JPH0210452Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a calorimeter that measures the concentration of fuel gas and uses that value to measure the calories of the fuel gas.

Conventionally, when calculating the calories of combustion gas, such as butane-air (mixed gas of butane and air),
The butane concentration in the butane-air is determined by measuring the specific gravity of the gas (air = 1), and the calories of the fuel gas are calculated from that concentration. This type of specific gravity type has the advantage of being able to perform span calibration using other inert gases such as argon instead of the butane-air standard gas, but the equipment is large because the specific gravity is measured mechanically. It has the disadvantages of being bulky and expensive. On the other hand, a calorimeter using a catalytic combustion type gas sensor is being considered, but with this method, it is difficult to directly measure the combustible gas concentration in fuel gas that contains a high concentration of flammable gas. This is impossible due to the principle of measurement. The reason for this is that this method utilizes the temperature rise of the gas sensor when the flammable gas in the test gas contacts the gas sensor and burns, generating heat. Therefore, the combustion state gradually becomes saturated and a temperature increase proportional to the gas concentration cannot be obtained, resulting in extremely inaccurate gas concentration indications.

However, since the concentration of combustible gas in fuel gas is above the practical explosive range, in actual measurements it is necessary to dilute it to an appropriate concentration, for example, to less than 1/4 of the lower explosive limit. This method requires an extra operation and has the disadvantage of reducing measurement accuracy.

Although it is sufficient to use a standard gas that is compatible with the span calibration of the measuring instrument, it is obvious that a stable inert gas such as the former cannot be substituted.

This idea was developed in consideration of the above-mentioned points. By using a gas thermal conduction type gas sensing element, there are no moving parts as a measuring element, which improves reliability. Furthermore, the entire device can be made smaller, and moreover, it can handle high-concentration gas. The object of the present invention is to provide a calorimeter that can be used to perform span calibration. This idea will be explained below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of this invention. In this figure, A is the gas detection section, B is the span calibration section, C is the indicator, D is the recorder, E,
F is a connection cable.

First, the gas detection section A will be explained. 1 is a gas detection chamber, the details of which are shown in cross section in FIG.

In FIG. 2, 2 is a housing provided with a gas inlet 3 and a gas outlet 4, with connecting fittings 5,
6 is installed. A porous case 7 made of sintered metal is attached inside the housing 2 . The case 7 further includes a gas thermal conduction type gas detection element (hereinafter simply referred to as a gas detection element) 8 and its compensation element 9, and the gas detection element 8 has a through hole 1.
0 and the compensating element 9 is capped by a sealing cap 12. Stems 13, 14, and 15 are made of conductors and support the gas detection element 8 and the compensation element 9, respectively. 16 is an insulating base;
1. The sealing lid 12, stems 13 to 15, etc. are insulated and supported, and the whole is housed in the case 7. 17
The case 7 is hermetically housed inside the housing 2 with an O-ring. Reference numeral 18 denotes a suction pump that sucks gas from the gas inlet 3 and discharges it from the gas outlet 4. During this time, the gas detection element 8 is passed through the case 7.
so that the gas comes into contact with the Resistors R ₁ and R ₂ are connected between the ends of stems 13 and 14, and between ends of stems 15 and 14, respectively. Reference numeral 19 denotes a terminal box, which has a connector 23 to which lead wires 20, 21, 22 respectively connected to the stems 13 to 15 of the gas detection chamber 1 are connected, and a connecting cable E is connected to this connector.
is connected.

Referring again to FIG. 1, 24 is a filter with a flow rate check, which removes dust from the sample gas and checks the flow rate, and is attached to the connection fitting 5 on the gas inlet 3 side of the gas detection chamber 1. 2
Reference numerals 5, 26, and 27 designate three-way switching valves, which are connected to the front stage of the filter 24, the connecting fitting 6 on the gas discharge port 4 side of the gas detection chamber 1, and the three-way switching valve 26, respectively. 28 is a two-way switching valve, and three-way switching valves 26 and 2
It is provided at the connection part of 7. With the above, gas detection part A
is configured.

Next, the span calibration section B will be explained. The span calibration section B consists of conduits 31 and 32 connected to the three-way switching valves 25 and 27, and a mixing tank 33 connected between these conduits 31 and 32. The mixing tank 33 has a rubber injection port 3.
4, from which a specified amount of highly concentrated gas can be injected using a syringe or the like. Reference numeral 35 denotes a piston, which is provided to be airtight and to move automatically in order to make the inside of the mixing tank 33 equal to the outside pressure.

The instruction section C includes an instruction amplification unit 41, a power supply unit 42, a terminal box 43, and the like. The instruction amplification unit 41 supplies power to the gas detection section A, receives a signal from the gas detection section A, and instructs the meter. The power supply unit 42 is configured not only to supply power to the instruction amplification unit 41 but also to issue an alarm in the event of an abnormality. Furthermore, connection cables E and F are connected to the terminal box 43 to connect required parts. Recorder D is connected to terminal box 43 by connection cable F when recording is required.

Connection cable E connects between terminal box 19 and terminal box 43. Furthermore, the connection cables F consist of F ₁ to _{F 3} , in which connection cable F ₁ is for power supply, connection cable F ₂ is for connection between terminal box 43 and recorder D, and connection cable F ₃ is for control output. This is used when performing calorie control, theoretical _O2 combustion control, etc. using the calorific value of the sample gas obtained by the instruction amplification unit 41.

Before explaining the operation of the embodiment shown in FIG. 1, the measurement principle will be explained with reference to FIGS. 3 and 4.

FIG. 3 mainly shows the electric circuit of the gas detection section A. In Fig. 3, 8 and 9 are the gas detection element and compensation element shown in Fig. 2, R ₁ and R ₂ are the resistors mentioned in Fig. 2, and RV is a variable resistor.
These make up the bridge. Then, a power supply voltage E ₀ of, for example, 0.5 to 5.0V is applied between the lead wires 20 and 22, and the lead wire 21 and the variable resistor are connected to each other.
Obtain the output voltage from between the sliders P of the RV.

As mentioned above, the gas detection element 8 is of the gas heat conduction type, and is made by coating a platinum wire with an inert material and sintering it. When another gas mixes into the air, its thermal conductivity changes, resulting in a change in the temperature of the gas detection element 8 and a change in the resistance value of the platinum wire. On the other hand, the compensation element 9 is the same as the gas detection element 8, and its outer periphery is sealed to prevent direct contact with the gas. Therefore, as described above, although the temperature of the gas detection element 8 changes due to the gas, the temperature of the compensation element 9 does not change, so that an output corresponding to the temperature change can be obtained from the bridge. This output is nothing but the gas concentration. Therefore, if the span is calibrated using a gas of known concentration whose calorie is known in advance, the calorie can be determined from the gas concentration.

FIG. 4 is a graph showing an example of instruction values for calorie values. If such a graph is created in advance, calories can be immediately determined from the indicated value of the concentration of the sample gas.

The embodiment shown in FIG. 1 operates based on the above principle, and the overall operation will be explained below with reference to FIGS. 5a, b, and c.

FIG. 5a shows the internal gas being purged and the zero point being calibrated, with the three-way switching valves 25 to 27 closed as shown, that is, the blacked portions are closed.
Make sure that the white parts communicate with each other, and insert zero gas as purge gas from the 3-way switching valve 27 using the arrow
Feed as shown in A ₁ and transfer to mixing tank 33, 3.
direction switching valve 25, filter 24, suction pump 18,
Arrow A ₂ via the 3-way switching valve 26 and 2-way switching valve 28
Perform purging in the exhaust passage.

Next, as shown in FIG. into the inlet 34 and add a specified amount of 100% concentration gas with known calories.
Inject into the mixing tank 33. Since the volume within the closed circuit is known, if the amount of gas to be injected is known, the gas concentration when the gas is uniformly diffused within the closed circuit is also known. That is, the suction pump 18
The injected gas circulates within the closed circuit and has a constant concentration. Span calibration is performed as described above.

Next, as shown in Fig. 5c, the three-way switching valves 25, 26
Switch to disconnect the mixing tank 33 side. Before this changeover, if necessary, the state shown in FIG. 5a is again performed for purging. Now, in Fig. 5c, sample gas is introduced from the three-way switching valve 25 as shown by arrow _C1 , passes through the filter 24 and gas detection chamber 1, passes through the three-way switching valve 26, and is discharged to the outside as shown by arrow _C2. .
The gas concentration at that time is indicated by the amplification unit 4 in Figure 1.
1 and calculate the calorie of the sample gas from that value.

In the above embodiment, the suction pump 18 was provided in the gas detection chamber 1 to be of an automatic suction type, but if there is a pressure difference, the suction pump 18 is not necessary. Further, although the porous case 7 is used to make it explosion-proof, it does not need to be used unless it is explosion-proof.

As explained in detail above, this invention uses a gas thermal conduction type gas detection element, so it is possible to perform span calibration using a highly concentrated gas, and therefore accurate measurement is possible. In addition, compared to conventional gravity type devices, there are no moving parts, so they are highly reliable, and can be extremely small, for example, about 1/10th the size, and can be constructed at low cost. Furthermore, since the gas detection chamber and the instruction amplification unit can be placed separately, the installation of the gas detection chamber becomes compact and easy. Also,
Since the indicator amplification unit can be installed at a location suitable for monitoring, constant monitoring is easy.

As described above, this invention can be used for calorie control, theoretical O ₂ combustion control on the burner side, etc., and is expected to be widely used in the future.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram showing an embodiment of this invention, Fig. 2 is a sectional view showing details of the gas detection section in Fig. 1, Fig. 3 is an electric circuit diagram related to Fig. 2, and Fig. 4
The figure is a graph showing an example of an instruction value for a calorie value, and FIGS. 5 a to 5 c are schematic diagrams of essential parts for explaining the operation of the embodiment of FIG. 1. In the figure, A is the gas detection section, B is the span calibration section, and C
is the indicator, D is the recorder, E and F are the connection cables,
1 is the gas detection chamber, 2 is the housing, 3 is the gas inlet, 4
is the gas exhaust port, 7 is the case, 8 is the gas detection element,
9 is a compensation element, 18 is a suction pump, 25, 26,
27 is a three-way switching valve, 28 is a two-way switching valve, 33 is a mixing tank, 34 is an inlet, 41 is an indicator amplification unit, and 42 is a power supply unit.

Claims (1)

[Scope of utility model registration request] A gas detection chamber that uses a gas thermal conduction type gas detection element to obtain an electrical output according to the gas concentration, and a gas detection chamber with a known calorific value installed at both ends of this gas detection chamber so that it can be freely approached and separated via a three-way switching valve. 1. A calorimeter comprising: a mixing tank into which gas can be filled; and an indicating amplification unit that indicates a gas concentration from the electrical output of the gas detection chamber.