Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/002—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by condensation
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/24—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by centrifugal force
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24C—DOMESTIC STOVES OR RANGES ; DETAILS OF DOMESTIC STOVES OR RANGES, OF GENERAL APPLICATION
  • F24C15/00—Details
  • F24C15/20—Removing cooking fumes
  • F24C15/2007—Removing cooking fumes from oven cavities
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2257/00—Components to be removed
  • B01D2257/70—Organic compounds not provided for in groups B01D2257/00 - B01D2257/602
  • B01D2257/702—Hydrocarbons
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2257/00—Components to be removed
  • B01D2257/70—Organic compounds not provided for in groups B01D2257/00 - B01D2257/602
  • B01D2257/702—Hydrocarbons
  • B01D2257/7027—Aromatic hydrocarbons
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2258/00—Sources of waste gases
  • B01D2258/02—Other waste gases
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2258/00—Sources of waste gases
  • B01D2258/02—Other waste gases
  • B01D2258/0275—Other waste gases from food processing plants or kitchens
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D45/00—Separating dispersed particles from gases or vapours by gravity, inertia, or centrifugal forces
  • B01D45/04—Separating dispersed particles from gases or vapours by gravity, inertia, or centrifugal forces by utilising inertia

Definitions

• the present invention refers to a method of purification of fumes with low vapor pressure contaminants, and therefore accompanied by a high boiling temperature, provided with a highly efficient fumes cooling device.
• US-A1-2016279556 illustrates a device for the purification of fumes in which the cooling phase of the flow is carried out by means of a device acting only on the peripheral part of the fume evacuation duct. This negatively impacts the effectiveness of the contaminant condensation process. Furthermore, the document refers to the treatment of cooking fumes of a kitchen. The treatment of fumes deriving from industrial heating processes in a closed chamber e.g. an oven such as the pyrolysis of wood, the vulcanization of polymers, the roasting of coffee, require to effectively process large fume quantities.
• a closed chamber e.g. an oven such as the pyrolysis of wood, the vulcanization of polymers, the roasting of coffee
• the object of the present invention is to provide a method for the purification of fumes which is effective and with low installation and operating costs.
• the object of the present invention is achieved by means of a method of purification of fumes with condensable gaseous contaminants, comprising the steps of:
• Low vapor pressure contaminants i.e. contaminants that at ambient pressure and temperature (10000 Pa and 24 ° C) are in the liquid state such as toluene, are for example present in fumes from bitumen, fried foods, smokehouses, plasticizers, rubbery substances, textiles.
• the method of the invention is also applicable to relatively small systems and may require a refrigeration system that is widespread, i.e. is already present, or is easily installed, both in industrial plants and in commercial establishments such as kitchens e.g. fast food etc.
• Substances are also used, i.e. air, water vapor, refrigerant fluid widely available and / or usable in a closed circuit, lowering operating costs.
• the inertial separator unit also contributes to this, notoriously easy to be efficiently maintained, also thanks to the cleaning operations that can be performed during operation e.g. by simple gravity action that allows evacuation into a collection container and / or an automatic disposal conveyor belt. Alternatively, by scraping, shaking and vibration.
• the method includes the steps of dehumidifying the air and, subsequently, cooling it to generate the cold air flow.
• the method comprises the step of injecting an auxiliary fluid into the flow rate of fumes to be treated.
• a low vapor pressure substance such as dipropylene glycol, is nebulized in the already at least partially cooled flow rate.
• the enlargement of the contaminant particles is favored and this improves the effectiveness of the separation in the inertial separator unit.
• the water is separated from the contaminant in the inertial separator unit and, in this way, it can be reused e.g. closed circuit without further treatment or be released into the external environment with low or zero environmental impact, in particular when the contaminant is not soluble in water, as in the case of oil used in food processes e.g. frying.
• the heated chamber is closed via a door or flap and the fumes leaving the inertial separator are reintroduced into the heated chamber.
• the flow of gas to be cooled is branched off downstream of the inertial separator and sent to the refrigeration system.
• the closed fume gas circuit allows the passage through the inertial separator to be carried out several times, increasing the quantity of contaminants eliminated. Furthermore, it is possible to avoid connecting the chamber to a fume gas disposal chimney into the atmosphere: this makes it particularly easy to retrofit existing chambers or ovens i.e. it is not necessary to provide a connection to the chimney and / or to move the heated chamber within the plant and therefore there is no need to redesign the connection to the chimney.
• the closed fume circuit is particularly suitable in industrial processes in which the fumes are not generated as a result of chemical reactions, but contain gaseous pollutants generated by change of state e.g. liquid to gaseous or solid to gaseous, due to process temperatures. Furthermore, according to the present invention, the pressure in the chamber, except for the operation of the fan, is close to the atmospheric pressure.
• FIG. 1 a schematic view of a plant for carrying out the method according to the present invention
• FIG. 2 an enlarged schematic view of the component of figure 1;
• - Fig. 3 refers to a diagram of a cross flow heat exchanger.
• Figure 1 indicates with 1 as a whole a combined fume generation and purification plant comprising a heated chamber 2, preferably closed by a supply door, inside which a material is heated, generating fumes comprising low vapor pressure contaminants, for example an oven for the vulcanization of an article comprising a thermosetting material such as an elastomer.
• a heated chamber 2 preferably closed by a supply door, inside which a material is heated, generating fumes comprising low vapor pressure contaminants, for example an oven for the vulcanization of an article comprising a thermosetting material such as an elastomer.
• the invention also to fumes with gaseous impurities at low vapor pressure in other industrial sectors, such as coffee roasting or in the pyrolysis process. It is also possible to apply the invention also to fumes generated in open heated areas, such as in the presence of a fryer.
• a fan 3 By means of a fan 3 the fumes to be treated are sucked from the heated chamber and conveyed into a duct 4.
• the duct 4 carries the fumes towards an inertial separator 5 and receives a flow of cold air through a duct 6 preferably interposed between the fan 3 and the inertial separator 5.
• the flow of cold air and the fumes exchange heat by mixing and this favors nucleation of condensed particles throughout the volume of fumes in the duct 4.
• cold air preferably at a temperature of about 100 ° C below the condensation temperature of the contaminant and / or below 0 ° C, induces a condensation process of the contaminants in the portion of the duct 4 downstream of the duct 6 towards the inertial separator 5.
• an aerosol i.e. a suspension of particles in which the terminal sedimentation speed in air is less than 1 meter / second corresponds to spherical particles with a density of 1000 kg / m 3 with an equivalent aerodynamic diameter of about 180 micrometers.
• the flow of cold gases is substantially mixed at the inlet of the inertial separator 5 and in this case the distance traveled by the fumes between the duct 6 and the inertial separator 5 is minimal e.g. less than 15 cm.
• inertial separator 5 Inertial separator 5 in which the separation process is favored by the inertial effect of the particles whose condensation is induced by the cold fluid.
• inertial separator 5 includes an outlet 7 from which the condensed substances are evacuated e.g. by gravity and an outlet 8 for the air purified from condensed substances.
• a closed flue gas circuit is provided through a duct 9 to connect the outlet 8 to the heated chamber 2.
• a fan 10 generates a flow of purified air from the inertial separator 5 to the heated chamber 2 and, in particular, it generates a vacuum at outlet 8 which favors the separation between air and condensed particles.
• fan 3 and design fan 10 as a radial flow fan: in this way it is possible to process large flow rates of fumes and, at the same time, benefit from the geometry of the impeller to evacuate any particles of contaminants adhering to the impeller itself thanks to centrifugal acceleration.
• the impeller is housed in a casing that will need to be cleaned periodically from the particles of contaminant evacuated by centrifugal acceleration.
• Conduit 6 receives a cold gas e.g. cold air from a refrigeration unit 11 which can either operate in open loop, e.g. taking air to be cooled from the external environment, or in a closed loop by branching off a flow of air to be cooled from duct 9, as shown in the figure.
• refrigeration unit 11 includes a closed circuit for a heat transfer fluid and in a known way it removes heat from the air through an evaporator in which the heat transfer fluid passes to be subsequently sucked by a compressor and release heat to the outside through a condenser.
• the refrigeration unit is two-stage with double lamination and double compression and the heat transfer fluid is carbon dioxide (R-744) to go through a subcritical cycle with evaporator around -30 ° C.
• Figure 2 illustrates a preferred example of construction of inertial separator 5. It is a cyclone separator comprising a hollow main body 20 open downwards to define outlet 7 and defining a converging surface towards outlet 7 itself.
• the hollow main body 20 is elongated and, on the longitudinal side opposite the exit 7, defines a preferably tangential entrance 21 and exit 8.
• the flue gas flow enters hollow main body 20 with a predetermined kinetic energy through the inlet 21 and, thanks to the downward converging shape of body 20, it favors the separation of condensed particles by coalescence and growth thanks to centrifugal force.
• the increasingly large and heavier particles tend to exit by gravity from outlet 7.
• the purified and lightened air tends to flow towards the center of body 20 and to exit from outlet 8, also thanks to the depression generated by fan 10.
• a fluid is injected through a special upper opening in order to remove residues adhering to the walls on which the coalescing particles grow.
• This fluid whose composition varies depending on the contaminant of the fumes, is evacuated from outlet 7.
• the separation and therefore purification action is not compromised.
• the scrubbing fluid is mixed with the condensed contaminant and then either the mixture is discarded or it has to be further treated to separate the fluid, washing.
• the evaporator of refrigeration unit 11 is integrated with a surface heat exchanger to decrease the temperature of the air to be injected into duct 4. Furthermore, it is preferable to provide a dehumidifier, e.g. through a cooling below the dew temperature to eliminate a good part of the water and a subsequent dehumidification using a desiccant e.g. silica gel or other hygroscopic material, to lower the water vapor level in the air to be cooled by refrigeration unit 11.
• a dehumidifier e.g. through a cooling below the dew temperature to eliminate a good part of the water and a subsequent dehumidification using a desiccant e.g. silica gel or other hygroscopic material, to lower the water vapor level in the air to be cooled by refrigeration unit 11.
• a flue of the heated chamber is connected to inertial separator 5 through duct 4 designed to receive cold air.
• the latter is generated by refrigeration unit 11 suitably installed or connected, as it pre-exists such as the heated chamber but is intended for other purposes.
• the flue gas circuit is closed by means of duct 9 with the relevant fan, possibly pre- existing, connected to an air intake A of chamber 2.
• the cold air circuit if the fume gas circuit is closed, can also be closed by connecting duct 9.
• the particles in the aerosol increase their mass in order to facilitate their capture in separator 5.
• the water for some condensed contaminants such as the organic matter in the fumes originating from the use of oils such as during frying, can be separated from the condensed contaminants after leaving the inertial separator.
• the fumes before entering intertial separator 5 pass through a cross-flow exchanger e.g. figure 3 configured in such a way as to extend the heat exchange surface through the flue gas flow i.e. by means of heat exchange surfaces interposed between a maximum transverse dimension of a passage area of the duct 4 and the relative axis. This allows to favor the nucleation of condensed particles in the entire volume of fumes.
• a cross-flow exchanger it is possible to use a liquid refrigerant fluid or one that can change phase from liquid to gaseous and vice versa in the cold generation circuit.
• the walls of cyclone separator 5 are also cooled by the cold fluid.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Analytical Chemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Separating Particles In Gases By Inertia (AREA)

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• 2021
  • 2021-10-29 EP EP21815263.5A patent/EP4237123A1/de active Pending
  • 2021-10-29 WO PCT/IB2021/060034 patent/WO2022091022A1/en active Search and Examination

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