This paper presents the estimating of maximum possible internal heat integration regarding individual processes by using the graphical technique, including basic knowledge of pinch analysis. The fraction of maximum possible internal integration during the process is calculated as from 1 to 0. This technique includes those additional sources which approach the fraction of the maximum possible internal integration to the value 1. The graphical technique is composed of two steps: First step - analysing efficiency. Second step - modifying the process Both steps are already used in the existing formaldehyde process and therefore the use of solution heat during higher pressure absorption was useful integrating with distillation, and so steam was unnecessary for heating the reboiler. (C) 2009 Elsevier Ltd. All rights reserved.