EP4276399A2 - Installation de séchage pour la mise en oeuvre d'un procédé de boues d'épuration - Google Patents

Installation de séchage pour la mise en oeuvre d'un procédé de boues d'épuration Download PDF

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Publication number
EP4276399A2
EP4276399A2 EP23198320.6A EP23198320A EP4276399A2 EP 4276399 A2 EP4276399 A2 EP 4276399A2 EP 23198320 A EP23198320 A EP 23198320A EP 4276399 A2 EP4276399 A2 EP 4276399A2
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EP
European Patent Office
Prior art keywords
sludge
steam
drying
water
extruded products
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP23198320.6A
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German (de)
English (en)
Other versions
EP4276399A3 (fr
Inventor
Giovanni Luca RIVA
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Vallecaudina Energie Rinnovabili Srl
Original Assignee
Vallecaudina Energie Rinnovabili Srl
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Publication date
Application filed by Vallecaudina Energie Rinnovabili Srl filed Critical Vallecaudina Energie Rinnovabili Srl
Publication of EP4276399A2 publication Critical patent/EP4276399A2/fr
Publication of EP4276399A3 publication Critical patent/EP4276399A3/fr
Pending legal-status Critical Current

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F26—DRYING
    • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
    • F26B23/00—Heating arrangements
    • F26B23/10—Heating arrangements using tubes or passages containing heated fluids, e.g. acting as radiative elements; Closed-loop systems
    • 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
    • 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

Definitions

  • the present invention is within the framework of the wastewater treatment sector and refers to a plant for drying sewage sludge.
  • a good deal of the domestic water purifiers uses suitable bacteria, which use polluting agents, transforming them into harmless agents (which can sometimes also be recovered and enhanced), such as carbon dioxide, fuel gas and others.
  • the purification occurs inputting wastewater into suitable tanks, where the bacteria are added in a known manner, selected for the purpose and where the air necessary for the aerobic part of the purification is adjusted and dosed.
  • the water in the tanks is kept under stirring, so as to increase the efficiency of the contact between the bacteria and the agents to be removed and to circulate better in the liquid, so as to purify the water necessary for bacterial life and for oxidation reactions which take place in the wastewater.
  • ozone is added, which - as known - is a strong oxidising agent, to accelerate and push the reactions.
  • the so-called sewage sludge is formed, consisting of dead bacteria and of reaction products.
  • the sludge tends to increase in volume over time and, if they were not removed, they would end up clogging up the plants. For this reason and to prevent overflowing thereof, undesired for the reasons illustrated above, they are removed from purification tanks, continuously or discontinuously. Discontinuously, there is a purification treatment for a certain time, then the purifier is stopped, the sludge is removed, and purification is resumed. Continuously, when the plant gets up to speed, part of the solids is sent to the exit from the tanks, like a sort of purge.
  • the destiny of sludge depends on the type of wastewater and on the type of treatment. The most frequent destinations are the agricultural one, combustion or landfill placement.
  • Agricultural use consists in the use of sludge as soil improvers, since they contain organic nitrogen matter, excellent elements for agriculture. This is possible if the concentration of heavy metals is below legal thresholds, otherwise it is resorted to combustion or to other actions to make the sludge harmless to health and to the environment and often to landfill placement which has, however, critical points (potential forming of percolates).
  • sludge is used in agriculture or is burnt, or must undergo other treatments, it is suitable for it to be previously dried.
  • non-dried sludge contains remarkable amounts of water which enormously increase the volume and weight thereof, so that even temporary storing thereof and displacing it become a non-negligible problem.
  • sludge volume is by far smaller and storing is no longer a problem. If the sludge must then undergo a combustion treatment, water presence, unless one resorts to co-combustion, for example with solid waste, prevents also ignition and combustion becomes impossible or extremely complicated and could nevertheless be incomplete, with the undesired development of harmful emissions.
  • Sludge drying is generally introduced into the dryer in forms and arrangements apt to expose the largest possible surface to the action of the drying agent. It is possible, for example, to extrude the sludge so as to create a sort of spaghetti, which are then arranged tied up in a small coil on a surface and which thus undergo the drying action of the air.
  • a wide variety of drying methods in general is reported in Industrial Superheated Steam Drying, Heft L 202, 2004, TNO Environment Energy and Process Innovation.
  • a special type of process is superheated steam drying, wherein steam is used to increase the temperature of the material to be dried, up until bringing the water therein contained to faster evaporation, drying it.
  • US 5 228 211 discloses a method and an apparatus for efficiently drying humid material, in this case laundry clothes, using superheated steam. Drying occurs in a humid environment, wherein the air present is heated inducing steam formation which gradually removes all the other gases present in said environment. The continuous steam recirculation turns it into superheated steam, which is partly flushed into a condensation system which thus allows to recover energy.
  • US 5 711 086 discloses an apparatus for the continuous drying of humid material with superheated steam.
  • the material is transported in the lines where the superheated steam circulates from a suitable conveyor belt.
  • US2013/014 678 discloses a method for drying wastewater treatment sludge which provides a first drying step with a heat transfer fluid, which leads to the formation of pre-dried sludge and water steam, a sludge-forming step at the exit from the first step and a second drying step, by means of a heated gas, for example air, to produce dried sludge, at least part of which goes to combustion to produce thermal energy, part of which supplies the heat transfer fluid.
  • a heated gas for example air
  • KR 101 565 315 discloses a sludge drying apparatus which uses newly heated steam, comprising a conveyor belt for the discharge of moisture from dehydration, contained in the sludge, while the sludge is moved. Means for discharging a fixed amount of dried sludge are provided. Also in this case, air-steam mixtures are used when fully operational for the drying of the supplied sludge. The residual moisture level remains very high (in an often unsatisfactory way).
  • the sludge is placed on belt surfaces, circulating due to a series of tiny holes with which toothed gears mesh; such tiny holes also serve for steam passage.
  • DE 196 44 465 concerns a process for the drying of sludge, transported through hot air or reduced-pressure steam or even under vacuum. It comprises two cocleas, which rotate at different speeds. The sludge is introduced discontinuously into the ring formed by the two cocleas which have heated core. The sludge moves from one coclea to the other and it cannot be understood why the cocleas rotate at different speeds, apart from possible reasons of better mixing.
  • KR 2012 0020709 discloses a sludge drying system with superheated steam, comprising a sludge supply, a steam supply, a hot air supply and an output of the dried sludge.
  • the steam is used to destroy the cellular membrane of the organisms contained in the sludge, while the actual drying occurs by means of hot air, which must then be vented.
  • a drawing of this document shows the alignment of the extruded products in parallel rows, but there are no conveyor belts on top of each other and in sequence.
  • the problem at the basis of the invention is to suggest a plant for a drying process of sewage sludges which overcomes the mentioned drawbacks, and which allow to obtain dried extruded products of sewage sludge of wastewater, with high efficiency, in a reduced space and in an economically sustainable manner.
  • This object is achieved through a drying plant of sewage sludge, which is caused to flow through some parallel conveyor belts, characterised in that it provides upstream a deposition unit of extruded products of moist sludge, apt to place such extruded products in rectilinear and orderly parallel rows.
  • the obtained sludge is taken from the corresponding tank, preheated and sent to an extruder which transforms it into a sort of noodles.
  • Said noodles may be continuous or of a preset length; such preset length may be obtained, for example, resorting to blades in the proximity of the extruders cutting the noodles at preset time intervals.
  • the preset length just mentioned may vary a lot and be so reduced to cause the extruded products to appear as pellets. Forms of this type allow to obtain advantages in transport.
  • the noodles thus obtained by extrusion, with a very high water contents, are supplied in 1 to the plant according to the present invention. As an example, it can be envisaged to supply 1 ton an hour in 1, but the initial flow rate is not limiting.
  • Supply 1 leads to a first shelf of a dryer 2.
  • Dryer 2 comprises a casing 3, closed and having meshed walls and a series of sliding shelves 4 one on top of the other, such as conveyor belts, said shelves carrying in sequence, from the uppermost to the lowermost, the noodles of extruded sludge being dried, so as to exploit as much as possible the available space. Thereby, subsequent drying steps are obtained with a low energy consumption per weight unit of the dried material, thus achieving energy savings.
  • a circuit 5 supplying superheated steam is provided.
  • Said belts 4 can, according to a preferred embodiment, carry on the resting surface thereof for the noodles spacing devices of the extruded products (not shown in the drawings), which can be nails or pins arranged at regular intervals or grooves within which the noodles would insert and lock in position, so as to maintain a regular layout for the entire path on belts 4.
  • the first exit 6, discharges the dried sludge; starting from the previously cited example, such exit has a flow rate of 0.2 tons/hour; the second exit, 7, removes the discharge steam, at a lower temperature, at the end of the drying operations.
  • Exit 7 supplies a separator 8, preferably a cyclone separator, to remove any solids from the steam, so as to avoid damaging the inner walls of the pipes, hence extending the service life thereof.
  • Exit 9 leads out the steam purified by separator 8 and supplies it, after partialisation, partly to a condenser 10 and partly to a heat exchanger 11.
  • Condenser 10 operates in cooperation with a cooling tower 12 or with potential users of thermal energy and, still in the example already described, leads to the removal of about 0.8 tons/hour of water.
  • Heat exchanger 11 preferably a shell and tube exchanger, gives to the steam inside itself heat coming from a heating fluid, contained in a suitable circuit 13, such fluid potentially being oil or process steam, generated by a dedicated boiler.
  • condenser 10 provides a removal of about 0.9 MW, while exchanger 11 provides an absorption of about 1 MW, but these figures are purely indicative and do not limit the scope of protection of the invention.
  • Heat exchanger 11 has an exit 14 which supplies a fan 15 which, in turn, supplies the circuit 5 supplying superheated steam.
  • condenser 10 On its part, condenser 10 has an exit 16, which leads to the final disposal of the condensed water, subject to the possible recovery of condensation heat for production purposes.
  • the extruded sludge noodles to be dried, with a high water content are supplied in 1 and arranged on the first one of the belts 4 of dryer 2.
  • the extruded noodles instead of being arranged in coils and in bulk on shelves 4, as normally occurs for the plants of the prior art, are arranged in an orderly manner, in parallel rows; in practice, the extruded products are placed substantially in a straight line onto said belts 4, in orderly parallel rows. It has been surprisingly ascertained that, unlike what was believed in the past, that is that an arrangement in coils would lead to a more rapid drying, the orderly rows are in actual fact much more efficient in he removal of moisture by evaporation.
  • Shelf 4 is a conveyor belt, which causes the noodles to move forward as far as the opposite end. While the noodles move forward, they are continuously exposed throughout the surface thereof to a jet of superheated steam, coming from steam supply circuit 5.
  • initially dryer 2 is full of air which heats up against exchanger 11. Heating up, it removes water from the noodles and produces steam.
  • Circuit 5 may be of any known type and may belong to any type of dryer.
  • a fan or other similar device can be provided for the circulation of the steam within dryer 2 .
  • the superheated steam being at high temperature (above 100°C, preferably at a temperature ranging between 130 and 300°C), causes the water contained in the noodles to heat up, gradually increasing its vapour pressure.
  • the evaporation process slows down as steam temperature decreases. Once the noodle has arrived at travel end, it moves to the lower level and moves into the opposite direction to the previous one on the new conveyor belt, returning towards the former end of dryer 2, thereby shedding further water. At travel end, it moves to the subsequent lower belt and returns into the direction of former belt 4, and so on. At the end of the process of the last belt, the sludge, by now dried up, leave from exit 6.
  • the parallel and consecutive arrangement of belts 4 allows to obtain a good drying of the noodles, ordered in longitudinal, parallel rows, which thus allow to save space.
  • separator 8 preferably a cyclone separator, which separates from the steam any solids which it has possibly dragged during the process (for example, sludge particles or metal impurities coming from the plant).
  • the removed solids are periodically discharged by separator 8, to avoid clogging up thereof, and are then disposed of in a known manner.
  • the steam freed from solid waste, comes out of exit 9. Part of the steam, with a flow rate corresponding to that of circuit 5, is supplied to heat exchanger 11. Therein, the steam is brought again to the original operating temperature, preferably by means of a heat exchange with a heating fluid contained in circuit 13. Once it is brought up to the temperature, the steam is sent, due to compressor 15, again to circuit 5 and resumes the drying operations.
  • the steam excess contained in exit 9 with respect to the flow rate of circuit 5 is sent to condenser 10, where it is cooled, condensed by means of a dedicated circuit connected to a cooling tower 12 or to thermal users.
  • the condensate is discharged from exit 16; the outgoing water in 16 makes up the only wastewater of the process and is a liquid, easily disposable waste, normally with no particular pollution problem.
  • excess steam can be used to pre-heat the sludge before the input thereof into dryer 2, so as to accelerate and push the process further or to supply thermal utilities of different types, for example, staying on topic, conventional-type air drying plants. Coupling a plant of the type described here with a conventional air dryer an assembly is obtained characterised by very high energy efficiency.
  • the plant according to the present invention hence allow to dry in a clean, fast and effective manner the standard sewage sludge, with no appreciable amounts of solid waste - limited to the wastes of separator 8 - with an easily disposable liquid waste and with a very reduced energy expense. Moreover, there is no leak of smelly gases from the plant, as occurs instead with the processes and plants of the prior art.
  • the present invention instead of using the steam only as indirect heating means - for example as vector fluid to be supplied to an exchanger - uses it also directly, investing therewith the sludge to be dried; the two steam flows never mix and always remain separate.
  • the extruded sludge noodles to be dried in straight and parallel rows allows fast drying of sewage sludge; moreover, it allows a simpler moving compared to coils of noodles, since the noodles can be brought forward from a belt 4 to the subsequent one with no problems, obtaining in fact a continuous process, without the need for interruptions.
  • Any provision of different speeds for each of belts 4 allows to exploit even more the advantages of this arrangement, maintaining the integrity of the noodles throughout the processing, so as to discharge a solid product, not in powdery form, better suited to the subsequent turning into a product to be disposed of or to be sold as fertiliser and with no dispersion of the dried material.
  • the extruder used for supplying the sludge to the plant according to the present invention can also be easily cleaned, using a pressurised water jet.
  • the drying process and the dryer 2 according to the present invention provide the entry into dryer 2 of moist sludge and the exit therethrough only of dried sludge and condensation.
  • Another great advantage of the present invention is that there is a high heat recovery and a high efficiency of drying.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Sustainable Development (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Treatment Of Sludge (AREA)
  • Drying Of Solid Materials (AREA)
EP23198320.6A 2019-07-23 2020-07-13 Installation de séchage pour la mise en oeuvre d'un procédé de boues d'épuration Pending EP4276399A3 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IT102019000012672A IT201900012672A1 (it) 2019-07-23 2019-07-23 Processo di essiccazione di fanghi di depurazione e impianto per mettere in pratica tale processo
EP20185522.8A EP3770539A1 (fr) 2019-07-23 2020-07-13 Processus de séchage de boue d'épuration et installation pour mettre en uvre un tel processus

Related Parent Applications (1)

Application Number Title Priority Date Filing Date
EP20185522.8A Division EP3770539A1 (fr) 2019-07-23 2020-07-13 Processus de séchage de boue d'épuration et installation pour mettre en uvre un tel processus

Publications (2)

Publication Number Publication Date
EP4276399A2 true EP4276399A2 (fr) 2023-11-15
EP4276399A3 EP4276399A3 (fr) 2024-01-31

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EP23198320.6A Pending EP4276399A3 (fr) 2019-07-23 2020-07-13 Installation de séchage pour la mise en oeuvre d'un procédé de boues d'épuration
EP20185522.8A Pending EP3770539A1 (fr) 2019-07-23 2020-07-13 Processus de séchage de boue d'épuration et installation pour mettre en uvre un tel processus

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EP20185522.8A Pending EP3770539A1 (fr) 2019-07-23 2020-07-13 Processus de séchage de boue d'épuration et installation pour mettre en uvre un tel processus

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IT (1) IT201900012672A1 (fr)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN118258210B (zh) * 2024-05-30 2024-07-19 吉林道森工程材料实业有限公司 一种路用颗粒状木质素纤维加工干燥设备

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5228211A (en) 1987-11-12 1993-07-20 Stubbing Thomas J Method and apparatus for energy efficient drying
US5711086A (en) 1993-08-26 1998-01-27 Heat-Win Limited Method and apparatus for continuous drying in superheated steam
DE19644465A1 (de) 1996-08-26 1998-03-05 Manfred Dipl Ing Boehme Verfahren und Vorrichtung zur Trocknung eines Trocknungsgutes, insbesondere von Schlamm
KR20120020709A (ko) 2010-08-31 2012-03-08 주식회사쿡웰 과열증기를 이용한 슬러지 건조 시스템
US20130014678A1 (en) 2009-12-30 2013-01-17 Degremont Method and facility for drying pasty materials, in particular sludge from wastewater treatment plants and generation of thermal energy
KR101565315B1 (ko) 2015-04-06 2015-11-04 주식회사 한국테크놀로지 재열증기를 이용한 슬러지 건조장치

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5228211A (en) 1987-11-12 1993-07-20 Stubbing Thomas J Method and apparatus for energy efficient drying
US5711086A (en) 1993-08-26 1998-01-27 Heat-Win Limited Method and apparatus for continuous drying in superheated steam
DE19644465A1 (de) 1996-08-26 1998-03-05 Manfred Dipl Ing Boehme Verfahren und Vorrichtung zur Trocknung eines Trocknungsgutes, insbesondere von Schlamm
US20130014678A1 (en) 2009-12-30 2013-01-17 Degremont Method and facility for drying pasty materials, in particular sludge from wastewater treatment plants and generation of thermal energy
KR20120020709A (ko) 2010-08-31 2012-03-08 주식회사쿡웰 과열증기를 이용한 슬러지 건조 시스템
KR101565315B1 (ko) 2015-04-06 2015-11-04 주식회사 한국테크놀로지 재열증기를 이용한 슬러지 건조장치

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Publication number Publication date
EP4276399A3 (fr) 2024-01-31
IT201900012672A1 (it) 2021-01-23
EP3770539A1 (fr) 2021-01-27

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