Zaiets O. Hot blast generating systems efficiency improvement via waste gases heat recovery

The thesis deals with the hot blast generating system consisted of three hot blast stoves, where the blast furnace gas enriched with coke oven gas is burned. The composition and temperature of flue gases, their rate, and the rate of combustion components, the required temperatures for air (air and fuel) preheating in the summer and winter periods were determined. In order to save the coke oven gas, four schemes of flue gas utilization systems were considered. The systems are based on using of bare-tube heat exchangers. The advanced mathematical model and the method of calculation of complex recuperative heat exchangers with the cross-countercurrent scheme of heat mediums movement, which is based on the heat exchanger surface partition on the base micro-heat exchangers, where the P-NTU method of calculation is used, was proposed and used at the first time for heat utilizators of hot blast stoves flue gases. Based on the results of calculations, a comparative analysis of utilization schemes was carried out, coke gas savings were calculated. Diagrams, which show the distribution over the heat transfer area of mediums temperature and difference between vapour saturation temperature and temperature of the wall, were built. The diagrams can be used for detection of possible zones of condensate formation and initiation of corrosion.