The cooler is also inclined at 2. The largest improvements would be made by design modifications adopting a novel energy conservation scenario by process integration and thereby decreasing the coal and water consumption and by decreasing the cold fresh air. Posted by Satyendra on Feb 14, in Technical 0 comments. Low ash content of the coal is necessary since the high ash leads to under-utilization of the kiln volume available for reduction. This heat balance calculation is very much useful while designing the furnace and in determining fuel efficiency.
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The processes and process concepts which have survived have several common or slightly differing features as given below. The reaction shows that the carbon monoxide CO is reducing gas which is obtained by controlled combustion of coal, according the Boudouard reaction as given below.
Coal based Direct Reduction Rotary Kiln Process
He has presented many papers in national and international journals. Posted by Satyendra on Feb 14, in Technical 0 comments. Apart from this, primary air and secondary air are supplied to the kiln to initiate the combustion and sustain the reaction process in the kiln.
The cooled product of the kiln after its discharge from the rotary kiln is sent to the product separation area where the DRI is magnetically separated from the char and is screened to various size fractions.
The gases then pass to the after burner chamber ABC where the residual carbon or CO is burned by the excess air available. Since the reaction takes place in several stages and each stage in succession, the stage with the least rate controls the rate of the reaction.
Energy survey of the coal based sponge iron industry - ScienceDirect
Low ash content of the coal is necessary since the high ash leads to under-utilization of the kiln volume available for reduction. Part of this energy is recovered in the WHRB. Char contains ash of coal and other impurities of iron ore. Percent reduction refers to the oxygen which has been removed in producing the DRI with reference to initial Fe as Fe2O3.
Common terminologies of Direct Reduction process are explained in a simple language. The sulphur in the coal is to be 0. The temperature inside the kiln is controlled by regulating the amount of combustion air admitted into the kiln through ports with the help kilb fans mounted on the kiln spojge and by controlled coal injection. The products of the kiln is screened and magnetically separated. The material and the hot gases move in the counter current direction, as a result the iron ore gets pre- heated and is gradually reduced by the time if reaches the discharged end.
Part of coal is used as fuel to supply the desired heat so as to take the raw materials to the desired temperature. The main quality requirements are i high Fe content with less gangue and deleterious elements like phosphorous and sulphur, ii good handling properties tumbler index and abrasion indexiii calibrated to size with less fines, iv high reducibility, v low decrepitation during reduction, and vi good compatibility with the reductant coal used.
Dolomite is used as sulphur scavenger which finally comes out with the char. Sarangi has an expertise in dealing with the projects on metallurgical investigations into titanomagnetic ores, and aluminothermic reduction of transition metal oxides.
Since these rings cannot be reached from outside of the kiln, they are rotsry impossible to be removed during the working of the kiln.
DRI being magnetic gets attracted and gets separated from non- magnetic char. The hot reduced material from the kiln then passes to the rotary cooler though transfer chute for cooling. Important stages of the process and the process concept are shown in Fig 2.
It has been observed that majority of the shut downs of the kiln is only due to the formation of the accretions. The iron ore and coal crushed and screened to respective sizes are fed to rotary kiln through feed tube in pre-determined ratio.
Depending on the reducibility, calibrated ore in the size range of 5 mm to 20 mm is generally used. Coal based direct reduction process is based on the solid reducing agent which is non-coking coal.
Metallurgical requirements of the ore include high reducibility, thermal stability, and a low tendency for sticking and disintegration during heating and reduction.
The reaction occurring inside the bed of iron ore and coal are heterogeneous in nature. The cooler is also inclined at 2. The major quality requirements of the non-coking coal are i non-coking characteristics, ii low ash content, iii low sulphur content, iv good reactivity, v high ash fusion temperature, and vi medium volatile matter.
Equivalent metallization — Carbon content in sponge iron at a given degree of metallization is important. Raw material mix consisting of iron ore, dolomite and non-coking coal is fed at the one end of the rotary kiln and is heated by coal burners to produce DRI.