Material Handling is the movement and control of materials throughout a process within a manufacture, distribution or consumption. Using material handling systems industries can have extraordinary effects on the cost, space and time utilization and that what makes it special. In this paper, an attempt to show how crucial this technology is when it comes to the iron and steel industry. Since the iron and steel industry carries enormous weight all the time, it requires a high diversity of material-handling equipment. Raw materials and finished products are constantly being moved by a heavy conveying machinery of all descriptions. The material handling is one important point in this industry because the process of moving and stocking material could have a really high cost.
Basically, steel is a metal made from iron and carbon. Iron is found throughout the earth, associated with oxygen and silica. Carbon is also richly found in nature and can be found in various forms.The steelmaking process starts processing of iron ore,which is iron oxide, sanded with fine sand. The iron ore is extracted directly from the ground using magnetic rollers and then they are grained and prepared properly to be used in the blast furnace. The next step is to clean coal impurities in a coke furnace. Once they are cleaned, the coal is in an almost pure form of carbon . The process of removing the oxygen from the iron is called direct reduced iron(DRI) and happened in a blast furnace. In the reduction process, the iron turns liquid and the pig iron is produced. From iron impurities slag is also produced. The next step in the process is refining. The pig iron goes to the steelworks, in a liquid state, to be transformed into steel by burning impurities and additions. The steel passes through continuous rollers and it is transformed into billets, blooms and slabs Finally, the steelmaking process of lamination. In this process, the steel is mechanically deformed and transformed into steel products processed by the processing industry. After the deformation, billets are transformed into rods and bars, blooms into beams and other structural shapes and slabs into flat products.
The process of the iron and steel industry (see Figure 1) is described and can be understood from the begging to the end detailed 1.
Figure 1: Detailed processes in the Iron and Steel industry
The raw material of a steelworks is the initial stage of a production cycle, whose final product is the steel. Considering this fact, it is always necessary to guarantee these raw materials has high quality and operability and a reasonable cost. The reason that has to be taken into account is because the quality and cost of the final product, in principle, are compromised in this initial stage of the steel process. If you have a lower grade raw material in the beginning of you process that will affect your final product quality as well. Another disadvantage is that the use of lower grade iron ore in the blast furnace process requires additional energy and coal. It also produces more slag and their emissions have proportionately higher rate than with quality materials, and reduces productivity 2. A major technical study called ‘Raw Materials Improvement in the Steel Industry’ has recently been completed by The World Steel Association 2. The project deals with the issues when lower grade raw materials are used. Raw materials improvement has been done upgrading existing raw materials handling and iron-making processes 2.
The objective of this paper is mainly to show how the raw material of the iron and steel industry is moved through the material handling system and how important this system is. In addition, the beginning of the manufacturing process comes from the raw material is in all industries but most people do not know the importance of them to successfully complete a process.
• Overhead traveling cranes are found in almost all areas of steelworks. This kind of equipment works moving from one direction to another, always in parallel runaways with a traveling bridge spanning the gap. Fixed-rail equipment and large industrial tractors are also using for transportation within this kind of industry 3.
• Steel production involves mainly, raw material, energy supply, and investment capital, consequently, the costs of those areas should be closely controlled 4.
• A small detail can affect the efficiency and safety of a plant that is the reason the design of custom material handling products is so important 5. Each industry has different needs due to different processes and plant type. Thinking about that, the design of a material handling equipment specifically for an industry comes to be necessary. In our current industrial scenario, the fabrication of a specific machine is becoming every day easier since companies are specializing in the design of a material handling equipment that suits perfectly a determined industry.
• The production of high-quality sinter is crucial to guarantee consistent, stable furnace productivity with a low consumption of reductants 6. Since the sinter is the primary material for making iron, it requires quality from making the proper selection to mixing it. If raw materials are poorly mixed it can affect permeability and also increase fuel consumption.
• The most popular construction material because of its unique combination of durability, workability, and cost. Stainless steel round bars are popular across a range of industries because of their wide implicational value in different sectors 7.
• The supply chain inventory management is a very critical and challenging task for an integrated iron and Steel plant. The most feasible area that can offer opportunities for reduction of production cost and improvements is the raw material inventory management consequently is an area that should be completely explored 8.
The iron and steel industry is a complex industry since it’s material handling is complex. Alternative material handling systems/technologies and equipment in this industry will be shared seeking process improvement. The information will be shared using the case study methodology.
A basic description of all raw materials processes in the system is made based on the following steps:
• The external raw material is received through a wagon dumper, a road-railway hopper, and a conveyor belt;
• Materials received are stored in yards and divided into raw material only, and blended material (a mix of other materials);
• Raw materials go through processors, which consume certain materials transforming them into another one to be used in another part of the system (Sinter and Blending Yards).
• Raw materials are consumed, Blast Furnaces and Calcination Plant just consume raw materials.
A complex system composed of conveyor belts transport the materials from their point of origin to their destination, either for storage or consumption. The system of a conveyor belt acts as a unit that transports the materials, creating routes of transportation. It has single routes and compound routes that serves the raw material handlings needs. The processing elements of the system are (i) the blending – the mixture of several materials of distinct characteristics and (ii) the sintering – a hot agglomeration process of iron ore fines, coke, fluxing and additions mixture of defined chemical dosages and compositions 9. The resulting product is called the sinter and it presents chemical, physical, and metallurgical characteristics compatible with blast furnaces requests. The raw material consuming elements are the blast furnaces, which produce pig iron. They have supply priority as lack of materials in their silos usually means production loss. Besides the blast furnaces, there is the Calcination Plant which consumes three different kinds of limestone 9.
The Flow of Raw Materials
Raw materials contribute to the major cost of production in today’s scenario. Consequently, any waste of raw materials and deterioration during storage should be totally avoided. In addition, the quality of raw material is crucial when controlling the cost within an industry. Lower quality raw materials have cheaper cost per ton, however, they have higher consumption of fuel and energy. Hence there is a big effect on the cost final product. Considering the importance raw materials have in the iron and steel industry we should assume that the material handling of those materials has to be done with high efficiency and avoiding any kind of waste and additional cost. The raw material is important in all kinds of industries because marks the beginning of the process, in this case, the ironmaking process.
The steel production demands raw materials such as coal, coke, iron ore, mill scale, sinter. During the process, they go through unloading, stacking, reclaiming, blending, crushing, grinding and screening and are finally conveyed to the sinter plant, coke oven battery, and blast furnace. Bhushan Steel Ltd. (BSL) is a globally renowned company and one of the prominent players in the steel Industry. It is one of India’s largest manufacturers of auto-grade steel and has transformed itself as the third largest producer of cold rolled steel in the country. The company recently extended their plant and they created the material handling flowchart shown below to illustrate it (Figure 2).
Figure 2: Material handling flowchart
The raw material handling system in a steel plant is designed to cater to these materials and is critical to achieving the desired production capacity. The course of the material in the system Bhushan Steel created is shown in Figure 2 and the procedure it follows is described below step by step 10.
• Coal, limestone, dolomite and iron ore are unloaded by wagon tipplers, track hoppers and truck unloading systems and stacked in the stockyard by yard machines and reclaimed.
• Coking coal is fed to the coke oven battery after blending, crushing and mixing. The quenched coke after segregation as per separation size is fed to blast furnace stock house or base blending system.
• Iron ore fines, limestone, dolomite from the stockyard, mill scale from trucks, nut coke/coke fines from coke oven, sinter fines from the stock house are fed to base blending system for production of base mix. The sinter produced from a base mix is fed to the blast furnace and emergency storage is available to ensure continuous feed to blast furnace.
• Iron ore fines from blast furnace stock house are fed to a stockyard and then it goes to the direct reduced iron(DRI) plant.
• Nut coke from blast furnace stock house is fed into base blending system.
• Non-coking coal is fed to coal washery and the washed coal is sent to the direct reduced iron plant for further processing. Iron ore lump from stockyard through Raw Material Processing Plant and dolomite from trucks/ground hoppers is also fed to the direct reduced iron plant for processing. The output DRI is then fed to the steel melting shop.
• Blast furnace once ignited need to operate continuously, hence to ensure continuous feed of material, all the raw materials such as blast furnace coke, sinter, iron ore, additives, pellets are stored in the stock house and proportionately fed to the blast furnace via charging conveyors.
• The slag generated from the blast furnace is conveyed to the wagon loading area for transportation outside the plant.
• Non-coking coal from the stockyard through coal crushing and screening system is fed to a captive power plant