A process for the production of large granular urea

Abstract

The present application belongs to the field of urea production, and particularly relates to a production method of large-granular urea, which comprises the following steps: mixing urea melt, molecular sieve powder, gelatin and lignin sulfonate to obtain granulation raw materials, and then granulating in an atomized fluidized bed; after granulation, drying and screening to obtain large-granular urea; wherein, the molecular sieve powder is 0.1-1 parts, the gelatin is 0.2-1.2 parts, and the lignin sulfonate is 0.5-1.5 parts, based on 100 parts of urea in the urea melt. The method does not need to use formaldehyde, is green and environmentally friendly, and the quality of the obtained large-granular urea is excellent.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of urea production, and particularly relates to a production method of large-particle urea. BACKGROUND

[0002] Urea is one of the main nitrogen fertilizers, and also an important chemical intermediate raw material, which has an important position in industry and agriculture. With the continuous development of urea industry, the particle size of urea particles is also changing. According to the particle size, urea is divided into small-particle urea and large-particle urea. Generally, large-particle urea refers to urea with a particle size of 4.00mm to 8.00mm or 2.00 to 4.75mm.

[0003] At present, the production process of large-particle urea of domestic enterprises mainly adopts the fluidized bed granulation process of HYDRO and TEC, wherein, the process of HYDRO is atomized fluidized bed process, and the process of TEC is jet fluidized bed process. Although the large-particle urea produced by the two technologies has good quality, since formaldehyde solution or urea-formaldehyde compound generated by the reaction of formaldehyde and urea solution needs to be added in the granulation process, the amount of formaldehyde needs to be accurately controlled, which increases the difficulty of production process, and the use of formaldehyde in the production process may also harm the health of workers; and if the amount of formaldehyde is not well controlled, the final product may contain excessive formaldehyde, which may also cause secondary pollution of the environment or secondary harm to the health of users. Therefore, the researchers in the industry have been committed to obtaining other process methods to replace the current scheme.

[0004] Therefore, it is of great significance to study a preparation process of large-particle urea without using formaldehyde. SUMMARY

[0005] In order to solve the above technical problems, the present application provides a production method of large-particle urea, which does not need to use formaldehyde, the process is green and environmentally friendly, and the quality of the obtained large-particle urea is excellent.

[0006] The basic idea of the technical scheme of the present application is as follows:

[0007] A production method of large-particle urea, comprising mixing urea melt, molecular sieve powder, gelatin and lignin sulfonate to obtain granulation raw materials, and then granulating in an atomized fluidized bed; after granulation, drying and screening to obtain large-particle urea; wherein, based on 100 parts of urea in the urea melt, the molecular sieve powder is 0.1 to 1 parts, the gelatin is 0.2 to 1.2 parts, and the lignin sulfonate is 0.5 to 1.5 parts.

[0008] As an embodiment of the present application, the mass fraction of urea in the urea melt is 90% to 98%.

[0009] As an embodiment of the present application, the lignin sulfonate is one or more of sodium lignin sulfonate, potassium lignin sulfonate and calcium lignin sulfonate.

[0010] As an embodiment of the present application, the molecular sieve powder is 0.2-0.6 parts, the gelatin is 0.4-0.8 parts and the lignin sulfonate is 1.1-1.5 parts, based on 100 parts of urea in the urea melt.

[0011] As an embodiment of the present application, the urea granules are dried at 75-90℃ in an NH3 atmosphere.

[0012] As an embodiment of the present application, the temperature of the fluidized bed is 100-120℃.

[0013] As an embodiment of the present application, the lignin sulfonate is a combination of sodium lignin sulfonate and calcium lignin sulfonate in a mass ratio of 1:2.

[0014] As an embodiment of the present application, the molecular sieve powder is one or more of X-type zeolite molecular sieve powder, Y-type zeolite molecular sieve powder and A-type zeolite molecular sieve powder.

[0015] The present application provides a large granular urea obtained by the production method according to any one of the above.

[0016] As an embodiment of the present application, the large granular urea has a particle size of

[0017] Compared with the prior art, the present application has the following advantages:

[0018] 1. The present application uses a simple process to prepare large granular urea with uniform particles, smooth surface and low breakage without using formaldehyde, which is green and environmentally friendly.

[0019] 2. The large granular urea obtained by the present application is not easy to cake and has almost no dust.

[0020] 3. The granulation process of the present application does not need to be carried out in multiple stages, simplifying the granulation process.

[0021] 4. The raw materials used in the present application are common and easy to obtain, harmless to the human body or the environment, and safer. DETAILED DESCRIPTION

[0022] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions of the embodiments of the present application are clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the described embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without any creative effort fall within the protection scope of the present application.

[0023] Embodiment 1

[0024] 1) Take 100 parts of urea melt with a mass concentration of 90%, add 0.9 parts of X-type zeolite molecular sieve powder, 1.08 parts of gelatin and 1.35 parts of sodium lignosulfonate, and stir to mix uniformly to obtain granulation raw materials;

[0025] 2) Under the conditions of a pressure of 0.55 MPa and a temperature of 125 ℃, send into an atomized fluidized bed for granulation; control the temperature of the fluidized bed to be 110 ℃ and the outlet product temperature to be 105 ℃;

[0026] 3) After the granulation is completed, dry the urea granules under the conditions of a temperature of 75 ℃ and an NH3 atmosphere;

[0027] 4) After the drying is completed, screen the urea granules, and screen out urea granules with a particle size of 0.8-1.2 mm as a product, and cool to below 40 ℃ to obtain large-particle urea.

[0028] Embodiment 2

[0029] 1) Take 100 parts of urea melt with a mass concentration of 92%, add 0.092 parts of A-type zeolite molecular sieve powder, 0.184 parts of gelatin and 0.46 parts of calcium lignosulfonate, and stir to mix uniformly to obtain granulation raw materials;

[0030] 2) Under the conditions of a pressure of 0.6 MPa and a temperature of 130 ℃, send into an atomized fluidized bed for granulation; control the temperature of the fluidized bed to be 115 ℃ and the outlet product temperature to be 108 ℃;

[0031] 3) After the granulation is completed, dry the urea granules under the conditions of a temperature of 80 ℃ and an NH3 atmosphere;

[0032] 4) After the drying is completed, screen the urea granules, and screen out urea granules with a particle size of 0.8-1.2 mm as a product, and cool to below 45 ℃ to obtain large-particle urea.

[0033] Embodiment 3

[0034] 1) Take 100 parts of urea melt with a mass concentration of 95%, add 0.19 parts of Y-type zeolite molecular sieve powder, 0.38 parts of gelatin and 1.425 parts of lignosulfonate (sodium lignosulfonate: calcium lignosulfonate = 1:2), and stir to mix uniformly to obtain granulation raw materials;​​

[0035] 2) The urea melt is sent into the atomized fluidized bed granulator under the conditions of pressure 0.6 MPa and temperature 125°C; the temperature of the fluidized bed is controlled at 120°C and the outlet product temperature is 115°C;

[0036] 3) After the granulation is completed, the urea granules are dried under the conditions of 90°C and NH3 atmosphere;

[0037] 4) After the drying is completed, the urea granules are screened to obtain the product with particle size of 0.3-0.8 mm; The product is cooled to below 40°C to obtain the large-particle urea.

[0038] Example 4

[0039] 3) 100 parts of urea melt with mass concentration of 98% is taken, 0.588 parts of A-type zeolite molecular sieve powder, 0.784 parts of gelatin and 1.078 parts of lignosulfonate (sodium lignosulfonate: calcium lignosulfonate = 1:2) are added, and the mixture is stirred and mixed uniformly to obtain the granulation raw material;

[0040] 4) The urea melt is sent into the atomized fluidized bed granulator under the conditions of pressure 0.6 MPa and temperature 125°C; the temperature of the fluidized bed is controlled at 115°C and the outlet product temperature is 105°C;

[0041] 3) After the granulation is completed, the urea granules are dried under the conditions of 85°C and NH3 atmosphere;

[0042] 4) After the drying is completed, the urea granules are screened to obtain the product with particle size of 0.3-0.8 mm; The product is cooled to below 40°C to obtain the large-particle urea.

[0043] Example 5

[0044] The difference from Example 1 is that, after the granulation is completed, the urea granules are dried under the conditions of 75°C and air atmosphere.

[0045] Comparative Example 1

[0046] The difference from Example 1 is that no molecular sieve is added, and the other conditions are the same as those in Example 1.

[0047] Comparative Example 2

[0048] The difference from Example 1 is that the amount of lignosulfonate is 1.6 parts, and the other conditions are the same as those in Example 1.

[0049] Comparative Example 3

[0050] The difference from Example 1 is that the amount of lignosulfonate is 0.3 parts, and the other conditions are the same as those in Example 1.

[0051] Experimental Example 1

[0052] The anti-crushing strength, caking index and attrition resistance of the large granular urea of Examples 1-5 and Comparative Examples 1-3 above were tested under the same test conditions as follows:

[0053] The anti-crushing strength was tested by applying a measuring force to urea particles having a diameter of 3.00 mm with a fixed travel speed of 10 mm / min by an automatic metal plunger. The force at which the particles were broken was measured as a measure of strength. The average strength of 20 particles was recorded.

[0054] An equal amount of urea particles was placed on a 70 cm 2 surface at 25-30°C, a pressure of 2 bar was applied for 24 h, and then the agglomerated material was removed and broken, and the force required to break the agglomerated material was measured as a measure of the caking index.

[0055] Attrition resistance refers to the property of resisting the formation of dust and fines due to the contact between particles and particles and between particles and devices. A sample of 100 cm 3 was accurately weighed (between 2 mm and 3.5 mm), and was introduced into an end drum together with 50 steel balls having a diameter of 7.9 mm. The drum was closed and rotated at 60 rpm for 2.5 minutes. Thereafter, the contents were removed, and were manually sieved on a 4.45 mm sieve to recover the steel balls, and finally on a 2.00 mm sieve. The material remaining on the 2.00 mm sieve was weighed, and the degradation rate % = 100-100 x [mass of broken material recovered having a particle size between 2 and 3.5 mm] / [mass of sample introduced having a particle size between 2 and 3.5 mm] was calculated, and the resulting value was used as a basis for comparison of attrition resistance.

[0056] The data obtained from the tests are shown in Table 1.

[0057] Table 1

[0058] Test sample Crushing strength, kg Caking index, kg Wear resistance, % Example 1 3.9 16 1.27 Example 2 3.8 14 1.11 Example 3 4.3 11 0.93 Example 4 4.7 8 0.85 Example 5 2.6 27 2.6 Comparative Example 1 1.3 120 5.5 Comparative Example 2 1.8 100 4.9 Comparative Example 3 1.5 110 6.1

[0059] Although the embodiments of the present application are disclosed as above, the above-described content is only an embodiment adopted for the purpose of facilitating the understanding of the present application, and is not intended to limit the present application. Any person skilled in the art to which the present application pertains can make any modification and change in the form and details without departing from the spirit and scope of the present application disclosed, and the patent protection scope of the present application shall be determined by the scope defined by the appended claims.

Claims

1. A process for the production of large granular urea, characterized in that, The granulation raw material is obtained by mixing urea melt, molecular sieve powder, gelatin and lignosulfonate, and then granulation is carried out in an atomized fluidized bed; after the granulation is completed, drying and screening are carried out to obtain large granular urea; The molecular sieve powder is one or more of X-type zeolite molecular sieve powder, Y-type zeolite molecular sieve powder and A-type zeolite molecular sieve powder. The granulation is completed at 75-90℃ under NH3 atmosphere; the temperature of the fluidized bed is 100-120℃. The mass fraction of urea in the urea melt is 90%-98%.

2. The production process of large granular urea according to claim 1, characterized by, The lignosulfonate is one or more of sodium lignosulfonate, potassium lignosulfonate and calcium lignosulfonate.

3. The method of producing large granular urea according to claim 1, characterized by, The lignosulfonate is a combination of sodium lignosulfonate and calcium lignosulfonate at a mass ratio of 1:

2.

4. The production process of large granular urea according to claim 3, characterized by, The production method is obtained by using any one of claims 1-4.

5. A granular urea characterized in that, The particle size is ø2-5mm.

6. The large granular urea of claim 5, characterized in that, ​