JPS6211609B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a gas parallel flow type solid-gas contact reactor for processing dirty exhaust gas containing dust such as denitrification and desulfurization of coal-fired boiler exhaust gas, heavy oil-fired boiler exhaust gas, coke oven exhaust gas, sintering furnace exhaust gas, and incinerator exhaust gas. The present invention relates to a dust cleaning method using a solid-gas contact reactor having a function of periodically sucking dust adhering to a packing and always maintaining the performance of the packing and the filling pressure loss value low. The problem with solid-gas contact reactors that treat dirty exhaust gas is that the dust contained in the exhaust gas adheres to the packed bed, increasing pressure loss due to partial clogging.
This is a decrease in catalyst performance due to dust adhesion to the catalyst surface. As a countermeasure to this problem, a gas parallel flow reactor using a lattice-like or honeycomb-like packing having a large number of through holes in the gas flow direction has been proposed. In this method, the catalyst surface is arranged parallel to the gas flow direction, so there is less dust collision with the catalyst surface, and therefore there is almost no dust adhesion.
It is said to be a type of dust-free solid-gas contact device. However, since the dust collides perpendicularly with the end face of the packing into which the exhaust gas flows, depending on the adhesion of the exhaust gas dust, some of the dust may adhere, accumulate, or bridge, resulting in partial blockage. Dust may be generated, and if left as it is, the performance of the packed catalyst will deteriorate and the pressure loss of the packed bed will increase, which will impede the operation of the smoke source equipment, so it is necessary to periodically remove the dust. Currently, as a means of removing adhered dust during process operation, steam is used to remove deposits, deposits, and cross-linked substances that are formed on the processing gas inlet side of a packed bed that has many through holes in the gas flow axis direction. Various methods have also been considered in which air or the like is locally blown toward the inlet or outlet surface of the packed bed (hereinafter referred to as the suit blow method). (Example: Japanese Patent Application Laid-Open No. 52-60273, Japanese Patent Application No. 54-152684) This method has a reliable dust removal effect, but in a solid-gas contact reactor that processes a large volume of exhaust gas such as boiler exhaust gas, the huge cross-section In order to suit-blow the entire surface of the gas inlet, a large amount of high-pressure air and steam are required. Alternatively, it is necessary to discharge the dust removed from the catalyst surface from the reactor outlet or to install a dust collector after the reactor outlet. Therefore, we have investigated an effective method for removing dust that is economical and does not affect the packing material, and have arrived at the present invention. In the present invention, a gas suction part having a slit-like hole is fixed to the inlet side of the processing gas in the packed bed, or
A gas flow is sequentially generated over the entire surface of the packing using a dust suction device in which the support having the gas absorption part can move in a direction substantially perpendicular to the processing gas flow to effectively remove the adhesion, accumulation, and crosslinking. We conducted various tests on the distance between the gas suction section and the inlet of the packed bed, and the suction gas flow rate at the inlet of the packed bed, and found and provided an economical and effective dust removal method. It is something. Hereinafter, details of the present invention will be explained using a dust absorbing device having a slit nozzle as an example, with reference to FIGS. 1, 2, 3, and 4. In FIG. 1, 1 is a combustion exhaust gas flowing in a vertical direction, 2 is a packed bed, and 3 is a combustion exhaust gas that has passed through this packed bed and has been purified by a solid-gas reaction. The packed bed, as shown in detail in Figure 3,
It consists of a filling with gas ventilation holes such as a lattice shape or a honeycomb shape, and is generally packaged in multiple pieces.
It is installed supported by the duct on the outer wall of the filling. Reference numeral 4 denotes a slit-like suction section which is an important part of the present invention, and is fixed on a support 5 that can be moved from side to side in the figure. In the packed bed 2, NOx and SOx in the combustion exhaust gas
The gas that has passed through the packed bed 2 is removed from the system as clean gas 3, as described above, because it is removed in a solid-gas catalytic manner, such as by reacting with the previously supplied reducing agent or being adsorbed by the packing. be discharged. On the other hand, part of the dust contained in the exhaust gas adheres to the end face of the inlet of the packed bed and grows as dust deposits 6. As shown in FIG. 4, the dust deposit 6 is formed along the end face of the packing in the direction opposite to the gas flow direction 1 (at the outlet of the packing, in the gas flow direction).
The deposits 6 that have grown due to gas drift etc. have a tendency to be partially crosslinked.
2a is a cross-sectional view of the filling. If pressure loss increases due to the growth and cross-linking of deposits, the second
As shown in the figure, a vacuum pump is used from outside the system to suck air from the support 5 that has a slit suction section, and the deposits on the end surface of the filling are sucked in through the slit suction section, thereby absorbing the deposits. Remove.
Further, the support body 5 can move left and right, and can move across the entire cross section of the packed layer, which has a huge cross section. The main features of the present invention are as follows when compared with the conventional suit blow removal method. (1) Since it only sucks dust, there is no need to worry about damage to the packed bed (catalyst layer). (2) The removal device can be moved to every corner of the cross section of the packed bed, and dust can be removed from every corner. (3) Fillings, such as dust particles trapped in honeycomb holes, can also be easily removed. (4) No special steam or air source is required. Next, the features of the present invention will be explained based on examples. In a gas parallel flow type solid-gas contact reactor that processes dirty exhaust gas from coal-fired and heavy oil-fired boilers, dust that has grown on the inlet and outlet end faces of the packing is absorbed from outside the system as shown in Figure 2 above. Various tests were conducted using a method in which deposits were removed by suctioning through a slit-shaped suction section. Example 1 When a coal-fired boiler exhaust gas having an exhaust gas composition as shown in Table 1 was passed through a solid-gas contactor as shown in Fig. 1, after about 100 hours of operation, the end face of the packed material was exposed as shown in Fig. 4. fly ash deposits were observed. Next, a suction device having a slit-type suction part,
The suction device was applied to the end face of the filling while changing the suction pressure, and the effect of removing dust deposits on the end face was examined, and the results shown in FIG. 5 were obtained. In the case of a slit-type suction part, the suction fluid is the same,
In the case of suction parts of the same size, the suction width is generally proportional to the distance between the suction port and the end face of the packed bed (hereinafter referred to as suction distance). Although suction can be carried out over a wide range and the distribution of the gas suction flow rate becomes smooth, the gas flow rate decreases. Conversely, the shorter the distance, the narrower the suction width. Therefore, in order to effectively remove dust, the suction distance must be within an appropriate range, preferably 0 to 20 cm.
It has been found that dust can be effectively removed within a range of 5 cm or less. In addition, the moving speed of the suction part is
The temperature was 1 cm/sec and the degree of vacuum was 760 H ₂ O.

[Table] Example 2 In order to determine the relationship between the suction flow rate and the removal effect using the same device and exhaust gas as in Example 1, the suction distance 2
A test was conducted in which the degree of vacuum was varied as cm, and the results shown in FIG. 6 were obtained. As shown in the test results, the suction gas flow rate is approximately 5 m/sec.
The removal effect is recognized above, and at suction flow speeds of 25 to 30 m/sec or higher, the removal effect reaches a plateau.
In addition, the gas suction speed increases as the vacuum level of the pump increases, but considering the power and economic efficiency of the suction speed, the gas suction speed is preferably 8 to 25
Possibly around m/sec. Power is proportional to gas flow rate and degree of vacuum. When removing a certain area, if the gas suction flow rate is low (low vacuum), the removal effect will be small. on the other hand,
When the gas suction flow rate is high (high vacuum), the removal effect becomes large, but the flow rate also increases. Therefore, the optimal gas suction flow rate requires sufficient consideration of the removal effect and power ratio. As shown in Figure 6, the gas suction speed is 5 to 40
It has been found that m/sec, preferably 8 to 25 m/sec, is suitable. Although the degree of vacuum was set at a constant level and the suction of dust was repeated 900 times in a row, no changes such as deformation or breakage of the filling were observed. The present invention provides a gas suction flow rate necessary for removing adhesion, deposits, and cross-linked substances from the filling material, thereby making it possible to remove them economically and effectively. This is a useful dust cleaning method for solid-gas contact reactors.

[Brief explanation of the drawing]

Fig. 1 is a solid-gas contact reactor having a dust removal device, Fig. 2 is a perspective view of the dust removal device having a suction section, and Fig. 3 is a perspective view showing an example of the packing applied to the present invention. figure. FIG. 4 is an explanatory diagram showing the growth of deposits on the end face of the filling material. FIG. 5 is a graph showing experimental results regarding the removal effect and suction distance. FIG. 6 is a graph showing experimental results regarding the removal effect and gas flow rate. 1... Combustion gas, 2... Solid gas contact packed bed, 3...
...Clean gas, 4...Slit-shaped suction section, 5...Support, 6...Dust deposits, 7...Gas suction flow,
2a...Solid gas contact packed bed cross section.

Claims (1)

[Claims] 1. A dirty bed that has a packed bed made of a packing material with a plurality of ventilation holes in the gas flow direction, and a suction part for guiding gas out of the system while fixing or moving the suction position on the surface of the packed bed at the inlet of the packed bed. Using a solid-gas contact reactor for exhaust gas, adhesion to the packed bed due to dust and other flying objects in the gas flow,
To remove accumulated and cross-linked substances, the distance between the suction part and the filling is 5 cm or less, and the gas suction speed at the inlet of the filling is 5 to 40 cm.
A method for cleaning dust in a solid-gas contact reactor, characterized in that dust cleaning is carried out in the range of m/sec.