CA1042279A - Method for controlling sulphur dust - Google Patents

Abstract

ABSTRACT
A process and apparatus are described which control and inhibit the generation of sulphur dust. Dry solidified sul-phur in the form of chunks, powder, flakes or slates is sprayed or wetted down with liquid sulphur. Sulphur dust that is generated and becomes air-borne is sucked off, and either returned to the dry system, or is melted, and then sprayed as liquid sulphur to "wet down" the dry solidified sulphur.
Contamination of the sulphur by other substances is mini-mixed; as is the loss of air-borne particles of sulphur into the atmosphere. Spraying of liquid sulphur is done at "transfer points" where dry solid pieces of sulphur are being handled, moved, conveyed or dumped from one location to another. Sulphur in liquid form sprayed onto the surface of dry pieces carried in open railway hopper cars is used, for example, to seal the surface against wind erosion. In a broad sense, the process can be applied to dry- solidified dust generating material that is capable of being liquified.

Description

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METHOD AND APPARATl~S ~OR C()NTROLLING . .
SUI.PHUR DIJ ST
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This invention rela~es to a method of controlling the generation of dust and air-borne particles arising from the handling of a dry material. More particularly, the inven-tion relates to controlling sulphur dust derived from dry pieces of solldified sulphur in the form of a powder, flakes, slates, chunks, or the like, ~y spraying liquid flowable sulphur onto the dry solid pieces of the same material.

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~ACKGROUND ~ THR INVENTIO~
One source of sulphur is a product extracted during re-fining of sour field gas in the natural gas industry. Thus, --problems in handling sulphur occur initially in the many gas plants which produce natural gas, as well as in other locations. ; -The sulphur which is extracted in molten form is then solidified ` -either for storage or shipment elsewhere, Traditionally, the molten sulphur has been poured into large forms creating large solid blocks. The base area of ;, these large blocks often ranges up to many tens of thousands ;~ of square feet in size. To handle such blocks of sulphur requires the breaking up of the massive block by means of various mechanical -devices, such as power shovels, or the like. The resultant broken pieces of solidified sulphur vary in particle si~e. For transport elsewhere, these broken pieces have normally been loaded into open-topped railroad hopper cars. Both loading and unloading of these cars often required belt conveyors, or the like, to transport the solid pieces of sulphur from, or to, storage facilities such as a ~ui~lding, a hold o~ a ship, or the like. In transferring and `
tran3p~rting the dry, solid p;eces of sulphur, the pieces are usually allowed to fall freely, ~ay, from one conveyor to an~ther, ' ~ ,., : , - 2 ~
''; ' ' ' ' ' '' . '' ' 1~34Z'~79 or from a hopper car to anoeher site. The physical jostling and handling of the dry, solid pieces of sulphur generates dust, an ; air borne suspension of fine particles of solidified sulphur.
This sulphur dust presents a serious hazard for fire and/or explosions. These hazards are well known in the natura] gas and sulphur industries. Should the air-borne particles of sulphur escape into the atmosphere, an air pollution problem is created. Further yet, such air-borne sulphur particles may ; '' '~ ' mix with water either in the form of rain, or in a la~e, river ~
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or other such body of water, and become a water pollutant. The ; presence of water in sulphur creates corrosion problems when the sulphur is burned ia chemical processes.

Increasingly stringent requirements are being set . :: .
down to govern maximum allowable levels of air and water pollutants ;: . .
of many kinds. The sulphur industry has had great difficulty in devising fully acceptable methods to solve the problem of dust ~
being generated from the handling, or even mere transporting of ;
dry, solld pieces of sulphur in open-topped vehicles, or on conveyor syAtems of one kind or another.
In one approach used to reduce problems in handling ~ dry, solid sulphur, the sulphur was carried first in a molten form ;i~` on a belt conveyor and is cooled with water. Thin slates ., of sulphur were tbus formed, and this technique is known as the slating method. That approach has reduced the pollution of air and water by sulphur dust, however, the costs of re-melting sulphur inventories is extremely high and in many cases prohibitive.

Further yet, this slating method is relatively time-consuming.
In another approach, the problem of dust being gen-erated by the handling or transporting of dry, solidified sulphur ~s l~een tackled by spraying water onto the sulphur. This has had

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only limited success. Additional problems have been created by the con~a~ination of the æulphur wlth extraneous and unwanted substances. -', ' '' Thus, a fully acceptable solution to this problem ~ ;
of controlling sulphur dust has remained out of the reach of per-sons in that industry. In spite of various methods that have been tried, a simple and economically viable ~oluti~n ~as not found by earlier.endeavours.
'' . . ' ' SUMMARY OF T~E INVENTION
The present invention provides a significant im- -provement in dealing with the problem of controlling ~he generation ` ;~
of sulphur dust. The present invention is embodied in a very simple technique, and one which will allieviate most of the ma~or drawbacks of approaches that have previously been tried. `-In accordance with one aspect of this invention, there i9 provided in a process of hnndling dry, solid pieces of a li~ iab~o material, preferably sulphur, which is prone to 8enerating dust particles of said material, the improvement which comprises the steps of spraying said material in a liquid form onto the dry solidified pieces of the same material to wet down any dust particles of that material generated during handling , thereof. The spraying is preferably done selectively, at pre-,.~, .. :. .
~ determined locations where dry, solid pieces of the material are ~ . . .
` being transferred from one conveyor or storage means to ano~her.

In a preferred imbodiment of this invention, there are also provided the steps of exhausting a gaseous medium containing the dust particles of said liquifiable materia~ to a separation device, ! separating the dust particles from the exhausted gaseous medium, ,:" :.:
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selectively heating the particles of material to liquify them, .. . :
and pumping the liquified material to a spray nozzle for spraying onto said dry, solidified pieces of that liquifiable material. `~
It will be apparent from the following details of the description that many advantages are derived from the present invention, especially as read in connection with the accompanying drawings. ~:
BRIEF DESCRIPTION OF THE DRAWINGS :
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The drawings illustrate by way of example only, some embodiments of the present invention. In the drawings: :
Figure 1 is a perspective view illustrating schematically one embodiment of this invention; -. .

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- ~4Z2~9 Figures 2 and 3 are side and end eleva~ion vlews ;-' of another embodiment of this invention;
Figure 4 illustrates schematically another embodiment of this invention; and ;

Figure 5 illustrates schematically one preferred "
embodiment of apparatus contemplated by this invention; and . . . .
Figure 6 illustrates yet another in which the invention can be embodied.
''DES'CKIPTI'O'N'O'F'THE'PR~ERR'ED'EMBODIMENTS
Turning now to Figure l of the drawings, one em- ;
bodiment of thls invention is shown schematically as being uti~ized ' in the context of an arrangement in which solid pieces of sulphur -are being transported from one location to another location. Dry, ,,~ i ,~
solid pieces of sulphur are shown being carried along at lO by ~`
means of a continous belt conveyor system 12. The solid pieces of sulphur lO have been broken out of blocks or piles of solidified ; ' , .
sulphur by means of a power shovel, front-end lo'ader, or other ` ~' ' 8uch power-operated mechanical devices. The pieces lO of sulphur "' ~ ' can be in the Porm of flakes, chunks, particles, slates, as well as powder, depending upon the particular arrangement used to handle ;, ,. :
~ the sulphur originally. The pieces lO of sulphur were loaded i'"'' "
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onto the conveyor system 12, for transport, say, from the first and source location from which those pieces were to be transported,to :' another location, either a storage facility or some other transport ,:: , ,:
means. In Figure l, the solid pieces lO of sulphur are transferred ~

from the conveyor system 12 onto another endless belt conveyor ~' '' .. ~ :.. .
'~ arrangement 14 which is adapted to convey those solid pieces of ~
sulphur to a pile 16 contained in a storage facility l8. In '-accordance with the present invention, the storage facility 18 could ;' be an open-topped railway car, the box of a transport truck, a supply hopper for loading railway cars, or simply a building or other such storage or transport me'~ns. The locations shown in Figure l ''~` ~ ' . .
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~ Z;~7 by reference numerals 20 and 22 can be considered as transfer points or locations. It ls evident that the solid pleces 10 of sulphur are being transferred from one handling or tranfiport facility (conveyor systems 12 and 14~ to another handling or storage facility (the conveyor system:l4 and storage facility 18~.
In Figure l, the solid pieces 10 of ~ -sulphur are selectively sprayed with molten sulphur. Accordingly, spray heads 24 and 26 are respect~ely provided at each of the t~ansfer locations 20 and 22. The spray heads 24 and 26 are made up of a number of spray nozzles 28, each adapted to be supplied with liquid sulphur, preferably from a spray header 30, at a rate required by the amount of dust generated. An inlet pipe 32 connects the discharge side of a pump to the spray header 30.
The suction side of the pump is connected to a furnace -I
that is operable to provide a supply of molten sulphur, preferably having a temperature in the range from about 270F. to about 330F.. More particularly, the molten sulphur is provlded for pumping at a temperature of about 300F. to the spray heads 24 and 26. The furnace ~eans and pump means used to supply and pump the molten sulphur are known in construction and operation to persons knowledgeable in this art. Solid pieces of sulphur can be melted by m~ans of steam, hot water, Dowtherm*, electricity, or other such sources of heat. If molten or liquid sulphur is already available and present, it may be used as the source of liquid sulphur for pumping of the sulphur from the furnace in which it is liquified to the ~pray nozzles 28, the conduit 32 and other piping required will be encased in a jacket through which steam, hot water, Dowtherm*of other such hot material will be pumped to ensure that the sulphur remains in a liquid and flowable condition. This ls called "tracing" and i9 known in this art.

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- 1~42Z79 It wlll be evident from ~igure 1 that molten sul-phur is spray~d selectively onto the solid pie~es 10 of dry, Solidified sulphur. This selective spraying takes place at transfer points or locations 20 and 22, which are likely to generate the largest quantities of sulphur dust, i.e., an air-borne suspension -of fine particles of solidified sulphur. Sulphur dust is shown ~
sche~atically at Figure 1 at 34. In order to wet or knock down the sulphur dust 34, a spray 36 of molten sulphur is sprayed over the locations or zones 20 and 22 in which the sulphur dust is being generated. The spray 36 of molten sulphur can be in the form of a spray of pressure dispersed droplets of molten sulphur; alterna-tively, a sultable in~ector device might also be used to provide a high velocity ~et of a carrier medium for the molten sulphur.
In using the latter arrangement, care is required to ensure that the carrier medium will not contaminate or react with the molten .. . . .
sulphur and thereby creat other unwanted problems. Thus, in most instances, it will be prefera61e to use a spray of pressure dispersed ~ ;
droplets of molten sulphur.
Figures 2 and 3 illustrate schematically another .
arrangment or configuration in which the present invention can be used. There, a standard open-topped railway hopper car is shown at 50, this car being adapted to be movable on rails 52. The hopper car 50 ls illustrated as carrying dry pieces 54 of solidified ~sulphur. As in the embodiment of Figure 1, the pieces 5~ of solidi-f~ed sulphur can be ln the form of chips, flakes, powder, slates, ~ -or the like. The hopper car 50 has a 6Ottom 56 which is provided with a number of discharge hoppers 58. These hoppers 58 are pro-vided with a gate or baffle mechanism (not shown) which functions to place the hopper 58 into an open or closed condition. The struc-ture and operation of such hoppers are well known in the art of ', ' '. .

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~ZZ79 railway cars and do not in themselves form any part of the present invention. The dlscharge ho~pers 58 are illustrated in Figures 2 and 3 as being in an open condition, thus allowing a stream 60 of the dry pieces 54 of solidified sulphur to issue from each hopper.
The streams 60 of sulphur in particulate form are illustrated as being dumped onto a storage pile 62 or transfer system- This storage pile 62 could be in the hold of an oceangoing ship, a transport truck or system, or simply a temporary storage facility.
In accordance with this invention, a plurality of spray no~les 64 are provided at locations spaced apart peripherally of the ~one in which the storage pile 62 of su~phur is located. The spray nozzles 64 may be part of a mo6ile spray system, if desired, or may be a more permanent installation, depending upon the parti-cular situation in which they are being used. These spray nozzles 64 are adapted to direct a spray 66 of molten sulph~r at sulphur particles 68 which are being generated by the streams 60 of pieces 54 of solidified sulphur belng dumped onto the storage pile 62.
Aq in the embodiment of Figure l, the spray 66 of molten sulphur ls provided preferab]y in ~he form of a pressure dispersed spray of droplets of molten sulphur. The molten sulphur will tend to wet and knock down the dust particles 68 of sulphur,thereby substantially minlmizing the tenclency for such particles to otherwise become air-borne. Since the spray 66 is of the same material as the pieces 54 and dust particles 68, namely, sulphur, there is no contamination of `, that material by other extraneous and unwanted substances. Further more, since water is not being used as the wetting agent, corrosion and contamination problems are reduced.
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of liquid. sulphur 36 or 66 will be governed by the extent to which sulphur dusts and air-borne particles of solidified sulphur are being generated under the particular conditions at hand. It will -be evident that the conduits which conduct molten sulphur to the spray nozzles 28 and 64 will have a control valve therein for regulating the volume flow rate of m~lten sulphuT being delivered by the pump in that circuit.
Another feature of the present invention is illus-trated in Figure 4. There, an open-topped railway hopper car is shown at ôO. This car 80 contains a load of pieces 82 of solidified su~phur, in the form of chunks, powder, flakes, chips, particles, --slates, or the like. As the hopper car 80 is moved along in a train consisting of a multiplicity of such cars similiarly loaded, :,: , '.
there is a considerable tendency for sulphur dust and sulphur "fines" ;
i.e., fine particles of sulphur, to be swept or blown off the load , , of sulphur 8~ belng carried along. Air friction drag generated by movement of the hopper car 80 has, in the past, tended to cause particle~ of sulphur to become air-borne, thereby constituting an air pollutan~. In accordance with this invention, the load of I l pieces 82 of~solidified sulphur in each hopper car 80 is ~prayed ! ``
over the entirety of surface 84 exposed to such air drag or wind forces. A spray 86 of molten sulphur, normally at a temperature in the range from about 270f. ~o about 330F. is sprayed onto the i`l surface 84. That spray 86 of molten sulphur is derived from a spray head 88 which is connected by a suitable conduit system 90 to a furnace or similiar source of molten sulphur, not shown in this Figure. As stated before ,the conduit 90 will generally be enca~ed in a Jacket containing steam, hot wster, hot Dowtherm* ¦
or some other heated medium which malntains the sulphur in a liqui~ ¦ ;
I condition capable of flow. Suitable pump mean~ are also provided *Trademark `' . 1 27~
in flow communication with conduit 90 in order to provide the spray 86 as a pressure-dispersed spray of droplets of molten sulphur. The spray 86 of molten sulphur can ~e derived from orifaces of an oval cross-sectional shape, or from suitable spray no~zles provided in the spray head 88. In spraying molten sulphur in finely divided form over the load 82 of sulphur in hopper car 80,what amounts to a film of sulphur is applied over that load. Such a film tends to hold down any small pieces or particles of solidified sulphur which might otherwise have a tendency to be picked up by wind forces, or air passing over a rapldly moving train pulling such cars 80. As stated before, since the spray 86 of molten sulphur is of the same material as that contained in ~he hopper car 80, there is a greatly reduced incidence of contamination of the sulphur pieces 82 by any other extraneous and unwanted substances. It is to be noted that the feature of this invention as illustrated in Figure 4 could also be applied to pieces of sulphur being carried along on a con-veyor, or other transport means travelling through a zone in which it was imperative to reduce any tendency for sulphur dust genera-tion to an absolute minimum.
Eigure 5 illustrates schematically and by way of example only one preferred form of an apparatus embodied by this invention. Here, dry, solid pieces 100 of sulphur are being carried along on a conveyor system 102 which discharges those solid pieces onto a second conYeyor system 104. That second conveyor system 104 may be transporting the pieces 100 of sulphur to a railway hopper car, a temporary storage pile, into the hold of a ship, into the box of a transport truck, or some other such storage facility. Such storage acilities are well known in this art, and need not be described at this time.
As stated earlier? the dry solid pieces 100 of su~phur may be in the form of chips, flakes, powder, chunks, or the ` ` , ~ ' ~ .; . . .
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~3L04~'~79 like which are prone to generating dust when they are transferred from one conveyor or transport facility onto another. In this instance, a transfer polnt or location is indicated at 106, with ~-the numeral 108 serving to identify sulphur dust or air-borne particles of solidified sulphuT . T~e sulphur dust 108 is evacuated from the region of the transfer point 106 by means of a suitable ;;~
exhaust hood 110. That exhaust hood 110 is in flow communication through conduits 112 and 114 to a suction fan 116 and a separater device 118. The sepaIater device 118 may be a conventional centri-fugal-type cyclone, or some other similiar dev~ce. A gaseous - -~
medium containing the sulphur dust 108 is drawn off through conduits ~-112 and 114 by the suction fan 116. The separater device 118 ~¦
functions to separate the solid particles of ~ùlphur from the gaseous I ;~
medium, and then to deliver those particles of sulphur by a conduit 120 to a furnace 122. This fuTnace 122 is adapted to receive and ! .: -heat the sulphur preferably to a temperature in the range from about 270F. to a~out 330~., thereby melting the sulphur to form liquld sulphur that is capable of being pumped to some other location. Heat for melting the sulphur can be derived from hot water, steam, hot Dowtherm* electrical heating coils, or some other :: :: ..
nrran8ement known in this particular art.
The liquified and flowable sulphur is drawn from the ; furnace 122 by the suction side of a pump 124 through conduit means 126. The discharge side of the pump 124 delivers molten sulphur under pressure through a regulating valve 128 in a discharge conduit 130 to a plurality of spraY nozzles 132. The spray nozzles 132 ~ are disposed to generally surround the transfer point 106 which is ¦

f the primary source sulphur dust and air-borne particles 108 of l ;
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sulphur. A6 abo~e~ the conduits126 and 130 are connectable with ~ -the furnace 122 and the pump 124 to form an operational system which causes l~q~if~ed sulphur to be discharged under pressure as a , ~ ;
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spray onto dry solid pieces of that same material, thereby wettlng and knocking down dust pa~ticles of that material. The configur-ation illustrated in Figure 4 represents schematically one particu-lar form of apparatus embodied by this invention. The arrangement of Figure 4 would probably be used primarly ln connection with loading the hold of a ship. This is discussed below. It will readily be apparent that the various system parameters such as pressures, flow rates and temperatures can be varied and engineered to suit a given set of circumstances. The following description of operating parameters is given by way of example only to indicate one operational version of apparatus contemplated herein.
EXAMPLE:
Rate of moving sulphur pieces 1600 ton/hr Particle size of sulphur pieces 300 mesh U.S. standard to lumps 8" in diameter, or larger X sulphur fines variable Suction fan capacity 0-1750 cu. ft./min.

Pressure in exhaust hood 1-3 inches of water below atmospheri,c Exhaust conduit size up to 4 ft. in diameter Separator device hydro-cyclone (eg "MINOTAURE*"~
Delivery rate of sulphur dust to furnace 500 lbs/hr.
Furnace heated by Natural gas `i ,~?
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~ Temperature Range 330 F. - ;
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;~ Sulphur pump capacity 32 ton/hr. or 60 gal/min Operating temperature 270 - 300 F.

Molten sulphur conduits diameter 1 - 3 inches ~ Steam temperature in Jacket 300 F. -~

; Spray nozzle or ~pray orifaces 0.125 diam.

Spray of molten sulphur 8 tons/hr to all nozzles ~,' Figure 6 illustrates schematically an arrangement commonly ;' used in the transporting and dumping of solidified pieces of dry .. . .
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SUIphur. Here, a railway hopper car 150 iB moved in~o a building enclosure 152 which houses a hopper car dumper 154.
The dumper 154 is known in both construction and operation ln the ,~ '', railway art, having commonly been used in dumping hopper cars of ...
coal, mineral ores, or the like. It will suffice here to state that the dumper 154 includes a base assembly 156 which carries rails .
158 on which the hopper car 150 is moved. The base assembly 156 ',~
is carried on a rotationally movable frame 160. This frame 160 '' :
has frame members 162 which are formed with a gear-like peripheral ~, surface 164. The surface 164 at each end of base assembly 156 ,: . ;
is adapted to be driven by a reversible gear-box and motor shown at 166. A clamp-down assembly is illustrated at 168, and generally ' i9 adapted to engage the wheels 170 or chassis of the hopper car .
150. The clamp-down assembly is conveniently acuated by hydraulic piston-cylinder combinations 172 or the like, and secures the ':
hopper car 150 firmly in place in the dumper 154. .~. :
The motor 166 is activated causing the dumper 154 to be rotated counterclockwise as seen in Figure 6, and hopper car .'~
, ~ , 150 with it. The dumper rotates through a predetermined angle of A degrees, sufficient to empty all of a load 174 of sulphur from ~," i the hopper car 150. It will be evident from the earlier description o Figures 2 - 4 that the load 174 will be constitute a wide variety of siæes of particulate sulphur. The pieces of ';
, ,:. sulphur making up the load 174 can vary from chunks weighing many ,, , pounds or even tons, to lumps having an effective diameter of say ,, 6 to 10 inches, to sulphur powder or fines of 300 mesh U.S. ,~

.' standard mesh siæe.

`~ In any event, dumping of the load 174 of particulate ',' ;

sulphur causes the dry solldified sulphur to be dumped onto a ': '~

~, conveyor system.. l7~. The.conveyor system 176 commonly is used to ,~l transport the pieces of sulphur to the hold of a ship, a storage ' , ' .
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cllity, or the like. In accordance ~i,h ~he present invention, a plurality of spray nozzles 17~ are provided beneath the dumper 154, and adjacent the conveyor system 176. Molten, liquified sulphur is sprayed as a pressure dispersed spray 1~0 onto the stream of dry pieces of sulphur formed each time a hopper car 150 is dumped. This can occur every few minutes, for example.
Any sulphur dust likely to be generated is kept to a minumum by having large charges of molten sulphur sprayed from nozzles 178 simultaneously with dumping, to wet down the sulphur. ~etween dumpings a relatively small spray of sulphur is used to ~et down the dry pieces or particles of sulphur to inhibit dust generation.
The quantities or flow rates of liquid sulphur being sprayed in any given instance will vary. When sulphur powder or fines, for example, make up a large proportion of the load 17~, more sulphur will have to be sprayed than on an occassion when primarily fist-sized lumps of sulphur are involved. Thus the flow rate -of liquid sulphur supplied to ~he nozzles 178 will be adjustably `
controlled by suitable valve means by varying the driving pressure or the like.
It should also be noted that in the context of ~he present invention, whenever pieces of solidified sulphur are being transferred from one transport or storage system to another, it is preferable to provide some ramp or guide means which cause the sulphur pieces to slide from one location to the next location, avoiding a free fall situation as far as this is -~
possible. It will be recognized that the free fall of large amounts of solidified pieces of sulphur increases the incidence '.
of breakage of those pieces. Thus, there is an increased tend~
ency to generate even more sulphur dust, i.e. air-borne particles of solidified sulphur. In this context, it has been found advan~ageous in filling the hold of a ship, for instance, ~co place a large exhaust duct into the hold and draw a nega~ive , ~ .
l pressure in the hold. This pressure wlll be abouc 1 - 3 .'`, 1~ . .
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inches of water below atmospheric pressure. Although it is difficult to avoid some free falling of the sulphur pieces in this situation, evacuation of air from the ship's hold will eliminate the tendency for the ~ulphur to replace or drive large quantities of air out of that hold. This is undesirable since the out-rushing air often carries with it quantities of sulphur dust and air-borne particles which might otherwise have remained in~ and precipitated out in the ship's hold. The suction will be sufficiently low to have no effect on diverting the spray of -~
liquified sulphur being sprayed, but strong enough to cause a flow of air into the hold.
The foregoing description has set out a number of embodiments of this invention. Some modifications and alternatives have also been indicated. It is intended within the spirit of this invention to encompass all such changes as would be obvious to those skilled in this art, and as embodied in the claims below.
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Claims (5)

The embodiments of the invention in which an ex-clusive property or privilege is claimed are defined as follows:

1. In a process of handling dry solid pieces of a liquifiable material which is prone to generating dust particles of said material, wherein the improvement comprises the steps of;
spraying said material in liquid form onto the dry pieces of the same material to wet down any dust particles of said material generated during handling thereof.

2. In the process defined in Claim 1, wherein the material is sulphur, and the spraying is done selectively at predetermined locations.

3. In the process defined in Claim 2, including the further steps of evacuating the dust particles of sulphur, melting said particles to form liquid sulphur at a temperature in the range from about 270°F. to about 330°F; and subsequently supplying the molten sulphur to a spray nozzle for spraying onto the dry pieces of sulphur.

4. In the process defined in Claim 1, wherein the steps are also provided of exhausting a gaseous medium containing said dust particles to a separation device; separating the dust particles from the exhausted gaseous medium; heating the separated dust particles to liquify the same; and pumping said liquified material to a spray nozzle for spraying onto said dry pieces.

5. In the process defined in Claim 4, wherein the material is sulphur in the form of one of a powder, chunks, pieces, flakes or slates.