JPS62227096A - Method for preventing corrosion by sulfurization - Google Patents

Abstract

PURPOSE:To effectively inhibit and prevent corrosion by sulfurization at high temp. by charging a slurry, powder or a soln. of an Al compound together with fuel into the combustion atmosphere in a heating furnace. CONSTITUTION:A slurry, powder or a soln. of an Al compound or a hydrate thereof is mixed with heavy oil, coal, oil coke or other fuel by dispersion and the mixture is charged into the combustion atmosphere in a heating furnace or a boiler. The Al compound or the hydrate reacts with free S and CO produced at the reducing part of the combustion atmosphere such as the high temp. part to make the free S and CO harmless, so corrosion by sulfurization is effectively inhibited.

Description

Detailed Description of the Invention (Field of Industrial Application) - This invention is applicable to industrial heating furnaces, boilers, diesel engines, gasoline engines, turbines, heat exchangers, and other combustion devices operated under low oxygen conditions. The present invention relates to a method for effectively suppressing and preventing high-temperature sulfide corrosion that often occurs.

(Prior art) Corrosion that occurs when burning heavy oil with an excessive amount of oxygen is known as high-temperature corrosion that occurs at metal temperatures of 600°C or higher, and sulfur M corrosion that occurs in low-temperature areas. Additives such as magnesium have been used to prevent corrosion.

High-temperature corrosion in this case is due to vanadium attack, and when an additive such as magnesium is used, vanadium attack is suppressed by the following mechanism.

MgO+V2O54Mg0-V2O.

nMgO+ mNazO・nV, Os → mNa
=o・n(MgO・V2O5) On the other hand, there has recently been a remarkable improvement in the combustion efficiency of boilers due to improved materials.

In particular, it has become possible to operate large boilers in low oxygen levels, resulting in a dramatic increase in thermal efficiency.

However, with the low-oxygen operation of this boiler, sulfide corrosion, which was almost never observed in conventional high-oxygen combustion, began to occur in high-temperature parts.

In other words, in high oxygen combustion, all of the ri and yellow content in the oil is SO□,
In low-oxygen combustion, sulfides are formed in the reducing atmosphere or in various places inside the furnace, and are observed to occur, especially on the wood pipe walls of the high-temperature parts of boilers with an excess oxygen content of 1.5z or less. Iron sulfide has started to be detected in large quantities.

This high-temperature sulfide corrosion tends to occur in the combustion chamber, in direct contact with the flame, or in the reducing atmosphere of the ultra-high-temperature part closest to the flame, and varies depending on the operating conditions. This is extremely terrifying corrosion, hundreds of times more severe.

(Problems to be Solved by the Invention) Since this high-temperature sulfide corrosion is different from the corrosion mechanism caused by vanadium attack, it cannot be solved using conventional additives made of magnesium.

In addition, as a method to suppress high-temperature sulfide corrosion, replacing the steel in the combustion chamber with a material with higher corrosion resistance has been implemented, but there are many problems such as expensive equipment and long repair times.

Additionally, measures such as using low sulfur fuel have been taken, but this method also has the disadvantage of being too expensive.

(Means for Solving the Problems) In order to solve the above problems, the inventors of the present application have conducted intensive research and found that slurry, powder, or liquid materials containing aluminum compounds or hydrates thereof as a main component can be used as fuel. In addition, we have discovered that the above-mentioned high-temperature sulfidation corrosion can be extremely effectively suppressed and prevented by introducing it into a combustion atmosphere.

The slurry, powder, or liquid used in the present invention may be composed of an aluminum compound or its hydrate alone, or may have an aluminum compound or its hydrate as a main component, and an alkaline earth metal compound or/and an aluminum compound or its hydrate as a main component. It may also be configured in the form of a combination or eutectic with one or more of transition metals, other metal compounds, or 1II4 or more.

When an aluminum compound or its hydrate and another metal compound are used in combination, the ratio of the combination is preferably 8 IJi/other metal oxide: 1 or more in terms of oxide.

The aluminum compound used in this invention may be a 'Ma compound or an organic metal salt, and specifically
Hydrates of aluminum such as 20i, AI(011)z, aluminum naphthenate, aluminum petroleum sulfonate, aluminum fatty acids, aluminum organic acids, etc., include alumina gel, which can be expressed by the chemical formula A1□03・nfl□0. It is a gel-like substance represented by.

Alkaline earth metals that can be combined with these include Mg, Ca, Ba'? , as a transition metal, F
Metals such as Si, Cu, etc. can be used as other metals such as e, Go, old, Mn, and Ti.Although other transition metals can also be used, they are expensive and inappropriate.

These metals may be in the form of inorganic compounds such as oxides and hydroxides, or organic substances such as naphthenates, sulfonates, fatty acid salts, and organic acid salts.

The present inventors have discovered that the use of one or more of the above-mentioned other metals in combination with an aluminum compound has a synergistic effect in preventing sulfide corrosion.

The metals and compounds used in this invention can be used in any form such as powder, slurry, or liquid.

If it is used in powder form, it should be as fine as possible; generally reprinted powders of about 100 liters or less can be used.

When making a slurry, petroleum-based solvents can generally be used as the solvent, and it is desirable that these petroleum-based solvents have a flash point of 70°C or higher, and in particular, reprinted surfactants are used in this. By doing so, it is possible to increase the dispersion power and obtain a uniform slurry.

Furthermore, when used in liquid form, organometallic salts can be dissolved in petroleum solvents, but compounds such as sodium aluminate can be used to prepare aqueous solutions.
Even if this is added, the effect is no different from that of the above-mentioned oil-based solution.

Fuels used in this invention include heavy oil, coal, oil coke, coke, etc., and powdered, slurry, and liquid additives containing the aluminum compound or its hydrate as a main component may be added to these fuels. It may be mixed and dispersed and then introduced into the combustion atmosphere, or it may be introduced into the combustion flame separately from the fuel, and the most suitable method may be selected depending on the type of boiler, combustion method, etc.

In this case, the amount of aluminum compound or its hydrate added that is effective in suppressing high-temperature sulfide corrosion may vary depending on the operating conditions and the composition of S and Na in the fuel used, or the amount of S in the fuel that is the cause of sulfide corrosion may vary depending on the operating conditions and the composition of S and Na in the fuel used. It is sufficient to have the amount necessary to suppress the effect of v1, and it is appropriate and preferably about 1/100 to 1/10.000 in terms of A1.03 for the above fuel containing S of 0.3 to 5z. 11500~1/:l, 00 mouth is good.

(Effects of the Invention) As in this invention, when a slurry, powder, or liquid material containing an aluminum compound or its hydrate as a main component is introduced together with fuel into a combustion atmosphere under low oxygen operating conditions, it is an amphoteric metal. Aluminum compounds or their hydrates react with free S or CO, etc., which are often generated in the above-mentioned reducing parts such as high-temperature parts in the combustion atmosphere, rendering them harmless and effectively suppressing the occurrence of sulfide corrosion. .

Therefore, according to the present invention, it is possible to effectively prevent high-temperature sulfidation corrosion that often occurs under low-oxygen operating conditions using an inexpensive and simple method that uses existing combustion conditions and equipment.

Furthermore, when one or more of the above-mentioned transition metals, other metals, or their compounds are used in combination with an aluminum compound or its hydrate, in addition to showing a synergistic effect in preventing sulfide corrosion, N
Other measures to prevent boiler failure, such as reducing oxygen, preventing vanadium corrosion, and taking measures against 801, can also be taken.

(Example) Examples of this invention will be shown below.

l) Additive manufacturing method (A) 8120: l (average particle size 5 l) 20 parts, g
(011) 210 parts fume kerosene 60 parts, lecithin and PO
While stirring 10 parts of E nonylphenol ether (IILBIO) using a homogenizer at 10,000 rpm, 2 to 3 ifl of water was added, and the mixture was stirred for 30 minutes to form a stable oil slurry.

(B.) 15 parts of oleic acid-treated AI (011) and 20 parts of oleic acid-treated triiron tetroxide are added to 45 parts of white kerosene and dispersed using a homogenizer to form a uniform and stable slurry.

(C) 6 parts of aluminum octenoate was dissolved in 94 parts of white kerosene to form a solution.

Example 1 The above three additives are forcibly mixed into the boiler fuel piping at a volume ratio of 1:1000 into the fuel using a plunger pump, and are combusted together with the fuel.

The boiler type and operating conditions used in the experiment are as follows.

Boiler model and operating conditions Maximum evaporation amount: : 150T/11. Maximum steam pressure crab 1
25Kg/cm2 Maximum steam temperature = 540℃, Fuel usage: 21Kl/11Fuel: C heavy oil (32.4%),
Excess oxygen amount: 1. OK To determine high-temperature sulfide corrosion, operate the boiler for six months without additives, cut out the tube in the high-temperature section where high-temperature sulfide corrosion is occurring, and replace it with a new tube.
As shown in Section 2, additives were added and combustion operation was performed continuously for six months, and the tube was cut at the same location, and the JIS G
When the state of sulfide adhesion was determined using the sulfur print test method for 0560 steel, sulfide formation was observed in the area facing the flow direction of high-temperature combustion gas, indicating that sulfide corrosion was occurring. .

In addition, the parts of the steel where sulfide corrosion occurred were observed using a microscope. As shown in Figure 1, if no additives (blank) are used, the metal surface of the tube will be uneven, and whether it is severe sulfide corrosion or if additives (A), (B), and (C) are used. , the sulfide layer is thin and the tube surface is smooth.

Example 2 The actual ash in the combustion furnace was pulverized, and the above additive (A) was added to it.
(B) (C) Add a total of 5X tolOX, further add 1% and 2% of carbon black, mix uniformly, place 10 parts in a crucible, and embed a 5TBA-24 test piece therein. Next C0t12%, 0□4%, 5O2250
The crucible was placed in an electric furnace in an atmosphere of 0 ppl test gas, the atmosphere temperature in the furnace was set to 650°C, and after heating for 3 hours, the corrosion loss of the test piece was measured.

The results are shown in FIG.

According to this, when additives (A), (B), and (C) were added, the corrosion loss was smaller than when no additives were added (blank).

[Brief explanation of drawings]

Figure 1 is a drawing showing the state of the cut tube steel material observed under a microscope in order to observe the state of high-temperature sulfide corrosion in Example 1. Figure (B) is a diagram when additives are used, Figure 2 is a diagram showing the relationship between the type of additive and the corrosion loss of the test piece in Example 2, and Figure 2 (A) is a diagram showing the relationship between the type of additive and the corrosion loss of the test piece in Example 2. Figure 2 (B) is a diagram when 2% of carbon black is added. Figure 1 (A) CB)

Claims (1)

[Claims] A sulfide corrosion prevention method characterized by introducing a slurry, powder, or liquid material containing an aluminum compound or its hydrate as a main component into a combustion atmosphere together with fuel to prevent sulfide corrosion in a high-temperature section of a combustion furnace. .