DE1928872A1 - Densified sodium cyanide and process for making one - Google Patents

Description

Condense tea Watriutaeyanid and method of rolling down such

The invention relates to a method for compressing sodium vacjanide and water-free pellets or briquettes obtained from the compressed sodium eyanide.

Bit extraction of. Natriuraeyanid by evaporation of an aqueous solution is familiar. But I> aa 30 preserved, dried product provides a feinas is ₅ crystalline material

Handle because of the irritating and toxic nature ijich in conjunction handling resulting dust MIFC eat tat "In order to redress this deficiency in the

ysraöiiiedetifc: applied Agglomerierteehnilcen, like a tablet feieren, pelletizing or briquetting dee crystalline Ji itsi * ial3 "These compacted forms, however, are subject to the previously ..rieugtöB form from the ainen reason or another in the Vi-j c over küminerjsiellan handling loss and breakage and lead soniib kuiü re-emergence of the dust problema. The participating

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Some reasons vary, but are generally related to uncomfortable inner softness, low density, and weak bonds between individuals Particle.

According to the method according to the invention, sodium cyanide crystals with a moisture content of not more than 0.05 Sew. $ Are compacted under Wärine und Drusk into a translucent ₍ non-crystalline sodium cyanide plate "or" tape body "), the body is broken into granules or grains with a maximum size of 4 , 76 mm! Corresponding to a US Sieve Series sieve No. 4, that is, with a clear Maaohenweita of 4 * 76 ram; ASTM test standard EH-SI) _1. The grain is no longer a 10 to 25 # a a sieve of O ₁ of 297 mm Maachenv / PAGE (U.S. sieve Series sieve No. ₀ 50) aufwaict- corresponding Teilohengrösss, and classified the Kara in the jew "ils necessary V / else aif a content of Peinatofffen einsr a SISB of. £ h297 mm dimension width corresponding part size a «νen no more than $ 20> and returns the remaining finest © ff β vcm compressor *

The invention further provides a sodium anide bridge. It has a grain inner part with a planar surface between the grains with a bond strength equal to the splitting ability of an Eatriumeyanidluristail and with a substantially uniform Shore D hardness of at least 65 and a compacted outer part of higher hardness, the briquette has a relative density of at least about 0.97 and a speed equivalent to about 8 to 11 minutes standard nozzle time «

© AD 009808/1120

In the drawings shows:

Figure 1 shows the method according to the invention schematically in Flow diagram,

FIG. 2 graphically shows the briquette durability as a puncture the grain loading temperature at different pressures,

FIG. 3 graphically shows the briquette durability ala puncture the pressure during briquette formation at a grain loading temperature of 170 ° C,

Figure 4o and 4b graphically the briquette Gletchniüsaigkeit as Function of the characters of Kornbeachiclcungj being the inside hardness has been determined on a cross-section parallel to the roll surface,

FIG. 5 shows a graph of the specific gravity of briquettes as a function of the formation pressures at a grain loading temperature of 170 ° C ₁

Figure 6 graphically shows the relationship of the briquette density to the Kri Stall density as puncture of the formation pressure at a corr. loading temperature from 170 C and

Figure 7 grapbf.ach-aie briquette »Lb'aeseit al :? Puncture dea formation dungadi'uc? .3 Lui a Kornbeschiolamgsteaptrrat jr of ¹ TO ⁰ C.

As shown in llfxiv, crystalline3! 'Atriumcyania _{ or hold through. \ ¹ .inöa:.: Pf-Concentration of a .- "'isö'r.igen, cMrcl. Chenji3che Ü ^v " i -; - tzv \ n ^ svrischen Cj'anvaaeerstoiT and v'l ^ zv'i.g-sv

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Caustic soda solution obtained, separated from the mother liquor by filtration on the rotary drum dryer filter 10. Of the Filter hood is through the air heater 15 and the line 12 from the blower, which also removes the mist, 11 hot air in the temperature range from 250 to 450, preferably 375 to 400 ° C fed. The hot air causes a certain pre-drying of the filter cake and minimizes the further drying requirement in the process. The pre-drying lowers the moisture content sufficiently (less than 5% by weight), since a continuous supply of material to the air dryer venturi part 14 can be maintained without sticking and caking.

The partially dried sodium cyanide passes through the Mie.chförderer 13 »which divides the partially dried cake so far» that no pieces with a maximum dimension of more than about 5 cm (2 inches) remain and an even material feed to the dryer venturi tube part 14 can be maintained in the heater Vy heated, substantially carbon dioxide-free hot air is introduced through the line 16 at a temperature in the range of 275 to 400, preferably 350 to 375 ° C. The wet, 2 to 5t in general, however, about 3 ^ water containing Natriumcyanidkriatalle are pneumatically transported in the conduit 17 and adiabatiach to a substantially bone-dry state, the hel9st a moisture content of below about O ₁₁ OS wt. #, Preferably 0.03 wt . ^ _f dried. The temperature and the proportion of Hsieslui't in relation to the solids in the feed to the venturi part 14 are set so that the dried product discharged by the dryer conveyor 17 o a temperature in the bar of 175 to 250, preferably

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180 to 225 ° C. The dried product is discharged into the cyclone 18 in order to separate the solids in the feed container 19 of the compressor, while the! Rock, tion air is fed through the line 21 to the blower 20.

They are dried sodium cyanide Feinatoffe on the roll press 22 under heat and pressure to a translucent, nichtkriatalllnen disk or tape body with a face of in the range from 1.550 to 1.590 and preferably a bead of approximately 3 _f 17 to 4.76 mm (1/8 up to 3/16 inch) compacted. The fine material compression can take place in a wide temperature and pressure range. For example, the temperature can be in the range from 125 to 225 ° C. and the pressing pressure in the range from approximately 333 to 1000 atm. (5000 to 15,000 pounds / square inch), although preferably at a temperature of 180 to 225 ° C and a bridge of about 400 to 667 atm. (6,000 to 10,000 pounds / square inch) works. Under these conditions, the fine matter is transformed into a continuous, semi-plastic (bendable) plate or tape body of uniform texture that shows no signs of crystalline activity and has the translucent nature of milky quartz and has a density of 1.550 to 1.590. For belt gaps substantially in excess of about 4.76 mm (3/16 inch), e.g., about 6.35 ram (1/4 inch) or more, i <rfc is generally characterized by a non-uniformity in compaction IrJCh ₁ . which may be based on difficulties which arise in maintaining a continuous, glolchiaasaigan feeding. Through the natural action of the solids, which occurs during their agglomeration and during the tendency of compression to distribute and distort, this becomes

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009808 / 112Q

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Difficulty complicated. From this and in connection with the The fact that a thicker belt is used for shredding to a size corresponding to a sieve with a mesh size of 4.76 mm If it has to be "cut up" more often, the result is an excessive amount of dust in the grinding stage.

The semi-plastic, compacted sheet or strip material is then fed to a primary crusher 23 and subjected to partial breaking into irregular pieces of about 2.5 to 5.1 cm (1 to 2 inches) in size and then fed to the granulator 24, which is in the Kind of a modified hammer mill specially designed for a steered comminution. Due to the compression of the sodium cyanide crystals to a flat shape with the properties described above, the comminution takes place in the primary crusher 23 and granulator 24 without accumulation of large amounts of undesirable "fines". At the end of the sieve, the granulator 24 delivers a grinding raw good, oil * sowing content of material finer than sieve No. 50 10 to 2: 5 5 », while the remainder of the grain in the TellchengrusasKheraich of sieves Hr -4, +50 is formed One can here, einsotzsn hammers of various types and bsi Kopfgaaehwindls * -.. (?. 5 NC to 100 UAO / sec) chains of about 15.24 to 30.48 a / s work, but operates sur Brsielung üer desired "the Hammers preferably at Kopfgesöhu? indigkeltsn of at v / a 18.29 to 22.36 m / 8ek. (60 bia 75 Puse / sec.). In & hnliölseY LIAISE can 3UA views sieves veraahisdeaer Artew a ^ ae warden ', the reaction is carried vorzugswsloe but with sieves ** with ain s * Öf fillings flax of at least 60 $ _t where the openings are set so that the particles are the highest

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Orösee can passleren. However, if the band temperature is too low or if the band is formed at a low compression pressure, the amount of orangles generated during the granulation increases Feinstoffe strongly increases and easily exceeds 50 ^ "e" Hahl raw goods.

The granulated sodium cyanide product is introduced into the constriction of the VenturiBuführsra 25 of the Klaeeierera 26 and pneumatically conveyed through the line 27 eu the classifier. For the conveyance of the pre-compressed grain product, the venturi part 25 is fed through the line 28 from the blower so that the same, essentially carbon dioxide-free air is used with which the moist crystals are conveyed around the compressor.

The product grain is in the classifier 26 in a hot air " system classified so that the product of the classifier does not contain more than 20% by weight of fine substances of a size corresponding to the sieve no such material (it contains a maximum of 15% by weight of fines finer than sieve Mr. 50) and has an elevated temperature. Sin part of the dense product grain is made by the Line 29 is branched off to the product grain filling container 30. The remainder of the pre-compacted product grain passes through the line 31 to the feed container 32 of the briquetting device and then arrives at the briquetting press 33.

To achieve the desired combination of properties, namely, equal view: "Durability and controlled Pound speed of the briquetted product, lies the Temperature of the pre-compacted, classified product grain in

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Range from 125 to 200 ° C and the briquetting of the product grains takes place with a brack in the range of about 533 to 3000 atm. (5,000 to 45,000 pounds / square inch). To achieve special and preferred product properties, however, the pre-twisted grain charge material is heated at a temperature in the range from 150 to 175 ° C. and a pressure in the range from approximately 533 to 1000 atm. (8,000 to 15,000 pounds / square inch), preferably about 666 to 867 atm. (10,000 to "15,000 pounds / square inch) briquetted" Under these last-mentioned conditions, a tough, permanent briquette is produced, which is leveled out by a high relative density, equal internal hardness and high reading speed. Fracture examinations and crystallographic examinations of the internal grain structure “peculiar to the fact that there is a flat surface between the grains and that the bond between some grains has essentially attained a strength corresponding to the strength of the hatriuracyanide crystals themselves. A permanent briquette is obtained which can be handled in drums, conveyors and eo welter without breakage and without dust.

After briquetting, the briquettes are placed on the rotary sieve 34 » on which the "burrs" or thin layers of material sitting on the periphery of the briquette center line are removed, and on top the Briketi filling container 35 supplied.

The fines separated in the classifier 26, that is the product is one grain size finer than sieve Ur. 50, will returned by the fan 37 through the line 36 sum feed tank 19 of the compressor, in which aie are separated by the cyclone 38, while the exhaust air from the line 39 from

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Fan 40 is fed through line 42 to a circuit washer and condenser 41, in which it is set to 50 to 60 ° C is cooled and any possible dead spots Hydrogen cyanide and fine sodium cyanide dust are removed. The air then passes through line 44 to “another Washer 43 in which what is received in the drying stage Water and any residual cyanide should be removed. The hot air used to pre-dry the filter cake on the filter 10 is also cooled and washed in turn 43 in order to remove the lye that has been entrained, and for this purpose it enters the line 44 through the line 45.

The air is returned through the line 46 to the blower 11 and then through the line 47 to the heater 13 and thus runs through the process in a cycle. The total confinement and circulation of the air eliminates the negative effect of carbon dioxide on the sodium cyanide. With this closed air loop in connection with adiabatic drying, a significant reduction in the sodium carbonate and sodium formate content of the product is obtained and an analytical minimum sodium yanide content of 99 fo <is achieved

The peculiar physical properties of the sodium cyanide briquettes are explained in more detail in FIGS. To obtain the laid down in the figures Hatriumeyanidkristalle values were obtained with a moisture content below 0.03 wt. <& At 180 to 190 ° C and a compression pressure of about 466-533 atm. (7000 to 8000 pounds / square inch) precompacted on a horizontal roller press. The briquetting = lorabesehielmng had a part size of 88 % in the range of sieve no. -4, +50 and 12 · £ finer than sieve no. 50

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This grain, which in the particle form had a density of at least 1.55, was then briquettes formed at various temperatures and bridges. .

The briquettes were then subjected to the following tests:

Reading speed: To determine the loosening speed of the roughly egg-shaped cyanide briquettes in water are added (under Use of the number of whole briquettes which, with their total weight, are closest to the desired total weight come) approximately 227 g (8 ounces) briquettes of approx Ht 2 g (0.5 ounces) in a stainless steel wire basket (constructed from US Sieve Series 30 sieve material with a mesh size of 0.59 mm made of stainless steel of the type. 316 with a wire diameter of 0.33 mm) of about 15.2 cm Height and 11.4 ca diameter, which is about 7.6 cm away from the bottom of a 4 ~ 1 beaker that is 3.785 1 Contains water. Keep the water temperature at 60 ° C for the test and make sure that there is no movement. The time required for the last trace of each briquette to disappear is recorded separately. The mean of this Times for all briquettes is equal to the "dissolving speed".

Compressive strength: The briquette to be tested is placed on its side on the bottom plate of a Carver laboratory press, then placed between the top plate and the Insert a steel cylinder 2.54 cm in diameter at the top of the briquette and slowly increase the hydraulic pressure, where the measuring pressure is 1. when entering the first one visible crack running along the Great Transversal Radisna the top surface of the briquette, and 2 »at the point

009808/1120

on which the briquette crumbles and disintegrates is recorded. The compressive strength is recorded as the pressure at which the erete visible blow appears.

Hard The hardness tests are carried out at room temperature in a Atmosphere of low relative humidity (less than 35 pounds) carried out. To measure the internal hardness, halve the briquettes by cutting the length of the main axis in a plane perpendicular to the plane connecting the leading and trailing edges. The exposed cut surfaces are smoothed with extra fine sandpaper. The external hardness is measured on the surface of the entire briquette along the intended cutting line. For the thickness of the outer shell higher Hardness results in a value of about 2.54 mm, although the thickness from point to point of the briquette surface and also slightly old varying briquetting pressures. To determine the hardness, one places selected reference points along the center line a hardness meter of the type "Shore Burometer", A3TM »Marking D224O, type D, brings one Sufficient pressure to act to see a firm contact between the reference plate of the measuring device and the one to be measured Surface and reads the display (0 to 100) within one second of making firm contact and draws it directly as a hatred of relative hardship & uf.

Specific gravity »To minimize random errors, the test is carried out on a sample comprising 10 briquettes (this size of the sample being selected as being typical for Bilaungabeaingurj & en). The weight of the 10 briquette sample (in grams) is recorded to the first decimal place (i.e. to 5/100 grams) * The briquettes are now grounded in

009808/1 12Q BAD ORIGfNAi.

Transferred to a calibrated container, into which one can dry a known volume, white luminous oils or another Enter the non-solvent, whereupon the total volume of the briquettes plus the liquid is read off to the nearest tenth of a milliliter and the briquette volume is calculated as the difference. The calculation of the specific weight of the briquettes is then based on the formula:

tinmvA * aa *%> ** m ä- * h «Λι + Qweight of the briquettes Specific weight» Volume rits

All measurements are made at ambient temperature. The accuracy of this determination is a good tenth of a percent.

Relative density: The size that applies to the briquette as a whole applies and represents a calculated value, corresponds to the ratio between the measured density in the compressed state (specific weight) and the true crystal thickness of 1.596. At a relative density of 1.00 the density in the compressed state would be equal to the true crystal density

The results of the above tests are shown in figures 2 to 7 shown. You figure 2 shows the effect of the temperature of the charge and the pressure in the briquette formation ' on the durability of the sodium cyanide briquette in. Form of the Compressive force that is necessary to break or crush the briquette. While the general pattern of development may be expected, the obvious is convergence of the curves for 2000 and 4000 atm. (30,000 and 60,000 pounds / square inch) pressures at higher temperatures surprised"

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The results of further investigations are reproduced in FIG. 3, which clearly shows the verbal peak to be assumed on the basis of FIG. Bas decrease in durability at pressures above 3000 atm. (45,000 founda / square inch) is based on the result of fracture undercuts on the formation of internal stress levels, which act as points of incipient cleavage. This is supported by the results shown in Figures 5 and 6, according to which at formation pressures of 2000 Atm. (30,000 founds / square inch) at a feed temperature * of 170 ° C densities of the compacted. Unit ("unit density ¹¹ ) of 1.594 (specific crystal density * 1.596), which corresponds to a relative density of 0.998 (see FIG. 6). At pressures of over 3000 atm. (45,000 founds / square inch) and after the Relative density of 1.00, the excess pressure is divided into friction losses and the formation of internal stresses. A relative density of at least 0.97, based on a careful determination of the briquette density, is a critical value. It corresponds to a specific briquette density of approx. 55. With a relative density of 0.961 (specific gravity 1.5?) And dig briquettes are much less durable, and although their dissolving speed is higher, they are hasadihabianggmäßig due to the accompanying handling

Broken and dusty but far less satisfied.

BqI printing up to 3000 Atm. (45,000 founds / square inch) aijia vorvsrdehensetera Charged briquettes produced show how a comparison of the graphical representations of FIGS. 4a and 4b reveals “a significant increase the inner regularity.

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Ba the reading speed of briquetted Natriuraeyanii What is important for many uses is the effect of the formation pressures at 170 ° C on this property Figure 7 shown. As this figure shows, a reading speed of approximately β to 11 minutes is required to achieve a reading speed Formation pressure of about 536 to 1000 atm. (8,000 to 15,000 founds / square target) applied. A reading speed of 9 to 10 minutes old is preferred Formation pressure of about 666 to 867 atm. (10,000 to 13,000 pounds per square inch).

You obtained under the preferred conditions mentioned Briquettes have a smooth, continuous surface of pronounced uniformity, with no porosity noticeable even at 4 to 8 times magnification. Di © Yourself » te such briquettes can, as described above, directly without further preparation can be determined. Briquettes that are produced under conditions other than those mentioned above, e.g. with lower formation pressure and bsw. or at lower temperatures of the charge, often have a porosity that can be seen with the naked eye. Such briquettes must be covered with a thin coating or film a clear lacquer or other impermeable material. closed and dry completely, be left open, be ^ or they are examined for their specific viewpoint. Without such treatment, liquid will penetrate into the briquette and the provisions become incorrect. .

According to the method according to the invention, potassium » cyanide com and briquettes can be produced. This material isf commercially less significant than Hatrlumoyanlti and the need The potassium cyanide market can be satisfied by the Process occasionally carries out with xalium cyanide crystals.

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Claims (2)

June 6, 1969 Claims A method of producing compacted sodium cyanide by drying of moist sodium cyanide to a fine, crystalline material and compacting the dried _f crystalline material, characterized in that, preferably by drying to a moisture content ^ dee crystalline material of less than about 0.05 wt. Under about 0.03 wt. ^, and compaction at a temperature of 125 to 225 ° C, preferably 180 to 225 ° C and a pressure of 340 to 1021, preferably 408 to 680 atm. a translucent, non-crystalline, pre-compressed form, in particular a plate or tape body with a density in the compressed state of 1.550 to 1.590, preferably with a thickness of about 3.17 to 4.76 mm, and the material in the pre-compressed form of a guided Subjected to size reduction, preferably by pre-breaking into irregular pieces, in particular into those with a particle size of 2.5 to 5.1 cm, and granulating the pieces using a hollow raw material that does not exceed 25 fines and a sieve of 0.297 mm mesh size The remaining material preferably has a particle size in the range of a sieve of 4.76 mm to a sieve of 0.297 mesh size, if necessary, the material subject to the size reduction to a fine matter content of 0.297 mm Mesh size corresponds to the particle size of not more than 20? S classified and, if desired, the size Material subject to reduction, possibly also classified material, briquetted. - 15 009808/1120 Jib 2. The method according to claim 1, characterized in that roan the briquetting at a temperature of 125 to 200, preferably 150 to 175 ° O, and a pressure of, 340 to 3062, preferably 544 to 1021, especially 680 to 885 atm. performs. 3 * Method according to claim 1 or 2, characterized in that man.die promotion of the load su the before. sealing, size reduction, classifying «and briquetting» operations, preferably pneumatic, in a closed Cycle essentially carbon dioxide-free hot air carries out and the latter at the same time to the adiabatic Drying of the load during the demand for The sealing process begins. / 4 J Natriumcyanidkörper, particularly briquette, characterized by a grain inner part with a plane surface swi sch en grains of substantially the Spaltfestig · * ness of a Hatriumcyanidfcristails corresponding Binäungafestigkeit and with a consistently io substantially equal "mäBsigen Shore C hardness of at least 65 and a compacted outer part, preferably about 2.54 mm thick, with a hardness greater than that of the inner part, preferably with a Shore IK hardness of about 70, the body having a relative density of at least about 0.97 and about 8 up to 11 minutes of standard dissolving time has an equivalent dissolving speed. - 16 - ORIGINALINSi = ECTEO 0 0 9 8 0 8/1120 Blank page