A new method based on the heat duty-time (Q-t) diagram is proposed for heat integration of heat exchanger networks featuring batch streams. Using the Q-t diagram method, the energy targets and the structure of the initial heat exchanger network can be easily obtained. The method can be used both for direct and indirect heat integration of batch streams. For indirect heat integration, the heat degradation of intermediate media is considered. A case study on optimizing the heat exchanger network of a hydrazine hydrate plant is used to illustrate the application of the method. The results show that integration of this heat exchanger network without considering its batch streams can limit the total energy savings. (C) 2013 Elsevier Ltd. All rights reserved.