Abstract: The invention relates to a pipe (13) for conveying a condensable gas or a gas comprising condensable components, comprising at least one portion (15) inclined relative to horizontal. A ring (17) is accommodated in the portion (15) inclined relative to horizontal, which ring is joined to the pipe (13) by a first end face (21) in a liquid-tight manner over its entire circumference and whose diameter decreases towards a second end face (25) opposite the first end face (21), such that a space (27) is formed between the ring (17) and the internal wall of the pipe (13), the ring (17) is positioned in such a way in the pipe (13) that liquid condensing on the pipe wall flows into the space (27) between ring (17) and internal wall of the pipe (13), and an outlet (19), through which the liquid may flow out, opens into the space (27) through the wall of the pipe (13). The invention further relates to a device for carrying out mass transfer processes and to use of the device.

Abstract: A process for preparing nitric acid by: catalytically oxidizing ammonia, to obtain a gas mixture containing NO and O2; cooling and condensing the gas mixture, thereby further oxidizing NO with O2, to obtain a gas stream containing NO2/N2O4 and an aqueous solution containing nitric acid; and countercurrently absorbing the NO2/N2O4 from the gas stream in an absorber with process water (H2O), to obtain nitric acid and an NOx-containing absorber offgas, wherein the water content of the nitric acid is regulated to a concentration in the range from 50 to 77.8% by weight and the NOx content of the absorber offgas to a concentration in the range from 20 to 500 ppm, by continuously measuring the water content of the process air supplied to the catalytic gas phase oxidation and, as a function of this, adjusting the amount of process water (Q-H2O) fed to the absorber.

Abstract: A process for preparing sulfuric acid, in which process gases comprising sulfur dioxide are obtained by combustion of liquid sulfur by means of process air introduced from the outside or by dissociation of waste sulfuric acids and the sulfur dioxide in the process gases comprising sulfur dioxide is oxidized to sulfur trioxide and converted into sulfuric acid by the contact process, wherein the process air which is introduced from the outside for combustion of sulfur or the process gases comprising sulfur dioxide which are obtained by dissociation of waste sulfuric acid have their water vapor content reduced by cooling them, is proposed.

Abstract: What is proposed is a process for preparing nitric acid with a concentration in the range from 50 to 77.8% by weight by catalytic gas phase oxidation of ammonia (1) with a superstoichiometric proportion of process air (2) to obtain a gas mixture (3) comprising NO and O2, cooling/condensation of the gas mixture (3) comprising NO and O2, in the course of which NO is oxidized further by O2 to NO2/N2O4 to obtain an aqueous solution (4) comprising nitric acid and a gas stream (5) comprising NO2/N2O4 and countercurrent absorption of the NO2/N2O4 from the gas stream (5) comprising NO2/N2O4 in process water (H2O) in an absorber (A) to obtain the nitric acid (7) with a concentration in the range from 50 to 77.8% by weight and an NOx comprising absorber offgas (6), wherein the water content of the nitric acid (7) is regulated to a concentration in the range from 50 to 77.