JPS6313733B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for activating a catalyst filled in a gas treatment device by washing with water when the performance of the catalyst deteriorates due to accumulation of poisonous substances during use, while the device is still filled with the catalyst and ready for use. It is applied to denitrification reactions in which exhaust gas from burning coal or oil is passed through a catalyst to reduce, render harmless, and remove nitrogen oxides in the exhaust gases, and reactions to oxidize and burn carbon monoxide or hydrocarbons. This is a particularly effective means when alkali metals (potassium, sodium, magnesium, etc.) contained in dust in combustion exhaust gas accumulate on various catalysts and their performance deteriorates. Alkali metals such as potassium and sodium are poisonous substances that inhibit the catalyst 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 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. Due to the deterioration of dust, dust has increasingly become a source of exhaust gas that has an adverse effect on catalysts in terms of dust amount and dust 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, and have adjusted the catalyst composition according to each exhaust gas source.
We offer highly active and long-lasting denitrification equipment with different shapes and manufacturing methods, and many practical equipment are already in smooth operation in boilers at thermal power plants and various chemical plants. In this case, dust like LNG-fired boiler,
With clean gas that does not contain SOx, there is no need to worry about SOx resistance or dust blockage resistance, so resistant gases such as Al ₂ O ₃
Even if the carrier has insufficient SOx properties, there is no practical problem and it is inexpensive, so Al ₂ O ₃ is used with V ₂ O ₅ , WO ₃ ,
Catalysts supporting active components such as Fe ₂ O ₃ and MoO ₃ are used, and there is no concern about dust clogging, so catalysts shaped into granules, cylinders, ellipses, etc. are used in fixed beds. ing. 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, it is resistant to dirty gas containing dust and SOx, such as heavy oil-fired boilers and coal-fired boilers.
It is necessary to select the optimal catalyst specifications by considering SOx resistance, dust toxicity resistance, dust occlusion resistance, dust abrasion resistance, etc., and by using TiO ₂ as a carrier, it is possible to
Because it has sufficient SOx properties, TiO ₂ contains V ₂ O ₅ , WO ₃ ,
Catalysts on which active components such as Fe ₂ O ₃ and MoO ₃ are supported are used. In addition, as catalyst shapes that do not become clogged with dust, there are two methods: using catalysts shaped like particles, cylinders, and ellipsoids as described above in a moving bed, and using catalyst structures such as plates, pipes, and honeycombs as fixed beds. Methods of passing exhaust gas in parallel flow have been compared and studied, and honeycomb catalysts, which are economical and easy to maintain, are currently the mainstream. A highly hard honeycomb catalyst has also been developed for denitrification reactions on the high-dust side of coal-fired boilers, and has 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. It is important to select active ingredients that are resistant to alkali or alkaline earth metals such as potassium (K), sodium (Na), and magnesium (Mg), which have a particularly negative effect on We have discovered the optimal catalyst composition. The K, Na, and Mg contents of heavy oil and coal vary greatly depending on where they are extracted, and the higher the content of these metals, the more alkali dust 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 the catalyst surface may become wet with water with dust attached to it, or damage to boiler evaporator pipes or economizer water supply pipes may occur. If dust-laden steam or water in the furnace wets the catalyst due to an accident, poisonous substances such as K, Na, and Mg will rapidly increase inside the catalyst.
There is a possibility that unexpected performance deterioration may occur and the boiler may not be able to operate. If the denitrification equipment no longer performs as expected due to an emergency accident like this, in the worst case scenario, the boiler may have to be shut down, so it is necessary to recover the performance in a short period of time. need to provide a method. As mentioned above, if dust mainly composed of alkali metals and alkaline earth metals such as K, Na, and Mg accumulates inside the catalyst or activated carbon, it is well known that it is best to take advantage of its water solubility and wash it thoroughly with water. Various inventions related to water washing regeneration methods have been proposed. Additionally, as a means of removing dust accumulated inside a catalyst layer using a honeycomb type catalyst during boiler operation, a high-pressure gas body may be injected through a nozzle from a suit blowing device installed on the gas inlet surface of the catalyst layer. Are known. These conventional methods will be explained with reference to FIG. 1, which is a layout diagram of a denitrification device commonly used at present. The combustion exhaust gas 2 of the boiler 1 passes through the economizer 3 and after removing soot from the combustion exhaust gas in the dust collector 4, or before soot removal, the flue gas is sent to the denitrification reactor 5.
After ammonia 6 is supplied as a reducing agent at the front, the exhaust gas 2 is introduced into the denitrification reactor 5 and brought into contact with the denitrification catalyst 7, converting nitrogen oxides (hereinafter referred to as NOx) in the exhaust gas into harmless N ₂ and water. Let it break down into . At this time, as mentioned above, as the combustion exhaust gas, for example, exhaust gas containing a high concentration of soot and dust from coal-fired combustion, or exhaust gas that targets highly adhesive soot, etc. Dust adheres and accumulates on the gas passage hole or on the catalyst surface that can come into contact with the internal gas, and as the pressure drop increases, the denitrification performance gradually decreases. In order to solve this problem, a soot blowing device 8 is provided at the inlet of the denitrification catalyst layer 7 to remove adhesion and deposits. This device was installed to ensure stable operation over a long period of time, and is used only periodically or when an increase in pressure drop in the catalyst layer is observed. By using this device, adhesion and deposits can be removed and the denitrification performance can be restored temporarily, but it is difficult to remove alkali metals such as potassium and sodium that inhibit the active sites of the denitrification catalyst, especially if they are immersed inside the catalyst. Needless to say, it is difficult to remove poisonous substances. Therefore, even if suit blowing is carried out, it is currently inevitable that the denitrification performance will gradually deteriorate as the operation progresses. Therefore, with the conventional method, a decrease in denitrification performance was observed,
If suit blowing alone does not restore performance, take advantage of the boiler inspection period to extract the catalyst layer outside the denitrification reactor system where the performance has particularly deteriorated and fill it with a new catalyst, or perform heat treatment, water washing, etc. Currently, the regenerated catalyst is refilled based on the regeneration method of There is also a risk of The present invention was made in order to eliminate the drawbacks of the conventional method described above, and when the catalyst performance deteriorates, the catalyst is efficiently activated while the catalyst is still packed in the device, and the catalyst performance is sufficiently improved. Regarding the recovery method, during the operation of a gas treatment device that incorporates a parallel plate catalyst (commonly known as a honeycomb catalyst) having a gas passage with a predetermined cross-sectional shape, that is, during operation or at least before stopping, the external A high-pressure gas is injected into the gas passage through a suit blow nozzle installed opposite to the end face of the gas passage to remove dust that has adhered to and accumulated on the catalyst layer, and then the operation of the apparatus is stopped. Next, the nozzle pipe into which the gas body was introduced is extracted from the system, the suit blow nozzle is replaced with a water washing nozzle, and a certain amount of washing water is injected at a predetermined pressure into the gas passage through the water nozzle to clean the inside of the catalyst. The present invention relates to a method for activating a catalyst, which is characterized by eluting and removing poisonous components that have penetrated and accumulated in a catalyst, thereby restoring catalyst performance. One embodiment of the present invention will be explained with reference to FIG. A line 8-1 for introducing cleaning water is provided in a part of the permanently installed suit blow piping 8. The pipe A section provided at the catalyst layer gas inlet of the denitrification device 5 and to which the soot blow nozzle is attached has a structure that allows it to be extracted to the outside of the denitrification device 5 system. That is, as shown in FIG. 3, which is an enlarged view of part A, the nozzle 9 has a replaceable structure, that is, it is screwed and fixed to ten screw-in type joints. First, a suit blowing nozzle is installed as a nozzle, and while the boiler is operating, gas (steam or air) is introduced from the suit blowing pipe 8, and a certain amount is injected at a constant pressure from the suit blowing nozzle, and it adheres to the catalyst layer. Remove accumulated dust. After dust removal, stop the operation of the equipment, pull out the pipe to which the nozzle installed inside the denitrification equipment is attached, replace the suit blow nozzle with a water washing nozzle, and insert the nozzle pipe into the catalyst bed gas inlet. , after fixing, cut off the gas inlet with valve 11, open valve 12 to switch to the water washing pipe 8-1, and inject a certain amount of washing water under a certain pressure from the washing nozzle to clean the inside of the catalyst. This removes poisonous substances that have penetrated and accumulated in the catalyst, restoring catalyst performance. A drain outlet 13 is provided on the lower surface of the denitrification device 5, and the drained liquid after cleaning is led to a permanently installed drain pit tank 14. Appropriate feeding conditions such as suit blow and water washing nozzle injection pressure can be selected depending on the shape, type, and hole diameter of the nozzle, but usually the pressure is 1 to 10
Kg/ ^cm2 . G, especially 2-5Kg/cm ² . G, injection speed is 10 to 60 m/sec, and injection distance is 0.3 to 1 m.
range is used. Water washing nozzles come in several shapes depending on the intended use, but generally they are full conical nozzles A shown in Figure 4.
A uniform fan-shaped nozzle B is used (n is the nozzle), and the former generates a full cone pattern a with a large jet amount,
It is composed of relatively rough large and small droplets and has the characteristic of uniform spraying over the entire surface with a rather strong hitting force. It has the characteristic of being a simple integrated type. Table 1 shows the relationship between the injection angle, injection pressure, and injection amount for both nozzles. The larger the spray angle, the more uniformly the spray will be spread over a wider area and the number of nozzles will be smaller.

[Table] The cleaning effect can be improved by appropriately combining these nozzle shapes, arrangement, spray pressure, etc. As described above, the present invention restores the catalyst performance in a short time by carrying out suit blowing and water washing while the catalyst is still filled in the device when the catalyst performance deteriorates. There is no need for complicated methods such as taking out the catalyst during the inspection period, regenerating the catalyst, and refilling the regenerated catalyst. The effect can be said to be very large. Although the method for activating a catalyst in a denitrification reaction has been described above as an example, the method of the present invention can be applied to activation of a catalyst in a gas treatment device in general.

[Brief explanation of the drawing]

FIG. 1 is a flow sheet showing a general form of a denitrification device, FIG. 2 is a diagram showing an example of the case where the present invention is applied to the denitrification method shown in FIG. 1, and FIG. FIG. 4 is an enlarged view of the nozzle piping section A of FIG. 4, and FIG. 4 is a diagram showing the structures and spray patterns of two types of nozzles.

Claims (1)

[Claims] 1. When a gas treatment device containing a built-in catalyst having a gas passage is in operation, a high-pressure gas is injected from a suit blow nozzle to remove dust that has adhered to and accumulated on the catalyst layer, and then the operation of the device is stopped, and then Replace the suit blow nozzle with a water washing nozzle,
A method for activating a catalyst, which comprises injecting washing water from the washing nozzle to elute and remove poisoning components that have entered and accumulated inside the catalyst.