Wastewater drying monitoring method and system based on variable-speed flow of gas

Abstract

The invention provides a waste water drying monitoring method and system based on gas variable-speed flow. The method comprises the following steps: S1, atomizing wastewater, feeding the atomized wastewater into a drying tower, introducing gas into the drying tower to evaporate and dry atomized wastewater liquid drops, and monitoring the inlet gas temperature, the on-way gas temperature and the outlet gas temperature of the drying tower in real time; s2, the gas retention time th is obtained through a formula; S3, the waste water flow and the gas flow are regulated and controlled according to the gas retention time th, and the retention time th and the drying tower outlet gas temperature are kept within a preset range. According to the method, the characteristics of the wastewater in the constant-speed evaporation stage and the reduced-speed evaporation stage are fully considered, an inverse function dynamical model of the gas flowing time and the flowing distance is established according to the relation between the gas flowing speed and the temperature in different evaporation stages, the calculation accuracy of the gas retention time in the drying tower is improved, and the calculation efficiency is improved. And the treatment effect and the operation stability of the system are ensured.

Description

Technical Field

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

[0002] Thermal power plants produce a large amount of high-salt wastewater (such as chemical regeneration wastewater, wet desulfurization wastewater, etc.) during the power generation process. This type of wastewater has complex components and direct discharge will cause serious pollution to the environment. In recent years, with the upgrade of national and local governments' control over the discharge of salt-containing industrial wastewater, zero discharge of high-salt wastewater from thermal power plants has become a hot topic in the power industry. At present, rotary atomization drying technology is one of the mainstream wastewater zero-discharge technologies in the industry. This technology sets up a wastewater drying tower, uses high-speed rotation to atomize the wastewater into droplets, and then sprays it into the drying tower, and draws high-temperature gas (flue gas or air) from the thermal power plant into the top of the drying tower. In the drying tower, the high-temperature gas and wastewater droplets fully exchange heat to achieve rapid drying of the wastewater.

[0003] The residence time of high-temperature gas in the drying tower determines the length of heat exchange time between gas and liquid phases, and is also a key parameter affecting the evaporation and drying effect of wastewater. During the operation of the drying tower, since parameters such as the temperature of the high-temperature gas will change with the operation of the thermal power unit, the gas residence time and the wastewater drying effect will also change accordingly. If the gas residence time is not reasonably calculated and regulated, the operation of the wastewater drying system will be unstable, and problems such as poor drying effect will easily occur. At present, the calculation of residence time is relatively extensive. Generally, the average flow rate of the gas in the tower can only 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 continue to decrease when it flows in the drying tower, and the decrease is different, its flow rate will also change accordingly. The existing calculation method of residence time cannot reflect the law of change of flow rate with temperature. The gas residence time is calculated by the method of average temperature and average flow rate, which is easy to lead to unreasonable operation and control of the wastewater drying system, resulting in insufficient system output or poor drying effect, and seriously affecting the stable operation of the system.

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

[0005] The purpose of the present invention is to provide a wastewater drying monitoring method and system based on variable-speed gas flow. According to the relationship between gas flow rate and temperature in different evaporation stages, an inverse function kinetic model of gas flow time and flow distance is established, which improves the accuracy of calculating the gas residence time in the drying tower and ensures the treatment effect and operation stability of the system.

[0006] The present invention provides a wastewater drying monitoring method based on variable speed gas flow, comprising the following steps:

[0007] 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, and the inlet gas temperature, the gas temperature along the drying tower and the outlet gas temperature are monitored in real time;

[0008] S2: The gas residence time t is obtained by the following formula h :

[0009]

[0010] Where: P is the gas pressure; S is the cross-sectional area of ​​the drying tower, which can be calculated by the tower diameter; n is the molar flow rate, which can be calculated by 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;

[0011] S3: According to the gas residence time t h The wastewater flow and gas flow are regulated and the residence time t h And the drying tower outlet gas temperature is maintained within the preset range.

[0012] In step S1, the upper part of the drying tower is a hollow cylinder, which is the main place for evaporation and drying of wastewater; the bottom of the drying tower is a hollow cone, which is mainly used for ash deposition; unless otherwise specified, the drying tower mainly refers to the hollow cylindrical part. A rotary atomizer is set at the top of the drying tower, and the rotary atomizer is used to atomize the wastewater. 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.

[0013] 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 surface of the droplets 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) is formed on the surface of the droplets. This stage is mainly carried out 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 is generally carried out in the lower part of the drying tower.

[0014] After the gas enters the drying tower, its vertical flow velocity is calculated according to the following formula:

[0015]

[0016] 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.

[0017] The gas temperature along the drying tower refers to the gas temperature at different heights of the drying tower, which is monitored by the corresponding temperature measurement components; specifically, the gas temperature along the drying tower may include the gas temperature at 1 / 8, 1 / 4, 3 / 8, 1 / 2, 2 / 3, and 5 / 6 of the top of the drying tower. In the constant-speed evaporation stage at the top of the drying tower, since the gas temperature changes dramatically, more temperature measurement components are set, which is conducive to improving the fitting accuracy of the model; in the deceleration evaporation stage at the lower part of the drying tower, since the gas temperature changes slowly, fewer temperature measurement components are set.

[0018] 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 the gas temperature and the vertical flow distance. The curve fitting formula is as follows:

[0019]

[0020] 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, 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.

[0021] The vertical velocity of gas is the derivative of the vertical flow distance and time t, that is:

[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 Control interval:

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

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

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

[0032] When the solid content of wastewater x is: 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 it is lower than the lower limit of the control interval, reduce 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 within the control range and maintained within the preset range;

[0035] When the gas residence time t h When the gas residence time 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 maintained within the control 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 arranged at the top of the drying tower, the rotary atomizer is connected to the wastewater pipeline, a wastewater regulating valve is arranged on the wastewater pipeline, the gas distributor is connected to the inlet airway, a gas regulating valve, an inlet thermometer and a flowmeter are arranged on the inlet airway, an outlet airway is arranged at the lower part of the drying tower, an outlet thermometer is arranged on the outlet airway, a pressure measuring component is arranged on the drying tower, a plurality of temperature measuring components along the process are arranged at intervals in the height direction of the drying tower, and a calculation module is arranged on the controller, and 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.

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

[0039] The pressure measuring assembly comprises a plurality of pressure gauges arranged at intervals 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 constant-rate evaporation and reduced-rate evaporation stages, the present invention establishes a wastewater drying monitoring method and system based on gas variable-speed 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 implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

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

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

[0044] Figure 3 It is a schematic structural diagram of a temperature measurement component along the way 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-way temperature measuring component; 10: Second along-the-way temperature measuring component; 11: Third along-the-way temperature measuring component; 12: Fourth along-the-way temperature measuring component; 13: Fifth along-the-way temperature measuring component; 14: Sixth along-the-way temperature measuring component; 15: Outlet air duct; 16: Outlet thermometer; 17: Pressure measuring component; i01: First along-the-way thermometer; i02: Second along-the-way thermometer; i03: Third along-the-way thermometer; i11: Fourth along-the-way thermometer; i12: Fifth along-the-way thermometer; i13: Sixth along-the-way thermometer; i21: Seventh along-the-way thermometer; i22: Eighth along-the-way thermometer; i23: Ninth along-the-way thermometer. DETAILED DESCRIPTION

[0047] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those 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 form also includes the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this description, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0049] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work 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 to a drying tower, and gas is introduced into the drying tower to evaporate and dry the atomized wastewater droplets. The inlet gas temperature, the gas temperature along the process and the outlet gas temperature of the drying tower are monitored in real time. The gas temperature along the process includes the gas temperatures at 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: The gas residence time t is obtained 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 curve fitting. The fitting method is: take T as the explained variable, 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 The wastewater flow and gas flow are regulated and 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 Control interval:

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

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

[0065] When the solid content x of wastewater 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 it is lower than the lower limit of the control interval, reduce 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 within the control range and maintained within the preset range;

[0068] When the gas residence time t h When the gas residence time 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 maintained within the control range.

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

[0070] Example 2

[0071] Combination 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 on the top of the drying tower 1. The rotary atomizer 2 is connected to a wastewater pipeline 4. A wastewater regulating valve 5 is provided on the wastewater pipeline 4. The gas distributor 3 is connected to an inlet air duct 6. A gas regulating valve 7, an inlet thermometer 8 and a flow meter (not shown) are provided on the inlet air duct 6. An outlet air duct 15 is provided at the lower part of the drying tower 1. An outlet thermometer 16 is provided on the outlet air duct 15. A pressure measuring component 17 is provided on the drying tower 1. A plurality of temperature measuring components along the process are provided at intervals in the height direction of the drying tower 1. 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 adjust the wastewater flow rate and the gas flow rate.

[0073] The upper part of the drying tower 1 is a hollow cylinder, and the bottom is a hollow cone. The rotary atomizer 2 is used to atomize the wastewater. The rotary atomizer 2 is arranged at the top center of the drying tower 1 and is connected to the wastewater pipeline 4. The wastewater regulating valve 5 is used to adjust the wastewater flow. The gas distributor 3 is arranged at the top of the drying tower 1. The gas distributor 3 is arranged in a circumferential shape, and is used to adjust the gas to a spiral downward flow field and then enter 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 top center of the drying tower 1. The gas regulating valve 7 is used to adjust the gas flow rate, the inlet thermometer 8 is used to monitor the inlet gas temperature T1 in real time, and the flowmeter is used to monitor the gas flow in real time. The inlet thermometer 8 and the flowmeter can be installed at a depth position of 1 / 2 diameter inside the inlet airway 6. The outlet thermometer 16 is used to monitor the outlet gas temperature T8 in real time, and can be installed at a depth position of 1 / 2 diameter inside 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-the-way temperature measurement assembly includes three along-the-way temperature measurement components arranged at intervals along the circumference of the drying tower 1. Figure 2 As shown, in one embodiment, each along-the-way temperature measurement component includes along-the-way temperature measuring meters arranged along the circumference of the drying tower 1, namely: the first along-the-way temperature measuring meter i01, the second along-the-way temperature measuring meter i02, and the third along-the-way temperature measuring meter i03. The along-the-way temperature measuring meter can be installed at a distance of 1 / 8 of the inner diameter of the inner wall of the drying tower, and can be arranged 120° away from the center of the cross section of the cylinder. The calculation module can calculate the average of the monitoring values ​​of the three along-the-way temperature measuring meters in each along-the-way temperature measurement component; namely:

[0076] T i =13(T i01 +T i02 +T i03 )

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

[0078] like Figure 3As shown, in another embodiment, each along-the-way temperature measuring component includes 9 along-the-way thermometers arranged along the circumference and radial direction of the drying tower 1. At this time, each along-the-way temperature measuring component includes a first along-the-way thermometer i01, a second along-the-way thermometer i02, a third along-the-way thermometer i03, a fourth along-the-way thermometer i11, a fifth along-the-way thermometer i12, a sixth along-the-way thermometer i13, a seventh along-the-way thermometer i21, an eighth along-the-way thermometer i22, and a ninth along-the-way thermometer i23. Among them, the first along-the-way thermometer i01, the second along-the-way thermometer i02, and the third along-the-way thermometer i03 can be installed at 1 / 8 of the inner diameter from the inner wall of the drying tower, the fourth along-the-way thermometer i11, the fifth along-the-way thermometer i12, and the sixth along-the-way thermometer i13 can be installed at 2 / 8 of the inner diameter from the inner wall of the drying tower, and the seventh along-the-way thermometer i21, the eighth along-the-way thermometer i22, and the ninth along-the-way thermometer i23 can be installed at 3 / 8 of the inner diameter from the inner wall of the drying tower. The first along-the-way thermometer i01, the fourth along-the-way thermometer i11, and the seventh along-the-way thermometer i21 can be installed along the same radial direction, the second along-the-way thermometer i02, the fifth along-the-way thermometer i12, and the eighth along-the-way thermometer i22 can be installed along the same radial direction, and the third along-the-way thermometer i03, the sixth along-the-way thermometer i13, and the ninth along-the-way thermometer i23 can be installed along the same radial direction, and 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 9 along-the-way thermometers in each along-the-way 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 result is:

[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 h This is close to the gas residence time obtained during actual operation, indicating that the above calculation method of this embodiment can more accurately obtain the gas residence time of the drying tower during operation.

[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 result is:

[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 h This is close to the gas residence time obtained during actual operation, indicating that the above calculation method of this embodiment can more accurately obtain the gas residence time of the drying tower during operation.

[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 result is:

[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 hThe relative error is only 4.1%. It can be seen that the gas residence time t calculated in this embodiment h This is close to the gas residence time obtained during actual operation, indicating that the above calculation method of this embodiment can more accurately obtain the gas residence time of the drying tower during operation.

[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 tower diameter of the drying tower was 10m, and 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 result is:

[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 h This is close to the gas residence time obtained during actual operation, indicating that the above calculation method of this embodiment can more accurately obtain the gas residence time of the drying tower during operation.

[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 / h, the corresponding gas residence time is actually 30s), and other parameters are the same as those in Example 3.

[0104] The actual operation is performed according to the gas flow rate adjusted as above; during the actual operation, the gas residence time t is 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 <35s and the gas temperature at the drying tower outlet is maintained at 423K-453K, the wastewater flow rate and gas flow rate are maintained unchanged;

[0106] When t h <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 time periods, 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 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 did 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 is performed according to the gas flow rate adjusted as above; during the actual operation, the gas residence time t is 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 <40s and the gas temperature at the drying tower outlet is maintained at 423K-453K, the wastewater flow rate and gas flow rate are maintained unchanged;

[0113] When t h <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 carried out according to the method of Example 6; the results showed that the ash moisture content at the drying tower outlet measured by five samplings was within the range of 1-2%, and the average ash moisture content measured by five samplings was 1.28%, which met 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 those in Example 5.

[0118] The actual operation is performed according to the gas flow rate adjusted as above; during the actual operation, the gas residence time t is 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 <45s and the gas temperature at the drying tower outlet is maintained at 423K-453K, the wastewater flow rate and gas flow rate are maintained unchanged;

[0120] When t h <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 carried out according to the method of Example 6; the results showed that the ash moisture content at the drying tower outlet measured by five samplings was within the range of 1-2%, and the average ash moisture content measured by five samplings was 1.39%, which met 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 / h, the corresponding gas residence time is actually 45s), and other parameters are the same as those in Example 6.

[0125] The actual operation is performed according to the gas flow rate adjusted as above; during the actual operation, the gas residence time t is 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 temperature of the gas at the outlet of the drying tower is maintained at 423K-453K, the wastewater flow rate and gas flow rate are maintained unchanged;

[0127] When t h <45s, reduce the wastewater flow and gas flow until 45s≤t h ≤50s and the gas temperature at the outlet of the drying tower 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 outlet of the drying tower 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 by five samplings was within the range of 1-2%, and the average ash moisture content measured by five samplings was 1.88%, which met the industry standard requirements.

[0130] Comparative Example 1

[0131] Except that the gas residence time is obtained by the average flow rate method, 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 h This is quite different from the gas residence time obtained during actual operation, indicating 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 value of gas residence time is 26.6s); actual operation was carried out according to the adjusted gas flow rate, and the results showed that the moisture content of ash at the outlet of the drying tower was 2.69%, which could not meet the industry standard requirements.

[0137] Comparative Example 2

[0138] Except that the gas residence time is obtained by the average flow rate method, 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 h This is quite different from the gas residence time obtained during actual operation, indicating 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 value of gas residence time is 29.9s); actual operation was carried out according to the adjusted gas flow rate, and the results showed that the moisture content of ash at the drying tower outlet was 3.29%, which could not 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 h This is quite different from the gas residence time obtained during actual operation, indicating 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 value of gas residence time is 34.9s); actual operation was carried out according to the adjusted gas flow rate, and the results showed that the moisture content of ash at the outlet of the drying tower was 3.44%, which could not meet the industry standard requirements.

[0151] Comparative Example 4

[0152] Except that the gas residence time is obtained by the average flow rate method, 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 h This is quite different from the gas residence time obtained during actual operation, indicating 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 actual value of gas residence time is 39.3s); actual operation was carried out according to the adjusted gas flow rate, and the results showed that the moisture content of ash at the outlet of the drying tower was 2.87%, which could not 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. According to 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℃, 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℃≤Tout≤160℃.

[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 the outlet of drying tower

[0169]

[0170] The results show that:

[0171] 1. The method of Example 7 is adopted to achieve good wastewater drying effect. The moisture content of ash at the outlet of the drying tower is stabilized between 1-2%, which can effectively overcome various problems caused by the unstable temperature of the high-temperature flue gas entering the drying tower. The moisture content of ash at the outlet of the drying tower meets the requirements of industry standards and will not have an adverse effect on the subsequent resource utilization of ash (i.e., fly ash). The operating stability of the drying tower is good, and no operating failures occur.

[0172] 2. When the method of Control Example 5 is adopted, 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, problems such as wet ash and blockage occur many times, and part of the 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 to adjust the system gas flow and / or wastewater flow using the drying tower outlet gas temperature as a reference value. The ash moisture content was difficult to stably meet the standard. Problems such as wet ash and blockage occurred during operation, which had a certain adverse effect on the normal operation of the drying tower. At the same time, part of the 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 aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned 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, and the inlet gas temperature, the gas temperature along the drying tower and the outlet gas temperature are monitored in real time; S2: The gas residence time t is obtained by the following formula h : 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; S3: According to the gas residence time t h The wastewater flow and gas flow are regulated and the residence time t h And the drying tower outlet gas temperature is maintained within the preset range.

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 temperatures 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.

4. The wastewater drying monitoring method according to claim 1, characterized in that: The model parameters a and b are obtained based on the monitoring values ​​of the drying tower inlet gas temperature, the gas temperature along the process and the outlet gas temperature and the following curve fitting formula: Wherein, T is the gas temperature; L is the vertical distance between the gas temperature monitoring position and the top of the drying tower.

5. The wastewater drying monitoring method according to claim 1, characterized in that: According to the solid content x of the wastewater, the gas residence time t is determined as follows h Control interval: 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.

6. The wastewater drying monitoring method according to claim 5, characterized in that: The wastewater flow and gas flow are regulated as follows: When the gas residence time t h When it is below the lower limit of the control interval, reduce 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 within the control range and maintained within the preset range; When the gas residence time t h When the gas residence time 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 maintained within the control range.

7. 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.

8. A wastewater drying monitoring system for implementing the wastewater drying monitoring method according to any one of claims 1 to 7, characterized in that: The invention comprises a drying tower and a controller. A rotary atomizer and a gas distributor are arranged on the top of the drying tower. The rotary atomizer is connected to a wastewater pipeline. A wastewater regulating valve is arranged on the wastewater pipeline. The gas distributor is connected to an inlet airway. A gas regulating valve, an inlet thermometer and a flowmeter are arranged on the inlet airway. An outlet airway is arranged at the bottom of the drying tower. An outlet thermometer is arranged on the outlet airway. A pressure measuring component is arranged on the drying tower. A plurality of temperature measuring components are arranged at intervals 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.

9. The wastewater drying monitoring system according to claim 8, characterized in that: Each along-the-way temperature measurement component includes a plurality of along-the-way temperature measurement components spaced apart along the circumference of the drying tower, and each along-the-way temperature measurement component includes at least one along-the-way thermometer arranged radially along the drying tower. The calculation module can calculate the average of the monitoring values ​​of the plurality of along-the-way thermometers in each along-the-way temperature measurement component.

10. The wastewater drying monitoring system according to claim 8, characterized in that: The pressure measuring assembly comprises a plurality of pressure gauges arranged at intervals 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.

Images