JPH0117739B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for separating and removing relatively small diameter ash produced during activated carbon regeneration.

Generally, granular activated carbon used for water treatment such as organic wastewater is regenerated in an activated carbon regeneration furnace and used repeatedly. By the way, when activated carbon is regenerated many times, the ash generated during the regeneration and the ash in the inflow water accumulate in the water treatment system. If ash accumulates in the water treatment system, not only will the physical adsorption capacity of activated carbon decrease, but the ash will migrate into the purified water after treatment, causing the purified water to become cloudy or reducing the regeneration capacity of the regeneration equipment. Problems such as For this reason, it is necessary to remove the ash from the activated carbon, but with the technology developed so far, it is difficult to separate and remove the ash, which has a particle size that is approximately equal to or smaller than the finely divided powdered activated carbon or granular activated carbon. Currently, activated carbon is recycled and used a predetermined number of times and then disposed of along with the ash.

The present invention has been made in view of the above circumstances, and its purpose is to provide a method that can efficiently separate and remove relatively small-diameter ash from activated carbon.

The present invention will be explained below.

In the present invention, activated carbon is regenerated in a regeneration furnace, and then classified and separated into an activated carbon system with at least a small ash content and a relatively large particle size, and a system of activated carbon and ash with a relatively small particle size, Water is added to the mixture containing the activated carbon, which has a relatively small particle size, and ash to dissociate the activated carbon particles and ash particles, and the ash is separated and removed by suspending the ash and allowing the activated carbon to settle.

The activated carbon is granular activated carbon with a size of about 4 to 100 meshes, which is regenerated in an activated carbon regeneration furnace, and then classified by sieving or sedimentation to reduce the size to about 100 meshes (149μ) or less, or about 200 meshes or less, for example.
A mixture containing finely broken activated carbon having a relatively small particle size of mesh size (74μ) or less and ash produced in a regeneration furnace is obtained. Most of the activated carbon with a large particle size has its ash removed through this classification operation, is recovered as recycled activated carbon, and is used again. This ash is an inorganic substance whose particle size is approximately the same as or smaller than that of powdered activated carbon or granular activated carbon, and is produced when organic substances adsorbed on activated carbon are oxidized and incinerated in an activated carbon regeneration furnace. This corresponds to the ignition residue specified in .

The above regeneration furnace is an activated carbon regeneration furnace such as a multistage furnace, rotary furnace, moving bed, or fluidized bed, and the activated carbon regeneration temperature is
The temperature is between 300℃ and 800℃.

When water is added to a mixture containing relatively small particle size activated carbon and ash, the solids concentration should be approximately 10% or less, but the amount of water added should be limited to the slurry of the mixture to which the water is added. Depends on total hardness. That is, unless the total hardness of the slurry is low, activated carbon and ash cannot be separated sufficiently, and the amount of water added must be increased. When the total hardness of the slurry is low, for example, when the total hardness is 100 or less, activated carbon and ash are easily separated. The total hardness of the added water is relatively high, and the total hardness of the slurry of the mixture is 100.
In the above cases, sodium hexametaphosphate,
Add an ion sequestering agent such as EDTA. This is due to the following reasons. Generally, the interfacial potential ζ of a particle is expressed by the following equation.

ζ=4πEd/D Here, E: Charge of the particles d: Average thickness of the diffusion double layer D: Dielectric constant of the dispersion medium When the total hardness of the slurry is high, the dielectric constant D of the dispersion medium is large and the interfacial movement is Potential ζ is low. If the interfacial potential ζ is low, the activated carbon and ash particles will not be sufficiently dissociated. For this reason, adding an ion sequestering agent to act as a dispersant helps dissociate the activated carbon and ash particles.

In addition, when adding sodium hexametaphosphate, the addition amount Q is calculated|required by the following formula.

Q = German hardness x 130 (mg/) However, German hardness = total hardness x 0.056 The above formula is the amount added that theoretically makes the hardness of the slurry of the mixture zero, but in reality it is the amount added to the mixture or added water. Sodium hexametaphosphate is consumed by the iron ions, barium ions, zinc ions, etc. that are present, so the total hardness of the slurry is reduced to approximately 100 or less, depending on the state of the activated carbon to be regenerated and the type of water added. It can be used as a guide.

Therefore, the water added to the mixture is preferably clean water with a relatively low total hardness, such as tap water, industrial water, or well water.

Next, regarding the equipment for carrying out the above method,
Referring to FIG. 1, which is an example of application to wastewater treatment, organic wastewater is sent from a pipe 30 to a fixed bed or fluidized bed type adsorption tower 31, in which organic matter is physically removed by granular activated carbon. The water is adsorbed, becomes purified water, and is discharged to the outside through the pipe 32. On the other hand, the granular activated carbon adsorbing organic matter is sent to a dehydration hopper 34 through a pipe 33, dehydrated, and then sent to a regeneration furnace 35. In the regeneration furnace 35, 300 to 400 granular activated carbon
It is heated at 0.degree. C. to evaporate moisture and desorb and carbonize adsorbed substances, and then activated and regenerated with oxidizing gas heated at 700 to 800.degree. The regenerated granular activated carbon is sent to a sieve 37 to classify the finely broken activated carbon and the ash produced during regeneration, and then returned to the adsorption tower 31. Moreover, fresh water is added to the mixture containing finely broken activated carbon and ash to form a slurry, and the mixture is sent to the ash separation tank 40.

The amount of fresh water to be added is determined by determining the relationship between the total hardness of the slurry in which the fresh water is added to the mixture and the amount of water added, and then determining the amount of water added and the amount of ion sequestering agent added according to the total hardness as described above. Decide accordingly. In the ash separation tank 40, activated carbon settles and accumulates at the bottom (see curve A of the graph in Figure 2), and about 50% of the absolute amount of ash is dissociated and suspended in the separated water, and the remaining 50% is The ash remains in the activated carbon and settles to the bottom. The activated carbon settled at the bottom of the ash separation tank 40 is returned to the adsorption tower 31 through the pipe 41 after the ash content is separated and removed in half. Also,
The ash separated and removed from the activated carbon is sent to the ash concentration tank 43 through a pipe 42 in a dissociated and suspended state in separated water, where it is coagulated and precipitated by a cationic coagulant of 1 to 2 ppm. (See curve B in the graph of Figure 2). The flocculated and settled ash becomes a concentrated slurry of approximately 10%, which is transferred to pipe 44.
After being sent to a dehydrator 45 and dehydrated, it is discharged to the outside.

By separating and removing ash in this manner, it becomes possible to maintain the ash concentration in the water treatment system at a constant low concentration, allowing water treatment to be performed in a stable state and improving treatment efficiency. In addition, approximately
With only less than 0.5% recycled activated carbon transferred, 99.5
% or more of the recycled activated carbon is recovered and sent to the adsorption tower 31 again.
will be returned to. Furthermore, there is no fear that ash will migrate into the purified water and cause it to become cloudy.

In addition, in the above example, the clear water after the ash content has been separated in the ash concentration tank 43 may be effectively used again as addition water to the mixture without being discharged. Furthermore, in the above example, fresh water was used as the water added to the mixture, but wastewater to be treated may be used instead of this fresh water. In this case, the clear water from the ash concentration tank 43 is sent to the adsorption tower 31. If you do it like these,
Although the total hardness of the slurry of the mixture may be high and a large amount of sequestering agent may have to be used, the advantage is that the amount of useful industrial water or well water can be reduced or not used at all.

Furthermore, in the above example, an example of an activated carbon adsorption tower was shown as wastewater treatment, but the present invention may also be used in a system that processes activated sludge by adding activated carbon to an aeration tank.
Furthermore, it goes without saying that the present invention may be applied to water treatment.

As explained above, according to the present invention, ash having a relatively small diameter can be efficiently separated and removed.
In addition, since only water is used to separate and remove the ash, there is no cost involved. By removing ash according to the present invention as described above, there is no need to dispose of activated carbon.

Furthermore, if an ion sequestering agent is added, ash can be separated and removed in a more stable state, and no problem will occur even if the total hardness of the mixture slurry changes.

Next, the present invention will be specifically explained with reference to Examples.

<Example> Ash produced when regenerating activated carbon using the apparatus shown in FIG. 1 was separated and removed. For this purpose, the used activated carbon was first regenerated in a regeneration furnace 35, and then classified in a sieve 37 to obtain a mixture consisting of finely broken activated carbon and ash. This mixture contains 100 kg/day of activated carbon of relatively small particle size and 100 kg/day of ash. 2 m ³ /day of fresh water was added to this mixture to form a slurry, and the slurry was sent to the ash separation tank 40. In the ash separation tank 40, 50 kg/day of ash was separated from the regenerated material and floated to the surface, while a mixture containing the remaining ash settled. Then, the flow rate is 1 from the bottom of the ash separation tank 40.
m ³ /day, activated carbon 99.5Kg/day, and ash content 50Kg/day were extracted and returned to the adsorption tower 31. This precipitate (regenerated activated carbon) contains 50 kg/day of ash, but the ash contained in the mixture (100 kg/day) is
Kg/day). Separated water is also drawn out from the upper part of the ash separation tank 40 at a flow rate of 1 m ³ /day and activated carbon 0.5 kg/day, and the separated water is transferred to the ash concentration tank 4.
3, and ash etc. are treated with a cationic flocculant (concentration 1
mg/). A concentrated slurry with a flow rate of 0.25 m ³ /day, activated carbon 0.5 kg/day, and ash content of 20% (50 kg/day) is drawn out from the bottom of the ash concentration tank 43 and sent to the dehydrator 45, where it is dehydrated and then activated carbon 0.5 kg/day. ,
It was disposed of as a dehydrated cake with an ash content of 50 kg/day and a moisture content of 40%. In addition, clear water is added from the top of the ash concentration tank 4.
0.75m ³ /day was derived. In addition, the analysis of ash content is based on JIS
An ignition residue heated at 600° C. for 2 hours according to K0102 was used.

[Brief explanation of drawings]

FIG. 1 is a flow sheet of an apparatus for carrying out the method of the present invention, and FIG. 2 is a graph showing the relationship between settling time and settling rate of activated carbon and ash. 35... Regeneration device, 40... Ash separation tank, 43... Ash content concentration tank.

Claims (1)

[Claims] 1. Activated carbon is regenerated in a regeneration furnace, and then classified into an activated carbon system with at least a small ash content and a relatively large particle size, and a system of activated carbon with a relatively small particle size and an ash content. The ash is separated and removed by adding water to the mixture containing the relatively small activated carbon and ash to dissociate the activated carbon particles and ash particles, suspending the ash and allowing the activated carbon to settle. A method for separating and removing ash mixed into activated carbon. 2. The method for separating and removing ash mixed in activated carbon according to claim 1, wherein an ion sequestering agent is added to the water.