KR100302640B1 - Removal of Sulfur Oxides and Nitrogen Oxides Using Natural Manganese Ore in a Continuous Fluidized Bed Reactor - Google Patents

Abstract

The present invention relates to a method for the simultaneous removal of sulfur oxides and nitrogen oxides using natural manganese ore (pyrolusite, β-MnO ₂ ) in a continuous fluidized bed reactor, more specifically sulfur oxides in the exhaust gas is chemisorption reaction And nitrogen oxides are simultaneously removed in a continuous fluidized bed reactor by selective catalytic reduction with manganese sulfide produced by chemical reaction between sulfur oxides and natural manganese ores using ammonia as a reducing agent. The catalyst can effectively remove the sulfur oxides and nitrogen oxides in the exhaust gas in a single reactor in the temperature range 300 ~ 500 ℃, residence time 10 ~ 40 minutes.

Description

Removal Method of Sulfur and Nitrogen Oxides Using Natural Manganese Ore in a Continuous Fluidized Bed Reactor

The present invention relates to a method of simultaneously removing sulfur oxides and nitrogen oxides by using natural manganese ore as an adsorbent or catalyst in a continuous fluidized bed reactor, more specifically, inexpensive and does not require special processing, sufficient wear resistance A method for removing sulfur oxides and nitrogen oxides from a single reactor by applying a natural manganese ore which has both adsorption removal efficiency of sulfur oxides and excellent reduction ability of nitrogen oxides using ammonia as a reducing agent to a continuous fluidized bed reactor will be.

Various methods for the removal of sulfur oxides and nitrogen oxides from fixed sources such as combustion furnaces and boilers are under development and researches are in progress. For the sulfur oxides, the wet method using limestone and slaked lime is mainstream In the case of, the selective catalytic reduction method using ammonia as the reducing agent in the metal oxide catalyst is recognized as the most appropriate method from the economic and technical aspects.

However, this method requires a separate treatment device for the removal of sulfur oxides and nitrogen oxides in the exhaust gas, resulting in a large loss of equipment installation and operating costs. Therefore, research is being conducted to simultaneously process sulfur oxides and nitrogen oxides in a single treatment device, and a method of using a metal oxide as in the present invention is as follows.

In the method of simultaneously removing sulfur oxides and nitrogen oxides using metal oxides, sulfidation reactions and selective catalytic reduction reactions occur simultaneously in a single reactor. First, as shown in Scheme 1, sulfur oxide is adsorbed to metal oxide in the presence of oxygen to form metal sulfide, and the metal oxide that does not react with the produced metal sulfide uses nitrogen ammonia as a reducing agent as in Schemes 2 and 3 below. Reduce.

As described above, the simultaneous removal of sulfur oxides and nitrogen oxides using metal oxides has been mainly studied using copper oxides [Yeh, JT, Demski, RJ, Strakey, JP and Joubert, JI, "Combined SO ₂ / NOx. Removal from Flue Gas ", Environ. Prog., 4 (4), 223-228 (1985): Centi, G., Passarini, N., Perathoner, S., Riva, A., and Stella, G., "Combined DeSOx / DeNOx Reactions on a Copper on Alumina Sorbent-Catalyst. 1. Mechanism of SO ₂ Oxidation-Adsorption ", Ind. Eng. Chem. Res., 31, 1947 (1992). Copper oxide acting as an adsorbent and a catalyst is supported on alumina or silica and can be regenerated by a reducing gas such as hydrogen or methane. However, the manufacturing process is complicated and does not have the wear resistance that can be used in the fluidized bed reactor has a disadvantage that can not be used in the actual process. Accordingly, there is a need for an adsorbent and a catalyst having excellent wear resistance in a fluidized bed reactor capable of simultaneously removing sulfur oxides and nitrogen oxides, having ease of manufacture and economy, and capable of treating a large amount of exhaust gas.

On the other hand, manganese dioxide, manganese nodule or manganese ore is also used for the desulfurization and / or denitrification of the exhaust gas. For example, Japanese Patent Laid-Open No. 8-155300 discloses a desulfurization and denitrification method using manganese ore containing 30 to 80 wt% manganese dioxide and 5 to 15 wt% ammonium oxide. However, the patent is limited only to the manganese ore as a constituent, there is no particular limitation, using a plurality of mobile bed reactors for the desulfurization and denitrification of the exhaust gas using this, there is a disadvantage that the desulfurization and denitrification efficiency is not high. . In addition, the reaction itself and the process is different from the fluidized bed reactor used in the present invention by using a moving bed reactor. In the present invention, the sulfur oxides are adsorbed and removed by sulfidation directly to manganese ore, and the reaction temperature range is between 300 and 500 ° C. In contrast, not only simple physical adsorption removal in the form of a salt (ammonium sulfate) in which sulfur oxide is reacted with ammonia, but also a low temperature of 90 to 150 ° C. has a large difference from the present invention.

In addition, although the applicant's inventor, Korean Patent Application No. 97-19125, uses the natural manganese ore used in the present invention as a catalyst for removing nitrogen oxides in the exhaust gas at 130 to 250 ° C. The ore itself is used as a catalyst for the selective catalytic reduction method, and the denitrification efficiency is very low above 300 ° C, and there is no mention or influence on sulfur oxides.

In order to solve this problem, the present inventors have conducted extensive research, and as a result, sulfur oxides in the exhaust gas can be directly utilized by using natural manganese ore existing in nature, which does not require the preparation of a catalyst using high technology and expensive metal oxides. And nitrogen oxides could be removed simultaneously in a single reactor, and the present invention was completed based on this.

Therefore, an object of the present invention is to remove sulfur oxides and nitrogen oxides carried out in a separate reactor at the same time in a single reactor, and also do not require any special processing, large-scale exhaust gas treatment using natural manganese ore which is very inexpensive The present invention provides a method for effectively removing sulfur oxides and nitrogen oxides from a fluidized bed reactor.

Removal of cargo, and the nitrogen oxides of the present invention sulfuric acid for achieving the abovementioned objects is manganese oxide which mainly forms a form of MnO _2,. The MnO ₂ is the diffraction main peak X-ray 28.7, 37.3., And 42.7 ( Natural manganese ore having a structure of β-MnO ₂ of 2θ) is used as an adsorbent for sulfur oxides and sulfur oxides of manganese ores produced by sulfidation reactions as a reduction catalyst for nitrogen oxides, and ammonia is used as a reducing agent. Removal in a continuous fluidized bed reactor by catalytic reduction.

1 is a graph showing the selective catalytic reduction capacity of manganese sulfide formed by reacting with a sulfur oxide in a fixed bed reactor according to Example 1 of the present invention.

2 is a graph showing the simultaneous removal efficiency of sulfur oxides and nitrogen oxides obtained by varying the temperature in a continuous fluidized bed reactor according to Example 2 of the present invention.

3 is a graph showing removal efficiency of sulfur oxides and nitrogen oxides according to changes in residence time and temperature during simultaneous desulfurization and denitrification in a continuous fluidized bed reactor according to Example 3 of the present invention.

Looking at the present invention in more detail as follows.

In the present invention, a natural manganese ore was used as an adsorbent for sulfur oxides and a catalyst for nitrogen oxides in the exhaust gas, and the average chemical composition and physical characteristics of the natural manganese ores are described in Tables 1 and 2, respectively.

Chemical Composition of Natural Manganese Ore (Average) Furtherance Mn SiO ₂ Al ₂ O ₃ Fe CaO MgO O ₂ balance of Mn and Fe * weight% 51.83 3.13 2.51 3.86 0.11 0.25 38.31 * Mn and Fe are MnO ₂ , Mn ₂ O ₃ , Mn ₃ O ₄ , Fe ₂ O ₃ , Fe ₃ O _{4 It} is difficult to express their composition because the presence of a different oxidation value, such as Mn and Fe respectively Combined with, displays the total amount of oxygen present.

Average Physical Properties of Manganese Ore (Average) Density (kg / m ³ ) 3980 Pore Volume (cm ³ / g) 0.0392 (5-3000 kPa) Surface area (m ² / g) 11.0

More specifically, the manganese ore that exists as a natural substance has various types such as pyrolusite, psilomelane, maganite, braunite, and hausmannite. Although present, the natural manganese ore used in the present invention is pyrrolusite having MnO ₂ as a main component of manganese oxide, and the lattice form of MnO _{2 has} a kind of α-, β-, γ-, δ-, but XRD analysis of the manganese ore sample of the invention revealed that β-MnO _2, whose main peaks were 28.7 °, 37.3 °, and 42.7 ° (2θ), was distinguished from other lattice forms of other MnO ₂ and its reactivity and produced metal. Sulfide forms are different.

For example, the manganese ore mentioned in Japanese Patent Application Laid-Open No. 8-155300 has peaks with an X-ray diffraction plane spacing of 2.15 ± 0.05 Hz, 2.39 ± 0.05 Hz, 3.11 ± 0.05 Hz. With α-MnO ₂ , the main reaction temperature ranges from 90 to 150 ° C., and sulfur oxides are removed in the form of ammonium sulfate rather than directly adsorbed on manganese ore. However, the natural manganese ore used in the present invention is pyrrolusite having β-MnO ₂ as a main component, and the main reaction temperature ranges from 300 to 500 ° C., and sulfur oxides are removed by direct sulfidation adsorption, depending on the form of manganese ore. It can be seen that the removal reaction zone and process are different.

In addition, as can be seen from the chemical composition of Table 1, natural manganese of the present invention includes a variety of metal oxides (Mn, Fe, and Mg) that are currently used for the adsorption of sulfur oxides and the reduction of nitrogen oxides It shows that ores can be used as adsorbents and catalysts. In the present invention, in order to use the natural manganese ore in the fluidized bed reactor as an adsorbent of sulfur oxides and a catalyst of nitrogen oxides to obtain a particle size through grinding (for example, average particle size 0.195, 0.359, 0.715, or 1.015mm), 100 It is only necessary to remove moisture attached to the surface by maintaining a dry state of more than ℃. This particle size is not affected by any particle size and distribution as long as fluidization is possible.

After the natural manganese ore was injected into the fluidized bed through the particle feeder, the filling amount in the fluidized bed was constant, and then sulfur oxides, nitrogen oxides, ammonia, and air mixed gas were introduced into the reactor to observe the conversion rate according to the temperature. In the existing denitrification catalysts, sulfur oxides poisoned the catalysts and the conversion rate decreased drastically, whereas the denitrification catalysts showed an excellent effect on the simultaneous removal of sulfur oxides and nitrogen oxides in the temperature range between 300 and 500 ° C. This wide range of working temperatures indicates that it is possible to apply variously to the conditions of each process to satisfy the emission temperature of the exhaust gas and the regulation of air pollutants. In addition, when using the catalyst of the present invention it can be adjusted in the range of 0.7 to 1.2 ammonia concentration ratio to nitrogen oxides. If the concentration ratio is less than 0.7, the efficiency is too low. If the concentration ratio exceeds 1.2, the unreacted ammonia is discharged and the amount of the catalyst is increased, which is uneconomical. In the present invention, the unreacted ammonia emission was 5 ppm or less at the concentration ratio of 1.05 times or less. .

In addition, according to the present invention, since the nitrogen oxides are first removed by the metal sulfide adsorbed and reacted with the sulfur oxide, the sulfided natural manganese ore discharged after the reaction may be regenerated and reused by thermal regeneration under a reducing gas such as hydrogen or carbon monoxide. .

Hereinafter, the present invention will be described in more detail with reference to the following examples, but the scope of the present invention is not limited to the following examples.

Example 1

In order to investigate the simultaneous removal of sulfur oxides and nitrogen oxides from natural manganese ores, the selective catalytic reduction capacity of nitrogen oxides according to the presence or absence of sulfur oxides in the exhaust gas was measured in a fixed bed reactor. And the result is shown in FIG.

In this embodiment, the natural manganese ore was pulverized to 40-50 mesh (average particle size 0.359mm), and the experiment was performed by filling about 3cc in a fixed bed reactor having an inner diameter of 8mm. The supplied sulfur oxide concentration was 1920ppm, the nitrogen oxide concentration was 480ppm, the ammonia concentration was 1.04 times that of nitrogen oxide and 3% oxygen, and the space velocity (GHSV) in the catalyst layer was 20,000h- ¹ .

As can be seen from FIG. 1, the conversion rate of nitrogen oxide is low at about 70% at 400 ° C. and about 12% at 500 ° C. in the portion (SCR region) where no sulfur oxide is injected, but the sulfur oxide is injected to the natural manganese ore. When manganese sulfide was formed on the surface, the conversion rate of nitrogen oxides increased rapidly, increasing to about 85% at 400 ° C and about 50% at 500 ° C. This indicates that the natural manganese ore used in the present invention is capable of reducing nitrogen oxides by the sulfur oxides produced by the sulfidation reaction simultaneously with the removal of the sulfur oxides. In the case of sulfur oxides, the adsorption capacity decreases rapidly with increasing time, so continuous supply of unreacted natural manganese ore can achieve the desired removal effect of sulfur oxides. The natural manganese ores are complementary to each other, which means that when used in a continuous reactor, sulfur oxides and nitrogen oxides can be removed simultaneously in one reactor with high efficiency.

Example 2

Based on the results of Example 1, a continuous reactor was prepared, and the following experiment was performed. The results of simultaneous removal of sulfur oxides and nitrogen oxides in a continuous fluidized bed reactor using natural manganese ore are shown in FIG. 2.

In this embodiment, the manganese ore was injected from the top of the fluidized bed and discharged from the bottom of the bed so that the aspect ratio 1 and the residence time of the natural manganese ore were maintained for 11 minutes in a fluidized bed reactor having an inner diameter of 4 cm and a height of 80 cm. The supplied sulfur oxide concentration was 1965 ppm, the nitrogen oxide concentration was 452 ppm, and the ammonia feed ratio was 1.04 times, which was mixed with air to maintain a constant flow rate of 0.204 m / sec and supplied into the fluidized bed.

As can be seen from Figure 2, as the metal sulfide is formed, the reducing ability of the nitrogen oxides greatly increases. When sulfur oxide was not adsorbed on the surface of the initial natural manganese ore, the conversion rate of nitrogen oxide was about 52% at 400 ℃. In the case of sulfur oxides, the removal efficiency was about 88%. In addition, the effects of temperature on the simultaneous removal of sulfur oxides and nitrogen oxides showed that the oxides of nitrogen oxides increased with increasing temperature, resulting in the highest conversion rate of 94% at 350 ° C, which is relatively low. In the case of removal by the chemisorption reaction, the conversion rate increased with increasing temperature, and the highest conversion rate of about 92% was obtained at 450 ° C.

Example 3

In order to maintain the optimum reaction conditions for each process during the actual process operation, the residence time of the natural manganese ore introduced into the fluidized bed reactor under the same conditions as in Example 2 was changed to 11, 24 and 32 minutes. Same as FIG. 3.

The effect of residence time was almost unaffected by the fast reaction time in the case of nitrogen oxides, but the sulfur oxides were removed by the surface adsorption reaction. Best.

Therefore, as shown in Examples 2 and 3, the optimum operating conditions can be selected according to the exhaust gas treatment conditions of the process of operating the influence of temperature and residence time.

The natural manganese ore according to the present invention serves as an adsorbent by sulfidation reaction for sulfur oxides, and in the removal of nitrogen oxides, the sulfurized natural manganese ore plays a role of catalyst along with ammonia, a reducing agent, at a temperature of 300 to 500 ° C. Nitrogen oxides and sulfur oxides can be removed simultaneously in one reactor in the range and residence time between 10 and 40 minutes.

Claims (3)

In the method for removing sulfur oxides and nitrogen oxides contained in the flue gas, natural manganese having β-MnO ₂ having (2θ) whose main X-ray diffraction peaks are 28.7 °, 37.3 °, and 42.7 ° (2θ) is the main crystal structure. Treating the flue gas at 300 ~ 500 ℃ in a continuous fluidized bed reactor using ore as a catalyst, sulfur oxide is adsorbed on the natural manganese ore catalyst and sulfided at the same time, and the sulfided natural manganese ore is a selective reduction catalyst. A method for removing sulfur oxides and nitrogen oxides using natural manganese ores, characterized in that the removal of nitrogen oxides using ammonia as a reducing agent. The method of claim 1, wherein the residence time of the natural manganese ore in the reactor is 10 to 40 minutes. The method for removing sulfur oxides and nitrogen oxides using natural manganese ores according to claim 1, wherein the concentration ratio of ammonia to nitrogen oxides is 0.7 to 1.2.