Method and apparatus for debagging dust-containing or hazardous materials

Abstract: A method and apparatus for removing dust-containing or hazardous material from bags includes a vertical bag feeding chute having one or more vertically disposed knife blades (20,22) fixed (no moving mechanical parts) in the chute to slice open the bag as it falls through the chute. The sliced bag is caught in a downwardly angled perforated basket (32) disposed below the bag feeding chute where an operator operating through a glove box removes solid material from the interior of the sliced bag after most of the bag contents have fallen through the perforated receiving basket and into a mixing tank. The apparatus and method are particularly useful for debagging acrylamide monomer in the production of polyacrylamide homopolymers and copolymers.

Description: FIELD OF THE INVENTION The present invention is directed to a method and apparatus for debagging dust-containing or hazardous materials, including method and apparatus for removing solid material from interior surfaces of a bag for complete removal of the contents of the bag and directing all of the bag contents into a holding tank. More particularly, the present invention is directed to a method and apparatus for removing dust-containing or hazardous material from a disposable bag by dropping the bag down a vertical bag feeding chute that includes one or more fixed knife blades for slicing open the bag without knife blade movement; and catching the sliced bag on a perforated receiving basket disposed above a solid or liquid level in a holding or mixing tank so that most of the contents drop downwardly into the holding tank. BACKGROUND OF THE INVENTION AND PRIOR ART It is well known to provide apparatus capable of opening and substantially emptying bags of particulate, powdered or pulverulent materials particularly for toxic or hazardous materials, to aid in the speed of production in a process using such materials, and especially for debagging hazardous materials to prevent or minimize human contact during operation and mechanical maintenance with the contents of the bag and to attempt to remove all of the material from the bag. Examples of patents directed to mechanical debagging apparatus are as follows: 2,107,995, Statham, et al., 2,706,567, Luna, et al.; 3,145,858, Helbig; 3,482,718, Moriarty; 3,739,471, Peres; 4,034,877, Bennison; 4,252,489, Mechalas; 4,289, 438, Murer; 4,627,781, Borgner; 4,798,508, Lewis. While the apparatus described in the above-identified patents are useful for debagging and removing most dust-containing and hazardous substances, such apparatus suffers from one or more of the following disadvantages: debagging apparatus used for debagging toxic and hazardous materials should not have a bag opening means that includes moving parts since some of the toxic or hazardous material may become clogged in an area of mechanical movement during operation, making operation and maintenance hazardous. The present invention departs from a debagging apparatus for non-hazardous material as shown and described in US-A-2818985. It is the object of the present invention to design such an apparatus in such a way that it becomes safe and to further devise a safe bag handling method. This object is achieved according to the characterizing features of the independent claims. In brief, the method and apparatus of the present invention remove dust-containing or hazardous material from bags, and include a vertical bag feeding chute having one or more vertically disposed knife blades immovably fixed in the chute to slice open the bag as it falls through the chute. The sliced bag is caught in a downwardly angled perforated basket disposed below the bag feeding chute where an operator removes solid material from the interior of the sliced bag with a fluid (liquid or gas) after most of the bag contents have fallen through the perforated receiving basket and into a mixing tank. Any wash liquid used can be metered so that the amount of wash liquid used (1) for rinsing entrained material from the interior surfaces of the bag and perforated basket and (2) for washing the inner surfaces of the bag feeding chute, including knife blades, is measured on each occasion so that the concentration of the bag contents in the mixing tank is always known. While the apparatus and method of the present invention are particularly useful for debagging acrylamide monomer in the production of polyacrylamide homopolymers and copolymers, the method and apparatus are useful for debagging, and optionally mixing with liquid, any bagged, dust-containing, hazardous or toxic solid material. Accordingly, one aspect of the present invention is to provide a method and apparatus for debagging dust-containing, toxic or hazardous solid materials including removing solid material from an interior surface of the bag with a fluid while directing the bag contents into a holding vessel. Another aspect of the present invention is to provide a method and apparatus for debagging dust-containing, toxic or hazardous material without human contact of the debagged material using fixed knife blades, providing a very greatly reduced maintenance exposure (no moving parts) in a bag-receiving chute disposed above a holding tank, while maintaining a negative pressure through the chute and holding tank, and including a glove-box worker station adapted for manual removal of solid material from interior bag surfaces with a fluid so that entrained material falls vertically by gravity into a mixing vessel. Still another aspect of the present invention is to maintain a negative pressure within a chute and holding tank to ensure all freely dispersed dust in the air will be drawn into the chute and holding tank. Air drawn out of the apparatus to generate the negative pressure is passed through a wet scrubber device. The above and other aspects and advantages of the present invention will become apparent from the following detailed description of the preferred embodiments of the present invention taken in conjunction with the drawings. Figure 1 is a perspective view of the apparatus of the present invention; Figure 2 is a side view of the apparatus of Figure 1 taken along the line 2-2 of Figure 1; Figure 3 is a top view of the blade box portion of the apparatus taken along the line 3-3 of Figure 2; Figure 4 is a side view of the apparatus of Figure 1, similar to Figure 2, showing a worker stationed in a glove box for rinsing the interior of sliced bags, rinsing the apparatus, and disposing of the bags; and Figure 5 is a more detailed, partially broken-away view of a perforated, bag-receiving basket portion of the apparatus of the present invention. Turning now to the drawings and initially to Figures 1 and 2, there is shown an apparatus for debagging dust-containing or hazardous materials generally designated by reference numeral 10. The apparatus includes an enclosure or blade box, generally designated by reference numeral 12, for directing a bag 14 of particulate solid material 16 downwardly from an uppermost blade box opening 18 for engagement with a pair of slicing blades 20 and 22, each fixed to an opposed inner surface 24 or 25 of the blade box 12. As best shown in Figure 3, the slicing blades 20 and 22 extend inwardly from the opposed inner surfaces 24 and 25, respectively, of the blade box 12, each beveled at 26 such that the beveled portions 26 of the opposed knife blades 20 and 22 lie in the same plane to achieve relatively dust-free and clean bag slicing. The slicing blades 20 and 22 extend downwardly and inwardly toward a transverse center of the enclosure or blade box 12 for gradually and cleanly slicing open the bag 14 of particulate material 16. The blades 20 and 22 may overlap at a transverse center 26, e.g. one half inch, to slice the bag into two halves. The bevel angle, α, (Fig. 3), of the blades 20 and 22 is not critical and the bevel generally is provided at an angle of about 30 to about 50°. As shown in Figure 2, the slicing blades 20 and 22 converge and meet at the transverse center of the blade box 12 to slice the bag 14 into two pieces. As shown in the drawings, the opening 18 in the blade box 12 of the preferred embodiment is eight inches by twenty-seven and one half inches and each blade 20 and 22 is sixty inches long, five inches wide and one half inch thick, to provide an angle, β between the slicing blades 20 and 22 of about 8°. Best results are achieved with an acute angle, α, e.g. 5-30°, between the slicing blades 20 and 22. In accordance with an important feature of the present invention, the slicing blades 20 and 22 are fixedly secured to inner opposed downwardly and inwardly inclined surfaces 24 and 25 of the enclosure or blade box 12 to slice open the bag 14 without any moving parts. The provision of slicing blades 20 and 22 fixed to interior opposed surfaces 24 and 25 of blade box 12 without moving mechanical parts is important to prevent the particulate material 16 from being caught between moving mechanical parts to make sure that the particulate material 16 within the bag 14 is completely emptied from the bag 14 and that all of the particulate material 16 proceeds downwardly into a holding tank 30 so that the amount or concentration of the particulate material 16 within the holding tank 30 is always known. This also greatly reduces the need for maintenance and the potential of toxic/chemical exposure. A downwardly angled perforated basket best shown in Figures 4 and 5, generally designated by reference numeral 32, is disposed beneath the slicing blades 20 and 22 such that an upper portion 34 of the perforated basket is mounted to the enclosure or blade box 12 and a lower, downwardly angled perforated bottom 36 of the basket 32 is disposed within the holding tank 30, extending within the holding tank 30 through a sealed upper opening 38 in an upper surface 40 of the holding tank 30. The downward angling of the bottom 36 of the basket 32 essentially empties the contents of the bag as the bag halves partially rotate during impact of one bag half on each side of the downwardly angled bottom 36 of basket 32. After the bag 14 is sliced open by the slicing blades 20 and 22, the opened bag 14, together with the particulate material 16, proceeds downwardly by gravity toward the downwardly angled bottom 36 of the perforated basket 32. The perforated basket 32 is formed from a plurality of rods 33 that are secured together at points of intersection, such as by welding, to form two side walls 32A, and a back wall 32B, integral with the downwardly angled bottom wall or floor 36, leaving the top open for receiving a sliced bag, and leaving the front 42 open for a worker to grasp and rinse the inner surfaces of each bag, remove the bags and deposit the empty bags into a waste container or plastic tube 49, disposed proximate to the open front of basket 32. Each bag half contacts an opposite side wall 32A of basket 32 and each bag half rotates by gravity upon impact to substantially completely empty each bag half through the bottom wall 36 of basket 32. The basket 32 is disposed directly beneath the chute 12 and open at its top so that the basket 32 receives a sliced bag of material 14 that comes to rest on the downwardly angled floor 36. The open top of basket 32 is sized and shaped to correspond with a lower end of chute 12 so that all material 16 from bag 14 falls through the basket 32 and into the mixing tank 30. The round cross section of the rods 33 prevent any particulate material 16 from substantially adhering to the basket 32. The perforations within the downwardly angled bottom 36 of basket 32 are sufficiently large such that the particulate and compacted material 16 passes through the angled bottom 36 of the basket 32; the impact breaks up relatively large agglomerates of material into smaller lumps; and the perforations are sufficiently small such that the bag 14 is retained by the basket 32 for manual solids removal and disposal, as will be described in more detail hereinafter. As best shown in Figures 4 and 5, a front portion of the basket 32 includes an open area 42 communicating with a glove box 48 adapted for manually grasping of the bag 14 and removal of solids from interior bag surfaces with a wash liquid or gas and for bag removal and disposal performed from an open front area 42 of the basket 32. In accordance with an important feature of the present invention, a work station, generally designated by reference numeral 44, is disposed adjacent to the open area 42 of the perforated basket 32 for positioning a worker 46 within an environmentally safe glove box, generally designated by reference numeral 48, so that the worker 46 can rinse an interior surface of the bags 14, remove and dispose of the bags 14 through an adjacent, impervious disposal receptacle window 47, e.g.1 into an elongated plastic tube or bag 49, without contacting the particulate material 16. In accordance with another feature of one embodiment of the present invention, a metered water supply, such as water from flexible hose 50, is disposed in close proximity to the perforated basket 32, outside of the glove box 48, and extends within the basket 32 for use by worker 46 to rinse the blades 20 and 22, interior surfaces 24 and 25 of the blade box 12, and metal rods 33 forming the basket 32. The glove box 48 includes a transparent wall 51 adjacent to and facing the open area 42 of the perforated basket 32 so that the worker 46 can insert his hands in flexible sleeves 52 and gloves 54, hermetically sealed to the transparent wall 51 for grasping, washing, and disposing of the washed bags 14 by inserting the rinsed bags 14 into the disposal bag 49 via window 47, without contacting the contents 16 of bag 14, after thoroughly washing the interior surfaces of the bags 14. If necessary, the worker 46 can also wash the interior of the blade box 12 and the slicing blades 20 and 22. All wash or rinse liquid falls into the holding vessel 30 together with all rinsed particulate material 16. The wash liquid supply hose 50 includes a remotely mounted meter (not shown) capable of measuring the amount of rinse liquid that passes through the hose 50 so that the operator 46 is, at all times, aware of the amount of rinse liquid falling by gravity into the holding vessel 30. In this manner, a precise and accurate determination of the concentration of particulate material 16 within the holding vessel 30 is known after rinsing of entrained particulate material is complete. Alternatively, if the solid material is not combined with liquid, a gas, e.g. air, can be supplied from hose 50 for removal of solids from the interior bag surfaces and from the blade box 12 and the slicing blades 20 and 22. As best shown in Figures 1 and 4, the glove box 48 is disposed to completely surround the basket 32 to prevent the escape of any particulate material into the surrounding atmosphere. A mixing blade 56 driven by motor 58 optionally extends into holding tank 30 for homogeneously mixing of solid materials with liquid in tank 30. As best shown in Figures 2 and 4, a gas (via liquid media) scrubber 64 is mounted on the upper surface 40 of the holding vessel 30 in sealed, vapor communication with the interior of the holding vessel 30 via a conduit 62, and a blower or vapor pump 60, in vapor communication with a scrubber outlet 65, through a conduit 66, draws air through the bag feeding chute or blade box 12 and into the holding vessel 30 to maintain a negative pressure through the apparatus. Any toxic vapors that pass into the scrubber 64 are neutralized, e.g., with sodium metabisulfite, and non-toxic vapors proceed through a blower outlet conduit 68 to the atmosphere. While the preferred embodiment of the present invention has been described with reference to the debagged material falling into a liquid holding or mixing tank 30, the method and apparatus are equally applicable to debagging materials that are kept dry, such as sugar, flour and other dusty materials whether or not the materials are hazardous or toxic. In the case of dry materials, entrained solids can be blown from the blade box 12, the blades 20 and 22 and from the rods 33 forming the basket 32 using compressed air or other pressurized gas instead of using a water wash. The dust then can be collected in a standard dry dust filtering media, as is well known in the art. It should be understood that the present disclosure has been made only by way of the preferred embodiment and that numerous changes in details of construction, combination and arrangement of parts can be resorted to within the scope of the invention as hereunder claimed.

Claims: Apparatus for removing dust-containing or hazardous material from bags (14), comprising a vertical bag feeding chute (12), including at least one vertically disposed knife blade (20, 22) adapted to slice open and separate said bag into two individual sections as it falls through said chute, a perforated receiving basket (32) disposed below said bag feeding chute to receive said blade-sliced bag, and a holding tank (30) disposed below said receiving basket for receiving the contents of said bag, characterized in that said at least one vertically disposed knife blade (20, 22) is immovably fixed in said chute (12). Apparatus according to claim 1, further characterized by means (50) for thoroughly removing material from interior surfaces of said sliced bag (14). Apparatus according to claim 1 or 2, further characterized by means (50) for thoroughly removing material from interior surfaces of said feeding chute (12. Apparatus according to claim 2, characterized in that said removing means comprises: (a) wash liquid supply means (50) for washing said receiving basket (32) and said slit bag (14) while directing said wash liquid and material washed from the interior of said slit bag into said holding tank (30) to control the concentration of said liquid/solid mixture therein, and (b) means for determining the amount of liquid supply directed into said holding tank. Apparatus according to claim 3, characterized in that said removing means comprises wash liquid supply means (50) for washing said bag feeding chute (12). Apparatus according to claim 1 further characterized by means (60) for maintaining a negative pressure within said apparatus to eliminate dust generation around the apparatus, wherein preferably the negative pressure maintaining means comprises a blower in fluid communication with the holding tank for the downward flow of gas through the feeding chute, basket and out of the mixing tank, and preferably further including a scrubber (64) in fluid communication with the negative pressure maintaining means for removing contaminants from gas removed from the apparatus by the negative pressure maintaining means. Apparatus according to claim 1 further characterized by a glove box (48) for protecting a worker from the contents of said bags. Apparatus according to claim 1, characterized in that said receiving basket (32) includes a downwardly angled perforated bottom (36) such that the basket facilitates discharge of the open bag sections to aid in emptying the contents of said bag. A method for directing dusty or hazardous solid material into a holding vessel from bags containing said material comprising guiding a bag containing dusty or hazardous solid material into an essentially vertical bag feeding chute, said chute including, on an interior surface thereof, a knife blade adapted to cleanly slit open said bag, substantially without generating bag particles, as said bag falls through said chute; causing the slit-open bag and its contents to drop from said chute onto a perforated bag-receiving basket; separating the slit open bag from its solid contents in the receiving basket; contacting the inside of said separated, slit-open bag with a pressurized fluid while allowing the solid material to fall through said perforated receiving basket; directing the solid material from the bag into a holding tank; and removing the opened bag from the bag-receiving basket, wherein the pressurized fluid is preferably compressed air having a pressure greater than ambient pressure. A method according to claim 9 further including establishing a negative pressure through the chute and holding tank to eliminate dust generation surrounding the apparatus wherein the negative pressure is preferably established by operating a blower in fluid communication with a scrubber and holding tank for pulling gas downwardly through the feeding chute, and out of the holding tank. A method according to claim 9 further including removing slit bags through a glove box to protect a worker from the contents of said bags. A method according to claim 9 further including neutralizing contaminants carried by gas within the apparatus in a scrubber in fluid communication with the holding tank. A method according to claim 9 further including directing the slit bag from the fixed knife blades onto a downwardly angled perforated basket such that the basket facilitates discharge of the open bag sections to aid in emptying the contents of said bag. A method according to claim 9, wherein the bagged material is fed from the bags to the holding vessel without liquid addition.

Inventors: MIKKELSEN ALAN R, SORTWELL EDWIN T, MIKKELSEN, ALAN R., SORTWELL, EDWIN T.
Applicants: DIATEC ENVIRONMENTAL
Application year: 1992
Main classification: B65B69
IPC codes: B65B69