1642419845 Exam 17 01 2022

Pagina 1

Fundamentals of Chemical Processes Prof. Gianpiero Groppi January 17 2022 Problem 1 (18 points) SR: CH4 + H2O ↔ 3 H2 + CO WGS: H2O + CO ↔ CO2 + H2 Syngas is produced in a reforming reactor (R1) where Steam Reforming (SR) and Water Gas Shift (WGS) reaction s simultaneously occur. Feed stream (1) contains methane and water with a 1:3.5 molar ratio at T1 = 500 K. The stream (1) is preheated in the heat exchanger HE up to T2 = 800 K, using the exhaust stream (5) from the burner as hot fluid, and fed to the Steam Reformer (R1) operating at P=30 atm. Equilibrium conditions are reached at the R1 outlet with a C selectivity to CO � 𝜎𝐶𝐶 𝐶 = 𝑛̇3,𝐶𝐶 𝑛̇1,𝐶𝐻4−𝑛̇3,𝐶𝐻4 � equal to 60 %. The steam reformer is heated by the burner, which provides the required heat duty Q . The burner is fed at 298 K by stream (4), which consists of methane and dry air (21% O 2 - 79% N 2) with 20% air excess. The burner secures complete methane combustion. Outlet stream (6) from the heat exchanger is at T6 = 650 K. Assuming: • Ideal gas behavior of all the streams • Ideal behavior with no heat losses of the heat exchanger • Isobaric reactors Calculate: 1. Temperature T3 and molar composition of outlet steam (3) from reactor R1 T3 H2 CO CO2 CH4 H2O 2. The heat Q entering in R1 per mole of feed methane to the steam reformer Q/nCH4,(1) 3. Exhaust burner temperature T5 and molar CH4 feed flow rate to the burner per mole of CH4 feed to the reformer T5 nCH4,(4)/ nCH4,(1) Thermodynamic data: ∆𝐺𝑅,𝑆𝑅 0 (𝑇) = 53717 − 60.25 ∙ 𝑇 � 𝑐𝑐𝑐 𝑚𝑚𝑐 � T in K, 600 K < T < 1500 K 𝛥𝐺𝑅,𝑊𝑊𝑆 0 = −8514 + 7.71 ⋅ 𝑇 � 𝑐𝑐𝑐 𝑚𝑚𝑐 � T in K, 600 K < T < 1500 K Reference: ideal gas at: 1 atm, 298 K 𝛥𝐻𝑅,𝑆𝑅 0 (298𝐾) = +49270 � 𝑐𝑐𝑐 𝑚𝑚𝑐 � Steam Reforming 𝛥𝐻𝑅,𝑊𝑊𝑆 0 (298𝐾) = −9830 � 𝑐𝑐𝑐 𝑚𝑚𝑐 � WGS 𝛥𝐻𝐶𝐶𝐶𝐶,𝐶𝐻4 0 (298𝐾) = −191591 � 𝑐𝑐𝑐 𝑚𝑚 𝑐� Species a b…