JPS6359998B2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to autoclave curing of concrete products such as concrete piles, and its purpose is to effectively utilize the hot water produced by condensation of water vapor introduced during autoclave curing in the can. This not only saves energy, but also improves the efficiency of autoclave utilization by shortening the total curing time.

In the autoclave curing of concrete piles, the heat retained in the autoclave can be divided into the steam charged in the can, the hot water, the heat retained by the product, and the heat retained by the trolley and can body.

Traditionally, waste steam after autoclave curing was released into the atmosphere, but recently there has been consideration of recovering some of it for effective energy use.
Attempts have been made to introduce can filling steam and hot water into other autoclaves and to use them as other heating sources.

The present invention saves energy by recovering a portion of these waste steam, hot water, etc., and more effectively utilizing the heat retained in the product and the heat retained in the trolley and can. This improves the efficiency of autoclave usage by shortening the curing time.

The present invention will be explained below with reference to the drawings.

The drawing shows the temperature curve of each part inside the autoclave from the introduction of steam to its discharge, with the vertical axis representing the curing temperature (pressure, i.e. the water vapor pressure inside the can) and the horizontal axis representing the curing time. It is ivy. The curing temperature is determined by the pressure.

Curve 1 (A-B-D-E) shows the atmospheric temperature inside the autoclave. Note that this atmospheric temperature is the one in which the curing temperature (pressure) is plotted on the vertical axis, and as seen in normal autoclave curing, the atmospheric temperature (curing temperature) inside the autoclave can is ) is determined by pressure.

Point A is the point at which temperature rise starts, and is the point at which steam starts to be introduced into the autoclave and the pressure inside the autoclave starts to increase. Point B is the point at which the atmospheric temperature inside the can stops rising and becomes constant, and until point D, steam is supplied in an amount commensurate with the amount of heat escaping to the outside of the can.
Maintain constant pressure inside the can. Point D is the point at which the temperature starts to decrease, and is the point at which the introduction of water vapor is stopped and the steam inside the autoclave starts to be discharged over several hours, and the pressure inside the autoclave starts to gradually decrease. Point E is the point at which the temperature of the atmosphere inside the can ends, the discharge of steam ends, and the pressure inside the can returns to normal pressure.

When the atmospheric temperature inside the autoclave is curve 1, the temperature of the charged concrete pile according to the conventional method is shown as curve 2 (A-C-D-F), and the temperature of the charged concrete pile according to the method of the present invention is shown as curve 3. It is shown as (AY-D-E).

The autoclave curing time is from the time when steam introduction starts and the pressure inside the can is increased, that is, the temperature rise starts (point A), to the time when the steam discharge is finished and the pressure inside the can has finished decreasing, that is, the end of temperature fall (point E). Under normal curing conditions in which 8 to 14 kg/ ^cm2 of steam is introduced, the autoclave curing time is 2 to 4 hours for the temperature rising stage, 4 to 6 hours for the constant temperature stage, and 2 to 4 people for the cooling stage. It is 14 hours.

The steam introduced during the temperature raising process heats the can, the truck, and the concrete pile, and sequentially condenses to become hot water. This generation of hot water occurs at the point of introduction of steam A.
It starts at , and continues until point C, where the temperature of the atmosphere inside the can and the temperature of the concrete pile charged in the can match, and after that, only a small amount of water vapor corresponding to the amount of heat dissipated from the can body condenses. The hot water thus condensed in the can is in a vapor-liquid equilibrium relationship with the water vapor and maintains the same temperature.

In the present invention, the above-mentioned hot water is used in each of the heating process and cooling process of the autoclave. The temperature of the hot water generated in the autoclave can fluctuates in accordance with the pressure inside the can in the same way as the atmospheric temperature inside the can shown by the curve in the drawing.

As is clear from the drawing, during the temperature rising process, the concrete pile has less fluidity than steam or hot water and has low thermal conductivity, so the temperature rises later than the ambient temperature inside the can. Therefore, in the present invention, generated hot water is directly sprayed onto the concrete pile to moisten the concrete pile, and heat is transferred between water vapor and concrete solid through the moistened hot water. This direct spraying accelerates the heating of the concrete pile by the difference in film coefficients between the gas and the liquid. This hot water is sprayed by sequentially spraying the generated hot water onto the surface of the concrete pile inside the can using a pump or the like and circulating it. Typically, this spreading cycle is started at point X, when hot water is available for spreading circulation, and is continued until point Y, when the temperature of the concrete pile corresponds to the ambient temperature inside the can. The concrete pile is
With hot water spraying, the ambient temperature inside the can is reached much faster than without spraying (see curve 3).

On the other hand, in the temperature decreasing process, a phenomenon opposite to that in the temperature increasing process occurs, as is clear from the drawing. In other words, the temperature of the atmosphere inside the can and the hot water decrease as the steam is discharged, but since the concrete pile has no fluidity and poor heat conduction, the temperature decreases slowly and the temperature difference between the concrete pile and the atmosphere reaches the end point of temperature decrease E. becomes larger as it approaches. Under normal curing conditions, the temperature of the concrete pile at the end of cooling is located at F, about 110-130°C. Therefore, when using the conventional method, the concrete pile is left in a can for several hours after the autoclave has finished cooling, and the concrete pile is left in a can to wait for the temperature to drop. Use methods such as guiding the concrete pile to promote temperature reduction to minimize the difference between the temperature of the concrete pile after curing and the temperature of the atmosphere (especially in winter) to prevent cracks from forming in the concrete pile. It was necessary to prevent this. Therefore, in this case, in addition to the normal autoclave curing time of 8 to 14 hours, at least 1 to 2 hours of slow cooling time is required, reducing the efficiency of autoclave utilization.

Therefore, the present invention aims to spray the hot water condensed in the can (temperature decreases as the pressure inside the can decreases) onto the concrete pile during autoclave curing again from point D when the temperature drops during autoclave curing. Circulation is started and continued until the end point of temperature reduction E. This hot water boils and releases heat of vaporization as the atmospheric temperature inside the can falls, that is, the pressure inside the can decreases, and the hot water becomes hot water at the same temperature as the atmosphere (steam), so the temperature of the hot water also decreases to steam. It gradually decreases as the temperature decreases. By directly spraying this hot water, the temperature of the concrete pile is accelerated by the difference between the film coefficients of the gas and the liquid. As a result, the temperature of the concrete pile inside the can approaches the atmospheric temperature inside the can, as shown by curve 3 in the figure, making it possible to significantly shorten the slow cooling time following autoclave curing, which was previously required. .

In winter, the effect of the present invention is particularly great because the atmospheric temperature is low and concrete piles are likely to crack due to temperature differences, requiring sufficient slow cooling time. Furthermore, in the summer when the atmospheric temperature is high, sufficient annealing time is not required as in the winter, so the temperature at which the air is taken out of the autoclave can be set high, but even in this case, when the method of the present invention is used It is possible to shorten the time required to lower the temperature.

As is clear from the above description, according to the method of the present invention, (1) energy can be saved because generated hot water is used as part of the heating source, and (2)
(3) The temperature of the concrete product at the end of cooling is lower than in the case of the conventional method, so the temperature rise time is shortened as the concrete product reaches a steady temperature more quickly than in the case of the conventional method. Cooling time is not required or is significantly shortened, and (4) as a result, the total curing time is shortened, resulting in excellent effects such as increased utilization efficiency of the autoclave.

[Brief explanation of drawings]

The drawing shows the temperature curves of various parts inside the autoclave during the curing time from the introduction of steam to its discharge. 1... Atmosphere temperature curve inside autoclave can, 2
...Temperature curve of concrete pile according to the conventional method; 3.Temperature curve of concrete pile according to the method of the present invention.

Claims (1)

[Claims] 1. When curing concrete products in an autoclave, water vapor introduced during the autoclave curing process is condensed in the can and hot water is used until the concrete product reaches a predetermined temperature inside the can and the temperature raising process of autoclave curing is completed. A method for curing concrete products characterized by spraying and circulating it on concrete products during each step of the temperature fall process from the start of temperature fall to the end of temperature fall during autoclave curing.