JPS5817843A - Activating method for catalyst - Google Patents

Abstract

PURPOSE:To replenish the portions of active components eluted during rinsing and recover denitration performance up to the performance of fresh catalysts in the stage of activating poisoned catalysts by rinsing by flowing an aq. soln. contg. catalytic components in the final of a rinsing stage. CONSTITUTION:In a denitrating device 6, etc. for waste gases of combustion from boilers, rinsing water is introduced through nozzles 2 for washing to elute the poisoned components contained in the catalysts when the catalysts in a reactor 1 are poisoned and their activity degrades. In the final of said rinsing stage, an active component soln. 3 is sprayed over the entire surface of the catalysts through the nozzles 2 to replenish the portions of the active components eluted by rinsing. The excess soln. 4 is collected in a recovering vessel 5. The activity of the catalysts is activated inexpensively in a short time by said method.

Description

[Detailed Description of the Invention] An improved method of activating a catalyst by washing it with water while the catalyst is still in a ready-to-use state when the performance is degraded due to the accumulation of poisonous substances in the device and the performance is restored by washing with water. Regarding
A denitrification reaction that passes exhaust gas from burning coal or oil through a catalyst to reduce and detoxify nitrogen oxides in the exhaust gas.
Alkali or alkaline earth metals (potassium, sodium, magnesium, etc.) contained in dust in combustion exhaust gas accumulate in various catalysts used in reactions that oxidize and burn carbon monoxide or hydrocarbons, resulting in decreased performance. This is a particularly effective method in cases where

Alkali metals such as potassium and sodium are poisonous substances that inhibit catalytic active sites in catalytic reactions targeting combustion exhaust gas, such as denitrification catalysts and combustion catalysts, so it is desirable to reduce their content as much as possible. Unlike catalysts used in synthesis reactions, the main purpose of catalysts for exhaust gas treatment is to improve the environment, and there is no consideration given to pre-treating the exhaust gas to protect catalyst activity and lifespan.
In recent years, due to worsening fuel conditions, dust has increasingly become a source of exhaust gas that has an adverse effect on catalysts due to its amount and composition, and the catalysts used there are required to be resistant to dust poisoning.

The present inventors have also developed a denitrification catalyst that is optimal for reducing and removing nitrogen oxides contained in the above exhaust gas with ammonia,
By changing the catalyst composition, shape, and manufacturing method to suit each exhaust gas source, we provide highly active and long-lasting denitrification equipment, which is already successfully used in many practical applications in boilers of thermal power plants and various chemical plants. It is in operation.

However, with clean gas that does not contain SOx, there is no need to worry about SOx resistance or dust blockage resistance, so AI! 20. Even carriers with insufficient SOX resistance such as A/
203 v2o5. WO5* ii'e203゜M
A catalyst containing active ingredients such as o Os is used, and since there is no concern about dust clogging, catalysts shaped into granules, cylinders, solids, etc. are used in a fixed bed.

There is also almost no dust in the exhaust gas, and it is no exaggeration to say that there is no deterioration in performance due to dust.

On the other hand, in the case of dirty gas containing dust and SOx, such as heavy oil-fired boilers and coal-fired boilers, the SOx resistance, dust toxicity resistance, dust clogging resistance, dust abrasion resistance, etc.
It is necessary to select the optimal catalyst specifications in consideration of TlO
2 as a carrier has sufficient SOx resistance,
T z O2 v2o5゜WO3, Fe2O2, MoO
Catalysts with combinations of active ingredients such as 3 have been used. In addition, as catalyst shapes that do not become clogged with dust, the above-mentioned method of using catalysts shaped like granules, cylinders, solids, etc. in a moving bed, and using catalyst structures such as plates, pipes, honeycomb shapes, etc. as fixed beds. Methods of passing exhaust gas in parallel flow have been compared and studied, and honeycomb catalysts are now mainstream because they are economical and easy to maintain.

A highly hard honeycomb catalyst has also been developed for denitrification reactions on the high-dust side of coal-fired boilers, and there are virtually no problems in practical use.

However, the only way to prevent dust components from entering the catalyst and reducing catalyst performance is to soften the effect as much as possible by creating a catalyst composition that makes it difficult for dust to enter the catalyst. Potassium (K) and sodium (N
a) It is important to select active ingredients that are resistant to alkali or alkaline earth metals such as magnesium (Mg);
The present inventors have also discovered optimal catalyst compositions compatible with various gas sources. The Na and Mg contents of heavy oil and coal vary greatly depending on where they are extracted, and the higher the metal content, the more alkali duct resistance is required of the catalyst. However, since most of these metals exist in the form of sulfates in exhaust gas, they are soluble in water, and they may become wet with water with dust attached to the catalyst surface, or they may be exposed to boiler evaporator pipes or economizer water supply pipes. If the catalyst is wetted by dust-laden steam or water in the furnace due to a breakage accident, poisonous substances such as Na and Mg will rapidly increase inside the catalyst.
There is a possibility that the boiler cannot be operated due to unexpected performance deterioration.

If the denitrification equipment no longer performs as expected due to such an emergency accident, in the worst case scenario, the boiler may have to be shut down, so we provide a method to restore performance in a short period of time. There is a need.

As mentioned above, it is known that if dust mainly composed of alkali or alkaline earth metals such as Ka and Mg accumulates inside the catalyst, it is sufficient to take advantage of its water solubility and wash it thoroughly with water. . However, this is a treatment method that takes the catalyst out of the denitrification equipment and then removes it from the pack that holds multiple catalysts together.In commercial boilers where large quantities of catalysts are used, they can be processed in a short period of time. It can be said that the method of activating by washing with water is completely impractical. In other words, stopping the boiler for a long period of time only to restore catalyst performance in an emergency is not allowed due to its mission as an exhaust gas treatment catalyst, as mentioned above. No.

Based on this idea, the present inventors conducted a stationary reaction using a water washing nozzle as a method to recover the catalyst performance by water washing treatment in the shortest possible time with a large amount of catalyst packed in an actual device. We have previously proposed a method in which poisoning components are eluted and the catalyst performance is restored by installing the water washing nozzle at the gas inlet in the bed and at the gas inlet or outlet in the horizontal reaction bed to wash the catalyst. However, the present invention relates to an improved method of this method.

As mentioned above, the performance of catalysts poisoned by alkali or alkaline earth metal components in exhaust gas dust can be restored by washing with water, but in our tests, the alkali or alkaline earth metal components were completely removed from the catalyst. Despite being eluted, the performance often did not return to its fresh state. In order to elucidate this phenomenon, the present inventors investigated the degree of recovery by water washing of all physical properties that affect performance, including specific surface area, pore volume, and changes in catalyst components. Partly eluted,
It was concluded that the main cause was a decrease in the concentration. The amount of eluted water increases as the amount of water washing increases, so if the catalyst is heavily poisoned by alkali or alkaline earth metals, increasing the number of water washings will worsen the performance recovery. Since the solubility of the catalyst component is much lower than that of alkali or alkaline earth metals, the negative effect of leaching is smaller than the performance recovery effect of removing the poisonous component. As a method to restore the performance of a fresh catalyst after washing with water still filled in the equipment, we have discovered and proposed here a method of replenishing the active ingredient eluted during washing at the end of washing and activating the catalyst. It is something.

That is, the present invention is a method for restoring the performance of a catalyst by washing it with water while the catalyst is still packed in an apparatus when its performance deteriorates, in which an aqueous solution containing a catalytically active component that is eluted during washing is used at the end of the washing step. The present invention relates to a method for activating a catalyst characterized by the following.

The present invention is not limited only to denitrification catalysts, but also applies to oxidation catalysts such as combustion catalysts,
It goes without saying that it is also applicable to desulfurization methods that use adsorbents ().

The present invention will be specifically described below.

FIG. 1 shows an example of application to a denitrification device for boiler combustion exhaust gas. During normal operation, the combustion exhaust gas 8 of the boiler 7 is introduced into the denitrification device 6, and nitrogen oxides in the exhaust gas and ammonia gas 14 supplied as a reducing agent react within the denitrification catalyst layer 1 and are harmless. The denitrified exhaust gas 9 is passed through the downstream air heater 10 for refueling, and then passed further downstream. The catalyst layer is washed with water by installing a cleaning nozzle 2 facing the gas passage surface of the reaction layer 1 and introducing cleaning water 3 from the outside to elute poisonous components contained in the catalyst and clean it. The waste water is collected in an exhaust treatment tank 5 as waste water 4. Once the water washing is completed, the next step is to replenish the eluted active ingredient (ii). This method is no different from the washing procedure, as the washing water is simply an active ingredient solution.

That is, the active solution 3 is sprayed over the entire catalyst through the nozzle 2, and the excess solution 4 is collected in the recovery tank 5. If the active solution in the recovery tank 5 has been thoroughly washed with water, there will be no alkali metal components mixed in, so it can be recycled.

However, if this active ingredient is sprayed on the catalyst immediately after washing, the amount of water absorbed by the catalyst will have decreased considerably, so if possible, drain the remaining water from the catalyst and dry the catalyst to reduce the amount of water absorbed. After increasing the concentration, it is desirable to proceed to the spraying operation of the active ingredient. The concentration of the solution to be sprayed must be determined by the amount of elution of the active ingredient and the amount of water absorbed by the catalyst, but the amount of elution can be easily estimated from its solubility as long as the amount of water used and the liquid temperature are known, and the amount of water absorbed can be determined by determining the amount of water absorbed by the remaining water. Since it can be determined from the amount of water, it is easy to change the concentration of the solution depending on the washing conditions. As in the case of normal catalyst preparation, compounds with high solubility such as nitrates and sulfates are used as raw materials for the active substance, and if they are sprayed on the catalyst as an aqueous solution, they will be rapidly converted into oxides depending on the gas temperature of the denitrification atmosphere. obtain.

As a method for drying the catalyst, for example, 1) the ventilation blower 13 is driven, air 11, 12 is passed through a boiler, and the air is supplied to the catalyst layer 1.

As described above, the present invention recovers the performance to the initial performance in a short period of time by re-supporting the active ingredient eluted after washing with water while the catalyst is still packed in the device when the performance of the catalyst deteriorates. There is no need for the conventional method of taking the catalyst out of the denitrification equipment, regenerating it, and refilling the regenerated catalyst, and by adopting the present invention, it can be done in a simple and economical manner in a short period of time. This makes it possible to regenerate the catalyst to its initial performance, making a major contribution to practical use.

Next, the method of the present invention will be explained with reference to examples.

[Example 1] Approximately 1 year in a denitrification equipment for heavy oil-fired boiler exhaust gas.

A TlO2-V205 catalyst with a track record of operation was wetted by spraying water, then dried, and the denitrification performance before and after was compared. As a result, the denitrification performance of the catalyst after wetting and drying was found to be degraded. This is due to the alkali metal component (
As a result of the compositional analysis of the catalyst shown in Table 1, it was found that the catalyst was dissolved and infiltrated into the catalyst. .

Table 1 The wet and dry catalysts 1a to 1d were stacked in four stages as shown in Fig. 2, a full cone spray nozzle 2 was installed on top of the stack, and washing water 5 was poured onto the catalyst at a rate of 55 l/mi.
The catalyst was continuously sprayed with water to wash and elute poisonous components such as alkali metal components contained inside the catalyst. The operation of washing with water was divided into intervals, drying was performed, the denitrification performance was measured, and the subsequent washing with water was repeated. Water washing was carried out for a total of 100 minutes, and although there was a tendency for the performance to decrease slightly after 60 minutes, no further increase could be expected, and the denitrification rate was 4% lower than from the initial stage.

From the solubility of the active ingredient v205 in water and the amount of water used, calculate the amount of v205 eluted per unit amount of catalyst.
To replenish the amount commensurate with this, the water absorption capacity and ■
■The concentration of the os04 solution, which is the raw material for 2o5, was determined and prepared. Add this solution in the same way as for washing with water,
The active solution was sprayed over the entire catalyst layer through a full-cone spray nozzle 2 installed on the stacked catalysts, and a portion of the recovered liquid was recycled and used. Activation conditions are as shown in Table 2. Further, Table 4 shows the results of measuring the denitrification performance under the conditions for measuring the denitrification rate shown in Table 6, and the denitrification performance was completely activated to the initial performance after application of the active solution.

Table 2 Activation conditions Table 3 Denitrification rate measurement conditions [Example 2] T1 using the method in Example 1 with Fe2O as the activator
Table 5 shows the results when applied to the 02-Fe2o3 catalyst, but the method of the present invention was also applicable to a catalyst whose active substance is Fe2O3 poisoned by an alkali metal component.

Table 5 [Example 3] As shown in Fig. 5, the entire catalyst layer 1 was washed with water for 60 minutes using the spray nozzle 2 installed at the top of the denitrification device 6 for the exhaust gas of a stopped heavy oil-fired boiler, and then the catalyst layer was partitioned. , catalyst layer 1-a
vO8 concentration was adjusted with a spray nozzle from the top of ~1d.
04 solution was sprayed over the entire catalyst layer. Drainage or excess solution 4
was put into a wastewater treatment tank or active solution recovery tank 5, and part of the active solution was recycled and used. The catalyst was washed and dried, and after restarting the boiler, the denitrification performance of the catalyst layer section that was only washed with water and the catalyst layer section that was sprayed with an active solution after water washing were compared. Table 6 shows the results.

Table 6 Exhaust gas temperature: 380°C In the above example, the active substance was U2O5°Fe2O.
3.V OSO4+ Fe SO4 as its raw material
Although only the cases described above are described, the active substance and its raw materials are not limited thereto.

[Brief explanation of drawings]

Figure 1 is a flow sheet when the method of the present invention is applied to a boiler combustion exhaust gas denitrification system, Figure 2 is a diagram showing the mode of catalyst washing with water or active solution spraying test, and Figure 3 is a practical denitrification equipment. FIG. 2 is a side view A and a plan view B showing an embodiment in which the effects of the method of the present invention and only water washing as a comparative example are compared. Sub-agents 1) Meiji agent Ryo Hagiwara - Figure 3 (A) (B) J-5

Claims (1)

[Claims] A method for restoring the performance of a catalyst by washing it with water while the catalyst is still packed in an apparatus when its performance deteriorates, characterized in that an aqueous solution containing a catalyst component that is eluted during washing is used at the end of the washing step. Activation method.