前苏联专利SU1424734A3 Method of removing reaction byproducts in producing melamine from urea

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专利摘要:
An improved process for the preparation of melamine from urea or thermal decomposition products thereof. A melamine containing reaction mixture is cooled with an aqueous medium to form an aqueous product stream containing melamine and reaction by-products. Product melamine is separated from the aqueous product stream leaving a residual aqueous stream which is recycled into the process. A portion of this residual aqueous stream still containing reaction by-product is treated to remove by-products therefrom prior to being recycled to the process.
公开号:SU1424734A3
申请号:SU833584512
申请日:1983-04-06
公开日:1988-09-15
发明作者:Ван Хардевельд Рудольф
申请人:Стамикарбон Б.В. (Фирма)；
IPC主号:

专利说明:

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This invention relates to a method for removing reaction by-products when a urea melt is obtained.
The purpose of the invention is to simplify the process.
The drawing shows an apparatus diagram for removing reaction by-products in the preparation of melamine from urea.
Example 1. Liquid urea is fed to melamine reactor 1 through line 2. Reactor 1 contains a fluidized bed of catalyst particles, such as silicon dioxide, and this layer is maintained in a fluidized state using gaseous ammonia fed through line 3. Hot molten salt introduced by 20
lines 4 to salt-heated coils 5, which maintain the temperature of the fluidized bed high enough to achieve the conversion of urea to melamine. After part of the heat is returned to the fluidized bed, the cooled molten salt is returned via line 6, tank 7 and line 8 to furnace 9, where it is reheated.
25
mixed with a filtration-promoting additive introduced through line 23, and with the mother liquor introduced through line 24, the resulting mixture through line 25, pump 26, heater 28 and line 29 are transferred to a dissolving tank 30, where melamine is dissolved in a liquid to form a concentrated melamine solution at 80-120 ° C. This melamine solution is then fed through line 31 to filter 32, where any solid contaminants and catalyst particles that remain in the liquid are filtered out. The filtered melamine solution is then fed via line 33 to recirculating line 34 of the crystallizer 35. A portion of the contents of the crystallizer is continuously recirculated through line 36, pump 37 and line 34.
Part of the suspended melamine crystals are taken from line 36 through line 38 and fed through pump 39 and line AO to hydrocyclone A1. Almost free from crystals of the upper stream from the cyclone 41 is fed through line 42 into the tank 43 of the mother liquor. Almost free from kris40
The reaction mixture, having a high 30 tal, upper stream from the crystallizer 35 is also fed through line 44 to the tank 43 of the mother liquor,
In the mold 35, a vacuum is maintained by a vacuum unit (not shown) connected to the mold through line 45, refrigerator 46 and line 48. Condensate formed in refrigerator 46 is fed to line 49.
The concentrated suspension of melamine crystals formed in hydrocyclone 41 is fed through line 50 and centrifuge 51, where almost all of the remaining water is removed from the melamine crystals. In fact, water-free crystals are introduced through line 52 into desiccant 53 and dried therein with hot air supplied through line 54. Dried melamine crystals are separated from the air in cyclone 55 and air is drawn through line 56, filter 57, line 58, blower 59 and line 60. The dry melamine product, separated in cyclone 55 and collected in filter 57, is sent for storage through lines 61-63.
The mother liquor accumulated in the mother liquor tank 43, externally and containing melamine, ammonia and carbon dioxide, leaves the reactor 1 through line 10 and is introduced into columns 11 and 12, where it is quenched (i.e. the reactions in the mixture are interrupted by oh-35 ) and is cooled with aqueous solutions introduced through lines 13 and 14 to form an aqueous suspension of solid melamine particles. This aqueous suspension is discharged from the bottom of column 12 through pump 15 and line 16 and fed to a hydrocyclone 17, where it is concentrated. The depleted melamine slurry coming out of hydrocycpone 17 through line 13 is returned to columns 11 and 12, while the more concentrated melamine suspension or slurry formed in Godro cyclone 17 is fed through line 18 to desorption / o column 19.
In the desorption column, 19 of the ammonia and carbon dioxide dissolved in the slurry are desorbed by heating, and the gas mixture thus formed is returned to column 12 via line 20.
A suspension leaving the bottom of the desorber 19 through line 21 is fed to the dissolving tank 22, where fee
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mixed with a filtration-promoting additive introduced through line 23, and with the mother liquor introduced through line 24, the resulting mixture through line 25, pump 26, heater 28 and line 29 are transferred to a dissolving tank 30, where melamine is dissolved in a liquid to form a concentrated melamine solution at 80-120 ° C. This melamine solution is then fed through line 31 to filter 32, where any solid contaminants and catalyst particles that remain in the liquid are filtered out. The filtered melamine solution is then fed via line 33 to recirculating line 34 of the crystallizer 35. A portion of the crystallizer content is continuously recirculated through line 36, the pump 37 and line 34.
Part of the suspended melamine crystals are taken from line 36 through line 38 and fed through pump 39 and line AO to hydrocyclone A1. Almost free from crystals of the upper stream from the cyclone 41 is fed through line 42 into the tank 43 of the mother liquor. Almost free from kris3142473A
loaded through line 64, pump 65 and line 66. Part of the mother liquor is fed through line 67 to the mother liquor purification section, starting with S from tank 69.
In tank 69, COj fed through line 70 is introduced into the mother liquor to lower the pH. From capacity 69
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the mother liquor is directed through carbon ligoxide in the desorption colony 71 to heater 72 and through line 19 and diluted with mother liquor 73 into the dissolving tank Ik. Zrom in the tank 22 dissolve. After
The mother liquor is passed through this concentrated melamine solution 75 to filter 76, where the precipitated sieve is filtered, crystallized and removed, which are 15 hours from the residual aqueous stream, and byproducts of the reaction are filtered off. After drying, melamine is obtained in an amount of 8000 kg / h
popped out and purified mother liquor
The upper stream from the mold 35 through line 44 and the upper stream from the hydrocyclone 41 through line 42 are directed to the tank 43 of the mother liquor at a total rate of 359770 kg / h. This mother liquor contains 2.0 wt.% Melamine and 0.2 wt.% Dissolved is led through line 77 to columns 11. and 12, where the reaction mixture is quenched and cooled. 20
The remaining part of the mother liquor, which is not processed in the purification section, from the tank 43 is sent as directly to the columns 11 and 12 through a line of 14 dp to 25 quench products. From the total amount and cooling of the reaction mixture, the vacuum solution was 9.6% directed to the dissolution rate 22 through the cleaning section tank 69 through line 49, the heat exchanger 68 and line 24. line 67. In the heat exchanger, there are 68 seed plants of 82 kg / h of carbon dioxide, the thief exchanges heat with a hot, low pH pH of the mother liquor with the gas mixture leaving the column from 9.5 to 8.3. After heating to 80-85 ° С
to dissolve any remaining melamine solid particles, a portion of the contaminating by-products, precipitating -jg in the sediment, is filtered out. Thereafter, the mother liquor thus treated is returned to the columns .11 and 12, where it is used to cool further quantities of hot water.
40 reaction mixture.
Example 2. Analogously to Example 1, melamine is obtained and separated from the reaction mixture. The remaining mother liquor contains 2.0 wt.% Melamine reactor 1 (through a 45 melamine compres- sion and 0.2 wt.% Dissolved spore 83, line 84, heater 85, and byproducts of the reaction. From mother-line 3), where It is used as a fluidizing gas. A dilute ammonium carbamate solution is removed from column 12 through line 78. During heat exchange, part of the gas mixture is condensed, and the condensate and uncondensed gas are fed through, respectively, LEDS 79 and 80 to the adsorption tower 81.
Liquid ammonia is fed to the top of the adsorption tower to condense any remaining carbon dioxide from the almost pure ammonia gas leaving the column 81 through line 82. Ammonia gas is recycled to
5% by weight of the total solution was taken to the purification section and treated with carbon dioxide (42 kg)
5% by weight of the total solution was taken to the purification section and treated with carbon dioxide (42 kg)
loaded from the bottom of the adsorption tank to set the pH of the solution to 7.5. Vy- columns 81 through line 86, pump 87 and line 88.
Example 1. In the apparatus described above, 24,320 kg / h of liquid urine-55 gases. The resulting melamine guilt is served in the melamine reactor 1 has a purity of 99.8%. through line 2. Reactors from this reactor are repeated. Example 3. Example 2 is repeated. The promotional gas mixture consisting of mother liquor is withdrawn 50% mainly from melamine, ammonia and the polluting side gases are processed into the purification section. the products are filtered off and the treated uterine liacTBop is returned to the melamine recovery step from carbon dioxide, discharged through line 10.
/ After cooling the gas mixture to 75-1AO C, for example, to 127 s, in columns 11 and 12, the resulting aqueous suspension of solid melamine in a saturated melamine solution is almost completely freed from a fc and is removed from the residual aqueous stream,
Thus, after drying, melamine is obtained in an amount of 8,000 kg / h.
The upper stream from the mold 35 through line 44 and the upper stream from the hydrocyclone 41 through line 42 are directed to the tank 43 of the mother liquor at a total rate of 359770 kg / h. This mother liquor contains 2.0 wt.% Melamine and 0.2 wt.% Dissolved by-products. From the total amount of the stock solution, 9.6% is sent to the tank 69 in the purification section via line 67. Approx. 2 is introduced into the tank 69. Example 2. Example 1 is used for preparing melamine and separating it from the reaction mixture. The remaining mother liquor contains 2.0% by weight of melamine and 0.2% by weight of dissolved by-products of the reaction. From the uterine
5% by weight of the total solution was taken to the purification section and treated with carbon dioxide (42 kg)
To adjust the pH of the solution to 7.5. You-
To adjust the pH of the solution to 7.5. You-
gases. The resulting melamine has a purity of 99.8%. Example 3. Example 2 is repeated, but 50% of the purification section is withdrawn from the purification section and the two precipitating contaminant by-products are treated and the treated uterine liacTBop is returned to the melamine recovery step
carbon monoxide (405 kg) until the pH of the solution is 9.0. Received lamin has a purity of 99.8%.
The process of obtaining and separating the lamina is carried out uninterruptedly, the processing of the part remaining in the stream.

权利要求:
Claims (1)
[1]
Formula of invention
The method of removing reaction by-products when obtaining melamine from urea at a temperature higher than the melting point of the latter and in the presence of a fluidized bed of silica particles as catalysts
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a torus in which the reaction mixture is cooled with an aqueous medium to form an aqueous stream of product containing melamine and reaction by-products, and melamine is separated and the residual water stream is returned to recycling, characterized in that, in order to simplify the process, The 50% residual vbd stream containing by-products is separated from the suction stream and, before being recycled into the process, is treated with carbon dioxide with a decrease in pH to 7.5-9.0 followed by filtration of the precipitate by-products.
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同族专利:

公开号 | 公开日

AT30586T|1987-11-15|

CS242683A2|1985-07-16|

ZA832405B|1983-12-28|

ES8402277A1|1984-01-16|

US4408046A|1983-10-04|

BG50277A3|1992-06-15|

EP0091174A1|1983-10-12|

HU190834B|1986-11-28|

JPH0480908B2|1992-12-21|

CS241054B2|1986-03-13|

BR8301744A|1983-12-13|

NO163009C|1990-03-21|

NL8201479A|1983-11-01|

KR840004414A|1984-10-15|

NO831230L|1983-10-10|

RO89260A|1986-03-15|

PL142730B1|1987-11-30|

PL241365A1|1983-11-21|

KR860001569B1|1986-10-08|

EP0091174B1|1987-11-04|

NO163009B|1989-12-11|

MX168144B|1993-05-06|

YU72783A|1986-02-28|

ES521272A0|1984-01-16|

DE3374311D1|1987-12-10|

DD209625A5|1984-05-16|

CA1244423A|1988-11-08|

JPS58185573A|1983-10-29|

IN158211B|1986-09-27|

YU43655B|1989-10-31|

引用文献:

公开号 | 申请日 | 公开日 | 申请人 | 专利标题

US3496176A|1968-06-19|1970-02-17|Allied Chem|Melamine purification|

NL161750C|1968-11-16|1980-03-17|Stamicarbon|Process for separating melamine from a gaseous reaction mixture of melamine, ammonia and carbon dioxide.|

RO74590A|1977-01-19|1981-08-30|Stamicarbon Bv,Nl|PROCEDURE FOR PREPARING MELAMINE FROM URINE|

NL7903473A|1979-05-03|1980-11-05|Stamicarbon|METHOD FOR PREPARING MELAMINE.|DE3546893C3|1984-01-05|1998-01-29|Melamine Chemicals Inc|Anhydrous high-pressure melamine synthesis|

CA1220476A|1984-01-05|1987-04-14|David E. Best|Anhydrous high-pressure melamine synthesis|

DE3500188C2|1984-01-05|1994-08-18|Melamine Chemicals Inc|Anhydrous high-pressure melamine synthesis|

US4565867A|1984-01-05|1986-01-21|Melamine Chemicals, Inc.|Anhydrous high-pressure melamine synthesis|

US4648955A|1985-04-19|1987-03-10|Ivac Corporation|Planar multi-junction electrochemical cell|

DE4035724A1|1990-11-09|1992-05-14|Jacobs Suchard Ag|DEVICE FOR RECEIVING AND DISPENSING LIQUIDS|

IT1261841B|1993-08-23|1996-06-03|Conser Spa|PROCEDURE FOR THE PRODUCTION OF HIGH PURITY MELAMINE.|

EP1129080B1|1998-11-13|2003-08-20|Agrolinz Melamin GmbH|Method for producing pure melamine|

NL1012466C2|1999-06-29|2001-01-02|Dsm Nv|Process for the preparation of melamine from urea.|

IT1315255B1|1999-11-16|2003-02-03|Eurotecnica Dev And Licensing|MELAMINE PURIFICATION PROCESS.|

IT1315265B1|1999-12-22|2003-02-03|Eurotecnica Dev And Licensing|PROCESS FOR THE PRODUCTION WITH OTHER HIGH-PURITY MELAMINE YIELDS|

ES2239236T3|2001-07-24|2005-09-16|Dsm Ip Assets B.V.|METHOD FOR OBTAINING A SOLUTION OF CARBAMATE AMMONIUM FROM A GAS MIXTURE CONTAINING AMMONIA, WATER AND CARBON DIOXIDE.|

NL1021287C2|2002-08-15|2004-02-17|Dsm Nv|Process for the preparation of melamine.|

NL1022414C2|2003-01-17|2004-07-20|Dsm Nv|Method for extracting energy from flue gases.|

DE102005028665A1|2005-06-15|2007-01-04|Ami-Agrolinz Melamine International Gmbh|Process for the purification of wastewater from melamine plants|

EP2098516A1|2008-03-04|2009-09-09|Urea Casale S.A.|Process for the production of high purity melamine from urea|

IT1400090B1|2010-05-06|2013-05-17|Eurotecnica Melamine Luxemburg Zweigniederlassung In Ittigen|LOW ENERGY CONSUMPTION PROCEDURE FOR THE PRODUCTION OF HIGH PURE MELAMINE THROUGH UREA PYROLYSIS, AND ITS EQUIPMENT|

法律状态:

优先权:

申请号 | 申请日 | 专利标题

NL8201479A|NL8201479A|1982-04-07|1982-04-07|METHOD FOR PREPARING MELAMINE.|

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