29 06 20text

Pagina 1

Dipartimento di Energia Politecnico di Milano Via Lambruschini 4 - 20156 MILANO “Fundamentals of Chemical Processes” Prof. Gianpiero Groppi June 29th, 2020 Exercise 1 (18 points) The synthesis of methanol is performed according to the process scheme reported below: In both reactor R 1 and reactor R2 the synthesis of methanol (MeOH) takes place according to the following stoichiometry: CO + 2 H2 ↔ CH3OH Inlet current (1), which is maintained at 453 K and has the composition reported in Table 1, is split in two parts, current (2) and current (3). Current (2) is supplied to reactor R 1. Reactor R1 operates at 70 bar and is cooled by 1500 cal per mole of feed current (2). Current (4) exits from reactor R1 at thermodynamic equilibrium conditions. Current (4) is then mixed with current (3), which acts as a quench. Current (5) obtained from the mixing is supplied to reactor R2, which is adiabatic and also operates at 70 bar. Current (6) which exits from reactor R2 reaches the thermodynamic equilibrium conditions at the outlet temperature T6 which is equal to 560 K. Assuming that: • the reacting mixture is a n ideal mixture of real gases, assuming 𝑘𝑘𝜑𝜑 𝑀𝑀𝑀𝑀𝑀𝑀𝑀𝑀 as reported in the thermodynamic dataset • pressure drops are negligible through the reactors, which can be considered as isobaric • CH4 and CO2 can be treated as inert species calculate: 1. temperature T4 and the molar composition of current (4) at the outlet of reactor R1 2. the ratio of flow rate of quench current (3) to the flowrate or current (2) 3. the molar composition of current (6) at the outlet of reactor R2 4. temperature T5 of current (5) which enters reactor R2. Table 1 – molar composition of current (1) CH4 H2 CO CO2 CH3OH Current (1) 0.05 0.70 0.15 0.10 0 Thermodynamic data Methanol synthesis…