EP0216067A1 - Process and apparatus for removing alkali nitrite from salt baths containing nitrate - Google Patents
Process and apparatus for removing alkali nitrite from salt baths containing nitrate Download PDFInfo
- Publication number
- EP0216067A1 EP0216067A1 EP86110169A EP86110169A EP0216067A1 EP 0216067 A1 EP0216067 A1 EP 0216067A1 EP 86110169 A EP86110169 A EP 86110169A EP 86110169 A EP86110169 A EP 86110169A EP 0216067 A1 EP0216067 A1 EP 0216067A1
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- European Patent Office
- Prior art keywords
- nitrite
- bath
- nitrate
- salt
- salt bath
- 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.)
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- 150000003839 salts Chemical class 0.000 title claims abstract description 25
- IOVCWXUNBOPUCH-UHFFFAOYSA-M Nitrite anion Chemical compound [O-]N=O IOVCWXUNBOPUCH-UHFFFAOYSA-M 0.000 title claims abstract description 16
- 229910002651 NO3 Inorganic materials 0.000 title claims abstract description 12
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 title claims abstract description 12
- 238000000034 method Methods 0.000 title claims description 8
- 239000003513 alkali Substances 0.000 title claims description 5
- 238000001816 cooling Methods 0.000 claims abstract description 14
- 238000005121 nitriding Methods 0.000 claims description 8
- 238000009423 ventilation Methods 0.000 claims description 7
- 230000003647 oxidation Effects 0.000 claims description 2
- 238000007254 oxidation reaction Methods 0.000 claims description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 abstract description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 abstract description 4
- 230000015572 biosynthetic process Effects 0.000 abstract description 3
- 229910000831 Steel Inorganic materials 0.000 abstract description 2
- 229910052742 iron Inorganic materials 0.000 abstract description 2
- 239000010959 steel Substances 0.000 abstract description 2
- 150000002826 nitrites Chemical class 0.000 abstract 2
- LPXPTNMVRIOKMN-UHFFFAOYSA-M sodium nitrite Chemical compound [Na+].[O-]N=O LPXPTNMVRIOKMN-UHFFFAOYSA-M 0.000 description 16
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 12
- HEMHJVSKTPXQMS-UHFFFAOYSA-M sodium hydroxide Inorganic materials [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 11
- 235000010288 sodium nitrite Nutrition 0.000 description 8
- 239000000203 mixture Substances 0.000 description 7
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 6
- VWDWKYIASSYTQR-UHFFFAOYSA-N sodium nitrate Chemical compound [Na+].[O-][N+]([O-])=O VWDWKYIASSYTQR-UHFFFAOYSA-N 0.000 description 6
- 235000017550 sodium carbonate Nutrition 0.000 description 3
- 229910000029 sodium carbonate Inorganic materials 0.000 description 3
- 235000010344 sodium nitrate Nutrition 0.000 description 3
- 238000011282 treatment Methods 0.000 description 3
- XFXPMWWXUTWYJX-UHFFFAOYSA-N Cyanide Chemical compound N#[C-] XFXPMWWXUTWYJX-UHFFFAOYSA-N 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- XLJMAIOERFSOGZ-UHFFFAOYSA-M cyanate group Chemical group [O-]C#N XLJMAIOERFSOGZ-UHFFFAOYSA-M 0.000 description 2
- 238000001784 detoxification Methods 0.000 description 2
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- 238000005273 aeration Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 230000008929 regeneration Effects 0.000 description 1
- 238000011069 regeneration method Methods 0.000 description 1
- 238000009877 rendering Methods 0.000 description 1
- 238000011144 upstream manufacturing Methods 0.000 description 1
Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/56—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering characterised by the quenching agents
- C21D1/607—Molten salts
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/34—Methods of heating
- C21D1/44—Methods of heating in heat-treatment baths
- C21D1/46—Salt baths
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C8/40—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using liquids, e.g. salt baths, liquid suspensions
Definitions
- the invention relates to a method for removing alkali nitrite from nitrate-containing salt baths used for cooling components after nitriding, and a corresponding device.
- DE-PS 25 14 398 describes a salt bath for cooling bath-nitrided iron and steel components, which contains sodium and potassium hydroxide with about 10% alkali nitrate.
- This salt bath is being used to an increasing extent in industry in order to convert the cyanide and cyanate residues adhering to the bath-nitrided components when they are removed from the nitriding bath, thereby rendering them harmless.
- These salt baths became particularly important when it was found that a significant increase in the corrosion resistance of nitrided components can be achieved under changed treatment conditions.
- the procedure is usually such that the workpieces remain in the cooling bath operated at a temperature of 330 to 400 ° C. until they have reached its temperature and the detoxification reaction or the anti-corrosion treatment has been completed.
- the workpieces are then removed from the cooling bath and cooled in cold water. If the cooling bath contains nitrite, this accumulates in the water used for cooling. Accordingly, this water must also be detoxified. This additional operation can be saved if the formation of the nitrite can be prevented or the nitrite can be destroyed immediately after its formation.
- nitrite formed in the salt bath is oxidized there to nitrate.
- air is preferably blown through the bath during the breaks.
- This bath regeneration is most effective when the air flows through the salt bath in a very fine distribution.
- This can best be achieved with an annular ventilation pipe, which is below the usually in suchi is attached to existing circulation stirrers.
- the annular ventilation pipe (4) is provided on the surface facing the circulation stirrer (3) with bores (5) so that the air emerging therefrom is passed directly into the circulation stirrer (3) and is distributed by it in the bath (2), which is in a crucible (1).
- the amount of air required naturally depends primarily on the amount of nitrite formed and thus on the amount of nitriding salt introduced into the cooling bath, ultimately on the size, shape and amount of the components treated. Arithmetically, there is an air requirement of approximately 1,625 liters per kg of sodium nitrite to be oxidized. The device described achieves a degree of utilization of 60 to 80%, which is why in practice 2,000 to 2,700 liters of air per kg of sodium nitrite are required.
- the percentage of sodium nitrite corresponded to an absolute amount of 0.9 kg. Calculated, the air requirement was 1,465 liters (with 100% utilization). Since the degree of utilization was not known beforehand, double air volume was used. With the available time of 7 hours, 420 liters of air per hour had to be passed through the bath. After just 4.5 hours, ongoing analytical monitoring showed that the sodium nitrite content had dropped to 0 percent. This results in a degree of utilization of the air of 78%. At the same time as the ventilation, the bath was desludged, so that the following bath composition was present in% by weight when work was restarted: NaOH 19.1 KOH 42.5 Na2CO3 27.6 NaNO3 10.8 NaNO2 0.0
- the absolute amount of NaNO2 formed was 18 kg, the calculated amount of air 29,250 liters.
- double air volume was used first.
- this large cooling bath had two circulators, so the ventilation was also carried out via two ventilation pipes. 1,220 liters of air were introduced per hour into each ventilation pipe. In this case too, it was found that the nitrite was completely converted after 15 hours, which corresponds to a degree of utilization of almost 80%.
- the composition of the bath after aeration corresponded to the specified starting composition except for slight differences.
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Physics & Mathematics (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Inorganic Compounds Of Heavy Metals (AREA)
- Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
- Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
Abstract
Beim Behandeln von salzbadnitrierten Bauteilen aus Eisen und Stahl in nitrathaltigen Abkühlbädern entstehen Nitrite, die aus dem Waschwasser entfernt werden müssen. Diese Nitritbildung kann man vermeiden, wenn man das im Salzbad gebildete Nitrit dort zu Nitrat oxidiert, vorzugsweise durch Einleiten von Luft in den Betriebspausen. When treating salt bath nitrided components made of iron and steel in cooling baths containing nitrate, nitrites are formed which have to be removed from the wash water. This nitrite formation can be avoided if the nitrite formed in the salt bath is oxidized there to nitrate, preferably by introducing air during the breaks in operation.
Description
Die Erfindung betrifft ein Verfahren zur Entfernung von Alkalinitrit aus nitrathaltigen, zum Abkühlen von Bauteilen nach dem Nitrieren verwendeten Salzbädern und eine entsprechende Vorrichtung.The invention relates to a method for removing alkali nitrite from nitrate-containing salt baths used for cooling components after nitriding, and a corresponding device.
In der DE-PS 25 14 398 wird ein Salzbad zum Kühlen badnitrierter Bauteile aus Eisen und Stahl beschrieben, das Natrium- und Kaliumhydroxid mit etwa 10 % Alkalinitrat enthält. Dieses Salzbad wird in zunehmendem Umfang in der Industrie eingesetzt, um die den badnitrierten Bauteilen bei Entnahme aus dem Nitrierbad anhaftenden Cyanid- und Cyanatreste zu Carbonat umzusetzen und damit unschädlich zu machen. Besondere Bedeutung erlangten diese Salzbäder, als sich herausstellte, daß unter veränderten Behandlungsbedingungen eine deutliche Erhöhung des Korrosionswiderstandes nitrierter Bauteile erreichbar ist.DE-PS 25 14 398 describes a salt bath for cooling bath-nitrided iron and steel components, which contains sodium and potassium hydroxide with about 10% alkali nitrate. This salt bath is being used to an increasing extent in industry in order to convert the cyanide and cyanate residues adhering to the bath-nitrided components when they are removed from the nitriding bath, thereby rendering them harmless. These salt baths became particularly important when it was found that a significant increase in the corrosion resistance of nitrided components can be achieved under changed treatment conditions.
Bei Betrieb dieser Salzbäder wird, besonders bei hohen Durchsätzen, durch die Umsetzung von Cyanid und Cyanat zu Carbonat ein Teil des Nitrates zu Nitrit reduziert. In der Praxis wird üblicherwiese so verfahren, daß die Werkstücke mindestens so lange in dem bei einer Temperatur von 330 bis 400° C betriebenen Abkühlbad verbleiben, bis sie dessen Temperatur angenommen haben und die Entgiftungsreaktion bzw. die Korrosionsschutzbehandlung abgeschlossen ist. Dann werden die Werkstücke dem Abkühlbad entnommen und in kaltem Wasser abgekühlt. Enthält des Abkühlbad Nitrit, reichert sich dieses in dem zum Abkühlen verwendeten Wasser an. Dementsprechend muß dieses Wasser ebenfalls entgiftet werden. Dieser zusätzliche Arbeitsgang kann eingespart werden, wenn die Entstehung des Nitrits unterbunden oder das Nitrit unmittelbar nach seiner Entstehung vernichtet werden kann.When these salt baths are operated, especially at high throughputs, some of the nitrate is reduced to nitrite by the conversion of cyanide and cyanate to carbonate. In practice, the procedure is usually such that the workpieces remain in the cooling bath operated at a temperature of 330 to 400 ° C. until they have reached its temperature and the detoxification reaction or the anti-corrosion treatment has been completed. The workpieces are then removed from the cooling bath and cooled in cold water. If the cooling bath contains nitrite, this accumulates in the water used for cooling. Accordingly, this water must also be detoxified. This additional operation can be saved if the formation of the nitrite can be prevented or the nitrite can be destroyed immediately after its formation.
Es war daher Aufgabe der vorliegenden Erfindung, ein Verfahren zur Entfernung von Alkalinitrit aus nitrathaltigen, zum Abkühlen von Bauteilen nach dem Nitrieren verwendeten Salzbädern zu entwickeln, um einen zusätzlichen Entgiftungsarbeitsgang zu vermeiden.It was therefore an object of the present invention to develop a method for removing alkali nitrite from nitrate-containing salt baths used for cooling components after nitriding in order to avoid an additional detoxification operation.
Diese Aufgabe wird erfindungsgemäß dadurch gelöst, daß das im Salzbad gebildete Nitrit dort zu Nitrat oxidiert wird. Vorzugsweise wird hierzu in den Betriebspausen Luft durch das Bad geblasen.This object is achieved in that the nitrite formed in the salt bath is oxidized there to nitrate. For this purpose, air is preferably blown through the bath during the breaks.
Mit dieser einfachen und einfach durchzuführenden Maßnahme gelingt es überraschenderweise, in der Salzschmelze das gebildete Nitrit zu Nitrat zu oxidieren. Die Behandlung des Abkühlbades erfolgt in Betriebspausen, z.B. nachts, an Wochenenden oder, wenn im vorgeschalteten Nitriersalzbad über längere Zeit keine Bauteilnitrierung erfolgt. Es ist von Vorteil, die Oxidationsbehandlungen in möglichst kurzen Zeiträumen durchzuführen, um das sich bildende Nitrit möglichst schon bei geringen Konzentrationen zu oxidieren.With this simple and simple measure, it is surprisingly possible to oxidize the nitrite formed to nitrate in the molten salt. The cooling bath is treated during breaks, e.g. at night, on weekends or when there is no component nitriding for a long time in the upstream nitriding salt bath. It is advantageous to carry out the oxidation treatments in as short a time as possible in order to oxidize the nitrite that is formed, if possible even at low concentrations.
Diese Badregenerierung ist am wirkungsvollsten, wenn die Luft in sehr feiner Verteilung durch das Salzbad strömt. Das läßt sich am besten erreichen mit einem ringförmigen Belüftungsrohr, das unterhalb des üblicherweise in derarti gen Bädern vorhandenen Umwälzrührers angebracht ist. Die Abbildung zeigt schematisch eine beispielhafte Ausführungsform. Das ringförmige Belüftungsrohr (4) ist an der zum Umwälzrührer (3) gerichteten Oberfläche mit Bohrungen (5) versehen, so daß die daraus austretende Luft direkt in den Umwälzrührer (3) geleitet und von diesem im Bad (2) verteilt wird, das sich in einem Tiegel (1) befindet.This bath regeneration is most effective when the air flows through the salt bath in a very fine distribution. This can best be achieved with an annular ventilation pipe, which is below the usually in suchi is attached to existing circulation stirrers. The figure schematically shows an exemplary embodiment. The annular ventilation pipe (4) is provided on the surface facing the circulation stirrer (3) with bores (5) so that the air emerging therefrom is passed directly into the circulation stirrer (3) and is distributed by it in the bath (2), which is in a crucible (1).
Die notwendige Luftmenge hängt naturgemäß primär von der Menge des entstehenden Nitrits ab und damit von der Menge des in das Abkühlbad eingebrachten Nitriersalzes, letzten Endes also von Größe, Form und Menge der behandelten Bauteile.
Rechnerisch ergibt sich ein Luftbedarf von ca. 1.625 Liter pro kg zu oxidierenden Natriumnitrits. Mit der beschriebenen Vorrichtung erreicht man einen Ausnutzungsgrad von 60 bis 80 %, weshalb man in der Praxis 2.000 bis 2.700 Liter Luft pro kg Natriumnitrit benötigt.The amount of air required naturally depends primarily on the amount of nitrite formed and thus on the amount of nitriding salt introduced into the cooling bath, ultimately on the size, shape and amount of the components treated.
Arithmetically, there is an air requirement of approximately 1,625 liters per kg of sodium nitrite to be oxidized. The device described achieves a degree of utilization of 60 to 80%, which is why in practice 2,000 to 2,700 liters of air per kg of sodium nitrite are required.
Folgende Beispiele sollen das erfindungsgemäße Verfahren näher erläutern.The following examples are intended to explain the process according to the invention in more detail.
1. In einer Salzbadnitrieranlage wurden in zwei Schichten stabförmige Bauteile salzbadnitriert und in einem Salzbad, das eine Temperatur von 370° C hatte, abgekühlt. Die Wanne, die das Abkühlsalzbad enthielt, hatte eine Größe von 800 x 600 x 900 mm und einen Salzinhalt von 900 kg mit folgender Ausgangszusammensetzung (in Gew.-%):
NaOH 18,4
KOH 42,5
Na₂CO₃ 28,3
NaNO₃ 10,8
NaNO₂ 0,01. In a salt bath nitriding plant, rod-shaped components were salt bath nitrided in two layers and cooled in a salt bath which had a temperature of 370 ° C. The tub, which contained the cooling salt bath, had a size of 800 x 600 x 900 mm and a salt content of 900 kg with the following starting composition (in% by weight):
NaOH 18.4
KOH 42.5
Na₂CO₃ 28.3
NaNO₃ 10.8
NaNO₂ 0.0
Nach einer Betriebsdauer von 16 Stunden (= 2 Schichten) hatte sich die Zusammensetzung des Bades in Gew.-% wie folgt geändert:
NaOH 18,2
KOH 41,8
Na₂CO₃ 29,2
NaNO₃ 10,7
NaNO₂ 0,1After an operating time of 16 hours (= 2 layers), the composition of the bath in% by weight had changed as follows:
NaOH 18.2
KOH 41.8
Na₂CO₃ 29.2
NaNO₃ 10.7
NaNO₂ 0.1
Der prozentuale Gehalt an Natriumnitrit entsprach einer absoluten Menge von 0,9 kg. Rechnerisch ergab sich ein Luftbedarf von 1.465 Liter (bei 100 % Ausnutzung). Da der Ausnutzungsgrad vorher nicht bekannt war, wurde mit der doppelten Luftmenge gearbeitet. Bei der zur Verfügung stehenden Zeit von 7 Stunden waren demnach 420 Liter Luft pro Stunde durch das Bad zu leiten. Bereits nach 4,5 Stunden zeigte die laufende analytische Überwachung, daß der Gehalt an Natriumnitrit auf 0 Prozent gesunken war. Es errechnet sich daraus ein Ausnutzungsgrad der Luft von 78 %. Gleichzeitig mit der Belüftung wurde das Bad entschlammt, so daß bei Wiederbeginn der Arbeit folgende Badzusammensetzung in Gew.-% vorlag:
NaOH 19,1
KOH 42,5
Na₂CO₃ 27,6
NaNO₃ 10,8
NaNO₂ 0,0The percentage of sodium nitrite corresponded to an absolute amount of 0.9 kg. Calculated, the air requirement was 1,465 liters (with 100% utilization). Since the degree of utilization was not known beforehand, double air volume was used. With the available time of 7 hours, 420 liters of air per hour had to be passed through the bath. After just 4.5 hours, ongoing analytical monitoring showed that the sodium nitrite content had dropped to 0 percent. This results in a degree of utilization of the air of 78%. At the same time as the ventilation, the bath was desludged, so that the following bath composition was present in% by weight when work was restarted:
NaOH 19.1
KOH 42.5
Na₂CO₃ 27.6
NaNO₃ 10.8
NaNO₂ 0.0
2. Wellenförmige Bauteile wurden salzbadnitriert und in einem Abkühlbad abgekühlt. Die Wannengröße betrug 1200 x 1700 x 1500 mm, der Salzinhalt 6000 kg, die Temperatur 370° C. Gearbeitet wurde in drei Schichten. Nachstehend wird die Ausgangszusammensetzung des Bades und dessen Zusammensetzung nach 112 Stunden Arbeitszeit angegeben:
Die absolute Menge an gebildetem NaNO₂ betrug 18 kg, die rechnerische Luftmenge 29.250 Liter. Auch hier wurde zunächst mit der doppelten Luftmenge gearbeitet. Allerdings verfügte dieses große Abkühlbad über zwei Umwälzer, daher wurde die Belüftung auch über zwei Belüftungsrohre durchgeführt. Je Belüftungsrohr wurden 1.220 Liter Luft pro Stunde eingeleitet. Auch in diesem Falle wurde festgestellt, daß bereits nach 15 Stunden das Nitrit völlig umgesetzt war, was einem Ausnutzungsgrad von nahezu 80 % entspricht. Die Zusammensetzung des Bades nach der Belüftung entsprach bis auf geringe Unterschiede der angegebenen Ausgangszusammensetzung.The absolute amount of NaNO₂ formed was 18 kg, the calculated amount of air 29,250 liters. Here too, double air volume was used first. However, this large cooling bath had two circulators, so the ventilation was also carried out via two ventilation pipes. 1,220 liters of air were introduced per hour into each ventilation pipe. In this case too, it was found that the nitrite was completely converted after 15 hours, which corresponds to a degree of utilization of almost 80%. The composition of the bath after aeration corresponded to the specified starting composition except for slight differences.
Claims (3)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AT86110169T ATE43647T1 (en) | 1985-09-24 | 1986-07-24 | METHOD AND APPARATUS FOR REMOVING ALKALINITRITE FROM NITRATE CONTAINING SALT BATHS. |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE3533935 | 1985-09-24 | ||
| DE3533935A DE3533935C1 (en) | 1985-09-24 | 1985-09-24 | Method and device for removing alkali nitrite from nitrate salt baths |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP0216067A1 true EP0216067A1 (en) | 1987-04-01 |
| EP0216067B1 EP0216067B1 (en) | 1989-05-31 |
Family
ID=6281734
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP86110169A Expired EP0216067B1 (en) | 1985-09-24 | 1986-07-24 | Process and apparatus for removing alkali nitrite from salt baths containing nitrate |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US4717429A (en) |
| EP (1) | EP0216067B1 (en) |
| JP (1) | JPH076055B2 (en) |
| AT (1) | ATE43647T1 (en) |
| DE (2) | DE3533935C1 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6117249A (en) * | 1998-02-13 | 2000-09-12 | Kerk Motion Products, Inc. | Treating metallic machine parts |
| US6746546B2 (en) | 2001-11-02 | 2004-06-08 | Kolene Corporation | Low temperature nitriding salt and method of use |
| SE530783C2 (en) * | 2007-01-16 | 2008-09-09 | Westinghouse Electric Sweden | Scatter grid for positioning fuel rods |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4268397A (en) * | 1978-07-29 | 1981-05-19 | The Furukawa Electric Co., Ltd. | Method of treating waste water |
| US4280914A (en) * | 1978-12-05 | 1981-07-28 | Deutsche Gold- Und Silber-Scheideanstalt Vormals Roessler | Process for automatically controlling the detoxification of waste waters containing nitrite ions |
| US4294706A (en) * | 1979-05-16 | 1981-10-13 | Osaka Gas Company, Limited | Process for treating waste water |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3793208A (en) * | 1973-01-04 | 1974-02-19 | Park Chem Co | Method of rectifying commercial salt baths |
| DE2340405C3 (en) * | 1973-08-09 | 1978-05-03 | Ekkehard 7050 Waiblingen Mohr | Process for the treatment of flush and waste water from salt bath hardening shops |
| US4149702A (en) * | 1976-03-25 | 1979-04-17 | Park Chemical Company | Method and apparatus for recycling heat treating salts |
| US4396439A (en) * | 1981-08-21 | 1983-08-02 | Park Chemical Company | Recovery and recycle of nitrate and nitrite salts from chloride containing quench bath solids |
| US4568352A (en) * | 1984-05-24 | 1986-02-04 | Olin Corporation | Alkali metal nitrate purification |
-
1985
- 1985-09-24 DE DE3533935A patent/DE3533935C1/en not_active Expired
-
1986
- 1986-07-24 DE DE8686110169T patent/DE3663688D1/en not_active Expired
- 1986-07-24 AT AT86110169T patent/ATE43647T1/en not_active IP Right Cessation
- 1986-07-24 EP EP86110169A patent/EP0216067B1/en not_active Expired
- 1986-08-05 US US06/893,513 patent/US4717429A/en not_active Expired - Lifetime
- 1986-09-24 JP JP61223963A patent/JPH076055B2/en not_active Expired - Lifetime
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4268397A (en) * | 1978-07-29 | 1981-05-19 | The Furukawa Electric Co., Ltd. | Method of treating waste water |
| US4280914A (en) * | 1978-12-05 | 1981-07-28 | Deutsche Gold- Und Silber-Scheideanstalt Vormals Roessler | Process for automatically controlling the detoxification of waste waters containing nitrite ions |
| US4294706A (en) * | 1979-05-16 | 1981-10-13 | Osaka Gas Company, Limited | Process for treating waste water |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS6286152A (en) | 1987-04-20 |
| DE3533935C1 (en) | 1986-06-05 |
| JPH076055B2 (en) | 1995-01-25 |
| US4717429A (en) | 1988-01-05 |
| ATE43647T1 (en) | 1989-06-15 |
| EP0216067B1 (en) | 1989-05-31 |
| DE3663688D1 (en) | 1989-07-06 |
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