WO2018111141A1

WO2018111141A1 - Method for producing structural expanded clay gravel

Info

Publication number: WO2018111141A1
Application number: PCT/RU2017/000118
Authority: WO
Inventors: Елена Васильевна Панкратова; Владимир Артемьевич ФЁДОРОВ
Original assignee: Елена Васильевна Панкратова; ВИБЕ, Алексей Зигфридович; Владимир Артемьевич ФЁДОРОВ
Priority date: 2016-12-16
Filing date: 2017-03-07
Publication date: 2018-06-21
Also published as: RU2639010C1

Abstract

The invention relates to the structural materials industry and can be used for producing increased-strength structural expanded clay gravel and lightweight structural concretes based thereon. A method for producing expanded clay gravel comprises feeding partially dried raw granules into a rotary furnace; in consecutive zones of the furnace, subjecting the granules to drying and calcining until expansion thereof while moving the granules from one end of the furnace to the other; and finally cooling the expanded clay granules. The characterizing feature of the method is that, in a first zone of the furnace, granules are dried while the temperature is increased to 450-500°C; then, in a second zone, preliminary calcining is performed while the temperature is increased from 500 to 1000°C at a higher rate than during drying; and in a third zone of the furnace, final calcining is performed at a temperature of 1050-1100°C. The process is conducted in an oxidizing medium. Following final calcining, the expanded clay granules are subjected to intensive cooling to 60°C by a stream of cold air. The method makes it possible to produce structural expanded clay gravel comprised of granules with a microporous outer layer and a solid core, and having a high mechanical strength and a density ranging from 600 to 800 kg/m3.

Description

METHOD FOR PRODUCING A STRUCTURAL

CERAMZITE GRAVEL

FIELD OF TECHNOLOGY

The invention relates to the building materials industry and can be used for the production of structural expanded clay gravel of increased strength and lightweight structural concrete based on it.

BACKGROUND

The known and most common method for producing traditional expanded clay gravel with a specific density of 200-500 kg / m ³ is the method, the first stage of which is plastic processing, which consists in mixing raw clay on special clay mixers, molding raw granules from it, which are further processed, giving them a spherical shape. Dusting of raw granules with refractory powders may be used. Then the granules are dried in a tumble dryer.

The dried granules are sent to a furnace made in the form of a rotating drum with a certain angle of inclination, where first the granules are dried by gradually heating to 200 ... 600 ° C, then when firing at about 1200 ° C, clay swells and the surface layer of the molded granule is melted . As a result of subsequent cooling, light expanded clay granules with a high degree of bulk porosity are formed (S. M. Itskovich, L. D. Chumakov, Yu. M. Bazhenov. CONCRETE FILLERS TECHNOLOGY. M: Higher School, 1991, chapter 8, “Technology expanded clay production. ”http://bibliotekar.ru/ spravochnik-98-beton / 72.htm) Despite the widespread use of lightweight expanded clay, their mechanical characteristics are not high (compressive strength in the cylinder does not exceed 1.5 MPa). Therefore, a very urgent problem is their hardening.

The solution to this technical problem will expand the scope of expanded clay gravel in the construction of various structures and roads, requiring, along with other useful properties, high strength characteristics.

SUMMARY OF THE INVENTION

The technical result of the present invention, which allows to solve this problem, is to obtain structural expanded clay granules (expanded clay gravel) with a solid microporous shell and a dense core, with high mechanical strength at a density in the range of 600-800 kg / m ³ .

The technical result is achieved by the method of producing expanded clay gravel, which consists in the fact that the dried raw granules are fed into a rotary kiln, the granules are dried in the successive zones of the kiln and fired when the granules move from one end of the kiln to the other and when the temperature rises along the kiln and then expanded clay granules they are cooled, and in the first zone of the furnace the granules are dried at a temperature increase up to 450-500 ° С, then in the second zone preparatory firing is carried out at a temperature increase from 500 to 1000 ° and at a higher temperature increase rate than in drying the pellets, and in the third zone of the furnace is carried out final annealing at 1050-1100 ° C. In addition, before drying the granules, they are dusted with a modified zeolite.

In addition, after the final firing, the expanded clay granules are intensively cooled to 60 ° C with a stream of cold air while the hot air is taken out with an additional smoke exhauster

The formation of the complex morphological structure of the expanded clay granule occurs due to the fact that its solid carbonaceous core interferes with gas formation processes, thus preventing the process of active expansion in the center of the granule.

As a result of the implementation of the proposed method, the formation of spherical granules of expanded clay gravel having a solid, mechanically strong core and microporous shell, which significantly distinguishes their morphology from granules obtained by known methods.

MODE FOR CARRYING OUT THE INVENTION

A method of obtaining structural expanded clay gravel is as follows.

Raw granules are produced using known technology. Clay raw materials from the developed quarry enter the territory of the site by truck and are unloaded in the clay reserve, where it is fed with a bulldozer to the clay-ripper, where primary grinding takes place. Further, the raw materials are dosed in accordance with the parameters of the technological regulations and through the box feeder and conveyor belt, is fed to the stone extraction rollers, where the clay is ground to the required size and removed stony inclusions. Then, through a conveyor belt, the crushed clay enters the twin-shaft paddle mixer, where it is further crushed and moistened with water to form moisture. Additives to the base material are also fed into the mixer when adjusting the mineralogical and chemical composition is required through the additive dispenser. After the mixer, the prepared material enters the forming rollers, where it granulates. Then, through a conveyor belt, the material enters the dryer drum, where the granules are dried to the required humidity. The temperature in the dryer drum is set according to the curve of firing in a rotary kiln 450 ° C at the entrance to the dryer drum and 150 ° C at the exit of the dryer drum. The material after the drying process has a moisture content of 8-12%. Pellets from the dryer drum through a conveyor belt enter the hopper of the technological stock of granules, having previously gone through the process of dusting with modified zeolite. Zeolite is a natural material, aqueous aluminosilicate, an igneous-sedimentary rock with a rigid framework. Zeolite undergoes two stages of modification - mechanical activation and thermal activation. Dusting is carried out through a hopper with a dispenser.

Powdered granules from the stock hopper through a metering device - a plate feeder enter the rotary kiln, where technological firing takes place. Firing is carried out in a rotary kiln, which is a cylindrical metal drum with a diameter of 2.5 m and a length of 40 m, lined with fireproof bricks from the inside. The furnace is installed with a slope of 3% and rotates around its axis. Due to this, raw granules fed to the upper end of the furnace, when rotation gradually move to the other end of the furnace, where a special burner with adjustable parameters is installed: torch length, power of the supplied air flow for combustion, selection of hot air - all this is achieved by adjusting the air flows of the supplied and drawn air and the operation of the blower fans, and the smoke exhaust. With the help of a smoke exhauster, the furnace is divided into technological zones: a drying zone, a preparation-softening zone for granules, a boiling-roasting zone and a pre-cooling zone. The firing curve is adjusted and the length of the technological zones is changed due to the operation of the exhaust fan and burner. The rotary kiln works according to the counterflow principle: raw granules move towards the flow of hot gases. The average residence time of the granules in the oven is 50 - 70 minutes. Firing is carried out according to a given temperature curve.

Dried raw granules enter the furnace at a temperature in the furnace of 350-450 ° C, four zones of the furnace pass. The first zone is the granule drying zone, the temperature of the granules in this zone gradually rises to 450-500 ° C. Then the second zone passes - the preparation zone, with a sharp increase in temperature from 500 to 1000 ° C. This is the main zone in which the formation of the active shell and the formation of a carbonaceous core inside the granule occurs - the effect of a black apple, which gives strength to the expanded clay granule. This process should proceed in a high-speed mode, on the surface of the granule Fe ₂ 0 ₃ prevails over FeO, and in the middle, on the contrary, this contributes to the formation of a porous structure on the surface. At a temperature of 950 ° С, clay shrinkage begins, and oxygen access to the center of the granule becomes more difficult, unburned carbon (carbonaceous) remains in the center balance). The preparation zone by technological methods is reduced, and the area of the explosion is increased. The formation of a black apple interferes with the processes of gas formation and prevents the process of bloating. The core is sealed, while the outer shell remains porous. The thickness of the outer shell is 225-250 microns. The whole process takes place in an oxidizing environment, which is created by supplying excess air. Ferrous impurities are present in clays in the form of oxide compounds. At a temperature of 950 ° C, oxide compounds are intensively reduced to sour, contributing to compaction. In this case, a black core remains inside the granules, which indicates the reduction of ferrous oxides to a metallic state. All these processes take place in the preparation zone. With the classical method of producing expanded clay, the preparation zone is not reduced, but lengthened.

Further, in the third zone - the zone of the blasting, firing occurs at a temperature of 1050-1 100 ° C, at which the outer shell of the granules swells.

Then in the fourth zone of the furnace there is a process of intensive cooling - a decrease in temperature from 1,100 to 800 ° C.

Then expanded clay enters the layered refrigerator, where the material is cooled to 60 ° C at a certain speed. Cooling occurs due to the supply of a cold air stream using a blower fan and an additionally installed smoke exhauster, which performs the selection of hot exhaust air. Then, through the conveyor belt, the calcined and cooled material along the bucket elevator enters the fractionation section. Then, through gravel sorting, a capacity of 300 m each is distributed into fractions in silo banks. Then, through the metering devices, a high-strength ceramic porous aggregate with an active shell is loaded into vehicles or containers (big bags). The whole technological process is controlled by ACS.

Compared with the known method, the proposed method is characterized by a longer drying period to a lower temperature, after which the heating rate of the granules increases sharply and preparatory firing takes place. The length of the preparation zone and the preparation time of the granules is reduced, the preparation process occurs with a sharper rise in temperature, and the temperature of the main firing and its time are reduced in comparison with the known method. This ensures the formation of granules with a dense core.

A feature of the proposed method is to change the classical mode of expanded clay firing, which leads to a decrease in gas consumption and an increase in productivity. This technology can be used on clays that contain a lot of organic matter, with early onset of the liquid phase and with a low expansion temperature range, the difference between the maximum possible firing temperature and the start temperature of expansion of this raw material is called. The temperature at which swelling begins is taken to be the temperature at which expanded clay with a granule density of 0.95 g / cm3 is already obtained. The maximum possible firing temperature is the temperature of the beginning of the fusion of the surface of the granules. The composition of the clay raw material, its moisture at the entrance to the kiln, dusting with modified zeolite, changing the kiln regimes, rebuilding the kiln zones, creating a black apple effect inside each granule, by analogy with ceramic bricks, maintaining an oxidizing environment in the preparation zone, installing additional equipment - a smoke exhauster selecting hot humid exhaust air from a layered refrigerator, using a burner device with adjustable parameters - all this makes it possible to obtain ceramic s filling with an active coating. In standard classical technology, these techniques are absent.

The obtained expanded clay granules have a spherical or oval shape, the diameter across is 10-20 mm with a porous shell 250-290 microns thick. The resulting expanded clay gravel has a density of 600-800 kg / m and is characterized by a strength that is 50-70% higher than the strength of traditional expanded clay gravel.

The resulting structural expanded clay gravel along with high strength has a number of competitive operational characteristics, such as low water absorption

(5-10%), high heat and sound insulating ability, water and frost resistance, as well as incombustibility.

It is shown that structural expanded clay concrete, in which gravel obtained by the proposed method is used as a filler, strength class B25-B50 has high impact strength, frost resistance, crack and seismic resistance compared to heavy concrete on crushed stone ability to withstand large bending loads, good abrasion performance. These competitive characteristics are due to close values of the coefficients of thermal expansion of expanded clay and concrete matrix, good interfacial adhesion (due to the close chemical affinity of the components of the mixture). The result is increased operational reliability and durability of concrete structures.

In addition to the above advantages, the use of structural expanded clay gravel (instead of crushed granite) in concrete structures can significantly reduce their weight, consumption of embedded reinforcement and, thereby, reduce the load on the foundation and other supporting structures.

The development and inclusion in the line of innovative types of modern equipment, devices and special non-standard devices, as well as changes in the standard technological process of firing and cooling, allows to obtain modified expanded clay gravel with other physical and mechanical properties.

Claims

FORMULA

1. The method of producing expanded clay gravel, which consists in the fact that the dried raw granules are fed into a rotary kiln, the granules are dried and calcined in successive zones of the kiln when the granules are moved from one end of the kiln to the other and the temperature increases along the kiln and then the expanded clay granules are cooled characterized in that in the first zone of the furnace the granules are dried at a temperature increase up to 450-500 ° С, then in the second zone preparatory firing is carried out at a temperature increase from 500 to 1000 ° С and at a growth rate temperatures higher than when drying granules, and in the third zone of the furnace carry out the final firing at 1050-1100 ° C.

2. The method according to claim 1, characterized in that before drying the granules they are dusted with a modified zeolite.

3. The method according to p. 1, characterized in that after the final firing, the expanded clay granules are intensively cooled to 60 ° C with a stream of cold air while the hot air is taken out.