A boiler shutdown protection agent for a thermal power plant

Abstract

The application provides a boiler shutdown protection agent for thermal power plant, which is an aqueous solution containing octadecylamine, triethanolamine, diethylenetriamine, morpholine and cyclohexylamine; when used, the shutdown protection agent is added into the boiler water, so that the octadecylamine in the boiler water is 1-5 mg / L, the triethanolamine is 10-30 mg / L, the diethylenetriamine is 5-15 mg / L, the morpholine is 5-20 mg / L, and the cyclohexylamine is 10-30 mg / L. The shutdown protection agent is non-toxic, has good water solubility, has no side effect on the thermal system, does not increase the dissolved solids in the system, and when used, the pH of the boiler water can be stabilized to 9.5-10.5 by using ammonia water. The laboratory research test, small-scale test and industrial test prove that the shutdown protection agent has good protection performance on the metal of the boiler unit water vapor system, and the protection agent is convenient to use and has no influence on the equipment in the boiler unit system; the industrial test proves that the protection agent has excellent atmospheric corrosion resistance, and can be widely applied to the shutdown protection of large boilers.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of boiler shutdown protection in the power industry, and particularly relates to a boiler shutdown protection agent and a preparation method thereof. BACKGROUND

[0002] Thermal power generating units, regardless of the parameters and the capacity, are inevitably shut down for maintenance or in standby state. During the standby period, if effective protection measures are not taken, the water-steam system of the unit will be exposed to the atmospheric environment, which will cause corrosion. This corrosion is called "standby corrosion", which is an electrochemical corrosion and is expressed as follows:

[0003] Anode reaction: 2Fe-4e→2Fe 2+

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

[0005] After the standby corrosion occurs, the corrosion products will increase the flushing and blowdown amount during the next unit startup, prolong the startup time, and at the same time, can increase the fouling rate of the boiler tube and aggravate the corrosion of the boiler operation, and in severe cases, will lead to pipe explosion.

[0006] At present, the methods for protecting the boiler unit during shutdown usually include nitrogen gas protection method, wet protection method by filling protective liquid, and high-temperature film protection by using octadecylamine protective liquid. These methods have their own advantages and disadvantages. The nitrogen gas protection agent and the protective liquid method are relatively cumbersome to operate, require strict control, and need to be detected regularly. If the detection control is not suitable, the protection effect will be reduced and the protection period will be shortened. The high-temperature film protection method by using octadecylamine protective liquid has the advantages of one-time film formation, no later maintenance and detection control, and stable protection performance, and is more and more widely used in power enterprises.

[0007] Single agent will have its inherent disadvantages. With the large application of octadecylamine shutdown protection agent in the standby process of domestic units, its disadvantages and side effects have gradually appeared. First, octadecylamine is a long-chain primary amine, which has the characteristics of high freezing point, large viscosity and low solubility in water. Therefore, improper addition operation is easy to cause blockage of the unit sampling and pressure detection system, affecting the normal operation detection of the unit. Second, the molecular chain of octadecylamine is long, which is easy to pollute the polishing resin. The polluted resin cannot be regenerated and recovered, which will cause the polishing equipment to be completely disabled. Third, after the film is formed by using the octadecylamine protective agent, a large amount of octadecylamine molecules will be adsorbed on the metal inner wall of the entire water-steam system. The polishing system cannot be put into operation during the next startup, and a large amount of water flushing must be carried out until the octadecylamine concentration in the boiler water is reduced to the qualified range, otherwise the polishing resin will be polluted. SUMMARY

[0008] The present application aims at overcoming the shortcomings of octadecylamine protective agent, and provides a protective agent with excellent protection performance and without affecting the safe operation of the boiler unit of a thermal power plant.

[0009] To achieve the above object, the present application adopts a thermal power plant boiler shutdown protective agent containing octadecylamine, triethanolamine, diethylene triamine, morpholine and cyclohexylamine in an aqueous solution; when used, the shutdown protective agent is added to the boiler water, so that the concentration of octadecylamine in the boiler water is 1-5 mg / L, the concentration of triethanolamine is 10-30 mg / L, the concentration of diethylene triamine is 5-15 mg / L, the concentration of morpholine is 5-20 mg / L, and the concentration of cyclohexylamine is 10-30 mg / L.

[0010] Further, when used, the present application preferably uses the following concentrations of the components in the boiler water: the concentration of octadecylamine is 3-5 mg / L, the concentration of triethanolamine is 15-25 mg / L, the concentration of diethylene triamine is 8-12 mg / L, the concentration of morpholine is 10-15 mg / L, and the concentration of cyclohexylamine is 15-20 mg / L.

[0011] The water in the above-mentioned shutdown protective agent can be deionized water or desalted water.

[0012] When the shutdown protective agent of the present application is prepared, the water is first heated to 40-50℃, then octadecylamine is added, and after uniform stirring, triethanolamine, diethylene triamine, morpholine and cyclohexylamine are added in sequence, and the mixture is continuously stirred until uniform.

[0013] When the shutdown protective agent of the present application is used, the pH of the boiler water needs to be strictly controlled within 9.5-10.5, and if the pH is lower, ammonia water needs to be added to control the pH of the boiler water within the range.

[0014] The use temperature of the shutdown protective agent of the present application is preferably 250-400℃.

[0015] The present application has the following beneficial effects:

[0016] 1. The present application reduces the use amount of long-chain macromolecular component octadecylamine, and uses four small-molecular components with different structures to form a film in cooperation, so that the film forming quality can be ensured, and the use amount of long-chain macromolecular component can be effectively reduced to reduce the influence of the protective agent on the resin of the polishing equipment.

[0017] 2. The furnace shutdown protective agent is a complex film forming protective agent with excellent solubility, is a nitrogen-containing compound, is non-toxic, has good water solubility, has no side effects on the thermal system, and does not increase the dissolved solids of the system. It has a hydrophilic group and a hydrophobic group, can react with metals to form a dense and complete protective film, the protective film has good stability and long protection period; the water supply pump, deaerator, steam turbine, high and low adding system, condenser steam side and the like can be effectively protected; the on-site use is convenient, the dosing system is simple, the on-site workload is small, and the non-planned furnace shutdown can also be used. DETAILED DESCRIPTION

[0018] The application will be further described in detail below in combination with examples, but the protection scope of the application is not limited to these examples.

[0019] Example 1

[0020] 800 mL of deionized water is heated to 40-50℃, 1 mg of octadecylamine is first added, after uniform stirring, 30 mg of triethanolamine, 10 mg of diethylenetriamine, 20 mg of morpholine, 20 mg of cyclohexylamine are sequentially added, and the medicament is uniformly mixed by continuing to stir for 1 hour, poured into a 1000 mL volumetric flask and diluted with deionized water to obtain a uniform and stable solution, namely the furnace shutdown protective agent.

[0021] Example 2

[0022] 800 mL of deionized water is heated to 40-50℃, 3 mg of octadecylamine is first added, after uniform stirring, 10 mg of triethanolamine, 15 mg of diethylenetriamine, 15 mg of morpholine, 15 mg of cyclohexylamine are sequentially added, and the medicament is uniformly mixed by continuing to stir for 1 hour, poured into a 1000 mL volumetric flask and diluted with deionized water to obtain a uniform and stable solution, namely the furnace shutdown protective agent.

[0023] Example 3

[0024] 800 mL of deionized water is heated to 40-50℃, 5 mg of octadecylamine is first added, after uniform stirring, 10 mg of triethanolamine, 5 mg of diethylenetriamine, 15 mg of morpholine, 10 mg of cyclohexylamine are sequentially added, and the medicament is uniformly mixed by continuing to stir for 1 hour, poured into a 1000 mL volumetric flask and diluted with deionized water to obtain a uniform and stable solution, namely the furnace shutdown protective agent.

[0025] Example 4

[0026] 800 mL of deionized water is heated to 40-50℃, 5 mg of octadecylamine is first added, after uniform stirring, 10 mg of triethanolamine, 10 mg of diethylenetriamine, 10 mg of morpholine, 15 mg of cyclohexylamine are sequentially added, and the medicament is uniformly mixed by continuing to stir for 1 hour, poured into a 1000 mL volumetric flask and diluted with deionized water to obtain a uniform and stable solution, namely the furnace shutdown protective agent.

[0027] In order to determine the technical solutions that prove the beneficial effects of the present application, the inventors have carried out a large number of research tests and industrial tests, the details of which are as follows:

[0028] 1. Research tests

[0029] Smoothed 20G, 15CrMo, 12Cr1MoV, T23, T91 material test pieces were hung in an autoclave containing the shutdown protection agent of Example 1, ammonia was added to control the pH of the shutdown protection agent to be between 9.5 and 10.5, and the test pieces were half immersed in the shutdown protection agent and half on the liquid surface, and film formation was carried out at 150°C, 250°C and 400°C for 2 hours. After film formation, it was found that the test pieces had good hydrophobicity under the three working conditions. The indicator pieces after film formation were hung in a naturally ventilated room, the relative humidity during the test period was 76% to 93%, and the room temperature was 20 to 38°C, corrosion detection was observed, and it was detected that the time range for rusting on the test pieces under the three working conditions was 85 to 92 days, 120 to 136 days and 143 to 152 days, respectively, indicating that the shutdown protection agent of the present application can completely meet the protection requirements during the 2 to 4 month overhaul period of the unit when the temperature is greater than 250°C, and the temperature is optimal in the range of 250°C to 400°C.

[0030] Similarly, smoothed 20G, 15CrMo, 12Cr1MoV, T23, T91 material test pieces were hung in an autoclave containing the shutdown protection agent of Example 2, ammonia was added to control the pH of the shutdown protection agent to be between 9.5 and 10.5, and the test pieces were half immersed in the shutdown protection agent and half on the liquid surface, and film formation was carried out at 150°C, 250°C and 400°C for 2 hours. After film formation, it was found that the test pieces had good hydrophobicity under the three working conditions. The indicator pieces after film formation were hung in a naturally ventilated room, the relative humidity during the test period was 76% to 93%, and the room temperature was 20 to 38°C, corrosion detection was observed, and it was detected that the time range for rusting on the test pieces under the three working conditions was 103 to 112 days, 162 to 170 days and 160 to 172 days, respectively, and similarly the optimal temperature range for the protection agent was 250°C to 400°C.

[0031] Similarly, the 20G, 15CrMo, 12Cr1MoV, T23, T91 material test piece is hung into the high pressure vessel containing the shutdown protection agent of Example 3, ammonia is added to control the pH of the shutdown protection agent between 9.5-10.5, and the test piece is half immersed in the shutdown protection agent and half on the liquid surface, respectively at 150°C, 250°C, 400°C for 2h. After film formation, it is found that the test pieces under the three working conditions have good hydrophobicity. The film-formed test piece is hung in a naturally ventilated room, the relative humidity in the test period is 76%-93%, the room temperature is 20-38°C, and the corrosion detection observation is carried out, and the rust time range of the test piece under the three working conditions is detected to be 108-117 days, 166-176 days, 169-178 days, and the protective agent is used at a temperature of 250°C-400°C.

[0032] 2. Industrial test

[0033] (1) The shutdown protection agent of Example 1 is used in an industrial test of a 300MW unit in the south of Shaanxi Province, and the test conditions are as follows:

[0034] Project introduction: The unit of the power plant is a 300MW boiler produced by Shanghai Boiler Plant. The shutdown protection range includes the condensate system, the feedwater system, the deaerator, the economizer, the water wall, the superheater system and the high-temperature reheater, among which the water system is about 800M 3 during operation. It involves the protection of various materials such as 20G, 210C, 12Cr1MoV, T23, T91, TP347H, etc.

[0035] During the shutdown maintenance of the unit, according to the following dosing steps, 1mg of octadecylamine, 30mg of triethanolamine, 10mg of diethylene triamine, 20mg of morpholine and 20mg of cyclohexylamine are added per liter of boiler water, and the film is formed during operation. Drainage during shutdown.

[0036] Dosing operation steps:

[0037] (1) 48 hours before the unit is shut down, sufficient ammonia water and shutdown protection agent are prepared, and the dosing system is tested well;

[0038] (2) 8 hours before shutdown, the chief engineer of the power plant informs the turbine, boiler, chemical and operation professionals to completely isolate the unit to be maintained from other running units, and no water or steam should enter other running units; the inlet and outlet doors of the high-speed mixed bed of the condensate polishing treatment are closed;

[0039] (3) When the unit is sliding to a main steam temperature of 400°C, the shutdown protection agent is added to the water and steam system, and the dosing time is controlled within 1.5 hours;

[0040] (4) When the water vapor temperature of the unit is reduced to 200-300℃, stable operation is carried out for 2-3 hours to ensure that the medicament is fully and uniformly circulated and a protective film is formed;

[0041] (5) If the unit is stopped during the medicament adding process, the high and low bypass circulation of the steam turbine should be started, and the medicament adding and circulation (or soaking for 3 hours) should be continued;

[0042] (6) After the unit is circulated for 2-3 hours, the water in the furnace is strictly discharged and the residual heat is dried to ensure that the water in the furnace is completely discharged.

[0043] After the discharge is completed and the condenser and the water supply system are opened, the metal surface is steel gray, and the surface has excellent hydrophobicity. The water-cooled wall, superheater and reheater system pipe samples are cut and sampled for inspection, and the inner wall of these system pipe samples has excellent film forming and strong hydrophobicity. The unit is shut down for maintenance for 78 days, and before the system is closed, the metal at these positions is still steel gray, without redness, yellowing and rusting.

[0044] (2) The shutdown protection agent of Example 2 is used in an industrial test of a 600MW forced circulation boiler unit in Shanxi, and the test conditions are as follows:

[0045] Brief introduction of the project: The unit of the power plant is a 600MW boiler, which is a HG-2028 / 17.45-YM7 type boiler produced by Harbin Boiler Plant. The shutdown protection range includes the condensate water system, the water supply system, the deaerator, the economizer, the water-cooled wall, the superheater system and the high-temperature reheater. The water system during operation is about 1600M 3 , which involves the protection of multiple materials such as 20G, 210C, 12Cr1MoV, T23, T91 and TP347H.

[0046] According to the above medicament adding steps, 3mg of octadecylamine, 10mg of triethanolamine, 15mg of diethylene triamine, 15mg of morpholine and 15mg of cyclohexylamine are added per liter of boiler water during the shutdown and maintenance of the unit, the film is formed, and the furnace is discharged. After the discharge is completed and the condenser and the water supply system are opened, the metal surface is steel gray, and the surface has excellent hydrophobicity. The water-cooled wall, superheater and reheater system pipe samples are cut and sampled for inspection, and the inner wall of these system pipe samples has excellent film forming and strong hydrophobicity. The unit is shut down for maintenance for 145 days, and before the system is closed, the metal at these positions is still steel gray, without redness, yellowing and rusting.

[0047] The above laboratory and industrial tests prove that the shutdown protection agent of the present application has good film forming and protection performance, and the implementation method is simple and easy to operate, which can be widely applied to the shutdown protection of large boilers.

Claims

1. A method of using a boiler shutdown protection agent for a fossil fuel power plant, characterized in that, The shutdown protection agent is an aqueous solution composed of octadecylamine, triethanolamine, diethylene triamine, morpholine and cyclohexylamine; In use, the shutdown protection agent is added into the boiler water to make the concentration of octadecylamine in the boiler water 1-5 mg / L, the concentration of triethanolamine 10-30 mg / L, the concentration of diethylene triamine 5-15 mg / L, the concentration of morpholine 5-20 mg / L and the concentration of cyclohexylamine 10-30 mg / L; The pH of the boiler water needs to be strictly controlled in the range of 9.5-10.5 when the shutdown protection agent is used, and if the pH is lower, ammonia water needs to be added to control the pH of the boiler water in the range; The temperature for use of the shutdown protection agent is in the range of 250-400℃.

2. The method of claim 1, wherein the method is characterized by: In use, the shutdown protection agent is added into the boiler water to make the concentration of octadecylamine in the boiler water 3-5 mg / L, the concentration of triethanolamine 15-25 mg / L, the concentration of diethylene triamine 8-12 mg / L, the concentration of morpholine 10-15 mg / L and the concentration of cyclohexylamine 15-20 mg / L.

3. The method of using a boiler shutdown protection agent for a thermal power plant according to claim 1 or 2, characterized in that, The water in the shutdown protection agent is deionized water or desalted water.

4. The method of claim 1 or 2, wherein the method is characterized by, In preparation of the shutdown protection agent, the water is heated to 40-50℃, then octadecylamine is added, and after uniform stirring, triethanolamine, diethylene triamine, morpholine and cyclohexylamine are added in sequence, and the mixture is continuously stirred until uniform and stable to form a uniform and stable solution. The shutdown protection agent is an aqueous solution composed of octadecylamine, triethanolamine, diethylene triamine, morpholine and cyclohexylamine; In use, the shutdown protection agent is added into the boiler water to make the concentration of octadecylamine in the boiler water 1-5 mg / L, the concentration of triethanolamine 10-30 mg / L, the concentration of diethylene triamine 5-15 mg / L, the concentration of morpholine 5-20 mg / L and the concentration of cyclohexylamine 10-30 mg / L; The pH of the boiler water needs to be strictly controlled in the range of 9.5-10.5 when the shutdown protection agent is used, and if the pH is lower, ammonia water needs to be added to control the pH of the boiler water in the range; The temperature for use of the shutdown protection agent is in the range of 250-400℃. In use, the shutdown protection agent is added into the boiler water to make the concentration of octadecylamine in the boiler water 3-5 mg / L, the concentration of triethanolamine 15-25 mg / L, the concentration of diethylene triamine 8-12 mg / L, the concentration of morpholine 10-15 mg / L and the concentration of cyclohexylamine 15-20 mg / L. The water in the shutdown protection agent is deionized water or desalted water. In preparation of the shutdown protection agent, the water is heated to 40-50℃, then octadecylamine is added, and after uniform stirring, triethanolamine, diethylene triamine, morpholine and cyclohexylamine are added in sequence, and the mixture is continuously stirred until uniform and stable to form a uniform and stable solution.