Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F26—DRYING
  • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
  • F26B23/00—Heating arrangements
  • F26B23/001—Heating arrangements using waste heat
• • C—CHEMISTRY; METALLURGY
  • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
  • C02F11/00—Treatment of sludge; Devices therefor
  • C02F11/12—Treatment of sludge; Devices therefor by de-watering, drying or thickening
  • C02F11/16—Treatment of sludge; Devices therefor by de-watering, drying or thickening using drying or composting beds
• • 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
  • C05F17/60—Heating or cooling during the treatment
• • 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
  • C05F17/936—Tunnels
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F26—DRYING
  • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
  • F26B1/00—Preliminary treatment of solid materials or objects to facilitate drying, e.g. mixing or backmixing the materials to be dried with predominantly dry solids
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F26—DRYING
  • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
  • F26B3/00—Drying solid materials or objects by processes involving the application of heat
  • F26B3/32—Drying solid materials or objects by processes involving the application of heat by development of heat within the materials or objects to be dried, e.g. by fermentation or other microbiological action
• • 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
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
  • Y02P70/10—Greenhouse gas [GHG] capture, material saving, heat recovery or other energy efficient measures, e.g. motor control, characterised by manufacturing processes, e.g. for rolling metal or metal working
• • 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

• the present invention relates to a method and tunnel composting plant for drying organic material, particularly for producing fuel from organic material, in particular from sludges and possible auxiliary materials, by utilizing mechanical composting.
• the organic materials are first brought to a total solids content that will permit composting, generally of about 30 %.
• the materials that have been mixed and pre-dried in this way are divided into the batches required for mechanical composting operating on the batch principle, the materials of each batch being dried to the desired solids content.
• the materials are dried using the heat produced during composting.
• the organic materials are pulp and paper industry fibre sludges, bio-sludges, paste sludges, and/or debarking plant sludges.
• bark material from the timber processing industry and other organic materials can also be considered.
• the sludges created in the pulp and paper industry can be divided mainly into the following sludges: fibre sludges, principally so-called noil (wood fibre) , bio-sludges, sludges from biological waste treatment plants, paste sludges, kaolin-content sludges from the coating kitchen, sludges from debarking plants.
• fibre sludges principally so-called noil (wood fibre)
• bio-sludges sludges from biological waste treatment plants
• paste sludges paste sludges
• kaolin-content sludges from the coating kitchen sludges from debarking plants.
• fibre sludge alone can be mechanically dried to a total solids content of up to 40 %, it is preferable to mix the sludges together to form mixed sludge, because especially bio- sludges (mostly bacterial material) cannot be drier to more than 12 - 16 %.
• Mixed sludge can be dried, for example, in a steam-screw press, to 30 % .
• mixed sludge is burned in bark-fired boilers, due to the lack and difficulty of exploiting it in other ways.
• the problem is the low solids content of the sludge, which results in losses in boiler capacity and increased emissions and costs.
• Thermal drying is also expensive (high drying temperature) , while detrimental odours also arise during the drying process.
• the water in organic material is so tightly bound to the cell structure that an unreasonable amount of energy is required to separate it by thermal drying or by pressing.
• Finnish patent 100191 discloses a method for manufacturing fuel from organic sludge or bio-waste. According to the method, the sludge is dried by composting, the nitrogen released in composting being collected in a scrubber. Composting provides several advantages. The quality of the material is homogenized and the detrimental microbes in it die. On the other hand, part of the combustion value of the material is lost in composting. Usually, the heat generated by composting is wasted.
• Swedish patent publication 447827 discloses a method of for stack-composting a material with a high water content, especially bark material, on top of an air-conditioned base, to dry it to make fuel.
• Exhaust air extractors are located inside the stack, the heat of the exhaust air being transferred to the replacement air by means of a heat exchanger.
• the heat obtained from composting is used to dry the material.
• the method disclosed is quite difficult. Initially, the arrangement is beneficial, but the biological process, and thus the production of heat, slows down and finally ceases as drying progresses.
• the present invention is intended to improve the process according to the state of the art and especially to increase the yield of fuel and its thermal value.
• the characteristic fea- tures of the invention are disclosed in the accompanying Claims.
• the invention is based on the obser- vation that the cell structure of the organic material that is most difficult to dry is rapidly broken down by means of composting, after which thermal drying becomes easier and mechanical composting can be discontinued.
• the composting of mixed sludge starts rapidly precisely with the aid of bio-sludge, which is the most difficult type of sludge to process.
• the wood fibres in fibre sludge are preserved for longer and the combustion value of the material is retained.
• the material can be dried easily and rapidly to a moisture content of less than 50 %, for instance, to 30 %.
• the invention differs from the method of the Swedish publication referred to above in that the effective drying phase becomes a separate process only after the material has decomposed sufficiently.
• the Swedish publication discloses the principle of using the heat from composting to dry the material, the system proposed is not efficient.
• the inventor in question has not understood the basic idea itself that the cell structure of the organic material should be broken by thorough composting, before thermal drying. Thermal drying in the start-up phase is partly wasted, because the capillary and colloidal water nevertheless does not separate from the unbroken network of cells.
• composting does not produce a great deal of excess heat.
• Figure 1 shows various alternatives of the drying process.
• Figure 2 shows the development of the air flow and temperature of the composting and drying process.
• Figure 3 shows one type of composting plant specially for drying .
• composting 11 which would normally last for 10 - 14 days, is interrupted after only 6 - 7 days.
• the partially composted material which has been separately dried for, e.g., two days, is moved outdoors, preferably into a stack formed under a canopy, where it continues to compost slightly for 2 - 3 weeks. In any event, the storage evens the moisture content through the entire batch, so that the fuel is of even quality.
• Mechanical drying reduces both the duration of the stack drying and its dependence on weather conditions.
• drying is completed with the aid of a longer period of mechanical drying than that described above (3 - 4 days 50 % target moisture content) . This entirely avoids dependence on weather conditions. Mechanical drying is also essential, if the target moisture content of the fuel is much below 50 %. Some power plants are prepared to accept fuel with a moisture content of 30 %, when it has quite a good combustion value.
• the process mainly comprises a normal composting process and a drying phase, in which a large quantity of air is used.
• the mixed sludge to be dried is mixed with a stabilizing substance such as bark or woodchips, and is then placed in a composting tunnel and is composted for 6 - 7 days, depending on the moisture content.
• a stabilizing substance may not be needed at all.
• One such batch of mixed sludge contained 8500 kg total solids of fibre sludge, 6500 kg of bio-sludge, and 2000 kg of paste sludge.
• 0,4 m 3 of bark/tonne of mixed sludge was used.
• the preferable mixed sludge contains 35 - 70 % total solids of fibre sludge, 15 - 45 % total solids of bio-sludge from a biological waste treatment plant, and possibly other sludges.
• the mixed sludge can be composted essentially as it is, with the proportion of the auxiliary substance being less than 10 % total solids.
• the optimization takes place by regulating the heat in the process phase to about 50°C. This takes place by regulating the ratio of circulation air to heated fresh air.
• the composting is started, however, by raising the temperature of the compost material considerably (to 60 - 70°C) for a short time, thus killing the detrimental bacteria.
• the material is dried, preferably in the same composting tunnel, in which the thermal energy produced by the composting of other batches is exploited.
• the moisture content of the compost material is 55 - 65 % (generally 68 - 50 %) , the moisture content being reduced as desired during post-drying, i.e. usually to 45 - 50 %, but sometimes to as little as 30 %.
• the drying phase (3 - 4 days) , the material is either taken directly to be burned, or else to an intermediate stockpile.
• a large quantity of circulation air is used in the starting phase and a large quantity of fresh air in the drying phase.
• composting has the following tasks: to produce the free energy required for drying to carry out pre-drying to 55 - 65 % to render the sludge odourless - to render the sludge hygienic to break down the cell structure of the organic material (water in the cells) , especially of bio-sludge, when thermal after-drying at a low temperature will become possible to reduce the amount of detrimental nitrogen in combustion.
• After-drying has the following advantages: the free energy produced by composting is exploited, so that the duration of the composting can be shortened and the size of the plant reduced the desired moisture content of the fuel is ensured under all conditions.
• the method can be used to manufacture fuel efficiently and economically from odorous sludges and other organic materials.
• the overall economy is greater than, for example, digesting, purely thermal drying, and mechanical drying, as the free energy of the process itself is used for drying.
• the process is simple and manageable.
• the end product can be utilized in existing boilers without any special arrangements, in which case it can be used to replace conventional fuels.
• environmental detriments can be effectively controlled.
• FIG. 3 shows one possible plant assembly, together with flow diagrams.
• the tunnel composting plant itself is otherwise conventional, except for a more comprehen- sive air treatment system than usual.
• the principal components of the tunnel composting plant in Figure 3 are composting tunnels 13 equipped with an air distribution base 13.1, in addition to a scrubber 15 and a biological air cleaner 16 for cleaning the exhaust gases.
• the composting plant 1 includes a comprehensive air- conditioning system.
• Fresh intake air brought from outside is heated in heat exchanger 17 with the heat of the scrubber 15 and led to distribution duct 10.
• the heated, oxygen- rich, and dry fresh air indirectly with circulation air through 3-way dampers 11 and propelled by fans 12 to the air-distribu- tion bases 13.1 of the composting tunnels 13.
• each composting tunnel 13 can be selected individually and be implemented for the process phase desired at the time, with the aid of 3-way dampers 11 and 14, as well as with the aid of fans 12.
• the air exhausted from the composting process has a temperature of 40 - 60°C and a relative humidity of nearly 100 %, so that the circulation air cannot be used for drying.
• the exhaust air in the drying phase is so cold that it is not worth recovering heat from it.
• it also does not require scrubbing, so that it can be led directly to the biological cleaner 16.
• Each of the three composting tunnels 13 of the plant in Figure 3 is shown as operating in a different phase. Usually, at least two of the composting tunnels are simultaneously in the process phase. There are preferably at least four composting tunnels, to be able to ensure an even and efficient production of heat.
• 100 % circulation air is fed under high pressure to the com- posting tunnel in the start-up phase in Figure 3, so that the material heats up and composting starts rapidly. The air is exhausted through exhaust line 18. At the very beginning of the start-up phase, when exhaust air is quite cold, exhaust air can be fed to the cold exhaust air line 18'. A day later, composting will have started effectively, moving next to the process phase .
• the final drying takes place using a separate dryer, through which the material is moved after composting.
• the dryer used can be a dryer intended for drying chicken manure, that is as such known, for example the 'Jansen drying system' manufactured by the Dutch firm Jansen Machinefabrik & Konstruktiebedrij f B.V., Barneveld.
• the material travels on belt conveyors, with drying air led transversely through the conveyor.

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• Engineering & Computer Science (AREA)
• Life Sciences & Earth Sciences (AREA)
• Chemical & Material Sciences (AREA)
• Microbiology (AREA)
• Biotechnology (AREA)
• Health & Medical Sciences (AREA)
• Molecular Biology (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Biochemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Biomedical Technology (AREA)
• Sustainable Development (AREA)
• Hydrology & Water Resources (AREA)
• Environmental & Geological Engineering (AREA)
• Water Supply & Treatment (AREA)
• Treatment Of Sludge (AREA)
• Solid Fuels And Fuel-Associated Substances (AREA)
• Fertilizers (AREA)

Applications Claiming Priority (5)

Publications (1)

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• 1999
  • 1999-04-23 FI FI990918A patent/FI108649B/sv active
  • 1999-09-07 EP EP19990941678 patent/EP1119598A1/en not_active Withdrawn
  • 1999-09-07 WO PCT/FI1999/000723 patent/WO2000014186A1/en not_active Application Discontinuation
  • 1999-09-07 AU AU55204/99A patent/AU5520499A/en not_active Abandoned

Non-Patent Citations (1)

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