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Hammer Mill Improves Craft Brewery’s Efficiency [Case Study]

Posted by Cassie Brown

Jul 31, 2013 10:07:00 AM

 

Tin Man Brewing Companytin man brewing company logo

1430 West Franklin Street

Evansville, IN 47710

www.tinmanbrewing.com

 

 

Processing:  Wheat, rye, malted barley, unmalted barley

End product:  Beer

 

Forward Thinking Brewers

The Tin Man Brewing Company of Evansville, Indiana is an early adopter in the craft brewery world.  They are one of the first craft breweries to utilize a mash filter in their brewing process. It’s a relatively simple, yet highly effective concept.  Tin Man’s Head Brewer Sean O’Rear describes the mash filter as a plate and frame filter that is loaded with brewer’s mash, a mixture of water and grains. The filter is then compressed to extract the liquid “wort”. The collected wort is then boiled with hops to produce beer.  Bonus:  the remaining solid portion, called spent grain, is given to a local farmer for use as cow feed!

The key benefit of mash filtering is that it allows for capturing up to 98% of the available sugar in the brewing grains, compared to 75% captured by more traditional methods. 

 tin man brewing company mash filter

Size Reduction Challenge

In order to achieve the goal of capturing 98% of the sugar, the grains had to be processed to a very small particle size prior to filtering. Initially, Tin Man was utilizing a two-roller stripper mill to reduce the grains. Unfortunately, the results were inconsistent at best, producing flour, uncracked kernels, and everything in between.  This  caused backups in filtering to occur, leading to significant loss of sugar portions from the grains, and prevention of the complete enzymatic activity that converts the grain starches to sugars. Ultimately, due to the inconsistency of the roller mill finished particle size, only 87% of the possible 98% grain efficiency was achieved. As a result, Tin Man was required to add approximately 10% more grain to their beer recipes to achieve the desired quality.

 tin man brewing company. grains

Roller Mill Out, Hammer Mill In

Unlike roller mills that reduce materials by compression, a hammer mill reduces by impact. A hammer mill is essentially an enclosed steel container, housing a rotor which spins at very high speed.  Flat steel hammers are attached to the rotor. As the rotor spins, the hammers flail out, and repeatedly impact material in the grinding chamber until it is able to pass through the steel mesh screen covering the mill’s discharge opening. Finished particle size is determined by a combination of rotor speed, hammer size, hammer configuration, and screen size.

In effort to solve their issue with finished particle size consistency, Tin Man purchased a Schutte- Buffalo Hammer Mill Model 18-7-301B Circ-u-Flow hammer mill. Custom configured to suit their specific materials, and production goals, the mill features a 10 hp motor, abrasion resistant steel hammers, and a 1/8” screen. 

The model 18-7-301B is a full circle screen hammer mill with 300 degree screen coverage of the rotor,  compared to  the 150 degree screen coverage seen in more traditional industrial hammer mill models. This means the properly sized material has a larger area to evacuate the grinding chamber. As a result, the full circle screen hammer mill has the highest throughput to horsepower ratio of all hammer mill styles.

model 187301b full circle screen hammer mill

O’Rear reports that following the hammer mill installation, the process improvements were instantly remarkable. The grains were processed to a very fine, consistent finished particle size with no additional milling time required, and thus no impact on labor. The resulting mash was much less viscous, and the loading of the mash filter was fast and easy, with no backups.

 Immediate Impact

The first beer produced from the hammer milled grain using the old grain weights came out with significantly higher sugar loads than the beers produced with the same weight of roller milled grain. According to O’Rear, the efficiency went from 87% to 94% immediately! As a result, they are able to reduce production costs by dropping grain amounts by 8.5%.

 tin man brewing company

“We will continue to optimize the system to achieve 98% mash efficiency, but no other improvement will have as large or as immediate an impact as our Schutte-Buffalo hammer mill.”

Sean O’Rear, Head Brewer
Tin Man Brewing Company


 

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Topics: finished particle size, hammer mill, full circle screen hammer mills, size reduction, brewing grains, grains, grain efficiency

Hammer Mill Application Focus: Grinding Grains for Animal Feed

Posted by Cassie Brown

Mar 29, 2013 9:37:00 AM

Producers of animal feed all know a simple truth: when processing cereal grains for animal feed, finished particle size matters.  A lot.corn before and after hammer mill processing

Blendability, and digestibility – even the economics of feed production – are all affected by the finished particle size of the grains.  But this is not a one-size-fits-all situation.¹  The ideal finished particle size varies by the grain being processed, and depending on the species, the life stage of the animal.²  With all of this in mind, selecting the proper method of size reduction is a critical decision.

 

Roller Mill or Hammer Mill

Unlike the angular shaped particles produced in a roller mill, the pulverizing action of the hammer mill results in particles that are more rounded. These smoother surfaces make it easier for the grains to be blended with other components of the feed.²

 

So Many Hammer Mills

A hammer mill is essentially a steel box surrounding a rotor. Swinging hammers attached to the rotor, flail out when the rotor spins. A screen covers the discharge opening to regulate the finished particle size.

As material enters the hammer mill, it is pulverized by a combination of hammer blows, particle on particle contact, and impact with the walls of the hammer mill. The material remains in the grinding chamber until it is able to pass through the screen covering the discharge area.

But those are just the basics. There are myriad styles of hammer mills: industrial mills, full circle screen hammer mills, horizontal grinders, tub grinders, and more.  As for size, hammer mills can range in size from 6” to more than 60” rotor widths.  Choosing the right hammer mill for your purposes depends greatly upon the material you are processing, and your production goals.

 

The Full Circle Solution

The design of the full circle screen hammer mill makes it the ideal method of size reduction when processing cereal grains for animal feed.  Let’s take a closer look:

Throughput

With swine operations reporting that up to 75% of their budget is allocated for feed production,³  the need for energy efficiency cannot be overstated.

As its name suggests, the full circle screen hammer mill differs from the traditional industrial hammer mill because it has nearly double the screen coverage of the rotor:

 screen coverage for full circle screen hammer mill                       screen coverage for industrial hammer mills                                     

    Full Circle Screen Hammer Mill                                 Industrial Hammer Mill

                                                                  

The greater screen coverage of the full circle mill means that there is more area for the material to evacuate the grinding chamber. As a result, a higher throughput rate can be achieved at a lower horsepower in comparison to industrial hammer mill models.  

Particle Size Flexibility

Precision and consistency of the finished particle size has a strong effect on the digestibility of the feed.  A finished particle size that is either too large or too small will have adverse effects on animal performance.²

The primary factor determining finished particle size is the measurement of the perforations in the screen covering the discharge area. The size of these perforations is equal to the maximum finished particle size of the material processed.

The ideal particle size range of 650 to 750 microns³ can easily and consistently be achieved through proper screen selection. In addition, screens can easily be changed to accommodate the processing goals of a variety of grains using the same hammer mill.

The secondary factor in determining finished particle size if the speed of the hammer mill. When the rotor spins, the hammers flail out and impact the material with great severity causing it to break down.  As a result, the higher the rotor speed, the greater the number of hammer mill blows, and thus a finer end product.  An optional component for the full circle screen hammer mill is a variable frequency drive electrical control. This control panel allows the operator to raise or lower the rotor speed as needed for different applications.

 

Summary

The pulverizing action of the hammer mill produces a finished particle that is easily blendable. The nearly 360 degree screen coverage of the full circle screen hammer mill allows for the greatest throughput to horsepower ratio of all hammer mill designs. A consistent and precise finished particle size can be achieved by screen selection. Finally, the ability to change screen size, and the option of a variable speed frequency drive control, enable processing a variety of grains using the same hammer mill.

 

References

¹ Steinhart, Terry L., Iowa State University (2012). Swine Feed Efficiency: Influence of Particle Size. Retrieved from  http://www.swinefeedefficiency.com

²Pork Production in Mississippi is Particle Size Important for Swine Diets?(2013). http://www.msucares.com/livestock/swine/particle.html

³Sayler, Julie. (2012). Small Particle Size Makes a Big Difference.http://swineperformance.vitaplus.com/2012/04/small-particle-size-makes-a-big-difference/  

intro to size reduction ebook

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Topics: finished particle size, full circle screen hammer mills, variable frequency drive, size reduction equipment, corn, animal feed, cereal grains

The Industrial Hammer Mill: A Versatile Workhorse

Posted by Cassie Brown

Mar 7, 2012 8:56:00 AM

One Design,  Many Applications

The basic design of the industrial hammer mill is really quite simple:

  • A steel chamber containing a shaft to which rectangular steel hammers are affixed.
  • Replaceable plates lining the mill's interior to reduce wear caused from grinding abrasive materials.
  • Steel screens or bar grates cover the mill's discharge opening.
Material is fed in through the top of the mill. Once in the grinding chamber, it is reduced by a combination of repeated hammer blows, particle on particle impact, and contact with the walls of the mill. The material will remain in the grinding chamber until it is reduced to a size that is able to pass through the screen covering the mill's discharge opening.
The simplicity of this design makes it a very versatile hammer mill, one that can be adapted to suit a wide variety of materials, such as:

 industrial hammer mill applicationsr

 Similar, Yet Different

The same hammer mill for fishmeal and coal?  Well, yes and no. The basic framework of the mill is the same. However, the configuration of the variable components is how they differ. That determination is based on the following criteria:

  • Material being processed -  Material characteristics such as: friability, flowability, moisture content, and infeed size
  • Desired finished particle size  - Gravel, granules, powder?
  • Desired production rate - 10 lbs/hr, 10 tph, etc.

With this information, the following can then be determined:

  • Hammer mill size - Rotor diameters between 6" and 44", and internal mill widths of 6" to 72".
  • Hammer size and style - Number of hammers, size, style and metallurgy.
  • Screens or bar grates - Style and thickness of screen or bar grates, and size of openings.
  • Choice of proper RPM
It's Optional
Finally, once the the mill is configured, the last determination is whether or not any optional peripheral equipment is needed. For this, the following questions must be answered:
  • How will the material be fed into the mill? By hand, auger, or belt conveyor?
  • How will the material be taken from the mill? Heavy materials such as stone or metal may evacuate via gravity, while light or low density materials will require pneumatic suction.
  • Is dust a concern?

Answers to these questions will help to determine the best types of optional equipment such as belt conveyors, augers, rotary feeders, and dust collection, as well as the most efficient design of the infeed and discharge chutes.  

And that's about it...If you would like more information, please click below to download our free eBook!

industrial hammer mill ebook

 

 

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Topics: finished particle size, hammer mill, hammer configuration, bar grates, moisture content, hammers, internal liner plates, size reduction equipment

How Do You Grind Pallets for Recycling?

Posted by Cassie Brown

Feb 14, 2012 10:30:00 AM

Pallets, Pallets Everywhere...

We all have them. Whether you buy, sell, ship or wherehouse, just about any business that handles merchandise in large quantities has pallets. They are the ideal tool for storing and moving myriad materials. But what happens when the pallets become broken, or are just no longer needed? All too often they become a costly waste handling problem. However, if we explore the possibility of recycling, this waste handling problem becomes a saleable product.

The following illustration shows some of the possiblities:

pallet recycling end products

Questions to Ask

Whenever comparing different methods of size reduction, certain general criteria must be considered:
  • Required throughput
  • Required finished particle size
  • Size and uniformity of in-feed material
  • Method of feeding and collecting


To achieve the majority of pallet grinding goals, a two-phase process is necessary to make the most valuable output product.

Phase One: Breaking Them Down

Given their dimensions and overall bulk, the ideal method for reducing both whole pallets and pallet scrap is the slow speed ram-fed grinder.

  • The open "deck" design of the ram fed grinder allows for easy infeed of whole or partial pallets whether by hand, or stacked on a fork truck.
  • The hydraulic ram forces the pallets into the grinding rotor which features four-way reversible tool-steel cutting teeth which are hard enough to cut through nails or other ferrous metals.
  • The pallet material is continuously ground until it is able to pass the screen covering the grinder's discharge area.


Screen size can vary, and screens may be changed to correspond with production goals. However, it is not recommended that a screen smaller than 1" be used in this application.  The smaller the screen, the longer the mill will need to work to produce the required size. Therefore, when processing a bulky product such as pallets or pallet scrap, use of a screen smaller than 1" will dramatically reduce the throughput of the ram fed grinder.

Phase Two: The Finish Grind

So, let's consider how we get to the finish line. For this phase, a finish grinding hammer mill is the best solution. Each of the items shown on the list of suggested end products require a specific finished particle size. The role of a finish grinding hammer mill is to produce the required finished size, anywhere from mulch to sawdust.

  • The pre-ground pallets are fed into the grinding chamber of the hammer mill where a combination of hammer blows, particle on particle contact, and impact with the internal breaker plate work in unison to further reduce the material.
  • The material remains in the grinding chamber until it is able to pass through the screen covering the mill discharge.
  • Screens are available in a variety of sizes, and can be interchanged to correspond with the operator's production goals.
  • If the finish grinding hammer mill is outfitted with an integral fan, the process is taken to the next level. The pneumatic suction pulls the material through the hammer mill, then conveys the finished material to storage.


Exponential Throughput!

Here's where it gets cool. Add the finish grinding hammer mill to the ram fed grinder and not only do you go from whole pallets to the exact desired finished particle size, but the throughput rate is increased as much as 400% over that of the ram fed grinder alone. Here's why:

  • Since the finish grinding hammer mill is producing the finished particle size, the ram fed grinder doesn't need to be concerned with it.  As a result, a larger screen (2" to 3") can be used on the ram fed grinder, thus providing less resistance and allowing material to flow through the system at a much higher rate while still liberating all metals from the wood.


Critical Middle Step

While the ram fed grinder and the finish grinding hammer mill are the stars of the show, it can't be overstated that the ideal set-up will also include two rotary magnet hump tunnels between the ram fed grinder and the finish grinding hammer mill. Anyone who handles pallets is aware that they contain metal fasteners, typically nails, which hold them together. All metals must be removed if the end product is to be saleable. And, while they are not hazardous to the initial grind, it is critical that all metals be removed prior to infeed into the finish grinding hammer mill to avoid a potentially explosive environment.

Putting it All Together

When you combine all of the essential elements, the system looks like this:

pallet grinding system

 


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Topics: finished particle size, hammer mill, miscellaneous wood scrap, pallet grinding system, pallet scrap, ram fed grinder, finish grinding hammer mill, pallets, tool-steel cutting teeth, rotary magnet hump tunnels, hump tunnel magnets, biofuels, briquetting, hammers

How to Convert Waste Wood to Biofuel Feedstock

Posted by Cassie Brown

Feb 14, 2012 10:06:00 AM

Got Waste Wood? Convert to Biofuels!
Size reduction solutions to two of the biggest challenges when converting waste wood to biofuels

Throughout our 80+ year history, wood processing has been one of our cornerstone industries. Among our largest customers are forest products companies, lumber yards, makers and recyclers of pallets, furniture manufacturers, truss plants and more. Each with unique products, but all with one common issue: wood waste. The level of waste varies depending on the industry.  An interesting example is forest products companies. When processing logs for lumber, up to 40% of the tree is deemed scrap in terms of its lumber value.

Traditionally, these by-products were considered waste, and at best, used as onsite boiler fuel or sold at a minimal profit to local buyers for such uses as landscape mulch and  animal bedding.  Enter biofuels.  Amid growing environmental concerns and the desire to reduce dependence on fossil fuel, the emphasis on biofuel creation continues to increase.  As a result, wood has emerged as an ideal feed stock. Now the wood waste once seen as a disposal problem is now a valuable product.

describe the image

But here is the hitch - each of the potential biofuel end products have specific material characteristics that are critical to their effieciency. As a result, there are a number of challenges inherent in using a non-uniform scrap material as biofuel feed stock. In two specific cases, hammer mills are instrumental in taking wood waste from the sawmill floor to the biofuel market.

To illustrate this point, let’s use the example of converting wood waste to pellets and briquettes.

Challenge No 1:                Particle size and uniformity

These are critical factors in the preparation of wood to biofuel feedstock. On average, most biofuels require a consistent feedstock particle size of -1/8”.  Typical waste wood as is much larger and non-uniform.

Hammer Mill Solution:

The first and most obvious consideration is size reduction. Can hogged wood scrap, bark, pallets, furniture scrap, etc be ground to a size that is appropriate for biofuel production? The answer is of course, yes. The solution lies in selecting the correct wood grinder for your production goals.

To determine this, the following must be considered:

    • Size and type of in-feed material
    • Desired finished particle size
    • Hourly production goals


Answering these questions will determine not only what wood grinder is most suitable for your application, but also whether your goals require a one or two stage grinding process.

For example, if your waste material is hogged wood scrap and your goal is a -1/8” for pelletizing, a finish grinding industrial hammer mill would be most appropriate.  From there, your production goals determine the size and style of the recommended mill.

Conversely, if your waste material is pallets and your goal -1/8” for pelletizing, you will require a two step process.  A slow speed ram fed grinder is ideal for the initial grinding of the whole pallets. However, this type of mill is not suitable for the fine grinding required for the optimal finished particle size for pelletizing. A secondary grind in a finish grinding industrial hammer mill will be necessary.  Typically, the material will be pneumatically drawn from the ram fed grinder, across magnets to remove all nails, and then though the finish grinder. The upside of this is that this pneumatic component can substantially increase the throughput rate and convey the finished product to storage.

Screen selection for the hammer mill is the second component in determining finished particle size. Referring again to our original three considerations, the desired end particle size will dictate the size of the openings on the perforated screen covering the discharge of the hammer mill.  For example:

Finished particle size of 1/8” will require a screen size of  1/4" or smaller.

The material will remain in the grinding chamber of the hammer mill until it is reduced to a size that will pass through the screen.

Challenge No 2:                Material moisture content

The majority of biofuel applications require a moisture content of ≤10%. However, it is not uncommon for waste wood, such as bark or green wood chips, to have ≥50% moisture content. Not only is the moisture content too high for fuel efficiency, it is also too high for a wood grinder to reduce the wood to a uniform particle size suitable for pelletizing.

Hammer Mill Solution

Under these circumstances, the solution is often a three phase process where hammer mills play a pivotal role. The following is an example of how one of our customers addressed this challenge. Their goal was to convert wood waste with an average 40 to 50% moisture content to suitable feed stock for pelletizing and briquetting.

An industrial wood grinder was used to pre-grind the green wood down to a uniform ½” particle size recommended for optimal drying in the rotary drier. The drier would reduce the moisture content down to the required ≤10%.   Finally, the material is fed into a second industrial wood grinder where it is ground to its finished particle size, ideal for the customer’s pellet and briquette production.

 

Download our eCatalog: Wood Grinders for Biofuels

 

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Topics: finished particle size, green wood chips, moisture content, finish grinding hammer mill, biofuels, briquetting, grinders, bio-fuel applications, pelletizing, waste wood, bark, feedstock, rotary drier, processing wood

Laboratory Scale Hammer Mills - Top Five FAQs

Posted by Cassie Brown

Feb 14, 2012 9:50:00 AM

Whether it is space constraints or small production, a laboratory scale hammer mill is often the right choice for size reduction.  Often used for testing and batch sampling, common installations include: colleges and universities, government testing facilities, and pilot plants.


laboratory scale hammer mill dimensions




Below are answers to the top five questions we receive about our laboratory scale hammer mills:


1. Can my material be processed in a lab scale hammer mill?

The laboratory scale hammer mill has the same full range of capabilities as larger industrial hammer mills.  Applications include: chemicals, glass, food waste, biomass, lathe turnings, metal powders and much more.  Material infeed size and production goals are the ultimate determining factors on whether or not a lab scale hammer mill is suitable for your operation.

2. How durable is the lab scale hammer mill?

The lab scale mills are constructed based on customer specification. The options include carbon steel and 304 or 316 stainless steel. Stainless steel models feature all stainless steel contact surfaces. Replaceable internal liner plates are also an option, The liner plates protect the grinding chamber from wear that results from processing abrasive  materials.

3. Can a lab scale hammer mill produce multiple particle sizes?

Yes. In an earlier post we discussed the factors determining particle size. In short: the screen size, shaft speed and hammer configuration selected give you the ability to steer the particle size in any direction you require. This principle holds true with the lab scale hammer mill as well.

Hammer configuration is determined by the material and processing goals, and is generally not changed once mill construction is complete. However, shaft speed and screen size are quite flexible. Screens can be purchased in multiple sizes and are easily interchanged. The smaller the opendings in the screen, the finer the product that is produced.  An optional Variable Frequency Drive (VFD) control allows the operator the ability to control the rotor speed. Faster rotor speed results in harder and more frequent blows, where as a slower speed allows for a tighter particle size distribution.


lab scale hammer mill variable frequency drive


4. Is the lab scale hammer mill scalable?

Absolutely. The lab scale hammer mill is, quite simply a miniature version of larger production models. Thus, the lab scale hammer mill production results can be extrapolated to that of its larger counterparts.

 

5. What can I expect in terms of set-up and maintenance?

The lab scale hammer mill is fully assembled upon delivery. The operator simply needs to connect the mill's motor or control panel to the main building power source. The top of the hammer mill hinges open to allow easy access for cleaning, screen changes and hammer rotation. As with larger hammer mills, optional dust collection systems can be integrated if needed.

 

Download our eBook: Industrial Hammer Mills- A Versatile Workhorse

  

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Topics: finished particle size, particle size, hammer configuration, variable frequency drive, internal liner plates, laboratory scale, size reduction equipment

Hammer Mills Bring Spice(s) to our Lives

Posted by Cassie Brown

Feb 14, 2012 9:12:00 AM

When asked what I do for a living, it is not uncommon for the conversation to go something like this:

Me:   I work for Schutte-Buffalo Hammermill, we manufacture –

New Friend:  Paper! You’re that paper company, right?

Me:   Well, no. Actually, we manufacture size reduction machinery, such as hammer mills.

New Friend:   (puzzled look)

At this point I usually find it helpful to give a real-life example…

Me:    You know that cinnamon you sprinkled on your toast this morning?

New Friend:     Yes…

Me :    It was made in a hammer mill! The dried, curled cinnamon bark “sticks” are ground in a hammer mill to make the fine powder that you are familiar with.

New Friend:    Cool!

cinnamon before and after hammer mill processing

Why a hammer mill?

Hammer mills can be used to process a seemingly infinite list of materials.  For spices it is the best tool for the job because of the operational flexibility, and the ability to control finished particle size. With the exception of high oil content spices such as nutmeg and mace (unless cryogenically frozen), the hammer mill is ideal for processing a wide variety of spices and dried herbs, such as : red pepper, white pepper, black pepper, coriander, cumin, cinnamon, oregano, thyme, cloves,  and turmeric just to name a few…

One mill, many spices

The simplicity of the hammer mill makes it very adaptable to the varying characteristics of different spices. It is this versatility that makes the hammer mill the ideal choice for those  processing more than one variety. Because the processing mechanism results in crushing by impact instead of compression, spices are ground to the exact desired particle size without significant heat increase that could cause loss of flavor or aroma.

Sizing

The importance of exact finished particle size cannot be overstated when grinding spices. The key component to a hammer mill processing the exact particle size is the perforated screen covering the mill’s discharge opening. Screen selection allows the processor to determine the largest allowable finished particle size. Material remains in the mill’s grinding chamber and continues to be pulverized until it is able to pass through the screen. Screens of varying sizes can be used interchangeably in the same mill. A 1/8” perforated screen will produce a coarser tea cut finished size. Whereas a 1/32” screen will produce a fine powder.  The second component of particle size determination is the rotor speed. As the rotor spins, the hammers impact the material in the grinding chamber with great severity.

Generally speaking:

High rotor speed  =  increased number of severe hammer blows = finer particle size
Slower rotor speed  =  decreased number of softer hammer blows = coarser particle size

In addition, very hard materials such as cloves, ginger and turmeric will require a higher rotor speed to produce the same finished particle size as softer materials like white and black pepper.  An optional variable frequency drive electrical control allows the operator to easily speed up or slow the rotor speed as needed for different applications.

Hammer mills in many styles and sizes

Finally, what size and style of hammer mill is best?  This is determined by infeed material characteristics and desired throughput rate.  For softer, easier to process materials,  a  hammer mill with a nearly full circle screen is most suitable. The 300 degree screen coverage allows for the greatest throughput at the lowest horsepower.

screen coverage for circ u flow hammer mill

 

Fibrous herbs, and roots such as kava, cassava, yam, carrot and ginseng are best ground in a more traditional industrial hammer mill. This style of hammer mill contains an internal ribbed breaker plate which is the first point of contact when material enters the grinding chamber. Given its ribbed construction, the breaker plate has a wash-board effect, breaking, down the material, thus making the pulverizing action of the hammers more efficient while reducing wear on the screens.
 
Both the circular screen and industrial hammer mill models range in size from pilot scale to high production models. The size of the mill and the recommended horsepower of the motor is dependent on the processor’s throughput goals.

 intro to size reduction ebook


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Topics: finished particle size, rotor speed, Uncategorized, variable frequency drive, circular hammer mill, industrial hammer mill, roots, hammer mills, spices

Size Reduction 101: How a Hammer Mill Works

Posted by Cassie Brown

Feb 14, 2012 8:57:00 AM



If you were looking for the latest magic bullet for trimming your waistline (and aren't we all?) unfortunately, Google has lead you astray. Material size reduction is our topic of discussion today. There are many terms that fall under this umbrella: crush, grind, pulverize, shred, de-lump, de-fiberize, just to name a few.  Likewise, there is a whole host of machinery styles that accomplish these goals: hammer mills, grinders, shredders, lumpbreakers, impactors, jaw crushers and more.

The core process is the common denominator:

larger to smaller

 

But how does it work?

The simplest way to describe the concept of size reduction is to look at the industrial hammer mill model:

hammer mill diagram

 

Hammer mills operate on the basic principle that most materials will crush, shatter or pulverize upon impact.  This is accomplished by a simple four step process:

  1. Material is fed into the mill, typically by gravity.
  2. Inside the grinding chamber, the material is repeatedly struck by flailing ganged hammers which are attached to a shaft that rotates at a specified speed. The material is crushed by a combination of hammer blows, collision with the walls of the grinding chamber and particle on particle impacts.
  3. Perforated metal screens or bar grates cover the discharge opening of the mill retain the coarse material for further processing while allowing properly sized material to pass through.
  4. Hard, heavy material such as stone, glass or metal can exit the mill via gravity. Lighter or low density materials such as wood and paper require pneumatic suction for effective discharge.


smartphones ground.ps resized 600

 

One size does not fit all

Well, that would be too easy, wouldn't it? Finished particle size is determined by a combination of the following: screen (or bar grate) size, shaft speed and hammer configuration.

For example, a fast shaft speed, small screen and large number of hammers typically produces a fine end product. Conversely, a larger screen, fewer hammers and slower shaft speed will result in a coarse product. Disclaimer alert:  It is important to know that this is a very simplistic explanation of a very complex engineering process.  Each of these factors is determined based on careful consideration of the the material being processed and the user's production goals.

Each of the key components: screen size, shaft speed and hammer configuration can be changed individually or in combination to achieve the precise finished particle size at the desired production rate.

intro to size reduction ebook

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Topics: finished particle size, bar grates, material size reduction, hammers, grinders, industrial hammer mill, hammer mills, lumpbreakers, shredders, jaw crushers, impactors

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