Optimising energy recovery in hydrothermal liquefaction of radiata pine and Kraft mill black liquor

Abstract

The aim of this paper is to develop a heat exchanger network for hydrothermal liquefaction that is co-located with an existing Kraft pulp mill. Hydrothermal Liquefaction (HTL) is an energy-intensive process that operates at high temperature and pressure. Process Modelling and Pinch Analysis are used to develop a mass and heat integration system considering Total Site Integration with the Kraft pulp. The HTL process is simulated using Aspen Plus to extract and calculate the thermodynamic properties of the process. Stream data is then extracted and Pinch Analysis is applied to calculate the utility and heat recovery targets. Process data are varied to further maximise the heat recovery targets. Mass integration of compatible water-based flows is considered in this process to reduce the complexity of the Heat Exchanger Network, which is initially designed with the aid of SuperTarget™. The result showed that the procedure simplified the Heat Exchanger Network from 15 to 6 heat exchangers.