Global warming resulting from the emission of carbon dioxide, one of the main greenhouse gases, has received widespread attention. Among the technologies available, amine absorption is the most mature technology with the capability of handling large exhaust streams, and it is cost-effective.
Recently, your company has received a project from a coal-fired power plant to design an amine absorption unit to remove the CO from the flue gas stream. The separation efficiency of amine absorption hinges on the type of amine solvent used. In view of this, your team has been assigned to determine the most suitable amine solvent for the CO capture. After some literature search, you have narrowed down the candidates to monoethanolamine, diethanolamine, and piperazine.
Your team needs to develop a model to predict the absorption rate of the CO in amine solvent. This process involves both diffusion and reaction of CO with amine solvent. The kinetics data of the three amines are provided in Appendix B. Besides the absorption rate, you are required to compare the amine solvents from different aspects such as ease of solvent regeneration, costing, safety, and environmental effect.
The report should consist of:
i. Background introduction: Introduction on the gas absorption process
ii. Derivation/Calculation: List all the assumptions used in derivation. Calculate the diffusivity of CO in each amine. Derive and compare the absorption rate of each amine solvent.
iii. Discussion/Comparison/Conclusion: Compare and discuss the suitability of each amine based on the five criteria - absorption rate, ease of solvent regeneration, costing, safety, and environmental effect. Propose the most suitable amine solvent for CO capture.
The reaction rate for the absorption is as follows: rco = ko.[CO]
ko = kA(mmolay) - [Am]
where [CO] is the concentration of CO in the gas stream, [Am] is the concentration of amine, k is the empirical kinetic constant, and n is the apparent order of reaction with respect to amine.
k and n for the three amines are tabulated as below:
Amine kA(mmolay) n
monoethanolamine 2.42 1.16
diethanolamine 8.06x10^(-4) 1.62
piperazine 4.30 1.41
