MELAMINE SYNTHESIS UNIT USING WASTE GAS IN AN ATTACHED UREA SYNTHESIS UNIT Russian patent published in 2022 - IPC C07C273/12 C07D251/60 B01J19/00 

FIELD: chemical processes.

SUBSTANCE: invention relates to a unit for producing melamine and urea. The unit includes a melamine synthesis unit (MEL) for producing melamine from urea resulting in a stream of melamine-containing product and a stream of waste gas containing NH₃ and CO₂ in gaseous form, and a waste gas urea synthesis unit (UR) intended for synthesising urea from a stream of waste gas, suitable for producing urea from ammonia and CO₂ and containing at least a high-pressure synthesis section operating under the synthesis pressure and an extraction section operating under an extraction pressure lower than the synthesis pressure. At least 90% of ammonia and CO₂ for the waste gas urea synthesis unit is therein supplied by the stream of waste gas. Also proposed are methods for modernising the urea synthesis unit and the urea/melamine production unit.

EFFECT: invention provides a possibility of using urea, in solid form or in the form of an aqueous solution, supplied from an external source and not produced on site, as the initial material, wherein in case of construction of a new melamine synthesis unit whereto urea is supplied from an existing unit, the latter does not require any modernisation or additional actions since the waste gas is used in a specially provided unit, and the operation of the "main" urea synthesis unit is not disrupted when the melamine synthesis unit is idle or in case of a malfunction capable of causing a change in the amount and/or composition of the exhaust gaseous by-products.

13 cl, 2 dwg