Urea solution concentration in method of urea synthesis

FIELD: chemistry.

SUBSTANCE: urea-containing solution (13) is produced in the section (10) of synthesis, the solution is purified in the section (14) of extraction, and an aqueous solution (15) containing mostly urea and water, which is produced from the above-mentioned section of the extraction is subjected to the concentration process. Herewith the concentration process includes a separation step through an elective membrane.

EFFECT: improvement of the current urea production process.

9 cl, 1 dwg

 



 

Same patents:

FIELD: process engineering.

SUBSTANCE: invention relates to production of urea solutions suitable for selective catalytic reduction of nitrogen oxides, namely, for their removal. Water flow containing urea produced at extraction section is subjected to evaporation to separate steam flow bearing water and ammonia and, hence, to produce concentrated solution not containing, in fact, said ammonia. Said solution is diluted to obtain solution with urea concentration suitable for use in selective catalytic reduction. Propose plant comprises synthesis section for conversion of ammonia and carbon dioxide into first water flow containing urea, ammonia urethane and unreacted free ammonia, extraction section to dissociate urethane and circulate ammonia and carbon dioxide to synthesis section so that second water flow containing urea, water and residual ammonia are produced. Said plant comprises extra section to convert a portion of second flow into solution with low urea concentration. Note here that said second section includes evaporator and mixer.

EFFECT: efficient production.

12 cl, 3 dwg, 1 ex

FIELD: process engineering.

SUBSTANCE: invention relates to extraction of ammonia contained in gaseous purge flow produced in urea synthesis. Proposed method comprises the following stages: a) flushing of gaseous purge flow by aqueous acid solution at pH 1-6 to produce first cleaned gas flow and aqueous solution bearing ammonium salt. b) stripping of aqueous solution with ammonium salt fed from stage (a) after treatment by strong base representing an ionic hydroxide with high solubility in water at 50-250C and 0.1-4 MPa to produce second gas flow including NH3, H2O and, possibly, CO2, and solution containing cation salt of said strong base; c) treatment of solution containing cation salt of strong base fed from stage (b) by membrane electrochemical process with formation of aqueous solution of acid used at stage (a), aqueous solution of base used at stage (b) and, possibly, diluted aqueous solution of cation salt of strong base. d) recycling said aqueous solutions of acid and base to stage (a) and stage (b) and recycling said second gas flow from stage (b) to urea synthesis process.

EFFECT: higher degree of ammonium extraction.

29 cl, 1 dwg, 1 ex

FIELD: chemistry.

SUBSTANCE: method involves crystallising carbamide and drying. Aqueous solution of carbamide is pre-heated to temperature of +30C to +130C and then subjected to electrodialysis treatment at voltage of 400 V - 600 V.

EFFECT: obtaining high-purity crystalline carbamide, which enables use thereof as an additive in the food industry and as a reagent in laboratory analyses.

2 cl, 1 dwg, 2 tbl

FIELD: chemistry.

SUBSTANCE: invention relates to a method of producing an aqueous solution containing urea, meant for use when removing nitrogen oxides from gaseous combustion products and flue gases. The method involves steps for: using carbon dioxide to wash at least a portion of concentrated aqueous urea solution obtained directly from or downstream the urea extraction section of an apparatus for producing urea and containing residual free ammonia, to obtain a first vapour phase containing carbon dioxide and possibly ammonia and concentrated aqueous urea solution containing carbamate and essentially not containing free ammonia, and dilution of said concentrated aqueous urea solution containing carbamate and essentially not containing free ammonia with water until the required urea concentration in the aqueous solution is achieved. Also disclosed is an apparatus for producing an aqueous solution containing urea (versions) and a method of modernising existing apparatus for producing urea (versions).

EFFECT: invention significantly reduces power consumption.

21 c, 2 dwg

FIELD: chemistry.

SUBSTANCE: invention relates to obtaining urea from ammonia and carbon dioxide. As a result of ammonia and carbon dioxide interaction at high pressure in reactor obtained is water solution, which contains urea, ammonium carbamate and ammonia. From obtained water solution carbamate and ammonia are separated by decomposing carbamate and thermal evaporation of ammonia and carbon dioxide in stripping apparatus, obtaining ammonia and carbon dioxide, which after that are again condensed in condenser obtaining carbamate, which is returned to reactor. All stages together with reaction of synthesis are carried out in fact at one and the same pressure. In addition, into reactor additionally supplied is passivating oxygen, obtained as a result of interaction waste gases, which contain carbon dioxide, ammonia and passivating oxygen which did not take part in the reaction, are removed from reactor and are supplied into bottom part of stripping apparatus for passivation of at least part of its internal surfaces. Installation for obtaining urea contains communicating with each other and forming closed high pressure contour reactor, stripping apparatus, condenser, section of final urea purification and pipelines for supply into reactor of carbon dioxide and ammonia. It is equipped with pipeline for supply into reactor of passivating oxygen and pipeline for connecting upper part of reactor with bottom part of stripping apparatus.

EFFECT: ensuring even and efficient passivation of all apparatuses of high pressure contour.

13 cl, 2 dwg

FIELD: chemistry.

SUBSTANCE: invention relates to production of urea from ammonia and carbon dioxide. A reaction mixture is obtained in a synthesis reactor at given high pressure as a result of a reaction between NH3 and CO2, where the said reaction mixture contains urea, ammonium carbamate and free ammonia in aqueous solution, from which ammonium carbamate and ammonia are extracted and subsequently returned to the synthesis reactor. Ammonium carbamate and ammonia are extracted from the reaction mixture on process steps for decomposing ammonium carbamate to NH3 and CO2 and their stripping and on the next process step for their re-condensation to obtain ammonium carbamate which is returned to the synthesis reactor. The reaction mixture obtained as a result of the reaction between ammonia and carbon dioxide is taken to the process steps for decomposition and stripping using a pump.

EFFECT: changing production capacity by changing pump parameters, possibility of horizontal assembling, reduced expenses on servicing and increased safety.

12 cl, 2 dwg

FIELD: chemistry.

SUBSTANCE: invention relates to a method of producing1,1-1,6-hexamethylene-3,3,3',3'-tetrakis(2-oxyethyl)-bis-urea, which can be used in medicine. The method involves reacting 1,6-hexamethylene diisocyanate with diethanolamine in an aqueous medium, where diethanolamine is taken in stoichiometric amount ranging from 1.001 to 1.01 and after synthesis, excess diethanolamine is removed on a cation exchange resin, which is added to the reaction mixture in amount ranging from 5 to 10% of the mass of initial components while stirring until pH of the reaction mixture falls to a value ranging from 7.0 to 7.2.

EFFECT: simplification of the method and increased output of the end product.

1 cl, 3 ex, 1 tbl

FIELD: equipment of synthesis stage of process for producing urea from ammonia and carbon dioxide.

SUBSTANCE: apparatus includes high-pressure section operating practically at the same pressure values of synthesis reactor and condenser arranged inside said reactor. Condenser includes large number of flat plate like practically rectangular heat exchangers whose long sides are parallel to reactor axis. Each heat exchanger is made of two placed one onto other metallic sheets mutually joined by welding along their perimeter and forming inside heat exchanger preset-width cavity between them. Sheets from which heat exchangers are made are mutually joined by spot welding and they define in cavity of heat exchangers wavy path for fluid flowing. Said path includes mutually connected portions communicated through branch pipes for inlet of flowing heat transfer agent to heat exchangers and outlet of said agent from it. Preferable ducts for distributing flowing heat transfer agent fed to heat exchanger and for collecting outlet heat transfer agent are formed by means of tubes arranged in inner cavity of heat exchanger and secured to its mutually opposite long sides. At least one heat exchanger has internal partition passing from its one side to other opposite side and spaced from said opposite side by some distance for forming in cavity of heat exchanger U-shaped path for flowing heat transfer agent. Said path has descending and raising portions communicated with respective branch pipes passing outside from heat exchanger. Portions of U-shaped path have smoothly increased cross section area.

EFFECT: simplified design of zone for synthesis and condensation of reaction mixture for producing urea at improved efficiency of the whole process.

15 cl, 7 dwg

FIELD: chemical industry; methods and devices for production of carbamide solution.

SUBSTANCE: the invention is pertaining to chemical industry, in particular, to the method and the installation for preparation of the carbamide solution applied as the agent for purification of nitrogen oxides from the exhaust gases of the combustion engines. The method of preparation of the carbamide solution provides for the dilution with the desalted water up to the necessary solution strength of the carbamide formed in its production process, desorption of the dissolved gases from the solution at its air blasting and the subsequent absorption of the impurities from the air by the solid adsorbent. If necessary the solution may be added with the agent to lower its freezing temperature. The installation for realization of the method consists of: the container of the source solution of the carbamide, the apparatus with the stirring device, the desorber, the adsorber, the means for feeding of the carbamide solution from the container of the source solution of carbamide into the apparatus with the stirring device, the means for feeding of the desalted water into the apparatus with the stirring device, the means for feeding of the carbamide solution from the apparatus with the stirring device into the desorber, the means for feeding of the air from the desorber into the adsorber, a means for feeding of the air into the desorber, the means for feeding of the air from the desorber into the adsorber. The technical result of the invention is development of the method and creation of the installation for preparation of the carbamide solution meeting the specification requirements for purification of nitrogen oxides from the exhaust gases of the combustion engines.

EFFECT: the invention ensures development of the method and creation of the installation for preparation of the carbamide solution meeting the specification requirements for purification of nitrogen oxides from the exhaust gases of the combustion engines.

4 cl, 1 dwg

The invention relates to improvements in the technology of production of urea from ammonia and carbon dioxide

FIELD: chemistry.

SUBSTANCE: invention relates to method of ecologically pure obtaining urea (CO(NH2)2) from wastes of any composition. Method includes the following stages: a) obtaining synthesis-gas, which contains CO, CO2 and H2, by high-temperature processing of wastes in reactor in presence of oxygen O2, obtained by the process of cryogenic air separation; b) conversion of CO, contained in synthesis-gas, with application of H2O, into CO2+H2 (shift reaction) and separation of CO2 from H2; c) conversion of H2, obtained at stage (b) with application of N2, obtained from the process of cryogenic air separation at stage (a), with obtaining ammonia (NH3), and d) conversion of NH3 from stage (c), with application of CO2 from stage (b) with obtaining urea (CO(NH2)2).

EFFECT: invention makes it possible to obtain urea by economical way without air-polluting gaseous emissions.

1 dwg

FIELD: chemistry.

SUBSTANCE: invention relates to a method of producing carbamide from ammonia and carbon dioxide at high temperature and pressure, molar ratio NH3:CO2=(3.4-3.7):1. The method is carried out in a carbamide synthesis reactor from which gases and a carbamide synthesis liquid melt are separately output, followed by separation of excess ammonia from the carbamide synthesis melt at pressure of 9-12 MPa, two-step distillation of the melt, condensation of distillation gases to form recyclable ammonium carbonate solutions. Distillation at the first step is carried out at pressure of 9-12 MPa in a current of carbon dioxide. After distillation, the melt is fed into the second distillation step, which is carried out at low pressure. Gases from the first distillation step are condensed in two successive areas at pressure of the first distillation step into which gases output from the synthesis reactor and excess ammonia from the separation step are also fed. In the first area, condensation is carried out while feeding a portion of the ammonium carbonate solution obtained from condensation of gases from the second distillation step, and the condensed vapour is cooled by a condensate which boils at excess pressure to obtain vapour. In the second condensation area of distillation gases from the first step, the condensed vapour is cooled by recycled water and uncondensed gases at the same pressure are washed by the other portion of the ammonium carbonate solution obtained during condensation of distillation gases from the second step. The formed ammonium carbonate solution is fed into the second condensation area and the ammonium carbonate solution coming out of the second condensation area is fed into the reactor. Distillation at the first step is carried out in a current of carbon dioxide which is used in amount of 35-40% of the total amount thereof fed into the process; 75-85% of gases separated at the separation step are fed into the first condensation area for distillation gases from the first step, and the remaining amount of gases separated at the separation step, along with gases output from the synthesis reactor, is fed into the second condensation area for distillation gases from the first step.

EFFECT: producing vapour with parameters which enable use thereof in the next steps of the carbamide synthesis process in the first condensation area of gases from the first distillation step.

1 dwg, 1 tbl, 2 ex

FIELD: oil and gas industry.

SUBSTANCE: invention can be used for production of fertilisers and mixed fuels of idle natural gas. The method for carbamide production includes extraction of idle natural gas, its mixing, removal of moisture and potential destructive substances, reforming, recovery of CO2 flow from natural reformed gas, combination of the recovered CO2 flow with ammonia flow and extraction of carbamide. The system for carbamide production includes a purification module, a reforming module, a conversion module, modules for production of ammonia and carbamide, at that one of the modules is transferrable.

EFFECT: invention allows optimisation of production process, simplification of design, reduction of time for carbamide production as well as operation of the system at well locations.

19 cl, 7 dwg, 1 tbl

FIELD: chemistry.

SUBSTANCE: invention relates to method of obtaining urea. Method includes reaction of ammonia and carbon dioxide in high pressure contour (1), which includes at least synthesis reactor (2, 200), section (3) of thermal steaming and section (4) of carbamate condensation. Urea solution (9), obtained in interaction of ammonia and carbon dioxide, is subjected to adiabatic steaming in section (10) of adiabatic steaming with supply (11) of carbon dioxide as means for steaming, with obtaining liquid urea solution (12) and vapour phase (13), which contains ammonia and carbon dioxide. Urea solution (12), obtained in the process of adiabatic steaming, is additionally subjected to thermal steaming in section (3) of thermal steaming and is returned to vapour phase (13) in reaction zone in synthesis reactor for recycling. Section of thermal steaming includes device for self-steaming without addition of some means for steaming or includes device for steaming with carbon dioxide, in which as means for steaming applied is carbon dioxide, and line (5) for carbon dioxide supply is divided into first section (11), directed into section (10) of adiabatic steaming, second section (8), directed into reactor (2), and third section (16), directed into section (3) of thermal steaming; on first section (11) supplied is amount o carbon dioxide, constituting 20-60% of total initial quantity. Also claimed are installation for urea obtaining and method of its modernisation.

EFFECT: invention makes it possible to increase reaction output, ensure higher productive capacity and reduce energy consumption.

9 cl, 4 dwg

FIELD: chemistry.

SUBSTANCE: method includes steps of cleaning starting biomass material in order to remove all inorganic substances, mixing the cleaned starting biomass material to obtain a homogeneous mixture, granulating the mixed starting biomass material to obtain granules with a primarily homogeneous size, crushing the granules to particle size of 1 mm or smaller, gasifying the crushed granules in a gas generator, compressing a CO2 stream to pressure of not less than about 6000 ft/in2 and not greater than about 7000 ft/in2, feeding a stream of NH3 into a by-pass recycling system with a 30% conversion factor and pressure of not less than about 6000 ft/in2 and not greater than about 7000 ft/in2, and merging the compressed CO2 stream with the compressed NH3 stream.

EFFECT: invention enables to carry out cost-effective, small-scale production of urea, based on a modular principle in order to improve process control and mobility, providing pure and homogeneous biomass starting material.

11 cl, 9 dwg

FIELD: chemistry.

SUBSTANCE: method involves reacting carbon dioxide and ammonia which is fed in excess, in a synthesis zone at high temperature and pressure to form a carbamide synthesis solution containing carbamide, water, ammonium carbamate, ammonia and carbon dioxide, distilling said solution while supplying heat at multiple pressure steps, including distillation at 1.5-2.5 MPa and 0.2-0.5 MPa, to form aqueous carbamide solution and distillation gases. Further, the distillation gases are condensed/absorbed while cooling, using aqueous absorbents and forming aqueous solutions of ammonium carbon salts, recycling the aqueous solution of ammonium carbon salts from the distillation gas condensation/absorption step at lower pressure to the distillation gas condensation/absorption step at higher pressure and then into the synthesis zone, evaporating the aqueous carbamide solution and further treatment thereof with known methods. The solution stream from the synthesis zone, before feeding to the distillation step at 1.5-2.5 MPa, is subjected to adiabatic separation at pressure of 8-12 MPa, followed by distillation at the same pressure in a current of carbon dioxide which is used in amount of 40-60% of the total amount fed into the process. Condensation/absorption of the separated gases, as well as a portion of adiabatic separation gases, is carried out at the same pressure in contact with the aqueous solution of ammonium carbon salts obtained during condensation/absorption of distillation gases at pressure of 1.5-2.5 MPa and cooling a condensate which boils under excess pressure to form a vapour, condensation/absorption at pressure of 1.5-2.5 MPa of the remaining portion of adiabatic separation gases at pressure of 8-12 MPa together with distillation gases at pressure of 1.5-2.5 MPa. The solution of ammonium carbon salts obtained from condensation/absorption at pressure of 8-12 MPa is recycled into the synthesis zone.

EFFECT: high degree of converting starting reactants in the synthesis zone.

3 cl, 3 dwg, 1 tbl, 5 ex

FIELD: agriculture.

SUBSTANCE: liquid ammonia and carbon dioxide are fed to a synthesis section (100) and exposed to a reaction in it in order to produce urea. At the same time the synthesis section comprises at least a reactor, a steaming device and a capacitor, which form a high-pressure circuit, and at least some carbon dioxide is sent to the synthesis section (100) in the liquid phase. Also a plant is proposed for production of urea, as well as a method to increase urea production plant efficiency.

EFFECT: increased energy efficiency of urea production method.

13 cl, 7 dwg

FIELD: chemistry.

SUBSTANCE: invention relates to a method of modernising a urea production apparatus (1) which employs a self-stripping process. The apparatus has high pressure loop which includes at least one synthesis reactor (5) in which ammonia (18) and carbon dioxide (15) are fed as raw material, a stripping section which includes at least thermal stripping column (7), a condensation section which includes at least one carbamate condenser (6) and medium and high pressure equipment for separating carbamate and ammonia. A feed line (18a) is also provided, through which initial carbon dioxide in amount of 20-50% of the entire stream is fed into the stripping section for use as a stripping agent. A urea synthesis apparatus and a urea synthesis method are also disclosed.

EFFECT: invention enables to modernise a urea production apparatus using a cheaper method.

12 cl, 2 dwg

FIELD: chemistry.

SUBSTANCE: invention relates to an improved method for synthesis of urea from ammonia and carbon dioxide at high pressure and temperature with formation of ammonium carbamate as an intermediate product. The method includes a high pressure synthesis section comprising at least one step for separating unreacted ammonium carbamate from ammonia via stripping decomposition, carried out in a vertical apparatus which is a stripping column. Said step also involves feeding a CO2 stream, heated to temperature 130-230C, into the bottom part of said stripping column, in amount of 1-15 wt % with respect to total weight of fresh CO2, containing a passivating agent, fed into the process. The amount of this agent is such that its equivalent O2 content in moles ranges from 0.05 to 0.8% with respect to the number of moles of CO2 in said stream. Fresh CO2 is compressed in a multiple-stage compressor having intermediate heat-exchange stages. Apparatus for realising the improved urea synthesis method is also provided. The invention enables to optimise the urea synthesis process.

EFFECT: invention enables to optimise the urea synthesis process.

21 cl, 3 dwg, 3 ex

FIELD: chemistry.

SUBSTANCE: invention relates to a method of modernising a urea production plant (1). The plant includes: a reactor (2) for urea synthesis, means (7, 8) for feeding ammonia and carbon dioxide into said reactor (2) for urea synthesis, an apparatus (3) for desorption with carbon dioxide for treating the reaction mixture from the reactor (2) and containing urea, carbamate and free ammonia in aqueous solution, with partial decomposition of carbamate and partial separation of free ammonia, thus obtaining a stream containing ammonia and carbon dioxide in vapour phase and a stream containing urea and residual carbamate in aqueous solution, a urea extraction section for treating the stream coming out of the desorption apparatus (3) and containing urea and residual carbamate in aqueous solution for separating urea from residual carbamate in aqueous solution, at least one at least one vertical film condensation apparatus (4) for partial condensation of the stream coming out of the desorption apparatus (3) and containing ammonia and carbon dioxide in vapour phase, thus obtaining a liquid stream containing carbamate in aqueous solution and a gaseous stream containing ammonia and carbon dioxide in vapour phase, means (15, 14) for respectively feeding the stream containing carbamate in aqueous solution and the gaseous stream containing ammonia and carbon dioxide in vapour phase into said reactor (2) for urea synthesis. Said at least one condensation apparatus (4) is provided with means for essentially full condensation of at least a portion of the stream coming out of the desorption apparatus (3) and containing ammonia and carbon dioxide in vapour phase to obtain a stream containing urea and carbamate in aqueous solution. The method involves the following stages: providing second desorption apparatus (47), providing means (9) for feeding a first portion of the stream of reaction mixture coming out of the reactor (2) and containing urea, carbamate and free ammonia in aqueous solution into said desorption apparatus (3), providing means (48) for feeding a second portion of the stream of reaction mixture coming out the reactor (2) and containing urea, carbamate and free ammonia in aqueous solution into said second desorption apparatus (47), and providing means (49) for feeding at least a portion of the stream coming out of said second desorption apparatus (47) and containing ammonia and carbon dioxide in vapour phase directly into the synthesis reactor (2). A method of producing urea and a urea production plant are also disclosed.

EFFECT: invention ensures high output of the product with low power consumption.

12 cl, 2 ex, 2 dwg

The invention relates to an improved catalytic method for the ammoxidation of lower paraffins to obtain unsaturated mononitriles, such as Acrylonitrile and Methacrylonitrile
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