Abstract:
This invention relates to a method and apparatus for gasifying or liquifying coal. In particular, the method comprises reacting a coal with a molten aluminum or aluminum alloy bath. The apparatus includes a reaction vessel for carrying out the reaction, as well as other equipment necessary for capturing and removing the reaction products. Further, the process can be used to cogenerate electricity using the excess heat generated by the process.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a method to gasify or liquefy coal and to capture and recover carbon, sulfur, hydrocarbons, and heavy metals from the coal using a molten aluminum or alloy bath composed of aluminum or an aluminum alloy that includes, but is not limited to zinc, iron, copper, silicon and calcium alloys. 
       BACKGROUND OF THE INVENTION 
       [0002]    Although a number of methods exist to gasify or liquefy coal, these methods are costly and in some cases create a secondary waste that can be more of a problem than the actual gas stream itself. Currently, coal gasification or liquefacation methods create greenhouse gases such as carbon monoxide carbon dioxide, as well as, other bi-products such as tar, ammonia, and tar-water emulsions. Further, these processes also produce slag, which currently must be land filled and there is currently no efficient method to recovery heavy metals, such as mercury, that typically are found in coal. While these processes work, they require significant energy input or create waste streams that must be disposed of at a cost to the operator and with potential future environmental impact. Thus, there is a need in the art for an improved method to economically gasify or liquefy coal while recovering the remaining carbon, sulfur and any heavy metals. 
       SUMMARY OF THE INVENTION 
       [0003]    The present invention provides an apparatus for gasifying or liquefying coal. The coal can be any coal from peat (a coal precursor) to lignite (60% carbon) to anthracite (90+ % carbon). The process utilizes a molten aluminum or molten aluminum alloy bath. The aluminum can be alloyed with metals that include, but are not limited to zinc, iron, copper, silicon, and calcium. The coal is ground and can be dried, and then the powder is introduced into the bath below the surface. The powdered coal is forced below the surface using an inert gas such as Nitrogen or argon. In the process excess heat is generated and can be used to facilitate other processes such as cogeneration of power. As the coal is passed through the bath, the aluminum or aluminum alloy bath reacts with the coal to break it down to its elemental parts. These elements are then removed from the bath using a gravimetric process and a gas capture process. The elements removed from the bath can include, but are not limited to, carbon, sulfur, hydrogen, nitrogen, mercury, copper, iron, as well as other heavy metals. The process can also produce methane and other hydrocarbons. The elemental materials can be recovered and sold and the hydrocarbons are recovered and sold or burned to facilitate the process. The inert gas is reprocessed and reused. 
         [0004]    The aluminum or aluminum alloy bath is able to remove oxygen compounds by chemically reacting with them at high temperature. This allows the carbon bonds of the coal to be broken, producing volatile organic compounds, as well as elemental compounds. 
         [0005]    This process has been evaluated in laboratory tests using ground lignite coal. The ground coal was passed through molten aluminum. The flue gas produced and the final alloy mass were analyzed using scanning electron microscope. (See Table 1). 
         [0000]    
       
         
               
             
               
               
             
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Process Mass Analysis 
               
             
          
           
               
                   
                 MOL % 
               
               
                   
                   
               
             
          
           
               
                   
                 H2 
                 25.181 
               
               
                   
                 CO2 
                 27.345 
               
               
                   
                 CO 
                 14.265 
               
               
                   
                 C 
                 19.898 
               
               
                   
                 C2 
                 2.824 
               
               
                   
                 C2 
                 2.999 
               
               
                   
                 C3 
                 0.939 
               
               
                   
                 C3 
                 2.228 
               
               
                   
                 C4 
                 0.199 
               
               
                   
                 C4 
                 1.034 
               
               
                   
                 C4 
                 0.000 
               
               
                   
                 C5 
                 0.199 
               
               
                   
                 C6 and above 
                 2.888 
               
               
                   
                   
                 100 
               
               
                   
                   
               
             
          
         
       
     
         [0006]      FIG. 1  shows the basic process flow. In the basic process, powdered coal is introduced below the surface of the molten metal bath  103  using an injection feed system  101  through feed line  102 . The elemental material, such as carbon, sulfur and the like, is captured  104 , less dense secondary compounds are removed from the surface of bath  105 , and denser secondary compounds are removed from the bottom of the bath  106 . While this has been described as a method to gasify or liquefy coal, use of this method to other organic compounds, such as, for example, peat, wood, and grass are also contemplated. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying Figures and drawings, in which: 
           [0008]      FIG. 1  shows the basic process flow; 
           [0009]      FIG. 2  shows a typical process flow; and 
           [0010]      FIG. 3 . shows a detailed cross sectional view of the reaction vessel wall. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0011]    The present invention provides a process to gasify or liquefy coal. The process utilizes a molten aluminum or molten aluminum alloy bath. The process utilizes a molten aluminum bath as the reactant. The coal, which is introduced below the surface of the molten aluminum bath, reacts with the aluminum to decompose the coal. In the process, elemental carbon, sulfur, copper, iron, and heavy metals and molecular hydrogen, nitrogen, methane, and other hydrocarbons are removed from the molten bath. The products can be sold and the nitrogen is either vented to the atmosphere or captured. 
         [0012]    The process utilizes a molten metal as the primary reactant. In the preferred embodiments the molten metal is aluminum or an aluminum bath. The aluminum can also be alloyed with other elements including, but not limited to, zinc, iron, copper, silicon, magnesium, and calcium. Other metals and metal alloys such as calcium and silicon are also envisioned. The flue gas stream, which contains oxygen containing greenhouse gases produced by combustion processes, is passed through the aluminum alloy bath to remove the oxygen-containing gases from the flue gas stream. 
         [0013]    In the process, excess heat is generated and can be used to facilitate other processes such as cogeneration of power. The excess generated by the process is a function of the makeup of the greenhouse gases in the flue gas feed. 
         [0014]    When the coal contains other compounds, those compounds can also be decomposed or captured. For example, if the coal contains inorganic compounds, such as chlorine, the process will produce an aluminum salt, in this case aluminum chloride. The present invention also provides a method and apparatus for capturing heavy metals, such as, but not limited to mercury, which is often found in coal. In the process, the molten metal bath breaks down the metal compounds as they are introduced into the molten metal bath. As additional aluminum is added to the bath, the heavy metals settle to the bottom of the reaction vessels and are removed from the reaction vessel. While some aluminum may be entrained in the heavy metals that are removed from the bottom of the reaction vessel, the aluminum can be removed and refined and the heavy metals can be captured. 
         [0015]    A detailed process flow is shown in  FIG. 2 . While the process described discusses processing coal, other organic materials can be processed using the invention. The ground coal is introduced into the treatment process through blower feed line  211 . Blower  210  is used to inject the ground coal into reaction vessel  220  through injection line  212 . Injection line  212  introduces the ground coal stream, which is entrained in an inert gas such as nitrogen, below the surface  222  of the molten aluminum compound  226 . Injection line  212  must be sufficiently below the surface  222  of the molten aluminum compound  226  to allow for sufficient mixing. The heavy products of the reaction, typically the heavy metals described above will settle out in the reaction vessel. The reaction vessel typically has a sloped bottom, however other designs such conical and the like can be utilized. Once the heavy products settle out, they are collected using collection lines  223 ,  224 , and  225 . Collection lines  223 ,  224 , and  225  allow for heavy metals of different densities to be removed. Depending on the size of the process, the heavy products can be continuously removed or a batch removal process can be used. 
         [0016]    Reaction vessel  220  also includes an aluminum feed line  221 , which is used to supply additional aluminum compound to replace that consumed by the reaction with the ground coal. Additional heat may be required during start-up, for example. Heater  227  is provided for this purpose. Heater  227  can be any type heater, including radiative, inductive, and convective. For example, heater  227  would be a microwave heater or a radio frequency heater wherein the frequency is tuned for the metal alloy used. 
         [0017]    Thus, the heat generated by the process must be removed. Section A, which is shown in more detail in  FIG. 3  shows one way the heat can be removed from the process. The reaction vessel  220  is lined with a refractory material  310 , which protects the vessel wall  320 . Cooling plate  330  is attached to the vessel wall  320  and cooling water is circulated in the channels created between the cooling plant  330  and the vessel wall  320 . Insulation  340  surrounds the cooling plate to maximize heat recovery, as well as for safety purposes. Once the cooling water picks up the heat generated from the process, it can be either sent to a cooling tower or the heat can be recovered and used for other purposes. If the process is used in a facility that needs a hot water source, then the heat recovery system can be designed for this purpose. However, the heat can also be used to generate electricity. 
         [0018]    Turning back to  FIG. 2 , a steam turbine electric generation process is represented. In this case, the cooling water is introduced thorough cooling feed  228 . As the cooling water travels around the reaction vessel  220 , it picks up heat and steam is generated. The steam generated is then sent via steam line  229  to steam turbine  232 . The steam passes through the turbine and as it condenses, turns the turbine blades of turbine  232 . Turbine  232  is coupled to generator  231 . As the turbine turns the rotor of generator  231  though the stator, it generates electricity. While this process is only briefly described, this steam turbine-electric generator process is well known in the art. And any steam turbine-electric generator process could be utilized. 
         [0019]    Also, as described above, the reaction will also produce elemental carbon, elemental sulfur, molecular nitrogen and molecular hydrogen. These will be removed from the reaction vessel using blower  250 . Blower  250  will pull high temperature elemental carbon, elemental sulfur, molecular nitrogen and molecular hydrogen from the reaction vessel  220  through heat exchanger feed line  241  into heat exchanger  240 . Heat exchanger  240  will then cool this material to enable further processing. Any hydrocarbons that are produced may also be condensed in heat exchanger  240 . These liquid hydrocarbons can be collected for further use or sale. Heat exchanger  240  can be any heat exchanger, however in the preferred embodiment, heat exchanger  240  is a forced air heat exchanger, however other heat exchangers, are also envisioned. The process steam then leaves the heat exchanger through line  242  and passes through blower  250  and blower discharge line  252  into two cyclone separators. The first separator  260  separates out carbon from process stream. The carbon is collected though separation line  263 . The remaining process stream through line  262  proceeds to the second separator  270 , which separates out sulfur from the process stream. The sulfur is collected through separation line  273 . The remaining process stream, which may include gaseous nitrogen and hydrogen, is then sent through line  272  and separated in cryo unit  280 . In this unit, the gas stream is cooled further and to allow the components to be separated into different components that are sent through lines  282  and  283 . 
         [0020]    Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.