Classifications

• • 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
  • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
  • C23F11/00—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent
  • C23F11/08—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent in other liquids
  • C23F11/10—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent in other liquids using organic inhibitors
  • C23F11/14—Nitrogen-containing compounds
  • C23F11/141—Amines; Quaternary ammonium compounds

Definitions

• the present invention relates to an alkalizing agent for aqueous media in the form of a mixture of amines.
• the alkalizing agent is particularly intended for use in water-steam cycles of power plants which have a once-through boiler as the steam generator.
• a very widely used possibility for conditioning is the alkalization of the water-steam cycle, which is based on the fact that the dissolution of iron from the apparatus parts, which is observed at high temperatures, is reduced by raising the pH.
• An overview of the conditioning of feed water with alkalizing agents can be found in the VGB guideline for boiler feed water, boiler water and Steam from steam generators over 68 bar permissible operating pressure (VGB-R 450 L), published by the VGB technical association of large power plant operators eV, Essen 1988.
• Forced-flow boiler systems are found particularly in power plants of the electricity supply companies and in large industrial plants because they allow in large units, even under supercritical conditions, i.e. to generate steam at very high pressures and high temperatures. It is known that the thermal efficiency of power plants improves with increasing operating temperature.
• Ammonia has been widely used as a volatile alkalizing agent.
• it has turned out to be disadvantageous that, due to its high volatility and its unfavorable distribution between water and steam, it is not possible to achieve a uniform alkalization of all parts of the circuit.
• One has therefore searched for less volatile bases and has already used mixtures of differently volatile amines in order to use the special conditions of Phase transition during evaporation, condensation and in the two-phase area of wet steam to inhibit the respective forms of corrosion.
• European Patent Application No. 0'134'365 discloses a means for corrosion inhibition in steam generators or for conditioning boiler feed water for power plants with a circulation boiler and operating conditions of 35 bar / 320 ° C in the boiler.
• the agent consists of a "film-forming" amine and at least one alkalizing amine.
• the object of the invention was to provide an alkalizing agent that meets the requirements specified above and is particularly suitable for use as a water conditioning agent in high-performance steam boiler systems for corrosion protection.
• the corrosion protection effect in the steam boiler should be achieved, and on the other hand, all downstream components, in particular the turbine, should be protected against corrosion.
• the agent is composed of at least three different types of amines, namely (a) a monoalkanolamine, (b) optionally substituted cyclohexylamine and (c) at least one film-forming long-chain aliphatic polyamine, also known as fatty polyamine.
• the role of the first component namely the monoalkanolamine, is seen in the fact that it primarily serves to permanently alkalize the aqueous phase including the condensate.
• the amino alcohol used is in particular one which has a boiling point between 150 and 190 ° C., for example monoethanolamine (1-aminoethanol) or isopropanolamine (2-amino-2-methyl-1-propanol).
• monoethanolamine 1-aminoethanol
• isopropanolamine 2-amino-2-methyl-1-propanol
• other amino alcohols can also be used, provided that they have the properties described above.
• the second component of the alkalizing agent according to the invention is optionally substituted cyclohexylamine. It is an amine volatile with water vapor, which forms an amine-containing, ie basic, protective layer and stabilizes the magnetite protective layer. It was found that the layer mentioned consists predominantly of dicyclohexylamine, which, under the conditions of use in a steam boiler, was formed from two molecules of cyclohexylamine according to the following scheme: 2 C 6 H 11 NH 2nd ⁇ (C 6 H 11 ) 2nd NH + NH 3rd
• the present invention proposes to use unsubstituted cyclohexylamine; but there are also inert substituted cyclohexylamines, such as. B. dicyclohexylamine, methylcyclohexylamine, ethylcyclohexylamine, dimethylcyclohexylamine and others. Such compounds are by hydrogenation of the corresponding aromatic amines or nitro compounds easily accessible.
• the optionally substituted cyclohexylamine acts as a hydrotrope in the preparation of the composition according to the invention and also has the property of increasing the volatility of the third component described below and of bringing it to the turbine in larger amounts than hitherto.
• the alkalizing agent according to the invention accordingly not only acts to set the desired pH value in the feed water and in the steam boiler, but also forms corrosion protection layers in all parts of the system.
• Examples of such polyamines are Dodecylaminomethylenamin, Dodecylaminodimethylenamin, Dodecylaminotrimethylenamin, the corresponding tetradecyl, hexadecyl and octadecylamine, Octadecenylaminotrimethylenamin, Octadecenylaminodi- (trimethylamino) -trimethylenamin, Palmitylaminotrimethylenamin, Hexadecenylaminotrimethylenamin, Dodecenylaminotrimethylenamin, etc.
• the N-oleyl-1,3-propanediamine ie octadecen (9) ylaminotrimethyleneamine
• the proportions of the three components of the alkalizing agent according to the invention described above can vary within wide limits depending on the conditions of use and the individual substances chosen in each case. If, for example, component (a) monoethanolamine, component (b) cyclohexylamine and component (c) oleylaminopropyleneamine are chosen, the weight fractions of components (a), (b) and (c) are pure, i.e. 100% related connections, such as (40-70) :( 30-50) :( 4-10), the sum of the three components adding up to 100.
• the alkalizing agent according to the invention can also contain other constituents, generally in very small amounts, so as not to impair the effect. For example, you can stain the labeling agent.
• the alkalizing agent according to the invention is preferably formulated as an aqueous, relatively concentrated solution which can be easily metered into the system to be conditioned.
• An aqueous mixture containing about 4 to 25% by weight of the alkalizing agent is a clear, stable solution, although it contains up to about 4% by weight of fatty alkyl polyamine, which is only slightly water-soluble per se.
• the cyclohexylamine is an effective solubilizer, that is to say a hydrotropic substance, for the fatty polyamine.
• the procedure is advantageously firstly to prepare a relatively concentrated aqueous solution of monoethanolamine, which is freely miscible with water, and then to stir in a previously prepared mixture of the fatty aminoalkylene amine and the cyclohexylamine.
• a relatively concentrated aqueous solution is obtained in this way, which can then be diluted without restriction with water, preferably pure, demineralized and non-carbonated water, preferably to an approximately 15% solution.
• the latter has a pH of about 12 to 12.5.
• the alkalizing agent according to the invention is generally used in proportions which correspond to an active ingredient concentration in the water of about 0.5 to 5 ppm. Higher shares can also be provided, should this be necessary in special cases. Since the agent of the invention can be provided as an aqueous solution, it is possible to dose easily and precisely.
• the alkalizing agent according to the invention was tested in a large-scale test for its effectiveness.
• a solution of the above-described alkalizing agent was added to the feed water in the metering station for conditioning agent of a power plant block, containing a once-through boiler, operating pressure 180 bar (18 MPa), main steam temperature 540 ° C, and a steam turbine with an output of 311 MW, such that a Concentration of 1 to 2 mg / l (1 to 2 ppm) was set and maintained.
• Steam samples were continuously taken from the live steam line, the samples through Cooling condenses, the condensate is passed through a strongly acidic ion exchanger and finally the conductance is measured in the outlet of the ion exchanger.
• the pH value of the condensate (in front of the ion exchanger) was in the range from 8.7 to 9.5 with a most common value of 9.4.
• the conductivity was approximately 0.15 to 0.16 ⁇ S ⁇ cm -1 . It must be said that the guidelines of the VGB (Technical Association of Large Power Plant Operators eV) for boiler feed water for corresponding power plants have a pH value of 9.5 ⁇ 0.2 and for conductivity a value of ⁇ 0.2 ⁇ S ⁇ cm -1 provide.
• alkalizing agent of the invention is not limited to a once-through boiler; it is clear to the person skilled in the art that the concept of the invention can be applied to all boiler and power plant systems, e.g. also circulation boiler.
• the alkalizing agent according to the invention can not only be used as a water conditioning agent for high-performance steam boilers, but it can also be used wherever a mixture of amines is to be used, for example as a neutralizing agent, for the production of soil waxes based on fatty acid amides and imides, complexing agents and the like.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Preventing Corrosion Or Incrustation Of Metals (AREA)
• Macromolecular Compounds Obtained By Forming Nitrogen-Containing Linkages In General (AREA)
• Steam Or Hot-Water Central Heating Systems (AREA)
• Jet Pumps And Other Pumps (AREA)

Priority Applications (3)

Applications Claiming Priority (1)

Publications (2)

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Cited By (5)

Citations (8)

• 1996
  • 1996-05-06 DE DE59602547T patent/DE59602547D1/de not_active Expired - Lifetime
  • 1996-05-06 AT AT96810289T patent/ATE182633T1/de active
  • 1996-05-06 EP EP96810289A patent/EP0807696B1/fr not_active Expired - Lifetime

Patent Citations (8)

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