Urea can be produced as prills, granules, pellets, crystals, and solutions.
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This produced prills of copper, embedded in lumps of slaggy matter, which were chemically indistinguishable from EBA examples of 'A' metal.
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The melt is then pumped to the top of a prill tower into a prill pot from which it is sprayed against an approaching stream of air from the bottom of the tower, in the process making solid ammonium nitrate prills. These prills are then coated with a 0.15% dolomite-based coating agent prior to bagging and dispatch.
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The Fertilizer Encyclopedia. John Wiley & Sons. . . Melted material may also be atomized and then allowed to form smaller prills that are useful in cosmetics, food, and animal feed.
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One particular technique to mitigate these disadvantages has been to encapsulate prills of urea with less-soluble chemicals. These coatings permit the gradual release of urea in a controlled fashion, allowing for less-frequent applications.
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In June 2015, John created the Primitive Technology Blog on WordPress. That blog was a primary source of his videos through August 2018 when he posted the "Iron Prills" Video, whereupon John moved exclusively to YouTube.
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Often solids are available as prills, a solid globule. Liquid fertilizers comprise anhydrous ammonia, aqueous solutions of ammonia, aqueous solutions of ammonium nitrate or urea. These concentrated products may be diluted with water to form a concentrated liquid fertilizer (e.g., UAN).
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The prills or granules may be further dried, cooled, and then coated to prevent caking. These prills or granules are the typical AN products in commerce. The ammonia required for this process is obtained by the Haber process from nitrogen and hydrogen. Ammonia produced by the Haber process can be oxidized to nitric acid by the Ostwald process. Another production method is a variant of the nitrophosphate process: :Ca(NO3)2 \+ 2 NH3 \+ CO2 \+ H2O -> 2 NH4NO3 \+ CaCO3 The products, calcium carbonate and ammonium nitrate, may be separately purified or sold combined as calcium ammonium nitrate.
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For its main use as a fertilizer urea is mostly marketed in solid form, either as prills or granules. The advantage of prills is that, in general, they can be produced more cheaply than granules and that the technique was firmly established in industrial practice long before a satisfactory urea granulation process was commercialized. However, on account of the limited size of particles that can be produced with the desired degree of sphericity and their low crushing and impact strength, the performance of prills during bulk storage, handling and use is generally (with some exceptions) considered inferior to that of granules. High-quality compound fertilizers containing nitrogen co-granulated with other components such as phosphates have been produced routinely since the beginnings of the modern fertilizer industry, but on account of the low melting point and hygroscopic nature of urea it took courage to apply the same kind of technology to granulate urea on its own.
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Sodium hydroxide is industrially produced as a 50% solution by variations of the electrolytic chloralkali process. Chlorine gas is also produced in this process. Solid sodium hydroxide is obtained from this solution by the evaporation of water. Solid sodium hydroxide is most commonly sold as flakes, prills, and cast blocks.
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Shalev, S. 1994. The change in metal production from the Chalcolithic period to the Early Bronze Age in Israel and Jordan. Antiquity 68: 630–637. The only production remains of metal are those of copper and include copper slag, prills, and amorphous copper lumps and small shallow ball-shaped clay crucibles with a socket.
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Charging a hole with ANFO for rock blasting In the mining industry, the term ANFO specifically describes a mixture of solid ammonium nitrate prills and diesel fuel. Other explosives based on the ANFO chemistry exist; the most commonly used are emulsions. They differ from ANFO in the physical form the reactants take. The most notable properties of emulsions are water resistance and higher bulk density.
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Prills are formed by allowing drops of the melted prill substance to congeal or freeze in mid-air after being dripped from the top of a tall prilling tower. Certain agrochemicals such as urea are often supplied in prilled form. Fertilizers (ammonium nitrate, urea, NPK fertilizer) and some detergent powders are commonly manufactured as prills.Vasant Gowariker, V. N. Krishnamurthy, Sudha Gowariker, Manik Dhanorkar, Kalyani Paranjape (2009).
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The prills are then extracted by crushing the slag, and then melted together to form ingots, which were fashioned into various items. The Chimú also shaped metals through hammering, as displayed in the image on the right of the silver Chimú beaker. Chimú metalsmiths achieved this technique with simple tools and a single sheet of gold. The artist would first carve a wooden mold.
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Coated urea fertilizers are a group of controlled release fertilizers consisting of prills of urea coated in less-soluble chemicals such as sulfur, polymers, other products or a combination. These fertilizers mitigate some of the negative aspects of urea fertilization, such as fertilizer burn. The coatings release the urea either when penetrated by water, as with sulfur, or when broken down, as with polymers.
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When distributed for this use, it usually takes the form of small, white spheres a few millimeters in diameter, called prills. Solutions of calcium chloride can prevent freezing at temperatures as low as −52 °C (−62 °F), making it ideal for filling agricultural implement tires as a liquid ballast, aiding traction in cold climates. It is also used in domestic and industrial chemical air dehumidifiers.
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For fertilizer use, granules are preferred over prills because of their narrower particle size distribution, which is an advantage for mechanical application. The most common impurity of synthetic urea is biuret, which impairs plant growth. Urea is usually spread at rates of between 40 and 300 kg/ha (35 to 270 lbs/acre) but rates vary. Smaller applications incur lower losses due to leaching.
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Blasting-grade AN prills are typically between 0.9 and 3.0 mm in diameter. Finely powdered aluminium can be added to ANFO to increase both sensitivity and energy; in commercial usages however, this has fallen out of favor due to cost. ANFO has a bulk density of about 840 kg/m3. In surface mining applications, it is typically loaded into boreholes by dedicated trucks that mix the AN and FO components immediately before the product is dispensed.
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They used arsenic to harden the metals after they were cast. Large-scale smelting took place in a cluster of workshops at Cerro de los Cemetarios. The process starts with ore extracted from mines or a river, which is heated to very high temperatures and then cooled. The result is a group of prills, such as small round sections of copper, in a mass of slag, which are other materials which are not useful for metallurgy.
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Tovex is a 50/50 aqueous solution of ammonium nitrate and methylammonium nitrate (sometimes also called monomethylamine nitrate, or PR-M), sensitized fuels, and other ingredients including sodium nitrate prills, finely divided (paint-grade) aluminum, finely divided coal, proprietary materials to make some grades cap sensitive, and thickening agents to enhance water resistance and to act as crystal modifiers.Guide for the Selection of Commercial Explosives Detection. The detonation velocity of Tovex is around 4,000 to 5,500 m·s−1. The specific gravity is 0.8–1.4.
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They show no signs of slag or metal prills suggesting that zinc minerals were heated to produce zinc vapor which reacted with metallic copper in a solid state reaction. The fabric of these crucibles is porous, probably designed to prevent a buildup of pressure, and many have small holes in the lids which may be designed to release pressure or to add additional zinc minerals near the end of the process. Dioscorides mentioned that zinc minerals were used for both the working and finishing of brass, perhaps suggesting secondary additions.Craddock and Eckstein 2003, p.
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Prills of paraffin wax: a versatile, inexpensive, and popular phlegmatizing agent used in the high explosive fillings of various munitions A phlegmatized explosive is an explosive that has had an agent added to stabilize or desensitize it. Sometimes this is desirable either to improve the handling properties of an explosive (e.g. when munitions are filled in factories) or to reduce its sensitivity, brisance or detonation velocity. TNT explosive can itself be used to phlegmatize more sensitive explosives such as RDX (to form Cyclotol), HMX (to form Octol) or PETN (to form Pentolite).
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The industrial production of ammonium nitrate entails the acid-base reaction of ammonia with nitric acid: :HNO3 \+ NH3 → NH4NO3 Ammonia is used in its anhydrous form (a gas) and the nitric acid is concentrated. The reaction is violent owing to its highly exothermic nature. After the solution is formed, typically at about 83% concentration, the excess water is evaporated off to leave an ammonium nitrate (AN) content of 95% to 99.9% concentration (AN melt), depending on grade. The AN melt is then made into "prills" or small beads in a spray tower, or into granules by spraying and tumbling in a rotating drum.
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Roman ingots of lead from the mines of Cartagena, Spain, Archaeological Municipal Museum of Cartagena The earliest metal manipulation was probably hammering (Craddock 1995, 1999), where copper ore was pounded into thin sheets. Beneficiation, or the process of ’making better’ could be carried out on the ore (if there were large enough pieces of metal separate from mineral) or after melting, where the prills of metal could be hand picked from the cooled slag. Melting beneficiated metal also allowed early metallurgists to use moulds and casts to form shapes of molten metal (Craddock 1995). Many of the metallurgical skills developed in the Bronze Age were still in use during Roman times.
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While the density of pure crystalline ammonium nitrate is 1700 kg/m3, individual prills of explosive-grade AN measure approximately 1300 kg/m3. Their lower density is due to the presence of a small spherical air pocket within each prill: this is the primary difference between AN sold for blasting and that sold for agricultural use. These voids are necessary to sensitize ANFO: they create so-called "hot spots".It was found by the IRA, in response to using low-brisance AN fertilizers, that "hot spots" can be created by blending powdered sugar into the ANFO mixture, effectively sensitizing the mixture to mining-standard prilled ammonium nitrate effectiveness in which the interaction of the detonation front with a spherical void concentrates energy.
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A video on safety precautions at blast sites The largest commercial application of explosives is mining. Whether the mine is on the surface or is buried underground, the detonation or deflagration of either a high or low explosive in a confined space can be used to liberate a fairly specific sub-volume of a brittle material in a much larger volume of the same or similar material. The mining industry tends to use nitrate-based explosives such as emulsions of fuel oil and ammonium nitrate solutions, mixtures of ammonium nitrate prills (fertilizer pellets) and fuel oil (ANFO) and gelatinous suspensions or slurries of ammonium nitrate and combustible fuels. In Materials Science and Engineering, explosives are used in cladding (explosion welding).
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Currently, no production remains or production sites of these prestige/cult objects were found. Unalloyed copper tools comprising mainly relatively thick- and short-bladed objects (axes, adzes, and chisels) and points (awls and/or drills) made from a smelted copper ore, cast into an open mould and then hammered and annealed into their final shape. The copper tools were produced in the Chalcolithic villages on the banks of the Be’er Sheva valley where slag fragments, clay crucibles, some possible furnace lining pieces, copper prills, and amorphous lumps were found, in addition to high-grade carbonated copper ore (cuprite). The ore was collected and selected in the area of Feinan in Trans-Jordan and transported to northern Negev villages some 150 km to the north, to be smelted for the local production of these copper objects.
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