Chemicals Based
Technologies - Synthetic High Alumina Aggregates
(58 To 86% Alumina)
Introduction
A wide variety of high alumina refractories
in the form of bricks or any shapes and monolithics
possessing stringent qualities are required, to meet
the increasing demand by iron and steel, cement, glass,
chemical and other industries. The efficiency of the
user industries and the quality of the product produced
depends mainly on the performance of the refractory
products they use, which, in turn, broadly the quality
and performance of the refractory materials from which
these refractories are made and their fabrication techniques.
Appropriate quality mineral-based high alumina raw materials
in the form of kyanite/ sillimanite/ alusite/ diaspore/
bauxite/ corrundum are becoming scarce. New sources
are the beneficiated concentrates of low-grade minerals
and development/import of substitute materials in the
form of synthetic products like sintered/fused high
alumina aggregates of mullite, mullite-corrundum and
corrundum. The requirement of high quality synthetic
aggregate is reported to be quite high and the demand
of such materials is mostly met through imports of synthetic
sinter mullite/ tabular-alumina/high alumina cements
etc.
The technology for making sintered
synthetic mullite/mullite corrundum/corrundum, involve
high technology requiring the use of high cost infra-structural
inputs in the form of high cost high duty briquetting
press machine for pelletisation, high temperature kiln
for sintering the synthetic compositions around 1600-1850°C,
like shaft kiln/ rotary kiln and other high cost processing
equipment and machinery.
The Central Glass and Ceramic Institute,
Calcutta, has developed the process which involves innovation
and improvement in the technology eliminating the use
of high cost and high technology infrastructure, as
also reducing the cost of production by introducing
new technique of sintering synthetic products containing
58 to 86% alumina.
Process
Institute had developed a process
of manufacturing synthetic high alumina aggregate and
their products through new technique of sintering by
utilizing indigenous raw materials of appropriate qualities.
Fireclay, china clay, technical/ hydrated alumina and
some other chemical additives are employed. . Conventional
machinery and equipment may be used. The process may
also be easily adaptable by small scale and mini scale
sectors. In this process, products are matured at temperature
ranging from 1350°C to 1550°C.
Different steps of the process include
blending of the raw materials, commination to fine sizes,
dewatering, mixing with green bond, shaping into hollow
ware, drying the green compacted wares, firing and reduction
of particle sizes to appropriate graded fractions. Ranges
of physico-chemical, thermal and mineralogical characteristics
of the sintered aggregates are as follows:
Alumina content wt.%
54-56
68-73
80-86
Sintering temp. 0 C
1400-1450
1450-1500
1450-1550
Bulk density, g/cc
2.67-2.90
2.82-3.00
2.95- 3.10
Porosity %
0.0-5.6
1.2-4.5
0.5-5.5
PCE, Ortons
38+
38+
38+
PLCR at
1500 0 C -5 hr, %
0.05-0.50
0.06-0.80
0.2-0.56
1600 0 C -5 hr, %
0.05-0.85
0.06-0.95
0.5-0.95
Mullite content %
70-78
88-92
55-60
Corrundun content, %
2.0-5.0
2.0-5.0
35-40
Fuel consumptio, Kg/T
120
130
140
Plant Parameters
Capacity, TPA
5000 or 2.8T/hr.
No.of Shifts / day
1
Working days / Yr
300
Toal Land Area, m2
40000
Covered Area, m2
140
Manpower
Managerial
1
Engineers
5
Skilled
50
Unskilled
100
Total
156
Raw Material
Per annum
Clay, MT ]
6800
Alumina, MT ]
Utilities
Power, KwH
200
Fuel , Kg/T
140
Plant & Machinery
Furnace
Vibromill
Vacuum extrusion pug mill
Impact mill
Jaw cum roll crusher
Tunnel drier
Sieving Machine
Muller Mixer
Advantages of Indian technologies:
Low capital investment
High employment potential
Maximum use of local raw materials
and manpower resources
Adaptable levels of sophistication
For further information please contact
:
National Research Development Corporation
( A Government of India Enterprise )
20-22, Zamroodhpur Community Center
Kailash Colony Extension
New Delhi 110 048. India
Tel: 91-11-26419904, 26417821, 26480767, 26432627
Fax: 011-26231877, 26460506, 26478010
Website: www.nrdcindia.com
