JP2011039011A - Sulfidation corrosion evaluation method - Google Patents

Abstract

The present invention provides a method for evaluating sulfide corrosion, which can evaluate corrosion of a material in a reducing atmosphere based on oxygen gas and sulfur gas.
The step of measuring the amount of corrosion of a material by setting the concentration of the sulfur compound gas constant and setting the partial pressure of the oxygen gas and the sulfur gas to a predetermined pressure is performed by changing the partial pressure of the oxygen gas and the sulfur gas. Measure the amount of corrosion for each partial pressure of oxygen gas and sulfur gas, and the oxygen gas and sulfur gas when the amount of corrosion does not change more than a predetermined amount with respect to the change in partial pressure of oxygen gas and sulfur gas The range of the partial pressure of the oxygen gas and sulfur gas when the amount of corrosion changes with respect to the change of the partial pressure of oxygen gas and sulfur gas is the second region, and the range of the partial pressure of oxygen gas and sulfur gas is the second region. In the region, the amount of corrosion of the material is evaluated only by the partial pressure of oxygen gas and sulfur gas. Further, in the first region, there is a range in which the corrosion amount decreases with respect to the decrease in the sulfur compound gas, but even in that case, the corrosion amount can be evaluated based on the partial pressure of oxygen gas and sulfur gas based on the safety evaluation.
[Selection] Figure 2

Description

  The present invention relates to a method for evaluating sulfide corrosion, and is particularly useful when applied to evaluate sulfide corrosion of a furnace wall tube of a thermal power boiler using pulverized coal as a fuel.

  2. Description of the Related Art In recent years, thermal power generation equipment using a mixture of pulverized coal in which coal that has been conventionally used as a fuel and another type of coal that has a large recoverable reserve is mixed at a constant ratio has been used. On the other hand, in the thermal power generation facilities, low NOx operation is strengthened from the viewpoint of environmental considerations, etc., but this creates a strong reducing atmosphere in the furnace of the thermal boiler, and the furnace wall tubes constituting the furnace, etc. There is a problem that the rate of progress of corrosion / thinning of the steel (hereinafter referred to simply as corrosion) increases.

  In addition to taking preventive measures against such corrosion, it is also important to predict the degree of corrosion quantitatively. As a prior art, there is a method for evaluating the life of a furnace wall tube based on the relationship between the corrosion of a furnace wall tube of a boiler and the concentration of hydrogen sulfide gas (sulfide gas) (see, for example, Patent Document 1). .

However, in view of the fact that thermal boilers are operated under various combustion conditions and the current situation that the types of coal are diversified as described above, it is possible to use only hydrogen sulfide (H ₂ S) gas as an evaluation standard. It is not necessarily valid, and it is considered that an accurate evaluation of corrosion cannot be performed.

  Such a problem is not limited to the furnace wall tube of a thermal boiler using pulverized coal, and similarly exists when evaluating the corrosion of materials used in a reducing atmosphere.

Japanese Patent Laid-Open No. 2003-4201

  In view of the above-described prior art, the present invention clarifies that corrosion of a material in a reducing atmosphere can be evaluated based on an index other than sulfide gas, and corrosion can be more accurately evaluated using the index. An object is to provide a method for evaluating sulfide corrosion.

As shown in Patent Document 1 and the like, conventionally, when evaluating the corrosion of a furnace wall tube, the H ₂ S concentration is used as an index.

However, the inventors of the present application have examined the validity of using only the index, and as a result of repeated experiments, have obtained knowledge that corrosion can be evaluated using other indices. That is, the inventor of the present application pays attention to the fact that the partial pressure of the gas other than the H ₂ S gas in the furnace atmosphere is different if the coal type and combustion conditions are different in the thermal power boiler. In the evaluation, the inventors have obtained the knowledge that the partial pressure of oxygen gas and sulfur gas, which are examples of such gas, can be used as an index.

  Based on this knowledge, the inventors of the present application have clarified that the corrosion of the material in a reducing atmosphere can be evaluated using the partial pressure of oxygen gas and sulfur gas as an index, and the corrosion can be more accurately performed using the index. An evaluation method for sulfide corrosion that can be evaluated was completed. Below, the evaluation method of sulfidation corrosion concerning the present invention is explained.

  A first aspect of the present invention for achieving the above object is a method for evaluating sulfidation corrosion of a material in a reducing atmosphere, wherein the concentration of the sulfur compound gas is constant, and the partial pressure of oxygen gas and sulfur gas The process of measuring the amount of corrosion of the material by setting the pressure to a predetermined pressure is performed by changing the partial pressure of oxygen gas and sulfur gas, and the amount of corrosion for each partial pressure of oxygen gas and sulfur gas is measured. The range of the partial pressure of the oxygen gas and sulfur gas when the corrosion amount does not change to a predetermined amount or more with respect to the change of the partial pressure of sulfur gas and the sulfur gas is defined as the first region, On the other hand, the range of the partial pressure of the oxygen gas and sulfur gas when the corrosion amount changes is set as the second region, and in the second region, the corrosion amount of the material is evaluated only by the partial pressure of oxygen gas and sulfur gas. It is in the characteristic evaluation method of sulfide corrosion.

  In the first aspect, in the second region, the corrosion amount of the material can be evaluated only by the partial pressures of oxygen gas and sulfur gas.

  According to a second aspect of the present invention, in the sulfidation corrosion evaluation method described in the first aspect, a boundary range between the first region and the second region is a transition region. The process of measuring the amount of corrosion of the material by setting the partial pressure of the sulfur gas constant and setting the concentration of the sulfur compound gas to a predetermined concentration is carried out by changing the concentration of the sulfur compound gas. The amount of corrosion of the material is measured, and the safety evaluation of the influence of the concentration of the sulfur compound gas on the amount of corrosion of the material is performed. Based on the safety evaluation, the partial pressure of oxygen gas and sulfur gas is determined in the transition region. This is an evaluation method for sulfide corrosion characterized by evaluating the amount of corrosion of a material only.

  In the second aspect, in the transition region, the corrosion amount of the material can be evaluated only by the partial pressures of oxygen gas and sulfur gas based on the safety evaluation.

  According to a third aspect of the present invention, in the method for evaluating sulfide corrosion described in the second aspect, as the safety evaluation, it is evaluated whether or not the corrosion amount with respect to an increase in the sulfur compound gas concentration is in a relation to change. In the case where the relationship does not change, there is a sulfide corrosion evaluation method characterized in that the corrosion amount of the material is evaluated by partial pressures of oxygen gas and sulfur gas.

  In the third aspect, as the safety evaluation, by evaluating whether or not the corrosion amount with respect to the increase in the sulfur compound gas concentration has a relationship to be changed, the corrosion amount in the transition region is the amount of oxygen gas and sulfur gas. It can be evaluated by pressure.

  According to a fourth aspect of the present invention, in the sulfidation corrosion evaluation method according to any one of the first to third aspects, the partial pressures of oxygen gas and sulfur gas are made constant for the first region, and sulfur is added. The process of measuring the amount of corrosion of the material by setting the concentration of the compound gas to a predetermined concentration is performed by changing the concentration of the sulfur compound gas, measuring the amount of corrosion for each concentration of the sulfur compound gas, and the concentration of the sulfur compound gas. The sulfur compound gas concentration range in which the increase in the corrosion amount with respect to the increase in the amount is saturated is defined as the 1-A region, and in the 1-A region, the corrosion amount of the material is evaluated only by the partial pressures of oxygen gas and sulfur gas. It is in the evaluation method of sulfide corrosion characterized by this.

  In the fourth aspect, the amount of corrosion of the material can be evaluated only by the partial pressures of oxygen gas and sulfur gas in the 1-A region.

  According to a fifth aspect of the present invention, in the sulfidation corrosion evaluation method according to the fourth aspect, a region other than the first-A region in the first region is defined as a first 1-A ′ region, In the 1-A ′ region, the safety evaluation is performed on the influence of the concentration of the sulfur compound gas on the corrosion amount of the material, and the corrosion amount of the material is determined only by the partial pressures of oxygen gas and sulfur gas based on the safety evaluation. It is in the evaluation method of sulfidation corrosion characterized by evaluating.

  In the fifth aspect, in the first 1-A ′ region, the corrosion amount of the material can be evaluated only by the partial pressures of oxygen gas and sulfur gas based on the safety evaluation.

  According to a sixth aspect of the present invention, in the sulfidation corrosion evaluation method described in the fifth aspect, as the safety evaluation, whether or not the corrosion amount is reduced with respect to the decrease in the sulfur compound gas concentration. In the method of evaluating sulfide corrosion, the amount of corrosion of the material is evaluated by partial pressures of oxygen gas and sulfur gas.

  In the sixth aspect, when the corrosion amount decreases with respect to the decrease in the sulfur compound gas concentration in the 1-A ′ region, the corrosion amount of the material can be evaluated only by the partial pressures of oxygen gas and sulfur gas. it can.

  According to the present invention, it is clarified that corrosion of a material in a reducing atmosphere can be evaluated based on an index other than sulfide gas, and evaluation of sulfide corrosion that can more accurately evaluate corrosion using the index. A method is provided.

It is a figure which shows schematic structure of the evaluation apparatus which concerns on Embodiment 1 of this invention. It is a flow which shows the implementation procedure of the evaluation method of sulfide corrosion which concerns on Embodiment 1 of this invention. It is a figure which shows the relationship between an apparent sulfur partial pressure and oxygen partial pressure, and the amount of corrosion. It is a graph showing the relationship between the concentration and the amount of corrosion of H _{2 S} gas and SO ₂ gas in the first region. The 1-A region is a diagram showing the relationship between the concentration and the amount of corrosion of H _{2 S} gas and SO ₂ gas in the 1-B region and the 1-C region. Is a graph showing the relationship between the concentration and the amount of corrosion of SO ₂ gas in the transition region. It is a graph showing the relationship between the concentration and the amount of corrosion of H _{2 S} gas in the transition region. It is a figure which shows that the amount of corrosion can be evaluated with an apparent sulfur partial pressure and oxygen partial pressure. It is a figure which shows schematic structure of the coal combustion equipment which concerns on Embodiment 2 of this invention.

<Embodiment 1>
The evaluation method for sulfidation corrosion according to the present invention is intended for a material in a reducing atmosphere. The evaluation of sulfidation corrosion of a material in the present invention clearly shows how the corrosion amount of a material in a reducing atmosphere is related to the partial pressure of sulfur gas and oxygen gas constituting the reducing atmosphere. To do.

  Hereinafter, in this embodiment, a case where the amount of corrosion of a material is evaluated using an evaluation apparatus that forms a reducing atmosphere will be described.

  FIG. 1 shows a schematic configuration of an evaluation apparatus according to the present embodiment. As shown in the figure, the evaluation apparatus I includes a test unit 10 made of a quartz tube and an electric furnace 11 for setting the inside of the test unit 10 to a desired temperature. The test unit 10 has a sample table 12 disposed therein, and can hold a sample 20 (material) on the sample table 12.

  The inside of the test unit 10 is kept airtight, reducing gas is introduced from one opening, and reducing gas is discharged from the other opening. Specifically, in the evaluation apparatus I, a gas cylinder 30 that stores various gases constituting the reducing gas, a gas mixer 31 that mixes the gas from each gas cylinder 30, and a gas mixer 30 that flows into the gas mixer 31 And a mass flow controller 32 for adjusting the flow rate to be transmitted.

The evaluation apparatus I is configured such that the gas from each gas cylinder 30 is adjusted in flow rate by a mass flow controller 32 and mixed by a gas mixer, and a reducing gas having a desired composition ratio is formed and introduced into the test unit 10. Has been. In addition, about Ar gas, oxygen is removed by the oxygen trap 33 and it mixes with the reducing gas formed by the gas mixer 31. FIG. The N ₂ gas is removed from the oxygen by the oxygen trap 34 and flows into the gas mixer 31 through the pure water in the humidifier 35 while being kept at a predetermined temperature.

  The reducing gas introduced into the test unit 10 reacts with the sample 20 to cause sulfidation corrosion in the sample 20 and is sent to the outside of the test unit 10. Then, the neutralizing tank 40, the mist catcher tank 41, the activated carbon tank 42, after being purified via a Pt catalyst 43 or the like that removes NOx or the like, and then discharged into the atmosphere.

  Further, gas sampling ports 13 and 14 for collecting reducing gas are provided between the gas mixer 31 and the test unit 10 and on the outlet side of the test unit 10, before and after reacting with the sample 20. It is possible to collect a reducing gas. Further, the test unit 10 is provided with a monitor thermocouple 15 having a tip portion disposed in the vicinity of the sample 20 and the other end portion disposed outside the test unit 10, and is provided in the vicinity of the sample 20 by the monitor thermocouple 15. It is possible to measure the temperature of the reducing gas from outside.

  In the evaluation apparatus I having such a configuration, a reducing gas having an arbitrary temperature and an arbitrary composition can be reacted with the sample 20, and the sample 20 reacted with the reducing gas can be obtained. Further, the reducing gas is collected from the temperature of the reducing gas in the vicinity of the sample 20 and the gas sampling ports 13 and 14, and the composition of the reducing gas can be obtained by a gas chromatography apparatus.

  Hereinafter, the execution procedure of the evaluation method for sulfide corrosion using such an evaluation apparatus I will be described.

FIG. 2 is a flow showing an execution procedure of the method for evaluating sulfide corrosion according to the present embodiment. First, the concentration of H ₂ S gas and SO ₂ gas (sulfur compound gas) in the test unit 10 is made constant, and the partial pressures of oxygen (O ₂ ) gas and sulfur (S ₂ ) gas in the test unit 10 are changed. Then, the amount of corrosion of the sample 20 for each partial pressure is measured (step S1). In the present embodiment, the sample 20 is STBA24 (low alloy steel, composed of iron, chromium (2.25 wt%), molybdenum (1 wt%)).

In order to make the concentration of H ₂ S gas and SO ₂ gas constant and to make the partial pressure of O ₂ gas and S ₂ gas optional, for example, by adjusting the flow rate supplied from each gas cylinder with a mass flow controller or the like. Do.

The concentrations of H ₂ S gas and SO ₂ gas in the test unit 10 can be measured using a known gas concentration measuring device (for example, a gas chromatography device or a gas concentration detection tube).

The partial pressure of O ₂ gas and S ₂ gas (hereinafter, the partial pressure of O ₂ gas is also expressed as P _O2 and the partial pressure of S ₂ gas is also expressed as P _S2 ) can be obtained as follows.

The gas composition constituting the atmosphere in the test unit 10 includes hydrogen (H ₂ ), moisture (H ₂ O), carbon monoxide (CO), carbon dioxide (CO ₂ ) in addition to O ₂ gas and S ₂ gas. , _H 2 S, becomes a gas, such as SO _2, of these _{measures H 2, H 2 O, CO} , CO 2, H 2 composition of S gas (concentration). On the other hand, the temperature of the reducing gas in the test unit 10 is measured.

In the test unit 10, each gas is in a state as shown in the following equation, and the partial pressure of O ₂ and S ₂ (equilibrium partial pressure) is determined from the equilibrium composition of the reducing gas and the equilibrium constant determined from the surface temperature of the sample 20. ) Can be calculated. Specifically, by adjusting the flow rate of the gas from each gas cylinder 30 by the mass flow controller 32, the atmosphere in the test section is 1000 ° C. to 1300 ° C., which is the same temperature as the combustion gas temperature in the furnace of the coal combustion facility. The atmosphere of the equilibrium composition is simulated, and the atmosphere is measured with the gas concentration measuring device to obtain the reducing gas composition. Further, the sample 20 corresponds to a furnace wall tube or the like constituting the furnace, but an equilibrium constant at the surface temperature (400 ° C. to 550 ° C.) of the sample 20 set using the electric furnace 11 is determined. It was.

Here, the _two reasons of O ₂ gas and S ₂ gas are focused on for the following reason. As described above, the atmosphere in the test unit 10 is composed of a plurality of gas types. If all these gases are evaluated as having an influence on corrosion, the amount of corrosion must be evaluated by using several tens of kinds of gas as an index.

However, the partial pressures of H ₂ , H ₂ O, CO, CO ₂ , H ₂ S to O ₂ and S ₂ can be obtained as shown in Equation 1 without considering all of the dozen types of gases. Since O ₂ and S ₂ are considered to be most related to the sulfide / oxide produced by reaction in the sample 20, O ₂ and S ₂ were selected. Thus, using only P _O2 and P _S2 as an index can be regarded as indirectly evaluating the influence of several tens of gas types on the corrosion amount, which is the conventional H ₂ S concentration. It is possible to evaluate the corrosion amount more accurately than to evaluate the corrosion amount with only one scale.

In general, the partial pressure of O ₂ and S ₂ uses an equilibrium constant at a temperature when various gases (H ₂ , H ₂ O, CO, CO ₂ , H ₂ S) have an equilibrium composition. The above partial pressure was calculated using an equilibrium constant at the surface temperature of the sample 20 different from the temperature. For this reason, hereinafter, the partial pressures of the O ₂ gas and the S ₂ gas are also referred to as “apparent P _O2 ” and “apparent P _S2 ”.

  Further, the corrosion amount of the sample 20 is measured by measuring a weight difference between the weight of the sample 20 before being placed in the test unit 10 and the weight of the sample 20 after being placed in the test unit 10 and progressing corrosion. The difference in weight can be measured as the weight per unit area divided by the surface area of the sample 20.

Next, a partial pressure range in which the amount of corrosion does not change with respect to _PO2 and _PS2 is set as a first region, and a changing partial pressure range is set as a second region. Further, the partial pressure range at the boundary between the first region and the second region is set as a transition region (step S2).

FIG. 3A is a graph showing the relationship between PO ₂ and PS ₂ and the amount of corrosion. The figure shows the corrosion amount for each of P _O2 and P _S2 under the condition that the H ₂ S concentration is kept constant at 300 ppm and the SO ₂ concentration is kept constant at 320 ppm. In addition, the dotted line range in a figure is the range of _PO2 and _PS2 assumed with an actual machine.

As shown in the figure, the same amount of corrosion is given the same color, and there is a range in which the corrosion amount changes and a range in which the corrosion amount does not change with changes in the apparent P _O2 and the apparent PS _2. I understand.

Specifically, regarding the apparent P _O2 , when the log P _O2 is in the range of about −20 to −21.5, the amount of corrosion increases as the apparent P _O2 decreases, and the apparent P _O2 decreases to about −21.5. In the smaller range, the change in the corrosion amount is gone. As for the _{P S2} apparent, in the range of logP _S2 about -6.5～ about -5.5, the corrosion amount as apparent _{P S2} is greater increases, apparent _{P S2} is about -5.5 In the larger range, the change in the amount of corrosion disappears.

Thus, although the values of apparent P _O2 and _PS2 differ depending on the test conditions for H ₂ S concentration and SO ₂ concentration, the amount of corrosion changes with changes in the apparent P _O2 and the apparent PS _2. There are no ranges and changing ranges.

The relationship between such concentration and partial pressure is shown in FIG. As shown in the figure, the range of the partial pressures of the gases in which the corrosion amount does not change with respect to the change of the apparent P _O2 and the apparent P _S2 under the constant concentration of the H ₂ S gas and the SO ₂ gas. Is the first region. Similarly, the range of the partial pressure of those gases in which the corrosion amount is changed is defined as the second region. Furthermore, the range of the partial pressure at the boundary between the first region and the second region is defined as a transition region.

  FIG. 3C shows the state of the surface of the sample 20 in each region. In the first region, as shown in type α, the sample 20 is formed with a layer of iron (Fe), chromium (Cr), sulfur (S) and oxygen (O) on the surface thereof, and A sulfur layer and an iron sulfide (FeS) layer are formed thereon. In the transition region, as shown in type β, a needle-like film made of iron sulfide and iron oxide is formed on the outermost surface side. In the second region, as shown in type γ, a layer made of iron, chromium and oxygen and an iron oxide layer thereon are formed, and iron sulfide is interspersed between these layers. .

As shown in FIG. 3A, when the H ₂ S gas and SO ₂ gas concentrations are constant and the manner of change in the corrosion amount is different for each of the first region, the second region, and the transition region, In the second region, the corrosion amount is evaluated only by P _O2 and P _S2 (step S3 (see FIG. 2)). That is, when the values of P _O2 and P _S2 are in the second region, the amount of corrosion can be evaluated with the values of P _O2 and P _S2 without using an index of H ₂ S gas or SO ₂ gas concentration. It becomes.

On the other hand, for the first region, the amount of corrosion of the sample 20 is measured by further changing the operating conditions. That is, the amount of corrosion for each concentration is measured by changing P _O2 and P _S2 constant and changing the concentrations of H ₂ S gas and SO ₂ gas (step S4 (see FIG. 2)). The measurement results are shown in FIG.

FIG. 4A shows a condition in which the apparent P _O2 and the apparent P _S2 are made constant (in this example, −21.25 and −5.0, respectively), and the SO ₂ concentration is made constant. Shows the relationship between the H ₂ S concentration and the amount of corrosion. FIG. 4B shows the relationship between the SO ₂ concentration and the corrosion amount under the condition that the apparent P _O2 and the apparent P _S2 are constant and the H ₂ S concentration is constant. As shown in these figures, as the H ₂ S concentration and SO ₂ concentration increase, the corrosion amount does not increase beyond a certain amount and is saturated, and there is no change in the corrosion amount. I understand.

Thus, the concentration range in which the corrosion amount with respect to the increase in H ₂ S and SO ₂ concentration does not change is defined as the 1-A region, and the other ranges are defined as the 1-B region and the 1-C region (step). S5 (see FIG. 2)). A graph summarizing these areas is shown in FIG. The first 1-A region shown in FIG. 4 corresponds to the range in which the corrosion amount does not change as the H ₂ S concentration and the SO ₂ concentration increase in FIGS. 4 (a) and 4 (b). In the H ₂ S and SO ₂ concentrations in the 1-A region, the corrosion amount is the same at any concentration. The symbol Δ indicates that the corrosion amount of the sample 20 was measured by its H ₂ S concentration and its SO ₂ concentration, and the state is type α (see FIG. 3C).

In such a first 1-A region, the corrosion amount is constant regardless of the H ₂ S and SO ₂ concentrations, and therefore, the corrosion amount is evaluated to be related to the apparent P _O2 and P _S2 (step S6). ).

The first 1-B region corresponds to the range in which the corrosion amount decreases with respect to the decrease in the SO ₂ concentration in FIG. 4B. In the present embodiment, the SO ₂ concentration corresponds to a range of about 200 ppm or less. In the 1-B region, the amount of corrosion is reduced at any H ₂ S concentration. The symbol ◇ indicates that the corrosion amount of the sample 20 was measured by its H ₂ S concentration and its SO ₂ concentration, and the state is type α (see FIG. 3C).

Similarly, the 1-C region corresponds to a range in which the corrosion amount decreases with respect to the decrease in the H ₂ S concentration in FIG. In the present embodiment, for example, when the SO ₂ concentration is 150 ppm, the H ₂ S concentration corresponds to a range of about 200 ppm or less. The symbol ◯ indicates that the amount of corrosion of the sample 20 was measured by its H ₂ S concentration and its SO ₂ concentration, and in this state, type α and type β are mixed (FIG. 3C). reference).

The first 1-B region and the 1-C region correspond to the 1-A ′ region other than the 1-A region according to claim 4. In the present embodiment, as the sulfur compound gas, _two of H ₂ S gas and SO ₂ gas are used. Therefore, for convenience, the 1-A ′ region is divided into the 1-B region and the 1-C region. Expressed.

Thus, in the 1st-B region and the 1st-C region (1st-A ′ region), the amount of corrosion also changes with respect to the change in the H ₂ S gas concentration and the SO ₂ gas concentration. In these regions, it is considered that the amount of corrosion cannot be evaluated as being dependent only on _PO2 and _PS2 . However, by performing safety evaluation, it can be evaluated that the amount of corrosion is dependent on P _{2 O 2} and PS ₂ , ignoring the gas concentration. The safety evaluation means judging whether or not the influence of the sulfur compound gas on the corrosion amount of the sample 20 can be ignored. Safety evaluation can include whether or not the amount of corrosion changes with increasing concentration of sulfur compound gas. If it does not change, it can be evaluated that the amount of corrosion depends only on the partial pressure. As another safety evaluation, it can be mentioned whether or not the corrosion amount is a predetermined value or less with respect to the increase in the concentration of the sulfur compound gas. When it is less than the predetermined value, it can be evaluated that the amount of corrosion depends only on the partial pressure.

In the present embodiment, as shown in FIGS. 4A and 4B, even if the H ₂ S gas and SO ₂ gas concentrations are increased, the corrosion amount does not increase beyond a certain level, and the gas concentrations thereof are not increased. If it decreases, the amount of corrosion also decreases. That is, the gas concentration is a small factor that increases the amount of corrosion. By such safety evaluation, it can be evaluated that the corrosion amount depends on P _O2 and P _S2 in these regions (step S7 (see FIG. 2)).

On the other hand, the transition region can be considered in the same manner as the first region. That is, with respect to the transition region, P _O2 and P _S2 are made constant, the concentrations of H ₂ S gas and SO ₂ gas are changed, and the corrosion amount for each concentration is measured (step S8 (see FIG. 2)). The measurement results are shown in FIGS.

FIGS. 6A and 6B show the relationship between the SO ₂ concentration and the corrosion amount under the condition that the apparent P _O2 , the apparent P _S2, and the H ₂ S concentration are constant. Further, FIG. 7 shows the relationship between the H ₂ S concentration and the corrosion amount under the condition that the apparent P _O2 , apparent P _S2 , and SO ₂ concentrations are constant.

As shown in these figures, the corrosion amount hardly changes with the increase of the H ₂ S concentration and the SO ₂ concentration, or the corrosion amount does not change at a certain concentration or higher. In such a case as well, as in the 1-B region and the 1-C region, it is considered that the influence of the H ₂ S concentration and SO ₂ concentration on the corrosion amount is small. It can be evaluated that there is dependence only on the _O2 gas and the _PS2 gas (step S9 (see FIG. 2)).

FIG. 8 shows a summary of the relationship between PO ₂ and SO ₂ and the amount of corrosion in each region. As shown in the figure, in the second region, it can be evaluated that the amount of corrosion depends only on _PO2 and _PS2 .

On the other hand, in the first region and the transition region, although the amount of corrosion changes with changes in the H ₂ S gas and SO ₂ gas concentrations, it is possible to evaluate with only PO ₂ and PS ₂ by safety evaluation. Absent.

As described above, according to the sulfide corrosion evaluation method according to the present embodiment, it can be evaluated that the amount of corrosion depends only on _PO2 and _PS2 . In addition, the problem that the influence of other gas types has not been considered because the amount of corrosion has been evaluated by only one scale, the concentration of H ₂ S, in the past, while all other gas types are considered. On the contrary, the problem that it is difficult to evaluate the corrosion amount can be avoided.

<Embodiment 2>
In the first embodiment, the evaluation method for sulfide corrosion according to the present invention is implemented using an evaluation apparatus. However, the present invention is not limited to this, and any apparatus that forms a reducing atmosphere may be used.

  For example, in a furnace of a coal combustion facility that burns pulverized coal, the present invention can also be applied when evaluating sulfidation corrosion of a furnace wall tube (corresponding to an example of a material) constituting the furnace.

  FIG. 9 is a diagram showing a schematic configuration of the coal combustion facility. As shown in the figure, a plurality of burners 103a and 103b are provided around a furnace 102 of the coal combustion apparatus 101, and each of the burners 103a and 103b is connected to a coal pulverizer 108a, via a pulverized coal passage 111a and 111b. 108b is connected to each. The coal crushers 108a and 108b are respectively connected to hoppers 109a and 109b for storing coal, and coal having different fuel ratios is charged into the hoppers 109a and 109b.

  When coal is put into each of the hoppers 109a and 109b, a predetermined amount of coal is conveyed to the coal crushers 108a and 108b. Each coal is adjusted to a desired particle size by the coal crushers 108a and 108b to become pulverized coal.

  In this way, the coals having different fuel ratios are adjusted in particle size, and then passed through the pulverized coal passages 111a and 111b, and then are introduced into the furnace 102 from the burners 103a and 103b provided around the furnace 102, and combust. On the other hand, air is fed into the furnace 102 through, for example, burners 103a and 103b. Further, an upper air nozzle 104 is provided at the upper portion of the furnace 102.

  In this manner, the pulverized coal is completely burned in the furnace 102 by the air sent from the burners 103 a and 103 b and the upper air nozzle 104 provided in the lower stage to the furnace 102. Eventually, the pulverized coal burned in the furnace 102 becomes combustion ash and is discharged from the coal ash discharge ports 112 at the upper right and lower portions of the furnace 102.

In the coal combustion apparatus 101 described above, for example, pulverized coal is supplied to the burner 103a located below, and pulverized coal having a fuel ratio lower than that of the pulverized coal is supplied to the burner 103b located above the burner 103a. it makes it possible to fuel ratio reduces the NO _X concentration with reducing ash in unburned concentration upon combustion of different types of pulverized coal.

In such coal burning apparatus 101, the furnace 102 is formed a reducing atmosphere (low NO _X concentration), the furnace 102 side surface of the Rokabekan 113 constituting the furnace 102, the corrosion proceeds.

  The same sulfidation corrosion evaluation method as that of the first embodiment can be performed on the coal combustion apparatus 101 as well. Here, differences from the method for evaluating sulfide corrosion described in the first embodiment will be described.

  First, regarding the amount of corrosion of the furnace wall tube, this is defined as the difference in the thickness of the furnace wall tube before and after the execution of the evaluation method.

  Further, when calculating the partial pressures of sulfur gas and oxygen gas, the combustion gas is extracted from the furnace 102, the composition thereof is analyzed, and the sulfur content is determined from the composition and the measured equilibrium constant at the surface temperature of the furnace wall tube 113. The partial pressure of gas and oxygen gas is calculated.

  Thereafter, by evaluating the corrosion amount of the furnace wall tube 113 according to the steps shown in FIG. 2, it is possible to evaluate how the corrosion amount is related to the sulfur gas and the oxygen gas.

  The present invention can be used in industrial fields where it is necessary to evaluate and predict the amount of sulfidation corrosion.

DESCRIPTION OF SYMBOLS 10 Test part 11 Electric furnace 12 Sample stand 13, 14 Gas sampling port 15 Monitor thermocouple 30 Gas cylinder 31 Gas mixer 32 Mass flow controller 33, 34 Oxygen trap 40 Neutralization tank 41 Mist catcher tank 42 Activated carbon tank 43 Pt catalyst 101 Coal Combustion device 102 Furnace 103a, 103b Burner 104 Upper air nozzle 108a Coal crushing device 109a Hopper 111a, 111b Pulverized coal passage 112 Coal ash outlet 113 Furnace wall tube

Claims (6)

A method for evaluating sulfide corrosion of a material in a reducing atmosphere,
The step of measuring the corrosion amount of the material by setting the concentration of the sulfur compound gas constant and setting the partial pressure of the oxygen gas and the sulfur gas to a predetermined pressure is performed by changing the partial pressure of the oxygen gas and the sulfur gas, Measure the amount of corrosion for each partial pressure of oxygen gas and sulfur gas,
The range of the partial pressure of oxygen gas and sulfur gas when the corrosion amount does not change to a predetermined amount or more with respect to the change in partial pressure of oxygen gas and sulfur gas is defined as the first region, and the partial pressure of oxygen gas and sulfur gas is The range of the partial pressure of the oxygen gas and sulfur gas when the amount of corrosion changes with respect to the change is the second region,
In the second region, the corrosion amount of the material is evaluated by partial pressures of oxygen gas and sulfur gas, and the sulfide corrosion evaluation method is characterized. In the method for evaluating sulfide corrosion according to claim 1,
The range of the boundary between the first region and the second region is a transition region,
For the transition region, the step of measuring the corrosion amount of the material by setting the partial pressure of oxygen gas and sulfur gas constant and setting the concentration of sulfur compound gas to a predetermined concentration is performed by changing the concentration of sulfur compound gas. Measure the amount of corrosion for each concentration of sulfur compound gas,
The safety evaluation is performed on the influence of the concentration of the sulfur compound gas on the corrosion amount of the material, and the corrosion amount of the material is evaluated based on the partial pressure of oxygen gas and sulfur gas in the transition region based on the safety evaluation. A method for evaluating sulfidation corrosion. In the evaluation method of sulfide corrosion according to claim 2,
As the safety evaluation, it is evaluated whether or not the amount of corrosion with respect to an increase in sulfur compound gas concentration is in a relationship of change, and in the case of a relationship of no change, the corrosion of the material with partial pressure of oxygen gas and sulfur gas. A method for evaluating sulfide corrosion, characterized by evaluating the amount. In the evaluation method for sulfide corrosion according to any one of claims 1 to 3,
For the first region, the step of measuring the corrosion amount of the material by setting the partial pressure of oxygen gas and sulfur gas constant and setting the concentration of sulfur compound gas to a predetermined concentration is performed by changing the concentration of sulfur compound gas. And measure the amount of corrosion for each concentration of sulfur compound gas,
The range of the sulfur compound gas concentration in which the increase in the corrosion amount relative to the increase in the sulfur compound gas concentration is saturated is defined as the 1-A region,
In the first-A region, the corrosion amount of a material is evaluated by partial pressures of oxygen gas and sulfur gas. In the evaluation method of sulfide corrosion according to claim 4,
Of the first region, a region other than the first-A region is a first 1-A ′ region,
In the 1-A ′ region, a safety evaluation is performed on the influence of the concentration of the sulfur compound gas on the corrosion amount of the material, and the corrosion of the material is performed with partial pressures of oxygen gas and sulfur gas based on the safety evaluation. A method for evaluating sulfide corrosion, characterized by evaluating the amount. In the evaluation method of sulfide corrosion according to claim 5,
As the safety evaluation, it is evaluated whether or not the amount of corrosion is reduced with respect to the decrease in the concentration of sulfur compound gas, and in the case of the relationship of decreasing, the partial pressure of oxygen gas and sulfur gas is used. A method for evaluating sulfide corrosion, comprising evaluating the amount of corrosion of the material.