JP2014161802A - Apparatus and method for removing selenium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus and a method for removing selenium, in each of which a resin or the like is used for adsorbing selenium so that selenium is removed from waste water or the like at a low cost.SOLUTION: The apparatus 1 for removing selenium includes: a sulfide method reaction tank 4 in which a sulfidizing agent S is added to selenium-containing waste water W1 so that heavy metals contained in the selenium-containing waste water are insolubilized to obtain sulfides; a barium salt reaction tank 6 in which barium salt B is added to the waste water W2 discharged from the sulfide method reaction tank to insolubilize a sulfate ion, a selenate ion and a selenite ion; a barium salt reaction tank 8 for subjecting the waste water discharged from the barium salt reaction tank to solid-liquid separation; and a resin column 11 for selectively adsorbing the selenium remaining in a filtrate F1 separated by the solid-liquid separator. The apparatus for removing selenium can further include a chemical injection control unit for controlling the amount of the barium salt to be added into the barium salt reaction tank according to the concentration of the sulfate ion contained in the filtrate separated by the solid-liquid separator.

Description

  The present invention relates to an apparatus and a method for removing selenium from waste water containing selenium such as filtrate obtained by washing chlorine bypass dust generated in a cement firing step.

  Selenium and selenium compounds are widely used in the production of various industrial products such as glass products, semiconductor materials, solar cells, movie films, infrared polarizers, pigments, sensitizers, dehydrogenating agents, foaming agents, and the like. .

  However, selenium-containing wastewater containing dissolved selenium is inevitably discharged from manufacturing factories of industrial products using such selenium and selenium compounds, and flue gas desulfurization wastewater from copper-fired power plants and wastewater from copper refineries. Oil refinery wastewater, etc., may contain selenium, which may cause environmental pollution. Therefore, selenium is regulated, and the uniform drainage standard for selenium based on the Water Pollution Control Law is set to 0.1 mg / L.

Therefore, for example, when desalinating chlorine bypass dust collected by a chlorine bypass system attached to a cement production facility, the selenium concentration in the waste water is set to be equal to or lower than a safe standard, as described in Patent Document 1. In the selenium removal method, waste water is passed through an ion exchange resin, and SO ₄ and selenium are simultaneously separated from the waste water.

  Patent Document 2 discloses that after adjusting the pH of the flotation wastewater generated when the slurry containing chlorine bypass dust is subjected to flotation, heavy metals and selenium contained in the wastewater are precipitated, and fluorine is further precipitated. A wastewater treatment method is described in which solid content in the slurry is removed by a solid-liquid separator, and heavy metals and selenium are adsorbed and removed by a chelate resin tower.

JP 2011-189300 A JP 2010-240587 A

  However, in the above prior art, heavy metal ions and coexisting salts present in the wastewater hinder the adsorption of selenium by the resin and significantly reduce the life of the resin, so that it has not been put into practical use.

  Therefore, the present invention has been made in view of the above-described problems in the prior art, and an object of the present invention is to use selenium for adsorption of selenium and to remove selenium from waste water or the like at a low cost.

  In order to achieve the above object, the present invention provides a pretreatment apparatus for removing selenium, comprising adding a sulfiding agent to selenium-containing wastewater to insolubilize heavy metals contained in the selenium-containing wastewater as sulfides. A barium salt reaction tank for adding barium salt to the waste water discharged from the sulfide method reaction tank to insolubilize sulfate ions, selenate ions, and selenite ions, and the barium salt reaction tank. And a solid-liquid separator that separates waste water into solid and liquid.

  According to the present invention, various heavy metal ions in the wastewater are precipitated as sulfides by adding a sulfurizing agent, and sulfate ions are insolubilized by adding barium salt, and the treatment liquid obtained by these operations is solidified. By separating the liquid, main adsorption-inhibiting factors can be removed, the load on the adsorbent in the subsequent selenium adsorption step can be reduced, and the adsorbent can be used for a long time.

  A chemical injection control device that controls the amount of barium salt added to the barium salt reaction tank according to the concentration of sulfate ions contained in the filtrate separated by the solid-liquid separator can be provided. A large amount of barium salt can be added, and it is possible to prevent an increase in cost due to excessive use of barium salt, and there is a sulfate ion that does not insolubilize due to an excessive amount of barium salt added. Inhibiting the adsorption of selenium can be prevented.

  In addition, the present invention is a selenium removal apparatus, comprising a resin tower that selectively adsorbs selenium remaining in the filtrate separated by the solid-liquid separator of any of the pretreatment apparatuses described above. According to the present invention, the selenium remaining in the waste water from which the adsorption inhibitory factor such as sulfate ion is removed is adsorbed and removed with the resin, so that the resin can be used for a long time, and selenium can be removed at low cost. it can.

  In the selenium removal apparatus, the resin tower can be filled with an ion exchange resin or a chelate resin, and selenium can be efficiently removed using a resin having a high ion exchange capacity.

  The selenium-containing wastewater can be made into a filtrate obtained by washing the chlorine bypass dust generated in the cement firing step with water, and selenium can be removed from this filtrate at low cost.

  The present invention also relates to a pretreatment method for removing selenium, which comprises adding a sulfiding agent to selenium-containing wastewater to insolubilize heavy metals contained in the selenium-containing wastewater as sulfides, and further adding barium salt to the wastewater. Then, sulfate ion, selenate ion and selenite ion are insolubilized, and the waste water is separated into solid and liquid. According to the present invention, by adding a sulfurizing agent, various heavy metal ions in waste water are precipitated as sulfides, and by adding barium salt, sulfate ions and the like are insolubilized. By separating, main adsorption inhibition factors can be removed, the load on the adsorbent in the subsequent selenium adsorption step can be reduced, and the adsorbent can be used for a long time.

  In the pretreatment method for removing selenium, water soda can be used as a sulfiding agent, and waste water can be sulfidized more efficiently.

  Further, the amount of the barium salt to be added can be 0.5 to 5 times the molar amount of the sulfate ion concentration, and this addition amount effectively insolubilizes sulfate ions and the like. can do.

  Furthermore, the present invention is a selenium removal method, characterized in that selenium remaining in the filtrate separated by solid-liquid separation in any of the pretreatment methods is selectively adsorbed on a resin. According to the invention, it is possible to remove selenium at low cost by adsorbing and removing the selenium remaining in the waste water from which the adsorption inhibiting factor such as sulfate ion is removed with the resin.

  The selenium-containing wastewater can be made into a filtrate obtained by washing the chlorine bypass dust generated in the cement firing step with water, and selenium can be removed from this filtrate at low cost.

  As described above, according to the present invention, selenium can be removed from waste water or the like at low cost.

It is a whole lineblock diagram showing one embodiment of the selenium removal device concerning the present invention.

  Next, although the form for implementing this invention is demonstrated in detail, referring drawings, this invention is not restrict | limited at all by these embodiment.

  FIG. 1 shows an embodiment of a selenium removal apparatus according to the present invention. This selenium removal apparatus 1 includes a drain tank 3 that stores selenium-containing waste water W, and a sulfurization agent that adds a sulfurizing agent S to the selenium-containing waste water W1. A solid-liquid separation of the solid-liquid separation of the physical method reaction tank 4, the barium salt reaction tank 6 for adding barium salt B to the waste water W2 discharged from the sulfide method reaction tank 4, and the waste water W3 discharged from the barium salt reaction tank 6 It comprises a liquid separator 8, a sulfate ion concentration meter 10 that measures the concentration of sulfate ions in the filtrate F 1 separated by the solid-liquid separator 8, and a resin tower 11 that adsorbs selenium remaining in the filtrate F 1. The

The selenium-containing wastewater W1 is, for example, wastewater obtained by solid-liquid separation after reacting the slurry produced when the chlorine bypass dust generated in the cement firing process is washed with water with a gas containing SO ₂ or CO _2. The waste water contains sulfate ions (SO ⁴⁻ ), selenate ions (SeO ₄ ²⁻ ), and selenite ions (SeO ₃ ²⁻ ).

The sulfide method reaction tank 4 is prepared to add a sulfiding agent S such as sodium hydrosulfide (NaSH) to the selenium-containing wastewater W1 discharged from the drainage tank 3 to insolubilize various heavy metal ions in the selenium-containing wastewater W1. It is done. In addition to sodium hydrosulfide, sodium sulfide (Na ₂ S) or the like can be used as the sulfiding agent S.

  The barium salt reaction tank 6 adds barium salts such as barium hydroxide, barium nitrate, barium carbonate, and barium chloride to the wastewater W2 in which heavy metal ions are insolubilized, and sulfate ions, selenate ions, and selenium selenium in the wastewater W2. Provided to insolubilize acid ions. Among the barium salts, it is preferable to use barium chloride from the viewpoints of cost and handling properties.

  The solid-liquid separator 8 is provided to separate the waste water W3 discharged from the barium salt reaction tank 6 into a solid and a liquid, and the waste water W3 is separated into a precipitate D and a filtrate F1.

  The sulfate ion concentration meter 10 is provided for measuring the concentration of sulfate ions in the filtrate F1 separated by the solid-liquid separator 8, and a barium salt according to the sulfate ion concentration measured by the sulfate ion concentration meter 10 is provided. A chemical injection control device (not shown) for controlling the amount of barium salt added to the reaction tank 6 is configured.

  The resin tower 11 is provided to adsorb selenium (selenate ion, selenite ion) remaining in the filtrate F1 that has passed through the sulfate ion concentration meter 10, and the resin includes an ion exchange resin, a chelate resin, and the like. Used.

  Next, a selenium removal method according to the present invention using the selenium removal apparatus 1 will be described with reference to FIG.

  The selenium-containing wastewater W1 stored in the drainage tank 3 is supplied to the sulfide method reaction tank 4, and the sulfide agent S is added in the sulfide method reaction tank 4, so that heavy metals contained in the selenium-containing wastewater W1 are insolubilized as sulfides. .

  Next, the waste water W2 is supplied from the sulfide method reaction tank 4 to the barium salt reaction tank 6, and in the barium salt reaction tank 6, the barium salt B is added to sulfate ions, selenate ions, selenite in the waste water W2. Insolubilizes ions. Here, it is preferable that the amount of the barium salt B to be added is 0.5 to 5 times the molar amount of the sulfate ion concentration.

  Table 1 shows changes in the concentrations of selenium and sulfate ions when barium chloride is added to the waste water W2. As shown in the same table, selenium ions (selenate ions in waste water) are added by adding 0.5 times mole amount, 1 times mole amount, and 2 times mole amount of barium chloride to the mole amount of sulfate ions. It can be seen that the concentration of selenite ion (sulfate ion) and sulfate ion is greatly reduced. In particular, the rate of decrease when a 1-fold molar amount and a 2-fold molar amount of barium chloride are added is remarkable.

次いで、バリウム塩反応槽６から排出された排水Ｗ３を固液分離機８で固液分離し、上記不溶化によって生じた析出物Ｄと、析出物Ｄが除去されたろ液Ｆ１とに分離する。

Next, the waste water W3 discharged from the barium salt reaction tank 6 is solid-liquid separated by the solid-liquid separator 8 and separated into the precipitate D generated by the insolubilization and the filtrate F1 from which the precipitate D has been removed.

  The concentration of sulfate ion in the filtrate F1 discharged from the solid-liquid separator 8 is measured by a sulfate ion concentration meter 10, and the amount of barium salt B added to the barium salt reaction vessel 6 is controlled according to the measured value. That is, when the measured sulfate ion concentration is higher than a predetermined value, the amount of barium salt B added to the barium salt reaction tank 6 is increased. When the measured sulfate ion concentration is lower than the predetermined value, barium is added. The amount of barium salt B added to the salt reaction tank 6 is decreased.

  Next, the filtrate F1 discharged from the solid-liquid separator 8 is supplied to the resin tower 11 to adsorb selenate ions and selenite ions remaining in the filtrate F1. As described above, since the selenate ion, selenite ion and sulfate ion in the filtrate F1 are greatly reduced by the addition of the barium salt, the selenate ion and selenite ion contained in the filtrate F1. The concentration of is low, the load on the resin tower 11 is reduced, and the adsorption resin can be used for a long time. The filtrate F2 in which selenate ions and selenite ions are adsorbed in the resin tower 11 is discharged out of the system.

  In the above-described embodiment, the configuration including the resin tower 11 that selectively adsorbs the selenium remaining in the filtrate F1 separated by the solid-liquid separator 8 has been described. In this case, the configuration of the drainage tank 3 to the solid-liquid separator 8 shown in FIG. 1 is regarded as a pretreatment device for removing selenium, and various heavy metal ions, sulfate ions, selenate ions, selenite in advance. By insolubilizing the ions and removing them from the waste water, the load on the adsorbent in the adsorption process can be reduced, and the adsorbent can be used for a long time.

  In addition, the selenium-containing wastewater W1 is exemplified as wastewater generated when the chlorine bypass dust generated in the cement firing process is washed with water, but wastewater from other industrial product manufacturing plants that use selenium and selenium compounds is targeted. You can also.

DESCRIPTION OF SYMBOLS 1 Selenium removal apparatus 3 Drain tank 4 Sulfide method reaction tank 6 Barium salt reaction tank 8 Solid-liquid separator 10 Sulfate ion concentration meter 11 Resin tower B Barium salt D Precipitate F1, F2 Filtrate S Sulfide W1-W3 (Selenium Contained) drainage

Claims (10)

A sulfide process reactor for adding a sulfurizing agent to selenium-containing wastewater to insolubilize heavy metals contained in the selenium-containing wastewater as sulfides;
A barium salt reaction vessel for adding barium salt to the waste water discharged from the sulfide method reaction vessel to insolubilize sulfate ions, selenate ions and selenite ions;
A selenium removal pretreatment apparatus comprising: a solid-liquid separator that separates the wastewater discharged from the barium salt reaction tank into a solid-liquid separator.   2. A chemical injection control device for controlling the amount of barium salt added to the barium salt reaction tank according to the concentration of sulfate ions contained in the filtrate separated by the solid-liquid separator. The pretreatment apparatus for selenium removal described in 1.   A selenium removal apparatus comprising a resin tower that selectively adsorbs selenium remaining in the filtrate separated by the solid-liquid separator of the pretreatment apparatus according to claim 1.   The selenium removing apparatus according to claim 3, wherein the resin tower is filled with an ion exchange resin or a chelate resin.   5. The selenium removal pretreatment device or selenium removal according to claim 1, wherein the selenium-containing wastewater is a filtrate obtained by washing chlorine bypass dust generated in a cement firing step with water. apparatus. Adding a sulfiding agent to selenium-containing wastewater to insolubilize heavy metals contained in the selenium-containing wastewater as sulfides,
Further adding a barium salt to the waste water to insolubilize sulfate ion, selenate ion and selenite ion,
A pretreatment method for removing selenium characterized by subjecting the waste water to solid-liquid separation.   7. A pretreatment method for removing selenium according to claim 6, wherein a hydrous soda is used as the sulfiding agent.   The pretreatment method for selenium removal according to claim 6 or 7, wherein the amount of the barium salt to be added is 0.5 to 5 times the molar amount of the sulfate ion concentration. .   A method for removing selenium, wherein selenium remaining in a filtrate separated by solid-liquid separation in the pretreatment method according to claim 6, 7 or 8 is selectively adsorbed on a resin.   10. The selenium removal pretreatment method or selenium removal according to any one of claims 6 to 9, wherein the selenium-containing wastewater is a filtrate obtained by washing chlorine bypass dust generated in a cement firing step with water. Method.

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