MicroGrinding News - Volume 2, Issue 1
The odd looking internet address above is rapidly becoming a common feature of business and industry today. Like the fax machines which have taken over a lot of communication needs over the past few years, the Internet promises to become an even more important business tool. MicroGrinding Systems has recently gone "on the net" with our own web site showing all our advertising literature, photos of the mills, and even this newsletter, which will be updated on the site with each new issue. At the end of each "page" at our site is and icon and internet E-mail address which is highlighted. Clicking on this icon opens up an E-mail form where anyone can contact us from anywhere in the world at no cost. It is also easy to print out what is shown on the web site, so there is no cost of delay in getting literature into the hands of interested prospects in China or New York. Check it out.
ULTRASONIC SCREENING TECHNOLOGY
The most important advance in screening technology in recent years has to be the application of ultrasonics in the field of screening powder materials. Micro Grinding Systems can offer both regular and ultrasonic screening equipment in the systems we design to grind and produce the proper size range of product to meet customer specs. The ultrasonic screens can screen down to -625 mesh with out blinding. We are pleased to be able to offer the Russell Finex standard and ultrasonic screens as part of our systems where ultrasonics provides the most effective means of particle separation and sizing. Multiple screen decks can be used to produce a clean particle size separation range in the smaller particle sizes where no other equipment can perform as efficiently.
CANADIAN SILICON CARBIDE GRINDING
A VKE 2080 production mill was recently commissioned in Canada to grind tough silicon carbide material. Silicon carbide is very abrasive and the mill included a replaceable steel liner. Future replacement will likely be a ceramic-lined tube and additional mills for this application may be ceramic-line or abrasion resistant steel, depending on how the standard steel liner would hold up.
Hardened steel rods are better for grinding such very tough materials, and we now offer optional D-2 steel rods heat treated to a Rockwell C hardness of 60, which is too hard to even drill. It takes a hard material to grind hard material and the harder the rods result in less wear and contamination. Internal induction heat grinding tubes are also now available which provides the same 60 Rockwell C hardness as the treated rods.
PILOT MILL IN OPERATION AT LAS VEGAS
Friendship Metals, a well known minerals research and process development firm located in Las Vegas and headed up by Stan Wardle, now has a VKE 1040 Pilot mill in operation grinding various ores for testing and process recovery design. Located at 1034 South Commerce, Stan has many years of experience in working with various ores and processes. Give him a call at 702-383-3026 if you need help in developing the best recovery system for your ore. He will be glad to show you a Micro Grinding Systems mill in operation. Go by and see Stan when you are in Las Vegas. Also win us some money!
FINE SILICA-STRONG MEDICINE IN CONCRETE
There is a great deal of interest and research going on today in the area of high strength concrete. The recent hour-long TV show on World News Tonight examined the need for stronger and longer life highways. It brought out the fact that longer lasting concretes have been made since Roman times. It was reported that the secret to stronger and better concrete appears to be the addition of silica in very fine particle form. The fine silica fills the tiny voids in the concrete mix, and makes it more dense and strong. Filling the voids keeps moisture out and prevents freeze cracking. Silica fume has been used for this application but the cost is relatively high.
There is more to the story, and the type of silica is very important in develping truly high strength concrete. Amorphous silica, the form found in organic matter, acts as a pozzolan and reacts with cement to fill the tiny voids and binds the concrete more tightly, hence more strength and greater chemical resistance. Rice hull char is a good source of amorphous silica, provided the rice hull burning temperature does not exceed the point where the silica converts to a crystalline, non-reactive form.
MicroGrinding has been involved in test grinding rice hulls and rice hull char for some time. We are now doing test grinds for Riceland Foods for mill evalutation and product sample production of ground rice hull ash for customer evaluation. Riceland has plans to produce fine high-silica amorphous rice hull char for the high strength concrete industry. A higher carbon content ground rice hull ash will be marketed by Riceland to the rubber industry.
GRINDING AND SIZING SYSTEMS DESIGN
We just talked about ultrasonic screening, and in the last Newsletter we told about the adjustable air cyclone classifiers. Each has it's place in terms of separation and classifying fine ground particles of whatever. In the design of a grinding system, however, we have to start with the feeder. MicroGrinding Systems offers both screw and vibratory feeders and again, each has it's place. Of course the feeder has to be sized to the mill, which is determined by the desired production rate, the particle size range, and to some extent the material and the mill itself. Practically all the feeders we sell are adjustable feed. You need that flexibility in most any system. The screw feeders are best for fine powders and the vibratory feeders tend to work best with lumpy or fairly coarse material. We have situations where a vibratory feeder is called for to feed a first stage coarse, rocky material, and a screw feeder is needed for a second stage grind where a much finer powder is being fed to produce an even finer grind material.
Both types of feeders can be used for either wet or dry grinding but of course liquid has to be metered in for wet grinding. I am going to save wet grinding for next time. Air ports on the side of the VKE mill permit low pressure air elutriation in the mill to sweep out already- ground fine particles and pull them to a screen, air classifier or directly to a dust collector. A certain amount of classification or concentration can be done without a screen or classifier but in cases where these are used, the oversize material is routed back into the mill for further grinding. Getting the fines out of the mill as soon as they are formed permits the mill energy to be expended only on larger particles which need to be ground, and this is one of the features which make VKE mills so efficient. If the dry material has a lot of lighter density waste material in it, like a clay-quartz ore, then a lot of the lighter waste can be pulled out through the air sweep outlet, and the heavier concentrates containing the values can be allowed to flow out the lower end discharge of the mill. Lots of versatility in the VKE system, and I haven't even talked about the selection of various shell linings and types of grinding media available to use. We will get into that more next time - or call me at the plant to discuss your particular needs.
UPDATES: VERMICULITE FINES; COLUMBUS CERAMICS SHOW; HONDURAS GOLD
We are still producing vermiculite fines and looking for a market for this interesting material.
We will be at the Columbus Ceramics Show in September. Booth #141. September 23-26th. See you there!
In the Honduras gold story in the last issue, did I mention the quarts "ledges" the old man found were large, flat one foot thick slabs? And he said there was only two large pieces of it? Well, the rest of the story is those pieces had to have come off a large vertical exposed vein of quartz-gold, fallen long ago from somewhere up the hill. And, no, I never did go up there and find it. I'm sure it is still there.
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