A small water quantity silver nitrate production process wastewater treatment system and method

Abstract

The application discloses a small-water-volume silver nitrate production process wastewater treatment system and method, and relates to the technical field of industrial wastewater treatment.The system comprises a regulating tank, a pretreatment unit, a roller drying unit, a terminal treatment unit and a control unit connected through pipelines in sequence; the pretreatment unit is used for solid-liquid separation and silver resource recovery of the wastewater; the roller drying unit is connected with the liquid outlet of the pretreatment unit and used for directly drying and solidifying the pretreated wastewater to form a salt solid; a feeding pump is arranged between the pretreatment unit and the roller drying unit; silver ion intelligent monitoring units are arranged at the liquid outlet of the regulating tank and the liquid outlet of the pretreatment unit; and the control unit is used for dynamically adjusting the process operation parameters of the pretreatment unit and the roller drying unit according to real-time data fed back by the silver ion intelligent monitoring units.The application has a very short process, high equipment integration and a very small floor area.

Description

Technical Field

[0001] This invention relates to the field of industrial wastewater treatment technology, and more specifically, to a treatment system and method for wastewater from a small-volume silver nitrate production process. Background Technology

[0002] In the processes of producing silver nitrate and silver powder using silver nitrate as a raw material (such as through chemical reduction), small amounts of high-concentration process wastewater are generated, mainly as washing wastewater. This wastewater is characterized by its small volume (typically several tons per day), complex composition, extremely high salt content (rich in nitrates, nitrites, and ammonium salts), acidity, and trace amounts of silver ions and organic impurities. This type of wastewater is highly toxic and has extremely poor biodegradability, making it a typical example of difficult-to-treat industrial wastewater.

[0003] Currently, the conventional approach to treating this type of wastewater is to mimic the treatment process for large-volume mixed wastewater, typically employing a lengthy combined process involving "chemical precipitation for silver removal - neutralization - flocculation - biological treatment - deep oxidation - membrane concentration - evaporation and crystallization." This treatment method has significant drawbacks for small-volume wastewater:

[0004] 1) The process flow is too long, the equipment investment is large, and the land area required is large;

[0005] 2) High operating energy consumption, especially the aeration of the biochemical unit, the reagents and energy consumption of deep oxidation, and the high energy consumption of evaporation and crystallization;

[0006] 3) The operation and management are complex, requiring coordination and control of multiple processing units, which places high demands on operators;

[0007] 4) Ultimately, concentrated liquid or miscellaneous salts that still need to be disposed of are still produced, and the problem is shifted rather than solved.

[0008] Therefore, there is an urgent need for an integrated treatment technology and system that can directly achieve near-zero wastewater discharge and solidification disposal for silver nitrate production wastewater with small volume and high salinity. This technology and system has an extremely short process, low energy consumption, simple operation, and can directly achieve near-zero wastewater discharge and solidification disposal. Summary of the Invention

[0009] In view of the problems in related technologies, this invention proposes a treatment system and method for wastewater from small-volume silver nitrate production processes, so as to overcome the above-mentioned technical problems existing in the existing related technologies.

[0010] Therefore, the specific technical solution adopted by the present invention is as follows:

[0011] In a first aspect, the present invention provides a treatment system for wastewater from a small-volume silver nitrate production process, comprising:

[0012] The system consists of a regulating tank, a pretreatment unit, a drum drying unit, a terminal treatment unit, and a control unit, connected sequentially via pipelines.

[0013] The pretreatment unit is used for solid-liquid separation and silver resource recovery of wastewater;

[0014] The drum drying unit is connected to the liquid outlet of the pretreatment unit and is used to directly dry and solidify the pretreated wastewater to form mixed salt solids.

[0015] A feed pump is provided between the pretreatment unit and the drum drying unit;

[0016] Silver ion intelligent monitoring units are installed at the liquid outlet of the equalization tank and the liquid outlet of the pretreatment unit.

[0017] The control unit is used to dynamically adjust the process operating parameters of the pretreatment unit and the drum drying unit based on the real-time data fed back by the silver ion intelligent monitoring unit, so as to realize intelligent operation and precise control of wastewater treatment under small water volume conditions.

[0018] Furthermore, the pretreatment unit includes a precision filter and a chemical precipitation device;

[0019] The precision filter is connected to the equalization tank and is used to remove suspended silver particles from the wastewater.

[0020] The chemical precipitation device is connected to the liquid outlet of the precision filter and is equipped with a stirring mechanism and a dosing mechanism. It is used to add a precipitant to the wastewater and selectively precipitate and recover dissolved silver ions.

[0021] Furthermore, the precipitant added to the chemical precipitation device is sodium chloride or hydrochloric acid, and the precipitation product is silver chloride;

[0022] The bottom of the chemical precipitation device is equipped with a precipitate collection mechanism and a discharge mechanism;

[0023] Both the precipitate collection mechanism and the discharge mechanism are connected to a precipitate washing device for multi-stage countercurrent washing of the silver chloride precipitate.

[0024] A composite monitor is installed at the liquid outlet of the chemical precipitation device to monitor the residual concentration of silver ions in the supernatant after chemical precipitation in real time and to determine the degree of completeness of the precipitation reaction.

[0025] An online silver ion monitor is installed at the liquid outlet of the equalization tank to monitor the concentration of silver ions in the wastewater before it enters the pretreatment unit in real time.

[0026] Furthermore, the drum drying unit is a steam indirect heating drum dryer;

[0027] The steam indirect heating drum dryer consists of a cloth feeder, drum, scraper and salt tank, and is used for continuous drying and solidification of the supernatant after chemical precipitation treatment.

[0028] Furthermore, the end-of-line treatment unit includes an exhaust gas treatment device and a miscellaneous salt collection and packaging device;

[0029] The exhaust gas treatment device is used to treat the water vapor and trace amounts of volatile substances that may be entrained during the drying process of the drum drying unit.

[0030] The salt collection device and the packaging device are used to collect the salt solids that are peeled off after drying by the drum drying unit.

[0031] Furthermore, the exhaust gas treatment device includes a condenser, a spray tower, and a demister;

[0032] The condenser is used to perform preliminary cooling and condensation on the high-temperature exhaust gas discharged from the drum drying unit, and to recover moisture and condensable substances in the exhaust gas.

[0033] The spray tower is used to deeply wash and purify the condensed exhaust gas through circulating spraying.

[0034] The demister is used to remove droplets and fine particulate matter carried in the exhaust gas.

[0035] Furthermore, the control unit includes a data preprocessing module, a dynamic adjustment module, and an execution feedback module;

[0036] The data preprocessing module is used to filter and analyze the influent silver ion concentration data, effluent silver ion residue data, pH data, and turbidity data collected by the silver ion online monitoring instrument and the composite monitoring instrument, and generate process parameter data.

[0037] The dynamic adjustment module is used to compare process parameter data with preset silver recovery rate target values, and to dynamically calculate the comparison results to generate standardized control commands.

[0038] The execution feedback module is used to input control commands to the chemical precipitation device and the drum drying unit in real time for adaptive optimization, so as to ensure that the silver recovery rate is stably maintained within the target range.

[0039] Furthermore, the dynamic adjustment module includes:

[0040] The data receiving module is used to receive process parameter data output by the data preprocessing module. The process parameter data includes influent silver ion concentration data after pretreatment, effluent silver ion residue data after precipitation after pretreatment, pH value data after pretreatment, and turbidity data after pretreatment.

[0041] The data comparison module is used to calculate the silver recovery rate in real time the silver ion concentration data of the influent after pretreatment and the silver ion residue data of the effluent after pretreatment and precipitation. It also compares the calculated silver recovery rate with the preset silver recovery rate target value to generate the comparison deviation value and the deviation change rate.

[0042] The fuzzification processing module is used to perform fuzzification processing on the deviation value and the rate of change of deviation based on a preset fuzzy rule library and a fuzzy PID control algorithm, to determine the proportional coefficient, integral time and derivative time, and to obtain the adjusted PID parameters.

[0043] The defuzzy calculation module is used to perform defuzzy calculations on the reagent dosage of the chemical precipitation device and the operating parameters of the drum drying unit based on the adjusted PID parameters, and generate a set of control quantity values.

[0044] The instruction conversion module is used to convert a set of control quantity values ​​into standardized control instructions through a preset instruction mapping relationship and a standardized protocol.

[0045] Furthermore, based on the adjusted PID parameters, the defuzzification calculation of the reagent dosage of the chemical precipitation device and the operating parameters of the drum drying unit is performed to generate a set of control quantity values, including:

[0046] Receive the adjusted PID parameters, which include the proportional coefficient, integral time, and derivative time;

[0047] Based on the adjusted proportional coefficient, integral time and derivative time, the amount of sodium chloride solution added to the chemical precipitation device is defuzzified to generate the control value of the amount of sodium chloride solution added.

[0048] Based on the adjusted proportional coefficient, integral time, and derivative time, the feeding speed and drying temperature of the drum drying unit are defuzzified and calculated respectively, generating control values ​​for the feeding speed and the drying temperature respectively.

[0049] The numerical range of the controlled values ​​for sodium chloride solution dosage, feed rate, and drying temperature is verified and outlier values ​​are filtered. The verified values ​​for sodium chloride solution dosage, feed rate, and drying temperature are then output.

[0050] The verified values ​​of sodium chloride solution dosage control, feed rate control, and drying temperature control are summarized to generate a set of control values.

[0051] Secondly, the present invention also provides a method for treating wastewater from a small-volume silver nitrate production process, the method comprising:

[0052] S1. The wastewater is collected in the equalization tank for homogenization and equalization. Suspended solids are removed by the pretreatment unit. Sodium chloride precipitant is added to the wastewater to carry out chemical precipitation reaction, and silver resources are separated and recovered. After settling, the supernatant is obtained.

[0053] S2. The supernatant is pumped to the drum drying unit through the feed pump. The temperature of the heating medium, the drum speed and the feed rate of the drum drying unit are controlled to form a uniform liquid film on the outer wall of the drum drying unit and quickly dry and solidify the supernatant. The dried and solidified uniform liquid film is peeled off from the inner surface of the drum drying unit and collected to obtain the mixed salt solid.

[0054] S3. The exhaust gas generated by the drum drying unit during the drying and curing process is condensed, recovered, washed, purified and demisted using the end-of-line treatment unit, and then discharged after meeting the standards.

[0055] The beneficial effects of this invention are as follows:

[0056] 1) The process of this invention is extremely short and the equipment is highly integrated. The entire system consists of only two core modules: pretreatment and drum drying. It eliminates many complex units such as biochemistry, membrane concentration, and crystallization. The equipment is compact and occupies a very small area, making it particularly suitable for placement in workshops or limited spaces.

[0057] 2) The drum dryer of the present invention uses indirect heating, which has high thermal efficiency and dries only a small amount of wastewater, thus avoiding the high energy consumption of traditional evaporation crystallizers when treating large amounts of water.

[0058] 3) This invention is easy to operate and highly automated. System operating parameters, such as temperature, speed and feed rate, are easy to control. It can achieve fully automatic operation by PLC without complicated manual intervention and biochemical system maintenance.

[0059] 4) This invention thoroughly reduces wastewater and renders it harmless, directly converting it into dry, mixed salt solids with low water content. This greatly reduces the final disposal volume of hazardous waste, and the solid form facilitates transportation and safe disposal. The pretreatment stage efficiently recovers precious metal silver, reducing resource loss and economic losses. Attached Figure Description

[0060] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0061] Figure 1This is a process flow diagram of a wastewater treatment system for a small-volume silver nitrate production process according to an embodiment of the present invention.

[0062] Figure 2 This is a schematic diagram of the structure of a drum drying unit in a wastewater treatment system for a small-volume silver nitrate production process according to an embodiment of the present invention.

[0063] Figure 3 This is a flowchart of a method for treating wastewater from a small-volume silver nitrate production process according to an embodiment of the present invention.

[0064] In the picture:

[0065] 1. Equalization tank; 2. Precision filter; 3. Chemical precipitation device; 4. Feed pump; 5. Drum drying unit; 5a. Distributor; 5b. Drum; 5c. Scraper; 5d. Mixed salt tank; 6. Condenser; 7. Spray tower; 8. Demister; 9. Silver ion intelligent monitoring unit; 10. Control unit. Detailed Implementation

[0066] To further illustrate the various embodiments, the present invention provides accompanying drawings, which are part of the disclosure of the present invention. These drawings are mainly used to illustrate the embodiments and can be used in conjunction with the relevant descriptions in the specification to explain the operating principles of the embodiments. With reference to these drawings, those skilled in the art should be able to understand other possible implementation methods and the advantages of the present invention.

[0067] According to an embodiment of the present invention, a treatment system for wastewater from a small-volume silver nitrate production process is provided.

[0068] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments, such as... Figure 1 As shown, a wastewater treatment system for a small-volume silver nitrate production process according to an embodiment of the present invention includes:

[0069] The system is sequentially connected via pipelines to the following components: equalization tank 1, pretreatment unit, drum drying unit 5, end-of-pipe treatment unit, and control unit 10.

[0070] The pretreatment unit is used for solid-liquid separation and silver resource recovery of wastewater;

[0071] The drum drying unit 5 is connected to the liquid outlet of the pretreatment unit and is used to directly dry and solidify the pretreated wastewater to form mixed salt solids.

[0072] A feed pump 4 is provided between the pretreatment unit and the drum drying unit;

[0073] Silver ion intelligent monitoring unit 9 is installed at the liquid outlet of the equalization tank 1 and the liquid outlet of the pretreatment unit.

[0074] The control unit 10 is used to dynamically adjust the process operating parameters of the pretreatment unit and the drum drying unit 5 based on the real-time data fed back by the silver ion intelligent monitoring unit 9, so as to realize intelligent operation and precise control of wastewater treatment under small water volume conditions.

[0075] Specifically, such as Figure 1 As shown, the system of this invention includes a pretreatment unit and a drum drying unit 5. Small volumes of high-salinity wastewater generated in the production workshop first enter the equalization tank 1 for water quality and quantity adjustment. Subsequently, the wastewater is pumped to a precision filter 2 to remove any trace suspended silver particles, and the filter residue is returned to the production process. After filtration, the wastewater enters a chemical precipitation device 3, where a quantitative amount of sodium chloride solution is added, and under stirring, a silver chloride precipitate is formed. After settling, the supernatant (mainly a high-concentration solution of nitrates, ammonium salts, etc.) is pumped by a feed pump 4 to the drum drying unit, and the silver chloride sludge is discharged from the bottom for recovery.

[0076] In this optional embodiment, the pretreatment unit includes a precision filter 2 and a chemical precipitation device 3;

[0077] The precision filter 2 is connected to the equalization tank 1 and is used to remove suspended silver particles from the wastewater.

[0078] The chemical precipitation device 3 is connected to the liquid outlet of the precision filter 2 and is equipped with a stirring mechanism and a dosing mechanism. It is used to add a precipitant to the wastewater and selectively precipitate and recover dissolved silver ions.

[0079] In this optional embodiment, the precipitant added to the chemical precipitation device 3 is sodium chloride or hydrochloric acid, and the precipitation product is silver chloride;

[0080] The bottom of the chemical precipitation device 3 is equipped with a precipitate collection mechanism and a discharge mechanism;

[0081] Both the precipitate collection mechanism and the discharge mechanism are connected to a precipitate washing device for multi-stage countercurrent washing of the silver chloride precipitate.

[0082] A composite monitor is installed at the liquid outlet of the chemical precipitation device 3 to monitor the residual concentration of silver ions in the supernatant after chemical precipitation in real time and to determine the degree of completeness of the precipitation reaction.

[0083] An online silver ion monitor is installed at the liquid outlet of the equalization tank 1 to monitor the concentration of silver ions in the wastewater before it enters the pretreatment unit in real time.

[0084] Specifically, the precipitant added to the chemical precipitation device 3 is sodium chloride or hydrochloric acid, and the precipitation product is silver chloride. The chemical reaction that occurs is: Ag + +Cl− =AgCl↓, the lower part of the chemical precipitation device 3 is provided with a precipitate collection mechanism and a discharge mechanism.

[0085] In this optional embodiment, the drum drying unit 5 is a steam indirect heating drum dryer;

[0086] The steam indirect heating drum dryer consists of a cloth feeder 5a, a drum 5b, a scraper 5c, and a salt tank 5d, and is used for continuous drying and solidification of the supernatant after chemical precipitation treatment.

[0087] Specifically, the drum drying unit 5 is the core and terminal unit of the system, directly receiving the pretreated supernatant. This drum drying unit 5 preferably employs an indirect heating (steam) drum dryer. Wastewater is evenly distributed onto the surface of the rotating, internally heated drum 5b, rapidly forming a thin liquid film and evaporating the moisture. The dried salt solids are scraped off and collected by a scraper. The drum drying unit 5 is subsequently connected to an exhaust gas treatment device, typically including condensation, washing, and demisting equipment, to ensure that the exhaust gas meets emission standards.

[0088] like Figure 2 As shown, the core of the drum drying unit 5 is the drum dryer. Preheated wastewater is evenly sprayed by a distributor 5a onto the surface of a rotating drum 5b, which is internally heated by a heating medium (0.6~0.8MPa saturated steam). The surface temperature of drum 5b is maintained at approximately 150℃. The wastewater rapidly evaporates on the surface of drum 5b, forming a thin layer of dried salt. A rotating scraper 5c scrapes off the dried salt, which falls into a salt collection tank 5d and is periodically packaged for hazardous waste disposal. Water vapor and trace amounts of volatile gases generated during the drying process enter the exhaust gas treatment system. Part of the moisture is recovered in a condenser 6 (which can be reused), and then trace amounts of ammonia or acidic gases are absorbed in a water washing spray tower 7. Finally, the gas is discharged after passing through a demister 8 and meets emission standards.

[0089] In this optional embodiment, the end-of-line treatment unit includes an exhaust gas treatment device and a miscellaneous salt collection and packaging device;

[0090] The exhaust gas treatment device is used to treat the water vapor and trace amounts of volatile substances that may be entrained during the drying process of the drum drying unit.

[0091] The salt collection device and the packaging device are used to collect the salt solids that are peeled off after drying by the drum drying unit.

[0092] In this optional embodiment, the exhaust gas treatment device includes a condenser 6, a spray tower 7, and a demister 8;

[0093] The condenser 6 is used to perform preliminary cooling and condensation on the high-temperature exhaust gas discharged from the drum drying unit 5, and to recover the moisture and condensable substances in the exhaust gas.

[0094] The spray tower 7 is used to deeply wash and purify the condensed exhaust gas through circulating spraying.

[0095] The demister 8 is used to remove droplets and fine particulate matter carried in the exhaust gas.

[0096] In this optional embodiment, the control unit 10 includes a data preprocessing module, a dynamic adjustment module, and an execution feedback module;

[0097] The data preprocessing module is used to filter and analyze the influent silver ion concentration data, effluent silver ion residue data, pH value data and turbidity data collected by the silver ion online monitoring instrument and the composite monitoring instrument (pH monitoring instrument and turbidity monitoring instrument) to generate process parameter data.

[0098] The dynamic adjustment module is used to compare process parameter data with preset silver recovery rate target values, and to dynamically calculate the comparison results to generate standardized control commands.

[0099] In this optional embodiment, the dynamic adjustment module includes:

[0100] The data receiving module is used to receive process parameter data output by the data preprocessing module. The process parameter data includes influent silver ion concentration data after pretreatment, effluent silver ion residue data after precipitation after pretreatment, pH value data after pretreatment, and turbidity data after pretreatment.

[0101] The data comparison module is used to calculate the silver recovery rate in real time the silver ion concentration data of the influent after pretreatment and the silver ion residue data of the effluent after pretreatment and precipitation. It also compares the calculated silver recovery rate with the preset silver recovery rate target value to generate the comparison deviation value and the deviation change rate.

[0102] The fuzzification processing module is used to perform fuzzification processing on the deviation value and the rate of change of deviation based on a preset fuzzy rule library and a fuzzy PID control algorithm, to determine the proportional coefficient, integral time and derivative time, and to obtain the adjusted PID parameters.

[0103] The defuzzy calculation module is used to perform defuzzy calculations on the reagent dosage of the chemical precipitation device and the operating parameters of the drum drying unit based on the adjusted PID parameters, and generate a set of control quantity values.

[0104] The instruction conversion module is used to convert a set of control quantity values ​​into standardized control instructions through a preset instruction mapping relationship and a standardized protocol.

[0105] In this optional embodiment, the step of performing defuzzification calculations on the reagent dosage of the chemical precipitation device and the operating parameters of the drum drying unit based on the adjusted PID parameters to generate a set of control quantity values ​​includes:

[0106] Receive the adjusted PID parameters, which include the proportional coefficient, integral time, and derivative time;

[0107] Based on the adjusted proportional coefficient, integral time and derivative time, the amount of sodium chloride solution added to the chemical precipitation device is defuzzified to generate the control value of the amount of sodium chloride solution added.

[0108] Based on the adjusted proportional coefficient, integral time, and derivative time, the feeding speed and drying temperature of the drum drying unit are defuzzified and calculated respectively, generating control values ​​for the feeding speed and the drying temperature respectively.

[0109] The numerical range of the controlled values ​​for sodium chloride solution dosage, feed rate, and drying temperature is verified and outlier values ​​are filtered. The verified values ​​for sodium chloride solution dosage, feed rate, and drying temperature are then output.

[0110] The verified values ​​of sodium chloride solution dosage control, feed rate control, and drying temperature control are summarized to generate a set of control values.

[0111] The execution feedback module is used to input control commands to the chemical precipitation device and the drum drying unit in real time for adaptive optimization, so as to ensure that the silver recovery rate is stably maintained within the target range.

[0112] Specifically, the data preprocessing module receives influent silver ion concentration data and effluent silver ion residue data collected by the silver ion online monitoring instrument, as well as pH value data and turbidity data collected by the pH monitoring instrument and turbidity monitoring instrument. It performs moving average filtering on these raw data to eliminate random noise, and performs trend analysis to identify abnormal fluctuations. When a sudden change in data is detected, it automatically uses the previous valid data for compensation to generate stable and reliable process parameter data.

[0113] After the data receiving module in the dynamic adjustment module acquires these preprocessed process parameter data, the data comparison module calculates the silver recovery rate in real time based on the ratio of the difference between the influent silver ion concentration and the residual silver ion concentration in the effluent after precipitation. The calculated result is then compared in real time with the preset silver recovery rate target value, generating a comparison deviation value and a deviation change rate. The fuzzification processing module, based on a preset fuzzy rule library, uses a fuzzy PID control algorithm to fuzzify the comparison deviation value and deviation change rate. The fuzzy rule library contains a complete set of rules covering various deviation combinations. Through fuzzy inference, the adjustment amounts of the proportional coefficient, integral time, and derivative time are determined, resulting in optimized PID parameters. The defuzzification calculation module, based on the adjusted PID parameters, applies different calculations to the chlorination process of the chemical precipitation device. The sodium chloride solution dosage, feed rate of the drum dryer, and drying temperature are calculated using defuzzification. For the sodium chloride solution dosage, the dosage ratio is dynamically adjusted based on the silver recovery rate deviation. For the feed rate and drying temperature of the drum dryer, the optimal control values ​​are calculated based on process stability requirements. All generated control value values ​​undergo rigorous range verification and outlier filtering to ensure that the sodium chloride solution dosage is within the safe operating range and that the feed rate and drying temperature are within the allowable process parameter range of the equipment. The verified control value values ​​are compiled into a control value set. The instruction conversion module accurately converts the control value set into standardized control instructions that can be recognized by the chemical precipitation device and the drum dryer through a preset instruction mapping relationship and standardized communication protocol.

[0114] The execution feedback module sends standardized control commands to the metering pump system of the chemical precipitation unit and the drive control system of the drum drying unit in real time. At the same time, it continuously monitors the execution effect, collects the actual operating parameters and compares them with the target values ​​in a closed loop. When the silver recovery rate is detected to deviate continuously from the target range, the parameter optimization mechanism is automatically triggered to readjust the parameter configuration of the fuzzy rule base. This ensures that the entire system can stably maintain the silver recovery rate within the preset target range under various operating conditions, achieving adaptive optimization control of the entire process.

[0115] In addition, the silver ion concentration in the influent of the equalization tank 1, the residual silver ion concentration in the effluent of the chemical precipitation device 3, the pH value and the turbidity data are collected in real time by the silver ion online monitoring instrument and the composite monitoring instrument (pH monitoring instrument and turbidity monitoring instrument). The purpose is to provide the control unit 10 with accurate process parameters, realize the adaptive optimization of the dosage of the chemical precipitation device and the operating parameters of the drum drying unit, and ensure that the silver recovery rate is stably maintained within the preset target range.

[0116] Specifically, based on real-time monitoring data, the control unit calculates the silver recovery rate deviation through a dynamic adjustment module, generates standardized control commands using a fuzzy PID control algorithm, and automatically adjusts the sodium chloride solution dosage of the chemical precipitation device as well as the feeding speed and drying temperature of the drum drying unit. This ensures stable system operation even when the influent water quality fluctuates, maximizing silver resource recovery efficiency and ensuring the economy and reliability of the treatment process.

[0117] like Figure 3 As shown, according to another embodiment of the present invention, a method for treating wastewater from a small-volume silver nitrate production process is also provided, the method comprising:

[0118] Step S1: Collect the wastewater into equalization tank 1 for homogenization and equalization. Remove suspended solids through the pretreatment unit and add sodium chloride precipitant to the wastewater for chemical precipitation reaction to separate and recover silver resources. After settling, obtain the supernatant.

[0119] Step S2: The supernatant is transported to the drum drying unit through the feed pump 4. The temperature of the heating medium, the drum speed and the feed rate of the drum drying unit 5 cause the supernatant to form a uniform liquid film on the outer wall of the drum drying unit 5 and dry and solidify rapidly. The dried and solidified uniform liquid film is peeled off from the inner surface of the drum drying unit 5 and collected to obtain the mixed salt solid.

[0120] Step S3: The exhaust gas generated by the drum drying unit 5 during the drying and curing process is condensed, recovered, washed, purified and demisted using the end-of-line treatment unit, and then discharged after meeting the standards.

[0121] Specifically, the heating medium is low-pressure saturated steam, and the surface temperature of the drum is controlled at 120℃-180℃; the moisture content of the dried salts is less than 5%.

[0122] The precipitant is sodium chloride, with chloride ions controlled in excess of 10%-30%. After the precipitation reaction, the supernatant enters the subsequent drying and solidification step, and the precipitate silver chloride is collected and returned to the silver nitrate production process.

[0123] The wastewater generation is less than 5 tons / hour, the total dissolved solids content is greater than 5%, and it mainly contains nitrates, nitrites, ammonium salts and trace amounts of organic matter.

[0124] To facilitate understanding of the above technical solutions of the present invention, the working principle or operation method of the present invention in actual process will be described in detail below.

[0125] In practical applications, this invention mainly consists of an equalization tank, a pretreatment unit, a drum dryer unit, an end-of-pipe treatment unit, and a control unit connected sequentially, without including conventional, lengthy units such as biochemical, membrane, and evaporation crystallization processes. The treatment method is as follows: first, the wastewater is filtered and selectively pretreated with silver precipitation to recover silver resources; then, the pretreated clarified liquid is directly pumped into a drum dryer, where a liquid film forms on the drum surface and is rapidly dried and scraped off, yielding solid impurities with extremely low water content, thus achieving complete wastewater reduction and harmlessness.

[0126] This invention simplifies the complex problem of treating multi-polluting wastewater into a two-step physicochemical process of resource recovery and direct drying and solidification. The process flow is extremely short, the equipment is compact and integrated, the footprint is small, and the operating energy consumption is significantly lower than traditional methods such as multi-effect evaporation. It is particularly suitable for washing wastewater generated in the production and deep processing of silver nitrate with small water volume and high salinity.

[0127] For example, a silver nitrate and silver powder production enterprise generates 1.65 tons of chemical reduction washing wastewater per hour. The wastewater has the following characteristics: water content 94.15%, pH 2~3, TDS (total dissolved solids) ~5.85%, mainly containing NaNO3, NH4NO3 and a small amount of organic matter, and silver ion concentration ~50mg / L.

[0128] The system of this invention processes wastewater by precipitation to remove silver (silver recovery rate >99%), and the clarified liquid enters a drum dryer. The drum is heated by 0.6MPa steam, with a surface temperature of 165℃ and a feed rate of 80L / h. The system operates continuously, producing approximately 92kg of mixed salt solids per hour. The exhaust gas is treated to be colorless and odorless, meeting emission standards. The entire system occupies approximately 150 square meters, and its energy consumption mainly consists of steam and electricity. Electricity consumption is approximately 72kWh; the steam consumption is equivalent to approximately 1.3t / h per ton of wastewater treated, which is 60% of that of traditional multi-effect evaporation processes. Furthermore, it requires no dedicated personnel for operation, achieving the goals of high efficiency, low consumption, and automation.

[0129] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A treatment system for wastewater from a small-volume silver nitrate production process, characterized in that, The system includes: The system consists of a regulating tank, a pretreatment unit, a drum drying unit, a terminal treatment unit, and a control unit, connected sequentially via pipelines. The pretreatment unit is used for solid-liquid separation and silver resource recovery of wastewater; The drum drying unit is connected to the liquid outlet of the pretreatment unit and is used to directly dry and solidify the pretreated wastewater to form mixed salt solids. A feed pump is provided between the pretreatment unit and the drum drying unit; Silver ion intelligent monitoring units are installed at the liquid outlet of the equalization tank and the liquid outlet of the pretreatment unit. The control unit is used to dynamically adjust the process operating parameters of the pretreatment unit and the drum drying unit based on the real-time data fed back by the silver ion intelligent monitoring unit, so as to realize intelligent operation and precise control of wastewater treatment under small water volume conditions.

2. The wastewater treatment system for small-volume silver nitrate production processes according to claim 1, characterized in that, The pretreatment unit includes a precision filter and a chemical precipitation device; The precision filter is connected to the equalization tank and is used to remove suspended silver particles from the wastewater. The chemical precipitation device is connected to the liquid outlet of the precision filter and is equipped with a stirring mechanism and a dosing mechanism. It is used to add a precipitant to the wastewater and selectively precipitate and recover dissolved silver ions.

3. The wastewater treatment system for small-volume silver nitrate production processes according to claim 2, characterized in that, The precipitant added in the chemical precipitation device is sodium chloride or hydrochloric acid, and the precipitation product is silver chloride; The bottom of the chemical precipitation device is equipped with a precipitate collection mechanism and a discharge mechanism; Both the precipitate collection mechanism and the discharge mechanism are connected to a precipitate washing device for multi-stage countercurrent washing of the silver chloride precipitate. A composite monitor is installed at the liquid outlet of the chemical precipitation device to monitor the residual concentration of silver ions in the supernatant after chemical precipitation in real time and to determine the degree of completeness of the precipitation reaction. An online silver ion monitor is installed at the liquid outlet of the equalization tank to monitor the concentration of silver ions in the wastewater before it enters the pretreatment unit in real time.

4. The wastewater treatment system for small-volume silver nitrate production processes according to claim 1, characterized in that, The drum drying unit is a steam indirect heating type drum dryer; The steam indirect heating drum dryer consists of a cloth feeder, drum, scraper and salt tank, and is used for continuous drying and solidification of the supernatant after chemical precipitation treatment.

5. The wastewater treatment system for small-volume silver nitrate production processes according to claim 1, characterized in that, The end-of-line treatment unit includes an exhaust gas treatment device, a miscellaneous salt collection device, and a packaging device; The exhaust gas treatment device is used to treat the water vapor and trace amounts of volatile substances that may be entrained during the drying process of the drum drying unit. The salt collection device and the packaging device are used to collect the salt solids that are peeled off after drying by the drum drying unit.

6. The wastewater treatment system for small-volume silver nitrate production processes according to claim 5, characterized in that, The exhaust gas treatment device includes a condenser, a spray tower, and a demister; The condenser is used to perform preliminary cooling and condensation on the high-temperature exhaust gas discharged from the drum drying unit, and to recover moisture and condensable substances in the exhaust gas. The spray tower is used to deeply wash and purify the condensed exhaust gas through circulating spraying. The demister is used to remove droplets and fine particulate matter carried in the exhaust gas.

7. The wastewater treatment system for small-volume silver nitrate production processes according to claim 3, characterized in that, The control unit includes a data preprocessing module, a dynamic adjustment module, and an execution feedback module; The data preprocessing module is used to filter and analyze the influent silver ion concentration data, effluent silver ion residue data, pH data, and turbidity data collected by the silver ion online monitoring instrument and the composite monitoring instrument, and generate process parameter data. The dynamic adjustment module is used to compare process parameter data with preset silver recovery rate target values, and to dynamically calculate the comparison results to generate standardized control commands. The execution feedback module is used to input control commands to the chemical precipitation device and the drum drying unit in real time for adaptive optimization, so as to ensure that the silver recovery rate is stably maintained within the target range.

8. The wastewater treatment system for small-volume silver nitrate production processes according to claim 7, characterized in that, The dynamic adjustment module includes: The data receiving module is used to receive process parameter data output by the data preprocessing module. The process parameter data includes influent silver ion concentration data after pretreatment, effluent silver ion residue data after precipitation after pretreatment, pH value data after pretreatment, and turbidity data after pretreatment. The data comparison module is used to calculate the silver recovery rate in real time the silver ion concentration data of the influent after pretreatment and the silver ion residue data of the effluent after pretreatment and precipitation. It also compares the calculated silver recovery rate with the preset silver recovery rate target value to generate the comparison deviation value and the deviation change rate. The fuzzification processing module is used to perform fuzzification processing on the deviation value and the rate of change of deviation based on a preset fuzzy rule library and a fuzzy PID control algorithm, to determine the proportional coefficient, integral time and derivative time, and to obtain the adjusted PID parameters. The defuzzy calculation module is used to perform defuzzy calculations on the reagent dosage of the chemical precipitation device and the operating parameters of the drum drying unit based on the adjusted PID parameters, and generate a set of control quantity values. The instruction conversion module is used to convert a set of control quantity values ​​into standardized control instructions through a preset instruction mapping relationship and a standardized protocol.

9. The wastewater treatment system for small-volume silver nitrate production processes according to claim 8, characterized in that, Based on the adjusted PID parameters, the dosage of reagents in the chemical precipitation device and the operating parameters of the drum drying unit are defuzzified to generate a set of control quantity values, including: Receive the adjusted PID parameters, which include the proportional coefficient, integral time, and derivative time; Based on the adjusted proportional coefficient, integral time and derivative time, the amount of sodium chloride solution added to the chemical precipitation device is defuzzified to generate the control value of the amount of sodium chloride solution added. Based on the adjusted proportional coefficient, integral time, and derivative time, the feeding speed and drying temperature of the drum drying unit are defuzzified and calculated respectively, generating control values ​​for the feeding speed and the drying temperature respectively. The numerical range of the controlled values ​​for sodium chloride solution dosage, feed rate, and drying temperature is verified and outlier values ​​are filtered. The verified values ​​for sodium chloride solution dosage, feed rate, and drying temperature are then output. The verified values ​​of sodium chloride solution dosage control, feed rate control, and drying temperature control are summarized to generate a set of control values.

10. A method for treating wastewater from a small-volume silver nitrate production process, comprising using the wastewater treatment system for small-volume silver nitrate production processes as described in any one of claims 1-9, characterized in that, The method includes: S1. The wastewater is collected in the equalization tank for homogenization and equalization. Suspended solids are removed by the pretreatment unit. Sodium chloride precipitant is added to the wastewater to carry out chemical precipitation reaction, and silver resources are separated and recovered. After settling, the supernatant is obtained. S2. The supernatant is pumped to the drum drying unit through the feed pump. The temperature of the heating medium, the drum speed and the feed rate of the drum drying unit are controlled to form a uniform liquid film on the outer wall of the drum drying unit and quickly dry and solidify the supernatant. The dried and solidified uniform liquid film is peeled off from the inner surface of the drum drying unit and collected to obtain the mixed salt solid. S3. The exhaust gas generated by the drum drying unit during the drying and curing process is condensed, recovered, washed, purified and demisted using the end-of-line treatment unit, and then discharged after meeting the standards.

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