Active organic amine anti-corrosion protective agent for shutdown of power generation boiler unit

Abstract

The invention discloses a power generation boiler unit shutdown active organic amine anticorrosion protective agent, which is prepared by adding 3-10 mg / L of cyclohexylamine, 1-5 mg / L of octanoic acid dicyclohexylamine, 10-30 mg / L of tetramethylmorpholine, 10-20 mg / L of diethylhydroxylamine and 10-20 mg / L of diethylaminoethanol into a solvent, and the solvent is deionized water or demineralized water. The use pH environment of the protective agent is 9.5-10.0, the temperature is 250-450 DEG C, the protective agent is good in water solubility, non-toxic, full-volatile and free of obvious side effects on a thermodynamic system, dissolved solids of the system cannot be increased, and when the protective agent is used, the pH of boiler water is stabilized to 9.5-10.0 by using ammonia water. A laboratory research test and an industrial test prove that the protective agent has good protection performance on metal of a water vapor system of a boiler unit, is convenient to use, has no influence on equipment in the boiler unit system, has an excellent atmospheric corrosion resistance effect, and can be widely applied to shutdown and standby protection of the power generation boiler unit.

Description

Technical Field

[0001] The present invention belongs to the technical field of boiler equipment shutdown protection in the power industry, and particularly relates to an anticorrosive protection agent of active organic amine for a deactivated power generation boiler unit. Background Art

[0002] In recent years, with the large-scale operation of new energy power generation, most thermal power generating units tend to operate in peak shaving mode, and the units are often in a standby state. During the standby period, if effective protection measures are not taken, oxygen corrosion will occur in the water-vapor system of the unit. The electrochemical corrosion process is as follows:

[0003] Anodic reaction: 2Fe - 4e → 2Fe 2+

[0004] Cathodic reaction: 2H2O + O2 + 4e → 4OH-

[0005] After the deactivation corrosion occurs, the corrosion products will increase the flushing and sewage discharge volume during the next unit startup, which not only prolongs the startup time, but also wastes a great deal of demineralized water, increasing the operation cost of the unit. At the same time, the occurrence of shutdown corrosion will also increase the scaling rate of the furnace tubes, accelerate the corrosion rate during boiler operation, and in severe cases, it may cause the furnace tubes to burst within a short period.

[0006] At present, the shutdown and standby protection methods for boiler units include the nitrogen filling protection method, the wet protection method of filling the protection liquid, and the octadecylamine high-temperature film-forming protection method, etc. The operability of these traditional methods is relatively poor, and most power plant operators are reluctant to use them. Among them, the nitrogen filling protection method and the wet protection method of filling the protection liquid are not only relatively cumbersome to operate, but also require detecting the concentration of the protection liquid or the gas pressure, and the control requirements are strict. Insufficient concentration of the protection liquid or insufficient gas pressure of the protection gas has a great impact on the protection effect, resulting in an unsatisfactory protection effect. The commonly used octadecylamine high-temperature film-forming protection method has the advantages of forming a film once, without post-maintenance, detection and control problems, and stable protection performance, but its disadvantages are also particularly obvious. First of all, octadecylamine is a long-chain primary amine with a high freezing point, high viscosity, and low solubility in water. Improper dosing operation is likely to block the sampling and pressure systems of the unit, affecting the normal operation and detection of the unit. Secondly, it is easy to contaminate the polishing resin, and the contaminated resin can hardly be regenerated and restored, which will cause the polishing equipment to completely fail. Finally, when a large number of octadecylamine molecules adsorb on the inner wall of the metal in the entire water-vapor system, a large amount of water flushing must be carried out during startup until the octadecylamine concentration in the boiler water drops to the qualified range, leading to new problems such as prolonged startup flushing time and increased water consumption. Therefore, similar products will also be gradually phased out. Summary of the Invention

[0007] The object of the present invention is to overcome the deficiencies of gas protection, wet protection, and octadecylamine-based protectants, and effectively solve the problems of cumbersome operation, increased flushing time, and water consumption in the shutdown protection of units. The present invention provides an active organic amine anti-corrosion protectant that is convenient to operate, has excellent protection performance, and does not affect the safe operation of the unit. This anti-corrosion protectant abandons the use of the long-chain macromolecular component octadecylamine, and uses five small-molecule organic amine components with different structures and vapor pressures to form a film synergistically. It can not only effectively ensure the film-forming quality, but also avoid the influence of the introduced long-chain macromolecular organic matter on the resin system. Moreover, the functional groups of the pharmaceutical molecules used are simple, and even if they decompose at high temperatures, they will not have a significant impact on the pH of the boiler water.

[0008] The active organic amine anti-corrosion protectant for shutdown of power generation boiler units provided by the present invention is prepared by compounding 3 - 10 mg of cyclohexylamine, 1 - 5 mg of dicyclohexylamine octanoate, 10 - 30 mg of tetramethylmorpholine, 10 - 20 mg of diethylhydroxylamine, and 10 - 20 mg of diethylaminoethanol in each liter of solvent, and the solvent is demineralized water or deionized water.

[0009] Furthermore, the active organic amine anti-corrosion protectant for shutdown of power generation boiler units of the present invention is preferably prepared by compounding 5 - 8 mg of cyclohexylamine, 3 - 4 mg of dicyclohexylamine octanoate, 18 - 25 mg of tetramethylmorpholine, 14 - 16 mg of diethylhydroxylamine, and 14 - 16 mg of diethylaminoethanol in each liter of solvent.

[0010] Furthermore, when using the active organic amine anti-corrosion protectant for shutdown of power generation boiler units of the present invention, it is necessary to strictly control the pH of the boiler water between 9.5 and 10.0. If the pH of the boiler water is lower than 9.5, ammonia water needs to be added to control the pH of the boiler water within the above range.

[0011] Furthermore, the preferred use temperature of the active organic amine anti-corrosion protectant for shutdown of power generation boiler units of the present invention is between 250 and 450 °C.

[0012] The preparation method of the active organic amine anti-corrosion protectant for shutdown of power generation boiler units of the present invention is as follows: Heat the solvent to 40 - 50 °C, first add cyclohexylamine and dicyclohexylamine octanoate, stir evenly, then add tetramethylmorpholine, diethylhydroxylamine, and diethylaminoethanol in sequence, and continue to stir for 30 - 60 minutes to obtain a uniform and stable protectant.

[0013] The beneficial effects of the present invention are as follows:

[0014] The protective agent of the present invention is a fully volatile nitrogen-containing compound, which is non-toxic, has good water solubility, has no side effects on the thermal system, and does not increase the dissolved solids in the system. The protective agent has hydrophilic groups and hydrophobic groups, and can form a dense and complete protective film on the inner wall of the metal through intermolecular adsorption complementarity. This protective film has good stability and a long protection period, and can effectively protect the economizer, water wall, steam drum / start-up system, superheater, reheater, feed water pump, deaerator, steam turbine, high and low pressure heaters system, condenser steam side, etc. It is convenient to use on-site and can be directly put into the furnace through the ammonia addition system. Detailed implementation mode

[0015] The following further details the present invention in conjunction with embodiments, but the protection scope of the present invention is not limited to these embodiments.

[0016] During the experimental stage, the researchers conducted a large number of single-component screening tests and multi-component orthogonal tests. During the tests, three test pieces of each of the materials 20G, 210C, 15CrMo, 12Cr1MoV, T23, and T91 with a roughness polished to Ra 0.8μm were hung into a high-pressure autoclave containing the prepared protective agent. The pH of the protective agent was controlled between 9.5 and 10.0. Half of the test piece was immersed in the protective agent and half was above the liquid surface, and the film was formed at 150°C, 250°C, and 450°C for 2 hours respectively. After film formation, it was found that according to the raw material composition and concentration ratio of the present invention, the test pieces had good hydrophobicity under the three working conditions. The rusting time ranges of the three groups of test pieces were detected to be about 75 - 82 days, 104 - 110 days, and 125 - 130 days respectively when the film-formed indicator pieces were hung indoors for corrosion resistance detection and observation. The representative test data are shown in Table 1. Different masses of organic amines were added to 1L of deionized water to prepare the protective agents No. 1 to No. 6 shown in Table 1, and the film formation test was carried out at 450°C according to the above method. The test results are shown in Table 1 below.

[0017] Table 1

[0018]

[0019] It can be seen from the data in Table 1 that the five components in the protective agent of the present invention act synergistically with each other, and the corrosion protection performance decreases significantly if any one component is missing.

[0020] Example 1

[0021] Heat 1L of deionized water to 40 - 50°C. First, add 3mg of cyclohexylamine and 5mg of dicyclohexylamine octanoate, and stir until the cyclohexylamine and dicyclohexylamine octanoate are completely dissolved. Then add 10mg of tetramethylmorpholine, 20mg of diethylhydroxylamine, and 20mg of diethylaminoethanol, and continue to stir for 1h to prepare a homogeneous and stable protective agent.

[0022] Example 2

[0023] Heat 1 L of deionized water to 40 - 50 °C. First, add 7 mg of cyclohexylamine and 4 mg of dicyclohexylamine octanoate. After stirring until the cyclohexylamine and dicyclohexylamine octanoate are completely dissolved, then add 15 mg of tetramethylmorpholine, 15 mg of diethylhydroxylamine, and 15 mg of diethylaminoethanol. Continue stirring for 1 h to prepare a homogeneous and stable protective agent.

[0024] Example 3

[0025] Heat 1 L of deionized water to 40 - 50 °C. First, add 8 mg of cyclohexylamine and 3 mg of dicyclohexylamine octanoate. After stirring until the cyclohexylamine and dicyclohexylamine octanoate are completely dissolved, then add 20 mg of tetramethylmorpholine, 12 mg of diethylhydroxylamine, and 12 mg of diethylaminoethanol. Continue stirring for 1 h to prepare a homogeneous and stable protective agent.

[0026] Example 4

[0027] Heat 1 L of desalted water to 40 - 50 °C. First, add 9 mg of cyclohexylamine and 2 mg of dicyclohexylamine octanoate. After stirring until the cyclohexylamine and dicyclohexylamine octanoate are completely dissolved, then add 25 mg of tetramethylmorpholine, 12 mg of diethylhydroxylamine, and 12 mg of diethylaminoethanol. Continue stirring for 1 h to prepare a homogeneous and stable protective agent.

[0028] Example 5

[0029] Heat 1 L of desalted water to 40 - 50 °C. First, add 10 mg of cyclohexylamine and 1 mg of dicyclohexylamine octanoate. After stirring until the cyclohexylamine and dicyclohexylamine octanoate are completely dissolved, then add 30 mg of tetramethylmorpholine, 10 mg of diethylhydroxylamine, and 10 mg of diethylaminoethanol. Continue stirring for 1 h to prepare a homogeneous and stable protective agent.

[0030] Test the anti-corrosion performance of the protective agents in Examples 1 - 5 above. During the test, three test pieces of each of the materials 20G, 210C, 15CrMo, 12Cr1MoV, T23, and T91 with smooth surfaces were respectively hung into an autoclave containing the protective agent. Control the pH of the protective agent between 9.5 and 10.0. Keep half of the test piece immersed in the protective agent and half above the liquid surface, and form a film at 150 °C, 250 °C, and 450 °C for 2 h respectively. After film formation, it was found that the test pieces had good hydrophobicity under all three working conditions. Hang the film-formed indicator pieces indoors for corrosion resistance detection and observation. The rusting time ranges of the test pieces at different temperatures were detected to be 75 - 82 days, 104 - 110 days, and 125 - 130 days respectively. The higher the temperature, the better the film-forming protection effect. Table 2 below shows the corrosion resistance effects of the test pieces after film formation at 450 °C of the protective agents in Examples 1 - 5.

[0031] Table 2 Corrosion resistance effects of the protective agents in Examples 1 - 5 after film formation at 450 °C against atmospheric corrosion

[0032]

[0033]

[0034] As can be seen from the data in Table 2, the protective agent of the present invention can fully meet the requirements of outage protection during the major overhaul of the unit for 2 to 3 months, and the optimal use effect is achieved within the temperature range of 250°C to 450°C.

[0035] In order to further verify the protective effect of the present invention, an industrial test was carried out on a 600MW supercritical unit in southern Shaanxi using the protective agent of Example 1. The test conditions are as follows:

[0036] Project introduction: The boiler of the 600MW unit in this power plant is manufactured by Shanghai Boiler Works. The outage protection scope includes the condensate system, feed water system, deaerator, economizer, water wall, superheater system and high-temperature reheater. Among them, the volume of the water-vapor system during operation is about 1600M 3 . The protection of metals of various materials such as 20G, 210C, 12Cr1MoV, 15CrMo, T23, T91, and TP347H is involved.

[0037] Before the unit shutdown, according to the ratio in Example 1, 4.8 kg of cyclohexylamine, 8 kg of dicyclohexylamine octanoate, 16 kg of tetramethylmorpholine, 20 kg of diethylhydroxylamine, 20 kg of diethylaminoethanol, and the balance being demineralized water were used to prepare 1 ton of protective agent. Before the unit shutdown, it was added into the furnace using the in-plant ammonia addition system, and the film was formed for 2 h, and then the furnace was stopped for drainage. After the drainage was completed and cooled, the condenser and the feed water system were opened to check that the metal surface was steel gray and had excellent hydrophobicity. For the water wall, superheater, and reheater system pipe samples, pipe cutting and sampling were carried out for inspection. The inner walls of these system pipe samples had excellent film formation and strong hydrophobicity. The unit was overhauled and out of service for 75 days. Before the system was sealed for inspection, the metals at these parts were still steel gray and there were no corrosion phenomena such as redness or yellowing.

[0038] An industrial test was carried out on a 300MW drum boiler unit in Henan using the protective agent of Example 2. The test conditions are as follows:

[0039] Project introduction: The unit of this power plant is a 300MW boiler unit manufactured by Harbin Boiler Works. The outage protection scope includes the condensate system, feed water system, deaerator, economizer, water wall, steam drum, superheater, and reheater. Among them, the volume of the water system during operation is about 1400M 3 . The protection of metals of various materials such as 20G, 210C, 12Cr1MoV, T23, T91, and TP347H is involved.

[0040] When the unit is shut down for maintenance, 1 ton of protective agent prepared from 9.8 kg of cyclohexylamine, 5.6 kg of dicyclohexylamine octoate, 21 kg of tetramethylmorpholine, 21 kg of diethylhydroxylamine, 21 kg of diethylaminoethanol and the balance of demineralized water is added using the in-plant ammonia addition system. It is run for film formation for 2 hours and then the boiler is stopped for drainage. After the drainage is completed and it cools down, the condenser and the feed water system are opened to check that the metal surface is steel gray and has excellent hydrophobicity. Samples are taken by cutting pipes from the water wall, steam drum, superheater and reheater systems. Excellent protective films are formed on the inner walls of these systems and they have strong hydrophobicity. The unit is shut down for maintenance for 92 days. Before the system is sealed, it is checked that the metal at these parts is still steel gray and there are no corrosion phenomena such as redness or yellowing.

[0041] Industrial tests show that the protective agent of the present invention has good film-forming protection performance, and the implementation method is simple and feasible, and it can be widely applied to the protection of large generator sets during shutdown and standby operation.

Claims

1. An active organic amine anticorrosion protective agent for deactivating a power generation boiler unit, characterized in that: The protective agent is prepared by adding 3-10 mg cyclohexylamine, 1-5 mg octanoic acid dicyclohexylamine, 10-30 mg tetramethylmorpholine, 10-20 mg diethylhydroxylamine and 10-20 mg diethylaminoethanol into each liter of solvent. The solvent is deionized water or deionized water.

2. The deactivation active organic amine anticorrosion protective agent for power generation boiler units according to claim 1, characterized in that: The protective agent is prepared by adding 5-8 mg of cyclohexylamine, 3-4 mg of dicyclohexylamine octanoate, 18-25 mg of tetramethylmorpholine, 14-16 mg of diethylhydroxylamine and 14-16 mg of diethylaminoethanol into each liter of solvent.

3. The deactivation active organic amine anticorrosion protective agent for power generation boiler units according to claim 1 or 2, characterized in that: When the protective agent is used, the pH of the boiler water needs to be strictly controlled between 9.5 and 10.

0.

4. The deactivation active organic amine anticorrosion protective agent for power generation boiler units according to claim 3, characterized in that: If the pH of the boiler water is lower than 9.5, add ammonia water to control the pH of the boiler water within the above range.

5. The deactivation active organic amine anticorrosion protective agent for power generation boiler units according to claim 1 or 2, characterized in that: The protective agent is used at a temperature between 250 and 450°C.

6. The deactivation active organic amine anticorrosion protective agent for power generation boiler units according to claim 1 or 2, characterized in that: When preparing the protective agent, the solvent is heated to 40-50° C., cyclohexylamine and dicyclohexylamine octanoate are first added, and after stirring evenly, tetramethylmorpholine, diethylhydroxylamine and diethylaminoethanol are added in sequence, and stirring is continued for 30-60 minutes to obtain a uniform and stable protective agent.

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