Cyclone grade efficiency

Practically all cyclone performance data have been related to a present cyclone set of geometric ratios. One model for cyclone grade-efficiency curves has been tested against reported commercial cyclone efficiencies (159). A good fit was obtained. 

Statistical Analysis of Cyclone Grade Efficiency Measurements... 

Determination of the cyclone grade efficiency needs reliable measurement of the size distribution at both the inlet and outlet of the cyclone. The inlet distribution is determined by probe 1. Probe 1 samples a rather broad size distribution. In principle one should aim for isokinetic conditions. Another complication is that the probe occupies a significant area in the duct which has a... 

Fig. 7. Cyclone generalized grade-efficiency curves. The soHd line is for the Lapple cyclone dimension ratios given in Figure 9. The dotted line is theoretical...

Cyclone Efficiency. Most cyclone manufacturers provide grade-efficiency curves to predict overall collection efficiency of a dust stream in a particular cyclone. Many investigators have attempted to develop a generalized grade-efficiency curve for cyclones, eg, see (159). One problem is that a cyclone s efficiency is affected by its geometric design. Equation 15 was proposed to calculate the smallest particle size collectable in a cyclone with 100% efficiency (157). 

This equation is for Eigure 9 cyclone dimension ratios. The term the effective number of spirals the gas makes in the cyclone, was found to be approximately 5 for Lapple s system (134). The soHd line grade-efficiency curve of Eigure 7 is also used with Lapple s cyclone, which is a somewhat taller, less compact cyclone than many commercial designs. 

Thus, the grade efficiency of the similar cyclone can be constructed from the grade efficiency of the known (tested) cyclone. 

Figure 1.55. Typical grade efficiency curves for cyclones and a self-induced spray wet collector 53)...

The experimental results reported in this paper demonstrate the ability of a flat-bottom hydrocyclone to separate the coarse fraction of ammonium sulfate crystals from a slurry which contains crystals of a wide size range. It appears that the grade efficiency curve, which predicts the probability of a particle reporting to the underflow of the cyclone as a function of size, can be adjusted by a change in the underflow diameter of the hydrocyclone. These two observations lead to the suggestion to use hydrocyclone separation to reduce the crystal size distribution which is produced in crystallisers, whilst using a variable underflow diameter as an additional input for process control. 

This paper presents the grade-efficiency curves of a 75 n flat bottom cyclone (RWB 1613) provided by the Amberger Kaolin Werke (AKW). It is tested for the ammonium sulfate-water system for both fines removal and product classification. Its results will be compared with the results for fines removal obtained when using an... 

In fines removal, both the cut size and the grade efficiency are difficult to assess because of the limited accuracy of the sieve analysis technique and the problems Involved in the determination of the solids concentration in the overflow. For a. 65 m cyclone, whilst using a 20 mm vortexfinder diameter, an apex diameter of 16 mm and a feed flow of 1.6 1/s, solids recovery is over 99 % This recovery corresponds to a cut size between 50 - 100 pm. Typical distributions of size by weight, for the feed flow as well as the overflow are shown in Figure 5 Results are summarised in Table 2. 

The TSS has less potential for maximum emission control as the WGS and electrostatic precipitator (ESP). While all three technologies were designed to meet NSPS/ MACT, only the WGS and ESP can meet more stringent requirements. TSS performance can typically achieve d50 grade efficiency down to 2 microns. Most reported performance values result in emissions of 0.4-0.8 Ib/Mlb coke. Future PM2 5 regulations are a concern for TSS applications. By definition, TSS units cannot effectively remove small particles due to the cyclonic operation. 

The computation of a cyclone fractional or grade efficiency depends on cyclone parameters and flow characteristics of particle-laden gases. The procedure involves a series of equations containing exponential and logarithmic functions. Koch and Licht [ 12] described a cyclone using seven geometric ratios in terms of its diameter as ... 

FIGURE 3.5.3 Grade efficiency of Stairotand cyclone correlated with particle size, inlet velocity, and cydoan diameter. Excerpted by special permission from Cfwarical Engineering, Nov. 7, 1977, pp. 80-88, by McGraw-Hill, Inc.. New York, NY 100(20. 

The overall efficiency rj is defined as the mass of particles removed divided by the mass entering the cyclone, per unit time. It may be calculated by integrating the grade efficiency over the particle size distribution ... 

Another application of hydrocyclones is for solid-solid separation by particle size. As the grade efficiency of a cyclone increases with particle size, it can be used to split the feed solids into fine and coarse fractions. This may be a process requirement, by which coarse and fine solids are separated to follow different routes in the plant, such as, for example, in closed circuit wet... 

Several authors have attempted to calculate particle trajectories in the cyclone and to derive formulae at least for the equiprobable size X50 if not for the whole grade efficiency curve. Some of these theories are discussed in section 6.6 certain observations are given here and refer to the probable behaviour of solid particles in sufficiently dilute suspensions. 

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