KR800001275B1 - Process for removing nox and so2 from waste gas - Google Patents

Abstract

The concn. ratio NO2/So2 of waste gas was adjusted to 0.1-0.3, and the gas was treated with radiations, ultrasound, to form aerosols of the NOx and SO2 which were removed from the gas by electrostatic precipitators. The sources of radiation and conditions of reactors were described.

Description

Method for removing sulfurous acid gas and / or nitrogen oxide contained in exhaust gas

1 is an example of a flow gheet showing a preferred state of the present invention.

2 is a graph showing desulfurization rate (.Table) and denitrification rate (X table) in Examples and Reference Examples of the present invention.

The present invention relates to a method for removing sulfur dioxide and / or nitrogen oxide contained in exhaust gas.

Sulfur oxides, nitrogen oxides and other toxic gases are contained in exhaust gases generated from various fuel furnaces and chemical plants using fossil fuels such as fuel oil and coal. Sulfur oxides, mainly SO ₂ , SO ₃ are 1,000 ~ 2,000ppm. Nitrogen oxides, mainly NO and NO _2, are contained in the range of 300 to 3,000 ppm, making them the main source of air pollution. In particular, nitrogen oxide NOx is regarded as one of the causative agents of photochemical smog, and the removal thereof is urgent, but the method has not yet been established.

The present inventors have invented a method of converting SO ₂ and NO x contained in exhaust gas into bees or solids by irradiation with radiation, and removing them with a dust collector or filter, but the present invention relates to the improved or selective invention. Based on the above-described invention, as a result, when the SO ₂ concentration and the NOx concentration contained in the exhaust gas at the entrance of the irradiation chamber are maintained at a preferable ratio, and the radiation or ultraviolet rays are irradiated, the desulfurization rate and the denitrification rate are greatly improved. As a result, it has been found that the energy absorbed in the exhaust gas is effectively used. That is, according to the present invention, after adjusting the exhaust gas containing SO ₂ and NOx or one of them, the ratio of NOx concentration and SO ₂ concentration (NOx / SO ₂ ) is adjusted to about 0.1 to 0.3, preferably 0.5 to 1.5. And by irradiating with radiation or ultraviolet rays, NOx and SO ₂ are efficiently converted into mists or solids.

Radiation in the present invention typically refers to particle beams such as α-rays, β-rays, X-rays, electron beams, neutron beams, and electromagnetic waves. Moreover, the mixed radiation which combined these two or more types can also be used.

However, when the amount of the processing gas is large, the electron beam from the particle beam accelerator is practical in view of the fact that a high radiation rate can be obtained, it is easy to control, and the transmittance is small compared with γ-rays and X-rays. In addition, when the amount of processing gas is small and even a low dose rate is obtained, γ-rays, X-rays, and the like are also practical.

Radiation sources other than particle accelerators include radioisotopes, fission products, spent nuclear fuel, and reactors.

Also is the exhaust gas of the present invention to say the gas containing SO ₂ and NO, or one of, for example, contains the exhaust gas discharged from chemical plants, steel mills, power plant.

However, since the ratio of NO x concentration and SO ₂ concentration in the exhaust gas varies depending on each plant, the fuel used, and the conditions of use, NOx or SO ₂ is added, and the ratio at the entrance to the irradiation chamber is about 0.1 to 0.3. Is adjusted to about 0.5 to 1.5, and the method of irradiation is used. It is to be noted that in the combustion furnace, the amount of NOx generated changes by adjusting the combustion temperature and the amount of oxygen supply.

Therefore, in the case of the exhaust gas from the combustion furnace, the NOx generation amount is adjusted by adjusting the combustion method, for example, supply air, feed fuel, combustion temperature, and the like, and the NOx concentration of the exhaust gas at the entrance of the irradiation chamber and SO _2. The ratio of concentration can be adjusted. On the other hand, when radiation is applied to a gas containing nitrogen and oxygen, NOx is generated by a radiochemical reaction, and the amount of NOx generation depends on the amount of N ₂ and O ₂ contained in the gas. For example, in the case of copper dose irradiation, the higher the amount of N ₂ and O _{2, the} higher the amount of NOx generated. Therefore, when the content of N ₂ and O ₂ or one of the exhaust gases is low, one or two or more of air, N ₂ , O ₂ , and O ₃ may be added to increase the amount of NOx generated by irradiation. In this case, the same result as that obtained by adjusting the ratio of NOx concentration and SO ₂ concentration in the exhaust gas at the irradiation entrance in the range of about 0.1 to 0.3, preferably 0.5 to 1.5 can be obtained. Also upon irradiation of radiation to the gas containing N ₂ and O _2, and the NOx emission amount is changed according to the dose rate. Therefore, by adjusting the dose rate, the amount of NOx generated by irradiation can be adjusted, and the ratio of NOx concentration and SO ₂ concentration in the exhaust gas at the entrance of the irradiation chamber is adjusted to about 0.1 to 3.0, preferably about 0.5 to 1.5. The same result can be obtained.

It goes without saying that it is also a good way to combine two or more of the above four methods. In addition, in order to reduce the amount of NOx that is a source of pollution in the combustion furnace, an uneconomical combustion method, which has a poor thermal effect such as a method of lowering the combustion temperature and an exhaust recirculation method, is used. It is possible to increase the combustion rate, which is economical. The temperature of the exhaust gas to be irradiated is equal to or higher than its dew point, and preferably below the decomposition temperature of the mist and the solid matter.

Hereinafter, specific embodiments of the present invention will be described with reference to the flow sheet of FIG. The exhaust gas from each fuel furnace and the chemical plant 1 is adjusted to the optimum temperature in the irradiation chamber by the heat exchanger 2, and the SO ₂ concentration and the NOx concentration measurement device 3 SO ₂ concentration and NO x concentration are measured. Each device described below and the SO ₂ concentration and NOx concentration measuring instrument 3 are linked to each other, and one or two or more of those apparatuses are selected so as to be economically economical by the signals of the SO ₂ concentration and NOx concentration measuring instrument 3. The ratio of NOx concentration and SO ₂ concentration at the entrance of the irradiation chamber is always adjusted to 0.1-3.0, preferably 0.5 to 1.5, by supplying important gas from the addition port 20, for example. Or by controlling the dose rate by the radiation or ultraviolet irradiation device 22, it is controlled in the state which can obtain the same result.

The device linked to the SO ₂ concentration and NOx concentration meter (3) includes (8) air adder, (10) oxygen supply, (12) ozone supply, (14) N ₂ supply, (6) NOx Feeder, (18) SO ₂ feeder, (22) radiation or UV irradiation, (23) combustion air supply, (24) fuel supply. (23) and (24) are limited to combustion furnaces. Moreover, not all these devices are necessary. The exhaust gas, which is brought to a predetermined state by the SO ₂ concentration and the NOx concentration meter 3, is guided to the irradiation chamber 4, where radiation or ultraviolet rays are irradiated, and the SO ₂ and NOx in the exhaust gas are mist or solids. The exhaust gas, which has been converted and removed by the dust collecting or filtration device 5, is purified and is discharged from the communication 21 via the SO ₂ concentration and the NOx concentration monitoring device 6. In addition, the SO ₂ concentration and NOx concentration monitoring device 6 and the respective devices 8, 10, 12, 14, 16, 18, 22, 23, 24 are connected to each other to exhaust gas discharged from the communication 21. The SO ₂ concentration and the NOx concentration can always be kept below the set value. Here, (7), (9), (11), (13), (15), (17), and (19) are valves for adjusting the amount of additive gas flow.

[Examples 1-5]

Using a Cockcroport-Walton type electron accelerator, an electron beam with a dose rate of 6.45 × 10 ⁵ rad / sec for 4.5 seconds, that is, a total dose of 3.5 Mrad, was used at a gas temperature of 150 ° C, O _{2 of} about 3%, and SO ₂ concentration of 1,000 ppm ( Constant and desulfurization rate and denitrification rate when irradiated with B heavy oil combustion exhaust gas 10 m ³ / H in which the NOx concentration was changed from 100 ppm to 3,000 ppm were shown by polymerization in Table-1 and FIG.

TABLE -1

[Reference Example 1-2]

(Reference Example 1-2) The conditions were substantially the same as those in Example 1-5 except that the ratio of NOx concentration and SO ₂ concentration was 0.05. It shows in FIG. 2 with Example 1-5. Reference Example -2 The conditions are substantially the same as those of Example 1-5 except that the ratio of NO x concentration and SO ₂ concentration is 4.1. It shows in FIG. 2 with Example 1-5. It is understood that the desulfurization rate is poor in Reference Example-1 and the denitrification rate is poor in Reference Example-2. Comparing Example 1-5 and Reference Example 1-2, the desulfurization rate is particularly bad when the ratio (NOx / SO ₂ ) between NOx concentration and SO ₂ concentration is 0.1 or less, and denitrification rate is particularly bad when 3.0 or more, and is in the range of 0.1-3.1. Is good, and it is particularly good in the range of 0.5-1.5.

Example 6

Fuel oil-only boiler lubrication B was burned by adjusting the ratio of oil and air, that is, fuel / air to 0.9, and the O ₂ concentration and the NOx concentration in the exhaust gas were measured. As a result, the SO ₂ concentration was 1020 ppm, the NOx concentration 980 ppm, and the oxygen 2.9 % Was contained. An electron beam of 4.5 seconds, or 2 Mrad of electric wire, was irradiated to this exhaust gas 10 m ³ / H at 4.3 x 10 ⁵ rad / sec at a gas temperature of 150 ° C. As a result, SO ₂ was reduced to 190 ppm and NOx to 140 ppm.

Example 7

The heavy oil-only boiler used in Example 6 was reduced in air volume to dry the fuel / air to 1.3, and the exhaust gas was added to 200 l / H in 10 m ³ / H and the oxygen concentration was adjusted to about 3%, As a result of measuring the SO ₂ concentration and the NO x concentration, the SO ₂ concentration was 990 ppm and the NO x concentration was 80 ppm. This exhaust gas was irradiated with an electron beam having a wire temperature of 2 Mrad for 4.5 seconds at 4.3 × 10 ⁵ rad / sec at a gas temperature of 150 ° C. for 10 m ³ / H. As a result, SO ₂ 280 ppm and NOx were almost undetectable.

Example 8

Example 6 Exhaust gas 10m ³ / H to 200ℓ / addition of O ₂ in H to review the same dose in the same conditions for the exhaust gas to adjust the O ₂ concentration of 5% as in Example 6, the result of, SO ₂ and NOx is Almost none were detected.

In Examples 6 and 7, by adjusting the combustion method, it is possible to adjust the ratio of NOx concentration and SO ₂ concentration in the exhaust gas, and the removal rate of harmful ships is higher when the method of reducing NOx generation is not used. Able to know. It is also easy to infer that the calorific value is high and economical.

In addition, in Examples 6 and 8, by adding less N ₂ and O ₂ contained in the exhaust gas (in this case, since the heavy oil combustion exhaust gas, the amount of O ₂ is less than that of N ₂ ). It is understood that SO ₂ and NO x can be removed together by adjusting the amount of NO x generated by

As described above, the present invention has an excellent effect of being able to efficiently remove SO ₂ and NO x in the exhaust gas stream simultaneously.

Claims (1)

Characterized by irradiating radiation or ultraviolet rays by adjusting the concentration ratio (NOx / SO ₂ ) of nitrogen oxides and sulfurous acid gas in the exhaust gas containing sulfurous acid and / or nitrogen oxides in the range of 0.1-3.0. Method for removing sulfurous acid gas and / or nitrogen oxides in exhaust gas.

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