plik Adobe PDF / Get full paper - Adobe PDF file

plik Adobe PDF / Get full paper - Adobe PDF file

1
ROBERT PURGERT
ANDRZEJ BALIŃSKI
JERZY SOBCZAK
PAWEŁ DARŁAK
MACIEJ SZOLC
NATALIA SOBCZAK
FLY ASH FOR SYNTHESIS OF NEW MOULDING SANDS
(FASAND)
Abstract
Fly ash materials as a waste by-product, are produced during combustion of coal by
thermal power plants and present a serious ecological problem associated with their storage and
disposal. Therefore, the development of suitable scientific, technical and economic solutions of fly
ash utilization is very pressing and important. This paper summarizes the work done at the
Foundry Research Institute (Poland) in collaboration with the Energy Industries of Ohio on an
attempt to visualize the effect of fly ash (DP&L, First Energy and LEG – Poland) as an additive to
green sand and as a filler for chemically bonded sand. The physical properties such as dimensions
(screen distribution), density, characteristic temperatures and chemical properties (pH value) as
well as technological parameters (compression strength, tensile strength, permeability, friability
and compatibility) for wide range of FASANDS have been investigated.
Key words: fly ash, moulding sands, bentonite, water glass
1.
INTRODUCTION
Fly ash materials as a waste by-product, are produced during combustion
of coal by thermal power plants and present a serious ecological problem
associated with their storage and disposal [1-3]. Therefore, the development of
suitable scientific, technical and economic solutions of fly ash utilization is very
pressing and important. A subject of the most passed research was the
characteristic fraction of fly-ashes (cenosphere) (fig.1) due her very good heatinsulating proprieties [4,5]. The moulding sands with a participation of the flyash consisting mostly from compact particles (fig.2) was also study in the aspect
of her wettability by the liquid aluminium alloy [6]. Ascertained the
1
2
insignificant wettability suchlike moulding sands, on the understanding that
technology of her producing is proper.
1
Fig.1 Structure of the cenosphere
with diameter about 100 μm
Rys.1 Struktura cenosfery o średnicy
około 100 μm (Western Fly Ash Co.)
Fig.2 Particles of the fly-ash with
compact structure (Western Fly Ash
Co.)
Rys.2 Cząsteczki popiołu lotnego o
zwartej strukturze (Western Fly Ash
Co.)
Because of the complex physical and mechanical properties with respect
to low price and low density, fly ash can be an extremely attractive material
applicable for the synthesis of composites [2,3,7,8]. This very unique and
inexpensive powder resource, unlike those synthetically produced in a favorable
spherical form with wide ranges of size and density, may be suitable in various
light weight structural applications (ALuminum – Fly Ash (ALFA composites))
[9-12]. Another promising application of fly ash can be its use as replacement
for foundry sand in mold and core production.
This report summarizes the work done at the Foundry Research Institute
(Poland) in collaboration with the Energy Industries of Ohio on an attempt to
visualize the effect of fly ash, as an additive to green sand and as a filler for
chemically bonded sand.
2.
GENERAL INFORMATION
Materials used for moulding sands (according to basic data obtained from
producers):
1.
Fly ash from following Power Plants (as received), chemical
composition in weight %:
• Dayton Power & Light (DP&L): 57,4 SiO2, 28,5 Al2O3, 5,8 Fe2O3, 1,5
TiO2, 1,1CaO, 1,0 MgO, 0,2 Na2O, 3,0 K2O, 0,3 SO3, 0,2 P2O5 0,1
Mn2O3, 0,1SrO,
2
3
•
•
2.
1.
2.
3.
4.
First Energy (FE): 52,5 SiO2, 30,2 Al2O3, 12,3 Fe2O3, 0,9 TiO2 3,5 CaO,
1,0 MgO, 0,5 Na2O,
LEG – Krakow (partially): 45,5 SiO2, 23,3 Al2O3, 7,1 Fe2O3, 0,9 TiO2 4,2
CaO, 3,0 MgO, 0,6 Na2O, 2,8 K2O, 0,5 SO3, 0,4 P2O5, 0,1BaO.
Quartz sand (silica sand) with main fraction 0.20/0.32/016 and
homogeneity index 88 for sands with bentonite as a clay.
Quartz sand with main fraction 0.20/0.40/032 and homogeneity index 87
for green sands with water glass as a binder.
Bentonite (Special – kind from Zębiec, Poland) with the expanding
index of Wk=17 cm2/g.min with the carbonates content max. 5%,
montmorylonite min. 70% and having 80% grains with diameter below
0.056 mm.
Water glass (sodium silicate) with density 1.471 g/cm2, oxide modulus
silicate-sodium M=2.3 and total amount of oxides SiO2+Na2O=41.39%.
Diacitate of ethylene glycol (ester) without any modification by glycol
propylene, with density 1.12 g/cm2 and acid number 16 mg KOH/g.
Alloys and metals for pouring:
1. Nickel-silicon cast steel (weight. %): C=0,08, Ni=20,0, Si=2,88,
Al=0,19, Mn=011, S=0,02, P=0,01, Fe=rest
2. Cast iron (two types):
(I)
Nickel-silicon cast iron: C=2,90, Ni=21,19, Si=2,82,
Cu=0,45, Mg=0,08, Mn=0,05, P=0,01, S=0,01, Fe=rest
(II)
Nickel-chromium cast iron: C=1,2, Ni=2,5, Cr=1,50,
Mo=0,40, Mn=0,40, Si=0,19, P=0,01, S=0,01, Fe=rest
3. Silicon bronze (BK331): Si=3,50, Zn=4,21, Mn=1,05, Fe=0,85,
Cu=rest
4. Aluminum-silicon alloy (AK9): Si=9,20, Mg=0,25, Mn=0,41,
Fe=0,35, Al=rest
5. Pure zinc
3.
EXPERIMENTAL PROCEDURE
3.1. Fly ash characterization
Some basic characteristics of investigated fly ashes have been given by
producers. However, for future application of fly ash as constituent of moulding
sand in mold and core production it is necessary to have an additional
information on its physical properties such as dimensions (screen distribution),
density, characteristic temperatures and chemical properties (eg. pH value).
3
4
Screen analysis of fly ash has been done using apparatus of type LPzE-2e. For
comparison, the same methodology was used for quartz sand.
Using gravimetric technique the following values of bulk density db
have been obtained for as-received materials:
• Dayton Power
and Light fly ash:
db = 1.04 – 1.08 g/cm3 (0.0376 – 0.0.390 lb/in3)
• First Energy fly ash:
db = 1.00 g/cm3 (0.0362 lb/in3)
• LEG fly ash:
db = 1.10 g/cm3 (0.0398 lb/in3)
• Quartz sand (for comparision): db = 1.40 – 1.45 g/cm3 (0.0506 – 0.0524 lb/in3 )
(true density of quartz is dt = 2.650 g/cm3 (0.0957 lb/in3 )
All 3 types of fly ash showed approx. 40% smaller bulk density than quartz
sand.
Such characteristic temperatures of fly ashes as temperature of sintering,
softening, melting and flow were estimated during heating fly ash cylindrical
samples in air using high temperature microscope PR-25/1750. For comparison, the
melting point of quartz sand has been also measured. The results of
investigations are shown in Table 1. Dayton Power & Light fly ash showed the
characteristic temperatures much higher than First Energy fly ash, and lower,
compared to quartz sand. The differences between these two fly ashes, most
probably, are resulted from of its chemical composition.
Table 1
Characteristic temperatures of investigated materials
Charakterystyczne temperatury badanych materiałów
Materials
Temperatures, 0C
First Energy fly ash
Sintering temperature
1130
Softening temperature
-
Melting temperature
Flow temperature
Dayton Power & Light fly
ash
1176–1180
1478–1485
1183 - 1198
1625–1640
1210 – 1217
1653–1662
Quartz sand
1710-1713
-
4
5
3.2. Technological properties of foundry sand containing fly ash
3.2.1. Green sands
Green (mechanically bonded) sands were prepared using standard edge
runner sand mill according to the following composition (weight percent):
sand grains – 93%, clay (bentonite) – 7%, water – 3,5%.
The sand grains contained the quartz sand (basic mass) and the mixture
of quartz sand & fly ash – 5, 10 and 20%.
It was noticed, that FE fly ash, contrary to DP & L and LEG fly ashes,
shows bonding properties. It was decided to investigate the technological
properties for mixture of clay (bentonite + FE fly ash) containing 25,50 and 70%
FE fly ash. 100% of FE fly ash green sand was also made. At the beginning the
loose ingredients (quartz sand + clay) were mixed for 2 min. After that, water
was added and mixing was continued for next 6 min. The obtained moulding
sands were used to prepare the samples for investigations of the following
technological properties: compression strength [Rcw, MPa], tensile strength [Rmw,
MPa], permeability [Pw, m · 10 –8 / Pa · s], friability [Sw, %], compactibility [Z,
%]. The results of tests are shown in Figs. 3- 6.
P
Technological
properties
300
Rcw x 1000
250
Rmw x
10000
Pw
200
150
100
Sw x 10
50
0
Z
0
5
10
15
20
Fly ash content, weight %
Fig.3 Effect of amount of FE fly ash on technological properties of green sands (Rcw –
compression strength, Rmw- tensile strength, Pw- permeability, Sw- friability, Zcompactibility)
Rys.3 Wpływ ilości popiołu lotnego FE na technologiczne właściwości mas z lepiszczem
bentonitowym (Rcw – wytrzymałość na ściskanie, Rmw- wytrzymałość na rozciąganie, Pwprzepuszczalność, Sw- osypliwość, Z- zagęszczalność)
5
6
Technological
properties
300
250
200
150
100
50
0
Rcwx1000
Rmwx10000
Pw
Swx100
Z
0
5
10
15
20
Fly ash content, weight.%
Fig.4 Effect of amount of DP&L fly ash on technological properties of green sands (Rcw –
compression strength, Rmw- tensile strength, Pw- permeability, Sw- friability, Zcompactibility)
Rys.4 Wpływ ilości popiołu lotnego DP&L na technologiczne właściwości mas z lepiszczem
bentonitowym (Rcw – wytrzymałość na ściskanie, Rmw- wytrzymałość na rozciąganie, Pwprzepuszczalność, Sw- osypliwość, Z- zagęszczalność)
300
Rcw x 1000
Technological
properties
250
Rmw x 10000
200
Pw
150
Sw x 100
100
Z
50
0
0
5
10
15
20
Fly ash content, weight.%
Fig.5 Effect of amount of LEG fly ash on technological properties of green sands (Rcw –
compression strength, Rmw- tensile strength, Pw- permeability, Sw- friability, Zcompactibility)
Rys.5 Wpływ ilości popiołu lotnego LEG na technologiczne właściwości mas z lepiszczem
bentonitowym (Rcw – wytrzymałość na ściskanie, Rmw- wytrzymałość na rozciąganie, Pwprzepuszczalność, Sw- osypliwość, Z- zagęszczalność)
350
Rcwx1000
Technological
properties
300
250
Rmwx10000
200
150
Pw
100
Swx10
50
0
0
20
40
60
80
100
Z
Fly ash amount in bentonite, weight.%
Fig.6 Effect of amount of FE fly ash in bentonite on technological properties of green sands
(Rcw – compression strength, Rmw- tensile strength, Pw- permeability, Sw- friability, Zcompactibility)
Rys 6. Wpływ ilości popiołu lotnego FE na technologiczne właściwości mas z lepiszczem
bentonitowym (Rcw – wytrzymałość na ściskanie, Rmw- wytrzymałość na rozciąganie, Pwprzepuszczalność, Sw- osypliwość, Z- zagęszczalność)
6
7
3.2.2.
Chemically bonded sands
Technological
properties
Chemically bonded moulding sands were prepared using standard ribbon
sand mill according to the following composition (weight parts): sand grains –
100.0, water–glass – 9.0, diacetate of ethylene glycol – 15% of water-glass.
The above composition has been optimized taking into account high
dispersion of sand grains. To study technological properties, the samples of
chemically bonded moulding sands were prepared in the same way like for green
sands. All characteristics have been measured after 3 and 24 hrs of chemical
hardening. The results of investigations are shown in Figs. 7 - 8.
6
5
4
3
2
1
0
Rc3
Rc24
Rg3
Rg24
0
20
40
60
80
100
Fly ash content, weight.%
Fig.7 Effect of amount of DP&L fly ash on compression and bending strength of chemically
bonded moulding sand (Rc – compression strength, Rg- bending strength, Rc3, Rg3 properties after 3 hrs chemical hardening, Rc24, Rg24 – the same after 24 hrs chemical
hardening)
Rys.7 Wpływ ilości popiołu lotnego DP&L na wytrzymałość na ściskanie i zginanie mas
formierskich utwardzanych chemicznie (Rc – wytrzymałość na ściskanie, Rg – wytrzymałość
na zginanie, Rc3, Rg3 – wytrzymałości po 3 godzinach utwardzania , Rc24, Rg24 – po 24
godzinach)
2
-8
Permeability, m 10 / Pa s
It was concluded that due to a lack of hardening reaction the FE fly ash
can not be recommended for the synthesis of sands with given binder (waterglass + diacetate of ethylene glycol).
350
300
250
200
150
100
50
0
P3
P24
0
20
40
60
80
100
Fly ash amount, weight.%
Fig.8 Effect of the amount of DP&L fly ash on permeability Pu of chemically bonded
moulding sands (P3, P24 – after 3 and 24 hrs of chemical hardening respectively)
Rys.8 Wpływ ilości popiołu lotnego DP&L na przepuszczalność Pu mas utwardzanych
chemicznie (P3, P24 – odpowiednio po 3 i 24 godzinach utwardzania chemicznego)
7
8
3.3. Molding and pouring
The open sand molds, made from both green and chemically bonded
sands, have been produced by adopting the same procedure, applied for the
samples preparation in testing of technological properties of the sands. Simple
axial symmetric conical part has been taken as a pattern. For sand molding, the
only DP&L fly ash has been used due to limited amount of delivered FE and
LEG fly ash. For green sand molds containing 10% and 20% fly ash, the
following selected alloys and zinc have been poured at corresponding
temperature:
1. Cast steel - 1500ºC, 2. Grey iron (I) - 1400ºC, Grey iron (II) - 1520ºC
3. Silicon bronze - 1050ºC, 4. Aluminum alloy - 720ºC, 5. Zinc - 420ºC
For chemically bonded molds containing 100% fly ash, silicon bronze,
aluminum and zinc alloys have been poured at the same temperatures indicated
above.
The solidified castings were removed from the molds, than cleaned to
estimate the quality of their surfaces and next, cut to characterize vertical
crossections.
4. Conclusions
1. Green sands
Almost all selected alloys can be poured successfully into green sands
containing up to 20% fly ash as a substitute of quartz sand. Because of binder
properties noted for FE fly ash, there is an opportunity to replace some clay (eg.
bentonite) by fly ash in green sands.
The surfaces of the obtained castings were free from any visible defects
and reaction products formed between molten metal and sand. Visual
observation of crossections showed that all castings were sound.
Among selected alloys, the only nickel-silicon cast steel demonstrates
strong interaction with sand. Therefore, to eliminate this unwanted phenomenon
the fly ash content was decreased to 10%.
2. Chemically bonded moulding sands
Silicon bronze, aluminum alloy and zinc can be poured successfully into
chemically bonded moulding sand molds containing up to 100% fly ash. The
quality of such castings, estimated by visual characterization of casting surfaces
and crossections, was satisfied. Additionally, the tests showed promising
8
9
applicability of 100% fly ash for core production. However, for this purpose, the
binder system has to be optimized to reduce the core friability and permeability.
References
1. Rohatgi P.K., “Low-Cost Fly Ash Containing Aluminum Matrix Composites”, JOM, 11
(1994), 55-59
2. Rohatgi P.K., Guo R.K., “Low Cost Cast aluminum-Fly Ash Composites for Ultra
Light Automotive Application” Processing, Properties, and Applications of Cast Metal
Matrix Composites, TMS publication, 1997, 157-168
3. Rohatgi P.K. et al., “Cast Aluminum - Fly Ash Composites for Engineering
Applications”, AFS Transactions, (1995) 575-586
4. Ignaszak Z., Baranowski A.,”Thermal conductivity determination method of fly ash
applied in high temperature”, in Proceedings of IV Canmet/ACI International
Conference on Fly Ash , Silica Fume and Natural Pozzolans in Concrete, 3-8 May, 1992,
Istambul
5. Ignaszak Z., “Termofizyczne parametry materiałów izolacyjnych w zastosowaniu do
projektowania zasilania odlewów I symulacji ich krzepnięcia”, Solidification of Metals
and Alloys, 1999, vol.1, Book no 40, pp. 125-131
6. Baliński A., Sobczak N., Radziwiłł W., Nowak R.,:”Badania oddziaływania ciekłego
stopu aluminium z popiołem lotnym, jako osnową ziarnową mas formierskich”,
Archiwum Odlewnictwa, 2006, rocznik 6, nr 18 (2/2), str. 379-384
7. Rohatgi P.K. et al., “Influence of Squeeze Pressure of AlSi9Zn3Cu3Fe1MnMg (52K)
Aluminum Alloy-Fly Ash Composites”, Transactions of the Foundry Research Institute,
XLIII (3) (1993) 143-160
8. Rohatgi P.K., Sobczak J., and Sobczak N., “Structure and Properties of Squeeze Cast
Aluminum Alloy-Flyash Composites”, Proceedings ICCE-2, ed. D. Hui, Aug. 20-24,
1995, New Orleans, USA, 689-690
9. Sobczak J., Sobczak N., and Rohatgi P.K., ”Using of Fly Ash for the Production of
Light Weight Composites”, Advanced Light Alloys and Composites, ed. R. Ciach,
NATO ASI Series, 3. High Technology, Kluwer Academic Publishers, 59 (1998), 109115
10. Sobczak J., Sobczak N., Purgert R.M., Rohatgi P.K. New Alfa Composites (Aluminum
Alloys and Fly Ash): Fly Ash Waste Material for the Synthesis of Light Weight Low
Cost Aluminum Matrix Composites. Proceedings of Seventeenth International
Pittsburgh Coal Conference, Pittsburgh, Pennsylvania, USA, September 11-14, 2000,
pp.1-14
11. Rohatgi P.K., Sobczak J., Purgert R.M. The Properties of ALFA Composites.
Proceedings of Seventeenth International Pittsburgh Coal Conference, Pittsburgh,
Pennsylvania, USA, September 11-14, 2000, 13 pp.
12. Sobczak J., Sobczak N., Rohatgi P.K., Purgert R.M. Squeeze Casting of ALFA (AK12
Aluminum Alloy – Fly Ash) Composites. Proceedings of Seventeenth International
Pittsburgh Coal Conference, Pittsburgh, Pennsylvania, USA, September 11-14, 2000,
pp.1-23
9
10
POPIÓŁ LOTNY DO SYNTEZY NOWYCH MAS FORMIERSKICH
Streszczenie
Popiół lotny jest materiałem odpadowym powstającym w procesie spalania węgla w
elektrowniach i elektrociepłowniach i stanowi poważny problem ekologiczny, związany z jego
magazynowaniem i utylizacją. Dlatego rozwój naukowych, technicznych i ekonomicznych
rozwiązań dotyczących sposobów wykorzystania popiołu lotnego jest ważnym zagadnieniem. W
niniejszym artykule przedstawiono wyniki pracy badawczej zrealizowanej w Instytucie
Odlewnictwa (Polska) we współpracy z Energy Industries of Ohio, dotyczącej zastosowania
popiołów lotnych jako dodatku do mas formierskich z lepiszczem bentonitowym oraz jako
materiału ziarnowego w masach utwardzanych chemicznie. Przeprowadzono badania takich
własności fizycznych zastosowanych popiołów lotnych, jak rozkład ziarnowy, gęstość,
charakterystyczne temperatury przemian występujących podczas ogrzewania popiołów lotnych
oraz własności technologiczne mas formierskich FASAND wykonanych z udziałem badanych
popiołów lotnych (wytrzymałość na ściskanie, rozciąganie, zginanie, osypliwość, zagęszczalność,
przepuszczalność).
Słowa kluczowe: popiół lotny, masy formierskie, bentonit, szkło wodne
MSc Robert PURGERT
Energy Industries of Ohio, Clevelnd, Park Center Plaza, Suite 200, 6100 Oak Tree Bouleward
Independence, OH 44131, tel.(01216) 216 643 2952, e-mail: [email protected]
dr hab. inż. Andrzej BALIŃSKI, prof. Akademii Pedagogicznej
Instytut Odlewnictwa, ul. Zakopiańska 73, 30-418 Kraków, tel. (012) 261 82 19
Akademia Pedagogiczna, Wydział Matematyczno-Fizyczno-Techniczny, Instytut Techniki,
ul Podchorążych 2, 30-048 Kraków, tel. (012) 662 63 31, e-mail: [email protected]
prof. dr hab. inż. Jerzy SOBCZAK
Instytut Odlewnictwa, ul. Zakopiańska 73, 30-418 Kraków, tel.(012) 261 85 64,
e-mail: [email protected]
mgr inż. Paweł Darłak
Instytut Odlewnictwa, ul. Zakopiańska 73, 30-418 Kraków, tel. (012) 261 85 96,
e-mail: [email protected]
inż. Maciej Szolc
Instytut Odlewnictwa, ul. Zakopiańska 73, 30-418 Kraków, tel. (012) 261 82 50,
e-mail: nie posiada
dr hab. inż. Natalia Sobczak
Instytut Odlewnictwa, ul. Zakopiańska 73, 30-418 Kraków, tel. (012) 261 85 26,
e-mail: [email protected]
10