KR20010069259A - A desalinizing composition and a desalinizing method by using it - Google Patents

Abstract

PURPOSE: Disclosed are a salt removal agent composite and method for removing salt using thereof to prevent environmental pollution and damage due to reclaimed coal ash wastes by reusing dumped coal ash to the utmost, to reduce cost in accordance with making new reclaimed land. CONSTITUTION: The salt removal agent composite comprises 8-15 wt% of sodium sulfite, 3-10 wt% of sodium thiosulfate, 1-4 wt% of sodium bisulfate, 3-9 wt% of sodium formate, 65-85 wt% of water for total composite.

Description

A desalinizing composition and a desalinizing method by using it}

The present invention relates to a salt remover composition for removing salts from raw materials of interest, in particular a salt remover composition for removing salts from coal ash embedded in the sea, and a method for removing salts using the same.

In Korea's thermal power plant, about 3.95 million tons of coal ash is generated every year by combining unleaded coal and soft coal in the combustion process, but only about 1.68 million tons is recycled as a material for construction and civil engineering, such as cement and concrete. 10,000 tons of coal ash are simply buried in the ash processing plant located in the sea, etc., and more than 14 million tons of coal ash are already buried in the sea lotus root.

Due to such low recycling rate and simple disposal method such as landfill, enormous amount of useful recycling resources are left every year, not only economic loss is national, but also the pollution problem of coal ash processing site (landfill) due to increasing coal ash waste every year. Due to problems with landfills and landfills, there are many difficulties in the construction of thermal power plants.

On the other hand, in the field of building civil engineering, most materials such as cement raw materials and aggregates are collected from natural resources, but this is due to the severe environmental damage caused by the development of source resources and the increase of development costs due to resource depletion. Prices continue to rise day by day.

The above problems can be solved through active recycling of coal ash, but the recycling business is concentrated only on fly ash, which is easy to use due to the technology and funds of coal ash-related companies. Therefore, research on more active recycling methods such as waste ash, such as bottom ash and landfill coal ash, is urgently required.

However, in the processing of fly ash embedded in the sea into fly ash, which is useful as a building material such as cement admixture, and recycled as a building material, salts introduced from seawater and penetrated into the landfill ash are always obstructed.

In general, concrete has a strong alkalinity of pH 12 or more, so that the steel reinforcement is hardly oxidized, but in concrete made of salt-containing cement admixture, NaCl, MgCl ₂ , and MgSO ₄ , which are the main components of salt, are used. and CaCl _2, such as the Cl ^- if so by ions and sO ₄ ^-2 ions is reinforced and water is neutralized oxidized causing the air and chemical reaction, and as a result the elapsed times out as a serious problem in that it is reinforced rust. Therefore, in the case of construction and civil engineering ready concrete, the salt content is regulated by Korean Industrial Standard (KS F 4009) to 0.04% or less.

In order to recycle the sea ash coal used for other purposes, the separation and removal of salinity from landfill coal ash should be carried out first of all. However, in the absence of effective desalination materials and methods for this purpose, so far recycling of landfill coal ash has been It could not be done at all.

Accordingly, the present invention provides a salt remover composition for removing salts, especially chlorine ions from these materials, and a method for removing salts using the same for recycling salt-containing raw materials such as coal ash waste embedded in the sea. I put it.

The salt remover composition of the present invention for achieving the above object is sodium sulfite (Na ₂ SO ₃ ), sodium thiosulfate (Na ₂ S ₂ O ₃ ), sodium bisulfite (NaHSO ₃ ), sodium formate (HCOONa) and water It contains (H ₂ O) as a main component.

The content of each component in the composition is 8 to 15% by weight of the sodium sulfite, 3 to 10% by weight sodium thiosulfate, 1 to 4% by weight sodium bisulfite, 3 to 9% by weight sodium formate And 65 to 85% by weight of water and water.

The salt remover composition preferably comprises 11.5% by weight of the sodium sulfite, 6.5% by weight sodium thiosulfate, 2.5% by weight sodium bisulfite, 6.0% by weight sodium formate and 73.5% by weight water.

The salt remover composition of the present invention is prepared by injecting the above components into a heat and chemical resistant container, and then stirring them so that the respective components are uniformly well blended.

The composition of the present invention prepared by the above method is present in a slightly acidic, clear and colorless liquid state having a pH of 6.2 to 6.8, the specific gravity is about 1.1 to 1.3.

The composition of the present invention provides the effect of separating and removing salts, especially chlorine ions (Cl ⁻ ) from these substances when used in materials containing salts, such as coal ash embedded in the sea.

In general, coal ash embedded in the sea is contaminated with salt and other components by the surrounding sea water over time.

Salt is present in seawater in the form of dissolved ions such as Na ⁺ and Cl ⁻ ions, and chlorine ions (Cl ⁻ ) are particularly problematic for the utilization of landfill coal ash.

Fly ash is composed of SiO ₂ , Al ₂ O ₃ , Fe ₂ O ₃ , CaO, NaO, MgO, K ₂ O, SO _3, etc., and most of the chlorine ions in the seawater are shown in Scheme 1 below. In combination with the coal ash components, it is present in a complex salt state.

^{NaO + Cl - → NaCl + O} 2

^{_{Fe 2 O 3 + Cl - →}} FeCl 3 + 2H 2 O

Therefore, coal ash buried in the sea for a long time is mostly contaminated with salt of about 0.1 to 0.5%.

In concrete that is processed with coal ash containing salt and used as a mixed material for cement, chlorine atoms that existed in the salted state are dissolved by water vapor or rainwater contained in the air and dissociated into ions, causing chemical reactions with the steel bars to oxidize the steel bars. Over time, these reinforcing bars will corrode, resulting in a weakening of the building itself.

Therefore, in order to prevent this, a process of effectively separating and removing chlorine ions present in a complex salt state in coal ash is essential.

In general, when the chlorine compound in a complex salt state is reacted with water as shown in Scheme 2, chlorine ions of anions which have been bound with metal cations are dissociated and are present in water in an ionic state.

_{NaCl + 2H 2 O → NaO +} Cl - + H 2 O

_{Fe 2 Cl 3 + 2H 2 O} → Fe 2 O 3 + Cl - + H 2 O

Such a chemical reaction has a problem that the reaction rate is too slow to greatly reduce the reaction efficiency, and the reactivity is dependent on the surrounding pH conditions, so that chlorine ions cannot be effectively separated from coal ash in a short time by a simple process of washing with water.

However, when the landfill coal ash is washed with water using the salt remover composition of the present invention, the salt remover composition of the present invention acts as a catalyst for the reaction to capture chlorine ions that are bound in the salt state with the metal ions to react with the chelate formation reaction. By forming flocs by forming water and insoluble salts, chlorine ions can be easily separated and removed from the landfill coal ash.

As a result of the reaction, the chlorine component present in the floc in water can be completely separated and removed from the coal ash by washing with coal ash and then draining it with water in the drainage process.

Accordingly, the present invention also relates to a method for removing salt from coal ash buried in the sea using the salt remover composition of the present invention with water.

More specifically, the salt removal method of the present invention is based on salt-containing raw materials including landfill coal ash including salt, 8 to 15% by weight sodium sulfite, 3 to 10% by weight sodium thiosulfate, and 1 to 2% sodium bisulfite, based on the total composition. Adding a salt removal composition comprising 4% by weight, 3-9% by weight sodium formate and 65-85% by weight of water, stirring the mixture, draining the supernatant and obtaining precipitated coal ash Include them.

Hereinafter, the process of removing the salt from the landfill coal ash will be described in detail.

First, the coal ash to be treated and a sufficient amount of water are put into a mixing tank designed to enable rotational operation, and the desalination agent composition of the present invention is added.

At this time, the amount of the desalination agent composition of the present invention depends on the amount of coal ash to be treated, the concentration of salt contained in the coal ash, the amount of washing water, the type and concentration of other contaminants, working conditions, etc. It is used in an amount of 0.1 to 1% by weight, preferably 0.3% by weight. In case of long period of reclamation in seawater, the pollution level of coal ash is more than 1% by weight, and the amount should be decided by the worker considering various conditions.

In addition, the water introduced with the desalination agent is used in the amount of fresh water capable of sufficiently washing the treated coal ash, typically 0.5 to 2 times the volume of the coal ash, preferably about 0.7 times the water.

After the input of the raw materials, the mixing tank is rotated to sufficiently stir each raw material so that the water and the desalinating agent composition are well mixed and reacted with the coal ash.

At this time, the rotation speed and time of the mixing tank are determined in consideration of the amount of coal ash to be treated, the concentration of salt contained in the coal ash, the amount of washing water, the type and concentration of other contaminants, and the working conditions. Is operated for about 30 minutes to 2 hours at a high speed of about 180 to 200 rpm.

As a result of the agitation, the water and the desalination agent composition of the present invention react with the coal ash particles in a rotational mixture in the tank to capture chlorine ions that were in the salted state on the coal ash to form floes, and the flocs formed are suspended in water. In addition, by the above washing process, various other contaminants are also washed with water to be present in the water.

On the other hand, coal ash particles having various salts and other contaminants removed are settled to the bottom of the tank.

Then, through the process of draining the supernatant, the floc and various pollutants of the chlorine component is discharged together with the water, the drained wash water is reused or discharged through a separate purification process,

In addition, the demineralized coal ash is collected and recycled for various purposes such as building materials through separate processing.

The present invention can be used for the purpose of removing salts in various materials containing salts as contaminants in addition to coal ash embedded in the sea.

The coal ash cleaning process described above includes a separate tank containing a mixing tank capable of accommodating coal ash, water, and a salt removing agent, a raw material input unit for inputting these raw materials, and an operation mechanism necessary for rotating the raw materials to be mixed well. If carried out in a washing apparatus, salt removal can be carried out more conveniently and efficiently.

Such coal ash cleaning apparatus is described in more detail in another patent application of the applicant filed on the same day as the present application.

By washing the coal ash embedded in the sea using the salt remover composition of the present invention by the above process, it is possible to remove 85 to 90% of the salt originally present on the coal ash.

This can be confirmed through the following Table 1, which is a result of the component analysis performed on the washed water collected by performing the washing process of the present invention to the landfill coal ash containing 0.21% salt.

Item unit shame pH - 6.5-7.5 COD Mg / l 48 SS Mg / l 750 Turbidity NTU 340 Cl ^- Mg / l 2540 SiO ₂ Mg / l 5720 Fe ₂ O ₃ Mg / l 1540 CaO Mg / l 650 MgO Mg / l 220 K ₂ O Mg / l 140 Al ₂ O ₃ Mg / l 2930 NaO Mg / l 65

When the coal ash washing process of the present invention is repeated several times, salinity up to 95% or more can be removed, and thereafter, after the separate coal ash processing, a civil engineering material manufactured according to the salinity level required by Korean Industrial Standards can be manufactured. Can be.

Hereinafter, the present invention will be described in more detail by way of examples focusing on the test for the effect of trapping and separating chlorine ions of the salt remover composition according to the present invention.

The following examples are provided to illustrate and explain the present invention in more detail, and the scope of the present invention should not be understood as being limited only to the following examples.

EXAMPLE

Measurement principle of chlorine ions

As shown in Scheme 3, chlorine ions quantitatively react with silver ions when silver nitrate is added to produce silver chloride, and excess silver ions react with chromic acid to form a red yellow chromium silver precipitate.

Ag ^{+ +} Cl ^- → AgCl

2Ag ⁺ + CrO ₄ ^2- → Ag ₂ CrO ₄ (Red yellow precipitate)

Therefore, when the concentration of chlorine ions is low, the excess silver ion concentration becomes high, and a large amount of red chromic acid precipitates are produced. On the contrary, when the concentration of chlorine ions is high, the excess silver ion concentration becomes low and the amount of the precipitate becomes small. .

The concentration of chlorine ions in the sample was reacted by adding 0.01 N silver nitrate (AgNO ₃ ) solution and 5% potassium chromate (K ₂ CrO ₄ ) to the sample as shown in Equation 1 below, and then measuring the appropriate amount due to red-yellow precipitation. You can decide.

MgCl ⁻ / l = (sample titer ml-blank titer ml) × 354.5 / sample ml

Chlorine Concentration Test

About 3000 to 5000 ppm of the salt remover composition of the present invention was added to a vessel containing a raw water sample containing chlorine ions, and stirred at 240 rpm for 30 minutes to 1 hour.

By adding caustic soda or sulfuric acid to the mixture to adjust the pH to 7 to 8, adding an organic polymer polymer, stirring at this rate for 10 minutes, and then standing at room temperature for about 1 to 2 hours to precipitate the floc , Primary chlorine separation process was performed.

At this time, since the high pH in the chloride ion measurement process, Ag ⁺ ions are precipitated in AgOH, since the low pH in the CrO ₄ ^2- ions are converted to CrO ₄ ^2- ion, the pH must be in the reaction naejineun of about 7 to 8, neutral It should be kept alkaline.

After precipitation, the supernatant was collected and the concentration of chlorine component remaining in the sample was measured by measuring the appropriate amount according to the red-yellow precipitate while adding 0.01N silver nitrate solution and 5% potassium chromate solution.

The results are shown in Table 2 below.

Thereafter, the supernatant was subjected to a secondary chlorine separation process and a residual chlorine concentration measurement process in the same manner as the above-described primary chlorine separation process.

In addition, the tertiary chlorine separation process and the residual chlorine concentration measurement process were repeatedly performed on the supernatant separated from the secondary chlorine in the same manner as in the above-described primary chlorine separation process.

At this time, the input amount of the salt remover was different as shown in Table 2 depending on the chlorine concentration.

The results of chlorine concentration measurement after performing the primary, secondary and tertiary chlorine separation processes using the salt remover composition of the present invention are shown in Table 2 below.

Residual chlorine concentration in water (ppm) Chlorine Removal Efficiency Desalination Agent Concentration (ppm) Sample before separation process 2300 After the first chlorine separation process 230 90 3000-5000 After the Second Chlorine Separation Process 69 70 2000-3000 After tertiary chlorine separation 24 65 1000-2000

As can be seen from the table, as a result of the primary separation process in which the chlorine ions in the raw water were separated using the salt remover composition of the present invention at 3000 to 5000 ppm, the amount of chlorine components present at the concentration of 2300 ppm in the raw water was 230 The removal efficiency reached 90%, and the removal efficiency reached 90%. As a result of the secondary separation process on the 230 ppm primary sample, the residual chlorine concentration in the water was 69 ppm, and by the third separation process 24 Reduced to ppm, the removal efficiencies of 70% and 24% respectively.

Therefore, according to the present invention, it can be seen that the chlorine component can be removed by 99% by performing the chlorine separation process three times on the chlorine-containing raw water.

When the coal ash embedded in the sea is washed using the desalination agent composition of the present invention, the discarded coal ash can be recycled as much as possible, thereby solving problems related to by-products and waste treatments generated in coal ash-related industries such as a thermal power plant, By eliminating the need for additional landfills, it is possible to achieve land utility and to minimize the environmental pollution and damage caused by landfill coal ash.

In addition, the recycling of the demineralized coal ash for use as a cement admixture through a separate processing process can supply a variety of construction materials from the waste without the development of original resources, providing a lot of effects in terms of resource reproduction and economics.

Claims (8)

8 to 15% by weight sodium sulfite, 3 to 10% by weight sodium thiosulfate, 1 to 4% by weight sodium bisulfite, 3 to 9% by weight sodium formate and 65 to 85% by weight water. Desalination agent composition. The method of claim 1, A salt remover composition comprising 11.5% by weight of sodium sulfite, 6.5% by weight of sodium thiosulfate, 2.5% by weight of sodium bisulfite, 6.0% by weight of sodium formate, and 73.5% by weight of water. The method of claim 1, Desalter composition, characterized in that for use in washing the coal ash waste embedded in the sea. The method of claim 3, wherein Salt removal composition, characterized in that used in an amount of 0.1 to 1% by weight based on the weight of the coal ash waste. The method of claim 4, wherein A salt remover composition, characterized in that used in an amount of 0.3% by weight based on the weight of the coal ash waste. To landfill coal ash containing salt, 8 to 15% by weight sodium sulfite, 3 to 10% by weight sodium thiosulfate, 1 to 4% by weight sodium bisulfite, 3 to 9% by weight sodium formate and 65 to 85 water A method of removing salt from landfill ash comprising the steps of introducing a salt remover composition comprising% by weight with water, stirring the mixture, draining the supernatant and obtaining precipitated coal ash. The method of claim 6, The mixture is stirred for 30 minutes to 2 hours at 180 to 200 rpm. The method of claim 6, Using the salt remover composition in an amount of 0.1 to 1% by weight based on the weight of the coal ash.