JPS5843285A - Automatic neutralizing method for alkaline waste liquid - Google Patents

Abstract

PURPOSE:To neutralize alkaline waste liquid by detecting the injection rate of an acid necessary for neutralizing the alkaline waste liquid and inputting the concn. of the acid and the injection rate of the acid detected by dynamic neutralization to a controller. CONSTITUTION:The acidic waste liquid of regeneration and the alkaline waste liquid of regeneration from a condensate desalting device are received in a neutralizing tank 1, and both liquides are mixed by using a circulating pump 2. Gaseous carbon dioxide 4 is injected into the alkaline waste liquid formed by the mixing through a circulation piping 3, whereby part thereof is converted to carbonate. Such alkaline waste liquid is drawn out into a filtration piping 6 and is removed of suspensions such as ion exchange resins with a cyclone separator 7. This liquid is filtered with a filter 8. A constant feed pump 14 varies the rate of inflow stepwise by a specified time in accordance with the signal of a controller 15 having calculating functions. The pH of the liquid is detected with a pH electrode 17 and the detected pH is converted to an electric signal with a signal transmitter 18. The electric signal is inputted to the controller 15.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the neutralization of alkaline waste liquid mainly consisting of alkali, and in particular to the automatic neutralization of the recycled waste liquid of ion exchange resin generated from the condensate desalination equipment of BWR type nuclear power plants. It concerns a method of neutralization.

A condensate desalination device is installed in the condensate system of a BWR nuclear power plant for the purpose of removing iron oxide and impurity ions from the condensate. The condensate desalination equipment usually uses a mixed bed of cation exchange resin and anion exchange resin, but when the mixed bed becomes saturated with iron oxide and impurity ions, both ion exchange resins are separated and the cation exchange resin is an acid such as sulfuric acid, and the anion exchange resin is regenerated with an alkali such as power pf + soda + M7fk.

Regeneration of the ion-exchange resin generates acidic recycled sintered liquid and alkaline recycled waste liquid, but since both liquids contain radioactive substances, they must be neutralized, concentrated, and treated with cement. administered.

When neutralizing both liquids (conventionally): J: 1llJThe following method is usually used.

That is, both solutions are first thoroughly mixed in a neutralization tank using a receiver.

In general, in the regeneration of ion exchange resin in condensate desalination equipment, the use of alkali is
Since there is more of the liquid, it becomes alkaline when both liquids are mixed.

Next, a small amount of the mixed alkaline I + waste liquid is collected from the medium tank 11, and neutralization titration is performed artificially using a beaker etc., and the amount of alkaline waste liquid stored in the neutralization tank is adjusted. Determine 1 d of neutralizing acid: ・ Next, add the determined amount of acid to the neutralization tank,
111. V) Neutralize the alkaline waste liquid by mixing it with 1b・'(Conventional neutralization of the alkaline waste liquid 1, ``S, 1.・Concerning'') 1+', +l
(Including artificial titration operations) There is also the disadvantage that neutralization itself is complicated by about 1° because it involves an artificial titration operation.

First, the alkaline waste liquid that is produced when the two recycled waste liquids discharged from the condensate desalination equipment are mixed is a strong alkali mainly consisting of a strong alkali such as strong soda, and its neutralization titration curve is The range of pHg to 7, which is the sum point, is, for example, the song a! in Figure 2. As shown in B, it has a steep slope and therefore has the disadvantage of being difficult to neutralize.

In other words, even if we perform neutralization titration on a small amount of alkaline waste liquid collected from the neutralization tank as mentioned above and calculate the amount of neutralizing acid for one cup of alkaline waste liquid stored in the neutralization tank, the amount of neutralizing acid actually in the neutralization tank may be calculated. When adding the -,
Although a slight mechanical error inevitably occurs, as mentioned above, the titration curve in the range of pH 9 to 7, which is neutralization 7, has a steep slope □', so acid addition in that range] The pH variation with respect to j1 is sensitive.

L, Therefore, even if a slight error occurs, the amount of silicic acid added may be insufficient due to the error, or &1-. , iA "A", and one addition of f111 medium [1p1-■
It's hard to eat.

Second, since the regenerated waste liquid from the condensate membrane 1'M side of the BWR type nuclear power plant contains radioactive substances at - and + h, as mentioned above, the artificial titration operation during the is undesirable in terms of reducing radiation exposure for workers and saving labor.

Thirdly, even if the conventional neutralization process is automated as is, the problems of neutralization and stability mentioned in the first part cannot be solved, and
The raw waste liquid from the condensate desalination equipment contains suspended matter such as iron oxide and fine ion exchange resin, which can contaminate pH electrodes and make it difficult to automate the process. There are also drawbacks.

In particular, the present invention is directed to converting the alkaline waste liquid, which is the recycled waste liquid of ion exchange resin generated from the condensate desalination equipment of the T3W Type 1/III I'-power power plant, which is mainly composed of alkaline alcohol, into the type described above. The purpose of the present invention is to solve the drawbacks of the previous methods and to automatically and accurately neutralize without the intervention of human operations.

That is, in the present invention, when neutralizing the alkaline waste liquid mainly composed of alkali in the neutralization tank, first, carbon dioxide gas is blown into the alkaline waste liquid in the neutralization tank to convert a part of the alkali into carbonate, After that, a small amount of alkaline waste liquid is passed through the piping from the neutralization tank at a constant flow rate, and acid at a constant concentration is injected into the piping stepwise for a certain period of time while changing the injection flow rate to adjust the pH after injection. By performing dynamic neutralization to measure, the injection flow rate of the acid necessary to neutralize the alkaline waste liquid flowing through the pipe is detected, and the amount of alkaline waste liquid stored in the neutralization tank is then measured. The flow rate of the alkaline waste liquid passed through the piping, the concentration of the acid, and the injection flow rate of the acid detected during dynamic neutralization were manually input to a control device with a calculation function, and the liquid was stored in the neutralization tank. A mono-alkaline waste liquid characterized by calculating the amount of acid to neutralize the alkaline waste liquid, and then adding the calculated amount of acid to a neutralization tank for mixing and neutralization. It concerns the sum method.

The present invention will be explained in detail below with reference to the drawings.

FIG. 1 is an explanatory diagram of a solo vehicle showing an example of an embodiment of the present invention. First, an acid +'1 beef cattle waste liquid and an alkaline regenerated waste liquid discharged from a condensate desalination apparatus are put into a neutralization tank 1. Then, thoroughly mix both waste liquids by circulating them once a month. 1.7 mentioned above? -, 1: When the two waste liquids are mixed, an alkaline waste liquid mainly becomes an alkaline waste liquid with a force of P1. - A part of J' Lucari is converted into carbonate. The amount of carbon dioxide gas 4 to be injected is preferably such that about 30 to 10% of the alkali becomes carbonate. Note that if the amount of the carbonate produced is a small amount of 30% or less, the pH buffering effect cannot be expected to be significant, and if the amount is 80% or more, the running cost will increase, so it is preferable.

To stir the liquid in the neutralization tank, as shown in Figure 1, open the circulation pipe 3 at the bottom of the neutralization tank, attach a spray tool such as a sparger 5 to the opening, and stir the liquid into the liquid. It is best to spray the liquid.

After converting a portion of the alkali into carbonate by the operations described in 2 below, the injection of carbon dioxide gas 4 is stopped and the following operations d-, l, and r are performed.

As mentioned above, the waste liquid contains a large amount of suspended matter such as iron oxide and fine ion exchange resin that are discharged during backwashing of the ion exchange resin layer, and therefore, the waste liquid is treated as described below while containing the suspended matter. - If dynamic neutralization is performed, suspended matter will arrive at the pH electrode, reducing its sensitivity and interfering with accurate pH measurement. Therefore, as shown in the figure, a small amount of alkaline and alkaline waste liquid is taken into the filtration pipe 6, and the cyclone separator 7 suspends relatively large particles of io-exchange resin. The treated liquid is filtered through a special filter 8 described below. The filter 8 has a cylindrical filter body 10 made of fine A-mesh wire mesh placed inside a cylindrical housing 9, and the alkaline waste liquid is passed through the housing 9 from the bottom.
The narrow gap formed by the filter body 10 and the height rAt, ,
'It passes with an upward flow of N4i, and this 31. By filtration with the filter 8 having a cooling shape, the above-mentioned gap is not clogged with suspended matter and the filter is effectively filtered.
Excess liquid force F j/7A body], '0 wo, 1l (l l,
-(,'t(Ij'+:/l,,'/+'Excess alkaline waste liquid flows from a part of the 1-noiler 8 to the neutralization tank via the flow pipe 6 and L7).

Next, with the filter 8, f bow 1, "h +-= yr=
γ Rutsunori waste liquid All waste liquid pipe] 1 is passed through b1 (1), and a sulfuric acid solution 1 diluted to 0.01 to 0.058 q/l, for example, is placed in the pipe before the mixer 12 such as a syringe mixer.
3. Inject using the metering pump 14. The pump 14 can vary its injection flow rate step by step for a certain period of time in response to a signal from a control device 15 having an arithmetic function. The pH after injection relative to the injection flow rate was determined by a thin film in the overflow tank 16 1)
H-〇-electrode] 7, converts the pH into an electrical signal via the transmitter 18, and inputs it to the control device 15. Through such dynamic neutralization, a sulfuric acid solution such that the pH of the mixed liquid in the overflow tank 16 reaches a predetermined neutralization point, for example, around 8, is added.
, Ko(i') Control the injection flow t Ql (/=/H)1
111 equipment] 5 is manually operated. ′! , to the neutralization pipe 11
・The alkaline waste liquid flow tilQ2 ()/1■) measured in 1 installation 11 [9] and the alkaline waste liquid in the neutralization tank l measured in the liquid level 20 attached to the neutralization tank] wave meter v
, (m″) is also input into the control device 15 + the concentration N(
eq//-), the control device 5 calculates the addition amount vz(A) of, for example, 98% sulfuric acid, which should neutralize the alkaline waste liquid stored in the neutralization tank 1, using the following equation.

(However, for 98% sulfuric acid, it is a6.teq/l.) After calculating the addition amount (2) by the calculation described in J-2 below, add 1 to I+\', i from the control device 15. .0 constant 111 Stop only pump 14 operation L 1i11'i
lζ°l Bonzo 2 operation and circulation piping: s + 7;
-: Vortex section '1'i II H Neutralizing plumber 1 liquid flow d' section: I: '+l 1., -C: L.

By the signal of the control device 15, t):, 9F3 of 9F3 of V:8 is driven, and the addition fig:V:8 is calculated by the above calculation.
Add 22% sulfuric acid to neutralization tank 1.

Note that the liquid amount is measured by, for example, the flow rate of the injection pump 21 and a timer built into the control device 15.

By adding sulfuric acid into the neutralization tank 1.

The alkaline waste liquid f(+, middle(ll) in the neutralization tank 1.

The pH of the neutralization solution is detected by the 6N flow tank 1 (Iil'Cf.
After confirming that the water supply reaches the neutralization point, stop driving the circulation pump 2 and then drive the discharge pump 6 □ to transfer the neutralized liquid to a concentrator, etc. As explained above, in the present invention, when pouring 4 u of alkali P1 waste liquid consisting of a strong alkali,
Carbonate gas is added to the alkaline waste liquid by 11° to convert some of the force alkali into carbonate, due to the pI4 buffering effect of the carbonate.

The neutralization curve in the range of pHg to "7", which is the neutralization point, can be made to have a gentle slope, so even if there is some mechanical error in the amount of acid added to the neutralization tank, it can be effectively neutralized. can be harmonized.

In addition, instead of the conventional artificial neutralization titration, a small constant flow rate of alkaline waste liquid is passed through the pipe from the neutralization tank, and acid at a constant concentration is sequentially injected into the pipe while changing the flow rate. Since dynamic neutralization is performed by injecting stepwise over a certain period of time and measuring the pH after injection, it is safe even if the waste liquid contains radioactive substances. Since the above-mentioned dynamic neutralization is performed after removing the suspended matter contained in the waste liquid using a special gas filter, the pH electrode etc. will not be contaminated with suspended matter.

The present invention will be explained in detail below.

-12- Example 1 Using a neutralization device as shown in Fig. 1, the acidic L IN liquid discharged from the condensate desalination device and the alkaline recycled waste liquid were neutralized as described above. That is, 6 liters of a mixed solution of both waste liquids was stored in a neutralization tank,
Stirring was carried out for 15 minutes at 60171"/H using a circulation pump. As a result of this stirring, the waste liquid in the neutralization tank became alkaline with a pH of 12.2. Next, while adding a total amount of carbon dioxide gas of about 20 ky to the circulation piping, stirring was continued. As a result, the pH of the alkaline waste liquid in the neutralization tank was 1006/-1.
Next, from the circulation pipe, connect the corresponding hole of 1, 1.004/II
Take out the liquid waste and insert it into the container and the housing with an inner diameter of 40.6111111.
1 (Outer diameter formed with mesh wire mesh: S”7.6
7. Process with a filter equipped with a mm h-i pot body. From the filter, 100t/1
'I took out the waste liquid. - Still let the Alunonori I11 waste liquid flow through the neutralization pipe, and add o, o25oq into the pipe.
/]-13-1 sulfuric acid solution] for 1 minute each 2.6]4/H to 62.3
The mixture was injected by increasing the flow rate by z and 61 t/H up to 1-/H, and the pH of the mixture was measured for each injection amount. As a result, the neutralization curve shown in A of FIG. 2 was obtained.

Next, the flow rate of the sulfuric acid solution to be made into pHB is Q1°51z/H.
, Flow rate of alkaline waste liquid flowing through the neutralization pipe Q2 , 1
00 t/H, concentration N of sulfuric acid solution.

Input the wave meter V 160 nl of the alkaline waste liquid stored in the neutralization tank 1 into a control device with arithmetic functions, and calculate the 9-day thiosulfuric acid solution to be added to the neutralization tank according to the above-mentioned formula. Amount v2. When zo and sz were mixed, the corresponding amount of 98% sulfuric acid was added to the neutralization tank and stirred thoroughly.
The pH after neutralization was .7.9, a value close to the standard neutralization point of 1.0.

On the other hand, for comparison, the recycled waste liquid from the same condensate desalination equipment in the second cycle was sufficiently stirred without adding carbon dioxide gas, and a small amount of waste liquid was sampled from the neutralization tank and neutralization titration was performed. 1,4-- However, as shown in the figure, the neutralization curve suddenly becomes 111'l4i1 (1,
-, no-'-' ll-6
iwo wl leopard', l-1-f-no full'r '6・中flll 41"f f" When cooled and thoroughly stirred, i-
7, middle 411fZ: pH 11mm), 1 and 1" mark middle f111), ll, l: 7/B/1 gap σ
), j<+ Z+ value.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the flow showing an example of the 11 children of the MII shop of Fukkatsu2, and Figure 2 is a graph showing the 11 neutralization curve, with the vertical axis showing pH and the horizontal axis showing the amount of 61 sulfuric acid. . Furthermore, the second
Does the song mA in the figure add carbon dioxide gas to the alkaline waste liquid in the neutralization tank? "
Curve 2 is the neutralization curve when dynamic neutralization is performed with 2 persons, and curve 2 is the neutralization 111 line when no carbon dioxide gas is added to the alkaline waste liquid in the neutralization tank. 11゜1...Neutralization tank ・''...Circulation pump 3・
...Circulation piping 4...Carbon dioxide gas 5...Sparger 6...7+1. if: "Mu piping 7...Zykron separator-8...Fino+〃--1,5-
- 9...Housing YuO...Filter body]]...
・Medium No. 11 pipe] 2...Mixer] 3...
Sulfuric acid KI liquid 14...Metric ponbu group...
Control device "6...Insect flow tank 1"/...pl
I electrode ] 8... Transmitter 19... Flow Hj-
Total 20...Liquid level gauge 21...Injection pump 22...98% sulfuric acid 23...Published by Debonpuno Gon. -16- Continued from page 1 ■Applicant Organo Co., Ltd. 5-5-16 Hongo, Bunkyo-ku, Tokyo

Claims (1)

[Claims] When neutralizing the alkaline waste liquid in the neutralization tank, which is mainly composed of alkali, carbon dioxide gas is blown into the alkaline waste liquid in the neutralization tank to convert a part of the alkali into carbonic acid. After that, a small constant flow of alkaline waste liquid 111 from the neutralization tank is passed through the piping, and acid at a constant concentration is sequentially injected into the piping without changing the flowmeter. We decided to carry out dynamic neutralization by injecting in stages over time and measuring 1 part after injection. It is necessary to detect the acid injection current meter and then store the alkali in the neutralization tank on January 11th.
7 (K llt of the waste liquid, (M l'+i of the alkaline waste liquid passed through the pipe, detected by the concentration of silicic acid and dynamic neutralization 17/this'+M acid injection flow rate)
Input the control function to the control ωIf j* position, and store the water in the neutralization tank. , lr anno [An alkaline waste solution characterized by calculating the amount of acid to neutralize 11 potash 1/1 waste vessels, and then adding the calculated amount of acid to the neutralization tank for mixing and neutralization. Automatic neutralization method.