# Aspen tutorial 4: Gibbs and kinetics reactors models

This class is given by Arthur Waeber (arthur.waeber@epfl.ch).

## Overview

The main goal of this lecture is to provide insights on the different reactor models and to let students differentiate them based on the type of reaction and the available data in the literature. Please refer to the Help page of Aspen for an overview of each type of reactor models. Concretely, the methanol (MeOH) synthesis from the produced syngas is analyzed in this tutorial. The 3 main reactions are simulated through the Gibb's equilibrium and the RPlug kinetic reactor model, allowing a nice comparison and a good comprehension of these 2 useful models.

## Questions

1)  Most of the catalytic reactions operate at relatively high pressure and temperature. The MeOH synthesis for instance require a pressure in the range of 50 to 100 bars, while the optimal temperature is around 250°C. To do so, a clever compression with intercooling steps has to be implemented to i) save electrical power in the compression steps ii) reduced the number of heat exchangers present in the system. Moreover for realistic purposes, the compression ratio should be kept under 4 to limit the investment costs in the compressor and material limitations.

- Make sure that the compression ratio is < 4 and check the effect of the second to last intercooling temperature on the power consumption and on the heat duty of the first heat exchanger.
- Based on the created model, define a design specification to ensure that the the duty of the heat exchanger HX1 == 0, varying the intercooling temparture of the second stage. 

*Answer 1:*

2)  For exothermic reactions, lower temperatures are known to shift the equilibrium constant towards the products. In the meantime, kinetics are favored at higher temperatures. Perform sensitivity analysis on the temperature to see the difference in the MeOH yield for the Gibb's equilibrium and the RPlug reactor models.

- Define a calculator block to relate all the operating temperatures to one single variable and let this variable vary from 200°C to 300°C.

*Answer 2:*

3) What is the effect of the pressure for these precise reactions? 

*Answer 3:*

4) The catalyst loading is a crucial parameter when considering reaction kinetics. How can it be used for a first approximation in the optimal reactor size? Perform multi-parametric sensitivity analysis to analysze the effect on the operating temperature on the saturating plateau.  

*Answer 4:*

