JP2607165B2 - Production equipment for cooled ready-mixed concrete - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[Industrial applications]

The present invention relates to an apparatus for producing cooled ready-mixed concrete.

[Prior art]

It is desirable to reduce the temperature of ready-mixed concrete.
In particular, the properties of hot concrete whose daytime temperature exceeds 25 ° C can be improved by cooling. Hot summer concrete has the disadvantage of low slumps, cracks and reduced strength. The slump drop is due to water evaporation. For example,
When the ready-mixed concrete with a kneading temperature of 30 ° C and a slump of 18 cm is transported by a truck agitator for about one hour,
Slump is said to drop about 6cm. When the slump is reduced, the driving becomes difficult. This fresh concrete needs to be remixed by adding a cement paste. Further, ready-mixed concrete has a characteristic that the slump decreases as the temperature increases, even if the amount of water added is adjusted to be the same. Cracks that occur during curing are due to internal heat generation. The hydration reaction, which is a reaction when concrete hardens, is an exothermic reaction. When heat is generated inside, there is a temperature difference between the inside and the outside surface of the concrete. The warmed interior expands thermally and the cooled outer surface shrinks and cracks. Cracks in concrete are detrimental to all applications. In particular, in the case of dams, piers of bridges installed in the sea, bulkheads of nuclear reactors, etc., it is a fatal defect. In addition, hot concrete also has reduced strength when hardened. These adverse effects can be eliminated by cooling the ready-mixed concrete. As an apparatus for producing cooled ready-mixed concrete, an apparatus for cooling water to be added has been developed. However,
Even if the added water is cooled, the temperature of the ready-mixed concrete cannot be lowered so much. This is because the amount of water added to the ready-mixed concrete is only 4-6% of the total amount. Also, a device for cooling cement added to ready-mixed concrete has been developed. Since this device cools cement with liquefied nitrogen gas, it has the feature that it can be cooled to a considerably low temperature of -100 ° C or less.

[Problems to be solved by the invention]

This device has the advantage that it can cool the cement without using water, but has the disadvantage that the running cost is extremely high. This is because the consumption of expensive liquefied nitrogen gas is large. For this reason, the device using liquid nitrogen for cooling has a disadvantage that it can be used only for special ready-mixed concrete. Aggregate is the material with the highest weight ratio added to concrete. Thus, cooling the aggregate is effective in lowering the temperature of the ready-mixed concrete.
In order to realize this, an apparatus for cooling the aggregate has been developed. As a device for cooling the aggregate, a device for cooling the aggregate by heat of vaporization of surface water has been developed (Japanese Patent Application Laid-Open No. 57-188317). In this apparatus, the aggregate is put into a closed tank, the closed tank is evacuated to forcibly evaporate water, and the aggregate is cooled by heat of vaporization of the water. This device requires a large pressure tank and a large-capacity vacuum pump, and has a drawback that the equipment cost is high. There is also a disadvantage that the aggregate cannot be cooled continuously. Further, an apparatus for spraying liquefied nitrogen gas to the aggregate to cool it has been developed (Japanese Patent Application Laid-Open Nos. 63-156045, 1-226407, 1-226408). These devices have the feature that they can be cooled without adding water to the aggregate. Another feature is that the aggregate can be cooled to a low temperature. However, these devices have the disadvantage that the running cost is high and they can be used only for special purposes, as in the case of cooling the sand with liquefied nitrogen gas. Further, with liquid nitrogen-
It is necessary to drive the machine at a place where the temperature is cooled to an extremely low temperature of 100 ° C. or less, and there is a disadvantage that maintenance and mechanism of the machine and equipment are extremely expensive. Further, a device for cooling by spraying cold water on the aggregate has been developed. However, it is difficult for a device that sprays cold water to uniformly cool a large amount of aggregate to the inside. Also,
There is a disadvantage that the fine particles having a small particle diameter attached to the surface of the aggregate are washed away. As the fines are washed away from the aggregate by cold water, a large turbid water treatment plant is required to separate the fines from the cold water. The turbid water treatment plant is quite large, since the chilled water to be treated for turbid water is quite large, and the equipment cost and the running cost increase. Further, there is a disadvantage that it is extremely difficult to dispose of a huge amount of sludge discharged from the turbid water treatment plant. A device that sprinkles cold water on aggregates with fine-grained components attached to the surface
Fine particles on the surface are washed away with cold water. Furthermore, an apparatus for immersing aggregates in liquid nitrogen for cooling has been developed (Japanese Patent Application Laid-Open No. 64-26408). The apparatus described in this publication has the same drawbacks as the apparatus using liquid nitrogen because the aggregate is placed on a belt conveyor and immersed in liquid nitrogen, and further removes fine particles adhering to the surface of the aggregate. There is also a disadvantage. This is because when the aggregate comes into contact with liquid nitrogen, the liquid nitrogen boils and is vigorously stirred at the surface of the aggregate. Liquid nitrogen has an extremely low boiling point of -196 ° C. Even if the aggregate is immersed in liquid nitrogen, the temperature of the aggregate is not cooled to the boiling point of liquid nitrogen. Aggregate having a temperature higher than the boiling point comes into contact with liquid nitrogen, and the liquid nitrogen boils on the surface of the aggregate. The liquid nitrogen boiling on the surface of the aggregate vigorously agitates the surface of the aggregate to separate fine particles adhering to the surface. The fine-grained components that are separated from the aggregate and mixed into the liquid nitrogen are:
It hardly adheres to the surface of the aggregate discharged from liquid nitrogen. This is because liquid nitrogen boils and is vigorously stirred on the surface of the aggregate. For this reason, the fine particle components contained in the liquid nitrogen gradually increase in concentration, so that it is necessary to separate the fine particle components from the liquid nitrogen. Since liquid nitrogen boils violently at room temperature and can be vaporized and disappeared, liquid nitrogen and fine particles can be relatively easily separated. However, in order to separate fine particles, it is necessary to discharge liquid nitrogen containing high concentration fine particles from the cooling water tank and discard it. And further increase running costs. SUMMARY OF THE INVENTION The present invention has been developed with the object of solving the conventional drawbacks. An important object of the present invention is to provide an apparatus for producing a cooled ready-mixed concrete capable of cooling the ready-mixed concrete to a low temperature at a low running cost. Is to provide. Another important object of the present invention is to provide an apparatus for producing ready-mixed concrete capable of preventing aggregates attached to a surface from being washed away and quickly and efficiently cooling aggregate.

[Means for Solving Conventional Problems]

An apparatus for manufacturing cooled ready-mixed concrete according to the present invention has the following configuration in order to solve the conventional problems. The apparatus for producing cooled ready-mixed concrete includes a mixer 1 for kneading the aggregate, a cooling water tank 2 for storing cold water for immersing the aggregate supplied to the mixer 1, and an immersion of the aggregate in the cold water for storing in the cooling water tank 2. Conveyor 3, which includes a conveyor belt 3A for transferring the cooling water, a cooling heat exchanger 4 for cooling the cold water supplied to the cooling water tank 2, a forced cooling machine 5 for supplying a refrigerant to the cooling heat exchanger 4, A circulation pump 6 for circulating cold water through the cooling heat exchanger 4 and the cooling water tank 2 is provided. This apparatus cools the aggregate placed on the conveyor belt 3A and transferred by immersing it in cold water in a cooling water tank 2 and supplying the cooled aggregate to the mixer 1 to knead the ready-mixed concrete.

[Action]

The apparatus for manufacturing cooled ready-mixed concrete of the present invention cools the aggregate and mixes it with a mixer. The operation of this device will be described with reference to FIG. 1 showing a preferred embodiment of the present invention. Aggregate K that is not cooled is supplied to the conveyor 3.
The supplied aggregate K is transported by the conveyor 3 into the cold water of the cooling water tank 2. Aggregate K conveyed by conveyor 3
Is forcibly cooled by contacting the cold water in the cooling water tank 2.
In the cooling water tank 2, the aggregate K is immersed in cold water and cooled. The cooled aggregate K is sent out by the conveyor 3 and supplied to the mixer 1. Cooling water is supplied to the cooling water tank 2 by a circulation pump 6.
The chilled water is circulated by the circulating pump 6 from the cooling water tank 2 to the cooling water channel 8 of the cooling heat exchanger 4, the circulating pump 6, and the cooling water tank 2. The circulating cold water is cooled by the cooling heat exchanger 4 and then supplied to the cooling water tank 2 to cool the aggregate K. A liquefied refrigerant is supplied to the refrigerant passage 7 of the cooling heat exchanger 4 from the forced chiller 5. The liquefied refrigerant evaporates in the refrigerant passage 7 of the cooling heat exchanger 4, and cools the cold water by the heat of evaporation. In the apparatus of the present invention, the aggregate can be cooled by immersing it in cold water, and the mixture can be kneaded with a mixer to lower the kneading temperature of the ready-mixed concrete. Tables 1 to 3 show the kneading temperature of ready-mixed concrete with respect to the mixed aggregate and cement temperature. In these tables, Table 1 shows an example in which the apparatus for manufacturing cooled ready-mixed concrete of the present invention is used, Table 2 shows an example in which the mixed material is not cooled, and Table 3 shows an example in which ice is used instead of water. The example which added is shown. As shown in Table 1, the apparatus of the present invention is capable of reducing the aggregate to 3 ° C.
The temperature of the ready-mixed concrete can be reduced to 14 ° C. As described above, the reason why the apparatus of the present invention can cool ready-mixed concrete to a remarkably low temperature is that the amount of heat of the aggregate having a very large amount of retained heat can be significantly reduced. As shown in Table 3, even if ice is used as the water to be added, the kneading temperature of the aggregate is only cooled to 22 ° C. The reason that the temperature of the ready-mixed concrete cannot be lowered by adding ice having a large heat of melting is that the amount of water added is small. As described above, the apparatus of the present invention has a feature that the fresh concrete temperature can be easily cooled to a low temperature and the concrete can be hardened in an extremely favorable environment.

[Preferred embodiment]

Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the embodiment described below is an example of an apparatus for embodying the technical idea of the present invention, and the apparatus of the present invention changes the material, shape, structure, and arrangement of the components to the following structure. Not specified. The device of the present invention can be variously modified within the scope described in the claims. Further, in this specification, to facilitate understanding of the claims, the numbers corresponding to the members shown in the embodiments are appended to the members shown in the claims. However, the members described in the claims are not limited to the members shown in the embodiments. 1 is a mixer 1 for kneading aggregate, cement, sand and water, a cooling water tank 2 for cooling the aggregate K before supplying it to the mixer, and a cooling water tank. Conveyor 3 for cooling while transferring the aggregate K, and a cooling heat exchanger 4 for cooling the cold water in the cooling water tank 2
And a forced chiller 5 for supplying a refrigerant to the cooling heat exchanger 4
And a circulating pump 6 for circulating cold water through the cooling heat exchanger 4 and the cooling water tank 2. As the mixer 1, all mixers capable of kneading cooled aggregate, sand, cement, and water can be used. The cooling water tank 2 has an elongated gutter shape with an upper opening. The cooling water tank 2 cools the aggregate K by immersion. The size of the cooling water tank 2 is determined by the cooling amount of the aggregate K per unit time. When the cooling amount of the aggregate K is 250 tons per hour, the size of the cooling water tank 2 is preferably 2 to 3.5 m in width,
The height is adjusted in the range of 0.6-1.5m and the length is 5-15m. The cooling time of the aggregate differs depending on the size. Large aggregates take longer to cool to the interior than smaller ones. Therefore, it is necessary to lengthen the cold water immersion time for large aggregates. The total length of the cooling water tank 2 can be increased, and the time for immersing the aggregate in cold water can be increased. Therefore, the cooling water tank 2 for cooling the large aggregate has a longer overall length. For example, the cooling water tank 2 that cools the aggregate of 5 to 150 mmφ by 250 tons per hour has a total length of 10 to 15 m, and the cooling water tank 2 that cools the aggregate of 5 to 40 mmφ has the total length of 5 to 8 m. . As the cooling water tank 2 is used, earth and sand is deposited on the bottom.
This is because the earth and sand adhering to the surface of the aggregate are washed off with cold water and settle to the bottom. At the bottom of the cooling water tank 2, a cleaning port 10 for discharging soil and the like deposited on the bottom is provided. Cleaning port 10
Is closed water-tight by a detachable plate 11. By removing the detachable plate 11, the sediment deposited on the bottom can be discharged. The cooling water tank 2 in FIG. 1 flows cold water from left to right, and transfers the aggregate K from right to left. In other words, the aggregate K is cooled by the supplied cold water and discharged. A circulation pipe 9 for supplying cold water is connected to the bottom of the cooling water tank 2. A circulation pipe 9 for supplying cold water is connected to the left side of the cooling water tank 2 on the discharge side of the aggregate K. Cooling water tank 2
Is connected to the circulation pipe 9 as a drain pipe. The cooling water tank 2 is provided with a vertical wall 39 between a connecting portion between the circulation pipe 9 for drainage and the circulation pipe 9 on the supply side. The vertical wall 39 is fixed to the inner surface of the cooling water tank 2 on both sides, and has an upper end extending below the porous conveyor belt 3A. As described above, when the vertical wall 39 is provided in the cooling water tank 2, the cold water supplied to the cooling water tank 2 can be permeated through the porous conveyor belt 3A from below and drained. Therefore, there is a feature that the aggregate K can be efficiently cooled with cold water. The circulation pipe 9 on the drain side is connected to the circulation pump 6 via a filter 12. The filter 12 filters the earth and sand contained in the cold water and circulates it to the cooling heat exchanger 4. The conveyor 3 continuously cools the aggregate K while transferring it. The conveyor 3 puts the aggregate K on the porous conveyor belt 3A, immerses it in the cold water of the cooling water tank 2, and transfers it. In FIG. 2, the porous conveyor belt 3A transfers the aggregate K from the right to the left of the cooling water tank 2. The transport conveyor 3 includes a porous conveyor belt 3A and a driving unit 3B thereof. As the porous conveyor belt 3A, a rubber belt or a pipe in which pipes are arranged in parallel can be used. As the rubber belt, one having an infinite number of holes penetrating therethrough can be used. Rubber belts are ideal for cooling relatively large aggregates. This is because, for large aggregates, cold water easily passes between the aggregates, so that the water permeability required for the porous conveyor belt 3A decreases. When a rubber belt is used for the porous conveyor belt 3A, the driving means 3B is composed of two rollers and a motor for rotating the rollers. As shown in FIG. 1, the two rollers are horizontally disposed at both ends of the cooling water tank 2, and are driven by applying a rubber belt to the two rollers. The rubber belt transfers the aggregate K immersed in cold water. The transport conveyor 3 shown in FIG. 1 lowers and transports a rubber belt between two rollers. As described above, the guide groove (not shown) is used to transfer the rubber belt.
Use The guide groove is provided at a position where both side edges of the rubber belt slide along the guide groove. The guide groove slides on both sides of the rubber belt to specify a movement locus. FIG. 2 shows an apparatus using a porous conveyor belt in which pipes are connected in parallel. The porous conveyor belt 3A of the apparatus shown in FIG. 2 is shown in FIGS. 3 and 4. The porous conveyor belt 3A shown in this figure has a belt unit 3U composed of four pipes 3P and a belt unit 3U.
And a chain 3C for driving the motor. The interval between the pipes 3P of the belt unit 3U is adjusted to a gap from which the aggregate K does not leak. Therefore, the interval between the pipes 3P is adjusted to, for example, 1 to 10 mm. 4 pipes 3P
Are connected to the end plate 3H, and are connected in parallel via the end plate 3H. The pipe 3P connected by the end plate 3H is connected to the chain 3C via a connecting piece 3R fixed to the end plate 3H. The interval between the pipes 3P connected to the chain 3C is also adjusted to the same interval as the pipe 3P connected to the end plate 3H. Therefore, the width of the belt unit 3U is made slightly smaller than the roller interval of the chain 3C. Partition walls 19 are vertically fixed to both ends of the belt unit 3U. The partition wall 19 prevents the aggregate K carried on the pipe 3P from leaking. The partition wall 19 is made of a plate material that can maintain a vertical posture. The partition walls 19 are fixed to both ends of each belt unit 3U. The partition walls 19 fixed to each belt unit 3U are connected via a flexible bellows 19A so that the porous conveyor belt 3A can be bent. The partition and the bellows can be used by being connected as separate members, but they can also be integrally formed of rubber. Further, as shown in FIGS. 5 and 6, a partition wall without using a bellows can be used. The partition walls 19 wrap with each other to prevent the aggregate K from leaking from between the belt units 3U. The partition 19 shown in these figures has an inverted trapezoidal shape in which the upper width is wider than the lower width. The inverted trapezoidal partition wall 19 wraps with a predetermined width between adjacent partition walls 19. As shown in FIG. 5, the partition wall 19 to be wrapped is slightly displaced inward and outward so that it can slide relative to each other at the wrap portion.
Are linked. Although not shown, the porous conveyor belt may be a belt unit made of a narrow plate material and connected to a chain. The porous conveyor belt 3A having the chain 3C includes a sprocket 15 that rotationally drives the chain 3C, a motor 16 that rotationally drives the sprocket 15, and a chain guide 17
Driven by The chain guide 17 is provided on the lower surface of the upper chain 3C on which the aggregate K is loaded and transferred. Chain guide 17
Determines the movement trajectory of the chain 3C on which the aggregate K moves. The chain 3C moves the porous conveyor belt 3A on which the aggregate K is placed into the cold water of the cooling water tank 2. Therefore, as shown in FIG.
The middle part which cools the lower part moves lower than the both parts. That is, the upper porous conveyor belt 3A gradually descends from the right sprocket 15, moves horizontally in the cold water in the middle, and further moves up the incline toward the left sprocket 15. Accordingly, in FIG. 2, the chain guide 17 is inclined upwardly toward both sides, and is disposed horizontally in the middle. The left sprocket 15 on which the chain 3C is hung is connected to a motor 16 via a speed reducer, and is driven to rotate by the motor 16. The conveyor 3 having this structure transfers the aggregate K supplied to the right end of the belt toward the left. The aggregate K is immersed in cold water during the transfer, is cooled, and is discharged from the left end. The aggregate cooled by immersion in cold water during the transfer is preferably drained and supplied to the mixer 1. Aggregate K
Drains the conveyor 3 on the discharge side, or connects another drainer between the conveyor 3 and the mixer 1 to drain the water. To drain the aggregate on the discharge side of the conveyor 3,
This can be realized by vibrating the belt of the conveyor. The draining device connected between the conveyor and the mixer is a device that removes moisture adhering to the aggregate by centrifugal force, or a device that removes moisture by placing the aggregate on a net and vibrating. Etc. can be used. The cooling heat exchanger 4 exchanges heat energy between the refrigerant and the cold water to cool the cold water. Cold water contaminated with earth and sand is circulated through the cooling heat exchanger 4 used for this purpose. Therefore, there is a demand for a structure that can easily clean cold water passages soiled with earth and sand. When soil accumulates in the cold water passage, the heat exchange efficiency decreases. FIGS. 7, 8, and 9 show the cooling heat exchanger 4 that can easily clean the cold water pipe 21 as the cold water channel. The cooling heat exchanger 4 includes a plurality of chilled water pipes 21 which hermetically penetrate end plates 23 at both ends of a cylindrical casing, and a communication chamber connecting end portions of the plurality of chilled water pipes 21. . Both ends of the casing 22 are hermetically sealed by end plates 23 so that a refrigerant chamber 24 is provided inside the casing 22 so that the refrigerant is vaporized and heat is removed. The refrigerant chamber 24 has an inlet 25 and an outlet 26 for the refrigerant. The inlet 25 is connected to a condenser 28 via an expansion valve 27, and the outlet 26 is connected to the suction side of a compressor 29. The cold water pipe 21 is formed to have a slightly longer overall length than the casing 22, and has both ends airtightly penetrating the end plate 23 of the casing 22 and further protruding from the end plate 23. An iron pipe can be used for the cold water pipe 21. Just a cold water pipe
When a titanium alloy, stainless steel, or the like is used for 21, the corrosion resistance is improved and the durability is improved. Outside the end plate 23, a caulking material that has a strong adhesive force to metal, is hardened and hardened, has cold resistance, and has little expansion is attached to the outer periphery of the cold water pipe 21. Further, as shown in FIG. 5, a caulking material can be attached to the entire outer surface of the end plate 23. Instead of stainless steel or titanium, a material that can be easily welded to the end plate 23, for example, a metal pipe such as iron, copper, brass, or aluminum can be used for the cold water pipe 21. The end of the cold water pipe 21 is connected to the cold water chambers 30 at both ends of the casing 22.
Watertight. The cold water chamber 30 includes a plurality of cold water pipes 21.
Are connected in series, in parallel, or in parallel with each other, and a liquid such as cold water flows through the cold water pipe 21. 8 and 9 show chilled water chambers located on the left and right of the chilled water pipe 21 shown in FIG. 7, in which three chilled water pipes 21 are connected in parallel and a partition wall 31 for connecting them in series. It has. The partition wall 31 is extended to the same plane as the inner surface of the open / close lid 32 so as to partition the cold water chamber 30 with the open / close lid 32 closed. The cooling heat exchanger 4 having the partition wall 31 as described above
Is characterized in that a plurality of cold water pipes 21 can be connected in series to lengthen a cold water channel. Both sides of the cold water chamber 30, that is, on the extension of the cold water pipe 21, are closed by an opening / closing lid 32 in a watertight manner so that the inside of the cold water pipe 21 can be easily cleaned. As shown in FIG. 7, the opening / closing lid 32 is mounted on the upper edge of the cold water chamber 30 via a hinge 33. The opening / closing lid 32 is provided with a flange 34 around its periphery so that the cold water chamber 30 can be hermetically sealed. The flange 34 is sandwiched between nuts 35. When opening, the nut 35 is removed, the lower part thereof is lifted and opened, and in this state, a cleaning tool or the like is pushed into the cold water pipe 21 to clean the inside. The cold water chamber 30 has an inlet 36 and an outlet 37 for cold water. The forced chiller 5 that supplies the refrigerant to the cooling heat exchanger 4 includes:
Compressor 29, condenser 28, condenser
A radiator 38 for cooling 28 and an expansion valve 27 are provided. The compressor 29 sucks the vaporized refrigerant from the cooling heat exchanger 4, pressurizes the refrigerant and sends it to the condenser 28. The condenser 28 cools and compresses the pressurized refrigerant. The radiator 38 cools the condenser 28 to liquefy the refrigerant. As the radiator, a cooling tower or an air-cooled heat exchanger can be used. The expansion valve 27 adjusts the supply amount of the refrigerant to the cooling heat exchanger 4. The refrigerant sent to the cooling heat exchanger 4 through the expansion valve 27 is expanded and vaporized in the cooling heat exchanger 4, takes vaporization heat from the surroundings, and cools the cold water pipe 21. The circulation pump 6 supplies the cold water cooled by the cooling heat exchanger 4 to the cooling water tank 2 to cool the aggregate K.

【The invention's effect】

The feature of the cooled ready-mixed concrete production apparatus of the present invention is that although the ready-mixed concrete temperature can be cooled to a low temperature,
The running cost can be significantly reduced. The reason is that cold water that is forcedly cooled in contact with the aggregate is circulated and reused, and the aggregate is placed on a conveyor belt and immersed in the cold water for cooling. It is preferable that the temperature of the cold water circulated and reused be as close to 0 ° C. as possible. This is because low-temperature cold water cools the aggregate to a low temperature in a short time. However, since water at 0 ° C or lower cannot be circulated by freezing, water at 0 ° C or higher, for example, cold water at 1 to 5 ° C, preferably 1 to 3 ° C is circulated. The cold water that cools the aggregate deprives the aggregate of heat energy and the temperature rises somewhat. For example, three aggregates
The temperature of the cold water cooled to 2 ° C. rises to 2 ° C. to 2.5 ° C.
The temperature of the cold water that cooled the aggregate is lower than that of water at normal temperature. For this reason, if it cools somewhat by the cooling heat exchanger 4, it will become the temperature which can cool the aggregate again. Therefore, the cooling efficiency can be increased as compared with a method in which the cold water that has cooled the aggregate is discarded and fresh water is cooled. For this reason, when the forced chiller is operated with electric power, the power consumption can be reduced and the aggregate can be efficiently cooled. The device of the present invention, which has a good power use efficiency and does not use expensive liquefied nitrogen gas as in the past, can be used very economically and has many advantages. Furthermore, the apparatus for producing ready-mixed concrete of the present invention has a feature that the temperature of ready-mixed concrete can be remarkably lowered by cooling the aggregate to a low temperature. This feature is realized by the unique configuration of the cooling water tank for cooling the aggregate and the conveyor. In other words, the apparatus for producing cooled ready-mixed concrete of the present invention is configured such that a conveyor belt is disposed in cold water of a cooling water tank, and the aggregate is immersed in the cold water and transferred by the conveyor belt. The device of this structure cools the aggregate from the entire surface by immersing the aggregate in cold water. For this reason,
There is a feature that cold water intrudes into the gap between the aggregates transported by the conveyor belt and can efficiently cool the aggregates in a short time. By the way, when using a normal rubber belt conveyor and spraying cold water of 2 ° C on the belt to cool the aggregate with cold water, the aggregate temperature became 8 ° C.
With the cold water temperature set at 1.5 ° C, the aggregate was successfully cooled to a remarkably low temperature of 2 ° C. In the summer, when the aggregate is cooled to 8 ° C and kneaded with a mixer, the temperature of the ready-mixed concrete reaches 17 ° C. On the other hand, when the aggregate can be cooled to 2 ° C, as shown in Table 1,
The temperature of ready-mixed concrete can be significantly reduced to 14 ° C. In large concrete plants, reducing the temperature at which ready-mixed concrete is mixed is extremely important because it prevents concrete cracking during hardening. Furthermore, a remarkable feature of the apparatus for manufacturing cooled ready-mixed concrete of the present invention is that the aggregate can be cooled while preventing fine components adhering to the cooled aggregate from being washed away. The aggregate before cooling has fine components of small particles attached to the surface. Raw materials for ready-mixed concrete are designed to have optimal values in consideration of the weight of fine-grained components in addition to aggregates, sand, cement, and the like. This is because the fine particles affect the physical properties of the ready-mixed concrete. If the fines are washed out when cooling the aggregate, the reduced fines need to be added to the ready-mixed concrete. A device that cools water by spraying cold water on the aggregate or immersing it in liquid nitrogen like a conventional device has a disadvantage that fine particles adhering to the surface of the aggregate are removed. In the device for sprinkling cold water on the aggregate, the cold water is used to wash away fine particles adhering to the surface of the aggregate.
In the apparatus in which the aggregate is immersed in liquid nitrogen, the liquid nitrogen boils on the surface of the aggregate and vigorously agitates, thereby forcibly removing fine particles adhering to the surface of the aggregate. The apparatus for producing cooled ready-mixed concrete of the present invention does not cool the aggregate by spraying cold water on the aggregate. Also, there is no dipping in liquid nitrogen for cooling. The aggregate is placed on a conveyor belt, immersed in cold water stored in a cooling water tank, and cooled. The aggregate immersed in the cold water releases a part of the fine particles adhering to the surface into the cold water. The fine particles separated from the aggregate into the cold water, when the aggregate is discharged from the cold water,
It adheres to the aggregate surface again and is discharged together with the aggregate.
At the beginning of operation, the concentration of fine particles in cold water is low, so the amount of fine particles separated into cold water from the surface of the aggregate is
It is larger than the amount that re-adheres to the aggregate surface from cold water. When the operation is performed for a predetermined time in this state, the concentration of the fine particle component in the cold water gradually increases. This is because the amount of the fine particle component supplied from the aggregate to the cold water is larger than the amount of reattachment. As the amount of the fine particles in the cold water increases, the reattachment from the cold water to the aggregate gradually increases. After the operation for a predetermined time, the amount of the fine component moving from the aggregate to the cold water and the amount of the fine component reattaching from the cold water to the aggregate are in an equilibrium state. In this state, the concentration of the fine component of the cold water does not increase. This is because the amount of the fine component separated from the aggregate into the cold water is equal to the amount of the fine component reattached to the aggregate from the cold water. In this state, the aggregate temporarily separates the fine particles into the cold water, but is reattached and discharged when discharged, so that all the fine particles supplied to the cold water are exposed to the surface of the aggregate. It adheres to and is discharged. For this,
The apparatus for producing ready-mixed concrete according to the present invention has a feature that the amount of fine particles adhering to the aggregate is maintained as designed and the aggregate can be efficiently cooled. In addition, since fine components adhering to the aggregate can be attached to the cooled aggregate and discharged, there is no need to treat cold water in a large turbid water treatment plant, and there is no need to dispose of an enormous amount of sludge. Another advantage is that the aggregate can be efficiently cooled by reducing the cost of the entire apparatus and the running cost to produce a fresh concrete cooled to a low temperature. Furthermore, the apparatus of the present invention has a feature that even if the amount of fine component adhering to the aggregate varies and becomes non-uniform, it can be uniformly discharged. This is because even if the amount of the fine particles attached to the aggregate fluctuates, the amount of the fine particles in the cold water does not fluctuate rapidly. For example, when the aggregate having a large amount of fine particles is temporarily immersed in the cold water, a large amount of the fine particles is separated from the aggregate into the cold water. In this state, the fine particle component amount of the cold water increases, but does not increase rapidly. This is because it takes several hours until the amount of the fine particles in the cold water becomes uniform. Aggregate in which some fine particles have been separated into cold water will reattach the fine particles in the cold water when discharged. However, the amount of the fine component reattached is smaller than the amount of the fine component separated into cold water. For this reason, the aggregate to which a large amount of the fine particle component adheres is discharged from the cold water with a small amount of the fine particle component. Conversely, if the aggregate with a small amount of fine particles is immersed in cold water, the amount of fine particles reattached to the aggregate from the cold water will be greater than the amount of fine particles separated from the aggregate into the cold water. The fine particle components attached to the water increase and are discharged from the cold water. Therefore, the apparatus of the present invention can uniformly discharge the fine particles of the aggregate to be cooled by being immersed in cold water and discharged.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an apparatus for producing cooled ready-mixed concrete showing one embodiment of the present invention, FIG. 2 is a sectional view showing an example of a cooling water tank, and FIGS. 3 to 6 are porous conveyor belts. FIG. 7 is a cross-sectional view showing an example of a cooling heat exchanger, and FIGS. 8 and 9 are cross-sectional views showing end portions of the cooling heat exchanger. 1 ... Mixer, 2 ... Cooling water tank, 3 ... Conveyor, 3A ... Porous conveyor belt, 3B ... Drive means, 3C ... Chain, 3U ... Belt unit, 3P ... Pipe, 3H ... End plate, 3R ... connecting piece, 4 ... heat exchanger for cooling, 5 ... forced cooler, 6 ... circulation pump, 7 ... refrigerant path, 8 ... cold water path, 9 ... circulation pipe, 10 ... Cleaning port, 11 ... Detachable plate, 12 ... Filter, 15 ... Sprocket, 16 ... Motor, 17 ... Chain guide, 19 ... ... Partition wall, 19A ... Bellows, 21 ... Cold water pipe, 22 ... ... casing, 23 ... end plate, 24 ... refrigerant chamber, 25 ... inlet, 26 ... outlet, 27 ... expansion valve, 28 ... condenser, 29 ... compressor, 30 ... cold water chamber, 31 … Partition wall, 32… Open / close lid, 33… Hinge, 34… Flange, 35… Nut, 36… Inlet, 37… Outlet, 38… Radiator, 39 …… vertical wall, K …… aggregate.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-64-26408 (JP, A) JP-A-64-26407 (JP, A)

Claims (1)

(57) [Claims] 1. A mixer (1) for kneading aggregates, a cooling water tank (2) for storing cold water for immersing the aggregates to be supplied to the mixer (1), and a cooling water tank for storing cold water in the cooling water tank (2). A conveyor (3) having a conveyor belt (3A) for immersing and transferring the material, a cooling heat exchanger (4) for cooling cold water supplied to a cooling water tank (2), and a cooling heat exchanger ( 4) a forced cooling machine (5) for supplying a refrigerant to the cooling belt, and a circulating pump (6) for circulating cold water through a cooling heat exchanger (4) and a cooling water tank (2). )
The aggregate placed and transported is cooled by immersing it in cold water in a cooling water tank (2), and the cooled aggregate is mixed with the mixer (1).
A device for producing cooled ready-mixed concrete, which is configured to be supplied to and kneaded with a concrete.