JPH0119940B2 - - Google Patents

Abstract

1. A horizontal axis cylindrical rotary pulverizer (1) for preparing pulverized material having two different degrees of fineness, said pulverizer including members in its stub axles (3) for inserting material and a drying gas and for removing pulverized material in the drying gas, said pulverizer being subdivided by a transverse partition (2) into two portions (G, D) which are isolated from each other, each portion including its own members for inserting (4, 5A) and removing (6) material and drying gas via the respective adjacent stub axle, characterized in that the outlet from each of said portions is connected to a separator (7, 11) for separating crushed grains according to their fineness, said separator being provided with a recycling duct (9A, 12), and that the separator (7) connected to the portion (G) of the pulverizer which yields the finer grains is provided with a duct (8) for conveying the larger grains to the feed duct (15) of the portion (D) of the pulverizer for yielding less finely pulverized material.

Description

[Detailed description of the invention]

The present invention relates to a cylindrical mill rotating about a horizontal axis for forming powdered materials with two different finenesses. This pulverizer has a mechanism in the shaft member for introducing the pulverizing material and the drying gas and then discharging the pulverized material together with the gas.
The pulverizer is separated into two parts by a transverse partition, each of which is provided with a mechanism for introducing and discharging material and drying gas through corresponding shafts. . This type of crusher is used in particular for the formation of pulverized coal for feeding the burners of boilers. This type of crusher has a horizontal axis about which it rotates. In these grinders, balls or other grinding means, usually made of hard material, are introduced, and the material to be ground is ground and ground into powder by these means. When processing materials other than coal, comminution may also be effected by mutual friction of the pieces of the material to be comminuted. Since the material to be crushed usually contains some moisture, a hot gas, usually air, is introduced into the crusher along with the material to be crushed to dry the material during the crushing, and then the crusher to allow the transported material to be transported by air. The material to be ground and the drying and transport gas are usually introduced into the grinder via two hollow-ended shafts. These shafts consist of a partition and a screw system for transporting the material to be ground, which is discharged again via these shafts. The pulverized material is discharged from the shaft with a fairly wide particle size range suspended in a drying gas and is normally sent to a separator which transports the fine particles to their final use. while the coarse grains are recirculated along with the raw material in the mill for further processing. British Patent Application Publication No. GB-A 2007112 has 2
A grinder is disclosed that is divided into two sections. Each section receives material through a different hopper, and the ground material is collected in one common separator as it exits the corresponding section by a flow of hot drying air, from where it is delivered to the application site in a uniform particle size. sent to. However, depending on the application, the material after milling may have to have two different finenesses. The object of the invention is to provide a rotary cylindrical mill with which two different finenesses can be obtained. The present invention is a cylindrical rotary mill with a horizontal axis for forming powdered materials with two different finenesses, in which the material to be milled and a drying gas are introduced via a shaft member. , and includes a mechanism for discharging the pulverized material together with said gas, the pulverizer being divided by a transverse partition into two mutually isolated parts, each part being connected to the material and drying via a corresponding axial part. A separate mechanism is provided for introducing and discharging the pulverized gas, and the discharge ports from these parts communicate with corresponding separators, and these separators separate the pulverized particles according to their fineness. Each separator is equipped with a recirculation conduit and communicates with the mill section intended for finer comminution for delivering the coarsest fractionated particles in the direction of the feed path to the mill section intended for lower fineness comminution. A pulverizer is provided having a transfer tube. The mill section used to form the finer powdered material is advantageously connected to a hot air source which is subjected to a greater pressure than the air source supplying air to the miller section for forming the coarser powdered material. It is. Specific example: As a non-limiting specific example based on the attached drawings,
A ball mill type pulverizer for coal for processing two types of coal from different production areas to be supplied to a burner of a boiler will be described. In this embodiment, a pilot burner is fed with finely ground pulverized coal, and a conventional heating burner is fed with coarser, more ash-rich pulverized coal. A ball mill 1 rotating about a horizontal axis has a partition 2 dividing it into a left-hand grinding chamber G and a right-hand grinding chamber D. The shaft parts 3 of this mill are arranged symmetrically and - support and rotation of the mill (rotation is carried out by a motor, not shown) - takes place via the conduit 3A, the annular space and the screw 4. supply of raw coal to the mill; - operation in which air for drying and transporting the pulverized coal enters via conduit 5 and feeds the mill via central conduit 5A; - discharge of the pulverized coal via the annular space and discharge pipe 6; enable operations to be performed. The separator 7 on the left is concerned with the production of finer pulverized coal. Due to the expansion of the separator in the conical space 7A, very coarse particles are first separated and guided along the wall towards a conduit 8 serving as a transfer pipe and sent to the right side of the mill. Medium sized particles fall into the inner conical section 9 of the separator and are sent to the left side of the mill via recirculation conduit 9A.
The fine particles are conveyed to the point of use via conduit 10 by a flow of transport air. The separator 11 on the right concerns the production of pulverized coal with normal fineness. This separator has no means for separating extremely coarse particles from medium coarse particles. These grains are guided together along the wall and sent through the recirculation conduit 12 to the right side of the mill where they join the coal in the feed pipe 15 and are subjected to recirculation. The ordinary fine powder coal is discharged via conduit 13 in the direction of the point of use. The mill parts function independently of each other. Each of these sections is separately connected to a raw coal reservoir and a supply device. In the drawing, only the feeding device 14 (consisting of a hopper and an endless belt) corresponding to the right side portion is shown. This supply device is connected to a supply conduit 15 which communicates with the aforementioned conduits 8 and 12. All the particles sent for recirculation in the right-hand separator 11, together with the very coarse particles sent for recirculation in the left-hand separator 7, are therefore combined with the raw coal fed to the right-hand part of the mill and sent for recirculation. It will be done.
Only the medium-sized particles separated in the left-hand separator are subjected to recirculation with the raw coal fed to the left-hand part of the mill. Typically, all of the particles shed by one separator cannot be subjected to another milling cycle. This is because these separators have a high recirculation rate, equal to about 2. The structure as described above further transfers a portion of the hard, ash-rich particles of the coal fed to the left part of the mill to the right part of the mill, i.e. of inferior quality to the left part, in order to provide powdered coal of better quality. This has the advantage that the pulverized coal can be sent back to the relevant mill section. This will be explained in detail using the following specific example. In this example, two types of coal of different quality are used. The characteristics of these coals and the fineness to be imparted to the crushed product are shown in the table below.

[Table] As is well known, in order to obtain a fineness of 90%, other things being equal, the length of the mill must be twice the length required for a fineness of 70%.
Therefore, in order to obtain outputs of 40 t/h and 80 t/h, it is necessary to place the bulkhead in the center of the mill. Further, the crushing energy ratio between coal with a friability of 40 and coal with a friability of 60 is 1.3/1. Therefore, this difference in friability is greater in the left part of the mill than in the right part.
offset by charging 30% more coal. Assuming a recirculation rate of 2, the particles sent to recirculation by the left separator are 40 t/h. This is mechanically divided into 30t/h and 10t/h.
30t/h is combined with raw coal from the same production area,
The 10t/h coal is combined with raw coal from another production area on the right side. This 10 t/h portion has a very high content of ash and other inert components (estimated at 30%), so if the amount supplied from outside is 50 t/h, the powdered coal production in the left portion will be 40 t/h. This means that 3t/h of ash will be removed. If raw coal with an ash content of 15% is supplied at 50 t/h, the ash content will be 7.5 t/h, and if 10 t/h containing 3 t of ash is removed, 40 t/h of powdered coal will be produced. Therefore, the ash content of the powdered coal in the left part is 11%, and the fixed carbon increases from 54% to 56.5%. Even so, the quality of the powdered coal on the right side does not deteriorate. This is because 70t/h of pulverized coal from outside containing 45% ash, or 31.5t, is mixed with 30% ash, or 3t/h.
This is because 10 tons/h of coal, equivalent to 100 tons, joins from the left part. Therefore, in the right part, 80t/h of powdered coal has ash content.
Produced at 34.5t/h or 43%, fixed carbon 25%
This will increase from 26% to 26%. This result is obtained because the carbon content of the coal sent for recirculation in the left part exceeds the carbon content of the raw coal in the right part. With the exception of conduit 8, the circuits are separated into two, so that the flow rate, temperature and pressure of the transport and drying air can be adjusted separately. However, the pressure of the air on the left side must be equal to or greater than that on the right side. This is so that the flow of air generated within the conduit 8 promotes the flow of falling particles from the left to the right. In addition, balls or other crushing means are not required to be used in the pulverizer section that forms the coarser powdered material, but balls or other pulverizers must be used in the pulverizer section that produces the finer powdered coal. . The separator does not need to be a heavy separator, and may be of the type that uses a sieve, for example. Although the crusher of the invention is particularly suitable for the crushing process of coal or other excavated solid fuels, the invention may also be used to crush other materials, especially minerals.

[Brief explanation of drawings]

The accompanying drawing is a partial sectional view showing a coal ball mill as a non-limiting example of the present invention. DESCRIPTION OF SYMBOLS 1... Rotating ball mill, 2... Partition wall, 3... Shaft-like member, 7, 11... Separator, G... Left part, D... Right part.

Claims (1)

Claims: 1. A cylindrical rotary crusher with a horizontal axis for producing two different relatively low fineness and relatively high fineness crushed materials, the crusher comprising: It has a plurality of supply pipes for materials, and a plurality of shaft-like members for introducing the material to be crushed and a drying gas and for discharging the crushed material together with the drying gas, The crusher is divided by a transverse partition into two mutually isolated sections, each of which is connected to the material and dryer via a corresponding one of the plurality of shaft members. The outlet of the section has a mechanism for introducing and discharging a gas for separating the crushed particles into finer fragments and coarser fragments and recycling the coarser fragments. a separator connected to one of the two parts of the crusher providing the material with a relatively high fineness, the separator being connected to a corresponding separator for recirculation through a conduit for recirculating the material with a relatively high fineness. A pulverizer, characterized in that the feed duct of the other part of the pulverizer, which provides the pulverized material with a fineness, is equipped with a transfer tube for conveying particles of coarser fractions. 2. The part of the mill for producing ground material with a higher fineness is connected to a hot gas source, and this gas source is connected to the part of the mill for producing ground material of a lower fineness. A crusher according to claim 1, characterized in that it is subjected to a pressure greater than the pressure of a gas source communicating with the section.