JPS61219853A - Method for automatically measuring concentration of ammonia - Google Patents

Abstract

PURPOSE:To continuously and automatically measure the concn. of ammonia, by providing an analytical specimen line, which consists of a pressure reducing valve, a cooler and a refractometer, so as to branch the same from an ammonia supply system and converting high temp. and high pressure aqueous ammonia to low temp. and low pressure aqueous ammonia. CONSTITUTION:In ammonia recovery equipment, an ammonia analytical specimen sampling line is branched on the way of the piping for connecting an ammonical liquor tank 9 and a rectifying column 10. That is, a pressure reducing valve 1, a blocking valve 2, a cooler 3 and a refractometer 4 are connected to a branch pipe 2 in series and the exit side of the refractometer 4 is connected to a conductor 6 and a recorder 5 for recording a measured value is connected to the refractometer 4. The high temp. and high pressure aqueous ammonia flowed in the branch pipe 12 is reduced in pressure by the pressure reducing valve 1 and further cooled to low temp. by the cooler 3 to be passed through the refractometer 4. Noticing that the change in a refractive index per 1 deg.C is 0.00173 in a liquid temp. range of 16.9-38.3 deg.C, a conversion mechanism is provided from the relational formula of ammonia concn. and a refractive index to measure the concn.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for automatically measuring the ammonia concentration in aqueous ammonia in a liquid bathing facility or the like that recovers ammonia in coke oven gas as liquid ammonia.

Ammonia, known for its pungent odor unique to conventional technology, is a suffocating and toxic gas that can be detected even at 5 ppm in the air, and is regulated at 5 ppm or less under the Offensive Odor Prevention Act.

The PHO3AHPROCESS was developed by US Steel as a method for recovering ammonia in coke oven gas as liquid ammonia.
) and is widely used in our country.

In this method, ammonia in coke oven gas is absorbed into an ammonium phosphate absorption liquid (hereinafter referred to as absorption liquid), and then the absorption liquid is introduced into a conductor through a heat exchanger.
After removing dissolved acidic gases such as H2S and CO2, the ammonia is introduced into a stripper and separated as aqueous ammonia using direct steam.The aqueous ammonia is introduced into a rectification column and heated with steam to remove ammonia. It's precise. In operation of this rectification column, the amount of heated steam is controlled by the ammonia concentration in the supplied ammonia water, so it is necessary to measure the ammonia concentration in the supplied ammonia water.

Conventionally, to measure the ammonia concentration in ammonia water fed to a rectification tower, a worker wears a gas mask and samples the ammonia water from the feed system. Because it is operated at high pressures such as 13 to 17, it not only releases ammonia into the atmosphere when it is cooled and sampled as ammonia water, but also when titrating ammonia concentration by adding sulfuric acid to the sampled ammonia water. Not only did ammonia emit and the pungent odor characteristic of ammonia worsen the working environment, but the measurement frequency was limited because it was done manually.

Furthermore, although the relationship between the ammonia concentration and the refractive index of an ammonia aqueous solution is known, the ammonia water supplied to the rectification column contains not only ammonia but also trace amounts of H2S and CO2.
It was impossible to install a process refractometer because the refractive index changes due to impurities such as, and the supply to the rectification column is operated at high pressure.

Problems to be Solved by the Invention Since the ammonia water supplied to the rectification column is at high temperature and high pressure, it is impossible to collect a sample as ammonia water as it is.

The present invention provides a method for automatically and continuously measuring the ammonia concentration in high-pressure ammonia water fed to the rectification column without causing ammonia to emit, thereby improving the working environment during analysis sample collection and analysis. It is something.

Measures to solve the problem] - After the ammonia in the gas furnace gas is absorbed into the ammonium phosphate absorption liquid, the ammonia-rich absorption liquid is introduced into the stripper to remove the ammonia, and the obtained ammonia water is rectified. When recovering liquid ammonia through fractional distillation in the column, an analysis sample collection line is installed in the supply system to the rectification column, and connected to a refractometer via a pressure reducing valve and a cooler.
This is an automatic ammonia concentration measuring method characterized by automatically and continuously measuring the ammonia concentration in cooled ammonia water.

Function: In this invention, an analysis sample line consisting of a pressure reducing valve, a cooler, and a refractometer is branched from the ammonia supply system, and high-temperature, high-pressure ammonia water is depressurized and cooled to become low-temperature, low-pressure ammonia water. The ammonia water is introduced into a process refractometer and the ammonia concentration is continuously and automatically measured.

In addition, the ammonia water from the refractometer can be introduced through a conduit into a low-pressure section, such as a conductor that removes acidic gases such as 12S and CO2 from the ammonia-rich absorption liquid before entering the stripper, during sampling or the like. Emissions during measurement of ammonia concentration can be completely prevented.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of this invention will be explained based on the drawings showing one embodiment thereof.

Figure 1 shows an example of ammonia recovery equipment from coke oven gas, where (7) is an absorption tower and (6) is a conductor.
1 (8) is a stripper, (9) is a cheap water tank, (10
) is a rectification tower, (11) is a liquid ammonium tank, and an absorption tower [7
) The coke oven gas is introduced from the lower part of the tower, brought into countercurrent contact with the absorption liquid injected into the tower, and the coke oven gas from which ammonia has been removed is sent to the next process from the upper part.

On the other hand, a portion of the ammonia-rich absorption liquid that has absorbed ammonia is sent to the conductor (6) via a heat exchanger, where dissolved acidic gases such as H2S5C02 are removed. The ammonia-rich absorption liquid from which acidic gas has been removed is sent to the stopper (8) via a heat exchanger. Steam is blown into the bottom of this stripper (8) to remove most of the ammonia from the ammonia-rich absorption liquid.

Ammonia from the above! ! The removed ammonia-poor absorption liquid is discharged from the bottom of the stripper (8), cooled through a heat exchanger and a cooler, and then circulated back to the absorption tower (7).

Then, the separated ammonia paper is removed by a stripper (
8), it is condensed in a heat exchanger and a cooler to become ammonia water, temporarily stored in an ammonium water tank (9), and then roughly sent to a rectification column (10). Inside the rectification column, steam is introduced from the bottom to heat and distill the ammonia vapor, which flows out from the top of the column as pure ammonia vapor and is stored in the ammonium tank (11).

In the ammonia recovery equipment described above, the present invention branches an ammonia analysis sample collection line from the middle of the piping connecting the ammonium water tank (9) and the rectification column (10). That is, the branch pipe (12) has a pressure reducing valve (1) and a cutoff valve (2).
, a cooler (3) and a refractometer (4) are connected in series, and the outlet of the refractometer (4) is connected to a conductor (6). or,
The refractometer (4) has a recorder (5) for recording the measured values.
Connect. Note that the shutoff valve (2) is for stopping the inflow of ammonia water when abnormal pressure fluctuation occurs.

Therefore, the high temperature and high pressure (12) flowing into the branch pipe (12)
Ammonia water at a temperature of 0 to 150°C, 13 to 17-4) is first reduced to a low pressure (3h4) by a pressure reducing valve (1), then cooled to a low temperature (20 to 40°C) by a cooler (3), and then refracted. Pass through total (4). This refractometer (4) is a commercially available one, but the present invention is capable of
．． The refractive index change per 1°C between 3°C is 0,000
173, a conversion mechanism is provided and the concentration is measured from the relational expression between the ammonia concentration and the refractive index.

Now, in an ammonia recovery facility where coke oven gas 140.0008 m'/H containing ammonia 9.27/Nm' is sent out from the ammonium water tank (9), the temperature is 140
℃, ammonia water with a pressure of 16 kiJ is branched and the temperature is 30
The concentration was measured using a refractometer at low temperature and low pressure ammonia water at 3°C and 14°C. That is, measurements were taken for 1 hour at 30-minute intervals six times a day over two days. The results are shown in Table 1 as average values. For comparison, a conventional method of manual analysis was also conducted. From this result, it can be seen that the difference in value between this invention method and the conventional method is within the range of a slight difference, and is sufficiently reliable in actual operation.

(Blank below) Effects of the Invention As described above, the present invention can continuously and automatically measure the concentration of separated ammonia solution without sampling in equipment for recovering ammonia from coke oven gas, thereby eliminating the irritating odor of ammonia. It does not emit light and does not deteriorate the working environment. Moreover, continuous automatic measurement makes it easier to manage the rectification column.

[Brief explanation of drawings]

FIG. 1 shows a Flowcinit system for recovering ammonia from coke oven gas, which is equipped with a continuous automatic ammonia concentration measuring device for carrying out the present invention. 1... Pressure reducing valve, 2... Shutoff valve, 3... Cooler, 4
...Refractometer, 5...Recorder, 6...Conductor
17... Absorption tower, 8... Stripper, 9 Ammonium water tank, 1G... Rectification tower, 11... Ammonium tank, 12.
... Branch pipe.

Claims (1)

[Claims] After the ammonia in the coke oven gas is absorbed into the ammonium phosphate absorption liquid, the ammonia-rich absorption liquid is introduced into the stripper to remove the ammonia, and the resulting ammonia water is fractionated in a rectification column and recovered as liquid ammonia. When doing this, an analytical sample collection line is branched from the supply system to the rectification column, connected to a refractometer via a pressure reducing valve and a cooler, and the ammonia concentration in the ammonia water obtained by reducing the pressure and cooling is continuously and automatically measured. An automatic ammonia concentration measuring method characterized by: