A wastewater drying monitoring method and system based on variable-speed gas flow

Abstract

The application provides a wastewater drying monitoring method and system based on variable flow of gas. The method comprises the following steps: S1: atomizing the wastewater and sending it into a drying tower, introducing gas into the drying tower to evaporate and dry the atomized wastewater droplets, and monitoring the gas temperature at the inlet, along the way and at the outlet of the drying tower in real time; S2: obtaining the gas residence time t h by a formula h : S3: controlling the wastewater flow and the gas flow according to the gas residence time t h , and maintaining the residence time t h and the gas temperature at the outlet of the drying tower within a preset range. The application fully considers the characteristics of wastewater in the constant-speed evaporation and the reduced-speed evaporation stages, establishes an inverse function dynamic model of the gas flow time and the flow distance according to the relationship between the gas flow rate and the temperature in different evaporation stages, improves the accuracy of the calculation of the gas residence time in the drying tower, and guarantees the treatment effect and the operation stability of the system.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wastewater treatment, in particular to a wastewater drying monitoring method and system based on variable speed flow of gas. BACKGROUND

[0002] The residence time of high-temperature gas in the drying tower determines the heat exchange time of the gas-liquid two-phase fluid, and is also a key parameter affecting the evaporation drying effect of wastewater. During the operation of the drying tower, the temperature and other parameters of the high-temperature gas will change with the operation of the thermal power generating unit, so the gas residence time and the wastewater drying effect will also change. If the gas residence time is not reasonably calculated and controlled, the wastewater drying system will be unstable and prone to poor drying effect and other problems. At present, the calculation of the residence time is relatively rough, and generally only the average flow rate of the gas in the tower can be calculated by the average value of the inlet gas temperature and the outlet gas temperature of the drying tower, and then the residence time is calculated by the tower height. However, since the temperature of the gas will continuously decrease when flowing in the drying tower, and the decrease amplitude is different, the flow rate will also change accordingly. The existing calculation method of the residence time cannot reflect the change rule of the flow rate with the temperature, and the gas residence time calculated by the average temperature and the average flow rate is prone to cause unreasonable operation control of the wastewater drying system, resulting in insufficient system output or poor drying effect, and seriously affecting the stable operation of the system.

[0003] In view of this, the present application is proposed. SUMMARY

[0004] The present application aims to provide a wastewater drying monitoring method and system based on variable speed flow of gas, which establishes an inverse function dynamic model of gas flow time and flow distance according to the relationship between the gas flow rate and the temperature in different evaporation stages, improves the accuracy of the calculation of the gas residence time in the drying tower, and ensures the treatment effect and the operation stability of the system.

[0005] The present application provides a wastewater drying monitoring method based on variable speed flow of gas, comprising the following steps:

[0006] S1: atomizing the wastewater and sending it into a drying tower, introducing gas into the drying tower to evaporate and dry the atomized wastewater droplets, and monitoring the inlet gas temperature, the along-the-way gas temperature and the outlet gas temperature of the drying tower in real time;

[0007] S2: obtaining the gas residence time t by the following formula h :

[0008]

[0009] Where: P is the gas pressure; S is the cross-sectional area of ​​the drying tower, which can be calculated from the tower diameter; n is the molar flow rate, which can be calculated from the gas volume flow rate; R is the gas constant; a and b are model parameters; h is the height of the hollow cylinder in the drying tower;

[0010] S3: According to the gas residence time t h Regulate the wastewater flow and gas flow, and make the residence time t h And the drying tower outlet gas temperature is maintained within the preset range.

[0011] In step S1, the upper portion of the drying tower is a hollow cylinder, which is the primary location for wastewater evaporation and drying. The lower portion of the drying tower is a hollow cone, which is primarily used for ash deposition. Unless otherwise specified, the drying tower primarily refers to the hollow cylindrical portion. A rotary atomizer is installed at the top of the drying tower to atomize the wastewater. The rotary atomizer rotates at a speed of 12,000-18,000 rpm, and the particle size of the atomized wastewater droplets ranges from 10-60 μm.

[0012] The evaporation and drying of wastewater droplets is divided into two stages: constant-rate evaporation and decreasing-rate evaporation. In the constant-rate evaporation stage, the water on the droplet surface absorbs the heat of the high-temperature gas and evaporates rapidly. The gas temperature drops sharply with the flow, and a solid shell (composed of soluble salts and suspended matter in the wastewater) forms on the droplet surface. This stage mainly takes place in the upper part of the drying tower. In the decreasing-rate evaporation stage, the water inside the solid shell slowly transfers to the surface and evaporates. The gas temperature slowly drops with the flow. This stage generally takes place in the lower part of the drying tower.

[0013] After the gas enters the drying tower, its vertical flow velocity is calculated according to the following formula:

[0014]

[0015] Where: v is the vertical flow velocity of the gas; V is the volume flow rate of the gas; n is the molar flow rate; R is the gas constant; T is the Kelvin temperature of the gas; P is the gas pressure; S is the cross-sectional area of ​​the drying tower.

[0016] Along-the-line gas temperature refers to the gas temperature at different heights in the drying tower, monitored by corresponding temperature measurement components. Specifically, along-the-line gas temperature can include the gas temperatures at 1 / 8, 1 / 4, 3 / 8, 1 / 2, 2 / 3, and 5 / 6 from the top of the drying tower. During the constant-rate evaporation phase at the top of the drying tower, where gas temperature fluctuates dramatically, more temperature measurement components are deployed to improve model fitting accuracy. During the decreasing-rate evaporation phase at the bottom of the drying tower, where gas temperature changes more slowly, fewer temperature measurement components are deployed.

[0017] Since the gas temperature drops sharply in the upper part of the drying tower (constant rate evaporation stage) and slowly drops in the lower part of the drying tower (decreasing rate evaporation stage), the inverse function model is used to fit the relationship between gas temperature and vertical flow distance. The curve fitting formula is as follows:

[0018]

[0019] Where: T is the gas temperature; L is the vertical distance between the gas temperature monitoring position and the top of the drying tower; a and b are model parameters, which are obtained based on the temperature monitoring value and curve fitting. The fitting method is: take T as the explained variable and The least squares method was used to calculate the model parameters a and b and the determination coefficient R of the fitting curve. 2 Should meet: R 2 ≥0.900.

[0020] The vertical flow velocity of the gas is the derivative of the vertical flow distance and time t, that is:

[0021]

[0022]

[0023] Since L = 0, t = 0, we can get:

[0024]

[0025] Let L = h, and we can get the gas residence time t h :

[0026]

[0027] Where: P is the gas pressure; S is the cross-sectional area of ​​the drying tower; n is the molar flow rate; R is the gas constant; a and b are model parameters; h is the height of the hollow cylinder in the drying tower.

[0028] According to the solid content x of the wastewater, the gas residence time t is determined as follows h The control interval is:

[0029] When the solid content of wastewater is x≤10%, control 30s≤t h <35s;

[0030] When the solid content of wastewater is x: 10%<x≤20%, control 35s≤t h <40s;

[0031] When the solid content of wastewater is x: 20%<x≤30%, control 40s≤t h <45s;

[0032] When the solid content of wastewater is x: 30%<x≤40%, control 45s≤t h ≤50s.

[0033] The wastewater flow and gas flow are regulated as follows:

[0034] When the gas residence time t h When the flow rate is lower than the lower limit of the control range, reduce the wastewater flow rate and gas flow rate until the gas residence time t h The temperature of the gas at the drying tower outlet is within the control range and is maintained within the preset range;

[0035] When the gas residence time t h When the flow rate is higher than the upper limit of the control range, increase the wastewater flow rate and gas flow rate until the gas residence time t h The temperature of the gas at the outlet of the drying tower is kept within the control range and within the preset range.

[0036] Furthermore, the preset range of the drying tower outlet gas temperature is 423K-453K.

[0037] The present invention also provides a wastewater drying monitoring system for implementing the above-mentioned wastewater drying monitoring method, comprising a drying tower and a controller, wherein a rotary atomizer and a gas distributor are provided at the top of the drying tower, the rotary atomizer is connected to the wastewater pipeline, a wastewater regulating valve is provided on the wastewater pipeline, the gas distributor is connected to the inlet air duct, a gas regulating valve, an inlet thermometer and a flow meter are provided on the inlet air duct, an outlet air duct is provided at the lower part of the drying tower, an outlet thermometer is provided on the outlet air duct, a pressure measuring assembly is provided on the drying tower, a plurality of temperature measuring assemblies are provided along the height direction of the drying tower at intervals, and the controller is provided with a calculation module, which can calculate and obtain the gas residence time t h , the controller is based on the gas residence time t h The wastewater regulating valve and the gas regulating valve are controlled to regulate the wastewater flow and the gas flow.

[0038] Each along-the-line temperature measurement assembly includes multiple along-the-line temperature measurement components arranged at intervals along the circumference of the drying tower, and each along-the-line temperature measurement component includes at least one along-the-line thermometer arranged along the radial direction of the drying tower. The calculation module can calculate the average of the monitoring values ​​of multiple along-the-line thermometers in each along-the-line temperature measurement assembly.

[0039] The pressure measuring assembly includes a plurality of pressure gauges spaced apart along the circumference of the drying tower, and the calculation module is capable of calculating the average of the monitoring values ​​of the plurality of pressure gauges.

[0040] Based on the characteristics of wastewater in the constant-rate evaporation and reduced-rate evaporation stages, the present invention establishes a wastewater drying monitoring method and system based on variable-speed gas flow, which can monitor key parameters in real time and provide a data basis for the establishment of a kinetic model; the method and system fully consider the relationship between gas flow rate and temperature in different evaporation stages, establish an inverse function kinetic model of gas flow time and flow distance, and improve the accuracy of calculating the gas residence time in the drying tower; according to the real-time calculation of the gas residence time by the kinetic model, corresponding intelligent control methods are formulated for different types of wastewater, ensuring the wastewater treatment effect and treatment capacity of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0042] Figure 1 It is a structural schematic diagram of the drying tower of the present invention;

[0043] Figure 2 This is a structural diagram of a temperature measurement component along the way according to one embodiment;

[0044] Figure 3 This is a schematic structural diagram of a temperature measurement component along the process according to another embodiment.

[0045] Description of reference numerals:

[0046] 1: Drying tower; 2: Rotary atomizer; 3: Gas distributor; 4: Wastewater pipeline; 5: Wastewater regulating valve; 6: Inlet air duct; 7: Gas regulating valve; 8: Inlet thermometer; 9: First along-the-process temperature measurement component; 10: Second along-the-process temperature measurement component; 11: Third along-the-process temperature measurement component; 12: Fourth along-the-process temperature measurement component; 13: Fifth along-the-process temperature measurement component; 14: Sixth along-the-process temperature measurement component; 15: Outlet air duct; 16: Outlet thermometer; 17: Pressure measuring component; i01: First along-the-process thermometer; i02: Second along-the-process thermometer; i03: Third along-the-process thermometer; i11: Fourth along-the-process thermometer; i12: Fifth along-the-process thermometer; i13: Sixth along-the-process thermometer; i21: Seventh along-the-process thermometer; i22: Eighth along-the-process thermometer; i23: Ninth along-the-process thermometer. DETAILED DESCRIPTION

[0047] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present application belongs.

[0048] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular also includes the plural. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0049] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0050] Example 1

[0051] The wastewater drying monitoring method based on variable-speed gas flow of this embodiment includes the following steps:

[0052] S1: The wastewater is atomized and sent into the drying tower. Gas is introduced into the drying tower to evaporate and dry the atomized wastewater droplets. The inlet gas temperature, along-the-way gas temperature and outlet gas temperature of the drying tower are monitored in real time. The along-the-way gas temperature includes the gas temperature at the 1 / 8 position, 1 / 4 position, 3 / 8 position, 1 / 2 position, 2 / 3 position and 5 / 6 position from the top of the drying tower respectively.

[0053] S2: Obtain the gas residence time t by the following formula h :

[0054]

[0055] Where: P is the gas pressure; S is the cross-sectional area of ​​the drying tower; n is the molar flow rate; R is the gas constant; a and b are model parameters; h is the height of the hollow cylinder in the drying tower.

[0056] The model parameters a and b are obtained based on the monitoring values ​​of the drying tower outlet gas temperature, the gas temperature along the process, and the outlet gas temperature and the following curve fitting formula:

[0057]

[0058] Wherein, T is the gas temperature; L is the vertical distance between the gas temperature monitoring position and the top of the drying tower; a and b are model parameters, which are obtained based on the temperature monitoring value and the curve fitting. The fitting method is: take T as the explained variable and The least squares method was used to calculate the model parameters a and b and the determination coefficient R of the fitting curve. 2 Should meet: R 2 ≥0.900.

[0059] S3: According to the gas residence time t h Regulate the wastewater flow and gas flow, and make the residence time t h And the drying tower outlet gas temperature is maintained within the preset range.

[0060] The wastewater is atomized by a rotary atomizer, the rotation speed of the rotary atomizer is 12000-18000r / min, and the particle size of the wastewater droplets formed by atomization is 10-60μm.

[0061] The gas residence time t is determined as follows h The control interval is:

[0062] When the solid content of wastewater is x≤10%, the gas residence time t h The control interval is 30s-35s;

[0063] When the solid content of wastewater x is: 10%<x≤20%, the gas residence time t h The control interval is 35s-40s;

[0064] When the solid content of wastewater x is: 20%<x≤30%, the gas residence time t h The control interval is 40s-45s;

[0065] When the solid content of wastewater x is: 30%<x≤40%, the gas residence time t h The control interval is 45s-50s.

[0066] The wastewater flow and gas flow are regulated as follows:

[0067] When the gas residence time t h When the flow rate is lower than the lower limit of the control range, reduce the wastewater flow rate and gas flow rate until the gas residence time t h The temperature of the gas at the drying tower outlet is within the control range and is maintained within the preset range;

[0068] When the gas residence time t h When the flow rate is higher than the upper limit of the control range, increase the wastewater flow rate and gas flow rate until the gas residence time t h The temperature of the gas at the outlet of the drying tower is kept within the control range and within the preset range.

[0069] The preset range of the drying tower outlet gas temperature is 423K-453K.

[0070] Example 2

[0071] Combine Figure 1-Figure 3 As shown, the wastewater drying monitoring system of this embodiment is a wastewater drying monitoring system for implementing the wastewater drying monitoring method of Example 1.

[0072] The wastewater drying monitoring system of this embodiment includes a drying tower 1 and a controller (not shown). A rotary atomizer 2 and a gas distributor 3 are provided at the top of the drying tower 1. The rotary atomizer 2 is connected to a wastewater pipe 4, on which a wastewater regulating valve 5 is provided. The gas distributor 3 is connected to an inlet air duct 6, on which a gas regulating valve 7, an inlet thermometer 8 and a flow meter (not shown) are provided. An outlet air duct 15 is provided at the bottom of the drying tower 1, on which an outlet thermometer 16 is provided. A pressure measuring assembly 17 is provided on the drying tower 1. A plurality of temperature measuring assemblies are provided along the height direction of the drying tower 1 at intervals. The controller is provided with a calculation module, which can calculate and obtain the gas residence time t h , the controller is based on the gas residence time t h The wastewater regulating valve 5 and the gas regulating valve 7 are controlled to regulate the wastewater flow and the gas flow.

[0073] The drying tower 1 has a hollow cylindrical top and a hollow conical bottom. A rotary atomizer 2 is used to atomize the wastewater. It is located at the center of the top of the drying tower 1 and connected to the wastewater pipe 4. A wastewater regulating valve 5 regulates the wastewater flow rate. A gas distributor 3 is located at the top of the drying tower 1. The gas distributor 3 is arranged in a circular pattern, forming a spiraling downward flow pattern for gas before entering the top of the drying tower 1. The inlet of the gas distributor 3 is connected to the inlet airway 6, and the outlet of the gas distributor 3 is located at the center of the top of the drying tower 1. A gas regulating valve 7 regulates the gas flow rate. An inlet thermometer 8 monitors the inlet gas temperature T1 in real time. A flowmeter monitors the gas flow rate in real time. The inlet thermometer 8 and the flowmeter can be installed at a depth of 1 / 2 the diameter of the inlet airway 6. An outlet thermometer 16 monitors the outlet gas temperature T8 in real time and can be installed at a depth of 1 / 2 the diameter of the outlet airway 15. The pressure measuring assembly 17 is used to monitor the gas pressure P in real time and can be installed at a 1 / 2 height position of the hollow cylinder and a 1 / 8 diameter depth position inside the hollow cylinder.

[0074] Six along-the-way temperature measuring components are arranged at intervals in the height direction of the drying tower 1, namely: a first along-the-way temperature measuring component 9, a second along-the-way temperature measuring component 10, a third along-the-way temperature measuring component 11, a fourth along-the-way temperature measuring component 12, a fifth along-the-way temperature measuring component 13, and a sixth along-the-way temperature measuring component 14. Each along-the-way temperature measuring component is arranged at the 1 / 8 position, 1 / 4 position, 3 / 8 position, 1 / 2 position, 2 / 3 position, and 5 / 6 position from the top of the drying tower 1 in sequence.

[0075] Each along-line temperature measurement assembly includes three along-line temperature measurement components spaced apart along the circumference of the drying tower 1. Figure 2 As shown, in one embodiment, each along-line temperature measurement component includes along-line thermometers arranged along the circumference of the drying tower 1, namely: a first along-line thermometer i01, a second along-line thermometer i02, and a third along-line thermometer i03. The along-line thermometers can be installed at a distance of 1 / 8 of the inner diameter of the drying tower inner wall and can be arranged 120° from the center of the cylindrical cross section. The calculation module is capable of calculating the average of the monitoring values ​​of the three along-line thermometers in each along-line temperature measurement component; that is,

[0076]

[0077] Among them: i = 2, 3, 4, 5, 6, 7.

[0078] like Figure 3 As shown, in another embodiment, each along-the-process temperature measuring component includes 9 along-the-process thermometers arranged along the circumference and radial direction of the drying tower 1. At this time, each along-the-process temperature measuring component includes a first along-the-process thermometer i01, a second along-the-process thermometer i02, a third along-the-process thermometer i03, a fourth along-the-process thermometer i11, a fifth along-the-process thermometer i12, a sixth along-the-process thermometer i13, a seventh along-the-process thermometer i21, an eighth along-the-process thermometer i22, and a ninth along-the-process thermometer i23. Among them, the first along-the-process thermometer i01, the second along-the-process thermometer i02, and the third along-the-process thermometer i03 can be installed at 1 / 8 of the inner diameter away from the inner wall of the drying tower, the fourth along-the-process thermometer i11, the fifth along-the-process thermometer i12, and the sixth along-the-process thermometer i13 can be installed at 2 / 8 of the inner diameter away from the inner wall of the drying tower, and the seventh along-the-process thermometer i21, the eighth along-the-process thermometer i22, and the ninth along-the-process thermometer i23 can be installed at 3 / 8 of the inner diameter away from the inner wall of the drying tower. The first along-line thermometer i01, the fourth along-line thermometer i11, and the seventh along-line thermometer i21 can be installed along the same radial direction, the second along-line thermometer i02, the fifth along-line thermometer i12, and the eighth along-line thermometer i22 can be installed along the same radial direction, and the third along-line thermometer i03, the sixth along-line thermometer i13, and the ninth along-line thermometer i23 can be installed along the same radial direction. The three radial directions can be arranged at 120° from the center of the cross-section of the cylinder. The calculation module can calculate the average of the monitoring values ​​of the nine along-line thermometers in each along-line temperature measurement component; that is:

[0079]

[0080] Among them: i = 2, 3, 4, 5, 6, 7.

[0081] The pressure measuring assembly 17 includes three pressure gauges spaced apart along the circumference of the drying tower 1 , and the calculation module can calculate the average of the monitoring values ​​of the three pressure gauges.

[0082] Example 3

[0083] The wastewater drying monitoring system of Example 2 was used to evaporate and dry the wastewater; the parameters were as follows: the solid content x of the wastewater was 5%, the inlet gas temperature T1 was 623K, the outlet gas temperature T8 was 453K, the tower diameter of the drying tower was 8.5m, and the height h of the hollow cylinder of the drying tower was 16m; the design value of the gas flow rate was 62300Nm 3 / h.

[0084] The curve fitting results are: R 2 =0.996

[0085] Gas residence time:

[0086] According to the above parameters, the actual value of the gas residence time of the drying tower is 32.2s, which is consistent with the gas residence time t h The relative error is only 6.8%. It can be seen that the gas residence time t calculated in this embodiment is h This is close to the gas residence time obtained during actual operation, indicating that the calculation method of this embodiment can more accurately obtain the gas residence time during operation of the drying tower.

[0087] Example 4

[0088] The wastewater drying monitoring system of Example 2 was used to evaporate and dry the wastewater; the parameters were as follows: the solid content x of the wastewater was 15%, the inlet gas temperature T1 was 633K, the outlet gas temperature T8 was 423K, the tower diameter of the drying tower was 8.5m, and the height h of the hollow cylinder of the drying tower was 16m; the design value of the gas flow rate was 56400Nm 3 / h.

[0089] The curve fitting results are: R 2 =0.982

[0090] Gas residence time:

[0091] According to the above parameters, the actual value of the gas residence time of the drying tower is 37.3s, which is consistent with the gas residence time t h The relative error is only 6.2%. It can be seen that the gas residence time t calculated in this embodiment is h This is close to the gas residence time obtained during actual operation, indicating that the calculation method of this embodiment can more accurately obtain the gas residence time during operation of the drying tower.

[0092] Example 5

[0093] The wastewater drying monitoring system of Example 2 was used to evaporate and dry the wastewater; the parameters were as follows: the solid content x of the wastewater was 26%, the inlet gas temperature T1 was 593K, the outlet gas temperature T8 was 453K, the tower diameter of the drying tower was 8.5m, and the height h of the hollow cylinder of the drying tower was 17m; the design value of the gas flow rate was 51800Nm 3 / h.

[0094] The curve fitting results are: R 2 =0.935

[0095] Gas residence time:

[0096] According to the above parameters, the actual value of the gas residence time of the drying tower is 41.7s, which is consistent with the gas residence time t h The relative error is only 4.1%. It can be seen that the gas residence time t calculated in this embodiment is h This is close to the gas residence time obtained during actual operation, indicating that the calculation method of this embodiment can more accurately obtain the gas residence time during operation of the drying tower.

[0097] Example 6

[0098] The wastewater drying monitoring system of Example 2 was used to evaporate and dry the wastewater; the parameters were as follows: the solid content x of the wastewater was 34%, the inlet gas temperature T1 was 613K, the outlet gas temperature T8 was 428K, the diameter of the drying tower was 10m, the height h of the hollow cylinder of the drying tower was 26m; the design value of the gas flow rate was 98000m 3 / h.

[0099] The curve fitting results are: R 2 =0.973

[0100] Gas residence time:

[0101] According to the above parameters, the actual value of the gas residence time of the drying tower is 48.5s, which is consistent with the gas residence time t h The relative error is only 7.2%. It can be seen that the gas residence time t calculated in this embodiment is h This is close to the gas residence time obtained during actual operation, indicating that the calculation method of this embodiment can more accurately obtain the gas residence time during operation of the drying tower.

[0102] Example 7

[0103] The wastewater drying monitoring method of this embodiment is based on the gas residence time t calculated by the method of Example 3. h ≈30s, the actual value of the regulated gas flow is 66768Nm 3 / h (ie: at 66768Nm 3 At an actual gas flow rate of 1 / h, the corresponding gas residence time is actually 30s), and other parameters are the same as those in Example 3.

[0104] The actual operation was performed according to the gas flow rate after the above adjustment; during the actual operation, the gas residence time t was calculated according to the method of Example 3. h , and the wastewater flow and gas flow of the drying tower are regulated as follows:

[0105] When 30s≤t h When the s is less than 35s and the temperature of the gas at the drying tower outlet is maintained at 423K-453K, the wastewater flow rate and gas flow rate are kept unchanged;

[0106] When t h When t<30s, reduce the wastewater flow and gas flow until 30s≤t h <35s and the gas temperature at the drying tower outlet is maintained at 423K-453K;

[0107] When t h ≥35s, increase the wastewater flow and gas flow until 30s≤t h <35s and the gas temperature at the drying tower outlet is maintained at 423K-453K.

[0108] Sampling was carried out after running for different periods of time, and the ash moisture content at the drying tower outlet was tested respectively. The results are shown in Table 1. The results show that the ash moisture content at the drying tower outlet measured by five samplings was all within the range of 1-2%, and the average ash moisture content measured by five samplings was 1.46%, which met the industry standard requirements (the ash moisture content at the drying tower outlet does not exceed 2%).

[0109] Example 8

[0110] The wastewater drying monitoring method of this embodiment is based on the gas residence time t calculated by the method of Example 4. h ≈35s, the actual value of the regulated gas flow is 60058Nm 3 / h (ie: at 60058Nm 3 / h actual gas flow rate, the corresponding gas residence time actual value is 35s), and other parameters are the same as Example 4.

[0111] The actual operation was performed according to the gas flow rate after the above adjustment; during the actual operation, the gas residence time t was calculated according to the method of Example 4. h , and the wastewater flow and gas flow of the drying tower are regulated as follows:

[0112] When 35s≤t h When the time is less than 40s and the temperature of the gas at the drying tower outlet is maintained at 423K-453K, the wastewater flow rate and gas flow rate are kept unchanged;

[0113] When t h When t<35s, reduce the wastewater flow and gas flow until 35s≤t h <40s and the gas temperature at the drying tower outlet is maintained at 423K-453K;

[0114] When t h ≥40s, increase the wastewater flow and gas flow until 35s≤t h <40s and the gas temperature at the drying tower outlet is maintained at 423K-453K.

[0115] Sampling and testing were performed according to the method of Example 6; the results showed that the ash moisture content at the drying tower outlet measured five times was within the range of 1-2%, and the average ash moisture content measured five times was 1.28%, meeting the industry standard requirements.

[0116] Example 9

[0117] The wastewater drying monitoring method of this embodiment is based on the gas residence time t calculated by the method of Example 5. h ≈40s, the actual value of the regulated gas flow is 53668Nm 3 / h (ie: at 53668Nm 3 / h actual gas flow rate, the corresponding gas residence time actual value is 40s), and other parameters are the same as Example 5.

[0118] The actual operation was performed according to the gas flow rate after the above adjustment; during the actual operation, the gas residence time t was calculated according to the method of Example 5. h , and the wastewater flow and gas flow of the drying tower are regulated as follows:

[0119] When 40s≤t h When the s is less than 45s and the temperature of the gas at the drying tower outlet is maintained at 423K-453K, the wastewater flow rate and gas flow rate are kept unchanged;

[0120] When t h When t<40s, reduce the wastewater flow and gas flow until 40s≤t h <45s and the gas temperature at the drying tower outlet is maintained at 423K-453K;

[0121] When t h ≥45s, increase the wastewater flow and gas flow until 40s≤t h <45s and the gas temperature at the drying tower outlet is maintained at 423K-453K.

[0122] Sampling and testing were performed according to the method of Example 6; the results showed that the ash moisture content at the drying tower outlet measured five times was within the range of 1-2%, and the average ash moisture content measured five times was 1.39%, meeting the industry standard requirements.

[0123] Example 10

[0124] The wastewater drying monitoring method of this embodiment is based on the gas residence time t calculated by the method of Example 6. h ≈45s, the actual value of the regulated gas flow is 105267Nm 3 / h (ie: at 105267Nm 3 At an actual gas flow rate of 1 / h, the corresponding gas residence time is actually 45s), and other parameters are the same as those in Example 6.

[0125] The actual operation was performed according to the gas flow rate after the above adjustment; during the actual operation, the gas residence time t was calculated according to the method of Example 6. h , and the wastewater flow and gas flow of the drying tower are regulated as follows:

[0126] When 45s≤t h When the time is ≤50s and the gas temperature at the drying tower outlet is maintained at 423K-453K, the wastewater flow rate and gas flow rate are kept unchanged;

[0127] When t h When t<45s, reduce the wastewater flow and gas flow until 45s≤t h ≤50s and the gas temperature at the drying tower outlet is maintained at 423K-453K;

[0128] When t h >50s, increase the wastewater flow and gas flow until 45s≤t h≤50s and the gas temperature at the drying tower outlet is maintained at 423K-453K.

[0129] Sampling and testing were performed according to the method of Example 6; the results showed that the ash moisture content at the drying tower outlet measured five times was within the range of 1-2%, and the average ash moisture content measured five times was 1.88%, meeting the industry standard requirements.

[0130] Comparative Example 1

[0131] Except for using the average flow rate method to obtain the gas residence time, the other conditions are the same as those in Example 3; the average flow rate is calculated as follows:

[0132] The average temperature is:

[0133] The average flow rate is:

[0134] The gas residence time is:

[0135] According to the above parameters, the actual value of the gas residence time of the drying tower is 32.2s, which is consistent with the gas residence time t h The relative error is 17.4%. It can be seen that the gas residence time t calculated in this comparative example is h There is a big difference between this and the gas residence time obtained during actual operation, which indicates that the above calculation method of this comparative example cannot accurately obtain the gas residence time of the drying tower during operation.

[0136] The gas residence time t obtained from the above calculation h ≈26.6s, the actual value of the regulated gas flow is 75826Nm 3 / h (ie: the actual gas flow rate is 75826Nm 3 / h, the corresponding actual gas residence time is 26.6s); actual operation according to the adjusted gas flow rate, the results show that: the ash moisture content at the drying tower outlet is 2.69%, which cannot meet the industry standard requirements.

[0137] Comparative Example 2

[0138] Except for using the average flow rate method to obtain the gas residence time, the other conditions are the same as those in Example 4; the average flow rate is calculated as follows:

[0139] The average temperature is:

[0140] The average flow rate is:

[0141] The gas residence time is:

[0142] According to the above parameters, the actual value of the gas residence time of the drying tower is 37.3s, which is consistent with the gas residence time t h The relative error is 19.8%. It can be seen that the gas residence time t calculated in this comparative example is h There is a big difference between this and the gas residence time obtained during actual operation, which indicates that the above calculation method of this comparative example cannot accurately obtain the gas residence time of the drying tower during operation.

[0143] The gas residence time t obtained from the above calculation h ≈29.9s, the actual value of the regulated gas flow is 70914Nm 3 / h (ie: the actual gas flow rate is 70914Nm 3 / h, the corresponding actual gas residence time is 29.9s); actual operation according to the adjusted gas flow rate, the results show that: the ash moisture content at the drying tower outlet is 3.29%, which cannot meet the industry standard requirements.

[0144] Comparative Example 3

[0145] Except that the gas residence time is obtained by the average flow rate method, the other conditions are the same as those in Example 5; the average flow rate is calculated as follows:

[0146] The average temperature is:

[0147] The average flow rate is:

[0148] The gas residence time is:

[0149] According to the above parameters, the actual value of the gas residence time of the drying tower is 41.7s, which is consistent with the gas residence time t h The relative error is 16.3%. It can be seen that the gas residence time t calculated in this comparative example is h There is a big difference between this and the gas residence time obtained during actual operation, which indicates that the above calculation method of this comparative example cannot accurately obtain the gas residence time of the drying tower during operation.

[0150] The gas residence time t obtained from the above calculation h ≈34.9s, the actual value of the regulated gas flow is 61640Nm 3 / h (ie: the actual gas flow rate is 61640Nm 3 / h, the corresponding actual gas residence time is 34.9s); actual operation according to the adjusted gas flow rate, the results show that: the ash moisture content at the drying tower outlet is 3.44%, which cannot meet the industry standard requirements.

[0151] Comparative Example 4

[0152] Except for using the average flow rate method to obtain the gas residence time, the other conditions are the same as those in Example 6; the average flow rate is calculated as follows:

[0153] The average temperature is:

[0154] The average flow rate is:

[0155] The gas residence time is:

[0156] According to the above parameters, the actual value of the gas residence time of the drying tower is 48.5s, which is consistent with the gas residence time t h The relative error is 19.0%. It can be seen that the gas residence time t calculated in this comparative example is h There is a big difference between this and the gas residence time obtained during actual operation, which indicates that the above calculation method of this comparative example cannot accurately obtain the gas residence time of the drying tower during operation.

[0157] The gas residence time t obtained from the above calculation h ≈39.3s, the actual value of the regulated gas flow is 120531Nm 3 / h (ie: the actual gas flow rate is 120531Nm 3 / h, the corresponding gas residence time is actually 39.3s); according to the actual operation of the adjusted gas flow rate, the results show that the moisture content of the ash at the drying tower outlet is 2.87%, which cannot meet the industry standard requirements.

[0158] Comparative Example 5

[0159] Except that the wastewater flow rate and gas flow rate are not regulated during the actual operation, the rest is the same as Example 7.

[0160] Sampling and testing were carried out according to the method of Example 7; the results are shown in Table 1.

[0161] Comparative Example 6

[0162] Except that the wastewater flow rate and gas flow rate are regulated in the following manner during the actual operation, the other conditions are the same as those in Example 7.

[0163] In this comparative example, the flue gas temperature Tout at the drying tower outlet is monitored during operation. Based on the flue gas temperature Tout at the drying tower outlet, the wastewater and gas flow rates entering the drying tower are adjusted in the following manner:

[0164] If 150℃≤Tout≤160℃, maintain the wastewater and gas flow rates unchanged;

[0165] If Tout is less than 150°C, reduce the wastewater flow rate entering the drying tower and / or increase the gas flow rate entering the drying tower until Tout rises to 150°C ≤ Tout ≤ 160°C;

[0166] If Tout>160°C, increase the wastewater flow rate entering the drying tower and / or reduce the gas flow rate entering the drying tower until Tout decreases to 150°C≤Tout≤160°C.

[0167] Sampling and testing were carried out according to the method of Example 7; the results are shown in Table 1.

[0168] Table 1 Detection of moisture content of ash at drying tower outlet

[0169]

[0170] The results show that:

[0171] 1. The method of Example 7 was used to achieve good wastewater drying effects. The moisture content of the ash at the drying tower outlet was stabilized between 1% and 2%. This method can effectively overcome various problems caused by the unstable temperature of the high-temperature flue gas entering the drying tower. The moisture content of the ash at the drying tower outlet met the industry standard requirements and did not adversely affect the subsequent resource utilization of the ash (i.e., fly ash). The drying tower had good operational stability and no operational failures occurred.

[0172] 2. When the method of Control Example 5 is used, when the gas flow rate and wastewater flow rate of the drying tower are not adjusted, the wastewater drying effect is poor, the ash moisture content is difficult to stably meet the standard, and problems such as wet ash and blockage occur many times. In addition, some ash agglomerates and compacts, which seriously affects the stable operation of the system and the resource utilization of fly ash.

[0173] 3. The method of Control Example 6 was adopted, with the drying tower outlet gas temperature as the reference value, to adjust the system gas flow and / or wastewater flow. However, the ash moisture content was difficult to stably meet the standard. During operation, problems such as wet ash and blockage occurred, which had a certain adverse impact on the normal operation of the drying tower. At the same time, some ash agglomerated and compacted, affecting the subsequent resource utilization of the ash.

[0174] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A wastewater drying monitoring method based on variable-speed gas flow, characterized in that: The steps include: S1: The wastewater is atomized and sent to a drying tower. Gas is introduced into the drying tower to evaporate and dry the atomized wastewater droplets. The inlet gas temperature, the gas temperature along the drying tower, and the outlet gas temperature are monitored in real time. S2: Obtain the gas residence time t by the following formula h : Where: P is the gas pressure, unit is Pa; S is the cross-sectional area of ​​the drying tower, unit is m 2 ; n is the molar flow rate, unit is mol / s; R is the gas constant; a and b are model parameters; h is the height of the hollow cylinder in the drying tower, unit is m; The model parameters a and b are obtained based on the monitored values ​​of the drying tower inlet gas temperature, the gas temperature along the drying tower, and the gas temperature at the outlet and the following curve fitting formula: Where: T is the gas temperature, unit is K; L is the vertical distance between the gas temperature monitoring position and the top of the drying tower, unit is m; S3: According to the gas residence time t h Regulate the wastewater flow and gas flow, and make the residence time t h and the drying tower outlet gas temperature is maintained within the preset range; According to the solid content x of the wastewater, the gas residence time t is determined as follows h The control interval is: When x≤10%, control 30s≤t h <35s; When 10%<x≤20%, control 35s≤t h <40s; When 20%<x≤30%, control 40s≤t h <45s; When 30%<x≤40%, control 45s≤t h ≤50s.

2. The wastewater drying monitoring method according to claim 1, characterized in that: The wastewater is atomized by a rotary atomizer, and the particle size of the wastewater droplets formed by atomization is 10-60μm.

3. The wastewater drying monitoring method according to claim 1, characterized in that: The gas temperature along the process includes the gas temperature at the 1 / 8 position, 1 / 4 position, 3 / 8 position, 1 / 2 position, 2 / 3 position, and 5 / 6 position from the top of the drying tower respectively.

4. The wastewater drying monitoring method according to claim 1, characterized in that: The wastewater flow and gas flow are regulated as follows: When the gas residence time t h When the flow rate is lower than the lower limit of the control range, reduce the wastewater flow rate and gas flow rate until the gas residence time t h The temperature of the gas at the drying tower outlet is within the control range and is maintained within the preset range; When the gas residence time t h When the flow rate is higher than the upper limit of the control range, increase the wastewater flow rate and gas flow rate until the gas residence time t h The temperature of the gas at the outlet of the drying tower is kept within the control range and within the preset range.

5. The wastewater drying monitoring method according to claim 1, characterized in that: The preset range of the drying tower outlet gas temperature is 423K-453K.

6. A wastewater drying monitoring system for implementing the wastewater drying monitoring method according to any one of claims 1 to 5, characterized in that: The invention comprises a drying tower and a controller. A rotary atomizer and a gas distributor are provided at the top of the drying tower. The rotary atomizer is connected to a wastewater pipe. A wastewater regulating valve is provided on the wastewater pipe. The gas distributor is connected to an inlet air duct. A gas regulating valve, an inlet thermometer and a flow meter are provided on the inlet air duct. An outlet air duct is provided at the bottom of the drying tower. An outlet thermometer is provided on the outlet air duct. A pressure measuring assembly is provided on the drying tower. A plurality of temperature measuring assemblies are provided along the height direction of the drying tower. The controller is provided with a calculation module. The calculation module can calculate and obtain the gas residence time t h , the controller is based on the gas residence time t h The wastewater regulating valve and the gas regulating valve are controlled to regulate the wastewater flow and the gas flow.

7. The wastewater drying monitoring system according to claim 6, characterized in that: Each along-the-line temperature measurement assembly includes a plurality of along-the-line temperature measurement components spaced apart along the circumference of the drying tower, and each along-the-line temperature measurement component includes at least one along-the-line thermometer arranged radially along the drying tower. The calculation module can calculate the average of the monitoring values ​​of the plurality of along-the-line thermometers in each along-the-line temperature measurement assembly.

8. The wastewater drying monitoring system according to claim 6, characterized in that: The pressure measuring assembly includes a plurality of pressure gauges spaced apart along the circumference of the drying tower, and the calculation module is capable of calculating the average of the monitoring values ​​of the plurality of pressure gauges.

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