Cyclone Separator

Objective:

In this project to perform an analysis on the cyclone separator model for different number of injected particles

Introduction:

Cyclone Separator:

Cyclone separators or simply cyclones are separation devices (dry scrubbers) that use the principle of inertia to remove particulate matter from flue gases.^[2] Cyclone separators is one of many air pollution control devices known as pre-cleaners since they generally remove larger pieces of particulate matter. This prevents finer filtration methods from having to deal with large, more abrasive particles later on. In addition, several cyclone separators can operate in parallel, and this system is known as a multi-cyclone.

It is important to note that cyclones can vary drastically in their size. The size of the cyclone depends largely on how much flue gas must be filtered, thus larger operations tend to need larger cyclones. For example, several different models of one cyclone type can exist, and the sizes can range from a relatively small 1.2-1.5 meters tall (about 4-5 feet) to around 9 meters

Working:

Cyclone separators work much like a centrifuge, but with a continuous feed of dirty air. In a cyclone separator, dirty flue gas is fed into a chamber. The inside of the chamber creates a spiral vortex, similar to a tornado. This spiral formation and the separation is shown in Figure 2. The lighter components of this gas have less inertia, so it is easier for them to be influenced by the vortex and travel up it. Contrarily, larger components of particulate matter have more inertia and are not as easily influenced by the vortex.

Since these larger particles have difficulty following the high-speed spiral motion of the gas and the vortex, the particles hit the inside walls of the container and drop down into a collection hopper. These chambers are shaped like an upside-down cone to promote the collection of these particles at the bottom of the container. The cleaned flue gas escapes out the top of the chamber

Effectiveness:

Cyclone separators are generally able to remove somewhere between 50-99% of all particulate matter in flue gas.^[2] How well the cyclone separators are actually able to remove this matter depends largely on particle size. If there is a large amount of lighter particulate matter, less of these par0ticles are able to be separated out. Because of this, cyclone separators work best on flue gases that contain large amounts of big particulate matter.

There are several advantages and disadvantages in using cyclone separators. First, cyclone separators are beneficial because they are not expensive to install or maintain, and they have no moving parts. This keeps maintenance and operating costs low. Second, the removed particulate matter is collected when dry, which makes it easier to dispose of. Finally, these units take up very little space. Although effective, there are also disadvantages in using cyclone separators. Mainly because the standard models are not able to collect particulate matter that is smaller than 10 micrometers effectively and the machines are unable to handle sticky or tacky materials well.

The four empirical models used for cyclone separator efficiency

Lapple model:

Lapple model is amongst the earliest of a model proposed and is still considered benchmark for the design of cyclone separators in many industries. This is comparatively a simple model based on force balance with considering the flow resistance. It assumes that the particles are evenly distributed across the inlet while entering the cyclone. It was based on the terminal velocity of particles in cyclone. From theoretical analysis is derived which gives the size of the smallest particle that will be collected by the cyclone.

Iozia and Leith model:

Iozia and Leith model. It considers simple force balance on a particle in a cyclone. It assumes that centrifugal force and drag force act on particles and balance each other. The collection efficiency η.

Leith and Licht:

Leith and Licht take into account the temperature on top of other factors. It assumes that there is no slip in the tangential direction between the particles and fluid, i.e. both particles and fluid have the same tangential velocity. Also, it considers relation VRn= constant for relation
between tangential velocity V and radius R.