US3428179A

US3428179A - In-line magnetic particle collector

Info

Publication number: US3428179A
Application number: US465404A
Authority: US
Inventors: David M Boyd Jr; Kenneth O Rockey
Original assignee: Universal Oil Products Co
Current assignee: Universal Oil Products Co
Priority date: 1965-06-21
Filing date: 1965-06-21
Publication date: 1969-02-18
Anticipated expiration: 1986-02-18
Also published as: GB1142261A; DE1276574B

Description

Feb. 18, 1969 o. M. BOYD, JR., ET

IN-LINE MAGNETIC PARTICLE COLLECTOH Filed June 21. 1965 wh Z 0 .d w i w W 7 M a I- V W m V n mm W M N 933 ,7

mwamt A ro/Mfrs United States Patent IN-LINE MAGNETIC PARTICLE COLLECTOR David M. Boyd, Jr., Clarendon Hills, and Kenneth, 0.

Rockey, Evanston, Ill., assignors to Universal Oil Products Company, Des Plaines, Ill., a corporation of Delaware Filed June 21, 1965, Ser. No. 465,404

US. Cl. 210-222 Claims Int. Cl. B01d /06; B03c 1/10 ABSTRACT OF THE DISCLOSURE A particle collector for removing magnetic particles from a fluid stream comprising an outer casing and an inner non-magnetic open-ended conduit extending through the casing. A train of permanent magnets is moved through the conduit, and the fluid stream is passed through the annular space between casing and conduit. The particles are attracted to the outer surface of the conduit and are swept therealong by the traveling magnetic field to'a particle collecting chamber which is periodically emptied of stored particles.

This invention relates to apparatus for the separation of magnetic particles from a fluid stream. More particularly, the present invention is directed to apparatus for effecting the continuous removal of magnetic particles from an acidic liquid stream.

In various chemical processes, the efiluent stream therefrom is contaminated with small metallic particles comprising iron and/or nickel in suflicient quantity as to be susceptible to magnetic collection. It is an object of this invention to provide means for purifying such streams by subjecting the particle-form contaminants to the action of a traveling magnetic field. Other objects and advantages of the inventionwill be made apparent hereinbelow.

In one embodiment this invention relates to a magnetic particle collector comprising a casing adapted to contain a fluid stream; spaced fluid inlet and outlet means connecting with said casing; a non-magnetic open-ended conduit supported within said casing adjacent to said inlet and outlet means, both ends of the conduit extending through the casing to the exterior thereof; a magnet train within said conduit comprising an elongate carrier means and a series of permanent magnets carried :by said carrier means; and drive means coupled to said magnet train for effecting movement thereof through said conduit.

A more specific embodiment of this invention is directed to a magnetic particle collector comprising an elongate shell adapted to contain a fluid stream; longitudinally spaced fluid inlet and outlet means connecting with such shell; a non-magnetic open-ended conduit supported within said shell opposite said inlet and outlet means and extending lengthwise through the shell to the exterior thereof; a magnet train comprising an endless belt-like carrier means adapted to travel longitudinally within said conduit in a forward direction and outside of said conduit in the reverse direction, and a series of permanent magnets carried by said carrier means substantially uniformly spaced along the entire length thereof; and rotary drive means operatively engaging said carrier means for effecting continuous unidirectional movement of the magnet train through the conduit.

The arrangement and operation of our invention are further described in connection with the accompanying drawings in which:

FIGURE 1 is a sectional elevation view of the apparatus.

FIGURE 2 is an enlarged view of a section of the magnet train.

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FIGURE 3 is a transverse view of the apparatus taken along line 3-3 of FIGURE 1.

FIGURE 4 is a plan view of the apparatus taken along line 44 of FIGURE 1.

With reference to FIGURE 1, the particle collector comprises an outer elongate shell or tube 10 having a fluid inlet conduit 11 and a fluid outlet conduit 12 longitudinally spaced therefrom. An inner open-ended conduit or tube 13 is concentrically mounted within shell 10, extending lengthwise the fulllength thereof. Annular gas ket or seal members 14, compressively inserted into each end of shell 10, serve as fluid-tight end closures for the shell as well as supporting the inner tube. Tube 13 is constructed of a suitable non-magnetic material such as glass, plastic, aluminum, copper or stainless steel, selected with due regard to the corrosiveness, if any, of the process fluid being handled.

A magnet train, indicated generally by numeral 15, is arranged to move longitudinally through tube 13. In a preferred embodiment of our invention, such magnet train comprises an endless elongate loop of flexible non-magnetic tubular woven braiding 16 and a series of spaced permanent magnets 17 carried within the braiding, the magnets being substantially uniformil spaced along the entire length of the braiding. Braiding 16 may be made of tinned copper, similar in construction to electrical shielding braid, or other non-magnetic material such as aluminum, stainless steel or plastic. Magnets 17 may be in the form of elongated cylinders with a diameter slightly greater than the inside diameter of braiding 16 when the latter is unstressed. As shown in greater detail in FIGURE 2, the magnets are spaced approximately one magnet length apart to increase the flexibility of the assembly and, as will be explained below, are preferably arranged to have successively repelling polarities, e.g., contiguous poles of any two adjacent magnets being of like'polarity, either north or south. When the braiding is placed under tension, as by engagement with mechanical drive means, the braiding wall necks down between magnets as indicated at sections 16a of FIGURE 2, thereb gripping the magnets and locking them in place within the braiding to limit or prevent any substantial movement of the magnets within the braiding.

The magnet train is engaged and driven by a pair of spaced pulley members or sheaves 19 and 20 disposed externally of shell 10 and in alignment with central conduit 13. Sheave 19 is a power sheave keyed to the shaft of a combination motor-speed reducer 22 (FIGURE 4) mounted upon a pedestal 23. Sheave 20 is an idler or takeup sheave mounted on a pedestal 21 which may be provided with through-bolted slots for regulating the tension imposed on the magnet train. The return run of the magnet train is taken through a lower external housing or guard tube 24 designed to protect the magnet train from dirt, moisture and falling objects, as well as to furnish some support therefor. The shell 10 and tube 24 are supported in horizontal positions by suitable spaced frame members 25.

A pair of eccentrically bored orifice plates 26 are transversely disopsed across the interior of shell 10. These plates are located a short distance beyond the fluid outlet conduit 12, away from the inlet conduit, and serve as baffle means dividing the interior of shell 10 into two functionally distinct chambers or zones; on the left, a particle separation zone and, on the right, a fairly quiescent particle storage zone. As shown in FIGURE 3, the, eccentric bore is somewhat larger than the diameter of conduit 13 so that the latter, which extends completely therethrough, rests in tangential contact upon the lower edge of the bore whereby to furnish additional support for conduit 13, and also to provide open communication along the external surface of conduit 13, via the crescent-shaped passageway 27, between the particle separation zone and the particle storage zone. Also as shown in FIGURES 1 and 3, each of plates 26 is provided with an upper gas vent hole 27a and a lower liquid back-flush hole 27b.

According to one particular application of our invention, the fluid to be clarified is a liquid comprising a mineral acid such as HCl, H 50 or HNO at concentrations ranging from dilute to highly concentrated, in which there are suspended metallic impurities in the form of minute metal particles, mainly colloidal agglomerates having a size of the order of 1-100 microns, and typically comprising iron, nickel and copper. In many cases, the particles themselves are attacked by the acid resulting in undesirable chemical contamination of the acid. Therefore the present apparatus is designed not only to separate the maximum weight of metal particles per pass but also to remove them from contact with the low pH region of the acid stream at a rapid rate.

With further reference to FIGURE 1, a feed stream comprising a suspension of minute magnetic metal particles in acid is charged to shell through inlet line 11. The stream flows through the annular particle separation zone and clarified acid is taken out through line 12. At the same time the magnet train is being driven from left to right, or cocurrently with the liquid flow, at a velocity which is preferably substantially differente.g., greater than or less than the superficial liquid velocity within the separation zone; the superficial liquid velocity is defined as the average velocity across the annular space between shell 10 and the tube 13, assuming perfect plug flow. The reason for maintaining the difference in velocities will become apparent from a consideration of the nature of the magnetic field generated by the magnet train. Looking for the moment at a single magnet 17, the field thereof is roughly ellipsoidal in form, the lines of force curving radially outward in all directions from one end of the magnet, cutting through the wall of conduit 13 and curving out through the annular particle separation zone and thence returning through the conduit Wall and converging into the other end of the magnet. The field generated by these series of magnets can be characterized as lobulate meaning a series of coaxial ellipsoids or three-dimensional lobes spaced apart in the direction of liquid flow and which cut through the conduit and project transversely into the particle separation zone. By arranging the magnets so as to have alternately opposing polarities, as above described, the fields of adjacent magnets coact in a manner which compresses each field in the axial or longitudinal direction and pushes the lines of force farther out in the radial direction; this in turn increases the magnetic field strength in the particle separa tion zone, for a given magnet strength and central conduit diameter, over and above that which would be obtained by a random arrangement of magnets or a pattern of mutually attracting polarities. By way of example, for conduit 13 outside diameters in the range of 0.5"2", field strengths of 100-1000 gauss at the outside surface of conduit 13 can be obtained utilizing commercially available alloy magnets. By maintaining a substantial difference in velocities between the liquid flow and the lobulate magnetic field, each impurity particle will pass through a number of lobes during its time of passage through the particle separation zone and there is a high probability of capture. However, as the relative velocity approaches zero, a given impurity particle will pass through fewer and perhaps no lobes, and the probability of capture is somewhat lower, resulting in reduced collection efficiency. The lower limit of field velocity is determined in accordance with the impurity content of the feed stream and the permissable residence time of the metal particles in the low pH region; obviously it should not be so low as to result in excessive accumulation of particles in the separation zone. The upper limit of field velocity is fixed by the capability of the magnet train drive mechanism and tolerable wear and tear on the magnet train itself. It is preferred, therefore, that the velocity of the magnet train be substantially less than the superficial liquid velocity; for example, very good results and very high collection etficiencies can be realized when the linear velocity of the lobulate magnetic field is maintained in the range of about 0.1-0.5 times the superficial liquid velocity within the separation zone. The maximum permissible liquid velocity, in turn, is determined by the point at which the drag forces acting on the particles are so great so to substantially prevent their capture by the magnetic field; by way of example, for iron-nickel-copper particles in the size range of 1l000 microns and a field strength of -600 gauss (existing midway between tube 13 and shell 10) such maximum superficial liquid velocity will be of the order of 25-125 feet per minute, depending, of course, on the density and viscosity of the liquid stream and the dimensions of the particular apparatus.

The magnetic metal impurity particles, upon intercepting the traveling magnetic field, are attracted to the outside or collecting surface of conduit 13. The particles accumulate thereon in a film or thin layer 36. Because of the presence of hydrogen bubbles occluded by the particle agglomerates, there exist buoyancy forces acting upon the particles in opposition to the magnetic forces; therefore the layer 36 tends to accumlate mainly on the upper surface of conduit 13, as illustrated in FIGURE 3. The traveling magnetic field simultaneously sweeps the layer of particles along the surface of conduit 13 from left to right in FIGURE 1, through openings 27 in orifice plates 26 and into the relatively quiescent particle storage zone defined by the right-hand portion of shell 10 beyond plates 26. Upon reaching the right endwall 14, the particles are blocked from further movement and so accumulate therein. Hydrogen which may accumulate withinrthe particle storage zone is released therefrom through upper vent holes 27a and eventually passes out of the apparatus through conduit 12. In certain instances it will be. desirable to provide a holding magnet 32, either a permanent magnet or an electromagnet, disposed exteriorly and in close proximity to the shell 10, of sufiicient strength to overcome the traveling field, causing the particles to be.pulled away from conduit 13-, and into a mass adhering to the shell wall. In such case, the end portion 10a of the shell will be fabricated of non-magnetic material and may be swaged down, as indicated in FIGURE l,-to increase the efiective strength of holding magnet 32. In order to reduce the hydrogen ion concentration in -1the particle storage zone, and thereby to inhibit dissolution of the metal particles by the acid, a stream of water may be continuously or intermittently introduced into the storage zone through a backflush line 28 and valve 29. The water backfiows through the storage zone and openings 27, as well as through lower backfiush holes 27b, into the separation zone and out through line 12. The quantity of water so injected is quite small in relation to the quantity of acid treated in order not to appreciably dilute the acid stream.

In some cases the amount of occluded hydrogen carried into the particle storage zone may be quite substantial and it will be advantageous to provide additional means for bleeding off the hydrogen trapped therein. This may be accomplished by a vertical standpipe 33 connecting at its lower end with the particle storage zone and terminating at its upper end in a gas disengaging tank 34. Hydrogen bubbles released from the storage zone pass upwardly through pipe 33 and the resulting collected hydrogen is vented through line 35. Line 35 may include a back pressure controller or may be connected to a separate external zone maintained under a regulated pressure somewhat less than the ambient pressure within the particle storage zone. The water inlet line may be connected to the standpipe 33 if desired. The volume of water within pipe 33 and tank 34 may also be utilized to assist in the removal of metal particles from the storage zone as explained below.

Ordinarily the volume of the particle storage zone will be sufficient to accommodate from several hours to several days collection of particles. But to permit the elimination of particles from the storage zone as periodically required when the storage area becomes full, there is provided a particle drain line 30 with a valve 31. In combination with this means, a short length of magnet train 15 contains one or more non-magnetic dummies or spacers 18, of approximately the same size as magnets 17, but which produce no magnetic field. When spacers 18 are moved into transverse alignment with line 30, the magnetic field in this region is greatly attenuated and the metal particles gain relatively free mobility and freeflowing characteristics during the brief interval that spacers 18 occupy this position. Therefore, to discharge particles from the storage zone, one merely waits until spacers 18 arrive opposite line 30 (if holding magnet 32 is employed, its field is also cut off or removed at this time) valve 29 is temporarily closed and valve 31 is briefly opened. The metal particles are thereupon pressured out through line 30 to a suitable drain. Also at this time the water stored within standpipe 33 may serve as a flushing medium to aid in the discharge of particles and also to minimize pressure fluctuations during the particle discharge cycle. The above-described discharge cycle may be automatically programmed by suitable control apparatus including a cycle timer, solenoid valves and a magnet train position sensor.

Given below are typical specifications for a horizontal magnetic particle collector designed to handle 60-75 g.p.m. of HCl solution, recovering 65 grams per hour of magnetic metal impurities at a collection efliciency of 98 percent:

Outer shell 6'' ID. glass pipe.

onds once every 2 hours.

Our apparatus as described above preferably incorporates cocurrent travel of the magnetic field relative to the direction of liquid flow. The invention may instead utilize countercurrent motion. This is less desirable, however, because then the highest concentration of particle agglomerates moving along the surface of conduit 13 occurs opposite the inlet line 11, and the relatively high turbulance at this point may tend to dislodge and scatter some of the particles. In some cases this may be avoided by using suitable baffling; frequently, however, the particles carried by the inflowing stream are too fragile to withstand impact on a baffle plate and would disintegrate into colloidal sized particles no longer susceptible to magnetic attraction.

Many variants in the above-described apparatus will be apparent to those skilled in the art and are embraced within the scope of our invention. With regard to the construction of the central conduit, this conduit, although preferably straight, may terminate in large radius bends adapted to permit free movement of the magnets therethrough and extending through the sidewall of the outer shell. With regard to the construction of the magnet train, this may comprise a series of hollow cylindrical or sleevelike magnets, the centers of which are packed with wood,

plastic or other easily workable material into which hooks are screwed or otherwise inserted, the hooks engaging each other to link the magnetic sleeves together, thereby forming a train. Alternatively, the magnet train may comprise other belt-like carrier means such as a ribbon, tape, belt or chain with the magnets fixedly attached thereto. Alternatively, the magnet train may take the form of a reciprocable rod driven by a pneumatic or hydraulic piston; such piston may have a dual speed capability providing a slow speed for the forward or particle sweep stroke, and a high speed for the return stroke during which no appreciable sweeping action can occur. Our apparatus may be employed to purify gas, vapor or mixed phase streams as well as liquid streams, and may be mounted in a vertical or inclined position as well as the horizontal.

Where a larger capacity apparatus is desired, the magnetic particle collector of our invention may comprise a plurality of magnet tubes mounted in parallel within a single shell in the manner of a shell and tube heat exchanger, with a magnet train running through each of said tubes. An alternative arrangement is to provide a second shell around the return run of the magnet train, e.g., in FIGURE 1 for example, around the guard tube 24, and to split the feed stream into two streams, one entering each shell. The relative motion of liquid flow and the magnetic field may be cocurrent in both shells, or countercurrent in both shells, or cocurrent in one shell and countercurrent in the other shell.

The invention may be practiced by other types of apparatus. -For example, instead of a traveling train of permanent magnets, one may utilize a series of stationary spaced electromagnets, disposed either within a central conduit or along the exterior of the outer shell, driven by a suitable timing circuit to provide a stepping magnetic field. In another form of apparatus, a series of permanent magnets may be mounted around the rim of a rotating wheel, with the separation chamber comprising a hollow :arcuate shroud surrounding a portion of the periphery of the wheel; a second magnet wheel rotating in the opposite direction adjacent to the first wheel may be used to pick up the particles collected in the shroud and sweep them through a back-flushed conduit to a storage chamber.

We claim as our invention:

1. A magnetic particle collector comprising:

( 1) a casing adapted to contain a fluid stream;

(2) spaced fluid inlet and outlet means connecting with said casing;

(3) a non-magnetic open-ended conduit supported within said casing adjacent to said inlet and outlet means, both ends of the conduit extending through the casing to the exterior thereof;

(4) a magnet train within said conduit comprising a series of longitudinally arranged permanent magnets constructed and arranged to travel in unison therethrough;

(5) drive means coupled to said magnet trains to effect movement thereof through said conduit;

(6) means defining a particle collection zone within said casing; and

(7) means to remove particles from said collection zone.

2. The apparatus of claim 1 further characterized in that said casing comprises an elongate shell, said fluid inlet and outlet means are longitudinally spaced with respect to said shell, and said open-ended conduit extends lengthwise through said shell.

3. The apparatus of claim 2 further characterized in that said magnet train comprises an endless belt-like carrier adapted to travel longitudinally within said conduit in a forward direction and outside of said shell in the reverse direction, said magnets being carried by and substantially uniformly spaced along the length of the carrier.

4. The apparatus of claim 3 further characterized in that said drive means is 'a rotary drive means operatively engaging said carrier and effecting continuous unidirectional movement of said magnet train through said conduit.

5. A magnetic particle collector comprising:

(1) an elongate shell adapted to contain a fluid stream;

(2) a fluid inlet line connecting with one end portion of said shell, a particle drain line connecting with the other end portion of said shell, and a fluid outlet line conecting with an intermediate portion of said shell;

(3) transverse perforate bafile means mounted within the shell between said fluid outlet line and said particle drain line to define a particle collection zone in said other end portion of said shell;

(4) a non-magnetic, substantially straight, open-ended conduit supported within said shell opposite said inlet and outlet lines and said drain line and extending lengthwise through said baffie means and said shell and both ends thereof;

(5) a magnet train within said conduit comprising a series of longitudinally arranged permanent magnets constructed and arranged to travel in unison longitudinally through said conduit in a forward direction and outside of said shall in the reverse direction; and

(6) drive means operatively engaging said magnet train for effecting continuous unidirectional movement thereof through said conduit.

6. The apparatus of claim 5 further characterized in that said perforate baffle means comprises a plurality of longitudinally spaced plate members.

7. The apparatus of claim 5 further characterized in that a baclcfiush line connects with said other end portion of said shell.

8. The apparatus of claim 5 further characterized in that said magnet train comprises an endless loop of flexible non-magnetic tubular braiding maintained under tension, said magnets being carried within the tubular braid ing and gripped by the braiding wall under tension whereby to inhibit displacement of the magnets relative to the braiding and said magnets being substantially uniformly spaced along the length thereof.

9. The apparatus of claim 8 further characterized in that a short length of said tubular braiding includes at least one non-magnetic spacer member instead of a magnet.

10. The apparatus of claim 5 further characterized in the provision of means to vent gas from said particle collection zone.

11. The apparatus of claim 5 further characterized in that said open-ended conduit is formed of stainless steel.

12. The apparatus of claim 5 further characterized in that a holding magnet is disposed exteriorly of said shell close to the wall thereof and adjacent to said other end portion of the shell.

'13. The apparatus of claim 5 further characterized in that a short length of said magnet train includes at least one non-magnetic spacer member instead of a magnet.

'14. The apparatus of claim 5 further characterized in that said perforate bafile means comprises at least one eccentrically bored orifice plate, the bore thereof being of larger size than said conduit, and the conduit extending through the bore in contact with a portion of the perimeter of the bore.

15. The apparatus of claim 5 further characterized in that said series of magnets are arranged so that adjacent poles of any two adjacent magnets are of like polarity.

References Cited UNITED STATES PATENTS 453,317 6/1891 Townsend 2 10-222 X 2,688,403 9/ 1954 Anderson 210222 2,717,080 9/1955 Anderson 210-222 2,759,606 8/1956 Nippert 210222 3,121,683 2/1964 Fowler 210-223 FOREIGN PATENTS 1,128,821 5/ 1962 Germany.

151,749 7/1962 U.S.S.R.

REUBEN FRIEDMAN, Primary Examiner.

W. S. BRADBURY, Assistant Examiner.

U.S. Cl. X.R.