An oxygen scavenger for boiler feed water auxiliary oxygen scavenging and a preparation method thereof

Abstract

The application discloses a deoxidizer for auxiliary deoxidization of boiler feed water and a preparation method thereof. The deoxidizer is composed of the following components in mass fraction: 280-350 parts of a deoxidization main agent, 100-160 parts of a deoxidization auxiliary agent, 10 parts of a dispersing agent, 50-80 parts of a pH regulator and 460-500 parts of soft water. The deoxidization main agent is a combination of 1-(1-((2-pyrrole) imine) ethyl) carbazide, 1-(1-((2-pyridyl) imine) ethyl) carbazide, 1-(1-((2-pyrimidyl) imine) ethyl) carbazide, 1-(1-((4-pyrimidyl) imine) ethyl) carbazide, 1-(1-((2-pyrazyl) imine) ethyl) carbazide, 1-(1-((2-imidazolyl) imine) ethyl) carbazide or 1-(1-((4-imidazolyl) imine) ethyl) carbazide. The deoxidizer has the advantages of low dosage, good deoxidization effect, use in the rear end of a thermal deoxidizer, deep deoxidization of boiler feed water, and corrosion and scale inhibition effects on the boiler body.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of oxygen scavenger for boiler feed water auxiliary deoxidation, also relates to the preparation method of the oxygen scavenger described above. BACKGROUND

[0002] Dissolved oxygen in boiler feed water is the main factor of chemical corrosion and electrochemical corrosion of boiler. Dissolved oxygen enters the boiler with boiler feed water, and under the working temperature and pressure of the boiler, the dissolved oxygen will cause corrosion of different degrees to the boiler body, pipe network, etc. At the same time, the corrosion products will adhere to the boiler heating surface to form iron scale which is difficult to dissolve and has poor heat transfer, resulting in a decrease in the thermal efficiency of the boiler, and in severe cases, the boiler may burst.

[0003] Currently, the deoxygenation of boiler feed water generally uses thermal deoxygenation, that is, according to Henry's law, the solubility of any gas in water is proportional to the partial pressure of the gas on the steam-water interface. In an open device, as the temperature increases, the water vapor partial pressure of the steam-water interface increases, and the oxygen partial pressure decreases. When the water temperature is 100℃, the oxygen partial pressure decreases to zero, and the dissolved oxygen in the water also decreases to zero. Although the thermal deoxygenator has high efficiency, it is difficult to remove the residual 0.1 mg / L of dissolved oxygen by the thermal deoxygenator. Therefore, in addition to thermal deoxygenation, chemical deoxygenation is also needed to reduce dissolved oxygen. When using chemical deoxygenation alone, the dosage and cost are usually high. In addition, high-concentration deoxygenation agents can cause the content of pollutants (such as total nitrogen) in the water to exceed the standard when the boiler drains. When thermal and chemical deoxygenation are combined, the working load of the thermal deoxygenator can be reduced, thereby reducing the operating temperature of the deoxygenator and the treatment cost. Therefore, chemical auxiliary thermal deoxygenation is a more reliable and economical treatment method.

[0004] The commonly used chemical deoxygenation agents currently include sulfite, oxime compounds, hydroxylamine compounds, and isoascorbate compounds. Although these deoxygenation agents have good deoxygenation effects, they all have certain usage drawbacks. For example, sulfite can cause the content of sulfate in the boiler to increase, and can generate difficult-to-clean sulfur scale. Hydroxylamine deoxygenation agents have unsatisfactory deoxygenation effects when used alone, and the deoxygenation effect is only obvious when the pH is greater than 11. Isoascorbate deoxygenation agents have low volatility and cannot prevent corrosion of subsequent equipment such as the condenser. Oxime compounds have a certain dissolving capacity for iron and copper in the early stage, and the metal passivation capacity is insufficient. SUMMARY

[0005] The present application aims to provide a deoxygenation agent for boiler feed water auxiliary deoxygenation, which has low dosage, good deoxygenation effect, and is used at the back end of the thermal deoxygenator. The deoxygenation agent can achieve deep deoxygenation of the boiler feed water and also has corrosion and scale inhibition effects on the boiler body. Another purpose of the present application is to provide a preparation method of the deoxygenation agent described above.

[0006] The technical scheme is: the deoxidizing agent for boiler feed water auxiliary deoxidization comprises the following components in mass fraction: 280-350 parts of deoxidizing main agent, 100-160 parts of deoxidizing auxiliary agent, 10 parts of dispersing agent, 50-80 parts of pH regulator and 460-500 parts of soft water.

[0007] The deoxidizing main agent is a combination of 1-(1-((2-pyrrole) imine) ethyl) carbazide, 1-(1-((2-pyridyl) imine) ethyl) carbazide, 1-(1-((2-pyrimidyl) imine) ethyl) carbazide, 1-(1-((4-pyrimidyl) imine) ethyl) carbazide, 1-(1-((2-pyrazyl) imine) ethyl) carbazide, 1-(1-((2-imidazolyl) imine) ethyl) carbazide or 1-(1-((4-imidazolyl) imine) ethyl) carbazide.

[0008] The branched chain at the alpha position of the nitrogen-containing heterocyclic compound is easy to react with oxygen to generate carboxylic acid at high temperature; the nitrogen-containing heterocyclic carboxylic acid reacts with dissolved oxygen at high temperature to generate a series of chemical reactions to generate straight-chain nitrogen-containing carboxylic acid compounds; taking 1-(1-((2-pyrrole) imine) ethyl) carbazide as an example, the branched chain at the alpha position is oxidized to carboxylic acid, i.e., pyrrole-2-acetic acid or pyrrole-2-carboxylic acid, and the remaining products are carbazic acid, hydrazine and methylamine; the pyrrole-2-acetic acid or pyrrole-2-carboxylic acid reacts with dissolved oxygen to generate intermediate product 1-hydroxypyrryl-2-carboxylic acid or 1-hydroxypyrryl-2-acetic acid, and the intermediate product is partially decomposed into straight-chain nitrogen-containing carboxylic acid, and the reaction process is as follows:

[0009]

[0010] Further, 1-(1-((2-pyrrolyl)imine)ethyl)carbazide, 1-(1-((2-pyridyl)imine)ethyl)carbazide, 1-(1-((2-pyrimidyl)imine)ethyl)carbazide, 1-(1-((4-pyrimidyl)imine)ethyl)carbazide, 1-(1-((2-pyrazinyl)imine)ethyl)carbazide, 1-(1-((2-imidazolyl)imine)ethyl)carbazide, 1-(1-((4-imidazolyl)imine)ethyl)carbazide and partial decomposition products thereof can form a good protective film on the surface of carbon steel, passivate the metal surface and effectively delay the corrosion of the boiler; can reduce the iron content in the feed water and prevent the overheating and corrosion damage of the metal pipe caused by the deposition of iron oxide. The reason is that the main decomposition products of the oxygen scavenging main agent are hydrazine, pyrrole carboxylic acid, pyridine carboxylic acid, pyrimidine carboxylic acid, imidazole carboxylic acid, methylamine, ethylamine, carbazide and other substances, these substances all contain N atoms or O atoms composed of lone pair electrons, these atoms are easy to coordinate and adsorb with metal surface atoms, so that the organic matter is staggered to form a thin film, so as to slow down the corrosion of the metal surface. In addition, the oxygen scavenging main agent and the decomposition products hydrazine and carbazide have strong reducing property, can react with iron and copper oxides to form a dense oxide film on the metal surface, passivate the metal, so as to achieve the purpose of corrosion prevention. The reaction equations of hydrazine and carbazide are as follows (the reaction of the oxygen scavenging main agent is too complex). After slowing down the corrosion of the metal, the amount of the metal oxidized is greatly reduced, so that the iron content in the water is reduced.

[0011] 12Fe2O3+(N2H3)2CO=8Fe3O4+3H2O+CO2↑+2N2↑

[0012] 8CuO+(N2H3)2CO=4Cu2O+3H2O+CO2↑+2N2↑

[0013] 6Fe2O3+N2H4=4Fe3O4+2H2O+N2↑

[0014] 4CuO+N2H4=2Cu2O+2H2O+N2↑

[0015] The preparation method of the oxygen scavenging main agent of the present application takes 1-1-(1-((2-pyrrolyl)imine)ethyl)carbazide as an example and comprises the following steps:

[0016] (1) 100 mL of softened water and 5 mL of acetic acid are added to a reactor under N2 atmosphere, and mixed uniformly to obtain A liquid;

[0017] (2) Acetyl compound and carbazide in a molar ratio of 1:1 are sequentially added to the A liquid under N2 atmosphere, and stirred at 45 DEG C constant temperature water bath and 300 rpm for 12 h, so that the solution is slowly volatilized and the solid is slowly precipitated to obtain a suspension B; wherein the acetyl compound is 2-acetylpyrrole;

[0018] (3) The obtained suspension B is centrifuged at 8000 rpm for 15 min at 0°C to obtain a solid, and the solid is washed twice with soft water at 0°C, and finally the solid is freeze-dried to obtain the oxygen scavenging main agent 1-(1-((2-pyrrolyl)imine)ethyl)carbazole.

[0019] Other oxygen scavenging main agents 1-(1-((2-pyridyl)imine)ethyl)carbazole, 1-(1-((2-pyrimidyl)imine)ethyl)carbazole, 1-(1-((4-pyrimidyl)imine)ethyl)carbazole, 1-(1-((2-pyrazinyl)imine)ethyl)carbazole, 1-(1-((2-imidazolyl)imine)ethyl)carbazole or 1-(1-((4-imidazolyl)imine)ethyl)carbazole are prepared by replacing the acetyl compound in the above-mentioned process with 2-acetylpyridine, 2-acetylpyrimidine, 4-acetylpyrimidine, 2-acetylpyrazine, 2-acetylimidazole or 4-acetylimidazole.

[0020] The reaction formula is as follows:

[0021]

[0022] The oxygen scavenging main agent of the present application can also be 1-(1-((2-pyrrolyl)imine)ethyl)carbazole prepared in the document "Polyolefin catalytic performance of pyridine / pyrrole ketone diamine Schiff base metal complex (Yan Tingyu, Xi'an Petroleum University)".

[0023] The oxygen scavenging auxiliary agent is a combination of gallic acid, 1,2-naphthoquinone, 4-(N,N)-dimethylaminophenol or 2-keto-d-gluconic acid. The oxygen scavenging auxiliary agent has a catalytic oxygen scavenging effect, can accelerate the reaction rate of the oxygen scavenging main agent and dissolved oxygen, thereby effectively improving the removal rate of low-concentration dissolved oxygen and reducing the dosage of the oxygen scavenging main agent.

[0024] The oxygen scavenging auxiliary agent is a reducing substance, which can effectively stabilize the redox potential of the system and improve the use efficiency of the oxygen scavenging main agent; the oxygen scavenging main agent mainly reacts with dissolved oxygen through a nitrogen-containing functional group, while the oxygen scavenging auxiliary agent mainly reacts with dissolved oxygen through an oxygen-containing functional group; gallic acid and 4-dimethylaminophenol contain a large number of phenolic hydroxyl groups, which are easy to react with dissolved oxygen to generate quinone compounds; 1,2-naphthoquinone and the intermediate quinone substance of gallic acid and 4-dimethylaminophenol can continue to react with dissolved oxygen to generate carboxylic acid substances; on the other hand, the quinone substance can be reduced to a polyhydroxy phenol by the oxygen scavenging agent main agent or its decomposition products such as hydrazine and carbohydrazide, and the polyhydroxy phenol continues to react with dissolved oxygen to generate quinone substances again, and the cycle continues; 2-keto-d-gluconic acid contains a ketone group, which is extremely easy to react with dissolved oxygen to generate carboxylic acid substances at a higher temperature, and the synergistic oxygen scavenging effect of the nitrogen-containing functional group in the oxygen scavenging main agent is obvious. At the same time, the oxygen scavenging auxiliary agent has a certain corrosion and scale inhibition effect, can chelate metal ions to avoid the formation of metal salt deposits in the pipeline or the inside of the boiler; and can form a very thin protective film on the surface of carbon steel to avoid corrosion of the carbon steel. This is because the oxygen scavenging auxiliary agent has an atom with a lone pair of electrons, which can share a free electron pair or undergo charge transfer with metal atoms, thereby forming a strong chemical bond and forming chemical adsorption on the metal surface, thereby blocking the reaction of dissolved oxygen and the metal. In addition, the aromatic ring π electrons of gallic acid, 1,2-naphthoquinone and 4-dimethylaminophenol can overlap with the 3d empty orbit of the metal Fe atom, and the formation of π-d bonds can enhance the adsorption capacity of the compound on the metal surface, thereby strengthening the chemical adsorption effect and enhancing the corrosion inhibition capacity; 2-keto-d-gluconic acid mainly chelates with metal ions to generate complexes, reducing the formation of Fe2O3 and CuO deposits, thereby avoiding the deposition of metal salt in the pipeline or the inside of the boiler. The oxygen scavenging auxiliary agent in the oxygen scavenging agent has a good synergistic effect with the oxygen scavenging main agent, can effectively reduce the dosage of the oxygen scavenging main agent, accelerate the reaction rate of the oxygen scavenging main agent and dissolved oxygen, and thereby improve the removal rate of dissolved oxygen.

[0025] The dispersant is polyethylene glycol 200 or polyethylene imine. The dispersant is used to ensure the relative stability of the entire oxygen scavenging agent system and prolong the storage period of the oxygen scavenging agent.

[0026] The pH regulator is a combination of several of cyclohexylamine, morpholine or N-methyldiethanolamine. The pH regulator can make the boiler feed water weakly alkaline to avoid acid corrosion of the boiler equipment; in addition, the pH regulator can effectively neutralize the CO2 generated by the decomposition of the oxygen scavenging main agent, avoiding corrosion of the decomposition products to the boiler system.

[0027] After the thermal deaerator, the water temperature is about 90℃, and at this temperature, the reaction rate of the oxygen scavenging main agent and dissolved oxygen is fast, and the oxygen scavenging efficiency is high.

[0028] The preparation method of the above oxygen scavenger is specifically as follows: formula amount of softened water is added into a reaction kettle, formula amount of dispersant is added under stirring to make it fully mixed, then formula amount of oxygen scavenging main agent is added, after the oxygen scavenging main agent is completely dissolved, formula amount of oxygen scavenging auxiliary agent is added to make it completely dissolved, finally formula amount of pH adjusting agent is added, and the oxygen scavenger is obtained after stirring and mixing.

[0029] The application of the above oxygen scavenger in auxiliary boiler thermal deoxygenation has the specific process that: after softened water or desalted water passes through a thermal deoxygenator, the dissolved oxygen in the water body is reduced to 0.1 mg / L or below, then the oxygen scavenger is added into an oxygen scavenging water tank or a pipeline of boiler feed water, and the dosage is generally about 3 times of the dissolved oxygen concentration, about 100-500 μg / L; after the oxygen scavenging reaction (25 min) of the oxygen scavenger, the dissolved oxygen in the boiler water is reduced to below 5 μg / L.

[0030] Beneficial effects: compared with the prior art, the present application has the following remarkable effects: (1) the oxygen scavenger is used after the thermal deoxygenator, can make up for the fact that the dissolved oxygen of the water out of the thermal deoxygenator cannot meet the requirements of the boiler feed water, and can effectively reduce the operating temperature of the thermal deoxygenator after using the oxygen scavenger, thereby reducing the energy consumption; (2) the oxygen scavenger is used after the thermal deoxygenator, compared with the traditional oxygen scavenger, the dosing amount is greatly reduced, thereby greatly reducing the concentration of pollutants (such as total nitrogen) in the waste water when the boiler is discharged; (3) the oxygen scavenger has the characteristics of fast reaction rate with low-concentration dissolved oxygen and high dissolved oxygen removal rate; at the same time, the oxygen scavenger also has certain corrosion and scale inhibition functions, can form a good oxidation protective film on the surface of carbon steel, passivate the metal surface, effectively delay the corrosion of the boiler, reduce the iron content in the feed water, and prevent the problems of overheating and corrosion damage of the metal pipe caused by the deposition of iron oxide in the boiler. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 The oxygen scavenging experimental device of the oxygen scavenger. DETAILED DESCRIPTION

[0032] Example 1

[0033] The oxygen scavenger of the present application is composed of the following components in mass fraction: 300 parts of oxygen scavenging main agent, 140 parts of oxygen scavenging auxiliary agent, 10 parts of dispersant, 80 parts of pH adjusting agent and 470 parts of softened water; wherein the oxygen scavenging main agent is composed of 1-(1-((2-pyrrolyl) imine) ethyl) carbazil and 1-(1-((2-pyridyl) imine) ethyl) carbazil, and the mixing mass ratio of the two is 7:3; the oxygen scavenging auxiliary agent is composed of gallic acid, 1,2-naphthoquinone and 2-keto-d-glucaric acid, and the mixing mass ratio is 5:2:3; the dispersant is polyethylene glycol 200; and the pH adjusting agent is composed of cyclohexylamine, morpholine and N-methyldiethanolamine, and the mixing mass ratio is 4:3:3.

[0034] The above oxygen scavenger is prepared by the following method, specifically comprising the following steps:

[0035] (1) 470 g of softened water is added to a reaction kettle, 10.0 g of industrial-grade polyethylene glycol 200 with an effective content of 99 wt.% is added, and stirring is performed to uniformly mix to obtain A liquid;

[0036] (2) 210 g of 1-(1-((2-pyrrolyl)imine)ethyl)carbazide and 90 g of 1-(1-((2-pyridyl)imine)ethyl)carbazide are added to the A liquid, and stirring is performed to uniformly mix to obtain B liquid;

[0037] (3) 70 g of gallic acid with an effective content of 99 wt.% is added to the B liquid, and fully dissolved; 28 g of 1,2-naphthoquinone with an effective content of 95 wt.% is further added, and fully dissolved; 42 g of 2-keto-d-gluconic acid with an effective content of 98 wt.% is further added, and fully dissolved to obtain C liquid;

[0038] (4) 32 g of cyclohexylamine, 24 g of morpholine, and 24 g of N-methyldiethanolamine (with effective contents of 99 wt.%, 98 wt.%, and 99 wt.% respectively) are sequentially added to the C liquid, and stirring is performed to uniformly mix to obtain the oxygen scavenger.

[0039] The preparation method of the above oxygen scavenger main agent 1-(1-((2-pyrrolyl)imine)ethyl)carbazide and 1-(1-((2-pyridyl)imine)ethyl)carbazide, specifically comprising the following steps:

[0040] (1) In a glove box under N2 atmosphere, 100 mL of distilled water and 5 mL of glacial acetic acid are added to a conical flask, and mixed uniformly to obtain D liquid;

[0041] (2) In a glove box under N2 atmosphere, 1.30 g of 2-acetylpyrrole and 1.08 g of carbazide (with a molar amount of 0.012 mol) are added to the above D liquid, or 1.45 g of 2-acetylpyridine (with a molar amount of 0.012 mol) and 1.08 g of carbazide (with a molar amount of 0.012 mol) are added to the above D liquid; stirring is performed at 45°C constant temperature water bath and 300 rpm for 12 h, the solution is slowly volatilized, and the solid is slowly precipitated to obtain suspension liquid E;

[0042] (3) The above obtained suspension liquid E is centrifuged at 8000 rpm for 15 min at 0°C to obtain a solid, the solid is washed with 0°C softened water for 2 times, and finally the solid is freeze-dried to obtain 1-(1-((2-pyrrolyl)imine)ethyl)carbazide or 1-(1-((2-pyridyl)imine)ethyl)carbazide.

[0043] Example 2

[0044] The oxygen scavenger of the present application is composed of the following components in mass fraction: 350 parts of oxygen scavenging main agent, 100 parts of oxygen scavenging auxiliary agent, 10 parts of dispersing agent, 80 parts of pH adjusting agent, and 460 parts of softening water; wherein the oxygen scavenging main agent is composed of 1-(1-((2-pyrrolyl) imine) ethyl) carbazide and 1-(1-((2-pyrazinyl) imine) ethyl) carbazide, and the mixing mass ratio of the two is 6:4; the oxygen scavenging auxiliary agent is composed of gallic acid, 1,2-naphthoquinone, 4-dimethylaminophenol and 2-keto-d-gluconic acid, and the mixing mass ratio is 4:2:1:3; the dispersing agent is polyethyleneimine; and the pH adjusting agent is composed of cyclohexylamine, morpholine and N-methyldiethanolamine, and the mixing mass ratio is 5:2:3.

[0045] The above-mentioned oxygen scavenger is prepared by the following method, specifically including the following steps:

[0046] (1) 460 g of softening water is added to the reaction kettle, 10.0 g of industrial-grade polyethylene glycol 200 with an effective content of 99 wt.% is added, and stirred and mixed uniformly to obtain A liquid;

[0047] (2) 210 g of 1-(1-((2-pyrrolyl) imine) ethyl) carbazide and 140 g of 1-(1-((2-pyrazinyl) imine) ethyl) carbazide are added to the A liquid, and stirred and mixed uniformly to obtain B liquid;

[0048] (3) 40 g of gallic acid with an effective content of 99 wt.% is added to the B liquid and dissolved fully; then 20 g of 1,2-naphthoquinone with an effective content of 95 wt.% is added and dissolved fully; then 10 g of 4-dimethylaminophenol with an effective content of 97 wt.% is added and dissolved fully; finally, 30 g of 2-keto-d-gluconic acid with an effective content of 98 wt.% is added and dissolved fully to obtain C liquid;

[0049] (4) 40 g of cyclohexylamine, 16 g of morpholine and 24 g of N-methyldiethanolamine (effective contents are 99 wt.%, 98 wt.% and 99 wt.% respectively) are sequentially added to the C liquid, and stirred and mixed uniformly to obtain the oxygen scavenger.

[0050] The preparation method of the above-mentioned oxygen scavenging main agent 1-(1-((2-pyrrolyl) imine) ethyl) carbazide and 1-(1-((2-pyrazinyl) imine) ethyl) carbazide, specifically including the following steps:

[0051] (1) In a glove box under N2 atmosphere, 100 mL of distilled water and 5 mL of glacial acetic acid are added to a conical flask, and mixed uniformly to obtain D liquid;

[0052] (2) In a glove box under N2 atmosphere, 1.30 g of 2-acetylpyrrole and 1.08 g of carbazate were added to the above D solution or 1.46 g of 2-acetylpyrazine and 1.08 g of carbazate were added to the above D solution; 45℃ constant temperature water bath, stirring at 300 rpm for 12 h, slowly volatilizing the solution, and slowly precipitating the solid to obtain a suspension E;

[0053] (3) The above obtained suspension E was centrifuged at 8000 rpm for 15 min at 0℃ to obtain a solid, and the solid was washed twice with 0℃ soft water, and finally the solid was freeze-dried to obtain 1-(1-((2-pyrrolyl) imine) ethyl) carbazate or 1-(1-((2-pyrazinyl) imine) ethyl) carbazate.

[0054] Example 3

[0055] The oxygen scavenger of the present application is composed of the following components in mass fraction: 280 parts of oxygen scavenging main agent, 160 parts of oxygen scavenging auxiliary agent, 10 parts of dispersing agent, 50 parts of pH adjusting agent, and 500 parts of soft water; wherein the oxygen scavenging main agent is composed of 1-(1-((2-pyrrolyl) imine) ethyl) carbazate and 1-(1-((2-imidazolyl) imine) ethyl) carbazate, and the mixing mass ratio of the two is 6:4; the oxygen scavenging auxiliary agent is composed of gallic acid, 1,2-naphthoquinone and 4-dimethylaminophenol, and the mixing mass ratio is 6:3:1; the dispersing agent is polyethylene glycol 200; and the pH adjusting agent is composed of cyclohexylamine, morpholine and N-methyldiethanolamine, and the mixing mass ratio is 4:3:3.

[0056] The above oxygen scavenger is prepared by the following method, specifically including the following steps:

[0057] (1) 500 g of soft water was added to a reaction kettle, 10.0 g of industrial grade polyethylene glycol 200 with an effective content of 99 wt.% was added, and stirred and mixed uniformly to obtain A solution;

[0058] (2) 168 g of 1-(1-((2-pyrrolyl) imine) ethyl) carbazate and 112 g of 1-(1-((2-imidazolyl) imine) ethyl) carbazate were added to the A solution, and stirred uniformly to obtain B solution;

[0059] (3) 96 g of gallic acid with an effective content of 99 wt.% was added to the B solution and dissolved thoroughly; then 48 g of 1,2-naphthoquinone with an effective content of 95 wt.% was added and dissolved thoroughly; and then 16 g of 4-dimethylaminophenol with an effective content of 97 wt.% was added and dissolved thoroughly to obtain C solution;

[0060] (4) 20 g of cyclohexylamine, 15 g of morpholine and 15 g of N-methyldiethanolamine (effective contents are 99 wt.%, 98 wt.% and 99 wt.% respectively) were sequentially added to the C solution, and stirred uniformly to obtain an oxygen scavenger.

[0061] The preparation method of the above-mentioned oxygen scavenging main agents 1-(1-((2-pyrimidinyl)imine)ethyl)carbazide and 1-(1-((2-imidazolyl)imine)ethyl)carbazide specifically comprises the following steps:

[0062] (1) In a glove box under N2 atmosphere, 100 mL of distilled water and 5 mL of glacial acetic acid were added to a conical flask, and mixed uniformly to obtain D solution;

[0063] (2) In a glove box under N2 atmosphere, 1.46 g of 2-acetylpyrimidine and 1.08 g of carbazide were added to the above-mentioned D solution, or 1.32 g of 2-acetylimidazole and 1.08 g of carbazide were added to the above-mentioned D solution; stirring at 45°C constant temperature water bath, 300 rpm for 12 h, slowly volatilizing the solution, and slowly precipitating the solid to obtain suspension E;

[0064] (3) The obtained suspension E was centrifuged at 8000 rpm for 15 min at 0°C to obtain a solid, and the solid was washed twice with 0°C softened water, and finally the solid was freeze-dried to obtain 1-(1-((2-pyrimidinyl)imine)ethyl)carbazide or 1-(1-((2-imidazolyl)imine)ethyl)carbazide.

[0065] Comparative Example 1

[0066] An oxygen scavenger, which is composed of the following components in mass fraction: 300 parts of oxygen scavenging main agent, 140 parts of oxygen scavenging auxiliary agent, 10 parts of dispersing agent, 80 parts of pH adjusting agent, and 470 parts of softened water; wherein the oxygen scavenging main agent is composed of 2-acetylpyrrole and 2-acetylpyridine, and the mixing mass ratio of the two is 7:3; the oxygen scavenging auxiliary agent is composed of gallic acid, 1,2-naphthoquinone and 2-keto-d-gluconic acid, and the mixing mass ratio of the three is 5:2:3; the dispersing agent is polyethylene glycol 200; and the pH adjusting agent is composed of cyclohexylamine, morpholine and N-methyldiethanolamine, and the mixing mass ratio of the three is 4:3:3.

[0067] The above-mentioned oxygen scavenger is prepared by the following method, which specifically comprises the following steps:

[0068] (1) 470 g of softened water was added to a reaction kettle, 10.0 g of industrial-grade polyethylene glycol 200 with an effective content of 99 wt.% was added, and stirred and mixed uniformly to obtain A solution;

[0069] (2) 210 g of 2-acetylpyrrole and 90 g of 2-acetylpyridine were added to the A solution, and stirred and mixed uniformly to obtain B solution;

[0070] (3) To B liquid, 70 g of gallic acid with effective content of 99 wt.% was added and dissolved thoroughly; then 28 g of 1,2-naphthoquinone with effective content of 95 wt.% was added and dissolved thoroughly; then 42 g of 2-keto-d-gluconic acid with effective content of 98 wt.% was added and dissolved thoroughly to obtain C liquid;

[0071] (4) To C liquid, 32 g of cyclohexylamine, 24 g of morpholine and 24 g of N-methyldiethanolamine (effective content of 99 wt.%, 98 wt.% and 99 wt.% respectively) were added in sequence and stirred uniformly to obtain the oxygen scavenger.

[0072] Comparative Example 2

[0073] An oxygen scavenger, which is composed of 300 parts of oxygen scavenging main agent, 10 parts of dispersing agent, 80 parts of pH adjusting agent and 610 parts of softening water; wherein the oxygen scavenging main agent is composed of 1-(1-((2-pyrrolyl)imine)ethyl)carbazide and 1-(1-((2-pyridyl)imine)ethyl)carbazide with a mixing mass ratio of 7:3; the dispersing agent is polyethylene glycol 200; and the pH adjusting agent is composed of cyclohexylamine, morpholine and N-methyldiethanolamine with a mixing mass ratio of 4:3:3.

[0074] The above oxygen scavenger is prepared by the following method, which specifically includes the following steps:

[0075] (1) 610 g of softening water was added to a reaction kettle, 10.0 g of industrial-grade polyethylene glycol 200 with effective content of 99 wt.% was added and stirred and mixed uniformly to obtain A liquid;

[0076] (2) To A liquid, 210 g of 1-(1-((2-pyrrolyl)imine)ethyl)carbazide and 90 g of 1-(1-((2-pyridyl)imine)ethyl)carbazide were added and stirred uniformly to obtain B liquid;

[0077] (3) To B liquid, 32 g of cyclohexylamine, 24 g of morpholine and 24 g of N-methyldiethanolamine (effective content of 99 wt.%, 98 wt.% and 99 wt.% respectively) were added in sequence and stirred uniformly to obtain the oxygen scavenger.

[0078] Comparative Example 3

[0079] An oxygen scavenger is composed of the following components in mass fraction: 100 parts of an oxygen scavenging main agent, 140 parts of an oxygen scavenging auxiliary agent, 10 parts of a dispersing agent, 80 parts of a pH adjusting agent, and 670 parts of softening water; wherein the oxygen scavenging main agent is composed of 1-(1-((2-pyrrolyl)imine)ethyl)carbazide and 1-(1-((2-pyridyl)imine)ethyl)carbazide, and the mixing mass ratio of the two is 7:3; the oxygen scavenging auxiliary agent is composed of gallic acid, 1,2-naphthoquinone and 2-keto-d-gluconic acid, and the mixing mass ratio of the three is 5:2:3; the dispersing agent is polyethylene glycol 200; and the pH adjusting agent is composed of cyclohexylamine, morpholine and N-methyl diethanolamine, and the mixing mass ratio of the three is 4:3:3.

[0080] The above oxygen scavenger is prepared by the following method, specifically including the following steps:

[0081] (1) 670 g of softening water is added to a reaction kettle, 10.0 g of industrial-grade polyethylene glycol 200 with an effective content of 99 wt.% is added, and stirred and mixed uniformly to obtain A liquid;

[0082] (2) 70 g of 1-(1-((2-pyrrolyl)imine)ethyl)carbazide and 30 g of 1-(1-((2-pyridyl)imine)ethyl)carbazide are added to the A liquid, and stirred uniformly to obtain B liquid;

[0083] (3) 70 g of gallic acid with an effective content of 99 wt.% is added to the B liquid and dissolved fully; then 28 g of 1,2-naphthoquinone with an effective content of 95 wt.% is added and dissolved fully; then 42 g of 2-keto-d-gluconic acid with an effective content of 98 wt.% is added and dissolved fully to obtain C liquid;

[0084] (4) 32 g of cyclohexylamine, 24 g of morpholine and 24 g of N-methyl diethanolamine (with effective contents of 99 wt.%, 98 wt.% and 99 wt.% respectively) are sequentially added to the C liquid, and stirred uniformly to obtain the oxygen scavenger.

[0085] The oxygen scavengers of the above Examples 1-3 and Comparative Examples 1-3 are used for oxygen scavenging experiments:

[0086] Experimental apparatus: a triangular flask with a rubber plug (as shown in Figure 1 ), a 3655 portable micro-dissolved oxygen analyzer, a constant-temperature water bath, a glove box

[0087] Experimental method: The whole experiment was carried out in a glove box under N2 atmosphere. A 1L flask was filled with softened water (about 1cm space was reserved), and was placed in a constant temperature water bath at 90℃. The dissolved oxygen in the flask was reduced to about 0.15mg / L by bubbling ultra-pure N2 (simulating the dissolved oxygen in the outlet water of a thermal deaerator), and the water clamps at both ends were closed. 450μL of the deaerating agent was added into the flask by a syringe, and the timing was started. The dissolved oxygen was measured at intervals, and the results are shown in Table 1.

[0088] Table 1: Deaerating effect of the deaerating agent in Examples 1-3 and Comparative Examples 1-3

[0089] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 0 min 150 μg / L 153 μg / L 149 μg / L 149 μg / L 151 μg / L 154 μg / L 5 min 102 μg / L 110 μg / L 99.4 μg / L 138 μg / L 119 μg / L 125 μg / L 10 min 69.2 μg / L 65.3 μg / L 58.9 μg / L 131 μg / L 89.4 μg / L 108 μg / L 15 min 27.7 μg / L 30.5 μg / L 25.1 μg / L 115 μg / L 74.7 μg / L 88.1 μg / L 20 min 11.3 μg / L 9.5 μg / L 10.4 μg / L 106 μg / L 39.2 μg / L 62.6 μg / L 25 min 4.9 μg / L 5.1 μg / L 4.8 μg / L 97 μg / L 21.5 μg / L 45.8 μg / L 30 min 4.0 μg / L 3.9 μg / L 3.8 μg / L 85 μg / L 11.3 μg / L 39.4 μg / L

[0090] As shown in Table 1, the dissolved oxygen in Examples 1, 2 and 3 was reduced to below 5μg / L within 30min, which can meet the deaerating requirement of boiler feed water. The dissolved oxygen in Comparative Examples 1-3 could not be reduced to below 5μg / L within 30min, and the deaerating rate was fast. In Comparative Example 1, 2-acetylpyrrole and 2-acetylpyridine were used as the main deaerating agent, and the effect was poor, which indicated that the newly synthesized deaerating agents 1-(1-((2-pyrrolyl)imine)ethyl)carbazide and 1-(1-((2-pyridyl)imine)ethyl)carbazide had good deaerating effect. In Comparative Example 2, there was no deaerating auxiliary agent, and the deaerating rate was obviously slower than that in Example 1, which indicated that the synergistic effect between the deaerating auxiliary agent and the deaerating main agent was obvious, and the deaerating auxiliary agent had the function of catalyzing deaerating. In Comparative Example 3, the effective content of the deaerating main agent was low, and the deaerating effect was also poorer than that in Example 1, which indicated that the deaerating main agent should reach a certain concentration.

Claims

1. An oxygen scavenger for auxiliary oxygen scavenging of boiler feed water, characterized by It is composed of the following components in mass fraction: 280-350 parts of oxygen scavenging main agent, 100-160 parts of oxygen scavenging auxiliary agent, 10 parts of dispersing agent, 50-80 parts of pH regulator and 460-500 parts of softening water; The oxygen scavenging main agent is a combination of 1-(1-((2-pyrrolyl)imine)ethyl)carbazide, 1-(1-((2-pyridyl)imine)ethyl)carbazide, 1-(1-((2-pyrimidyl)imine)ethyl)carbazide, 1-(1-((4-pyrimidyl)imine)ethyl)carbazide, 1-(1-((2-pyrazinyl)imine)ethyl)carbazide, 1-(1-((2-imidazolyl)imine)ethyl)carbazide or 1-(1-((4-imidazolyl)imine)ethyl)carbazide; the oxygen scavenging auxiliary agent is a combination of gallic acid, 1,2-naphthoquinone, 4-(N,N)-dimethylaminophenol or 2-keto-d-gluconic acid; The oxygen scavenging main agent is prepared by the following method comprising the following steps: (1) Under N2 atmosphere, softening water and acetic acid are added into a reactor and mixed uniformly to obtain liquid A; (2) Under N2 atmosphere, 1:1 acetyl compound and carbazide are sequentially added into liquid A, constant temperature water bath is used at high temperature, the solution is slowly volatilized, and the solid is slowly precipitated to obtain suspension B; the acetyl compound is 2-acetylpyrrole, 2-acetylpyridine, 2-acetylpyrimidine, 4-acetylpyrimidine, 2-acetylpyrazine, 2-acetylimidazole or 4-acetylimidazole; (3) The suspension B is centrifuged at not higher than 0°C to obtain a solid, the solid is washed with softening water at not higher than 0°C by centrifugation, and finally the solid is freeze-dried to obtain the oxygen scavenging main agent.

2. The oxygen scavenger for boiler feed water auxiliary deoxidation according to claim 1, characterized in that: In step (2), the molar ratio of the acetyl compound to carbazide is 1:

1.

3. The deoxidizer for boiler feed water auxiliary deoxidation according to claim 1, characterized in that: In step (2), constant temperature water bath is used at 45-50°C, and stirring is performed at 300-400 rpm for 10-12 h.

4. The deoxidizer for boiler feed water auxiliary deoxidation according to claim 1, characterized in that: The dispersing agent is polyethylene glycol 200 or polyethylene imine.

5. The deoxidizer for boiler feed water auxiliary deoxidation according to claim 1, characterized in that: The pH regulator is a combination of cyclohexylamine, morpholine or N-methyldiethanolamine.

6. The method of claim 1, wherein the oxygen scavenger is prepared by the steps of: Specifically, the formula amount of softening water is added into a reaction kettle, the formula amount of dispersing agent is added under stirring, and they are mixed uniformly; then the formula amount of oxygen scavenging main agent is added, and after the oxygen scavenging main agent is completely dissolved, the formula amount of oxygen scavenging auxiliary agent is added and completely dissolved; finally, the formula amount of pH regulator is added, and they are stirred and mixed uniformly to obtain the oxygen scavenging agent.

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