Measuring compositional changes in the effluent of multiple parallel packed columns to which is fed a liquid mixture of components

Abstract

Equipment for measuring compositional changes in the effluent of multiple parallel packed columns, said packed columns comprising particulate material for removing at least one component A from a liquid feed mixture of components fed to such packed columns, from a liquid feed mixture of components fed to such packed columns. The invention further relates to a process of using such equipment.

Description

[0001] MEASURING COMPOSITIONAL CHANGES IN THE EFFLUENT OF MULTIPLE PARALLEL PACKED COLUMNS TO WHICH IS FED A LIQUID MIXTURE OF COMPONENTS

[0002] Introduction

[0003] The present invention relates to equipment for measuring compositional changes in the effluent of multiple parallel packed columns, said packed columns comprising particulate material for removing at least one component A from a liquid feed mixture of components fed to such packed columns, from a liquid feed mixture of components fed to such packed columns. The invention further relates to a process of using such equipment.

[0004] Background of the invention

[0005] Adsorption of liquid components onto solid adsorption material is a well-known way to remove one liquid compound from another liquid compound. Examples of such are the purification of xylene (removal of o- and m-xylene to obtain pure p-xylene, e.g. for PET production), the separation of aromatic hydrocarbon mixtures such benzene, toluene and xylene, and removal of water from water-containing lower alcohols. The commercial application for adsorption as a means for purification are expected to grow due to rising energy costs, which makes distillation columns less attractive. In short: separation and purification of liquid mixtures of mostly organic compounds.

[0006] For optimizing adsorption methods research is required, e.g. on testing various adsorption materials for a plethora of liquids that are to be adsorbed, and the conditions (e.g. temperature) such can best be done. An important feature of such research is to measure a breakthrough curve for a combination of adsorption material and compound to be adsorbed. An example of this is given by MSP Silva et al, Chem. Eng.

[0007] Technol. 2012, 35, No. 10, 1777-1785, in which a single column of 100 ml volume is used for testing adsorbents for the separation of p-xylene from C8-isomers.

[0008] For efficient testing, parallel testing of small amounts of adsorption or absorption material is desired. Performing small-scale experiments in parallel fashion as such is a known technique, but not yet in research on adsorption of liquid components on solid adsorption material. A complicating factor specific for such testing of adsorption of liquids to solid matter is that ideally immediately after an adsorption column the composition of the effluent is to be analysed for presence of the component to be adsorbed. This is in particular the matter for establishing a breakthrough curve. More specifically, the liquid effluent produced by the column is prone to axial dispersion (also known as back-mixing), which means that a breakthrough curve cannot be established with accuracy as desired. This is in particular the case when analysis (e.g. by GC) cannot be performed immediately after the reactor. Such immediate analysis is possible with a single reactor, or possibly two, where each adsorption column has its own analytical tool, but such is not practical or economical when e.g. 8 or 16 adsorption reactors are to be operated in parallel for large scale screening and testing. The latter in particular since multiple parallel testing usually results in small-scale test columns (to avoid too large amounts of liquid). Not all pieces of equipment can be scaled down as efficiently for technical reasons as the adsorption columns, e.g. effluent lines and valves, for example. Such comparatively large effluent lines and valves results in a relatively large volume downstream of the adsorption bed and upstream of the analytical means.

[0009] Hence, there is a desire for a system to perform research on testing adsorption or absorption of liquid components on a solid medium, in an efficient way, e.g. when a multitude of materials that can remove a (liquid) component from a liquid is to be screened, in which there is quick analysis of the effluent composition. Preferably, the equipment should be such that it is less sensitive to axial dispersion.

[0010] Summary of the invention

[0011] It has now been found that the above objective(s) may be achieved, at least in part, by equipment for measuring compositional changes in the effluent of multiple parallel packed columns, said packed columns comprising particulate material for removing at least one component A from a liquid feed mixture of components fed to such packed columns, said equipment comprising: at least two parallel packed columns comprising particulate material which removes a component A from the liquid feed mixture of components, each column equipped with an inlet line upstream of said column and an effluent line downstream of said column, the inlet lines of said adsorption columns feeding said liquid feed mixture of components to said adsorption columns, a device present in the effluent line downstream of the packed columns that ensures a higher pressure upstream of said device and / or a higher temperature downstream of said device, the temperature conditions and / or pressure conditions downstream of said device being such that downstream of said device at least part of the effluent in the effluent line is in gaseous phase, a valve having as input lines the effluent lines downstream of said devices , and as output at least one line for feeding to detection means, detection means for detecting presence or absence of component A in gaseous form, said detection means being downstream of the valve.

[0012] The invention further relates to a process for measuring compositional changes in the effluent of multiple parallel packed columns, said packed columns comprising particulate material for removing at least one component A from a liquid feed mixture of components fed to such packed columns, said process comprising: a. feeding a liquid feed mixture of components via a manifold to at least two parallel packed columns comprising particulate material which removes a component A from the liquid feed mixture, each column equipped with an inlet line upstream of said column and an effluent line downstream of said column, b. maintaining a pressure and a temperature of the liquid whilst in the packed column such that the feed mixture remains liquid in the column, c. feeding the effluent of the packed column to a device, which reduces the pressure of the effluent downstream of said device and / or increases the temperature of the effluent downstream of said device such that downstream of this device at least part of the effluent is in a gaseous state, d. feeding the gaseous effluent so-obtained to a valve having as input lines the effluent lines downstream of the devices under c., and as output at least one line for feeding to detection means, e. feeding the output of the valve of d. to detection means for detecting presence or absence of component A in gaseous form.

[0013] Detailed description of the invention

[0014] There are various classes of particulate material which can remove a component or multiple components from a liquid mixture of various components. Typically such materials have the functionality of chemisorption, physisorption or act like a molecular sieve. Examples of the latter are e.g. zeolites.

[0015] Examples of the chemisorption and physisorption are sorbents, both absorbent and adsorbent materials. Many of such materials are (micro-) porous. Examples of such porous materials are activated carbon, metal organic framework (so-called MOF's), zeolite, silica, and alumina. There are also non-porous materials that can be used in the present invention to effect the removal of one component from the liquid feed. An example of such is an ion exchange resin. Hence, in the present invention it is preferred that the particulate material is a porous material or an ion exchange resin. In case the particulate porous material is a porous material, it is preferred such material comprises one or more of: activated carbon, metal organic framework, zeolite, silica, alumina. Preferred particulate material for the columns in the equipment and process of the present invention are adsorbents.

[0016] It is referred to in the present invention that the parallel packed columns comprise particulate material. The reason is that the liquid feed needs to be able to flow through the column which is packed with such material. Hence, there needs to be a certain porosity of the packed bed, such that there is interstitial space between the particles is such that liquid can flow through the bed in the column from inlet to outlet. In order to establish such, the particulate material can be a powder or e.g. be a shaped material. In view of the preceding, it is preferred in the present invention that the particulate material is such that at least 80% by weight has a particle size of between 1 pm and 6 mm, preferably between 10 pm and 5 mm, as measured by sieve analysis. Examples of particles with larger sizes (e.g. above 0.5 mm) are extrudates and spheres.

[0017] A key feature of the present invention is that the feed to the columns is a liquid mixture, yet that at least part of the effluent of the multiple columns should be in a gas phase at a point downstream of the columns and upstream of the valve that channels the effluent of a column to the detection means. This means that at some point downstream of the packed columns and upstream of the valve a phase transfer should be effected of at least part of the effluent, from all-liquid to gaseous, for at least part of the effluents. This can be effected by various means. In the above it says "at least part", as already when e.g. half of the liquid effluent is made to evaporate this already ensures that the effluent travels much faster to the detection means than if it were all liquid. It is possible to evaporate all of the liquid effluent to a gaseous phase, but not needed. However, it may be preferred that all of the effluent in the effluent line upstream of the detection means is in gaseous phase.

[0018] A first option is by ensuring that the pressure in the columns is high enough in the columns for the mixture to be liquid, and reduced at some point downstream of the column such that the effluent at least partially evaporates. This can be effected e.g. by ensuring the pressure of the feed to the columns is high enough for the feed to be a liquid, and a pressure regulator (e.g. a back pressure regulator) in the effluent of the column, that maintains such pressure in the columns, whilst causing a pressure drop, so that downstream of this device in the effluent line the pressure is low enough for at least part of the effluent to be in gaseous phase.

[0019] A second option to ensure that the effluent is gaseous downstream of the columns and upstream of the valve is to have a heating device in the effluent lines. Heating by such device will then cause the effluent to evaporate to become at least part in gaseous phase. Both two options can be combined.

[0020] Hence, in the present invention it is preferred that the device present in the effluent line downstream of the packed columns is a pressure regulator or a heating device. A combination of both is also encompassed herein. A preferred pressure regulator in this connection is a back pressure regulator, which, in combination with sufficient pressure provided by e.g. a pump in the feed to the columns, provides sufficient pressure in the columns for the feed to be all-liquid. Whether a pressure regulator or heating device or both are chosen in the design is in part dependent on e.g. what the mixture of components of the feed is: at what temperature and pressure is the feed mixture liquid, and at what pressure are the components gaseous. For a convenient operation, it is preferred that the packed columns being operated at a pressure of at least 2 bar over atmospheric pressure.

[0021] The present invention allows liquid mixtures to be fed to multiple packed columns, on which columns at least one component is removed from the mixture, and the effluent is made gaseous. Now the effluent is gaseous, inventors found it can be avoided that liquid samples have to be collected and stored for analysis later on. The gaseous effluent travels via the effluent line and (selector) valve much quicker to the analytical device than it would do as a liquid. This effect can be further enhanced by injecting a diluent gas (usually an inert gas such as nitrogen) into the effluent line. This can be done downstream of the columns and upstream of the device present in the effluent line downstream of the packed columns that ensures a higher pressure upstream of said device and / or a higher temperature downstream of said device. Or it can be done between such device and the valve. Or it can be done between valve and detection means. Also injection of such diluent gas at two or three locations jointly may also be chosen.

[0022] Hence, in the present invention it is preferred that there is a gas inlet positioned in an effluent line downstream of the adsorption column, for supplying an inert diluent gas under pressure to the effluent line. As mentioned in the previous paragraph inlet is provided upstream of the device present in the effluent line downstream of the packed columns that ensures a higher pressure upstream of said device and / or a higher temperature downstream of said device. A preferred inert diluent gas here is nitrogen, carbon dioxide, or a noble gas.

[0023] As to the lines feeding the liquid feed mixture to the multiple columns: as there is usually at least one feed storage container, and multiple columns, a manifold (or splitter) is generally needed to distribute the feed over the individual packed columns. Typically, there will also be a storage container with a carrier liquid, so that at a given moment the feeds to the columns can be switched from carrier liquid to feed which contains a component to be selectively removed. Also may be present multiple feed containers to be able to switch between feeds. Care must be taken that the flow to each column is predictable. One way of achieving this for small packed columns (e.g. up to 20 ml volume) is feeding via capillaries, but other options are possible. Capillaries can be made such that they give predictable flows. Hence, in the present invention it is preferred that the inlet line upstream of a packed column contains a capillary channel having an inlet and an outlet, the outlet connected to the packed column, the inlet of each capillary connected to a manifold or splitter.

[0024] As mentioned, the liquid that is fed to the columns is, at some point downstream of the packed columns, at least partially turned into gaseous streams after each column. This means that the volume increases considerably. Not all gas can or need be led to the detection means: a substantial proportion of the gas can be led to a vent stream, as long as sufficient remains for analytical purposes. Hence, in the present invention, it is preferred that there is a vent line downstream of said device present in the effluent line downstream of the packed columns that ensures a higher pressure upstream of said device and / or a higher temperature downstream of said device for venting part of the gaseous mixture.

[0025] The vent line can originate at any point downstream of the device present in the effluent line downstream of the packed columns that ensures a higher pressure upstream of said device and / or a higher temperature downstream of said device. Preferably, the gas vent line originates from the valve.

[0026] As mentioned, there is prior art for doing experimental work on e.g. adsorption in a single column, of e.g. 100 ml volume. Clearly, it would be an advantage if multiple adsorption or absorption experiments can be carried out simultaneously, also with smaller reactors, yet changes in composition, such as around breakthrough curves beaning measured as the experiment is being conducted (i.e. online measurements). Considering such, it is preferred that in the present invention, the multiple parallel packed columns comprise at least 4, preferably at least 8, parallel packed columns, more preferably at least 16 parallel packed columns. The volume of each packed column is suitably below 20 ml, preferably below 10 ml, so as to minimize expenditure of liquid to be analysed. Suitable detection means for e.g. measuring a breakthrough curve in adsorption or absorption is has chromatography. Hence, in the present invention it is preferred that the detection means comprises gas chromatography.

[0027] The above set out preferred ways for the equipment also apply to the process claimed herein. More specifically, it is also preferred in the process according to the present invention that said particulate material is a porous material or an ion exchange resin. Preferred particulate porous material in the present process comprises one or more of: activated carbon, metal organic framework, zeolite, silica, alumina.

[0028] Figure 1 shows a possible set-up of the arrangement, with a pressure regulator downstream of each column to ensure a conversion of all liquid to at least part gaseous effluent, and with the optional inert gas dilution and the valve being a multi-position selector valve.

[0029] In figure 1:

[0030] 1. Carrier liquid

[0031] 2. Liquid with component to be adsorbed plus carrier liquid

[0032] 3. Pump

[0033] 4. Packed columns

[0034] 5. Nitrogen gas supply pressure

[0035] 6. Nitrogen gas mass flow controller

[0036] 7. Pressure regulator

[0037] 8. Multi position selector valve

[0038] 9. Gas chromatograph

[0039] 10. Vent line

[0040] EXAMPLE

[0041] A set up according to the invention was used for measuring the breakthrough curve of a toluene / heptane mixture of 90 wt% toluene and 10 wt% heptane that changes instantly to 90 wt% heptane in 10 wt% toluene, this to mimic an adsorption process where breakthrough is also an instant concentration change. SiC was as inert particles to form the adsorption bed and varied the particle size from 425 micrometer to 1600 micrometer. Materials and equipment

[0042] Equipment similar as in figure 1 was employed, with four parallel columns.

[0043] The columns had an internal diameter of 4 mm, a length of 25 cm, and a volume of 3.14 ml.

[0044] The column was packed with SiC material. The top and bottom of the packed bed was hold in place by silica wool. Upstream of the columns two feed pumps pumped two liquids to a splitter manifold. Within the manifold the two streams where mixed and split into four streams. Every stream was directed into a separate column. The upstream pumps were connected to two liquid supply containers, one with Toluene, the other with Heptane. The pressure in the columns was 10 barg and the columns were maintained at a temperature of 45°C. Downstream of each column was a back pressure regulator maintaining the pressure within the columns at 10 barg, yet giving a reduction of the pressure downstream of the regulator to a pressure of 1 barg. The temperature in the effluent lines was approximately 160 °C. All effluent lines after the pressure regulators were fed to a selector valve, from which one line went to a gas chromatograph and a vent line for all effluents not selected to go to the gas chromatograph. After the selection valve, the flow was mixed with 80 ml / min of nitrogen to reduce the concentration to a level that the gas chromatograph is able to measure. After the mixing the stream was split into a 20 ml flow to the gas chromatograph.

[0045] Procedure

[0046] Three columns were packed with the SiC material to be tested. One column was left empty. The SiC material in each column had a different particle size. The particle size was measured using sieving resulting in fractions of well-defined sizes. The amount of adsorption material per column is in table 1.

[0047] Table 1

[0048] Run steps

[0049] Flush setup with N2

[0050] Purge cooling system • Heat-up of system to desired temperatures

[0051] • Column Fill Up with Feed: 90% Toluene / 10% heptane (wt%)

[0052] • Liquid Flow Stabilization at 50 g / h (total)

[0053] • Column Pressurization at 10 barg • Heating to 45 °C

[0054] • When system stable swap Feed to: 10% Toluene / 90% heptane (wt%) at 50 g / h (total)

[0055] • Sample is automatically measured on-line via a GC using a commercially available column to measure polar organic components.

[0056] • Sample results are automatically written to a database for later study • When experiments finished switch to Water Cooling of 35 °C

[0057] • Flush system with N2

[0058] • Shut-down

[0059] Results The analytical device was a compact gas chromatograph from Interscience equipped with 2 FID's and commercial polar columns able to separate organic components. The results are in table 2, and schematically in figure 2.

[0060] Table 2

Claims

CLAIMS1. Equipment for measuring compositional changes in the effluent of multiple parallel packed columns, said packed columns comprising particulate material for removing at least one component A from a liquid feed mixture of components fed to such packed columns, said equipment comprising: at least two parallel packed columns (4) comprising particulate material which removes a component A from the liquid feed mixture of components, each column equipped with an inlet line upstream of said column and an effluent line downstream of said column, the inlet lines of said adsorption columns feeding said liquid feed mixture of components to said adsorption columns, a device (7) present in each effluent line downstream of the packed columns that ensures a higher pressure upstream of said device and / or a higher temperature downstream of said device, the temperature conditions and / or pressure conditions downstream of said device being such that downstream of said device at least part of the effluent in the effluent line is in gaseous phase, a valve (8) having as input lines the effluent lines downstream of said devices, and as output at least one line for feeding to detection means (9), detection means (9) for detecting presence or absence of component A in gaseous form, said detection means being downstream of the valve (8).

2. Equipment according to claim 1, wherein said particulate material is a porous material or an ion exchange resin.

3. Equipment according to claim 2, wherein the particulate porous material comprises one or more of: activated carbon, metal organic framework, zeolite, silica, alumina.

4. Equipment according to any of the previous claims, wherein all of the effluent in the effluent line upstream of the detection means is in gaseous phase.

5. Equipment according to any of the preceding claims, wherein the device (7) present in the effluent line downstream of the packed columns is a pressure regulator or a heating device.

6. Equipment according to claim 5, wherein the pressure regulator is a back pressure regulator.

7. Equipment according to any of the preceding claims, wherein said packed columns are being operated at a pressure of at least 2 bar over atmospheric pressure.

8. Equipment according to any of the preceding claims, wherein the inlet line upstream of a packed column contains a capillary channel having an inlet and an outlet, the outlet connected to the packed column, the inlet of each capillary connected to a manifold.

9. Equipment according to any of the preceding claims, wherein there is a gas inlet positioned in each effluent line downstream of a packed column, for supplying an inert diluent gas under pressure to the effluent line.

10. Equipment according to claim 9, wherein said gas inlet is provided upstream of the device present in the effluent line downstream of the packed columns that ensures a higher pressure upstream of said device and / or a higher temperature downstream of said device.

11. Equipment according to any of the preceding claims, wherein there is a gas vent line downstream of said device present in the effluent line downstream of the packed columns that ensures a higher pressure upstream of said device and / or a higher temperature downstream of said device, for venting part of the gaseous mixture.

12. Equipment according to claim 11, wherein the gas vent line originates from the valve.

13. Equipment according to any of the preceding claims, wherein the multiple parallel packed columns comprise at least 4, preferably at least 8, parallel packed columns.

14. Equipment according to any of the preceding claims, wherein the detection means (9) comprises gas chromatography.

15. Process for measuring compositional changes in the effluent of multiple parallel packed columns, said packed columns comprising particulate material for removing at least one component A from a liquid feed mixture of components fed to such packed columns, said process comprising: a. feeding a liquid feed mixture of components via a manifold to at least two parallel packed columns (4) comprising particulate material which removes a component A from the liquidfeed mixture, each column equipped with an inlet line upstream of said column and an effluent line downstream of said column, b. maintaining a pressure Pcoiumn and a temperature Tcoiumn of the liquid whilst in the packed column such that the feed mixture remains liquid in the column, c. feeding the effluent of each packed column to a device (7), which reduces the pressure of the effluent downstream of said device and / or increases the temperature of the effluent downstream of said device such that downstream of this device at least part of the effluent is in a gaseous state, d. feeding the gaseous effluent so-obtained to a valve (8) having as input lines the effluent lines downstream of the devices under c., and as output at least one line for feeding to detection means, e. feeding the output of the valve of d. to detection means (9) for detecting presence or absence of component A in gaseous form.

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