KR20200100218A - Methods To manufacture alkaline waste neutralizer of solids containing large amounts of active calcium oxide by mixing raw lime with bauxite residues and neutralizing sulfuric acid as industrial materials such as cement condensation retardant - Google Patents

Abstract

The present invention relates to a method for producing a solid alkali waste acid neutralization agent. The method comprises a mixing step of mixing bauxite residue with 20% or more of moisture and quicklime at a ratio of 1:0.25-0.7 to cause hydration and exothermic reaction, an aging and drying step of converting the component of the mixture from calcium oxide (CaO) to calcium hydroxide (Ca(OH)_2) and giving a moisture reduction time using heat generation, and a pulverizing step of pulverizing the mixture from the aging and drying step to 200 μm or less to increase reactivity with sulfuric acid. According to the present invention, in order to improve neutralization performance, a solid alkali waste acid neutralization agent containing a large amount of active calcium oxide can be produced.

Description

A method of preparing solid alkali waste acid neutralizers containing a large amount of active calcium oxide by mixing quicklime with bauxite residues, and using neutralized sulfuric acid waste as industrial materials such as cement setting retardants.{Methods To manufacture alkaline waste neutralizer of solids containing large amounts of active calcium oxide by mixing raw lime with bauxite residues and neutralizing sulfuric acid as industrial materials such as cement condensation retardant}

The present invention uses a bauxite residue as a main raw material and quicklime as a subsidiary material to use as a neutralizing agent for waste acid, thereby economically drying about 40% of the moisture contained in the bauxite residue by chemical bonding and heat generation. And pulverization to produce a solid alkali acid neutralizer containing a large amount of calcium oxide and a low moisture content, and using this waste acid neutralizer to more efficiently and economically neutralize spent sulfuric acid generated in industrial sites such as steel and semiconductors. It is invented so that it can be utilized and by-products generated after neutralization can be used as a setting retardant of cement and an industrial material.

As is well known, in industrial sites that manufacture metals or semiconductors, etc., when neutralizing waste acids, sodium hydroxide (NaOH), sodium carbonate (Na2CO ₃ ), calcium oxide (CaO), calcium hydroxide (Ca(OH) ₂ ) , Calcium carbonate (CaCO ₃ ), ammonia (NH ₃ ), etc. can be treated, and a liquid sodium (Na) compound or a slurry state calcium (Ca) compound is added to the waste acid, neutralized and precipitated, followed by filtration.

However, the method using sodium compounds has a disadvantage that the material cost is high. Therefore, the neutralization technology commonly used in the industry is a mixture of waste acid with liquid slaked lime to agglomerate and filter the neutralized product.

In addition, the treatment method of liquid slaked lime is cheaper than sodium compounds in equipment and material costs, but when treating waste acid with a high concentration, the consumption of raw materials increases, and operation costs such as agglomeration and filtration are greatly increased.

Therefore, the neutralization method of the acidic liquid + alkaline liquid or alkaline slurry reaction has the disadvantage that the secondary by-products are neutralized sludge and wastewater simultaneously, and the two by-products must be treated stably.

Liquid slaked lime containing a certain moisture without using direct neutralization such as solid slaked lime (Ca(OH) ₂ ) and calcium oxide-containing quicklime (CaO), calcium carbonate (CaCO ₃ ), which are the main raw materials of liquid slaked lime The reason for neutralization by using is that when a solid alkali component is directly mixed with waste sulfuric acid or other strong waste acid, it boils with rapid heat generation, which causes powder and fume to scatter, making handling difficult.

On the other hand, according to Korean Patent Registration No. 10-1751691 (hereinafter referred to as'pre-registered patent'), an alkali ceramic admixture is prepared by mixing an inexpensive but low calcium oxide solidifying agent with the bauxite residue. Although the purpose of neutralizing treatment is to neutralize, for example, if an alkali ceramic admixture is used as a neutralizing agent with sulfuric acid having a concentration of 50% by weight, weight ratio 1: 2.0~2.5 (waste acid: neutralizing agent) is consumed, and by-products after neutralization are weight ratio 1: 3~ It occurs excessively at a rate of 3.5 (waste acid: by-product).

In addition, since the by-products generated after neutralizing sulfuric acid waste as a neutralizing agent in the prior patent are recycled as gypsum, a cement setting retardant, the content of sulfur trioxide (SO ₃ ) is lower than 25% by weight of type 2 gypsum, lowering to 10-15% of cement condensation. The quality is not suitable for recycling as a retarder, and it may contain chlorine (Cl), an impurity, from subsidiary materials such as solidifying agents used in the process of manufacturing neutralizers, reducing the strength and durability of cement, so it is recycled as a cement subsidiary material. It is as shown in Table 1 below that it is not suitable for the following.

Pre-registered patent implementation Results of analysis of neutralized product Cl using alkaline ceramic admixture Sample name Analysis item unit Analysis method Analysis Waste sulfuric acid neutralization Cl (Chlorine) mg/kg CIC 1,080

In order to improve the neutralization performance with the present invention, a solid alkali waste acid neutralizer containing a large amount of active calcium oxide is prepared, and by-products generated after neutralizing sulfuric acid waste acid with this neutralizing agent are improved to a quality that can be recycled as a cement setting delay agent. It aims to provide something.

The method of producing a solid alkali waste acid neutralizer containing a large amount of active calcium oxide according to the present invention to achieve the above object, contains a bauxite residue of 20% or more and quicklime (CaO 85% or more) of 1: 0.25 to 0.7. Mixing step to cause a hydration exothermic reaction by mixing at a weight ratio; An aging drying step of converting the mixture into calcium oxide (CaO) → calcium hydroxide (Ca(OH) ₂ ) and giving time to reduce moisture due to heat generation; A pulverizing step of pulverizing the mixture to 200 µm or less to increase reactivity with sulfuric acid; A method of producing a solid alkali waste acid neutralizer containing a large amount of active calcium oxide including, and a weight ratio of 1.0: 0.5 to 1.5 (sulfate waste acid: neutralizing agent) of sulfuric acid waste acid (50% by weight) to the alkali waste acid neutralizing agent of the present invention. Neutralization step of neutralizing by adding and mixing the furnace; Neutralization aging step for stabilizing the pH of the neutral product and reducing additional moisture; It is an industrial material that contains 25% or more by weight of sulfur trioxide (SO ₃ ) content, which is the quality standard of 2 types of gypsum, and does not contain impurities such as chlorine (Cl). It has features that provide a way to produce recyclable by-products.

The method of producing a solid alkali waste acid neutralizer containing a large amount of active calcium oxide by mixing quicklime of the practice of the present invention, and producing a neutralized product of neutralizing sulfuric acid waste acid with the waste acid neutralizing agent of the present invention with a quality that can be used as a cement setting delay agent It provides the following effects.

First, since it is used as a useful neutralizing material by improving the quality of alkali bauxite residues, it has an excellent effect in solving environmental problems such as landfill treatment of bauxite residues.

Second, there is no generation of sludge and wastewater, which are generally generated during neutralization of high concentration waste sulfuric acid by using the alkali waste acid neutralizer of the present invention, and the neutralization reaction process is simple, so that the treatment cost can be reduced. It is very effective in preventing environmental pollution.

Third, when the alkali waste acid neutralizing agent of the present invention is used, the generation of by-products is reduced to 70% or less than that of the alkali ceramic admixture generally known so far, thereby providing a remarkable effect of preventing environmental pollution and reducing the cost burden.

Fourth, since the by-products generated after the neutralization treatment are not landfilled and are manufactured in a quality that can be recycled as a cement setting delay agent, it provides the effect of reducing and preventing environmental pollution caused by landfilling.

Fifth, the present invention blocks environmental pollution by replacing environmental pollution by-products generated in industrial technology processing sites such as metal processing or semiconductors with various active ingredients, and at the same time is a very eco-friendly and economical cement setting delay material or block filler and pigment, heavy metal adsorbent. It has a characteristic that it can be used for various purposes such as a phosphorus adsorbent, a soil conditioner, and a grouting material, so it can be used as a material for the invention of a new material, so it provides a very useful and excellent effect that can be expected to import foreign currency.

Sixth, the alkali waste acid neutralizer produced by the practice of the present invention has a low neutralization ratio with the waste acid and the treatment process is simple, so that hydrochloric acid, nitric acid, hydrofluoric acid including sulfuric acid, and waste acid in which they are mixed can be treated at low cost and can be mixed in the waste acid. Since it is difficult to elute by adsorbing heavy metals, it is possible to secure stability during landfilling, thereby preventing secondary environmental pollution of by-products, so that the world can effectively prevent environmental pollution and protect nature at the same time. It provides an effect that can provide even phosphorus effect.

1 is a flowchart of a production process step according to the present invention
2 is an XRD analysis result table analyzing the components of the solid alkali acid neutralizer containing a large amount of active calcium oxide developed in the present invention.
3 is an XRD analysis result table analyzing the components of by-products generated after neutralizing spent sulfuric acid using the alkali waste acid neutralizer developed in the present invention.

1 is a flow chart of the production process step according to the present invention, and FIG. 2 is an XRD analysis result table analyzing the components of the solid alkali waste acid neutralizer containing a large amount of active calcium oxide developed in the present invention, and FIG. As an XRD analysis result table analyzing the components of by-products generated after neutralizing sulfuric acid waste by using the developed alkaline waste acid neutralizing agent. Hereinafter, with reference to the above drawings, a general technique in the technical field belonging to the present invention It will be described in detail so that those who have it can be easily implemented.

Meanwhile, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and the same reference numerals are assigned to the same or similar components throughout the specification.

Throughout the specification, when a part is said to be connected to another part, this includes not only a case that is directly connected, but also an indirect connection through another member.

In addition, when a part includes a certain component, it means that other components may be further included rather than excluding other components unless specifically stated to the contrary.

Terms used in the present invention are terms excluded in consideration of functions in the present invention, and since these may vary according to the intention or custom of users and operators, the definitions of these terms correspond to the technical matters of the present invention. And should be interpreted as a concept.

In addition, optional terms in the following embodiments are used to distinguish one component from other components, and the component is not limited by the terms. Hereinafter, in describing the present invention, detailed descriptions of related known technologies that may unnecessarily obscure the subject matter of the present invention will be omitted.

Next, a method of preparing a solid alkali waste acid neutralizer containing a large amount of activated calcium oxide by mixing quicklime with the bauxite residue, and using the neutralized product neutralized with sulfuric acid as a cement setting delay will be described in detail.

The method of preparing a solid alkali waste acid neutralizer containing a large amount of active calcium oxide by mixing quicklime with the bauxite residue in the practice of the present invention, and using the neutralized sulfuric acid waste as a cement setting delay agent, is an active calcium oxide (CaO ) In the method of preparing a waste acid neutralizer containing 15% or more by weight and neutralizing it with 30% or more by weight of waste sulfuric acid,

Mixing step (100) for causing a hydration exothermic reaction by mixing bauxite residues with a moisture content of 20% or more by weight and quicklime (85% by weight of CaO) in a weight ratio of 1: 0.25 to 0.7;

In the mixing step, the mixture is converted to calcium oxide (CaO) → calcium hydroxide (Ca(OH) ₂ ), and an aging drying step 200 for giving a moisture reduction time by heat generation;

A pulverizing step (300) of pulverizing the mixture of the additional mixing step to 200 μm or less to increase reactivity with sulfuric acid;

Neutralization step 400 of neutralizing by adding and mixing 30% or more of waste sulfuric acid in a weight ratio of 1.0: 0.5 to 1.5 (waste acid: neutralizing agent) to the mixture in the grinding step;

Neutralization aging step 500 for stabilizing the pH of the neutralized product in the neutralization step and reducing additional moisture; By mixing quicklime with the bauxite residue of the present invention, including a large amount of active calcium oxide, a solid alkali waste acid neutralizer is prepared, and the neutralized product neutralized with sulfuric acid is used as a cement setting retardant and the method thereof. It provides the manufactured industrial mixed material 600.

In general, waste sulfuric acid generated in industry often contains impurities such as heavy metals, but it can be said that waste sulfuric acid generated from semiconductors has a relatively low content of impurities and high recyclable value.

However, in recycling waste semiconductor sulfuric acid discharged at a high concentration of 50% or more by weight, the development of economical treatment and recycling methods is difficult due to the limitation of the sulfuric acid market that can be recycled as a water treatment agent and the excessive amount of generation due to the expansion of semiconductor factories. Is required.

Accordingly, the present invention can economically treat high-concentration waste sulfuric acid, and the by-products after treatment can be utilized in new recycling markets such as cement setting retardants, heavy metal adsorbents, soil modifiers, grouting agents, and phosphorus adsorbents.

On the other hand, in the practice of the present invention, as a step of preparing a waste acid neutralizer, quicklime (CaO 85% or more) with a small impurity content is added to the bauxite residue of alkali, which is the main raw material containing sodium carbonate (Na ₂ CO ₃ ). The neutralization efficiency is supplemented by increasing the alkali content.

The reason for preparing waste acid neutralizer by adding high-purity quicklime (CaO) to the bauxite residue is to minimize the amount of neutralizing agent when using high-concentration waste sulfuric acid, so that the sulfur trioxide (SO ₃ ) content of by-products is maintained at 25% or more. It is to do.

The bauxite residue and quicklime (85% or more by weight of CaO) may be added in a ratio of 1.0: 0.15 to 0.7, and more preferably 1.0: 0.25 to 0.45 by weight.

In general, the bauxite residue containing about 40% moisture and quicklime (CaO) can be mixed through a mixer such as a ribbon mixer, and CaO + by hydration reaction of calcium oxide within 5 to 10 minutes after mixing. H ₂ O → Ca(OH) ₂ + 15.6Kcal (Scheme 1) Heat is accompanied and the temperature of the mixed raw materials rises to 80~120℃.

The exotherm at this time may last for more than 3 hours, and calcium oxide is converted to calcium hydroxide as shown in FIG. 2 by the hydration of calcium oxide during the exothermic process, and this calcium hydroxide (Ca(OH) ₂ ) inhibits a sudden reaction during the neutralization reaction. Plays a role.

In performing the exothermic drying and hydration steps, a stabilization time of 4 to 48 hours or more is required, and preferably, a time of 24 hours or more is required.

Upon completion of the exothermic drying and hydration at this stage, a solid waste acid neutralizer intermediate material having a moisture content of 10% or less is acquired.

Bauxite residues and waste acid neutralizer intermediates dried by the hydration reaction of quicklime are not homogeneously mixed with each other, do not maintain a certain size, and each component is present in a state in which each component is separately agglomerated.

For this reason, when it is directly used as a raw material for neutralization, it is not suitable for a homogeneous reaction, and it is difficult to transport and transport.

To improve this, one of pin mill, hammer mill, jet mill, roll mill, ball mill to make the particle size uniform and the mixture of the bauxite residue and calcium oxide component is homogeneous by pulverizing the waste acid neutralizer intermediate material to an appropriate size of 200 μm or less. Crush it with the above equipment.

When the above process is completed, the production of an alkali waste acid neutralizer containing a large amount of calcium oxide having high neutralization efficiency is completed.

The completed waste acid neutralizer is weighed and added to a facility capable of mixing such as a ribbon mixer, and the spent sulfuric acid is weighed at a concentration of 30% or more, more suitably 50% or more, and gradually introduced into the mixer while the mixer is operated for neutralization. Conduct.

At this time, the neutralization ratio of the spent sulfuric acid and the spent acid neutralizing agent is 1.0: 0.5 to 1.0 (waste acid: neutralizing agent), more suitably 1.0: 0.7 to 1.0 (waste acid: neutralizing agent) to neutralize the weight ratio.

In the neutralization process, boiling during the neutralization reaction is suppressed by the characteristics of the clay-like bauxite residue contained in the waste acid neutralizer, and the constant moisture contained in the sulfuric acid waste is exothermic due to the neutralization reaction as in Scheme 2 below. It evaporates as it occurs.

[Scheme 1]

Ca(OH) ₂ + H ₂ SO ₄ → CaSO ₄ + 2H ₂ O + 47.53Kcal

2NaOH + H ₂ SO ₄ → Na ₂ SO ₄ + 2H ₂ O + 26.67Kcal

The neutralization reaction is completed in about 5 to 10 minutes, but when discharged after completion of the neutralization reaction, 15% of moisture and heat of 80° C. or more are included.

On the other hand, the neutralization reaction of the waste acid neutralizing agent and the liquid sulfuric acid waste acid is carried out in a semi-liquid state after mixing, so that the neutralization rate proceeds more than 90%, but the agitation alone is not enough to completely stabilize the neutralization*?* aging step is required. Is done.

The neutralization*?* aging time of the aging stage requires 12 to 48 hours, and more suitably, it must be maintained for more than 24 hours to complete neutralization reaction and evaporate additional moisture to obtain solid by-products.

The initial hydrogen ion concentration index (pH) of neutralization discharged from the neutralization reactor shows 4-5, but neutralization*?* After the aging time is completed, the pH is maintained at 7-8, and calcium sulfate and sodium sulfate in the form of dihydrate gypsum are used. The inclusion can be confirmed as shown in FIG. 3, and in Table 2 below, it can be seen that the concentration of sulfurous acid (SO ₃ ) is 25% or more, and the results of analyzing the content of X-rays (XRF) are shown in Table 3 below.

Types of gypsum include anhydrous gypsum, semihydrated gypsum, and dihydrate gypsum, but the dihydrate gypsum type is most suitable for use as a set delay material for cement because it has little effect of moisture absorption, and the neutralization by-product of the present invention is in the form of dihydrate gypsum for recycling as a cement setting delay agent More suitable than

Table of results of analysis of sulfur trioxide (SO ₃ ) of neutralized neutralized alkali with sulfuric acid waste acid neutralizing agent containing a large amount of calcium oxide (CaO) Sample name Analysis item unit Analysis method Analysis method Analysis result Ceramic admixture neutralizer SO ₃ % KSL:5313, KSL:9003 29.8

The concentration of sulfur trioxide (SO ₃ ) in the neutralized by-product analyzed by KS analysis is 29.8%, and it is suitable for the standard of recycling as gypsum because 25% or more of KS natural gypsum standard is based on 30% or more of 2 type gypsum.

Analysis result table of XRF of neutralized alkali acid neutralizing agent containing a large amount of calcium oxide (CaO) with sulfuric acid waste acid ingredient SO ₃ CaO Fe ₂ O ₃ Al ₂ O ₃ SiO ₂ Na ₂ O TiO ₂ MgO
Etc Cl content(%) 34.00 19.30 14.00 13.80 9.15 5.51 3.24 1.00 0.0146

As can be seen from the results of the component analysis in Table 3, it was found that it is composed of mineral materials including sulfur trioxide (SO ₃ ), and is suitable for use as a cement subsidiary material at 146 ppm below 1,000 ppm, which is the management standard for chlorine (Cl) of cement. I can.

Hazardous substances also satisfy the criteria for dissolution of heavy metals according to the waste process test criteria, and these are shown in Table 4 below.

Analysis result table of waste process test standard for neutralized neutralized waste sulfuric acid and high concentration of alkali ceramic admixture containing a large amount of calcium oxide (CaO) Inspection items unit standard result Lead (Pb) Mg/ℓ 3.0 or less Not detected Copper (Cu) Mg/ℓ 3.0 or less 0.033 Arsenic (As) Mg/ℓ 1.5 or less Not detected Mercury (Hg) Mg/ℓ Less than 0.005 Not detected Cadmium (Cd) Mg/ℓ 0.3 or less Not detected Hexavalent chromium (Cr+6) Mg/ℓ 1.5 or less Not detected Cyan (CN) Mg/ℓ 1.0 or less Not detected Oil component % 5.0 or less Not detected Organic Mg/ℓ 1.0 or less Not detected Trichloroethylene (TCE) Mg/ℓ 0.3 or less Not detected Tetrachloroethylene (TeCE) Mg/ℓ 0.1 or less Not detected Judgment Standard

Therefore, as shown in all the above analysis results, it can be seen that the by-product of the present invention satisfies all of the sulfur trioxide (SO ₃ ) content, the content of chlorine (Cl) as an impurity, and the heavy metal elution criteria, and is suitable for recycling of cement, etc.

In conclusion, the method of manufacturing an alkali waste acid neutralizer of the present invention and the method of acquiring recyclable by-products after neutralization of sulfuric acid waste acid are treated easily, economically and eco-friendlyly without generating waste water, and thus can be said to be a clean technology suitable for recycling industrial by-products in modern society.

100: mixing step
200: aging drying step
400: grinding step
500: neutralization stage
600: neutralization aging stage
700: industrial material

Claims (4)

In the method of preparing a solid alkali waste acid neutralizer containing a large amount of activated calcium oxide by mixing quicklime with the bauxite residue, and using the neutralized product neutralized with sulfuric acid as a cement setting delay agent.
Mixing step of causing a hydration exothermic reaction by mixing the bauxite residue with a moisture content of 20% or more and quicklime in a weight ratio of 1: 0.25 to 0.7;
An aging drying step of converting the mixture to calcium oxide (CaO) → calcium hydroxide (Ca(OH) ₂ ) and giving a moisture reduction time by heat generation;
A pulverizing step of pulverizing the mixture of the aging and drying step to 200 μm or less to increase reactivity with sulfuric acid; A method for producing a solid alkali acid neutralizing agent containing a large amount of active calcium oxide by mixing quicklime with the bauxite residue, characterized in that it consists of. The method according to claim 1,
Neutralizing step of neutralizing the prepared alkali waste acid neutralizing agent by mixing waste sulfuric acid with waste sulfuric acid in a weight ratio of 1.0: 0.5 to 1.5;
A neutralization aging step for stabilizing the pH of the neutralized product and reducing additional moisture in the neutralization step; A method of neutralizing and manufacturing a neutralized product obtained by neutralizing sulfuric acid waste, characterized in that it is made of, so that it can be used as a cement setting delay agent. The method according to claim 1,
A method of using the prepared alkaline waste acid neutralizer as a neutralizing agent for waste acid, including waste sulfuric acid, waste acid, hydrochloric acid, waste hydrofluoric acid, waste phosphoric acid, or a mixed waste acid in which one or more of the waste acids are mixed. The method according to claim 2,
A method of using neutralized sulfuric acid waste acid as an industrial material such as heavy metal adsorbent, soil conditioner, grouting agent, and phosphorus adsorbent.

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