Top Gas Recycling Research Articles

Raceway Design for the Innovative Blast Furnace

This study tries to design the combustion zone in the highly efficient blast furnace for aiming at great reduction of energy consumption and environmental loads by use of raceway mathematical model. The model treats strictly the discontinuous movement of lump coke particles inside and around raceway, and it considers heat exchange with gas and chemical reactions with gas. In this study, first, the verification of the model is performed. Next, the controllability of raceway by blast conditions is investigated. Finally, the raceway in the top gas recycling process is evaluated in terms of the suitability as combustion zone of the novel blast furnace and of the possibility of its realization. The gas recycling process has the characteristic of blowing top gas without CO 2 , pure oxygen and plastics from tuyere. The results obtained in this work are as follows. 1) Raceway mathematical model has the sufficient ability to represent the characteristics of raceway in all cokes operation and PCI operation. 2) The shape and size of raceway and gas temperature in raceway can be controlled by blast temperature and gas compositions. In addition, nitrogen enrichment in blast is effective to form the uniform and low temperature combustion zone. Raceway in top gas recycling process becomes larger, gas temperature in and around raceway is lower and volumetric flow rate of bosh gas is less than conventional process. Therefore, raceway conditions in the recycling process enable high productivity and high efficiency.

Prediction of Blast Furnace Performance with Top Gas Recycling.

Top gas recycling has been suggested as a method for reducing blast furnace fuel rates and thus reducing carbon emissions from the ironmaking process. Three methods of top gas recycling are numerically investigated using a mathematical model to predict the furnace performance at fixed blast volume and constant coke, ore and pulverised coal compositions with varying recycle volumes. For each recycling method, a first calculation sequence is performed varying recycle volume at fixed ore : fuel ratio, and also a second sequence at fixed average liquid metal outflow temperature. Simple replacement of normal blast gases with recycled top gas is predicted to cause the production rate to decrease and the fuel rate to increase. Likewise, oxygen enriched blast replacement has similar effects, although the severity is less as the blast oxygen rate is maintained in this case. Both of these methods reduce furnace efficiency. Hot reducing gas (HRG) replacement, where CO2 is stripped from the recycled gas, leads to an increase in production of up to 25 % with a simultaneous decrease in fuel rate of 20 % at fixed metal temperature. These calculations show that top gas recycling could be used to increasing furnace efficiency while decreasing carbon emissions thus making a positive contribution to efforts to prevent global warming.