JP2006272150A - Gas mixer and gas mixing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gas mixer and a gas mixing method for surely and highly efficiently mixing at least two kinds of gases. <P>SOLUTION: The gas mixer is provided with: a main pipe 1 whose cross section is circular or roughly circular and through which a first gas flows; and a gas blowing nozzle 2 whose jetting port 2a is opened to the inner surface of the main pipe 1 and which blows a second gas into the main pipe 1, wherein the gas blowing nozzle 2 is provided such that the jetting direction of the second gas is the tangential direction of the main pipe 1 or is roughly the tangential direction, and the jetting flow rate of the second gas from the gas blowing nozzle 2 is double or more a gas flow rate after mixing. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a gas mixer and a gas mixing method for mixing two or more kinds of gases such as city gas and coke oven gas, and various industrial gases such as oxygen, air and nitrogen.

  In general, gas mixers used industrially are equipped with devices for promoting mixing, such as swirl vanes and rectifying plates, inside the mixer. 9A and 9B are explanatory views showing a conventional swirl vane mixer, in which FIG. 9A is a configuration diagram of the mixer, and FIG. 9B is a cross-sectional view taken along line AA of FIG. This mixer has a straight circular tube 40 having swirl vanes 41 inside, and three straight circular tubes having swirl vanes are connected by a flange 45 installed at the end of the circular tube. It is the composition of being. Gas A is supplied from the introduction pipe 42 and another type of gas B is supplied from the introduction pipe 43, and flows in the circular pipe while swirling by the swirling blades, thereby causing swirling turbulence and promoting stirring and mixing. The mixed gas flows out from the outlet 44. According to this, it can mix efficiently in a short distance.

However, the above-described conventional mixer has the following problems.
(1) Since it is swirled by swirl vanes, the pressure loss of the gas when passing through the mixer is large.
(2) Since the swirl vane is essential, the structure is complicated, the production takes time, and the production cost and the production period become long.
(3) In the case of gas containing dust, dust tends to adhere to the swirl vane, and when it is attached, it is necessary to remove and clean the dust. It takes time.

In order to prevent such inconvenience, a cylindrical mixing tank for introducing the mainstream gas, and a branch pipe that is provided with a nozzle that opens in a tangential direction of the mixing tank and that introduces the follower gas into the mixing tank are provided. A mixer has been proposed (Patent Document 1).
Japanese Patent Laid-Open No. 9-287883

  However, in the technique of the above-mentioned Patent Document 1, the gas mixing property is not always sufficient, and the mixing distance until the gas is sufficiently mixed may become very long, resulting in poor efficiency.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a gas mixer and a gas mixing method capable of reliably mixing at least two kinds of gases with high efficiency.

  In order to solve the above-mentioned problems, the present invention has a circular or substantially circular cross section, a main pipe through which a first gas flows, an injection port opened on the inner surface of the main pipe, and a second gas in the main pipe. A nozzle for blowing gas, and the nozzle for blowing gas is provided so that a jet direction of the second gas is a tangential direction or a substantially tangential direction of the main pipe, and the first nozzle from the gas blowing nozzle is provided. A gas mixer is characterized in that the injection flow rate of the gas No. 2 is twice or more the gas flow rate after mixing.

  In the present invention, the cross-section is circular or substantially circular, the main pipe through which the first gas flows, the injection port is opened on the inner surface of the main pipe, and at least two of the second gas are blown into the main pipe Gas injection nozzles, and the two gas injection nozzles are configured such that the injection direction of the second gas is a tangential direction or a substantially tangential direction of the main pipe, and the swirl directions are the same. A gas mixer is provided that is provided.

  Furthermore, the present invention provides a main pipe through which a first gas flows, a nozzle for injecting a second gas into the main pipe, and an injection port that opens to the inner surface of the main pipe. The gas blowing nozzle includes the first and second gases using a gas mixer provided such that the injection direction of the second gas is a tangential direction or a substantially tangential direction of the main pipe. The gas mixing method is characterized in that an injection flow rate of the second gas from the gas blowing nozzle is at least twice the gas flow rate after mixing.

  According to the present invention, the structure has only the main pipe through which the first gas flows and the nozzle for blowing the second gas into the main pipe, the injection port opening on the inner surface of the main pipe. After the mixing, the second gas injection direction from the gas blowing nozzle is tangential or substantially tangential to the main pipe, and the second gas injection flow rate from the gas blowing nozzle is mixed. Therefore, at least two gases can be reliably and efficiently mixed.

  Further, two or more gas blowing nozzles are used by using two or more gas blowing nozzles so that the injection direction of the second gas is a tangential direction or a substantially tangential direction of the main pipe and the same turning direction. In this case, at least two gases can be mixed efficiently and reliably.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a transverse sectional view showing a mixer according to a first embodiment of the present invention, and FIG. 2 is a longitudinal sectional view. 1 is a cross-sectional view taken along line AA in FIG.

  This gas mixer includes a main pipe 1 having a circular cross section, a gas A flowing therethrough, and an injection port 2a that opens to the inner surface of the main pipe 1 and a gas blowing nozzle 2 that blows gas B into the main pipe 1. Yes. The injection direction of the gas B from the gas blowing nozzle 2 is the tangential direction of the main pipe 1.

  The gas A flows inside the main pipe 1 from the direction of the arrow in the figure. When the gas B is blown from the gas blowing nozzle 2, the gas B swirls along the inner peripheral surface of the main pipe 1 as indicated by an arrow 3 and mixed with the gas A, and the arrow indicating the traveling direction of the gas A Flow in the direction. Then, when it reaches a certain distance, it mixes completely.

  Here, one of the performances of the gas mixer is the mixing distance, which is the distance necessary to mix the gas A and the gas B from the place where the gas A and the gas B start to mix to a certain degree of mixing. If the pipe diameter of the mixing section is the same, the shorter the distance, the better the mixing efficiency and the size of the mixer body can be reduced. The distance indicated by the symbol X shown in FIG. 2 indicates the mixing distance.

  Further, the dimensionless mixing distance is obtained by dividing the mixing distance by the pipe inner diameter after mixing. That is, in general, if the gas flow rate is large, the pipe diameter for transporting the gas will inevitably increase. Therefore, it is not sufficient to discuss only the absolute mixing distance when comparing the performance of the mixer. . Therefore, when discussed in terms of dimensionless mixing distance, the influence of the pipe diameter is eliminated, and the performance can be compared according to the mixer type.

  However, if the gas B is simply blown from the gas blowing nozzle 2, the mixing distance becomes long and the mixing efficiency is not sufficient. According to the examination results of the present inventors, in order to increase the mixing efficiency, it is effective to increase the value obtained by dividing the nozzle blowing flow rate by the mixed gas flow rate (this is called the speed ratio). There was found.

FIG. 3 shows the test results of the degree of mixing when the speed ratio is 1.1 and 3.3.
Here, air 193 Nm ³ / h and oxygen gas 17 Nm ³ / h were mixed. Since oxygen in the air is 20.9%, the oxygen concentration when completely mixed at the above flow rate ratio is 27.3%. In the test, air was allowed to flow through a 80A (inner diameter 80.7 mm) straight tube, and oxygen gas was injected and mixed from a 20A (inner diameter 21.6 mm) blowing nozzle ejected in a tangential direction in the straight tube. 200 mm downstream from the mixing location (dimensionalless mixing distance = 2.5), 400 mm (dimensionalless mixing distance = 5), 600 mm (dimensionalless mixing distance = 7.5), 800 mm (dimensionalless mixing distance = 10), At each distance of 1000 mm (dimensionless mixing distance = 12.5), the oxygen concentration at 9 points in the cross section of the flow path in the pipe was measured. The absolute value of the difference between the maximum value and the minimum value of oxygen concentration (%) measured in each cross section was defined as oxygen concentration deviation (%). Since mixing progresses as it goes downstream, the oxygen concentration deviation becomes smaller. However, a distance where the oxygen concentration deviation Δ is less than 2.5% is obtained from experiments, and the smaller the distance, the higher the degree of mixing.

  As test conditions, one oxygen blowing nozzle was used, and the nozzle diameter was two types, 20A (inner diameter 21.6 mm) and 10A (nozzle inner diameter 12.7 mm). The speed ratio at this time is 1.1 for 20A nozzles and 3.3 for 10A nozzles.

  According to the graph shown in FIG. 3, the oxygen concentration deviation Δ is 2.5% when the speed ratio is 1.1 and is about 900 mm (dimensionless mixing distance = 11), and when the speed ratio is 3.3. Is about 450 mm (dimensionless mixing distance = 5.6), and it is confirmed that the oxygen concentration deviation becomes smaller at a shorter mixing distance when the speed ratio is larger than when the speed ratio is small. It was found that the degree was obviously higher when the speed ratio was larger.

  Next, the dimensionless mixing distance at which the oxygen concentration deviation Δ was 2.5% was determined by the same experiment with various speed ratios changed. The result is shown in FIG. From this figure, in the range where the speed ratio is smaller than 2, the mixing distance does not increase even if the speed ratio increases, but when the speed ratio becomes 2 or more, the degree of mixing increases rapidly (the dimensionless mixing distance decreases). ) Was confirmed. For this reason, the speed ratio is set to 2 or more, that is, the injection flow rate of the second gas from the gas blowing nozzle is set to be twice or more the gas flow rate after mixing, the mixing distance is shortened, and efficient gas mixing is performed. .

  Tables 1 and 2 show the main results obtained in a series of tests when the speed ratio is 1.1 and 3.3. For comparison, Table 3 shows the results of a similar test performed with a conventional swirl vane mixer. As shown in these tables, when the speed ratio is 3.3, it can be seen that the mixing ratio (mixing distance at which the oxygen concentration deviation becomes 2.5%) is inferior to that of the conventional swirl vane mixer. . In addition to the mixing distance, the pressure loss is also important as a characteristic of the mixer, and in particular, it is important that the pressure loss on the gas A side is low. The pressure loss was as low as Δ3 mmAq. On the other hand, in the swirl vane mixer, it was confirmed that the pressure loss on the gas A side was Δ77 mmAq, which was clearly large.

  In the first embodiment, the cross-sectional shape of the main tube 1 is not limited to a circle, and may be a substantially circular shape, for example, a hexagon or more polygon. The cross-sectional shape of the gas blowing nozzle 2 is not limited to a circular shape, and may be any shape such as a flat shape or a rectangular shape.

  Further, the size of the gas blowing nozzle 2 is not particularly limited. However, as shown in FIG. 5, the size h of the gas blowing nozzle 2 when viewed in a section of the main tube 1 is ¼ or less of the inner diameter d of the main tube 1. It is preferable that By doing so, a preferable swirl flow can be easily formed. This effect can be obtained regardless of the cross-sectional shape of the gas blowing nozzle 2 as long as these dimensions are satisfied.

  Furthermore, although the example in which the gas blowing nozzle 2 is provided so that the gas injection direction is the tangential direction of the main pipe 1 has been shown, it may not be completely tangential, and the cross-sectional shape of the main pipe 1 may be Even if it is not a circle, it may be a tangential direction or a substantially tangential direction of a circumscribed circle.

Next, a second embodiment of the present invention will be described.
FIG. 6 is a transverse sectional view showing a mixer according to a second embodiment of the present invention, and FIG. 7 is a longitudinal sectional view. 6 is a cross-sectional view taken along line BB in FIG.

  In the present embodiment, the two gas blowing nozzles 2 with respect to the main pipe 1 are arranged such that the injection direction of the gas B with respect to the main pipe 1 is the tangential direction of the main pipe 1 and the swirl directions are the same. is set up.

  In this embodiment, by providing the two gas blowing nozzles 2 in this way, the mixing distance can be shortened, and the two gases can be mixed efficiently.

FIG. 8 shows the test results of a comparison of the mixing degree when the number of nozzles is one and two. Here, as in the first embodiment, air 193 Nm ³ / h and oxygen gas 17 Nm ³ / h were mixed. In the test, air was allowed to flow through a 80A (inner diameter 80.7 mm) straight tube, and oxygen gas was injected and mixed from a 20A (inner diameter 21.6 mm) blowing nozzle ejected in a tangential direction in the straight tube. 200 mm downstream from the mixing location (dimensionalless mixing distance = 2.5), 400 mm (dimensionalless mixing distance = 5), 600 mm (dimensionalless mixing distance = 7.5), 800 mm (dimensionalless mixing distance = 10), At each distance of 1000 mm (dimensionless mixing distance = 12.5), the oxygen concentration at 9 points in the cross section of the flow path in the pipe was measured. The absolute value of the difference between the maximum value and the minimum value of oxygen concentration (%) measured in each cross section is defined as oxygen concentration deviation (%), and the distance by which the oxygen concentration deviation Δ is less than 2.5% is obtained from experiments. The smaller the distance, the higher the degree of mixing. The above was performed in the case of one blowing nozzle and in the case of two blowing nozzles, and the degree of mixing was compared. Table 4 shows main results obtained in a series of tests in the case of two gas blowing nozzles.

  According to the graph of FIG. 8, the oxygen concentration deviation Δ becomes 2.5% when the number of nozzles is one, about 900 mm (dimensionless mixing distance = 11), and when the number of nozzles is two, about 400 mm (dimensionless). It was confirmed that the mixing distance = 5) and the oxygen concentration deviation becomes smaller at a shorter mixing distance by using two blowing nozzles. That is, it was confirmed that the mixing efficiency is extremely improved by using two gas blowing nozzles. The speed ratio is 1.1 for one nozzle and 0.55 (same flow rate) for two nozzles. By using two nozzles, the mixing distance is shortened even if the speed ratio is smaller than two. can do.

  As shown in Table 4, when there are two gas blowing nozzles, not only the pressure loss on the A gas side is as low as Δ3 mmAg, but also the speed of the B gas may be small. It was confirmed that Δ4 mmAq was extremely low.

  In the second embodiment, the cross-sectional shape of the main pipe, the cross-sectional shape of the gas blowing nozzle, the ratio between the size of the gas blowing nozzle and the inner diameter of the main pipe, the direction of the gas blowing nozzle, etc. This is the same as the embodiment. Furthermore, although two examples of the gas blowing nozzles have been shown, three or more nozzles may be used. Furthermore, although an example in which two gas blowing nozzles are arranged at the same cross-sectional position of the main pipe has been shown, two or more gas blowing nozzles may be arranged at intervals in the longitudinal direction of the main pipe. Furthermore, although the gas blown from the two gas blowing nozzles is the same gas, different gases may be blown, and in that case, three kinds of gases are mixed. When three or more gas blowing nozzles are used, four or more kinds of gases can be mixed. However, for the gas to be blown from one gas blowing nozzle, the gas injection flow rate from the gas blowing nozzle needs to be at least twice the mixed gas flow rate as in the first embodiment. is there.

  According to the present invention, since at least two gases can be reliably and efficiently mixed with a simple structure, it is optimal for mixing various fuel gases and various industrial gases, and has high industrial utility value.

The cross-sectional view which shows the gas mixer which concerns on the 1st Embodiment of this invention. The longitudinal cross-sectional view which shows the gas mixer which concerns on the 1st Embodiment of this invention. The figure which shows the relationship between the distance from the mixing start and oxygen concentration deviation in speed ratio 1.1 and 3.3. The figure which shows the relationship between a speed ratio and the dimensionless mixing distance used as oxygen concentration deviation 2.5%. The figure for demonstrating the preferable dimension of the nozzle 2 for gas blowing. The cross-sectional view which shows the gas mixer which concerns on the 2nd Embodiment of this invention. The longitudinal cross-sectional view which shows the gas mixer which concerns on the 2nd Embodiment of this invention. The figure which shows the relationship between the distance from the mixing start in the case of 1 and 2 blowing nozzles, and oxygen concentration deviation. The side view and sectional drawing which show the structure of the conventional gas mixer.

Explanation of symbols

1 Main Pipe 2 Gas Injection Nozzle 2a Injection Port 3 Turning Direction

Claims (3)

A main pipe having a circular or substantially circular cross section through which the first gas flows;
An injection port that is open to an inner surface of the main pipe and includes a gas blowing nozzle that blows a second gas into the main pipe, and the gas blowing nozzle has a jet direction of the second gas that is tangential to the main pipe or A gas mixer provided so as to be in a substantially tangential direction, wherein an injection flow rate of the second gas from the gas blowing nozzle is at least twice a gas flow rate after mixing. A main pipe having a circular or substantially circular cross section through which the first gas flows;
The injection port has an inner surface of the main pipe, and includes at least two gas blowing nozzles for blowing the second gas into the main pipe, and the two gas blowing nozzles are in the second gas injection direction. Is provided so that the tangential direction or substantially tangential direction of the main pipe is the same, and the swirl directions are the same.   A cross section having a circular or substantially circular cross section, and a main pipe through which a first gas flows, a gas injection nozzle having an injection port opened on an inner surface of the main pipe, and a second gas blown into the main pipe. A gas mixing method in which the blowing nozzle mixes the first and second gases using a gas mixer provided so that the injection direction of the second gas is a tangential direction or a substantially tangential direction of the main pipe The gas mixing method is characterized in that an injection flow rate of the second gas from the gas blowing nozzle is at least twice the gas flow rate after mixing.

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