JPS6113960Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to an improvement of the gas control system of a thermal analysis device such as a thermogravimetric measurement device.

In the field of thermal analysis, thermogravimetry (TG), along with differential thermal analysis (DTA), has traditionally been widely used to analyze physical properties. This TG (thermal balance) is often used to test the corrosion resistance of metal materials. In this case, a reaction tube is used to heat the sample while flowing a corrosive gas to cause a contact reaction and measure the weight change over a long period of time. This reaction tube is made of quartz and has a double structure, and the sample is placed on a platinum sample plate, with a platinum suspension wire passing through the inner tube of the reaction tube and suspending the sample plate from the balance pole. . The corrosive reaction gas is introduced at a constant flow rate from the gas inlet provided at the top of the reaction tube, passes through the inner tube, and comes into contact with the sample.
The gas passes through the outer tube and is discharged from the gas outlet at the top of the outer tube. At this time, in order to prevent the reaction gas from flowing into the balance rod, fulcrum, balance mechanism parts such as weights and pans, and the weighing detection part, an inert purge gas such as air or _N2 gas is usually added at 20 to 50 ml/min. It is made to flow into the purge chamber from the gas inlet at a flow rate of about 10 min, merge with the reaction gas in the reaction tube inner tube, and be discharged together. As long as this purge gas is flowing normally, the reaction gas will not flow into the balance chamber, and there is no fear that metal parts such as the balance mechanism will be corroded. However, conventionally, the reactant gas piping and purge gas piping in thermobalances, etc., are separate, and separate valves and pressure regulating valves (bellows valves, etc.) are provided to shut off each gas or adjust the flow rate. Normally, the control systems for both channels are not provided with any kind of mobility.
For this reason, for example, if the reaction gas tank and purge gas tank are closed almost simultaneously at the end of a measurement, the reaction gas will remain in the sample section in the reaction tube along with the purge gas, and this will diffuse into the balance chamber over time, causing the above-mentioned Corrodes the metal parts of the balance mechanism and weighing detection part, destroying their functions. Also, if you accidentally open the reaction gas tank before the purge gas tank at the start of a measurement, the reaction gas will flow into the balance chamber, albeit temporarily, and enter various parts of the mechanism, and even if the purge gas flows next, the mechanism will not be able to function properly. There is a risk that reactive gases may remain in small gaps, etc., which can cause corrosion accidents as described above. Conventional thermal analyzers typically take measurements over a long period of time, especially corrosion resistance tests on metal samples, which can take several hundred to 1,000 hours.Therefore, there are limit switches that automatically stop the measurement after an arbitrary period of time, power outage countermeasures, and heating furnace temperature. Although many of them are equipped with various safety features such as measures to prevent runaway, there are no thermal analysis instruments equipped with functions to prevent corrosion accidents caused by instantaneous operational errors by the operator as mentioned above, and expensive instruments are often required. It may become unusable due to corrosion.
Nowadays, thermal analysis in corrosive environments is becoming popular, and there is a strong demand for equipment equipped with safety functions.

This idea was made in view of the above-mentioned current situation, and it prevents the corrosive gas that reacts with the sample material of conventional thermal analysis devices such as thermal balances from diffusing into the device mechanism other than the reaction tube, such as the balance mechanism. By eliminating the shortcomings of relying on the operator to operate the purge gas, and by making improvements to the purge gas and reaction gas flow paths, we have completely prevented the reaction gas from diffusing into the inside of the device other than the reaction tube. The object of the present invention is to provide a device that is equipped with a function that allows measurement, is free from corrosion accidents, and is simple and easy to operate for a measurer. In other words, in a device that measures the thermal change of a substance in a corrosive reactive gas flowing atmosphere, a means is provided in the flow path of the purge gas that purges the reactive gas, and a means is provided to check the flow only when the flow is present. The present invention relates to a thermal analysis apparatus characterized in that an on-off valve of a reaction gas flow path is configured to open.

An embodiment of the invention will be explained below with reference to the drawings. Figure 1 is a block diagram (including a cross-sectional view of the reaction tube) showing the configuration of this invention when applied to a thermobalance. 1 is the electronic balance rod, and 2 is the fulcrum, which is a tote band type, the supporting part of which is not shown in the figure. Omit. 3 is a suspension wire, 4 is a sample, 5 is a count weight, and 6 is a weighing quantity detection section, which has a built-in lamp, shutter, photoelectric conversion device, etc. 7 is a glass container that seals the balance chamber 10 from the outside air. Reference numeral 11 denotes an upper outer tube of a double reaction tube, which is provided with an insertion port for a thermocouple 12 and a reaction gas inlet 14, and an inner tube 15 is fused at its lower end 11A. Reference numeral 16 denotes a lower outer tube of a double reaction tube, and a gas outlet 17 is provided therein. Gas outlet 17
Some are located at the bottom depending on the mechanism. 18 is a heating furnace. Block 20 is a purge gas supply source, such as a blower when the purge gas is air, and a gas cylinder when the purge gas is _N2 . 21 is a corrosive reaction gas supply source, which is a gas cylinder such as SO ₂ , NO ₂ , C ₂ , NH ₃ , etc., and 22 and 23 are respective flow paths. 24
is the purge gas inlet of the balance chamber. The above configuration is the same as the conventional thermobalance air test equipment, but the feature of this invention is the solenoid valve described below.
The automatic control system includes SV ₁ , SV ₂ and a solenoid valve control device 25 . 26 is an AC power supply, S _A , S _B , S _C
are operation signals for various safety functions during the long-term measurement described above, which are transmitted from a recorder, thermal analyzer, etc. (not shown) and transmitted to the control device 25, and will be explained in detail with reference to FIG. Figure 2 shows the electric circuit of the solenoid valve control device 25, where 26 is the AC power terminal, S is the power switch, and PB is the manual operation automatic return contact for starting analysis.When this is turned on, the timer contact Ts is always on. Relay R ₁ is energized and its a contact R _1a is turned on, self-holding R ₁ . R ₁
At the same time as energizing, open the solenoid valve SV ₁ of the purge gas flow path shown in Fig. 1 and let the purge gas P _G flow into the balance chamber 10 at a flow rate of 20 to 50 ml/min as shown by the arrow.
The purge gas PG flows into the upper outer tube 11 from the upper inlet of the reaction tube, further flows into the inner tube 15 from the upper end 15A of the inner tube 15, contacts the sample 4, and is discharged from the gas outlet 17 of the lower outer tube 16. Ru. The time chart in FIG. 3 shows that the flow of purge gas PG occurs at time _t1 in the diagram.
Next, at time _t2 in FIG. 3, the delay time TD until the flow of the reactant gas RG is generated is arbitrarily set to, for example, 30 seconds or 1 minute using the delay relay TL shown in FIG. this delay time
After TD, TL's a contact TL _a1 turns ON and reactant gas solenoid valve SV ₂ opens. At the same time, another a contact of TL, TL _a2 , turns on, but this circuit is connected to the b of relay _R2.
Contact _R2b is OFF and does not conduct until time _t3 , which will be described later. LS _A , LS _B , and LS _C in this series circuit are all limit switches, etc., and these are always
When ON, _LSA is a reset switch that manually stops the gas at the end of the measurement, and this is located on the analysis operation panel. LS _B is a limit switch for protecting the heating furnace 18, which is set to operate at a limited temperature in the recorder, for example. LS _C is a limit switch for power outage protection, and this is a b contact such as a relay that turns off in the event of a power outage. Returning to Fig. 1, when the solenoid valve SV ₂ opens, the reaction gas RG flows in from the gas inlet 14 of the reaction tube outer tube as shown by the dotted arrow, but is pushed by the flow of the purge gas PG and enters the balance chamber 1.
0, but joins with the purge gas from the inner tube inlet 15A, causes a contact reaction with the sample 4, and is then discharged from the outlet 17. The flow of these two gases is continued in a steady state for a measuring time TA, for example, several hundred hours, and the corrosion test is performed. Next, when the scheduled time has elapsed and the reset switch of LS _A is turned off at time _t3 , solenoid valve SV ₂ is closed. At this time, relay R ₂ turns OFF at the same time, and the b contact R _2b of R ₂ turns OFF as shown in the figure.
When turned on, a mechanical timer (built-in wind-up clock)
The clutch coil TC of T operates to release the clutch, the timer T starts operating, and SV ₁ remains open for a certain period of time △t during which the purge gas PG completely purges the residual gas in the reaction tube of the reaction gas RG. Keep it. After Δt has elapsed, at time _t4 , timer contact TS turns OFF for the first time, solenoid valve SV ₁ closes, and the measurement is completed. The above is the automatic control operation of the flow of purge gas and reaction gas of this invention, so there is no need to worry about reaction gas flowing in when purge gas is not flowing, and corrosive gas remaining in the reaction tube after measurement will diffuse into the balance chamber. It is now possible to prevent this from happening. Furthermore, since a mechanical timer is used, the cleaning time of Δt can be ensured even if there is a power outage when the measurement is completed. However, if the power outage is long, SV ₁ will also be closed, so it is necessary to install a bypass and manually flow purge gas for △. The gas flow paths 22 and 23 are kept as short as possible to improve controllability. The above is an explanation of an example in which the gas control system of this invention is applied to a thermal balance. However, this invention is not limited to thermal balances, and uses a corrosive reactive gas, which may corrode the analyzer. It is equally applicable to any existing thermal analysis device. Further, the electromagnetic valve control circuit is not limited to that shown in the drawings, and the delay time TD may be provided using a two-stage push button at the first start, for example. In short, any device that can form a time chart like the one shown in FIG. 3 will suffice, and it goes without saying that various possible devices fall within the scope of this invention.

This idea is structured as above, so
In conventional thermal analyzers, especially thermobalances,
The flow path control of the corrosive reaction gas and purge gas was mainly performed manually by the measurer, so an inappropriate measurement method or mistake could corrode the expensive device mechanism and destroy the function of the analyzer. The reactor gas is configured to flow only when the purge gas is flowing, completely preventing the inflow and diffusion of corrosive gases into the mechanical parts of the device, allowing for safe use without any risk of corrosion accidents, and It can be said that we have provided a convenient device that is easy to operate.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a reaction tube and other components of a thermogravimetric measuring device (thermobalance) as an embodiment of this invention, Fig. 2 is an electric circuit diagram of a solenoid valve control device, and Fig. 3 is a block diagram showing other components. This is a time chart of the flow of purge gas and corrosive reaction gas. RG...Corrosive reactive gas (SO ₂ , NO ₂ , C
₂ , _NH3, etc.), PG...purge gas (air, N2 _, etc.), 1...balance rod, 2...balance fulcrum, 3...hanging wire, 4...sample, 5...weight, 6
...Weight detection unit, 10...Balance chamber, 11...
... Reaction tube upper outer tube, 14 ... Reaction gas inlet, 15
... Reaction tube inner tube, 16 ... Reaction tube lower outer tube, 17
...Gas outlet, 18...Heating furnace, SV ₁ ...Purge gas flow path solenoid valve, SV ₂ ...Reaction gas flow path solenoid valve, _R1 , _R2 ...Relay coil, TL...Delay relay, T ...Mechanical timer, TC...Timer clutch coil, TD...Time for only purge gas before measurement, △t...Time for only purge gas after measurement.

Claims (1)

[Scope of utility model registration request] In an apparatus for measuring thermal changes of a substance in a corrosive reaction gas flow atmosphere, a means for checking the flow of the reaction gas is provided in the purge gas flow path for purging measurement parts other than the sample chamber part. 1. A thermal analysis device characterized in that the on-off valve of the reactant gas flow path is opened only when the flow is present.