Abstract: A urea production process combining lower pressure urea concentration and carbamate recovery steps into a single non-vacuum operation. Following high pressure stripping wherein a bulk of unreacted carbamate is recovered from the reaction effluent, remaining carbamate is stripped by heated air at atmospheric pressure wherein urea is concurrently concentrated without the use of vacuum evaporators. Weak carbamate solution subsequently formed is stripped of water (and residual urea is hydrolyzed) using air and steam at a medium pressure single tower hydrolyzer/stripper to obtain a concentrated carbamate stream suitable for recycle to the reactor. The process employs heat integration for enhanced energy efficiency and produces a good quality aqueous condensate suitable for direct use as boiler feed water. Thus the aqueous condensate produced requires no additional cooling and ammonia treatment. The process employs simplified and reduced process unit operation to eliminate equipment for cost reduction.

Abstract: Disclosed are a fixed-bed, cross-flow catalytic reactor wherein reaction heat can be exchanged against a heat exchange medium circulating indirectly through the catalyst bed, and a catalytic process comprising operation of the cross-flow reactor. The reactor comprises a catalyst bed having internally embedded banks of heat exchange tubes. An inlet distributor distributes reactants along the axial length of the bed. The distributed fluid passes through the bed in a cross-flow path wherein a catalytic reaction occurs. The reaction effluent is then collected from the bed by an outlet product collector. A heat exchange medium circulated through the internal heat exchange tubes adds or removes reaction heat as required for enhanced conversion in the reactor. Multiple heat exchange tubes can be used, and inlet and discharge manifolds are provided for distributing the circulating heat exchange medium.

Abstract: A process and unit for the recovery of ammonia in ammonia production are disclosed. All or a portion of a high pressure liquid ammonia product stream is introduced into a syngas makeup stream to produce a mixed vapor-liquid refrigeration medium for condensing ammonia from a synthesis loop product stream. Following the product stream ammonia condensation step, the vapor component of the mixed vapor-liquid stream is compressed and cooled for condensing ammonia therefrom. Liquid ammonia separated from the low pressure mixed vapor-liquid stream can be withdrawn as a low pressure liquid ammonia product. An ammonia-lean makeup gas is then combined with the ammonia-containing product recycle gas stream from the synthesis loop and further compressed. The process preferably includes recycle of all or a portion of the low pressure liquid ammonia product as a supplemental refrigerant.

Abstract: An improved process for manufacturing melamine from urea simplifies the recovery of melamine, carbamate and ammonia from a fluidized bed reactor effluent stream by operating the process at a pressure between 1.4 and 2 MPa. In such a manner, a carbamate solution can be produced at a sufficiently high concentration for use in a urea plant without an intervening concentration step. In addition, ammonia recycled as a fluidizing gas can be condensed against cooling water to permit easy separation of noncondensables such as oxygen which used in the process as a passivator for carbamate corrosion inhibition. The melamine product is produced as an aqueous solution free of melamine solids. Heat is recovered from the carbamate condensation and used for the vaporization of ammonia which is recycled to the reactor for fluidization.

Abstract: A high temperature heat exchanger having an improved support apparatus for suspending a tube bundle. The improved support comprises a skirt from which the tube sheet and the bundle are supported, and a lip on an upper end of the skirt engaged in a flange assembly receiving the lip. A first refractory lining on an inside face of the skirt extends downwardly from the lip, and overlaps a second refractory lining on an outside surface of the skirt extending upwardly from adjacent the tube sheet toward the lip. By securing the support apparatus in the cold flange assembly, the interior refractory is not used for supporting the tube bundle and can maintain its integrity, have a lower incidence of premature failure and yield an optimum refractory life.

Abstract: A process furnace and method of operating a furnace are disclosed. The furnace comprises a radiant heating chamber, a primary convection section leg, a secondary convection section leg with two or more parallel flow channels, convection burners to heat the primary and/or secondary convection sections and dampers to adjust flue gas flow and temperature through the parallel flow channels. Combustion air comprising a mixture of gas turbine exhaust and fresh air which has been preheated in one of the parallel flow channels s supplied to the burners. The split flue design facilitates greater control of the flue gas temperature for improved operating efficiency.

Abstract: An integrated process for making methanol and ammonia from a hydrocarbon feed stock and air is disclosed. An air separation unit is used to produce substantially pure oxygen and nitrogen gas streams. The oxygen gas is used in the secondary reformer to increase the operating pressure of the reformers so that compression to methanol synthesis pressure may be done by a single stage compressor. The nitrogen gas is used to remove carbon oxides impurities from a ammonia synthesis feed stream in a nitrogen wash unit in addition to supplying the nitrogen reactant in the ammonia synthesis gas. Use of nitrogen wash obviates the need for steam shift and methanation reactions used in prior art processes.

Abstract: Ammonia synthesis gas is partially converted over iron-based synthesis catalyst, cooled, and further converted over a more active synthesis catalyst.