Industry-wise analysis of waste heat from factories in the Shikoku region, Japan, to enable optimum waste heat usage in future

In order to determine the current status of industrial waste heat, we created a database of waste heat from internal industries by investigating high-energy-consumption industries. This database was intended to improve knowledge of the exhaust heat characteristics of chemical and paper factories in 2008 with the maximum accuracy possible. Therefore, such factories in the Shikoku region of Japan were investigated by a questionnaire survey, and the responses were used to create the database. We investigated the chemical and paper factories in the Shikoku region of Japan in order to determine the real state of industrial waste heat. We particularly aimed to improve upon the existing knowledge of the exhaust heat characteristics of these two types of factories, quantifying these as accurately as possible, for the year 2008. To achieve this, we used a questionnaire survey, the responses to which were used to create a database of waste heat generated by the target industries, all of which can be considered high-energy-consumption industries. The questionnaire data were compared with observations obtained by visiting typical factories in high-energy-use industries, and the differences between these two datasets were examined in detail. In general, the results obtained by the survey were similar to those observed. However, considerable waste heat was omitted in the questionnaire responses in the cases of large factories incorporating many processes. These are thresholds for classification of usable heat, such that gas, warm water, and solids can be considered usable at temperatures of 100°C, 40°C, and 200°C, respectively by considering the conditions of waste heat exhausting in the facilities and surrounding areas (1). A large proportion of waste heat is exhausted as steam or hot water from "typical" plants in the aspects discussed (2). However, many of the plants investigated in the present study exhausted large amounts of waste heat at higher grades. Correlation analysis was applied to analyze the waste heat and estimate its volume, on the basis of a method proposed previously (3). In this analysis, the waste heat volume (including waste gas, warm water, and solids) in the plants was represented by a dependent variable and the total volume of waste heat from the main factories (obtained by the questionnaire) was represented by an independent variable (4). The correlation expression y = ax was also used. Waste gas exhibited the highest estimation accuracy, followed by warm water and solids, as well as a significant correlation for both industries.