RU2844088C1 - Method of processing mineral wool production wastes - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: invention relates to construction, particularly, to production of mineral wool in gas furnaces. Invention can be used to recycle wastes formed during production of mineral wool. In the method of processing mineral wool production wastes, the mineral wool production wastes are crushed while simultaneously mixing with a hydraulic binder and water, followed by moulding to form granules which are then subjected to hydrothermal drying under pressure. According to the invention, the hydraulic binder is represented by a mixture of quicklime and limestone, wherein the ratio of components of the dry mixture is, wt. %: wastes of mineral production 70; quicklime finely ground 7.5-9.6; limestone 20.4-22.5.

EFFECT: invention improves environmental friendliness of the process of recycling wastes from mineral wool production.

9 cl, 6 ex

Description

Field of technology

The invention relates to the field of construction, in particular, to the production of mineral wool in gas furnaces. The invention can be used for the disposal of waste generated during the production of mineral wool, in particular, stone wool.

State of the art

A method for producing briquettes for the production of mineral wool and a method for producing mineral wool are known, disclosed in the Russian Federation patent for invention No. 2090525 (IPC: C03C 1/00, C03B 37/00, publication date: 20.09.1997). According to the known method for producing briquettes for the production of mineral wool, finely ground mineral raw materials, a binder and water are mixed, the resulting mixture is formed into briquettes and cured. Finely ground waste from the production of mineral wool, flotation waste or waste from the production of glass are used as mineral raw materials. A slag-alkaline binder is used as a binder, in particular, crushed granulated blast-furnace slag having a glassy structure, activated by an alkaline component - a compound of an alkali metal, in particular a carbonate. An additive of CaO (ground quicklime), or Ca(OH) ₂ (slaked lime), or Portland cement clinker in an amount of 1-10% of the slag mass is also introduced into the mixture of mineral raw materials and the binder. The said additive can be introduced separately or during joint grinding with granulated blast-furnace slag. The said additive acts as an activator (accelerator of the curing process).

The disadvantage of the analogue is that the resulting processed product is subject to destruction of its fibers when stored in open areas due to the fact that alkali metals, in particular sodium and potassium, tend to oxidize quickly when exposed to air. Also, increased energy consumption when returning the processed product back to production is due to the fact that cement at a temperature equal to or greater than 500 ° C disintegrates into components, which provokes an endothermic reaction that reduces the temperature inside the kiln. In this regard, constant heating of the kiln is required to reduce the negative impact of cement on the production process.

Another disadvantage of the known method is that it involves the production of briquettes for the production of mineral wool based on slag. In this case, slag is the main binder that provides strength to the briquettes, and the alkaline additive, which can be lime (CaO or Ca(OH) ₂ in an amount of 1-10% of the slag weight), acts only as a hardening activator. The known method also requires the introduction of additional corrective additives into the batch, additional grinding of both the mineral raw materials and the binder, as well as prolonged drying of the resulting briquettes.

A method for reusing solid waste in the production of mineral wool is known, disclosed in Chinese patent application No. 106904820 (IPC: C03B 37/00, C04B 28/04, publication date: 30.06.2017). According to the known method, mineral wool production waste is mechanically crushed to obtain a fine powder state, in particular, to obtain particles of 0.2-10 mm in size. In this case, a filler in an amount of 28-35% and a silicate binder in an amount of 8-15%, as well as water in an amount of up to 6-10% are added to the mixture, while the waste makes up from 40 to 48% of the mixture. Next, the mixture is pressed through a molding device into blocks and dried, in particular, naturally or in a drying chamber. The pressed blocks can then be used for the production of mineral wool. Cement can be used as a silicate binder.

The disadvantage of the analogue is the increased energy consumption when returning the processed product back to production, due to the fact that cement at a temperature equal to or greater than 500 ° C disintegrates into components, which provokes an endothermic reaction that reduces the temperature inside the furnace. In this regard, constant heating of the furnace is required to reduce the negative impact of cement on the production process.

A building material obtained from solid waste and a method for obtaining it are known, disclosed in Chinese patent application No. 118495987 (IPC: C04B 28/04, C04B 38/10, C04B 111/40, publication date: 08/16/2024). According to the known method, solid waste (70-75%), cement (10-15%), an auxiliary binder, cellulose (0.23%), a chemical foaming agent (0.13-0.17%), a reinforcing agent and water (10-11%) are mixed. The mixture is stirred at a speed of 40-60 rpm for 20-30 minutes to obtain a homogeneous composition of the mixture, then the resulting mixture is poured into a mold and pressed, heat treated, pressure treated, and then the pressed mixture hardens. In this case, the auxiliary binder is fly ash, quicklime, aluminum powder, or a combination of the above components. Cement can be represented by silicate cement, and a combination of light magnesium oxide (magnesium oxide E530) and calcium nanocarbonate can be used as a reinforcing agent. The auxiliary binder is used to accelerate the hardening of the mixture due to hydration (consumption of water contained in the mixture).

The disadvantage of the analogue is the increased energy consumption when returning the processed product back to production, due to the fact that cement at a temperature equal to or greater than 500 ° C disintegrates into components, which provokes an endothermic reaction that reduces the temperature inside the furnace. In this regard, constant heating of the furnace is required to reduce the negative impact of cement on the production process. As a result, increased energy consumption reduces the environmental performance of the mineral wool production waste disposal process.

A method for producing mineral wool products is known, disclosed in patent EP 0115817 A1 (IPC: C03C 1/02, C03C 13/06, C03C 13/00, C03C 1/00, publication date: 15.08.1984) - prototype. According to the known method, a mixture is formed having a composition similar to that of mineral wool, including mineral wool production waste, with the addition of a binder and water to form briquettes. The said briquettes, calculated on a dry matter basis, contain at least 20 wt. % of mineral wool production waste (20-50 wt. %) and at least 35 wt. % of a binder in the form of clay (35-75 wt. %). The clay composition is represented by the following ratios: 50-70 wt. % SiO ₂ , 10-20 wt. % Al ₂ O ₃ , 2-7 wt. % Fe ₂ O ₃ , 5-30 wt. % CaO, 1-4 wt. % MgO, 1-8 wt. % Na ₂ O + K ₂ O. Water is used in the amount of 10-18 wt. %. The use of clay as a binder allows to achieve greater homogeneity of the mixture, however, the use of a large amount of clay leads to high viscosity of the mixture. This necessitates the addition of lime or other components that reduce viscosity, therefore the use of clay with a relatively high lime content makes it possible not to use additional components or to use them in small quantities. The formation of briquettes from the mixture is carried out by pressing, in particular by roller pressing or extrusion, while the briquettes take a shape, mainly cylindrical. After pressing, the resulting briquettes are loaded into a smelting furnace for processing.

The disadvantage of the known method chosen as a prototype is that the resulting processed product is subject to destruction of its fibers when stored in open areas due to the fact that alkali metals, in particular sodium and potassium, tend to oxidize quickly when exposed to air. As a result, the resulting granules dust during transportation and storage. In other words, small particles formed as a result of granule cracking are carried by the wind at the production site or into the environment along the transportation route. This can lead to air pollution and also have a negative impact on the health of workers and residents of the territories adjacent to the production site. This problem is especially relevant for large-scale production facilities that receive production waste in large quantities.

At the same time, the disadvantage of the known method is the low efficiency of processing mineral wool production waste, due to the relatively low specific content of waste (20-50 wt.%) in the composition of the batch, and the high content of binder, which occupies at least 35 wt.%.

The above predetermines a technical problem, which consists in the need to eliminate the shortcomings of analogues and prototypes, which in general consist in the low environmental friendliness of the process of recycling mineral wool production waste.

Disclosure of the essence of the invention

The technical result achieved by the claimed invention consists in increasing the environmental friendliness of the process of recycling mineral wool production waste.

Additional technical results include reduced requirements for storage and transportation of the obtained granules, reduced binder consumption, increased proportion of waste in the mixture, and reduced energy consumption during remelting of granules at the stage of their return to production.

The claimed invention discloses a method for processing mineral wool production waste, in which mineral wool production waste is crushed while simultaneously mixing with a hydraulic binder and water, then granules are formed by pressing, which are then subjected to hydrothermal drying under pressure. Unlike the prototype, the hydraulic binder is represented by a mixture of quicklime and limestone, with the ratio of the dry mixture components being, wt. %:

waste from mineral wool production 70 quicklime finely ground 7.5-9.6 limestone 20.4-22.5

Additional advantages and essential features of the present invention can be presented in the following particular embodiments.

In particular, waste from mineral wool production is pre-pressed and dehydrated on a hydraulic baling press of the PP-300 series.

In particular, screenings of substandard fibre and non-fibrous inclusions formed during the production of mineral wool fibre are used as waste from mineral wool production.

In particular, the activity of finely ground quicklime ranges from 70 to 95%.

In particular, calcium lime is used as finely ground quicklime.

In particular, pressing and formation of granules is carried out using the semi-dry pressing method.

In particular, pressing and forming of granules is carried out using the vibration pressing method.

In particular, hydrothermal drying of granules is carried out in an autoclave chamber at a steam pressure of 1 atmosphere for 8 hours.

In particular, hydrothermal drying of granules is carried out in an autoclave chamber at a steam pressure of 2-8 atmospheres for 4 hours.

The achievement of the technical result is due to the increased strength of granules obtained from mineral wool production waste. The strength of these granules means that they do not crack when stored openly, and when the granules are remelted at the stage of their return to production, the binder in these granules does not break down under high thermal effects. The use of a mixture of quicklime and limestone as a binder allows eliminating the use of rapidly oxidizing substances as a binder and increasing the strength of the granules, which ensures environmental safety during their storage and transportation.

The destruction of the binder in granules during the remelting of granules at the stage of their return to production is due to the use of materials with lower thermal resistance than lime as a binder. Thus, the use of cement as a binder leads to its disintegration in the furnace at a temperature equal to or greater than 500 ° C. This provokes an endothermic reaction that reduces the temperature inside the furnace, which requires constant heating of the furnace to reduce the negative impact of cement on the production process. A binder containing a mixture of slaked lime and limestone has greater thermal resistance when returning the processed product back to production. Thus, limestone is calcined at a temperature of about 860-950 ° C, and complete decomposition of limestone to lime and carbon dioxide occurs at a temperature of about 1300-1500 ° C.

Implementation of the invention

In the proposed method for processing mineral wool production waste, mineral wool production waste is used as the starting material, which in a particular embodiment of the invention can be represented by screenings of substandard fiber and non-fibrous inclusions.

The waste has a high humidity of 20-30%. The most energy-intensive process in preparing waste for processing is drying. Excess moisture is removed by preliminary pressing of waste on a hydraulic baling press of the PP-300 series with an operating pressure of 250 bar. The specified press is designed for baling scrap, that is, for pressing metal waste and giving it a rectangular shape, and contains a system for removing moisture. When pressing mineral wool production waste, the specified press allows bringing the residual moisture of the waste to 5-7%, reducing its volume by three times, which significantly facilitates its further processing. The bulk density of mineral wool production waste upon entering the press is from 400 to 700 kg/ ^m3 depending on the humidity.

Mineral wool production waste, pre-dehydrated in a press, is fed into a raw material unloading tank, for example, into a receiving bin. Then, along a conveyor belt, mineral wool production waste is fed into a storage bin. From the storage bin, the waste is fed into a ball mill or disintegrator, where the waste is mixed and crushed.

A ball mill is a rotating container partially filled with solid spherical bodies in which mineral wool production waste is crushed and ground.

The disintegrator is a device with rotors rotating in opposite directions, in which mineral wool production waste is subjected to crushing and/or grinding and/or mixing.

Simultaneously with mixing and grinding of waste, a hydraulic binder is added to the mixture in the following ratio, wt. %:

waste from mineral wool production 70 hydraulic binder 30

A mixture of quicklime and limestone in the following ratio, wt. %, is used as a hydraulic binder:

quicklime finely ground 7.5-9.6 limestone 20.4-22.5

The quantity of components is measured using weigh batchers on a conveyor belt.

Calcium lime with an activity of 70% to 95% and a magnesium oxide content of no more than 5% can be used as finely ground quicklime. In accordance with GOST 9179-2018 (Building lime. Technical conditions), calcium lime is divided into three grades depending on the activity standard. For the third grade of calcium lime, the activity standard is 70%, for the second grade - 80%, for the first grade - 90%. The activity of lime is determined by the content of active CaO and MgO in it. At the same time, when using lime with a higher activity, it is necessary to use a smaller amount of lime.

Water is also added to the mixture in an amount of 10-16% above the volume of the mixture to carry out the process of mixing and slaking the lime. The production laboratory controls the humidity of the mixture. The required volume of water intended for adding to the dry mixture is limited by turning the pump on and off. When mixing the mixture in a ball mill or disintegrator and adding a mixture of quicklime and limestone to it, the finely ground lime is slaked:

This reaction is exothermic, i.e. accompanied by the release of heat, due to which part of the water used in mixing passes into a gaseous aggregate state (steam). When slaking lime, residual drying of the mixture components occurs.

The use of a mixture of quicklime and limestone as a hydraulic binder is due to the fact that mineral wool production waste contains about 43-45% SiO ₂ . During the production of products containing CaO, SiO ₂ and water, hydrosilicate hardening of lime occurs, which is described by the following formula:

The chemical interaction between lime and silicon oxide during hydrothermal drying occurs mainly on the surface with the formation of crystalline calcium hydrosilicates. The introduction of finely ground calcium carbonate (limestone) improves the workability of solutions, accelerates their hardening and increases mechanical strength.

The mass ratio of lime and limestone is due to the fact that the presence of less than 7.5% quicklime in the mixture leads to a decrease in the strength of the granules. The limestone content exceeding 22.5% leads to excessive plasticity of the mixture, which will not allow the formation of granules.

At the exit from the ball mill, a powder mixture is obtained and fed into a mixer for moistening in order to obtain the mixture moisture required for pressing, in particular, up to 5-7%. Water or a 1-5% solution of calcium chloride is added to the mixture and mixed until homogeneous.

Next, the mixture is sent to a pellet press, where the mixture is pressed and granules are formed, mainly of cylindrical shape. Pressing and forming of granules is carried out by the method of semi-dry pressing or vibration pressing. The pellet press can change the compression force during granulation of the mixture, and the dies of the pellet press can be characterized by different ratios of the working length of the die to its diameter. In accordance with the specified parameters, the density of the resulting granules and their consistency (dry, semi-dry, wet) are selected. The size and quality of the granule are regulated by changing the gap between the working mechanisms, replacing the matrix, adjusting the humidity of the mixture.

The size of the granules should be commensurate with the size of the base material loaded into the furnace (up to 20 mm).

The granules are then subjected to hydrothermal treatment, which is carried out in an autoclave chamber at a steam pressure of 1 atmosphere for 8 hours or at a steam pressure of 2-8 atmospheres for 4 hours.

The resulting granules are suitable for reuse in the mineral wool production process. The granules are sent to a gas (bath) furnace for remelting to produce mineral wool.

The chemical composition of which the granules are composed immediately before remelting in a gas furnace is completely identical to the original mixture of mineral wool production waste and does not affect the quality characteristics of the fiber obtained after remelting.

The presence of a small amount of magnesium oxide (no more than 5%) in the calcium lime allows us to exclude its participation in the technological process, since at a temperature in a gas furnace above 1300°C it is burned out.

The claimed invention is illustrated by the following examples.

Example 1.

70 kg of mineral wool production waste, which consists of screenings of substandard fiber and non-fibrous inclusions, are placed in the receiving bin. The waste is then sent to the storage bin along a conveyor belt. After that, the waste is loaded into a ball mill. In this case, 7.5 kg of quicklime, the activity of which is 95%, is added to the waste, as well as 22.5 kg of limestone and 10-16 liters of water. The process of grinding the waste and mixing the entire mixture lasts from 40 minutes to 1.5 hours, while slaking the finely ground lime leads to drying of the mixture components. At the exit from the ball mill, a powdery mixture is obtained and fed to a mixer for moistening in order to obtain the moisture content of the mixture required for pressing. Water is added to the mixture and mixed until smooth. Then the mixture is sent to a semi-dry pressing granulator, where cylindrical granules are formed.

After pressing, the granules are sent to the autoclave chamber. The hydrothermal drying process lasts for 8 hours at a steam pressure of 1 atmosphere. As a result of the actions taken to utilize mineral wool production waste, high-strength granules are obtained. The granules do not crack during storage and do not dust during transportation. The temperature in the furnace during granule remelting is maintained at a constant level.

Example 2.

70 kg of mineral wool production waste, which is represented by screenings of substandard fiber and non-fibrous inclusions, are placed in the receiving bin. Then, the waste is sent to the storage bin along the conveyor belt. After that, the waste is loaded into the ball mill. In this case, quicklime with an activity of 90% is added to the waste in the amount of 7.9 kg, limestone in the amount of 22.1 kg and water in the amount of 10-16 liters. The process of grinding the waste and mixing the entire mixture lasts from 40 minutes to 1.5 hours, while slaking the finely ground lime leads to drying of the components of the mixture. At the exit from the ball mill, a powdery mixture is obtained and fed to the mixer for moistening in order to obtain the moisture content of the mixture required for pressing. A 5% solution of calcium chloride is added to the mixture and mixed until smooth. Then the mixture is sent to a semi-dry pressing granulator, where cylindrical granules are formed.

After pressing, the granules are sent to the autoclave chamber. The hydrothermal drying process lasts for 4 hours at a steam pressure of 3 atmospheres. As a result of the actions taken to utilize mineral wool production waste, high-strength granules are obtained. The granules do not crack during storage and do not dust during transportation. The temperature in the furnace during granule remelting is maintained at a constant level.

Example 3.

70 kg of mineral wool production waste, which consists of screenings of substandard fiber and non-fibrous inclusions, are placed in the receiving bin. The waste is then sent to the storage bin along a conveyor belt. After that, the waste is loaded into a ball mill. In this case, 8.3 kg of quicklime, the activity of which is 85%, is added to the waste, as well as 21.7 kg of limestone and 10-16 liters of water. The process of grinding the waste and mixing the entire mixture lasts from 40 minutes to 1.5 hours, while slaking the finely ground lime leads to drying of the mixture components. At the exit from the ball mill, a powdery mixture is obtained and fed to a mixer for moistening in order to obtain the moisture content of the mixture required for pressing. Water is added to the mixture and mixed until smooth. Then the mixture is sent to a semi-dry pressing granulator, where cylindrical granules are formed.

After pressing, the granules are sent to the autoclave chamber. The hydrothermal drying process lasts for 4 hours at a steam pressure of 5 atmospheres. As a result of the actions taken to utilize mineral wool production waste, high-strength granules are obtained. The granules do not crack during storage and do not dust during transportation. The temperature in the furnace during granule remelting is maintained at a constant level.

Example 4.

70 kg of mineral wool production waste, which consists of screenings of substandard fiber and non-fibrous inclusions, are placed in the receiving bin. The waste is then sent to the storage bin along a conveyor belt. After that, the waste is loaded into a ball mill. In this case, 8.7 kg of quicklime, the activity of which is 80%, is added to the waste, as well as 21.3 kg of limestone and 10-16 liters of water. The process of grinding the waste and mixing the entire mixture lasts from 40 minutes to 1.5 hours, while slaking the finely ground lime leads to drying of the mixture components. At the outlet of the ball mill, a powdery mixture is obtained and fed to a mixer for moistening in order to obtain the moisture content of the mixture required for pressing. A 3% solution of calcium chloride is added to the mixture and mixed until smooth. Then the mixture is sent to a semi-dry pressing granulator, where cylindrical granules are formed.

After pressing, the granules are sent to the autoclave chamber. The hydrothermal drying process lasts for 8 hours at a steam pressure of 1 atmosphere. As a result of the actions taken to utilize mineral wool production waste, high-strength granules are obtained. The granules do not crack during storage and do not dust during transportation. The temperature in the furnace during granule remelting is maintained at a constant level.

Example 5.

70 kg of mineral wool production waste, which is represented by screenings of substandard fiber and non-fibrous inclusions, are placed in the receiving bin. Then, the waste is sent to the storage bin along the conveyor belt. After that, the waste is loaded into the ball mill. In this case, quicklime with an activity of 75% is added to the waste in the amount of 9.1 kg, limestone in the amount of 20.9 kg and water in the amount of 10-16 liters. The process of grinding the waste and mixing the entire mixture lasts from 40 minutes to 1.5 hours, while slaking the finely ground lime leads to drying of the components of the mixture. At the exit from the ball mill, a powdery mixture is obtained and fed to the mixer for moistening in order to obtain the moisture content of the mixture required for pressing. Water is added to the mixture and mixed until smooth. Then the mixture is sent to a semi-dry pressing granulator, where cylindrical granules are formed.

After pressing, the granules are sent to the autoclave chamber. The hydrothermal drying process lasts for 4 hours at a steam pressure of 2 atmospheres. As a result of the actions taken to utilize mineral wool production waste, high-strength granules are obtained. The granules do not crack during storage and do not dust during transportation. The temperature in the furnace during granule remelting is maintained at a constant level.

Example 6.

70 kg of mineral wool production waste, which consists of screenings of substandard fiber and non-fibrous inclusions, are placed in the receiving bin. The waste is then sent to the storage bin along a conveyor belt. After that, the waste is loaded into a ball mill. In this case, 9.6 kg of quicklime, the activity of which is 70%, is added to the waste, as well as 20.4 kg of limestone and 10-16 liters of water. The process of grinding the waste and mixing the entire mixture lasts from 40 minutes to 1.5 hours, while slaking the finely ground lime leads to drying of the mixture components. At the outlet of the ball mill, a powdery mixture is obtained and fed to a mixer for moistening in order to obtain the moisture content of the mixture required for pressing. A 1% solution of calcium chloride is added to the mixture and mixed until smooth. Then the mixture is sent to a semi-dry pressing granulator, where cylindrical granules are formed.

After pressing, the granules are sent to the autoclave chamber. The hydrothermal drying process lasts for 4 hours at a steam pressure of 8 atmospheres. As a result of the actions taken to utilize mineral wool production waste, high-strength granules are obtained. The granules do not crack during storage and do not dust during transportation. The temperature in the furnace during granule remelting is maintained at a constant level.

Claims (10)

1. A method for processing mineral wool production waste, in which mineral wool production waste is crushed while simultaneously mixing with a hydraulic binder and water, then granules are formed by pressing, which are then subjected to hydrothermal drying under pressure, characterized in that the hydraulic binder is a mixture of quicklime and limestone, wherein the ratio of the components of the dry mixture is, wt.%: waste from mineral wool production 70 quicklime finely ground 7.5-9.6 limestone 20.4-22.5 2. The method according to paragraph 1, characterized in that the waste from mineral wool production is pre-pressed and dehydrated in a hydraulic baling press. 3. The method according to paragraph 1, characterized in that the waste from mineral wool production is the screening of substandard fiber and non-fibrous inclusions formed during the production of mineral wool fiber. 4. The method according to paragraph 1, characterized in that the activity of the finely ground quicklime is from 70 to 95%. 5. The method according to paragraph 1, characterized in that calcium lime is used as finely ground quicklime. 6. The method according to paragraph 1, characterized in that the pressing and formation of samples is carried out by the method of semi-dry pressing. 7. The method according to paragraph 1, characterized in that the pressing and formation of samples is carried out using the vibration pressing method. 8. The method according to paragraph 1, characterized in that the hydrothermal treatment of the samples is carried out in an autoclave chamber at a steam pressure of 1 atm for 8 hours. 9. The method according to paragraph 1, characterized in that the hydrothermal treatment of the samples is carried out in an autoclave chamber at a steam pressure of 2-8 atm for 4 hours.