EP0300242B1 - Verfahren und Vorrichtung zur Uberwachung der partiellen Dichte von Metall und Säure in Beizbädern - Google Patents

Verfahren und Vorrichtung zur Uberwachung der partiellen Dichte von Metall und Säure in Beizbädern Download PDF

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Publication number
EP0300242B1
EP0300242B1 EP88110434A EP88110434A EP0300242B1 EP 0300242 B1 EP0300242 B1 EP 0300242B1 EP 88110434 A EP88110434 A EP 88110434A EP 88110434 A EP88110434 A EP 88110434A EP 0300242 B1 EP0300242 B1 EP 0300242B1
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EP
European Patent Office
Prior art keywords
pickling
acid
pipe
substances
density
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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
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EP88110434A
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German (de)
English (en)
French (fr)
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EP0300242A1 (de
Inventor
Jürgen Dr. Dipl.-Ing. Behringer
Dieter Dr. Evers
Dieter Dipl. Ing. Schönert
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Laboratorium Prof Dr Rudolf Berthold GmbH and Co KG
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Laboratorium Prof Dr Rudolf Berthold GmbH and Co KG
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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

Definitions

  • the invention relates to a method and a device for measuring and monitoring the partial density of metal and acid in pickling baths.
  • Chemical descaling after hot forming takes place e.g. for semi-finished products made of iron and iron alloys in mineral acids such as sulfuric acid, hydrochloric acid, nitric acid, nitric acid / hydrofluoric acid mixtures or phosphoric acid.
  • mineral acids such as sulfuric acid, hydrochloric acid, nitric acid, nitric acid / hydrofluoric acid mixtures or phosphoric acid.
  • Reaction products of the pickling process are predominantly iron (II) ions as the cation of the iron (II) salt of the pickling acid in question, and water until the critical free iron surface is reached; If the potential of the metal / metal oxide mixing potential is further reduced, atomic hydrogen is added, which recombines to form molecular hydrogen at lattice vacancies and forms gas bubbles.
  • salt salts crystallize out in various hydration forms depending on temperature and concentration.
  • the pickling speed is the essential parameter; This is not only influenced by the nature of the scale, but is above all a function of the acid concentration and the iron content that accumulates with the scale dissolution. Other important factors are the temperature of the pickling solution and the movement of the pickling product; In addition, the addition of inhibitor, metallic and non-metallic impurities and turbidity in the pickling solution influence the pickling time.
  • the salt content affects the pickling rate differently for the different pickling acids. While e.g. in the case of sulfuric acid, increasing iron (II) sulfate contents reduce the pickling rate and the iron (II) ions have an inhibiting effect on iron attack, the pickling time in hydrochloric acid decreases with increasing the iron (II) chloride content to just below the saturation limit; the iron attack remains unchecked.
  • Modern pickling processes are coupled with regeneration systems for processing the pickling. While e.g. When pickling with sulfuric acid, the iron (II) sulfate that forms must be constantly removed from the pickling process and the consumption is replenished with fresh sulfuric acid. In the case of hydrochloric acid, the pickling is almost completely regenerable, i.e. a fresh acid supplement is not necessary.
  • the drop in acidity is signaled in good time, an increase in the pickling time can be avoided by increasing the fresh acid supply. Conversely, the acid consumption can be reduced by avoiding an excessive acid content in the pickling solution.
  • Monitoring and precise adjustment of the acid and iron content have the result that the pickling result becomes more uniform with the same pickling material, and the utilization of the regeneration system is also more uniform.
  • Operational pickling baths are mainly monitored by manual titration, e.g. by titrating the free acid with sodium hydroxide solution NaOH and titrating the iron (II) content with potassium permanganate KMnO4 or potassium dichromate K2Cr2O7.
  • Fe2+ is oxidized to Fe3+; this means that Fe3+ present in industrial pickling acid is not detected in this way.
  • the problem is different for pickling lines, in which the programs change in a short time sequence from easily pickable to difficult to pickle pickling.
  • the pickling temperature, acid concentration and pickling time have to be constantly adapted to the different pickling properties of the pickling material, the iron contents change accordingly.
  • the ongoing changes require monitoring of the pickling process at much shorter intervals; In retrospect, analyzes can show certain correlations, but it is usually too late to intervene in the pickling process in the sense of an adaptation to the pickling program.
  • Process titrators are sometimes used in combination with photometric measuring methods, the latter for the determination of the iron content.
  • the indirect determination of the Fe (III) proportion is the difference from the e.g. total iron (dissolved) determined with thioglycolic acid and e.g. certain Fe (II) content possible with ortho-phenantroline.
  • Photometric measuring methods can only be used to a limited extent because of their sensitivity to impurities in the pickling solution.
  • Operational pickling acid with a fluctuating content of hydrated salts, colloidally precipitated silicates (SiO2. Aq), etc. contaminates the measuring cells.
  • the gases and turbid substances that form during scale dissolution also have a disruptive effect.
  • the pickling acid is not a pure solution, but a suspension. Filters are installed upstream to retain the suspended particles. These need to be changed frequently. Checks, cleanings and re-calibrations are constantly necessary - a method of operation that is very complex for the operator and does not meet the safety requirements when operating pickling baths.
  • Density and substance content in acidic, aqueous Fe (II) salt solutions can be put into a mathematical context with sufficient accuracy for practical purposes, see J. Pearson and W. Bullough: J. Iron Steel Inst. 167 (1951), p.439 / 445, and W. Fackert: Z. Stahl & Eisen 72 (1952), p.1196 / 1207 as well as G. Dunk and B. Meuthen: Z. Stahl & Eisen 82 (1962) pp. 1790/1796.
  • the density of the solution is calculated from the concentrations of acid and iron. To calculate a size, the other two must be known. The relationships only apply to a certain temperature, the temperature influence on the density is not taken into account.
  • the device consists of a density sensor (air bubble method) immersed in the pickling solution and a conductivity measuring cell immersed in the pickling solution. Problems are caused by the short shelf life of the sensors and the falsification of the conductivity measurements due to oil separation on the glass electrodes (when oiled strips are pickled, greasy oil gets into the pickling acid). It has also been found that the measuring method cannot be transferred to pickling with hydrochloric acid.
  • the conductivity responds to all ionized charge carriers, which can accumulate in the pickling baths depending on the pickling program.
  • charge carriers include the cations Fe2+, Fe3+, Mn2+, Al3+, Cr3+ and the hydronium ion H3O+ as well as the anions Cl ⁇ , SO 2- 4th , PO 3- 4th .
  • the conductivity is the product of the elementary charge, the valence of the respective charge carrier, the mobility and the number of particles of the respective charge carrier. The more different the type of charge carriers and the larger their number, the more involved the electrochemical processes. Reliable information on the mobility of the particles in concentrated solutions is not available.
  • the free acid content in the pickling bath can be calculated from the density and temperature measured there, if the acid content of the incoming fresh acid is known.
  • the calculation procedure is designed so that the determination of the iron content can be dispensed with.
  • the result is used to regulate the acid supply with the aim of keeping the free acid content in the pickling tank as constant as possible.
  • the method has the disadvantage that only the last pickling tank, which is supplied directly with fresh acid or regenerate, is monitored directly.
  • the acid and iron contents change from container to container in the direction of strip travel in a clear gradation: While, for example, with sulfuric acid pickling in the first container acid contents between 200 and 280 g / l and iron contents between 60 and 100 g / l found, the acidity in the last container is between 250 and 350 g / l with iron contents between 20 and 60 g / l.
  • the contents fluctuate considerably in the first containers; the change in the conditions in the first container caused by a change in the fresh acid supply in the last container is difficult to control.
  • the management of the pickling process is further complicated by the temperature gradient from the last, monitored container to the first container into which the strip runs.
  • JP PS 56 136 982 does not contain any information about the type of density measurement, so that it cannot be seen whether the above-mentioned disadvantages of density measurement according to US Pat. No. 2,927,871 can be remedied.
  • a basic possibility for density determination is to use gamma emitters such as Cs 137 (Measurement and Control, Vol. 10, March 1977 "Level and density measurement using non-contact nuclear gauges").
  • the object of the invention is to provide a measuring method which makes it possible to measure acid and iron contents in several containers of a pickling line independently of the material flow, i.e. to be determined independently of the throughput and the nature of the pickling material.
  • the absorption of the gamma radiation is a function of the density.
  • the three essential components - the water as a solvent, the free acid and the fully dissociated iron salt - make a contribution to the density of the pickling solution, depending on their share in the pickling solution.
  • Each substance component absorbs the gamma radiation in a manner typical of the substance, characterized by the mass attenuation coefficient.
  • the resulting attenuation of intensity is thus divided into three parts determined by the product of the attenuation coefficient by density (content per unit volume of pickling solution):
  • the left side of the equations (2) contains the measurement result from the respective radiation measuring probe multiplied by the reciprocal of the measuring length L, the right side with the partial densities r1, r2 and r3 three unknowns.
  • the increase in density with the acidity r2 is still a function of the iron salt content r3: the more iron salt in the pickling solution, the smaller the density increase with increasing acidity.
  • This relationship applies analogously to the density of an iron salt solution, which is gradually mixed with acid.
  • the linearity of the relationship remains as long as the content of one of the two dissolved substances changes in the three - substance system water - acid - iron salt.
  • the temperature correction of the density requires a measurement of the temperature T ist ; this is indispensable for the management of the pickling process anyway, for example in the case of sulfuric acid pickling, the separation of monohydrate FeSo4 ⁇ . To avoid H2O.
  • T ist temperature
  • concentration lines may not be exceeded depending on the pickling temperature.
  • the possibility given by the measuring method to precisely determine the instantaneous acid and iron contents allows the pickling process to be carried out just below the saturation limits without fear of iron salts crystallizing out.
  • the product element with the coefficient k3 in (6) represents a correction factor; it ultimately causes the quadratic character of (2) and its solutions (7).
  • Calibration measurements can be used for this, which are essentially based on the successive measurement of individual substance components and selected combinations of such substances.
  • the mass attenuation coefficients from (2) can also be successively determined, so that a detailed statement is unnecessary here.
  • the pickling liquid that is to say the liquid consisting of the substance components water-acid-iron salt
  • the pipeline 10 is guided in such a way that, in particular, the hydrogen gas which may arise during the scale dissolution can not jam and falsify the measurements; In terms of construction, this means that the pipeline 10, at least in the pipeline sections 10B ... 10E, has a vertically upward component at every point, so that no gas cushions can become lodged in the area of the radiometric measuring sections.
  • the inlet section 10A of the pipeline 10 has a shut-off valve 13 and an outlet valve 13A
  • the adjoining pipe section 10B contains a resistance thermometer 15 for temperature measurement and leads, bent at right angles upwards, into the first radiometric measuring section 11, which consists of a radiation source 11A and a scintillation counter 11B exists.
  • the gamma radiation emitted by the radiation source 11A, a 13 -Cs emitter extends coaxially to the longitudinal axis of the tube section 10C, which in turn is inclined at an angle ⁇ of approximately 45 ° to the horizontal.
  • radioactive probes used are known measuring devices which do not need to be explained in detail.
  • a device which is commercially available under the designation "LB 379" from the applicant can be used for the radiometric measuring probe 12, and a system “LB 386-1C” from the applicant can be used for the radiometric measuring device 11A / 11B.
  • the two radiometric measuring probes thus deliver the counting rates I x and I y at their corresponding outputs, from which, as explained in detail above, the partial densities of the pickling liquid flowing through are obtained.
  • the mass attenuation coefficients can also be compared in a comparable manner and determine.
  • This calibration which enables the design according to the invention, ensures simple and safe handling of the device according to the invention.
  • FIG. 2 shows how the radiometric measuring device according to the invention for determining the partial densities is integrated in a pickling plant.
  • the radiometric measuring sections 11 and 12 and the associated valves 13A and 14 are shown schematically within a dash-dot field F, G.
  • the storage containers 20, 21, 22 of the respective pickling baths connected to one another by pumps 26 are shown, which are supplied by a treatment tank 24.
  • the treatment tank 24 receives (also via pumps 26 and flow meters 27) acidic water, fresh acid and treated acid, so that a first mixture of the substances is obtained in the treatment tank 24, the partial densities of which are to be determined. This mixture is heated in a ring line via a steam heat exchanger.
  • the first radiometric density measuring device F is located between the two shut-off valves 13, 16 in the bypass of this heating circuit, the flow ratio being able to be set via a throttle valve 29.
  • a second density measuring device G is located in a separate circuit (pipeline 10) to the working container 20.
  • control and evaluation units 25 can be combined, in which case they control, for example, the pump 26 intended for the fresh acid supply in order to determine the current, i.e. continuously adapt the composition of the pickling liquid to the current needs of the product being processed.

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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)
  • Analysing Materials By The Use Of Radiation (AREA)
EP88110434A 1987-07-23 1988-06-30 Verfahren und Vorrichtung zur Uberwachung der partiellen Dichte von Metall und Säure in Beizbädern Expired - Lifetime EP0300242B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE19873724335 DE3724335A1 (de) 1987-07-23 1987-07-23 Verfahren und vorrichtung zur ueberwachung der partiellen dichte von metall und saeure in beizbaedern
DE3724335 1987-07-23

Publications (2)

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EP0300242A1 EP0300242A1 (de) 1989-01-25
EP0300242B1 true EP0300242B1 (de) 1992-02-26

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EP88110434A Expired - Lifetime EP0300242B1 (de) 1987-07-23 1988-06-30 Verfahren und Vorrichtung zur Uberwachung der partiellen Dichte von Metall und Säure in Beizbädern

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Country Link
US (1) US5065417A (enrdf_load_stackoverflow)
EP (1) EP0300242B1 (enrdf_load_stackoverflow)
JP (1) JPS6466551A (enrdf_load_stackoverflow)
DE (1) DE3724335A1 (enrdf_load_stackoverflow)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5452720A (en) * 1990-09-05 1995-09-26 Photoelectron Corporation Method for treating brain tumors
AT404030B (de) * 1995-02-15 1998-07-27 Andritz Patentverwaltung Verfahren zur beize von materialien aus stahl, insbesondere edelstahl
GB2381862A (en) * 2001-11-10 2003-05-14 Schlumberger Holdings Fluid density measurement
US8129692B2 (en) * 2007-10-11 2012-03-06 Quantum Technical Services, LLC Method for monitoring fouling in a cooling tower
CN110257847A (zh) * 2019-07-29 2019-09-20 温州宪江防腐设备有限公司 一种可循环加热的酸洗槽

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2927871A (en) * 1956-03-26 1960-03-08 Bethlehem Steel Corp Control of pickling baths
US3074277A (en) * 1958-03-20 1963-01-22 Inland Steel Co Method and apparatus for automatic control of acid concentration in pickling system
US3074271A (en) * 1960-02-25 1963-01-22 Budd Co Photoelastic strain gauges
US3062223A (en) * 1962-02-15 1962-11-06 Leonard E Malin Apparatus for controlling pickling baths
FR2029181A5 (enrdf_load_stackoverflow) * 1969-01-15 1970-10-16 Commissariat Energie Atomique
GB1421755A (en) * 1972-05-18 1976-01-21 British Steel Corp Material analysis
DE2622175C3 (de) * 1976-05-19 1982-04-01 Gkss - Forschungszentrum Geesthacht Gmbh, 2000 Hamburg Verfahren zum Ermitteln der Volumenanteile eines Drei-Komponenten-Gemisches
JPS5920750B2 (ja) * 1980-03-29 1984-05-15 住友金属工業株式会社 酸洗液の酸濃度制御方法及び装置

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EP0300242A1 (de) 1989-01-25
JPS6466551A (en) 1989-03-13
DE3724335C2 (enrdf_load_stackoverflow) 1992-06-25
US5065417A (en) 1991-11-12
DE3724335A1 (de) 1989-02-02

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