Recovery Of Residual-heat Resource In Steel Producing Process

There is a lot of residual-heat created in the steel producing process which consumes much energy. The residual-heat resource per ton steel in iron and steel industry has been calculated to be 8.4GJ/t-s. It is very important to analyze the total quantity and recovery of residual-heat resource using the thermodynamic theory and discuss the recovery scheme to increase the recovery ratio of residual-heat resource.The method using the first law of thermodynamic only considers the quantity of energy, which is not agreed with the utilization of energy. The exergy analysis method is used to analyze the reduction of available enengy in energy using process.The energy level analysis method analyses energy utility in the view of quality. The quality and quantity of energy are both considered in the paper, using exergy analysis combining energy level analysis to analyze the residual-heat recovery. It is indicated that the amount of energy saving in a process or an enterprise is the evaluating indicator. The model of residual-heat recovery system is constructed, so as to bring forward the basic principle for heat recovery and power recovery of residual-heat:"recovery according to quality, temperature concordance and cascade utilize". The recovery modes of coke/sinter heat, slag heat, exhaust gas heat are discussed, and the effect of saving energy is analyzed. Based on this, the direction of future development is pointed out.The energy consumption and residual-heat recovery of the main processes for An Steel is investigated. The amount and the residual-heat recovery are analyzed using the thermodynamic method, and the exergy recovery rate of An Steel is 11.8%. The suggestion about residual-heat recovery combining the development of residual-heat recovery technology is put forward. If all the revovery thchnologies are applied,90.2 kgce per ton steel can be saved.The heat of sinter is one of important residual-heat in an iron and steel enterprise, which is about 20kgce/t-s. The cooling machine in An Steel is investigated, It is cauclated that the exergy recovery rate is 23.1% and the energy amount saved is 6.1 kgce per sinter; the model of heat revoery of the cooler is constructed, so as to discuss the influence of air initial temperature and brink effect on the residual heat:the higher the air initial temperatureand and the smaller the brink, the better the recovery effect. The scheme of residual-heat recovery in the cooler is put forward:â‘ the high-temperature part of belt cooler and exhaust-heat boiler are actualized closed-circuit through the waste air, which can produce high-quality steam to generate electricity.â‘¡the waste air in low-temperature part is introduced to sintering machine for the combustion-supporting air of the ignition furnace. It is cauclated that after the new scheme actualized, the exergy recovery rate is 41.5% and the saving energy amount is 11.7kgce per sinter, which is 5.6kgce per sinter less than before.