wood chips +NaOH +Na₂S->BlackLiquor
•  After digestion for about four hours at a temperature of 170 ℃, the pulp is separated by filtration
•  This process uses a basic digestion medium.
  • B. The Sulphite Process : Uses a cooking liquor (digestion) solution of sodium bisulphate or magnesium bisulphate digester at a pH of about 3 in a pulp.
• The action of the hydrogen sulphide ions at 60 ℃ over 6 to 12 hours dissolves the lignin and separates it from the cellulose.
• After the process is complete, the pulp is recovered by filtration.
• The wood pulp achieved from the Sulphite or Kraft processes is washed to remove chemicals and passed through a series of screens to remove foreign materials.

4. Bleaching: It is the process of removing coloring matter from wood pulp and increasing its brightness.
   The most common bleaching agents are strong oxidizing agents such as chlorine, chlorine oxide, ozone and hydrogen peroxide.
5. Making paper from pulp: the pulp is processed into liquid stock that can be transferred to a paper mill.
6. The suspension is poured onto a continuously moving screen belt and the liquor is allowed to seep away by gravity to produce paper sheet.
7. The continuous sheet then moves through additional rollers that compress the fibers and remove the residual water to produce fine paper.

3.4.6 Tannery

 Tanning is a process of converting raw animal hides and skin to leather, using tannin.
 Tannin is an acidic chemical that permanently alters the protein structure of skin so that it can never return to raw hide or skin again.
 Leather production involves various preparatory stages, tanning, and crusting.

1. Preparatory stages are those in which the hide or skin is prepared for tanning.
    This stage includes curing, soaking, flesh removal, hair removal, scudding, and deliming.
   a. Curing – is process involves salting or drying the hide to prevent bacterial infection and dehydrate the skin.
    Brine curing is the simplest and fastest method.
   b. Soaking- is process, cured hides are soaked in water for several hours to several days to remove salt, dirt, debris,
   blood and excess animal fat from the skin and make the skin soft.
   c. Flesh removal- is process; remove unwanted flesh from the skin by machine.
   d. Hair removal- the soaked hides are immersed in a mixture of lime and water. This process is called liming.
    It loosens the hair from the skin and makes hair-removal easier.
   e. Scudding- is the process in which hair and fat missed by the machines are removed from the hide with a plastic
   tool or dull knife.
   f. Deliming- is process involves the removal of lime from the skin or hides in a vat of acid.
2. Tanning is a process that converts the protein of the raw hide or skin into a stable material.
    There are two main types of tanning:
   a. Vegetable or natural tanning- the skin is placed in a solution of tannin.
    Tannins occur naturally in the barks and leaves of many plants.
    The primary barks used in modern times are chestnut, oak, tanoak, hemlock, quebracho, mangrove, wattle (acacia) and myrobalan.
    Naturally tanned hide is flexible and is used for making shoes, luggage and furniture.
   b. Mineral tanning- the skin is placed in solutions of chemicals such as chromium sulphate and other salts of chromium.
    Chrome tanning is faster than natural (vegetable) tanning and requires only twenty four hours.
    The leather is greenish-blue in color derived from the chromium.
    This process produces stretchable leather that is used for making garments and handbags.
3. Crusting- is the final stage in leather manufacturing and includes dyeing, rolling the leather to make it strong,
   stretching it in a heat-controlled room and performing a process that involves covering the grain surface with
   chemical compounds such as wax, oil, glazes etc. to make the leather very attractive.
   3.4.7 Food Processing and Preservation
    Food preservation is the process of treating and handling food to stop or greatly reduce spoilage, loss of quality, edibility or nutritive value caused or accelerated by microorganisms.
    Preservation usually involves preventing the growth of bacteria, fungi and other microorganisms, as well as reducing the oxidation of fats which causes rancidity.
   Modern methods of food preservation are:
   A. Freezing: is used to preserve prepared foods that do not require freezing in their normal state.
   Example: potatoes
   B. Freeze-drying- involves the gentle escape of water vapor.
    The process leaves the product close to its original shape, taste, and color and there is no loss of aroma or flavor .

For example, liquids such as coffee, tea, juices and other extracts, vegetables, segments of fish and meat products.
 Freeze-drying is a superior preservation method for a variety of food products and food ingredients.
C. Vacuum-packing- Stores food in a vacuum environment, usually in an air-tight bag or bottle.
 The vacuum environment strips bacteria of the oxygen needed for survival, slowing down the rate of spoiling.
 Vacuum-packing is commonly used for storing nuts to reduce loss of flavor from oxidation.
Inorganic and organic preservatives
 Some inorganic and organic preservatives are available for food preservation.
 Some examples of inorganic preservatives are sodium chloride (NaCl), nitrate and nitrite salts, sulfites, and sulfurdioxide (SO2).
 NaCl lowers water activity and causes plasmolysis by withdrawing water from cells.
 Nitrites and nitrates are curing agents for meats (hams, bacons, sausages, etc.) to inhibit Clostridium botulin under vacuum packaging conditions.
 Sulfur dioxide (SO2), sulfites (SO3), bisulfite (HSO3-2), and met bisulfites (S2O5-2) form sulfurous acid in aqueous solutions, which is the antimicrobial agent.
 Sulfites are widely used in the wine industry to sanitize equipment and reduce competing microorganisms.
 Wine yeasts are resistant to sulfites.
 Sulfites are also used in dried fruits and some fruit juices.
 Sulfites have been used to prevent enzymatic and no enzymatic browning in some fruits and vegetables(cutpotatoes).
 A number of organic acids and their salts are used as preservatives.
 These include lactic acid and lactates, propionic acid and propionates, citric acid, acetic acid, sorbic acid, and sorbates, benzoic acid and benzoates, and methyl and propyl parabens (benzoic acid derivatives).
For example, propionic acid and propionate salts (calcium most common) are active against molds at pH values less than 6.
 They have limited activity against yeasts and bacteria.
 They are widely used in baked products and cheeses.
 Acetic acid is found in vinegar at levels up to 4–5%.
 It is used in mayonnaise, pickles, and ketchup, primarily as a flavoring agent.
 Acetic acid is most active against bacteria, but has some yeast and mold activity, though less active than sorbates or propionates.

3.4.8 Manufacturing of Ethanol

 Ethanol is one of the constituents of all alcoholic beverages. ‘Tella’, ‘Tej’, beer, wine, ‘Katikalla’, ouzo, gin and whisky contain ethanol.
 There are a number of methods for preparing ethanol using different materials.
Industrial preparation of Ethanol
 Ethanol is manufactured industrially by:
1.Fermentation of carbohydrates such as sugar:
 Fermentation is the slow !decomposition of carbohydrates such as sucrose, starch and cellulose in the
presence of suitable enzyme that results in the formation of ethanol and carbon dioxide.

Fermentation can produce an alcoholic beverage whose ethanol content is 12 – 15% only.
 The alcohol kills the yeast and inhibits its activity when the percentage is higher.
 To produce beverages of higher ethanol content, distillation of the aqueous solution is required.
 Most liquor factories in Ethiopia use molasses, a by-product of sugar industries, as a raw material to produce ethanol.
 In the brewing industry, germinated barley called malt (in Amharic, ‘Bikil’) is used as the starting material.
 The whole process taking place in breweries is summarized as follows:

2.Catalytic Hydration of Ethene:
 Most ethanol is manufactured at present by this method.
 In this process, ethene is treated with steam at 573 K and 60 atm pressures in the presence of phosphoric acid,
H3PO4, catalyst.

Beer
 The raw materials for beer are barley and hops.
 The first step is to bring the barley to germination whereby starch is converted into a type of sugar called malt sugar.
 Heat stops this process and the material is now called malt.
 After drying and grinding the barley, water is added in the mash tubes.
 After adding hops and yeast the process of fermentation begins.
 Then it is stored in tanks for a period of time as required by a type of the product.
 Later it is pasteurized and carbon dioxide is added under pressure and supplied to consumers.
 The average beer has alcohol content between 2-6 % by volume.
Wine
 Grapes are the most common raw materials for producing wines.
 Grapes (or tether fruits) are first crushed and then steamed.
 The liquid that is derived from the crushing process is called must.
 It then goes to a fermentation takes place.
 The must then passes to a settling tank where sediment is allowed to settle, and proceeds from there to a filter.
 The clear liquid is cooled in a refrigerator tank and it is pasteurized as it passes through a flash pasteurizer

It finally goes to a storage tank where it is kept for months or years.
 The older a wine is kept, the more mature it becomes and usually is considered to have a higher quality fetching higher price.
 Most wines have an alcohol content varying from 10-16 per cent by volume.
Liquor
 Compared with beer and wine liquor contains a higher percentage of pure alcohol.
 To get drinks with higher concentration of alcohol the alcohol has to be separated from the solution by distillation.
 Liquors (e.g. cognac) are made by distillation of grape wine; rum is produced from sugar cane, and whisky from rye.
 Different types of liquors have different alcohol concentration.
 Most of them however range between 30-45 percent of alcohol by volume.
Local Preparation of Ethanol (Araki)
 Araki is the local Ethiopian alcohol which is prepared almost everywhere with certain local differences.
 In fact, the differences are in the ingredients and not in the process of making it.
 First, the barley is made into “Bikel”.
 The help of water, the Bikel is mixed with Gesho powder to make starter “Tinses”.
 The starter is left to ferment for about four days, (It depending upon the local’s humidity and temperature).
 The bread is baked from ingredients of Teff, Barley, Wheat, and Sorghum, depending upon their availability and local preferences.
 The bread is broken down into small pieces, mixed with prepared starter and left to stand to ferment for a couple of days (5 to 10 days).
 After it is fully fermented, a proportional amount of water is added to liquidity the tick dough-like mixture and left for 1 to 2 days for further fermentation.
 Finally, the liquid mixture is boiled and distilled in the traditional ways.
 The distillate is called “Araki”. While the leftover residue or the un-distilled component is locally called “Atela” and it is usually used to feed cattle.

3.4.9 Soap and Detergent

Soaps
 Soaps are metallic salts of higher fatty acids.
 Animal fat and vegetable oils are used for manufacturing soap.
 Fats and oils are naturally occurring esters of glycerol and the higher fatty acids.
 Soaps are substances used to remove dirt.
 They are also called surfactants or surface-active agents, because they reduce the surface tension of water and change the surface properties.
 Soaps are either sodium or potassium salts of higher (long-chain) carboxylic acids.
 Soaps that are sodium salts are called hard soaps and potassium salts are soft soaps.
 Soaps are prepared by boiling animal fat or vegetable oil with a base.
 The reaction that produces soap is called saponification.

3C₁₇ H₃₆ COOCH₂ + NaOH → C₁₇ H₃₅COONa + glycerol

In industry, tallow, lard, cotton seed oil, palm oil, castor oil, olive oil, whale oil and the oil of soybeans are used to prepare ordinary soap.
The structure of soap.

The long covalent hydrocarbon chain gives rise to the hydrophobic (water hating) and oil-soluble (non-polar) properties of the soap molecule.The charged carboxylate group is attracted to water molecules (hydrophilic). In this way, soaps are composed of ahydro philic head and a hydro phobic tail:

in solution a soap molecule consists of along non-polar hydro carbontail(e.g. C₁₇H₃₅ -) and a polar head(-COO-).

Industrially soap is produced in four basics steps Saponification- Admixture of tallow(animal fat)or coconut oil is mixed with sodium hydroxide and heated. The soap produced is the salt of along chain carboxylic acid.
Glycerin removal-glycerin is more valuable than soap,so most of it is removed.Some itself in the soap to help make it soft and smooth.
Soap is not very soluble in salt water, whereas glycerin is, so salt is added to the wet soap causing it to separate out into soap and glycerin in saltwater.
Soap purification – Any remaining sodium hydroxide is neutralized with a weak acid such as citric acid and two-thirds of the remaining water removed.Finishing-Additives such as preservatives, color and perfume are added and mixed in with the soap and it is shaped into bars for sale.

ADVANTAGES: Soaps are eco-friendly and bio degradable
DISADVANTAGES:
 Soaps are not suitable in the hard water
 They have weak cleansing properties than detergents.

Detergents
 Detergents are sodium salts of sulphonated long chain organic alcohols, R-C₆H₄SO₃ Na, where: R is an alkyl group with a chain of 10 to 18 carbon atoms.
 The water-soluble group is –SO3Na while the fat soluble one is the –R-C₆H₄ groups.
 They are called soap less soaps because they lather well; they are very different from ordinary soaps in their chemical composition.
 Long open chain alcohols and alkyl benzene sulphonic acid can be used for the production of detergents
 The advantage of detergents – is lather well with both soft and hard water and even with water that contains common salt or acids.
 They are more soluble than soap in water, form stable emulsions with grease and do not form a scum with hard water because their calcium and magnesium salts are soluble. Example Sodium lauryl sulphate or sodium n-dodecylsulphate is prepared first by reacting do-decyl (lauryl) alcohol with sulphuric acid followed by reaction with sodium hydroxide.
The reaction equation is:

DISADVANTAGES OF DETERGENTS; Detergents are not biodegradable and elimination from municipal waste waters by the usual treatments is a problem. Surfactants are used for their preparation pose a danger to aquatic life.

Cleansing action of detergents
The cleansing action of detergent and soap is fundamentally same.
When a detergent dissolves in water, its molecule will dissociate to form sodium or potassium ion and detergent ion (detergent anion).
The detergent ion such as R-O-SO₃-can be represented in a simplified form by structure below.

Dry Cleaning
 Dry cleaning refers to the use of different chemicals that are capable of dissolving grease and other dirt stains in a similar manner as soaps without the use of water.
 The most commonly used chemicals in dry cleaning are organic chemicals such as tetra chloro methane, CCl₄; tetra chloro ethylene, (Cl₂C = CCl₂), benzene and gasoline.
Example: Silk will turn yellow if it is treated with strong soap during laundering.
 Often the instruction for cleaning clothes contains the sentence: Use only lukewarm water for cleaning. Otherwise the quality of the product will decrease. Because natural fibers are mostly mixed with artificial ones, laundering should not be applied.
 Instead of laundering, dry cleaning is applied.
 To dry clean, means to use different chemical those are able to dissolve grease and stains in a similar manner as soaps, the only difference being that contact with water is avoided .