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CHE4: SUGAR CHEMISTRY

This unit talks about how sugar is prepared and its functions

Sugar is a carbon-hydrate.

Cane sugar-it is a two unit sugar make up of one molecule of glucose and one molecule of sucrose. Sugar is a food or drink sweetener.

 Manufacture of sugar in Uganda

It is manufactured from sugar cane, the cane is cut into smaller pieces which are crushed to produce juice which contains about 20% sugar and impurities .The juice is heated in large tanks into which lime is added to prevent sucrose from hydrolyzing to simple sugars. The mixture is then filtered.

The clear filtrate is diluted with water then concentrated by evaporation and cooled crystallize. Brown sugar crystals separate out. The residue is a thick liquid called molecules. Used in preparation alcohol.

To obtain white sugar, the brown sugar is dissolved in water and the solution boiled with charcoal. After filtration to remove the charcoal and any other solid impurities. The solution is concentrated and crystallized to form white sugar crystals. They are filtered out dried and packed.

Molasses used to make alcoholic drinks and as cattle feed.

Cement and its manufacture

The most common way to manufacture cement is through a dry method. The first step is to quarry the principal raw materials, mainly limestone, clay, shale and other materials. After quarrying the rock is crushed. This involves several stages. The first crushing reduces the rock to a maximum size of about 6 inches. The rock then goes to secondary crushers or hammer mills for reduction to about 3 inches or smaller.

These raw materials are then blended in the correct proportions.


The crushed rock is combined with other ingredients such as iron ore or fly ash and ground, mixed, and fed to a cement kiln.

This blended raw material is called the ‘raw feed’ or ‘kiln feed’ is combined with other ingredients such as iron ore or fly ash and ground, mixed, and fed to a rotary kiln where it is heated and reaches a temperature of about 1400 C to 1500 C. In its simplest form, the rotary kiln is a tube up to 200 metres long and perhaps 6 metres in diameter, with a long flame at one end. The raw feed enters the kiln at the cool end and gradually passes down to the hot end, then falls out of the kiln and cools down.

The material formed in the kiln is described as ‘clinker’ and is typically

The finely ground raw material or the slurry is fed into the higher end. At the lower end is a roaring blast of flame, produced by precisely controlled burning of powdered coal, oil, alternative fuels, or gas under forced draft.

As the material moves through the kiln, certain elements are driven off in the form of gases. The remaining elements unite to form a new substance called clinker. Clinker comes out of the kiln as grey balls, about the size of marbles.

Clinker

Clinker is discharged red-hot from the lower end of the kiln and generally is brought down to handling temperature in various types of coolers. After cooling, the clinker may be stored temporarily in a clinker store, or it may pass directly to the cement mill.The heated air from the coolers is returned to the kilns, a process that saves fuel and increases burning efficiency.

After the clinker is cooled, cement plants grind it and mix it with small amounts of gypsum – a form of calcium sulfate and limestone. The gypsum controls the setting properties of the cement when water is added.

Cement is so fine that 1 pound of cement contains 150 billion grains.  The cement is now ready for transport to ready-mix concrete companies to be used in a variety of construction projects.

A rotary kilnBIO GAS

Chemistry of bio gas, preparation, composition, pollution effect on environment

It is formed by bacteria action on animal and vegetable waste. It consists mainly methane, other gases, include carbondioxide, ammonia, hydrogen sulphide.

A simple bio gas generator consists of a container in which animal and vegetable wastes are mixed with limited water the covered to exclude air. At temps of 250-300c the bacteria present decompose the wastes to form bio gas.

High quality bio gas depends on type of waste. A mixture of human execrator and cow dung and bean stalks produces high quality bio gas. It is used as a fuel for cooking and lighting.

 Advantages related to bio gas production

  • Bio gas is easy and cheap to produce
  • Forests and wild life would be saved if rural communities turned to using bio gas instead of wire wood.
  • Water hyacinth which choking our water masses can be harvested and used for making bio gas.
  • Sewage material can be converted into bio gas.
  • Solid waste from bio gas plant has high nitrogen content . It is used as an excellent fertilizer.

 Disadvantages

It releases carbon dioxide, sulphur dioxide, ammonia and hydrogen sulphide which pollute air.

THIS VIDEO EXPLAINS MORE ABOUT SUGAR CHEMISTRY

ASSIGNMENT : SUGAR CHEMISTRY MARKS : 10  DURATION : 1 week, 3 days

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