A new catalyst has been proposed that converts CO2 to methanol, and a
commercial scale reactor is to be built to test it further. While the process works
at the moderate temperature of 200°C, a pressure of 130 bar is required. The
reactor is designed as a cylindrical vessel with hemispherical ends, with an inner
diameter of 1.2 m and an internal height of 3.7 m. A decision needs to be made
as to whether it is preferable to use low alloy steel or a titanium alloy to build
the reactor. Relevant data for both is given in Table Q2.
Note that there is a supporting formula sheet in the appendix related to this
subject area.
Table Q2 - Material Properties
Steel Titanium
Cost per tonne / USD/t 1100 9900
Density / kg/m3 7850 4600
Yield strength / MPa 550 1000
Ultimate strength / MPa 700 2300
NAME_1’s modulus / GPa 210 115
Fracture toughness / MPa.m(1/2) 60 65
NAME_2’s ratio 0.31 0.18
a) Estimate the cost of building the reactor from each of the materials. Explain
choices you made for the calculations, and clearly state the resulting total
cost in USD.
If you require the design strength you may assume it here to be 0.7 times
the yield strength. [15]
b) For the vessels costed in a), what is the difference in height between
atmospheric and the operating pressure? [10]
c) Will both materials/vessels leak before they burst? [6]
d) Which material would you propose to use based on the calculations in a)-
c). Briefly state why? [4]
e) State which other properties you may wish to consider before making a final
decision, and how they could affect your decision? [5 Give two different versions of responses. Please separate the responses with 6 asterisk symbols: ******.
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