Coal Tar and its Distillation Processes Dec26

Coal Tar and its Distillation Processes...

Coal Tar and its Distillation Processes Coal tar, also known as crude tar, is the 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. It is acidic in nature and is water insoluble. 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. In the process of coal carbonization the constituents of the tar escape from the coke ovens in the form of vapour, with a little solid free carbon (C) in an extremely finely divided state. The tar is precipitated in the hydraulic main, in the condensers, and scrubbers etc., in a liquid state, at the same time as the ammoniacal liquor is formed. The tar formed in the hydraulic main is, of course, poorer in the more volatile products than that formed in the condensers and scrubbers, and is consequently much thicker than the latter. The normal yield of coal tar during the coal carbonizing process is around 4 %. Coal tar has a specific gravity normally in the range of 1.12 to 1.20, but exceptionally it can go upto 1.25. It depends on the temperature of carbonization. The lower specific gravity tars are generally produced when low carbonization temperatures are used. Viscosity of tar affected similarly. The heavier tars contain lesser benzol than the lighter tars, and more fixed carbon. The nature of the raw material and the temperature of carbonization affect the chemical composition,...

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...

Management and Managers...

Management and Managers Management is an important part of an organization. In fact the discipline of management is developed over a period of time to its present level. On the other hand managers of tomorrow are developed from the young, educated people who are knowledge workers of today. Both the management and the managers are vital component of the organization for its smooth functioning. Present day society has become a ‘knowledge society’, a ‘society of organizations’, and a ‘networked society’. Today, the major social tasks are being performed in and through structured organizations, large and small, of all kinds and sizes. And every organization is entrusted to ‘managers’ who practice the ‘management’. History of management The word ‘management’ was first popularized by Frederick Winslow Taylor to describe what he had formerly (and more accurately) called ‘work study’ or ‘task study’ which is today being called ‘industrial engineering’. But when Taylor talked about what is being called today ‘management’ and ‘managers’, he said ‘the owners’ and ‘their representatives’. The roots of the discipline of management go back to more than 200 years. But management as a function, management as a distinct work, management as a discipline and area of study, all are the products of the twentieth century. And most people became aware of management only in 1950s. Some recent studies on management give the impression that the management is an invention of late 1940s. True, before this period interest in and study of management was confined to small groups. The popular interest in management as a discipline and a field of study is fairly recent. But management, both as a practice and as a field of study, has a respectable history, in many different countries, going back almost two centuries. When the early economists,...

Coking Pressure Phenomena and its Influencing Factors Dec17

Coking Pressure Phenomena and its Influencing Factors...

Coking Pressure Phenomena and its Influencing Factors Coking pressure is a phenomenon which has become important because of the use of the double-heated wall, vertical, slot-type coke ovens. In the round beehive ovens as well in the heat recovery coke ovens, which are also being used for coke production, the coal can freely expand upwards and thus the swelling of the charge is accommodated by this free expansion. On the other hand, in the slot-type coke ovens, the expansion of the coal horizontally to the heated wall is restricted. There are several cases of premature failure of oven walls during the coal carbonization process. The erection of the new, larger and taller coke ovens has been accompanied by undesirable occurrences of distorted walls due to the coking pressure resulting in several studies regarding the expansion behaviour of coal during carbonization. The efforts have been focused on developing a reliable test so that coal blends can be tested for safety prior to their use in the coke ovens. Development of coking pressure During carbonization process, coal passes through the plastic stage and volatile matter (VM) evolves during and, to a lesser extent, after that stage. It is normally accepted that coking pressure arises in the plastic stage. In a coke oven chamber, two vertical plastic layers parallel to the heating walls are formed from the beginning of carbonization. As the carbonization proceeds these layers move towards the centre of the oven. At the same time, similar horizontal layers are formed at the top and bottom of the charge. These are joined with the two vertical layers and the whole forms a continuous region that surrounds the uncarbonized coal and it is usually referred to as the ‘plastic envelope’. The permeability of the plastic layers is...

Properties and Structure of Metallurgical Coke...

Properties and Structure of Metallurgical Coke Metallurgical coke is a porous, fissured, silver-black solid and is an important part of the ironmaking process since it provides the carbon (C) and heat required to chemically reduce iron burden in the blast furnace (BF) to produce hot metal (HM). It is a porous C material with high strength produced by carbonization of coals of specific rank or of coal blends at temperatures around 1100 deg C in coke ovens. It is composed of both the organic and inorganic matter. C is the major component of the organic part. Small amounts of sulphur (S), nitrogen (N2), hydrogen (H2) and oxygen (O2) also occur in the organic part. The inorganic matter in coke is called coke ash (mineral matter) and is typically around 12 % on dry basis. Both the organic and inorganic components influence coke reactivity. Thus, coke characterization is an important aspect to understand the quality of coke formed. The basic understanding of coke quality is an important task as it determines the high temperature and gasification behaviours of coke in the blast furnace (BF). As the coke moves towards the lower zones of BF, it degrades and generates fines, which affects the bed permeability and the process efficiency. Hence, superior coke quality is critical for a stable and efficient BF operation. Coke quality is influenced by many factors such as the rank, the maceral composition (leading to isotropic or anisotropic coke structures), the ash composition and the fluidity of the starting coals, the carbonization conditions including peak temperature, heating rate, particle size, pressure and bulk density as well as heat treatment conditions. The important properties of coke, including mechanical strength and reactivity, are governed by the arrangement of the constituent C atoms. The principal features...