CA1091937A - Process for the separation of a gaseous mixture - Google Patents
Process for the separation of a gaseous mixtureInfo
- Publication number
- CA1091937A CA1091937A CA261,574A CA261574A CA1091937A CA 1091937 A CA1091937 A CA 1091937A CA 261574 A CA261574 A CA 261574A CA 1091937 A CA1091937 A CA 1091937A
- Authority
- CA
- Canada
- Prior art keywords
- metal
- absorbent
- gaseous mixture
- reduction
- vapour
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F27—FURNACES; KILNS; OVENS; RETORTS
- F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
- F27D17/00—Arrangements for using waste heat; Arrangements for using, or disposing of, waste gases
- F27D17/004—Systems for reclaiming waste heat
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- General Chemical & Material Sciences (AREA)
- General Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Analytical Chemistry (AREA)
- Environmental & Geological Engineering (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Treating Waste Gases (AREA)
- Manufacture And Refinement Of Metals (AREA)
- Gas Separation By Absorption (AREA)
- Industrial Gases (AREA)
- Solid-Sorbent Or Filter-Aiding Compositions (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
The present invention provides a process for separating a gaseous mixture which is formed during the reduction of a compound and which contains the vapour of at least one of an elemental metal and a semimetal by contact with an absorbent selected from metals and metal salts in solid or liquid form, the gaseous mixture being contacted with the absorbent which is capable of absorbing the metal vapour under such thermodynamic conditions that the absorbent directly absorbs the metal vapour from the gas phase.
The present invention provides a process for separating a gaseous mixture which is formed during the reduction of a compound and which contains the vapour of at least one of an elemental metal and a semimetal by contact with an absorbent selected from metals and metal salts in solid or liquid form, the gaseous mixture being contacted with the absorbent which is capable of absorbing the metal vapour under such thermodynamic conditions that the absorbent directly absorbs the metal vapour from the gas phase.
Description
3 ~
The present invention relates to a process for the separation of a gaseous mixture which contains the vapours of metals and/or semimetals. Gaseous mixtures of this kind are formed in various processes, for example ln the thermal decomp-osition of hydrides, nitrides, sulphides and halides, and also in the reduction of oxides with hydrogen, water gas, generator gas, natural gas and other gaseous reducing agents, but also with liquid or solid reducing agents, such as fuel oil, coal and coke or petroleum coke.
In the interests of simplicity, processes such as these will hereinafter be generically referred to as "reduction", because they are always accompanied by the formation of elemental metal or semimetal vapour, albeit in mechanical admixture with other gaseous substances.
In addition, metals, including the metals of the First and Second Group of the Periodic System, and semimetals, also mixtures thereof, will be referred to in the interests of sim-plicity as "metal" and their corresponding compounds and mixtures of these compounds as "compound 1l .
Again in the interests of simplicity, the gaseous substances mixed with -the vapours of elemental metal will be referred to hereinafter as "gases". Gaseous substances of this kind are, for example, CO, CO2, H2O, SO2, H2S, 2' N2~ gaseous sulphur, gaseous low-grade halides, oxides and sulphides, also saturated gaseous metal and semimetal compounds.
Hitherto, vain attempts have been made economically to separate the vapour of elemental metal present for example in the gaseous mixtures resulting from the reduction of oxides with solid, liquid or gaseous carbon-containing and hydrogen-containing substances, in order to recover metals. For example, the quenching of a gaseous mixture of Mg-vapour and CO was only partly successful and by no means economical because a large part 3~
of the Mg-vapour is reoxidised by the CO into magnesium oxide.
This is because, if a gaseous mixture formed, for example, by reduction consisting of metal vapour and other reduction products, such as CO, CO2 and H2O, is cooled, the temperature-dependent thermodynamic vapour-gas equilbrium is reversed, metal vapour being reoxidised into the metal oxide, in many cases even with the simultaneous formation of carbon black. Accordingly, the quenching of gaseous mixtures such as these always results in the formation of metal powders which are contaminated by an uneconomically large amount of oxide. This also applies in the same way to any other reversible temperature-dependent gas-metal vapour equilibrla. Accordingly, these processes have never been successfully worked on an industrial scale both for technical and Eor economic reasons.
In other known processes, hot gaseous mixtures contain-ing metal vapours, such as are formed in carbothermal reduction, are quenched with much cooler metal melts at a temperature below the respective condensation level of the metal vapours to be separated. In said process at first the metal vapours are condensed, then the condensates (e.g. as a mist consisting of small droplets) form liquid alloys with the molten quenching metals whilst a part of the metals to be gained is again reformed into the original metal oxides. The metal yield is not satis-factory.
Attention is drawn to the fact that the term "absorption"
in many publications is not correctly used. In physics and chemistry "absorption" means the taking up of gases by liquids and solids, e.g. the taking up of CO2 by water or of Mg-vapour by molten Sn. In contrast hereto, the taking up of a mist or 3Q an aerosol consisting of fine droplets by a liquid ~melt) is no "absorp-tion" but a mixing or solving procedure.
In another known process for separating carbon monoxide from a gaseous mlxture containing magnesium vapour, the mixture is brought into contact with metal carbides, the carbon monoxide oxidising the surface oE the carbide partlcles to form metal oxides with deposition of carbon. The carbide particles are then regenerated with the carbon deposited to form the carbides.
The formation of oxide-carbide mixtures, a residue oE CO left for thermodynamic reasons in the magnesium vapour obtained and considerable superheating and supercooling of the solicls make this proposed process both technically and economically impract-icable.
The recovery of metals by melt electrolysis was finallyleft as a possible method of obtaining numerous metals. The disadvantages of these processes which, today, are almost exclus-ively used the large-scale recovery of aluminium, magnesium and many other metals, lie above all in the poor volume-time yield, the expensive electrical installations and the consumption of large quantities of electrical energy.
Accordingly, the present invention reduces and desirably removes the disadvantages referred to above by providing a process for the separation of a gaseous mixture (which is formed during the reduction of a compound and which contains the vapour of elemental metal and/or semimetal ? by contact with an absorbent (metals and metal salts in solid or liquid form) which can be carried out simply and economically and which in particular enables electrical energy to be saved.
According to the invention the gaseous mixture is con-tacted with an absorbent which is capable of absorbing the metal vapour, preferably in the form of a melt, under such -thermodynamic conditions that the absorbent directly absorbs the metal vapour from the gas phase.
It has been found that the vapour of elemental metal and/or semimetal is absorbed in the absorbent (metals and metal salts in solid or liquid form) to a large extent or completely, depending upon the particular procedure adopted in practice, whereas the other gaseous constituents are not.
In the application of the process according to the invention, therefore, -the metal vapour contained in the gaseous mixture must remain gaseous-en route to the absorbent and also during absorption. In the application of the process according to the invention, a gaseous mixture will generally arrive at the absorption stage in the thermodynamic state which is assumed lQ during its formation. The thermodynamic conditions have to be taken into consideration in the event of any changes in temperature or pressure by changing the pressure or temperature or the comp-osition of the gaseous mixture in such a way that the gas phase remains intact. Shortly, the absorption of the metal vapour according to the invention always is effected at a temperature (absorption temperature) above the respective condensation level of the metal vapour to be separated. Condensation level means that temperature at which a gas or vapour depending ~rom its partial pressure condenses to a liquid or a solid. The normal condensation level is only a special case, viz. that temperature at which a gas or vapour condenses at a partial pressure of 1 at.
The necessary quantitative temperature and pressure conditions may be thermodynamically calculated with the means known at the present time for any reversible equilibrium and gaseous mixture, and may be experimentally determined.
In contrast to the process according to the invention, the hot metal vapour to be separated in conventional processes condenses in the surroundings and in the vicinity of the surface of the much cooler metal (for example in bubbles or in droplets), with which the gaseous mixture is brought into contact, to form the liquid or solid metal. In these processes, absorption o-f the metal vapour to be separated from the gas phase directly into the metal i5 by nature impossible because, due to cooling far below the boiling point or below the melting point of the gaseous metal, it always has to pass first into the liquid or solid phase before it can be absorbed in the metal.
The absorbent used in accordance with the invention should have as high an "absorption capacity" (alloying affinity, chemical affinity) as possible for the metal to be absorbed, coupled with an extremely low vapour pressure at the working temperature, in addition to which, when it is used in the form of a melt, it should have as low a melting point as possible for technical reasons and, when it is additionally used for transport-ing heat in endothermic reduction reactions, it should have as high as possible a heat capacity and/or evaporation enthalpy and, finally, it should incur the lowest possible production costs for economic reasons. In many cases, these requirements give rise to the need to combine with one another several metals and/or semimetals according to their chemical, physical and thermodynamic properties and also their prices.
The metals, metal and semimetal salts and semimetals used in accordance with the invention for the absorption of metal vapours, also every possible mixture, solution, alloy and compound thereo, are hereinafter referred to simply as "absorbent". The absorbent may be used in solid form, for example in the form of small beads, Raschig rings or nests of tubes, in liquid form or gaseous form.
It is known that chemical and physical reactions are accelerated when the reactants, as far as possible in statu nascendi, are intimately mixed with and whirled through one another in finely distributed form. Accordingly, it is of advantage vigorously to whirl the compound with the absorbent during reduction, i.e. the gaseous mixture during its formation.
In this way, absorption of the metal vapours is accelerated and the need for a separate absorption chamber is eliminated.
During the separation of a metal vapour from an already formed gaseous mixture, which takes place in countercurrent with an absorbent, the amount of metal vapour in the gaseous mixture decreases. As a result, the tendency which the compound has to reform is reduced, so that the temperature can decrease accordingly during absorption or along the absorption path without the com-pound being reformed. Accordingly, it is not absolutely essential for the entire separation of the gaseous mixture to be carried out at the reduction temperature. However, any reformation of the compound in the gaseous mixture is reliably avoidecl in the .
temperature of the absorbent, on being brought into contact with the gaseous mixture, is at least as high as the temperature of the gaseous mixture during its formation.
In endothermic reduction reactions, the reactants and, optionally, the absorbent as well are known to cool down when no heat is conveyed to the system. Heat may be applied in known manner, for example by means of electrical energy or by heating with fuels. However, in order to simplify the apparatus and to avoid problems of materials, it is preferred in accordance with the invention to adopt a procedure in which, during its formation, which is accompanied by reduction, the gaseous mixture is brought into contact with the absorbent with a heat content which is used at least partly for maintaining the reduction temperature.
According to the invention, it is even possible to manage with a smaller quantity of absorbent providing its heat of the evaporation is utilised. Accordingly, another feature of the invention is that, during its formation accompanied by re-duction, the gaseous mixture is brought into contact with at least part of the absorbent in gaseous form which is condensed.
In order to heat the absorbent before it is used for separation, heat may be conveyed to it in known manner indirectly, i.e. through a container wall, with smoke gases and flame gases of burners, by radiation from electrical resistance heating elements, by induction heating or by direct electrical resistance heating or in any other manner.
So far as the transfer of heat and the outlay on apparatus are concerned, it is of particu:Lar advantage in accordance with the invention to heat the absorbent before sep-aration by direct contact with smoke and flame gases and, during combustion, to adjust the fuel/air or oxygen ratio in such a way that the absorbent cannot be oxidised, or to add the necessary amount of reducing gas to the smoke and flame gases.
In cases where it is desired to recover the absorbed metal from the gaseous mixture, it is removed from the absorbent in known manner preferably by desorption by reducing pressure and/or increasing temperature or by rectification, and the result-ing metal vapour is cooled so that either liquid or solid metal is obtained.
However, the solution of absorbed metal and absorbent may also be used otherwise as an alloy or as a chemical reagent
The present invention relates to a process for the separation of a gaseous mixture which contains the vapours of metals and/or semimetals. Gaseous mixtures of this kind are formed in various processes, for example ln the thermal decomp-osition of hydrides, nitrides, sulphides and halides, and also in the reduction of oxides with hydrogen, water gas, generator gas, natural gas and other gaseous reducing agents, but also with liquid or solid reducing agents, such as fuel oil, coal and coke or petroleum coke.
In the interests of simplicity, processes such as these will hereinafter be generically referred to as "reduction", because they are always accompanied by the formation of elemental metal or semimetal vapour, albeit in mechanical admixture with other gaseous substances.
In addition, metals, including the metals of the First and Second Group of the Periodic System, and semimetals, also mixtures thereof, will be referred to in the interests of sim-plicity as "metal" and their corresponding compounds and mixtures of these compounds as "compound 1l .
Again in the interests of simplicity, the gaseous substances mixed with -the vapours of elemental metal will be referred to hereinafter as "gases". Gaseous substances of this kind are, for example, CO, CO2, H2O, SO2, H2S, 2' N2~ gaseous sulphur, gaseous low-grade halides, oxides and sulphides, also saturated gaseous metal and semimetal compounds.
Hitherto, vain attempts have been made economically to separate the vapour of elemental metal present for example in the gaseous mixtures resulting from the reduction of oxides with solid, liquid or gaseous carbon-containing and hydrogen-containing substances, in order to recover metals. For example, the quenching of a gaseous mixture of Mg-vapour and CO was only partly successful and by no means economical because a large part 3~
of the Mg-vapour is reoxidised by the CO into magnesium oxide.
This is because, if a gaseous mixture formed, for example, by reduction consisting of metal vapour and other reduction products, such as CO, CO2 and H2O, is cooled, the temperature-dependent thermodynamic vapour-gas equilbrium is reversed, metal vapour being reoxidised into the metal oxide, in many cases even with the simultaneous formation of carbon black. Accordingly, the quenching of gaseous mixtures such as these always results in the formation of metal powders which are contaminated by an uneconomically large amount of oxide. This also applies in the same way to any other reversible temperature-dependent gas-metal vapour equilibrla. Accordingly, these processes have never been successfully worked on an industrial scale both for technical and Eor economic reasons.
In other known processes, hot gaseous mixtures contain-ing metal vapours, such as are formed in carbothermal reduction, are quenched with much cooler metal melts at a temperature below the respective condensation level of the metal vapours to be separated. In said process at first the metal vapours are condensed, then the condensates (e.g. as a mist consisting of small droplets) form liquid alloys with the molten quenching metals whilst a part of the metals to be gained is again reformed into the original metal oxides. The metal yield is not satis-factory.
Attention is drawn to the fact that the term "absorption"
in many publications is not correctly used. In physics and chemistry "absorption" means the taking up of gases by liquids and solids, e.g. the taking up of CO2 by water or of Mg-vapour by molten Sn. In contrast hereto, the taking up of a mist or 3Q an aerosol consisting of fine droplets by a liquid ~melt) is no "absorp-tion" but a mixing or solving procedure.
In another known process for separating carbon monoxide from a gaseous mlxture containing magnesium vapour, the mixture is brought into contact with metal carbides, the carbon monoxide oxidising the surface oE the carbide partlcles to form metal oxides with deposition of carbon. The carbide particles are then regenerated with the carbon deposited to form the carbides.
The formation of oxide-carbide mixtures, a residue oE CO left for thermodynamic reasons in the magnesium vapour obtained and considerable superheating and supercooling of the solicls make this proposed process both technically and economically impract-icable.
The recovery of metals by melt electrolysis was finallyleft as a possible method of obtaining numerous metals. The disadvantages of these processes which, today, are almost exclus-ively used the large-scale recovery of aluminium, magnesium and many other metals, lie above all in the poor volume-time yield, the expensive electrical installations and the consumption of large quantities of electrical energy.
Accordingly, the present invention reduces and desirably removes the disadvantages referred to above by providing a process for the separation of a gaseous mixture (which is formed during the reduction of a compound and which contains the vapour of elemental metal and/or semimetal ? by contact with an absorbent (metals and metal salts in solid or liquid form) which can be carried out simply and economically and which in particular enables electrical energy to be saved.
According to the invention the gaseous mixture is con-tacted with an absorbent which is capable of absorbing the metal vapour, preferably in the form of a melt, under such -thermodynamic conditions that the absorbent directly absorbs the metal vapour from the gas phase.
It has been found that the vapour of elemental metal and/or semimetal is absorbed in the absorbent (metals and metal salts in solid or liquid form) to a large extent or completely, depending upon the particular procedure adopted in practice, whereas the other gaseous constituents are not.
In the application of the process according to the invention, therefore, -the metal vapour contained in the gaseous mixture must remain gaseous-en route to the absorbent and also during absorption. In the application of the process according to the invention, a gaseous mixture will generally arrive at the absorption stage in the thermodynamic state which is assumed lQ during its formation. The thermodynamic conditions have to be taken into consideration in the event of any changes in temperature or pressure by changing the pressure or temperature or the comp-osition of the gaseous mixture in such a way that the gas phase remains intact. Shortly, the absorption of the metal vapour according to the invention always is effected at a temperature (absorption temperature) above the respective condensation level of the metal vapour to be separated. Condensation level means that temperature at which a gas or vapour depending ~rom its partial pressure condenses to a liquid or a solid. The normal condensation level is only a special case, viz. that temperature at which a gas or vapour condenses at a partial pressure of 1 at.
The necessary quantitative temperature and pressure conditions may be thermodynamically calculated with the means known at the present time for any reversible equilibrium and gaseous mixture, and may be experimentally determined.
In contrast to the process according to the invention, the hot metal vapour to be separated in conventional processes condenses in the surroundings and in the vicinity of the surface of the much cooler metal (for example in bubbles or in droplets), with which the gaseous mixture is brought into contact, to form the liquid or solid metal. In these processes, absorption o-f the metal vapour to be separated from the gas phase directly into the metal i5 by nature impossible because, due to cooling far below the boiling point or below the melting point of the gaseous metal, it always has to pass first into the liquid or solid phase before it can be absorbed in the metal.
The absorbent used in accordance with the invention should have as high an "absorption capacity" (alloying affinity, chemical affinity) as possible for the metal to be absorbed, coupled with an extremely low vapour pressure at the working temperature, in addition to which, when it is used in the form of a melt, it should have as low a melting point as possible for technical reasons and, when it is additionally used for transport-ing heat in endothermic reduction reactions, it should have as high as possible a heat capacity and/or evaporation enthalpy and, finally, it should incur the lowest possible production costs for economic reasons. In many cases, these requirements give rise to the need to combine with one another several metals and/or semimetals according to their chemical, physical and thermodynamic properties and also their prices.
The metals, metal and semimetal salts and semimetals used in accordance with the invention for the absorption of metal vapours, also every possible mixture, solution, alloy and compound thereo, are hereinafter referred to simply as "absorbent". The absorbent may be used in solid form, for example in the form of small beads, Raschig rings or nests of tubes, in liquid form or gaseous form.
It is known that chemical and physical reactions are accelerated when the reactants, as far as possible in statu nascendi, are intimately mixed with and whirled through one another in finely distributed form. Accordingly, it is of advantage vigorously to whirl the compound with the absorbent during reduction, i.e. the gaseous mixture during its formation.
In this way, absorption of the metal vapours is accelerated and the need for a separate absorption chamber is eliminated.
During the separation of a metal vapour from an already formed gaseous mixture, which takes place in countercurrent with an absorbent, the amount of metal vapour in the gaseous mixture decreases. As a result, the tendency which the compound has to reform is reduced, so that the temperature can decrease accordingly during absorption or along the absorption path without the com-pound being reformed. Accordingly, it is not absolutely essential for the entire separation of the gaseous mixture to be carried out at the reduction temperature. However, any reformation of the compound in the gaseous mixture is reliably avoidecl in the .
temperature of the absorbent, on being brought into contact with the gaseous mixture, is at least as high as the temperature of the gaseous mixture during its formation.
In endothermic reduction reactions, the reactants and, optionally, the absorbent as well are known to cool down when no heat is conveyed to the system. Heat may be applied in known manner, for example by means of electrical energy or by heating with fuels. However, in order to simplify the apparatus and to avoid problems of materials, it is preferred in accordance with the invention to adopt a procedure in which, during its formation, which is accompanied by reduction, the gaseous mixture is brought into contact with the absorbent with a heat content which is used at least partly for maintaining the reduction temperature.
According to the invention, it is even possible to manage with a smaller quantity of absorbent providing its heat of the evaporation is utilised. Accordingly, another feature of the invention is that, during its formation accompanied by re-duction, the gaseous mixture is brought into contact with at least part of the absorbent in gaseous form which is condensed.
In order to heat the absorbent before it is used for separation, heat may be conveyed to it in known manner indirectly, i.e. through a container wall, with smoke gases and flame gases of burners, by radiation from electrical resistance heating elements, by induction heating or by direct electrical resistance heating or in any other manner.
So far as the transfer of heat and the outlay on apparatus are concerned, it is of particu:Lar advantage in accordance with the invention to heat the absorbent before sep-aration by direct contact with smoke and flame gases and, during combustion, to adjust the fuel/air or oxygen ratio in such a way that the absorbent cannot be oxidised, or to add the necessary amount of reducing gas to the smoke and flame gases.
In cases where it is desired to recover the absorbed metal from the gaseous mixture, it is removed from the absorbent in known manner preferably by desorption by reducing pressure and/or increasing temperature or by rectification, and the result-ing metal vapour is cooled so that either liquid or solid metal is obtained.
However, the solution of absorbed metal and absorbent may also be used otherwise as an alloy or as a chemical reagent
2~ (for example for deoxidising crude metal melts, as a blowing agent for producing foamed concrete, etc.).
Following separation, it is possible in accordance with the invention either to desorb the entire solution of absorbed metal and absorbent or further to use only parts thereof (for example as an alloy and/or chemical reagent) and to desorb the rest and then to reuse the absorbent for the separation thereof or of another gaseous mixture.
Most of the waste gases from reduction reactions contain large quantities of CO and H2. According to the invention, therefore, the eaonomy of the process is improved if, following separation, the non-absorbed waste gas or at least a part of this waste gas is used as a fuel and/or another part as chemical reagent (for example as a reducing agent, for the synthesis of NH3 of plastics).
If an absorbent can be chemically attacked by the gases formed during reduction, this effect is avoided in accordance with the invention by the addition of an adequate quantity of a gas preventing this chemical attack to the gaseous mixture during its formation either during or after reduction.
In the still process, the gases leaving the absorbent take with them a small amount of the absorbed metal in vapour form. According to the invention, this may be avoided by bringing the gaseous mixture into contact with the absorbent in countercurrent during its formation during and/or after reduction. The fresh absorbent absorbs the last traces of the metal vapour in counter-current, becomes enriched with metal from the gaseous mixture along the absorption path and leaves the apparatus saturated with the absorbed metal.
According to the invention, it is of particular advant-age to combine the countercurrent process with the recycle process.
The gaseous mixture is continuously brought into contact with the absorbent in countercurrent during its formation during and/or after reduction. The absorbent is continuously desorbed, is directly or indirectly heated in countercurrent, optionally continuously, and is continuously reused for absorption.
In cases where solids such as coke or coal are used for reduction and/or for directly heating the absorbent, the absorbent takes up small quantities of metals, emanating from the mineral constituents of the solid reducing agents and/or fuels, such as iron, aluminium, silicon, alkali and alkaline earth metals, from the fly dust entrained by the gaseous mixture or on contact with the reduction reactants and/or smoke gases. In order to avoid harmful accumulations or enrichments, especially in cases where the absorben~ is recycled, the absorbent is in accordance with the invention periodically or continuously freed from impurities in known manner until only harmless residues are left. For example, alkali and alkaline earth metals are removed by desorption, aluminium and silicon are vaporized by the action of halogens or halides and iron is oxidised with air and the solid iron oxides separated from the absorbent.
The invention is illustrated by the following Examples.
In the reduction of Na2O with C at 1000C, a gaseous mixture with the following composition is formed:
64.212 % by volume of Na-vapour 35.788 ~ by volume of CO
The reaction pressure is 3.5 atms. After reduction, this mixture is brought into contact in countercurrent with molten lead heated to 1030C as absorbent. It absorbs the Na-vapour whilst pure CO
escapes. A melt with the following composition:
83 % by weight of Pb and 17 % by weight of Na, is obtained and is desorbed in a rectification column at 1050C/
2Q 0.1 atm (76 (Torr). The Na-vapour escaping from the rectification colume is condensed and the lead melt containing a small residue o~ sodium is reused as absorbent for separating the Na-vapour from the CO.
50 t/h of calcined magnesite are continuously reduced at 1650C with 33,000 Nm3/h of natural gas (85 % by volume of CH4 and 15 % by volume of N2) in a tower consisting of several chambers.
Whilst the mixture of magnesite dust and the cracking products of the natural gas flows upwards, a gaseous mixture of 27,630 Nm3/h of magnesium vapour, 27,640 Nm3/h of carbon monoxide, 55 ! 350 Nm3/h of hydrogen and 4950 Nm3/h of nitrogen i9 formed.
330 m3/h of absorbent consisting of 42.8 % by weight of lead and 57.2 % by weight of tin, which has been heated to a temper-ature of 1840C, are passed continuouslv through the chambers in countercurrent (downwards). A further quantity of absorbent, in the form of 106,700 Nm3/h of hot lead vapour distributed among the individual chambers is introduced at a temperature of 1840C.
The reaction pressure during the reduction of MgO with natural gas at a temperature of 1650C is approximately 0.5 atm.
A working pressure of approximately 1 atm is reached by the introduction of lead vapour.
The lead vapour and the Pb/Sn melt cool down to the reduction temperature, the lead vapour being condensed into liquid lead. The heat of evaporation of the lead vapour and the sensible heat o~ lead vapour and Pb/Sn melt supply the heat required ~or reduction, the entire Pb/Sn melt dlrectly absorbing the magnesium vapour from the gaseous mixture as it is formed; CO, H2 and N2 leave the tower at its uppermost part.
450 m3/h of a mel-t consisting of 4.4 % by volume of Mg, 48.5 ~ by volume of Sn and 47.1 % by volume of Pb, flow off continuously from the lower end of the tower Whereas the vapour pressure in the chambers of the tower during reduction and absorp-tion amounts -to approximately 1 atm, the melt is desorbed in a rectification column under a pressure of only 10 Torr, 30 t/h of Mg-vapour escaping continuously from the melt. The Mg-vapour is cooled to 720C, liquefying in the process.
During desorption, the melt is left with a residue of approximately 0.01 % by weight of Mg which is continuously en-trained in the recycle process. The melt is again continuously heated to 1840C, 106,700 Nm3/h of lead evaporating again. As already described, lead vapour and residual melt are again intro-duced into the tower. For heating the melt and evaporating the lead the 87,940 Nm /h of (CO + H2 + N2) continuously escaping during separation of the gaseous mixture and in addition 19,000 Nm3/h of natural gas are burnt with air in gas burners. Before combustion, the air is heated by the smoke gas of the gas burner, which has a temperature of 1900C, in a radiation recuperator.
Impurities emanating from the calcined magnesite, such as iron, aluminium, silicon, calcium, sodium and potassium, accumulate in the recycled (heating-absorption-desorption-heating) Pb-Sn melt. The melt is periodically cooled as required to 1000C
and treated with airl resulting in the formation of mixed oxides Of Fe3O4, Al2O3, SiO2, CaO, MgO, K2O and Na2O. They flow as crusts on the liquid Pb-Sn melt and are separated off.
A gaseous mixture formed during the reduction of pure MgO with natural gas can o course also be separated in accordance with the invention, which affords the additional advantage that no impurities accumulate in the absorbent so that the need for purifying the absorbent according to Example 2 is eliminated.
Pure MgO is obtained for example in the reduction of pure aluminium chloride, followed by burning of the MgCl2 formed or in the reduction of pure Al2O3 with Mg to form pure aluminium.
Processes such as these are now of outstanding significance because, in a recycle process comprising for example l) reduction of Al2O3 with Mg (to form Al and MgO) 2) the reduction of MgO with natural gas (to form Mg-vapour and CO)
Following separation, it is possible in accordance with the invention either to desorb the entire solution of absorbed metal and absorbent or further to use only parts thereof (for example as an alloy and/or chemical reagent) and to desorb the rest and then to reuse the absorbent for the separation thereof or of another gaseous mixture.
Most of the waste gases from reduction reactions contain large quantities of CO and H2. According to the invention, therefore, the eaonomy of the process is improved if, following separation, the non-absorbed waste gas or at least a part of this waste gas is used as a fuel and/or another part as chemical reagent (for example as a reducing agent, for the synthesis of NH3 of plastics).
If an absorbent can be chemically attacked by the gases formed during reduction, this effect is avoided in accordance with the invention by the addition of an adequate quantity of a gas preventing this chemical attack to the gaseous mixture during its formation either during or after reduction.
In the still process, the gases leaving the absorbent take with them a small amount of the absorbed metal in vapour form. According to the invention, this may be avoided by bringing the gaseous mixture into contact with the absorbent in countercurrent during its formation during and/or after reduction. The fresh absorbent absorbs the last traces of the metal vapour in counter-current, becomes enriched with metal from the gaseous mixture along the absorption path and leaves the apparatus saturated with the absorbed metal.
According to the invention, it is of particular advant-age to combine the countercurrent process with the recycle process.
The gaseous mixture is continuously brought into contact with the absorbent in countercurrent during its formation during and/or after reduction. The absorbent is continuously desorbed, is directly or indirectly heated in countercurrent, optionally continuously, and is continuously reused for absorption.
In cases where solids such as coke or coal are used for reduction and/or for directly heating the absorbent, the absorbent takes up small quantities of metals, emanating from the mineral constituents of the solid reducing agents and/or fuels, such as iron, aluminium, silicon, alkali and alkaline earth metals, from the fly dust entrained by the gaseous mixture or on contact with the reduction reactants and/or smoke gases. In order to avoid harmful accumulations or enrichments, especially in cases where the absorben~ is recycled, the absorbent is in accordance with the invention periodically or continuously freed from impurities in known manner until only harmless residues are left. For example, alkali and alkaline earth metals are removed by desorption, aluminium and silicon are vaporized by the action of halogens or halides and iron is oxidised with air and the solid iron oxides separated from the absorbent.
The invention is illustrated by the following Examples.
In the reduction of Na2O with C at 1000C, a gaseous mixture with the following composition is formed:
64.212 % by volume of Na-vapour 35.788 ~ by volume of CO
The reaction pressure is 3.5 atms. After reduction, this mixture is brought into contact in countercurrent with molten lead heated to 1030C as absorbent. It absorbs the Na-vapour whilst pure CO
escapes. A melt with the following composition:
83 % by weight of Pb and 17 % by weight of Na, is obtained and is desorbed in a rectification column at 1050C/
2Q 0.1 atm (76 (Torr). The Na-vapour escaping from the rectification colume is condensed and the lead melt containing a small residue o~ sodium is reused as absorbent for separating the Na-vapour from the CO.
50 t/h of calcined magnesite are continuously reduced at 1650C with 33,000 Nm3/h of natural gas (85 % by volume of CH4 and 15 % by volume of N2) in a tower consisting of several chambers.
Whilst the mixture of magnesite dust and the cracking products of the natural gas flows upwards, a gaseous mixture of 27,630 Nm3/h of magnesium vapour, 27,640 Nm3/h of carbon monoxide, 55 ! 350 Nm3/h of hydrogen and 4950 Nm3/h of nitrogen i9 formed.
330 m3/h of absorbent consisting of 42.8 % by weight of lead and 57.2 % by weight of tin, which has been heated to a temper-ature of 1840C, are passed continuouslv through the chambers in countercurrent (downwards). A further quantity of absorbent, in the form of 106,700 Nm3/h of hot lead vapour distributed among the individual chambers is introduced at a temperature of 1840C.
The reaction pressure during the reduction of MgO with natural gas at a temperature of 1650C is approximately 0.5 atm.
A working pressure of approximately 1 atm is reached by the introduction of lead vapour.
The lead vapour and the Pb/Sn melt cool down to the reduction temperature, the lead vapour being condensed into liquid lead. The heat of evaporation of the lead vapour and the sensible heat o~ lead vapour and Pb/Sn melt supply the heat required ~or reduction, the entire Pb/Sn melt dlrectly absorbing the magnesium vapour from the gaseous mixture as it is formed; CO, H2 and N2 leave the tower at its uppermost part.
450 m3/h of a mel-t consisting of 4.4 % by volume of Mg, 48.5 ~ by volume of Sn and 47.1 % by volume of Pb, flow off continuously from the lower end of the tower Whereas the vapour pressure in the chambers of the tower during reduction and absorp-tion amounts -to approximately 1 atm, the melt is desorbed in a rectification column under a pressure of only 10 Torr, 30 t/h of Mg-vapour escaping continuously from the melt. The Mg-vapour is cooled to 720C, liquefying in the process.
During desorption, the melt is left with a residue of approximately 0.01 % by weight of Mg which is continuously en-trained in the recycle process. The melt is again continuously heated to 1840C, 106,700 Nm3/h of lead evaporating again. As already described, lead vapour and residual melt are again intro-duced into the tower. For heating the melt and evaporating the lead the 87,940 Nm /h of (CO + H2 + N2) continuously escaping during separation of the gaseous mixture and in addition 19,000 Nm3/h of natural gas are burnt with air in gas burners. Before combustion, the air is heated by the smoke gas of the gas burner, which has a temperature of 1900C, in a radiation recuperator.
Impurities emanating from the calcined magnesite, such as iron, aluminium, silicon, calcium, sodium and potassium, accumulate in the recycled (heating-absorption-desorption-heating) Pb-Sn melt. The melt is periodically cooled as required to 1000C
and treated with airl resulting in the formation of mixed oxides Of Fe3O4, Al2O3, SiO2, CaO, MgO, K2O and Na2O. They flow as crusts on the liquid Pb-Sn melt and are separated off.
A gaseous mixture formed during the reduction of pure MgO with natural gas can o course also be separated in accordance with the invention, which affords the additional advantage that no impurities accumulate in the absorbent so that the need for purifying the absorbent according to Example 2 is eliminated.
Pure MgO is obtained for example in the reduction of pure aluminium chloride, followed by burning of the MgCl2 formed or in the reduction of pure Al2O3 with Mg to form pure aluminium.
Processes such as these are now of outstanding significance because, in a recycle process comprising for example l) reduction of Al2O3 with Mg (to form Al and MgO) 2) the reduction of MgO with natural gas (to form Mg-vapour and CO)
3) the separation of Mg and CO in accordance with the invention l) the reduction of Al2O3 with Mg the process according to the invention enables substantially non-reducible metals, such as Mn, Cr, Al, Ti and Zr to be recovered surprisingly economically.
If in accordance with Example 2 the heat required for endothermic reduction of the MgO were to be conventionally supplied and if pure lead were to be used for separating the gaseous mixture (Mg-vapour + H2 + Co + N2), 1200 m /h of Pb melt would be required for absorbing the 30 t/h of Mg-vapour. If pure tin were to be used, only 300 m3/h of Sn melt would need to be introduced because under the Mg partial pressure prevailing tin is able to absorb considerably more magnesium than lead. If the heat required was to be supplied by means of a melt of absorbent, as much as 8580 m3/h of lead (1730C) or 3150 m3/h o tin (1840C) would be necessary (the boilin~ point of lead is 1753C).
However, if as in Example 2 condensing lead vapour is used as heat source for the reduction of MgO and, in addition, if molten tin is used as the principal absorbent, a Pb-Sn-melt is formed as absorbent. From the kechnological point of view, the problem of heat supply for the endothermic reduction of MgO is elegantly solved in this way. I then following separation the magnesium is removed from the melt and the melt reheated to 1840C, lead vapour is again formed, although on this occasion, depending upon the temperature, pressure and activity conditions prevailing, a proportion of lead remains behind in the melt and is continuously circulated together with the tin in the recycle process. Out o this there arises the optimum input of 330 m3/h of Pb-Sn melt containing 42.8 % by weight of Pb and 57.2 % by weight of Sn as liquid absorbent, and 10~,700 Nm3/h of condensed lead vapour as the additional amount of absorbent and heat carrier, coupled with elimination of the need for separate heating of the reduction apparatus.
In the reduction of zinc oxide with carbon at 1000C, a gaseous mixture of 3G 50.37 % by volume of ~n vapour r 48.89 % by volume of CO and 0.74 % by volume of CO2 is formed. This mixture is brought into contact with steel elements (as absorbent) in an absorption chamber. The steel absorbs the zinc vapour, whilst the zinc-free waste gas consist-ing of CO and CO2 leaves the absorption chamber. The zinc is absorbed in the surface of -the steel elements up -to a content of 70 % by weight which in a 1 mm thick surface layer decreases inwards to 0 % of Zn.
In the reduction of MnO with low-sulphur petroleum coke at 1750C, a gas mixture consis-ting of 50 % by volume of manganese vapour and 50 % by volume of CO is formed. Since the reaction pressure is only 0.3 atm, this pressure or a lower pressure as the working pressure would have to be produced by evacuation.
Technically it is simpler to add nitrogen ln order to reach a working pressure of 1 atm. In this case the gas mix-ture consists of 15 % by volume of CO, 15 ~ by volume of Mn vapour and 70 % by volume of N2 The nitrogen is obtained from part of the smoke gas of a burner freed from CO2, SO2 and steam by washing with water under pressure.
It is then heated to 1650C in a countercurrent heat exchanger by means of the hot smoke gas and added to the CO/manganese vapour mixture during its formation from the MnO/petroleum coke mixture.
The gaseous mixture is passed through a melt consisting of 82 % by weight of Sb and 18 % by weight of Al. Whereas the antimony has a particularly high solvent action on manganese, the addition of aluminium prevents the boiling off of antimony whose normal boiling point is 1635C.
The gaseous mixture is separated in the Sb-Al melt, giving on the one hand a gas of CO and N2, which contains traces of SO2, and on the other hand an Sb-Al melt containing 40 ~ by weight of manganese. The manganese is removed from the Sb-Al melt in a rectification column.
By heating Bi2S3 to 90QC while argon is passed through, a gas mixture is formed by thermal decomposition, containing in addition to argon 57.1 ~ by volume of Bi vapour and 42.9 % by volume of S2 vapour It is introduced into molten tellurium heated to 930C, resulting in formation of the commercially significant intermetallic compound Bi2Te3 (melting point 585C). The sulphur vapour sep-arated from the Bi vapour escapes.
A reaction pressure which is above or below or equal to 1 atm is adjusted both in dependence upon the thermodynamic properties of the reduction reactants and in dependence upon the reduction temperature. Since the separation of gaseous mixtures in accordance with the invention can be carried out technically more simply when the working pressure is not signif-icantly below 1 atm, it is of advantage in accordance with the invention to add to the gaseous mixture during its formation during and/or after reduction such a quantity of a gas which does not have too adverse an effect upon the metal vapour/gas equili-brium that the required working pressure is reached.
In Example 2, it was pointed out that the reaction pressure of the gaseous mixture of Mg vapour + CO + ~2 + N2 amounts to approximately 0O5 atm and that this pressure is in-creased by the introduction of lead vapour to a working pressure of approximately 1 atm. If no lead vapour were to be introduced and if separation of the gaseous mixture were to be carried out at a working pressure of 1 atm for example, 1 Nm of for example hydrogen, argon or zinc vapour would have to be introduced per Nm3 of gaseous mixture.
3~
As expected, it has been found that, when absorbent and gaseous mixture are brought into contact after reduction, i.e. in the absence of the reduction reactants, metal vapour is absorbed in a quantity which corresponds thermodynamically to its partial pressure, to the vapour pressure of this metal in its pure form and to its activity in the absorbent at the absorption temperature.
However, if the absorbent is brought into contact with the gaseous mixture as it is formed during reduction, i.e. in the presence of the reduction reactants, and then removed as ~uickly as possible, it contains a much larger quantity of absorbed metal vapour than corresponds to the thermodynamic laws. Accordingly, an important feature of the invention is that the gaseous mixture is brought into contact with the absorbent as briefly as possible during its formation during reduction.
In cases where an absorbent has a considerable vapour pressure at the working temperature prevailing so that a signifi-cant amount of its vapour is entrained by the non-absorbed waste gases, the waste gas pipe is initially encrusted and finally blocked through cooling of the waste gases and condensation of absorbent vapour. This also applies correspondingly to the direct heating of the absorption metal with smoke or -flame gases.
According to the invention, this danger is obviated by passing the waste gas and the smoke gas after they have left the absorbent through a condenser from which the condensate either flows back to the absorption metal or from which is it removed mechanically, physically or chemically ~for example by scrapers, melting off or vaporization with chlorine).
In order as far as possible to recover for the process the heat removed from the waste gas in the condenser and the heat content of the smoke gas from the burners which heat the absorben-t and also the heat given off during condensation of -the metal evaporating off during desorption (collectively "waste heat"), the air and/or the fuel for the burner and/or the reducing agent and/or the compound to be reduced are in accordance with the invention heated in known manner (for example in countercurrent heat exchangers) by the waste heat before they are used for combustion or for reduction. In this way, the need for additional fuel is kept to a minimum which ensures maximum economy of the process according to the invention.
The costs of the process according to the invention are surprisingly low and the consumption of electrical energy minimal, amounting solely to the handling costs of the process where the absorbent and endothermically reacting reduction mixtures are not completely or partly heated by electrical energy. Accordingly, an improtant economic feature of the invention is that the metal separated off is either directly used as a vapour after desorption or rectification or cooled and liquefied into a melt or in solid form for processes which are still extremely expensive or which hitherto it has not been possible to work on a commercial scale for reasons of poor economy. An acute example is the reduction 2Q of substantially difficultly reducible metal oxides or halides with metals of the First and Second Group of the Periodic System.
If in accordance with Example 2 the heat required for endothermic reduction of the MgO were to be conventionally supplied and if pure lead were to be used for separating the gaseous mixture (Mg-vapour + H2 + Co + N2), 1200 m /h of Pb melt would be required for absorbing the 30 t/h of Mg-vapour. If pure tin were to be used, only 300 m3/h of Sn melt would need to be introduced because under the Mg partial pressure prevailing tin is able to absorb considerably more magnesium than lead. If the heat required was to be supplied by means of a melt of absorbent, as much as 8580 m3/h of lead (1730C) or 3150 m3/h o tin (1840C) would be necessary (the boilin~ point of lead is 1753C).
However, if as in Example 2 condensing lead vapour is used as heat source for the reduction of MgO and, in addition, if molten tin is used as the principal absorbent, a Pb-Sn-melt is formed as absorbent. From the kechnological point of view, the problem of heat supply for the endothermic reduction of MgO is elegantly solved in this way. I then following separation the magnesium is removed from the melt and the melt reheated to 1840C, lead vapour is again formed, although on this occasion, depending upon the temperature, pressure and activity conditions prevailing, a proportion of lead remains behind in the melt and is continuously circulated together with the tin in the recycle process. Out o this there arises the optimum input of 330 m3/h of Pb-Sn melt containing 42.8 % by weight of Pb and 57.2 % by weight of Sn as liquid absorbent, and 10~,700 Nm3/h of condensed lead vapour as the additional amount of absorbent and heat carrier, coupled with elimination of the need for separate heating of the reduction apparatus.
In the reduction of zinc oxide with carbon at 1000C, a gaseous mixture of 3G 50.37 % by volume of ~n vapour r 48.89 % by volume of CO and 0.74 % by volume of CO2 is formed. This mixture is brought into contact with steel elements (as absorbent) in an absorption chamber. The steel absorbs the zinc vapour, whilst the zinc-free waste gas consist-ing of CO and CO2 leaves the absorption chamber. The zinc is absorbed in the surface of -the steel elements up -to a content of 70 % by weight which in a 1 mm thick surface layer decreases inwards to 0 % of Zn.
In the reduction of MnO with low-sulphur petroleum coke at 1750C, a gas mixture consis-ting of 50 % by volume of manganese vapour and 50 % by volume of CO is formed. Since the reaction pressure is only 0.3 atm, this pressure or a lower pressure as the working pressure would have to be produced by evacuation.
Technically it is simpler to add nitrogen ln order to reach a working pressure of 1 atm. In this case the gas mix-ture consists of 15 % by volume of CO, 15 ~ by volume of Mn vapour and 70 % by volume of N2 The nitrogen is obtained from part of the smoke gas of a burner freed from CO2, SO2 and steam by washing with water under pressure.
It is then heated to 1650C in a countercurrent heat exchanger by means of the hot smoke gas and added to the CO/manganese vapour mixture during its formation from the MnO/petroleum coke mixture.
The gaseous mixture is passed through a melt consisting of 82 % by weight of Sb and 18 % by weight of Al. Whereas the antimony has a particularly high solvent action on manganese, the addition of aluminium prevents the boiling off of antimony whose normal boiling point is 1635C.
The gaseous mixture is separated in the Sb-Al melt, giving on the one hand a gas of CO and N2, which contains traces of SO2, and on the other hand an Sb-Al melt containing 40 ~ by weight of manganese. The manganese is removed from the Sb-Al melt in a rectification column.
By heating Bi2S3 to 90QC while argon is passed through, a gas mixture is formed by thermal decomposition, containing in addition to argon 57.1 ~ by volume of Bi vapour and 42.9 % by volume of S2 vapour It is introduced into molten tellurium heated to 930C, resulting in formation of the commercially significant intermetallic compound Bi2Te3 (melting point 585C). The sulphur vapour sep-arated from the Bi vapour escapes.
A reaction pressure which is above or below or equal to 1 atm is adjusted both in dependence upon the thermodynamic properties of the reduction reactants and in dependence upon the reduction temperature. Since the separation of gaseous mixtures in accordance with the invention can be carried out technically more simply when the working pressure is not signif-icantly below 1 atm, it is of advantage in accordance with the invention to add to the gaseous mixture during its formation during and/or after reduction such a quantity of a gas which does not have too adverse an effect upon the metal vapour/gas equili-brium that the required working pressure is reached.
In Example 2, it was pointed out that the reaction pressure of the gaseous mixture of Mg vapour + CO + ~2 + N2 amounts to approximately 0O5 atm and that this pressure is in-creased by the introduction of lead vapour to a working pressure of approximately 1 atm. If no lead vapour were to be introduced and if separation of the gaseous mixture were to be carried out at a working pressure of 1 atm for example, 1 Nm of for example hydrogen, argon or zinc vapour would have to be introduced per Nm3 of gaseous mixture.
3~
As expected, it has been found that, when absorbent and gaseous mixture are brought into contact after reduction, i.e. in the absence of the reduction reactants, metal vapour is absorbed in a quantity which corresponds thermodynamically to its partial pressure, to the vapour pressure of this metal in its pure form and to its activity in the absorbent at the absorption temperature.
However, if the absorbent is brought into contact with the gaseous mixture as it is formed during reduction, i.e. in the presence of the reduction reactants, and then removed as ~uickly as possible, it contains a much larger quantity of absorbed metal vapour than corresponds to the thermodynamic laws. Accordingly, an important feature of the invention is that the gaseous mixture is brought into contact with the absorbent as briefly as possible during its formation during reduction.
In cases where an absorbent has a considerable vapour pressure at the working temperature prevailing so that a signifi-cant amount of its vapour is entrained by the non-absorbed waste gases, the waste gas pipe is initially encrusted and finally blocked through cooling of the waste gases and condensation of absorbent vapour. This also applies correspondingly to the direct heating of the absorption metal with smoke or -flame gases.
According to the invention, this danger is obviated by passing the waste gas and the smoke gas after they have left the absorbent through a condenser from which the condensate either flows back to the absorption metal or from which is it removed mechanically, physically or chemically ~for example by scrapers, melting off or vaporization with chlorine).
In order as far as possible to recover for the process the heat removed from the waste gas in the condenser and the heat content of the smoke gas from the burners which heat the absorben-t and also the heat given off during condensation of -the metal evaporating off during desorption (collectively "waste heat"), the air and/or the fuel for the burner and/or the reducing agent and/or the compound to be reduced are in accordance with the invention heated in known manner (for example in countercurrent heat exchangers) by the waste heat before they are used for combustion or for reduction. In this way, the need for additional fuel is kept to a minimum which ensures maximum economy of the process according to the invention.
The costs of the process according to the invention are surprisingly low and the consumption of electrical energy minimal, amounting solely to the handling costs of the process where the absorbent and endothermically reacting reduction mixtures are not completely or partly heated by electrical energy. Accordingly, an improtant economic feature of the invention is that the metal separated off is either directly used as a vapour after desorption or rectification or cooled and liquefied into a melt or in solid form for processes which are still extremely expensive or which hitherto it has not been possible to work on a commercial scale for reasons of poor economy. An acute example is the reduction 2Q of substantially difficultly reducible metal oxides or halides with metals of the First and Second Group of the Periodic System.
Claims
THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for separating off a metal vapour or a semi-metal vapour or both from a gaseous mixture which is formed during the reduction of a compound and which contains the vapour of an elemental metal and/or semi-metal, consequently in a rever-sible chemical-thermodynamic equilibrium with the other gaseous components, by absorption of the metal and/or semi-metal vapour directly from the gaseous state, whereas the other non-absorbed gaseous components remain as residual gas, comprising contacting the said gaseous mixture with a liquid or solid absorbent metal or metal salt under such temperature and pressure conditions, i.e.
thermodynamic conditions, that the metal and/or semi-metal vapour cannot be reformed to the original compound.
2. A process as claimed in claim 1, characterised in that the gaseous mixture is brought into contact with the absor-bent as it is formed during reduction.
3. A process as claimed in claim 1, characterised in that the temperature of the absorbent on contact with the gaseous mixture is at least as high as that of the gaseous mixture during its formation.
4. A process as claimed in claim 2, characterised in that the gaseous mixture is brought into contact during its forma-tion with an absorbent having a heat content which is used at least partly for maintaining the reduction temperature.
5. A process as claimed in claim 4, characterised in that the gaseous mixture is brought into contact during its forma-tion in the course of reduction with at least part of the absor-bent in gaseous form which is condensed.
6. A process as claimed in claim 3, 4 or 5 characterised in that before separation the absorbent is heated by direct con-tact with smoke and flame gases and during burning the fuel/air or oxygen ratio is adjusted in such a way that the absorbent can-not be oxidised, or the necessary quantity of reducing gas is added to the smoke and flame gases.
7. A process as claimed in claim 1 characterised in that the absorbed metal is removed from the absorbent, by desorption or rectification, and the resulting metal vapour is cooled.
8. A process as claimed in claim 1, 2 or 3, character-ised in that the solution of absorbed metal and absorbent is used as an alloy or chemical reagent.
9. A process as claimed in claim 1, 2 or 3, character-ised in that following separation only parts of the solution of absorbed metal and absorption metal are reused and the rest is desorbed and the absorbent subsequently used for the separation thereof for the separation of another gaseous mixture.
10. A process as claimed in claim 1, 2 or 3 character-ised in that following separation the non-absorbed waste gas or at least a part thereof is used as fuel and/or another part as chemical reagent.
11. A process as claimed in claim 1, 2 or 3 character-ised in that for avoiding a possible chemical attack by the gas formed during reduction on the absorbent, a sufficient quantity of a gas preventing this attack is added to the gaseous mixture during its formation in the course of or after reduction.
12. A process as claimed in claim 1, 2 or 3, character-ised in that the gaseous mixture is brought into contact, with the absorbent in countercurrent during its formation in the course of and/or after reduction.
13. A process as claimed in claim 1, 2 or 3, character-ised in that the gaseous mixture is continuously brought into con-tact with the absorbent during its formation in the course of and/
or after reduction, the absorbent is then continuously desorbed, directly or indirectly heated in countercurrent, optionally con-tinuously, and is continuously reused for absorption.
13. A process as claimed in claim 1, 2 or 3, character-ised in that impurities are periodically or continuously removed from the absorption metal in known manner.
15. A process as claimed in claim 1, 2 or 3, character-ised in that a gas which does not have too adverse an effect upon the metal vapour/gas equilibrium is added to the gaseous mixture during its formation in the course of and/or after reduction in such a quantity that a desired working pressure is reached.
16. A process as claimed in claim 1, 2 or 3, character-ised in that the gaseous mixture is brought into contact with the absorbent as briefly as possible during its formation in the course of reduction.
17. A process as claimed in claim 3, 4 or 5, character-ised in that after leaving the absorbent the waste gas and the smoke gas are passed through a condenser from which the condensate flows back to the absorbent or from which it is mechanically, physically or chemically removed.
18. A process as claimed in claim 1, 2 or 3 character-ised in that the waste heat of the waste gas and/or of the smoke gas and/or of the desorbed metal vapour are used for heating the air and/or the fuel for the burner and/or the reducing agent and/
or the compound to be reduced.
19. A process as claimed in claim 7, characterised in that following desorption or rectification of the absorbent the metal separated off from the gaseous mixture is used for the reduction of metal oxides or halides.
20. A process for recovering of a metal using the separation process claimed in claim 1, characterised in that an oxide compound of the metal to be recovered is initially reduced with a metallic reducing agent, after which the metal to be recovered is separated from the oxide of the metallic reducing agent so obtained, the oxide of the metallic reducing agent is reduced to form a gaseous mixture and the gaseous mixture is brought into contact with an absorbent, and in that the metallic reducing agent recovered by absorption and desorption is subsequently reused for the first stage of the recycle process.
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for separating off a metal vapour or a semi-metal vapour or both from a gaseous mixture which is formed during the reduction of a compound and which contains the vapour of an elemental metal and/or semi-metal, consequently in a rever-sible chemical-thermodynamic equilibrium with the other gaseous components, by absorption of the metal and/or semi-metal vapour directly from the gaseous state, whereas the other non-absorbed gaseous components remain as residual gas, comprising contacting the said gaseous mixture with a liquid or solid absorbent metal or metal salt under such temperature and pressure conditions, i.e.
thermodynamic conditions, that the metal and/or semi-metal vapour cannot be reformed to the original compound.
2. A process as claimed in claim 1, characterised in that the gaseous mixture is brought into contact with the absor-bent as it is formed during reduction.
3. A process as claimed in claim 1, characterised in that the temperature of the absorbent on contact with the gaseous mixture is at least as high as that of the gaseous mixture during its formation.
4. A process as claimed in claim 2, characterised in that the gaseous mixture is brought into contact during its forma-tion with an absorbent having a heat content which is used at least partly for maintaining the reduction temperature.
5. A process as claimed in claim 4, characterised in that the gaseous mixture is brought into contact during its forma-tion in the course of reduction with at least part of the absor-bent in gaseous form which is condensed.
6. A process as claimed in claim 3, 4 or 5 characterised in that before separation the absorbent is heated by direct con-tact with smoke and flame gases and during burning the fuel/air or oxygen ratio is adjusted in such a way that the absorbent can-not be oxidised, or the necessary quantity of reducing gas is added to the smoke and flame gases.
7. A process as claimed in claim 1 characterised in that the absorbed metal is removed from the absorbent, by desorption or rectification, and the resulting metal vapour is cooled.
8. A process as claimed in claim 1, 2 or 3, character-ised in that the solution of absorbed metal and absorbent is used as an alloy or chemical reagent.
9. A process as claimed in claim 1, 2 or 3, character-ised in that following separation only parts of the solution of absorbed metal and absorption metal are reused and the rest is desorbed and the absorbent subsequently used for the separation thereof for the separation of another gaseous mixture.
10. A process as claimed in claim 1, 2 or 3 character-ised in that following separation the non-absorbed waste gas or at least a part thereof is used as fuel and/or another part as chemical reagent.
11. A process as claimed in claim 1, 2 or 3 character-ised in that for avoiding a possible chemical attack by the gas formed during reduction on the absorbent, a sufficient quantity of a gas preventing this attack is added to the gaseous mixture during its formation in the course of or after reduction.
12. A process as claimed in claim 1, 2 or 3, character-ised in that the gaseous mixture is brought into contact, with the absorbent in countercurrent during its formation in the course of and/or after reduction.
13. A process as claimed in claim 1, 2 or 3, character-ised in that the gaseous mixture is continuously brought into con-tact with the absorbent during its formation in the course of and/
or after reduction, the absorbent is then continuously desorbed, directly or indirectly heated in countercurrent, optionally con-tinuously, and is continuously reused for absorption.
13. A process as claimed in claim 1, 2 or 3, character-ised in that impurities are periodically or continuously removed from the absorption metal in known manner.
15. A process as claimed in claim 1, 2 or 3, character-ised in that a gas which does not have too adverse an effect upon the metal vapour/gas equilibrium is added to the gaseous mixture during its formation in the course of and/or after reduction in such a quantity that a desired working pressure is reached.
16. A process as claimed in claim 1, 2 or 3, character-ised in that the gaseous mixture is brought into contact with the absorbent as briefly as possible during its formation in the course of reduction.
17. A process as claimed in claim 3, 4 or 5, character-ised in that after leaving the absorbent the waste gas and the smoke gas are passed through a condenser from which the condensate flows back to the absorbent or from which it is mechanically, physically or chemically removed.
18. A process as claimed in claim 1, 2 or 3 character-ised in that the waste heat of the waste gas and/or of the smoke gas and/or of the desorbed metal vapour are used for heating the air and/or the fuel for the burner and/or the reducing agent and/
or the compound to be reduced.
19. A process as claimed in claim 7, characterised in that following desorption or rectification of the absorbent the metal separated off from the gaseous mixture is used for the reduction of metal oxides or halides.
20. A process for recovering of a metal using the separation process claimed in claim 1, characterised in that an oxide compound of the metal to be recovered is initially reduced with a metallic reducing agent, after which the metal to be recovered is separated from the oxide of the metallic reducing agent so obtained, the oxide of the metallic reducing agent is reduced to form a gaseous mixture and the gaseous mixture is brought into contact with an absorbent, and in that the metallic reducing agent recovered by absorption and desorption is subsequently reused for the first stage of the recycle process.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP2542595.0 | 1975-09-24 | ||
| DE2542595A DE2542595C2 (en) | 1975-09-24 | 1975-09-24 | Process for separating metal vapors from gaseous mixtures |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1091937A true CA1091937A (en) | 1980-12-23 |
Family
ID=5957293
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA261,574A Expired CA1091937A (en) | 1975-09-24 | 1976-09-20 | Process for the separation of a gaseous mixture |
Country Status (14)
| Country | Link |
|---|---|
| JP (1) | JPS6055573B2 (en) |
| AT (1) | AT365093B (en) |
| AU (1) | AU500562B2 (en) |
| CA (1) | CA1091937A (en) |
| CH (1) | CH611177A5 (en) |
| DD (1) | DD127424A5 (en) |
| DE (1) | DE2542595C2 (en) |
| FR (1) | FR2325418A1 (en) |
| GB (1) | GB1532460A (en) |
| IL (1) | IL50450A (en) |
| IT (1) | IT1070836B (en) |
| NL (1) | NL7610527A (en) |
| NO (1) | NO151863C (en) |
| ZA (1) | ZA765460B (en) |
Families Citing this family (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AU8857782A (en) * | 1981-09-21 | 1983-03-31 | Julian M. Avery | Process for recovering magnesium |
| SE448740B (en) * | 1982-03-02 | 1987-03-16 | Skf Steel Eng Ab | SET AND DEVICE FOR THE REGENERATION OF COW 712 LAUNDRY BY REDUCING IRON OXIDE WITH REDUCING GAS |
| JPS6040048U (en) * | 1983-08-24 | 1985-03-20 | ナカミチ株式会社 | cassette tape recorder |
| DE3411529C2 (en) * | 1984-03-26 | 1994-10-06 | Friedrich Erich Freitag | Process for removing sulfur dioxide and related contaminants from gases |
| US5354363A (en) * | 1993-07-22 | 1994-10-11 | Brown Jr Jesse J | Heavy metal/particulate trap for hot gas clean-up |
| JP2012021185A (en) * | 2010-07-13 | 2012-02-02 | Nisso Engineering Co Ltd | Method and apparatus for recovering magnesium |
| WO2018140468A1 (en) * | 2017-01-30 | 2018-08-02 | Arconic Inc. | Aluminum material for fluxfree cab brazing |
| DE112019004536T5 (en) | 2018-09-11 | 2021-06-02 | Uacj Corporation | METHOD OF MANUFACTURING A HARD SOLDER PLATE |
| JP7165553B2 (en) | 2018-10-01 | 2022-11-04 | 株式会社Uacj | Brazing sheet and its manufacturing method |
| WO2021199116A1 (en) | 2020-03-30 | 2021-10-07 | 株式会社Uacj | Aluminum alloy brazing sheet, and method for manufacturing same |
| CN116987536B (en) * | 2023-06-15 | 2024-03-08 | 英德市西洲气体有限公司 | Argon removal process for methane tower |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| BE479569A (en) * | ||||
| US2416255A (en) * | 1945-03-24 | 1947-02-18 | Dow Chemical Co | Method and apparatus for condensing metallic vapors |
| US3145097A (en) * | 1960-07-04 | 1964-08-18 | Metallurgical Processes Ltd | Shock-chilling condensers for a zinc blast-furnace |
| DE1931481B2 (en) * | 1969-06-20 | 1970-10-22 | Rheinische Braunkohlenw Ag | Process for separating lead fumes from gases |
| BE791823A (en) * | 1971-11-29 | 1973-03-16 | Isc Smelting | COOLING, CONDENSATION AND PURIFICATION OF VAPORS, ESPECIALLY ZINC OR CADMIUM VAPORS |
| JPS526842B2 (en) * | 1972-03-24 | 1977-02-25 | ||
| JPS5213170B2 (en) * | 1972-06-30 | 1977-04-12 | ||
| JPS5718921B2 (en) * | 1974-02-16 | 1982-04-20 |
-
1975
- 1975-09-24 DE DE2542595A patent/DE2542595C2/en not_active Expired
-
1976
- 1976-09-10 ZA ZA765460A patent/ZA765460B/en unknown
- 1976-09-10 IL IL50450A patent/IL50450A/en unknown
- 1976-09-15 AT AT0684476A patent/AT365093B/en not_active IP Right Cessation
- 1976-09-15 AU AU17770/76A patent/AU500562B2/en not_active Expired
- 1976-09-20 GB GB38864/76A patent/GB1532460A/en not_active Expired
- 1976-09-20 CA CA261,574A patent/CA1091937A/en not_active Expired
- 1976-09-21 NO NO763234A patent/NO151863C/en unknown
- 1976-09-22 JP JP51114351A patent/JPS6055573B2/en not_active Expired
- 1976-09-22 DD DD194934A patent/DD127424A5/xx unknown
- 1976-09-22 NL NL7610527A patent/NL7610527A/en not_active Application Discontinuation
- 1976-09-23 IT IT27561/76A patent/IT1070836B/en active
- 1976-09-24 CH CH1215276A patent/CH611177A5/en not_active IP Right Cessation
- 1976-09-24 FR FR7628806A patent/FR2325418A1/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| DE2542595A1 (en) | 1977-04-07 |
| IL50450A (en) | 1979-03-12 |
| NL7610527A (en) | 1977-03-28 |
| JPS6055573B2 (en) | 1985-12-05 |
| ZA765460B (en) | 1977-08-31 |
| AT365093B (en) | 1981-12-10 |
| IT1070836B (en) | 1985-04-02 |
| JPS5240475A (en) | 1977-03-29 |
| FR2325418A1 (en) | 1977-04-22 |
| NO151863C (en) | 1985-06-19 |
| FR2325418B1 (en) | 1983-02-04 |
| DD127424A5 (en) | 1977-09-21 |
| GB1532460A (en) | 1978-11-15 |
| ATA684476A (en) | 1981-05-15 |
| NO151863B (en) | 1985-03-11 |
| CH611177A5 (en) | 1979-05-31 |
| DE2542595C2 (en) | 1986-04-30 |
| AU500562B2 (en) | 1979-05-24 |
| AU1777076A (en) | 1978-03-23 |
| NO763234L (en) | 1977-03-25 |
| IL50450A0 (en) | 1976-11-30 |
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Legal Events
| Date | Code | Title | Description |
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| MKEX | Expiry |