GRINDING PULVERIZER

Abstract: A rotary shaft is provided in a vertical treatment cylinder, and an agitation layer and a pulverization layer are formed at the upper and lower portions, respectively, of the interior of the treatment cylinder, a material to be treated being inserted through the upper portion of the treatment cylinder thereinto. When the material is in the treatment cylinder, it is first stirred in the agitation layer so that the particles of the material become smaller due to the dissolving effect, and the material is then pulverised in the pulverization layer to be turned into fine particles. A discharge port is provided at the upper or intermediate portion of the treatment cylinder, and a discharge pipe so as to extend upward from the discharge port. An agitator may be provided in the discharge pipe.

Description: The present invention relates to a pulverizing apparatus for pulverizing a material into a slurry form. It is known to spray slaked lime in the form of slurry onto exhaust gas as a method of desulphurisation. A conventional apparatus for producing such slaked lime is shown in Fig. 5. This apparatus comprises a vertical shell 1 filled with a pulverizing medium b . A screw shaft 2 extends vertically in the shell 1. A quick lime material s and water are fed into the shell at its top. The material s is pulverized as a result of friction with the pulverizing medium b and with other particles of material s while reacting with water to turn into slaked lime in the form of slurry which continuously flows out through an outlet 3 in the upper part of the shell 1 into a settling separator 4. A circulating pump is indicated by the letter P. Since there are solid impurities such as calcium carbonate and gravel in the material the slaked lime c in the form of slurry also contains these impurities. If the impurities are not pulverised to form fine particles they will cause nozzles used for desulphurization spraying to clog. During the above-described pulverizing operation, any quick lime material s which is too large to be mixed into the layer of pulverizing medium b tends to flow directly to the outlet 3 from the inlet. These large-diameter particles are liable to flow through the settling separator 4 and mix into the end product d , lowering its commercial value. The larger the ratio of the quick lime material to water, the more likely this is to occur. This is because an increase in concentration of material s causes the viscosity of the slurry to increase and the separation efficiency as a result of settling to decrease. Thus a conventional apparatus such as that described above has to be operated under conditions of low-concentration. This lowers the production efficiency. It is known that a soluble material such as soil stuck to solid pieces serves to bind them together. If the soluble material dissolves, the solid pieces will separate. The quick lime material s , contains impurities which have soluble materials such as quick lime and the like stuck thereto. If the quick lime and the like dissolves as a result of reaction, the diameter of the particles will decrease. In other words, the particle diameter of the quick lime material can be reduced and thus it can easily be encouraged to mix into the layer of pulverizing medium b by promoting its reaction and dissolving. The pulverising apparatus shown in Figure 5 and the similar pulverising apparatus disclosed in our JP-A-61233091 comprises a pulverizing apparatus comprising a vertical shell for containing material including a liquid and a pulverising medium, and a rotary shaft rotatably mounted in said vertical shell having a screw portion for forming a pulverising layer with the pulverising medium. In accordance with the present invention, there is provided an apparatus as defined in the preceding paragraph characterised in that the screw portion is formed at a lower portion of the rotary shaft and in that a plurality of agitating vanes are mounted at an upper portion thereof for forming an agitating layer. It is an advantage of the present invention that it can be used to enhance the reaction and dissolving of quick lime and to smoothly mix the material to be pulverized into the pulverizing layer by agitating the material in a vertical shell. The agitating vanes may be shaped to produce a downward current of the material. The vertical shell may comprise an inlet disposed at the top of the vertical shell for receiving material to be pulverised, said shell being formed with a discharge port at the middle portion thereof, and a discharge pipe being provided so as to extend upwardly from said discharge port. The discharge pipe may be provided with a gate for adjusting the liquid level in the vertical shell. An agitator means may be mounted in the discharge pipe. The agitator means may comprises at least one agitator. The agitator means may comprise two agitators, one of which is smaller than the other and located nearer the discharge port than the other. The apparatus may comprise a further vertical shell, a rotary shaft rotatably mounted therein and having a screw portion for providing with further pulverising medium a further pulverising layer, and a communication hole formed between said shells providing communication between said pulverising layers, said hole being covered by a screen for preventing passage of the pulverising medium therethrough. Figs. 1 to 4 are schematic views of four embodiments of the pulverizing apparatus according to the present invention; and Fig. 5 is a schematic view of an example of the prior art apparatus. As shown in Fig. 1, a rotary shaft 11 is provided along the central axis of a vertical cylindrical shell 10. The rotary shaft 11 is provided at is upper part with radially extending agitating vanes 12 arranged at axially equal intervals. An agitating layer (or slaking layer) A is formed in the shell 10 at its upper portion. The agitating vanes 12 are mounted inclined with their leading edges raised in the direction of rotation so that they form a downward current while in rotation. The angle of inclination of the agitating vanes 12 may be determined suitably according to the application. They may be arranged so that their widths extend in the axial direction of the rotary shaft 11, instead of being inclined. Also, the rotary shaft 11 is provided at its lower portion with a screw portion 13, and a pulverizing layer B filled with pulverizing medium b is formed in the shell at its lower portion. Accordingly, when the quick lime material s is fed from the upper part of the shell 10 into the region of influence of the agitating vanes 12 together with water, it will be agitated and react with water in the agitating layer A. Thus the slaked lime dissolves and turns into slurry and the material s is pulverized. In the material, the particles which have been pulverized to a sufficiently small size are entrained on a current toward an outlet port 14 which is to be described later, whereas the remaining portion of the material s (the lime left unreacted and the impurities) will settle down into the pulverizing layer B where it is pulverized into fine particles by friction with the pulverizing medium b and with other particles of the material s . The particles thus pulverized will rise in the shell with the upward current. An outlet port 14 is formed in the shell 10 on the opposite side to the inlet port for the quick lime material. A slurry of slaked lime c containing the particles carried on the upward current will flow through the outlet port 14 into a settling separator 15, in which the coarser particles (the unreacted lime and impurities) will settle. The remainder (the fine particles) will overflow the separator and be taken out as the end product d. The coarser particles which have settled are carried back to the shell 10 by a pump P. The volume ratio between the agitating layer A and the pulverizing layer B should be determined suitably through experiments. In the drawings, letter M indicates a driving means. In the embodiment shown in Fig. 2, the outlet (discharge) port 14 is formed in the shell 10 at the middle portion thereof. A discharge pipe 16 is provided to extend obliquely upwardly from the outlet port 14. An agitator 17 is provided in the discharge pipe 16 to prevent the pipe 16 from getting clogged with the slurry of slaked lime c . This is especially useful when pulverization is being effected under high-concentration conditions. The outlet port 14 may be covered with a screen to prevent the pulverizing medium b from flowing out. An opening 25 is formed in the upper part of the discharge pipe 16 at the side facing the settling separator 15. This opening is closed with an adjustable plate 18 which is axially movably mounted so as to be fixed at a desired position. The top edge of this adjustable plate 18 serves as a gate 19. By moving the adjustable plate 18, the level of the gate 19 and thus the liquid level in the shell 10 are determined. The adjustable plate 18 may be fixed in position by bolts or the like. A plate 20 extending downwardly beyond the level of the outlet port 26 is provided in the settling separator 15 to prevent the slurry from going to the outlet 26 directly. The slaked lime will thus remain in the settling separator for a longer period of time. This anti-shortcircuitting plate 20 has an adjustable position. In this embodiment, the material s to be pulverized (quick lime material) is sure to pass through the agitating layer A. This promotes the reaction and dissolving of the material. Also, the downward current formed in the agitating layer A allows the material to settle down smoothly and allows the coarser particles to mix smoothly into the pulverizing layer B. In the embodiment shown in Fig. 3, the single agitator means 17 used in the embodiment 2 is replaced with two agitators 17a and 17b. One agitator 17b is smaller than the other and is located nearer the outlet port 14 than the other in order to agitate the material near the outlet port where clogging is most likely to take place. The number of agitators 17 is not limited to two. They may be provided in any appropriate number. In the embodiment shown in Fig. 4, two vertical shells 10a are provided. The vertical shell 10 has an agitating layer A and a pulverizing layer B and the vertical shall 10a has a rotary shaft 11a and a screw portion 13a to form only a pulverizing layer B. A communication hole 21 is formed between the shells providing communication between the pulverizing layers B. The hole 21 is covered with a screen 27 to prevent passage of the pulverizing media b in the respective shells 10 from passing through the hole 21 and mixing together. With this arrangement, the pulverizing time can be extended. Three or more shells 10,10a may be used. The specific embodiments described are useful for pulverising any material which reacts with water or other liquid and dissolves into a slurry form, such as quick lime or dolomite. With pulverizers having the constructions described in the specific embodiments, when the material to be pulverized is fed into the shell from its upper part with the rotary shaft in rotation it will be agitated and dissolve while settling down in the agitating layer. By arranging the agitating blades so as to form a downward current, the material to be pulverized will reliably mix into the agitating layer and will be agitated. By encouraging the material to dissolve, the material will turn rapidly into slurry and its particle diameter will be reduced because the material acting as a binder dissolves. If for example, the material to be pulverized is quick lime, not only will the above mentioned action occur but the reaction of the quick lime will also be promoted. Thus the material will turn into slurry more rapidly and the particle diameter will be reduced still further. As described above, the particle size of the material to be pulverized reduces as it settles down in the agitating layer. Particles which are sufficiently small will be entrained on a current toward the outlet, whereas particles too coarse to be entrained on this current will mix in the pulverizing layer and then be pulverized into fine particles. This operation is carried out in the agitating layer and the pulverizing layer in a continuous and complex manner so that the material to be pulverized leaves the shell in a slurry form. In the specific embodiments in which the inlet port is formed in the upper part of the vertical shell, the discharge port is formed at a middle portion of the shell, a discharge pipe is provided so as to extend upwardly from the discharge port, and the discharge pipe is formed with a gate for determining the liquid level in the vertical shell, the material to be pulverized will flow through the agitating layer without fail, thus improving the agitating efficiency. Further, by the provision of an agitator in the discharge pipe, clogging in the latter will be prevented. The specific embodiments can efficiently produce slaked lime in a slurry form and the slaked lime obtained can be used for the desulphurisation of exhaust gas. It can also be dissolved in water or other liquid for use in the production of other material.

Claims: A pulverizing apparatus comprising a vertical shell (10) for containing material including a liquid and a pulverising medium, and a rotary shaft (11) rotatably mounted in said vertical shell (10) having a screw portion (13) for forming a pulverising layer (B) with the pulverising medium characterised in that the screw portion (13) is formed at a lower portion of the rotary shaft (11) and in that a plurality of agitating vanes (12) are mounted at an upper portion thereof for forming an agitating layer (A). A pulverizing apparatus as claimed in claim 1, wherein said agitating vanes (12) are shaped to produce a downward current of the material. A pulverizing apparatus as claimed in claim 1 or 2, wherein the vertical shell (10) comprises an inlet disposed at the top of the vertical shell for receiving material to be pulverized, said shell (10) being formed with a discharge port (14) at a middle portion thereof, and a discharge pipe (16) being provided so as to extend upwardly from said discharge port (14). A pulverizing apparatus, according to claim 3 wherein said discharge pipe (16) is provided with a gate (19) for adjusting the liquid level in said vertical shell (10). A pulverizing apparatus, according to claim 3 or 4 wherein an agitator means (17) is mounted in said discharge pipe (16). A pulverising apparatus according to claim 5 wherein the agitator means comprises at least one agitator. A pulverising apparatus according to claim 6, wherein the agitator means comprises two agitators (17a,17b), one (17b) of which is smaller than the other and located nearer the discharge port (14) than the other. A pulverising apparatus according to claim 1 or 2 wherein the apparatus comprises a further vertical shell (10a), a rotary shaft (11a) rotatably mounted therein and having a screw portion (13a) for providing with further pulverising medium a further pulverising layer B, and a communication hole (21) formed between said shells providing communication between said pulverising layers, said hole being covered by a screen (27) for preventing passage of the pulverising medium ( b ) therethrough.

Inventors: GANSE, AKIRA,KYUHOJI FACTORY OF KUBOTA, LTD., IHARA, YOSHITAKA,KYUHOJI FACTORY OF KUBOTA, LTD., IKEBUCHI, IWAO,KYUHOJI FACTORY OF KUBOTA, LTD., OYANAGI, HARUHIKO,KYUHOJI FACTORY OF KUBOTA, LTD.
Applicants: KUBOTA, LTD
Application year: 1989
Main classification: B02C17
IPC codes: B02C17