WO2017097302A1 - Installation ou équipement de traitement comprenant un article avec un revêtement permettant d'inhiber les dépôts de struvite, et procédé de fabrication et d'utilisation de celui-ci - Google Patents

Installation ou équipement de traitement comprenant un article avec un revêtement permettant d'inhiber les dépôts de struvite, et procédé de fabrication et d'utilisation de celui-ci Download PDF

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Publication number
WO2017097302A1
WO2017097302A1 PCT/DK2015/050386 DK2015050386W WO2017097302A1 WO 2017097302 A1 WO2017097302 A1 WO 2017097302A1 DK 2015050386 W DK2015050386 W DK 2015050386W WO 2017097302 A1 WO2017097302 A1 WO 2017097302A1
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Prior art keywords
struvite
coating
treatment plant
manure
equipment
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PCT/DK2015/050386
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English (en)
Inventor
Stefan Holberg
Claus Bischoff
Thomas Poulsen
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Teknologisk Institut
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Priority to PCT/DK2015/050386 priority Critical patent/WO2017097302A1/fr
Publication of WO2017097302A1 publication Critical patent/WO2017097302A1/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
    • C02F5/00—Softening water; Preventing scale; Adding scale preventatives or scale removers to water, e.g. adding sequestering agents
    • C02F5/08—Treatment of water with complexing chemicals or other solubilising agents for softening, scale prevention or scale removal, e.g. adding sequestering agents
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D183/00—Coating compositions based on macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon, with or without sulfur, nitrogen, oxygen, or carbon only; Coating compositions based on derivatives of such polymers
    • C09D183/04—Polysiloxanes
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
    • C09D5/16—Antifouling paints; Underwater paints
    • C09D5/1656—Antifouling paints; Underwater paints characterised by the film-forming substance
    • C09D5/1662—Synthetic film-forming substance
    • C09D5/1675—Polyorganosiloxane-containing compositions
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/02—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by thermal decomposition
    • C23C18/12—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by thermal decomposition characterised by the deposition of inorganic material other than metallic material
    • C23C18/1204—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by thermal decomposition characterised by the deposition of inorganic material other than metallic material inorganic material, e.g. non-oxide and non-metallic such as sulfides, nitrides based compounds
    • C23C18/122—Inorganic polymers, e.g. silanes, polysilazanes, polysiloxanes
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2303/00—Specific treatment goals
    • C02F2303/22—Eliminating or preventing deposits, scale removal, scale prevention

Definitions

  • the present invention relates to a manure, landfill leachate, sewage and/or wastewater treatment plant, treatment equipment or downstream conveying equipment.
  • the present invention also relates to a method for making an article with a coated surface.
  • Struvite scaling impairs the function of various articles, such as, for example, pipes and pumps. Struvite scaling may grow over time, blocking the flow and involving costly cleaning operations.
  • Struvite is known to deposit especially in manure, sewage or wastewater treatment plants or equipment and in particular after treatment of liquid manure, sewage or wastewater in anaerobic digesters. Struvite scaling may also occur in the treatment of landfill leachate or in manure treatment plants, in particular liquid manure storing, treatment of processing plants, for example lagoons or equipment for spreading liquid manure in the fields.
  • the theoretical chemical composition of struvite is H 4 MgP0 4 -6H 2 0, it is thus also referred to as ammonium magnesium phosphate (AMP) or magnesium ammonium phosphate (MAP). It comprises by weight 6.57% H, 5.71% N, 65.20% O, 9.90% Mg, and 12.62% P, which corresponds to 7.35% 3 ⁇ 4 + , 9.90% Mg 2+ , 38.7% P0 4 3" and 44.05% H 2 0.
  • AMP ammonium magnesium phosphate
  • MAP magnesium ammonium phosphate
  • struvite When referring to struvite scaling, struvite describes a class of materials rather than an exact chemical composition. In observed, real struvite scales in the respective plants, struvite deviates from the exact sum formula. Furthermore, such scales also contain inorganic and organic impurities that are not struvite. However, all scales where am- monium and magnesium cations, phosphate anions and water are the dominant components and represent together the main part of the scale are commonly referred to as struvite. Herein, struvite refers to this class of materials. Various compositions of observed struvite scales are herein provided as non- restricting examples:
  • Li & Zhao (Ecological Engineering, 20 (2003), 171-181) treated landfill leachate to precipitate struvite comprising: 4.9% N, 8.6% Mg and 16% P.
  • Mohajit et al. (Biological Wastes 30 (1989), 133-147) precipitated struvite when treating wastewater from a pig farm with a composition of 5.01% H 4 + , 10.25%) Mg 2+ , 38.99% P0 4 3" , and 44.66% H 2 0.
  • Miinch & Barr (Water Research 35 (2001), 151-159) precipitated struvite in waste water treated by anaerobic digesters comprising 5.1% N, 9.1% Mg, 12.4% P and 39% crystalline water.
  • the consistency of struvite scale can according to Miinch & Barr differ widely and occur in the form of large crystals, small crystals, large curds, or a gelatinous mass.
  • the precipitation of struvite occurs, likewise any precipitation, from a supersaturated solution, for example a slightly basic aqueous solution at a pH of 7-1 1, for example according to the general scheme: Mg 2+ + H 4 + + HP0 4 2" + OH " + 5H 2 0 ⁇ Mg H 4 P0 4 6H 2 0.
  • a supersaturated solution for example a slightly basic aqueous solution at a pH of 7-1 1 1
  • the pKsp value for the solubility product of struvite in water at 25 °C is 13.36 ⁇ 0.07.
  • struvite scale can also occur by agglomeration of struvite particles that are already precipitated and thus from a struvite suspension.
  • suspensions may optionally be colloidal suspensions of struvite nanoparticles.
  • Anaerobic di- gesters are usually mesophilic or thermophilic digesters in which organic carbon compounds are digested under formation of biogas.
  • Biogas is a mixture of gases, with the main component being Methane.
  • a mesophilic digester runs at elevated temperatures of typically approx. 35-40 °C, while thermophilic digesters typically run at temperatures of 45-55 °C.
  • the temperature is usually lowered, e.g. passively to adapt to a lower temperature of the surroundings, such as ambient air or soil/ground (when using underground pipes for transporting treated waste water), or actively, e.g. by using heat exchangers or heat pumps, to transfer heat from the outlet of the anaerobic digester to another part of the plant or to other processing steps, e.g. to the inlet to the anaerobic digester for preheating thereof prior to entry into the anaerobic digesters.
  • Struvite scale deposits may be removed by mechanical cleaning, e.g. using abrasive tools and/or mechanical impact, e.g.
  • struvite scale deposits may be removed by dissolving the deposits using an aqueous acidic cleaning solution.
  • Scale removal is usually repeated regularly and cause regular down time periods. This leads to less effective utilisation of the treatment plant or equipment and may cause increased production costs due to increased working hours by staff and/or by increased costs due to the use of chemicals, i.e. acids and/or acidic detergents. Further, struvite scale removal by chemical or mechanical methods may require hard manual labour and/or risk of potential hazardous situations if staff comes into physical contact with acidic cleaning solutions acidic cleaning
  • PMMA ⁇ PVC polyvinyl chloride
  • PVC ⁇ Techite ⁇ cast iron (Borgerding et al., Journal of the Water Pollution Control Federation 44 (1972), 813-819) Techite is a glass fibre reinforced plastic. Borgerding expects the result is due to surface roughness also being in the order from lowest to highest of PVC ⁇ Techite ⁇ cast iron.
  • the disclosures apply bulk materials and do not mention a coating to combine the superior mechanical stability of metals with the desired surface properties of the polymer.
  • the proposed polymers have drawbacks such as being rather soft thermoplastic materials with limited scratch and abrasion resistance and, in the case of PVC and PTFE, applying less environmental friendly halogenated polymers.
  • the object of the invention is to mitigate struvite scaling on articles which are in con- tact with suspensions containing struvite particulates and/or supersaturated struvite solutions.
  • the present invention relates to a manure, landfill leachate, sewage and/or waste water treatment plant, treatment equipment or downstream conveying equipment, such as a treatment plant comprising one or more biological treatment reactors, where said treatment plant or equipment comprises at least one component, wherein the at least one component and/or the at least one or more reactors or a drain of the treatment plant or equipment comprise at least one surface, which is exposed to a suspension comprising struvite particulates or colloids or to a supersaturated struvite solution, and where said reactor(s), pipes and/or said component is coated with a coating, said coating being a different material than the underlying component and said coating being applied to at least a part of said surface exposed to the struvite containing suspension or supersaturated solution.
  • struvite scaling may occur over a longer distance and involve various articles such as, for example pipes, pumps, valves or heat exchangers. Surprisingly, a coating can significantly reduce struvite scale formation.
  • the coating can provide a surface from which struvite scale is easily removed. Any formation of struvite scale on the coated surface is easily removed, e.g. by hand cleaning, or by low impact mechanical cleaning, possibly automated, e.g. using a brush or high pressure liquid impact.
  • the inventive coating on the component can be easily cleaned without the use of hard impact tools, such as when using a chisel and a hammer or the like.
  • the coated article is used in contact with a supersaturated struvite solution.
  • struvite scale in principle can be caused by surface agglomeration of struvite particles dispersed in a fluid
  • the main cause of struvite scaling in manure, landfill leachate, sewage or waste water treatment plants is by direct nucleation of struvite on a surface from a supersaturated solution. Thereafter, the initial nuclei grow by deposition of further struvite.
  • a manure, landfill leachate, sewage or waste water treatment plant may be solely referred to as a wastewater treatment plant.
  • the manure, landfill leachate, sewage and/or waste water treatment plant comprises one or more biological treatment reactors.
  • At least one of the bioreactors is an anaerobic digester or a bioreactor comprising at least an anaerobic step, preferably at least one anaerobic digester provided for biogas generation.
  • the bioreactor is preferably running under mesophilic or thermophilic anaerobic digesting conditions.
  • Components provided downstream to an anaerobic bioreactor or a reactor comprising at least an anaerobic step are especially prone to struvite scaling caused by e.g. reduction of the temperature or pH in the liquid which is transported or processed in downstream process equipment or components, e.g. pipes or pumps or similar as mentioned below.
  • the respective equipment with the inventive coating is a downstream conveying equipment, subsequent to a process step that leads to struvite precipitation.
  • Examples for such equipment are pipes, pumps, valves or heat exchangers.
  • struvite precipitation in some cases is an undesired side reaction
  • many treatment plants induce struvite precipitation on purpose by adding solutions of the respective ions to purify the wastewater and to regain nutrients.
  • the precipitation typically occurs in designated equipment or basins.
  • Even when precipitated on purpose small changes, especially in pH and temperature, but also in other physi- cal and chemical parameters, can trigger a secondary, undesired precipitation in downstream equipment adjacent to the designated precipitation equipment or basin.
  • this secondary precipitation in downstream components which is a main cause of costly cleaning operations, is mitigated or at least reduced significantly when providing a coating on the one or more components according to the present invention and as outlined above.
  • said component is used in a wastewater treatment plant or at a drain of a waste water treatment plant, or in plants or equipment for treating and/or handling sewage, landfill leachate or manure, the latter refers in particular to liquid and/or liquidized manure.
  • components or equipment used in waste water treatment or biogas production facilities are pipes, such as internal pipe connections between processing equipment in the treatment plant, and/or sewers, outlets for purified waste water from the treatment plant.
  • Other examples of components used in waste water treatment plants are channels, valves, pumps, heat exchangers, heat pump surfaces in contact with the liquid from which struvite may precipitate, internal surfaces of reactors, such as aerobic, anoxic and/or anaerobic reactors, struvite crystallizers, etc., because internal surfaces of such processing equipment are particularly prone to struvite scaling.
  • components which are used in handling and/or treating liquid or liquidized manure are e.g. lagoons, manure spreaders, such as slurry tankers, and/or parts thereof.
  • parts are pipes, pumps, or manure mixing means, such as impellers or nozzles, which reintroduce slurry or manure into a lagoon after circulating through one or more pipes and/or pumps.
  • said article is a pump, a valve, a pipe or a heat exchanger or a part of the mentioned articles in contact with waste water or any fluid produced by processing waste water.
  • said articles are prone to struvite scaling.
  • pipes can be very difficult to access for cleaning.
  • said article is a pump or a part of a pump, such as a casing or rotor or impeller. Due to the possible mixing of waste water with air, pumps are especially prone to struvite scaling. It is in particular preferred to coat the rotor or im- peller of a pump.
  • Rotors or impellers of pumps are not suitable for mechanical cleaning as any damage caused during mechanical cleaning of the impeller or rotor may cause the rotor or impeller to rotate in an instable manner resulting in increasing the level of noise from the pump or even damage. The risk thereof is elegantly eliminated or at least reduced significantly.
  • said coating comprises by weight 30% to 70% carbon (C), 10% to 35% oxygen (O), 5% to 40% silicon (Si) and optionally further elements, where the sum of carbon, oxygen, silicon and hydrogen (H) is 70% to 100%). At least 5% silicon is bound to x carbon and y oxygen atoms, where x is 1 or 2 and y is 4 - x.
  • At least 90% of the carbon atoms are bound to 0 or 1 silicon atoms and to 1 to 4 atoms chosen from the group of hydrogen, boron (B), carbon, nitrogen (N), oxygen, fluorine (F), phosphor (P), sulphur (S), chlorine (CI), bromine (Br), iodine (I) and/or combinations thereof.
  • These intervals and the binding situation of C and Si define the nature of a coating matrix that is especially effective against struvite fouling.
  • Such an organic-inorganic hybrid coating comprises a significant organic part (at least 30% carbon) consisting of carbon based structures (organic chains or networks), optionally including other non- metal atoms, especially H, O, and/or N, but optionally also B, F, P, S, CI, Br and/or I.
  • Examples are alkyl or aryl groups or networks, optionally halogenated, any common functionalities known from technical organic coatings such as, for example, alcohols, esters, ethers, epoxides, amines, amides, urethanes, thiourethanes, ureas and/or combinations thereof, but also phosphonic and/or boronic esters.
  • technical organic coatings such as, for example, alcohols, esters, ethers, epoxides, amines, amides, urethanes, thiourethanes, ureas and/or combinations thereof, but also phosphonic and/or boronic esters.
  • the organic part provides the necessary flexibility and provides the surface with the anti-struvite-scaling properties as compared to inorganic surfaces such as bare metal surfaces.
  • the coating according to this preferred embodiment comprises a significant inorganic part (at least 5% Si bound to at least two oxygen atoms) that forms Si- O chains or networks, which are referred to as siloxane chains or networks.
  • the inorganic part provides chemical and mechanical stability and can, if necessary, additionally provide improved adhesion to metallic surfaces by creating chemical bonds to metal surfaces (Si-O-M), as compared to solely organic polymers.
  • the organic and inorganic parts of the coating are connected at molecular level through Si-C bonds (at least 5% by weight of Si, which is bound to at least one carbon atom).
  • the coating performs as a homogenous surface layer and acts as a homogenous material to combine the benefits of organic and inorganic part.
  • the coating does not solely comprise inorganic particles in an organic matrix. Such a coating may lead to a heterogeneous surface without the desired proper- ties.
  • organic inorganic hybrid coatings are especially robust against abrasion, for example by traces of sand and/or other particulate matter in the waste water, land fill leachate, sewage or liquid/liquidized manure or from cavitation .
  • cavitation may be caused by the turbulent flow of water containing gases in a pump housing. The soluble gases, and potentially also water vapour, creates bubbles in the pump housing and causes wear on the rotor or the pump housing or both.
  • a paint system can comprise different layers, such as, for example, a primer, a base coat and a top coat.
  • the present composition refers to the last layer of the coating according to the invention, which is applied on top of the other layers, as this is the layer in contact with the struvite sus- pension.
  • the inventive coating comprises by weight 35% to 60% carbon (C) and 7% to 30% silicon (Si), and a sum of hydrogen, carbon, nitrogen, oxygen, sulphur and silicon of 90-100%).
  • Such coating provides an optimised com- promise of hardness and flexibility and reduces or mitigates struvite fouling on the coated surface.
  • At least 7% by weight Si is chemically bound to three oxygen atoms and one carbon atom for further improved structural stability by guaranteeing a three-dimensional siloxane network.
  • the coating on the article has a thickness of 0.1 to 100 ⁇ .
  • a minimum thickness is required for structural stability and distinguishes the coating from monolayers or ultrathin films.
  • a thickness above 100 ⁇ is not advantageous due to the increased possibility of tensions in the coating film.
  • the thickness refers solely to the coating according to the invention.
  • the thickness is below 15 ⁇ to save materials, but above 0.5 ⁇ to provide sufficient mechanical stability of the coating layer itself.
  • an article is coated with a coating providing a receding water contact angle of at least 70°.
  • the receding contact angle is a measure for the work required to remove a substance from a surface.
  • such coating with a high receding contact angle also reduces the adhesion, in case struvite deposits anyway, and facilitates cleaning of the coated surface.
  • such receding water contact angle as outlined above is achieved by applying a silane with a perfluoroalkyl moiety and/or by applying polydimethylsiloxane (PDMS) that is capable of forming chemical bonds to the coating matrix in the preparation of the coating.
  • PDMS polydimethylsiloxane
  • an article provides a receding water contact angle of at least 70° and is coated with a coating comprising polydimethylsiloxane chains, which on one terminus are chemically bound to the cross-linked coating matrix, and on the other terminus chemically bound to a terminating group that is not chemically bound to other parts of the coating matrix and is thus dangling.
  • Such type of polydimethylsiloxane can merge to the surface during curing of the coating to provide the hydrophobic surface with the respective receding contact angle as outlined above.
  • the preferred terminating groups of the PDMS are alkyl groups. As compared to other hydrophobic surfaces, such surface will provide further improved reduction of struvite nucleation and struvite adhesion to the coated surface by providing a surface with flexible groups, which show significant movement at ambient temperatures.
  • Such type of PDMS is, for example, disclosed by C. Nagel et al. (European Coatings Journal 2010 (04), 32-39).
  • the coating preferably comprises at least 0.005% by weight of PDMS, preferably 0.05-5% by weight, or more preferred 0.05-2%) or in particular 0.1-1%.
  • PDMS preferably 0.05-5% by weight, or more preferred 0.05-2%) or in particular 0.1-1%.
  • Such low amounts of PDMS additive effectively provide the hydrophobic surface with the respective receding contact angle as outlined above.
  • a component is coated with a coating, where said coating comprises, by weight, at least 2% C which is tetravalent and covalently bound to exactly three atoms, where the first atom is N, the second is O, and the third atom is either N, O, or S, such as organic nitrogen containing groups selected from urea, ure- thane, thiourethane, oxazolidinone, biuret, uretdion, cyanurate and/or combinations thereof.
  • Such carbon atoms are part of nitrogen-containing derivates of carbonic acid.
  • Such groups are usually formed from industrially available isocyanates, for example by reaction with alcohols, thiols, amines, other isocyanates (and optionally water) and/or epoxides and can provide further improved scratch resistance due to strong intramolecular hydrogen bridging.
  • a coating with such groups provides a certain re- flow effect when the surface has been scratched. Thus, the reflow effect re-closes the scratch in the surface, i.e. the coating layer becomes, at least to some extent, "self- repairing".
  • the precursor for said groups is a commercially available, and thus cost effective isocyanate resin, optionally a blocked isocyanate.
  • Non-limiting examples for such resins are 4,4'-Methylenebis(cyclohexylisocyanate) and trimers of hexamethylene diisocyanate or isophorone diisocyanate, optionally blocked with bu- tanonoxime and/or mixtures thereof.
  • a method for preparing a coated article for use in an environment where at least part of the article's coated surface is exposed to a struvite suspension, which is optionally a colloidal suspension, or a supersaturated struvite solution comprising the steps of
  • Such a method is an economic way to provide a coating film as compared to, for example, gas phase deposition, and allows to apply thin coatings to save material, as compared to powder coatings, and provides the struvite repellent surface coating.
  • the liquid coating may be applied by conventional methods, e.g. by dipping, spraying or by using an applicator, such as a brush, a roller or similar conventional application means.
  • said liquid coating composition used in the method or on a component of the treatment plant as mentioned above comprises by weight based on solids at least 40%, preferably 60% of one or more silanes having at least one silicon atom bound to at least two, preferably at least three atoms chosen from the group of O, N, F, CI Br or combinations thereof, and/or or any hydrolysation and/or condensation product of said silanes.
  • silanes form, when cured, a strong siloxane network that allows to provide mechanical and chemical stability at low film thickness, e.g. below 15 ⁇ , while at the same time, said silanes provide the effect against struvite scaling. Low film thickness leads to material and cost savings.
  • the higher silane ratio of at least 60% and/or a higher crosslinking density achieved by three hydrolysable groups improves mechanical and chemical stability even further.
  • Such silanes have hydrolysable groups such as, for example, F, CI, Br, R 2 or OR that react with water while forming Si-OH groups and the respective leaving group. Water may be added or may come from atmospheric moisture. The Si-OH groups condense subsequently either with one of the mentioned hydrolysable groups or with a Si-OH group of another silane molecule. In both cases, a siloxane bond is formed.
  • hydrolysable groups such as, for example, F, CI, Br, R 2 or OR that react with water while forming Si-OH groups and the respective leaving group. Water may be added or may come from atmospheric moisture.
  • the Si-OH groups condense subsequently either with one of the mentioned hydrolysable groups or with a Si-OH group of another silane molecule. In both cases, a siloxane bond is formed.
  • the full siloxane (Si-O) network is usually formed upon curing.
  • Such coatings comprise, at least partly, an inorganic siloxane network and provide besides the effect against struvite nucleation high mechanical stability and chemical stability when compared to organic coatings.
  • solid content When referring to a coating or a coating composition's solid content in this description, it is the sum of solids used for preparing the coating composition. This takes not only the evaporation of solvents into account, but also the evaporation of volatile components that are set free during curing, such as blocking agents or hydrolysable groups.
  • Silanes form condensed siloxane networks during curing illustrated by
  • such silanes are commercially available silanes bearing two or three methoxy and/or ethoxy groups per silicon atom, such as, for example, Methyltriethoxysilane, (3 -Aminopropyl)tri ethoxy silane, (3- Aminopropyl)trimethoxysilane, (3-Aminopropyl)methyldiethoxysilane, Bis[3- (triethoxysilyl)propyl]amine, (3-Mercaptopropy)trimethoxysilane or (3- Glycidyloxypropyl)trimethoxysilane and/or mixtures thereof.
  • Methyltriethoxysilane 3 -Aminopropyl)tri ethoxy silane
  • 3- Aminopropyl)trimethoxysilane (3-Aminopropyl)methyldiethoxysilane
  • Bis[3- (triethoxysilyl)propyl]amine (3-Mercaptopropy)
  • said liquid coating composition is preferably free of particulate, inorganic fillers.
  • the vast majority of technical coatings contain inorganic fillers, for example as colour pigments, thixotroping agents, or fumed silica or anticorrosive pigments.
  • the particles can be at ⁇ -size as well as at the size of several nm.
  • said liquid coating composition comprises, based on solids,
  • a silane comprising at least one silicon atom, said silicon atom comprising at least two methoxy- or ethoxy substituents or a combination of methoxy and ethoxy substituents, said silicon atom being further connected to at least one organic substructure via a Si-C bond, said organic substructure comprising at least one func- tional group from the group of amine, thiol, epoxide and/or combinations thereof,
  • said isocyanate groups may optionally be blocked,
  • Preferred embodiments of said organic substructure(s) are derived from commercially available alkoxy silanes, for example 3-(glycidyloxy)propyl, 2(3,4- epoxycyclohexyl)ethyl, 3-mercaptopropyl, 3-aminopropyl, 3-(N-butyl-amino)propyl, 3-[(2-aminoethyl)amino]propyl or p-aminophenyl and/or mixtures thereof.
  • the respective functional group(s) can react with the isocyanate.
  • Preferred silanes are (3-Glycidyloxypropyl)trimethoxysilane, (3- Aminopropyl)trimethoxysilane, (3-Aminopropyl)methyldimethoxysilane, Bis-[3- (trimethoxysilyl)propyl]amine, [3-(2-Aminoethyl)aminopropyl]trimethoxysilane, (3- Mercaptopropyl)trimethoxysilane and the respective derivates of the mentioned silanes bearing ethoxy groups instead of methoxy groups or mixtures of methoxy- and ethoxy groups.
  • Preferred isocyanate resins are commercially available isocyanate resins, such as reaction products of hexamethylene diisocyanate, toluene diisocyanate or isophorone diisocyanate, optionally blocked, for example with butanone oxime or caprotlactame.
  • Such coating composition leads to a further optimised combination between a hard and chemical resistant inorganic siloxane network and a flexible organic network based on urethanes, carbamates, thiourethanes, ureas, biurets, uretdions, cyanurates, and/or oxazolidinones and/or combinations thereof.
  • a coating based on reaction products of an isocyanate resin, and thus comprising urethanes, ureas, thiourethanes, oxazolidinones or combinations thereof is especially advantageous to withstand mechanical and chemical impact from wastewater, sewage and/or liquid/liquidized manure streams while also ensuring a surface which reduces or eliminates nucleation of struvite deposits on the surface.
  • FIG. 1 shows a side view, schematic illustration of a sewage pump
  • Fig. 2 shows a top view of the lower casing of the pump
  • FIG. 1 shows a side view of the pump
  • Fig. 2 shows a view into the lower casing of the pump, seen from the top (6, see below).
  • the upper part 3 of the casing contains the motor.
  • a lower surface 4 of the upper casing is in contact with liquid inside the pump housing. This surface 4 was not coated in example 1 below.
  • the pump comprises an impeller 5, which rotates when pumping. After dismantling the pump, the impeller 5 was coated in the example below. 6.
  • the lower part 6 of the casing is surrounding the impeller 5.
  • the inner side of the lower casing part 6 is also in contact with the pumped liquid.
  • the inner surface of the lower casing 6 was also coated in example 1 below.
  • the inlet 7 to the pump housing is not visible in side view at Fig. 1).
  • the pumped liquid exits the pump through an outlet 8.
  • Byk Silclean 3700 is a polyacrylate from Byk with OH functions and polydime- thylsiloxane side chains as 25% solution in 2-Methoxy-l-methylethyl acetate. OH equivalent weight, based on solids, -1870 g/mol. Calculations based on XPS data provided by Esmaeilpour et al. (Progress in Organic Coatings 90 (2016), 317-323, online available in 2015) lead to a PDMS content, based on solids, of 32-42%.
  • Desmodur BL 4265 SN is a 65% solution of a blocked aliphatic polyisocyanate based on isophorone diisocyanate in solventnaphtha 100.
  • the approximate chemical composition of a cured film, calculated/estimated from the single components is: 56.9% C, 8.2% H, 4.1% N, 16.8% O, 13.8% Si, 0.1% Zn. Based on total solids after curing, the PDMS content is approximately 0.31%, and the amount of solids contributed from silanes is about 66%.
  • a new sewage pump was dismantled.
  • the impeller and the inner side of the lower part of the casing were coated.
  • the drawing provides a schematic of the pump to illustrate which parts were coated. These parts are factory-providedly coated with a cathodic epoxy coating.
  • the coating according to this example was applied by spraying on top of the epoxy coating.
  • a bare aluminium panel was spray coated. All coated objects were cured for 1 h at 185°C to result in a clear, 2-4 ⁇ thick film.
  • the sewage pump was assembled again. On the aluminium panel, the coating provides a receding water contact angles of about 93°.
  • the pump was installed in a waste water treatment plant in Denmark in a drain containing water that is prone to struvite scaling and was run for three weeks. Thereafter, the test was stopped and the pump was inspected. Impeller and casing of the pump were besides single spots practically free of struvite. These single struvite spots are about 3-4 mm thick, but cover no more than 2% of the surface. In addition, these spots were very easy to remove by rubbing lightly with the fingers only. Furthermore, the coating itself had not shown any loss of adhesion or visible degradation.
  • the pump was reassembled and run for further 9 weeks. Thereafter, the impeller was inspected again. Solely 3% of the impeller surface was covered by 2-4 mm thick struvite scale, the rest was clean.

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  • Organic Chemistry (AREA)
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  • Wood Science & Technology (AREA)
  • General Chemical & Material Sciences (AREA)
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  • Environmental & Geological Engineering (AREA)
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Abstract

L'invention concerne une installation de traitement, un équipement de traitement ou un équipement de transport en aval, de fumier, de lixiviat de décharge, d'égout et/ou d'eaux usées tel qu'une installation de traitement de fumier, de lixiviat de décharge, d'égout et/ou d'eaux usées comprenant un ou plusieurs réacteurs de traitement biologique, où ledit équipement ou installation de traitement comprend au moins un composant, ledit au moins un composant et/ou ledit ou lesdits réacteurs ou une évacuation de l'équipement ou installation de traitement comprend au moins une surface, qui est exposée à une suspension comprenant des matières particulaires ou colloïde de struvite ou à une solution sursaturée de struvite, et où le(s)dit(s) réacteur(s), le tuyau et/ou ledit composant sont revêtus d'un revêtement, ledit revêtement étant appliqué à au moins une partie de ladite surface exposée à la suspension ou solution sursaturée contenant de la struvite. Le revêtement est de préférence préparé à l'aide d'organosilanes. Le revêtement est appliqué par un procédé comprenant les étapes consistant à (i) préparer une composition de revêtement liquide, (ii) appliquer ladite composition de revêtement liquide sur au moins une partie de la surface d'un article et (iii) durcir pour former un film de revêtement solide sur ledit article. Le revêtement réduit ou élimine la formation de dépôts de struvite sur la surface revêtue, découlant d'une suspension de particules de struvite ou d'une composition sursaturée de struvite.
PCT/DK2015/050386 2015-12-08 2015-12-08 Installation ou équipement de traitement comprenant un article avec un revêtement permettant d'inhiber les dépôts de struvite, et procédé de fabrication et d'utilisation de celui-ci WO2017097302A1 (fr)

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CN110066085A (zh) * 2019-03-13 2019-07-30 杭州电子科技大学 垃圾中转站渗滤液资源化处理回用方法

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110066085A (zh) * 2019-03-13 2019-07-30 杭州电子科技大学 垃圾中转站渗滤液资源化处理回用方法

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