TWI612014B - method for treating boron-containing wastewater using fluidized-bed ?homogeneous granulation technique - Google Patents

Abstract

The invention relates to a method for treating boron-containing wastewater by a fluidized bed homogeneous granulation technique. The method comprises the steps of: reacting hydrogen peroxide with boron ions, and adding a coagulant (calcium chloride) to the fluidized bed reactor, and producing a moisture content of less than 5% and a particle size greater than 0.5 mm. Calcium perborate homogenized particles, to achieve the effect of volume reduction, which is conducive to subsequent recycling and reuse.

Description

Method for treating boron-containing wastewater by fluidized bed homogenization granulation technology

The invention relates to a method for treating recycling of boron-containing wastewater, in particular to an oxidation/granulation of boron recovered from boron-containing wastewater having a boron content of several hundred to several thousand ppm or more in a low water content particle manner. The technology has the advantages of reduced capacity and high purity, which are beneficial for subsequent recycling.

Boron related compounds have a wide range of applications in modern industry. The boricides are used in thermal power plants, nuclear power plants, glass, ceramic glaze plants, or a large amount of boric acid used in TFT-LCD manufacturing processes. It is also commonly used in laundry bleaching powders, laundry detergents, fertilizers used in agriculture, and pesticides. The wastes released by them often enter the environment. In particular, the recycling and treatment technology of boron-containing wastewater is not yet mature, and there is no way to effectively recover high-purity and low-water content boron-containing salts.

The current boron removal technology can be roughly divided into six types, namely chemical precipitation method, ion exchange method, adsorption method, reverse osmosis, extraction method and electrochemical method, but each method has its limitations. The ion exchange method, adsorption method and reverse osmosis are only suitable for low concentration boron-containing waste liquid. The ion exchange method and the adsorption method have excellent selectivity, and commercially available resins and adsorbents can be purchased, but most of them are commercially available. The asking price is not high and the regeneration is not easy. Reverse osmosis is currently the most widely traded technology, but it is limited to low concentration of boron-containing wastewater or seawater desalination, especially in order to increase the boron removal effect, the pH is often adjusted to more than 10 to produce a negative borate ion. However, if the hardness is too high, it will cause the problem of film fouling. The electrochemical method is suitable for low-concentration boron-containing wastewater, and the effect on the treatment of high-concentration boron-containing wastewater will be drastically reduced, and the cost of the sacrificial anode will be considered in application, and the equipment cost is high. Both chemical precipitation method and extraction method are very suitable for the treatment of high concentration boron-containing wastewater. The solvent used in the extraction method is mostly dihydric alcohol, but the toxicity and subsequent treatment of the solvent are relatively difficult; and the chemical precipitation method is the most widely used in the industry. Acceptable techniques, but traditional coagulation precipitation methods often require high temperature conditions to simulate hydrothermal methods to produce poorly soluble species.

US Patent No. 6039789 (Removal of boron and fluoride from water) is an integrated procedure that involves removing B and F compounds from wastewater and then using the resulting sludge from a sulfur or sulfur A method of recovering gold in a mine, wherein the treatment of B and F is carried out by adding a hydroxide containing Mg. US Patent No. 5,925,255 (Method and apparatus for high efficiency reverse osmosis operation) is a method for treating ultrapure water by RO thin film technology. After pre-treatment to remove hardness alkalinity, the pH value is raised above 10.5 to remove B. Procedures for substances such as Si and TOC. U.S. Patent No. 4,0004,402 (Radioactive waste water treatment) is mainly for the treatment of nuclear waste reduction. The wastewater is adjusted to pH by adding alkali, and then concentrated by evaporation, and calcium hydroxide is added to produce borate, and finally the concentrated liquid is solidified by solidification. Treated or treated by evaporative drying.

In response to the above problems of the boron-containing wastewater, after the inventors of the present invention developed, the method of "treatment of boron-containing wastewater" No. 538008 was proposed. The treatment method utilizes an oxidation/coagulation treatment of adding an oxidizing agent (for example, hydrogen peroxide) and a coagulant (for example, calcium hydroxide) to greatly reduce the boron content, and then the ion exchange resin method or the reverse osmosis method is used to remove the residual low. Concentration part. However, this treatment requires a double coagulation step to reduce thousands of ppm of boron to about 15 ppm.

The inventor of the present invention further developed the application method No. 538008 "Process for the treatment of boron-containing wastewater", and proposed the application method 104100411 "Process for treating high-concentration boron-containing wastewater", which utilizes a pretreatment step and a precipitation step. Thousands of ppm of boron can be effectively low to remove boron to an average concentration of 5 ppm below seawater boron, but there are still problems with the subsequent treatment of a large amount of sediment, which has a high water content, a large volume, and requires additional equipment and costs in processing. .

Accordingly, the main object of the present invention is to provide a method for treating boron-containing wastewater by a fluidized bed homogenization granulation technique, which can be used to effectively treat boron from waste water having a boron content of several hundred to several thousand ppm or more. The borate form is recovered, and the method combines the fluidized bed homogenization granulation technology to produce perborate homogenous particles with low water content, thereby achieving the effects of volume reduction and high purity.

According to an embodiment of the invention, the method for treating boron-containing wastewater by a fluidized bed homogenization granulation technique comprises providing a fluidized bed reaction tank having a lower section and an upper section, the lower section being provided with a wastewater inlet port and a coagulant inlet port, the upper section is provided with a water outlet, and a reflux line is provided between the lower section and the upper section; hydrogen peroxide and boron-containing wastewater are continuously fed and mixed in a mixing tank, The concentration of the boron-containing wastewater is between 100 and 15000 ppm; the boron-containing wastewater reacted with the hydrogen peroxide and the other coagulant are separately introduced from the wastewater inlet port and the coagulant inlet port. Mixing the lower portion of the reaction tank; and flowing the boron-containing wastewater mixed with the coagulant from the lower portion to the upper portion and returning to the lower portion via the return line to circulate, so that boron ions in the boron-containing wastewater and the The coagulant reacts to produce perborate homogeneous particles.

In one embodiment, the coagulant is a calcium-containing compound, and the molar concentration of the calcium ions in the coagulant relative to the boron ions of the boron-containing wastewater is preferably between 0.5 and 2. The crystallization efficiency of borate and the effect of recovering boron.

The method for treating boron-containing wastewater by fluidized bed homogenization granulation technology further comprises a hydrogen peroxide concentration control step to maintain the hydrogen peroxide concentration stable in the granulation reaction. In one embodiment, the Mohr concentration ratio of the hydrogen peroxide relative to the boron ions in the boron-containing wastewater is between 0.5 and 4. In a preferred embodiment, the Mohr concentration ratio of the hydrogen peroxide to boron ions in the boron-containing wastewater is 1-4.

The method for treating boron-containing wastewater by fluidized bed homogenization granulation technology further comprises a flow acid pH control step to maintain a proper pH value of the fluidized bed homogenization granulation process to maintain high granulation recovery. rate. In one embodiment, the outflow water pH is controlled between 8 and 11. In a preferred embodiment, the pH of the effluent water is controlled between 9 and 10.6.

The method for treating boron-containing wastewater by fluidized bed homogenization granulation technology further comprises a particle bed high control step, and if the bed height is higher than a certain height, the perborate crystal recovery rate can be effectively improved. In a preferred embodiment, the bed height is controlled above 40 cm.

Other objects, advantages and features of the present invention will become apparent from

The invention mainly provides a method for treating boron-containing wastewater by fluidized bed homogenization granulation technology, which is used for recovering boron in boron-containing wastewater, and uses high-purity, low-water content perborate homogenous particles as a product, Effectively achieve the effect of reducing the volume of pollutants and improving the purity, which is superior to the traditional coagulation and sedimentation method, which is beneficial for recycling and reuse in the future. In this method, a fluidized bed reaction tank 10 (see FIG. 4) is first provided. The reaction tank 10 has a tubular lower section 12 and a tubular upper section 14, the upper section 14 having an outer diameter greater than the outer diameter of the lower section 12. The lower section 12 is provided with a waste water inlet 16 and a coagulant inlet 18, the upper section 14 is provided with a water outlet 20, and the lower section 12 and the upper section 14 have a return line 22. In the present embodiment, the bottom portion of the lower portion 12 of the reaction tank 10 is tapered to facilitate uniform dispersion of the return flow force. A pH value detector (not shown) is provided at the water outlet 20 to monitor the pH of the outlet, and a water sample is collected for water quality analysis.

Next, the hydrogen peroxide 28 and the boron-containing wastewater 30 are individually subjected to a continuous feeding step by a pump 24, 26 to sufficiently mix the reaction in a mixing tank 32. Next, the boron-containing wastewater 30 reacted with hydrogen peroxide and the other coagulant 38 are separately introduced into the reaction tank 10 from the wastewater inlet port 16 and the coagulant inlet port 18 by means of the pumps 34 and 36. The lower section 12 is uniformly mixed. Next, the boron-containing wastewater 30 mixed with the coagulant 38 is flowed from the lower section 12 to the upper section 14 and returned to the lower section 12 via the return line 22 for circulation, so that boron ions in the boron-containing wastewater 30 are mixed. The condensing agent 38 performs a granulation reaction to generate perborate solid particles, and utilizes the cross-sectional area of the reaction tank 10 and the reflux cycle to allow the solid particles to pass through sufficient collision to form homogeneous particles having a low water content, and to use continuous feed to contain Boron in the boron wastewater 30 is recovered as perborate to remove boron ions from the boron-containing wastewater 30. In the present embodiment, the coagulant 38 is a calcium-containing compound (for example, calcium chloride), but is not limited thereto.

According to the method of the present invention, the Mohr concentration ratio (H ₂ O ₂ /B) of the added hydrogen peroxide relative to the boron ions in the boron-containing wastewater 30, and the calcium ions in the coagulant 38 relative to the boron-containing wastewater 30 The Mohr concentration ratio (Ca/B) of the boron ion, the pH value of the outflow water (pHe), and the height of the particle bed (the height of the particles accumulated in the reactor when the fluidized bed is at rest) will affect the boron-containing wastewater 30, respectively. The boron ion removal rate in the medium and the granulation rate after the particles are stabilized. According to the test result, the Mohr concentration ratio of the H ₂ O ₂ /B is preferably between 0.5 and 4, and the Mo/concentration ratio of the Ca/B is preferably between 0.5 and 1.5. The value (pHe) is preferably controlled between 8 and 11, and the particle bed height is preferably controlled to be higher than 40 cm.

Referring to FIG. 1 , it is shown that the residence time is controlled in the fluidized bed homogenization granulation step (the time required for the boron-containing wastewater 30 to enter the reaction vessel 10 and flow out from the upper outlet 20 ) is 18 min, and CR[B]r, TR[B] under operating conditions of H ₂ O ₂ /B=2, pH of outlet water (pHe)=10, particle bed height=80 cm, initial boron concentration of 1000 ppm r will change with Ca/B change, and Ca/B=0.5~0.7 is better.

Please refer to Fig. 2, which shows that the residence time is 18 min in the fluidized bed homogenization granulation step, and the H ₂ O _{2 /} B= _2, Ca/B=0.7, particle bed height=80 cm, initial Under the operating conditions of boron concentration of 1000 ppm, CR[B]r and TR[B]r will change with the pH value of the flowing water. When the pHe is higher than 10.6, the reactor load is too large. While the granulation rate drops drastically, the pHe should be controlled below 10.6.

Please refer to FIG. 3, which shows that the residence time is 18 min in the fluidized bed homogenization nucleation precipitation step, and the H ₂ O ₂ /B= _2, Ca/B=0.7, pHe=9.6, initial boron concentration. Under the operating conditions of 1010 ppm, CR[B]r and TR[B]r will change with the change of particle bed height. When the particle bed height is lower than 50 cm, it means that the reaction surface area provided by the particles is insufficient. The granulation rate is greatly reduced and the operation should be such that the particle bed height is higher than 50 cm.

In the foregoing specification, the invention has been described in terms of a particular embodiment, and various changes or modifications may be made in accordance with the features of the invention. Therefore, obvious substitutions and modifications may be made by those skilled in the art, and will still be incorporated in the scope of the claimed invention.

10. Reaction tank 12. Lower section

14. Upper section 16. Wastewater inlet

18. Coagulant inlet 20. Water outlet

22. Return line 24, 26. Pump

28. Hydrogen peroxide 30. Boron-containing wastewater

32. Mixing tank 34, 36. Pump

38. Coagulant

Figure 1 is a graph showing the relationship between the removal ratio, crystallization rate and residual boron concentration of different calcium/boron (Ca/B) ratios in the fluidized bed homogenization granulation step; where [B]t represents the boron concentration of the filtered solution. [B]c represents the unfiltered solution boron concentration, TR[B]r represents the total removal rate of boron, and CR[B]r represents the granulation rate of boron.

Figure 2 is a graph showing the relationship between the pH value of different outflow waters, the granulation rate, and the residual boron concentration in the fluidized bed homogenization granulation step.

Figure 3 is a graph showing the relationship between the bed height of different static particles in the fluidized bed homogenization granulation step, the removal rate, the granulation rate, and the residual boron concentration.

4 is a schematic view of a fluidized bed reaction tank in accordance with an embodiment of the present invention.

10. Reaction tank 12. Lower section 14. Upper section 16. Wastewater inlet port 18. Coagulant inlet port 20. Water outlet 22. Return line 24, 26. Pump 28. Hydrogen peroxide 30. Boron-containing wastewater 32 Mixing tank 34, 36. Pump 38. Coagulant

Claims (8)

The method for treating boron-containing wastewater by fluidized bed homogenization granulation technology comprises: providing a fluidized bed reaction tank having a lower section and an upper section, wherein the lower section is provided with a wastewater inlet port and a coagulant inlet port, The upper section is provided with a water outlet, and a reflux line is provided between the lower section and the upper section; the hydrogen peroxide and the boron-containing wastewater are continuously fed and mixed in a mixing tank, and the concentration of the boron-containing wastewater is between 100 Between 15000 ppm, the Mohr concentration ratio of the hydrogen peroxide relative to the boron ions in the boron-containing wastewater is between 0.5 and 4; the boron-containing wastewater after reacting with the hydrogen peroxide and another coagulant Individually mixing from the wastewater inflow port and the coagulant inlet into the lower portion of the reaction tank; and flowing the boron-containing wastewater mixed with the coagulant from the lower section to the upper section and refluxing through the reflux line To the lower stage for recycling, the boron ions in the boron-containing wastewater are reacted with the coagulant to produce perborate homogeneous particles, wherein the coagulant is a calcium-containing compound, and the calcium ions in the coagulant are relative to Boron ion of boron wastewater Ratios in the range between 0.5 and 2, wherein the particle bed height 40 cm higher than the control, wherein the water pH is controlled between 8-11. The method of claim 1, wherein the coagulant is a calcium-containing compound, and a molar concentration of calcium ions in the coagulant relative to boron ions of the boron-containing wastewater is between 0.5 and 1.5. . The method of claim 1, wherein the outflow water pH is controlled between 8 and 10.6. The method of claim 1, wherein the molar ratio of the hydrogen peroxide to the boron ions in the boron-containing wastewater is 1-4, and the calcium ions in the coagulant are relative to the boron-containing wastewater. The molar concentration ratio of boron ions is between 0.5 and 0.7. The method of claim 1, wherein the molar ratio of the hydrogen peroxide to the boron ions in the boron-containing wastewater is 2, and the calcium ions in the coagulant are relative to the boron ions in the boron-containing wastewater. The Mohr concentration ratio is 0.7, and the pH of the outflow water is controlled between 9 and 10.6. The method of claim 1, wherein the particle bed height is controlled to be higher than 50 cm, and the molar ratio of the hydrogen peroxide to the boron ion in the boron-containing wastewater is 2, in the coagulant. The Mohr concentration ratio of the calcium ion to the boron ion of the boron-containing wastewater is 0.7, and the pH value of the outflow water is controlled at 9.6. The method of claim 1, wherein the particle bed has a height of 80 cm and the outlet water has a pH of 10. The method of claim 1, wherein the hydraulic retention time of the boron-containing wastewater is controlled to be 18 minutes.