PROCESS INTEGRATION OF A PULP MILL BASED ON PINCH ANALYSIS

Abstract

Energy savings and increased efficiency is important to a large energy consuming industry such as the pulp and paper industry. To give industries incentives to do something about their energy consumption, policy instruments are used. Research in the pulp and paper field also shows that large savings can be achieved. One way to save steam is process integration, a tool to find steam saving opportunities is pinch analysis. Thermo mechanical pulp (IMP) mills are large consumers of both steam and electricity. Large energy savings can be achieved through investments in thermal process integration or more energy efficient process equipments. Thermal process integration can help to reduce the hot and cold utility consumptions in a mill. In the present work process integration study using pinch analysis on a recently reported pulp mill has been done to improve the heat exchanger network design and to solve the pinch violation. Pinch analysis was used to identify the major sources of inefficient heat exchange it pinch violations in the system. The major source of pinch violations is the paper machine heat recovery system, the cooling system and the district heating system. In the proposed retrofits the total clean steam consumption is decreased by improved process integration. The improved HEN design decreases the consumption of stream by around 14.2%. It also optimizes the cost of heat exchanger network and estimate the cost of the improved HEN design. It results annualized energy saving of around 9638.50 UD$/year. The payback period of the optimized heat exchanger design is found to be 6.6 years.