JP2002113423A - Method and device for manufacturing crushed sand - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing technique of crushed sand, in which in dry manufacturing method for crushed sand, the same of good quality satisfying a conventional quality standard of crushed sand can be manufactured at a low cost. SOLUTION: The manufacturing device consists of both a crushing part B performing a crushing process for crushing a raw stone and a classification part C classifying crushed sand crushed in the crushing part B into a prescribed size. In the classification part C, two air separators 5, 6 equipped with nearly equal classification capacity are connected in series and arranged. The same classification work is repeated at two times by two air separators 5, 6. Thereby, fine powder is classified and removed while leaving the component of crushed sand having a necessary size in a product as the component of the same even if crushed sand is fine by realizing classification operation by comparatively feeble air.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for producing crushed sand, and more particularly, it is suitably used, for example, as fine aggregate for concrete or as fine aggregate for asphalt mixture used for road pavement. Technology for dry production of crushed sand.

[0002]

2. Description of the Related Art For example, fine aggregate for concrete refers to a material constituting concrete of 5 mm or less, which includes natural sands such as river sand, mountain sand and sea sand, and crushed stone maker. There is artificial sand such as crushed sand to produce.

[0003] The method of producing crushed sand, which is artificial sand, is roughly classified into a wet method and a dry method. The former wet method requires washing and sewage treatment equipment, and the mass production cost of crushed sand is low. Due to the difficulty of the production, the latter dry production method is becoming mainstream.

In this dry manufacturing method, as shown in FIG. 4, in general, after a raw stone is supplied from a raw material hopper a to a crusher c by a feeder b and crushed, the crushed sand crushed by the crusher c is passed through a sieve d. While the crushed sand larger than the reference size is supplied and crushed again by the crusher c, the crushed sand smaller than the reference size is supplied to the air separator e and classified into a predetermined size, that is, fine powder having a particle size of 0.074 mm or less. Is removed as much as possible to obtain a product (crushed sand) having a fine powder content of a predetermined value or less.

[0005]

The crushed sand, which is an artificial sand, does not have a quality which can be used as a fine aggregate by itself. There was no use as such, but only as a sand (mixed sand) for adjusting the quality of natural sand such as sea sand and mountain sand, that is, only as a filler.

On the other hand, in recent years, there has been a shortage of high-quality natural sands, such as river sand used to be used in the past. We have begun to focus on improving the quality of crushed sand and reducing mass production so that it can be used as fine aggregate.

[0007] In terms of the quality of the crushed sand, excessive fines in the crushed sand are not preferred because they cause the initial cracking of the concrete.

[0008] In this regard, the content of fine powder in crushed sand is specified to be 7% or less in JISA5005 "Crushed stone and crushed sand for concrete" which specifies the quality standard of crushed sand. The standard of the ready-mixed concrete industry, which is an actual user, specifies 5% or less, preferably 2 to 4%.

However, in the conventional general dry production method as described above, the content of fine powder in the crushed sand is reduced to 10%.
It is practically very difficult to control the amount to below, and there is still room for improvement in reducing the mass production cost of crushed sand production, such as adding a washing step to this dry production method or combining it with a wet production method. Was.

[0010] In addition, in a research paper on initial cracks in concrete, there is a theory that the content limit of fine powder is about 11%. Therefore, in order to reduce the mass production cost of crushed sand by the dry manufacturing method, fine powder is required. Current standard of quantity 7%
It has also been proposed to correct the following to less than 10%.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide an inexpensive method for producing high-quality crushed sand satisfying the conventional quality standards of crushed sand in a dry crushed sand production method. It is an object of the present invention to provide a method for producing crushed sand.

It is another object of the present invention to provide an apparatus for producing crushed sand having a configuration suitable for carrying out the above-described production method.

[0013]

In order to achieve the above object, a method for producing crushed sand of the present invention comprises a crushing step of crushing a rough stone and a classification step of classifying the crushed sand crushed in the crushing step to a predetermined size. In the classification step,
It is characterized in that a multi-stage classification process is performed by at least two dry classification devices having substantially the same classification capability.

Here, the term "classification ability" means the ability to classify and remove fine powder from crushed sand by a dry classification apparatus, and is the same throughout the specification.

In a preferred embodiment, at least two air separators having substantially the same classification capability are used as the dry classification device. Further, as the dry classification device, two air separators having substantially the same classification capability are used, and the classification capability of the air separator on the upstream side is determined for fine powder having a particle size of 0.074 mm or less in the crushed sand after classification. The residual rate is set to be 6 to 8%, and the classification ability of the air separator on the downstream side is adjusted so that the residual rate of fine powder having a particle size of 0.074 mm or less in the crushed sand after the classification is 2 to 4%. Set to.

In the crushing step, crushing is performed in a plurality of stages by at least two crushers, and more preferably, at least two crushers having substantially the same crushing capacity as the crusher. Use

The apparatus for producing crushed sand of the present invention is for carrying out the above-mentioned production method, and comprises a crushing section for performing a crushing step of crushing a rough stone, and a crushed sand crushed by the crushing section to a predetermined size. The classifying section comprises a classifying section to be classified,
It is characterized in that two air separators having substantially the same classifying ability are connected and arranged in series.

In a preferred embodiment, the classification capacity of the two air separators is such that the residual ratio of fine particles having a particle size of 0.074 mm or less in the classified sand is at least 6 to 8% by at least the air separator on the upstream side. It is set to be.
More specifically, the classification capacity of the air separator on the upstream side is set so that the residual ratio of fine powder having a particle size of 0.074 mm or less in the crushed sand after classification is 6 to 8%, and The classification ability of the air separator is set so that the residual ratio of fine powder having a particle size of 0.074 mm or less in the crushed sand after classification is 2 to 4%.

Further, the crushing section is configured by connecting two crushers having substantially the same crushing capacity in series.

In the crushed sand production technology, the following three important points are the particle size distribution, the washing test, and the actual performance of the particle shape judgment, and these are caused by differences in specific production methods.

(1) The particle size distribution is called an FM value, and it is required that fine sand having a particle size of about 0.15 mm to 0.6 mm is sufficiently ensured in crushed sand.

(2) In the washing test, the particle size was 0.074 mm in the crushed sand.
Express the percentage of the following fines contained,
As mentioned above, it is less than 7% in JIS,
According to the ready-mixed concrete industry, which is an actual user, 2% to 4% is the best.

(3) The grain shape determination actual rate is a standard for determining the degree of roundness of the crushed sand, and a more cubic grain shape with less flatness is required.

The inventors of the present invention have been conducting tests and studies on crushed sand for many years in order to improve these important points, and as a result, have completed the dry manufacturing technique according to the present invention.

That is, the dry production includes a crushing step of crushing a rough stone and a classification step of classifying the crushed sand crushed in the crushing step to a predetermined size. In the latter classification step, a particle size of 0.074 mm is obtained. It is important and difficult to efficiently remove fine powder having a particle size of 0.074 mm or less while leaving large fine sand as much as possible.

In the present invention, in the classifying step, the crushed sand component of a required size is left by performing a multi-stage classifying process using at least two dry classifiers having substantially the same classifying ability. Unnecessary micro-sized crushed sand components can be removed, and an optimal particle size distribution and washing can be obtained. Specifically, the content of fine powder with a particle size of 0.074 mm or less in the crushed sand should be set to 4% to 2%, which is the best in the ready-mixed concrete industry, as well as 7% or less specified by JIS. Also enable.

For example, in the conventional dry production, a particle size of 0.1
The most common device for classifying and removing fine particles of 074 mm or less is a dry classifier called an air separator.
It is configured to classify heavy (large) and light (small) objects in the flow of air.

Then, approximately 15%
In order to reduce the fine powder having a particle size of 0.074 mm or less existing at a rate of 5% or less with a single air separator, the particle size is reduced to 0.15% in a fast air flow.
Fine sand with a size of about mm is blown away, resulting in coarse crushed sand as a product.

In the present invention, for example, two air separators having substantially the same classifying ability are connected in series, and these air separators are successively passed through the air separators so that the crushed sand is removed. The residual amount (content) of the fine powder having a particle size of 0.074 mm or less in the inside was reduced to about half with the first upstream air separator and half with the second downstream air separator, and the target In addition to the value (for example, a content of 4% or less), fine sand having a required particle size of more than 0.074 mm can be left as much as possible.

This is achieved by repeating the same classification operation.
A classifying operation using relatively weak air is realized, and the crushed sand component of a required size, even if it is minute, does not ride on the air flow of the air-separator. This is because the sediment is collected.

In the above-mentioned crushing step, the same crushing operation is repeated at least twice with respect to the total amount of the ore by performing the crushing process in a plurality of stages by at least two crushers having substantially the same crushing ability. Particle size and particle shape can be obtained.

[0032]

Embodiments of the present invention will be described below in detail with reference to the drawings.

Embodiment 1 FIG. 1 shows an apparatus for producing crushed sand according to the present invention. Specifically, the crushed sand manufacturing apparatus is for dry-manufacturing crushed sand used as fine aggregate for concrete or as fine aggregate for asphalt mixture used for road pavement. Part A, a crushing part B for performing a crushing step of crushing the ore, a classification part C for classifying the crushed sand crushed in the crushing part B to a predetermined size, and a product and fine powder classified in the classification part C. The recovery section D for recovery is configured as a main section.

The supply section A is mainly provided with a raw material hopper 1 for stocking raw stones and a feeder 2 for supplying a predetermined amount of the raw stones. The feeder 2 converts the raw stones stocked in the raw material hopper 1 to a predetermined amount. With an interval of
Alternatively, a predetermined amount is supplied to the crushing section B by a predetermined amount.

The crushing section B is composed mainly of one crusher 3 and a sieve 4. The crusher 3 is a dry crusher having a conventionally known structure, and crushes raw stones supplied by a predetermined amount from the feeder 2 of the supply unit A. In addition, sieve 4
Is a device that sorts crushed sand crushed by the crusher 3, and specifically includes a sieve mesh having a sieve having a size corresponding to the particle size of the crushed sand, and a crushed sand component having a size equal to or less than a reference size and the crushed sand component. It is classified into crushed sand components that need to be re-crushed. Then, the crushed sand larger than the reference size is re-supplied to the crusher 3 again, while the crushed sand smaller than the reference size is supplied to the classification unit C.

The classifier C is provided with two air separators 5 and 6 as a dry classifier. These two air separators 5 and 6 have substantially the same classifying ability and are connected and arranged in series with each other. That is, the product outlet of the first air separator 5 on the upstream side is connected to the supply port of the second air separator 6 on the downstream side.

More specifically, the classifying ability of the air separators 5 and 6 is such that the residual ratio of fine particles having a particle size of 0.074 mm or less in the classified crushed sand is at least 6 to 8 by the first air separator 5 on the upstream side. % Is set. In the illustrated embodiment, the classification capacity of the first air separator 5 is set so that the residual ratio of fine powder having a particle size of 0.074 mm or less in the crushed sand after classification is 6 to 8%, and Is set so that the residual ratio of fine powder having a particle size of 0.074 mm or less in the crushed sand after classification is 2 to 4%.

Although not specifically shown, the collection section D includes a product collection section for collecting crushed sand W as a product discharged from the second air separator 6, and first and second air separators 5, 6. And a fine powder collecting unit for collecting fine powder discharged from the apparatus.

In the above configuration, although not specifically shown, the respective components are interconnected with each other by a conventionally well-known suitable transport means such as a belt conveyor device or a bucket conveyor device.

Thus, in the manufacturing apparatus configured as described above, the ore that is quantitatively supplied from the raw material hopper 1 of the supply unit A to the crushing unit B by the feeder 2 is crushed by the crushing machine 3 of the crushing unit B. After that, it is charged and supplied to the sieve 4,
Here, the crushed sand larger than the reference size is returned to the crusher 3 again and crushed again, while the crushed sand smaller than the reference size is supplied to the classification section C.

In the classifying section C, the crushed sand having a size smaller than the reference size supplied from the crushing section B is successively passed through two air separators 5 and 6 connected and arranged in series to perform a classification process. Then, the crushed sand is classified into a predetermined size, and the crushed sand having a fine powder content of not more than a predetermined value is collected as a product in the product collection section of the collection section D. On the other hand, the fine powder removed by the air separators 5 and 6 is collected by the fine powder collecting section of the collecting section D and used for other purposes.

That is, in the present embodiment, in the classifying section C, two air-separators 5 and 6 having the same classifying ability are connected and arranged in series, and these air-separators 5 are arranged in series. , 6 are successively passed, so that the residual amount (content) of the fine powder having a particle size of 0.074 μm or less in the crushed sand is reduced to about half (fine) by the first air separator 5 on the upstream side. The residual ratio of the powder is 6 to 8%, and the second air separator 6 on the downstream side has another half (the residual ratio of the fine powder is 2 to 4).
%) And the target content of 4% or less, as much as possible, and fine sand larger than the required particle size of 0.074 mm remains as much as possible. As a result, the product (crushed sand) having a fine powder content of a predetermined value (4% or less) is collected in the product collection section of the collection section D.

This is because the same classifying operation is repeated twice so that each of the air separators 5 and 6 realizes the classifying operation with relatively weak air. The reason is that, like the large-sized crushed sand component, the product component is settled and recovered without getting into the airflow of the separators 5 and 6.

Embodiment 2 This embodiment is shown in FIG. 2 and is a modification of the configuration of Embodiment 1. Specifically, the crushing section B includes two crushers 10 and 11. Become.

That is, the crushing section B of the present embodiment includes two crushers 10 and 11 having substantially the same crushing capacity connected in series, and the crushed sand discharged from the first crusher 10 on the upstream side. The outlet is connected to the supply port of the second crusher 11 on the downstream side.

The concrete structure of the crushers 10 and 11 is the same as that of the crusher 3 of the first embodiment and is well known in the art.
With the adoption of such a configuration, the first embodiment
The sieve 4 used in is omitted. Note that, depending on the purpose, also in the present embodiment, between the first crusher 10 on the upstream side and the second crusher 11 on the downstream side, the downstream side of the second crusher 11, or both of these positions. In addition, a sieve 4 may be interposed.

In the crushing process of the crushing section B, the crushed sand producing apparatus configured as described above performs two-stage crushing by two dry crushers 10 and 11 having substantially the same crushing ability. In this way, the same crushing operation is repeated twice for the entire amount of the ore, so that the best particle size and grain shape can be obtained. Other configurations and operations are the same as those of the first embodiment.

Next, a description will be given of the results of a test performed to examine the classification effect of the dry production method of the present invention in comparison with that of the conventional method.

In the test, as an apparatus for carrying out the method of the present invention,
The crushed sand production apparatus according to the second embodiment described above was used, and a crushed sand production apparatus having the configuration shown in FIG. 4 was used as an apparatus for implementing the conventional method. The test was performed a plurality of times under the same conditions using a rough stone having the same composition as a sample, and each sample was collected and measured in the manufacturing process, and the average value of these measurement results was defined as a measured value.

Table 1 shows the test results by the method of the present invention, and Tables 2 and 3 show the test results by the conventional method, respectively. From the results of these tests, the following was found.

[0051]

[Table 1]

[0052]

[Table 2]

[0053]

[Table 3]

(A) As in the conventional method in which the classification process is performed with one air separator d, the residual ratio of the fine powder having a particle size of 0.074 mm or less in the crushed sand of the product is set to 2 to 4% in order to reduce the residual ratio. When the operating conditions, that is, the classification capacity (wind speed in this case) are set, as shown in Table 2, the crushed sand with a particle size of 0.15 to 0.6 mm that is desired to remain in the crushed sand (Fig. 4) as the final product is also blown off. The fine powder (FIG. 4) is eliminated and reduced (the fine powder residual ratio in the test results is 2.9%).

(B) On the other hand, when the operating condition of the air separator d is set so that the crushed sand component having a particle size of 0.15 to 0.6 mm remains as much as possible in the final product (FIG. 4), as shown in Table 3, The residual ratio of fine powder having a diameter of 0.074 mm or less exceeds the range of 2 to 4%, which is appropriate as fine aggregate for concrete (the fine powder residual ratio in the test results is 8.2%).

(C) On the other hand, according to the method of the present invention in which the classification process is performed by two air separators 5 and 6 having the same classification capability, as shown in Table 1, In the first air separator 5, the residual ratio of fine powder having a particle size of 0.074 mm or less was about half (the residual ratio of fine powder in the test results in FIG. 2 was 7.3%), and the second air separator 6 and about half of that (the fine powder residue in the test results in Fig. 2 was 3.
2%) and the target value of 2-4%, which is eliminated as much as possible, and the crushed sand component with a particle size of 0.15-0.6 mm that you want to remain in the crushed sand (Fig. 2) as the final product Is left as much as possible.

FIG. 3 shows the particle size distribution of the crushed sand obtained from the test results. In FIG.
, And (a, b) show the respective manufacturing steps in FIG. 2 (the device of the present invention) and FIG.
, And shows the particle size distribution curves of the crushed sand obtained respectively, wherein a is the particle size distribution of the crushed sand when the classification capacity of the air separator d of the conventional apparatus is set as described in (a) above. B shows the distribution curve, and b shows the particle size distribution curve of the crushed sand when the classification capability of the air separator d of the conventional apparatus is set as described in (b) above.

The above-described first and second embodiments merely show preferred embodiments of the present invention, and the present invention is not limited to these embodiments, and various design changes can be made within the scope. .

For example, in the illustrated first and second embodiments, each of the classifying sections C is provided with two airflows in accordance with the currently required classification accuracy and in consideration of the equipment facility cost and the running cost. Although it is configured to have a separator, the number of installed units is not necessarily limited to this,
It is also possible to perform a multi-stage classification process using three or more dry classifiers having substantially the same classification capability in response to the improvement of the classification accuracy and the processing capacity required in the future.

Similarly, the number of crushers installed in the crushing section B may be one or more as in the first embodiment, two as in the second embodiment, or three or more according to the purpose. You may.

Further, other specific structures of each of the constituent parts A to D can appropriately adopt various structures within the scope of the present invention. In particular, the processing steps before the classifier C is put into the air separator are performed. Conventionally, there are various combinations of crushers and sieves, and the design can be appropriately changed depending on the purpose and conditions.

[0062]

As described in detail above, according to the present invention,
In a dry sand crushing process including a crushing step of crushing a rough stone and a classifying step of classifying the crushed sand crushed in the crushing step into a predetermined size, the classifying step includes at least two units having substantially the same classifying ability. Since a plurality of classification processes are performed by the dry classification device, high-quality crushed sand satisfying the quality standard of the conventional crushed sand can be produced at low cost.

That is, in the classification process in the dry production, after leaving the fine sand having a particle size of more than 0.074 mm as much as possible,
Although it is important and difficult to efficiently remove fine powder having a particle size of 0.074 mm or less, in the present invention, a multi-stage classification process using at least two dry classification devices having substantially the same classification capability is performed. By doing so, unnecessary fine crushed sand components can be removed while leaving the required crushed sand components, and an optimum particle size distribution and washing can be obtained.

Specifically, the particle size in crushed sand is 0.074 mm
The content of the following fine powder is 2% or less, which is considered to be the best in the ready-mixed concrete industry, as well as 7% or less specified by JIS.
It can be set to 4%.

In the above-mentioned crushing step, the same crushing operation is repeated at least twice with respect to the total amount of the ore by performing the crushing processing in a plurality of stages by at least two crushers having substantially the same crushing ability. It is also possible to obtain a grain size and a grain shape.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of a dry crushed sand manufacturing apparatus according to a first embodiment of the present invention.

FIG. 2 is a block diagram illustrating a schematic configuration of a dry crushed sand manufacturing apparatus according to a second embodiment of the present invention.

FIG. 3 is a particle size distribution diagram showing the particle size distribution of the crushed sand produced by the crushed sand production device according to the present invention, in comparison with the particle size distribution by a conventional crushed sand production device.

FIG. 4 is a block diagram showing a schematic configuration of a conventional dry sand crushing apparatus.

[Explanation of symbols]

 W Crushed sand (product) A Supply unit B Crushing unit C Classification unit D Recovery unit 1 Raw material hopper 2 Feeder 3 Crusher 4 Sieve 5 Upstream air separator 6 Downstream air separator 10 Upstream crusher 11 Downstream crusher

Claims (10)

[Claims] 1. A method for producing crushed sand, comprising: a crushing step of crushing a rough stone; and a classifying step of classifying the crushed sand crushed in the crushing step into a predetermined size. A method for producing crushed sand, wherein a plurality of classification processes are performed by at least two dry classification devices having a capacity. 2. The method for producing crushed sand according to claim 1, wherein at least two air separators having substantially the same classification capability are used as said dry classification device. 3. As the dry classification device, two air separators having substantially the same classification capability are used, and the classification capability of these two air separators is determined by at least the upstream air separator. 3. The method for producing crushed sand according to claim 2, wherein the residual ratio of fine powder having a particle size of 0.074 mm or less is set to 6 to 8%. 4. The dry classifier uses two air separators having substantially the same classifying capacity, and determines the classifying capacity of the air separator on the upstream side with a fine particle having a particle size of 0.074 mm or less in the crushed sand after classification. The residual ratio of powder is 6-8%
While setting to be, the classification capacity of the air separator on the downstream side, the particle size 0.074m in the crushed sand after classification
The method for producing crushed sand according to claim 2, wherein the residual ratio of fine powder having a particle size of m or less is set to be 2 to 4%. 5. The method for producing crushed sand according to claim 1, wherein in the crushing step, crushing is performed in a plurality of stages by at least two crushers. 6. The method for producing crushed sand according to claim 5, wherein at least two crushers having substantially the same crushing capacity are used as the crushers. 7. An apparatus for producing crushed sand, comprising: a crushing unit for performing a crushing step of crushing a rough stone; and a classifying unit for classifying the crushed sand crushed by the crushing unit into a predetermined size, wherein the classifying unit comprises: An apparatus for producing crushed sand, comprising two air separators having substantially the same classifying capacity connected in series. 8. The classifying ability of the two air separators is such that the residual ratio of fine powder having a particle size of 0.074 mm or less in the crushed sand after classification is 6 to at least by the air separator on the upstream side.
The apparatus for producing crushed sand according to claim 7, wherein the setting is made to be 8%. 9. The classifying capacity of the air separator on the upstream side is set such that the residual ratio of fine powder having a particle size of 0.074 mm or less in the crushed sand after classification is 6 to 8%, and the downstream side of the air separator. 8. The method for producing crushed sand according to claim 7, wherein the classification capacity of the air separator is set such that the residual rate of fine powder having a particle size of 0.074 mm or less in the crushed sand after classification is 2 to 4%. apparatus. 10. The crushed sand according to claim 7, wherein the crushing unit comprises two crushers having substantially the same crushing capacity connected in series. manufacturing device.