CA1145243A - Suppression of respirable dust - Google Patents
Suppression of respirable dustInfo
- Publication number
- CA1145243A CA1145243A CA000387057A CA387057A CA1145243A CA 1145243 A CA1145243 A CA 1145243A CA 000387057 A CA000387057 A CA 000387057A CA 387057 A CA387057 A CA 387057A CA 1145243 A CA1145243 A CA 1145243A
- Authority
- CA
- Canada
- Prior art keywords
- foam
- particles
- bubbles
- dust
- contact
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Landscapes
- Separation Of Particles Using Liquids (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
This invention suppresses dust, and particularly respirable dust, by preventing the dust from becoming airborne at locations where it could escape from the dusty material with which it is associated, for example, at transfer points and other locations where the respirable dust can be released into the surrounding atmosphere. Foam, having bubbles small enough to be broken by respirable dust particles, is brought in con-tact with the respirable dust where small bubbles, small enough to be bursted by respirable dust particles, are imploded and the bubbles wet the dust particles and cause adherence of the particles to adjacent surfaces, such as other foam or other parts of the dusty material. The foam may be discharged into dusty material at transfer points where the dusty material falls by gravity and thereby opens up spaces between portions of the material which are at zero gravity as a result of their free fall.
This invention suppresses dust, and particularly respirable dust, by preventing the dust from becoming airborne at locations where it could escape from the dusty material with which it is associated, for example, at transfer points and other locations where the respirable dust can be released into the surrounding atmosphere. Foam, having bubbles small enough to be broken by respirable dust particles, is brought in con-tact with the respirable dust where small bubbles, small enough to be bursted by respirable dust particles, are imploded and the bubbles wet the dust particles and cause adherence of the particles to adjacent surfaces, such as other foam or other parts of the dusty material. The foam may be discharged into dusty material at transfer points where the dusty material falls by gravity and thereby opens up spaces between portions of the material which are at zero gravity as a result of their free fall.
Description
BACKGROUND AND SIlMMARY OF THE I2~VENTION
The term ~foam", as used herein, designates a mixture . . .
of liquid, gas, and a surfactant ~hat gives the liquid a film strength which permits the forma~ion of long lasting bubbles when the mixture is agitated to con~er~ it into a mass of bubbles. The liquid used is normally water, and the gas is usually air, because these ingredients are of low cost, but
The term ~foam", as used herein, designates a mixture . . .
of liquid, gas, and a surfactant ~hat gives the liquid a film strength which permits the forma~ion of long lasting bubbles when the mixture is agitated to con~er~ it into a mass of bubbles. The liquid used is normally water, and the gas is usually air, because these ingredients are of low cost, but
2~ bther gas and/or liquid can be used when compatible with the fiur actant. ~ ~
Various compounds are used as surfactants, and these can be purchased on the open market. Some of these compounds are proprietary. The strength of the film depends upon the characteristics of the surfactant, and the amount of the sur-factant in the liquid-gas mixture, as will be more fully explained.
In order to have small particulate matter efficiently trapped, it is necessary for the particle to contact with a bubble of the foam and burst the bubble. As the bubble bursts, the gas in the bubble escapes; the bubble implodes; and the liquid film of which the bubble was made coats the particle.
Small particles do not burst large bubbles and are not wetted or trapped by the foam. The smaller the bubble, the smaller the particles that can be trapped. This invention traps all detectable particles as a result of smaller buhbles made with higher strength foam.
The foam described in this specification has the bubbles burst by contact with small particles of material (dust) and the bursting bubble wets the particle. Particles as small as one micron are readily wetted. As this effect proceeds, the foam is destroyed by contact with the particles. The wetted particles must then be either 1) brought together, 2) made to contact larger particles, or
Various compounds are used as surfactants, and these can be purchased on the open market. Some of these compounds are proprietary. The strength of the film depends upon the characteristics of the surfactant, and the amount of the sur-factant in the liquid-gas mixture, as will be more fully explained.
In order to have small particulate matter efficiently trapped, it is necessary for the particle to contact with a bubble of the foam and burst the bubble. As the bubble bursts, the gas in the bubble escapes; the bubble implodes; and the liquid film of which the bubble was made coats the particle.
Small particles do not burst large bubbles and are not wetted or trapped by the foam. The smaller the bubble, the smaller the particles that can be trapped. This invention traps all detectable particles as a result of smaller buhbles made with higher strength foam.
The foam described in this specification has the bubbles burst by contact with small particles of material (dust) and the bursting bubble wets the particle. Particles as small as one micron are readily wetted. As this effect proceeds, the foam is destroyed by contact with the particles. The wetted particles must then be either 1) brought together, 2) made to contact larger particles, or
3) brought into contact with a surface, which may be additional foam.
If the foam is injected into a free-falling aggregate (at a transfer point between belts, for example, or injected into a crusher along with the aggregate), the mechanical motion of the aggregate will provide the required particle-to-particle contact. When the foam is injected into an aggregate which is all fines (one to two hundred micron), some means must be provided to cause the wetted particles to coalesce. This is readily accomplished by use of a cyclone.
Another advantage of small bubble foam is that it can be ejected from nozzles at considerable pressure and resulting high velocity. This will be explained more fully in the des-cription of the preferred embodiment.
According to a broad aspect the invention relates to a method of preventing respirable dust and other particulate matter from becoming airborne, which method comprises causing contact of the particular and the outside surfaces of foam, which is made of water, surfactant and air and which has bubbles of an average size less than .015 inch in diameter when in contact with the particles, wetting the particles by implosion of the foam bubbles which are burst by contact with the particles, trapping the wetted particles on the surfaces of adjacent material and carrying the wetted particles away from the zone on said adjacent material.
Other objects, features and advantages of the inven-tion will appear or be pointed out as the description proceeds.
BRIEF DESCRIPTION OF DRAWINGS
In the drawing, forming a part hereof, in which like reference characters indicate corresponding parts in all the views-Fig. 1 is a diagrammatic sectional view showing a foamgenerator for making small bubble foam which is used with this invention;
Figure 2 is a diagrammatic view showing a cyclone separator e~uipped with a foam supply and with means for withdrawing particulate matter from the cyclone chamber in a foam slurry;
Fig. 3 is a sectional view taken on the line 3-3 of Fig. 2; and Fig. 4 is a diagrammatic view of a transfer point for dust-laden material with foam projected into the transferring material. _ 4 _ DESCRIPTION OF PREFERRED EMBODIMENT
. . . _ . ~
The mixture used for this invention is preferably a mixture of air, water and a surfactan~ that is made for "high expansion foam." Such a foam has a high expansion ratio when the foam is developed by conventional fire equipment; that is, an ultimate volume of foam which is from 100 to 1000 times, or more, of the volume of the water and surfactant from the foam is formed~
If the foam is injected into a free-falling aggregate (at a transfer point between belts, for example, or injected into a crusher along with the aggregate), the mechanical motion of the aggregate will provide the required particle-to-particle contact. When the foam is injected into an aggregate which is all fines (one to two hundred micron), some means must be provided to cause the wetted particles to coalesce. This is readily accomplished by use of a cyclone.
Another advantage of small bubble foam is that it can be ejected from nozzles at considerable pressure and resulting high velocity. This will be explained more fully in the des-cription of the preferred embodiment.
According to a broad aspect the invention relates to a method of preventing respirable dust and other particulate matter from becoming airborne, which method comprises causing contact of the particular and the outside surfaces of foam, which is made of water, surfactant and air and which has bubbles of an average size less than .015 inch in diameter when in contact with the particles, wetting the particles by implosion of the foam bubbles which are burst by contact with the particles, trapping the wetted particles on the surfaces of adjacent material and carrying the wetted particles away from the zone on said adjacent material.
Other objects, features and advantages of the inven-tion will appear or be pointed out as the description proceeds.
BRIEF DESCRIPTION OF DRAWINGS
In the drawing, forming a part hereof, in which like reference characters indicate corresponding parts in all the views-Fig. 1 is a diagrammatic sectional view showing a foamgenerator for making small bubble foam which is used with this invention;
Figure 2 is a diagrammatic view showing a cyclone separator e~uipped with a foam supply and with means for withdrawing particulate matter from the cyclone chamber in a foam slurry;
Fig. 3 is a sectional view taken on the line 3-3 of Fig. 2; and Fig. 4 is a diagrammatic view of a transfer point for dust-laden material with foam projected into the transferring material. _ 4 _ DESCRIPTION OF PREFERRED EMBODIMENT
. . . _ . ~
The mixture used for this invention is preferably a mixture of air, water and a surfactan~ that is made for "high expansion foam." Such a foam has a high expansion ratio when the foam is developed by conventional fire equipment; that is, an ultimate volume of foam which is from 100 to 1000 times, or more, of the volume of the water and surfactant from the foam is formed~
- 4 a -~5~'~3 While the present inVention uses a surfactant of this type in order to obtain great film strength, the expansion ratio is reduced by the fact that the foam is made with small bubbles.
Bubble formation in making foam with my equipment is the result of vortex effect in a passage. The boundary layer of the un-foamed mixture drags on the sides of the passage, and the smallex the passage, the more the turbulence and vortex action. -Fig. 1 is a diagrammatic sectional view of apparatus for making the small bubble oam of this invention. The mixture of water, air and surfactant ("foaming agent") is forced by the pump 10 into a foamer 12 which contains a cartridge pad 14.
This pad 14 has a myriad of small interconnecting interstices. It may be a sponge made of polyurethane or other plastic; but the preferred structure is a stainless steel scouring pad sold under the trademark "CHORE BOY" and manufac tured by Metal Textile Co., P.O. Box 315, South Bound Brook, New Jersey, 08B80.
One or more of these pads 14 are stuffed into the hollow interior of the container 12 until the full cross-section of the container is evenly filled across one end of the interior of the container, as shown in Fig. 1. A perforated partition 16 in the container is positioned to divide the container into a pad chamber 18 and a foam chamber 20. The small bubble size is obtained by pushing the unfoamed mixture through a myriad of tortuous passages under sufficient pressure to obtain a high velocity that will result in the small foam bubbles.
With the CHORE BOY scouring pad 14 stuffed into the chamber 18 of the container 12, with a diameter "D" of three inches, and with the scouring pad of an axial length of approxi-mately three inches, the foam should be discharged rom an outlet22 at the rate of from five to ten cubic feet per minute in order
Bubble formation in making foam with my equipment is the result of vortex effect in a passage. The boundary layer of the un-foamed mixture drags on the sides of the passage, and the smallex the passage, the more the turbulence and vortex action. -Fig. 1 is a diagrammatic sectional view of apparatus for making the small bubble oam of this invention. The mixture of water, air and surfactant ("foaming agent") is forced by the pump 10 into a foamer 12 which contains a cartridge pad 14.
This pad 14 has a myriad of small interconnecting interstices. It may be a sponge made of polyurethane or other plastic; but the preferred structure is a stainless steel scouring pad sold under the trademark "CHORE BOY" and manufac tured by Metal Textile Co., P.O. Box 315, South Bound Brook, New Jersey, 08B80.
One or more of these pads 14 are stuffed into the hollow interior of the container 12 until the full cross-section of the container is evenly filled across one end of the interior of the container, as shown in Fig. 1. A perforated partition 16 in the container is positioned to divide the container into a pad chamber 18 and a foam chamber 20. The small bubble size is obtained by pushing the unfoamed mixture through a myriad of tortuous passages under sufficient pressure to obtain a high velocity that will result in the small foam bubbles.
With the CHORE BOY scouring pad 14 stuffed into the chamber 18 of the container 12, with a diameter "D" of three inches, and with the scouring pad of an axial length of approxi-mately three inches, the foam should be discharged rom an outlet22 at the rate of from five to ten cubic feet per minute in order
-5-52~3 to have the necessary velocity through the foaming pad 14 to produce the small bubbles required by this invention. This example is given merely by way of illustration. The mixture supplied to the foamer 12 has water equal to from 1 to 4% of the volume of the air and the surfactant is from 1 to 6~ of the volume of the water and preferably 2%. The expansion ratio of the foam may be from 25 to 100.
Expansion Ratio -Vol. gas Vol. liquid Suitable surfactants can be purchased from suppliersof fire-fighting foam as listed in the yellow pages of the telephone directory of any city of moderate size. It can also be obtained from the DeTer Company, Inc., of Mountain Lakes, New Jersey.
Conventional foams can flow by gravity and can be pushed through passages if the pressure is low. High velocity foam has to have considerable pressure behind it, and this is possible with foam having very small bubbles but cannot be used for large bubble foam because the bubbles collapse. Thus small bubble foam can be penetrated into a dusty mass of material such as at material transfer points already described. The equipment shown in Fig. 1 will produce foam having bubbles between .0005 and .015 inch. This will trap particulate matter as small as 1 micron in diameter and ~arry large pieces up to 1 inch in size. The foam can effectively trap such small par-ticles if the average size of the foam bubbles in less than .015 inch; but the same amount of foam will trap more particles if all of the bubbles are smaller than .015 inch and preferably between .0005 and .015 inch, as already described.
r,~43 The outlet 22 of the fo~mex 12 has a flexible pipe or hose 24 leading to a nozzle 26 from which foam 27 is discharged under substantial velocity for permeation through a mass of dusty . material at a transfer point or other location where the material is in motion, and dust would be discharged into the ambient atmosphere if the foam 27 were not used to suppress the dust.
Fig. 2 of the drawing shows a cyclone separator 30 which has a frusto-conical separation chamber 32 with a wall 34 that extends downward to an opening 36.
-. 10 Gas, laden with particulate matter, flows into the chamber 32 from a passage 40 at the upper end of the chamber 32.
This passage 40 is positioned to discharge its gas stream tangentially around the circumference of the upper part of the chamber 32 and in contact with the wall 34.
The passage 40 discharges gc3s into the separation chamberr which has a cover 35 and the gas flows downwardly with a swirling movement and increasing velocity as the cross-section of the separation chamber decreases. Particulate matter in the gas is thrown outward by centrifugal force, and the gas, separated from its particulate matter, reverses its Xlow at the center region of the separation chamher and flows upward to an outlet discharge 44 which extends upward through the top of the chamber and in substantial alignment with the axis of ~he chamber 32~ The construction and operation of the cyclone separator, thus far described, is in accordance with conventional practice.
This invention introduces foam into the particulate laden gas stream~ In the illustrated embodiment, the foam is injected into the gas stream by a nozzle 46 which extends into the gas inlet passage 40 upstream fro~ the outlet of this passage 40 where the gas flows into the separation chamber 32. The ~5i~3 foam traps the particulate matter and forms, with the particu-late matter, a slurry.
The coating of slurxy, indicated by the reference : character 48, on the wall of the separation chamber is indicated in elevation by stippling in the drawing and i5 shown in section where the wall 34 is shown in section. The slurry 48 runs down the wall and accumulates in the lower part of the separa-tion chamber 32 at the opening 36 which is normally closed by a ` bottom 50.
5~L3~ .;
In the c~nstruction illustrated, the bot~om 50 ;.s supported from the wall 34 b~ a bracket 52 to which the b~ttom is connected by a hinge comprisins a pin 54 ~7hich extends : through one 5i~e of the bottom 50 and through aligned openings S in the brac~et 52. A spring 56 is connected at one en~ to the bracket 52,.and the other end of the spring 56 contacts ith the bottom 50 to hold the bottom in a position to close the op~ning 36, as indicated in full lines in Fig.2. When sufficient ~7eight ~f slurry accumulates in ~he lower end ~f ln the separation cham~er 32, the weight of the slur~y overcomes the force of the spring 56 and causes the bottom ~0 to swiny into an open position, as indicated in dotted lines in ~ig~ ~.
The accumulated slurry drops out of the chamber, and the spxiny 56 pushès the bottom 50 back into closed position.
1~ A foam generator 60 supplies the nozzle ~6. ~oam generators are well-known, and the :block diagram of Fig. 2 is sufficient for a complete understanding of this invention.
Water, air and foaming.ag~nt are supplied to the foamer 60 ~rom a mixer 62; and the water, air and-~oaming agent are supplied to the mixer 6~ through pipes 6~, 65 and 66, re-spectively.
Each of the pipes 64, 65 and 66 is shown ~Jith a ~àlve 68 for regulating the supply of water, air or foaming agent, and the proportions in which these ingredients are supplied to the mixer 62~ These valves 68 are merely repre-sentatiYe of means for controlling the supply o~ the ingre-dients to the mixe- 62 and for proportioning the ingredients.
~9-- .
5f~
.
.
~lore elaborate controls for t~e ingredients supplied to the mixers 62 can be used, such as fluid flow regulators that rec~ive flui~ at variable pressure and - deliver it at a uniform pressure and/or flow. Tnese controls are adjustable to regulate the pro~ortions supplied to a mixer. Such controls are also well-known,~nd ~he particulax apparatus used for controlling the ~low and proportions of the ingredients is a matter of choice ~xperie*ce has shown that it is not essential to .:
supply foam continuously to the separator. It is sufficient that the wall of the separation chamber be at least.partially coated with foam at all times. In order to conserve foa~, a control valve 70 is located bet~een the mixer and the foamer ~or shutting off the mixture at times when no foam is required.
. In order to program the sup21y of foam with the opera.ion of the cyclone separator of a cycle timer 72 control~
a po-~er supply to a solenoid or other actuator 7a for the valve 70. The cycle timer 72 opens.and closes the ~alve 70 periodically and for such length of time as necessary to maintain th~ required amount of foam in the separation chamber . In accordance with conven~ional practice, the gas and par~iculate matter is supplied to the separa~or by a centrifugal blower 76 or other apparatus for moving the air and solids.
~52~
., .
Fig. 4 shows a belt conveyor ~0 ~hich transfers coal 82i or other dusty material, to truc~ 86. As the coal falls into the truck 86, dust would float off into the ambient atmosphere; and the s,maller particles are the most objectionable because they are lighter and remain airborne for larger periods of time.
Fo~m nozzles discharye small bubble foam 90 into the moving mass of coal, and the foam contacts with the dust present in the fàlling coal. The dust particles burst the bubbles wlth ~hich they contact, and the implosion of the bursting bubble traps and coats the dust particles with ~he liquid of which the bubble was formed.
This traps the wetted particles on the sur~ace of adjacent mzterial. ~7ith broken dusty material, the dust is suppressed by projecting the small bubble foam into the broken material whi~e ~aid ma~erial is in motion.
~ere the transfer of dusty material from one support to another is by free fall to the other support, the small bubble foam is projec~ed into the material to trap ~he dust thereo~ while larger particles of the material are separated from one another as a result of the free fall.
The preferxed embodiment of this invention has been illus rated and described, but changes and modifications can be made, and some features can be used in different combinations without departing from the invention as de-fined in the claims.
Expansion Ratio -Vol. gas Vol. liquid Suitable surfactants can be purchased from suppliersof fire-fighting foam as listed in the yellow pages of the telephone directory of any city of moderate size. It can also be obtained from the DeTer Company, Inc., of Mountain Lakes, New Jersey.
Conventional foams can flow by gravity and can be pushed through passages if the pressure is low. High velocity foam has to have considerable pressure behind it, and this is possible with foam having very small bubbles but cannot be used for large bubble foam because the bubbles collapse. Thus small bubble foam can be penetrated into a dusty mass of material such as at material transfer points already described. The equipment shown in Fig. 1 will produce foam having bubbles between .0005 and .015 inch. This will trap particulate matter as small as 1 micron in diameter and ~arry large pieces up to 1 inch in size. The foam can effectively trap such small par-ticles if the average size of the foam bubbles in less than .015 inch; but the same amount of foam will trap more particles if all of the bubbles are smaller than .015 inch and preferably between .0005 and .015 inch, as already described.
r,~43 The outlet 22 of the fo~mex 12 has a flexible pipe or hose 24 leading to a nozzle 26 from which foam 27 is discharged under substantial velocity for permeation through a mass of dusty . material at a transfer point or other location where the material is in motion, and dust would be discharged into the ambient atmosphere if the foam 27 were not used to suppress the dust.
Fig. 2 of the drawing shows a cyclone separator 30 which has a frusto-conical separation chamber 32 with a wall 34 that extends downward to an opening 36.
-. 10 Gas, laden with particulate matter, flows into the chamber 32 from a passage 40 at the upper end of the chamber 32.
This passage 40 is positioned to discharge its gas stream tangentially around the circumference of the upper part of the chamber 32 and in contact with the wall 34.
The passage 40 discharges gc3s into the separation chamberr which has a cover 35 and the gas flows downwardly with a swirling movement and increasing velocity as the cross-section of the separation chamber decreases. Particulate matter in the gas is thrown outward by centrifugal force, and the gas, separated from its particulate matter, reverses its Xlow at the center region of the separation chamher and flows upward to an outlet discharge 44 which extends upward through the top of the chamber and in substantial alignment with the axis of ~he chamber 32~ The construction and operation of the cyclone separator, thus far described, is in accordance with conventional practice.
This invention introduces foam into the particulate laden gas stream~ In the illustrated embodiment, the foam is injected into the gas stream by a nozzle 46 which extends into the gas inlet passage 40 upstream fro~ the outlet of this passage 40 where the gas flows into the separation chamber 32. The ~5i~3 foam traps the particulate matter and forms, with the particu-late matter, a slurry.
The coating of slurxy, indicated by the reference : character 48, on the wall of the separation chamber is indicated in elevation by stippling in the drawing and i5 shown in section where the wall 34 is shown in section. The slurry 48 runs down the wall and accumulates in the lower part of the separa-tion chamber 32 at the opening 36 which is normally closed by a ` bottom 50.
5~L3~ .;
In the c~nstruction illustrated, the bot~om 50 ;.s supported from the wall 34 b~ a bracket 52 to which the b~ttom is connected by a hinge comprisins a pin 54 ~7hich extends : through one 5i~e of the bottom 50 and through aligned openings S in the brac~et 52. A spring 56 is connected at one en~ to the bracket 52,.and the other end of the spring 56 contacts ith the bottom 50 to hold the bottom in a position to close the op~ning 36, as indicated in full lines in Fig.2. When sufficient ~7eight ~f slurry accumulates in ~he lower end ~f ln the separation cham~er 32, the weight of the slur~y overcomes the force of the spring 56 and causes the bottom ~0 to swiny into an open position, as indicated in dotted lines in ~ig~ ~.
The accumulated slurry drops out of the chamber, and the spxiny 56 pushès the bottom 50 back into closed position.
1~ A foam generator 60 supplies the nozzle ~6. ~oam generators are well-known, and the :block diagram of Fig. 2 is sufficient for a complete understanding of this invention.
Water, air and foaming.ag~nt are supplied to the foamer 60 ~rom a mixer 62; and the water, air and-~oaming agent are supplied to the mixer 6~ through pipes 6~, 65 and 66, re-spectively.
Each of the pipes 64, 65 and 66 is shown ~Jith a ~àlve 68 for regulating the supply of water, air or foaming agent, and the proportions in which these ingredients are supplied to the mixer 62~ These valves 68 are merely repre-sentatiYe of means for controlling the supply o~ the ingre-dients to the mixe- 62 and for proportioning the ingredients.
~9-- .
5f~
.
.
~lore elaborate controls for t~e ingredients supplied to the mixers 62 can be used, such as fluid flow regulators that rec~ive flui~ at variable pressure and - deliver it at a uniform pressure and/or flow. Tnese controls are adjustable to regulate the pro~ortions supplied to a mixer. Such controls are also well-known,~nd ~he particulax apparatus used for controlling the ~low and proportions of the ingredients is a matter of choice ~xperie*ce has shown that it is not essential to .:
supply foam continuously to the separator. It is sufficient that the wall of the separation chamber be at least.partially coated with foam at all times. In order to conserve foa~, a control valve 70 is located bet~een the mixer and the foamer ~or shutting off the mixture at times when no foam is required.
. In order to program the sup21y of foam with the opera.ion of the cyclone separator of a cycle timer 72 control~
a po-~er supply to a solenoid or other actuator 7a for the valve 70. The cycle timer 72 opens.and closes the ~alve 70 periodically and for such length of time as necessary to maintain th~ required amount of foam in the separation chamber . In accordance with conven~ional practice, the gas and par~iculate matter is supplied to the separa~or by a centrifugal blower 76 or other apparatus for moving the air and solids.
~52~
., .
Fig. 4 shows a belt conveyor ~0 ~hich transfers coal 82i or other dusty material, to truc~ 86. As the coal falls into the truck 86, dust would float off into the ambient atmosphere; and the s,maller particles are the most objectionable because they are lighter and remain airborne for larger periods of time.
Fo~m nozzles discharye small bubble foam 90 into the moving mass of coal, and the foam contacts with the dust present in the fàlling coal. The dust particles burst the bubbles wlth ~hich they contact, and the implosion of the bursting bubble traps and coats the dust particles with ~he liquid of which the bubble was formed.
This traps the wetted particles on the sur~ace of adjacent mzterial. ~7ith broken dusty material, the dust is suppressed by projecting the small bubble foam into the broken material whi~e ~aid ma~erial is in motion.
~ere the transfer of dusty material from one support to another is by free fall to the other support, the small bubble foam is projec~ed into the material to trap ~he dust thereo~ while larger particles of the material are separated from one another as a result of the free fall.
The preferxed embodiment of this invention has been illus rated and described, but changes and modifications can be made, and some features can be used in different combinations without departing from the invention as de-fined in the claims.
Claims (6)
1. The method of preventing respirable dust and other particulate matter from becoming airborne, which method comprises causing contact of the particulate and the outside surfaces of foam, which is made of water, surfactant and air and which has bubbles of an average size less than .015 inch in diameter when in contact with the particles; wetting the particles by implosion of the foam bubbles which are burst by contact with the particles; trapping the wetted particles on the surface of adjacent material and carrying the wetted particles away from the zone on said adjacent material; and characterized by transferring broken dusty material from one support to another, and suppressing the dust by projecting the small bubble foam into the broken material while said material is in motion and agitated by the transfer.
2. The method described in claim 1 characterized by trapping the wetted particles on the surfaces of the material or foam bubbles adjacent to those that have been bursted by the particles.
3. The method described in claim 1 characterized by causing the particles to contact with a foam having bubbles between .0005 and .015 inch in diameter at the time of the contact with the particles, and coordinating the rate of foam supply with the quantity of particles to maintain a supply of foam during the entire operation for preventing additional particles of dust from becoming airborne and as foam is destroyed by contact of the particles with the bubbles of the foam.
4. The method described in claim 1 characterized by trapping particulate matter of small size between 1 and 50 microns by bringing the particulate matter into contact with foam bubbles of a diameter between .0005 and .15 inch.
5. The method described in claim 1 characterized by the transfer including the discharge of the dusty material from one support by free fall to the other support, and projecting the small bubble foam into the material to trap the dust thereof while larger particles of the material are separated from one another as a result of the free fall.
6. The method described in claim 1 characterized by projecting the foam from a plurality of nozzles at different locations around the falling dusty material for obtaining penetration into the falling material from different sides far enough to reach into the center region of the falling material.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000387057A CA1145243A (en) | 1978-10-10 | 1981-09-30 | Suppression of respirable dust |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA313,008A CA1114281A (en) | 1978-10-10 | 1978-10-10 | Suppression of respirable dust |
| CA000387057A CA1145243A (en) | 1978-10-10 | 1981-09-30 | Suppression of respirable dust |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1145243A true CA1145243A (en) | 1983-04-26 |
Family
ID=25668788
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000387057A Expired CA1145243A (en) | 1978-10-10 | 1981-09-30 | Suppression of respirable dust |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1145243A (en) |
-
1981
- 1981-09-30 CA CA000387057A patent/CA1145243A/en not_active Expired
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