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Method for removing fluorides from coal conversion wastewater

A fluoride and wastewater technology, applied in chemical instruments and methods, water pollutants, water/sewage treatment, etc., can solve the rare application of fluoride removal, affecting membrane flux and membrane service life, calcium fluoride precipitation It can reduce the problem of small particles and difficult to separate, so as to prolong the cleaning cycle and service life, improve the scaling problem on the membrane surface, and reduce the concentration of fluoride ions.

Inactive Publication Date: 2018-09-28
TIANJIN UNIV
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  • Summary
  • Abstract
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  • Application Information

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Problems solved by technology

[0005] (2) After biochemical treatment of coal chemical industry wastewater, the fluoride in the wastewater cannot be effectively removed, and the fluoride ion concentration is about 50-60mg / L. 500mg / L) as circulating water replenishment, the circulation concentration process produces extremely insoluble calcium fluoride precipitation, which affects the equipment, and the circulating water sewage generated after recycling has unprecipitated calcium fluoride, which enters the membrane system. After membrane treatment and concentration, the concentration of fluoride ion and calcium ion increases, and calcium fluoride scaling occurs on the membrane surface, which seriously affects the membrane flux and membrane service life.
[0006] (3) After biochemical treatment of coal chemical industry wastewater, the fluoride in the wastewater cannot be effectively removed, and the fluoride ion concentration is about 50-60 mg / L, which is different from the circulating water sewage with high hardness (the average calcium ion concentration is about 400 mg / L) Mixing, entering the membrane system for common treatment, concentrated by membrane treatment, the concentration of fluoride ion and calcium ion increases, and calcium fluoride scaling occurs on the membrane surface, which seriously affects the membrane flux and membrane service life
For coal conversion wastewater with large water volume, complex water quality and fluoride ion concentration of 50-60 mg / L, the adsorption method, ion exchange resin method and electrocoagulation method cannot be widely used in industry due to their high economic costs, while chemical precipitation methods such as Using anhydrous calcium chloride as precipitant, the removal rate of fluoride ions in coal conversion wastewater can only reach 61%, and the precipitation process is slow, and the resulting calcium fluoride precipitates are small and difficult to separate
The coagulation and sedimentation method has been widely used in water treatment technology. Aluminum salt series coagulants have a good effect on the removal of fluoride ions in water, but they are rarely used in the removal of fluoride in coal conversion wastewater.

Method used

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  • Method for removing fluorides from coal conversion wastewater
  • Method for removing fluorides from coal conversion wastewater
  • Method for removing fluorides from coal conversion wastewater

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0021] Prepare a water sample containing 55mg / L fluorine, and the pH value of the water sample is measured by the Shanghai Lei Magnetic pH meter. 0.08g, 0.09g, 0.1g crystalline aluminum chloride AlCl 3 , the water sample is less and the water quality is simple, just simply stir until the crystalline aluminum chloride is completely dissolved in the water, let it stand for 5 minutes, and the flocculation and precipitation can completely settle. The experimental data show that with the increasing amount of crystalline aluminum chloride, the removal rate of fluoride ions increases, as shown in Table 1. Fluoride ion meter selective electrode method to test the concentration of fluoride ion.

[0022] Table 1

[0023]

[0024]

Embodiment 2

[0026] Water samples containing 100mg / L, 200mg / L, 300mg / L, and 400mg / L of fluorine were respectively configured in the laboratory, and with the experimental method of the above-mentioned embodiment 1, different amounts of crystalline aluminum chloride were added, and the selective electrode of the fluoride ion meter method to measure the fluoride ion concentration, the experiment found that:

[0027]For water samples containing 100mg / L fluorine, when the amount of crystalline aluminum chloride added is 0.5g / L, the fluoride ion removal rate reaches the best of 99.33%, and the fluoride ion concentration is 0.37mg / L;

[0028] For water samples containing 200mg / L fluorine, when the amount of crystalline aluminum chloride added is 1.0g / L, the removal rate of fluoride ion reaches the best of 99.28%, and the concentration of fluoride ion is 1.44mg / L;

[0029] For water samples containing 300mg / L fluorine, when the amount of crystalline aluminum chloride added is 1.5g / L, the removal r...

Embodiment 3

[0033] Water samples from biochemical treatment wastewater from coal gasification plant, the main water quality indicators are: fluoride ion concentration is 55.0mg / L, calcium ion concentration is 10.57mg / L, ammonia nitrogen concentration is 13.2mg / L, sulfate ion concentration is 475.5mg / L L, the chloride ion concentration is 50.8mg / L, the COD is 342mg / L, and the pH value is 7.4.

[0034] Take 300mL of this water sample and divide it into 3 parts of 100mL each, add 0.5g / L crystalline AlCl 3 , polyaluminum chloride, anhydrous calcium chloride, the fluoride ion concentrations measured by the selective electrode method of fluoride ion meter are 4.95mg / L, 7.15mg / L, 19.25mg / L respectively, and the removal rates are 91% and 87% respectively , 65%, it can be seen from the experimental data that under the same addition amount, the use of crystalline AlCl 3 The defluoridation effect of the coagulant is the best.

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Abstract

The invention discloses a method for removing fluorides from coal conversion wastewater, particularly fluorides in high-concentration brine of the coal conversion wastewater. The method comprises thespecific steps: draining the wastewater into a treatment tank, then, adding crystals AlCl3, and lowering the fluoride ion concentration of the coal conversion wastewater by adopting a coagulation settling method, wherein the mass / volume ratio of the crystals AlCl3 to the wastewater is 0.3g / L to 0.5g / L, and the fluoride ion content of treated wastewater is lower than 6mg / L. The coal conversion wastewater is complicated in water mass, is subjected to pretreatment and biochemical treatment, then, is subjected to ultrafiltration and reverse-osmosis membrane treatment and is subjected to advanced wastewater treatment and recycling. If the fluorides in the coal conversion wastewater enter a reverse osmosis membrane system for circulating concentration and produce calcium fluoride scales, flux and service lives of reverse osmosis membranes are seriously affected. According to the method disclosed by the invention, for complicated coal conversion wastewater, the crystals AlCl3 are selected asa coagulant, the coal conversion wastewater prior to entering the membrane system and the high-concentration brine subjected to membrane treatment are subjected to fluorine removing treatment, thus, the wastewater can meet the requirements of reverse osmosis concentrating, and the calcium fluoride scales are not produced.

Description

technical field [0001] The invention relates to a method for removing fluoride in coal conversion wastewater, through coagulation and sedimentation mechanism, adding crystalline AlCl 3 Reduce the concentration of fluoride in coal conversion wastewater to prevent calcium fluoride scaling from entering the membrane treatment system. The invention belongs to the technical field of water treatment. Background technique [0002] The coal chemical industry is currently a national key development project, but the coal conversion process consumes a large amount of water resources and produces a large amount of wastewater, and my country is facing a situation of rich coal and water shortage, so the coal chemical industry pursues "zero discharge of wastewater". Coal conversion wastewater can be recycled through pretreatment, biochemical treatment, and membrane treatment technologies. The membrane technologies commonly used in water treatment are ultrafiltration and reverse osmosis. ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C02F1/58C02F101/14
CPCC02F1/583C02F2101/14C02F2209/055C02F2209/06
Inventor 姜忠义苏延磊薛静
Owner TIANJIN UNIV
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