Method of heat-moisture treatment products

 

(57) Abstract:

The invention relates to the construction materials industry and can be used for heat treatment and drying of building materials. Method of heat-moisture treatment products in the slit camera products of combustion of natural gas includes the supply and recirculation of the coolant through the heat generator installed at a distance of 2/3 of the length of the chamber from its inlet with the inlet and the intake duct installed with the formation of conditionally closed loop of fluid flow which lead into the lower zone of the chamber perpendicular to the branch return conditionally closed loop. 3 Il.

The invention relates to the construction materials industry and can be used for heat treatment and drying of materials.

Known heat source, [1] for the implementation of the steam curing of concrete products. The disadvantage of this method of treatment is to increase the temperature of the medium, which leads to destructive phenomena and lower quality products.

There is also known a method of heat treatment of concrete products products of combustion of natural gas [2] with the application of the heat treatment with a violation of the heat transfer in the upper zone of the chamber due to overlay contours recycling.

The objective of the invention is to reduce gas consumption and increase the quality of treatment by gradually increasing the level of temperature fields and uniformity of heating products.

The problem is achieved by setting the heat source at a distance of 2/3 of the length of the chamber from its inlet and coolant in the bottom area of the camera perpendicular to conditionally closed loop recirculation of the coolant with the organization of heat and mass transfer. in the upper part of the chamber from the open surface of products.

In Fig. 1 shows the layout of the generators of Fig. 2 - cut a slit camera; Fig. 3 the temperature distribution in the center of the panel depending on the temperature in the upper zone of the chamber.

The heat source 1 and the recirculation fan 2 (Fig. 2) installed on the floor of a slit camera 5. In the chamber 5 is equipped with a pallet-trolley 4, which are expanded clay, concrete panel 3.

For the study of heat and mass transfer in the working chamber 5 were installed chromel-kopelove thermocouple on the camera height and thickness of the product 3, indicated by numerals 1 to 8 in Fig. 2, which corresponds to temperatures

1 coolant in the upper nonpoverty panel;

6 pallet form;

7 coolant in the lower zone of the chamber;

8 the temperature of the concrete in the center of the control cube.

An example of the method. The study was conducted in one of the four slit cameras Poltava house-building plant.

In Fig. 1 shows the layout of generators. Chamber length 88 m, width 4 m and height 2 m Distance from the rail head to cover is 1.2 m In the slit camera is 11 pallet trolleys length of 8.8 m Material enclosing structures of heavy concrete. On the floor of each chamber according to the project there are three heater CURRENT 1.

One is in the area of heating, two in the area of the isothermal heating products. System piping and fans on each camera form a recirculation system that provides heat exchange of the combustion products of natural gas panels.

According to the latest recommendations in the Manual for heat treatment of concrete products products of combustion of natural gas (SNiP 3.09.01-85) one heat source in the area of isothermia has been disabled.

Research was initially conducted with two remaining generators - mode 1. The camera has three heat is the Amer at the same time is 35 m3concrete exterior wall panels, the weight of the metal mold and the pallet trolleys is 121 so

After research work of a slit camera mode 1 were carried out detailed studies of the operation of one boiler, installed in the area of isothermia at a distance of 2/3 of the length from the entrance into the camera.

This is particularly important installation location of the heat source along the length of the camera, which is one of the main points of the invention. In this case, investigated three possible modes (first with two generators, the second boosted with a single heat source, the processing time of 14 hours and extended - 22 h mode 3 with one generator).

A significant role is played by way of the coolant in the slit camera. It turned out that the process of heat-moisture treatment (TWT) can be carried out using only one heat source. For this heat source should be placed at 2/3 of the length from its inlet (58 m), and the coolant should be submitted under the panel, perpendicular to the movement of the trolleys. As a result of this arrangement of the heat generator and method of supplying fluid obtained optimal recirculation of products of combustion of natural gas in the chamber to ensure that the her and a sharp reduction in natural gas consumption.

Found in the studies of optimal dimensions of the cross section of the upper zone, allowed to exclude this partition separating thermal zone of a slit camera. As a result, the rate of recirculation of products of combustion in the upper zone of the chamber increased and accordingly, the resulting intensification of the process of heat exchange between the environment and panels. The dimensions of the cross section of the upper zone of a slit camera above the panels was 4,0x0,2 (h) m (Fig. 2).

The proposed scheme of installation of one of the heat generator in accordance with the invention is shown in Fig. 1. As a result of changing temperatures and determination of evaporation (moisture) in cross sections of the camera as the movement of the panels on the pallet trolleys found the most effective mode of heat-moisture treatment within a given performance.

In Fig. 3 shows the temperature change in the center of the panel and the environment along the camera for three of the investigated modes.

the 1st type of modes. Worked two heater CURRENT 1 (one in the preheating zone, the second zone isothermia) the duration of the heat treatment t 17 h curves of temperature changes in the center of the panel depending on the temperature of the environment showed that when outlinename when forced mode above, than a slender 20 - 25oC and 23 39oC than in mode 1. The heating rate of the concrete in the center of the panel was extended mode 2 4oC per hour, when forced mode 2 and mode 1 4 6oC.

Also noted a rapid rise of temperature in the initial stage of heating in modes 1 and 2, which leads to intensive evaporation of the mixing water of concrete at the stage of heating and prevents hydration of the cement, which leads to the dryness of the surface of the external wall panels.

the 2nd type of modes. Worked one heater CURRENT 1 in the area of isothermia, duration of heat treatment t 14 h (forced mode).

the 3rd type of modes. Worked one heater CURRENT 1 in the area of isothermia, duration of heat treatment t 22 h (extended mode).

Thus, the elongated mode 3 is less energy intensive than the "forced" mode and mode 1 with two generators, as at the stage of isothermal heating is additional heating of the concrete by isothermal reactions hardening of the concrete, which does not require increasing the consumption of natural gas for the heat treatment of the wall panels.

The operation of the two generators in the area of isothermia and Denmark in the upper zone of the chamber;

b) results in excessive gas 1.6 times;

C) leads to "thermal shock" at the stage of heating the exterior wall panels, which leads to destructive phenomena at the boundary layers of expanded-clay lightweight concrete finishing layer and the destruction of adhesion between them.

One heat source (mode 3) allows to reduce the temperature to heat the concrete in the area of isothermia to 74 85oC, preventing its increase up to 120 140oC, as recommended SNiP 3.09.01-85 and does not reduce the daily performance of slit cameras.

Research and optimization of thermal regimes will reduce the number of generators and recommend change p. 7.2 "Manual on heat treatment of concrete products products of combustion of natural gas (SNiP 3.09.01-85) in terms of mandatory installation of two generators in the cells of continuous operation of more than 200 m3(in our case the volume of the chamber was 650 m3and optimal thermal regime provided one heat source.

Soft mode of heat treatment with a single heat source in the area of isothermia eliminates the destructive effects associated with the evaporation of moisture from the body of concrete, has a positive impact on the quality of the item is and the heat and humidity processing concrete 1.6 times, while also improving the quality of the exterior concrete panels. Soft mode of heat-moisture treatment panels contributes to the quality of products within a given performance.

When steam curing due to the intensification of recirculation of products of combustion gas obtained by reducing the cross-sectional space of the upper zone of the camera, intensified heat and mass transfer in the slit camera by increasing the coolant flow rate. Provides reduced output humidity external wall panels (about 8.6%) after heating. (According to GOST 13015.083 handling moisture lightweight concrete external wall panels should not exceed 13% close to the equilibrium (5 6%), which significantly improves thermal characteristics of external wall panels).

It is established that the efficiency of slit cameras using the coolant of the combustion products of natural gas at the specified method is 82.5 percent, which far exceeds the efficiency of the pit cameras operate on the same carrier (24%).

One boiler will reduce the temperature to heat the concrete in the area of isothermia to 74 85oC, preventing its increase up to 120 - 140oC, which recommended SNiP 3.09.01-85, without reducing the daily performance of slot kamaki products in the slit camera products of combustion of natural gas, including supply and recirculation of the fluid products of combustion through a heat source placed on the roof of the tunnel chamber with inlet and the intake duct installed with the formation of conditionally closed loop of fluid in the chamber, wherein the heat source is installed at a distance of 2/3 of the length of the chamber from its inlet, and the flow of the coolant is carried out in a lower zone of the chamber perpendicular to the branch return conditionally closed loop.

 

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