KR100916517B1 - Blending method of coal for reducing internal gas pressure during coal carbonization in coke oven - Google Patents

Abstract

The present invention relates to a raw coal blending method for reducing the gas pressure generated in coal coking in a coke oven, and has a volatile matter (VM) of 25.6 to 28.7 in a blending index of blended coal composed of raw coal used in the manufacture of metallurgical coke. It is characterized by adjusting so that wt%, the fluidity | liquidity (LMF) may be 2.5-2.7, the total inert substance (TI) is 26.1-31.3 wt%, and the general carbon compounding ratio is 40-60 wt%.

Coke oven, raw coal, blended coal, volatile matter, fluidity

Description

Blending method of coal for reducing internal gas pressure during coal carbonization in coke oven}

1 is a schematic diagram of a coke test furnace used in an embodiment of the present invention.

<Description of Symbols for Main Parts of Drawings>

1 fixed wall 2 moving wall 3 SiC heater

4: oven 5: carbonized car 6: gas pressure measurement probe

7 damper 8 LPG burner 9 air supply unit

10: year 20: gas pressure measurement life 21: pressure sensor

22: thermocouple 23: gas pressure measuring probe installation point

The present invention relates to a raw coal blending method for reducing the gas pressure generated during coal coking in a coke oven, and more particularly, to reduce the maximum gas pressure generated at the center of coal charged during coal coking in a coke oven. The present invention relates to a method for blending raw coal for adjusting the blending index of blended coal consisting of blending of raw coal used for production.

As the coke ovens are rapidly aging around 20 years of operation, and environmental aspects are being strengthened, the extension of oven life and furnace management are one of the most important problems in the metallurgical coke manufacturing process. In particular, one of the most important problems in the metallurgical coke manufacturing industry is to suppress the damage of the coke oven wall by the dangerously high expansion pressure acting on the coke oven wall generated during the coal distillation process. Coal or coal blends with such high expansion pressures can damage the oven walls and ultimately shorten the 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 the coal is dried in a slot-type oven, two softening layers are formed parallel to the oven walls. These two softening layers are joined together to form an additional softening layer which forms an envelope, sleeve and tube of softened coal at the bottom and top of the charged coal. As dry distillation progresses, the softening layer gradually moves to the center of the oven and eventually meets at the center of the oven. In this softening layer certain particles of coal are converted into porous molten coke. It is usually accompanied by the generation of a gas pressure reaching a maximum level in the softening layer when the two softening layers are coalesced at the center of the oven for a coal having a volatile content of 17 to 25 wt% (daf). This pressure is transferred to the oven wall through a semi-coke layer between the center of the oven and the oven wall, where the pressure on the oven wall is called the expansion pressure. Significantly higher pressures will cause damage to the oven. Coal with similar properties under chemical analysis and swelling properties shows very different behavior for pressure generation.

Commonly encountered coal expansion pressure and gas pressure are defined as the coal expansion pressure acting on the oven wall due to coal distillation, and the gas pressure is defined as the pressure measured by the probe inserted in the coal / coke layer during coal distillation. do. In general, there is little method for directly measuring the inflation pressure, which is the pressure applied to the oven wall in coal drying in commercial ovens, and the inflation pressure is measured using a test furnace. The relationship between the expansion pressure and the gas pressure generated during the coal distillation process shows that in commercial ovens, the maximum gas pressure generated at the center of the oven remains as the expansion pressure at the oven wall, but in the test furnace the softened layer where two softening layers are coalesced at the center of the oven It is known that the gas pressure becomes twice or more than the expansion pressure because the cross sectional area of s becomes less than half the cross sectional area formed on the oven wall by the initially charged coal.

As described above, excessive expansion pressure in the coal coking process in the coke oven causes extrusion blockage or damage to the oven wall during extrusion, which may cause a stable operation of the coke oven and shorten the oven life. In addition, it is required to secure operating conditions to prevent 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 utilization rate, in order to manufacture high quality coke and reduce the cost on the cost. .

Thus, the limit of expansion pressure that occurs in coal coking in a coke oven is 7kPa in 6m coke oven and 14kPa in 4m coke oven, depending on the oven size, and the gas pressure at the center of the oven for stable oven operation in commercial coke oven It is known to be less than 350 mm H 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 during coal drying in the coke oven depends on the characteristics of raw material charcoal, oven charging and drying conditions, and is estimated by various complex actions occurring in the oven during the drying process. There is a lot of difficulty.

Many researchers (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). Although the analysis was conducted using a walled test furnace, the technique for managing the raw coal mixture index for reducing the gas pressure at the coal center generated by coal distillation process has not been clearly presented.

The present invention has been made in view of the above problems, the gas pressure at the center of coal generated during the coal distillation process in the coke oven in order to reduce the extrusion blockage and oven damage caused by excessive expansion pressure during the coal distillation in the coke oven of the steelworks It is an object of the present invention to provide a raw coal blending method for adjusting the blending index of the coal briquettes composed of the blend of raw coal used in metallurgical coke production so as not to become excessive.

In order to achieve the above object, the present invention, in the method for blending the raw coal so that the gas pressure generated in the coal distillation process in the coke oven is not excessive, comprising a mixture of the raw coal used in the manufacture of metallurgical coke In the blending index, the volatile matter (VM) is adjusted to 25.6 to 28.7 wt%, the flow rate (LMF) to 2.5 to 2.7, the total inactive substance (TI) to 26.1 to 31.3 wt%, and the general carbon compounding ratio to 40 to 60 wt%. It is characterized by.

Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the drawings.

In general, the limit of expansion pressure for coal coking in a coke oven depends on the oven size, 7 kPa for commercial coke ovens above 6 m and gas pressure at the center of the oven for stable oven operation in commercial coke ovens of 350 mmH2O or less. Known. In the present invention, the gas pressure at the center of the coal was measured while changing the mixing index of the raw coal used in the manufacture of metallurgical coke in order to prevent excessive expansion pressure during the operation of the oven and to ensure stable operation.

In the present invention, as shown in Figure 1 using a coke test furnace of 50kg capacity, by changing the mixing index of the raw coal used in the manufacture of metallurgical coke under the conditions of charging and dry distillation conditions are generated during coal drying The change of gas pressure was analyzed, and the results were used to propose a method for blending raw coal to reduce the gas pressure generated during coal distillation.                     

That is, the gas pressure generated at the coal center during coal distillation was measured using a test furnace having a moving wall having a capacity of 50 kg shown in FIG. 1. The coal used for gas pressure was mixed with raw coal used for coke production in a commercial coke oven, and the heating wall temperature of the test furnace was charged at 850 ° C. so that the heating conditions of the test furnace were the same as in the commercial coke oven. When the charged coal temperature reached 600 ° C., it was heated at 3 ° C./min to 1100 ° C., which was the final drying temperature, and maintained at 1.5 ° C. for the final drying temperature.

The main body 1 of the oven has a fixed wall 2 on one side thereof, and a moving wall 3 on the other side thereof, and a plurality of probes 4 on the inner center of the main body 1. Is installed, and the carbonized car 5 is installed in the lower part. SiC heaters 6 of the same capacity were horizontally installed on both the fixed wall 2 and the moving wall 3 for heating the coal charged in the oven. The movable wall 3 has a rail and wheels installed at the bottom to move, and the carbonized car 5 is also installed at the bottom so that the coal coke 5 can be pulled out of the oven to discharge red coke.

In the upper part of the oven, a charging inlet (not shown) was installed for charging coal, and a discharge pipe 7 was installed to discharge the generated gas. A damper (8) was installed in the discharge gas discharge pipe to adjust the pressure in the oven, and a pressure gauge (not shown) was installed at the bottom of the discharge pipe to control the pressure in the oven so that positive pressure was applied to 1 mm H 2 O.

The red coke dried in the oven moved carbonized tea to a pusher outside the oven after the end of the dry distillation, and then pushed the coke in the width direction of the oven using a 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. Coke oven gas (COG) generated during the drying is burned with the LPG and the air of the air supply unit 10 in the LPG burner (9) installed at the rear end of the damper, the exhaust gas is discharged to the outside by the flue (11) ventilation power.

Gas pressure generated at the center of coal during coal distillation was measured by using a probe 4 having a K-type thermocouple 41 therein. The probe 4 is parallel to the heating wall, three in the center of the oven in the width direction of the oven, a rectangular hole 42 is installed at one end of the probe to measure the gas pressure, The pressure was measured using a pressure sensor 43 connected to the probe.

<Example 1>

With respect to the coal briquettes having a water content of 8.7 wt%, the maximum gas pressure change at the coal center according to the change in the volatile matter (V.M) of the coal blends was measured. The coal used is a mixture of 9 to 10 types of raw coal used in the manufacture of metallurgical coke. The blending index (volatility (VM), fluidity (LMF), total expansion (TD), strength index (SI), total inactivity) Material (TI), General Coal Blend Ratio] was formulated in the same range as the coal blend used in coke ovens for the manufacture of metallurgical coke. The blended coal used to manufacture the metallurgical coke is blended in a proportion of 50 wt% of coking coal and 50 wt% of ordinary coal. In addition, the volatile matter (VM) of the coal briquettes was changed from 23.6 wt% to 28.7 wt%, the other mixture index of the coal blend (LMF) was 2.5 to 2.55, total expansion (TD) was 97 to 100 wt%, The strength index (SI) was 4.2 to 4.5, and the blend ratio of the normal coal was maintained at 50 wt%, which was almost constant.

The gas pressure change was shown in Table 1 when the volatilization of the blended coal was changed from 23.6 wt% to 28.7 wt%.

      Volatilization (V.M, wt%) 23.6 24.6 25.6 26.5 27.5 28.7 Gas pressure (mmH2O) 187 131 79 63 61 53

As can be seen from Table 1, as the volatile fraction of coal blended in the oven increases, the maximum gas pressure at the center of coal generated during coal drying is drastically decreased. This increases the rate of gas generation in the coal softening layer as the volatile fraction of coal blend increases, but the effect of reducing the thickness and viscosity of the soft melt layer acts more greatly, so that the force of pushing the coke to the oven wall by the generated gas is increased. As it decreases, the gas pressure decreases with increasing volatiles. As shown in Table 1, when the volatile fraction of the coal blend is less than 24.6wt%, the gas pressure increases rapidly, which may cause extrusion clogging or oven damage in a commercial oven. In addition, the volatilized fraction of the coal briquettes used in the manufacture of coke for metallurgical coke is not more than 29% in view of the quality of the manufactured coke and the recovery of goose coke at the end of dry distillation. Therefore, the volatilization index, which is the compounding index of the coal briquettes charged, should be controlled in the range of 25.6 to 28.7 wt%, in consideration of the smooth coke oven operation and the damage of the oven.

<Example 2>

With respect to the coal briquettes having a water content of 8.8 wt%, the change in the gas pressure at the center of coal according to the change in the flow rate (LMF), which is the blending index of the coal blends, was measured. At this time, the coal briquettes used were 9-10 types of raw coals used in the manufacture of metallurgical coke as in Example 1, and the blending index (volatile matter (VM), fluidity (LMF), total expansion (TD), strength index) was used. (SI), total inert matter (TI), and general carbon compounding ratio] were formulated in the same range as the coal briquettes used in coke ovens for the manufacture of metallurgical coke. The blended coal used in the manufacture of metallurgical coke is blended in a proportion of 50 wt% of coking coal and 50 wt% of ordinary coal. The flow rate (LMF) of the coal briquettes was changed from 2.3 to 2.8, and the volatilized powder (VM), which is another blending index of the coal blend, was 25.7 to 26.5, 90 to 101 wt% of total expansion (TD), and the strength index (SI). Is 4.0 to 4.3, and the blend ratio of the ordinary coals is blended to remain almost constant at 50 wt%.

When the flow rate of the blended coal was changed from 2.3 to 2.8, the change in gas pressure was shown in Table 2.

       Flow rate (LMF) 2.3 2.4 2.5 2.6 2.7 2.8 Gas pressure (mmH2O) 179 143 86 71 83 133

As can be seen from Table 2, as the flow rate of the blended coal, which is the blending index, increased from 2.3 to 2.8, the gas pressure rapidly decreased above a certain flow rate and then increased again above a certain flow rate. This suggests that for some coals, the flow rate of coal tends to increase the gas pressure due to the increase of molten product in the softening bed, but for coal blended coals, the minimum gas pressure in the proper flow range is shown due to the coal mixing characteristics. . Therefore, as can be seen from the above results, the flow rate of the coal briquettes to prevent the gas pressure at the center of coal from increasing rapidly and excessive expansion pressure is generated should be managed in the range of 2.5 to 2.7.

<Example 3>                     

With respect to the coal briquettes having a water content of 8.6 wt%, the change in the gas pressure according to the change of the total inert material (TI), which is the compounding index of the coal blends, was measured. At this time, the coal briquettes used were blended 9 to 10 types of raw coals used in the manufacture of metallurgical coke, as in Examples 1 and 2, and the blending index (volatile matter (VM), flow rate (LMF), total expansion (TD)). ), Strength index (SI), total inert material (TI), and general carbon compounding ratio) are formulated in the same range as the coal blend used in coke ovens for the manufacture of metallurgical coke. Coal briquettes used in the manufacture of metallurgical coke are blended in a proportion of 50 wt% coking coal and 50 wt% general coal. The total inert material (TI), which is the blending index of the blended coal, was changed from 24.3 wt% to 33.5 wt%, and the volatile matter (VM), which is another blending index of the blended coal, was 25.3-26.2wt%, and the fluidity (LMF) was 2.5-2.7, total expansion (TD) was 94-105 wt%, the strength index (SI) was 4.1-4.4, and the compounding | mixing ratio of a normal carbon was mix | blended so that it might be maintained to be nearly constant.

As the total inert matter (TI) of the blended coal varies from 24.5 wt% to 33.5 wt%, the gas pressure change is shown in Table 3.

      Total inactive substance (TI) 24.3 26.1 27.8 29.6 31.3 33.5 Gas pressure (mmH2O) 166 97 84 83 72 45

As can be seen in Table 3, the gas pressure decreased as the total inert material (TI), which is the blending index of coal blends, increased. This is because the increase in total inerts in the coal mixture decreases the gas pressure because gas generated in the softening layer is discharged through these inerts when dry. As shown in the table, the total inert matter of the coal blend is 26.1. Below it, the gas pressure increased rapidly, and as the total inert material increased above 31.3, the gas pressure decreased rapidly. Excessive expansion pressure leads to extrusion blockage and oven damage, and too low gas pressure results in the quality of the coke produced by coal dry distillation not being secured. Therefore, as derived from this embodiment, the total inert material, which is the blending index of the coal briquettes, must be managed in the range of 26.1 to 31.3 wt% for stable coke oven operation.

<Example 4>

With respect to the coal briquettes having a water content of 8.7 wt%, the change in the gas pressure according to the change of the general coal compounding ratio, which is the compounding index of the coal mixtures, was measured. The coal briquettes used were 8-10 types of raw coals used in the manufacture of metallurgical coke. The blending index (volatile matter (VM), fluidity (LMF), total expansion (TD), strength index (SI), total) Inert matter (TI), general coal blend ratio] was formulated in the same range as the coal blend used in the coke oven for the manufacture of metallurgical coke. Coal briquettes used in the manufacture of metallurgical coke are blended in a proportion of 50 wt% coking coal and 50 wt% general coal. The blending ratio of the coal blend, which is the blending index of the blended coal, was changed from 30wt% to 70wt%. The expansion (TD) was 95-103, the strength index (SI) was 3.8-4.1, and the total inert material (TI) was 26.7-28.3 wt%, and it was mix | blended so that it might be maintained substantially constant.

The gas pressure change is shown in Table 4 when the mixing ratio of the general coal of the blended coal is changed from 30wt% to 70wt%.

   General coal compounding ratio (wt%) 30 40 50 60 70 Gas pressure (mmH2O) 159 97 78 71 46

As can be seen in Table 4, since the non-coking coal content increases as the coal blending ratio in the coal blend increases, the gas pressure decreases during coal distillation. As shown in Table 4, the gas pressure increased drastically when the ratio of the coal mixture was less than 40wt%, whereas it rapidly decreased when it exceeded 60wt%. Therefore, in order to operate a stable coke oven, the blending ratio of the coal mixture, which is the blending index of coal coal, should be managed in the range of 40wt% to 60wt%.

From the above examples, the effect of the mixing index of the coal briquettes charged into the oven on the gas pressure under constant charging and dry distillation conditions of the coke oven was derived, and stable coke oven operation and damage to the oven under given charging and dry distillation conditions in the coke oven. It is expected to be useful in blending raw coal for prevention.

As described above, the present invention mixes the raw coal so that the gas pressure of the coal center generated in the coal drying process is not excessive by managing the blending index of the coal blend composed of the raw coal used for the manufacture of metallurgical coke in the coke oven. Stable operation at given charging and distillation conditions, and also prevents excessive expansion pressure when coal coal distills from raw coal mixture as described above, thereby lowering productivity due to oven wall damage caused by excessive expansion pressure and poor extrusion By preventing, it has the effect of contributing to stabilization of the oven operation and reducing the damage to the furnace body.

Claims (1)

In the method of blending the raw coal so that the gas pressure generated during the coal drying process in the coke oven does not become excessive, the volatile matter (VM) is 25.6 to 28.7 in the blending index of the coal blend composed of the raw coal used to manufacture metallurgical coke. wt%, the flow rate (LMF) is 2.5 to 2.7, the total inert matter (TI) is 26.1 to 31.3 wt%, and the coking oven is characterized in that the coking oven, characterized in that Raw coal blending method for reducing gas pressure.

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