JP2013152196A - Apparatus for evaluating minimum ignition energy of powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus for evaluating minimum ignition energy, which can easily evaluate the minimum ignition energy of powder at intended concentration of a combustion supporting gas even in structure without vacuum pressure resistance.SOLUTION: An apparatus for evaluating minimum ignition energy includes: a cylindrical container 11 storing powder; gas supply pipes 13 which are inserted into the container 11 from an upper part and which supply gas having predetermined concentration of a combustion supporting gas to the inside of the container 11; a discharge device including a discharge electrode installed in the container; and a gas diffusion/ejection member which ejects the gas from a bottom part of the container into the container so as to make the powder stirred up inside the container. The gas supply pipes can move vertically in the container.

Description

  The present invention relates to an apparatus for evaluating the minimum ignition energy of a powder, useful for preventing dust explosions.

When handling powder, it is the dust explosion that you must pay attention to in terms of safety. Items for evaluating the risk of dust explosion include the lower explosive limit concentration, the limit oxygen concentration, and the minimum ignition energy. Above all, the minimum ignition energy is an important value when considering safety measures against dust explosions.
As an apparatus for evaluating the minimum ignition energy, an apparatus for performing an explosion test under pressure as described in Patent Document 1 is known.

  However, for example, in a non-pressure-resistant structure that cannot withstand a reduced pressure of -0.1 MPa or less or a high pressure of 1 MPa or more, the minimum ignition energy is evaluated at any supporting gas concentration such as oxygen, and the handling conditions in the actual process ( There has been a demand for an apparatus and method that can easily evaluate visually the risk of dust explosion by the oxygen concentration in the atmosphere.

Japanese Utility Model Publication No. 62-134055

  The subject of this invention is providing the minimum ignition energy evaluation apparatus which can evaluate the minimum ignition energy of dust easily by visual observation etc. by arbitrary flame-supporting gas density | concentration also in a non-pressure | voltage resistant structure.

As a result of intensive studies to solve the above problems, the present inventors have found a solution means having the following configuration, and have completed the present invention.
(1) A cylindrical container containing powder, a gas supply pipe which is inserted into the container from above and has a predetermined combustion-supporting gas concentration, and is installed in the container. An ignition means including a discharge electrode, and a gas diffusion discharge member for discharging gas into the container from the bottom of the container and causing the powder to rise into the container, wherein the gas supply pipe is disposed in the container. An apparatus for evaluating the minimum ignition energy of powder, characterized in that it can be moved up and down.
(2) The minimum ignition energy evaluation according to (1), further including a gas supply source, wherein a gas flow path extending from the gas supply source is branched into the gas supply pipe and the gas diffusion discharge member. apparatus.
(3) The minimum ignition energy evaluation apparatus according to (1) or (2), wherein the gas supply pipe has a lower end bent in a substantially horizontal direction.
(4) The minimum ignition energy evaluation apparatus according to (3), wherein the lower end portion of the gas supply pipe is parallel to the tangential direction of the inner wall of the container at a position closest to the gas supply pipe in plan view.
(5) A plurality of gas supply pipes are inserted into the container from above, and these gas supply pipes are formed by branching a gas flow path extending from a gas supply source. The minimum ignition energy evaluation apparatus in any one.
(6) A minimum ignition energy evaluation method for powder using the minimum ignition energy evaluation apparatus according to any one of (1) to (5), wherein powder as a sample is loaded in the container, After replacing the gas in the container by supplying gas from the gas supply pipe so that the inside of the container has a desired combustion-supporting gas concentration, the gas is discharged from the bottom of the container into the container by the gas diffusion discharge member. A method for evaluating the minimum ignition energy of powder, wherein the minimum ignition energy is evaluated by confirming the presence or absence of ignition by an ignition means while raising the body.

According to the apparatus for evaluating the minimum ignition energy of the present invention, there is an effect that the minimum ignition energy of dust can be easily evaluated with a target support gas concentration even in a structure with no pressure resistance. In particular, in the present invention, since the gas supply pipe inserted into the cylindrical container from above is capable of moving up and down in the container, the gas supply is performed when the atmospheric gas having a predetermined combustion-supporting gas concentration is introduced into the container. The gas supply port at the lower end of the pipe is located in the lower part of the container, and at the time of ignition, the gas supply pipe is pulled up to the upper part of the container or outside the container and ignited to quickly replace the atmospheric gas and supply the gas at the time of ignition Avoid disturbances caused by pipes (such as the flame itself or the ambient gas whose temperature has been raised by the flame is cooled by the gas supply pipe, making it difficult for combustion to propagate, extinguishing the flame due to the cooling effect of the gas supply pipe, physical inhibition of the rising of powder) be able to.
As described in (2) above, the gas flow path extending from the gas supply source is branched into two parts, the gas supply pipe and the gas diffusion discharge member, so that one gas supply source is provided. It is possible to prevent a decrease in the reliability of the experimental data due to an error in gas concentration adjustment between the gas supply sources assumed when a plurality of gas supply sources are used.
Further, by configuring as described in (3), (4) and (5) above, the atmosphere gas in the container can be replaced more quickly, and it is arranged in advance in the cylindrical container at the time of replacement. It becomes easy to prevent the movement of the powder.
According to the minimum ignition energy evaluation method for powder described in (6) above, the minimum ignition energy of dust can be easily evaluated.

It is a schematic diagram which shows the minimum ignition energy evaluation apparatus which concerns on one embodiment of this invention. It is an enlarged side view which shows the lower end part of the gas supply pipe | tube in the broken-line surrounding part of FIG. It is a schematic plan view of the container which shows arrangement | positioning of the gas supply pipe | tube in a container. It is a schematic diagram which shows an example of operation | movement of a gas diffusion discharge member, Comprising: (A) is a figure which shows the state before sample raising, (B) is a figure which shows the state at the time of dust raising. It is a graph which shows an example of the relationship between the oxygen concentration in the atmosphere where the sample powder is placed, and ignition energy.

  FIG. 1 is a schematic diagram showing a minimum ignition energy evaluation apparatus according to an embodiment of the present invention. As shown in FIG. 1, the minimum ignition energy (MIE) evaluation apparatus 1 according to this embodiment is configured so that a gas having a predetermined combustion-supporting gas concentration is introduced into a container 11 containing a powder 18. A gas supply pipe 13 for supplying the gas into the inside is inserted from above, and a discharge device 2 including a discharge electrode 22 installed in the container 11 is provided. 11 is provided with a gas diffusion discharge member 19 for causing the gas diffusion discharge member 19 to rise. Further, an oxygen concentration meter 14 is inserted into the container 11.

  The cylindrical container 11 is entirely or partially formed of a transparent member such as glass or transparent plastic so that the danger of dust explosion can be visually confirmed. The shape of the cylindrical container 11 may be cylindrical or rectangular. The magnitude | size of a container should just be about 0.5-3L.

The upper part of the container 11 is open, and the opening at the upper part of the container is closed with the filter paper 3. The gas supply pipe 12 and the oxygen concentration meter 14 pass through the filter paper 3 and are inserted into the container 11. The powder 18 accommodated in the container 11 has a value obtained by dividing the amount of the powder by the internal volume of the container 11 of about 0.1 to 8000 g / m ³ , preferably about 1 to 5000 g / m ³ . Is good.
In the present invention, the powder 18 has a particle size of 500 μm or less, and can explode by reacting with a combustion-supporting gas.
In the present invention, the combustion-supporting gas refers to, for example, oxygen, fluorine, chlorine, and the like, and the support-supporting gas concentration refers to the oxygen concentration in the mixed gas in the case of a mixed gas of oxygen and nitrogen, for example. .

  As shown in FIG. 1, the gas supply pipe 13 is connected to the gas supply source 12 via a gas flow meter 15 as necessary. The gas flow rate is about 1-1000 mL / second, preferably 10-500 mL / second, and the gas linear velocity is about 1-50 m / second, preferably 5-30 m / second.

  The length of the gas supply pipe 13 is preferably such that the lower end is located in the vicinity of the lower part of the container 11 and does not come into contact with the powder 18 deposited on the bottom of the container 11 when replacing the atmospheric gas. . As shown in FIG. 2, the lower end gas ejection part 131 of the gas supply pipe 13 is bent horizontally. In the present invention, the bending angle θ of the lower end gas ejection part 131 is preferably in the range of 90 ° ± 10 °. If the bending angle θ of the gas ejection part 131 is less than 80 °, the discharge port at the tip is directed upward, so that the atmospheric gas in the container 11 cannot be replaced efficiently. On the other hand, when the bending angle θ exceeds 100 °, the gas hits the deposited powder 18, and therefore, the powder 18 moves to a place away from the gas diffusion discharge member before the powder 18 is blown up. .

  Further, as shown in FIG. 3, the lower end gas ejection part 131 of the gas supply pipe 13 is bent so as to be parallel to the tangential direction of the inner wall of the container at a position closest to the gas supply pipe in a plan view. . As a result, as shown by arrows in FIG. 3, the gas discharged from the discharge port at the tip forms a horizontal swirling flow that flows in the circumferential direction along the inner wall of the cylindrical container 11, and becomes a rising airflow near the center. As a result, the powder 18 deposited on the bottom of the container 11 can be made difficult to move from the bottom of the container 11 by the air flow, and the atmosphere gas can be replaced quickly. be able to. For this reason, it is desirable that the gas supply pipe 13 be as close as possible to the inner wall of the container.

  Furthermore, since two gas supply pipes 13 and 13 are inserted into the container 11 from above, the linear velocity of the atmospheric gas in the container 11 can be reduced, so that the replacement can be further performed without moving the powder 18. It can be done quickly. These gas supply pipes 13 and 13 are obtained by branching a gas flow path extending from the gas supply source 12. Note that the number of branches is not limited to two, but may be three or more as necessary, or may be only one without branching.

Examples of the gas supply source 12 include an oxygen cylinder 121 and a nitrogen cylinder 122 connected through valves 123 and 123, respectively. By adjusting the flow rate of each gas with these valves 123 and 123, any gas supply source 12 can be used. It is possible to prepare a mixed gas having an oxygen concentration of 5%. Instead of nitrogen gas, other inert gas or other gas may be used.
A gas flow path extending from the gas supply source 12 is branched into two flow paths toward the gas supply pipe 13 and the intermediate tank 16, and valves 4 and 5 for opening and closing are provided in the respective flow paths. . The intermediate tank 16 is connected to the gas injection nozzle 20 via the electromagnetic valve 17.

In the present invention, the gas supply pipe 13 can move up and down in the container 11. That is, the gas supply pipe 13 is configured to move up and down between the lower part and the upper part of the container 11. The upper end is preferably located as close as possible to the filter paper 3, but as long as the flame extinguishing effect caused by cooling of the gas supply pipe 13 and the physical hindrance of the powder 18 rising can be suppressed when ignited. The gas supply pipe 13 may be extracted from the container 11 if necessary. For example, a part of the gas flow path leading to the gas supply pipe 13 in the container 11 is made of an elastic material (for example, a rubber pipe), and the gas supply pipe 13 is moved up and down manually or using a machine. May be.
Since the gas supply pipe 13 can be moved up and down in this way, when the atmosphere gas in the container 11 is replaced, the gas supply pipe 13 is lowered to the lower part of the container 11 to perform gas replacement, and during discharge, the gas supply pipe 13 is discharged. 13 is raised to the upper part of the container 11, and it is possible to prevent or suppress the flame that has been ignited from being extinguished due to physical inhibition of the rising of the powder 18 and the cooling effect of the gas supply pipe 13.

  The discharge device 2 used in the apparatus of the present invention includes a pair of discharge electrodes 22 and 22 arranged to be spaced apart from each other in the container 11, and further includes a high-voltage DC power source 21, a capacitor 23, and a switch 24. When the switch 24 is turned on, a high-voltage current flows and discharge is generated between the electrodes 22 and 22 so that a spark is generated. The powder 18 is ignited by this spark.

A gas diffusion discharge member 19 is provided at the bottom of the container 11. The gas diffusion discharge member 19 has a shape such as a cap shape or a plate shape. The gas diffusion discharge member 19 closes the gas injection nozzle 20 at the bottom by its own weight, and when the gas is ejected from the gas injection nozzle 20, the pressure of the ejection gas The gas is diffused and ejected in the circumferential direction of the container 11 along the periphery, that is, the bottom surface instead of upward. As a result, all the samples 18 deposited on the bottom of the container 11 can be raised into the container 11 (to generate dust).
In addition, a stopper 191 located in the nozzle 20 is provided below the gas diffusion discharge member 19 to regulate the floating height of the gas diffusion discharge member 19 when the gas is ejected.

  As shown in FIG. 1, the gas injection nozzle 20 is connected to the intermediate tank 16 via a solenoid valve 17. The intermediate tank 16 is filled with the high-pressure gas sent from the gas supply source 12.

  Next, a method for evaluating the minimum ignition energy (MIE) using the apparatus of the present invention will be described with reference to FIG.

First, a predetermined amount of sample powder 18 is put into the container 11 from the upper opening, and the upper opening of the container 11 is covered with the filter paper 3 and fixed with a rubber band or the like. Next, the gas supply pipe 13 is passed through the filter paper 3, and the lower end gas ejection part 131 is inserted from the lower part of the container 11 to at least 3 cm, preferably about 1 cm, and a mixed gas adjusted to a predetermined oxygen concentration is blown into the container 11. The inside of the container 11 is set to a predetermined oxygen concentration. At the same time, the valve 5 is opened and the mixed gas is also sent to the intermediate tank 16 to obtain a predetermined oxygen concentration.
Before the evaluation, it is confirmed by the oxygen concentration meter 14 whether the container 11 is replaced with a gas having a predetermined oxygen concentration.

  After confirmation, the gas supply pipe 13 is moved to a range where the evaluation does not affect (upper part of the cylinder or outside of the cylinder), the electromagnetic valve 17 is opened and the powder 18 is raised, and immediately after the powder 18 is raised (about 0.1 to 2 seconds later), the switch 24 of the discharge device 2 is turned on, a voltage is applied between the discharge electrodes 22 and 22 to cause discharge in the container 11, and whether or not dust is ignited is visually observed. The minimum ignition energy is evaluated.

  When dust is ignited, the discharge energy is gradually decreased. On the other hand, when it is not ignited, the discharge energy is increased stepwise, and the minimum discharge energy to be ignited is set as the minimum ignition energy. That's fine. The discharge energy is adjusted by changing the capacitor capacity of the discharge device 2 and the voltage applied to the capacitor.

  Specifically, the minimum ignition energy (MIE) of a specific sample powder was evaluated using the apparatus of the present invention. When the oxygen concentration in the atmosphere was about 21% (air), the sample powder was ignited with an ignition energy of about 30 mJ, but was not ignited when the ignition energy was lowered to about 25 mJ. Therefore, it was found that the MIE of the sample powder in the air was about 30 mJ.

  It was also found that when the oxygen concentration was about 18%, the ignition energy was not ignited at about 70 mJ, but the ignition energy was gradually increased to ignite at about 80 mJ. Therefore, it was found that the MIE of the sample powder in an atmosphere having an oxygen concentration of about 18% was about 80 mJ.

  FIG. 5 shows an example in which the relationship between the MIE and the oxygen concentration in the atmosphere (mixed gas of oxygen and nitrogen) in which the sample powder is placed in this way is shown. By preparing the MIE graph as shown in FIG. 5, it is possible to know the concentration of flammable gases such as oxygen that is safe during storage and transfer of powder, which can be useful for preventing dust explosions. it can.

DESCRIPTION OF SYMBOLS 1 Minimum ignition energy (MIE) evaluation apparatus 11 Cylindrical container 12 Gas supply source 13 Gas supply pipe 131 Lower end gas ejection part of gas supply pipe 14 Oxygen concentration meter 15 Flow meter 16 Intermediate tank 17 Solenoid valve 18 Sample 19 Gas diffusion discharge member 191 Stopper 2 Discharge device 22 Electrode 24 Switch

Claims (6)

A cylindrical container containing powder;
A gas supply pipe which is inserted into the container from above and supplies a gas having a predetermined combustion-supporting gas concentration into the container;
A discharge device including a discharge electrode installed in the vessel;
A gas diffusion discharge member for discharging gas from the bottom of the container into the container and causing the powder to rise into the container,
The apparatus for evaluating minimum ignition energy of powder, wherein the gas supply pipe is capable of moving up and down in a container.   The minimum ignition energy evaluation apparatus according to claim 1, further comprising a gas supply source, wherein a gas flow path extending from the gas supply source is branched into two parts, the gas supply pipe and the gas diffusion discharge member.   The minimum ignition energy evaluation apparatus according to claim 1, wherein a lower end portion of the gas supply pipe is bent in a substantially horizontal direction.   The minimum ignition energy evaluation apparatus according to claim 3, wherein the lower end portion of the gas supply pipe is parallel to a tangential direction of the inner wall of the container at a position closest to the gas supply pipe in a plan view.   5. The gas supply pipe according to claim 1, wherein a plurality of gas supply pipes are inserted from above into the container, and the gas supply pipes are branched from a gas flow path extending from a gas supply source. Minimum ignition energy evaluation device. A minimum ignition energy evaluation method for powder using the minimum ignition energy evaluation apparatus according to claim 1,
The sample powder is loaded into the container, the gas is supplied from the gas supply pipe so that the inside of the container has a desired combustion-supporting gas concentration, and the gas in the container is replaced, and then the gas supply pipe is raised. Letting the gas diffusion discharge member discharge gas into the container from the bottom of the container and make the powder rise, confirming the presence or absence of ignition by the ignition means, and evaluating the minimum ignition energy, Evaluation method of minimum ignition energy of powder.

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