JPS58146462A - Cyclone separator - Google Patents

Abstract

PURPOSE:To flocculate fine dust particles into coarse particles and to improve dust capturing efficiency, by giving the temp. difference between the gas to be treated and the outside cylindrical wall surface of a cyclone body in such a way that the wall surface is lower in temp. with respect to the temp. of the gas to be treated. CONSTITUTION:A water jacket 8 is disposed on the outside circumference of the circulferential walls of a cylindrical part 3 and a conical part 4 constituting a cyclone body. While the inside wall surface of the cyclone body is cooled by supplying water to the jacket 8, the exhaust gas of high temp. discharged from an internal combustion engine 7 is introduced into the cyclone body through an inlet pipe 1. While the gaseous flow of high temp. swirls in the cyclone body, temp. gradient is generated in the gas, and the fine particles in the gas move toward the cooling surface by receiving the thermal force. When such operation is effected continuously, the flocculation of the fine particles to each other progresses, and particles of large sizes are formed. The coarse particles settle in the cyclone body and are captured in a dust capturing part 5.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cyclone separator applied, for example, to the purification of exhaust gas containing particulate dust discharged from internal combustion engines or other gas combustion equipment.

A cyclone separator, which has a simple structure and is inexpensive, is well known as a means for purifying gas by removing dust from a gas containing fine particles.

The conventional general structure of this type of cyclone separator will be explained with reference to FIG. In the figure, the cyclone separator includes a cyclone body including an inlet pipe 1 and an outlet pipe 2, an intersecting cylindrical part 3, and a conical part 4 connected to the cylindrical part 3, and a cylindrical dust collecting part 5 connected to the cyclone body. It consists of When a processing gas containing dust is introduced through the entire inlet pipe as shown by the arrow 6, the airflow flowing into the cylindrical part 3 in the direction II-line descends while swirling along the inner walls of the cylindrical part 3 and the conical part 4. Then, in the conical part 4, the radius of rotation is gradually reduced to increase the speed, and when it reaches near the end, most of the main airflow 61 becomes a reversed airflow 62 and rises toward the outlet pipe 2. I will do it. In addition, a part of the live air fi61 passes through the throat of the conical part 4, continues to descend, and flows into the dust collecting part 5, becomes indoor swirling air fi63, and after swirling inside the dust collecting part 5,
The air is reversed and becomes an outflow airflow 64 from near the center of the room and rises toward the outlet pipe 2. On the other hand, the dust particles contained in the processing gas are given centrifugal force by the swirling flow of the main airflow 61, and centrifugal acceleration due to this K acts. Its size is the gravitational acceleration lI of the gravitational field! Generally 300-20 compared to
00 times more. Therefore, the dust particles move downward along the inner wall surface of the cyclone body along with the swirling airflow due to the action of this centrifugal acceleration, and the gravitational velocity is also added to this, passing through the throat from the end of the conical part 4 and collecting dust in the dust collecting part 5. (enter) and deposit.

By the way, the separation limit particle diameter of this type of conventional Suicron separator is up to several micrometers, and the collection efficiency of submicron particles of 1 micron or less is extremely low. Moreover, when high-temperature exhaust gas is treated as mentioned above, the efficiency tends to further decrease. This is because the smaller the particle size of the dust, the lower the sedimentation speed due to centrifugal force, so the separation effect from the airflow is not sufficient, and the viscosity coefficient of the particles changes depending on the temperature, which changes the sedimentation speed. It's for a reason. To this end, various efforts have been made in the past.1 For example, by combining an electrical industrial device with a cyclone separator, submicron fine dust is charged and charged, and Coulomb force is used to transfer it onto an electrode. A method is known in which fine particles are aggregated into coarse particles by gathering them together, and then collected using a cyclone. However, electric industrial dust equipment is expensive and difficult to maintain, so the original features of cyclones cannot be fully utilized. For this reason, there is a desire for a cyclone separator that can efficiently collect submicron particles by a simple means without the need for electrical dust equipment.

In this regard, if by some means the fine dust particles sent into the cyclone body can be made coarser by promoting agglomeration of the fine particles during the centrifugal separation process within the cyclone, it is possible to improve the collection efficiency of fine dust particles. However, in the cyclone separator shown in FIG. 1, it is difficult to coagulate and coarsen fine particles only by centrifugal force. According to the inventor's thoughts on this point, it was found that the boundary layer, which is one of the causes, has a large influence.
Ta. In other words, the airflow distribution within the cyclone and the swirling speed distribution of the airflow are as shown in Fig. 2. Near the surface of the inner wall surface of the cylindrical portion 39 and the cone 114 constituting the cyclone body, the airflow speed is zero K due to the formation of a boundary layer. is rapidly decreasing. Although the thickness of this boundary layer varies depending on the conditions, it is microscopically larger than the submicron particle size. On the other hand, the dust contained in the gas to be treated moves along the inner wall surface of the cylindrical part 31 and the conical part 4 under the effect of centrifugal force caused by the swirling airflow, but the centrifugal force effect in this case is weak and As mentioned above, since there is a boundary layer in the area opposite to the wall surface, most of the dust particles cannot reach the inner wall surface, and most of the dust particles move outside this boundary layer in a dispersed state along with the swirling air current. Then it becomes. For this reason, the dust particles do not aggregate sufficiently, and as a result, the submicron particles are not separated and collected sufficiently, so the collection effect is low. If the microparticles can be transferred to the inner wall surface and deposited on the wall surface, the aggregation of the microparticles will be promoted on the inner wall surface and the particles will become coarse. When the dust agglomerates and coarsens and grows into large-diameter particles, it is received by the swirling airflow tube and scattered from the inner wall surface, swirling again within the region of the swirling airflow, and this time a large centrifugal force acceleration acts on it, making it more efficient. Can be separated and collected well.

This invention was made in consideration of the above points, and its purpose is to move fine particles within the boundary layer toward the inner wall surface by skillfully applying the principle of thermophoresis, thereby reducing the amount of fine dust particles on the inner wall surface. It is an object of the present invention to provide a cyclone separator which is particularly suitable for purifying high-temperature exhaust gas and is capable of improving the collection efficiency of submicron fine dust by coarsening the agglomeration.

According to the present invention, a temperature difference is created between the gas to be treated and the wall surface of the outer cylinder constituting the cyclone body so that the wall surface becomes a cold surface with respect to the temperature of the gas to be treated. This will be accomplished.

The present invention will be described in detail below based on illustrated embodiments.

In FIG. 3 KJP, the cyclone body is the same as that in FIG. 1, and the inlet pipe 1 is installed, for example, in the exhaust pipe of an internal combustion engine 7. According to the present invention, Fi is provided on the outer periphery of the circumferential wall of the cylindrical portion 3 and the conical portion 40 constituting the cyclone body, and a quarter jacket 8 is provided as a cooling means for the inner wall surface, and the cooling water is provided through the inlet vibe 81 and the outlet vibe 82. It is configured such that cooling water 83 is supplied from the outside. Note that the means for cooling the inner wall surface is not limited to the illustrated water jacket, and various other cooling means may also be used.Next, the effects of the above structure will be described. As shown in the figure, the high temperature exhaust gas discharged from the internal combustion engine is introduced into the cyclone body through the inlet pipe 1 while cooling the inner wall surface of the cyclone body by supplying a water pipe to the water jacket 8.
When the high-temperature gas airflow swirls inside the cyclone body and leaves the cyclone body, a temperature gradient is created between the boundary layer KFi gas near the surface of the inner wall surface as a high-temperature part and the inner wall surface as a cooling surface. When there is such a temperature gradient in the gas, the particles in the gas receive thermal force and move toward the cooling surface at a rate proportional to the temperature gradient. This phenomenon is well known as thermophoresis. FIG. 4 shows a model of this situation. In the figure, TtFi is the gas temperature, and T is the wall temperature (T1) of the cyclone body as a cooling surface.T! ], δ is the thickness of the boundary layer, D is the fine particles of dust contained in air, V is the speed of movement of the particles, and D' is the large-diameter particles aggregated and coarsened on the wall surface. Then, targeting fine particles with a particle diameter of 0.1 μm,
Comparing numerically the particle movement speed within the boundary layer when a temperature gradient of 250°C/m is applied and when the centrifugal force of the airflow swirling speed is applied under normal cyclone operation conditions, it is found that when only the centrifugal force of the cyclone operation is applied is 0.6 78, whereas thermophoresis provides a migration speed of 23 78.

As a result, during actual cyclone operation, the dust particles that have reached the outside of the boundary layer due to centrifugal force move further toward the inner wall surface due to the addition of the above-mentioned thermophoretic action, and easily move toward the inner wall surface. deposits on top of. In addition, since this operation is continued, the agglomeration of fine particles progresses, and eventually coarse particles 1) with a large diameter are formed on the inner wall surface.

When the agglomeration and coarsening of the dust particles progresses sufficiently, the large-diameter particles 1) are scattered from the wall surface under the influence of the swirling air current, and then settle in the main cyclone due to the action of centrifugal force. The dust is collected by the dust collecting section 5. Moreover, since the dust particles have sufficiently large diameters, high dust collection efficiency can be obtained.

The temperature of the exhaust gas from the internal combustion engine is 200 to 400 degrees Celsius, so simply cooling the cyclone body with water using a water jacket will generate a large temperature in the boundary layer.

A gradient can be formed. Furthermore, high-temperature exhaust gas generated from other combustion equipment can be treated in the same manner.

As mentioned above, according to the present invention, by using a simple cooling means, a large temperature gradient is given to the boundary layer by using the inner wall of the cyclone body as a cooling surface, and the effect is exerted in the field of this temperature gradient. By thermophoresis, fine dust particles are guided and deposited on the inner wall surface, promoting coagulation and coarsening of the particles, and improving dust collection efficiency.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of the configuration of a general cyclone separator, Figure 2
The figure is an airflow swirling speed distribution diagram inside the cyclone, and FIG. 3 is a cross-sectional view of the configuration of an embodiment of the present invention. FIG. 4 is an explanatory diagram of the thermophoresis operation in FIG. 3. l...Inlet pipe, 2...Outlet pipe, 3...Cylindrical part, 4
...Conical part, 5...Dust collecting part% 8...Water jacket as a cooling means.

Claims (1)

[Scope of Claims] l) The inner wall surface of the outer cylinder constituting the cyclone body is used as a cooling surface between the gas to be processed and the inner wall surface of the outer cylinder for the high-temperature processing gas containing dust swirling inside the cyclone main body. A cyclone separator characterized in that it operates by applying a temperature difference to the cyclone separator. 2. The cyclone separator according to claim 1, wherein the cylindrical portion and the conical portion constituting the cyclone body are provided with cooling means for cooling the peripheral wall thereof. 3) The cyclone separator according to claim 2, wherein the cooling means is a water jacket provided on the outer periphery of the cylindrical portion and the conical portion.