JPS5928259B2 - Gas vitreous index measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for measuring the vomit index of paraffinic hydrocarbons and olefinic hydrocarbons.

The whiskey index WI is defined by the first equation.

wl-- (1) Here, Q is the total calorific value of the gas to be measured, and ρ1 is the density of the gas to be measured.

To determine the vodka index, the total calorific value and density must be measured. Conventionally, in order to measure the total calorific value of a gas to be measured, for example, the gas to be measured is actually mixed with combustion gas, combusted continuously in a constant state, and the resulting combustion gas is guided to a heat exchanger. The heat of combustion is absorbed by the cooling water that constantly flows in the heat exchanger.

In this case, the temperatures and flow rates of the gas to be measured, combustion air, and cooling water, as well as the air temperature, are kept constant.
The temperature, flow rate, and air temperature described above must be measured, and the total calorific value of the gas to be measured must be calculated based on these measured values. In such prior art, there are many factors that cause measurement errors in the total calorific value, and therefore it is difficult to improve the measurement accuracy of the vodka index. Therefore, the main object of the present invention is to easily and accurately measure the vomit index of paraffinic hydrocarbons and olefinic hydrocarbons.

FIG. 1 is a system diagram of an apparatus for carrying out the present invention.

In this example, the vomit index of natural gas obtained by vaporizing liquefied natural gas (LNG) used as city gas is measured. The natural gas to be measured is paraffinic hydrocarbon C. It is a mixed gas consisting of H2O+2. A pair of acoustic tubes 2 and 3 are provided within the constant temperature bath 1. Natural gas, which is a gas to be measured, is introduced into one acoustic tube 2 from a gas pipe 4 via a pipe line 5 . A pressure reducing valve 6 and a flow meter 7 are interposed in the pipe line 5 . The other acoustic tube 3 is filled with natural gas having a composition similar to that of the gas to be measured as a standard gas. The acoustic tubes 2, 3 have the same dimensions and have the same structure. A microphone 8 and a speaker 9 are attached to both ends of the acoustic tube 2, and an output electrical signal from the microphone 8 is given to the speaker 9 via an amplifier 10. By appropriately selecting the length of the acoustic tube 2, and thus the distance t1 between the microphone 8 and the speaker 9, the distance t1 can be adjusted.
Oscillation (howling) occurs within the acoustic tube 2 at a frequency f1 corresponding to the sound velocity u1 of the gas to be measured. This frequency f1 is, for example, about 5 KHz. The other acoustic tube 3 is also provided with a miter 11, a speaker 12, and an amplifier 13, similarly to the acoustic tube 2 described above. The distance T2 between the microphone 11 and the speaker 12 is chosen equal to t1 (t1=T2). The acoustic standing wave with respect to the distance T2 in the acoustic tube 3 and the sound speed U2 of the standard gas has a frequency F2
oscillates. A temperature measuring element 17 is provided within the constant temperature bath 1 .

Also, a heater 1 for increasing the atmospheric temperature in the constant temperature bath 1.
8 is provided. The temperature control electric circuit 19 energizes the heater 18 in response to the output of the temperature measuring element 17, thereby keeping the ambient temperature of the thermostatic oven 1 constant. Reference numeral 20 is a fan for stirring the atmosphere inside the constant temperature bath 1. The pressure p1 in the acoustic tube 2 and the pressure P2 in the acoustic tube 3 are adjusted to the same pressure by the pressure correction device 21. (p1=P
2). There is a relationship expressed by the second equation between the sound velocity u in gas and the gas density ρ. t: Gas temperature ρ: Density at 00C α: Temperature coefficient R: Gas specific heat ratio (R2 constant pressure specific heat Cp/constant volume specific heat CV) Between the measured gas in the acoustic tube 2 and the standard gas in the acoustic tube 3 The third equation holds true.

The subscript 1 of each term in the third equation represents a term related to the gas to be measured, and the subscript 2 represents a term related to the standard gas. Therefore, in the acoustic tube 2, the fourth equation holds true between the sound velocity u1, the frequency f1, and the wavelength λ1.

In the illustrated embodiment, J! ．． 1. As mentioned above, t1=T2. Since the gas compositions of the target gas and the standard gas are similar and the pressures of both gases are equal, R
1? It is R2.

Further, t1=T2. Therefore, Equations 6 and 7 are established based on Equations 3 to 5. The density ρ2 and frequency F2 of the standard gas are known.

Therefore, the beat frequency Δ of the output from the mixed detector 14
It can be seen that the density ρ1 of the gas to be measured can be determined from the seventh equation depending on f. There is a relationship expressed by Equation 8 between the specific gravity γ of the gas to be measured relative to air and the density ρ1. The inventor of the present invention found that there is a relationship shown in FIG. 2 between the specific gravity γ of the gas to be measured and the total calorific value Q.

The gas to be measured is a homolog of methane Cn at the volume ratio shown in Table 1.
．． In the case of a mixed gas consisting of H2n+2, the specific gravity γ and the total calorific value Q can be calculated as follows. Specific gravity γ2 of gas to be measured 0.554×0.8834+1.0
38×0.0651+1.522×0.0354+2.
006×0.0069+2.006×0.0084++
2.491×0,000820.643 Total calorific value of gas to be measured Q=9530×0.8834+16820×0.
0651+24320×0.0354+32010X0
90069+32010X0,0084+37670X
0.0008 / 10895 Kca 1 Am3 The specific gravity γ and the total calorific value Q of the gas to be measured depend on the composition of the gas to be measured, and the specific gravity γ and the total calorific value Q for each gas to be measured having different compositions are determined in the same way as above. Figure 2 is obtained by calculating and graphing the results.

Therefore, by determining the density ρ1 of the gas to be measured from the seventh formula and determining the specific gravity γ based on the eighth formula, the total calorific value Q can be determined from FIG. Therefore, it will be understood that the votive index WI can be obtained according to the first equation. Referring again to FIG. 1, the output from the mixed detector 14 has a beat frequency Δf, and the output from the frequency-to-voltage converter 15 has a voltage value corresponding to the beat frequency Δf.

The output from the frequency-to-voltage converter 15 corresponds to the density ρ1 and the total calorific value Q. The recorder 26 receives the output from the frequency-to-voltage converter 15 and records the total calorific value Q.
indicate. The arithmetic unit 27 receives the output from the frequency-to-voltage converter 15, performs the calculation according to the first equation, and causes the recorder 28 to record and display the vodka index W2, which is the result of the calculation. This embodiment has the excellent advantage that it is possible to measure not only the water index WI, which is an important characteristic of city gas, but also the specific gravity γ and the total calorific value Q.

In the present invention, the gas to be measured may be a mixed gas consisting of homologues of olefinic hydrocarbons, in addition to a mixed gas consisting of homologues of paraffinic hydrocarbons.

The standard gas is likewise a mixture of paraffinic hydrocarbon congeners and an olefinic hydrocarbon congener. ``The standard gas has a composition similar to that of the gas to be measured. As described above, the present invention
Focusing on the fact that the sound speed in the gas being measured corresponds to the density and calorific value, this method converts the sound speed into an electrical signal related to the value of the sound speed, and calculates the water vapor index based on that electrical signal. .

Therefore, in the present invention, it is not necessary to actually heat and burn the gas to be measured in order to measure the total calorific value necessary for calculating the water vapor index, as has been the case in the past.
Accordingly, there are fewer factors that cause measurement errors, and the measurement accuracy of the votive index can be improved. Furthermore, the present invention can be implemented with a static, relatively simple electrical configuration and is easy to operate. Furthermore, in the present invention, one acoustic tube is filled with a standard gas, the other acoustic tube is supplied with a gas to be measured, and the beat frequency caused by the difference in the sound speed of the two gases is detected. Since the index is measured, accuracy can be further improved. Moreover, even if the flow rate of the gas to be measured changes,
The beat frequency and therefore the measured beat index do not change, which also allows the accuracy to be improved. Furthermore, it is highly sensitive, easy to maintain, and can continue measuring with high precision over an extremely long period of time.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of an apparatus for carrying out the present invention, and FIG. 2 is a graph showing the specific gravity γ and the total calorific value Q of a gas to be measured obtained by the inventor of the present invention. 1... Constant temperature chamber, 2, 3... Acoustic tube, 8
, 11...Microphone, 9,12...Speaker, 10,13...Amplifier, 14...
・Mixed detector, 15...Frequency-voltage converter,
27... Arithmetic unit, 26, 28... Recorder.

Claims (1)

[Claims] 1. Microphones 8, 11 and speakers 9, 12 are attached to both ends of each of the pair of acoustic tubes 2, 3, respectively.
The output electric signal from 11 is amplified by amplifiers 10 and 13 and applied to speakers 9 and 12 to generate oscillation, while a mixed gas of paraffinic hydrocarbon homologs is injected into one acoustic tube 3. The other sound tube 2 is sealed as a standard gas.
A mixed gas of paraffinic hydrocarbon homologues is supplied as a gas to be measured, and the standard gas has a composition similar to that of the gas to be measured, and the outputs from each amplifier 10 and 13 are fed into a mixed detector. 14 to derive a beat signal having a beat frequency Δf, and measure a wafer index of a gas to be measured corresponding to the beat frequency of the beat signal. 2. Microphones 8, 11 and speakers 9, 12 are attached to both ends of each pair of acoustic tubes 2, 3, respectively.
The output electric signal from 11 is amplified by amplifiers 10 and 13 and applied to speakers 9 and 12 to generate oscillation, while a mixed gas of olefinic hydrocarbon homologs is injected into acoustic tube 3. sealed as a standard gas, and the other acoustic tube 2
A mixed gas of homologues of olefinic hydrocarbons is supplied as a gas to be measured, the standard gas has a composition similar to that of the gas to be measured, and the outputs from each amplifier 10 and 13 are sent to a mixed detector. 14 to derive a beat signal having a beat frequency Δf, and measure a wafer index of a gas to be measured corresponding to the beat frequency of the beat signal.