JPH02157050A - Crusher - Google Patents

Abstract

PURPOSE:To prevent the materials to be crushed from short passing between crushing rollers by arranging guide members for guiding the materials to be crushed on a crushing table from its axis to the outer circumferential side in a swirling series. CONSTITUTION:A plurality of guide members 40 is arranged on a crushing table 31 in a swirling series with their heights becoming lower from the axis thereof toward and outer circumferential side thereof. Most of the particles resulting from the crushing of the materials dropped onto the table 31 are stayed within these guide members 40 on the table 31 for many hours and then carried onto the crushing races 36 of a crushing ring 35 instead of short passing between crushing rollers 32. The particles are finely pulverized on the race 36 by the pressing and shearing action caused under the rollers 32 in rolling motion. This crushing method prevents the particles from short passing between rollers 32 and improve the crushing efficiency, yet permitting the crushing power to be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pulverizer for pulverizing materials to be pulverized, such as coal, raw materials for cement, or raw materials for new materials, into fine powder.

[Conventional technology] In recent years, in Japan, due to the tight supply of heavy oil, in order to reduce the dependence on oil, there has been a shift from traditional heavy oil-burning to coal-fired fuel, especially in commercial thermal power boilers. A large-capacity coal-fired thermal power plant is being constructed.

On the other hand, as a feature of recent electricity demand, with the growth of nuclear power generation, the difference between the maximum and minimum loads has also increased, and there is a tendency to shift boilers for thermal power generation from base-low 1 to load adjustment. The power generation boiler is operated under variable pressure by changing the pressure according to the load, so-called variable pressure operation boiler is operated in the supercritical pressure region for full load operation and in the subcritical pressure region for partial load operation, which enables partial load operation. It is possible to improve the power generation efficiency by several percentage points.

For this reason, in these coal-fired thermal power plants, there are few cases in which the boiler load is always operated at full load, and the load is reduced to 75% during the day.
Daily Start and Stop operations include increasing and decreasing the load to 5% load, 50% load, and 25% load, or stopping operation at night.
There is a transition to coal-fired thermal power that handles intermediate loads through S top (hereinafter simply referred to as DSS) operation.

Furthermore, among coal-fired boilers that perform DSS operation, there are few that operate the entire load range from startup to full load using only pulverized coal;
At low loads, light oil, heavy oil, gas, etc. other than pulverized coal are used as fuel.

This is because, at startup, exhaust gas and heated air for mill warming cannot be obtained from the boiler, and therefore the mill cannot be operated, so coal cannot be pulverized into pulverized coal.

In addition, light oil, heavy oil, gas, etc. are used because the turndown ratio of the mill cannot be maintained at low loads, and the ignitability of pulverized coal itself is poor.

For example, if light oil or heavy oil is used at startup, the boiler is fired using light oil from startup until 15% load, and from 15% load to 40% load, the fuel is changed from light oil to heavy oil and fired. When the load exceeds 40%, heavy oil and pulverized coal are co-fired, the amount of heavy oil and fuel is gradually reduced, and pulverized coal is increased to increase the ratio of pulverized coal co-firing, resulting in a substantial transition to coal-only combustion.

FIG. 10 is a schematic system diagram of a pulverized coal-fired boiler, and FIGS. 11 and 12 are longitudinal and cross-sectional views of the crusher.

In Fig. 10, lower stage burners 4, 5, middle stage burners 6゜7, and second stage burners 8, 9 are arranged in order from the bottom to the top of the boiler furnace 1 on the front side v, 2 and rear side wall 3 of the boiler furnace 1. has been done.

An after air port 1-1.0.11 is provided above the upper stage burners 8, 9 to reduce NO, and each burner 4. , 5, 6, 7, and 8.9 from the morning air box 12 and afternoon air box 13, and the after air port 1-10.1.1 from the can front after air air box 14 and the afternoon after air air box 15, respectively. is supplied.

On the other hand, in order to supply coal to the lower burners 4 and 5, the interrupted burners 6 and 7, and the upper burners 8 and 9, the coal in the coal bunker 16 is sent from the coal feeder 17 to the crusher 18, and is crushed in the crusher 18. .

Then, the coarse coal in the pulverized coal in the pulverizer 18 is separated by a classifier (not shown), returned to the crushing section in the pulverizer 18, and re-pulverized to become pulverized coal.

This pulverized pulverized coal is conveyed from the pulverizer 18 via the pulverized coal pipes 23 to each burner 4.5.6, 7, 8.9 by primary air from the primary air duct 22.

On the other hand, the combustion air to the morning air box 12, afternoon air box 13, can front after air air box 14, and afternoon after air air box 15 is pressurized by the forced draft fan 19, and then passed through the air preheater 2.
The air passage 21, the air volume adjustment damper 24, the air passage 2
5 to each wind box 12°13.14.15.

In addition, the boiler is supplied with exhaust gas to a hopper 26 for steam temperature control during partial load from an exhaust gas recirculation fan 27 and an exhaust gas recirculation passage 28, and from the outlet of the exhaust gas recirculation fan 27 to an air passage 25 for low NOo measures. An exhaust gas duct 29 is provided for mixing exhaust gas into the combustion air of the engine.

The above describes the general flow of combustion air, exhaust gas, and pulverized coal in a pulverized coal-fired boiler, and the structure of the pulverizer 8 will be described below.

As shown in FIGS. 11 and 12, the crusher 18 is a disk-shaped crushing table that is located at the lower part of the cylindrical casing 3o and rotates at low speed on a horizontal plane, and is immediately driven by a motor having a speed reducer (not shown). 31, and a plurality of crushing rollers 32 which are rotated by being press-contacted by hydraulic pressure or a spring at positions that equally divide the outer periphery of the two surfaces in the circumferential direction. The material to be crushed 34, which is supplied to the center of the crushing table 3j from the raw material supply pipe 33, moves to the outer periphery while drawing a spiral trajectory on the crushing table 31 due to the rotation of the crushing table 31 and centrifugal force. It is caught between the surface of the crushing race 36 of the crushing ring 35 on the crushing table 31 and the crushing roller 32 and is crushed. Hot air 37 that has been sent into the duct 1 (not shown) is guided to the bottom of the cylindrical casing 30, and this hot air 37 connects the outer periphery of the rotary table 31 and the inner periphery of the cylindrical casing 30. Air throw between 1 to 3
It's blowing up from 8. The powder fluid after being crushed is air-filled.
The hot air 37 blowing up from the throat 380 moves up inside the cylindrical goo sink 30 and dries it.

The powder and granules transported to the upper part of the cylindrical casing 30 are classified by a cyclone separator or a rotary classifier 39 provided at the upper part of the cylindrical casing 30, and fine powder with a predetermined particle size or less is crushed by hot air 37. The pulverized coal is transported outside the boiler furnace 1 to pulverized coal burners 4 to 9 or to a pulverized powder storage bin (not shown). Coarse powder having a predetermined particle size or more that does not pass through the rotary classifier 39 falls onto the crushing table 31 and is crushed again together with the material to be crushed 34 that has just been fed into the crusher 18 . In this way, crushing is repeated by the crushing roller 32 and crushing ring 35.

The crushing mechanism in such a crusher (vertical roller mill) 18 includes a crushing ring 35 mounted on a crushing table 31.
One is due to compression between the surface of the crushing race 36 and the crushing roller 32, and the other is due to shear. In order to optimize such grinding conditions, the grinding roller 32 and the grinding ring 3 are
Five different structures have been proposed.

In this way, the object to be crushed 34 on the crushing table 31 is
It is a mixture of coarse raw material particles supplied from the raw material supply pipe (shoe h) 33 and relatively fine particles that are circulated after being subjected to secondary classification or secondary classification within the crusher 18 and returned to the crushing section.

[Problems to be Solved by the Invention] In the conventional pulverizer 18, a mixture of coarse raw material particles fed into the feed pipe 33 and fine particles that have been primarily classified and secondarily classified in the pulverizer top 8 is turned into minute particles. The crushing part (including particles) is indiscriminately crushed (
The powder is fed to the grinding roller 32 and the grinding race 36 of the grinding ring 35, and passes between the grinding rollers 32 without being crushed, resulting in a reduction in grinding efficiency.

In particular, in operating conditions where the rotary classifier 39 is used to increase the amount of circulation within the crusher 18, the amount of fine powder returned to the crushing section is large, and the problem of fine powder inclusion in the crushing section increases significantly. If the particle size becomes smaller, the particles may aggregate with each other, the cushioning effect due to compression of particle groups, or the crushing roller 32
There is a drawback that the grinding power is not consumed effectively due to the slippage between the grinding surface and the particle group. In addition, if this phenomenon increases, stick-slip (stick-5li) will occur.
p) also increases the vibration of the grinding roller 32. If the coarser particles are preferentially caught in the crushing roller 32 and crushed, the crushing efficiency of the crusher 18 will be significantly improved, but recent crushers 18 have adopted a rotary classifier 39. , as the amount of circulation from the classification section increases, the above-mentioned problems become more serious.

The present invention aims to eliminate such conventional drawbacks,
The purpose is to prevent the material to be crushed on the crushing table from making a short pass between the crushing rollers.
Furthermore, it is intended to increase the crushing efficiency by the crushing rollers and reduce the crushing power by the particle size segregation effect induced by the flow resistance of the material to be crushed.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention includes a method of arranging a guide member in a spiral shape on a grinding table to guide a material to be ground from the center of the grinding table to the outer periphery of the grinding table. solved by.

[Function] Since the guide members are arranged in a spiral manner, coarse particles are collected by the guide members and are bitten into the crushing rollers, which improves the crushing efficiency.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a cross-sectional view of a crusher according to an embodiment of the present invention, and FIG.
The figure is a vertical sectional view of FIG. 1, FIG. 3 is a developed view showing the main parts of the present invention, FIG. 4 is a schematic diagram explaining the crushing action in the crusher of the present invention, and FIGS. 5 to 9 are It is a characteristic curve diagram of experimental data conducted by the present inventors.

In FIGS. 1 to 4, numbers 18 to 39 are the first
1 and 12 are shown.

Reference numeral 40 denotes a guide member provided on the rotary table 31, and the guide member 40 is arranged in a spiral shape from the center of the rotary table 31 toward the outer periphery.

In such a structure, the material to be crushed 34 is transported through the raw material supply pipe (
The powder is supplied from the center shoes 1 to 233 and falls onto the grinding table 31 rotating at a low speed.

As shown in FIGS. 1, 2, and 3, on the grinding table 31, there are a plurality of guide members 4o whose height decreases from the central axis side of the grinding table 31 toward the outer circumferential side of the grinding table 31. A guide member 4o divided into pieces is arranged in a spiral shape on the crushing table 31. Guide member 4o
The reason why the is divided into a plurality of flat plates is not only to facilitate processing and construction, but also to allow the material to be crushed to leak from the gaps between the guide members 40, thereby reducing the gap between the guide members 40. This is to prevent particle clogging. Many of the raw material particle groups of the material to be crushed 34 are crushed by the crushing rollers 32, 32.
It reaches the grinding race 36 of the grinding ring 35 while remaining on the grinding table 31 for a long time within these guide members 4o without being lost due to a short pass.

The group of raw material particles of the material to be crushed 34 is rolled on the crushing race 36 of the crushing ring 35 by the crushing roller 32 that rolls under pressure.
It is pulverized by compression and extrusion. The powder and granules generated by the destruction are blown into hot air 3 from an air throat 38 arranged in an annular shape on the outside of the crushing table 3.
7 and conveyed upward in the crusher 18. Among these pulverized bodies, large particles do not reach the rotary classifier 39 and fall to the pulverizing section by gravity for circulation (primary classification) and are re-pulverized. Among the particles that have passed through this primary classification, fine particles pass through the rotary classifier 39 and are recovered as product fine powder from the product fine powder discharge duct 1 (not shown).

The arrow indicated by the solid line A in FIG. 1 indicates the locus of the object to be crushed 34 on the crushing table 31-hi in the crusher 18 of the present invention,
The arrow indicated by the broken line B depicts the locus of the object 34 to be crushed on the crushing table 31 in the crusher 18 of the prior art. In the conventional crusher 18, because the guide member 4o is bad, the object to be crushed 34 moves in the direction of the arrow indicated by the broken line B in FIG. and reaches the crushing ring 35.

On the other hand, on the grinding table 31 in the embodiment of the present invention, the guide member 40 is arranged in a spiral shape as shown in FIGS. First, as shown in FIG. 4, the proportion of coarse particles that settle to the crushing table 3 in the guide member 40 increases.

FIG. 4 schematically shows the behavior of particles of the material to be crushed 34 on the crushing table 31 of the crusher 18 according to the embodiment of the present invention. In FIG. 4, the guide member 40 on the grinding table 31 is omitted to avoid complexity.

Coarse particles in the material to be crushed 34 are moved along the guide member 40 in the first direction.
Since the particles flow in the direction of the arrow indicated by the solid line A in the figure, the residence time within the guide member 40 becomes longer, and the coarse particles are crushed by the crushing roller 32 with high efficiency.

If the crushing roller 32 actively bites coarse particles in this way, it is possible to prevent excessive so-called 1' over-grinding caused by the crushing roller 32 biting into fine particles, and the crushing efficiency increases. improves.

Furthermore, sliding vibration caused by fine particles entering between the crushing roller 32 and the crushing ring 35 can also be prevented. This vibration suppression effect is particularly effective when the crusher 18 is operated under low load.

Figure 5 shows the experimental results, comparing the crushing performance of a conventional crusher and a crusher according to the implementation section of the present invention (both small pilot scale) in terms of the relationship between the product fine particle size and the coal supply load ratio. It is. At all the feed load ratios tested, the mill of the present invention has a higher fine particle size, as shown by curve C in FIG. Furthermore, during low-load operation, the particle size tends to decrease in the conventional crusher as shown by the curve in Figure 5, but in the crusher of the present invention, the finer particle size improves as the load decreases, and the crushing is improved. It turned out that it was more active.

This is considered to be because, as described above, the sliding vibration was prevented by the selective crushing effect of the coarse particles by the guide member 4° of the present invention.

Figure 6 shows the measurement results of mill and differential pressure changes with respect to coal supply load ratio. When compared at the same coal supply load ratio, the crusher of the present invention has a considerably lower specific Bemill differential pressure as shown by curve E in Figure 6 than that shown by curve F, and this tendency was observed in all experiments. Consistent with range. This is considered to be because the guide member 40 of the present invention increases the coarse particle selective crushing effect and reduces the amount of coarse particles circulated in the crusher 8.

FIG. 7 shows experimental results in which the coal type (Hartgrove index HGI) was varied. In general, coal with a high HGI has good crushability and increases the fine particle size.

Both the conventional pulverizer and the pulverizer of the present invention have curve G in FIG.
, H, the tendency is the same, but the same I(G
For coal of T, the crusher according to the present invention has curve G
As shown in , it can be seen that the grinding capacity is much higher and fine powder with high particle size can be obtained.

Pulverized coal actually pulverized by a pulverizer was combusted to demonstrate the effectiveness of the pulverizer of the present invention. Figure 8 shows the results: unburned fraction in ash and NO in exhaust gas.

Using the relationship between concentrations as a map, the grinding capacities of the conventional grinder and the grinder of the present invention are compared using curves I and J. It is better to use the crusher according to the present invention, as shown in FIG.
As shown in , both the unburned content and NO9 concentration in the ash are low. This is because when the crusher of the present invention is used, ignition and flame stabilization properties are improved due to the improvement in particle size, and a high temperature, low air ratio combustion zone is formed in the vicinity of the burner. In other words, it is predicted that this is due to the fact that the combustion is accelerated, the burnout is accelerated, the amount of unburned matter in the ash is reduced, and at the same time, a large amount of intermediate products for reducing NO to N2 are released in the high-temperature, low-air combustion region.

Figure 9 shows the vibration measurement results of the crusher. The dimensionless vibration displacement δ/δ゛ on the vertical axis is the vibration displacement δ of the cylindrical casing 30.
is made dimensionless by dividing by the displacement δ° when there is no coal on the crushing ring 35 (complete metal touch). In the conventional crusher, the vibration displacement rapidly increases under low load operating conditions, as shown by the curve in Figure 9, but in the crusher of the present invention, the vibration displacement is approximately half that, as shown in the curve in Figure 9. be. This suggests that sliding vibration due to fine particles does not occur between the crushing roller 32 and the crushing ring 350 in the crusher of the present invention, and the effect of selectively crushing coarse particles, which is a function of the present invention, can be seen from the side. It corroborates this.

As described above, by implementing the present invention, the crusher 1
This not only improves the pulverization performance in Section 8, but also leads to the achievement of low pollution and high efficiency combustion in coal-fired boilers.
It can contribute to improvement of overall operability.

As described above, in the embodiments of the present invention, a pulverized coal-fired boiler or a solid combustion boiler such as petroleum coke has been described. It can also be applied as a fine grinder or, as a special purpose, as a fine grinding line for ceramic raw material fine grinding or pigment/talc production.

[Effects of the Invention] According to the present invention, it is possible to prevent the material to be crushed from making a short pass between the crushing rollers, and moreover, it is possible to increase the crushing efficiency and reduce the crushing power.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a crusher according to an embodiment of the present invention, and FIG.
The figure is a vertical sectional view of FIG. 1, FIG. 3 is a developed view showing the main parts of the present invention, FIG. 4 is a schematic diagram explaining the crushing action in the crusher of the present invention, and FIGS. 5 to 9 are A characteristic curve diagram of experimental data conducted by the present inventors, Fig. 10 is a schematic system diagram of a pulverized coal-fired boiler, Fig. 11 is a longitudinal cross-sectional view showing a conventional crusher,
FIG. 12 is a cross-sectional view of FIG. 11. 31... Grinding table, 32... Grinding roller, 34
- Object to be crushed, 35... Grinding ring, 36... Grinding race, 40... Guide member. ('10' lY!, St"hni"(00;E) T
h#'! ',%-(ovuuuJ) 7ji/115

Claims (1)

[Claims] A grinding ring with a grinding race perforated on a grinding table that performs rotational movement, and a grinding roller that rolls with its circumference pressed against the surface of the grinding race. A pulverizer for pulverizing a pulverized material, characterized in that a guide member for guiding the pulverized material from the center of the pulverizing table to the outer periphery of the pulverizing table is arranged in a spiral shape on the pulverizing table.