Device for preparing a vapour-gas mixture

Abstract

The invention is intended for reproducing the volume fraction of hydrocarbons in vapour-gas mixtures by dynamically mixing two flows. The technical problem addressed is that of creating a device capable of preparing a vapour-gas mixture of different substances which in their normal state are in a liquid phase. The device comprises a housing with a control unit, connecting pipes, and a dilution gas flow regulator and a liquid flow regulator which are equipped with PID controllers and are connected via a mixing device to an evaporator, the liquid flow regulator also being connected to a tank for liquid. The gas flow regulator is configured in the form of a mass flow meter with a control valve. The liquid flow regulator is configured in the form of a mass flow meter. The mixing device is configured in the form of a three-way mixer with a control valve. The evaporator is configured in the form of a heat exchanger with an electric heater and is equipped with a temperature sensor.

Description

[0001] Device for preparing a steam-gas mixture

[0002] The invention pertains to metrology and is designed to reproduce the unit volume fraction of hydrocarbons in vapor-gas mixtures by dynamically mixing two gas flows. The device can be used for testing, adjusting, and verifying instruments for measuring the content of components in gas and gas condensate environments, such as gas analyzers, alarms, gas analysis transducers (sensors), and other gas analysis channels and systems.

[0003] In the field of gas metrology and analysis, several methods and devices exist for preparing vapor-gas mixtures used for the calibration and verification of gas analysis instruments. However, existing solutions do not always meet modern requirements for accuracy, stability, and process automation.

[0004] A capillary vapor-gas mixture dispenser (RU2280246) uses capillaries of varying cross-sections to create mixtures. The use of capillaries of a fixed cross-section limits the device's applicability to various substances.

[0005] A gas-dynamic test rig with a dosing device for creating vapor-gas mixtures using diffusion dosing units (RU2284498) is known. These units operate by diffusing molecules from the surface of a liquid substance into a flow of dried carrier gas. Diffusion dosing units depend on many factors, such as the surface area of ​​the liquid substance and the ambient temperature, making precise control of the vapor-gas mixture concentration difficult. They are limited in their operating concentration range due to the dependence of the diffusion rate on the surface area and physical properties of the substance. They require special conditions and adaptation for each specific substance, as well as a long time to reach steady-state conditions and stabilize the concentration.

[0006] A device for preparing vapor-gas mixtures (RU2194567) is known. These mixtures can be obtained from a liquid substance by purging a chamber containing the liquid with air. The device comprises a vessel for saturating the gas with vapor, partially filled with liquid, a device for diluting the vapor-gas mixture, designed as a tee, one end of which is connected to a gas supply line, the second end to the vessel's interior, and the third end to a vapor-gas mixture outlet line, a flow rate inducer, and a detector, all installed in series in the vapor-gas mixture outlet line. The device does not provide the ability to set the required flow rate of the prepared vapor-gas concentration at the device outlet, limiting the capabilities for testing, adjusting, and verifying instruments for measuring the component content in gas and gas condensate environments.

[0007] A device for preparing vapor-gas mixtures (patent RU126468, selected as a prototype) is known. It produces vapor-gas mixtures by dynamically mixing two gas streams: a vapor-gas mixture obtained by bubbling a gas-air mixture through a liquid, and a diluent gas. The device comprises a gas system, an analytical unit, a thermostatically controlled saturator, and a test chamber. Bubbling gas through a liquid requires a larger volume of liquid. The device has a limited number of possible concentrations at the device's outlet. Purging the chamber with the liquid component often leads to concentration fluctuations, limiting the accuracy and stability of the generated mixtures. When switching to a different vapor-gas mixture, considerable time is required for flushing and subsequent purging of the gas line.

[0008] The technical objective of the invention is to create a device with the ability to prepare a steam-gas mixture of various substances that are normally in the liquid phase, with a pre-explosive concentration in the range from 5 to 50% of the lower concentration limit of flame propagation and with the ability to regulate the flow rate of steam-gas mixtures in the range from 500 to 4000 cm 3 / min. The technical result is an increase in the accuracy of the concentration value of the vapor-gas mixture, as well as a reduction in the time required to conduct a series of measurements with different vapor-gas mixtures.

[0009] The technical result is achieved in a device for preparing a steam-gas mixture, including a housing with a control unit, connecting pipelines, a diluent gas flow controller (DGF) and a liquid flow controller (LFC), equipped with PID controllers and connected via a mixing device to an evaporator. The liquid flow controller is connected to a liquid reservoir secured to the housing. The diluent gas flow controller is implemented as a mass flow meter with a control valve controlled by a PID controller. The liquid flow controller is implemented as a mass flow meter. The mixing device is implemented as a three-way mixer with a control valve controlled by a PID controller of the liquid flow controller. The evaporator is implemented as a heat exchanger with an electric heater and equipped with a temperature sensor.

[0010] The invention is explained by the following drawings: Fig. 1 - basic gas diagram; Fig. 2 - evaporator; Fig. 3 - heat exchanger.

[0011] The device for preparing a steam-gas mixture (hereinafter also referred to as the "device") is a first-class standard and is designed to reproduce the volume fraction of hydrocarbons in steam-gas mixtures. The device comprises a metal housing (not shown) housing the gas system and a control unit. The control unit (not shown) contains a controller, a touchscreen display, and a power source and is designed to control the operation of all elements of the gas system with the ability to automate the mixture preparation process. The control unit allows for setting and monitoring operating parameters, including temperature, concentration, and flow rate of substances.

[0012] The gas system includes connecting pipelines, a diluent gas flow regulator 1 with a control valve RRG, and a liquid flow regulator 2, connected via a mixing device 3 to an evaporator 4, as well as mechanical two-way and three-way valves. Mixing device 3 is designed as a three-way mixer with a control valve 17.

[0013] Liquid flow controller 2 (LFC 2) is designed to set and measure the flow rate of liquid supplied under pressure from tank 5. LFC 2 is calibrated for each specific substance, taking into account its specific heat capacity. LFC 2 is designed as a liquid mass flow meter with a PID controller (for example, M-FLOW thermal liquid flow meters with a PID controller, manufactured by Bronkhorst, can be used). Its operation is based on a capillary tube with two sensor elements, which serve both as heaters and temperature meters. The temperature difference measured by the sensors depends on the heat absorbed by the liquid. The temperature sensors are part of a bridge circuit; the ratio is linearized and amplified to the required output signal level. The relationship between the liquid flow rate and the output signal is described by an equation (the equation is not shown).Structurally, the RRZh 2 consists of: a housing (the housing is made of corrosion-resistant materials resistant to the effects of chemically active liquids) with inlet and outlet openings for liquid; a liquid mass flow meter consisting of a capillary tube with two sensor elements; an electronic board including a microprocessor and a PID controller, which process data from the sensors and control the control valve 17, which is part of the mixing device (the operating mode of the electronic board is set by the control unit).

[0014] The RWG 2 is connected via a pipeline to a liquid reservoir 5, which is secured to the housing, for example, via an internal or external bracket, to facilitate filling with liquid by bulk. Reservoir 5 serves as a container for storing and subsequently dispensing liquid into the RWG 2 during operation. The reservoir is designed to be hermetically sealed and create positive pressure, ensuring a constant flow of liquid into evaporator 4.

[0015] Diluent Gas Flow Controller 1 (DGFC 1) is designed to set and measure the flow rate of a diluent gas (inert to the liquid, such as nitrogen or air). It is designed as a mass flow meter with a DGFC control valve controlled by a PID controller (for example, Bronkhorst's EL-FLOW thermal gas flow meters with a control valve can be used). It is also calibrated for specific substances (nitrogen and air) based on their specific heat capacity, further enhancing the accuracy of mixture preparation.Structurally, the RRG 1 includes: a housing made of corrosion-resistant materials resistant to the effects of chemically active liquids, with inlet and outlet openings for the diluent gas; a gas mass flow meter consisting of a main gas line and a capillary tube with two sensor elements, between which a gas flow heater is located; an electronic board including a microprocessor and a PID controller, which process data from the sensors and control the RRG control valve (the operating mode of the electronic board is set by the control unit); RRG control valve.

[0016] The use of PID controllers (proportional-integral-differential controllers) for controlling the RRG and 17 control valves, which are part of the RRG 1 and the mixing device, provides the following advantages: precise control of gas and liquid flow rates, which is important for maintaining stable and precise concentrations in the vapor-gas mixture; fluctuations and deviations from the set parameters are minimized, which is especially important for reproducing stable conditions during the mixture preparation process; rapid response to changing conditions, such as pressure or temperature fluctuations, rapid control of the RRG and 17 control valves, ensuring process stability; correction of deviations from the set parameters not only instantaneously, but also with the ability to predict their change, which ensures high adjustment accuracy; the differential component of the PID controller helps reduce system fluctuations, ensuring smoother and more stable valve control.Unlike other types of controllers, the PID controller combines the advantages of proportional, integral and differential control, which ensures optimal control under complex and dynamic conditions.

[0017] Evaporator 4 is designed to evaporate liquid at a controlled temperature of approximately 50°C and is constructed as a heat exchanger 6 with an electric heater 7 and equipped with a temperature sensor 8. This ensures stability and high repeatability of the set vapor-gas mixture concentration. Evaporator 4 maintains a stable temperature to ensure complete liquid evaporation and, consequently, a stable concentration in the vapor-gas mixture, which improves the accuracy of the vapor-gas mixture concentration value. At the inlet of evaporator 4, a mixing device 3 is installed with a control valve 17 (an electromagnetic valve consisting of a housing and a solenoid with a core on which a plunger is mounted, closing / opening the liquid inlet to mixing device 3). To prevent pressure surges at the initial moment of operation, the opening of control valve 17 is regulated by a PID controller.The PID controller is located in the RRZh 2, specifically, it is integrated into the RRZh 2 electronic board and connected to the control valve 17 via a cable. This allows the PID controller to smoothly open / close the control valve 17 within a few milliseconds, which improves the accuracy of liquid dosing and, ultimately, the accuracy of the vapor-gas mixture preparation. Normally, the control valve 17 does not allow liquid to pass through; it is closed. The plunger is pressed against the inlet by a mechanical spring. When a signal from the PID controller is received by the control valve 17, a gradual, smooth retraction of the plunger from the inlet occurs, allowing the liquid flow to slowly increase. The magnitude of the plunger retraction is determined by the PID controller, depending on the set and measured liquid flow rate. Thanks to this, the RRZh 2 regulates ultra-low liquid flow rates in the range of up to 33.00 mg / min, which also improves the dosing accuracy and the accuracy of the preparation of the steam-gas mixture.

[0018] Backflow or ingress of diluent gas into the RRG is prevented by the pressure maintained in tank 5 and, accordingly, throughout the entire liquid supply line up to the plunger of control valve 17. Backflow or ingress of liquid into the RRG is prevented by the pressure maintained in the RRG and, accordingly, throughout the diluent gas supply line up to the plunger of control valve RRG. The temperature of heat exchanger 6 is regulated by a temperature controller (e.g., with an PT 100 sensor, type M-K 2515 1PT100), connected to the control unit. Electric heater 7 consists of two series-connected electric heating elements with a resistance of approximately 26 ohms each and is equipped with a protective switch.

[0019] The device enables the preparation of vapor-gas mixtures for substances that cannot be stored in pressurized cylinders 15 due to their tendency to condense. Cylinders 15 with pressure reducers 16 serve as gas sources for supplying a diluent gas (nitrogen, air) under pressure, as well as for supplying pneumatic power (INPUT 1111) to tank 5 containing liquid. Connecting pipeline 9 for supplying pneumatic power to tank 5 is equipped with a mechanical safety valve 10 (designed for automatic emergency pressure relief from tank 5 in the event of exceeding the set pressure, to prevent tank 5 failure). Valve 11 is designed to relieve pneumatic pressure on the tank containing the liquid target component for tank removal. Valve 12 is designed to shut off the liquid drain line. Three-way valve 13 is designed to purge the liquid line and the entire system upon completion of work. Filter 14 serves to protect the RRZh 2 regulator from mechanical particles getting into it.

[0020] The control unit's software automates process control, accounts for the specific heat capacity of each feedstock, and ensures precise component dosing. It automatically calculates the necessary parameters for preparing the steam-gas mixture, ensures high process accuracy and stability, and allows for real-time monitoring and, if necessary, parameter adjustments.

[0021] Sub-explosive concentrations of substances with low saturated vapor pressures can only be prepared using the steam generation method, as when pumping these concentrations into a cylinder, the partial pressure of the substance begins to exceed its saturated vapor pressure, leading to condensation. The steam generation method, including with sub-explosive concentrations, ensures high accuracy and reliability in the preparation of mixtures.The device is capable of preparing steam-gas mixtures for various target components (liquids), including: Ethanol (C2H5OH), Methanol (CH3OH), Toluene (CbH3CH3), Benzene (C6H6), Acetone ((CH3)2CO), Methyl tert-butyl ether (C5H12O), Ortho-xylene (o-C3H1), Para-xylene (p-CbH1), Meta-xylene (m-CbH1), Heptane (CvHie), Isopropyl alcohol (C3H3O), Ethylbenzene (CbH1), Cyclohexane (CbH2), Butyl acetate (CbH2O2), Ethyl acetate (C4H2), 1-Butanol (C4H9OH), Octane (CsH2), Diethylamine ((C2H3NH3), n-Nonane (C9H2O), Styrene (CsHs), Chlorobenzene (CeHsCl), 1-Octene (CsHie), 1-Propanol (C3H3O), Acetic acid (C2H4O2), Hexane (CbHm), 1,2-Dichloroethane (C2H4Cl2).

[0022] The device operates by mixing a liquid with a diluent gas, followed by evaporation in evaporator 4. The required concentration of the vapor-gas mixture and the required flow rate at the device's outlet are set using the touchscreen display. The process is controlled and monitored automatically using built-in software.

[0023] The device is installed on a laboratory bench away from sources of vibration and heating devices. Connect cylinder 15 with a diluent gas (e.g., nitrogen or air) to the device inlet via reducer 16. Fill reservoir 5 with liquid (the target component in the liquid phase). All parameters can be adjusted manually, via the touchscreen on the housing, or via an external computer when connected to the device. Fill the device with liquid: connect cylinder 15 to the inlet fitting "INLET 1111". Close valves 11 and 12. Connect a tube to the "DRAIN" outlet and set the nitrogen pressure to 0.2±0.05 MPa. Open valve 12 until liquid flows out of the outlet, without the gas phase. Close valve 12. Set the evaporation temperature: for specific tasks and testing of measuring instruments for other substances, it is possible to adjust the evaporation temperature. Set the liquid evaporation temperature (from 30 to 60 °C) using the touch display.For implemented components, the evaporation temperature can be set automatically in the software. Gas and liquid flow is started: open cylinder 15 with diluent gas, and the pressure at the "GAS INLET" inlet is set to 0.2 ± 0.05 MPa. Diluent gas flow is started by pressing the "RGD" button on the display. Purge the gas system for 10 minutes. For manual mode, set and start the liquid flow rate, calculating the flow rates according to the formulas (provided in the Appendix). The required flow rates are entered using the touchscreen. During automatic mixing, this process is controlled automatically by the device's built-in software. The built-in software and touchscreen allow for continuous monitoring and display of the device's current operating parameters, including diluent gas and liquid flow rates, temperature, and the actual concentration value at the device's outlet.Upon completion of the work, turn off the diluent gas and liquid flow rates. Drain the liquid from tank 5, first relieving the pressure in tank 5 using valve I. Set valve 13 to the "PURGE" position, open valve 12, and purge the connecting lines 9 of liquid. This significantly reduces the time required to perform a series of measurements with different vapor-gas mixtures (and different liquids).

[0024] The device's technical performance is achieved through its design features and the integration of advanced control and monitoring technologies. The RRZh 2 is calibrated for specific substances based on their specific heat capacity, significantly improving accuracy. Specially developed software creates an optimal operating mode for each substance individually. Gas and liquid mass flow controllers 1 and 2 ensure highly accurate setting and measurement of liquid and gas microflow rates, which is critical for reproducing precise volume fractions of target components in the vapor-gas mixture. This enables the desired concentration to be achieved with minimal errors. Embedded software controls the RRZh 2; it is configured for each substance based on the specific heat capacity of each source liquid and automates the process of preparing the vapor-gas mixture, reducing the influence of human error and improving the stability and repeatability of results.Industrial standards and regulations specify concentrations of explosive substances as volume fractions or as a percentage of the lower flame limit (LEL). Therefore, gas analysis instruments measure in volume fractions or LEL. Conversion from volume fractions or % LEL to mass concentration at the outlet is described in the Appendix. Accurate liquid and carrier gas dosing is achieved using mass flow meters in the RRG 1 and RRZh 2 models because the mass flow is independent of external conditions (atmospheric pressure, temperature) and the density of the starting materials. Since mass flow meters are used, there is no need to consider these factors in calculations. This increases the accuracy and stability of the device as a reference. Automation also allows for real-time monitoring and adjustment of parameters.The use of a thermostatically controlled evaporator 4 and other components that maintain stable temperature and flow rates enables highly stable and repeatable results. This is especially important when preparing reference mixtures for calibrating and verifying gas analysis instruments. Built-in filters and safety valves ensure safe operation, protecting the device from mechanical damage and gas leaks. Its single-unit design facilitates transportation, installation, and maintenance.

[0025] Example: Calculating the operating modes of a device

[0026] 1. Recalculation of the specified output content into mass concentration C (g / m3) 3 )

[0027] 1.1 If given in volume fraction C% ; , Then where / / is the molar mass, g / mol.

[0028] 1.2 If specified in % LEL C% Н CPR, then

[0029] C = ^ Co / aNKPR -C ^NKPR -001 > where is the value of the lower concentration limit of flame propagation according to GOST R IEC 60079-20-1-2011, mass concentration, g / m3 3

[0030] Note: 1) C% LEL can vary from 2 to 50% LEL;

[0031] 2) Reference values ​​of molar mass (g / mol) and LCL (%, g / m 3 ) from GOST R IEC 60079-20-1-2011 are specified in Appendix B.

[0032] 2. Calculation of liquid mass flow rate ()) ж , mg / min (actual value) * where C исх - mass fraction of the original component, %;

[0033] QB IX - outlet flow rate, cm 3 / min.

[0034] 3. Calculation of the diluent gas consumption Q r , cm 3 / min To convert liquid flow rate into device readings, it is necessary to use the calibration table for the corresponding component.

[0035] Calculation of output content based on flow measurement results

[0036] Calculation of mass concentration (g / m 3 )

[0037] If the required output content is in % or % LEL, then formulas 1.1 and 1.2

Claims

Invention formula 1. A device for preparing a steam-gas mixture, including a housing with a control unit, connecting pipelines, a diluent gas flow regulator and a liquid flow regulator, equipped with PID controllers and connected through a mixing device to an evaporator made in the form of a heat exchanger with an electric heater and equipped with a temperature sensor, the liquid flow regulator is connected to a liquid reservoir fixed to the housing.

2. The device according to item 1, characterized in that the mixing device is made in the form of a three-way mixer with a control valve controlled by a PID controller of the liquid flow regulator.

3. The device according to item 1, characterized in that the diluent gas flow regulator is made in the form of a mass flow meter with a control valve controlled by a PID controller.

4. The device according to I.1, characterized in that the liquid flow regulator is made in the form of a mass flow meter. and

Images