Process for the production of melamine crystals at high pureness
AssigneeCasale Chemicals S.A.
InventorGiorgio Pagani
Life of this patent
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Abstract
A process for producing melamine crystals at high pureness is distinguished by the fact that it comprises a crystallisation step of a flow comprising substantially pure melt melamine by cooling with liquid ammonia and a thickening step of the resulting suspension of melamine crystals in liquid ammonia by separation of a portion of the liquid ammonia present in said suspension, whereby the liquid ammonia separated in said thickening step is reused as coolant in the crystallisation step.
Claims21
Process for the production of melamine crystals at high pureness comprising the steps of:
- feeding a flow comprising substantially pure melt melamine and a flow comprising liquid ammonia as coolant in a crystallisation section;
- mixing said flow comprising substantially pure melt melamine and said liquid ammonia in said crystallisation section thus obtaining a suspension of melamine crystals in liquid ammonia;
- feeding said suspension of melamine crystals in liquid ammonia to a thickening section;
- extracting in said thickening section a portion of said liquid ammonia from said suspension of melamine crystals, thus obtaining a slurry of melamine crystals;
- recycling to said crystallisation section at least a portion of said liquid ammonia extracted in said thickening section;
- feeding said slurry of melamine crystals to a separation section in order to remove the liquid ammonia still present and obtain melamine crystals at high pureness substantially free of ammonia.
Plant for the production of melamine crystals at high pureness, comprising:
- a crystallisation section of a flow comprising substantially pure melt melamine with a flow comprising liquid ammonia as coolant, for obtaining a suspension of melamine crystals in liquid ammonia;
- a thickening section of the melamine crystals;
- a separation section for obtaining melamine crystals at high pureness substantially free of ammonia;
- said sections being provided in series,
- means for feeding to said crystallisation section a flow comprising substantially pure melt melamine and a flow comprising liquid ammonia, and means for recycling a flow comprising liquid ammonia from said thickening section to said crystallisation section;
- connecting means between said sections provided in series.
Dependencies are inferred from the claim text.