JP2003021471A - Operating method of exhaust gas sensible heat recovery equipment having heating furnace recuperator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the operating method of exhaust gas sensible heat recovery equipment having a heating furnace recuperator capable of efficiently cooling the recuperator inlet side exhaust gas down to below the heat-resisting temperature of the recuperator, without increasing the flow rate of exhaust gas excessively. SOLUTION: In the operating method of the exhaust gas sensible heat recovery equipment having the heating furnace recuperator 13 provided in the exhaust gas flue 12 on the outlet side of the heating furnace 11, water is blown into an exhaust gas flue 12 between the heating furnace and the heating furnace recuperator from a sprinkler 21, so as to cool down exhaust gas.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for operating an exhaust gas sensible heat recovery facility having a heating furnace recuperator (preheater) attached to an industrial furnace such as a steel material heating furnace, a continuous annealing furnace, and a heat treatment furnace. Is.

[0002]

2. Description of the Related Art Exhaust gas recuperators attached to industrial furnaces such as steel heating furnaces, continuous annealing furnaces and heat treatment furnaces recover exhaust heat from the high temperature exhaust gas discharged from the furnaces and preheat air with the heat. Although it is a heat exchanger for use as combustion air, in order to make the temperature of the introduced exhaust gas below the heat-resistant temperature of the recuperator, conventionally, dilution air was added to the high temperature exhaust gas at the exhaust gas inlet of the recuperator. It is thrown in to cool the exhaust gas.

FIG. 7 is a layout view of a conventional recuperator for introducing such dilution air. A recuperator 13 for recovering exhaust heat is installed in a flue 12 of exhaust gas discharged from the heating furnace 11, and an exhaust blower 14 and a chimney 15 for sucking the exhaust gas are arranged in the subsequent stage. On the inlet side of the recuperator, dilution air is introduced into the exhaust gas to cool the high temperature exhaust gas to a temperature lower than the heat resistant temperature (melting temperature) of the recuperator. Is equipped with a dilution air blower). When the exhaust gas temperature detected by the exhaust gas thermometer 17 on the recuperator inlet side is equal to or higher than the heat resistant temperature of the recuperator 13, or the preheated air installed on the recuperator outlet side of the preheated air piping system 16. When the preheated air temperature detected by the thermometer 18 becomes equal to or higher than the heat resistant temperature of the recuperator 13, the dilution air blower 20 is activated, and air is introduced into the flue through the dilution air introducing portion 19 to collect the Cool the exhaust gas on the inlet side to the temperature below the heat-resistant temperature of the recuperator.

Further, in Japanese Patent Application Laid-Open No. 8-199231, in a heating furnace composed of a pretropical zone, a heating zone and a soaking zone, a plurality of regenerative burners are alternately and alternately heated to heat in the pretropical zone, Method of operating a heating furnace in which low temperature flue gas is introduced into high temperature flue gas on the inlet side of the air preheater (air recuperator) to cool the flue gas to a temperature below the melting temperature of the air preheater It is shown.

[0005]

However, the above-mentioned conventional technique has the following problems. The diluted air blower and exhaust blower of the exhaust gas system are designed according to the furnace specifications of the heating furnace, but if the blower capacity is insufficient, the equipment capacity may be insufficient. This is because when there is a need to increase the throughput of the heating furnace, the amount of exhaust gas and the temperature of the exhaust gas increase due to the increase in the combustion amount of the heating furnace.
In that case, in the conventional dilution air system, the blower needs to be renewed or added, and the equipment cost becomes high. In addition, even when a new heating furnace is installed, the dilution air blower
A large-capacity exhaust blower must be installed, and the equipment cost will be high. In addition, there is a problem in running cost that power consumption of the dilution air blower and the exhaust blower increases.

Further, in the method of Japanese Patent Laid-Open No. 8-199231, instead of the dilution air of about 30 ° C., the combustion exhaust gas of about 200 ° C. which has passed through the heat storage from the heat storage combustion device is introduced into the inlet side of the air preheater. In order to lower the high temperature combustion exhaust gas temperature on the inlet side of the air preheater to below the melting temperature of the air preheater, a larger amount of the exhaust gas for dilution is introduced than when diluting air is used. There is a need. For this reason, the pressure loss increases due to the increase in the exhaust gas flow rate on the inlet side of the air preheater, and as a result, there is a risk of impairing the operation when the combustion load of the heating furnace is large.

Therefore, the object of the present invention is to solve the above-mentioned problems of the prior art and to efficiently cool the exhaust gas temperature on the recuperator inlet side to a temperature lower than the heat resistant temperature of the recuperator without excessively increasing the exhaust gas flow rate. An object of the present invention is to provide a method of operating an exhaust gas sensible heat recovery facility having a heating furnace recuperator capable of operating.

[0008]

Means for Solving the Problems The inventors of the present invention have studied the method of cooling exhaust gas on the inlet side of the recuperator, injecting water into the flue and utilizing the latent heat of vaporization of water to cool the exhaust gas. By doing so, it becomes possible to efficiently cool the exhaust gas without increasing the volume of the exhaust gas after cooling, and by using a mist sprinkler as the sprinkler that performs this water injection, the exhaust gas can be more efficiently It was found that it can be cooled effectively.

The present invention has been made on the basis of such findings and has the following features.

(1) In an operating method of an exhaust gas sensible heat recovery facility having a heating furnace recuperator provided in the middle of an exhaust gas flue on the outlet side of the heating furnace, the exhaust gas between the heating furnace and the heating furnace recuperator. A method for operating an exhaust gas sensible heat recovery facility having a heating furnace recuperator, characterized in that water is blown into a flue from a water sprinkler to cool the exhaust gas.

(2) The method for operating an exhaust gas sensible heat recovery facility having a heating furnace recuperator according to (1) above, wherein the water sprinkler is a mixed two-fluid mist water sprinkler.

(3) The distance between the water injection position of the sprinkler and the recuperator is set to a distance such that substantially all the sprinkled water evaporates before reaching the recuperator. An operating method of an exhaust gas sensible heat recovery facility having the heating furnace recuperator according to (1) or (2).

[0013]

1 to 3 show one embodiment of a method for operating an exhaust gas sensible heat recovery facility having a heating furnace recuperator according to the present invention, and FIG. 1 has a heating furnace recuperator. FIG. 2 is an overall explanatory view of the exhaust gas sensible heat equipment, FIG. 2 is a cross-sectional view of a flue portion in which a sprinkler is installed, and FIG. 3 is a cross-sectional view of a sprinkler nozzle of the sprinkler.

1 to 3, reference numeral 12 is a flue for discharging exhaust gas from the heating furnace 11, and a recuperator 13 for recovering exhaust heat of exhaust gas is installed in the flue 12 in the middle thereof. Exhaust blower 14 that sucks exhaust gas in the subsequent stage
And the chimney 15 is arranged.

The recuperator 13 is a heating furnace 11.
It is a heat exchanger for recovering exhaust heat from the high temperature exhaust gas discharged from the exhaust gas, and preheating the air with that heat to use as combustion air. The exhaust gas temperature is detected by the exhaust gas thermometer 17 on the inlet side of the recuperator. It A preheated air piping system 16 passes through the recuperator 13 to preheat the air,
A preheated air thermometer 18 for detecting the preheated air temperature is installed on the exit side of the recuperator of the preheated air piping system 16.

In the flue between the heating furnace 11 and the recuperator 13, water is blown into the exhaust gas to cool the high-temperature exhaust gas to a temperature lower than the heat resistant temperature (melting temperature) of the recuperator. A sprinkler device 21 is provided for this purpose.

The sprinkler device 21 has a pair of sprinkler nozzles 22 provided so as to face each other on both sides of the flue 12. Water and air are supplied to the water spray nozzles 22 from a water supply pipe 23 and an air supply pipe 24, respectively.
Water is blown into the flue in a mist state. Although the embodiment of FIG. 2 uses a pair of nozzles,
Any number of nozzles may be arranged according to the required amount of water to be blown. At this time, it is desirable to make the mixing of the exhaust gas and the mist inside the flue uniform in order to shorten the evaporation time and to prevent the inner surface of the flue from being wet with water.
For example, in the case of a circular flue, it is desirable that the nozzles are arranged so as to face each other around the axis.

FIG. 3 shows an example of the structure of the water spray nozzle 22. The water spray nozzle 22 comprises a main body 26 having a double pipe structure and a nozzle tip 25 attached to the tip thereof.
The main body 26 of the double pipe structure has an air flow passage a between the outer pipe and the inner pipe and a water flow passage b inside the inner pipe, and the air flow passage a and the water flow passage b are provided with the air. An air supply port 28 and a water supply port 27 for supplying air and water through the supply pipe 24 and the water supply pipe 23 are provided, respectively.

Further, the nozzle tip 25 mixes air flowing in from the air flow path a and water flowing in from the water flow path b to form a mist.

Further, in order to control the amount of water blown by the water sprinkling device 21, the water supply pipe 23 of each water spray nozzle 22 has an individual shutoff valve and a flow rate adjusting valve attached to the base of the water supply pipe 23. Similarly, in order to control the amount of air blown by the water sprinkler 21, the air supply pipe 24 of each water spray nozzle 22 has an individual shutoff valve and a flow rate adjustment valve attached to the base of the air supply pipe 24.

In the exhaust gas sensible heat recovery equipment having the heating furnace recuperator as described above, water is blown into the flue 12 from the water sprinkler 21. Regarding the control of water injection, when the exhaust gas temperature detected by the exhaust gas thermometer 17 on the inlet side of the recuperator becomes equal to or higher than the heat resistant temperature of the recuperator 13, or the preheated air piping system 16
Preheated air thermometer 1 installed on the outlet side of the recuperator
The preheated air temperature detected by 8 is the recuperator 1
When the temperature exceeds the heat resistant temperature of 3, the water sprinkler 21 is operated, and the amount of water required for the exhaust gas temperature on the inlet side of the recuperator to be lower than the heat resistant temperature of the recuperator is added to cool.

Next, a method of controlling the amount of water injected will be described. As the temperature and amount of the exhaust gas change depending on the combustion amount of the heating furnace, the required amount of water injection to cool the high temperature exhaust gas on the inlet side of the recuperator to less than the heat-resistant temperature of the recuperator also changes. It is necessary to control the amount to be variable. There are two possible control methods. One is for multiple nozzles, and the water supply pipe 23 for each nozzle is
An individual shutoff valve is provided for each nozzle, and the amount of water blown into each nozzle is kept constant, and the number of operating nozzles is changed by ON / OFF to control the amount of water blown in steps. The other is to adjust the flow rate of air blown by a flow rate adjusting valve at the base of the water supply pipe, and in this case, the amount of water blown into each nozzle changes uniformly. FIG. 2 illustrates only one pair of watering nozzles 22 of the plurality of pairs of nozzles. The amount of blown air is also controlled in the same manner as the amount of blown water.

Generally, the limit value of the exhaust gas temperature on the inlet side of the recuperator, which is determined by the heat resistant temperature of the heating furnace recuperator, is 800 to 850 ° C., and when the exhaust gas temperature is higher than this, cooling is performed by blowing water. If the high-temperature state of 800 to 850 ° C. before the water injection and the amount of water injection after the water injection are controlled by turning the nozzles ON / OFF, the nozzles that do not perform the water injection are exposed to the high-temperature exhaust gas. . At this time, if the injection of water is stopped at the same time as the injection of air is stopped, the nozzle tip will be burned, leading to a problem. Therefore, the injection of air is always performed regardless of whether the water injection is ON or OFF to protect the nozzle tip. It is preferable to carry out.

From the water injection position of the sprinkler to the recuperator, almost all the sprinkled water evaporates before reaching the recuperator, depending on the sprinkling amount and the particle size of the sprinkled water particles. It is preferable to set such a distance.

As an example, when the particle size of the mist ejected from the two-fluid nozzle is 300 μm, the evaporation time is 0.4 seconds, and wetting should not occur with water from the water injection position before the recuperator. Therefore, it is necessary to secure the distance to the exhaust gas thermometer in the exhaust gas moving time of 0.4 seconds or more.

FIGS. 4 and 5 show another embodiment of the method for operating an exhaust gas sensible heat recovery facility having a heating furnace recuperator according to the present invention. The arrangement of the water spray nozzle is different from that shown in FIGS. It is what

Regarding the nozzle arrangement inside the flue, the mist is sprayed toward the outlet side of the flue in order to evenly mix the exhaust gas and the mist and to prevent the inner wall of the flue from getting wet with water. Is preferred. Therefore, in the embodiment of FIG. 4, the pair of water spray nozzles 22 are installed obliquely toward the downstream side of the flue 12, and in the embodiment of FIG. Is bent toward the downstream side of.

[0028]

EXAMPLES A comparison of the amount of exhaust gas after cooling between the method for cooling a recuperator by blowing water according to the method of the present invention and the method for cooling a recuperator using a conventional dilution air system is shown in FIG. The equipment shown in FIG. 7 was used, and the equipment shown in FIG. 7 was used for the conventional method under the following conditions. The water-blowing nozzle used in the method of the present invention was of the opposed type as shown in FIG.

The heating furnace outlet side exhaust gas temperature is 1050 ° C. and the recuperator inlet side exhaust gas temperature is 850 ° C., and the heating furnace outlet side exhaust gas amount (exhaust gas amount before cooling) is changed from 30,000 Nm ³ / H to 50000 Nm ³ / H. The amounts of exhaust gas after cooling were compared. The results are shown in FIG. 6 together with the dilution air flow rate during cooling of the conventional dilution air type recuperator. As is apparent from FIG. 6, in the case of the water blowing method of the present invention, the amount of exhaust gas after cooling can be reduced as compared with the case of the conventional dilution air method. Exhaust gas amount on outlet side of heating furnace is from 30,000 Nm ³ / H to 5
In any case of changing to 0000 Nm ³ / H, it is possible to reduce the amount of exhaust gas after cooling by about 15% in the case of the water blowing method as compared with the case of the conventional dilution air method.

[0030]

According to the present invention described above, the exhaust gas temperature on the inlet side of the recuperator can be efficiently lowered to below the heat resistant temperature of the recuperator without excessively increasing the exhaust gas volume. Therefore, a dilution air blower is not required, and the recuperator can be cooled with inexpensive equipment. Further, since the latent heat of vaporization of water can be utilized by the water injection, the increase in the exhaust gas flow rate after cooling is small as compared with the case where the dilution air is input, and the power consumption of the exhaust blower downstream of the recuperator is achieved.

[Brief description of drawings]

FIG. 1 is an overall explanatory view of an exhaust gas sensible heat recovery facility having a heating furnace recuperator showing an embodiment of a method of operating an exhaust gas sensible heat recovery facility having a heating furnace recuperator of the present invention.

FIG. 2 is a cross-sectional view of a flue section in which a sprinkler is installed, showing an embodiment of an operating method of an exhaust gas sensible heat recovery facility having a heating furnace recuperator of the present invention.

FIG. 3 is a cross-sectional view of a water injection nozzle of a water sprinkler showing an embodiment of an operating method of an exhaust gas sensible heat recovery facility having a heating furnace recuperator of the present invention.

FIG. 4 is a sprinkling nozzle arrangement view showing another embodiment of the operating method of the exhaust gas sensible heat recovery equipment having the heating furnace recuperator of the present invention.

FIG. 5 is a sprinkling nozzle arrangement view showing another embodiment of the operating method of the exhaust gas sensible heat recovery equipment having the heating furnace recuperator of the present invention.

FIG. 6 is a graph comparing the amounts of exhaust gas after cooling according to the method of the present invention and the conventional method.

Fig. 7 Layout of recuperator with conventional dilution air input

[Explanation of symbols]

11 heating furnace 12 flue 13 Recuperator 14 Exhaust blower 15 chimney 16 Preheated air piping system 17 Recuperator inlet exhaust gas thermometer 18 Preheated air thermometer 19 Dilution air inlet 20 diluted air blower 21 Sprinkler 22 Watering nozzle 23 Water supply piping 24 Air supply piping 25 nozzle tip 26 Double tube structure body 27 Water supply port 28 Air supply port

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kenji Madate             1-2-1, Marunouchi, Chiyoda-ku, Tokyo             Main Steel Pipe Co., Ltd. (72) Inventor Noriaki Sueto             1-2-1, Marunouchi, Chiyoda-ku, Tokyo             Main Steel Pipe Co., Ltd. (72) Inventor Akihiro Nagahiro             1-2-1, Marunouchi, Chiyoda-ku, Tokyo             Main Steel Pipe Co., Ltd. F-term (reference) 3K023 QA03 QB00 QC08                 3K070 DA37 DA50 DA58                 4K056 AA08 AA09 CA02 DA02 DA22                       DA32 FA06

Claims (3)

[Claims] 1. A method for operating an exhaust gas sensible heat recovery facility having a heating furnace recuperator provided in the middle of an exhaust gas flue on the heating furnace exit side, wherein exhaust gas smoke between the heating furnace and the heating furnace recuperator. Blow water from the sprinkler into the road,
A method for operating an exhaust gas sensible heat recovery facility having a heating furnace recuperator, characterized by cooling exhaust gas. 2. The method for operating an exhaust gas sensible heat recovery facility having a heating furnace recuperator according to claim 1, wherein the water sprinkler is a mixed-fluid mist water sprinkler of air and water. 3. A distance between the water injection position of the sprinkler and the recuperator is set to a distance such that substantially the entire amount of sprinkled water evaporates before reaching the recuperator. An operating method of an exhaust gas sensible heat recovery facility having the heating furnace recuperator according to 1 or 2.