KR100357524B1 - Solidity material for reapplication of assignment waste harding foam having excellent compressive strength using the solidity material - Google Patents

Abstract

The present invention relates to a hardener using a solidifying agent (solidifying agent) for solidifying a designated waste containing heavy metals and a solidifying agent which has stability against heavy metal elution with excellent strength and can be recycled as an industrial material through addition of the hardening agent. It is about.

The solidifying agent according to the present invention comprises 40 to 60% of CaO, 15 to 20% of SiO ₂ , 5 to 10% of Al ₂ O ₃ , _{2 to} 6% of Fe ₂ O ₃ , 4 to 5% of MgO, 0.5 to 1% of S, It is characterized by having a composition ratio of CaCO ₃ 2-20%.

In addition, the cured product according to the present invention is characterized by curing by mixing 12 to 20% of the solidifying agent, 25 to 35% of designated waste, 20 to 28% of cement, 25 to 35% of sand.

Description

Solidified material for recycling designated wastes and hardened material with excellent compressive strength manufactured using the same. {SOLIDITY MATERIAL FOR REAPPLICATION OF ASSIGNMENT WASTE HARDING FOAM HAVING EXCELLENT COMPRESSIVE STRENGTH USING THE SOLIDITY MATERIAL}

The present invention relates to a solidifying agent (solidifying agent) for solidifying a designated waste containing heavy metals. In addition, the present invention relates to a cured product produced by using a solidifying agent which can be recycled as an industrial material and has stability against heavy metal elution with excellent strength through the addition of the solidifying agent.

Recently, the rapid increase of hazardous industrial wastes containing heavy metals has become a serious environmental problem.

In particular, steelmaking dust from steel and steel mills and plating sludge from wastewater treatment plants in metallurgical plants contain a large amount of heavy metals, which, when left in nature, itself releases harmful substances to animals and plants and humans. As a result, it causes pollution of the natural environment such as soil, rivers and groundwater in the ecosystem, causing a great problem for humans and the natural environment.

These hazardous industrial wastes are likely to contaminate the surrounding soil and groundwater with harmful heavy metals if they are landfilled and disposed of as they are. Therefore, landfilling should be carried out after solidifying in an appropriate manner.

Most of the designated wastes are heavy metals, and heavy metals exist in elemental state which can no longer be decomposed by general treatment methods. Therefore, when the designated wastes containing heavy metals are landfilled, they contain a considerable amount of inorganic and harmful substances. Subsequent decomposition may occur after disposal, and at the same time cause secondary environmental pollution due to heavy metal leaching.

In consideration of the characteristics of these heavy metals, the solidification method is selected at the time of final disposal, and according to the domestic waste management law, certain hazardous wastes are to be solidified with cement and landfilled in landfills.

In this case, the solidification refers to a process of changing the physical properties (tension, compressibility, permeability) of the waste during the solidification process by adding an additive, and the method of solidifying the waste includes cement solidification, asphalt solidification, and plastics. There are solidification, lime solidification, water glass solidification and sintering methods, which are explained in more detail.The method is to compress and harden the waste, and then seal it with concrete, and the solidification method is mixed with the waste to make a solid block at room temperature. There is a solidification method and a sintering method in which waste is heated to a high temperature together with glass or clay.

Solidification for final disposal is a method that is carried out when the sludge contains a certain amount of harmful substances and is removed as a secondary pollutant at the time of final disposal. It minimizes the outflow rate of hazardous substances physically and chemically by hardeners and stabilizers. .

Therefore, the physically isolated and chemically stable sludge in the sludge has a very low rate of environmental contamination since the outflow rate to the natural world is very low, but the solidified waste has the disadvantage that the volume increases and the transportation cost increases.

The solidification treatment is widely applicable to inorganic wastes in general, and the considerations in selecting the sludge solidification treatment method should include the cost of the process, increase in volume, pretreatment method and disposal method.

Recycling for the purpose of solidification requires higher strength and lower elution values than for final disposal.

To this end, in most cases, by adding fly ash and chemicals to waste and cement, solidification experiments for building and construction materials are being tested.

The solidification system can be classified into organic process and inorganic process. In the inorganic process, cement-based method is most widely used, and most of them are monolithic using portland cement, lime, clay and other silica mixtures. Phosphorus is the process of making the final material.

In addition, the low temperature solidification method and the high temperature solidification method are classified according to the solidification temperature. Among them, the low temperature solidification method includes cement solidification method, asphalt solidification method, lime pozzolanic solidification method, and compression method. There are a sinter solidification method in which the incineration material generated during the incineration process is combined with the solidified material and melted, and a high temperature melt solidification method in which the incineration material is melt slagd using fuel or electricity.

Cement solidification technology is used to solidify high concentrations of heavy metals and organic toxic substances. In general, the mechanism of immobilization of toxic substances by solidification of cements is that toxic substances are involved in the hydration reaction of cement when the cement particles are hydrated with water. High molecular compounds, in particular chemical immobilization by the production of chelate compounds, or by trapping in pores in solidified bodies with dense tissue formed by immobilization by adsorption of additive mixtures and reaction products, formation of poorly soluble substances and hydration reactions. It is mainly classified into blocking contact with the surrounding environment by physical encapsulating or the like.

Cement solidification is known to be particularly suitable for inorganic wastes containing heavy metals. Due to the high pH of the cement, metals are present in the form of insoluble hydroxide carbonates in the hardened material structure. Lead, copper, zinc, tin, and cadmium are easily formed by incorporating insoluble compounds by chemical immobilization, whereas mercury It is mainly fixed by physical microcapture.

Organic contaminants, on the other hand, interfere with the hydration reaction, reducing the final binding and are not easily stabilized.

Organic contaminants also reduce the formation of crystal structures, resulting in amorphous materials. Additives are often used in combination with cement to reduce organic contaminants from interfering with cement hydration and to increase stabilization.

These additives include organically modified clays, natural clays, weathered Vermiculte and soluble sodium silicates.

The most important thing in stabilizing and solidifying hazardous wastes containing heavy metals is that the solids must be able to withstand the external environment and, in particular, be able to suppress the release of harmful substances by acid rain.

Meanwhile, the cement solidification method that has been developed and put into practical use is stabilized by adding steelmaking dust, heavy metal stabilizing agent and a small amount of water to the mixer, and then adding about 2-3% cement by the weight ratio of dust to exothermic reaction by cement. It is composed of a process of natural drying by solar heat, and it can maintain the strength of solidified waste material and fix heavy metals in the waste relatively stably, and it is recognized in various fields as an economical treatment method.

However, this method can elute harmful heavy metals contained in solid specimens due to the specific environment, such as acid rain or seawater, and in the presence of metal ions, it delays the hydration reaction of cement and inhibits the curing reaction of the specimen, thereby reducing the compressive strength. There is such a problem.

Above all, since the groundwater is acidic and the cement is severely affected by causing structural collapse under acidic conditions, it is important to treat the heavy metal waste to suppress elution in acidic solution.

Although cement-based stabilization techniques have many advantages, one of the major drawbacks is that the sensitivity of the cement to pollutants that delays or hinders proper hydration results in problems affecting the hardening of the material. Technology development is required to solve this problem.

The present invention was devised in view of the above problems and necessities, and an object of the present invention is to promote the hydration reaction of cement when solidifying a designated waste together with cement, thereby suppressing the hardening interference effect by heavy metal ions or the like. It is to provide a topic.

Another object of the present invention is to provide a cured body using a solidifying agent that is manufactured with the above-described solidifying agent and can be variously utilized as construction materials, building materials and civil engineering materials through recycling of designated wastes.

1 is a process flow diagram for producing a cured body using a solidifying agent for recycling designated waste according to the present invention,

2A and 2A are tissue photographs of 7-day intensity specimens of the cured body according to the present invention observed at different magnifications using an electron microscope (SEM).

In order to achieve the above object, CaO 40-60%, SiO ₂ 15-20%, Al ₂ O ₃ 5-10%, Fe ₂ O ₃ 2-6%, MgO 4-5%, S 0.5-1% And a caking agent for recycling designated wastes, comprising 2 to 20% CaCO ₃ .

In addition, there is provided a cured product having excellent compressive strength, characterized in that 12 to 20% of a solidifying agent having the above composition ratio, 25 to 35% of designated waste, 20 to 28% of cement, and 25 to 35% of sand are mixed and cured.

In addition, the designated waste provides a hardened body having excellent compressive strength, characterized in that the steelmaking dust and plating sludge.

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

The solidifying agent for recycling designated waste according to the present invention is CaO 40 to 60%, SiO ₂ 15 to 20%, Al ₂ O ₃ 5 to 10%, Fe ₂ O ₃ 2 to 6%, MgO 4 to 5%, S The composition ratio is 0.5 to 1% and CaCO ₃ 2 to 20%.

Moreover, the hardening body which concerns on this invention mixes and hardens 12-20% of said hardening | curing agents, 25-35% of designated wastes, 20-28% of cement, and 25-35% of sand.

The reason for numerical limitation of the said composition ratio is as follows.

If CaO is less than 40%, the hydration reaction occurs less and hardening does not occur, and if it is 60% or more, the hydration reaction occurs too much, causing cracks in the hardened body, and thus acting as an obstacle to hardening, limited to 40% to 60%. do.

In addition, the compositional value of SiO ₂ , Al ₂ O ₃ , Fe ₂ O ₃ is limited by the content that the SiO ₂ / R ₂ O ₃ ratio is usually within 1.5 according to the general cement theory, where R ₂ O ₃ Denotes the sum of Al ₂ O ₃ and Fe ₂ O ₃ .

In addition, the amounts of MgO and S are the amounts calculated based on the Lime Saturation Factor (LSF) equation in general cement theory after the values are determined.

CaCO ₃ actually reduces the cracks caused by overheating of CaO and improves the strength.If it is less than 10%, the strength is not enhanced. It is limited to.

In addition, when the amount of cement is less than 20%, the strength value for recycling falls, and when added in excess of 28%, the economical efficiency is reduced, so limited to 20 to 28%.

The amount of the hardening agent to 12 to 20% is limited in relation to the economics of the hardened body as in the above cement, and it is preferable that the addition amount of the cement and the hardening agent does not exceed 40% of the total blending ratio.

The amount of sand is limited to 25 to 35%, and the sand is added at about 2.45 times that of cement in the cement mortar test method. However, in the present invention, the designated wastes are also replaced with cement aggregates such as sand to limit the amount of sand added.

The amount of the designated waste is limited to 25 to 35% in order to make the amount of the designated waste and sand added more than 60% of the total mixing ratio.

If the designated waste is to be solidified, the solidifying agent should be harmless, capable of solidifying even at high moisture content sludge, and no harmful substances shall be eluted from the cured product. In addition, the solidifying agent should be stable for a long period of time so as not to collapse, and it should not cause pollution by the solidification operation.

The four types of solidifying agents used for this purpose are classified into cement-based hardeners using a hydration reaction, coal-based hardeners using a Pozzolan reaction, asphalt-based hardeners, and flocculants such as water glass urethane.

In the present invention, the hydration reaction and the Pozzolan reaction were used through a method of solidifying by mixing solidified portland cement and fly ash in a designated waste.

In Portland cement, which is a solidifying agent, CaO, SiO2, Al2O3, Fe2O3 are the main components, and these components are 90% or more of the total composition.They are easily solidified by hydration reaction when they are mixed with sludge. The hydration reaction is as follows.

2 (3CaOSiO ₂ ) + 6H ₂ O → 3CaO 2SiO ₂ 3H ₂ O + 3Ca (OH) ₂ (1)

2 (2CaOSiO ₂ ) + 4H ₂ O → 3CaO · 2SiO ₂ · 3H ₂ O + Ca (OH) ₂ (2)

_{3CaO · Al 2 O 3 + 6H} 2 O → 3CaO · Al 2 O 3 · 6H 2 O (3)

_{4CaO · Al 2 O 3 · Fe} 2 O 3 + 2Ca (OH) 2 + 10H 2 O →

_{3CaO · Al 2 O 3 · 6H} 2 O + 3CaO · Fe 2 O 3 · 6H 2 O (4)

Hereinafter, the present invention will be described in more detail with reference to Examples.

In solidifying designated wastes, solidification aids such as cement and clay and various chlorides added to assist in the combination of these components are selected to evaluate the compressive strength and dissolution characteristics of the prepared cured product, In order to evaluate the impact on the waste, the designated wastes were steel sludge from steel mill and plating sludge discharged from wastewater treatment plant.

Solidification experiments were conducted according to the solidifying agent, the solidification aid, the mixing ratio, and the curing days, and the strength test (uniaxial compressive strength) and the dissolution test were carried out.

(1) Experimental Materials and Flow Sheets

The sample used in the present invention is a heavy metal-containing waste, which is a powder form of steelmaking dust and plated sludge which is dried and crushed after drying for 2 days (48 hours) in a dryer at about 100 to 110 ° C through a sieve of about 1.19 mm. As a solidifying agent having a composition ratio, fly ash as a solidifying aid, sand and clay having a particle size of about 0.85 mm or less were used.

In general, the waste process test method is to dry the temperature and time for measuring the moisture content of the solid wastes at 100 to 110 ℃ for 4 hours.

However, in the present invention, it is not dried for the purpose of obtaining moisture of the waste, but for the purpose of obtaining a sample in a state where the moisture is completely dried. Therefore, the designated waste is dried in a dryer at 100 to 110 ° C. for 2 days.

In addition, the reason for using a sieve of about 1.19 mm is to apply the waste as a relatively coarse aggregate rather than sand, and the reason for using sand having a particle size of about 0.85 mm or less is that the specification has a particle size of at least 0.8 mm or less. Although it is supposed to be applied, sand of 0.85 mm or less in actual application is considered to be efficient in terms of sand utilization, and sand of relatively large grains is used.

In addition, to increase the uniaxial compressive strength and suppress the dissolution, Doojin's chemical GS (see Green Star, patent application No. 96-32376 (filed date: 96.3.2)) and the solidifying agent such as SN 3, a chemical prepared by the laboratory Drugs were used.

SN 3 is an initial solidification model for the preliminary experiment of SN 5, and SN 3 is a cement, sand, and many more combinations than when SN 5 is used, but SN 3 itself is composed only of CaO and MgO. As a result, it did not express very high intensity.

A test method and a process diagram for determining the compressive strength and the elution characteristics of solidified and solidified bodies prepared by mixing designated waste, waste sludge, inorganic solidifying agent, and solidifying aid are shown in FIG. 1.

(2) Specimen manufacturing device and compressive strength measuring device

In the apparatus used in the present invention, a mold for preparing a specimen was prepared by using a specimen frame having a size of 5 × 5 × 5 cm as a cast iron that is resistant to cement chemical reaction and is non-absorbent.

Cement, designated waste, and various chlorides prepared by using the specimen frame for the production of specimens are mixed at an appropriate ratio to produce solids. For the necessary matters related to the production, refer to KSF 2403, the standard for the production of specimens for concrete. Produced.

Prepared cement and the designated waste, solidifying agent, sand, solidification aid, etc. were prepared by adding them to a mortar mixer according to each mixing ratio, and the appropriate amount was controlled by a flow tester.

In addition, the compressive strength was measured using a compressive strength in order to measure the uniaxial compressive strength of the prepared specimen.

The specimen frame, the mortar mixer, the flow tester, and the compressive strength are the devices shown in the KT standard and the mortar fabrication specification.

(3) Test method of uniaxial compressive strength

After mixing each mixture according to the ratio of each condition, measure the amount of water (ml) by mixing with a mortar mixer, and then mix the mixer at a low speed for about 9 to 10 minutes and measure the flow rate with a flow tester. .

At this time, the flow degree is about 11.5 ~ 12.5 cm in diameter and the sample is filled with three layers of compaction and compacted 25 to 30 times.

After the compaction, use a trowel or similar tool to spag along the sides and ends of the mold.

When this is dried for 2 to 3 days at room temperature and demolded, it becomes a specimen which can measure the uniaxial compressive strength.

According to the specification, most of the specimens are cured for 7 to 28 days. Sometimes concrete requires a long curing period, but considering the curing period that most cement products can use, it is common to measure the strength after curing for 7, 14 and 28 days.

The specimens were measured for compressive strength every 7 days, 14 days, and 28 days, and the compressive strength was measured using a Torsee's Universal Testing Machine (UTM). At this time, the compressive strength (kgf / ㎠) is calculated as follows.

Uniaxial compressive strength (kgf / ㎠) = maximum load (kgf) / cross section of test body (㎠)

Example 1

The waste (plating sludge and steelmaking dust) and cement were mixed with a solidifying aid named SN 5 to recycle the designated waste as brick.

The mixing composition ratio at this time is shown in Table 1.

At this time, cement and SN 5 were 50:50 and 70:30, respectively, and experiments were performed with SN 5 having three composition ratios.

As a result, specimens showing higher strength than 100 kg / ㎠ higher than 80 ㎏ / ㎠, the strength value that can be used for the actual brick production, appeared. After 14 days of curing in case of mixing cement and SN 5 at 70:30 The intensity value of 200 kg / cm <2> or more was shown.

In particular, SN 5 alone showed more than 80 ㎏ / ㎠ and showed the best compressive strength when added CaO ₃ to 20% of CaO ₃ , but there was no increase in strength when CaCO ₃ was excessively injected. It is considered to be.

In addition, when CaCO ₃ and CaSO ₄ were injected at the same time, there was no particular increase in strength and cracking occurred on the 28-day specimen and the strength value was not developed.

In addition, when the ratio of cement and SN 5 is injected at 70:30, the strength is higher than that of injection at 50:50. It is more economical to use it as a solidification aid, which is a countermeasure against strength, and it is considered that it can be used not only as brick but also as concrete by expressing excellent strength.

Theoretically, it is crystallization that determines the compressive strength of the cured material.

However, plated sludge and steelmaking dust contain heavy metals that inhibit this crystallization.

In addition, proper heat generation may promote crystallization between the solidifying agent components, so temperature control is also required.

2a and 2b are observed by the electron microscope (SEM) of the microstructure of the cured body according to the present invention, 7 days strength was measured to be 100 kg / ㎠ or more.

Example 2

If secondary contaminants are caused by heavy metals when hardened bodies using designated wastes are reused as bricks, they should be reconsidered even if they show very high strength.

In this respect, the fixed ratio of heavy metals can be used as an indicator of the long-term environmental impact of reuse of hardened materials.

In particular, if the long-term dissolution test shows high heavy metal fixing efficiency, the product is sufficiently reusable.

In the solidification test of steelmaking dust and plated sludge, after breaking the fractured specimen to the appropriate size based on the waste process test method, the heavy metal content was eluted and the analysis results are shown in Table 2. .

Overall, the solidification under these experimental conditions resulted in dissolution test results that were below the regulated concentrations under the Waste Management Act.

ND (Not Detected): Beauty

(1) Dissolution test method

To evaluate the long-term dissolution characteristics after 7, 14, and 28 days of solidified specimens, they were eluted using the dissolution test method based on the domestic waste process test method and the TCLP method used in the United States. .

1) Waste process test method-For solid or semi-solid wastes, the wastes are analyzed according to the Ministry of Environment's Notification Waste Process Tests applicable to the determination of the designated wastes and the intermediate treatment or landfill method prescribed in the Waste Management Act.

2) U.S. TCLP-TCLP (Toxicity Characteristic Leaching Procedure) is a test method that is currently used in the US RCRA standards and is a batch test method to test the dissolution possibility of organic or inorganic liquid, solid, and mixed waste.

The instrument used for heavy metal analysis was measured using an Inductively Coupled Plasma Emission Spectrophotometer (ICP), which is a high-precision measuring instrument. The model used was Perkin Elmer Plasma 2000.

As a result of the first dissolution test after the solidification treatment, arsenic (As) was not eluted at all in the steel waste and the plating sludge, and the heavy metal dissolution concentrations of the two wastes were very low below the reference value.

However, in the case of steelmaking dust, total chromium (T-Cr) was eluted relatively lower than that of plating sludge, whereas plating sludge showed lower lead (Pb) than steelmaking waste.

It is considered that there is no problem of dissolution of heavy metals in the range of this experiment. In particular, it can be seen that heavy metals are well fixed due to the high compressive strength and the solidification of the solidification aid.

The heavy metal removal rate according to solidification is calculated and shown in Table 3.

Overall, the removal efficiency of heavy metals is almost 99% except for lead and chromium, especially for arsenic and cadmium, and even for lead and chromium, the removal rate is slightly lower but less than the regulated concentration. It appears that there is no big problem.

As shown in the above table, the dissolution test results according to the present invention showed a concentration below the reference value in all items in the short-term dissolution, and even in the long-term dissolution, the initial concentration of about 1.3 mg / L was below the reference value. In the long-term repeated elution, the average concentration value was lower than that of 0.3 to 0.75 mg / L.

Through the examples, it was confirmed that the cured product using the hardener according to the present invention had no strength and environmental impact due to heavy metal dissolution.

As described above, according to the present invention facilitates the curing of the designated wastes together with the cement, improves the compressive strength of the solidified cured body, retains stability even in heavy metal dissolution and does not adversely affect the environment of cement bricks and sidewalks It can be recycled as construction materials such as blocks.

In the above description, the technical idea of a hardener for recycling designated waste according to the present invention and a hardened body having excellent compressive strength prepared by using the same is described together with the accompanying drawings, which is illustrative of a preferred embodiment of the present invention. It is not intended to limit.

In addition, it is obvious that any person skilled in the art can make various modifications and imitations without departing from the scope of the technical idea of the present invention.

Claims (4)

By weight% 15 to 20% SiO ₂ , 5 to 10% Al ₂ O ₃ , _{2 to} 6% Fe ₂ O ₃ , MgO 4 to 5%, S 0.5 to 1%, CaCO ₃ 10 to 20% and CaO 40 to A solidifying agent for recycling of designated wastes, comprising 60%. As weight percent, 15 to 20% SiO ₂ , 5 to 10% Al ₂ O ₃ , _{2 to} 6% Fe ₂ O ₃ , MgO 4 to 5%, S 0.5 to 1%, CaCO ₃ 10 to 20% and CaO 40 to A hardened product having excellent compressive strength, characterized by mixing and curing 12 to 20% of solidifying agent (60%), 25 to 35% of designated waste, 20 to 28% of cement, and 25 to 35% of sand. The method of claim 2, Hardened material excellent in compressive strength, characterized in that the designated waste is steelmaking dust and plating sludge. delete