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Photo/thermochemical Hydrogen Production Plant Design

aspen plus energy integration

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#1 Elmansi

Elmansi

    Junior Member

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Posted 08 April 2020 - 03:58 PM

I am designing a hybrid photo/thermochemical process to produce 1 kmol/s Hydrogen and shed light on the viability of the Cu2O/CuO subcycle using ASPEN PLUS

 

These are the reactions for the complete cycle

H2O + 2 NH3 + SO2 --> (NH4)2SO3 (25 degrees celsius, chemical absorption)
(NH4)2SO3 + H2O--> (NH4)2SO4 + H2 (65 degrees celsius, solar photocatalytic step)
(NH4)2SO4 --> H2SO4 + 2 NH3 (250 degrees celsius, thermocatalysis) Also some of the unconvered ammonium sulfite decomposes to SO2, NH3 and water
H2SO4 --> SO3 + H2O (400 degrees celsius, thermocatalysis)
SO3 + Cu2O --> 2 CUO + SO2 (650 degrees celsius, thermocatalysis)
2 CUO --> Cu2O + 1/2 O2 (1050 degrees celsius, thermocatalysis)

 

My Problem

I want to circulate 15 kmol/sec to ensure liquid operation and that no precipitation of the ammonium sulfate and sulfite takes place. Unfortunately, I think because of this, high heat duty is required in the Low temperature reactor where ammonium sulfate decomposition takes place. I have added a component separator to separate the gaseous mixture SO2, NH3 from the aqeous solution H2O. From this point in the process, H2O serves no purpose and is considered a drawback because more heat duty is required. How can we go about this problem of seperating H2SO4 from water without the addition of new chemicals.Cu2O exiting the reactor operating at 1050 is added directly to heat the SO3-H2O feed to the reactor (650), the gaseous mixture from this reactor is used to heat H2SO4 + SO3 + some of the ammonium sulfate, and finally returned to the absorber, significant heat is wasted. As a result, the calculated efficiency is not satisfying, 13 %. Also in one of the heat exchangers I am not sure whether at the specified outlet temperature the SO2-H2O will undergo phase change , so how can I account for the phase change if any in the specification of the MHeatx should I include in the phases vapor-liquid?

How can I input manually the heat capacities for the components of my system and allow aspen to heat based on these heat capacities.


Edited by Elmansi, 08 April 2020 - 05:14 PM.





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