Classifications

• • C—CHEMISTRY; METALLURGY
  • C05—FERTILISERS; MANUFACTURE THEREOF
  • C05F—ORGANIC FERTILISERS NOT COVERED BY SUBCLASSES C05B, C05C, e.g. FERTILISERS FROM WASTE OR REFUSE
  • C05F17/00—Preparation of fertilisers characterised by biological or biochemical treatment steps, e.g. composting or fermentation
  • C05F17/90—Apparatus therefor
  • C05F17/921—Devices in which the material is conveyed essentially horizontally between inlet and discharge means
  • C05F17/943—Means for combined mixing and conveying
• • C—CHEMISTRY; METALLURGY
  • C05—FERTILISERS; MANUFACTURE THEREOF
  • C05F—ORGANIC FERTILISERS NOT COVERED BY SUBCLASSES C05B, C05C, e.g. FERTILISERS FROM WASTE OR REFUSE
  • C05F17/00—Preparation of fertilisers characterised by biological or biochemical treatment steps, e.g. composting or fermentation
  • C05F17/90—Apparatus therefor
  • C05F17/964—Constructional parts, e.g. floors, covers or doors
  • C05F17/971—Constructional parts, e.g. floors, covers or doors for feeding or discharging materials to be treated; for feeding or discharging other material
  • C05F17/979—Constructional parts, e.g. floors, covers or doors for feeding or discharging materials to be treated; for feeding or discharging other material the other material being gaseous
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P20/00—Technologies relating to chemical industry
  • Y02P20/141—Feedstock
  • Y02P20/145—Feedstock the feedstock being materials of biological origin
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
  • Y02W30/00—Technologies for solid waste management
  • Y02W30/40—Bio-organic fraction processing; Production of fertilisers from the organic fraction of waste or refuse

Definitions

• This invention is directed to the curing and odor control phases of the composting process. More particularly, the invention comprises apparatus and a method of operation which enables the two functions of curing and odor control to be carried out by a unique windrow assembly.
• Prior art systems for composting solid waste and sewage sludge typically employ one or more multi-stage digesters in which material being treated undergoes staged microbial decomposition.
• the conventional digester is divided into two or more compartments or stages and during material processing is rotated while air is circulated through the digester at controlled rates at predetermined conditions in a flow direction counter to the material flow.
• the climate in each stage is maintained to achieve the optimum development of the type and species of microorganism predominant in that stage.
• Spent air is vented from the digester as needed to maintain optimum climatic conditions in each of the operating stages. Temperatures are kept between 40°C and 55°C to ensure the maximum rate of composting consistent with maintenance of the microbial population.
• the interior of the digester is divided into a series of compartments or chambers by a plurality of traverse partitions spaced along the axis of rotation. Each partition is provided with transfer . buckets which are selectively opened and which when opened transfer material from compartment to compartment from the higher to the lower end of the drum, the waste material being fed into the digester at the higher end and partially cured or raw compost being withdrawn at the lower end.
• the output of the digester must undergo final curing and deodorizing before it is suitable for use in commercial applications. It is to this phase of the composting process that the present invention is directed.
• the compost curing and odor control system comprising the present invention utilizes windrows to provide a unique duality of function, to provide both curing of the compost and deodorizing of compost emissions.
• the system comprises a series of elongated compost piles or windrows. Each pile overlays a floor adapted for passage of air therethrough. The floor overlies a trough or plenum.
• the plenum and windrow are operationally divided into a number of treatment zones. In the example to be described and illustrated there are three such zones.
• the compost forming the windrow is turned and moved along the windrow periodically. Raw compost enters the system at the first treatment zone and is systematically moved through the several treatment zones by manually operated or automatic turning machines.
• Cured and deodorized compost is discharged from the third treatment zone.
• a blower is disposed within or adjacent to the plenum which forms the first and second treatment zones. In operation, the blower draws air through compost overlying the first treatment zone and disperses it through compost overlying the second treatment zone.
• a third section of the plenum is isolated from the other sections by a physical or backflow preventor barrier to form the third treatment zone. Air is drawn from the outside atmosphere and blown through compost overlying the third treatment zone.
• Fig. 1 is an overview of a composting facility showing the overall composting system and compost curing area to which the present invention has specific application;
• Fig. 2 is a perspective showing details of one bay of the compost curing and odor control system comprising the present invention
• Fig. 3 is a cross-sectional detail of the system shown in Fig. 2 including one type of turning apparatus;
• Figs. 4 "A” and 4 “B” are sectional showings of alternate floor plank designs
• Figs. 5 and 6 are sectional details of the blower system forming the first and second treatment zones.
• Fig. 7 illustrates a computer controlled, retractable thermo-couple means for monitoring the compost pile temperature.
• Rapid rate aerobic composting is dependent on a number of factors. The most important are the ready supply of oxygenated air, optimization of temperature, optimization of compost moisture, and maximization of surface area through particulation of the partially cured compost. In order to achieve the above factors the compost must be aerated, agitated and moisturized on a regular basis.
• the invention will be described in connection with the windrow curing of raw compost previously processed through rotary digesters and passed through a 1 " trommel screen. It will be understood, however, that the principles of operation described have application to the curing and odor control of biodegradable material from whatever source derived.
• a composting facility comprised of three major areas; the tipping area 10 a processing area 12 and an aeration or curing area 14. Solid waste is dumped and sorted in the tipping area 10. Unacceptable waste, such as white goods, car batteries, tires, large pieces of wood, etc., is rejected and sent to a land fill. Acceptable waste is then fed into digesters 16. Sewage sludge delivered to the plant is stored in a liquid sludge tank from where it is pumped by liquid sludge pumps directly into the digester 16 as needed to maintain the proper carbon/nitrogen ratio essential to efficient composting. Material is discharged from the digester after approximately 3 days of residence time.
• the material now partially cured or raw compost plus non degradables, is transported by belt conveyors 18 and 20 to a 1 " trommel screen 22 where is it rough screened into two fractions.
• One is residue, which fails to pass through the screen. This residue is discharged back onto the tipping floor from where it is transported to a landfill for disposal.
• the second fraction is rough, or partially cured compost which has passed through the 1 W screen.
• the raw compost is transported to the curing area 14 by a tripping conveyor 24 or front-end loader. As previously noted, it is the curing area to which the present invention has specific application.
• the curing area 14 is comprised of a series of elongated windrows or bays 26 located outdoors.
• Each ,bay is approximately 400" in length and 8' wide.
• the bays may be of varying length depending on the specific application.
• the raw compost is fed into the bay at the right end and cured and deodorized compost discharged at the opposite end.
• An alternate form of air floor is shown in Fig. 4 "B”.
• the air floor overlies a plenum 30.
• the plenum and overlying windrow are operationally divided into a number of treatment zones.
• the plenum and windrow are operationally divided into three such zones.
• the process to be described can be repeated, extended, or the number of treatment zones increased or reduced to produce the desired result.
• each zone is approximately 1/3 the total length of the bay.
• a blower 32 which acts to draw ambient air through compost overlying the first treatment zone through the aeration floor into the plenum and to disperse the somewhat malodorous air upward through compost overlying the second treatment zone.
• the compost is fully aerated accelerating the curing process while concomitantly deodorizing gasses emanating from the early stages of the composting process which are redirected through the more mature compost in the second treatment zone.
• the compost in zone two thus acts in the dual capacity of a curing medium and as a biofilter.
• a physical barrier 33 is placed in the plenum to form a third treatment zone. This section of the plenum as shown is physically isolated from the remainder of the plenum.
• a fresh air fan 34 blows ambient air into this section of the plenum forcing clean ambient air through the aeration floor up through compost overlying the third treatment zone. This step completes the final curing stage.
• Compost forming the windrow is periodically turned and moved along the windrow by a turning machine 36 (Fig. 3) at a rate to facilitate curing and deodorizing of the compost.
• a turning machine 36 Fig. 3
• the compost is moved between 10 to 15 feet toward the discharge end.
• the turning machine is returned to its starting position to repeat the next cycle of operation. This procedure can be accomplished manually or automatically.
• the length of each channel is determined by the specific characteristics of a particular application.
• the compost After each traverse of the length of the windrow by the turner, the compost is moved a distance sufficient to accommodate a fresh load of raw compost added at the feed end.
• the rawest compost is at the feed end and the most mature or fully treated compost is at the discharge end.
• Compost which has traversed the full length of the bay is fully cured and ready for final screening.
• the floor 38 on which the compost is deposited is of sufficient strength to support a diesel compost turner of the type illustrated.
• Compost turners are well known in the trade and are per se not a feature of the present invention.
• the windrows as illustrated are formed to facilitate automatic turning by such machines.
• this unique floor is comprised of a series of structural concrete elements or planks 40 from eight to ten feet in length having the general cross-sectional configuration shown in Fig. 4.
• the planks are placed in abutting relation as seen in that Fig.
• This arrangement provides for a very thin point of contact between adjacent elements.
• a thin rotary saw blade or rake is passed along the point of contact. The slit is narrow enough to prevent most compost stacked on the floor from falling through the slits.
• Such an arrangement in combination with the plenum 30 provides uniform distribution of air through the overlying compost and is substantially clog free.
• the planks shown are made from pre-cast concrete reinforced with steel bars as reguired. A typical plank is 12" wide at the top and 8" thick.
• the plenum 30 underlying the floor is formed using a high density polyethylene liner 44. To optimize operation of the biological systems the plenums may be converted to oxidation ditches or ponds by partially filling the plenum with water which acts to collect leachate from the biofiltering and compost curing units.
• the plenum also serves as a retention device for water runoff from the overlying compost. The runoff may be used to irrigate the windrows to prevent dryout of the material.
• the biological objectives of aeration during curing are to provide optimal temperature and oxygen content within the compost pile to meet the biological needs of the composting microorganisms. Temperature should not exceed 65° Celsius.
• the oxygen content as expressed as a percentage of oxygen among gases present in the atmosphere being tested should desirably be in excess of 15%.
• a blower is selected having an output sufficient to meet these operational parameters.
• the thickness of the compost pile should preferably be between six and eight feet.
• the fan is suspended on rail 48.
• the fan is powered by motor 50 and with its separation baffle moveable along rail 48 by an independent motor drive system 52.
• the drive motor is connected by a flexible power cord 54 to external control means. This arrangement permits balancing of the air flows through the first and second treatment zones.
• a maximum temperature for compost curing is 65°C. A higher temperature inhibits the growth of mesophilic organisisms and lowers decomposition. To maintain optimum operating temperatures and oxygen concentrations above 15% the blower systems are connected to temperature monitoring devices 50 located in the compost pile and timing devices
• thermo-couples inserted into the curing pile at strategic locations as diagrammatically illustrated in Fig 2.
• One technique for automatic monitoring of the compost pile temperature is illustrated in Figure 7.
• a computer controlled retractable thermocouple probe 58 is selectably inserted into the compost pile by means of solenoid 60 connected to computer 62 programmed to achieve optimum operation.
• Oxygen concentrations can be determined by use of oxygen probes 64 to insure that the oxygen content of the piles does not fall below 15%. Information on temperature and oxygen content can be used to adjust the aeration rate as needed. This information is fed to computer 62 for automatic control of blowers 32 and 34. In instances in which atmospheric air temperatures are layered, a condition known as thermal inversion occurs. To counteract this problem, the use of a wind machine 66 is employed as taught in the aforementioned application. The wind machine is capable of dispersing the filtered air at elevations as high as 700 feet, well above normal inversion levels, resulting in an environmentally acceptable operation under the most adverse conditions.

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• Chemical & Material Sciences (AREA)
• Health & Medical Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Biochemistry (AREA)
• Biotechnology (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Microbiology (AREA)
• Molecular Biology (AREA)
• Organic Chemistry (AREA)
• Fertilizers (AREA)

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• 1996
  • 1996-06-24 EP EP96922551A patent/EP0778818A1/de not_active Withdrawn
  • 1996-06-24 AU AU63385/96A patent/AU6338596A/en not_active Withdrawn
  • 1996-06-24 WO PCT/US1996/010752 patent/WO1997001519A1/en not_active Application Discontinuation

Non-Patent Citations (1)

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