Coking wastewater spray purification and residual liquid resourceization collaborative control method

Abstract

The present application relates to the technical field of industrial wastewater treatment and waste gas purification, and particularly relates to a coking wastewater spray purification and residual liquid resourceization collaborative control method, which comprises the following steps: obtaining the salt content, chloride content and ammonia content of coking wastewater to determine a front-end spray purification mode; guiding the residual liquid at the bottom of the tower into a drying device to perform an initial drying path; obtaining the bulk density and repose angle of the miscellaneous salt at the outlet of the drying device to determine the salt precipitation stability tendency; in response to the salt precipitation stability tendency being an implicit stable tendency, determining the wall sticking tendency based on the fluctuation amplitude of the stirring motor current, and switching to a segmented evaporation drying path or a back-mixing steady-state drying path accordingly; obtaining the moisture content of the miscellaneous salt and the ammonia residual feedback data of the condensed water to correct the operating parameters of the front-end spray purification mode. The present application realizes the collaborative optimization of spray purification and residual liquid resourceization through the collaborative control method of front-end mode self-recognition, rear-end path self-adaptation and result feedback self-correction, and improves the operation stability and product quality.

Description

Technical Field

[0001] This invention relates to the field of industrial wastewater treatment and exhaust gas purification technology, and in particular to a method for the synergistic control of coking wastewater spray purification and residual liquid resource utilization. Background Technology

[0002] Coking wastewater is a high-concentration organic wastewater generated during coal-to-coke production, coal gas purification, and coking product recovery. It is characterized by complex composition, high salinity, high ammonia nitrogen concentration, and large fluctuations in water quality. During coking production, coke oven exhaust gas needs to be scrubbed to remove pollutants such as ammonia, hydrogen sulfide, and particulate matter. The scrubbing liquid is typically coking wastewater or its circulating liquid, achieving the goal of treating waste with waste.

[0003] Existing coking wastewater spray purification and residual liquid treatment processes typically employ a series process of a primary spray tower, a drying device, and a secondary spray tower. In the primary spray tower, the coking wastewater is atomized and then comes into countercurrent contact with the coke oven tail gas to complete the initial purification of the tail gas. The residual liquid generated at the bottom of the tower is sent to the drying device for evaporation and crystallization or drying treatment to obtain miscellaneous salts and condensate. The tail gas from the outlet of the primary spray tower enters the secondary spray tower and is further purified by the washing liquid before being discharged.

[0004] However, the above-mentioned traditional processes have the following shortcomings in actual operation: First: The operating parameters of the primary spray tower are usually set to fixed values ​​based on experience and are not adjusted according to fluctuations in the quality of coking wastewater. When the ammonia content in the coking wastewater increases, it is difficult to guarantee the ammonia absorption efficiency with a fixed liquid-to-gas ratio. When the salt or chloride content increases, a fixed atomization particle size is prone to salt mist entrainment and salt condensation on the tower wall, thus making it difficult to balance the contradiction between purification efficiency and equipment stability. Secondly, the feeding conditions of the drying equipment are entirely determined by the discharge state of the primary spray tower. The drying path is singular and lacks identification and adaptation of the residual liquid properties. The salt precipitation stability and adhesion tendency of the bottom residue generated under different water quality conditions are significantly different during the concentration process. The product of the unstable salt precipitation residue is powdery and easily absorbs moisture and returns to brine when directly evaporated. The high viscosity residue is easy to stick to the wall and coke in the drying equipment, which leads to a surge in stirring resistance and even forced shutdown. Third, the relationship between front-end spray purification and back-end residual liquid resource utilization is only a material series relationship, lacking information feedback; while the high moisture content of miscellaneous salts produced by the drying equipment or the excessive ammonia residue in the condensate directly reflects the inappropriate front-end spray intensity, drainage timing or circulating liquid quality, but traditional processes cannot transmit back the quality information of the back-end products to the front end to trigger parameter correction. Therefore, there is an urgent need for a collaborative control method that can dynamically adjust the spray mode according to the water quality of coking wastewater, adaptively switch the drying path according to the physical properties of residual liquid, and establish a closed-loop correction of the front-end operation based on the back-end results, in order to solve the shortcomings of the existing technologies. Summary of the Invention

[0005] To address this, the present invention provides a synergistic control method for coking wastewater spray purification and residual liquid resource utilization, which addresses the technical shortcomings of existing coking wastewater spray purification and residual liquid resource utilization processes, such as fixed front-end spray operation parameters, a single back-end drying path, and a lack of information feedback between front and rear units. The method dynamically switches the spray mode by online detection of the salt, chloride, and ammonia content of the coking wastewater, determines salt precipitation stability based on the bulk density and angle of repose of the dried products, assesses the risk of wall adhesion by combining stirring current fluctuations, and adaptively switches the drying path. Finally, the front-end operation parameters are corrected based on feedback from the moisture content of the back-end mixed salts and the residual ammonia in the condensate, achieving closed-loop synergistic optimization of the entire process.

[0006] To achieve the above objectives, the present invention provides a method for the synergistic control of coking wastewater spray purification and residual liquid resource utilization, comprising: Step S1: Obtain physical property data of coking wastewater to determine the current front-end spray purification mode of coking wastewater; The physical property data include at least salt content, chloride content and ammonia content, and the front-end spray purification mode includes enhanced mass transfer mode, anti-entrainment and wall-hanging mode and graded difference mode. Step S2: Control the atomizer of the first-stage spray tower to execute the setting parameters of the corresponding front-end spray purification mode so that the atomized droplets will generate residual liquid at the bottom of the tower after contacting the coke oven exhaust gas. Step S3: The bottom residue of the tower is introduced into the drying equipment to perform the initial drying path, and the bulk density and angle of repose of the mixed salts at the outlet of the drying equipment are obtained to determine the salt precipitation stability tendency. Step S4: In response to the salt precipitation stabilization tendency being a latent stabilization tendency, the wall adhesion characterization tendency is determined based on the amplitude of the stirring motor current fluctuation during the drying process. Step S5, switching the drying path according to the wall adhesion tendency, includes: Switch to the segmented evaporation drying path, or switch to the back-mixing steady-state drying path; Step S6: Obtain the moisture content feedback data of the mixed salt product and the ammonia residue feedback data of the condensate recovery unit to correct the operating parameters of the front-end spray purification mode.

[0007] As a preferred technical solution for the synergistic control method of coking wastewater spray purification and residual liquid resource utilization, the process of determining the current front-end spray purification mode of coking wastewater in step S1 includes: In response to an ammonia content not being less than the ammonia mass transfer threshold, the front-end spray purification mode is determined based on the salt content or chloride content, wherein: Based on the determination that the salt content and / or chloride content is not less than the corresponding salt formation risk threshold, the front-end spray purification mode is determined to be a graded differential mode. Based on the determination results that both the salt content and chloride content are less than the corresponding salt formation risk threshold, the front-end spray purification mode is determined to be an enhanced mass transfer mode. In response to an ammonia content lower than the ammonia mass transfer threshold, the front-end spray purification mode is determined based on the salt content or chloride content, wherein: Based on the determination that the salt content and / or chloride content is not less than the corresponding salt formation risk threshold, the front-end spray purification mode is determined to be an anti-entrapment and wall-hanging mode. Conversely, the front-end spray purification mode is kept at the default baseline mode.

[0008] As a preferred technical solution for the synergistic control method of coking wastewater spray purification and residual liquid resource utilization, in step S3, the initial drying path is a direct evaporation crystallization drying path, which includes sending the bottom residual liquid of the tower into the evaporator crystallizer, and performing single-stage evaporation crystallization under default evaporation temperature and default vacuum conditions to obtain mixed salt products and condensate.

[0009] As a preferred technical solution for the synergistic control method of coking wastewater spray purification and residual liquid resource utilization, the process of determining the salt precipitation stability tendency in step S3 is as follows: During the drying process, the packing density and angle of repose of the mixed salt samples at the outlet of the drying equipment were periodically collected. In response to the bulk density and angle of repose satisfying the molding conditions, the salt precipitation stability tendency is determined to be an dominant stability tendency; In response to the fact that the packing density and angle of repose do not meet the molding conditions, the salt precipitation stability tendency is determined to be a latent stability tendency; The molding conditions are that the bulk density is not less than the preset bulk density and the angle of repose is not greater than the preset angle of repose.

[0010] As a preferred technical solution for the synergistic control method of coking wastewater spray purification and residual liquid resource utilization, in step S3, in response to the salt precipitation stabilization tendency being an overt stabilization tendency, the current initial drying path is maintained.

[0011] As a preferred technical solution for the synergistic control method of coking wastewater spray purification and residual liquid resource utilization, in step S4, in response to the salt precipitation stabilization tendency being a latent stabilization tendency, the current sampling sequence of the stirring motor during the drying process is obtained and the peak-to-peak value of the current sampling sequence is calculated. The peak-to-peak value is recorded as the current fluctuation amplitude. In response to the current fluctuation amplitude being greater than the current fluctuation reference value, the wall adhesion characterization tendency is determined based on its relationship with the current fluctuation threshold, including: Based on the determination that the current fluctuation amplitude is not greater than the current fluctuation threshold, the wall adhesion tendency is determined to be a medium viscosity tendency. Based on the determination that the current fluctuation amplitude is greater than the current fluctuation threshold, the wall adhesion tendency is determined to be a high adhesion tendency.

[0012] As a preferred technical solution for the synergistic control method of coking wastewater spray purification and residual liquid resource utilization, in step S5, the drying path is switched according to the wall adhesion tendency, including: In response to the wall adhesion tendency being medium viscosity, the initial drying path was switched to a segmented evaporation drying path; In response to the wall adhesion tendency being a high viscosity tendency, the initial drying path is switched to a back-mixing steady-state drying path.

[0013] As a preferred technical solution for the synergistic control method of spray purification and residual liquid resource utilization of coking wastewater, in step S5, the segmented evaporation and drying path includes sequentially sending the bottom residual liquid into the preheating section, the low-temperature evaporation section and the high-temperature crystallization section, with intermediate residence buffer tanks set between each section to release viscosity stress. The backmixing steady-state drying path includes premixing the bottom liquid of the tower with the dried mixed salt powder according to a preset backmixing ratio, and then sending the mixture into the drying equipment for contact drying.

[0014] As a preferred technical solution for the synergistic control method of coking wastewater spray purification and residual liquid resource utilization, the process of modifying the operating parameters of the front-end spray purification mode in step S6 includes: Based on the judgment result that the moisture content feedback data is in the excessively wet range, an instruction to correct the timing of liquid discharge is generated in advance and the residence time of the residual liquid at the bottom of the first-stage spray tower is shortened. The advance correction instruction for the timing of liquid discharge includes lowering the control setting value of the liquid level at the bottom of the first-stage spray tower or increasing the opening of the liquid discharge valve at the bottom of the tower. The excessively humid range is defined as a humidity level greater than a preset humidity level.

[0015] As a preferred technical solution for the synergistic control method of coking wastewater spray purification and residual liquid resource utilization, step S6, in which the operating parameters of the front-end spray purification mode are modified, further includes: Based on the judgment result that the ammonia residue feedback data is in the excess range, a liquid-to-gas ratio reduction correction command is generated; The liquid-to-gas ratio reduction correction command includes reducing the liquid inlet flow rate of the primary spray tower atomizer or maintaining the coke oven tail gas flow rate unchanged. The above-limit range refers to ammonia residual concentration exceeding a preset ammonia residual concentration.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: The co-control method for coking wastewater spray purification and residual liquid resource utilization provided by the present invention obtains the salt, chloride and ammonia content of coking wastewater online, and automatically determines the current optimal spray mode between mass transfer requirements and anti-clogging requirements. This solves the contradiction that traditional fixed parameters cannot simultaneously take into account high ammonia absorption and high salt anti-clogging, improves the system's adaptability to fluctuations in incoming water, and realizes dynamic adaptation between front-end spray purification and wastewater properties. The stability of salt precipitation is determined by the bulk density of mixed salts and the angle of repose, and the risk of wall adhesion is assessed by the amplitude of stirring current fluctuations. The optimal path is automatically switched between direct evaporation, segmented evaporation and back-mixing steady state, effectively avoiding the risk of wall blockage caused by residual liquid in the high viscosity intermediate state, extending the continuous operation cycle of the drying equipment, and realizing adaptive matching between the drying path and residual liquid properties. The moisture content of mixed salts and the ammonia residue in condensate are used as feedback signals to reversely adjust the timing of front-end liquid discharge and the liquid-to-gas ratio, upgrading the traditional unidirectional material series connection to bidirectional information collaboration, enabling the coking wastewater and exhaust gas treatment process to have self-diagnosis and self-correction capabilities. In particular, by comparing ammonia content with mass transfer thresholds and salt and chloride content with salt formation risk thresholds in a stratified manner, precise matching between the front-end spray mode and the dynamic characteristics of coking wastewater quality was achieved: when ammonia content is high and salt formation risk is low, the system automatically enters the enhanced mass transfer mode, improving gas-liquid contact efficiency by optimizing atomization parameters to ensure ammonia absorption; when salt formation risk is high and ammonia load is low, the system switches to the anti-entrainment and wall-hanging mode, suppressing salt mist entrainment and deposition on the tower wall by adjusting droplet size; when high ammonia and high salt formation risk coexist, the system activates the graded differential mode, focusing on absorption and interception in different tower sections respectively, resolving the contradiction between mass transfer requirements and anti-clogging requirements; this ensures that the spray tower can balance purification efficiency and operational stability under different water quality conditions, avoiding fluctuations in treatment effect or equipment failure caused by fixed parameters; In particular, the stability tendency of salt precipitation is determined by collecting the bulk density and angle of repose of the mixed salts at the outlet of the drying equipment. The physical morphology of the product is used as an indirect indicator of whether the residual liquid properties are suitable for direct evaporation: high bulk density and small angle of repose indicate that the salt precipitates in an orderly manner as regular crystals, and the product particles are dense and have good flowability. In this case, maintaining the initial direct evaporation path can balance quality and energy consumption. Conversely, it indicates abnormal salt precipitation behavior, and the product is powdery or flocculent, requiring further assessment of the necessity for intervention. Under the premise of unstable salt precipitation, the amplitude of the stirring motor current is introduced as a classification basis for the risk of wall adhesion. The amplitude of the current fluctuation reflects whether the material enters a high-viscosity intermediate state during the concentration process and causes wall adhesion. By setting the current... The fluctuation threshold distinguishes between medium and high viscosity tendencies, enabling accurate identification of different risk levels. Then, differentiated intervention paths are matched according to the wall adhesion tendency: when the viscosity tendency is medium, segmented evaporation drying is switched to, using multiple temperature zones and intermediate residence buffers to release viscosity stress before the high viscosity zone, avoiding viscosity runaway caused by one-time concentration; when the viscosity tendency is high, back-mixing steady-state drying is switched to, dividing the continuous liquid phase into particle surface liquid films by pre-mixing dry powder and residual liquid, inhibiting wall scaling from the root. This avoids the risk of wall blockage during direct evaporation and prevents excessive intervention in low-risk conditions, ensuring long-term stable operation of the drying equipment while taking into account both operational economy and product quality. In particular, by establishing a closed-loop correlation between the quality indicators of the downstream products and the operating parameters of the upstream, the coking wastewater and exhaust gas treatment process has the ability to self-sensitize and self-correct its operating status: when the moisture content of the mixed salts is too high, it indicates that the feed concentration of the drying equipment is too high, and the timing of liquid discharge is automatically advanced to shorten the residence time of the residual liquid at the bottom of the tower, suppress the natural concentration effect, thereby reducing the drying load and improving the dryness of the product; when the ammonia residue in the condensate exceeds the standard, it means that the entrainment of atomized droplets is aggravated or the circulating liquid ammonia accumulates. By reducing the liquid-to-gas ratio, the escape of fine droplets is reduced, effectively blocking the path of ammonia migration to the condensate; this feedback correction does not require manual intervention, and integrates the originally independent spray purification unit and drying and recovery unit into an information-linked whole, which not only ensures the quality of the mixed salt products and the feasibility of condensate reuse, but also avoids continuous abnormal operation caused by the lagging adjustment of operating parameters. Attached Figure Description

[0017] Figure 1 This is a process diagram of the co-control method for spray purification and residual liquid resource utilization of coking wastewater according to an embodiment of the present invention; Figure 2 This is a flowchart illustrating the synergistic control method for coking wastewater spray purification and residual liquid resource utilization in an embodiment of the present invention. Detailed Implementation

[0018] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0019] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0020] It should be noted that in the description of this invention, the terms "upper", "lower", "left", "right", "inner", "outer", etc., which indicate directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and is not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0021] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0022] Please see Figure 1-2 As shown, these are, respectively, the process diagram of the coking wastewater spray purification and residual liquid resource utilization synergistic control method according to an embodiment of the present invention and the working flowchart of the coking wastewater spray purification and residual liquid resource utilization synergistic control method according to an embodiment of the present invention.

[0023] The conventional process for treating coking wastewater by spraying and removing residual liquid involves coking wastewater and coke oven gas undergoing mass transfer in a primary spray tower. The residual liquid discharged from the primary spray tower is directly sent to a drying device for evaporation and crystallization or drying to obtain mixed salts and condensate. The exhaust gas from the primary spray tower enters a secondary spray tower for further purification with washing liquid before being discharged. The washing wastewater generated by the secondary spray tower is sent to a biochemical treatment system, and the treated water is reused as greywater. However, considering the significant changes in ammonia, salt, and chloride content in coking wastewater during the production cycle, this invention treats it as a dynamically changing process medium rather than a constant-property-value ordinary spray liquid. This creates more stable feeding conditions for downstream drying while ensuring the purification effect of the exhaust gas. Simultaneously, by observing the formability and frictional characteristics of the dried product, the invention actively adapts to the residual liquid properties, thereby reducing the risk of wall fouling and downtime and improving the quality of the mixed salt product. Furthermore, the invention determines the suitability of the primary spray process operating parameters by using the moisture content of the mixed salt produced by the drying equipment and the residual ammonia concentration in the condensate recovery unit, and provides feedback for correction. Finally, the invention integrates the independent primary spray purification and residual liquid resource recovery units into a collaborative processing system with information sharing and parameter linkage.

[0024] Specifically, the salt content was obtained by an online conductivity meter installed in the inlet pipe of the primary spray tower. The online conductivity meter is equipped with a temperature compensation function and converts the conductivity value into the total dissolved solids value. The chloride content was obtained by an online chloride ion selective electrode analyzer installed in the same sampling branch. The ammonia content was obtained by an online ammonia nitrogen analyzer using the ammonia gas sensitive electrode method.

[0025] In practice, the mass transfer threshold for ammonia content is typically 800 mg / L to 1500 mg / L (calculated as NH3-N). When the ammonia content is below this threshold, the driving force for the volatility of free ammonia in coking wastewater is weak, and the primary spray tower can control the ammonia concentration in the tail gas within the emission limit through physical absorption under conventional liquid-to-gas ratio conditions without the need for enhanced mass transfer. When the ammonia content is above this threshold, the concentration of free ammonia in the wastewater is high, and the ammonia partial pressure difference between the gas and liquid phases is large. If conventional spray parameters are still used, the ammonia absorption efficiency will be insufficient, leading to excessive ammonia escape in the tail gas. In this case, it is necessary to switch to an enhanced mass transfer mode to improve the absorption driving force. The salt content... The risk threshold for salt deposition is typically 15,000 mg / L to 30,000 mg / L (TDS). After multiple cycles of concentration, the TDS of coking wastewater increases. When the TDS exceeds this threshold, the moisture on the droplet surface evaporates rapidly upon contact with the high-temperature coke oven exhaust gas, causing dissolved salts to precipitate as crystal nuclei on the droplet surface. If the droplet size is small, it may be carried by the airflow to the top demister or flue before mass transfer is complete, forming a salt-laden aerosol, leading to demister blockage and excessive particulate matter in the exhaust gas. The risk threshold for salt deposition due to chloride content is typically 5,000 mg / L to 10,000 mg / L (Cl... - ), Cl - When the concentration is high, the salt precipitated from the atomized droplets is mainly chloride. Chloride salts are highly hygroscopic, and the deposits formed on the tower wall or demister surface are moist and sticky, which are not easy to fall off, thus accelerating the wall adhesion and corrosion. At the same time, after the high-chlorine residual liquid enters the subsequent drying equipment, the chloride ion content in the product miscellaneous salt is high, which will cause the miscellaneous salt to easily absorb moisture and return to brine, and the quality of solid products will decline.

[0026] It is understandable that (1) when the ammonia content is not less than the ammonia content mass transfer threshold and the salt content and chloride content are both less than the corresponding salt formation risk threshold, it indicates that the high ammonia mass transfer demand of the waste liquid is dominant. At this time, fine droplets are needed to provide a larger specific surface area to improve the gas-liquid mass transfer efficiency and ensure that ammonia absorption meets the standards. Meanwhile, fine droplets with low salt and low chloride have no salt formation risk and will not cause entrainment problems. In practice, the atomization particle size of the enhanced mass transfer mode is 50μm~80μm and the liquid-to-gas ratio is 2.5L / m 3 ~4.0L / m 3The spraying level is assigned as upper layer dense spraying (increasing gas-liquid contact area), and the liquid discharge time is when the liquid level is 40% to 50% and the circulation frequency is increased; (2) When the ammonia content is not less than the ammonia content mass transfer threshold and the salt content and / or chloride content is not less than the corresponding salt formation risk threshold, high ammonia requires fine mist to enhance absorption, while high salt and high chloride require coarse mist to prevent entrainment. There is a target conflict, so it is necessary to switch the graded difference mode, that is, to use fine mist droplets in the lower layer of the tower to ensure ammonia absorption efficiency and to use coarse mist droplets in the upper layer of the tower to intercept the escaping fine mist and prevent salt mist entrainment in order to take into account both mass transfer and anti-blocking requirements; In implementation, the lower layer particle size of the graded difference mode is 80μm to 120μm, the upper layer particle size is 120μm to 180μm, and the lower layer liquid-gas ratio is 1.5L / m 3 ~2.5L / m 3 The liquid-to-gas ratio in the upper layer is 0.8 L / m³. 3 ~1.5L / m 3 The spraying layer is divided into two levels: the lower layer focuses on absorption and the upper layer focuses on interception and anti-entrainment. The timing of liquid discharge is when the liquid level is 35% to 45% and the liquid is discharged in zones. (3) When the ammonia content is less than the ammonia content mass transfer threshold and the salt content and / or chloride content is not less than the corresponding salt formation risk threshold, the mass transfer demand is not urgent but the salt formation risk is high. It is necessary to increase the droplet size and reduce the droplet specific surface area, thereby reducing the surface evaporation rate and inhibiting the premature precipitation of salt on the droplet surface. The coarse droplets accelerate the settling speed and reduce the probability of airflow entrainment, effectively preventing the demister from being blocked by salt and the tower wall from being hung with salt. In practice, the atomization particle size of the anti-entrainment wall hanging mode is 120μm to 200μm and the liquid-to-gas ratio is 1.0L / m 3 ~2.0L / m 3 The spraying layer is mainly sprayed in the lower layer to reduce the generation of fine mist in the upper layer. The liquid is drained when the liquid level is 30% to 40% and the residence time is shortened. (4) Under the default benchmark mode, the waste liquid is relatively clean, with no high ammonia mass transfer pressure or salt formation risk. The spraying can be carried out using the conventional parameters with the lowest energy consumption and simplest operation. The atomization particle size is 80μm to 120μm and the liquid-to-gas ratio is 1.5L / m 3 ~2.5L / m 3 The spray layer is configured as a single-layer uniform spray, and the liquid is drained when the liquid level is 50% to 60%.

[0027] In practice, the first-stage spray tower is a vertical cylindrical gas-liquid countercurrent contact device. The tower body is arranged from bottom to top as follows: bottom liquid storage area, air inlet, multi-layer spray area, demisting area and top air outlet. The multi-layer spray area is arranged with at least two spray layers along the height of the tower. Each spray layer consists of an annular liquid distribution pipe and several atomizing nozzles. Each spray layer is connected to the coking wastewater supply main pipe through an independent inlet branch pipe. Each inlet branch pipe is equipped with a flow regulating valve to adjust the amount of spray liquid in a single layer and the liquid-to-gas ratio. The atomizing nozzles are pressure atomizing nozzles, and the atomized particle size can be adjusted by adjusting the supply pressure or by replacing the nozzles with different orifice diameters. The liquid storage area at the bottom of the tower is equipped with a liquid level sensor interlocked with the drain pump, and the timing of draining is controlled by adjusting the liquid level setpoint. The coke oven tail gas enters from the air inlet at the bottom of the tower, passes through each spray layer in sequence, and comes into countercurrent contact with the atomized droplets. After the entrained droplets are removed by the demister at the top of the tower, the purified tail gas is discharged from the air outlet. The residual liquid at the bottom of the tower is sent to the drying equipment by the drain pump.

[0028] Specifically, the bottom residue of the coking wastewater primary spraying process mainly contains inorganic salts such as sodium chloride, sodium sulfate, and calcium chloride, as well as a small amount of organic matter. Under normal or slightly negative pressure conditions, the boiling point of water is about 100℃. If the evaporation temperature is set too high (>90℃), the small amount of tar-like organic matter remaining in the residue may undergo thermal polymerization, leading to coking on the heat exchange surface. In addition, the high temperature under high chlorine conditions accelerates metal corrosion. If the evaporation temperature is set too low (<60℃), the evaporation rate will decrease significantly, resulting in insufficient equipment processing capacity, requiring a larger heat exchange area, and poor economic efficiency. The range of 65℃ to 85℃ can ensure a reasonable evaporation rate, avoid coking of organic matter and aggravated equipment corrosion, and match well with the subsequent vacuum system. In implementation, the default evaporation temperature of the initial drying path is 65℃ to 85℃. Understandably, reducing the operating pressure lowers the boiling point of water, allowing the evaporation process to occur at a lower temperature. This is beneficial for utilizing low-grade heat sources and reducing scaling tendency. When the vacuum range is -0.06MPa to -0.08MPa (gauge pressure, i.e., absolute pressure of approximately 20kPa to 40kPa), the boiling point of water drops to approximately 60℃ to 75℃, which matches the default evaporation temperature of 65℃ to 85℃. This ensures that the boiling heat transfer maintains a high and stable heat transfer coefficient in the nucleation boiling zone. Excessive vacuum (absolute pressure < 10kPa) significantly increases the requirements for equipment sealing and vacuum pumps, raising operating costs and potentially causing violent boiling and entrainment of the liquid. In practice, the default vacuum level for the initial drying path is -0.06MPa to -0.08MPa.

[0029] In practice, a sample of mixed salt from the outlet of the drying equipment is dried in an oven at 105℃ until constant weight, then cooled. The sample is then allowed to fall freely through a funnel into a stainless steel graduated cylinder (e.g., 100mL) of fixed volume. After filling, the cylinder is leveled without vibration, and the mass of the sample inside is weighed. The mass divided by the volume is the single-batch density. The dried mixed salt sample is then allowed to fall freely through a funnel from a fixed height (e.g., 10cm) onto a horizontal disk to form a conical accumulation. The height h and the radius r of the base are measured, and the angle of repose is calculated as arctan(h / r). In one implementation, the determination of the bulk density and angle of repose is repeated three times, and the average value is taken to avoid single-batch experimental errors. It is understandable that bulk density reflects the compactness and crystal integrity of solid particles. During evaporation and crystallization, if the residual liquid exhibits stable salt precipitation behavior, the salt precipitates in an orderly manner in crystalline form, resulting in smooth particle surfaces, regular shapes, low porosity, and high bulk density during packing. Conversely, if the salt precipitation is unstable, the salt precipitates as amorphous particles or flocculent aggregates, resulting in irregular particle shapes, rough surfaces, high porosity, and significantly reduced bulk density during packing. The angle of repose reflects the internal friction and flow resistance between particles. Particles with intact crystal structures have a small angle of repose, good flowability, and are less prone to bridging and clogging. Amorphous powders have a large specific surface area, resulting in enhanced van der Waals forces and capillary coagulation between particles, leading to a larger angle of repose. This makes the material more prone to arching and bridging at the outlet of the drying equipment or within the silo. Specifically, when the mixed salt product simultaneously satisfies the following conditions: high bulk density (bulk density not less than a preset bulk density, the preset bulk density is 0.9 g / cm³),... 3 The typical crystalline bulk density of pure crystals of mixed salts in coking waste liquid is approximately 1.0 g / cm³. 3 ~1.2g / cm 3 When the actual value is lower than 0.90 g / cm³ 3 When the proportion of powder exceeds 20%–30%, the product has poor formability; when the angle of repose is small (not greater than the preset angle of repose, which is 40°; generally, granular materials are free-flowing when the angle of repose is <35°, viscous flow when the angle of repose is 35°–45°, and non-free-flowing when the angle of repose is >45°), the salt precipitation process is stable, and the residual liquid is suitable for direct evaporation crystallization drying. Conversely, if the bulk density is low or the angle of repose is large, it indicates that the salt precipitation process is disordered, the product is powdery, and it is prone to absorbing moisture and returning to brine. Continuing to use direct evaporation crystallization will lead to poor product quality and high equipment operation risk, and it is necessary to switch the drying path.

[0030] Specifically, the implicit stability tendency indicates that the precipitation behavior of salts in the residual liquid has deviated from the normal crystallization law, and the products are mainly amorphous powders or flocculent agglomerates. This abnormal salt precipitation is often related to the interference of specific impurities (organic matter, high concentration of chloride ions) in the solution with crystal nucleus formation, and is usually accompanied by the appearance of a high-viscosity intermediate. In addition, when the salt precipitation is abnormal, the residual liquid is prone to a phenomenon of rapid increase in viscosity when it is concentrated to a solid content range of about 40% to 70%. If direct evaporation is continued forcibly at this time, the high-viscosity material will adhere to the stirring blades and the heat exchange cylinder wall, resulting in a sharp drop in heat transfer efficiency, overload of the stirring motor, and even forced shutdown of the equipment for cleaning. Therefore, when the stirring blade pushes the high-viscosity material, the motor current rises rapidly, and when the material is pushed away from the blades or the agglomerates fall off the wall, the current drops instantly. This cycle of loading and unloading will cause large pulses in the current waveform. Therefore, the more severe the adhesion to the wall, the larger the agglomerate size, the stronger the adhesion, and the greater the current fluctuation amplitude. In implementation, the current fluctuation benchmark value is 1.5 times the statistical average value of the peak-to-peak current of the stirring motor of the drying equipment under normal operating conditions (when treating clean water or low-salt wastewater) (the benchmark value is calibrated during the equipment commissioning stage). The current fluctuation threshold is 2.5 to 3.5 times the current fluctuation benchmark value, preferably 3 times. When the current fluctuation amplitude exceeds the current fluctuation threshold, it indicates that serious wall adhesion or agglomeration has occurred and direct evaporation can no longer maintain normal operation. At this time, it is necessary to switch to the back-mixing steady-state drying path to reduce the apparent viscosity of the feed by pre-mixing the residual liquid with the finished dry powder, improve the contact state between the material and the heat exchange surface, and inhibit the continued deterioration of wall adhesion. If the current fluctuation amplitude does not exceed the current fluctuation threshold, it indicates that the viscosity of the material has increased but has not yet formed a firm wall adhesion. At this time, it is necessary to switch to segmented evaporation drying. By setting multiple temperature zones and intermediate buffer zones, the material can obtain sufficient viscosity stress release time before leaving the high viscosity zone, avoiding entering the high-risk concentration zone all at once.

[0031] Specifically, the initial path is maintained in response to the current fluctuation amplitude not exceeding the current fluctuation reference value.

[0032] It is understandable that the residual liquid at the bottom of the coking wastewater tower has a peak viscosity concentration range (usually 40% to 70% solid content) during the evaporation and concentration process. If single-stage direct evaporation is used, the material will continuously experience this high viscosity range on the heat exchange surface, which can easily lead to scaling on the heat exchange wall and a surge in stirring resistance. Segmented evaporation divides the concentration process into two stages in space and sets an intermediate buffer before entering the high viscosity range. Utilizing the Ostwald ripening effect in crystal growth kinetics, small crystal nuclei dissolve and large crystal nuclei grow under isothermal static conditions, reducing the total surface energy of the system and causing the viscosity to naturally decrease. When the material re-enters the high-temperature crystallization stage, the crystals have reached a certain size, and the solution viscosity is significantly lower than that of a one-time rapid concentration, thus safely passing through the high-risk range. Specifically, the specific process of the segmented evaporation and drying path is as follows: (1) Preheating section: The residual liquid at the bottom of the tower first enters the preheating heat exchanger, and the residual liquid is preheated to 45℃~60℃ by using the residual heat of the system (such as the secondary steam generated by the high-temperature crystallization section or the sensible heat of the condensate); (2) Low-temperature evaporation section: After preheating, the residual liquid enters the first-effect evaporator, and is initially concentrated under the conditions of 55℃~65℃ and -0.06MPa~-0.08MPa, evaporating water and concentrating the residual liquid to a solid content of about 15%~25%; (3) First intermediate residence buffer tank: The material discharged from the low-temperature evaporation section enters the belt A buffer tank with slow stirring (slow anchor or frame stirring, speed 3 rpm to 10 rpm) is used, and the residence time is controlled to be 20 to 60 minutes. During this stage, the salt in the concentrate gradually precipitates crystal nuclei, and the viscosity is naturally released under constant temperature and static conditions to avoid a sharp increase in viscosity during subsequent heating. (4) High temperature crystallization section: The material discharged from the buffer tank is sent to the second-effect evaporator crystallizer, and is further concentrated at 75℃ to 85℃ and -0.07MPa to -0.09MPa until the solid content is ≥60%, and solid salt crystal slurry is precipitated. After centrifugation or filtration, the mixed salt product is obtained.

[0033] It is understandable that the reason why the residual liquid at the bottom of the tower adheres to the wall during direct drying is the presence of a continuous liquid phase (the residual liquid is a homogeneous liquid or a high-concentration slurry; after contact with the high-temperature wall, the water evaporates rapidly, and the dissolved salt precipitates on the wall and adheres firmly). After back-mixing the dry powder, the dry powder particles act as a skeletal carrier to adsorb the residual liquid, dividing the originally continuous liquid phase into a dispersed liquid film that wraps around the particle surface. The system changes from liquid-encased solid to solid-encased liquid particle aggregates. When the material in this state comes into contact with the heat exchange wall, water evaporation occurs on the particle surface rather than in a continuous liquid layer on the wall. The precipitated salts adhere to the dry powder particles and grow, rather than nucleating on the wall. At the same time, the rolling friction of the particle group replaces the sliding shearing of the sticky material, the load on the stirring motor is stable, and even if slight adhesion occurs locally, the scraping action of the stirring paddle can easily peel off the adhering material, thus maintaining the long-term stable operation of the drying equipment. Specifically, the preset backmixing ratio is dry powder mass: residual liquid mass = 1:1 to 1:3. If the backmixing ratio is too small, the mixture will still be in a slurry or paste state, failing to effectively reduce the apparent viscosity and easily adhering to the walls of the drying equipment. If the backmixing ratio is too large, the dry powder circulation volume increases, raising the equipment volume and conveying energy consumption. The premixing time is 3 to 5 minutes to ensure that the dry powder and residual liquid are fully in contact and coated, with the residual liquid being adsorbed into the internal pores by the dry powder particles, while the surface remains dry and loose. The moisture content of the mixed material is 25% to 40%, so that the material no longer has a continuous liquid phase. The interparticle liquid bridge effect is weakened and the stirring resistance is significantly reduced. At this time, the drying equipment mostly adopts paddle dryers or disc dryers with self-cleaning function (indirect heating through jacket steam or heat transfer oil, and the remaining moisture is evaporated to obtain the mixed salt product under stirring conditions). The paddle or scraper is in close contact with the heat transfer surface, which can remove the adhering material in time. After the pre-treatment of back-mixing, it can maintain long-term stable operation. The drying temperature is 120℃~160℃. The material temperature is maintained at 80℃~100℃ through indirect heating, which is higher than the atmospheric pressure evaporation temperature, thus accelerating the drying rate.

[0034] Specifically, when the moisture content of the mixed salts produced by the drying equipment is in the excessively moist range (i.e., the moisture content is greater than the preset moisture content), it indicates that the current drying load and feed characteristics are mismatched, and intervention is needed in the drainage operation of the front-end primary spray tower, including: Lowering the control setpoint for the bottom liquid level of the first-stage spray tower shortens the residence time of the residual liquid in the bottom storage zone. Alternatively, increase the opening of the drain valve at the bottom of the tower to accelerate the discharge rate of residual liquid; Understandably, during the residence time of the residual liquid at the bottom of the primary spray tower in the storage zone, it will undergo a certain degree of natural concentration due to continuous contact with the high-temperature coke oven exhaust gas and the evaporation of entrained moisture. The longer the residence time, the higher the residual liquid concentration, and the greater the initial solid content of the feed to the drying equipment. When the feed concentration is too high, the drying equipment cannot fully evaporate the remaining moisture within the rated heat exchange area and residence time, resulting in excessive moisture content of the outlet impurities. By draining the liquid in advance (lowering the liquid level setpoint or increasing the opening of the drain valve), the residence time of the residual liquid at the bottom of the tower can be effectively shortened, the natural concentration effect can be suppressed, and the concentration of the residual liquid entering the drying equipment can be kept within the design range. Under the same operating conditions, the drying equipment can fully complete the evaporation of moisture, and the moisture content of the impurities can be restored to the normal range. In addition, early drainage also indirectly reduces the supersaturation accumulation of salt in the residual liquid, which is conducive to the orderly growth of crystals during the subsequent evaporation and crystallization process and reduces the proportion of powdery amorphous salts generated. In practice, the preset moisture content is 10%. When it is below 10%, the mixed salts are loose granules that do not clump or stick to the walls, which meets the requirements for ton bag packaging and open-air storage.

[0035] Specifically, when the residual ammonia concentration in the condensate recovery unit is outside the limit range (i.e., the residual ammonia concentration is greater than the preset upper limit for residual ammonia), it indicates that the absorption and removal of ammonia from the coke oven exhaust gas by the front-end primary spray tower is insufficient, and intervention is required in the spray operation parameters, including: Reducing the inlet flow rate of the primary spray tower atomizer or maintaining the coke oven gas flow rate unchanged (i.e., reducing the liquid-to-gas ratio) is crucial. It's understood that ammonia in coke oven gas is primarily removed through spray absorption, and the liquid-to-gas ratio (the ratio of spray flow rate to tail gas flow rate) is a key parameter determining ammonia absorption efficiency. Increasing the liquid-to-gas ratio within a certain range can improve the mass transfer area and enhance ammonia absorption. However, when the liquid-to-gas ratio is too high, the atomized droplet size decreases and the number increases. While this increases the gas-liquid contact area, it also exacerbates mist entrainment. Ammonia-containing droplets are carried by the airflow through the demister into the subsequent condensation system, leading to an increase in ammonia residue in the condensate. Therefore, when excessive ammonia residue is detected in the condensate, appropriately reducing the liquid-to-gas ratio can increase the average droplet size, reduce the entrainment and escape of fine droplets, and thus reduce the ammonia pollution load in the condensate. In practice, the preset ammonia residual concentration is usually 50mg / L to 150mg / L (calculated as NH3-N, preferably 100mg / L). The condensate is usually collected as steam condensate from the drying equipment or planned to be reused as system makeup water. If the ammonia residual concentration is too high, the condensate will release ammonia gas during storage and reuse, causing secondary pollution and deterioration of the working environment. At the same time, if high ammonia condensate is directly returned to the spray system, it will further aggravate the vicious cycle of ammonia accumulation in the circulating liquid.

[0036] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

[0037] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for synergistic control of coking wastewater spray purification and residual liquid resource utilization, characterized in that, include: Acquire physical property data of coking wastewater to determine the current front-end spray purification mode for coking wastewater; The physical property data include at least salt content, chloride content and ammonia content, and the front-end spray purification mode includes enhanced mass transfer mode, anti-entrainment and wall-hanging mode and graded difference mode. The enhanced mass transfer mode has an atomized particle size of 50 μm to 80 μm and a liquid-to-gas ratio of 2.5 L / m³. 3 ~4.0L / m 3 The spray layer is configured with an upper layer of denser spraying, and liquid is drained when the liquid level reaches 40%–50% while increasing the circulation frequency. The lower layer particle size in the graded differential mode is 80μm–120μm, the upper layer particle size is 120μm–180μm, and the lower layer liquid-to-gas ratio is 1.5L / m³. 3 ~2.5L / m 3 The liquid-to-gas ratio in the upper layer is 0.8 L / m³. 3 ~1.5L / m 3 The spray layer is configured with the lower layer focusing on absorption and the upper layer focusing on interception and anti-entrainment. Liquid is drained in sections when the liquid level is 35%–45%. The atomized particle size of the anti-entrainment wall-hanging mode is 120μm–200μm, and the liquid-to-gas ratio is 1.0L / m³. 3 ~2.0L / m 3 The spraying level is mainly lower-level spraying, and the liquid is drained when the liquid level is 30% to 40% in a timely manner and the residence time is shortened. Control the atomizer of the first-stage spray tower to execute the setting parameters of the corresponding front-end spray purification mode so that the atomized droplets will generate residual liquid at the bottom of the tower after contacting the coke oven exhaust gas; The bottom residue of the tower is introduced into the drying equipment to perform the initial drying path, and the bulk density and angle of repose of the mixed salts at the outlet of the drying equipment are obtained to determine the salt precipitation stability tendency. In response to the fact that the salt precipitation stabilization tendency is a latent stabilization tendency, the wall adhesion characterization tendency is determined based on the amplitude of the stirring motor current fluctuation during the drying process. Switching the drying path based on the wall adhesion tendency includes: Switch to the segmented evaporation drying path, or switch to the back-mixing steady-state drying path; The segmented evaporation and drying path includes sequentially feeding the bottom residue into a preheating section, a low-temperature evaporation section, and a high-temperature crystallization section, with intermediate buffer tanks set between each section to release viscous stress. The backmixing steady-state drying path includes premixing the bottom liquid of the tower with the dried mixed salt powder according to a preset backmixing ratio, and then sending the mixture into the drying equipment for contact drying. The operating parameters of the front-end spray purification mode are corrected by obtaining feedback data on the moisture content of the mixed salt product and the ammonia residue of the condensate recovery unit.

2. The method for synergistic control of coking wastewater spray purification and residual liquid resource utilization according to claim 1, characterized in that, The process of determining the current front-end spray purification mode for coking wastewater includes: In response to an ammonia content not being less than the ammonia mass transfer threshold, the front-end spray purification mode is determined based on the salt content or chloride content, wherein: Based on the determination that the salt content and / or chloride content is not less than the corresponding salt formation risk threshold, the front-end spray purification mode is determined to be a graded differential mode. Based on the determination results that both the salt content and chloride content are less than the corresponding salt formation risk threshold, the front-end spray purification mode is determined to be an enhanced mass transfer mode. In response to an ammonia content lower than the ammonia mass transfer threshold, the front-end spray purification mode is determined based on the salt content or chloride content, wherein: Based on the determination that the salt content and / or chloride content is not less than the corresponding salt formation risk threshold, the front-end spray purification mode is determined to be an anti-entrapment and wall-hanging mode. Conversely, the front-end spray purification mode is kept at the default baseline mode.

3. The method for synergistic control of coking wastewater spray purification and residual liquid resource utilization according to claim 1, characterized in that, The initial drying path is a direct evaporation crystallization drying path, which includes sending the bottom residue of the tower into an evaporator crystallizer and performing single-stage evaporation crystallization under default evaporation temperature and default vacuum conditions to obtain mixed salt products and condensate.

4. The method for synergistic control of coking wastewater spray purification and residual liquid resource utilization according to claim 1, characterized in that, The process of determining the salt precipitation stability tendency is as follows: During the drying process, the packing density and angle of repose of the mixed salt samples at the outlet of the drying equipment were periodically collected. In response to the bulk density and angle of repose satisfying the molding conditions, the salt precipitation stability tendency is determined to be an dominant stability tendency; In response to the fact that the packing density and angle of repose do not meet the molding conditions, the salt precipitation stability tendency is determined to be a latent stability tendency; The molding conditions are that the bulk density is not less than the preset bulk density and the angle of repose is not greater than the preset angle of repose.

5. The method for synergistic control of coking wastewater spray purification and residual liquid resource utilization according to claim 4, characterized in that, In response to the salt precipitation stabilization tendency being a dominant stabilization tendency, the current initial drying path is maintained.

6. The method for synergistic control of coking wastewater spray purification and residual liquid resource utilization according to claim 4, characterized in that, In response to the salt precipitation stabilization tendency being a latent stabilization tendency, the current sampling sequence of the stirring motor during the drying process is acquired and the peak-to-peak value of the current sampling sequence is calculated. The peak-to-peak value is recorded as the current fluctuation amplitude. In response to the current fluctuation amplitude being greater than the current fluctuation reference value, the wall adhesion characterization tendency is determined based on its relationship with the current fluctuation threshold, including: Based on the determination that the current fluctuation amplitude is not greater than the current fluctuation threshold, the wall adhesion tendency is determined to be a medium viscosity tendency. Based on the determination that the current fluctuation amplitude is greater than the current fluctuation threshold, the wall adhesion tendency is determined to be a high adhesion tendency.

7. The method for synergistic control of coking wastewater spray purification and residual liquid resource utilization according to claim 6, characterized in that, Switching the drying path based on the wall adhesion tendency includes: In response to the wall adhesion tendency being medium viscosity, the initial drying path was switched to a segmented evaporation drying path; In response to the wall adhesion tendency being a high viscosity tendency, the initial drying path is switched to a back-mixing steady-state drying path.

8. The method for synergistic control of coking wastewater spray purification and residual liquid resource utilization according to claim 1, characterized in that, The process of correcting the operating parameters of the front-end spray purification mode includes: Based on the judgment result that the moisture content feedback data is in the excessively wet range, an instruction to correct the timing of liquid discharge is generated in advance and the residence time of the residual liquid at the bottom of the first-stage spray tower is shortened. The advance correction instruction for the timing of liquid discharge includes lowering the control setting value of the liquid level at the bottom of the first-stage spray tower or increasing the opening of the liquid discharge valve at the bottom of the tower. The excessively humid range is defined as a humidity level greater than a preset humidity level.

9. The method for synergistic control of coking wastewater spray purification and residual liquid resource utilization according to claim 1, characterized in that, The process of correcting the operating parameters of the front-end spray purification mode also includes: Based on the judgment result that the ammonia residue feedback data is in the excess range, a liquid-to-gas ratio reduction correction command is generated; The liquid-to-gas ratio reduction correction command includes reducing the liquid inlet flow rate of the primary spray tower atomizer or maintaining the coke oven tail gas flow rate unchanged. The above-limit range refers to ammonia residual concentration exceeding a preset ammonia residual concentration.

Images