DE2223143A1 - Separating centrifuge - Google Patents

Description

ALEXANDER R. HERZFELD 6 fran kfurt α, μ.

LAWYER SORH, ENSTRASSE5 ₂

AT THE LAN DGERICHT FRAN KFURTAM MAY N

'f223H3

Applicant: United States Atomic Energy Commission Washington D. C, USA

Separating centrifuge

The invention relates to a centrifugal separator for separating Material components of small particle size, which are called aerosols or are contained in another suspended form in a gas stream.

Small-sized particles suspended as aerosol or the like, z. B. in the size range of a few / U or even smaller, which may also be radioactive, as constituents of exhaust gases, breathing air, etc., represent an increasing source of danger The determination of their concentration and size distribution is due to strong deviations in their shape and Homogeneity very difficult. The behavior of aerosol particles in gases, the air we breathe, and especially the internal airways living organisms depends on their so-called aerodynamic size. They are therefore not sorted according to their actual

209849/0111 - 2 - ■

ORIGINAL INSPECTED

-2- 2223H3

measurement or density but classified according to their so-called aerodynamic diameter, a measuring unit that is based on the real size, density or shape not necessarily corresponding settling speed of spherical particles of a given density in the air is based as a unit of comparison. . The study of such suspended matter in the atmosphere requires their exact aerodynamic Grosenklas si tion, z. B. for measurement of air pollution.

The object of the invention is a device suitable for this purpose simple, portable and easy to calibrate construction, which allows the individual components to be classified into easily analyzable and measurable form.

The object is achieved by the centrifugal separator of the invention, which is characterized in that the centrifuge rotor contains a channel that expands in a spiral shape from the center of the rotor, and a feeder contains the material to be separated in the middle of the rotor in the channel, a laminator one Gas flow from the center passes through the channel and the separated particles as separate classes in different places be knocked down along the canal.

The drawings are based on the further explanation.

- 3 - 209849/0111

-3- 2223U3

FIG. 1 shows the centrifugal separator according to the invention in a longitudinal section along the section line A-A of FIGS. 2 and 5;

FIG. 2 shows the centrifuge rotor and channel from above with the cover removed;

Figures 3 ″ and 3a show enlarged with the inventive Centrifuge used laminator or feeder;

FIG. 4a shows the feeder enlarged from the side;

FIG. 4b shows the feeder in section along the cutting line B-B of Figure 4a;

FIG. 5 shows a top view of the rotor arm with the carrier gas supply and removal;

FIG. 6 shows schematically the separate material components deposited at various points on the receiving device;

Figure 7 shows a diagram of the settling points of different component sizes at different centrifuge speeds.

The rotor 10 is equipped with a spiral-shaped channel 12, the configuration of which according to the invention to the desired Component separation of the input material contributes.

209849/0111 _ ₄ _

The rotor 10 is essentially cylindrical and the required passages and spiral channel can be machined from the solid cylinder block or he can be assembled from individual parts. The channel 12 can either be passed completely through the rotor material are, the rotor cover 14 and the rotor arm 16 the form the upper and lower boundaries of the channel or it can be partially guided through the rotor cylinder, wherein in the In the manner shown, material remains on the base of some rotor segments. The channel 12 is provided with an arcuate or curved, Inside wall running spirally from the rotor center outwards and forming at least part of the channel length 18 and an arcuate, spiral-shaped outer wall 20 running outwards with increasing distance from the inner wall educated. The inner and outer walls of the channel can be designed as real spirals or modifications of the spiral shape be; The only important thing is that the canal widens smoothly without any jagged transitions. When executing the walls 18 and 20 in a real spiral shape, the canal width expands evenly from the beginning to the end of the canal.

In the embodiment shown, the channel walls consist of arch segments, z. B. the inner wall 18 forms an arc of 180 ° and an arc of 276.1 / 2 ° with a larger radius, while the outer wall consists of an arc of 180 ° and a second bot gen of 180 ° with a larger radius, as well as a third arc

- 5 -209849/0111

of 96.1 / 2 ° with an even larger radius is built up »The radii are chosen so that a relative expansion from the initial width of the channel to the final width z. B. results in a ratio of 1: 3; other expansion ratios can also be selected within the limits of the overall rotor dimensions the separable particle region with some deterioration in resolution as the expansion ratio increases increases. The expansion ratio of 1: 3 represents a favorable compromise here.

The separated particles can be placed directly on the outer wall 20 of the channel 12 or collected on a film or plate or the like along the outer wall with suitable clip fastening 24 be knocked down. The film 22 consists, for. B. from a material ensuring the adhesion of the particles, which is suitable as a basis for particle analysis. Possibly Means for continuously taking one or more particle classes for continuous investigation can also be used are provided.

There are suitable recesses or mounting points at the beginning of the duct on the rotor 10 or the rotor cover 14 for inclusion a laminator 24 (FIG. 3) and a material feeder 26 (Fig. 4a and 4b) attached.

- 6 209849/0111

2223U3

The laminator 24 includes a channel 28 aligned with the beginning of the channel and an air or gas inlet groove 30 in the rotor 10. The channel 28 includes a plurality of thin strips or plates 32 attached to the laminator 24 in the channel 28. the Passages between the individual plates 32 are through their entire length, width and height of the same diameter, so that a laminar flow is generated at the beginning of the channel 12 will. The uniform expansion of the channel 12 keeps the laminar flow over the entire length of the channel as it decreases Gas velocity upright. To eliminate or reduce the appearance of turbulence due to irregularities of the channel walls 12, 28 at their joints, these two channels must be aligned with one another at the beginning of the channel 12. The recess 34 which receives and carries the laminator 24 The rotor 10 is shaped in such a way that the alignment of the channel 28 with the inlet 30 and the channel 12 is possible » The laminator strips can be made of stainless steel, brass or copper foil about 0.006 inches thick spaced about 0.05 inches apart and on the laminator 25 be attached by suitable adhesive or air means. The laminator body consists, for. B. from a block of material in which the channel 28 is incorporated or they are made of four correspondingly shaped and assembled parts according to FIG. The further smoothing and polishing the surfaces and joints is z. B. with a soft material such as lead or solder as a filler at the polishing points relieved.

2098A9 / 0111 _ _? _

-7 -. 2223U3

The material feeder 26 for the task of. to be examined Particles in the device are e.g. B. next to the laminator 24 in a recess 36 of the rotor 10 and is so shaped in such a way that a position relative to the channel 12 which ensures a gas flow that is as free from turbulence as possible in the channel 12 is possible. The feeder 26 contains a passage 38 which is aligned with the central axis of the rotor 10 and an inner wall 18 of the channel continuing, aligned with it and having the same radius as the first arc of the wall 18 as well as area 40 reaching up to the passage 38. A further part 42 of the feeder 26 forms part of the inner wall 18 of the channel 12 and ends shortly before the surface 40, so that a gap 44 connecting the passage 38 to the channel 12 is created. To simplify production, a segment of the feedthrough 38 and of the part 42 can be made from one on the feeder 26 as a filler piece attached separate component exist. The separating effect can also be changed by adding filler pieces can be used with different gap and passage sizes. Furthermore, the feeder can be manufactured in one piece or separately End plates 48 and 50 can be fitted into the Recesses 36 and 52 in the cover 14 fit. The part 42 is produced with smooth curved surfaces as far as possible and the inner wall 18, again in order to obtain the most turbulence-free flow possible.

209849/01 ι -j

-8- 2223H3

In addition, the part 42 is shaped so that the gap length 44 is as small as possible, preferably about 0.05 inches or less to avoid particle precipitation in this column. Because of the position of parts 42 and 40 to the inner wall 18, the gap 44 is preferably provided at such a point that the material particles in the implementation 38 and centrifugal forces acting in the gap as low as possible see Figures 4a and 4b.

As described in more detail in connection with FIG the gas through a passage 54 in the rotor arm 16 into the Inlet 30 and laminator 24 and channel 12 given while the material to be examined and separated through a bore 56 in the rotor cover into the implementation 38 arrive. Implementation 56 is with the implementation 38 and coupled to an inlet nozzle 58 for the material secured by the support 60 to the cover 14. In the embodiment shown, the nozzle rests on bearings 64 and 66 so that it does not rotate and the aerosol or other material e.g. B. can absorb from the atmosphere, e.g. B. from a particle feeder which is suitable Way of guiding the flow to the implementation 38 with a Bore is connected. In the case of small particles, a suitable carrier gas, e.g. B. Air through the bores and passages headed into the sewer.

- 9 - 2U9849 / 0111

The rotor 10 is by suitable means, bolts or the like attached to the rotor cover 14 and the carrier 16. The carrier 16 in turn rests on one over the drive system 80, the bearings 72, 74 · "and. 76" and the housing driven or supported shaft 70. The rotor arm 16 contains a tapered or otherwise suitably shaped, a correspondingly shaped piece of the shaft 70 adapted Drilling. Shaft 70 and carrier 16 can by suitable means, z. B. a thread groove 84 · be connected. The shaft 70 includes several equidistantly parallel and symmetrically arranged around the axis of the shaft and over several radial bores 88 with an annular groove 90 - in turn with the bore 54 in the carrier 16 and the air inlet 30 of the rotor 10 - connected bores 86, which suitably lie around the shaft 70, so that a balance is given, wherein the exposed end is clogged. The bores 86 are connected at their other end to an annular groove 92 of the ring 94, which in turn via radial lines 96 with an air inlet opening 98 in the base 78 is in connection. The ring 94 lies between bearings 72 and 74 and is opposite other parts as well as the atmosphere are sealed in this way. A suitable pressure filter system 100 is pure Air or gas through the opening 98 in the laminar flow into the Channel 12 routed.

- 10 209849/0111

2223H3

The carrier 16 and the shaft 70 can also be provided with a groove or recess 102 (see also FIG. 5) extending from the center of the shaft 70 to a point below the air or gas outlet chamber 104 at the widened channel end. Chamber 104 and groove 102 are connected to one _{another by a series of holes t} 106 in rotor 10 through the base or bottom wall of chamber 104. The gas flowing out of the chamber is filtered in a suitable manner in order to retain particles not precipitated along the outer wall 20 of the channel 12 in the filter 108 fastened on the bracket 110. The filter can consist of conventional filter material and can be omitted or removed if all the particles are retained on the wall 20. The gas freed from the suspended particles can be conducted through the groove 102 and a central bore 112 and passage 114 in the shaft, as well as an annular collector 116 similar to the ring 94, to an outlet opening 118 Lm base 78. The gas flow through the device can be increased and regulated by a pump 120 which not only draws clean air but also the aerosol sample from the bore 62 through the corresponding passages and so on.

A normal motor with single or variable speed is used as AnbrLeb 80. When examining similar samples can use a simple, cheaper motor without re-calibration

-IL- 2 0 ü H /, f) / Π! 1 1

2223H3

simple speed can be used. Through suitable Balancing of the rotor, a perfectly balanced centrifuge run is achieved.

As an example, FIG. 6 shows a material collection film with the class distribution of the precipitated particles. Each particle group is good and according to its aerosol characteristics exactly separated. In the exemplary embodiment, a centerpiece with a rotor with an outside diameter was used for separation of 7 ", an expanded spiral 18" long and 1.25 "high," with a total throughput of about 5 l / min, and a regulated aerosol supply of about 0.4 l / min., As well as a pure air supply of about 4.6 l / min, and a rotational speed of about 4,500 rpm. The first Particle band 124 contained particles with an aerodynamic diameter of 3 / rev, the other bands 126, 128, 130, 132, 134 particles with diameters of 2, 1, 0.8, 0.66, O.56 / U, with the first band about 5 cm from the beginning of the canal and the last tape came to lie 25 cm from the beginning of the sewer. Particle sizes below 0.35 / u were recorded as separate band classes on the filter 108. Particle precipitation is possible here from 5 or more / u to less than O.3 / u.

Figure 7 shows the influence of different centrifuge speeds, using the example of an aerosol throughput of around 0.4 l / min and a total air throughput of around

- 12 209849/0111

-! 2- 2223H3

5 l / min. Curves 136, 138 and 140 correspond to speeds of rotation from 4-500, 3000 and 1500 revolutions per minute. As the speed increases, precipitation occurs closer to the beginning of the spiral.

The speed of the aerosol supply is within the limits of the dimensions of the throughflow 38 and the gap 44 in the feeder 26 any, e.g. B. 1 - 1.5 l / min. An air can be from 5-25 l / min, with increasing supply for a given The speed of rotation limits the particle sizes that can be precipitated along a given film length. The centrifuge speed can be about 1 - 10,000 revolutions per minute or more and is preferably between 1500 - 6000, with higher speeds increasing the range of particle sizes. With a given clean air supply and a given At the speed of the centrifuge, the same classes are knocked down in the same places, so there is no calibration further possible.

During operation, the aerosol particles flow as a result of centrifugal force easily through the pure air flow and are deposited on the outer wall of the duct. When passing through the particles experience through the air flow depending on their size and other features have a different resistance and are so according to the different settling speed classified dejected in different places. the

- 13 2098A9 / 0111

_ ₁₃ - 2223U3

Laminar air flow distributes the particles depending on their respective aerodynamic diameter. Particle whose to small diameter the air flow is not allowed to cross are also reflected in separate bandwidths on the filter 108 at the channel output. Through the spiral Formation of the channel 12 act on the aerosols as the flow progresses through the channel, increasing centrifugal forces while the speed of the laminar air flow decreases steadily as a result of the channel widening. Both features cause the accumulation of particles with a relatively small aerodynamic diameter along a relatively short section of canal. The knocked down particles form a visible band with a substantially parabolic shape, corresponding to the dimensions of the column 45 in the material feeder 26th

The comparatively narrow, short particle bands make this possible easy analysis with known analysis methods, e.g. B. also radioactive measuring methods. The individual classes or Ribbons can be analyzed separately by cutting the strip in half. The narrow bandwidth and high particle concentration facilitates radioactive or other analysis. The design of the centrifuge also reduces material losses by precipitation in other places. The manufacture of the centrifuge is simple and inexpensive and can be

- IA- -209849/0111

2223Η3

Turning of components ζ. B. made of aluminum or other alloys can be manufactured with light weight and small size.

- 15 209849/0111

Claims (2)

2223U3 claims 1. Separating centrifuge, characterized in that the centrifuge rotor contains a channel (12) that expands in a spiral shape from the rotor center point, a feeder (26) puts the material to be separated into the channel at the center of the rotor, a laminator (24) passes a gas flow through from the center conducts the channel and precipitates the separated particles as separate classes at different locations along the channel will. 2. Separating centrifuge according to claim 1, characterized in that that the channel has an arched inner wall and an arched outer wall with a uniform expansion without any abrupt transitions. 5. Separating centrifuge according to claim 2, characterized in that the particle classes on one along the channel outer wall attached foil 'are knocked down. 4-, separating centrifuge according to claim 3, characterized in that that a filter is placed over the end of the duct. - 16 209849/0111 -ie- 2223U3 5. Separating centrifuge according to claim 2, characterized in that that the feeder has a feedthrough that is aligned with the center of the rotor and one that forms part of the inner wall of the duct on the latter Implementation "has beginning wall. 6. Separating centrifuge according to claims 1-5), characterized in that that the laminator contains several parallel plates aligned with the beginning of the channel. 7. Separating centrifuge according to claims 1-6, characterized in that the channel spirals once around the center of the rotor is led. 2 U 9 S A 9/0 1 1 1