US3767918A

US3767918A - Multiple pass fluid irradiator with sediment removal capability

Info

Publication number: US3767918A
Application number: US00074014A
Authority: US
Inventors: C Graybeal
Original assignee: Individual
Current assignee: Individual
Priority date: 1970-09-21
Filing date: 1970-09-21
Publication date: 1973-10-23
Anticipated expiration: 1990-10-23

Abstract

The disclosure is directed to an irradiator for fluent materials wherein the same traverse a single flow path through the irradiator which flow path is repeatedly reversed. The reversing flow path is defined, in part, by a plurality of passages which are concentric with a source of radiation. Curved end walls are provided at opposite ends of each passage to repeatedly direct the flow path along different ones of the concentric passages past the source of radiation at varying radial distances therefrom and in substantially surrounding relation thereto. Conveyor means in the form of screw conveyors are embedded in each passage wall for the intermittent or continuous removal of sediment derived from the fluent material traversing the flow path.

Description

United States Patent 1 Graybeal [451 Oct. 23,1973

[ 1 MULTIPLE PASS FLUID IRRADIATOR WITH SEDIMENT REMOVAL CAPABILITY [22] Filed: Sept. 21, 1970 [211 App]. No.: 74,014'

521 u.s;c| .,...'.'..250/433,25014 25008 H Primary Examiner-James W. Lawrence Assistant Examiner-Harold A. Dixon Attorney-Colton and Stone [57] ABSTRACT The disclosure is directed to an irradiator for fluent materials wherein the same traverse a single flow path through the irradiator which flow path is repeatedly reversed. The reversing flow path is defined, in part, by a plurality of passages which are concentric with a source of radiation. Curved end walls are provided at opposite ends of each passage to repeatedly direct the flowpath along different ones of the concentric passages past the source of radiation at varying radial distances therefrom and in substantially surrounding relation thereto. Conveyor means in the form'of screw conveyors are embedded in each passage wall for the intermittent or "continuous removal of sediment derivedfrom the fluent material'traversing the flow path.

10 Claims, 3 Drawing Figures P PATENIEI] It! 23 B13 SHEET 10F 2 mm mm INVENTOR CICERO R. GRAYBEAL aiw/lzz ATTORNEYS.

INVENTOR CICERO R. GRAYBEAL SHEET 2 BF 2 PATENIED 0U 23 8 75 m a: v v N am ATTORNEYfi.

MULTIPLE PASS FLUID IRRADIATOR WITH SEDIMENT REMOVAL CAPABILITY BACKGROUND OF THE INVENTION monomers; and as a sterilizing process step in the re-' processing of chicken manure.

The apparatus conventionally used to irradiate fluent materials provides a source of radiation past which the material being treated is caused to flow either in surrounding relation thereto or adjacent one side thereof. In either event, the complete radiation dosage must be absorbed in a single pass of the treated material past the source. Where a high dosage is required, the same is achieved by increasing the source strength, decreasing the fluent material flow rate or providing an elongated source to increase the time interval during which the material undergoes treatment. Although it is apparent that precise control of the above factors may result in a predetermined overall dosage being applied to the treated material, the disadvantages associated with apparatus constructed in accordance with known practices are many.

One of the more obvious disadvantages is in the fact that, in most cases, the fluent material is not uniformly irradiated. In the absence of some means of agitating the material as it flows past the source, that part of the flow stream adjacent the source receives a greater dosage than that remote from the source. This is particularly true where the irradiator is relatively small and a large dosage is required. Even where conditions permit the use of a relatively long flow path in conjunctionwith an elongated source, that portion of the material in greater proximity to the source receives a harder dose than'theremaining portions of the stream. Present day efforts to achieve uniformity of irradiation nor mally'require the use of an external power source "to operate an agitator.

When the radiation source is radioactive, heavy shielding is required to absorb that radiation which passes through the material undergoing treatment. Because of the fact that known single pass irradiators may, at different times, require sources having varying degrees of penetration, the outer shielding must be sufficiently heavy to shield any source contemplated for a particular irradiator.

A further disadvantage in known irradiators, which is related to the shielding problem referred to above, is that the total energy of the source is not fully utilized.

tion of the treated material due to the relative positions of the source and flow path but also lack the capacity to provide uniform flow through the same due to the flow path configuration.

There are many materials which require a low initial dose of radiation followed by a subsequent maximum dosage while others require a heavy initial dose which decreases to a minimum. Present day irradiators lack the capacity to meet these demands in a single irradiator.

In any irradiator construction adapted for the processing of materials of the type referred to above, it is critical thatmeans be provided for the removal of sediment. This is particularly true where a radioactive source is used because of the health hazards incident to the cleaning of the same as by disassembly or the like. The use of the irradiator for sewage treatment and in the reprocessing of chicken manure are typical of those uses where sludge or settlement tend to build up very quickly to the point of rendering the irradiator incapable of maintaining a preprogrammed flow rate and, ulti- Thus, the radiation that passes'into the shielding is lost 'to useful work and no provision has been previously mately, to completely block the path of flow.

SUMMARY OF THE INVENTION It is a primary object of the invention to provide an irradiator for fluids that will permit maximum utilization of a radiation source in a manner insuring uniform irradiation of the material undergoing treatment and to provide for the independent removal of sediment from the irradiator.

It is among the further objects of the invention to provide an irradiator having an extremely long flow path in comparison to the dimensions of the source and the external dimensions of the irradiator; to provide an irradiator which is particularly adaptable for use with a radioactive source that requires minimal external shielding; to provide an irradiator whose-flow path configuration insures that the total volume of fluid is maintained in constant motion along the flow path; to provide an irradiator which has the inherentcapacity to provide either a high initial radiation dosage followed by a lower dosage or a low dosage followed by a high dosage merely by reversing the direction of fluid flow;

and to provide an irradiator which is admirably suited for the mixing of various fluent materials, especially chemicals, wherein some of the materials may be par- DESCRIPTION OF THE DRAWINGS DESCRIPTION OF THE PREFERRED EMBODIMENT One form of an irradiator 10 embodying principles of the present invention is depicted in FIG. 1 as including an elongated radioactive source 12 contained within the sealed interior of the innermost one of a plurality of concentric tubes 14 whose peripheral walls define a plurality of concentric flow passages 16, 18, 20, 22 suitably supported in housing 24 by conventional shielding 26. Any suitable support means, not shown, may be used to maintain the concentric relationship of tubes [4. Suitable supports 28 are provided for housing 24 which is traversed by

conduits

30, 32 communicating the exterior of housing 24 with inner and outer flow passages 16, 22, respectively.

Conduits

30 and 32 are in open fluid communication through a single reversing flow path which traverses concentric passages 16, 18, 20, 22. Communication between adjacent pairs of the concentric flow passages is alternately established and blocked at one end of the irradiator by end walls 34. End walls 36, at the other end of the irradiator, establish communication between those adjacent passages which are blocked by end walls 34 and block communication between those adjacent passages which are communicated by end walls 34. The result of this construction is to produce a reversing flow path of substantial length in relation to the dimensions of source 12.

A fluent material to be irradiated may be supplied through either of

conduits

30 or 32 and the irradiated material delivered to a point of use through the other of the conduits after traversing the single flow path through irradiator 10. The longer solid line arrows indicate the flow path followed by material introduced through conduit 30 and the broken arrows depict the alternate flow direction when conduit 32 is used as the supply line.

Because of the fact that the material undergoing treatment is constantly reversing its flow direction, at end walls 34 and 36, the material is kept in a constant state of agitation assuring that all portions of the fluent material are equally exposed to radiation. It will be apparent from an inspection of FIG. 1 that the material undergoing treatment substantially equally surrounds the source 12 which further contributes to the uniformity of radiation dosage and is of substantial importance in shielding the source. I

In known flow through irradiators, particularly where a hard dose is required, the enrgy output of source 12 exceeds that which can be absorbed by the material undergoing treatment. The present practice not only fails to utilize the source radiation fully but requires heavy shielding to absorb the excess radiation. By arranging the material flow path as disclosed in FIG. 1 to include any desired number of passes, not only is the radioactive source fully utilized but the material undergoing treatment, itself, acts as a shield permitting the use of less of the conventional shielding 26.

In those instances where it is desirable to expose the material to an initial hard dose subsequently diminishing to a minimum, the material to be treated is introduced through conduit 30 opening into inner passage 16 immediately adjacent the source. As the material reverses flow at one end and returns past the source through passage 18 it receives a lesser dose. During its passage through the outermost passage, the material receives its last and smallest dose before passing into delivery conduit 32. When it is desired to gradually increase the dosage, with time, the material to be treated is introduced through conduit 32 and follows the path indicated by the broken arrows to receive a hard dose on its last pass immediately adjacent the source before exiting through conduit 30.

It is, of course, obvious that any desired number of tubes 14 may be used to provide any desired number of passes for a particular application.

The irradiator is designed to be run full at all times and inflow will approximate outflow. The total dosage applied may be varied by varying the source strength, or by varying the fluent material flow rate to control total exposure time.

Although the cross-sectional areas of the concentric flow passages are illustrated as being substantially equal, these areas may be varied to that extent consistent with the requirement that inflow approximate outflow.

Conduits

30 and 32 may be so arranged in relation to irradiator 10 that the flow therethrough is by gravity and, under such conditions, no external power source is required to maintain the flow rate.

End walls 34 and 36 include curved wall portions 38 which insures smooth flow reversal and a uniform flow rate while eliminating any possibility of deposits collecting in the reversal areas.

With the passage of time and particularly in the case of certain treated materials, such as sewage, sediment tends to collect along the runs of the flow path from which it may be intermittently or continuously removed by conveyor system 40. A plurality of

screw conveyors

42, 44, 46, 48,having progressively longer flight sections, are housed within elongated recesses 50 formed integrally with the lower wall portion of each tube 14 as shown in FIG. 2. Alternate ones of the screw conveyors have oppositely directed flights so that sediment collecting in the innermost passage 16 is transferred to the right hand end thereof, as viewed in FIG. 1, whereupon it is delivered to the intake end 52 of the longer, underlying conveyor 44 for conveyance to the opposite end of the irradiator in conjunction with that sediment collected from passage 18. The transfer and reversal of collected sediment is continued, as indicated by the shorter solid line arrows 54, until the same reaches the delivery end 56 of the outermost conveyor 48 whereupon the same is delivered to a suitable removal area 58. It will be apparent that the flow path afforded by the conveyor 48 does not intersect the flow path of the conduit 32. Otherwise, all sediment would be washed off the screw conveyor 48 by fluent material passing through the conduit 32 so that the delivery end 56 and the removal area 58 would be useless. The conveyor shafts are journalled in opposite ends of the irradiator and rotation is imparted thereto in any suitable manner as by a motor, not shown, and flexible drive 60 in dirving engagement therewith.

In the formation of certain chemical compositions it is sometimes desirable to subject some of the components to more irradiation than others. Addditionally, thorough mixing or agitation of the component materials is usually required. The modified form of the invention, shown in FIG. 3, is particularly adapted for this purpose.

Conduits

30 and 32, not shown in FIG. 3, represent the supply and delivery lines, respectively, for a first fluent component which is to be given a hard dose of radiation and subsequently mixed with one or more additional fluent components that may be introduced via

conduits

62 or 64 having control valves 66. The additional component or components could be added or the mixture withdrawn at any point along the reversing flow path by providing additional conduits having appropriate valve controls and proportioning the cross sectional area of the flow path accordingly. Agitator 68, having an external power source 70, is positioned in the flow line to provide for additional mixing of the components.

The irradiator, in both forms of the invention, is provided with a removable end cap 72 for access to the source and, in the case of the embodiment shown in P16. 3, provides access tothe agitator.

The irradiator herein described may be made very small or quite large and permits full utilization of the radioactive source due to the fact that the material undergoing treatment is maintained for a relatively long period of time in surrounding relation to the source.

Any or all of the conduits communicating with the flow path through the irradiator may be provided with appropriate fluid pumps and control valves for maintaining a more accurate flow control rate.

The sediment which is removed by the conveyor system, in many instances, has utility as a raw. material. The utilization of that sedimentation removed during a sewage irradiation processas a raw fertilizer pl'odu'ct'is exemplary. For this reason it is' important that the conveyor system have the capability of insuring that'the sedimentary material by fully irradiated just as 'is the fluent material. Thus the conveyor flights are'so sized relative to. the permissible drive rates therefor that, by

sitioned within said flow path.

3. A self-shielding multiple pass fluid irradiator, comprising: a source of radiation, wall means defining a plurality of reversing flow passages concentric with said source, said wall means blocking communication between adjacent pairs of flow passages at one end of said irradiator and intercommunicating said adjacent pairs of flow passages at the other end of said irradiator, conduit means opening into the inner and outermost of said concentric passages, and means for removing sediment from each of said passages including a plurality of serial delivery conveyors, the discharge end of one of said conveyors extending outwardly of said irradiator;

4. A fluent material irradiator, comprising; a source of radiation, fluent material passage means adjacent said source defining a first path of material movement controlling the conveyor drive rate, the sedimentary material can be retained in the irradiatorfor as long or longer than thatperiod of time required for the fluent material to traverse the irradiator. In the-case of sewage treatment, for example, the conveyance time'ofthe sedimentary material will equal or exceed that of the .fluent material as maybe found necessary in a particular installation to insure the complete sterilization of both the fluent and sedimentary'material...

I claim: 7 g

l. A singleflowpath multiple pass fluent material. irradiator, comprising; a source of radiation, peripheral wall means defining at least three fluent flow passages concentric with said source, end wall means adjacent one end of said irradator intercommunicating the innermost two of said three flow passages, end wall means adjacent the other end of said irradiator intercommunicating the outermost of said two flow passages and the third flow passage, at least two conduits opening into separate ones of said flow passages for supply and delivery of fluent material to be irradiated to and from said irradiator, screw conveyor means in each of said passages defining a reversing flow path for sediment removal, and means for rotating said conveyorpast said source, means for separating sedimentary material from the fluent material, and conveyor means intercommunicating said passage means and an external area thereof and defining a second different path of 'rnaterial movement past said source for removing sedimentary material from said passage means and for irradiating said sedimentary material.

5. A method of simultaneously irradiating flowable and sedimentary material comprising; flowing said flowable material pasta source of radiation and concommunicating withthe interior of said housing, means defining a tortuous path of fluid flow between said first and second conduit means, a third conduit opening into s aid path of fluid flow. intermediate the ends thereof and communicating with the exterior of said housing and means for controlling the addition of an additional fluid component through said third conduit.

7. The irradiator of claim 6 including a power driven agitator in said path of fluid flow adjacent the third conduit. p

8. The irradiator of claim 6 wherein said path defining means includes means defining a plurality of concentric flow passages and means for reversing the direction of fluid flow at housing,

v 9. The irradiator of claim 8 wherein said source-of radiation lies on the axis of said concentric flow passages.

10. The irradiator of claim 8 wherein said means defining a'plurality] of concentric flowpassages includes opposite ends of the irradiator a plurality of concentric walls.

l l l l

Claims

1. A single flow path multiple pass fluent material irradiator, comprising; a source of radiation, peripheral wall means defining at least three fluent flow passages concentric with said source, end wall means adjacent one end of said irradator intercommunicating the innermost two of said three flow passages, end wall means adjacent the other end of said irradiator intercommunicating the outermost of said two flow passages and the third flow passage, at least two conduits opening into separate ones of said flow passages for supply and delivery of fluent material to be irradiated to and from said irradiator, screw conveyor means in each of said passages defining a reversing flow path for sediment removal, and means for rotating said conveyor means.

2. The irradiator of claim 1 including an agitator positioned within said flow path.

3. A self-shielding multiple pass fluid irradiator, comprising: a source of radiation, wall means defining a plurality of reversing flow passages concentric with said source, said wall means blocking communication between adjacent pairs of flow passages at one end of said irradiator and intercommunicating said adjacent pairs of flow passages at the other end of said irradiator, conduit means opening into the inner and outermost of said concentric passages, and means for removing sediment from each of said passages including a plurality of serial delivery conveyors, the discharge end of one of said conveyors extending outwardly of said irradiator.

4. A fluent material irradiator, comprising; a source of radiation, fluent material passage means adjacent said source defining a first path of material movement past said source, means for separating sedimentary material from the fluent material, and conveyor means intercommunicating said passage means and an external area thereof and defining a second different path of material movement past said source for removing sedimentary material from said passage means and for irradiating said sedimentary material.

5. A method of simultaneously irradiating flowable and sedimentary material comprising; flowing said flowable material past a source of radiation and concurrently separating sedimentary material therefrom into a flowable material rich portion and a sedimentary material rich portion, separately mechanically conveying said sedimentary material rich portion past said source, and limiting the rate of sediment conveyance to not exceed the flowable material flow rate.

6. A single flow path multiple pass fluid irradiator, comprising; an irradiator housing, a source of radiation within said housing, first and second conduit means communicating with the interior of said housing, means defining a tortuous path of fluid flow between said first and second conduit means, a third conduit opening into said path of fluid flow intermediate the ends thereof and communicating with the exterior of said housing and means for controlling the addition of an additional fluid component through said third conduit.

7. The irradiator of claim 6 including a power driven agitator in said path of fluid flow adjacent the third conduit.

8. The irradiator of clAim 6 wherein said path defining means includes means defining a plurality of concentric flow passages and means for reversing the direction of fluid flow at opposite ends of the irradiator housing.

9. The irradiator of claim 8 wherein said source of radiation lies on the axis of said concentric flow passages.

10. The irradiator of claim 8 wherein said means defining a plurality of concentric flow passages includes a plurality of concentric walls.