JPS5817127B2 - How to regenerate granular activated carbon - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for regenerating granular activated carbon used in a neutralization treatment device for recycled waste liquid from an ion exchange device.

In recent years, the water quality of water sources used for industrial water has become increasingly polluted, and industrial water containing large amounts of organic matter has no choice but to be used as raw water for ion exchange equipment such as water purification equipment. be.

When such raw water is treated with a water purification system, a coagulation sedimentation device is generally installed as a pretreatment, but not all of the organic matter in the raw water is removed by the coagulation sedimentation treatment, and only some of the organic matter is removed. The organic matter will be supplied to the pure water production equipment.

Furthermore, in most cases, organic substances contained in natural water are adsorbed by anion exchange resins, and most of them are desorbed when the anion exchange resins are regenerated.

Therefore, the organic matter present in the raw water is contained in the recycled waste liquid of the anion exchange resin in a concentrated form, and in some cases, the COD concentration may reach 100 pPasO or more.

The recycled waste liquid containing a large amount of organic matter cannot be discharged simply by neutralizing it, but it is necessary to remove the organic substances in the recycled waste liquid by some method.

One possible method for removing the organic matter is to subject the liquid after neutralization to coagulation and sedimentation treatment, but the organic matter in question is organic matter that could not be removed by coagulation and sedimentation treatment, which is a pretreatment for the water purification equipment. Therefore, even if this is subjected to coagulation and precipitation treatment again, the removal effect is small.

Another possibility is to split the organic matter using an oxidizing agent such as sodium hypochlorite, but this method requires a large amount of oxidizing agent, so it is difficult to say that this is an economical method. The best way is to do so.

There are two types of activated carbon: powdered activated carbon and granular activated carbon, but the former is difficult to regenerate and is disposable, whereas the latter can be activated and reused by roasting and recycling, so the latter is better in terms of cost.

On the other hand, when acidic waste liquid and alkaline waste liquid generated from pure water production equipment are mixed and neutralized, there is a problem in that a large amount of insoluble precipitates are generated in the neutralized liquid. The waste liquid contains a large amount of cations such as calcium ions, magnesium ions, and sodium ions along with excess acid, and the alkaline waste liquid generated from the anion exchange resin regeneration process contains excess alkali and chlorine. ions, sulfate ions, carbonate ions, and anions such as silica.

Therefore, when the two are mixed, insoluble precipitates caused by calcium carbonate and the like are generated, and it is currently necessary to separate these insoluble precipitates.

The present inventors have proposed a method for neutralizing the recycled waste liquid of an ion exchange device, which contains a large amount of organic matter and insoluble precipitates as explained above, by using an acidic waste liquid discharged from a cation exchange resin regeneration process. The alkaline waste liquid discharged from the anion exchange resin regeneration process is received in a separate receiver tank, and the sessile liquid is taken out from the receiver tank and mixed instantly to bring the pH to 3 or less, and then the acidic mixed solution is aerated or deaerated. Then, the acidic mixture from which the free carbonate was removed is passed through granular activated carbon to adsorb and remove the organic matter in the solution, and then an alkali is added to the treated solution of the granular activated carbon and re-treated. A neutralization treatment method for neutralization was proposed.

In this method, the pH of both solutions is instantaneously mixed to bring the pH to 3 or less, the free carbonic acid generated therein is removed, the acidic mixture is passed through granular activated carbon, and then the granular activated carbon-treated water is alkalised. This method prevents the generation of insoluble precipitates by releasing carbonate ions as free carbonic acid, and removes organic matter by setting the pH of the solution to the acidic side and passing it through granular activated carbon. Neutralization treatment is performed by increasing adsorption capacity.

The present invention relates to a method for regenerating granular activated carbon of a neutralization treatment device as described above, in which the amount of organic matter adsorbed by the regenerated activated carbon is recovered to the same level as new activated carbon, and the organic matter adsorbed by the regenerated activated carbon is Effectively adsorbs and removes
Furthermore, the main objective is to economically neutralize the alkaline washing waste liquid and acid washing waste liquid used for the regeneration treatment of activated carbon without providing a separate neutralization device.

That is, the present invention receives the acidic waste liquid discharged from the cation exchange resin regeneration process and the alkaline waste liquid discharged from the anion exchange resin regeneration process in separate receiving tanks, and extracts both liquids from the receiving tanks and instantly processes them. The acidic mixture is mixed to a pH of 3 or less, and then the acidic mixture is aerated or deaerated to remove free carbonic acid from the liquid.Then, the acidic mixture from which free carbon particles have been removed is passed through granular activated carbon to submerge it in the liquid. adsorbs and removes organic matter,
Next, when regenerating the granular activated carbon in the neutralization treatment equipment that re-neutralizes the granular activated carbon by adding alkali to the treatment solution, the alkali cleaning is performed after roasting and regeneration, and then the acid cleaning is performed, and the alkali cleaning brightness is The present invention relates to a method for regenerating granular activated carbon, which comprises mixing a liquid and the acid washing waste liquid with the alkaline waste liquid and the acidic waste liquid, respectively.

The present invention will be explained in detail below.

In general, granular activated carbon saturated with organic matter can be activated and reused by being roasted and regenerated in a conventional manner using a regeneration furnace such as a vertical furnace or rotary kiln. The granular activated carbon that has saturated adsorption is taken out, roasted and regenerated in a regeneration furnace, and then filled into the activated carbon tower of the neutralization treatment equipment and passed through the decarboxylated acidic mixture.The pH of the treated solution for the granular activated carbon increases. However, it turned out that it became alkaline and could not achieve the intended purpose.

The reason why the pH of the granular activated carbon treatment solution increases and becomes alkaline is that calcium, magnesium, etc. contained in the treated solution are adsorbed to some extent by the granular activated carbon, and this is converted into calcium oxide, magnesium oxide, etc. during roasting and regeneration. It is thought that this is because the acidic mixture remains in the granular activated carbon as oxides such as oxides, and the granular activated carbon also adsorbs the acid in the liquid to be treated to some extent. It is undesirable for the value to rise.

In other words, in the above-mentioned neutralization treatment device, the purpose of making the pH of the mixed liquid acidic and passing the liquid through the granular activated carbon is to make the pH of the mixed liquid acidic so that the amount of organic matter adsorbed on the granular activated carbon is reduced, so that the pH increases. This is undesirable because the amount of organic matter adsorbed decreases.Also, when the acidic mixture passes through the granules, the pH increases and becomes alkaline, since the mixture contains a large amount of magnesium ions. This is not preferable because magnesium hydroxide precipitates within the activated carbon layer and increases pressure loss.

Therefore, it is preferable to wash the regenerated activated carbon with an acid after roasting and regenerating the granular activated carbon.

In other words, by washing the regenerated activated carbon with acid, the calcium oxide and magnesium oxide remaining on the activated carbon dissolve and separate from the activated carbon, and by contacting the activated carbon with acid in advance, the activated carbon sufficiently adsorbs the acid. Even if the treated recycled activated carbon is packed into an activated carbon tower of a neutralization treatment device for recycled waste liquid and the decarboxylated acidic mixture is passed therethrough, the pH of the granular activated carbon after treatment will not increase.

However, if the roasted and regenerated activated carbon is simply washed with acid, the activated carbon will not be activated to that extent, and the organic matter adsorption amount, that is, the COD adsorption amount of the new activated carbon, and the COD adsorption amount of the regenerated activated carbon are large, as shown in Figure 2. It became clear that there was still a gap.

Generally, when granular activated carbon saturated with organic matter is roasted and regenerated by a conventional method, the amount of COD adsorbed by the regenerated activated carbon is usually almost equal to that of new activated carbon. Regarding the roasted and regenerated granular activated carbon used in the neutralization treatment device of the exchange device, its CO
The amount of D adsorbed was approximately 50% lower than that of the new product.

As a result of various studies on the regeneration method of the granular activated carbon, the present inventors found that in regenerating the granular activated carbon, after roasting and regenerating, first alkali cleaning and then acid cleaning were performed, as shown in Fig. 2. The COD adsorption amount of recycled activated carbon is almost equal to that of new carbon, and by filling the activated carbon of the neutralization treatment equipment with the recycled activated carbon, it is possible to effectively adsorb and remove organic matter without increasing the pH of the treated liquid. I found out.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an explanatory diagram showing the flow of a neutralization treatment apparatus that implements the method of the present invention and the flow of a regeneration facility for granular activated carbon used in the neutralization treatment apparatus.

First, to explain the flow of the neutralization treatment equipment, the acidic waste liquid 1 discharged from the cation exchange resin regeneration process and the alkaline waste liquid 2 discharged from the anion exchange resin regeneration process are transferred to the pickling liquid receiving tank 3 and the alkaline waste liquid respectively. The waste liquids are received separately in a receiving tank 4, and each waste liquid is taken out using a pickling liquid pump 5 and an alkaline waste liquid pump 6, and is instantaneously mixed in an ejector 7.
The pH after mixing is set to 3 or less.

Generally, recycled waste liquid from ion exchange equipment such as water purification equipment has a larger alkali equivalent than acid equivalent, so the pH was detected by a pH controller 8 installed immediately after the ejector 7, and the pH was linked to the pH controller 8. pH 3 with acid injection pump 9
Add 10 ml of acid so that:

Next, the acidic mixture having a pH of 3 or less is flowed into the upper part of the decarboxylation tower 11, and air is blown from the lower part of the decarboxylation tower using the blower 12 to remove free carbonic acid from the acidic mixture.

Next, the acidic mixture from which free carbonate has been removed is pumped to the decarbonation liquid pump 1.
The liquid is passed in series through adsorption towers 15A and 15B filled with granular activated carbon 14 which has been regenerated using No. 3, and organic substances in the liquid are adsorbed and removed.

Since the treated liquid in the adsorption tower is acidic, it is re-neutralized with alkali, but in this case also, ejector 7/ is used, and the pH is adjusted so that the pH of the liquid immediately after ejector 7' is around 7, which can be discharged.
Re-neutralization is carried out while regulating the flow rate of the alkali 17 using the H controller 8' and the regulating valve 16 interlocked therewith.

The neutralization device operates as described above (by reducing the pH of carbonate ions contained in the alkaline waste liquid 2 to 3 or less, releasing it as free carbonic acid in the decarboxylation tower 11, and then converting the pH-acidic mixed liquid into granules. It is treated with activated carbon,
Neutralizes without generating insoluble precipitates, and
During the neutralization process, organic substances are efficiently adsorbed and removed using granular activated carbon.

Next, to explain the regeneration of granular activated carbon of the present invention, the adsorption towers 15A and 15B shown in FIG.

15c is a so-called two-column merry-go-round system, and the adsorption tower 15c in the figure passes 15c in the previous cycle.
→ 15A, the granular activated carbon in the adsorption tower 15c in the previous stage became saturated with organic matter and was cut off from the liquid passageway.

The adsorption tower 15 is cut off from the liquid passage in this way.
The entire amount of the granular activated carbon 14 in c is transferred in slurry form to the granular activated carbon receiving tank 19 using the transfer pipe 18.

Next, the granular activated carbon 14 in the receiving tank 19 is transferred to the rotary kiln 2 while draining the granular activated carbon through a dehydrator 20.
1, and the granular activated carbon is roasted and regenerated by a conventional method.

Note that the regeneration furnace for granular activated carbon is not limited to a rotary kiln, but a vertical furnace or the like may also be used.

The roasted and regenerated granular activated carbon is dropped into water in the quench tank 22 to be rapidly cooled, and then the regenerated carbon is again charged into the adsorption tower 15c using the transfer pipe 18'.

After filling the adsorption tower 15c with a specified amount of regenerated granular activated carbon, the following treatment is performed.

First, alkaline cleaning liquid 23 is passed through the granular activated carbon layer for alkaline cleaning, and alkaline cleaning waste liquid 24 is sent to alkaline waste liquid receiving tank 4 and mixed with alkaline waste liquid 2 .

As the alkaline cleaning liquid 23 to be used, a 2 to 10% (by weight) caustic soda aqueous solution is suitable, and the amount of the liquid is 1 to 6 times the volume of the granular activated carbon.

Note that when the alkaline concentration of the alkaline waste liquid 2 to be neutralized is within 2 to 10% (by weight), the alkaline waste liquid 2 can also be used as the alkaline cleaning liquid 23.

In addition, if the alkaline concentration of alkaline waste liquid 2 is low,
It is also possible to add a concentrated alkali to the alkaline waste liquid 2 to raise the alkali concentration to a predetermined level and use this as an alkaline cleaning liquid.

After the granular activated carbon is washed with alkali, it is thoroughly washed with water, and then an acid washing liquid 25 is passed through the granular activated carbon for acid washing, and the acid washing waste liquid 26 is sent to the pickling liquid receiving tank 3 and mixed with the acidic waste liquid 1.

As the acid washing liquid 25 to be used, a 0.1 to 1% (by weight) hydrochloric acid aqueous solution is suitable, and the amount of the liquid is 1 to 10 times the volume of the granular activated carbon.

Note that the acid concentration of the acidic waste liquid 1 to be neutralized is 0.1.
~1% (weight), the acidic waste liquid 1 can be used as the acid cleaning liquid 25, and if the acidic waste liquid 1 has a low acid concentration, add a concentrated acid to the acidic waste liquid 1 to reach the predetermined acid concentration. It may be used as an acid cleaning solution.

After washing the granular activated carbon with acid in this way, it is thoroughly washed with water and kept on standby for the next time the liquid is passed.

The used granular activated carbon in other adsorption towers is regenerated in the same way by the above procedure.

In the present invention, the above-mentioned alkaline washing waste liquid and acid washing waste liquid are mixed with alkaline waste liquid and acidic waste liquid, respectively.
The granular activated carbon that is subject to alkaline cleaning and acid cleaning has already been roasted in a regeneration furnace and the adsorbed organic matter has decomposed, so even if both cleaning waste liquids are mixed with alkaline waste liquid and acidic waste liquid, respectively, organic substances will increase. There's nothing to do.

In addition, when carrying out alkali washing and acid washing of the granular activated carbon after roasting and regeneration, it is necessary to carry out the acid washing after the alkali washing.

For example, when granular activated carbon that has been washed with alkali is used to adsorb organic matter in an acidic mixed solution, the pH of the treatment solution increases in the early stage of liquid passage, insoluble precipitates precipitate within the granular activated carbon layer, and organic matter is added to the treatment solution. This is not desirable as it may leak.

As explained above, according to the regeneration method of the present invention, the amount of organic matter (COD) adsorbed by the regenerated activated carbon can be made almost equal to that of new activated carbon, and by providing the regenerated treated carbon to a neutralization device, the pH of the treated liquid can be adjusted. It is possible to effectively adsorb and remove organic substances without increasing the

Furthermore, by mixing the alkaline washing waste liquid and acid washing waste liquid generated during alkali washing and acid washing with the alkaline waste liquid and acidic waste liquid targeted for the neutralization treatment equipment, it is possible to perform neutralization treatment at the same time. There is no need to install a separate device for neutralizing waste liquid and acid washing waste liquid.

The present invention will be explained in detail below.

EXAMPLE The acidic waste liquid and alkaline waste liquid shown in Table 1 were neutralized based on the neutralization process flow shown in FIG.

That is, an acidic waste liquid of 9i/H and an alkaline waste liquid of 14i/H are mixed in an ejector, and the p of the mixed liquid immediately after the ejector is
35% (by weight) hydrochloric acid was injected using an injection pump equipped with an electroservo so that H was 2.5 to 3.0, and then the acidified mixture was placed inside a cylindrical Raschig ring made of vinyl chloride (inner diameter Inner diameter 7 filled with 40mm, length 30mm)
70i1, height 2.740 mN, and free carbonic acid in the acidic mixture was removed by blowing air at about 65 ON/H from the bottom of the decarboxylation tower with a blower.

Next, the mixed liquid from which free carbon dioxide has been removed is passed in series through two adsorption towers each having an inner diameter of 1,800 mm and a height of 4.50011 mm each filled with 6 pieces of granular activated carbon Diahope 008 (registered trademark). of organic matter is adsorbed, and 0.3% caustic soda solution is added to the treated liquid in the adsorption tower to adjust the pH.
was neutralized to around 7.

At this time as well, the ejector was used as a mixer, the pH immediately after the ejector was measured with a pH controller, and the flow rate of the caustic soda solution was adjusted using a control valve linked to this pH controller.

When 460 times the amount of the thus decarboxylated acidic mixed solution was passed through the granular activated carbon in the first column, the granular activated carbon was saturated with organic matter, so it was roasted and regenerated under the following conditions.

Conditions for roasting and regeneration Regeneration furnace Rotary kiln Regeneration temperature: 950°C Regeneration time: 40 minutes Next, the roasted and regenerated granular activated carbon is passed through 0.5% hydrochloric acid aqueous solution, which is 1.7 times the volume of the granular activated carbon, at SV2. After draining, wash thoroughly with water, and on the other hand, pass 3 times the amount of 4% caustic soda aqueous solution to the granular activated carbon volume at SV2, wash thoroughly with water, and add 0.5 times the amount of 1.7 times the volume of granular activated carbon.
% of hydrochloric acid aqueous solution was passed through it at SV2 and thoroughly washed with water.

The equilibrium adsorption amount of COD was measured for the acid-washed sample, the alkali-washed sample, and the acid-washed sample, as well as the alkaline waste liquid, using the method described below.

Note that an alkaline waste liquid whose pH was adjusted to 3.0 by adding hydrochloric acid was used as an equilibrium adsorption liquid.

Equilibrium adsorption measurement method 500rrll of the alkaline waste liquid shown in Table 1 whose pH was adjusted to 3.0 was collected in each of four Erlenmeyer flasks, and 50ml of activated carbon pulverized to 325 mesh or less was added to each of the four Erlenmeyer flasks. ~.

100~, 200~, 300~ are added and the organic matter is adsorbed while being vibrated at a constant temperature for 120 minutes.
Measure the COD concentration of the liquid and calculate the COD at each concentration.
D equilibrium adsorption amount was calculated.

Using this method, the equilibrium adsorption amount was measured for three types of samples: activated carbon that had been acid-washed only, activated carbon that had been acid-washed after alkaline washing, and new activated carbon.

When the equilibrium adsorption amount of each activated carbon was measured using the method described above, an equilibrium adsorption isotherm as shown in FIG. 2 was obtained.

As is clear from FIG. 2, for example, COD concentration 50~a
In terms of sO/A, the equilibrium COD adsorption amount of recycled coal that has been acid-washed only is 130 to as O/9, whereas the equilibrium COD adsorption amount of recycled coal that has been acid-washed after alkali washing is 2.
The adsorption isotherm increased to 50rr19as O/g, and an adsorption isotherm almost equal to that of new activated carbon was obtained.

Next, the regenerated coal that has been acid washed after alkali washing is refilled into the adsorption tower, and the alkaline waste liquid mixed with the alkaline washing waste liquid and the acidic waste liquid mixed with the acid washing waste liquid are processed into the neutralization treatment equipment shown in Figure 1. When neutralized, 5p of insoluble precipitate
- A treated liquid with a COD of 10 pI) Illas O or less was obtained, and there was no difference between the pH at the inlet and the pH at the outlet of the adsorption tower, and no increase in pressure loss occurred.

Furthermore, the processing amount of recycled activated carbon did not decrease.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the flow of a neutralization treatment equipment that implements the method of the present invention and the flow of a regeneration facility for granular activated carbon used in the neutralization treatment equipment. It is a graph showing the COD equilibrium adsorption isotherm of each activated carbon for the alkaline waste liquid discharged from the regeneration process of the anion exchange resin of the water production device, where the vertical axis shows the COD equilibrium adsorption amount and the horizontal axis shows the COD concentration. 1... Acidic waste liquid, 2... Alkaline waste liquid, 3... Pickling liquid receiving tank, 4... Alkaline waste liquid receiving tank, 5...... Pickling liquid pump, 6...
...Alkali waste pump, 7...Ejector, 8
... pH controller, 9 ... acid injection pump, 10 ... acid, 11 ... decarboxylation tower, 1
2... Blower, 13... Decarbonated liquid pump, 14... Granular activated carbon, 15... Adsorption tower, 16... Control valve , 17... Alkali, 18... Transfer pipe, 19... Granular activated carbon receiving tank, 20... Dehydrator, 21...
・Rotary kiln, 22...Quick cooling tank, 23・
...Alkaline cleaning liquid, 24...Alkali washing waste liquid, 25...Acid washing liquid, 26...
・Acid cleaning waste liquid.

Claims (1)

[Claims] 1 The acidic waste liquid discharged from the cation exchange resin regeneration process and the alkaline waste liquid discharged from the anion exchange resin regeneration process are received in separate receiving tanks, and both waste liquids are taken out from the receiving tank and instantly mixed to bring the pH to 3. The acidic mixture is then aerated or deaerated to remove free carbonic acid in the liquid, and then the acidic mixture from which free carbonic acid has been removed is passed through granular activated carbon to adsorb and remove organic matter in the liquid, Next, when regenerating the granular activated carbon in the neutralization treatment equipment that re-neutralizes the granular activated carbon by adding alkali to the treated solution, the alkaline cleaning is performed after roasting and regeneration, and then the acid cleaning is performed, and the alkali cleaning waste liquid is and a method for regenerating granular activated carbon, which comprises mixing the acid washing waste liquid with the alkaline waste liquid and the acidic waste liquid, respectively.