KR20160080912A - Solidifying agent composition for sludge and manufacturing method thereof - Google Patents

Abstract

An exemplary embodiment of the present invention provides a multi-functional solidifying agent composition for sludge comprising: 35 to 55 wt% of an absorbent agent including a paper combustion material and steel slag; 40 to 60 wt% of a functional mixture, wherein the absorbent agent including a waste catalyst used in an oil-refining process and a pH regulator having an acid-loaded waste catalyst used in an oil-refining process are mixed in a ratio of 20 to 80 : 20 to 80 in the mixture; and 1 to 5 wt% of cement, and a manufacturing method thereof. The purpose of the present invention is to provide the multi-functional solidifying agent composition for sludge responding effectively to odor remaining for a long time by delaying or preventing a treated solid material from forming into sludge, and a manufacturing method thereof.

Description

TECHNICAL FIELD [0001] The present invention relates to a composite functional solidifying agent composition for sludge,

The present invention relates to a multifunctional solidifying agent composition for sludge and a process for preparing the multifunctional solidifying agent composition for sludge, and more particularly, to a multifunctional solidifying agent composition for sludge recycled by industrial by-products and a method for producing the same.

Domestic sewage sludge has been rapidly increasing from 7,631 tons / day in 2007 to 10,259 tons / day in 2007 due to improvement in people's living standards and conditions. To cope with this situation, the government has been working on sewage sludge treatment And establishing a treatment plan.

In the case of incineration and landfill, however, the Ministry of Environment is concerned about the occurrence of environmental pollutants such as dioxins, the prevention of greenhouse gas emissions, and the recycling I am reluctant to promote.

Most of the components of the sewage sludge are inorganic substances such as silica (SiO _{2 )} , alumina (Al ₂ O _{3 )} , iron oxide (Fe ₂ O _{3 )} and the like, There is a problem that dehydration is very difficult due to the water content due to the capillary force, and the water and organic matter contained in the sewage sludge provide a habitat and breeding environment for pathogens, flies and mosquitoes, It is possible to generate secondary pollutants such as ground water pollution and odor.

At present, many sludge solidification facilities are solidified by solidifying agents in solidifying treatment establishments. However, when the sludge is conveyed or unloaded, a high concentration of unpleasant odor is generated, and the sludge is solidified There is a problem that stench of a car is generated. In addition, since a high-priced drug such as aluminum sulfate is used as a pH adjusting agent contained in a conventional solidifying composition, it is disadvantageous in terms of economy.

Therefore, there is a need to develop a solidifying composition capable of delaying or preventing sludge formation of a solidified product to effectively cope with a long-term odor.

Disclosure of Invention Technical Problem [8] Accordingly, the present invention has been made to solve the above-mentioned problems occurring in the prior art, and an object of the present invention is to provide a composite functional solidifying composition capable of effectively retarding or preventing sludge- .

In order to achieve the above object, one aspect of the present invention is a method for producing a steel sheet, comprising: 35 to 55% by weight of an absorbent comprising a papermaking material and steelmaking slag; 40 to 60% by weight of an adsorbent composed of a spent catalyst in a petroleum refining process and a pH adjuster carrying acid on a spent catalyst in a petroleum refining process are mixed at a weight ratio of 20 to 80:20 to 80, respectively; And 1 to 5% by weight of cement.

In one embodiment, the papermaking burner may be a fly ash generated after incinerating the paper sludge.

In one embodiment, the steel slag is lime generated in the steel refining process (CaO), iron oxide (Fe ₂ O _3), silica (SiO _2), manganese oxide (MnO), alumina (Al ₂ O _3), and And a mixture of two or more thereof.

In one embodiment, the spent petroleum refining catalyst may be the spent catalyst used in the fluidized bed catalytic cracking process.

In one embodiment, the spent catalyst may be a spherical catalyst in which zeolite is supported on silica-alumina.

In one embodiment, the acid supported on the spent catalyst may be one selected from the group consisting of sulfuric acid (H ₂ SO ₄ ), hydrochloric acid (HCl), nitric acid (HNO ₃ ), and mixtures of two or more thereof.

In one embodiment, the sludge may be domestic sewage, sewage, industrial wastewater, livestock manure, and food sludge.

According to another aspect of the present invention, there is provided a method of manufacturing an absorbent article, comprising the steps of: (a) mixing a papermaking material and a steelmaking slag to prepare an absorbent; (b) mixing an adsorbent composed of a waste catalyst in a petroleum refining process and a pH adjusting agent loaded with acid on a spent catalyst in a petroleum refining process at a weight ratio of 20 to 80:20 to 80, respectively, to prepare a functional mixture; And (c) preparing a solidifying agent by mixing 35 to 55% by weight of the absorbent, 40 to 60% by weight of the functional mixture, and 1 to 5% by weight of cement to prepare a multi-functional solidifying composition for sludge ≪ / RTI >

In one embodiment, in the steps (a) to (c), the mixing may be performed using one or more stirrers.

In one embodiment, the rotating speed of the stirrer may be 300 to 450 rpm.

The composite functional solidifying composition for sludge according to one aspect of the present invention can prevent re-sludge formation of solidified sludge containing cement and an absorbent made of paper-making material and steel making slag, and cement, Petroleum refining process It is possible to improve economical efficiency and environmental friendliness by using waste catalyst as precursor of adsorbent and pH adjusting agent.

It should be understood that the effects of the present invention are not limited to the above effects and include all effects that can be deduced from the detailed description of the present invention or the configuration of the invention described in the claims.

1 is a schematic representation of a method of making a composite functionalized solidifying agent for sludge according to an aspect of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

Throughout the specification, when an element is referred to as "comprising ", it means that it can include other elements, not excluding other elements unless specifically stated otherwise.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

For sludge  Complex functionality Solidifying agent  Composition

One aspect of the present invention relates to an absorbent article comprising 35 to 55% by weight of an absorbent comprising a papermaking material and a steelmaking slag; 40 to 60% by weight of an adsorbent composed of a spent catalyst in a petroleum refining process and a pH adjuster carrying acid on a spent catalyst in a petroleum refining process are mixed at a weight ratio of 20 to 80:20 to 80, respectively; And 1 to 5% by weight of cement.

The absorbent, the adsorbent, and the pH adjuster contained in the multifunctional solidifying agent composition for sludge can be produced by using industrial by-products such as paper-making materials, steel making slag, and waste catalysts in petroleum refining processes as precursors. That is, it is possible to maximize the utilization value and the environment-friendliness by converting and recycling the byproducts generated in a plurality of industrial fields into the solidifying composition for sludge without landing or disposal.

The absorbent mixed with the paper ground material and the steel making slag in a weight ratio of 30 to 70: 30 to 70, respectively, has a function of absorbing heat, so that the solidified sludge solidified material is re-sludged .

The paper refractory material may be a fly ash generated after incinerating the paper sludge. In order to reduce the amount of pulp used during the paper making process and to improve the quality of the paper, the paper mill uses a limestone fine powder as a filler. In the course of incinerating the surplus limestone fine powder discharged in the form of sludge, A fly ash having a high content of carbonated lime (CaO) may occur.

Among the materials contained in the fly ash, silica (SiO ₂ ) and alumina (Al ₂ O ₃ ) are low in hydraulic property, but when finely pulverized and water is present, they generate a solid material by pozzolanic reaction with a lime- can do. As used herein, the term "pozzolanic reaction" refers to a substance that does not have a property of curing by reacting with water alone, or a reaction in which water reacts with lime (CaO) in water.

The specific surface area of the fly ash may be 10 to 500 m ² / g. If the specific surface area is less than 10 m ² / g, the effect of reducing the moisture content may be insufficient when the organic sludge is solidified due to insufficient particulate matter. If the specific surface area is more than 500 m ² / g, the bulk density of the solidifying agent is low during transportation, And the facility operation can be degraded.

Further, the steel slag is lime generated in the steel refining process (CaO), iron oxide (Fe ₂ O _3), silica (SiO _2), manganese (MnO), alumina (Al ₂ O _3), and at least two of these oxidation And mixtures thereof, but is not limited thereto.

The steelmaking slag contains a large amount of lime (CaO) and iron oxide (Fe ₂ O ₃ ), whereby the content of the heavy metal component in the solidifying agent composition can be reduced. The lime (CaO), iron oxide (Fe ₂ O ₃ ) and other oxides contained in the steel making slag can form heavy metal hydroxide in the alkali state and can stabilize the heavy metal component by adsorption and precipitation.

In particular, the water content of the sludge can be lowered by effectively dewatering the sludge by the heat absorption function of the lime (CaO) contained in the papermaking material and the steel making slag.

The spent catalyst in the petroleum refining process may be a spent catalyst used in the fluidized bed catalytic cracking process. Specifically, the spent catalyst may be a spherical catalyst supported with zeolite on silica-alumina. Fluidized catalytic cracking (FCC) is a widely used process in petroleum refinery plants to produce valuable hydrocarbon materials from crude oil. In the fluidized bed catalytic cracking process, a spherical catalyst prepared by mixing silica-alumina with zeolite Y is used. The zeolite particles are contained in the large pores of silica-alumina, and large reactants are firstly decomposed first in silica- It is diffused and converted into a hydrocarbon having a high octane number.

Generally, the waste catalyst generated in the fluidized bed catalytic cracking process has been used as a raw material for producing cement after firing in air to remove precipitated carbon. In addition, although recycling is considered as a raw material for producing bricks or other zeolite, it is mixed with limestone because of its high production amount and low economic efficiency.

Since the waste catalyst hardly contains other components besides silica and alumina, there is no fear of pollution and is excellent as a raw material for producing cement because of excellent mechanical strength, but the amount of recycle is insufficient compared with the amount of generated. However, since a large amount of zeolite component remains in the waste catalyst, it can be used as a substance that functions as an adsorbent in the composite functional solidifying agent composition for sludge according to one aspect of the present invention.

On the other hand, since the waste catalyst has a specific surface area of 100 m ² / g or more and a pH of 7 to 10, the odor of the neutral gas and the solvent can be effectively adsorbed.

The acid supported on the spent catalyst may be one selected from the group consisting of sulfuric acid (H ₂ SO ₄ ), hydrochloric acid (HCl), nitric acid (HNO ₃ ), and a mixture of two or more thereof.

In addition, an acid may be supported on the spent catalyst to impart a function as a pH adjusting agent in the multifunctional solidifying agent composition for sludge. The spent catalyst used in the preparation of the pH adjuster is the same as the spent catalyst used in preparing the adsorbent. That is, the precursors of both the adsorbent and the pH adjuster are the same as the spent catalyst in the petroleum refining process. The prepared pH adjusting agent can reduce the pH of the solidified material and prevent the generation of odor and the elution of heavy metals.

In particular, since the absorbent, adsorbent, and cement contain a large amount of basic substances, acidic and neutral odors can be controlled, but they are susceptible to basic odors, so that it is preferable to carry a strong acid on the spent catalyst to control pH.

Meanwhile, the weight ratio of the adsorbent and the pH adjusting agent may be 20 to 80:20 to 80, respectively, to form a functional mixture. If the weight ratio of the adsorbent is less than 20, it is difficult to impart adsorption functionality. If the weight ratio of the adsorbent is more than 80, the relative content of the pH adjuster is low, and it is difficult to control the pH of the solid product to the target range.

In addition, the composite functional solidifying composition for sludge may further include a heating agent when the sludge is excessively high in water content due to environmental factors such as climate and geography, when additional heating is required.

The exothermic agent may be one selected from the group consisting of quicklime powder, light dolomite powder, petro coke incineration powder, and a mixture of two or more thereof, but is not limited thereto.

The quicklime powder is a material obtained by calcining limestone at a high temperature to be decarbonated and then processing it into a powder having a predetermined particle size, and it is preferable that the content of lime (CaO) is 85% or more in general. The calcined dolomite powder is calcined dolomite at a high temperature to be decarbonated and then processed to have a certain particle size. It is preferable that the content of lime and manganese oxide (CaO + MnO) is 80% or more. Petrocoke ash is a fuel that can be used instead of coal when high calorific value and combustion efficiency are required. Desulfurization of limestone occurs and particles of decarbonated lime (CaO) occupy most of the incineration ash. The petrocoke ash can be absorbed, exothermic, and bulky when it is in contact with water.

The heating material may be incorporated in an amount of 5 to 50 parts by weight based on 100 parts by weight of the papermaking material. If the amount of the exothermic material is less than 5 parts by weight, the exothermic effect may be reduced when the exothermic material is reacted with the sludge. If the exothermic material is more than 50 parts by weight, the strength of the solidifying agent may be excessively increased.

The sludge to which the multifunctional functional solidifying composition for sludge is applied may be a functional sludge containing a certain level of water or more and may specifically be domestic sewage, sewage, industrial wastewater, animal manure, and food sludge, It is not.

For sludge  Complex functionality Solidifying agent  Method for producing a composition

1 is a schematic representation of a method of making a composite functionalized solidifying agent for sludge according to an aspect of the present invention.

Referring to FIG. 1, a method of manufacturing a composite functional solidifying composition for a sludge according to an embodiment of the present invention includes the steps of: (a) preparing an absorbent by mixing a papermaking material and steelmaking slag (S100); (b) a step (S200) of preparing a functional mixture by mixing an adsorbent composed of a spent catalyst in a petroleum refining process and a pH adjusting agent loaded with acid on a spent catalyst in a petroleum refining process at a weight ratio of 20: 80: 20 to 80; And (c) mixing the absorbent in an amount of 35 to 55 wt%, the functional mixture in an amount of 40 to 60 wt%, and the cement in an amount of 1 to 5 wt% to prepare a solidifying agent (S300).

In the step (a) (S100), an absorbent having an absorbent heat generating function can be manufactured by mixing the paper ground material and the steel making slag at a weight ratio of 30 to 70: 30 to 70, respectively . Other types of paper millable materials that can be used, types of steelmaking slag, functions, and roles are the same as those described above.

In the step (b) (S200), the functional mixture can be prepared by mixing the adsorbent composed of the spent catalyst in the petroleum refining process and the pH adjusting agent loaded with acid on the spent catalyst in the petroleum refining process at a weight ratio of 20: 80: 20 to 80: have. That is, an adsorbent and a pH adjusting agent can be prepared using a waste catalyst of a petroleum refining process, which is a by-product, as a precursor, and the functional mixture can be prepared by mixing the both at a certain ratio. In addition, the kind, function, role and acid type of the spent catalyst are as described above.

Meanwhile, in the above steps (a) to (c), the mixing may be performed using one or more stirrers. Specifically, the above steps (a) to (c) can be carried out by sequentially feeding the absorbent, the functional mixture, and the cement into a single stirrer, and if necessary, each step may be performed separately in three stirrers , Two or more steps may be performed on a single stirrer, and the remaining one step may be performed on a separate stirrer.

The stirrer may be in the form of a horizontal arrangement or a vertical arrangement, but is not limited thereto. As compared with the horizontal arrangement type, the vertical arrangement type can realize kneading by gravity, and it is possible to eliminate an additional means for inputting, moving, and discharging the kneaded material, so that effective kneading can be performed. In some areas, It is preferable to use a vertically arranged shape because the stirring efficiency can be improved while the kneaded material and the like are repeatedly raised and dropped.

Also, the rotating speed of the stirrer may be 300 to 450 rpm. If the rotation speed of the agitator is less than 300 rpm, a necessary level of kneading effect can not be achieved. If the rotation speed of the agitator is more than 450 rpm, excessive rotation speed of the blade or screw in the agitator is excessive. The load can be applied to shorten the life of the stirrer.

Further, in each of the steps (a) to (c), the mixing time may be 2 to 4 minutes. If the mixing time of the stirrer is less than 2 minutes, a necessary level of kneading effect can not be achieved, and if it is more than 4 minutes, the productivity may be lowered.

Hereinafter, embodiments of the present invention will be described in detail.

Example  1-1: Absorbent production with absorption heat generation function

The papermaking materials generated in the papermaking process of Jeonju Paper and the steelmaking slag generated in the POSCO iron refining process were each added to a high-speed shear omni mixer (CHIYODA OMH-30NA, Japan) at a weight ratio of 50:50, At 350 rpm for 3 minutes to prepare an absorbent having an absorbing heat generating function. Table 1 and Table 2 below show the properties of the papermaking materials and the steelmaking slag used, respectively.

pH Constituent Ca Si Al Fe Mg Cl Ti S 12.58 XRF analysis (%) 65.67 10.17 6.57 2.52 2.4 1.52 10.2 0.93 XRD analysis _{Ca (CO 3) (calcite)} , Ca (OH) 2 (portlandite), Ca 2 (SiO 4) (calcium silicate)

pH Constituent Ca Si Al Fe Mg Mn Zn F 12.79 XRF analysis (%) 37.59 4.42 0.95 40.65 3.73 4.92 2.46 1.53 XRD analysis _{Ca (CO 3) (calcite)} , CaO (lime), Ca (OH) 2 (portlandite), SiO 2 (quartz), Ca 3 Si 2 O 7 (rankinite), MgFe +3 O 4 (magnesioferrite)

Example  1-2-1: Preparation of functional mixture 1 (adsorption and pH  control)

The waste catalyst produced in Hyundai Oilbank, S-Oil and GS-Caltex oil refining process and the pH adjuster carrying the sulfuric acid on the spent catalyst were mixed with a high-speed shear omni mixer (CHIYODA OMH-30NA ) And mixed at 350 rpm for 3 minutes under constant temperature and humidity conditions to prepare a multi-functional mixture. Table 3 and Table 4 show the properties of the pH adjusting agent carrying sulfuric acid on the used catalyst and the spent catalyst, respectively.

pH Constituent Ca Si Al Fe La P TI S 4.53 XRF analysis (%) 0.13 42.47 40.21 1.6 8.76 0.87 1.3 2.09 XRD analysis _{Na 48 .8 (Al 48 .8 Si} 143 .2 O 384) (sodium aluminum silicate)

pH Constituent S Si Al Fe La Ti V Ca 0.14 XRF analysis (%) 43.9 23 20.9 2 2.5 1.8 1.7 One XRD analysis Si ₁₂ O ₂₄ (Silicon Oxide), (Al ₂ O ₃ ) _1.333 (Aluminum Oxide)

Example  1-2-2: Preparation of functional mixture 2 (adsorption and pH  control)

The waste catalyst from Hyundai Oilbank, S-Oil and GS-Caltex petroleum refining process and the pH adjuster containing sulfuric acid were added to the waste catalyst at a weight ratio of 40:60, respectively, using a high-speed shear omni mixer (CHIYODA OMH-30NA ), A complex functional mixture was prepared in the same manner as in Example 1-2.

Example  1-2-3: Preparation of functional mixture 3 (adsorption and pH  control)

The waste catalyst produced in Hyundai Oilbank, S-Oil and GS-Caltex oil refining process and the pH adjuster carrying the sulfuric acid on the spent catalyst were mixed with a high-speed shear omni mixer (CHIYODA OMH-30NA ), A complex functional mixture was prepared in the same manner as in Example 1-2.

Example  1-2-4: Preparation of functional mixture 4 (adsorption and pH  control)

The waste catalysts from Hyundai Oilbank, S-Oil and GS-Caltex oil refining processes and the pH adjusters containing sulfuric acid were added to the waste catalysts at a weight ratio of 80:20, respectively, using a high-speed shear omni mixer (CHIYODA OMH-30NA ), A complex functional mixture was prepared in the same manner as in Example 1-2.

Example  1-3: Complex Functionality Solidifying agent  Composition manufacturing

45.0% by weight of the absorbent heat absorptive absorbent prepared in Example 1-1, 54.0% by weight of the functional mixture prepared in Example 1-2-1, and 1.0% by weight of Portland cement were mixed with a high-speed shear omni mixer (CHIYODA OMH-30NA) and mixed at 350 rpm for 3 minutes under constant temperature and humidity conditions to prepare a composite functional solidifying composition.

Experimental Example  : In sludge  apply

The sludge used in this experiment is the sludge collected at the I smelting facility in I, and the 22 odorous substances including sulfur compounds and nitrogen compounds are generated. 50 g of the briquette was added to 500 g of the sludge, and 75 g of the multifunctional solidifying agent composition prepared in Example 1-3 was added thereto. The mixture was stirred for 5 minutes and pH and moisture content were measured. Lt; / RTI > Nitrogen was injected into the sampler and allowed to stand at room temperature for 2 hours. Then, odor trends were analyzed with a detector tube, GC-PFPD, HPLC and GC-MSMS. Table 5 shows the results of the analysis by setting the solidifying agent being applied at the I solidifying treatment establishment as a control group.

Analysis contents Example 1-3 Solidifying agent (control group) Odor concentration
(ppm) Hydrogen sulfide N.D. 1.718 Methyl mercaptan N.D. 2.48 Methyl sulfide 0.907 6.063 Methyl disulfide 0.078 0.128 Acetaldehyde 0.039 0.127 Propionaldehyde N.D. 0.012 Butylaldehyde N.D. 0.007 Valeraldehyde N.D. 0.009 Isovaleraldehyde N.D. 0.002 ammonia 300 75 Trimethylamine 1.3 0.9 Styrene N.D. N.D. toluene N.D. 0.011 Xylene N.D. N.D. Methyl ethyl ketone N.D. N.D. Methyl isobutyl ketone N.D. 0.002 Butyl acetate 0.001 0.005 Propionic acid N.D. 0.002 Butyric acid N.D. 0.008 Valeric acid N.D. N.D. Isobutyl alcohol N.D. 0.007 Properties pH (high load) 9.7 7.4 Moisture content (high cargo%) 64.5 68.5

Referring to Table 5, it can be seen that the amount of sulfur compound, aldehyde, VOCs, and the like is significantly reduced when the composite functional solidifying agent composition of Example 1-3 is applied as compared to the control group. However, the generation of odor substances such as ammonia and amine was slightly increased due to the absorption and exothermic reaction caused by the CaO component contained in the absorbent, but this was easily removed by a known basic odor control system such as a deodorant spraying facility .

It will be understood by those skilled in the art that the foregoing description of the present invention is for illustrative purposes only and that those of ordinary skill in the art can readily understand that various changes and modifications may be made without departing from the spirit or essential characteristics of the present invention. will be. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. For example, each component described as a single entity may be distributed and implemented, and components described as being distributed may also be implemented in a combined form.

The scope of the present invention is defined by the appended claims, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present invention.

Claims (10)

35 to 55% by weight of an absorbent comprising paper milled material and steelmaking slag;
40 to 60% by weight of an adsorbent composed of a spent catalyst in a petroleum refining process and a pH adjuster carrying acid on a spent catalyst in a petroleum refining process are mixed at a weight ratio of 20 to 80:20 to 80, respectively; And
1 to 5% by weight of cement.
The method according to claim 1,
Wherein the paper burning material is fly ash generated after incineration of paper mill sludge.
The method according to claim 1,
The steelmaking slag is a mixture of lime (CaO), iron oxide (Fe ₂ O ₃ ), silica (SiO ₂ ), manganese oxide (MnO), alumina (Al ₂ O ₃ ) Lt; RTI ID = 0.0 > a < / RTI > sludge.
The method according to claim 1,
Wherein the spent catalyst in the petroleum refinery process is a spent catalyst used in a fluidized bed catalytic cracking process.
5. The method of claim 4,
Wherein the waste catalyst is a spherical catalyst in which zeolite is supported on silica-alumina.
6. The method of claim 5,
Wherein the acid supported on the spent catalyst is one selected from the group consisting of sulfuric acid (H ₂ SO ₄ ), hydrochloric acid (HCl), nitric acid (HNO ₃ ) and a mixture of two or more thereof.
The method according to claim 1,
Wherein the sludge is domestic sewage, sewage, industrial wastewater, livestock manure, and food sludge.
(a) mixing the papermaking material and steelmaking slag to produce an absorbent;
(b) mixing an adsorbent composed of a waste catalyst in a petroleum refining process and a pH adjusting agent loaded with acid on a spent catalyst in a petroleum refining process at a weight ratio of 20 to 80:20 to 80, respectively, to prepare a functional mixture; And
(c) preparing a solidifying agent by mixing 35 to 55% by weight of the absorbent, 40 to 60% by weight of the functional mixture, and 1 to 5% by weight of cement to form a solidifying agent .
9. The method of claim 8,
In the above steps (a) to (c), the mixing is carried out using one or more stirrers.
10. The method of claim 9,
Wherein the rotating speed of the stirrer is 300 to 450 rpm.

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