Method for measuring film-forming property of polyamine boiler water treatment agent for simulating boiler steam-water system

Abstract

The invention relates to the technical field of analytical chemistry, in particular to a method for measuring the film-forming property of a polyamine boiler water treatment agent for simulating a boiler steam-water system. A high-temperature and high-pressure reaction kettle is used for simulating a boiler steam-water system, and the film-forming property of the polyamine boiler water treatment agent on the metal surface at the temperature of 250-330 DEG C is measured. According to the method, the film-forming performance of the polyamine boiler water treatment agent on the metal surface in the steam-water systems corresponding to boilers with different pressure grades can be measured, data support can be provided for practical application of the agent in the boiler system by measuring the film-forming performance in the simulated boiler steam-water system, and the effect of measuring the film-forming performance of the agent is achieved. Whether the polyamine boiler water treatment agent has a corrosion inhibition effect in an actual boiler steam-water system can be preliminarily evaluated.

Description

Technical Field

[0001] The present invention relates to the technical field of analytical chemistry, and particularly relates to a method for determining the film-forming performance of a polyamine boiler water treatment agent that simulates the boiler steam-water system. Background Art

[0002] The steam-water system is an important part of the boiler system. As the basic condition for ensuring the operation of the boiler, the boiler water quality directly affects the operation efficiency and safety of the boiler system. Adding water treatment agents to the boiler water is a common water treatment technology for adjusting the boiler water quality. Due to the many limitations of traditional boiler water treatment agents such as ammonia water, hydrazine, and sodium phosphate, polyamine water treatment agents mainly composed of film-forming amines have gradually replaced traditional agents and are applied in industries such as oil refining, power generation, paper making, food, and textiles.

[0003] Film-forming amines are usually fatty amines containing 10-18 carbon atoms, and the structural formula is R1-[NH-(R2)-] n -NH 2 , where n is an integer from 0 to 7, R1 is a straight-chain alkyl group containing 12-18 carbon atoms, and R2 is an alkyl group containing 1-4 carbon atoms. The nitrogen in the film-forming amine has a lone pair of electrons and has a strong affinity for the metal surface. Since polyamines contain multiple nitrogen atoms, they have a stronger affinity for metals; the long carbon chain connected to the amine group in the film-forming amine is hydrophobic and forms a hydrophobic protective film on the metal surface, isolating corrosive substances such as oxygen and carbon dioxide from contacting the metal. Film-forming amines are volatile. After adding polyamine water treatment agents mainly composed of film-forming amines to the boiler water, a protective film can be formed in the steam and condensate systems, thereby reducing the metal corrosion of the boiler steam-water system.

[0004] The internal structure of the boiler system is complex, and the temperature, pressure, and medium environment of different components are different. The film-forming performance of polyamine boiler water treatment agents directly affects their corrosion inhibition effect on the equipment of the boiler steam-water system. Therefore, before adding boiler water treatment agents to the boiler water for actual application, it is necessary to determine their film-forming performance to evaluate their corrosion inhibition effect on the metals of the boiler steam-water system. However, there is no relevant method for determining the film-forming performance of polyamine boiler water treatment agents in the prior art. Summary of the Invention

[0005] Aiming at the above deficiencies in the prior art, the purpose of the present invention is to provide a method for determining the film-forming performance of a polyamine boiler water treatment agent that simulates the boiler steam-water system.

[0006] To achieve the above invention purpose, the technical solution adopted by the present invention is as follows:

[0007] A method for measuring the film-forming performance of polyamine boiler water treatment agents that simulates the boiler steam-water system is provided. A high-temperature and high-pressure reactor is used to simulate the boiler steam-water system, and the film-forming performance of polyamine boiler water treatment agents on the metal surface is measured at 250 - 330 °C.

[0008] Furthermore, it specifically includes the following steps:

[0009] Step 1: Place the polyamine boiler water treatment agent in a high-temperature and high-pressure reactor to simulate the boiler steam-water system;

[0010] Step 2: Divide the metal specimens into upper and lower groups and place them in the high-temperature and high-pressure reactor. The lower group of metal specimens is immersed in the reagent test solution, and the distance from the liquid surface is not less than 5 cm. The upper group of metal specimens does not contact the reagent test solution, and the distance from the liquid surface is not less than 10 cm;

[0011] Step 3: Set the test temperature of the high-temperature and high-pressure reactor to 250 - 330 °C for the film-forming test; at the same time, set up a blank test without adding polyamine boiler water treatment agent;

[0012] Step 4: Prepare an acidic copper sulfate solution, drop the copper sulfate solution on the metal specimens after the test, and record the time when the liquid drops on the metal specimen surface turn red;

[0013] In the blank test and the film-forming test with the added agent under the same conditions, the time difference when the copper sulfate solution drops on the surface of the lower group of metal specimens turns red represents the film-forming performance of the polyamine boiler water treatment agent in the liquid phase environment; the time difference when the copper sulfate liquid drops on the surface of the upper group of metal specimens turns red represents the film-forming performance of the polyamine boiler water treatment agent in the gas phase environment.

[0014] The beneficial effects of the present invention are as follows:

[0015] The present invention uses a high-temperature and high-pressure reactor to simulate the boiler steam-water system and measures the film-forming performance of polyamine boiler water treatment agents on the metal surface at different temperatures (250 - 330 °C). It can measure the film-forming performance of polyamine boiler water treatment agents in the simulated boiler steam-water system. The method is simple and feasible, and can be used to preliminarily evaluate whether the agent has a corrosion inhibition effect in the actual boiler steam-water system. Specific Embodiments

[0016] The following describes the specific embodiments of the present invention to facilitate those skilled in the art of this technology to understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those of ordinary skill in the art of this technology, as long as various changes are within the spirit and scope of the present invention defined and determined by the appended claims, these changes are obvious, and all inventions and creations using the concept of the present invention are within the scope of protection.

[0017] Test Examples

[0018] This test example provides a method for determining the film-forming performance of polyamine boiler water treatment agents by simulating the boiler steam-water system. This method uses a high-temperature and high-pressure reactor to simulate the boiler steam-water system, providing a high-temperature and high-pressure environment for film-forming performance determination. The experimental temperature is set according to the saturated steam temperature corresponding to the boiler pressure. The film-forming performance of polyamine boiler water treatment agents on the metal surface of medium- and high-pressure boilers is determined.

[0019] According to different pressure grades, boilers can be divided into medium-pressure boilers, sub-high-pressure boilers, high-pressure boilers, and ultra-high-pressure boilers, as shown in Table 1. Therefore, according to the minimum pressure corresponding to boilers of different pressure grades, the saturated steam temperature is calculated and used as the set experimental temperature in the film-forming performance determination simulation experiment, as shown in Table 2.

[0020] Table 1 Classification of boiler pressure grades

[0021] Boiler pressure grade Medium-pressure boiler Sub-high-pressure boiler High-pressure boiler Ultra-high-pressure boiler Pressure range / MPa 3.8≤p＜5.3 5.3≤p＜9.8 9.8≤p＜13.7 13.7≤p＜16.7

[0022] Table 2 Set values of experimental temperature during film-forming performance determination

[0023] Boiler pressure grade Medium-pressure boiler Sub-high-pressure boiler High-pressure boiler Ultra-high-pressure boiler Set experimental temperature / °C 250 270 300 330

[0024] The specific test procedure is as follows:

[0025] I. Treatment of metal specimens

[0026] 1. Wipe the rust-preventive grease on the metal specimens with filter paper, and then scrub them with absorbent cotton in acetone and absolute ethanol respectively (not less than 50 mL of absolute ethanol is used for every 10 metal specimens);

[0027] 2. After the metal specimens are scrubbed clean, blot them dry with filter paper and place them in a desiccator for 4 h.

[0028] II. Film-forming experiment

[0029] 1. Pipette 20 mL of polyamine boiler water treatment agent into a 1000 mL volumetric flask, dilute it to the mark with water, and shake well. Transfer all the test solution to a high-temperature and high-pressure reactor;

[0030] 2. Take 6 treated metal specimens, hang 3 metal specimens on the top and bottom of the specimen hanging rack respectively, and place the specimen hanging rack in the reactor. The metal specimens at the bottom of the specimen hanging rack should be immersed in the test solution, and the distance from the liquid surface should be not less than 5 cm. The metal specimens at the top of the specimen hanging rack should be not less than 10 cm from the liquid surface. The specimen hanging rack shall not contact the reactor wall, and the distance between specimen hanging racks shall be not less than 1 cm;

[0031] 3. Close the reactor and check its airtightness. Then, introduce nitrogen into the reactor through the gas pipe to remove oxygen for 1 h. After that, set the test temperature according to Table 2, turn on the heating device, and start timing after the temperature rises to the set temperature and the temperature and pressure are stable.

[0032] 4. After 1 h, turn off the heating device. Wait for the reactor to cool to room temperature, open the reactor, take out the metal specimens at the top and bottom of the specimen hanger, and blot them dry with filter paper.

[0033] 5. Conduct a blank test without adding polyamine boiler water treatment agent, that is, transfer 1000 mL of pure water into the reactor in Step 1, and then operate according to Steps 2 - 4 in sequence.

[0034] III. Film - forming performance determination

[0035] 1. Prepare acidic copper sulfate solution: Add 20 mL of sodium chloride solution (100 g / L) and 1.5 mL of hydrochloric acid solution (0.1 mol / L) to 40 mL of copper sulfate solution (0.4 mol / L), add water to 100 mL, and shake well.

[0036] 2. Place the metal specimens horizontally on the experimental table. Randomly select 5 dispersed points on the surface of each metal specimen. Use a dropper to drop 1 drop of acidic copper sulfate solution on each point. Start timing with a stopwatch at the moment the liquid drop falls onto the metal specimen, record the time when the liquid drops on the 5 points on the metal specimen surface turn red, and calculate the average value as the measurement result.

[0037] 3. Calculate the time difference when the copper sulfate liquid drop turns red on the bottom - layer metal specimen of the specimen hanger in the blank test and the film - forming test with the added agent under the same conditions, which represents the film - forming performance of the polyamine boiler water treatment agent in the liquid phase environment. The time difference when the copper sulfate liquid drop turns red on the top - layer metal specimen of the specimen hanger represents the film - forming performance of the polyamine boiler water treatment agent in the gas phase environment. When the time difference when the copper sulfate liquid drop turns red ≥ 10 s, it indicates that the film - forming performance of the agent is good.

[0038] In this test example, 2 commercially available polyamine boiler water treatment agents (Specimen 1 and Specimen 2) were used for test verification to determine their film - forming performance on the metal surface of the medium - pressure boiler steam - water system. Therefore, the test temperature was set at 250 °C. The test results are shown in Table 3.

[0039] Table 3 Data of film - forming performance determination of agents at 250 °C

[0040]

[0041] As can be seen from the results in Table 3, the film - forming performance of Specimen 1 is good in both the liquid and gas phase environments, and the film - forming performance of Specimen 2 is only good in the gas phase environment.

[0042] In summary, the present invention can realize the measurement of the film-forming performance of polyamine boiler water treatment agents on the metal surface in the steam-water systems corresponding to boilers of different pressure grades. By measuring the film-forming performance in a simulated boiler steam-water system, it can provide data support for its actual application in the boiler system. Through the measurement of its film-forming performance, it can preliminarily evaluate whether the polyamine boiler water treatment agent has a corrosion inhibition effect in the actual boiler steam-water system.

[0043] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention.

[0044] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for determining the film-forming properties of a polyamine boiler water treatment agent simulating a boiler steam-water system, characterized in that: A high temperature and high pressure reactor was used to simulate the boiler steam-water system, and the film-forming performance of polyamine boiler water treatment agents on metal surfaces was determined at 250-330°C.

2. The method for determining the film-forming performance of a polyamine boiler water treatment agent for simulating a boiler steam-water system according to claim 1, characterized in that: The specific steps include: Step 1: placing a polyamine boiler water treatment agent in a high-temperature and high-pressure reactor to simulate a boiler steam-water system; Step 2, divide the metal test pieces into two groups, upper and lower, and place them in a high-temperature and high-pressure reactor. The lower group of metal test pieces are immersed in the reagent test solution and are at least 5 cm away from the liquid surface. The upper group of metal test pieces do not contact the reagent test solution and are at least 10 cm away from the liquid surface. Step 3, setting the test temperature of the high temperature and high pressure reactor to 250-330°C, and conducting a film forming test; and setting a blank test without adding a polyamine boiler water treatment agent; Step 4, prepare an acidic copper sulfate solution, add the copper sulfate solution dropwise onto the metal test piece after the test, and record the time when the droplets on the surface of the metal test piece turn red; In the blank test and the film-forming test with the addition of the reagent under the same conditions, the time difference when the copper sulfate solution drops on the surface of the lower group of metal test pieces to turn red indicates the film-forming performance of the polyamine boiler water treatment reagent in the liquid environment; The time difference for the copper sulfate droplets to appear red on the surface of the upper group of metal test pieces indicates the film-forming performance of the polyamine boiler water treatment agent in the gas phase environment.

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