JPS58210562A - Method and apparatus for determining methane and non-methane hydrocarbons - Google Patents

Abstract

PURPOSE:To determine also components other than CH4 which are incorporated in sample air in slight amounts, with the same apparatus with high precision as well, by sampling sample air in a cooled collecting tube for hydrocarbons other than CH4, first separating CH4 and O2 and heating the collecting tube, thus releasing hydrocarbons other than CH4. CONSTITUTION:Sample air is made to flow from an inlet A through a solenoid value V3 and taps V1 and V2 in order along the flow passage shown with dotted lines. A collecting tube T is cooled, captutres hydrocabons other than CH4, and discharges the other gaseous components via a measuring tube L. Then, the tap V2 is turned to the flow passage shown with solid lines, and CH4 and O2 and the like in the measuring tube L are separated into CH4 and O2 and the like with a column C2, to determine the concentration of CH4 with a hydrogen flame detector D. After the determination of CH4, when the suction volume (or the suction time) attains a prescribed value, a pump P is stopped, the solenoid valve V3 is turned to the flow passage shown with solid lines, gaseous carrier is introduced from an inlet N, the collecting tube T is heated to release gasenous non-CH4 hydrocarbons then each hydrocarbon is isolated with a column C1, and each concentration is determined with the hydrogen flame detector D. Thus, using a single apparatus, it makes possible to determine successively even slight amounts of non-CH4 hydrocarbons with high precision as well.

Description

DETAILED DESCRIPTION OF THE INVENTION Hydrocarbons in the atmosphere are a causative agent of photochemical air pollution, and measurement of their concentration is important for air management purposes.

Hydrocarbon is a general term for many substances, and when measuring it, we use methane, which is one of the natural components of the atmosphere, and hydrocarbons other than methane (non-methane hydrocarbons), which are thought to mainly consist of anthropogenic pollutants. It is stipulated that the measurement should be carried out separately.

Conventionally, the method used for this measurement was to collect several milliliters of sample air and separate and measure it using a hydrogen flame ionization detector and gas chromatography, but in recent years, with advances in air quality control, air The concentration of hydrocarbons in water is decreasing, and the conventional methods described above lack sensitivity and are no longer capable of accurate measurement.The current situation is that there is a need to develop a highly sensitive measurement method.

The present invention has been made in consideration of the current situation and aims to provide a method and apparatus for measuring methane and non-methane hydrocarbons with higher sensitivity.

That is, the present invention makes it possible to accurately measure low-concentration non-methane components by using a collection tube and collecting and measuring a significantly larger amount of non-methane components in sample air than in conventional methods. At the same time, it was devised to be able to measure methane, which is difficult to capture, at the same time.

Examples of the present invention will be described below, but before doing so, a collection analysis method, which is one element of the present invention, will be briefly explained.

This is because Figure 1 explains the principle, and Figure 9 shows T.
is a collection tube, which is a glass tube filled with an appropriate filler.
A heater H is wound around it.

■l is the cock, and C1 is the gas chromatograph column.

D is a detector, N is a carrier gas inlet, and 9M is a mass flow controller that controls the carrier gas flow rate.

P is the pump and A is the sample air inlet.

Now, when the cock vl is in the state shown by the dotted line.

When the pump P is operated, sample air is sucked in from the sample air inlet A, and is sent to the outside of the yarn through the collection tube T and the pump P. The collection tube T is kept at a relatively low temperature, and the filler inside the collection tube T has a sufficiently large holding capacity for the components to be collected at this temperature. , the air passes through, but the components to be collected are trapped in the collection tube T.

After suctioning a certain amount of sample (for a certain period of time if the sample flow rate is constant), stop the pump P, switch the cock Vl to the solid line side, and energize the heater H of the collection tube T to heat it. The collected component substances are washed out, carried by the carrier gas, and separated while passing through the column C1, and the amount thereof is measured by a detector. M is a mass flow controller, and the collection tube T is heated. The flow rate is controlled so that a constant flow rate of carrier gas flows even if the resistance changes.

Such a collection analysis method has already been put to practical use in the analysis of odor components in the atmosphere.

Attempts have been made to apply this kind of collection analysis method to the measurement of hydrocarbons in the atmosphere, but since methane has a low boiling point (approximately -160°C), collection of methane is difficult. There are technical difficulties in that the tube T must be kept at an extremely low temperature or a very long collection tube (several meters) must be used, so it cannot be used as a practical method for measuring hydrocarbons in the atmosphere. .

Now, FIG. 2 shows an apparatus according to an embodiment of the present invention. In the figure, the parts with the same reference numerals as in Fig. 1 are the same as those in Fig. 1, and constitute a non-methane hydrocarbon analysis system.
A methane analysis system consisting of a two-carrier gas pressure regulator B and a solenoid valve V3 are added. Note that D uses a hydrogen flame ionization detector in this case.

Jin's example device is operated and analyzed in the following manner.

(When Rikotsukku vl, v2 and solenoid valve v3 take the dotted line flow paths, when pump P is operated, sample air enters from sample air population A, passes through collection pipe T, metering pipe, and passes through pump P to the system. An example of the collection tube T has an inner diameter of 4 mm,
A glass tube with a length of 20cm.

It is filled with a polymer bead-based filler and maintained at dry ice temperature (approximately -60°C) at this stage.

Under this condition, only non-methane components are collected, and methane flows through the collection pipe T and through the metering pipe without being collected.

(2) In this state, when cock V2 is switched to the solid line flow path side, the sample (methane, oxygen, etc.) that was passing through the metering pipe at that time is sampled, and methane and oxygen are separated in column C2, resulting in hydrogen Methane concentration is measured with a flame ionization detector.

(3) When the suction air amount reaches a predetermined amount (or when the suction time reaches a predetermined time), stop the small pump P and switch the magnetic valve v3 to the solid line flow path.Then, nitrogen gas (carrier gas) flows into the resistor R9 solenoid. It flows into the collection tube T through the valve v3, expelling the air (oxygen) remaining in the tube T. This is to prevent the filler from oxidizing when the collection tube T is heated.

(4) After completing the methane measurement in (2) above, switch the cock Vl to the solid line flow path, energize the heater H, and
When the collection tube T is heated to 50-200°C.

The collected non-methane components are washed out by the carrier gas, pass through the column c1, and reach the detector, where their amount is measured. Column C1 is simply a resistor with no separation ability, and the non-methane components are not separated but measured all at once.

(5) Cool the collection tube T and prepare for the first analysis.

Cook vl and v2 explained above. Pump P, heater II
.

The analysis is automatically performed by programming the electromagnetic valve (3) in advance and controlling it using a sequence controller or the like.

As explained above, the analysis method of the present invention first measures methane by sampling the sample air that has passed through a collection tube that collects only non-methane components during sample collection, and then Since the non-methane components are washed out from the collected collection tube and measured, the non-methane components in a large amount of sample are collected and measured, so a sensitivity 10 to 100 times higher than conventional methods can be easily obtained.

The sensitivity of methane is the same as that of the conventional method, but it is known that methane exists anywhere on the earth at least around 1.2 PPm, so it can be sufficiently measured with the sensitivity of the conventional method.

In addition, since non-methane components are removed from the sample air used in the methane measurement system in the collection tube at the front stage, there is no need to use a complicated analysis system such as a Brekaratona, and a simple column (filling material: Molecuila sieve, etc.) is not required. The analysis can be carried out stably even under high conditions.

In addition, in the unlikely event that the packing material in the collection tube deteriorates or the collection temperature is inappropriate, complete collection of non-methane components becomes impossible (low-boiling hydrocarbons pass through, and these is detected.

Another advantage is that the quality of the collection tube can be checked.

In addition, in the above analysis process (υ ~ (5)), the process (3) is necessary only when heating in the presence of oxygen deteriorates, such as with polymer bead-based packing materials.
If the filler does not pose such a risk, it may be omitted.

Fig. M3 shows another embodiment of the apparatus of the present invention, in which one 12-point stock is used instead of two 6-point stock, thereby simplifying the apparatus configuration and analysis operation.

In the figure, parts given the same reference numerals as those in FIG. 2 are the same as those in FIG. 2, and have the same functions.

In the apparatus of the embodiment shown in FIG. 3, analysis is performed in the following process.

(1)-Ezu cock V is in the dotted line flow path, cooling the collection tube T to a predetermined temperature, a predetermined amount of material air is sampled, and methane and oxygen are separated in column C2. Methane content is measured.

During this time, the collection tube T remains cooled and the carrier gas flows to expel air.

(3) After the methane measurement is completed, turn on the heater H,
Measure by expelling non-methane components. In this case, the direction of the gas flow during flushing of the collection tube T is the same direction (forward direction) as when collecting the sample (in the case of the embodiment device shown in FIG. Since T acts as a separation column, the non-methane components tend to separate somewhat.

This can be solved by data processing technology during measurement (quantification by peak area).

(Cool the 4-inch collection tube.

As mentioned above, according to the present invention, much higher sensitivity can be obtained for non-methane hydrocarbons compared to conventional methods, and moreover, it is possible to obtain a much higher sensitivity for non-methane hydrocarbons, which was a problem when simply applying the collection analysis method. This solves the problem of not being able to measure methane, making it possible to measure methane and methane simultaneously.

In addition, by analyzing the sample that has passed through the collection tube and measuring methane, which is difficult to capture, even if the usage conditions of the collection tube are inappropriate.

Another advantage is that this can be checked when measuring methane. Another great advantage is that this analytical system for measuring methane does not require a Brecut, and can be a very simple analytical system.

[Brief explanation of the drawing]

Figure 1 is a diagram explaining the collection analysis method, which is one of the conventional methods.
FIG. 2 shows an embodiment of the present invention. FIG. 3 is a diagram showing another example device. In the figure, A is the sample air inlet, T is the collection tube, H is the heater, and N
is carrier gas inlet, L is metering tube, C2 is gas chromatograph 7 column, D is detector, VtVztj: cock,
v3 is a solenoid valve and pump from two companies. Figure 3

Claims (1)

[Claims] 1. Sample air is sampled through a collection tube cooled to collect only non-methane components. After separating the methane component and oxygen using a gas chromatography column and measuring the methane concentration using a flame ionization detector, the collection tube is heated to drive out the collected non-methane components, and the collected non-methane components are transferred to the flame ionization detector. Lead to non-methane lI
Methane, which is characterized by being designed to measure I degrees.
Non-methane hydrocarbon measurement method. 2. A collection tube equipped with a carrier gas inlet, a sample air inlet, cooling and heating means, and filled with a suitable filler;
In an apparatus equipped with a meter lid tube, a suction pump, a gas chromatography column, a hydrogen flame ionization detector, and one or more flow path switching cocks, (1) a sample air inlet, a collection tube,
Measuring tube. A flow path consisting of a suction pump connection. (2) A flow path consisting of a carrier gas inlet, a metering tube, a gas chromatography column, and a flame ionization detector connection. (3) A flow path consisting of a carrier gas inlet, a collection tube, and a hydrogen flame ionization detector.
can be selectively switched by the cock, and when the flow path of (1) is selected, the collection tube is cooled by the cooling means, and the flow paths of (2) and (3) are selected. When the measurement with the hydrogen flame ionization detector in the flow path (2) is completed, the collection tube in the flow path (3) is heated by a heating means, and the t% A methane/non-methane hydrocarbon measuring device characterized by carrying out the described measuring method.