Formation of solids in ammonia-based CO2 capture processes — Identification of criticalities through thermodynamic analysis of the CO2–NH3–H2O system

Estimating speciation of aqueous ammonia solutions of ammonium bicarbonate: application of least squares methods to infrared spectra

“…1 Ternary phase diagram for the CO 2 -NH 3 -H 2 O system at 15°C and 1 bar obtained using the thermodynamic model proposed by Darde et al 6 The compositions are expressed in weight fractions and its construction and use have been described in detail elsewhere. 18 The black dots (•) indicate the composition of the stable solid phases, namely ammonium bicarbonate (BC), ammonium carbonate monohydrate (CB), ammoniumsesquicarbonate (SC), and ammonium carbamate (CM). The dashed isopleths (black lines) refer to CO 2 , NH 3 , and H 2 O mixtures characterized by a constant ratio, ζ, between the nitrogen and carbon species, while a colorcode is used to indicate the pH of the liquid phase calculated using the thermodynamic model proposed by Darde et al 6…”

“…The segregation of these peaks is complicated by the pronounced overlap with the spectrum of the other species; the extent of speciation, in general, does not allow for a direct measurement of the actual concentration of the carbamate ion. In light of these considerations, two of the three characteristic peaks of the carbamate ion have been modeled, after subtraction of the spectrum of the solvent, using Gaussian functions such as: (18) in which the location of each peak, μ, has been set based on the available literature data 10,11 and its broadness, σ, has been chosen by appling an optimization procedure discussed in sec. Reaction Chemistry & Engineering Paper 5.6.1.…”

“…Reaction Chemistry & Engineering Paper 5.6.1. In eqn (18), a is the infrared absorbance function of the wavenumber , and the values of m and s are respectively equal to 1545 cm −1 and 1413 cm −1 , and 43.1 cm −1 and 19.2 cm −1 for the two modeled peaks of the carbamate ion. The carbamate band located at 1120 cm −1 , characterized by a much lower absorptivity compared to the other characteristic peaks, 10,11 has been neglected from the modeling procedure without significantly affecting the representation of the system.…”

Recovery and concentration of ammonia from return liquor to promote enhanced CO2 absorption and simultaneous ammonium bicarbonate crystallisation during biogas upgrading in a hollow fibre membrane contactor

“…Ammonium bicarbonate crystallisation was first considered in CCS to reduce the heat requirement for regeneration (Darde et al, 2009). However, the homogeneous nucleation and growth of crystals within the mixed phase of a packed column introduced clogging of equipment, making implementation difficult (Sutter et al, 2015). McLeod et al (2015) successfully demonstrated the feasibility of ammonium bicarbonate crystallisation in a HFMC using a synthetic ammonia solution.…”

Is Chemically Reactive Membrane Crystallization Faciliated by Heterogeneous Primary Nucleation? Comparison with Conventional Gas–Liquid Crystallization for Ammonium Bicarbonate Precipitation in a CO2–NH3–H2O System

“…This reduces the process heat demand 7 . However, management of the crystalline solid product within packed columns was difficult, resulting in clogging of the packing 8 .…”