TOTEM Co Ltd.

 

15 ARGUMENTS WHY PREFERENCE SHOULD BE GIVEN TO THE BELL-LESS ROTARY CHARGING UNIT (BRCU)

The Technological benefits of charging blast furnaces through the Rotary charging apparatus

 

1. Soft dumping of material on the burden surface

The charging through BRCU does not destroy the profile of the preceding batch of material, which improves the possibility of prognostication and modeling of the burden layer-wise stacking topography. Besides, the soft charging of material would not result in the formation of excessively compacted volumes of burden, which would otherwise may impede the gas permeability. It is achieved thanks to splitting the material flow into five equal parts, that thereafter are strewed from surfaces of the rotor vanes in wide streams without impediments. Therefore, the kinetic energy of material streams , falling down from each vane, becomes five times less. In case of charging through a chute-type apparatus, material would be loaded from the chute in one concentrated stream , which is the reason why the burden surface is deformed.

2.High rate of circular distribution of burden and averaging of the loaded batch of material.

As BRCU is used, material is stacked on the surface of burden in five thin layers at one turn of the rotor. Up to 30-50 layers of burden would be stacked from one batch of material. Owing to the multi-layer charging of material it becomes averaged and circularly distributed in a highly uniform manner. In case of the charging through chute-type apparatus when circular loading is practiced, only 6-8 layers would be stacked. And in case of a spiral charging , it would be only one layer. Besides, as the chute-type apparatuses are used, there is a problem of having the rings closed. As the beginning and end of the ring do not meet, some layers might be not be superimposed adequately, which would result in non-uniform distribution of material.

3. Flexible control of the radial distribution of material at the blast furnace top.

It is achieved due to the fact that material is shifted along the furnace radius by varying the centrifugal force which would affect material as the turning speed of the rotor is being varied. The width of the flow of material, as it is falling from the rotor, is equal approximately to the rotor half radius and quite thin , therefore, as the rotor turning speed is being varied the ore/coke ratio would be also varied in a graduate manner. This would make it possible to optimize ore/coke ratios along the furnace radius thus minimizing the rate of coke.

4. Fast rate of charging

It is achieved owing to the fact that material is loaded into the furnace with the burden gate being kept fully open. In case of chute-type apparatuses, to achieve circular uniformity the charging is performed the burden gate being partly closed. The outflow time of burden materials in BRCU is 1.5-2. times shorter then that in chute-type apparatuses. Owing to the faster rate of charging, BRCU does not create difficulty in operate the furnace in a catch-up mode.

Design advantages

5.Longer service life of the rotor as compared with the chute.

Over the years of operating rotors at the West Siberia Steel Plant and Bhilai Steel Plant in India , none of them happened to fail. It was necessary only to replace the protective plates on the vanes. At BSP the rotor has been in operation for more then 10 years. The protective plates were replaced after 7 years of operation. This long life is accounted for by a reduced abrasive effect of material upon the rotor vanes, because material is moving on them as a thin and wide layer. At that the lower layer, which is closer to the vanes, would move slower, thus protecting the vanes against erosion by the upper, faster moving layers. The upper part of rotor vanes is provided with a possibility of self-lining.

6. BRCU central gearbox is simple in design

BRCU central gearbox consists of only one cylindrical gear pair. To distribute material it is only the rotary motion of the rotor which is needed, with a possibility to control its speed. The central gearbox of a chute-type apparatus, which is used for varying the chute inclination angle and rotating the water cooling system, is of a complicated planetary design, in addition, it includes also two worm reducing gears.

7. Long service life of BRCU burden gates.

As there is no need to control the falling speed of material on the rotor, practically there is no wear of burden gate wings. In its opened position, BRCU burden gate does not contact with burden.

8. Less number of mechanisms

In BRCI there are two burden gates and two gas sealing valves. In a two hopper chute apparatus there are two burden gates, four gas sealing valves and a flinging chute. On balance, a smaller number of equipments makes the dependability of the whole system better.

9. No weighing system

For BRCU there is no need to weigh up the transfer hopper. This makes the design of the charger and the charging process automatic control system simpler, which contributes to the dependability of the apparatus as a whole. In a chute-type apparatus to control the speed of material outflow its is necessary to measure the weight of the transfer hopper.

10. Central flow of material

In BRCU burden travels along one through path, which goes along the central line of the apparatus, without turns in the charging direction from the conveyer (skip) to the rotor. This arrangement is conducive to a uniform distribution of material thanks to the symmetrical loading into the furnace, to a lower wear rate of the equipment .
In a two-hopper chute-type apparatus material would go firstly from the center to the periphery with the help of a flinging chute under the conveyer, and after that in reverse to the center through the lower bank of valves, which causes a one-sided wearing of equipment and ellipsoid , unsymmetrical stacking of burden at the furnace top.

11. BRCU compact design

By force of the its design features, BRCU is of a lower height , as compared with the chute-type apparatuses. . This makes it possible to install it on the extant blast furnaces to substitute the extant chargers without modifications in basic steel structures at the top and in the upper segment of the skip bridge.

Cost efficiency

12. Shorter pay-back period (ROI) - not longer than 1 year.

It is achieved due to a reduced rate of coke (by 4 6%) and enhanced productivity of the blast furnace (by 4-8% and more). TOTEM Co. Ltd. obtained data from the field that corroborated improvements in the operating indices in four steel plants in India and Russia This information has been published at large and their trustworthiness would not evoke any doubts. So, BRCU makes it possible to reduce substantially the production cost of hot metal even in the period of crises, which would make the way out of it easier.

13. BRCU environment friendliness

The BRCU implied reduction in coke rate is achieved owing to a better utilization of the reducibility of gases, not by substituting one type of fuel with another, i.e. by a more beneficial method. Therefore, effluents of gas into the ambient air , CO2 inclusive, will be curtailed in proportion to the reduction in coke rate. Such an ecology index is the topic of to-day (Kyot Protocol) and CO2 effluents are expected to be put under rigid control soon in many states. Thanks to a reduced rate of coke in iron making the hazardous effluents in coke making production will be also reduced.

14. BRCU installation project is characterized by a comparatively low cost and longer service life of the equipment.

Thanks to that, BRCU installation project will pay for itself by a sheer replacement of morally obsolete equipment with a new, advanced equipment, nothing to say about reduced coke rate and enhanced productivity of the furnace. implementation of this project can be funded as a scheduled maintenance work

15. BRCU project is a technicaly intensive affair

It includes an original automatic control system and mathematical models, which apart from other economic benefits, will give rise to a better culture of production work.

To illustrate the efficiency of the rotary charging unit, we are giving the operating indices of the blast furnaces with rotary distribution of burden and chute-type distribution obtained from Bhilai Steel Plant (BSP) in India. Also the performance data of blast furnace No2 at JSPL (Jindal Group) with BRCU, as compared with the performance data of blast furnace G at Tata Steel with Paul Wurth apparatus.

A long-lasting operation of the rotary charging unit on BF-3, BSP (more then 10 years) has proved that in comparison with Paul Wurth apparatuses (BF-4,5,6,7) the coke rate was reduced by not less then 5% and furnace productivity enhanced ( by 6-8 as minimum). These results have been obtained on the basis of analysis of the formal annual reports at BSP and are given below in column diagrams.

The implementation of BRCU has proved that in comparison with Paul Wurth apparatuses the specific productivity of the blast furnace had been increased by 8.86-19.83 %, the summary fuel rate decreased by 4.21-6.5%, and summary carbon rate decreased by 6.53-8.75.

2000-2001 Performance

2003-2004 Performance

2004-2005 Performance

Juxtaposition of the adjusted yearly mean indices
of blast furnaces performance at the Bhilai Steel Plant

(BF-1 and BF-2 are equipped with double-bell apparatuses)

Working parameters of BF-G of Tata Steel and BF-2 ofJSPL (Jindal)

PARAMETERS

BF- G

BF-2

PLANT

Tata Steel

JSPL

JSPL

JSPL

Month/year

.07

Feb.08

Apr.08

Feb.09

1. Productivity, t/day

 

5476

3341,3

3612,74

3702,9

2. Down time,%

 

0

0,98

1,74

2,57

3. Specific prod-ty , t/m3day

 

2,37

2,29

2,47

(6,7%) 2,53

4. Coke rate (dry), kg/t

 

366

400

396

378,9

5. Coke nut rate, kg/t

 

53

26,37

25,37

28,45

6. PCI rate, kg/t

 

141

102,6

116,77

124,03

7. Total fuel rate, kg/t

 

560

529

538,14

(5,1%)531,4

8. Fuel intensity rate, t/m3day

 

1,158

1,051

1,156

1,17

9. Carbon rate, kg/t

 

477

439,3

443,78

438,37

10. Ore rate (dry), kg/t

 

502

500

519

543

11. Sinter rate kg/t,

 

1042

1150

1147

1094

12. Quartzite rate, kg/t

 

13

17

14,67

15,05

13. Fe in ore part of burden, %

 

58,97

56,67

57,25

57,54

14 Blast rate (calculated), m3/min

 

/

3139

3149

..

15. Blast temperature, ?C

 

1136

1182

1200,77

1199

16. Blast pressure, bar

 

3,17

2,4

2,47

2,54

17. Top pressure, bar

 

1,54

0,9

0,92

0,95

18. Pressure differential, bar

 

1,63

1,5

1,55

1,59

19. O2 in blast, %

 

25,35

23,7

23,74

24,63

20. Blast moisture, g/m3

 

31

37

30,9

37,8

21. Slag yield, kg/t

 

263

330

327,25

(20%) 312

22. . Ore/coke ratio, t/t

 

4,26

4,17

4,24

4,37

23. Top temperature, ?C

 

/

120,5

99,3

79

24. Top gas analises,%

26,42

24,62

24,27

24,9

 

2

21,06

20,41

20,9

20,85

25. CO utilization rate, %

 

44,36

45,3

46,27

45,37

26. Si in hot metal, %

Si

0,8

0,6

0,64

0,62

27. Hot metal temperature, ?C

 

1483

1481,8

1473

1463

28. Slag basisity

CaO/SiO2

0,99

1

0,99

1,0

 

CaO+MgO/SiO2

1,18

1,24

1,25

1,27

29. Fe in iron ore, %

 

63,59

63,56

63,89

64,36

30. Sinter composition, %

Fe

57,66

54,52

54,96

55,03

31. Sinter basisity

CaO+MgO/SiO2

/

2,31

2,26

2,3

32. Coke, %

Moisture

/

7,22

6,64

5,51

 

Ash

13,72

12,15

12,11

12,98

 

Carbon

/

87,11

87,18

86,15

 

M40

84,2

83,63

86,93

88,19

 

M10

5,2

5,27

5,21

5,61

33. Coal dust compjsition, %

Ash

10,41

10,39

9,85

9,5

 

Volatiles

/

22,61

21,69

19,64

Parameters as adjasted to equal condition

34. Productivity, /

 

5476

3777,5

4069,79

4152,7

35. Specific prod-ty , t/m3day.

 

2,37

2,58

2,78

2,84

36. Diference from BF-G

 

0

8,86%

17,3%

19,83%

37. Total coke rate, kg/t

 

419

422,58

419,68

399,5

38. Diference from BF-G

 

 

0,85%

0,16%

-4,65%

39. Total fuel rate, kg/t

 

560

525,18

536,5

523,54

40. Diference from BF-G

 

0

-6,22%

-4,21%

-6,5%

41. , /

 

477

435,21

445,83

440,21

42. Diference from BF-G

 

0

-8,76%

-6,53%

-7,71%

 

Up

 

 

TOTEM Co Ltd.

""