EA016901B1 - Method of producing liquid nitrogen fertilizer - Google Patents

Abstract

Invention relates to production of fertilizers and can be used for production of liquid nitrogen fertilizers based on carbamide and ammonium nitrate. A method for production of liquid nitrogen fertilizer comprises mixing solutions of carbamide containing a partially recirculating cooled finished fertilizer with ammonium nitrate solution acidated by nitric acid in an amount depending on the concentration of free ammonia in the initial carbamide solution and deluted by water. According to the invention the stabilization of ratio of predetermined amount of initial components in finished fertilizer is obtained by continuous automatic measurement of actual discharge and density of finished liquid nitrogen fertilizer, density and discharge of initial components of ammonium nitrate, carbamide and water. By the predetermined recovery of finished liquid nitrogen fertilizer and specific discharge of initial components of carbamide and ammonium nitrate to said predetermined amount a mass discharge of initial components is corrected, wherein by the value of their density the initial concentration and volume flow are automatically determined. By measuring electroconductivity of finished liquid nitrogen fertilizer stabilization of ratio of predetermined amount of necessary components in finished product is controlled.

Description

The invention - a method for producing liquid nitrogen fertilizer - relates to the technology of mineral fertilizers and can be used to produce liquid nitrogen fertilizers based on urea and ammonium nitrate.

A known method of producing liquid nitrogen fertilizer with a low ammonia content, including mixing solutions of urea and ammonium nitrate with each other and with water, cooling the mixture and neutralizing excess ammonia with nitric acid to a residual content of fertilizer controlled by the pH value [1].

The disadvantage of this method is the lack of automatic control over the amount of nitric acid added, depending on the ammonia content supplied to the technological scheme for producing UAN with the starting products urea and ammonium nitrate, which ultimately affects the quality (strictly regulated) of the finished fertilizer, which is determined by the content of nitrate carbamide and nitrogen in general.

The closest in aggregate and in technical essence to the proposed method is a method for producing liquid nitrogen fertilizer with a low ammonia content, including mixing the initial solutions of urea and ammonium nitrate, neutralizing the excess ammonia with nitric acid to a residual content controlled by the pH of the fertilizer, and cooling the mixture. Nitric acid is metered into the initial solution of ammonium nitrate depending on the concentration of free ammonia in the initial urea solution, to neutralize which an acidified solution of ammonium nitrate is fed, which is mixed with the initial urea solution, previously combined with a partially recirculated cooled mixture [2].

The disadvantages of the prototype are partial control and automation of the technological process for producing liquid nitrogen fertilizer.

The objective of the invention is to use the relationship of the physicochemical properties of the finished product and the starting components to automate the process of producing liquid nitrogen fertilizer, thereby allowing to intensify the process as a whole.

The objective of the invention is solved as follows. A method for producing liquid nitrogen fertilizer involves mixing urea solutions containing partially recirculated cooled ready-made fertilizer with an ammonium nitrate solution acidified with nitric acid in an amount depending on the concentration of free ammonia in the initial urea solution and diluted with water. According to the invention, the stabilization of the ratio of a given amount in the finished fertilizer of the starting components is obtained by continuously measuring the actual flow rate and density of the finished liquid fertilizer, the density and flow rate of the starting components of ammonium nitrate, urea and water flow. Given the output yield of the finished JAU and the specific costs for this amount of the initial components of urea and ammonium nitrate, the mass flow rate of the initial components is adjusted, and the initial concentration and volumetric flow rate are automatically determined by the value of their density. By measuring the electrical conductivity of the finished ZhAU, thereby controlling the stabilization of compliance with a given ratio of the necessary components in the finished product.

Significant differences of the invention from the prototype is the following.

Due to the continuous automatic measurement of the actual yield and density of the finished liquid nitrogen fertilizer, the density and flow rate of the starting components of ammonium nitrate, urea and water flow using an automatic process control system, the ratio of the required amount in the finished fertilizer of the starting components of ammonium nitrate and urea is optimally stabilized.

Due to the given output performance of the finished ZhAU and the specific costs for this amount of the initial components of urea and ammonium nitrate, the mass flow rate of the initial components is automatically adjusted.

By measuring the density of the starting components, their initial concentration and volumetric flow rate are automatically determined.

Thanks to the measurement of the electrical conductivity of the finished ZhAU, the stabilization of compliance with a given ratio of the necessary components in the finished product is automatically monitored.

The proposed invention a method for producing liquid nitrogen fertilizer is illustrated by example. Example.

Based on the given ratio per 1 ton of finished liquid nitrogen fertilizer, the content of 100% urea in it is 342 kg / t, and 100% ammonium nitrate is 447 kg / t. To obtain 125 t / h of liquid nitrogen fertilizer according to the specific consumption rates of the starting components, their consumption is automatically calculated: 125 t / h -0.342 t / h (specific urea consumption) = 42.75 t / h of 100% carbamide and 125 t / h-0.447 = 55.87 t / h of 100% ammonium nitrate. The density of a 72% urea solution entering the mixing step is automatically measured as follows.

The density of an aqueous urea solution in the temperature range from -10 to 155 ° C and a concentration of 0 to 100% is automatically determined by the process control system according to the following formula:

- 1 016901

6 _K = φ + 2.82854 · ΙΟ ' ³ · χκ + 2.42713 · 10 ~ ⁶ · χκ ² + 9.88406 · ΙΟ' ⁹ · χ _κ ³ - 7.72694

10 ' ⁶ · ΐ · χκ + 4.13334 · ΙΟ' ⁸ · ΐ ² χκ + 3.33625 · 10 ~ '° · ΐ · χ _κ ² , where x _k is the concentration of urea in the aqueous solution, wt.%;

ΐ is the temperature of the solution, ° C;

άι is the density of water at ΐ, g / cm ³ ;

it is equal to 1.195 t / m ³ , and according to the formula 42.75: 0.72 = 59.4 t / h: 1.195 t / m ³ (T = 110 ° C) we obtain a volumetric flow rate of urea of 72% urea for a given unit capacity (125 t / h) in an amount of 49.7 m ³ / h.

The density of an 89% solution of ammonium nitrate, which enters the mixing stage, is measured.

The density of an aqueous solution of ammonium nitrate in the temperature range from 0 to 230 ° C and concentration from 0 to 100% is automatically determined by the process control system according to the following formula:

= Ф + 4.19221 -ΙΟ ' ³ · x ac + 8.86614 · 10' ⁶ · xas ² + 1.28686 · 10 ' ⁸ · x _ac ³ -9.62983 · 10' ⁶ · 1 · Xas-2 , 87463 · ΙΟ ' ⁸ · ΐ ² ' xas + 5.52508 · ΙΟ ' ⁸ · ΐ · x _as ² where x _as is the concentration of ammonium nitrate, wt.%;

ΐ is the temperature of the solution, ° C;

άι is the density of water at ΐ, g / cm ³ ;

the density is 1.341 t / m, and according to the formula 55.87: 0.89 = 62.78 t / h: 1.341 t / m ³ (140 ° C) we obtain the volumetric flow rate of 89% ammonium nitrate for a given unit capacity (125 t / h) in an amount of 46.8 m ³ / h.

The content of the components (ammonium nitrate, urea) in the finished fertilizer mixture is controlled by measuring the conductivity of the solution. The ratio of the concentration of components and electrical conductivity (Ohm / m) is determined by the following formula:

χ = 10,9090-0,377954 · x _k + 5,868 x 10 ^'3 · x ^ ² - 3.57618 · 10 ^"5 · 10 · -298,741 xk' ^{8 4} · xk + 1.93234 · Has - 2.32435 x 10 ^'2 · Has ² + 7.58074 · 10 ^"5 · Has ³ - 5.32556 × 10" ⁷ · Has ⁴ - 1.04353 x 10' ² · Xk Huse *>

where x _as - the content of ammonium nitrate, wt.%;

x _{to the} content of urea, wt.%.

These data are analyzed by an automatic process control system and due to constant measurements of the densities of urea and ammonium nitrate, their volumetric costs are adjusted depending on the value of the initial concentrations, by supplying signals to actuators that control the costs, and the content of ammonium nitrate and urea in the finished product is controlled .

Using the proposed method for producing liquid nitrogen fertilizer in comparison with the prototype allows, through the existing interconnection of the physicochemical properties of the finished product and the starting components, to automate the continuous process for producing liquid nitrogen fertilizer with optimal stable flow coefficients of the starting components and, thereby, to intensify the process.

Claims (1)

A method for producing liquid nitrogen fertilizer, comprising mixing urea solutions with partially recirculated cooled ready-made fertilizer with ammonium nitrate solution, acidified with nitric acid in an amount depending on the concentration of free ammonia in the initial urea solution, and diluted with water, characterized in that the actual yield and density of the finished liquid nitrogen fertilizer, density and consumption of the starting components of ammonium nitrate, urea and water consumption and then, according to a given yield rate of the finished liquid nitrogen fertilizer and specific consumption for this amount of the initial components of urea and ammonium nitrate, the mass flow rate of the initial components is adjusted, and their initial concentration and volumetric flow rate are automatically determined by the density, in addition, the electrical conductivity of the finished liquid nitrogen is measured fertilizers, controlling, thereby, maintaining compliance with a given ratio of the necessary components in the finished product.