JPS5949532B2 - Gas concentration analyzer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gas concentration analyzer, and an object of the present invention is to provide a gas concentration analyzer that has a relatively simple structure and can perform accurate analysis over a wide range of concentrations using a single detector.

Gas concentration analysis methods include gas chromatography,
There are infrared analysis methods, chemiluminescence methods, flame ionization methods, flame photometry methods, etc. In order to shorten measurement time and improve response performance, for example, NDIR, GLD, FID, FP
A dedicated detector such as D is used.

However, all these detectors have common drawbacks. Each detector has a certain measurement concentration range with excellent analytical sensitivity, and a single detector can only accurately measure within a limited measurement concentration range; It is not possible to analyze gas concentration. In order to widen this measurement concentration range even a little,
Methods such as connecting two cells in series and electrically changing the amplification rate have been adopted. However, these methods pose few problems when measuring concentrations from low to high; (In the case of gas) It is necessary to purge with zero gas for a considerable period of time to eliminate tailing. Also, in order to shorten the purge time, it is possible to introduce a large flow rate of zero gas, but if a large flow rate of zero gas is introduced into the detection part, the operating state of the detector will change (for example, if the temperature The measurement conditions must be adjusted each time (such as when the pressure decreases or internal pressure changes occur, etc.). In addition, especially when changing the amplification rate electrically, the relationship between the detector output and the gas concentration is not linear in either method, so a calibration curve for each range is required, which is cumbersome. . The present invention
This conventional drawback has been solved by making the structure as simple as possible.

An embodiment of the present invention will be described below with reference to the drawings.

In the figure, reference numeral 1 denotes a sample gas flow path through which a sample gas introduced from an inlet 2 flows, and is connected to a detector (eg, FID) 3.

Reference numerals 4, 5, 6, 7, and 8 denote filters, coolers, and the like, which are provided in the sample gas flow path 1 in this order from the upstream side, respectively.
A pressure pump, a constant differential pressure regulator, and a capillary tube as a fixed fluid resistance element are used. Dust in the sample gas is removed by a filter 4, and mist and moisture that interfere with analysis are removed by a cooler 5.

The pump 6 is provided to introduce the sample gas, and is not limited to a pressurizing pump as in this embodiment, but a suction pump may be provided downstream of the detector 3. The constant differential pressure regulator 7 maintains a constant differential pressure between the inlet and outlet sides of a capillary tube 8 having a predetermined length and inner diameter so that a constant flow rate Q of gas always flows through the capillary tube 8. The capillary tube 8 (length and inner diameter) and the differential pressure at both ends thereof are selected so that the constant flow rate Q coincides with the optimum flow rate in the detector 3. Next, reference numeral 9 denotes a dilution gas passage through which a dilution gas (for example, a gas such as N2 gas that does not interfere with the analyzer) flows, and the end of this dilution gas passage 9 is connected to a plurality of branch passages 101, 2. ．． ．． ．． ．． ．． 1 can be connected to the sample gas flow path 1 upstream from the capillary tube 8 and downstream from the connection point of a bypass 15 to be described later. Each branch flow path 101, 2 . ．． ．． ．． ．． ．． Capillary tubes 121, 2 . ．． ．． ．． ．． ．． n is provided.

The switching unit 11 switches the branch channels 10, 2, . ．． ．． ．． ．． ．． The diluent gas is made to flow through any desired channel among the channels. (In addition, in the figure, the dilution gas is
, is shown. ) 13 is the dilution gas flow path 9
A variable regulator provided therein, 14 is a capillary tube (12
1, 2. ．． ．． ．． ．． ．． This meter indicates the differential pressure between the inlet side and the outlet side of a branch flow path (any one of 101, 2... n) having a
By operating the variable regulator 13 while observing the instructions in step 4, a desired predetermined flow rate can be made to flow through the capillary tube (any one of 121, 2...n). (As is well known, the amount of diluent gas flowing through each capillary tube 121, 2...
．． It is determined by the length of n, the inner diameter, the differential pressure at both ends, etc. ) Next, 15 is a bypass branched from the sample gas flow path 1 on the upstream side of the constant differential pressure regulator 7, and is
Surplus sample gas other than the sample gas sent to is discharged from the outlet 16 through the bypass 15.

Note that the gas (sample gas + dilution gas) that has been sent to the detector 3 and has been analyzed is also discharged from the discharge port 16 via the discharge flow path 17 . By operating the switching unit 11, let the dilution gas flow from the branch flow path 10 as shown in the figure, and by operating the variable regulator 13, the capillary tube 12 will be changed when the meter 14 shows a predetermined indicated value. , the dilution gas flow rate flowing through the pump 6 is q1 (constant flow rate), and the constant flow rate of the sample gas introduced by the pump 6 (a large flow rate on the order of negligible response) is Q, then as mentioned above, the constant differential pressure Due to the action of the regulator 7, a constant flow rate Q of gas flows through the capillary tube 8, so the detector 3 receives dilution gas q1 and sample gas (Q,
q, ) will flow in.

Then, from the concentration of the component to be measured (for example, hydrocarbons other than methane) analyzed by the detector 3 and the dilution rate by the diluent gas (calculated from the constant flow rate Q and q1), the component to be measured in the sample gas is determined. Concentration can be determined. When analyzing the gas concentration, the component to be measured in the sample gas is estimated in advance, and the branch flow path 121 is
,2. ．． ．． ．． ．． 1. Decide which path the diluent gas will flow in and what the differential pressure between both ends of the capillary in the branched flow path (selected one of 12, 2...) will be. The dilution rate is determined based on the characteristics of the detector 3 used, and the dilution is performed so that the concentration of the component to be measured in the diluted gas falls within the measurement concentration range in which the detector 3 has excellent analytical accuracy. . Furthermore, due to the action of the constant differential pressure regulator 7, the excess sample gas (Q1 (Q,
-Q,)) passes through the bypass 15 and is discharged from the outlet 16. As described above, in accordance with the characteristics of the detector used, the sample gas is diluted with a diluent gas at a desired ratio so that the concentration falls within the measurement concentration range in which the analytical sensitivity of the detector is excellent. , since it flows to the detector,
By appropriately changing the dilution rate, a single detector can perform accurate sample gas analysis over a wide range of concentrations.

Furthermore, since the diluted gas is flowed to the detector as described above, tailing phenomenon is less likely to occur, accuracy is further improved, and purging with zero gas can be done in a very short time. In addition, only a small amount of zero gas is required for purging, and the diluted sample gas is flowed to the detector at the optimum flow rate for the detector, so changes in the operating state of the detector (temperature drop, internal pressure Therefore, there is no need to adjust the measurement conditions each time. Also, unlike when electrically changing the amplification rate, the work of creating a calibration curve for each range becomes unnecessary, and only one calibration curve is required. The amplification section for the detector output becomes very simple, and the processing of the output from the amplification section also becomes simple. In this way, we were able to eliminate all of the conventional drawbacks mentioned at the beginning, but in particular, by providing a fixed fluid resistance element, a constant differential pressure regulator, a bypass, etc. on the sample gas flow path side,
While the detector is configured to always supply a constant flow rate of gas, the diluent gas flow path is equipped with a variable regulator, a branch flow path for selectively changing the flow rate, a pressure meter, etc. Since the structure is such that a desired flow rate of dilution gas is always supplied to the sample gas flow path upstream of the fixed fluid resistance element, the structure is relatively simple and does not require a complicated calculation circuit. The dilution rate of the sample gas can be switched in multiple stages over a wide range, and after switching, it is possible to supply the sample gas to the detector while reliably maintaining a predetermined dilution rate.

The supply amount can also be maintained at a constant flow rate suitable for concentration analysis, thereby preventing response delays due to stagnation of the sample gas.

[Brief explanation of the drawing]

The drawings are explanatory diagrams showing one embodiment of the present invention. 1... Sample gas flow path, 3... Detector, 7... Constant differential pressure regulator, 8...
・Fixed fluid resistance element, 9... Dilution gas flow path, 1
0... Branch flow path, 11... Switching section, 1
2... fixed fluid resistance element, 13... variable regulator, 14... pressure meter, 15...
·····bypass.

Claims (1)

[Claims] 1. In a gas concentration analyzer configured such that a detector is connected to a sample gas flow path and the detector performs concentration analysis of a sample gas supplied from the sample gas flow path, a detector is fixed to the sample gas flow path. A fluid resistance element and a constant differential pressure regulator that maintains a constant differential pressure between the inlet and outlet sides of the fluid resistance element are provided, and a bypass is connected to the sample gas flow path upstream of the constant differential pressure regulator. and is configured to always supply a constant flow rate of gas into the detector through the fixed fluid resistance element, and to a sample gas flow path upstream from the fixed fluid resistance element and downstream from the bypass connection point. , a dilution gas flow path equipped with a variable regulator is connected to the dilution gas flow path, a plurality of branch flow paths each having a fixed fluid resistance element are connected to the dilution gas flow path, and a switching unit that selectively selects the plurality of branch flow paths. and a pressure meter for measuring the differential pressure between the inlet side and the outlet side of the branch flow path, and is configured to supply a desired flow rate of dilution gas to the sample gas flow path. Gas concentration analyzer.