Automatic acid and alkali adding neutralization method and device for wastewater neutralization tank

Abstract

This invention relates to the field of wastewater discharge, and particularly to an automatic acid and alkali addition method and apparatus for wastewater neutralization tanks. The method comprises: Step S1: Activating the cumulative acid and alkali addition statistics module and resetting both modules to zero; Step S2: Activating the automatic neutralization module to automatically calculate the required volume of acid or alkali for neutralization; Step S3: The automatic neutralization module corrects the calculated volume of acid or alkali to obtain the actual added value of acid or alkali; Step S4: The automatic neutralization module controls the outflow of acid or alkali to neutralize the wastewater in the neutralization tank; Step S5: After the neutralization tank continues to circulate for half an hour, if the pH value is unqualified, returning to Step S2, the automatic neutralization module repeats steps S2 to S4; if the pH value is qualified, the neutralization operation is completed. This invention enables precise acid and alkali addition based on the water volume and pH value in the neutralization tank, effectively avoiding over-addition of acid or alkali and achieving rapid acid-base neutralization in wastewater neutralization tanks.

Description

Technical Field

[0001] This invention relates to the field of wastewater discharge, and in particular to a method and apparatus for automatic acid and alkali addition for neutralization in a wastewater neutralization tank. Background Technology

[0002] The main function of the wastewater neutralization tank for adding acid and alkali is to receive industrial wastewater from the system. Before the wastewater is discharged, the pH of the received wastewater needs to be adjusted to the range of 6.2-8.8 to meet the relevant regulatory requirements before it can be discharged.

[0003] The wastewater neutralization system is mainly divided into an acid addition device and an alkali addition device. When the pH is less than 7, the wastewater is acidic and needs to be neutralized by adding alkali solution; when the pH is greater than 7, the wastewater is alkaline and needs to be neutralized by adding acid solution. The entire process requires the discharge water pump to be continuously running to stir along the recirculation.

[0004] The pH value in wastewater neutralization tanks is affected by the layout of pipelines and sampling pipelines during the neutralization process. The pH value cannot accurately reflect the actual pH value of the wastewater in the neutralization tank in real time; it generally requires a certain amount of stirring time to reach pH equilibrium. The stirring time is related to the recirculation flow rate and the layout of the circulation pipeline, typically requiring more than half an hour. Sampling pipelines are generally located at the pump outlet. When the acid / alkali addition pipeline is far from the pump inlet pipeline, the neutralized solution needs time to diffuse to the pump suction inlet, causing the pH meter reading to lag. If the correct pH value is reached, it will result in excessive acid / alkali addition. When the acid / alkali addition pipeline is close to the pump inlet pipeline, the neutralized solution diffuses immediately to the pump suction inlet, while other parts of the neutralization tank have not yet been neutralized, resulting in a leading pH meter reading. If the correct pH value is reached, the dosage is insufficient, requiring multiple additions. Based on the pipeline layout, the main methods for adding acid and alkali to wastewater neutralization tanks are:

[0005] 1. Based on experience, the addition of acid or alkali is stopped when the pH reaches a certain value. However, this method is difficult to control based on experience and critical points, and automatic dosing is not possible. It is easy to add too much or too little.

[0006] Second, adding a small amount of acid or alkali each time, then circulating and mixing, and then adding a fixed amount of acid or alkali according to the pH value, and then circulating and mixing again. Since the pH value changes exponentially with the amount of acid or alkali to be added, if the amount of chemicals added each time remains the same, multiple additions will be needed in the early stages when the pH value change is not obvious, and the dosing time will be too long. In the later stages, less amount of chemicals will be needed, and quantitative dosing can easily lead to overdosing. In addition, this method does not take into account the impact of the total amount of wastewater on the amount of acid and alkali to be added.

[0007] The above two methods do not include statistics on the amount of chemicals added, which is not conducive to the statistical analysis of acid and alkali losses. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide an automatic acid and alkali addition method and device for wastewater neutralization tank, which accurately adds acid and alkali and realizes rapid acid and alkali neutralization in wastewater neutralization tank.

[0009] This invention provides an automatic acid and alkali addition neutralization method for wastewater neutralization tanks, comprising the following steps:

[0010] Step S1: Input the cumulative acid addition statistics module and the cumulative alkali addition statistics module, and then clear both modules to zero;

[0011] Step S2: Activate the automatic neutralization module to automatically calculate the volume of acid or alkali required for neutralization;

[0012] Step S3: The automatic neutralization module corrects the calculated volume of acid or alkali added to obtain the actual added value of acid or alkali solution;

[0013] Step S4: The automatic neutralization module controls the output of acid or alkali solution to neutralize the waste liquid in the neutralization tank;

[0014] Step S5: After the neutralization tank continues to circulate for another half hour, if the pH value is not up to standard, return to step S2, and the automatic neutralization module will repeat the operation of steps S2 to S4; if the pH value is up to standard, the neutralization operation is completed.

[0015] In a specific embodiment of the present invention, step S2 specifically includes the following steps:

[0016] The amount of water in the neutralization tank is automatically calculated based on the liquid level in the neutralization tank;

[0017] The drainage pump will automatically start circulating for half an hour.

[0018] The system automatically calculates the required volume of acid or alkali to be added for neutralization based on the calculated water volume and pH value in the tank.

[0019] In a specific embodiment of the present invention, the correction method in step S3 is as follows:

[0020] Multiply the calculated volume of acid or alkali added by a coefficient between 0 and 1.

[0021] In one specific embodiment of the present invention, the coefficient is 0.5 to 0.7.

[0022] In one specific embodiment of the present invention, the coefficient is 0.6.

[0023] In a specific embodiment of the present invention, step S4 specifically includes the following steps:

[0024] The automatic neutralization module calculates the drop in liquid level in the acid neutralization metering tank or alkali neutralization metering tank based on the actual amount of acid or alkali added.

[0025] The system automatically adds acid or alkali until the calculated drop in liquid level is reached, at which point it stops.

[0026] The dosage is accumulated in the corresponding acid addition statistics module or alkali addition statistics module.

[0027] This invention provides an automatic acid and alkali addition device for wastewater neutralization tanks, comprising:

[0028] The cumulative acid addition statistics module is used to record the amount of acid added;

[0029] The cumulative alkali addition statistics module is used to record the amount of alkali solution added;

[0030] The automatic neutralization module is used to automatically calculate the amount of acid or alkali needed for neutralization and control the addition of acid or alkali to the neutralization tank.

[0031] Compared with the prior art, the automatic acid and alkali addition neutralization method and apparatus for wastewater neutralization tank of the present invention has the following beneficial effects:

[0032] (1) It can accurately add acid and alkali according to the water volume and pH value of the neutralization tank, effectively avoiding the situation of excessive addition of acid and alkali and effectively reducing the loss of neutralizing acid and alkali;

[0033] (2) Rapid acid-base neutralization of wastewater in the neutralization tank was achieved;

[0034] (3) Since the amount of acid and alkali to be added changes exponentially when the pH of the wastewater neutralization tank changes, the automatic acid and alkali addition neutralization method of the wastewater neutralization tank of the present invention can realize the function of needing to add more acid and alkali at the beginning and less acid and alkali to be added later.

[0035] (4) Because the automatic dosing stop point is when the dosing amount reaches the dosing amount calculated by the system based on the initial pH, it is not affected by pH fluctuations during the dosing process. Therefore, the impact of the layout of circulation pipelines, acid and alkali pipelines on neutralization can be reduced.

[0036] (5) It can realize automated acid and alkali addition and neutralization logic, and the amount of acid and alkali added is more convenient to count. Attached Figure Description

[0037] Figure 1 A schematic diagram showing the structure of the neutralization device in the wastewater neutralization tank;

[0038] In the diagram, 1-wastewater neutralization tank; 2-wastewater inlet valve; 3-acid addition valve; 4-acid neutralization metering tank; 5-acid inlet valve of acid metering tank; 6-alkali addition valve; 7-alkali neutralization metering tank; 8-alkali inlet valve of alkali metering tank; 9-first drainage pump; 10-second drainage pump; 11-circulation valve; 12-discharge valve; 13-pH meter. Detailed Implementation

[0039] To further understand the present invention, embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the present invention.

[0040] An embodiment of the present invention discloses an automatic acid and alkali addition neutralization method for wastewater neutralization tanks, comprising the following steps:

[0041] Step S1: Input the cumulative acid addition statistics module and the cumulative alkali addition statistics module, and then clear both modules to zero;

[0042] Step S2: Activate the automatic neutralization module to automatically calculate the volume of acid or alkali required for neutralization;

[0043] Specifically, the following steps are included:

[0044] The amount of water in the neutralization tank is automatically calculated based on the liquid level in the neutralization tank;

[0045] The drainage pump will automatically start circulating for half an hour.

[0046] The system automatically calculates the required volume of acid or alkali to be added for neutralization based on the calculated water volume and pH value in the tank.

[0047] Step S3: The automatic neutralization module corrects the calculated volume of acid or alkali added to obtain the actual added value of acid or alkali solution;

[0048] The correction method is as follows:

[0049] Multiply the calculated volume of acid or alkali added by a coefficient between 0 and 1.

[0050] The coefficient is preferably 0.5 to 0.7, and more preferably 0.6.

[0051] Step S4: The automatic neutralization module controls the output of acid or alkali solution to neutralize the waste liquid in the neutralization tank;

[0052] Specifically, the following steps are included:

[0053] The automatic neutralization module calculates the drop in liquid level in the acid neutralization metering tank or alkali neutralization metering tank based on the actual amount of acid or alkali added.

[0054] The system automatically adds acid or alkali until the calculated drop in liquid level is reached, at which point it stops.

[0055] The dosage is accumulated in the corresponding acid addition statistics module or alkali addition statistics module.

[0056] Step S5: After the neutralization tank continues to circulate for another half hour, if the pH value is not up to standard, return to step S2, and the automatic neutralization module will repeat the operation of steps S2 to S4; if the pH value is up to standard, the neutralization operation is completed.

[0057] Embodiments of the present invention also disclose an automatic acid and alkali addition device for a wastewater neutralization tank, comprising:

[0058] The cumulative acid addition statistics module is used to record the amount of acid added;

[0059] The cumulative alkali addition statistics module is used to record the amount of alkali solution added;

[0060] The automatic neutralization module is used to automatically calculate the amount of acid or alkali needed for neutralization and control the addition of acid or alkali to the neutralization tank.

[0061] The automatic acid and alkali addition device for the wastewater neutralization tank described in this invention also includes the neutralization device of an existing wastewater neutralization tank. Existing wastewater neutralization tank neutralization devices include... Figure 1 As shown. The normal wastewater neutralization process in the neutralization tank is as follows: When the water level in the neutralization tank 1 reaches a certain level and discharge is required, close the wastewater inlet valve 2, confirm that the discharge valve 12 is closed, open the circulation valve 11, and start the first drainage pump 9 or the second drainage pump 10. At this time, the wastewater in the neutralization tank is mixed, and the pH meter 13 displays the pH value. Acid and alkali are added according to the pH value. When pH < 7, alkali needs to be added. When adding alkali, open the alkali adding valve 6, and the alkali solution in the alkali neutralization metering tank 7 enters the wastewater neutralization tank 1. When the alkali solution level in the alkali neutralization metering tank 7 is low, open the alkali inlet valve of the alkali neutralization metering tank 8 to replenish alkali. When pH > 7, acid needs to be added. When adding acid, open the acid adding valve 3, and the acid solution in the acid neutralization metering tank 4 enters the wastewater neutralization tank 1. When the acid solution level in the acid neutralization metering tank 4 is low, open the acid neutralization metering tank inlet valve 5 to replenish acid. When the pH is within acceptable limits, open the discharge valve 12 and close the circulation valve 11 to discharge the wastewater from the neutralization tank.

[0062] The automatic acid and alkali addition neutralization method for wastewater neutralization tanks of the present invention can rely on existing equipment to achieve fully automatic wastewater neutralization through automatic program control, without human intervention. Since pH value and the required dosage are exponentially related, this method sets the dosage based on the pH value after mixing. Initially, if the pH value deviates significantly from the neutral point, a larger amount of acid and alkali is calculated for rapid coarse adjustment. Subsequently, if the pH value deviates less from the center, a smaller amount of acid and alkali is calculated for fine adjustment, achieving rapid acid and alkali neutralization in the wastewater neutralization tank. It achieves precise acid and alkali addition, effectively reducing acid and alkali losses during neutralization. The dosage is determined by calculating the pH value and liquid level after mixing. pH fluctuations during the dosing process do not affect the dosage, reducing the impact of circulation pipelines, acid and alkali addition pipelines, etc., on neutralization. All the above wastewater neutralization steps are automatically completed by the DCS system program, achieving automated acid and alkali addition neutralization with simpler logic and easier statistical analysis of acid and alkali addition amounts.

[0063] To further understand the present invention, the automatic acid and alkali addition neutralization method and apparatus for wastewater neutralization tank provided by the present invention will be described in detail below with reference to the embodiments. The scope of protection of the present invention is not limited by the following embodiments.

[0064] Example 1

[0065] Step 1: Before starting neutralization, first input the cumulative acid addition statistics module and the cumulative alkali addition statistics module, and then clear the cumulative acid addition statistics module and the cumulative alkali addition statistics module to zero in order to count the amount of acid and alkali added during this wastewater tank neutralization.

[0066] Step 2: Activate the automatic neutralization module. After activation, the module automatically calculates the volume of wastewater in the neutralization tank based on the tank's level. The calculation formula is: Vtank = Sbottom * L = 16 * 9 * L. The wastewater neutralization tank is 16m long and 9m wide, where H is the wastewater level in the neutralization tank (in meters). After automatically starting the drainage pump and circulating the wastewater for half an hour, the module automatically calculates the required volumes of acid and alkali to be added for neutralization based on the calculated volume and pH value.

[0067] When pH < 7, the wastewater is acidic and requires neutralization with alkali. In a certain project, the neutralizing alkali solution is a 31% NaOH solution. The automatic neutralization module calculates the required alkali volume based on the wastewater volume and pH value using the following formula:

[0068] V 碱 =H*16*9*10 (-X) *40÷0.31÷1.34 (unit: L)

[0069] In the formula, X is the pH value, 40 is the molar mass of NaOH (40 g / mol), 0.31 is the mass concentration of the added alkali solution (31%), and 1.34 is the density of the 31% sodium hydroxide solution (1.34 g / cm³).3 .

[0070] When pH > 7, the wastewater is alkaline and requires neutralization with acid. In a certain project, the neutralizing acid is a 31% HCl solution. The automatic neutralization module calculates the required acid volume based on the wastewater volume and pH value using the following formula:

[0071] V 酸 =H*16*9*10 (X-14) *36.5÷0.31÷1.15 (unit: L)

[0072] In the formula, X is the pH value, 36.5 is the molar mass of HCl (36.5 g / mol), 0.31 represents the mass concentration of the added alkali solution (31%), and 1.15 represents the density of the 31% hydrochloric acid solution (1.15 g / cm³). 3 .

[0073] Step 3: The automatic neutralization module multiplies the calculated amount of acid and alkali added for neutralization by a coefficient less than 1 to determine the amount of acid and alkali added for this step. For example, if 0.6 is selected:

[0074] V 本次酸碱 =V 酸 or V 碱 *0.6, unit: L;

[0075] Multiplying by a coefficient less than 1 is primarily to account for the large errors in pH meters below 2 and above 12. The relationship between pH and ion concentration is exponential; a 0.1 change in pH below 2 or above 12 results in a significant difference in the amount of acid or alkali needed. For example, the amount of alkali needed for a pH of 1.4 is 1.26 times that needed for a pH of 1.5. Therefore, to avoid overdosing, a coefficient less than 1 is used to determine the dosage. Based on the pH meter's error, a coefficient below 0.7 is generally safer. However, a coefficient that is too low will result in insufficient dosage each time, requiring multiple additions. Therefore, the coefficient should be above 0.5. When the coefficient is 0.5, four additions are sufficient to achieve over 93% of the required dosage. Thus, the coefficient should be between 0.5 and 0.7. For example, if a coefficient of 0.6 is selected in this case, it is expected that four additions will complete the neutralization of the wastewater in the neutralization tank.

[0076] Step 4: The automatic neutralization module automatically calculates the drop in the acid and alkali metering tank based on the calculated amount of acid and alkali to be added. After adding the calculated amount of chemicals, the addition stops, and the acid and alkali valves in the wastewater neutralization tank are closed.

[0077] L 酸碱 =V 本次酸碱 / S 酸碱 / 10 units cm

[0078] In the formula S 酸碱 =π / 4 * 0.5 * 0.5 (unit: m) 3.

[0079] If L 酸碱 When the calculated value is <2cm, in order to facilitate the calculation of the dosage and for automated control, and also because the reversible reaction of weak acid and weak base in the wastewater requires the addition of more acid or base to neutralize it, L 酸碱 The forced value is 2cm.

[0080] Step 5: If the pH value is not up to standard after the wastewater neutralization tank continues to circulate for half an hour, the automatic neutralization module will repeat steps 2-4 until the pH value is up to standard.

[0081] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0082] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for automatically adding acid and alkali to a wastewater neutralization tank for neutralization, characterized in that, Includes the following steps: Step S1: Input the cumulative acid addition statistics module and the cumulative alkali addition statistics module, and then clear both modules to zero; Step S2: Activate the automatic neutralization module to automatically calculate the volume of acid or alkali required for neutralization; Step S3: The automatic neutralization module corrects the calculated volume of acid or alkali added to obtain the actual added value of acid or alkali solution; The correction method is as follows: Multiply the calculated volume of acid or alkali added by a coefficient between 0.5 and 0.7; Step S4: The automatic neutralization module controls the output of acid or alkali solution to neutralize the waste liquid in the neutralization tank; Step S5: After the neutralization tank continues to circulate for another half hour, if the pH value is not up to standard, return to step S2, and the automatic neutralization module will repeat the operation of steps S2 to S4; if the pH value is up to standard, the neutralization operation is completed.

2. The automatic acid and alkali addition neutralization method for wastewater neutralization tank according to claim 1, characterized in that, Step S2 specifically includes the following steps: The amount of water in the neutralization tank is automatically calculated based on the liquid level in the neutralization tank; The drainage pump will automatically start circulating for half an hour. The system automatically calculates the required volume of acid or alkali to be added for neutralization based on the calculated water volume and pH value in the tank.

3. The automatic acid and alkali addition neutralization method for wastewater neutralization tank according to claim 1, characterized in that, The coefficient is 0.

6.

4. The automatic acid and alkali addition neutralization method for wastewater neutralization tank according to claim 1, characterized in that, Step S4 specifically includes the following steps: The automatic neutralization module calculates the drop in liquid level in the acid neutralization metering tank or alkali neutralization metering tank based on the actual amount of acid or alkali added. The system automatically adds acid or alkali until the calculated drop in liquid level is reached, at which point it stops. The dosage is accumulated in the corresponding acid addition statistics module or alkali addition statistics module.

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