The process of pelletizing limestone into a premium product is growing in popularity for the many benefits that pelletized lime can offer over traditional lime products. This presentation looks at the process of pelletizing lime into a premium limestone soil amendment product.

1. Pelletizing
Experts in process design and material
processing for over 60 years.
Limestone

2. Limestone is a sedimentary rock used
frequently throughout the agricultural industry
as a soil amendment for raising soil pH and
unlocking nutrients for plant uptake.

3. While traditional products such as
agricultural and powdered lime have
served their purpose, both of these products
present many problems.

4. While traditionally products such as
agricultural and powdered lime have
served their purpose, both of these products
present many problems.
Pelletized lime was created to
resolve these issues.

5. Ag Lime (Agricultural Lime)
Though effective, ag lime is inconsistently
sized, and coarse in nature. This results in
delayed product breakdown and nutrient
delivery, sometimes taking years for results to
be seen.

6. Ag Lime (Agricultural Lime)
Though effective, ag lime is inconsistently
sized, and coarse in nature. This results in
delayed product breakdown and nutrient
delivery, sometimes taking years for results to
be seen.
Furthermore, because this product is
inconsistently sized, results can be
difficult to predict.

7. Powdered Lime
Powdered lime negates the problems of ag
lime, because it offers increased surface
area and much faster nutrient delivery.

8. Powdered Lime
Powdered lime negates the problems of ag
lime, because it offers increased surface
area and much faster nutrient delivery.
However, because it is in a powder form, it is
difficult to transport, apply, and handle. This
can also result in windblown product
reaching unintended areas.

9. Pelletized Lime
Pelletized lime is a limestone that has been
finely ground, and then processed into a
pellet form, mitigating any dust-related
issues. This product offers many benefits:
• Dust-free product handling
• Improved product formulations
• Simplified transportation
• More accurate and easier application
• Mitigation of product lost as dust
• Opportunity for including desirable additives

10. Limestone Pelletizing
Basics

11. Gypsum fines are fed into the pin mixer, with
the addition of a binder.
Pelletizing limestone results in a durable pellet
that can withstand handling, but still break
down quickly under standard field conditions.

12. Pelletizing is carried out via tumble growth
agglomeration, utilizing three main pieces of
equipment: a pin mixer, disc pelletizer, and
rotary dryer.
Pin Mixers Disc Pelletizers Rotary Dryers

13. Simplified Pelletizing Diagram
1. Raw feed
2. Pin/Paddle Mixer
3. Binder Feed
4. Spray Rate
5. Disc Pelletizer
6. Feed Onto Pelletizer
7. Binder Feed
8. Liquid Spray System
9. Transfer Conveyor
10. Rotary Dryer
11. Vibrating Screen
12. Oversize Mill
13. Recycle
14. Surge hopper

14. Pre-Conditioning

15. A pin mixer serves as a primary feed
conditioner, mixing limestone powder with a
binder. This produces densification and
prepares the material for pellet formation on
the disc pelletizer.
Note: not all operations utilize a pin
mixer/pre-conditioning stage, but
those that do often see many
benefits, such as reduced binder
costs, more uniform binder
distribution resulting in more uniform
pellets, higher throughput, and
more on-size pellets.

16. Pelletization

17. Once limestone is fed
onto the disc pelletizer,
the rotating motion of the
disc gradually rolls the
tacky material to the
desired size, with binder
and feed being
constantly added,
making this a
continuous process.

18. Drying

19. Once pellets have reached the desired size,
they exit the disc pelletizer and are carried
via conveyor to a limestone dryer.

20. A rotary dryer is commonly chosen when
drying limestone, because of its high
throughput capacity, heavy-duty
construction, and ability to accept variance
in feedstock.

21. In a rotary dryer, limestone pellets tumble
through the drum, with flights picking up the
material and showering it through a stream
of hot air or combustion gas.

22. In a rotary dryer, limestone pellets tumble
through the drum, with flights picking up the
material and showering it through a stream
of hot air or combustion gas.
This efficiently dries and hardens the pellets
into their final form. Fluid bed dryers are also
an option here.

23. It is sometimes desirable to cool limestone
pellets prior to bagging or storage. In this
case, a rotary cooler is often used, offering
the same advantages as a rotary dryer.
Again, fluid bed coolers are also an option.

24. While there are many things to consider in a
limestone pelletizing operation, two of the
most important factors are:
- Binder
- Equipment

25. Binder

26. A binder aids in pellet formation and also
helps to achieve the desired end product
crush strength.

27. A binder aids in pellet formation and also
helps to achieve the desired end product
crush strength.
Most commonly, lignosulfonate, or “lignin” is
used in limestone pelletizing. If only water
were to be used, the result would be a
weak pellet.

28. Different types of lignins are available,
depending on the needs of the process.
Some lignins may add extra nutrients, while
others will be more cost-effective.
Consulting an agglomeration expert can
help in deciding which binder will best suit
your needs.

29. Equipment

30. Choosing quality equipment will go a long
way in providing for an efficient, long-lasting
operation that produces an optimum
product.

31. Choosing quality equipment will go a long
way in providing for an efficient, long-lasting
operation that produces an optimum
product.
Instead of a one-size-fits-all approach,
equipment should be designed around
limestone’s unique characteristics for best
results.

32. Limestone processing can be rigorous
and demanding, so equipment should
be heavy-duty and designed with such
rigors in mind.

33. Limestone processing can be rigorous
and demanding, so equipment should
be heavy-duty and designed with such
rigors in mind.
Choosing quality equipment will not only
aid in process efficiency, but will also
typically require less maintenance and
down time, and will often result in
prolonged equipment life.

34. has been working with limestone for over 60
years, providing testing, process design and
development, and manufacturing of custom
limestone processing equipment.
FEECO

35. Want to learn more?
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Limestone Processing
E-book.
Limestone Processing E-book
Processing Techniques
Challenges
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