Studies were made on certain characteristics of gas-lift reactor. This type of reactor is called Pachuca tank in hydrometallurgy and is used widely as gas-liquid-suspended solid particles 3-phase reactor. Methods were developed to calculate gas-liquid and gas-liquid-solid particles circulation capacity through the central tube of the reactor based on energy balance principle. Starting from the force balance on a solid particle

equations with dimensionless groups were also developed to calaulate the critical settling velocity of particles at the reactor bottom. Based on experimental results

the critical plug-up velocity of reactor can be calculated by an equation developed. Results can be used for the design and operation of this kind reactor.