Random and Miscellaneous

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Alfalfa

August 15, 1996 Rev. March 2001

Throughout the years there has been a fascination with pressing alfalfa. At this point the activities in the United States have almost all ceased operation; however, we know many plants are in operation in Europe. Recently we learned of seventeen alfalfa pressing plants in France alone.

Generally incoming shredded alfalfa will have a moisture content of 80% to 85%. This is reduced to 65% to 72% in the press cake. This corresponds with producing approximately 55 pounds of press liquor (with 7% dissolved solids) for every 100 pounds of alfalfa introduced into the press.

Our applications file indicates that fresh cut alfalfa will have a bulk density of 10 to 12 pounds per cubic foot (p/cf). This increases to about 24 p/cf when the alfalfa is run through a shredder. At the same time, a project in Minnesota that is in the study stages calls for macerated alfalfa at 40 p/cf. In any case, it is important to harvest the green, young alfalfa during the morning hours while it has its highest moisture content.

The principal product made from pressing alfalfa is a chicken feed additive. The additive is very high in protein content, and, like marigold extract, it results in yellow egg yolks in layers and yellow skins in broilers.

To make this additive, alfalfa press liquor is run across screens to take out fiber and suspended solids. Then the greenish juice is heated to 190º to 195º F which coagulates the green protein. This forms a brown mass (that looks like cottage cheese or curd) that is centrifuged to pull out the coagulated material. These solids are run through a rotary dryer to produce the high value feed additive.

The liquor from the centrifuge is concentrated and sold as molasses. A waste heat evaporator is used in the concentration process to take advantage of waste energy from the drum dryer. Early installations had Vincent WHE's, dryers and presses.

In 1993 the U.K. based sugar beet company, Western Sugar of Denver, Colorado, did some testing on alfalfa. They bought a Vincent VP-12 press for the tests with the idea of using their existing sugar evaporators in the off season. They knew this was being done in Denmark. The tests were successful, but the project was never funded.

At Western Sugar it was found that our press achieved close (90%?) to the "brochure" throughput rating when the alfalfa was macerated. On the other hand, a capacity de-rating of 40% was evident when the alfalfa was only forage chopped (1" to 1-1/2" pieces).

When large volumes of forage chopped material are fed to Vincent presses, the machines require a great deal of horsepower. For this reason very heavy duty drive components and screens are used on alfalfa machines. Starting with double the normal horsepower, we go to a large diameter shaft and thicker screw flighting.

There is a project at Phytolife Science. Their original work used a Russian technology that involves growing alfalfa on soils that have been contaminated with radioactivity. As the alfalfa grows, it absorbs the radioactive particles. The alfalfa is pressed in the process of concentrating the radioactive waste. They use electromembrane separation of the juice to take out the fraction with the contaminants. Fortunately from the pressing standpoint, they macerate the alfalfa to destroy the cell wall.

When DOE funding for the radioactive project was delayed, the same group shifted to working with a cosmetics firm. Their program called for pressing alfalfa to produce a component for cosmetics. A pilot test plant was built with a Vincent press.

In 1966 Vincent sold a VP-12 press to Standard Process of Palmyra, Wisconsin. The company produces natural vitamins and herbs. They successfully press alfalfa as part of a process of producing health foods for human consumption.

Testing with the new Vincent Twin Screw Press indicates that this machine design may be superior to other presses for use on alfalfa.

Issue 48


Automotive Oil Filters

April 30, 1998

Vortex of Santee, California (near San Diego, 619-258-9660) operates a CP-4 screw press in an oil filtering recycling process. This came about after a Thomas Register inquiry led to tests in Tampa in 1994.

The raw material at Vortex is used automotive oil filters. These metal canisters contain a paper filter element along with automobile oil and sludge. The patented Vortex Mega Crusher process uses a 200-ton mechanical punch press to pound the filters through an extrusion die at 8,000 psi. This process separates the oil and air, rendering a near solid extrusion that does not drip oil. The solids from the used oil filters go directly to a steel furnace. All the liquids are treated as drain oil and recycled.

In this process about ten filters at a time are crushed in less than one second, generating high hydraulic pressures and velocities. The action, along with some cheese grating of the paper against the die, produces a lot of sludge in the drain waste oil. This mixture is pumped at 5 to 12 gpm into a fine rotating drum screen that is almost horizontal, 30" in diameter and 4' long. The paper pulp rolls into a 1-1/2" to 10" diameter log in the screen, building fibrous consistency. As the log rotates, it cleans the screen. The log and barrel screen also serve as an accumulator to smooth out the surges in the continuous flow process.

The log end breaks off as it rotates and drops into the Vincent CP-4 screw press hopper. The press liquor is pumped at 1.8 gpm back into the barrel screen with the unfiltered sludge. The cake drops into a continuous flow pusher centrifuge, yielding an additional 0.1 gpm of oil The cake then is blown into an extruded solids hopper. The Vortex machine can produce 45 tons of scrap steel and 3,800 gallons of oil a day from 400 barrels of used oil filters.

The recovered oil is sold to refiners who process it into usable lubricant.

The Vortex oil recovery system is run only periodically. Don Kleine, inventor of the process, points out that they would have to collect all of the used oil filters in California in order to run ten hours a day. Nevertheless, the operation is profitable and the process is available under technical license or machine purchase.

This is a higher horsepower application for a screw press than usual. The press has been upgraded to a 2 hp drive, 15 rpm screw, with 3/4" long resistor teeth and pie-cut flights.

Issue 76

Bioresin

June 9, 2006

Bioresin and bioplastics are two new words to add to your spell checker. They refer to polymer plastics that are made from biomass organic materials instead of traditional petroleum feedstock. The one in commercial use is mostly corn, although development work is underway with stover, switch grass, wheat straw, and rice straw, among others. The high price of crude oil has given impetus to the industry.

Metabolix and ADM (Archer Daniels Midland) are Vincent customers making the most news. They have recently announced they will build a 100 million pounds per year (mpy) plant in Clinton, Iowa. Metabolix, a 1992 spin-off by MIT, acquired technology from Monsanto in 2001 for the production of organic PHA, polyhydroxyalkanoate.

PHA is produced by fermenting corn sugar with genetically modified bacteria. The resulting mash is separated in Vincent screw presses, after which the resulting polymer resin is dried in a steam tube dryer.

A key characteristic of bioplastics is that, unlike petroleum based plastics, they biodegrade in a few months. This occurs either in soil or sea water. At the same time, bioplastic products have an indefinite shelf life.

PHA is a thermoplastic that serves as a substitute for PET (2-liter Coke bottles) and polystyrene. It can also replace polyethylene and polypropylene. The initial product to be produced by ADM is agricultural stakes. Plastic cutlery, coated paper cups, bottle caps, drinking straws, cosmetic cases and foam coffee cups will follow.

An alternate, better established bioresin is corn-based PLA, polylactide. This has been produced in Blair, Nebraska since 2002 by NatureWorks. Starting as a 1992 joint venture, NatureWorks had an ownership change in January 2006, when Cargill bought out their partner, Dow Chemical. The Blair plant has a capacity of 300 mpy. This bioplastic is used to make containers and packaging for produce, pineapples, melons, drinking cups, and deli containers. Newman's Own salad dressing containers and Biota drinking water bottles are made from PLA.

Foreign firms are also producing bioplastics. BASF in Germany calls their Ecovio, and they produce 13 mpy, targeting the carrier bag and packaging film markets. Novamont in Italy has production capacity of 80 mpy of polyester-based bioresin, serving bioplastic film markets. Grenidea Technologies in Singapore has been producing their Agroresin from palm oil biomass since 2003, for bakery trays and fresh produce containers. In Japan, Mitsui Chemicals produces their Lacea PLA for packaging electronics, envelope windows, prepaid phone cards, and industrial strapping. Worldwide production capacity is currently estimated to be 800 mpy.

Issue 174

 

 

Bulk Densification

December 31, 1997

We think of our screw presses as machines that separate flows of wet solids into a stream of dirty press liquor and damp press cake. We rarely get out a flow of clear press liquor, and there is always some moisture left in the press cake.

An unusual application was tested at the recent Sales Rep meeting. A sample of dry, fluffy paper fiber was brought to see if the air could be removed. The idea was to deaerate the material, increasing the bulk density.

Bulk densification is called for when there is a need to transport or store dry materials that are light and fluffy. In their natural state such materials are difficult to manage because they rapidly fill the storage facility or truck.

The initial trials were encouraging enough that Merfin, the paper company in British Columbia, sent larger samples to Tampa. Pressing the air dry bleached pulp fibers with a KP-6 press, it was found that the press cake occupied only one quarter of the original volume. The final cake measured 22 #/cf bulk density. During pressing there was a flow of air to be seen coming out of the press liquor discharge. A brief, interesting video was made.

Another similar application that was tested previously was to deaerate Kaolin clay that is used as a paint ingredient. These tests were successful, although there was an indication that more than normal press horsepower was required.

We hope to pursue this market in the coming year.

Issue 71

Crumb Rubber

May 18, 2006

Vincent Corporation recently placed two CP-4 screw presses at the largest volume tire manufacturing facility in the United States. Their purpose is to dewater crumb rubber.

This facility performs all functions of the tire manufacturing process, from the receipt of raw materials (such as rubber bales, chemicals, textiles, and steel) to x-ray inspection of the finished tire.

The rubber compound is composed of two major components, the raw rubber and the filler. The most popular fillers are carbon black and silica. Carbon black usually comprises one third of the rubber by weight, giving it its strength and characteristic black color. Rubber for whitewalls and white letters does not require the same strength, thus the absence of carbon black.

Steel and fabric cords are calendered - an operation in which the rubber compound is pressed onto and into the cords - to form steel belts and plies. The inner liner is also calendered. Then, after preparation of the bead component and extrusion of the tire tread and tire sidewall components, the tire building process begins.

The tire building process is complicated and highly mechanized. Of most relevance to Vincent is the method by which whitewalls and raised white letters are created. A ply of white rubber is laid just below a thin layer of black rubber wherever the white is to show through. After the tire is cured - a high-temperature, high-pressure operation during which the rubber flows to form the tread pattern and sidewall details - the thin layer of black is ground off to expose the whitewall or white letter. The resultant crumb rubber is pneumatically conveyed to a Rotoclone, which uses water as its filter media. The discharge from the Rotoclone is saturated and must be disposed of.

Current disposal costs are quite high at $37 per ton to landfill. With up to 40 cubic yards to dispose of per week, annual landfill costs easily exceed $62,000. The CP-4 presses achieve a greater than 50% reduction in weight, or a greater than $30,000 per year savings in landfill costs. Press liquor is returned to the Rotoclone to reduce make-up water requirements.

Better yet, the dewatered crumb now has a market value, and the current plan calls for an end user to pick up the crumb at no cost. There is even a possibility the plant may be able to sell the crumb.

This is a high torque application and the standard speed presses use 2 hp motors. A moderately tight slot screen (0.015" or less) is desirable.

Issue 173

Diaper Factory

November 3, 2004
Rev. 2008

A successful application for a Vincent screw press has been found at a diaper factory.

Diapers, and similar sanitary products, used to be rectangular. Today, they are hourglass shaped. This configuration can either be achieved by using a water jet to cut the pattern from a continuous strip or band of material, or it can be die-cut. It is in the former process that a screw press is valuable.

Manufacture starts by continuously unwinding large rolls of woven inner liner, cellulose fiber or matting (with SAP - super absorbent powder), and waterproof outer liner. These layers are sandwiched together. The laminate band produced is fed through high pressure rolls to form crease marks, checkered patterns, and the hourglass shape.

Next, the water jet cuts the material on the outlined crease marks. The water jet uses high pressure water, at 50,000 to 60,000 psi, to cut the desired shape. The cutting water passes into a tank under the cutting table. This tank is fed additional water to cushion the jets and to dilute the flow.

It is the water from this tank that is fed to the Model KP-6 screw press. Featuring a wedgewire screen and rotating cone, this press separates the solids from the water. The solids, mostly paper fiber, with some SAP and liner material, come out very hard and dry. They go to landfill, while the press liquor is clean enough for the sewer system.

The flow has a very high degree of freeness. The KP-6 easily handles a 30-gpm flow from four diaper lines.

July 2008 Update

We thought we were on to a neat market niche. Unfortunately the diaper industry has moved on to using a die-cutting procedure for cutting out the diapers. If the diapers aren't wet, a screw press can't do anything with them.

Issue 154

Fiberglass

May 19, 1997

An unusual application for a dewatering screw press is found in factories that produce fiberglass wool.  This insulating material is produced in continuous wide (20' or more) blankets.  The factory building we visited was long, over a quarter of a mile.  The wool is formed in a large chamber at one end, and it is either rolled or sheared into panels at the other end.  In between the two ends of the factory the material is coated with a binder resin that is baked on, and the material is then cooled to where it can be handled.

Once running, the equipment is only rarely shut down.  As the material comes from the chamber where the fibers are formed, it is white in color.  It turns to the familiar tan color only after the resin is baked.

Considerable volumes of waste material are created.  Because of impurities, recycling is the exception.  Generally the dry waste is compacted in large industrial compactors. (Marathon is a supplier of these.)  The compacted material is landfilled.

The application for the Vincent press is to dewater waste at the beginning of the process.  The fine strands of fiberglass (angel hair) are formed by injecting molten glass through dies with tiny holes.  The extruded glass goes into a large chamber, surrounded by a hood, where it solidifies.  The hood walls are cooled with a water film, and the glass that hits the walls solidifies and is washed to a collection pit.

The water, fiberglass, and some glass particles the size of marbles accumulate in the pit.  This is pumped to shaker screens to remove a large part of the water.  The tailings from the shaker screens, amounting to only 200 pounds per hour each, were found to contain 90% moisture.  The high water content of the tailings presents a problem in that water drips from them as they are carried through the plant.  Also, they drip water when placed in the compactors along with the dry waste.

By running the tailings from the shaker screens through a screw press, we were able to remove one half to three quarters by weight as water.  This solved the dripping problem. A new problem created was that the water coming from the press contained a significant amount of ground glass.  This was created in the pressing action.  We feared that it would be abrasive; however, only the tan (baked) material is abrasive.

In our first testing, at Knauf Fiber Glass GMBH in Alabama, we were up against a Hycor Helixpress.  Both it and our CP-4 press had problems with the tailings bridging at the inlets to the presses.  This was solved by the addition of sluicing water (available from the shaker screens).

The 8" Hycor machine costs about $20,000 versus $12,000 for our CP-4 press.  In the end the Hycor unit was selected because it was better at passing chunks of glass and other
waste.  It was only later that we were able to resolve this problem in our press with the invention of the Sterile screw (see Pressing News #37).

Subsequently we learned of another identical application at Evanite in Oregon.  They were debating between buying an additional Oberlin machine for about $30,000, or a Hycor.  Their existing Oberlin, which they described as a semi-continuous belt press, produced press liquor with only 3 ppm solids and 45% press cake moisture.  In contrast, the Hycor they tested gave them 600 to 700 ppm in the pressate.  They could not accept the higher solids content in the wastewater, so they stuck with Oberlin.  Their objection to the Oberlin was primarily mechanical deficiencies which they were assured had been corrected.

We declined to test at Evanite because we knew our solids in the press liquor would be excessive.

The advent of the new KP presses gives us an excellent machine for the fiberglass application.  Bridging problems will be minimal because the press will grab anything that
will fall through the 8" pipe inlet.  Plus, the Sterile screw will not jam with large pieces of trash.  Cost is still an advantage as the KP-6 sells for the same as the CP-4.

The only remaining problem is ground glass in the press liquor.  This will have to be removed separately, probably by decanting in a pit.  After all, it is a screw press, not a filter press.

Issue 61

 

 

Foots

December 11, 1997
Rev. March 2004

In 1994 we were called as a result of an ad we had placed in a food processing journal. The caller wanted to know if we could press foots. We answered positively and then asked what they were.

The caller, West Central Coop, is an Iowa firm that uses Anderson and Dupps screw presses to extract oil from soybeans. This is unusual because the conventional process is to use solvent extraction to pull out the oil because higher yields are achieved. On the other hand, the oil extracted with heavy duty expeller type presses has different characteristics that make it more suitable for specialty markets. That is West Central's niche.

The Anderson and Dupps machines squeeze the beans so hard that some solid fiber material comes through with the oil that is extracted. This press liquor is pumped to a tank where the bean fiber sinks to the bottom. This fiber, which they drag to the top and skim off, is called foots.

We know that a Vincent press will not produce oil by liquefying the solid fat in soybeans or peanuts. However, we were confident of separating foots into oil and press cake fiber. A high yield was not necessary because the fiber (still containing considerable oil) is re-introduced to the expeller presses.

We asked why the foots were not sent directly to the Dupps expellers. It turned out that they would not feed properly. Because of the high oil content, the foots only churned in the inlet hopper.

At the time of the original telephone call the customer decided to make their own foots press. It did not work very well. It was not until late last year that Todd & Sargent, a consulting engineering firm in Ames, called to tell us a plant expansion was underway. Today it contains two Vincent VP-12 presses that are used for pressing foots.

Issue 70

Hide Curing

April 30, 2002

We had an interesting visit to Pacific Hide and Fur Depot in Nampa, Idaho. The plant processes 3,000 hides a day, for which they pay $15 for a #3 grade, $20 for a prime. The hides are circulated in a large pit containing a salt solution which cures the leather. The plant only cures hides (that is, they do not do leather tanning). The cured cow hides are shipped to China where they are made into leather goods that are exported back to the States, while the thicker bull hides are sold to Mexican firms for use as shoe soles.

An important byproduct from the plant is #1 Yellow Fancy oil. This high quality oil is extracted in cookers that alternately heat and cool the waste flows at the plant. The oil is used to soften tobacco, among other things. (Smokers can ponder that one.)

Oil recovery involves pumping the plant's flushing water first to a 30' long skimmer tank, then to a settling tank, and finally to a DAF. The sludges from the skimmer, settling tank, and DAF are all directed to the cookers. Heating and cooling cycles separate the oil. The solids float, water goes to the bottom, and oil stays in the middle. Once the process is complete, the water is drained and the oil is recovered. The solids that remain are an additional source of oil.

The main application for a screw press at this plant is to squeeze oil and water from these remaining cooker solids. The solids are pumped to a gravity screen, from which they fall into a screw press. The press in service is an old, but very effective, wine press. This press has a 12" diameter screw with a tapered shaft, starting at about 5" and going up to 10" at the cake discharge. The flights on the screw have reducing (tightening) pitch, adding to the squeezing power of the press. The drive was about 15 hp going 10 rpm, which is a lot of torque. The bar screen looked homemade, with bars laid into staves and TIG welded in place. Surprisingly, the drive shaft diameter was only 2". There was not much motivation to replace this old press.

Another screw press application involved five pounds of material that are trimmed from each of the hides. The trim is piled, allowing water to drain, and then it is sent to landfill. (This trim cannot be sold to a rendering company because it contains too much salt.) We were asked about supplying a screw press to improve the water separation, but the financial incentive was insufficient.

Another press need was to dewater what is referred to as manure mud. Unfortunately it is more mud than manure. The particles were so small that it clearly would not dewater without a press aid. We discussed using the press cake from the wine press as a press aid for the manure mud, but even with that the solids capture rate is likely to be unacceptable.

Plant wastewater goes to a DAF unit that handles 5,000 gpd. The filtrate flows by gravity to 50 and 30 micron cartridge filters. The plant did test a Model FF-6 Fiber Filter as a replacement for these cartridge filters, but the testing was not successful.

Issue 127

Laundry Muck

February 23, 1995
Rev May 1999

Very large commercial laundries represent a potential market for Vincent equipment. This is particularly true of laundries that do industrial uniforms and wipe rags as these contain grease that blinds competitive screening devises. This application is important because of the desire by laundries to recycle and re-use their hot water.

Another need at a laundry exists because of the fees associated with sewering water containing muck and lint. Muck is the residue that is filtered from wash water; typically it consists of dirt, lint and grease. Lint is also cleaned from the exhaust gas of the dryers; it is normally sluiced with water into a small bag filter.

The Vincent system for filtering these flows requires a pump to pull water from a sump into a Fiber Filter. Sludge from the Fiber Filter are in turn fed into a Series KP screw press.

For the system to operate effectively, the washer water first must be run through basket filters ahead of the Fiber Filter. This is done to catch rags and strings that will tend to foul the equipment. These baskets are normally below the floor level in the path between the washers and the wash water sump.

The Fiber Filter works well at separating thin concentrations of muck from the large volumes of water (200 to 800 gpm) that are discharged from the washing machines. At the same time it easily handles the thicker lint slurry from the cyclone separator used with the dryers. A chief advantage of the Fiber Filter is that it is self cleaning, in contrast to conventional dewatering screens (gravity, vibratory, and drum types).

When the sludge from the Fiber Filter is run through the screw press, more water is removed. The press cake is quite dry and ideally suited for landfill. It does not drip, which facilitates handling and transport.

Many laundries use flocculation systems for final cleaning of their waste water. This requires the use of a polymer additive, which is a significant operating expense. We have one case where the use of the Fiber Filter reduced this expense by two thirds.

Issue 22

Medical Waste

January 4, 1996
Rev. Feb 1999

New methods for the disposal of medical waste are evolving, and Vincent is in the thick of it.

Historically infectious biological waste has been disposed of by incineration. It is expensive to build an incinerator as well as to operate one. Another factor that mitigates against incineration is the amount of attention received from environmental regulators.

Although the waste has some BTU value, fuel is required to maintain the high temperatures needed to assure complete incineration. There are many materials in the waste that contain chlorine, everything from antiseptics to plastic scissors and syringes. When these burn hydrochloric acid is generated and must be removed in a scrubber. Up to 500 hp worth of fans are needed to overcome the pressure drop through the scrubber. The acid is corrosive to all of the equipment in the system, and a considerable amount of caustic is used to neutralize it.

Using gas or oil, the cost of incineration is 14 to 22 cents per pound. An alternative, burning with plasma, is even more expensive.

Sterile Technologies, an Indiana firm, has developed an alternative to incineration. Their first installation was sold to Bridgeview, Inc., a processor of medical waste with multiple treatment facilities. It is handling 1,500 pounds per hour of medical waste.

The system starts with a ram to force boxes of "red bag" waste through two stages of low speed shredders, the second of which has 3/4" teeth. Before and during the shredding process, the waste is doused with a solution of water and Sodium Hypochlorite (NaOCl).

Next the shredded and chemically treated waste falls into the hopper of a Vincent CP-10 press.

The effluent that squeezes out through the press screen is filtered, recharged with enough NaOCl to maintain a minimum 1000 ppm concentration, and used again.

The dewatered waste drops from the press into a Steam Clave (continuous autoclave) manufactured by Vincent. The Steam Clave is a 24' long, totally enclosed and insulated, elevating screw conveyor. There are steam injecting nozzles all along the conveyor and thermocouple ports at the beginning and end. Enough steam is introduced to maintain a temperature between 200 and 210º F. The screw turns slow enough that the resident time in the conveyor is about 30 minutes.

By the time the waste exits the Steam Clave into the back of a truck, it has been rendered inert and ready to be taken to a landfill.

The cost to process infectious waste using this system is expected to be less than 10 cents per pound.

The two main problems we encountered were with the press.

First, the medical waste dewatered so easily and quickly that it bound inside the press. This was countered by using a specially designed screw to "open up" the press. This design configuration was named the "Sterile Screw". It has become our standard in other applications that involve pressing "high freeness" materials.

The other problem was abrasion. The glass containers and hypodermic needles wore down the screw and screens at a surprising rate. This was controlled by using harder, more abrasion resistant materials and by opening up the screw-to- screen clearance. (Ceramic coatings failed in short order due to the flexing of the screw flights.)

Sterile Technologies planed to market the system nationwide, but they met with little success. A Vincent press was to be tested by another firm in Virginia that has a smaller scale batch system for use on-site at the hospital. It also failed to proceed, due to a lack of funding.

Overall we have been disappointed by the medical waste market. It appears that excess disposal capacity was put in place in anticipation of environmental regulations.

Issue 37


 

Dewatering Mica Flake

February 23, 1996

Engineered Process Equipment, our sales representative in Virginia and the Carolinas, has developed a new application for the Vincent screw press. It involves dewatering mica flake at a mica mine.

In the Southwest part of the United States, mica is extracted from quartz rock. This is generally a dry process. However, in North Carolina it is mined from dirt and mud.

Initially the mica is broken into manageable sized particles in a rod mill. The sand and mica mixture that results is separated in spiral washers. These spirals are about 24" in diameter and stand about 8' high. They resemble miniature amusement park water slides, and over a thousand are used at the mine. The difference in density allows the sand to be spun away from the mica.

The mica slurry that results is pumped to a vibratory dewatering screen where further washing takes place. Water sprays roll the mica uphill while gravity pulls it down. The tailings from the screen fall into a CP-10 Vincent press.

Previous to purchasing the screw press, the mine was using a Bird centrifuge to remove water. This reduced the mica to a 35% moisture content. Since there is some sand left with the mica, heavy abrasion resulted in severe maintenance costs.

We were surprised that a rental Vincent press was able to achieve 30% moisture. This is of great value to the mine because the dewatered mica must be dried to a bone dry condition in a rotating drum dryer. The trial resulted in the immediate sale of a screw press.

An added benefit is that less degradation of the flakes is occurring in the press. End users have commented favorably on the larger flake size they are now receiving.

Initial operation with the press was a failure because the screens blinded with the mica platelets. This problem was solved by bolting polyurethane wipers to the outer edge of the screw flights. The wipers keep the screens clear.

Issue 39

 

Pond Remediation

March 26, 1998

Not infrequently we receive calls from firms seeking assistance with pond remediation.  They will have a contract to remove sludge from a pond, and they want to dewater the sludge.  Almost always the pond sludge is made up of biologically decomposed material that cannot be dewatered with the metal screens of a screw press.  We explain that it is a belt press that they are looking for.

Recently a paper mill requested a proposal for pond remediation presses.  Before we could explain why it would not work, it was explained to us how it did work:  The mill had found that they could blend a press aid to make the sludge pressable.  Furthermore, they had several sources of reject fiber in their operation that were quite suitable as press aid.  They referred to this reject fiber as "sweetener".

In order to remediate the pond within six months, a large 30" press was called for.  However previously the mill had rented a 10" press and tried it out at several locations in the plant.  Because of the success of these other applications, our recommendation has been that they acquire four 16" presses.  These will be available for use elsewhere in the mill following the pond remediation program.

September, 2013

This use of fiber as a press aid will not always work.  In some cases, especially with sludge from a food plant, the biological particles do not adhere well to the fibers of the press aid.  The result is that an excessive amount of the sludge passed through the screen of the press.  The total capture rate of solids can be inadequate.

Issue 74

 

 

Safety-Kleen

September 3, 1997

A 16" Vincent press that was originally sold to an Israeli citrus plant has ended up in Kentucky.  The new application is truly unique.

The press is used to separate combustible liquid from shredded hazardous waste.  Safety-Kleen, a national industrial waste disposal firm, operates a licensed facility that processes industrial wipe rags and liquid wastes.  The hazardous materials, mostly oils and paints, arrive on pallets, in drums, Gaylord containers, and pails.

The truckloads of waste, including the 55-gallon drums, pallets, and 5-gallon pails, are chemically analyzed and then rough shredded.  Most of the metal is removed with magnets.  Then the material is run through the Vincent screw press.

Since the waste includes fist-sized chunks of wood, plastic, glass and metal, the press had to be modified.  The screw flights were "pie cut" to enlarge the passages (although the Sterile configuration would have been a better bet).  The 3/32" citrus screen was changed to 1/2" thick plate with 3/4" perforations!  The drive was increased from 20 to 60 horsepower.  A reversing starter is used on the press so that it automatically reverses upon jamming, and then resumes forward operation.  Surprisingly, the machine runs a year between major overhauls.

The press processes about 15,000 pph (pounds per hour).  About 30% of the material comes out as press liquor.  This has a high BTU content and is sold as fuel for about $0.25 a gallon.  On the other hand, the press cake is a hazardous waste that must be incinerated, at a cost of about $0.30 a pound.  The scrap metal is sold separately.


Issue 66

 

Scrap Shredding

 January 10, 2016 

There are many scrap yards which use gigantic shredders to process scrap metal from flattened automobiles, household appliances, and a wide range of other steel industrial and consumer equipment. These shredders are driven by motors ranging from a few thousand up to ten thousand horsepower.

Years ago these items were shredded with snag-tooth type low rpm shredders. These were pre-shredders. They went out in the 1960's with the invention, by someone named Newell, of the giant swing hammer shredders now in service everywhere.

Along with the scrap, a large flow of water is sprayed into the shredders. The water adds important lubricity, and it is also used to cool the heating which comes with the shredding operation (all those horsepower go into heat enegy). The water is also added partly to suppress fire which occurs from time to time when they hit a gasoline tank or propane bottle.

California had regulated VOC emissions from the shredders, so gasses from the shredder must go through a combustion furnace. This is not required in other states. California has equally exotic regulations governing disposal of sludge from the wastewater; it must combined with cement as part of chemical treatment.

The flow from the shredder, with all its water, is run past magnets to separate ferrous metal. That leaves a flow of fluff and non-ferrous. This flow is screened into coarse, medium and fines. These three flows are run past eddy current separators. The non-ferrous scrap is repelled, and it is thrown the furthest from the end of the belt conveyor. The fluff falls a shorter distance, thus separating the flows. Magnets hold any residual ferrous metal to the belt, and it is scraped off into a third flow.

The fluff is made up of the plastic, rubber hoses and moldings, wood scraps, foam rubber from car seats, fabric, headliners, insulation, and other non-metallic trash. This is from the mopeds, busses, stoves, washing machines, bed springs and everything else which is fed into the shredder.

It is interesting that flattened cars in England have 2% wood by weight. People must be disposing of pallets and scrap lumber along with the cars.

Vincent's interest was in separating the water from the fluff. This was an extremely challenging application for a screw press. Some tramp metal is always entrained with the fluff. And some of the fluff can be thick plastic boards, conveyor belting, hydraulic hoses, and other things which tended to jam a press unless it had high torque capacity. These larger pieces required the screw press to have a large diameter screw.

The material is also very abrasive, which requires restoring hardsurfacing to the screw of the press every month or so.

The material has high freeness – the water tends to fall easily from it. This allowed a screw press with a short L/D (length of the screen divided by the diameter of the screw) to be used.

Unfortunately for Vincent, a solution more practical than a screw press turned out to be a large industrial compactor.

It was fun while it lasted.

Still, there are other viable applications in the scrap yard. These include dewatering WWTP sludge and recovering oil from automotive oil filters. Some yards add magnetite to the fluff in order to separate certain forms of plastic. It was found that the magnetite, which is costly, could be separated into the press liquor.

Styrofoam

March 27, 2006                                                                                                                                                                                                    ISSUE #171

Back in the 1980's, Vincent sold a pair of presses to Dart Container in a Styrofoam dewatering application, for their re-cycling operation. These are used to squeeze wash water from shredded Styrofoam. The technology works, and both presses are still in service.

In 2005, financial as well as technical success was achieved at Georgia-Pacific's Green Bay, Wisconsin recycle paper mill. This is a very large mill, as far as secondary fiber operations go. The mill capacity is rated at over 1,000 tons per day.

A long standing problem at Georgia-Pacific had been the disposal of Styrofoam and other floating waste that accumulated in the mill's two large primary clarifiers. With an operation this large, the floating waste amounted to several tons per day. This material was skimmed, drained, and allowed to accumulate. This resulted in problems with run-off water. In addition, wind would disperse the dried material, creating an unsightly situation.

The solution to these problems was found in a Vincent Model KP-16 screw press. This press has been built, in quantity, for many years. Most units are for dewatering applications at produce processing plants and dairy farms. At the produce plants, the service is simply dewatering trash like corn husk, lettuce leaves, carrot shavings, onion skins, pea pods, and such. At the dairy farms, the task is to dewater manure. The manure is separated into dry bedding for the cows or compost, with the press liquor being used for irrigation or barn flushing.

At Georgia-Pacific, the floating waste is now skimmed and drained by gravity into the single 16" screw press. The waste is compacted into a form that is readily handled for landfill disposal. The press liquor is directed back to the clarifiers.

Initially, a perforated screen, with 3/32" holes, was used in the press. In order to improve the solids capture rate, this was changed to a profile bar screen, with 0.015" slots. Bar screens have about half the open area of perforated screens. Nevertheless, the bar screen has ample hydraulic capacity for the high-freeness flow seen by the screw press.

Simplicity, low maintenance, and unattended operation were features that led to the selection of a screw press over a baling machine. In addition, a screw press removes a greater percentage of the water in the waste, avoiding runoff problems.

Guayule

January 30, 2013

Guayule

Between 2008 and 2010 Vincent ran tests involving guayule for two firms.  Neither project went ahead, and at this point the NDA's have expired.

Guayule is a 2'x2' plant that can be grown, with little water, in the Southwest and Australia.

The technology had roots in an Arizona factory which Firestone built on an Indian reservation in the late 1980's.  That facility is now long gone.  The idea was to extract latex from the guayule plant to make natural rubber.

Our original testing was done with material which was simply ground guayule plant mixed in water.  The as-received was 9% solids; we got 50% solids in the press cake and 4% solids in the press liquor.  Those were encouraging results.

A year later more sample material was sent to Tampa.  This may not have been representative.  It apparently was made from some guayule 3/8" pellets, presumably with the latex removed.  These were reconstituted with latex and solvents (hexane and acetone).  That is what we pressed.

The press cake from testing this sample came out an incredible 82% solids!  The press liquor was 11% solids.  This was achieved with a light cone pressure.

We started at 10 rpm and the screen blinded.  Of all things, cranking the speed up to 70 rpm got us a strong flow of press liquor which seemed to continue without blinding.

We tripped out on high amps.  However, this was most likely because the latex formed rubber cement which got between the cone and the shaft of the screw.

We were using a wedgewire screen with slots that were 0.015" wide.  That worked fine.  There was no sign of material plugging elsewhere in the press.

Our third round of testing was conducted in a rubber laboratory.  In the research center a 5-gallon charge from a reactor vessel was fed to a Vincent CP-4 screw press.  This material was guayule latex dissolved in acetone and hexane.  The material was 18% solids, but this was deceiving; it looked like the insoluble solids (woody fiber) were much lower.

It was the press liquor, containing the latex, which they were trying to produce. 

The press cake also had some latex left in it.  This was not a problem because it was easy to wash the press cake with solvent and recover its latex.

The main problem they had was excessive insoluble solids in the press liquor.  These ranged from 7% to 16%.  (That must have been a percentage of the final latex, not a percentage by weight of the press liquor.)  These solids were "sawdust & dirt".  It looked like fine dust mixed with very fine woody fiber.  We had expected the dust to go through the screen, but we could not explain why the woody fiber also came through.  They started with a screen with 0.017" slots and went to a 0.011".  This change reduced the amount of fines in the press liquor.

The CP-4 laboratory press in the testing was highly modified.  Instead of the normal 1-1/2 hp motor, it had a 7.5 hp motor.  This allowed the screw to be run at 150 rpm. 

Another very unusual feature was incorporated so that the cone was made bullet shaped and mounted off a pedestal at the end of the press.  This eliminated cone bushings which had gummed to the screw shaft a year before.  This arrangement for mounting the cone allowed us to end the screw short, at the end of the flights.  That is, the screw was supported only by the gearbox, in a cantilever form.  A similar press is seen in the photo, with a black UHMW cone.

The operation of the press was highly unusual.  When they blew a couple gallons from their reactor into the press, the press sat there and churned for fifteen minutes.  During that period there was a minimal flow of press liquor through the screen.  We concluded it was a blinded screen and the situation was hopeless.  But, quite suddenly, after fifteen minutes, the press liquor started coming through the screen, and soon there was a flow of press cake.  We wonder if some chemical change was going on before the press would start working.

The press cake did seem to come out in surges, like a typical (oversized) knots press.  That is, the press went through cycles of packing itself full before it would push the solids from the screened area.

As with our previous testing, the press cake was extremely dry.  However, there was no indication of any jamming. 

As soon as the solvent evaporated, there was rubber cement left.  This cement dried just like ordinary rubber cement, all over everything.  Still, when we took the press apart after we had run a 5 gallon batch from their reactor, we saw that the screw had cleaned itself extremely well.

The test data said that the solvent in the press cake had ranged from 30% to 48%, with cone pressures of only 5, 10, and 15 psi.  The percentage of rubber in the press liquor ran from 4% to 6%.

Issue 253

Larvae

February 7, 2012
 

Organic Nutrition is a new firm being funded by private equity.  Their concept is to take food waste and grow fly larvae in it.  The larvae have nutritional value, potentially making them a commercial fish food. 

A KP-6 being rented by Organic Nutrition is being used to dewater the garbage in which the larvae grow.  They also have a VS-8 shredder which is used to reduce the particle size of that garbage.

Last year the client flew to Tampa, bringing two 5 gallon pails of Black Soldier Fly larvae.  These were brought as checked luggage.  It is a option to remember for transporting samples.

The purpose of our experiments with the CP-4 was to see if, with steam injection, we could separate the lipids (fat).  Apparently the larvae have too much fat.

The larvae went through the press very well.  It looked like we were squeezing all the juice from inside the bugs through the screen.  The cake being produced was mostly the outer skin of the larvae, which is chitin.  We got about 70% by weight press liquor at 28 rpm, 20 psi cone pressure, with strong steam injection, using a tapered shaft screw in the press. 

We had two buckets, one with larvae that had been killed by freezing, and one with live critters.  The live ones could not move fast enough to get out of the press, but they would have gotten off the tray in the moisture balance oven.  (So we froze them in order to get a moisture analysis.)

The as-received larvae were about 78% moisture, and there were 13% solids in the press liquor.  The press cake was interesting:  with very low cone pressure and low steam, the press cake came out 73% moisture.  But with 20 psi cone pressure and heavy steam, the moisture content of the press cake dropped to 63%.

To see the testing in a YouTube video, go to https://www.youtube.com/watch?v=MyngcM5D5E4

 

Issue 242

Permawick

MAY 22, 2015

The Permawick Company, a manufacturer of specialty lubrication systems, is headquartered in Birmingham, Michigan with manufacturing facilities in Michigan, Indiana, and Japan. They utilize a Vincent screw press to recover oil from their reject PermaWick engineered fiber-oil lubrication products.

Years ago Permawick was best known for the little felt lubricating washers used in automobile generators and starters. Today their engineered fibers provide permanent lubrication for sleeve bearing systems, and they are the industry standard for Fractional Horsepower Electric Motor lubrication. The Permawick technology has replaced oil-soaked wool felts, which were messy, consumed critical space and absorbed water.

Two years ago, an opportunity developed to salvage oil from fiber-oil lubricators which failed to pass inspection. A significant quantity had accumulated and Permawick rented a Vincent model CP-4 laboratory screw press to process this waste. Since the lubricators are 85% oil by weight, 99% oil by volume, the potential for oil recovery was of high value to the company.

A year later, the problem was re-addressed by the rental of a significantly larger Vincent screw press, the CP-10. While this press achieved far greater processing rates, the residual oil in the fiber press cake was excessive, yielding only a 30% oil recovery rate.

In an effort to improve this, Vincent supplied a tapered shaft replacement screw for the press. The tapered shaft configuration pushes the material both outward and parallel to the shaft, thereby increasing compression of the material. The results were superb; oil recovery increased to 70%.

                         STANDARD SCREW                                                   TAPERED SHAFT SCREW

Issue 273
 

Pods & Pillows

July 14, 2013

The first Vincent heard of pods and pillows was in early 2011.  Within months of each other we received phone calls from companies who had found us on the internet.  Both were quite secretive and had little to reveal even after we had signed Non Disclosure Agreements.

Both had capsules with some sort of liquid inside.  They wanted to run these through a screw press in order to separate the liquid.  It sounded much like the work we had just completed in developing a press to break open gel caps to separate oil emulsion pharmaceutical from the cap material.  Only in this new case the articles we were to press were the size of golf balls.

One company called them pillows and the other, pods.  One company was a firm contracted to dispose of waste and reject material for Procter & Gamble.  With the other company we were dealing with a research office in Scottsdale, Arizona.

Today most housewives in North America are familiar with what we were working with.  A revolution in laundry detergent has taken place, going from powder form to a plastic encased liquid.  Most people probably first heard about this when multiple cases arose of children trying to eat the capsules thinking they were candy.

Within days of being called we were able send out rental screw presses.  One firm got a Model CP-4 laboratory press, while the other took one each of two presses, a CP-6 and a KP-10.

It turned out to be a daunting challenge for a screw press.  The water soluble (but not soap soluble) skin of the capsules was prone to binding together into a clump.  If it did not pass on through the press, it was apt to melt into a mass that would tear open screens and rip flights off their shafts.  At the same time we needed to burst open every single one of those capsules.  But some, slippery with soap, would slip un-ruptured past the discharge cone.

Huge amounts of reject capsules were generated during the start-up and de-bugging of the soap capsule production lines.  At one point we had nine presses rented out, all running around the clock.  Several billion pods were run through our machines.

Most recently Vincent has supplied the first Vincent Pillow/Pod Slicer.  The VPS-42 is a dual shaft machine designed to slice open sheets, bags, and rolls of soap capsules.  Each shaft has its own ten horsepower direct coupled motor.  Each shaft has twenty one 10" meat slicer blades mounted on it.  The machine is mounted over the inlet to the screw press.  Its successful operation requires that not a single capsule gets through the screw press without being opened.

CONSUMER PRODUCT FEED TO SCREW PRESS

CONSUMER PRODUCT

FEED TO SCREW PRESS

CAKE AND SEPARATED SOAP IN SCREW PRESS

CAKE AND SEPARATED SOAP IN SCREW PRESS

POD/PILLOWS SLICER

INLET HOPPER OF POD/PILLOW SLICER

INLET HOPPER OF POD/PILLOW SLICER

Issue 257

 

Swarf

August 9, 2002

Almost all screw press applications call for the separation of liquids and solids in organic materials, plant and animal. Consequently we were reluctant to test a sample calling for the separation of coolant oil from swarf. Swarf is the name given to the grinding dust and metal chips generated in a machine shop.

The sample supplied came from American Saw. This firm is a very large producer of saw blades. They produce hacksaw blades, band saw blades, hole drills, demolition blades, jig saw blades, etc. The saw teeth can be either ground or milled, depending on the specific blade requirements, and the cutting tools are cooled with either oil or water. The many tons of swarf and cutting chips generated by the plant are processed in briquetting machines that produce dense steel "pucks". These slugs are about 2" in diameter, 1-1/2" thick; they are sold as scrap metal.

The problem at American Saw was that the swarf from oil-cooled grinders contained too much oil for the puck machines to work properly. A partial solution was found by running the swarf through an Oberlin Pressure Screen. The Oberlin is a belt press type machine that has the belt surface covered with a continuous roll of filter paper. The four Oberlin Pressure Screens at American saw produce a layer of swarf 48" wide, about 3/8" thick. Even after pressing in the Oberlin, the swarf, which is very spongy, retained too much oil.

To our surprise a small Vincent screw press has proven successful in removing the residual oil in the cake from the Oberlin presses. Currently the customer is using a Model KP-6 from the rental fleet. A custom version, with a 52" inlet hopper, has been quoted. For abrasion resistance it will have the screw flighting made of AR alloy with Stellite edges, instead of stainless. The gearbox has been selected to turn the screw at a quarter of the normal rpm; a small 3/4 hp motor has proven to be a suitable drive.

Most of the saw blades produced at American Saw are bi-metal. The manufacturing process starts by drawing a high alloy wire into a square shape. This wire is fused to a base metal strip with electron beam welding. Next, the tooth profile is machined into the edge of the band to which the wire has been welded. This machining cuts through the wire, into the base metal, leaving each freestanding tooth individually welded to the base metal strip. The part is then hardened by heat treating so that the tooth becomes extremely durable. Then the part is annealed so that the base metal strip returns to a soft, pliable condition. Band-saw blades in this fashion bend around the band saw pulleys, without breaking, while still having extremely hard (and brittle) teeth.

Issue 130

Truck Wash

 

July 31, 2010                                                                                                                                                                                                                                                                              ISSUE 224

 

TRU SHINE TRUCK WASH

 

Tru Shine Truck Wash operates a truck wash for trucks that are used to haul pigs and some cattle to a next door slaughterhouse.  There are a lot of wood shavings, some manure, and a nasty amount of sand, rocks and pebbles in the flow.  They pump from a collection pit, with a 4" Houle, to a paired set of Vincent VDS-42M sidehill screens.  From there the solids go into a  Model KP-16 screw press.

 

What a surprising application!  This truck wash has 30 to 35 employees.  They haul away two to three big dump truck loads a day of press cake.  They run 24-hours a day.  It is a locally owned business, and there is no trade journal or association.  How do we find the rest of them?

 

They use 2.5 million gallons of water per month.  The press must run at something around 150 to 250 gpm when the pump is on.

 

They replaced the screw after about a year.  Seven months later it was already badly worn down again.  This time we sent a screw with lots of Ultinium.  Fortunately for Tru Shine, it is a rental press.

 

Each morning they open the cone and spray lubricant on the screw shaft.  They do this because they noticed that otherwise wood chips get into the cone bushing and the amps go up.

 

This press uses the rotating cone feature.  When the press was new, they had to replace the cone drive pins a few times.  The current design, with big diameter pins, has been working just fine.

 

They have large diameter wheels with bronze bushings.  These have worked well.  They replaced the wheel bushings just once.  They run around 50 psi air pressure on the discharge cone.

 

The Racing Ring wore down once so they turned it around to wear down the other side.

 

They had wanted to interlock the press so that it would not run unless the pit pump was running.  (The impeller in the pit pump has lasted two years.)  But the pump runs on and off most of the time, so the press is left in continuous operation.

 

When the pump turns on it floods the sidehills.  The inlet hopper of the press fills up, and then the collection pan of the sidehills fills.  They have a timer set to shut off the pump at that point.  The press rapidly draws down the level.  Then the press keeps running empty until the pump kicks on again in a couple minutes.

 

The screw turns 23 rpm.  We have considered changing to a 1200 rpm motor for the press, to reduce screw wear; a 900 rpm is not available.  They put on their ammeter for me.  Amps run 18 and 20, on 208 volt power, so we are not at all short of power or torque.

 

There was a heavy layer of sand in the bottom of the press liquor collection pan.  This must be coming from where the wedgewire screen has worn down to where the slots are quite wide near the discharge.  If it wears through or bursts, they will weld on a patch.

 

Intermittently you can hear rocks and pebbles going through the press.  These likely come from the road grit they wash off the trucks.

 

The cone rotates, but there is no real stripper pin on the inside face of the cone, just four bolt heads.  The cone opens about 2" and the cake comes out very well.

 

They have a TR Blossom (Kerry Doyle's old company in Abbotsford) drag flight draining conveyor.  It had a 6" squeezer screw at the discharge.  This did not work for them.

 

They found us on the internet.

 

We'd have a great business if all our customers were as smart and able as these people.

 

Waste Destruction

May 8, 2001

Antaeus Group, a Maryland firm, has been running tests with the small Model KP-6 screw press. Thi firm has developed a system for on-site destruction and sterilization of medical waste. More recently the technology has been extended to the destruction of classified documents

The principle used in the Antaeus system is to liquify batches of waste material with water. The waste is recirculated in a mixing tank with a carefully selected chopper pump. The waste material is disintegrated by the pump, producing a slurry.

In the case of medical waste, the recirculating slurry is heated with steam. This sterilizes the material.

The action with classified documents is very similar to that achieved by a hydrapulper in the secondary fiber paper recycling industry. The hydrapulpers used in paper mills are much larger in physical size, and they operate on a continuous basis. However the pulping action, a total disintegration of the paper, is very similar.

Typically 75 pound batches of waste material are treated in the Antaeus system. This is done with 150 gallons (about 1,200 pounds) of water. A typical cycle is 30 minutes.

The function of the KP screw press is to filter and dewater the suspended solids from the slurry. These solids are discharged as a cake mass that is dry and suitable for disposal along with other non-sensitive solid waste at the customer's facility. At the same time the filtrate "press liquor" is sufficiently clean for disposal in the sewer system.

The simplicity, economy and reliability of the stainless steel screw press makes it well suited for these applications.

Issue 117