RU2099308C1 - Method for manufacture of clayware by semidry molding and plant for preparation of powder from argillaceous raw material - Google Patents

Abstract

FIELD: technology of manufacture of clayware and materials possessing high strength and frost resistance from low-plastic and moderately plastic argillaceous and argillaceous-like raw materials with low content of argillaceous particles. SUBSTANCE: method includes grinding of argillaceous-like and argillaceous raw materials, milling and drying in fluidized bed by means of heat carrier vortex flow with vertical and horizontal components, moistening, homogenization, molding and firing. Argillaceous raw materials are preliminarily crushed and then dried in fluidized bed and milled to produce particles sizing not more 300 mcm. Noncooled powder with temperature 50-80 C is moistened and homogenized. In this case the articles of the highest quality are manufactured with the use of powder of the following fraction composition, wt.-%: up to 20 mcm, 40-50; 20-100, 20-30; 100-300 mcm, the balance. Drying chamber of the plant additionally has movable cone located in chamber lower part, oval body in center of chamber under loading feeder. Guide blade are movable due to its mounting on activating wheel above which false wall is fastened and provided with louvers. Activating wheel and false wall are communicated with air distributor by means of separate gas ducts. EFFECT: higher efficiency. 3 cl, 1 dwg , 1 tbl

Description

 The invention relates to techniques and technologies for producing ceramic materials, and products having high strength and frost resistance, from low-plastic and moderately plastic clay and clay-like raw materials with a low content of clay particles.

A known method for producing ceramic bricks by the method of semi-dry pressing, including coarse grinding of quarry clay (crushing), drying clay, grinding dry clay into powder (grinding), sieving, preparation of press powder and its steam humidification, pressing bricks and firing [1]
The disadvantage of this method is that the products obtained with its help have low bending strength and low frost resistance, which is reflected in GOST 530-80.

The closest technical solution selected for the prototype is the method by which the crushing, drying and grinding of clay raw materials is carried out in one apparatus: a pipe-dryer. In this case, crushing is carried out using a hammer mill, which is built into the pipe-dryer, and drying and grinding is carried out by means of a vortex coolant stream having vertical and horizontal components. After wetting, the brick is pressed from the obtained powder and burned [2]
The disadvantage of this method is that the efficiency of the line according to this method decreases with increasing career humidity of the raw materials, and the resulting ceramic products have a low tensile strength in bending and frost resistance.

A device for grinding and drying, designed for viscous clay materials, including a vertical cylindrical body with estrus, which feeds raw materials, a crushing chamber with a rotor and grates, a grinding chamber with a set of beats, a perforated disk with a conical glass, air supply channels with shutters, and crushing and grinding chambers are made gas permeable [3]
The disadvantage of this device is the large number of nodes and parts that block the gas stream. Mechanical parts rubbing against each other become clogged with dust and lead to frequent stops and breakdowns. In addition, when processing raw materials for quarry moisture in the area of the hammer mill, a shotcreting effect is observed: that is, clay raw materials are pressed onto reflective plates, grates and clogs the grinding chamber, which leads to the unit shutting down.

The closest solution selected for the prototype of the device is a Spin-flash dryer, which has only one moving device: a carousel-type mixing device for mechanical crushing of the material. The known technical solution includes a screw conveyor, a vertically located drying chamber (dryer pipe) with a rotary-type mixing device, an air distributor, a set of guide vanes and nozzles for supplying and discharging a heat carrier, a heat generator, a cyclone (classifier) and a hopper. The apparatus is used to obtain fine-grained powder when drying masses, sludges and pastes [4]
A disadvantage of the known installation is that when crushing clay raw materials with quarry moisture by a carousel-type mixer, raw materials stick to it and a shotcrete effect is observed, which leads to a unit shutdown. In addition, the known device does not provide the necessary properties of the obtained powder from low-plastic and moderately plastic clay and clay-like raw materials necessary to obtain high-quality ceramic products in accordance with the claimed method.

 The problem solved by the claimed technical solutions is to increase the stability and productivity of the process of obtaining high-strength and frost-resistant ceramic products from low-plastic and moderate plastic clay and clay-like raw materials even in conditions of its high humidity.

This object is achieved in that in the inventive method, including crushing clay raw materials, grinding and drying it in a fluidized bed by means of a vortex of a coolant having vertical and horizontal components, moistening, homogenization, pressing and firing, clay raw materials are preliminarily crushed and then subjected to drying and grinding in a fluidized bed to a particle size of not more than 300 microns, and the un-cooled powder, with a temperature of 50-80 ^o With moisturize and homogenize.

 It is preferable to obtain a powder of the following fractional composition, wt. up to 20 microns 40-50; 20-100 microns 20-30; 100-300 microns rest.

 The problem is also solved due to the fact that in the inventive installation for producing powder from clay raw materials, including a vertically located drying chamber with a feeder, an air distributor, a set of guide vanes and nozzles for supplying and discharging a heat carrier, a heat generator, a smoke exhauster, a cyclone and a hopper, the drying chamber additionally contains a movable cone located in its upper part, an oval body fixed in the center of the chamber under the loading feeder, the guide vanes are movable azmescheniya their wheel-activator, over which is fixed a "false" wall provided with blinds, wheel-activator and "false" wall by separate gas ducts are connected to the air distributor.

 The claimed technical solution is novel.

The inventive method in relation to the prototype has the following significant differences: clay raw materials are previously crushed; pre-crushed clay raw materials are subjected to simultaneous grinding and drying and vortex flow to a maximum particle size of 300 microns; humidification and homogenization is subjected to hot powder with a temperature of 50-80 ^o C.

 A private distinguishing feature of the proposed method is that they receive a hot powder of the following fractional composition, wt. up to 20 microns 40-50; 20-100 microns 20-30; 100-300 microns rest.

 The inventive installation with respect to the prototype has the following essential features: a drying chamber (pipe-dryer_ additionally contains a movable cone located in its upper part; a drying chamber (pipe-dryer) further comprises an oval body fixed in the center of the chamber under the loading feeder; guide vanes made movable by placing them on the activator wheel; a “false” wall equipped with blinds is fixed above the activator wheel; the activator wheel and the “false” wall are connected to separate gas ducts with air distributor.

 The set of essential distinguishing features of the claimed technical solutions, as well as their relationship allow us to solve the problem and make a conclusion about the conformity of the claimed technical solutions to the criterion of "inventive step".

 The drawing shows a General view of the installation for the preparation of powder from clay raw materials in the context.

 The powder preparation plant comprises a drying chamber (pipe-dryer) 1 with a screw feeder 2 for loading pre-crushed raw materials, which prevents the intake of cold air into the drying chamber, a movable cone 3, which controls the fractional composition of the obtained powder, an oval body 4 with low aerodynamic resistance for the organization of the fluidized bed, where fine grinding, mechanization and drying of raw materials are carried out in the area above the loading feeder and the creation of an air cushion below this area to prevent Ia spillage of raw materials down. The installation also contains an activator wheel 5, which has a set of blades tangentially located on it to capture the coolant and create a vortex flow, in which the horizontal velocity component is many times greater than the vertical. The heat carrier, separated by an air distributor 6, enters the drying unit through an activator due to its operation as a fan and through the blinds of the “false” wall 7 due to injection. The transportation of dried and crushed raw materials is carried out to a greater extent by a smoke exhauster 8. The installation also contains a heat generator 9, a cyclone 10 and a silo with a hermetic discharge device 11.

 Installation works as follows.

 Raw materials of career humidity, previously crushed to a homogeneous fractional composition by a feeder 2, excluding suction of cold air, are uniformly fed into the drying chamber 1, through which the coolant (hot gases) passes, the volume and temperature of which is determined by the capacity of the installation and the career humidity of the raw materials. Hot gases from the heat generator pass through the air distributor 6, which controls the direction of the resulting flow rate, and some of them are captured by the lower blades of the activator 5, and the remaining coolant enters the drying chamber through the blinds of the "false" wall 7 due to injection. In the drying chamber, the heat flow is twisted by the activator and rises up it due to the operation of the smoke exhauster 8 and to a lesser extent due to the operation of the activator wheel. It is necessary that the resulting speed of the air vortex inside the drying chamber be equal to the feed rate of the clay particles entering the unit. In this case, the previously crushed raw material is in a state of fluidization, dried in a heat stream, subjected to fine grinding and mechanical activation due to abrasion of particles on the inner surface of the dryer pipe and impact of them against each other in a vortex flow moving at high speed around the circumference. Large pieces of raw materials that are accidentally caught are held by an air cushion in the zone of the oval body 4, where the flow rate due to a change in the cross section of the dryer pipe exceeds the velocity of particles, and is crushed in the lower part of the fluidized bed 12. In this case, the activator wheel does not become clogged with raw materials, and the drying chamber operates stably. Using the movable cone 3 from the fluidized bed, it is possible to select the powder of the desired fractional composition.

 Powder with a high specific surface can be obtained in this drying chamber. In this case, the contact area between particles of different mineral types increases, they undergo mechanical activation during such grinding, which results in deep structural disturbances due to disordering of crystal lattices. The disordering is expressed in an oriented or random displacement of layers and grids relative to each other. Displacements of this kind lead to the appearance of dislocation interactions, and mechanically activated particles of different mineral types bind to each other already in the zone of the fluidized bed.

 Mechanically activated powder by pneumatic transport due to the operation of the smoke exhauster 8 enters the cyclone 10 and enters the silo 11 after cleaning the dust-air mixture. The product obtained differs in technological properties from the powder obtained by the prototype. It has a low sensitivity to drying; the strength of samples made on its basis increases with compression and bending, and frost resistance also increases (see table).

 The most high-quality is considered a powder having the following fractional composition, wt. up to 20 microns 40-50; 20-100 microns 20-30; 100-300 microns rest.

From silo 11, the powder with a moisture content of 2-3% and a temperature of 50-80 ^o C is sent to humidification and homogenization to obtain a press powder used in the manufacture of ceramic products by semi-dry pressing. Moreover, the resulting powder is directed to hydration and homogenization, as well as pressing necessarily hot; its storage and operating time for the future are unacceptable, since over time the effects of mechanical activation are smoothed, which subsequently affects the strength characteristics of the products obtained.

 The inventive method is confirmed by the examples shown in the table (examples 1-8).

 As can be seen from the table, the physico-mechanical properties of ceramic products made by the present method are qualitatively different from the properties of products made by the prototype. The resulting products are transferred to the class of facial ceramics, which allows them to be used in structures without a protective coating. In addition, the processing of raw materials due to fine grinding eliminates the harmful effect of carbonate inclusions, which is expressed in the formation of "dutiks" inside and on the surface of products.

 The claimed method and device provide the possibility of a stable high-performance process for producing mechanically activated powder from low and moderate plastic clay or clay-like raw materials for the production of ceramic products with high strength and frost resistance.

 Upon receipt of a powder with a particle size of more than 300 microns, products based on it sharply decrease bending strength and frost resistance.

 All tests were carried out on one moderately ductile raw material; humidity of the press powder, pressing pressure, drying and firing conditions were the same.

Claims (2)

1. A method of producing ceramic products by semi-dry pressing, including crushing clay raw materials, grinding and drying them in a fluidized bed by means of a vortex of a coolant having vertical and horizontal components, moistening, homogenization and firing, characterized in that the previously crushed clay raw materials are subjected to grinding particle sizes of not more than 300 microns, and moisturizing and homogenization serves unrefined powder with a temperature of 50 80 ^o C.  2. The method according to p. 1, characterized in that receive the powder of the following fractional composition, wt. Up to 20 μm 40 50
20 100 μm 20 30
100 300 μm Else
3. Installation of preparation of powder from clay raw materials, including a vertically located drying chamber with a feeder, an air distributor, a set of guide vanes and nozzles for supplying and discharging a heat carrier, a heat generator, a smoke exhauster, a cyclone and a hopper, characterized in that the drying chamber further comprises a movable cone placed in its upper part, an oval body fixed in the center of the chamber under the loading feeder, the guide vanes are movable by placing them on the activator wheel, above which th fixed false wall provided with shutters, the wheel-activator and a false wall separate gas ducts are connected to an air distributor.

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