GB2585373A

GB2585373A - Measurement instrumentation for a process vessel and process vessel and process vessel system

Info

Publication number: GB2585373A
Application number: GB1909614.8A
Authority: GB
Inventors: behrendt Andreas; Stützle Elke; Gartung Bodo; Rußmann Stefan; Schuster Paul
Original assignee: Linde GmbH
Current assignee: Linde GmbH
Priority date: 2019-07-04
Filing date: 2019-07-04
Publication date: 2021-01-13
Also published as: RU2020120845A; GB201909614D0

Abstract

Measurement instrumentation 18 for measuring a level 16 of a cryogenic fluid 14 contained in a process vessel 12 comprises a reference chamber 20 connected at a first connection point 22 and a second connection point 24 to the process vessel 12 and forming a flow path between the first connection point 22 and the second connection point 24, wherein the first connection point 22 is located at a vertically higher level than the second connection point 24. The measurement instrumentation further comprises a measurement element float 26 for detecting a level of the cryogenic fluid 14 in the reference chamber 20 within the flow path between the first connection point 22 and the second connection point 24, and a drain line 28 connecting a lower portion 20b of the reference chamber 20 with a drain 32, wherein the drain 32 is located at a vertically lower level than the second connection point 24. The drain line may be permanently open during level measuring, and adapted to generate a permanent flow through the drain line when the level of cryogenic fluid is equal to or higher than the connection 24.

Description

Measurement instrumentation for a process vessel and process vessel system

Technical Field

The invention relates to measurement instrumentation for measuring a level of a cryogenic fluid contained in a process vessel and a process vessel system comprising such a measurement instrumentation.

Prior Art

Natural gas typically contains a ratio of methane and heavy hydrocarbon gases, as well as carbon dioxide, nitrogen, water and a range of other unwanted components. As NGL, LPG, condensate or the pure components as e.g. methane, ethane, propane and butane have higher sales values as compared to the pipeline gas itself, the different components are frequently extracted and fractionated in different processing plants. Cryogenic processes represent economical solutions to reject or recover natural gas components and increase the sales values. Prior to liquefaction, natural gas often has to be pre-treated in order to remove unwanted components. Depending on the concentration of sour gas components and downstream processing steps, it may be necessary to remove CO2 from the natural gas. As during the processing of the gas CO2 mainly is dissolved within the liquid phase of the gas, a further accumulation (e.g. due to heat ingress) of CO2 might lead to a precipitation of solid 002. Therefore in prior art only natural gases with a maximum content of 50 ppmv can be treated within cold plants.

The risk of constrictions and/or occlusions especially exists in parts or sections of a production line having relatively small opening diameters, small tubing diameters and/or dead spaces, such as measuring instrumentation, in which no regular flow of cryogenic fluid is present and where due to heat ingress and evaporation of light components remaining heavy components might accumulate until they precipitate.

In prior art local level indicators typically consists of a reference chamber with two side connections to the process vessel, in which the cryogenic fluid is stored and/or flowing. Within the reference chamber a measurement element, such as a floater, is typically installed which lowers and rises with level in the process. Vent and drain connections are typically provided, wherein the drain connection guides the fluid and/or solid constituents to a drain for wasting it.

Such a level measurement often represents a dead space where heat ingress might lead to an evaporation of light components and hence an accumulation and precipitation of CO2 and/or other heavy components within the liquid phase.

Therefore, the present invention aims to provide measurement instrumentation for a process vessel, in particular a local level measurement instrumentation, which is suitable for cryogenic fluids having constituents prone to accumulation and/or solidification, in order to facilitate a safe and failure free operation of the process vessel and/or measurement instrumentation with a reduced or eliminated risk of constriction and/or occlusion.

Disclosure of the Invention

This object is achieved by measurement instrumentation for a process vessel and a process vessel system comprising the features of the respective independent claims. Preferred embodiments are the subject-matter of the dependent claims and the following description and figures.

The invention relates to measurement instrumentation for measuring a level of a cryogenic fluid, preferably a liquid, contained in a process vessel. The measurement instrumentation comprises a reference chamber connected at a first connection point and a second connection point to the process vessel, wherein the first connection point is located at a vertically higher level than the second connection point. The measurement instrumentation further comprises a measurement element for detecting a level of the cryogenic fluid in the reference chamber, and a drain line connecting a lower portion of the reference chamber with a process line at a drain connection point, wherein the drain connection point is located at a vertically lower level than the second connection point.

In another aspect the invention relates to a process vessel system comprising a process vessel and measurement instrumentation according to the invention.

Most preferably the drain line has to be arranged at a low or the even the lowest point of the measurement instrumentation and preferably comprise a permanent sloping to prevent occlusions and/or constrictions at any place within the drain line and/or allow an efficient wash out from the reference chamber into the drain line without any dead spaces.

The measurement instrumentation and/or the process vessel system may be adapted to process a cryogenic fluid, which may comprise a high CO2 content, such as for example up to 5000 ppmv or even more. The process vessel may be any container containing said cryogenic fluid or being suitable for containing a cryogenic fluid, wherein the process vessel is not necessarily required to satisfy any further specific requirements.

Most preferably measuring a level of a cryogenic fluid relates to locally measuring a level of cryogenic fluid contained in a process vessel.

The invention provides the beneficial technical effect that dead spaces within the measurement instrumentation can be efficiently prevented. As in case of evaporation of lighter components of the cryogenic fluid within the reference chamber, the heavier components will be washed out through the drain line by means of gravity. By this, any potential of an undesired accumulation and/or concentration of heavier components of the cryogenic fluid in the measurement instrumentation can be reliably avoided and, hence, the precipitation of solid components can be prevented.

Additionally, when at least the lower part of the tubing is flooded with liquid cryogenic fluid from the process vessel via the second connection point, a preferably permanent flow of cryogenic fluid through the bypass towards the drain occurs. This keeps particularly the liquid cryogenic fluid inside at least the lower part of the reference chamber and the drain in a flow motion if a flow via the main line through the process vessel, thus, preventing dead spaces within at least the lower part of the reference chamber. By this, the formation of solidified constituents of the cryogenic fluid within the reference chamber can be prevented, or in case of solidified constituents being present, the solidified components are at least partially washed out through the bypass towards the drain. Therefore, the invention provides the beneficial effect that a formation and/or gathering of solidified constituents inside the measurement instrumentation can be prevented. Consequently, the measurement instrumentation according to the invention is well suited for process vessels and/or production lines and/or plants for storing and/or processing cryogenic fluids having constituents, which tend to solidification under certain pressure and/or temperature conditions. Particularly, the invention provides measurement instrumentation and a process vessel system being well suited for processing lines and/or plants processing natural gases having for instance carbon dioxide among their constituents.

The invention further provides the advantage that by using the measurement instrumentation and a process vessel system according to the invention within the production line and/or a plant does not require a separation of the carbon dioxide constituents of the cryogenic fluid. Therefore, the invention provides the benefit that the production costs for the cryogenic fluid and/or for the production line and/or plant may be reduced and/or the production effort for the cryogenic fluid may be reduced.

In addition, the invention provides the beneficial effect that the reliability of measurements by the measurement instrumentation, such as level measurements of the liquid cryogenic fluid within the process vessel, can be increased, since the danger of constrictions and/or occlusions can be reduced.

Moreover the invention offers the advantage that by reducing the risk of constrictions and/or occlusions within the plant or even completely avoiding them increases the safety of the respective plant and minimizes the risk of operational failures of the plant. Especially possibly required shut-downs of the plant may be avoided, which might occur due to constrictions and/or occlusions in the plant, sine according to the invention locally measuring the level of the cryogenic fluid is possible without the risk of generating occlusions and/or restrictions.

Preferably the drain line is connected to the lower portion of the tubing at the vertical level of the second connection point or below. This provides the beneficial effect that dead spaces within the reference chamber, particularly within the lower part of the reference chamber, can be efficiently prevented. As long as the level of the liquid fluid, within the process vessel exceeds the vertical level of the second connection point, a permanent flow of liquid fluid from the process vessel through the lower portion of the reference chamber and through the drain line can be maintained, which efficiently prevents a gathering of solidified components in the lower portion of the reference chamber Preferably, the drain line is connected with a permanent sloping to the outlet and/or to a sump line and/or an outlet process piping of the process vessel below the vertical level of the lower connection point.

Preferably the drain line comprises a drain line tubing having a smaller diameter than the reference chamber. Sloping within the drain line has to be ensured in order to prevent also dead spaces within the drain line. For instance, the reference chamber may have a diameter between 2 cm and 20 cm and/or wherein the drain line tubing may have a diameter between 0,5 cm to 5 cm. Preferably, the reference chamber may comprise 2-inch tubes (50,8 mm), while the drain line tubing may comprise 1/2-inch tubes (12,7 mm) and/or pipe.

Preferably the reference chamber and/or the drain line are sloped such as to facilitate a gravitationally assisted wash out of aggregated and/or accumulated components of the fluid 14 from the reference chamber. This allows an efficient wash out of possibly aggregated and/or accumulated solid components. Most preferably, the reference chamber is fully vertically oriented to minimize the risk of aggregation and/or accumulation and for allowing an efficient local level measurement.

Preferably the drain line is adapted to be permanently opened during operation of the level measurement instrumentation. This provides a permanent flow of cryogenic fluid at least within the lower portion of the reference chamber and the drain line tubing when the level of the liquid cryogenic fluid within the process vessel exceeds the vertical level of the second connection point. By this, a reliable washout of heavy and/or eventual solidified constituents can be achieved.

Preferably the drain line is adapted to generate during operation of the measurement instrumentation, i.e. in particular when the respective valve is open, a permanent flow of cryogenic fluid at least through the drain line and through the lower portion of the reference chamber when the level of the cryogenic fluid within the cryogenic fluid container is equal to or higher than the vertical level of the second connection. This allows reducing the risk of aggregation and/or accumulation to a minimum.

Preferably the measurement element comprises a floating device arranged in the reference chamber between the first connection point and the second connection point. This offers a cheap and/or reliable solution for locally measuring the level of the cryogenic fluid while a technical effort is reduced to a minimum. Most preferably the measurement instrumentation is constructed as a level indicator or comprises such.

Preferably the drain line is connected with slope to an outlet of the process vessel and/or a sump line. In other words, preferably the drain connection point is located at and/or in an outlet line of the process vessel and/or in and/or at a sump line.

Therefore, the cryogenic fluid flowing via the drain line is not necessarily wasted and/or to be fed to a flare, but can be maintained in the process and, thus, be available for its intended use.

Preferably the measurement instrumentation is constructed as a level indicator.

Preferably the measurement element comprises a floating device arranged in the reference chamber between the first connection point and the second connection point. More preferably, the reference chamber comprises an essentially vertically arranged portion, which may be a tube, in which the floating device is movably stored. The level of liquid cryogenic fluid in this reference chamber can be identical to the level of liquid cryogenic fluid in the process vessel and, thus, may allow the level of liquid cryogenic fluid inside the process vessel to be visible from outside the process vessel. The floating device can be adapted such as to be floatable on top of the liquid cryogenic fluid within the reference chamber, in particular within the vertically extending portion of the reference chamber. Preferably, the dimensions of the floating device are adjusted to the dimensions of the reference chamber, in particular to the dimensions of the vertically extending portion of the reference chamber and/or to the properties of the measured cryogenic fluid, e.g. its density, to allow a vertical movement of the floating device inside the vertical tubing with a rising and/or falling level of the cryogenic fluid inside the vertical section of the reference chamber. For instance the floating device may be formed at least partly from magnetic material, wherein a magnetic interaction may be used for the level detection. Therefore, by means of a floating device the measurement element can be provided in a cost efficient and reliable manner.

Further advantages and preferred embodiments of the invention are disclosed in the

following description and figures.

It is understood by a person skilled in the art that the preceding and the following features are not only disclosed in the detailed combinations, but that also other combinations or the features alone can be used without exceeding the scope of the present invention.

The invention will now be further described with reference to the accompanying drawing showing a preferred embodiment.

Brief description of the drawing

Fig. 1 schematically shows a process system comprising measurement instrumentation according to a preferred embodiment.

Detailed description of the drawing

Figure 1 depicts a process vessel system 10 comprising a process vessel 12 containing a cryogenic fluid 14. The cryogenic fluid 14 may be stored at a low temperature, such as at its boiling point at ambient pressure, which may be about -160° C, wherein a part of the cryogenic fluid 14 is present in the liquid phase 14a which reaches up to a level 16, as well as in the gaseous phase 14b, which mostly is present vertically above the liquid phase 14a. In addition, the process vessel system 10 comprises measurement instrumentation 18, which is connected and attached to the outside of the process vessel 12. According to the depicted embodiment, the measurement instrumentation 18 is provided as a level indicator for indicating the level 16 of the liquid fluid inside the process vessel 12. For this purpose the measurement instrumentation 18 comprises a reference chamber 26 comprising a vertical pipe. The reference chamber 26 is connected to the process vessel 12 at a first connection point 22 and a second connection point 24 by means of fluid permeable connections. For maintenance reasons it can be advantageous to install block valves 15 at the connection points 22 and/or 24 between the process vessel 12 and the reference chamber 26, and/or an additional vent valve 37 on top of the reference chamber 26 and/or drain valve 40 (not connected to the process). Further, the measurement instrumentation 18 comprises a measurement element 26a, which is adapted to indicate the vertical level 16 of the fluid inside the process vessel 12 at the reference chamber 26. Preferably the measurement instrumentation 18, comprises a measurement element 26a, which may comprise a floating device or consist of such and being adapted to float on the liquid phase 14a of the fluid inside the reference chamber 26. The measurement instrumentation 18 may comprise an indicator tube 27 comprising a lightweight magnetized indicator or a series of metallic flags attached to the reference chamber 26. The indicator in the indicator tube 27 may be magnetically coupled to the floating device 26a and may be adapted to move up and down in dependence of the level of the cryogenic fluid to indicate the level of the cryogenic fluid inside the reference chamber 26. Since the reference chamber 26 is in fluid connection with the process vessel 12, the liquid level in the reference chamber 26 is essentially the same as the liquid level 16 of the liquid phase 14a inside the process vessel 12.

Furthermore, the process vessel system 10 comprises a drain line 28, which according to the presented preferred embodiment is permanently open, comprising a drain line tubing 30, which connects at a low point 26b of the reference chamber 26. Alternatively or additionally the drain line tubing 30 may connect the reference chamber 26 with a flare (not shown). Particularly, the drain line 28 provides, if a flow exists in a sump outlet/process line 36, a flow of liquid fluid 14a through the lower portion 20b, the reference chamber 26 and through the drain line 28 to the connection point 32 into the sump outlet line 36 of the process vessel 12. The drain line 28 may feed the drained liquid fluid 14a back into the process line 36, such that the drained liquid fluid 14a is not wasted.

This occurs, because the level 16 of the liquid phase 14a of the fluid 14 is higher than the vertical level of the second connection point 24 and therefore the liquid fluid 14a enters the drain line 28 at least at the low point 26b of the reference chamber 26 and exits at least partially through the drain line 28 to the drain 32. As a consequence, a steady flow of liquid fluid 14a through the low point 26b of the reference chamber 26 is achieved, which prevents aggregation or gathering of heavy and/or solidified constituents of the cryogenic fluid 14 in the reference chamber 26.

In case the fluid level 16 exceeds also the vertical level of the first connection point 22, also an upper portion 21 of the reference chamber 26 might be flooded by liquid fluid. If heavy and/or solidified components of the fluid 14 accumulate and/or aggregate in the upper portion 21 of the reference chamber 26, gravity will assist in transferring these constituents to the lower portion 20b of the reference chamber 26, where again the flow will wash out these constituents through the drain line 28 to the process connection and/or to the process connection 32. According to a preferred embodiment the drain line 28 is sloped to facilitate a gravitationally assisted wash out of the aggregated and/or accumulated components of the fluid 14.

Therefore, the measurement instrumentation 18 does not suffer from constrictions and/or occlusions due to solidified constituents, such as carbon dioxide, since the formation of solidified constituents can be reliably avoided and/or solidified constituents can be washed out from the reference chamber 26 by means of the drain line 28, providing a permanent flow of liquid fluid 14a through at least the lower portion 20 of the reference chamber 26.

Although it might be advantageous to keep the drain line 28 permanently opened during operation of the measurement instrumentation 18 and/or the cryogenic process vessel system 10, the drain line 28 may be provided with a valve 34 to open and/or close and/or regulate the effective diameter of the drain line 28.

According to the depicted embodiment, the drain line 28 is connected to an outlet tube 36, which may be a sump outlet and/or a process line, which is connected to the lower end of the process vessel 12, through which liquid fluid 14a flows, once a shutter, which may be a spectacle blind and/or a spacer 38, and/or a downstream process valve 39 is open. Therefore, the liquid fluid 14a flowing through the drain line 28 is not necessarily wasted, but can be brought back to its intended use by connecting the drain line 28 to the outlet tube 36.

Claims

Claims 1. Measurement instrumentation (18) for measuring a level (16) of a cryogenic fluid (14) contained in a process vessel (12), comprising: a reference chamber (26) connected at a first connection point (22) and a second connection point (24) to the process vessel (12), wherein the first connection point (22) is located at a vertically higher level than the second connection point (24); a measurement element (26a) for detecting a level of the cryogenic fluid (14) in the reference chamber (26); and a drain line (28) connecting a lower portion (20) of the reference chamber (26) with a process line (36) at a drain connection point (32), wherein the drain connection point (32) is located at a vertically lower level than the second connection point (24).
2. Measurement instrumentation (18) according to claim 1, wherein the drain line (28) is connected to the lower portion (20) of the reference chamber (26) at the vertical level of the second connection point (24) or below.
3. Measurement instrumentation (18) according to claim 1 or 2, wherein the drain line (28) comprises a drain line tubing (30) having a smaller diameter than the reference chamber (26).
4. Measurement instrumentation (18) according to claim 3, wherein the reference chamber (26) has a diameter between 2 cm and 20 cm and/or wherein the drain line tubing (30) has a diameter between 0,5 cm to 5 cm.
5. Measurement instrumentation (18) according to any one of the preceding claims, wherein the reference chamber (26) and/or the drain line (28) is sloped such as to facilitate a gravitationally assisted wash out of aggregated and/or accumulated components of the fluid 14 from the reference chamber (26).
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11.Measurement instrumentation (18) according to any one of the preceding claims, wherein the drain line (28) is adapted to be permanently opened during operation of the measurement instrumentation (18).Measurement instrumentation (18) according to any one of the preceding claims, wherein the drain line (28) is adapted to generate during operation of the measurement instrumentation (18) a permanent flow of cryogenic fluid (14) at least through the drain line (28) and through the lower portion (20) of the reference chamber (26) when the level of the cryogenic fluid (14) within the cryogenic fluid container (12) is equal to or higher than the vertical level of the second connection (24).Measurement instrumentation (18) according to any one of the preceding claims, wherein the drain connection point (32) is located at and/or in an outlet line of the process vessel (12) and/or in and/or at a sump line.Measurement instrumentation (18) according to any one of the preceding claims, wherein the measurement element (26) comprises a floating device arranged in the flow path between the first connection point (22) and the second connection point (24).Measurement instrumentation (18) according to any one of the preceding claims, wherein the measurement instrumentation (18) is constructed as a level indicator.Process vessel system (10) comprising a process vessel (12) and measurement instrumentation (18) according to any one of the preceding claims.