Case

Philippines TSC Steel Plant

By introducing China’s hot iron charging technology of EAF and popularizing LF technology, the production cost in the plant has been greatly reduced and considerable economic benefits have been created.
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Project description

Technical service case for TSC in Philippines

 

From 2011 to 2013, appointed by TTIC as Chinese general manager for TSC in Philippines, and led Chinese team to introduce domestic hot-iron charging process on EAF for TSC, and train local workers regarding LF operation process and technology.

1. Factory background

TSC was built during Marcos's reign. It was designed and built by Japanese company. There were two 60t EAFs (but one only was allowed to operate under the condition of insufficient power supply at that time), one EAF with trough-tapping made in Japan, one EBT ultra-high power EAF manufactured by Xi'an EAF manufacturer, and one 4-strand CCM with 120 × 120mm billet . After that, a new 180m3 blast furnace was built for providing hot iron for EAF. At the same time, there are mechanical processing plants for TSC.

Before our team arrived, I was invited to carry out a field survey against the factory. During a week inspection, I carefully observed raw materials and finished billets on the site, and found that there were many defects in the equipment management. At the same time, there were many problems in the raw material logistics and scrap treatment management. Moreover, compared with the advanced EAF at that time, the transformer capacity configuration of EAF was low. There is great room promoted for improvement of smelting indexes.

I collected the parameters of EAF of TSC and some smelting indexes at that time and compared them with those of advanced EAF. See table below.

 

Table-1 Comparison parameters of EAF of TSC with advanced EAF worldwide:

 

 

Advanced EAF

Treasure Steel

EAF Capacity(t)

    80 - 200

60

Transformer Capacity

  (MVA)

22

Specific input power (kwh/t)

>= 700

440 - 480

Power on time (min)

<= 40

120

TTT(min)

 60

>= 180

Electric consumptionkwh/t)

<= 350

 700

Loading times

2  3

4  5

Oxygen consumption (m3/t)

30  40

a few

 

In view of this situation, we focused on the improvement of raw material management, equipment management and operation process, and optimized various steel-making production processes for TSC, greatly promoted steel-making capacity.

The first stage:

1. In the first three months, under the conditions at that time, we organized the production under the condition of full scrap because no hot iron was produced in blast furnace. We have formulated two sets of schemes: 1) high density crossing power on. In other words, when a EAF is cut off and charged, power is transmitted to another furnace immediately. 2) A EAF has priority in power on. That is to say, the operation of two EAFs is mainly based on one EAF. One EAF is given priority to finalize a complete smelting process to make it operate continuously. The other EAF delivers electricity during its intermittent period. After tapping of the priority EAF, another furnace is given priority to tapping operation, and the cycle starts again and again.

After a week's production practice, the statistical data show that the second method is a more scientific process with lower electricity consumption, which will be popularized in production later.

2. During this period, equipment maintenance should be strengthened to eliminate the hidden trouble of equipment failure to the maximum extent, so as to prepare for the next high-speed production.

3. Perfected the auxiliary equipment of EAF to make it reach the required state of hot charging.

4. Trained workers to promote their operation level and skills.

5. Formulated and completed the standardized management system of each process.

6. Improved scrap management and auxiliary material management.

In addition to the above work, Chinese employees, mechanical maintenance personnel, electrical and smelting personnel worked in accordance with the two shift system to improve production efficiency, strengthen the training of Philippine workers, and improve their operation skills as soon as possible.

Through above series of work, the daily output was increased from 600 tons / day to 1200 tons / day. The intended target of the first stage has been achieved.

No.

Comparison index

Unit

Before service

After service

Remark

1

Scrap

%

100

100

 

2

Hot iron

%

0

0

 

3

Daily output

hd

10

20

 

4

Monthly output

hm

250

500

 

5

TTT

min

144

72

 

6

Oxygen consumption

Nm3t

a few

35

 

7

Electric consumption

kwh∕t

~700

520

 

8

Electrode consumption

kg∕t

6.2

3

 

9

Daily yield

t

600

1200

 

Note:produce25 days per month

 

At this stage, we have done a lot of modification with low investment technical and carried out a lot of training for local workers, and achieved above remarkable results. Our technical transformation and training are as follows:

Technical modification

1. EAF area

1.1.Classification and logistics management of scrap

Instead of the usual unscientific management method that the cargo ship did not do any classification, it is directly transported into the workshop by truck. Starting from the scrap unloading from ship at the wharf, the preliminary classification of iron and steel materials, i.e. the classification of light and heavy scrap, is carried into the workshop by truck. During the unloading process, the closed vessels are picked out and treated to make them into open and then stacked on the corresponding scrap piles respectively; the iron parts in heavy scrap are classified and stacked separately for carbon distribution in EAF smelting; heavy scrap is used for charging distribution in EAF. Scrap with unqualified size should be stacked by category after cutting. Such scrap treatment and logistics management established a foundation for reducing the charging times and shortening the smelting time.

After the implementation of this measure, scrap logistics is orderly, scrap classification management is in place, made previous four chargings to three chargings, the smelting efficiency of EAF is greatly promoted.

1.2.Exhausting hole of lower shell of EAF

According to the Convention, Exhausting hole must be designed to ensure the exhaust of refractory and the water discharge of water-cooling parts while microleakage in the process of production. The water-cooling wall leakage in the production process leads to abnormal damage of EAF lining During production, and the production is forced to stop. After careful inspection, it was found that there was no exhausting hole in the previous design of lower shell. When we re-built the furnace lining, we should reasonably set the lower shell with exhausting hole was installed to avoid the recurrence of such accidents.

1.3.Grounding wire

In the production process, there is always the phenomenon of arcing in power-on process, which made the water-cooling parts leak. Before that, the local people were interrupted the production frequently. After investigation, the furnace shell grounding wire was in disrepair for many years, and it has been corroded. Therefore, we made a new grounding wire to overcome the recurrence of this accident.

1.4.Optimization of power supply system

In the production process, it was found that the power supply curve of the previous  operation was extremely unreasonable. In view of this situation, we provided technical training for local workers and explained the correct power supply curve, that is, if different power gears were used correctly during the process from charging and arcing, well penetrating, well penetrating to molten pool, in order to achieve the maximum efficiency of electric energy use and ensure that the power consumption can meet the requirements of the power department At the same time, it can save electricity.

1.5.Reasonably arrange the operation of two EAFs

Due to the power supply of the local electric power department, the two EAFs in the factory can not supply power at the same time, and the capacity is only enough for one EAF.

We have formulated two sets of schemes: 1) high density cross transmission. In other words, when one electric furnace is cut off and charged, power is transmitted to the other furnace immediately. 2) One electric furnace has priority in power transmission. That is to say, the operation of two electric furnaces is based on the priority tapping of one electric furnace, and the other electric furnace delivers electricity during its intermittent period. After tapping of the priority electric furnace, the steel tapping operation of the other electric furnace is given priority to again and again.

The comparison of the two methods shows that the output is the same, but the second method has lower power consumption, more reasonable and scientific.

1.6.Equipment spot checking

There are two reasons regarding low production capacity in the factory. One is that the logistics of scrap is disorderly and the management of scrap classification processing is not in place, which makes the three times of loading become the four times. The second reason is that the equipment spot check is not in place, and the local maintenance personnel are not in place at ordinary times, resulting in sudden equipment failure in production process, which makes the production forced to stop, affecting the entire production efficiency; the team formulates scientific points Inspection plan, strengthen equipment point inspection, basically avoid the production process equipment failure and stop the phenomenon; for continuous production to do a good equipment support, greatly changed the passive situation at that time.

2.CCM area

2.1.Optimization of casting process

When local workers start casting, they only consider the convenience of operation. The middle strands are first casted, and then side two strands are opened. The molten steel is often forced to return to the furnace due to the failure of side two strands , which causes great economic losses to the company. We trained the casting workers to understand that the two strands on the side of tundish are low temperature areas and the middle strand is the high temperature area. The strands in low temperature zone should be started before casting Since then, there has been no such error. The billet yield of continuous casting machine is greatly increased.

2.2.Optimization of distance between tundish and CCM vibration platform

Due to the lack of distance between tundish and CCM vibration platform, workers could not monitor the liquid level of copper mold during casting process, and they are in a blind zone. They often had to stop casting because of the rapid fluctuation of molten steel coming out of copper mold, which made the operation fail.

The ladle support arm of the turret is padded up 250mm, that is, the distance between tundish and the vibration platform of continuous caster is increased by 250mm, so that the operators can monitor the liquid level well and prevent the recurrence of similar accidents.

2.3.Solution on the problem of decoupling between dummy bar and billet

Due to the CCM has been used for many years, the equipment status is not ideal due to the shortage of spare parts. Therefore, the problem of uncoupling between the dummy bar of CCM and the billet often occured at the pinch roller position of the three-point straightening. We have solved this problem thoroughly by overlaying the worn parts of the dummy bar.

Technical training

1. Formulated systematic training materials for EAF, LF and CCM operation procedures.

2. Formulated safety operation procedures for various types of post.

3. Formulated emergency response plan for EAF, LF and CCM area.

4. Made the plan of EAF resuming and preheating.

5. Formulated operation and maintenance manual and point inspection system for EAF, LF and CCM.

6. The technical standards of raw materials and auxiliary materials were compiled.

7. Making hot charging process of hot iron for EAF

The local workers were organized to carry out irregular training for several months according to the type of post, which achieved remarkable results.

1. The local workers have mastered the operation skills of charging hot iron.

2. The workers have mastered LF operation skills.

3. The local workers have standardized the EAF lining preheating process.

4. The maintenance ability of the equipment was improved.

Technical training is very important for an enterprise, which can improve the technical level and quality of workers as a whole, realize the efficient application of practical technology, and the enterprise is approaching to the fine and strict standardized management, and maximize the potential of the overall equipment, with less production input, higher output and higher efficiency.

 

The second stage:

The charging amount of hot iron was based on the hot iron output of BF at that time. At the same time, the peripheral conditions of the plant, such as hot hot supply, oxygen supply, oxygen blowing equipment, personnel operation level, raw material management, etc., were also in place. No2 EAF cooperated with LF in production, and the charging hot iron process was implemented from the second stage.

After the equipment hot charging conditions were met, BF could supply hot iron normally, charging 20-30% hot iron. In these three months, the new hot charging process was straightened out, and local workers were trained how to operate hot charging process and oxygen operation safely. At the same time, the storage of charged hot iron and the capacity of hot iron pot were solved. The designed capacity of hot iron is 60%, that is 30-40 tons. This is a transitional process. By taking advantage of the combination of No2 EAF and LF, the plant's output has steadily increased on the basis of the first stage.

 

No.

Comparison index

Unit

Before service

First stage

Second stage

1

Scrap

%

100

100

70-80

2

Hot iron

%

0

0

20-30

3

Daily output

h∕d

10

20

24

4

Monthly output

h∕m

250

500

600

5

TTT

min

144

72

65

6

Oxygen consumption

Nm3t

A few

35

40

7

Electric consumption

kwh∕t

~700

520

450

8

Electrode consumption

kg∕t

6.2

5

4.2

9

Daily yield

t

600

1200

1330

 

The third stage:

Hot iron of BF's normal and sufficient supply provided conditions for continuous improvement on proportion of charging hot iron. On the basis of the second stage, we would start from 20-30% of hot charging hot iron proportion, and gradually transited to 50-60% until reaching this goal. See the below table for smelting index and production capacity.

No.

 

Comparison index

Unit

Before service

First stage

Second stage

Third stage

1

Scrap

%

100

100

70-80

40-50

2

Hot iron

%

0

0

20-30

50-60

3

Daily output

h∕d

10

20

24

26

4

Monthly output

h∕m

250

500

600

650

5

TTT

min

144

72

65

55

6

Oxygen consumption

Nm3t

A few

35

40

50

7

Electric consumption

kwh∕t

~700

520

450

380

8

Electrode consumption

kg∕t

6.2

5

4.2

2.5

9

Daily yield

t

600

1200

1330

1570

With joint efforts of Chinese team led by me, I basically completed the task of stable production and Optimization in 9 months, and since then, TSC production line has been kept in a stable state; Party A's production capacity has been greatly improved, production costs have been significantly reduced, and considerable economic benefits have been created for the factory. At the same time, it has greatly improved the operation level and skills of local workers. They have gradually and steadily transferred from full scrap smelting to charging hot iron. They have mastered LF technology with EAF charging hot iron and successfully wrapped out established goal of technical service, which has been highly appraised by owner.

 

Shengdu

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5-503, Beichen Building, Beichen District, Tianjin

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