Introduction

The iron ore fines (below 150 micron in size) containing silica ( upto 8%) are subjected to physical beneficiation consisting of one more of the following unit operations viz, hydrocycloning, tabling, magnetic separation and flotation of silica to produce a concentrate assaying about 0.3% silica. This concentrate is the subjected to chemical beneficiation for further desilication. Concentrates from this step normally contains silica to the extent of 0.05%. Mn-Zn and Ni-Zn ferrites are synthesised from this superconcentrate by mixing the same with additives, compacting and calcining at 110-1200 deg C.. The calcined product is milled to get micron sized powder, dried and compacted into toroids using binders. The toroids are then sintered at temperature of 1250-1350 deg C. and coloed slowly . The microstructure and magnetic characteristics viz., coercive force, magnetic induction etc are measured.. After optimising the parameters, proto-type samples are prepared from external agency and properties viz., sintered density, Curie temperature, initial permeability, loss factor and power loss are measured to find its acceptability.

Details of Present/existing/Technology. Shortfall/Technological gaps in the existing technology

The production of soft ferrites based on ferric oxide is an important area since the requirement of iron oxide by the Indian soft ferrite industries is met through imports mostly. The demand for soft ferrites in India in the year 2000 was estimated to be about 10,000 tonne valued at 1,000 million rupees. The iron oxide for soft ferrite should be of at least 99.4% purity and their silica, alumina and calcium content should also be low. India has vast reserve of blue dust which is very high in iron content and low in silica and alumina. However, there is no any available process for reduction of silica and alumina to such level suitable for soft ferrite manufacture.

Approach adopted in new technology to evade technological gap in the existing one

Process has been developed for superconcentration of blue dust and other ultrafine natural iron oxide fines for reduction of silica and alumina to a level suitable for soft ferrite synthesis followed by development of process for synthesis of soft ferrites from this superconcentrate by optimisation of the parameters.

Advantage

India is endowed with vast reserves of iron ore. Blue dust is present with almost all hematitic deposits. Due to fine granulometry, it poses problem during iron ore processing and many of the plants, it finds place in tailing dumps. Thus, it does not find much of application in iron and steel industry while due to its high purity it may be considered for synthesis of ferrites. Similarly concentrate recovered from slimes can be a good source for the above application. Slimes in most of the iron ore processing plants are discarded as wastes. A part of the concentrate from magnetite beneficiaton plant can also constitute a source for the above. Thus, indigenously very low cost material can be a good feed stock. This will help in better usage and conservation of natural resources and minimising environmental pollution.

Applications

Magnets Ferrites as electronin components in TV, radio etc.

Status of Development

Soft ferrite conforming to the industrial specification has been synthesised in the laboratory scale

Ecological/Environmental Impact

No toxic effluents are generated in this process and as such it has no adverse effect on environment

Technology Transfer Assistance Offered

(a) Process Know-How,
(b) Details of the Equipment
(c) Plant lay-out
(d) Assistance in setting up a plant on separate terms

Contact for more information:

Director
National Metallurgical Laboratory
Jamshedpur-831 007, India
Tel: (0)657-2271715, 2270092
Fax:(0)657-2270527
Email: director@nmlindia.org