Double-contact-flow absorbers with liquid column/screen flow type are investigated experimentally using systems of different length scales, where SO2 is the absorbate and limestone slurry is the sorbent. The study of the flow characteristics shows that the practical bed height coefficient can be expressed as an exponential function of the Froude number (and essentially insensitive to the spray pipe pattern and the scale of system). The main parameters influencing the desulfurization rate include the liquid flow rate, flue gas flow rate, and different spray pipe patterns; their effects are tested on systems with two different scales. Under moderate working conditions, the desulfurization efficiency can reach a high level of above 95%. A method is established to describe the detailed mass transfer process in a double-contact-flow reactor, which may be applied to absorbers of different scales. An empirical formula is derived to predict the desulfurization rate which is in good agreement with experiment data, making it a potential tool for estimating the desulfurization performance in practical applications. (C) 2009 Elsevier Ltd. All rights reserved.