JPS6120512B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for removing autoclaved concrete products in a dry state and at a high temperature.

Autoclave curing of concrete products is widely used because it significantly shortens the curing time of concrete products, improves formwork rotation rate, shipping efficiency, etc., and is economically advantageous. However, these methods are only for the purpose of shortening the curing time, and in most cases, the curing-treated products are cooled to as low a temperature as possible before being taken out. To do this, after curing time (usually several hours at a saturated steam pressure of 10 to 15 atm), the temperature and pressure are lowered while gradually releasing the steam inside the autoclave, and once atmospheric pressure is reached, the lid is opened and the product is finished. A method is being implemented to extract the

In recent years, slate tiles and concrete tiles have been increasingly used as concrete products, replacing ceramic tiles because of their good dimensional stability and low cost. However, concrete tiles as they are are inferior in appearance and water resistance, so tiles coated with weather-resistant synthetic resin (for example, Ukrylic paint) are being used.

When this resin coating is produced in a factory, the use of soluble paint tends to be restricted due to the air pollution caused by the volatilization of the solvent. The disadvantage is that the performance of the membrane is easily inhibited, careful handling is required, and as a result, the number of defective products is likely to increase. In contrast,
Powder coating has been gaining attention in recent years because it does not cause such problems. However, in this powder coating, bubbles are generated in the molten coating film due to vaporization expansion due to heating of occluded gases and moisture contained in the concrete product during melt film formation after powder coating, and the resin In addition to the poor mechanical stability of the foam protrusion portion of the membrane and the drop in water resistance due to the lack of this portion, there were also disadvantages in that the product was likely to have a significantly poor aesthetic appearance. For this reason, after heating the concrete tile to a high temperature to volatilize most of the contained moisture, a resin coating without bubbles is created by applying powdered resin, fusing and curing the concrete tile without raising the temperature. A method for forming such a structure has also been proposed.

Cement roof tiles such as those mentioned above are usually manufactured by atmospheric pressure steam curing and underwater curing, or normal pressure steam curing and autoclave curing, but currently, cement roof tiles are manufactured by organically combining the autoclave treatment process and the powder coating process. This idea is rarely considered, and after the product has been autoclaved in a conventional manner and once cooled, or after the internal pressure of the autoclave has reached atmospheric pressure, the product is taken out and immediately introduced into a high-temperature heating furnace to undergo a dehydration process. , the proposal of processing by a powder resin coating process is currently considered to be quite reasonable. A normal cement tile cured in an autoclave has a moisture content of about 3 to 4% immediately after being removed from the autoclave, while a cement tile cured in water has a moisture content of 7%.
This is a considerable improvement compared to ~12%.
However, the moisture content required for powder coating is 1% or less, preferably 0.5% or less, and a considerable amount of drying equipment is required to dry the powder to this state.

In the current situation as described above, in the present invention,
This project proposes a method for taking out a concrete product from an autoclave container after curing in an autoclave, without lowering the temperature of the product, and in a dry state with a potential moisture content of 1 to 0.5% or less, which allows immediate powder coating. By introducing it into the powder coating process immediately after taking out the product, the pre-drying heat treatment process before powder coating can be significantly shortened, or
Alternatively, we propose a new autoclave processing method and apparatus that can be omitted entirely.

That is, in the method of the present invention, a concrete molded product is held in an autoclave under high temperature and high pressure saturated steam pressure for several hours to complete curing and hardening of the concrete, and when the product is taken out, the pressurized steam in the autoclave is gradually released to the outside. When releasing into
High-temperature pressurized gas (air, CO ₂ , etc.) is gradually introduced to replace the water vapor in the autoclave with high-temperature dry gas, and the pressure inside the autoclave is gradually lowered. After this reaches atmospheric pressure, This method involves opening the autoclave lid and taking out the concrete product. This method has the characteristic that it is possible to obtain concrete products that are dried to a moisture content of 1% or less while maintaining a high temperature, and the drying and high temperature conditions required for powder coating are all achieved at once. This allows immediate transition to the powder coating process.

In the above method of the present invention, by releasing the water vapor inside the autoclave to the outside and simultaneously introducing high-temperature, high-pressure drying gas, a sudden drop in pressure and temperature within the autoclave is suppressed, and at the same time only the water vapor component is gradually removed. descend. This reduction in water vapor content acts to evaporate and release moisture in concrete products with a high moisture content, and the drying action of the products progresses. Eventually, the autoclave reaches a state where it is replaced with dry gas, so the water vapor in the concrete product decreases significantly.
It will be in a dry state.

Since the temperature of the concrete product does not fall below the temperature inside the autoclave, that is, the temperature of the drying gas introduced into the autoclave, the temperature at which the concrete product is taken out can be adjusted by adjusting the temperature of the introduced gas. The drying gas is heated by exchanging heat between the drying gas, which is pressurized above the pressure inside the autoclave, and the pressurized steam released from the autoclave, so that the temperature of this steam can be reached without using any other heating source. Since heating can be performed efficiently, it can be carried out extremely economically.

In order to reduce the pressure inside the autoclave, if a high temperature is required to take out the concrete product, dry pressurized gas heated to this temperature is introduced into the autoclave, and the water vapor concentration inside the autoclave is significantly reduced. After reaching a degraded state,
By stopping the introduction of dry pressurized gas and gradually releasing the gas inside the autoclave, only the pressure can be lowered without lowering the temperature inside the autoclave. The rate of pressure drop in this case can be reduced much faster than in normal cases, since there is almost no moisture in the concrete product, so explosion phenomena due to rapid expansion of gas in the concrete product are unlikely to occur.

In addition, if the concrete product removal temperature is low,
Without introducing dry pressurized gas from the beginning, first release the pressurized steam inside the autoclave, and after the temperature inside the autoclave has decreased to almost the required temperature, dry pressurized gas at this temperature is introduced, and the pressure inside the autoclave is After the vapor concentration has decreased, the product at the required temperature can be taken out by performing a pressure reduction operation. In this case, the pressure of the dry pressurized gas does not need to be high, and may be slightly higher than the saturated water vapor pressure at the required temperature.

In this case, there is no problem even if high-pressure drying gas is introduced from the beginning, and it is preferable to introduce only the gas temperature adjusted to around the required temperature.

In addition, when CO ₂ or combustion gas is used as a high-temperature pressurized gas, alkaline components such as calcium hydroxide on or near the surface of concrete products are converted to CO ₂ or other acidic gas components in the gas. As a result, it is neutralized and the alkalinity decreases. For this reason, the adhesion and durability of the coating film after powder coating are improved.

As shown in the figure, an autoclave apparatus for carrying out the method of the present invention as described above connects a boiler 1 for pressurized steam generation and an autoclave container 3 via a valve 2, and connects a valve 5 of a steam discharge pipe 4 to a container side 3. A conduit 8 connects a heat exchanger 6 (usually equipped with a drain trap, not shown) and a pressurized gas source 7 (usually an air compressor) on the side to be heated, and a conduit 9 on the heating gas system side. is kept warm and connected to the container 3 via a valve 10.
Note that the container 3 is provided with a thermometer 11 and a hygrometer 12.

When an air compressor is used as the pressurized gas source 7, a drain trap or other dehumidifier is provided in the middle of the conduit 8. Note that when using dried nitrogen, carbon dioxide, or other high-pressure gas (usually in a cylinder) as the gas source 7, a dehumidifier is not necessary.

[Brief explanation of the drawing]

The accompanying drawings are schematic diagrams showing an embodiment of the concrete product curing device of the present invention. DESCRIPTION OF SYMBOLS 1... Boiler for pressurized steam generation, 2... Valve, 3... Autoclave container, 4... Steam discharge pipe, 5... Valve, 6... Heat exchanger, 7... Pressurized gas source, 10... Valve, 11...Thermometer, 1
2...Hygrometer.

Claims (1)

[Claims] 1. When a concrete molded product is held in an autoclave at high temperature and high pressure under saturated steam pressure, and when the pressure in the autoclave is reduced after a curing period, the residual steam in the autoclave is released to the outside. At the same time, high-temperature dry pressurized gas is introduced into the autoclave to replace the water vapor in the autoclave with high-temperature dry gas, reducing the pressure inside the autoclave, and after reaching atmospheric pressure, the autoclave lid is opened and the high-temperature concrete is heated. A method for curing concrete products, characterized by taking out a cured product. 2. The high temperature dry pressurized gas introduced into the autoclave is a gas obtained by heat-exchanging air pressurized by a compressor with water vapor discharged from the autoclave. Curing method for concrete products. 3 Connect the boiler 1 for pressurized steam generation to the autoclave container 3 via the valve 2, connect the steam discharge pipe 4 with the valve 5, and connect the pressurized gas source 7 to the autoclave container 3 via the valve 10.
A curing device for concrete products connected to 4. A curing device for concrete products according to claim 3, wherein the steam exhaust pipe 4 and the pressurized gas source 2 are connected to each other via a heat exchanger 6. .