JP3632298B2 - Spontaneous ignition test equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a spontaneous ignition test apparatus that measures conditions for spontaneous ignition of a sample.
[0002]
[Prior art]
In the manufacturing process of chemical substances, it may be necessary to temporarily store intermediate products generated in the middle of manufacturing. Among such intermediate products, there are those that spontaneously ignite when left for a long time in a temperature environment of a certain level or more, and there are those whose temperature and time conditions leading to this spontaneous ignition are unknown. The auto-ignition test equipment keeps the intermediate product sample at a constant set temperature for a long time and measures the time until the auto-ignition starts. It is for checking time beforehand.
[0003]
As shown in FIG. 3, the spontaneous ignition test apparatus includes an apparatus main body 11 and an operation box 12. The apparatus main body 11 is configured such that a sample holder 13 provided with a sample holding container 14 for storing a sample at the lower end can be inserted from the upper part and mounted therein. The apparatus main body 11 is provided with a temperature control device so that the sample temperature of the sample stored in the sample holding container 14 inside the apparatus can be held at a constant set temperature. Further, a front port of the apparatus main body 11 is provided with a first port 15 that receives supply of an inert gas such as nitrogen gas, and a second port 16 that receives supply of oxygen gas, air, or the like. These ports 15 and 16 are for allowing gas to flow into the inside of the apparatus via electromagnetic valves, respectively. The operation box 12 performs an operation of setting a set temperature of the temperature control device, an operation of switching a gas flowing into the apparatus main body 11 by operating a solenoid valve, and the like.
[0004]
In the spontaneous ignition test apparatus, first, a sample to be examined for spontaneous ignition conditions is stored in the sample holding container 14, and the sample holder 13 is attached to the apparatus main body 11. Next, the operation box 12 is operated to allow the inert gas from the first port 15 to flow into the apparatus main body 11 and to set the set temperature of the temperature control device to start the temperature control. Then, as shown in FIG. 4, the temperature control is started at time t11, whereby the sample temperature T gradually rises, reaches the set temperature Tset at time t12, and becomes stable. When the sample temperature T is stabilized, the gas supplied to the inside of the apparatus main body 11 is switched to oxygen gas or the like from the second port 16 to measure the time until the sample in the sample holding container 14 starts spontaneous ignition. Start.
[0005]
Here, when the sample is spontaneously ignited by being held at the set temperature Tset for a long time, the sample temperature T starts to rise from about time t13. Then, the measurement is finished at time t14 when the sample temperature T rapidly increases, and the time from the time t12 when the measurement is started to this time t14 is defined as the time until the sample starts spontaneous ignition.
[0006]
By the way, when the sample actually spontaneously ignites, the inside of the apparatus main body 11 becomes extremely hot, which causes inconveniences such as the sample holder 13 being damaged or the apparatus being broken. In view of this, this spontaneous ignition test device has conventionally been provided with a safety device that detects in advance the occurrence of actual ignition by detecting a temperature rise immediately before the sample starts spontaneous ignition.
[0007]
As shown in FIG. 5, the safety device includes a sample temperature detector 2, a temperature comparison / determination circuit 3, and an electromagnetic valve drive circuit 5. The sample temperature detector 2 detects the sample temperature T of the sample S stored in the sample holding container 14 by the thermocouple 1 disposed in the sample holding container 14 inside the apparatus main body 11. The temperature comparison / determination circuit 3 compares the sample temperature T detected by the sample temperature detector 2 with a predetermined temperature Tth. The predetermined temperature Tth is set to a temperature sufficiently higher than the set temperature Tset by operating the operation box 12 in advance. The solenoid valve drive circuit 5 is a drive circuit that controls opening and closing of the solenoid valves 6 and 7 provided in the apparatus main body 11. The electromagnetic valve 6 is connected to the first port 15 that receives the supply of the inert gas shown in FIG. 3, and the electromagnetic valve 7 is connected to the second port 16 that receives the supply of oxygen gas or the like. The electromagnetic valve drive circuit 5 opens the electromagnetic valve 7 and causes oxygen gas or the like to flow into the apparatus main body 11 during measurement. However, the temperature comparison determination circuit 3 causes the sample temperature T to exceed the predetermined temperature Tth. When it is determined that the electromagnetic valve 7 is closed, the electromagnetic valve 7 is closed and the electromagnetic valve 6 is opened, so that a large amount of inert gas flows into the apparatus main body 11.
[0008]
As shown in FIG. 4, in this safety device, when the sample temperature T suddenly rises immediately before spontaneous ignition and exceeds a predetermined temperature Tth at time t14, the temperature comparison determination circuit 3 determines this. The solenoid valve drive circuit 5 causes a large amount of inert gas to flow into the apparatus main body 11. Therefore, since the sample S can be prevented from actually igniting due to the interruption of the oxygen supply due to the inflow of the inert gas and the decrease in the sample temperature T, damage to the apparatus and the like can be avoided.
[0009]
[Problems to be solved by the invention]
However, the predetermined temperature Tth must be reset every measurement according to the set temperature Tset of the sample S, and the possibility of being set to an incorrect temperature due to an operation error or the like cannot be completely eliminated. The setting error of the predetermined temperature Tth is easily overlooked even after the measurement is started unlike the setting error of the setting temperature Tset. For this reason, the conventional spontaneous ignition test apparatus has a problem that the ignition of the sample S cannot be prevented in advance due to an error in setting the predetermined temperature Tth and the apparatus may be damaged.
In addition, the predetermined temperature Tth must be sufficiently higher than the set temperature Tset in order to reliably detect the influence of temperature fluctuations and noise due to disturbances, etc., but the inert gas is not activated until the actual ignition starts. It is also necessary to set the temperature as low as possible so that the air can flow in reliably. For this reason, in the conventional spontaneous ignition test apparatus, it may be difficult to set the predetermined temperature Tth to an appropriate temperature. When the predetermined temperature Tth is too high, the inflow of the inert gas is not in time, and the sample When S starts to ignite, the apparatus is damaged, and the set temperature Tth is too low, the measurement ends at an irrelevant time due to malfunction, and a reliable measurement result cannot be obtained.
[0010]
Further, when the sample S spontaneously ignites, the oxidation reaction increases in a chain, so that not only the sample temperature T increases rapidly but also the rate of increase of this temperature increases rapidly. Therefore, when the sample temperature T actually reaches the predetermined temperature Tth, the rate of temperature increase is already extremely high, so that the solenoid valve drive circuit 5 starts switching operation of the solenoid valves 6 and 7 from this point. In this case, the sample S may start firing before the inert gas is introduced. For this reason, in the conventional spontaneous combustion test apparatus, there is a case where the ignition of the sample S cannot be reliably prevented in advance, and the inside of the apparatus is exposed to a high temperature until the fire is extinguished by the inflow of the inert gas. There was also a problem that there was something.
[0011]
The present invention has been made in view of such circumstances. When the differential value of the sample temperature exceeds a predetermined value, the sample is reliably ignited in advance by introducing an inert gas and taking measures to prevent ignition. An object of the present invention is to provide a self-ignition test apparatus that can be prevented.
[0012]
[Means for Solving the Problems]
That is, according to the present invention, in order to solve the above problems, the sample temperature detecting means detects the sample temperature, the differentiating means differentiates the sample temperature with time, and the judging means compares the differential value with a predetermined value as needed. It is then determined whether a predetermined value has been exceeded. When the sample temperature rises immediately before the sample starts spontaneous ignition, and the rate of increase of the sample temperature, that is, when the differential value becomes a high value different from usual, the determination means determines that the differential value has exceeded a predetermined value. Take measures to prevent ignition, such as inflow of a large amount of inert gas. Therefore, the spontaneous ignition of the sample can be accurately determined in advance, and the ignition of the sample can be reliably prevented.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
1 and 2 show an embodiment of the present invention. FIG. 1 is a block diagram showing the configuration of a safety device of a spontaneous ignition test device, and FIG. 2 is a time chart showing the operation of the spontaneous ignition test device. is there. In addition, the same number is attached | subjected to the structural member which has a function similar to the prior art example shown in FIGS.
[0014]
The spontaneous ignition test apparatus according to the present embodiment includes an apparatus main body 11 and an operation box 12 similar to those shown in FIG. 3, and a sample holder 13 is attached to the apparatus main body 11, whereby a sample holding container 14. Is placed inside the device. As shown in FIG. 1, the sample holding container 14 is a container having a vent hole at the bottom, and the sample S is stored in the container. A thermocouple 1 is disposed in the sample holding container 14. The thermocouple 1 is connected to the sample temperature detector 2 of the safety device, and the sample temperature detector 2 measures the electromotive force of the thermocouple 1 to thereby obtain the sample temperature T which is the temperature of the sample S or the vicinity of the sample S. It comes to detect. The thermocouple 1 and the sample temperature detector 2 can be shared with those used in a temperature control device that performs temperature control for maintaining the sample temperature T at the set temperature Tset.
[0015]
The sample temperature T detected by the sample temperature detector 2 is sent to the temperature comparison / judgment circuit 3 and the differential operation circuit 4. The temperature comparison / determination circuit 3 compares the sample temperature T detected by the sample temperature detector 2 with a predetermined temperature Tth set in advance, as in the conventional example shown in FIG. Then, the determination result of the temperature comparison determination circuit 3 is sent to the electromagnetic valve drive circuit 5. The solenoid valve drive circuit 5 is also a drive circuit that controls the opening and closing of the solenoid valves 6 and 7 provided in the apparatus main body 11 as in the conventional example shown in FIG. During the measurement, the electromagnetic valve drive circuit 5 opens only the electromagnetic valve 7 and allows oxygen gas or the like to flow into the apparatus main body 11. However, the sample temperature T exceeds the set temperature Tset by the temperature comparison determination circuit 3. If it is determined, the electromagnetic valve 7 is closed and the electromagnetic valve 6 is opened. For this reason, also in the case of the safety device of the present embodiment, when the sample temperature T detected by the sample temperature detector 2 increases due to spontaneous ignition of the sample S during measurement and exceeds the predetermined temperature Tth, Since the comparison determination circuit 3 determines this and the electromagnetic valve drive circuit 5 causes a large amount of inert gas to flow into the apparatus main body 11, it is possible to prevent the sample S from actually igniting.
[0016]
The differential calculation circuit 4 is a circuit that obtains a differential value D (D = dT / dt) by differentiating the sample temperature T detected by the sample temperature detector 2 with respect to time t. Therefore, when the sample temperature T is analog data, the differential operation circuit 4 can be configured by an RC circuit or an analog differential circuit obtained by adding an operational amplifier (operational amplifier) to the sample temperature T. In this case, a circuit that calculates the difference between the sampling data of the sample temperature T and the immediately preceding sampling data can be used. In addition, these circuits are a kind of HPF (high-pass filter), and some analog filters and digital filters having other configurations substantially perform differentiation. Moreover, in order to avoid the influence of, for example, noise, it may be preferable to use a higher-order filter. Accordingly, any circuit configuration can be used as long as an output mainly including a differential component of dT / dt is obtained.
[0017]
The differential value D calculated by the differential calculation circuit 4 is sent to the differential value comparison determination circuit 8. The differential value comparison / determination circuit 8 compares the differential value D with a predetermined value Dth, and can be constituted by a comparison circuit using an operational amplifier or a circuit that compares and calculates the magnitude of digital data. Further, in order to avoid the influence of noise or the like, the predetermined value Dth is set to a high and low binary value, for example, as in a Schmitt circuit, so that the comparison operation has hysteresis characteristics, or the differential value D is equal to or longer than a predetermined time or a predetermined sampling number It is also possible to determine that the predetermined value Dth has been exceeded only when the predetermined value Dth is actually exceeded. The predetermined value Dth of the differential value comparison determination circuit 8 may be set by operating the operation box 12 in the same manner as the predetermined temperature Tth of the temperature comparison determination circuit 3, or a predetermined fixed value may be used. it can. The predetermined temperature Tth is set to a temperature sufficiently higher than the set temperature at the time of measurement, and needs to be reset every time measurement is performed according to the set temperature. However, the differential value D indicating the degree of change in the sample temperature T at the time of spontaneous ignition shows substantially the same change characteristics even if the sample S or the set temperature changes, so the predetermined value Dth is equal to the sample S or the set temperature. Regardless of this, it is possible to set a fixed value.
[0018]
Similar to the determination result of the temperature comparison determination circuit 3, the determination result of the differential value comparison determination circuit 8 is also sent to the solenoid valve drive circuit 5. The electromagnetic valve drive circuit 5 receives the differential value D from the differential value comparison / determination circuit 8 as well as when the determination result that the sample temperature T exceeds the predetermined temperature Tth is sent from the temperature comparison / determination circuit 3. Even when a determination result indicating that the predetermined value Dth has been exceeded is sent, the electromagnetic valves 6 and 7 are switched to allow a large amount of inert gas to flow into the apparatus main body 11.
[0019]
An operation in the case where the time until the sample S starts spontaneous ignition using the spontaneous ignition test apparatus having the above configuration will be described with reference to FIG. By starting temperature control in the sample holding container 14 at time t1, measurement starts when the sample temperature T reaches the set temperature Tset and stabilizes at time t2. At this time, the differential value D calculated by the differential calculation circuit 4 becomes a certain large value due to the temperature change when the sample temperature T rises to the set temperature Tset. However, since the temperature increase due to temperature control is more gradual than the temperature increase due to spontaneous ignition, the differential value D at this time does not normally exceed the predetermined value Dth. However, until the measurement is started at time t2, even if the differential value D exceeds the predetermined value Dth, the differential value comparison determination circuit 8 does not output the determination result to this effect, and the solenoid valve drive circuit 5 malfunctions. It can also be prevented from occurring.
[0020]
When the sample S spontaneously ignites after the start of the measurement, the sample temperature T starts to increase from about time t3, and the rate of increase gradually increases. Then, the differential value D calculated by the differential calculation circuit 4 also increases accordingly, and immediately before spontaneous ignition, the rate of increase in the sample temperature T becomes extremely high because the oxidation reaction of the sample S increases in a chain. Thus, the differential value D also increases rapidly. Accordingly, at time t4 immediately before spontaneous ignition, the differential value D exceeds the predetermined value Dth, and the differential value comparison / determination circuit 8 outputs a determination result to this effect. 7 is switched. Then, since a large amount of inert gas flows into the inside of the apparatus main body 11, the ignition of the sample S can be reliably prevented in advance.
[0021]
Assuming that the differential value comparison / determination circuit 8 does not output this determination result, the sample temperature T exceeds the predetermined temperature Tth at time t5, and the temperature comparison / determination circuit 3 outputs the determination result to that effect. Become. However, since the sample temperature T is obtained by integrating the differential value D, even if the differential value D increases rapidly, there is a slight time delay until the temperature actually becomes sufficiently high. Therefore, when both the predetermined temperature Tth and the predetermined value Dth are set to optimum values, the time t4 is earlier than the time t5 as shown in FIG. The determination by the differential value D increases the possibility that the spontaneous ignition of the sample S can be detected at an earlier stage.
[0022]
As described above, according to the spontaneous ignition test apparatus of the present embodiment, the spontaneous ignition of the sample S is accurately detected in advance by detecting an increase in the differential value D immediately before the sample S starts spontaneous ignition. can do. In addition, since the determination is based on the differential value D indicating the rate of increase in the sample temperature T, the sign of spontaneous ignition of the sample S is detected earlier than the determination based on the conventional sample temperature T, and the sample S actually ignites. Can be reliably prevented. In addition, as in the present embodiment, if the safety device is configured by combining the determination based on the differential value D with the conventional determination based on the sample temperature T, double safety can be achieved. Note that the present invention is preferably implemented in combination with the conventional determination based on the sample temperature T as described above, and the measurement is stopped even when the measurement time exceeds a predetermined time. It can also be combined. However, the safety device can be configured only by the determination based on the differential value D.
[0023]
Furthermore, according to the spontaneous ignition test apparatus of the present embodiment, the predetermined value Dth to be compared with the differential value D by the differential value comparison determination circuit 8 is less dependent on the sample S to be measured and the set temperature Tset. It is not always necessary to reset every measurement, and a fixed value can be set.
In the present embodiment, the sample temperature detection means is constituted by the thermocouple 1 and the sample temperature detector 2, but any other configuration may be used as long as the sample temperature T can be detected. Further, in the present embodiment, the case where the ignition preventing means is configured by the solenoid valve driving circuit 5 and the solenoid valves 6 and 7 and the ignition preventing measure for allowing a large amount of inert gas to flow around the sample S has been described. However, in order to prevent ignition of the sample S, it is sufficient to cut off the sample S from oxygen or forcibly lower the sample temperature T. Therefore, the ignition preventing means of the present invention is at least one of these. Other measures may be used as long as they are executed.
[0024]
Furthermore, in this embodiment, the differentiating means and the determining means are configured by the differential operation circuit 4 and the differential value comparison / determination circuit 8, and are realized by an analog circuit or a digital circuit. It can also be configured by hardware.
[0025]
Further, in the present embodiment, the spontaneous ignition test apparatus for measuring the time until the spontaneous ignition starts while keeping the sample at the set temperature has been described, but the present invention is not limited to this, and the sample temperature T is controlled by temperature control, for example. It is also possible to implement such a method that changes gradually or measures only the sample temperature T, not the time.
[0026]
【The invention's effect】
As is clear from the above description, according to the spontaneous ignition test apparatus of the present invention, it is possible to quickly and accurately detect the temperature rise immediately before the spontaneous ignition of the sample and take measures to prevent the ignition. It is possible to reliably prevent ignition and improve the safety of the device.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of a safety device of a spontaneous ignition test device according to an embodiment of the present invention.
FIG. 2, showing an embodiment of the present invention, is a time chart showing the operation of a spontaneous ignition test apparatus.
FIG. 3 is a diagram showing an external appearance of a spontaneous ignition test apparatus.
FIG. 4 shows a conventional example and is a time chart showing the operation of the spontaneous ignition test apparatus.
FIG. 5 shows a conventional example and is a block diagram showing a configuration of a safety device of a spontaneous ignition test device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Thermocouple 2 Sample temperature detector 4 Differential operation circuit 5 Solenoid valve drive circuit 6 Solenoid valve 7 Solenoid valve 8 Differential value comparison judgment circuit S Sample T Sample temperature D Differential value Dth Predetermined value

Claims (1)

In a spontaneous ignition test device that measures the conditions of spontaneous ignition of a sample in an atmosphere containing oxygen,
Sample temperature detecting means for detecting the temperature of the sample or the vicinity of the sample;
Differentiating means for differentiating the sample temperature detected by the sample temperature detecting means with time,
Determining means for determining whether the differential value calculated by the differentiating means exceeds a predetermined value;
A spontaneous ignition test apparatus comprising: an ignition prevention means for taking measures to prevent the ignition of a sample when the determination means determines that the differential value exceeds a predetermined value.

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