 Hello friends, myself Dr. Narendra Kartikar, Assistant Professor, Department of Mechanical Engineering, Valachandra Institute of Technology, Solapur. Now we are going to discuss Study of Furnaces, Part 3. At the end of this lecture or this session, student will be able to understand the construction and working of cupola furnace. The discussion points are as follows, introduction, cupola furnace, zones of cupola furnace, operation of cupola, advantages, limitations and applications of cupola furnace. You can see the first image on the screen. This is one of the type of cupola furnace. Basically, the furnace means to convert the solid metal into the liquid state itself. You can have one more look on the one of the type of cupola furnace. You can see how the molten metal can be taken out from the cupola furnace. These three images just I had shown you just to get the idea about the cupola furnace. Cupola furnace is a melting device used in foundries that can be used to melt cast iron, resistant and some bronzes. For many years, the cupola was the primary method of melting used in iron foundries. The cupola furnace has several unique characteristics which are responsible for its widespread uses as a melting unit for cast iron. Cupola furnace is employed for melting scrap metal or pig iron for production of various cast iron. It is also used for production of nodular and malleable cast iron. It is available in good wearing sizes also. This is the detailed construction of cupola furnace. You can read out the various parts being present for the cupola furnace. A big shell structure right from the particular footing rather the base to the spark arrester. We are going to discuss the parts rather the sections of cupola furnace in detail. This is another image or the conceptual diagram which elaborates the particular parts of cupola furnace. At this stage of this session, are you able to recall share some of the casting part with the different ferrous and non-ferrous metals which you had seen earlier anywhere in real time. Just enlist few of them. Let us go with the zones of cupola furnace. Well, combustion zone, reducing zone, melting zone, preheating zone and stack zone. All these zones are positioned and shown in this diagram for cupola furnace. The well is at the bottom most side. Above the same combustion zone is there. Then reducing zone, melting zone and preheating zone while we are going from bottom to top side of the cupola. Let us go one by one. First one well, the space between the bottom of the two years and the sand bed inside the cylindrical shell of the cupola is called as well of the cupola. As the melting occurs, the molten metal is get collected in this portion before tapping out. Second is the combustion zone. The combustion zone of cupola is also called as oxidizing zone located between the upper of the two years and theoretical level above it. The total height of this zone is normally from 15 centimeter to 30 centimeter. The combustion actually take place in this zone by consuming the free oxygen completely from the air blast and generated tremendous amount of heat. The heat generated in this zone is sufficient enough to meet the requirement of other zone of cupola. The heat is further evolved also due to oxidation of silicon and manganese. The temperature is about 1540 degree Celsius to 1870 degree Celsius is achieved in this zone. Few exothermic reaction take place in this zone. These are represented as follows. Combination of carbon and oxide, carbon dioxide plus heat, silica plus oxygen, silica oxide plus heat. Manganese plus oxygen, manganese oxide plus heat. Reducing zone, it is also known as the protective zone which is located between upper level of combustion zone and upper level of coke bed. In this zone, carbon dioxide is changed to the carbon monoxide through an endothermic reaction as a result of which the temperature falls from combustion zone temperature to about 1200 degree Celsius at the top of this zone. The important chemical reaction take place in this zone which is given as under carbon dioxide plus heat that is carbon present from the coke generate carbon monoxide and heat energy. Nitrogen does not participate in the chemical reaction occurring in this zone as it is also the other main constituent of the upward moving hot gases because of the reducing atmosphere in this zone the charge is protected against the oxidation. Melting zone, the lower layer of metal charge above the lower layer of the coke bed is termed as the melting zone of cupola. The metal charge starts melting in this zone and trickles down through the coke bed and gets collected in the well. Sufficient carbon content pickled by the molten metal in this zone is represented by chemical reaction as follows, iron plus carbon monoxide, iron carbide plus carbon dioxide. Preheating zone Preheating zone starts from the upper end of the melting zone and continues up to the bottom level of the charging door. This zone contains a number of alternate layers of coke bed, flux and metal charge. The main objective of this zone is to preheat the charge from the room temperature to about 1090 degrees Celsius before entering the metal charge to the melting zone. The preheating takes place in this zone due to the upward movement of the hot gases. During the preheating process the metal charge in solid form picks up some sulfur content in this zone. Stack the empty portion of the cupola above the preheating zone is called as stack. It provides the passage to hot gases to go to the atmosphere from the cupola furnace. These are all about the zones of cupola furnace. Now let us look to the operation of cupola. The operation of cupola as follows. Preparation of cupola, slag and metal adheres to the cupola lining from the previous run is removed and lining of cupola is remade. The bottom plates are swung to closing positions supported by probe. The sand bed is then prepared with a molding sand such that it slopes towards the tap hole. Firing the cupola, the cupola is fired by kindling wood at the bottom. This should be done 2.5 to 3 hours before the molten metal is required. On the top of kindling wood a bed of coke is built. The height of coke bed may vary from 50 cm to 125 cm according to the size of cupola. Soaking of iron, when the furnace is charged fully it is maintained for about 45 minutes. The charge is slowly heated during the stage of air blast is shut off and iron is soaked. Opening of blast air, at the end of soaking period the air blast is opened. The tapping hole is closed by a plug. When the melting proceeds and molten metal is collected at the bottom. Pouring of molten metal, when the sufficient amount of metal has collected in the heart of the slag hole is opened and the slag is removed. Then tapping hole is opened and the molten metal flows out in the table. The same procedure is repeated until the charge is melted and the operation is over. Closing of cupola, when the operation is over the air blast is shut off. The bottom of furnace is opened by removing the prop. Advantages of cupola furnace, it is a simple and economical to operate can refine the metal charge, removing impurities out of slag. Cupola is capable of accepting a wide range of material without reducing melt quality and dirty. Only scrap can be melted as well as a wide range of steel and iron. They therefore play an important role in metal recycling industry. Cupolas are more efficient and less harmful to the environment than electric furnace because they derive energy directly from coke rather than from electricity that first has to be generated. The continuous rather than batch process suits the demand of repetition foundry. The cupolas can be used to reuse foundry by products and to destroy other pollutants such as VOC from the core making area. High melt rate ease of operation and efficiency of cupola varies from 30 to 50%. Adequate temperature control and chemical composition control is another advantage. It required less floor paste area compared with the other furnaces. Some of the limitations in molten iron and coke are in contact with each other. Certain elements like silicon, manganese are lost and other like sulphurs are picked up. This changes final analysis of molten metal. Close temperature control is difficult to maintain for cupola furnace. Conditions more widely used for melting practices for production of grey cast iron, nodular cast iron, malleable cast iron, alloy cast iron. It can be used for melting some copper based alloys in duplexing and triplexing operation for making steel malleable cast iron and ductile cast iron. Steel can be also prepared in cupola by employing duplexing and triplexing operation. At last you can have a look for the particular image. References for this discussion are as follows. Thank you.