Neutralization method

Abstract

To provide a neutralization treatment method capable of accurately subjecting a waste liquid to neutralization treatment when applied to an actual machine.SOLUTION: A neutralization treatment method comprises: a first step of adding a predetermined amount of a neutralizing agent after introducing a waste liquid into a neutralization treatment tank 1 to measure pH (primary pH), and stirring the waste liquid to measure pH (secondary pH); and a second step of determining a neutralizing agent addition amount based on a neutralizing agent addition amount and a pH change value in the first step, the primary pH, the secondary pH, and target pH, and adding the determined amount of a neutralizing agent. The neutralizing agent addition amount in the first step is determined by the target pH, the primary pH, the secondary pH, a coefficient, and an addition time by a neutralizing agent addition device, and the neutralizing agent addition amount in the second step is determined based on the target pH, the primary pH, the secondary pH, the coefficient, and the addition time.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a neutralization method for adjusting the pH of a waste liquid to a near-neutral pH, and more particularly to a neutralization method for adjusting the pH of a waste liquid to a near-neutral pH by adding an aqueous solution of an acid or alkali to the waste liquid. [Background technology]

[0002] In the neutralization of chemical wastewater, the neutralization titration curve of the target wastewater is unknown, so even if the pH value is known, it is difficult to determine the amount of neutralizing agent (acid or alkali) required. Therefore, in the actual chemical wastewater neutralization process, a trial and error method is used in which the pH is monitored and the neutralizing agent is gradually added to bring the solution closer to a neutral pH.

[0003] Therefore, the process of stirring, measuring the pH value, and adding neutralizing agent must be repeated multiple times before neutralization is complete, which takes a long time. Also, if too much neutralizing agent is added during the neutralization process, there is the issue that unnecessary chemicals are used to neutralize the excess chemicals.

[0004] Japanese Patent Laid-Open Publication No. 05-253579 discloses a method in which a fixed amount of neutralizing agent based on the pH value is added using a theoretical curve of a group of neutralization titration curves stored in advance in a memory unit, the pH value is measured again after stirring, the pH change and pH change rate relative to the amount of neutralizing agent added are determined, the initial pH value and pH change rate are compared with the group of neutralization titration curves stored in the memory, and the closest neutralization titration curve (a curve of chemical dosage amount-reaction characteristics) is selected. With this method, information on the waste liquid properties (such as the buffering action of the waste liquid) is obtained by adding the first neutralizing agent, and the amount of neutralizing agent added the second time can be adjusted to an appropriate amount.

[0005] Japanese Patent Publication No. 2011-240298 describes the use of a model information storage unit that stores physicochemical model information of a control tank, an evaluation function storage unit that stores an evaluation function that evaluates at least one of the state of the liquid to be adjusted or the amount of pH adjuster to be injected, and a calculation unit that determines the optimal amount of pH adjuster to be injected based on the pH value of the liquid to be adjusted, the physicochemical model information, and the evaluation function. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 05-253579 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-240298 Summary of the Invention [Problem to be solved by the invention]

[0007] In the methods of Patent Documents 1 and 2, it is necessary to prepare a curve or modeling of the chemical injection-reaction characteristics in advance.

[0008] Furthermore, Patent Documents 1 and 2 simply calculate the chemical injection amount, but do not take into account the actual behavioral trends of the chemical injection device. In other words, in a typical chemical injection device, the valve or pump operates for a predetermined period of time based on an electrical signal sent to the valve or pump, thereby injecting the neutralizing chemical. However, the operating time of the chemical injection device is based on this electrical signal and does not completely match the actual chemical injection time; there is a discrepancy. Furthermore, the initial chemical injection amount when the valve begins to open or the pump begins to operate is not strictly the same as the subsequent chemical injection amount, which stabilizes and stabilizes. Furthermore, in chemical injection devices that use gravity to drain the chemical solution from a tank into a neutralization treatment tank, the amount of chemical solution discharged per unit time varies depending on the liquid level in the tank. Furthermore, because the viscosity of the chemical and the valve opening / closing status change very slightly from day to day, the chemical injection amount can vary slightly even for the same chemical injection time. As a result, the pH after chemical injection may not reach the target value. Patent Documents 1 and 2 also address this issue by using equipment to measure and control the chemical injection amount, but this is extremely costly.

[0009] An object of the present invention is to provide a neutralization method that can accurately neutralize wastewater when applied to an actual machine. [Means for solving the problem]

[0010] The present invention solves the above problems as follows.

[0011] [1] A neutralization method in which waste liquid is introduced into a neutralization tank and a neutralizing agent consisting of an acid or alkali is added to the waste liquid in the neutralization tank by a neutralizing agent adding device to neutralize the waste liquid to a target pH, a first step of introducing waste liquid into the neutralization tank, measuring the pH (first pH), adding a predetermined amount of neutralizing agent, stirring the waste liquid, and measuring the pH (second pH); a second step of determining the amount of neutralizer to be added based on the amount of neutralizer added and the pH change value in the first step, the first pH, the second pH, and the target pH, and adding the determined amount of neutralizer; A neutralization treatment method comprising: The amount of neutralizing agent added in the first step is determined based on the target pH, the primary pH, a coefficient, and the addition time by the neutralizing agent adding device; The amount of neutralizing agent to be added in the second step is determined based on the target pH, the first pH, the second pH, the coefficient, and the addition time. A neutralization treatment method characterized by:

[0012] [2] The waste liquid is acidic, If the primary pH is a, the secondary pH is b, and the target pH is m, the amount of neutralizer added in the first step is (10 -a -10 -m ) × (conversion factor) × (dosing factor) × (addition time) It was decided by The amount of neutralizer added in the second process (10 -b -10 -m )×(10 -a -10 -m ) / (10 -a -10 -b ) / [(conversion factor) × (dosing factor) × (addition time)] The neutralization treatment method [1] is determined by the following.

[0013] Here, the conversion coefficient is a unit conversion coefficient that converts the chemical dosage amount into the valve opening and closing time, and the chemical dosage coefficient is a value set according to the pH change situation during wastewater neutralization. For example, the chemical dosage coefficient is a value adjusted so that the pH changes by about 1.5 to 3 when the pH of the wastewater is less than 10, by about 0.5 to 1.5 when the pH of the wastewater is 10 to less than 12, and by about 0.3 to 0.5 when the pH of the wastewater is 12 or more. The chemical dosage coefficient is adjusted so that the pH changes within the above ranges in a specified chemical dosage time (e.g., 10 to 15 seconds).

[0014] [3] The waste liquid is alkaline, having a pH of 10 or higher; If the primary pH is a, the secondary pH is b, and the target pH is m, the amount of neutralizer added in the first step is (10 -(14-a) -10 -(14-m) ) / [(conversion factor) × (dosage factor) × (injection time)] It was decided by The amount of neutralizer added in the second process (10 -(14-b) -10 -(14-m) )×(10 -(14-a) -10 -(14-m) ) / (10 -(14-a) -10 -(14-b) ) / [(conversion factor) × (dosing factor) × (addition time)] The neutralization treatment method [1] is determined by the following.

[0015] [4] The waste liquid is alkaline with a pH of less than 10, If the primary pH is a, the secondary pH is b, the target pH of the first step is m1, and the target pH of the second step is m2, then the amount of neutralizer added in the first step is (10 -(14-a) -10 -(14-7) +10 -m1 ) × (conversion factor) × (dosing factor) × (addition time) It was decided by The amount of neutralizer added in the second process (10 -(14-b) -10 -(14-7) +10 -m2 )×(10 -(14-a) -10 -(14-7) +10 -m1) / [(10 -(14-a) -10 -(14-b) ) × (conversion factor) × (dosing factor) × (addition time)] The neutralization treatment method of claim 1, wherein the neutralization treatment method is determined by the following formula.

[0016] however, m1=log(-(10 -(14-a) -c) m2=log(-(10 -(14-b) -c) and c is the value obtained by subtracting the amount of ions at pH 7 from the amount of ions at pH 10 for calculations below pH 10, which is 0.0000999(10 -4 -10 -7 )

[0017] [5] The neutralization method according to any one of [1] to [4], wherein the waste liquid is introduced into the neutralization tank, stirred, and then the primary pH is measured, and if the pH of the waste liquid is not neutral, the first step is carried out. [Effects of the Invention]

[0018] The present invention provides a neutralization control method adapted to actual equipment by determining a chemical dosing coefficient in a theoretical pH calculation formula that will result in an effective pH change in the first chemical dosing. In this invention, it is sufficient to set a coefficient or chemical dosing time that will allow the pH to be adjusted in the first chemical dosing to calculate the second chemical dosing amount; a strict pH change range is not required. Therefore, chemical dosing can be completed in a shorter time than the methods of Patent Documents 1 and 2, which determine reaction characteristic curves and modeling.

[0019] Furthermore, even if the chemical injection-pH change situation of the actual machine fluctuates, it is only necessary to set a coefficient or chemical injection time that allows calculation of the second chemical injection amount from the first chemical injection, and there is no need to perform reaction characteristic curve or modeling again. Furthermore, because the second chemical injection amount is calculated from the pH change due to the first chemical injection, it is possible to continuously respond to pH changes and improve the accuracy of pH adjustment compared to the methods using reaction characteristic curves and modeling in Patent Documents 1 and 2. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 2 is a schematic vertical cross-sectional view of a neutralization treatment tank. [Figure 2] 1 is a flow chart illustrating the method of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] 1 is a schematic vertical cross-sectional view of a neutralization treatment tank to which a neutralization treatment method according to an embodiment of the present invention is applied. Waste liquid is introduced into this neutralization treatment tank 1 through a pipe 2. An acid (hydrochloric acid in this embodiment) or an alkali (caustic soda in this embodiment) is added to the neutralization treatment tank 1 as a neutralizing agent.

[0022] Hydrochloric acid (aqueous hydrogen chloride solution) is stored in a hydrochloric acid tank 3, and is added to the neutralization treatment tank 1 from the hydrochloric acid tank 3 by gravity when a valve 3a is opened.

[0023] The aqueous caustic soda solution is contained in a caustic soda tank 4, and is added to the neutralization treatment tank 1 from the caustic soda tank 4 by gravity when a valve 4a is opened.

[0024] To agitate the liquid in the neutralization treatment tank 1, air is supplied from a blower 5 to an air diffuser 6.

[0025] A pH meter 7 is installed to detect the pH of the liquid in the neutralization treatment tank 1.

[0026] A transfer pipe 9 having a pump 8 is provided to transfer the liquid after the neutralization treatment from the neutralization treatment tank 1.

[0027] In this embodiment, the waste liquid is ion exchange resin regeneration waste liquid, which is an acidic or alkaline waste liquid containing hydrochloric acid or caustic soda and salts, and other substances stripped from the ion exchange resin, but is not limited to this.

[0028] To neutralize this waste liquid, as shown in FIG. 2, the waste liquid is introduced into a neutralization treatment tank 1, stirred, and the pH (primary pH) is measured with a pH meter 7.

[0029] If the pH is neutral (for example, 5 to 8), the solution is transferred by pump 8 without neutralization. If the pH is acidic or alkaline, the first step is carried out. That is, a predetermined amount of neutralizing agent is added, followed by stirring and measurement of the pH (secondary pH). The first chemical dosage is the amount of chemical to be added that generates a pH change that allows for the second chemical dosage calculation (an amount of addition that changes the pH by approximately 1.5 to 3 when the waste liquid pH is less than 10, approximately 0.5 to 1.5 when the waste liquid pH is 10 to less than 12, and approximately 0.3 to 0.5 when the waste liquid pH is 12 or higher. This is determined by preliminary testing or as an empirical value).

[0030] If the measured secondary pH is neutral (for example, 5 to 8), the solution is transferred by pump 8. If the secondary pH is not neutral, the second step is carried out.

[0031] That is, the amount of neutralizer to be added for the second time is determined taking into consideration the results of the pH adjustment in the first step, and this amount of neutralizer is added and stirred, and the pH (third pH) is measured. If the result shows that the pH is neutral (for example, 5 to 8), the mixture is transferred using pump 8. If the third pH is not neutral, the process returns to the first step.

[0032] Next, a method for determining the amount of neutralizing agent to be added in each of the first and second steps will be described.

[0033] In one embodiment of the present invention, the waste liquid is acidic. In this embodiment, when the primary pH is a, the secondary pH is b, and the target pH is m, the amount of neutralizing agent added in the first step is (10 -a -10 -m ) × (conversion factor) × (dosing factor) × (addition time) It was decided by The amount of neutralizer added in the second process (10 -b -10 -m )×(10 -a -10 -m ) / (10 -a -10 -b) / [(conversion factor) × (dosing factor) × (addition time)] The decision will be made at the following.

[0034] The conversion coefficient is a unit conversion coefficient that converts the amount of chemical dosing into the valve opening and closing time, and is set according to the pH change during wastewater neutralization. For example, the chemical dosing coefficient is a value adjusted so that the pH changes by approximately 1.5 to 3 when the pH of the wastewater is less than 10, by approximately 0.5 to 1.5 when the pH of the wastewater is 10 to less than 12, and by approximately 0.3 to 0.5 when the pH of the wastewater is 12 or higher. The chemical dosing coefficient is adjusted so that the pH changes within the above ranges in a specified chemical dosing time (e.g., 10 to 15 seconds).

[0035] In another embodiment of the present invention, the waste liquid is alkaline with a pH of 10 or more. In this embodiment, when the primary pH is a, the secondary pH is b, and the target pH is m, the amount of neutralizing agent added in the first step is (10 -(14-a) -10 -(14-m) ) / [(conversion factor) × (dosage factor) × (injection time)] It was decided by The amount of neutralizer added in the second process (10 -(14-b) -10 -(14-m) )×(10 -(14-a) -10 -(14-m) ) / (10 -(14-a) -10 -(14-b) ) / [(conversion factor) × (dosing factor) × (addition time)] The conversion coefficient and chemical dosing coefficient are as above.

[0036] In yet another embodiment of the present invention, the waste liquid is alkaline with a pH of less than 10. In this embodiment, when the primary pH is a, the secondary pH is b, the target pH in the first step is m1, and the target pH in the second step is m2, the amount of neutralizing agent added in the first step is (10 -(14-a) -10 -(14-7) +10 -m1 ) × (conversion factor) × (dosing factor) × (addition time) It was decided by The amount of neutralizer added in the second addition step (10 -(14-b) -10 -(14-7) +10 -m2 )×(10 -(14-a) -10 -(14-7) +10 -m1 ) / [(10 -(14-a) -10 -(14-b) ) × (conversion factor) × (dosing factor) × (addition time)] However, m1=log(-(10 -(14-a) -c) m2=log(-(10 -(14-b) -c) and c is the value obtained by subtracting the amount of ions at pH 7 from the amount of ions at pH 10 for calculations below pH 10, which is 0.0000999(10 -4 -10 -7 )

[0037] According to this embodiment, even if the properties of the regeneration wastewater change, the pH can be adjusted satisfactorily by performing the second chemical feeding based on the primary pH and secondary pH.

[0038] Furthermore, even if the level in the pH adjuster storage tank fluctuates, the pH can be adjusted satisfactorily by performing a second chemical injection based on the primary pH and secondary pH.

[0039] Furthermore, even if the viscosity of the pH adjuster changes due to a temperature change, the pH can be adjusted satisfactorily by performing a second chemical injection based on the primary pH and secondary pH.

[0040] Even if the amount of regeneration waste liquid fluctuates, the pH can be adjusted satisfactorily by performing a second chemical injection based on the primary and secondary pH values.

[0041] For this reason, the pH after chemical injection is efficiently brought to the target neutral value. [Explanation of symbols]

[0042] 1 Neutralization tank 3 Hydrochloric Acid Tank 4 Caustic soda tank 5 Blower 6. Ventilation pipes

Claims

1. A neutralization method in which regenerated waste liquid from an ion exchange resin is introduced into a neutralization tank, and a neutralizing agent consisting of an acid or alkali in a tank is added to the waste liquid in the neutralization tank by a neutralizing agent adding device to neutralize the waste liquid to a target pH, wherein the neutralizing agent adding device adds the neutralizing agent in the tank by gravity when a valve is opened, a first step of introducing the waste liquid into the neutralization treatment tank, measuring the pH (primary pH), adding a predetermined amount of neutralizing agent, stirring the waste liquid, and measuring the pH (secondary pH); a second step of determining the amount of neutralizing agent to be added based on the amount of neutralizing agent added and the pH change value in the first step, the primary pH, the secondary pH, and the target pH, and adding the determined amount of neutralizing agent; A neutralization treatment method comprising: The amount of neutralizing agent to be added in the first step is determined based on the target pH, the primary pH, a coefficient, and the addition time by the neutralizing agent addition device; A neutralization method in which the amount of neutralizing agent to be added in the second step is determined based on a target pH, a first pH, a second pH, the coefficient, and the addition time, the waste liquid is acidic, When the primary pH is a, the secondary pH is b, and the target pH is m, the amount of neutralizing agent added in the first step is (10 －ａ -10 －ｍ ) x (conversion factor) x (dosing factor) x (addition time) It was decided by The amount of neutralizer added in the second process (10 －ｂ -10 －ｍ ) x (10 －ａ -10 －ｍ ) / (10 －ａ -10 －ｂ ) / [(conversion factor) x (dosing factor) x (addition time)] The neutralization treatment method is determined by the above. The conversion factor is a unit conversion factor for converting the dosage amount into the valve open time. The dosage factor is a value determined by preliminary tests or empirical values ​​so that the pH changes by 1.5 to 3 over a specified dosage time (10 to 15 seconds).

2. A neutralization method in which regenerated waste liquid from an ion exchange resin is introduced into a neutralization tank, and a neutralizing agent consisting of an acid or alkali in a tank is added to the waste liquid in the neutralization tank by a neutralizing agent adding device to neutralize the waste liquid to a target pH, wherein the neutralizing agent adding device adds the neutralizing agent in the tank by gravity when a valve is opened, a first step of introducing the waste liquid into the neutralization treatment tank, measuring the pH (primary pH), adding a predetermined amount of neutralizing agent, stirring the waste liquid, and measuring the pH (secondary pH); a second step of determining the amount of neutralizing agent to be added based on the amount of neutralizing agent added and the pH change value in the first step, the primary pH, the secondary pH, and the target pH, and adding the determined amount of neutralizing agent; A neutralization treatment method comprising: The amount of neutralizing agent to be added in the first step is determined based on the target pH, the primary pH, a coefficient, and the addition time by the neutralizing agent addition device; A neutralization method in which the amount of neutralizing agent to be added in the second step is determined based on a target pH, a first pH, a second pH, the coefficient, and the addition time, The waste liquid has an alkaline pH of 10 or more, When the primary pH is a, the secondary pH is b, and the target pH is m, the amount of neutralizing agent added in the first step is (10 －（１４－ａ） -10 －（１４－ｍ） ) / [((conversion factor) x (dosage factor) x (injection time)] It was decided by The amount of neutralizer added in the second process (10 －（１４－ｂ） -10 －（１４－ｍ） ) x (10 －（１４－ａ） -10 －（１４－ｍ） ) / (10 －（１４－ａ） -10 －（１４－ｂ） ) / [(conversion factor) x (dosing factor) x (addition time)] The neutralization treatment method is determined by the above. The conversion factor is a unit conversion factor for converting the dosage amount into the valve open time. The dosage factor is a value determined by preliminary tests or empirical values ​​so that the pH changes by 0.5 to 1.5 in a predetermined dosage time (10 to 15 seconds) when the pH of the waste liquid is less than 10 to 12, and the pH changes by 0.3 to 0.5 in a predetermined dosage time (10 to 15 seconds) when the pH of the waste liquid is 12 or higher.

3. A neutralization method in which regenerated waste liquid from an ion exchange resin is introduced into a neutralization tank, and a neutralizing agent consisting of an acid or alkali in a tank is added to the waste liquid in the neutralization tank by a neutralizing agent adding device to neutralize the waste liquid to a target pH, wherein the neutralizing agent adding device adds the neutralizing agent in the tank by gravity when a valve is opened, a first step of introducing the waste liquid into the neutralization treatment tank, measuring the pH (primary pH), adding a predetermined amount of neutralizing agent, stirring the waste liquid, and measuring the pH (secondary pH); a second step of determining the amount of neutralizing agent to be added based on the amount of neutralizing agent added and the pH change value in the first step, the primary pH, the secondary pH, and the target pH, and adding the determined amount of neutralizing agent; A neutralization treatment method comprising: The amount of neutralizing agent to be added in the first step is determined based on the target pH, the primary pH, a coefficient, and the addition time by the neutralizing agent addition device; A neutralization method in which the amount of neutralizing agent to be added in the second step is determined based on a target pH, a first pH, a second pH, the coefficient, and the addition time, The waste liquid is alkaline with a pH of less than 10, If the primary pH is a, the secondary pH is b, the target pH in the first step is m1, and the target pH in the second step is m2, then the amount of neutralizing agent added in the first step is (10 －（１４－ａ） -10 －（１４－７） +10 －ｍ１ ) x (conversion factor) x (dosing factor) x (addition time) It was decided by (Note that the conversion factor is a unit conversion factor for converting the dosage amount into the valve open time. The dosage factor is a value determined by preliminary tests or empirical values ​​so that the pH changes by 1.5 to 3 over a specified dosage time (10 to 15 seconds).) The amount of neutralizer added in the second process (10 －（１４－ｂ） -10 －（１４－７） +10 －ｍ２ ) x (10 －（１４－ａ） -10 －（１４－７） +10 －ｍ１ ) / [(10 －（１４－ａ） -10 －（１４－ｂ） ) × (conversion factor) × (dosing factor) × (addition time) The neutralization treatment method is determined by the above. however, m1=log(-(10 －（１４－ａ） -c) m2=log(-(10 －（１４－ｂ） -c) and c is 0.0000999.

4. 4. The neutralization method according to claim 1, wherein the waste liquid is introduced into the neutralization tank, stirred, and then the primary pH is measured, and the first step is carried out if the pH of the waste liquid is not neutral.

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