Appelpolscher has just left a meeting with Stella J. Smarly, IGC?s vice-president for Process Operations and Development. Smarly is concerned about an upcoming extended plant test of a method intended to improve the yields of a large packed-bed reactor. The basic idea, which came front IGC?s university consultant and was recently tested for feasibility in a brief run, involves operating the reactor cyclically so that nonlinearties in the system cause the time-average yield at the exit to exceed the steady-state value. Smarly is worried about the possibility of sintering the catalyst during an extended run, particularly in the region of the ?hotspot? (axially about one-third of the way down the bed and at the centerline) where temperature invariably peak. Appelpolscher, who plans to leave the next day on a two-week big game photo safari, doesn?t want to cancel his vacation. On the other hand, Smarly has told him he faces early, unexpected retirement in Botswana if the measurement device (located near the hot spot) fails to alert operating people and the reactor catalyst sinters, Appelpolscher likes Botswana but doesn?t want to retire there lie manages to pull together the following data and assumptions before heading for the airport and leaves them with you for analysis with the offer to use his swimming pool while he is gone. What do you report to Smarly?

Data:

Frequency of cyclic operation = 0.1 cycles/min.

Amplitude of thermal wave (temperature) at the measurement point obtained experimentally in the recent brief inn 15?C

Average operating temperature at measurement point, T_meas = 350 ?C

Time constant of temperature sensor and thermowell = l.5 min

Temperature at the reactor wall = 200 ?C

Temperature at which the catalyst sinters if operated for several hours 700 ?C

Temperature at which the catalyst sinters instantaneously 715 ?C

Assumptions:

The reactor operational cycle is approximately sinusoidal at the measurement point.

The thermowell is located near the reactor wall so as to measure a ?radial average? temperature rather than the centerline temperature.

The approximate relation is

which also holds during transient operation.

Transcribed Image Text:

Tenter + 27wall 3 T= Teenter т.