KR20040021244A - Method for certifying stable gas pressure of coke oven - Google Patents

Abstract

PURPOSE: A method for checking stabilized gas pressure of coke oven is provided to accurately predict gas pressure generated during coal dry distillation in coke oven from various operation conditions including coal charging conditions and oven dry distillation conditions. CONSTITUTION: The method comprises first step of calculating P (unit: mmH2O) that is a gas pressure generated during dry distillation of the coal from the following expression when moisture of coal charged into coke oven is M (unit: %), a ratio in which grain size of the coal is 3 mm or less is dp (unit: %), temperature during charging of the coal is Tcharging (unit: deg.C), and final dry distillation temperature of the coal is Tdry distillation (unit: deg.C): P=3.09x10¬9x{1/(M)¬2.520}x{1/(Tdry distillation)¬5.281}x{(Tcharging)¬5.206}x{1/(dp)¬2.303}; and second step checking whether the calculated gas pressure is less than or the same as the limit gas pressure by comparing the calculated gas pressure with a limit gas pressure of the coke oven, wherein the method further comprises a step of changing any one or more values in the M, dp, Tcharging and Tdry distillation and repeatedly performing the first and second steps using the changed values if the calculated gas pressure is larger than the limit gas pressure in the second step.

Description

Method for certifying stable gas pressure of coke oven}

The present invention relates to a method for producing coke, and more particularly, to a method for confirming a stable gas pressure of the coke oven by calculating in advance the gas pressure generated during coal drying.

As the coke oven is rapidly aging around 20 years after the start of operation, and the environmental aspects are strengthened, the extension of the life of the oven and the management of the furnace are one of the most important problems in the metallurgical coke manufacturing process. In particular, one of the most important challenges in the metallurgical coke manufacturing industry is to prevent dangerously high expansion pressures on the coke oven walls from damaging the coke oven walls.

Coke ovens have been replaced by slot-type ovens in early honeycomb ovens, with much interest in the potential for very high expansion pressures on the coke oven walls, especially when considering the use of low volatile coal. Brought it. Coal or coal blends with high expansion pressures will damage the oven walls and shorten oven life.

In the coke oven, the expansion pressure generated during the coal distillation, that is, the process of generating the maximum gas pressure at the coal center will be described.

When coal is carbonized in a slotted coke oven, two softening layers are formed parallel to the oven walls. These two softening layers are joined to form an additional softening layer that forms the envelope, sleeve, and tube of softened coal at the bottom and top of the charged coal. As dry distillation proceeds, the softening layer gradually moves towards the center of the oven and eventually meets at the center of the oven, where the coal of the particles is converted into porous molten coke.

Usually for coals with a volatile content of 17 to 25% (daf), when the two softening layers are coalesced at the center of the oven, they are accompanied by the generation of gas pressures which reach maximum levels in the softening layer. This pressure is transferred to the oven wall through a semi-coke layer between the oven center and the oven wall, where the pressure acting on the oven wall is called the expansion pressure. If this pressure is high enough, it will cause oven damage. Coal with similar properties under chemical analysis and swelling properties can exhibit completely different behavior for pressure generation, so some coals are dangerous while others are safely distilled.

Coal expansion pressure and gas pressure generally encountered are defined as follows. First, the coal expansion pressure is defined as the pressure acting on the oven wall due to coal distillation, and the gas pressure is defined as the pressure measured by a probe inserted in the coal and coke bed during coal distillation.

Normally there is no direct measurement of the expansion pressure, which is the pressure on the oven wall during coal drying in commercial ovens, and the expansion pressure is measured using a test furnace. The relationship between the expansion pressure and the gas pressure generated during the coal distillation process is known to indicate that the maximum gas pressure generated at the center of the oven in the commercial oven is the expansion pressure on the oven wall, and the gas pressure is twice the expansion pressure in the test furnace.

As described above, an excessive expansion pressure in the coal drying process of the coke oven may cause blockage of the extrusion or damage of the oven wall during extrusion, which may cause a stable operation of the coke oven and shorten the life of the oven. In addition, it is required to secure operating conditions for preventing excessive expansion pressure in the case of operating environment changes such as coal humidification facilities that control the moisture of coal charged into the oven and high operation rate for high quality coke production and cost reduction.

In general, the limit of expansion pressure that occurs in coal coking in a coke oven depends on the size of the oven.For example, in 6 m coke ovens the limit of expansion pressure is 7 kPa, and in 4 m coke ovens. The limit tolerance of is 14 kPa and the gas pressure at the center of the oven for stable oven operation in commercial coke ovens is known to be below 350 mmH ₂ O (Loison, R et. Al, Coke quality and production, 1989, Lindert, MT and van der Velden, B., Ironmaking Conf. Proceedings, 1994).

However, the expansion pressure generated by coal drying in the coke oven depends on the raw material properties, the oven charging and the drying conditions, and it is difficult to estimate the expansion pressure generated during drying by various complicated actions occurring in the oven during the drying process. many.

In order to solve this problem, many researchers analyzed the effects of raw material elasticity and operating conditions on the expansion pressure and the dominant factors by using a test wall with moving walls (Latshaw, GH et al., ISS Ironmaking Proceedings, 1984, Nomura). , S. and Thomas, KM, Fuel, 1996, Tucker, J. and Everitt, G., Ironmaking Conf. Proceedings, 1989, Grimley, JJ and Radley, CE, Ironmaking Conf.Proceedings, 1995, Rohde, W. et al , Ionmaking Conf. Proceedings, 1988), which is a simple and accurate technique for predicting the expansion pressure occurring in the coal drying process, and therefore, a technique for predicting the expansion pressure is required.

The present invention has been made to solve the problems as described above, the object is to predict the gas pressure at the center of the coal generated in the coal drying process in the coke oven.

Another object of the present invention is to be able to control the operating conditions such that excessive expansion pressure does not occur on the oven wall.

Another object of the present invention is to prevent oven wall damage due to excessive expansion pressure to extend the life of the oven.

1 is a cross-sectional view schematically showing a coke test furnace used in the experiment of the present invention.

2 is a cross-sectional view showing a probe for measuring the gas pressure generated in the coal center during coal distillation.

3 is a graph showing a comparison between the experimentally measured gas pressure and the gas pressure predicted by Equation 1 of the present invention.

** Description of symbols for the main parts of the drawing **

1: oven 2: moving wall 3: fixed wall

4: carbide car 5: SiC heater 6: 7, wheels

8: coal inlet 9: gas outlet 10: damper

11: LPG burner 12: Air supply unit 13: Year

14 gas pressure measuring probe installation point 20 gas pressure measuring probe

21: thermocouple 22: measuring hole 23: pressure sensor

In order to achieve the above object, in the present invention, the gas pressure in the coke oven is calculated using the moisture, coal particle size ratio, charging temperature, and dry distillation temperature of the coal charged in the coke oven, and the calculated gas pressure is the corresponding coke oven. Check whether the gas pressure is less than or equal to the limit gas pressure, and if the calculated gas pressure is greater than the limit gas pressure, the stable gas pressure of the coke is confirmed by changing the condition until the calculated value is less than or equal to the limit value.

That is, in the method for confirming the stable gas pressure of coke according to the present invention, the moisture of coal charged into the coke oven is referred to as M (unit:%), and the proportion of coal having a particle size of 3 mm or less is referred to as dp (unit:%). The temperature at the time of _charging is referred to as T _charging (unit: ℃), and the final drying temperature of coal is T _{dry distillation} (unit: ℃), P (unit: mmH ₂ O) which is the gas pressure generated when coal is dried. Is calculated from the following equation: P = 3.09 x 10 ⁹ x (M) ^-2.520 x (T _{dry distillation} ) ^-5.281 x (T _charging ) ^5.206 x (dp) ^-2.303 ; Comparing the calculated gas pressure with the limit gas pressure of the coke oven and confirming that the calculated gas pressure is less than or equal to the limit gas pressure, and when the gas pressure calculated in the second step is greater than the limit gas pressure, M, dp It is characterized by changing at least one of T, T _charging , and _{dry distillation} , and repeating the first and second steps using the changed value.

In this formula, M is 5.6 to 9.0%, dp is 77 to 86%, T _loading is 850 to 1000 ° C, and T _{dry distillation} is 1050 to 1200 ° C.

Hereinafter, a method for confirming a stable gas pressure of a coke oven according to the present invention will be described in detail.

First, the moisture M of the coal charged into the coke oven, the ratio dp having a particle size of 3 mm or less, the temperature T _{charging at the} time of _{charging the} coal and the final dry temperature T _drying of the coal are substituted into the following equation (1). Calculate the gas pressure, P, generated during the drying of coal.

P = 3.09 × 10 ⁹ × (M) ^-2.520 × (T _dry ) ^-5.281 × (T _charging ) ^5.206 × (dp) ^-2.303

Next, the gas pressure calculated from Equation 1 is compared with the limit gas pressure of the coke oven to confirm that the calculated gas pressure is less than or equal to the limit gas pressure. At this time, the limit gas pressure varies depending on the size and type of the coke oven. In a typical commercial coke oven, the limit gas pressure is generally known to be in the range of 350 to 400 mmH ₂ O.

If the gas pressure calculated from Equation 1 is greater than the limit gas pressure of the corresponding coke, one or more of M, dp, T _charging and T _{dry distillation} are changed, and the gas pressure is again obtained from Equation 1 using the changed value. This recalculation is performed until the calculation is less than the threshold to ensure that the calculation is less than or equal to the threshold.

As described above, in the present invention, the gas pressure generated during the drying process in the coke oven is calculated and estimated from Equation 1. Then, in order to obtain the equation (1) will be described in detail for performing the experiment to measure the gas pressure while changing the coal loading conditions and dry distillation conditions.

In the experiment of the present invention, the charging conditions such as moisture, particle size, coal charging temperature and the dry distillation conditions, such as the final drying temperature, are selected using the charged coal used for the manufacture of metallurgical coke in a 50 kg coke test furnace. 1 is a cross-sectional view schematically showing the coke test furnace used in the experiment of the present invention.

The coal used in the gas pressure measurement experiments was made of coal used for the manufacture of metallurgical coke in a commercial coke oven, and the physical properties of the coal were as follows. That is, as a result of industrial analysis, 26.0 wt% of volatile matter, 65.8 wt% of fixed carbon, and 8.2 wt% of ash, and elemental analysis showed that 88.5 wt% of carbon (C), 4.9 wt% of hydrogen (H), and 1.8 wt% of nitrogen (N). %, Sulfur (S) 0.6% by weight, oxygen (O) 4.2% by weight, and the loaded coal particle size is 80% of 3mm or less.

The oven main body 1 is provided with a moving wall 2 and a fixed wall 3 on both sides, respectively, and the oven main body 1 is provided on the carbonized car 4. At the end of coal dry distillation, a rail and a wheel 7 are installed at the bottom to draw the oven to discharge the coke. SiC heaters 5 of the same capacity were horizontally installed on both the moving wall 2 and the fixed wall 3 for heating the charged coal. Rails and wheels 6 were installed at the bottom of the movable wall to move.

In the upper part of the oven 1, a charging inlet 8 was installed for charging coal, and a discharge pipe 9 was installed for exhausting the generated gas. A damper (10) was installed in the gas discharge pipe (9) to adjust the pressure in the oven (1), and a pressure gauge was installed in the lower part of the discharge pipe (9) to control the pressure in the oven (1). (0 to 1 mmH ₂ O) was taken.

The red coke moved the carbonized tea 4 to the pusher outside the oven 1 after the end of the dry distillation, and then pushed the coke in the width direction of the oven using the pusher to extrude the extinguishing device. The red coke transported to the fire extinguishing device was sealed with a steel box and digested with nitrogen. Gas (COG) generated during the drying is burned together with the LPG in the LPG burner 11 installed at the rear end of the damper 10, and the combusted exhaust gas is discharged from the flue 13 by the ventilation force of the air supplied from the air supply unit 12. Through the outside.

FIG. 2 is a cross-sectional view illustrating a probe for measuring gas pressure generated at a coal center during coal distillation, and as shown therein, a K-type thermocouple 21 is provided inside the probe 20. The probe 20 was parallel to the heating wall, and was installed at the central portion 14 in the oven width direction. At one end of the probe 20, a rectangular hole 22 was installed to measure the gas pressure. The pressure generated was measured using a pressure sensor 23 connected to the probe 20.

Experiment 1

In the test furnace, charged coal having a particle size of 80% or less of 3 mm was charged at 850 ° C., and when the coal center temperature reached 600 ° C., it was heated at 3 ° C./min to 1100 ° C. and 1150 ° C. for 1 hour. At this time, the change in the gas pressure according to the change in the charged coal moisture was measured. The charged coal moisture was controlled by drying in a forced circulation oven.

At the final dry distillation temperature of 1100 ℃ and 1150 ℃, the gas pressure according to the change of charged coal moisture was obtained as shown in Table 1 below.

moisture(%) 5.6 6.0 6.5 6.8 7.0 7.5 7.8 8.5 8.6 Gas pressure (mmH ₂ O) 1100 ℃ 205 159 132 107 78 1150 ℃ 225 112 104 98

The water content of the charcoal charged to the commercial coke oven is controlled by the coal humidification plant (CMCP) at 6.0-7.0%. As can be seen in Table 1 above, when the moisture of the charged coal charged in the oven decreases, the gas pressure generated in the dry distillation process increases rapidly due to an increase in the charged density. If the water content of the coal is less than 6.5%, the gas pressure increases rapidly, so the water content of the coal should be managed at 6.5% or more.

Experiment 2

In the manufacture of metallurgical coke, in addition to the charge coal moisture, the charge coal particle size is one of the important management items. In general, coal particle size is controlled at 3 mm or less based on 3 mm. In the test furnace, charged coal (humidity: 8.6 to 8.8%) and dry coal (humidity: 6.0 to 6.5%) are charged at 850 ° C. When the coal core temperature reaches 600 ° C, the final dry distillation temperature is 3 ° C up to 1100 ° C and 1150 ° C. When heated to / min and maintained for 1 hour, the gas pressure change according to the particle size change of the charged coal was measured.

The particle size was separated by more than 3 mm of coal and then mixed at a weight ratio of 3% or less of the ratio of 77% to 86%. The horizontal shrinkage for the wet and dry coals at the final dry distillation temperatures of 1100 ° C and 1150 ° C was obtained as shown in Table 2 below.

Charging coal particle size (rate less than 3mm) 77% 80% 83% 86% Gas pressure (mmH ₂ O) 1100 ℃ Pulverized coal (8.6-8.8%) 112 78 61 49 Dry coal (6.0-6.5%) 364 205 140 252 1150 ℃ Pulverized coal (8.6-8.8%) 109 98 55 60 Dry coal (6.0-6.5%) 310 112 79 82

As shown in Table 2, the gas pressure was rapidly decreased due to the decrease in the loading density as the ratio of 3 mm or less of the charged coal particle size increased. In particular, the dry coal has a higher gas pressure than the wet coal because the charging density is much higher. From Table 2, in each case where the dried coal was heated to the final dry distillation temperature of 1100 ° C. and 1150 ° C. and maintained for 1 hour, a ratio of 3 mm or less of the coal particle size charged under the coal humidification facility, which is a coal pretreatment facility, for stable oven operation was It should be managed to be over 80%

Experiment 3

In the test furnace, charged coal (humidity: 8.6 to 9.0%) and dry coal (humidity: 6.0 to 6.5%) having a particle size of 3 mm or less at 80% were charged at 850 ° C to change the final dry distillation temperature from 1050 ° C to 1200 ° C. The change of gas pressure with the final dry distillation temperature was measured. The wet and dry coals were charged at 850 ° C. and heated to a final dry distillation temperature at 3 ° C./min at a central temperature of 600 ° C. and maintained at the final dry distillation temperature for 1 hour. The final dry distillation temperature in the coke oven is advantageously kept low in terms of energy efficiency as a factor related to the operating rate, calories burned and the coke quality. The gas pressure change according to the final dry distillation temperature is shown in Table 3 below.

Final dry temperature 1050 ℃ 1100 ℃ 1150 ℃ 1200 ℃ Gas pressure (mmH ₂ O) Marquette 119 78 98 116 Dry coal 183 205 112 251

As can be seen in Table 3 above, the gas pressure generated during coal distillation does not show a constant tendency as the final dry distillation temperature is increased for the wet and dry coal. This is because the gas pressure generated during dry distillation occurs before the coal solidification temperature of 600 ° C., so that the final dry distillation temperature is not significantly affected. On the other hand, the gas pressure of the dry coal showed a high expansion pressure because the charging density is higher than the wet coal.

Experiment 4

Changes in operating rates in coke ovens affect the coal drying behavior by changing the heating rate of the coals dried in the oven. In other words, increasing the operation rate increases the heating rate at the coal center. For wet and dry coals with a particle size ratio of 3 mm or less of 3 mm, change the charging temperature from 850 ° C to 1000 ° C to change the heating rate at the center of the coal in the test furnace, and heat the final dry distillation temperature to 1100 ° C and 1150 ° C. The change of gas pressure was measured when hold | maintained for 1 hour.

The charging temperature was changed to change the heating rate at the center of coal. When the central temperature reached 600 ℃, it was heated to 3 ℃ / min until the final dry distillation temperature. The gas pressure change according to the change of the coal charging temperature is shown in Table 4 below.

Charging temperature 850 ℃ 900 ℃ 950 ℃ 1000 ℃ Gas pressure (mmH ₂ O) 1100 ℃ Pulverized coal (8.6-9.0%) 78 109 142 200 Dry coal (6.0-6.7%) 205 315 428 575 1150 ℃ Pulverized coal (8.5-8.7%) 98 66 72 100 Dry coal (6.5-6.7%) 112 58 219 300

As can be seen in Table 4 above, as the charging temperature, that is, the heating rate at the center of the oven, the gas pressure increased due to the increase in gas generation rate in the coal softening-melt layer. Especially for dry coal, high gas density showed higher gas pressure than that of wet coal, and the gas pressure increased rapidly with increasing charging temperature, that is, heating rate.

As a result of Experiment 4 described above, when the charging temperature is changed at the final dry distillation temperature of 1100 ° C. and 1150 ° C., the charging temperature should be controlled to 950 ° C. or lower for stable oven operation.

Influence of the coal loading condition, the coal loading condition, the coal loading condition and the particle size less than 3mm, and the final drying temperature, that is, the final coke temperature, the coal loading temperature, and the heating rate Equation 1, which is a correlation between these charging conditions and dry distillation conditions, was obtained using the regression method. The correlation coefficient for Equation 1 is 0.86, which is very high. Equation 1 is applied when M is 5.6 to 9.0%, dp is 77 to 86%, T _loading is 850 to 1000 ° C, and T _{dry distillation} is 1050 to 1200 ° C.

3 is a comparison graph of the gas pressure experimentally measured and the gas pressure predicted by the gas pressure estimating method of the present invention. As shown in FIG. 3, Equation 1 shows a very high correlation with the actual measured value, and thus, it can be seen that the equation 1 can be practically used to accurately predict and estimate the gas pressure generated when coal coal is dried from charging conditions and dry conditions.

As described above, according to the present invention, it is possible to accurately predict the gas pressure generated in coal coking in a coke oven from various operating conditions such as coal charging conditions and oven drying conditions.

In addition, it is possible to adjust the operating conditions appropriately so that the expansion pressure can be properly adjusted to prevent the occurrence of excessive expansion pressure during coal distillation, thereby improving the oven wall damage caused by excessive expansion pressure and productivity due to poor extrusion. It is effective in preventing the fall and contributing to stabilization of the oven operation and reduction of damage to the furnace body.

Claims (2)

The moisture of coal charged into the coke oven is called M (unit:%), the ratio of the particle size of the coal is 3 mm or less is called dp (unit:%), and the temperature when charging the coal is T _charged (unit: And a final dry distillation temperature of the coal is T _{dry distillation} (unit: deg. C), the first step of calculating P (unit: mmH ₂ O), which is a gas pressure generated during dry distillation of the coal, from the following equation: : P = 3.09 × 10 ⁹ × (M) ^-2.520 × (T _{dry distillation} ) ^-5.281 × (T _charging ) ^5.206 × (dp) ^-2.303 ; Comparing the calculated gas pressure with a limit gas pressure of the coke oven to confirm that the calculated gas pressure is less than or equal to the limit gas pressure, When the calculated gas pressure is greater than the threshold gas pressure in the second step, one or more of M, dp, T _charging and T _{dry distillation} are changed, and the first and second steps are made using the changed value. Method for checking the stable gas pressure of the coke oven, characterized in that for repeating. The method of claim 1, Wherein M is 5.6-9.0%, dp is 77-86%, the T _loading is 850-1000 ° C, and the T _{dry distillation} is 1050-1200 ° C. Way.