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Electromagnetic & Ultrasonic Methods for Processing Coal & Oil Shale









Plasma Torch

US Patent # 3,122,212: Method & Apparatus for Drilling of Rock ~
High voltage /low current is introduced to an air-fuel flame to drill rock.

USP # 3,443,639: Consolidating Sand w/ Plasma Jet ~
 Boreholes are consolidated by fusion of sand w/ a plasma torch.

WIPO Patent # WO 01/33056 A1 ~  PCT/US00/25293 (1 May 2001): Low Power Compact Plasma Fuel Converter ~
Fuel-air mixture is treated w/ ~40 KV @ ~ 10 milliamps to 1 amp to reform the fuel by glow discharge. The High-V/Low-A Plasmatron is low cost, has long electrode life, uses a simple power supply & control, & eliminates need for an air compressor. A catalytic reaction zone can be added downstream.

US Patent Application 2002/0012618 A1 (Jan. 31, 2002): Plasmatron-Catalyst System ~
The system generates hydrogen-rich gas by catalytic reformation of air-fuel-water/steam. The system increases H yield and decreases the amount of carbon monoxide.

Koks, Smola, Gaz (Pol.) 29(8-9) 215-217 (1984) ~ Chemical Abstracts (CA) 102:151899 ~ Gasification of lignite by low temperature H plasma ~
Highest yields of C2H2 (25.3% based on converted coal) and CO (19.8 %) were obtained w/ countercurrent powdered coal-plasma flow. In addition to C2H2 and CO, the reaction also gave C2H4, CO2, and C6H6.

Japan Patent # JP 11-3,542,900 (1999): Pulverized Coal Igniting Plasma Torch

USP # 4,487,683 ~ (CA 102:81593): Acetylene from Coal & Electric Arc ~
Pulverized coal & methane is introduced into an electric arc to form a plasma at 8000-10,000* F, which is then cooled to 5000-6000 & held @ this temp for ~ 60 ms. Liquid slag & product exit. Product contains primarily C2H2, C6H6, & a medium BTU fuel gas.


Radio Frequencies

Hungarian Patent # 19,498 ~ (CA 95:135690) ~ Coal Refining by GHz EMF ~
Lower quality coals, lignites, and oil shales were fractionated by treatment in high freq. EM fields at 100-160*. Thus, a lignite (caloric value 1700 KCal/kg, H2O 51%, ash 13%) was heated 46 minutes in a 2.55 GHz EM field at 120* in air to give a coal with calorific value 4649 Kcal/kg containing 51.3% C, 8.4% H2O, and 15.4% ash plus 350 gr H2O, oil & gas 10 gr, & tar 32 gr/kg

Belgian Patent # 481,314 ~ (CA 44:3246) ~ Conversion of Crude Oils & Shale Oils into Gasoline by Ultra-Short EM Waves ~
“Very short EM waves produce an effect similar to thermal cracking but at a lower temperature & w/ higher yields.”

French Patent # 973,715 ~ (CA 47:2461) ~ Destructive Hydrogenation @ Low Temp & Low Pressure w/ Radio Frequencies (1-3 MHz) ~
Stationary waves are established w/ points of high T & P & conditions that usually are obtainable only in an autoclave can be obtained in contact w/ atmosphere. Shale, lignite, coal, peat, &c., are treated to produce oxides, aldehydes, alcohols or acids.

German Patent # DE 901,048 (7 Jan. 1954) ~ Gas Reactions in a Magnetic Field ~
Gas reactions in a magnetic field w/ Si & Ni alloy w/ Co & Fe (catalysts for oil cracking) increases susceptibility. Lines of force concentrate in the reaction space, & side reactions are prevented. The catalyst can be made to vibrate by interruption of the magnetic field (i.e., magnetostriction ultrasonics)

Oil Shale Symp. Proc. 12: 283-298 (1979) ~ (CA 92: 211198 ) ~ Comparison of Dielectric Heating & Pyrolysis of USA Oil Shales ~
Dielectric heating is advantageous in terms of rate of heating, product recovery, effects of gas pressure, temp distribution, net energy ratios, in-situ gasification, & U leaching.

Japan Patent JP 84 49,292  ~ (CA 101 113850) ~ Microwave Molding of Lignite ~
Lignite is softened at 120* by microwave heating @ 2450 MHz and molded (400 kg/cm)


Ultrasound

Report DOE/PC/30143-T4 ~ Energy Res. Abstr. 7(10), Abstr. # 27651 (1982) ~ (CA 97:58220 ) ~ Ultrasonic Coal Cleaning ~
Ultrasonic activation of several coal cleaning processes in all cases "demonstrated effects that would translate in production to processing efficiencies and/or capital equipment savings. Specifically, in the chlorinolysis process, pyritic S was removed 23 times faster w/ ultrasonics than w/o it. In NaOCl leaching, the total S extraction rate was 3 times faster w/ ultrasound. Two benefits were seen w/ oxydesulfurization: ultrasonics doubled the reaction rate and at slightly accelerated rates allowed a pressure reduction from 960 to 500 psi".

British Patent # 737,555 ~ (CA 50:6109): Ultrasonic Gasification of Lignite ~
Gas-gas & gas-aerosol reactions are increased several hundred times by passing a supersonic shock wave through the mixture. Lignite dust having a caloric value of 5060 Kcal/kg is gasified in air at 1200-1700* & 0.8-1.5 atmospheres to give a gas having a caloric value of 745 KCal/cu meter by passing a shock wave of 125 MHz/sec through the mixture. The shock wave is generated by the periodic compression obtained by the exothermic reaction of coal dust with air.

Gov. Rep. Announce. Index (US) 90(23), Abstr. # 060,438 (1990) ~ Report, 1990, GRI-90/-163.1; Order #PB90-269622 ~ CA 115:32418 ~ Ultrasonic Gasification of Coal ~
Numerous operating conditions, catalysts & reactor configurations; "Overall, at the conditions and with the catalysts and slurry media tested, ultrasound was not effective in sustaining coal gasification reactions. The most favorable results were obtained w/ lignite-water slurry irradiated w/ high intensity ultrasound w/ KOH catalyst @ 550 F & 1050 psig. After 1 hour sonification, the C conversion to gas was about 5%... Ultrasound significantly increased the types & quantities of components that were solubilized... and reduced the particle size of lignite..."

French Patent # 973,715 ~ Cracking of Lignite & Shale w/ Ultrasound ~
Hydrogenation of oil shale & lignite @ low temperature & low w/ 1-3 MHz ultrasound.

USP # 2,722,498 ~ Ultrasonic Extraction of Oil Shale ~
Solvent extraction of shale oil is improved w/ ultrasound (400 KHz). The amount of organic material extracted is tripled and the time required is reduced by 90%.

USP # 4,280,558 ~ (CA 95:153539) ~ Ultrasonic Recovery of Oil from Sand ~
Water is pumped into an oil-bearing formation and ultrasound is applied to drive out the oil.

USP # 4,151,067 ~ Ultrasonic Extraction of Oil Shale ~
Oil is separated from a slurry of oil shale by treatment w/ ultrasound.

Brazil Patent # PI BR 82 04,258 ~ (CA 99:161300) ~ Ultrasonic Extraction of Oil Shale ~
A mixture of powdered oil shale & bitumen is heated to 300-400* and treated w/ ultrasound. "The process produces a higher yield than previous techniques, produces relatively few and environmentally acceptable emissions, and uses a minimal amount of water."

Brazil Patent # PI BR 80 08,635 ~ (CA 96:165417) ~ Ultrasonic Extraction of Oil Shale ~
Application of 20 KHz & 80 kg/cm2 to crushed oil shale for 1 minute generates internal temperatures up to 315*, liberating petroleum extracts.

Brazil Patent # PI BR 81 06,361 ~ (CA 97:112397) ~ UV-Ultrasonic Gasification of Oil Shale ~
Pulverized oil shale & TiO2-RuO2-Pt catalyst & H20 are irradiated w/ UV light @ 0.83u to give H & CO2. Ultrasound is used to maintain movement of the particles.

Fuel 68(10):1227-1233 (1989) ~ (CA 111:198237 ) ~ Ultrasonic Extraction of Coal ~
Ultrasound (0.455-1.46 W/cm2 ) can extract at least 58% of mobile organic matter w/o rupturing any chemical bonds. The average molecular weight of the extract is 340-1055

British Patent # GB 2,139,245 ~ (CA 102:64815) ~ Coal Cleaning w/ Ultrasound ~
Coal slurry (pH 6-9) is agitated w/ ultrasound and separated by centrifuging or froth flotation. A second treatment w/ ultrasound and ozone releases more contaminants.

Probl. Obog. Tverd. Goryuch Iskop. 5 (2): 70-80 (1976); Increasing Effectiveness of Coal Flotation w/ Ultrasound ~ (CA 87:154619 ) ~
15 sec treatment increases yield of concentrates to 78% (originally 66%). Exposure of slurry containing both collector (kerosene) and frothing agent sharply decreased flotation efficiency.

USP # 4,156,593 ~ (CA 91:94260) ~ Ultrasonic Wet-Grinding Coal ~
Coal contaminants (e.g., pyrites, clay) are removed from coal slurry @ relatively low temp & press & @ increased throughput rates by an ultrasonic source. Pyrites are reduced from ~ 30 % to ~ 0.7 %.

USP # 4,151,067 ~ ( CA 91:60105) ~ Ultrasonic Production of Shale Oil ~
A slurry of pulverized oil shale is treated w/ ultrasound to emulsify it. The emulsion is separated by aeration. "The process has only moderate requirements for heat and energy".

An. Quim. 86(2):175-181 (1990) ~ Ultrasonic Extraction of Tar Sand ~ (CA 113:234362 ) ~
Extraction of tar sands w/ a solution of sodium-silicate & ultrasound produces bitumen w/ very low ash content & virtually free of metals and asphaltenes, w/ ~ 95% cumulative recovery (based on C content) in a continuous operation.

USP # 4,054,506 ~ (CA 88:25480) ~ Extraction of Tar Sand w/ Solvent & Ultrasound ~
78% of the bitumen was removed in 60 sec; all of the bitumen was removed in 4 extractions w/ 60 KHz

Japan Patent JP 81,127,684  ~ (CA 96:71736) ~ Ultrasonic Hydrogenation of Coal ~
Powdered coal & catalyst (CuCl2-AnCl2) was hydrogenated w/ ultrasound (20 KHz) for 1 hr to nearly double the yield of the same reaction w/o ultrasound.

USP # 4,226,879  ~ (CA 93:222950 ) ~ Fluid Resonator ~
 A fluid resonator for recovery of oil, drilling, emulsification, & secondary recovery of oil; the fluid flows through and around cylinders positioned in the stream and parallel to the flow causes ultrasonic vibrations in fluid.

Japan Patent # JP 97 40,980 ~ (CA 126: 253301) ~
Dry coal preparation for a wide range of particle sizes; high efficiency removal of impurities (esp. sulfides).

Ranliao Huaxue Xuebao 24(4): 360-363 (1996) ~ Ultrasonic Treatment of Coal Slurry ~ (CA 125:304721 ) ~
Ultrasound greatly decreases viscosity & improves static stability of slurried coal; "All these results show that the ultrasonic treatment is a practical method to improve the high-load coal water slurry".

Prepr. Paper: Am. Chem. Soc., Div. Fue Chem 39(4):1223-7 (1994) ~ (CA 121:259407 ) ~ Deashing of Coal w/ Ultrasound ~
A crossbow filter w/ sonic waves radiated parallel to the filtering surface prevents buildup of solids at filter medium, eliminates clogging.

Proc. Intl. Conf. Coal Slurry Technol. 16: 323-334 (1991) ~ (CA 120: 275037 ) ~ Ultrasonic Ash/Pyrite Liberation ~
 Enhancement of ash & pyrite separation from coal by pretreatmnt w/ ultrasound.

USP # 4,391,608 ~ (CA 99:90944) ~ Ultrasonic Beneficiation of Coal ~
Slurried coal is deashed & desulfurized by treatment w/ ultrasound (20 KHz @ 0.7 W/cm2/30 min) followed by separation & washing. Froth flotation alone resulted in coal containing 5.03% ash & 1.22% S. Ultrasonic treatment resulted in 4.07% ash & 0.125% S.

USP # 4,537,599 : Ultrasonic Deashing/Desulfurization of Coal ~
Sulfur, clay & pyrite are removed from slurried coal by treatment w/ ultrasound

S. African Patent # ZA 80 06,424 ~ (CA 96:18067) ~ Ultrasonic Coal Cleaning ~
Slurried coal is irradiated w/ ultrasound to produce cavitation, reduce particle size, & detach pyrites & ash from the coal. The impurities are removed by density differences.

Japan Patent # JP 82,128,791 ~ (CA 98:56945) ~ Deashing of Coal w/ Ultrasound ~
Slurried coal is deashed by ultrasound; ash content is reduced from 14.1 to 5.4% by weight.

Japan Patent # JP 84,223,793 ~ (CA 102:206456) ~ Ultrasonic Deashing of Coal ~

Japan Patent # JP 84,142,289 ~ (CA 102:9523) ~ Ultrasonic Deashing of Coal ~

Japan Patent # JP 76,138,055 ~ (CA 87: 28575 ) ~ Removal of Oil from Waste Water ~
Emulsified oil (1 liter) is mixed w/ inorganic salt (CaCl, 40 gr), flocculant or electrolytic surfactant & exposed to ultrasound (20 KHz / 20 W / 10 min ) and settled 10 min, followed by removal of the floated oil. Treatment reduced wastewater content from 850 ppm oil & 1030 ppm COD to 15 ppm oil & 65 ppm COD.

USSR Patent # 126,072 ~ Apparatus for Concentration of Coal Fines Using Ultrasound ~

Report DOE/PC/88883-T9 ~ Energy Res. Abstr. 17(4), # 8452 (1992) ~ (CA 118: 237345 ) ~  ElectroAcoustic Dewatering (EAD) of Fine Coal ~
Pilot plant study for economic dewatering of -100 mesh & -325 mesh coal by synergistic combination of electric & ultrasonic fields in conjunction w/ conventional mechanical processes.

Godishnik Upravlen. Geol. Prouch., Otdel A-12: 97-104 (1961/62) ~ Ultrasonic Extraction of Bituminous Material from Sedimentary Rock ~
Ultrasonic vibration for 12 hrs nearly doubled the yield of material extracted, w/ no change in the character of the extracted bitumen.

Can. J. Chem. Engg. 61(5):697-702 (1983) ~ Ultrasonic Irradiation of Coal-Solvent Extraction ~

Japan Patent # JP 94,220,457 ~ (CA 121:304495) ~ Coal Liquefaction w/ Ultrasound ~
A slurry of coal and solvent is liquefied in an high-pressure H2 atmosphere w/ a catalyst and ultrasound. See also: JP 94 108,062 & JP 94 108,061 &  JP 94,108,060 (CA 121:13753 )

~ Powder Technology 40(1-3):187-194 (1984) ~ (CA 102:48468 ) ~ Selective Agglomeration of Coal Slimes w/ Ultrasound ~
Acoustic agitation is much more efficient than mechanical-rotational agitation w/ an impeller mixer.

 Sudovye Energ. Ustanovki 1981, pp. 21-24 ~ (CA 98:21738 ) ~ Ultrasonic Separation of Oil-Water Emulsion ~
10-15 minutes irradiation of unstabilized water-oil emulsions, e.g., petroleum-containing ship wastewaters, w/ an asymmetric sound field increases the rate of emulsion separation 15 times compared w/ untreated emulsions.

Japan Patent 81,52,613 (CA 96:180491): Ultrasonic Mixing ~
Fuel oil & water are mixed & atomized in air by ultrasonic apparatus designed to increase the efficiency of fuel combustion.

J. Appl. Chem. 20(8): 245-251 (1970): Ultrasonic Solubilization of Coal ~
"The amount of coal solubilized is a function of time & particle size. The use of char prepared at the temperature of maximum coal fluidity increased the amount of material solubilized".

Wien. Mitt.: Abwasser-Gewasser 1971, 6, K1-K18 ~ (CA 79:57346 ) ~ Ultrasonic Clarification of Oil Industry Waste Water ~
"Ultrasound provides an effective means for clarification of waste water from the oil, metal , and pharmaceutical industries..."

Neftepererab. Neftekhim. (Moscow) 10:14-16 (1981) ~ Ultrasonic Stabilization of Fuel ~
"Ultrasound disperses asphaltenes and tars present in diesel fuels, thus improving their storage stability... Ultrasound (15 KHz) disperses all sedimenting impurities in a few minutes giving stable fuels".

Japan Patent # JP 82,119,822 ~ (CA 97:219406) ~ Ultrasonic Emulsification of Oil-Water ~

USP # 4,126,547 ~ (CA 90:156672) ~ Ultrasonic Oil Spill Removal ~

Belgium Patent # BP 874,315 ~ (CA 91:177966) ~ Ultrasonic Preparation of Coal Slurries ~


Electro-Carbonization/Gasification

Univ. Missouri School Mines & Met., Bull., Tech. Ser. No. 78 (1952), 84 pp.: The Process of Underground Electrocarbonization ~
Review of methods used in 8 Euro countries & USA: chamber, stream, borehole, filtration linking, and hydrolinking. Electrocarbonization (EC) involves drilling boreholes, installing steel pipe, pre-heating, electro-linking (~ 30 min), EC (3-4 hrs), electro-gasification (w/ air/steam injection) yields producer gas, 120-300 BTU. Electro-carbonization takes place in a dumb-bell-shaped elliptical zone, the long axis being fixed by the electrodes. Fire channel fractures form, and considerable fusion occurs.

Producers Monthly 16(11):14-20 (1952) ~ (CA 50: 2151 ) ~
At a critical voltage level, current may be caused to flow through an oil shale or sand bed, resulting in the gradual development of a path of carbonized particles from one electrode to another. Oil & gas are produced by low-wattage electrical heating of shale and tar sand; the path of carbonization is used as a heating element.


Electro-Osmosis

There are dozens of patents for various forms of electro-osmosis, some of which also may be applicable to coal. The following are specific to coal:

USP # 2,799,641 ~ Electrolytic Promotion of Oil Well Flow ~
Pulsed DC stimulation of oil flow can double production.

USP # 3,417,823 ~ Electro-Osmosis of Oil Well Water ~
Water is electrically transported to the cathode and removed to improve the permeability of the remaining oil.

J. Canadian Petroleum Technology 3:8-14 (Spring 1964): Electro-osmotic Increase of Reservoir Flow Rate ~


Electro-Chemical

USP # 4,043,884 ~ (CA 87:143348) ~ Electrolytic Hydrogenation of Oil Shale ~
Kerogen is upgraded by extracting it from oil shale and treatment w/ reductive electrolysis.

Sci. Technol. Oil Shale 1976, pp. 83-101 ~  Electrolytic Oxidation & Reduction of Oil Shale ~
Almost all the higher hydrocarbons are removed by the process; about 73% of the hydrocarbons were oxidized & dissolved. See also: USP # 4,045,313 ( CA 87:143372 ).

Report 1984, DOE/FE/60339-T2 ~ Energy Res. Abstr. 10(1), Abstr # 8 (1985) ~ (CA 102:169454 ) ~
Electrochemical desulfurization w/ simultaneous production of H @ 75*, 1.2-1.3 V, almost 100% electrical efficiency, ~ 53% removal of S. Addition of HI catalyzes reaction: 83% removal of S.

USP # 4,043,885 (CA 87:143346 ) ~ Electrolytic Removal of Pyrite from Oil Shale ~
75-95% of the total S is removed after 1-5 hr of electrolysis and 83-95% of S converted to sulfate.

CA 85:49084 ~ Fuel 55(1):75-78 (1976) ~ Electrolytic Removal of Pyrite from Oil Shale ~
Electrolytic treatment of kerogen concentrates removes pyrite. The process uses alkali existing in the shale as electrolyte.

USP # 4,045,313 ~ Electrolytic Recovery of Bitumen from Oil Shale ~
About 75% of the organic hydrocarbons are oxidized & dissolved in the alkaline electrolyte.

Proc. Electrochem. Soc. 84-5: 492-509 (1984) ~ Anodic Oxidation of Coal Slurries ~
Up to 50% of the lignite slurry in NaOH @ rm temp & electrolyzed (1.2 V) dissolved as humic acids (= fertilizer). An increase in potential (2.5 V) gave more humic acids. Higher potential decreases formation of humic acids. Other reaction products: CO2 & H @ anode & cathode, & removal of over 70% of total S.

J. Electrochem. Soc. 128(10):2097-2102 (1981) ~ Electrolysis of Coal Slurries ~
"Coal slurry electrolysis as a method for cheap H evolution is not a good prospect, because of the low c.d. available after the removal of Fe. [Add Fe?]

USP # 4,043,881  ~ (CA 87:143370) ~ Electrolytic Recovery of Oil From Retort Water ~
Electrolysis of shale oil retort water yields ammonia; 40-50% of the total residue and 80-90% of the organic chemicals were recovered at the anode. The COD value was reduced to ~ 65%.

USP # 3,915,819 ~ Electrolytic Purification of Oil ~
Sulfur is removed from crude oil and an electrolyte w/ low-V/High-A DC .

USP # 555,511 ~ Coal Battery ~
Coal logs (produced by LTC) in electrolyte (molten NaOH), bubbled w/ air: "Average electrical HP developed: 2.16 HP ~ Average electrical HP used by air pump: 0.11 ~ Average net electrical HP developed: 2.05 ... ~ Carbon consumed in pots per electrical HP: 0.223 lb  ~ Coal consumed on grate per electrical HP: 0.336. "

Total fuel consumed per electrical HP: 0.559 ~ Electricity obtained from 1 lb of coal*: 1336 watt hours (32% of that theoretically obtainable) ~ (* 0.4 lb in pots & 0.6 lb on grate). Thus the efficiency of this particular generator was 12 times greater than that of the average electric light and power plant in use in this country, and 40 times greater than plants of corresponding size.

Fuel 28(1):6-11 (1949) ~ (CA 43:1664 ) ~ Production of Electricity from Coal by Electrochemical Means ~


Electrostatics

Chem. Engg. Commun. 108: 49-66 (1991) ~ (CA 116:43943 ) ~  Electrostatic [ES] Beneficiation of Oil Shale ~
Oil shale pulverized to 5 microns can be completely liberated of mineral inclusions from the organic matrix by electrostatic treatment with a copper tribocharger. Kerogen is enriched from 12% in feed to ~ 34% in the product stream.

CIM Bull. 73(822): 51-61 (1980) ~ (CA 88:194216 ) ~ ES Beneficiation of Fluidized Coal ~
"Recoveries & ash contents of beneficiated coal are comparable to recoveries by water washing, but the dry process avoids potential water pollution problems".

J. Powder Bulk Solids Technol. 1(3):22-26 (1977) ~
An ES separation tower & ES beneficiation loop were tested; yields coking concentrate high in vitrinite and low in pyrite & ash.

J. Coal Res. Inst. (Jap.) 2:97-104 (1951) ~ ibid., 3:11-16 (1952) ~  (CA 49:7220 ) ~
ES beneficiation w/ 30-35 KV produced a concentrate of coal.

Suiyokaishi 15: 51-56 (1963): ES Concentration of Coal ~
Low-Fe coal is attracted to the corona-discharge rollers & high ash/high-Fe coal is repelled.

Feiberger Forschungsh. A326: 161-165 (1964): ES Enrichment of Coal ~
The coal concentrate w/ low-ash/Fe is attracted to the grounded cylinder of a Huff separator. Coal particles w/ high ash/Fe are repelled in the corona field. "Separation is more effective in the corona field compared w/ that without corona discharge".

Nenryo Kyokai-shi 48(512):869-876 (1969): ES Separation of Coal ~
Coal was concentrated in a Huff-type electrostatic separator w/ or w/o corona discharge (15-20 KV) The recovery rate was >96% and the optimum relative humidity was nearly 60%.

Braunkohlenarchiv. 56:29-48 (1949) ~
Up to 94% of metal impurities can be separated from powdered coal by ES treatment w/ 25 KV.

Obogaschen. Polenz. Iskop., Akad. Nauk SSSR, Inst. Gorn. Dela 1960, pp 168-174 ~ ES Separation of Large Particles from Coal ~
Pilot plant for electrostatic precipitation of large particles from coal fines. Grounded collector electrode, DC corona discharge. 90-95% efficiency.

Ind. Eng. Chem. Fundamentals 1(1):48-52 (1962) ~ ES Mixing ~
ES forces produce an extremely fine dispersion w/o moving parts.

Nauch. Soob. Inst. Gorn. Dela (Moscow) 45:31-38 (1968): Electroseparation of Coals ~
Corona discharge separation of coking coal used for sulfonation gives simultaneous partial removal of coal impurities. Power consumption: ~ 0.1 KW-br/metric ton. Efficiency: 90%


Magnetism

Magnetic Separation is a well- established technology that need not be treated here. The following example will suffice:

Coal Process Tech. 5: 19-23 (1979) ~ (CA 92:183360 ) ~  Coal Beneficiation w/ Magnetic Fields ~
"The process is useful in supplementing conventional dense-media washing".





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