Abstract:
A method and system for using plastic material as a fuel includes dissolving the plastic material in biodiesel to form a solution. After the solution is created, it is filtered to remove insoluble contaminants and is then fed to a generator that oxidizes the solution to create power and/or heat. Heat from the oxidation of the solution can be utilized to facilitate the further dissolution of plastic material in biodiesel and to reduce the viscosity of the resulting solution.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention pertains generally to systems and methods for using plastics. More particularly, the present invention pertains to the use of plastics in fuel for power/heat generating units. The present invention is particularly, but not exclusively, useful in methods or systems that dissolve plastic material in biodiesel for use as fuel.  
       BACKGROUND OF THE INVENTION  
       [0002]     The world&#39;s annual consumption of plastic materials has increased from around 5 million tons in the 1950s to nearly 100 million tons today. While recycling efforts have been made to reduce the amount of plastic waste landfilled, applications or markets for recycled plastics are often limited. Additionally, the costs involved in collecting, transporting, and separating plastic waste often result in recycled plastic products that are more expensive than new plastic products. This is particularly true for situations in which special storage and transport of the waste is required. For instance, shipboard waste or waste at remote forward military bases may require special disposal procedures.  
         [0003]     As with the concerns for handling waste, the storage and transport of fuel incurs high costs for many operations, such as on ships and military bases. Therefore, a reduction in the need for fuel can significantly reduce costs. One fuel source that can be used in such operations is biodiesel. Biodiesel, i.e. fatty acid alkyl esters, is a fuel made from fatty acids and oils from animals and plants, particularly soybeans. It is fully renewable and can be used in many diesel engines. Its high cost, however, currently prevents it from competing with traditional diesel fuel. Nevertheless, by somehow increasing the output from the oxidation of biodiesel, it can be made more cost competitive.  
         [0004]     With the above in mind, consideration is given here for dissolving plastic material in biodiesel before using it as fuel. As a result, the amount of plastic material that must be transported for landfilling or other recycling is reduced. Additionally, the plastic material that is transported (in fuel form) is far less bulky and far easier to ship. Furthermore, the heating value of the plastic material can make the biodiesel cost competitive as a fuel.  
         [0005]     In light of the above, it is an object of the present invention to provide methods and systems for using plastic material dissolved in biodiesel as fuel. Another object of the invention is to provide methods and systems for recycling plastic waste as a component of a fuel. Another object of the present invention is to provide methods and systems for increasing the output of biodiesel as fuel. It is yet another object of the present invention to provide methods and systems for reducing the volume of plastic material, particularly plastic waste. Still another object of the present invention is to provide systems for using plastic material as a fuel, and methods of using the systems, that are relatively easy to create, simple to use and comparatively cost effective.  
       SUMMARY OF THE INVENTION  
       [0006]     In accordance with the present invention, a system and method are presented for dissolving plastic material in a fuel for the purpose of increasing the heating value of the fuel. Specifically, the system includes a holding tank for storing a biodiesel fuel, and the holding tank is connected in fluid communication with a dissolution chamber. Biodiesel can then be selectively transferred from the holding tank to the dissolution chamber. Additionally, the dissolution chamber is provided with an access port for dumping plastics and other plastic-type wastes into the dissolution chamber. The purpose here is to dissolve the plastics in the biodiesel to thereby create a supplemented biodiesel fuel.  
         [0007]     A tube is provided that leads from the dissolution chamber to a filter where insoluble products are removed from the supplemented biodiesel. Once the insoluble products are removed, the supplemented biodiesel can then be transferred via a storage inlet tube to a storage container. Outlet pipes from the storage container and the filter are also provided to selectively transfer the supplemented biodiesel from the storage container, or directly from the filter, for use by a heat or power-generating device (generator) such as an engine, turbine, heater or burner.  
         [0008]     Another aspect of the present invention is that the output heat from the generator can be provided to other systems or devices as desired. For instance, the heat can be provided back to the holding tank or the dissolution chamber, or both, to heat the biodiesel to assist in dissolving the plastics that are introduced into the dissolution chamber to create the supplemented biodiesel. Additionally, the heat can be provided back to the dissolution chamber or storage container, or both, to heat the supplemented biodiesel. Heating the supplemented biodiesel reduces its viscosity and allows it to be more easily fed to, and burned by, the generator.  
         [0009]     In operation, biodiesel is released from the holding tank to the dissolution chamber. Plastic waste material can then be added to the dissolution chamber. Additives or heat may also be added to the dissolution chamber to facilitate dissolution of the plastic material within the biodiesel. The consequence of this addition is that as the soluble plastic material dissolves, the biodiesel and plastic material form a supplemented biodiesel solution. If insoluble plastic material or other non-plastic materials (nonsoluble materials) are included within the supplemented biodiesel solution, the solution and nonsoluble materials form a slurry which needs to be filtered.  
         [0010]     After dissolution is completed, the slurry is pumped out of the dissolution chamber through the chamber exit tube. The slurry then passes through a filter which separates the nonsoluble materials from the supplemented biodiesel solution. From the filter, the solution is fed to the generator which burns the solution as a fuel to create heat and/or power. For immediate use of the solution as fuel, a generator feed conduit delivers the solution directly from the filter to the generator. In other cases, the solution may be piped to containers for storage or transport. When needed, the solution is fed from the storage containers to the generator.  
         [0011]     Depending on the composition of the filtered solution, i.e., the ratio of plastic to biodiesel, the solution may be too viscous to be used as a fuel. In such cases, the solution is heated to reduce its viscosity. Alternatively, solvents or additives may be utilized to lower the solution viscosity. In order to maximize efficiency of the system, at least a portion of the heat output of the generator is directed to the dissolution chamber or storage containers to reduce the viscosity of the solution. Furthermore, heat may be provided to the dissolution chamber to facilitate dissolution of the plastic waste.  
         [0012]     While the invention has been described as using plastic waste material, it is contemplated that non-waste plastic material may also be used. 
     
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0013]     The novel features of this invention, as well as the invention itself, both as to its structure and its operation, will be best understood from the accompanying drawing, taken in conjunction with the accompanying description, in which the FIGURE is a process flow diagram of a system for using plastic material as fuel in accordance with the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0014]     Referring to the FIGURE, a system for using plastic material as fuel in accordance with the present invention is shown and generally designated  10 . As shown, the system  10  includes a holding tank  12  that stores biodiesel  14 . A biodiesel conduit  16  provides fluid communication between the holding tank  12  and a dissolution chamber  18 . Additionally, an additive hose  20  provides fluid communication between the dissolution chamber  18  and an additive reservoir  22  that holds additives  24  such as solvents. Further, the dissolution chamber  18  includes a port  26  for receiving the plastic material  28 .  
         [0015]     As shown in the FIGURE, a chamber exit tube  30  provides an outlet to the dissolution chamber  18  and leads to a filter  32 . The filter  32  includes a sieve, grate or other filtering mechanism. Downstream of the filter  32  is a generator  34 , which may be an engine, turbine, heater or burner. A generator feed conduit  36  provides direct fluid communication between the filter  32  and the generator  34 . Alternatively, a storage container  38  may be positioned between the filter  32  and generator  34 . In such a case, a storage inlet pipe  40  leads from the filter  32  to the storage container  38  and a storage outlet pipe  42  leads from the storage container  38  to the generator  34 .  
         [0016]     The output  44  of the generator  34  includes power and/or process heat  46 . Additionally, the output  44  may include recyclable heat  48 . As shown in the FIGURE, the recyclable heat  48  is directed to system components to provide heat where desired. Specifically, a tank heating conduit  50  connects the recyclable heat  48  to the holding tank  12 , a chamber heating conduit  52  connects the recyclable heat  48  to the dissolution chamber  18 , and a container heating conduit  54  connects the recyclable heat  48  to the storage container  38 .  
         [0017]     During operation of the system  10 , a desired amount of biodiesel  14  is fed from the holding tank  12  through the biodiesel conduit  16  to the dissolution chamber  18 . Then, the plastic material  28  is added to the biodiesel  14  in the dissolution chamber  18 . Preferably, the plastic material  28  is polymeric and may comprise polystyrene, polyethylene, polypropylene or other thermopolymers.  
         [0018]     Once the plastic material  28  is received within the dissolution chamber  18 , the biodiesel  14  begins to dissolve at least a portion of the plastic material  28  to form a supplemented biodiesel solution  56 . In certain cases, particularly for polyethylene and polypropylene, the biodiesel  14  may require heating to over 120° C. to facilitate dissolution of the plastic material  28 . For polyethylene, the biodiesel  14  should be heated to about 130° C. to prompt dissolution. For polypropylene, the biodiesel  14  needs to be heated to about 160° C. to prompt dissolution. Some polymers, however, such as polystyrene, may be dissolved by biodiesel  14  at ambient temperature.  
         [0019]     In addition to the biodiesel  14  and plastic material  28 , additives  24  including solvents may also be introduced to the dissolution chamber  18 . The additives  24  may facilitate dissolution of the plastic material  28  or provide desired characteristics to the resulting supplemented biodiesel solution  56 . If the plastic material  28  includes any nonsoluble material  58 , such as non-plastic material or insoluble plastics, then a slurry  60  of the supplemented biodiesel solution  56  and nonsoluble material  58  is formed in the dissolution chamber  18 .  
         [0020]     As shown in the FIGURE, the slurry  60  is fed from the dissolution chamber  18  to the filter  32  by the chamber exit tube  30 . The filter  32  removes the nonsoluble material  58  from the supplemented biodiesel solution  56 . While a static filter  32  is shown in the FIGURE, it is contemplated that a movable filter can be used to remove the nonsoluble material  58  from the dissolution chamber  18  or from the slurry exit tube  30 .  
         [0021]     After removal of the non-soluble material  58 , the supplemented biodiesel solution  56  is fed to the generator  34  through the generator feed conduit  36 . Alternatively, the supplemented biodiesel solution  56  is fed to the storage container  38  through the storage inlet pipe  40 . In such a case, the storage container  38  is filled with supplemented biodiesel solution  56  and is stored and/or transported. When use of the supplemented biodiesel solution  56  is desired, fluid connection between the storage container  38  and the generator  34  is established via a storage outlet pipe  42 . After such connection, the supplemented biodiesel solution  56  may be fed to the generator  34 . If the supplemented biodiesel solution  56  is too viscous for use as fuel, it may be heated prior to delivery to the generator  34 . Typically, high viscosity is encountered when the plastic material  28  comprises about 20-50 wt. % of the supplemented biodiesel solution  56 . Supplemented biodiesel solutions  56  comprising less plastic material  28 , such as a solution  56  comprising 90 wt. % biodiesel and 10 wt. % polystyrene, may exhibit a lower viscosity and not require heating.  
         [0022]     The generator  34  burns the supplemented biodiesel solution  56  upon receiving it from the generator feed conduit  36  or the storage outlet pipe  42 . Due to the increased energy value of the supplemented biodiesel solution  56 , as compared to the original biodiesel  14 , the generator  34  creates an increased output  44 . The output  44  comprises process heat and/or power  46  in addition to recyclable heat  48 . As shown, the recyclable heat  48  may be communicated to other system components. For instance, the recyclable heat  48  may be communicated to the holding tank  12  via the tank heating conduit  50  to heat the biodiesel  14 . Further, the recyclable heat  48  may be communicated to the dissolution chamber  18  via the chamber heating conduit  52  to heat the biodiesel  14  or the supplemented biodiesel solution  56  or slurry  60  formed therein. Finally, the recyclable heat  48  may be communicated to the storage container  38  to heat the supplemented biodiesel solution  56 .  
         [0023]     While the particular system for using a plastic material as fuel as herein shown and disclosed in detail is fully capable of obtaining the objects and providing the advantages herein before stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of construction or design herein shown other than as described in the appended claims.