KR102120114B1 - Manufacturing method of geopolymer using liquid slag - Google Patents

Abstract

Disclosed is a method for preparing a geopolymer by improving the compressive strength of a geopolymer using IGCC molten slag by introducing a pre-curing process in which the specimen is left at room temperature before curing at high temperature. The present invention (a) crushing the molten slag discharged from the coal gasification process; (b) mixing the pulverized molten slag and an alkali activator to prepare a dough sample; (c) pre-curing the molded body filled with the dough sample in a mold at 23-25°C; (d) curing the molded body subjected to step (c) in a dryer at 70 to 80° C. for 24 hours; And (e) demolding the molded body after step (d) to aging at 23 to 25° C. to provide a method for manufacturing a geopolymer using molten slag.

Description

Manufacturing method of geopolymer using molten slag {Manufacturing method of geopolymer using liquid slag}

The present invention relates to a method for producing a geopolymer, and more particularly, to a method for producing a geopolymer using IGCC molten slag.

Recently, as interest in low-carbon inorganic binder materials capable of substituting cement has increased due to environmental problems, the possibility of cement replacement of geopolymers produced by activating alumina silicate-based raw materials with an alkali solution has attracted attention.

Geopolymers are reported to have low carbon dioxide emissions during production as well as high heat and chemical resistance, high initial strength and freeze-thaw resistance, and crack, corrosion and weathering resistance when compared to Portland cement. In addition, alumina silicate-based geopolymers can be manufactured as industrial raw materials such as coal ash or blast furnace slag as mentioned, which is recognized as a very important research in terms of recycling of waste resources.

Meanwhile, a method of manufacturing a geopolymer based on molten slag discharged from IGCC (Integrated Gasification Combined Cycle), which is a form of coal power generation, is receiving attention, but in the case of IGCC molten slag, a compressive strength value of 20 MPa or less As it is expressed, a higher compressive strength expression is required for commercialization.

Korean Patent Publication No. 2015-0005019 discloses a geopolymer using inorganic sludge waste, but does not describe the method of improving the compressive strength of the geopolymer using the IGCC molten slag of the present invention.

The present invention is to provide a method for preparing a geopolymer by improving the compressive strength of a geopolymer using IGCC molten slag by introducing a pre-curing process in which a specimen is left at room temperature before curing at high temperature.

In order to solve the above problems, the present invention (a) crushing the molten slag discharged from the coal gasification process; (b) mixing the pulverized molten slag and an alkali activator to prepare a dough sample; (c) pre-curing the molded body filled with the dough sample in a mold at 23-25°C; (d) curing the molded body subjected to step (c) in a dryer at 70 to 80° C. for 24 hours; And (e) demolding the molded body after step (d) to aging at 23 to 25° C. to provide a method for manufacturing a geopolymer using molten slag.

In addition, in the step (a), the molten slag provides a method for manufacturing a geopolymer using molten slag, characterized in that the average particle diameter is 128㎛ or less.

In addition, in the step (b), the mixing ratio of the molten slag and the alkali activator is 1:0.24 ~ 0.28 provides a method for producing geopolymer using molten slag, characterized in that.

In addition, step (c) provides a method for producing a geopolymer using molten slag, characterized in that the molded body is pre-cured for 1 to 27 days.

In addition, step (e) provides a method for manufacturing a geopolymer using molten slag, characterized in that the molded body is regenerated for 1 to 27 days after step (d).

In addition, the geopolymer using the molten slag provides a method for producing a geopolymer using molten slag, characterized in that the size of the zeolite phase observed by a scanning electron microscope is 0.5 to 1.5 μm and the compressive strength is 20 to 40 MPa.

According to the present invention, it is possible to provide a method for preparing a geopolymer in which the compressive strength of a geopolymer using IGCC molten slag is improved by introducing a pre-curing process in which a specimen is left at room temperature before curing at a high temperature.

1 is a graph showing the flow value according to the mixing ratio (W/S) of the molten slag and the alkali activator,
Figure 2 is a graph showing the compressive strength of the geopolymer according to the number of days of curing,
Figure 3 is a graph showing the compressive strength according to the total curing time and age of specimens with a total number of trial days 3 days,
Figure 4 is a graph showing the compressive strength according to the total curing time and age of the specimen with a total of 7 days of trial,
Figure 5 is a graph showing the compressive strength according to the total curing time and age of the specimens with a total of 28 days of trial,
Figure 6 is a graph showing the results of XRD analysis of the specimen with a total of 7 days of trial,
7 is a graph showing the results of FT-IR analysis of specimens with a total number of trial days of 7 days;
8 is a SEM photograph of the P0-A6 specimen and the P2-A4 specimen,
9 is a graph showing the results of XRD analysis of IGCC molten slag,
10 is a flow chart of a method for producing a geopolymer according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail. In the description of the present invention, when it is determined that a detailed description of related known technologies may obscure the subject matter of the present invention, the detailed description will be omitted. Throughout the specification, when a part “includes” a certain component, this means that other components may be further included instead of excluding other components, unless specifically stated to the contrary.

Geopolymer manufacturing method using the molten slag according to the present invention comprises the steps of: (a) crushing the molten slag discharged from the coal gasification process; (b) mixing the pulverized molten slag and an alkali activator to prepare a dough sample; (c) pre-curing the molded body filled with the dough sample in a mold at 23-25°C; (d) curing the molded body subjected to step (c) in a dryer at 70 to 80° C. for 24 hours; And (e) demolding the molded body after step (d) to aging at 23 to 25°C.

The geopolymer is a new concept of'new material' that does not require Portland cement as a binder, and instead of using Portland cement, minerals such as fly ash rich in Si and Al are added to the alkaline liquid. It is activated and used as a binder. The polymerization process of Geo-polymer refers to a process of forming a Si-O-Al-O bond of a polymer by chemical reaction of Al-Si mineral in a high alkali state. Geopolymer cement is based on a curing mechanism by dissolving and synthesizing aluminum and silica components with an alkali activator having a high pH, and the physical properties and material properties of the binder vary depending on the type of the raw material and the activator. In order to apply the properties of these geopolymers, the composition and component ratio of the raw materials are very important, and in the case of molten slag, they are amorphous and most of the constituent materials are Si and Al. Is possible.

In the step (a), the molten slag is a material discharged from the coal gasification process, and the sample shape has various sizes and is very hard crystal form, and thus, grinding is performed to improve reactivity and uniformize the component ratio. When considering reactivity and component ratio, it is preferable that the average particle diameter of the crushed molten slag is 128 µm or less. In addition, the molten slag discharged from the coal gasification process may be washed with washing water to remove impurities, and drying or dehydration may be performed so that moisture of the washed molten slag is 10% or less.

The components of the pulverized molten slag analyzed using XRF (XRF, ZSX Primus, RIGAKU, Japan) and ICP-AES (OPTIMA 8300, Perkin-Elmer, USA) are shown in Table 1 below. .

division SiO ₂ Al ₂ O ₃ Fe ₂ O ₃ CaO MgO Na ₂ O K ₂ O TiO ₂ Total IGCC slag 49.2 20.2 5.6 21.7 1.3 0.5 0.5 1.1 100

Referring to Table 1, the IGCC molten slag mainly contains SiO ₂ and Al ₂ O ₃ as main components, and also contains a certain amount of CaO. In addition, the geopolymer conversion reaction is that Si and Al are ionized and then combined, and the strength and structure of the final material are changed according to the composition ratio of Si and Al. In general, in order to prepare a geopolymer, the Si:Al ratio is known to be 1.5 to 2.5.

In addition, referring to Figure 9 showing the results of XRD (Rigaku MiniFlex2, Japan) for the analysis of the crystal phase of the molten slag, IGCC slag is made of an amorphous phase because it is rapidly quenched in a high temperature environment. It is suitable for use as a material for geopolymers because the elution of Si and Al ions is easier than crystalline.

The step (b) is a step of making a dough sample by mixing the pulverized molten slag and an alkali activator, and the dough sample having completed dough is filled into a mold designed/manufactured to produce a desired shape.

In step (b), the mixing ratio (W/S) of the molten slag and the alkali activator is melted before curing according to ASTM C 1437-07 in order to satisfy not only the high compressive strength of the geopolymer but also the fluidity for product molding. It is preferable that the flow value of the slag geopolymer paste is 100% or more, and referring to FIG. 1 showing a flow value according to the mixing ratio (W/S) of the molten slag and the alkali activator, the molten slag according to the present invention The mixing ratio of the alkali activator may be 1:0.24 to 0.28. In this case, the alkali activator is an aqueous solution of sodium hydroxide (NaOH) and distilled water, and the concentration may be 10 to 18 moles/L.

The (c) pre-curing (pre-curing) step is a process for leaving the molded body at room temperature for a certain time, a step for increasing the strength of the specimen, and in the present invention, the pre-curing can be performed for 1 to 27 days.

The step (d) is a step of curing (high temperature curing) for 24 hours in a dryer at 70 to 80° C. for the molded body subjected to the step (c). The present invention can prepare a geopolymer using IGCC molten slag with improved compressive strength by controlling the conditions of the (c) pre-curing and high-curing (e) age-old steps before high temperature curing.

The (e) aging step is a process of leaving the finished geopolymer through high temperature curing at room temperature, and is carried out at a specific ratio together with the pre-curing to improve the compressive strength of the geopolymer. In the present invention, the age may be 1 to 27 days.

Hereinafter, properties of the geopolymer prepared according to the present invention will be described through specific examples and comparative examples.

Examples and comparative examples

The crushed molten slag having an average particle diameter of 128 µm or less was screened by sieving the molten slag using a Planetary Ball Mill. The selected molten slag is mixed with an alkali activator (NaOH (DAEJUNG CHEMICALS, 97%, Korea) 15M) at a mixing ratio of 1:0.26 to make a dough sample. After filling the finished dough sample into a mold (50×50×50mm ³ ) for molding a specimen, and sealing it with a plastic bag, the specimen is demolded after pre-curing (23℃) and high-temperature curing (70℃) in a dryer. Geopolymer specimens using IGCC molten slag were completed by carrying out the re-aging (23°C) (the total number of days of pre-curing, high-temperature curing and re-treatment is summarized in Table 2 below).

Psalm name
(Sample ID) Total number of days Total number of days High temperature curing days Age of Age P0-A2 3 0 One 2 P1-A1 One One P2-A0 2 0 P0-A6 7 0 One 6 P1-A5 One 5 P2-A4 2 4 P3-A3 3 3 P4-A2 4 2 P5-A1 5 One P6-A0 6 0 P0-A27 28 0 One 27 P7-A20 7 20 P14-A13 14 13 P21-A6 21 6 P27-A0 27 0

※ The name of the specimen was named as the number of days of p-curation/the number of days of age A.

Test example

The characteristics of the specimens were analyzed according to the following measurement methods for the specimens of the Examples and Comparative Examples.

1) Using UTM (UTM-900NH Series DAEKYUNG, Korea), compressive strength of specimens with different curing age, high temperature curing, and age was measured.

2) XRD was used to analyze the crystal phase of the specimens for 7 days.

3) FT-IR (IFS66v-S, BRUKER, USA) was used to analyze the binding characteristics of specimens with a total of 7 days.

4) Observing the microstructure of P0-A6 and P2-A4 specimens using SEM (Scanning Electron Microscope, S-4800, HITACHI, Japan).

2 is a graph showing the compressive strength of the geopolymer according to the number of days of curing.

Referring to FIG. 2, after compressing the pre-curing period within a range of 0 to 6 days, the compressive strength of a specimen prepared through high temperature curing for 1 day and aging for 3 days has a pre-curing time of 1 The single specimen improved compared to the specimen prepared without pre-curing, and when the pre-curing time was 2 days, the maximum compressive strength of 23.0 MPa, which was 60% higher than the compressive strength (14.4 MPa) of the non-precured specimen, was shown. However, the compressive strength of the specimen gradually decreased when the total curing time was over 3 days.

Figure 3 is a graph showing the compressive strength according to the total curing time and age of specimens with a total number of trial days of 3 days.

Referring to FIG. 3, both the specimen (P0-A2) that was 2 days old only without pre-curing or the specimen (P2-A0) that was pre-cured for 2 days and had a low compressive strength of about 15 MPa Although it was shown, the specimens (P1-A1) that were subjected to pre-curing and re-aging time for 1 day each showed 21 MPa, which was 32% higher than the other specimens.

Figure 4 is a graph showing the compressive strength according to the total curing time and age of specimens with a total number of trial days of 7 days.

Referring to Figure 4, compared to the compressive strength of the P0-A6 specimen not subjected to pre-curing, the compressive strength of the P2-A4 specimen undergoing pre-curing for 2 days increased by about 36% to 23.5 MPa. From this, it can be seen that the pre-curing has an effect on enhancing the geopolymer strength, but it was confirmed that the specimens prepared with excessive pre-curing time and low age were rather deteriorated in strength.

5 is a graph showing the compressive strength according to the total curing time and age of the specimen with a total of 28 days of trial.

5, the compressive strength of the P0-A27 specimen without pre-curing was 17.8 MPa, but the compressive strength of the P14-A13 specimen undergoing pre-curing for 14 days increased by about 87% to 33.2 MPa. However, when the total curing time became 21 days or more and the age-old time decreased to 6 days or less, the compressive strength of the geopolymer decreased again.

Overall, pre-curing performed at room temperature has the effect of increasing the strength of the geopolymer, but it has been shown to decrease the compressive strength of the geopolymer rather than proceeding for too long. In general geopolymer reactions, Si and Al ions eluted by an alkali activator form monomers, and in high-temperature environments, the monomers undergo condensation/polymerization reactions, and strength is enhanced. It is believed that the amount of Si and Al ions eluted before curing increases, and ultimately, it is effective in enhancing strength due to an increase in monomers capable of condensation polymerization.

6 is a graph showing the results of XRD analysis of a specimen with a total number of trial days of 7 days.

Referring to FIG. 6, sodium aluminum silicate hydroxide hydrate [Na ₈ (Al ₆ Si ₆ O ₂₄ )(OH) _2.04 (H ₂ O) _2.66 ], which is a type of zeolite, and calcium silicate hydrate (CSH) ) A gel phase was observed. These phases are known to be the result of the geopolymer reaction, so it can be seen that the geopolymer reaction occurred in these specimens. Looking at the vicinity of 31.6° of the P6-A0 specimen graph, it can be seen that the peak on the CSH gel phase grew finely compared to the P0-A6 specimen, and it is believed that the increase in precuring time promotes the formation of the CSH gel phase. However, since the corresponding peak size of the phase is not large, and other peaks or zeolite phase peaks are not significantly different in all specimens, it is considered that an additional analytical study is needed.

7 is a graph showing the results of FT-IR analysis of specimens with a total number of trial days of 7 days.

7, the absorption peak at 453cm ^-1 will by Si-O-Si bonds, the absorption peak at 675 ~ 685cm ^-1 is a Si-OT (T = Si, Al) bond, 946 ~ 961cm ^{- In 1} , Si-O-Na bond, and in 995-1150 cm ^-1 , SiO ₄ bond. In addition, the absorption peak of 1430 cm ^-1 is OCO bond, 1650 cm ^-1 is HOH bond, and 3427 to 3464 cm ^-1 is due to T-OH...H ₂ O (T=Si, Al) bond. Geopolymer synthesis was confirmed from Si-OT and T-OH...H ₂ O bonding peaks, but it was difficult to confirm each peak change by pre-curing.

8 is a SEM photograph of the P0-A6 specimen and the P2-A4 specimen.

Referring to FIG. 8, in any specimen, a square crystal-shaped zeolite phase was observed on a surface made of C-S-H gel. In addition, it was found that in the case of the specimen (b) subjected to pre-curing, a zeolite phase having an average size of 1 µm was generated, while in the case of the specimen (a) not pre-curing, the average size of the generated zeolite was as small as about 0.5 µm. . In the specimens subjected to pre-curing, more Si and Al ions were eluted, and it is believed that this undergoes high-temperature curing and generates more zeolite phases through a polycondensation reaction and consequently contributes to the enhancement of the compressive strength of the geopolymer.

Therefore, the geopolymer prepared according to the present invention is preferably within 40-70% of the total number of trial days (pre-curing + high-temperature curing + age), and the size of the zeolite phase observed with a scanning electron microscope. It may be 0.1 ~ 2.0㎛, preferably 0.5 ~ 1.5㎛. In addition, the geopolymer using the molten slag prepared according to the present invention may have an excellent compressive strength of 20 to 40 MPa compared to the molten slag geopolymer prepared by a general method.

The preferred embodiments of the present invention have been described above in detail. The description of the present invention is for illustration only, and those skilled in the art to which the present invention pertains will appreciate that other specific forms can be easily modified without changing the technical spirit or essential features of the present invention.

Therefore, the scope of the present invention is indicated by the following claims rather than the above detailed description, and it should be interpreted that all changes or modified forms derived from the meaning, scope and equivalent concepts of the claims are included in the scope of the present invention. do.

Claims (6)

(A) grinding the molten slag discharged from the coal gasification process;
(b) mixing the pulverized molten slag and an alkali activator to prepare a dough sample;
(c) pre-curing the molded body filled with the dough sample in a mold at 23 to 25°C;
(d) curing the molded body subjected to step (c) in a dryer at 70 to 80° C. for 24 hours; And
(e) a step of demolding the molded body after the step (d) and re-aging at 23 to 25°C; as a method for manufacturing a geopolymer using molten slag comprising:
In the step (a), the molten slag has an average particle diameter of 128 μm or less,
In the step (b), the mixing ratio of the molten slag and the alkali activator is 1:0.24 to 0.28,
In the step (c), the molded body is pre-cured for 1 to 27 days,
In the step (e), after the step (d), the molded body is re-elected for 1 to 27 days,
The method for producing geopolymer using molten slag is characterized in that the duration of the pre-curing is 40-70% of the total duration of the pre-curing, high-temperature curing, and age. delete delete delete delete According to claim 1,
The geopolymer using the molten slag has a size of 0.5 to 1.5 µm, and a compressive strength of 20 to 40 MPa, the size of the zeolite observed by a scanning electron microscope.

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