JPS6120334B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a deodorizing method using a metal catalyst and ozone, and particularly to a continuous deodorizing method suitable for long-term continuous operation. In recent years, pollution caused by the diffusion of gases containing malodorous components into the atmosphere has become a social problem, and along with this, there has been a demand for the development of technology for treating and deodorizing the gases. In response to these demands, conventional deodorization methods such as chemical cleaning, adsorption, direct combustion, catalytic oxidation, and ozone oxidation have been used, but these methods have advantages and disadvantages and are not practical. I don't like it. That is, the chemical cleaning method has a low ability to deodorize and remove low concentrations, and requires treatment of used waste liquid. The adsorption method cannot be applied to high-concentration deodorization and removal, and there is a risk of secondary pollution caused by the used adsorbent. The direct combustion type has a simple system, but requires high temperatures of over 700°C, resulting in high running costs and high-temperature combustion that generates large amounts of harmful NOx. The catalytic oxidation type oxidizes malodorous components at a relatively low temperature of 250 to 450°C, so it has lower running costs and generates less NOx than the direct combustion type, but other chemical cleaning types that deodorize at near room temperature, Compared to the adsorption type, it has the disadvantage of higher fuel costs. The ozone oxidation method utilizes the strong oxidizing power of ozone to oxidize malodorous components, and in recent years, a method that exhibits good deodorizing performance when used in combination with activated carbon has been developed and put into practical use. However, this ozone oxidation method is not suitable for deodorizing highly concentrated malodorous components, and cannot remove methyl sulfide.Furthermore, if there is a large amount of moisture in the gas containing malodorous components, the performance of activated carbon will decrease, and the deodorization process will deteriorate. There were drawbacks such as a significant drop in performance. For these reasons, the present inventors previously proposed a new ozone-catalytic oxidation method that combines the conventional catalytic oxidation method and ozone oxidation method. This ozone-catalytic oxidation method has the same deodorizing performance as the conventional catalytic oxidation method at a low temperature of 100 to 150℃, and also removes highly concentrated malodorous components, removes methyl sulfide, and has no effect on moisture. It has various advantages that can solve all problems of deodorizing performance caused by deodorization. However, since this ozone-catalytic oxidation formula is carried out at low temperatures, for example, when hydrogen sulfide, methyl sulfide, or methyl mercaptan is used as the malodorous component, H ₂ S + O ₃ → SO ₂ + H ₂ O (CH ₃ ) as shown in the following equation. ₂ S＋nO ₃ →(CH ₃ ) ₂ SOn＋nO ₂ (n=
1, 2, 3) The reaction of CH ₃ SH + O ₃ → CH ₃ SO ₃ H produces sulfur dioxide gas, dimethyl sulfoxide, and oxidation products of methyl sulfuric acid, which adhere to the catalyst and do not desorb and accumulate in the catalyst. This has the disadvantage that the catalyst activity is significantly reduced and the deodorizing performance is significantly reduced. In view of the above points, the present invention improves the drawbacks of the ozone-catalytic oxidation method and provides a deodorizing method suitable for continuous operation that can maintain stable deodorizing efficiency without impairing catalyst activity even during long-term continuous operation. The purpose is to provide. The present invention can convert gases containing malodorous gases into Pt, Pd,
A step of deodorizing by an ozone-catalytic oxidation method under a catalyst containing at least one selected from Rh, Ru, Cu, Fe, Co, Ni, and Ti, and a step of heating the catalyst used in the above step to 250 to 450°C. This is a continuous deodorizing method that includes the steps of regenerating the catalyst and deodorizing malodorous components using the oxidizing function of the catalyst. That is, in the method of the present invention, malodorous components can always be removed by the ozone-catalytic oxidation method or the catalytic oxidation method, and furthermore, the catalytic activity is regenerated at the same time as the catalytic oxidation method. Catalysts used in the present invention include Pt, Pd,
Examples include metals made of one or more of Rh, Ru, Cu, Fe, Ti, Ni, and Co, or metals supported on a carrier such as alumina. In addition, the temperature conditions in the ozone-catalytic oxidation malodorous component removal step in the method of the present invention are usually 70 to 70°C.
The temperature is preferably in the range of 150°C. The regeneration time interval in the present invention may be appropriately selected depending on the concentration of malodorous components in the gas to be treated. In the present invention, the heating temperature in the catalyst regeneration step, which is carried out simultaneously with the removal of malodorous components by catalyst oxidation, is set at 250°C.
The reason for the range of ~450℃ is that if it is less than 250℃, it will be difficult to desorb and remove the oxidation products accumulated in the catalyst, and if it exceeds 450℃, the fuel consumption will increase and the running cost will rise. This is because, if the catalyst is composed of an alumina carrier, there is a risk that a reaction between alumina and acidic oxides may occur, or a structural change in alumina may cause a decrease in the activity of the catalyst. In the catalyst regeneration step of the present invention, ozone essentially separates and loses its oxidizing function.Also, from the viewpoint of reducing running costs, it is desirable to stop the supply of ozone. The regeneration step may be performed while ozone is supplied. Hereinafter, the present invention will be explained in detail using an example of an apparatus using the method of the present invention. FIG. 1 is an example of a schematic diagram of a deodorizing apparatus using the method of the present invention. Waste gas containing malodorous components is sucked from a malodor source through a duct 1 by a blower 2, sent to a preheating heat exchanger 3, and heated to 50 to 80°C. The heated waste gas is further mixed with ozone supplied from the ozone generator 4 and then introduced into the catalytic reaction chamber 5. Catalytic reaction chamber 5
is provided with a platinum oxidation catalyst layer 6, and is further heated with a kerosene burner 7 to heat the oxidation catalyst layer 6 to 100 to 150°C.
Alternatively, an electric heater 8 is installed, and the waste gas is oxidized by ozone while passing through the oxidation catalyst layer 6, turning into harmless and odorless carbon dioxide and water, and passing through the heat exchanger 3 to the outside of the system. is discharged. During the deodorizing operation of waste gas as described above, the oxidation catalyst layer 6 is heated to 250 °C using a kerosene burner 7 or an electric heater 8.
Heating to an arbitrary set temperature of ℃ or higher and 450℃ or lower to desorb oxidation products adsorbed on the catalyst,
Regenerate the catalyst. During the regeneration of the catalyst, deodorization of the waste gas is also carried out at the same time, so there is no need to stop the deodorization operation. Although regeneration may be performed as appropriate, it is preferable to perform regeneration at regular intervals, and the time interval is determined depending on the concentration of malodorous substances in the waste gas to be treated. The time required for regeneration is determined by the total amount of sulfur compound concentration supplied during deodorization operation from the previous regeneration to the current regeneration.
Heating for approximately 1 hour is sufficient. According to the method of the present invention, the disadvantage of introducing clean outside air instead of waste gas during regeneration, as seen in the conventional thermal regeneration catalyst deodorization method, is that the deodorization of waste gas is stopped during regeneration. Therefore, the disadvantage of generating odor pollution is eliminated. The method of the present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples. Example 1 Waste gas containing malodorous components such as hydrogen sulfide, methyl mercaptan, methyl sulfide, and methyl disulfide discharged from a human waste treatment plant was treated with an apparatus using the method of the present invention as shown in FIG. 1 above. A platinum catalyst was used as the catalyst, and the deodorizing treatment conditions were an oxidation catalyst layer temperature of 120°C, a space velocity of 2×10 ⁴ 1/hr, and a linear velocity.
After operating for 8 hours at a speed of 0.3 m/sec and an ozone concentration of 100 ppm, thermal regeneration treatment was performed. Thermal regeneration treatment conditions were such that the temperature of the oxidation catalyst layer was raised to 300° C. and maintained at this temperature for 1 hour while the above-mentioned waste gas and ozone were kept flowing. Repeat the cycle of 8 hours of deodorization and 1 hour of heat regeneration, operate the deodorizer, and after 500 hours,
The hydrogen sulfide removal rate was measured after 1000 hours and after 1500 hours, and the results shown in Table 1 were obtained. As a comparative example, the results were also shown in Table 1, in which the deodorizing treatment was performed under the same conditions with the same specifications as above, but the 1-hour heat regeneration treatment was not performed.

[Table] As described above, according to the method of the present invention, the activity of the catalyst is maintained for a long time, and the life of the catalyst is significantly extended. Example 2 Using the same deodorizing equipment as in Example 1, waste gas containing 50 ppm of hydrogen sulfide was removed under the same deodorizing treatment conditions.
After 24 hours of treatment, a thermal regeneration treatment was performed for 1 hour. The temperature of thermal regeneration treatment is 200, 250, 350, 450,
The deodorizing treatment was carried out at 600°C, and after thermal regeneration, the same waste gas as above was used again to deodorize. After repeating the deodorization and regeneration treatment 10 times as described above, the hydrogen sulfide removal rate was measured. The results are shown in FIG. As is clear from this result, it was confirmed that excellent deodorizing efficiency could be maintained by setting the heating step in the regeneration step to 250 to 450°C. As described above, by using the method of the present invention, excellent deodorizing efficiency can be maintained without impairing catalyst activity even during long-term continuous operation. Additionally, the present invention can facilitate automation as follows. That is, in the continuous deodorization method of the present invention, the time interval for performing the thermal regeneration step depends on the total amount of sulfur compounds supplied during the low-temperature deodorization operation at 100 to 150°C, that is, the total amount of sulfur compounds adsorbed and accumulated on the catalyst. Therefore, as shown in FIG. 3, a sulfur compound concentration sensor 9 is attached to the inlet of the deodorizing device, and the sulfur compound concentration in the waste gas can be measured constantly or at regular intervals, and controlled by a microcomputer 10. The microcomputer 10 adds the output signal value from the sulfur compound concentration sensor 9, and starts the regeneration process when the set value is reached. In other words, kerosene burner 7
Alternatively, the oxidation catalyst layer 6 is heated to a set temperature and for a set time using the electric heater 8 to remove oxidation products accumulated on the catalyst and regenerate the catalyst. By controlling in this way, it is possible to automatically perform continuous deodorization with high efficiency over a long period of time.

[Brief explanation of the drawing]

FIGS. 1 and 3 are schematic diagrams showing an example of a deodorizing apparatus using the method of the present invention, and FIG. 2 is a curve diagram showing the malodor removal rate versus heating temperature, which shows the thermal regeneration performance of the catalyst. 1...Duct, 2...Blower, 3...Heat exchanger, 4...
Ozone generator, 5... Catalytic reaction chamber, 6... Oxidation catalyst layer, 7... Kerosene burner, 8... Electric heater, 9... Sulfur compound concentration sensor, 10... Microcomputer.

Claims (1)

[Claims] 1 Gases containing malodorous components such as Pt, Pd, Rh, Ru,
A step of deodorizing using an ozone-catalytic oxidation method under a catalyst containing at least one type selected from Cu, Fe, Co, Ni, and Ti. A continuous deodorizing method comprising the steps of regenerating and deodorizing malodorous components using the oxidizing function of a catalyst.