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| Number | Title | Issue Date |
| 7045623 | Method for contacting molten urea with a gas stream The invention relates to a method for contacting molten urea with a gas stream that contains ammonia and/or carbon dioxide, in which use is made of an additional stream the temperature of which differs from the temperature of the molten urea and/or the gas stream. T... | 05/16/2006 |
| 6881862 | Process for the preparation of urea The invention relates to a process for the preparation of urea from ammonia and carbon dioxide, which preparation takes places wholy or partly with the application of a synthesis reactor, a condenser, a scrubber and a stripper, wherein an outlet of the stripper, thr... | 04/19/2005 |
| 6858755 | Process for the preparation of urea Process for the preparation of urea from ammonia and carbon dioxide, wherein the waste gases released at virtually atmospheric pressure in a urea plant are compressed by an ejector driven by the waste gas from the high-pressure synthesis and are supplied to a medium... | 02/22/2005 |
| 6696026 | Process for combined production of ammonia and urea A process for the combined production of ammonia and urea of the type comprising an ammonia synthesis reactor (2), a urea synthesis reactor (5) and a urea recovery section (21) stands out for the fact of submitting at least a part of a flow comprising car... | 02/24/2004 |
| 6552092 | Defoamers for aqueous media The invention relates to compositions for defoaming aqueous media, comprising as defoamers urea derivatives of the formula I ##STR1## where R1 --is a hydrocarbon radical, preferably having 4 to 30 carbon atoms or a hydrocarbon radical, preferab... | 04/22/2003 |
| 6417396 | Quenching reagents for solution phase synthesis A method for enhancing the purity of a desired compound comprising: Step (a) treating a crude reaction product which contains at least one desired compound, unreacted starting materials and/or byproducts with at least one bifunctional quenching agent that is c... | 07/09/2002 |
| 6392096 | Process for the preparation of urea The invention relates to a process for the preparation of urea from ammonia and carbon dioxide, the preparation being effected in whole or in part in a vertical combi-reactor. The gas stream leaving the stripper is fed to the condenser section of a vertic... | 05/21/2002 |
| 6287525 | Process and plant for urea production with reaction spaces having differentiated yields In a process for urea production, substantially pure ammonia and carbon dioxide are reacted in a main reaction space from which outgoes a reaction mixture subjected to stripping to obtain a partially purified mixture sent to a urea recovery section. From ... | 09/11/2001 |
| 6284922 | Method for modernizing a urea production plant A method for the modernization of a plant for urea production of the type comprising a reactor (2) for urea synthesis, a stripping unit (3) with carbon dioxide and at least one vertical condensation unit (4) of the film type, foresees the provision of mea... | 09/04/2001 |
| 6278021 | Reduced particle-size urea A process for producing an urea preparation of reduced particle-size and narrow particle-size distribution by using an air milling process is provided. Also provided is an urea preparation of reduced particle-size, narrow particle-size distribution, and h... | 08/21/2001 |
| 6121488 | Quenching reagents for solution phase synthesis A method for enhancing the purity of a desired compound comprising: Step (a) treating a crude reaction product which contains at least one desired compound, unreacted starting materials and/or byproducts with at least one bifunctional quenching agent that is c... | 09/19/2000 |
| 6084129 | Process for reducing the residual free ammonia emissions from an urea production plant A process for reducing the residual free ammonia emissions from an urea production plant comprises the step of feeding a gas flow comprising carbon dioxide (8) to a melt urea flow (3) coming from the concentration section (13) of the plant.... | 07/04/2000 |
| 5847209 | Process for recovery of solid and reusable urea from the urea adduction process A process for recovery of solid and reusable urea from the urea adduction process. Refinery streams are subjected to a step of urea adduction for removal of unwanted branched products, aromatics and sulphur. The adduct is purified, dried and then subjecte... | 12/08/1998 |
| 5744009 | Method and apparatus for recovering condensables in vapor from a urea vacuum evaporator An improved urea recovery process is presented. In the improved process, multiple vacuum rated surface condensers used to condense water vapor evolved during urea vacuum evaporation/concentration are replaced by a direct contact cooler/absorber to obtain ... | 04/28/1998 |
| 5686647 | Process for the preparation of urea Process for the preparation of urea, wherein in a first step ammonia and carbon dioxide react in suitable conditions so as to form a first mixture containing a quantity of urea, wherein in one or more subsequent steps ammonia and carbon dioxide are remove... | 11/11/1997 |
| 5650090 | Compositions for thermal energy storage or thermal energy generation A composition for thermal energy storage or thermal energy generation comprising a silica based gel or dry powder in the form of silica particles containing a water/urea phase change material for thermal energy storage or an endothermic or exothermic comp... | 07/22/1997 |
| 5597454 | Process for producing urea 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, remaini... | 01/28/1997 |
| 5527961 | Process for reducing the ammonia content of a gaseous effluent from urea production plants A process for neutralizing the ammonia present in the molten urea originating from the concentration section of a plant for its production, comprising adding to the molten urea a small quantity of an acid.... | 06/18/1996 |
| 5446200 | Process for the purification of technical-grade N-alkyl urea A process for the purification of technical-grade N-alkyl urea, particularly mono-ethyl urea, including an alkali metal sulphate, characterised in that it includes the steps of: treating the technical alkyl urea with a C1 -C4 alcoholic so... | 08/29/1995 |
| 5273623 | Process for concentrating urea solution under vacuum Process for vacuum-concentrating urea solutions in which the final step of evaporation of the urea solution under vacuum is carried out within the injection of overheated water vapor in the overhead portion of the concentrator, in order to counteract the ... | 12/28/1993 |
| 5266097 | Aminoureaformaldehyde fertilizer method and composition A new method of preparing a new aminoureaformaldehyde fertilizer composition which exhibits high cold water insoluble nitrogen (CWIN) levels and high Availability Indices (AI). The method utilizes the discoveries that ammonia compounds, usually ammonium s... | 11/30/1993 |
| 5223238 | Method for treating ammonia and urea condensates A method is described which enables ammonia plant process condensate contaminated with ammonia, carbon dioxide and methanol and urea plant condensate contaminated with urea, ammonia, carbon dioxide and other combined forms of ammonia and carbon dioxide to... | 06/29/1993 |
| 5177205 | Method for obtaining a solid polycrystalline material Method for obtaining an organic polycrystalline material having in particular electro-optical properties, said material obtained and an electro-optical modulator comprising said material. This method includes a stage (1) for preparing a powder having a size ... | 01/05/1993 |
| 5176800 | Process for the modernization of existing urea plants and a modernized urea plant A process to modernize existing urea plants which use a stripping with carbon dioxide, and to increase urea yields and flexibility under overload conditions while at the same time reducing energy consumption, corrosion phenomena and possible risks of expl... | 01/05/1993 |
| 4879413 | Process for the preparation of a solid adduct of sulfuric acid and urea A method for processing exposed and developed photographic silver dye-bleach materials, in which the exposed and developed material is treated with aqueous bleaching preparations which contain (a) an acid component, (b) a silver complexing agent, (c) one ... | 11/07/1989 |
| 4866207 | Process for concentrating an urea solution by evaporation An improved process and apparatus for the concentration of an aqueous urea solution by evaporation of water in a single pass shell and tube heat exchanger having a substantially vertical tube bundle within the shell. The aqueous urea solution is introduce... | 09/12/1989 |
| 4801747 | Process for preparing urea An improved process for the preparation of urea from carbon dioxide and excess ammonia at an elevated temperature and pressure to form a urea synthesis solution containing uncoverted ammonium carbamate and free ammonia. A portion of the ammonium carbamate... | 01/31/1989 |
| 4758311 | Method for avoiding the corrosion of the strippers in the urea manufacturing plants A method for passivating the surface of the strippers of the urea plants, where the temperatures are very high, where the pressures range from 120 to 240 Kg/cm2 and where the effluent process flow from the synthesis reactor undergoes one or mor... | 07/19/1988 |
| 4747915 | Falling-film process for the cocurrent evaporation of a solution A falling-film process and apparatus for the cocurrent evaporation of a solution is disclosed. The process utilizes a tube-bundle heat exchanger in which the upper ends of the individual tubes of the tube-bundle are closed. Apertures, preferably in the fo... | 05/31/1988 |
| 4701555 | Methods for removing biuret from urea by adsorption The biuret content of biuret-containing urea is reduced by contacting a solution or melt of biuret-containing urea with a polar adsorbent under conditions sufficient to remove at least a portion of biuret from the urea. The resulting biuret-containing ads... | 10/20/1987 |
| 4698443 | Biuret purification Purified biuret is recovered from mixtures containing biuret and higher molecular weight urea condensation products by contacting melts or solutions of such mixtures with a polar adsorbent and extracting biuret from the adsorbent with a polar desorbent. T... | 10/06/1987 |
| 4658059 | Methods for removing biuret from urea by ion exchange Methods are provided for removing biuret from biuret-containing aqueous urea solutions which methods involve contacting a quantity of a biuret-containing aqueous urea feed solution with the hydroxide ion form of an anion exchanger under conditions suffici... | 04/14/1987 |
| 4654442 | Methods for removing biuret from urea Biuret is removed from biuret-containing aqueous urea solutions in a multi-cycle process which involves sequential (A) removal of biuret by contact with an anion exchanger and (B) regeneration of the anion exchanger, in which method, in one or more cycles... | 03/31/1987 |
| 4652678 | Process for the recovery of valuable components from the waste streams obtained in the preparation of urea An improved process for recovering usable components from waste streams containing urea, including a dilute aqueous urea solution, which result from the preparation of particulate urea products. The dilute aqueous urea solution is used to wash a urea cont... | 03/24/1987 |
| 4650901 | Ion exchange methods for removing biuret from urea Methods are provided for removing biuret from biuret-containing aqueous urea solutions by contacting the biuret-containing urea solutions with the hydroxide ion form of an anion exchanger under anion exchange conditions in which methods one or more aqueou... | 03/17/1987 |
| 4645859 | Methods for purifying biuret Methods are provided for recovering purified biuret from aqueous solutions containing biuret and higher molecular weight urea condensation products by contacting such solutions with the hydroxide ion form of an anion exchanger and extracting biuret from t... | 02/24/1987 |
| 4645860 | Biuret manufacture Methods are provided for recovering biuret from aqueous urea solutions and for producing relatively concentrated biuret-containing extracts which involve contacting a biuret-containing aqueous urea solution with the hydroxide ion form of an anion exchange... | 02/24/1987 |
| 4616094 | Isolation of liquid urea from the off-gas of the synthesis of melamine A process for isolating liquid urea and its thermal decomposition products from the off-gas of melamine synthesis, which gas has been freed from melamine by fractional condensation and then been washed with molten urea, wherein the off-gas, containing 2-1... | 10/07/1986 |
| 4613696 | Process for urea production A process for the production of urea from ammonia and carbon dioxide via synthesis where the urea formation takes place in a synthesis zone (or zones) in which an excess of free ammonia is kept to favor high conversions, said synthesis zone (or zones) bei... | 09/23/1986 |
| 4613697 | Process for the displacement to the gaseous phase of the excess of NH3 A process for the displacement to the gaseous phase, at 80-250 Kg/cm2, of the excess NH3 contained in an aqueous urea solution, coming, at 150°-230° C., from a former stripping, isobaric with the urea synthesis, and containing also... | 09/23/1986 |
