Abstract:
An apparatus and a method for improving the flowability of hygroscopic materials from a hopper wherein a desiccant containment device containing a desiccant material is located within a hopper that is used for transporting or storing granular or powdered bulk materials. The desiccant material captures moisture from the hopper atmosphere in order to promote the flowability of the bulk material.

Description:
FIELD OF THE INVENTION 
     The present invention relates to the removal of moisture from the atmosphere of a transport or storage hopper for powdered or granular bulk materials. More specifically, the present invention relates to improving the flowability of powdered or granular bulk materials by using desiccant to remove an appropriate amount of moisture from the atmosphere of a transport or storage hopper. 
     BACKGROUND OF THE INVENTION 
     Powdered and granular bulk materials are often shipped or stored in hoppers. Often, these materials are hygroscopic in that under certain conditions they will exchange moisture with the surrounding atmosphere. Significant changes in ambient temperature and humidity levels will trigger hygroscopic activity in the bulk material, making the bulk material difficult to discharge and unload from the hopper. 
     The problem is especially common in the interstate shipping industries like railroads and trucking where the bulk material contained in a hopper car or trailer is subjected to significant climatic changes as the material is transported across the country. For example, a bulk material like granular sugar, powdered flour, or cement is loaded into a covered hopper rail car in a warm humid southern state. The loaded car is then shipped to a colder northern climate. As the car moves further north, the interior surfaces of the hopper, i.e., its sidewalls, endwalls, and ceiling, become colder. The moisture in the atmosphere of the hopper condenses out of the atmosphere onto the sidewalls, endwalls, and ceiling. The moisture falls from the ceiling or runs down the walls to saturate the bulk material in various locations. The saturated bulk material may remain wet or it may dry into hardened chunks. In either case, the flowability of the bulk material is decreased, the result being that the load will not easily flow from the hopper when unloaded, especially the parts of the load that were saturated. Likewise, as the car moves it is subjected to various humidity levels, which can cause the bulk material to absorb or give-up additional moisture, again resulting in hardening or clumping of the bulk material. 
     Consequently, there is a need in the art for a technique for improving the flowability of hygroscopic materials from a hopper by capturing available moisture from the atmosphere within the hopper. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention, in one embodiment, is a railcar for improving the flowability of sugar from a hopper. The rail car includes at least one hopper, a hatch located in an upper wall of the rail car, the hatch allowing access to the at least one hopper, and a desiccant containment device adapted to hold a desiccant, the desiccant containment device located within the hopper above a fill level and secured to the rail car within the hatch. 
     Another embodiment of the present invention is a method for improving the flowability of hygroscopic materials from a hopper. The method includes opening a hatch into the hopper, locating one or more desiccant containment devices within the hopper, placing a desiccant within the desiccant containment devices, and closing the hatch. 
     While multiple embodiments are disclosed, still other embodiments of the present invention will become apparent to those skilled in the art from the following detailed description. As will be apparent, the invention is capable of modifications in various obvious aspects, all without departing from the spirit and scope of the present invention. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not restrictive. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a side sectional view of a modified rail car adapted for transporting bulk materials. 
     FIG. 2 shows a side section view of a net desiccant containment device installed in a hatch of a rail car, according to one embodiment of the present invention. 
     FIGS. 3A-3C show side sectional views of a basket desiccant containment device installed in a hatch of a rail car, according to a second embodiment of the present invention. 
     FIGS. 4A and 4B show side sectional views of a desiccant containment device installed in an access door of a rail car, according to a third embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 shows a side sectional view of a transport system  10  adapted for transporting bulk materials in a rail car modified according to the present invention. While the following discussion describes the system of the present invention for use with a rail car, it will be apparent from the following description that the system could also be used with other transport methods, such as trucking or shipping. 
     As shown in FIG. 1, the transport system  10  includes a rail car  11 , which includes a first hopper  12   a , a second hopper  12   b , and a third hopper  12   c . As further shown, each of the hoppers  12   a ,  12   b ,  12   c  includes a corresponding set of hatches  14  and  16  and a dispensing chute  18 . Each of the hatches  14   a ,  14   b ,  14   c  includes a corresponding desiccant containment device  20  therein. Each of the hoppers  12  is loaded with bulk material  22 . 
     The bulk material  22  may be any type of hygroscopic powdered or granular material, including for example, sugar, salt, flour, grain, cement, potash, silicates, or plastic granules. In other embodiments of the present invention, the rail car  11  has a greater or lesser number of hoppers  12 . In other embodiments, the hoppers  12  have a greater or lesser number of hatches  14 ,  16 . Also, as further described below with reference to FIGS. 4A and 4B, in some embodiments, the desiccant containment device  20  is placed within an access door, rather than within one of the standard rail car hatches  14 ,  16 . Where the bulk materials  22  are food materials, the desiccant containment device  20  should be constructed of FDA approved materials. Where the bulk materials  22  are materials other than food, the desiccant containment device  20  should be constructed of materials that will be inert to the bulk materials  22 . 
     FIG. 2 shows a side sectional view of a desiccant containment device  20 , which includes a net  24  installed in the hatch  14 . As shown in FIG. 2, the hatch  14  is located in the roof  26  of the rail car  11 . In the embodiment shown, the hatch  14  has a filling neck  28 , a hatch cover  30 , and a hinge  32 . The filling neck  28  extends above and below the roof  26  and allows access to the interior hopper  12  of the rail car  11 . This access allows the rail car to be filled with bulk materials  22  for rail shipment. The access may also allow workmen and their equipment to enter the hoppers  12  for cleaning and repair purposes. The hatch cover  30  covers the filling neck  28  and is rotatably connected to the filling neck  28  by one or more hinges  32 . 
     The net  24  is suspended from lugs  34  (or similar attachment devices like hooks, rings or snaps) connected around to the filling neck  28  around its periphery. In one embodiment, the net  24  is made of heavy-duty nylon. In other embodiments, the net  24  is made of other materials including, for example, synthetic materials like the various polymers or synthetic rubbers, natural materials like cotton, canvas, silk or rubber, or metallic materials like stainless steel wire mesh. In one embodiment, the lugs  34  are stainless steel and are welded to the filling neck  28 . In another embodiment, the lugs  34  are constructed of materials other than stainless steel, such as other metals or synthetic materials and are connected to the filling neck  28  by mechanical means such as bolts or screws. The lugs  34  could also be connected to other areas on the interior of the hopper depending on where the desiccant containment device  20  is ultimately located (see for example FIGS.  4 A and  4 B). In one embodiment, the net  24  is a basket. In another embodiment, the net  24  is a gas and/or water vapor permeable bag. The bag is suspended from the filling neck  28  (or another location within the hopper  12 ) by the lugs  34 . The bag could be made of materials such as cotton, canvas, silk, nylon, rayon, or any other suitable material. 
     As further shown in FIG. 2, the net  24  holds and supports one or more packages of desiccant  36 . The net  24  holds an appropriate amount of desiccant  36 , as further described below. 
     FIGS. 3A-3C show sectional views of a desiccant containment device  20 , which includes a basket  38  mounted inside the hatch  14 . As shown in FIGS. 3A,  3 B, and  3 C, the basket  38  includes perforations  39  to allow communication of gases, liquids, and vapor between the hopper  12  and the desiccant inside the desiccant containment device  20 . As shown in FIG. 3A, the basket  38  includes a U-shaped lip  40  adapted to mate with the filling neck  28 , such that the basket  38  is suspended from the filling neck  28 . In one embodiment, the basket  38  is a mesh or wire construction. In various embodiment, the basket is made of metallic materials such as stainless steel, cotton, canvas, synthetic materials such as polymers, or any other suitable material. In the embodiment shown in FIG. 3B, the basket  38  includes a ledge  42  extending generally outward around an upper circumference, and the filling neck  28  includes a circumferential lip  44 . When placed into the hatch  12 , the ledge  42  of the basket  38  is supported by the circumferential lip  44 . In one embodiment either the ledge  42  or the circumferential lip  44  further includes a rubber gasket (not shown). In one embodiment, the ledge  42  of the basket  38  is supported by lugs, hooks, or rings located around the periphery of the filling neck  28 . In the embodiment shown in FIG. 3C, the basket  38  includes a ledge  42  extending generally outward around an upper circumference. The ledge  42  shown in FIG. 3C is sized to mate with an upper end of the filling neck  28 , to support, the basket  38 . 
     FIGS. 4A and 4B show a sectional view of a desiccant containment device  20 , which includes a container  48  installed in an access port  50 . As further shown in FIGS. 4A and 4B, the access port  50  is covered by an access door  52 . The size of the container  48  and the access port  50  will vary depending upon the amount of desiccant necessary, as further described below. In various embodiments, the container  48  is either a net or a basket, made of any of the materials set forth above. Also, in various embodiments, the container is mounted in the access port  50  using any of the various techniques set forth above. The embodiment shown in FIGS. 4A and 4B allows mounting of the desiccant without blocking any of the hatches  14 ,  16 . A skilled artisan will recognize that the transport system  10  of the present invention will be effective as long as the desiccant containment device  20  is located within the hopper  12  and above the level of the bulk material  22 . 
     In one embodiment, the desiccant  36  (shown in FIG. 2) is simply located within the desiccant containment device  20 . In another embodiment, the desiccant  36  is single, double, or tripled bagged before being placed within the desiccant containment device  20 . The bags are constructed of vapor-permeable materials such as cotton, canvas or synthetic materials like very fine, high-density polyethylene fibers similar to the fabric available from E.I. duPont de Nemours and Company under the name TYVEK®. Again, where the bulk materials  22  are food materials, the desiccant  36  and the bags should be made of FDA approved materials. Where the bulk materials  22  are materials other than food, the desiccant  36  and the bags should be made of materials that will be inert to the bulk materials  22 . 
     An example of one method of utilizing the subject invention will now be narrated with reference to FIGS. 1 and 2. While the following example is given in the context of sugar being shipped in a covered rail hopper with six round hatches and a double bagged desiccant, it must be noted that the following method is equally applicable to shipment of other materials, for use with other transport or storage hoppers, for use with other hatch types or configurations, and for use with other desiccant bagging arrangements. 
     After a rail car  11  is loaded to capacity with sugar, a desiccant containment device  20  is located at the hatches  14  in each hopper  12 , using a technique set forth above. Ideally, the desiccant containment devices  20  will be installed so that they are suspended above the sugar. In one embodiment, approximately 500 grams of the desiccant is placed inside primary bags, and secondary bags are each filled with approximately thirty-five sealed primary bags. Since this example is in the context of food materials, the desiccant will be a FDA approved food grade silica gel desiccant. The secondary bag will be made of a FDA approved food grade loosely woven cotton or canvas material while the primary bags will be made of a FDA approved material like very fine, high-density polyethylene fibers similar to the fabric available from E.I. duPont de Nemours and Company under the name TYVEK®. 
     After the primary bags are inserted into the secondary bags, the secondary bags are sealed and placed within the desiccant containment device  20 . The hatch covers  30  are then secured shut. The desiccant will how capture moisture within the hopper that is released from the sugar or present in the hopper atmosphere as a result of changes in humidity and ambient temperature as the rail car  11  travels from its origin to its destination. By capturing the released moisture, the desiccant containment devices  20  preserve the flowability of the sugar and reduce unloading difficulties at the destination. The number of desiccant containment devices  20  employed will depend on the type, amount, and moisture content of the bulk material  22  shipped or stored and the expected changes in humidity and ambient temperature to be encountered. 
     In one example, the amount of desiccant is based on tests conducted with rail cars filled with approximately 200,000 pounds of sugar and shipped from southern Florida to the northeastern part of the United States. In this example, about 105 pounds of desiccant were used (roughly one pound of desiccant for every 1900 pounds of sugar). This amount was found to significantly decrease or eliminate the amount of moisture condensation on the interior roof and sidewalls of the covered hopper rail car as compared to the amounts of moisture normally encountered without the use of the desiccant containment devices  20 . Also, utilizing this amount of desiccant significantly improved the flowability of the sugar and decreased the amount of unloading difficulties as compared to the flowability and unloading difficulties encountered without the use of the desiccant containment devices  20 . In another embodiment of the present invention, one pound of desiccant is used for every 1500 to 2500 pounds of sugar. 
     In other embodiments, the ratio of desiccant to bulk material will change depending on the particular climactic changes expected during shipment, as will be apparent to one skilled in the art. Those skilled in the art will be able to arrive at the amount of desiccant appropriate for the amount and type of bulk material  22  being transported or stored and the amount of moisture that will be released from the bulk material  22  or present in the atmosphere of the hopper on account of climatic conditions. Therefore, the subject invention should not be limited only to applications involving sugar, but should instead be interpreted to include all powdered or granular bulk material  22 . 
     Although the present invention has been described with reference to preferred embodiments, persons skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.