Page 312 - Introduction to chemical reaction engineering and kinetics

11.3 Problems for Chapter 11 293

11-4 The first chemical step in making sulfuric acid from elemental sulfur is burning the sulfur
(completely) to form SOz. Calculate the temperature of the gas leaving the burner based
on the following: the burner operates adiabatically, sulfur enters as liquid at 140°C and
excess air (79% mol N;?, 21% 02) enters at 25°C; AH (S(9, 140°C + S(s, rh), 25°C) =
-5.07 kJmol-‘; the outlet gas contains 9.5 mol % SO2; other data required are given in
Table 11.1.
11-5 The gas from the sulfur burner (problem ll-4), after reduction of T in a “waste-heat boiler,”
enters a catalytic converter for oxidation of SO2 to SOs in several stages (see Figure 1.4). If
the gas enters the converter at 700 K, calculate fso, and the temperature (T/K) of the gas at the
end of the first stage, assuming the reaction is adiabatic and equilibrium is attained. Assume
P = 1 bar. See Table 11.1 for data.
11-6 The gas leaving an ammonia oxidation unit in a continuous process is cooled rapidly to 20°C
and contains 9 mol % NO, 1% NOz, 8% 02, and 82% N2 (all the water formed by reaction
is assumed to be condensed). It is desirable to allow oxidation of NO to NO2 in a continuous
reactor to achieve a molar ratio of NO2 to NO of 5 before absorption of the NO2 to make HNOs .
Determine the outlet temperature of the reactor, if it operates adiabatically (at essentially 6.9
bar). The following data (JANAF, 1986) are to be used; state any assumptions made. (Based
on Denbigh and Turner, 1984, pp. 57-64.)

9,298 C, (approx.)/
Species J mol-’ J mol-’ K-’
02 0 29.4
N O +90,291 29.9
NOz +33,095 39.0
N2 0 29.1