Solid Pollutants and Solid Pollution...

Solid Pollutants and Solid Pollution Solid Pollutants are more popularly known as solid wastes. The types and quantity of solid pollutants generated in iron and steel industry differ from plant to plant. Thus, a steel plant based on direct reduced iron – electric furnace (electric arc furnace or induction furnace) route generates different types and quantities of solid wastes than the integrated steel plant based on the blast furnace – basic oxygen furnace route. The solid wastes generated in iron and steel industry can be broadly categorized as (i) process solid wastes, and (ii) non-process solid wastes. Examples of process solid wastes are slag, dust, sludge, scrap, refractories, scale, muck, and debris etc. Examples of non-process waste materials are rubber, packing materials, electric wires, plastics and glass, and office and canteen wastes, etc.  Solid waste materials are usually generated in mixed condition which means that during generation, one solid waste material gets contaminated with other waste material. These waste materials are to be segregated for their recycling and reuse.  There are two types of waste streams which generates solid wastes. One stream is related to the production process, which also includes the waste from laboratories and sludge from effluent treatment plants. The second solid waste stream is due to the maintenance of offices and canteens.   The type and quantity of solid wastes’ generation depends on production process and the production technology employed. The quantity of solid waste generation is mainly dependent on two factors namely (i) the size of production unit, and (ii) efficiency of the technology. The solid wastes generated of iron and steel industry are of two types, i.e., ferruginous wastes and non-ferruginous wastes (Fig 1). The major ferruginous wastes are iron bearing wastes and consist of iron bearing dust and fines,...

Water Pollutants and Water Pollution...

Water Pollutants and Water Pollution Water pollutants refer to the substances which are capable of making any physical, chemical or biological change in the water body. These have undesirable effect on living organisms. Water is called polluted when the water is contaminated with domestic waste and industrial effluents. When this contamination reaches beyond certain allowed concentrations then the water pollution occurs. Water is considered polluted if some substances or condition is present in the water changes it’s physical, chemical, or biological characteristics to such an extent that the water cannot be used for its intended use or for a specific purpose. Pollution affects the quality of water is an adverse way due to the addition of large amounts of unwanted materials to the water. Water pollution occurs due to the presence of excessive amounts of a hazard (pollutants) in water in such a way that it is no long suitable for its intended use. Water pollution has a duel effect on nature. It has harmful effects on the living beings and also on the environment. Water pollution has many sources and characteristics. Pollution to the water environment can come from a wide range of sources. These include agriculture (crops and livestock), atmosphere (acid rain), aquaculture, forestry, illegal dumping of waste, industry, mines, sewage, and urban areas and roads etc. When the polluted water seeps into the ground and enters an aquifer it results into ground water pollution. The pollution of ground water is a matter of serious concern. Ground water gets polluted in a number of ways. The porous layers of soil hold back solid particles while the liquid is allowed to pass through. The soluble pollutants are able to mix with the groundwater. In addition to these, the excessive use of nitrogenous fertilizers...

Air Pollution and Air Pollutants...

Air Pollution and Air Pollutants Clean air is vital to sustain the delicate balance of life on Earth. However the quality of air can be affected by air pollution. Air pollution occurs when certain gases and particles build up in the atmosphere to such levels that they can cause harm to human health, causing breathing and respiratory problems, and even resulting in premature death, as well as damaging the environment around the world. These gases and solid particles (known as pollutants) tend to come from man-made sources, including the burning of fossil fuels such as coal, oil, petrol or diesel, but can also come from natural sources such as volcanic eruptions and forest fires. Air pollutants are those substances which causes pollution of the atmospheric air. They are those chemical, biological and physical agents which modify the natural characteristics of the atmospheric air. Air pollutants arise both from natural processes (volcanic activities, oceans, and forests etc.) and human activities (fossil fuel combustion, transportation, power plant emissions, or emissions from other industrial processes). Air pollution is the contamination of the indoor or outdoor air by a range of gasses and solid particles which modify its natural characteristics. It occurs when gases, dust particles, fumes (or smoke) or odour are introduced into the atmosphere in a way which makes it harmful to humans, animals and plants. Air pollution is often not visible to the naked eye as the size of the pollutants is smaller than the human eye can detect. They can become visible in some situations for example in the form of sooty smoke, and smog etc. The fact that air pollution cannot be seen does not mean that it does not exist. Air pollution threatens the health of humans and other living beings and...

Crude Benzol and its major Components...

Crude Benzol and its major Components Crude benzol is a product which is produced during carbonization of coking coal. Benzol (also called as benzole) is the name normally applied in the chemical industry to a mixture of hydrocarbons of the benzene series, in which benzene itself predominates, in association with certain of its homologues and various impurities. The term is not applied to any particular mixture or quality of the liquids. The recovery of benzol from the coke oven gas implies the removal of vapours of the benzene series, and their subsequent conversion by condensation into different liquid products. The CAS number of crude benzol is 65996-78-3. Benzol fraction produced during the high temperature carbonization of the coal is around 0.7 % to 1.1 % of dry coal. It is present in the coke oven gas in the range of 25 grams per normal cubic meters (g/N cum) to 40 g/N cum of coke oven gas. The benzene series is the most important group of substances in the class of aromatic hydrocarbons.  It is the series of carbon-hydrogen compounds based on the benzene ring, with the general formula CnH2n-6, where ‘n’ is 6 or more. Examples are benzene (C6H6), toluene (C7H8), and xylene (C8H10). The members of particular interest of this series are the first three namely benzene, toluene and xylene, which at normal temperatures are clear colourless liquids having very similar properties. Crude benzol also contains some amount of naphthalene (C10H8). Crude benzol is also known as light oil and contains small quantities of a large number of impurities which consists of the unsaturated and sulphur compounds. These impurities have negative effects on the organic processes. Even insignificant sulphur impurities in benzene and toluene used in organic processes cause fast poisoning of the catalyst, and resinous...

Comparison of By-product Coke Ovens and Heat Recovery Coke Ovens...

Comparison of By-product Coke Ovens and Heat Recovery Coke Ovens There are three proven processes for the carbonization of coal for the production of metallurgical coke. These are (i) beehive oven process, (ii) the by-product coke oven process, and (ii) the heat recovery coke oven process. The heat recovery coke oven process is also known as non-recovery or energy recovery coke oven process. It is a modification of the beehive oven process and, and hence, it has largely phased out the beehive oven process. Thus, for the carbonization of the metallurgical coal the only two cokemaking technologies which are being used are (i) the by-product coke oven technology, and (ii) heat recovery (HR) coke oven technology. Both of these cokemaking technologies offer opportunities to produce high quality coke and to develop the energy balance while achieving the lowest possible operating cost. The by-product coke ovens are prone to high level of pollution because of the positive pressure maintained in them. The stringent pollution laws and the high cost involved in the installation of pollution control equipment led to the revival of interest in the non-recovery coke oven technology during 1980s and 1990s. These non-recovery coke ovens complied with the stringent pollution control regulations. These non-recovery coke ovens are the heat recovery ovens since they are used not only for the production of coke, but also for the generation of power by means of waste gas heat recovery. Hence, the heat recovery type of coke ovens is energy efficient and environment friendly. The selection of the appropriate technology for a particular situation needs a careful study since many different factors can affect the decision, including, for example, availability of land, plant energy balance and available energy sources and their costs, steel plant configuration and energy...

Coal Tar and its Products...

Coal Tar and its Products Coal tar is a by-product generated during the high temperature carbonizing of coking coal for the production of the metallurgical coke in the by-product coke ovens. It is a black, viscous, sometimes semi-solid, fluid of peculiar smell, which is condensed together with aqueous ‘gas-liquor’ (ammoniacal liquor), when the volatile products of the carbonization of coking coal are cooled down. Its CAS number is 8007-45-2. It is acidic in nature and is water insoluble. Coal tar represents a mixture of condensable volatile products formed during the destructive distillation of bituminous coal. Composition is variable, but generally consists of 0 % to 2 % of light oils (chiefly benzene, toluene, and xylene), 16 % to 18 % of middle oils (chiefly phenols, cresols, and naphthalene), 8 % to 10 % heavy oils (naphthalene and derivatives), 16 % to 20 % anthracene oils, and around 50 % pitch. It is composed primarily of a complex mixture of condensed-ring aromatic hydrocarbons. It can contain phenolic compounds, aromatic nitrogen (N2) bases and their alkyl derivatives, and paraffinic and olefinic hydrocarbons. Coal tar is a complex mixture of chemical compounds, mainly consisting of the aromatic series. Both the method by which the coal tar is produced and the nature of the raw material (coal) influence to a wide extent the chemical composition and physical properties of the coal tar. The specific gravity of coal tar at 15 deg C varies between 1.12 and 1.20, depending upon the temperature of carbonization or kind of coke ovens used. In exceptional cases it can go upto 1.25. The coal tar with lower specific gravity is generally produced when low carbonization temperatures are used. Viscosity of the coal tar is affected in a similar manner. The heavier tars contain...