SU1293172A1 - Method of producing granulated carbamide - Google Patents

Abstract

The invention relates to carboxylic acid amides, in particular the preparation of granular urea (CA). An increase in the strength of the granules is achieved by using boiling water for cooling. The acquisition of spacecraft is carried out by supercooling the melt to a temperature of 1 9-129 ° C by heat exchange through the wall using boiling followed by spraying of the melt in air. The method provides the strength of the granules, it is 540-840 HG / granules versus 450 HG / granules in the known method, while the content of large granules in the product remains at the level of the known method. 1 tab.

Description

one

The invention relates to the synthesis of urea, in particular, to an improved method for the preparation of urea in the form of granules.

The purpose of the invention is to increase the strength of the granules by using cooling water at its boiling point.

It was found that cooling the melt with boiling water with water makes it possible to obtain stronger granules during its subsequent granulation than when it is cooled by a known method — ordinary cooling (circulating) water with a temperature of 30-40 s. In this case, a higher strength of the granules is achieved in the proposed method at the same final supercooling temperatures as in the known method.

When the melt is supercooled by heat exchange with relatively cold water (for example, up to 60 ° C) during the supercooling process, only the physical heat of the melt can be removed without removing at least part of the heat of crystallization. This is consistent with the description of the known method. An attempt to divert part of the heat of crystallization leads to disruption of the flow of the system. I

When the melt is supercooling by heat exchange with boiling water (steam condensate), it becomes possible to divert an additional 30–70% of the heat of crystallization without disturbing the flow of the system.

PRI me R 1. 100.2 kg / h of urea melt with a temperature of 133 C are fed to the tubes of a shell-and-tube heat exchanger. Steam condensate with a temperature of 100 ° C is fed to the annular space of the heat exchanger. The melt temperature at the exit of the heat exchanger is 129 C, maintains homogeneity and enters gra. a null torus tube with a height of 37 m, into which air with a temperature of about 20 ° C is supplied in an amount of 12 kg per 1 kg of melt. The strength of the obtained granules, determined in accordance with GOST 2081-75 as the force of destruction of granules with a diameter of 2 mm, is 540 HS / granule.

At the outlet from the annular space of the heat exchanger, the amount of evaporated condensate is measured which is 3.7 kg / h, which

five

31

0 5 0

0 5 0 5

five

722

corresponds to a heat load of 3.7-539.4 1996 kcal / hh 539.4 kkap / kg evaporation heat of water at 100 ° C). The heat of cooling of the melt is 0.51-100.2- (33-129j 204 kcal / h (0.51 kcap / kg. ° C is the heat capacity of molten urea). The degree of heat of crystallization of the melt

 1996 - 204. „,,„, „is -100 31%

(57.8 kcal / kg - heat of crystallization of urea).

PRI mme R 2. The process is carried out analogously to example 1. A carbamide melt (104.7 kg / h) is cooled from 133 to 123 ° C and then granulated. The strength of the granules is 670 HS / granule, the amount of evaporated condensate is 6.6 kg / h, the heat load of the heat exchanger is 3560 kcal / .h, the heat of cooling of the melt is 523 kcal / h, the degree of removal of the heat of crystallization is 50%,

PRI me R 3 (comparative).

The process is carried out analogously to example 1, but with the difference that the melt is cooled by condensate with a temperature of 56 ° C (15 kg / h). The carbamide melt (102 kg / h) is cooled from 133 to 125 ° C, and then granulated. The strength of the granules is 440 g / granule, the condensate temperature at the outlet of the annular space is 84 ° C, the heat load of the heat exchanger is 15.1 (84-56) 420 kcal / h, the heat of cooling of the melt 102 O, 51 (133-125) 416 kcal / h, t . practically these heat are equal,

EXAMPLE 4 The process is carried out analogously to Example 1. A carbamide melt (102.3 kg / h) is cooled from 133 to 119 ° C, and then granulated. The strength of the granules 810 HS / granule. The amount of evaporated condensate is 9.3 kg / h, the heat load of the heat exchanger is 5016 kcal / h, the heat of cooling of the melt is 730 kcal / h, the degree of removal of the heat of crystallization is 72%.

PRI me R 5 (prototype). The process is carried out analogously to example 4. The carbamide melt (103.2 kg / h) is cooled with condensate with a temperature of 38 ° C (15 kg / h) from 133 to 117 ° C, and then granulated. The strength of the granules is 450 gf / granule. Condensate outlet temperature; of

3I293I

annular space 92 ° C, heat load of heat exchanger 15-1 (92-38) 810 kkap / h, heat of cooling of the melt 103.2-O, 51 (133 117) 842 kcal / h, i.e., practically 5 of these heats are equal.

Data on the content of granules are presented in the table.

3 (comparison)

125

50

Compiled by N.Kulikov Editor M. Dylyn Tehred A. Kravchuk Proofreader 0. Lugov.

Order 343/25 Circulation 372Subscription

VNIIPI USSR State Committee

for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5

Production and printing company, Uzhgorod, st. Project, 4

72

4 Continuation of the table

Claims (1)

The proposed method makes it possible to increase the strength of the granules to 540-840 HS / granules versus 450 gf / granules in the known method, while the content of large granules in the product remains at the level of the known method. The formula is invented and .. The method of obtaining granulated carbamide by supercooling the melt to 119-129 C by heat exchange through the wall with cooling water, by spraying the melt in air, characterized in that, in order to improve the strength of the granules, the cooling water is introduced into the heat exchange zone at its boiling point.