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Method for the purification of wastewaters from melamine systems

A technology for melamine and waste water, which is applied in the direction of chemical instruments and methods, separation methods, water pollutants, etc., can solve the problems of complicated process and no longer guaranteed decomposition degree, and achieve the effect of short residence time, stable and safe operation mode

Inactive Publication Date: 2008-06-11
UREA CASALE SA
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The disadvantage of this method is that the process is complicated and the precipitated OAT must be additionally treated
However, as soon as operating conditions arise where the wastewater varies with the concentration and type of components, the desired degree of decomposition can no longer be guaranteed

Method used

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  • Method for the purification of wastewaters from melamine systems

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0065] Example 1: Thermal pretreatment with downstream hydrolysis

[0066] Reaction mixture in thermal hydrolysis stage

[0067] NH 3 [weight%] 1.7%

[0068] CO 2 [weight%] 1.1%

[0069] h 2 O [wt%] 97.3%

[0070] Temperature [°C] 240

[0071] Pressure [bar] 45

[0072] Proportion of gas phase [weight%] 2.3%

[0073] reference sign

[0074] 1 heat pretreatment

[0075] 2 heat exchangers

[0076] 3 steam generators

[0077] 4 thermal hydrolysis

[0078] 5 waste water stripper

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Abstract

The invention relates to a method for purifying wastewaters of melamine systems. The method is characterized in that triazine-containing wastewater is subjected to a thermal pretreatment stage, whereupon the vapors are condensed from the gas phase of the thermal pretreatment stage, and the liquid phase of the thermal pretreatment stage is subjected to a thermal hydrolysis stage while NH3 is isolated from the obtained liquid phase containing H2O, CO2, and NH3. The inventive method makes it possible to compensate varying wastewater qualities, thus allowing the melamine system and wastewater station to be operated in a constant and safe fashion. Furthermore, the strain on the subsequent thermal hydrolysis stage is relieved with the aid of the thermal pretreatment stage of the inventive method.

Description

technical field [0001] The invention relates to a method for purifying waste water of a melamine production plant according to claim 1 and an apparatus according to claim 21 . Background technique [0002] Melamine is prepared almost exclusively from urea according to the following reaction equation: [0003] 6H 2 N-CO-NH 2 →C 3 N 3 (NH 2 ) 3 +6NH 3 +3CO 2 [0004] The preparation methods of melamine can be divided into two categories. One type is the non-catalytic high-pressure process in which melamine is produced in the liquid phase at a pressure of >70 bar. One is the catalytic low-pressure method, in which melamine is synthesized in the gas phase at about atmospheric pressure. [0005] Common to all melamine production processes is that the crude melamine from the synthesis stage must subsequently be purified since it contains by-products. In order to decompose the by-products, the crude melamine is usually treated in the presence of water, since the by-p...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C02F1/04C02F1/20C07D251/60C02F101/38C02F101/16C02F103/36
CPCB01D3/148C02F2101/38C02F2101/16B01D3/38C07D251/62C02F1/025C02F1/04C02F1/10C02F1/001C02F2103/36C02F1/20C02F2103/38
Inventor 沃尔夫冈·吕希克里斯托夫·诺伊米勒托马斯·瓦勒克
Owner UREA CASALE SA