WO2009132750A1 - Procédé pour la récupération de mélamine solide - Google Patents

Procédé pour la récupération de mélamine solide Download PDF

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Publication number
WO2009132750A1
WO2009132750A1 PCT/EP2009/002501 EP2009002501W WO2009132750A1 WO 2009132750 A1 WO2009132750 A1 WO 2009132750A1 EP 2009002501 W EP2009002501 W EP 2009002501W WO 2009132750 A1 WO2009132750 A1 WO 2009132750A1
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WO
WIPO (PCT)
Prior art keywords
melamine
ammonia
carbon dioxide
aqueous
bar
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PCT/EP2009/002501
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English (en)
Inventor
Tjay Tjien Tjioe
Original Assignee
Dsm Ip Assets B.V.
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Publication date
Application filed by Dsm Ip Assets B.V. filed Critical Dsm Ip Assets B.V.
Publication of WO2009132750A1 publication Critical patent/WO2009132750A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D251/00—Heterocyclic compounds containing 1,3,5-triazine rings
    • C07D251/02—Heterocyclic compounds containing 1,3,5-triazine rings not condensed with other rings
    • C07D251/12—Heterocyclic compounds containing 1,3,5-triazine rings not condensed with other rings having three double bonds between ring members or between ring members and non-ring members
    • C07D251/26—Heterocyclic compounds containing 1,3,5-triazine rings not condensed with other rings having three double bonds between ring members or between ring members and non-ring members with only hetero atoms directly attached to ring carbon atoms
    • C07D251/40—Nitrogen atoms
    • C07D251/54—Three nitrogen atoms
    • C07D251/62—Purification of melamine
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D251/00—Heterocyclic compounds containing 1,3,5-triazine rings
    • C07D251/02—Heterocyclic compounds containing 1,3,5-triazine rings not condensed with other rings
    • C07D251/12—Heterocyclic compounds containing 1,3,5-triazine rings not condensed with other rings having three double bonds between ring members or between ring members and non-ring members
    • C07D251/26—Heterocyclic compounds containing 1,3,5-triazine rings not condensed with other rings having three double bonds between ring members or between ring members and non-ring members with only hetero atoms directly attached to ring carbon atoms
    • C07D251/40—Nitrogen atoms
    • C07D251/54—Three nitrogen atoms
    • C07D251/56—Preparation of melamine
    • C07D251/60—Preparation of melamine from urea or from carbon dioxide and ammonia

Definitions

  • US Patent 3,496,176 disclosing also a process where solid melamine is recovered from an aqueous suspension and the resulting mother liquor is recycled into the process, unwanted oxygen containing byproducts, such as ammeline and ammelide, build up in the recycled mother liquor and result in an unwanted impurity level of the resultant solid melamine.
  • US Patent 3,496,176 suggests to first strip the aqueous mother liquor after separation of the solid melamine to remove ammonia, cooling the liquid and precipitating ammeline and ammelide by acidification. After removal of the precipitated ammeline and ammelide by filtration the filtrate is recycled to the process. Although these measures result in a reduced impurity level the energy consumption is rather high.
  • EP 91 174 teaches to treat only a portion of the recycled mother liquor by acidification by introduction of carbon dioxide and heating to dissolve any remaining suspended melamine whereby a precipitate of impurities is formed and filtered off. The thus purified part of the mother liquor is recycled into the process.
  • the drawback of the process described in EP 91 174 is that still a purification treatment of a part of the mother liquor is necessary, resulting in energy consumption and the resultant purity is still not satisfactory.
  • WO 01/00596 also deals with the problem of formation of oxygen containing impurities, like ammelide and cyanuric acid, and suggests rapid cooling of a gaseous mixture comprising melamine, ammonium and carbon dioxide by direct contact with an evaporating medium that is sprayed in order to have a certain specific minimum area of liquid and a minimum impulse while having a minimum residence time within the cooling unit.
  • the evaporating medium used for cooling may be ammonia, water or ammonium carbamate solution.
  • WO 02/14289 deals with a process wherein the gaseous effluents from a low pressure catalytic process for the production of melamine comprising melamine, ammonia and carbon dioxide are quenched with an aqueous ammonium carbamate solution recycled from a condensation absorption unit wherein the gaseous effluents from the quenching step are condensed and absorbed in an aqueous phase resulting in an aqueous carbamate solution.
  • the advantage of that process is that solutions of a higher ammonium carbamate concentration are obtained in the absorption condensation step that can be directly exported without further concentration to a urea plant.
  • the object of the present invention is to provide a process for recovering solid melamine from a gaseous mixture containing melamine, ammonia and carbon dioxide which results in an improved purity of the recovered solid melamine, especially a reduced amount of oxygen containing impurities, without the necessity of energy consuming purification steps, like recrystallization of the recovered melamine or purification of the recycled mother liquor.
  • This object has been surprisingly attained by a process for recovering solid melamine from a gaseous mixture containing melamine, ammonia and carbon dioxide comprising: a) quenching said gaseous mixture with an aqueous ammonium carbamate containing solution thereby producing an aqueous melamine containing slurry or solution, said aqueous melamine containing slurry or solution comprising 24 to 80 wt-% of combined ammonia and carbon dioxide based on the total weight of the aqueous phase; b) cooling said aqueous melamine containing slurry or solution obtained in step a) to a temperature of 80 to 120 0 C thereby precipitating solid melamine to form a melamine slurry; c) optionally concentrating the melamine slurry obtained in step b); and d) separating the solid melamine from said slurry obtained in step b) or c) to obtain recovered solid melamine and a mother liquor.
  • the aqueous ammonium carbamate containing solution used in the quenching step according to the present invention contains preferably less than 0.5 wt-%, more preferred less than 0.05 wt-%, and most preferred less than 0.005 wt-%, and most preferred substantially no alkali metal or alkali earth metal hydroxide.
  • the recovered solid melamine obtained from step d) of the process of the present invention is not subjected to a recrystallization step.
  • the present invention relates to a process for the production of solid melamine comprising: i) obtaining a gaseous mixture containing melamine, ammonia and carbon dioxide from urea by a catalytic or non-catalytic reaction; and ii) subjecting the gaseous mixture containing melamine, ammonia and carbon dioxide to a process as defined above.
  • a gaseous mixture containing melamine, ammonia and carbon dioxide is quenched in step a) with an aqueous ammonium carbamate containing solution thereby producing an aqueous melamine containing slurry or solution comprising 24 to 80 wt-% of combined ammonia and carbon dioxide based on the total weight of the aqueous phase. Consequently, in step a) if a melamine containing slurry is formed the precipitated melamine is not considered when calculating the weight percentage of ammonia and carbon dioxide.
  • the weight percentage of ammonia and carbon dioxide is only based on the total weight of the aqueous phase that in addition to ammonia and carbon dioxide contains water, dissolved melamine and very limited amounts of byproducts.
  • the weight percentage of combined ammonia and carbon dioxide based on the total weight of the aqueous phase is 24 to 80 wt-%, preferably 27 to 75 wt-%, and even more preferably 30 to 70 wt-%.
  • this gaseous mixture has a temperature between 300 0 C and 500 0 C, preferably 36O 0 C to 440 0 C, and more preferred 400 0 C to 430 0 C, and a pressure between 3 and 150 bar.
  • the gaseous mixture has a pressure at the lower end of the above range if a catalytic low pressure process is used for making melamine from urea, and has a pressure of preferably 45 to 150 bar if a non-catalytic high pressure process is used for providing the gaseous mixture.
  • the gaseous mixture is quenched with an aqueous ammonium carbamate containing solution as defined above, and thereby cooled.
  • the quenching step can be conducted as a single step or as a multiple step. Thereby the aqueous ammonium carbamate containing solution can be brought into contact with the gaseous mixture either in cocurrent or countercurrent manner. It is also possible to contact the gaseous mixture in a multiple quenching step first in a cocurrent manner with the aqueous ammonium carbamate containing solution and in a second quenching step in a countercurrent manner with the aqueous ammonium carbamate containing solution.
  • the quench pressure is equal or lower than the reactor pressure.
  • the aqueous melamine containing slurry or solution as obtained in step a) has preferably a temperature of 100 0 C to 179°C, more preferred of 121 0 C to 169°C.
  • the molar ratio of ammonia to carbon dioxide in said aqueous melamine containing slurry or solution obtained in step a) is preferably at least 2.1 , more preferred at least 2.5, even more preferred at least 3.0, and most preferred at least 3.4.
  • the molar ratio of ammonia to carbon dioxide in said aqueous melamine containing slurry or solution does not exceed 14 and is preferably less than 10 and more preferred less than 7. Higher ratios are not preferred since they result in the necessity of high pressure and thus increased process cost.
  • the pressure in the quenching step depends on the pressure of the melamine containing gaseous mixture that is provided to the quenching step and thus depends on whether the low pressure catalytic process is used for the production of melamine, or whether a non-catalytic high pressure process is used.
  • the pressure can vary in a wide range and is preferably between 3 and 45 bar, more preferred between 14 and 45 bar, and most preferred between 17 to 35 bar.
  • aqueous melamine containing slurry or solution is subsequently cooled in a cooling step b) to a temperature of 80 0 C to 120 0 C.
  • Cooling means that the temperature of the melamine containing slurry or solution obtained in quenching step a) is reduced in cooling step b) which is the common understanding of the term "cooling" by a person skilled in the art.
  • the melamine containing slurry or solution is cooled to a temperature between 86°C and 115°C and more preferred 90 0 C to 110°C. Cooling causes further precipitation of solid melamine.
  • cooling causes further precipitation of solid melamine.
  • cooling causes the formation of a melamine containing slurry by precipitation of solid melamine.
  • the cooling in step b) may be either effected by mixing the melamine containing slurry or solution obtained in the quenching step with a coolant or cooling by heat exchange and/or by depressurization.
  • the cooling is preferably conducted by mixing and/or depressurization at a pressure of 0.5 to 8 bar, preferably 0.8 to 4 bar, most preferred 0.9 to 2 bar.
  • a coolant recycled mother liquor obtained in the separating step d) of the process according to the present invention can be used.
  • at least a part of the recycled mother liquor is purified prior to recycling to the cooling step b). But this purification step is not mandatory in order to achieve the desired low level of oxygen containing impurities. If, however, extraordinarily high purity is required a purification step can be added.
  • the aqueous melamine containing slurry obtained from cooling step b) is preferably further concentrated by means known to a person skilled in the art, like a hydrocyclone to effect further precipitation of solid melamine.
  • Either the melamine slurry obtained in cooling step b) or the concentrated melamine containing slurry obtained in concentrating step c) is subjected to a separation step in order to recover solid melamine and mother liquor that may be recycled to cooling step b). Any known methods for solid/liquid separation, like centrifugation or filtration, may be used.
  • the solid melamine obtained by the process according to the present invention has a very low content of oxygen containing impurities, like ammeline, ammelide or cyanuric acid.
  • the process for recovering solid melamine from a gaseous mixture containing melamine, ammonia and carbon dioxide is combined with a process for the production of melamine that comprises:
  • melamine is produced using urea as raw material.
  • the urea is fed as a melt into a reaction section and is reacted at a pressure of 45 to 150 bar, preferably 50 to 80 bar at elevated temperature to form melamine and the by-products ammonia and carbon dioxide in accordance with the above mentioned reaction equation.
  • the reaction conditions in the reaction zone are selected in order to obtain melamine in the liquid state.
  • the reaction temperature is preferably 360 to 440 0 C, more preferred 400 0 C to 43O 0 C, even more preferred 401 0 C to 419°C.
  • reaction mixture comprising molten melamine and the gaseous reaction by-products carbon dioxide and ammonia
  • a vaporization step whereby without separating the molten melamine from the gaseous reaction by-products, the melamine is vaporized in order to form a gaseous mixture comprising the vaporized melamine and the reaction offgases.
  • Vaporization can be achieved by any means known to the person skilled in the art, like increase of temperature or reduction of pressure.
  • the pressure is kept approximately constant but vaporization is achieved by feeding ammonia into the vaporization section in order to reduce the partial pressure of melamine, thereby vaporizing the melamine.
  • vaporization of the melamine can be achieved by feeding ammonia in an amount of 0.5 to 3 kg ammonia/kg urea to the vaporization section, preferably 1.05 to 1.9 kg ammonia/kg urea at an evaporator temperature between 401 0 C and 419°C.
  • the melamine content in the gaseous phase from the evaporator is lower than the saturation pressure of melamine at the prevailing process conditions.
  • reaction step A) and the evaporation step B) according to the present invention can be conducted in different vessels, but it is preferred to conduct these process steps in different sections of the same vessel.
  • the reactor/evaporator contains a draught tube for improving the contact between the melamine liquid and the ammonia gas.
  • the ammonia may be split to the different sections, irrespective whether they are part of the same or different vessels.
  • the gaseous mixture obtained from the vaporization step B) comprising melamine, carbon dioxide and ammonia is directed to a cooling unit wherein the gas mixture is quenched by contact with an aqueous ammonium carbamate solution.
  • the pressure in the quenching step a) is preferably at least 5 bar lower than in the evaporation step B). In order to achieve an even faster quenching it is preferred that the pressure in the quenching step is less than 75%, even more preferred less than 60% of the pressure in the evaporation step B).
  • the pressure in the quenching step a) is preferably at least 16 bar, more preferred at least 19 bar, and most preferred at least 22 bar.
  • the gaseous phase comprising water, ammonia and carbon dioxide separated from the quenching step is preferably directed to a condensation/absorption step d) where the gaseous phase is at least partially condensed, optionally in presence of additional water to form a concentrated aqueous ammonium carbamate solution and a gaseous fluid comprising ammonia.
  • additional water optionally together with carbon dioxide and ammonia, may be introduced into the condensation/absorption step from stripping the aqueous ammonium carbamate solution in the work-up section to isolate solid melamine.
  • the pressure in the condensation/absorption step C) is virtually the same as in the quenching step a). Higher pressures in the absorption condensation step C) are preferred in order to produce higher concentrated ammonium carbamate solutions that can be directly used without any intermediate concentration steps in a urea plant. Thus it is preferred to operate the quenching step a) and thus the condensation and absorption step C) at a pressure of at least 16 bar, preferably at least 19 bar, and more preferred at least 22 bar, as already mentioned above.
  • the pressure drop between the evaporation step B) and the quenching step a) can be adjusted to find an optimum balance between fast quenching (achieved by high pressure differences between the evaporation step and the quenching step) and high concentration of the ammonium carbamate solution obtained in the absorption condensation step C) (achieved by high pressure in the condensation absorption step).
  • the process according to the present invention provides a highly concentrated ammonium carbamate solution that can be directly introduced into a urea plant without a further concentration step.
  • part of the obtained highly concentrated ammonium carbamate solution is preferably recycled to the quenching step a) in order to obtain in the quenching step a) an aqueous melamine containing slurry or solution comprising the high level of ammonia and carbon dioxide as required by the present invention.
  • the concentrated carbamate solution obtained in the condensation/absorption step contains less than 50 wt.-% water, preferably less than 30 wt.-% water.
  • the gaseous effluent from the condensation/absorption step C) consists essentially of ammonia and can be after optional separation or purification steps and after repressurization recycled to the reactor/evaporation unit.
  • the gaseous ammonia from the condensation/absorption section may be condensed partially and used as a reflux to increase the purity of the gaseous ammonia. Virgin liquid ammonia may also be used as an absorption liquid for purification of ammonia gas.
  • Melamine was produced from urea melt (1.4 t/h, 140 0 C) at 55 bar in a combined liquid-phase reactor/evaporator, which was heated with molten salt.
  • the liquid melamine was evaporated at 422 0 C by introducing 1.6 t/h ammonia of 330 0 C.
  • the gas from the reactor/evaporator (containing mainly ammonia, CO 2 and melamine vapor) was quenched rapidly with recycled aqueous carbamate solution (from the hydrocyclone and from the off-gas condensation) in a quenching tower at a temperature of 138 0 C and a pressure of 19 bar.
  • a melamine slurry in aqueous carbamate solution (CS1 ) and quench off-gas were produced.
  • the quench off-gas was sent to the absorption column operating at almost the same pressure as the quenching tower.
  • water and CO 2 was removed from the quench off-gas by partial condensation and by washing with liquid ammonia producing an aqueous carbamate solution (CS2) as a bottom stream and ammonia gas as a top stream.
  • CS2 aqueous carbamate solution
  • Part of the aqueous carbamate solution was returned to the quenching tower and used as a cooling agent. Water was mixed with this carbamate solution before returning to the quenching tower to balance the water export.
  • the composition of CS1 was: 23 wt-% ammonia, 12 wt-% carbon dioxide, 13 wt-% dissolved melamine and byproducts, the balance being water.
  • the melamine slurry was concentrated in a hydrocyclone and cooled to 100 0 C by mixing with a saturated melamine mother liquor of 95 0 C recycled from the melamine filtration. After depressurization to atmospheric conditions the melamine was filtered and dried.
  • EXAMPLE 2 Melamine was produced from urea melt (1.4 t/h, 140 0 C) at 55 bar in a combined liquid-phase reactor/evaporator, which was heated with molten salt. The liquid melamine was evaporated at 422 0 C by introducing 1.6 t/h ammonia of 330 0 C. The gas from the reactor/evaporator (containing mainly ammonia, CO 2 and melamine vapor) was quenched rapidly with recycled aqueous carbamate solution (from the hydrocyclone and from the off-gas condensation) mixed with additional water in a quenching tower at a temperature of 138 0 C and a pressure of 19 bar.
  • aqueous carbamate solution from the hydrocyclone and from the off-gas condensation
  • a melamine slurry in aqueous carbamate solution (CS) and quench off-gas were produced.
  • the composition of CS was: 23 wt-% ammonia, 12 wt-% carbon dioxide, 13 wt-% dissolved melamine and byproducts, the balance being water.
  • the melamine slurry was concentrated in a hydrocyclone and cooled to 86 0 C by mixing with a saturated melamine mother liquor of 81 0 C recycled from the melamine filtration.
  • the melamine was filtered and dried.
  • Melamine was produced from urea melt (1.4 t/h, 140 0 C) at 55 bar in a combined liquid-phase reactor/evaporator, which was heated with molten salt.
  • the liquid melamine was evaporated at 422 0 C by introducing 1.6 t/h ammonia of 330 0 C.
  • the gas from the reactor/evaporator (containing mainly ammonia, CO 2 and melamine vapor) was quenched rapidly with recycled aqueous carbamate solution (from the hydrocyclone and from the off-gas condensation) mixed with additional water in a quenching tower at a temperature of 136 0 C and a pressure of 26 bar.
  • a melamine slurry in aqueous carbamate solution (CS) and quench off-gas were produced.
  • the composition of CS was: 29 wt-% ammonia, 22 wt-% carbon dioxide, 13 wt-% dissolved melamine and byproducts, the balance being water.
  • the melamine slurry was concentrated in a hydrocyclone and cooled to 83 0 C by mixing with a saturated melamine mother liquor of 78 0 C recycled from the melamine filtration.
  • the melamine was filtered and dried.
  • Melamine was produced from urea melt (1.4 t/h, 140 0 C) at 55 bar in a combined liquid-phase reactor/evaporator, which was heated with molten salt.
  • the liquid melamine was evaporated at 422 0 C by introducing 1.6 t/h ammonia of 330 0 C.
  • the gas from the reactor/evaporator (containing mainly ammonia, CO 2 and melamine vapor) was quenched rapidly with recycled aqueous carbamate solution (from the hydrocyclone and from the off-gas condensation) mixed with additional water in a quenching tower at a temperature of 120 0 C and a pressure of 7 bar.
  • a melamine slurry in aqueous carbamate solution (CS) and quench off-gas were produced.
  • the composition of CS was: 10 wt-% ammonia, 2.6 wt-% carbon dioxide, 8.7 wt-% dissolved melamine and byproducts, the balance being water.
  • the melamine slurry was concentrated in a hydrocyclone and cooled to 70 0 C by mixing with a saturated melamine mother liquor of 65 0 C recycled from the melamine filtration.
  • the melamine was filtered and dried.
  • Melamine was produced at 400 0 C and 10 bar by introducing urea melt (1.4 t/h, 140 0 C) and ammonia (2.6 t/h at 330 0 C) in gas fluidized-bed reactor.
  • the gas from the reactor (containing mainly ammonia, CO 2 and melamine vapor) was quenched rapidly with recycled aqueous carbamate solution (from the hydrocyclone and from the off-gas condensation) mixed with additional water in a quenching tower at a temperature of 145 0 C and a pressure of 10 bar.
  • a melamine slurry in aqueous carbamate solution (CS) and quench off-gas were produced.
  • the composition of CS was: 9.5 wt-% ammonia, 1.5 wt-% carbon dioxide, 13 wt-% dissolved melamine and byproducts, the balance being water.
  • the melamine slurry was concentrated in a hydrocyclone and cooled to 85 0 C by mixing with a saturated melamine mother liquor of 80 0 C recycled from the melamine filtration.
  • the melamine was filtered and dried.
  • Melamine was produced at 400 0 C and 23 bar by introducing urea melt (1.4 t/h, 140 0 C) and ammonia (2.6 t/h at 330 0 C) in gas fluidized-bed reactor.
  • the gas from the reactor (containing mainly ammonia, CO 2 and melamine vapor) was quenched rapidly with recycled aqueous carbamate solution (from the hydrocyclone and from the off-gas condensation) mixed with additional water in a quenching tower at a temperature of 158 0 C and a pressure of 23 bar.
  • a melamine slurry in aqueous carbamate solution (CS) and quench off-gas were produced.
  • the composition of CS was: 18 wt-% ammonia, 5 wt-% carbon dioxide, 20 wt-% dissolved melamine and byproducts, the balance being water.
  • the melamine slurry was concentrated in a hydrocyclone and cooled to 70 0 C by mixing with a saturated melamine mother liquor of 65 0 C recycled from the melamine filtration.
  • the melamine was filtered and dried.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Abstract

La présente invention porte sur un procédé permettant la récupération de mélamine solide dans un mélange gazeux contenant de la mélamine, de l'ammoniac et du dioxyde de carbone. Le procédé comprend : a) le refroidissement rapide dudit mélange gazeux avec une solution aqueuse contenant du carbamate d'ammonium, de manière à produire une bouillie ou une solution aqueuse contenant de la mélamine, ladite bouillie ou solution aqueuse contenant de la mélamine présentant 24 à 80 % en poids d'ammoniac et de dioxyde de carbone combinés par rapport au poids total de la phase aqueuse; b) le refroidissement de ladite bouillie ou suspension aqueuse contenant de la mélamine obtenue à l'étape a) à une température de 80 à 120°C, de manière à faire précipiter la mélamine solide pour former une bouillie de mélamine; c) éventuellement, la concentration de la bouillie de mélamine obtenue à l'étape b); et d) la séparation de la mélamine solide de ladite bouillie obtenue dans l'étape b) ou c) pour obtenir de la mélamine solide récupérée et une liqueur mère. L'invention porte également sur un procédé pour la fabrication de mélamine solide consistant : i) à obtenir un mélange gazeux contenant de la mélamine, de l'ammoniac et du dioxyde de carbone à partir d'urée par réaction catalytique ou non catalytique; et ii) à soumettre le mélange gazeux contenant de la mélamine, de l'ammoniac et du dioxyde de carbone au procédé ci-dessus.
PCT/EP2009/002501 2008-04-29 2009-04-04 Procédé pour la récupération de mélamine solide WO2009132750A1 (fr)

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Application Number Priority Date Filing Date Title
EP08008158 2008-04-29
EP08008158.1 2008-04-29

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WO2009132750A1 true WO2009132750A1 (fr) 2009-11-05

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104788394A (zh) * 2015-04-14 2015-07-22 四川金象赛瑞化工股份有限公司 一种三聚氰胺精制方法
CN108128971A (zh) * 2017-12-22 2018-06-08 杭州师范大学钱江学院 含二硫代甲酸盐废水处理装置
CN108178411A (zh) * 2017-12-22 2018-06-19 杭州师范大学钱江学院 一种回收含二硫代甲酸盐废水中二硫化碳的装置

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3711479A (en) * 1970-04-03 1973-01-16 Stamicarbon Process for separating melamine from a hot synthesis gas mixture which contains melamine vapor
WO2001000596A2 (fr) * 1999-06-29 2001-01-04 Dsm N.V. Procede permettant de separer la melamine des melanges gazeux contenant de la melamine
WO2001056999A1 (fr) * 2000-02-03 2001-08-09 Dsm N.V. Procede de preparation de melamine a partir d'uree
WO2002014289A1 (fr) * 2000-08-14 2002-02-21 Dsm N.V. Procede de preparation de melamine a partir d'uree
WO2003066605A1 (fr) * 2002-02-07 2003-08-14 Dsm Ip Assets B.V. Procede de preparation de melamine

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3711479A (en) * 1970-04-03 1973-01-16 Stamicarbon Process for separating melamine from a hot synthesis gas mixture which contains melamine vapor
WO2001000596A2 (fr) * 1999-06-29 2001-01-04 Dsm N.V. Procede permettant de separer la melamine des melanges gazeux contenant de la melamine
WO2001056999A1 (fr) * 2000-02-03 2001-08-09 Dsm N.V. Procede de preparation de melamine a partir d'uree
WO2002014289A1 (fr) * 2000-08-14 2002-02-21 Dsm N.V. Procede de preparation de melamine a partir d'uree
WO2003066605A1 (fr) * 2002-02-07 2003-08-14 Dsm Ip Assets B.V. Procede de preparation de melamine

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104788394A (zh) * 2015-04-14 2015-07-22 四川金象赛瑞化工股份有限公司 一种三聚氰胺精制方法
CN108128971A (zh) * 2017-12-22 2018-06-08 杭州师范大学钱江学院 含二硫代甲酸盐废水处理装置
CN108178411A (zh) * 2017-12-22 2018-06-19 杭州师范大学钱江学院 一种回收含二硫代甲酸盐废水中二硫化碳的装置
CN108178411B (zh) * 2017-12-22 2020-06-16 杭州师范大学钱江学院 一种回收含二硫代甲酸盐废水中二硫化碳的装置
CN108128971B (zh) * 2017-12-22 2023-05-23 杭州师范大学钱江学院 含二硫代甲酸盐废水处理装置

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