Corrosion monitoring device for urea hydrolyzer of thermal power plant and use method of corrosion monitoring device

Abstract

The invention discloses a heat-engine plant urea hydrolyzer corrosion monitoring device and a use method thereof, and belongs to the field of corrosion prevention of heat-engine plant industrial equipment, and the heat-engine plant urea hydrolyzer corrosion monitoring device comprises a corrosion factor detection sensor, a urea corrosion monitoring device control cabinet and a urea solution regulation and control device; the corrosion factor detection sensor comprises a first oxidation-reduction potential test sensor and a chloride ion concentration test sensor which are arranged in the urea solution preparation tank, and a second oxidation-reduction potential test sensor which is arranged on the urea solution conveying pipeline; the urea corrosion monitoring device control cabinet is electrically connected with the first oxidation-reduction potential test sensor, the chloride ion concentration test sensor and the second oxidation-reduction potential test sensor and is used for collecting corrosion factors and flow information; according to the device, an oxidizing agent is added into a urea solution, damage of ammonium carbamate to a passive film on the stainless steel surface is relieved, the adding amount of the oxidizing agent is regulated in real time through an oxidation-reduction potential test, and corrosion damage and maintenance cost are reduced.

Description

Technical Field

[0001] The present invention belongs to the field of anti-corrosion of industrial equipment in thermal power plants, and particularly relates to a device for anti-corrosion of a urea hydrolyzer in a thermal power plant and a using method thereof. Background Art

[0002] In the selective catalytic reduction (SCR) denitration of flue gas in thermal power plants, ammonia gas is mostly used as a reducing agent. Previously, ammonia gas was mainly provided by liquid ammonia storage tanks. However, liquid ammonia storage tanks belong to major hazard sources. Therefore, thermal power plants have begun to choose thermal decomposition and hydrolysis to produce ammonia. Compared with ammonia production by urea thermal decomposition, ammonia production by urea hydrolysis has lower energy consumption and less operation and maintenance workload, and it is the main technical route for urea ammonia production in coal-fired units.

[0003] A urea hydrolyzer is a device for producing ammonia by urea hydrolysis. During the operation of this device, a urea solution with a mass percentage of about 50% enters the tank body from a feed hole near the bottom of the container. After being heated to 140°C to 150°C by an internal heater, a hydrolysis reaction occurs, and the generated mixed gas containing ammonia gas is discharged through a pipeline at the top of the tank body. After the urea hydrolysis reaction, a small amount of residual liquid is regularly discharged through a pipeline at the bottom of the tank body. Generally speaking, the feed rate of the urea solution is 1 m 3 / h, and the waste liquid discharged per week is about 0.2 m 3 / week. This means that non-volatile impurities in the urea raw material liquid will be highly concentrated in the reaction device.

[0004] During the urea hydrolysis process, key components of the hydrolyzer, such as heat exchanger tubes and the hydrolyzer kettle body, have to come into contact with high-temperature solutions. The urea solution itself is not highly corrosive, but intermediate products formed during the urea hydrolysis process, such as ammonium carbamate, have strong reducibility and cause serious damage to the passivation film on the stainless steel surface. The corrosion problem of urea hydrolyzers has always been the main bottleneck affecting the stability of this process. Key components of foreign urea hydrolysis devices are all made of urea-grade austenitic stainless steel or duplex stainless steel, and anti-corrosion is mainly achieved by the corrosion resistance of the materials, without special processes and measures. After the localization of urea hydrolysis devices, researchers evaluated the corrosion resistance of candidate materials for urea hydrolyzers through laboratory simulation tests. The research results show that urea-grade 316Lmod has better corrosion resistance in this environment, mainly showing uniform corrosion; while the corrosion resistance of TC4 alloy, Inconel718 alloy, and HR3C stainless steel is even better. However, due to cost considerations, most domestic hydrolyzer shells and heat exchanger tubes are still made of 316L stainless steel and do not choose materials with better corrosion resistance.

[0005] Inside the hydrolyzer, in addition to the strong corrosiveness of the intermediate products of urea hydrolysis, stainless steel also faces the threat of high-concentration chloride ions in the environment. There is no quality control standard for the purchased urea in thermal power plants, lacking in-plant inspection and supervision means, and the quality of raw materials is uneven. Most of the urea purchased by thermal power plants contains impurities Cl. During the urea hydrolysis process, the urea solution continuously enters the reactor, and the impurities are gradually concentrated in the urea hydrolysis residual liquid, forming a high-concentration Cl - environment. According to the results of previous investigations, Cl was detected in the residual liquid of the urea hydrolyzers in some thermal power plants - with a mass concentration exceeding 60000 mg / L. In such a high-concentration Cl - environment, stress corrosion may occur at positions with residual stress such as the elbows of the heat exchange tubes of the heater and the partition support parts, and the stainless steel materials at other positions also face a high risk of pitting corrosion. As the service time of some domestic urea hydrolysis devices increases, the corrosion and safety problems of the devices gradually become prominent. Cracks have formed in the shells of some hydrolyzers that have been in service for less than 1 year, and even the whole has been scrapped.

[0006] 316L stainless steel faces corrosion under the synergistic action of hydrolysis intermediate products and high-concentration Cl - in the urea hydrolysis solution. The hydrolysis intermediate products will cause uniform corrosion on the surface of the stainless steel, while high-concentration Cl - is prone to induce local corrosion problems in the stainless steel, which makes the corrosion reaction of the stainless steel in this environment more complex. Compared with other environments, the corrosion problem of stainless steel in the urea hydrolysis solution environment lies in that: since the corrosion problem of the urea hydrolyzer has not been exposed for a long time, the corrosion environment inside the hydrolyzer is relatively harsh, and there is currently no mature corrosion monitoring device for the urea hydrolyzer, so there are relatively large potential safety hazards when thermal power plants use this kind of equipment. Summary of the Invention

[0007] To solve the problems existing in the prior art, the present invention provides a corrosion monitoring device for a urea hydrolyzer in a thermal power plant and its usage method. An oxidant is added to the urea solution to slow down the damage of ammonium carbamate to the passivation film on the surface of the stainless steel, and the addition amount of the oxidant is real-time regulated by using the measurement of the redox potential, so as to reduce the corrosion damage and maintenance costs.

[0008] To achieve the above object, the present invention provides the following technical solutions.

[0009] In a first aspect, the present invention provides a corrosion monitoring device for a urea hydrolyzer in a thermal power plant, comprising a corrosion factor detection sensor, a control cabinet for the urea corrosion monitoring device, and a urea solution regulation device; the corrosion factor detection sensor includes a first redox potential test sensor and a chloride ion concentration test sensor disposed inside the urea solution preparation tank, and a second redox potential test sensor disposed on the urea solution delivery pipeline; the urea solution regulation device includes an oxidant dosing tank, an oxidant dosing tank valve, an oxidant dosing valve, an oxidant dosing pump, and an oxidant dosing pipe sequentially connected to the oxidant pipeline of the urea solution preparation tank, and a urea solution tank stirrer disposed inside the urea solution preparation tank; the control cabinet of the urea corrosion monitoring device is electrically connected to the first redox potential test sensor, the chloride ion concentration test sensor, and the second redox potential test sensor respectively for collecting corrosion factors and flow information; the urea solution preparation tank is connected to the urea hydrolyzer through a urea solution delivery pipeline, and the urea solution delivery pipeline is provided with a urea solution delivery pipeline valve; the control cabinet of the urea corrosion monitoring device is electrically connected to the oxidant dosing tank valve, the oxidant dosing valve, the oxidant dosing pump, the urea solution tank stirrer, and the urea solution delivery pipeline valve respectively for regulating the corrosion factors in the urea solution.

[0010] As a further improvement of the present invention, the corrosion factor detection sensor further includes a residual liquid chloride ion concentration test valve connected to the bottom of the urea hydrolyzer through a urea hydrolysis residual liquid chloride ion concentration test interface; the control cabinet of the urea corrosion monitoring device is also electrically connected to the residual liquid chloride ion concentration test valve; the urea solution regulation device further includes a blowdown door switch and a blowdown valve disposed at the bottom of the urea hydrolyzer.

[0011] As a further improvement of the present invention, the residual liquid chloride ion concentration test valve is connected to the urea hydrolysis residual liquid chloride ion concentration test interface through a cooling device.

[0012] As a further improvement of the present invention, the corrosion factor detection sensor further includes a conductivity meter disposed on the heater drain pipeline of the urea hydrolyzer; the control cabinet of the urea corrosion monitoring device is also electrically connected to the conductivity meter.

[0013] As a further improvement of the present invention, the corrosion factor detection sensor further includes an oxidant dosing flowmeter disposed on the pipeline of the urea solution preparation tank between the oxidant dosing tank valve and the oxidant dosing valve; the control cabinet of the urea corrosion monitoring device is also electrically connected to the oxidant dosing flowmeter.

[0014] In a second aspect, the present invention provides a method for using a corrosion monitoring device for a urea hydrolyzer in a thermal power plant, comprising the following steps: When the measured data of the first redox potential test sensor is less than the lower limit of the critical redox potential, the control cabinet of the urea corrosion monitoring device controls the opening of the oxidant dosing tank valve and the oxidant dosing valve; starts the oxidant dosing pump, and adds oxidant to the urea solution; When the measured data of the first redox potential test sensor is greater than the upper limit of the critical redox potential, the control cabinet of the urea corrosion monitoring device controls the shutdown of the oxidant dosing pump; closes the oxidant dosing tank valve and the oxidant dosing valve, and stops adding oxidant to the urea solution.

[0015] As a further improvement of the present invention, when the measured data of the chloride ion concentration test sensor is less than the lower limit of the critical chloride ion concentration, the control cabinet of the urea corrosion monitoring device controls the opening of the urea solution conveying pipeline valve; conveys the urea solution to the urea solution feed hole, and thus enters the urea hydrolyzer; when the measured data of the chloride ion concentration test sensor is greater than the upper limit of the critical chloride ion concentration, the control cabinet of the urea corrosion monitoring device controls the closing of the urea solution conveying pipeline valve; stops conveying the urea solution to the urea solution feed hole.

[0016] As a further improvement of the present invention, when the difference between the measured value of the second redox potential test sensor and the measured value of the first redox potential test sensor exceeds 10% of the lower value of the two, the control cabinet of the urea corrosion monitoring device controls the urea solution tank stirrer to increase the rotation speed; When the difference between the measured value of the second redox potential test sensor and the measured value of the first redox potential test sensor is lower than 5% of the lower value of the two, the control cabinet of the urea corrosion monitoring device controls the urea solution tank stirrer to decrease the rotation speed.

[0017] As a further improvement of the present invention, when the measured value of the residual liquid chloride ion concentration test valve exceeds the upper limit of the residual liquid chloride ion concentration, the control cabinet of the urea corrosion monitoring device controls the opening and closing of the sewage discharge valve switch.

[0018] As a further improvement of the present invention, when the measured value of the conductivity meter is higher than the upper limit of the hydrophobic conductivity, the control cabinet of the urea corrosion monitoring device issues an alarm signal.

[0019] Compared with the prior art, the present invention has the following beneficial effects: A corrosion monitoring device for a urea hydrolyzer in a thermal power plant constructs a complete corrosion monitoring closed-loop system. It can real-time monitor key corrosion parameters (oxidation-reduction potential, chloride ion concentration) in the urea solution preparation tank and the conveying pipeline through multiple sensors, and achieve automatic regulation in combination with the control cabinet. This system can actively identify corrosion risks, adjust the solution composition in real time through the regulation device, avoid the lag of traditional passive anti-corrosion, and significantly improve the equipment safety and service life. The uniqueness of this device lies in adding an oxidant to the urea solution, which can inhibit the strong reduction effect of the intermediate product of urea hydrolysis and slow down the damage of ammonium carbamate to the passivation film on the stainless steel surface. This device uses oxidation-reduction potential testing to real-time regulate the addition amount of the oxidant and can achieve automatic control. The present invention reduces the corrosion of the intermediate product to the stainless steel from the source, helps to improve the safety and reliability of the urea hydrolyzer, and reduces the damage and maintenance costs caused by corrosion.

[0020] Preferably, through the chloride ion concentration test interface at the bottom of the hydrolyzer, samples are directly taken from the hydrolyzer to detect the accumulation of corrosive substances in the residual liquid. Then, according to the test value of the residual liquid chloride ion concentration test valve and the regulation of the sewage discharge valve switch, the entry of chloride ions into the urea hydrolyzer is controlled from the source, reducing the risk of stress corrosion and pitting corrosion of the stainless steel in the urea hydrolyzer. At the same time, considering the highly concentrated characteristics of the urea hydrolysis residual liquid, the chloride ion concentration in the urea hydrolysis residual liquid is monitored, and the sewage discharge of the urea hydrolyzer is controlled according to this value to ensure that the stainless steel is not in a high-concentration chloride ion environment.

[0021] Preferably, a cooling device is installed after the chloride ion concentration test interface of the urea hydrolysis residual liquid to reduce the temperature of the incoming residual liquid, protect the sensor from high-temperature damage, and improve the service life of the sensor. The cooled residual liquid is more stable, which is conducive to the sensor for more accurate measurement.

[0022] Preferably, a conductivity meter is installed on the heater drain pipe, which can real-time monitor the water quality condition in the heater drain pipe and be used as a basis for judging whether there is leakage or pollution in the pipeline.

[0023] Preferably, an oxidant dosing flow meter is installed on the oxidant pipeline, which can accurately measure the addition amount of the oxidant to ensure that the oxidant concentration in the urea solution is maintained within an appropriate range. According to the actual addition amount of the oxidant, the control cabinet can more accurately regulate the oxidation-reduction potential of the urea solution.

[0024] The present invention also discloses a usage method of a corrosion monitoring device for a urea hydrolyzer in a thermal power plant. Through preset critical values of oxidation-reduction potential and chloride ion concentration, the control cabinet can automatically regulate the addition of the oxidant and the conveyance of the urea solution to achieve intelligent management. Precise and automatic regulation reduces unnecessary energy waste, lowers the equipment operation cost, and improves the production efficiency. The regulation maintains the passivation state of the solution and ensures the safety of the urea hydrolyzer.

[0025] Optionally, an oxidant is automatically added according to the potential data to maintain the passivation state of the solution; dynamically adjusting the dosing strategy can reduce manual operation errors, ensure that the potential is stable within a safe range, and extend the corrosion-free operation time of the equipment.

[0026] Optionally, when the chloride ion concentration in the residual liquid exceeds the standard, the control cabinet can quickly open the drain valve to prevent corrosive substances from accumulating in the urea hydrolyzer; timely draining helps reduce the damage caused by corrosion and extends the service life.

[0027] Optionally, by comparing the oxidation-reduction potential difference between the inside of the tank and the pipeline, the rotation speed of the stirrer is automatically adjusted to optimize the solution homogeneity; adjusting the stirring speed can promote the rapid dispersion of the oxidant and enhance the anti-corrosion response efficiency.

[0028] Optionally, automatic draining is carried out based on the chloride ion concentration in the residual liquid to avoid omissions in manual inspection; timely removal of corrosive residual liquid can reduce the continuous damage to the inner wall of the equipment and extend the maintenance cycle.

[0029] Optionally, the alarm signal issued when the conductivity meter is abnormal can give an early warning, providing enough time for the operator to take countermeasures; reducing the risk of equipment failure or water quality pollution and ensuring the safety of the equipment and personnel. Description of the Drawings

[0030] The drawings described herein are for illustrative purposes only and are not intended to limit the scope of the disclosure of the present invention in any way. Additionally, the shapes and proportional dimensions of the various components in the drawings are only schematic and are used to assist in understanding the present invention, rather than specifically defining the shapes and proportional dimensions of the various components of the present invention. In the drawings: Figure 1 It is a schematic diagram of a corrosion monitoring device for a urea hydrolyzer in a thermal power plant according to the present invention.

[0031] Figure 2 It is a schematic diagram of installing a sensor in the urea hydrolyzer according to the present invention.

[0032] In the figure, 1 is a urea solution preparation tank; 2 is an oxidant dosing pipe; 3 is a first oxidation-reduction potential test sensor; 4 is a chloride ion concentration test sensor; 5 is a second oxidation-reduction potential test sensor; 6 is a urea solution; 7 is a valve of the oxidant dosing tank; 8 is a control cabinet of the urea corrosion monitoring device; 9 is an oxidant dosing tank; 10 is an oxidant dosing valve; 11 is an oxidant dosing flowmeter; 12 is a conductivity meter; 13 is a sewage drain valve switch; 14 is a gas production discharge pipe; 15 is a heating pipe; 16 is a urea hydrolyzer; 17 is a heater; 18 is a cooling device; 19 is a residual liquid chloride ion concentration test valve; 20 is a residual liquid chloride ion concentration test interface; 21 is a sewage drain valve; 22 is urea hydrolysis residual liquid; 23 is a urea solution transfer pipe; 24 is an oxidant dosing pump; 25 is a first test cable; 26 is a stirrer of the urea solution tank; 27 is a urea solution feed hole; 28 is a valve of the urea solution transfer pipe. Detailed implementation manners

[0033] In order to enable those skilled in the art of this technology to better understand the technical solutions in the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0034] It should be noted that when an element is referred to as being "disposed on" another element, it can be directly on the other element or there may also be an intermediate element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be an intermediate element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are only for the purpose of illustration and do not represent the only embodiments.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field of the present invention. The terms used in the description of the present invention in this specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0036] Embodiment As Figure 1 shown, the urea solution preparation tank 1 contains the urea solution 6. This embodiment provides a corrosion monitoring device for a urea hydrolyzer in a thermal power plant, including a corrosion factor detection sensor, a control cabinet 8 of the urea corrosion monitoring device, and a urea solution regulation device.

[0037] Among them, the corrosion factor detection sensor includes a first redox potential test sensor 3 and a chloride ion concentration test sensor 4 disposed inside the urea solution preparation tank 1, and a second redox potential test sensor 5 disposed on the urea solution delivery pipeline 23. The first redox potential test sensor 3 and the second redox potential test sensor 5 are respectively inserted into the urea solution in the urea solution preparation tank 1 and the urea solution delivery pipeline 23 to test the redox potential in the urea solution to evaluate the corrosion tendency of the solution; the higher the potential, the stronger the oxidizing property; the lower the potential, the weaker the oxidizing property. The chloride ion concentration test sensor 4 measures the Cl - concentration; the Cl - concentration is one of the common corrosion factors. The first redox potential test sensor 3 and the chloride ion concentration test sensor 4 are electrically connected to the control cabinet 8 of the urea corrosion monitoring device through the first test cable 25. The second redox potential test sensor 5 is electrically connected to the control cabinet 8 of the urea corrosion monitoring device through the second test cable.

[0038] Among them, the urea solution regulation device includes an oxidant dosing tank 9, an oxidant dosing tank valve 7, an oxidant dosing valve 10, an oxidant dosing pump 24, and an oxidant dosing pipe 2 connected in sequence on the oxidant pipeline of the urea solution preparation tank 1, and a urea solution tank stirrer 26 disposed at the inner bottom of the urea solution preparation tank 1. The oxidant dosing tank valve 7 is electrically connected to the control cabinet 8 of the urea corrosion monitoring device. The design of the urea solution regulation device is to ensure that the urea solution 6 maintains a stable and uniform redox potential and Cl - concentration during the preparation and delivery processes, thereby reducing the corrosion risk and improving the use efficiency and safety of the urea solution 6.

[0039] Preferably, an oxidant dosing flowmeter 11 is installed between the oxidant dosing tank valve 7 and the oxidant dosing valve 10 on the oxidant pipeline of the urea solution preparation tank 1; the control cabinet 8 of the urea corrosion monitoring device is also electrically connected to the oxidant dosing flowmeter 11 to read the oxidant dosing flow detection information for accurately quantifying the oxidant dosing amount and improving the regulation accuracy.

[0040] Among them, the control cabinet 8 of the urea corrosion monitoring device is electrically connected to the first redox potential test sensor 3, the chloride ion concentration test sensor 4, and the second redox potential test sensor 5 respectively for collecting corrosion factor and flow information.

[0041] The control cabinet 8 of the urea corrosion monitoring device is electrically connected to the oxidant dosing tank valve 7, the oxidant dosing valve 10, the oxidant dosing pump 24, and the urea solution tank stirrer 26 respectively, and is used to regulate the corrosion factors in the urea solution 6 by adjusting the opening and closing of the valves and the rotation speed of the stirrer.

[0042] As shown Figure 2 in the figure, the urea hydrolyzer 16 contains urea hydrolysis residual liquid 22, a gas production discharge pipe 14 is arranged at the upper part, a heating pipe 15 is connected to the bottom on the left side, and the heating pipe 15 is connected to a heater 17; a residual liquid chloride ion concentration test interface 20 is connected to the bottom on the right side. A urea solution feed hole 27 is arranged at the bottom of the urea hydrolyzer 16. The urea solution feed holes 27 are arranged in rows at equal intervals on a long pipe or a long groove, and the long pipe or the long groove is communicated with a urea solution delivery pipe 23, and the on-off state is controlled by a urea solution delivery pipe valve 28.

[0043] Preferably, the corrosion factor detection sensor further includes a residual liquid chloride ion concentration test valve 19; the residual liquid chloride ion concentration test interface 20 leads out the residual liquid to the residual liquid chloride ion concentration test valve 19. The residual liquid chloride ion concentration test valve 19 measures the Cl - concentration in the residual liquid, and then transmits the reading to the control cabinet 8 of the urea corrosion monitoring device, and then the control cabinet 8 of the urea corrosion monitoring device controls the sewage discharge door switch 13 at the bottom of the urea hydrolyzer 16 to open and close the sewage discharge valve 21, so as to discharge the urea hydrolysis residual liquid 22 containing a high concentration of Cl - from the urea hydrolyzer 16.

[0044] Preferably, the residual liquid chloride ion concentration test valve 19 is connected to the urea hydrolysis residual liquid chloride ion concentration test interface 20 via a cooling device 18. The cooling device 18 is used to reduce the temperature of the incoming residual liquid, protect the sensor in the residual liquid chloride ion concentration test valve 19 from high temperature damage, improve the service life of the sensor, and improve the measurement accuracy.

[0045] Preferably, the corrosion factor detection sensor further includes a conductivity meter 12; the conductivity meter 12 is arranged on the drain pipe of the heater 17 of the urea hydrolyzer 16 and is used to measure the drain water quality of the heater 17. When the conductivity meter 12 detects a significant increase in the conductivity of the drain water, it can be initially judged that the heating pipe network has corroded and leaked. Specifically, the wall thickness of the heater 17 is about 2 mm. Once corrosion occurs in the urea hydrolysis residual liquid 22 or even the heating pipe 15 breaks, the urea hydrolysis residual liquid 22 will enter the drain system, and in severe cases, it may enter the feed water system of the unit. Therefore, monitoring the drain water quality of the heater can not only monitor the corrosion condition of the urea hydrolyzer 16, but also improve the operating safety of the unit. When the conductivity meter 12 is abnormal, an alarm signal is sent to indicate a device failure or drain water quality pollution of the heater 17 to ensure the safety of the device and personnel; at this time, the temperature of the heater 17 should be controlled to decrease, and the urea hydrolyzer 16 is gradually taken out of operation.

[0046] The second object of the present invention is to provide a method for using a corrosion monitoring device for a urea hydrolyzer in a thermal power plant, Including: when the measured data of the first redox potential test sensor 3 is less than the lower critical limit of the redox potential, the control cabinet 8 of the urea corrosion monitoring device controls the opening of the oxidant dosing tank valve 7 and the oxidant dosing valve 10; starts the oxidant dosing pump 24 to add oxidant to the urea solution 6; when the measured data of the first redox potential test sensor 3 is greater than the upper critical limit of the redox potential, the control cabinet 8 of the urea corrosion monitoring device controls the closing of the oxidant dosing pump 24; closes the oxidant dosing tank valve 7 and the oxidant dosing valve 10 to stop adding oxidant to the urea solution 6. Specifically, the lower critical limit of the redox potential is A, and the upper critical limit is B.

[0047] The present invention also provides a method for using a corrosion monitoring device for a urea hydrolyzer in a thermal power plant, including: when the measured data of the chloride ion concentration test sensor 4 is less than the lower critical limit of the chloride ion concentration, the control cabinet 8 of the urea corrosion monitoring device controls the opening of the urea solution delivery pipeline valve 28; delivers the urea solution 6 to the urea solution feed hole 27, as Figure 2 shown, and thus enters the urea hydrolyzer 16; when the measured data of the chloride ion concentration test sensor 4 is greater than the upper critical limit of the chloride ion concentration, the control cabinet 8 of the urea corrosion monitoring device controls the closing of the urea solution delivery pipeline valve 28; stops delivering the urea solution 6 to the urea solution feed hole 27. Specifically, the lower critical limit of the chloride ion concentration is C, and the upper critical limit is D.

[0048] The present invention also provides a method for using a corrosion monitoring device for a urea hydrolyzer in a thermal power plant, including: when the difference between the measured value of the second redox potential test sensor 5 and the measured value of the first redox potential test sensor 3 exceeds 10% of the lower value of the two, the control cabinet 8 of the urea corrosion monitoring device controls the urea solution tank stirrer 26, as Figure 1 shown, to increase the rotation speed; when the difference between the measured value of the second redox potential test sensor 5 and the measured value of the first redox potential test sensor 3 is lower than 5% of the lower value of the two, the control cabinet 8 of the urea corrosion monitoring device controls the urea solution tank stirrer 26 to reduce the rotation speed.

[0049] The present invention also provides a method for using a corrosion monitoring device for a urea hydrolyzer in a thermal power plant, including: when the measured value of the residual liquid chloride ion concentration test valve 19 exceeds the upper limit of the residual liquid chloride ion concentration, the control cabinet 8 of the urea corrosion monitoring device controls the opening and closing of the drain valve switch 13. Specifically, the upper limit of the residual liquid chloride ion concentration can be 500 mg / L; more stringent quality control specifications for urea in thermal power plants require that the chloride ion content in the urea hydrolysis solution be strictly controlled below 100 mg / L.

[0050] The present invention also provides a method for using a corrosion monitoring device for a urea hydrolyzer in a thermal power plant, including: when the measured value of the conductivity meter 12 is higher than the upper limit of the hydrophobic conductivity, the urea corrosion monitoring device control cabinet 8 emits an alarm signal.

[0051] Upon reading the above description, many embodiments and many applications other than the provided examples will be apparent to those skilled in the art. Therefore, the scope of this teaching should not be determined with reference to the above description, but should be determined with reference to the full scope of the foregoing claims and the equivalents thereof. For the sake of completeness, all articles and references including patent applications and published announcements are incorporated herein by reference. The omission of any aspect of the subject matter disclosed herein in the foregoing claims is not intended to abandon such subject matter, nor should the applicant be regarded as not considering such subject matter as part of the disclosed inventive subject matter.

[0052] The above content is a further detailed description of the present invention. It cannot be determined that the specific implementation of the present invention is limited thereto. For those of ordinary skill in the technical field to which the present invention pertains, without departing from the concept of the present invention, several simple deductions or substitutions can be made, and all should be regarded as belonging to the protection scope determined by the claims submitted for the present invention.

Claims

1. A corrosion monitoring device for a urea hydrolyzer in a thermal power plant, characterized in that: It includes a corrosion factor detection sensor, a urea corrosion monitoring device control cabinet (8), and a urea solution regulation device; The corrosion factor detection sensor includes a first redox potential test sensor (3) and a chloride ion concentration test sensor (4) arranged inside a urea solution preparation tank (1), and a second redox potential test sensor (5) arranged on a urea solution delivery pipeline (23); The urea solution regulation device includes an oxidant dosing tank (9), an oxidant dosing tank valve (7), an oxidant dosing valve (10), an oxidant dosing pump (24), and an oxidant dosing pipe (2) connected in sequence on the oxidant pipeline of the urea solution preparation tank (1), and a urea solution tank stirrer (26) arranged inside the urea solution preparation tank (1); The urea corrosion monitoring device control cabinet (8) is electrically connected to the first redox potential test sensor (3), the chloride ion concentration test sensor (4), and the second redox potential test sensor (5) respectively, and is used for collecting corrosion factor and flow information; The urea solution preparation tank (1) is connected to a urea hydrolyzer (16) through a urea solution delivery pipeline (23), and the urea solution delivery pipeline (23) is provided with a urea solution delivery pipeline valve (28); The urea corrosion monitoring device control cabinet (8) is electrically connected to the oxidant dosing tank valve (7), the oxidant dosing valve (10), the oxidant dosing pump (24), the urea solution tank stirrer (26), and the urea solution delivery pipeline valve (28) respectively, and is used for regulating the corrosion factors in the urea solution.

2. A corrosion monitoring device for a urea hydrolyzer in a thermal power plant according to claim 1, characterized in that: The corrosion factor detection sensor further includes a residual liquid chloride ion concentration test valve (19) connected to the bottom of the urea hydrolyzer (16) through a urea hydrolysis residual liquid chloride ion concentration test interface (20); The urea corrosion monitoring device control cabinet (8) is also electrically connected to the residual liquid chloride ion concentration test valve (19); The urea solution regulation device further includes a blowdown door switch (13) and a blowdown valve (21) arranged at the bottom of the urea hydrolyzer (16).

3. The corrosion monitoring device for the urea hydrolyzer in a thermal power plant according to claim 2, characterized in that: It further includes a cooling device (18), and the residual liquid chloride ion concentration test valve (19) is connected to the urea hydrolysis residual liquid chloride ion concentration test interface (20) through the cooling device (18).

4. A corrosion monitoring device for a urea hydrolyzer in a thermal power plant according to claim 1, characterized in that: The corrosion factor detection sensor further includes a conductivity meter (12), and the conductivity meter (12) is arranged on the drain pipeline of a heater (17) of the urea hydrolyzer (16); The urea corrosion monitoring device control cabinet (8) is also electrically connected to the conductivity meter (12).

5. A corrosion monitoring device for a urea hydrolyzer in a thermal power plant according to claim 1, characterized in that: The corrosion factor detection sensor further includes an oxidant dosing flowmeter (11) arranged on the pipeline of the urea solution preparation tank (1) between the oxidant dosing tank valve (7) and the oxidant dosing valve (10); The control cabinet (8) of the urea corrosion monitoring device is also electrically connected to the oxidant dosing flowmeter (11).

6. The method for using a corrosion monitoring device for a urea hydrolyzer in a thermal power plant according to any one of claims 1-5, characterized in that: When the measured data of the first redox potential test sensor (3) is less than the lower limit of the critical redox potential, the control cabinet (8) of the urea corrosion monitoring device controls the opening of the oxidant dosing tank valve (7) and the oxidant dosing valve (10); starts the oxidant dosing pump (24), and adds an oxidant to the urea solution (6). When the measured data of the first redox potential test sensor (3) is greater than the upper limit of the critical redox potential, the control cabinet (8) of the urea corrosion monitoring device controls the closing of the oxidant dosing pump (24); closes the oxidant dosing tank valve (7) and the oxidant dosing valve (10), and stops adding the oxidant to the urea solution (6).

7. The method for using a corrosion monitoring device for a urea hydrolyzer in a thermal power plant according to any one of claims 1-5, characterized in that: When the measured data of the chloride ion concentration test sensor (4) is less than the lower limit of the critical chloride ion concentration, the control cabinet (8) of the urea corrosion monitoring device controls the opening of the urea solution delivery pipeline valve (28); Transports the urea solution (6) to the urea solution feed hole (27), and thus enters the urea hydrolyzer (16); When the measured data of the chloride ion concentration test sensor (4) is greater than the upper limit of the critical chloride ion concentration, the control cabinet (8) of the urea corrosion monitoring device controls the closing of the urea solution delivery pipeline valve (28); Stops transporting the urea solution (6) to the urea solution feed hole (27).

8. The method for using a corrosion monitoring device for a urea hydrolyzer in a thermal power plant according to any one of claims 1-5, characterized in that: When the measured value of the second redox potential test sensor (5) differs from the measured value of the first redox potential test sensor (3) by more than 10% of the lower value of the two, the control cabinet (8) of the urea corrosion monitoring device controls the urea solution tank stirrer (26) to increase the rotation speed; When the measured value of the second redox potential test sensor (5) differs from the measured value of the first redox potential test sensor (3) by less than 5% of the lower value of the two, the control cabinet (8) of the urea corrosion monitoring device controls the urea solution tank stirrer (26) to decrease the rotation speed.

9. The method for using a corrosion monitoring device for a urea hydrolyzer in a thermal power plant according to claim 2 or 3, characterized in that: When the measured value of the residual liquid chloride ion concentration test valve (19) exceeds the upper limit of the residual liquid chloride ion concentration, the control cabinet (8) of the urea corrosion monitoring device controls the opening and closing of the blowdown valve switch (13).

10. The method for using a corrosion monitoring device for a urea hydrolyzer in a thermal power plant according to claim 4, characterized in that, Including: When the measured value of the conductivity meter (12) is higher than the upper limit of the hydrophobic conductivity, the control cabinet (8) of the urea corrosion monitoring device emits an alarm signal.

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