IEEES-1 Proceedings of the First Exergy, Energy and Environment Symposium 13-17 July 2003, Izmir, Turkey Paper No.

ENERGY BALANCE APPLICATION FOR ERDEMIR COKE PLANT WITH THERMAL CAMERA MEASUREMENTS M. Emre Ertem, Abdulkadir Özdabak Ereğli Iron & Steel Works Inc. 67330 KDZ. Ereğli [email protected] [email protected]

ABSTRACT Ereğli Iron and Steel Works Inc. (Erdemir) began its activities on May 15th, 1965 with a capacity of 470.000 tons/year and has made important contributions to our country’s economy ever since. Today with a total annual crude steel production capacity of 3.0 million tons, it is the largest iron & steel factory and only integrated flat steel producer in Turkey. It is producing sheet, hot and cold rolled coils, zinc, tin and chromium plated steel. In this study, energy balance application has been done for Coke Plant of Erdemir. Heat losses by radiation was determined by thermal camera. By using thermal camera measurement results and other data, Sankey Diagram was prepared for Erdemir Coke Plant.

results were distributed to related departments via company intranet systems. As long as the blast furnace (BF) integrated route remains a dominant means for producing steel, coke will continue as a major source of energy to the industry. Total coke consumption has been reduced significantly over recent years, attribute primarily to increased levels of coal, oil and gas injection to the BF, and varies between <300-530 kg/thm. In addition, because of the by-product gas produced during coke making, the process forms an integral part of the energy balance for the entire integrated works. Thus, despite efforts to the level of coke consumption, coke making will continue as an important component of the steel making process into the future. COKE PLANT

INTRODUCTION Coke Making A Coke Plant is very important part of an integrated steel plants. Metallurgical coke from blend of different coking coals, which is the one of main input of blast furnace as energy source and as chemical reagent, produced in Coke Plants. This is achieved by heating coal in a oxygen free atmosphere, a process also called: dry distillation. From the volatiles, produced during the carbonization of coal, tar, ammonia, hydrogen sulphide, naphthalene and benzene are removed.

Coal in its basic form is not suitable for direct use in the blast furnace burden. It contains too many harmful or useless elements for the melting process in a reducing atmosphere and is not strong enough to carry the blast furnace burden. It must therefore be converted to metallurgical coke. A coke battery cross section and production process of coke can be seen in the Figure 1.

Erdemir Coke Plants are set to meet the metallurgical coke requirements of blast furnace No 1 and No 2. Their annual capacity is 1.022.000 tons. Two batteries having 37 furnaces each and the other battery having 85 furnaces have come on stream in 1964 and 1978 respectively. In Erdemir, equipment failures, corrosions, heat losses and wear of refractors are determined by Thermal Camera measurements since 1994. It is used as a predictive maintenance tool. Obtained data are analyzed with the computer program and

Fig. 1. Conversion of Coal Into Coke Coke is produced by heating particulate coals of very specific properties in a refractory oven in the absence of oxygen to about 1100 oC (2000 oF). As

temperature increases inside the coal mass, it melts or becomes plastic, fusing together as devolatilization occurs, and ultimately resolidifies and condenses into particles large enough for blast furnace use. During this process, much of the hydrogen, oxygen, nitrogen, and sulfur are released as volatile by-products, leaving behind a poorly crystalline and porous product. The quality and properties of the resulting coke is inherited from the selected coals, as well as how they are handled and carbonized in coke plant operations. Energy Consumption in the Coke Plant The coking process was developed to overcome the problems of using coal as a reductant in smelting type processes, such as the Blast Furnace. The properties of coal are such that it softens at elevated temperatures, reducing the permeability of the burden, and, therefore, the efficiency of the blast operation. Thus, coking provides a means of carbonizing coal particles into lumps with the appropriate physical and chemical characteristics, by the removal of volatile materials, to allow for efficient BF operation. That is, coke provides the heat source to ensure efficient reduction of iron ore, the chemical reductant, in the form of carbon, and a permeable support to allow free flow of gasses within the furnace shaft. A coke works may include a coal yard, where coals are received and stored, a coal permanent system, for crushing, mixing and preheating the coal, a coal moisture control process (CMCP), to control moisture in order to improve quality and productivity, the coke battery, where the coal is carbonized in a series of heated chambers, a wet or dry coke quenching station, where hot coke is rapidly cooled to reduce oxidation, an exhauster system, to collect the hydrocarbons and by-product gas produced during carbonization and by-product plant, where the hydrocarbons and by-product gas are treated prior to sale or use. From the viewpoint of energy consumption, the major areas include:

Erdemir Coke Plant General The plants are set to meet the metallurgical coke requirements of the blast furnaces. Their annual capacity is 1,022,000 tons. Coal is separated in Coal Preparatory Units according to its types, weighed, mixed and filled into coal silos via conveyors. There are three Koppers Becker type batteries in Coke Plants. Two batteries having 37 furnaces each and the other battery having 85 furnaces have come on stream in 1964 and 1978 respectively. There are 159 furnaces in total. These furnaces are operated independently by computers. The charging vehicle that takes coal from coal silos unloads approximately 22 tons of coal into the furnace from above. The temperature of this furnace is 0 approximately 1,600 C. The coal stays in a atmosphere with no oxygen for approximately 18 hours. The undesired elements in coal are decomposed by means of the high temperature and 20 tons of metallurgical coke coal is obtained. (Figure 3) The by-products, which come out as coal turns into coke, are used in the factory. These byproducts are bitumen, benzol, ammonium sulphate, fertiliser, toluol and xysolium. The coal is unloaded into railway cars with pushing cranes after the furnace door is opened. The coal starts burning when the door is opened as it changes into an atmosphere containing oxygen from a non-oxygen atmosphere. In order to end this burning, the locomotive approaches near to the cooling towers and pouring on approximately 3,000 m3 of water cools the coke.

1. Fuel used for under firing on the coke battery, Figure 2, 2. Steam used for exhauster operation and byproduct treatments, 3. Electricity used for pumps, motors, blowers etc. Radiation and Others 481 MJ/t-coke

Underfring Gas 3185 MJ/t-coke Coke Ovens 3.508 MJ/tcoke Reaction Energy 323 MJ/t-coke

Waste Gas 470 MJ/t-coke Coke Oven Gas 866 Hot Coke 1691 MJ/t-coke

Fig.2 Thermal Balance of the Coke Making [1]

Fig.3. Coke Ovens, Coke Side Energy Consumption in Erdemir Coke Plant Each coking chamber of Erdemir Coke Plant measures 0,42 meters wide, 4,5 meters high and 12

meters deep and is fitted at both ends with removable full height doors. Coal is charged through four 40-45 mm diameter holes above each coke chamber from a special car that runs along the top of the battery. Once charged, the coal is leveled, the doors and charge lids are sealed and heating (under firing) commences. Distillation products in the form of tar and coke oven gas, driven off during the heating process, are collected in mains which run the length of the battery and are transported to the by-products

plant. When the heating cycle is complete, the oven isolated from the main, the end doors are removed and solid coke is pushed into a coke car. The coke car travels along the side of the battery to the quench tower where new or recycled water is sprayed on to the hot coke to reduce its temperature o to 100-150 C. Energy balance for the coke plant of Erdemir in 2001 was given in table 1 and 2

Table 1. Energy Consumption at Erdemir Coke Plant Salty Coal COG BFG Electricity Steam Water Total Water Mcal/TP 872 2300 800 125 500 7680 4384 kcal/Nm3 kcal/kwh kcal/kg kcal/m3 Kcal/m3 kcal/kg kcal/Nm3 610,7 22,2 136,7 30,0 3,0 10626,5 1256,8 62,9 Nm3/TP Kwh/TP kg/TP m3/TP m3/TP kg/TP Nm3/TP Table 2. Energy Production (Recovery) at Erdemir Coke Plant Coke COG Tar Light Oil Total Net Total 9000 10032 7680 4384 Mcal/TP Mcal/TP 3 kcal/kg kcal/kg kcal/kg kcal/Nm 38,9 8,9 9418,1 1208,4 1000 452,6 kg/TP kg/TP kg/TP Nm3/TP COG : Coke Oven Gas BFG : Blast Furnace Gas ENERGY BALANCE APPLICATION FOR COKE BATTERIES WITH THERMAL CAMERA MEASUREMENTS

Thermal differences in cooling systems helps to calculate heat losses that are directly related to energy consumption and, Sankey Diagrams can be drawn easily by using the thermal measurements.

Thermal Camera Applications Coke Batteries Energy Balance Thermal image cameras are instruments that create pictures of heat rather than light. They measure radiated IR energy and convert the data to corresponding maps of temperatures. Today, instruments provide temperature data at each image pixel and, typically, cursors can be positioned to each point with the corresponding temperature read out on the screen or display. Images may be digitized, stored, manipulated, processed and printed out. Industry-standard image formats, such as the tagged image file format (TIFF), permit files to work with a wide array of commercially available software packages. The subject of infrared radiation and the related technique of thermography are still new to many who are in a position to make use of Thermal Cameras. Advantages of thermography • Quick problem detection without interrupting service • Prevention of premature failure and extension of equipment life • Identification of potentially dangerous or hazardous equipment • Reduction in insurance premiums • Effective infrared scanning in order to save revenue and prevent down-time

Some measurements and 20 thermal images has been taken in December 2002 in order to find energy and mass balance of coke batteries. By using these measurements and thermal images, energy balance efficiency of coke chambers has been calculated. The calculation method and process flow chart was given at figure 4 and table 1. Energy Input A. Combustion of Coke Oven Gas Composition of Coke Oven Gas % 0,0800 % 0,0100 % 0,5900 % 0,0430 HLow. HHigh.

CO C2H6 H2 N2

% 0,2220 % 0,0200 % 0,0050 % 0,0300

= 4.354 Kcal/Nm3 = 4.895 Kcal/Nm3

Under Firing Gas 1.931 Nm3/p * 4.354 Kcal/Nm3 Q1 :

CH4 C4H8 O2 CO2

8.407.574 kcal/p

(1)

3

3

Coke Oven Gas (285 Nm -345 Nm ) 3 3 315 Nm /kg Coal, 5.905 Nm /p 2.917 kg/p o 700 C o Cp: 0,965 kcal/kg C

Hard Coal 18.745 kg/p o 20 C o Cp: 0,31 kcal/kg C

Radiation & Convection + Others

CHA MBER

CHA MBER

COMBUSTION

Coke Oven Gas 3 (117 m /h*16,5 h) 1931 Nm /p, 955 kg/p o 60 C o Cp: 0,712 kcal/kg C 3

COK E

Combustion Air 3 16.144 kg/p, 12.540 Nm /p o 20 C o Cp: 0,241 kcal/kg C

COMBUSTION

CHA MBER

Flue Gas 3 13.871 Nm /p, 17.099 kg/p o 250 C o Cp: 0,259 kcal/kg C

Coke (Coal/1,25) 14.996 kg/p (10% Ash) o 1100 C o Cp: 0,359 kcal/kg C

Fig.4. Flow Chart of Coke Battery

Control Volume o Ambient Temperature : 20 C MASS BALANCE

Air COG

: 16.144 kg/p : 955 kg/p

Combustion Chamber

Flue Gas : 17.099 kg/p

Coal

: 18.745 kg/p

Coke Chamber

Coke : 14.966 kg/p COG : 2.917 kg/p Others* : 862 kg/p

Temperature of Coke : 1100 oC Amount of Coke : 14.996 kg/p

B. Sensible Heat of Coke Oven Gas COG Cp : 0,712 Kcal/Kg Co (at 60 oC) Ambient Temperature : 20 oC 955 kg/p * 0,712 Kcal/Kg Co * (60-20) oC Q2 : 27.198 kcal/p

14.966 kg/p * 0,359 Kcal/Kg oC * (1100-20) oC

(2)

Q1 :

(6)

5.802.618 Kcal/p

B. Sensible Heat of Produced Coke Oven Gas C. Reaction Energy (RE) Q3 :

: 0,965 Kcal/Kg oC (at 700 oC) COG Cp Amount of COG : 5.905 Nm3/p, 2.917 kg/p COG Temperature : 700 oC

3

8% CO 473 Nm → 591 kg 3% CO2 177 Nm3 → 348 kg

2.917 kg/p * 0,965 Kcal/Kg oC * (700-20) oC

Reaction Energy from CO 591 kg *943 kcal/kg= 557.313 kcal/p Reaction Energy from CO2 348 kg *2.316 kcal/kg= 743.328 kcal/p

(7)

(3) Q2 :

1.914.135 kcal/p

(4) C. Sensible Heat of Flue Gas

Total Reaction Energy Q3 : 1.300.641 kcal/p

Flue Gas Temp. Flue Gas Amount Flue Gas Cp

D. Sensible Heat of Combustion Air Q4 :

: 250 oC : 17.099 kg/p : 0,259 kcal/kg oC (at 250 oC)

17.099 kg/p * 0,259 kcal/kg oC * (250-20) oC

0 (Reference and ambient temperature are same)

Q3 :

(8)

1.018.587 Kcal/p

E. Sensible Heat of Coal D. Radiation and Convection (Table 3 & Figure 5) Q5 :

0 (Reference and ambient temperature are same)

Total Input Energy Q1+Q2+Q3+Q4+Q5 8.407.574+27.198+1.300.641+0+0 (kcal/p) QT :

Qr = E*20,248*((Ts/100)4-(To/100)4)*0,2388 kcal/m2h; (9) E = 0,90 (10) Qc = B*(Ts-To)1,25 *0,2388 kcal/m2-h B Horizontal Walls and ve Top Heat Losses 11,721 Vertical Walls and ve Bottom Heat Losses 9,209 Horizontal Walls and Bottom Heat Losses 6,279

(5)

9.735.413 kcal/p

3.2.2 Energy Output 3.2.3 Energy Balance A. Sensible Heat of Coke o

According to the calculations, energy balance of one of coke chamber has been realized by actual data. 0,22% heat losses by radiation and convection has been found by using thermal measurements. Balance table was given in table 5.

o

Coke Cp 0,359 Kcal/Kg C (at 1100 C with 10% ash) (Koppers Handbuch der Brennstoff Technik 1953)

Surface Top Bottom Coke Side Pusher Side Surface Top Bottom Coke Side Pusher Side Total

Table 3. Heat Losses by Radiation and Convection Average Surface Area Temperature (m2) 14,242 126 oC 14,242 53 oC 5,285 94 oC 5,285 95 oC Area (m2) 14,242 14,242 5,285 5,285

Qr 10,96 0,34 3,39 3,54

Ambient Temperature 20 oC 20 oC 20 oC 20 oC

Qc (Qr+Qc)*A 951,99 13.714,32 118,60 1.693,82 477,29 2.540,42 485,37 2.583,88 Q4= 20.532,44 kcal/h

Top

Pusher Side

Coke Chamber

Coke Side

Bottom

Fig.5. Heat Losses from Coke Chamber by Radiation and Convection CONCLUSION Coke making plants is very important facilities for integrated steel production process. Also this facilities can be defined as a power house because of its product (coke) and by-products (tar, coke oven gas, light oil). According to our studies, It seems to be that Erdemir Coke Plant has a great potential for recovering energy from coke sensible heat. The sensible heat of this red-hot coke accounts for approximately 59,60% of the total heat output from the coke oven, a considerably large heat quantitiy. To recover this sensible heat in the form of high pressure, high temperature steam using the inert gas as a medium, coke dry quenching (abbreviated to CDQ) equipment should be installed tu utilize it for generating system. In addition, sensible heat of produced coke oven gas can be recovered by an economizer.

Also radiation heat from the outside wall of regenerative chamber and radiation heat from oven door can be prevented by efficient heat insulators. REFERENCES 1. “Energy Use in the Steel Industry” International Iron and Steel Institute, Brussels, September 1998 2. Coke Plant Operation Data, December 2002 th 3. Perry J.H. “Chemical Engineers Handbook, 4 Edition” McGraw-Hill Book Company, 1963 4. Çağlayan F., Özdabak A., Ertem M.E., “Determining the Infrared Thermography with Thermal Difference Principle at Erdemir”, 12th International Conference on Thermal Engineering and Thermogrammetry (THERMO), 13-15 June 2001, Budapest, Hungary 5. “Final Report for Consultancy Services and Technical Assistance on Energy Conservation Program in Turkish Industry, Iron and Steel Sector”, Nippon Steel Cooperation, August 1984

Table 4. Coke Oven Gas Combustion in Combustion Chamber FUEL COMP.

%VOL

AIR (KMOL)

REACTION KG/KMOL

COG

EXCESS AIR % X 100

PRODUCTS (KMOL)

O2

N2

CO2

H2O

O2

N2

SO2

32

28

44

18

32

28

64

0,465

TOTAL

28

CO+1/2O2 +1/2(3.76)N2 = CO2 + 1.88 N2 0,058400

0,219695

0,0800

0,0184

0,2197

0,0000

0,3181

CH4

0,2220

16

CH4 + 2O2 +2(79/21)N2 = CO2 + 2H2O + 2(79/21)N2 0,648240

2,438617

0,2220

0,4440

0,2042

2,4386

0,0000

3,3089

C2H6

0,0100

30

C2H6 +7/2O2 +3/2(3.76)N2 = 2CO2 + 3H2O + 5.64 N2 0,051100

0,192233

0,0200

0,0300

0,0161

0,1922

0,0000

0,2583

C4H8

0,0200

56

C4H8 +6O2 +6(79/21)N2 = 4CO2 + 4H2O + 6(79/21)N2 0,175200

0,659086

0,0800

0,0800

0,0552

0,6591

O2

0,0050

32

H2

0,5900

2

N2

0,0430

28

N2 = N2

CO2

0,0300

44

CO2 = CO2

TOPLAM

1,0000

O2 = O2 1,620252

0,5900

0,1357

1,6203

0,0000

0,0050

0,0000

2,3460

0,0430

5,129884

6,494

8,360

17,91

0,0300

0,4320

1,1440

0,4346

5,1729

0,0000

7,1835

0,06014

0,15925

0,06051

0,72010

0,0000

1,0000

Table 5. Energy Balance of Coke Plant Energy Input (9.735.413 kcal/p) Under firing Gas 8.407.574 Sensible Heat of Coke Oven Gas 27.198 Reaction Energy 1.300.641 Energy Output (9.735.413 kcal/p) Sensible Heat of Coke 5.802.618 Sensible Heat of Coke Oven Gas 1.914.135 Sensible Heat of Flue Gas 1.018.587 Heat Losses by Radiation and Convection 20.532 Others 979.541 12,332 m

86,36% 0,28% 13,36% 59,60% 19,66% 10,46% 0,22% 10,06%

12,332 m

0,4 m

0,476 m Coke Side

0,756 m 4,572 m

0,680 m Pusher Side

Fig.6. Dimensions of Coke Battery

8,855 8,855

0,0430

0,0300

1,363640

0,494

0,8743

0,0050

H2+1/2O2 +1/2(3.76)N2=H2O + 1.88 N2 0,430700

Coke Chamber

KG FLUE GAS/KG FUEL

0,460

0,0800

Pusher Side

MASS BALANCE AIR PRODUCTS KG

CO

4,572 m

FUEL

Combustion Chamber

Coke Side