MECHANOCHEMICAL PHENOMENONS TAKE PLACE DURING COMMINUTIONS OF
CONVENTIONAL BRICK CLAYS ON PAN MILL
Dr. László A. Gömzeassociated professor
UNIVERSITY OF MISKOLCFACULTY OF MATERIAL SCIENCE AND ENGINEERING
Dept. of Ceramics and Silicate Engineering
http://keramia.uni-miskolc.hu [email protected]
Habilitációs tudományos kollokviumMiskolc, 2011. január 20.
THEMES
1. Our goals
2. Properties of clay minerals and conventional brick clays
3. The aims of crushing and fine comminution of brick clays
4. Mechano-chemical processes during fine comminution
5. Mechano-chemical phenomenons take place during grinding clay
materials on laboratory pan mill
6. Conclusions
MECHANOCHEMICAL PHENOMENONS TAKE PLACE DURING COMMINUTIONS OF CONVENTIONAL
BRICK CLAYS ON PAN MILL
OUR GOALS
1. Understand the essence of mechano-chemical processes take place during
grinding and fine comminution of clay minerals.
2. Understand the effects of mechano-chemical activation on the physico-chemical
and technological properties of the main components of conventional brick
clays and clay minerals.
3. Increase the efficiency of crushing of conventional brick clays and clay minerals
through understanding the mechano-chemical processes take place during
their fine comminutions.
MECHANOCHEMICAL PHENOMENONS TAKE PLACE DURING COMMINUTIONS OF CONVENTIONAL
BRICK CLAYS ON PAN MILL
PROPERTIES OF CLAY MINERALSAND CONVENTIONAL BRICK CLAYS
THE CLAY MINERALS• Clay minerals are hydrous aluminium phylosilicates, sometimes contain Fe+2,
Mg+2, Na+, K+ and other cations;• Clay minerals are products of common weathering and low temperature
hydrothermal alteration;• Generally they are built of tetrahedral (t) and octahedral (o) sheets;• Clay minerals are ultra fine grained, dmax< 2 µm;• Typical t-o clay is kaolinite AS2H2 Al2O3*2SiO2*2H2O;• t-o-t clays are illite, smectite and others.
Octahedral structureTetrahedral structure
• The conventional brick clays are mix of minerals like:• Quartz: SiO2 and its modifications• Feldspars:
• Albite: NAS6 Na2O*Al2O3*6SiO2
• Orthoclas: KAS6 K2O*Al2O3*6SiO2
• Anorthite: CAS2 CaO*Al2O3*2SiO2
• Clay minerals of the following groups: • Kaolin group: AS2H2 Al2O3*2SiO2*2H2O
• Kaolinite and their modifications (dickite, halloysit, nacrite)• Smectite group:
• Montmorillonite (Na, Ca)0,33(Al,Mg)2(Si4O10)(OH)*nH2O• Montronite (CaO0,5,Na)0,3Fe3+
2(Si,Al)4O10(OH)2*nH2O• Saponite CaO0,25(Mg, Fe)3((Si,Al)4O10)
(OH)2*nH2O• Illite group: illite and clay micas• Chlorite group: wide variety of similar minerals
• Other minerals: carbides, oxides and organic materials and pollutions
THE CONVENTIONAL BRICK CLAYS
PROPERTIES OF CLAY MINERALSAND CONVENTIONAL BRICK CLAYS
THE TYPICAL STRUCTURES OF CONVENTIONAL BRICK CLAYS
Magnification: 1000X Magnification: 2000X Magnification: 3000X
Magnification: 1000X Magnification: 1000X Magnification: 10 000X
60. évf. 4. szám 2008/4 építőanyag
STRUCTURE AND TOTAL VOLUME OF PORES IN CLAY MINERALS
Where:A and B – the total numbers of opened and closed poresC and D – the total numbers of capillares and gaps between the grainsV – VolumeVnpi – the volume of „i-th” open poreVzpj – the volume of „j-th” closed poreVkpk – the volume of „k-th” capillaryVhtl – the volume of „l-th” void (gap)
D
lht
C
kkp
B
jzp
A
inppö
alkji
VVVVV1111
1. Decrease the sizes and volumes of grains, individual pores, gaps (voids) and capillaries through grinding.
2. To get the required grain sizes and their distributions of the clay minerals as raw materials.
3. Increase the chemical reactivity of the grains and particles of clay minerals throught obtaining the required values of surface and specific surface areas.
4. Use mechanical energy to change physico-mechanical properties of clay minerals as raw materials.
5. Change the chemical and mineralogical compositions of clay minerals through mechanical activation of their atoms and ions.
THE AIMS OF CRUSHING AND FINE COMMINUTION OF CLAYS
The tensile stress (pk) in water-droppes generated by surface stress:
rpk
cos2
α – contact wetting angle; [°]
σ - surface tension (N/m);
r – radius of water drop (m)
Radius of the pore, (the radius of water drop)
The required mechanical stress to overtake the surface
tension of waterMPaMPaMPaMPa
RELATIONSHIPS BETWEEN THE VOLUMES OF INDIVIDIUAL PORES AND WATERS IN THEM
Atoms and ions at the surface have less neighbouring atoms and ions as inside of the body They have extra energy and activity at the surfaces. During grinding the total volume of grain surfaces are increasing, because of which the surfaces become chemically activated.These chemically activated states of clays are appeared in:• increased adsorption activity,• aggregation and agglomeration phenomenons,• mechano-chemical processes and phase transformations,• increased volume of amorphous phases.
MECHANO-CHEMICAL PROCESSES DURING FINE COMMINUTIONS
Theoretical Practical
THE INITIAL MODEL OF MECHANO-CHEMICAL PROCESSES
(Taken from Jushchenko, V. S, Grivtsov, A. G., andShchukin, E. D.) DAN, SSSR 215 148 (1974)
(Taken from Jushchenko, V. S, Grivtsov, A. G., andShchukin, E. D.) DAN, SSSR 219 162 (1974)
Cavity wall adsorbed with alien atoms (medium)
Cavity is not adsorbedPropagation of brittle crack with deformation at low temperature; Formation of dislocation with deformation of high temperature Formation of crack through penetration of alien atoms (medium)
into the stressed and deformed system
Cch – Chemical composition and structure;Ccm – Mineralogical composition and structure;Ccr – Crystal structures of mineralogical components;Dgs – Grain sizes and structures of components;Fcr – Crushing forces and their loadings;Fib – Interatomic bonding forces;Poc – Porosity, pore sizes and structures;Rmc – Mechanical properties, strength and hardnesses.
SOME IMPORTANT FACTORS INFLUENCE ON MECHANO-CHEMICAL PROCESSES DURING
FINE COMMINUTIONS
Mcp=f(Cch, Ccm, Ccr, Dgs, Fcr, Fib, Poc, Rmc)
USED EQUIPMENT AND TESTING INSTRUMENTS
a. Used equipment for crushing and comminution
Hosokawa mechanofusior Pan grinder
b. Used instruments for testing
Bruker D8 Advance X-ray diffractometer
Hitachi TM 1000 Scanning Electronmicroscope
Tristar 3000 Specific surface tester Derivatograph
INFLUENCE OF CRUSHING TIMES ON SPECIFIC SURFACES OF CLAY
MINERALS USED IN CERAMIC BRICK INDUSTRY
MINERAL CONTENTS OF MINED CLAY RAW MATERIALS USED IN CERAMIC ROOF-TILES
INDUSTRY IN LENTI, HUNGARY
INFLUENCE OF CRUSHING TIME ON MINERAL CONTENTS OF „LENTI” MINED
CLAY RAW MATERIALS
CHANGES IN MINERAL CONTENTS OF MINED CLAY RAW MATERIALS USED IN
CERAMIC ROOF-TILES INDUSTRY IN LENTI, HUNGARY
CHANGES IN MINERAL CONTENTS OF „LENTI” CLAY RAW MATERIALS AS
FUNCTION OF MOISTURE AND CRUSHING TIME
INFLUENCE OF CRUSHING TIMES ON MINERAL CONTENTS AND SPECIFIC SURFACE OF MINED CLAYS USED IN CERAMIC BRICK INDUSTRY IN TISZAVASVÁRI,
HUNGARY
INFLUENCE OF GRINDING TIME ON THERMO-ANALYTICAL PROPERTIES
OF CONVENTIONAL BLUE CLAY FROM TISZAVASVÁRI
MODELING OF CHEMICAL ACTIVITY OF FINE QUARTZ GRAINS IN WET CLAY MINERALS
OF CERAMIC BRICKS AND ROOF-TILES
a: adsorption layerb: diffusion layer of cationsm: number of molecules in the coren: number of molecules in the colloid outside of the coreR1: radius of the coreR2: radius of the colloid particleR3: radius of the micell
[(SiO2)m*nSiO32-*2(n-x)H+]*2x*H+
(SiO2*4H2O)m
CONCLUSIONS• Clay minerals of ceramic brick and roof-tile industries having high values
of specific surface area are mechano-chemically very actives during crushing on pan grinder.
• Because of the dissipation of minerals, like Muscovite 2M and significant growth of volumes of Quartz, the specific surfaces of Lenti clay decrease considerably, depending on crushing times.
• During the fine comminution of clay minerals of brick and roof-tile industries the Muscovite 2M and Illite are the most instable components, meanwhile the quantity of Albite and Quartz can be formed.
• The free moisture – water – in mined clay minerals and dehydration and dissociation of sum of their components can mechano-chemically activate the fine Quartz crystals, generating colloids and micells. These micells are chemically very active and can participate in forming new minerals of Illite or Muscovite 2M, as well.
• During grinding conventional brick clays on laboratory pan grinder a considerably volume of amorphous phase can be formed.
ACKNOWLEDGEMENT
The author acknowledge to the colleagues and PhD students at :
Dept. of Mineralogy and Petrology for XRD examinations,
Dept. of Metallurgical and Foundry Engineering for specific surface measurements,
and to the colleagues, PhD students and technicians at
Dept. of Ceramics and Silicate Engineering for the collaboration in laboratory tests and measurements.
Thank you very much for your time and kind attention !
Habilitációs tudományos kollokviumMiskolc, 2011. január 20.
Dr. László A. Gömzeassociated professor
University of MiskolcFACULTY OF MATERIAL SCIENCE AND ENGINEERING
Dept. of Ceramics and Silicate Engineering
