JPH0376977B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for crushing and classifying materials to be crushed such as coal, and more particularly to a crushing and classifying apparatus with increased classification ability.

Due to recent changes in the fuel situation, the value of coal as a fuel has been reconsidered, and coal is being co-fired with heavy oil in large boilers for business use, including large boilers for thermal power plants.
Alternatively, a considerable number of coal-fired boilers are used. In this case, from the viewpoint of improving coal combustion efficiency and controllability, a method is often adopted in which the coal is pulverized to a predetermined particle size and then air-flow conveyed to the burner section. Coal undergoes a process in which the volatile matter is first burned, and then the fixed carbon in the coal is burned, so as the coal particles become smaller, the combustion time per particle decreases, and the combustion of coal as a whole becomes less controlled. It becomes easier. Furthermore, the reduction in particle size naturally increases the surface area of coal and increases its combustibility. In other words, from the standpoint of controlling combustion and improving combustion efficiency, pulverized coal should have as high a content of pulverized coal (e.g., 70-80% passing through 200 mesh) as possible, and should have a particle size larger than this. It is necessary to reduce the content of certain coarse coals. However, the larger capacity of the boiler cannot be kept up with the increase in the size of the coal crushing equipment, and the load on each crushing equipment tends to increase, and the actual situation is that the classification rate of the crushed coal is decreasing. . In other words, the flow rate of air supplied to the classifier in the crushing device is increased to cope with the increase in load, so coarse coal that would otherwise fall into the crushing section due to its own weight before reaching the classifier also flows into the classifier. I did it,
Many situations have arisen in which the amount of pulverized coal flowing into the classifier increases significantly, resulting in a decrease in classification efficiency.

An object of the present invention is to provide a pulverizing and classifying apparatus that can eliminate the above-mentioned problems and increase both the amount of pulverized coal classified per unit time and the classification rate.

In short, the present invention provides a conical portion at the bottom of the cyclone classifier, with an internal hopper 53 having a plurality of openings on its wall surface, provided inside the conical portion in the form of a double hopper and spaced apart from the wall surface of the conical portion. This is a crushing and classifying device characterized by:

First, the outline of a ball mill for carrying out this invention will be explained.

In Figure 1, the ball mill is a coal supply pipe 2.
0, coal crushing section 30, power transmission section 90, classifier 5
0, a pulverized coal outlet pipe 60, a foreign matter discharge port 70, a primary air supply pipe 80, etc. Coal is supplied from the upper part of the coal feed pipe 20 located at the center of the mill housing 10 to the center of the coal crushing section 30 as shown by arrow C. The coal crushing section 30 has a stationary rotating lower ring 11 connected to a power transmission section 90.
It is constructed by placing a plurality of balls 12 that revolve and rotate on their own axis, and above which a fixed upper ring 14 pressurized by a spring or a nitrogen (N ₂ ) gas compression cylinder 13 is installed. . The supplied coal is sent to the crusher 30 through the lower ring 11 and balls 12.
It is crushed by the rotation of the lower ring 11 and discharged to the outside of the crushing section 30.

On the other hand, primary air A is supplied from the primary air supply pipe 80 to the throat portion 40 to blow the pulverized coal upwards into the mill housing 10, and a swirling force is applied by the guide vanes 52. The pulverized coal in the classifier 50 is centrifugally separated into pulverized coal and coarse granulated coal, and the pulverized coal rises toward the outlet pipe 60 and is supplied to a burner section (not shown). On the other hand, the coarse coal descends toward the lower part of the classifier 50 and is re-pulverized in the crushing section 30.
Note that foreign substances such as metals and rocks contained in the coal are not crushed even if they pass through the coal crushing section 30, so they fall out of the mill housing 10 from the foreign substance discharge port 70 and are discharged.

In the above apparatus, with the recent increase in the capacity of the combustion equipment, the amount of pulverized coal flowing into the classifier 50 has increased and the classification rate has decreased. The present invention also relates to a crushing and classifying device in which the classification rate does not decrease.

FIG. 2 shows a first embodiment of the invention.

In the figure, reference numeral 54 is an external hopper formed in a funnel shape, and an internal hopper 53 having substantially the same central axis is arranged inside this external hopper 54. 53a is a slit formed in the internal hopper 53 in the direction of its generatrix. In this device, an airflow containing crushed coal given a swirling force by a guide vane 52 swirls within an internal hopper 53, and coarse coal passes through a slit 53a and flows through a space between an internal hopper 53 and an external hopper 54. It descends, is discharged from the coarse coal discharge port 51, and is re-pulverized. On the other hand, pulverized coal with less mass rises in the inner cylinder 60 along with the swirling airflow and is supplied to the burner. In other words, the coarse coal passes through the slit 53a, reaches the space between the internal hopper 53 and the external hopper 54, and descends within this space, so there is no floating up of the coarse coal, and even when a large amount of pulverized coal flows in, the classification rate remains low. Can be maintained at a high rate.

FIG. 3 shows another embodiment. Reference numeral 55 denotes a partition wall, which is arranged in the space between the inner hopper 53 and the outer hopper 54 so that its upper edge is located at the side edge 53a' of the slit 53a located on the upstream side of the swirling flow X. Ru. In other words, the space formed by the internal hopper 53 and the external hopper 54 is
5 into substantially fan-shaped planes.

In this device, the coarse coal passes through the slit 53a as indicated by arrow Y into each space, and descends within each space along the generatrix direction of each of the inner and outer hoppers.

In this embodiment, the coarse coal that has flowed into the space through the slit descends without swirling, so the time it takes to reach the crushing section is shortened, and the efficiency of re-grinding can be increased.

In the above embodiments, all the openings formed in the internal hopper are elongated slits, but the invention is not limited to this, and the internal hopper may be formed with a large number of small diameter holes such as circular shapes.

By carrying out this invention, it becomes possible to classify even a large amount of pulverized coal with a high classification rate, and it is possible to sufficiently cope with an increase in the capacity of a combustion device.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a ball mill, FIG. 2 is a sectional view of a crushing and classifying device according to the present invention, and FIG. 3 is a cutaway perspective view of a mill hopper showing another embodiment of the present invention. 50... Classifier, 53... Internal hopper, 53a
...Slit, 54...External hopper, 55...Partition wall.

Claims (1)

[Scope of Claims] 1. An internal hopper 53 having a plurality of openings on the wall surface of the conical section at the bottom of the cyclone classifier is provided inside the conical section in the form of a double hopper while maintaining a distance from the wall surface of the conical section. A crushing and classifying device characterized by: 2. The crushing and classifying device according to claim 1, wherein the opening provided in the conical internal hopper is a slit 53a in the generatrix direction of the cone. 3. The internal hopper has a plurality of slits in the wall surface, and between the slits, partition walls 55 are provided in the conical generatrix direction to partition the spaces between the lower conical part and the internal hopper, respectively. A pulverizing and classifying device according to claim 2.