A chilled ammonia-based carbon dioxide removal system is provided. The system includes a direct contact cooler, a carbon dioxide absorber and a water wash station.

The present application provides an air quality control system for cleaning a flue gas from a fluid catalytic cracking unit. The air quality control system may include a selective catalytic reduction system in communication with the flue gas to remove nitrogen oxides and a wet scrubber positioned downstream of the selective catalytic reduction system and in communication with the flue gas to remove sulfur oxides and particulates.

The air pollution control system including: a flue gas duct through which flue gas flows; a heat exchanger provided to the flue gas duct; a limestone supply device for reducing SO.sub.3 in the flue gas supplies CaCO.sub.3 to the flue gas flowing in an upstream of the heat exchanger; an upstream SO.sub.3 measurement device measures the SO.sub.3 in the flue gas flowing in a stream upper than a position where the limestone supply device supplies the CaCO.sub.3; and a control device determines a quantity supplied of the CaCO.sub.3 based on a relationship between a quantity of the SO.sub.3 measured by the upstream SO.sub.3 measurement device and a molar ratio of SO.sub.3 to CaCO.sub.3 and which supplies the determined quantity supplied of the CaCO.sub.3 from the limestone supply device to the flue gas duct.

The description relates to a process for reducing acid plume from stacks from coal-fired combustors operating at varying loads, which have typically been treated by back-end calcium carbonate (limestone) which has not been able to effectively control visible acid plume as power is ramped up from low load. According to the process, as high sulfur and high iron coals are burned in a combustor, magnesium hydroxide slurry is introduced into hot combustion gases in or near the combustion zone. And, during ramp up to high load from a period of operation at low load, additional magnesium hydroxide is introduced into an intermediate-temperature zone.

A method for treating a gas is shown which includes the steps of: injecting a powdered compound into the gas line, injecting an aqueous phase in droplet form into the line, capturing pollutants from the gases, and recovering the powdered compound separately. The step for injecting an aqueous phase in droplet form is done so as to moisten those particles of powdered compound in the gas line, when they are injected.

The air pollution control system including: a flue gas duct through which flue gas flows; a heat exchanger provided to the flue gas duct; a limestone supply device for reducing SO.sub.3 in the flue gas supplies CaCO.sub.3 to the flue gas flowing in an upstream of the heat exchanger; an upstream SO.sub.3 measurement device measures the SO.sub.3 in the flue gas flowing in a stream upper than a position where the limestone supply device supplies the CaCO.sub.3; and a control device determines a quantity supplied of the CaCO.sub.3 based on a relationship between a quantity of the SO.sub.3 measured by the upstream SO.sub.3 measurement device and a molar ratio of SO.sub.3 to CaCO.sub.3 and which supplies the determined quantity supplied of the CaCO.sub.3 from the limestone supply device to the flue gas duct.

A desulfurization wastewater zero discharge treatment method and system suitable for multiple working conditions. A tail flue of a boiler and a bottom outlet of a wastewater drying tower are both communicated with an inlet of a dust collector; an outlet of the dust collector is communicated with flue gas inlets of a wastewater concentration tower and a desulfurization absorption tower; the wastewater concentration tower is communicated with the desulfurization absorption tower; the desulfurization absorption tower is communicated with a chimney; the desulfurization absorption tower is communicated with a gypsum cyclone; the gypsum cyclone is communicated with a filtrate water tank; the gypsum cyclone is communicated with a gypsum dewatering machine; the gypsum dewatering machine is communicated with a gas liquid separating tank; and a flue gas port of the tail flue of the boiler is communicated with the flue gas inlet of the wastewater drying tower.