The effect of the ammonium paratungstate source on the tungsten crystallite size

In an investigation into the effects of CaCl₂ on the sulfation of limestones in a laboratory furnace simulating fluidized-bed coal combustion conditions, small additions of CaCl₂ (<1 mole%) to the limestone prior to calcination were found to increase the extent of sulfation by changing the limestone pore structure. These changes were effected by trace amounts of liquid in the system in a synthetic SO₂/O₂ flue gas at 850°C. At much higher concentrations of CaCl₂, large amounts of a liquid phase are produced, containing a substantial quantity of dissolved CaO and leading to greatly enhanced sulfation when exposed to SO₂/O₂. The use of CaCl₂ additive in fluidized-bed combustion would reduce the quantity of limestones required to meet air pollution standards for SO₂ and also reduce the quantity of solid waste generated.