JP3211489B2 - Evaluation method of high temperature corrosion wear characteristics - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for evaluating high-temperature corrosive wear characteristics of a fluidized bed boiler for evaluating the high-temperature corrosive wear characteristics under relatively moderate wear conditions, such as inner tube of a fluidized bed boiler and fluidized bed incinerator materials. Things.

[0002]

2. Description of the Related Art Various fluidized-bed boilers and fluidized-bed refuse incinerators are arranged in a fluidized bed in order to fluidize a fluidizing medium such as a bed material to form a fluidized bed and burn fuel at a high temperature. The fluidized medium collides with an inner tube such as a heat transfer tube or a furnace or the like, which causes wear, and the heat transfer tube and the like are corroded.

[0003] Relatively gentle wear conditions (about 5 m / m) of the inner tube of the various fluidized bed boilers and the fluidized bed refuse incinerator materials and the like.
It has been proposed that the evaluation of high-temperature corrosion wear characteristics under flow conditions (lower than or equal to s) be performed using an in-powder rotary wear tester. That is, as shown in FIG. 1, the rotating wear test apparatus in a powder introduces a flowing gas from the bottom of the measuring vessel 1 to fluidize a fluidizing medium to form a fluidized bed 3 and a fluidized bed at a predetermined temperature. The test piece 6 is rotated in the layer 3,
Since the plot of the rotation speed of the test piece 6 and the speed of the wear loss becomes almost linear, the wear characteristics of the extrapolated material are evaluated using the straight line.

[0004]

However, in the evaluation of the high-temperature corrosion wear characteristics described above, when evaluating a material under relatively mild wear conditions (flow conditions of about 5 m / s or less), the rotation of the test piece is considered. When the speed condition of the speed is increased, the acceleration condition may not be satisfied. That is, erosion accelerated oxidation is dominant on the low speed side, and erosion dominates on the high speed side. For this reason, for example, in an inner tube of an actual fluidized bed boiler, the wear rate is low (about 1 to 2 m / s), so that simple erosion control is not performed, so that the obtained evaluation may be inappropriate.

Accordingly, the present invention has been made in view of such circumstances, and an object of the present invention is to provide a method for evaluating a high-temperature corrosion wear characteristic capable of more accurately evaluating a material under relatively mild wear conditions. Is to provide.

[0006]

Means for Solving the Problems The inventors of the present invention have studied under relatively moderate abrasion conditions (flow conditions of about 5 m / s or less) such as inner tubes of various fluidized-bed boilers and fluidized-bed refuse incinerator materials. As a result of intensive studies to more accurately evaluate the hot corrosion wear characteristics, the present invention has been completed, the present invention is to fluidize the fluidizing medium to form a high-temperature fluidized bed,
In the method of rotating the test piece in the fluidized bed and evaluating the wear characteristics of the test piece, the rotation speed is changed and the wear thinning rate of each test piece is measured. Is expressed by a linear function, an inflection point at which the slope changes is obtained, and the wear characteristics are evaluated based on measured values measured in the following range from the inflection point.

[0007] That is, conventionally, this kind of wear test is performed on a material having a large amount of erosion due to high-speed particles together with the rotation of a turbine or a propeller, so that the rotational speed of the material (test piece) is increased to 10 m / s or more. I often plot data. When the flow rate is high as described above, the wall thickness is extremely large and the measurement is easy. But,
When evaluating high-temperature corrosion wear characteristics under relatively mild wear conditions (flow conditions of about 5 m / s or less), if the flow rate is increased as in the conventional wear test, the obtained evaluation becomes inappropriate. Was found. In other words, the rotational speed (V) of each test piece was measured using a rotating wear tester in powder to measure the wear thinning rate of each test piece, and the correspondence between the rotational speed and the logarithm of the wear thinning rate was determined. Expressed as a linear function,
It was found that the slope changed at a certain point (inflection point (Vt)). Therefore, the form of wear due to high-temperature erosion can be defined as the following two.

The region of V <Vt is oxidation-dominated erosion wear. The region of V> Vt is erosion wear. Here, since the speed is low under fluidized bed conditions, the region of V <Vt is oxidation-dominated erosion wear. By evaluating the wear characteristics based on the measured values, the evaluation of the material under relatively moderate wear conditions (flow conditions of about 5 m / s or less) becomes more accurate.

[0009] Since the wear particles have small kinetic energy, when the oxide particles hit the oxide scale formed on the surface at a high temperature, the thin scale is locally broken or scraped, and peels off and loses its thickness. Go. Since the scale is an oxide, it is very hard and reduces the rate of wall thinning due to erosion. As a result, as shown in FIG. 4, the slope of the straight line indicating the speed dependency is extremely low when V <Vt. Pure erosion wear occurs in the region of V> Vt where high-speed particles hit, and the base material is worn through a thin scale, so that the effect of the scale can be ignored.

Therefore, the inflection point is determined, and the wear characteristics are evaluated based on the measurement values measured in the following range from the inflection point. It will be possible to more accurately evaluate high-temperature corrosion wear characteristics of materials and the like under relatively mild wear conditions.

[0011]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

In FIG. 1, reference numeral 1 denotes a measuring container of a rotating wear test apparatus for powder, which is filled with a fluidizing medium such as fused quartz.

An introduction pipe 2 for introducing a flowing gas such as air is connected to the bottom of the measuring vessel 1. The gas from the introduction pipe 2 fluidizes the fused quartz in the vessel 1 to form a fluidized bed 3. It has become so. Further, the measurement container 1 is provided with a temperature maintenance device (not shown) for maintaining the temperature inside the container 1 at a predetermined temperature.

Further, a variable rotating device 4 is provided above the measuring container 1, and a test piece 6 such as a round bar is supported on a rotating shaft 5 of the rotating device 4.
Is rotated in the fluidized bed 3.

The high temperature corrosion wear characteristics of a test piece (round bar) of stainless steel (HR3C), which is a candidate material for a pressurized fluidized bed boiler (PFBC), was examined using the above-described rotary wear test apparatus in powder. Was. Test conditions are room temperature (RT)
And at a temperature of 500 ° C. and a rotation speed of 2, 5, 8, 14 m / s (rotation speed (V) of the test piece). Eight test pieces are processed into a perfect circle in advance (outer diameter tolerance: 1 micron or less), surface is polished, and a test is performed. After the test, the amount of thinning of each test piece is measured, and the wear thinning rate is measured. FIG. 2 shows the relationship between the obtained rotation speed and the wear thinning speed, and FIG. 3 shows the relationship between the rotation speed and the logarithm of the wear thinning speed.

As a result, as shown in FIG. 3, at RT, a linear relationship was shown in the relationship between the rotational speed and the logarithm of the abrasion thinning speed, but at 500 ° C., the speed became higher at a boundary of 7 m / s. The slope changed early and late. The point at which the inclination changes is defined as an inflection point (Vt).

Here, how to determine the Vt point will be described.

At a high temperature, the wear rate always changes at a certain speed. For example, in PFBC, the superficial velocity is about 1 m / s, so that the speed is close to 2 m / s, and furthermore, 5 m / s.
Test at m / s. 8m / s, 1
The test is performed at 4 m / s. As a result, data of 2 m / s is A, data of 5 m / s is B, data of 8 m / s is C,
It is assumed that data of 4 m / s is obtained as D. And
As shown in FIG. 4, A, B, C and D are plotted, and A
−B and CD are connected by a straight line, and a Vt point is obtained as an intersection of the two straight lines. According to a wide range of experiments under relatively mild wear conditions (flow conditions of about 5 m / s or less),
It was found that the Vt point was almost between 5 m / s and 8 m / s.

Next, how to determine the life evaluation method (thinning rate) will be described.

Assuming that the superficial velocity of the fluidized bed is Vs, the average bed particle velocity is usually 0.5 to 0.8 Vs, and the maximum velocity does not exceed 3 Vs by measurement. For example, if the superficial velocity is 1 m / s, 3 m / s is the maximum speed. Therefore, the thinning speed Vs-max at the maximum speed of the actual machine can be obtained on the oxidation-controlled erosion wear characteristic line on the AB line. Further, the actual rate of wall thinning is obtained by multiplying the environmental factor Fa by the powder factor Fp.

Vmax = Fa × Fp × (Vs-max) Further, for example, in estimating the life of PFBC, the present inventors studied a method of measuring the thinning rate at a low speed.
The roundness of the test piece (round bar) was measured (sensitivity: 0.1 micron). That is, the dimensions of 1000 points on the circumference of the end of the round bar are measured, stored in a computer (personal computer), the data is calculated, and the concentric circle interval when the circular form is sandwiched between two concentric circles is the minimum. The difference between the radii of the two circles (MZC) at the time of was defined as the wall thickness reduction. By this means, the amount of wall thinning in sub-micron units can be accurately determined, and the rate of wall thinning at a flow rate of 10 m / s or less can be accurately determined. For example, 5,8,
When the thickness of the round bar (HR3C) at 14 m / s is measured, measurement examples as shown in FIGS. 5A to 5C are obtained.

Accordingly, relatively gentle wear conditions (about 5 to 5 mm) for the inner tubes of various fluidized-bed boilers and the fluidized-bed refuse incinerator materials, etc.
In order to evaluate the high-temperature corrosion wear characteristics under flow conditions (m / s or less), first, tests were performed at several rotation speeds, and the wear reduction rates of the test pieces after these tests were determined. Find points. Then, an oxidation-dominated erosion wear characteristic line (AB line in the example shown in FIG. 4) is obtained from a value measured in a range equal to or lower than the rotation speed at the inflection point, and the wear characteristic is evaluated by extrapolating the straight line. Therefore, the material can be more accurately evaluated.

[0023]

In summary, according to the present invention, an excellent effect that the material can be more accurately evaluated under relatively mild wear conditions is exhibited.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an example of an in-powder rotational wear test apparatus.

FIG. 2 is a diagram showing a relationship between a rotation speed and a wear thinning speed.

FIG. 3 is a diagram showing the relationship between the rotational speed and the logarithm of the wear thinning speed.

FIG. 4 is a diagram showing a relationship between a rotation speed and a wear thinning speed.

FIG. 5 is a diagram showing a measurement example of a wear thinning speed.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References 37th Annual Meeting of the Japan Society for Heat Treatment Technology Lecture summary, Tomizawa, Namba, November 1993 p. 77-78 “Study on Rotating High Temperature Erosion Test Method in Powder and Wear Characteristics” (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 3/56 G01N 17/00 JICST file (JOIS)

Claims (1)

(57) [Claims] 1. A method for fluidizing a fluidizing medium to form a high-temperature fluidized bed and rotating a test piece in the fluidized bed to evaluate the wear characteristics of the test piece. The wear thinning rate of each test piece was measured, and the corresponding relationship between the rotational speed and the logarithm of the wear thinning rate was represented by a linear function, and the inflection point at which the slope was changed was determined. A method for evaluating high-temperature corrosion wear characteristics, wherein wear characteristics are evaluated based on the measured values measured in step (1).