I/EC
Reports
Chemicals make mining easier N e w uses for menhaden fish Graphite ink on back of stamps permits automatic mail handling Marketing areas opening up for Polyox resins Woolens get new protection from chlorinated hydrocarbon
Tunneling with Chemicals Che mical soil s t a b i l i z a t i o n helps beat quicksand hazard • ICKS AND SHOVELS stepped aside and watched while chemicals took over during the ticklish part of a tunneling operation at a Minnesota iron-ore mine. When quicksand halted progress, chemicals were pumped in to stabilize the soil. Pickands Mather & Co. were digging a tunnel—972 feet long and 9 feet in diameter—through the pit bank of its Tioga No. 2 open-pit mine near Grand Rapids, Minn. T h e tunnel would house a conveyor belt which would carry crushed ore from the bottom of the pit to a mill. Three-man crews began digging from both the upper and lower faces. Progress was good until they hit the fine, gray sands. The company tried to stabilize the soil by grouting, but this failed. After a run of wet mud and sand occurred at the face
of the lower heading, grouting was discontinued and chemical soil-solidification experts took over. T h e Chemical Soil Solidification Co. used the Joostcn process to stabilize the sand in the tunnel's path. This process, named after Hugo J. Joostcn, a Netherlands mining engineer, chemically solidifies loose soils and sands that arc permeable to water. Two solutions are injected into the trouble spot. T h e first is an almost saturated solution of sodium silicate (watcrglass) and the second is a strong saline solution, such as calcium chloride. These solutions react chemically with the soil to precipitate, instantly, a silicic gel. The gel coats individual sand particles with a thin film of high surface tension. This cements the particles and, as the gel fills the spaces between particles, scaling is effected. As cementing continues, additional pressure pushes excess water beyond the solidifying range. For this kind of work, the Joosten process has these advantages : • Immediate solidification occurs with no setting time required. • Ground waters do not dilute the chemical solutions.
• Solidification is independent of the nature of the soil and little affected by its chemical properties. • Few items of equipment are needed. • True solutions arc used to penetrate small-pored and fine-fissured material that would filter out cement in suspension. At the Tioga No. 2 mine, work began by chemically stabilizing the quicksand at the upper heading. T h e solutions were prepared at the tunnel entrance and compressed-air pumps forced the solutions to the heading through 1-inch lines. Three scries of pipes were driven at the face to inject the solutions into the soil. One series was driven around the circumference of the tunnel to a depth of 3 feet ; a second series went ahead of the face and flared to the sides to solidify a section into a truncated cone; the third scries of pipes was driven ahead of the tunnel, in the line of advance, to a distance of 8 feet. This pattern gave a solidified area large enough to permit a safe tunnel advance of 6 to 10 feet with a 2-foot thickness of firm ground left in the face. With the pipes in place, the sodium
Stabilized ground 2 2 ' layer quicksand
l " d i a . pipes
CALCIUM CHLORIDE
GRAND RAPIDS HERALD-R EVI EW. GRAND RAPIOS, MINN.
Schematic of injection e q u i p m e n t used to solidify quicksand b y the Joosten process d u r i n g tunneling operations a t T i o g a N o . 2 mine 36 A
INDUSTRIAL AND ENGINEERING CHEMISTRY
CHEMICAL SOIL SOLIDIFICATION CO.
Previously unstable quicksand is now safe f o r operations a f t e r chemical t r e a t m e n t
tunneling
Information silicate solution was injected under pressure. This forced out and replaced the water in the area. T h e pipes were flushed sparingly with water and then the calcium chloride solution was injected. T h e pipes were withdrawn 1 foot and the two solutions were again pumped into the face. This process was repeated until the pipes were withdrawn from the holes. After a section had been stabilized, crews advanced the face 6 to 8 feet, leaving a 2-foot plug of firm ground in advance of the face. Once through the quicksand, they resumed normal tunneling operations. T h e pattern and spacing of pipes, injection pressures, and viscosities of solutions vary depending upon the particular soil solidification job. All of this, of course, is planned in advance on the basis of soil's grain size, permeability, and laboratory solidification tests. Although chemical soil solidification solves many tough tunneling problems, it is definitely not a cureall. Clays and fine silts cannot be stabilized yet. Swiftly flowing ground waters pose a problem because they may wash away the solutions before they have a chance to be effective. And finally, cost may become prohibitive in areas containing large crevices and voids. E.V.A.
Menhaden — a Fish with a Tale Chemicals, mainly BHT antioxidant, protect fish meal, upgrade it as animal supplement I HE menhaden, a prolific fish found along Atlantic and Gulf coasts, plays the hero of an industrial story that brings in "royalties" of about $49,000,000 a year. This figure, the current value of three main menhaden products— meal, condensed solubles, and oil— is a far cry from the rural economics of a couple of centuries ago. Then,
Analysis Interpretation
I/EC
Two purse boats (right) pay out seine in menhaden waters off North Carolina coast, as smaller "striker" boat drives fish toward seine
American Indians and colonists used the fish as fertilizer. Nobody made much money from it. Today, little or no menhaden goes into fertilizer. Use in agriculture has turned from plants to animals as feed supplements. Its oil is an important industrial commodity in the U. S.; most goes abroad, however, for making margarine. Processing of old with manual mashing and grinding has given way to modern mechanical techniques with little manual labor from the time the boats dock until the products leave the factories in tankers or freight cars. And chemicals, chemical research, and engineering have found an important place in the industry. One company, for instance, Marine Chemurgics, Inc., of Morehead City, N. C , exists solely to serve the industry. Its j o b : process and product improvement, quality control, new uses, and myriad other duties. Among chemicals, antioxidants have stepped into the scene in recent years. Fast catching on, the trend is toward more use. One of the leading suppliers is Eastman Chemical with its Tenox BHT, a food-grade antioxidant known chemically as butylated hydroxytoluene. According to Theodore M . Miller, president of Marine Chemurgics, antioxidant improves handling properties and quality of fish scrap (scrap is the solid material to be ground into meal). T h e Morehead City-Beaufort, N. C , area is one of the centers of the menhaden industry, listing these major firms: Wallace Fisheries Co.,
Beaufort Fisheries, Fish Meal Co., Brunswick Navigation Co., Standard Products of N. G , and R. W. Taylor. Plants vary a bit in detail, but little in basic processing methods. Once the fishing boats return from a day's catch, they unload their valuable cargo by fish pumps. A rotating hopper measures the catch (96 gallons of menhaden means 1000 fish by industry definition ; average weight of 1000 is 666 pounds). From the hopper, fish go into a storage compartment called a raw box, then into cookers. A screw conveyor or revolving paddles move the fish through this long narrow cooker, equipped with a line of live steam jets, where positive steam pressure remains at about 10 pounds. The raw material cooks about 5 minutes, and the trick is to coagulate the protein and break the fat from the surrounding tissues without overheating. Temperature of the cooked product rarely exceeds 180° F. The resulting solids and liquors move into presses that squeeze out additional liquor, leaving a wet scrap called press cake, about 5 0 % water. This is sent through direct heat or steam dryers which reduce moisture to 9 to 10%. During drying the raw material needs constant attention. If moisture content gets much below 10%, the material overheats and damages protein. Marine Chemurgic chemists regularly test for moisture at plants they serve. B H T enters the process after the drying operation. It is thoroughly mixed into the scrap, and pneumatic VOL. 5 1 , NO. 2
·
FEBRUARY 1959
37 A
