Quantification and optimization of waste heat recovery at a textile fibre facility : a case study of Infinited Fiber Kemi Oy

Abstract

This thesis investigates the quantification and optimization of waste heat recovery in textile fiber production under cold-climate conditions, using the Infinited Fiber Kemi Oy plant in Northern Finland as a case study. The study is based on pre-operational environmental permit data and aims to quantify recoverable heat potential and identify suitable recovery technologies. Six major waste heat streams were identified across a temperature range of 10–150 °C. Engineering analyses were conducted using pinch analysis, the log mean temperature difference (LMTD) method for heat exchanger sizing, and heat pump coefficient of performance (COP) calculations based on the Carnot approach. Scenario analysis was applied to estimate annual recovery potential under varying recovery fractions.

The results indicate that approximately 10–35% of the plant’s total energy consumption (450 GWh/year) can be recovered, corresponding to 45–158 GWh/year. Pinch analysis revealed a process pinch at 62–67 °C, enabling direct utilization of high-grade waste heat for district heating, while low-grade streams require heat pump upgrading. A wastewater heat recovery system alone demonstrates a potential of approximately 80.5 GWh/year. Heat pump analysis shows that wastewater-source systems can achieve up to 2.5 times higher efficiency than air-source systems under Northern Finnish winter conditions. The findings highlight the significant potential of integrating waste heat recovery with district heating networks in cold climates. The study provides a practical framework for pre-operational assessment of industrial waste heat recovery and demonstrates how circular textile manufacturing can contribute to improved energy efficiency and regional decarbonization.