Roller Mill Grinders - Advantages, limitations and how roller mill grinders are changing for the better by GFMT


In this current economic climate, companies are constantly searching for new processes, technologies and equipment to add value to their organisations and reduce costs. In this article by Scott Will, we will cover how roller mill grinders add value to many applications and reduce long-term processing costs. We also discuss recent technology improvements that further improve roller mill capabilities and efficiencies.

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									                 Digital Re-print - March | April 2010
                         Feature title: Roller Mill Grinders
- Advantages, limitations and how roller mill grinders are changing for the better

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                                                                                       Roller mills              Feature               Feature                Roller mills

                                                                                                                                                                                                                                Side bar: Obtaining a narrow particle size distribution
                                                                                                                                                                                                                                                   should add value to your process.
                                                                                                                                       less energy than an attrition mill of the same       However, materi-

      r Mill Grinders
                                                                                                                                       capacity. If you are wondering what savings      als like wood, rubber,

                                                                                                                                       that means in dollars, an additional 10hp        and soft plastics are
                                                                                                                                       costs our factory US$6500/year (based on         not good candidates
                                                                                                                                       24/7/365 at US$0.10/kWhr).                       for roller grinding.

                                                         changing for the better
                        and how roller mill grinders are
                                                                                                                                                                                            Limited feedstock
                                                                                                                                       Product Limitations
Advantages, limitations
                                                                                                                                                                                        size: The maximum
                                                                                                                                           Due the low-impact grinding nature of        size of the feedstock
                                                                                         ses, technologies and
                                                           y searching for new proces
                              ate, companies are constantl                            Scott Will, we will cover
                                                                                                                                       roller mills, it is typically best suited for    (unground material fed
In this current economic clim                           uce costs. In this article by
                            their organisations and red                                   sing costs. We also
                                                                                                                                       materials that break apart under pressure,       to the roller grinder)
equipment to add value to                                 and reduce long-term proces
                             value to many applications                                   and efficiencies.
                                                                                                                                       otherwise know at ‘friable’ materials. This      varies based on the
how roller mill grinders add                               rove roller mill capabilities
                               rovements that further imp                                                                              can range from polyester plastics used in        material properties; roll
 discuss recent technology imp                                                                                                         solid surface countertops to coffee. Roller      speeds and corruga-
                                                                                                                                       mills are also superior grinding systems for     tions, and other factors.                         “Roller-Style Grinders are typically
                                                                                                         by Scott Will                 various abrasive materials such as limestone         Generally, the feedstock must
                                                                                                                                                                                                                                          more expensive than hammer
                                                                                                                                       and elemental silicon.                           be 25.4mm (1 inch) or smaller.
                                                                                                                                           In any case, we have listed the two most                                                       mills but give better particle size
                                                                                     more of these days.
                   Change for the better! Now that is something we all need a little                                                   common product requirements for success-         Changing for the better                           distributions. If the only sizing
                                                                                                                                       ful roller mill operation.                           Roller mill technology continues              concern is to reduce the material
                                                                                                                                           Only suitable for friable materials: The     to evolve.                                        below a certain size with no
                                                                                                                                       product to be ground must fracture under             One of the greatest advances in               limits to the permissible amount
                                                                                                                                       stress rather than flatten or deform. This       technology involves roll materials.
                                                                                                                                                                                                                                          of dust or size consistency, then
                                                                                                                                       does not mean that the product must be           Today, various material advances
                                                                                                                                       brittle; a roller-style grinder can be used      allow roller mills to be utilized in              a roller mill grinder may not be
                                                                                                                                       for products as hard as elemental silicon or     increasingly abrasive applications.               appropriate for your needs”

      or those of you unfamil-                                                        rial in size to a narrow particle size           limestone.                                           No longer are we limited to steel
      iar with roller mills, the                                       Figure 1       distribution and with few unwanted
      basic principal of operation                                                    fines (see Figure 2).
is simple: Two parallel rolls
rotate towards one another                                                            Roller mill advantages
at high speeds, say 400 –                                                                 Now that we understand the basic
3000rpm. Material is gravity                                                          principles of operation, there are four
fed between the parallel rolls                                                        main advantages that direct people to                     We pride ourselves in implementing             > Turnkey installations
and as it enters the ‘nip’ of                                                         use a roller mill rather than a hammer-                   the latest technological
the rollers, it experiences both                                                      mill, ball mill, cone mills or some other                 improvements                                   > Cleaning equipment
crushing and shearing forces                                                          attrition grinding method.                                                                               > Milling equipment
                                                                                                                                                We strive for the highest quality
that grind the particle into                                                              Narrow particle size distributions.
                                                                                                                                                & con dence in our products &                  > Transfer equipment
smaller pieces. Roll surfaces can                                                     Fracturing of the material is accom-                      services
be either corrugated or smooth                                                        plished only by the induced stress/shear                                                                 > Extraction Control
on the surface, depending                                                             action of the roll surface on the prod-                   Our goal is complete customer                  > Packaging
on the need, and typically a                                                          uct. There is no attrition, high speed                    satisfaction in the production of
                                                                                                                                                our our milling machines                       > Complementary machines
speed differential between the                                                        impact, or internal screening.
rolls, ranging from 1:1 to 3:1,                                                           For many materials, this results in
is necessary (see figure 1).                                                          significant narrowing of the particle size
    Most roller mills are compromised                                                     Minimal dust (fines) creation:
of multiple grinding sections vertically                                              Without high speed impact, dust gen-
stacked on top of one another and                                                     eration is reduced.
material falls by gravity from one pair                                                   Low temperature rise: With no
of rollers to the next.                                                               high speed impact and since there            Konya Organize Sanayi Bölgesi 7 Sokak
    The number of sections is deter-                                                  is no recirculation of product inside
                                                                                                                                   No: 3 Konya/TÜRKİYE
mined by the material properties and                                                  the grinder, heat generation is mini-
the amount of reduction required to                                                   mal. Also, grinding rolls can be cooled      T: +90 332 239 1016 (pbx)
achieve the desired grind size.                                                       internally for especially heat sensitive     F: +90 332 239 1348
    The roll corrugations, speed                                                      products.                                    E:
ratio between the rolls, and the gap                                                      Low energy consumption: There is
between the grinding rolls are all                                                    no high speed particle impact and zero
precisely engineered for each product.
The objective is to reduce the mate-
                                                                                      friction between particles; thus, a roller
                                                                                      mill grinder typically uses 30-50 percent
                                                                                                                                                                      Realizing your future by your voice
                                                                                                                                   Unormak.indd 1                                                                                                                             24/11/2009 15:56
18 | march - april 2010                                                                   Grain  &feed millinG technoloGy              Grain  &feed millinG technoloGy                        PREVIOUS PAGE        NEXT PAGE                                      march - april 2010 | 19
                                                                                                           Roller mills             Feature

                                              s crudest
“Some may still   think of roller mills in it
                                    y pulverizing
form, w  ith “crushers” haphazardl
                                               But today’s
friable materials  down to a reduced size.
                                      to produce
precisio n roller mills are designed
 “controlled explos ions” that achieve a com
                                  d particle size”
 contro lled and highly-engineere

                                                       Modern manufacturing methods and              grinding, especially with polyester, acrylics
or even hardened steel rollers. Modern roller       CNC machines provide precision equipment         and other hard plastics. This is no longer
mills use exotic roll materials, various coatings   tolerances that were simply not possible         necessary with the advent of water-cooling
and in extreme cases ceramics that offer hard-      years ago.                                       on roller mill grinders.
ness values above the Rockwell C hardness              Today, roll gaps can be held to 10                Additionally, various foods such as coffee
                                                                                      microns        and pepper boil off volatile oils and aromas
                                                                                      (+/-0.0005     above 35 degrees C (95 degrees F). Water-
                                                                       Figure 2       inch) while    cooling eliminates product temperature rise
                                                                                      rotating at    as materials pass through the grinder, thus
                                                                                      3000rpm.       eliminating the need for expensive liquid
                                                                                      This allows    nitrogen and simultaneously improving prod-
                                                                                      roller mills   uct quality.
                                                                                      to    grind
                                                                                      materi-        Today’s precision rollers
                                                                                      als down           Roller mill technology has evolved and
                                                                                      to       50    become much more refined over the past
                                                                                      microns,       50 years.
                                                                                      continu-           Some may still think of roller mills in
                                                                                      ously and      its crudest form, with ‘crushers’ haphaz-
                                                                                      accurately,    ardly pulverizing friable materials down to
                                                                                      day after      a reduced size. But today’s precision roller
                                                                                      day     and    mills are designed to produce ‘controlled
                                                                                      year after     explosions’ that achieve a completely con-
                                                                                      year.          trolled and highly-engineered particle size.
                                                                                          Water-     Friable materials can now be reduced in size
                                                                                      cooling also   with less dust, greater uniformity and higher
scale. These coatings and ceramics can virtually    plays a part in expanding applications.          efficiencies.
eliminate wear numerous applications.                  In the past, cryogenic grinding methods           Not only is this change for the better,
                                                    were required on a number if applications        but this is change for the better than can be
                                                              to eliminate heat elevation during     proven and quantified.

                                                                                                       More    InforMatIon:

                                                                                                       Modern Process Equipment, Inc.
                                                                                                       3125 S Kolin Avenue
                                                                                                       Chicago, IL 60623, USA
                                                                                                         Tel: +1 773 254 3929
                                                                                                         Fax: +1 773 254 3935

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                        •	 Regulating	
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                                                                           In this issue:
                                                             •        Designing bagging
                        •	 Roller	Mill	                                     lines to meet

                                                                                                    •	   Contact	the	GFMT	Team
                             Advantages, limitations
                                                                             - Specifying and
                             and how roller mill
                                                                     designing bagging lines
                             grinders are changing
                                                                     for the food processing
                             for the better

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