|1. What is a lump
|2. Lump breaker
|3. Lump breakers
|4. Industrial lump breakers|
Lump breakers are used in bulk solids handling to reduce the size of undesirable agglomerate that may form typically when storing powders. This page is focusing on the best design of lump breakers found in the industry.
Bulk solids are sometimes subject to lumping, caking, leading to the agglomeration of the individual solids particles into a bigger chunk that can reach several cm or dozens of cm in some cases. When this happens, lumps are causing important operational problems as they can block pipe, equipment, and reduce the capacity and or / quality of a production process.
A typical example is sugar, if sugar is submitted to variation of humidity, water may condensate, then evaporate, creating solid links in between sugar granule, thus creating a lump.
Lump breaker aim at crushing the agglomerate so that the individual particles are recovered, as well as the properties of the bulk solids, especially its flowability.
It is important to understand that lump breakers (usually) are not aiming at getting a finer material than the solids caked, but just separate the individual particles and recover the original particle size distribution observed in the material before caking.
Lump breakers are made of a rotor and a stator. The rotating part is typically designed with one shaft on which are welded pins. The stator part is also made of pins, sometimes called "comb", the rotating pins are passing in between 2 static ones.
The find powder is flowing easily through the machine, in between the pins, and with the rotation of the pins. However lumps are stuck in between pins and crushed. The fineness of the product obtained is then a function of the gap in between the pins.
Some more specific designs are using 2 rotating shafts, counter rotating, with the "combs" on the side of the lump breaker. Some other designs are using principles closer to hammer mills with some kind of beaters and a perforated plate allowing to size the material leaving the breaker.
The simpler lump breakers are using a system of static pins that are intermeshing with the teeth or blades of the agitator in order to break the lumps. The gap in between the "comb" of static pins (also called a breaker grid or breaker bars) and those of the agitator is determining up to which size the lumps will be crushed.
Figure 1 : Lump breaker top view diagram
Other designs of lump breakers, allowing to reach a more define and often finer particle size distribution are equipped with a mesh or perforated plate at the outlet of the crusher, and have also agitators that are more looking like beaters found on other kind of grinders.
Figure 2 : Lump breaker with sizing grid at outlet
It is possible to have 2 shafts, instead of one, especially for the crushers without sizing grids but a comb. The shafts are indeed counter-rotating and thus each shaft can contribute to the grinding in crushing material on the combs installed on each sides of the crusher.
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Due to the nature of the unit operation they perform, lump breakers can be subject to overload in case, for example, too hard lumps are processed, or sticky material accumulates and blocks the crusher. As a consequence, it is important to consider a current overload protection. For big lump breaker, mechanical protection may be required, such as an air clutch.
It is preferable to control the feed to the lump breaker (at least roughly) by a dosing equipment such as a vibrating tube, a screw conveyor, or an airlock rotary valve. In some cases, the breaker may be operated in load, below a hopper, but in any case the outlet must be free of product otherwise the rotation of the shaft is not possible.
Small lump breakers can be mounted on chassis. It is then possible, for small capacity applications, to 1st pass the material through the lump breaker and collect it in bags before tipping it to the main process.
There are typically 2 main risks linked to lump breakers :
Operating a lump breaker must therefore be done ONLY when occupational and dust explosion risk analysis have been performed and the conclusions implemented.
Lump breakers can be used in many bulk solids industries whenever there is a risk to have an unwanted agglomeration of the processed material. The following examples give an idea of the variety of application in which are used those crushers :
In general dry and friable products are the ones that perform best in lump breakers. It is however possible to proceed more humid, sticky materials, but in this case, a transparent exchange with the supplier is required as the design may have to be adapted (for instance sticky materials may block a sizing screen).Source