Exercise 5 Text

Pagina 1

INDUSTRIAL ORGANIC CHEMISTRY – EXERCISE 5 Methanol synthesis: simplified ICI layout A simplified layout of an ICI process for the methanol production consists of two adiabatic reactors in series with intermediate quench. The fresh feed (1) is split in two streams: the first (2) is sent to the first adiabatic reactor (R -1) where the conversion of CO and H 2 to CH 3OH occurs. The stream (4) leaving the reactor is mixed with the remaining feed (3) and with a make-up stream (9) consisting of pure CO2 (at 453 K) to obtain a temperature of stream (5) equal to 520 K and sent to the second reactor (R-2). The stream (6) leaving the reactor is isoenthalpically laminated and sent to an isothermal methanol condenser (F-1). By assuming: • The gas mixture is ideal and consists of real gas. As a first approximation, a 𝐾𝜙 𝑀𝑒𝑂𝐻 = 𝜙𝑀𝑒𝑂𝐻 𝜙𝐻2 2 𝜙𝐶𝑂 = 0.7 and 𝐾𝜙 𝑊𝐺𝑆 = 𝜙𝐶𝑂2𝜙𝐻2 𝜙𝐻2𝑂𝜙𝐶𝑂 = 1.2 can be assumed for the evaluation of the 𝐾𝑝 of the methanol synthesis and of the WGS, respectively. The liquid mixture is ideal and the Poynting correction is negligible • The pressure in each reactor is equal to 70 bar and pressure drops are negligible , while the separator works at 10 bar. • The reactor R-1 is designed to work with a conversion of CO equal to the 90% of the equilibrium one at the adiabatic temperature. • The molar fraction of CO2 in stream (5) is equal to 0.15 • The reactor R-2 is designed to achieve thermodynamic equilibrium at the temperature of 570 K. • The methanol condenser (F-1) is designed to obtain a recovery efficiency of methanol equal to 70 % in stream (8) • As a first approximation, supercritical components can be assumed as not dissolved in the liquid. It is required to evaluate: 1. The temperature and the composition (molar fractions) of the stream leaving reactor R-1 2.…