Properties and Uses of Steelmaking Slag...

Properties and Uses of Steelmaking Slag Steelmaking slag is an integral part of the steelmaking process. It is produced during the separation of the liquid steel from impurities in steelmaking furnace and is a non-metallic by-product of steelmaking process. It occurs as a molten liquid melt and is a complex solution of silicates and oxides which solidifies upon cooling. It primarily consists of silicates, alumina silicates, calcium aluminum silicates, iron oxides and crystalline compounds. During steelmaking, slag is produced in the hot metal pretreatment processes (desulphurization, desiliconization, and dephosphorization etc.), in the primary steelmaking processes (basic oxygen furnace, electric arc furnace, and induction furnace), slag formed during the secondary refining processes (this slag is sometimes called ?secondary refining slag? or ?ladle slag?), and slag formed in tundish during continuous casting of steel (also known as tundish slag). The slag generated in the basic oxygen furnace (BOF) and electric arc furnace (EAF) is of basic nature while the slag is of acidic nature in induction furnace because of the use of silica ramming mass as the lining material. Since most of the steel produced in the world is by BOF and EAF processes, hence slag from these processes is discussed in this article. The processing of the steelmaking slag (Fig 1) is normally carried out by (i) solidifying and cooling of the hot liquid slag, (ii) crushing and magnetic separation treatment of the slag to recover the scrap, (iii) crushing and classification of the slag for grain size adjustment to manufacture the slag product, and (iv) aging treatment of the slag product for improving its quality and volumetric stability. These processes are explained below.   Fig 1 Processing of steelmaking slag As steelmaking slag is formed, it is in a molten or red-hot state at...

Planning for Organizational Future...

Planning for Organizational Future Future is always unpredictable (Fig 1), though it is an important aspect for planning for an organization. Future can be described only by two things namely (i) it is not known in the present and only people can make a guess about it, and (ii) it is going to be different than what exists today and from what is expected now. Fig 1 Unpredictable future The above statements are not principally new or particularly unusual. But these statements have far-reaching following implications. If present day actions and commitments are based on the predictions of future events then these are wasted attempts. The best thing which the people can hope to do is to anticipate the future effects of the events which have already permanently taken place. But it does not precisely mean that because the future is going to be different and cannot be predicted, people continue to function in the present way with the comfortable assumption that nothing is going to change. Though it is risky to make the unexpected and unpredicted future, still it is a normal activity. And it is less risky than sailing along on the comfortable assumption that nothing is going to change and also less risky than following a possibility of ‘what must happen’ or ‘what is most probable’. Management is required to accept the need to work systematically on making of the organizational future. But this does not mean that the management can work for the elimination of risks and uncertainties since this is not feasible. The one thing the management can try to do is to find, and occasionally to create, the right risk and to exploit uncertainty. The purpose of the work on making the future is not to decide what...

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,...

Hot Metal

Hot Metal Hot metal (HM) is the output of a blast furnace (BF). It is liquid iron which is produced by the reduction of descending ore burden (iron ore lump, sinter, and pellet) by the ascending reducing gases. HM gets collected in the hearth of the BF. From the hearth, the HM is tapped from the taphole of the BF after an interval of time. Normally in large BFs, HM tapping rates of 7 ton/min and liquid tapping velocities of 5 m/sec, in tap holes of 70 mm diameter and 3.5 m long, are typically encountered. The tapping rate of HM is strongly influenced by the taphole condition and taphole length. Generally the temperature of tapped HM varies in the range of 1420 deg C to 1480 deg C. The tapped HM is handled in the two stages namely (i) handling of the HM in the cast house i.e. from taphole to the hot metal ladles (open top or torpedo), and (ii) transport of HM ladles to the point of HM consumption. Presently most of the HM is consumed within integrated steel plants for steel making. The HM is transferred to the steel melting shop for making of steel. The HM which is not sent for steel making is cast into pig iron in pig casting machine for use in steel making later as cold charge or is sold to foundries or to mini steel plants having induction furnaces as merchant pig iron. HM can also be granulated by a process which is known as ‘Granshot’ process. Presently the Granshot plants for the production of GPI are working at six places namely (i) Uddeholm, Sweden, (ii) SSAB Lulea, Sweden, (iii) Voest Alpine, Donawitz, (iv) Saldanha steel, South Africa, (v) SSAB Oxelosund, Sweden, and (vi)...

Task and Work Oriented Organizational Structure...

Task and Work Oriented Organizational Structure The organizational structure for the organizing of the activities and reporting relationships can be organized in five distinct methods (Fig 1). These are (i) structure based on functions, (ii) team organization, (iii) decentralized structure, (iv) simulated decentralization, and (v) systems structure. The first two of them are traditional structures while the remaining three are new ways of organizing the organizational activities. Fig 1 Methods for organizing and reporting relationships for an organization structure Each of the above five structures have been developed to meet specific needs. Hence, one may get an impression that each of them suits certain convenience and does not represent any reasoning. But in reality, each of these structures expresses different type of reasoning. Each takes one general aspect of managerial organization and builds a structure around it. Organization structure is needed to satisfy the minimum requirements with respect to (i) clarity, (ii) economy, (iii) direction of vision, (iv) understanding by the employees of their own task and the common task, (v) decision making, (vi) stability and adaptability, and (vii) maintenance and self-renewal. These are described below and given in Fig 2. Clarity – Clarity means that all the managerial components, and all the employees within the organization, particularly all the executives, need to know where they belong, where they stand, where they have to go for whatever is needed, whether it is information, cooperation, or decision. Clarity is not to be confused with simplicity. Actually, structures which appear simple may lack clarity. And apparently complex structures can have complete clarity. A structure in which the employees do not know without an elaborate organizational manual where they belong, where they have to go, and where they stand creates friction, wastes time, causes disputes and frustration,...