JPH04187257A - Controlling method for spraying atomization in exhaust gas cooling tower - Google Patents

Abstract

PURPOSE:To easily control the atomized amount of water in a cooling tower by stopping atomization of water until the temp. of exhaust gas discharged from the cooling tower reaches the prescribed upper limit temp. and atomizing water at the low atomization amount of tolerance after the temp. of exhaust gas reaches the upper limit temp. CONSTITUTION:The atomization amount of water atomized into a cooling tower 2 from spray nozzles 10a-10d is controlled by the flow rate controlling valve 20 of a water return pipe 19. A controller for controlling the divergence of the valve 20 is shown by 22. The signals of the measured temp. are inputted to this controller 22 from temp. measuring instruments T1, T2. When operation of a melting furnace 1 is started, the temp. of exhaust gas discharged from the furnace 1 is made gradually high according to the lapse of time. The amount of heat discharged from the furnace 1 is gradually increased. Atomization of water is not performed until temp. T2 reaches the upper limit temp. being the heat resistant temp. of the filter of a bag house 3. When the temp. T2 reaches this upper limit temp., atomization of water is started at 4l/min being minimum atomization amount of the respective spray nozzles 10a-10d. Thereby the temp. of exhaust gas discharged from the cooling tower is surely stabilized at the aimed temp.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention is directed to a cooling tower, where exhaust gas discharged from industrial facilities such as melting furnaces and incinerators is guided to a cooling tower and sprayed with water. The present invention relates to a spray control method for an exhaust gas cooling tower that cools the exhaust gas to a certain temperature.

[Prior Art] Bag filters have traditionally been used as an effective means of collecting dust containing harmful substances in the exhaust gas discharged from furnaces.
is used. Since bag filters generally have a filter heat resistance temperature of about 350°C, the exhaust gas must be cooled to below such heat resistance temperature. For this purpose, conventionally the exhaust gas discharged from the furnace is guided to a cooling tower and sprayed with water to reduce the exhaust gas to 200~
It is cooled to about 250°C. Conventionally, the method of controlling the temperature of the exhaust gas is to install a temperature sensor on the exhaust gas outlet side of the cooling tower, measure the temperature of the exhaust gas that has passed through the cooling tower, and perform feedback control of the amount of water sprayed from the cooling tower. It was an automatic control system that ensured that the exhaust gas temperature after passing through the cooling tower reached a predetermined target temperature.

[Problem M to be solved by the invention] By the way, 1. Generally, a spray nozzle has an upper and lower limit (rangeability) for the amount of water sprayed due to its structure, so it is not possible to control the amount of water sprayed beyond these ranges.

However, immediately after starting a furnace such as a melting furnace or incinerator (Start 1 o'clock), the temperature of the exhaust gas gradually increases, and even if the above automatic control function is activated and the above spray starts, it will not work due to the above reasons. Since the amount of spray cannot be lowered below the lower limit, the temperature of the useful gas passing through the cooling tower will not only drop too much, but it will also contain a large amount of water droplets. If the exhaust gas flows into the bag filter, the filter becomes wet and becomes unusable.To avoid such a situation, conventionally, when the furnace starts operating, the waste gas is discharged by bypassing the bag filter. There is a problem that a large amount of dust blocks ducts or causes air pollution.

Further, even when the operation of the furnace is stopped, the amount of heat discharged from the furnace gradually decreases, so it is very difficult to control the amount of water sprayed in the cooling tower.

[Means for Solving the Problems] The spray control method for an exhaust gas cooling tower of the present invention is intended to solve the above problems, and includes cooling the exhaust gas by spraying water into the exhaust gas exhaust system of the furnace. Exhaust gas cooling in which a cooling tower is installed, the temperature of the exhaust gas that has passed through the cooling tower is measured, and the amount of water sprayed by the cooling tower is feedback controlled to automatically control the temperature of the exhaust gas after passing through the cooling tower to a predetermined target temperature. In the cooling tower, when the amount of exhaust heat discharged from the furnace gradually increases at the start of operation of the furnace, water spraying is stopped until the temperature of the exhaust gas discharged from the cooling tower reaches a predetermined upper limit temperature. After reaching the target temperature, water is sprayed at the minimum permissible spray amount, and when the exhaust gas temperature becomes equal to or lower than the predetermined target temperature, automatic control using the feedback control is started. .

Further, the spray control device for the exhaust gas cooling tower when the furnace is stopped according to the present invention is provided with a cooling tower that cools the exhaust gas by spraying water into the exhaust gas exhaust line of the furnace,
In the exhaust gas cooling tower, the temperature of the exhaust gas that has passed through the cooling tower is measured and the amount of water sprayed in the cooling tower is feedback-controlled to automatically control the temperature of the exhaust gas after passing through the cooling tower to a predetermined target temperature. It is characterized in that when the amount of exhaust heat discharged from the furnace gradually decreases when the operation is shut down, water spraying is stopped at the same time as the temperature of the exhaust gas discharged from the furnace falls below a predetermined upper limit temperature. be.

[Example] Next, one embodiment of the present invention will be described with reference to the drawings.

Fig. 2 shows the entire exhaust gas treatment system of this melting furnace, in which 1 is the melting furnace, 2 is a cooling tower installed in the exhaust gas discharge line, 3 is a bag house with a bag filter installed,
4 is an exhaust gas suction fan, and 5 is a bypass path for the baghouse 3. The exhaust gas discharged from the melting furnace 1 is sent to the cooling tower 2. It passes through the baghouse 3°, is sucked into the suction fan 4, and is discharged into the atmosphere. T1 is a temperature measuring device that measures the temperature of the exhaust gas at the inlet of the cooling tower 2, and T2 is a temperature measuring device that measures the temperature of the exhaust gas that has passed through the cooling tower 2 at the exit side of the cooling tower 2. Further, 6 is an artificial damper of the baghouse 3, 7 is an exit damper, 8 is a bypass damper provided in the bypass path 5,
Reference numeral 9 denotes a flow rate adjustment damper that adjusts the amount of exhaust gas sucked by the suction fan 4.

The cooling tower 2 is provided with spray nozzles 10a to 10d for spraying water, as shown in detail in FIG. 11
1 is a pump that pumps water to the spray nozzles 10a to 10d, and 12 is a service tank that stores the water. The pump 11 supplies water drawn from the service tank 12 through a supply valve 13 and a water supply pipe 15 to water supply pipes 14a to 14d detailed in FIG. 3. The water supply pipes 14a-1
4d are provided with on-off valves 16a-16d, respectively, and the spray nozzles 10a-10d are connected to the on-off valves 16a-16d.
Pressure water is supplied to each. The spray nozzle 10a
-10d are provided with return pipes 17a-17d, and the return pipes 17'a-17d are provided with on-off valves 18a-18d, respectively, and the return pipes 17a-17d converge into a return pipe 19, which A flow rate control valve 20 is provided in the flow rate control valve 20 .

The return pipe 19 is connected to the service tank 12. In addition, 21 is a pressure regulating valve provided between the water supply pipe 15 and the return pipe 19 in order to keep the water pressure of the water supply pipe 15 constant.

The amount of water sprayed into the cooling tower 2 from the spray nozzles 10a to 10d is adjusted by a flow rate control valve 20 of the return pipe 19. Reference numeral 22 denotes a controller that controls the opening degree of the flow rate regulating valve 20, and measured temperature signals are inputted to the controller 22 from the temperature measuring devices T1 and T2.

A heater 23 is provided in the baghouse 3 to dry the filter.

When the operation of the melting furnace 1 is started, as shown in Fig. 1, the temperature of the exhaust gas discharged from the furnace 1 gradually increases as time passes, and the amount of exhaust gas gradually increases. The amount of heat discharged from the furnace 1 gradually increases. In the figure, T2 indicates the temperature measured by the temperature measuring device T2. However, in this spray control method, until this T2 temperature reaches the upper limit temperature (320°C) which is the heat-resistant temperature of the filter of the baghouse 3,
When the T2 temperature reaches its upper limit temperature without spraying water in the cooling tower 2, each spray nozzle 10a to 10
Water spraying is started at 4 11 /rrtn, which is the minimum spray amount of d. This water spray brings the T2 temperature to the first level.
Descend as shown. Then, when the T2 temperature becomes 250° C. or less, which is the target temperature of automatic control, automatic control by the feedback control is started, and the amount of water sprayed by the flow control valve 20 is adjusted according to the T2 temperature. do. By activating automatic control in this manner, the T2 temperature can be reliably stabilized at the target temperature.

On the other hand, when the amount of exhaust heat discharged from the furnace 1 gradually decreases by stopping the operation of the furnace 1, the measured value of the exhaust gas temperature discharged from the furnace 1 by the temperature measurement T1 is the upper limit temperature 350. Supply valve 1 when the temperature drops below ℃.
3. Close the flow control valve 20 and open the spray nozzles 10a to 1.
Stop all water eruptions caused by 0d. In other words, when the reactor is shut down, the required amount of water is supplied to the nozzle 10 by feedback control based on the T2 temperature until the T1 temperature reaches the upper limit temperature.
Although spraying starts from a to 10d, the spraying is stopped when the T1 temperature falls below the upper limit temperature. Like this T
By controlling the spray stop timing according to one temperature, unnecessary spray can be eliminated and a large amount of moisture can be prevented from flowing into the bag filter, allowing a smooth termination.

Note that FIG. 4 shows the relationship between the opening degree of the flow rate control valve 20 and the amount of water sprayed in the cooling tower 2 for each number of spray nozzles 10a to 10d used.
When the on-off valves 18a to 18d are opened and all spray nozzles 10a to 10d are operated, the spray amount is 4Q.
It shows that adjustment is possible from /lll1n to 40 Q/min, and when only one spray nozzle is operated, adjustment is possible within the range of IQ/win to 10 Q/min. In actual operation, when increasing the amount of spray, move the flow control valve 2 as shown by the solid arrow.
When the opening degree of 0 becomes 15% or more, the number of ' is increased. On the other hand, when reducing the spray amount, the number of spray nozzles is reduced when the opening degree of the flow control valve 20 reaches 100% and the spray amount of each spray nozzle reaches its minimum, as indicated by the broken line arrow.

By doing this, the on-off valves 16a to 16d, the on-off valve 1
The operating frequency of 8a to 18d is reduced, and the spray amount can be smoothly and linearly controlled.

[Effects of the Invention] As described above, the control method according to the present invention provides
Since water is sprayed into the cooling tower after waiting for the temperature of the exhaust gas to reach the upper limit temperature, the minimum amount of spray is applied and water is sprayed into the cooling tower.
There is less risk of getting it wet.

In addition, even when the furnace is shut down, the timing of stopping water spraying is properly controlled, and the exhaust gas can always be discharged through the back filter, which has beneficial effects such as reducing the risk of releasing harmful substances into the atmosphere. effective.

[Brief explanation of drawings]

The drawings show an embodiment of the spray eruption control method for an exhaust gas cooling tower according to the present invention, and FIG. 1 is a temperature history diagram of exhaust gas, FIG. 2 is a system diagram of the entire exhaust gas treatment device, and FIG. 4 is a piping system diagram of the spray nozzles of the cooling tower, and FIG. 4 is a diagram showing the relationship between the opening degree of the flow control valve and the spray amount for each number of spray nozzles opened. 1... Melting furnace, 2... Cooling tower, 3... Bag house,] Oa ~ lod spray nozzle, 15... Water supply pipe,
19 ・Return pipe, 20...Flow rate control valve, ]゛1...
Temperature measuring device, T2...Temperature measuring device.

Claims (2)

[Claims] (1) A cooling tower is provided that cools the exhaust gas by spraying water into the exhaust gas exhaust line of the furnace, and the temperature of the exhaust gas that has passed through the cooling tower is measured to feedback control the amount of water sprayed by the cooling tower. In an exhaust gas cooling tower that automatically controls the temperature of the exhaust gas after passing through the cooling tower to a predetermined target temperature, when the amount of exhaust heat discharged from the furnace gradually increases at the start of operation of the furnace, the amount of heat discharged from the cooling tower is Water spraying is stopped until the exhaust gas temperature reaches a predetermined upper limit temperature.
After reaching the upper limit temperature, spray water at the minimum allowable spray amount,
A spray control method for an exhaust gas cooling tower, characterized in that automatic control by the feedback control is started when the exhaust gas temperature becomes equal to or lower than a predetermined target temperature. (2) A cooling tower is provided to cool the exhaust gas by spraying water into the exhaust gas exhaust line of the furnace, and the temperature of the exhaust gas passing through the cooling tower is measured to feedback control the amount of water sprayed by the cooling tower. In an exhaust gas cooling tower that automatically controls the exhaust gas temperature after passing through the cooling tower to a predetermined target temperature, the exhaust gas discharged from the furnace when the furnace is shut down and the amount of exhaust heat discharged from the furnace gradually decreases. A spray control method for an exhaust gas cooling tower, characterized in that spraying of water is stopped as soon as the temperature falls below a predetermined upper limit temperature.