JPS629366B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gas cleaning device that circulates and cleans a solution containing a chemical that reacts with harmful components in a gas to be treated to convert them into odorless reaction products and remove them, and in particular a batch method. The present invention relates to a gas cleaning device that renews cleaning liquid at a gas cleaning device.

A conventional device of this type is shown in FIG. FIG. 1 is a flow diagram showing a conventional gas cleaning device. In the figure, 1 is a cleaning tower, 2 is a packed layer provided in this cleaning tower for gas-liquid contact, and 3 is a packed layer for making gas-liquid contact. The bottom liquid stored at the bottom of the layer, 4 and 5 are arrows indicating the inflow direction of the gas to be treated and the outflow direction of the process gas, 6 is a demister,
7 is a circulation pump that circulates the bottom liquid 3 over the packed bed 2; 8 is a concentration controller that adjusts the concentration of sodium hypochlorite in the bottom liquid 3; and 9 is a medicine that injects a chemical into the circulating liquid. Injection pump, 10 is a chemical tank, 11
12 is a power line for the chemical dosing pump 9, 12 is makeup water supplied to the cleaning tower 1, and 13 is a liquid level controller for keeping the volume of the bottom liquid 3 constant. Adjust. 14 is a level gauge for the bottom liquid 3, 15
16 is a signal line, 16 is a cleaning liquid renewal device, and 17 is a power line for controlling the opening and closing of the electromagnetic valve 18, which is output from the cleaning liquid renewal device 16. Reference numeral 19 denotes a power line for controlling the opening and closing of the solenoid valve 20 for the make-up water 12, which is also output from the cleaning liquid renewal device 16. 21 is a drain discharged from the cleaning tower 1.

Next, the operation will be explained. The gas to be treated that has been pumped or sucked into the cleaning tower 1 is sent and atomized by the circulation pump 7 while passing through the packed layer 2 in the direction of the arrow 4, and is mixed with the cleaning liquid flowing down the packed layer 2. Upon contact with the liquid, harmful components in the gas to be treated are absorbed and removed by the cleaning liquid, react with the chemical solution in the cleaning liquid, and are converted into odorless reaction products.

Here, part of the moisture in the tower bottom liquid 3 evaporates during the process of cleaning the gas to be treated, and the liquid volume gradually decreases. To prevent this, make-up water 12 is supplied via the liquid level controller 13. The liquid volume is always maintained at a constant level.

In addition, since the chemicals in the bottom liquid 3 also disappear during the process of absorbing and removing harmful components, a part of the cleaning liquid pumped by the circulation pump 7 is guided to the concentration controller 8, and the next liquid in the bottom liquid 3 is The concentration of sodium chlorite is monitored, and the injection amount of sodium hypochlorite stock solution in the chemical tank 10 is controlled by starting and stopping the chemical injection pump 9, so that the sodium hypochlorite in the tower bottom liquid 3 is maintained at a constant concentration. to hold.

Now, the case of cleaning and removing odor components discharged from each treatment process of a human waste treatment plant or a sewage treatment plant will be explained. In this case, each odor component in the gas to be treated, that is, ammonia, hydrogen sulfide, methyl mercaptan, methyl sulfide, methyl disulfide, etc., contains sodium hypochlorite while passing through the packed layer 2. It is absorbed and removed by contact with the cleaning liquid, and the chemical reaction at this time is shown by the following equation.

2NH ₃ +3NaClO→N ₂ +3NaCl+3H ₂ O 3H ₂ S+6NaClO+2NaOH→ Na ₂ SO ₄ +6NaCl+2S+4H ₂ O CH ₃ SH+3NaClO+NaOH→ CH ₃ SO ₃ Na+3NaCl+H ₂ O (CH ₃ ) ₂ S+NaClO→(CH ₃ ) ₂ SO+NaCl (CH ₃ ) _{2S 2} +5NaClO+2NaOH→ 2CH ₃ SO ₃ Na + 5NaCl + H ₂ O In this way, the odor in the gas to be treated is washed away in the packed layer 2, and after passing through the demister 6 and removing the accompanying cleaning liquid mist, the gas to be treated is It is discharged from the washing tower 1 as shown by the arrow 5. On the other hand, sodium sulfate, sodium methanesulfonate, dimethyl sulfoxide, which are generated by absorption and removal by the cleaning solution, and sodium chloride, which is a depleted substance of sodium hypochlorite that acts to remove the above-mentioned odor components, remain in the cleaning solution and gradually will be accumulated. Here, if the cleaning liquid is alkaline, carbon dioxide gas in the gas to be treated is also absorbed according to the following equation, and accumulated as carbonates in the cleaning liquid.

CO ₂ +NaOH→NaHCO ₃ CO ₂ +2NaOH→Na ₂ CO ₃ +H ₂ O FIG. 2 shows the solubility curves of typical reaction products found in the washing liquid of this type of washing tower. Although the solubility differs depending on each substance and cannot be generalized, from Figure 2, the concentration of each component is 8 to 20 (wt%) near room temperature, and 4 to 7 (wt%) near 0℃.
(wt%), it is expected that the solute will precipitate and problems such as clogging will occur in various parts. For this reason, it is necessary to periodically renew the cleaning liquid.

Conventionally, the cleaning liquid renewal device 16 was operated periodically to renew the cleaning liquid. In other words, when the preset time is reached, the power output from the cleaning fluid renewal device 16 is transferred to the power line 17.
The solenoid valve 18 is opened via the column bottom liquid 3 to the drain 21.
more excreted. At the same time, the power that had been connected to the power line 19 stops and the solenoid valve 20
is closed, the supply of make-up water 12 is stopped, and the bottom liquid 3 is easily discharged. When the level of the bottom liquid 3 has fallen to a certain depth, this is detected by the level gauge 14 and transmitted to the cleaning liquid renewal device 16 via the signal line 15, and the power that opens the solenoid valve 18 is stopped. Conversely, the solenoid valve 20 is reenergized and opened. Water is then supplied again via the liquid level controller 13, and the supply of makeup water 12 is stopped when the water level rises to the original level. In this way, conventionally, the column bottom liquid 3 was diluted with makeup water 12 to renew the cleaning liquid.

Conventional gas cleaning equipment is configured as described above, so the update interval for the bottom liquid 3 can be predicted in advance through desktop calculations, confirmed through trial runs, and then set to a safer side. I needed to make it shorter. For this reason, it takes time to set the update interval, and in order to set the update interval on the safer side, medicine is discharged unnecessarily, leading to waste of medicine.

This invention was made in order to eliminate the drawbacks of the conventional methods as described above, and uses a solution containing a chemical that reacts with harmful components in the gas to be treated and removes them by converting them into odorless reaction products as a cleaning liquid. In a gas cleaning device that performs circulating cleaning, a hydrometer is attached to the cleaning tower to monitor the specific gravity of the bottom liquid so that the cleaning liquid is updated by detecting changes in the specific gravity of the cleaning liquid due to the reaction products. It is an object of the present invention to provide a gas cleaning device that can easily and appropriately renew the cleaning fluid by operating the cleaning fluid renewal device at a point where the specific gravity of the tower bottom liquid exceeds a set value.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 3 is a flowchart showing a gas cleaning apparatus according to an embodiment of the present invention, and in the figure, 1 to 21 indicate the same or corresponding parts as in FIG. 1. 2
2 is a hydrometer for monitoring changes in the specific gravity of the bottom liquid 3; 23 is a hydrometer that detects when the specific gravity of the bottom liquid 3 has exceeded a preset value and transmits the detected value to the cleaning liquid renewal device 16; This is a signal line for

FIG. 4 shows the relationship between the concentration of each aqueous solution of typical reaction products produced in the cleaning solution and the specific gravity of the solution. As is clear from Figure 4, when odors discharged from human waste treatment plants and sewage treatment plants are absorbed and removed by sodium hypochlorite cleaning, the solution specific gravity of typical reaction products generated in the cleaning solution. is 1~
It can be seen that there is a linear relationship in the concentration range of 10%, and the concentrations of the respective aqueous solutions showing the same specific gravity of each component fall within about ±20% of the intermediate value. For example, the minimum aqueous solution concentration exhibiting a solution specific gravity of 1.04 is 4.2 wt% of sodium carbonate, and the maximum aqueous solution concentration exhibiting a solution specific gravity of 1.04 is 6 wt% of sodium chloride. Therefore, the intermediate value is 5.1%, and the concentration of each aqueous solution is 5.1%.
This means that the concentration range is ±0.9wt%. In this way, the concentrations of each aqueous solution showing the same specific gravity fall within the accuracy range of ±20% with respect to the intermediate value of 5.1 wt%. Therefore, by using this, it is possible to know the average concentration of each component in the solution by measuring the specific gravity after cleaning, and thereby it is possible to accurately know when to renew the cleaning liquid.

In FIG. 3, when the solution specific gravity of the tower bottom liquid 3 exceeds a set value, the hydrometer 22 transmits it to the cleaning liquid renewal device 16 via a signal line 23. In response to the input signal, the cleaning liquid renewal device 16 executes an operation for renewing the column bottom liquid 3. That is, the solenoid valve 20 is closed via the power line 19 and the solenoid valve 18 is opened via the power line 17 to discharge the bottom liquid 3. Then, when the level gauge 14 detects via the signal line 15 that the level of the bottom liquid 3 has fallen to a certain level, the solenoid valve 18 is closed and the solenoid valve 20 is opened to adjust the level of the supply of make-up water 12. 13 in total, and the liquid volume of the tower bottom liquid 3 returns to its original level. Then, the bottom liquid 3 is diluted, and the diluted sodium hypochlorite is injected by the action of the concentration controller 8.
The sodium hypochlorite concentration is increased to the set concentration, and the renewal operation of the tower bottom liquid 3 is completed.

The cleaning liquid renewal device 16 is connected to the signal line 2 from the hydrometer 22.
Once the input has been obtained via 3, if the time to complete the update operation has not elapsed, the hydrometer 2 is input again.
It is desirable to provide a protection circuit that prevents input of signals from 2 and to have a circuit configuration that allows smooth supply of make-up water 12.

Note that in the above embodiment, a cleaning device using sodium hypochlorite as the cleaning liquid was explained.
Gas cleaning equipment using other chemical solutions including, but not limited to, sulfuric acid, hydrochloric acid, sodium hydroxide, hydrogen peroxide, potassium permanganate, sodium chlorite, sodium hypobromite, sodium thiosulfate The present invention may also be applied to a gas cleaning device using an aqueous solution containing one or more chemicals such as the above as a cleaning liquid, and the same effects as those of the above embodiments can be obtained.

Further, in the above embodiment, the solution specific gravity of the tower bottom liquid 3 is automatically measured.
may be operated manually, with the same effect as above.

As described above, according to the present invention, since the cleaning liquid is updated by measuring the specific gravity of the cleaning liquid,
Unlike conventional devices, cleaning liquid is not discharged unnecessarily, and the components to be cleaned and removed become more concentrated than expected, reaction products accumulate, and troubles due to crystal precipitation are eliminated. Additionally, the amount of supplementary water can be kept to a minimum, which helps save energy.

[Brief explanation of the drawing]

Figure 1 is a flow diagram showing a conventional gas cleaning device.
Figure 2 is a solubility curve diagram of reaction products that accumulate in the cleaning solution when sodium hypochlorite is cleaned to remove human waste and sewage odors, and Figure 3 is a flow diagram showing a gas cleaning device according to an embodiment of the present invention. , FIG. 4 is a relationship curve diagram between the aqueous solution concentration of the reaction product accumulated in the cleaning liquid and the solution specific gravity. In the figure, 1 is a cleaning tower, 2 is a packed bed, 3 is a bottom liquid, 4 is an arrow showing the inflow direction of the gas to be treated, 5 is an arrow showing the outflow direction of the gas to be treated, 6 is a demister, and 7 is a circulation Pump, 8 is a concentration controller, 9 is a chemical injection pump, 10 is a chemical tank, 11, 17, 19 are power lines, 12 is makeup water, 13 is a liquid level controller, 14
1 is a level gauge, 15 and 23 are signal lines, 16 is a washing liquid renewal device, 18 and 20 are electromagnetic valves, 21 is a drain, and 22 is a hydrometer. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. A gas cleaning device that circulates and cleans, as a cleaning liquid, a solution containing a chemical that reacts with harmful components in the gas to be treated and removes them by converting them into odorless reaction products,
A gas cleaning device comprising a cleaning liquid renewal device that detects a change in the specific gravity of the cleaning liquid due to the reaction product and renews the cleaning liquid. 2. The gas cleaning device according to claim 1, comprising a hydrometer that detects a change in the specific gravity of the cleaning fluid, and a cleaning fluid renewal device that automatically renews the cleaning fluid by detecting the change in the specific gravity. . 3. The cleaning solution is an aqueous solution containing one or more agents selected from sodium hypochlorite, sulfuric acid, hydrochloric acid, sodium hydroxide, hydrogen peroxide, potassium permanganate, sodium chlorite, sodium hypobromite, and sodium thiosulfate. A gas cleaning device according to claim 1 or 2, characterized in that: