Optimal operation of heat exchanger networks with stream split: Only temperature measurements are required

Abstract For heat exchanger networks with stream splits, we present a simple way of controlling the split ratio. We introduce the “Jaschke Temperature”, which for a branch with one exchanger is defined as TJ = (T − T0)2/(Th − T0), where T0 and T are the inlet and outlet temperatures of the split stream (usually cold), and Th is the inlet temperature of the other stream (usually hot). Assuming the heat transfer driving force is given by the arithmetic mean temperature difference, the Jaschke Temperatures of all branches must be equal to achieve maximum heat transfer. The optimal controlled variable is the difference between the Jaschke Temperatures of each branch, which should be controlled to zero. Heat capacity or heat transfer parameters are not needed, and no optimization is required to find the optimal setpoints for the controlled variables. Most importantly, our approach gives near-optimal operation for systems with logarithmic mean temperature difference as driving force.

[1]  Sigurd Skogestad,et al.  An industrial and academic perspective on plantwide control , 2009 .

[2]  Vesa Ojalehto,et al.  An interactive multi-objective approach to heat exchanger network synthesis , 2010, Comput. Chem. Eng..

[3]  Manfred Morari,et al.  Area and capital cost targets for heat exchanger network synthesis with constrained matches and unequal heat transfer coefficients , 1990 .

[4]  Dominique Bonvin,et al.  Dynamic Optimization in the Batch Chemical Industry , 2001 .

[5]  John R. Flower,et al.  Synthesis of heat exchanger networks: I. Systematic generation of energy optimal networks , 1978 .

[6]  Sigurd Skogestad,et al.  Problems with Specifying ¢Tmin in the Design of Processes with Heat Exchangers , 2008 .

[7]  S. Janardhanan,et al.  OPTIMAL MEASUREMENT COMBINATIONS AS CONTROLLED VARIABLES , 2007 .

[8]  Sigurd Skogestad,et al.  NULL SPACE METHOD FOR SELECTING OPTIMAL MEASUREMENT COMBINATIONS AS CONTROLLED VARIABLES , 2007 .

[9]  Sigurd Skogestad,et al.  Optimal operation of heat exchanger networks , 1999 .

[10]  Manfred Morari,et al.  Studies in the synthesis of control structures for chemical processes: Part I: Formulation of the problem. Process decomposition and the classification of the control tasks. Analysis of the optimizing control structures , 1980 .

[11]  Martin Grötschel,et al.  Online optimization of large scale systems , 2001 .

[12]  Dominique Bonvin,et al.  Dynamic Optimization under Uncertainty via NCO Tracking: A Solution Model Approach , 2004 .

[13]  Sigurd Skogestad,et al.  Optimal controlled variables for polynomial systems , 2012 .

[14]  Manfred Morari,et al.  Design of resilient processing plants—VIII. A resilience index for heat exchanger networks , 1985 .

[15]  D. L. Westphalen,et al.  A methodology for improving heat exchanger network operation , 2003 .

[16]  Néstor E. Aguilera,et al.  Optimizing and controlling the operation of heat-exchanger networks , 1998 .

[17]  Sigurd Skogestad,et al.  Control structure design for optimal operation of heat exchanger networks , 2008 .

[18]  Tore Lid,et al.  On-line Optimization of a Crude Unit Heat Exchanger Network , 2002 .

[19]  Sigurd Skogestad,et al.  Chemical and Energy Process Engineering , 2008 .

[20]  Manfred Morari,et al.  Design of resilient processing plants—IV: Some new results on heat exchanger network synthesis , 1984 .

[21]  Alexandre Leruth.  Heat exchanger network self-optimising control : Application to the crude unit at Mongstad refinery , 2012 .

[22]  Sigurd Skogestad,et al.  Optimizing control of Petlyuk distillation : Understanding the steady-state behavior , 1997 .

[23]  M. J. Wheeler.  Heat and Mass Transfer , 1968, Nature.

[24]  Truls Gundersen,et al.  Improved sequential strategy for the synthesis of near-optimal heat exchanger networks , 1997 .

[25]  Sigurd Skogestad,et al.  Bypass selection for control of heat exchanger networks , 1992 .

[26]  Ignacio E. Grossmann,et al.  Simultaneous optimization models for heat integration—II. Heat exchanger network synthesis , 1990 .

[27]  Sigurd Skogestad,et al.  NCO tracking and self-optimizing control in the context of real-time optimization , 2011 .

[28]  B. Linnhoff,et al.  The pinch design method for heat exchanger networks , 1983 .

[29]  David A. Cox,et al.  Using Algebraic Geometry , 1998 .

[30]  Sigurd Skogestad,et al.  Problems with Specifying ¢Tmin in the Design of Processes with Heat Exchangers , 2008 .

[31]  Sigurd Skogestad.  Plantwide control: the search for the self-optimizing control structure , 2000 .

[32]  Sigurd Skogestad,et al.  An industrial and academic perspective on plantwide control , 2011, Annu. Rev. Control..

[33]  S. Skogestad,et al.  Control structure selection for optimal operation of a heat exchanger network , 2012, Proceedings of 2012 UKACC International Conference on Control.

[34]  Kevin C. Furman,et al.  A Critical Review and Annotated Bibliography for Heat Exchanger Network Synthesis in the 20th Century , 2002 .