Does the quality of urea affect melamine production?
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As a downstream product of urea, does the quality of the raw material urea have an impact on the production of melamine? If so, what are the main adverse effects? Everyone is welcome to speak up and discuss actively.
As far as I know, a high level of biuret has basically no impact. Oil, rust, and formaldehyde in urine can have an impact, but as long as the activated carbon for triamines is functioning properly, there are no major issues.
Dicyandiamide has no effect on the reactor, but it does have an impact on evaporation, affecting its efficiency. This post was last edited by lxq700918 on 2009-4-18 21:09.]
The water content in urea has an impact; 1 unit of water consumption requires 3 units of urea.
Urea reacts under boiling conditions at temperatures of 380–400°C, with ammonia as a carrier and silica gel as a catalyst; this process first results in the decomposition to form cyanic acid, which then undergoes further condensation to yield melamine. 6 (NH2)2CO → C3H6N6 + 6 NH3 + 3 CO2. The resulting melamine gas is cooled and captured to obtain a crude product, which is then dissolved, impurities are removed, and recrystallization yields the final product. This post was last edited by lxq700918 on 2009-4-19 11:23.]
As far as I know, the triamine system has an evaporation process to concentrate the urine to 99% before reuse; therefore, the concentration of urine after triamine removal has no impact on product quality.
The presence of formaldehyde can poison the catalyst used in the reaction
Personally, I believe that urea moisture and biuret have almost no effect on them, but the levels of formaldehyde and iron do have an impact.
1 part of water consumes 3 parts of urea; formaldehyde can poison the catalyst required for the triamine reaction, while biuret makes the liquid urine produced thicker, affecting its circulation rate.
Water decomposes urea, increasing consumption; formaldehyde leads to a decline in the quality of triamines; oil causes the catalyst to become inactive; biuret has virtually no effect
Water, provided that the load on the concentration system permits it, has basically no impact on product quality； However, a high degree of urea hydrolysis reduces yield and increases the burden on the condensate treatment process in the concentration stage. Formaldehyde and oils are affected by the use of catalysts; even the high-pressure method without catalysts has an impact, as it accelerates reactor scaling and requires frequent acid cleaning. Biuret has little effect, but it can cause pipeline blockages at low loads. Colored impurities increase the workload associated with product purification and result in a higher color intensity of the product. As for other elements such as ammonia, carbon dioxide, and iron, their concentrations should not be too high. These are just my humble opinions, for reference only