JP3280098B2 - Ammonia degasser - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ammonia degassing apparatus for removing ammonia in a liquid using a degassing membrane.

[0002]

2. Description of the Related Art In recent years, as a method for removing ammonia from a liquid, a membrane deaeration method has been proposed in which odor pollution is not caused and the removed ammonia can be recovered as ammonia water, and is being put to practical use. In this method, a liquid containing ammonia is supplied to a degassing membrane device equipped with a degassing membrane module partitioned by a degassing membrane that allows gas to permeate but does not permeate the liquid, and supplies the liquid to be treated to one side. Supply, and the other side is evacuated so that the ammonia in the liquid to be treated permeates through the membrane together with the water vapor, and the ammonia and the water vapor moved to the vacuum side are cooled by a condenser provided at the vacuum pump inlet, whereby the ammonia is supplied. A degassing membrane device that recovers as water is employed.

[0003]

However, when ammonia is degassed by such a conventionally used degassing membrane device, the concentration of the recovered ammonia water passes through the degassing membrane and is on the vacuum side. Although it is determined by the amount of water vapor and the amount of ammonia that have migrated, there is a problem that only low-concentration aqueous ammonia can be obtained.

[0004]

The present inventors have conducted intensive studies to solve the problems associated with the degassing of ammonia by the above-mentioned conventional degassing membrane device, and have found that the behavior of water vapor and ammonia in the degassing device. Means that most of the water vapor and ammonia that have moved to the vacuum side through the degassing membrane are converted to condensed water in vacuum even if they pass through the condenser on the inlet side of the conventional vacuum pump. However, some ammonia is absorbed by this condensed water, but most of the ammonia passes through the condenser together with some water vapor, and a new condenser is provided at the outlet side of the vacuum pump. After studying the condensation, they found that high-concentration aqueous ammonia could be recovered, leading to the present invention.

The present invention has been accomplished as a result of further studies based on the above findings. The gist of the present invention is to provide an ammonia degassing apparatus using a degassing membrane, and a vacuum pump for the degassing apparatus. An ammonia degassing apparatus characterized in that a condenser is connected to each of an inlet pipe and an outlet pipe. Hereinafter, a specific configuration of the method of the present invention will be described in detail with reference to the illustrated embodiment.

FIG. 1 is a flow chart showing an example of a method for removing ammonia from a liquid, and FIG. 2 is a schematic conceptual view of the apparatus of the present invention. In FIG. 1, the ammonium ion-containing liquid sent from a storage tank 1 by a pump 2 is stirred by a mixer 3 after alkali addition to adjust the pH. The pH is adjusted to around pH 9 to 10 at which ammonium ions are converted to ammonia. pH
The adjusted liquid to be treated is added to the heater 5 as needed.
After heating to ４０40 ° C., it is supplied to a deaerator 7 equipped with a degassing membrane module, and the degassed ammonia is cooled together with water vapor in a condenser 10 at the outlet of a vacuum pump 9 and is absorbed by generated condensed water. It is collected in the recovery tank 12 as ammonia water.

In FIG. 2, ammonia and water vapor moved from the liquid side to the vacuum side in the degassing membrane module 7 are cooled to about 5 ° C. in the condenser 10 on the vacuum side, and most of the water vapor becomes condensed water. From the vapor-liquid equilibrium of ammonia on the water vapor side and the condensed water side, only part of the ammonia is dissolved in the condensed water. Part of the water vapor leaked from the condenser 10 on the vacuum side and most of the ammonia are sent to the condenser 14 on the normal pressure side provided at the outlet of the vacuum pump 9 and are recovered as ammonia water. Since the solubility of ammonia in water is very large even in a small amount, a high concentration of aqueous ammonia can be obtained.

The cooling temperature of the condenser 10 on the vacuum side needs to be lower than 11.2 ° C. at which the steam pressure becomes 10 mHg when the degree of vacuum is 10 Torr, and preferably 5 to 8 ° C. On the other hand, on the normal pressure side, the lower the liquid temperature, the higher the solubility of ammonia. However, the solubility of ammonia in water is 34.6 wt% at a temperature of 20 ° C. and 40.6 wt% at a temperature of 10 ° C.
wt%, and the condenser cooling temperature is desirably 10 ° C or less. The condenser is not particularly limited as long as it can convert steam into condensed water.

[0009]

EXAMPLE An experiment was conducted using the apparatus shown in the flow chart of FIG. NaOH solution was added to a solution containing 1,000 mg / l of ammonium ion at pH 7 to adjust the pH to 10, and 25
After heating to ° C., an experiment was conducted in which the hollow fiber membrane type hydrophobic porous membrane module (outer diameter 30 mm, length 200 mm, effective membrane area 0.4 m ² ) was used.

The pressure on the vacuum side of the vacuum pump is 10 mmH.
g, the cooling water temperature of the vacuum side condenser was 5 ° C., and the cooling water temperature of the normal pressure side condenser was 10 ° C. The amount of condensed water is
The liquid amount in 2 hours of the degassing treatment was measured. Table 1 shows the results.

[0011]

[Table 1]

[0012]

As described above, according to the apparatus of the present invention, high-concentration aqueous ammonia which cannot be obtained by the conventional apparatus can be recovered.

[Brief description of the drawings]

FIG. 1 is a flowchart showing an example of a conventional ammonia degassing membrane device.

FIG. 2 is a conceptual schematic diagram of an ammonia degassing apparatus in which a condenser is connected to each of an inlet pipe and an outlet pipe of a vacuum pump of the degassing membrane device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Storage tank 2 Pump 3 Mixer 4 pH detector 5 Heater 6 Temperature detector 7 Deaeration membrane device 8 Processing water tank 9 Vacuum pump 10 Condenser (vacuum side) 11 Cooling water 12 Recovery tank 13 Condensed water tank 14 Condenser (Normal pressure side) )

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shigeyuki Yoshida 1-1 Kurosaki Castle Stone, Yawatanishi-ku, Kitakyushu City Inside the Kurosaki Plant of Mitsubishi Chemical Co., Ltd. (72) Inventor Yukio Nagahashi 3-2-2 Marunouchi, Chiyoda-ku, Tokyo No. Nippon Rensui Co., Ltd. (72) Inventor Tsutomu Watanabe 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Nippon Rensui Co., Ltd. (56) References JP-A-6-182149 (JP, A) JP-A Heisei JP-A-6-182325 (JP, A) JP-A-6-182325 (JP, A) JP-A-4-171004 (JP, A) JP-A-63-310719 (JP, A) (58) Fields investigated (Int. Cl. ^7, DB name) B01D 19/00 C02F 1/20 C02F 1/58

Claims (1)

(57) [Claims] An ammonia deaerator using a deaeration film, wherein a condenser is connected to each of an inlet pipe and an outlet pipe of a vacuum pump of the deaerator. apparatus.