kai dong*, wenjuan liu and rong zhu study on indirect

Kai Dong*, Wenjuan Liu and Rong Zhu

Study on Indirect Measuring Technology of EAF Steelmaking Decarburization Rate by Off-gas Analysis Technique in Hot State Experiment

Abstract: In this paper, measurement method of EAF Steelmaking decarburization rate is studied. Because of the fuel gas blown and air mixed, the composition of hot temperature off-gas is measurand unreally, and the flow rate is unknown too, the direct measurement of EAF de-carburization rate by furnace gas analysis is unrealized. Firstly, the off-gas generation process is discussed. After that, dynamic concentration of CO2, CO, and O2 in off-gas and EAF oxygen supply rate are monitored in real time. Finally, the concentration and volume flow rate of off-gas are obtained to measure the EAF decarburization rate in-directly. The results of the hot state experiments show that the decarburization rate in oxidization step can reach up to about 0.53 mol/s, and the forecasting carbon concentra-tion is 1.14% corresponding to the average carbon concen-tration (1.43%) in finial metal samples. The measurement of decarburization rate by off-gas analysis technique can be reasonable in EAF production process.

Keywords: decarburization rate, off-gas analysis, hot state experiment, EAF steelmaking

PACS® (2010). 81.05.Bx, 81.20.-n

DOI 10.1515/htmp-2014-0076Received May 7, 2014; accepted August 22, 2014;published online October 24, 2014

1 IntroductionOff-gas analysis technique has been widely applied in steel making process. In the BOF steelmaking process [1–3], AOD [4] and RH [5, 6] refining process, measuring

decarburization rate by off-gas analysis technique is suc-cessfully applied, and many control models are further developed based, such as forecasting carbon concentra-tion, real-time temperature prediction, splash control and so on. In the BOF Steelmaking process, based on the con-centration of CO and CO2 in off-gas measured with the gas analyzer and the off-gas flow rate measured by the flow-meter, the decarburization rate can be calculated with Eq. (1) directly.

2

12( )22.4

B B B BC CO COV Q C C= × + × (1)

Short steelmaking process represented by EAF pro-cess is developing rapidly. EAF steel annual production in China was 70,900 thousand tons, accounting for ap-proximately 10.4% of annual totals steel production in 2011, far less than the world’s average of 29.4% [7]. EAF may instead of BOF to be the dominant in steelmak-ing industry [8]. However, automation and intelligent control is low in the EAF steelmaking process, as a conse-quence of lacking a reliable online monitoring method. The off-gas analysis technique is be expected a great potential [9].

Ignoring the difficulties that EAF off-gas has a high concentration of dust, and gas analyzer works in a harsh condition, the measurement of EAF steelmaking de-carburization rate by off-gas analysis technique still has following technical difficulties, as the decarburization rate cannot be calculated directly by Eq. (1) in the EAF steelmaking:1. In the oxygen supply process, fuel gas is injected and

combusted. Vast amounts of CO2, H2O and CO, which is unrelated to decarburization, are brought into the off-gas.

2. The hot off-gas must be cooled into room tempera-ture to be analyzed, so that, the H2O in gas phase will condense into liquid phase, and some CO and O2 may combine to CO2 too. The measured gas composition data is different from the hot state.

3. The flow rates of the air drawn into the furnace through the slag door, the air mixed in the duct, and

*Corresponding author: Kai Dong: School of Mechanical Engineering, University of Science and Technology Beijing, Beijing 100083, China. E-mail: [email protected] Liu: Beijing Safetech Pipeline Co., Ltd, Beijing 100083, ChinaRong Zhu: School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China

High Temp. Mater. Proc. 2015; 34(6): 539–547

K. Dong et al., Indirect Measuring of EAF Decarburization Rate

the off-gas at the sampling point cannot be measured directly.

4. The common gas analysis technique, for example, chemical analysis or infrared analysis, cannot measure the concentration of N2 and H2O in off-gas directly.

Risonarta et al. [10] did some research work on the EAF steelmaking process optimization in Eeutsche Edel-stahlwerke plant in Germany. In their work, water-cooled lances and filters were used to connect with the gas ana-lyzer equipment and infrared absorption spectrometry and paramagnetism methods were employed for measur-ing the off-gas concentration like CO, CO2, and O2. How-ever, the specific calculation of the decarburization rate measurement method by off-gas analysis data was not mentioned. They also propose the continuous off-gas ana-lyzing system to minimize chromium oxidation by moni-toring the CO and CO2 products in the off-gas [11].

Thomas Echterhof and Marcus Kirschen show their layout of the off-gas analysis system for NOx measurement and the install location in EAF steelmaking respectively [12, 13]. But in these studies, there is nothing with the measuring method for gas flow or decarburization rate.

In this paper, the process of off-gas generation in the EAF steelmaking is carefully analyzed. And then, based on the off-gas analysis data, together with reasonable assumption and theoretical calculation, the functions of decarburization rate measurement in EAF by off-gas anal-ysis technique are built. Finally, hot state experiment is designed to simulate the EAF steelmaking process, to verify the reliability of the measured decarburization rate data by off-gas analysis technique. It is promising to realize the real time prediction of steel composition and the end point dynamic control in EAF steelmaking process, and the automation in EAF steelmaking should be greatly

improved. It’s quite a meaningful work to raise competi-tiveness of EAF steelmaking industry.

2 Measuring principle of EAF decarburization rate by off-gas analysis technique

2.1 Off-gas generation process in the EAF steelmaking

The EAF steelmaking off-gas mainly consists of CO2, CO, O2, N2, H2O, SO2 and NOX. The concentration of SO2, and NOX is low compared to other species mentioned above, and can be omitted in determining the EAF decarburiza-tion rate. Three stages can be divided in the EAF steel-making off-gas generation process. The first stage is the combustion of the oxygen and fuel, the second stage is the decarburization in the EAF steelmaking, and the third stage is the post combustion of off-gas in the EAF furnace and duct. The off-gas generation process is shown in Figure 1. In this paper, the off-gas generated in the three stages is defined as original off-gas, decarburization off-gas, and final off-gas, respectively.

2.1.1 Oxygen and fuel injection and combustion process in the EAF steelmaking

In EAF steelmaking process, Oxygen is injected to acceler-ate the melting rate and enhance the mixing effect. Coher-ent oxygen lance has been commonly equipped in EAF at present. High temperature annular gas flow can be formed by fuel injection around the main oxygen jet, which can

Fig. 1: Off-gas generation in the EAF steelmaking process

540

K. Dong et al., Indirect Measuring of EAF Decarburization Rate

improve the jet velocity and blowing distance, speed up the scrap melting and increase the efficiency of oxygen [14]. Fuel gas combustion results in the emission of large amounts of CO2, CO, and H2O, which form the original off-gas.

2.1.2 Decarburization process in the EAF steelmaking

During the EAF decarburization process, O2 acts as oxidant and reacts with C element in the scrap metal. The reaction is generally divided into two types: direct oxidation and indirect oxidation. The main element in the scrap metal is Fe, so the majority of O2 will first react with Fe element and then generate [O]. The indirect decarburization reac-tion of [O] and [C] integration occur. Direct product of decarburization reaction in the steelmaking process is mainly CO gas. As shown in Figure 2, at 1600 °C, when the carbon concentration in the bath is above 0.2%, the con-centration of CO2 gas in decarburization reaction product is well below 1%, while the concentration of CO gas is 99% or more. The O2 in original off-gas reacts with C element by direct oxidation or indirect oxidation, O2 is consumed and CO is formed, so original off-gas translates into decarburi-zation off-gas. The chemical equation is shown in Table 1. The decarburization off-gas constituted by O2, CO2, CO and H2O.

2.1.3 Off-gas post combustion in EAF steelmaking

The EAF furnace is half-open design, and air is drawn in through the slag door, gaps, or electrode openings during

the steelmaking process. At the same time, oxygen supply is in excess for oxygen decarburization reaction. So it remains a strong oxidizing atmosphere in the furnace. As a result, part of the CO gas which is the product of the decarburization reaction will be oxidized, which is called post combustion reaction. The decarburization off-gas begins to translate into final off-gas in the furnace.

After partial post combustion in the furnace, the off-gas is collected into a water-cooled gas duct through the fourth hole. To lower the temperature of the hot gas and prevent CO hazard, air gas will be mixed into the duct, which will burn down the CO gas. The decarburization off-gas then completely converts into the final off-gas. The final off-gas will be removed dust qualified and emitted.

In the whole process of decarburization off-gas post combustion and air mixing, a large amount of air is drawn into the off-gas, the CO post combustion occurs as equation:

2 22 2 .CO O CO+ = (1)

Usually, off-gas sampling point is located in the EAF furnace cover or the entrance of the gas duct. During the process of off-gas transportation, the off-gas flow rate changes as the amount of mixed air increases. So the flow meter set in the duct cannot measure the off-gas flow at the sampling point.

2.2 Measure principle of EAF decarburization rate

The EAF off-gas mainly consists of CO2, CO, O2, N2 and H2O, Table 2 shows the sources of the off-gas compositions in EAF steelmaking.

The key to realize the EAF decarburization rate mea-surement is achieving the exact result of off-gas com-position and off-gas flow rate indirectly, by assump-tion, deduction, and computation, and eliminating the interference.

Fig. 2: Relationship between CO2 concentration in decarburization products and [C] in metal (1600 °C) [15]

Table 1: Chemical reaction in steelmaking decarburation process

No. Chemical equation

Gθ∆ (kJ/mol)

1 + =22[ ] 2C O CO −279.72 − 85.24T2 + =( ) 2 ( )2 2l lFe O FeO −459.4 + 0.087T3 = +( ) [ ]lFeO Fe O 121.38 − 0.053T4 + =[ ] [ ]C O CO −23.52 − 0.039T

541

The commonly off-gas analysis method in industry can measure the components of CO2, CO, and O2 out accu-rately. According to the off-gas compositions, the chemi-cal balance of the elements during the off-gas generation process is researched. The off-gas compositions in differ-ent reaction steps is calculated. In the calculation, a unit volume of off-gas in normal pressure and temperature is used as standard.

At room temperature, the saturated vapor pressure of H2O is low. In off-gas analysis process, as temperature drops, the redundant vapor will condense to water and be removed from the off-gas, and H2O vapor in off-gas keeps in the saturation state. At room temperature and normal pressure, saturated concentration of H2O can be denoted as

23%R

H OC = . At the same time, it is assumed that the concentration of CO2 and CO does not change as the sample gas cools down, the concentration of N2 in off-gas sample can be expressed in Eq. (2).

2 2 2 2100 R

N O CO CO H OC C C C C= − − − − (2)

To eliminate the interference of C element coming from fuel gas, under the schemed oxygen supply setting, off-gas samples from empty furnace should be analyzed. Without metal decarburization reaction, the C and H ele-ments in the off-gas are only provided by fuel gas as shown in Table 2. Based on the composition of the fuel gas and the C concentration in original off-gas, the concentration of H2O in high temperature original off-gas can be ob-tained. The concentration of CO (denoted as E

COC ) and CO2 (denoted as

2E

COC ) in off-gas from empty furnace can be set as the basic C concentration in original off-gas. The C/H ratio of fuel gas is 3/8, and the concentration of H2O in hot off-gas from empty furnace can be expressed as Eq. (3).

2 2

4 ( )3

H E EH O CO COC C C= × + (3)

H2O is not involved in the decarburization reaction in the EAF steelmaking process. If it is assumed that the O2 only combines with the C element in the decarburiza-tion process, thus the O/H ratio in the original off-gas and decarburization off-gas are the same. The concentration of H2O in the decarburization off-gas can be expressed as Eq. (4).

2 2 2 2

2 2 2

21( / 2 )79

/( / 2 )H O CO CO O N

H E E EH O CO CO O

C C C C C

C C C C

= + + −

× + + (4)

As mentioned in Table 2, N2 in EAF off-gas comes from air only, and the N2 does not participate in chemical reac-tion. It is known that the N2 concentration in air is 79% and the O2 concentration in air is 21%. Thus the N2 concen-tration in the off-gas can be used to calculate the O2 con-centration brought from air. And the composition of the EAF off-gas deducted air can be calculated as shown in Eqs. (5–9).

2 2 2

21( ) /79O O N AllC C C C′ = − (5)

20NC ′ = (6)

2 2/H O H O AllC C C′ = (7)

2 2( ) /CO CO CO CO AllC C C C C′ ′+ = + (8)

2 2 2 2

21( )79All O N H O CO COC C C C C C= − + + + (9)

In the off-gas deducted air, it can be considered that the O element is all provided by oxygen injection, and the flow rate is related to the intensity of oxygen injection. The off-gas flow rate deducted air is shown in Eq. (10).

′ ′′ ′= + + +2

2 2 2/( )

2 2H O CO

O O COC CQ Q C C (10)

In the process of off-gas cooling, CO and CO2 may in-terconvert into each other. Nevertheless, the total C ele-ment remains unchanged. The

2CO COC C′ ′+ in decarburiza-tion off-gas composition and off-gas flow rate, which are all deducted air gas, can be used to calculate EAF decar-burization rate, as shown in Eq. (11).

2

121000 ( )22.4

EC CO CO CV Q C C V′ ′= × × + × − (11)

Table 2: Sources of off-gas compositions in EAF steelmaking

No. Compositions Element Source

1 H2O H Fuel gasO Oxygen

2 CO C Decarburization reaction and Fuel gas

O Oxygen3 CO2 C Decarburization reaction

and Fuel gasO Oxygen and Air

4 O2 O Oxygen and Air5 N2 N Air

542 K. Dong et al., Indirect Measuring of EAF Decarburization Rate

Based on the assumptions and calculations above, to realize the measurement of EAF steelmaking decarburiza-tion rate by Off-gas analysis technique, it is necessary to analyze the dynamic concentration of CO2, CO, and O2 in EAF off-gas, and record the flow rate of oxygen injection, and an empty furnace blowing experiment at the same oxygen supply scheme without decarburization reaction should be conducted to obtain the background concentra-tion of CO and CO2 in original off-gas.

3 Experimental

3.1 Preparation of hot state experiment

Cylinder furnace equipped with coherent oxygen lance is selected to conduct hot state experiment, and the co-herent jet flow can melt the scrap and decarburize. The off-gas generation in the experiment is similar to that in the EAF steelmaking process. Pig iron is used for steel material, and the chemical compositions are shown in Table 3. Bottled oxygen and propane are prepared as jet source gas. According to EAF steelmaking pro-cess, the gas injection parameters in melting step and oxi-dation step are schemed. The first experiment step is melting step, which lasts 14 minutes. To improve the jet flow temperature, little excess oxygen should remain

after the complete combustion of the fuel gas. The second experiment step is the oxidation step, which lasts 12 minutes, more excess oxygen is supplied to form high oxygenated jet flow. The parameter setting are shown in Table 4.

As it shows in Figure 3, the oxygen and fuel gas flow from the gas bottle are limited by the flowmeter as injec-tion parameters, and the coherent oxygen lance inject the gas into the cylinder furnace. In the furnace, solid metal has be charged, and the high temperature coherent jet flow melts and decarburizes the metal, at the same time, off gas generates and spreads through the furnace port. Air pump is used to draw off-gas from the furnace, and the sample off-gas are collected into air bags. After the exper-iment, the concentration of CO, CO2, and O2 in the off-gas are analyzed by chemical method.

3.2 Schedule of hot state experiment

The schedule of the experiment is shown detailed in Figure 4. Basing on the preparation and according to the research result in part 2, oxygen and flue gas are blown into empty furnace just as the parameter setting in Table 4, and off-gas samples are collected and ana-lyzed respectively to obtain the background concentra-tion of CO and CO2. Two gas samples are collected in each step. According to Eqs. (5) to (9), the compositions of original off-gas deducted air are calculated and shown in Table 5.

In the original off gas of melting step, the average CO2 concentration is 15.26%, the CO concentration is 18.56%, and the concentration of H2O calculated according to Eq. (3) is 45.10%. On the other side, in the original off gas of oxidation step, the average CO2 concentration is 11.72%, CO is 16.41%, and H2O is 37.51%.

In the decarburization experiment, 150 kg of pig iron is charged into the cylinder furnace, and oxygen and

Table 3: Chemical composition of metal raw material

No. Elements Wt.(%)

1 C 4.22 Si 0.93 Mn 0.84 P 0.25 S 0.046 Fe 93.86

Table 4: Parameter setting of oxygen and fuel supply

Step Time (min)

Path Component Flow rate (Nm3/h)

Lance position (mm)

Pressure (Mpa)

Melting step 14 main oxygen pipe O2 50 500 >0.5Fuel gas pipe C3H8 10 500 >0.15secondary oxygen pipe O2 20 500 >0.5

Oxidation step 12 main oxygen pipe O2 100 400 >0.5Fuel gas pipe C3H8 15 400 >0.15secondary oxygen pipe O2 30 400 >0.5

543K. Dong et al., Indirect Measuring of EAF Decarburization Rate

propane are injected by the coherent oxygen lance as injection parameters, the front 14 minutes are melting step, and the following 12 minutes are oxidation step. Every 2 minutes, decarburization off-gas samples are collected. After flameout, metal samples are collected from the cylinder furnace. In the end, the compositions of the off-gas samples and the metal samples are analyzed.

3.3 Off-gas analysis and verification of decarburization rate at hot state experiment

Decarburization experiment in cylinder furnace complete following Figure 4 and Table 4, and the decarburization off-gas samples are collected every 2 minutes. Finally there are 13 off-gas samples collected.

Fig. 3: Schematic diagram of hot state experimental equipment

Fig. 4: Schedule diagram of hot state experiment


In the pump gas process, there is air pumped into the off-gas samples, and calculation of the decarburization is difficult. With the help of Eqs. (5)–(9), the compositions of the decarburization off-gas deducted air are calculated out, and the off-gas flow rates deducted air are calculated by Eq. (10). All data of decarburization off-gas deducted air are shown in Table 6, eliminating the influence from the mixed air.

Decarburization rates in the hot state experiments are estimated according to Eq. (11), on the comparison of the decarburization off-gas in Table 6 and the original off-gas in Table 5. In the melting step, the concentration of CO and O2 decrease with decreasing the CO2 concentration, and there is almost no decarburization from the metal. In the oxidation step, as the concentration of CO2 in the decar-burization off-gas increases evidently, the concentration of O2 decreases clearly, but the concentration of CO fluc-

tuates and has a tendency to decrease as decarburization is processed. As shown in Figure 5, with excess oxygen supply, the average decarburization rate can reach up to 0.53 mol/s, and the decarburization rate reduces over time.

It is assumed that the measured decarburization rates are the average rates in every sampling interval, and the total decarburization quantity can be calculated by mul-tiplying the time by the decarburization rate. As shown in Figure 6, the decarburization rate reduces following the C concentration decreases, and the trend between the decarburization and the C concentration is indicated as Eq. (12) in the experimental range.

Table 5: Components original off-gas deducted air at empty furnace blowing experiment

No. Step CO2 (%)

CO (%)

O2 (%)

H2O* (%)

1-1 Melting step 15.05 18.56 21.57 44.821-2 15.47 18.57 20.57 45.39Average 1 15.26 18.56 21.07 45.10

2-1 Oxidation step 11.62 16.46 34.49 37.442-2 11.83 16.36 34.22 37.59Average 2 11.72 16.41 34.35 37.51

* H2O is calculated according to Eq. (3).

Table 6: Concentrations and flow rates of decarburization off-gas deducted air

No. Step Timestamp (Min)

CO2 (%)

CO (%)

O2 (%)

H2O* (%)

Flow rate** (Nm3/h)

3-1 Melting step 2 24.84 8.54 5.20 61.42 107.663-2 4 24.33 6.89 6.36 61.72 107.123-3 6 23.91 7.55 6.55 61.62 107.313-4 8 24.36 6.49 6.84 61.97 106.713-5 10 24.34 7.81 5.92 61.52 107.473-6 12 27.34 4.25 5.00 62.50 105.793-7 14 25.00 6.31 6.21 61.97 106.70

4-1 Oxidation step 16 32.24 22.91 5.81 41.17 188.344-2 18 29.73 23.61 7.82 41.02 189.024-3 20 30.30 24.19 6.84 40.90 189.584-4 22 38.49 11.35 7.68 43.60 177.874-5 24 37.59 12.90 7.51 43.27 179.204-6 26 38.94 11.25 7.30 43.62 177.78

* H2O is calculated according to Eq. (3). **Flow rate is calculated according to Eq. (10).

Fig. 5: Decarbonizing rate changing over time in the hot state experiment


0.040483 0.3614C CV C= × + (12)

The forecasting carbon concentration changing over time are calculated as show in Figure 7. The total decar-burization quantity in hot state experiment is calculated as 4584.9 g, so the finial carbon concentration is predicted as 1.14%. On the contrary, the carbon concentration in melting step is almost unchanged. There are 5 metal samples collected from the experiment, and the analysis results are shown in Table 7. The average carbon concen-tration is 1.43%. As the metal samples appears, the finial C concentration is lightly higher than the forecasting value. Consider of the total metal in the cylinder furnace is unable to be weighted, because of the mix of the slag, the steel and the refractory, and the metal should lose quality

in theory. The measured decarburization quality and de-carburization rates should be receivable.

In the calculation of EAF decarburization date by off-gas analysis technique, it is assumed that all O element in injection flow goes into the off-gas. While in real steel-making process, a small amount of O element will react with Fe, Si or Mn, so the calculated off-gas flow rate and the measured decarburization rate may be higher than the real value. As the losting of Si and Mn elements in the metal sample appears. In future research, modification on O element should be further studied.

4 ConclusionsMeasuring technology of EAF steelmaking decarburiza-tion rate by off-gas analysis technique is researched in this paper, and the conclusions are as follows:1. The EAF off-gas generation process can be divided

into three steps: Combustion of the oxygen and fuel, decarburization in the EAF steelmaking, and the post combustion of off-gas in the EAF furnace and duct. The off-gas generated in the three steps corresponds to the original off-gas, decarburization off-gas, and final off-gas. Base on the research of the off-gas gen-eration process, the EAF decarburization rate can be measured by the data of dynamic concentration of CO2, CO, and O2 in EAF off-gas, the flow rate of oxygen injection, and the background concentration of CO and CO2 in the original off-gas obtained from empty furnace blowing experiment.

2. The compositions of off-gas compared with the origi-nal off-gas shows that: In the melting step, the con-centration of CO and O2 decrease with decreasing the concentration of CO2. In the oxidation step, as the concentration of CO2 in decarburization off-gas in-creases evidently, the concentration of O2 decreases clearly. But the concentration of CO fluctuates and has a tendency to decrease as decarburization is processed.

Table 7: Final components of metal samples in hot state experiment

No. C (%) Si (%) Mn (%)

B-1 1.32 0.21 0.53B-2 1.43 0.17 0.57B-3 0.95 0.19 0.62B-4 2.10 0.23 0.72B-5 1.35 0.16 0.37

Fig. 6: Decarbonizing rate changing over the forecasting carbon concentration in oxidation step

Fig. 7: Carbon concentration changing over time


3. In the oxidation step, the average decarburization rate can reach up to 0.53 mol/s, and the total de-carburization quantity in hot state experiment is 4584.9 g, so the finial forecasting carbon concentra-tion is 1.14%. Metal samples compositions show that, the average carbon concentration is 1.43%, which is slightly higher than the forecasting carbon concen-tration. The measured decarburization quality and decarburization rates by off-gas analysis technique should be receivable.

4. In the steelmaking process, the Si and Mn elements lost a little, and it is different to the assumption that all O element in injection flow goes into the off-gas. So the calculated off-gas flow rate and the measured de-carburization rate may be higher than the real value. In future research, modification on O element should be further studied.

NomenclatureVC

B Decarburization rate in BOF steelmakingQB Off-gas flow rate in BOF steelmakingCCO B Concentration of CO in BOF off-gas

2B

COC Concentration of CO2 in BOF off-gas

2NC Concentration of N2 in off-gas samples

2OC Concentration of O2 in off-gas samplesCCO Concentration of CO in off-gas samples

2COC Concentration of CO2 in off-gas samples

2R

H OC Concentration of H2O in off-gas samples at room temperature

2H

H OC Concentration of H2O in off-gas samples at high temperature

CCO E Concentration of CO in original off-gas

2E

COC Concentration of CO2 in original off-gas

2E

OC Concentration of O2 in original off-gas

2H OC Concentration of H2O in decarburization off-gas at high temperature

2OC ′ Concentration of O2 in decarburization off-gas

deducted air

2NC ′ Concentration of N2 in decarburization off-gas deducted air

2H OC ′ Concentration of H2O in decarburization off-gas deducted air

COC ′ Concentration of CO in decarburization off-gas deducted air

2COC ′ Concentration of CO2 in decarburization off-gas deducted air

CAll Total concentration of decarburization off-gas deducted air

Q Flow rate decarburization off-gas deducted air gas

2OQ Flow rate of oxygen injectionVC EAF decarburization rateVC

E Background carbon flow rate in the original off-gas

CC Concentration of C in metal

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kai dong*, wenjuan liu and rong zhu study on indirect

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