Mixing apparatus and method

A mixing apparatus including a frame, a housing, and a pair of thrust generators are disclosed. The housing is pivotably mounted to the frame and is movable between a retracted position substantially parallel with the frame and an extended position substantially perpendicular to the frame. The thrust generators are opposingly mounted to the housing and face opposite directions both when the housing is in the retracted position and when the housing is in the extended position. Various mixing and disposal methods are also described.

BACKGROUND OF THE INVENTION

This invention generally relates to a mixing apparatus and a related mixing method. More particularly, the present invention relates to a mixing apparatus for mixing liquid and solid constituents of a substance to a homogenous liquid/solids mixture and to a related method of mixing a substance including liquid and solid constituents.

Many industrial processes require raw materials in the form of solids and liquid mixtures that tend to separate into solids and liquid constituents when stored or transported. For example, mixtures, such as calcium carbonate in water or clay water slurries, are extremely difficult to transport and store because dense solid materials settle on the bottom of storage containers during transportation and/or storage. When the container is drained, the liquid portion of the mixture is readily removed, but a portion of the solid sediment remains in the storage container. Thus, it is difficult to completely unload all of the solid material.

Calcium carbonate exemplifies a substance used as a component in the manufacture of many common household and medical products from antacids to toothpaste. Additionally, the paper industry uses this material as a substitute for wood pulp paper filler to eliminate the need for unnecessary destruction of forestry. Calcium carbonate is a fine powder substance that is normally mixed with water to create a solid and liquid suspension that is relatively easy to handle for transport in railroad tank cars or tank trucks. Because of the great demand for the end products produced by these industries, extremely large quantities of calcium carbonate must be transported.

While the liquid/solids mixture is within the tank of a transportation or storage device, the solids settle in the liquid and gradually form sediment on the bottom of the tank. This solid sediment is extremely difficult to remove from the tank when the tank is unloaded. The retention of solids in the bottom of the tank poses numerous disadvantages. First, the solids/liquid ratio of the removed mixture is reduced by the retained solids. Secondly, the backhaul of a mobile tank to pick up another load requires unnecessary rehauling of the solids back to the original pickup point, making the tank heavier and wasting fuel. Additionally, the build-up of solids reduces the capacity of the tank so that each subsequent refill of the tank includes less and less volume. Therefore it is desirous to remove substantially all of the settled solid material along with the liquid when the mixture is unloaded. This removal process can be extremely time consuming and expensive.

By way of another example, the invention may be used in the waste industry for mixing solid and liquid constituents of waste products. The invention can be used for example, to blend organic waste having a BTU value (such as K-waste, paint waste, coal tar, or other burnable materials) before it is off-load and burned at an incinerator or cement kiln.

SUMMARY OF A FEW ASPECTS OF THE INVENTION

The advantages and purposes of the invention are set forth in part in the description which follows, and in part may be evident from the description, or may be learned by practice of the invention. The advantages and purposes of the invention may be realized and attained by the elements and combinations particularly pointed out in the appended claims.

In accordance with the invention, a mixing apparatus may include an elongated support structure, and a mixing unit pivotably mounted to the support structure for movement between a retracted position substantially parallel with the support structure and an extended position oriented angularly relative to the support structure, the mixing unit having a pair of opposingly operable thrust generators facing in opposite directions in all angular positions of the mixing unit.

In another aspect, the invention may be directed to a method for mixing liquid and solid constituents contained in a tank having a floor, with a pivotal mixing unit having a pair of opposing thrust generators. The method may include lowering the mixing unit into a tank with the thrust generators in a first position such that one of the thrust generators substantially faces the floor of the tank, clearing the settled solid constituents from an area of the floor of the tank, moving the thrust generators to a second position generally parallel to the floor of the tank at the area cleared of the settled solid constituents, and mixing the liquid and solid constituents of the substance, including the settled solid constituents, with the thrust generators in the second position.

Additional objects and advantages of the invention may be set forth in part in the description which follows, and in part may be evident from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

In accordance with the invention, there may be provided a mixing apparatus having an elongated support structure, and a mixing unit pivotably mounted to the support structure for movement between a retracted position substantially parallel with the support structure and an extended position oriented angularly relative to the support structure.

As embodied herein and illustrated most clearly inFIGS. 1 and 2, one example of a mixing apparatus made in accordance with the invention is generally designated by the reference number10and may include an elongated support structure12and a mixing unit14pivotably mounted to the support structure12. The support structure12may be carried in a vertical orientation by an handling pallet16having a depending bushing18secured by gusset plates20in alignment with an upstanding housing22and a hydraulic header23having hydraulic fluid fitting pairs24,26and28. A tubular shaft30may be journalled in the bushing18and may be supported against axial movement relative to the handling pallet16by a thrust bearing32in the housing22. A motor34may also be contained in the housing22and may be operable by hydraulic fluid supplied to and exhausted from the fitting pair24to rotate the shaft30. One example of a suitable motor is a Permco wheel gear motor, operated remotely by a Permco high displacement hydraulic pump. Of course, throughout this patent, the invention in its broadest sense is not necessarily limited to the structures or equipment described. Alternative structures, equipment and methods may be used without departing from the spirit of and scope of the invention.

A bifurcated unit frame40may be suspended from a stainless steel tube42secured to the shaft30against both rotational and axial movement by appropriate joining means (not shown). The unit frame40may include two spaced apart elongated plates44joined at their top ends, such as by welding, to a bracket46welded to the tube42and reinforced by welded gusset plates48. The plates44may be joined to each other intermediate their length by transverse reinforcing plates50and52that may be located respectively above and below a hydraulic motor54. Motor54may have an output pulley/sprocket56and to which hydraulic fluid is supplied and exhausted through conduits (not shown) connected to the hydraulic fitting pair26. At their lower ends, the plates44may support pivotal bearings58associated with the mixing unit14to which a pulley/sprocket60is fixed. An endless belt/chain62may be trained about pulley/sprockets56and60on the outside of one of the plates44so that operation of the motor54may control pivotal movement of the mixing unit14relative to the frame40.

InFIG. 3of the drawings, various positions to which the mixing unit14may by moved by the motor54are shown to include an extended position E14shown in solid lines and in which the mixing unit is oriented perpendicular to the frame40; a retracted position R14shown in dashed lines and in which the mixing unit14is aligned with the frame40; and a variable intermediate position V14shown in dot-dash lines and in which the mixing unit14is inclined relative to the frame40. As will be described in more detail below, each of these positions, as well as other intermediate positions, may be used in operation of the mixing apparatus10.

In accordance with the invention, the mixing unit may have a pair of opposingly operable thrust generators facing in opposite directions in all angular positions of the mixing unit.

In the illustrated embodiment, as shown inFIG. 1, the mixing unit14may include a central, integrated housing (or frame)70pivotably supported by the bearings58at the lower end of the bifurcated frame40, and enclosing a pair of axially aligned, hydraulic motors72and74operated by hydraulic fluid supplied to and exhausted from the fitting pair28though hydraulic conduits (146inFIG. 6) extending from the fitting pair28to a rotary flow divider76mounted to the housing70. Opposingly operable thrust generators78and80may be mounted to opposite ends of the housing70. Each of the thrust generators78and80, in the illustrated embodiment, may be defined by propellers82and84, driven by the respective motors72and74. The propellers may be enclosed by open ended shrouds86and88, supported by struts90that may be secured to the opposite ends of the housing70. The propellers82and84may be pitched and rotated in a direction to direct a flow of liquid outwardly through the shrouds in opposite directions. Alternatively, shrouds may be omitted. In addition, the blades may be pitched in any direction capable of performing the desired level of mixing. Other conventional and known thrusting devices, including but not limited to pumps and jet propulsion devices may be used as the thrust generators78and80. For example, propellers for watercraft may work well with the invention. An example of such a propeller includes a 14″×18″ stainless steel chopper propeller.

The flow divider76may function to direct an equal volume of hydraulic fluid to each motor72,74. An equal volume of hydraulic fluid to each motor ensures that the thrust generated by each propeller82,84is equal and opposite. This equal and opposite thrust, in turn, ensures that the reaction forces exerted on the housing70by the propellers82and84are equal and cancel each other. Accordingly, no substantial net force is exerted on the housing70or the frame40by simultaneous operation of the propellers82and84.

A sled-like bearing foot92may be secured by brackets94to the underside of the housing70in the horizontal orientation thereof shown in FIG.1. The bearing foot92may be spaced from the housing70and shrouds86,80so that it may engage the floor of a tank in which the apparatus10is used and prevent damage to the thrust generators78and80.

In use, the mixing apparatus10may be suspended from the handling pallet16engaged by a lifting device, such as a high reach fork lift truck100, as depicted inFIG. 4of the drawings. To facilitate this engagement, the handling pallet16may be formed with slot-like apertures102, shown inFIG. 2, to receive the fork tines of the fork lift truck100. In this manner, the handling pallet16may be retained against rotation under any reaction torque that may occur by operation of the motor34to rotate or oscillate the frame40. Alternatively, the unit can also be adapted to be lowered into tall tanks from a crane. With such an arrangement, the unit may be strapped to the tank's roof.

The illustrated organization of the handling pallet16and motor driven rotation or oscillation of the frame40may enable the operator of the fork lift truck100to control all operating components of the apparatus10, using a hydraulic control unit (not shown) connected to the fitting pairs24,26, and28. Alternatively, the mixing apparatus could be suspended from a cable connected directly to the header22. In this alternative, the handling pallet16could be replaced by a hand wheel fixed to the shaft30to facilitate manual rotational positioning of the frame40, thus eliminating the need for the motor34.

In accordance with the present invention, a method may be provided for mixing a substance having liquid and solid constituents contained in a tank having a floor, with a pivotal mixing unit having a pair of opposing thrust generators. Substances with which the invention may be used include calcium carbonate, other clay or clay-like materials, particulates, granules, powders, and other sedimentary substances. The invention may be used with hazardous and non-hazardous waste, substances, raw materials, and any other category of sedimentary substance. The invention may also be used to mix two liquids, where one liquid is lighter than the other and therefore the liquids tend to separate. The mixing may be performed on a substance that, after loading into the tank is separated into subcomponents, or, the mixing may be performed on two components that are separately loaded, and thereafter require mixing.

The method may include lowering the mixing unit into a tank with the thrust generators in a first position such that one of the thrust generators substantially faces the floor of the tank, clearing settled solid constituents from an area of the floor of the tank, moving the thrust generators to a second position generally parallel to the floor of the tank at the area cleared of the settled solid constituents, and mixing the liquid and solid constituents of the substance, including the settled solid constituents, with the thrust generators in the second position. In addition, since the thrust generators may be operable in varying positions, the pitch and angular orientation may be altered during mixing or at periodic intervals in order to accomplish either a more thorough and faster mixing, depending on the substances being mixed.

As shownFIG. 4, a tank110, having a top access opening112, is filled with a liquid/solids mixture generally designated by the reference number114. The tank110may be any of many different types of tanks, including but not limited to rail tank cars, tank trucks, roll-off boxes, stationary tanks, any other mobile tanks and ISO containers. As depicted inFIG. 4, the mixture114is separated into an upper, primarily liquid component116and a solids component118settled on the floor120of the tank110. This separation might occur over time, or the tank may be loaded with the components in substantially separate form. In order to unload the whole of the mixture114from the tank either by pumping it out through the opening112, or by draining it through a drain conduit (not shown) in the floor120, it is preferable to mix the sediment118with the liquid component116, to cause a substantially homogenous mixture.

The mixing apparatus10may be operated to carry out the mixing method by lowering the mixing unit14down through the access opening112and into the tank110with the mixing unit14in the retracted position aligned with the elongated support structure12to fit through the reduced size of the access opening112. If the access opening112large enough, however, the mixing unit14may be lowered into the tank110while it is in the extended position or in an intermediate position.

When the mixing unit14is submerged in the mixture14, the mixing apparatus10may be used to clear the settled solid constituents112from an area of the floor94. For example, as the mixing apparatus10is lowered into the tank110with the unit14in the retracted position R14(FIG.3), one of the thrust generators78,80faces the floor120. Accordingly, operating one or more of the thrust generators78,80for sufficient period of time will clear the settled solid constituents118from an area of the floor120under the mixing apparatus10. Thereafter, the mixing unit14kmay be adjusted to an inclined intermediate position V14(FIG. 3) and the frame40rotated by operation of the motor34to enlarge the cleared area of the floor120.

After an area of the floor120is cleared of the settled solid constituents118, the mixing unit14may be moved to the extended position E14. With the mixing unit14in the extended position, the mixing apparatus10may be further lowered into the tank110such that the foot92engages the area of the floor120cleared of the settled solid constituents118. When engaged with the floor12of the tank, the foot92may prevent the mixing unit14from moving toward the retracted position. However, the frame40may rotate around its longitudinal axis when the foot92engages the floor120.

With the mixing unit14in the extended position, the thrust generators78and80may be used to mix the liquid and solid constituents of the mixture114, including the settled solid constituents118. The thrust generators78and80may produce sufficient thrust and flow to mix the mixture114in a short period of time. For example, each thrust generator50may produce flow of up to twenty-three thousand gallons per minute. This flow equates to forty-six thousand gallons per minute, the equivalent of rolling a tank car every thirty seconds.

The flow produced by the thrust generators78and80in the extended position may cause a thrust toward the side walls of the tank110near the floor120so that the solid constituents118of the mixture114, including the settled solid constituents118, may be undermined and thrust into the flow pattern developed by the thrust generators78and80. The solid constituents may then return to the suction side of the thrust generators78,80where they may be chopped and thrust out again and again until shortly, a homogenous mixture may be reached and may be ready to be off-loaded from the tank110. The mixing apparatus20may be designed to handle slurries up to sixty percent solids and viscosities to ten thousand centipoises. The mixing apparatus may be permanently mounted in a tank or may be movable from tank to tank. Alternatively, the mixing apparatus may be mounted in a tanker or railcar.

Exemplary uses of the invention include the waste industry. For example, hazardous waste may be safely disposed of through incineration. To that end, hazardous waste may be used as fuel for cement kilns. Since the hazardous waste may be made up of solid and liquid constituents, the invention may include mixing the waste to form a substantially uniform mixture in the tank. A substantially uniform mixture ensures a substantially constant BTU valve across the tank resulting in substantially constant burning properties. And mixing helps ensure that minimal residue remains on the tank floor after unloading.

The invention may be employed with fixed tanks, tanks mounted on vehicles such as tanker trailers, or other movable containers such as roll-off boxes. For example, roll-off boxes can be used to contain K-waste from the refinery industry. Such K-waste may take the form of sludge derived from the refinery process and/or the tank cleaning process in refineries. A method of the invention may include adding a thin liquid, such as diesel fuel, to the sludge. A mixing unit may be used to blend the thin liquid with the sludge in order to put the mixture into a pumpable slurry form for disposal in an incinerator such as a cement kiln.

Another method of the invention may involve emptying large tanks (e.g., tank150inFIG. 5) having sludge layers on their bottoms. By way of example only, a tank of 10-200 feet in diameter containing a layer of sludge may be difficult to clean or empty. One or more holes152(for example, 8 feet by 8 feet) may be cut in the side of the tank150above the sedimentary layer. A liquid material such as, for example, diesel fuel or waste oil may be added to the tank. If the method involves disposal of a product to be burned, the added liquid is preferably burnable. A mixer10(such as the one previously described), suspended from the end of boom148, may be inserted into the tank through the opening152in the tank wall and then activated by energizing hydraulic fluid power unit156. The boom148may be part of an extendable bend forklift154, which may have a reach of up to 70 feet or more. Through entering the tank at various angles and also extending the forklift to various lengths, the tank may be blended. Other insertion structures or methods may alternatively be used. The tank contents may then be pumped off or vacuumed into an agitator tanker trailer (such as the one described in U.S. Pat. No. 6,333,446, incorporated herein by reference). The contents may thereby be transported to a cement kiln or other incinerator for disposal.

In one example, one foot of diesel fuel was added to a 70 foot diameter tank containing 8 feet of sludge on the bottom. Using the structure described herein, it was possible to blend the tank in 48 hours, emptying it to 3 inches of sludge without any personnel having to enter the tank. Typical units may run at 200-300 horsepower, and larger units may extend to 600 horsepower or greater. While the mixing unit described herein may be used in connection with methods of the invention, in its broadest sense the various mixing methods of the invention are not limited to any particular structure.

It will be apparent to those skilled in the art that various modifications and variations can be made to the invention without departing from the scope or spirit of the invention. Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein.