(187l) Energy Analysis of Non-Aqueous Solvents (NASs) for CO2 Capture Process

Energy analysis of non-aqueous solvents (NASs) for CO₂ Capture
Process

Aravind V.
Rayer, Paul Mobley, Vijay Gupta, Jak Tanthana, Mustapha Soukri, Marty
Lail and S. James Zhou

RTI International, 3040 E.
Cornwallis Rd., Research Triangle Park, NC 27709-2194, USA

Abstract

            To
develop a cost-effective absorption-based CO₂ capture process, it is
necessary to evaluate the energy consumption of the scrubbing process which is
the large contribution to the cost. This task needs the detailed solvent
properties such as reaction enthalpy, Vapor-Liquid Equilibrium (VLE) and Liquid
heat capacity. Investigation of both aqueous and non-aqueous solvents were done
in this work based on a short-cut method using the in-house measured
properties. The non-aqueous solvents reduced the heat of vaporization due to
the low water content and high boiling points at the regeneration temperatures.
The sensible heat contribution to the energy was reduced by the lower specific
heat capacities of NASs and the higher working capacities for CO₂
capture.

            In
this work, the comparison of aqueous MEA with NASs showed that heat of
absorption of NASs are lower than aqueous MEA as shown in Figure 1 and NASs are
having higher working capacities as shown in Figure 2. The heat of absorption
of NASs decreased with increase in temperature, whereas for aqueous systems
heat of absorption increased with increase in temperature as shown in Figure 1.
The effect of increasing reactive amine concentrations, water and alcohols on
the heat of absorptions, heat capacities and VLEs were investigated. Increasing
the amount of hydrophobicity of amine for NASs were also investigated. Specific
reboiler duty (SRD) calculated using short-cut method showed that 1.94 MJ/kg_CO2
could be achievable with an optimized NAS as shown in Figure 3.

Figure  SEQ Figure \* ARABIC 1. Comparison of heat of absorption of aqueous and
non-aqueous system

Figure  SEQ Figure \* ARABIC 2. Comparison of Vapor-Liquid Equilibrium (VLE) of aqueous
and non-aqueous solvent

Figure  SEQ Figure \* ARABIC 3. Comparison of Specific Reboiler Duties (SRDs) of
aqueous and non-aqueous system