JPH07110494B2 - Cooling device for concrete mixed sand - Google Patents

Description

The present invention relates to an apparatus for cooling sand mixed in concrete.

[Conventional technology]

It is a well-known fact that the pre-cooling method of lowering the kneading temperature of concrete is effective for suppressing temperature cracks generated in a mass concrete structure.

For example, in JP-A-62-74603, JP-A-62-77907 and JP-A-63-4169, latent heat during vaporization of liquefied nitrogen is used as a cold heat source for precooling of this concrete. The invention to be utilized has been proposed.

[Object of the Invention]

An object of the present invention is to provide a device for simply cooling sand mixed with concrete by using liquefied nitrogen.

[Structure of Invention]

The cooling apparatus for concrete-mixed sand of the present invention is a spiral classifier having a cooling function,
The gist of the point is that one end of a spiral-type scraping machine with spiral blades attached to the rotary shaft is immersed in a water tank filled with sand, and the other end is positioned above the water surface of the water tank. In the fire, the rotating shaft is configured as a hollow cylinder, the hollow cylinder is connected to a liquefied nitrogen supply pipe, and the liquefied nitrogen supplied into the hollow cylinder is discharged below the water surface of the water tank. It is characterized in that an opening is provided in the.

That is, when pouring mass concrete, a large amount of sand is consumed, and normally, raw sand is washed and classified with water to obtain a product sand. In the present invention, liquefied nitrogen is used for the washing and classification. We devised a device that efficiently cools sand by utilizing the so-called "Spiral Classifier" while maintaining the same function as a spiral classifier and easily cooling it at the same time.

An embodiment of the device of the present invention shown in the drawings will be described below.

〔Example〕

In FIG. 1, reference numeral 1 indicates a sand spiral classifier having a cooling function according to the present invention. This spiral classifier 1 is a spiral-type scraper 4 in which a spiral wing 3 is attached to a rotary shaft 2 made of a hollow cylinder.
Is connected to the water tank 5 in such a manner that one end 7 is immersed below the water surface 6 and the other end 8 is located above the water surface 6, and the motor is driven not shown in the figure. By rotating the rotary shaft 2 with, the raw sand put into the water tank 5 is continuously scraped up by the spiral blade 2 to the other end 8 above the water surface 6. At that time, the raw sand 9 and the water 10 are continuously supplied to the water tank 5, fine particles and impurities adhering to the raw sand 9 are suspended and separated in the water tank 5, and classification is performed in the process of scraping by the spiral blade 2. Then, the classified sand to which the water is attached is taken out from the other end 8. On the other hand, muddy wastewater is discharged from the overflow port 11 of the water tank 5.

In the present invention, the rotary shaft 2 of such a spiral classifier 1 is configured as a hollow tube through which a fluid can flow, and liquefied nitrogen is introduced into the hollow rotary shaft 2. In the illustrated example, the upper end 12 (position above the water surface 6) of the hollow shaft 2 is provided with a connection point with the liquefied nitrogen supply pipe 13, and the lower end 14 of the hollow shaft 2 is configured as an open end, thereby
The liquefied nitrogen introduced from 12 into the hollow shaft 2 flows through substantially the entire length of the hollow shaft 2 and is then discharged below the water surface from the lower end opening 14. The nitrogen supply pipe 13 is connected to a liquefied nitrogen tank truck 15 via a control valve 16.
The opening degree of 16 is adjusted based on the detection value of the sand temperature sensor 17 installed on the sand discharge end side of the scraping device 4.

In this way, by discharging liquefied nitrogen from the lower end opening 14 of the hollow shaft 2 below the water surface of the water tank, the liquefied nitrogen is instantaneously vaporized by touching water, and the latent heat and sensible heat of this vaporization are utilized. The vicinity of the opening 14 is cooled to an extremely low temperature, and this cold heat is transmitted to the surroundings. That is, the hollow shaft 2 itself is cooled while cooling the water in the water tank 5 and the introduced sand, and the spiral blade 3 connected to the hollow shaft 2 is also cooled to a low temperature as a whole.
Therefore, the sand scraped upward by the spiral blade 3 is efficiently cooled while being put into the water tank and taken out from the discharge end 12.

The cooled sand containing water continuously taken out from the discharge end 12 is sent to the dehydrator 18 and dehydrated by the dehydrator 18 to be product sand. The dehydrator 18 uses, for example, a vibrating screen centrifuge.

[Advantageous effects of the invention]

The device of the present invention achieves a decrease in concrete mixing temperature for preventing temperature cracking of mass concrete by cooling compounded sand which is a material having a large sensible heat amount. Especially in the summer dam construction where the amount of solar radiation is large, it is necessary to consume a large amount of sand with a high temperature. To obtain product sand from raw sand, it is necessary to easily obtain the product sand that has been cooled during the cleaning and classification process. Is advantageous in that And the device configuration can be added to the cooling function by liquefied nitrogen without impairing the function of the spiral classifier by simply modifying the rotary shaft of the spiral classifier into a hollow shaft with a lower end opening. The equipment cost for doing so is very low, good and easy to operate. According to the implementation experience of the present inventors, the temperature difference between the raw sand and the product sand is
It was demonstrated that a cooling effect of about 15 to 20 ° C. can be easily obtained by the device of the present invention. In addition, the drainage of the spiral classifier will also be at a low temperature, so if you purify this drainage and use it directly for concrete mixed water, or if you heat-exchange this low-temperature drainage and mixed water to cool the mixed water, the cold energy will be further improved. It can be effectively used.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing the main configuration of the device of the present invention. 1 …… Spiral classifier, 2 …… Hollow rotating shaft, 3 …… Spiral blade, 4 …… Scraping machine, 5 …… Water tank, 11
...... Lower end opening of hollow shaft, 17 ...... Sand temperature sensor, 16 ...... Liquefied nitrogen supply adjustment valve, 18 ...... Dehydration device.

Claims (1)

[Claims] 1. A sand spiral classifier in which one end of a spiral scraper having spiral blades attached to a rotary shaft is immersed in a water tank filled with sand, and the other end is positioned above the water surface of the water tank. In the above, the rotating shaft is configured as a hollow cylinder, the hollow cylinder is connected to a liquefied nitrogen supply pipe, and the liquefied nitrogen supplied into the hollow cylinder is opened in the hollow cylinder so as to be discharged below the water surface of the water tank. A cooling device for concrete-mixed sand, characterized by being provided with.