RU2798692C1 - Stationary flow chamber for sampling gases at the water-atmosphere boundary - Google Patents

Abstract

FIELD: gas extraction.

SUBSTANCE: invention relates to forwarding equipment for sampling gases emitted from the surface of a liquid in the field of gas geochemistry, geochemistry, hydrochemistry, etc. The stationary flow chamber for sampling gases at the water-atmosphere boundary includes a floating base with an anchor fastening and an air chamber made of two chambers installed coaxially and tightly connected by a threaded adapter: the lower one, in the form of a dome with an open base, and the upper one, in the form of a bicone or a bipyramid with truncated tops, equipped in the upper part with a removable lid and a tight elastic seal, a spherical plug with positive buoyancy relative to 30% brine, and two tubes, a gas intake tube and a drain tube. The inlet and outlet of the intake tube are located with gaps between the base of the tight elastic seal and the base of the threaded adapter, the inlet of the drain tube is located on the surface of the threaded adapter, and its end is located outside the body of the flow chamber and is equipped with a dropper with a flow rate regulator, the diameter of the spherical plug exceeds the diameter of the inlet drain tube.

EFFECT: creation of an autonomous flow chamber for sampling gas at the water-atmosphere boundary, reduction of measurement error.

1 cl, 1 dwg

Description

The invention relates to the field of expeditionary equipment for sampling gases released from the surface of a liquid, and can be used in gas geochemistry, geochemistry, hydrochemistry, microbiology, hydrobiology, geoecology in the conduct of monitoring studies both on land and in marine and freshwater areas.

There are many different solutions for gas sampling at the ground-air interface using indirect, laboratory and direct measurements. The latter are the most accurate for measuring gas emission levels and are usually carried out using flow chambers (FCs) that allow measurements of gas concentrations over time.

A typical PC is a base, usually cylindrical, mounted on the surface to be examined, with a lid/dome superimposed on it, forming an air chamber. There are other design modifications, but for each of them the most important factors are the design of the cover, materials, geometry, size and volume of the air chamber. Another important aspect is the stationarity of the PC, as well as the possibility of periodic sampling.

For example, a PC is known for measuring the flow of CO2 on pastures, which includes a series-connected air chamber of a trapezoidal shape, the lower part of which is equipped with a ring mounted on the base of the PC in the form of a cylinder for placing on the surface under study. The top cover of the air chamber is equipped with an air intake and an air outlet, and the side wall is equipped with a temperature sensor. (CN No. 201429595 Y)

Known PC for collecting landfill gases at the landfill, made in the form of a cylinder, in the lid of which there are outlet valves connected to one line through which sampling is carried out, and an inlet valve through which clean, dry purge air enters from the cylinder, mixes with gases coming from the surface and transports these gases through the outlet valve. The device also contains thermometers for measuring the air temperature inside the chamber, a thermometer for measuring the soil temperature under the chamber, and a pressure sensor inside the chamber. The concentrations of emitted substances of interest are measured in the effluent gas, which are then used to calculate the emission rate of each type. (D. Reinhart et al., "Flux Chamber Design and Operation for the Measurement of Municipal Solid Waste Landfill Gas Emission Rates" ISSN 1047-3289 J. Air Waste Manage. Assoc. 42:1067-1070, 1992).

However, this PC design underestimates the actual emissions due to artificially forced air, and the need to use an additional element - a clean air cylinder to purge the chamber - limits the sampling time. The chamber does not ensure the accumulation of the test gas and requires the operator to work with it constantly.

A flow chamber is known in the form of a flat box without a bottom, including an air intake, a main body divided into two sections by a partition, five fans, aerodynamic edges of the inner surface of the chamber, an exhaust air valve located in the side slab of the PC, and an inlet air valve located in the upper part. PC. Thanks to the design using fans, a dividing plate and aerodynamic elements, atmospheric air is supplied through the inlet valve in parallel and evenly over the entire soil surface. Part of the air passing inside the chamber is taken through the exhaust valve. The speed of the air inside the chamber is controlled by the speed of the fan and the flow rate of the air supplied through the inlet valve. Thus, a cylinder with a carrier gas is removed from the design, however, when working with this PC, a carrier gas is still used - atmospheric air - which undoubtedly leads to an increase in measurement errors, and also necessitates additional analysis of the composition of the supplied atmospheric air . The PC works with air circulation in the space under the camera, however, this design requires the use of fans and requires a power supply. (Atmospheric Pollutant and Trace Gas Design and Performance of a Dynamic Gas Flux Chamber Rivka Reichman, Dennis E. Rolston (https://acsess.onlinelibrary.wiley.com/doi/full/10.2134/jeq2002.1774)

Known flow chamber Onose-8®, which consists of a hemisphere without a bottom, and a chamber without a top cover, installed inside the hemisphere, which is installed directly on the source to collect emissions of gases coming from the surface. At the same time, an inlet valve is located in the lower part of the chamber, through which gases released from the soil surface enter the chamber. At the top of the hemisphere is a sampling outlet valve and an overpressure outlet. In the lower part of the side wall of the hemisphere there is an inlet valve for supplying carrier gas, connected to a tubular line located along the perimeter of the inner part of the chamber parallel to the lower base of the chamber, while holes are provided in the line for supplying carrier gas to the chamber in such a way as to create a turbulent circulation inside the chamber. To create this turbulent airflow, the PC must be connected to a clean air source with an inlet valve. Further, the calculation is carried out on the basis of an analysis of the difference between the concentration of the carrier gas in the chamber and the initial one. ( https://onose.ca/work/flux-chamber/?lang=en)

The use of such a PC makes it possible to take gas samples from a local source without disturbing the emission surface. However, such devices require the supply of a carrier gas. It is a good idea for the designers to circulate inside the chamber by supplying the carrier gas in a specific way and not to use ventilators. In this case, the solution to the problem of excess pressure in the form of an outlet will obviously lead to the loss of a significant amount of sampled gas and will affect the correctness of the results.

Known PC for monitoring and sampling soil gas containing: a housing including an internal cavity for collecting soil gas and having a hermetic seal, a valve for supplying compressed inert gas to the specified internal cavity coming from an external source of compressed inert gas, a plurality of holes provided in the specified housing, both for the inlet of inert gas through the specified pipe, and for the release of excess inert gas and / or for monitoring parameters during control and / or for sampling the control gas collected in the specified cavity (EP #3346253 A1)

Known PC for the boundary of the water-atmosphere, the air chamber which is made in the form of an oblate hemisphere, equipped with a floating base located on the outer perimeter of the chamber. On opposite sides, in the lower part of the chamber above the water mirror, an inlet valve is installed to balance the internal pressure by supplying atmospheric air into the chamber and an outlet valve for sampling. In addition, the upper part of the chamber is equipped with an air pump, a timer and a battery to ventilate the chamber. The problem of excessive air pressure inside the chamber is solved by adding structural elements that make the device overly complex and reduce its autonomy. (Kenneth Thorø Martinsen and etc. Technical note: A simple and cost-efficient automated floating chamber for continuous measurements of carbon dioxide gas flux on lakes. Biogeosciences, 15, 5565-5573, 2018; https://doi.org/10.5194/ bg-15-5565-2018).

All the PCs described above have a complex design, are equipped with additional equipment, and require the use of a carrier gas (in an external cylinder or atmospheric air), which makes their autonomous use in water areas difficult. The problem of excess pressure relief is solved by the method of venting gases from the chamber into the atmosphere. The use of a carrier gas and the release of excess pressure into the atmosphere leads to a complication of the design, lack of autonomy, and contact with the atmosphere increases the measurement error. As a rule, the design of the chambers in most cases involves their use at the border either land - air or water - air, while the latter are much smaller.

Known streamingToa camera related to equipment for environmental monitoring of the environment, in particular, to the gas PC at the water-air border, which we consider as the closest in technical essence to the claimed solution (p. CN No. 202057528U). PC consists of a trapezoidal gas chamber and a gas chamber base in the form of a rectangular parallelepiped, connected in series, the gas chamber cover is equipped with inlet and outlet air valves. A gas collection system, a handle, a temperature sensor and a pressure equalization system are installed in the upper part of the chamber. The chamber is equipped with a fan for uniform gas mixing in the box. This chamber also assumes the use of a carrier gas. The design of the chamber provides a small volume of the device, light weight and easy to carry, short gas collection time, uniform mixing of the carrier gas with the gas at the water-air interface, reducing the error of subsequent measurements. However, the presence of a fan, which involves the use of a battery, as well as the use of a carrier gas, overly complicates the design and does not imply its use at the ground-air interface.

The proposed solution is aimed at expanding the range of universal gas flow sampling devices at the water-atmosphere boundary .

The problem is solved by the inventive design of the flow chamber, equipped with a floating base with an anchor mount and an air chamber made of two coaxially mounted on top of each other and tightly connected to each other by a threaded adapter chambers: the lower one, in the form of a dome with an open base, and the upper one, made in the form bicone or bipyramid with truncated tops, equipped in the upper part with a removable cover and a hermetic elastic seal, as well as a spherical plug with positive buoyancy, a gas intake and a drain tube, while the inlet and outlet of the intake tube are located with gaps between the bases of the hermetic elastic seal and threaded adapter, the inlet of the drain tube is located on the surface of the threaded adapter, and the end is located outside the body of the flow chamber and is equipped with a dropper with a flow rate regulator, while the diameter of the spherical plug exceeds the diameter of the inlet of the drain tube.

The proposed design of the device is completely closed, which excludes the contact of the contents of the PC with the atmosphere and thereby significantly reduces the measurement error, solves the problem of overpressure relief. The inlet of the drain tube can be equipped with a metal ring, and the spherical plug can contain a magnet in its body, which will increase the reliability of fixing the plug on the inlet of the drain tube. The absence of batteries makes the chamber completely autonomous, thanks to which it is possible to set any necessary time interval for sampling the gas flow, by calculating and setting the necessary operating mode of the dropper.

The main purpose of the chamber is to extract gas lighter than air, which is released at the water-air interface, in particular, methane, which will inevitably accumulate in the upper part of the device. However, the device, with some design modifications, can be used for other gases, as well as at the ground-air interface. The seal may be made of any elastic sealing material, such as natural or synthetic rubbers or plastics.

In FIG. one of the possible schemes of the proposed device for the water surface is shown, where: 1 - upper chamber for collecting gases, 2 - lower chamber, 3 - threaded adapter, 4 - intake air tube, 5 - drain tube, 6 - dropper with speed controller, 7 - removable hermetic elastic seal, 8 - cover, 9 - plug for drain tube 5, 10 - floating base, 11 - fixing rings.

Collection and operation of the device.

The device can be made of glass, or inert plastic, or metal.

The device consists of a chamber 1, connected by a sealed adapter 3 to the chamber 2, which can be made in the form of a sphere or a pyramid. Through the adapter 3, the hermetically installed intake tube 4 and the drain tube 5 pass vertically. its end goes outside the flow chamber from the side part of the adapter 3 and is equipped with a dropper 6 with speed control. The cover 8 closes the rubber seal 7. The plug 9 is made in the form of a ball and has a density that ensures its buoyancy in a 30% saline solution, and its size exceeds the inner diameter of the drain tube 5. The connection points of the elements 1-2, 3-4 3-5 are sealed . On the outer perimeter of the dome 2 there is a floating base 10, made with the possibility of vertical movement. When placing on the object, the base 10 is installed so that the lower part of the dome 2 is immersed in water. Mounting rings 11 are installed around the perimeter of the floating base 10 with equal spacing for attaching the device to the anchor. Depending on the tasks, for example, medical transfusion systems, including a speed controller and a drip chamber, can be used as a dropper.

At the beginning of work, the chamber 1 is filled with a 30% saline solution that prevents the dissolution of gases, leaving the top of the intake tube 4 open. The device is placed at the point of study. Floating base 10, equipped with anchors, provides a stable position of the device. The dropper 6 is opened and the saline solution begins to pour out of the chamber 1 through the tube 5; The rate of filling chamber 1 with gas will directly depend on the rate of draining the brine through tube 5 and can be adjusted by the dropper regulator 6. As the brine is poured out and the selected gas fills chamber 1 through tube 4, the plug 9 goes down and closes the inlet the opening of the drain tube 5 after almost all of the brine has left the chamber 1. Thus, the circulation in the chamber 1 will be stopped, and the brine remaining at the bottom of the chamber 1 will prevent the entry of external atmospheric air through the drain tube 5 and thus perform the function of a water seal. At the end of the selection of gases and their accumulation in chamber 1, the cover 8 is dismantled and the rubber seal 7 is pierced with a syringe needle and a gas sample is taken. Depending on the required sampling time interval, chamber 1 may have a different volume. The time of collection of gases in the chamber 1 can also be adjusted using the dropper 6, which allows the device to be installed autonomously at the point of study and to collect gases in a given time period.

The proposed device for gas sampling is distinguished by its versatility, ease of use and design, completely prevents contact with the external atmosphere, which is a necessary condition for gas sampling during gas-geochemical, chemical, microbiological analyzes, monitoring environmental changes in marine and freshwater water areas. Applying the principle of equilibrium concentrations keeps the pressure inside the device constant. The use of interchangeable droppers for the drain tube allows you to set the required time interval for sampling. In addition, chamber 1 and chamber 2 can be of different sizes, depending on the required time for collecting gases. The ease of execution of the proposed device and the ability to set the time interval make it possible to place a network of such devices in the study area.

Claims (1)

Stationary flow chamber for sampling gases at the water-atmosphere boundary, including a floating base with an anchor mount and an air chamber made of two coaxially mounted on top of each other and hermetically connected by a threaded adapter chambers: the lower, in the form of a dome with an open base, and upper, made in the form of a bicone or bipyramid with truncated tops, equipped in the upper part with a removable lid and a hermetic elastic seal, as well as a spherical plug with positive buoyancy relative to 30% brine, two tubes - a gas intake and a drain, while the inlet and the outlet of the intake tube is located with gaps between the base of the hermetic elastic seal and the base of the threaded adapter; drain tube.

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