SU832472A1 - Device for introducing samples into gas chromatograph - Google Patents

Description

The invention relates to gas chromatography and can be used to analyze mixtures of gases and / or vapors in process streams of various industries. Advantageously, the invention is intended to control the composition of liquids and gases in the process streams of chemical petrochemical industries. A device is known for introducing a gas chromatograph containing a liquid sample metering device and an evaporator connected to a carrier gas inlet channel and to the inlet of a chromatographic column 1. The device’s disadvantage is low operational reliability due to the fact that the plunger sample liquid metering unit The type has movable ground working surfaces and quickly goes out of operation when clogging of the rubbing elements and leakage. It is also known to have a device for introducing samples into a gas chromatograph containing a carrier gas channel in which a pressure regulator, an evaporator and a pneumatic resistance are installed, with the "two channels connected by a bypass line at points in front of the chromatographic column in the carrier gas channel and before pneumatic resistance in the channel for supplying the analyzed mixture t2l The drawback of the device is that abrupt changes in pressure drop occur at the column inlet, which causes the zero line to oscillate and, in some cases, flameout of the ionization detector. The purpose of the invention is to increase the reliability of the device. The goal is achieved by the fact that the device is equipped with an additional bypass line with a shut-off valve that is controlled from the timer and whose connection point with the carrier gas channel is located between the flow regulator and the connection point of the main bypass line, and the connection point is located behind the pneumatic resistance, moreover, at the output of the indicated line, additional pneumatic resistance is established. FIG. 1 is a schematic diagram of the proposed device in a working position preceding the moment of introduction of the sample in FIG. 2 is a schematic diagram of the device at the time of sample introduction.

The device contains a channel 1 gas-analyzer connected to the entrance to the chromatographic column 2, at the exit of which detector 3 is installed. In channel 1 of the carrier gas, before entering the chromatographic column 2, a gas flow regulator 4 is installed.

Parallel to the channel 1 of the carrier gas, a channel 5 is installed for supplying the analyzed mixture of gases or vapors in which the pneumatic resistance is installed. Channel 5 for supplying the analyzed mixture of gases or vapors is connected to the channel 1 of the carrier gas, through the bypass line 7 at points before pneumatic resistance 6 in channel 5 to supply the analyzed mixture and before the chromatographic column 2 in channel 1 of the carrier gas. In the feed channel 5 of the analyzed mixture, the flow controller 8 is also installed.

Channel 1 of the carrier gas is connected to channel 5 for supplying the analyzed mixture of an additional bypass line 9. The connection point of the additional bypass line 9 with the channel 1 of the carrier gas is located between flow control valve -4 and the point of connection of the main bypass line 7 with channel 1 the carrier gas, and the point of connection of the additional bypass line .9, with channel 5 for supplying the analyzed mixture is located between the point of connection of the main bypass line 7 and the pneumatic resistance b.

In the carrier gas channel 1 and in the additional bypass line 9, shut-off valves 11 and 12 are controlled by timer 10 and a pneumatic resistance 13 is installed behind the connecting point of the additional bypass line 9 with channel 5.

The device works as follows.

The carrier gas flow, stabilized by pressure and flow, with valve 11 open and valve 12 closed (Fig. 1) is continuously fed through channel 1 to chromatographic column 2. The flow of the analyzed mixture of gases or vapor through channel 5 does not flow through channel 5. pneumatic resistance 6 and 13 is either emitted to the atmosphere (if the gas mixture is analyzed) or to the vapor condenser if the mixture of liquid vapors is analyzed.

The flow rate of the carrier gas through the chromatographic column 2 is set so that the pressure at the connection point of the bypass line 7 with the channel 1 of the carrier gas slightly exceeds the pressure at the connection point of the bypass line 7 with channel 5 for supply

analyzed mixture. This is also provided by adjusting the pneumatic resistance 13 or additional pneumatic resistance established between column 2 and detector 3. This prevents the flow of the analyzed mixture into the channel 1 of the carrier gas and into the chromatographic column 1. Under these conditions, the chromatograph is output to the mode along the channels of the device is shown by arrows in Fig. 1).

 At the time of sampling (Fig. - 2), on command from timer 10, valves 11 and 12 are automatically switched, with valve 11 closing and valve 12 opening. The flow of carrier gas through the additional bypass line 9 and pneumatic resistance 13 goes into the atmosphere. The inlet pressure to the chromatographic column 2 decreases and the flow of the analyzed mixture through the bypass line 7 enters the chromatographic column 2 during the time specified by the timer 10. After a predetermined time has elapsed, valves 11 and 12 are again switched, valve 11 is opened, and valve 12 closes. At this position, the valves stop feeding the analyzed mixture to column 2, and the quantity of mixture that is pre-dosesed is transferred by carrier gas through chromatograph column 2, where the separation of mixture components that are detected at the outlet of column 2 by detector 3 is complete. Upon completion of the chromatographic analysis of the sample mixture or, up to this point in time, according to a command from timer 10, the valves 11 and 12 are automatically switched to the position shown in FIG. 2, during which a sample is taken from channel 5 to chromatographic column 2 of the next sample of the analyzed mixture for a given period of time.

The proposed device eliminates the sudden drop in pressure of the carrier gas at the inlet to the chromatographic column when the shut-off valve 11 is opened after sampling, which is caused by the displacement of the zero line, which generally improves the reliability of the device.

Claims (2)

Invention Formula A device for introducing samples into a gas chromatograph containing a carrier gas channel in which a pressure regulator is installed, a check valve controlled by a timer, a chromatographic column, a detector, and a channel for feeding the analyzed gas mixture and / or vapor, in which the Pressure regulator, the evaporator and the pneumatic resistance are installed, both channels are connected by a bypass line at points in front of the chromatographic column in the channel of the carrier gas and before the pneumatic resistance in the channel for feeding the analyzed mixture, which is In order to improve the reliability of the device, it is equipped with an additional bypass line with a shut-off valve, controlled by a timer, the connection point of which with the carrier gas channel Ahd / tu}. CfKct located between the flow regulator and the point of the main bypass line connection, and the point of connection with the line of the analyzed mixture is located behind the pneumatic resistance, and an additional pneumatic resistance is installed at the output of the specified line. Sources of information taken into account in the examination 1, US patent W 4007626, class, 73-23.1, 1975. 2. US patent 3668834, cl. 55-67, 1972 (prototype). 0 Gas Hocume / il