JPS58247A - Regenerating method for denitrating catalyst - Google Patents

Abstract

PURPOSE:To regenerate poisoned catalysts virtually perfectly with simple operations by washing the cataslysts poisoned by denitration with inorg. acids and immersing these in a tungsten-contg. soln., then drying and calcining the same. CONSTITUTION:In the stage of regenerating denitrifying catalysts contg. vanadium and titania used in a catalytic reduction process, first the poisoned catalysts are washed with inorg. acid solns. of hydrochloric acid, sulfuric acid, etc., then they are immersed in a tungsten-contg. soln., to allow 0.01-10kg tungsten compd. in terms of WO2 in 1m<3> apparent volume of the catalyst to deposit thereon, after-which they are dried and are further calcined at 400-650 deg.C. Their denitration rate and SO2 conversion rate are restored virtually perfectly by such simple operations.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a poisoned denitrification catalyst containing at least vanadium and titania, which is used for catalytic reduction removal of nitrogen oxides in the exhaust gas discharged from each pole combustion device in the presence of ammonia. It concerns the regeneration method.

Nitrogen oxides contained in the gas emitted from various combustion devices are one of the causes of air pollution, and various methods have been proposed to remove them. by contacting the exhaust gas with a catalyst in the presence of
Many catalytic reduction methods for decomposing nitrogen oxides into nitrogen and water have been put into practical use.

As the denitrification catalyst used in this catalytic reduction method, catalysts containing vanadium and titania are most often used because they have excellent activity and long life. however,
These denitrification catalysts containing vanadium and titania also cause the accumulation of dust contained in exhaust gas and the SO□ gas contained in exhaust gas due to the denitration catalyst due to long-term use.
The reaction with ammonia gas based on the conversion to 3 produces ammonium sulfate, and its il! lIl! Due to so-called catalyst poisoning, such as ammonium depositing mt11 and ζ layers on the denitrification catalyst, it was inevitable that the denitrification properties would be greatly reduced. Conventionally, as a method for regenerating such a poisoned denitrification catalyst, for example, after washing with water α~SOO
℃ firing method (Japanese Patent Application Laid-open No. 5 T-Toburi No. 6), method of washing with water or reheating TS acid solution or spraying with steam (Japanese Patent Application Laid-open No. 5 Co., Ltd. A method (Japanese Patent Application Laid-open No. 39-102911) has been proposed and implemented, in which a part of the vanadium component is extracted by contacting the material, and then impregnated and supported with a vanadium compound and fired. With these cleaning treatment methods, dust adhering to the catalyst and water-soluble substances that cause catalyst deterioration can be removed to a certain extent, so the effect of restoring the catalyst performance can be recognized to a considerable extent.

However, it was not possible to sufficiently reduce and recover the S02 conversion rate that increased due to catalyst poisoning, and this method was not necessarily a satisfactory method for regenerating the denitrification catalyst.

The denitrification catalyst regeneration method of the present invention has been developed to solve these conventional drawbacks, and is a catalyst regeneration method that is particularly excellent in recovering the characteristics of catalyst performance and SO2 conversion rate. At least phosphorus oxide is removed by catalytic reduction in the presence of ammonia.

In a method for regenerating a denitrification catalyst containing vanadium and titania, the poisoned catalyst is treated with water or without 4iI111! After washing with a solution, it is immersed in a solution containing tungsten, and the apparent appearance of the catalyst is 0.0/79-10 in terms of WO3 per body@im3.
This is a method for regenerating a denitrification catalyst, in which kg of a tungsten compound is impregnated and supported on the catalyst, and then dried and then calcined at a temperature of 00-≦SO''C.

The present invention will be explained in more detail below.

Vanadium-titania thread catalyst, vanadium component, stainless steel catalyst, or molybdenum, iron, #l, chromium, nickel among these components.

The so-called poisoned denitrification catalyst, which is made of a denitrification catalyst containing at least vanadium and titania and contains l or more of catalytically active substances such as cobalt and cerium, and whose denitrification performance has deteriorated due to long-term use, is washed with water at room temperature to up to ℃ or hot water. , or hydrochloric acid or sulfuric acid at a concentration of 10% or less! ! for example, by ultrasonic cleaning or the like in an inorganic acid solution such as This cleaning removes the dust that has entered the catalyst surface and inside, as well as water-soluble poisonous substances that have reacted with alkali metal compounds and catalyst components.
I4* will be done. In this case, the time required for cleaning depends on conditions such as the adhesion status of dust F and poisonous substances, the temperature of the cleaning liquid, the concentration of inorganic acid, and stirring, but it is usually about 10 minutes to 3 hours. The catalyst from which dust and poisonous substances have been removed by this washing is dried, and the catalyst is immersed in a solution containing tungsten.
olJ19~lokg, preferably 0. / to 9~3I1
After impregnating and supporting the tungsten compound of No. 9 on the catalyst, w
oo℃~tso'c, preferably joo℃~100℃
This is a catalyst regeneration method that involves firing the catalyst. As the solution containing tungsten used for impregnation, it is preferable to use a solution obtained by dissolving ammonium paratungstate in an im solvent such as monoethanolamine or methanolamine, or a commercially available aqueous tungstic acid solution.

In addition, as a method for impregnating and supporting WO3, the concentration of WO3 may be reduced to #1 and impregnated at once depending on the target support lid, or it may be repeatedly impregnated and supported using a 111 degree solution. However, the supported amount of WO3 is 0.0/le
If it is less than 10 Vm3, the recovery effect on the denitrification rate and 802 conversion rate is unfavorable, and if it is more than 10 Vm3, neither the denitrification rate nor the SO2 conversion rate can be expected to improve much, so it is not economically meaningful. This is because there is no.

Furthermore, the reason why the firing temperature after supporting is set to 100"C to tso"c is because the supported tungsten compound cannot completely become WO3 below tioo"c, and 6jO
This is because when the temperature exceeds .degree. C., the vanadium component contained in the original catalyst melts, leading to a decrease in the specific surface area of the catalyst, resulting in a decrease in the denitrification rate and an increase in the So and conversion rate. The denitrification catalyst containing at least vanadium and titania that can be regenerated in the present invention may be a so-called coated catalyst in which an active substance is supported on a base material such as mullite or cordierite, or a so-called solid catalyst in which an active substance is formed as a catalyst. The shape of the catalyst may be honeycomb, pellet, pipe, etc.

Next, the present invention will be specifically explained using examples.

Catalyst component: Tiv2o, z, o%, TiO, 97S
tp la'j honeycomb catalyst (hereinafter referred to as catalyst) and VQO.

/, 0%, wo, 7.0%, Tie, vx%6
Honeycomb A catalyst (hereinafter referred to as catalyst B) % V, O, /
, 0%, 100354%, T10□riJ, 1%, Henicam catalyst (hereinafter referred to as catalyst 0), v, o, J
,o%,Fe,O,3,0%,OuOko,jlTiO□
deλ, 5%, mu catalyst (hereinafter referred to as catalyst), V2O5/, 0%, Woo3J, 0 regret, wo,
When used for 12,000 hours in boiler exhaust gas under the conditions shown in Table 1 using a non-taming catalyst (hereinafter referred to as catalyst E) consisting of z, o, TiO□qi, and o%, the temperature reached 310°C.
As shown in Table 2, the denitrification rate and S02 conversion rate decreased compared to the initial stage.

Table 1 Table 2 These poisoned catalysts with degraded performance are shown in Table 3. Under the conditions shown in Table 3, the apparent appearance of the catalysts is reduced by ultrasonic cleaning in three times the volume of water or an aqueous solution of inorganic acid. After washing, the catalyst was immersed in a solution of ammonium halatungstate in monoethanolamine, impregnated with a cap as shown in Table 3 in terms of WO2, and then dried under the conditions listed in Table 3. A regenerated catalyst Todoroki/-An was obtained. Then, the denitrification rate and 802 conversion rate of these regenerated catalysts were comparatively measured under the exhaust gas conditions shown in Table 1. The results are as shown in Table 3. For comparison, those outside the scope of the present invention are listed as comparative examples, and those made using conventional methods are listed as conventional examples in Table 3.

As is clear from the results in Table 3, according to the catalyst regeneration method of the present invention, both the denitrification rate and the 802 conversion rate can be completely restored to their initial characteristics. Both the denitrification rate and the SO□ conversion rate could not be recovered to their initial values.

As described above, the present invention improves the denitrification rate by impregnating and supporting a predetermined amount of tungsten after cleaning the poisoned denitrification catalyst containing vanadium and titania.
This is a regeneration method that can completely restore the conversion rate to its initial value, and is currently used to regenerate denitrification catalysts containing vanadium and titania, which are widely used for removing nitrogen oxidation from boiler exhaust gas at thermal power plants. extremely useful as a law;
This is an industrially useful method for regenerating poisoned denitrification catalysts.

Claims (1)

[Claims] Li1 - At least vanadium for removing nitrogen oxides in gas by catalytic reduction in the presence of ammonia. In a method for regenerating a denitrification catalyst containing titania, the poisoned catalyst is washed with water or an inorganic acid solution and then soaked in a solution containing tungsten, so that the apparent appearance of the catalyst is 0.0/m3 in terms of WO2/volume tm3. A method for regenerating a denitrification catalyst, which comprises supporting 9 to 10 kg of a tungsten compound on the catalyst, drying it, and then firing it at 4100N≦SO°C.