A Macro Model for Steel Usage Pattern in Japan Using the Population Balance Model

Abstract

The macro model for evaluating the amount of CO₂ emission by virgin production, disposal and recycling of steels in Japanese society is proposed. The steels are classified into two groups for machinery and constructions, and it is assumed that steels are discharged from the society in accordance with each lifetime distribution, which is approximated by the gamma distribution. The amount of recycling steel and the stock are calculated using the population balance model with the input data of the statistics and estimated values for basic steel production, domestic consumption ratio and consumption ratio for constructions. The validity of this model is verified by the comparison with the calculated results and statistics of stock and steel production by electric furnaces. The copper concentration in recycling steel and the amount of total CO₂ emission are also calculated. The effect of recycling ratio on the total amount of CO₂ emission is analyzed under the assumption that recycled steel is diluted with virgin steel not so as to exceed the allowable copper concentration. The results show that recycling ratio is upper-bounded at 21st century because of the necessary dilution and that the total amount of CO₂ emission is not much reduced by increase of recycling ratio.