• 专利附录
  • 专利说明
  • 权利要求
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  • 同族专利
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  • 法律状态
  • 优先权
    • 专利摘要:
    An improved process for the preparation of urea from carbon dioxide and ammonia at elevated temperature and pressure whereby unconverted ammonia, substantially free of carbon dioxide and water is recovered from a urea and ammonium carbamate containing liquid process stream. An urea and ammonium carbamate containing process stream is expanded to a pressure of between about 1 and 25 kg/cm2 absolute and heated, thereby decomposing ammonium carbamate and forming a gas mixture containing ammonia, carbon dioxide and water vapor. The improvement comprises the steps of (a) introducing this gas mixture into a carbon dioxide separation column along with sufficient diluting water to form a first residual liquid phase, containing ammonia, carbon dioxide and from about 65 to 96 percent by weight water, in the bottom of such column, and separately removing therefrom an off-gas of carbon dioxide substantially free of ammonia, and the first residual liquid phase; (b) introducing this first residual liquid phase into a desorption column wherefrom a second off-gas containing ammonia, carbon dioxide and water vapor, is removed; (c) introducing the second off-gas into an ammonia separation column and separately removing therefrom a third off-gas of ammonia substantially free of carbon dioxide and water vapor, and a liquid phase containing ammonia, carbon dioxide and water; and (d) recycling the third gas phase back to the urea synthesis zone. The carbon dioxide separation column, desorption column and ammonia separation column are all operated at substantially the same pressure of between about 1 and 25 kg/cm2 absolute.
    公开号:SU1153825A3
    申请号:SU772539550
    申请日:1977-11-03
    公开日:1985-04-30
    发明作者:Йоханнес Бирманс Андреас；Йонкерс Кес
    申请人:Уни Ван Кунстместфабрикен Б.В. (Фирма)；
    IPC主号:
    专利说明:

    d11 The invention relates to methods for producing urea. A known method of producing urea by reacting NH j and COg at elevated temperature and pressure to form urea in the synthesis zone as a solution: treatment of this urea solution in the first decomposition zone, at which the elevated temperature is maintained, where the gaseous mixture NHj, COj and separates from the solution, treatment of the remaining urea solution containing residual NHj, CO and carbamate in the second decomposition zone, at which elevated temperature and pressure are maintained, which is lower than the pressure in the first zone and where carbam ammonium decomposed and separated gas mixture is NH, and C02 and is obtained as a product a urea solution almost free of the one carbamyl ft. The disadvantage of returning unconverted NHi and CO-in the form of a solution is that water has a detrimental effect on the conversion of carbamate to urea, so the carbamate should be decomposed more and you need to spend more steam for the heat of conversion. There is also a way that the section W and COg in exhausted gas mixtures by selective absorption of C02, for example, with a solution of monoethanolamine. 12 The disadvantage of this method is that. that the absorbed CQ must be removed again from the absorbing agent by heating. The closest to the proposed technical essence is the method of urea recovery by reacting ammonia and carbon dioxide at 180-190 ° C and pressure 130-140 kg / 2 / cm, o6pia6oTKH in the first zone of decomposition of the resulting reaction mass with gaseous carbon dioxide supplied countercurrent) com at 1402 5 ° C and a pressure equal to the synthesis pressure to produce a gaseous mixture of ammonia, carbon dioxide and water vapor, which recycle the synthesis stage, and the subsequent processing leaves the reaction mixture in the second decomposition zone and a pressure of 2.5-5 kg / cm. Absorption of gaseous mixture of W and SOU with 5 Or water mixed with water or an aqueous solution and removal of free from this solution at atmospheric pressure by distillation is carried out followed by the separation of CO2 in a separation column at a pressure of 5-20 atmospheres, although with such methods, NHj and CO are obtained separately, so that they can be recycled without water and with the help of Compressors fsj. The disadvantage of this method is high energy costs, since it is necessary first to expand the gas mixture to atmospheric pressure, and after NHJ is distilled off, the remaining solution should be brought to a pressure of 3 to 20 atmospheres. If the solution remaining after removing COj is used again to absorb the fresh gas mixture, it must again be expanded to atmospheric pressure. In addition, NH is supplied at atmospheric pressure and returning it to the synthesis of urea requires a further expenditure of energy. The purpose of the invention is to squash energy costs. I. The goal is achieved in that According to the method of producing urea by reacting ammonia and carbon dioxide at 180-190 ° C and pressure T30-J40 kg / cm, processing the resulting reaction mass in the first zone of decomposition with gaseous carbon dioxide supplied by countercurrent at 140-215 C and pressure equal to the pressure of synthesis, thereby obtaining a gaseous mixture of ammonia, carbon dioxide and water vapor, which is reclaimed at the synthesis stage, and the subsequent treatment of the remaining reaction mixture in the second decomposition zone under pressure At 2.5–5 kg / cm. With the formation of a gaseous mixture of ammonia, carbon dioxide and water vapor and a solution of urea, the gaseous mixture obtained in the second decomposition zone is treated in a separation column at a pressure of 2.3 kg / cm temperature in the lower part and in the upper part of 40 ° C water introduced along the column, to obtain an aqueous solution of III (1mioka and carbon dioxide containing 90% water, and a gas stream of carbon dioxide followed by ammonia and carbon dioxide from the aqueous solution with an acute vapor at a pressure of 2 , 3 kg / cm- from the floor HAND aqueous stream containing no gas, and secondary gas stream comprising ammonia, the residual amount of carbon dioxide and water vapor, and the subsequent processing of the secondary gas stream under a pressure of 2.5 kgUsm water to produce a gas stream containing ammonia.
    The method allows the decomposition of carbamate and the recycling of NHj C02 without unnecessary energy expenditure with cost savings and includes a combination of processing steps for a mixture of NHj, COj and H20 obtained by decomposing ammonium carbamate, which COj and U are separated. specified conditions.
    The drawing shows the implementation of the proposed method.
    In the urea synthesis zone 1, a urea solution is formed under a pressure of 130-140 kg / cm at. This solution is fed through line 2 to the stripper column 3, which operates under synthesis pressure and is connected countercurrently (when heat is applied) to fresh CO supplied through line 4. A gas mixture of the state from and H – O goes through line 5 to condenser 6, which works 1r1 is preferable. At synthesis pressure and into which iodine is the amount of solution formed in the lower part of reactor 1 through pipelines 7 and 8 using ejector 9 to increase the condensation temperature, so that high temperature. With this heat, steam is obtained with a pressure of 1-6 kg / cm, which can be used elsewhere in the process. The ejector operates using NHj, which is supplied by pump 10 from reservoir 11. Fresh NHj is fed through line 12. Condensate {1 6: full or partial condensation and absorption of the gas mixture supplied through line 5 The carbamate solution thus formed and the rest (if there is ) the gas mixture is sent to the urea reactor 1. through line 13, along with the carbamate solution formed by condensation of NH, COj and from the gas mixture leaving line 14 from the top of the urea reactor 1, and which contains inert components coming from air CO, NH- and possibly air or oxygen used to passivate equipment and pipelines. This condensation takes place in the purge gas condenser 15, which is connected to the pipeline 13 or to the lower part of the urea reactor 1 by a pipe 16. The gas mixture not condensed in the purge condenser can be directed through a pipeline 17 to an absorber (not shown) operating at low pressure to extract the NH that is still present. However, it is also possible to feed the solution obtained in the purge gas condenser to the condenser 6 through the ejector 9.
    The distilled urea solution from the stripping column after expansion to a pressure of 2-5 kg / cm in the reduction valve 18 enters via line 19 into the carbamate decomposition apparatus 20, in which the carbamate present is almost completely decomposed by heating. The gas mixture leaving the heating zone of the apparatus 20 together with the urea solution is separated from the solution in the separator 21 and then enters the separation unit NHj, COj and H20. The aqueous solution of urea produced in the separator 21 of the apparatus 20 is expanded in the expander 22 to atmospheric pressure, where some more dissolved H and water vapor released through the line 23 is released. Through the pipeline 24 the aqueous solution of urea goes to section 25, wherein it is already concentrated by evaporation in a known manner or crystallizes or can be processed in another known manner. The final product goes
    through exit 26.
    one,
    The gas mixture, separated from the urea solution in the separator 21, is directed through line 27 to the separation unit W, COg and H20, which mainly consists of a column 28 for separating CO, a desorption column 29 and a column 30 for separating NH. These columns practically operate at the same pressure of 1–25 kg / cm abs. A particular advantage is obtained if the separation system is operated under a pressure of 1-6 kg / cm abs, as in this case the solution supplied to the desorption column 29 can be distilled off by the steam formed in the condenser 6. The separation system is most efficient. pressure, as in the apparatus for the decomposition of carbamate 20 and in the outlet 21. In the lower part of the column 28, the gas mixture comes into contact with so much water that III and almost completely absorbed or condenses and CO, containing only very little NHJ and HjO, rises into the upperPart of the column. For this, water or a water solution, i.e. process condensate, from section 25 is fed through line 31; further, the aqueous solutions from the subsequent stages are separated and recirculated through lines 32 and 33. In the upper part of the column 28, the rising gas mixture is washed with water supplied through line 34 to remove small amounts of NHj that is still present. This water with absorbed NH is also included in the bottom of the column. The total weight of water supplied to the bottom of the column 28 through lines 31 to 34 is such that the solution coming out from the bottom of the column contains 65-69% by weight of water, i.e. 5 to 20 times the weight of the gas mixture supplied through line 27. As a rule, the optimum water content is 80-95% by weight. therefore, the weight amount of water added is preferably 8 to 15 times the weight of the gas mixture. In this operation, the removal of CO and NHj from the gas mixture separated in separator 21 is carried out with very low total energy consumption in the separation section. Temperature in the lower part of the column from 70190С5 in the upper part of the column, the temperature is maintained at 30 -. From the top of the column, 28 is discharged along line 35 CO, containing only a few percent of water and at the most traces of NHj. This gas is released. Bottom product columns. 28 practically contains all NHj present in the gas mixture supplied via line 27, unseparated COg and water. This solution is sent via line 36 to a desorption column 29, in which almost all of NH and COg is desorbed using, for example, a fine steam supplied by the source. DII 37, The bottom product of the desorption column 29 is water, which now contains such amounts of NH and CO, which lie below
    The operational reliability increases as unreliable carbamate pumps are no longer required. permissible limits for discharge into the environment according to the existing rules, and discharged along line 38, to which line 32 of column 28 is attached to separate CO. Part of the underflow can be sent along line 34 to column 28 as wash water, the remaining part is discharged along line 39 or partially returned to section 25. I The head product of desorption column 29, having a temperature of 105-t75 ° C and in addition to CO and water containing almost all of the NH separated in separator 21, as well as the amount of circulating NHj, is sent to column 30 to separate NH through line 40, through cooler 41 and line 42 and in this column using water supplied through line 43, and liquid ammonia supplied through line 44, CO and in yes removed. The practically pure product thus obtained is sent via line 45 to a cooling unit 46, in which condensation is formed. Liquid NHj then passes through line 47 to a storage tank for NHj. The bottom solution, formed in the NH separation column and consisting of CO and water through line 33, is recycled to the column 28 for the separation of CO2. In the process described, water does not return to the synthesis of urea from the low pressure stage, i.e. parts of the process after the reduction valve 18. As a result, a significantly higher conversion rate in the urea reactor is achieved, so that a solution is obtained containing less carbamate. Since it is necessary to decompose the carbamate less in the stripping column and distilling it better in view of the low water content of the solution, less steam is required for the stripping column. The consumption of steam for the separation of NH is compensated by a decrease in the amount of steam when processing the urea, as the amount of water that must be evaporated is less. Since it is not the solution, but only NHj gas that is recirculated from the low pressure stage, the operation of the entire installation is simplified. Example 1 (quantities given in kmol per hour). NHi is fed to the described urea synthesis unit at 180 and 140 kg / cm pressure through line 12 and 2317 kmol 1143 kmol of production of 1019 kmol urea in aqueous solution is fed through line 4. The pressure in the urea reactor 1, the stripping column.3, the condenser 6 and the purge gas condenser 15-140 kg / cm In the stripping column 3 using fresh CO when heated with steam 2. from the urea solution of the reactor T is distilled off 551.0 km CO2 and 132 kmol .f. The condenser 6, the gaseous mixture coming in through line 5, is partially condensed with the mixture of fresh III-solution fed through line 8 and sucked in from the urea reactor. From the gas-liquid mixture thus formed and the carbamate solution formed in the purge condenser 15, consisting of 497 km NH, 169 km CO2, 33 kmol HjO, is formed. the solution of synthesis in the reactor of urine 1 at an average temperature of 183 C, along with 1061 kmol of urea, contains 2683 kmol NH, 627 kmol C and 119 mol H20. Therefore, CO conversion reaches 62.8%. A solution consisting of 1019 kmol of urea, 225 kmol NHj, 118 kmol of CO and 1019 kmol is produced and. the stripping column 3 is heated to .124 ° C in apparatus 20 for decomposition to Bamate, after expansion to a pressure of 2.5 kg / cm. The gas mixture, consisting of 151 kmol NHj, .98 kmol COj and 159 kmol, is separated in separator 21 from the rest of the urea solution, which in addition to 1019 kmol of urea and 8bO kmol of water still contains 74 kmol NH and 20 kmol COg. Most of the NHg and CO is removed in the expansion tank 22 and thus an aqueous solution of urea is obtained. The gas mixture, separated in separator 21, is fed to the lower part of the separation column 28 for carbon dioxide, in which a pressure of 2.5 kg / cm is maintained, and processes there with condensation from the horse stage of the process, which contains 1117 kmol% 0, 5 , 5 kmol NHj. and 2.25 kmol of CO. In addition, 3,700 kmol H O, containing traces on line 33, 739 kmol kmol NH and 134 kmol CO are fed to column 28 via line 32, and line 34 is fed 157 kmol. Temperatures of solutions fed at 32 and 33 respectively 88 lines and 85 ° C, and the temperature of industrial effluent through line 34. an equal gas mixture leaving the top of column 28 consists of; 143 kmol SOL and 3 kmol The lower solution, having a temperature of 106 ° C and consisting of 5939 kmol H20, 92 kmol CO, 461 kmol., Y, a desorption column 29. A gas mixture from the upper product of the condenser is also fed into this column. 15 purge gas, consisting of 156.5 kmol NH, 39.2 kmol CO / j and 371 kmol, and in the lower part of the desorption column. 29 steam is introduced with a temperature. A portion of the bottom product of this column, which consists of 6972 kmol and traces of NH and COg, is fed through lines 32 and 34 and separation column 28 and the rest partially as washing water - into column 30 through line 43, and the residue is used in process or discharged into the sewer. The gas mixture coming out of the top of the desorption column 29 with a temperature of 110 ° C and consisting of 618 kmol NHj, 134 kmol CC and 709 kmol, after cooling down to chiller 41, is separated in column 30 pu40 ° C. kmol NHg at -15 C and, thus, get 490 kmol of pure NHg. EXAMPLE 2 (quantities are given in 1mol per hour). In the described plant for the synthesis of urea, at a pressure of 130 kg / cm2, line 12 supplies 2317 kmol NH 5 and line 4 yields 1143 kmol CO to obtain 1019 kmol urea in aqueous solution. The pressure in the urea reactor 1, the stripping column 3, the condenser 6 and the purge gas condenser is 15,130 kg / cm In the stripping column 3, fresh CO is distilled off from the urea solution of reactor 1 with steam by removing the urea solution 1, 551 km CO and 132 kmol Hjo. In the condenser 6, the gas mixture coming in through line 5 is partially condensed with a mixture of fresh NH and a solution of urea sucked in from the reactor supplied through line 8. From the gas-liquid mixture thus formed and the carbamate solution formed in the purge condenser 15, consisting of 497 kmol NHj, 169 kmol CO, 33 kmol, a synthesis solution is formed in the urea reactor, 1 at an average temperature of 183 ° C, which, along with 1061 kmol of urea contains 2683 kmol of NH, 627 kml of COj and 119 kmol. Therefore, the conversion of CO / reaches 62.8%. A solution consisting of 10 ml kmol of urea, 225 kmol NHj, 1 T8 kmol COg, 1019 kmol C0, j, and 1019 kmol is discharged from the stripping column 3 heated to the apparatus 20 to decompose the carbamate after expansion to a pressure of 25 kg / cm. The resulting gas mixture, consisting of 151 kmol NHj, 98 kmol CO2 and T59 kmol, is separated in separator 21 from the remaining urea solution, which in addition to 1019 kmol urea and 8.60 kmol water still contains 74 kmol NH and 20 kmol CO. Most of the NHj and CO2 are removed in the expansion tank 22, and thus an aqueous solution of urea is obtained. The gas mixture separated in separator 21 is fed to. the lower part of the separation column 28 for carbon dioxide, in which the pressure is maintained at 2.5 kg / cm, and is processed there with condensate from the final stage of the process, which contains 1117 kmol, 5.5 kmol NHj and 2.25 kmol COj. In addition, 3,700 kmol containing traces of NHj are fed to line 28 via line 32, 739 kmol, 298 kmol NHj and 134 kmol CO are fed through line 33 and 157 kmol is fed through line 34. The temperature of the solutions. supplied and on lines 32 and 33 of ours are 88 and 85s, and the temperature of the wash water ,. feed through line 34 is 40 ° C. The gas mixture leaving the top of the column 28 consists of J43 iCO and 3 kmol H20. The bottom solution, the temperature and contents of 1 2510 5939 kmol, 461 kmol NHj and 92 kmol COg, are fed by a BI desorption column 29. This column also supplies a gas mixture separated from the top product of the purge gas condenser 13, consisting of 156.5 kmol NHj, 39.2 kmol CO2 and 371 kmol, and steam with a temperature of 138 C is introduced into the lower part of the desorption column 29. Part of the bottom product of this column, which consists of 6972 kmol H20 and traces of NHj and COj, Jlodethats along the line 32 and 34 into separation column 28 and the rest partially as washing water into the column 30 through line 43, and the remainder is used, somewhere in the process, or collected in a sewer. The gas mixture leaving the top of the desorption column 29 with a temperature and: consisting of 618 kmol NH, 134 kmol 00 and 709 kmol after cooling to 8 ° C in refrigerator 41, is separated in column 30 by washing 29 kmol at 40c and 170 kmol NH, j when and, thus obtained 490 kmol of pure NHj. Compared to the known method, the operating costs of using the proposed method are about 1 guilder per 1 ton of urea lower, capital investments of between 1 and 1.5 guilder per ton of urea are also lower (calculations are made based on Dutch prices for raw materials and equipment). Other important advantages of the process are as follows: there is no low pressure steam discharge; there is no return of water from the low pressure decomposition unit to the synthesis reactor; Carbamate feed pumps (and accessories) with complex pipelines are no longer required; . The amount of wastewater that is known in the known process is about 1.35 mol per t mol of urea, and is reduced to about 1 mol per 1 mol of blasting.
    权利要求:
    Claims (1)
    [1]
    METHOD FOR PRODUCING UREA by reacting ammonia and carbon dioxide at 180-190 ° С and a pressure of 130-140 kg / cm 2 , treating the reaction mixture in the first zone with gaseous carbon dioxide supplied by countercurrent at a temperature of 140 - 215 ° С and pressure, equal to the synthesis pressure, thereby obtaining a gaseous mixture of ammonia, carbon dioxide and leading of steam which is recycled to the synthesis step and the subsequent processing of the remaining reaction mixture in the second decomposition zone at a pressure of 2.5-5 kg / cm2 to form a gas different mixtures of ammonia, carbon dioxide and water vapor and a urea solution, characterized in that, in order to reduce energy costs, the gaseous mixture obtained in the second decomposition zone is treated in a separation column at a pressure of 2.5 kg / cm at the bottom of 106 ° C and in the upper part 40 ° C with water introduced along the column until an aqueous solution of am- '§ ammonia and carbon dioxide containing 90% water and a gas stream of carbon dioxide, followed by desorption of ammonia and carbon dioxide from the aqueous solution with rum at a pressure of 2.5 kg / cm ^ to obtain an aqueous stream containing no gas, and secondary gas stream comprising ammonia, the residual amount of carbon dioxide and water vapor, and subsequent treatment with a secondary, r gas stream at a pressure of 2.5 kg / a vent to produce a gas stream containing ammonia.
    1 1153825
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    同族专利:
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    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    US1782723A|1926-03-02|1930-11-25|Arthur B Lamb|Manufacture of urea|
    US3107149A|1961-05-12|1963-10-15|Chem Processes Inc|Method of separating ammonia from carbon dioxide|
    NL168506C|1970-12-31|1982-04-16|Stamicarbon|METHOD FOR THE PREPARATION OF UREA.|NL8101174A|1981-03-11|1982-10-01|Unie Van Kunstmestfab Bv|METHOD FOR THE PREPARATION OF UREA.|
    NL8104040A|1981-09-01|1983-04-05|Unie Van Kunstmestfab Bv|METHOD FOR THE PREPARATION OF UREA.|
    NL8201652A|1982-04-21|1983-11-16|Unie Van Kunstmestfab Bv|METHOD FOR THE PREPARATION OF UREA.|
    NL8303888A|1983-11-13|1985-06-03|Unie Van Kunstmestfab Bv|METHOD FOR THE PREPARATION OF UREA.|
    DE102011078749A1|2011-07-06|2013-01-10|Evonik Degussa Gmbh|Process for the preparation of trisilylamine from monochlorosilane and ammonia|
    WO2016153354A1|2015-03-25|2016-09-29|Stamicarbon B.V.|Integrated production of urea for diesel exhaust fluid and urea ammonium nitrate|
    法律状态:
    优先权:
    申请号 | 申请日 | 专利标题
    NL7612162A|NL7612162A|1976-11-03|1976-11-03|PROCESS FOR PREPARING A UREA SOLUTION FROM NH3 AND CO2.|
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