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MicroGrinding News

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MicroGrinding News - Volume 1, Issue 2

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MicroGrinding Systems has recently added a new low-cost fine particle air classification cyclone option to the VKE system where an accurate five to ten micron range of particle size product is desired. After stripping out the fine particles, the oversize rejects are returned to the mill for further grinding. The precision air cyclone is adjustable to select the desired product particle size, which is then sent to a rotary valve equipped dust collector to recover the final product.

This system supplements the standard VKE air elutriation system which injects air into the sides of the mill to fluidize the charge and help float already-ground fine particles out of the mill to avoid any “cushioning” effect and thereby more efficiently reduce the un-ground particles to the desired fineness. The goal of this two stage system is to provide a much lower cost alternative to fine particle production and separation than conventional jet milling and air classifiers which can cost ten times as much to purchase and operate. We plan on showing this new cyclone, supplied by Fisher-Klosterman, at the MINExpo96 show in Las Vegas in September. See you at Booth 4485 at the show!


The new small Laboratory size 640 VKE fine grinding mill, (pictured at right with the next larger 1040 Pilot mill in the background), has been thoroughly tested and is now in production.  Orders are currently being booked for this small lab size mill which is ideal for small scale test grinding of various materials.  The action is the same for all the VKE mills and test results are easily scaled up to the larger size mills.  

The lab mill tube is six inches inside diameter and twenty four inches long, and the overall mill size is roughly 2-1/2 feet  by 2-1/2 feet by 3-1/2 feet long. It is powered by a 1/2 hp, 3ph, 480v motor and is capable of producing 30 to 50 pounds per hour of fine ground hard material.

This mill has a list price of $7,500 but as a MINExpo show special we will be accepting orders at the show, at the show special price of $6,000.00. A new small auger feeder will also be available, along with the adjustable air cyclone classifier described in the previous article. This unit will be useful for initial test grinds of experimental work, plus is easily transported to various locations for on-site grinds. The VKE line now consist of three basic models; the standard 2080 VKE Production mill (20 inch ID x 80 inches long), the 1040 Pilot mill (10 inches ID x 40 inches long), and the 624 Laboratory mill (6 inches ID x 24 inches long). We will have a Lab mill on display at the Las Vegas show.


A custom grinding project of MicroGrinding Systems is producing vermiculite fines from the milling of vermiculite ore. Vermiculite is used in many different applications and we have found the fine fraction of the vermiculite milling has many applications as well. This fine ground natural silicate material finds application as a replacement for asbestos in brake linings, and as an additive in cements and mortars to improve flow and texture characteristics.

Fine vermiculite also finds use in certain ceramics and refractories, and as fillers in plastic and coatings for high temperature applications and where added ultraviolet protection is desired. Certain oil drilling muds utilize fine vermiculite to reduce viscosity, help plug off formations, and provide high temperature resistance in deep drilling where temperatures can reach several hundred degrees.

Due to the ion exchange effect of finely devided vermiculite, some work has been done in using this material to scavenge heavy metals from liquids containing heavy metal contaminants. The resulting residue is rich in the heavy metals and does not generate a bulky sludge, as does the more common flocculating agents used for this purpose. For samples of this fine vermiculite call or fax us here at Microgrinding Systems. We have a continuous supply of this material at a very attractive price.


Microgrinding Systems is purchasing a new particle size analyzer, complete with all the bells and whistles, to replace the faired badly due to a truck hitting a utility transformer pole at the plant. The impact sent spike electrical surges over our lines and knocked out the fax machine and the particle size analyzer. We should be back on line in a few days with the latest in particle size analysis technology with a range down to sub-micron particle size range. The industry specifications all across the board appear to be demanding closer tolerance of fine particle products and the new analyzer, coupled with the new air classification system, will permit control of the test grinds and subsequent recommendations for continuous production of precise sized products.


Footnote and Commentary Regarding Combined Operations

Down in Honduras a few years ago, I knew a man named Ray Jones, a real living legend on the Paulaya River in eastern Honduras. Ray had gone to great trouble and expense years back to bring a small crusher upriver by dugout canoe to crush a quartz ledge ore running over 9 oz/ton, and process it over a mercury table he had made from a copper sheet. Ray reported it was just heartbreaking to see the crushed ore, complete with the gold, go right over the mercury table without doing a thing. He abandoned the project and, as he was 83 years old at the time, I didn’t have the heart to tell him about the “keg mills” used in South Africa years ago. Just a wooden keg, filled with ore and mercury and mounted on a paddle wheel in the river. The tumbling action grinds the ore and washes out the gold. Combined operations! Ray is dead now and I never did go out and locate that deposit. I’m sure it’s still there!

The VKE mills are very versatile and can be operated either wet or dry. A goal of Microgrinding Systems has been to combine unit operations wherever possible in order to reduce operating cost for the producer.   Combined grinding and classification, as discussed in another article, is a good example of this approach.

The fact that the VKE mills can be operated wet opens up a potential route to combined operations through leaching during the grind cycle. The intense activity in the mill increases the leaching action greatly, and as the particles are fractured they are immediately exposed to the violently agitated leach solution, rapidly dissolving the values into the leach solution. Adding a hydrocyclone at the discharge end serves the same purpose as the dry cyclone in rejecting any oversize material back through the mill to be reground in order to insure that all values are released and put into the solution. The product slurry goes directly to a filter press where the pregnant liquor is drawn off for final recovery of the values.

There are many possible variations of this simple example, but the main idea is the same - use the action of the mill to further process the material. Of course some leach solutions require special liners and conditions and the VKE mills can be produced in stainless steel or lined with a special tough polyurethane for chemical and abrasion resistance, and to avoid contamination. The mills can be operated as a sealed system with inert gas blanket in situations where a process may need to be isolated from the environment.

MicroGrinding News is published every now and then by the staff of MicroGrinding Systems for the enlightenment, amusement, and amazement of that rare group of rugged individuals who are involved with the special science of beating rocks and other hard stuff into little bitty pieces. Call or fax us at (501)-374-8402 for questions regarding your special applications, or news of interest to the industry. MicroGrinding Systems, Inc., 1823 East 17th Street, Little Rock, AR 72202 USA

ArchivePatrick Marston