DE102023002568A1 - Method for collecting CO2 with the isotopes 12C and/or 13C and/or 14C - Google Patents

Abstract

The invention relates to a method for collecting CO ₂ , in particular CO ₂ with the isotopes ¹² C and/or ¹³ C and/or ¹⁴ C from a sample gas, in particular from the exhaust gas of combustion plants, in which the CO ₂ gas present in the sample gas is collected through at least one membrane permeable to CO ₂ in a CO ₂ gas-absorbing or CO ₂ gas-binding liquid, in particular in sodium hydroxide solution.

Description

The invention relates to a method for collecting CO ₂ , in particular CO ₂ with the isotopes ¹² C and/or ¹³ C and/or ¹⁴ C from a sample gas, in particular from the exhaust gas of combustion plants, in which the CO ₂ gas present in the sample gas is collected through at least one membrane permeable to CO ₂ in a CO ₂ gas-absorbing or CO ₂ gas-binding liquid, in particular in sodium hydroxide solution.

The collection of CO ₂ in the liquid can be achieved, for example, by dissolving the CO ₂ gas in the liquid or by chemically binding it. For example, caustic soda binds the CO ₂ to form sodium carbonate. Another suitable liquid is calcium hydroxide lye.

Such a method can be used, for example, to determine the proportions of fossil or biogenic components in a combustion process, since it is known that fossil and biogenic starting components have different proportions of carbon isotopes. The isotope ratios in the CO ₂ gas can thus be used to determine the respective proportions of fossil and biogenic starting components.

There are known methods that can perform such a task. One of these is the method of combining the sample gas with soda lime. This has some disadvantages.

The containers containing the soda lime powder must be filled and emptied using protective suits and compressed air breathing apparatus; there is a high risk that _CO2 from the laboratory technicians' breath will get into the sample and falsify the result.

Furthermore, it is questionable whether the entire amount of _CO2 gets into the soda lime and is bound; for this to happen, the contact surface must be very large. Used soda lime is considered waste that requires special monitoring; proof is required to ensure proper disposal.

In another known method, the sample gas is bubbled into a liquid that absorbs CO ₂ gas, e.g. sodium hydroxide solution, which creates direct contact between the CO ₂ bubbles and the liquid. It is questionable whether the entire amount of CO ₂ in the solution is bound in this way, particularly because the surface of the bubbles shields gas lying deeper in the bubble. The residence time of the bubbles in the liquid is still uncertain and cannot be controlled.

To generate bubbles, an element made of sintered glass through which gas flows, such as a Nutsche filter, can be used. The problem is that if caustic soda is used as a liquid that binds or absorbs _{CO 2 gas} , the sintered glass does not last long, as the sintered glass, in particular the contact points between the fine glass beads, are dissolved by the caustic in combination with the gas flowing through. Such an element that generates bubbles does not therefore last long.

Another disadvantage of the aforementioned methods is that the supply and discharge of the sample gas is not separated from the liquid absorbing or binding the gas. Therefore, all materials, in particular the elements supplying the liquid and/or leading away from the liquid, must be made of alkali-resistant material. The risk of leakage of the liquid reacting with the gas or binding the gas, e.g. caustic soda, at the connectors for the supply and discharge of sample gas cannot be effectively prevented.

Another disadvantage is that leaks in places or pipe connections where liquids come into contact can lead to dilution of the sample gas with the ambient or outside air. The sample gas can therefore contain CO ₂ gas components from the ambient air.

Furthermore, it is clear from the patent application DE 10 2020 005 098 A1 The same applicant has disclosed the possibility of diffusing the sample gas through a membrane into a liquid and thus collecting it in the liquid.

The sample gas from a combustion plant, for example from an exhaust pipe or chimney, naturally has a high temperature and a high water vapor or water content. Such components in the sample gas can also distort the collection of CO ₂ from the sample gas.

The invention has set itself the task of developing a method with which CO ₂ , in particular CO ₂ with the isotopes ¹² C and/or ¹³ C and/or ¹⁴ C, is collected from a sample gas in a reliable and structurally simple manner and in an economical manner, preferably the entire proportion of CO ₂ is collected from the proportion of sample gas fed to the liquid and preferably the collected CO ₂ is prepared in such a way that it is suitable for an evaluation, e.g. with accelerator mass spectrometry (AMS), of the ratio of the isotope proportions of ¹² C and/or ¹³ C and/or ¹⁴ C are suitable for each other and this relationship is evaluated.

Preferably, this method is used to detect the proportion of biogenic fuels in combustion plants, in particular by avoiding the supply of false air, in particular from room air with a proportion of only 0.004% CO ₂ compared to 5% to 10% CO ₂ in the sample gas, in particular in order to avoid losses when claiming or crediting CO ₂ certificates and higher costs or lower revenues for the plant.

This object is achieved according to the invention in that the sample gas is first passed through a cold trap and dried in the process and the CO ₂ gas present in the dried sample gas is collected through at least one membrane permeable to CO ₂ in a CO ₂ gas-absorbing or CO ₂ gas-binding liquid, in particular in sodium hydroxide solution.

Dried sample gas is understood to mean a sample gas which has a lower water content than the non-dried sample gas; preferably, dried sample gas no longer has any water components.

A cold trap is a section of pipe through which the sample gas is passed and cooled at least to the point where water components condense out of the sample gas, meaning that the dried sample gas leaving the cold trap is drier than the sample gas entering it. The drying is more effective the colder the cold trap is, especially the deeper it is cooled below zero degrees Celsius.

The invention can provide that the sample gas is guided in a heated line section upstream of the cold trap in order to avoid condensation of water in line areas upstream of the cold trap.

By drying the sample gas, the invention ensures that water components from the sample gas cannot cover the CO ₂ -permeable membrane, or at least that they can cover less than non-dried sample gas, so that the diffusion of CO ₂ through the membrane is not impaired or at least less impaired by water deposits. This ensures better than the prior art that the CO ₂ from the sample gas can pass into the liquid and be collected in it, e.g. by chemical bonding to the liquid or dissolving in the liquid.

Preferably, the sample gas is introduced into a container in which a container region carrying the sample gas is separated from a container region containing the liquid by means of at least one CO ₂ permeable membrane. Such a membrane can in principle have any shape, e.g. be designed as a flat membrane.

Such a membrane is preferably formed by a tube made of a CO ₂ -permeable material, in particular silicone, in particular wherein the container region carrying the sample gas comprises the inner volume of the at least one tube and the container region containing the liquid is formed around the at least one tube. The tubular membrane can thus simultaneously take on the function of a conduit element by means of which the sample gas is guided through the container. The sample gas can be guided simultaneously in the container through several tubes made of a CO ₂ -permeable material. The media can also be guided in exactly the opposite way, i.e. the liquid can be guided in the tube made of a CO ₂ -permeable material, in particular silicone, and the sample gas can be guided around the outside of the tube.

The invention preferably further provides that the CO _{2 content of the sample gas flowing away from the container is determined downstream of the container by means of a sensor in a line area leading away from the container. Preferably, the residence time of the sample gas in the container is also regulated depending on the measured CO 2 content} .

For example, it may be provided that if the measured CO ₂ content is greater than zero, the residence time is extended so that the CO ₂ content of the sample gas is reduced by this extension.

Preferably, the invention provides that the CO ₂ content in the sample gas which has undergone the method according to the invention reaches a predetermined target value, in particular the value zero, i.e. that all CO ₂ from the dried sample gas has been collected in the liquid. This ensures that the isotope ratios can be measured correctly, which is not the case if the permeation rates for CO ₂ of different isotopes are different and CO ₂ would remain in the sample gas.

It can also be provided that the CO ₂ content of the sample gas flowing to the container is determined upstream of the container by means of a sensor in a line section leading to the container. For example, by measuring Quality assurance can be carried out by measuring the _CO2 content before and after the container.

The residence time in the container can be changed, for example, by changing the outflow cross-section in the outgoing line area or by guiding the sample gas in a circuit through the container. In particular, it can be provided that by changing control variables, such as the aforementioned outflow cross-section or the residence time of the gas in a circuit, the CO ₂ content is regulated to a setpoint value, in particular to the value zero.

The invention preferably provides that the sample gas is taken as a portion from an exhaust gas-carrying exhaust line of an exhaust gas-producing plant, in particular an incineration plant, by means of a pump. In particular, the invention makes use of the fact that CO ₂ is usually evenly distributed in the sample gas, so that a collection of CO ₂ from a portion of the exhaust gas is sufficient.

In this case, it is preferably provided that a measured value for the mass flow / volume flow of the exhaust gas flowing in the exhaust line is measured in the exhaust line by means of a mass flow sensor / volume flow sensor and the pump is regulated or controlled depending on the measured value. In particular, this achieves that if the measured value increases, the pump delivery rate is increased and/or that if the measured value decreases, the pump delivery rate is reduced.

In order to achieve drying of the sample gas, the cold trap is preferably operated at a temperature that is lower than the temperature of the sample gas. In one possible design, this operating temperature can be selected so that it is greater than zero degrees Celsius. This achieves condensation of water from the sample gas, but prevents the cold trap or the line for the sample gas through the cold trap from freezing over. In this way, the sample gas can preferably be continuously guided through the cold trap. The condensate that accumulates in the cold trap can preferably be collected, e.g. in a condensate container or pumped away from the cold trap.

In order to achieve particularly high-quality drying of the sample gas in the cold trap, in particular to the extent that the dried sample gas no longer contains any water components, or these are at least negligible, the invention provides that the cold trap is operated at a temperature of less than zero degrees Celsius, in particular less than -50 degrees Celsius, but greater than -78 degrees Celsius.

This ensures that CO ₂ does not condense out in the cold trap, but that water does condense out safely. The pipe routing in the cold trap can be dimensioned in such a way that the cold trap remains open to the sample gas despite the formation of water ice. In particular, the cold trap can still be operated intermittently in this mode of operation, i.e. defrosted after a predetermined operating time. A technically particularly simple operation of the cold trap with very efficient water condensation can, however, be achieved if it is operated at a temperature of less than -70 degrees Celsius, preferably less than -78 degrees Celsius, in particular at the temperature at the sublimation point of CO ₂ , in particular -78.5 degrees Celsius. This can be achieved, for example, if the cold trap is operated with dry ice, i.e. ice-like/solid CO _2, as a coolant. For example, pipe areas of the cold trap through which the sample gas flows can be wetted on the outside with dry ice floating in alcohol. Such low temperatures can also be achieved by other technical measures.

If the sample gas is cooled so strongly in the cold trap, it cannot be ruled out that _CO2 components in the sample gas may also condense out in the cold trap.

Irrespective of the type of operation, the invention provides in an advantageous further development that the CO ₂ gas contained in the condensate of the cold trap is also collected through at least one membrane permeable to CO ₂ in a CO ₂ gas-absorbing or CO ₂ gas-binding liquid, in particular in caustic soda.

CO ₂ can, for example, be dissolved in condensed water or can condense itself at a sufficiently low temperature. The invention aims to collect such CO ₂ components.

Thus, the invention can preferably also be used to collect and record this CO ₂ portion, in particular this dissolved or condensed CO ₂ portion, or to evaluate it with regard to the isotope ratios. The invention thus preferably ensures that all CO ₂ portions are collected from the sample gas.

For example, the invention provides for the condensate, e.g. condensed water with CO ₂ dissolved in it, or previously condensed CO ₂ that has returned to the gas phase, to pass through a CO ₂ -permeable membrane into a CO ₂ -collecting / binding liquid and to collect in it. For example, condensate water can be pumped out directly from the cold trap using a condensate pump and passed along a membrane through a container with CO ₂ collecting liquid, e.g. as mentioned above through a hose membrane that is surrounded by the liquid on the outside. Previously condensed CO ₂ that has returned to the gas phase can also be conveyed or flows automatically into/through such a container due to expansion.

The invention can, for example, provide that the condensate is led into another container in which a container region carrying the condensate is separated by means of at least one CO ₂ -permeable membrane from a container region containing the liquid collecting CO ₂ , preferably wherein the at least one membrane is formed by a tube made of a CO ₂ -permeable material, in particular silicone, in particular wherein the container region carrying the condensate comprises the inner volume of the at least one tube and the container region containing the liquid is formed around the at least one tube.

However, it is particularly preferred in the invention that the CO ₂ gas contained in the condensate of the cold trap is collected in the same liquid in which the CO ₂ gas from the dried sample gas is collected. In this case, only this one liquid needs to be examined with regard to the isotope ratios, which simplifies the evaluation.

According to the invention, it is provided in a further development that the condensate from the cold trap is at least partially, preferably completely, passed through the same container as the dried sample gas, in particular the dried sample gas is passed through at least a first container region, e.g. hose made of a CO ₂ -permeable material, and the condensate is at least partially, preferably completely, passed through at least a second container region, in particular hose made of a CO ₂ -permeable material.

According to the invention, the different _CO2 components from dried sample gas and condensate pass through different container areas / tube membranes in the container, but are collected in the same liquid.

At least partial passage of the condensate through the same container is preferably understood to mean that at least the CO ₂ portion of the condensate is passed through the container, but preferably not the other components of the condensate, such as water.

If the cold trap is operated at a temperature below the sublimation temperature of CO ₂ , it is preferably provided that, in order to transfer condensed CO ₂ from the cold trap into the container, in particular for guiding it through the at least one tubular membrane, the cold trap is heated to a temperature of greater than -78 degrees Celsius, preferably greater than -70 degrees Celsius, but in particular less than zero degrees Celsius, after a step of sample gas drying.

This ensures that the CO ₂ condensed in the cold trap returns to the gaseous state, while preferably the condensed water remains in the cold trap in the form of ice. The cold trap preferably remains at a temperature of less than -60 degrees Celsius during this heating process.

However, it can also be provided that the cold trap is heated to a temperature above zero degrees Celsius after a step of drying the sample gas and the liquid condensate including the water content is passed to the at least one membrane, in particular through at least one tubular membrane, in order to transfer the gaseous CO ₂ and/or CO ₂ dissolved in the water through the membrane into the liquid and to collect it therein.

The invention can provide that the cold trap is operated intermittently between two temperature ranges, preferably wherein the temperature in a first temperature range is suitable for drying the sample gas, i.e. for reducing the water content, preferably for eliminating it, preferably this temperature is lower than the temperature at the sublimation point of CO ₂ and in a second temperature range the temperature is suitable for at least partially conducting the previously obtained condensate to/through the at least one membrane, in particular this temperature is higher than the temperature at the sublimation point of CO ₂ , but preferably less than zero degrees Celsius, preferably less than -20 degrees Celsius, preferably less than minus 50 degrees Celsius. In the second temperature range, the CO ₂ from the condensate can thus be collected in the liquid, in particular in the same liquid in which the CO ₂ from the dried sample gas is also collected.

At an operating temperature of the cold trap with a temperature greater than zero degrees Celsius, in particular in the range of 10 to 1 degrees Celsius, more preferably 5 to 1 degrees Celsius, a Freezing is avoided, but the sample gas is still dried sufficiently. The liquid water condensate can, for example, be passed through another or the same container as described above at the same time as the dried sample gas in order to transfer CO ₂ from the container into the liquid.

In a further development, the invention can also provide that downstream of the container, the CO ₂ content of the condensate flowing away from the container is determined by means of a sensor in a line section leading away from the container and the residence time of the condensate in the container is regulated depending on the measured CO ₂ content, in particular if the CO ₂ content is greater than zero, the residence time is extended, in particular by changing the outflow cross-section in the line section leading away or by circulating the condensate through the container.

The invention preferably provides that the sample gas, in particular also the condensate, is continuously passed through one, preferably a common container in order to transfer the CO ₂ through a membrane into the liquid and to collect it therein.

In a possible embodiment, the invention can also provide that the container area carrying the dried sample gas and/or the condensate is filled until a predetermined pressure measured in the container area is reached, in particular after the predetermined pressure is reached, further filling is stopped and the dried sample gas and/or the condensate remains in the container area for the collection of CO _2. For this purpose, it can be provided that after the predetermined pressure is reached, a valve in the supply line of the container is closed and remains closed together with a valve in the outlet line of the container for the purpose of transferring CO ₂ into the liquid.

The sample preferably remains in the container until the pressure falls below a predetermined value or pressure gradient measured in the same container area or until a predetermined period of time has elapsed. After this tested condition has occurred, the dried sample gas and/or the condensate is then released from the respective container area. In this version, the container is therefore not filled continuously, but in batches with dried sample gas and/or condensate.

Due to the filling according to the invention, the preferably tubular membrane acts like an expandable balloon. It is preferably provided that liquid from the area around the membrane can be displaced when the membrane is pressurized with sample gas and/or condensate, e.g. into an equalizing vessel.

Based on the undershoot of a pressure measurement value and/or the temporal gradient of this measurement value in the respective container area that includes the dried sample gas or the condensate, or based on the elapse of a predetermined time, it can be determined or ensured, for example, whether or that all CO ₂ in the liquid has been collected, in particular because after this state has been reached the pressure value and/or the gradient does not fall any further or the selected time period ensures complete collection, e.g. based on empirical values.

The gradient in particular can be used to determine whether the liquid is exhausted in terms of its ability to collect _CO2 , particularly to chemically bind it or dissolve it, preferably because the rate of collection per unit of time and thus the gradient decreases with increasing exhaustion. If the gradient falls below a minimum required value, this can indicate that the liquid is approaching exhaustion and needs to be replaced. The size of the gradient can also be used to test the function of the membrane. If, for example, the temporal gradient exceeds a predetermined limit, it can be concluded that the membrane is defective and is also allowing gas to pass through convectively.

The invention can thus preferably also provide for monitoring this gradient in order to indicate the need to replace the liquid and/or the membrane.

The measured pressure value can preferably represent a differential pressure compared to the atmospheric ambient pressure or a CO ₂ partial pressure, in particular in the dried sample gas and/or in the (preferably again gaseous) condensate.

The invention can also provide for the conductivity of the liquid to be measured and evaluated. Since the conductivity changes as the amount of _CO2 accumulates in the liquid, exceeding and/or falling below a limit value of the conductivity can indicate the need to replace the liquid.

In all possible embodiments, the invention preferably provides that the liquid used to collect the CO ₂ gas, in particular Caustic soda, after removal from the container or a product made from the liquid, is analyzed by means of mass spectrometry for the proportions, in particular relative proportions, of carbon isotopes, in particular in order to draw conclusions about the proportion of biogenic and/or fossil starting materials in the combustion.

For example, the liquid can be thickened, in particular dried, before the mass spectrometric analysis, preferably with a remaining powder being analyzed by mass spectrometry.

The invention can provide that the sample gas, which is initially conveyed via a heated line and is thus still hot, is fed to a cold trap and dried therein.

Embodiments of the invention are described below.

The preferably dried sample gas is passed over a membrane, preferably over a gas mixer-water separator (18), a gas sensor (4) and over a connector (14), in particular whereby the membrane can have any geometric shape. Downstream of the membrane (17, 21, 22), the sample gas, now depleted of CO _{2 ,} is preferably measured with a gas sensor with regard to the CO ₂ content, preferably a zero value of the gas sensor measurement value is ideally measured. This ensures that the entire gas content / CO ₂ content of the sample gas to be collected has also been collected.

However, it cannot be ruled out that parts of the _CO2 gas to be collected are contained in the liquid previously condensed in the cold trap / refrigeration dryer, e.g. are dissolved or have condensed themselves.

However, in order to detect or collect almost 100% of the proportion of CO ₂ and thus the proportion of the biogenic CO ₂ components of the sample gas, preferably of the sample gas conveyed by a pump (2), it is preferably provided to bring the liquid (25) condensed in the cold trap (3) into contact in a container with a membrane, in particular of any geometric shape (17, 21, 22), which separates the condensed liquid and a gas-absorbing or gas-binding liquid (16) located in the container (19). There, the gas components dissolved in the condensed liquid will then permeate through the membrane and be collected/bound in the gas-absorbing or gas-binding liquid (16). This can therefore be referred to as a liquid-liquid method.

Mode of operation of the method using the embodiment shown in Figure 1

The sample gas with the CO ₂ content to be collected enters the collection line, e.g. coming from the chimney via a heated pipe at (1), conveyed by the pump (2).

In the cold trap with water separator (3), the gas is dried and enters, for example, the container (18) with buffer and mixing volume. The container (18), which is preferably used, also serves as a water separator if the water outflow from the cold trap (3) is disrupted.

The dried and particularly now well-mixed sample gas is preferably measured for the current CO ₂ content using the CO ₂ sensor (4). The value is preferably transferred to a data logger using the signal output (6) and recorded. The sample gas flows via the connector (14) into the membrane (17), here e.g. a hose membrane to the connector (15).

After the gas to be collected, e.g. CO ₂ , has been absorbed from the sample gas through the membrane (17) by means of permeation by the liquid (16) absorbing the gas or reacting with the gas, it is measured and checked in the gas sensor (5) for a lower gas content than in sensor (4).

In the mass flow controller (9), the signal coming from the combustion plant at the inlet (8), which depends on the current amount of flue gas, is evaluated and displayed, and the sample gas quantity is regulated according to the volume of flue gas in the chimney. A signal is transmitted to the data logger via the output (10).

The pressure gauge (11) with signal output (20) is used to monitor and record the correct execution of the process.

The gas portion that permeates into the gas-absorbing liquid (16) or reacts with the gas is collected and exchanged for fresh liquid, for example after a predetermined period of time or after exhaustion has been determined. The loaded liquid (16) is sent to a laboratory for further treatment such as drying and weighing. The sample is sent to a suitable location to determine the ratio of ¹² C to ¹³ C to ¹⁴ C.

Mode of operation of the method using the embodiment shown in Figure 2

The sample gas with the portion to be collected enters the collection section. The gas is dried in the cold trap with water separator (3) and preferably enters the container (18) with buffer and mixing volume. The container (18) that is preferably used also serves as a water separator if the water outflow of the cold dryer (3) is disrupted.

In this application, a mass flow meter and indicator (25) is connected behind the container (18). This is followed by a remote-controlled valve (23). The dried and preferably now well-mixed sample gas is measured in the CO ₂ sensor (4) for the current CO ₂ content. The value is transferred to a data logger, for example, using the signal output (6), and recorded. The sample gas flows into the membrane (22), here in a cylindrical design, via the connector (14).

The process for collecting the sample gas is as follows: The pump (2) presses the sample gas against the closed inlet valve (23). The outlet valve (24) is also closed. The inlet valve (23) now opens, the sample gas flows via the sensor (4), the connector (14) into the membrane (22), the plug connection (15) and the gas sensor (5) against the closed outlet valve (24). The pressure in the pressure gauge (11) increases until a set threshold is reached and the switching contact closes. This signal closes the inlet valve (23). The sample gas quantity is now in the container area that takes in this sample gas, here in the membrane. Due to the effect of the liquid (16) absorbing the gas or reacting with the gas, the gas to be collected permeates into the liquid (16); according to the invention, a negative pressure is created within the membrane. The negative pressure is measured by the pressure gauge (11), the closed contact opens again when the pressure falls below a limit, the valves (23) and (24) open again. New sample gas flows into the membrane (22) until the valves close again.

Adjustments to the amount of exhaust gas in the chimney can be made by changing the switching duration, pause times for the pumping or the pump speed.

Mode of operation of the method using the embodiment shown in Figure 3

The sample gas with the portion to be collected enters the collection section at (1), conveyed by the pump (2). The gas is dried in the cold trap with water separator (28) and enters the preferably used container (18) with buffer and mixing volume. From there, the sample gas flows on as described in examples 1 and 2.

Unlike in the aforementioned examples 1 and 2, the condensate is not disposed of. The condensate, in particular condensate water, is conveyed by the pump (27) via the line (26) into a membrane (17, 21, 22) and degassed on the way through the membrane into the liquid (16) in the vessel (31) which reacts with the gas or absorbs the gas. The condensate degassed according to the invention is disposed of via the outlet for degassed condensate (30). According to 3 Condensate and sample gas are fed into the same container, which has separate hose membranes for sample gas and condensate, whereby the respective CO ₂ portion passes into the same liquid and is collected therein.

The execution of the 4 differs essentially only in this from the execution of the 3 that separate containers are used for sample gas and condensate in order to transfer the respective CO ₂ portion into a suitable liquid. The transfer therefore does not take place into the same liquid, but in particular into the chemically identical liquid.

list of reference symbols

1

sample gas inlet

2

sample gas pump

3

cold trap with water separator

4

CO ₂ input measurement before the membrane

5

CO ₂ output measurement after the membrane

6

signal output for documentation of input gas

7

signal output for documentation of output gas

8

Signal input for controlling the flow rate of exhaust gas in the exhaust pipe

9

mass flow controllers and indicators

10

Signal output for documenting the sample gas throughput

11

Pressure indicator with switching contact and output signal

12

pinhole

13

sample gas outlet

14

plug connection sample gas inlet

15

Plug connection output of the sample gas-free or reduced sample gas

16

CO ₂ -collecting liquid

17

membrane, here e.g. tubular membrane

18

safety water separator and sample gas mixture

19

container for collecting the gas-collecting liquid

20

signal output for documenting pressure conditions

21

membrane, e.g. flat membrane

22

Membrane, e.g. in cylindrical shape

23

Remote-operated inlet valve

24

Remotely operated outlet valve

25

mass flow meters and indicators

26

inlet of the condensate

27

Adjustable pump

28

refrigeration dryer with condensate pump

29

gas outlet

30

outlet for degassed condensate

31

container for collecting the gas-collecting liquid

32

Sample gas flow as described in Examples 1 and 2.

Mode of operation of the method using the embodiment shown in Figure 1

The sample gas with the CO ₂ content to be collected enters the collection section, e.g. coming from the chimney via a heated pipe at (1), conveyed by the pump (2). In the cold trap with water separator (3), the gas is dried and enters the container (18) with buffer and mixing volume. The container (18) also serves as a water separator if the water outflow from the cold trap (3) is disrupted.

The dried and now well mixed sample gas is measured for the current CO ₂ content using the CO ₂ sensor (4). The value is transferred to a data logger using the signal output (6) and recorded. The sample gas flows into the membrane (17) via the connector (14), here e.g. a hose membrane to the connector (15).

After the gas to be collected, e.g. CO2, has been absorbed from the sample gas through the membrane (17) by means of permeation by the liquid (16) absorbing the gas or reacting with the gas, it is measured and checked in the gas sensor (5) for a lower gas content than in sensor (4).

In the mass flow controller (9), the signal coming from the combustion plant at the inlet (8), which depends on the current amount of flue gas, is evaluated and displayed, and the sample gas quantity is regulated according to the volume of flue gas in the chimney. A signal is transmitted to the data logger via the output (10).

The pressure gauge (11) with signal output (20) is used to monitor and record the correct execution of the process.

The gas portion that permeates into the gas-absorbing liquid (16) or reacts with the gas is collected and exchanged for fresh liquid, for example after a predetermined period of time or after exhaustion has been determined. The loaded liquid (16) is sent to a laboratory for further treatment such as drying and weighing. The sample is sent to a suitable location to determine the ratio of ¹² C to ¹³ C to ¹⁴ C.

Mode of operation of the method using the embodiment shown in Figure 2

The sample gas with the portion to be collected enters the collection section at (1), conveyed by the pump (2). The gas is dried in the cold trap with water separator (3) and enters the container (18) with buffer and mixing volume. If the water outlet of the cold dryer (3) is faulty, the container (18) also serves as a water separator.

In this application, a mass flow meter and indicator (25) is connected behind the container (18). This is followed by a remote-controlled valve (23). The dried and now well-mixed raw or measuring gas is measured in the CO ₂ sensor (4) for the current CO ₂ content. The value is transferred to a data logger via the signal output (6) and recorded. The sample gas flows into the membrane (22) via the connector (14), here for example in a cylindrical design.

The process of collecting the sample gas is as follows: The pump (2) presses the sample gas against the closed inlet valve (23). The outlet valve (24) is also closed. Now the inlet valve (23) opens, the sample gas flows via the sensor (4), the connector (14) into the membrane (22), the connector (15) and the gas sensor (5) against the closed outlet valve (24). The pressure in the pressure gauge (11) increases until a set threshold is reached and the switch contact closes. The inlet valve (23) is closed with this signal. The sample gas quantity is now in the membrane. Due to the effect of the liquid (16) absorbing the gas or reacting with the gas, the gas to be collected permeates into the liquid (16); a vapor is formed inside the membrane. According to the invention, a negative pressure is created. The negative pressure is recorded by the pressure gauge (11), the closed contact opens again when the pressure falls below a limit, the valves (23) and (24) open again. New sample gas flows into the membrane (22) until the valves close again.

Adjustments to the amount of exhaust gas in the chimney can be made by varying the switching duration, pause times for the pumping or the pump speed.

Mode of operation of the method using the embodiment shown in Figure 3

The sample gas with the portion to be collected enters the collection section at (1), conveyed by the pump (2). The gas is dried in the cold trap with water separator (28) and enters the container (18) with buffer and mixing volume. From there, the raw gas flows on as described in examples 1 and 2.

Unlike in the aforementioned examples 1 and 2, the condensate is not disposed of. The condensate, in particular condensate water, is conveyed by the pump (27) via the line (26) into a membrane (17, 21, 22) and degassed on the way through the membrane into the liquid (16) in the vessel (31) which reacts with the gas or absorbs the gas. The condensate degassed according to the invention is disposed of via the outlet for degassed condensate (30).

Mode of operation of the method using the embodiment shown in Figure 4

The mode of action is identical to the 3 , but here separate containers (19 and 31) are shown for the gas-absorbing liquid (16). This also allows separate evaluation of the values of the gases or condensates to be collected.

QUOTES INCLUDED IN THE DESCRIPTION

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Cited patent literature

• DE 10 2020 005 098 A1 [0011]

Claims (12)

Method for collecting CO ₂ gas, preferably CO ₂ gas with the isotopes ¹² C and/or ¹³ C and/or ¹⁴ C, from a sample gas, in particular from the exhaust gas of combustion plants, preferably from combustion plants or power plants using biogenic and/or fossil fuels, in which the CO ₂ gas present in the sample gas is collected through at least one membrane permeable to CO ₂ in a liquid that absorbs CO ₂ gas or binds CO ₂ gas, in particular in sodium hydroxide solution, characterized in that the sample gas is first passed through a cold trap and dried in the process, and the CO ₂ gas present in the dried sample gas is collected through at least one membrane permeable to CO ₂ in a liquid that absorbs CO ₂ gas or binds CO ₂ gas, in particular in sodium hydroxide solution. procedure according to claim 1 , characterized in that the sample gas is introduced into a container in which a container region carrying the sample gas is separated from a container region containing the liquid by means of at least one CO ₂ -permeable membrane, preferably wherein the at least one membrane is formed by a tube made of a CO ₂ -permeable material, in particular silicone, preferably wherein the container region carrying the sample gas comprises the inner volume of the at least one tube and the container region containing the liquid is formed around the at least one tube. Method according to one of the preceding claims, characterized in that downstream of the container, the CO ₂ content of the sample gas flowing away from the container is determined by means of a sensor system in a line region leading away from the container, preferably wherein the residence time of the sample gas in the container is regulated or controlled as a function of the measured CO ₂ content, in particular with a CO ₂ content greater than zero, the residence time is extended, in particular by changing the outflow cross-section in the line region leading away or by circulating the sample gas through the container. Method according to one of the preceding claims, characterized in that the sample gas is taken by means of a pump as a portion from an exhaust gas-carrying exhaust gas line of an exhaust gas producing plant, in particular an incineration plant. procedure according to claim 4 characterized in that a measured value for the mass flow / volume flow of the exhaust gas flowing in the exhaust line is measured in the exhaust line by means of a mass flow sensor / volume flow sensor and the pump is regulated or controlled depending on the measured value, in particular if the measured value increases the delivery rate of the pump is increased and / or if the measured value decreases the delivery rate of the pump is reduced. Method according to one of the preceding claims, characterized in that the CO ₂ gas contained in the condensate of the cold trap is also collected through at least one membrane permeable to _{CO 2} in a liquid absorbing or binding CO ₂ gas, in particular in sodium hydroxide solution. procedure according to claim 6 , characterized in that the CO ₂ gas contained in the condensate is collected in the same liquid in which the CO ₂ gas from the dried sample gas is also collected, in particular for which the condensate from the cold trap is at least partially, preferably completely, passed through the same container as the dried sample gas, in particular the dried sample gas is passed through at least one first tube made of a CO ₂ -permeable material and the condensate is at least partially passed through at least one second tube made of a CO ₂ -permeable material. Procedure according to one of the preceding Claims 6 or 7 , characterized in that for the transfer of CO ₂ condensed in the cold trap from the cold trap into the container, the cold trap is heated to a temperature of greater than -78 degrees Celsius and less than zero degrees Celsius. Procedure according to one of the preceding Claims 6 until 8 , characterized in that downstream of the container, the CO ₂ content of the condensate flowing away from the container is determined by means of a sensor in a line region leading away from the container, in particular wherein the residence time of the condensate in the container is regulated as a function of the measured CO ₂ content, in particular if the CO ₂ content is greater than zero, the residence time is extended, in particular by changing the outflow cross-section in the line region leading away or by circulating the condensate through the container. Method according to one of the preceding claims, characterized in that the container area carrying the dried sample gas and/or the condensate is filled until a predetermined pressure measured in the container area is reached, in particular after reaching When the predetermined pressure is reached, further filling is stopped and the dried sample gas and/or the condensate for collecting CO ₂ remains in the container area, preferably until a predetermined pressure value or pressure gradient measured in the same container area is undershot or until a predetermined period of time has elapsed, and is then released from the container area, preferably, wherein the pressure value measured in each case represents a differential pressure compared to the atmospheric ambient pressure or a CO ₂ partial pressure. Method according to one of the preceding claims, characterized in that the liquid used to collect the CO ₂ gas, in particular sodium hydroxide solution, after removal from the container or a product made from the liquid, is analyzed by means of mass spectrometry for the proportions, in particular for the relative proportions of carbon isotopes. procedure according to claim 11 , characterized in that the liquid is thickened, in particular dried, before the mass spectrometric analysis, preferably with a remaining powder being examined by mass spectrometry.

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