阅读说明：本技术 废热回收锅炉及废热回收锅炉的传热管的温度的控制方法 (Waste heat recovery boiler and method for controlling temperature of heat transfer pipe of waste heat recovery boiler ) 是由 三轮佳祐 野口学 石川荣司 松冈庆 长洋光 于 2020-02-17 设计创作，主要内容包括：提供能够抑制传热管的腐蚀的废热回收锅炉。本发明的废热回收锅炉(100)具备：管道(120)；传热管(320),其具有水入口(322)和水出口(324)且配置于管道(120)内部；水供给配管(400),其与水入口(322)连接,具有第1配管(420)和与第1配管(420)分支后再次与第1配管(420)合流的第2配管(440)；储存容器(160),其与水出口(324)流体连通且第2配管(440)的至少一部分配置在其内部；水量调节阀(500),其调节流经第1配管(420)的水的流量与流经第2配管(440)的水的流量的比率；计测装置(600),其计测管道(120)内部的腐蚀速度；和控制装置(800),其根据计测结果调节水量调节阀(500)。(Provided is an exhaust heat recovery boiler wherein corrosion of a heat transfer pipe can be suppressed. An exhaust heat recovery boiler (100) is provided with: a conduit (120); a heat transfer pipe (320) which has a water inlet (322) and a water outlet (324) and is disposed inside the duct (120); a water supply pipe (400) connected to the water inlet (322) and having a 1 st pipe (420) and a 2 nd pipe (440) branching off from the 1 st pipe (420) and then merging again with the 1 st pipe (420); a storage container (160) which is in fluid communication with the water outlet (324) and in which at least a part of the 2 nd pipe (440) is disposed; a water amount adjusting valve (500) that adjusts the ratio of the flow rate of water flowing through the 1 st pipe (420) to the flow rate of water flowing through the 2 nd pipe (440); a measuring device (600) for measuring the corrosion rate inside the pipe (120); and a control device (800) for adjusting the water quantity adjusting valve (500) according to the measurement result.)

1. An exhaust heat recovery boiler is provided with:

a duct having a flow path through which exhaust gas flows;

a heat transfer pipe having a water inlet and a water outlet and disposed inside the pipe;

a water supply pipe connected to the water inlet of the heat transfer pipe, the water supply pipe including a branching portion, a merging portion located downstream of the branching portion, a 1 st pipe forming a portion between the branching portion and the merging portion, and a 2 nd pipe branching off from the 1 st pipe at the branching portion and merging again with the 1 st pipe at the merging portion, the water supply pipe supplying water having passed through the merging portion to the water inlet of the heat transfer pipe;

a storage container that is in fluid communication with the water outlet of the heat transfer pipe, and in which at least a part of the 2 nd pipe is disposed inside the storage container;

a water amount adjusting valve that adjusts a ratio of a flow rate of water flowing through the 1 st pipe to a flow rate of water flowing through the 2 nd pipe;

a measuring device for measuring at least one of a corrosion rate, a temperature, and an exhaust gas component inside the pipe;

and a control device for controlling the water amount regulating valve according to the measurement result of the measuring device.

2. The waste heat recovery boiler of claim 1,

the storage container is a drum that separates water and water vapor.

3. The waste heat recovery boiler of claim 1 or 2,

at least a part of the 2 nd pipe is disposed in a part of the storage container where the water is stored.

4. The waste heat recovery boiler of any one of claims 1 to 3,

further comprises a water temperature meter for measuring a water temperature between the merging portion of the water supply pipe and the water inlet of the heat transfer pipe,

the control device adjusts and controls the water quantity adjusting valve according to the measurement result of the water temperature meter.

5. The waste heat recovery boiler of any one of claims 1 to 4,

the measuring device comprises a corrosion monitoring probe comprising a 1 st corrosion sensor and a probe temperature adjusting mechanism, wherein the 1 st corrosion sensor comprises an electrode member exposing an electrode surface to the inside of the pipe, the probe temperature adjusting mechanism adjusts the temperature of the electrode member,

the controller controls the probe temperature adjusting means of the corrosion monitoring probe to measure the corrosion rates at a plurality of different temperatures by the corrosion monitoring probe, determines the temperature of the water supplied to the heat transfer pipe at which the corrosion rate is lower than an allowable value based on the measurement results of the corrosion rates at the plurality of different temperatures, and adjusts and controls the temperature of the water supplied to the heat transfer pipe to the determined temperature.

6. The waste heat recovery boiler of any one of claims 1 to 5,

the measuring device comprises a 2 nd corrosion sensor, the 2 nd corrosion sensor comprises an electrode component exposed in the pipeline, and can measure the corrosion speed,

the control device performs control to increase a ratio of a flow rate of water flowing through the 2 nd pipe to a flow rate of water flowing through the 1 st pipe when the corrosion rate measured by the 2 nd corrosion sensor exceeds an allowable value.

7. The waste heat recovery boiler of any one of claims 1 to 6,

the measuring device has a thermometer for measuring the temperature near the heat transfer tube,

the control device performs control to increase a ratio of a flow rate of the water flowing through the 2 nd pipe to a flow rate of the water flowing through the 1 st pipe when the temperature in the vicinity of the heat transfer pipe measured by the thermometer is lower than a predetermined reference temperature.

8. The waste heat recovery boiler of any one of claims 1 to 7,

the measuring device includes SO for measuring the concentration of sulfur oxides as exhaust gas components in the duct_xAt least one of an analyzer, an HCl analyzer for measuring a concentration of hydrogen chloride, and a water content meter for measuring a concentration of water,

the control device predicts a dew point temperature based on a measurement result of at least one of the sulfur oxide concentration, the hydrogen chloride concentration, and the moisture concentration, and determines a reference temperature.

9. The waste heat recovery boiler of any one of claims 1 to 8,

the water quantity control valve includes a 1 st valve attached to the 1 st pipe for controlling a flow rate of water flowing through the 1 st pipe, and a 2 nd valve attached to the 2 nd pipe for controlling a flow rate of water flowing through the 2 nd pipe.

10. A method of controlling the temperature of a heat transfer tube of an exhaust heat recovery boiler using the exhaust heat recovery boiler, wherein the exhaust heat recovery boiler comprises:

a duct having a flow path through which exhaust gas flows;

a heat transfer pipe having a water inlet and a water outlet and disposed inside the pipe;

a water supply pipe connected to the water inlet of the heat transfer pipe, the water supply pipe including a branching portion, a merging portion located downstream of the branching portion, a 1 st pipe forming a portion between the branching portion and the merging portion, and a 2 nd pipe branching off from the 1 st pipe at the branching portion and merging again with the 1 st pipe at the merging portion, the water supply pipe supplying water having passed through the merging portion to the water inlet of the heat transfer pipe; and

a storage container connected to the water outlet, wherein at least a part of the 2 nd pipe is disposed inside the storage container,

comprises the following steps:

a measuring step of measuring at least one of a corrosion rate, a temperature, and an exhaust gas component inside the pipe;

a temperature determining step of determining the temperature of the water supplied to the heat transfer pipe based on the measurement result of the measuring step; and

a temperature adjusting step of adjusting a ratio of a flow rate of the water flowing through the 1 st pipe to a flow rate of the water flowing through the 2 nd pipe to adjust a surface temperature of the heat transfer pipe to the temperature determined in the temperature determining step.

11. The method of controlling the temperature of the heat transfer pipe of the waste heat recovery boiler according to claim 10,

the measuring step includes a step of measuring corrosion rates at a plurality of different temperatures in the pipe,

the temperature determining step includes a step of determining the temperature of the water supplied to the heat transfer pipe at which the corrosion rate becomes a value lower than an allowable value, based on the measurement results of the corrosion rates at the plurality of different temperatures.

Technical Field

The present invention relates to a waste heat recovery boiler and a method of controlling the temperature of a heat transfer pipe of the waste heat recovery boiler.

Background

The exhaust heat recovery boiler is provided with heat exchangers for recovering heat, such as a superheater, an evaporator, and an economizer (economizer), and accommodates a heat transfer pipe. Exhaust gas having a high temperature is supplied from the upstream side of the duct of the exhaust heat recovery boiler, and contacts the exhaust gas through the heat transfer pipe to perform heat exchange. The exhaust gas contains Sulfur Oxides (SO) generated by combustion_x) Water vapor (H)₂O). A part of the sulfur oxides reacts with water vapor to generate sulfuric acid (H)₂SO₄). Therefore, when the surface temperature of the heat transfer tube subjected to heat exchange is equal to or lower than the dew point of sulfuric acid, the sulfuric acid is condensed on the surface of the heat transfer tube, so that the corrosion rate of the surface of the heat transfer tube is significantly increased, and the steel material constituting the heat transfer tube is significantly corroded. In addition, the exhaust gas generated from the municipal refuse incinerator often contains chlorides such as hydrogen chloride (HCl), and the heat transfer pipe is similarly corroded even when the temperature is below the dew point of hydrogen chloride. Moreover, chlorides containing alkali metals and heavy metals are attached to the heat transfer surface,the heat transfer tube corrodes due to deliquescence and melting of the chloride. Therefore, in a boiler in which the heat transfer pipe is in contact with the exhaust gas, there is a concern about failure due to corrosion, and a method of suppressing corrosion is considered. For example, patent document 1 describes a boiler for controlling the corrosion rate.

The boiler described in patent document 1 includes a dew point corrosion monitoring probe, an exhaust gas duct, and an economizer. The economizer is provided with a heat transfer pipe disposed in the exhaust gas duct, an economizer temperature control device that controls water supply to the heat transfer pipe and adjusts the temperature of the heat transfer pipe, and a system control device that controls the economizer.

The dew point corrosion monitoring probe is disposed close to the heat transfer tube of the economizer, and the boiler uses the dew point corrosion monitoring probe to measure the corrosion rate. The system control device determines the operation target temperature based on the measured data of the corrosion rate so that the corrosion rate becomes a practically unproblematic value. Then, the temperature of the heat transfer pipe of the economizer is controlled to the operation target temperature. As the control method, any of a method of adjusting the amount of heat generated in the boiler and a method of adjusting the amount of cooling water flowing through the heat transfer pipe of the economizer controlled by the economizer temperature control device is used. Thus, the boiler protects the heat transfer tubes from corrosion.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2006 and 258603

Disclosure of Invention

As described above, the boiler described in patent document 1 adjusts the temperature of the heat transfer tube by adjusting the amount of heat generated in the boiler or the amount of cooling water flowing through the heat transfer tube so that the corrosion rate of the heat transfer tube becomes a practically unproblematic value.

However, when the exhaust heat recovery boiler including the heat transfer pipe is used in a waste disposal facility, the amount of waste to be disposed of is determined, and therefore the amount of waste to be burned may not be increased. In addition, since various wastes are incinerated, it is difficult to adjust the heat generated from the wastes, the temperature of the exhaust gas, and the components. In this case, the amount of heat generated in the boiler cannot be increased, and corrosion of the heat transfer pipe cannot be suppressed.

In addition, the temperature of water flowing inside the heat transfer pipe has a stronger influence on the surface temperature of the heat transfer pipe than the temperature of exhaust gas contacting the surface of the heat transfer pipe. Therefore, even if the amount of water flowing inside the heat transfer pipe is reduced, the surface temperature of the heat transfer pipe cannot be increased significantly as long as the temperature of the water is kept constant. Therefore, although there is a certain effect in adjusting the amount of water flowing through the heat transfer pipe, the temperature of the heat transfer pipe cannot be increased greatly. Therefore, when the method of adjusting the amount of cooling water flowing through the heat transfer tube is adopted, it may be difficult to increase the surface temperature of the heat transfer tube to a temperature at which the corrosion rate becomes practically an unproblematic value. In this case, corrosion of the heat transfer pipe cannot be suppressed.

In view of the above problems, it is an object of the present invention to provide an exhaust heat recovery boiler and a method of controlling the exhaust heat recovery boiler, which can suppress corrosion of a heat transfer pipe without adjusting the amount of heat generated in the boiler or adjusting the amount of water flowing through the heat transfer pipe.

(scheme 1)

The exhaust heat recovery boiler of claim 1 includes: a duct having a flow path through which exhaust gas flows; a heat transfer pipe having a water inlet and a water outlet and disposed inside the duct; a water supply pipe connected to the water inlet of the heat transfer pipe, the water supply pipe including a branching portion, a merging portion located downstream of the branching portion, a 1 st pipe forming a portion between the branching portion and the merging portion, and a 2 nd pipe branching from the 1 st pipe at the branching portion and merging again with the 1 st pipe at the merging portion, the water supply pipe supplying water having passed through the merging portion to the water inlet of the heat transfer pipe; a storage container that is in fluid communication with the water outlet of the heat transfer pipe, and in which at least a part of the 2 nd pipe is disposed inside the storage container; a water amount adjusting valve for adjusting a ratio of a flow rate of water flowing through the 1 st pipe to a flow rate of water flowing through the 2 nd pipe; a measuring device for measuring at least one of a corrosion rate, a temperature, and an exhaust gas component inside the pipe; and a control device for controlling the water amount regulating valve according to the measurement result of the measuring device.

In the exhaust heat recovery boiler according to claim 1, the water or the steam having a high temperature and passing through the heat transfer pipe flows into the storage container. Since at least a part of the 2 nd pipe is disposed in the storage container, the temperature of the water passing through the 2 nd pipe is higher than that of the water passing through the 1 st pipe. Further, the control device can adjust the ratio of the flow rate of water flowing through the 1 st pipe to the flow rate of water flowing through the 2 nd pipe by controlling the water amount adjustment valve. That is, the control device can control the temperature of the water flowing into the heat transfer pipe by controlling the flow rate of the low-temperature water passing through the 1 st pipe and the flow rate of the high-temperature water passing through the 2 nd pipe. Here, the temperature of the water flowing inside the heat transfer pipe acts more dominantly on the surface temperature of the heat transfer pipe than the temperature of the exhaust gas contacting the surface of the heat transfer pipe. Therefore, the exhaust heat recovery boiler can greatly change the surface temperature of the heat transfer pipe. That is, the control device can perform control for greatly changing the surface temperature of the heat transfer pipe based on the measurement result of at least one of the corrosion rate, the temperature, and the exhaust gas component, and can adjust the corrosion rate of the heat transfer pipe having a negative correlation with the surface temperature of the heat transfer pipe in the vicinity of the dew point. Therefore, according to the exhaust heat recovery boiler, corrosion of the heat transfer pipe can be suppressed.

(scheme 2)

In the exhaust heat recovery boiler according to claim 2, in the exhaust heat recovery boiler according to claim 1, the storage container is a drum (steam-water separator) for separating water and steam.

The exhaust heat recovery boiler may be provided with a drum for separating steam from water. In the exhaust heat recovery boiler according to claim 2, the boiler drum is used as the storage container described in claim 1. That is, the exhaust heat recovery boiler of claim 1 can be configured without newly providing another storage container.

(scheme 3)

In the exhaust heat recovery boiler according to claim 3, in the exhaust heat recovery boiler according to claim 1 or 2, at least a part of the 2 nd pipe is disposed in a portion of the storage container that stores water.

According to the exhaust heat recovery boiler of claim 3, at least a part of the 2 nd pipe is in direct contact with the water that has been heated by the heat transfer pipe. Therefore, the water in the reservoir can directly heat the 2 nd pipe. That is, the exhaust heat recovery boiler can raise the temperature of water flowing through the 2 nd pipe to a high temperature, compared to the case where the 2 nd pipe is in contact with only water vapor inside the storage container. In addition, the exhaust heat recovery boiler can supply water of a higher temperature to the heat transfer pipe.

(scheme 4)

The exhaust heat recovery boiler according to claim 4 further includes a water temperature meter for measuring a water temperature between the merging portion of the water supply pipe and the water inlet of the heat transfer pipe in the exhaust heat recovery boiler according to any one of claims 1 to 3, and the controller adjusts and controls the water amount adjusting valve based on a result of measurement by the water temperature meter.

In the exhaust heat recovery boiler according to claim 4, the water temperature of the water supplied to the heat transfer pipe is measured by a water temperature meter. Therefore, the controller can adjust the temperature of the water supplied to the heat transfer pipe to a specific temperature by adjusting the water amount adjustment valve based on the measurement result of the water temperature meter. That is, in the exhaust heat recovery boiler, water having a specific temperature can be supplied to the heat transfer pipe.

(scheme 5)

The waste heat recovery boiler according to claim 5 is the waste heat recovery boiler according to any one of claims 1 to 4, wherein the measuring device includes a corrosion monitoring probe including a 1 st corrosion sensor including an electrode member having an electrode surface exposed to the inside of the pipe and probe temperature adjusting means for adjusting the temperature of the electrode member, and the control device controls the probe temperature adjusting means of the corrosion monitoring probe to measure corrosion rates at a plurality of different temperatures by the corrosion monitoring probe, determines the temperature of the water supplied to the heat transfer pipe at which the corrosion rate is lower than an allowable value based on the measurement results of the corrosion rates at the plurality of different temperatures, and adjusts the temperature of the water supplied to the heat transfer pipe, The control is the determined temperature.

In the exhaust heat recovery boiler according to claim 5, since the corrosion monitoring probe has the probe temperature adjusting mechanism, the corrosion monitoring probe can measure the corrosion rate at different temperatures. Thus, the controller can acquire the relationship between the corrosion rate and the temperature in the pipe, and can determine the temperature at which the corrosion rate is lower than the allowable value. The control device can control the temperature of the water supplied to the heat transfer pipe based on the determined temperature. That is, the exhaust heat recovery boiler can be controlled so that the corrosion rate is lower than the allowable value.

(scheme 6)

The exhaust heat recovery boiler according to claim 6 is the exhaust heat recovery boiler according to any one of claims 1 to 5, wherein the measuring device includes a 2 nd corrosion sensor having an electrode member exposed to an inside of the pipe and capable of measuring a corrosion rate, and the control device performs control to increase a ratio of a flow rate of the water flowing through the 2 nd pipe to a flow rate of the water flowing through the 1 st pipe when the corrosion rate measured by the 2 nd corrosion sensor exceeds an allowable value.

According to the exhaust heat recovery boiler of claim 6, when the corrosion rate exceeds the allowable value, the temperature of the water supplied to the heat transfer pipe can be increased by controlling the flow rate ratio. Therefore, the exhaust heat recovery boiler can prevent the corrosion rate from exceeding the allowable value.

(scheme 7)

The exhaust heat recovery boiler according to claim 7 is the exhaust heat recovery boiler according to any one of claims 1 to 6, wherein the measuring device includes a thermometer that measures a temperature near the heat transfer tube, and the control device performs control to increase a ratio of a flow rate of the water flowing through the 2 nd pipe to a flow rate of the water flowing through the 1 st pipe when the temperature near the heat transfer tube measured by the thermometer is lower than a predetermined reference temperature.

It is known that near the dew point, temperature has a negative correlation with corrosion rate. Therefore, if the temperature is known, the corrosion rate can be inferred. That is, if the surface temperature of the heat transfer pipe is kept at a constant temperature or higher, the corrosion rate can be kept at a constant value or lower. The exhaust heat recovery boiler according to claim 7 increases the temperature of the water supplied to the heat transfer pipe based on the temperature measured by the thermometer. Therefore, the exhaust heat recovery boiler can keep the corrosion rate below a certain value.

(scheme 8)

The exhaust heat recovery boiler according to claim 8, wherein the measuring device is provided with an SO measuring device for measuring a sulfur oxide concentration of the exhaust gas component in the duct, in the exhaust heat recovery boiler according to any one of claims 1 to 7_xAnd a controller that predicts a dew point temperature based on a measurement result of at least one of the sulfur oxide concentration, the hydrogen chloride concentration, and the water concentration, and determines a reference temperature.

It is known that the etching rate varies depending on the sulfur oxide concentration, the hydrogen chloride concentration, and the water concentration in addition to the temperature. Therefore, when the exhaust heat recovery boiler estimates the corrosion rate, a more accurate corrosion rate can be estimated by considering at least one of the sulfur oxide concentration, the hydrogen chloride concentration, and the water concentration measured.

(scheme 9)

The exhaust heat recovery boiler according to claim 9 is the exhaust heat recovery boiler according to any one of claims 1 to 8, wherein the water amount adjustment valve includes a 1 st valve that is attached to the 1 st pipe and adjusts a flow rate of water flowing through the 1 st pipe, and a 2 nd valve that is attached to the 2 nd pipe and adjusts a flow rate of water flowing through the 2 nd pipe.

The exhaust heat recovery boiler of claim 9 can individually adjust the flow rate of water flowing through the 1 st pipe and the flow rate of water flowing through the 2 nd pipe by using different valves. Therefore, the exhaust heat recovery boiler can easily control the flow rate of water flowing through the 1 st pipe and the flow rate of water flowing through the 2 nd pipe.

(scheme 10)

A method of controlling the temperature of the heat transfer tube of the exhaust heat recovery boiler according to claim 10 uses an exhaust heat recovery boiler including: a duct having a flow path through which exhaust gas flows; a heat transfer pipe having a water inlet and a water outlet and disposed inside the duct; a water supply pipe connected to the water inlet of the heat transfer pipe, the water supply pipe including a branching portion, a merging portion located downstream of the branching portion, a 1 st pipe forming a portion between the branching portion and the merging portion, and a 2 nd pipe branching from the 1 st pipe at the branching portion and merging again with the 1 st pipe at the merging portion, the water supply pipe supplying water having passed through the merging portion to the water inlet of the heat transfer pipe; and a storage container connected to the water outlet, wherein at least a part of the 2 nd pipe is disposed inside the storage container, and the method includes: a measuring step of measuring at least one of a corrosion rate, a temperature, and an exhaust gas component inside the pipe; a temperature determining step of determining the temperature of the water supplied to the heat transfer pipe based on the measurement result of the measuring step; and a temperature adjusting step of adjusting a ratio of a flow rate of the water flowing through the 1 st pipe to a flow rate of the water flowing through the 2 nd pipe to adjust a surface temperature of the heat transfer pipe to the temperature determined in the temperature determining step.

The method of controlling the temperature of the heat transfer tube of the exhaust heat recovery boiler according to claim 10 adjusts the surface temperature of the heat transfer tube by adjusting the flow rate of the low-temperature water passing through the 1 st pipe and the flow rate of the high-temperature water passing through the 2 nd pipe to adjust the temperature of the water flowing into the heat transfer tube. Therefore, in the method for controlling the temperature of the heat transfer tube of the exhaust heat recovery boiler, the surface temperature of the heat transfer tube can be changed greatly, as in the case of embodiment 1. Therefore, the method for controlling the temperature of the heat transfer tube of the exhaust heat recovery boiler can suppress corrosion of the heat transfer tube.

(scheme 11)

The method of controlling the temperature of the heat transfer tube of the exhaust heat recovery boiler according to claim 11 is the method of controlling the temperature of the heat transfer tube of the exhaust heat recovery boiler according to claim 10, wherein the measuring step includes a step of measuring corrosion rates at a plurality of different temperatures in the pipe, and the temperature determining step includes a step of determining the temperature of the water supplied to the heat transfer tube at which the corrosion rate has a value lower than an allowable value, based on the measurement results of the corrosion rates at the plurality of different temperatures.

In the method of controlling the temperature of the heat transfer tube of the exhaust heat recovery boiler of claim 11, the corrosion rate can be made lower than the allowable value, as in claim 5.

Drawings

Fig. 1 is a structural diagram showing a structure of an exhaust heat recovery boiler according to embodiment 1 of the present invention.

Fig. 2 is a detailed view showing details of a portion of an economizer of the exhaust heat recovery boiler shown in fig. 1.

Fig. 3 is a sectional view showing the structure of a corrosion monitoring probe of the exhaust heat recovery boiler shown in fig. 2.

Fig. 4 is a plan view showing a main part of the corrosion monitoring probe shown in fig. 3.

Fig. 5 is a flowchart showing a sequence of a control process of the exhaust heat recovery boiler shown in fig. 1.

Detailed Description

Embodiments of the present invention will be described below with reference to the drawings. In the drawings described below, the same or corresponding components are denoted by the same reference numerals, and redundant description thereof is omitted.

[ embodiment 1]

< Structure >

Fig. 1 is a structural diagram showing a structure of an exhaust heat recovery boiler according to embodiment 1 of the present invention. Referring to fig. 1, the exhaust heat recovery boiler 100 includes a duct 120, a superheater 140, an economizer 300, a drum 160, a high-pressure steam container 180, and an evaporator (not shown). The exhaust heat recovery boiler 100 is a device that generates steam using the heat of exhaust gas. The exhaust heat recovery boiler 100 is, for example, a vertical type in which the exhaust gas flows vertically, but may be a cross-flow type in which the exhaust gas flows horizontally. The steam generated in the exhaust heat recovery boiler 100 is supplied to a steam turbine (not shown) as an example to drive a generator.

Hereinafter, each component of the exhaust heat recovery boiler 100 will be separately described.

The upstream side of the duct 120 is, for example, in fluid communication with an exhaust gas duct (not shown) of a combustion facility such as a garbage incinerator. The combustion device supplies high-temperature exhaust gas toward the exhaust gas duct. Therefore, a flow path through which the exhaust gas flows is formed in the duct 120. The exhaust gas contains sulfur oxides, hydrogen chloride, water vapor, and the like, which are generated by combustion in the combustion equipment.

The economizer 300 is located downstream of the superheater 140 described later in the flow path formed in the duct 120. Water is supplied from water supply unit 900 to economizer 300. The economizer 300 preheats the supplied water using the exhaust gas, and supplies the preheated water to the drum 160.

The drum 160 is a container for containing water and steam, and has a function of separating water and steam. The steam separated in the drum 160 is supplied to a superheater 140 described later. On the other hand, the water separated in the drum 160 is supplied to an evaporator (not shown).

The evaporator is a heat exchanger that further heats the water supplied from the drum 16. The evaporator heats the supplied water to convert at least a part of the water into steam.

The superheater 140 is a heat exchanger that further superheats the supplied steam. The superheater 140 turns the supplied steam into superheated steam and supplies the superheated steam to the high-pressure steam container 180.

The high-pressure steam container 180 contains superheated steam. The high-pressure steam container 180 is connected to a steam turbine, for example, and supplies the stored superheated steam to the steam turbine.

As described above, since each component of the exhaust heat recovery boiler 100 has the above-described configuration, the water supplied to the economizer 300 can be converted into superheated steam and supplied to the steam turbine.

Next, referring to fig. 2, the structure of the economizer 300 of the exhaust heat recovery boiler 100 will be described in more detail. Fig. 2 is a detailed view showing details of a part of the economizer 300 of the exhaust heat recovery boiler 100. Referring to fig. 2, the exhaust heat recovery boiler 100 further includes a water supply pipe 400, a water amount adjusting valve 500, a measuring device 600, a water temperature meter 700, and a control device 800.

The economizer 300 includes a heat transfer pipe 320. The heat transfer pipe 320 has a water inlet 322 and a water outlet 324, and water flows from the water inlet 322 toward the water outlet 324. The heat transfer pipe 320 is disposed inside the duct 120. In other words, the heat transfer pipe 320 is disposed at a position where the surface of the heat transfer pipe 320 can contact the exhaust gas flowing inside the duct 120. Thus, the heat transfer tubes 320 have a function of exchanging heat between water flowing inside the heat transfer tubes 320 and exhaust gas contacting the surfaces of the heat transfer tubes 320.

The water supply pipe 400 is connected to the water supply unit 900 and the water inlet 322 of the heat transfer pipe 320. The water supply pipe 400 includes a flow dividing portion 462, a joining portion 464 located on the downstream side of the flow dividing portion 462, and the 1 st pipe 420 and the 2 nd pipe 440. The 1 st pipe 420 forms a portion from the flow dividing portion 462 to the flow joining portion 464. The 2 nd pipe 440 branches off from the 1 st pipe 420 at the branching portion 462 and merges again with the 1 st pipe 420 at the merging portion 464. The water supply pipe 400 supplies the water that has passed through the merging portion 464 to the water inlet 322 of the heat transfer pipe 320. Therefore, the water supply pipe 400 can divide the water supplied from the water supply unit 900 into the water flowing through the 1 st pipe 420 and the water flowing through the 2 nd pipe 440 at the dividing portion 462, and can cause the water flowing through the 1 st pipe 420 and the hydration water flowing through the 2 nd pipe 440 at the merging portion 464. In other words, the water supply pipe 400 can supply the water passing through the 1 st pipe 420 or the 2 nd pipe 440 to the water inlet 322.

The water quantity regulating valve 500 includes, for example, a 1 st valve 520 and a 2 nd valve 540. The 1 st valve 520 is attached to the 1 st pipe 420. Thus, the 1 st valve 520 can adjust the flow rate of water flowing through the 1 st pipe 420. On the other hand, the 2 nd valve 540 is attached to the 2 nd pipe 440. Thus, the 2 nd valve 540 can adjust the flow rate of water flowing through the 2 nd pipe 440. That is, the water amount adjusting valve 500 can adjust the ratio of the flow rate of water flowing through the 1 st pipe 420 to the flow rate of water flowing through the 2 nd pipe 440.

The drum 160 is in fluid communication with the water outlet 324 of the heat transfer tube 320. Thereby, the water passing through the heat transfer pipe 320 and heated flows into the drum 160. In other words, the water contained in the drum 160 has a higher temperature than the water supplied from the water supply unit 900. In the drum 160, at least a part of the 2 nd pipe 440 is disposed inside. Therefore, the water passing through the 2 nd pipe 440 is heated by the water or steam inside the drum 160. The water passing through the 2 nd pipe 440 has a higher temperature than the water passing through the 1 st pipe 420. Therefore, when the ratio of the flow rate of water flowing through the 1 st pipe 420 to the flow rate of water flowing through the 2 nd pipe 440 is adjusted, the temperature of water supplied to the heat transfer pipe 320 changes. In the present embodiment, at least a part of the 2 nd pipe 440 is disposed in the portion of the drum 160 that stores the water. That is, the 2 nd pipe 440 is in contact with the water stored in the drum 160.

The measuring device 600 measures at least one of the corrosion rate, temperature, and exhaust gas component inside the pipe 120. More specifically, the measuring apparatus 600 includes, as an example, a corrosion monitoring probe 620 (hereinafter, referred to as a probe 620). Since the probe 620 includes a probe temperature adjustment mechanism 624 described later, the corrosion rate of the inside of the pipe 120 can be measured at a set temperature.

Here, an example of the probe 620 will be described in more detail. Fig. 3 is a sectional view showing the structure of the probe 620 of the exhaust heat recovery boiler 100. Fig. 4 is a plan view showing a main part of the probe 620. Referring to fig. 3 and 4, the probe 620 includes: the corrosion sensor 1 includes a pair of electrode members 622a and 622b for measuring corrosion rate, a probe temperature adjusting mechanism 624, an electrode 626 for measuring temperature such as a thermocouple, a support 628, a cover 630, a lead 636, a lead 637, a connecting pipe 638, an impedance measuring device 640, and a temperature measuring device 650. The probe temperature adjustment mechanism 624 includes a temperature adjustment gas source 648, a temperature adjustment valve 642, a gas supply pipe 644, a flow meter 645, and a probe electrode temperature control device 646.

In the present embodiment, the electrode members 622a and 622b are formed of two conductors made of the same material. More specifically, the electrode members 622a and 622b are made of the same material as the heat transfer pipe 320, for example, from the viewpoint of detecting the corrosion rate of the heat transfer pipe 320. The electrode members 622a and 622b are cubes having a substantially square planar shape, and are adjacent to each other with a space therebetween (see fig. 4). Thus, a flow path forming portion 634 for forming a flow path of the condensed water is formed in a portion between the electrode members 622a and 622 b. The electrode members 622a, 622a are embedded in the support 628. One surface (hereinafter, referred to as a front surface side surface) of each of the electrode members 622a and 622b is exposed to the inside of the duct 120, and the other surface (hereinafter, referred to as an inner surface) is connected to a lead 636. The lead 636 is connected to the impedance measuring device 640 through the inside of the connection tube 638. Thus, the impedance measuring device 640 applies an ac voltage to the electrode members 622a and 622b, and can measure the impedance between the electrode members 622a and 622 b. The impedance measuring device 640 is connected to the control device 800. Thereby, the control device 800 can acquire the measured impedance. The controller 800 can separately determine the reaction resistance and the solution resistance by performing frequency analysis on the measured impedance. The controller 800 can calculate the etching rate from the reaction resistance and the solution resistance by using a known method. That is, the controller 800 can acquire data of the etching rate.

The temperature measuring electrode 626 is embedded in the support 628, similarly to the electrode members 622a and 622 b. One face of the electrode 626 is exposed to the inside of the pipe 120, and the other face is connected to a lead 637. The lead 637 is connected to the temperature detector 650 via the inside of the connection tube 638. Thus, the temperature measuring device 650 can measure the temperature of the electrode 626, that is, the temperature in the vicinity of the electrode members 622a, 622b for measuring the etching rate. The temperature detector 650 is connected to the control device 800. Thereby, the control device 800 can acquire data of the temperature in the vicinity of the electrode members 622a, 622 b.

The cover 630 forms a thermal medium space 632 by being in close contact with the supporting base 628. Thus, the surfaces of the electrode members 622a and 622b on the side connected to the lead line 636 and the surfaces of the electrodes 626 on the side connected to the lead line 637 are exposed to the thermal medium space 632, respectively. Further, a connection pipe 638 for allowing a heat medium such as air or water to flow into the heat medium space 632 is attached to the cover 630. A gas supply pipe 644 is inserted into the connection pipe 638. The gas supply pipe 644 connects a temperature adjusting gas source 648 such as a compressor or a gas cylinder to the heat medium space 632. Further, a temperature control valve 642 and a flow meter 645 are provided between the temperature control gas source 648 and the heat medium space 632. Therefore, the temperature control gas supplied from the temperature control gas source 648 is supplied to the heat medium space 632 by adjusting the temperature control valve 642. That is, the temperature of the heat medium space 632 is close to the temperature of the supplied temperature adjustment gas. Thus, the probe electrode temperature control device 646 can adjust the electrode members 622a, 622b for measuring the corrosion rate and the electrode 626 for measuring the temperature to a set temperature. That is, the probe 620 can measure the corrosion rate at a set temperature by adjusting the temperature of the electrode members 622a and 622b for measuring the corrosion rate using the probe temperature adjusting mechanism 624.

The above description is of the probe 620 provided in the measurement device 600. The probe 620 may not have the above-described structure as long as it has a function of measuring the corrosion rate of the inside of the pipe 120 at a set temperature.

Reference is again made to fig. 2. In the exhaust heat recovery boiler 100, the probe 620 is disposed in the vicinity of the heat transfer pipe 320, for example. Thus, the probe 620 can measure the corrosion rate close to the corrosion rate of the heat transfer pipe 320. Here, the vicinity of the heat transfer pipe 320 refers to a position where the same material as that of the heat transfer pipe 320 is disposed at a position in the vicinity, and the heat transfer pipe 320 and the material disposed at the position in the vicinity have the same corrosion rate.

The water temperature gauge 700 is disposed, for example, between the junction 464 of the water supply pipe 400 and the water inlet 322 of the heat transfer pipe 320. Thus, the water temperature meter 700 has a function of measuring the water temperature between the joining portion 464 of the water supply pipe 400 and the water inlet 322 of the heat transfer pipe 320. That is, the water temperature meter 700 can measure the temperature of the water supplied to the heat transfer pipe 320.

The controller 800 can control the probe temperature adjustment mechanism 624 of the probe 620 to enable the probe 620 to measure the corrosion rate at a plurality of different temperatures. Further, the controller 800 can determine the temperature of the water supplied to the heat transfer pipe 320 such that the corrosion rate is lower than the allowable value, based on the measurement results of the corrosion rates at the plurality of different temperatures of the probe 620. The allowable value is a value that can be arbitrarily determined. More specifically, the allowable value can be determined according to the life of the equipment, the operating conditions, and the like. The controller 800 adjusts and controls the temperature of the water supplied to the heat transfer pipe 320 to the determined temperature by adjusting the water amount adjustment valve 500 based on the measurement result of the water temperature meter 700.

< method for controlling temperature of heat transfer pipe of waste heat recovery boiler >

Next, a method of controlling the temperature of the heat transfer pipe 320 of the exhaust heat recovery boiler 100 according to the present embodiment will be described. In describing the method of controlling the temperature of the heat transfer pipe 320 of the exhaust heat recovery boiler 100, the initial states of the components constituting the exhaust heat recovery boiler 100 will be described.

In the initial state, the inside of the duct 120 contains exhaust gas. The water supply unit 900 supplies water to the water supply pipe 400. Therefore, the supplied water is supplied to the heat transfer pipe 320 through the water supply pipe 400. Then, the water supplied to the heat transfer pipe 320 is heated by the heat transfer pipe 320 and supplied to the drum 160.

With the above as a premise, a method of controlling the temperature of the heat transfer pipe 320 of the exhaust heat recovery boiler 100 will be described with reference to the drawings. Fig. 5 is a flowchart showing a procedure of a method of controlling the temperature of the heat transfer pipe 320 of the exhaust heat recovery boiler 100.

Referring to fig. 5, in step S100, controller 800 uses water temperature meter 700 to check the feed water temperature to heat transfer pipe 320. Then, the control device 800 acquires information on the feed water temperature. In step S200, the temperature of the probe 620 is changed to a predetermined temperature and is controlled to be maintained for a predetermined time by controlling the probe temperature adjustment mechanism 624.

Next, in step S300, the control device 800 acquires the temperature of the probe 620 based on the output of the probe 620. Then, the control device 800 confirms that the probe 620 is at the predetermined temperature.

Next, in step S400, the controller 800 measures the etching rate corresponding to the temperature for a certain period of time based on the output of the probe 620, and acquires information on the etching rate.

Next, in step S500, the controller 800 determines whether or not the etching rate at a predetermined temperature obtained from the output of the detector 620 is equal to or higher than an allowable value. When the etching rate at the predetermined temperature is not equal to or higher than the allowable value, the controller 800 returns the process to step S200. In step S200, the controller 800 sets a temperature at which the etching rate is not measured and which is lower than the temperature of the probe 620 set in the previous step S200, as a new predetermined temperature. Then, the controller 800 controls the probe temperature adjustment mechanism 624 to lower the temperature of the probe 620 to the newly set predetermined temperature. In this way, the controller 800 can acquire information on the corrosion rate at a temperature that is not measured in the next repeated execution.

On the other hand, if the etching rate is equal to or higher than the allowable value in step S500, the controller 800 advances the process to step S600. In this manner, the controller 800 repeats the processing from step S200 to step S400 until the etching rate becomes equal to or higher than the allowable value, and thereby the controller 800 acquires information on the etching rates at a plurality of different temperatures.

Next, in step S600, the controller 800 grasps the relationship between the temperature and the etching rate based on the information on the temperature and the etching rate obtained from the output of the probe 620. In addition, it is known that there is a negative correlation between the temperature near the dew point of sulfuric acid and the corrosion rate.

Next, in step S700, the control device 800 determines an allowable temperature at which the etching rate can be equal to or lower than an allowable value. More specifically, first, the controller 800 compares the corrosion rate corresponding to the highest temperature among the measured temperatures with an allowable value. Next, the controller 800 compares the corrosion rate corresponding to the second highest temperature among the plurality of measured temperatures with an allowable value. Then, the controller 800 compares the corrosion rate corresponding to the third highest temperature among the plurality of measured temperatures with an allowable value. In this manner, the controller 800 compares the corrosion rate corresponding to the high temperature among the plurality of measured temperatures with the allowable value in order. Then, the controller 800 finds a temperature at which the corrosion rate is higher than the allowable value for the first time among the measured temperatures, and sets the next high temperature to the found temperature as the allowable temperature. Then, the control device 800 determines the allowable temperature as the feed water temperature. In order to further reduce the corrosion rate, the controller 800 may determine a temperature higher than the allowable temperature by a predetermined value as the feed water temperature.

Next, in step S800, control device 800 determines whether or not the feed water temperature of the current feed water, that is, the feed water temperature confirmed in step S100, exceeds the allowable temperature. More specifically, control device 800 compares the feedwater temperature identified in step S100 with the feedwater temperature determined in step S700.

If the feed water temperature determined in step S100 is lower than the temperature determined in step S700, control device 800 increases the feed water temperature in step S700 so that the feed water temperature of the current feed water becomes the feed water temperature determined in step S700. The controller 800 controls the water amount adjusting valve 500 to increase the feed water temperature. Thus, the exhaust heat recovery boiler 100 performs control to keep the corrosion rate at an allowable value or less.

On the other hand, if the feed water temperature determined in step S100 is higher than the feed water temperature determined in step S700, the control device 800 decreases the feed water temperature of the current feed water to the feed water temperature determined in step S500 in step S800. The controller 800 controls the water amount adjusting valve 500 to lower the feed water temperature.

Next, in S900, the water temperature meter 700 is used to check the temperature of the feed water to the heat transfer pipe 320. Then, the control device 800 acquires the information of the feedwater temperature, and confirms whether or not the feedwater temperature is the feedwater temperature determined in step S700.

After the process of step S900 is completed, control device 800 repeats the process from step S100 again after a certain time period has elapsed in S1000. Thus, the exhaust heat recovery boiler 100 performs the following control: the surface of the heat transfer pipe 320 is prevented from becoming too high in temperature and reducing the amount of heat recovery, and the surface of the heat transfer pipe 320 is prevented from becoming too low in temperature and corroding, whereby heat energy can be recovered efficiently.

< action, Effect >

Next, the operation and effect of the exhaust heat recovery boiler 100 of the present embodiment will be described below.

(1 st Effect)

The exhaust heat recovery boiler 100 of the present embodiment includes a control device 800 that controls the temperature of the water supplied to the heat transfer pipe 320 based on the corrosion rate measured by the detector 620. Therefore, the exhaust heat recovery boiler 100 can greatly change the surface temperature of the heat transfer tubes 320 by adjusting the temperature of the water supplied to the heat transfer tubes 320. When the surface temperature of the heat transfer tubes 320 is changed, the exhaust heat recovery boiler 100 does not need to increase the temperature of the exhaust gas contacting the heat transfer tubes 320, and does not need to increase the flow rate of the exhaust gas flowing through the duct 120. Therefore, the exhaust heat recovery boiler 100 can keep the corrosion rate of the heat transfer tubes 320 at the allowable value or less, and can suppress corrosion of the heat transfer tubes 320.

(effect 2)

The exhaust gas used for heat recovery is heat-recovered in the heat transfer pipe 320, and then discharged from the duct 120. When the surface of the heat transfer pipe 320 becomes too high, the temperature of the exhaust gas is close to the temperature of the surface of the heat transfer pipe 320, and therefore the amount of heat recovery from the exhaust gas at the position of the heat transfer pipe 320 decreases. Therefore, the exhaust heat recovery boiler 100 is caused to discard the exhaust gas of high temperature. Discarding the exhaust gas of high temperature is equivalent to not recovering the heat energy that can be recovered in the exhaust heat recovery boiler 100. However, since the exhaust heat recovery boiler 100 controls the temperature of the water supplied to the heat transfer pipe 320 according to the corrosion rate, the temperature of the gas discharged from the duct 120 does not become excessively high. That is, the exhaust heat recovery boiler 100 can efficiently recover heat energy without excessively discarding the heat energy of the exhaust gas in a limited heat transfer area.

(effect 3)

Further, a part of the 2 nd pipe 440 of the water supply pipe 400 is disposed inside the drum 160. Thus, the water passing through the 2 nd pipe 440 is heated by the high-temperature water or steam inside the drum 160. That is, the exhaust heat recovery boiler 100 can increase the temperature of the water supplied to the heat transfer pipe 320 without providing another heating structure for heating the water supplied to the heat transfer pipe 320.

(effect No. 4)

Further, a part of the 2 nd pipe 440 is in contact with the water having a high temperature in the drum 160. Therefore, the water passing through the 2 nd pipe 440 is heated more quickly than when the water stored in the drum 160 does not contact the 2 nd pipe 440 (when the 2 nd pipe 440 is heated by the steam inside the drum 160). That is, if the flow rate of water passing through the 2 nd pipe 440 is the same, the temperature of water passing through the 2 nd pipe 440 becomes higher in the structure in which the 2 nd pipe 440 is in contact with the water stored in the drum 160 than in the structure in which the 2 nd pipe 440 is not in contact with the water stored in the drum 160. Therefore, the exhaust heat recovery boiler 100 can make the water passing through the 2 nd pipe 440 higher in temperature.

(5 th Effect)

The exhaust heat recovery boiler 100 is provided with a water temperature meter 700 capable of measuring the temperature of the water supplied to the heat transfer pipe 320. The controller 800 controls the temperature of the water supplied to the heat transfer pipe 320 based on the measurement result of the water temperature meter 700. This enables the exhaust heat recovery boiler 100 to supply water at a specific temperature to the heat transfer tubes 320, and facilitates temperature adjustment of the heat transfer tubes 320.

< modification example >

Next, a modification of the exhaust heat recovery boiler 100 of the present embodiment will be described below.

(modification 1)

The waste heat recovery boiler 100 may also have a storage vessel in fluid communication with the water outlet 324 of the heat transfer tube 320 in addition to the drum 160. In this case, at least a part of the 2 nd pipe 440 is disposed inside the storage container. In this case, too, the water or the steam inside the storage container can heat the water flowing through the 2 nd pipe 440. Further, by using the storage container in fluid communication with the water outlet 324, the exhaust heat recovery boiler 100 can use the water heated by the heat transfer pipe 320 and the steam obtained by further heating the water as the heat source for heating the 2 nd pipe 440. That is, the exhaust heat recovery boiler 100 can heat the water supplied to the heat transfer pipe 320 without providing any other heating means such as a heater. Here, the storage container is a device that stores at least one of water and steam, and the drum 160 is an example of the storage container. The high-pressure steam container 180 is also an example of a storage container.

(modification 2)

In the present embodiment, the probe 620 is disposed in the vicinity of the heat transfer pipe 320. However, the probe 620 may be disposed at a certain position inside the pipe 120 as long as it can measure data necessary for estimating the corrosion rate of the heat transfer pipe 320. For example, when it is considered that the flow of the exhaust gas is biased to one side and the temperature distribution in the duct is not uniform, the probe may be disposed at a position where it is considered that the corrosion rate of the heat transfer pipe 320 is most suitable to be estimated, after the temperature distribution in the duct is grasped in advance. This is because if the corrosion rate of the heat transfer pipe 320 can be estimated using the data measured by the detector 620, the temperature of the water supplied to the heat transfer pipe 320 can be determined in accordance with the corrosion rate.

(modification 3)

The measuring device 600 may further include a 2 nd corrosion sensor for measuring the corrosion rate in the vicinity of the heat transfer pipe 320. In this case, the controller 800 performs control to increase the ratio of the flow rate of water flowing through the 2 nd pipe 440 to the flow rate of water flowing through the 1 st pipe 420 when the corrosion rate measured by the 2 nd corrosion sensor exceeds the allowable value. This is because, even if the exhaust heat recovery boiler 100 does not include the probe 620, the 2 nd corrosion sensor is provided in the limited space inside the duct 120, so that the corrosion rate of the heat transfer pipe 320 can be prevented from exceeding the allowable value, and excessive corrosion of the heat transfer pipe 320 can be suppressed.

(modification 4)

In the present embodiment, the 1 st corrosion sensor includes a pair of electrode members 622a and 622b, measures the impedance between the electrode members 622a and 622b, and obtains data of the corrosion rate by analysis. The short-circuit current when the dissimilar electrode is short-circuited by the condensed phase can be measured, and the resonance frequency of the crystal resonator on the surface of the electrode can be measured. By analyzing the output of any one of the sensors, data on the etching rate can be obtained. Further, by using the electrode member of the same material as the heat transfer pipe 320 for the 1 st corrosion sensor, the corrosion rate of the heat transfer pipe 320 can be estimated from the output of the 1 st corrosion sensor. Further, by changing the electrode material to a material having higher corrosiveness than the material of the heat transfer pipe 320, the tendency of corrosion of the heat transfer pipe 320 can be grasped in advance.

(modification 5)

The measuring device 600 may have a thermometer for measuring the temperature in the vicinity of the heat transfer pipe 320. In this case, the controller 800 performs control to increase the ratio of the flow rate of water flowing through the 2 nd pipe 440 to the flow rate of water flowing through the 1 st pipe 420 when the temperature measured by the thermometer is lower than a predetermined reference temperature. As described above, it is known that the temperature in the vicinity of the dew point of sulfuric acid has a negative correlation with the corrosion rate. Therefore, the corrosion rate can be estimated by measuring the temperature of the portion of the heat transfer pipe 320. Therefore, even if the exhaust heat recovery boiler 100 does not include the probe 620, the corrosion of the heat transfer tubes 320 can be suppressed by controlling the temperature of the water supplied to the heat transfer tubes 320 based on the temperature measured by the thermometer. The reference temperature may be arbitrarily determined in consideration of the relationship between the temperature and the etching rate.

(modification 6)

The measuring device 600 may further include an SO measuring the sulfur oxide concentration in the vicinity of the heat transfer pipe 320 in addition to the thermometer of modification example 4_xAt least one of an analyzer, an HCl analyzer for measuring a hydrogen chloride concentration, and a moisture meter for measuring a moisture concentration. In this case, the controller 800 determines the reference temperature to be compared with the temperature measured by the thermometer based on the measurement result of at least one of the sulfur oxide concentration, the hydrogen chloride concentration, and the moisture concentration. The controller 800 performs control to increase the ratio of the flow rate of the water flowing through the 2 nd pipe 440 to the flow rate of the water flowing through the 1 st pipe 420 when the temperature measured by the thermometer is lower than the reference temperature.

As described above, it is known that the etching rate changes depending on the sulfur oxide concentration, the hydrogen chloride concentration, and the moisture concentration in addition to the temperature. In this way, the corrosion rate can be estimated more accurately by taking into account at least one of the measured sulfur oxide concentration, hydrogen chloride concentration, and water concentration. In addition, the exhaust heat recovery boiler 100 can suppress corrosion of the heat transfer pipe 320 in consideration of a more accurate corrosion rate.

(modification 7)

In modification 6, controller 800 may predict the sulfuric acid dew point from the sulfur oxide concentration and the water concentration by using the tsukau formula, and set the sulfuric acid dew point as the reference temperature. Further, the tsukamur formula is represented by formula (1).

[ number 1]

T_DP＝20logV+A...(1)

In this case, the amount of the solvent to be used,

[ number 2]

T_DP: sulfuric acid dew point (. degree. C.)

V: concentration of trisulfide in exhaust gas (vol%)

A: a constant based on moisture in the exhaust gas (moisture concentration 5%: 184, 10%: 194, 15%: 201).

It is known that the sulfuric acid dew point can be calculated from the sulfur oxide concentration and the water concentration by using the tsukau formula. Thus, the exhaust heat recovery boiler 100 can prevent the temperature in the vicinity of the heat transfer tubes 320 from falling below the dew point of sulfuric acid, and can suppress corrosion of the heat transfer tubes 320. In order to further suppress corrosion of the heat transfer pipe 320, the controller 800 may set a temperature higher than the dew point temperature of sulfuric acid as the reference temperature. Further, the calculation formula is an example, and controller 800 may predict the dew point temperature from the exhaust gas component using another calculation formula. Further, the exhaust gas component contains sulfur oxides, hydrogen chloride, moisture, and the like.

(modification 8)

The measuring device 600 includes SO for measuring the concentration of sulfur oxides in the vicinity of the heat transfer pipe 320_xIn the case of at least one of the analyzer, the HCl analyzer for measuring the hydrogen chloride concentration, and the water content meter for measuring the water content concentration, the thermometer of modification 4 may not be provided. In this case, the controller 800 performs control to increase the ratio of the flow rate of water flowing through the 2 nd pipe 440 to the flow rate of water flowing through the 1 st pipe 420 when the measurement result of at least one of the sulfur oxide concentration, the hydrogen chloride concentration, and the moisture concentration is higher than a predetermined value or lower than a predetermined value.

As described above, it is known that the dew point temperature can be predicted from the exhaust gas component. Therefore, in a case where the temperature inside the duct 120 is substantially constant or the like is predictable, the dew point temperature predicted from the exhaust gas component can be compared with the predicted temperature inside the duct 120. Thus, the exhaust heat recovery boiler 100 can prevent the predicted temperature inside the duct 120 from falling below the predicted dew point temperature, and can suppress corrosion of the heat transfer pipe 320. That is, if the measurement device 600 can measure the exhaust gas components, the exhaust heat recovery boiler 100 can suppress corrosion of the heat transfer tubes 320. The predetermined value to be compared with the measurement result of the measurement device 600 may be arbitrarily determined.

(modification 9)

In addition, in the case of modification 8, the control device 800 may perform the following control: the ratio of the flow rate of water flowing through the 2 nd pipe 440 to the flow rate of water flowing through the 1 st pipe 420 is increased so that the temperature of water supplied to the heat transfer pipe 320 becomes higher than the dew point temperature predicted from the exhaust gas component.

Thus, the exhaust heat recovery boiler 100 can set the temperature of the water flowing inside the heat transfer pipe 320 to a temperature higher than the dew point temperature. Further, since heat is recovered from the exhaust gas by the water flowing inside the heat transfer pipe 320, the temperature of the exhaust gas contacting the heat transfer pipe 320 is higher than the temperature of the water flowing inside the heat transfer pipe 320. That is, the temperature of the water flowing inside the heat transfer pipe 320 and the temperature of the exhaust gas contacting the heat transfer pipe 320 are both higher than the dew point temperature, and the temperature of the surface of the heat transfer pipe 320 is naturally higher than the dew point temperature. Therefore, the exhaust heat recovery boiler 100 can suppress corrosion of the heat transfer pipe 320.

(modification 10)

In the present embodiment, the water amount regulating valve 500 has the 1 st valve 520 and the 2 nd valve 540. However, the water amount adjusting valve 500 may not have one of the 1 st valve 520 and the 2 nd valve 540. This is because even if the water amount adjustment valve 500 has only one of the 1 st valve 520 and the 2 nd valve 540, the ratio of the flow rates of the water flowing through the 1 st pipe 420 and the 2 nd pipe 440 can be adjusted. This is because the exhaust heat recovery boiler 100 can adjust the temperature of the water supplied to the heat transfer pipe 320 as long as the ratio of the flow rates can be adjusted. The water amount adjusting valve 500 may include a three-way valve for allowing water to flow to either the 1 st pipe 420 or the 2 nd pipe 440. Also, this is because the three-way valve can adjust the ratio of the flow rates of water flowing through the 1 st pipe 420 and the 2 nd pipe 440. The water amount adjusting valve 500 may have any configuration as long as the water amount adjusting valve 500 can adjust the ratio of the flow rate of water flowing through the 1 st pipe 420 to the flow rate of water flowing through the 2 nd pipe 440.

While the embodiments of the present invention have been described above, the embodiments of the present invention are provided for easy understanding of the present invention and do not limit the present invention. The present invention can be modified and improved without departing from the scope of the invention, and the invention includes equivalents thereof. In addition, in a range in which at least a part of the above-described problems can be solved or in a range in which at least a part of the effects can be obtained, the respective components described in the claims and the description can be arbitrarily combined or omitted.

Description of the reference numerals

100: waste heat recovery boiler

120: pipeline

140: superheater

160: boiler barrel

300: energy saver

320: heat transfer tube

322: water inlet

324: water outlet

400: water supply pipe

420: no. 1 pipe

440: no. 2 pipe

462: flow dividing part

464: confluence part

500: water quantity regulating valve

520: 1 st valve

540: no. 2 valve

600: measuring device

620: detector

624: detector temperature adjusting mechanism

700: water temperature meter

800: control device

900: a water supply part.