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
Carbon dioxide storage by mineralisation applied
to a lime kiln
Inês Romão a,b , Matias Eriksson c,d , Experience Nduagu a , Johan Fagerlund a ,
Licínio M. Gando-Ferreira b and Ron Zevenhoven a
a Åbo Akademi University, Dept. of Chemical Engineering, Åbo / Turku, Finland,
iromao@abo.fi (CA)
b University of Coimbra, Dept. of Chemical Engineering, Coimbra, Portugal
c Nordkalk Corporation, Pargas / Parainen, Finland
d Umeå University, Sweden
This paper describes a design, for a pilot-scale application, of a two-staged process that is under study at
Åbo Akademi University (ÅA), for Carbon dioxide Storage by Mineralisation (CSM). The ÅA route implies the
production of brucite (besides Ca- and Fe- based by-products) from a magnesium/calcium silicate rock,
using recoverable ammonium sulphate (AS), followed by carbonation of the Mg(OH)2 in a pressurised
fluidised bed at ~ 500°C, 20-30 bar CO2 partial pressure. An assessment is reported for operating the CSM
process on waste heat from a limekiln (lime production: 210 t/day) in Pargas, Southwest Finland, i.e. without
external energy input apart from what is needed for crushing the rock to the required particle size (a few % of
the overall CSM process energy requirement) and compressing the flue gas to be treated. Part of the off-gas
from the limekiln (CO2 content ~21%-vol) will be processed without a CO2 separation step. The feature of
operating without CO2 separation makes CSM an attractive and cost-competitive option when compared to
conventional CCS involving underground storage of CO2. An exergy analysis is used to optimise process
layout and energy efficiency, and at the same time maximise the amount of CO2 that can be bound to
MgCO3 given the amount of waste heat available from the kiln. Also, experimental results are reported for
producing Mg(OH)2 (and Fe,Ca(OH)2) from local rock material.
Keywords:
CO2 mineral sequestration, Scale-up, Lime kiln.
1. Introduction
1.1 CO2 mineralisation
For Finland, carbon dioxide storage by mineralisation (CSM) was identified as the only option for
CCS (carbon dioxide capture and storage) application. It is a permanent storage option and has an
estimated storage potential that is much larger than underground storage as pressurized CO2 [1-2],
the currently most intensively studied option for CO2 disposal. The purpose of CSM is to promote
CO2 fixation by metal oxides into thermodynamically stable carbonates while benefiting of the
exothermicity of the carbonation reaction:
(Ca,Mg)*ySiO2*zH2O (s) + CO2 (g) → (Ca,Mg)CO3 (s) + ySiO2 (s) + z H2O (g) + HEAT (R1)
Magnesium in particular is abundant in the earth’s crust, as silicates such as serpentinite and
olivine. These reactions occur in nature over geological timescales (hundreds of thousands of
years). Research has focused on improving the reaction rates by treating the mineral rock by
thermal, mechanical or chemical means [1-4]. Due to the exceptionally large scale of CCS
processes, all additives must be recovered, and the energy input minimised.
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