Design - Cyclone Separation System to Produce Fine Particles of Zinc Oxide

Executive summary:

Representatives of a lead and zinc processing plant have consulted to our company, the theme is requested our company to design a cyclone separation system to produce fine particles of zinc oxide, the system is designed to reach at least 95% efficiency of colleting particles. Moreover, the other request for the clients is giving some suggestions about using baghouses. (Whether the plant can only use a baghouse instead using a baghouse in series with a cyclone system.)

The details of design are shown in appendix calculation part. The single high efficiency cyclone separator can only achieve 50% collection efficiency, and far away from the client’s requests unless they will invest much more money. The efficiency of a parallel system achieves 70% collection efficiency, although it is still not achieve 95% efficiency, it is much better than single high efficiency cyclone separation system. The system need approximate 2200 bag filters with size of 7 inches in diameter and 32 inches in length. More design specifications are shown in following papers.

Introduction:

The client’s company is producing zinc oxide particles by using slag from a blast furnace, the maximum temperature in slag will achieve 1300 degree to generate zinc vapour. Then, the zinc vapour will be cooled to produce zinc oxide particles as the final product. However, the clients want to boost production by design a cyclone separation system with at least 95% collection efficiency.

The desire operation temperature for cyclone separator system is 1000 degree and 8320 , the specific gravity of the zinc fume is 5.6, and the furnace gases are combined with 70.5% nitrogen, 18.2% water, 10.2% carbon dioxide and 1.1% oxygen. And the mesh size of particles are given from 0.5 um to 200 um.[pic 1]

Background:

The principle of cyclone separation system is using the particle inertia to separate particles from air, gas and liquid flow. The features of system are including: 1. the initial cost of system are cheaper than bag filters systems. 2. The operation cost are cheap as well. 3. The system can effectively separate particles which greater than 5um. 4. The system can work in high temperature conditions. 5. The space required for system is relative small. However, the most awful defect of cyclone separation system has low efficiency for collecting small particles.

Bag filters as the most effective system to remove small particle, and it is very suitable for this case. The advantages of using bag filters can be conclude as low operating cost and effective removing small particles. However, the disadvantages of this system are fourfold: 1. the bags must be cleaned almost every hour. 2. The initial cost of system are very high. 3. Require a large space for the system.4. The flow conditions are limited, cannot be hot, corrosive and wet flow.

Design:

The design of system can be separate as three parts. The first part is design a single high-efficiency cyclone separator, including determine collection efficiency, pressure drop and discuss the suitability of design. The second part is design a series/parallel system. The last part is design how many bag filters required. The assumptions of design are including: ideal gas, steady state, constant flow rate , the normal condition is 25 degree in temperature and 101.3 kpa in pressure, the pressure in cyclone separation system is in atmospheric pressure as well, and the particle’s velocity in bag filter is 0.01 m/s.