A reaction system for reducing the biuret content of carbon dioxide urea process products

Abstract

This invention relates to the field of urea production technology and discloses a reaction system for reducing the biuret content in carbon dioxide urea process products. The system includes a first-stage evaporator and a second-stage evaporator connected sequentially, via a U-shaped tube. Each of the first-stage evaporator, the second-stage evaporator, and the bottom of the U-shaped tube is equipped with an online monitoring component and a control component. The control component includes a timer and a controller. During the reaction, the biuret content in the first-stage evaporator is controlled to be below 0.32%, and the biuret content at the bottom of the U-shaped tube is controlled to be below 0.6%. By online monitoring of the biuret content at these specific locations and timely control of the material's processing time in the evaporator, the biuret content in the product can be effectively controlled to always remain below the upper limit of the standard value.

Description

Technical Field

[0001] This invention relates to the field of urea production technology, and more specifically, to a reaction system for reducing the biuret content in carbon dioxide urea process products. Background Technology

[0002] Urea is a carbon-nitrogen compound commonly used in agriculture and industry. It is mostly synthesized using nitrogen dioxide as a raw material, hence it is often called nitrogen dioxide urea. As the application areas and usage scenarios of urea expand, the quality requirements for urea products are also becoming increasingly stringent.

[0003] The biuret content is one of the important indicators for evaluating the quality of urea produced from carbon dioxide. In practical applications of urea, a high biuret content can easily cause seedling burn in crops; therefore, in most cases, the biuret content in urea is required to be less than 0.9%.

[0004] Currently, when urea is prepared using carbon dioxide stripping, the biuret content is often at a high level of 0.88% due to limitations in the production process. When fluctuations or other unstable conditions occur in the production system, the biuret content in the product is very likely to exceed the standard.

[0005] Therefore, we now continue with a carbon dioxide urea reaction system that can control the biuret content in urea to always be below the standard requirement value. Summary of the Invention

[0006] The technical problem to be solved by this invention:

[0007] Currently, the urea produced by the reaction system used to prepare urea from carbon dioxide generally has a high biuret content of 0.88%. After the reaction system has been used for a period of time, performance fluctuations and other instabilities will occur, which can easily lead to excessive biuret content in the urea product.

[0008] The technical solution adopted in this invention is as follows:

[0009] This invention provides a reaction system for reducing the biuret content in carbon dioxide urea process products, comprising a first-stage evaporator and a second-stage evaporator connected in sequence, wherein the first-stage evaporator and the second-stage evaporator are connected by a U-shaped tube, and the bottom of the first-stage evaporator, the second-stage evaporator and the U-shaped tube are each equipped with an online monitoring component and a control component, wherein the control component includes a timer and a controller.

[0010] Preferably, the biuret content is monitored in real time by an online monitoring component. When the biuret content exceeds a set value, the controller shortens the reaction time of the material in the system.

[0011] Preferably, during the reaction process, the biuret content in the first stage of the evaporator is controlled to be less than 0.32%, and the biuret content at the bottom of the U-shaped tube is less than 0.6%.

[0012] Preferably, the liquid level baseline of the first-stage evaporator and the second-stage evaporator is controlled below 70-95% of the total height of the evaporator.

[0013] Preferably, the positional difference between the bottom of the U-shaped tube and the inlet of the second-stage evaporator is less than 11.9m; ​​further, the height difference between the two ends of the U-shaped tube is less than 25.8m.

[0014] The beneficial effects of this invention are as follows:

[0015] This invention addresses the problem of high biuret content in urea products produced during the carbon dioxide urea process by improving and adjusting the reaction system and control conditions as follows: First, by shortening the material transport path, the residence time of materials in each production stage is reduced, thus decreasing the reaction time of the urea product within the system and preventing excessive biuret formation due to reverse reactions. Second, by adjusting parameters such as the reaction temperature in each stage of the system, the forward reaction is controlled, further reducing biuret production. This invention's reaction system not only improves the problem of high biuret content in urea products but also shortens the reaction time for urea formation, thereby increasing production efficiency. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the evaporator and U-tube in Example 1. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0018] This invention provides a reaction system for reducing the biuret content in carbon dioxide urea process products, including a first-stage evaporator and a second-stage evaporator connected in sequence, the first-stage evaporator and the second-stage evaporator being connected by a U-shaped tube, and the bottom of the first-stage evaporator, the second-stage evaporator and the U-shaped tube being equipped with online monitoring components and control components, the control components including a timer and a controller.

[0019] The biuret content is monitored in real time by an online monitoring component. When the biuret content exceeds the set value, the controller shortens the reaction time of the material in the system. During the reaction, the biuret content in the first-stage evaporator is controlled to be less than 0.32%, and the biuret content at the bottom of the U-tube is controlled to be less than 0.6%.

[0020] In this invention, the liquid level baseline of the first and second stage evaporators is controlled below 70-95% of the total height of the evaporators; the positional difference between the bottom of the U-tube and the inlet of the second stage evaporator is less than 11.9m, and the height difference between the two ends of the U-tube is less than 25.8m. By using a shorter material transport path, the residence time of materials in each production stage is reduced, and the reaction time of the product after urea production in the system is reduced, thus avoiding the generation of excessive biuret due to reverse reactions of the product.

[0021] Example 1

[0022] like Figure 1 As shown, E702 is a single-stage evaporator, and J703 is a two-stage evaporator. This embodiment provides a reaction system for reducing the biuret content in carbon dioxide urea process products, including a reaction section and an evaporation section. The evaporation section includes, as shown in the figure... Figure 1 The diagram shows a first-stage evaporator and a second-stage evaporator, connected by a U-shaped tube. Each of the first-stage, second-stage, and U-shaped evaporators is equipped with an online monitoring and control system. The control system includes a timer and a controller. The online monitoring system monitors the biuret content in real time. When the biuret content exceeds a set value, the controller shortens the reaction time of the material in the system. During the reaction, the biuret content is controlled to be less than 0.32% in the first-stage evaporator, less than 0.6% at the bottom of the U-shaped tube, and less than 0.88% in the second-stage evaporator. When these upper limits are exceeded, the controller receives a signal and shortens the reaction time of the material in the evaporator, using a timer and pump to transport the raw material.

[0023] This embodiment uses a processing capacity of 2700t / d as the standard. Through analysis of the process piping layout, it is found that the U-tube in the evaporation system is only a material flow channel and does not involve any material reaction or exchange. Therefore, changing the length of this pipe is the most effective and simplest way to reduce biuret production. Ultimately, by increasing the height of the U-tube, the distance between the lowest point of the pipe and the inlet of the second-stage evaporator is reduced, thereby achieving the goal of reducing the pipe distance.

[0024] Specifically, during the production process, the pressure of the first-stage evaporation section is controlled at 35 kPa, and the pressure of the second-stage evaporation section is controlled at 4 kPa. The outlet of the first-stage evaporator is higher than the inlet of the second-stage evaporator, with a height difference of 1.5 m. The actual material density is 1.1 kg / cm³. 3 Therefore, the bottom of the U-shaped tube is positioned approximately 4.18m below the inlet of the second-stage evaporator, thus controlling the tube length to be below 25.8m. Based on the relationship between material residence time, flow rate, and pipeline length, it is estimated that the material residence time will be shortened.

[0025] h = H / (Q / Πr) 2)

[0026] Where: h ------- material residence time, s

[0027] H-------Pipeline length, mm

[0028] Q-------Material flow rate, mm 3 / s

[0029] Π-------π (pi constant)

[0030] r--------pipe diameter radius, mm

[0031] Calculations show that, based on the actual production standards mentioned above, using the reaction system of this invention can shorten the residence time of materials in the tube by 7.23 seconds. Through multiple experiments, it has been found that using this reaction system to prepare urea can control the biuret content in urea to below 0.82%, thereby improving the product's compliance rate.

[0032] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A reaction system for reducing the biuret content in carbon dioxide urea process products, characterized in that, The system includes a first-stage evaporator and a second-stage evaporator connected in sequence, with the first-stage evaporator and the second-stage evaporator connected by a U-shaped tube. Each of the first-stage evaporator, the second-stage evaporator, and the bottom of the U-shaped tube is equipped with an online monitoring component and a control component. The control component includes a timer and a controller. The online monitoring component monitors the biuret content in real time. When the biuret content exceeds a set value, the controller shortens the reaction time of the material in the system.

2. The reaction system for reducing the biuret content in carbon dioxide urea process products according to claim 1, characterized in that, During the reaction, the biuret content in the first stage of the evaporator is controlled to be less than 0.32%, and the biuret content at the bottom of the U-tube is less than 0.6%.

3. The reaction system for reducing the biuret content in carbon dioxide urea process products according to claim 1, characterized in that, The liquid level baseline of the first-stage evaporator and the second-stage evaporator is controlled below 70-95% of the total height of the evaporator.

4. The reaction system for reducing the biuret content in carbon dioxide urea process products according to claim 1, characterized in that, The positional difference between the bottom of the U-shaped tube and the inlet of the second-stage evaporator is less than 11.9m.

5. The reaction system for reducing the biuret content in carbon dioxide urea process products according to claim 4, characterized in that, The height difference between the two ends of the U-shaped tube is less than 25.8m.

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