A. K. Mandal

Production of thermal insulation blocks from bottom ash of fluidized bed combustion system

The issues of disposal and environmental problems are increased by the generation of bottom ash from the thermal power plants day by day; hence, its recycling is required. The present study aimed to make thermal insulation blocks using as raw material bottom ash and iron ore slime as a binder and to characterize their engineering properties. Two different fineness values of bottom ash were considered with varying amounts of iron ore slime (0–10%) to make the blocks. Blocks were dried followed by firing at 1000, 1100 and 1200°C, respectively. Cold crushing strength, density and thermal conductivity of these fired blocks showed increasing behaviour with firing temperature, fineness of bottom ash and iron ore slime content. In contrast, a reverse trend was observed in the case of porosity. With increasing firing temperature, the formation of lower melting phases like iron silicate followed by iron aluminium silicate was observed, which imparts the strength inside the blocks. The coarser particles of bottom ash increase the interparticle spaces, which enhances the apparent porosity, resulting in higher thermal insulation property in the blocks. Blocks having better thermal insulation property could be possible to make effectively from coarse bottom ash by adding iron ore slime as a binder.

Effective utilisation of waste fines in preparation of high-basicity double-layer DRI pellets for minimisation of sticking

Sinter of high basicity is well known for affecting the permeability of the burden in the lower portion of the blast furnace due to the formation of more viscous slag. The high-basicity pellets possess less weather resistance if hardened below 1200°C due to the presence of free lime particles. When hardened above 1200°C, the weather resistance increases with increasing sticking tendency among the pellets due to the formation of low-melting eutectics. In the present investigation, efforts were made to make composite-coated iron ore-fluxed pellets to minimise the problems mentioned above. Lime addition to the core of pellets varied from 5 to 100%. The composite pellets subsequently were fired at 1150, 1200 and 1250°C for 30 min. Increasing lime content in the pellets resulted in increasing crushing and drop strength of the green pellets. The percent of reduction and cold crushing strength were found comparable to the conventional pellets with varying lime content up to 30% (core basicity 4.68). Weathering resistance was also found increasing trends with increasing firing temperature. XRD analysis revealed the presence of free lime particles inside the core of composite pellets with increasing lime content. From the present work, it could be concluded that the composite-fluxed pellet made with 20% lime in the core (core basicity 3.0) has enough physical strength (187 kg), a high percentage of reduction (96%) and excellent weather resistance properties.

Preparation and Characterization of Fired Bricks Made from Bottom Ash and Iron Slime

AbstractThis paper presents experimentally investigated results of iron slime addition as additives in making bottom ash bricks. Bottom ash from coal burning thermal power stations of two different...

Smelting Reduction of Bottom Ash in Presence of Liquid Steel Bath for Recovery of Aluminium

For the recovery of aluminium from industrial waste bottom ash, a new concept was developed for smelting reduction in presence of metal solvent bath. Nitrogen plasma arc was generated by passing current and nitrogen gas through a hollow graphite electrode. Nitrogen plasma generated heat for reduction as well as melting under inert atmosphere inside the furnace. Pellets containing 50%bottom ash, 50% iron slime and charcoal were fed in the plasma zone above the liquid steel bath which was acted as for the absorption of reduced metals after reduction of oxides present in the wastes. Due to the immediate absorption of aluminium in the liquid steel bath after subsequent reduction from waste, vaporization loss of aluminium metal got minimized. The percent recovery of aluminium were determined in case of different exposure time, types of arcing and plasma gas etc. Maximum recovery of aluminium was recovered upto 21% with 30 minute exposure of pellets containing 50% bottom ash and 50% iron slime. It was observed that aluminum, could be recovered effectively from the wastes.