SU1142444A1 - Method of obtaining calcium cyanamide - Google Patents

Abstract

A method for producing calcium cyanamide, including heating urea and a calcium-containing substance at 140-400 ° C, then calcining the resulting product in a nitrogen atmosphere, so that, in order to ensure continuity of the process and increase its performance, heating is first carried out at 140230 ° C, the resulting pasty product is granulated, the resulting granules are heated to 300-400 ° C, and then calcined in a known manner.

Description

N3

The invention relates to methods for producing calcium cyanamide, in particular, to the stage of heating the starting materials.

A known method for producing calcium cyanamide from calcium oxide or products containing it and urea at a temperature above 400 ° C, preferably BOO-BOO C, the essence of which is the interaction of calcium oxide with cyanic acid, which is obtained in the gaseous state or by evaporation of urea in a separate unit (device), or at the contact of hardwood-1 of solid or molten urea with calcium oxide at temperatures of 40Ci ° C Simultaneously with the formation of cyanic 1MODE during dissociation of urea Vdtsol ammonia l.

- one of the known methods is a significant nitrogen fixation due to the thermal decomposition of ammonia, which, depending on the conditions, is 20-95%.

The closest in technical essence and the achieved result to the proposed method is the method of obtaining calcium cyanamide, including heating the urea and the calcium-containing substance at 140400 ° C, the subsequent calcination in a nitrogen atmosphere at 2.

However, in the known method, when urea with calcium oxide (hydroxide, carbonate) is heated at temperatures up to 400 ° C, the reaction mass after melting of 1 urea is a mobile suspension, which gradually thickens and turns into a solid monolithic mass. or create an inefficient periodic process. Grinding a highly viscous product at a temperature of 30400-C is a technical problem, the solution of which leads to the creation of complex bulky and poorly-produced apparatus. Moreover, under the conditions of the formation of a solid, inactive product, the heat transfer conditions deteriorate too much, as a result of which the productivity of the apparatus also decreases.

The purpose of the invention is to ensure the continuity of the process and increase its productivity.

The goal is achieved by the fact that according to the method of producing calcium cyanamide, including heating urea and a calcium-containing substance at 140–40 U ° C, the subsequent calcination of the product obtained in nitrogen atmosphere is first heated at 140–230 0, the resulting paste is granulated, the resulting the granules are heated to 300-400 ° C, and then calcined in a known manner.

A distinctive feature of the proposed method is a two-stage heating of the starting materials in the temperature range 140-400 s at first at 140-230 s, the resulting pasty product is garnished and the resulting granules are heated to 300400 ° C and then calcined in nitrogen atmosphere at 700 ° C.

Heating in the first stage is performed at a temperature up to a temperature not exceeding 230 ° C, when the reactive mixture is in a state of mobile suspension, which turns into a pasty product. The latter is granulated, and then the granules are heated at 300-4 OO-s under conditions that prevent agglomeration of the granulate, for example in a fluidized bed.

Under the proposed conditions, the solid highly viscous state no longer occurs in the mass of a substance, but only in each individual particle. This allows heat to be supplied to the reaction mixture under the most optimal conditions for both the liquid and the solid state of the mixture. In addition, the energy consumption for granulation is significantly less than for grinding. All this allows us to create a continuous process for obtaining calcium cyanamide.

Example. Grind and mix thoroughly, prepare; mixture

5 3 mol of urea and 1 mol of oxo or calcium hydroxide. The mixture is placed in 10 test tubes, each heated at one of the temperatures (150, 170, 190, 210, 230 C) and the time is noted for which the reaction mixture in the test tubes retains its fluidity and becomes paste-like. The data are given in the table.

5 At all temperatures during the existence of the suspension, 90% of the initial amount of calcium-containing product in calcium cyanate is bound. Example 2. In the mixer serves

f. at. hour 2-17 kg CO (NK) n 68 kg CaO. The residence time of the reaction mixture at 160 ° C is 100 minutes. The resulting product is sent to an extruder, where at the same temperature and residence time of 20 minutes the pasty product is formed into cylindrical granules and fed to a fluidized bed apparatus. The product obtained in the apparatus at 390 ° C is transferred to the next fluidized bed apparatus, where

0 760 ° С receive 102 kg / h of the finished product with a cyanamyl nitrogen content of 32.4%. Urea consumption 6.57 kg per 1 kg of cyanamide nitrogen,

Example Used mixer serves

5 urea and calcium oxide in the same quantities as in at least 2, the residence time in the mixer at 11. In the extruder at the same temperature. and a residence time of 1.5 minutes, the product is formed into granules, which are then treated in the same manner as in Example 2, 103 kg / h of product are obtained with a cyanamide nitrogen content of 32.3%. The consumption of urea is 6.52 kg per 1 kg of cyanamide nitrogen. P p li mper 4, I supply to the mixer per hour 217 kg of Ca (NH2) .2 and 68 kg of CaO. The residence time of the reaction mixture in the 45 mic mixer, the HBO-Co temperature. The suspension in the amount of 242 kg / h is sent to the extruder where, at 205 ° C and the residence time of the mine, a paste-forming product B of 230 kg / h is formed, which is molded into granules of cylindrical form and fed into the apparatus boiling, m layer. The product obtained in the apparatus at 390 ° C in the amount of 157 kg / h in the form of granules is poured into the next apparatus with a bale layer where at 760 ° C the finished product is obtained in the amount of 102 kg / h. The content of cyanamide nitrogen in the product is 32.4%, the consumption of urea is 6.57 kg of CO (N1-12) 2 per cyanamide nitrogen. Pr and frost. 217 kg of CO (LZH) and 89 kg of Ca (OH) are fed to the mixer per hour. During the residence time, I react ayy smksk in the mixer at 165 C 45 μK. The resulting suspension in a flask: of 260 kg / h is sent to an extruder, where it remains at the same time; 2 minutes, a pasty product is formed in an amount of 245 kg / h, which (is formed into cylindrical granules and fed into a fluidized bed apparatus. The product obtained in an apparatus at 390 ° C in an amount of 158 kg / h is poured into granules in the following apparatus fluidized bed, where the finished product in an amount of 103 kg / h with a cyanamide nitrogen content of 32.1% is obtained at 760 ° C. Urea consumption is 6, it is kg per 1 kg of cyanamide nitrogen, the production of calcium cyanamide according to the proposed method is It is carried out in a continuous manner without nitrogen depletion, n and maximal-but favorable conditions for heat transfer as the liquid and to solid reactants and produk-tam.

Cao

150 0-9090-120

Sa (OH).

0-100 100-130

Claims (1)

'METHOD FOR PRODUCING CALCIUM CYANAMIDE, including heating of urea and a calcium-containing substance at 140-400 ° С, subsequent calcination of the obtained product in a nitrogen atmosphere, with a rain and the fact that, in order to ensure the continuity of the process and increase it productivity, heating is first carried out at 140230 ° C, the resulting pasty product is granulated, the obtained granules are heated to 300-400 ° C, and then calcined in a known manner.