JPS6316170B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a solution for reducing the performance of a parallel flow catalyst packed in a horizontal reactor such as a gas treatment equipment due to dust adhesion or accumulation of poisonous components during use. The purpose of the present invention is to provide an improved activation method for restoring the performance of a catalyst while still being filled with the catalyst.

Alkali or alkaline earth metals such as potassium, sodium, and calcium are poisonous substances that inhibit catalytic activity in catalytic reactions targeting combustion exhaust gas, such as denitration catalysts and combustion catalysts, so it is necessary to reduce their content as much as possible. be. However, in recent years, due to worsening fuel conditions, dust has increasingly become a source of exhaust gas that has a negative impact on catalysts in terms of dust amount and dust composition, and the catalysts used there are required to be resistant to dust toxicity. There is a need for an effective activation method for poisoned catalysts.

The present inventors have already proposed numerous methods for activating catalysts. For example, the water washing method (patent application from 1984)
128831), a method of forcibly abrading the catalyst surface using coarse particle assemblies (Japanese Patent Application No. 57-32988), and a method in which a slurry containing a large amount of coarse particles is injected onto the catalyst surface under a high-pressure gas body, and a final washing with water is performed. (Patent Application No. 57-61710).

However, the above-mentioned proposed method is mainly for a vertical reactor in which a catalyst is arranged vertically, and there is no specific disclosure regarding a horizontal reactor in which a catalyst is arranged horizontally. In addition, when the catalyst packed in a horizontal reactor is immersed in water, there is no liquid flow, so the rate of elution of poisonous components inside the gas passage holes of the catalyst is slow, and the catalyst is placed horizontally. The washing liquid cannot be drained completely due to the presence of water.

Possible methods for this purpose include a method of tilting the horizontal reactor or a spray washing method under pressure, but the former has disadvantages such as the complexity of the equipment, while the latter has some disadvantages as shown in the proposed method above. Although it is effective, especially in the case of a horizontal reactor, there is a drawback that the amount of water for washing and the activation time are too large compared to a vertical reactor.

Therefore, the present inventors have completed the present invention as a result of extensive research into a method that can significantly reduce the amount of washing water and activation time used during catalyst activation in a horizontal reactor.

That is, the present invention provides a method for injecting a high-pressure gas-liquid multiphase flow onto the surface of the catalyst while the catalyst is packed in the reactor when the performance of the catalyst in a horizontal reactor filled with a parallel flow catalyst decreases. This is a method for activating a catalyst.

The parallel flow type catalyst in the present invention refers to a conventional catalyst in which gas and catalyst are brought into contact in parallel, and generally includes a honeycomb catalyst and a plate-shaped catalyst.

The method of the present invention is particularly effective when applied to catalyst activation in a so-called horizontal reactor in which the parallel flow catalyst is installed horizontally. In addition, the high-pressure gas-liquid multiphase flow injected onto the surface of a parallel flow catalyst (hereinafter referred to as catalyst) with degraded performance includes air and water, a cleaning solution containing air and mineral acid (H ₂ SO ₄ , HCl), and air and drain. Combinations such as large quantities of wet steam and carbon dioxide, other gases and cleaning media such as cleaning liquids can be used. Dry steam can also be used as the gas for the above gas-liquid multiphase flow. The gas:liquid ratio in the present invention is
The pressure of the gas-liquid multiphase flow is 1 to 20 gas to 1 liquid.
2 to 10 Kg/cm ² G is appropriate.

The high-pressure gas-liquid multiphase flow of the present invention can be injected from either the inlet side or the outlet side of the gas passage hole portion of the catalyst.

The present invention provides a catalyst that is applied to a denitrification reaction in which exhaust gas from burning coal or oil is passed through a catalyst to reduce and detoxify nitrogen oxides in the exhaust gas. It is particularly effective for reactivating a catalyst when its performance has deteriorated due to accumulation of alkali or alkaline earth metals such as calcium and ash, or clogging of catalyst pores.

Hereinafter, the present invention will be explained in more detail with reference to the accompanying drawings.

FIG. 1 is a graph showing the relationship between the elution rate of poisonous substances and the washing time when the catalyst is arranged vertically and horizontally with respect to the exhaust gas flow based on the conventional spray washing method. The test conditions in Figure 1 are as follows: The amount of washing water was 300/min per ^m2 of catalyst, the spray nozzle was a uniform fan-shaped nozzle, and the washing pressure was 2Kg/ ^cm2・G. b is the result when placed horizontally.

In the case of a vertical arrangement, it takes approximately 50 minutes for the elution of the poisonous substance to reach equilibrium, and the amount of water used for washing at that time is approximately 15 ^m3 , whereas in the case of a horizontal arrangement, the equilibrium time is approximately 50 minutes.
It took 180 minutes, and the amount of water needed for washing was approximately ^54m3 .
The results clearly show that the spray washing method is more effective when the catalyst is arranged vertically. This difference is due to the fact that in the case of horizontal installation, some of the washing water that collides with the end face of the catalyst gas passage hole has already fallen to the bottom of the reactor at that point, whereas in the case of vertical installation, the washing water is sprayed from the top. The difference in cleaning efficiency is due to the fact that most of the water passes through the catalyst gas passage hole and there is little loss of washing water.

When the catalyst is washed with water in a horizontal position, it is necessary to compensate for the loss described above. Therefore, we investigated whether it would be possible to inject at a slightly higher pressure than the injection pressure of the conventional method, reduce the amount of water used for washing, and maintain the elution rate of poisonous substances at the same level as when washing with water when the conventional catalyst is placed vertically. As a result of repeated experiments, we thought that injecting a high-pressure gas-liquid multiphase flow would be effective, and as a result of experiments, we obtained the following experimental results and confirmed the effects of the present invention.

FIG. 2 is a graph showing the relationship between the elution rate of poisonous substances and the washing time in the experiment. The experimental conditions were: 1 m ² of catalyst, 100/min of washing water, and approximately 1.3 ml of air.
A gas-liquid multiphase flow of m ³ /min was applied at a pressure of 5 Kg/cm ² G using a uniform fan-shaped nozzle. As a result, the time it takes for the elution rate of the poisonous substance to reach equilibrium is the second
As shown in the figure, the amount of water used for washing was 6 in about 1 hour.
^The amount of air used was approximately ^80m3 .

As a result, according to the method of the present invention, the catalyst packed in the horizontal reactor in which the catalyst is placed horizontally also
It was confirmed that the catalyst can be activated with the same amount of washing water and the same amount of time as the activation of the catalyst packed in a vertical reactor.

Figure 2 shows data regarding the injection of a gas-liquid multiphase flow of air and water, but air and mineral acids (H ₂ SO ₄ ,
Almost similar results were obtained with a gas-liquid multiphase flow consisting of a cleaning liquid containing HCl), wet steam containing air and a large amount of condensate, carbon dioxide gas, other gases, and the cleaning liquid. Furthermore, when water vapor was further mixed into the gas-liquid multiphase flow of the above combination, the effect further increased.

The vapor mixed in the gas-liquid multiphase flow condenses into a liquid, and in this case, as the temperature of the cleaning liquid increases, the effect of dissolving the poisonous component becomes slightly better. According to experiments, the elution rate of poisonous substances increases from room temperature (20℃) to 20℃.
It increases by about 10% when the temperature rises by ℃, and by about 15% when the temperature rises by 40℃. The amount of steam to be added varies depending on the temperature of the steam and liquid, and in particular, the temperature of steam varies considerably depending on the source of use, so it is difficult to set upper and lower limits, but the liquid temperature before injection is 20℃. It is recommended to add enough steam to bring the temperature to ~60°C. It is also possible to spray the cleaning liquid using dry steam, but in this case the steam must be considered as air. In terms of the amount added in this case, the appropriate lower limit is 1 to 20 per liquid 1 under standard conditions.

The flow of one embodiment of the present invention is shown in FIG. 3 below.

In Figure 3, 1 is the washing liquid supply line, 2 is air,
3 indicates the steam supply line. Depending on the usage conditions, each supply line is opened and the catalyst gas is injected from the upstream or downstream side of the horizontal reactor. The waste liquid after washing with water may be led to a permanently installed waste water bit via the hopper 9. 4 indicates an injection nozzle installed opposite the gas passage hole of the catalyst in the reactor. 5 is a horizontal reactor main body, 6 is a denitrification catalyst, 7 is a duct, and 8 is a gas flow direction.

As described above, the present invention performs regeneration by injecting a pressurized multiphase flow of a combination of air, water, etc. onto the catalyst surface, and has the following effects.

(1) When a liquid single-phase spray is applied to a long horizontally arranged catalyst,
In the area close to the spray nozzle, the droplets hit the entire wall surrounding the gas passage port uniformly, and the entire surface is evenly wetted, but as it reaches the end of the catalyst, the number of droplets that reach the top surface gradually decreases, and a liquid film on the bottom surface is formed. It gets thicker. For this reason, the catalyst cleaning of the upper surface of the rear end portion becomes insufficient.
To prevent this, it is necessary to increase the injection pressure and the amount of water, but this would require the use of extra cleaning fluid. If it is a gas-liquid multiphase flow, the water becomes small droplets and can be sprayed uniformly all the way to the inside of the catalyst hole (gas passage port). Therefore, the amount of cleaning liquid used can be reduced.

(2) Increasing the injection pressure with single-phase liquid spray increases the impact force on the catalyst surface, which may damage the catalyst. Furthermore, the increase in power is also considerable. In gas-liquid multiphase flow,
Compared to the case of single-phase liquid, the particles of the liquid droplets are smaller, so even if the injection pressure is increased considerably, the impact force on the catalyst does not increase much. Therefore, the injection pressure can be set sufficiently high to uniformly spray fine droplets over a long distance. Also, the increase in power is relatively small.

The method of the present invention is particularly suitable for horizontal reactors in which injection nozzles cannot be installed between each unit catalyst, such as those in which a plurality of unit catalysts are stacked at small intervals to form a catalyst pack. suitable for applying.

[Brief explanation of the drawing]

Fig. 1 is a graph showing the relationship between the elution rate of poisonous substances and the washing time when the catalyst is arranged vertically and horizontally relative to the exhaust gas flow based on the conventional spray washing method, and Fig. 2 is based on the method of the present invention. FIG. 3 is a graph showing the relationship between the elution rate of poisonous substances and the washing time, and FIG. 3 is a diagram showing the flow of an embodiment of the method of the present invention.

Claims (1)

[Claims] 1. When the performance of the catalyst in a horizontal reaction device filled with a parallel flow catalyst deteriorates, a high-pressure gas-liquid multiphase flow is injected onto the surface of the catalyst while the catalyst is packed in the reaction device. A method for activating a catalyst.