The collection efficiency is one of the key parameters to evaluate the performance of washing columns, and the gas-liquid flow characteristic is an important factor affecting collection efficiency. In this work, the gas-liquid flow characteristic and its effect on collection efficiency in a fixed valve column have been investigated. The experimental results show that the fixed valve washing column is capable of generating higher gas holdup than a standard bubble column under similar situations. For different particle sizes, with increasing gas holdup, the changes of the trends in collection efficiency are different. For particles larger than 1 pm, the collection efficiency increases with gas holdup while for particles finer than 1 pm, the collection efficiency either decreases (0.5-1 mu m) or decreases initially and then increases again (0.3-0.5 mu m). The collection efficiency increases with liquid-to-gas ratio but decreases with bubble size, bubble velocity and particle loading. The contribution of each tray to the collection efficiency is different. A correlation is developed for predicting the collection efficiency of particles and the experimental values agree well with the predicted values. (C) 2014 Elsevier B.V. All rights reserved.