Aqueous iron hydrolysis products and chloride complexes influence steel corrosion kinetics and dictate the amount and type of corrosion products formed. Here, we compile a thermodynamic database devoted to aqueous iron species and solid oxides as well as chloride complexes, aiming to describe their speciation and solubility within the prevailing chemical environment of interest for cementitious systems. We compare thermodynamic calculations to empirical data on the elemental composition of pore solutions from cementitious systems.It is found that dissolved iron concentrations in cement pore solutions can differ considerably from thermodynamic predictions. In particular, measured Fe(II) concentrations can exceed the thermodynamic limit by 2-5 orders of magnitude. Additionally, experimentally obtained iron solubility in the presence of chloride exceed thermodynamic predictions. We discuss that these differences may be explained by so far unknown iron complexes, stabilisation of intermediate phases such as chloride green rust, or due to (kinetic) hindrance of precipitation.
In the pursuit of shifting technology towards sustainable, environmentally benign processes, post-combustion carbon capture technology is recognised to be a timely mitigation option. This paper presents the development of a novel sodium carbonate-based post combustion carbon capture process utilising the carbonate mineral trona (trisodium hydrogendicarbonate dihydrate) as main sorbent feedstock source. The energy penalty, the fraction of energy sacrificed to capture CO 2 relative to the net energy produced serves as main performance indicator. Investigations on the correlative relationship between energy penalty as a function of capture efficiency are carried out by retrofitting the process to a 600 M W reference coal-fired power plant. The energy penalty of the global system features a distinct local minimum of 3.99 %, corresponding to a CO 2 capture efficiency of 90.00 % and a CO 2 outlet purity of 99.90%. The Specific Primary Energy Consumption for CO 2 Avoided (SPECCA) index corresponding to this minimum is evaluated to be SPECCA = 0.514 M J kg CO −1 2 . Sensitivity analyses on the effect of increasingly high SO 2 flue gas volume fractions y SO 2 show that the capture efficiency is virtually unimpaired for calcination temperatures of 190 ≤ T ≤ 280 • C and y SO 2 ranging from 0.50 to 0.70 %. Whilst commercially available CO 2 capture technology is energy intense and prone to sorbent degradation, the process developed retains high capture efficiencies of calcium oxide-based looping cycles at low operating temperatures and eliminates the predisposition of amine-based sorbents utilised in scrubbing capture schemes to deplete due to the presence of SO 2 in the inlet flue gas stream. It can be concluded that sodium carbonate based post-combustion capture processes are a competitive alternative to existing CO 2 capture technologies.
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