Abstract:
A dual chamber aerobic reactor for continuous flow oxidation reduction of organic wastes which includes an elongated rectangular skid, a blending chamber fixed on the skid, and an elongated drum mounted on the skid for rotation relative to the blending chamber. A device is within the blending chamber for mixing and seeding the organic waste to initiate the reduction process and the drum providing a single continuous cylindrical chamber for completion of the oxidation reduction of the organic waste. The reactor includes a device for recovering excess liquid from the blending chamber and a bio-filter for removing odors and condensing moisture from the reactor to form compost tea.

Description:
The present invention relates to an aerobic reduction reactor and more particularly to an improved biological reactor which is particularly adapted for rapid oxidation reduction of solid organic wastes on a continuous flow basis. 
     BACKGROUND 
     In carrying out the variety of oxidation processes which have been proposed in the waste management field, it has been common to utilize an elongated, cylindrical vessel to enclose and enhance the decomposition of organic wastes. As shown in U.S. Pat. No. 2,241,734-Peterson and U.S. Pat. No. 2,954,285-Carlsson et al, a cylindrical container or vessel is typically mounted on rollers for rotation about its longitudinal axis. A discharge opening is provided in one end of the vessel and a loading or feed opening is provided in the opposite end. A hopper and associated feed mechanism are positioned adjacent the feed opening to supply waste material to be processed within the vessel. A fan or blower is frequently employed to draw or force air through either opening and into contact with the waste material in the vessel to provide the oxygen necessary for the aerobic reduction process. 
     Aerobic biological conversion vessels, such as described in the Peterson patent and as suggested by the patentee, may be combined with sorting devices, grinding mills, conveyors, drying apparatus, etc. to form an industrial plant, but are not readily adaptable to on-site, stand alone waste reduction applications because of the problems encountered in handling of the waste materials. For the best efficiency of such biological conversion vessels, the waste material should be dropped into the hopper in a continuous stream so it can be fed into the vessel to maintain the oxidation process at a constant level. However, the typical dairy barns, feedlots and poultry houses are not cleaned continuously, but rather, only at certain intervals. Therefore, provision must be made to accumulate the waste material and then dispense it to the vessel in a constant stream . This usually takes the form of a relatively large storage bin of an inverted cone or inverted pyramid configuration in association with a conveyor system to move the material from the bin to the hopper. The convergent walls of the storage bin define a relatively narrow opening at the bottom of the bin through which a continuous stream of material is directed by gravity onto the conveyor for transport to the biological conversion vessel. Such apparatus works well with dry, granular or similar discrete-particle materials which tend to pour easily. However, moist or wet solid waste materials, particularly when combined with sawdust, straw or other bedding materials, are not of uniform consistency and tend to clump together and to bridge between the convergent walls of the storage bin, thus disrupting the flow of material onto the conveyor. To overcome this problem, as well as the tendency of the moist waste material to clog the conveyors, and to thereby maintain a constant stream of material to the biological conversion vessel has required pre-conditioning the material with specialized equipment which is expensive to install and to maintain. 
     To facilitate close control of the environment within the rotating vessel it has been proposed to provide temperature and/or humidity monitoring devices and air supply &amp; evacuation tubes inside the vessel, such as shown by U.S. Pat. No. 5,591,635-Young et al and U.S. Pat. No. 4,028,189-Fagerhaug et al. Since such control devices require at least occasional maintenance or replacement, some means, such as access ports, must be provided for entry into the interior of the vessel. Such access ports typically take the form of removable covers or hatches which are aligned with openings provided in the cylindrical surface of the vessel. The initial construction of such access ports is both time consuming and expensive and the use of them to gain access to the equipment mounted within the vessel requires the biological conversion process to be shut down and the vessel to be at least partially emptied. The control permitted with such equipment is thus obtained only at the price of substantial increase in costs of both the initial construction and subsequent operation of the resultant conversion vessels. 
     SUMMARY OF THE INVENTION 
     The present invention avoids the shortcomings of the prior known waste material biological conversion equipment by provision of an aerobic reduction reactor in which material handling requirements are minimized, maintenance procedures are simplified and operational shut down of the biological conversion process for equipment maintenance or repair is virtually eliminated. 
     The above objects are realized in the present invention by the provision of a dual chamber aerobic reactor which includes a generally rectangular blending chamber in which the biological process is initiated in a biomass while it is being blended, and an elongated cylindrical vessel operatively connected to the blending chamber in which the oxidation reduction of the biomass is completed. The blending chamber is stationary and has a smaller capacity than the cylindrical vessel which is mounted on rollers for rotation about its longitudinal axis. The blended biomass is continually moved from the chamber into the vessel by a combination of gravity and rotation of the vessel. A blower is provided to draw air into the reactor to feed the aerobic reduction process and to evacuate gases produced by the process, and means is provided for monitoring the environment within the reactor from the exterior of the vessel and chamber. 
    
    
     DRAWINGS 
     The best mode presently contemplated of carrying out the present invention will be understood from the detailed description of the preferred embodiments illustrated in the accompanying drawings in which: 
     FIG. 1 is a side view, partly in section, of a dual chamber aerobic reactor according to the present invention; 
     FIG. 2 is a sectional view taken along lines  2 — 2  of FIG. 1; 
     FIG. 3 is an exploded view in perspective, partly in section, of the collar  26  and mechanical seal  31  which join the two chambers of the present reactor; 
     FIG. 4 is a perspective view of the blending mill cage of FIG. 2 showing how it is joined to the cylindrical vessel; 
     FIG. 5 is a sectional view taken along lines  5 — 5  of FIG. 1 showing the interior of the discharge end of the cylindrical vessel; and 
     FIG. 6 is an elevation view, partly in section, of an oxygen sensor used with the aerobic reactor of FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring more particularly to the invention as depicted in FIG. 1 of the drawing, the present invention comprises a dual chamber aerobic reactor  11  for oxidation reduction of organic wastes. The reactor  11  includes a stationary blending chamber  12 , a cylindrical vessel  13  and a skid  14  which supports the blending chamber and the vessel. The cylindrical vessel  13  is supported on pairs of rollers  15  &amp;  16  which are mounted on skid  14  to facilitate revolution of the vessel about its longitudinal axis. The blending chamber  12  has a generally-rectangular configuration and, as shown in FIG. 2, is both higher and wider than the cylindrical vessel. The blending chamber and cylindrical vessel are made of sheet steel or similar material and the exterior surfaces of both are well insulated. The blending chamber is formed with side panels  17  &amp;  18 , end panels  19  &amp;  21 , a bottom grid  22  and a lid  23  which is pivotally connected along the upper edge of panel  17  by a hinge  24 . A seal (not shown) is affixed to the lower surface of the lid  23  to contact the upper edges of the side and end panels and seal the chamber  12  when the lid is closed. At the end of the cylindrical vessel  13  removed from the blending chamber, an annular end plate  27  is provided which defines a discharge opening  29 . A cylindrical spout  28  is secured to the exterior surface of the end plate  27  surrounding the opening  29 . As shown in FIGS. 2 &amp; 3, a circular opening  25  is formed in the side panel  17  of the blending chamber and it is surrounded by a horizontally-protruding cylindrical collar  26  which extends several inches beyond the outer surface of the side panel  17  toward the cylindrical vessel. Referring more particularly to FIG. 2, the end of the cylindrical vessel  13  adjacent the blending chamber  12  is open and is telescoped over the cylindrical collar  26  with a mechanical seal  31  between the outer surface of the collar and the inner surface of the vessel. A plurality of elongated, radially-extending vanes  32  are mounted at intervals around the interior of the vessel and extend from the end plate  27  to the mechanical seal  31 . The vanes  32  are preferably of C-channel cross-section and are welded, or otherwise firmly secured, to the interior surface of the vessel with the closed side of each channel facing in the direction of normal rotation of the vessel. As shown in FIGS. 1 &amp; 4, a plurality of angle irons  33  are firmly secured to the vanes  32  and extend through the collar  26  and opening  25  and across the width of the blending chamber  12  into proximity with the inner surface of side panel  18 . The distal ends of the angle irons are joined by lateral braces  34  to form a strong, rigid cage  35  which serve as the movable member of a blending mill. The opening  25  and collar  26  are centered along the vertical centerline of side panel  17  so as to leave a substantial clearance between the rotating cage  35  and the end panels  19  &amp;  21  and the bottom grid  22  of the blending chamber  12 . 
     Referring to FIG. 3, an elongated notch  36  is formed in the free edge of an upper quadrant of the collar  26 . The mechanical seal  31  includes a pair of metal rings  37  &amp;  38 , each approximately one half inch thick, which are welded, or otherwise secured, to the inner surface of the vessel  13  adjacent its open end. The rings  37  &amp;  38  are positioned parallel to each other and arc joined at intervals over their entire circumference by short bars  39  of similar material which span the intermediate space between the rings. The bars  39  are generally parallel to each other and are slanted relative to the rings  37  &amp;  38  at an acute angle opposite to the direction of normal rotation of the vessel. 
     As shown in FIG. 5 of the drawing, a pair of oppositely-directed retaining strips  41  &amp;  42  are mounted on the inner surface of the end plate  27 . Each of the strips extends from one of the vanes  32  to an edge of the discharge opening  29 . The distal ends  43  &amp;  44  of the respective strips are each displaced at an angle of approximately forty five degrees to the body of the strip and the two strips  41  &amp;  42  are tilted toward each other so as to overlie portions of opening  29 . 
     The side and end panels of the blending chamber  12  are reinforced by airways  45 - 47  of square tubing which encircle the chamber at vertically-spaced intervals. The airways are connected to each other and to the low pressure side of a vacuum pump  48  by a system of tubing shown generally at  49 . A series of perforated tubes  51  are positioned within the blending chamber  12  and are shielded by inverted V-shaped members  52 . Each of the tubes  51  is connected to one of the airways  45 - 47  and through tubing  49  to the vacuum pump  48 . The high pressure side of the vacuum pump  48  is shown as connected to a bio-filter  53  by means of tube  54 , but if desired, the vacuum pump may be located downstream of the bio-filter with the high pressure side thereof discharging to the atmosphere. A rectangular pan  55  having a slanted bottom surface is positioned at the bottom of the blending chamber  12  below the grid  22 . A liquid holding tank  56  is connected to the pan  55  and the bio-filter  53  by drain tubes  57  &amp;  58 , respectively. 
     The cylindrical vessel  13  is rotated by means of an electrical motor  59  acting through a chain drive  61  in response to control signals generated by a Programmable Logic Controller or computer  62 . A plurality of infra-red sensors  63 - 65  are mounted on the exterior surfaces of the blending chamber  12  and the cylindrical vessel  13  and are connected to the computer to provide measurements of the temperatures at such surfaces. An oxygen sensor  66  is illustrated in FIG. 6 mounted in an air passageway  67  in conjunction with an electrical heater  68  and connected to the computer to provide measurements of the oxygen level within the reactor. Sensor  66  may be any suitable oxygen sensor, such as, Oxygen Sensor for a 1990 Pickup Truck K10/K1 360 CI/5.7L V8 Engine and is located in a tube  67  which can be attached to tube  49  or  54  to sample the air/gases discharged from the reactor. The heater  68  is a Vulcan Thunderbird Cartridge Heater 150 Watt 120 Volts-1600 Degree Rated and it heats the air/gas sample to 800° F. before it passes the sensor  66 . 
     OPERATION OF THE INVENTION 
     In the operation of the present aerobic reduction reactor, the computer  62  is turned on and rotation of the cylindrical vessel  13  is initiated. The lid  23  is raised and the blending chamber  12  is filled with organic waste material. The lid is then closed and the vacuum pump  48  is activated to draw air/gases from blending chamber  12  and begin continuous circulation of air through discharge opening  29 , into cylindrical vessel  13 , and then through blending chamber  12  and bio-filter  53 . The cylindrical vessel  13  normally functions efficiently when filled to between 85% and 90% of its capacity, therefore each of the C-channel vanes  32  will be in communication with the atmosphere through discharge opening  29  during approximately 10% to 15% of each cycle of rotation of the vessel. A portion of the fresh air drawn into each vane  32  travels the length of the vane and is drawn into the chamber  12  by the reduced pressure therein created by vacuum pump  48 . The remainder of the air passes out of the vane through the open side of the channel and percolates through the bio-mass within the vessel  13  to provide the oxygen necessary for the aerobic decomposition process. At the same time gases formed by the decomposition of the bio-mass flow into the open side of the vane and are then transmitted to chamber  12  where they are exhausted through perforated tubes  51  and airways  45 - 47  by vacuum pump  48 . Gases that rise to the top of the cylinder are similarly drawn into the blending chamber and exhausted through the bio-filter by the vacuum pump. 
     The initial quantity of waste material may be inoculated with suitable bacteria to expedite the aerobic reduction process within the blending chamber. As the cylindrical vessel  13  is rotated, the cage  35  is similarly rotated within the chamber  12  producing a churning action to blend the waste material and distribute the bacteria throughout the bio-mass. Since the blending chamber  12  is wider than the cylindrical vessel  13  and the cage  35 , waste material will accumulate along both sides of the chamber and will remain there nurturing the biological process while the bulk of the bio-mass is moved through the cage  35  into the cylindrical vessel. When the blending chamber  12  is reloaded, pieces of the accumulated waste, which are by then rich in bacteria, will break off and seed the biological process within the newly added waste material as it is blended by rotation of the cage  35 . The capacity of the blending chamber  12  is smaller, ⅓ to ⅔, than that of the cylindrical vessel  13 . Therefore, as long as the chamber  12  is refilled at regular intervals and the necessary oxygen is supplied to the biomass, the biological reduction process will function continuously without interruption. The blended material, or biomass, is moved from the blending chamber  12  into the cylindrical vessel  13  by a combination of gravity and the rotation of the cage  35 . As the biomass is forced from the blending chamber  12 , the leading edge of the biomass continually crumbles and falls forward as it exceeds the angle of repose of the material and thus advances through the cylindrical vessel  13  toward the discharge opening  29 . At the discharge end of the vessel  13  the biomass is initially restrained from passing through the opening  29  by the retaining strips  41 ,  42 . Since the retaining strips are slanted towards each other and overlie opposite edges of the opening  29  they restrict the size of the opening and tend to force the biomass away from the annular end plate  27  as the vessel  13  is rotated. The biomass is thus retained within the vessel  13  to ensure completion of the oxidation process. If, for any reason, it becomes necessary to empty the vessel or accelerate discharge of the biomass, the direction of rotation of the vessel can be reversed so the distal ends  43 ,  44  of the retaining strips will then scoop the composted material into the opening  29 . 
     As waste material is loaded into the blending chamber  12 , excess moisture will drain off through the grating  22  at the bottom of the chamber and accumulate in the pan  55 . It can then be used for various agricultural purposes or treated to become potable. Moisture driven off the bio-mass during the aerobic reduction process is transported with the air/gases by vacuum pump  48  to bio-filter  53  where it is condensed and drawn off as “compost tea” for use as a fertilizer or insecticide. The material of the biomass carried from the blending chamber into the cylindrical vessel is retained within the vessel by means of the mechanical seal  31  between the vessel and the chamber. Individual fragments of the bio-mass which may accumulate at the bottom of the cylindrical vessel are prevented from migrating out the open end of the vessel to the exterior of the reactor by the rings  37  and  38 . Any fragments which overflow ring  37  are trapped in the spaces between the rings and the bars  39 . As the vessel rotates, the bars and ring  37  carry the material fragments vertically and then drop them back into the biomass through the notch  36  in the collar  26 . The mechanical seal  31  does not rely upon contact between the rings  37  &amp;  38  and the outer surface of collar  26  to prevent leakage of fragments of the biomass from the vessel, but instead, utilizes rings  37 ,  38  and bars  39  to trap any fragments and return them to the biomass for continued processing. 
     The PLC or computer  62  is programmed to provide automatic control of the reactor  11  in response to readings of temperature, oxygen content, pH, moisture content, CN ratio, etc. A major feature of the present invention is that measurements of the various characteristics needed for control of the aerobic reduction process are obtained from the exterior of the reactor. Therefore, there is no necessity for gaining access to the interior of the reactor for the purpose of repair, calibration or replacement of the sensors utilized to monitor the aerobic reduction process. Measurements of temperatures which correspond closely to those within the blending chamber and the cylindrical vessel are obtained by infra red sensors  63 - 65  positioned immediately adjacent the exterior surfaces of the chamber and vessel. The sensors for the cylindrical vessel may be positioned to read the temperatures of the non-insulated tracks traced by the pairs of rollers  15 ,  16 . 
     When the reactor is operating in a continuous feed mode, the bacterial decomposition process within the blending chamber  12  is carried out by bacteria and fungi operating in the mesophilic-thermophilic range, whereas the decomposition accomplished in the cylindrical vessel  13  is by thermophilic bacteria and fungi. To achieve a finished compost within approximately  48  hours, it is desirable that the temperature within the cylindrical vessel be stabilized near 158° F. and the moisture content of the biomass be maintained at 55-65% with a Carbon/Nitrogen ratio of 24-30:1. The moisture content, the C/N ratio and pH of the biomass may be measured when the lid  23  is open or at the discharge spout  28  as desired. To ensure that there is adequate oxygen present within the reactor the oxygen content of the discharge air/gases should be maintained at about 18%. The oxygen content within the reactor can be controlled by varying the amount of air drawn into chambers  12  and  13  by the vacuum pump  48 . Similarly, the temperature of the bio-mass can be controlled by varying the rate at which air flows through the cylindrical vessel  13 . 
     While the invention has been described with reference to specifically illustrated embodiments, it should be understood that various changes may be made without departing from the disclosed inventive subject matter particularly pointed out and claimed here below.