JP2010274160A - Deodorization apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a deodorization apparatus capable of efficiently removing ammonia nitrogen in an absorption liquid with a simple structure over a long period. <P>SOLUTION: The deodorization apparatus includes an exhaust cleaning device 11 absorbing ammonia nitrogen in exhaust gas into the absorption liquid; a nitrification device 12 aerating the absorption liquid having absorbed the ammonia nitrogen to convert part of the ammonia nitrogen into nitrite nitrogen and nitrate nitrogen; and an inorganic nitrogen removing device 13 reducing the nitrate nitrogen in a nitrification liquid containing nitrite nitrogen, nitrate nitrogen and residual ammonia nitrogen into nitrite nitrogen with anaerobic ammonia oxidizing bacteria, and reacting the ammonia nitrogen with nitrite nitrogen to remove nitrogen. The concentration of the ammonia nitrogen in the nitrification liquid in the nitrification device is set to ≥1.3 times of the total concentyration of the nitrite nitrogen and nitrate nitrogen. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a deodorizing apparatus, and more specifically, the ammonia nitrogen in the exhaust gas is absorbed into the absorption liquid to remove it from the exhaust gas for deodorization treatment, and the ammonia nitrogen absorbed in the absorption liquid is biologically treated. The present invention relates to a deodorizing apparatus that removes water.

  The ammonia gas, which is an odor component in the exhaust gas, is absorbed into the absorption liquid and removed from the exhaust gas, so that the exhaust gas is deodorized and the ammonia nitrogen in the absorption liquid that has absorbed the ammonia nitrogen is removed. By nitrifying a part of the nitrite so that no nitrate is produced by the nitrite bacterium to produce ammonium nitrite, and by denitrifying the anammox bacteria by biologically reacting ammonia nitrogen and nitrite nitrogen Ammonia nitrogen is removed (for example, refer to Patent Document 1).

JP 2005-34726 A

  However, in the one described in Patent Document 1, nitritation is performed so that nitric acid is not generated, but it is impossible to completely eliminate nitrifying bacteria. Since generation of nitric acid is inevitable, there is a problem that nitric acid accumulates in the system due to continued operation and the pH gradually decreases, making it difficult to perform predetermined deodorization treatment and denitrification treatment.

  Accordingly, an object of the present invention is to provide a deodorizing apparatus that can efficiently remove ammoniacal nitrogen in an absorbing solution over a long period of time with a simple configuration.

  In order to achieve the above object, a deodorizing apparatus according to the present invention comprises an exhaust cleaning device that absorbs ammonia nitrogen contained in exhaust gas into an absorbing solution, and an ammonia absorbing solution that has absorbed the ammonia nitrogen by the exhaust cleaning device. A nitrification device that nitrifies a part of the ammonia nitrogen by aeration to produce nitrite nitrogen and nitrate nitrogen, and nitrite nitrogen and nitrate nitrogen produced in the nitrification device and residual ammoniacal The nitrate nitrogen in the nitrification solution containing nitrogen is reduced by anaerobic ammonia oxidizing bacteria to nitrite nitrogen, and the ammonia nitrogen and nitrite nitrogen are reacted by the anaerobic ammonia oxidizing bacteria And removing the nitrogen from the nitrification liquid, and the concentration of the ammoniacal nitrogen in the nitrification liquid in the nitrification apparatus is It is characterized in that it is set to more than 1.3 times the total concentration of oxygen and the nitrate nitrogen.

  Furthermore, the deodorizing apparatus of the present invention includes a path for supplying at least a part of the nitrifying liquid in the nitrifying apparatus as an absorbing liquid to the exhaust gas cleaning apparatus, and the nitric acid in the nitrifying liquid in the nitrifying apparatus. The nitrogen concentration is set to 20% or less of the nitrite nitrogen concentration.

  According to the deodorization apparatus of the present invention, a part of ammonia nitrogen is converted into nitrite nitrogen and nitrate nitrogen in a predetermined concentration range by aeration treatment in the nitrification apparatus, and the generated nitrate nitrogen is converted into the following inorganic nitrogen removal apparatus. Therefore, since it is reduced to nitrite nitrogen by anaerobic ammonia oxidizing bacteria, nitric acid does not accumulate in the system, and long-term continuous operation is possible. In addition, the absorption efficiency of ammonia nitrogen in exhaust gas should be improved by using at least a part of the nitrification liquid in the nitrification apparatus whose pH has dropped due to the production of nitrite nitrogen and nitrate nitrogen as the absorption liquid. In addition, the oxygen in the exhaust gas and the nitrification liquid can be contacted to oxidize ammonia nitrogen in the nitrification liquid to nitrite nitrogen or nitrate nitrogen. Can be reduced. Furthermore, by reducing the concentration of nitrate nitrogen to be lower than the concentration of nitrite nitrogen, reduction treatment and denitrification treatment with an inorganic nitrogen removing device can be performed more efficiently.

It is a systematic diagram which shows the 1st form example of the deodorizing apparatus of this invention. It is a systematic diagram which shows the 2nd example of a deodorizing apparatus of this invention.

  First, the deodorizing device of the first embodiment shown in FIG. 1 includes an exhaust cleaning device 11 that absorbs ammonia nitrogen contained in exhaust gas into an absorption liquid, and ammonia that has absorbed the ammonia nitrogen by the exhaust cleaning device 11. A nitrification device 12 that performs aeration treatment of an absorption liquid (hereinafter also referred to simply as an absorption liquid), and a nitrification liquid from the nitrification apparatus 12 is biologically treated with anaerobic ammonia-oxidizing bacteria for denitrification treatment. And an inorganic nitrogen removing device 13.

  Exhaust gas containing ammonia nitrogen, which is an odor component, is introduced into the exhaust cleaning device 11 from the exhaust gas introduction path 21, and comes into gas-liquid contact with the absorption liquid introduced into the exhaust cleaning device 11 from the absorption liquid introduction path 22. Nitrogen is absorbed in the absorbent and deodorization is performed. The exhaust gas after the deodorizing process is discharged from the exhaust cleaning device 11 through the cleaned exhaust path 23.

  The absorption liquid that has absorbed and dissolved ammonia nitrogen is introduced into the nitrification apparatus 12 through the ammonia-containing absorption liquid path 24, and aeration processing is performed by the aeration apparatus provided in the nitrification apparatus 12. Ammonia nitrogen in the ammonia absorption liquid reacts with oxygen in the aerated air to be nitrified, and a part of the ammonia nitrogen becomes nitrite nitrogen and nitrate nitrogen.

NH ₄ ⁺ + 3 / 2O ₂ → NO ₂ ⁻ + H ₂ O + 2H ⁺
NO ₂ ⁻ + 1 / 2O ₂ → NO ₃ ⁻
In this nitrification apparatus 12, the concentration of ammonia nitrogen is 1.3 times or more of the total concentration of nitrite nitrogen and nitrate nitrogen without nitrifying the entire amount of ammonia nitrogen in the absorption liquid, preferably 1. Adjust the amount of aeration to be 5 times or more. Furthermore, it is preferable to adjust the concentration of nitrate nitrogen in the nitrification device 12 to be 20% or less of the concentration of nitrite nitrogen. Moreover, a preferable nitrite nitrogen concentration is 300 to 500 mg / L, and a pH meter or an ORP meter is installed in the nitrification device 12, and the concentrations of nitrite nitrogen and nitrate nitrogen are determined based on fluctuations in these measured values. By estimating and feeding back to the control of the aeration amount, the concentrations of the ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen in the nitrification liquid in the nitrification device 12 can be controlled within an optimum range. For example, by measuring the pH of the nitrifying solution in the nitrification device 12 and adjusting the amount of aeration so that the pH falls within the range of 7.0 to 7.5, the nitrification reaction can be effectively performed.

  At least a part of the nitrification liquid nitrified by the nitrification apparatus 12 is introduced into the exhaust cleaning apparatus 11 via the absorption liquid introduction path 22 and used as an absorption liquid for absorbing ammonia nitrogen in the exhaust gas. . Since the nitrification liquid has a low pH due to the production of nitrous acid and nitric acid, it is possible to increase the absorption efficiency of ammonia nitrogen in the exhaust cleaning device 11, and the oxygen in the exhaust gas and the nitrification liquid are in contact with each other. Can oxidize ammonia nitrogen in the nitrification solution to nitrite nitrogen or nitrate nitrogen, thereby reducing the amount of aeration in the aeration process and reducing the energy required for aeration. .

  The remaining portion of the nitrification liquid in the nitrification apparatus 12 is sent from the nitrification apparatus 12 to the inorganic nitrogen removal apparatus 13 through the nitrification liquid path 25. Anaerobic ammonia-oxidizing bacteria are introduced into the inorganic nitrogen removing device 13, and ammonia nitrogen remaining in the nitrification liquid flowing into the inorganic nitrogen removing device 13 and the sublimation generated by the nitrification treatment. Nitrate nitrogen and nitrate nitrogen react with the action of anaerobic ammonia-oxidizing bacteria to remove nitrogen from the nitrification solution. The treatment liquid from which the nitrogen content has been removed circulates through the circulation path 26 to the nitrification device 12.

The anaerobic ammonia oxidation reaction between ammoniacal nitrogen and nitrite nitrogen at this time is
NH ₄ ⁺ + 1.32NO ₂ ⁻ → 1.02N ₂ + 0.26NO ₃ ⁻
And at the same time,
NO ₃ ⁻ → NO ₂ ⁻
As the reaction proceeds, nitrate nitrogen is reduced to nitrite nitrogen, and nitrite nitrogen generated by this reduction reaction is denitrified by reacting with ammoniacal nitrogen in the anaerobic ammonia oxidation reaction.

Therefore, the ammonia nitrogen concentration necessary for denitrification in the inorganic nitrogen removing device 13 is based on the total concentration of nitrite nitrogen and nitrate nitrogen.
NH ₄ ⁺ · N = 0.76 (NO ₂ ⁻ · N) + 0.76 × 0.26 (NO ₃ ⁻ · N) = 0.95 N
Theoretically, the ammonia nitrogen concentration may be equal to the total concentration of nitrite nitrogen and nitrate nitrogen, but in the actual reaction obtained through experiments, the ammonia nitrogen concentration is By setting the treatment conditions in the nitrification device 12 to be 1.3 times or more, preferably 1.5 times or more, with respect to the total concentration of basic nitrogen and nitrate nitrogen, nitrite nitrogen and nitrate nitrogen Can be efficiently denitrified. Moreover, it is preferable that the inside of the inorganic nitrogen removal apparatus 13 at this time is pH 7.5-8.0.

  If the ammonia nitrogen concentration relative to the total concentration of nitrite nitrogen and nitrate nitrogen in the nitrification liquid flowing into the inorganic nitrogen removing device 13 is too high, the amount of ammonia nitrogen is reduced, so that the nitrite property is reduced. The ammoniacal nitrogen concentration with respect to the total concentration of nitrogen and nitrate nitrogen is preferably set to 2.0 times or less, and usually the aeration treatment conditions in the nitrification apparatus 12 can be set to 1.5 times. desirable. In addition, even if the nitrite nitrogen concentration is too low or too high, the denitrification efficiency by the anaerobic ammonia oxidizing bacteria decreases, so the nitrite nitrogen concentration is adjusted to 100 to 500 mg / L as described above. It is preferable to do.

  In this way, by setting the ammoniacal nitrogen concentration to 1.3 times or more with respect to the total concentration of nitrite nitrogen and nitrate nitrogen and performing denitrification treatment by the action of anaerobic ammonia oxidizing bacteria, the produced nitrous acid Nitrogen and nitrate nitrogen can be effectively removed, and accumulation of nitric acid in the system can be prevented to enable continuous operation for a long period of time.

  Further, by using at least a part of the nitrification liquid in the nitrification apparatus 12 whose pH has been lowered due to the generation of nitrite nitrogen and nitrate nitrogen as the absorbing liquid of the exhaust cleaning apparatus 11, exhaust gas in the exhaust cleaning apparatus 11 is used. In addition to improving the absorption efficiency of ammonia nitrogen in the exhaust gas, the oxygen nitrogen in the nitrification liquid is oxidized by contacting oxygen in the exhaust gas with the nitrification liquid to nitrite nitrogen and nitrate nitrogen. Therefore, the amount of aeration in the aeration process in the nitrification device 12 can be reduced.

  Furthermore, in the nitrification apparatus 12, the denitrification treatment in the inorganic nitrogen removal apparatus 13 can be efficiently performed by adjusting the concentration of the generated nitrate nitrogen to be 20% or less of the concentration of nitrite nitrogen. It is possible to more reliably prevent nitric acid from accumulating in the system.

  Further, as shown in FIG. 2, by providing a makeup water introduction path 27 in the absorption liquid introduction path 22 and providing a drainage path 28 in the circulation path 26, the amount of liquid in the system can be adjusted.

  DESCRIPTION OF SYMBOLS 11 ... Exhaust cleaning apparatus, 12 ... Nitrification apparatus, 13 ... Inorganic nitrogen removal apparatus, 21 ... Exhaust gas introduction path, 22 ... Absorption liquid introduction path, 23 ... Washed exhaust path, 24 ... Ammonia containing absorption liquid path, 25 ... Nitrification Liquid path, 26 ... circulation path, 27 ... makeup water introduction path, 28 ... drainage path

Claims (3)

  An exhaust cleaning device that absorbs ammonia nitrogen contained in exhaust gas into an absorption liquid, and a part of the ammonia nitrogen is nitrified by aeration treatment of the ammonia absorption liquid that has absorbed the ammonia nitrogen in the exhaust cleaning apparatus The nitrifying nitrogen and nitrate nitrogen generated in the nitrification nitrogen, and the nitrate nitrogen in the nitrification liquid containing the nitrite nitrogen and nitrate nitrogen generated by the nitrification device and the remaining ammonia nitrogen are anaerobically produced. An inorganic nitrogen removing device that reduces the nitrite nitrogen by reducing the oxidative ammonia-oxidizing bacteria and removes the ammoniacal nitrogen and the nitrite-nitrogen from the nitrification liquid by reacting with the anaerobic ammonia-oxidizing bacteria. A concentration of the ammoniacal nitrogen in the nitrification liquid in the nitrification apparatus is 1.3 times or more of a total concentration of the nitrite nitrogen and the nitrate nitrogen Deodorizing apparatus characterized by being configured.   The deodorizing apparatus according to claim 1, further comprising a path for supplying at least part of the nitrifying liquid in the nitrifying apparatus as an absorbing liquid to the exhaust gas cleaning apparatus.   3. The deodorizing apparatus according to claim 1, wherein a concentration of the nitrate nitrogen in the nitrification liquid in the nitrification apparatus is set to 20% or less of the concentration of the nitrite nitrogen.

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