Abstract:
The present invention provides an apparatus for waste sorting and uses thereof for the separation of said waste into organic and inorganic material, including processes for its use and in some embodiments subsequently producing biogas from said waste material.

Description:
FIELD 
       [0001]    This invention relates to an apparatus for separating waste and uses thereof. 
       BACKGROUND 
       [0002]    Significant amounts of waste are generated on a daily basis by organizations and households, the majority of which is currently deposited in landfills. Apart from the decreasing amount of land available for such landfills, depositing waste in landfills causes many other problems as well, including pollution of water resources, objectionable odors and other impacts on the surrounding population. Furthermore, environmentally harmful green house gases (GHG) are produced in large quantities in landfills. 
         [0003]    In order to overcome the environmentally harmful effect of GHG bioorganic waste can be converted into biogas, through a process that both reduces the volume and quantity of material to be deposited in landfills and also generates a new source of energy. Waste streams such as agriculture waste and household waste contain a high percentage of bioorganic matter. Anaerobic reactors can be used to convert the bioorganic matter into biogas. However, most of the waste stream contains other elements such as plastic, metal, glass, grit etc, which cannot be converted to biogas. Such non-bioorganic elements tend to physically block the reactor, interfere with the digestion process and contaminate output materials that could otherwise be used/reused, such as compostable organic residue for example. 
         [0004]    Various methods and systems have been proposed to overcome this problem for biogas generation from waste streams. U.S. Pat. No. 5,679,263 describes an apparatus in which three different types of waste materials are fed into the system at three different points: liquid, solid and “sludgy” waste. However, non-bioorganic waste must be separated out before the bioorganic waste can be used for biogas generation. U.S. Pat. No. 4,111,798 relates to an apparatus for separating waste according to a selected density threshold: material that is less dense than a particular threshold floats while material that is denser than the threshold sinks, thereby allowing the two types of material to be separated. U.S. Pat. No. 2,202,772, relates to a digester which maintains sludge in a suspended state. 
       General Description 
       [0005]    The present invention provides an apparatus comprising: a reactor for receiving waste material; a mixer for mixing said material with a liquid; a skimmer for removing a portion of said waste material having similar or lighter density than said liquid; and a settler for removing a portion of said waste material having higher density than said liquid. 
         [0006]    The term “waste material” should be understood to encompass any type of waste material (being non or partially sorted) from any source (being household, landfill, industrial, agricultural, marine, municipal, sewer, drain and so forth). Said waste material separated by an apparatus and process of the invention comprises organic materials from a biological source, non-bio organic material (i.e. organic material that is not from a biological source, any organic synthetic material such as for example organic plastic material, organic polymeric material of any kind) and inorganic material from any source. 
         [0007]    In an apparatus of the invention said waste material is mixed homogenously with a liquid in a reactor (in some embodiments equipped with a mixer). Said reactor having a higher top portion and a lower portion. During said mixing a portion of said waste material having density similar or lighter than the density of said liquid in said reactor (i.e. having the same density as said liquid or having density less than said liquid) is suspended at the top portion of said reactor and a portion of said waste material having density higher than the density of said liquid in said reactor settles to the lower portion of said reactor. 
         [0008]    A skimmer (in some embodiments having a mechanical rotating arm) situated at the top portion of said reactor and is capable of receiving and skimming said waste material having density similar or lighter than the density of said liquid in said reactor to an outlet situated at said top portion of said reactor. 
         [0009]    A settler (in some embodiments having a conical shape) situated at the lower portion of said reactor is capable of receiving said portion of said waste material having higher density than said liquid in said reactor and removing it through an outlet situated at said lower portion of said reactor. 
         [0010]    In some embodiments said portion of said waste material having similar or similar or lighter density than said liquid comprises organic and non-bio organic waste material. 
         [0011]    In other embodiments said portion of said waste material having higher density than said liquid comprises inorganic waste material. 
         [0012]    In further embodiments said liquid in said reactor is water. 
         [0013]    In other embodiments an apparatus of the invention further comprises a diffuser for blowing gas bubbles into said reactor. In some embodiments said gas bubbles are micro-bubbles. In other embodiments, said gas is methane (in further embodiments said gas is biogas). 
         [0014]    In further embodiments said reactor further comprises anaerobic bacteria. Such anaerobic bacteria is capable of producing biogas from said waste material. 
         [0015]    In further embodiments said waste material comprises less than 10% wt of solids. In other embodiments said waste material comprises between about 2% wt 8% wt of solids. When referring to weight percent of solids in said waste material it should be understood to relate to the weight amount of solids in said waste material that is not dissolved or hydrated prior to input into said apparatus of the invention. Since the solid weight in said waste material is low, hydrolyzation of said waste is performed with substantially no extraction or acetalyzation and/or methanolyzation of said waste. 
         [0016]    In a further aspect the invention provides a process for separating waste material composing: inserting said waste material into an apparatus comprising a reactor for receiving waste material; mixing said waste material with a liquid in said reactor using a mixer; removing a portion of said waste material having similar or lighter density than said liquid using a skimmer; and removing a portion of said waste material haying higher density than said liquid using a settler. 
         [0017]    Further embodiments of a process of the invention comprises diffusing gas bubbles into said reactor. 
         [0018]    fn yet further embodiments of a process of the invention said reactor further comprises anaerobic bacteria. Thus, in some embodiments, a process of the invention further provides biogas from said waste material. 
         [0019]    In some embodiments of a. process of the invention said waste material comprises less than 10% wt of solids. In other embodiments, said waste material comprises between about 2% wt-8% wt of solids. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    In order to understand the disclosure and to see how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which: 
           [0021]      FIG. 1  shows an exemplary, illustrative apparatus according to at least some embodiments of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0022]    The present invention is directed to a separating reactor and method of its use for the efficient waste separation including the removal of non bioorganic matter as part of the process and, in some embodiments, generation of biogas from partially sorted waste. 
         [0023]    The waste material is further characterized according to at least some embodiments of the present invention by optionally comprising at least about 40% organic waste, in other embodiments at least about 55%, in other embodiments at least about 65% organic waste, in further embodiments at least about 75% organic waste, in further embodiments at least about 85% organic waste and is some further embodiments at least about 95% organic waste. 
         [0024]    As a non-limiting example, such waste may optionally be provided through a waste stream that is separated at the source and/or separated after collection, which may comprise also non-organic materials. 
         [0025]    Said waste materials are separated in a reactor of the invention by use of a skimmer capable of removing similar or lighter (less dense) non-bioorganic materials, and a gravity dependent removal device to remove heavier (more dense) non-bioorganic materials. 
         [0026]    The principles and operation of the present invention may be better understood with reference to the drawings and the accompanying description. 
         [0027]    Referring now to the drawings,  FIG. 1  is of an exemplary, illustrative apparatus according to at least some embodiments of the present invention. According to this embodiment, the waste stream is preprocessed before entering the apparatus; however optionally the apparatus could itself perform the preprocessing (not shown), The waste stream has the previously described characteristics with regard to the percentage of organic material. The waste stream is also assumed to contain at least some solid elements. 
         [0028]    For preprocessing, the waste stream is liquefied in a mixer. During the liquefaction process, previously processed effluent is added to the waste in the mixer. The mixed effluent/waste is pumped into the reactor of the system. 
         [0029]    As shown, a system  100  features a reactor  102 . Reactor  102  comprises a settler  1 , a mixing volume  2  and a skimmer  3 . Said reactor is filled with water up to the top level portion of the reactor. Settler  1  is formed from a conical lower section of reactor  102 . The middle section of reactor  102  is a cylinder for smoother mixing and reduced turbulence within mixing volume. 
         [0030]    The waste stream is pumped through at least one entry  6 , of which only one is shown for the purpose of description only and without any intention of being limiting, A mechanical or hydraulic homogenizing mechanism ( 4 ) is applied to the reactor  102 ; for example, homogenizing mechanism  4  may optionally be a simple mixer, whether mechanical or fluid based, but may also optionally feature other homogenizing components. The waste is mixed in the reactor  102  by homogenizing mechanism  4 , after which the heavy material that has a greater density (i.e. material having a specific gravity greater than the effluent) tends to drop down into the settler ( 1 ), due to gravity. 
         [0031]    A mechanical element such as belt or screw conveyor ( 5 ) removes the heavy materials from the reactor  102 , which is connected to settler  1  through some type of separator and/or exit. As shown below, metals, glass and other heavy materials drop down to settler  1  and exit through a heavy materials exit  13  to conveyor  5 . Heavy materials exit  13  may optionally comprise a tube and/or a hole anchor a more elaborate separation apparatus, or a combination thereof. 
         [0032]    Organic matter and light non-bioorganic materials such as plastic with similar specific densities remain in mixing volume  2  of reactor  102 , as their lower density prevents such materials from entering heavy materials exit  13 . To remove such non-bioorganic materials, a skimmer  3  removes these materials. 
         [0033]    Optionally, according to at least some embodiments of the present invention, and in order to accelerate the further separation of bioorganic and non-bioorganic materials, fine bubble diffusers ( 7 ) are provided to reactor  102 , which in some embodiments attached in the lower section of the reactor  102 , in close proximity to but somewhat above the settler ( 1 ), so as to prevent the materials having density similar or lighter than water from entering settler  1 , while still maintaining circulation of the mixture of materials. In some embodiments processed biogas is optionally pumped to the diffusers  7  by a biogas blower ( 8 ). In other embodiments biogas from an external source (and/or another type of gas) could optionally be used. The bubbles are blown from the diffusers  7  and then move towards the top of the reactor  102  and hence towards skimmer  3 . 
         [0034]    The bubbles blown from diffusers  7  are fine biogas bubbles, by which it is meant that the size of the bubbles is preferably from 10 to 100 microns and more preferably from 20 to 50 microns. As a non-limiting example only, the biogas bubbles may optionally be produced under a pressure of 100 psi for example; the pressure is determined according to the height of reactor  102 . The use of such bubbles permits a higher separation rate and greater separation efficiency of reactor  102 . The bubbles are sized and pressured so as to flow upward with minimal turbulence or perturbations in the material within reactor  102 . Without wishing to be limited by theory, it is expected that these bubbles would nucleate on and cling to particle surfaces to increase the buoyant force of light materials such as plastics and bioorganic. Materials such as plastics that have a greater surface area would tend to capture more bubbles and hence would tend to float higher within reactor  102 . 
         [0035]    Furthermore, injecting such bubbles into the fluid material in reactor  102  increases the overall amount of gas within reactor  102  and further enables phase separation between the different materials as described herein. 
         [0036]    As noted above, it is stipulate that non-bioorganic material such as for example plastic material tends to capture the biogas bubbles; such bubbles reduce the overall specific weight of the material. The material therefore floats toward the top of the reactor  102  and hence toward skimmer  3 , floating on the top or upper surfaces of the effluent. An exit pipe ( 9 ) is located in the upper section of the reactor  102 , near skimmer  3 . The non-bioorganic and organic waste exits reactor  102  through this pipe  9 . A mechanical skimming element  10  such as a rotating skimming element or hydraulic flow assists the non-bioorganic material to flow in the exit direction and prevent it from blocking pipe  9 , if necessary optionally through the application of mechanical and/or fluid pressure. In some embodiments, the water (or general fluid or fluid/material mixture) level in reactor  102  is above pipe  9 , so as to prevent biogas generated or used during the separation process from escaping from reactor  102  through pipe  9 . 
         [0037]    Reactor  102  may also produces biogas, optionally in addition to biogas provided through diffusers  7 . Biogas production for the purpose of this discussion is assumed to be an anaerobic process, although the present invention is not necessary limited to anaerobic biogas production. Such an anaerobic process may optionally comprise digestion and/or fermentation. Digestion is optionally performed by organisms, such as bacteria or yeast, which are known to be suitable for this task. For example, the process may optionally start with bacterial hydrolysis of the more complex organic materials to simpler sugars and amino acids, followed by conversion of the sugars and amino acids into carbon dioxide, hydrogen, ammonia, and organic acids by Acidogenic bacteria. Acetogenic bacteria then convert these resulting organic acids into acetic acid, along with additional ammonia, hydrogen, and carbon dioxide. Optionally, methanogens (methane producing bacteria.) convert these products to methane and carbon dioxide, which is biogas; however reactor  102  may optionally not feature such methanogens. 
         [0038]    In embodiments of the invention where biogas is produced in reactor  102 , it is removed through a biogas exit tube ( 11 ), which is located in the top of the reactor  102  and connected to the biogas blower ( 8 ) (the connection is not shown in the diagram), in order to provide the gas to the diffusers  7 . More specifically, biogas exit tube  11  is connected (through a tube or other connector(s) that are not shown) to an inlet of biogas blower  8  which is shown. A gas accumulator or other storage facility may also optionally be present in this circuit (not shown). Additionally or alternatively, some of the gas may be “bled off” or otherwise removed, for example for use as an energy source, and/or to maintain a preferred pressure (or pressure range) within the above described circuit and/or reactor  102 . Valves, pressure gauges and other components of such a circuit could easily be designed and implemented by one of ordinary skill in the art, in order to maintain the desired pressure(s), as different pressure(s) may optionally be implemented within different parts of the circuit (for example and without limitation, different pressures may optionally be implemented between reactor  102  and the remainder of the circuit). 
         [0039]    Optionally the organic sludge or slurry (i.e. bio-organic material) may optionally be removed from reactor  102  through a bio-organic materials exit  12 , for example for recirculation and/or further processing (not shown). Bio-organic materials exit  12  may optionally comprise a tube and/or other connectors (not shown). 
         [0040]    In addition, it is possible that plastic or heavy materials may be contaminated or mixed with desirable bio-organic material. Optionally, such mixtures are still removed as described above from reactor  102 ; however, optionally such non bio-organic materials are reprocessed (for example optionally through post separation in a different unit or element such as for example magnet eddy current—not shown) in order to capture and separate additional bio-organic materials from such a mixture. 
         [0041]    While the invention has been described with respect to a limited number of embodiments, it will be appreciated that many variations, modifications and other applications of the invention may be made.