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
