Catalyst for removing ammonia escape from denitration tail gas and preparation method thereof

Abstract

The application discloses a catalyst applied to removal of ammonia escape of denitration tail gas and a preparation method of the catalyst, and steps of the preparation method of the catalyst are as follows: S1: respectively dissolving a cobalt salt, a cerium salt, an iron salt and a manganese salt in deionized water; S2: uniformly mixing the cobalt salt solution and the cerium salt solution, then slowly dropping into an ammonia water solution, then sequentially adding the iron salt solution and the manganese salt solution, uniformly mixing, and finally continuously slowly dropping into the ammonia water solution and precipitating; S3: vacuum filtering, washing, drying and calcining the precipitate of S2, so that the catalyst is obtained. The application realizes high removal rate of ammonia gas under low-temperature conditions, and has practical significance for reducing NH3 escape in tail gas of a denitration system of a non-power industry.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of catalyst technology, in particular to a catalyst for removing ammonia escape of denitration tail gas and a preparation method thereof. BACKGROUND

[0002] The ultra-low emission of power, coking, steel and other industries has also been mentioned at a new height, especially the ultra-clean emission of nitrogen oxides (NO x ). At present, SCR technology is the main effective technical means for treating NO x , and its reaction principle is that the reducing agent ammonia (NH3) reacts with NO x in flue gas to generate non-toxic nitrogen (N2) and water (H2O) under the action of a catalyst. However, in the actual operation process, due to unstable working conditions, uneven gas flow distribution and other factors, excess reducing agent NH3 is discharged. With the introduction of national and local air standards, ammonia escape has also been included in the agenda. The treatment of nitrogen oxides in the power industry belongs to the front denitration method, and after the wet or semi-dry desulfurization and dust removal process at the back end, ammonia escape can be controlled to a certain value. However, for non-power industries, due to the characteristics of low temperature, complex composition and other characteristics of flue gas, the post-denitration process route is often adopted, and the flue gas at the outlet of the denitration reactor is directly discharged into the chimney. NH3 escape is more obvious, and through optimization of flow field simulation, upgrading of SCR catalyst formula, improvement of catalytic performance and reasonable operation management, the concentration of NH3 escape can be reduced, but it is still difficult to meet the national and local air emission standards. At the same time, the ammonia oxidation applied in the market is mainly for exhaust treatment systems of diesel vehicles, and the catalyst designed for the system operates at a high temperature (300-500℃), while the denitration temperature of non-power industries is relatively low, generally below 200℃. Although there are ammonia collection processes applied in non-power industries, the operating temperature is still relatively high (above 250℃), and the technologies of the two cannot better solve the amount of NH3 escape in the denitration tail gas system.

[0003] Therefore, how to develop a catalyst for removing ammonia escape of denitration tail gas is a problem that those skilled in the art need to solve. SUMMARY

[0004] Based on the technical problems existing in the background technology, the present application provides a catalyst for removing ammonia escape of denitration tail gas and a preparation method thereof, which realizes high removal rate of ammonia at low temperature and has important practical significance for reducing NH3 escape in the tail gas of denitration systems in non-power industries.

[0005] The catalyst for removing ammonia escape of denitration tail gas provided by the present application is a perovskite type transition metal catalyst, and its structural general formula is CeCo 1-x-y Fe x Mny O3;

[0006] Wherein: 0.1<=x<=0.3, 0.2<=y<=0.5.

[0007] The preparation method of the catalyst for removing ammonia escape of denitration tail gas is as follows:

[0008] S1: respectively dissolve cobalt salt, cerium salt, iron salt and manganese salt in deionized water;

[0009] S2: mix the cobalt salt solution and the cerium salt solution, then slowly drop the ammonia solution, then sequentially add the iron salt solution and the manganese salt solution, mix, and finally continue to slowly drop the ammonia solution and precipitate;

[0010] S3: vacuum filter, wash, dry and calcine the precipitate of S2, to obtain the catalyst.

[0011] Preferably, the molar ratio of the cerium salt, the cobalt salt, the iron salt and the manganese salt is 1:1-x-y:x:y, wherein: 0.1<=x<=0.3, 0.2<=y<=0.5.

[0012] Preferably, the temperature for drying in S3 is 80-120 DEG C, and the time is 10-14h.

[0013] Preferably, the temperature for calcining in S3 is 400-550 DEG C, the heating rate is 2-5 DEG C / min, and the calcining time is 4-8h.

[0014] Mechanism

[0015] The cerium in the catalyst has certain oxygen storage and release functions, the cerium-doped cobalt-iron-manganese composite oxide can change the electronic properties and dispersity of Mn in the catalyst, widen the active temperature window of the catalyst, enhance the sulfur resistance and water resistance of Fe in the catalyst, and further stabilize the solid solution effect of Co in the catalyst. At the same time, a certain amount of sulfur dioxide and excess ammonia gas remains in the denitration tail gas, which will inevitably form ammonium bisulfate substances adhering to the surface of the catalyst, and inhibit the deamination reaction, and the introduction of iron generates a ferrous ammonium sulfate substance that can be decomposed at low temperature, which can better protect the catalytic action of manganese oxide. The cerium-doped cobalt-manganese-iron composite oxide promotes the synergistic effect of the stabilizer and the active agent.

[0016] Beneficial technical effects

[0017] The catalyst for treating ammonia escape in denitration system tail gas is prepared by selecting and adjusting the addition ratio of transition metals, and can realize 0-30mg / Nm 3100ppm of ammonia removal of SO2 and 0-30vol.% of water vapor, and at 100-140℃, 30000-100000h - The removal rate of ammonia is up to more than 90% under the condition of high space velocity, and the catalyst is suitable for purification treatment of flue gas from fixed sources such as steel, coking and cement. At the same time, the high-efficiency catalysis of high space velocity is better matched with the existing denitration device, the investment cost is low, and the effect is reliable, stable and up to standard. DETAILED DESCRIPTION

[0018] The application will be further described below in combination with specific embodiments.

[0019] Embodiment 1

[0020] The preparation method of the catalyst for removing ammonia escape of denitration tail gas provided by the application is as follows:

[0021] S1: respectively dissolve cobalt salt, cerium salt, iron salt and manganese salt in deionized water;

[0022] S2: mix the cobalt salt solution and the cerium salt solution, then slowly drop into the ammonia water solution, then sequentially add the iron salt solution and the manganese salt solution, mix, and finally continue to slowly drop into the ammonia water solution and precipitate;

[0023] S3: vacuum filter, wash, dry and calcine the precipitate of S2, and the catalyst is obtained.

[0024] The molar ratio of the cobalt salt, the cerium salt, the iron salt and the manganese salt is 1:0.4:0.4:0.2.

[0025] The temperature of drying in S3 is 100℃, and the time is 12h.

[0026] The temperature of calcining in S3 is 475℃, the heating rate is 4℃ / min, and the calcining time is 6h.

[0027] Embodiment 2

[0028] The preparation method of the catalyst for removing ammonia escape of denitration tail gas provided by the application is as follows:

[0029] S1: respectively dissolve cobalt salt, cerium salt, iron salt and manganese salt in deionized water;

[0030] S2: mix the cobalt salt solution and the cerium salt solution, then slowly drop into the ammonia water solution, then sequentially add the iron salt solution and the manganese salt solution, mix, and finally continue to slowly drop into the ammonia water solution and precipitate;

[0031] S3: vacuum filter, wash, dry and calcine the precipitate of S2, and the catalyst is obtained.

[0032] The molar ratio of the cobalt salt, the cerium salt, the iron salt and the manganese salt is 1:0.7:0.2:0.1.

[0033] The temperature for drying in S3 is 80℃, and the time is 10h.

[0034] The temperature for calcining in S3 is 400℃, the heating rate is 2℃ / min, and the calcining time is 4h.

[0035] Example 3

[0036] The preparation method of the catalyst for removing ammonia escape of denitration tail gas provided by the application is as follows:

[0037] S1: respectively dissolve the cobalt salt, the cerium salt, the iron salt and the manganese salt in deionized water;

[0038] S2: mix the cobalt salt solution and the cerium salt solution, then slowly drop the ammonia water solution, then sequentially add the iron salt solution and the manganese salt solution, mix, and finally continue to slowly drop the ammonia water solution and precipitate;

[0039] S3: vacuum filter, wash, dry and calcine the precipitate of S2, and the catalyst is obtained.

[0040] The molar ratio of the cobalt salt, the cerium salt, the iron salt and the manganese salt is 1:0.2:0.5:0.3.

[0041] The temperature for drying in S3 is 120℃, and the time is 14h.

[0042] The temperature for calcining in S3 is 550℃, the heating rate is 5℃ / min, and the calcining time is 8h.

[0043] The performance of the catalysts prepared in Examples 1-3 in treating ammonia escape in denitration system tail gas is tested, and the test results are shown in Table 1. Among them:

[0044] The test method of catalyst activity is: 100ppm of NH3, 5% of O2, 95.5% of N2, the space velocity is 100000h - , and the reaction temperature is 100-220℃.

[0045] The test conditions of the sulfur resistance and water resistance of the catalyst are: 100ppm of NH3, 5% of O2, 50ppm of SO2, 20% (volume ratio) of H2O, N2 as the balance gas, the space velocity is 100000h - , and the reaction temperature is 110℃.

[0046] Table 1

[0047]

[0048] As can be seen from the experimental results in Table 1, the catalyst prepared by this invention has high ammonia catalytic activity and good sulfur and water resistance. It still has high catalytic activity under the conditions of 50 ppm SO2 and 20% (volume ratio) H2O.

Claims

1. A method for preparing a catalyst used to remove ammonia slip from denitrification tail gas, characterized in that, The catalyst is a perovskite-type transition metal catalyst with the general structural formula CeCo. 1-x-y Fe x Mn y O3; Where: 0.1≤x≤0.3, 0.2≤y≤0.5; Catalyst at 100-140℃ for 30,000-100,000 hours -1 Under the given air velocity conditions, the ammonia removal rate reaches over 90%. The steps for preparing the catalyst are as follows: S1: Dissolve cobalt salt, cerium salt, iron salt and manganese salt in deionized water respectively; S2: Mix the cobalt salt solution and cerium salt solution, then slowly add the ammonia solution dropwise, then add the iron salt solution and manganese salt solution in sequence, mix well, and finally continue to slowly add the ammonia solution dropwise to precipitate; S3: The precipitate of S2 is vacuum filtered, washed, dried and calcined to obtain the catalyst; The calcination temperature in S3 is 400-550℃, the heating rate is 2-5℃ / min, and the calcination time is 4-8h.

2. The method for preparing the catalyst for removing ammonia slip from denitrification tail gas according to claim 1, characterized in that, The drying temperature in S3 is 80-120℃, and the time is 10-14h.

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