Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
  • A61M5/00—Devices for bringing media into the body in a subcutaneous, intra-vascular or intramuscular way; Accessories therefor, e.g. filling or cleaning devices, arm-rests
  • A61M5/42—Devices for bringing media into the body in a subcutaneous, intra-vascular or intramuscular way; Accessories therefor, e.g. filling or cleaning devices, arm-rests having means for desensitising skin, for protruding skin to facilitate piercing, or for locating point where body is to be pierced
  • A61M5/422—Desensitising skin
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
  • A61M5/00—Devices for bringing media into the body in a subcutaneous, intra-vascular or intramuscular way; Accessories therefor, e.g. filling or cleaning devices, arm-rests
  • A61M5/178—Syringes
  • A61M5/20—Automatic syringes, e.g. with automatically actuated piston rod, with automatic needle injection, filling automatically
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
  • A61M5/00—Devices for bringing media into the body in a subcutaneous, intra-vascular or intramuscular way; Accessories therefor, e.g. filling or cleaning devices, arm-rests
  • A61M5/178—Syringes
  • A61M5/31—Details
  • A61M5/315—Pistons; Piston-rods; Guiding, blocking or restricting the movement of the rod or piston; Appliances on the rod for facilitating dosing ; Dosing mechanisms
  • A61M5/31565—Administration mechanisms, i.e. constructional features, modes of administering a dose
  • A61M5/31576—Constructional features or modes of drive mechanisms for piston rods
  • A61M5/31578—Constructional features or modes of drive mechanisms for piston rods based on axial translation, i.e. components directly operatively associated and axially moved with plunger rod
  • A61M5/31581—Constructional features or modes of drive mechanisms for piston rods based on axial translation, i.e. components directly operatively associated and axially moved with plunger rod performed by rotationally moving or pivoting actuator operated by user, e.g. an injection lever or handle
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
  • A61M5/00—Devices for bringing media into the body in a subcutaneous, intra-vascular or intramuscular way; Accessories therefor, e.g. filling or cleaning devices, arm-rests
  • A61M5/178—Syringes
  • A61M5/31—Details
  • A61M5/315—Pistons; Piston-rods; Guiding, blocking or restricting the movement of the rod or piston; Appliances on the rod for facilitating dosing ; Dosing mechanisms
  • A61M5/31565—Administration mechanisms, i.e. constructional features, modes of administering a dose
  • A61M5/3159—Dose expelling manners
  • A61M5/31593—Multi-dose, i.e. individually set dose repeatedly administered from the same medicament reservoir
  • A61M5/31595—Pre-defined multi-dose administration by repeated overcoming of means blocking the free advancing movement of piston rod, e.g. by tearing or de-blocking
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
  • A61M5/00—Devices for bringing media into the body in a subcutaneous, intra-vascular or intramuscular way; Accessories therefor, e.g. filling or cleaning devices, arm-rests
  • A61M5/178—Syringes
  • A61M5/31—Details
  • A61M5/315—Pistons; Piston-rods; Guiding, blocking or restricting the movement of the rod or piston; Appliances on the rod for facilitating dosing ; Dosing mechanisms
  • A61M5/31565—Administration mechanisms, i.e. constructional features, modes of administering a dose
  • A61M5/31576—Constructional features or modes of drive mechanisms for piston rods
  • A61M2005/31588—Constructional features or modes of drive mechanisms for piston rods electrically driven
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
  • A61M2205/00—General characteristics of the apparatus
  • A61M2205/58—Means for facilitating use, e.g. by people with impaired vision
  • A61M2205/583—Means for facilitating use, e.g. by people with impaired vision by visual feedback
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
  • A61M2205/00—General characteristics of the apparatus
  • A61M2205/82—Internal energy supply devices
  • A61M2205/8206—Internal energy supply devices battery-operated
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
  • A61M5/00—Devices for bringing media into the body in a subcutaneous, intra-vascular or intramuscular way; Accessories therefor, e.g. filling or cleaning devices, arm-rests
  • A61M5/178—Syringes
  • A61M5/24—Ampoule syringes, i.e. syringes with needle for use in combination with replaceable ampoules or carpules, e.g. automatic
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
  • A61M5/00—Devices for bringing media into the body in a subcutaneous, intra-vascular or intramuscular way; Accessories therefor, e.g. filling or cleaning devices, arm-rests
  • A61M5/42—Devices for bringing media into the body in a subcutaneous, intra-vascular or intramuscular way; Accessories therefor, e.g. filling or cleaning devices, arm-rests having means for desensitising skin, for protruding skin to facilitate piercing, or for locating point where body is to be pierced
  • A61M5/425—Protruding skin to facilitate piercing, e.g. vacuum cylinders, vein immobilising means

Definitions

• the present invention relates to apparatus and methods adapted for use in waste recycling and conversion, more especially n association with the recycling and conversion of municipal solid waste (MSW) derived for example from domestic and commercial refuse or garbage.
• MSW municipal solid waste
• the apparatus and methods of the invention are especially although not exclusively adapted for use in association with waste management procedures which avoid the problems associated with land filling and incineration, as all the products are marketable, and there are no toxic or hazardous air emissions nor is there release of land pollutants .
• the present invention provides a trommel for classifying municipal solid waste (MSW) comprising an inclined cylindrical drum driven to rotate about its axis and having perforations in its side wall through which fragments conforming to a predetermined size range may fall, means for introducing MSW at an upper end of the drum, and means for inducing flow of a stream of gas inwardly through the perforations in said side wall and outwardly through the lower end of the drum to retain and remove relatively less dense materials through the lower end of the drum.
• MSW Municipal solid waste
• the trommel may advantageously be used as part of an initial stage of treatment of MSW.
• known trommels of which applicant is aware serve to classify materials only as to size
• the present trommel also serves to classify materials according to the density of the components of the waste.
• the stream of gas referred to serves to retain within the trommel and separate out relatively light weight materials such as paper and plastics to provide an output stream which can be treated in conventional manner to separate paper and plastics to provide saleable outputs of recycled paper and plastics, respectively.
• a further advantage of the arrangement of the invention is that it avoids the need for air classifiers in later stages of the treatment and this reduces the energy requirements for operation of the system.
• the invention provides a method of digestion and decontamination of MSW comprising digestible organic material, lignin coated cellulose fiber, and mercury contaminant, comprising: slurrying said MSW in an aqueous phase; subjecting the slurry to a primary stage of anaerobic digestion to digest at least a substantial portion of the organic material; separating aqueous phase to yield a primary solid digested residue,- steam heating the primary solid residue to yield a water and mercury vapor containing vapor phase and a substantially mercury free solid phase; collecting the vapor phase separately from the solid phase and condensing the vapor phase to yield water and mercury in liquid form; compressing and explosively decompressing the heated solid phase to yield a treated solid phase comprising the fibers in ruptured condition exposing the cellulosic internal surfaces thereof; slurrying the treated solid phase in an aqueous phase and subjecting the slurry to a secondary stage of anaerobic digestion; and recovering a secondary solid residue .
• the MSW material treated in this method comprises material that has undergone treatment in a trommel as described above and has been treated to remove paper, plastics, ferrous materials and aluminum and other non-ferrous metals, and hence is a principally organic substrate.
• the digestate moves in a substantially straight line path through the digesters, and temperatures of the various zones of the digester are controlled by supply to the ⁇ e zones of a mixture of heated and unheated recirculated compressed digester gas.
• the invention provides a method of heavy metal recovery from anaerobically digested municipal solid waste, preferably the residue obtained from the second stage of anaerobic digestion referred to above.
• This aspect of the invention provides a method of heavy metals recovery from anaerobically digested waste residue municipal solid waste containing lignin and heavy metals, comprising providing said waste residue,- mixing the waste residue with mineral acid solution and obtaining a heavy metal salt solution containing heavy metal cations and lignin in solution and an insoluble residue,- separating the solution from the insoluble residue; electrolyzmg the separated solution, and causing electrodeposition of the heavy metal cations in the presence of the lignin to yield a heavy metal electrodeposit,- and recovering the electrodeposi .
• the presence of lignin preferably obtained as a residue from an anaerobic digestion procedure as described above, increases the efficiency of the plating out of the heavy metals .
• plastics residues remaining in the anaerobic digested material are recovered in the acidification step, wherein the specific gravity of the acid solution is sufficient to cause the plastics and any undigested organics to float on the surface of the acid solution, whereby they may be separated, for example by skimming them off .
• FIG. 1, 2 and 3 illustrate partially schematically, in the nature of a flow sheet, successive stages of apparatus for use in carrying out a waste recycling and conversion process in accordance with the invention.
• Figure 4 shows on an enlarged scale a trommel m accordance with the invention preferably forming part of the apparatus of Figs . 1 to 3.
• Figs. 5, 6 and 7 illustrate partially schematically a top plan view, side view and bottom view of preferred forms of digesters in accordance with the invention.
• Fig. 8 shows somewhat schematically m the nature of a flow diagram a preferred form of steam explosion apparatus in accordance with the invention.
• Fig. 1 shows a first portion of a waste recycling and conversion process in accordance with the invention wherein municipal solid waste is tipped at a tipping floor 10, preferably in an enclosed environment wherein a negative pressure is maintained by withdrawing air along a line 11 through a fan or blower 1 2 feeding into a bag house filter 13 to a further fan 14, the output of which may be, for example, used as combustion air in, for example, a power plant (not shown) in association with which the process may preferably be operated.
• the waste from the tipping floor 10 is fed by conveyor along a manual sorting line 16 from which large items are removed by operatives .
• Large pieces of ferrous metal are moved to a storage bin 17 by a conveyor 18 and large pieces of cardboard to a storage bin 19 by a conveyor 21 from which they may periodically be removed and compressed at a baler 22 for transport.
• Adjacent the end of the manual sorting line 16 is a conveyor 23 that feeds the waste from the manual sorting 16 to a conventional form of bulk shredder 24. Small fragments of waste that do not require shredding may fall through a gap between the line 16 and 23, as indicated by arrow 26 and fall direct to a conveyor 27 which also receives the output from the shredder 24.
• the shredded waste is fed to a trommel 28 shown in more detail in Fig. 4.
• the trommel 28 comprises a downwardly inclining cylindrical drum 29.
• the dimensions of the cylinder 29 depend upon the nature of the waste material, but in a typical example the cylinder 29 may be about 12 feet m diameter and about 70 feet long. Its side wall is formed as a series of screens opening size that progressively increases toward a lower end of the cylinder. In Fig. 4, for the sake of simplicity of illustration, only two zones 29a and 29b are shown, but as will be understood, typically the trommel will comprise a number of different zones of progressively increasing screen opening size. For example, a first zone 29a may have holes in the range 2 to 3 inches in transverse dimension and a second zone holes about 4 to about 6 inches m transverse dimension.
• the drum 29 may be provided with conventional breaking spikes extending inwardly on its inner side n order to break up or shred material passed into the trommel.
• the solid waste is introduced at the upper end as indicated by the arrow 31 m Fig. 4.
• the drum 29 is driven by a conventional drive to rotate continuously about its longitudinal ax s 30 as indicated by the arrow 30a in Fig. 4.
• the waste is therefore tumbled within the drum 29 and is subject to the action of the breaking spikes.
• Small and heavy waste falls through an initial screen such as screen 29a, as indicated by arrow 32 and may pass to a conveyor 33, as seen in Fig. 1, which feeds onto a further conveyor 34.
• Larger heavy waste falls through the screen 29b, as indicated by the arrow 36 and may be passed by a belt 37 to a shredder 38, the shredded output of which is deposited on the belt 34.
• screens that may be intermediate screens 29a and 29b may feed either to the belt 33 or to shredder 38 or may feed to other forms of size reduction apparatus especially adapted for handling materials in the size range concerned.
• a gas stream is induced to flow inwardly through the perforations of the screens 29a and 29b and downwardly and outwardly through the lower end 39 of the trommel 28.
• the gas stream is preferably air, but other gases may, if desired, be employed, for example an inert gas such as nitrogen or carbon dioxide.
• the gas stream creates a zone of negative pressure relative to the ambient atmosphere at the upper end of the trommel 28 and causes light weight materials, principally paper and plastic, to be retained in the drum 29 without falling out through the perforated portions 29a, 29b and the like, and to be entrained in the gas steam and to exit outwardly through the lower end 39 of the trommel as indicated by the arrow 41 in Fig. 4.
• the MSW comprises paper, plastics and relatively more dense non- paper non-plastics materials, for example metals and organic materials for example wood or other materials of plant or vegetable origin
• the trommel therefore function ⁇ to classify the MSW into a dense phase (streams 32 and 36) relatively poor in said paper and plastics and rich in said non-paper non-plastics materials and a light phase (stream 41) relatively poor m said non-paper non-plastics and rich m said paper and plastics
• the gas stream may be induced by blowers 42 arranged to blow obliquely on the outer side of the drum 29 in the region of the screens 29a, 29b, etc., or the stream may be induced by withdrawing gas, for example with a fan, blower or the like, at a zone spaced axially from the lower end 39 of the trommel 28
• the paper and plastics material entrained m the stream 41 may be separated.
• the mixture of paper and plastic may be exposed to a hot gas or vapor, for example steam, in order to shrink or collapse the plastic materials to a denser form that tends to segregate laterally from the stream In the preferred form, as shown in Fig.
• the stream 41 is passed to a hot drum or other separating device 42 where paper is ⁇ eparated from plastics.
• the plastics tend to adhere to the drum and is removed by a scraper or the like, while the paper tends to continue through the drum, and is blown by a blower 43 to a paper storage and compaction arrangement comprising for example a negative slope container 44 from which it is removed and compacted in a baler 46 for shipment
• the polyethylene or other plastics removed at the drum 42 are likewise passed to a plastics storage and compaction arrangement comprising for example a negative slope container 47 from which the plastic s compacted at a baler 48 for shipment.
• the environment adjacent each of the shredders 24 and 38 and adjacent the paper storage device 44 may be maintained at subatmospheric pressure in order to inhibit emissions of dust.
• Air may be removed from these regions by lines lla, lib and lie, respectively, feeding through respective blowers 12a to 12c to baghouse filters 13a to 13c, respectively.
• the dust free air may be exited to the atmosphere by respective blowers 14a to 14c, or may if desired be supplied as combustion air to an adjacent power plant.
• the lower portion of the drum 29 adjacent the end 39 may be provided wich a magnetic separator arrangement for separating ferrous and like magnetic materials.
• the separator may provide a magnetic field that is effective around the periphery of the drum except at an upper quadrant thereof.
• the field applying means may comprise electromagnets 29c connected to the drum 29 that are arranged to switch off when they approach the upper part of the drum's rotation, or may comprise fixed magnets extending around the periphery of the drum except at the upper quadrant, so that ferrous materials and the like are attracted to the inner wall of the drum and are carried upwardly with the drum' s rotation and then fall from the inner side of the drum adjacent the upper part of its rotation onto a conveyor 49 that conveys the ferrous materials, to a point indicated by an arrow 51 in Fig. 4 and to a conveyor 52 and a ferrous metals storage and compactor arrangement 53.
• the heavy waste proceeding along the conveyor 34 is subjected to the action of a magnetic separator 54 which lifts the ferrous or other magnetic materials from the conveyor 34 and passes them to the ferrous metals conveyor 52 to join the stream 51 passing to the storage and compactor arrangement 53.
• the remaining, non-magnetic fraction passes to a conveyor 56 on which it may be subjected to the action of conventional eddy current equipment 57 that induces eddy currents in conductive metals remaining in the waste stream, principally aluminum, and repels these materials forcefully laterally from the conveyor 56 onto a conveyor 58 feeding to an aluminum or non-ferrous metals storage and compactor arrangement 59.
• conventional eddy current equipment 57 that induces eddy currents in conductive metals remaining in the waste stream, principally aluminum, and repels these materials forcefully laterally from the conveyor 56 onto a conveyor 58 feeding to an aluminum or non-ferrous metals storage and compactor arrangement 59.
• the remainder of the waste on the conveyor 56 is mostly organic at this point.
• it may include material of plant or vegetable origin, such as wood, wood fibres, vegetable refuse and the like, and non-vegetable digestible organics. Often, it contains mercury contaminant
• This material in the preferred form is fed to a two stage anaerobic digester arrangement illustrated m Fig 2 and in Figs . 5 to 8
• the two stage anaerobic digester illustrated m Fig. 2 comprises anaerobic digesters 61 and 62 for decomposing organic waste to produce digester gas These digesters effect almost complete digestion of organics (approximately 95% of the organics are digested) , thus reducing the need to treat excess liquor
• the process involves a two stage anaerobic digestion process, and an organics cooker 63 shown n more detail m Fig 8
• Known designs of digester which applicant s aware involve the u ⁇ e of cylindrical vats with a wall at the middle and a ramp like bottom. These impede the movement of the digestate as it moves from the inlet to the outlet of the digester.
• known design ⁇ add steam at the inlet of the digester to increase the temperature of the feedstock to either mesophilic or thermophilic conditions
• the known processes therefore do not offer freedom of temperature control withm the digester in the same manner a ⁇ in the proce ⁇ of the invention
• the proce ⁇ of the invention also ha ⁇ the ability to remove a mercury content from the orgamc ⁇ and yield ⁇ a ⁇ table ⁇ aleable product
• both the primary and secondary digester ⁇ 61 and 62 are continuou ⁇ ly fed horizontal vat ⁇ with their bottoms at a slight incline and with no internal, mechanical movmg parts This arrangement allows for a les ⁇ expensive system and allow the facility to run all year round with minimal or no maintenance work.
• digester ⁇ 61 and 62 are horizontal vat ⁇ , there is free, usually straight line, movement of the digestate or organics from the inlet to the outlet of the digester Shredded municipal wastes, typically comprising dige ⁇ tible organic material, lignin coated cellulose fiber, and mercury contaminant, may be mixed with recirculated digester liquids, leachate from a near by landfill and/or water before entering the digester Using leachate from a landfill aids in the anaerobic digestion proces ⁇ As the wastes move through the digester 61 or 62, it is mixed and heated, preferably by recirculated, compressed digester gas.
• the recirculated digester gas may be heated by any convenient source of heat, for example from the waste heat of the flue gas of an adjacent power plant via a heat exchanger or by use of part of the digester gas as fuel to provide hot gas for a heat exchanger
• the primary digester 61 serves to digest non-fibrous organic waste and some of the fibrous organic waste.
• the secondary digester 62 serves to completely digest the fibrous organic waste after being passed through a ⁇ team explosion process denoted at 63. This avoids problems of production of exces ⁇ proce ⁇ s water or liquor as encountered other anaerobic digestion proces ⁇ in Europe and North America.
• the steam explo ⁇ ion stage 63 may be similar to a conventional ⁇ team explo ⁇ ion process used in the production of fiberboard, as sold under for example the name MASONITE
• the steam explosion process in the present invention may be operated with considerably greater flexibility of choice of the processing pressures and temperatures since the precise temperature and pres ⁇ ure at which explo ⁇ ion occurs l ⁇ of little importance.
• any mercury that was entrained in the waste exiting digester 61 evolves from a liquid state to a vapor state
• the vaporized mercury is mixed with the steam Thi ⁇ gives an opportunity to remove the mercury by condensing the vaporized mercury and steam mixture in a condensing unit
• the mercury can be ⁇ eparated easily
• the mercury may be drained first and then the aqueous condensate.
• the lignm may then be used as a catalyst for an electrolysi ⁇ stage of product polishing described in more detail later, or may be left m the aggregate at the end of the process, or may be isolated to be sold.
• the solid waste passing along line 56 from the sorting and reclamation proces ⁇ which as noted above is mostly organic, is fed to the primary anaerobic digester 61.
• the wa ⁇ te continuously enters the digester 61 which in the preferred form may be maintained in one or more regions thereof at mesophilic conditions (about 35 to about 40°C) and one or more other regions thereof at thermophilic conditions (about 55 to about 60°C)
• Liquid enters the digester 61 pumped by a pump 64 along a line 66 at the same point as the waste enters the digester 61 to further aid in the digestion process
• Sufficient liquid phase which may be water, leachate or recirculated digester liquid, is added to form a slurry of the solid waste of the flowable consistency As shown m more detail n Figs.
• digester gas is collected at the top of the digester 61 along lmes 67 While F gs. 5 to 7 show details of the structure of the digester 61, it will be appreciated the structure of digester 62 is similar.
• Some of the digester gas collected along lines 67 is recirculated along a line 69 for mixing and heating while the bulk pas ⁇ ed along a line 71 is either used as fuel a power plant or stored for some other utilization.
• the recirculated gas passes through a compressor 68 to allow for easier mixing.
• a controlled quantity of the recirculated gas passes along a line 72 through a heat exchanger 73 in which any conveniently available heating medium is used to heat the gas typically to a temperature of about 55 to about 60°C. In the case where the process is used in combination with a power plant this medium may be flue gas.
• the remainder of the recirculated gas bypasses the heat exchanger along line 74.
• control valves 76 By use of control valves 76, the ratio of heated gas passed along line 77 and unheated gas from line 74 entering each region of the digester 61 can be regulated and controlled and hence the temperature of each region can be controlled to promote establishment and maintenance of different bacterial domains, for example, thermophilic and mesophilic regions throughout the digester 61 to optimize digestion. Further the flows through the inlets 78 and passing upwardly through a pervious inclined bottom 79 are controlled to control the fluidization of the wa ⁇ te slurry and hence control flow rates and retention times in digester 61.
• the rate of flow of the slurry through the digester 61, and the residence time in the digester can be controlled by controlling the flow of gas upwardly through the inlets 78.
• the angle of the bottom 79 with respect to the horizontal is preferably about 0.2 to about 0.4 degrees .
• a solid-liquid separator for example a pre ⁇ s 82 along line 83 that captures digester liquor which is recirculated by line 84 to .the front of the digester.
• the primary digester 61 only digests the exposed cellulose and not fibrous waste coated with lignin.
• the solid phase of the waste from separator 82 pas ⁇ es along line 86 through a compressor 87 to a steam explosion drum 88 shown in more detail in Fig. 8. Compression of the waste serves to facilitate continual operation of the drum 88.
• the compres ⁇ ed material i ⁇ then injected into the drum 88.
• superheated steam at a temperature about 300 to about 500°C, more preferably about 400°C and at a pressure preferably excess of about 1200 psia is supplied through the line 89.
• the direct heating of the contents of the drum 88 is continued until it is heated and pressurized sufficiently to provide adequate exposure of cellulose fiber on subsequent explosive decompression.
• a saturated steam pressure of about 800 to about 1200 psia is attained, corresponding to a temperature of about 270 to about 300° C.
• a valve 90 is opened, allowing steam and other vapors to exit the drum 88 and pas ⁇ through one or more condensers 93 ⁇ o that mercury evolved in the manner de ⁇ cribed earlier may be recovered.
• the lower layer of liquid mercury is periodically bled off by opening valves 93a and is recovered.
• the water recovered separately may be returned to digester 61.
• the initial stage of steaming is continued until the batch of material in the drum 88 is substantially mercury free.
• the valve 90 is closed before the valve 91 is opened.
• the wa ⁇ te from flash tank 92 is transported by a conveyor 94 to the secondary digester 62.
• the remaining organic waste is digested in the ⁇ ec ⁇ ndary dige ⁇ ter 62 in almost the same manner as described above for the primary digester 61. That is, the digester gas is collected off the top of the digester 62 along line 96 and some is recirculated through a heat exchanger 97 to be used for heating and mixing the digestate and some is directed along line 98 only for mixing.
• the remaining waste exits the digester 62 along line 99 and consist of mainly inerts with a small amount of undigested organics, including lignin, and an even smaller amount of plastics and heavy metals.
• the waste passes through a separator such a ⁇ pre ⁇ 101 to recover dige ⁇ tate liquor which is recirculated to the front of the digester 62 by line 102.
• both anaerobic digesters 61 and 62 are preferably rectangular in shape havmg the appropriate dimensions for handling the incoming feedstock for the digester. Since the shape of the digester is rectangular, and the side walls 61a guide the slurry in the digesters 61 and 62 in a substantially straight line path from their inlet ⁇ to their outlets, there is no hindrance to the flow of the digestate. Gas compres ⁇ ors 68 and 68a ensure that the pressure required to overcome the head of the dige ⁇ tate in digesters 61 and 62 is achieved.
• the retention time is approximately 20 day ⁇ for each of the digesters 61 and 62.
• the digester pH is preferably maintained at approximately 7 by addition of conventional buffering agents as necessary.
• the organics digested in the first digester 61 amount to about 50% of the incoming organic mass, and the organics digested in the second digester 62 amount to about 90% of the incoming mass, so that the combined digestion amounts to about 95% of the total organic waste.
• An energy input of about 66000 Btu/tonne (metric ton) hour is required for each of the digesters 61 and 62 to heat them to thermophilic conditions (approx.
• the gas compressors 68 and 68a compress the recirculated gas to preferably about 15 psig to facilitate mixing of the waste in the digester. Thi ⁇ compression results in a pressure of 1 to 3 psig in the digesters . This increased pressure aids in transport of the digester gas.
• the processing time of each batch in the drum 88 is about 1 to 2 minutes, and the heating requirements to raise the temperature and pressure inside the steam explosion drum 88 to attain a saturated steam pressure in the region of 800 to 1200 psia amounts to about 1 MBtu/tonne hour, based on the weight of the feed along line 86.
• the solid phase of the digestate from digester 62 separated at ⁇ eparator 101 comprises inert materials, undigested organic material including lignin, some plastics materials and a small content of heavy metals. In a preferred form this solid phase is passed along a line 103 to a product polishing and heavy metal recovery stage shown in Fig. 3.
• stage of the preferred proces ⁇ de ⁇ cribed below ⁇ olve ⁇ thi ⁇ problem by creating a ⁇ table aggregate which can be utilized a ⁇ an inert filler, a ⁇ aggregate for concrete making, or for other similar uses.
• This stage of the proces ⁇ allows for a profitable, continuous recovery of heavy metals and at the same time recovers other valuable resources from anaerobically digested solid waste.
• the heavy metals are removed from the aggregate by dissolving them in an inorganic or mineral acid solution in an acid tank 104 at which point pla ⁇ tics may also be recovered.
• the metals are then electrolytically plated out of the acid solution in a separate tank in which undigested lignin is utilized to produce a purer plated metal.
• sulfuric acid or hydrochloric acid as the mineral acid or acids the proces ⁇ has the ability to recover most heavy metals including: Sn, Mo, Ni, Cu, Pb, Zn, Cd, and Cr.
• the solids portion of digested waste, from which excess moisture has been previously removed in press 101, so that acid concentrations can be maintained at a sufficiently high level enters the acid tank 104.
• This waste may have a concentration of heavy metals in the range of 5 to 10 percent of the total mass.
• the acid tank 104 is made of a corrosion resistant material and contains mineral acid solution, preferably sulfuric acid with a concentration of approximately 50 percent, or hydrochloric acid. Sulfuric acid is preferably used for reason ⁇ of economy while hydrochloric acid may be required to dissolve metals, if present, which are otherwise insoluble in sulfuric acid, such a ⁇ lead.
• ⁇ ome of the acid is lost during the process, either as hydrogen gas and hydrogen sulphides, or is bound up physically in the aggregate, or by reduction in concentration due to the addition of water with the digested waste, and to make up thi ⁇ loss new acid is added through line 106 as need be in order to maintain the desired concentration.
• This solids waste entering the tank is mixed with the acid solution to yield a heavy metal salt solution containing heavy metal cations and lignin in solution.
• the specific gravity of the solution in the tank 104 is maintained in the range about 1.0 to about 1.4, usually in the range of the specific gravities of concentrated hydrochloric acid (1.2) and 50% sulfuric acid (1.4) .
• the acid tank 104 when the waste enter ⁇ the acid tank 104 light materials float to the top. These materials include most plastics and undigested organics. The light materials, mostly plastics, are skimmed from the surface of the tank 104 and passed along line 107 to storage 108. As the digested waste is added to the acid tank 104 hydrogen ga ⁇ and hydrogen sulphides form due to several reactions: volatile organics can be destroyed and the metal - acid reaction produces hydrogen gas.
• the tank 104 is pres ⁇ urized to keep hydrogen in solution in the acid tank to allow later regeneration of acid in the electrolysis tank 109. Hydrogen that escapes is collected along line 111 and either is used as a fuel in a gas power plant or i ⁇ returned to the electrolysis tank 109.
• the tank 104 i ⁇ operated on an intermittent basis.
• it is loaded with waste during a day time operating shift while the recycling plant i ⁇ operated and the waste is left in contact with the acid overnight and the acid solution containing dissolved metal salt ⁇ drawn off along line 112.
• the depleted ⁇ olid wa ⁇ te compri ⁇ ing an in ⁇ oluble residue i ⁇ exited along line 113 before recommencing filling the tank with wa ⁇ te and acid.
• the device- 104 may if desired operate continuously with countercurrent flow of acid and waste.
• the spent acid freed from solid waste and relatively rich in heavy metal salt ⁇ i ⁇ pa ⁇ sed along line 112 to the electrolysis tank and the barren waste freed from liquid acid may be passed along lme 113.
• Any conventional countercurrent solid-liquid treatment ⁇ cheme may be adopted for thi ⁇ purpose.
• the acid salt solution passed along lme 112 contains lignm from the digested waste stream and this aids in the plating process.
• the electrolysis tank 109 is made of a corrosion resistant and electrically insulating material . Large plates of appropriate metals are su ⁇ pended in the ⁇ olution in the tank and large electrical currents (roughly 100 kA per tonne metal to be deposited) are passed through the tank to ensure maximum plating of the metals.
• the plates of metal 114 are removed from the tank by crane 116 or similar device and placed in ⁇ torage 117. As the metals are plated out of the solution acid is regenerated from dissolved hydrogen at the anode and is returned to the acid tank 104 along line 118.
• hydrochloric acid When the use of more than one mineral acid is required, for example hydrochloric acid is required to dissolve lead m a batch of waste containing appreciable lead values, it is not always possible to use a mixture of acids since hydrochloric acid, for example, reacts with concentrated sulfuric acid to produce chlorine In such case, after treatment with one acid, for example sulfuric acid as described in detail above, the depleted solid waste may be washed to free it from sulfuric acid, pressed or otherwise subjected to a liquid ⁇ / ⁇ olid ⁇ separation to free it from liquid phase and then the above procedure described above in detail with reference to Fig. 3 is repeated u ⁇ ing hydrochloric acid a ⁇ the mineral acid solution in the tank 104.
• the digested waste or aggregate now free of nearly all heavy metals, with a concentration of heavy metals the range of 0.05 to .1 percent of mass, exits the acid tank along l e 113.
• the aggregate is acidic in nature and needs further processing to rebalance its pH. This takes place in a neutralizing tank 119 where the aggregate is mixed with calcium carbonate or other base fed through line 121. The pH is monitored to control addition of the base and ensure maximum efficiency of the neutralization. From here the aggregate is put into storage 122 along line 123, and may be compacted at 124 for shipping.
• the average electrical power requirements for electrolysis in tank 109 are typically 0.5 MW/tonne of recovered heavy metals in the case in which the process is run 24 hours per day.
• the typical ⁇ urface area of the metal plate ⁇ in the electrolysis tank 109 is 5000 sq. ft./tonne of metal to be deposited.
• the pH in tank 104 is preferably maintained at 5.
• a maximum of about l tonne of acid is consumed for every 50 tonnes of wa ⁇ te passed along line 103 while 1 tonne of base/25 tonnes of wa ⁇ te, based on the weight of barren waste fed along line 113, is typically used to neutralize the acid.

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• 1996
  • 1996-12-09 EP EP96940939A patent/EP0879066A4/de not_active Withdrawn
  • 1996-12-09 CA CA 2243945 patent/CA2243945A1/en not_active Abandoned
  • 1996-12-09 WO PCT/AU1996/000792 patent/WO1997020588A1/en not_active Application Discontinuation

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