LT6689B - Method of producing ceramic products with slag (bottom ash) - Google Patents

Abstract

The invention relates to the field of industrial ecology and building materials and can be adapted for the production of clay masonry units. The invention provides a method for producing clay masonry units with an additive of about 50 % SiO2 and heavy metals produced during the incineration of municipal solid waste. Clay masonry units are made from the following components: clay and municipal solid waste incinerator slag (bottom ash). A new feature is that, by varying the amount of slag in the mass formation and burning in the appropriate mode, clay masonry units with a gross dry density of 1770 to 1840 kg/m³, a compressive strength of 35 to 45 N/mm², a water absorption of 12 to 14.5 %, frost resistance > 100 cycles.

Description

The present invention relates to the field of industrial ecology and to the building materials industry, more particularly to the field of building ceramics, and can be applied to the production of ceramic products with cogeneration waste from municipal incineration residues (bottom ash) by replacing natural lean additive used in ceramic products.

Currently, Lithuania has already built one and plans to build two more cogeneration plants for municipal waste incineration. The majority of municipal waste incineration is slag - about 95-97%, the remainder (3% to 5%) fly ash (Van Herck et al., Application of Computer Modeling to Predict Leaching Behavior of Heavy Metals from MSWI) a sequential extraction method, Waste Management 203-210, 2000; Wunsch et al., Investigation of Binding of Heavy Metals in Thermally Treated Residues from Waste Incineration, Chemosphere 32: 2211-2218, 1996). Although classified in the European Waste Catalog as a non-hazardous waste (code 19 01 12) (European Waste Catalog (EWC) 2015), it contains heavy metals, chlorides and sulphates which may have adverse effects on nature and human health. The use / disposal of slag is a pressing issue.

There are known methods for producing ceramic products for various purposes using municipal waste incineration slag. KR20130096855A describes specimens made from 20-60% slag, 10-40% water treatment sludge and 40-60% clay. Depending on the application (bricks, blocks, lightweight aggregates) at temperatures of 1000-1300 ° C, the specimens were found to be free of heavy metals leaching and good mechanical properties.

EP 2511251A1 describes ceramic articles for various purposes (tiles, bricks, tiles) made from 25-100% slag, burned at 8501200 ° C and maintained at the highest combustion temperature for 2 hours. Products from 100% slag, burning at 1100 ° C, maintaining at maximum combustion temperature for 2 hours, density 2.4 g / cm ³ , wettability 15%, bending strength 25 MPa. Products of 80% slag and 20% feldspar burn at 1100 ° C, maintain at maximum combustion temperature for 2 hours, density 2.5 g / cm ³ , absorbency 0.5%, flexural strength 44 MPa.

There are known attempts to use secondary raw materials of various compositions of municipal incineration waste slag for the production of lightweight aggregates (expanded clay). The authors of WO2016133463A1 propose to use 50% slag, 30% glass waste and 20% clay and to burn it at a temperature of 1000-1150 ° C. The resulting products have a density of 0.25-0.9 g / cm ³ and a compressive strength of 0.8-18 MPa. The authors of WO2006074944A1 state that in order to obtain 100% slag light fillers having a density of 1.5-1.8 g / cm ³ , they must be burned at 1070-1080 ° C. SU 1534028A1 states that 47.62% of municipal waste slag, 25-35% of carbon slag, 8-10% of clay, 3-5% of galvanic-chemical waste, 2-3% of anode production waste, lightweight aggregates burnt 930-940 ° C, density up to 150kg / m ³ , compressive strength 1.5 MPa, water absorption 16-17%.

The patents listed above describe methods for obtaining various ceramic products using a municipal waste slag additive, focusing on the physical-mechanical properties of the products. However, such articles are burned at relatively high temperatures and do not address the longevity of the products in terms of frost resistance and some patents fail to assess the environmental toxicity (leaching of heavy metals, chlorides and sulphates).

The object of the present invention is to obtain ceramic products by varying the formation weight of KDA slag containing about 50% SiO ₂ , as well as hazardous heavy metals, from an easily melting local clay additive, ensuring their performance within certain limits (density not less than 1700 kg / m ³ , compressive strength not less than 30 MPa, water absorption not more than 15%, frost resistance for more than 100 cycles) and environmental toxicity requirements.

The ceramic products on offer are new in the composition of their molding compound, in their quantities and in their combustion conditions. 90% to 95% by weight of clay and 5% to 10% by weight of KAD slag were used for the formulation mixture. In the manufacture of such articles, the combustion was carried out at 1000 ° C and maintained at the highest combustion temperature for 1 hour.

The chemical composition (%) of the clay used is as follows: 51.43 - SiO ₂ , 20.54 - Al ₂ O ₃ , 7.44 - Fe ₂ O ₃ , 4.26 - CaO, 3.07 - MgO, 3.3 - K ₂ O, 0.42 - Na ₂ O, 9.54 - Fuses. The identified clay minerals are H - hydro - mica, Q - quartz, K - kaolinite, Ls - feldspar (Fig. 1).

Chemical composition of the slag (%) is as follows: 47.6 - S1O2, 8.4 - AI2O3 9.7 - Fe2Os and 20.8 - CaO 2.7 - MgO 2.9 - SO ₃ 1.2 - K ₂ O, 3.0 - Na ₂ O, 0.4 - Cl, 3.2 - Fuses. The amounts of heavy metals in the slag are given in Table 1. The identified slag minerals are Q quartz and C calcite (Fig. 2).

table. Heavy metals (eluate) test results

The title Test results and units of measurement. Arsenic <0.01 mg / kg Lead <24.63 mg / kg Cadmium <0.005 mg / kg Chrome 0.158 mg / kg Copper 3.65 mg / kg Nickel <0.1 mg / kg Mercury <0.002 mg / kg Zinc 11.89 mg / kg Barry 1.88 mg / kg Molybdenum 0.269 mg / kg Antimony 0.0405 mg / kg Selenium <0.03 mg / kg

Note: Heavy metals content is determined according to EN ISO 11885-E22

The microstructure of the slag contains porous, coarse, coarse-grained particles of various shapes, which consist of finer particles (Fig. 3). The main elements of these particles are Ca (19.03%), Al (6.65%), O (57.60%), Si (9.50%), Mg (2.20%), K (1.40 %), Zn (2.71%), Cl (0.91%) (Figure 3 1). There are also (Fig. 3 2) from 5 pm to 10 pm elongated smooth surface with sufficiently dense structure particles. At some places we see smaller, round particles on their surface. The main elements of these particles are Ca (24.20%), Al (5.73%), O (65.41%), Si (2.63%), Mg (0.40%), K (0.28) %), Zn (0.90%), Cl (0.46%).

Method of obtaining ceramic products with slag additive:

preparation of raw materials (crushing, sieving through a 1.25 mm sieve) -> mixing the components -> wetting the mixture to a suitable moisture content (20-22%) -> forming semi-finished products (by plastic molding) -> drying and burning in optimum time and temperature (Drying at 105 ± 5 ° C, combustion at 1000 ° C, maintaining at maximum combustion temperature for one hour)

Ceramic products are obtained using lightly melted hydro-clay and clay additive of municipal incineration waste, which at present is practically neutralized in Lithuania, as well as comparatively low combustion temperature. The optimum quantities and technological parameters of the components included in the forming masses were determined by experiments. With this manufacturing method, the natural lean additive - sand, which is commonly used in ceramic products - can be replaced by slag additive, maintaining high product performance, good durability, frost resistance, and ensuring that heavy metals, chlorides and sulphates do not leach from ceramic combs. The main features and advantages of the invention are set forth in Tables 2 and 3.

table. Main features and advantages of the invention

Composition of molding compound (% by weight) Burning temperature, ° C Apparent (gross) dry density, kg / m ³ Compressive strength, N / mm ² Water absorption,% Resistant to frost, cycles Clay content The amount of thinning additive (sand) WHEN the amount of slag 90-95 5-10 0 1000 1920-1950 35-40 9-10.0 > 100 90-95 0 5-10 1000 1770-1840 35-45 12.5-14.5 > 100

Note: The apparent (gross) dry density is determined in accordance with LST EN 77213: 2003, the compressive strength LST EN 772-1: 2011 + A1: 2015, the water absorption according to LST EN 772-21: 2011, the frost resistance according to LST EN 1985: 2006 table . Assessment of the Environmental Toxicity of Ceramic Products with KAD Slag Additive (Heavy Metal, Chloride, Sulphate Leaching Studies)

The values of heavy metals, chlorides and sulphates leached from ceramic products were determined Ceramic products Limit values according to 2003/33 / EC Clay 90% + sand 10% Clay 90% + slag 10% Inert waste pH 6.93 7.86 - Sel, pS / cm 120 233 - Cu, mg / kg 0.01 1.2 2.0 Cd, mg / kg 0.003 0.012 0.04 C r, mg / kg 0.011 0.12 0.5 Pb, mg / kg 0.009 0.086 0.5 Zn, mg / kg 0.42 0.79 4.0 Ni, mg / kg 0.08 0.18 0.4 Chlorides, mg / kg 170 340 800 Sulphates, mg / kg 450 762 1000

Note: Heavy metal leaching studies have been performed according to LST EN 124572: 2003 test methodology

The technical-economic justification for the production of such ceramic products is the efficient utilization / utilization of municipal incineration waste slag containing about 50% SiO _{2 in} cogeneration plants. By varying the amount of municipal incineration slag additive and selecting the optimal time and temperature regime, ceramic products with improved performance are obtained. The resulting ceramic products could be used for the construction of residential and industrial buildings, for the restoration of various architectural monuments, since heavy metals, chlorides and sulphates contained in slag are securely bound in ceramic combs to thermodynamically stable compounds and their leaching values do not exceed inert leaching limit values 33 / EC document requirements.

Claims (2)

Definition of the Invention 1. Ceramic products containing clay and sand, characterized in that the sand is replaced by a slag additive from municipal incineration residues, with the following component-by-mass ratio: clay 90-95, slag 5-10. 2. The method of making ceramic products includes crushing clay and slag additive, sieving through a 1.25 mm sieve, wetting the molding mixture to a moisture content of 20-22%, molding semi-finished products by plastic molding, drying the semi-finished products at 105 ± 5 ° C and firing at 1000 ° C. at the highest combustion temperature for 1 hour.