A post-furnace flue gas water cooling integrated temperature control system and matching cooling water volume control method

Abstract

The present invention discloses a post-furnace flue gas water-cooling integrated temperature control system and a matching cooling water volume control method, which specifically relates to the field of flue gas purification and environmental protection technology, including a semi-dry desulfurization tower, a cyclone dust collector, a bag filter and a low-temperature SCR denitrification device connected in series in sequence at the output end; the outlet flue of the cyclone dust collector and the inlet flue of the bag filter are respectively fixedly connected with a connecting flue connected in series with an electric damper, and also includes a surface water-cooled flue gas cooling system, which includes a water-cooled flue gas cooler connected to at least one cooling water supply pipeline. The invention adopts a comprehensive temperature control system combining a surface water-cooled flue gas cooling system with a flue gas emergency water spray cooling system, and formulates a matching cooling water volume control algorithm based on the enthalpy value heat balance principle, accurately controls the surface cooling water flow and the spraying water volume, effectively ensures that the post-furnace flue gas temperature meets the flue gas purification process requirements, and at the same time recovers the heat released during the flue gas cooling process, further improving the power plant cycle efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of flue gas purification and environmental protection, and in particular to a post-furnace flue gas water-cooling integrated temperature control system and a matching cooling water volume control method. Background Art

[0002] The phenomenon of calorific value fluctuation is common in urban domestic waste, and it becomes more prominent with the classification of domestic waste. When the calorific value of waste fuel fluctuates to a higher value, it has exceeded the initial design range of fuel calorific value of waste incineration power plants, causing the exhaust gas temperature at the incinerator outlet to be higher than the flue gas temperature range required by the flue gas purification process after the furnace, resulting in the reduction or even failure of flue gas purification measures, and even exceeding the temperature limit that the flue gas purification facilities after the furnace can withstand, seriously threatening the safe operation of the flue gas purification facilities after the furnace. The filter bags of the bag filter dust collectors after the furnace have been burned in some power plants.

[0003] On the other hand, with the continuous improvement of people's environmental awareness, most power plants are also driven to continuously improve the post-furnace flue gas purification process. In this process, many new environmental protection processes have been applied, which effectively reduced the emission of flue gas pollutants. While these new environmental protection processes have been effectively applied, they have also put forward new and higher requirements for the control of post-furnace flue gas temperature, such as the publication number: CN106268230A, publication date: 2017-01-04, which discloses a system and process for recovering and purifying waste heat from coke oven flue gas. Or the publication number: CN112902683A, publication date: 2021-06-04, which discloses an electric furnace flue gas treatment system, an environmentally friendly steelmaking arc furnace, and an electric furnace steelmaking production method. In the existing technologies based on the above two patents, methods for effectively controlling the flue gas temperature in the post-furnace flue gas purification process are disclosed, so as to ensure that when the fuel calorific value fluctuates to a higher value, the post-furnace flue gas temperature can still meet the requirements of each process link of the flue gas purification. For example, the low-temperature SCR denitrification process requires the flue gas temperature to be no less than 180°C, while the high-efficiency activated carbon adsorption process and most bag dust removal processes require the flue gas temperature to be no higher than 200°C. Therefore, how to ensure that the flue gas meets the above temperature requirements during operation needs to be well solved. Summary of the invention

[0004] The purpose of the present invention is to provide a post-furnace flue gas water cooling comprehensive temperature control system and a matching cooling water volume control method to solve the above problems.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A post-furnace flue gas water-cooling integrated temperature control system, comprising a semi-dry desulfurization tower, a cyclone dust collector, a bag dust collector and a low-temperature SCR denitrification device which are sequentially connected in series at the output end;

[0007] The outlet flue of the cyclone dust collector and the inlet flue of the bag dust collector are respectively fixedly connected with a connecting flue connected in series with an electric damper, and also include a surface water-cooled flue gas cooling system, which includes a water-cooled flue gas cooler connected to at least one cooling water supply pipeline, the two connecting flues are connected to two interfaces of the shell side of the water-cooled flue gas cooler, and the two connecting flues are also connected with a bypass flue connected in series with the electric damper;

[0008] The semi-dry desulfurization tower is provided with a flue gas emergency water spray cooling system, which includes an atomizing spray device located in the semi-dry desulfurization tower with the spray surface facing downward, a spray water pipeline and an atomizing compressed air pipeline;

[0009] An activated carbon injection device is fixedly installed at the inlet flue of the bag filter.

[0010] Preferably, the water-cooled smoke cooler is a high-efficiency plate and shell heat exchanger; the cyclone dust collector can be replaced by either a multi-tube dust collector or an electrostatic dust collector.

[0011] Preferably, it also includes a cold demineralized water pipeline drawn from the boiler feed water system and a hot demineralized water pipeline returning to the boiler feed water deaerator, the water inlet of the water-cooled smoke cooler is connected to the cold demineralized water pipeline, and the water outlet is connected to the hot demineralized water pipeline.

[0012] A cooling water volume control method, comprising the post-furnace flue gas water cooling integrated temperature control system described in the above scheme, is characterized in that it comprises the following steps:

[0013] S01, obtain the key control data of the preset monitoring point, the key control data includes the inlet flue gas temperature value t of the water-cooled smoke cooler y1 ;

[0014] S02, determining the inlet flue gas temperature value t of the water-cooled smoke cooler y1 Is it lower than the preset maximum allowable operating temperature of the flue gas after the furnace? yH If it is lower than , the electric dampers on the inlet and outlet flues of the water-cooled smoke cooler remain closed, and the electric dampers on the bypass flue remain open. If it is not lower than , the electric dampers on the bypass flue are closed and the electric dampers on the inlet and outlet flues of the water-cooled smoke cooler are opened. At the same time, the surface water-cooled flue gas cooling system is put into use to cool the inlet flue gas of the water-cooled smoke cooler from the flue temperature t y1 Cool down to the target smoke temperature t y0 ;

[0015] S03, calculate the flue gas temperature t of the water-cooled smoke cooler inlet y1 Cool down to the target smoke temperature t y0 The cooling water flow value D required by the surface water-cooled flue gas cooling system iss , so as to generate a target instruction to be transmitted to the surface water-cooled flue gas cooling system;

[0016] S04, during the execution of the target instruction, the inverse value t of the outlet smoke temperature of the water-cooled smoke cooler of the water-cooled smoke cooler is obtained in real time. y2 , to coordinate the emergency water spray cooling system and the surface water-cooled flue gas cooling system, the water-cooled smoke cooler outlet flue gas temperature back-calculation value t y2 is the maximum desalination cooling water flow rate D of the surface water-cooled flue gas cooling system max Less than the cooling water flow value D required by the surface water-cooled flue gas cooling system s When the maximum desalted water volume D max Obtained by reverse calculation.

[0017] Preferably, in step S04, if the inverse calculated value of the outlet smoke temperature of the water-cooled smoke cooler is t y2 Greater than the maximum allowable smoke temperature t yH , then the flue gas emergency water spray cooling system is put into use, and at the same time, the flue gas at the outlet of the water-cooled smoke cooler is calculated from the smoke temperature inverse value t y2 Cool down to the target smoke temperature t y0 The required spray water volume D ps If the inverse value of the outlet flue gas temperature of the water-cooled smoke cooler is t y2 Less than the target value of flue gas temperature after furnace control t yH , the surface water-cooled flue gas cooling system operates alone, and the opening of the regulating valve of the water-cooled flue gas cooler water inlet pipeline is set to 100%.

[0018] Preferably, the key control data in step S01 includes the flue gas temperature t y1 , and the flue gas temperature after the furnace is t y1 The temperature is obtained through the flue gas temperature measuring points deployed on the flue between the cyclone dust collector and the water-cooled smoke cooler.

[0019] As a preferred embodiment, the cooling water flow value D required by the surface water-cooled flue gas cooling system in step S03 is s The calculation includes:

[0020] S31, calculate the smoke temperature as t y1 With t y0 When the enthalpy value of unit volume of flue gas under standard conditions is I y1 with I y0 Values:

[0021] (1);

[0022] Among them, t y1 is the flue gas temperature at the inlet of the water-cooled smoke cooler, ty0 is the target value of flue gas temperature control at the outlet of water-cooled smoke cooler, I y V is the enthalpy of flue gas per unit volume at temperature t under standard conditions, CO2 、V N2 、V O2 and V H2O are the volume contents of CO2, N2, O2 and water vapor in flue gas, respectively, h V is the mass concentration of fly ash per unit volume of flue gas under standard conditions, CO2 、V N2 、V O2 、V H2O and W h All of them are obtained through the CEMS flue gas composition online monitoring system deployed on the flue between the cyclone dust collector and the water-cooled smoke cooler, (ct) CO2 、(ct) N2 、(ct) O2 and (ct) H2O are the enthalpy values ​​of CO2, N2, O2 and water vapor per unit volume at temperature t under standard conditions, (ct) h is the enthalpy of unit mass of flue gas fly ash at temperature t, (ct) CO2, (ct) N2, (ct) O2, (ct) H2O and (ct) h The enthalpy value can be obtained by Figure 2 Find the endpoint temperature and corresponding enthalpy value of the temperature range and calculate them using the interpolation method.

[0023] S32, according to I obtained by (1) y1 with I y0 The value of the overall enthalpy loss of the flue gas after leaving the furnace is calculated H y ,

[0024] (2);

[0025] Among them, V y is the volume flow rate of flue gas after the furnace;

[0026] S33. For the calculation of the enthalpy increment on the desalination cooling water side, the desalination cooling water temperature t at the inlet of the water-cooled smoke cooler measured by the temperature measuring point is s1 The desalination cooling water temperature setting value t of the water-cooled smoke cooler outlet s0 Substituting them into equation (3) respectively, we can obtain the enthalpy value i of the desalinated cooling water at the inlet and outlet of the water-cooled smoke cooler per unit mass: s1 with i s0 ,

[0027] (3);

[0028] Among them, t is the water temperature, i s is the enthalpy of unit mass of water when the water temperature is t;

[0029] S34, calculate i from (3) s1 with i s0 Substitute the value into (4) to calculate the overall enthalpy increase of the desalinated cooling water passing through the water-cooled smoke cooler tube per unit time: H s ,

[0030] (4);

[0031] Among them, D s is the desalinated cooling water flow rate through the water-cooled smoke cooler tube in the required unit time;

[0032] S35. Based on the enthalpy heat balance principle, we get:

[0033] H y = H s ,

[0034] That is V y ×(I y1 -I y0 )=D s ×(i s0 -i s1 ), the flue gas at the inlet of the water-cooled smoke cooler is changed from the flue gas temperature t y1 Cool down to the target value t of the flue gas temperature at the outlet of the water-cooled smoke cooler y0 When the surface water-cooled flue gas cooling system requires a cooling water flow value D s The calculation is as follows:

[0035] (5).

[0036] As a preferred embodiment, the inverse calculation value t of the outlet smoke temperature of the water-cooled smoke cooler in step S04 is y2 is the maximum desalination cooling water flow rate D of the surface water-cooled flue gas cooling system max Less than the cooling water flow value D required by the surface water-cooled flue gas cooling system s When the maximum desalted water volume D max The back calculation is performed by calculating the flue gas at the outlet of the water-cooled smoke cooler by the back calculation value t y2 Cool down to the target smoke temperature t y0 The required spray water volume D ps The calculations include:

[0037] S41, the industrial water temperature value t that is not sprayed into the flue gas is detectedps1 Substituting into equation (3), we can find the enthalpy value i of the initial industrial water per unit mass: ps1 ;

[0038] S42. The industrial water sprayed into the flue gas turns into water vapor because the heat absorbed from the flue gas reaches the latent heat of vaporization value, and continues to absorb the heat of the flue gas until it reaches the same temperature as the flue gas. The flue gas temperature value t y1 is the water vapor temperature value, and the flue gas temperature value t y1 Convert to Kelvin temperature T y1 , then T y1 = t y1 +273.25, and then the obtained flue gas at the water spray point, that is, the water vapor gauge pressure value P by1 Convert to absolute pressure value P jy1 , then P jy1 =(P by1 +101325)÷10 5 , according to T y1 With P jy1 Find the enthalpy of water vapor i ps2，

[0039] (8);

[0040] S43. Based on the enthalpy heat balance principle, calculate the required spray water volume D ps，

[0041] (9);

[0042] In the formula, I y2 Smoke temperature y2 The enthalpy value of unit volume of flue gas under standard conditions is calculated by formula (1);

[0043] In the step S04, the emergency flue gas water spray cooling system is called to coordinate with the surface water-cooled flue gas cooling system:

[0044] If the inverse calculation value of the outlet flue gas temperature of the water-cooled smoke cooler is t y2 Greater than the maximum allowable smoke temperature t yH , then the flue gas emergency water spray cooling system is put into use, and at the same time, the flue gas outlet of the water-cooled smoke cooler is calculated to be reduced from the flue gas temperature t y2 Cool down to the target smoke temperature t y0 Required spray water value D ps ;

[0045] If the inverse calculation value of the outlet flue gas temperature of the water-cooled smoke cooler is t y2 Less than the target value of flue gas temperature after furnace control t yH, the surface water-cooled flue gas cooling system operates alone, and the opening of the regulating valve of the water-cooled flue gas cooler water inlet pipeline is set to 100%.

[0046] Preferably, an interlock protection mechanism is also included for ensuring the atomization quality of the spray water of the flue gas emergency water spray cooling system, and the interlock protection mechanism includes: based on the difference between the obtained pipeline pressure value and the interlock protection action value, generating an execution instruction of the pneumatic fast closing valve on the compressed air pipeline for atomization and the spray water pipeline according to the result;

[0047] The pipeline pressure is obtained from a pressure signal sensor on the compressed air pipeline for atomization in the flue gas emergency water spray cooling system.

[0048] Preferably, the pneumatic quick closing valve execution instruction includes:

[0049] If it is a negative value, the pneumatic quick-closing valve will close to quickly cut off the compressed air pipeline for atomization and the spray water pipeline;

[0050] If it is a positive value, the pneumatic quick-closing valve remains open to keep the compressed air pipeline for atomization and the spray water pipeline unobstructed.

[0051] In the above technical solution, the present invention provides a post-furnace flue gas water-cooling integrated temperature control system and a matching cooling water volume control method, which have the following beneficial effects:

[0052] 1. The surface water-cooled flue gas cooling system can recover the heat released by the flue gas during the cooling process, increase the boiler feed water temperature, reduce the consumption of feed water deoxygenation steam, and help improve the economic efficiency of power plant operation.

[0053] 2. Incorporating the flue gas emergency water spray cooling system into the comprehensive temperature control system of the flue gas water cooling after the furnace as a flue gas cooling emergency measure and a supplement to the surface water cooling flue gas cooling system can effectively improve the operating reliability of the flue gas temperature control system after the furnace, and the flue gas cooling range is large, the response speed is fast, and the temperature control effect is good.

[0054] 3. Combining the flue gas emergency water spray cooling system with the semi-dry desulfurization process and moderately increasing the water content of the flue gas in the semi-dry desulfurization device is beneficial to promoting the desulfurization reaction and improving the flue gas desulfurization efficiency.

[0055] 4. By limiting the temperature of the hot desalted water at the outlet of the water-cooled smoke cooler of the surface water-cooled flue gas cooling system, the hot desalted water is prevented from vaporizing in the pipeline, causing cavitation or water hammer damage to the equipment and pipeline. In addition, by reasonably limiting the temperature reduction range, the water spraying amount of the flue gas emergency water spray cooling system is ensured to be appropriate, the moisture content of the flue gas is not too high, and a reliable dry flue gas state is maintained, preventing the resulting excessive flue gas flow and corrosion problems.

[0056] 5. By setting up a corresponding flue gas bypass for the water-cooled smoke cooler, the flue gas switches to pass through the bypass when it does not need to be cooled and cooled, which not only reduces the flow resistance of the flue gas, but also reduces the corrosion and scouring of the water-cooled smoke cooler by the flue gas, and also facilitates the inspection and maintenance of the water-cooled smoke cooler. In addition, the inlet and outlet flues of the water-cooled smoke cooler are equipped with electric partition doors to effectively cut off the flue gas backflow path and prevent corrosion caused by the flue gas leaking into the water-cooled smoke cooler.

[0057] 6. Combining the respective advantages and limitations of the surface water-cooled flue gas cooling system and the flue gas emergency water spray cooling system, a reasonable overall control strategy for the temperature control system is formulated to achieve automatic control of the flue gas temperature. It can adapt to the impact of fluctuations in the calorific value of the fuel entering the furnace on the flue gas temperature after the furnace, and the control is flexible, convenient and reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0059] Figure 1 A flowchart provided for an embodiment of the present invention;

[0060] Figure 2 (ct) provided by the embodiment of the present invention CO2 、(ct) N2 、(ct) O2 、(ct) H2O and (ct) h The enthalpy values ​​of the main components of flue gas at different temperatures. DETAILED DESCRIPTION

[0061] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0062] Embodiment 1:

[0063] like Figure 1 As shown, a post-furnace flue gas water-cooling integrated temperature control system includes a semi-dry desulfurization tower, a cyclone dust collector, a bag dust collector and a low-temperature SCR denitrification device which are sequentially connected in series at the output end;

[0064] The outlet flue of the cyclone dust collector and the inlet flue of the bag dust collector are respectively fixedly connected with a connecting flue connected in series with an electric damper, and also include a surface water-cooled flue gas cooling system, which includes a water-cooled flue gas cooler connected to at least one cooling water supply pipeline, the two connecting flues are connected to two interfaces of the shell side of the water-cooled flue gas cooler, and the two connecting flues are fixedly connected with a bypass flue connected in series with the electric damper;

[0065] The semi-dry desulfurization tower is provided with a flue gas emergency water spray cooling system, which includes an atomizing spray device located in the semi-dry desulfurization tower with the spray surface facing downward, a spray water pipeline connected to the factory industrial water system, and an atomizing compressed air pipeline connected to the factory compressed air system;

[0066] It also includes a cold desalted water pipeline drawn from the boiler feed water system and a hot desalted water pipeline returning to the boiler feed water deaerator. The water inlet of the water-cooled smoke cooler is connected to the cold desalted water pipeline, and the water outlet is connected to the hot desalted water pipeline.

[0067] Specifically, in the above technology, the flue gas at the outlet of the incinerator flows through a semi-dry desulfurization tower, a cyclone dust collector, a bag dust collector and a low-temperature SCR denitrification device in succession, and undergoes corresponding desulfurization, deacidification, dust removal and denitrification purification treatments, and activated carbon is sprayed into the flue gas through an activated carbon injection device arranged at the inlet flue of the bag dust collector to adsorb and remove heavy metals, dioxins and other toxic and harmful substances in the flue gas.

[0068] Further, combined with Figure 1It can be seen that the flue gas at the outlet of the incinerator enters the tower from the lower part of the semi-dry desulfurization tower and flows from bottom to top. The acidic substances such as SO2 in the flue gas react with the calcium hydroxide particles sprayed into the tower at a very high mass transfer rate to generate reaction products such as CaSO4 and CaSO3. A very small part of these dry products falls to the bottom of the reaction tower, and most of them are carried away by the flue gas. The dusty flue gas after desulfurization is discharged laterally from the upper part of the desulfurization tower, and then tangentially enters the cyclone dust collector cylinder. The cyclone dust collector can capture the larger particle size of the flue gas through centrifugal action, and at the same time, it can also eliminate the spark particles in the flue gas to prevent it from entering the bag dust collector. The multi-tube cyclone dust collector or electrostatic dust collector also has the same function and can be used to replace the cyclone dust collector. After preliminary dust removal and the removal of sparks, the flue gas is discharged from the top outlet of the cyclone dust collector and goes to the bag dust collector through the connecting flue. Before entering the bag dust collector, activated carbon particles are sprayed into the flue gas through the activated carbon injection device set at the inlet flue of the bag dust collector to adsorb and remove toxic and harmful substances such as heavy metals and dioxins in the flue gas. The dusty flue gas then enters the diversion flue located in the middle of the bag dust collector. After being diverted by the partition plate, the flue gas is evenly distributed to each chamber. Under the action of the ash hopper baffle in the chamber, the flue gas flow rises evenly and steadily. Relatively large dust particles settle into the ash hopper under the action of primary sedimentation and their own gravity, and fine dust particles continue to flow with the flue gas. The flue gas passes through the filter bag under the negative pressure of the induced draft fan, and the fine dust particles in it are filtered and adsorbed on the surface of the filter bag. The dust-removed flue gas enters the clean air chamber and is discharged from the bag filter outlet. It enters the low-temperature SCR denitrification device through the connecting flue, and under the action of the catalyst, NO in the flue gas is X It reacts with the reducing agent and is reduced to N2 and H2O. The purified flue gas flows out through the outlet of the low-temperature SCR denitrification device, and then is discharged into the chimney after connecting the flue and the induced draft fan, and finally enters the atmosphere under the lifting and guidance of the chimney.

[0069] During the process, when the flue gas temperature after the furnace meets the temperature requirements of the flue gas purification process, the surface water-cooled flue gas cooling system does not need to be put into operation, and the flue gas passes through the corresponding bypass of the flue gas cooler without passing through the flue gas cooler. When the flue gas needs to be cooled and the surface water-cooled flue gas cooling system is put into operation, the flue gas cooler bypass is closed, and the flue gas flows through the flue gas cooler. At the same time, the cold desalted water from the boiler feed water pipeline enters the pipe side of the flue gas cooler through the desalted water pipeline, and fully cools the flue gas flowing through the shell side of the flue gas cooler. After the heat exchange is completed, the hot desalted water leaves the flue gas cooler and carries the heat absorbed from the flue gas to the boiler feed water deaerator. The temperature of the cold desalted water is close to the ambient temperature, usually 20~30℃. Considering the safety of the operation of the boiler feed water deaerator system, the water temperature of the hot desalted water at the outlet of the surface water-cooled flue gas cooling process flue gas cooler needs to be limited. It is usually required that the outlet water temperature of the flue gas cooler is lower than 80℃ to prevent the hot desalted water from vaporizing in the pipeline, thereby causing water hammer or cavitation damage to the pipeline and equipment.

[0070] Furthermore, when the flue gas emergency water spray cooling system is put into operation, the industrial water filtered by the filter enters the atomizing spray device, and the compressed air used in the plant enters the atomizing spray device as the atomizing medium through the compressed air pipeline for atomization, and the spray water flow in the atomizing nozzle on the atomizing spray device is fully atomized, and fully mixed with the flue gas flowing through the semi-dry desulfurization tower in the form of small mist droplets. Because the compressed air flow rate and the spray water volume have a certain proportional relationship, they change accordingly with the adjustment of the spray water flow rate. It should be noted that the industrial water temperature of the plant is usually slightly lower than the ambient temperature. Since the phase change process of water from liquid to gas needs to absorb the same amount of heat as its own latent heat of vaporization, compared with the surface water-cooled flue gas cooling without the liquid-gas phase transition process, the mixed flue gas water spray cooling has the advantages of large cooling range, fast response speed and good temperature control effect. However, the water spray cooling process will inevitably increase the moisture content in the flue gas. Excessive water spraying may cause dry flue gas to turn into wet flue gas, resulting in significantly increased corrosion of equipment such as flue ducts and induced draft fans. In addition, excessive water spraying will also increase the flue gas flow rate and flow resistance, resulting in a corresponding increase in the power consumption of the induced draft fan. Surface water-cooled flue gas cooling will not only not affect the flue gas composition, but also recover and utilize the heat released by the flue gas during the cooling process, which helps to improve the overall thermal efficiency and economy of the power plant operation. Therefore, from the perspectives of ensuring the safety, reliability and economy of the power plant operation, the present invention is based on the surface water-cooled flue gas cooling system, and only uses the flue gas water spray cooling system as an emergency measure in the comprehensive temperature control system of the flue gas after the furnace, and limits the amount of water sprayed into the flue gas by limiting the flue gas cooling range generated by the flue gas emergency water spray cooling system. The cooling range is usually limited to within 30°C.

[0071] The water-cooled smoke cooler is a high-efficiency plate and shell heat exchanger, and the cyclone dust collector can be replaced by either a multi-tube dust collector or an electrostatic dust collector.

[0072] Secondly, the flue gas output end of the SCR denitration device is fixedly connected to an induced draft fan, and the output end of the induced draft fan is fixedly connected to a chimney. The treated flue gas is introduced into the chimney by the induced draft fan and then discharged.

[0073] Embodiment 2:

[0074] like Figure 1As shown, based on the integrated temperature control system for water-cooling of the flue gas behind the furnace provided in the above-mentioned embodiment, this embodiment aims to obtain the smoke temperature data of the flue gas behind the furnace and the pipeline pressure data of the flue gas emergency water spray cooling system based on the temperature sensors and pressure sensors at the preset monitoring points, and to obtain the required parameter values ​​through an algorithm, so as to coordinate the surface water-cooled flue gas cooling system and the flue gas emergency water spray cooling system according to the parameter values, so that the temperature of the flue gas meets the requirements within the flue gas temperature range treated by the bag filter and the low-temperature SCR denitrification device.

[0075] The cooling water volume control method provided in this embodiment includes the following steps:

[0076] S01. Obtain the key control data of the preset monitoring point, including the inlet flue gas temperature value t of the water-cooled smoke cooler y1 (The flue gas after the furnace is obtained by the flue gas temperature ty1 through the flue gas temperature measuring point deployed on the flue between the cyclone dust collector and the water-cooled smoke cooler)

[0077] S02. Determine the inlet flue gas temperature value t of the water-cooled smoke cooler y1 Is it lower than the preset maximum allowable operating temperature of the flue gas after the furnace? yH If it is lower than , the electric dampers on the inlet and outlet flues of the water-cooled smoke cooler remain closed, and the electric dampers on the bypass flue remain open. If it is not lower than , the electric dampers on the bypass flue are closed and the electric dampers on the inlet and outlet flues of the water-cooled smoke cooler are opened. At the same time, the surface water-cooled flue gas cooling system is put into use to cool the inlet flue gas of the water-cooled smoke cooler from the flue temperature t y1 Cool down to the target smoke temperature t y0 ;

[0078] S03, calculate the flue gas temperature t of the water-cooled smoke cooler inlet y1 Cool down to the target smoke temperature t y0 The cooling water flow rate D required by the surface water-cooled flue gas cooling system s ,include:

[0079] S31, calculate the smoke temperature as t y1 With t y0 When the enthalpy value of unit volume of flue gas under standard conditions is I y1 with I y0 Values:

[0080] (1);

[0081] Among them, t y1 is the flue gas temperature at the inlet of the water-cooled smoke cooler, t y0 is the target value of flue gas temperature control at the outlet of water-cooled smoke cooler, I yV is the enthalpy of flue gas per unit volume at temperature t under standard conditions, CO2 、V N2 、V O2 and V H2O are the volume contents of CO2, N2, O2 and water vapor in flue gas, respectively, h V is the mass concentration of fly ash per unit volume of flue gas under standard conditions, CO2 、V N2 、V O2 、V H2O and W h All of them are obtained through the CEMS flue gas composition online monitoring system deployed on the flue between the cyclone dust collector and the water-cooled smoke cooler. (ct) CO2 、(ct) N2 、(ct) O2 and (ct) H2O are the enthalpy values ​​of CO2, N2, O2 and water vapor per unit volume at temperature t under standard conditions, (ct) h is the enthalpy of unit mass of flue gas fly ash at temperature t, (ct) CO2 、(ct) N2 、(ct) O2 、(ct) H2O and (ct) h The enthalpy value can be obtained by Figure 2 Find the endpoint temperature and corresponding enthalpy value of the temperature interval in , and calculate them by interpolation method;

[0082] S32, according to I obtained by (1) y1 with I y0 The value is used to calculate the overall enthalpy loss of the flue gas after it leaves the furnace. H y ,

[0083] (2);

[0084] Among them, V y is the volume flow rate of flue gas after the furnace;

[0085] S33. For the calculation of the enthalpy increment on the desalination cooling water side, the desalination cooling water temperature t at the inlet of the water-cooled smoke cooler measured by the temperature measuring point is s1 The desalination cooling water temperature setting value t of the water-cooled smoke cooler outlet s0 (usually not more than 80℃) are substituted into formula (3) to obtain the enthalpy value i of the desalinated cooling water at the inlet and outlet of the water-cooled smoke cooler per unit mass. s1 with i s0 ,

[0086] (3);

[0087] Among them, t is the water temperature, i s is the enthalpy of unit mass of water when the water temperature is t;

[0088] S34, calculate i from (3) s1 with i s0 Substitute the value into (4) to calculate the overall enthalpy increase of the desalinated cooling water passing through the water-cooled smoke cooler tube per unit time: H s ,

[0089] (4);

[0090] Among them, D s is the desalinated cooling water flow rate through the water-cooled smoke cooler tube in the required unit time;

[0091] S35. Based on the enthalpy heat balance principle, we get:

[0092] H y = H s ,

[0093] That is V y ×(I y1 -I y0 )=D s ×(i s0 -i s1 ),

[0094] The inlet flue gas of the water-cooled smoke cooler is y1 Cool down to the target value t of the flue gas temperature at the outlet of the water-cooled smoke cooler y0 When the surface water-cooled flue gas cooling system requires cooling water flow value D s The calculation is as follows:

[0095] .

[0096] To generate target instructions for feedback to the surface water-cooled flue gas cooling system;

[0097] S04, during the execution of the target instruction, the inverse value of the outlet smoke temperature of the water-cooled smoke cooler t will be obtained in real time y2 , in order to coordinate the flue gas emergency water spray cooling system and the surface water-cooled flue gas cooling system, that is, the compensation mechanism of the flue gas emergency water spray cooling system for the surface water-cooled flue gas cooling system, the back-calculated value of the flue gas temperature at the outlet of the water-cooled smoke cooler t y2 is the maximum desalination cooling water flow rate D of the surface water-cooled flue gas cooling system max Less than the cooling water flow rate D required by the surface water-cooled flue gas cooling system s When the maximum desalted water volume Dmax Back calculation acquisition;

[0098] In step S04, if the inverse calculated value of the outlet smoke temperature of the water-cooled smoke cooler is t y2 Greater than the maximum allowable smoke temperature t yH , then the flue gas emergency water spray cooling system is put into use, and at the same time, the flue gas at the outlet of the water-cooled smoke cooler is calculated from the flue gas temperature inverse value t y2 Cool down to the target smoke temperature t y0 The required spray water volume D ps ;

[0099] If the inverse calculation value of the outlet flue gas temperature of the water-cooled smoke cooler is t y2 Less than the target value of flue gas temperature after furnace control t yH , the surface water-cooled flue gas cooling system operates alone, and the opening of the regulating valve of the water-cooled flue gas cooler water inlet pipeline is set to 100%.

[0100] In the above steps, the flue gas at the outlet of the water-cooled smoke cooler is calculated from the smoke temperature t y2 Cool down to the target smoke temperature t y0 The required spray water volume D ps The calculations include:

[0101] S41, the industrial water temperature value t that is not sprayed into the flue gas is detected ps1 Substituting into equation (3), we can find the enthalpy value i of the initial industrial water per unit mass: ps1 ;

[0102] S42. The industrial water sprayed into the flue gas turns into water vapor because the heat absorbed from the flue gas reaches the latent heat of vaporization value, and continues to absorb the heat of the flue gas until it reaches the same temperature as the flue gas. The flue gas temperature value t y1 is the water vapor temperature value, and the flue gas temperature value t y1 Convert to Kelvin temperature T y1 , then T y1 = t y1 +273.25, and then the obtained flue gas at the water spray point, that is, the water vapor gauge pressure value P by1 Convert to absolute pressure value P jy1 , then P jy1 =(P by1 +101325)÷10 5 , according to T y1 With P jy1 Find the enthalpy of water vapor i ps2，

[0103] (8);

[0104] S43. Based on the enthalpy heat balance principle, calculate the required spray water volume D ps，

[0105] (9);

[0106] In the formula, I y2 Smoke temperature y2 The enthalpy value of unit volume of flue gas under standard conditions is calculated by formula (1).

[0107] Embodiment three:

[0108] Based on the above-mentioned embodiment 2, this embodiment aims to provide a water-cooled smoke cooler outlet hot desalted water actual water temperature value t s2 The future prediction method is used to predict the required desalination cooling water flow value D of the surface water-cooled flue gas cooling system. s The calculation is corrected to ensure the safe and reliable operation of the desalted water system, including the following steps:

[0109] S05, the hot desalted water temperature t obtained continuously and in real time by the temperature measuring point set on the hot desalted water pipe at the outlet of the water-cooled smoke cooler s2 Store according to preset time windows to form multiple data sets;

[0110] S06. Calculate the temperature t of the hot desalted water in each set s2 The average water temperature t s2pj , compare the data set of the most recent window with the average water temperature value t of the data sets of the consecutive windows adjacent to the above window s2pj By comparison, the rate of increase of the hot desalted water temperature F is calculated, and the future expected hot desalted water temperature t is generated. s2n ;

[0111] S07, the future expected hot desalted water temperature t s2n Feedback to the control system, the desalination cooling water flow value D of the surface water-cooled flue gas cooling system s The set value of the desalination cooling water temperature at the outlet of the water-cooled smoke cooler in the calculation is t s0 Make corrections; at the same time, if t s2n Exceed the set value of desalination cooling water temperature at the outlet of water-cooled smoke cooler t s0 , an early warning log is generated.

[0112] Specifically, the calculation formula of the cooling water flow rate increase rate F in the above embodiment is F=(the average temperature of the hot desalted water in the data set of the last two adjacent windows in reverse time order / the average temperature of the hot desalted water in the data set of all recent continuously collected data windows);

[0113] The future expected hot desalted water temperature t s2n The average temperature of the hot desalted water in the data set of the most recent window is t s2pj *F.

[0114] In step S06, the future estimated hot desalted water temperature t s2n Exceed the set value of desalination cooling water temperature at the outlet of water-cooled smoke cooler t s0 , an early warning log will be generated to prompt, and the hot desalted water temperature prediction value t s2n When the temperature continues to rise and reaches the desalted water temperature limit (usually 80°C), the early warning log will call the management personnel to perform manual control intervention, such as emergency cooling of the hot desalted water through the open circulation cooling water of the whole plant or starting the flue gas emergency water spray cooling system to reduce the flue gas temperature in advance, and repairing the surface water-cooled flue gas cooling system at an appropriate time.

[0115] Through the above method, not only the desalination cooling water flow value D of the surface water-cooled flue gas cooling system is further improved s The calculation accuracy is improved, and the temperature of the hot desalted water at the outlet of the water-cooled smoke cooler is strictly limited to ensure that the temperature of the hot desalted water does not exceed the limit value, prevent the hot desalted water from evaporating in the pipeline, avoid cavitation or water hammer damage to the equipment and pipeline, and ensure the safe and reliable operation of the system.

[0116] Embodiment 4:

[0117] Based on the above-mentioned third embodiment, this embodiment further provides an interlock protection mechanism for ensuring the quality of spray water atomization of the flue gas emergency water spray cooling system. The interlock protection mechanism includes: based on the difference between the obtained pipeline pressure value and the interlock protection action value, generating a pneumatic fast closing valve execution instruction on the compressed air pipeline for atomization and the spray water pipeline according to the result;

[0118] The pipeline pressure is obtained from the pressure signal sensor on the compressed air pipeline for atomization in the flue gas emergency water spray cooling system.

[0119] The above-mentioned pneumatic quick closing valve execution instructions include:

[0120] If it is a negative value, the pneumatic quick-closing valve will close to quickly cut off the compressed air pipeline for atomization and the spray water pipeline;

[0121] If it is a positive value, the pneumatic quick-closing valve remains open to keep the compressed air pipeline for atomization and the spray water pipeline unobstructed.

[0122] In summary, when the smoke temperature at the smoke cooler inlet is t y1 ≥t yH At this time, the surface water-cooled flue gas cooling system is put into operation, the electric dampers set on the inlet and outlet flues of the smoke cooler are opened, and the electric dampers of the bypass flue are closed. At the same time, the post-furnace flue gas is cooled to the target flue temperature t y0 The desalination cooling water flow rate D required by the surface water-cooled flue gas cooling system s, when the maximum flow value of desalinated cooling water available is D max Greater than D s When the system calculates the value D according to the flow rate s Control the opening of the regulating valve of the water inlet pipeline of the smoke cooler, and compare it with the measured flow value fed back by the flow meter to accurately calibrate the opening of the regulating valve. At the same time, the measured value of the smoke temperature at the outlet of the smoke cooler as the control object is fed back. y0 The calculated flow value and the corresponding electric regulating valve opening are further corrected by comparing the deviation of the calculated flow value and the corresponding electric regulating valve opening. max Less than D s , then refer to the above calculation steps to calculate the maximum available desalination cooling water flow value D max Under the condition of smoke cooler outlet smoke temperature value t y2 If t y2 Lower than the maximum allowable smoke temperature t yH , that is, t y2 <t yH , the surface water-cooled flue gas cooling system operates alone, and the opening of the regulating valve of the water inlet pipeline of the smoke cooler is set to 100% full open. y2 ≥t yH , then the flue gas emergency water spray cooling system is also put into operation at the same time, and the system calculates the value D according to the spray water flow rate ps The corresponding compressed air flow rate for atomization is used to control the opening of the regulating valve on the water inlet pipeline and the compressed air pipeline of the atomizing spray device, and compared with the measured flow value fed back by the flow meter to accurately calibrate the opening of the regulating valve. At the same time, the measured value of the smoke temperature at the outlet of the smoke cooler as the control object is fed back. The measured value of the smoke temperature is compared with the target value t y0 By comparing the deviation, the calculated flow value and the corresponding electric control valve opening are further corrected.

[0123] It should be noted that the boiler (incinerator), semi-dry desulfurization tower, cyclone dust collector, bag dust collector and low-temperature SCR denitrification device, water-cooled smoke cooler, activated carbon injection device, atomizing spray device and compressed air pipeline for atomization in the above embodiments are all well-known equipment to those skilled in the art, so the detailed equipment models and corresponding pipeline designs are not overly explained.

[0124] The above description is only by way of illustration of certain exemplary embodiments of the present invention. It is undoubted that those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A cooling water volume control method, which is applied to a flue gas water cooling comprehensive temperature control system after a furnace, characterized in that: The system comprises a semi-dry desulfurization tower, a cyclone dust collector, a bag dust collector and a low-temperature SCR denitration device which are sequentially connected in series at the output end; The outlet flue of the cyclone dust collector and the inlet flue of the bag dust collector are respectively fixedly connected with a connecting flue connected in series with an electric damper, and also include a surface water-cooled flue gas cooling system, which includes a water-cooled flue gas cooler connected to at least one cooling water supply pipeline, the two connecting flues are connected to two interfaces of the shell side of the water-cooled flue gas cooler, and the two connecting flues are also connected with a bypass flue connected in series with the electric damper; The semi-dry desulfurization tower is provided with a flue gas emergency water spray cooling system, which includes an atomizing spray device located in the semi-dry desulfurization tower with the spray surface facing downward, a spray water pipeline and an atomizing compressed air pipeline; An activated carbon injection device is fixedly installed at the inlet flue of the bag filter; The method comprises the following steps: S01, obtain the key control data of the preset monitoring point, the key control data includes the inlet flue gas temperature value t of the water-cooled smoke cooler y1 ; S02, determining the inlet flue gas temperature value t of the water-cooled smoke cooler y1 Is it lower than the preset maximum allowable operating temperature of the flue gas after the furnace? yH If it is lower than , the electric dampers on the inlet and outlet flues of the water-cooled smoke cooler remain closed, and the electric dampers on the bypass flue remain open. If it is not lower than , the electric dampers on the bypass flue are closed and the electric dampers on the inlet and outlet flues of the water-cooled smoke cooler are opened. At the same time, the surface water-cooled flue gas cooling system is put into use to cool the inlet flue gas of the water-cooled smoke cooler from the flue temperature t y1 Cool down to the target smoke temperature t y0 ; S03, calculate the flue gas temperature t of the water-cooled smoke cooler inlet y1 Cool down to the target smoke temperature t y0 The cooling water flow value D required by the surface water-cooled flue gas cooling system is s , so as to generate a target instruction to be transmitted to the surface water-cooled flue gas cooling system; S04, during the execution of the target instruction, the inverse value t of the outlet smoke temperature of the water-cooled smoke cooler will be obtained in real time y2 , to coordinate the flue gas emergency water spray cooling system with the surface water-cooled flue gas cooling system; The back-calculated value of the flue gas temperature at the outlet of the water-cooled smoke cooler t y2 is the maximum desalination cooling water flow rate D of the surface water-cooled flue gas cooling system max Less than the cooling water flow value D required by the surface water-cooled flue gas cooling system s When the maximum desalted water volume D max Back calculation acquisition; In step S04, if the inverse calculated value of the outlet smoke temperature of the water-cooled smoke cooler is t y2 Greater than the maximum allowable smoke temperature t yH , then the flue gas emergency water spray cooling system is put into use, and at the same time, the flue gas at the outlet of the water-cooled smoke cooler is calculated from the smoke temperature inverse value t y2 Cool down to the target smoke temperature t y0 The required spray water volume D ps ; If the inverse calculation value of the outlet flue gas temperature of the water-cooled smoke cooler is t y2 Less than the target value of flue gas temperature after furnace control t yH , the surface water-cooled flue gas cooling system operates alone, and the opening of the regulating valve of the water-cooled flue gas cooler water inlet pipeline is set to 100%.

2. A cooling water quantity control method according to claim 1, characterized in that: The water-cooled smoke cooler is a high-efficiency plate and shell heat exchanger; the cyclone dust collector can be replaced by either a multi-tube dust collector or an electrostatic dust collector.

3. A cooling water volume control method according to claim 1, characterized in that: It also includes a cold demineralized water pipeline drawn from the boiler feed water system and a hot demineralized water pipeline returning to the boiler feed water deaerator. The water inlet of the water-cooled smoke cooler is connected to the cold demineralized water pipeline, and the water outlet is connected to the hot demineralized water pipeline.

4. A cooling water quantity control method according to claim 1, characterized in that: The key control data in step S01 include the flue gas temperature t y1 , and the flue gas temperature after the furnace is t y1 It is obtained through the flue gas temperature measuring points deployed on the flue between the cyclone dust collector and the water-cooled smoke cooler.

5. A cooling water quantity control method according to claim 1, characterized in that: The cooling water flow value D required by the surface water-cooled flue gas cooling system in step S03 s The calculation includes: S31, calculate the smoke temperature as t y1 With t y0 When the enthalpy value of unit volume of flue gas under standard conditions is I y1 with I y0 Values: ； Among them, t y1 is the flue gas temperature at the inlet of the water-cooled smoke cooler, t y0 is the target value of flue gas temperature control at the outlet of water-cooled smoke cooler, I y is the enthalpy of flue gas per unit volume at temperature t under standard conditions, , , and are the volume contents of CO2, N2, O2 and water vapor in flue gas, respectively, h is the mass concentration of fly ash per unit volume of flue gas under standard conditions, , , and and W h All of them are obtained through the CEMS flue gas composition online monitoring system deployed on the flue between the cyclone dust collector and the water-cooled smoke cooler. , , and are the enthalpy values ​​of CO2, N2, O2 and water vapor per unit volume at temperature t under standard conditions, (ct) h is the enthalpy of unit mass of flue gas fly ash at temperature t; S32, according to I obtained by (1) y1 with I y0 The value is used to calculate the overall enthalpy loss ∆H of the flue gas after it leaves the furnace. y , ； Among them, V y is the volume flow rate of flue gas after the furnace; S33, for the calculation of the enthalpy increment on the desalination cooling water side, the desalination cooling water temperature t s1 The desalination cooling water temperature setting value t of the water-cooled smoke cooler outlet s0 Substituting them into equation (3) respectively, we can obtain the enthalpy value i of the desalinated cooling water at the inlet and outlet of the water-cooled smoke cooler per unit mass: s1 with i s0 , ； Among them, t is the water temperature, i s is the enthalpy of unit mass of water when the water temperature is t; S34, calculate i from (3) s1 with i s0 Substitute the value into (4) to calculate the overall enthalpy increase ∆H of the desalinated cooling water passing through the water-cooled smoke cooler tube per unit time. s , ； Among them, D s is the desalinated cooling water flow rate through the water-cooled smoke cooler tube in the required unit time; S35. Based on the enthalpy heat balance principle, we get: ， ； The inlet flue gas of the water-cooled smoke cooler is y1 Cool down to the target value t of the flue gas temperature at the outlet of the water-cooled smoke cooler y0 When the surface water-cooled flue gas cooling system requires a cooling water flow value D s The calculation is as follows: 。 6. A cooling water quantity control method according to claim 1, characterized in that: In step S04, the flue gas at the outlet of the water-cooled smoke cooler is calculated from the smoke temperature t y2 Cool down to the target smoke temperature t y0 The required spray water volume D ps The calculations include: S41, the industrial water temperature value t that is not sprayed into the flue gas is detected ps1 Substituting into equation (3), we can find the enthalpy value i of the initial industrial water per unit mass: ps1 ; S42. The industrial water sprayed into the flue gas turns into water vapor because the heat absorbed from the flue gas reaches the latent heat of vaporization value, and continues to absorb the heat of the flue gas until it reaches the same temperature as the flue gas. The flue gas temperature value t y1 is the water vapor temperature value, and the flue gas temperature value t y1 Convert to Kelvin temperature T y1 ,but , and then the obtained flue gas at the water spray point, that is, the water vapor gauge pressure value P by1 Convert to absolute pressure value P jy1 ,but , according to T y1 With P jy1 Find the enthalpy of water vapor i ps2， (8); S43. Based on the enthalpy heat balance principle, calculate the required spray water volume D ps， ； In the formula, I y2 Smoke temperature y2 The enthalpy value of unit volume of flue gas under standard conditions is calculated by formula (1).

7. A cooling water quantity control method according to claim 6, characterized in that: It also includes an interlock protection mechanism for ensuring the quality of spray water atomization of the flue gas emergency water spray cooling system, and the interlock protection mechanism includes: based on the difference between the obtained pipeline pressure value and the interlock protection action value, generating an execution instruction for the pneumatic fast closing valve on the compressed air pipeline for atomization and the spray water pipeline according to the result; The pipeline pressure is obtained from a pressure signal sensor on the compressed air pipeline for atomization in the flue gas emergency water spray cooling system.

8. A cooling water quantity control method according to claim 7, characterized in that: The pneumatic quick closing valve execution instruction includes: If it is a negative value, the pneumatic quick-closing valve will close to quickly cut off the compressed air pipeline for atomization and the spray water pipeline; If it is a positive value, the pneumatic quick-closing valve remains open to keep the compressed air pipeline for atomization and the spray water pipeline unobstructed.

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