Waste Plastics injection in a Blast Furnace Nov14

Waste Plastics injection in a Blast Furnace...

Waste Plastics injection in a Blast Furnace The recycling of waste plastics (WP) by injecting them in a blast furnace (BF) is being practiced in few BFs especially in japan and Europe. The use of plastics in the BF also recovers energy from the WP and so it is sometimes considered as energy recovery. BF based ironmaking processes can utilize WP by any of the following methods. Carbonization with coal to produce coke. Top charging into the BF, although this generates unwanted tar from the decomposition of the plastics in the shaft. Gasifying the plastics outside the BF. The resultant synthesis gas is then injected through the tuyeres. Injection as a solid through the tuyeres in a similar way to pulverized coal (PC). Normally it is done as a co-injection of WP and coal into the BF. The first attempt for the waste plastics injection (WPI) in a BF was made at the Bremen Steel Works in 1994, with commercial injection starting a year later. The first integrated system for injecting plastic wastes was at NKK’s (now JFE Steel) Keihin Works in Japan. Injecting WP into BF has several environmental, operational and economic advantages. These include the following. Reduction in the amount of plastic wastes being landfilled or incinerated. Lower consumption of both coke and PC, thus saving coal resources. However, neither WP nor PC can completely replace coke. The amount of coke replaced in the BF is partly dependent on the quality of the WP. There is energy resource savings. The benefit of saved resources from mixed WPI is around 11 giga calories per ton (Gcal/t). There is decrease in the carbon dioxide (CO2) emissions since the combustion energy of WP is generally at least as high as that of PC normally injected,...

Understanding Blast Furnace Ironmaking with Pulverized Coal Injection Nov04

Understanding Blast Furnace Ironmaking with Pulverized Coal Injection...

Understanding Blast Furnace Ironmaking with Pulverized Coal Injection Injection of pulverized coal in the blast furnace (BF) was initially driven by high oil prices but now the use of pulverized coal injection (PCI) has become a standard practice in the BF operation since it satisfies the requirement of reducing raw material costs, pollution and also satisfies the need to extend the life of ageing coke ovens. The injection of the pulverized coal into the BF results into (i) increase in the productivity of the BF, i.e. the amount of hot metal (HM) produced per day by the BF, (ii) reduce the consumption of the more expensive coking coals by replacing coke with cheaper soft coking or thermal coals, (iii) assist in maintaining furnace stability, (iv) improve the consistency of the quality of the HM and reduce its silicon (Si) content, and (v) reduce greenhouse gas emissions. In addition to these advantages, use of the PCI in the BF has proved to be a powerful tool in the hands of the furnace operator to adjust the thermal condition of the furnace much faster than what is possible by adjusting the burden charge from the top. Pulverized coal has basically two roles in the operation of a BF. It not only provides part of the heat required for reducing the iron ore, but also some of the reducing gases. For understanding the HM production in a BF with the injection of pulverized coal, it is necessary to understand what is happening inside the BF as well as the chemical reactions and the importance of permeability within the furnace and how the raw materials can affect this parameter. The BF is essentially a counter-current moving bed furnace with solids (iron ore, coke and flux), and later molten...

Understanding Pulverized Coal Injection in Blast Furnace Oct21

Understanding Pulverized Coal Injection in Blast Furnace...

Understanding Pulverized Coal Injection in Blast Furnace Pulverized coal injection (PCI) is a well-established technology for hot metal (HM) production in a blast furnace (BF). It is practiced in most of the BFs and all the new BFs are normally built with PCI capability. The composition and properties of the coal used for injection can influence the operation, stability and productivity of the BF, the quality of the HM, and the composition of the BF gas. The coals being used for the PCI are described in the article under link ‘http://ispatguru.com/coal-for-pulverized-coal-injection-in-blast-furnace/’. The critical aspects of PCI systems include coal preparation, its storage and distribution to ensure uniform feed of coal to each tuyere without fluctuations in the coal delivery rate and its combustion through lance design and oxygen (O2) injection. Coal preparation Pulverization of coal is carried out in a single or multiple grinding mills (pulverizers) depending on the requirements. Grinding and distribution of the coal to the injection lances constitute a major operating cost. Coal reclaimed from coal storage is screened for the removal of the foreign material and any large lump of coal is crushed. The coal is then fed into the mill where it is pulverized and dried. Coal of the required size is transported out of the mill by the hot gas stream, collected in a bag filter and conveyed to the storage bins. Grinding and transport are carried out under an inert atmosphere to minimize the risk of ignition of the dry coal particles. The resultant particle size distribution of the pulverized coal affects it handleability in pneumatic transport equipment and, at high injection rates, its combustibility. Pulverizers grind coal to one of the two size fractions namely (i) pulverized coal where around 70 % to 80 % of...

Gravity separation and Ore Beneficiation Oct12

Gravity separation and Ore Beneficiation...

Gravity separation and Ore Beneficiation Gravity separation is the oldest known ore beneficiation technique and is practiced extensively in ‘Nature’. Earliest recorded human use of gravity separation was recovery of gold by panning from the Upper Nile by ancient Egyptians, dating back to 1900 BCE. Gravity separation is a physical process which consists of the separation of different mineral types in the ore from one another based on differences in their specific gravities using the force of gravity, which can be influenced by one or more of other forces such as centrifugal force, resistance to motion by a fluid (e.g. air, water) etc. Hence, besides gravity, other factors, such as size, shape etc., also have an influence on the relative motion and thus in the separation. The effect of centrifugal action on the gravity force is given at Fig 1. It can be seen that as the gravity force increases, settling velocity of smaller particles becomes higher. Fig 1 Effect of centrifugal force on gravity force Separation of the ore particle by gravity is dependent on two factors namely (i) settling rate of the particles, and (ii) difference in specific gravity when compared against the medium in which they are being separated, this gives differential settling rate and has been termed the ‘concentration criteria’.Settling rate of a particle is dictated by ‘Stoke law’ and is equal to kd2g(Ds-Df), where k is a constant, d is particle diameter, g is force of gravity, and Ds is the specific gravity of solid and Df is the specific gravity of the fluid medium. The ‘concentration criteria’ (CC) gives an idea of the amenability of separation of two ore particles and can be expressed by (Dh-Df)/(Dg-Df) where Dh is the specific  gravity of heavier component of the ore,...

Magnetic Separation and Iron Ore Beneficiation Oct04

Magnetic Separation and Iron Ore Beneficiation...

Magnetic Separation and Iron Ore Beneficiation Magnetic separation is an old technique for the concentration of iron ores and for the removal of tramp iron. Since 1849, a number of patents on magnetic separation have been issued in USA, and texts of some of the patents before 1910 describe a variety of magnetic separators for mineral processing. Magnetic separation methods are used to take the advantage of the difference in the magnetic properties for separating iron ore from the non-magnetic associated gangue materials. Magnetic separation can be conducted either in a dry or in a wet environment, although wet systems are more in use. Magnetic separation is a physical separation of discrete particles based on the three way competition between tractive (i) magnetic forces, (ii) gravitational, hydro-dynamic drag, frictional, or inertial forces, and (iii) attractive or repulsive inter-particle forces. These forces combine to act differentially on particles of differing magnetic properties in the feed material. Fig 1 shows the principle of the magnetic separation. Fig 1 Principle of magnetic separation The forces in the magnetic separators which compete with the magnetic forces and act on all of the particles which travel through the separator are those of gravity, hydrodynamic drag, friction, and inertia. Depending on the type of magnetic separator, certain of these forces can have higher or lesser importance. The gravitational force is significant for large particles while the hydrodynamic drag force is significant for the small particles. Thus in the magnetic separator which treats large particles in dry form, the feed material passes through the force of gravity. The magnetic forces need to be sufficient to hold the magnetic particle against the competing force of gravity. In a wet separator for small particles, the magnetic force need to be larger than the...

Low grade Iron Ore Beneficiation and the Process of Jigging Sep25

Low grade Iron Ore Beneficiation and the Process of Jigging...

Low grade Iron Ore Beneficiation and the Process of Jigging Iron ore resources are getting consumed at an accelerated rate because of the growth in the production of iron and steel. Due to this reason the availability of high grade iron ore is reducing and the supply of high grade iron ore to iron and steel plants is declining sharply. Hence, the scenario is steadily shifting towards the use of low grade iron ores and slimes which are stock piled in the mine’s sites for years. These dumped slimes also, in fact, falls in the category of low grade iron ore.  Also, some of the ores of iron have a complex mineralogical composition and do not respond to conventional beneficiation techniques. Modern beneficiation processes allow for effective and low cost upgrading of lump, fines and ultra-fines of such ores. Since the iron ores consist of several compositions, mineralogies, shapes, and sizes, so there is no ‘one size fits all’ approach to the beneficiation of iron ore. Most of the ‘run-of-mine’ (ROM) iron ore contain a large percentage of other materials which need to be removed through the process of beneficiation before the ore attains the specifications needed for its use. The extent of the beneficiation techniques employed depends on the level and nature of diluents and the form of distribution of the gangue and impurities in the ore structure. Liberation of ore is an essential step for making it responsive to the beneficiation techniques. For selection of appropriate techniques, it is necessary to carry out first the mineralogical assessment of the ore so as to get the insight into the ore and to know the gangue association, and grain size etc. There are several issues relating to categorization and beneficiation of low grade iron...