HRP960575A2 - Process for producing pure melamine - Google Patents
Process for producing pure melamine Download PDFInfo
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- HRP960575A2 HRP960575A2 HRA1994/95A HRP960575A HRP960575A2 HR P960575 A2 HRP960575 A2 HR P960575A2 HR P960575 A HRP960575 A HR P960575A HR P960575 A2 HRP960575 A2 HR P960575A2
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- Prior art keywords
- melamine
- ammonia
- temperature
- partial pressure
- bar
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- JDSHMPZPIAZGSV-UHFFFAOYSA-N melamine Chemical compound NC1=NC(N)=NC(N)=N1 JDSHMPZPIAZGSV-UHFFFAOYSA-N 0.000 title claims description 113
- 229920000877 Melamine resin Polymers 0.000 title claims description 111
- 238000000034 method Methods 0.000 title claims description 47
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims description 132
- 229910021529 ammonia Inorganic materials 0.000 claims description 57
- 239000007788 liquid Substances 0.000 claims description 30
- 238000007711 solidification Methods 0.000 claims description 25
- 230000008023 solidification Effects 0.000 claims description 25
- 238000001816 cooling Methods 0.000 claims description 17
- 239000007787 solid Substances 0.000 claims description 15
- 239000000126 substance Substances 0.000 claims description 9
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 claims description 7
- 239000004202 carbamide Substances 0.000 claims description 7
- 238000006243 chemical reaction Methods 0.000 claims description 6
- 238000004519 manufacturing process Methods 0.000 claims description 6
- 229920006395 saturated elastomer Polymers 0.000 claims description 3
- 238000010583 slow cooling Methods 0.000 claims 1
- 239000002674 ointment Substances 0.000 description 9
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 8
- 229910000069 nitrogen hydride Inorganic materials 0.000 description 8
- 238000004140 cleaning Methods 0.000 description 5
- 230000014759 maintenance of location Effects 0.000 description 5
- 239000007789 gas Substances 0.000 description 4
- 239000000155 melt Substances 0.000 description 4
- YZEZMSPGIPTEBA-UHFFFAOYSA-N 2-n-(4,6-diamino-1,3,5-triazin-2-yl)-1,3,5-triazine-2,4,6-triamine Chemical compound NC1=NC(N)=NC(NC=2N=C(N)N=C(N)N=2)=N1 YZEZMSPGIPTEBA-UHFFFAOYSA-N 0.000 description 3
- 239000012535 impurity Substances 0.000 description 3
- 239000012071 phase Substances 0.000 description 3
- 240000000278 Syzygium polyanthum Species 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 239000007791 liquid phase Substances 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 238000010791 quenching Methods 0.000 description 2
- 230000000171 quenching effect Effects 0.000 description 2
- 239000011541 reaction mixture Substances 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 101000797621 Rattus norvegicus Ameloblastin Proteins 0.000 description 1
- JHEXGENUDVZLKI-UHFFFAOYSA-N [(4,6-diamino-1,3,5-triazin-2-yl)amino]urea Chemical compound NC(=O)NNC1=NC(N)=NC(N)=N1 JHEXGENUDVZLKI-UHFFFAOYSA-N 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 238000010924 continuous production Methods 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 150000007974 melamines Chemical class 0.000 description 1
- 239000012265 solid product Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 238000004381 surface treatment Methods 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 238000005979 thermal decomposition reaction Methods 0.000 description 1
Classifications
-
- 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
-
- 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
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
- Phenolic Resins Or Amino Resins (AREA)
- Sorption Type Refrigeration Machines (AREA)
- Processes Of Treating Macromolecular Substances (AREA)
Description
Iz literature je već poznat velik broj postupaka za proizvodnju melamina. Pri tome polazni materijal je ponajprije urea, koja se ili pod visokim tlakom i nekatalitički ili pod niskim tlakom i uz upotrebu katalizatora kemijski pretvara u melamin, amonijak i CO2. A large number of procedures for the production of melamine are already known from the literature. The starting material is primarily urea, which either under high pressure and non-catalytically or under low pressure and with the use of a catalyst is chemically converted into melamine, ammonia and CO2.
Poznati visokotlačni postupci, po Melamine Chemicals, Montedisonu ili Nissanu, po kojima se najprije stvara melamin kao tekućina, u usporedbi s niskotlačnim postupcima imaju doduše neznatan utrošak energije, ako nema nikakvih faza čišćenja nečištoća kao melama, melem, amelina ili ureidomelamina, koji smetaju kod većina postupaka dalje prerade melamina. Well-known high-pressure processes, according to Melamine Chemicals, Montedison or Nissan, which first create melamine as a liquid, compared to low-pressure processes, have an admittedly insignificant energy consumption, if there are no stages of cleaning impurities such as melam, salve, amelin or ureidomelamine, which bother most processes further process melamine.
Obrada melamina, proizvedenog visokotlačnim postupkom, odvija se, primjerice po US 4565867 (Melamine Chemicals), odvajanjem plinovitih CO2 i NH3 iz tekućeg melamina, pri čemu se tlak i temperatura drže ponajprije pri istim vrijednostima koje postoje u reaktoru. Konačno, tekući melamin se dovodi u jedinicu za hlađenje proizvoda, gdje se rasterećuje sa 105 do 175 bara na otprilike 14 do 42 bara i istovremeno se brzo hladi, odnosno gasi (gašenje) s tekućim amonijakom s 350 do 430°C na 48 do 110°C, čime se melamin izlučuje kao čvrsti proizvod. The processing of melamine, produced by a high-pressure process, takes place, for example, according to US 4565867 (Melamine Chemicals), by separating gaseous CO2 and NH3 from liquid melamine, whereby the pressure and temperature are primarily kept at the same values that exist in the reactor. Finally, the liquid melamine is fed to the product cooling unit, where it is relieved from 105 to 175 bar to approximately 14 to 42 bar and simultaneously rapidly cooled, i.e. quenched (quenched) with liquid ammonia from 350 to 430°C to 48 to 110 °C, whereby melamine is excreted as a solid product.
Prema US 3,116,294 (Montecatini) također se najprije odvajaju plinoviti CO2 i NH3, a tekući melamin se obrađuje u protustruji s NH3 da se odstrani još otopljeni CO2, skuplja se u slijedećem reaktoru i tamo se pusti stajati određeno vrijeme. Na kraju se melamin uzima iz drugog reaktora i brzo se ohladi gašenjem s vodom ili miješanjem s hladnim plinovima. According to US 3,116,294 (Montecatini) gaseous CO2 and NH3 are also first separated, and liquid melamine is treated in countercurrent with NH3 to remove still dissolved CO2, collected in the next reactor and allowed to stand there for a certain time. Finally, the melamine is taken from another reactor and rapidly cooled by quenching with water or mixing with cold gases.
Čistoća melamina, dobivenog po jednom od tih postupaka, nije dovoljna za mnoge primjene, kao na primjer za proizvodnju melamin-formaldehidnih smola za površinske preinaze, jer je posebno sadržaj melema previsok. The purity of the melamine obtained by one of these processes is not sufficient for many applications, such as for the production of melamine-formaldehyde resins for surface treatments, because the content of the melamine is particularly high.
Prema US 3,637,686 (Nissan) sirova melaminska talina, dobivena toplinskim raspadom uree, brzo se ohladi s tekućim NH3 ili s hladnim plinom NH3 na 200 do 270°C, a u drugoj fazi se dalje hladi s vodenom otopinom NH3 na 100 do 200°C. Na kraju se prekristalizira čime se dobije melamin zadovoljavajuće čistoće. Zadatak predloženog izuma bio je, prema tome, naći postupak koji omogućuje proizvodnju čistog melamina čistoće od najmanje iznad 99, 8% s jasno smanjenim sadržajem nečistoća, naročito melema i melama. According to US 3,637,686 (Nissan) the raw melamine melt, obtained by the thermal decomposition of urea, is rapidly cooled with liquid NH3 or with cold NH3 gas to 200 to 270°C, and in the second stage it is further cooled with an aqueous NH3 solution to 100 to 200°C. At the end, it is recrystallized to obtain melamine of satisfactory purity. The task of the proposed invention was, therefore, to find a process that enables the production of pure melamine with a purity of at least above 99.8% with a clearly reduced content of impurities, especially salam and melam.
Taj zadatak neočekivano je riješen postupkom, po kojem se tekući melamin, koji sadrži amonijak, brzo rasterećuje pri temperaturi skrućivanja melamina ili tijesno iznad temperature skrućivanja melamina, koja ovisi o dotičnom vladajućem parcijalnom tlaku amonijaka, pri čemu se temperatura skrućivanja, ovisno o temperaturi na početku rasterećenja i željenom krajnjem, tlaku povisi za otprilike 60°C i izlučuje se čvrsti melamin. This task is unexpectedly solved by a process, according to which the liquid melamine, which contains ammonia, is rapidly relieved at the melamine solidification temperature or narrowly above the melamine solidification temperature, which depends on the relevant prevailing partial pressure of ammonia, whereby the solidification temperature, depending on the temperature at the beginning of unloading and the desired final pressure increases by approximately 60°C and solid melamine is excreted.
Predmet predloženog izuma je, prema tome, postupak za proizvodnju čistog melamina, naznačen time, da se tekući melamin, koji sadrži amonijak, pri temperaturi koja je za 0 do 60°C iznad temperature skrućivanja melamina, koja ovisi o dotičnom vladajućem parcijalnom tlaku amonijaka, pri čemu viši tlakovi omogućuju veću udaljenost temperature od temperature skrućivanja melamina, nego niži tlakovi, brzo se rastereti od parcijalnog tlaka amonijaka p1 između 400 i 50 bara na parcijalni tlak amonijaka između 200 bara i atmosferskog tlaka, pri čemu je p1 uvijek viši od p2, čime se čisti melamin izlučuje u čvrstom obliku, a nakon čega se proizvoljnim redoslijedom dalje rasterećuje na atmosferski tlak, ohladi na sobnu temperaturu i izolira čisti melamin. The subject of the proposed invention is, therefore, a process for the production of pure melamine, characterized by the fact that liquid melamine, which contains ammonia, at a temperature that is 0 to 60°C above the solidification temperature of melamine, which depends on the prevailing partial pressure of ammonia, where higher pressures allow a greater temperature distance from the solidification temperature of melamine, than lower pressures, it is quickly relieved from an ammonia partial pressure p1 between 400 and 50 bar to an ammonia partial pressure between 200 bar and atmospheric pressure, where p1 is always higher than p2, whereby pure melamine is excreted in solid form, after which it is further relieved to atmospheric pressure in an arbitrary order, cooled to room temperature and isolated pure melamine.
Postupak prema izumu prikadan je za čišćenje melamina, izlučenog po bilo kojem postupku poznatom iz stanja tehnike, i koji sadrži posebno nečistoće kao melem i melam, pri čemu melamin može biti prisutan kao talina, odnosno u tekućoj fazi ili u kristaliničnom obliku. The method according to the invention is suitable for cleaning melamine, extracted by any method known from the state of the art, and which contains especially impurities such as salam and melam, whereby melamine can be present as a melt, i.e. in a liquid phase or in crystalline form.
Ako se melamin za čišćenje već nalazi kao talina, odnosno kao čvrsta tvar, kao primjerice u priključku na visokotlačni reaktor za sintezu melamina kemijskom pretvorbom uree, tada se tlak i temperatura taline, odnosno tekućeg melamina dovode pod početni parcijalni tlak amonijaka, poželjan za rasterećenje, veličine između otprilike 400 i 50 bara, ponajprije između otprilike 400 i 80 bara, a posebno korisno između otprilike 300 i 100 bara, i na odgovarajuću gore definiranu vrijednost temperature, tj. na temperaturu koja je za otprilike 0 do 60°C, ponajprije za otprilike 0 do 40°C, iznad dotične temperature skrućivanja melamina koja ovisi o vladajućem parcijalnom tlaku amonijaka. Pri tome treba paziti da kod viših tlakova razlika temperature između temperature skrućivanja melamina i namještene temperature na početku rasterećenja može biti veće nego kod nižih tlakova, jer temperatura skrućivanja taline kod viših tlakova leži pri nižim temperaturama nego kod nižih tlakova. If the melamine for cleaning is already found as a melt, or as a solid substance, such as in the connection to a high-pressure reactor for the synthesis of melamine by chemical conversion of urea, then the pressure and temperature of the melt, or liquid melamine, are brought under the initial partial pressure of ammonia, which is desirable for relief, between about 400 and 50 bar, preferably between about 400 and 80 bar, and particularly usefully between about 300 and 100 bar, and at the appropriate temperature value defined above, i.e. at a temperature of about 0 to 60°C, preferably for approximately 0 to 40°C, above the respective solidification temperature of melamine which depends on the prevailing partial pressure of ammonia. At the same time, care should be taken that at higher pressures the temperature difference between the melamine solidification temperature and the set temperature at the beginning of unloading may be greater than at lower pressures, because the melt solidification temperature at higher pressures lies at lower temperatures than at lower pressures.
Da bi se postiglo željenu vrijednost temperature za rasterećenje, temperatura se po potrebi spušta. Ta temperatura je posebno korisno pri otprilike ispod 350°C. Pri tome hlađenje se može provesti brzo, ali također i polagano. Ponajprije se odvija polako, s brzinom hlađenja od 0,8 do 10°C/min. Budući da melaminska talina pri nižoj temperaturi može prihvatiti više amonijaka, tada se korisno dovodi amonijak. Naročito je korisno to rasterećenje tekućeg melamina koji sadrži amonijak provoditi što je moguće bliže pri ili iznad temperature skrućivanja melamina, koja ovisi o dotičnom parcijalnom tlaku amonijaka. In order to reach the desired value of the temperature for relief, the temperature is lowered if necessary. This temperature is particularly useful at approximately below 350°C. In this case, the cooling can be carried out quickly, but also slowly. First of all, it takes place slowly, with a cooling rate of 0.8 to 10°C/min. Since the melamine melt can accept more ammonia at a lower temperature, then ammonia is advantageously supplied. It is particularly useful to carry out this unloading of the ammonia-containing liquid melamine as close as possible to or above the solidification temperature of the melamine, which depends on the ammonia partial pressure in question.
S predloženim postupkom može se, nadalje, očistiti čvrsti, onečišćeni melamin. Melamin za čišćenje, u kristaliničnom obliku, ili obliku praha, zagrije se najprije pod parcijalnim tlakom amonijaka između otprilike 400 i 50 bara, ponajprije između otprilike 400 i 80 bara, posebno korisno između 300 i 100 bara, na temperaturu koja je za otprilike 0 do 60°C, ponajprije za otprilike 0 do 40°C, iznad temperature skrućivanja melamina, koja ovisi o vladajućem parcijalnom tlaku amonijaka. Za sigurnije taljenje čvrstog amonijaka svrhovito je najprije zagrijati melamin do otprilike 370°C i tada ohladiti na željenu temperaturu rasterećenja, da je melamin sigurno potpuno rastaljen. Željena temperatura rasterećenja leži ponajprije ispod otprilike 350°C. With the proposed process, solid, contaminated melamine can also be cleaned. The cleaning melamine, in crystalline or powder form, is first heated under an ammonia partial pressure of between about 400 and 50 bar, preferably between about 400 and 80 bar, particularly usefully between 300 and 100 bar, to a temperature which is by about 0 to 60°C, preferably by about 0 to 40°C, above the solidification temperature of melamine, which depends on the prevailing partial pressure of ammonia. For a safer melting of solid ammonia, it is expedient to first heat the melamine to approximately 370°C and then cool it down to the desired relief temperature, to ensure that the melamine is completely melted. The desired discharge temperature is preferably below approximately 350°C.
Treba opet paziti da razlika temperature kod viših tlakova može biti veća nego kod nižih tlakova. Postupak prema izumu provodi se ponajprije neposredno u nastavku na viskotlačni postupak proizvodnje melamina. Primjeri visokotlačnih postupaka su eventualno postupak tvrtke Melamine Chemicals, postupak Montedisona ili Nissanov postupak, kako su opisani primjerice u Ullmannovoj Enciklopediji Industrijske kemije, 5. izdanje, vol. A16, str. 174-179. Kemijska pretvorba uree po tim postupcima odvija se najćešće u temperaturnom području od otprlilke 370 do 430°C i pod tlakom od otprilike 70 do 300 bara. Pri tome nastali melamin dobije se konačno kao tekuća faza. Again, care must be taken that the temperature difference at higher pressures can be greater than at lower pressures. The process according to the invention is primarily carried out immediately following the viscopressure process of melamine production. Examples of high-pressure processes are possibly the Melamine Chemicals process, the Montedison process or the Nissan process, as described for example in Ullmann's Encyclopedia of Industrial Chemistry, 5th edition, vol. A16, p. 174-179. The chemical conversion of urea by these procedures takes place most often in the temperature range from approximately 370 to 430°C and under a pressure of approximately 70 to 300 bar. The resulting melamine is finally obtained as a liquid phase.
Po postupku prema izumu, ako je potrebno, za brzo rasterećenje željeni parcijalni tlak amonijaka podešava se između otprilike 400 i 50 bara. Za namještanje odgovarajuće početne temperature za rasterećenje, tekući melamin, dobiven iz procesa kemijske pretvorbe uree, ohladi se s temperature koja vlada u reaktoru pomoću prikladnih rashladnih uređaja, eventualno toplinskog izmjenjivača, na odgovarajuću vrijednost, tj. na temperaturu, koja je za oko 0 do 60°C iznad temperature skrućivanja melamina koja ovisi o dotičnom namještenom parcijalnom tlaku amonijaka. Pri tome, hlađenje se može provesti po volji brzo ili također polagano. Hlađenje se ponajprije odvija brzinom između 0,8°C/.min i 10°C/min, ponajprije uz daljnje dovođenje amonijaka. Temperatura se također može sniziti pomoću rashladnog programa, pri čemu se mogu izmjenjivati primjerice faze hlađenja i faze održavanja, ili različite brzine hlađenja. According to the process according to the invention, if necessary, the desired ammonia partial pressure is adjusted between approximately 400 and 50 bar for rapid relief. To set the appropriate initial temperature for unloading, liquid melamine, obtained from the process of chemical conversion of urea, is cooled from the temperature prevailing in the reactor using suitable cooling devices, possibly a heat exchanger, to an appropriate value, i.e. to a temperature, which is about 0 to 60°C above the solidification temperature of melamine which depends on the respective set partial pressure of ammonia. At the same time, cooling can be carried out quickly or slowly as desired. The cooling preferably takes place at a rate between 0.8°C/.min and 10°C/min, preferably with further introduction of ammonia. The temperature can also be lowered by means of a cooling program, whereby cooling phases and maintenance phases can be alternated, for example, or different cooling speeds can be used.
Prije hlađenja, mješavina NH3/CO2/ koja nastaje u reakciji, odvaja iz tekućeg melamina, i CO2 otopljen u tekućem melaminu smanji se uvođenjem plinovitog amonijaka. Može se, nadalje, prije rasterećenja, tekući melamin pustiti stajati pod namještenim parcijalnim tlakom amonijaka tijekom otprilike od 5 minuta pa sve do 20 sati. Melamin se pušta stajati ponajprije između 10 minuta i 10 sati, posebno korisno između 30 minuta i 4 sata. Po potrebi također su moguća dulja vremena zadržavanja. Before cooling, the NH3/CO2/ mixture formed in the reaction separates from the liquid melamine, and the CO2 dissolved in the liquid melamine is reduced by introducing gaseous ammonia. Furthermore, before unloading, the liquid melamine can be allowed to stand under the adjusted partial pressure of ammonia for approximately 5 minutes and up to 20 hours. Melamine is preferably left to stand between 10 minutes and 10 hours, especially useful between 30 minutes and 4 hours. If necessary, longer retention times are also possible.
Melamin za čišćenje, koji sadrži amonijak, prije rasterećenja nalazi se u tekućem obliku. Pri rasterećenju tlak se brzo smanjuje, ovisno o namještenom početnom tlaku, na vrijednost između atmosferskog tlaka i otprilike 200 bara, ponajprije na vrijednost između atmosferskog tlaka i otprilike 150 bara, posebno korisno na vrijednost između atmosferskog tlaka i otprilike 50 bara. The cleaning melamine, which contains ammonia, is in liquid form before unloading. During unloading, the pressure is rapidly reduced, depending on the set initial pressure, to a value between atmospheric pressure and approximately 200 bar, preferably to a value between atmospheric pressure and approximately 150 bar, particularly advantageously to a value between atmospheric pressure and approximately 50 bar.
Pri tome izlazi amonijak otopljen u melaminu, čime se temperatura skrućivanja melamina, sada maksimalno oslobođenog od amonijaka, povisuje za otprilike 60°C, tako da se tekući melamin odmah skrućuje, i spriječena je tvorba sporednih proizvoda, naročito melema. Rasterećenjem se s jedne strane snizuje temperaturu u sistemu, a s druge strane skrućivanjem se oslobađa toplina kristalizacije. Pretpostavlja se, da se odvija proces koji je zbirno otprilike autoterman. During this, ammonia dissolved in melamine comes out, which increases the solidification temperature of melamine, now maximally free from ammonia, by approximately 60°C, so that liquid melamine solidifies immediately, and the formation of side products, especially salve, is prevented. On the one hand, unloading lowers the temperature in the system, and on the other hand, solidification releases the heat of crystallization. It is assumed that a process takes place that is collectively roughly autothermal.
Korisno je da je melaminska talina prije rasterećenja zasićena s amonijakom. Može se također provesti i rasterećenje melaminske taline koja nije zasićena s amonijakom, pri čemu se onda ne može potpuno iskoristiti prednost povišenja tališta. It is useful that the melamine melt is saturated with ammonia before unloading. Unloading of the melamine melt that is not saturated with ammonia can also be carried out, in which case the advantage of increasing the melting point cannot be fully exploited.
Rasterećenje se može provesti izravno u spremniku, odnosno aparaturi, u koju je unešen tekući melamin. Rasterećenje se, međutim može provesti također i prijenosom, odnosno ubrizgavanjem tekućeg melamina u jedan ili više daljnjih spremnika pomoću prikladnih uređaja za brizganje. Pri tome, korisno je imati u spremnicima atmosferu amonijaka. Nadalje, posebno je korisno rasterećivati u spremniku u kojem vlada otprilike jednaka temperatura kao u posudi u kojoj se vrši rasterećenje. Unloading can be carried out directly in the container, i.e. the apparatus, into which the liquid melamine was introduced. Unloading, however, can also be carried out by transferring or injecting liquid melamine into one or more further containers using suitable injection devices. At the same time, it is useful to have an ammonia atmosphere in the tanks. Furthermore, it is particularly useful to unload in a tank in which the temperature is roughly the same as the container in which the unloading is carried out.
Sada čvrsti melamin može se po želji još neko vrijeme, otprilike 1 minutu do 20 sati, držati pod sada vladajućim parcijalnim tlakom amonijaka i vladajućim temperaturama. Čvrsti melamin pusti se stajati pod tim uvjetima ponajprije 10 minuta do 10 sati, posebno korisno između 30 minuta i 3 sata. Pri tome temperatura mora biti otprilike ispod 290°C. The now solid melamine can, if desired, be kept under the now prevailing partial pressure of ammonia and the prevailing temperatures for some time, approximately 1 minute to 20 hours. Solid melamine is allowed to stand under these conditions preferably for 10 minutes to 10 hours, especially useful between 30 minutes and 3 hours. The temperature must be approximately below 290°C.
Sada se čvrsti melamin može posebno korisno držati pri temperaturi između otprilike 280 i 250°C, pri čemu se tijekom tog vremenskog razdoblja temperaturu održava konstantom ili ju se može mijenjati kontinuirano ili postupno. U nastavku tog postupka rasterećenja, odnosno zadržavanja, sada se čvrsti melamin može na proizvoljan način i ovisno o tehničkim okolnostima, ohladiti najprije na sobnu temperaturu i tada dalje rasteretiti na atmosferski tlak, ili istovremeno, ili obrnutim redoslijedom dalje rasteretiti i ohladiti. Now solid melamine can be particularly usefully held at a temperature between about 280 and 250°C, during which time the temperature is held constant or can be varied continuously or gradually. In the continuation of this process of unloading, i.e. retention, solid melamine can now be cooled in an arbitrary way and depending on the technical circumstances, first to room temperature and then further unloaded to atmospheric pressure, or simultaneously or in the reverse order further unloaded and cooled.
Korisno je najprije ga dalje rasteretiti i nakon toga ohladiti na sobnu temperaturu. It is useful to first unload it further and then cool it to room temperature.
Hlađenje već čvrstog melamina na sobnu temperaturu odvija se primjerice gašenjem s hladnim, tekućim sredstvom, eventualno s tekućim amonijakom, miješanjem s hladnim plinovima, hlađenjem pomoću izmjenjivača topline, primjerice s temperaturnim programom, ili jednostavnim odstranjivanjem sredstva za grijanje. Cooling already solid melamine to room temperature takes place, for example, by quenching with a cold, liquid agent, possibly with liquid ammonia, mixing with cold gases, cooling using a heat exchanger, for example with a temperature program, or simply removing the heating agent.
Postupak prema izumu može se po potrebi provesti postupno, ali također i kao kontinuirani postupak. Posebno je korisno provesti postupak prema izumu kontinuirano. The process according to the invention can, if necessary, be carried out gradually, but also as a continuous process. It is particularly useful to carry out the process according to the invention continuously.
U izvedbi, kojoj se daje prednost, nakon odvajanja NH3 i CO2, melaminsku talinu pusti se stajati pod tlakom amonijaka od otprilike 70 do 300 bara, ponajprije pod tlakom koji vlada u reaktoru, temperaturu se snizi uz daljnji dovod amonijaka što je moguće bliže temperaturi skrućivanja pod tim vladajućim parcijalnim tlakom amonijaka, zatim se rastereti na otprilike 50 bara do atmosferskog tlaka, po potrebi se i dalje rasteretiti i ohladi na sobnu temperaturu. In a preferred embodiment, after separation of NH 3 and CO 2 , the melamine melt is allowed to stand under an ammonia pressure of approximately 70 to 300 bar, preferably under the pressure prevailing in the reactor, the temperature is lowered with a further feed of ammonia as close as possible to the solidification temperature under this prevailing partial pressure of ammonia, it is then relieved to approximately 50 bar to atmospheric pressure, if necessary it is further relieved and cooled to room temperature.
Pojedine faze postupka prema izumu, kao Certain stages of the procedure according to the invention, such as
- po potrebi odvajanje mješavine plinova NH3/CO2 sa - if necessary, separation of the gas mixture NH3/CO2 with
- po potrebi, nadovezanim smanjenjem sadržaja otopljenog CO2, - if necessary, by subsequent reduction of dissolved CO2 content,
- po potrebi, sa zadržavanjem i hlađenjem na temperaturu rasterećenja, - if necessary, with retention and cooling to the unloading temperature,
- rasterećivanje, - unloading,
- po potrebi, stajanje melamina u čvrstom stanju, - if necessary, standing of melamine in a solid state,
- po potrebi, daljnje rasterećenje na atmosferski tlak, - if necessary, further relief to atmospheric pressure,
- hlađenje na sobnu temperaturu, mogu se, pri tome primjerice provesti u odvojenim spremnicima, odnosno aparaturama prikladnim za dotičnu fazu. Međutim, također se mogu provoditi 2 ili više od tih faza u zajedničkim aparaturama. - cooling to room temperature, they can, for example, be carried out in separate containers, or apparatus suitable for the phase in question. However, 2 or more of these stages can also be carried out in common apparatus.
Međutim, vođenje procesa mora se prilagoditi dotičnim okolnostima. However, the management of the process must be adapted to the circumstances in question.
Da bi se odredilo temperaturu skrućivanja melamina ovisnu o vladajućem parcijalnom tlaku amonijaka, provedeni su odgovarajući pokusi hlađenja. In order to determine the solidification temperature of melamine depending on the prevailing partial pressure of ammonia, appropriate cooling experiments were carried out.
Postupkom prema izumu dobije se melamin u kristaliničnom obliku, odnosno kao prah čistoće iznad 99, 8% i ima jasno smanjeni sadržaj posebno melema i melama. The process according to the invention produces melamine in crystalline form, i.e. as a powder with purity above 99.8% and has a clearly reduced content, especially of salves and melams.
Primjeri 1-6 Examples 1-6
Određivanje temperature skrućivanja melamina ovisne o parcijalnom tlaku amonijaka Determination of the solidification temperature of melamine depending on the partial pressure of ammonia
9, 9 g melamina s 0,1 g melema odvagne se i rastali s količinom amonijaka potrebnom za namještanje određenog tlaka p u autoklavu. Da se omogući uspostavljanje ravnoteže, reakcijsku smjesu pusti se stajati nekoliko sati pri 370°C. Nakon toga pusti se reakcijsku smjesu hladiti i kontrolira se tijek temperature, pri čemu se temperaturu skrućivanja prepozna po kratkom porastu temperature. Parametri postupka kao tlak, vrijeme zadržavanja kao i određena temperatura skrućivanja (Fp) navedeni su u tablici 1. Ovisnost temperature skrućivanja melamina o dotičnom vladajućem parcijalnom tlaku amonijaka prikazana je na slici 1. 9.9 g of melamine with 0.1 g of salve are weighed and melted with the amount of ammonia necessary to set a certain pressure p in the autoclave. To enable equilibrium to be established, the reaction mixture is allowed to stand for several hours at 370°C. After that, the reaction mixture is allowed to cool and the temperature is controlled, whereby the solidification temperature is recognized by a short rise in temperature. The process parameters such as pressure, holding time as well as the specified solidification temperature (Fp) are listed in Table 1. The dependence of the solidification temperature of melamine on the relevant prevailing partial pressure of ammonia is shown in Figure 1.
[image] [image]
Primjeri 7-19 Examples 7-19
U laboratorijski autoklav volumena 70 ml stavljeno je 9, 9 9 melamina sa sadržajem melama od 1300 ppm i 0, 1 g melema, te količina amonijaka potrebna za postizanje tlaka p1 prije rasterećenja. Na kraju je autoklav zagrijan na temperaturu T1 po potrebi tijekom x minuta ohlađen na temperaturu T2 i držan t1 minuta pri toj temperaturi. Nakon toga brzo je rasterećen na određen tlak p2 i po potrebi konačno držan t2 minuta pod sada vladajućim uvjetima reakcije. In a laboratory autoclave with a volume of 70 ml, 9.99 melamine with a melamine content of 1300 ppm and 0.1 g of melamine, and the amount of ammonia required to reach the pressure p1 before unloading, were placed. At the end, the autoclave was heated to temperature T1 if necessary for x minutes, cooled to temperature T2 and kept at that temperature for t1 minutes. After that, it was quickly relieved to a certain pressure p2 and, if necessary, finally kept for t2 minutes under the currently prevailing reaction conditions.
Po završetku tog postupka naglo je ohlađen u vodenoj kupelji i rasterećen, a dobiveni melamin je analiziran. At the end of that process, it was cooled suddenly in a water bath and unloaded, and the resulting melamine was analyzed.
Parametri postupka kao tlak p1 i p2, temperatura T1 i T2, vrijeme hlađenja s T1 na T2 tijekom x minuta, vrijeme zadržavanja t1 i t2, kao i krajnji sadržaj melema (ME) i melama (MA) navedeni su u tablici 2. Process parameters such as pressure p1 and p2, temperature T1 and T2, cooling time from T1 to T2 for x minutes, retention time t1 and t2, as well as the final content of salve (ME) and salve (MA) are listed in Table 2.
[image] [image]
Primjeri 20-36 Examples 20-36
U laboratorijski autoklav A1 volumena 100 ml stavljeno je x g melamina (M0) sa sadržajem melama (MA0) od 1300 ppm i y g melema, te količinom amonijaka potrebnog za postizanje tlaka p1 prije rasterećenja. Na kraju je autoklav zagrijan na temperaturu od 370°C (T1) držan je t1 minuta pri T1. Na kraju je za z1 minuta ohlađen na temperaturu T2 i pri toj temperaturi držan ie t2 minuta. X g of melamine (M0) with a melamine content (MA0) of 1300 ppm and y g of melamine, and the amount of ammonia required to reach the pressure p1 before unloading, were placed in the laboratory autoclave A1 with a volume of 100 ml. At the end, the autoclave was heated to a temperature of 370°C (T1) and kept for t1 minutes at T1. In the end, it was cooled to temperature T2 in z1 minutes and kept at that temperature for t2 minutes.
U primjerima 20-32 u nastavku je zatim melamin, koji se je nalazio u A1 laboratorijskom autoklavu, izbrizgan u autoklav A2 volumena 1000 ml, koji je bio držan pri temperaturi T3 i pod tlakom p3. In examples 20-32 below, melamine, which was in A1 laboratory autoclave, was then injected into autoclave A2 with a volume of 1000 ml, which was kept at temperature T3 and under pressure p3.
U primjerima 33 i 34 u autoklavu A temperatura T2 je za t2s minuta spuštena na temperaturu T2s. Istovremeno, u autoklavu A2 temperatura T3 namještena je na temperaturu T2s i tlak na vrijednost p3 i melamin je izbrizgan iz A1 u A2. In examples 33 and 34, in autoclave A, the temperature T2 was lowered to the temperature T2s in t2s minutes. At the same time, in the autoclave A2, the temperature T3 was set to the temperature T2s and the pressure to the value p3 and melamine was injected from A1 to A2.
U primjerima 35 36 lz autoklava A1 samo dio tekućeg melamina izbrizgan je u autoklav A2, pri čemu je ventil u cijevi između A1 i A2 kratko otvoren i opet zatvoren. Time je održan mali pad tlaka u A1 i mali porast tlaka u A2. In examples 35 36 out of autoclave A1, only part of the liquid melamine was injected into autoclave A2, whereby the valve in the pipe between A1 and A2 was briefly opened and closed again. This maintained a small pressure drop in A1 and a small pressure increase in A2.
Pri tome se je nakon prijenosa proizvoda u A1 temperatura T2 promijenila na vrijednost T2.1, tlak p1 na vrijednost p2. U autoklavu A2 promijenila se je temperatura T3 na vrijednost T3.1 i tlak p3 na vrijednost p3.1. Melamin (M1) koji je ostao u A1 za. z2 minuta ohlađen je na temperaturu T4, zatim je rasterećen, brzo ohlađen i analiziran (ME1, MA1) . After transferring the product to A1, the temperature T2 changed to the value T2.1, the pressure p1 to the value p2. In autoclave A2, the temperature T3 changed to the value T3.1 and the pressure p3 changed to the value p3.1. Melamine (M1) which remained in A1 for. It was cooled to temperature T4 for 2 minutes, then it was unloaded, quickly cooled and analyzed (ME1, MA1).
Melamin (M2) ubrizgan u A2 ohlađen je u temperaturu T5 za z3 minuta, rasterećen, brzo ohlađen i analiziran (ME2, MA2). Melamine (M2) injected into A2 was cooled to temperature T5 in z3 minutes, unloaded, rapidly cooled and analyzed (ME2, MA2).
Parametri postupka kao tlak p1, p2, p3 i P3.1, temperatura T1, T2, T2.1, T2s, T3, T3.1, T4 i T5, vrijeme hlađenja z1, z2 i z3 minuta, vrijeme zadržavanja t1, t2 i t2s, kao i odvaga melamina (Mo), količine melamina (M1, M2), kao i početni sadržaj melema (MEo) i krajnji sadržaj melema (ME1, ME2) i melama (MA1, MA2) navedeni su u tablici 3. Process parameters such as pressure p1, p2, p3 and P3.1, temperature T1, T2, T2.1, T2s, T3, T3.1, T4 and T5, cooling time z1, z2 and z3 minutes, retention time t1, t2 and t2s, as well as the weight of melamine (Mo), the amount of melamine (M1, M2), as well as the initial content of salve (MEo) and the final content of salve (ME1, ME2) and salve (MA1, MA2) are listed in Table 3.
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Claims (11)
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AT0199495A AT403579B (en) | 1995-12-07 | 1995-12-07 | METHOD FOR PRODUCING HIGH PURITY MELAMINE |
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| HRP960575A2 true HRP960575A2 (en) | 1997-12-31 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| HRA1994/95A HRP960575A2 (en) | 1995-12-07 | 1996-12-05 | Process for producing pure melamine |
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| EP (1) | EP0874832B1 (en) |
| JP (1) | JP2000501404A (en) |
| KR (1) | KR100462920B1 (en) |
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| WO (1) | WO1997020826A1 (en) |
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| NL1006095C2 (en) * | 1997-05-21 | 1998-11-25 | Dsm Nv | Preparation of melamine from urea via a high pressure process |
| WO1998052928A1 (en) | 1997-05-21 | 1998-11-26 | Dsm N.V. | Method for preparing melamine |
| NL1006147C2 (en) * | 1997-05-28 | 1998-12-01 | Dsm Nv | Pure melamine is formed from urea by spray cooling the melamine melt |
| JP2002500664A (en) | 1997-05-28 | 2002-01-08 | ディーエスエム エヌ．ブイ． | Melamine production method |
| JP2002502416A (en) * | 1997-06-02 | 2002-01-22 | ディーエスエム エヌ．ブイ． | Melamine production method |
| CA2291627C (en) * | 1997-06-02 | 2008-12-09 | Dsm N.V. | Crystalline melamine |
| NL1006191C2 (en) * | 1997-06-02 | 1998-12-03 | Dsm Nv | Multi-crystalline melamine powder is prepared from urea |
| NL1006192C2 (en) * | 1997-06-02 | 1998-12-03 | Dsm Nv | Melamine is prepared from urea in a high pressure process |
| NL1008571C2 (en) * | 1998-03-12 | 1999-07-28 | Dsm Nv | Crystalline melamine. |
| TR200101341T2 (en) | 1998-11-13 | 2001-11-21 | Agrolinz Melamin Gmbh | Method for producing pure melamine |
| AU758664B2 (en) | 1998-12-23 | 2003-03-27 | Agrolinz Melamin Gmbh | Method for purifying melamine |
| EP1035117A1 (en) * | 1999-03-08 | 2000-09-13 | Dsm N.V. | Method for preparing melamine from urea |
| PL351565A1 (en) | 1999-03-15 | 2003-05-05 | Agrolinz Melamin Gmbh | Method for producing solid melamine |
| AU6697600A (en) * | 1999-07-27 | 2001-02-13 | Agrolinz Melamin Gmbh | Method for producing solid melamine |
| NL1013217C2 (en) * | 1999-10-05 | 2001-04-06 | Dsm Nv | Process for the preparation of melamine. |
| EP1138676A1 (en) * | 2000-03-27 | 2001-10-04 | Casale Chemicals SA | Process for producing melamine at high pureness |
| AT410210B (en) | 2000-08-07 | 2003-03-25 | Agrolinz Melamin Gmbh | METHOD FOR PRODUCING MELAMINE |
| AT500297B8 (en) * | 2000-11-08 | 2007-02-15 | Agrolinz Melamin Gmbh | PROCESS FOR CLEANING MELAMINE AMMONIA |
| AT410793B (en) * | 2000-12-27 | 2003-07-25 | Agrolinz Melamin Gmbh | METHOD FOR PRODUCING MELAMINE |
| KR20050025132A (en) | 2001-11-16 | 2005-03-11 | 아엠이-아그로린츠 멜라민 인터내셔날 게엠베하 | Method for producing melem-free melamine and quenching agents |
| FR2843964B1 (en) * | 2002-08-29 | 2004-10-01 | Sanofi Synthelabo | DIOXANE-2-ALKYLCARBAMATES DERIVATIVES, THEIR PREPARATION AND THEIR THERAPEUTIC APPLICATION |
| RU2417992C2 (en) * | 2009-07-20 | 2011-05-10 | Открытое акционерное общество "Научно-исследовательский и проектный институт карбамида и продуктов органического синтеза" (ОАО "НИИК") | Method of producing melamine and method of removing dissolved gases from aqueous solution of crude melamine |
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| US3116294A (en) * | 1963-12-31 | Process- for preparing high-purity melamine from urea | ||
| US3637686A (en) * | 1969-02-10 | 1972-01-25 | Nissan Chemical Ind Ltd | Process for recovering purified melamine |
| DE3500188C2 (en) * | 1984-01-05 | 1994-08-18 | Melamine Chemicals Inc | Anhydrous high-pressure melamine synthesis |
| US4565867A (en) * | 1984-01-05 | 1986-01-21 | Melamine Chemicals, Inc. | Anhydrous high-pressure melamine synthesis |
| DE3546893C3 (en) * | 1984-01-05 | 1998-01-29 | Melamine Chemicals Inc | Anhydrous high-pressure melamine synthesis |
| AT402294B (en) * | 1994-12-23 | 1997-03-25 | Agrolinz Melamin Gmbh | METHOD FOR PRODUCING HIGH PURITY MELAMINE |
| AT402296B (en) * | 1995-02-03 | 1997-03-25 | Agrolinz Melamin Gmbh | METHOD FOR PURIFYING MELAMINE |
| US5514797A (en) * | 1995-06-07 | 1996-05-07 | Melamine Chemicals, Inc. | Method for increasing purity of melamine |
| US5514796A (en) * | 1995-06-07 | 1996-05-07 | Melamine Chemicals, Inc. | Melamine of improved purity produced by high-pressure, non-catalytic process |
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