Mini Blast Furnace and Iron making Oct10

Mini Blast Furnace and Iron making...

Mini Blast Furnace and Iron making Mini blast furnaces (MBF) are generally viewed as miniature versions of the conventional large blast furnaces (BF). These furnaces are ideally suited for small scale operations. In fact, they are basically the forerunner to modern conventional last blast furnaces and hence they have operated for a longer period of time. MBFs are located in many countries but the majority of the MBFs are located in China, India, Brazil and Indonesia. Plant availability as well as the perfection achieved in this technology has made MBF an accepted route for iron making. Further, these days, most of the technologies of design, burdening and operation which have become the norm for today’s modern large furnaces have also been adopted in MBFs. MBF is a vertical shaft furnace with a crucible like hearth. Burden materials consisting of iron ore, coke or charcoal used as a reducing agent as well as fuel, and fluxes, usually limestone or dolomite, are charged into the top of the furnace. The furnace works on the principle of a counter current reactor. As the burden descends through the shaft, it is preheated and pre-reduced by the hot gases ascending from the furnace bottom. The gases are generated by introducing hot air blast enriched with oxygen through tuyeres. The hot blast burns the reducing agent, producing reducing gases and heat required for the reduction process taking place in the furnace. The reduced burden material melts to form HM (liquid iron) which becomes saturated with carbon and descends to the hearth. The fluxes combine with the impurities in the burden materials to produce a molten slag which accumulates on top of the liquid iron in the hearth. Liquid iron and liquid slag are periodically tapped from the furnace. MBF exhibits...

Blast Furnace Tuyeres and Tuyere Stocks May29

Blast Furnace Tuyeres and Tuyere Stocks...

Blast Furnace Tuyeres and Tuyere Stocks The blast furnace (BF) has the objective of extracting the hot metal (liquid iron) from iron ore lump, sinter and/or pellet, coke and injected fuel. This objective is achieved by passing a hot enriched air flow (hot blast air) through the ore and coke burden which goes down in the internal column of the BF. The hot blast air and auxiliary fuel are injected into the blast furnace through tuyeres located around the perimeter of the BF. The upper zone of the hearth wall of the blast furnace contains the openings for the tuyeres which are used to introduce the hot blast air into the furnace. The furnace jacket in the tuyere zone contains steel reinforced openings within which copper (Cu) cooled elements are installed, similar to that shown in Fig 1. The steel reinforcements in the jacket are called tuyere cooler holders. The large Cu cooler which is installed within the machined inner surface of the cooler holder is called the tuyere cooler. The Cu cooler which actually introduces the hot blast air into the furnace is called the tuyere. It is installed within a machined, inner seating surface on the tuyere cooler. The blowpipe is part of the tuyere stock air distribution piping, which delivers the hot blast air from the bustle pipe, and which mates with the tuyere, to direct the hot blast air into the furnace. The tuyere breast walls are usually made of carbon brick and the cooling is generally external with jacketed cooling channels on the outside of the shell. Some furnaces have internal staves in the tuyere breast between the tuyere coolers as a cooling design for the tuyere breast. Fig 1 also shows the arrangement of the tuyere cooler holder,...

Evolution of Blast Furnace Iron Making Jan10

Evolution of Blast Furnace Iron Making...

Evolution of Blast Furnace Iron Making The origin of the first smelting of iron is concealed in the unrecorded history of human civilization. The first evidence of iron implements being used in ancient times actually comes from Egypt where an iron tool was found in a joint between two stones in a pyramid. The origin of many prehistoric iron implements was probably meteoric iron. Meteoric iron contains 5 % to 26 % nickel (Ni) while smelted iron contains only traces of Ni and hence iron artifacts made from meteors can be differentiated from objects of smelted iron. More than 4,000 years ago, people discovered meteoric iron. But it was another 2,000 years before the production of iron from mined iron ore began. The earliest finds of smelted iron in India date back to 1800 BCE (Before Common Era).  The smelting of iron is said to have taken place among the Calybes of Armenia, subjects of the Hittite Empire, at about 1500 BCE. When their empire collapsed around 1200 BCE, the various tribes took the knowledge of iron making with them, spreading it across Europe and Asia. The knowledge of ironworking in all of Europe and Western Asia is ultimately traced to this source. The Iron Age began with the discovery of smelting of iron. Beginning of iron smelting As with the reduction of cop­per sulfide ores, the first reduction of iron oxide was probably accidental. It was the powers of observation that led these ancient metallurgists (who were the miners, chemists, and technologists of their day) to realize that iron could be produced in simple furnaces by direct carbon (C) reduction of the oxide ore. The first recorded depiction of a smelting process was found on the wall of an Egyptian tomb dating to...

Protection of Blast Furnace hearth lining by the addition of TiO2 Jun09

Protection of Blast Furnace hearth lining by the addition of TiO2...

Protection of Blast Furnace hearth lining by the addition of TiO2 The refractories of the blast furnace (BF) hearth is the most critical material in the iron making process by the blast furnace since the BF campaign life greatly depends on its condition. The most critical region is the transition region between the furnace wall and bottom of the hearth. The hearth refractory wear is a serious concern for many of the BF operators. The abrasive and erosive effect on hearth zone of a blast furnace are due to various conditions namely high ambient temperatures, continuous movement of the liquid smelting products, chemical activity from the products, pressure and chemical activity from the gases and entry of moisture into the BF hearth. The main reasons for the wear out of the BF hearth refractories are (i) high furnace productivity, (ii) frequency of long furnace shut downs (> 2 days), (iii) water leakage from furnace water cooling system and (iv) quality of charge materials. The wearing of the hearth refractories affects the campaign life of a blast furnace. Blast furnace operators use the following methods to decrease the wear rate of the BF hearth refractories. Lowering the BF productivity Reducing coal injection rates Grouting of the ramming mass between staves and carbon blocks Temporary plugging of the tuyeres Increasing the cooling rates of the wall Addition of the TiO2 containing materials Improvement of the lining life of the BF hearth by the addition of TiO2 containing compounds is the most widely used method. TiO2 provides protection to BF hearth lining against premature erosion. Process of BF hearth protection The addition of TiO2 containing compounds results in the precipitation of Ti (C,N) (titanium carbonitrides) onto the bottom and the walls of the BF hearth (Fig 1...