KR100395097B1 - Method and apparatus for treating wastewater by using coke breeze - Google Patents

Abstract

PURPOSE: A method for efficiently treating wastewater by using coke breeze that is a byproduct generated from the coke manufacturing process instead of existing activated carbon as an adsorbent is provided, and an apparatus for treating wastewater by using the coke breeze is provided. CONSTITUTION: In a wastewater treatment apparatus(30) using an adsorbent, the apparatus for treating wastewater by using coke breeze comprises an adsorbent hopper(31) for continuously injecting a certain quantity of coke breeze into the mixing reactor; a mixing reactor(33) in which a screw(32) is installed so that the screw mixes up wastewater and the coke breeze injected from the adsorbent hopper by rotary power; a sedimentation basin(34) installed next to the mixing reactor so that the sedimentation basin contains the wastewater discharged from the mixing reactor to precipitate coke breeze adsorbed to the wastewater; and a filter(36) in which a membrane(35) is installed to filter wastewater overflown from the sedimentation basin and discharge filtered effluent, wherein a grain size sorter(31a) is attached to the adsorbent hopper to sort the coke breeze.

Description

Wastewater treatment method using powder coke and apparatus used therefor

The present invention relates to a wastewater treatment method using by-products generated in the coke plant and an apparatus used therein.

Recently, many researches have been conducted in the environmental field to fundamentally suppress the generation of environmental pollutants. In particular, these are called clean technologies. Developed countries are investing enormous research funds to develop clean technologies that can cope with existing environmental pollutant treatment technologies.

Until now, most wastewater treatment methods using activated carbon have been adopted for wastewater treatment. Representative examples of the conventional wastewater treatment method using activated carbon include a method using the adsorption tower 12 as shown in FIG. That is, as shown in FIG. 1, wastewater is introduced from the bottom of the adsorption tower 12 filled with activated carbon. The reason is that when the wastewater is introduced from the upper part of the adsorption tower, tunneling occurs inside the adsorption tower, and the adsorption efficiency is lowered. Wastewater passing through the adsorption tower is treated and discharged. At this time, an extra preliminary adsorption tower must be provided to recharge the adsorption box. Most processes have adopted this method. Figure 1 shows the most advanced method of the existing method, and because it is continuously supplemented with regeneration activated carbon and new activated carbon without a preliminary adsorption tower, there is an advantage that it is possible to operate continuously and to treat a large amount of waste water.

However, the wastewater treatment method as described above has a problem of treating waste activated carbon when continuously operated in spite of the above improvement. That is, the waste activated carbon generated in the adsorption tower 12 has to be incinerated or regenerated. In the incineration, waste activated carbon storage facilities are required, and a lot of energy and pollutants are generated during incineration. In particular, a large-scale wastewater treatment plant has facilities such as a regeneration furnace 14 for continuously regenerating activated carbon. In this case, too, steam and a lot of energy are required for revitalization of activated carbon, and a large amount of pollutants are generated during the regeneration treatment. do.

For this reason, wastewater treatment using activated carbon has a disadvantage in that it is carried out only in places where high wastewater treatment is particularly necessary because of the large and expensive equipment.

Moreover, in addition to these plant problems, activated carbon is known to generate a large amount of pollutants in its manufacturing process, which means that wood, coal, and coconut shells, which are used in the manufacturing process of activated carbon, are carbonized at about 1000 ° C. This is because it generates a large amount of volatile pollutants.

Accordingly, an object of the present invention is to provide a method for efficiently treating wastewater while using powdered coke generated as a dispersion in a coke manufacturing process instead of conventional activated carbon as an adsorbent, and a simple wastewater treatment apparatus used therein.

1 is a schematic configuration diagram of a conventional wastewater treatment

2 is a process diagram of coke production to explain the process of generating coke.

3 is a block diagram of a wastewater treatment apparatus according to the present invention

4 is a graph showing the adsorption rate change for activated and untreated CDQ powdered coke.

5 is the sedimentation curve of the particle size of CDQ

6 is a graph showing the removal rate of the monthly change of CDQ powder coke by the particle size

7 is a graph showing the change of flux of water according to the change of membrane permeation pressure of waste water

Explanation of symbols on the main parts of the drawings

30 ..... Wastewater Treatment System 31 ..... Adsorbent Feeder

33 ..... Mixer 34 ..... Settling basin

36 ..... Strainer

The present invention for achieving the above object is a method for treating wastewater by using an adsorbent, comprising the step of adding a powdered coke having a specific surface area of 15 m 2 / g or more and a particle size of 5-170 mesh as an adsorbent to the waste water; :

Adsorbing the injected coke and wastewater for 5-60 minutes;

Precipitating the adsorbed powdered coke while flowing the wastewater at a flow rate of 10-60 m / hr;

The precipitated powdered coke is regenerated and transferred to a coke process, and the overflowed wastewater is discharged through a separator in a range of 0.1-0.5 μm at a pressure of 0.5-2 bar; The present invention relates to a wastewater treatment method using powdered coke.

In addition, the present invention is a wastewater treatment apparatus using an adsorbent,

Adsorbent injector which continuously inputs a certain amount of powdered coke; A mixing reactor having a built-in screw that stirs the coke and wastewater introduced from the adsorbent injector by rotational force; A sedimentation basin, which is located subsequent to the mixing reactor and contains the wastewater discharged therefrom, to settle adsorbed powdered coke; And a filter having a separator built therein to filter the wastewater flowing out of the sedimentation basin and discharging the filtered treated water.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

First, as the coke suitable for the present invention, the BET specific surface area is 15 m 2 / g or more, and the particle size range is preferably 5-170 mesh. The powdered coke having such a specification includes coke dry quendring (hereinafter referred to as 'CDQ') generated when dry fire is fired during the coke manufacturing process.

FIG. 2 shows a general coke production process. As shown in FIG. 2, powder coke generated in steel mills is roughly classified into three types. That is, the coke produced in the coke oven is charged with coal is cooled by the wet digestion 22 with water and the dry digestion 24 with gas, the wet or dry digested coke is the furnace 26 Used as feedstock for At this time, the powdered coke is powdered coke generated during wet digestion (hereinafter referred to as 'digestion tank coke'), CDQ generated during dry extinguishing, and wet or dry digested coke raw material falling when conveyed to the belt conveyor 25. (Hereinafter referred to as `` naked powder coke ''). Of these, it is CDQ that satisfies the physical condition according to the present invention.

For example, BET specific surface area and particle size distribution of nitrogen with respect to powdered coke generated in the ironworks coke process as described above are shown in Tables 1 and 2.

TABLE 1

TABLE 2

As can be seen from Table 1, the BET surface area of each powder coke was measured, and as a result, the light fall powder coke 0.68, digester powder coke 1.21, and CDQ powder coke 16.7 m 2 / g. Therefore, it can be seen that it is most preferable to use the CDQ powder coke as the adsorbent.

In addition, Table 2 shows that the size of the particle size is falling light> digester> CDQ powdered coke, it can be seen that the CDQ is suitable as the adsorbent. In particular, larger ones are adsorbents for fixed bed adsorption towers, and smaller ones are suitable for fluidized beds.

On the other hand, a suitable apparatus for treating wastewater in accordance with the present invention using such a coke is shown in FIG. That is, in the wastewater treatment apparatus 30 according to the present invention, the adsorbent injector 31 for continuously feeding a predetermined amount of powdered coke is followed by a mixed reactor 33 for adsorbing the injected powdered coke and the introduced wastewater. A sedimentation basin 34 which is installed and deposits the wastewater adsorbed in the mixing reactor 33 is positioned continuously in the mixing reactor 33, and then the wastewater overflowed from the sedimentation basin at the rear end of the settling basin 34. Finally the filtration comprises a filter 36.

Specifically, the adsorbent injector 31 serves to constantly input powdered coke because 90% or more of the powdered coke generated in the ironworks coke manufacturing process is 50 mesh or less. Preferably, the adsorbent injector 31 may be attached to a particle size selector 31a for selecting the powdered coke for each mesh.

In addition, the mixed reactor 33 mixes and reacts the introduced wastewater and the powdered coke, thereby adsorbing the environmental pollutants in the wastewater to the powdered coke. In other words, the screw 32 is embedded in the mixing reactor, and the coke is adsorbed and removed from the waste water by the stirring action of the screw to adsorb and remove environmental pollutants.

The following is a theory introduced to optimally operate the mixed reactor of the present invention. The mixed reactor analysis established the following model and established a relational expression.

The above equation is represented by a number:

The above equation is a general formula for the amount adsorbed on the adsorbent for a spherical adsorbent of radius R, assuming that the volume from any radius r to Δr is 4πr ² Δr * q (r). Where C is concentration, t is time, and F is flow rate. Expressed in relation to the adsorbent dose, the equation is:

Therefore, by using the above equation, it is possible to optimize the dose of the powdered coke adsorbent and the adsorption time of the mixed reactor in the mixing reactor, so that the size and processing time of the mixing reactor can be determined. In the present invention, since CDQ powdered coke is used, the treatment time with wastewater is preferably about 5-60 minutes.

In addition, the sedimentation basin 34 functions to separate and settle the powdered coke in the wastewater discharged from the mixing reactor 33. That is, the powdered coke adsorbed pollutants are sedimented by gravity to separate them from the wastewater. The sedimentation basin of the present invention has to act specifically to make the powdered coke suitable for the next step, the microfiltration process, and the theoretical basis thereof is as follows.

Since there is no interaction between particles in the case of powder coke precipitation of the present invention, it was found that the precipitation of powdered coke has a constant sedimentation rate regardless of the concentration. That is, the powder coke was settled under acceleration until the gravitational force acting on the particles became equal to the resistance of the water when placed on the stationary water buffalo.

Therefore, the relation is expressed as follows.

Where F _G is gravity,

F _D is the frictional force,

V _P is the particle volume,

C _D is the coefficient of friction (Frictional Drag Coeff.)

A _P is the projection area of the particle,

V is the settling velocity,

ρ _P is the particle density,

ρ _L is the density of water

The sedimentation relation of the particles derived from this equation is as follows.

At this time, the friction coefficient is , (a and n are constants).

TABLE 3

Meanwhile, considering the shape factor Ψ, the friction coefficient is as follows.

TABLE 4

Here, if the particles are small, such as powdered coke can be assumed to be spherical, and because the flow of the sedimentation basin is generally a flow of flow, the sedimentation rate can be obtained by the following method using the values in Tables 3 and 4. Of course, even in the case of non-flow flow, the sedimentation velocity can be obtained by the following equation using the above table values.

The above formula represents That is, in the settling tank, when the wastewater overflows and the particles with sedimentation rate Vs are removed, the removal rate of these particles is

Vs / Vo

(Vo = Q / A, Q is the flow rate, A is the planar area of the settling tank)

It can be represented as.

However, in practice, the particles of powdered coke are not constant but are distributed in various ways, and thus the following sedimentation equation is established.

Where 1-Fo represents the removal rate of particles having a sedimentation rate greater than Vo,

Shows the removal rate of particles with sedimentation rate less than Vo.

According to the sedimentation rate, the flow rate of the wastewater flowing in the sedimentation basin varies depending on the particle size of the powdered coke, and in the case of the CDQ powdered coke of the particle size size 5-170 mesh range used in the present invention, the flow rate of the wastewater is 10-60 m / hr. Is suitable.

Specifically, when the particle size of the coke is 5-35 mesh, the monthly flow of wastewater is in the range of 10-41 m / hr, and when the minute coke has a particle size of 35-70 mesh, the monthly flow of the wastewater is 20. When the powdered coke has a particle size of 70-100 mesh, the monthly flow of wastewater is in the range of 10-55m / hr, and the powdered coke has a particle size of 100-170 mesh. It is preferable to make the monthly amount of waste water into the range of 10-25 m / hr.

Finally, the filtration process serves to finally remove the fine powdered coke that has not precipitated in the settling basin 34. That is, this process serves to separate and remove the fine powdered coke that has not been removed from the sedimentation basin 34 by using a separation membrane 35 such as a micro filter.

In the membrane separation process, important factors are pressure and flux. Transmembrane Pressure represents the pressure applied to the membrane module, and the correction of the flux is as follows in consideration of the viscosity of water.

Where J is plus

μ is the viscosity of water

In the above formula, the plus of water increases in proportion to the transmembrane pressure.

Separation membrane suitable for the present invention is a microfiltration membrane having a diameter of about 0.1-0.5 ㎛ range, the membrane permeation pressure of the incoming waste water is preferably a pressure of 0.2-2 bar.

Meanwhile, the waste coke generated in the sedimentation basin 34 and the filter 36 is regenerated all by using the existing coke oven (Oven) 20. The recovered coke is recycled back to the waste water treatment. That is, the powdered coke separated in the precipitation process and the filtration process contains a large amount of contaminants, and therefore, incineration or regeneration treatment should be performed. The present invention is characterized in that the waste coke is charged into the existing coke oven and recycled. When incineration or re-treatment of wastewater treatment agents (adsorbents) such as activated carbon by conventional methods, a large amount of pollutants are generated by treatment in an oxidizing atmosphere (eg, water vapor, carbon dioxide, oxygen, etc.). For example, the sulfur compounds in the waste water are oxidized to SOx, nitrogen compounds (such as proteins) to NOx, carbon compounds to carbon dioxide or carbon monoxide, etc., to release enormous amounts of pollutants. However, when the coke oven is used as in the present invention, since the coke oven has a reducing atmosphere (about 60% of hydrogen content) at 1100 ° C., sulfur compounds in the waste water are reduced so that hydrogen sulfide and nitrogen compounds (such as proteins) are ammonia. Or cyanide and carbon compounds are methane or organic compounds. Coke ovens in steel mills are already equipped with hydrogen emulsification and ammonia removal facilities, which do not release these substances into the atmosphere. In other words, the current iron and steel removal facilities are plant fertilizer manufacturing facilities. In addition, since the carbon compound is methane or an organic compound, there is an advantage of increasing the calorific value of the gas generated in the coke oven. The coke regenerated in the reducing atmosphere can be recycled 100% as a wastewater treatment agent.

Hereinafter, the present invention will be described in detail through examples.

Example 1

First, in this embodiment, CDQ powdered coke having a specific surface area and particle size distribution as shown in Tables 1 and 2 were used.

The adsorption rate was experimentally determined for the activated and untreated CDQ powdered coke at 1000 ° C. for 30 minutes, and the results obtained using the equation derived from the theory are shown in FIG. 4.

In FIG. 4, the adsorption of activated and untreated CDQ powdered coke to chemical wastewater showed little change after 60 minutes. In comparing the adsorption of the treated and untreated CDQ powdered coke for 180 minutes, the adsorption amount for 1 minute was 53.6 and 70.2% for 180 minutes adsorption, 71.0 and 75.4% for 3 minutes respectively, and the adsorption amount for 5 minutes was The adsorption amounts of 74.9 and 78.8% and 10 minutes were 82.7 and 84.0%, and the 15 minutes were 87.1 and 88.0%, and the 20 minutes were 89.9 and 89.0% and the 30 minutes were 92.3 and 90.5%, respectively.

In other words, it was found that the waste water treatment time in the mixed reactor design was appropriate for 5-60 minutes.

On the other hand, theoretically, the predictive line generally showed a similar tendency to the experimental value, especially after 120 minutes, very consistent with the experimental value. Therefore, it can be seen that the theory according to the present invention can be utilized in the treatment of industrial wastewater and the like by using coke.

Example 2

In the sedimentation experiment, the sedimentation velocity and the residual weight ratio of the suspended solids were determined by using a cylindrical tube (made settling column) having a diameter of 17 cm and a height of 100 cm.

The results are shown in FIG.

As shown in FIG. 5, the powder coke corresponding to 35-70Mesh among the powder coke produced in the coke dry fire extinguishing process has the largest particle diameter, so the sedimentation rate is large, and thus the residual weight ratio having a sedimentation rate smaller than the given sedimentation rate. Is the smallest. Next, the sedimentation rate decreases in the order of CDQ 70-100 Mesh and CDQ 100-170 Mesh, indicating that the remaining weight ratio is increasing. In the case of the original powder coke without sieving, the sedimentation curve can be obtained between the CDQ 70-100 mesh and the CDQ 100-170 mesh, so that the average diameter may exist between them. In addition, in the case of powder coke that does not pass through the 170 mesh above, since no particles have escaped the 170 mesh, the average particle diameter is larger than that of the original powder coke that is not sifted, so the settling curve is also present at a lower position. The experimental results can be used to determine the sedimentation rate for the design of the sedimentation basin when wastewater treatment with various CDQ particles is performed.

In order to apply to the sedimentation tank design using the results obtained from the sedimentation rate experiment, the relationship between the removal rate in the sedimentation tank and the overflow rate (Overflow rate-Design Settling Velocity = Q / A, q is the flow rate, A is the sedimentation tank cross section) The same is shown.

If the removal rate of powdered coke is 80-99% in the sedimentation basin, the monthly flow of powdered coke corresponding to no screening of CDQ is 10-41m / hr and 20-60m for 35-70 Mesh. / hr, CDQ 70-100 Mesh corresponds to 10-55m / hr, CDQ 100-170 Mesh corresponds to 10-25 m / hr, and powder coke that does not pass through 170 Mesh 10-50 m / hr appeared to be valid.

Example 3

When the residual powder coke was removed by filtration, the following test was conducted to investigate the effect of powder coke on the flux.

That is, the quality of the membrane was measured using Zr ₂ O ₃ , pore size 0.14 μm, 60 cm in length, distilled water mixed with CDQ powdered coke, and water flux of the membrane according to pressure. . The experimental results are shown in FIG.

FIG. 7 shows the positive change according to the pressure change when maintaining the concentration of powdered coke below 170 Mesh at 2000ppm, wherein the unit of flux is LMH.

The plus for powdered coke increased the flux as the pressure changed. However, it is expected to decrease above 2 atm.

Example 4

The wastewater generated in the steelmaking coke production process was compared with the existing activated carbon wastewater treatment method and the present invention.

If the amount of wastewater treated is 40,000 tons per day, activated carbon is required to reduce the chemical oxygen demand (COD) by about 25%, the suspended solids by about 100%, the cyan by about 50-60%, and the color by 70-90%. The amount and cost of coke were as shown in Table 5 below.

Table 5

Existing methods other than those shown in Table 5 can be seen that the present invention is more economical than the conventional one, considering the operation costs, labor costs, pollution prevention equipment operation costs, and waste water treatment facility costs during initial investment.

As mentioned above, the present invention

First, it is easy to purchase the adsorbent and the price is low. Second, there is no burden of incineration (or reprocessing) cost in the treatment of the waste adsorbent. Third, the cost of storing and transporting the waste adsorbent can be reduced. Fourth, the installation is simple compared to the existing effect.

Claims (8)

In the method of treating wastewater using an adsorbent, Step of introducing the powdered coke having a specific surface area of 15 m 2 / g or more and having a particle size of 5-170 mesh as an adsorbent to the wastewater: Adsorbing the injected coke and wastewater for 5-60 minutes; Precipitating the adsorbed powdered coke while flowing the wastewater at a flow rate of 10-60 m / hr; The precipitated powdered coke is regenerated and transferred to a coke process, and the overflowed wastewater is discharged through a separation membrane in the range of 0.1-0.5 μm at a pressure of 0.5-2 bar; Wastewater treatment method using coke. The wastewater treatment method according to claim 1, wherein when the powdered coke has a particle size of 5-35 mesh, the monthly flow of the wastewater is in the range of 10-41 m / hr. The wastewater treatment method according to claim 1, wherein when the powdered coke has a particle size of 35 to 70 mesh, the monthly flow of the wastewater is in the range of 20 to 60 m / hr. The wastewater treatment method according to claim 1, wherein when the powdered coke has a particle size of 70-100 mesh, the monthly flow of the wastewater is in the range of 10-55 m / hr. The wastewater treatment method according to claim 1, wherein when the powdered coke has a particle size of 100-170 mesh, the monthly overflow of the wastewater is in the range of 10-25 m / hr. The wastewater treatment method according to any one of claims 1 to 5, wherein the powdered coke is powdered coke generated when dry extinguishing the coke produced in the coke manufacturing process. In the wastewater treatment apparatus using the adsorbent, An adsorbent injector 31 for continuously feeding a predetermined amount of powdered coke; A mixing reactor (33) having a built-in screw (32) that stirs the powdered coke and wastewater introduced from the adsorbent injector (31) by rotational force; A sedimentation basin 34 which is located after the mixing reactor 33 to contain the wastewater discharged therefrom and precipitates the adsorbed powdered coke; And a filter (36) having a separator (35) embedded therein to filter the wastewater flowing over from the settling basin (34) and discharging the filtered treated water. Device. 8. The apparatus according to claim 7, wherein the adsorbent injector (31) is attached to a particle size sorter (31a) for sorting powder coke.