Abstract: The invention relates to solid particles and to a method for the production thereof from a flowable starting material and a solid part, wherein the flowable starting material is split into droplets which are introduced along a trajectory into a solidification liquid in which they are solidified in the form of the solid particles. The invention is characterized by the use of solidification liquid and, if the flowable starting material contains actinide oxide, the solidification liquid steadily flows, thereby making it possible to produce solid particles having a greater sphericity and a narrow particle sized distribution.

Abstract: A two-stage process is provided for purifying off-gases from a high-pressure melamine plant. In the first stage, the off-gases are contacted with a recirculated urea melt containing melamine precursors and NH3. In the second stage, the off-gases are contacted with a fresh urea melt.

Abstract: The invention relates to a method for producing pure melamine in a high-pressure method. According to said method, in the first stage, the melamine melt is brought into contact with hot NH3 and NH3 from the second stage and in the second step is brought into contact with cold NH3 in such a way that it is cooled to a temperature, which is 1–30° C. above the pressure-dependent melting point of the melamine, before being optionally rested in a third stage and subsequently treated in various ways.

Abstract: A process for the production of melamine by pyrolysis of urea in a high-pressure reactor having a vertical central pipe is provided. The melamine flows upwards into the reactor from below, mixes in the lower part of the reactor with a urea melt, and optionally NH3, introduced into the reactor from below, and emerges from the central pipe in the upper part of the central pipe. Part of the melamine formed flows downward in the annular space between the central pipe and reactor wall, and the remainder is expelled for further work-up. The off-gases are removed at the top of the reactor. A reactor for carrying out the process is also provided.

Abstract: The invention relates to a method for producing pure melamine in a high-pressure method. According to said method, in the first stage, the melamine melt is brought into contact with hot NH3 and NH3 from the second stage and in the second step is brought into contact with cold NH3 in such a way that it is cooled to a temperature, which is 1-30° C. above the pressure-dependent melting point of the melamine, before being optionally rested in a third stage and subsequently treated in various ways.

Abstract: A process for preparing melamine by pyrolysis of urea in a high-pressure process, in which urea is reacted together with NH3 to give melamine and the melamine melt formed is fed together with further urea to a cooling reactor, with the melt being cooled to a temperature which is 1-50° C., preferably 1-30° C., above the melting point of the melamine, which is dependent on the prevailing NH3 pressure. Introduction of NH3 in countercurrent drives out the CO2 formed, after which the melamine melt is worked up in any appropriate way.

Abstract: A process for purifying gaseous melamine containing ammonia is provided. The method comprises partly condensing the gaseous melamine-containing ammonia to form melamine in liquid NH3 and purified NH3 gas. The melamine and purified NH3 gas are taken off.

Abstract: A two-stage process is provided for purifying off-gases from a high-pressure melamine plant. In the first stage, the off-gases are contacted with a recirculated urea melt containing melamine precursors and NH3. In the second stage, the off-gases are contacted with a fresh urea melt.

Abstract: A process for the production of melamine by pyrolysis of urea in a high-pressure reactor having a vertical central pipe is provided. The melamine flows upwards into the reactor from below, mixes in the lower part of the reactor with a urea melt, and optionally NH3, introduced into the reactor from below, and emerges from the central pipe in the upper part of the central pipe. Part of the melamine formed flows downward in the annular space between the central pipe and reactor wall, and the remainder is expelled for further work-up. The off-gases are removed at the top of the reactor. A reactor for carrying out the process is also provided.

Abstract: A process for the production of melamine by pyrolysis of urea in a high-pressure reactor having a vertical central pipe is provided. The melamine flows upwards into the reactor from below, mixes in the lower part of the reactor with a urea melt, and optionally NH3, introduced into the reactor from below, and emerges from the central pipe in the upper part of the central pipe. Part of the melamine formed flows downward in the annular space between the central pipe and reactor wall, and the remainder is expelled for further work-up. The off-gases are removed at the top of the reactor. A reactor for carrying out the process is also provided.

Abstract: The invention relates to a method for producing pure melamine. According to this method, the melamine melt, which is produced from urea in a high-pressure process, is cooled and ammonia is added until it reaches a temperature of approximately 1 to 50° C. above the melting temperature of the melamine as dependent on the respective pressure of ammonia and then either a) quenched with water or an aqueous solution or suspension containing ammonia and/or melamine so that the melamine solidifies or b) quenched with cold liquid or gaseous ammonia, so that the melamine solidifies, the melamine then being cooled further with water or an aqueous solution or suspension containing ammonia and/or melamine and c) the melamine is then isolated.

Abstract: The invention relates to a method for purifying the by-product gases that originate in a high-pressure melamine manufacturing installation in a urea wet scrubber. According to said method, CO2 is added to the by-product gases before or during their entry into said urea wet scrubber.

Abstract: The invention relates to a method for the purification of melamine-containing gaseous NH3, by means of partial condensation, whereby pure NH3 gas and liquid NH3 enriched with melamine are obtained.

Abstract: A process for the production of melamine by pyrolysis of urea in a high-pressure reactor having a vertical central pipe is provided. The melamine flows upwards into the reactor from below, mixes in the lower part of the reactor with a urea melt, and optionally NH3, introduced into the reactor from below, and emerges from the central pipe in the upper part of the central pipe. Part of the melamine formed flows downward in the annular space between the central pipe and reactor wall, and the remainder is expelled for further work-up. The off-gases are removed at the top of the reactor. A reactor for carrying out the process is also provided.

Abstract: A process for preparing melamine by pyrolysis of urea in a high-pressure process, in which urea is reacted together with NH3 to give melamine and the melamine melt formed is fed together with further urea to a cooling reactor, with the melt being cooled to a temperature which is 1-50° C., preferably 1-30° C., above the melting point of the melamine, which is dependent on the prevailing NH3 pressure. Introduction of NH3 in countercurrent drives out the CO2 formed, after which the melamine melt is worked up in any appropriate way.

Abstract: The invention relates to a method for producing solid melamine by expanding liquid, ammoniacal melamine which is mixed with excess ammonia, whereby a dispersion is produced. Said dispersion is expanded, optionally after it has been held under ammonia pressure, whereby solid melamine is deposited. The solid melamine is optionally held under ammonia pressure. Expansion is then optionally carried out in any particular order, along with cooling to room temperature and the pure melamine is isolated.

Abstract: The invention relates to a method for producing urea. According to said method, the off-gases which originate from a melamine plant and essentially consist of NH3 and CO2 are introduced into the high-pressure zone of the urea plant by means of ejectors.

Abstract: The invention relates to a method for purifying melamine in which impure melamine is heated to a temperature range above 325°C. but lower than the melting point of melamine which depends on the prevailing ammonia pressure. In addition, the impure melamine is held in said temperature range under an ammonia pressure ranging from 1 to 150 bar for a duration lasting from 1 minute up to 20 hours. The melamine is provided in solid form. Afterwards, the melamine is relieved from pressure and cooled in any order.

Abstract: A process for the preparation of pure melamine, in which liquid, ammonia-containing melamine is rapidly depressurized from an ammonia partial pressure p1 between 400 and 50 bar to an ammonia partial pressure p2 between 200 bar and atmospheric pressure, where p1 is always greater than p2, at a temperature which is 0 to 60° C. higher than the melamine solidification point dependent oil the particular prevailing ammonia partial pressure, higher pressures permitting a greater temperature interval from the melamine solidification point than lower pressures, by which means pure melamine separates out in solid form, whereupon, in any sequence, the product is further depressurized if appropriate to atmospheric pressure, cooled to room temperature and the pure melamine is isolated.

Abstract: Process for cooling liquid melamine by mixing with solid melamine or with solid inert substances or with a mixture of solid melamine and solid inert substances.