JP7202252B2 - mixing device - Google Patents

Description

The present invention relates to a mixing device (mixer) for mixing exhaust gas from a combustion engine with a liquid additive (for example, a reducing agent) used in an exhaust treatment device (for example, a NOx reduction catalyst).

It is an important issue to purify the exhaust from combustion devices such as internal combustion engines to suppress the spread of environmental pollution. It has been proposed to interpose urea SCR (Selective Catalytic Reduction), which is effective in reducing NOx, in an exhaust passage. Urea SCR is a selective reduction NOx catalyst that has the property of selectively reacting NOx with a reducing agent even in the presence of oxygen. and carbon dioxide gas, and the produced ammonia is used as a reducing agent to reduce and purify NOx in the exhaust on a selective reduction NOx catalyst.
In this specification, an additive (such as urea water) that is a source of generating a reducing agent (such as ammonia) in the NOx reduction catalyst may be expressed as an additive that is added to the exhaust gas.

More specifically, in a conventional exhaust treatment device, for example, a diesel particulate filter with an oxidation catalyst is interposed at a position where the exhaust gas temperature is relatively high on the upstream side of the exhaust passage of the diesel engine from the viewpoint of regeneration efficiency. A urea water addition device, a mixer, and a urea SCR catalyst are interposed on the downstream side.

Further, for example, in an exhaust gas system as described in Patent Document 1, an oxidation catalyst is interposed at a position where the exhaust gas temperature is relatively high on the upstream side of the exhaust passage of the diesel engine, and a urea water addition device and a mixer are provided on the downstream side. , a diesel particulate filter and a urea SCR catalyst.
Japanese Patent Publication No. 2015-537145

However, in these conventional exhaust treatment devices, the urea water is evaporated in a relatively short distance from the urea water addition device where the urea water is added to the exhaust gas, converted into ammonia, and mixed uniformly with the exhaust gas. There is a current situation that it is required to carry the urea to the urea SCR catalyst.
At the same time, from the viewpoint of maintaining fuel consumption, etc., the mixer is also required to keep the exhaust resistance low.

In addition, when the exhaust temperature is low (before warming up (cold engine) immediately after starting), the urea water is favorably evaporated and converted to ammonia until the internal combustion engine and the exhaust treatment device are warmed up to a predetermined level. Even if an attempt is made to activate the urea SCR catalyst early, the reducing agent may not be supplied satisfactorily and the NOx may not be sufficiently reduced and purified.
Therefore, the mixer is required to efficiently and reliably evaporate and atomize the urea water sprayed and supplied from the urea water addition device to convert it into ammonia and to uniformly mix it with the exhaust gas. be.

In addition, ammonium carbamate is produced when urea water is dehydrated in the process of conversion to ammonia. It has been found that there is a problem in terms of durability, and the reality is that mixers are also required to withstand this corrosion and enable long-term use.

The present invention has been made in view of the above-mentioned various circumstances, and the additive (for example, urea water) sprayed and supplied to the exhaust gas from the additive addition device (urea water addition device) is satisfactorily atomized and evaporated to be reduced. In addition, the reducing agent can be effectively and well mixed with the exhaust gas while keeping the exhaust resistance low. An object of the present invention is to provide a mixer (mixing device) that can contribute to the reduction of NOx emissions caused by a catalyst).

Therefore, the present invention provides
A mixing device for mixing a liquid additive injected and supplied to exhaust gas flowing through an exhaust passage of a combustion device and exhaust gas,
One longitudinal end of one strip-shaped plate,
one end in the longitudinal direction of another strip-shaped plate arranged adjacent to and in parallel with the same posture as the one strip-shaped plate when viewed from the direction along the thickness direction of the plate;
When viewed from a direction perpendicular to the longitudinal direction of the plate and perpendicular to the thickness direction of the plate, the one strip-shaped plate and the other strip-shaped plate intersect at a predetermined angle and connect to
the other end in the longitudinal direction of the other strip-shaped plate;
one end in the longitudinal direction of another strip-shaped plate that is arranged adjacent to and in parallel with the other strip-shaped plate in the same orientation as the other strip-shaped plate when viewed from the direction along the thickness direction of the plate;
When viewed from a direction orthogonal to the longitudinal direction of the plate and orthogonal to the thickness direction of the plate, the other strip-shaped plate and the other strip-shaped plate intersect at a predetermined angle It is composed of a zigzag-shaped plate formed by connecting a plurality of zigzag-shaped elements connected in the following manner ,
The zigzag -shaped plate is disposed so that exhaust gas flows in from a direction perpendicular to the longitudinal direction of the plate and perpendicular to the thickness direction of the plate, and the injected additive is injected into the plate. It is characterized by being arranged so as to collide from a direction along the thickness direction .

In the mixing device according to the present invention, the zigzag-shaped plate is made of metal, and the zigzag-shaped plate is electrically heated to function as a heating wire heater using the zigzag-shaped plate as a heating wire. can be characterized.

The mixing device according to the present invention is
The zigzag-shaped plate can be characterized by being formed in a zigzag shape by making cuts in a flat metal plate .

The mixing device according to the present invention is
The zigzag-shaped plate is made of a Ni—Cr alloy, and the Ni—Cr alloy has an electrical resistance of 100 to 150 μΩ·m, Cr: 40 to 50% by mass, and Mo: 0.1. It can be characterized as being a Ni-based alloy containing up to 2.0% by mass .

According to the present invention, the additive (for example, urea water) sprayed and supplied to the exhaust gas from the additive addition device (urea water addition device) can be satisfactorily atomized and evaporated to be converted into a reducing agent (for example, ammonia). In addition, the reducing agent can be effectively and well mixed with the exhaust gas while keeping the exhaust resistance low, thereby contributing to the reduction of NOx emissions by the NOx reduction catalyst (for example, urea SCR catalyst) from an early stage after starting. It is possible to provide a mixer (mixing device) capable of

1 is a block diagram showing a configuration example of an internal combustion engine exhaust treatment system according to an embodiment of the present invention; FIG. Fig. 3 is a side view showing parts of a mixer and an additive adding device extracted from the same embodiment. (A) is a perspective view of the same mixer viewed obliquely from the exhaust upstream side toward the downstream side, and (B) is a perspective view of the same mixer viewed obliquely from the exhaust downstream side toward the upstream side. (A) is a view (front view) of the same mixer as viewed from the exhaust upstream side (front view), and (B) is a view (rear view) of the same mixer as viewed from the exhaust downstream side. (A) is a view (plan view) of the same mixer seen from above perpendicular to the exhaust flow, (B) is a right side view of (A), and (C) is a left side view of (A). be. (A) is a perspective view showing an example when the mixer according to the embodiment is configured to function as an electric (heating wire) heater, and (B) is a strip-shaped plate (strip-shaped (C) is a table showing calculated values and measured values of the heating capacity of the same mixer. FIG. 10 is a diagram showing the behavior of droplets in a model experiment in which the states of atomization and atomization when urea water is sprayed toward a wall surface are confirmed according to temperature. (A) is a table showing the compositional components of the Ni--Cr alloy according to the present embodiment, and (B) is a table showing the electric resistance of the same Ni--Cr alloy. 4 is a graph showing experimental data on corrosion resistance of Ni—Cr alloys according to the present embodiment.

An embodiment according to the present invention will be described below with reference to the accompanying drawings. It should be noted that the present invention is not limited by the embodiments described below.

As shown in FIG. 1, an exhaust treatment apparatus according to an embodiment of the present invention is located at a position where the exhaust gas temperature is relatively high on the most upstream side of an exhaust passage 2 of an internal combustion engine 1 such as a diesel combustion engine. From the point of view, an oxidation catalyst 3 and a diesel particulate filter 4 are interposed, and a urea water addition device (additive addition device) 5 and a urea SCR catalyst (NOx reduction catalyst) 6 are interposed downstream thereof. 1, 2, 3, and 5, symbol E indicates the flow direction of the exhaust gas.

However, the oxidation catalyst 3 and the diesel particulate filter 4 may be omitted, or may be arranged downstream of the urea water addition device 5 and the urea SCR catalyst 6 in the exhaust gas.

The urea water addition device 5 includes a solenoid valve type urea water injection nozzle 5A for injecting urea water (an additive that is a source of a reducing agent) into the exhaust gas at a predetermined timing. The urea water is sent from a urea water tank (not shown) to the urea water injection nozzle 5A via a urea water supply pump (not shown).

The urea water sprayed and supplied from the urea water spray nozzle 5A collides with a mixer (mixing device) 10 provided in the exhaust passage 2 and is atomized to promote evaporation.

As shown in FIGS. 3(A) and 3(B), the mixer 10 according to the present embodiment is a single continuous piece formed of a thin plate adjusted to a predetermined thickness and length by cold rolling. A strip-shaped plate (strip-shaped plate) 11 is folded back in a zigzag shape to form a straight portion 11A (for example, a width of about 2 mm and a thickness of about 0.5 mm) (however, the width is about 1.5 to 10 mm (preferably, 2 to 5 mm) and a thickness of about 0.3 to 1.5 mm) and folded portions 11B.

Specifically, for example, a thin metal flat plate (for example, a thickness of 0.5 mm) (however, the thickness can be about 0.3 to 1.5 mm) is attached to a plate shown in FIG. Cuts as shown in are made in a zigzag shape by laser processing or the like, and then stretched so that the intervals between the straight portions 11A are spaced apart in the thickness direction (height direction) as shown in FIGS. 3 and 4. can be formed by However, by alternately joining one ends of the plurality of linear portions 11A, it is possible to create a structure similar to that shown in FIGS. In FIGS. 5B and 5C, symbol Z indicates the center of the injection direction of the additive (urea water).

The bracket 12 is fixed inside the exhaust passage 2, and is fixed so as to be arranged as shown in FIG. 4A when viewed from the upstream side to the downstream side of the exhaust flow.

Therefore, exhaust gas discharged from the diesel combustion engine 1, passing through the oxidation catalyst 3 and the diesel particulate filter 4 and flowing from the upstream side passes through the gaps 11C formed between the straight portions 11A. flow to the downstream side.
Therefore, the mixer 10 according to the present embodiment can keep the ventilation resistance of the exhaust gas low.

On the other hand, the urea water jetted and supplied from the urea water jet nozzle 5A is jetted downward from above the mixer 10 as shown in FIG. In FIG. 2, the symbol X indicates a urea water supply passage, and the symbol Y indicates an example of the state of spraying of the urea water sprayed from the urea water injection nozzle 5A.

At this time, when the mixer 10 is viewed from the urea water injection nozzle 5A side, as shown in FIG. Therefore, the urea water sprayed and supplied from the urea water spray nozzle 5A surely collides with the upper surface (collision surface 11D) of the straight portion 11A, and the atomization and atomization can be promoted.

That is, according to the mixer 10 according to the present embodiment, the urea water can effectively collide with the wall surface having a large area while keeping the ventilation resistance of the exhaust gas low, so that the atomization and atomization can be promoted. It can contribute to promotion of conversion of urea water to ammonia.

Furthermore, according to the mixer 10 according to the present embodiment, the exhaust gas flowing from the upstream side passes through the plurality of gaps 11C formed between the plurality of straight portions 11A. Since it collides with the upper surface (collision surface 11D) of the portion 11A and is mixed with the atomized and atomized urea water, it flows downstream, so that the exhaust gas and the urea water can be uniformly mixed. can also be played.

In other words, when looking at the cross section (radial cross section) of the exhaust passage 2, as shown in FIGS. Since a plurality of urea SCRs exist within the cross section and are dispersed within the cross section, the urea water and ammonia can be evenly dispersed within the cross section of the exhaust passage. It can contribute to improving the NOx reduction efficiency of the catalyst 6 .

Thus, in the present embodiment, the thin belt-shaped plates 11 constituting the mixer 10 are formed in a zigzag shape, and the thickness direction (thickness direction of the thin belt-shaped plate 11) is formed between the adjacent belt-shaped plates 11. The gap (gap 11C) is formed in the gap (gap 11C) (stretched in the thickness direction), and the exhaust gas is arranged to flow in from the direction (thickness direction) in which the gap (gap 11C) is formed. Also, the additive is sprayed from a direction that intersects the flow of the exhaust gas (the direction facing the upper surface of the thin belt-like plate 11).

That is, in the mixer 10 according to the present embodiment, a predetermined gap 11C is formed along the thickness direction between the thin belt-shaped plates 11 formed in a zigzag shape, and the adjacent belt-shaped plates 11 in the width direction. In addition, the mixer 10 is arranged so that the exhaust gas flows in from the direction in which the gap 11C is formed (the thickness direction of the belt-shaped plate 11), and the injected additive is thin. They are arranged so as to collide from the direction intersecting the width direction surface (collision surface 11D) of the strip-shaped plate 11 (the direction facing at a predetermined angle).
The predetermined angle may be substantially a right angle, but may be any other intersection angle (greater than 0 degrees and less than 180 degrees).

As a result, the exhaust gas passes through the gap (gap 11C), so that the ventilation resistance can be kept small, while the additive is formed by the thin belt-like plate 11 which is arranged in such a manner that there is no gap when viewed from the injection direction. Since it collides with the upper surface of the NOx reduction catalyst, it can promote atomization of the additive, thereby promoting atomization, evaporation, and conversion of the additive to a reducing agent, and can contribute to improving the NOx reduction effect of the NOx reduction catalyst. is.

In the present embodiment, as shown in FIGS. 3B and 5A, a folded portion 11B (top portion 11B1 ) and a plurality of folded portions 11B (parts on the downstream side of the exhaust gas) are provided. By providing the plate (belt-shaped plate) 11, the opportunity for exhaust gas to come into contact with the straight portion 11A is increased, thereby further promoting the mixing of the exhaust gas and the evaporated urea and ammonia. It is possible to omit it if it is possible or if the installation space is limited.

However, by providing a strip-shaped plate (strip-shaped plate) 11 also on the exhaust downstream side (rear side) from the folded portion 11B (uppermost portion 11B1), the mixing of the exhaust gas with the evaporated urea and furthermore ammonia is further promoted. Therefore, it is possible to contribute to the improvement of the NOx reduction effect of the NOx reduction catalyst.

By the way, as described above, when the exhaust gas temperature of the internal combustion engine 1 is low (before warm-up (during cold) immediately after starting), urea It is difficult to evaporate water well and convert it to ammonia, and even if the urea SCR catalyst 6 is activated early, the reducing agent is not well supplied and NOx cannot be sufficiently reduced and purified. There is a fear that

For this reason, mixer 10 according to the present embodiment, as shown in FIG. By covering the periphery with an insulator 11E such as alumina, the strip-shaped plate (strip-shaped plate) 11 can be configured to be electrically heated.

That is, the mixer 10 according to the present embodiment can be configured to function as an electric (heating wire) heater. As shown in FIG. 6(B) (white portions indicate high-temperature portions) and FIG. 6(C), the mixer 10 according to the present embodiment has sufficient heating capability as a heater. has been confirmed (when the linear portion 11A is made of Ni—Cr alloy with a width of about 2 mm and a thickness of about 0.5 mm, for example).

FIG. 7 shows the results of a model experiment in which the state of atomization and atomization when urea water was sprayed toward the wall surface was confirmed according to the temperature (for 10-odd milliseconds immediately after injection at each temperature) ). In the figure, the stronger the degree of atomization/atomization, the stronger the degree of whiteness. In FIG. 7, the uppermost stage shows an image immediately after the start of urea water injection, and thereafter, the images obtained by frame-advancing the photographed moving image every several milliseconds are shown as it goes to the lower stage. From this figure, it can be seen that there is no atomization/atomization at 100° C. or less, and atomization/atomization is completed in a short time as the temperature rises above 100°C.
<Injection>
The second row from the top of the frame-advance image in Fig. 7 corresponds to the spraying, but for urea water with a boiling point of 87 ° C, the spray atomizes only by collision and reflection of the mixer surface temperature up to 100 ° C. I understand that it is difficult to do. That is, it can be seen that the degree of whiteness is low.

On the other hand, when the surface temperature of the urea collision wall surface (corresponding to the upper surface of the straight portion 11A of the mixer 10 (collision surface 11D with urea water)) is set to a predetermined temperature (for example, 125° C.) or higher, It was found that immediately after the urea water sprayed from the urea water spray nozzle collides with the wall surface, atomization due to evaporation progresses.

<After injection>
The third and subsequent steps from the top of the frame-advance image in FIG. 7 correspond to after injection, but after injection (after the end of injection), if the surface temperature of the urea impinging wall surface is lower than 100°C, evaporation does not occur. observed as
At 125°C or higher, the evaporation rate (the degree of evaporation) differs depending on the surface temperature, and from the viewpoint of promoting atomization, it is preferable to set the temperature to 150°C or higher.

That is, when the exhaust gas temperature of the internal combustion engine 1 is low (before warm-up (during cold) immediately after starting) (so-called cold start), the exhaust temperature near the exhaust inlet of the mixer 10 is a predetermined temperature (injected urea The mixer 10 is energized to function as an electric heater until the temperature reaches 150° C. (preferably 180° C. at which the urea water evaporates) at which the atomization and evaporation of the water is promoted, and the urea water is evaporated. Accelerating the conversion to ammonia by promoting atomization and atomization can contribute to exhibiting the NOx reduction effect of the urea SCR catalyst 6 early after starting.

After the internal combustion engine 1 and the exhaust treatment system are warmed up (predetermined temperature (exhaust temperature near the exhaust inlet of the mixer 10), the atomization and evaporation of the injected urea water are accelerated to 150°C ( Preferably, when the temperature is higher than 180° C.)) at which the urea water evaporates, the power supply to the mixer 10 is stopped and the engine controller (ECU) 100 ( 1) is preferably controlled. In FIG. 1, reference numeral 101 denotes an additive injection supply control signal, and reference numeral 102 denotes an electric heater power supply control signal.

As described above, the mixer 10 according to the present embodiment has the elongated thin strip plate (strip plate) 11 folded in a zigzag shape, and can be used directly as a heating wire. Since it is not necessary to provide a type heater or the like, it is possible to contribute to the promotion of atomization and evaporation of the urea water in the mixer 10 while simplifying the configuration, reducing the cost, and reducing the weight and size.

Furthermore, as described above, ammonium carbamate is produced when the urea water is dehydrated, and this causes severe corrosion of the mixer with conventional general stainless steel materials (such as SUS436 material), resulting in poor durability. Problems can arise. Moreover, even if SUS447 material (30% Cr) with high corrosion resistance was used, corrosion could not be effectively suppressed.

For this reason, in the present embodiment, portions of the belt-like plate (band-like plate) 11 and the bracket 12 of the mixer 10 that are subject to severe corrosion (places where the urea solution collides and evaporates) are made of a Ni—Cr alloy. It was confirmed that corrosive wear of the mixer 10, which collides with urea water at a relatively high temperature, can be effectively suppressed.
Although FIG. 9 is a substitute test using a test piece, it shows an example of experimental results comparing the corrosion rate in boiling nitric acid of a Ni--Cr alloy with that of other materials.

The “Ni—Cr alloy” refers to a Ni-based alloy containing 40 to 50% by mass of Cr. Among them, a high Cr-containing Ni-based heat- and corrosion-resistant alloy (representative component: Ni-45Cr-1Mo (mass%)) that exhibits excellent properties in both corrosion resistance and heat resistance is preferable (the composition is shown in FIG. 8(A) as "Ni -Cr-based alloy"). Particularly preferred component ranges are as follows.

% by mass, Cr: 40 to 50%, Mo: 0.1 to 2.0%, Fe: more than 0% and 3% or less, Mn: more than 0% and 0.5% or less, Si: 0% exceeding 0.1%, Al: exceeding 0% and 0.3% or less, Ti: exceeding 0% and 0.3% or less, Mg: 0.01% or less, N: 0.04% or less , B: 0.01% or less, and further, as selective elements, Co: 3% or less, V: 0.1% or less, Zr: 0.05% or less, Cu: 0.02% or less, W: 0.1% or less, Nb: 0.1% or less, Ca: 0.002% or less, the balance of which is Ni and unavoidable impurities. .

Further, in order to exhibit the heating capacity of the heater, the parts (where the urea water collides and evaporates) such as the band-shaped plate (band-shaped plate) 11 and the bracket 12 of the mixer 10 which are severely corroded must have electrical resistance. It is preferably between 100 and 150 μΩ·m. The electrical resistance of the representative Ni--Cr alloy shown in FIG. 8(A) is 110 μΩ·m as shown in FIG. 8(B). On the other hand, stainless steel, which is a conventional material, has a low electrical resistance and cannot be heated in a practical size, so that the cross-sectional area must be reduced, which is not preferable.

Thus, according to the present embodiment, the material of at least the strip-shaped plate (strip-shaped plate) 11 of the mixer 10 is a high-Cr-containing Ni-based heat- and corrosion-resistant alloy (Ni-45Cr-1Mo (mass%)). , it can effectively suppress corrosion of ammonium carbamate generated in the process of converting urea water to ammonia, so even if it is used as a mixer for urea SCR catalyst 6, it can withstand long-term use. becomes possible.

As described above, according to the present embodiment, the additive (e.g., urea water) injected and supplied from the additive addition device (urea water addition device) to the exhaust gas is atomized and evaporated satisfactorily, and the reducing agent (e.g., ammonia), and the reducing agent can be effectively and well mixed with the exhaust gas while keeping the exhaust resistance low. A mixer (mixing device) that can contribute to the reduction of NOx emissions can be provided.

By the way, in the present embodiment, the diesel combustion engine 1 has been described as an example, but the present invention is not limited to this, and any combustion device involving exhaust gas, such as a gasoline engine, a gas turbine, or other internal combustion engine, can be used. Alternatively, an external combustion engine can be used, and any mobile or stationary combustion device can be used regardless of the combustion method.

Further, in the present embodiment, the urea SCR catalyst 6 is exemplified as the NOx reduction catalyst, and urea water is used as the additive to generate the reducing agent supplied to the NOx reduction catalyst, but the present invention is limited to these. The present invention can be applied to a mixer (mixing device) that is required to add a liquid additive to the exhaust gas flowing through the exhaust passage and mix the additive and the exhaust gas. Applicable.

For example, when an HC (hydrocarbon) selective reduction NOx catalyst {HC-SCR (HC-Selective Catalytic Reduction) type catalyst (HC-SCR catalyst) is interposed as a NOx reduction catalyst instead of the urea SCR catalyst, A liquid additive such as light oil or kerosene, which is a source of generating HC, which is a reducing agent of the HC selective reduction NOx catalyst, corresponds to an example of the liquid additive according to the present invention.

The embodiment described above is merely an example for explaining the present invention, and various modifications can be made without departing from the gist of the present invention.

1 Internal combustion engine (diesel combustion engine, etc.)
2 exhaust passage 3 oxidation catalyst 4 diesel particulate filter 5 urea water addition device 5A urea water injection nozzle 6 urea SCR catalyst 10 mixer (mixing device)
11 strip-shaped plate (strip-shaped plate) (thin strip-shaped plate according to the present invention)
11A straight part 11A
11B folded portion 11C gap 11D collision surface (upper surface of straight portion 11A)
11E insulator 12 bracket

Claims (4)

A mixing device for mixing a liquid additive injected and supplied to exhaust gas flowing through an exhaust passage of a combustion device and exhaust gas,
One longitudinal end of one strip-shaped plate,
one end in the longitudinal direction of another strip-shaped plate arranged adjacent to and in parallel with the same posture as the one strip-shaped plate when viewed from the direction along the thickness direction of the plate;
When viewed from a direction perpendicular to the longitudinal direction of the plate and perpendicular to the thickness direction of the plate, the one strip-shaped plate and the other strip-shaped plate intersect at a predetermined angle and connect to
the other end in the longitudinal direction of the other strip-shaped plate;
one end in the longitudinal direction of another strip-shaped plate that is arranged adjacent to and in parallel with the other strip-shaped plate in the same orientation as the other strip-shaped plate when viewed from the direction along the thickness direction of the plate;
When viewed from a direction orthogonal to the longitudinal direction of the plate and orthogonal to the thickness direction of the plate, the other strip-shaped plate and the other strip-shaped plate intersect at a predetermined angle It is composed of a zigzag-shaped plate formed by connecting a plurality of zigzag-shaped elements connected in the following manner ,
The zigzag -shaped plate is disposed so that exhaust gas flows in from a direction perpendicular to the longitudinal direction of the plate and perpendicular to the thickness direction of the plate, and the injected additive is injected into the plate. A mixing device characterized by being disposed so as to collide from a direction along the thickness direction . 2. The method according to claim 1, wherein the zigzag-shaped plate is made of metal , and the zigzag-shaped plate is made to function as a heating wire heater using the zigzag-shaped plate as a heating wire by energizing and heating the zigzag-shaped plate. mixing device. 3. The mixing apparatus according to claim 1 , wherein the zigzag-shaped plate is formed by cutting a metal flat plate into a zigzag shape . The zigzag-shaped plate is made of a Ni—Cr alloy, and the Ni—Cr alloy has an electrical resistance of 100 to 150 μΩ·m, Cr: 40 to 50% by mass, and Mo: 0.1. 4. The mixing device according to any one of claims 1 to 3, characterized in that the Ni-based alloy contains up to 2.0% by mass .

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