RU2357936C1 - Method for thermal processing of adobe brick granules and separating medium for its realisation - Google Patents

Abstract

FIELD: technological processes; chemistry; construction.

SUBSTANCE: invention is related to production of granulated fillers for building mortars, concrete or used as independent loose heat-insulating material. Method for thermal processing of adobe bricks granules includes swelling of adobe brick granules in rotary furnace at efficient temperature in presence of powdery separating medium at ratio of separating medium and adobe granules of less than 1:1, but not less than 1:2 in volume. Adobe granules are used, which are produced from crushed basaltic andesite of Baranovskoe deposit with the following chemical composition (wt %): SiO₂ - 55.6-60.84; TiO₂ - 1.65-2.27; Al₂O₃ -13.97-16.26; Fe₂O₃ - 0.99-3.61; FeO - 3.98-6.89; CaO - 3.63-5.19; MgO - 2.11-4.22; MnO - 0.07-0.10; P₂O₅ - 0.22-0.44; K₂O - 3.00-4.33; Na₂O - 2.66-3.45; LoI (loss on ignition) - 0.41-2.56, with addition of at least sodium hydroxide solution in efficient amount.

EFFECT: reduced amount of powdery separating medium, reduced power inputs in production of granulated fillers.

11 cl

Description

The invention relates to the field of production of building materials, in particular the production of granular aggregates for mortars, concrete or used as an independent filling insulating material. The present invention also relates to the use of industrial waste as auxiliary materials in the heat treatment of granules of porous aggregates for their expansion and annealing.

It is known from the prior art that in the technological process for producing granular materials, the heat treatment process can be carried out in the presence of a separating medium, which is a powder material that prevents the sintering of raw granules between themselves during the heat treatment.

A known technology for the manufacture of granular foam glass in which granules obtained from ground glass is dried and foamed in a rotary kiln with ground quartz as a separation medium at a temperature of 780-820 ° C, the granules are annealed to a temperature of 30 ° C and the separation medium is removed [Demidovich B .TO. "Production and use of foam glass." - Minsk: Science and technology, 1972, p.198-201]. In another similar technology for the production of granular glass from cullet, ground quartz, talc or industrial alumina powders are used as a separating medium, and, for example, quartz river sand is used as quartz using this technology at a ratio of the separating medium and granules 1: 1, granules fired in a rotary kiln, and the separation of the granules from the separating medium is carried out after annealing [patent RU 2162825, publ. 02.10.2001]. In another similar method for producing granular foam silicate, dry ground clay, chalk or cement mixed with quartz sand less than 20 wt.% Are used as a separating medium [patent RU 2291126, publ. 01/10/2007]. The disadvantage of the technology of using a separating medium in the heat treatment process is increased energy consumption, because part of the furnace heat is spent on heating the separating medium itself.

As a prototype, the method of heat treatment of raw granules to obtain granular glass is selected, including swelling of raw granules at an effective temperature in the presence of a powdery separating medium in the form of fireclay sand, where heat treatment is carried out at a ratio of the separating medium and raw granules 1: 4 by volume [AT 257079 A, publ. 09/25/1967]. Despite the relatively small amount of separating medium used, this method cannot be effectively used for heat treatment of raw granules from other raw materials, for example, from rocks such as andesitobasalts.

The technical problem to which the present invention is proposed is to optimize the heat treatment of raw granules based on andesitobasalt in the presence in order to use the minimum possible amount of a separating medium to reduce energy consumption in the production of granular aggregates based on andesitobasalt.

The problem is solved by two proposed technical solutions.

A method for heat treatment of raw granules is proposed, including swelling of raw granules in a rotary kiln at an effective temperature in the presence of a powdery separating medium with a ratio of separating medium and raw granules less than 1: 1 by volume. New is that they use raw granules obtained from a measure of ground andesitobasalt with the addition of at least a solution of sodium hydroxide in an effective amount, and they use andesitobasalt from the Baranovsky deposit with a chemical composition, wt.%: SiO ₂ 55.60-60.84; TiO ₃ 1.65-2.27; Al ₂ O ₃ 13.97-16.26; Fe ₂ O ₃ 0.99-3.61; FeO 3.98-6.89; CaO 3.63-5.19; MgO 2.11-4.22; MnO 0.07-0.10; P ₂ O ₅ 0.22-0.44; 3,00-4,33 K ₂ O; Na ₂ O 2.66-3.45; PPP 0.41-2.56, and heat treatment is carried out at a ratio of the separating medium and raw granules of at least 1: 2 in volume. The specified lower limit of 1: 2, sufficient to effectively prevent the adhesion of raw granules to each other during the heat treatment, was determined theoretically and confirmed in practice, as will be shown below.

The ratio of the separating medium and granules 1: 2 in volume is better to use with a grain shape coefficient of raw granules of not more than 1.5.

After heat treatment, the powdery separating medium can be separated from the finished granules and sent for reuse.

As a powdery separating medium, it is better to use a powdery material with a grain size of fractions up to 0.63 mm.

At least one powdery material or a mixture of powdery materials selected from the group can be used as a powdery separating medium: dry ground clay, chalk, limestone flour, cement, river quartz sand, chamotte sand, ash from an incinerator, ashes of a heat and power plant of dry selection.

Raw granules obtained from ground andesitobasalt with an additional sodium nitrate solution can be used.

It is also proposed the use of ash containing unburned combustible substances, as a powder separating medium for the above method. The burning of such unburned combustible substances during the heat treatment leads to the release of additional heat, due to which energy costs are further reduced.

Ash with an unburned substance content of up to 15 wt.%, For example ash from incinerators, can be used.

You can also apply dry ash CHP, usually containing up to 10% wt. unburned coal.

It is better to use ash with a grain size of fractions up to 0.63 mm.

The invention is illustrated by the example of the developed production technology for the production of porous aggregate - porobasalt.

Porobasalt is an artificial porous aggregate obtained by heat treatment of granules prepared by granulating a raw material mixture containing andesitobasalt with the addition of sodium hydroxide and, if necessary, the production of a lighter aggregate, additional sodium nitrate.

As the main raw materials in the technology, andesite-basalts of the Baranovsky deposit of the Primorsky Territory, sodium hydroxide (NaOH), sodium nitrate (NaNO ₃ ), and separation powder are used.

The composition of the andesite-basalt rock of the Baranovsky deposit: plagioclase 40%, glass 30%, pyroxenes 30%, magnetite 1-3%, rarely apatite. Andesitobasalts have the following chemical composition (wt.%): SiO ₂ 55.6-60.84; TiO ₂ 1.65-2.27; Al ₂ O ₃ 13.97-16.26; Fe ₂ O ₃ 0.99-3.61; FeO 3.98-6.89; CaO 3.63-5.19; MgO 2.11-4.22; MnO 0.07-0.10; P ₂ O ₅ 0.22-0.44; K ₂ O 3,00-4,33; Na ₂ O 2.66-3.45; RFP 0.41-2.56. The density of the rock in the average field 2.39 g / cm ³ . Fluctuations in the natural moisture of the rocks are from 1.60 to 9.12%, an average of 3.21% in the field. True density ranges from 2.66 to 2.84 g / cm ³ ; field average 2.78 g / cm ³ . Water absorption - from 0.38 to 3.55%; field average 1.49%. Porosity from 3.75 to 29.95%.

As a separation powder, ash from the Vladivostok waste incineration plant with a share of unburned combustible substances of 7-15 wt.% Was used. Also used for these purposes were limestone flour (used in agriculture for deoxidizing the soil), cement, fine river quartz sand, or dry-ash CHP ash with a share of unburned coal of 4-10 wt.%, Not sintering in the sinter at temperatures up to 1000 ° C. Additionally, dry ground clay, chalk, and any other suitable powdered materials may be used. It is better when the fineness of powdered material fractions up to 0.63 mm is used.

Porobasalt production technology includes the following main operations: grinding of andesitobasalt gravel; preparation of the working mixture, production of raw granules; drying granules; sieving of dry granules into fractions; pellet firing; annealing (cooling) of expanded granules and sieving of the finished product into fractions.

The grinding of andesitobasalt gravel is carried out by dry method with a fineness of grinding with the residue after sieving in a sieve of 0.08 mm 5-15%. The grinding coefficient in relation to the cement clinker is taken equal to 1.

In preparing the working mixture is dosed into the mixer andesite ground with simultaneous supply NaOH solution and, if necessary, a solution of NaNO ₃ in an effective amount. The content of NaOH in the charge should be from 10 to 13% by weight of the charge, where this range is explained by the unequal content of alkaline oxides in andesitobasalts. The content of NaNO ₃ can be up to 1% (over 100%) of the mass of the charge. The resulting mixture is mixed in a twin roll batch mixer with a further dosed supply of the resulting mixture to the granulator.

Raw granules are obtained in a disk granulator having two stages and containing a dusting system for raw granules with andesitobasaltic powder in the second stage. The bulk of the raw granules should have a size of 3-8 mm. The moisture content of the raw granules after granulation is 14-18%.

Drying of raw granules is carried out in a countercurrent drying drum with exhaust gases from the furnace with a temperature of not more than 600 ° C. The residual moisture of the dried raw granules after drying should not exceed 5%. The bulk density of the dried raw granules, depending on the size, is 965-1210 kg / m ³ .

Further, the scattered raw granules are distributed over the hoppers of fractions up to 3 mm, 3-10 mm and more than 10 mm.

Raw pellet firing is carried out in fractions in a rotary kiln. Raw granules are fed into a rotary kiln by a belt feeder, to which a powdery separating medium is simultaneously supplied at a ratio of the separating medium to raw granules 1: 2 by volume. The firing time is 12-15 minutes. The load factor of the furnace is 5-6%, depending on the size of the raw granules. The temperature in the firing zone is 840-880 ° C. To establish the optimal mode of expansion of raw granules in the design of a rotary kiln should be provided with a device for controlling the speed of rotation. Also, the rotary kiln should be equipped with a two-stage system for cleaning gases from dust. The yield factor of the finished product is 2.8-3.2, depending on the size of the raw granules.

From the rotary kiln, the expanded granules in a mixture with a separating medium enter a hopper mounted under the head of the rotary kiln. The bunker must be lined with bricks from the inside, and its volume must be at least the hourly capacity of the rotary kiln. The hopper is designed for slow cooling (annealing) of granules. From the annealing hopper, the cooled granules are conveyed by a conveyor belt to the elevator, which transports them to gravity sorting.

In gravity sorting, the powder separating medium is first screened out using sieves with a mesh size of 1 mm, and then the granules are sorted into fractions of 1 -5 mm; 5-10 mm; 10-20 mm and more than 20 mm. The screened powdery separating medium can be returned for reuse or, with appropriate verification and a feasibility study, used as an additive or component for mortars or concrete.

The obtained granular porous filler, porobasalt, has the following grades in bulk density: 200 - from 150 to 210 kg / m ³ ; 250 - from 210 to 265 kg / m ³ ; 300 - from 265 to 320 kg / m ³ . The compressive strength in the cylinder (according to the method of GOST 9758-90), not less than: grade 200 0.3 MPa; grade 250 0.4 MPa; 300 grade 0.5 MPa. Losses in mass after 15 cycles of alternate freezing and thawing are less than 5%; losses after boiling, when tested for silicate decomposition, when calcined, less than 2%. The softening coefficient is at least 0.75, water absorption within 1 hour - less than 6%; the shape factor of the grains is less than 1.45.

The above technology, in comparison with known technologies that use a 1: 1 ratio of powdery separating medium and granules, requires a smaller amount of this consumable by about 34%. This allows you to reduce energy consumption both for the heat treatment itself and for its auxiliary operations (loading, unloading, separation) by about 17% when using traditional materials such as dry powdered clay, chalk, limestone flour, cement, river quartz or fireclay sand.

The ratio of the powdered separation medium to the raw granules 1: 2 by volume is used based on the fact that the total bulk volume of the granules is the sum of the volume of the granules and the volume of space between the granules, which must be filled with the powdered separation medium. The volume of one granule, taken in the form of an ideal ball, is 4 / 3πR ³ . The amount of space to be filled around one granule is defined as the difference between the volume of a cube with a side length 2R, 8R equal to ^3, and the volume of granules of the inscribed therein in the form of an ideal sphere, equal 4πR ^3/3. Thus, the volume of space to be filled around one granule is (8-4π / 3) R ³ , and this volume is the minimum volume of powdery separating medium required to completely fill the space around one granule. We get that the ratio of the minimum volume of the powdery separating medium to the bulk volume of granules is (8-4π / 3): 8 or approximately equal to 1: 2. The effectiveness of the use in this invention of this lower boundary of the ratio of the powdered separating medium and granules, as 1: 2, has been confirmed in practice not only for heat treatment of andesite basalts, as described above, but also for heat treatment of raw granules from cullet and other materials, while reducing efficiency no adhesion of raw granules to each other was noted.

The use of dry sampling ash or waste incineration ash containing unburned combustible substances as a powdery separating medium showed even better results, namely, a reduction in energy consumption of directly to heat treatment by up to 80% due to the autothermal nature of these ashes. their heating is not required to spend a large amount of heat due to the presence in them of a sufficient amount of unburned combustible substances. This is especially true for the ash of an incineration plant containing a greater amount of unburned combustible substances, and the suitability of using such ash of a garbage plant for the indicated purposes and the appropriateness of its use have been sufficiently verified not only in the production of porobasalt, as described above, but also in the study of the technology for producing granulated foam glass and was tested in the factory at an experimental installation at the Crystal factory. In addition, during the preliminary check, it turned out that after burning the ash of the incinerator, it has good astringent properties - this fact is of great interest for the subsequent disposal of this ash as an additive or component for mortars or concrete, for example, instead of part of cement.

In addition, the above-described technology for the production of porobasalt can be used with slight modifications for the production of the following materials: expanded clay (dry method); expanded perlite; vermiculitis; ash gravel; granular foam glass based on perlite, zeolite, glass break; for calcining limestone and ash and slag mixtures.

The above example is used only to illustrate the possibility of carrying out the invention. It is not intended to limit the scope of legal protection presented in the claims, while a person skilled in the art is relatively simply able to implement other ways of carrying out the invention within the framework of the claims.

Claims (11)

1. The method of heat treatment of raw granules, including swelling of raw granules in a rotary kiln at an effective temperature in the presence of a powder separation medium with a ratio of separation medium and raw granules of less than 1: 1 by volume, characterized in that raw granules obtained from ground andesitobasalt with an additive are used at least a sodium hydroxide solution in an effective amount, using andesitobasalt of the Baranovsky deposit with the following chemical composition, wt.%: SiO ₂ - 55.6-60.84; TiO ₂ - 1.65-2.27; Al ₂ O ₃ - 13.97-16.26; Fe ₂ O ₃ - 0.99-3.61; FeO - 3.98-6.89; CaO 3.63-5.19; MgO - 2.11-4.22; MnO 0.07-0.10; P ₂ O ₅ - 0.22-0.44; K ₂ O - 3.00-4.33; Na ₂ O - 2.66-3.45; PPP - 0.41-2.56, and heat treatment is carried out at a ratio of separating medium and raw granules of at least 1: 2 in volume. 2. The method according to claim 1, characterized in that the ratio of the separating medium and granules is 1: 2 by volume with a grain shape coefficient of raw granules of not more than 1.5. 3. The method according to claim 1, characterized in that after heat treatment the powdery separating medium is separated from the finished granules and sent for reuse. 4. The method according to claim 1, characterized in that as a powdery separating medium using a powdery material with a grain size of fractions up to 0.63 mm 5. The method according to claim 1, characterized in that at least one powdery material or a mixture of powdery materials selected from the group of dry powdered clay, chalk, limestone flour, cement, river quartz sand, fireclay sand is used as a powdery separating medium, ash of an incinerator, ash of a heat and power plant of dry selection. 6. The method according to claim 1, characterized in that they use raw granules obtained from ground andesitobasalt with an additional addition of a solution of sodium nitrate. 7. The use of ash containing unburnt combustible substances, as a powder separating medium during heat treatment of granular aggregate according to the method according to claim 1. 8. The use according to claim 7, characterized in that the ash is used with an unburned substance content of up to 15 wt.%. 9. The use according to claim 7, characterized in that the ashes of incinerators are used. 10. The use according to claim 7, characterized in that dry ash of a heat and power plant of dry selection is used. 11. The use according to claim 7, characterized in that ash is used with a particle size of fractions up to 0.63 mm.