JPH0231837A - Method for regenerating activated carbon for desulfurization - Google Patents

Abstract

PURPOSE:To regenerate activated carbon powder for desulfurization by adding water and oil to activated carbon powder contg. dust after desulfurization, by molding the active carbon after being removed the dust, with a binder and thereafter by heating. CONSTITUTION:The activated carbon is aggregated with oil component by adding circulating water to the powder 1 generated in a desulfurization equipment to make an aq. slurry, by adding tar from a oil component-adding tank 14 thereto and by strongly stirring with an impeller in a mixing and stirring machine 2. The aggregated activated carbon powder is sent to a washer 3 together with the slurry contg. dust powder, and poured with washing water from above a vibrating screen 15. Thereby, the aggregated activated carbon powder is left on the vibrating screen 15, and the dust is sent to a thickener 4 by washing away and discharged from the system as precipitated dust 5. The aggregated activated carbon powder is removed the water attached on the surface thereof with a centrifugal dehydrator 6, introduced to a kneader 7 and sufficiently kneaded with the binder and, as occasion demands, coal powder. The kneaded mixture is molded with an extruder 8 and then, heated under a gas atmosphere mixing nitrogen gas with steam in an electric heating furnace to obtain firm activated carbon.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for recycling granular activated carbon used for desulfurizing exhaust gas in, for example, sintering equipment in steel plants, thermal power plants, chemical factories, etc. be.

(Prior Art) As a method for removing sulfur oxides and nitrogen oxides contained in various waste gases, there are many desulfurization and denitrification processes using wet or dry methods. Among these, in the dry method, granular or shaped activated carbon is widely used as an adsorption-reduction agent due to its adsorption-reduction performance. Generally, activated carbon uses wood, coal, or petroleum pitch as its main raw materials and is manufactured using rotary kilns, multistage bed furnaces, fluidized bed furnaces, etc. However, activated carbon used for exhaust gas desulfurization requires repeated adsorption and regeneration for a long period of time. Since it is used in a moving layer, etc., it is necessary to have high adsorption capacity and mechanical strength such as impact resistance and abrasion resistance.

However, if the adsorption capacity is increased, the mechanical strength decreases, and conversely, if an attempt is made to increase the mechanical strength, the adsorption capacity tends to be lost. A method for producing activated carbon has been desired.

As such a technique, for example, there is a method as disclosed in Japanese Patent Application Laid-Open No. 53-26792, in which lignite is formed, carbonized by carbonization, and the formed carbon material is used as a raw material and heated by direct current during activation. Activated carbon has low strength such as pressure resistance, abrasion resistance, and impact resistance, and when used repeatedly for adsorption and regeneration in moving bed or fluidized bed processes, it suffers from large wear and tear, making it uneconomical. Molded activated coke is attracting attention because it has a smaller specific surface area than activated carbon, but has higher strength and excellent desulfurization ability. A method for producing activated coke is, for example, as described in Japanese Patent Application Laid-Open No. 57-100910, which uses semi-formed coke with high activity as the main raw material, and molds a raw material in which a binder is added to mixed coal, which is made by blending several types of coal. There are methods such as carbonization, carbonization, and activation.

However, no method has been found to date to regenerate and utilize activated carbon that has been pulverized in desulfurization equipment.

(Problem to be solved by the invention) Activated carbon that has become powdered due to wear and tear due to repeated use of adsorption and regeneration in moving bed and fluidized bed processes must be discharged from the system if it is smaller than a certain particle size in order to prevent gas flow. However, for example, in exhaust gas desulfurization equipment after the sintering process in steel plants, the dust concentration in the exhaust gas is high, so sintered powder dust adheres to the activated carbon surface, and the activated carbon powder discharged contains dust components.
Since it is mixed in an amount of 0 to 70% by weight, it is not reused and is simply returned to the sintering process as a raw material for blast furnaces, or used only as an inexpensive carbon source instead of expensive activated carbon, such as when mixed into cold bond pellets.

The present invention separates expensive activated carbon powder, which still has sufficient adsorption capacity, from dust and molds it, thereby reusing it in desulfurization equipment and reducing the cost of desulfurization treatment.

(Means and effects for solving the problem) In the case of the exhaust gas treatment system after the sintering process, the activated carbon discharged from the desulfurization equipment is 1 mm mixed with 30 to 70% by weight of dust (sintered ore powder) as described above. The following activated carbon powder is used.

Of course, if the treated exhaust gas is different, the properties and components of the generated mixture will also be different.

There is no big difference in that it is a mixed powder of activated carbon powder and iron oxide powder. The method of separating only activated carbon powder from such a mixed powder is to add moisture and oil and mix and stir using the lipophilicity of activated carbon powder and the hydrophilicity of iron oxide powder, because the activated carbon powder coagulates with oil. The iron oxide powder in the water can be separated by pouring washing water over the vibrating sieve in the next water washer.

At this time, the oil content is not particularly limited, such as heavy oil, light oil, or tar, but it is economical to use an oil that is dispersible and can be heated, volatilized, and condensed in a subsequent process to be reused. The amount to be added has an optimum value depending on the mixed powder produced, but it is generally desirable to add it within the range of 5 to 30% by weight. If the amount added is too small, the activated carbon powder will not coagulate sufficiently, and if it is too large, the dust powder will also tend to coagulate, which is not preferable. The dust remaining in the water can be separated with a thickener, etc. and reused as an iron source like normal ironmaking dust. After removing the water adhering to the surface of the aggregated activated carbon powder with a dehydrator, it can be mixed with a binder and coal if necessary with a kneading machine. Add flour and mix thoroughly.

The binder is not particularly limited as long as it has appropriate fluidity and adhesiveness under molding conditions and can maintain the shape of the molded product even when fired at high temperatures.
Various binders can be used, such as pitch, asphalt, phenol resin, urethane resin, or water glass, and one type or a mixture of two or more types can be used. The amount added is preferably within the range of 5 to 60% by weight based on dry activated carbon powder, and it is greatly affected by the type of binder, so it is necessary to determine the amount added in advance to achieve the required strength by experiment. Good.

Coal powder is added to compensate for the amount of activated carbon consumed in the activation process, and to adjust the blend of coking coal and non-caking coal to produce strong activated carbon. It is to be blended. Suitable caking coals include subbituminous coal and bituminous coal, and suitable non-caking coals include lignite, lignite, anthracite, etc., and the blending ratio of caking coal is preferably 5 to 50% by weight.

The mixed powder whose physical properties have been adjusted as described above is kneaded using a kneader or the like, and then molded by a known method. The molding machine is, for example, a briquette machine, a pelletizer, an extrusion molding machine, a relocation type granulator, etc., and is molded into a spherical, cylindrical, almond-shaped, etc. shape with a diameter of 1 to 10 mm, preferably 2 to 10 mm. can.

The molded product is heated in an internally or externally heated rotary kiln, vertical kiln, or other heating furnace in an atmosphere of N2 gas, combustion waste gas, or a mixture of these gases and up to 50 volumes of water vapor. It is also possible to heat at a temperature of about 600 to 1000'C for about 1 to 3 hours. Further, after heating, an activation treatment can be performed using steam or the like. The oil content evaporates during heating, and at this time, minute pores are generated, which contribute to improving the adsorption capacity of the regenerated activated carbon. It is more economical to reuse the volatilized oil by condensing it.

The regenerated activated carbon thus obtained can be filled into an adsorption tower or an adsorption tank according to a conventional method and used as a fixed bed or fluidized bed for desulfurization of exhaust gas.

(Examples) The present invention will be described in more detail below using Examples, but the present invention is not limited to the following Examples unless the gist of the invention is exceeded.

In the drawing, in order to suppress the rise in pressure drop in the adsorption tower, the mixed powder generated from the exhaust gas desulfurization equipment is discharged from the system when the activated carbon is worn down to less than one layer.

At this time, the adsorption tower adsorbs dust powder in addition to SO□ in the exhaust gas, so the weight ratio of activated carbon powder with an average particle size of 0.6+ma and dust powder with an average particle size of 0.1 mm is about 426. Since the SO adsorbed in the activated carbon in the mixed state is desorbed in the heat treatment in the post-process, there is no particular problem. Circulating water is added to the powder 1 generated by the desulfurization equipment to form a water slurry of 15 wt.
Yoshitar was added at a ratio of zooz/l to the weight of the generated powder, and the activated carbon powder was agglomerated to a particle size of 2 to 3 # by tar by vigorously stirring with an impeller in the mixer agitator 2.

Send to washing machine 3 together with water slurry containing dust powder, 1
Washing water is sprayed from above the dragon vibrating sieve 15, and the aggregated activated carbon powder remains on the sieve 15, while the dust powder is washed away.
Thickener 4 is sent to thickener 4 and discharged as settled dust 5 to the outside of the system and reused, for example, as a sintering raw material.
The water from which the dust has been separated is also introduced into the mixing agitator 2 via the circulation system 16 for reuse.The aggregated activated carbon powder is introduced into the centrifugal dehydrator 6, where the surface water is removed and the water content is adjusted to 3 to 4 ml. Then, the coal-based pitch from the hopper 12 and the caking coal of 15 gm are introduced into the kneading machine 7 to serve as a binder with an average particle diameter of about 10% by weight based on the weight of the dried activated return powder.
The crushed pus was added to the pus from the hopper 13 and thoroughly mixed. The resulting mixture is introduced into an extruder 8,
It was shaped into a cylinder with a diameter of 2 drops and a length of 5 drops.

Next, it was fired in an electric heating furnace 9 at 900° C. for 1 hr. The atmosphere gas was pre-activated by mixing 20 volumes of water vapor with N2. Most of the cool evaporates during heating;
It can be condensed and reused, and some remains to act as a binder to create strong activated carbon.

During volatilization, a narrow gas passageway is formed, which has a significant effect on the surface area amplifier of activated carbon.

As a result, the specific surface area of the recycled activated carbon is 200~30Of
f1''/y, which had sufficient performance for desulfurization, so it was used by directly returning to the desulfurization equipment without passing through the activation furnace 10 in the next step.

Table 1 shows the quality evaluation results of recycled activated carbon produced by varying the binder brand and addition ratio.

Table 1: 1 long sample of rice was placed in the lower part of a 25 A cylindrical container, and a weight of ~3601 was dropped from a height of o, 5 m 10 times, resulting in a weight ratio of +0.51 m. 2 samples of rice, approximately 2602 cm, were kept at a constant temperature. Approximately 1000 ppm of 802 was added to the reaction vessel in the tank.
The absorbed SO2 was desorbed by heating after passing a concentrated moist gas for 5 hours, and the amount of desorbed SO2 was measured by absorbing and titrating with a H20□ solution.

(Effect of the invention) By doing so, the activated return powder for desulfurization can be regenerated reliably, and the running cost of the desulfurization treatment can be significantly reduced. In addition, recycled activated carbon has excellent desulfurization ability, strength, etc.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a manufacturing process flow diagram of the present invention.

Claims (2)

[Claims] (1) Add water and oil to the dust-containing activated carbon powder after desulfurization, add a binder to the activated carbon from which the dust has been separated, and shape it.
A method for regenerating activated carbon for desulfurization, which comprises subsequently heating it. (2) The method for regenerating activated carbon for desulfurization according to claim 1, characterized in that a binder and coal powder are mixed with the dust-separated activated carbon.