A white plume removal energy-saving control method and system

Abstract

The present application relates to a kind of white plume removal energy-saving control method and system, belong to the device field of handling smoke and waste gas.By control module, the real-time change of air parameter is collected, using air saturation humidity database, air temperature-enthalpy / density calculation model, establish white plume removal system operating cost mathematical model.According to the constantly changing atmospheric conditions, slagging condition etc., with operating cost as optimization goal, determine the best exhaust point, the best operation combination, using numerical analysis to seek global optimal solution, make actual operation curve quickly approach optimal curve, to adjust air cooler fan frequency, then on the basis of not affecting white plume removal effect, maximize the energy consumption of white plume removal is reduced, and make actual operating cost minimum.

Description

Technical Field

[0001] This invention belongs to the field of devices for treating smoke and waste gas, and relates to the removal of white plumes from blast furnaces, specifically an energy-saving control method and system for white plume removal. Background Technology

[0002] During flue gas emissions from processes such as blast furnace slag flushing or wet desulfurization, the wet flue gas emitted from the chimney mixes with the surrounding cold air and cools down. During this cooling process, the water vapor contained in the flue gas condenses, and the condensed water droplets refract and scatter light, giving the flue gas a white or gray appearance, known as "white plume" or "big white smoke." Although after desulfurization and other processes, the main components of white plume are carbon dioxide and water vapor, posing no threat to environmental quality, the large-scale emission of this white plume in a short period can obscure the sky, affecting sunlight exposure for vegetation and causing visual pollution for humans. Because its impact is relatively minor, the government has not made mandatory requirements for its management, thus the control of white plume remains controversial. Some argue that eliminating white plume would lead to energy waste and increase additional production costs.

[0003] Currently, the main technical approach for controlling white plumes is through a combination of condensation and dehumidification followed by heating and reheating. Condensation and dehumidification primarily utilize air-cooled or water-cooled heat exchangers, while heating and reheating employ GGH, MGGH, or direct mixed-air heating. For example, Chinese patent CN 214501286U provides a colored plume removal system, including a dust removal device, a water cooling device, an induced draft fan, a desulfurization device, a condensation separation device, a demisting device, and a gas-liquid mixing heating device. The dust removal device is installed at the boiler's outlet flue, the cooling device is located at the desulfurization device's inlet flue, and the water cooling device is connected to the dust removal device. The induced draft fan is located in the desulfurization device's inlet flue and connected to the water cooling device. The condensation separation device is located at the desulfurization device's outlet flue. The demisting device and the gas-liquid mixing heating device are both located in the flue between the desulfurization device's outlet and the chimney, and the gas-liquid mixing heating device is connected to the chimney. The water cooling device and the gas-liquid mixing heating device are interconnected to form a closed loop. This colored plume removal system eliminates the need for separate circulating water systems and large amounts of thermal energy input, achieving thermal energy recovery and utilization and reducing operating costs.

[0004] However, while existing technologies have reduced the construction cost of colored plume removal systems and can achieve heat recovery and reuse to some extent, the power consumption of devices such as fans and water pumps remains high during long-term operation, resulting in high operating costs.

[0005] Therefore, there is an urgent need for an energy-saving control method and system for white plume removal to reduce the energy consumption of the plume removal system and thus reduce operating costs. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide an energy-saving control method and system for white plume removal, which further reduces the energy consumption of the system without affecting the removal effect of the plume removal system, thereby reducing operating costs.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A method for energy-saving control of white plume removal includes the following steps:

[0009] S1. Real-time detection of atmospheric temperature and humidity near the exhaust stack; and detection of flue gas emission temperature and humidity at the current fan frequency;

[0010] S2. Establish an absolute humidity-temperature table using an air saturated humidity database and obtain a saturated humidity curve; divide the theoretical temperature range required for condensation and heating of the white plume removal system based on the saturated humidity curve; the theoretical temperature range includes the visible area and the invisible area of ​​the white plume.

[0011] S3. Locate atmospheric temperature and humidity point B on the absolute moisture content-temperature table based on the atmospheric temperature and humidity; locate flue gas temperature and humidity point A on the absolute moisture content-temperature table based on the emission temperature and emission humidity;

[0012] S4. Connect the ambient temperature and humidity point B and the smoke temperature and humidity point A with a straight line AB, and determine whether the straight line AB passes through the visible area of ​​the white feathers to obtain the judgment result;

[0013] S5. If the judgment result is yes, then adjust the frequency of the fan in the air cooler according to the judgment result.

[0014] Furthermore, the area below the saturated moisture content curve is the region where white feathers are visible, and the area above the saturated moisture content curve is the region where white feathers are not visible.

[0015] Furthermore, in S5, the method for adjusting the fan frequency based on the judgment result is as follows: draw a tangent line to the saturated moisture content curve through the ambient temperature and humidity point B; set the saturation point of the dehumidified and cooled flue gas as point C, and mix the dehumidified and cooled flue gas with hot air, and calculate the mixed flue gas point D through the air temperature-enthalpy / density model; connect point C and point D to obtain a straight line CD, and determine the intersection point D' of the straight line CD and the tangent line; calculate the fan speed based on the temperature and humidity change from point C to point D'.

[0016] Furthermore, the operating cost mathematical model is used to calculate the wind turbine's rotational speed. The specific operating cost mathematical model is as follows:

[0017] Energy consumption P of the feather removal device f Determine the total input power of the system:

[0018] P = P f

[0019] Where P is the total input power of the system, P f Where Q is the energy consumption of the feather removal device, and Q is the flue gas flow rate.

[0020] P f Satisfying Relationship:

[0021]

[0022] Where ΔP is the pressure loss energy consumption of the feather removal device, and η b For the efficiency of white feather removal, η f For fan efficiency;

[0023] Calculate ΔP and η b :

[0024]

[0025] η b =(1-αΔP) β )×100

[0026] Where, ρ t v is the density of the flue gas. t S represents the airflow velocity at the heat exchange surface. t L is the cross-sectional area of ​​the heat exchange channel. g α represents the length of the heat exchange channel; α and β are correction coefficients, the values ​​of which are determined through device efficiency tests depending on the different equipment.

[0027] At the same time, the constraint condition for maximum whitening efficiency is met:

[0028] 1-(1-η f )≥η

[0029] Where η is a preset constraint value.

[0030] Furthermore, based on the aforementioned mathematical model of operating costs, the optimal value of the fan speed is calculated:

[0031] P = kn2

[0032] Where k is the fan speed and power conversion parameter.

[0033] Furthermore, in step S4, if the determination result is negative, the rotational speed of the fan in the air cooler remains unchanged.

[0034] A white plume removal energy-saving control system includes a temperature and humidity detection module, a first calculation module, a second calculation module, a comparison module, and an adjustment module that are electrically connected to each other.

[0035] The temperature and humidity detection module detects the air temperature and humidity in real time and transmits the data to the first calculation module.

[0036] The first calculation module calculates the theoretical flue gas emission temperature range that the white plume removal system needs to achieve;

[0037] The second calculation module calculates the actual emission temperature reached by the white plume after heat exchange and mixing in the air cooler at the current fan frequency;

[0038] The comparison module compares the theoretical temperature range with the actual emission temperature to determine whether the actual emission temperature is within the theoretical temperature range, and sends the comparison result to the adjustment module.

[0039] The adjustment module adjusts the frequency of the fan based on the comparison results.

[0040] Furthermore, the temperature and humidity detection module is an air thermometer, which is located next to the chimney of the blast furnace and is covered with a protective cover.

[0041] Furthermore, the adjustment module is a PLC controller.

[0042] The beneficial effects of this invention are as follows:

[0043] This solution achieves control over the exhaust gas temperature, forming an effective closed-loop control process. The frequency of the air cooler fan is controlled based on the exhaust gas temperature, ensuring optimal fan speed under white plume removal conditions. This avoids the air cooler fan operating at full load, improving the energy-saving control of the white plume removal system.

[0044] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0045] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein:

[0046] Figure 1 This is a flowchart of the control method according to an embodiment of the present invention;

[0047] Figure 2 This is a schematic diagram of the energy-saving control principle of the whitening system of the present invention;

[0048] Figure 3 This is a schematic diagram of the saturated moisture content curve of the present invention;

[0049] Figure 4 This is a saturated moisture content curve of an embodiment of the present invention. Detailed Implementation

[0050] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0051] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0052] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0053] Please see Figures 1-4 This invention relates to an energy-saving control method and system for white plume removal, wherein the real-time fan frequency control method includes:

[0054] S1. Real-time detection of atmospheric temperature and humidity near the exhaust stack; and detection of flue gas emission temperature and humidity at the current fan frequency.

[0055] S2. Establish an absolute humidity-temperature table using an air saturated humidity database and obtain a saturated humidity curve; divide the theoretical temperature range after condensation and heating required for the white plume removal system according to the saturated humidity curve; the theoretical temperature range includes the visible area and the invisible area of ​​the white plume; the area below the saturated humidity curve is the visible area of ​​the white plume, and the area above the saturated humidity curve is the invisible area of ​​the white plume.

[0056] S3. Based on the atmospheric temperature and humidity, find the atmospheric temperature and humidity point B on the absolute moisture content-temperature table; based on the emission temperature and emission humidity, find the flue gas temperature and humidity point A on the absolute moisture content-temperature table.

[0057] S4. Connect the ambient temperature and humidity point B and the smoke temperature and humidity point A with a straight line AB, and determine whether the straight line AB passes through the visible area of ​​the white feather to obtain the judgment result.

[0058] S5. If the judgment result is yes, then adjust the frequency of the fan in the air cooler according to the judgment result.

[0059] The method for adjusting the fan frequency based on the judgment result is as follows: A tangent line is drawn to the saturated moisture content curve through the ambient temperature and humidity point B; the saturation point of the dehumidified and cooled flue gas is set as point C, and the dehumidified and cooled flue gas is mixed with hot air. The mixed flue gas point D is calculated using the air temperature-enthalpy / density model; points C and D are connected to obtain a straight line CD, and the intersection point D' of the straight line CD and the tangent line is determined; the fan speed is calculated based on the temperature and humidity change from point C to point D'. In other words, a tangent line is drawn to the saturated moisture content curve based on the ambient temperature, intersecting with the straight line corresponding to the moisture content at the temperature after the white plume cools, to obtain the flue gas temperature corresponding to the required temperature increase after de-whitening.

[0060] This embodiment uses an air temperature and humidity sensor installed near the exhaust outlet to detect atmospheric temperature and humidity. Based on a basic database and the initial temperature of the white feather flue gas, it calculates the temperature range required for condensation (or cooling) and heating after white feather removal. The flue gas emission temperature is directly related to the air cooler fan speed. Therefore, the flue gas emission temperature can be controlled in real time by adjusting the air cooler fan speed. Within the safe temperature range, the fan speed is determined using an operating cost mathematical model, thus achieving the goal of energy-saving optimization of the white feather removal system.

[0061] The mathematical model for calculating the operating cost of the white plume removal system is as follows:

[0062] The formula for calculating the total input power of the whitening system is derived. Using this formula, the minimum value of the total input power of the whitening system is found. In the process of finding the minimum value of the total input power, the constraint condition of maximum whitening efficiency must be met.

[0063] The total input power is mainly due to the energy consumption P of the feather removal device. f It is determined that the relationship between them is as follows:

[0064] P = P f

[0065] The controller in the control module reads and collects runtime variables (both uncontrollable and controllable variables) in the system, including:

[0066] n: Fan speed

[0067] Q: Flue gas flow rate

[0068] ρ t : Flue gas density (which can be obtained from the temperature at point D' in S5)

[0069] η f Fan efficiency

[0070] White Feather Removal Device Resistance Model

[0071] The pressure loss energy consumption of the feather removal device is related to pressure loss ΔP, flue gas flow rate Q, and fan efficiency η. f Feather removal efficiency η b They can be calculated using the following formula:

[0072]

[0073] The pressure loss of the feather removal device is determined by the airflow velocity Vt on the heat exchange surface, the cross-sectional area St of the heat exchange channel, and the length Lg of the heat exchange channel. Their relationship is as follows:

[0074]

[0075] Feather removal efficiency η b The pressure loss ΔP of the whitening unit, the correction factors α and β, are related, and their relationships are as follows:

[0076] η b =(1-αΔP) β )×100

[0077] In the formula, α and β are determined through device efficiency tests depending on the equipment used.

[0078] Simultaneously, the white feather removal system must meet the white feather removal efficiency η. f (i.e., the constraints for maximizing whitening efficiency), and the relationships between them are as follows:

[0079] 1-(1-η f )≥η set value

[0080] Based on the above calculation model, the energy consumption of the feather removal system is calculated.

[0081] P = kn 2

[0082] In the formula, k is the conversion parameter between the fan speed and power.

[0083] In actual operation, adjusting the fan speed *n* changes the resistance of the feather removal device and thus the feather removal efficiency. Under the constraint of overall feather removal efficiency, a reasonable fan speed needs to be determined. It should be noted that the determination of the fan speed also needs to refer to the fan performance curve to obtain the best energy-saving effect.

[0084] In S2 above, the theoretical temperature range (i.e. the effective temperature range) for the removal of white plumes is derived based on the current temperature of the white plumes and the ambient temperature, combined with the saturated moisture content curve.

[0085] like Figure 2 As shown, a white plume removal energy-saving optimized operation control system includes a temperature and humidity detection module (such as a temperature and humidity meter), a first calculation module, a second calculation module, a comparison module, and an adjustment module that are electrically connected to each other.

[0086] The first calculation module calculates the theoretical temperature range that the white plume removal system needs to reach;

[0087] The second calculation module calculates the emission temperature reached by the white plume after heat exchange and mixing of the air cooler at the current fan frequency;

[0088] The comparison module compares the theoretical temperature range with the actual emission temperature to determine whether the actual emission temperature is within the theoretical temperature range, and sends the comparison result to the adjustment module.

[0089] The adjustment module adjusts the frequency of the fan based on the comparison results.

[0090] The temperature and humidity detection module can be a thermometer and hygrometer. The air thermometer and hygrometer is located next to the exhaust stack and is equipped with a protective cover. It is used to detect the temperature and humidity of the air in the exhaust stack environment.

[0091] The functions of the first calculation module, the second calculation module, the comparison module, and the adjustment module can be implemented by an industrial control computer (ICC). The relevant calculation methods mentioned above are stored in the ICC. The ICC calculates parameters such as the flue gas emission temperature of the plume removal system under different ambient air parameter conditions. At the same time, the ICC can also be used to compare and judge the preset flue gas temperature with the emission temperature. Then, the PLC controller receives the instructions from the ICC and performs corresponding operation control according to the instructions corresponding to the comparison results to adjust the speed (or frequency) of the fan.

[0092] The principle of the energy-saving control method in this scheme is as follows:

[0093] This embodiment detects atmospheric temperature and humidity by installing an air temperature and humidity sensor near the exhaust pipe outlet. From a thermodynamic perspective, the mixing of humid air, humid flue gas, and air is a heat and mass transfer process; the hotter gas transfers heat to the air, and the more concentrated vapor diffuses into the air. During this heat and mass transfer process, the state of the mixed gas changes from unsaturated (superheated, no plume) to saturated (critical point) to subcooled (with plume). For example... Figure 3 As shown, an absolute humidity-temperature table (obtained by those skilled in the art through existing methods) and a saturated humidity curve can be directly obtained through fixed natural laws by establishing an air saturated humidity database.

[0094] The following is a practical example to illustrate this. For example... Figure 4 As shown in Figure A, the flue gas temperature from the blast furnace slag exhaust stack is approximately 80℃, and the humidity is 280 g / kg; the ambient temperature is 15℃, and the humidity is 8 g / kg, as shown in Figure B. Without de-whitening treatment, the area from A to B will enter the visible white feather region (the line connecting A and B passes through this region).

[0095] The flue gas is cooled to 60°C through cooling and dehumidification, at which point it is saturated (i.e., a preset estimated value), as shown at point C in the figure. Then, the cooled and dehumidified flue gas is mixed with hot air until the temperature reaches 50°C (calculated using an existing air temperature-enthalpy / density model), as shown at point D in the figure. The line connecting point D and point C does not pass through the visible area of ​​the white feathers, thus achieving white feather removal.

[0096] In actual production, the temperature and humidity of the exhaust gas and the atmosphere are constantly changing, so the positions of points A and B in the diagram are constantly changing. A tangent is drawn between point B and the saturated moisture content curve. Then, by increasing or decreasing the fan speed (i.e., first estimating a value and making rough adjustments), the temperature of the cooled exhaust gas at point C is controlled. Point D is calculated based on the air temperature-enthalpy / density model. Connecting points C and D yields a straight line CD. The intersection point D' of line CD and the tangent (i.e., the tangent of point B to the saturated moisture content curve) is determined, which gives the optimal exhaust gas parameters after whitening. The required cooling airflow for whitening is determined through point C. Combining the system resistance and fan performance curves of the whitening device, the most energy-efficient fan speed is finally determined using the optimal exhaust gas parameters and an operating cost mathematical model (i.e., further adjusting the calculated speed based on rough adjustments to achieve the most energy-efficient speed control). The fan operates at its lowest speed while the white feathers are not visible.

[0097] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for energy-saving control of white plume removal, characterized in that, Includes the following steps: S1. Real-time detection of atmospheric temperature and humidity near the exhaust stack; and detection of flue gas emission temperature and humidity at the current fan frequency; S2. Establish an absolute humidity-temperature table using an air saturated humidity database and obtain a saturated humidity curve; divide the theoretical temperature range required for condensation and heating of the white plume removal system based on the saturated humidity curve; the theoretical temperature range includes the visible area and the invisible area of ​​the white plume. S3. Locate atmospheric temperature and humidity point B on the absolute moisture content-temperature table based on the atmospheric temperature and humidity; locate flue gas temperature and humidity point A on the absolute moisture content-temperature table based on the emission temperature and emission humidity; S4. Connect the ambient temperature and humidity point B and the smoke temperature and humidity point A with a straight line AB, and determine whether the straight line AB passes through the visible area of ​​the white feathers to obtain the judgment result; S5. If the judgment result is yes, then adjust the frequency of the fan in the air cooler according to the judgment result; In S5, the method for adjusting the fan frequency based on the judgment result is as follows: A tangent line is drawn to the saturated moisture content curve through the ambient temperature and humidity point B; the saturation point of the dehumidified and cooled flue gas is set as point C, and the dehumidified and cooled flue gas is mixed with hot air. The mixed flue gas point D is calculated using the air temperature-enthalpy / density model; points C and D are connected to obtain a straight line CD, and the intersection point D' of the straight line CD and the tangent line is determined; the fan speed is calculated based on the temperature and humidity change from point C to point D'. The operating cost mathematical model is used to calculate the wind turbine's rotational speed. The specific operating cost mathematical model is as follows: Energy consumption P of the feather removal device f Determine the total input power of the system: = Where P is the total input power of the system. Where Q is the energy consumption of the feather removal device, and Q is the flue gas flow rate. Satisfying Relationship: in, The pressure loss energy consumption of the feather removal device. White feather removal efficiency For fan efficiency; calculate and : in, For the density of the flue gas, The airflow velocity at the heat exchange surface. This refers to the cross-sectional area of ​​the heat exchange channel. This refers to the length of the heat exchange channel; and The correction factor is determined through device efficiency tests, depending on the specific equipment used. At the same time, the constraint condition for maximum whitening efficiency is met: 1-(1- )≥η Where η is a preset constraint value; Based on the aforementioned mathematical model of operating costs, the optimal value of the fan speed is calculated: P=kn 3 Where k is the fan speed to power conversion parameter, and n is the fan speed.

2. The energy-saving control method for white plume removal according to claim 1, characterized in that, The area below the saturated moisture content curve is where white feathers are visible, while the area above the saturated moisture content curve is where white feathers are not visible.

3. The energy-saving control method for white plume removal according to claim 1, characterized in that, In step S4, if the judgment result is negative, the speed of the fan in the air cooler remains unchanged.

4. A white plume removal energy-saving control system for executing the white plume removal energy-saving control method according to any one of claims 1-3, characterized in that, It includes a temperature and humidity detection module, a first calculation module, a second calculation module, a comparison module, and an adjustment module that are electrically connected to each other; The first calculation module calculates the theoretical temperature range that the white plume removal system needs to reach; The second calculation module calculates the actual emission temperature reached by the white plume after heat exchange and mixing in the air cooler at the current fan frequency; The comparison module compares the theoretical temperature range with the actual emission temperature to determine whether the actual emission temperature is within the theoretical temperature range, and sends the comparison result to the adjustment module. The adjustment module adjusts the frequency of the fan based on the comparison results.

5. The white plume removal energy-saving control system as described in claim 4, characterized in that, The temperature and humidity detection module is an air thermometer, which is located next to the chimney of the blast furnace and is covered with a protective cover.

6. The white plume removal energy-saving control system as described in claim 4, characterized in that, The adjustment module is a PLC controller.

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