Calculation method for maximum output of hydrolysis reactor in urea hydrolysis ammonia production system

Abstract

This invention discloses a method for calculating the maximum output of a hydrolysis reactor in a urea hydrolysis ammonia production system, comprising the following steps: (1) recording the initial liquid level of the urea solution storage tank and the initial liquid level of the hydrolysis reactor, and calculating the solution volume corresponding to the initial liquid level of the hydrolysis reactor; (2) after the urea hydrolysis ammonia production system has been running for a period of time, recording the liquid level of the urea solution storage tank and the liquid level of the hydrolysis reactor after operation, and calculating the solution volume corresponding to the liquid level of the hydrolysis reactor after operation; (3) calculating the actual output value of the hydrolysis reactor according to the law of conservation of mass; (4) finding the urea hydrolysis rate corresponding to the actual average operating temperature according to the urea hydrolysis rate versus temperature curve; (5) calculating the maximum output value of the hydrolysis reactor. This method achieves accurate measurement and calculation of the maximum output of the hydrolysis reactor, providing a basis for mastering the design parameters of the hydrolysis reactor.

Description

Technical Field

[0001] This invention belongs to the field of urea hydrolysis ammonia production technology, and specifically relates to a method for calculating the maximum output of a hydrolysis reactor in a urea hydrolysis ammonia production system. Background Technology

[0002] Flue gas generated by thermal power plants needs to be treated by an SCR flue gas denitrification system to reduce NOx to N2 and release it into the atmosphere. Thermal power plants generally use liquid ammonia as the denitrification reducing agent. With economic development and increased awareness of safe production, liquid ammonia, due to storage and transportation restrictions, has been classified as a major hazard source. Ammonia can be produced by heating and vaporizing liquid ammonia, or indirectly through the evaporation of ammonia water or the decomposition of urea. Urea is not classified as a hazardous material, and its transportation and storage are relatively safe; it decomposes upon heating to produce ammonia. The main equipment in a urea hydrolysis ammonia production system includes a urea dissolving tank, a urea dissolving pump, a urea solution storage tank, a urea solution transfer pump, and a urea hydrolysis reactor. Urea granules are added to a dissolving tank and dissolved in water to form a urea solution with a mass fraction of approximately 40% to 60%. The solution is then transported to a urea solution storage tank via a urea dissolving pump. The urea solution is then pumped into a urea hydrolysis reactor, where it decomposes to produce NH3, H2O, and CO2. The product gas is then sent to the furnace side and mixed with dilution air before being injected into the SCR inlet flue via an ammonia injection device.

[0003] Currently, most thermal power plants across the country have completed the urea replacement of liquid ammonia and generally adopt the urea hydrolysis ammonia production process. Each thermal power plant usually has 2 to 3 hydrolysis reactors. Considering that the power plant's power generation load is subject to grid dispatch and the coal quality used in daily operations is relatively mixed, the output of the hydrolysis reactors generally has a large margin. In actual operation, it is impossible to reach the maximum design output, and it is impossible to verify whether the performance indicators of the maximum output of the hydrolysis reactor meet the requirements.

[0004] Currently, the output of the hydrolysis reactor is calculated by recording the ammonia injection rate of each furnace on the furnace-side SCR system DCS. The sum of the ammonia injection rates of all furnaces is the current ammonia production of the hydrolysis reactor. However, the ammonia flow meter of the furnace-side SCR system only displays the flow rate of the mixed gas (the urea solution concentration is inaccurate, and the ammonia content in the product gas varies at different temperatures). In addition, the mixed gas contains corrosive and crystallizing substances due to on-site vibrations, resulting in large measurement deviations. Furthermore, the maximum output of the hydrolysis reactor cannot be verified by statistically analyzing the ammonia injection rate. Summary of the Invention

[0005] To address the aforementioned technical problems, the present invention aims to provide a method for calculating the maximum output of a hydrolysis reactor in a urea hydrolysis ammonia production system. This method enables accurate measurement and calculation of the maximum output of the hydrolysis reactor, providing a basis for understanding the design parameters of the hydrolysis reactor, thereby enabling the determination of whether the maximum output performance parameters of the urea hydrolysis reactor meet the requirements.

[0006] To achieve the above-mentioned technical objectives and effects, the present invention is implemented through the following technical solution:

[0007] A method for calculating the maximum output of a hydrolysis reactor in a urea hydrolysis ammonia production system, wherein the urea hydrolysis ammonia production system includes a urea solution storage tank, a urea solution transfer pump, and a hydrolysis reactor. The urea solution in the storage tank enters the hydrolysis reactor via the urea solution transfer pump, and the urea decomposes in the hydrolysis reactor to generate NH3. The method includes the following steps:

[0008] (1) Record the initial liquid level of the urea solution storage tank and the initial liquid level of the hydrolysis reactor, and calculate the solution volume corresponding to the initial liquid level of the hydrolysis reactor.

[0009] (2) After the urea hydrolysis ammonia production system has been running for a period of time, record the liquid level of the urea solution storage tank and the liquid level of the hydrolysis reactor after operation, and calculate the solution volume corresponding to the liquid level of the hydrolysis reactor after operation.

[0010] (3) Calculate the actual output value M of the hydrolysis reactor according to the law of conservation of mass. t The calculation formula is:

[0011] M t =ρ×[π×Φ 2 / 4×(L1-L2)+V1-V2]×W×2M1 / M2 / t

[0012] In the formula, Φ is the diameter of the urea solution storage tank, ρ is the density of the urea solution, L1 is the initial liquid level of the urea solution storage tank, L2 is the liquid level of the urea solution storage tank after operation, V1 is the solution volume corresponding to the initial liquid level of the hydrolysis reactor, V2 is the solution volume corresponding to the liquid level of the hydrolysis reactor after operation, W is the concentration of the urea solution; M1 is the relative molecular mass of NH3, M2 is the relative molecular mass of urea, and t is the operating time of the urea hydrolysis ammonia production system.

[0013] (4) Retrieve the temperature and liquid level operating curves of the hydrolysis reactor during the operating time from the DCS of the urea hydrolysis ammonia production system. Obtain the actual average operating temperature based on the temperature operating curve and the actual average liquid level of the hydrolysis reactor based on the liquid level operating curve. Find the urea hydrolysis rate corresponding to the actual average operating temperature based on the urea hydrolysis rate versus temperature curve.

[0014] (5) Calculate the maximum output value M of the hydrolysis reactor using the following formula. s :

[0015]

[0016] Among them, M s—Maximum output of the hydrolysis reactor, kg / h;

[0017] M t —Actual output value of the hydrolysis reactor, kg / h;

[0018] V s —The urea hydrolysis rate when the hydrolysis reactor operates at the design temperature;

[0019] V t —The urea hydrolysis rate corresponding to the actual average operating temperature;

[0020] Q s —The solution volume (m) corresponding to the design value of the hydrolysis reactor liquid level. 3 ;

[0021] Q t —The solution volume corresponding to the actual average liquid level in the hydrolysis reactor, in meters. 3 .

[0022] Furthermore, this method is carried out under the condition of operating a hydrolysis reactor and a urea solution storage tank.

[0023] Furthermore, the urea hydrolysis ammonia production system should operate for no less than 4 hours.

[0024] Furthermore, the calculation formulas for the solution volume V1 corresponding to the initial liquid level in the hydrolysis reactor and the solution volume V2 corresponding to the liquid level after the hydrolysis reactor has been running are as follows:

[0025]

[0026]

[0027] Where L is the length of the cylindrical part in the middle of the hydrolysis reactor, a is the radius of the spherical parts at both ends of the hydrolysis reactor, h1 is the initial liquid level of the hydrolysis reactor, and h2 is the liquid level of the hydrolysis reactor after operation.

[0028] Furthermore, the design temperature of the hydrolysis reactor is 150℃, and the design value of the liquid level in the hydrolysis reactor is equal to the radius of the spherical part of the hydrolysis reactor.

[0029] Furthermore, the concentration of the urea solution is 40% to 60%.

[0030] The beneficial effects of this invention are:

[0031] This invention accurately calculates the actual output of the hydrolysis reactor by precisely statistically analyzing the urea consumption over a fixed time period, based on the principle of urea hydrolysis reaction. Then, based on the relationship between urea hydrolysis rate and temperature, it achieves accurate measurement and calculation of the maximum output of the hydrolysis reactor, providing a basis for mastering the design indicators of the hydrolysis reactor, thereby enabling the determination of whether the maximum output performance indicators of the urea hydrolysis reactor meet the requirements. Attached Figure Description

[0032] Figure 1 This is a flowchart illustrating the method of the present invention.

[0033] Figure 2 This is a schematic diagram of the hydrolysis reactor.

[0034] Figure 3 This is a curve showing the relationship between the urea hydrolysis rate and temperature in the method of the present invention. Detailed Implementation

[0035] The technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] like Figure 1 As shown, this invention provides a method for calculating the maximum output of a hydrolysis reactor in a urea hydrolysis ammonia production system. The urea hydrolysis ammonia production system includes a urea solution storage tank, a urea solution transfer pump, and a hydrolysis reactor, as well as a urea dissolving tank and a urea dissolving pump. Urea granules are added to the urea dissolving tank and dissolved in water to form a urea solution with a mass fraction of approximately 40%–60%, which is then transported to the urea solution storage tank via the urea dissolving pump. The urea solution in the storage tank enters the hydrolysis reactor via the urea solution transfer pump. In the hydrolysis reactor, urea decomposes to generate NH3, H2O, and CO2. The NH3 is sent to the furnace side and mixed with dilution air before being injected into the SCR inlet flue via an ammonia injection device. Based on the above urea hydrolysis ammonia production system, this calculation method includes the following steps:

[0037] (1) The urea dissolving tank stops supplying urea solution to the urea solution storage tank, and ensures that only one hydrolysis reactor and one urea solution storage tank are in operation.

[0038] Record the initial liquid level of the urea solution storage tank and the initial liquid level of the hydrolysis reactor, and calculate the solution volume corresponding to the initial liquid level of the hydrolysis reactor.

[0039] (2) After the urea hydrolysis ammonia production system has been running for a period of time, record the liquid level of the urea solution storage tank and the liquid level of the hydrolysis reactor after operation, and calculate the solution volume corresponding to the liquid level of the hydrolysis reactor after operation; wherein, the operation time of the urea hydrolysis ammonia production system shall not be less than 4 hours.

[0040] The formulas for calculating the solution volume V1 corresponding to the initial liquid level in the hydrolysis reactor and the solution volume V2 corresponding to the liquid level after the hydrolysis reactor has been running are as follows:

[0041]

[0042]

[0043] Among them, such as Figure 2 As shown, the hydrolysis reactor consists of a cylindrical section in the middle and spherical sections at both ends; L is the length of the cylindrical section in the middle of the hydrolysis reactor, a is the radius of the spherical sections at both ends of the hydrolysis reactor, h1 is the initial liquid level of the hydrolysis reactor, and h2 is the liquid level of the hydrolysis reactor after operation.

[0044] (3) Calculate the actual output value M of the hydrolysis reactor according to the law of conservation of mass. t The calculation formula is:

[0045] M t =ρ×[π×Φ 2 / 4×(L1-L2)+V1-V2]×W×2M1 / M2 / t

[0046] In the formula, Φ is the diameter of the urea solution storage tank, ρ is the density of the urea solution at room temperature, L1 is the initial liquid level of the urea solution storage tank, L2 is the liquid level of the urea solution storage tank after operation, V1 is the solution volume corresponding to the initial liquid level of the hydrolysis reactor, V2 is the solution volume corresponding to the liquid level of the hydrolysis reactor after operation, W is the concentration of the urea solution, which is generally 40% to 60%; M1 is the relative molecular mass of NH3, M2 is the relative molecular mass of urea, and t is the operating time of the urea hydrolysis ammonia production system.

[0047] (4) Retrieve the temperature and liquid level operating curves of the hydrolysis reactor during the operating time from the DCS of the urea hydrolysis ammonia production system. Obtain the actual average operating temperature from the temperature operating curve and the actual average liquid level of the hydrolysis reactor from the liquid level operating curve. Figure 3 The curve showing the relationship between urea hydrolysis rate and temperature can be used to find the urea hydrolysis rate corresponding to the actual average operating temperature.

[0048] (5) Calculate the maximum output value M of the hydrolysis reactor using the following formula. s :

[0049]

[0050] Among them, M s —Maximum output of the hydrolysis reactor, kg / h;

[0051] M t —Actual output value of the hydrolysis reactor, kg / h;

[0052] V s —The urea hydrolysis rate when the hydrolysis reactor operates at the design temperature;

[0053] V t —The urea hydrolysis rate corresponding to the actual average operating temperature;

[0054] Q s —The solution volume (m) corresponding to the design value of the hydrolysis reactor liquid level. 3 ;

[0055] Q t —The solution volume corresponding to the actual average liquid level in the hydrolysis reactor, in meters. 3 .

[0056] The design temperature of the hydrolysis reactor is 150℃, and the design value of the liquid level in the hydrolysis reactor is equal to the radius of the spherical part of the hydrolysis reactor.

[0057] Example 1

[0058] A 350MW unit at a power plant in Yulin, Shaanxi Province

[0059] The urea hydrolysis reactor has a main body size of approximately 1.7m (diameter of the spherical sections at both ends of the reactor) × 6.0m (length of the cylindrical section in the middle of the reactor), with a = 1.7 / 2 and L = 6.0m. The designed output is 546 kg / h; the urea solution concentration is 50%, and the urea solution density is 1127 kg / m³. 3 The density of the urea solution was measured using a densitometer; the diameter Φ of the urea solution storage tank was 7m; the initial liquid level L1 of the urea solution storage tank was recorded as 2779mm and the initial liquid level h1 of the hydrolysis reactor was recorded as 833mm. After 5 hours of operation, the liquid level L2 of the urea solution storage tank was 2604mm and the liquid level h2 of the hydrolysis reactor was 832mm.

[0060] The formulas for calculating the solution volume V1 corresponding to the initial liquid level in the hydrolysis reactor and the solution volume V2 corresponding to the liquid level after the hydrolysis reactor has been running are as follows:

[0061]

[0062]

[0063] The initial liquid level in the hydrolysis reactor corresponds to a solution volume V1 = 7.26 m³. 3 The solution volume V2 corresponding to the liquid level after the hydrolysis reactor is operational is 7.25 m³. 3 .

[0064] According to formula M t =ρ×[π×Φ 2 The actual output value M of the hydrolysis reactor is calculated as follows: [4×(L1-L2)+V1-V2]×W×2M1 / M2 / t. t = 424.8 kg / h.

[0065] The temperature and liquid level operating curves of the hydrolysis reactor during the operation period were retrieved from the DCS of the urea hydrolysis ammonia production system. The actual average operating temperature was obtained from the temperature operating curve, and the actual average liquid level of the hydrolysis reactor was obtained from the liquid level operating curve. The average temperature of the hydrolysis reactor over five hours was calculated to be 144.9℃. Figure 3 , to obtain V s / V t It is 1.41.

[0066] Calculate the solution volume Q corresponding to the hydrolysis reactor liquid level at the design value, based on the design value and actual average liquid level of the hydrolysis reactor, and referring to the calculation formula of V1 or V2 (where h1 or h2 is replaced by the design value or actual average liquid level of the hydrolysis reactor). s and the solution volume Q corresponding to the actual average liquid level in the hydrolysis reactor. t Then, it is calculated using the following formula:

[0067]

[0068] The maximum output value M of the hydrolysis reactor at the design operating temperature of 150℃ s =619kg / h, which meets the requirement that the hydrolysis reactor is designed to have an output of more than 546kg / h.

[0069] Example 2

[0070] A 350MW unit at a power plant in Chizhou, Anhui

[0071] The urea hydrolysis reactor has a main body size of approximately 1.5m (diameter of the spherical sections at both ends of the reactor) × 5.0m (length of the cylindrical section in the middle of the reactor), with a = 1.5 / 2 and L = 5.0m. The designed output is 300 kg / h; the urea solution concentration is 50%, and the urea solution density is 1134 kg / m³. 3The density of the urea solution was measured using a densitometer; the diameter Φ of the urea solution storage tank was 5.5m; the initial liquid level L1 of the urea solution storage tank was recorded as 3086mm and the initial liquid level h1 of the hydrolysis reactor was recorded as 728.5mm. After 4 hours of operation, the liquid level L2 of the urea solution storage tank was 2986mm and the liquid level h2 of the hydrolysis reactor was 730.0mm.

[0072] The formulas for calculating the solution volume V1 corresponding to the initial liquid level in the hydrolysis reactor and the solution volume V2 corresponding to the liquid level after the hydrolysis reactor has been running are as follows:

[0073]

[0074]

[0075] The initial liquid level in the hydrolysis reactor corresponds to a solution volume V1 = 4.68 m³. 3 The solution volume V2 corresponding to the liquid level after the hydrolysis reactor is in operation is 4.69 m³. 3 .

[0076] According to formula M t =ρ×[π×Φ 2 The actual output value M of the hydrolysis reactor is calculated as follows: [4×(L1-L2)+V1-V2]×W×2M1 / M2 / t. t =187.4 kg / h.

[0077] The temperature and liquid level operating curves of the hydrolysis reactor during the operating time were retrieved from the DCS of the urea hydrolysis ammonia production system. The actual average operating temperature was obtained from the temperature operating curve, and the actual average liquid level of the hydrolysis reactor was obtained from the liquid level operating curve. The average temperature of the hydrolysis reactor over four hours was calculated to be 140.5℃. Figure 3 , to obtain V s / V t It is 1.67.

[0078] Calculate the solution volume Q corresponding to the hydrolysis reactor liquid level at the design value, based on the design value and actual average liquid level of the hydrolysis reactor, and referring to the calculation formula of V1 or V2 (where h1 or h2 is replaced by the design value or actual average liquid level of the hydrolysis reactor). s and the solution volume Q corresponding to the actual average liquid level in the hydrolysis reactor. t Then, it is calculated using the following formula:

[0079]

[0080] The maximum output value M of the hydrolysis reactor at the design operating temperature of 150℃ s=320.4 kg / h, which meets the requirement that the hydrolysis reactor is designed to have an output of more than 300 kg / h.

[0081] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for calculating the maximum output of a hydrolysis reactor in a urea hydrolysis ammonia production system, wherein, The urea hydrolysis ammonia production system includes a urea solution storage tank, a urea solution transfer pump, and a hydrolysis reactor. The urea solution in the storage tank enters the hydrolysis reactor via the urea solution transfer pump, where urea decomposes to generate NH3. The method is characterized by the following steps: (1) Record the initial liquid level of the urea solution storage tank and the initial liquid level of the hydrolysis reactor, and calculate the solution volume corresponding to the initial liquid level of the hydrolysis reactor. (2) After the urea hydrolysis ammonia production system has been running for a period of time, record the liquid level of the urea solution storage tank and the liquid level of the hydrolysis reactor after operation, and calculate the solution volume corresponding to the liquid level of the hydrolysis reactor after operation. (3) Calculate the actual output value M of the hydrolysis reactor according to the law of conservation of mass. t The calculation formula is: ； In the formula, Φ is the diameter of the urea solution storage tank, in meters (m); ρ is the density of the urea solution, in kilograms per cubic meter (kg / m³). 3 L1 is the initial liquid level of the urea solution storage tank, in mm; L2 is the liquid level of the urea solution storage tank after operation, in mm; V1 is the solution volume corresponding to the initial liquid level of the hydrolysis reactor, in m³. 3 V2 represents the solution volume corresponding to the liquid level after the hydrolysis reactor has been running, in cubic meters (m³). 3 W represents the concentration of the urea solution, in percentage; M1 represents the relative molecular mass of NH3; M2 represents the relative molecular mass of urea; and t represents the operating time of the urea hydrolysis ammonia production system, in hours. (4) Retrieve the temperature and liquid level operating curves of the hydrolysis reactor during the operating time from the DCS of the urea hydrolysis ammonia production system. Obtain the actual average operating temperature based on the temperature operating curve and the actual average liquid level of the hydrolysis reactor based on the liquid level operating curve. Find the urea hydrolysis rate corresponding to the actual average operating temperature based on the urea hydrolysis rate versus temperature curve. (5) Calculate the maximum output value M of the hydrolysis reactor using the following formula. s : ； Among them, M s --Maximum output of the hydrolysis reactor, kg / h; M t --Actual output value of the hydrolysis reactor, kg / h; V s --Urea hydrolysis rate (%) / min when the hydrolysis reactor operates at the design temperature; V t --Urea hydrolysis rate at the actual average operating temperature, % / min; Q s --The solution volume in m³ corresponding to the hydrolysis reactor level at the design value. 3 ; Q t --The solution volume corresponding to the actual average liquid level in the hydrolysis reactor, in m 3 .

2. The method for calculating the maximum output of a hydrolysis reactor in a urea hydrolysis ammonia production system according to claim 1, characterized in that, This method was carried out under the condition of operating a hydrolysis reactor and a urea solution storage tank.

3. The method for calculating the maximum output of a hydrolysis reactor in a urea hydrolysis ammonia production system according to claim 1, characterized in that, The urea hydrolysis ammonia production system should operate for no less than 4 hours.

4. The method for calculating the maximum output of a hydrolysis reactor in a urea hydrolysis ammonia production system according to claim 1, characterized in that, The formulas for calculating the solution volume V1 corresponding to the initial liquid level in the hydrolysis reactor and the solution volume V2 corresponding to the liquid level after the hydrolysis reactor has been running are as follows: ； ； Where L is the length of the cylindrical section in the middle of the hydrolysis reactor, in meters; a is the radius of the spherical sections at both ends of the hydrolysis reactor, in meters; h1 is the initial liquid level of the hydrolysis reactor, in millimeters; and h2 is the liquid level of the hydrolysis reactor after operation, in millimeters.

5. The method for calculating the maximum output of a hydrolysis reactor in a urea hydrolysis ammonia production system according to claim 1, characterized in that, The design temperature of the hydrolysis reactor is 150℃.

6. The method for calculating the maximum output of a hydrolysis reactor in a urea hydrolysis ammonia production system according to claim 1, characterized in that, The design value of the liquid level in the hydrolysis reactor is equal to the radius of the spherical sections at both ends of the hydrolysis reactor.

7. The method for calculating the maximum output of a hydrolysis reactor in a urea hydrolysis ammonia production system according to claim 1, characterized in that, The concentration of the urea solution is 40%~60%.

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