JPS6333889B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for utilizing irradiated exhaust gas treatment process by-products. More specifically, the present invention provides SO ₂ and/or
This invention relates to a method for rendering harmless an aerosol-like reaction product produced by the mutual reaction of NOx with NH ₃ added under the influence of radiation, and taking it a step further to effectively utilize it. A typical flow sheet for the radiation irradiation exhaust gas treatment process is shown in FIG. This process will be explained according to FIG. 1. The exhaust gas generated in the exhaust gas generation source 1 is introduced into the reactor 3 in the irradiation chamber 2, where it is exposed to radiation from the radiation generator (electron beam generator) 4. (usually an electron beam) and SO ₂ and/or contained in the exhaust gas
NOx reacts with ammonia added from the ammonia addition device 5 or 6 provided at the front or rear of the reactor to generate an aerosol-like reaction product (by-product). These products are collected by a dust collector 7, and the dust-removed exhaust gas is discharged into the atmosphere via a blower 8 and a chimney 9. In the above process, the by-products collected by the dust collector 7 are mainly composed of ammonium sulfate and a double salt of ammonium sulfate and ammonium nitrate (ammonium sulfate), based on the results of X-ray diffraction analysis, infrared absorption, chemical analysis, etc. It has been confirmed that it is a substance that In this specification, exhaust gas refers to combustion exhaust gas from petroleum, coal, etc., and exhaust gas from various industrial processes. Possible ways to use the byproducts of the exhaust gas treatment process are to use them as nitrogenous fertilizers and to recover and use active ingredients through thermal decomposition.
The method of the present invention is a comprehensive method belonging to the latter category, and is characterized in that it makes effective use of the gas produced by thermal decomposition and that the final product is only solid particles that are convenient to handle and harmless. Conventionally, the above-mentioned by-products are difficult to handle because they are fine powders with low specific gravity, and some of them may aggregate during handling, and during thermal decomposition treatment, impurities (such as acidic ammonium sulfate) may be generated due to local heating. Although there have been disadvantages such as an increased risk of explosion, the method of the present invention is free from these disadvantages and can be carried out conveniently. The method of the present invention uses sulfur dioxide gas (SO ₂ ) and/or
Alternatively, ammonia (NH ₃ ) is added to exhaust gas containing nitrogen oxides (NOx) and irradiated with an electron beam, or an aerosol-like reaction product obtained by adding NH ₃ after irradiating the exhaust gas with an electron beam. After being separated and recovered from the gas stream in a dust collector, it is granulated together with inorganic substances in the presence of the required amount of water in a fluidized bed granulator at a relatively low temperature while generating gas containing _NH3 . The solid granules obtained in this way are further thermally decomposed at a high temperature to generate a gas containing dinitrogen oxide, and the main component of the granules is converted to gypsum. A method of utilizing the by-product, which further comprises effectively using the dinitrogen oxide-containing gas as a combustion aid for fuel, and decomposing the dinitrogen oxide to completely render it harmless. . FIG. 2 is a flow sheet showing a preferred embodiment of the present invention. Referring to FIG. 2 below, the reaction products (by-products) of the radiation irradiation exhaust gas treatment process are made into an aqueous solution in a dissolution tank 2-1.
At this time, the weight ratio of the byproduct/water is preferably 10 or less. The optimal ratio is fluidized bed granulator 2
-2 is determined by the operating conditions. Fluidized bed granulation device 2
-2, the aqueous solution from the dissolution tank 2-1 is sprayed by the spray device 2-5, while inorganic substances (e.g. calcium oxide, CaO) are sprayed into the quantitative feeder 2-2.
-3 and a portion of the final solid product (e.g. gypsum) are fed by feed pipes via metering feeder 2-4. The amount of inorganic substances added should be 20% by weight or more based on the by-products (raw materials), and 0.5% by weight of the by-products (raw materials) should be added.
It is preferably within the range of 20 times to 20 times (weight ratio). The optimum amount thereof varies depending on the granulation conditions, but good results can be obtained by using 0.9 to 1.3 times the equivalent amount of SO ₄ ^2- in the product. Inorganic substances that can be added include calcium oxide, magnesium oxide, limestone (main component CaCO ₃ ), slaked lime, dolomite (main component
CaCO ₃ , MgCO ₃ ), dolomite hydroxide, etc., and those whose main component is preferably a substance with a melting point of 400°C or higher. The particles sent to the fluidized bed granulator 2-2 through the supply pipe are forced to circulate and flow by the air from the hot blast furnace 2-6 and the spray from the spray device 2-5, and the reaction between the particles and the liquid and the physical A granule is formed by this combination. Ammonia nitrogen, which was an ammonium sulfate component in the raw material by-product (reaction product of the radiation irradiation process), is desorbed to generate ammonia gas. The particles in the fluidized bed apparatus are grown to a predetermined particle size. The reaction in this case is as shown in the following equation (1). * represents the component of particles produced by granulation. The temperature at which the reaction (1) proceeds is 80-150℃,
Preferably it is 90-110°C. The ammonia-containing gas generated by the reaction of formula (1) is recovered as ammonia gas or ammonium water by an ammonia recovery device 2-7 and stored in an ammonia tank 2-8. The recovered ammonia gas or ammonium water can be used as additive ammonia in the radiation irradiation exhaust gas treatment process. The particles formed are preferably controlled so that they are spherical particles with a particle size of 0.2 to 6 mm, and can be controlled in this manner. Particle size depends on residence time in the device, amount of aqueous solution sprayed, amount of feedback such as gypsum, particle size, temperature, NH ₄ ⁺ in the product,
Since it changes depending on the concentration of NO ₃ ^- , SO ₄ ^2- , etc., the amount of calcium oxide added, the particle size, etc., the optimum conditions can be determined by changing the variable conditions under the given conditions. The residence time is preferably 5 to 40 minutes. Most preferably 15-25 minutes. As shown in equation (1), the ammonium nitrate content in the raw material is granulated together with the generated gypsum, but the nitrate ammonium content is reduced by further processing the obtained granules in the pyrolysis device 2-9. can be thermally decomposed to generate a gas containing dinitrogen oxide. This reaction can be expressed by the following equation (2). 4 [NH ₄ NO ₃ , 2CaSO ₄・nH ₂ O] - → 3N ₂ 0 + N ₂ + 1/2O ₂ + 8H ₂ O + 8CaSO ₄・nH ₂ O...(2) The reaction expressed by formula (2) is 100 to 350 ℃, preferably 180-250℃. A certain amount of the decomposition residue gypsum is transferred to the fluidized bed granulator 2- as necessary.
2, and the remaining gypsum is collected. The gas containing dinitrogen oxide can be recovered by a dinitrogen oxide recovery device 2-11 and stored in a dinitrogen oxide tank 2-12. Alternatively, dinitrogen oxide can be used as a mixed gas without being separated, as a fuel, particularly as a combustion improver for gaseous fuels. After combustion, dinitrogen oxide decomposes into N ₂ and O ₂ ,
Since it is completely rendered harmless, NOx will not be generated again. As an example of a method for processing and utilizing dinitrogen oxide (N ₂ O), an example of a combustion burner that can be used when using dinitrogen oxide (N 2 O) as a combustion improver for gaseous fuel is shown in FIG. Note that the N ₂ O produced by the method of the present invention is effective not only when used with gaseous fuel but also when used with solid and liquid fuels such as coal and oil, or when both are mixed and burned. In FIG. 3, gaseous fuel is supplied from a gaseous fuel supply pipe A. The gaseous fuels mentioned here include dry gas, wet gas, coal gas, generator gas, water gas, heated water gas, pyrolysis oil gas, catalytic cracking oil gas, etc., and these may be used singly or in combination. A mixture of the above is used. On the other hand, dinitrogen oxide is supplied from dinitrogen oxide introduction pipe B. The optimal ratio of gaseous fuel to dinitrogen oxide varies depending on the type of gaseous fuel used, the shape of the burner, etc., but in general, the volume ratio of dinitrogen oxide/gaseous fuel should be within the range of 0.1 to 20. It is desirable to The fuel and N ₂ O thus supplied are mixed and combusted in the combustion chamber C, and are ejected from the nozzle D to the outside of the furnace at high speed. The temperature of the combustion chamber C is desirably kept at 300° C. or higher in order to improve the efficiency of the auxiliary combustion effect of N ₂ O. Reactions in the combustion chamber when natural gas is used as fuel proceed according to the following equation. 2N ₂ O→O ₂ +2N ₂ ...(3) CH ₄ +2O ₂ →CO ₂ +2H ₂ O ...(4) As can be seen from the above reaction formula, N ₂ O serves as a source of O ₂ . Moreover, by using N ₂ O,
This results in an increase in calorific value compared to when natural gas is combusted using conventional methods. The rate of increase in calorific value varies depending on the type of fuel, N ₂ O mixture ratio, combustion method, combustion conditions, structure of the combustion device, etc., but in general it is 5%.
You can get an increase of ~50%. Examples will be explained below. Example 1 The reaction product (ammonium nitrate/ammonium sulfate = 0.6, weight ratio) collected by a dust collector in the radiation irradiation exhaust gas treatment process was continuously supplied to the dissolution tank at a rate of 44 kg/hour. Water was continuously supplied at a rate of 47 Kg/hr. The solution thus obtained in the dissolution tank was withdrawn from the dissolution tank at a rate of 91 kg/hour and sprayed into a fluidized granulation device via a spray device. At the same time, 12Kg/hour of calcium oxide and 15Kg/hour of gypsum were sent to the granulator using quantitative feeders, and air (110Kg/hour) was fed from the hot blast furnace.
℃) was blown into the granulator at a rate of 100 kg/hour.
Pelletization was carried out with the residence time of the by-products in the granulator being 20 minutes. Gas containing ammonia was generated in the fluidized bed granulator. From the analysis results, the amount of ammonia gas generated was as shown in Table 1.

[Table] Granulated pellets formed with a fluidized granulator are 2 mm.
It was a spherical body with a diameter of φ, and the results of X-ray diffraction analysis were as shown in Table 2.

[Table] Example 2 The pellets formed in the fluidized granulator in Example 1 were supplied to the pyrolysis furnace at a rate of 63 kg/hour, and at the same time hot air at 230°C was blown into the pyrolysis furnace at a rate of 60 kg/hour. Pyrolysis was carried out. Gas containing dinitrogen oxide was generated in the pyrolysis furnace. The gas amount determined from the analysis results and the X-ray analysis results of the decomposition residue were as shown in Table 3.

[Table] Comparative Example 1 A by-product of the irradiated exhaust gas treatment process, which was the same as that used as the raw material in Example 1, was directly put into a pyrolysis furnace without fluidized bed granulation and pyrolyzed at 220°C. After removing ammonium nitrate by generating dinitrogen oxide, it was taken out and subjected to chemical analysis and X-ray diffraction analysis. As a result of analysis, the main component is ammonium sulfate,
It was found that it contained about 10% of acidic ammonium sulfate, and several percent of ammonium hydrogen sulfate and ammonium pyrosulfate. In addition, some products agglomerated and adhered in the pyrolysis furnace. In Example 2, such aggregation and adhesion were not observed, and the decomposition residue was only gypsum. Example 3 The nitrogen dioxide-containing gas generated in the pyrolysis furnace in Example 2 was fed together with natural gas into a combustion device equipped with a radiant nozzle burner at a volume ratio of nitrogen dioxide-containing gas/natural gas of 10. supplied and burned. N ₂ O concentration and temperature were measured at the combustor outlet. No N ₂ O concentration was detected.
The temperature was 1250℃. Comparative Example 2 The same natural gas as in Example 3 was combusted using the same combustion device as in Example 3 at an air/natural gas volume ratio of 1.0, and the temperature was measured at the outlet of the combustion device in the same manner as in Example 3. However, the temperature was 1210°C, which was almost the same as in Example 3. As is clear from the above, by the method of the present invention,
It has become possible to thermally decompose by-products of the radiation irradiation exhaust gas treatment process efficiently, with less impurity generation, and with high safety. In addition, since ammonia in ammonium sulfate can be treated during granulation,
The pyrolysis equipment can be simplified. The N ₂ O-containing gas generated by thermal decomposition is separated from the N ₂ O and converted into N ₂ O.
Although it can be used for normal purposes, it can also be used as a fuel as a mixed gas, especially as a combustion aid for gaseous fuels, so a large amount of N ₂ can be removed without the need for special recovery and separation equipment. O can be used industrially with great advantage. Owing to the above-mentioned effects, the ammonia-added radiation irradiation exhaust gas treatment process can now be carried out more advantageously.

[Brief explanation of the drawing]

FIG. 1 shows a flow sheet for a typical irradiation exhaust gas treatment process. FIG. 2 shows a flow sheet of one preferred embodiment of the method of the invention. FIG. 3 shows an example of a combustion apparatus that can be used to use the N ₂ O gas produced by the method of the invention as a combustion improver for gaseous fuels according to the method of the invention. The symbols in the figure represent the following. 1... Exhaust gas generation source, 2... Irradiation chamber, 3... Reactor, 4... Radiation (electron beam) generator,
5, 6... Ammonia addition device, 7... Dust collector,
8... Blower, 9... Chimney, 2-1... Dissolution tank, 2-2... Fluidized tank granulation device, 2-3... Quantitative feeder, 2-4... Quantitative feeder, 2-5...
...Spray device, 2-6...Hot air stove, 2-7...
Ammonia recovery device, 2-8...Ammonia tank, 2-9...Pyrolysis device, 2-10...Sieving device, 2-11...Dinitrogen oxide recovery device, 2
-12... Dinitrogen oxide recovery tank, A... Gaseous fuel supply pipe, B... Dinitrogen oxide introduction pipe, C... Combustion chamber, D... Nozzle, GF... Gaseous fuel, N ₂ O...
Dinitrogen oxide, BG...heat flow (combustion gas).

Claims (1)

[Claims] 1. Ammonia (NH ₃ ) is added to the exhaust gas containing sulfur dioxide gas (SO ₂ ) and/or nitrogen oxides (NOx).
or after irradiating the exhaust gas with electron beams, the reaction product obtained by adding NH ₃ is placed in a fluidized bed granulator together with an inorganic substance in the presence of moisture. Along with granulation,
A method of using a byproduct of an electron beam irradiation exhaust gas treatment process, which is characterized by generating a gas containing ammonia. 2. The inorganic substance is calcium oxide or/and calcium hydroxide,
The method according to claim 1. 3. The fluidized bed granulation is carried out for a residence time of 5 to 40 minutes to obtain spherical particles with a diameter of 0.2 to 6 mm.
The method according to claim 1 or 2. 4 Ammonia (NH ₃ ) is added to exhaust gas containing sulfur dioxide gas (SO ₂ ) and/or nitrogen oxides (NOx).
The reaction product obtained by adding NH 3 and irradiating the exhaust gas with an electron beam or by adding NH ₃ after irradiating the exhaust gas with an electron beam is placed in a fluidized bed granulator together with an inorganic substance in the presence of moisture. Along with granulation,
It is characterized by generating a gas containing ammonia, and then thermally decomposing the obtained granulated product in a pyrolysis device to generate a gas containing dinitrogen oxide.
How to use byproducts of electron beam irradiation exhaust gas treatment process. 5. A method according to claim 4, characterized in that the thermal decomposition is carried out at a temperature within the range of 100 to 350°C. 6 Ammonia (NH ₃ ) in exhaust gas containing sulfur dioxide gas (SO ₂ ) and/or nitrogen oxides (NOx)
or by irradiating the exhaust gas with electron beams, or by irradiating the exhaust gas with electron beams and then adding NH ₃ , the reaction product obtained is granulated in the presence of moisture together with an inorganic substance in a fluidized bed granulator. While granulating, a gas containing ammonia is generated, and then the obtained granulated product is thermally decomposed in a pyrolysis device to generate a gas containing dinitrogen oxide, and the gas containing dinitrogen oxide is combusted together with fuel. A method of utilizing an electron beam irradiation exhaust gas treatment byproduct, characterized by supplying it to a room. 7. A patent characterized in that the dinitrogen oxide-containing gas is supplied to the combustion chamber together with gaseous fuel at a volume ratio of dinitrogen oxide to gaseous fuel (dinitrogen oxide/gaseous fuel) of 0.1 to 20. The method of claim 6. 8 The gaseous fuel is any one of dry gas, wet gas, coal gas, generating furnace gas, water gas, heating water gas, oil gas, or 2 selected from these.
8. A method according to claim 7, characterized in that it is a mixture of more than one species of gas.