RU2433102C1 - Method of drying moulded air bricks - Google Patents

Abstract

FIELD: process engineering. ^ SUBSTANCE: invention relates to drying damp capillary-porous materials and may be used in production of ceramic bricks. Proposed method comprises placing moulded brick on metal cathode with filtration layer wherefrom moisture is removed by convective drying and arranging node with clamping appliance atop said brick. Note here that air brick is coated by heat-insulating waterproof cap and anode is secured to said clamping appliance. Said clamping appliances represents a spring to be secured to cap inner surface. ^ EFFECT: higher efficiency. ^ 1 ex, 2 dwg

Description

The invention relates to methods for drying wet capillary-porous materials and may find application in the production of ceramic bricks and large-format ceramic products.

There is a method of drying large-sized ceramic building products by electroosmosis (RU 2004520 C1, class C04B 33/02, publ. 12/15/1993, (II), pillar 5, 10-11, Fig. 13-14, total 13 s.), including placing the dried product on a metal cathode with a filtering layer of sand, placing the anode on top of the product with a load.

The disadvantages of this drying method include the inconvenience of performing the operation of installing the anode, which is installed with a load, which takes additional time, as well as the low quality of the dried product due to the heterogeneity of the moisture content of individual parts of the dried brick, which occurs as a result of:

- accelerated uncontrolled drying of the side surfaces of the dried product, due to evaporation of moisture into the environment, which leads to cracking of the raw brick;

- slowing down the drying of the lower surface, as moisture from the filter layer is removed by gravity. Thus, a large amount of moisture remains in the filter layer and in the dried product, in the area of their contact with the cathode, which leads to cracking and delamination of the product during further heat treatment (firing).

The invention solves the problem of increasing the drying efficiency of raw brick by reducing the number of preparatory operations to install the anode and the time that must be spent on their implementation, and improving the convenience of installing the anode, as well as improving the quality of dried brick by increasing the uniformity of its moisture content.

To obtain the desired technical result in the known drying method, which includes placing the dried product on a metal cathode with a filter layer, placing an anode equipped with a pressing device on top of the product, it is proposed to cover the raw brick with a heat-insulating moisture-proof hood, to attach the anode to the pressing device, in which quality use a spring, which is fixed on the upper inner surface of the cap, and remove moisture from the filter layer by forced convection th drying the bottom surface.

The graphic materials attached to the description show:

figure 1 - drying scheme described in the closest analogue;

figure 2 - drying scheme of the proposed method;

figure 3 - schematic representation of the cathode electrode in the form of a grid on the surface of the filter layer;

figure 4 - section aa in figure 3.

The following notation is used on the attached diagrams:

1 - raw brick; 2 - filter layer; 3 - anode electrode; 4 - cathode electrode; 5 - voltage source; 6 - electroosmotic diffusion of moisture from the raw material into the filter layer; 7 - drainage of moisture from the filter layer; 8 - heat-insulating moisture-proof cap; 9 - clamping spring; 10 - convective evaporation of moisture; 11 - coolant flow.

The proposed method of drying a raw brick (figure 2) is as follows. The molded raw brick is placed on a metal cathode electrode, laid in a filter layer, and covered with a moisture-proof, heat-insulating cap made of polyethylene equipped with an anode electrode (a metal plate made of corrosion-resistant steel). The anode electrode is attached to the spring to provide pressure to the upper surface of the dried raw brick. The spring is fixed on the inner upper surface of the hood. As the filter layer, a porous material with high water absorption and high moisture capacity (for example, foam lightweight with an average density of up to 300 kg / m ³ ) is used.

The cathode is made in the form of a grid (Fig. 3, Fig. 4) laid in a filter layer so as not to impede the diffusion of moisture from the raw brick.

Under the action of an external electric field, the liquid filling the raw brick moves to the cathode, and moisture is removed from the filter layer by a convective drying method.

The current from the anode to the cathode, the temperature and velocity of the coolant are selected in such a way that the moisture removal from the filtering layer by convective drying should not be less than the amount of moisture removed from the dried product. This achieves the absence of overmoistening of the dried product in the cathode zone, and hence the uniform humidity in the body of the dried raw brick, i.e.:

Q _e <Q _k ,

where Q _e - the amount of moisture released from the dried product by electroosmotic forces;

Q _to - the amount of moisture released from the filter layer by convective drying.

where S is the cross section of the raw brick in the plane of contact of the electrodes, cm ² ,

U is the voltage applied to the electrodes, V;

t - current transmission time, s;

L is the distance between the electrodes, see

Q _k = β · (U _pt -U _t ),

where β is the coefficient of surface moisture, kg / m ² h;

U _pt - moisture content of the filter layer, kg / kg;

U _t - moisture content of the coolant, kg / kg.

Drying of the outer side layers of the product does not occur due to the use of a thermally insulating moisture-proof hood covering the product to be dried. Thus, the occurrence of cracks on the lateral surfaces of the raw brick due to evaporation of moisture into the environment is excluded.

A specific example of the method.

Raw brick 250 × 120 × 65 mm with an initial volumetric moisture content of Q _in = 0.5 (which corresponds to a moisture content of 25%) enters the dryer, where it is installed on the cathode with a filter layer and covered with a heat-insulating moisture-proof hood, to which the fixture is attached to the upper inner surface for clamping the anode to the product, made in the form of a spring to which the anode is attached.

Drying is performed by electroosmosis by applying a voltage of 10 V to the anode and cathode, and moisture from the filter layer is removed by convective drying using a coolant flowing around the bottom surface of the filter layer with parameters: temperature - 60 ° C, relative humidity - 30% and speed - 1.3 m / s Drying time to a final moisture content of 3.5% raw brick is about 14 hours.

An experiment was conducted comparing the known and proposed drying methods.

When drying raw brick by a known method, the time to install the anode and load was 18 s. When drying according to the proposed method, the installation time of the cap with the anode attached to the product to be dried was 6 s, which, with a dryer capacity of 10 million bricks per year, would amount to more than 33,000 hours.

Also, the results of the experiment confirmed an increase in the quality of the dried raw brick in comparison with the known drying method. The bricks dried according to the proposed method had a greater uniformity of moisture content, which was expressed in the absence of cracking and delamination after drying and their further firing, which had a positive effect on improving the quality of the final product.

Claims (1)

A method of drying a molded raw brick, comprising placing a dried product on a metal cathode with a filter layer, placing an anode equipped with a pressing device on top of the product, characterized in that the raw brick is covered with a heat-insulating moisture-proof hood, the anode is attached to the pressing device, in which quality use a spring, which is fixed on the upper inner surface of the cap, and moisture from the filter layer is removed by forced convective drying of its lower surface awns.

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