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...

The Process of Blowing-in of a Blast Furnace Apr29

The Process of Blowing-in of a Blast Furnace...

The Process of Blowing-in of a Blast Furnace  The process of starting a blast furnace after its construction or after its relining is called blowing-in. The blowing-in process is carried out in several steps (Fig 1) which consist of (i) drying out the lining, (ii) filling of the blast furnace with a specially arranged high coke blow-in furnace charge, (iii) igniting of the coke or lighting of the blast furnace, and (iv) gradually increasing the hot blast (wind rate) with frequent castings to ensure the raising of temperature of the blast furnace hearth. During the period of blow-in, the burden ratio (ratio of the ore to coke) is adjusted according to a predetermined schedule until the normal operation of the blast furnace is achieved and the blast furnace starts producing the normal  quality of the hot metal. Fig 1 Steps in the blowing-in process of a blast furnace  Newly constructed or relined blast furnace is to be carefully dried before the coke is ignited. It is  because the large amount of water contained in the slurry used for refractory brick laying and the water absorbed by the refractory brick work is to be driven off as much as possible for avoiding  extreme thermal shock. There is sufficient data available that blowing-in of a blast furnace can cause damage to the refractory lining even when it has been properly dried. Furthermore, if the water from these sources is not removed from the blast furnace before it is put into operation, it absorbs heat more than that provided for the blow-in charge and hence prevents the hearth from reaching the desired temperature. In such cases, hot metal and liquid slag entering the hearth can freeze there and in such case it becomes impossible to remove them...