Like gravity settlers, cyclones can be used in high temperature, high pressure applications. This piece of process equipment is known as a cyclone.
When a gravity settler is insufficient, centrifugal separation can be employed. The advantages of using gravity settlers for particle separations would be the low cost and their applications in high temperature, high pressure, or corrosive environments.
The addition of baffles causes higher pressure drops than in simple settling chambers, but also allow for particle sizes down to 10um to be collected. Impingement separators use many baffles in this way to collect solid particles. The effectiveness of the settling chambers can be increased by disrupting gas flow with such features as baffles. Large particle sizes (>50um) can be removed from the system this way. Over the length of the chamber larger particle settle out of the gas stream. However, there are other reasons to separate solids from gases, such as to prevent buildup of combustible dusts, as in the instance of the Domino sugar factory explosion, or to recover an expensive catalyst from a fluidized bed reactor.Īs the name implies, gravity settlers are simply a long chamber through which gas-solid systems are sent. However, it is an extremely important topic in industrial chemical plant design for reasons of employee health and EPA guidelines. A sector of this field, known as air pollution control is often glossed over in most chemical engineering undergraduate courses. The most industrially important pieces of equipment are used to separate solid particles from gasses. Other types include hydraulic and pneumatic conveyors.Ĭurrently there are many different ways to separate solids from liquids or gases. Screw conveyors have been used since the time of Archimedes who made them famous with his Archimedes screw. There are also screw conveyors, which are used to convey free-flowing solids over short distances. The most familiar of these ways is a belt conveyer, like the ones used at the Domino sugar plant. Solids may be conveyed in a number of ways. From a silo or bunker solids will move out of an orifice, or hopper, to a feeder. Bins with height to diameter ratio less than this are called bunkers. Large bins with with roughly a height to diameter ratio of 1.5 are called silos. A bin is a vertical vessel used for storing solids. There are many pieces of process equipment aimed at handling solids. While rheology is a well studied field for fluids, powder rheology is not a well characterized field. Flow of solids is also difficult to predict. They can cause respiratory illnesses and, in cases of combustible dust such as the Domino sugar plant, cause explosions in confined spaces. Solids are often more difficult to handle than liquids because the process equipment consumes more energy to operate, are more prone to mechanical failure, and can create dust. Solids-involved equipment are important pieces of many processes.