(25b) Combustion Pyrolysis of Light Hydrocarbons

Balamurali Nair, Pankaj Gautam, and Sreekanth Pannala

SABIC technology Center, Sugarland TX-77478

The growing abundance of natural gas resources and their competitive advantage with respect to other light paraffinic hydrocarbons make the production of chemical intermediates and other high value chemicals from natural gas an attractive option.  At SABIC (Saudi Basic Industries Corporation), we are committed to efficient and optimal utilization of natural resources.  One method to convert the natural gas resource to high value products is through combustion pyrolysis.  Combustion pyrolysis involves partial oxidation of hydrocarbons to produce smaller unsaturated molecules which can be used as building blocks for commodity chemicals.  In addition, combustion pyrolysis can also be used to upgrade low value off gases/ feed streams to produce valuable products instead of using these streams as fuel or for flaring.  Although combustion pyrolysis technology is five decades old, it is not widely practiced commercially due to several reasons including operational and scalability challenges. The homogeneous nature of the reaction without catalysts, simple reactor design and favorable economics could make this process attractive in the coming decades.  In this work, a brief review of the existing combustion pyrolysis technology followed by experimental results on a pilot unit will be discussed.

 The performance of a two stage combustion pyrolysis pilot unit for the production of chemical intermediates acetylene and ethylene- from a variety of hydrocarbon feeds is elucidated here.  Combustion pyrolysis uses oxy-fuel combustion for heat generation.  The extreme temperatures prevalent in the combustor (2500-2800 C) make the process development challenging.  The hot gases from the combustor are mixed with the reactor feed and fed into a reactor where pyrolysis reactions takes place.  The important parameters which determine the performance of a combustion pyrolysis unit are the combustor firing rate, residence time, and type of feedstock.  Some of the key aspects of this technology include feed flexibility and modularity. The process development challenges include the heat management, combustor material stability, and scalability to industrial sizes.  The variation of acetylene and ethylene yield with firing rate, residence time and type of feedstock will be discussed.  The results of piloting help to scaleup the process to commercial level.