Urea synthesis control method

Abstract

The invention provides a urea synthesis control method which comprises the following steps: S1, constructing a control parameter calculation table which is a two-dimensional table with n rows and m columns; s2, indexing a first element and a plurality of second elements from a control parameter calculation table according to the detected temperature difference value E and the temperature difference value change rate Ec; s3, according to the detected temperature difference value E and the temperature difference value change rate Ec, calculating a weighting coefficient omega 1i of the first element and each second element, and according to the omega 1i, weighting to obtain a first control parameter; and S4, calculating a weighting coefficient omega 2j of the first control parameter and the second control parameter according to the second control parameter calculated by the traditional controller, the detected temperature difference value E and the temperature difference value change rate Ec, and weighting according to the omega 2j to obtain the control parameter. The temperature control device is used for temperature control in the urea synthesis process.

Description

Technical Field

[0001] The present invention relates to the technical field of urea synthesis control, and particularly relates to a urea synthesis control method. Background Art

[0002] Urea, also known as carbamide, has the chemical formula CH4N2O or CO(NH2)2. It is a white crystal, odorless and tasteless, soluble in water, ethanol and benzene, and slightly soluble in ether and chloroform. Urea is one of the simplest organic compounds and is the main nitrogen-containing end product of protein metabolism decomposition in mammals and certain fish. It can be used as chemical fertilizer, animal feed, explosive, glue stabilizer and chemical raw material, etc. Since this substance is contained in human urine, it is named urea. As a neutral fertilizer, urea is suitable for various soils and plants. It is easy to store, convenient to use, and has little destructive effect on the soil. It is a chemical nitrogen fertilizer with a large usage amount. Urea contains 46% nitrogen (N), which is the highest nitrogen content in solid nitrogen fertilizers.

[0003] Industrially, urea is synthesized from ammonia and carbon dioxide under certain conditions. Patent CN107663162B, a 13C urea synthesis control method, includes the following steps: S100, raw material filling: Weigh methanol and sulfur and load them into the reaction kettle. The reaction kettle is cooled with liquid nitrogen, and 13CO and NH3 are connected in sequence, and the liquefied filling of 13CO and NH3 into the reaction kettle is completed; S200, urea synthesis reaction: Seal the reaction kettle, control the temperature to 80 - 120 °C, and detect the pressure value in the reaction kettle until the pressure in the reaction kettle drops to a constant value, and the reaction ends. The present invention uses a cooling technology to fill the raw material gas in a pressure-resistant reaction kettle, so that the liquid 13CO, NH3 and solid elemental S in the reaction system synthesize 13C urea in the pressure-resistant reaction kettle, making the temperature and pressure conditions in the reaction kettle reach the conditions required for urea synthesis, and realizing the large-scale preparation of 13C urea. However, due to the complexity of the system, it is difficult for traditional controllers, such as PID controllers, to control the temperature within the set range.

[0004] In view of this, the present invention is specifically proposed. Summary of the Invention

[0005] The purpose of the present invention is to provide a urea synthesis control method for temperature control during the urea synthesis process.

[0006] To solve the above technical problems, the present invention provides a urea synthesis control method, including the following steps: S1: Construct a control parameter calculation table. The control parameter calculation table is a two-dimensional table with n rows and m columns, where the rows correspond to the temperature difference E and the columns correspond to the temperature difference change rate Ec; S2: Index the first element and several second elements from the control parameter calculation table according to the detected temperature difference E and the temperature difference change rate Ec. The first element is the element directly corresponding to the temperature difference E and the temperature difference change rate Ec, and the second elements are the elements surrounding the first element in the control parameter calculation table. S3: Calculate the weighting coefficients ω of the first element and each second element according to the detected temperature difference E and the temperature difference change rate Ec 1i , and obtain the first control parameter by weighting according to ω 1i . S4: Calculate the second control parameter according to the traditional controller, calculate the weighting coefficients ω of the first control parameter and the second control parameter according to the detected temperature difference E and the temperature difference change rate Ec 2j , and obtain the control parameter by weighting according to ω 2j .

[0007] Furthermore, in S1, divide the obtained temperature difference E range into n equal parts, and index the rows from the control parameter calculation table according to the detected temperature difference E in S2; in S1, divide the obtained temperature difference change rate Ec range into m equal parts, and index the columns from the control parameter calculation table according to the detected temperature difference change rate Ec in S2.

[0008] Furthermore, in S2, the element directly indexed from the control parameter calculation table according to the detected temperature difference E and the temperature difference change rate Ec is the first element, and the eight elements around the first element are the second elements.

[0009] Furthermore, in S2, when the first element is the element at the vertex, the three elements around the second element are the second elements; when the first element is the element at the edge, the five elements around the second element are the second elements.

[0010] Furthermore, the said S3 includes the following steps: S31: Construct a weighting coefficient calculation rectangle, where one side length of the weighting coefficient calculation rectangle is the range step of the temperature difference E corresponding to the first element, and the other side length is the range step of the temperature difference change rate Ec corresponding to the first element; S32: Draw a calculation point in the weighting coefficient calculation rectangle according to the detected temperature difference E and the temperature difference change rate Ec; S33: Draw a horizontal line and a vertical line passing through the calculation point in the weighting coefficient calculation rectangle. The horizontal line and the vertical line divide the weighting coefficient calculation rectangle into several sub-rectangles; S34: Calculate the area S0 of the weighting coefficient calculation rectangle, and the areas S1~S8 of the sub-rectangles in different orientations, and calculate ω according to the following formula 1i , j = 0, 1,..., 8 S34: Calculate the first control parameter u1 according to the following formula 。

[0011] Further, in step S4, calculate the control parameter u through the following formula: 。

[0012] Further, in step S4, calculate ω through the following steps 21 : S41: When the detected temperature difference E < E' and the detected rate of change of the temperature difference Ec < Ec', ω 21 = 0, where E' is the warning value of the temperature difference and Ec' is the warning value of the rate of change of the temperature difference; S42: When the detected temperature difference E ≥ E' and the detected rate of change of the temperature difference Ec < Ec', calculate ω according to the following formula 21 ; S43: When the detected temperature difference E < E' and the detected rate of change of the temperature difference Ec ≥ Ec', calculate ω according to the following formula 21 ; S43: When the detected temperature difference E < E' and the detected rate of change of the temperature difference Ec ≥ Ec', ω 21 = 1.

[0013] The present invention provides a urea synthesis control method, which has the following beneficial effects: 1. When both the detected temperature difference E and the rate of change of the temperature difference Ec are small, that is, both are less than the corresponding warning values, use a traditional controller for control; when one of them is large, that is, one of them is greater than or equal to the corresponding warning value, obtain the control parameter in a weighted form; when both are large, that is, both are greater than or equal to the corresponding warning values, obtain the control parameter through S1 - 3 of the present invention; thus, the temperature can be effectively controlled within the set temperature range; 2. When calculating the first control parameter, the first element directly corresponding to the detected temperature difference E and the rate of change of the temperature difference Ec, as well as the second element surrounding the first element, are weighted, so the calculated first control parameter has a high calculation accuracy. Description of the Drawings

[0014] Figure 1 is a flowchart of a urea synthesis control method; Figure 2Schematic diagram of weighted coefficient calculation principle Figure 1 ; Figure 3 Schematic diagram of weighted coefficient calculation principle Figure 2 。 Specific implementation manner

[0015] The core of the present invention is to provide a urea synthesis control method for temperature control in the urea synthesis process.

[0016] 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 described clearly and completely below. Obviously, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0017] Embodiment 1: A urea synthesis control method, as Figure 1 shown, includes the following steps: S1: Construct a control parameter calculation table, which is a two-dimensional table with n rows and m columns, where the rows correspond to the temperature difference E and the columns correspond to the temperature difference change rate Ec.

[0018] In this embodiment, the values in each cell of the control parameter calculation table can be filled according to historical experience or by relevant experts.

[0019] In this embodiment, the temperature difference E refers to the difference between the detected temperature value and the set temperature range.

[0020] S2: Index the first element and several second elements from the control parameter calculation table according to the detected temperature difference E and temperature difference change rate Ec. The first element is the element directly corresponding to the temperature difference E and temperature difference change rate Ec, and the second elements are the elements surrounding the first element in the control parameter calculation table.

[0021] S3: Calculate the weighted coefficient ω 1i , and according to ω 1i weight to obtain the first control parameter.

[0022] S4: Calculate the second control parameter according to the traditional controller, calculate the weighted coefficient ω 2j of the first control parameter and the second control parameter based on the detected temperature difference E and temperature difference change rate Ec, and according to ω 2j weight to obtain the control parameter.

[0023] For the urea synthesis control method of this embodiment, when both the detected temperature difference E and the temperature difference change rate Ec are small, that is, both are less than the corresponding warning values, a traditional controller is used for control; when one of them is large, that is, one of them is greater than or equal to the corresponding warning value, the control parameter is obtained in a weighted form; when both of them are large, that is, both are greater than or equal to the corresponding warning values, the control parameter is obtained through S1 - 3 of the present invention; thus, the temperature can be effectively controlled within the set temperature range. For the urea synthesis control method of this embodiment, when calculating the first control parameter, the first element directly corresponding to the detected temperature difference E and the temperature difference change rate Ec, as well as the second elements surrounding the first element, are weighted. Therefore, the calculated first control parameter has a high calculation accuracy.

[0024] In an alternative embodiment, in S1, the obtained temperature difference E range is equally divided into n parts, and in S2, row indexing is performed from the control parameter calculation table according to the detected temperature difference E; in S1, the obtained temperature difference change rate Ec range is equally divided into m parts, and in S2, column indexing is performed from the control parameter calculation table according to the detected temperature difference change rate Ec.

[0025] In this alternative embodiment, the obtained temperature difference E range refers to the range of the temperature difference E obtained based on historical data. When the detected temperature difference E is greater than the maximum value of the obtained temperature difference E, it can be made equal to the maximum value of the obtained temperature difference E; different rows of the control parameter calculation correspond to different ranges of the temperature difference E. Therefore, in S2, row indexing can be performed from the control parameter calculation table according to the detected temperature difference E.

[0026] In this alternative embodiment, the obtained temperature difference change rate Ec range refers to the range of the temperature difference change rate Ec obtained based on historical data. When the detected temperature difference change rate Ec is greater than the maximum value of the obtained temperature difference change rate Ec, it can be made equal to the maximum value of the obtained temperature difference change rate Ec; different columns of the control parameter calculation correspond to different ranges of the temperature difference change rate Ec. Therefore, in S2, column indexing can be performed from the control parameter calculation table according to the detected temperature difference change rate Ec.

[0027] In this alternative embodiment, in S2, row indexing is performed from the control parameter calculation table according to the detected temperature difference E, and column indexing is performed from the control parameter calculation table according to the detected temperature difference change rate Ec, and a unique cell can be indexed from the control parameter calculation table, and the value therein is the first element.

[0028] In an alternative embodiment, in S2, the element obtained by directly indexing from the control parameter calculation table based on the detected temperature difference E and the rate of change of temperature difference Ec is the first element, and the eight elements surrounding the first element are the second elements.

[0029] In an alternative embodiment, in S2, when the first element is the element at the vertex angle, the three elements surrounding the second element are the second elements; when the first element is the element at the edge, the five elements surrounding the second element are the second elements.

[0030] In an alternative embodiment, S3 includes the following steps: S31: Construct a weighted coefficient calculation rectangle, where one side length of the weighted coefficient calculation rectangle is the range step of the temperature difference E corresponding to the first element, and the other side length is the range step of the rate of change of temperature difference Ec corresponding to the first element.

[0031] S32: Draw a calculation point within the weighted coefficient calculation rectangle according to the detected temperature difference E and the rate of change of temperature difference Ec.

[0032] Reference Figure 2 , in S31, the length of the height of the constructed weighted coefficient calculation rectangle is the range step of the temperature difference E, where a is the range of the obtained temperature difference E, which is equally divided into n parts in S1, so the length of the height of the constructed weighted coefficient calculation rectangle is a / n; the length of the width of the constructed weighted coefficient calculation rectangle is the range step of the rate of change of temperature difference Ec, where b is the range of the obtained rate of change of temperature difference Ec, which is equally divided into m parts in S1, so the length of the width of the constructed weighted coefficient calculation rectangle is b / m.

[0033] In S32, c is the magnitude of the detected temperature difference E exceeding the lower limit value of the temperature difference E range corresponding to the current first element, and d is the magnitude of the detected rate of change of temperature difference E exceeding the lower limit value of the rate of change of temperature difference Ec range corresponding to the current first element.

[0034] S33: Draw a horizontal line and a vertical line passing through the calculation point within the weighted coefficient calculation rectangle. Reference Figure 3 , the horizontal line and the vertical line divide the weighted coefficient calculation rectangle into several sub-rectangles.

[0035] S34: Calculate the area S0 of the weighted coefficient calculation rectangle, and the areas S1~S8 of the sub-rectangles in different directions, and calculate ω according to the following formula 1i , j = 0, 1,..., 8 .

[0036] Among them, the area of the upper-left rectangle is S1, which is used to calculate the weighting coefficient of the second element in the upper-left corner of the first element; the area of the rectangle composed of the upper-left and upper-right corners is S2, which is used to calculate the weighting coefficient of the second element directly above the first element; the area of the upper-right rectangle is S3, which is used to calculate the weighting coefficient of the second element in the upper-right corner of the first element; the area of the rectangle composed of the upper-right and lower-right corners is S4, which is used to calculate the weighting coefficient of the second element on the right side of the first element; the area of the lower-right rectangle is S5, which is used to calculate the weighting coefficient of the second element in the lower-right corner of the first element; the area of the rectangle composed of the lower-right and lower-left corners is S6, which is used to calculate the weighting coefficient of the second element directly below the first element; the area of the lower-left rectangle is S7, which is used to calculate the weighting coefficient of the second element in the lower-left corner of the first element; the area of the rectangle composed of the lower-left and upper-left corners is S8, which is used to calculate the weighting coefficient of the second element on the left side of the first element. In addition, when the first element is located at the vertex or edge, resulting in the absence of some second elements, the corresponding area can be set to zero.

[0037] S34: Calculate the first control parameter u1 according to the following formula 。

[0038] In an optional embodiment, in the S4, calculate the control parameter u through the following formula: 。

[0039] Among them, u2 is the output of the traditional controller, such as a PID controller.

[0040] In an optional embodiment, in the S4, calculate ω through the following steps 21 : S41: When the detected temperature difference E < E' and the detected temperature difference change rate Ec < Ec', ω 21 = 0, where E' is the temperature difference warning value and Ec' is the temperature difference change rate warning value.

[0041] S42: When the detected temperature difference E ≥ E' and the detected temperature difference change rate Ec < Ec', calculate ω according to the following formula 21 。

[0042] S43: When the detected temperature difference E < E' and the detected temperature difference change rate Ec ≥ Ec', calculate ω according to the following formula 21 。

[0043] S43: When the detected temperature difference E < E' and the detected temperature difference change rate Ec ≥ Ec', ω 21 = 1.

[0044] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the broadest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for controlling urea synthesis, characterized in that, It includes the following steps: S1: Construct a control parameter calculation table, which is a two-dimensional table with n rows and m columns. The rows correspond to the temperature difference E, and the columns correspond to the temperature difference change rate Ec; S2: Index the first element and several second elements from the control parameter calculation table according to the detected temperature difference E and temperature difference change rate Ec. The first element is the element directly corresponding to the temperature difference E and temperature difference change rate Ec, and the second elements are the elements surrounding the first element in the control parameter calculation table; S3: Calculate the weighting coefficients ω of the first element and each second element according to the detected temperature difference E and the temperature difference change rate Ec 1i , and based on ω 1i weight to obtain the first control parameter; S4: Calculate the second control parameter according to the traditional controller, and detect the obtained temperature difference E and the rate of change of temperature difference Ec to calculate the weighting coefficient ω of the first control parameter and the second control parameter 2j , and according to ω 2j weight them to obtain the control parameter.

2. The urea synthesis control method according to claim 1, wherein In S1, the obtained temperature difference E range is equally divided into n parts, and in S2, the row index is performed from the control parameter calculation table according to the detected temperature difference E; in S1, the obtained temperature difference change rate Ec range is equally divided into m parts, and in S2, the column index is performed from the control parameter calculation table according to the detected temperature difference change rate Ec.

3. The urea synthesis control method according to claim 2, characterized in that, In S2, the element directly indexed from the control parameter calculation table according to the detected temperature difference E and temperature difference change rate Ec is the first element, and the eight elements around the first element are the second elements.

4. A method for controlling urea synthesis according to claim 2, characterized in that, In S2, when the first element is a corner element, the three elements around the second element are the second elements; when the first element is an edge element, the five elements around the second element are the second elements.

5. A method for controlling urea synthesis according to claim 2, characterized in that, The S3 includes the following steps: S31: Construct a weighted coefficient calculation rectangle. One side length of the weighted coefficient calculation rectangle is the range step of the temperature difference E corresponding to the first element, and the other side length is the range step of the temperature difference change rate Ec corresponding to the first element; S32: Draw a calculation point in the weighted coefficient calculation rectangle according to the detected temperature difference E and temperature difference change rate Ec; S33: Draw a horizontal line and a vertical line passing through the calculation point in the weighted coefficient calculation rectangle. The horizontal line and the vertical line divide the weighted coefficient calculation rectangle into several sub-rectangles; S34: Calculate the weighted coefficient. Calculate the area S0 of the rectangle and the areas S1 to S8 of the sub-rectangles in different orientations, and calculate ω according to the following formula 1i , j = 0, 1, ..., 8 S34: Calculate the first control parameter u1 according to the following formula 。 6. The urea synthesis control method according to claim 1, characterized in that, In the S4, calculate the control parameter u through the following formula: 。 7. A method for controlling urea synthesis according to claim 1, characterized in that, In S4, ω is calculated through the following steps 21 :[[]] S41: When the detected temperature difference E < E' and the detected temperature difference change rate Ec < Ec', ω 21 = 0, where E' is the temperature difference warning value and Ec' is the temperature difference change rate warning value; S42: When the detected temperature difference E ≥ E' and the detected temperature difference change rate Ec < Ec', calculate ω according to the following formula 21 ; S43: When the temperature difference E obtained by detection satisfies E < E' and the change rate Ec of the temperature difference obtained by detection satisfies Ec ≥ Ec', calculate ω according to the following formula 21 ; S43: When the detected temperature difference E < E' and the detected temperature difference change rate Ec ≥ Ec', ω 21 = 1.

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