Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
  • B09B—DISPOSAL OF SOLID WASTE NOT OTHERWISE PROVIDED FOR
  • B09B3/00—Destroying solid waste or transforming solid waste into something useful or harmless
• • 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
• • 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
  • C02F11/121—Treatment of sludge; Devices therefor by de-watering, drying or thickening by mechanical de-watering
• • 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
  • C02F11/13—Treatment of sludge; Devices therefor by de-watering, drying or thickening by heating
• • 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
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F26—DRYING
  • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
  • F26B21/00—Arrangements or duct systems, e.g. in combination with pallet boxes, for supplying and controlling air or gases for drying solid materials or objects
  • F26B21/06—Controlling, e.g. regulating, parameters of gas supply
  • F26B21/10—Temperature; Pressure
• • 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
  • F26B23/002—Heating arrangements using waste heat recovered from dryer exhaust gases
• • 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
  • C02F11/14—Treatment of sludge; Devices therefor by de-watering, drying or thickening with addition of chemical agents
  • C02F11/143—Treatment of sludge; Devices therefor by de-watering, drying or thickening with addition of chemical agents using inorganic substances
• • 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
  • C02F11/14—Treatment of sludge; Devices therefor by de-watering, drying or thickening with addition of chemical agents
  • C02F11/143—Treatment of sludge; Devices therefor by de-watering, drying or thickening with addition of chemical agents using inorganic substances
  • C02F11/145—Treatment of sludge; Devices therefor by de-watering, drying or thickening with addition of chemical agents using inorganic substances using calcium compounds
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F26—DRYING
  • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
  • F26B2200/00—Drying processes and machines for solid materials characterised by the specific requirements of the drying good
  • F26B2200/18—Sludges, e.g. sewage, waste, industrial processes, cooling towers
• • 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
  • Y02W10/00—Technologies for wastewater treatment
  • Y02W10/30—Wastewater or sewage treatment systems using renewable energies

Definitions

• the invention relates to a method for drying sludges according to the preamble of claim 1.
• the invention particularly relates to the sludge treatment of municipal wastewater plants.
• the purpose of drying sludges is to obtain products suitable for utilisation from sludge material. Water needs to be removed from the sludge. It is advantageous to mix the sludge with binding hydraulic components, then the sludge can be more easily dried.
• the sludge is further dried, post-treated with suitable methods and sorted.
• the end product is stored and supplied for further use or processing. Removing water requires a considerable quantity of energy, which increases the costs of sludge treatment. To ensure cost-effective sludge treatment, the energy efficiency of the process has to be kept at a level adequately high.
• Patent US 5318184A describes a drying and granulating method of sludge implemented by a multi-step process in which the drying takes place in a high temperature. Due to its complexity, the method requires considerable investments in both factory buildings and process devices.
• Patent FI 113470B describes a sludge composting method in which the purpose is to dry sludge by mixing the sludge with peat or prepared solid sludge grains. A layer of compostable sludge is formed on the surface of grains and by circulating the grains to the sludge are obtained several layers. The grains are dried by circulating them several times through the process.
• a disadvantage of the method is, inter alia, that the purpose is to dry the sludge by adding in it e.g.
• the object of the invention is to introduce a method which solves the above problems and eliminates disadvantages of known prior art as well as provides an energy-efficient method with reasonable investment costs for drying sludges.
• the method according to the invention enables the drying of waste sludge in an energy-efficient way.
• the size of sludge aggregates formed in a heating device can be adjusted by means of the quality and volume of hydraulic binder added in the sludge.
• the suitable size of sludge aggregates formed in the heating device also enhances drying, because the heating of sludge aggregates to the drying temperature and the conduction of humidity from inside the sludge aggregate to the surface require some time.
• the sludge-binder mixture and the sludge aggregates formed of it are heated in the heating device to a level suitable for drying.
• the heated sludge aggregates formed in the heating device are conveyed to a drying device in which they encounter a drying air flow.
• heated water contained by the sludge aggregates transfers to drying air due to vapour partial pressure differences and the humidity and energy content of the drying air increase due to it.
• the temperature of the sludge aggregate is significantly higher than the air flow entering the drying device, whereby drying occurs effectively.
• the quick drying of sludge aggregates is caused by the higher vapour partial pressure of heated water contained by the sludge aggregates compared to the vapour partial pressure of drying air in chosen drying conditions.
• Humidity contained by the sludge aggregate effectively transfers to drying air by adjusting the circulation speed of drying air such that the humidity rises to the saturation point or close to it.
• Energy contained by humid drying air is recovered by a heat exchanger, which energy can be utilised in the process e.g. for producing required drying air.
• the invention enables controlled temperature and vapour pressure conditions, whereby drying occurs optimally.
• the process is energy-efficient, because the treatment temperature in connection with heating is not increased unnecessarily high. Then, the over-speedy drying of the surface of sludge aggregates is also avoided, whereby no skin is created on the sludge aggregates to decelerate drying.
• the absorbed thermal energy of sludge aggregates is utilised as a physical event to drive drying when, in the drying process in chosen temperature conditions, the vapour pressure of water in the sludge aggregates is adequately higher than the vapour pressure of drying air entering the drying device.
• the applicant has named the process as the exithermal drying process, because the drying utilises thermal energy absorbed in the sludge aggregates to be employed in the drying process.
• raw materials such as sludge and suitable hydraulic binders
• a separate mixer or said materials mix during the process.
• hydraulic binders such as flyash, cement or lime
• the mixture is conveyed to a process device which forms sludge aggregates of various sizes from the mixture.
• the temperature of the process device is increased with a suitable burner, whereby the sludge-mixture mass and sludge aggregates formed of it are heated to a temperature suitable for drying. Flue gases of the process are circulated back to the process, whereby energy efficiency improves and removed flue gases become as clean as possible.
• the formed sludge aggregates are conveyed from the heating device to a dryer in which they encounter a dry air or gas flow.
• the drying air is air obtained from outdoor air which is heated with the heat exchanger to a temperature which is 10-30°C lower than the one of the sludge aggregates being dried. This temperature difference is equivalent to a water vapour partial pressure difference of 100-600 millibar.
• the thermal energy released to the drying air by the sludge particles when cooling and drying is recovered in the cross-flow of the heat exchanger.
• the cooled cross-flow and water are conveyed out of the process.
• the dried product particles are conveyed after post-treatments either to sorting or directly to end-storage.
• FIG. 1 shows a process to implement a method according to the invention.
• Fig. 2 shows the drying of a particle in the process according to the method.
• Fig. 3 schematically shows the exithermal forming of sludge-binder particles and their drying according to the method of Fig. 1.
• Figs. 1-3 show a method for drying sludges. The process according to the method includes pre-treating and mixing raw materials 1, heating and forming sludge aggregates 2, drying sludge aggregates and recovering energy 3, post-treating 4. sorting product particles 5 and intermediate storing of end product 6.
• the pre-treating and mixing of raw materials 1 takes place with process devices suitable for the purpose depending on the materials being treated.
• the object is to prepare the materials such that sludge aggregates of suitable size for drying would be formed.
• Pre-treated sludge 2b is conveyed to a heating device 2a through which it proceeds with a speed required by the process.
• the temperature of the device is increased by a burner 2c such that the temperature of formed sludge aggregates 3b is 80°C, the range of variation being 70-90°C which is optimal for the drying of sludge aggregates.
• Flue gases 2d of the process are circulated back to the process via a return channel 2e, whereby energy efficiency improves and removed exit gases 2f become as clean as possible.
• the sludge aggregates are formed of suitable size for the drying of sludge before conveying them to a dryer 3 a by adding an appropriate quantity of suitable hydraulic binder in the sludge.
• suitable hydraulic binder e.g. flyash which chemically reacts with water contained by the sludge, whereby the quantity and quality of ash can affect the size and other properties of the sludge aggregates.
• the size of the sludge aggregates varies between 3-20 mm depending on the properties of the sludge and the hydraulic binder.
• the sludge aggregates 3b are conveyed to the lower end of the drying device 3a being obliquely positioned, in which the sludge aggregates proceed by means of suitable transfer elements (not shown in the figures) to the upper end of the device.
• suitable transfer elements not shown in the figures
• air is blown with adequate flow the temperature of which is significantly, such as 10-30°C, lower than the temperature of sludge aggregates entering the lower end of the drying device and its humidity is equivalent to the absolute humidity of outdoor air.
• the optimal temperature of blow air is 60°C, the range of variation being 55-75°C.
• the heated water contained by the sludge aggregates transfers to drying air 3h such that the temperature of the drying air 3d exiting the lower end of the device is almost equivalent to the temperature of the sludge aggregates entering the lower end of the drying device and its relative humidity is almost 100%. Drying is effective as it is based on the variation of vapour partial pressure of water as the temperature varies. It is enough for drying that the temperatures of the process are kept in the above values, whereby water transfers from a higher vapour partial pressure state towards lower vapour partial pressure.
• the dried sludge aggregates 3c are transferred after the post-treatings 4 and the sorting 5 to the storage 6.
• the drying air 3d exiting the drying device is conveyed via a suitable heat exchanger 3e out of the process along a channel 3f. Condensation water 3k formed by the humidity contained by the air flow 3d is recovered in the heat exchanger.
• the drying air 3h is generated of outdoor air 3g the temperature of which can vary between -25°C and +25°C.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Life Sciences & Earth Sciences (AREA)
• Environmental & Geological Engineering (AREA)
• Hydrology & Water Resources (AREA)
• Water Supply & Treatment (AREA)
• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• General Engineering & Computer Science (AREA)
• Sustainable Development (AREA)
• Treatment Of Sludge (AREA)
• Drying Of Solid Materials (AREA)

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Publications (2)

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ID=41136348

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Citations (7)

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• 2009
  • 2009-09-23 FI FI20090348A patent/FI20090348A/fi not_active Application Discontinuation
• 2010
  • 2010-09-22 WO PCT/FI2010/050735 patent/WO2011036344A1/en active Application Filing
  • 2010-09-22 EP EP10818466A patent/EP2480506A4/de not_active Withdrawn
  • 2010-09-22 CN CN201080042626.9A patent/CN102639452B/zh not_active Expired - Fee Related
  • 2010-09-22 RU RU2012116146/05A patent/RU2543888C2/ru active

Patent Citations (7)

Non-Patent Citations (1)

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