JPS5836625B2 - Regeneration method of inorganic adsorbent - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the regeneration of inorganic adsorbents, and in particular to a method for regenerating inorganic adsorbents using liquid ammonia.

The use of inorganic adsorbents such as activated carbon (described below using activated carbon as an example) has been increasing in popularity in recent years. Activated carbon is also being used, and recycling spent activated carbon is now becoming increasingly important from a resource standpoint.

Conventionally, various methods have been considered for regenerating activated carbon, such as a thermal regeneration method and a wet method, but a perfect wet method has not yet been found.

This was because no fluid was found that could desorb all the organic matter adsorbed on activated carbon.

For example, activated carbon that has adsorbed phenol can be regenerated by washing it with a caustic soda solution and dissolving it into phenolate.
Various methods are also known, including a method for regenerating activated carbon by electrolytic oxidation using a salt solution.

However, in wet methods including these, the substances to be adsorbed are limited, and it is almost impossible to regenerate activated carbon, which has adsorbed various organic substances, such as activated carbon used for treating municipal sewage.

This is the first drawback of the wet regeneration method of activated carbon, and it lacks versatility.

Another disadvantage is that the fluid used for desorption must be treated, and the wet method is currently only applicable to activated carbon used for a specific purpose.

In addition, the thermal regeneration method is a method in which activated carbon is placed in a heating furnace, the substances adsorbed on the activated carbon are carbonized, and then the oxidizing gas (steam or air) supplied into the heating furnace is condensed with the carbide to regenerate the activated carbon. Therefore, the adsorption capacity after regeneration usually decreases significantly due to loss due to combustion of activated carbon itself, decrease in surface area, etc.

An object of the present invention is to provide a novel method for regenerating an inorganic adsorbent, which eliminates the drawbacks of the prior art described above and can also regenerate activated carbon used in the treatment of municipal sewage.

In view of this, the present invention regenerates ammonia, which is a gas at room temperature and pressure, by bringing it into contact with an inorganic adsorbent in a liquid state, and dissolving the adsorbed substance in the liquid ammonia.

In other words, in the regeneration method of the present invention, liquid ammonia is a solvent that dissolves organic substances very well and also dissolves salt compounds. It is possible to reproduce it without changing its properties.

In addition, in the conventional wet method, liquid is used at room temperature and pressure, and post-treatment of the liquid used for regeneration becomes a problem, but in the regeneration using liquid ammonia of the present invention, the pressure is released to normal pressure. By doing so, it can be gasified and easily separated from the adsorbed substance.

Although some ammonia remains on the inorganic adsorbent washed with liquid ammonia and gives off an ammonia odor, it can be removed by washing with water.

An embodiment of the present invention will be described below based on the accompanying drawings.

In FIG. 1, liquid ammonia in a liquid ammonia storage tank 1 is sent to a regeneration tower 7 by a high-pressure liquid sending pump 8, and maintained in a liquid state by a pressure regulating valve 6.

In this case, at a temperature (normal temperature) of 25°C, the saturated vapor pressure is 10 kg.
/crA, so if the pressure is maintained at about 15 kg/crA, ammonia can be sufficiently liquefied in the regeneration tower γ.

Liquid ammonia and activated carbon come into contact within the regeneration tower T, and the adsorbed substance is dissolved or reacted with the liquid ammonia and desorbed.

After the liquid ammonia containing the adsorbed substance exits the pressure control valve 6, it is released to normal pressure, and the ammonia and the desorbed organic substance are separated in the gas separator 5.

Gaseous ammonia is liquefied by a compressor 4, moisture is removed by a dehydration tower 2 (for example, an alumina-packed tower), and then returned to the liquid ammonia storage tank 1.

Here, the heat accompanying the compression and expansion of liquid ammonia is cooled or radiated by the blower fan 3, and the temperature is made uniform.

After performing the regeneration operation, the stop valves 12 and 14 are closed, the stop valve 13 is opened, and the three-way switching valve 16 is set to the compressor side to remove liquid ammonia in the regeneration tower with the compressor.

After that, the stop valve 13 is closed, and the three-way switching valves 15, 16, 1
Keep 7 so that it becomes a water flow path.

Water is sent to the regeneration tower 7 by the water washing pump 10, and a trace amount of remaining ammonia gas is dissolved in the water, and the water is introduced to the washing water tank 9.

Ammonia dissolved in water is H-type cation exchange resin tower 1
1 is removed.

When this cation exchange resin is saturated with ammonia,
Regenerated by washing with sulfuric acid water.

Most organic compounds are much more soluble in liquid ammonia than in water; hydrocarbons, alcohols, carboxylic acids, esters, aldehydes, ketones, ethers, alkyl sulfates, amines, amides, heterocyclic compounds, etc. have very high solubility. big.

Also, salts (NH4Ci) and metals (alkali metals, etc.)
It is also known that it is a solvent that dissolves carbon, and it has been found that it is an excellent solvent for use in the regeneration of inorganic adsorbents such as activated carbon.

Example 1 Regeneration by this method was investigated using sodium dodecylbenzenesulfonate (hereinafter referred to as DBS), which is one of the detergents such as ABS that cannot be removed by the activated sludge method, as an adsorbed substance.

The equilibrium adsorption amount of 1 g of spherical activated carbon at 60 ppm of DBS2 is 48 ■ DBS/P activated carbon. After drying this activated carbon, 51 g of activated carbon is placed in a regeneration tower, and 1 g of liquid ammonia is added to the activated carbon.
．． The flow rate was 2 ml/min.

At this time, the room temperature was 21℃, and the pressure was adjusted to 20kg using the pressure control valve.
/crti was maintained.

Figure 2 shows the relationship between the distribution time of liquid ammonia (the amount of liquid ammonia) and the regeneration rate.

Here, the regeneration rate is the equilibrium adsorption amount of DBS of the activated carbon after washing with liquid ammonia and the equilibrium adsorption amount (
(from the adsorption isotherm).

As is clear from the figure, the regeneration rate was 55% with a flow time of 15 minutes and a liquid ammonia amount of 18 ml (approx.
! , 24f), a regeneration rate of approximately 85% was obtained.

Further increase the amount of liquid ammonia to 108rrLl (36g)
A regeneration rate of 92% was obtained.

If the amount was higher than this, the reproduction rate did not improve much.

The reason why a 100% regeneration rate could not be obtained is considered to be that it is extremely difficult to desorb the adsorbed substances that entered the micropores of the activated carbon.

However, if a regeneration rate of 80 to 90% is achieved, it can be said that the objective has been fully achieved.

DBS probably became an ammonium salt and dissolved in liquid ammonia.

After more than ten experiments, a thin layer of white powder was observed near the inner surface of the inlet pipe of the gas separator 50 and on the inner surface of the separator.

Example 2 Regeneration by this method was investigated using the amino acid phenylalanine as a representative of amine and carboxylic acid compounds as an adsorbed substance.

As in Example 1, spherical activated carbon was used, and the equilibrium adsorption amount at 110 ppm of phenylalanine was 120 μ/1 activated carbon.
Example 10 51 of this adsorbed activated carbon was put into a regeneration tower.
Playback was performed under these conditions.

Figure 3 shows the relationship between the distribution time of liquid ammonia (the amount of liquid ammonia) and the regeneration rate.

A regeneration rate of 78% was obtained with 7 amounts of liquid ammonia (18rrLl (12P)), indicating that phenylalanine dissolves much better in liquid ammonia than in the previous DBS.

It was found that approximately 90% regeneration was possible with an amount 4.8 times the weight of activated carbon.

In this case as well, it is thought that the carboxyl group of phenylalanine becomes an ammonium salt and dissolves in liquid ammonia.

Example 3 Regeneration was carried out using this method using phenol as the adsorbed substance.

Spherical activated carbon was used as in Example 1, but the equilibrium adsorption amount at 200 ppm of phenol was 160.
Regeneration was carried out under the same conditions as in Example 1 using /1 activated carbon.

FIG. 4 shows the relationship between the distribution time of liquid ammonia (the amount of liquid ammonia) and the regeneration rate.

As is clear from the figure, phenol is more soluble in liquid ammonia than phenylalanine.

In other words, the regeneration rate is 82 with a liquid ammonia amount of 18rrLl.
%, which is 2.4 times the weight of activated carbon, indicating that regeneration is possible with small amounts of liquid ammonia.

Furthermore, a regeneration rate close to 100% was obtained with an amount of liquid ammonia of 108 liters and 71 liters (82 grams).

This result shows that it is a very effective solvent for the desorption, or regeneration, of alcohols and benzene with hydroxyl groups from activated carbon.

Comparative Example I Activated carbon (49μ/g activated carbon) 51 which had adsorbed DBS was placed in a regeneration tower, and the regeneration tower temperature was maintained at 110°C and the regeneration tower internal pressure was maintained at 60ky/c4 and the flow rate was 1.75TILl/Tni.
! Regeneration was performed at L (pump instruction) for 1 hour.

The regeneration rate was 22%, and regeneration was difficult under these conditions.

By the way, under these regeneration conditions, ammonia is in a high-density gas state.

Comparative Example 2 Activated carbon adsorbed with DBS (4877I!l; I/
1 activated carbon) into the regeneration tower, the regeneration tower temperature was 140℃,
The regeneration tower pressure was maintained at 120 kg/crA, and the flow rate was 1.
It was regenerated at 75 ml/min for 1 hour.

The DBS adsorption amount of activated carbon after regeneration is 20.21n9
/P activated carbon, and the regeneration rate was 42%.

Under these regeneration conditions, ammonia was in a supercritical state, and the regeneration rate was better than when a high-density gas was used, but it was less than half the regeneration rate when the liquid of Example 1 was used.

As described above, in the present invention, by using ammonia in a liquid state, it is possible to regenerate inorganic adsorbents such as activated carbon that have adsorbed various organic substances.

[Brief explanation of drawings]

Figure 1 is a system diagram for carrying out the present invention, and Figures 2, 3, and 4 show the relationship between liquid ammonia flow time (liquid ammonia amount) and regeneration rate for different adsorbed substances, respectively. It is a diagram. 1...Liquid ammonia storage tank, 2...
...Dehydration tower, 4...Compressor, 5...
...Gas separator, 6...Pressure control valve, 7...
... Regeneration tower, 8 ... High pressure liquid pump, 9.
. . . Washing water tank, 10 . . . Washing pump, 11 . . . Cation exchange resin tower.

Claims (1)

[Scope of Claims] 1. A method for regenerating an inorganic adsorbent by washing it, characterized in that liquid ammonia (excluding supercritical fluid) is used as a cleaning agent. 2. A method for regenerating an inorganic adsorbent by washing it, which comprises washing the inorganic adsorbent with liquid ammonia (excluding supercritical fluid) and then washing it with water. 3 In a method of regenerating an inorganic adsorbent by washing it, the inorganic adsorbent is washed with liquid ammonia (excluding supercritical fluid) to dissolve the adsorbed substance in liquid ammonia, and then the liquid ammonia is gasified. A method for regenerating an inorganic adsorbent, which is characterized by separating adsorbed substances.