In the solid-waste processing industries, a trommel is a type of screening apparatus. It makes use of the principle of centrifugal force to remove coarse materials from smaller ones and separate them from each other. Not just Trommels in waste, Trommels are used in a wide variety of applications, including both industrial and agricultural operations.
The History of Trommels
The history of Trommels is a long and illustrious one. The first machine of this type was invented by the Romans, who used them in gold mining facilities to separate out the finer material from waste. In 1823, the Scottish inventor Andrew Meikle improved on the design by adding a spiral grill.
Simple and slow
A trommel is a screening device that consists of an inclined cylinder covered with screening cloth. This cylinder rotates slowly and continuously, while it is being fed with material to be screened. The inclined walls of this rotating cylindrical screen separate the material being fed into different fractions.
How Trommels works
The cylinder is generally inclined at an angle of 3 to 4 degrees with the horizontal. The angle of inclination depends on the size of the material being processed and its moisture content. The cylinder should be inclined as steeply as possible without causing plugging or jamming. If the inclination is too great, material may fall out of suspension before it has been sufficiently ground; if too little, insufficient grinding will take place and a large percentage of fines will remain.
The machine can be used in stationary or revolving mode; this choice depends on whether it is desirable for materials to be fed continuously through a single set of cylinders or whether it is necessary to have individual sets working simultaneously (e.g., one set receiving material while another is discharging).
Widely used in the solid-waste processing industries.
Trommels are widely used in the solid-waste processing industries. Trommels can be used to separate minerals from rocks and sand, as well as other materials from waste streams. What’s more, trommels are also widely used for reducing waste volume and recovering valuable resources (such as metals).
Here’s the science bit
Trommels are used to separate materials by size, for the purpose of material recovery and waste reduction. Trommel screens consist of a cylindrical drum with a rotating spiral flight or “slide”. The solid waste fed into the trommel is centrifuged on this flight under the action of gravity; the heavier pieces fall through lower spaces between flights while lighter materials remain at the top.
The screening efficiency can be calculated using mass weight in following way: E=c(f-u)(1-u)(c-f)/f(c-u)^2(1-f)
Trommels are primarily used in the mineral and solid-waste processing industries.
Trommels are primarily used in the mineral and solid-waste processing industries. Trommel screens are used for the separation of materials by size, shape and density.
The primary goal of using a trommel screen is to separate materials by size, shape and density. These machines can be configured to handle many different types of materials including:
- Municipal solid waste (MSW)
- Municipal compostable refuse
- Biowastes (food waste)
- Demolition and Construction Waste Grading
- Bulky items
Read more about Trommels in the latest Edition of Skip & Waste Magazine