KR101772880B1 - Corrosion preventive method of heat exchange facilities or boiler - Google Patents

Abstract

The present invention relates to a liquid additive composition containing magnesium ions, a dispersant, a corrosion inhibitor, an emulsifier and a solvent.
In the present invention, by using the liquid additive composition containing magnesium ions, neutralization of the corrosion product and the base material exposed on the surface suppress corrosion by using the corrosion inhibitor, so that the integrity of the outer surface exposed to the exhaust gas of the boiler using the fossil fuel .

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method for preventing external corrosion of a heat exchanger or a boiler,

The present invention relates to a heat exchange device or a method for preventing corrosion of the outer surface of a boiler.

Corrosion of high-temperature parts and low-temperature parts generated by the exhaust gas occur differently depending on the fuel. In particular, sulfur oxides generated by sulfur in fossil fuels have a significant impact on cold corrosion. For example, SO ₃ generated in heavy oil combustion is generated in the boiler furnace and the exhaust gas flow path. In the furnace, the design of the furnace greatly influences the generation of SO _{3. In} the high temperature portion of the exhaust gas, Thereby increasing the corrosion and the SO ₃ conversion rate, and the SO ₃ is condensed at the low temperature portion to corrode the metal iron and raise the temperature of the AH, thereby greatly affecting the power generation efficiency.

In order to effectively remove this, a method of using an undifferentiated and dispersed magnesium compound as an additive for lubricating oil or fuel oil (high-sulfur heavy oil) is widely practiced in foreign countries.

In addition, a method of using magnesium in the form of slurry is disclosed in Japan.

The magnesium compound can control SO ₃ , a corrosive substance in the boiler exhaust gas, by the following three actions.

1) controls the SO ₂ → catalytic action to promote the conversion to SO ₃ caused by the deposit (V2O5) in the boiler tube outer surface

2) Neutralize sulfuric acid condensed at low temperatures through the formation of magnesium sulfate.

3) Removes gaseous SO ₃ by gas-solid reaction to form magnesium sulphate.

However, when the slurry form is used, reactivity is problematic and workability is poor. In addition, since it is mixed with fuel oil, it is inevitably limited.

A method of using magnesium in the form of slurry is disclosed in Korean Patent Publication No. 10-2005-0043355. In the conventional patent as in the above patent, in order to solve the corrosion problem occurring in the power plant using the heavy sulfur heavy fuel as a fuel, it is main to add magnesium in the form of slurry in the oil as a fuel additive. The use of magnesium in the form of slurries in the oil is expensive, and incidentally, the additive remains excessively in the boiler bottom and low temperature areas, resulting in adherent problems (waste disposal, lower attachment buildup). In addition, the additive is designed to dissolve only in the oil, and it is difficult to remove the corrosion product from the power plant using water for improvement of combustion or the outer surface of the tube where the irregularity is severe and the corrosion is proceeding.

The prior art is mainly limited to use as an additive for liquid fuels, and measures for the generation of sulfur oxides are insufficient at present in solid fuels. There is a need for a versatile anti-corrosive additive in coal-fueled boilers, wood, pellets, and other solid fuel fired boilers, and gas-fired boilers.

The present invention relates to a chemical composition (a liquid additive composition or a solid phase additive) added to a liquid and a solid fuel to remove corrosion products such as a HRSG fin tube and an outer surface of an iron structure having a concave- The present invention relates to a method for removing corrosive organisms and corrosion of a base material using a composition.

The present invention relates to a liquid additive composition containing magnesium ions, a dispersant, a corrosion inhibitor, an emulsifier and a solvent.

Hereinafter, the additive composition according to the present invention will be described in more detail.

The ionic magnesium compound according to the present invention contains magnesium ions, a dispersant, a corrosion inhibitor, an emulsifier and a solvent.

In the present invention, magnesium ions can neutralize corrosion products. In the present invention, by using magnesium ion, it can be used in facilities having various structures as compared with the conventional magnesium oxide.

 The magnesium ion may be included in the additive composition in the form of magnesium chloride or magnesium hydroxide. The magnesium chloride or magnesium hydroxide is ionically present in the additive composition by the dispersant described below. The magnesium ion may be contained in an amount of 10 to 30 parts by weight, preferably 15 to 20 parts by weight, based on 100 parts by weight of the liquid additive composition. If the content is less than 10 parts by weight, corrosion prevention effect may be insufficient. If the content is more than 30 parts by weight, magnesium ions not participating in the neutralization reaction may be discharged to the outside, causing environmental pollution, .

In the present invention, the dispersing agent allows the magnesium ions to be uniformly dispersed in the additive. As the dispersing agent, an anionic surfactant having a carbon number of 25 or more can be used. Specifically, one or more selected from the group consisting of olefin-sodium maleate and condensed phosphate can be used.

In the present invention, the dispersant may be included in an amount of 5 to 20 parts by weight, preferably 10 to 15 parts by weight, based on 100 parts by weight of the liquid additive composition. If the content is less than 5 parts by weight, the effect of dispersing magnesium ions may be insignificant. If it exceeds 20 parts by weight, the material cost may increase.

In the present invention, the corrosion inhibitor plays a role in suppressing the corrosion of the base material exposed on the surface, so that the integrity of the outer surface exposed to the exhaust gas and the like can be secured. As the corrosion inhibitor, any conventional corrosion inhibitor used in the art can be used without limitation. Specifically, one or more selected from the group consisting of hexadecylpyridinium compound, thiourea and triclosan can be used. The corrosion inhibitor may be contained in an amount of 0.01 to 1.0 part by weight, preferably 0.1 to 0.3 part by weight based on 100 parts by weight of the liquid additive composition. If the content is less than 0.01 part by weight, the corrosion prevention effect of the base material may be insignificant.

In the present invention, an emulsifier is used to facilitate mixing of magnesium ions with a solvent or the like. As the emulsifier, a common emulsifier used in the art can be used. Specifically, at least one selected from the group consisting of lauryl alcohol, lauryl alcohol sulfate ester, sodium salt, oleic acid and glycerin can be used. The emulsifier may be included in an amount of 0.01 to 1.0 part by weight, preferably 0.1 to 0.3 part by weight based on 100 parts by weight of the liquid additive composition. If the content of the emulsifier is less than 0.1 part by weight, there is a fear that the emulsification will not be performed properly. If the amount is more than 0.3 part by weight, there is a fear that the emulsifier is injected excessively without being economical.

The solvent used in the present invention may be any solvent commonly used in the art. Specifically, one or more selected from the group consisting of water and alcohol may be used, and preferably a mixture of water and alcohol may be used. In this case, the mixing ratio of water to alcohol may be 7: 3 to 9: 1. The solvent may be contained in an amount of 60 to 80 parts by weight based on 100 parts by weight of the liquid additive composition, and preferably in an amount of 64.4 to 74.8 parts by weight.

The liquid additive composition according to the present invention has the following effects.

First, vanadium pentoxide, which occurs mainly in the combustion process, is converted into a vanadium compound having a high melting point to prevent accumulation in the boiler, thereby preventing the generation of sulfur trioxide due to the catalytic reaction.

The melting point of the vanadium pentoxide is easily melted in the boiler at about 600 ° C and attached to the inner wall of the boiler, thereby causing scale formation. This vanadium pentoxide not only becomes a catalyst for the production of sulfur trioxide as described above, but also oxidizes the outer wall of the boiler.

When the liquid additive composition according to the present invention is added during the combustion process, magnesium ions react with vanadium pentoxide to form magnesium sulfate, and the magnesium sulfate is discharged together with the exhaust gas to the outside of the boiler to accumulate the vanadium pentoxide in the boiler prevent. This can reduce the amount of sulfur trioxide produced during the combustion process. The magnesium sulfate can neutralize sulfuric acid condensed at a low temperature.

Further, when the liquid additive composition is applied to the surface of a solid raw material such as coal, scattering of the solid raw material can be prevented.

The liquid additive composition described above in the present invention can be mixed with dry ice and used as a solid phase additive.

In the present invention, by using the solid phase additive including dry ice, it is easy to remove the external corrosive matter, the contaminants do not remain, and the liquid phase corrosion inhibiting substance remains as the dry ice evaporates, so that the subsequent corrosion can be prevented.

In the present invention, the liquid additive composition may be included in an amount of 1 to 20 parts by weight based on 100 parts by weight of the solid phase additive, and the dry ice may be included in an amount of 80 to 99 parts by weight based on 100 parts by weight of the additive.

In the present invention, the liquid additive composition may be prepared by mixing the magnesium ions, the dispersant, the corrosion inhibitor, the emulsifier, and the solvent described above using a general mixing method used in the art.

In addition, the solid additive composition including the liquid additive composition and the dry ice can be prepared by rapid freezing through the lyophilization method.

The present invention also relates to an outer surface corrosion prevention method comprising contacting the above-described liquid additive composition or solid phase additive with an iron structure.

In the present invention, the iron structure may be a boiler or a heat exchanger having a concave and convex structure, and may be a batch recovery steam generator (HRSG). The HRSG is used to recover energy in a high temperature exhaust gas discharged after combustion in a gas turbine or the like, and has a cylindrical tube shape. Specifically, in order to improve the heat exchange ability of a tube, which is an iron structure, a structure (fin tube) in which a pin is inserted into a columnar tube at regular intervals and is rotated around the cylinder is densely arranged, The pin tubes of the same shape are piled up in a staggered manner and the fin tubes are piled up. In the exhaust steam generator, a high-temperature exhaust gas may flow outside the cylinder, and a heating medium such as water or steam may pass through the cylindrical steam generator.

Conventionally, in order to prevent the corrosion of the HRSG, which is a composite structure, the tube is washed using high-pressure water from the upper part and the corrosion products that fall off are collected at the discharge port. However, It is difficult to spray evenly the washing water, only the loose corrosive matter on the surface directly contacting the water is removed, and it is difficult to completely remove the water. Therefore, when the boiler is operated after the washing, the exhaust gas and the exhaust gas are discharged to the outside. As a result, the corroded area causes continuous corrosion, causing many problems in the stable operation of the equipment.

On the other hand, the liquid additive composition or solid phase additive according to the present invention can have an excellent corrosion prevention effect by being in contact with the outer surface of the cylinder of the heat exchanger having the concavo-convex structure, in particular, the batch recovery steam generator.

Specifically, the additive can be injected into the outer tube of the boiler or heat exchanger through a nozzle or the like. At this time, the injection pressure is not particularly limited, and may be 10 kg / cm ^{2 or} more. The additive can be evenly sprayed on the surface of the concavities and convexities at the above pressure. The upper limit of the injection pressure may be 100 kg / cm < ² >.

The liquid additive composition or solid phase additive in the present invention can preferably be injected at the outlet of the gas turbine where the fuel is burned. Since the iron structure (boiler and heat exchanger) used in the present invention is installed at the rear end of the gas turbine, corrosion of the iron structure can be easily prevented by injecting the liquid additive composition or the solid phase additive at the outlet of the gas turbine.

The liquid additive composition or solid phase additive of the present invention can be applied to the surface of a solid fuel such as coal to neutralize the sulfuric acid produced during combustion of the solid fuel and prevent the scattering of solid fuel, particularly coal.

In the present invention, by using the liquid additive composition or the solid phase additive, neutralization of the corrosion product and the base material exposed to the surface are inhibited by the corrosion inhibitor, thereby ensuring the integrity of the outer surface exposed to the exhaust gas of the boiler using the fossil fuel . It can be used for facilities having various structures than the conventional slurry-type magnesium oxide-based corrosion inhibitor, and the ion phase increases the reactivity by using magnesium, which is very advantageous in terms of cost.

When the liquid additive composition or the solid phase additive is injected into the heavy oil power plant, the operating cost can be reduced by about 30% compared with the slurry type currently being operated, and the savings can be achieved by a total of 7.8 billion won / year. Since only 10 large boilers are used in domestic heavy oil power plants, the cost savings of about 20 billion won can be seen. In terms of cost of additives used for coal power, Since 50 boilers are operated, it is possible to reduce the cost of drugs by 30% annually by about 30%.

Figure 1 shows the main reaction zone where the neutralization reaction takes place on the tube surface of the heat exchanger.
2 shows the injection position of the boiler tube outer surface slagging filler additive.
Figure 3 shows a method for injecting a liquid additive composition according to the present invention into a boiler furnace.
Fig. 4 is a micrograph of the emulsification test result of the liquid additive composition prepared by the examples. Fig.

The content of the present invention will be described in detail with reference to the following drawings.

In the present invention, Figure 1 shows the main reaction zone in which the neutralization takes place on the tube surface of the heat exchanger.

A liquid additive composition containing magnesium ions is injected in order to remove corrosion and various obstacles caused by corrosive substances contained in the exhaust gas generated by the combustion of fossil fuel, And if the amount of injection is large, the material cost is increased, and there is a possibility that environmental pollution may occur due to discharge through the chimney.

Since the liquid additive composition injected with the neutralization material is in a state of being mixed with the solvent, the injection is possible. However, it is technically impossible to continuously and uniformly spray the additive on the surface of a tube (ex: HRSG: batch recovery steam generator) of a heat exchanger having a concave and convex structure continuously operated over an area of 5 m in length and width. The expected technical difficulties are as follows.

As shown by the distribution of the flow field, the flow of the exhaust gas is very stable. Since the additive composition has very small particles (droplets) in a stable flow of exhaust gas, the momentum force due to the injection of the particles is very small, which causes the particles injected from the nozzles not to spread widely, . Therefore, the additive can not be uniformly distributed inside the HRSG.

At present it is necessary to increase the number of nozzles in order to even out the distribution of the injected additive composition. However, if the additive composition is divided into a plurality of nozzles, it is difficult to distribute the flow rate because the amount of injected per nozzle is so small that the problems of mounting the plurality of nozzles and increasing the resistance of the exhaust gas flow Lt; / RTI >

The neutralization reaction zone can be largely divided into a pre-heat exchanger zone, a tube bank zone, or a combination of two zones, and the most effective neutralization zone is the one-stage reaction zone shown in FIG. 1 . It is possible to prevent corrosion in the heat exchanger tube group which is a problem in the first-step reaction region. However, the position at which the injection nozzle can be installed is generally in the vicinity of the first-step reaction zone. It is difficult to obtain a smooth particle distribution in the first-step reaction region in a state where the flow of the exhaust gas is stable.

In order to maximize the neutralization reaction in the first-step reaction zone, the best way to solve this problem is to inject the gas at a position far away from the position (HRSG) of the first-step reaction zone. In this case, the contact time between the exhaust gas and the additive composition becomes longer, and the flow of the exhaust gas is somewhat more complicated than the position at which the nozzle is currently installed, so that the diffusion effect of the particles is considered to be larger. When the neutralization material (liquid additive composition) is injected at the rear end of the turbine and the neutralization material (liquid additive composition) is injected at the position which is judged to be the most favorable position, the neutralization reaction of the corrosive gas is promoted by mixing smoothly with the exhaust gas.

FIG. 2 is a view showing an injection position of an additive composition for preventing corrosion of an outer surface of a boiler tube, specifically, a position where an additive is injected to neutralize the exhaust gas of a thermal power boiler. If the injection position of the additive is low, the coating phenomenon occurs on the outer surface of the boiler tube near the flame. Therefore, it is a principle to inject into the upper burner. In FIG. 2, an area where the adhesion rate of various foreign matters in the exhaust gas is high is shown in a specific region while the exhaust gas proceeds along the flow.

Figure 3 also shows a method for injecting an additive composition according to the invention into a furnace of a boiler or heat exchanger.

As shown in FIG. 3, the additive composition may be injected in various forms depending on the type of the nozzle, and the nozzle may be injected at a position apart from the first-step reaction region (see FIG. 1).

Hereinafter, the present invention will be described in more detail with reference to the following examples and comparative examples, but the scope of the present invention is not limited by the following examples.

Example 1

(1) Preparation of liquid additive composition

, 20 parts by weight of magnesium ion, 10 parts by weight of Triton X100 (dispersant), 0.3 part by weight of ascorbic acid (corrosion inhibitor), 0.3 part by weight of lauryl alcohol (emulsifier), and 69.4 parts by weight of a solvent having a ratio of water and alcohol of 8: To prepare a liquid additive composition.

The characteristics of the formed emulsion were tested by injecting the prepared ionic magnesium compound, heavy oil and water at a certain concentration (500 ppm of fuel) using an emulsification testing apparatus.

The stability test of the sample tested in the emulsion performance device was measured by the sedimentation rate method and the shape of particles was observed with a microscope.

When the concentration of the emulsifier and the experimental method (sedimentation rate method) are the same, the performance of the emulsifier is maintained for 24 hours.

Figure 4 shows a micrograph of a sample tested in an emulsification performance apparatus.

4, the additive + heavy oil + water (ionic magnesium) was prepared by adding the additive + heavy oil + water to the conventional additives (magnesium oxide instead of ionic magnesium ), The heavy oil + water shows a microscopic photograph as a result of the emulsification test when the additive is not used. As shown in FIG. 4, when the additive containing magnesium ions is used, it can be confirmed that the emulsification performance is superior to that in the case where additives and additives containing magnesium oxide are not used.

(2) Manufacture of solid phase additives

10 parts by weight of the liquid additive composition prepared in (1) and 90 parts by weight of dry ice were mixed and rapidly frozen using a freeze-drying method to prepare a solid phase additive.

The prepared additive is sprayed on the irregular structure to eliminate the formation of corrosion, and the corrosion inhibitor and the ionic magnesium compound are deposited on the surface by the evaporation of the dry ice, thereby protecting the base material and neutralizing the sulfur oxide, .

Example 2.

A certain amount of a solution containing 10 parts by weight of the liquid additive composition of Example 1 (1) was applied (1 kg / m < ² >) to coal low in the coal loading dock and the additive was injected (1 kg / m ² ) to neutralize the sulfur oxides generated in the combustion of coal and prevent the scattering of the coal at the same time.

Claims (14)

Magnesium ions, a dispersant, a corrosion inhibitor, an emulsifier and a solvent,
The magnesium ions are contained in the form of magnesium chloride or magnesium hydroxide,
Wherein the solvent is at least one selected from the group consisting of water and an alcohol,
A liquid additive composition comprising 10 to 30 parts by weight of magnesium ions, 5 to 20 parts by weight of a dispersant, 0.01 to 1.0 part by weight of a corrosion inhibitor, 0.01 to 1.0 part by weight of an emulsifier and 60 to 80 parts by weight of a solvent, based on 100 parts by weight of the liquid additive composition .
delete The method according to claim 1,
Wherein the dispersant is an anionic surfactant having 25 or more carbon atoms.
The method according to claim 1,
The corrosion inhibitor is at least one selected from the group consisting of hexadecylpyridinium compounds, thiourea, and triclosan.
The method according to claim 1,
Wherein the emulsifier is at least one selected from the group consisting of lauryl alcohol sulfate ester, sodium salt, oleic acid, and glycerin.
delete delete A liquid additive composition containing a magnesium ion, a dispersant, a corrosion inhibitor, an emulsifier and a solvent; And
Including dry ice,
The magnesium ions are contained in the form of magnesium chloride or magnesium hydroxide,
Wherein the solvent is at least one selected from the group consisting of water and an alcohol,
A solid additive comprising 10 to 30 parts by weight of magnesium ions, 5 to 20 parts by weight of a dispersant, 0.01 to 1.0 part by weight of a corrosion inhibitor, 0.01 to 1.0 part by weight of an emulsifier and 60 to 80 parts by weight of a solvent, based on 100 parts by weight of the liquid additive composition.
9. The method of claim 8,
1 to 20 parts by weight of the liquid additive composition and 80 to 99 parts by weight of dry ice based on 100 parts by weight of the solid additive.
A method for preventing corrosion of an iron structure comprising the step of contacting the additive composition according to claim 1 or the solid additive according to claim 8 to an iron structure.
11. The method of claim 10,
The iron structure is a method for preventing corrosion of a steel structure that is a heat exchanger or a boiler.
11. The method of claim 10,
A method for preventing corrosion of a steel structure in which a liquid additive composition or a solid phase additive is injected into an outlet of a gas turbine in which fuel is burnt.
11. The method of claim 10,
A method for preventing corrosion of a steel structure by applying a liquid additive composition or a solid phase additive to a steel structure at a pressure of 10 kg / cm ² or more.
A method for preventing scattering of coal, comprising applying the liquid additive composition according to claim 1 or the solid additive according to claim 8 to the surface of coal.

Images