The effect of temperature and milling process on steel scale utilized as a pigment for ceramic glaze

This study is focused on the evaluation of the re-utilizability of scale originated during the steel casting and steel rolling processes as a pigment for glazes. Non-oiled scale with Fe3O4 as the major phase were used as a coloring component of transparent glaze matrix in: (i) as received state, (ii) thermally pre-treated at 700 and 900 degrees C, (iii) mechanically treated in planetary ball mill (60, 120 and 240 min) and (iv) mechanically treated in vibratory disc mill (60 and 120 min). Prepared glazes were applied on the surface of ceramic tiles prepared from a commercially available white ceramic slurry. The resulting tiles with given glaze were thermally treated at 800, 900 and 1060 degrees C. The pigments were characterized by X-ray powder diffraction method (XRD), X-ray fluorescence spectroscopy (XRF), granulometry (PSD), thermogravimetric analysis (TG) and differential thermal analysis (DTA), scanning electron microscopy (SEM/EDAX). The color of the samples was described by the coordinates L*a*b* from CIELAB color space. The results showed that the non-oiled scale is suitable as the pigment for ceramic glazes. Careful control of the scale treatment process (mechanical as well as thermal) together with the temperature of final glaze firing is necessary to obtain the glaze of desired color and quality.Web of Science138art. no. 181

Hydraulic properties of ladle slags

The article presents results of examining of hydraulic properties of ladle slags formed during production of steel. The studied ladle slags were subjected to different cooling mode from the molten state. Based on the ability of the slag react with the water was assessed their hydraulic activity. The hydraulic properties are caused by the presence of minerals dicalcium silicate, tricalcium aluminate, mayenite, brownmillerite and dicalcium ferite. The emergence of required hydrating phases in the ladle slags is conditioned by a sufficient CaO content and their cooling rate. The contact the slag with water during processing and their ageing has a negative effect. The experiment has shown that the phase transformation of the mineral dicalcium silicate which occurs during cooling of the ladle slags cause their volume instability.Web of Science55340239

The corrosion effect of fly ash from biomass combustion on andalusite refractory materials

The main problem affecting the life of refractory linings in furnaces is alkaline corrosion formed during biomass combustion, especially in systems with SiO2–Al2O3 . This corrosion effect is very intensive compared to using conventional technologies designed for burning traditional fuels. This study focuses on the development of a new type of andalusite refractory material with a higher corrosion resistance to K2CO3 and fly ash after biomass combustion. The original andalusite refractory material is labeled A60PT0, with an oxide content of 60 wt.% Al2O3 and 37 wt.% SiO2 , a compressive strength parameter of 64 MPa, and an apparent porosity of 15%. In the experiment, four mixtures (labeled A60PT1–A60PT4) were modified primarily using the raw materials and granulometry. The fly ash was characterized by an X-ray diffraction analysis with the following phases: quartz, calcite, microcline, leucite, portlandite, and hematite. According to the X-ray fluorescence analysis, the samples contained the following oxides: 47 wt.% CaO, 12 wt.% K2O, 4.6 wt.% SiO2 , 3.5 wt.% MgO, and some minority oxides such as P2O5 , MgO, MnO, and Fe2O3 between 2 and 5 %. The tendency for slagging/fouling of the ash was determined with the help of the indexes B/A, TA, Kt , and Fu. The final material was a shaped andalusite refractory material labeled A60PT4 with a content of 65 wt.% Al2O3 and 36 wt.% SiO2. The properties of the andalusite material were a compressive strength of 106.9 MPa, an apparent porosity of 13%, and the recommended temperature of use up to 1300 ◦C. For corrosion testing, a static crucible test was performed according to the norm CSN CEN/TS 15418 and ˇ the company’s internal regulation. The exposure time of the samples was 2 h and 5 h at temperatures of 1100 ◦C and 1400 ◦C for K2CO3 and ash, respectively. For the evaluation of tested samples, an X-ray powder differential analysis, an X-ray fluorescence analysis, scanning electron microscopy, and energy-dispersive X-ray spectroscopy were used.Web of Science133art. no. 35

Corrosive effect of wood ash produced by biomass combustion on refractory materials in a binary Al-Si system

In terms of its chemical composition, biomass is a very complex type of fuel. Its combustion leads to the formation of materials such as alkaline ash and gases, and there is evidence of the corrosive effect this process has on refractory linings, thus shortening the service life of the combustion unit. This frequently encountered process is known as "alkaline oxidative bursting". Corrosion is very complex, and it has not been completely described yet. Alkaline corrosion is the most common cause of furnace-lining degradation in aggregates that burn biomass. This article deals with an experiment investigating the corrosion resistance of 2 types of refractory materials in the Al2O3-SiO2 binary system, for the following compositions: I. (53 wt.% SiO2/42 wt.% Al2O3) and II. (28 wt.% SiO2/46 wt.% Al2O3/12 wt.% SiC). These were exposed to seven types of ash obtained from one biomass combustion company in the Czech Republic. The chemical composition of the ash is a good indicator of the problematic nature of a type of biomass. The ashes were analyzed by X-ray diffraction and X-ray fluorescence. Analysis confirmed that ash composition varies. The experiment also included the calculation of the so-called "slagging/fouling index" (I/C, TA, Sr, B/A, Fu, etc.), which can be used to estimate the probability of slag formation in combustion units. The corrosive effect on refractory materials was evaluated according to the norm CSN P CEN/TS 15418, and a static corrosion test was used to investigate sample corrosion.Web of Science1516art. no. 579

Tuhé odpadní zbytky z vysokoteplotních procesů a jejich vliv na vyzdívky pecních agregátů

Prezenční635 - Katedra tepelné technikyNeuveden

Binders Preparation by Alkaline Activation of Alternative Materials

Import 04/04/2011Disertační práce „Příprava pojiv alkalickou aktivací alternativních surovin“ shrnuje výsledky, které byly součástí řešení projektu Grantové agentury České republiky „Vliv fázového složení a mikrostruktury na funkční vlastnosti geopolymerních systémů z technogenních pucolánů“ (číslo projektu 106/09/0588). Práce byla řešena na katedře Tepelné techniky – Ústavu průmyslové keramiky, FMMI VŠB-TU Ostrava. Experimentální část je v úvodu zaměřena na zdůvodnění výběru vhodných vstupních surovin – druhotných produktů metalurgie a energetiky. Dále se hodnotily vlastnosti těchto surovin, realizovaly se experimenty jejich mechanické aktivace mletím a bylo navrženo několik variant složení surovinových směsí. Ty potom byly zpracovány se dvěma typy alkalických aktivátorů a optimalizovanými postupy se připravily a dále ošetřovaly laboratorní vzorky. Výsledky přinášejí nové informace o souvislostech mezi složením konkrétních směsí, kvalitou surovin a výslednými parametry alkalicky aktivovaných, tzv. geoplymerních, bezcementových pojiv a kompozitů. Mletí EP zvyšuje dlohodobé pevnosti hmot, pro konnkrétní způsob mletí lze najít optimalní podmínky, zaručující vyšší reaktivitu EP. Přídavek popílku ke GVS se mění hydratační děje v systému, vznikající C-S-H fáze doplněné hydráty typu C-A-S-H a tím se zlešuje korozní odolnost hmot.PhD thesis "Binders preparation by alkaline activation of alternative materials", summarizes the results of which were part of the project of the Grant Agency of the Czech Republic, "Influence of phase composition and microstructure on the functional properties of the geopolymer systems technogenic pozzolana" (project number 106/09/0588). The work was solved at the Department of Thermal Engineering - Institute of Industrial Ceramics, FMMI VSB-TU Ostrava. Experimental part in the introduction is focus on the rationale for the selection of suitable raw materials - by-products of metallurgy and energy. Furthermore were appraised properties of raw materials, realized the experiments by mechanical activation - milling and has been designed some variations composition of mixtures raw material. These mixtures were treated with two types of alkaline activators and with optimized procedures were prepared laboratory samples. The results bringing new informations in context between the concrete composition of mixtures, quality materials and finall parameters of alkali-activated composites and binders so-called geopolymer cement-free. Grinding FA increases long-time compressive strength of materials for concrete way of milling. Can be found optimal conditions, guarantee higher reactivity of FA. Addition fly FA to GBFS changes hydration action in system and formed CSH phase supplemented hydrates type of C-A-S-H and thus improves the corrosion resistance of materials.Prezenční635 - Katedra tepelné technikyvyhově

Slags from steel production: Properties and their utilization

During steel production a considerable amount of slags is produced. In addition to its usual processing, as recycling in device for steel production and preparation of aggregates, it is also possible to apply less common slag processing ways. Depending on cooling mode of the steel slags these may show some binding properties. Geopolymer type binders can be prepared from the slag using alkali activators or the hydraulic properties of the dicalciumsilicate present in the slag can be induced by water. The paper summarizes present state of material utilisation of the steel slags with focus on emphasize of the possible sources of the slag volume instability. The infl uence of process of slag cooling on its phase composition is documented. It was also found that slags from real sources show diff erent parameters compared to samples obtained for laboratory examination.Web of Science52333332

Potential modification of hydration of alkali activated mixtures from granulated blast furnace slag and fly ash

Alkali activated binders (AAB) and composites from suitable latent hydraulic raw materials represent an alternative to materials based on Portland cements. The paper deals with possibilities to influence functional parameters of AAB by setting the mixtures of GBFS and fly ash to the selected chemical composition or by fly ash reactivity change effected by milling. In this way course of hydration process is modified, the alkali activation products phase composition is changed as well as their final characteristic. The amorphous character of the hydration products limits the evaluation of the composition during the massing phase. Part of the study is the search for possibilities of identifying the differences in composition and properties of specially drafted mixtures of original raw materials after their alkali activation.Web of Science56217616

Metallurgy dusts as a pigment for glazes and engobes

This study is focused on using the dust from metallurgy as a pigment. The agglomerating dust is formed during metallurgical processes. This waste product is interesting for recycling process. The main mineralogical phase of dust is hematite alpha-Fe2O3. Both synthetic and natural iron oxides are commonly used as pigments in ceramic industry. In this experiment the metallurgy dusts were used as a pigment for preparation of glazes and engobes. Agglomerating dusts were used both precalcined thermally at 700 degrees C and 900 degrees C and in an original state. The prepared glazes were composed of a transparent glaze base with 10 wt% agglomerating dusts as pigment. The glazes calcined at 1060 degrees C were finally yellow colored and glazes calcined at 900 degrees C were brown colored. Engobes contained a ceramic clay base with 1, 5, 10 and 50 wt% of dust as pigment. Engobes calcined at 900 degrees C were red and grey colored. The pigments were characterized by X-ray diffraction (XRD), chemical (XRFS) analysis, granulometry (PSD), thermogravimetric (TG) and differential thermal (DTA) analysis, scanning electron microscopy (SEM) and CIELab values.Web of Science43107796778

Effect of mass ratio and milling on compressive strength and corrosion resistance of blast-furnace slag/fly ash geopolymer activated by solid alkali activator

Fly ash and granulated blast-furnace slag can be considered "multifunctional waste." This study is focused on properties of a non-cement binder prepared from slag and fly ash activated by solid alkali activator. Fly ash was milled (2.5, 5.0, and 7.5 min) in order to increase its reactivity, and particle size distribution, specific surface area, and grain morphology were determined for all milled FA samples. Two GBFS +FA mixtures (70:30 and 85:15 w/w) were studied. Prepared mixtures were activated by solid alkali activator (Na2SiO3). Optimal weight ratios were calculated for CaO, SiO2, and Al2O3 components. Properties of the mixtures were studied in dependence on the GBFS:FA mass ratio and FA milling time (0-7.5 min). After 2 and 28 days of hydration, compressive strength of all mixtures exceeded 20 and 60 MPa, respectively. The 85:15 ratio led to generally higher compressive strength 108.3 MPa was reached after 90 days using FA milled for 7.5 min. Corrosion resistance was tested by exposing mixtures to distilled water, 0.5% HCl, and 3% Na2SO4 for 65 days, and evaluated by measuring changes in CS. Also the corrosion resistance was found higher (Na2SO4) than and comparable (HCl, water) to the 70:30 ratio. This study aims to show that GBFS +FA mixtures (70:30 and 85:15 w/w) activated by solid Na2SiO3 can achieve high CS and good corrosion resistance.Web of Science841974196