Selection of Coal for inclusion in Coal Blend in Coke Making Sep26

Selection of Coal for inclusion in Coal Blend in Coke Making...

Selection of Coal for inclusion in Coal Blend in Coke Making Blending of coals is necessary from economical point of view by reducing the percentage of high cost, prime or hard coking coals and replacing it with medium or soft coking coals. In some coke oven plants even a small percentage of non-coking or steam coals have also been used in the blend. Selection of a proper coal blend for use in by product coke ovens is always a big challenge for the coke producer since the blend has to meet the following requirements. It is to meet the requirement of crushing during coal preparation. All the components of the coals are neither be over crushed or under crushed. The sized coal blend for charging the coke ovens is to meet the requirements of density, flow, and the size fractions. It is to have necessary coking and caking properties for producing coke of quality which meets the quality requirements of blast furnace (BF) coke. The three basic quality requirements of BF coke are (i) to provide heat for the endothermic reactions taking place in the blast furnace, (ii) to act as a reducing agent by producing the necessary reduction gases, and (iii) to provide a permeable support in the BF for the iron bearing burden. It is to provide safe pushing performance in coke ovens. It must not put excessive pressure on coke oven walls during the process of coking and damage them. It should meet the yield requirements not only of BF coke but also of coke oven gas. A proper coal blend will not produce excessive nut coke and coke breeze. It is to be economical. In view of the above varied types of requirements, the decisions regarding coal blends are not...

Understanding Coke Making in Byproduct Coke Oven Battery Mar09

Understanding Coke Making in Byproduct Coke Oven Battery...

Understanding Coke Making in Byproduct Coke Oven Battery  Coke is one of the basic materials used in blast furnaces for the conversion of iron ore into hot metal (liquid iron), most of which is subsequently processed into steel. The major portion of coke produced is used for the production of hot metal. Coke is also used by a number of other industries, namely iron foundries, nonferrous smelters, and chemical plants. It is also used in steel making as a carburizing material. Coke and coke by-products, including coke oven gas, are produced by the pyrolysis (heating in the absence of air) of suitable grades of coal. The process also includes the processing of coke oven gas to remove tar,  ammonia (usually recovered as ammonium sulphate), phenol, naphthalene, light oil, and sulphl, and sulfs under links n of coal)  period.e doorg nitrogen gas is used for the production of steam and then power.ur before the gas is used as fuel for heating the ovens. The coke making industry consists of two sectors, integrated plants and merchant plants. Integrated plants are owned by or affiliated with iron-and steel producing plants who produce blast furnace coke primarily for consumption in their own blast furnaces. Independent merchant plants produce furnace and/or foundry coke for sale in the open market. These plants sell most of their products to other plants engaged in blast furnace, foundry, and nonferrous smelting operations. A good quality coke is generally made from carbonization of good quality coking coal. Coking coals are defined as those coals that on carbonization pass through softening, swelling, and re-solidification to coke. One important consideration in selecting a coal blend is that it should not exert a high coke oven wall pressure and should contract sufficiently to allow the coke to...

Silica Refractories

Silica Refractories Silica refractories were first produced in United Kingdom in 1822 from Ganister (caboniferous sandstone) or from so called Dinas sand. Silica occurs in a variety of crystalline modifications, e.g. quartz, tridymite, and cristobalite and also as an under-cooled melt called quartz glass. The crystalline modifications each have a high and low temperature forms which can transform reversibly. The crystal structure of the individual SiO2 modifications can differ widely, so that distinct density changes occur during transformation. This is of great importance during heating and cooling because of the change in the volume. Quartz requires the smallest volume and the quartz glass the largest. During firing above approximately 900 deg C, quartz transforms into the other modifications and melt completely at 1725 deg C. During slow cooling , reversible volume decreases take place  which are a result of the spontaneous transformation of the crystal structure from the high to the low temperature modification (Fig 1). The reversible and irreversible volume effects can cause considerable stress within the refractory brick structure. Fig 1 Calculated volume and density changes Production of silica refractories The silica refractories are manufactured as multiple asymmetric shapes, which are normally keyed or interlocked with each other by means of tongues and grooves. It is the objective of the manufacturer of silica refractory bricks to select the raw materials and the firing process in such a manner that the degree of quartz transformation is suitable for the intended application of the brick. The raw material for silica brick is naturally occurring quartzite which must meet certain requirements in order to achieve optimum brick properties. If refractoriness or thermal expansion under load (creep) are the main requirements, a quartzite of high chemical purity must be selected. Raw materials for volume stable products...

Carbonization of Coal for Metallurgical Coke Production Nov15

Carbonization of Coal for Metallurgical Coke Production...

Carbonization of Coal for Metallurgical Coke Production Carbonization of coal is also known as coking of coal. The process consists of thermal decomposition of coals either in the absence of air or in controlled atmosphere to produce a carbonaceous residue known as coke. Carbonization of coal can be carried out at the following three temperature ranges. Low temperature carbonization is normally carried out in the temperature range of 500 deg C to 700 deg C. In this type of carbonization, the yields of liquid products are higher and there is lower gaseous product yield. The coke produced is having higher volatile matter and is free burning. Medium temperature carbonization is done at temperature range of around 800 deg C. This carbonization produces smokeless soft coke. By products produced are similar in characteristics to high temperature carbonization. Medium temperature carbonization is rarely practiced these days. High temperature carbonization is carried out at a temperature which is above 900 deg C. This carbonization gives higher yield of gaseous products and lower yield of liquid products. This carbonization produces hard coke and is normally employed for the production of metallurgical coke from coking coals. Process of carbonization of coal The coal to coke transformation takes place as the coal is heated. When the state of fusing is reached, the layer of heated coal softens and fuses. From about 375 deg C to 475 deg C, the coal decomposes to form plastic layer.  Destructive distillation reactions proceed rapidly in the plastic layer with evolution of volatile products. At about 475 deg C to 600 deg C, there is a marked evolution of tar, and aromatic hydrocarbon compounds. The gas and condensable vapour are entrapped in the plastic mass and, as they expand tend to swell it. As the...