Operating efficiency and hydrodynamics of conical dust collectors with swirling counterflows

Abstract

The operating principle of dust collectors with swirling counterflows (SC) is examined. An efficiency of 80-85% is achieved during tests of an SC vessel under industrial conditions. The velocity fields of the gas flow in different sections are analyzed over the height of the SC vessel. The influence exerted by the taper of the effective zone of the SC vessel on the dust-entrapment efficiency is investigated. Results are presented for comparative hydrodynamic tests of cylindrical and conical SC dust collectors.Reduction in dust emissions to the atmosphere in the production lines of modern industrial factories is achieved by different effective gas-cleaning methods. Dust collectors with swirling counterflows (SC) had come into increasingly widespread use as fine-cleaning vessels by the start of the 1990s. The operating principle of these vessels is based on a hydrodynamic effect -interaction between swirling gaseous counterflows [1-4]. Vekua [3] and Ovcharenko and Petrov [4] have investigated the overall dust-entrapment effectiveness of SC vessels.During the testing of an SC vessel with a diameter D v = 0.6 m ( Fig. 1) as the third stage of dust entrapment for an expanded-pearlite powder, therefore, an efficiency η = 80-85% was achieved at the Stroiperlit Combine (Fig. 1).This high efficiency of the SC vessel makes it competitive with bag filters traditionally used on production lines of the manufacturing in question [4].The hydrodynamic structure of the gas flows in the SC vessels operating under conditions of maximum dust-entrapment efficiency has been investigated by Sazhin et al. [5]. Analysis of the velocity fields of the gas flow in various sections over the height of the SC vessel has indicated that a reduction in the tangential component of the velocity vector of the flow takes place as it moves from top to bottom (in the direction of the turn in flow -discharge). Frolov [2] has established that the tangential component of the velocity vector of the flow exerts a determining influence on the dust-entrapment process in centrifugal vessels; this obviously leads to a reduction in dust-entrapment efficiency. Investigations of the traditional design of SC vessel with axial-vane swirlers (Fig. 2) of primary and secondary gas flows have therefore indicated that when particles of medicinal talc (d m = 8 µm, ρ = 2200 kg/m 3 ) are trapped in a vessel with a diameter D v = 0.3 m, the maximum overall cleaning efficiency η = 98%.To enhance the dust-entrapment efficiency, it is necessary to ensure constancy of the tangential component of the vector v ϕ of the gas flow over the entire height of the vessel, for which a conical design of SC vessel has been proposed [6]; the testing of this vessel as a component part of an experimental plant was conducted to evaluate its efficiency (Fig. 3). The hydrodynamic structure of the gas flow in the vessel was preliminarily analyzed, and the dust-entrapment efficiency evaluated [7].The vessel was tested under similar conditions to permit comparative evaluation of results obtained and...