JPH06182326A - Removing method for ammonium ion - Google Patents

Abstract

PURPOSE:To remove ammonium ions with a stabilized efficiency which cannot be attained by the conventional removing methods of ammonium ions in a liquid by setting the temperature of liquid fed into a deaeration film device at 20 deg.C or over in a method of removing ammonia ions by means of membrane permeation. CONSTITUTION:An alkali is added to an ion containing-liquid from a storage tank 1, and then the liquid is agitated by a mixer 3, and its pH is adjusted, then it is heated by a heater 5 up to 20 deg.C or over and fed into a dearation device 7. A hydrophobic porous deaeration module is fitted on the deaeration membrance device 7, and the temperature of the liquid through-side of the deaeration film module is set high and the water vapor pressure is set sufficiently high to make the movement amount of water vapor from the liquid through- side to the vacuum side through a film sufficiently mush, and the accompanying and moving ammonia mount increases, the removing ratio of ammonium ions in the liquid also increases. On the other hand, the water vapor and ammonia moved to the vacuum side are cooled by a condenser 10, and the water vapor is recovered as condensate, while ammonia is absorbed and recovered as ammonia water.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing ammonium ions, and more particularly to improvement of a method for removing ammonium ions using a degassing membrane device.

[0002]

As a method for removing ammonium ions from a liquid containing ammonium ions, the present inventors have added alkali to the liquid to make it alkaline, and after making ammonium ions into ammonia, gas permeates but water We proposed a method for removing ammonium ions in a liquid, which is supplied to a non-permeating deaeration membrane device to permeate the ammonia together with water vapor to remove ammonium ions.

This method of removing ammonium ions degasses the liquid to be treated through the membrane, so that the device can be made compact and the degassing can be performed as compared with the method of directly degassing the liquid to be treated by directly contacting it with a vacuum. The vaporized ammonia has a great advantage that it can be easily recovered as ammonia water without causing odor pollution. However, in the method using the degassing membrane, the degassing performance of ammonium ion in the liquid per module is limited due to the capacity of the degassing membrane module, so that it is always stable to the extent required by various applications. However, it has a drawback that it is difficult to perform an operation in which the degassing performance of ammonium ions in the liquid is enhanced.

[0004]

In order to obtain high removal performance by the method using a degassing membrane, generally, the membrane area of the degassing membrane module is increased, that is, the degassing membrane module is passed in the liquid passing direction. A method of increasing the length or a method of connecting a plurality of degassing membrane modules in series in multiple stages is used. Therefore, when degassing ammonium ions with a degassing membrane, as a result of diligent studies to improve the degassing performance of ammonium ions, when degassing ammonium ions in the liquid, the ammonium ions in the liquid were changed to ammonia and degassed. It was found that the liquid temperature decreased at the outlet of the degassing membrane module when the liquid was passed through the gas membrane module. That is, in the degassing membrane module, when a part of the liquid to be treated entrains ammonia as water vapor and moves from the liquid side to the vacuum side through the membrane, the latent heat of vaporization is removed from the liquid, so that the liquid of the liquid to be treated is removed. It was considered that the temperature gradually decreased until the vapor pressure on the liquid side became equal to the pressure on the vacuum side, and when the liquid temperature decreased, the generation of water vapor on the liquid side decreased, so that the movement of ammonia also decreased.

Further, in degassing and removing after changing ammonium ions to ammonia, even if the degassing membrane module is lengthened in the liquid passage direction to widen the membrane area, the modules are connected in series and treated in multiple stages. It was found that even if the removal performance of ammonium ions in the liquid is not improved even if it is used. Therefore, the present inventors examined the removal performance of ammonium ions by changing the temperature of the liquid at the inlet of the degassing membrane module when performing the treatment in the degassing membrane module after changing the ammonium ions in the liquid to ammonia. As a result, when the liquid temperature is less than 20 ° C, the water vapor pressure of the liquid is low, and the amount of water vapor moving from the liquid side to the vacuum side through the membrane is not sufficient, so the amount of movement of ammonia is also small, but the liquid temperature is 20 ° C or more. Then, it was found that the moving amount of water vapor was sufficient, and stable high deaeration performance was obtained, and the present invention was completed.

[0006]

Means for Solving the Problems The present invention has been achieved as a result of further studies based on the above findings, and the gist thereof is to remove ammonium ion from a solution containing ammonium ion After adding alkali to make it alkaline and changing ammonium ion into ammonia, the liquid is supplied to a degassing membrane device equipped with a degassing membrane module that allows gas to permeate but does not allow water to permeate, and the ammonia is mixed with water vapor into a membrane. In the method of removing ammonium ions by permeation, the temperature of the liquid supplied to the degassing membrane device is supplied at 20 ° C. or higher, which is a method of removing ammonium ions.

The specific constitution of the method of the present invention will be described below in detail with reference to the embodiments shown in the drawings. FIG. 1 is a flow chart showing an example of a method for removing ammonium ions in a liquid of the present invention, and FIG. 2 is a conceptual schematic diagram of a treatment method when degassing membrane modules are connected in series in multiple stages. In FIG. 1, the ammonium ion-containing liquid sent from the storage tank 1 by the pump 2 is stirred by the mixer 3 after the addition of alkali, and the pH is adjusted. The pH is 9 to 1 at which ammonium ion is converted to ammonia.
Adjust to around 0. The pH-adjusted liquid to be treated is heated to 20 ° C. or higher by the heater 5 and then supplied to the degassing membrane device 7.

The degassing membrane device 7 is equipped with a hydrophobic porous degassing membrane module, and the degassing membrane module is divided into a liquid-passing side and a vacuum side through the membrane. By increasing the temperature of the liquid side and making the water vapor pressure sufficiently high, the amount of water vapor moving from the liquid passage side to the vacuum side through the membrane becomes sufficient, and the amount of ammonia that is entrained and moved increases, and the ammonium in the liquid The removal rate of ions increases.

On the other hand, the water vapor and ammonia that have moved to the vacuum side are cooled to 10 ° C. or less by the condenser 10 at the outlet of the vacuum pump 9, and the water vapor becomes condensed water, and the condensed water absorbs ammonia. Can be collected as. It is an essential condition that the pressure on the vacuum side be lower than the water vapor pressure on the liquid side, but the pressure on the vacuum side is preferably 8 to 12 mmHg in order to cause sufficient movement of water vapor.

Further, if the liquid temperature of the liquid to be treated is 20 ° C. or higher, a stable high removal rate of ammonium ions can be obtained. Therefore, the liquid temperature of the liquid to be treated is preferably 20 to 40 ° C. in order to obtain a high concentration of the recovered ammonia water. Further, when a plurality of modules are connected in series, it is advisable to directly connect a heater to the inlet of each module so that the liquid to be treated can be heated. Hereinafter, the effects of the present invention will be described in more detail with reference to examples.

[0011]

EXAMPLE An experiment was conducted according to the flow of FIG. pH
7. After adding a NaOH solution to a liquid containing 1,000 mg / l of ammonium ion to adjust the pH to 10, a hollow fiber membrane type hydrophobic porous membrane module (outer diameter 30 mm, length 200
mm, effective area 0.4 m ² ) was tested.
At that time, the liquid temperature on the liquid passing side is changed to reduce the pressure on the vacuum side to 10
mmHg, and the cooling temperature of the condenser was 10 ° C. For the removal performance of ammonium ions in the degassing membrane module, the removal rate of ammonium ions in the liquid to be treated and the concentration of recovered aqueous ammonia were checked. The result was as shown in FIG.

As shown in FIG. 3, when treated with a degassing membrane module, the removal rate of ammonium ions at a liquid temperature (11.2 ° C.) at which the water vapor pressure on the liquid passing side is equal to the pressure on the vacuum side,
It becomes 0%, and the removal rate rapidly increases as the liquid temperature rises to 20 ° C., and the ammonium ion removal rate becomes almost constant at the liquid temperature of 20 ° C. or higher. On the other hand, the ammonia concentration of the recovered ammonia water is higher as the liquid temperature is higher, and sharply decreases when the liquid temperature exceeds 40 ° C.

[0013]

As described above, according to the method of the present invention, stable and efficient removal, which cannot be obtained by the conventional method of removing ammonium ions in the liquid, can be performed.

[Brief description of drawings]

FIG. 1 is a flow chart showing an example of a method for removing ammonium ions in a liquid.

FIG. 2 shows that the liquid temperature at each stage inlet of the degassing membrane module of the present invention is 2
Schematic sketch of the process of supplying at 0 ° C or higher.

FIG. 3 is a graph showing a relationship diagram between the removal rate of ammonium ions and the concentration of recovered ammonia at each temperature.
In the figure, the left vertical axis shows the ammonium ion removal rate, the right vertical axis shows the recovered ammonia concentration (wt%) and the horizontal axis shows the temperature (° C), curve 1 shows the ammonium ion removal rate, and curve 2 shows the ammonia ion removal rate. The relationship of concentration is shown.

[Explanation of symbols]

 1 Storage Tank 2 Pump 3 Mixer 4 pH Detector 5 Heater 6 Temperature Detector 7 Degassing Membrane Device 8 Treated Water Tank 9 Vacuum Pump 10 Condenser 11 Cooling Water 12 Recovery Tank N Number of Module Stages

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inoue Munehisa Okada 2-5-2, Marunouchi, Chiyoda-ku, Tokyo Sanryo Kasei Co., Ltd. (72) Inventor Yukio Nagahashi 3- 2-3, Marunouchi, Chiyoda-ku, Tokyo In Nihon Renshui Co., Ltd. (72) Inventor Tsutomu Watanabe 3 2-3 Marunouchi, Chiyoda-ku, Tokyo In Nihon Renrenshi Co., Ltd.

Claims (1)

[Claims] 1. When removing ammonium ions from a solution containing ammonium ions, alkali is added to the solution to make it alkaline, and the ammonium ions are changed to ammonia. In the method of supplying the liquid to a degassing device equipped with a gas film module and removing ammonium ions through the permeation of ammonia with water vapor, the temperature of the liquid supplied to the degassing device is 20 ° C. or higher. A method for removing ammonium ions, comprising: