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...

Ammonium Sulphate – A By-product of Coal Coking Process...

Ammonium Sulphate – A By-product of Coal Coking Process Ammonium sulphate is produced as a by-product during removal of ammonia (NH3) from the raw coke oven gas generated during the coking of the metallurgical coal in by-product coke ovens. Its industrial production began over a century ago, as by-product in gas cleaning in coke and coal gasification plants. Ammo­nium sulphate is produced as crystals. It is an organic, white odorless solid and crystalline salt with a number of commercial uses. It contains around 21% nitrogen (N2) and 24% sulphur (S). The Chemical Abstracts Service (CAS) registry number for ammonium sulphate is 7783–20–2. Its EC number is 231-984-1. Its IUPAC ID is Diazanium sulfate. It is currently classifiable under Harmonized Tariff Schedule of the United States (HTSUS) subheading 3102.21.0000. This process by which ammonium sulphate is produced consists of absorption of ammonia in the coke oven gas in a solution of ammonium sulphate and sulphuric acid. The absorption reaction is 2NH3 + H2SO4 = (NH4)2SO4. The ammonium sulphate produced by the reaction of NH3 with H2SO4 is recovered by crystallization. The crystals are then centrifuged, washed and dried. Since ammonium sulphate is produced as a by-product during the recovery of ammonia from coke oven gas, there are normally a lot of impurities from different sources. These are organic impurities as well as the inorganic impurities. The combined effects of these impurities are complex and influence the purity and the crystal shape and size. Ammonium sulphate is available in a variety of grades, including granular and standard grades. Granular grade accounts for the vast majority of the market.  Its relatively large particle size (typically 2.5 mm) makes it well suited for mixing with other fertilizers and application by spreading machines.  Standard grade has a smaller particle size (less than 2 mm) and...

Hydrogen gas and its use in Iron and Steel industry...

Hydrogen gas and its use in Iron and Steel industry Hydrogen is a chemical element, ranking first in the periodic table with element symbol of ‘H’. The (atomic number of hydrogen element is 1 and atomic weight is 1.008. It is the smallest atom in the universe and the simplest element in nature. Its molecule consists of two hydrogen atoms. It is the lightest gas, being about 1/14 times as dense as air. It has three isotopes named (i) protium, (ii) deuterium, and (iii) tritium. Pure hydrogen is odourless, colourless and tasteless. Hydrogen has lowest atomic weight of any substance and therefore has very low density both as a gas and a liquid. The vapour density of hydrogen at 20 deg C and 1 atmosphere pressure is 0.08376 kg/cum. The specific gravity of gaseous hydrogen is 0.0696 and hence, it has around 7 % the density of air. The density of liquid hydrogen at normal boiling point and 1 atmosphere pressure is 70.8 kg/cum. The specific gravity of liquid hydrogen is 0.0708 and is thus, it has around 7 % the density of water. Hydrogen is a liquid below its boiling point of -253 deg C and a solid below its melting point of – 259 deg C at atmospheric pressure. It is non-toxic but can act as a simple asphyxiant by displacing the oxygen in the air. When hydrogen is stored as a high-pressure gas at 250 kg/cum and atmospheric temperature, its expansion ratio to atmospheric pressure is 1:240. The molecules of hydrogen gas are smaller than all other gases, and it can diffuse through many materials considered airtight or impermeable to other gases. This property makes hydrogen more difficult to contain than other gases. Leaks of liquid hydrogen evaporate very quickly since the...

Coal Tar Pitch

Coal Tar Pitch  Coal tar pitch, derived from by-product coke ovens, is the preferred material for use as a binder in the manufacture of carbon and graphite electrodes. Coal tar pitch is a coal conversion product. Its IUPAC name is ‘Coal Tar Pitch, High temperature”. Its CAS number is 65996-32-2 and EINECS number is 266-028-2. It is the shiny, dark-brown to black residue produced by distillation of coal tar. Coal tar pitch contains a large number of substances. It is solid at room temperature and consists of a complex mixture of numerous polycyclic aromatic hydrocarbons (PAHs), their methyl and polymethyl derivatives, and heterocyclics, and shows a broad softening range instead of a defined melting temperature. The hydrogen (H2) aromaticity of coal tar pitch (ratio of aromatic to total content of H2 atoms) varies from 0.7 to 0.9. Production of coal tar pitch Coal tar pitch is currently produced from coal tar, which is a byproduct of high temperature coking of coal in the manufacture of metallurgical coke. The tar predominantly contains a mixture of bi- and poly-condensed aromatic hydrocarbons and also compounds with heteroatoms in rings (predominantly nitrogen bases from the quinoline and acridine series, 1 % to 2 %) and phenols (1 % to 2 %). Upon distillation, 8 % to 12 % of a naphthalene fraction, 5 % to 9 % of an absorption fraction, and 21 % to 26 % of an anthracene fraction, which boiled away to 360 deg ?, are separated. The residual part of the tar is the pitch which contains nonvolatile and low volatile substances, whose average yield is around 2 % of the coking coal charge used for high temperature carbonizing. The industrial production of coal tar pitch consists of the fractional distillation of the coal...

Coal Ash

Coal Ash Coal ash is the mineral matter present in the coal. It is a waste which is left after coal is combusted (burned). It is the particulate material which remains after coal is burned. It includes fly ash (fine powdery particles which are carried up the smoke stack and captured by pollution control devices) as well as coarser materials which fall to the bottom of the furnace. It has different physical and chemical properties depending on the geochemical properties of the coal being used and how that coal is burned. Coal ash is also referred to as coal combustion residuals. It has very little organic fraction. Chemical constituents of coal ash may include nitrogen (N2), sulphur (S), unburned carbon (C), heavy metals, radioactive elements, and polycyclic aromatic hydrocarbons (PAHs). Coal ash also contains coarse particles and fine particles which can be inhaled and may contribute to public health and environmental problems. Coal ash contains many toxic contaminants. When coal ash spills, leaks or leaches into nearby ground water or waterways, the toxins contained within pose serious health risks to nearby communities. Depending on where the coal was mined, coal ash typically contains heavy metals including arsenic, lead, mercury, cadmium, chromium and selenium, as well as aluminum, antimony, barium, beryllium, boron, chlorine, cobalt, manganese, molybdenum, nickel, thallium, vanadium, and zinc. If eaten, drunk or inhaled, these toxicants can cause cancer and nervous system impacts such as cognitive deficits, developmental delays and behavioral problems. They can also cause heart damage, lung disease, respiratory distress, kidney disease, reproductive problems, gastrointestinal illness, birth defects, and impaired bone growth in children. A large amount of coal ash is disposed in dry landfills, frequently at the power plant where the coal was burned. Coal can also be mixed with...