Patent Application
20240399285
The invention relates to a process and equipment for conducting research on adsorption of compounds (typically: compounds that are gaseous or can be evaporated easily) to solids. More specifically the invention relates to equipment for performing the above on small scale and in parallel, so that various adsorption materials and/or compounds to be adsorbed can be tested efficiently.
Low concentrations of various compounds like volatile organic compounds (VOC's) but also (in)organic gasses like NH3, SO2, H2S, CO, CO2 etcetera can be present in (chemical) industrial environments in gasses such as air. Similarly, vapours of fuel (diesel, petrol, kerosene) or solvents like cyclohexane, benzene etc can form in air when handling fuel. Presence of such compounds in air is often undesired, and hence techniques have been developed to scavenge such compounds. Typically, this is done by passing the gas (typically air) that contains such undesired compounds over or through a bed of adsorptive material. A well-known material for such is activated carbon.
Adsorption of low concentrations of the various stated compounds (hereafter: adsorbate) to solids like activated carbon (but also other materials) is a topic of research for e.g. production of gasmasks for personal protective equipment (also known as respiratory protective device), and for other areas like on handling chemical compounds. Adsorption of higher concentrations of adsorbates can be employed for separation processes (like removal of hydrogen from industrial gas mixes and removal of CO2 for exhaust gas) or purification processes, like obtaining oxygen from air. Research is being conducted for these various areas of application of adsorption. Typically, such research is done using amounts of adsorbent material of around 10-200 gram. See e.g. S. Marsteau et al, INRS Hygiène et Sécurité de Travail, 222, pages 19-25, 2011. Additionally, such is typically done in single test beds. It involves generally pre-conditioning the adsorbent material with a carrier gas. For reliable results typically such carrier gas is the same as the gas that contains the adsorbate, but then without such adsorbate being present. As an example, when it is desired to test a new activated carbon for adsorption of NH3 from air, the pre-conditioning is done with air without NH3. As moisture is generally present in air to some extent, the pre-conditioning is then to be done with air with the same moisture content as the gas with the adsorbate, which in turn mimics the conditions of actual use.
In order to facilitate research in this area, there is a desire to be able to do such research in a more efficient way, typically on a smaller scale than life size. However, results should be such that they are a good predictor for adsorption on actual desired scale. Parallel testing is commonly known in other areas of chemical research, and also small scale.
U.S. Pat. No. 4,489,593 discloses a method for determining the amount of gas adsorbed or desorbed form a solid sample. Wherein a gas is introduced or withdrawn from a sample containing chamber at a substantially constant mass flow rate while measuring the pressure change within said chamber as a function of time is disclosed. An apparatus for conducting said method which uses a mass flow controller is also disclosed.
US 2007/012234 discloses a microfluidic substrate assembly and method for making same are disclosed. The substrate assembly comprises a multi-layer laminated substrate defining at least one fluid inlet port and at least one microscale fluid flow channel within the multi-layer substrate in fluid communication with the inlet port for transport of fluid.
Precise control of gas flow is required for reliable adsorption tests. Such becomes challenging when testing on small scale, as for adsorption testing on small scale (e.g. bed volumes of 0.1-10 ml) the (gas) flows are comparatively low as well (e.g. 20 to 200 Nml/min per column). Such control of gas flow becomes an even greater challenge when serving multiple adsorption beds with one feed with adsorbate, as such requires some kind of flow divider or splitter. Such divider may also cause different flows for different reactors, which will make results unreliable. Flow is typically controlled with mass flow controllers. However, mass flow controllers usually have moving parts, which results in potential breakdown or disruption, and increased complexity.
Hence, there is a need for being able to test (properties of) particulate solid adsorbent materials for adsorbate compounds like VOC's but also inorganic gasses such as NH3, SO2, H2S, CO, CO2 in an efficient and reliable way. Preferably, the test method or equipment should contain as few as possible (mass) flow controllers, as such need to be calibrated, may lead to condensation of the adsorbate, and/or are prone to disruption due to technical failure, and may have parts that are sensitive to the adsorbate.
It has now been found that the above objective can be met, at least in part, by an apparatus for conducting research on adsorption properties of particulate solid adsorption materials for an adsorbate in at least two parallel adsorption beds, the equipment comprising:
Hence, the invention further relates to a process for adsorbing an adsorbate to particulate solid adsorption materials in a plurality N adsorbent beds, said process comprising:
In the above, reference is made to “adsorption bed”. An adsorption bed is herein to be understood as a container (typically a column) which contains particulate adsorption material (e.g. particles of activated carbon) and which container has an inlet and an outlet, generally at opposite ends.
It was found by the present inventors that the adsorption properties of solid particulate material to various adsorbates as are usually researched for potential application in e.g. respiratory protective device (but also for adsorption fields outside this area of application) may be done in parallel on small scale, with reliability and relatively easy, when the gas composition to be tested is manufactured at a single point at some pressure (e.g. 2-100 barg), and then by a splitter (e.g. a manifold), and reduced in pressure by capillary channels. Such capillary channels can be made fairly reliably and in a reproducible way to ensure that the pressure drop over each capillary is the same. This arrangement also ensures that any small variation in pressure drop after the splitter have comparatively little influence in the actual flow after the capillary Hence, all capillaries in a test arrangement for comparative testing preferably cause the same pressure reduction. Preferred pressure reduction by the capillaries is from 2 to 80 bars, more preferably from 5 to 50 bars, even more preferably from 5 to 30 bars. Feeds A and B should be prepared at a pressure just above the pressure drop caused by the capillaries.
It was found that having the switching valve for switching flow with and without adsorbate after the capillaries ensures that the switching has no influence on pressure on the source gas, and hence that evaporation of a more or less volatile into one of the feeds is not disrupted by variations in flow caused by switching.
To be able to provide various flows (to adapt e.g. to different adsorption materials or adsorption beds) it is preferred that the capillaries can be easily exchanged with capillaries causing a lower or higher pressure drop. An easy way to do this is to have the capillaries as part of or mounted to a cassette-like structure.
Capillaries suitable for the above can easily be made in glass, quartz, or plastics like PEEK, and typically have a diameter of between 10 and 100 μm and a length of between 0.05 and 2 meters. For practical reasons, such long capillaries are preferably constructed as a spiral-would structure, e.g. as part of a chip-like structure or cassette. Hence, in the present invention (apparatus and method) it is preferred that the capillary channels are part of a chip, preferably of glass, quartz, fused silica, or plastic (e.g. PEEK).
If all capillaries in use at the same time are part of one chip or cassette, the splitter (e.g. a manifold) may be integrated with the capillaries in the cassette or chip. This makes the equipment more robust and reduces the length of any connecting tubing. Hence, it is preferred in the present apparatus and method that sets of capillary channels are integrated with a feed splitter, preferably as part of a chip. Preferably such is done on a glass, quartz or plastic (e.g. made of PEEK) chip.
As stated, with the present apparatus a plurality of adsorption beds can be tested at the same time, in parallel, all with the same feed. This means that “N” in the above is at least 2, preferably at least 4. With such arrangement, various adsorption materials (different active material, different physical properties, particle sizes, pretreatments etcetera) can be tested and compared in performance quickly. Hence for the apparatus and method of the present of the present invention, it is preferred that number N (herein representative for the number of adsorption beds) is from 2 to 32, preferably from 4 to 16. Such beds may be mounted all together in one apparatus ensuring the same temperature for all.
In order to monitor the composition of the gas coming out of the adsorption bed and/or to perform measurements to create a breakthrough curve for the adsorbent material being tested it will be clear that downstream of the adsorption bed will need to be some form of detection means or analytical tool. Preferred analytical tools or detection means in the context of this invention are: a sensor and/or a gas chromatography (GC) analyser, infrared (IR) analyser or mass spectrometer (MS) analyser. Hence, it is preferred that the apparatus according to the present invention comprises a sensor and/or a gas chromatography (GC) analyser, infrared (IR) analyser or mass spectrometer (MS) analyser. Likewise, in the method according to the present invention it is preferred that the detection means comprises a sensor and/or a gas chromatography (GC) analyser, infrared (IR) analyser or mass spectrometer (MS) analyser, optionally via a selector valve.
There can be detection means or an analytical tool per adsorption bed, but a plurality of adsorption beds may also be served with one such detection means or analytical tool. To enable the latter, it is suitable that there is one or more selector valves situated between adsorption bed and detection means or analytical tool. For example, four adsorption beds may be connected with an 8-port selector valve, of which there are four outlets, one of which is connected to e.g. a gas chromatography (GC) analyser, infrared (IR) analyser or mass spectrometer (MS) analyser, and the other three are vents. Or four adsorption beds may be connected to two 4-port selector valves, with two outlets being connected to analytical means and two connected to vents. Hence, it is preferred for the apparatus of the present invention that downstream of the adsorbent and upstream of the detection means there are one or more selector valves for selecting one or more outlets of the adsorbent bed. And likewise other set ups may be possible, e.g. 8 adsorption beds coupled with a 16-port selector valve of which one outlet is connected to analytical means, etcetera.
In operation, adsorption beds will typically be first flushed with a feed that contains the carrier gas without the adsorbate that is being tested on the adsorption material, to condition the adsorption bed. Typically, the carrier gas, but also the carrier gas plus the adsorbate to by analysed, will be reminiscent of air, e.g. in the case of research on respiratory protective devices. Hence, it is preferred that for the apparatus and method of the present invention feed streams A and/or B further comprise moisture (i.e. water) in a concentration of 0 to 6 vol. %, preferably between 0.5 and 5 vol. %.
The adsorbate can be present in the feed in a wide range of concentrations, depending upon the gas and adsorbates that are being studied. Two extremes can be envisaged: one in which the adsorbate is considered a contaminant (e.g. H2S, or a volatile organic compound) in a gas like air. Then the concentration of the adsorbate will be low, typically (for apparatus and method according to the present invention) then the adsorbate will be present in a concentration of at least 50 ppmv. Preferably, the concentration of the adsorbate in such situation will be a concentration of between 50 and 5000 ppmv. However, if the adsorbate that is subject of the study is a component that is to be adsorbed for obtaining it (e.g. CO2 from an exhaust gas, or oxygen from air) then the concentration will be much higher, e.g. up to 50% by volume. Hence, the concentration of the adsorbate is preferably between 50 ppmv and 50% by volume, and then dependent on the adsorbate at aim.
In many cases vents from the switching valve located between capillary and adsorption bed will be open to atmospheric pressure. This will also mean that the adsorption beds operate at or around atmospheric pressure, which may be representative for research on respiratory protective devices. For other cases, it may be preferred that the adsorption tests are done under pressure. To enable such, it may be preferred that the vents are under pressure. Hence, it may be preferred that in the apparatus or method according to the present invention the vents from the valve are pressure controlled, e.g. with a back-pressure regulator.
As to the process according to the present invention, such is preferably conducted for performing research on adsorption properties of adsorbing an adsorbate to particulate solid adsorption materials.
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| Number | Date | Country | Kind |
|---|---|---|---|
| 21205320.1 | Oct 2021 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/079699 | 10/25/2022 | WO |
