Automatic acid adding control method for circulating cooling water

Abstract

The invention relates to an automatic acid adding control method for circulating cooling water. The method comprises the following steps that S1, an online monitoring meter is installed in a circulating cooling water system; s2, monitoring data of the online monitoring meter, judging whether abnormity exists or not, if not, executing the step S3, and if not, executing the step S4; s3, processing the data of the online monitoring meter, and controlling the acid pump according to the processed data; and S4, performing decision logic judgment processing on the abnormal data. Compared with the prior art, the automatic acid adding device has the advantages that automatic acid adding and accurate control of the circulating water system are achieved, manual operation of operators is comprehensively replaced, and equipment damage and pipeline corrosion caused by out-of-control acid adding can be effectively prevented.

Description

Technical Field

[0001] The invention relates to the technical field of water treatment, in particular to a method for automatically controlling the acid addition of circulating cooling water. Background Art

[0002] The system that uses water to cool the process medium is called a cooling water system. According to its operation mode, the cooling water system can be divided into a direct cooling water system and a circulating cooling water system.

[0003] In the circulating cooling water system, cooling water exchanges heat with the heat exchanger and then directly contacts the air in the cooling tower to cool down before being recycled. In the cooling tower, the cooling water temperature is mainly reduced by evaporation and heat absorption, and the evaporated water vapor contains almost no salt, which leads to the continuous concentration of ions in the water. As the concentration of circulating water increases, the insoluble salts such as CaCO3 and MgCO3 will precipitate and scale due to supersaturation, and the degree of scaling increases with the increase of the excess saturation. In order to prevent scaling of the system, in addition to the need to regularly discharge a portion of the circulating water and add fresh water, the circulating cooling water also needs to be chemically treated, and acidification is a direct and simple approach.

[0004] Acid is usually added to the circulating cooling water, which is sulfuric acid, so that the bicarbonate in the water reacts with the acid to convert into CaSO4. Since the solubility of CaSO4 is relatively high (1,750 mg / L at 0°C), it can prevent the precipitation of carbonate scale, thereby greatly improving the concentration rate of the circulating water. In addition, the free CO2 generated by the reaction is also conducive to inhibiting the precipitation of carbonate scale.

[0005] There are two existing technologies for acidification of circulating water: one is manual acidification, in which the operator manually controls the amount of sulfuric acid added according to the monitored pH value or other indicators; the other is automatic acidification, in which the acidification pump is set to be linked to the pH value. When the pH value is higher than the set value, the acidification pump is started, and when it is lower than the set value, the acidification is stopped.

[0006] Both of the above two acid addition technologies have certain problems. Manual acid addition is labor-intensive and has poor control accuracy. It is also difficult to respond in a timely manner according to changes in water quality, resulting in large fluctuations in the pH value of the circulating cooling water, which can easily lead to insufficient or excessive sulfuric acid addition. Moreover, the sulfuric acid added is generally concentrated sulfuric acid with a mass fraction of 98%, and manual operation is risky. Automatic acid addition can effectively improve the above problems, greatly reduce manual workload, and achieve automatic control of acid addition. However, the existing automatic acid addition technology only uses a single pH value as a control indicator. Once the pH meter fails and cannot be discovered in time, it will cause the acid addition to be out of control, causing irreversible damage to the system and equipment.

[0007] After searching, Chinese patent publication number CN207148028U discloses an online monitoring system for circulating water that can automatically add acid, including an online monitoring system, a control system and an automatic acid adding device. The online monitoring system collects the water quality signal of the circulating water and transmits it to the control system through a transmitter. The control system converts and displays the water quality parameters of the circulating water in real time, and controls the acid addition amount of the acid adding metering pump of the automatic acid adding device. The online monitoring system for circulating water with automatic acid addition is scientifically designed and reasonably structured. It solves the problem of untimely adjustment of pH value and threat to safe production caused by the lag of manual analysis data. At the same time, automatic continuous acid addition solves the defect of manual intermittent acid addition, and is easy and reliable to use. However, the existing patent still has the following problems:

[0008] 1. Poor control accuracy. At present, the acid addition in the circulating cooling water system is adjusted according to the monitoring results of a single pH meter. However, the circulating cooling water system has a large amount of water, the water quality fluctuates significantly, and it takes a certain amount of time for sulfuric acid to dissolve in water and mix evenly. Therefore, the use of a single pH meter for monitoring has certain lag and instability, resulting in poor acid addition control accuracy for the entire system.

[0009] 2. The risk control capability is weak. A single pH meter is used to control the amount of acid added. Once the measurement result of the pH meter deviates, the amount of acid added will inevitably get out of control. There is currently no effective way to solve this problem. The only option is for operators to continuously monitor in order to detect pH meter failures in a timely manner. However, this places very high demands on operators.

[0010] Therefore, how to improve the control accuracy and control reliability of acid addition in the circulating water system has become a technical problem that needs to be solved. Summary of the invention

[0011] The purpose of the present invention is to provide a circulating cooling water automatic acid addition control method in order to overcome the defects of the above-mentioned prior art, realize automatic acid addition and precise control of the circulating water system, completely replace the manual operation of the operator, and effectively prevent equipment damage and pipeline corrosion caused by uncontrolled acid addition.

[0012] The purpose of the present invention can be achieved by the following technical solutions:

[0013] According to one aspect of the present invention, a method for automatically adding acid to circulating cooling water is provided, the method comprising the following steps:

[0014] Step S1, installing an online monitoring meter in a circulating cooling water system;

[0015] Step S2, monitor the data of the online monitoring meter and determine whether there is an abnormality. If not, execute step S3, otherwise execute step S4;

[0016] Step S3, processing the data of the online monitoring meter and controlling the acid pump according to the processed data;

[0017] Step S4, performing decision logic judgment processing on the abnormal data.

[0018] As a preferred technical solution, the online monitoring meters in step S1 are pH meters, and two of them are provided.

[0019] As a preferred technical solution, the two pH meters are respectively installed near the cooling tower outlet and the circulating water pump inlet, and the interval between the two pH meters is greater than the set distance.

[0020] As a preferred technical solution, the step S2 specifically comprises:

[0021] The output data of the two pH meters are monitored in real time, and the readings of the two pH meters are compared to calculate the difference between the two to determine whether it is within the preset error range a. If yes, execute step S3, otherwise execute step S4.

[0022] As a preferred technical solution, the step S3 specifically comprises:

[0023] Select the smaller value of the two pH meters for judgment:

[0024] If pH value>A2, start the acid pump;

[0025] If the pH value is less than A1, stop the acid pump;

[0026] If the pH value is between A1 and A2, no action occurs.

[0027] As a preferred technical solution, the step S4 specifically comprises:

[0028] When it is determined that the readings of the two pH meters are inconsistent, the system enters the decision logic stage and calculates the pH (theoretical value) according to the preset algorithm. If "pH (measured value) > (pH (theoretical value) + a / 2)" or "pH (measured value) < (pH (theoretical value) - a / 2)", the pH meter reading is determined to be unreliable, otherwise it is credible.

[0029] As a preferred technical solution, the preset algorithm is specifically:

[0030] pH (theoretical value) = 10.568 + 0.8126 × lg [HCO3 - ], where [HCO3 - ]It is automatically converted from the alkalinity value detected by the system; in order to maintain the same accuracy as the instrument detection value, the pH (theoretical value) is rounded to two decimal places according to the rule of "rounding up to the nearest even number".

[0031] As a preferred technical solution, considering that the pH value of the circulating water is about 8.5, most of the alkalinity is composed of HCO3 - composition, if alkalinity = a mg / L, then [HCO3 - ] = a / 50×10 -3 mol / L.

[0032] As a preferred technical solution, after confirming that a pH meter reading is unreliable, the pH meter is marked as a fault state;

[0033] When one pH meter fails and the other is normal, the system automatically switches to the normal pH meter;

[0034] If both pH meters fail, the system will issue a strong alarm, shut down and lock the sulfuric acid dosing pump.

[0035] As a preferred technical solution, the system issues an alarm through sound, light, email or text message to notify the operator of the fault and failover situation;

[0036] The maintenance team diagnosed and repaired the faulty pH meter, and the repaired pH meter was put back into use through manual reset;

[0037] The faulty pH meter was repaired and tested to be normal, and the system was restored to dual redundancy.

[0038] Compared with the prior art, the present invention has the following advantages:

[0039] 1) The present invention introduces automatic control technology into the circulating water treatment system, and realizes automatic control of acid addition in circulating water by adding a pH meter, inventing a logic control method for two pH meters, setting control values, etc., thereby improving the operating reliability of the system;

[0040] 2) The present invention proposes a calculation method for the theoretical pH value of circulating cooling water based on the water quality characteristics of circulating cooling water, providing a basic basis for determining the accuracy of pH value monitoring;

[0041] 3) The present invention can avoid the problem of uncontrolled acid addition when a single pH meter is damaged in the original control method by installing two pH meters and designing a joint control method, greatly reducing the workload of operators, improving the reliability, stability and scientificity of system control, effectively solving the problem of large fluctuations in the pH value of circulating water, and saving the amount of sulfuric acid added. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 is a flow chart of the method of the present invention;

[0043] Figure 2 This is a flow chart of Embodiment 1 of the present invention;

[0044] Figure 3 This is a flow chart of Example 2 of the present invention. DETAILED DESCRIPTION

[0045] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0046] Example 1

[0047] Compared with other dosing treatments, uncontrolled acid addition is the most harmful because excessive acid addition will cause H + If the content is too high, it will cause corrosion of the pipes and equipment through which the circulating cooling water flows, reduce the load capacity of concrete, shorten the service life of equipment, and even cause perforation and scrapping of equipment in severe cases, affecting safe production. If the amount of acid added is too low, it will cause scaling on the heat exchange wall. The heat transfer coefficient of scale is much smaller than that of metal, which affects the heat exchange efficiency and causes economic waste.

[0048] Therefore, the acid treatment has obvious effect and simple operation, but from the comprehensive perspective of safety and economy, the amount of acid addition needs to be strictly controlled, which puts higher requirements on the operators. Starting from this problem, the present invention attempts to propose a specific method suitable for circulating cooling water acid addition control with the help of control logic and calculation method, in order to realize automatic, accurate and intelligent acid addition in the circulating cooling water system.

[0049] like Figure 2 As shown, the automatic control method for acidification of circulating cooling water of the present invention specifically comprises:

[0050] 1. Install online monitoring meters

[0051] In the circulating cooling water system, select a suitable location and install two pH meters near the cooling tower outlet and the circulating water pump inlet respectively.

[0052] Make sure the distance between the two pH meters is greater than 3 meters to accurately monitor the pH value of the circulating water before the heat exchanger.

[0053] 2. Monitoring and judgment

[0054] Monitor the output data of two pH meters in real time.

[0055] Compare the readings of the two pH meters, calculate the difference between the two, and determine whether it is within the preset error range (a=0.5).

[0056] 3. Data processing and control

[0057] When the difference between the two is ≤0.5, the system selects the smaller value for judgment:

[0058] If pH value > 8.5, start the acid pump;

[0059] If the pH value is less than 8.0, stop the acid pump;

[0060] If the pH is between 8.0 and 8.5, no action occurs.

[0061] 4. Abnormal data processing

[0062] If the difference between the two values ​​is greater than 0.5, it is determined that the readings of the two pH meters are inconsistent, and the system enters the decision logic stage.

[0063] 5. Decision logic operation

[0064] The system calculates the pH (theoretical value) according to a preset algorithm. If "pH (measured value) > pH (theoretical value) + 0.25" or "pH (measured value) < pH (theoretical value) - 0.25", the pH meter reading is judged to be unreliable, otherwise it is reliable.

[0065] The default algorithm is pH (theoretical value) = 10.568 + 0.8126 × lg [HCO3 - ], where [HCO3 - ] It is automatically converted from the alkalinity value detected by the system, and the unit is mol / L; in order to maintain the same accuracy as the instrument detection value, the pH (theoretical value) is rounded to two decimal places according to the rule of "rounding up to the nearest even number". Considering that the pH value of the circulating water is about 8.5, most of the alkalinity is composed of HCO3 - If alkalinity = a mg / L (calculated as CaCO3), then [HCO3 - ] = a / 50×10 -3 mol / L.

[0066] 6. Fault confirmation

[0067] After confirming that a pH meter reading is not reliable, the pH meter is marked as having a fault condition.

[0068] 7. Failover

[0069] When one pH meter fails and the other is normal, the system automatically switches to the normal pH meter.

[0070] If both pH meters fail, the system will issue a strong alarm, shut down and lock the sulfuric acid dosing pump.

[0071] 8. Alerts and Notifications

[0072] The system notifies operators of fault and failover situations by sound, light, email or text message alarms.

[0073] 9. Maintenance and repair

[0074] The maintenance team diagnosed and repaired the faulty pH meter.

[0075] The repaired pH meter can be put back into use by manual reset.

[0076] 10. System returns to normal

[0077] The faulty pH meter was repaired and tested to be normal, and the system was restored to dual redundancy.

[0078] Example 2

[0079] like Figure 3 As shown, the process flow of a circulating cooling water automatic acid addition control method mainly includes:

[0080] 1. Along the flow direction of the circulating cooling water, install a pH meter at 50 meters and 100 meters behind the acid addition port, and transmit the test results of the two pH meters to the control system.

[0081] 2. Compare the test values ​​of the two pH meters, and set the error range a to 0.4.

[0082] A) If the difference between the two is ≤0.4, select the smaller value for judgment:

[0083] If pH value > 8.4, start the acid pump;

[0084] If the pH value is less than 8.0, stop the acid pump;

[0085] If the pH is between 8.0 and 8.4, no action occurs.

[0086] B) If the difference between the two is greater than 0.4, the readings of the two pH meters are determined to be inconsistent, and the system enters the decision logic stage.

[0087] 3. Decision-making logic judgment

[0088] The system calculates the pH (theoretical value) according to a preset algorithm. If "pH (measured value) > pH (theoretical value) + 0.20" or "pH (measured value) < pH (theoretical value) - 0.20", the pH meter reading is judged to be unreliable, otherwise it is reliable.

[0089] The default algorithm is pH (theoretical value) = 10.568 + 0.8126 × lg [HCO3 - ], where [HCO3 -] It is automatically converted from the alkalinity value detected by the system, and the unit is mol / L; in order to maintain the same accuracy as the instrument detection value, the pH (theoretical value) is rounded to two decimal places according to the rule of "rounding up to the nearest even number". Considering that the alkalinity of the circulating water is mostly composed of HCO3 - If alkalinity = a mg / L (calculated as CaCO3), then [HCO3 - ] = a / 50×10 -3 mol / L.

[0090] 4. Fault confirmation

[0091] According to the decision logic judgment method, it is determined whether the pH meter reading is credible. If it is not credible, the pH meter is marked as faulty.

[0092] 5. Failover

[0093] When one pH meter fails and the other pH meter is normal, the system automatically switches to the normal pH meter.

[0094] If both pH meters fail, the system will issue a strong alarm, shut down and lock the sulfuric acid dosing pump.

[0095] 6. Maintenance and repair

[0096] The maintenance team diagnosed and repaired the faulty pH meter.

[0097] The repaired pH meter can be put back into use by manual reset.

[0098] 7. System returns to normal

[0099] The faulty pH meter was repaired and tested to be normal, and the system was restored to dual redundancy.

[0100] The pH meter in the process can be replaced by an online sulfate detector. The amount of sulfuric acid added can be reasonably controlled according to the pH meter or the sulfate content. Compared with the two, the pH meter has a wider range of applications, lower purchase costs, and lower requirements for operation and maintenance; while the sulfate online detector system is more complex, less used, has not been tested in the market, and has high manufacturing and operating costs. Therefore, the pH meter is preferred.

[0101] The circulating cooling water in the present invention refers to a water system that exchanges heat through a heat exchanger or a direct contact heat exchange method to exchange medium heat and is circulated after being cooled by a cooling tower.

[0102] The automatic acid addition control method proposed in the present invention is suitable for a circulating cooling water system, and therefore can be applied to any field involving circulating cooling water, such as the manufacturing industry, the construction industry, the energy industry, and the like.

[0103] The application prospects of the present invention are as follows: the automatic acid addition control system improves the efficiency and reliability of the circulating water system by accurately controlling the pH value. It reduces the excessive use of water treatment agents, reduces operating costs, and reduces the impact on the environment. At the same time, it can effectively reduce the workload of operators and improve the accuracy of system management. Therefore, the automatic acid addition control of circulating cooling water plays an important role in many industries and has broad application prospects, especially in improving industrial efficiency and environmental protection.

[0104] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the present invention, and these modifications or replacements should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A circulating cooling water automatic acidification control method, characterized in that: The method comprises the following steps: Step S1, installing an online monitoring meter in a circulating cooling water system; Step S2, monitor the data of the online monitoring meter and determine whether there is an abnormality. If not, execute step S3, otherwise execute step S4; Step S3, processing the data of the online monitoring meter and controlling the acid pump according to the processed data; Step S4, performing decision logic judgment processing on the abnormal data.

2. A circulating cooling water automatic acid addition control method according to claim 1, characterized in that: The online monitoring meters in step S1 are pH meters, and two of them are provided.

3. A circulating cooling water automatic acid addition control method according to claim 2, characterized in that: The two pH meters are respectively installed near the outlet of the cooling tower and the inlet of the circulating water pump, and the interval between the two pH meters is greater than the set distance.

4. A circulating cooling water automatic acid addition control method according to claim 2, characterized in that: The step S2 specifically includes: The output data of the two pH meters are monitored in real time, and the readings of the two pH meters are compared to calculate the difference between the two to determine whether it is within the preset error range a. If yes, execute step S3, otherwise execute step S4.

5. The method for controlling automatic acid addition of circulating cooling water according to claim 2, characterized in that: The step S3 specifically includes: Select the smaller value of the two pH meters for judgment: If pH value>A2, start the acid pump; If the pH value is less than A1, stop the acid pump; If the pH value is between A1 and A2, no action occurs.

6. A circulating cooling water automatic acid addition control method according to claim 2, characterized in that: The step S4 specifically includes: When it is determined that the readings of the two pH meters are inconsistent, the system enters the decision logic stage and calculates the pH (theoretical value) according to the preset algorithm. If "pH (measured value) > (pH (theoretical value) + a / 2)" or "pH (measured value) < (pH (theoretical value) - a / 2)", the pH meter reading is determined to be unreliable, otherwise it is reliable.

7. A circulating cooling water automatic acid addition control method according to claim 6, characterized in that: The preset algorithm is specifically: pH (theoretical value) = 10.568 + 0.8126 × lg [HCO3 - ], where [HCO3 - ]It is automatically converted from the alkalinity value detected by the system; in order to maintain the same accuracy as the instrument detection value, the pH (theoretical value) is rounded to two decimal places according to the rule of "rounding up to the nearest even number".

8. A circulating cooling water automatic acid addition control method according to claim 7, characterized in that: Considering that the pH value of the circulating water is about 8.5, most of the alkalinity is composed of HCO3 - composition, if alkalinity = a mg / L, then [HCO3 - ] = a / 50×10 -3 mol / L.

9. A circulating cooling water automatic acid addition control method according to claim 6, characterized in that: After confirming that a pH meter reading is unreliable, mark the pH meter as a fault state; When one pH meter fails and the other is normal, the system automatically switches to the normal pH meter; If both pH meters fail, the system will issue a strong alarm, shut down and lock the sulfuric acid dosing pump.

10. A circulating cooling water automatic acid addition control method according to claim 9, characterized in that: The system issues an alarm via sound, light, email or text message to notify operators of faults and failover situations; The maintenance team diagnosed and repaired the faulty pH meter, and the repaired pH meter was put back into use through manual reset; The faulty pH meter was repaired and tested to be normal, and the system was restored to dual redundancy.

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