87. The calcium oxide–carbon dioxide system in the pressure range 1—300 atmospheres

Abstract

The calcium oxidecarbon dioxide equilibrium has been studied a t pressures of carbon dioxide up to 304 atm. by using a pressure vessel with an internal heating arrangement. For the reaction CaCO,(s) = CaO(s) + CO,(g), in the pressure range 1-39.5 atm., the results agree well with those of previous authors and can be expressed by the relation, AGO = 38,000 -32.4T. The eutectic point has been estimated to lie a t 1242" f 3' and 39.5 f 0.5 atm. Above the eutectic point, the pressure-temperature relations have been plotted for the binary melts in equilibrium with solid calcium carbonate and solid calcium oxide, severally. By means of a special quenching device, the compositions of these melts have been determined and a phase diagram has been derived for the eutectic portion of the system. The eutectic composition has been found to be CaCO, 88.3 moIe %, CaO 11.7 mole yo.THE equilibrium CaCO, + CaO + CO, has been well studied at pressures up to 1 atm. and many thermodynamic expressions have been derived for the pressure-temperature relation.lPa At higher pressures, however, the only systematic thermodynamic study has been that of Smyth and Adams who used thermal analysis to follow the dissociation up to a pressure of 1000 atm. These workers found that at above 1240" and 39.5 atm. dissociation was accompanied by fusion of the resultant oxide with unchanged carbonate to give a single liquid phase.Since the system involves both gas-solid and gas-liquid equilibria at high temperatures its study is particularly useful for establishing techniques of general application to moltensalt systems of this type. As a result of the present work on the equilibrium, special apparatus has been developed, for example, a device for quenching samples, and furnaces which are stable in high-pressure carbon dioxide. Knowledge of the equilibrium has been extended by determining the oxide and carbonate contents of the binary melts which are formed and from these results a phase diagram has been constructed for the eutectic portion of the system.

Changes in Limestone Sorbent Morphology during CaO‐CaCO3 Looping at Pilot Scale

“…Initial fluidized bed carbonation resulted in carbonator flue gas outlet CO 2 concentrations near equilibrium levels, based on the equilibrium vapor pressures reported by Baker [9] for the first 10 to 20 minutes of reaction. After this period, the CO 2 concentration in the carbonator outlet rose rapidly to a value 1 to 4 percentage points below the CO 2 inlet concentration.…”

Capture of CO2 from combustion gases in a fluidized bed of CaO

“…The first limit arises from the equilibrium in the carbonation-calcination reaction, which for the temperature interval of interest can be given by (Baker, 1962) C CO2,eq ϭ 1.462 10…”

Cone calorimeter study of inorganic salts as flame retardants in polyurethane adhesive with limestone filler

“…This reaction, however, takes place when the temperature is roughly 750-800 C -depending on conditions. [31][32][33][34][35] These temperatures are too high for flame retarding effects when the sample starts to decompose.…”