Computational fluid dynamics‐based steam cracking furnace optimization using feedstock flow distribution

Nonuniform temperature fields in steam cracking furnaces caused by geometry factors such as burner positions, shadow effects, and asymmetry of the reactor coil layout are detrimental for product yields and run lengths. The techniques of adjusting burner firing (zone firing) and feedstock mass flow rate (pass balancing) have been practiced industrially to mitigate these effects but could only reduce the nonuniformities between the so-called modules (a group of many coils).An extension of the pass balancing methodology is presented to further minimize the intra-module nonuniformities, thatis, variation between the coils within a module, in floor fired furnaces. Coupled furnace-reactor computational fluiddynamics-based simulations of an industrial ultraselective conversion (USC) furnace were performed to evaluate fourdifferent feedstock flow distribution schemes, realizing equal values for coil outlet temperature, propene/ethene massratio, maximum coking rate and maximum tube metal temperature (TMT), respectively, over all the reactor coils. It isshown that feedstock flow distribution creates a larger operating window and extends the run length. Out of the fourcases, the coking rate as criterion leads to the highest yearly production capacity for ethene and propene. Uniform maximum coking rates boost the annual production capacity of the USC furnace with a nameplate ethene capacity of 130 103 metric tons per year with 1000 metric tons for ethene and 730 metric tons for propene. For industrial application, achieving uniform maximum TMT is more practical due to its measurability by advanced laser-based techniques. Most steam cracking furnaces can be retrofitted by optimizing the dimensions of venturi nozzles that regulate the feedstock flow to the coils. VC 2017 American Institute of Chemical Engineers AIChE J, 63: 3199–3213, 2017Keywords: computational fluid dynamics, steam cracking, optimization, flow rate distribution, economics, ethylene

[1]  A. Balakrishnan,et al.  Thermal radiation by combustion gases , 1973 .

[2]  Guy Marin,et al.  Effect of radial temperature profiles on yields in steam cracking , 2004 .

[3]  David Van Cauwenberge,et al.  CFD-based design of 3D pyrolysis reactors: RANS vs. LES , 2015 .

[4]  Geraldine Heynderickx,et al.  Calculation of three-dimensional flow and pressure fields in cracking furnaces , 2003 .

[5]  Gilbert F. Froment,et al.  Kinetics and reactor design in the thermal cracking for olefins production , 1992 .

[6]  C. Westbrook,et al.  Simplified Reaction Mechanisms for the Oxidation of Hydrocarbon Fuels in Flames , 1981 .

[7]  M. Shahrokhi,et al.  Optimal Temperature Control of a Propane Thermal Cracking Reactor , 2002 .

[8]  Ramin Karimzadeh,et al.  Multivariable optimization of thermal cracking severity , 2011 .

[9]  Gilbert F. Froment,et al.  Simulation of the run length of an ethane cracking furnace , 1990 .

[10]  Martin Denison,et al.  Towards comprehensive computational fluid dynamics modeling of pyrolysis furnaces with next generation low-NOx burners using finite-rate chemistry , 2009 .

[11]  Mark Saeys,et al.  Construction of an ab initio kinetic model for industrial ethane pyrolysis , 2011 .

[12]  H. Dulot,et al.  Molecular reconstruction of heavy petroleum residue fractions , 2010 .

[13]  Peter J.T. Verheijen,et al.  Model-based, thermo-physical optimisation for high olefin yield in steam cracking reactors , 2010 .

[14]  F. Qian,et al.  Comprehensive CFD simulation of product yields and coking rates for a Floor- and wall-fired naphtha cracking furnace , 2011 .

[15]  Geraldine J. Heynderickx,et al.  CFD simulations of steam cracking furnaces using detailed combustion mechanisms , 2006, Comput. Chem. Eng..

[16]  Guy Marin,et al.  Challenges of Modeling Steam Cracking of Heavy Feedstocks , 2007 .

[17]  Geraldine Heynderickx,et al.  Simulation and comparison of the run length of an ethane cracking furnace with reactor tubes of circular and elliptical cross sections. , 1998 .

[18]  Gilbert F. Froment,et al.  The Uno-Quattro coil: high severities for increased ethylene selectivity , 1991 .

[19]  Kevin Van Geem,et al.  Dimensional analysis for scaling up and down steam cracking coils , 2007 .

[20]  David Van Cauwenberge,et al.  Computational fluid dynamics‐based design of finned steam cracking reactors , 2014 .

[21]  Kevin Van Geem,et al.  Molecular reconstruction of complex hydrocarbon mixtures: An application of principal component analysis , 2010 .

[22]  Feng Qian,et al.  Impact of Radiation Models in Coupled Simulations of Steam Cracking Furnaces and Reactors , 2015 .

[23]  Simon Barendregt,et al.  Towards synthesis of an optimal thermal cracking reactor , 2008 .

[24]  Kevin Van Geem,et al.  Automatic reaction network generation using RMG for steam cracking of n‐hexane , 2006 .

[25]  B. Hjertager,et al.  On mathematical modeling of turbulent combustion with special emphasis on soot formation and combustion , 1977 .

[26]  Carl Schietekat,et al.  Impact of Flue Gas Radiative Properties and Burner Geometry in Furnace Simulations , 2015 .

[27]  Kevin Van Geem,et al.  Two Severity Indices for Scale-Up of Steam Cracking Coils , 2005 .

[28]  Kevin Van Geem,et al.  First principle‐based simulation of ethane steam cracking , 2011 .

[29]  Honggang Wang,et al.  Coupled simulation of an industrial naphtha cracking furnace equipped with long-flame and radiation burners , 2012, Comput. Chem. Eng..

[30]  S. Orszag,et al.  Development of turbulence models for shear flows by a double expansion technique , 1992 .

[31]  Jafar Towfighi,et al.  Simulation, optimization and control of a thermal cracking furnace , 2006 .

[32]  Geraldine J. Heynderickx,et al.  Impact of radiation models in CFD simulations of steam cracking furnaces , 2007, Comput. Chem. Eng..

[33]  David Van Cauwenberge,et al.  Necessity and Feasibility of 3D Simulations of Steam Cracking Reactors , 2015 .

[34]  Guy B. Marin,et al.  Molecular reconstruction of naphtha steam cracking feedstocks based on commercial indices , 2007, Comput. Chem. Eng..

[35]  Erik Dick,et al.  Three‐dimensional flow patterns in cracking furnaces with long‐flame burners , 2001 .

[36]  Gilbert F. Froment,et al.  Scaling up of naphtha cracking coils , 1981 .

[37]  S. M. Sadrameli.  Thermal/catalytic cracking of hydrocarbons for the production of olefins: A state-of-the-art review I: Thermal cracking review , 2015 .

[38]  Meihong Wang,et al.  Optimal operation of tubular reactors for naphtha cracking by numerical simulation , 2009 .

[39]  Guy Marin,et al.  Three-Dimensional Asymmetric Flow and Temperature Fields in Cracking Furnaces† , 2001 .