Abstract: An apparatus for removing SO.sub.2 from flue gas treats the hot flue gas with a sump liquid to quench the flue gas and saturate it with water while concentrating ammonium sulfate in the recycled liquid. The gas is then scrubbed in a packed scrubbing zone with a solution of ammonia water, untreated recycled ammonium sulfite and ammonium hydrogen sulfite, and ammonium sulfate solution from an oxidizer to which a partial stream of the scrubbing liquid is fed.

Abstract: SO.sub.2 containing flue gas is scrubbed with a scrubbing solution made up from ammonia water, untreated ammonium sulfate scrubbing solution recycled from the bottom of the scrubbing zone and ammonium sulfate solution formed by oxidizing a portion of the recovered ammonium sulfite scrubbing solution. The ammonium sulfite/ammonium sulfate mixing ratio is maintained at 15:1 to 3:1. The ammonium sulfite containing scrub liquid in combination with aqueous ammonia and an ammonium sulfate solution which has undergone oxidation can have an unusually high sulfur dioxide absorption capacity while minimizing the formation of aerosols.

Abstract: A nozzle arrangement in which the nozzles have a scrubber, especially for flow gas desulfurization, are laid in accordance with the following: (a) liquid concentrations of a component to be absorbed from a gas stream scrubbed in the column are measured above a plane of the nozzle assembly at N locations of a grid of equal area elements of a cross section of the column; (b) the N concentration values are compared with a predetermined value; (c) upon deviation of a measured concentration value from the predetermined value, a position of at least one of the nozzles is varied by selection of a length and location of an intermediate pipe section connecting the one of the nozzles to a respective branch pipe laterally thereon; and (d) repeating (a) through (c) until the concentration values measured above the plane are approximately equal except for at a wall region of the column.

Abstract: A nozzle arrangement for a scrubbing column for a flue gas in desulfurization, in which the scrubbing column has a sump, a baffle-free zone above the sump and a nozzle arrangement above the absorption zone. The nozzles, preferably by selective connection of intermediate pipe sections are connected to a branch pipe system extending from a distributor. Flow density profiles are formed in predetermined cross sectional planes of the scrubbing column by the spray cones of the nozzles. In each of these cross sectional planes, the flow density profiles of different spray cones are superimposed on one another. The flow density profiles of different cross sectional planes are superimposed upon projection of them onto a one of the planes to form a flow density complete profile in this one plane over the entire cross section of the scrubbing column.

Abstract: The CaCO.sub.3 content of a scrubbing suspension, especially for a desulfurizing apparatus for flue gas is measured by injecting an acid into a constant mass flow of the suspension circulating along a bypass and measuring the pH before and after such injection. The change in pH is compared with reference measurements and used as a basis for calculating the CaCO.sub.3 concentration.