Patent Grant
11253804
The present application is a National Stage Application of PCT International Application No. PCT/SG2019/050275 (filed on May 27, 2019), under 35 U.S.C. § 371, which claims priority to Singapore Patent Application No. SG10201804693U (filed on Jun. 1, 2018), which are each hereby incorporated by reference in their complete respective entireties.
The present invention relates to an apparatus and a method of cleaning particle loaded or “dirty” fluid by removing particles therefrom using a multi flow-splitter technology in combination with at least one cyclone system. The new technology requires minimal energy to operate due to low pressure drops used to generate the rotation of the fluid whilst exerting high centrifugal (or “G-”) Force on the incoming fluid stream. Operating without the need for conventional filter media, the technology operates also with a significantly reduced, if not fully eliminated need for maintenance and/or repair. Low internal fluid turbulence ensures a very high separation efficiency. Additional explosion safe low-energy down-stream cleaning stages, preferably with variable speed system fan, provides optimal operational performance and operational flexibility.
Cyclonic separators have been in existence for over a century with patents filed as early as 1920. This cyclone separation process is a simple and reliable process used to separate particles from a particle loaded contaminated fluid-stream, such as air or water. In a typical cyclone, the fluid flows in a helical pattern or vortex, beginning at the wide (typically top) end of the cyclone which has a narrowing diameter towards the opposite end (typically the bottom). The main portion of the fluid, if not essentially all, exits the cyclone through a straight central pipe in the wide portion, typically at the top. The heavier particles carried within the incoming fluid-stream are forced to the outside of the vortex flow pattern and towards the outer wall of the cyclone by the centrifugal force created by the rotating fluid-stream. With the heavier particles now on the outside of the vortex, these particles touch the outer walls of the system body and with resulting friction these particles slow down and eventually fall out of the fluid stream whilst cleaner fluid is removed from the center of the vortex. Over time, thousands of process enhancements have been described and implemented. These enhancements typically related to cyclone diameters, internal geometries, arrangement of multiple cyclones, or by adding various vibrating mechanisms within the system (see e.g., EP2587980, Dyson). The majority of these enhancements aimed at reduced energy consumption and/or higher separation performances. Higher separation performances are typically achieved by increasing G-Force and/or reducing internal turbulence and/or increasing internal dwell time. Reducing energy consumption is typically carried out by reducing the pressure drop created across the cyclone, which directly saved main system fan or pump power savings. Such savings are significant as world-wide millions of cyclones are in operation. The grain handling sector for instance has spent significant effort to reduce energy consumption, as just a 1-2% energy drop can save the grain handling sector millions of dollars in energy savings.
Despite this R&D effort over the past century the overall design and process functionality of typical cyclonic separators have remain unchanged. Typically, fluid enters the cyclone at the top, mostly from the side, a helical vortex is created, separated particles are removed from the base of the outlet funnel of the cyclone body and cleaned fluid is removed from the top center of the cyclone. Although functional, cyclonic separators require significant energy to operate when compared to other filtration systems such as with filter media, like bag-houses, and as such are not used in multiple applications across multiple industries. For example, when considering an air separator cyclone, pressure drops across a cyclone often range from about 500 to 1500 Pa (2-6 inches of water gauge) meaning high powered main system fans are needed to keep the cyclone running. In the nuclear industry where a higher G-Force is needed, pressure drop can go far beyond 5000 Pa (20 inches of water gauge).
Also, whilst traditional cyclonic separators are functional, their separation performance is not ideal and, e.g., as often seen for air separators, smaller particles typically below 10 μm are particularly affected by turbulence in the lower portion of the cyclone process, causing disturbance to the particle flow which then cause these smaller particles to break away from the particle loaded (“dirty”) stream exiting the base of the funnel and instead to exit the process through the clean fluid stream.
On the positive side, traditional cyclonic separators have a huge advantage in that filter media is indeed not required and the technology often operates with low or even zero maintenance and repair costs. Furthermore, cyclonic separators can also handle both elevated as well as very low temperatures which other separators like bag-houses and drum filters often cannot process.
It is also known to connect multiple cyclones, wherein the outlet of a primary cyclone is sequentially connected to several parallel secondary cyclones, see e.g. WO2017173542A1.
Thus, there is still a need for an efficient separation process, which operates at higher centrifugal (G-) force (smaller diameter). Furthermore, in particular for air separation processes the separation efficiency especially for smaller particles should be increased by reducing or eliminating turbulence within the cyclone, thus allowing particles below 10 microns to remain stable during the separation process. Also, there is a need for the energy consumption to be reduced.
As an alternative to cyclones, it is also known to separate particles from a gas stream in an apparatus also referred to as an air splitter, such as described in EP2334407A1, relating to the flue gases of power plants or incineration units. As described therein, a “dirty”, particle loaded gas stream is submitted to a centrifugal movement, whereby the particles are moved towards the outward region of a splitter equipment and the separated in a side stream from the main stream. This technology is capable of providing the main air stream with only a low particle load, and avoids—in comparison to a cyclone—the energy consuming re-directing of the main air stream. However, the “dirt” loaded air stream still requires a further treatment step to remove the particles as it exhibits a relatively high air to particle load ratio. In EP2334407, this is achieved by a spray dryer absorption apparatus.
Thus the object of the present invention is to overcome the limitations of the cyclone as well of the flow splitter technologies by combining multiple units of the latter with a cyclone into an easy to operate, low energy consuming process which negates the need to change direction of the main fluid streams of a cyclone and may thus result in a significant energy reduction, such as for example of up to 70% versus conventional cyclonic-only separators.
Thus, the present invention is a method for removing particles from a particle loaded fluid stream, the method comprising the following process steps:
The method may further comprise one or more of the process steps selected from the group consisting of
The method is particularly useful in the manufacturing environment for producing fast moving consumer goods, preferably selected from the group consisting of open type or closed pant type diapers for babies or adults, or feminine hygiene articles, wherein the fluid is air, and wherein the particle loaded air stream result from pre-processes, preferably one or more selected from the group consisting of
In another aspect, the present invention is an apparatus for removing particles from a particle loaded fluid stream, wherein the apparatus comprises
A at least one, preferably a multiplicity of fluid splitter device(s), each comprising
Optionally the apparatus may comprise one or more elements selected from the group consisting of
Same numerals in various figures refer to same or equivalent features or elements.
Thus, the present invention is directed to an apparatus for and a method of cleaning a particle loaded “dirty” fluid using a combination of cyclone and fluid splitter technology. Whilst the present invention is particularly useful for applications of separating particles from a gas stream, and in particular an air stream, all embodiments of this invention can be used for essentially all kinds of fluids, liquid and gas types, that can carry matter, especially particles, suspended therein, with this matter exhibiting a higher density than the fluid which may be gas like air, or a liquid like water, mercury, sewage, and may be applied under ambient conditions or at temperatures between about 0° C. to about 50° C. or even ranging from just above 0 Kelvin up to 2500 Kelvin and pressures from 0.1 bar to well over 100 bar.
A first element useful in the present invention is a cyclone. In case of the fluid being a liquid, such as water or a water based fluid, reference may be made to a “hydrocyclone”, whilst in case of a gas being the fluid it is referred to as a gas cyclone. Within the present context, the term “cyclone” refers to a cyclone for a liquid fluid or a gaseous fluid. The present invention is particularly applicable to the fluid being air, which is loaded with particles, such as with contaminants.
The principle of a conventional cyclone is generally explained in the context of
As seen in
Whilst the cyclone is shown in a “vertical” positioning, i.e., the fluid is entering the cyclone horizontally, the clean fluid upwardly, and the particles downwardly, relative to gravity, cyclones may also be operated in a position angled relative to gravity.
The pressure drop of a cyclone can be linked to the following important contributing effects:
In the case of air cyclones, the third category (energy required to remove the particle depleted air out of the center of the cyclone) is often around two times the energy of the second category (energy required to rotate the air in a helical or cyclonic form) which can be easily explained as the radius of curvature is indeed sharper. For high performance cyclonic air separators as may have a diameter of the inlet portion 1300 ranging between 200-500 mm, the air is often removed through the center portion 1150 of the cyclone with a much smaller radius, on average around half of the 200-500 mm diameter and in some instances, the radius of this air-flow is as low as just 10 mm radius, inducing the large pressure drop.
Cyclones can be optimized by design and operating conditions, however, there is a general trade-off of particle removal efficiency versus pressure drop that has to be overcome. Also, turbulence in the cyclone may result in carrying particles into the particle depleted outlet stream.
Well known options for improving the efficiency are connecting multiple cyclones, either parallel, such that the smaller cyclones have a better particle removal efficiency whilst the multiplication of these is adapted to cope with the total fluid flow rate, or sequentially, whereby decreasing sizes along the sequence or stages improves the cleaning efficiency over the stages.
The operation of a cyclone is often linked to the centrifugal forces, which are often expressed relative to the gravity force, i.e. a G-force of x corresponds to a force as exerted to a mass, such as a particle, is x-times as high as the gravity force. For example, the separation performance of a cyclone may be increased by increasing the G-Force, which equates to (mass of the particle times square of the velocity) divided by the radius—such that better separation can be achieved by higher velocity of the fluid flow or reducing the radius of the cyclone (see 1109 in
Based on the above G-Force calculations, it is clear that a higher separation performance can be achieved with a smaller cyclone diameter. A smaller diameter equates to smaller air-flows meaning multiple systems would be needed to handle meaningful air-flows. For example, for one larger cyclonic separator of radius R=1000 mm, the resulting G-force exerted on the incoming particle loaded air stream is just 40.7886 G. Taking another example of distributing the same incoming particle loaded air stream into 10 smaller systems in parallel with just a radius R=100 mm the resulting G-force exerted on the incoming particle loaded air stream is 407.886 G, thus enabling better separation efficiency, however at an increased energy consumption due to a higher pressure drop in the multiple smaller cyclones.
The present invention aims at employing the benefits of a cyclone system, namely a good particle removal efficiency, whilst avoiding a large pressure drop of the fluid stream. This is achieved by connecting at least one, preferably a multiplicity of pre-separators with one cyclone separator, whereby the pre-separators are executed as “flow splitters”, whereby a fluid stream is guided into a generally curved, such as a circular, flow, such that—with nomenclature in analogy to the description of a cyclone in the above—the particles accumulate at the outward portion and then the fluid stream is split into a particle enriched (“dirty”) fluid stream and a particle depleted (“clean”) fluid stream with a very low particle load, both relative to the incoming particle loaded fluid stream. Thus, only a very small portion of the incoming particle load is in the particle depleted fluid stream.
Consequently, the outgoing particle enriched fluid stream carries most, preferably all of the particle load, at a moderately high particle load ratio, the latter referring to the ratio of the weight of particle and fluid, as may be expressed in kg particles per kg of fluid, or for steady flow conditions also as a flow ratio, i.e., kg/min of particle flow per kg/min of fluid flow. Such a fluid splitter is generally known in the art (see e.g., above referenced EP2334407 with respect to an air splitter) and can be operated at a low pressure drop.
Then, the particle enriched fluid streams of several pre-separators are merged and fed to a cyclone separator with a high separation efficiency for the particles at higher pressure drop, however this pressure drop applies only to a relatively small fluid stream.
The principle of a suitable pre-separator is schematically depicted in
Thus, an incoming particle loaded fluid stream vsi 2110, comprising incoming pure fluid stream vsi 2112, incoming particle stream psi 2113, thus exhibiting incoming particle load Psi 2111 is delivered to a fluid flow splitter 2100 in an inlet section 2102. As shown in
As shown in the figure, the particles are gently directed outwardly such that after the splitter blade 2107 the particle depleted stream and the particle enriches stream may exit the separate at exits 2106 and 2108, respectively, from where they may be further guided to downstream processes or to the environment.
The exact positioning of the splitter blade allows to determine, and vary, if desired, the sharpness of the separation, i.e., the more the splitter blade is positioned inwards, the more particles are separated into the particle enriched fluid stream, however also more fluid is directed thereto.
In
Typically in such an arrangement and when the fluid is a compressible fluid, such as a gas such as air, the fluid velocity is higher at the point of splitting, i.e. just before the edge of the splitting device, as compared to the inlet section 2102. Thus, a slight vacuum is created which reduces flow disturbances and eases transfer of the particles towards the outlet section 2108 for the particle enriched fluid stream
After exiting the fluid splitter device, the particle depleted fluid stream 2410, 2410′, or 2410″ may then be released to the ambient, or in case of even lower required particle loads, to a high efficiency filter means, such as a bag filter. The particle enriched or high particle load fluid streams 2107′ and 2107″ are then directed via further duct work duct work towards further processing.
This results in good separation of particles and a low particle load in the low load stream at a very low pressure drop, however, there is a relatively low particle load (in kg particles per kg fluid) in the particle enriched fluid stream.
As indicated before, both a cyclone and a fluid splitter are well known and used and each can be adapted to its optimum settings for a given application, however, both systems also have their trade-offs, especially energy usage and separation efficiency for the various “cleaned” and “dirty” fluid streams.
Henceforth it is a particular feature of the present invention to combine a cyclone with relatively good separation performance at relatively higher pressure drop, and hence poor energy usage, and fluid splitter technology with a poorer separation performance at significantly better energy performance in a particular way. To this end, an overall ingoing particle loaded fluid charge is directed to at least one but preferably a multiplicity of fluid splitter devices. The fluid splitter devices deflect the fluid stream into a curved flow direction, such as a half a turn, preferably a full turn, more preferably about two turns, but possibly also more than two turns, whereby the energy loss is relatively low, as the change of direction is gradual and along a smooth, preferably almost circular flow path. Through this generally rotary movement, the particles accumulate towards the outwardly oriented portions of the duct, and a particle depleted and a particle enriched fluid stream may be separated by a splitter blade, as described in the above. The positioning of the fluid splitter blade may be adjusted so as to vary the amount of particles and “pure” fluid being directed into the particle enriched fluid stream. Preferably, the settings are such that the “clean” fluid stream has a very low, if any, particle load, and does not need to undergo further treatment before being released into the environment. Of course, this fluid stream may be further treated, such as, without limitation by bag or HEPA filters.
This results in good separation of particles and a low particle load in the particle depleted fluid stream at a very low pressure drop, however, there is still too high fluid flow in the particle enriched fluid stream.
Thus, the particle enriched fluid stream of one or more of the one or multiplicity of pre separator(s) are now collected and guided to a cyclone adapted match the flow rates and separation efficiencies of the pre-separators, where the solids are now separated with high efficiency at a moderate pressure drop, which, however only effects a significantly smaller amount of fluid than if only cyclones without the primary separators were used.
This principle is further explained by referring to
For example, if the fluid splitter blades of the splitter devices were set to a 5% split (i.e. 5% of the fluid stream in the splitter devices are separated into the particle enriched fluid stream), these 5% of the total fluid flow would be transferred as collected fluid stream 3040 to the cyclone 3041, and contain at least 90%, preferably at least 95% more preferably at least 99% and most preferably essentially all of the particles of the incoming particle loaded fluid stream.
Such a combination system would operate using lower energy as not inducing the sudden change in fluid-flow direction of the most of the fluid as with traditional cyclonic separators as shown in
The benefits of such a system are clearly evident, not just in terms of energy, but also in terms of significantly reduced, if not completely eliminated maintenance effort, for example when comparing to a system where the collected fluid streams after the fluid splitter devices (see 3040 in
Considering exemplarily an air cleaning system with 10 air-splitter devices in parallel, each processing 500 m3/hr. The pressure drops across such air-splitters is around 250 Pa (1 Inch of water gauge) and as such, each splitter would require 0.03 kW electric power to operate, thus the total system would require 10×0.03 kW, i.e. 0.3 kW. Assuming further for simplicity, that the splitters are set-up to split 10% of the total air stream and this particle loaded air-stream would flow into the conventional cyclonic air separator as depicted in
If we compare this with a system made up of conventional cyclonic air separators, then the total energy for this system would require (10×0.1 kW)=1 kW in total. The differences in power requirements are clear 0.31 kW versus 1 kW or 31% which equates to a saving of 69% versus traditional cyclonic air separators. Such a multi splitter and cyclone system technology not only achieves a saving of 69% versus conventional cyclonic air separators but also achieves an almost or fully zero maintenance system and also a far higher separation performance versus traditional cyclonic air separators due to significantly reduced internal turbulence.
Further option for executing the present invention are outlined in
Thus it may be preferable in such instances to add a balancing means such as a booster fan or pump 3060 (
Yet a further independent embodiment of this invention aiming at stabilizing the process is outlined also in
If, however, the infeed particle loaded fluid streams 3011, . . . are not operating with the same differential pressure then all flow splitters 3001, . . . would operate with a different pressure, meaning the entire system would not be balanced. Thus, it may be preferred to create a pressure balancing void space 3051, . . . connecting the infeeds prior to the splitter devices, which ensures the system is balanced and the infeed particle loaded fluid streams are at the same differential pressure such that all flow splitters 3001, . . . are operating at the same or similar pressure, meaning the entire system is balanced.
In some operational environments, a different centrifugal (G-) Force may be desirable. Further embodiments of the present invention aim at improving the operation by varying speed and/or centrifugal (G-) Force. Assuming for example that in
The trim suction process air stream is mainly clean and could now and again receive a large contamination pieces, whilst the process operation process air stream is mainly clean with occasional smaller contamination, whilst conveyor vacuum air stream is mainly of contaminant particles of between about 50 μm to about 200 μm in diameter, whilst dust control operation vacuum air stream is mainly of contaminant particles of between 1 μm and 200 μm in diameter, whilst core laydown process vacuum air stream is mainly of contaminant fine particles of between 0.1 μm and 10 μm in diameter, whereby diameter refers to the diameter of spherical particles of equivalent diameter of particles of other shape.
A skilled person will readily realize, that it is neither desirable to operate the air-splitters of the trim suction process air stream at a high centrifugal (G-) Force, as this stream is largely clean, nor to operate the air-splitters of the core laydown process vacuum air stream at a low centrifugal (G-) Force, as this stream is contaminated with fine particles of between 0.1 μm to 10 μm in diameter and would require a higher G-Force to separate efficiently.
With all of these scenarios, the higher the centrifugal (G-) Force is, the higher the energy is needed to operate the system. Considering a production unit and process for fast moving consumer goods, such as hygiene articles, for which the present invention is particularly suited, various pre-processes may provide particle loaded fluid stream requiring quite different conditions for a good separation performance, e.g.,
Setting the design (e.g. diameter, or number of turns) and/or the operating parameters, especially air flow rate or speed, for each pre-separation device accordingly an excellent separation would take place whilst reducing energy even further in in such circumstances, energy savings of 90% can be achieved versus traditional cyclonic air separators.
Thus various executions of the present invention are depicted in
The skilled person will readily realize that there are numerous options within the described scenarios and within the scope of the present invention to connect
In an optional embodiment of the present invention, a variable speed main system fan 3160 may be added, which is connected to a vacuum pressure sensor, with before or after or within the multi-fluid-splitter. Adjusting fan speed influences the inlet pressure of the system and as such, making fine or coarse adjustments to the speed of the speed main system fan can maintain inlet pressure at a constant which is for many up-stream or down-stream processed an advantage. Obviously, in case of liquid fluids, the fan may be replaced by a pump.
A further execution of the present invention is to add particular optional downstream filtration processes, either, passive or active. With the down-stream filtration processes acting as a safe filtration stage for air filtration, and/or to improve air quality, with an explosion safe low energy up-stream multi fluid-splitter-cyclone system, it would be not preferred to add any downstream filtration processes that would compromise significantly on safety or energy requirements. Whilst adding down-stream passive air filtration is a relatively cheap equipment upgrade to install, such passive technology adds significantly to the on-going running costs through increased media replacement costs as the passive filter media has to be replaced once clogged, but also more significantly, the increased pressure drop which occurs when the filter media is clogged.
To further explain this aspect, a passive filtration stage is assumed for processing 50,000 m3/hr (50 KCMH) with a pressure drop at time of installation of 250 Pa (1 inch of water gauge) which is replaced upon clogging when the filtration stage reaches 750 Pa (3 inches of water gauge). Assuming a 85% fan efficiency and 85% motor efficiency, a total power consumption of 4.78 kW is required at start at 250 Pa (1 inch of water gauge). However, as the filter clogs over time, at 750 Pa (3 inches of water gauge), also assuming a 85% fan efficiency and 85% motor efficiency, a total power consumption of 12.21 kW is required, equating to a difference of 8.14 kW versus start up. Assuming a moderate energy costs of 8 USD Cents per kWh, this equates to an annual loss of 5563 USD per stage per system.
To avoid such losses, increasing filter media area and moving to active filtration where the filter media is kept clean, reduces significantly on-going energy costs and also filter replacement costs as active filtration systems are automatically cleaned and do not clog.
However, active filtration systems especially for air as fluid, come with a further negative: During the cleaning cycle air-born dust is typically blown throughout the filter. Not only does this dust, once settled, require cleaning, this dust also adds to the explosion fuel. As the air-borne dust is a direct fuel for the explosion, all is needed is an ignition source and the dust to be within the range between LEL (lower explosion limit) and UEL (lower explosion limit).
Therefore, air-borne dust may be captured by an automated moving hood which directly removes air-borne dust from the system once the dust has been ejected from the filter cassette. Optional additional downstream air jets may help to eject contaminants from the filter cassette and optional air reservoir connected to the air jet increases the strength of the pulse which increases contaminant ejection performance further. Optional additional upstream air jets clean the surrounding filter cartridge area to ensure the total filter system is clean prior to the moving hood departing and moving onto the next cleaning cycle.
One aspect of such safe active air-filtration stage is the need to keep all non-explosion proof electrical systems on the down-stream clean side of the air-filtration stage so as to operate it below the lower explosion limit. To achieve this, and to eliminate the number of drives, a multi-link arm system is encompassed on both the up-stream and down-stream stages. With the end of the arm on the down-stream stages connect to a drive system, with one drive system the total system can follow the needed path and operating in two axes despite only one drive axis installed on the down-stream stage. To achieve this, for each arm, a dedicated drive shaft passes from the down-stream stage to the up-stream stage.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10201804693U | Jun 2018 | SG | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/SG2019/050275 | 5/27/2019 | WO | 00 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2019/231398 | 12/5/2019 | WO | A |
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