HIGH PERFORMANCE
OPERATION OF THE NEW JINDAL SOUTH WEST BLAST FURNACE WITH A
BELL-LESS ROTARY CHARGING UNIT BPCU.
During the second half
of 2006 two new blast furnaces (1462 m3 WV) from the Jindal Group
were successfully blown in. Both furnaces are identical and are
equipped with a bell less rotary charging unit BRCU, an innovative
new charging apparatus. During the filling of the furnace before the
blow-in experiments were performed to demonstrate the effect of
different charging modes of the BRCU on the layer build up.
The ultimate goal is
to achieve a high productivity (>2.5 tHM/24hr/m3WV) at high PCI
rates (>150 kg/tHM) which is challenging with local raw materials
available. This will secure a place for JSW in top 5 of Indian blast
furnace performance.
Together with the
state of the art design and operations, a campaign life of over 15
years is targeted. This paper describes the results of the JSW blast
furnace in the first 8 months of operation.
Material distribution, rotary charging unit.
XXXVII Ironmaking and
Raw Materials Seminar / VIII Brazilian Symposium on Iron Ore,
September 18-21, 2007, Salvador – BA – Brazil
T.K. Naha, Vice
President (Iron), Avtar Singh, Dy. Manager (Iron),
Jindal South West
Steel Limited (India);
Dr B. Boranbaev,
Director General, Yu. Glazer, Chief Engineer,
TOTEM Co. Ltd.
(Russia);
G-J. Gravemaker, Lead
Engineer, H. Toxopeus, Lead Engineer,
Danieli Corus (The Netherlands)
In August and November
2006 two blast furnaces of 1462 m3 of working volume had
been commissioned successfully at Jindal South West (JSW) and Jindal
Steel and Power Limited steel plants (JSPL) in India. Two bell-less
rotary charging units (BRCU) were installed on both the furnaces
which was the first experience of this kind in the world.
Hereinafter there is an analysis of research carried on the basis of
performance data, generated on blast furnace No.2 at JSW.
The general view and
basic dimensions of the unit are shown in Figure 1. The makeup of
BRCU is as follows: a receiving funnel, upper and lower banks of
valves, transfer hopper, burden gate with compensator, central
gearbox, rotor and its drive. While designing BRCU attempts were
made to simplify it as much as possible, as to make the equipment
more dependable. The main (central) gear box of BRCU has only one
cylindrical gear in combination with a bearing, two sealing rings
and quiescent water cooling system. The upper and lower banks of
valves are of the same design; they consist of burden gates and gas
sealing valves. The gas sealing valve is a closing device with
“metal-to-metal” contact, there is a provision to change this
principle and make it as “metal-to-rubber” contact.
The BRCU components
are arranged in such a way that burden stock is fed strictly along
the charger central line, which would decrease segregation and
improve the circular uniformity in distributing stock in the blast
furnace top.
The salient features
of the charging technology with the help of BRCU that make it more
advantageous as compared with the other existing charging
apparatuses are as follows:
a) A multi layer charging of material in wide streams which
makes it possible to average the charged batch of stock. As one
batch is being charged, five vanes of the rotor will lay down up to
40 and even more layers of stock;
b) high circular uniformity, which is achieved thanks to the
fact that the stream of material is split by the rotor into 5
equal rotating flows;
c) Soft dumping of stock on the surface, which would not destroy
the profile of the preceding batch of material. This is achieved
thanks to the splitting of stream into 5 flows and laying stock in
wide flows of small thickness. The soft dumping of stock makes it
possible to forecast better how it is distributed layer after layer.
d) A flexible control of stock distribution along the radius. It
is achieved thanks to the smooth variations of rotor RPM.
Before blow-in, the performance parameters of the charging apparatus
were studied. When the cold furnace was being filled, the profiles
of burden in the stack and top were measured. It was done with the
help of a profile meter, consisting of a movable pipe, elastic rope
and weight. The burden profiles were measured after dumping each
batch of the last 18 batches. Figure 2 shows the measuring results.
All in all 22 batches were measured. Visually it was observed that
the circular uniformity of layers proved to be very high. The
burden surface was smooth, with no ends and traces of rings. It was
established that the speed of the rotor had a distinct impact upon
the distribution of material along the radius. This impact appeared
to become more and more conspicuous as the furnace was being filled.
A comparison of the profile of batch 15 as coke was dumped on ring 2
and batch 17 as coke was dumped on ring 4 shows that the thickness
of layer in the periphery in the second case became substantially
bigger.

Fig.1
General view of BRCU
When
material was loaded into the furnace centre (ring 1) batches 5, 9,
21, and 22, there was no pronounced pick of coke; the layers looked
flat, just repeating the preceding profile. However if this profile
is developed, (Fig.3) it may be seen that the profile has a
pronounced centre and with more material being charged, the centre
would become more conspicuous. This behavior of material can be
explained by the fact the material leaves the rotor not as a stream
of a small diameter, but rather in wide and flat flows, with the
furnace centre being filled gradually. As was mentioned earlier,
this is the advantage of the rotary charging technology (by thin
wide layers).
As
coke is loaded on R1, the batch would be distributed on rings in the
following order (mean value of 3 batches: 8, 9 è 14): R1 – 28,8%, R2 – 25,5%, R3 – 21,2%, R4 – 13,4%, R5 – 7,4%, R6 –
3,8%. R1 is not only effective instrument in loading coke to the
center with any stock level, but it also makes possible to
distribute coke batch with gradual decrease of the layer height
along the whole radius and to create coke interlayer in between of
two ore batches. If there is a deep pit at the burden surface (batch
21, pit depth 1,8 m) then coke fills up the pit and is being
distributed in following order: R1 – 45%; R2 – 36,2%; R3 – 15,9%; R4
– 2,9%.

1].C-R1-9,57 t; 2] O-R2-R6-(25-17-17-8-33)-27,5 t; 3] C-R1-9,57 t;
4] C-R2-R3-(70-30)-9,54 t; 5] O-R2-R6-(33-17-17-8-250-27,74; 6]
C-R1-9,91 t; 7] C-R6-R2-(26-17-7-7-43)-9,83 t; 8] O-R3-28,19 t; 9]
C-R1-10,32 t; 10] C-R2-R6-(53-7-7-7-26)-9,91 t;
11]
O-R2-28,53 t; 12] C-R2-R3-(50-50)-10,50 t; 13] O-R2-28,95 t; 14]
C-R1-10,56 t; 15] C-R2-10,82 t; 16] O-R2-28,07 t; 17] C-R4-10,24 t;
18] O R5-28,51 t; 19] C-R2-R6-(53-7-7-7-26)-9,63 t; 20] O-R5 29,4 t;
21] C-R1-9,54 t; 22] C-R1-4,56 t;
Fig.2
The burden profiles
BRCU
is equipped with a captive automatic control system, which consists
of the rotor controlling mathematical model, which in turn is based
on controlling the rotor speed. For that reason experiments were
carried out to determine the corrective factors to be inserted into
the mathematical model so that it could be adapted to the production
conditions. To this end first of all the rotor RPMs had to be
determined, when material would reach the upper rim of the top
cylindrical section. The diagram of the experiment is shown in
Figure 4. As the research showed, when coke was charged this speed
was 15 RPM, in case of ore-bearing material it was 13.2 RPM. Table 1
shows the position of the loaded material ridge (on equal-in-area
rings), depending of the rotor speed).

Fig.3 Developed profiles
Table 1
Rotor speed impact upon the burden ridge position.
Ridge
position |
Centre,
R1 |
R2 |
R3 |
R4 |
R5 |
R^ |
Coke RPM |
In
reverse |
5.5 |
8.0 |
10.3 |
12.5 |
15.0 |
Ore, RPM |
In
reverse |
4.8 |
7.4 |
9.7 |
11.5 |
13.2 |
On the basis of analysis of the radial distribution of stock
correction were made in the rotor controlling algorithm.
The time factor is a very essential parameter for the radial
distribution of burden. The longer is the time of distribution,
the more layers would be laid into the furnace top.
During commissioning we determined the rate of material passing
through the calibrated rings of 800, 725 and 6500 mm diameter.
The results are given in Table 2.
As Table 2 shows, with the calibrated ring diameter dwindling
from 800 mm to 650 mm, the material charging rate decreased in
terms of coke by 1.9 times. In terms of ore bearing material -
by 1.76 times. At that the circular distribution was improved.
However, the measuring of the real time of stock charging and
charging cyclograms showed that the burden charging rate maximum
had exceeded the rated demand of the furnace for raw material by
30-40%. So, even in case of the calibrated ring being 650 mm,
the charging rate will be sufficiently high and for that reason
ultimately it was decided to go for a 650 mm ring.
Table
2
Impact of the calibrated ring diameter in the transfer hopper upon
the charging rate
Ring
diameter |
800 mm |
725mm |
650mm |
Coke, t/sec |
0.486 |
0.379 |
0.249 |
Coke m3/sec |
0.75 |
0.61 |
0.402 |
Ore material
t/sec |
1.476 |
1.368 |
0.836 |
Ore
material, m3/sec |
0.765 |
0.72 |
0.435 |

Fig.4
The diagram of experiment
In
the running furnace, the charging time of each batch of material is
picked by the sensors, detecting the emptiness of the transfer
hopper and the system would be kept adapted to the variations in
burden conditions.
Analysis of heats
To
analyse the smelting technology two periods were chosen when the
furnace run was steady. The data acquired are shown in Table 3.
In
the first period after blow-in the following charging pattern was
implemented:
1) C1-R3-R5-(50-20-30)
9.7 t
2)
O1--R4-R5-(50-50) 32.1 t
This
means that coke was charged in the first batch, from ring 3 to ring
5. In brackets it is time spent by the rotor for each ring in
percentage of the total charging time, and the last figure - 9.7 t
is the weight of the batch. Further, in the second batch
Table
3
Blast
furnace performance
Technological parameters |
Period 1
17-31.05.07 |
Period 2
22-28.02.07 |
1. Ðroductivity,
t/day |
3248 |
3077 |
2. Coke
rate, kg/t |
528 |
467 |
3. CDI
rate, kg/t |
69 |
70 |
4. Total
fuel rate, kg/t |
592 |
537 |
5. Sinter
rate, kg/t |
617.8 |
1046 |
6. Pellets rate, kg/t |
377 |
534 |
7. Iron
ore rate, kg/t |
364 |
- |
8. Limestone rate, kg/t |
11 |
9 |
9. Dolomite rate, kg/t |
73,5 |
54 |
10. Quartzite rate, kg/t |
44 |
42 |
11. Si in
hot metal, % |
0.96 |
0.64 |
12. Temperature of blast, C0 |
1119 |
1055 |
13. Blast
pressure, bar |
2,7 |
2,69 |
14. Top
pressure, bar |
1,3 |
1,35 |
15. Oxygen
in blast, % |
25,4 |
23,4 |
16. CO
content in top gas, % |
26,3 |
24,4 |
17. CO2 content in top gas, % |
21,3 |
22,9 |
18. CO
utilization rate, % |
44.3 |
48,4 |
19. Temp-ure
distribution on the top, C0 1 |
167 |
118 |
2 |
160 |
81 |
3 |
123 |
100 |
4 |
100 |
171 |
Center 5 |
89 |
325 |
of
the cycle an ore-nearing part was loaded onto ring 4 and 5, with
time spent 50 -50%.
In
the second period the charging pattern consisted of 6 batches.
1) C1-R2-100-9.1t - ring-wise charging of coke, 100% of time on ring2;
2) O1-R4-100-37t - ring-wise charging of ore-bearing material, 100% of
time on ring 4;
3) C2-R3-R5 -(40-10-50) - 9.1 t, multi-ring charging of coke
distribution by time
4) O2-R4-100-9.1t -ring-wise charging of ore-bearing material;, 100% of
time on ring 4;
5) C3-R4-R5 (50-50) - 37 t , multi-ring charging of coke,
distribution by time
6) 6)
O3-R4-100 - ring-wise charging of ore-bearing material, 100% of
time on ring 4
A
mathematical model was developed specifically to visualize the
laying of burden in the upper section of the furnace. Account was
taken of the impact by rotor performance parameters upon the burden
distribution, as well as descends rate and angles of repose of
material. In detail the impact of the rotor performance parameters
upon the distribution of material are discussed in publication [1].
Figure 5 shows the diagrams of variations in ore/coke ratio along
the furnace top radius, as calculated by the model in application to
the conditions of periods 1 and 2 of heats.

Fig.5
Full cycle Ore/Coke ratio
From
the data of Table 3 it follows that in the second period the furnace
performance indices in terms of fuel rate were substantially
better. The summary rate of fuel in the second period was less by
55kg/thm as compared with the first period. This can be explained
basically by a better burden stock. In the second period the summary
rate of fluxes and quartzite was by 23.5kg.thm lower than it was in
the first period. Besides, in the second period the raw ore was
completely replaced with pellets and sinter. A positive impact was
exerted upon the reduced fuel rate by a better distribution of
material along the furnace central line in the second period. So, in
the second period the ore/coke ratio in the furnace periphery was 5,
while in the first period it was 3.5 (Figure 5). In both cases in
the furnace centre the ore/coke ratio was almost the same. By
increasing the ore/coke ratio in the periphery thus reducing the
periphery flow of gas in the second period, the technologists
managed to shift the gas flow towards the furnace centre. This
shift is substantiated by the temperature of gas flow measured along
the top radius. In the second period the gas temperature in the
center was 325°C as compared with 89°C in the first period. A
better distribution of material and gas flow along the radius had
naturally resulted in a better use of CO in the blast furnace. In
the second period the utilization of CO was 48.45%, while in the
first period it was 44.3%. These data on heats operation show that a
rotary method of burden distribution makes it possible to have a
flexible control over the distribution of burden along the furnace
radius.
In
conclusion it should be noted that all the data given in this paper,
pertain to the starting period when the bell-less charging apparatus
was adopted. This research will be continued and there is a
substantial potential for further improvements and optimization of
the charging operation for this furnace.
Reference.
[1]
B.M. Boranbaev, S.K. Nosov, A.N. Lavrik “New concept of blast
furnace charging”
XXXII
Ironmaking Seminar, November, 6 to 8, 2002, Vitoria-TS-Brasil.
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