The 4th International Congress on the Science and Technology/Osaka, Japan, 26-30 Nov. 2006.

FUNDAMENTALS ASPECTS AND INDUSTRIAL PRACTICE OF COAL INJECTION IN THE BLAST FURNACE AT DONETSK METALLURGICAL WORKS

Volodymyr Kochura, Stanislav Yaroshevskiy, Valeriy Popov and Vitaliy Braga

Donetsk National Technical University; Donetsk Metallurgical Works, Donetsk, UKRAINE 83000

ABSTRACT

The operational experience of the first in Europe industrial complex on preparation and coal injection in the blast furnace at Donetsk Metallurgical Works is described.  Technical and economical parameters of blast furnace operation with pulverized coal injection have been examined.Quality of a grinding of coal and uniformity of distribution on tuyere have been investigated.The tuyere design with pulverized coal injection has been developed.Theoretical and experimental researches of pulverized coal burning process have been carried out.
Research of pulverized coal burning has been carried out with sampling of materials from blast furnace dust, sludge and slag.  Unused pulverized coal and coke particles in blast furnace dust, sludge and slag were investigated by means of microscopic and chemical analysis. Effect of coal composition on its use efficiency in blast furnace operation has been examined.

1. INTRODUCTION

  Last 20 years the Ironmaking technology with pulverized coal injection (PC) into blast furnace (BF) hearth continuously extends in the world.  In XXI century PC is used already more than 25, as a rule, the most advanced countries, about 300 million tons of iron is annually produced with injection of fine coal.  PC consumption per 1 t of iron has reache 100-260 kg, coke rate is 250-350 kg, a share of replacement of coke by PC is 30-50 %1).
The first in Europe commercial complex for PC preparation and injection was built in 1980 at Donetsk Metallurgical Works (DMW) in Ukraine.  In 2002 it has been reconstructed to improve explosion and fire safety and protection of an environment.  The complex is provided with modern devices and automatics, that on determining operational parameters gives the basis to attribute it to the installations of IV generation maintained in the world in mass scale.On the basis of the given equipment in 2002-2005

There is a development of highly effective technology with injection into the BF hearth of pulverized coal, natural gas (NG) and the hot blast enriched with oxygen (technology "PC+NG+О2").

1. Fundamentals of the theory and practice of full and complex compensating for negative changes of the technology determined by burning of additional fuel and reduction of a share of coke in the burden

  PC burningand replacement of coke with it are inevitably accompanied by deterioration of determining parameters of blast furnace technology: reduction of a share of coke in burden and, accordingly, deterioration of porosity and gas permeability of charge, reduction theoretical and real temperatures in raceway zone, content of oxygen in hearth gas on the raceway length and other.  Therefore without application of special compensating measures optimum PC rate usually did not exceed 30-50 kg /tHM2-4).
Variants of compensating for injection of additional fuels from a condition of preservation of constant base theoretical flame temperature are known.  However, at significant amount of additional fuel and reduction of the coke consumption, the conditions of PC burning and heating of melting, gas permeabilyty and other parameters should be compensated. 
At an estimation of a complex of the technological conditions determining efficiency of PC application, for the characteristic of a thermal mode of a hearth have accepted received of the equation of thermal balance for the bottom zone of heat exchange the equation of necessary theoretical temperature of burning2,3)

For the characteristic of gas regime, reduction processes, time of combustion of coal particles the equations and methods of A.Ramm, B.Kitaev, V.Babiy were used5-7). Theoretical researches, the analysis of results of the trial and industrial data which have been carried out in Ukraine and abroad, show, that at size of total replacement ratio SКr1 and preservation at a base level or increase of theoretical temperature of burning increase of PC rate does not cause reduction of efficiency of its application and deterioration of base values of the blast furnace operation.  
Donetsk Metallurgical Works was one of the first in world practice on the basis of a mode of full and complex compensation has introduced in 1986-1991 technology with injection into hearth PC+NG+О2, provided reduction of the coke charge untill 400 kg/tHM and replacement of  30-35 % of coke by additional fuels.
Experience of the countries of Europe has showed that, as a rule, development of technology with high (150-200 kg/tHM and more) PC rate occured in regime of supercompensation (SКr1), that with preservation of high base replacement ratio of coke promoted significant growth of productivity of furnaces and reduction of the specific charge of conditional fuel9).

2. Technological and Burden conditions of blast furnace operation

The blast furnace No 2 with useful volume 1033 m3 blown up after the first category overhaul in April 2002 has 16 tuyeres (d=145 mm), 2 iron taphole, valve two bell apparatus; it is provided with heating of blasting up to 1150 оС at enrichment by oxygen (26 %), supplie of NG and PC8,10). 
The furnace smelted pig-iron from imported agglomerates and pellets, the share of the last in the charge changed from 35 up to 65 %.  Since December 2002 for increase of stability of a chemical composition of the charge as the basic components began to use pellets of Lebedinsky Mining and Processing Plant and agglomerate of Southern Mining and Processing Plant.  As the basic fuel the coke of Rutchenkovo Coke Oven Plant used is used10).  
Parameters of PC quality are characterized high grinding, low and steady humidity. On a measure of development of complex of PC preparation and improvement of coal base, chemical compound of PC has improved, the average median size of PC particleschanged from 10 up to 40 microns.

3 Development of blast furnace technology with injection into hearth PC+NG+О2 (2003-2005)

  Commercial operation of the PC complex in DMW is started in September, 2002.  In 2003 and 2004 for PC preparationused about 150 thousand tons of coal.  The basic stages of development of technology are submitted in tab. 1.
During development of technology with PC injection as the major factors promoting maintenance of the regime of full and complex compensation were used:

• oxygen enrichment of blast from 22.75 up to 25.73 %;
• increase of blast temperature up to 1090-1098оС;
• decrease of NG rate from 99 to 50 m3/tHM;
• usage of pellets (more than 50% in the burden);
• replacement of total or share of limestone by flux dolomite;
• transition to the most effective system of charging;
• decrease of coke fines in the coke;
• improvement of PC quality;
• PC injection into 15 tuyeres with irregularity ± 5-10%;
• decrease of the tuyere diameter from 165 to 145 mm;
• decrease of slag basicity from 1.29 to 1.20.

Table 1  Parameters of BF-2 operation

*- screen analysis, ** - laser particle sizer analyzer

PC from lean coal have been started to apply since January, 2003. The basic results of industrial efforts are submitted in tab. 1. Development of technology with PC injection of 92-131 kgwas accompanied by reduction of the coke consumption from 566 to 392 kg/tHM at simultaneous reduction of NG rate and increase of the oxygen flow rate up to 81 m3/tHM.  Tab. 1 shows that total economy of coke has made 230 kg/tHM that more than twice exceeds efficiency of a technological regime with NG+О2 injection.  Thus productivity of a blast furnace has increased from 2046 up to 2202-2220t/day (by 156-174 t/day or 7.6-8.5 %).
At maintenance of indemnification with increase of the charge of oxygen on enrichment of blasting, increase in charge PC up to 120 kg / t of pig-iron promoted decrease of the resulted charge of coke to 440 kg / t of pig-iron.. Thus at increase of charge PC from 70 up to 100 kg / t of pig-iron the factor of replacement of coke PC (КЗ) both on experimental data, and on settlement on a method [5] was identical and has made 1,1 kg / kg. At increase of chargePCup to 120 kg /t of pig-iron, however, КЗ settlement has decreased up to 1 kg / kg, and experimental has raised - up to 1,23 kg / kg. Average on the period settlement КЗ has made 1,06 kg / kg, and experimental - 1,18 kg / kg.
Earlier, in 1990, it has been shown, that at work of a blast furnace with inflation PC and on the agglomerate containing 20-25 % of a trifle of-5 mm, having thereof the extremely intense газодинамику, enrichment of blasting by oxygen and respective significant decrease of an output gases promoted favorable redistribution and stabilization of a gas stream, improvement схода шихты, that has defined respective increase of a degree of use of thermal and chemical energy of gases, additional decrease of the charge of coke and essential excess of size actual КЗ above settlement [8]. The marked feature has proved to be true and per 2003-2004: development of the blasting enriched with oxygen, in a combination to increase of charge PC was accompanied, as well as in 1990, reception high, exceeding settlement, КЗ, increase of a degree of use of regenerative ability of gas (СО) with 37,3 up to 41,1-46,5 % ( tab. 1).
Research of the maintenance of carbon in slag, колошниковой a dust, шламе, macroresearches of slag and колошниковой a dust at work of furnaces with application and without application PC have confirmed practical absence of a gain of the maintenance in them of carbon, in particular, asPC, that testifies to a high degree of gasification of carbon PC in a forge.
In the period of 3 tab. 1 (May - August, 2003) the basic compensating factor was decrease of chargeNG: by research it is shown, that the optimum size of factor of indemnification PC-NG for the given technological conditions is equal 0,5-0,6 m3 / kgPC.

It is known, that on a measure of perfection of the technological conditions causing decrease of an output{exit} горновых of gases on 1 t of pig-iron, the level of theoretical temperature of burning raises, for example, in modern technological conditions of domain shops of Europe up to 2150-2200 оС [9, 10].
Similar change is marked and at development of technology on a blast furnace № 2 per 2003-2004: enrichment of blasting by oxygen, has defined significant decrease of an output gases on 1 t pig-iron and increase of a level of optimum theoretical temperature of burning up to 2100-2150 оС. At the same time the specified changes and decreas of the charge of coke have naturally define decrease of size of optimum intensity swimming trunks on carbon with 1100-1150 up to 1000-1050 kg, that has not prevented a gain of productivity of the furnace on 65 т/change (9,3 %).

The material - thermal balance domain swimming trunks with inflation and without inflation PCis executed. From tab. 2 follows, that the compared periods are characterized as inflation on 1 t pig-iron of 103 kg PC, and decrease of charge NG with 95 up to 73 m3 / t of pig-iron (on 22 m3 / t of pig-iron), rise in temperature of blasting with 1022 up to 1080 оС (on 58 оС) and the charge of oxygen with 48 up to 74 m3 / t of pig-iron, improvement of quality железорудной шихты, first of all, due to transition to agglomerate ЮГОК , decrease of the charge of limestone and basicity of slag СaO/SiO2 - with 1,25 up to 1,21. In a result the generalized parameters of indemnification - outputs of slag and gases on 1 т pig-iron - has decreased according to 458 up to 370 kg and with 2084 up to 1800 m3.
Thus, inflation in a forge of pig-iron PC of 103 kg / t in a combination to the compensating actions described above has defined decrease of the charge of coke with 534 up to 407 kg / t of pig-iron (on 127 kg / t of pig-iron), including accordingly for account PC- 109 kg. That has made more than 1 kg / kg, the theoretical temperature of burning has increased with 1967 up to 2035 оС, that testifies that development of PC-TECHNOLOGY was carried out in an optimum mode of superindemnification. To it testify the actual performance level of the furnace exceeding resulted to equal conditions settlement, significant increase of a degree of use of regenerative and thermal work of gases 39,95 and 45,3 % accordingly, efficiency of heat in the furnace - with 82,19 up to 84,42 %.

Conclusions

Lead in 2002 г reconstruction of one of first-ever plants on preparation and inflation пылеугольного fuel in a forge of blast furnaces gives the basis to attribute it to installations of IV generation, in mass scale maintained now in the world. In a mode of long commercial operation swimming trunks with inflation in forge PC+NG+О2, provided are developed and mastered a complex of the equipment for preparation of inflation PC in a blast furnace and technology domain at inflation in a forge on 1 t pig-iron of 92-131 kg PC additional decrease of the charge of coke on 96-174 kg / t of pig-iron (17-30 %) and a gain of productivity of the furnace for 156-174 t/day (7,6-8,5 %). The total economy of coke due to inflation PC and NG has made 230 kg / t of pig-iron (40 %), that more than in two exceeds efficiency of a technological mode with inflation in forge NG+О2.

References

1. Savchuk N.A., Курунов I.F.domain manufacture on boundary ХХІ of a century // News of ferrous metallurgy abroad. - 2000.-Part ІІ.-the Appendix 5. - M.: joint-stock company Chermetinformatsija. - 42 with.
2. Dunaev N.E., Kudrjavtseva Z.M., JU.M.inflation's Smiths пылевидных materials in blast furnaces. - M.: Metallurgy, 1977. - 207 with.
3. Emushintsev V.V., Galemin I.M., Dunaev N.E.melt передельного pig-iron with the various charge пылеугольного fuel // Steel. - 1969. - № 6. - With. 489-493.
4. Work of a blast furnace at joint application of natural gas, пылеугольного fuel and enrichment by oxygen of blasting / Z.I.Nekrasov, L.D.Jupko, P.JA.Mukhin, etc. // the Intensification of processes domain swimming trunks and development of furnaces of great volume. - M.: Metallurgy, 1978. - Вып. 4. - with 1-5.
5. Рамм A.N.modern domain process. - M.: Metallurgy, 1980. - 304 m.
6. Kitaev B.I.heat exchange in a blast furnace. - M.: Metallurgy, 1966.
7. Babij V.I., Ivanov I.V.duration of ignition and burning of particles of a dust of various marks углей // Materials of III All-Union conference under the theory of burning of firm fuel « Burning of firm fuel ». - Novosibirsk: the Science, 1969.
8. Nozdrachev V.A., Jaroshevskij S.L., Терещенко V.P.perspective of technology domain swimming trunks with application of oxygen and пылеугольного fuel, 1996. - Donetsk: the New world, 1996. - 173 with.
9. Efficiency and prospects of application of oxygen in domain плавке / S.L.Yaroshesky, V.A.Nozdrachev, A.I.Babich, etc. // the Collection of proceedings of Donetsk state technical university. Metallurgy. Release 8. - Donetsk: ДонГТУ, 1999. - From 39-55.
10. Technology domain swimming trunks with inflation in a forge{bugle} пылеугольного fuel, natural gas and oxygen / A.N.Ryzhenkov, A.I.Kovalev, S.L.Yaroshesky, etc. - Donetsk: the New world, 2003. - 35 with.
11. Optimization of technology domain swimming trunks / S.L.Yaroshesky, Л.В. Bulls, E.I.Chetyrkin, etc. // the Metallurgist. - 2000. - № 10.-С. 35-37.
12. Research and optimization of technology domain swimming trunks / L.F.Litvinov, А.М. Smiths, V.P.Padalka, etc. // Metal and moulding of Ukraine. - 2003. - № 11-12. - With. 7-10.