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Section 2. Biotechnology sciences
https://doi.org/10.29013/ESR-20-3.4-7-11
Dzhakupova Inkar Borisovna, senior teacher, master of ecology Almaty Technological University E-mail: [email protected] Bozhbanov Alikhan Zhaksybekovich, associate professor, candidate of Biology Almaty Technological Universit, Shynybekova Sholpan Sakanovna, senior teacher, candidate of Biology Kazakh National PedagogicalUniversity
SYNTHETIC WALLASTONITE - AS AN INNOVATIVE MATERIAL PROCESSED FROM INDUSTRIAL WASTE
Abstract. This article discusses current environmental problems associated with the interaction of a phosphorus plant with the environment, with the distribution of soluble phosphorus compounds, the formation of a significant amount of waste and harmful emissions.
Keywords: ecology, wollastonite, synthetic, phosphorus production waste, asbestos.
Introduction This work is aimed at processing industrial waste
Modern industry lays the material foundation for with the organization of the production of innova-
human life. Most of the basic human needs can be tive material - synthetic wollastonite, which provides
met through goods and services provided by indus- for the solution of environmental problems.
try. The environmental impact of industry depends Wollastonite is a natural calcium silicate with the
on the nature of its territorial localization, the con- molecular formula CaSiO3. The color of wollastonite
sumption of raw materials, materials and energy, the is white with a grayish or brownish tint. The mineral
possibility of waste disposal and the degree of com- is chemically pure, contains a small amount of impu-
pletion of energy production cycles. As a result of the rities in the form of oxides of manganese, iron and
production activities of enterprises of the Republic titanium. Wollastonite is not soluble in water and or-
of Kazakhstan in the production of phosphorus and ganic solvents, but reacts with hydrochloric acid. The
phosphorus-containing substances, industrial waste mineral was named after the English chemist William
in the amount of over 60 million tons was accumulat- Wollaston (1766-1828). Wollastonite did not receive
ed in the dumps of enterprises, of which more than wide industrial distribution until the 50 s of the XX
7 million tons of electrothermophosphorus slag were century, when, during the post-war building boom, it
accumulated over the years. began to be used for the production of paints, primers,
putties and ceramics [1]. Wollastonite is formed by contact and deep regional limestone metamorphism. Most often found at the contact of limestone with igneous rocks, where it forms significant accumulations. Wollastonite belongs to calcium silicates, due to a definitely ordered crystal lattice, it has a number of valuable properties, the main of which is increased reinforcing ability. A significant advantage is the absence of harmful effects on the human body. So, its small additives (5-20%) increase the strength ofvari-ous materials by two orders of magnitude, reduce the technological time and heat treatment temperature, increase the heat resistance, chemical resistance and wear resistance of products, improve electrical insulating and dielectric characteristics [2-5].
It is expected that synthetic wollastonite produced by the proposed technology, due to phase uniformity and a certain microstructure, will allow improving the quality parameters of the final product (cement, plastic, rubber, ceramics, glass, radio-insulating materials, electrical products, paint and varnish products, etc.) and will open new opportunities in innovative materials science.
In countries that do not have personal reserves of natural wollastonite, or in countries where existing reserves are not developed on an industrial scale, the requirements for this filler are met by the production of synthetic wollastonite. This significantly intensified the search for new technological solutions, including in Kazakhstan, in particular the use of cheap raw materials in the synthesis of wollastonite and lowering the firing temperature. The characteristics of synthetic wollastonite are almost the same as those of natural wollastonite. The target product can be supplied in the form of granules (diameter 5-25 mm).
Objects and research methods
The objects of study are phosphorus slag, waste from the phosphorus industry resulting from the electrothermal production of yellow phosphorus.
This paper presents a highly efficient technology for the production of synthetic wollastonite by solidphase synthesis and determines the optimal produc-
tion parameters. To achieve this goal, a number of experimental studies were carried out aimed at increasing the brightness ofthe resulting wollastonite product. As a result of the studies, corrective changes were made in the technology for producing synthetic wollastonite, in particular in the technology for producing wollastonite, which includes heat treatment of a mixture from a CaO-containing component - electrothermal slags of phosphorus production, as a SiO2-containing component, quartz sand in the presence of a bleaching component, into the composition ofthe bleaching component zinc oxide is additionally added, that is, in technology, as a bleaching component, instead of sodium sulfate, t used a mixture ofzinc oxide and sodium sulfate in the ZnO/SiO2 ratio. Zinc oxide is used to neutralize the staining effect of iron oxides and sulfates.
Results and its discussion
The technology for producing synthetic wollastonite involves the use of the following materials and chemicals: electrothermophosphoric slag; siliceous additive (silica sand); zinc oxide (ZnO) and sodium sulfate, Na2SO4, both in laboratory and in pilot (enlarged) conditions.
1) Granulated electrothermophosphoric slag is a calcium silicate waste from the sublimation of phosphorus during the electrothermal processing of Karatau phosphorites (Novo-Dzhambul phosphoric plant - Taraz city).Currently, replenishment oflong-term reserves of electrothermophosphoric slag at the existing NDPP is 700 thousand tons / year, and about 3.8 million tons of slag are in the dumps of Shpos "Phosphorus".
Granular electrothermal slags ofphosphorus production of water cooling have the following chemical composition, mass.%: CaO = 47.98-48, 21; Si02= = 40-41.36; A12O3 = 1.22-2.88; MgO = 3.66-4.31; Fe2O3 = 0.14-0.30; SO3 = 0.4-0.97; P2O5 = 1.25-1.5; F = 2.02-2.8; C = 1-2. The granule size is from 0.14 to 5 mm.
The color is light gray. Mohs hardness is 3.5-4. Abrupt cooling of the slag melt during water granulation mainly determines its glassy structure. The
vitreous phase content is 90% crystalline 10%. The crystalline phase is represented by the high-temperature form of wollastonite - pseudo-wollastonite a -CaSiO3 and melilite Ca (A1, MgSi)S precisely, the ackermanite variety of the latter.
The possibilities of using slags for the electrothermal production of phosphorus in the production of building materials are quite wide. The presence of impurities of phosphorus and fluorine compounds, a higher content of silica and less alumina determine some features of the use of this type of waste. Most phosphoric slag is used in the cement industry. Phosphorus slag meets the requirements for active mineral additives of artificial origin. The relatively low Al203 content leads to lower hydraulic activity of phosphorus slag compared to blast furnace.
Under normal temperature conditions, the slag of electrothermophosphorus production does not have astringent properties, and its strength under steaming conditions is also insignificant. However, phosphorus slag is well activated by alkaline pathogens, and therefore they are used in the production of slag alkaline binders.
2) Quartz sand is a natural mineral SiO2 (silicon dioxide). The mineral contains almost no impurities, only about 0.5% can be foreign inclusions. Chemically inert, does not emit soluble compounds. Quartz sand does not form toxic compounds in the air and in wastewater. He chemical composition of quartz sand (in wt.%): SiO2-94.2; CaO - 1.6 Al203-0.34; MgO --0.4; Fe2O3-0.3; Na2O - 0.9. Granulometric composition: content in% of grains with a size of 1-0.05 mm = 94.3; the content in% of grains of more than 1 ^m and less than 0.05 = 5.7. Unrefined quartz sand is controlled by sifting through a sieve of81 holes / cm2, there should be no residue on the sieve, humidity is not more than 5%. By the degree ofexposure to the body, quartz sand refers to substances of the 3 hazard class according to GOST 12.1.007-76, fire and explosion safety.
Quartz sand dust has fibrogenic properties and is capable of exerting a local irritant effect on the mucous membranes of the eyes and respiratory tract.
Quartz sand is used as a corrective component of the chemical composition of slag.
3) Bleaching additive - zinc oxide (zinc oxide) ZnO - a colorless crystalline powder, insoluble in water, yellowing when heated and sublimated at 1800 °C. It is soluble in acids, alkalis, in a solution of ammonia and ammonium chloride. Zinc oxide refers to substances of the 2nd hazard class according to GOST 12.1.007-76. The maximum permissible concentration of zinc oxide in the air of the working area is 0.5 mg/m.
In the production of glass crystalline materials and glaze, it is used to neutralize the staining effect of iron oxides and as an initiator of crystallization of the wollastonite phase, due to the proximity of the parameters of the ZnS and ft - CaO • SiO2 crystal lattices. Zinc oxide is toxic. The ingestion of soluble zinc salts in the body leads to digestive upset, irritation of the mucous membranes.
4) The bleaching additive is sodium sulfate, Na2SO4 is the sodium salt of sulfuric acid. Sodium sulfate of the Aralsulfate plant of the Kyzylorda region. GOST 1363-65 Technical sodium sulfate. The composition of technical sodium sulfate, mass.%: Na2SO4-97; CaO - 0.3; SiO2-0,1; Al2O3-0.2; MgO -- 0.2; Fe2O3-0,01. Composition of natural sodium sulfate, mass%: Na SO-86; CaSO-7; NaCl - 4;
' 2 4 ' 4 ' '
MgSO4-3. GOST 6318-68 Natural sodium sulfate.
5) Water for granulation of slag mixtures: GOST 2874-82 Drinking water; GOST 23732-79 Water for concrete and mortar.
The initial data were the following constant components: the composition of the mixture of the proposed technology for the production of synthetic wollastonite, including:
- granulated electrothermophosphorus slag (calcium containing component) - 80-90%;
- quartz sand - 10-20%;
- bleaching additive (zinc oxide or sodium sulfate) - 5-10%.
The technological scheme of the pilot production of synthetic wollastonite is shown in (Figure 1). The stages of the technology are described below.
Figure 1. Technological scheme of the
From the warehouse, raw materials (slag, sand and raw granules) are fed to the dryer to rotate into a tubular tube. Drying temperature 200-300 °C.
After drying, the raw materials arrive at the dosing section, including a chain elevator for lifting the dried components (slag or sand) and feeding the conveyor belt for loading into the hopper: the dried slag hopper, the dried sand hopper and the bleaching additive hopper. The hoppers are equipped with weighing batchers for feeding the weighed components to the prefabricated conveyor belt (above the hoppers) or to the moving weight trolley (under the hoppers).
From the collection conveyor, the weighed components enter a vortex component mixer (mixing for 10-15 minutes). Component mixer volume per 100-200 kg.
Grinding a mixture of components. The mixed mixture of components with a bucket belt elevator (or belt inclined conveyor) is fed into the hopper of the grinding unit, which is used as an elliptical mill. Milling fineness - up to a particle size of3-20 microns.
pilot production of synthetic wollastonite
Preparation (molding) of raw granules (granulation). The ground raw mix from an elliptical mill is sent to the raw material bunker, from where it is fed with a batcher (auger) for wet granulation to the molding granulator. Granules (pellets) are dried under natural conditions (25-40 °C) for 2 days to set the required strength or dried in a furnace of a tubular rotating component storage room.
Firing of raw granules for wollastonite. After drying, the raw granules are fed for firing (1050 °C) in a rotary kiln 01.5 m, L = 20 m.
Products after firing at 1050 °C (45-60 min.) Are rather strong sintered granules (hardness on the Mohs scale of 5-7, with a diameter of 7-10 mm of wollastonite composition and can be sold to a consumer who has a grinding mill for grinding to the required composition or fineness of grinding.
The grinding of fired granules of wollastonite is carried out in the same elliptical mill. This requires preliminary crushing of the granular product of firing on a hammer mill to particles up to 3-5 mm in size.
The firing product is sent to the finished goods warehouse in bags both in the form of fired granules of wollastanite composition, and in ground form (up to the fineness of grinding required by the customer) for delivery to consumers.
Ecological aspects ofthe technology for producing synthetic wollastonite based on silicate waste - elec-trothermophosphoric slag and corrective additives were studied and considered based on an environmental impact assessment. Environmental impact assessment of the existing enterprise is carried out in accordance with Art. 36 by the Environmental Code of the Republic of Kazakhstan No. 212 dated January 27, 2007 (as amended on April 25, 2016) [6].
Calculation of surface concentrations for the existing situation is performed on the ERARA 2.0 software package (Novosibirsk).
According to the significance and completeness of the environmental impact assessment according to Art. 40 of the Environmental Code of the Republic of Kazakhstan, production falls into 4 hazard categories. Sanitary and hazard class according to SanPiN No. 237 from March 20, 2015 - V, SPZ --50 m. Analysis of the results of calculations for the existing situation shows that at the border of the SPZ
the maximum concentration for all substances does not exceed 1 maximum concentration limit.
Conclusion
The paper considers the mechanisms of formation of natural and synthetic wollastonite. Elec-trothermophosphoric slag, which is a waste of the phosphorus industry, which undergoes special processing, is used as a feedstock for its production. A highly efficient technology for the production of synthetic wollastonite by solid-phase synthesis has been developed and optimal technological conditions have been determined: the initial components are granulated slag NDPP, quartz sand; Na2SO4 and (or) ZnO bleaching additives - technical: firing temperature - 1050 °C, holding time at the final temperature - 20-60 minutes. The environmental aspects were studied - by the significance and completeness of the environmental impact assessment in accordance with Art. 40 of the Environmental Code of the Republic of Kazakhstan, production falls into 4 hazard categories. Sanitary and hazard class according to San PiN No. 237 from March 20, 2015 - V SPZ - 50 m. Analysis of the results of calculations for the existing situation shows that at the border ofthe SPZ the maximum concentration for all substances does not exceed 1 MPC.
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