Put Your Intuition to Rest: Write Mole Balances Systematically


  • Sagar B. Gadewar Process Design Center, Inc.
  • Michael F. Doherty University of California
  • Michael F. Malone University of Massachusetts


A systemic method for writing stoichiometric mole balances for complex reaction systems is developed, based on the concept of reaction invariants. This methodology also identifies the degrees of freedom for solving the balances. The methodology is useful in checking the consistency of experimental data and greatly simplifies the task of writing material balances for complex reaction chemistries essential in the conceptual design of chemical processes. We apply the method to a reaction system producing acetonitrile and to a system with multiple reactors producing bisphenol-A. The procedure can be implemented easily using widely available spreadsheet programs or mathematical computation program.

Author Biographies

Sagar B. Gadewar, Process Design Center, Inc.

Sagar B. Gadewar is Consultant at PDC Process Design Center Inc., in Santa Barbara, CA. He received his BS in Chemical Engineering from the Department of Chemical Technology, University of Mumbai (UDCT), and his PhD in Chemical Engineering from the University of Massachusetts at Amherst. His research interests include reaction combined with distillation, conceptual design for complex chemistries, and modeling crystal shape evolution.

Michael F. Doherty, University of California

Mike Doherty is Professor of Chemical Engineering at the University of California, Santa Barbara. He received his BSc in Chemical Engineering from Imperial College, London, and his PhD in Chemical Engineering from Trinity College, Cambridge. His research and teaching interests include chemical process design and synthesis, separation systems design with special interests in simultaneous reaction and separation, and crystallization of organic materials.

Michael F. Malone, University of Massachusetts

Mike Malone is the Ronnie and Eugene Isenberg Distinguished Professor at UMass, Amherst. He studied chemical engineering at Penn State and UMass where he joined the faculty in chemical engineering. He has also been Visiting Scientist at the DuPont Company twice. He has won the UMass Distinguished Teaching Award and the "Computing in Chemical Engineering" Award from CAST Division of the AIChE for joint work with M. F. Doherty described in the text Conceptual Design of Distillation Systems.