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
  • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
  • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
• • 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
  • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
  • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
  • C23G1/14—Cleaning or pickling metallic material with solutions or molten salts with alkaline solutions
  • C23G1/19—Iron or steel
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B08—CLEANING
  • B08B—CLEANING IN GENERAL; PREVENTION OF FOULING IN GENERAL
  • B08B9/00—Cleaning hollow articles by methods or apparatus specially adapted thereto 
  • B08B9/08—Cleaning containers, e.g. tanks
• • 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
  • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
  • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
  • C23G1/14—Cleaning or pickling metallic material with solutions or molten salts with alkaline solutions
  • C23G1/20—Other heavy metals
• • 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
  • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
  • C23G5/00—Cleaning or de-greasing metallic material by other methods; Apparatus for cleaning or de-greasing metallic material with organic solvents
  • C23G5/02—Cleaning or de-greasing metallic material by other methods; Apparatus for cleaning or de-greasing metallic material with organic solvents using organic solvents
  • C23G5/032—Cleaning or de-greasing metallic material by other methods; Apparatus for cleaning or de-greasing metallic material with organic solvents using organic solvents containing oxygen-containing compounds
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F22—STEAM GENERATION
  • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
  • F22B37/00—Component parts or details of steam boilers
  • F22B37/02—Component parts or details of steam boilers applicable to more than one kind or type of steam boiler
  • F22B37/48—Devices for removing water, salt, or sludge from boilers; Arrangements of cleaning apparatus in boilers; Combinations thereof with boilers
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F22—STEAM GENERATION
  • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
  • F22B37/00—Component parts or details of steam boilers
  • F22B37/02—Component parts or details of steam boilers applicable to more than one kind or type of steam boiler
  • F22B37/48—Devices for removing water, salt, or sludge from boilers; Arrangements of cleaning apparatus in boilers; Combinations thereof with boilers
  • F22B37/483—Devices for removing water, salt, or sludge from boilers; Arrangements of cleaning apparatus in boilers; Combinations thereof with boilers specially adapted for nuclear steam generators
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28G—CLEANING OF INTERNAL OR EXTERNAL SURFACES OF HEAT-EXCHANGE OR HEAT-TRANSFER CONDUITS, e.g. WATER TUBES OR BOILERS
  • F28G9/00—Cleaning by flushing or washing, e.g. with chemical solvents
• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
  • G21F9/00—Treating radioactively contaminated material; Decontamination arrangements therefor
  • G21F9/001—Decontamination of contaminated objects, apparatus, clothes, food; Preventing contamination thereof
  • G21F9/002—Decontamination of the surface of objects with chemical or electrochemical processes
• • G—PHYSICS
  • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
  • G21F—PROTECTION AGAINST X-RADIATION, GAMMA RADIATION, CORPUSCULAR RADIATION OR PARTICLE BOMBARDMENT; TREATING RADIOACTIVELY CONTAMINATED MATERIAL; DECONTAMINATION ARRANGEMENTS THEREFOR
  • G21F9/00—Treating radioactively contaminated material; Decontamination arrangements therefor
  • G21F9/28—Treating solids
  • G21F9/30—Processing

Definitions

• the invention relates to a method for the removal of magnetite and copper-containing deposits from containers of industrial and power plants, especially from steam generators of nuclear power plants.
• the copper comes from components such as pumps, valves, brass-plated capacitors and the like. and is present in metallic form, but also in part as copper oxide.
• Most of the installations of the water-steam circuit of nuclear power plants consist of carbon steel or low-alloy steels.
• Some of the deposits adhere to the component surfaces as deposits, and some of them settle as sludge in containers, such as the steam generators, such as a steam generator.
• the deposits must be removed from time to time because, for example in the case of steam generators, they hinder the heat transfer to heat exchanging walls or cause selective corrosion.
• the inner surfaces of the container are contacted with a cleaning solution, usually at elevated temperature, to dissolve the deposits containing magnetite (Fe 3 O 4 ), copper oxide (Cu 2 O) and metallic copper.
• a cleaning solution usually at elevated temperature
• the material of the container which is referred to below as the base metal
• the base metal is generally in alkaline solution (pH> 7 ) worked.
• Metallic copper leaves dissolve only in the presence of an oxidizing agent.
• the dissolution of the magnetite is usually under reducing conditions to avoid oxidative dissolution of the base metal. In such methods, the magnetite is first dissolved under reducing conditions with the addition of a complexing agent.
• the metallic copper is dissolved with an alkaline cleaning solution in the presence of an oxidizing agent and a complexing agent.
• an oxidizing agent strong oxidizing agents such as oxygen and hydrogen peroxide are used, which would convert the dissolved Fe 2+ immediately into Fe 3+ . Therefore, the container must be emptied before performing the copper dissolution, which increases the amount of cleaning solution to be disposed. If the reaction solution of the magnetite dissolution were not removed and an oxidizing agent was added to this solution, this would convert the complex-dissolved iron-II into iron-III, which would react with the parent metal with the dissolution of elemental iron.
• the magnetite and copper dissolution is carried out with a single cleaning solution, which is changed after the completion of the iron dissolution so that it is suitable for the copper dissolution.
• the container is treated with an alkaline cleaning solution at a temperature of about 160 0 C, which contains a reducing agent, such as hydrazine, and as a complexing agent nitrilotriacetic acid (NTA).
• NTA forms a soluble complex with Fe-II ions, accelerating the magnetite dissolution and keeping the iron II in solution in complexed form.
• the reducing agent Due to the reducing agent is in Magnetite containing iron-III to iron-II and the Cu-I of the above-mentioned copper oxide reduced to metallic copper.
• the alkalizing agents used are, for example, ammonia or morpholine.
• the cleaning solution is cooled to 50 ° C. to 160 ° C., its pH is increased, and oxygen is introduced to adjust the oxidizing conditions or hydrogen peroxide is added.
• a disadvantage of this method is a relatively high base metal removal.
• the object of the invention is to propose a method of the aforementioned type, which achieves a low base metal removal without draining the cleaning solution between the magnetite and the copper dissolution.
• This object is achieved according to claim 1 by a method in which, in a first step, the container is treated with an alkaline cleaning solution comprising a complexing agent which forms a soluble complex with iron (II) ions, a reducing agent and an alkalizing agent contains, and in a second step in the cleaning solution of the first step in the container, another complexing agent which forms a more stable complex with ferric ions than the complexing agent used in the first step, and an oxidizing agent are metered.
• an alkaline cleaning solution comprising a complexing agent which forms a soluble complex with iron (II) ions, a reducing agent and an alkalizing agent contains, and in a second step in the cleaning solution of the first step in the container, another complexing agent which forms a more stable complex with ferric ions than the complexing agent used in the first step, and an oxidizing agent are metered.
• the dissolution of the magnetite is carried out in virtually the same way as in the method of DE 198 57 342.
• An attack of the cleaning solution on the base metal and a corresponding material removal are relatively low in such a procedure, especially if at temperatures from 140 0 C to 180 0 C, as in a preferred process variant, worked. At such temperatures, the reaction between the complexing agent and the iron II originating from the magnetite proceeds much faster than the base metal attack, which also proceeds via iron II.
• the cleaning agent still contains the iron II complex of the first process step.
• iron (III) complexes of the complexing agents used in processes of the present type such as EDTA and NTA, are less stable in alkaline solution than the corresponding iron (II) complexes, ie, under the conditions prevailing in the second process step, they can be destroyed, with the liberated iron -III ions with hydroxide ions present in the solution form a sparingly soluble precipitate of iron hydroxide, which would have to be removed by extensive rinsing out of the container.
• this undesired reaction is at least suppressed by adding a complexing agent which, under the conditions prevailing in the second step, forms a complex with iron (III) ions which is more stable than the corresponding complex of the complexing agent of the first process step. In this way, the concentration of free iron (III) ions is reduced by, for example, immediately trapping freshly formed iron (III) ions. A Grundmetallabtrag in the second process step is thereby prevented or at least reduced.
• the further complexing agent and then the oxidizing agent are added first.
• any free, that is not complexed, iron II ions are bound by the further complexing agent in the cleaning solution so that, upon addition of the oxidizing agent, there are no longer any free iron II ions from which iron (III) ions can form.
• This effect is particularly effective if, before the addition of the oxidizing agent, thorough mixing of the cleaning solution takes place, preferably by blowing in a gas which is weakly or only slightly oxidizing, such as air or better an inert gas such as nitrogen or argon.
• the oxidizing agent added in the second process step has two functions.
• the addition of the polyethyleneimine is primarily for the purpose of preventing the formation of free Fe-III ions. Accordingly, in a preferred variant of the method, a quantity which is substoichiometric in relation to the amount of copper to be dissolved is added. At best, some of the copper ions are complexed by the polyethyleneimine. To bind the remaining amount of copper or in general to complex the copper, the cleaning solution is used a further complexing agent, for example a complexing agent already used in the first process step, such as EDTA or NTA.
• the used is polyethyleneimine at least on a part of the N-atoms of the main chain a carboxyl group, for example CH 3 COO "bound.
• the copper dissolution is accelerated in a preferred process variant in that the cleaning solution ammonium in the form of at least one ammonium salt, preferably ammonium carbonate is supplied.
• Ammonium ions catalyze the dissolution of copper in the presence of an oxidizing agent in a manner known per se. Unlike chloride or sulfate-containing ammonium salts, ammonium carbonate does not cause corrosion. Further acceleration of the copper dissolution takes place with the aid of ammonium nitrate.
• the first process step is preferably carried out at a temperature of 140 0 C to 180 0 C.
• the addition of a corrosion inhibitor is not required because a corrosive attack of the complexing agent on the base metal is practically not to be feared. Namely, at such high temperatures, the complexing reaction between the complexing agent and iron II and / or iron III ions originating from the magnetite proceeds much faster than the Dissolution of the base metal by the complexing agent.
• the first process step does not necessarily have to be carried out in the stated high-temperature range. Also conceivable is a temperature below 100 ° C., for example in the range from 80 ° C. to 95 ° C.
• the addition of a corrosion inhibitor is expedient, since the complexing of the magnetite-derived iron (II) and / or iron (III) Ion is slowed down and accordingly more complexing agent is available for the dissolution of the base metal.
• the implementation of the second process step is generally carried out at a temperature of below 100 0 C, preferably in the range of 80 0 C to 95 0 C. At low temperatures, the risk of hydroxylamine decomposing to NO 2 is significantly lower than at higher temperatures. NO 2 would decompose the complexing agents used.
• This experiment relates to a variant of the method in which the Magnetitankans at a temperature of more than 100 0 C, specifically at 160 0 C and the copper in the unpressurized range, ie at a temperature below 100 0 C temperature, namely at about 90 0 C. , After heating the autoclave to 160 0 C, 445 ml of deionized are filled and purged with argon to remove air or dissolved in the deionized oxygen.
• reaction solution containing 65.6 g of (NH 4 ) 3 -EDTA is added, which is an excess of 5% over the stoichiometric amount, that is, the amount of EDTA required to complex the amount of iron contained in the magnetite.
• the reaction solution also contains 22 ml of a 25 percent hydrazine hydrate solution.
• the metered amount of hydrazine is four times the stoichiometric amount. The excess ensures that despite a loss of hydrazine due to thermal or catalytic decomposition (due to the presence of metallic copper) is always a sufficient amount for reducing the magnetite present in the magnetite available.
• a pH of approx. 9 is set in the cleaning solution.
• the second process step is initiated by the solution is cooled to 80 0 C and a complexing agent is metered, compared to the complexing agent used in the first step 1 (EDTA) Fe III ions bind more firmly, namely a polyethyleneimine available under the trade name Trilon P from BASF in the form of the 1: 3.4 diluted aqueous original BASF solution.
• Trilon ⁇ P has a molecular weight of about 50,000 and a nitrogen / carbon atom ratio in the main chain of 0.5.
• this complexing agent binds possibly present free iron (III) ions, which is the case, for example, when the amount of magnetite sludge present in a container was underestimated and therefore an insufficient amount of EDTA was added.
• the cleaning solution is mixed by blowing an inert gas. Now, 200 ml of an aqueous solution containing 36 ml of a 50 percent hydroxylamine solution is fed. The amount of hydroxylamine contained therein is double stoichiometric with respect to the presence of metallic copper and residual hydrazine.
• EDTA is fed into the autoclave in an amount which is more than stoichiometric with respect to the amount of copper present (dissolved Cu-II), for example with an excess of 7.2%, in order to bind the Cu-II formed.
• small samples of the cleaning solution are continuously withdrawn and their copper content is determined, for example by titration.
• the first process step is carried out at a temperature below 100 ° C., specifically at 92 ° C.
• a container to be cleaned can be opened to the atmosphere. Accordingly, no autoclave is required for the experiment.
• an open container a beaker
• the 68 g (NH 4 J 2 -EDTA, 3.8 g of hydrazine hydrate, 10 ml Korantin PM and 2 ml of Plurafac contains Korantin PM is a corrosion inhibitor
• Plurafac is a surfactant Both are available from BASF A surfactant improves the adhesion of the inhibitor on the bare surfaces of the parent metal.
• the amount of EDTA used corresponds to 111% of the stoichiometric amount required for complexing the amount of iron present (10.4 g).
• the reducing agent (hydrazine) is gem.
• Experiment 507 added in excess (about 4-fold stoichiometric).
• a pH of about 9 is maintained.
• the process step 2 is initiated by dosing 50 ml of a 1: 3.4 diluted aqueous solution of Trilon P whereby the cleaning solution is cooled to about 85 ° C. , After mixing by blowing an inert gas, 100 ml of a reaction solution containing 26 ml of a 50% aqueous hydroxylamine solution are added, which corresponds to about 20 g of hydroxy lamin. This amount is four times stoichiometric with respect to the existing metallic copper and residual hydrazine.
• Experiment 512 essentially forms the method acc. US Pat. No. 3,627,687, in which the magnetite and the copper dissolution is carried out with one and the same alkaline cleaning solution.
• the cleaning solution acc. essentially contains EDTA and as further complexing agent a polyethyleneimine, which is used in the present experiment in the form of Trilon P.
• the copper-containing magnetite slurry used in the other experiments and 550 ml of deionized are added. After rinsing with inert gas is heated to 160 0 C and 240 ml of a added to aqueous reagent solution.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Physics & Mathematics (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Materials Engineering (AREA)
• High Energy & Nuclear Physics (AREA)
• Combustion & Propulsion (AREA)
• Thermal Sciences (AREA)
• Electrochemistry (AREA)
• Life Sciences & Earth Sciences (AREA)
• Food Science & Technology (AREA)
• Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
• Cleaning By Liquid Or Steam (AREA)
• Detergent Compositions (AREA)
• Processing Of Solid Wastes (AREA)
• Preventing Corrosion Or Incrustation Of Metals (AREA)

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• 2007
  • 2007-05-18 DE DE102007023247A patent/DE102007023247B3/de not_active Expired - Fee Related
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