EP0380169B1 - A process for the cleaning of metallic, for example iron or steel, internal surfaces of industrial equipment - Google Patents

A process for the cleaning of metallic, for example iron or steel, internal surfaces of industrial equipment Download PDF

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Publication number
EP0380169B1
EP0380169B1 EP90200135A EP90200135A EP0380169B1 EP 0380169 B1 EP0380169 B1 EP 0380169B1 EP 90200135 A EP90200135 A EP 90200135A EP 90200135 A EP90200135 A EP 90200135A EP 0380169 B1 EP0380169 B1 EP 0380169B1
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EP
European Patent Office
Prior art keywords
vessel
cleaning fluid
cleaning
steel
acid
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 - Lifetime
Application number
EP90200135A
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German (de)
English (en)
French (fr)
Other versions
EP0380169A1 (en
Inventor
Paulus Wilhelmus Nicolaas Maria Kok
Thomas Everhardus Henricus Maria Kok
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Individual
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Individual
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Publication of EP0380169A1 publication Critical patent/EP0380169A1/en
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    • 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
    • C23G1/02—Cleaning or pickling metallic material with solutions or molten salts with acid solutions
    • C23G1/08—Iron or steel
    • 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
    • C23G1/02—Cleaning or pickling metallic material with solutions or molten salts with acid solutions

Definitions

  • the invention relates to a process for the cleaning during idle periods of metallic, comprising iron or steel, internal surfaces of equipment used in the chemical industry, in which a cleaning fluid containing water, an acid and a corrosion inhibitor is pumped through the interior of the equipment at a flow rate of at least 0.5 m/s.
  • a cleaning fluid containing water, an acid and a corrosion inhibitor is pumped through the interior of the equipment at a flow rate of at least 0.5 m/s.
  • Such equipment include reactors, heat exchangers, pipes, pumps, valves distillation columns and steam boilers.
  • Corrosion by ferric ions cannot be combated adequately by the use of corrosion inhibitors such as hexamethylene-tetramine, hydrazine, alkaloids and quaternary ammonium compounds and may even occur to such a degree that after the cleaning operation pitting and scoring are observed in the metal of the cleaned equipment.
  • corrosion inhibitors such as hexamethylene-tetramine, hydrazine, alkaloids and quaternary ammonium compounds
  • US-A-3,440,170 proposes that in a cleaning fluid which is pumped around in the interior of iron or steel equipment for the removal of rust, for example, and which contains water, an acid and a corrosion inhibitor, in addition a stannous salt be dissolved and that the composition of the cleaning fluid be controlled during operation by measurement of the redox potential.
  • the addition of fresh stannous salt, as the need arises, during operation serves as a means to keep the redox potential of the cleaning fluid below a limiting value which, when measured with a platinum electrode against a saturated calomel-KCl electrode, amounts to 280 mV.
  • the preferred stannous salt soluble in the cleaning fluid is stannous chloride and the preferred cleaning acid is hydrochloric acid.
  • the object of the present invention is to provide an environmentally acceptable, efficient, fully controllable process for the cleaning during idle periods of metallic, for example iron or steel, internal surfaces of equipment used in the chemical industry, in such a fashion that no corrosion of the surfaces to be cleaned occurs.
  • a process of the type mentioned hereinbefore is according to the invention characterized in that the cleaning fluid is passed through a reduction filter disposed outside the equipment, which filter substantially comprises a vessel with mutually spaced strainer discs between which a substantially metallic packing is contained in the form of roll-up mats being coiled round a core of the vessel, whereby the vessel is provided near either end with an inlet and an outlet port, respectively, for the cleaning fluid.
  • substantially metallic (for instance, steel, iron or aluminium) packing which is preferably steel wool with a surface-to-weight ratio of e.g. 15 m2/kg, ensures that ferric ions formed through the action of the acid are very effectively reduced to ferrous ions. Thus, corrosive attack on the surfaces to be cleaned is obviated in an environmentally acceptable manner.
  • steel-wool mats are used.
  • One embodiment of a process according to the invention is characterized in that the redox potential is measured in a filtrate of the reduction filter.
  • the process according to the invention can be carried out in practice as follows. After calculation of the overall surface area to be cleaned of, for instance, a steam boiler the reduction filter is provided with a steel-wool packing having a surface area at least ten times as large. Thereupon the boiler is filled with a one-percent inhibited hydrochloric-acid solution which is circulated at room temperature, i.e. 20°C, at a rate in m3/h at least four times as high as that of the contents of the boiler. This procedure ensures that the iron oxides slowly pass into solution whereas the ferric compounds are quickly reduced. Then, the acid concentration is slowly raised to the requisite level, normally 4 to 5%.
  • the outlet for draining the cleaning acid from the steam boiler must be disposed as low as possible, such that the hydrochloric acid, which may be rich in ferric ions, can be discharged most quickly to the reduction filter.
  • the temperature of the circulating acid may, if desired, be raised to, say, 50°C.
  • the hydrochloric acid is neutralized with sodium hydroxide to a pH of 7 or 8, whereby sodium chloride and water are formed.
  • the iron compounds present are quickly oxidized to ferric compounds, which does not give rise to environmental problems.
  • the corrosion inhibitor is biologically degradable, hence also ecologically acceptable.
  • the process according to the invention makes it possible to clean the internal surfaces of industrial equipment without any corrosive attack, when constructed in any of the following metals: steel 37; carbon steel 50-60; 1% Cr - 1 ⁇ 2% Mo steel; 5% Cr - 1 ⁇ 2% Mo steel; copper nickel 70-30; inconel; nionel; nickel; monel; hastelloy.
  • the invention also relates to a reduction filter suitable for use in a process according to the invention, which reduction filter is characterized in that it substantially comprises a vessel with mutually spaced strainer discs between which a substantially metalic, for example iron or steel, packing in the form of roll-up mats being coiled round a core of the vessel is contained, which vessel is provided near either end with and inlet and an outlet port, respectively, for the cleaning fluid.
  • a substantially metalic for example iron or steel
  • a further embodiment of a reduction filter according to the invention is characterized in that the reduction filter is transportable.
  • the process according to the invention can be flexibly operated, for instance on board of (sea-going) vessels.
  • Patents abstracts of Japan, Volume 5, No. 4 (C-38) [676] dated January 13, 1981 and the Japanese patent publication No. JP-A-55131183 describe a process for removing scale adhered to a surface of metallic material by chemical washing, whereby a washing fluid is circulated through a strainer packed with granular, powdered or fibrous iron in order to reduce oxidizing, corrosive metallic ions (Fe3+, Cu2+, Cu+) which are dissolved in the washing fluid.
  • the strainer packed with granular, powdered or fibrous iron is disposed outside the equipment.
  • Figure 1 represents a reduction filter in the form of a vessel 1 which has been made of a pressure-resistant material that is impervious to acids up to a temperature of at least 70°C.
  • pressure resistance it is to be noted that the vessel 1 must be capable of withstanding a pressure of at least 3 bar.
  • the vessel 1 should preferably be made in a glass fibre-reinforced acid-proof polyester.
  • the vessel 1 is provided with two detachable, fixed or movable strainer discs 2, 3, preferably consisting of perforated polypropylene trays, whilst fine steel-wool mats 5 have been coiled round a core 4 of the vessel 1.
  • the cleaning fluid which contains water, an acid and a corrosion inhibitor is, after having been pumped through the interior of the equipment to be cleaned, introduced through an inlet 6 (arrow 7) into the vessel 1 and, after having been filtered, passes through an outlet 8 (arrow 9) to the interior of the equipment to be cleaned.
  • the vessel 1 has a drain cock 10, permitting check measurements to be carried out in the circulating cleaning fluid.
  • this drain cock 10 the cleaning fluid may be discharged, if necessary.
  • a hose may be connected for the continuous measurement of redox potentials, the determination of the non-corrosivity of the cleaning fluid and the removal of air bubbles, if any.
  • this fluid is passed, for instance by means of a three-way cock mounted near the inlet 6, direct through the core 4 - instead of over the steel wool 5 - and then withdrawn.
  • the cleaning fluid is neutralized with, for instance, caustic soda or another base, whereupon it is processed by a waste-water purification plant.
  • caustic soda or another base whereupon it is processed by a waste-water purification plant.
  • the reduction filter removes harmful ferric, cupric, cuprous and other corrosive ions from hydrochloric acid (at concentrations of 0.5 - 15%), but also from the cleaning acids: hydrofluoric acid (at concentrations of 0.5 - 10.0%), sulphuric acid (at concentrations of 0.5 - 20.0%), citric acid (at concentrations of 3.0 - 15.0%), phosphoric acid (at concentrations of 1.0 - 10.0%), hydroxyacetic acid (at concentrations of 1.0 - 10.0%), formic acid (at concentrations of 2.0 - 15.0%), sulphamic acid (at concentrations of 1.0 - 15.0%), ethylenediaminetetra-acetic acid (at all usable concentrations), and from mixtures of these acids or their salts.
  • hydrofluoric acid at concentrations of 0.5 - 10.0%
  • sulphuric acid at concentrations of 0.5 - 20.0%
  • citric acid at concentrations of 3.0 - 15.0%
  • phosphoric acid at concentrations
  • Figure 2 affords a clear picture of the conditions that may occur during chemical cleaning of, for instance, a fouled steam boiler with inhibited hydrochloric acid, without specification of the relevant corrosion values which have been established.
  • the redox potential will be 280 mV or lower, which means no corrosion ("safe area; no attack").

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
EP90200135A 1989-01-18 1990-01-18 A process for the cleaning of metallic, for example iron or steel, internal surfaces of industrial equipment Expired - Lifetime EP0380169B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
NL8900106A NL8900106A (nl) 1989-01-18 1989-01-18 Werkwijze voor het reinigen van metalen, bijvoorbeeld ijzeren of stalen, inwendige oppervlakken van industriele apparatuur.
NL8900106 1989-01-18

Publications (2)

Publication Number Publication Date
EP0380169A1 EP0380169A1 (en) 1990-08-01
EP0380169B1 true EP0380169B1 (en) 1995-11-08

Family

ID=19853970

Family Applications (1)

Application Number Title Priority Date Filing Date
EP90200135A Expired - Lifetime EP0380169B1 (en) 1989-01-18 1990-01-18 A process for the cleaning of metallic, for example iron or steel, internal surfaces of industrial equipment

Country Status (4)

Country Link
EP (1) EP0380169B1 (nl)
DE (1) DE69023359T2 (nl)
ES (1) ES2081338T3 (nl)
NL (1) NL8900106A (nl)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NO175906C (no) * 1992-05-18 1995-01-04 Leif Inge Aanestad Fremgangsmåte for metallbelegging av innvendige flater i tanker og rör
US6837985B2 (en) * 1999-09-20 2005-01-04 Aeromet Technologies, Inc. External counter electrode
US9102604B1 (en) 2010-02-15 2015-08-11 Baxter International Inc. Methods for cleaning distilling columns

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR423829A (fr) * 1910-12-19 1911-04-27 Robert Augustus Chesebrough Procédé de filtration
JPS55131183A (en) * 1979-03-29 1980-10-11 Mitsubishi Gas Chem Co Inc Corrosion-preventing method in chemical washing

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL155315B (nl) * 1964-06-09 1977-12-15 Ver Kunstmestfabriekn Mekog Al Werkwijze voor het reinigen van ijzeren of stalen, inwendige oppervlakken van industriele apparatuur
US3686123A (en) * 1971-04-05 1972-08-22 Kurita Industrial Co Ltd Cleaning composition
DE2457235A1 (de) * 1974-12-04 1976-06-10 Peter Vodicka Verwendung von metallen und/oder wasserloeslichen chemischen verbindungen zum schutz der in sauren inhibierten loesungen vom zunder gebeizten oder von eisen-iii-haltigen belaegen chemisch gereinigten metallischen gegenstaenden und/oder geschlossenen anlagen vor dem angriff der ferrikationen und anordnung zum erreichen dieses schutzes
FR2562914A1 (fr) * 1984-04-16 1985-10-18 Solvay Procede pour inhiber la corrosion d'une masse metallique au contact d'un bain acide contenant un oxydant

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR423829A (fr) * 1910-12-19 1911-04-27 Robert Augustus Chesebrough Procédé de filtration
JPS55131183A (en) * 1979-03-29 1980-10-11 Mitsubishi Gas Chem Co Inc Corrosion-preventing method in chemical washing

Also Published As

Publication number Publication date
ES2081338T3 (es) 1996-03-01
EP0380169A1 (en) 1990-08-01
DE69023359D1 (de) 1995-12-14
DE69023359T2 (de) 1996-04-25
NL8900106A (nl) 1990-08-16

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