On-line monitoring method and device for polymer type anionic scale inhibitor

Abstract

The invention discloses an online monitoring method and device for a polymer type anionic scale inhibitor. Based on a multipoint chelation reaction principle, after circulating cooling water is sampled, a sodium citrate solution is firstly added for pretreatment to eliminate metal ion interference, then a benzethonium chloride solution is added, a quaternary ammonium group of the benzethonium chloride solution and a plurality of anion groups on a molecular chain of the polymer type anion scale inhibitor are subjected to a multipoint chelation reaction, and the polymer type anion scale inhibitor is obtained. A cross-linked macromolecular network structure is formed, a stable turbidity signal is generated, the intensity of the optical signal is detected through a scattered light detector, and the concentration of the scale inhibitor is calculated in combination with a multi-curve automatic identification technology. The device adopts a modular design, takes an intelligent control system as a core, and integrates six functional modules of sampling, reagent adding, reaction, detection, discharge and communication. The method is suitable for online monitoring of polymer type organic phosphonic acid, carboxylic acid and sulfonate scale inhibitors, realizes unattended real-time monitoring, and provides an effective technical means for accurate control of addition of the scale inhibitors in a circulating cooling water system.

Description

Technical Field

[0001] The present invention relates to the technical field of online monitoring, and in particular to an online monitoring method and device for a polymer anion scale inhibitor. Background Art

[0002] Circulating cooling water systems are widely used in industries such as petrochemicals, power generation, and steel, resulting in significant water consumption. To prevent scaling of heat exchange equipment, an appropriate amount of scale inhibitors must be added to the circulating cooling water. Currently, the scale inhibitors widely used in industry are primarily anionic, including organic phosphonic acids (such as ATMP, HEDP, and PBTCA) and polycarboxylic acids (such as polyacrylic acid (PAA), hydrolyzed maleic anhydride (HPMA), and AA / AMPS copolymers). These scale inhibitors contain anionic groups in their molecular structures, including phosphonic acid (-PO3H2), carboxyl (-COOH), and sulfonic acid (-SO3H).

[0003] Too little scale inhibitor will not be effective, while too much can lead to economic waste and potentially increase the difficulty of subsequent water treatment. Furthermore, due to losses of circulating cooling water during operation due to evaporation, wind blowdown, and sewage discharge, timely and appropriate replenishment of scale inhibitors is necessary. Therefore, accurately monitoring the concentration of anionic scale inhibitors in circulating cooling water is crucial for the economic and safe operation of the system.

[0004] Currently, the detection of scale inhibitor concentration in circulating cooling water relies primarily on manual sampling and laboratory analysis, which presents challenges such as long testing cycles, poor real-time performance, and high labor costs. While some online monitoring devices exist on the market, most rely on indirect parameters such as conductivity and pH, resulting in limited accuracy and susceptible to variations in water quality. In particular, there is a lack of online monitoring technology that can directly measure the concentration of anionic scale inhibitors.

[0005] Therefore, there is an urgent need to develop an online monitoring technology that can directly, accurately and in real time monitor the concentration of anionic scale inhibitors in circulating cooling water. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a method and device for online monitoring of polymer anionic scale inhibitors in circulating cooling water based on the chelating reaction principle, which can directly, accurately and in real time monitor the concentration of organic phosphonic acid, carboxylic acid and sulfonate anionic polymer scale inhibitors, thereby overcoming the defects of low detection accuracy and poor real-time performance of the existing technology.

[0007] Technical Solution

[0008] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0009] A method for online monitoring of a polymer anionic scale inhibitor comprises the following steps:

[0010] Step S1: sampling 100 mL from the circulating cooling water system;

[0011] Step S2: adding a certain amount of sodium citrate solution to the water sample and mixing for a certain time;

[0012] Step S3: adding a certain amount of benzethonium chloride solution to the pretreated water sample and mixing thoroughly to allow the benzethonium chloride to react with the polymeric anionic scale inhibitor;

[0013] Step S4: let the reaction stand for a certain time;

[0014] Step S5: using a scattered light detection device to detect the optical signal intensity of the suspended particles in the solution after the reaction;

[0015] Step S6: converting the optical signal intensity into a concentration value of the polymer anion scale inhibitor according to a pre-established standard curve;

[0016] Step S7: Data output: display and record the test results.

[0017] An online monitoring device for polymer anionic scale inhibitors comprises: a sampling system, a reaction system, a discharge system, a reagent adding system, a detection system, and a communication system, each of which is interconnected with an intelligent control system;

[0018] The sampling system includes a sampling pump, a pre-filter, a flow regulator, and a pressure sensor, and is used to continuously sample from the circulating cooling water system;

[0019] The reaction system comprises a first mixer, a pre-reaction tank, a second mixer and a main reaction tank; wherein the residence time of the pre-reaction tank is 10-60 seconds, and the residence time of the main reaction tank is 2-8 minutes;

[0020] The discharge system includes a waste liquid collection tank, an automatic cleaner, a liquid discharge pump, and a liquid level detector, which are used to collect the waste liquid after detection;

[0021] The reagent adding system includes a sodium citrate storage tank, a benzethonium chloride storage tank, a first metering pump, a second metering pump, and a liquid level detector, and is used for quantitatively adding reaction reagents;

[0022] The detection system includes a scattered light detector, a temperature sensor, an A / D converter, and a signal amplifier, which are used to detect the optical signal intensity of suspended particles in the solution after the reaction and perform temperature compensation;

[0023] The communication system includes RS485 communication, Ethernet interface, and alarm;

[0024] The intelligent control system includes a PLC controller, an interactive interface, data processing and communication, and is used to control the entire detection process and process detection data.

[0025] The reaction mechanism of the present invention is as follows: benzethonium chloride is used as a cationic reagent, and its quaternary ammonium group [C6H5CH2N(CH3)3] + With multiple anionic groups (phosphonic acid group-PO3 2- , carboxyl -COO-, sulfonic acid group -SO3-) undergo multi-point chelation. One benzethonium chloride molecule can combine with multiple anionic groups to form a cross-linked macromolecular chelate network structure. The solubility of this network structure in water is significantly reduced, and precipitation produces turbidity changes. The turbidity intensity is proportional to the concentration of the scale inhibitor.

[0026] Beneficial effects

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) High detection accuracy and wide application range: Based on the direct detection principle of multi-point chelation reaction, the detection accuracy reaches ±5% and the detection limit can reach 0.5 mg / L; it is suitable for various anionic scale inhibitors such as polymer-type organic phosphonic acid, carboxylic acid and sulfonate, covering the main needs of industrial circulating cooling water treatment;

[0029] (2) Strong real-time performance and strong anti-interference ability: the entire detection cycle is less than 10 minutes, which can achieve accurate online monitoring;

[0030] (3) High degree of automation and significant economic benefits: It has the function of automatic recognition of multiple curves, unattended operation, and reduced labor costs; by accurately controlling the amount of scale inhibitor added, it can significantly reduce operating costs and reduce chemical waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a system structure diagram of the online monitoring device of the present invention. DETAILED DESCRIPTION

[0032] The present invention discloses a method and device for online monitoring of polymer anionic scale inhibitors. The method is based on the principle of multi-point chelation reaction. 100 mL of circulating cooling water is sampled, sodium citrate solution is first added for pretreatment to eliminate metal ion interference, and then benzethonium chloride solution is added. The quaternary ammonium group thereof is used to react with multiple anionic groups on the molecular chain of the polymer anionic scale inhibitor to form a cross-linked macromolecular network structure, generate a stable turbidity signal, and the optical signal intensity is detected by a scattered light detector. The scale inhibitor concentration is calculated by combining multi-curve automatic recognition technology. The device adopts a modular design with an intelligent control system as the core, integrating six functional modules: sampling, reagent addition, reaction, detection, discharge and communication. The present invention is suitable for online monitoring of polymer organic phosphonic acid, carboxylic acid and sulfonate scale inhibitors, with a detection accuracy of ±5%, a detection limit of 0.5 mg / L, and a detection period of less than 10 minutes. It realizes unmanned real-time monitoring and provides an effective technical means for the precise control of circulating cooling water systems.

[0033] The technical solution of the present invention is described in detail below with reference to the accompanying drawings:

[0034] A method for online monitoring of a polymer anionic scale inhibitor comprises the following steps:

[0035] Step S1: sampling 100 mL from the circulating cooling water system;

[0036] Step S2: adding a certain amount of sodium citrate solution to the water sample and mixing for a certain period of time; the concentration of the sodium citrate solution is 0.5-2.0%, and the amount added is 1-5% of the volume of the water sample;

[0037] Step S3: adding a certain amount of benzethonium chloride solution to the pretreated water sample and mixing thoroughly to allow the benzethonium chloride to undergo a chelating reaction with the polymeric anionic scale inhibitor; the concentration of the benzethonium chloride solution is 0.1-0.5%, and the amount added is 3-8% of the volume of the water sample; the pretreatment mixing time is 10-60 seconds; the pretreatment reaction stabilization time is 2-8 minutes; the polymeric anionic scale inhibitor is at least one of a polymeric organic phosphonic acid scale inhibitor, a polymeric carboxylic acid scale inhibitor, and a polymeric sulfonate scale inhibitor; the chelating reaction is a multi-point chelating reaction between the quaternary ammonium group of the benzethonium chloride and multiple anionic groups on the molecular chain of the polymeric anionic scale inhibitor to form a cross-linked macromolecular chelate network structure;

[0038] Step S4: standing the reaction for a certain period of time; the temperature range of the standing reaction is 15-45° C., and the pH value of the reaction system is controlled within the range of 6.5-7.5;

[0039] Step S5: Using a scattered light detection device to detect the optical signal intensity of suspended particles in the post-reaction solution; the detection range is 0.5-80 mg / L for polymeric organic phosphonic acid scale inhibitors, 0.5-50 mg / L for polymeric carboxylic acid scale inhibitors, and 0.5-60 mg / L for polymeric sulfonate scale inhibitors, with a detection accuracy of ±5%;

[0040] Step S6: converting the optical signal intensity into a concentration value of the polymer anion scale inhibitor according to a pre-established standard curve;

[0041] Step S7: Data output: display and record the test results.

[0042] like Figure 1 , as a system structure diagram of the online monitoring device of the present invention, it adopts a modular design, with six subsystems arranged around a central intelligent control system. The operation of each system is coordinated by a PLC controller to achieve full-process automated detection from sampling to result output.

[0043] An online monitoring device for a polymer anionic scale inhibitor, comprising: a sampling system, a reaction system, a discharge system, a reagent addition system, a detection system, and a communication system, each of which is interconnected with an intelligent control system;

[0044] The sampling system includes a sampling pump, a pre-filter, a flow regulator, and a pressure sensor, and is used to continuously sample from the circulating cooling water system;

[0045] The reaction system comprises a first mixer, a pre-reaction tank, a second mixer and a main reaction tank; wherein the residence time of the pre-reaction tank is 10-60 seconds, and the residence time of the main reaction tank is 2-8 minutes;

[0046] The discharge system includes a waste liquid collection tank, an automatic cleaner, a liquid discharge pump, and a liquid level detector, which are used to collect the waste liquid after detection;

[0047] The reagent adding system includes a sodium citrate storage tank, a benzethonium chloride storage tank, a first metering pump, a second metering pump, and a liquid level detector, and is used for quantitatively adding reaction reagents;

[0048] The detection system includes a scattered light detector, a temperature sensor, an A / D converter, and a signal amplifier, which are used to detect the optical signal intensity of suspended particles in the solution after the reaction and perform temperature compensation. The scattered light detector adopts the 90° scattered light detection principle, has a detection wavelength of 860nm, a detection range of 0-1000 scattered light intensity units, and an accuracy of ±2%;

[0049] The communication system includes RS485 communication, Ethernet interface, and alarm;

[0050] The intelligent control system includes a PLC controller, an interactive interface, and data processing and communication systems, which are used to control the entire detection process and process detection data. The intelligent control system has a multi-curve automatic recognition function, which can establish a corresponding standard curve library for different types of anionic scale inhibitors, automatically identify the scale inhibitor type, and select the corresponding calculation model.

[0051] An online monitoring device for polymer anionic scale inhibitors also includes an automatic cleaning system for regularly cleaning optical windows and pipelines to ensure detection accuracy; and a communication system that supports 4G / Ethernet remote data transmission.

[0052] Example 1: Detection of organic phosphonic acid scale inhibitor (ATMP)

[0053] Take 100mL of circulating cooling water sample, water quality conditions: Ca 2+ Concentration 200mg / L, Mg 2+ Concentration 50 mg / L, pH=7.2, temperature 25°C, ATMP theoretical concentration 15 mg / L.

[0054] The test steps are as follows: add 2 mL of 1.0% sodium citrate solution to the water sample and stir for 30 seconds to complex the metal ions; add 5 mL of 0.2% benzethonium chloride solution and mix thoroughly to allow the phosphonic acid groups in the ATMP molecules to complex with the benzethonium chloride; let the reaction stand for 5 minutes to reach equilibrium; use a scattered light detector to detect the water sample, with a reading of 180 light intensity units; calculate the scale inhibitor concentration to be 14.7 mg / L based on the ATMP standard curve; the detection error is -2.0%, meeting the ±5% accuracy requirement.

[0055] Example 2: Polycarboxylic acid scale inhibitor (PAA) detection

[0056] Take 100mL of circulating cooling water sample, water quality conditions: Ca 2+ Concentration 180mg / L, Mg 2+ Concentration 45 mg / L, pH=7.0, temperature 30°C, PAA theoretical concentration 12 mg / L.

[0057] The steps are as follows: add 2 mL of 1.0% sodium citrate solution to the water sample and stir for 30 seconds; add 5 mL of 0.2% benzethonium chloride solution and mix thoroughly to allow the carboxyl groups in the PAA molecules to react with the benzethonium chloride; let the reaction stand for 5 minutes; use a scattered light detector to detect, and the reading is 295 light intensity units; based on the PAA standard curve, the scale inhibitor concentration is calculated to be 12.2 mg / L; the detection error is 1.7%, which meets the ±5% accuracy requirement.

[0058] Example 3: Detection of compound anionic scale inhibitor (HEDP+AA / AMPS)

[0059] Take 100mL of circulating cooling water sample, water quality conditions: Ca 2+ Concentration 220mg / L, Mg 2+ Concentration 60 mg / L, pH = 7.1, temperature 28 ° C, total concentration of compound scale inhibitor (HEDP 8 mg / L + AA / AMPS 5 mg / L) 15 mg / L.

[0060] The steps are as follows: add 2 mL of 1.0% sodium citrate solution to the water sample and stir for 30 seconds; add 5 mL of 0.2% benzethonium chloride solution and mix thoroughly; let it react for 5 minutes; use a scattered light detector to detect, and the reading is 260 light intensity units; the system automatically recognizes it as a compound scale inhibitor, selects the corresponding standard curve, and calculates the total scale inhibitor concentration to be 15.3 mg / L; the detection error is 2.0%, which meets the ±5% accuracy requirement.

[0061] Example 4: Detection of Polymeric Sulfonate Scale Inhibitor (PVS)

[0062] Take 100mL of circulating cooling water sample, water quality conditions: Ca 2+ Concentration 180mg / L, Mg 2+ Concentration 45 mg / L, pH=7.0, temperature 30°C, PVS theoretical concentration 15 mg / L.

[0063] The steps are as follows: add 2 mL of 1.0% sodium citrate solution to the water sample and stir for 30 seconds to complex the metal ions; add 5 mL of 0.2% benzethonium chloride solution and mix thoroughly to allow the sulfonic acid groups in the PVS molecules to undergo a multi-point chelation reaction with the benzethonium chloride; let the reaction stand for 5 minutes until the chelation reaction reaches equilibrium; use a scattered light detector for detection, with a reading of 295 light intensity units; calculate the scale inhibitor concentration to be 15.1 mg / L based on the PVS standard curve; the detection error is 0.7%, which meets the ±5% accuracy requirement.

[0064] Example 5: Online monitoring device operation

[0065] Applied to petrochemical enterprise circulating cooling water system, with a designed processing capacity of 5000m 3 / h, using ATMP type scale inhibitor, the designed dosage concentration is 20mg / L.

[0066] Device operating parameters:

[0067] (1) Continuous sampling flow rate: 200mL / min

[0068] (2) Single test sample volume: 100mL

[0069] (3) Detection cycle: 10 minutes / time

[0070] (4) Reagent consumption: sodium citrate 0.3 L / day, benzethonium chloride 0.8 L / day

[0071] (5) Continuous operation for 60 days, detection accuracy rate of 98.8%

[0072] (6) Through precise control, the consumption of scale inhibitor is reduced by 18% compared with manual control

[0073] (7) The system automatically identifies the type of scale inhibitor, eliminating the need to manually switch detection modes.

[0074] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, and all of these should be included in the scope of the present invention.

Claims

1. A method for online monitoring of polymer anionic scale inhibitors, characterized in that The following steps are involved: Step S1: sampling 100 mL from the circulating cooling water system; Step S2: adding a certain amount of sodium citrate solution to the water sample and mixing for a certain time; Step S3: adding a certain amount of benzethonium chloride solution to the pretreated water sample and mixing thoroughly to allow the benzethonium chloride to react with the polymeric anionic scale inhibitor; Step S4: let the reaction stand for a certain time; Step S5: using a scattered light detection device to detect the optical signal intensity of the suspended particles in the solution after the reaction; Step S6: converting the optical signal intensity into a concentration value of the polymer anion scale inhibitor according to a pre-established standard curve; Step S7: Data output: display and record the test results.

2. The online monitoring method according to claim 1, characterized in that: The concentration of the sodium citrate solution in step S2 is 0.5-2.0%, and the amount added is 1-5% of the volume of the water sample; the concentration of the benzethonium chloride solution in step S3 is 0.1-0.5%, and the amount added is 3-8% of the volume of the water sample; the mixing time of the pretreatment in step S3 is 10-60 seconds; and the reaction stabilization time of the pretreatment is 2-8 minutes.

3. The online monitoring method according to claim 1, characterized in that: The polymer anion scale inhibitor in step S3 is at least one of a polymer organic phosphonic acid scale inhibitor, a polymer carboxylic acid scale inhibitor, and a polymer sulfonate scale inhibitor.

4. The online monitoring method according to claim 1, characterized in that: The chelation reaction in step S3 is a multi-point chelation reaction between the quaternary ammonium group of benzethonium chloride and multiple anionic groups on the molecular chain of the polymeric anionic scale inhibitor, forming a cross-linked macromolecular chelate network structure.

5. The online monitoring method according to claim 1, characterized in that: The temperature range of the static reaction in step S4 is 15-45° C., and the pH value of the reaction system is controlled within the range of 6.5-7.

5.

6. The online monitoring method according to claim 1, characterized in that: The detection range is 0.5-80 mg / L for polymeric organic phosphonic acid scale inhibitors, 0.5-50 mg / L for polymeric carboxylic acid scale inhibitors, and 0.5-60 mg / L for polymeric sulfonate scale inhibitors, with a detection accuracy of ±5%.

7. An online monitoring device for realizing the online monitoring method of polymer anionic scale inhibitor according to any one of claims 1 to 6, characterized in that include: Sampling system, reaction system, discharge system, reagent addition system, detection system, and communication system that are interconnected with the intelligent control system respectively; The sampling system includes a sampling pump, a pre-filter, a flow regulator, and a pressure sensor, and is used to continuously sample from the circulating cooling water system; The reaction system comprises a first mixer, a pre-reaction tank, a second mixer and a main reaction tank; wherein the residence time of the pre-reaction tank is 10-60 seconds, and the residence time of the main reaction tank is 2-8 minutes; The discharge system includes a waste liquid collection tank, an automatic cleaner, a liquid discharge pump, and a liquid level detector, which are used to collect the waste liquid after detection; The reagent adding system includes a sodium citrate storage tank, a benzethonium chloride storage tank, a first metering pump, a second metering pump, and a liquid level detector, and is used for quantitatively adding reaction reagents; The detection system includes a scattered light detector, a temperature sensor, an A / D converter, and a signal amplifier, which are used to detect the optical signal intensity of suspended particles in the solution after the reaction and perform temperature compensation; The communication system includes RS485 communication, Ethernet interface, and alarm; The intelligent control system includes a PLC controller, an interactive interface, data processing and communication, and is used to control the entire detection process and process detection data.

8. The online monitoring device according to claim 7, characterized in that: The scattered light detector adopts the 90° scattered light detection principle, has a detection wavelength of 860nm, a detection range of 0-1000 scattered light intensity units, and an accuracy of ±2%.

9. The online monitoring device according to claim 7, characterized in that: The intelligent control system has a multi-curve automatic recognition function, and can establish a corresponding standard curve library according to different types of anionic scale inhibitors, automatically identify the type of scale inhibitor and select the corresponding calculation model.

10. The online monitoring device according to claim 7, characterized in that: It also includes an automatic cleaning system that regularly cleans the optical windows and pipelines to ensure detection accuracy; and a communication system that supports 4G / Ethernet remote data transmission.

Images