Runaway limits for adiabatic packed-bed catalytic reactors

✍ Scribed by Evangelia L. Christoforatou; Vemuri Balakotaiah; David H. West

• Publisher: American Institute of Chemical Engineers
• Year: 1998
• Tongue: English
• Weight: 847 KB
• Volume: 44
• Category: Article
• ISSN: 0001-1541
• DOI: 10.1002/aic.690440216

✦ Synopsis

Most existing criteria for predicting the critical residence time (or jlow rate) at which runaway occurs in an adiabatic catalytic packed-bed reactor do not account for interphase heat-transfer resistance and intraparticle diffusion. When these transport limitations exist, the critical residence time at which runaway occurs is given by This simplified equation gives the runaway locus as a function of the feed temperature (To), adiabatic temperature rise ( ATad), activation energy (E), reaction rate constant at feed temperature [k(To)], jluid -solid heat-transfer coeficient (h), the inte$acial area per unit bed volume (au), and the normalized Thiele modulus {cPo). The finction f (40) accounts for the intraparticle diffusional efsects and may be approximated by the two asymptotes, f(40) = 1 when c$o < 1/2 and f(+,,) = 240 when 4o > 1/2. Similar analytical results are presented for other reactor models and also for more complicated reaction networks. A practical example shows the calculation of the runaway boundary for industrial hydrogenation reactions obeying Langmuir -Hinshelwood kinetics.

Vol. 44, No. 2 ' " ' 1 " " I ' " ' I " ' ' I " " I " " I