4 process improvement after 30 years of development, INMETCO made in the production process a wealth of experience in equipment maintenance and production operations, rotary hearth furnace after several overhaul, gradually improved, major improvements are as follows: improve the furnace the entire roof masonry lining of way, etc. from the previous amorphous refractory castable refractory into shape, bite by way of hanging tiles, effective refractory improve the roof off the problem, greatly improving the life of Refractories; furnace added within the combustion zone and, nesting areas from the previous spray paint wall to wall brick walls hung with bite, effectively improve the stability of the wall; by optimizing the control of furnace gas consumption throughout the combustion system greatly can decrease the amount of about 50%, greatly improving the thermal efficiency, reduce energy consumption; combustion system uses oxygen, effectively reducing the nitrogen oxide output, energy consumption can be reduced, for each 1% increase in oxygen to reduce cubic meters of natural gas by about 6N; different from the rolling of the furnace, rolling mill billet is the big deal, but dealing with hearth furnace ironmaking is a small particle pellet, so the bottom hearth furnace lining design is very important, bottom of the block and the expansion joints lining the reasonable decision of the rotary hearth furnace reserved for the production of smooth or not, it is necessary to ensure the production of thermal expansion of the full bottom, and will not relative to the top of the lateral side wall of death production, but also to ensure that after the shutdown to a cold bed, pellet stove furnace under Bu Zhiyu expansion into cracks, expansion joints will be blocked. Currently INMETCO effective solution to this critical problem; water-cooled discharge screw rotary hearth furnace is the normal operating rate of production of key high assurance, through continuous improvement and optimal design structure of the screw material, life continues to increase. 5 Conclusion hearth furnace using coal completely, no ****, but the sulfur content in coal and volatile requirements; for raw materials are more flexible and can handle the end of grade powder ore, steel-making flue dust, rust, leather, etc. ; raw materials, the mechanical strength of less demanding; compared to other direct reduction process, rotary hearth furnace and its equipment is relatively simple structure, relatively low investment costs; easy to control and master the process operation and production costs are lower; rotary hearth furnace products for the sponge iron can be used directly with submerged arc furnace producing hot metal, scrap can be used as a substitute for the converter production of steel with higher purity requirement, or to join a large proportion of the scrap for smelting furnace replacement parts; the converter process equipment constraints, the current size of the world's largest production capacity for the annual 50 million tons. This greatly limits the ability of large iron and steel enterprises in the ironworks of the application, can not meet the needs of large-scale factory production scale, but small-scale iron and steel enterprises seemed like a good choice; the contrary, in the processing of iron dust, Block 1 million ton per year steel plant producing iron-containing dust produced about 50 million tons, while the rotary hearth furnace technology used to process iron dust is a more appropriate way. The author Note: At present, China's steel industry is in rapid growth phase, on the one hand a large number of metallurgical enterprises have to deal with recycling of dust, can be used as a rotary hearth furnace good raw materials, efficient recycling of metal; on the other hand is the need to quality of sponge iron to meet the high-quality alternative to steel melting scrap. Therefore I believe that the rotary hearth furnace technology is suited to China's national conditions, and INMETCO technology to today has been very mature, very good to meet the domestic steel industry recycling, processing and production of high quality sponge iron dust and other areas of need. Fire Man