1. Introduction - Firenze University Press

Abstract:
PROCEEDINGS OF ECOS 2012 - THE 25 TH INTERNATIONAL CONFERENCE ON
EFFICIENCY, COST, OPTIMIZATION, SIMULATION AND ENVIRONMENTAL IMPACT OF ENERGY SYSTEMS
JUNE 26-29, 2012, PERUGIA, ITALY
Influence of regeneration condition on cyclic CO2
capture using pre-treated dispersed CaO as high
temperature sorbent
Stendardo Stefano a , Calabrò Antonio a
a ENEA, Italian National Agency for New Technologies, Energy, and the Sustainable Economic
Development Via Anguillarese, 301, S. Maria di Galeria, 00123, Rome, Italy
In this experimental investigation the effect of calcination temperature and atmosphere composition on CO2
uptake of a solid sorbent have been analysed. The sorbent were synthesized by means of a CaO hydrolysis
technique to generate sorbents with 75% and 85% of active phase CaO. The material at hand also contains
a calcium aluminate phase acting as a binder of the active phase. Pre-treatment was accomplished in a
thermo-gravimetric analyser (TGA) exposed in an atmosphere of 86% N2 and 14% CO2 under 600 °C. The
as-synthesised sorbent and the pre-treated sorbent have been characterised by scanning electron
microscope, nitrogen physic-sorption tests, and multi-cycling carbonation-calcination test in TGA (160
cycles). Here, the CO2 uptake took place at programmed temperature (600 °C) with three different
regeneration condition tested:
a) mild condition: regeneration under 900 °C with 14% CO2 and 86 % N2;
b)moderately severe condition: regeneration under 1000 °C with 14% CO2 and 86 % N2;
c) severe condition: regeneration under 1000 °C with 86% CO2 and 14 % N2.
The experimental results show significant improvement in the stability of the CO2 uptake capacity over
multiple cycles when comparing the synthetic sorbents to natural dolomite. For an instance, the 75% CaO
synthetic sorbent shows a good reversibility for the CO2 uptake (0.13 g-CO2/g-sor) up to 150th cycle under
severe condition.
Keywords:
Keywords: solid sorbent, carbon capture, carbonate chemical looping, self-reactivation.
1. Introduction
Carbon capture technologies are expected to be a promising route to meet the objective of a low
carbon electricity production and the increasing of coal foreseen by the scientific and industrial
community. Hydrogen production from renewable energy sources, coal and biomass is a priority for
Italian medium and long term energy policy. Thus, in Italy technologies for CO2 capture are
considered a main topic to be studied and demonstrated, and represent a significant opportunity for
industries. In order to promote carbon capture technologies, ENEA has constructed an experimental
platform, named ZECOMIX, to investigate both the gasification of coal and the separation of CO2
from synthetic gas fuel or flue gas. Particularly the decarbonisation of the gaseous stream happens
by means of a carbonate looping (CaL) technology with a CaO based solid sorbent. When the CaO
is converted to the calcium carbonate, the spent solid sorbent is sent back to the regeneration
process where an active sorbent is regenerated for a new carbonate looping. As reported in the
scientific literature: [1-4], when naturally occurring material as calcite or dolomite are used as CO2
acceptor in a CaL, there is a decay of reversibility. The ideal CO2 sorbent in a CaL should show a
number of properties: high and stable CO2 uptake capacity throughout continuous decarbonisingregeneration
cycling, fast reaction kinetics, uptake capacity and kinetics close to theoretical
maximum values, and also mechanical stability and sintering resistance. In an attempt to achieve
this goal, researchers have developed novel synthetic sorbents based on e.g. CaO dispersed on
calcium aluminate ceramic supports. [5]. In this work a number of experimental results on the
175