Abstract: The invention relates to a method for producing alkali metal cyanides as solids, comprising the steps: i) an absorption step in the form of the absorption of hydrogen cyanide from a syngas containing hydrogen cyanide in an aqueous alkali metal hydroxide solution; ii) a preparation step for the waste gases containing cyanide that have accumulated in step i); iii) a crystallization step in the form of the introduction of the alkali metal cyanide solution into an evaporative crystallizer; iv) a condensation step for the vapour containing cyanide that has accumulated in step iii) to obtain a vapour condensate containing cyanide; v) a recirculation step, in which the vapour condensate containing cyanide that has been obtained in step iv) is used as an aqueous liquid in step ii).

Abstract: The invention relates to a process for the preparation of alkali metal cyanides as a solid substance, comprising the steps of: i) an absorption step in the form of an absorption of hydrogen cyanide from a hydrogen cyanide-containing synthesis gas in an aqueous alkali metal hydroxide solution; ii) a crystallization step in the form of introducing said alkali metal cyanide solution into an evaporative crystallizer; iii) a separation step; iv) a recycle step; v) a drying step.

Abstract: The invention relates to a method for producing alkali metal cyanides as solids, comprising the steps: i) an absorption step in the form of the absorption of hydrogen cyanide from a syngas containing hydrogen cyanide in an aqueous alkali metal hydroxide solution; ii) a preparation step for the waste gases containing cyanide that have accumulated in step i); iii) a crystallization step in the form of the introduction of the alkali metal cyanide solution into an evaporative crystallizer; iv) a condensation step for the vapour containing cyanide that has accumulated in step iii) to obtain a vapour condensate containing cyanide; v) a recirculation step, in which the vapour condensate containing cyanide that has been obtained in step iv) is used as an aqueous liquid in step ii).

Abstract: A process for the production of sodium cyanide crystals comprising; (a) contacting impure hydrogen cyanide and sodium hydroxide in a reactor with mixing for a maximum contact time of about 5 seconds; (b) feeding the resulting mixture to a continuous evaporative crystallizer to produce a slurry of sodium cyanide crystals; (c) passing the slurry of sodium cyanide crystals from the crystallizer over a hot surface to precipitate onto the surface and remove sodium carbonate, and passing said slurry back to the crystallizer; and (d) separating the sodium cyanide crystals from the slurry.

Abstract: The invention relates to a process for producing carbon fibres, in which polyacrylonitrile (PAN) is pyrolytically carbonized with liberation of hydrocyanic acid (HCN) to form carbon fibres and also a plant for carrying out the process. It is an object of the invention to make the process more economical. This is achieved by utilization of the hydrocyanic acid as material by collecting the hydrocyanic acid liberated and scrubbing it by means of an alkaline medium to give a liquor containing cyanide salt.

Abstract: A reactor for converting methane, ammonia and oxygen and alkaline or alkaline earth hydroxides into alkaline or alkaline earth cyanides by two-stage reactions comprising a first stage with a gas inlet, wherein the first stage is formed by a cone with distribution plates providing an even gas distribution over the catalyst material wherein the distribution plates are located between the gas inlet of the reactor and catalyst material and the distribution plates being perforated with a number of holes, with the distribution plates spaced from each other in the flow direction of the gas, the first distribution plate(s) functioning mainly to distribute the gas, whereas the last distribution plate works as a heat radiation shield and as a distribution plate facing the catalyst material, and wherein the catalyst material is present in the form of catalyst gauze fixed by catalyst weights.

Abstract: The present invention relates to solutions comprising water and at least one metal cyanide, at least a part of the water being obtained from wastewater which occurs as depleted wastewater in a process for extracting noble metals from noble metal-containing ores by the cyanide process, the process for the preparation of solutions according to the invention and to the use of the solutions according to the invention in a process for extracting noble metals from noble metal-containing ores by the cyanide process, to a process for extracting noble metals from noble metal-containing ores by the cyanide process, wherein the solution according to the invention is used, and to the use of depleted wastewater occurring in the extraction of noble metals from noble metal-containing ores by the cyanide process to the preparation of solutions comprising water and at least one metal cyanide.

Abstract: The present invention relates to an improved process for producing hydrocyanic acid by reaction of ammonia with methane in which a small amount of at least one sulphur-containing compound corresponding to the general formula R S (S)x—R? is added, in which R and R? which are identical or different, represent a linear or branched alkyl or alkenyl radical containing from 1 to 5 carbon atoms, and x is a number ranging from 1 to 5, to the reactive gas mixture before it passes over the catalyst. The process according to the invention makes it possible to obtain improved yields of HCN. Another subject of the invention relates to the use of the resulting product for producing methionine, acetone cyanohydrin, adiponitrile or sodium cyanide.

Abstract: A process for the production of sodium cyanide crystals comprising; (a) contacting impure hydrogen cyanide and sodium hydroxide in a reactor with mixing for a maximum contact time of about 5 seconds; (b) feeding the resulting mixture to a continuous evaporative crystallizer to produce a slurry of sodium cyanide crystals; (c) passing the slurry of sodium cyanide crystals from the crystallizer over a hot surface to precipitate onto the surface and remove sodium carbonate, and passing said slurry back to the crystallizer; and (d) separating the sodium cyanide crystals from the slurry.

Abstract: A method is shown for raising the pH of a cyanide leach solution of the type used in a heap leaching mining operation. Lime slurry is mixed with a side stream of barren cyanide solution in a reactor vessel in order to remove carbonate hardness, to regenerate the hydroxide alkalinity and to raise the pH of the resulting recausticized leach solution. A portion of the calcium carbonate precipitate formed in the reactor vessel is retained in order to encourage further crystal growth. Overflow from the reactor vessel passes through one or more cyclone separation stages in order to remove particulate solids. A cyclone overflow stream is directed back to the process to upwardly adjust the pH of the bulk of the barren cyanide solution. A cyclone underflow stream is directed back to the reactor vessel to provide seed crystal nuclei for precipitate growth.

Abstract: A process that can be used to produce NaCN is provided. The process comprises contacting hydrogen cyanide with sodium hydroxide solution to produce a NaCN solution and crystallizing the NaCN solution wherein the process is carried out in the presence of an acid or a metal salt of the acid in which the acid has a pKa?4.4. The NaCN crystals can be separated from the slurry and dried.

Abstract: A process that can be used to produce NaCN is provided. The process comprises contacting hydrogen cyanide with sodium hydroxide solution to produce a NaCN solution and crystallizing the NaCN solution wherein the process is carried out in the presence of an acid or a metal salt of the acid in which the acid has a pKa≦4.4. The NaCN crystals can be separated from the slurry and dried.

Abstract: Methods for producing cyanide salts using a metathesis process using ion exchange to facilitate a double-decomposition reaction where components of a cyanide-containing compound are exchanged to produce a cyanide salt product are provided. In one embodiment of the invention, HCN may be converted to an alkali salt using a base. The alkali cyanide salt undergoes ion-exchange to yield the desired cyanide salt product. In another embodiment of the invention, hydrogen cyanide is directly converted to cyanide salts in an ion exchange bed without first being converted to a basic salt.

Abstract: Methods for producing cyanide salts using a metathesis process using ion exchange to facilitate a double-decomposition reaction where components of a cyanide-containing compound are exchanged to produce a cyanide salt product are provided. In one embodiment of the invention, HCN may be converted to an alkali salt using a base. The alkali cyanide salt undergoes ion-exchange to yield the desired cyanide salt product. In another embodiment of the invention, hydrogen cyanide is directly converted to cyanide salts in an ion exchange bed without first being converted to a basic salt.

Abstract: A sodium cyanide composition having a paste-like consistency is provided which comprises sodium cyanide, a base, water, and a rheology modifier. Also provided are processes for producing and using the composition. The composition can be used in applications that require sodium cyanide solution.

Abstract: A process for the direct preparation of alkali metal cyanide and alkaline earth metal cyanide granules from an HCN-containing gas and an aqueous solution or suspension of an alkali metal or alkaline earth metal hydroxide. The reaction is performed in a reactor for fluidized bed spray granulation, wherein a solution or suspension of the hydroxide is sprayed onto seed granules of the cyanide being prepared and at the same time a hydrogen cyanide-containing gas is supplied to the reactor and water is evaporated by means of a fluidizing gas. The preferred fluidizing gas is steam. The reaction gases from a BMA or Andrussow process may be quenched with water and the gas mixture used as fluidizing gas. By using a CO.sub.2 -free HCN-containing gas, alkali metal cyanide granules with advantageous properties, including a combined concentration of alkali metal carbonate and alkali metal formate of less then 0.4 wt. %, are obtainable.

Abstract: Provided is a process for the production of hydrogen cyanide by reacting methane, ammonia and oxygen in the presence of a catalyst. The process, more specifically, comprises first establishing a temperature for the catalyst in the reaction using air as a source for oxygen. This essentially establishes the gauze temperature of the plant. Additional oxygen is then provided to the reaction to provide oxygen enrichment of the reaction feed, while also adjusting the amount of ammonia and methane reactants in the reaction feed such that the volume percent of the ammonia and methane is above the upper flammability limit and the temperature of catalyst is maintained within 50.degree. C. of the temperature of the catalyst originally established as the fixed gauze temperature of the plant. The process of the present invention allows one to increase production of hydrogen cyanide while maintaining safe operation and not sacrificing catalyst performance in return.

Abstract: Process for recovering cyanide values from a mill tailings stream remaining after gold and silver have been leached from an ore, by treating the tailings stream containing both ore insolubles and remaining cyanide leachant, without a preliminary filtration, to acidification with an acid to a pH of at least 4, stripping the cyanide values therefrom with a stripping gas in a stripping column such as a baffle plate column wherein the average residence time of the column is sufficiently low that the pH of the stream does not rise above about 4 and the ore insolubles do not plug the column, introducing the stripping gas and stripped cyanide values into an absorbing column containing an alkaline liquor to absorb the cyanide values, recovering the absorbed cyanide values, and removing a stripped tailings stream reduced in cyanide values.

Abstract: A method for treating cyanide-contaminated water in order to remove dissolved (e.g. free) cyanide (HCN and/or CN.sup.-) therefrom. Cyanide-contaminated water is a significant problem in the gold processing industry wherein cyanide compounds are used to remove gold from ore. The remaining cyanide solution after gold extraction is treated to reduce free cyanide levels therein by combining the solution with a crystalline waste by-product of the metal galvanizing industry having the following formula: (Fe.multidot.Zn)SO.sub.4 .multidot.7H.sub.2 O. This material preferably has a zinc content of about 1-14% by weight, and is added to the water in an amount equal to about 1-5 pounds per ton of ore being processed. As a result, a stable, solid, non-toxic complex is produced from the toxic free cyanide materials. This is accomplished without the generation of harmful acids, heavy metals, excessive iron levels or other undesired by-products.

Abstract: A process for recycling hydrogen cyanide from a cyanide-containing slurry is provided. The process includes the steps of adjusting the pH of a cyanide-containing slurry, volatilizing HCN contained in the pH adjusted slurry and contacting the volatilized HCN with a precious metals-containing slurry to recover precious metals therefrom. Alternatively, the HCN can be contacted with reclaim, or decant, water to recover cyanide, thereby conserving resources.

Abstract: Mill tailings containing cyanide species can be treated with carbon dioxide in order to drive-off and/or recover the cyanide content of said tailings.

Abstract: A process for removing and recovering cyanide from a cyanide-containing mixture. The process includes the steps of adjusting the pH of the cyanide-containing mixture to between about 6 to about 9.5, volatilizing the HCN contained in the pH adjusted mixture and contacting the volatilized HCN with basic material. Preferably, the cyanide recovery process is performed on tailings slurries resulting from metal recovery processes.

Abstract: A process for removing and recovering cyanide from a cyanide-containing solution. The process includes the steps of adjusting the pH of the cyanide-containing solution to between about pH 6 and about pH 9.5, volatilizing the HCN contained in the pH adjusted solution and contacting the volatilized HCN with basic material. Preferably, the cyanide recovery process is performed on tailings slurries resulting from metal recovery processes.

Abstract: A process for producing anhydrous sodium cyanide crystals by absorbing hydrogen cyanide synthesis gas that contains oxides of carbon and water in aqueous sodium hydroxide and crystallizing the sodium cyanide solution that results from the absorption. The sodium carbonate that forms in the absorption is not removed prior to crystallization.

Abstract: Reaction products of hydrogen cyanide are prepared by a process in which hydrogen cyanide prepared in a conventional manner by pyrolysis at from 250.degree. to 650.degree. C. over a solid under from 5 to 200 mbar is cooled to a temperature of from 200.degree. to -10.degree. C. together with the other pyrolysis products, the hydrogen cyanide is then fed to a chemisorption reaction with a base or with a carbonyl compound, and the reaction products of hydrogen cyanide which are formed therein are removed from the system and brought to atmospheric pressure. In this process, the handling of large amounts of hydrogen cyanide is avoided.

Abstract: A process is described by which copper and optionally silver and gold are recovered from sulfide and oxide ores, concentrates or slag, which contain the metals. The particulate materials are treated with an aqueous solution of an alkali cyanide or alkaline earth cyanide, the laden solution is filtered, if desired, a water-soluble sulfide compound is added to the laden solution or filtered laden solution, the laden solution is subsequently adjusted to a pH value below 5 by an addition of acid to precipitate the metal sulfide, which is filtered off, and the resulting hydrocyanic acid is recovered. The process steps of precipitation and filtration of the metal sulfide and the recovery of the free hydrocyanic acid contained in the filtrate are carried out under superatmospheric pressure of 1.5 to 15 bars. The precipitation is preferably effected at a pH value of 1.5 to 2.0. The free hydrocyanic acid is recovered as alkali cyanide or alkaline earth cyanide and is recirculated to the leaching stage.

Abstract: The residual gases obtained in the production of cyanuric chloride having a pressure of 1-5 bar (absolute) preferably 1-4 bar, are worked up by leading them into the lower portion of a column, reacted in the column with at least the equivalent amount of hydrogen cyanide to form cyanogen chloride and led in countercurrent flow to the water charged to the upper portion of the column whereupon the aqueous solution of cyanogen chloride formed is withdrawn from the lower portion of the column and preferably is returned into the production portion of the plant for recovery of the cyanogen chloride while the purified waste gas of the column leaves in the upper portion of the column.

Abstract: A process for dissolving metals, alloys or metallic compound materials in metal cyanamide and/or thiocyanate and/or cayanide and/or halide melts containing optionally metal carbonate and/or cyanide, characterized in that substances are added to the melt which form or liberate CN, and/or CNO and/or SCN radicals in the melt under the reaction conditions.

Abstract: Sodium hydroxide and hydrogen cyanide are reacted in aqueous solution to produce sodium cyanide of maximum crystal size at temperatures and with residence times selected to produce less than about 0.3% by weight sodium formate in the sodium cyanide product.

Abstract: A process for the preparation of gaseous cyanogen chloride by a procedure involving reaction of hydrogen cyanide with chlorine in the presence of water with formation of hydrogen chloride as a by-product at a concentration of about 10 to 25% by weight and further involving converting by chlorination ammonium chloride, formed through acid-catalyzed hydrolysis of cyanogen chloride and admixed with the hydrogen chloride by-product, to nitrogen trichloride under pressure and at elevated temperature and decomposing the nitrogen trichloride to nitrogen and chlorine thermally or by U.V. radiation.

Abstract: Cyanogen halides, particularly cyanogen bromide and cyanogen chloride, are prepared in an electrolysis cell with cathode and anode chambers separated by a semi-permeable diaphragm, by reacting halide ions with hydrogen cyanide or a salt thereof in the anode chamber by means of a direct current, the pH value of the reactant in the anode chamber being lower than 4.

Abstract: Cyanogen chloride is purified and the service life of activated carbon is increased in the subsequent trimerization of the cyanogen chloride to cyanuric chloride by process comprising reacting hydrogen cyanide with chlorine, in a given case in the presence of cyanogen chloride produced in the presence of water, which in a given case contains chlorine. The improvement comprises passing the cyanogen chloride over granular gamma aluminum oxide with an alkali metal or in a given case an alkaline earth metal content of 0 to 3 weight % at 20.degree.-100.degree.C., preferably 30.degree.-60.degree.C.

Abstract: Cyanogen chloride is purified and the service life of activated carbon is increased in the subsequent trimerization of the cyanogen chloride to cyanuric chloride by process comprising reacting hydrogen cyanide with chlorine, in a given case in the presence of cyanogen chloride produced in the presence of water, which in a given case contains chlorine. The improvement comprises passing the cyanogen chloride over granular commercial sodium aluminum silicate or a molecular sieve of the mordenite type, at 20.degree.-100.degree.C., preferably 30.degree.-60.degree.C.

Abstract: Production of cyanogen chloride by reacting hydrogen cyanide and chlorine in the gaseous phase in the presence of a low activity carbon catalyst.