Portable high rate anaerobic digester apparatus and method of operation

Abstract

An apparatus for digesting waste comprises a tank, a tube, a propeller, and a trough. The tube is disposed within the tank. The propeller is disposed within the tube and configured to propel a waste material upward through the tube from a lower portion of the tank towards an upper portion of the tank. The waste material comprises heavy solids that fall to the lower portion of the tank and light solids that rise to a waste material top level located near a top of the tank. The trough is configured to collect the light solids that rise to the waste material top level. A top portion of the tube is disposed far enough below the waste material top level such that the heavy solids fall to the lower portion of the tank after being propelled up the tube rather than being propelled to at or above the waste material top level and collected by the trough.

What is claimed is: 
     
         1 . An apparatus for digesting waste, comprising:
 a tank;   a tube disposed within the tank;   a propeller disposed within the tube and configured to propel a waste material upward through the tube from a lower portion of the tank towards an upper portion of the tank, wherein the waste material comprises heavy solids that fall to the lower portion of the tank and light solids that rise to a waste material top level located near a top of the tank; and   a trough configured to collect the light solids that rise to the waste material top level;   wherein a top portion of the tube is disposed far enough below the waste material top level such that the heavy solids fall to the lower portion of the tank after being propelled up the tube rather than being propelled to at or above the waste material top level and collected by the trough.   
     
     
         2 . The apparatus of  claim 1 , further comprising:
 a controller configured to operate the propeller to maintain at least a portion of the heavy solids in suspension within the waste material in the tank during at least part of a recycle operation.   
     
     
         3 . The apparatus of  claim 1 , further comprising:
 an auger disposed inside the trough and configured to pull the light solids collected by the trough toward a discharge tube of the tank; and   a skimmer disposed at an edge of the drainage trough and configured to push the light solids over the edge of the trough into the trough.   
     
     
         4 . The apparatus of  claim 3 , wherein the skimmer comprises at least one of a brush or a blade. 
     
     
         5 . The apparatus of  claim 1 , further comprising:
 an outlet tube located at the lower portion of the tank through which the heavy solids are purged from the tank.   
     
     
         6 . The apparatus of  claim 5 , further comprising:
 a double valve chamber configured to collect the heavy solids purged from the tank, the double valve chamber including:
 a first valve; 
 a second valve; and 
 a column; 
 wherein the first valve and the second valve are located at a lower portion of the column. 
   
     
     
         7 . The apparatus of  claim 6 , further comprising a controller configured to operate the double valve chamber. 
     
     
         8 . The apparatus of  claim 6 , further comprising a second tank configured to store discharge from the trough. 
     
     
         9 . The apparatus of  claim 1 , wherein the trough is offset from a center of the tank and a drive shaft configured to drive the propeller is positioned vertically along the center of the tank. 
     
     
         10 . The apparatus of  claim 1 , further comprising a chassis, wherein the tank is mounted on the chassis and the apparatus is movable between locations. 
     
     
         11 . The apparatus of  claim 1 , wherein the digester tank has a height to width ratio between 2.5 and 4.5. 
     
     
         12 . The apparatus of  claim 1 , wherein the trough is U-shaped and is positioned horizontally, wherein an edge of the trough is positioned at the waste material top level. 
     
     
         13 . A digesting system comprising:
 a plurality of digester devices coupled together, each of the digester devices comprising:   a tank;   a tube disposed within the tank;   a propeller disposed within the tube and configured to propel a waste material upward through the tube from a lower portion of the tank towards an upper portion of the tank, wherein the waste material comprises heavy solids that fall to the lower portion of the tank and light solids that rise to a waste material top level located near a top of the tank;   a trough configured to collect the light solids that rise to the waste material top level; and   a chassis, wherein the tank is mounted to the chassis;   
       wherein a top portion of the tube is disposed far enough below the waste material top level such that the heavy solids fall to the lower portion of the tank after being propelled up the tube rather than being propelled to at or above the waste material top level and collected by the trough. 
     
     
         14 . The digesting system of  claim 13 , wherein the digester devices are coupled together in series such that an output of a first digester device is an input of a second digester device. 
     
     
         15 . The digesting system of  claim 14 , wherein the first digester devices is configured to perform hydrolysis and acidogenesis and the second digester devices is configured to performmethanogenesis. 
     
     
         16 . The digesting system of  claim 13 , wherein the digester devices are coupled together in parallel such that a common input feeds into each of the plurality of digester devices and an output of each of the plurality of digester devices feeds into a common output. 
     
     
         17 . A method of digesting waste, the method comprising:
 controlling a propeller within a tube disposed within a tank to propel a waste material upwards through the tube from a lower portion of the tank towards an upper portion of the tank, wherein the waste material comprises heavy solids that fall to the lower portion of the tank and light solids that rise to a waste material top level located near a top of the tank; and   collecting the light solids that rise to the waste material top level in a trough,   wherein a top portion of the tube is disposed far enough below the waste material top such that the heavy solids fall to the lower portion of the tank after being propelled up the tube rather than being propelled to at or above the waste material top level and collected in the trough.   
     
     
         18 . The method of  claim 17 , further comprising discharging the light solids collected in the trough through a discharge tube. 
     
     
         19 . The method of  claim 17 , further comprising purging the heavy solids from the tank through an outlet tube located at the lower portion of the tank. 
     
     
         20 . The method of  claim 19 , further comprising controlling a double valve chamber to collect the heavy solids purged from the tank.