JPS62174293A - Method of dehydrating coking coal - Google Patents

Abstract

PURPOSE:To enable the drying apparatus, etc., to be miniaturized while decreasing the absolute value of coal moisture content and its range of variation without the need of any expensive heating facility, etc., by conducting dehydration of a coking coal at a particular range of centrifugal acceleration prior to pulverization. CONSTITUTION:Coal 2 in an outdoor coal storage yard 1 is shifted with a sieve 3. The coal grains having a diameter of 25mm or more are directly fed to a pulverization facility 4 and pulverized. On the other hand, the coal grains 14 having a diameter of 25mm or more are fed to a centrifugal dehydrator 15 by which dehydration oat a centrifugal acceleration of 300 to 800 times acceleration of gravity is performed so as to attain a moisture content of 6% or less and a range of moisture content variation of 1% or less. The coal 16 after dehydration is fed to the pulverization facility 4. The wash liq. is concentrated in a concentrating tank 17 and then likewise dehydrated using a centrifugal separator 18. The coal is fed together with coal 16 after dehydration to the pulverization facility 4, and pulverized. The pulverization product is compounded in a compounding facility 5, dried in a drying apparatus 7 and fed to a coke oven 9.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for dewatering coal for coke production.

(Prior Art) Coal for coke production is usually stored in open-air yards. Therefore, the amount of adhering moisture (hereinafter abbreviated as moisture) varies from about 6 to 13 inches depending on the influence of rainfall and the particle size specific to the brand. Coal moisture evaporates when coal is carbonized in a coke oven. Therefore, the absolute value of moisture and its temporal variation affect the absolute value of the required heat amount for coke oven carbonization and its temporal variation, and greatly influence coke oven productivity.

Therefore, as a measure to stabilize the amount of heat required for carbonization in a coke oven at a low level, there is a conventional technique of drying coal to be supplied to a coke oven in advance to reduce its moisture content. Drying methods include air flow type, fluidized bed type, and indirect heating type.As for the drying heat source, as shown in Japanese Patent Application Laid-open No. 58-129087, ``Method and Apparatus for Manufacturing Coke,'' exhaust heat from a coke oven is used. There are ways to collect and use it. In addition to drying, a method using a centrifugal dehydrator may be considered as a method for reducing the moisture content of coal for coke production.

A centrifugal dehydrator is a machine that feeds wet granular material into a cylindrical or conical screen that rotates at high speed, thereby shaking off the water content of the granular material and reducing the moisture content.
It has been widely used for chemical products (for example, Chemical Engineering Handbook, pages 1121 to 1127). However, its use for coal was limited to the coal preparation process in coal mines.

(Problems to be Solved by the Invention) The moisture content of coal for coke production varies depending on the brand and the weather, and exhibits a distribution as shown in Figure 4 (Blended Coal Moisture Distribution in Steelworks X). This fluctuation in coal moisture causes the following disadvantages.

First, the case of the coal processing flow for coke production provided with the coal drying equipment that utilizes the coke oven exhaust heat described above will be described. In this case, if the coal moisture exceeds the limit moisture that can be dried using the recovered heat, it becomes necessary to supplementally supply heat to the drying equipment from outside in order to keep the moisture supplied to the coke oven constant. Specifically, in drying equipment that recovers coke oven waste heat as heat carrier sensible heat and uses this heat carrier to heat and dry coal in an indirect heater, an auxiliary heating furnace equipment using externally supplied fuel is installed in the middle of the heat carrier transport line. Fuel for the equipment will be required.

Second, we will discuss the case of a coal processing flow for coke production that does not include coal drying equipment. In this case, fluctuations in moisture directly lead to fluctuations in the time required for carbonization in the coke oven and the amount of heat required, which poses a major problem in terms of production control and quality control.

That is, the first. In either of the second cases, the problem can be solved by reducing the absolute value of the coal moisture content and its fluctuation range.

By the way, it has already been mentioned that centrifugal dehydrators for coal mines exist as means for reducing the moisture content of coal. Approximately 100g (,
By dewatering using centrifugal acceleration (acceleration of gravity), the water content of the coal is reduced to about 5%.

However, there are the following problems when applying dehydrators for coal mines to coal processing for coke production.

According to experiments conducted by the present inventors, as shown in Figure 5,
For brands with a fine powder content of 0.5 B or less and a content of 22 inches or more, the water content that can be dewatered at a centrifugal acceleration of 100 g is 14 inches or more, so it is not possible to lower the moisture content of coal stored in the yard (moisture content: 6 to 13 inches).

On the contrary, in order to reduce the absolute value and fluctuation of the moisture content of coal stored in the yard using a dehydrator for coal mines (centrifugal acceleration: approximately 100 g), the first step is
Some of the representative brands shown in the table require wet sieving equipment to remove fine particles before dehydration, which is extremely uneconomical.

That is, it is impossible to economically and reliably reduce the absolute value and fluctuation range of moisture content of coal for coke production using conventional dehydrators.

In view of the above-mentioned current situation, the present inventors provide a treatment method for reducing the absolute value and fluctuation range of moisture content of coal for coke production without prior sieving operation.

In addition, in the centrifugal dehydration test by the present inventors mentioned above, a centrifugal dehydrator whose basic structure is shown in FIG. 8 was used. This machine has a rotating screen maximum diameter: soomi, rotation speed: maximum 20
00 rpm, coal throughput; 20 t7'h. Moreover, FIG. 5 shows the result of intentionally increasing the water content at the dehydrator inlet in order to investigate the water content that can be dehydrated.

Note that, since the centrifugal acceleration is defined below, in the case of a truncated cone-shaped rotating screen, the centrifugal acceleration also differs depending on the axial position of the screen when the diameter of the screen differs. However, since the moisture content of coal after dewatering is determined by the maximum centrifugal acceleration obtained at the maximum diameter part of the screen, hereinafter, centrifugal acceleration as a representative specification of a centrifugal dehydrator will refer to the maximum centrifugal acceleration.

However, 2: Centrifugal acceleration (mis) n: Number of revolutions (rpm) r: Radius of rotation (m) (Means for solving the problem) In the present invention, coal for coke production is
This is a method for dehydrating coking coal, which is characterized by reducing coal moisture content and reducing its fluctuation range by applying centrifugal acceleration of 800 g or less.

Next, the basis for determining the configuration conditions of the present invention will be explained. First, we will discuss the installation location of the centrifugal dehydrator. As shown in Figure 5, the water content after dehydration under the same centrifugal effect is fine powder (-0
, 5mm), the higher it becomes.

Therefore, the centrifugal dehydrator should be installed in front of the crushing equipment.

Second, we will discuss the appropriate range of centrifugal acceleration.

Coke factories in steel mills usually mix and use 5 to 20 brands of coal at a time for the purpose of ensuring coke quality, reducing raw material coal costs, and suppressing variations in coke quality due to variations in the properties of one brand of coal. For example, in a certain year, X steelworks used the brands of coal shown in Table 1, but the particle size composition in the table is F) Q. The content of fines below 5 mx varies greatly depending on the brand. I understand. However, according to experiments conducted by the present inventors, as shown in FIG.
The moisture content after dehydration differs depending on the fine powder content as shown below. Therefore, a dehydration test was conducted at X Steel Works using the 20 t/h centrifugal dehydration tester described above, and the results are shown in FIG.

The usage ratio of each brand of coal during this test period is also shown in Table 1. The fluctuation range consisting of the upper and lower limits of the moisture content after dehydration of the coal after blending in FIG. 6 is due to the fluctuation of the moisture content of the coal before dehydration depending on the brand of coal used and weather conditions, which are determined at a timely manner depending on various circumstances. As a result, as shown in FIG. 6, it was found that when the centrifugal acceleration was 300 g or more, the fluctuation range of the water content after dehydration of the coal after blending was significantly reduced.

It was also found that when the centrifugal acceleration exceeds SOO,@, the water content after dehydration becomes almost constant.

Incidentally, the brand used and the ratio used are determined by the location conditions of the steelworks, the coal market conditions, etc., and are unique to each steelworks. For example, at Y steelworks, the brand used and the usage ratio in a certain year are
Now shown in the table. Therefore, a dehydration test was also conducted at Y Steel Works using the aforementioned 20 t/h centrifugal dehydration tester. The results also show that 1 centrifugal acceleration is 3 as shown in Figure 7.
When the centrifugal acceleration was 800 g or more, the fluctuation range of the water content after dehydration was significantly reduced, and when the centrifugal acceleration was 800 g or more, the water content after dehydration became constant.

Naturally, the weather conditions at Y Steelworks and X Steelworks are different. In other words, regardless of the brand used, the usage ratio, and the moisture content of each brand coal (varies depending on weather conditions), the centrifugal acceleration is 300%.
By setting the value to y or more and soog or less, it is possible to significantly reduce the fluctuation range of the water content after dehydration of the blended coal and reduce the absolute value.

(Function) When the present invention is not used, each brand of blended coal has a water content of 7.5 to 12.5%, for example, as shown in Fig. 4, so that the moisture content is 30ON or more before being crushed into the coal according to the present invention! By applying a centrifugal acceleration of less than i, as shown in Figure 6, the average value of moisture fluctuates within 6 cm! @ allows you to pay within 1 inch. Although Fig. 6 is based on the operation results of the 20 t/h centrifugal dehydrator mentioned above, apart from this,
We also operated a centrifugal dehydrator, and the appropriate range of centrifugal acceleration was 300 p or more, as in the case of the 20 t/h machine.
It was less than 001.

(Example) Hereinafter, the present invention will be explained using examples shown in the drawings. First, a coal processing flow for coke making using a conventional coal drying membrane shown in FIG. 2 will be described.

Coal 2 sent from outdoor coal storage yard 1 is sent to crushing equipment 4
After being processed in a blending facility 5 and dried in a dryer 7, it is supplied to a coke oven 9. As the structure of the dryer, for example, a rotary dryer with a built-in indirect heating tube shown in FIG. 3 is used. That is, the heat transfer tubes 34 are arranged concentrically in the rotating cylinder 31, and the heating medium enters from the heat medium outlet 36 and exits from the heat medium outlet 37. In addition, the coal 35 is the coal input port 3.
After the coal enters from 2 and is dried, it exits from coal outlet 33.

On the other hand, in FIG. 2, the heating heat medium 12 is heated by the flue heat exchanger 11 and the riser tube heat exchanger 10, and if the coal moisture is high, it is further heated by the auxiliary heating equipment 20 and supplied to the dryer 7. be done. The heat medium whose temperature has been lowered by heat exchange in the dryer 7 is circulated and used by increasing the pressure in the bomb f13.

Next, an embodiment of the present invention will be described using FIG.

The coal 2 is first separated by a sieve 3 in the amount of 251 m or more and sent to the crushing equipment 4, and the coal 14 of 25 m or less is dehydrated in the centrifugal dehydrator 15 and then sent to the crushing equipment 4. In addition, 2
The reason why coal of 5 mm or more is not passed through the dehydrator is that coal of 25 mm or more tends to clog in the dehydrator due to its large particle size, and it also has less moisture attached to the weight of the coal particles, so dewatering is not necessary. This is because there is little sex. On the other hand, the waste liquid from the centrifugal dehydrator 15 is concentrated in a concentration tank 17, and the concentrated liquid is further reduced in water content in a centrifugal separator 18.
It is also sent to the crushing equipment 4. The coal discharged from the crushing equipment 4 is processed in the blending equipment 5, then dried in the dryer 7 and supplied to the coke oven 9. In this example, there is no need for auxiliary heating equipment for the heat medium, which is different from the prior art shown in FIG. Now, the structure of the centrifugal dehydrator used by the present inventors in the test will be explained with reference to FIG. Coal 41 passes through a coal supply chute 42 which is vibrated by a vibration motor 40 and is supplied to a rotating screen 43 which is driven by a motor 46 and which expands in the shape of a bow. The coal is subjected to centrifugal force within the rotating screen, and while adhering water is blown away as waste liquid 44, the coal is directed to the outlet of the multi-rotary screen by a component of the centrifugal force, and after dewatering is discharged as coal 45 out of the rotating screen. Figure 9 is an example of a similar coal dehydrator. In this case as well, the movement of the coal is basically the same as in Figure 8. However, a stone/4-47 is installed at the outlet of the rotating screen to quantify emissions. The stock horn rotates at the same speed as the rotary screen while reciprocating in a straight line in the axial direction, and has the function of adjusting the amount of coal cut out.

In addition to this example, there are centrifugal dehydrators with various discharge methods. In either case, if the dehydrator is of the type that rotates the screen, it is the same in that it can exhibit the feature of the present invention, which is to remove moisture from the coal for producing coke using a centrifugal acceleration of 300 to 800 g.

(Effects of the Invention) According to the method of the present invention, the coal moisture can be kept at 6% or less and the moisture fluctuation range can be kept at 1% or less. Therefore, in so-called pre-drying equipment for drying coal charged into a coke oven, expensive heat medium auxiliary heating equipment and its fuel, which were conventionally required when coal moisture increases due to rainfall, are no longer required. Furthermore, because the average moisture content of the coal is reduced, the amount of heat that must be added to the coal in the pre-drying equipment is small, and the dryer itself and the heat exchanger for waste heat recovery can also be made smaller and smaller in capacity. Therefore, installing a dehydrator will reduce the overall equipment cost and operating cost compared to installing a pre-drying equipment alone.

In addition, even in coke manufacturing plants without pre-drying equipment, by using the centrifugal dehydrator according to the method of the present invention, production and quality problems caused by moisture fluctuations can be resolved. The benefits outweigh the cost of installing the machine.

As described above, regardless of the presence or absence of pre-drying equipment, the present invention has unprecedented features as a means for removing moisture from coal for coke production, and its effects are significant.

[Brief explanation of drawings]

Fig. 1 is a diagram showing an example of a coal processing flow for coke production according to the present invention, Fig. 2 is a diagram showing a conventional coal processing flow diagram for coke production, and Fig. 3 (a) is an example of a rotary dryer. 3(b) is a cross-sectional view of FIG. 3(a), FIG. 4 is a diagram showing an example of moisture distribution in coke-making coal, and FIG. Figures 6 and 7 are diagrams showing the dewaterable moisture content of a single brand, Figures 6 and 7 are diagrams showing the moisture content when blending coal after dehydration at steelworks X and Y, respectively, and Figure 8 is the structure of the centrifugal dehydrator used in the dehydration test. Figure 9 is a diagram showing an example of the structure of a similar centrifugal dehydrator, where Figure 9 (a) shows the stopper position at the left limit (closed) and Figure 9 (b) shows the stopper position at the right limit (open).
It is a figure showing a state. 1: Outdoor coal storage yard 2: Coal 3: lJ equipment 4: Grinding equipment 5: Blending equipment 6: Blended coal 7: Dryer 8: Dried coal 9: Coke oven 10: Riser heat exchanger 11: Flue heat Exchanger 12: Heat medium oil 13: Pon 7'
14: 25 sets of coal under the plate 15: Centrifugal dehydrator 1
6: Dehydrated coal 17: Concentration tank 18: Centrifugal separator 19: Centrifugal separation liquid 20: Heat medium auxiliary heating equipment 2
1: Fuel 31: Rotating cylinder 32: Coal input port 33: Coal outlet 34: Heat transfer tube 35: Coal 36: Heat medium inlet 37: Heat medium outlet 40: Vibration motor 41: Coal before dehydration 42: Coal supply sheet 43
: Rotating screen 44: Drainage liquid 45: Coal after dehydration 46: Motor 47: Stolen arm - 48:
Stopper reciprocating device '10 '7, 56.08. s9.0 da, 510.0
10. ．． 511.011. -5 P2.01:2. S
13.0 minutes (%) Fig. 5 Ml ni Itto 04IL C'/sO] Fig. 6 Mu 辷加*a:X (Kashida) Fig. 7 Mu cfIOtJL:!(-/sri4 O) ;hair

Claims (1)

[Claims] A method for dehydrating coking coal, which comprises applying centrifugal acceleration of (300 to 800) x gravitational acceleration to reduce moisture adhering to the coking coal before pulverizing the coking coal.