The topics discussed this week are about Paper and related products, and Iron and Steel. As a person who loves books, paper production is an interesting industry for me. Imagine what the world would be without papers. I want to learn the process how paper is produced from the raw materials to the end products. A brief introduction of paper was discussed followed by its history. We all know that Egyptians used papyrus paper and this is one of their greatest contributions in the world. From that, several modifications and improvements were carried out in different parts of the world. A technology used for conversion of wood into wood pulp consisting of almost pure cellulose fibers is known as Kraft pulping process. The main ingredient of paper is the pulp; this is recovered from raw materials from separating fibers and lignin by adding white liquor in the raw materials- wood chips for instance. Inside the digester, the woodchips will undergo a cooking process with the white liquor. Delignification reaction takes place when the woodchips is heated, 135°C - 175°C is the Kraft cooking specific temperature that the lignin structure and other organic compounds are broken down into small fragments and solubilized into the alkaline solution. In the recovery process, the organic part of black liquor is added with water and burned in a recovery boiler that generates steam for the turbines and provide electricity for the mill. The inorganic part of the black liquor is burned and then mixed with water which is called green liquor. Green liquor contains sodium carbonate and sodium sulfide so it is mixed with calcium oxide to regenerate the white liquor that is used in the pulping process. The bleaching process is done in order to remove the remaining lignin causing the pulp to have a brown color. Several processes also include Digester System, Pulp Washing System, Delignification System, Bleaching System, Forming Section and Calender. Unit processes involved are pulping, screening, pulp washing, bleaching, and paper making. Some of the end uses are printing papers, book, paper money, newspaper, paper bags, milk and juice packages, toilet paper, coffee filters, paper grades for medical uses and a lot more.
For the steel and iron industry, the steps involved are Raw material Processing, Steel making and Casting, Hot Rolling, Cold Rolling, and Strip Processing. The hot metals from the blast furnace, steel scrap or a mixture of both are the most common raw materials of steel. The basic process involved into the iron and steel production is the refinement of iron ore. Coal and limestone are usually used for this refinement. The heat harnessed from coal is required to run blast furnaces. Limestone is used as fluxing material, which helps to remove impurities from iron ore. The product thus produced is widely known as pig iron. The further processing of pig iron produces cast iron, wrought iron and finally steel. Some examples of steel products include the metal roofing, steel beams, reinforcing steel and mounting brackets which are mainly used in buildings. For medical uses, steel are used to produced scalpels, hip implants, suture needles, and surgical pins. There are a lot of application of iron and steel and we also used it in our daily lives such as paper clips, scissors, kitchen sink units, cutlery and a lot more.
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