WO2022219136A1 - Procédé et installation de traitement de boues contenant des substances chimiques polluantes - Google Patents

Procédé et installation de traitement de boues contenant des substances chimiques polluantes Download PDF

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Publication number
WO2022219136A1
WO2022219136A1 PCT/EP2022/060056 EP2022060056W WO2022219136A1 WO 2022219136 A1 WO2022219136 A1 WO 2022219136A1 EP 2022060056 W EP2022060056 W EP 2022060056W WO 2022219136 A1 WO2022219136 A1 WO 2022219136A1
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WIPO (PCT)
Prior art keywords
sludges
flow
dryer
chemical substances
treating
Prior art date
Application number
PCT/EP2022/060056
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English (en)
Inventor
Massimo VEZZANI
Original Assignee
Vomm Impianti E Processi S.P.A.
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Filing date
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Application filed by Vomm Impianti E Processi S.P.A. filed Critical Vomm Impianti E Processi S.P.A.
Publication of WO2022219136A1 publication Critical patent/WO2022219136A1/fr

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F9/00—Multistage treatment of water, waste water or sewage
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D5/00—Condensation of vapours; Recovering volatile solvents by condensation
    • B01D5/0027—Condensation of vapours; Recovering volatile solvents by condensation by direct contact between vapours or gases and the cooling medium
    • B01D5/003—Condensation of vapours; Recovering volatile solvents by condensation by direct contact between vapours or gases and the cooling medium within column(s)
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D5/00—Condensation of vapours; Recovering volatile solvents by condensation
    • B01D5/0033—Other features
    • B01D5/0054—General arrangements, e.g. flow sheets
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • C02F1/441—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by reverse osmosis
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • C02F1/442—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by nanofiltration
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • C02F1/444—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by ultrafiltration or microfiltration
    • 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
    • C02F11/06—Treatment of sludge; Devices therefor by oxidation
    • 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
    • C02F11/127—Treatment of sludge; Devices therefor by de-watering, drying or thickening by mechanical de-watering by centrifugation
    • 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
    • C02F2101/00—Nature of the contaminant
    • C02F2101/30—Organic compounds
    • C02F2101/36—Organic compounds containing halogen
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
    • C02F2103/18—Nature of the water, waste water, sewage or sludge to be treated from the purification of gaseous effluents

Definitions

  • the present invention relates to the treatment of sludges, for example coming from civil and/or industrial wastewater purification plants.
  • the present invention refers to a process for treating sludges containing polluting chemical substances, for recovering and thermally destructing the latter, and to a plant suitable for performing it.
  • the sludges coming from civil and/or industrial wastewater purification plants are usually treated inside sludge treatment lines, present in large-sized purification plants.
  • a pre-thickening step of the sludges is firstly carried out, during which the dry matter content thereof is increased; such operation is anyway performed through decantation and disposal of wastewater.
  • the latter can be sent in the front of the purifier.
  • biogas produced in this way can be sent to a generator for producing electric energy or to a boiler.
  • the digestate that is the residual sludge coming from the digestion, undergoes further treatments, including a dehydration step, thereby obtaining a dehydrated sludge.
  • the dehydrated sludge may be recovered for agricultural use or a diying step inside a diyer may be carried out, thereby obtaining dried sludge which can be used as fuel, in particular in cement plants.
  • US 5426866 A discloses a process and a system for dewatering of sludges, particularly from sewage treatment facilities; in particular a sticky and wet solid undergoes a first diying step inside a drum centrifuge, thereby obtaining a flowable solid granulate having a diy matter content of 25-35 wt%, the latter being subjected to a subsequent diying step in a convection dryer in order to obtain pre-dried wet solids having a dry matter content of approximately 65 wt%. Pre-dried wet solids are precipitated in a cyclone and, after additional dehydration, are then incinerated or subjected to other treatments.
  • EP 0692679 A2 discloses a process to dry and incinerate sludges, wherein the sludges are de-watered and dried in a centrifuge, thereby obtaining dried sludges having a diy matter content of about 60 wt%. After being discharged from the centrifugal diyer with the diying gases and fed to a cyclone separator, the dried sludges are then delivered into a pulsating incinerator operated at 850°C.
  • PFASs perfluoroalkyl substances
  • perfluoroalkyl substances refers to a class of compounds having a (linear or branched) perfluoroalkyl structure with a length between 4 and 14 carbon atoms and a sulfonic or carboxylic functional end group.
  • fluorine-containing chemicals have been widely applied in the industrial field and have been used, for example, as surfactants, products for the protection of carpets, leather, tissues, floors, food packaging, flame retardants, shampoos and toothpastes, photographic films, and flameproof foams.
  • PFOS perfluorooctanesulfonic acid
  • PFOA perfluorooctanoic acid
  • Perfluoroalkyl substances have particular physical-chemical properties such as a simultaneous hydrophobicity and oleophobicity, chemical and biological stability and low surface tension. These characteristics are due to the fluorine atoms of the alkyl chain, which protect carbon-carbon bonds from possible attacks.
  • PFASs are deemed to act on the endocrine system, thereby jeopardizing growth and fertility, and to be carcinogenic substances.
  • a long exposure to these substances is related to the onset of kidney and testis tumors, to the development of thyroid diseases, to gravidic hypertension and to ulcerative colitis.
  • the problem underlying the present invention is to provide a process for treating sludges which is efficient from an energetic and applicative point of view, effective in destroying polluting chemical substances contained therein, as well as a plant suitable for performing it.
  • the above-mentioned problem was solved providing a process for treating sludges containing polluting chemical substances comprising the steps of: a) drying sludges containing polluting chemical substances in a diyer at a temperature between 40°C and 300°C, preferably between 100°C and 280°C, thereby obtaining a flow comprising dried sludges and vapors; b) feeding the above-mentioned flow to at least one cyclone, thereby obtaining a solid precipitate comprising dried sludges containing polluting chemical substances and a vapor flow; c) feeding the solid precipitate comprising dried sludges containing polluting chemical substances to a waste heat valorization unit and burning it at a temperature which is higher than or equal to 700°C, preferably higher than or equal to 850°C, thereby obtaining ashes and an exhaust gas; and, at the same time, feeding the above-mentioned vapor flow to a wet scrubber, so as to bring
  • the term “sludges” means a heterogeneous mixture in which the dispersant phase is substantially water and the dispersant phase is substantially made of solids, as well as generally of organic and/or inorganic compounds which are not water-soluble.
  • the dispersant phase can also comprise a liquid oily possibly emulsified component, as well as air, or, more in general, gas.
  • the sludges containing polluting chemical substances may come from wastewater purification plants.
  • these sludges are residues deriving from the purification processes of wastewater, which may consist of domestic wastewater, that is wastewater coming from residential settlements and services and mainly deriving from human metabolism and domestic activities, industrial wastewater, that is any type of waste water coming from buildings or installations in which economic activities or activities for producing goods are carried out, or urban waste water deriving from the mixture of domestic wastewater, industrial wastewater and/or run-off rainwater channelled in sewage systems.
  • wastewater may consist of domestic wastewater, that is wastewater coming from residential settlements and services and mainly deriving from human metabolism and domestic activities
  • industrial wastewater that is any type of waste water coming from buildings or installations in which economic activities or activities for producing goods are carried out
  • urban waste water deriving from the mixture of domestic wastewater, industrial wastewater and/or run-off rainwater channelled in sewage systems may consist of domestic wastewater, that is wastewater coming from residential settlements and services and mainly deriving from human metabolism and domestic activities
  • industrial wastewater that is any type of waste water coming from buildings or installations in which economic activities or activities for producing goods are carried
  • pre-thickening, thickening, digestion and/or more or less partial dehydration treatments of these above-mentioned sludges may be preliminaiy carried out.
  • sludges having a content of dry matter between 2 wt% and 25 wt%, more preferably between 15 wt% and 20 wt%, on their total weight, are dried.
  • the expression “flow comprising dried sludges and vapors” means a flow comprising dried sludges in powder form and vapors, wherein said vapors are obtained by evaporating the volatile component of the sludges during the drying step a).
  • the flow obtained by carrying out said drying step a) may consist of dried sludges and vapors.
  • the process according to the present invention allows to dehydrate conventional sludges, deriving from the purification processes of wastewater and possibly subjected to partial dehydration treatments, by carrying out essentially a single aforementioned drying step a), which - as it will be more extensively disclosed in the following - is performed inside a conventional dryer or turbo dryer, in a very simple and efficient manner.
  • said dried sludges contained in the flow comprising dried sludges and vapors, as obtained in the aforementioned drying step a) have a content of dry matter between 75 wt% and 90 wt%, more preferably between 80 wt% and 90 wt%, even more preferably equal to 80 wt%, on their total weight.
  • the process according to the present invention therefore allows to dry sludges containing polluting chemical substances, thereby obtaining a flow comprising dried sludges and vapors; in the following, the latter is fed inside at least one cyclone, thereby effectively abating the dried sludges and obtaining a solid precipitate comprising dried sludges containing polluting chemical substances which is finally thermally destructed by combustion inside a waste heat valorization unit.
  • ashes and exhaust gas are obtained by the combustion of said solid precipitate comprising dried sludges containing polluting chemical substances, wherein the ashes and the exhaust gas are suitably devoid of polluting chemical substances originally contained in the sludges containing polluting chemical substances, which are fed to the dryer in the above- mentioned step a).
  • both the solid ashes obtained by combustion, substantially comprising the mostly metallic inorganic component of the original sludges, and the exhaust gases obtained in this way are devoid of polluting chemical substances, are devoid of perfluoroalkyl substances (PFASs), such as perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) or derivates thereof.
  • PFASs perfluoroalkyl substances
  • PFOS perfluorooctanesulfonic acid
  • PFOA perfluorooctanoic acid
  • said polluting chemical substances may comprise halogenated compounds, wherein the halogenated compounds may be more preferably perfluoroalkyl substances (PFASs).
  • PFASs perfluoroalkyl substances
  • the solid precipitate collected during the cyclonic abatement step b) allows recovering about 99% of the diy matter and most of the polluting chemical substances such as perfluoroalkyl substances (PFASs) contained therein.
  • PFASs perfluoroalkyl substances
  • the process according to the present invention is not only particularly effective in recovering polluting chemical substances from sludges, but also provides the destruction and waste heat valorization thereof, thereby allowing an advantage also regarding consumptions and environmental sustainability of the process itself.
  • the above-mentioned solid precipitate comprising dried sludges containing polluting chemical substances is the only fuel which is fed to the waste heat valorization unit, thereby maintaining therein a temperature higher or equal to 700°C and allowing the correct thermal destruction of the polluting chemical substances comprised in said dried sludges.
  • the waste heat valorization unit may be further fed with a fuel of mineral or vegetal origin, preferably with biomass of vegetal origin, for example derivatives of wood or wood chips.
  • step c) of the process according to the invention the solid precipitate comprising dried sludges containing polluting chemical substances may be burned at a temperature between 850°C and 1100°C.
  • the above-mentioned diyer is a turbo diyer.
  • the turbo dryer comprises a cylindrical tubular body having at least one inlet opening and at least one discharge opening, a heating jacket to bring the cylindrical tubular body to a predetermined temperature value, and a rotor, arranged in the cylindrical tubular body and comprising a shaft provided with elements which project radially from it
  • the drying step a) for sludges comprising polluting chemical substances comprises the following sub-steps: i) feeding into the cylindrical tubular body of the turbo dryer a continuous flow of the above-mentioned sludges; ii) centrifuging these sludges against the inner wall of the cylindrical tubular body of the of the turbo dryer, the rotor being put in rotation at a speed higher than or equal to 100 rpm, more preferably between 200 rpm and 1000 rpm, the particles of the sludges advancing substantially in contact with said inner wall towards the discharge opening, so as to form said flow comprising dried sludges and vapors; and, iii)
  • performing the step a) inside a turbo dryer makes the diying of the sludges more efficient and faster, thereby also obtaining a flow comprising dried sludges and vapors, wherein the solid particles of the dried sludges have a more homogeneous average dimension.
  • the drying step a) is performed at atmospheric pressure.
  • the following abatement step b) inside at least one cyclone can be in turn performed in a more effective way, thereby allowing a substantially full abatement of the solid particles of dried sludges comprised in the above-mentioned flow fed to the cyclone.
  • the cylindrical tubular body of the turbo diyer is kept at a temperature between 40°C and 300°C, more preferably between 100°C and 280°C, by heating said inner wall by means of the heating jacket.
  • the flow of sludges containing polluting chemical substances fed in this way is brought into contact with a flow of heated air, said heated air having a temperature between 40°C and 300°C, more preferably between 100°C and 280°C.
  • said flow of heated air is fed to the turbo dryer in co-current with the continuous flow of sludges containing polluting chemical substances.
  • the heating jacket of the cylindrical tubular body of the turbo diyer is crossed by a heat exchange fluid, more preferably the heat exchange fluid consists of steam or diathermal oil.
  • the average residence time of the above- mentioned sludges inside the turbo diyer is between 30 seconds and 20 minutes, more preferably between 1 minute and 15 minutes, still more preferably between 5 minutes and 15 minutes.
  • the following abatement step b) can be performed inside two or more cyclones which are parallel to each other, with the same volume and hourly flow rate.
  • At least part of the partially purified vapor flow obtained in step c) is fed to the diyer or to the turbo diyer.
  • said at least part of the partially purified vapor flow is fed to the dryer or the turbo dryer upon heating to a temperature between 40°C and 300°C, more preferably between 100°C and 280°C, and optional admixing with the above-mentioned flow of heated air.
  • the heating of said part of the partially purified vapor flow to be fed to the dryer or to the turbo dryer is performed inside a heat exchange unit, for example comprising a heat exchanger with indirect heat exchange, as can be seen in the following in relation to the plant according to the present invention.
  • said condensation column is a packed column.
  • step d) at least a part of the gaseous effluent flow obtained in step d) may be fed to the above-mentioned waste heat valorization unit as comburent gas.
  • the low-boiling chemical substances which are not water-soluble, possibly present in the gaseous effluent flow are thermally destructed by combustion inside the waste heat valorization unit, which gaseous effluent gas - as said - is completely deprived of polluting chemical substances which are originally present in the sludges.
  • step c) during which the vapour flow as obtained from previous step b) is fed into a wet scrubber, the process according to the invention allows to abate emissions containing malodorous substances contained therein.
  • step d) when at least a part of said gaseous effluent flow obtained in step d) is fed to said waste heat valorization unit as comburent gas, any residual malodourous or polluting substances contained therein is thermally destroyed, thereby avoiding any unwanted emission of these malodourous or polluting substances in the environment.
  • the process according to the present invention actually determines the provision of a closed circuit in which the gaseous effluents obtained in the washing step c) and of the following purification step d) are recycled and whose thermal potential, understood as heat transmissible by conduction or convention or, when at least a part of said gaseous effluent flow obtained in step d) is fed to said waste heat valorization unit as comburent gas, as inherent calorific value of the organic molecules present therein, is completely used.
  • the process according to the present invention comprises the following further steps:
  • polluting chemical substances contained therein such as halogenated compounds and, possibly, perfluoroalkyl substances (PFASs), which are not absorbed or adsorbed in the particles of the solid precipitate comprising dried sludges, containing polluting chemical substances, produced during the previous abatement step b).
  • PFASs perfluoroalkyl substances
  • this latter embodiment of the process according to the present invention determines on one side the production of a second liquid filtrate, which is completely devoid of polluting chemical substances, such as halogenated compounds and, possibly, perfluoroalkyl substances (PFASs), and which can be therefore released in the environment without risk of damaging the ecosystems or can be used for other uses, for example a part thereof may be fed to the above-mentioned wet scrubber.
  • PFASs perfluoroalkyl substances
  • the concentrated suspension obtained during the ultrafiltration operation, as well as the concentrated crude liquid obtained by the nanofiltration or reverse osmosis operation, containing potentially dangerous substances and residues, are suitably sent in the front of the diyer or the turbo diyer, in order to avoid further specific treatments for this waste product.
  • the polluting chemical substances contained in the concentrated suspension and in the concentrated crude liquid may be therefore advantageously disposed and destroyed by carrying out the following steps:
  • the exhaust gas produced during the above-mentioned combustion step c) may be fed in an abatement scrubber, said abatement scrubber using a basic aqueous solution as washing liquid for the above-mentioned exhaust gas, so as to obtain a discharge washing liquid and a purified gaseous flow.
  • the exhaust gas produced during the combustion step c) can be indeed possibly rich in hydrohalic acids.
  • halogenated compounds such as perfluoroalkyl substances (PFASs)
  • PFASs perfluoroalkyl substances
  • the anhydrides then combine with hydrogen radicals present in the flame, thereby determining the formation of halides and, therefore, of hydrohalic acids, such as for example hydrofluoric acid and hydrochloric acid.
  • hydrohalic acids such as for example hydrofluoric acid and hydrochloric acid.
  • the aqueous solution may be a sodium hydroxide solution.
  • the discharge washing liquid comprises the neutralization salts formed in this way; for example, the formation of sodium chloride is caused by the reaction of hydrochloric acid and caustic soda.
  • the discharge washing liquid may be therefore conveyed from the abatement scrubber to an ultrafiltration unit for the treatment and purification thereof.
  • the non-polluting salts dissolved in water pass the following reverse osmosis or nanofiltration unit, remaining in the filtrate, and continue towards the superficial water body, being thereby discharged in the environment, while the polluting chemical substances possibly contained in the concentrated crude liquid formed by the reverse osmosis or nanofiltration operation are recycled upstream of the dryer.
  • the purified gaseous flow may be sent to a chimney for releasing it in the atmosphere, directly or upon treatment inside a fume filtering system, for example by an activated carbon filter.
  • At least one cyclone for the abatement of said dried sludges and for obtaining a solid precipitate comprising dried sludges containing polluting chemical substances and a vapor flow, wherein said at least one cyclone is, upstream, in fluid communication with the dryer;
  • waste heat valorization unit for the combustion of said solid precipitate, wherein the waste heat valorization unit is, upstream, in fluid communication with said at least one cyclone;
  • wet scrubber for washing the above-mentioned vapor flow and obtaining a polluted washing liquid and a partially purified vapor flow, wherein the wet scrubber is, upstream, in fluid communication with the above-mentioned at least one cyclone;
  • the above-mentioned diyer is a turbo dryer comprising a cylindrical tubular body having at least one inlet opening and at least one discharge opening, a heating jacket to bring the cylindrical tubular body to a predetermined temperature value, and a rotor, arranged in the cylindrical tubular body and comprising a shaft provided with elements which project radially from it, more preferably wherein the discharge opening is in fluid communication with said at least one cyclone.
  • the plant for treating sludges containing polluting chemical substances comprises a unit for generating a forced air flow; wherein the above- mentioned at least one inlet opening of the turbo dryer is in fluid communication with the unit for generating a forced air flow so as to allow the feeding thereof in the cylindrical tubular body of the turbo dryer, upon possible heating thereof inside the heat exchange unit, with reference to the following paragraphs, thereby obtaining a flow of heated air.
  • the above-mentioned wet scrubber is, downstream, in fluid communication with the dryer or with said at least one inlet opening of the turbo dryer.
  • At least part of the partially purified vapor flow exiting the wet scrubber may be recovered and sent to the dryer or to the turbo dryer, possibly upon admixing thereof with said flow of heated air.
  • a heat exchange unit is installed along a fluid path from the wet scrubber to the dryer or to said at least one inlet opening of the turbo dryer.
  • Said heat exchange unit is suitable for heating the partially purified vapor flow which may be sent from the wet scrubber to the diyer or to the turbo diyer.
  • said exchange unit comprises a heat exchanger with indirect heat exchange, which is crossed by a heat exchange fluid, wherein, in a veiy preferred manner, said heat exchange fluid is steam or diathermal oil.
  • said condensation column is a packed column.
  • the present plant for treating sludges comprises an ultrafiltration unit for treating the above-mentioned polluted washing liquid and the above-mentioned liquid condensate, wherein the ultrafiltration unit is, upstream, in fluid communication with the wet scrubber and with the condensation column, respectively, and said plant further comprises an additional filtration unit, suitable for performing operations of nano-filtration or reverse osmosis.
  • the waste heat valorization unit comprises at least one discharge opening and the same plant comprises an abatement scrubber, wherein the abatement scrubber is, upstream, in fluid communication with said at least one discharge opening of the waste heat valorization unit.
  • Figure 1 shows a schematic view of a plant in which the process according to the present invention can be performed according to a preferred embodiment thereof. Detailed description of a preferred embodiment
  • a turbo diyer 100 which comprises a cylindrical tubular body 101, closed at the opposite ends by the bottoms 102 and 103, and coaxially provided with a heating jacket 104, which is optional and intended to be crossed by a heat exchange fluid, for example water or diathermal oil, in order to maintain the inner wall of the cylindrical tubular body 101 at a predetermined temperature.
  • a heat exchange fluid for example water or diathermal oil
  • Said heating jacket 104 has an inlet opening 104a and a discharge opening 104b, which are generally provided to let the heat exchange fluid in and to let the heat exchange fluid out, respectively.
  • the direction of the arrows drawn at the openings 104a and 104b exemplifies the direction of said incoming flow of the heat exchange fluid and the outgoing flow of the heat exchange flow, respectively.
  • the tubular body 101 is provided with inlet openings 106 and 105 for the sludges containing polluting substances to be treated and for a flow of heated air, respectively.
  • the tubular body 101 rotatably supports inside it a rotor comprising a shaft 108 provided with elements 109 which project radially in form of blades, said blades 109 being helically oriented to admix, centrifuge and at the same time convey towards a discharge opening 107, the flow comprising dried sludges and vapors which can be obtained inside it.
  • the direction of the arrows drawn at the openings 105, 106 and 107 exemplifies the direction of said incoming flows and the outgoing flow comprising dried sludges and vapors, respectively.
  • the turbo dryer 100 is therefore suitably designed to perform the drying step a).
  • a motor which is not shown is suitably provided to operate the rotor of the turbo diyer 100 at variable speeds, which may be equal or higher than 100 rpm, preferably between 200 and 1000 rpm.
  • the discharge opening 107 is in fluid communication with a discharge duct 112 in which a continuous flow comprising dried sludges and vapors exiting the cylindrical tubular body 101 is conveyed.
  • a cyclone 10 Downstream with respect to the turbo dryer 100, a cyclone 10 is arranged which is provided with an opening 15 to let the flow comprising dried sludges and vapors in, which is suitable for carry out the abatement step b).
  • the cyclone 10 is also provided with a first and a second discharge openings 17 and 18, suitable for discharging a solid precipitate comprising dried sludges containing polluting chemical substances and a vapor flow, respectively.
  • the solid part discharged from the bottom of the cyclone contains the polluting chemical substances, for example PFASs, which are then thermally destroyed in the unit 20.
  • the discharge opening 17 is in fluid communication with a waste heat valorization unit 20; the discharge opening 18 is in fluid communication with the wet scrubber 30 for washing the vapor flow exiting the cyclone 10.
  • the plant 1 furthermore comprises a wet scrubber 30 for washing the vapor flow and allows to obtain a polluted washing liquid and a partially purified vapor flow.
  • the wet scrubber 30 comprises a discharge outlet 37 in fluid communication with a discharge duct 212 in which the polluted washing liquid is conveyed.
  • the wet scrubber 30 also comprises a discharge outlet 38 in fluid communication with a condensation column 40, in particular a packed column, towards which at least part of the partially purified vapor flow is conveyed.
  • the discharge opening 38 is also in fluid communication with the inlet opening 105 of the cylindrical tubular body 101 of the turbo diyer 100 in order to allow to send and feed to the cylindrical tubular body of the latter at least part of the partially purified vapor flow exiting the wet scrubber 30.
  • a heat exchange unit 31 is installed, which comprises a heat exchanger with indirect heat exchange for heating said at least part of the partially purified vapor flow by a heat exchange fluid, for example diathermal oil.
  • a fan may be also arranged which is not represented since it is absolutely conventional.
  • said partial ⁇ purified vapor flow is admixed with a flow of heated air, in which also the latter may be fed to the cylindrical tubular body 101 of the turbo dryer 100 through the inlet opening 105, as said.
  • the present plant thus also comprises the condensation column 40, in particular a packed column, for treating the partially purified vapors and allows to obtain a liquid condensate and a gaseous effluent flow.
  • the condensation column 40 comprises a discharge outlet 47 in fluid communication with a discharge duct 212 in which the liquid condensate is conveyed.
  • the condensation column 40 also comprises a discharge outlet 48 in fluid communication with the waste heat valorization unit 20 towards which the gaseous effluent flow is conveyed.
  • the discharge duct 212 puts in fluid communication the discharge outlet 37 of the washing and condensation unit 30 and the outlet 47 of the condensation column 40 with an ultrafiltration unit 51, contained in the filtration block 50 for treating the polluted washing liquid and the liquid condensate.
  • the filtration block 50 comprises, in the order upstream to downstream along a fluid path, the ultrafiltration unit 51 and an additional filtration unit 52, suitable for performing nanofiltration operations.
  • system 1 may comprise an additional filtration unit suitable for performing a reverse osmosis operation.
  • the ultrafiltration unit 51 is, downstream, in fluid communication with the inlet opening 106 of the cylindrical tubular body 101 of the turbo dryer 100, as well as with the additional filtration unit 52, in order to be able to feed to the latter the concentrated suspension obtained in this way by the ultrafiltration operation; a first liquid filtrate may be instead suitably sent to the additional filtration unit 52.
  • the additional filtration unit 52 has two fluid discharges: a fluid discharge of concentrated crude liquid and a fluid discharge of second liquid filtrate, permeated in this way.
  • the first discharge of concentrated crude liquid is sent towards the inlet opening 106 of the cylindrical tubular body 101 of the turbo dryer 100 in order to send the polluting chemical substances, such as for example the perfluoroalkyl substances (PFASs), at the beginning of the drying process of the sludges.
  • PFASs perfluoroalkyl substances
  • the second liquid filtrate, permeated in this way and devoid of the polluting substances, may be discharged in the environment or reused for other processes of the treatment site, such as for example the supply of water, as washing liquid, to the wet scrubber 30.
  • the waste heat valorization unit 20 comprises a first discharge opening 27 and a second discharge opening 28 suitable for discharging inorganic ashes and a flow of exhaust gas, respectively. Downstream with respect to the waste heat valorization unit 20 and in fluid communication with the second discharge opening 28 an abatement scrubber 60 is installed, which is suitable for abating and neutralizing the anhydrides and the hydrohalic acids contained in the exhaust gas exiting the combustion chamber of the waste heat valorization unit.
  • the abatement scrubber 60 comprises a first discharge outlet 67 for the above-mentioned discharge washing liquid, comprising neutralization salts of anhydrides and hydrohalic acids contained in the combustion fumes, as well as a second discharge outlet 68 for a purified gaseous flow.
  • the first discharge outlet 67 is in fluid communication with the ultrafiltration unit 51 through a duct which is not represented.
  • the second discharge outlet 68 is instead in fluid communication with the external environment, for releasing in the atmosphere the purified gaseous flow, upon treatment thereof inside a fumes filtering system, for example an activated carbon filter, which is also not represented because it is absolutely conventional.
  • a fumes filtering system for example an activated carbon filter
  • the process according to invention has been carried out as explained in the following, the process being performed by means of the above-mentioned apparatus starting with a flow of sludges containing polluting chemical substances and coming from an urban wastewater purification plant.
  • a flow of sludges containing polluting chemical substances with diy matter equal to 18 wt% on their total weight was fed to the turbo diyer 100 of the company Vomm through the inlet opening 106.
  • the flow rate of the feeding of the sludges to the turbo diyer was equal to 5 tons/ hour.
  • the motor of the turbo diyer 100 was kept at a speed equal to around 800 rpm.
  • diathermal oil was made to flow in the heating jacket 104, so as to maintain the temperature inside the cylindrical tubular body 101 of the turbo diyer 100 at a value equal to around 250°C.
  • a flow of preheated air (with flow rate of about 30,000 m 3 /h) was fed through the inlet opening 105 at a temperature of about 250°C and in co-current with the flow of sludges advancing inside the same cylindrical tubular body 101.
  • the drying step was performed at atmospheric pressure.
  • the sludges were maintained inside the turbo diyer 100 for a time equal to around 15 minutes.
  • a flow comprising dried sludges and vapors was thus obtained, which was subsequently fed to the cyclone 10 thereby obtaining a solid precipitate comprising dried sludges containing polluting chemical substances and a vapor flow.
  • the solid precipitate comprising dried sludges containing polluting chemical substances was discharged from the cyclone 10 through the discharge opening 17 and subsequently fed to the unit 20.
  • the solid precipitate comprising dried sludges containing polluting chemical substances had a content of diy matter equal to 80 wt% on their total weight and was fed to the waste heat valorization unit 20 according to a flow rate of 1.125 tons/ hour.
  • the solid precipitate comprising dried sludges containing polluting chemical substances had a calorific value PCI equal to around 3000 kcal/kg.
  • the combustion chamber of the waste heat valorization unit 20 was also fed with biomass of vegetal origin and of origin which is external with respect to the diying process of the sludges, specifically woodchip with a calorific value PCI equal to around 3900 kcal/kg and fed with a flow rate of 150 kg/ hour.
  • the combustion step c) may be in any case performed also without additional calorific supply since the temperature reached inside the combustion chamber of the waste heat valorization unit can be also high enough with the combustion only of the solid precipitate comprising dried sludges containing polluting chemical substances.
  • the temperature reached in this way inside the combustion chamber was equal to 900°C.
  • the vapor flow coming from the outlet 18 of the cyclone 10 was fed to a wet scrubber 30 in which mains water was sprayed as abatement and washing liquid.
  • the condensation column 40 Exiting the wet scrubber 30, the remaining part of the partially purified vapor flow was fed to the condensation column 40 in order to bring to full condensation the low-boiling polluting chemical substances which are water-soluble. Exiting the condensation column 40, the gaseous effluent flow, completely deprived of low-boiling polluting chemical substances which are water-soluble, was fed in the combustion chamber of the waste heat valorization unit 20 as comburent gas.
  • the fluid flow entering in the ultrafiltration unit 51 had a flow rate equal to 6 m 3 /h and had an overall content of suspended solids (TSS) equal to 0.4 wt%, as well as a concentration of NH 3 equal to 200 ppm and a chemical oxygen demand (COD) value equal to 10000 mg/L.
  • TSS suspended solids
  • COD chemical oxygen demand
  • the first liquid filtrate obtained in this way was fed from the ultrafiltration unit 51 to the additional filtration unit 52 to perform the nanofiltration operation thereby producing a concentrated crude liquid having a flow rate of 500 litres/ h.
  • the concentrated crude liquid, containing both ammonia and perfluoroalkyl substances (PFASs), was finally recirculated to the drying unit 100.
  • the concentrated suspension exiting the ultrafiltration unit was instead sent to the turbo dryer 100 after it was partially thickened by means of a belt press, which is not represented in figure 1 since it is fully conventional.
  • the exhaust gas exiting from the combustion chamber of the waste heat valorization unit 20 was treated inside the abatement scrubber 60 thereby producing a purified gaseous flow, completely devoid of polluting chemical substances, and a discharge washing liquid, comprising salts such as sodium fluoride, sodium sulphate and sodium chloride, which is afterwards sent with a flow rate of 100 litres /hour to the ultrafiltration unit 51.
  • a discharge washing liquid comprising salts such as sodium fluoride, sodium sulphate and sodium chloride

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Hydrology & Water Resources (AREA)
  • Engineering & Computer Science (AREA)
  • Environmental & Geological Engineering (AREA)
  • Water Supply & Treatment (AREA)
  • Organic Chemistry (AREA)
  • Treatment Of Sludge (AREA)

Abstract

L'invention concerne un procédé de traitement de boues contenant des substances chimiques polluantes, par exemple des substances de perfluoroalkyle (PFAS), par récupération et destruction thermique de celles-ci, ainsi qu'une installation appropriée pour la mise en oeuvre d'un tel procédé.
PCT/EP2022/060056 2021-04-16 2022-04-14 Procédé et installation de traitement de boues contenant des substances chimiques polluantes WO2022219136A1 (fr)

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IT102021000009617 2021-04-16

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116217021A (zh) * 2023-02-14 2023-06-06 重庆水利电力职业技术学院 一种气旋式含油污泥处理设备

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5426866A (en) 1991-06-25 1995-06-27 Lucia Baumann-Schilp Method and apparatus for dewatering of sludges
EP0692679A2 (fr) 1994-07-13 1996-01-17 Klöckner-Humboldt-Deutz Aktiengesellschaft Procédé et schéma d'installation pour le séchage et l'incinération de boues d'égout

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5426866A (en) 1991-06-25 1995-06-27 Lucia Baumann-Schilp Method and apparatus for dewatering of sludges
EP0692679A2 (fr) 1994-07-13 1996-01-17 Klöckner-Humboldt-Deutz Aktiengesellschaft Procédé et schéma d'installation pour le séchage et l'incinération de boues d'égout

Non-Patent Citations (1)

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Title
CRISTIAN GÓMEZ-CANELA ET AL: "Occurrence and fate of perfluorinated compounds in sewage sludge from Spain and Germany", ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH - INTERNATIONAL, SPRINGER BERLIN / HEIDELBERG, LA, vol. 19, no. 9, 31 July 2012 (2012-07-31), pages 4109 - 4119, XP035120798, ISSN: 1614-7499, DOI: 10.1007/S11356-012-1078-7 *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116217021A (zh) * 2023-02-14 2023-06-06 重庆水利电力职业技术学院 一种气旋式含油污泥处理设备
CN116217021B (zh) * 2023-02-14 2023-09-29 重庆水利电力职业技术学院 一种气旋式含油污泥处理设备

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