JPH04225091A - Operation of steam tube dryer for humidifying coal - Google Patents

Abstract

PURPOSE:To prevent excessive drying of coal remaining in a dryer during emergency stopping and to reduce dust during reoperation. CONSTITUTION:A steam pipe 4 and a drain pipe 25 to a tube dryer 1 of humidifying coal using steam as a heat source are provided with a shut-off valve 21 and a shut-off valve 22, respectively. When the dryer 1 is stopped in an emergency, feed of coal to the dryer 1 is suspended and revolution of the dryer 1 is stopped, the two shut-off valves 21 and 22 are closed, steam in a heat transfer tube 2 is sealed, is isolated from a heat source and coal remaining in the dryer 1 is prevented from being dried exccessively.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is a humidity control equipment for raw coal charged into a coke oven, and more specifically, a steam tube dryer that uses steam as a heat source to prevent overdrying of coal moisture. The present invention relates to a method of operating a steam tube dryer.

0002

[Prior Art] In order to improve the productivity and economic efficiency of coke ovens, moisture control coal (CMC) has traditionally been used as a pre-treatment method for coking coal.
), briquette and preheated charcoal methods are known. Among these methods, the moisture-controlled coal method reduces the amount of heat of carbonization by adjusting the moisture content of coking coal, which varies in the range of 7-12% depending on the weather, to usually 5-6% before charging it into a coke oven. The aim is to improve productivity by reducing the amount of carbon and increase bulk density, and to reduce raw material costs by incorporating a large amount of slightly cohesive coal. As humidity controllers, indirect heating type tube dryers that use water vapor or heat medium as the heat source, and direct heating multi-stage disc type humidity controllers that use hot air are in operation in Japan.

FIG. 3 shows the flow of a moisture-conditioning coal facility using a conventional indirect heating type steam tube dryer 1 (hereinafter referred to as a dryer). Heat exchanger tube 2 for indirect heating
Low-pressure steam is discharged into this heat transfer tube 2 through a steam pipe 4 branched from a steam source pipe 3, and the raw coal charged in the dryer 1 is heated by the heat of condensation when the steam condenses. Heat and dry.

[0004] Raw coal conveyed by a coal conveyor 5 is charged into a charging port 6 and then continuously charged into a dryer 1 by a screw feeder 7 . Dryer 1
The raw coal heated and dried inside is discharged from the discharge port 8 at the other end to the discharge side screw feeder 9, and further conveyed to the next process by the moisture-controlled coal conveyor 10. A carrier gas is introduced into the dryer 1 from a carrier gas supply pipe 11 from one end, and moisture evaporated from raw coal by heating is brought into the carrier gas, and an exhaust port 12 connected to the other end is introduced into the dryer 1.
Since it contains dust, it is removed by a dust collector (not shown) and then discharged into the atmosphere. By heating and drying in this way, wet coal with a moisture content of about 7 to 12% is reduced to 5 to 6%.
Humidity is controlled by dry charcoal. In addition, the drain water resulting from steam condensation is discharged from the drain outlet 13 to the drain tank 14 via the drain pipe 25, and the drain water is recovered.

[0005] In order to control the moisture content of raw coal at the outlet of the dryer 1 to a constant level, a coal flow meter 16 and a moisture meter 17 are installed.
The amount of raw coal supplied to the dryer 1 and the moisture content are measured by the controller 1, and the data on the amount of coal supplied and the data on the inlet moisture content are input to the control device 18. The control device 18 normally adjusts the rotation speed of the dryer 1 by the dryer driving device 20 in response to fluctuations in the amount of coal supplied, and also adjusts the rotation speed of the dryer 1 by the dryer drive device 20 in response to fluctuations in the amount of evaporated water (the difference between the amount of water at the inlet and the amount of water at the outlet). The steam pressure supplied to the heat transfer tubes 2 of the dryer 1 is adjusted by the steam pressure control valve 19, and the dryer is operated so that the moisture content of the humidity-controlled raw coal reaches a target value.

[0006]

[Problems to be Solved by the Invention] In addition to the normal startup and shutdown operations, the steam tube dryer operation method described above includes emergency shutdowns in case of trouble with downstream transportation equipment, or when the coal tank of a coke oven is full. , there is a restart operation. FIG. 4 shows an example of a dryer operation pattern during an emergency stop and restart. As shown in Figure 4, during steady operation, automatic feed-forward control is performed to respond to fluctuations in the moisture content at the coal inlet, but in the event of an emergency stop, the coal supply to the dryer can be stopped and the steam pressure and dryer rotation speed can be controlled at the same time. set to the minimum value.

The main purpose of venting the steam at the minimum pressure is to keep the dryer body warm so that it can be restarted immediately when the emergency stop is canceled. The reason why the dryer continues to rotate at a low speed is to prevent deformation due to the temperature difference between the coal contact area (20 to 30% of the dryer shell cross-sectional area) and the space. The above operating method has the following problems.

That is, at the time of emergency shutdown, raw coal remains in the dryer, and heat from low-pressure steam is supplied to the raw coal even though the temperature is low, so that drying of the residual coal progresses. If the emergency stop is canceled within a few minutes, the degree of dryness is low, but if it lasts for a long time, the moisture limit for dust generation may be 5.
Dry to ~6% or less. When the dryer is restarted from such a state, overdried coal with a large amount of dust is discharged from the dryer outlet, which poses an extremely serious problem in terms of handling and the environment. In addition, even at low rotation speeds, coal is discharged little by little from the dryer outlet due to the rotation of the dryer, and if the dryer is stopped for a long period of time, the chute may become clogged.

[0009] The present invention aims to solve the above-mentioned problems.
It is an object of the present invention to provide a method of operating a steam dryer for controlling humidity of coal to prevent overdrying of coal moisture within the dryer.

0010

[Means for Solving the Problems] To achieve the above object, the present invention provides a method of operating a steam tube dryer for controlling the humidity of coal using steam as a heat source. A cutoff valve is provided in each line, and when the dryer is stopped in an emergency, the two cutoff valves are also closed at the same time as the supply of coal to the dryer is stopped, thereby stopping the supply of heat source steam. This is a method of operating a steam tube dryer for controlling humidity of coal, which is characterized by preventing overdrying of coal.

[0011] In the above method, when the dryer is stopped in an emergency, it is preferable that the rotation of the dryer is also stopped, and a small-diameter bypass cutoff valve is provided separately from the steam supply line cutoff valve, and the dryer is restarted after the emergency stop. In this case, it is preferable to first open the bypass cutoff valve to fill the inside of the dryer heat exchanger tube with pressure, and then open the steam supply line cutoff valve and the drain discharge line cutoff valve to restart the operation.

[0012] In addition, if the emergency stop time is long, it is preferable to rotate the dryer intermittently to prevent thermal distortion of the dryer furnace body, and furthermore, it is possible to predict in advance whether the dryer will stop or restart. In this case, the steam supply can be stopped a certain period of time before the dryer is stopped, and steam supply can be started a certain period of time before the dryer is restarted to eliminate fluctuations in the moisture content of the coal discharged from the dryer.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the flow of a humidity control coal facility using an indirect heating type steam tube dryer 1 of the present invention. In FIG. 1, the same parts as the conventional example shown in FIG. This is intended to be simplified.

In the present invention shown in FIG.
A steam supply line cutoff valve 21 is provided on the downstream side of the steam pressure control valve 19 provided on the steam supply line to, that is, the steam pipe 4 branched from the steam main pipe 3, and a drain discharge line cutoff valve 22 is provided on the drain pipe 25. . Note that it is preferable that a bypass pipe 23 is connected to the steam pipe 4, and that a small-diameter bypass cutoff valve 24, which is normally closed, is provided in the bypass pipe 23.

During steady operation of the dryer 1, feedforward automatic control is mainly carried out in response to fluctuations in inlet moisture content, and the rotational speed of the dryer 1 is controlled in response to fluctuations in the amount of coal supplied, as in the conventional example described above. . On the other hand, for an emergency stop of the dryer 1, as shown in Fig. 2, the coal conveyor 5
Then, the supply side screw feeder 7 is stopped to stop the supply of raw coal, and the dryer drive device 20 is stopped to stop the rotation of the dryer 1.

At the same time, the steam supply line cutoff valve 21 disposed in the steam pipe 4 and the drain discharge line cutoff valve 22 disposed in the drain pipe 25 are closed to completely stop the supply of steam serving as a heat source. Although the remaining coal in the dryer 1 will dry slightly due to the heat retained in the dryer body and heat transfer tubes, the evaporated water content is only about 0.5 to 1.0%, and the furnace is not large enough to cause dust generation when restarting operations. It is possible to prevent over-drying of the raw material coal inside. Further, by stopping the rotation of the dryer 1, almost no coal is discharged from the outlet of the dryer 1 to the coal discharge port 8.

Although the inside of the heat exchanger tube 2 is in a vacuum state during steam cutoff, the drain discharge line cutoff valve 22 is closed, so drain water or flash steam generated from the drain is prevented from flowing back into the heat exchanger tube 2. can do. In addition, when restarting the dryer 1 after an emergency stop, first open the small-diameter bypass cutoff valve 24 and gradually supply steam to the heat transfer tubes 2 from the bypass pipe 23 to fill the pressure, and then open the steam supply line cutoff valve 24. 21 and the drain discharge line cutoff valve 22 are opened to start operation, the steam pressure supplied to the heat transfer tubes 2 is adjusted by the steam pressure control valve 19, and normal operation is started by automatic feedforward control against inlet moisture fluctuations.

Furthermore, if the emergency stop time is long, the dryer drive device 20 may be driven intermittently to stop the dryer 1.
It is preferable to prevent thermal distortion of the furnace body. Furthermore, dryer 1
If the stoppage and restart of the dryer 1 can be predicted, the steam supply is stopped a certain period of time before the dryer stops, and the steam supply is started a certain period of time before the dryer restarts, so that the coal moisture discharged from the dryer 1 can be reduced. Fluctuations can be reduced.

[0019]

Effects of the Invention As explained above, according to the present invention, it is possible to prevent the residual coal in the dryer from overdrying when a steam dryer for controlling humidity of coal is stopped in an emergency, thereby reducing dust generation when restarting the dryer, thereby improving the environment. can eliminate all problems. Additionally, the dryer can be restarted smoothly.

[Brief explanation of the drawing]

FIG. 1 is a flow diagram of an apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a dryer operation pattern according to an example of the present invention.

FIG. 3 is a flow diagram of a conventional device.

FIG. 4 is a diagram showing a dryer operation pattern according to a conventional example.

[Explanation of symbols]

1 Steam tube dryer 2 Heat exchanger tube 3 Steam main pipe 4 Steam pipe 5 Coal conveyor 6 Loading port 7 Supply side screw feeder 8 Coal discharge port 9 Discharge side screw feeder 10 Humidity control coal conveyor 11 Carrier gas supply pipe 12 Exhaust port 13 Drain outlet 14 Drain tank 16 Coal flow meter 17 Moisture meter 18 Control panel 19 Steam pressure control valve 20 Dryer drive device 21 Steam supply line shutoff valve 22 Drain discharge line shutoff valve 23 Bypass piping 24 Bypass shutoff valve 25 Drain pipe

Claims (5)

[Claims] 1. A method of operating a steam tube dryer that uses steam as a heat source to condition the humidity of coal, wherein a shutoff valve is provided in a steam supply line to the dryer and a drain discharge line from the dryer, and when the dryer is stopped in an emergency, the method comprises: At the same time as the supply of coal to the dryer is stopped, each of the two shutoff valves is also closed to stop the supply of heat source steam, thereby preventing the residual coal in the dryer from overdrying. How to operate a steam tube dryer. 2. The method of operating a steam tube dryer for controlling humidity of coal according to claim 1, wherein when the dryer is stopped in an emergency, the rotation of the dryer is also stopped. 3. A small-diameter bypass cutoff valve is provided separately from the steam supply line cutoff valve, and when resuming operation after an emergency stop, the bypass cutoff valve is first opened to fill the inside of the dryer heat transfer tube, and then the steam 2. The method of operating a steam tube dryer for controlling humidity of coal according to claim 1, wherein the operation is restarted by opening a supply line cutoff valve and a drain discharge line cutoff valve. [Claim 4] If the emergency stop time extends for a long time,
2. The method of operating a steam tube dryer for controlling humidity of coal according to claim 1, wherein the dryer is rotated intermittently to prevent thermal distortion of the furnace body of the dryer. [Claim 5] When the stoppage and restart of the dryer can be predicted in advance, the steam supply is stopped a certain time before the dryer stops, and the steam supply is started a certain time before the dryer restarts, and the steam is discharged from the dryer. 2. The method of operating a steam tube dryer for controlling humidity of coal according to claim 1, wherein fluctuations in coal moisture are eliminated.