JP5988396B2 - Exhaust gas cooling method - Google Patents

Description

The present invention relates to a method for cooling high-temperature exhaust gas discharged from a blast furnace or a coke oven. Specifically, the mist is sprayed from one fluid nozzle toward the exhaust gas, and the exhaust gas is cooled by the heat of evaporation of the mist.

  Since exhaust gas from blast furnaces, coke ovens, and various melting furnaces contains a lot of dust, it must be removed before being released into the atmosphere. However, since the temperature of the exhaust gas is a high temperature of 800 ° C. to 1000 ° C., if the exhaust gas is sent to the dust collector as it is, the dust collector will break down. Therefore, at present, a cooling tower is provided at the rear stage of the blast furnace or the like to cool the exhaust gas and send it to the dust collector.

  In a general cooling tower, mist (mist-like cooling liquid) is sprayed from the nozzle toward the exhaust gas, and cooling is performed by the heat of evaporation of the mist. As the nozzle at this time, a large-diameter one-fluid nozzle using a pressure of around 1 MPa or a low-pressure and large-diameter two-fluid nozzle having a spray amount of several tens of L / min or more is used. .

  The one-fluid nozzle sprays mist having a particle size of several hundred μm. However, since the velocity energy of the mist particles sprayed from the nozzle is large, there is a lot of wasted spray water, such as a lot of turbid water that falls without evaporating and accumulates in the sludge reservoir below the cooling tower. Moreover, when speed energy is large, the mixing contact efficiency with exhaust gas will worsen. Therefore, in order to ensure a long contact time, the cooling tower has to be made large (high), and the equipment cost increases. Moreover, since the mist particle size is large and does not evaporate completely, the mist particles are carried to the subsequent dust collector together with the exhaust gas. And the problem of the filter of a dust collector getting wet and clogging generate | occur | produces. In addition, it is difficult to control the exhaust gas temperature because it is difficult to calculate how much of the sprayed mist particles will evaporate and it is difficult to calculate the cooling efficiency.

  On the other hand, the two-fluid nozzle mixes high-pressure or low-pressure air into the coolant to be sprayed (hereinafter, “water” will be described as an example), and uses the energy that expands the air to produce fine mist. Spray. This two-fluid nozzle can have an average particle size of around 60 μm and a maximum particle size as small as around 150 μm, so that it has high cooling efficiency and is suitable for cooling exhaust gas.

  However, the ratio of air and water must always be kept constant, and proportional control for that purpose is very difficult. This is because the opening degree of the valve provided in the air and water piping can generally be adjusted only to about 15% to 100%.

  Moreover, since it will become like a shower when there is much quantity of water with respect to air, it is necessary to keep the flow ratio of the air with respect to water rich, and a lot of air is required. Specifically, when high-pressure air is used, an air amount of about 130 to 150 times that of water is required, and when low-pressure air is used, an air amount of about 300 times that of water is required. Therefore, an extremely large air tank is required and a high-performance air compressor is also required, so that the initial cost is increased. If such a huge air tank is not provided, a large amount of air is required at the time of mist spraying, so the necessary air is taken away at other factories adjacent to it, and the operation of other factories is stopped. End up.

  Furthermore, the amount of electric power for generating compressed air increases and the running cost also increases. Further, since air is ejected from the nozzle, the amount of gas processed by the subsequent dust collector is increased by about 5 to 10% as compared with the case of using a one-fluid nozzle. Moreover, since the velocity energy of each particle | grains of water and air is large, similarly to the case of the one fluid nozzle, there is much waste of the water to spray (a lot of surplus water amount).

  In addition, since the amount of air ejected from the nozzle is large, the velocity energy of water particles increases. Therefore, as in the case of the one-fluid nozzle, a large amount of turbid water is generated, and the efficiency of mixing contact with exhaust gas and water also decreases. And in order to prevent this, if the height of a cooling tower is made high, equipment cost will increase. Moreover, if the velocity energy of water particles is large, the bag filter of the subsequent dust collector will get wet and clogging will occur. At the same time, when a hot gas flows through the wet bag filter, problems such as a clinker appearing on the surface of the filter also occur.

  On the other hand, the temperature and amount of the exhaust gas sent from the blast furnace or the like to the cooling tower, the dust content of the exhaust gas, the acid gas concentration in the exhaust gas, and the like are various. However, in any case, the exhaust gas temperature at the outlet of the cooling tower is generally 200 ° C. or lower. In order to prevent the generation of dioxins, it is necessary to lower the temperature to 170 ° C. or lower.

  At this time, if the temperature of the exhaust gas after cooling is too high, the dust collector may be damaged by the heat of the high-temperature gas. On the other hand, if the temperature of the exhaust gas after cooling is too low, water contained in the exhaust gas adheres to the dust collector or condensation occurs in the dust collector (particularly when the temperature outside the dust collector is high). These waters react with the exhaust gas to become acidic water, which corrodes the dust collector. In addition, the filter of the dust collector may get wet and the filter may become clogged. From the above, control of the temperature of the exhaust gas after cooling is extremely important.

Conventionally, the following patent documents 1-3 exist about a 1 fluid nozzle and a 2 fluid nozzle. In these patent documents, pressurized hot water having a temperature equal to or higher than the boiling point of water is sprayed from a nozzle. The pressure used in the spray this time is about ^{3kgf / cm 2 ~3.5kgf / cm 2} .

JP 2000-274654 A JP 2004-28558 A JP 2001-324128 A

  However, the pressurized hot water is inferior in cooling efficiency of the exhaust gas as compared with the case of spraying cold water. Therefore, there is a problem that a large amount of hot water must be sprayed.

Therefore, the main subject of this invention is providing the exhaust gas cooling method with high cooling efficiency.

  The present invention that has solved the above problems is as follows.

<Invention of Claim 1>
A cooling tower having an exhaust gas inlet at the lower part and an exhaust gas outlet at the upper part for cooling the exhaust gas rising in the cooling tower to 200 ° C. or less ;
A storage tank for storing cooling water used for cooling the exhaust gas;
A pump for sending cooling water of the storage tank to the cooling tower;
Extending from the inner wall of the side surface of the cooling tower toward the center of the cooling tower, and a plurality of pipes provided at different heights of the cooling tower ;
A plurality of one-fluid nozzles disposed in the cooling tower, provided in plural along the longitudinal direction from the proximal end side to the distal end side of the pipe, and spraying a mist of cooling water downward.
Using an exhaust gas cooling device having
An exhaust gas cooling method for performing cooling by spraying cooling water on exhaust gas,
One supply system for supplying cooling water connected to a plurality of pipe groups in the height direction of the cooling tower from one pump is regarded as one unit, and this unit is provided as a plurality of units in the height direction of the cooling tower. And
Each of the nozzles is a one-fluid nozzle having an orifice having a diameter of 1.5 mm or less , and at a pressure of 2 MPa or more, cooling water having a temperature of 10 ° C. to 30 ° C. is atomized as a mist having a Sauter average particle diameter of 60 μm or less. Spraying and cooling the exhaust gas with sprayed cooling water mist ,
Controlling the amount of mist sprayed from the nozzle group by controlling the number of revolutions of the pumps in the unit group based on the temperature difference between the temperature of the exhaust port part and the temperature of the exhaust port part of the exhaust gas. ,
Blowing air from the blower to prevent dust from adhering around the nozzle,
An exhaust gas cooling method comprising:

(Function and effect)
When the Sauter average particle size of the sprayed coolant is 60 μm or less, the range in which the mist-like coolant (hereinafter also referred to as “mist”) diffuses is narrow, and the sprayed mist can be instantly evaporated. . Specifically, the sprayed mist originally has low velocity energy and loses velocity energy immediately. Therefore, it only diffuses within a radius of several hundred mm from the nozzle. And it evaporates instantaneously in the diffusion process. Therefore, generation | occurrence | production of the excess water amount can be suppressed as much as possible. Further, since the mist is instantly evaporated and the exhaust gas is cooled by the latent heat of evaporation, the cooling efficiency with respect to the amount of sprayed mist can be detected quickly.
Moreover, since the temperature of the sprayed cooling liquid is low, the cooling effect is higher than in the case of spraying pressurized hot water from the nozzle as in the conventional example.
A plurality of pipes extending from the inner wall of the side surface of the cooling tower toward the center of the cooling tower are provided. Then, a plurality of nozzles are provided along the longitudinal direction from the proximal end side of the pipe toward the distal end side. With such a configuration, since the spray range of the coolant is widened, uneven cooling is less likely to occur and the cooling effect is enhanced.
Further, the exhaust gas moves in the cooling tower in the height direction from below to above or from above to below. Therefore, by providing a plurality of pipes at different heights of the cooling tower, a long cooling time of the exhaust gas can be ensured, and the cooling efficiency is increased.

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  The spray port of the nozzle is directed below the cooling tower, and sprays mist toward the exhaust gas entering from the air supply port at the bottom of the cooling tower.

When the temperature of the exhaust gas to be supplied or the temperature of the exhaust gas to be discharged is higher than the set value, the amount of the coolant sent to the nozzle is increased, and the temperature of the exhaust gas to be supplied or the temperature of the exhaust gas to be discharged is lower than the set value. The amount of coolant sent to the nozzle can be reduced.

  Preventing situations where the amount of coolant is sprayed unnecessarily, or conversely, the amount of coolant spray is insufficient, by increasing or decreasing the amount of coolant based on the temperature of the exhaust gas to be supplied or the temperature of exhaust gas to be discharged. Can do. Further, since the mist of the present invention instantly evaporates and cools the exhaust gas, the cooling efficiency with respect to the amount of sprayed mist can be detected quickly. Therefore, the cooling accuracy can be improved promptly by immediately reflecting the detection result in the mist spray amount. In the present invention, the spray amount of the coolant may be increased or decreased based on both the temperature of the exhaust gas to be supplied and the temperature of the exhaust gas to be discharged.

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The nozzle further provided with a blower for sending air to the (single fluid) nozzle and stopping spraying of the cooling liquid, or the nozzle having a small amount of spraying of the cooling liquid can eject the air sent from the blower. .

It is possible to prevent dust from adhering and sticking due to the vortex generated around the nozzle ejection hole. It is also possible to prevent the scale from occurring in the nozzle.

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When the spray amount of the cooling liquid is reduced and the Sauter average particle diameter of the coolant to be sprayed is larger than 60 μm only by the liquid pressure of the coolant, switch to the two-fluid system in which the coolant and the compressed air are sprayed simultaneously. The Sauter average particle diameter can be kept at 60 μm or less .

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  According to the present invention, an exhaust gas cooling device and a cooling method with high cooling efficiency can be provided.

It is a simplified diagram for explanation of an exhaust gas cooling device and method concerning the present invention.

  Hereinafter, preferred examples of a ventilation facility and a ventilation method according to the present invention will be described with reference to the drawings. Note that the following description and drawings are merely examples of embodiments of the present invention, and the contents of the present invention should not be construed as being limited to these embodiments.

(Exhaust gas G1)
The exhaust gas G1 discharged from the blast furnace is generally composed mainly of carbon monoxide, nitrogen, and carbon dioxide, and contains dust such as zinc, potassium oxide, sodium oxide, and sulfur. The exhaust gas G1 discharged from the coke oven is generally composed mainly of hydrogen, methane, carbon monoxide, and tar oil, and dust such as benzene, toluene, xylene, nitrogen oxides, dust, sulfur oxides, etc. Contains. In addition, examples of the melting furnace include a cupola, a reflection furnace, a flat furnace, an electric furnace, a Luppo furnace, a rotary furnace, an arc furnace, and a converter. The components of the exhaust gas G1 discharged from the melting furnace differ depending on the metal to be dissolved, but the exhaust gas G1 generally contains various dusts such as zinc, iron, and chlorine. In addition, the temperature of each said waste gas G1 is generally high temperature of 800 to 1000 degreeC.

(Cooling tower 2)
The cooling tower 2 shown in FIG. 1 has a cylindrical shape, and the lower portion of the cooling tower 2 has a conical shape whose diameter gradually decreases downward like a funnel. At the lower end of the cooling tower 2, a sludge storage part 5 for storing sludge is provided. This sludge is formed by the reaction of the exhaust gas G1 and the mist W2. However, in the exhaust gas cooling device 1 of the present invention, the mist W2 evaporates almost completely, so that almost no sludge is generated. The stored sludge is periodically discharged by the vacuum of the sludge collecting device 14. In addition, an air supply port 3 for the high temperature exhaust gas G1 is provided on the lower side surface of the cooling tower 2, and an exhaust port 4 for the cooled gas G2 is provided on the upper top surface of the cooling tower 2. . The shape of the cooling tower 2 may be an arbitrary shape such as a rectangular tube. Further, the air supply port 3 may be provided in the upper part of the cooling tower 2 and the exhaust port 4 may be provided in the lower part.

(Pipe 6)
A plurality of rod-shaped pipes 6 are provided at the upper and middle portions of the cooling tower 2. The number of pipes 6 provided in the cooling tower 2 can be arbitrarily determined. For example, a total of 20 pipes can be provided. The pipe 6 extends in the horizontal direction from the inner wall of the cooling tower 2 toward the center of the cooling tower 2. The cooling towers 2 are arranged radially. In addition, the extension direction and arrangement | positioning location of the said pipe 6 are examples, and can be changed arbitrarily, such as extending below and arrange | positioning only to one side of the cooling tower 2. FIG.

  As an arrangement example of the pipes 6, a plurality of pipes 6 can be provided at the same height of the cooling tower 2. Also, a plurality of pipes 6 at the same height may be used as one set S, and a plurality of sets S may be provided in the height direction. In addition, the pipes 6 may be alternately provided in the height direction or provided in a spiral shape. Further, the pipes 6 may all be arranged at different heights.

  The exhaust gas G1 moves in the cooling tower 2 in the height direction from below to above or from above to below. Therefore, by providing a plurality of pipes 6 in the height direction, it is possible to ensure a long cooling time of the exhaust gas G1, and the cooling efficiency is increased.

(Nozzle 7)
The pipe 6 is provided with a plurality of nozzles 7. The number of the nozzles 7 can be arbitrarily determined. For example, 40 nozzles 7 are attached to each pipe 6, and a total of 20 such pipes 6 are arranged in the cooling tower 2, thereby providing a total of 800 nozzles 7 in the cooling tower 2. Can do. These nozzles 7 are provided at intervals in the longitudinal direction of the pipe 6. The spray port of the nozzle 7 is directed below the cooling tower 2, and sprays mist W <b> 2 toward the exhaust gas G <b> 1 entering from the air supply port 3 below the cooling tower 2.

  A single fluid nozzle 7 is used as the nozzle 7. The one-fluid nozzle 7 sprays the mist W2 at a high pressure. The one-fluid nozzle 7 in FIG. 1 sprays 1.28 L / min of mist W2 using a pressure of 8 MPa. The particle diameter of the mist W2 sprayed from such a one-fluid nozzle 7 is uniform, the average particle diameter is 40 to 60 μm, and the maximum particle diameter is very small as 100 μm or less. Therefore, the sprayed mist W2 can be completely evaporated instantaneously. That is, the sprayed mist W2 originally has low velocity energy, and quickly loses velocity energy. Therefore, the sprayed mist W2 only diffuses within a radius of several hundred mm from the nozzle 7, and instantly evaporates in the process of diffusion. Therefore, generation | occurrence | production of the excess water amount can be suppressed as much as possible. Moreover, since the mist W2 evaporates instantaneously and cools the exhaust gas G1, the cooling effect on the amount of sprayed mist can be detected earlier than before. Then, as will be described later, the effect of cooling can be improved by immediately reflecting the effect on the mist spray amount.

  In addition, the average particle diameter of this invention means what measured the particle | grains which pass an interference fringe with a laser diffraction method, and calculated | required the Sauter Mean Particle Diameter (Sauter Mean Diameter, SMD) from the measurement result. The Sauter average particle diameter is a particle diameter having the same surface area to volume ratio as the total volume of all particles relative to the total surface area of all particles, and can be determined by dividing the total volume by the total surface area.

  As the nozzle 7, for example, one having an orifice diameter of 0.15 mm to 1 mm can be used. Specifically, when the orifice diameter is 1 mm and the fluid pressure is 2.8 MPa, 3.5 MPa, 5 MPa, 6 MPa, 7 MPa, and 8 MPa, the average particle diameter is 52 μm, 50 μm, 45 μm, 44 μm, 43 μm, and 42 μm, respectively. A product (Model KN-100) manufactured by Noyu Co., Ltd. which sprays particles can be used. For the selection of the nozzle 7, it is preferable to employ a nozzle whose average particle size of the coolant is 50 μm or less even when the output of the high-pressure pump 11 is set to a minimum value (for example, 58% of the maximum output).

  Further, when the one-fluid nozzle 7 is employed as in the present invention, air is not used unlike the two-fluid nozzle, so that it is not necessary to generate compressed air, and the power consumption can be greatly reduced. In addition, as will be described later, an air compressor or a blower 13 may be used, but even in that case, the power consumption can be significantly reduced as compared with the case of using a two-fluid nozzle. According to the estimation of the present inventor, the power of 800 kw using the two-fluid nozzle is reduced to 200 kw or less by adopting the exhaust gas cooling device 1 (device equipped with the air compressor and the blower 13). it can. It is clear from this trial calculation that the present invention can greatly reduce the initial cost and the running cost.

  Moreover, since the exhaust gas cooling device 1 is a small amount even when compressed air is used, it is possible to avoid the occurrence of a situation where air from other factories is temporarily taken. In addition, there is an advantage that the load on the subsequent dust collector is small.

  Further, since the particles of the coolant sprayed from the nozzle 7 have small velocity energy, spraying the mist W2 has almost no influence on the airflow of the exhaust gas G1. Since there is no fear of disturbing the airflow of the exhaust gas G1 in this way, the nozzle 7 can be arranged at a free place. In addition, since the nozzles 7 can be freely arranged, restrictions on the shape of the cooling tower 2 are reduced.

(Spray liquid W2)
As described above, it is preferable to use economical water as the coolant W2 sprayed from the nozzle 7. You may add chemical | medical agents, such as chlorine and hydrogen peroxide which suppress the proliferation of Legionella bacteria to this water W2. In addition, chemicals such as a rust inhibitor, a scale inhibitor, and a slime control agent may be added.

  The temperature of the spray liquid W2 is preferably lower. For example, water at about 20 ° C. can be used. Conventionally, the sprayed water is set to 100 ° C. or higher for the purpose of instantly evaporating the water sprayed from the nozzle 7. That is, conventionally, the sprayed water particle size cannot be made 100 μm or less, and spraying low temperature water with a particle size larger than 100 μm will not completely evaporate, and turbid water will be generated, so the temperature of the sprayed water must be raised. Did not get. However, the lower the temperature of the spray liquid W2, the higher the cooling effect of the exhaust gas G1. Therefore, by making the particle size of the spray liquid W2 extremely small as in the present invention, the low-temperature coolant W2 can be instantly evaporated, and generation of excess water can be prevented. Moreover, since the cooling effect of the exhaust gas G1 is enhanced by using the low-temperature coolant W2, the amount of spray of the coolant W2 can be reduced.

(Temperature sensors A and B)
The air inlet 3 of the cooling tower 2 is provided with an air inlet temperature sensor A for detecting the temperature of the exhaust gas G1 from the blast furnace or the like. Further, an exhaust port temperature sensor B for detecting the temperature of the cooled exhaust gas G2 is provided at the exhaust port 4 of the cooling tower 2. And the said temperature sensors A and B transmit measurement data to the cooling control apparatus 8 mentioned later. FIG. 1 shows an example in which the temperature sensor A is provided in the air supply pipe 15 and the temperature sensor B is provided in the exhaust pipe 16.

(Cooling control device 8)
The cooling control device 8 is connected to the temperature sensors A and B and the inverter 9. Then, based on the temperature of the exhaust gas G1 at the air supply port 3 detected by the temperature sensor A and the temperature of the exhaust gas G2 at the exhaust port 4 detected by the temperature sensor B, a difference between the two temperatures is obtained and the amount of spray of the mist W2 is determined. The cooling efficiency, the amount of mist W2 sprayed in the future, and the like are determined. In FIG. 1, a programmable logic controller (PLC) is used as the cooling control device 8.

(High pressure pump 11)
The cooling control device 8 is connected to the inverter 9 and transmits an instruction signal to the inverter 9 so as to spray the spray amount of mist W2 calculated by the cooling control device 8. The inverter 9 that has received the signal changes the output of the pump 11 by changing the rotational speed of the motor 10. The output of the pump 11 can be arbitrarily changed within a range of 100% to 58% of the maximum output, for example. In FIG. 1, five high-pressure pumps 11 having an output of 190 L / min are provided. And in the situation where it is not necessary to spray a large amount of mist, the spray amount of the entire apparatus 1 is adjusted by reducing the number of operating pumps 11.

  The pump 11 sends water W1 stored in a water storage tank (not shown) to each nozzle 7. By changing the output of the pump 11, the amount of mist spray from the nozzle 7 changes. Note that a filter 12 is provided between the water storage tank and the pump 11, and the water stored in the water storage tank is purified by the filter 12 and then sent to the pump 11.

(Unit U)
A plurality of pipes 6, nozzles 7, pumps 11, motors 10, and inverters 9 in FIG. 1 are provided. At this time, one pump 11, one motor 10, one inverter 9, five pipes 6, and a total of 160 nozzles 7 attached to the five pipes 6 constitute one unit U. In FIG. 1, five units U are provided. In addition, one spare unit U including only one inverter 9, one motor 10, and one pump 11 is provided in case the inverter 9, the motor 10, and the pump 11 fail. In addition, you may change the number of the pipe 6, the nozzle 7, the pump 11, the motor 10, and the inverter 9 which comprise one unit to arbitrary numbers. Further, the number of units U can be arbitrarily changed.

  It is easy to control the spray amount from the nozzle 7 for each unit U. That is, when increasing or decreasing the spray amount of the coolant W2, the spray amount of all the units U may be increased or decreased uniformly, but only the spray amount of a specific unit U may be changed. For example, when the temperature of the exhaust gas G1 supplied to the cooling tower 2 is higher than expected, the unit U having the nozzles 7 disposed at the lower part of the cooling tower 2 is controlled to cool the exhaust gas G1 faster than expected. It is preferable to increase the amount of the coolant W2 sprayed from the nozzle 7 arranged in the nozzle.

(air compressor)
Since the nozzle 7 cannot change the size (orifice diameter) of the spray hole, if the transport amount of the cooling liquid W1 from the pump 11 to the nozzle 7 is reduced, the particle diameter of the mist W2 becomes large. Therefore, an air compressor may be provided to send the compressed air G3 to the flow path between the pump 11 and the nozzle 7. That is, when the transport amount of the cooling liquid W1 from the pump 11 to the nozzle 7 becomes equal to or less than a predetermined value, the air compressor is started and the compressed air G3 is mixed into the transport liquid. Thus, by using the compressed air G3, the spray speed of the mist W2 sprayed from the nozzle 7 can be maintained, and the particle diameter (average particle diameter of 60 μm or less) of the mist W2 can be maintained. As an example of the predetermined value that triggers the start of the air compressor, the actual transport amount is 60% or less with respect to the maximum amount of the coolant W1 that can be transported by the pump 11, and the average particle size is The case where it exceeds 60 micrometers can be mentioned.

(Protection of nozzle 7)
A vortex may be generated around the spray hole of the nozzle 7, which may cause dust to adhere to and adhere to the nozzle. Further, there is a possibility that scale is generated in the nozzle 7. Those dusts and scales gradually block the spray holes and make it difficult to spray the mist W2. In particular, the nozzle 7 of the present invention is easily blocked because the orifice is very small.

  In order to solve this problem, a nanoscale filter 12 may be used as the filter 12 for purifying the spray liquid. For example, a fouling index value (FI value) may be set to 3 or less using a 0.1 μm filter 12. Thereby, generation | occurrence | production of a scale in the nozzle 7 can be suppressed.

Next, protection of the nozzle 7 while the high-temperature exhaust gas G1 is being cooled will be described. The exhaust gas cooling device 1 of the present invention has a large number of nozzles 7 because the amount of mist W2 sprayed from one nozzle 7 is small. When the flow rate of the exhaust gas G1 supplied to the cooling tower 2 is small or when the temperature of the exhaust gas G1 is low, the entire mist amount is controlled by not spraying the mist W2 from some of the nozzles 7. . However, the nozzle 7 that does not spray the mist W2 is deteriorated or damaged by being exposed to the heat of the exhaust gas G1. Therefore, in the present invention, water is passed through the nozzle 7 that has not been sprayed with the mist W2 to spray a small amount of mist W2, thereby cooling the nozzle 7 and protecting the nozzle 7 from the exhaust gas G1. In order to spray a small amount of mist W2, it is necessary to flow 1 m ³ / min of air at a pressure of 0.5 MPa, for example, and thereby, for example, 80 L / min of mist W2 can be sprayed. In order to flow this air, it is preferable to provide a blower 13 (blower 13), send the air G4 from the blower 13 to the nozzle 7, and eject the air G4 from the nozzle 7. Further, as will be described later, the blower 13 can be used while the cooling of the exhaust gas G1 is stopped.

  When the cooling of the exhaust gas G1 is finished, the supply amount of the exhaust gas G1 from the air supply port 3 is gradually reduced, and the spray amount of the mist W2 is also gradually reduced accordingly. In this process, since the amount of exhaust gas G1 to be cooled is small and the amount of sprayed mist W2 is also small, it is preferable to switch to the two-fluid system. And if the temperature in the cooling tower 2 falls to a temperature at which the metal of the nozzle 7 does not corrode, the operation of the high-pressure pump 11 is stopped and the spraying of the coolant W2 is stopped. Thereafter, clean air G4 may be ejected from the nozzle 7 at a high pressure to remove water droplets remaining on the nozzle 7 to prevent scale deposition and adhesion during drying.

  Next, protection of the nozzle 7 while the exhaust gas G1 is not cooled will be described. Specifically, the air G4 may be sent from the blower 13 into the nozzle 7 and the air G4 may be ejected from the nozzle 7. By blowing out the air G4, dust can be prevented from adhering around the nozzle 7. In addition, since the clean air G4 ejected from the nozzle 7 is preferable, a high-precision filter (not shown) may be provided between the blower 13 and the nozzle 7.

(Cooling method)
The exhaust gas cooling method according to the present invention will be described. First, high-temperature (for example, 1000 ° C.) exhaust gas G1 discharged from a blast furnace or the like is sent from the air supply port 3 into the cooling tower 2. The supplied exhaust gas G1 ascends in the cooling tower 2 and is exhausted from the exhaust port 4 provided in the upper part of the cooling tower 2 and then sent to the subsequent dust collector. In the cooling tower 2, the mist W2 is sprayed downward from the nozzle 7. The particle diameter of the mist W2 to be sprayed is, for example, an average particle diameter of about 50 μm, and since it is homogeneous, it evaporates instantaneously. The exhaust gas G1 is cooled by this latent heat of vaporization to become cooled exhaust gas G2, and when exhausted from the exhaust port 4, it is cooled to 200 ° C. or lower. In addition, in order to prevent the production | generation of a dioxin, it is preferable to cool to 170 degrees C or less.

  Since the nozzle 7 of the present invention is a one-fluid nozzle, a large amount of air is not required unlike a large-diameter two-fluid nozzle. Therefore, it is not necessary to install an air generation device, the initial cost of the entire exhaust gas cooling device can be greatly reduced, and the running cost required for the maintenance of the air generation device is not generated. Moreover, the installation place of an air generation apparatus becomes unnecessary. Furthermore, since compressed air is not sprayed from the nozzle 7, the gas amount in the cooling tower 2 does not increase. Therefore, the processing capacity of the subsequent dust collector is not increased. Although the air compressor and the blower 13 may be provided, even in this case, the amount of air required by the exhaust gas cooling device 1 as a whole is much smaller than before, and each of the effects described above is sufficient. Demonstrated.

  Further, since the mist W2 sprayed from the nozzle 7 evaporates instantaneously, even if the mist W2 is sprayed on the exhaust gas G1, the humidity of the exhaust gas G1 hardly changes and becomes extremely low. Therefore, it is possible to prevent the filter of a dust collector (not shown) in the subsequent stage from getting wet and causing clogging, or the water and the exhaust gas G1 adhering to the filter from reacting to corrode the dust collector.

  Further, since the mist W2 of the present invention evaporates instantaneously, it is not necessary to ensure a long time until the mist particles fall and evaporate as in the prior art. Therefore, the cooling tower 2 can be made more compact than before (the height of the cooling tower 2 can be reduced), and the initial cost can be reduced.

  Further, the sprayed mist W2 does not drip and no waste occurs. For this reason, part of the sprayed mist does not evaporate and does not collect as turbid water in the sludge storage part. Therefore, there is little work amount which processes the sludge of the sludge storage part 5. FIG.

  The exhaust gas cooling device 1 of the present invention measures the temperature of the exhaust gas G1 at the air supply port 3 and the temperature of the exhaust gas G2 at the exhaust port 4, and controls to increase the spray amount of the mist W2 when the exhaust gas G1 is insufficiently cooled. Do. Conversely, when the exhaust gas G1 is excessively cooled, control is performed to reduce the spray amount of the mist W2. The sprayed mist W2 instantly evaporates and is less wasteful, so the control accuracy for cooling the exhaust gas G1 to the set temperature is high. Moreover, since the sprayed mist W2 is easy to evaporate and the effect of cooling the exhaust gas G1 is high, the temperature of the exhaust gas G1 can be immediately reduced even immediately after the exhaust gas cooling device 1 is started.

  The nozzle 7 used in the exhaust gas cooling device 1 of the present invention is a one-fluid nozzle, and the cooling temperature of the exhaust gas G1 is adjusted only by adjusting the spray amount (water amount) of the mist W2. This eliminates the need for a valve or the like that adjusts the air flow rate, unlike the two-fluid nozzle, so that the valve stand can be made compact.

DESCRIPTION OF SYMBOLS 1 Exhaust gas cooling device 2 Cooling tower 3 Air supply port 4 Exhaust port 5 Sludge storage part 6 Pipe 7 Nozzle 8 Cooling control device 9 Inverter 10 Motor 11 Pump 12 Filter 13 Blower (blower)
14 Sludge recovery device 15 Air supply pipe 16 Exhaust pipe A Inlet thermometer B Outlet thermometer G1 Inlet gas G2 Exhaust gas G3 Compressor air G4 Nozzle protection air S Set U Unit W1 Coolant W2 Mist (coolant)

Claims (2)

A cooling tower having an exhaust gas inlet at the lower part and an exhaust gas outlet at the upper part for cooling the exhaust gas rising in the cooling tower to 200 ° C. or less ;
A storage tank for storing cooling water used for cooling the exhaust gas;
A pump for sending cooling water of the storage tank to the cooling tower;
Extending from the inner wall of the side surface of the cooling tower toward the center of the cooling tower, and a plurality of pipes provided at different heights of the cooling tower ;
A plurality of one-fluid nozzles disposed in the cooling tower, provided in plural along the longitudinal direction from the proximal end side to the distal end side of the pipe, and spraying mist of cooling water;
Using an exhaust gas cooling device having
An exhaust gas cooling method for performing cooling by spraying cooling water on exhaust gas,
One supply system for supplying cooling water connected to a plurality of pipe groups in the height direction of the cooling tower from one pump is regarded as one unit, and this unit is provided as a plurality of units in the height direction of the cooling tower. And
Each of the nozzles is a one-fluid nozzle having an orifice having a diameter of 1.5 mm or less , and at a pressure of 2 MPa or more, cooling water having a temperature of 10 ° C. to 30 ° C. is atomized as a mist having a Sauter average particle diameter of 60 μm or less. Spraying and cooling the exhaust gas with sprayed cooling water mist ,
Controlling the amount of mist sprayed from the nozzle group by controlling the number of revolutions of the pumps in the unit group based on the temperature difference between the temperature of the exhaust port part and the temperature of the exhaust port part of the exhaust gas. ,
Blowing air from the blower to prevent dust from adhering around the nozzle,
An exhaust gas cooling method comprising: The spraying amount of cooling water is reduced by only the hydraulic pressure of the cooling water when the Sauter mean particle diameter of the cooling water to be sprayed is greater than 60 [mu] m,
2. The exhaust gas cooling method according to claim 1 , wherein the Sauter average particle diameter is maintained at 60 μm or less by switching to a two-fluid system in which the cooling water and compressed air are sprayed simultaneously.

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