Patent Grant
9352331
The present invention relates to robust, high capacity magnetic filters for removing paramagnetic and/or diamagnetic materials from gas and liquid streams.
Paramagnetic substances can be magnetized under an external magnetic field. Paramagnetic materials include, for example, manganese, chromium, cerium, iron, cobalt, potassium, vanadium, and their oxides or sulfides. Without influence of the external magnetic field, the magnetic dipole in a paramagnetic molecule points in random directions, so it has zero magnetism. As a suitable external magnetic field is applied, a paramagnetic substance is magnetized since the number of magnetic dipoles aligned parallel toward the direction of the magnetic field is more than those aligned away from the field.
Conventional magnetic filters remove paramagnetic substances or particles from gas or liquid fluids through the influence of an external magnetic field generated by permanent magnetic or electromagnetic sources. For example, magnetic filters disclosed in U.S. Pat. No. 8,506,820 to Yen et al, U.S. Pat. No. 8,636,907 to Lin et al, and U.S. Pat. Nos. 8,900,449 and 9,080,112 both to Yen et al, can remove paramagnetic particles from liquid streams in refinery and chemical facilities. The paramagnetic particles which include FeS, FeO, Fe(OH)2, Fe(CN)6, etc. are formed when carbon steel, which is a common material in plant construction, corrodes in the presence of acidic contaminants in the process stream to yield ferrous ions, which react with sulfur, oxygen and water. These paramagnetic contaminants tend to adhere to magnets.
Diamagnetic substances contain pairs of magnetic dipoles which tend to cancel out the magnetism internally. Diamagnetic materials include, for example, carbon (diamond), carbon (graphite), silica, alumina, bismuth, phosphorous, mercury, zinc, lead, tin, copper, silver, gold, water, ethyl alcohol, etc. In the presence of an external magnetic field, the magnetic dipoles of diamagnetic substances align parallel and in reverse direction to the magnetic field and therefore exhibit no magnetism. Prior art magnetic filters cannot remove diamagnetic substances.
Filtration with mesh screens and the like is the standard employed to separate diamagnetic particles from gas or liquid fluids but this technique is not efficient for small particles. For example, nano carbon particles such as particulate matter PM 2.5 emitted from power plants, steel mills, and mobile sources including cars and motorcycles cannot be effectively abated. Similarly, nano particles in the form of catalyst fines, steel rust, carbon residue or polymerized slurry found in refinery and chemical plants cannot be effectively filtered. Solid particles comprising FeS, FeO, sand, carbon residue, etc. of various sizes are also present in natural gas processes. Paramagnetic and diamagnetic materials are major constituents of both natural and industrial pollutants and contaminants.
It is highly desirable to develop systems for removing both of paramagnetic and diamagnetic particles, or at least the diamagnetic particles, of all sizes from the gas and liquid fluids.
The present invention is based in part on the demonstration that common diamagnetic solid substances can be magnetized under an external magnetic field through coordinated interaction of the diamagnetic solid substances with an inducing or inducement paramagnetic material (IPM). The IPM which is solid should preferably not be in direct contact with the magnet which generates the external magnetic field. On the other hand, the diamagnetic solid substance preferably is in direct contact with the IPM or is uniformly mixed with the IPM. The position and distance of a magnetic source, such a magnetic bar or electromagnet, to the solid mixture of diamagnetic and IPM are adjusted and maintained so as induce sufficiently strong magnetism in the diamagnetic solids which causes the diamagnetic solids to be attracted by the magnetic field as well. In this fashion, both diamagnetic and paramagnetic substances can be removed from a liquid or gaseous stream in which the solid mixture is entrained or fluidized. Not all paramagnetic substances can induce magnetism in diamagnetic solid substances in the presence of an external magnetic field in the magnetic filters of the present invention. Thus, “inducement paramagnetic material” or “IPM” refers to solid paramagnetic material that can cause diamagnetic solid materials to exhibit sufficient magnetism to be attracted by a magnetic field and be removed or captured with the magnetic filter of the present invention.
Accordingly, in one aspect, the invention is directed to a method of removing diamagnetic material from a carrier stream that includes the steps of:
In another aspect, the invention is directed to a magnetic filter for separating diamagnetic contaminants from a carrier stream that includes:
a housing having (i) a stream inlet, (ii) a stream outlet and (iii) an interior region between the inlet and outlet;
inducement paramagnetic material (IPM) distributed within the interior region wherein the IPM is configured to come into physical contact with the diamagnetic contaminants; and
a magnet disposed within the interior region to generate a magnetic field sufficient to render the IPM magnetic.
The magnetic filter serves as a robust separation zone created by the presence of IPM and magnets that are shielded from the IPM by non-magnetic partitions. Preferably, elongated magnet assemblies are employed to generate a uniform magnetic field in the separation zone. The elongated magnet assemblies can be arranged in parallel or traverse to the fluid flow within the filter. The IPM in the void volume or space between the magnets afford a large surface area onto which diamagnetic and paramagnetic materials in the fluid steam can contact and be attracted to. While the invention will be described using permanent magnets to establish the magnetic field, it is understood that electromagnets can be employed.
A cover plate 20 is fastened by bolts 22 to an annular flange 24 that is welded to the outer perimeter along the top opening in housing 4. A polymer gasket or other suitable sealing means may be inserted between cover plate 20 and flange 24 to insure a tight seal during the operation cycle. A top supporting plate 26, which is fastened to the top rim of wire cage 28 around the perimeter by bolts 30, facilitates the removal of the entire core assembly from filter housing 4 during the clean-up cycle. Both the top supporting plate 26 and the top rim of wire cage 28 are placed on a supporting ring 42 which is permanently connected to filter housing 4. The weight of the core assembly causes top supporting plate 26 and the top rim of wire cage 28 to press tightly against supporting ring 42 to prevent the open end of each holder sleeve 32 and, thus magnetic bar assemblies 34, from coming in contact with the process fluid during the filtration process.
The core assembly includes multiple, vertically oriented removable permanent magnetic bar assemblies 34 with each being fitted into an elongated diamagnetic sleeve holder 32, IPM packing elements or substances 36 which fill up the space in between the sleeve holders 32 as the magnetic inducing media for solid diamagnetic substances in the process stream. Wire cage 28, as a holder of IPM packing 36, is preferably made of coarse wire of diamagnetic substances, such as stainless steel, with mesh size slightly smaller than the size of IPM packing substance 36 to prevent their loss to the process flow.
Preferably the IPM packing elements 36 are in layered arrangement with the largest ones on top and the smallest ones at the bottom. This gradient packing matrix configuration enables the magnetic filter to capture diamagnetic and paramagnetic substances of different sizes without causing significant pressure drops and throughput reductions.
The IPM is preferably formed of materials with high and positive mass susceptibility. Suitable IPM include, for example, Ce, CeO2, CsO2, Co, CoO, Ni, CuO, NiO, NiS, Fe, FeO, Fe2O3, FeS, Mn, Ni/γAl2O3, Cr2O3, Dy2O3, Gd2O3, Ti, V, V2O3, Pd, Pt, Rh, Rh2O3, KO2, and mixtures thereof with Co, CoO, Ni, Fe, FeO, Fe2O3, FeS, Ni/γAl2O3, Cr2O3, Dy2O3, and Gd2O3 being particularly preferred. Preferred configurations of the IPM packing elements include but not limited to conventional random packing such as rings, saddles, chips, and wires, structure packings, and macro-pore catalyst supports, such as guard-bed materials used in a fixed-bed reactor.
It is critical to keep the distance between the adjacent vertically oriented magnetic bar assembles 34 sufficiently close so that the IPM substances, which are packed in the filter, can induce sufficient magnetism to attract the diamagnetic substances from the process stream. The distance, which is measured from exterior surfaces of adjacent sleeve holders 32, should be from 0.1 to 5 cm and preferably from 0.1 to 2 cm. The magnetic flux intensity within the interior region 14 in magnetic filter 2 should be from 2,000 to 20,000 GS, and preferably from 2,000 to 10,000 GS, and most preferably from 6,000 to 10,000 GS.
Each sleeve holder 32, which is highly permeable to magnetic fields, has a sealed bottom and an open top end which is preferably welded at its perimeter to the fitted hole at the top supporting plate 26. This prevents the open end of each holder sleeve 32 and the associated magnetic bar assembly 34 from coming into direct contact with the process fluid during filtration. Top supporting plate 26 bears the weight of the plurality of permanent magnetic bar assemblies 34 with their associated holder sleeves 32, the IPM packing substances 36, and wire cage 28.
In use, each permanent magnetic bar assembly 34 or 110 is supported within a sleeve holder 32. It has been observed that the magnetic flux density of these encased permanent magnets as measured by a Tesla meter was essentially the same with or without a 304SSL sleeve. That is, the presence of the diamagnetic barrier (sleeve holder) did not result in a significant decay of the magnetic flux density. In contrast, permanent magnetic bar assemblies consisting of a plurality of magnet blocks that are arranged in tandem as shown in
It has also been observed that diamagnetic and paramagnetic particles are not attracted to the entire surface of the magnetic bar assembly as shown in
To compare the performance of the preferred magnetic bar assembly of
As shown in
In the clean-up cycle, control valves 8 and 12 are closed in sequence. Cover plate 20 is opened and the entire core assembly, including permanent magnetic bar assemblies 34, top supporting plate 26 along with sleeve holders 32, wire cage 28 containing IPM packing substances 36, is withdrawn from filter housing 4. Thereafter, permanent magnetic bar assemblies 34 are withdrawn from the sleeve holders 32 to remove the magnetic field from the interior 14 thereby releasing the attracted solids of paramagnetic and diamagnetic substances from the outer surface of sleeve holders 32 and surfaces of the IPM packing. The core assembly is washed with water or other suitable fluid before the magnetic bar assemblies 34 are reinserted into sleeve holders 32. The cleaned core assembly is then re-positioned into filter housing 4 and the top opening is closed and sealed with cover plate 20 and the fitted gasket. Before starting the operation cycle, control valves 46 and 48 are opened to briefly introduce high pressure fluid, such as water, process stream or air from line 47 to flush out the residual solids in filter housing 4, and to remove the flushed solids through control valve 48 and drain line 49. Finally, control valves 46 and 48 are closed and control valves 8 and 12 are opened to start the operation cycle again.
The left cover plate 68 is fastened, by bolts 70 to an annular flange 72 that is welded to the outer perimeter along left side opening of housing 52, while the right cover plate 74 is fastened, by bolts 76 to an annular flange 78 that is welded to the outer perimeter along right side opening of housing 52. A polymer gasket may be inserted between cover plates and flanges.
The filter assembly includes horizontal multiple permanent magnetic bar assemblies 80 that are removable from filter housing 52. Each bar assembly 80 fits into an elongated diamagnetic sleeve holder 82, which is constructed of a diamagnetic metal such as stainless steel 304SSL. Each of the sleeve holders 82 is sealed at one end and the open end is preferably welded to the fitted hole in cover plate 68 to form integral units therewith. To secure the position and support the weight of sleeve holders 82 and the magnetic bar assembly 80, each sleeve holder is fitted into a hole of the partition plate 88 which is welded to housing 52 to divide filter interior into two equal chambers. To induce the magnetism to solid diamagnetic substances in the process stream, wire cages 90 is filled with IPM packing substances 92 which are inserted into the space between the sleeve holders 82 from both sides of the filter openings. Wire cage 90, as a holder of IPM packing substances 92, is preferably made of coarse wire of diamagnetic substances with mesh size slightly smaller than the size of IPM packing substances 92 to prevent their loss to the process flow.
Preferred IPM packing substances and configurations are the same as those used in the vertically oriented magnetic filter 2 shown in
As depicted in
The configuration of the magnetic filter 50 directs the process stream entering filter housing 52 via line 54 to flow downward in left chamber toward the bottom opening between partition plate 88 and filter housing 52. The process stream then flows upward in right chamber toward the exit and treated process stream exits filter housing 52 through control valve 60 and line 58. In both chambers of the filter, the process stream travels through the outer surfaces of sleeve holders 82, and the wire cage 90 contacting the IPM packing substances 92 under influence of a strong magnetic field generated by the permanent magnetic bar assemblies 80. Solid paramagnetic substances in the process stream 54 will be attracted to the outer surfaces of sleeve holders 82, and to the surfaces of IPM packing substances 92. Diamagnetic solids in the process stream 54 having magnetism induced by the IPM packing substances will be attracted to outer surfaces of sleeve holders 82 and to the surfaces of IPM packing substances 92.
In the clean-up cycle, permanent magnetic bar assemblies 80 are withdrawn from the sleeve holders 82 from the filter to remove the magnetic field from interior space 62 of the filter, releasing the attracted solids of paramagnetic and diamagnetic substances from the outer surfaces of sleeve holders 82 and surfaces of the IPM packing 92. After control valves 56 and 60 are closed, control valves 66 and 120 are opened to introduce high pressure fluid via line 122, such as water, process stream or air to flush out the released solids through control valve 66 and drain line 64. To start the operation cycle, magnetic bar assemblies 80 are replaced into sleeve holders 82, control valves 66 and 120 are closed and control valves 60 and 56 are opened in sequence.
The magnetic filters of the present invention are particularly suited for abatement programs to remove airborne contaminants especially particles that are 0.1 nm to 1.0 mm in size, such as particulate matter PM 2.5. Both diamagnetic and paramagnetic particles can be removed from the streams. For example, filters can be installed in clean room operations or in airplanes to clean recirculated air, in electric power plant or steel mill to clean up flue gas, or in mobile emission sources, such as cars to reduce air pollution. The magnetic filters can also be employed to remove diamagnetic particles in liquid streams in refineries, chemical plants and other facilities in continuous operations where particles in process streams can accumulate and damage equipment. For instance, inorganic catalysts, that become free flowing or otherwise detached from a catalyst bed, can be effectively removed from streams with the inventive magnetic filter. Furthermore, this filter can be installed in ultra-pure water production facility to remove the ultra-fine diamagnetic and paramagnetic particles from the product stream. Similarly, a filter can be positioned upstream of a natural gas treatment plant to remove ultra-fine diamagnetic particles, such as sand, carbon residual, and diamagnetic metal oxides, and ultra-fine paramagnetic particles, such iron sulfide, iron oxides, etc., from a natural gas stream at the gas field in order to protect plant equipment and improve plant efficiency.
The following examples are presented to further illustrate different aspects and embodiments of the invention and are not to be considered as limiting the scope of the invention. To demonstrate the interaction between paramagnetic and diamagnetic substances under the influence of an external magnetic field generated by permanent magnets, paramagnetic and diamagnetic powders were selected for various experiments. The substances are classified into paramagnetic and diamagnetic based on their mass susceptibilities (MS).
Mass susceptibility is the magnetic susceptibility of a substance per gram and magnetic susceptibility is the magnetization of a material per unit applied field. It describes the magnetic response of a substance to an applied magnetic field. All substances are characterized by mass susceptibility (MS) values. Paramagnetic substances have higher and positive MS values whereas diamagnetic substances have lower or negative MS values. Table 1 lists the MS values of selected substances.
The degree or strength of magnetism exhibited by selected solid substances with high MS values in a magnetic field was measured. A permanent magnetic bar assembly with a magnetic strength of 6,000 GS was employed. The selected solid powders were: cobalt (Co), iron (Fe), nickel (Ni), nickel oxide (NiO), iron oxides (FeO and Fe2O3), iron sulfate (FeSO4), iron chloride (FeCl3), Ni supported on γ-alumina catalyst (Ni/γAl2O3), dysprosium oxide (Dy2O3), gadolinium oxide (Gd2O3), and chromium oxide (Cr2O3).
For each test, approximately 0.5 grams of powder were weighed by a precision balance (to 10−4 grams) and placed into a (precision weighed) glass vessel. The permanent magnetic bar assembly was then placed near the powder. After attracting of the power, the magnetic bar was removed and the vessel with residual powders (if any) was weighed. Weight percent (%) of the powders attracted by magnetic bar was calculated.
As shown in the data set forth in Table 2, metals and their oxides with MS values of approximately 600 to 7,000×10−6 c.g.s. unit are readily attracted by the permanent magnetic bar assembly, except for NiO (no attraction) and Cr2O3 (only 82%). As expected, Dy2O3 and Gd2O3 with their very high susceptibilities showed complete attraction. Surprisingly, however, even with very high MS values (over +10,000×10−6), iron sulfate (FeSO4) and iron chloride (FeCl3) showed no magnetism and were not attracted by the MB. This experiment suggests that mass susceptibility serves only a guideline for selecting suitable inducement paramagnetic materials. Metals or metal oxides are possible candidates as suitable inducing paramagnetic substances while metal salts such as FeSO4 or FeCl3 are excluded from the consideration, despite of their high MS values.
This experiment confirmed that diamagnetic substances by themselves are not attracted to a magnetic bar. The diamagnetic substances tested were silicon, silicon carbide (SiC), γ-alumina (γAl2O3), non-magnetic butadiene, titanium oxide (TiO2), ceramic, activated carbon, polyethylene, and elemental sulfur. Magnetic butadiene was also tested. A permanent magnetic bar assembly with a magnetic strength of 6,000 GS was positioned next to powder samples; none of the powders was attracted onto the magnetic bar, except the magnetic butadiene (containing paramagnetic substance). The presence of the magnetic field did not induce magnetism in the diamagnetic materials.
Simply coating a permanent magnetic bar assembly with a paramagnetic substance does not render the assembly attractive to diamagnetic materials. In this example, the permanent magnetic bar assembly coated with iron oxide (FeO) powder was positioned each of various diamagnetic powders that included Si, SiC, SiO2. Al2O3, non-magnetic butadiene, magnetic butadiene, TiO2, ceramics, activated carbon, and polyethylene. None of the diamagnetic powders was attracted by permanent magnetic bar assembly, except for the magnetic butadiene which contained a paramagnetic substance.
In mixing a diamagnetic substance with a suitable IPM substance, the paramagnetic substance acts as a magnetic inducing agent. The diamagnetic substance in the mixture exhibits magnetism when the mixture is exposed to a magnetic field that is created by a permanent magnetic bar or electromagnetic. Both the paramagnetic and diamagnetic substances in the mixture are attracted to the magnet.
Experiments were performed in air (gas phase) at ambient conditions. For each test, approximately 1.0 gram of diamagnetic powders and 0.1 grams of paramagnetic powders were weighed by a precision balance (to 10−4 grams) and the mixture was placed into a precision weighed glass vessel. A permanent magnetic bar assembly with magnetic power of 6,000 GS was position adjacent the mixture to attract powders from the vessel. The magnet was removed and the vessel with residual mixed powders was weighed. The weight percent (%) of the mixed powders attracted by the magnet; the data is summarized in Tables 3 and 4.
As set forth in Table 3, with Ni/γAl2O3 as the inducing agent, the magnetic bar showed only mild attractions for γ Al2O3, SiC, resid fluid cracking catalyst (RFCC-Al2O3/SiO2: 70/30), elemental sulfur (S), and activated carbon, but exhibited a significantly higher attraction for silicon.
As set forth in table 4, FeO is a better inducing agent than Ni/γAl2O3 since the magnetic bar attracted a much higher percentage of the paramagnetic and diamagnetic mixtures.
This experiment is similar to that of Example 4 except that an IPM in the form of thin carbon steel wires (CSW) was used instead of iron powder. As shown in Table 5, 70 to nearly 100% of the diamagnetic substance were attracted by the magnet, except in the case the elemental sulfur.
Liquid phase testing was conducted at ambient conditions. Specifically, for each test, approximately 50 grams of water were mixed with 1.0 gram diamagnetic powder in a precision weighed vessel. Thereafter, paramagnetic powder was added into the mixture. A permanent magnetic bar assembly, with a magnetic power of 6,000 GS, was inserted into the liquid mixture, allowing the suspended solid powders to be attracted by the magnet. The magnet was removed and solid powders scrapped off and the cleaned magnet was reinserted into the solvent and allowed to attract additional powder. After removing the magnet the second time, the vessel with the solution containing the residual powders was weighed. The weight percent (%) of the mixed powders attracted by magnet was calculated.
Table 6 are the results for testing using water as the solvent, RFCC powder (equilibrium resid fluid cracking catalyst (SiO2/Al2O3: 7/3) as the diamagnetic material (DM), and Fe2O3 as the IPM. Approximately 0.1, 0.3, 0.5, and 0.7 grams of Fe2O3 were added in each instance and the results show that 60 to nearly 100% of the mixed powders was attracted by the magnet, depending upon the amount of Fe2O3 added and the position of the magnet (related to magnetic strength). The amount of powder attracted was proportional to the amount of Fe2O3 added to the mixture.
This experiment was similar to that of Example 6 except diesel was the solvent. The results as set forth in Table 7 demonstrate that approximately 39 to 92% of the mixed solid powders was attracted by the magnet with the amount of powder in diesel attracted by the magnet was proportional to the amount of Fe2O3 added to the mixture with one exception.
This experiment demonstrates that the magnetic strength of the 6000 GS permanent magnets employed in the above examples decreased exponentially (with 104 power) with distance from a magnet. The magnetic field strength of the permanent magnet was measured at increments from 0 to 5.00 cm distances. The results as shown in Table 8 illustrate the substantial decay of its magnetic strength. It is expected that electromagnetic bars will exhibit similar decay. With the present invention, the strength of the magnetic field generated by the magnets must be strong enough to activate the inducing paramagnetic substances to magnetize the diamagnetic substances as the diamagnetic and inducing paramagnetic substances interact. Given that magnetic strength decays dramatically with distance, it is necessary to keep the distance between sleeve holders to a relatively small gap as discussed previously.
With the present invention, in order to function as an effective magnetic filter to remove diamagnetic materials, the filter must use magnets, which can be permanent magnets or electromagnets, capable of generating sufficient magnetic fields to impart or induce the requisite magnetism in the diamagnetic materials so as to be attracted by a magnetic field. The intensity of the induced magnetism in the diamagnetic materials must to be strong enough to cause the attraction by the magnetic field. To demonstrate the importance of the magnetic field strength, 2,000 GS and 6,000 GS permanent magnetic bars were compared in a test similar to that in Example 6 where the magnets removed RFCC powders in water solution at room temperature.
The results are as summarized in Table 9 show that with the 2,000 GS magnet, only about 40% of the mixed powder was attracted. The amount of paramagnetic powder present in the solution did not affect the level of attraction. In contrast, with the 6,000 GS magnet, 90% and 92% of the mixed powder was removed under a PM/DM ratio of 0.1 and 0.3, respectively. Therefore, it is preferred to use magnets with higher magnetic strength to attract the diamagnetic substances through induced magnetism by the paramagnetic substances. The influence of the amount of paramagnetic powder present in the solution was comparatively less important with respect to the diamagnetic material being attracted.
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