optimalization of heat transfer for …seaisi.org/file/5b-2 optimalization wchgl pt krakatau...

SEASI 2018 CONFERENCE , 25-28 JUNE 2018, JAKARTA

of 11

OPTIMALIZATION OF HEAT TRANSFER FOR

WATER COOLED HOT GAS LINE IN DEDUSTING

SYSTEM SLAB STEEL PLANT

Dinaryuda Dwi Kurniawan1), Mardono2), Arief Budi Artha3)

Maintenance Service Iron and Steel Making,

PT. Krakatau Steel (Persero) Tbk.

Jl. Industri No 5, Cilegon, Banten 42435 Indonesia

e-mail: [email protected]), [email protected])

Abstract

Dedusting Plant is one of the system that is a part of Slab Steel Plant. This Dedusting

Plant aims to take up hot gas which is produced by Electric Arc Furnace (EAF) on Steel

Making Process. Water Cooled Hot Gas Line is one of heat transfer part of this Dedusting

Plant. Performance of Water Cooled Hot Gas Line can be indicated by the values of the

temperature (T) fluid that flowing in and out.In this Water Cooled Hot Gas Line, The

Temperature of water flowing out, exceed standart temperature. So this high temperature outlet

make the system trip/off. So that need to evaluating heat transfer of water cooled hot gas line

to remove delay process because of the high temperature outlet water cooled hot gas line.

This optimalization aimed to evaluate the heat transfer performance of water flow in a

water cooled duct in section 1 and 2 EAF 6. This sections consisted of three parts, namely inlet

header, pipe line, and outlet header. The inlet header has a diameter nominal pipe 125, the pipe

line has a diameter pipe 76.1 mm, and the outlet header has a diameter nominal pipe 125. The

water entry to inlet header which is has 3 branch in that is come to pipe channel, then from pipe

channel the water exit to the 3 branch out of oulet header. In this optimalization used the theory

heat transfer equation to calculate the performance of heat transfer and use 3D drawing

software to design a new modification on water cooled duct.

The results of the calculation of heat transfer showed that the water cooling system need

to be improve because the design of header and branch are not optimum. Then, based on the

heat transfer calculation, modification can be made for the inlet and outlet header and for the

branch of pipe line. The inlet header and outlet header is changed from nominal diameter pipe

125 to 150. The Branch of pipe line is changed from 3 Branch which have length of cooling

pipe 233.577 meter each part to 6 Branch which are have length of cooling pipe 109.448 meter

each part. So the water that flow to the pipe channel now have a shorter circuit than the

existing.. Optimalization of the Header and the pipe branch show a better heat transfer for the

water cooled hot gas line system on dedusting plant.

Keyword : heat transfer, water cooled duct, header inlet and outlet, branch, pipe line

mailto:[email protected]

mailto:[email protected]


of 11

I. INTRODUCTION

Dedusting Plant is one of the system that is a part of Slab Steel Plant. This Dedusting

Plant aims to take up hot gas which is produced by Electric Arc Furnace (EAF) on Steel

Making Process. In this Dedusting System have a several part, for example : water cooled hot

gas line, canopy, drop out box, forced draught cooler, mixing chamber, bag filter house, ID fan

and etc. The Main problem is in the Water cooled hot gas line.

Water Cooled Hot Gas Line is one of heat transfer part of this Dedusting Plant. This

water cooled hot gas line is a ducting which is consist of pipe-pipe around the wall.

Performance of this water cooled hot gas line can be indicated by the values of the temperature

(T) fluid that flowing in and out. In this Water Cooled Hot Gas Line, The Temperature of water

flowing out in one of this section exceed standart temperature. So this high temperature outlet

make the system trip/off. So that need to evaluating heat transfer of water cooled hot gas line

to remove delay process because of the high temperature outlet water cooled hot gas line. This

High temperature occur in EAF number 6 on section 1 and section 2. The main background of

optimalization necessity was shown in this section. The main problem of the high temperature

of water cooled hot gas line in Dedusting Plant was explained in Section II. Section III

presented the new design of water cooled hot gas line. The result of implementations was

described and analyzed in Section IV. Section V provided the conclusions.

II. MAIN PROBLEM IN DEDUSTING PLANT

A. Overview Of Dedusting Plant

Figure 1. Dedusting Plant of Electric Arc Furnace

Water cooled drop out box

Water cooled duct

Canopy

hood

Forced draft cooler

Filter and stack


of 11

The dedusting system is designed with two duct systems consists of the primary duct

(includes water cooled and uncooled duct) and the secondary duct (canopy duct) are both mixed

in the mixer duct before the filter. Off gas or waste gas from the EAF consecutive sucked

through some water cooling hot section of gas line, uncooled hot gas line, force draft cooler

and filter by operation 2 ID fan (1 standby). Negative pressure inside the EAF is measured and

controlled and regulated by the dilution Electric Control (DEC) damper.

Figure 2. Dedusting Plant of Electric Arc Furnace (Top View)

The temperature at the inlet filter is controlled by mixing chamber which is the equipment

where the mixing temperature occur between the primary duct to the secondary duct canopy.

While the water emergency damper acts to lower the temperature in the duct system in case of

over temperature.

Filter bag in the filter plant is cleaned through the cleaning system by cooling air jet

instrument, dust will descend into the filter hopper and passed continuously by a chain

conveyor / rotary valve and bucket elevator to the silo and ends in an open container or truck.

Water Cooled Hot Gas Line

Water Cooled Hot Gas Line is made by using pipe boiler ST. 35.8.I. Water cooled hot gas

line consists of furnace elbow, sliding sleeve, and water cooled duct section. To prevent

overheating in hot gas line as a result of heat radiation or heat impact or due to lack of the flow


of 11

of cooling water, water temperature sensor and flow meter measurement are installed to

monitor each circuit water cooling line.

Furnace elbow or elbow is fixed to face each other with the elbow roof so that under normal

conditions (sliding sleeve close) has a clearance of approximately 50 mm. The distance

between the elbow with a fixed roof can be adjusted via a mechanism elbow sleeve sliding

back and forth with the motor electric drive system (open and close). The main function of the

sliding sleeve is for additional input from atmospheric oxygen so that the exothermic reaction

CO can take place completely in the hot gas line. Under conditions of automatic, sliding

movement of the sleeve is set based mode operating conditions EAF is happening.

Figure 2. Uncooled Duct

Un-cooled duct is made from high resistant material which is steel plate 16Mo3. For

avoiding the over-heating in the un-cooled duct and controlling the inlet temperature of Force

Draft Cooler (FDC), the system is equipped with emergency water dilution damper. Emergency

water dilution damper is designed by using the motor driving system AUMA (open and close)

with the set point temperature sensor at the inlet FDC 550oC so that the temperature un-cooled

would be restrained.


of 11

Force Draught Cooler

\

Figure 4. Forced Draught Cooler

Force draft cooler is designed to reduce the temperature of primary duct into 250oC. Hot gas

from un-cooled duct enters the draft force cooler through the inlet header then distributed to

the heat exchanger package casing (the casing has several chamber). Hot air from the inlet

transfering heat to the walls of the chamber (heat exchange area), the walls of the chamber

receiving heat from the inside is cooled by blowing air from the outside (outside force

convection) through 9 pieces of axial cooling fan that works by setting the temperature of the

temperature sensor placed in the outlet side of FDC.

B. Water Cooled Hot Gas Line

Figure 5. Piping and instrumentation diagram


of 11

Piping and instrumentation diagram of section 1 and 2 water cooled hot gas line is shown in

the Figure 5. The flue gas flow from EAF to fixed elbow 1, then fixed elbow 2, then come to

Drop Out Box. After DOB the flue gas entry section 1 then section 2. The standart of flow and

temperature is shown on the piping line. Figure 6. Shows that drawing of the section 1 which

have pipe around the wall and have header inlet and outlet. This sections consisted of three

parts, namely inlet header, pipe line, and outlet header. The inlet header has a diameter nominal

pipe 125, the pipe line has a diameter pipe 76.1 mm, and the outlet header has a diameter

nominal pipe 125. The water entry to inlet header which is has 3 branch in that is come to pipe

channel, then from pipe channel the water exit to the 3 branch out of oulet header.

Figure 6. Structure of piping in section 1

Figure 7. Mechanical Drawing of section 1

Table 1. Actual condition of section 1


of 11

In The Table 1, the high temperature of section 1 occurs in 3 sample data with maximum

temperature 82° C. Therefore the condition of this section 1 that often causes trip in Dedusting

System and then EAF will be delayed. So The operation of EAF is stop for a while until the

temperature decrease to normal, Then the Furnace can start again. This method is done to make

the Furnace still operates until pouring time, but it will be make the tap to tap time longer and

the cost production high.

III. DESIGN OF NEW WATER COOLED HOT GAS LINE

A. New Design Of Section 1 WCHGL

In the high temperature problem in section 1 the dedusting plant has been calculated on fluid

velocity, heat transfer, and outlet temperatures of section 1 pipes (data attached) conducted by

the maintenance engineering division. From the data it can be seen that to reach the outlet

temperature of 53 ° C, the cooling water velocity should be about 2.5 m/s and the pipe branch

is change from 3 to 6 branch. Calculation is made to compare the length of the pipe between 3

branch and 6 branch as shown on Table 2.

Table 2. Comparasion length of pipe branch

PIPE

BRANCH

EXISTING NEW

L (3 BRANCH)m L (6 BRANCH)m

1 233.577 109.448

2 233.577 109.448

3 216.877 109.448

4 - 109.448

5 - 109.448

6 - 92.748

NO

AKTUAL STANDART

HEADER SUPPLY OUTLET SECTION 1 HEADER SUPPLY OUTLET SECTION 1

T (C) P (BAR) T (C) Q (m3/hr) T (C) P (BAR) T (C) Q (m3/hr)

1 33 7 66 84 35 7 52 80

2 32 7 78 85 35 7 52 80

3 32 7 82 84 35 7 52 80


of 11

Figure 8. Ilustation of 6 branch pipe

The results of the calculation on Table 2 show that in 3 branch, length of the pipe is

233.577 meter and for 6 branch, length of the pipe is 109.448 meter. So The Branch of pipe

line is changed from 3 Branch which have length of cooling pipe 233.577 meter each part to 6

Branch which are have length of cooling pipe 109.448 meter each part. So the water that flow

to the pipe channel now have a shorter circuit than the existing. Because of the additional

branch in section 1, So Modification is needed for header inlet and header outlet as shown in

Figure 8. The inlet header and outlet header is also changed from nominal diameter pipe 125

to 150. It should be done to increase the capacity of the header for accommodate the additional

branch.

The project was executed directly on the plant. The modification starts with fabrication

of header inlet and outlet according to new drawing design and then assembly on section 1.

Figure 9 show that the comparasion betwen section 1 existing and new design. This

modification is continued to section 2 too.


of 11

Figure 9. Modificaton of section 1

IV. RESULT & ANALYSIS

Hot commissioning test has been conducted to examine the function of Water cooled hot

gas line which is concerned on section 1 and section 2. The individual test result are as follow:

a.

60 °C (LIMIT)

46 °C (ACTUAL)


of 11

b.

Figure 10. Graph of Temperature section 1& 2 ( a & b sample data)

The result of the test is shown in figure 10. Figure 10a and 10b are a graph taken from HMI

when furnace on. In figure 10a and 10b show that temperature is lower than 60° C that is the

limit of outlet temperature of section. Based on standart the temperature is in 53° C and

based on figure 10a and 10b the maximum temperature is approximately in 45° C. The

Temperature also can checked in the HMI figure 11 that show under the limit. So the

temperature for section 1 and section 2 is in the nomal condition (below the limit). This

testing was already tested for a month and the maximum temperature is still under 45° C.

Figure 10. Temperature of section 1 in HMI.

60 °C (LIMIT)

45 °C (ACTUAL)


of 11

V. CONCLUSION

Based on the results of the implementations and analysis, some conclusions could be obtained

as follows:

1) In the system cooling water, the solution of the over heating problem on the section is

increasing the flow rate of the cooling water, by considering capacity of water treatment

plant. In this case, modification for section 1 is to make additional flowrate for water

cooling and to make shorter pipe line for the water cooling. That can be done by the

new design of header inlet and outlet and also the change of branch pipeline.

2) Additional flowrate for a system cooling should consider the optimalization of heat

transfer. If the heat looses of the system is to high, Furnace will release amount of

energy looses too.

ACKNOWLEDGEMENTS

The acknowledgement was mainly given to the Board of Management of PT Krakatau Steel

(Persero) Tbk for issuing the permission to the authors in publishing this paper. The authors

would also like to acknowledge the Optimalization Team for their total supports in succeeding

the whole project phases.

REFERENCES

Siemens VAI Team. Technical Specification of SSP 1 Revitalization Project. Cilegon: PT

Krakatau Steel. 2010.

PTKS Team. Profile of Maintenance Engineering PT Krakatau Steel. Cilegon: PT Krakatau

Steel. 2013.

Cengel, Yunus A.,& Afshin J.G. (2015), Heat and Mass Transfer, 5th., McGraw-Hill,

Newyork.

Holman, J.P. (1990). Perpindahan Kalor. Edisi kelima. Erlangga: Jakarta .

optimalization of heat transfer for …seaisi.org/file/5b-2 optimalization wchgl pt krakatau...

Documents