JP2002531700A - Apparatus and method for controlling the pickling process of steel - Google Patents

Abstract

(57) Abstract: An apparatus and a method for controlling an acid pickling step are described, wherein the controller is means (C) for collecting a sample of a tank to be analyzed; the oxidation-reduction potential value of the sample and its temperature Means (CA, D, EM) for analyzing the sample to measure a number of parameters according to the specific conductivity and potentiometric methodologies as well as to restore the values of the parameters to desired levels according to the measured values. Recovery means for appropriately calculating the amount of correction chemical to be added to the pickling tank and activating at least one device for adding said amount of correction chemical into the pickling tank. The parameter measured according to the conductivity methodology is the concentration of sulfuric acid, hydrofluoric acid, or another inorganic acid; the parameters measured according to the potentiometer methodology are the concentrations of divalent and trivalent iron ions and hydrogen peroxide. Available correction chemicals are sulfuric acid, hydrofluoric acid and oxidizing agent

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001] The present invention resides in an apparatus and method for controlling the pickling process for carbon steel, austenitic, ferritic and martensitic stainless steels, duplex stainless steels and special alloys, wherein the apparatus comprises: The pickling bath sampling and the analysis of said sample are automatically operated to define precise process parameters (according to specific conductivity and potentiometric methodology) and to restore the desired concentration of essential chemicals in the pickling bath.

[0002] The present invention also specializes in the processing of steel through the clarification of remotely operable operating procedures that automatically retrieve and implement the most appropriate operating conditions for pickling of a particular type of material during processing. It is also possible to control the pickling conditions.

BACKGROUND OF THE INVENTION In the rolling, drawing, extrusion and heat treatment of steel products (such as plates, strips, tubes, bars), not only passivation and corrosion resistance but also a fine finished appearance and further work are required. An oxide layer is formed on the surface which must be removed both to allow for

The oxide layer on the surface, usually at an appropriate dilution and temperature, comprises one or more acids containing inorganic mineral acids (sulfuric, hydrochloric, nitric, hydrofluoric) alone or in a mixture with one another. The action of the bath is followed by a chemical treatment (pickling) based on at least one finishing rinse with water.

[0005] For stainless steel, the usual pickling process (either dipping, spraying or turbulent)
Requires a mixture of nitric acid and hydrofluoric acid; the process is not only due to the problem of large amounts of nitrates in the wastewater, but also due to the release of reaction by-products (extremely toxic nitrogen oxides) into the atmosphere. Dragging serious ecological problems.

[0006] Therefore, a number of "ecological" alternative processes have recently been devised which are characterized by the elimination of nitric acid.

Among such processes, those particularly effective on an industrial scale are those that use a mixture of sulfuric acid or hydrochloric acid, hydrofluoric acid and ferric ions, where the mixture in a pickling tank is used. The proper concentration of such ions is maintained by the addition of hydrogen dioxide. Some of such steps are described in Italian Patents 1,245,594 and 1,255,655.

[0008] In traditional pickling techniques, the control of the process is usually performed by manual titration of the acidity or by measuring the conductivity of the solution and its iron content (or total metal by measuring solution density). Includes ad hoc control; it also allows for the measurement of hydrofluoric acid content by specific ion selective electrodes.

[0009] Some of these techniques have been used to automate the single operation of a pickling process based on nitric acid in stainless steel.

US Pat. No. 4,060,717 (LECO) measures the concentration of nitric acid (or other strong acid) and hydrofluoric acid in a pickling bath containing nitric acid and hydrofluoric acid. Discloses the use of ion-selective electrodes for fluorine and hydrogen ions; the voltage data collected by the control circuit is carefully processed by a microprocessor to calculate the concentrations of the two acids and adjust the relevant concentrations. Is done.

[0011] Japanese Patent No. 55040908 (Nippon Steel) discloses that to adjust the concentration of acid, hydrofluoric acid and another hydrofluoric acid are determined through ion-selective electrode determination of the relevant anions after the solution has passed through the ion exchange membrane. A method for determining one strong acid (nitric acid, hydrochloric acid, sulfuric acid) is disclosed.

US Pat. No. 5,286,368 (Foxboro) discloses nitric acid and hydrogen fluoride through the ability to complex ferric ions towards fluoride ions, which allows the determination of the concentration of acid in the mixture. The concentration of hydrofluoric acid in the acid mixture is measured.

[0013] The continuous automatic control of such pickling processes based on nitric acid is better than, for example, manual or automatic control sometimes performed two or three times a day, but for processes relating to the quality of the material to be treated. Is not essential, since the functional properties of such tanks, especially in pickling stainless steel, such tanks usually have a high nitric acid concentration (about 12-15%) and about 2-5% hydrofluoric acid. This is because it has a concentration. The high nitric acid concentration simultaneously ensures both high acidity and almost constant oxidizing power, making it possible to operate the process through the occasional addition of chemicals. Moreover, the determination of the acid concentration is sufficient to have adequate control of the pickling capacity of the bath.

On the contrary, the nitric acid-free pickling system as cited above has a ferric ion (F
e ³⁺ ) concentration measurements, or better, the oxidation properties of the system with respect to the Fe ³⁺ / Fe ²⁺ ratio.

In this case, 2Fe ³⁺ + FeO → 3Fe ²⁺ (1) trivalent due to the pickling reaction (1) in a continuous process for producing stainless steel strip or an automatic, high-productivity facility for pickling bars. The iron ion concentration, the Fe ³⁺ / Fe ²⁺ ratio and therefore the oxidizing capacity of the solution tend to decrease rapidly and change the behavior of the vessel continuously and intensely.

Therefore, the optimum conditions must be continuously adjusted with an oxidizing agent such as hydrogen peroxide.

Furthermore, fluctuations in the concentration of trivalent iron also indirectly affect the concentration of free acid present in the tank.

For example, in a pickling system based on a mixture of sulfuric acid, hydrofluoric acid and ferric salt, this effect is related to the following preferred equilibrium equation: Fe ³⁺ + nF ⁻ → FeF _n ^{(3 -n) +} Fe ²⁺ + SO ₄ ^2- → FeSO ₄ Therefore, during the oxidation / reduction reaction of a pair of Fe ³⁺ / Fe ²⁺ , from the complex salts involved in the release of sulfuric acid and hydrofluoric acid respectively. Occurs, thus altering the composition of the bath.

The occasional process control by analytical measurements, followed by the large addition of chemicals to restore the best pickling conditions, is therefore too great to have opposite conclusions regarding product quality and process cost. Causes changes in tank parameters.

On the other hand, adjusting the composition associated with frequent manual control is time consuming and costly.
Therefore, this requires a lot of manpower to ensure a sufficient control frequency (e.g., one control per hour).

The criticality of the nitric acid-free pickling process is the total amount of iron dissolved per unit time, the number of pickling tanks to be controlled, the number of substances requiring different operating conditions and the It is clearly related to the performance required to frequently add the acid manually.

[0022] Control of the stainless steel pickling process as previously cited for stainless steel strip continuous pickling equipment or high productivity automated equipment for the bar process has proven critical to the quality of the final product; It can also be uneconomical without the use of automated systems for reactant sampling, control and dosing.

The control apparatus and method according to the present invention require the use of unique techniques and analytical methods for proper management of such steps.

DISCLOSURE OF THE INVENTION It is an object of the present invention to provide a means for taking a sample of a tank to be analyzed; Means for analyzing the sample to determine a number of parameters according to the concentration of another inorganic strong acid) and potentiometer (to find the concentration of trivalent and divalent iron); Calculate the amount of correction chemicals (preferably hydrofluoric acid, sulfuric acid and oxidizing agent) to be added to the pickling tank to restore the value of A control device and a control method for a nitric acid-free pickling tank, comprising a recovery means for operating at least one device added to the washing tank.

FIG. 1 schematically shows a facility comprising an analyzer according to the invention, comprising: a plurality of pickling tanks V; (V1,..., Vn); In the embodiment described here, the analyzer A (comprising a simplified schematic diagram of FIG. 2) comprising a set of analyzers (A1, A2) working simultaneously on different parameters A plurality of containers S (S1, S2, S3) each of which is a correction chemical (strong acid, preferably sulfuric acid, hydrofluoric acid and oxidizing agent) to be added into one of the tanks V; (Preferably not necessarily hydrogen peroxide) at a given concentration. A plurality of permanent recirculation pipes connecting the tank V to the sampling inlet I of the analyzer A (FIG. 2); a plurality of pipes connecting the container S to the tank V, supplying correction chemicals; An adding means for allowing the analyzer A to add the correction chemical contained in the container S into the tank V;

For the sake of simplicity, FIG. 1 omits not only other circuit parts but also parts not relevant to the invention, such as valves, pumps, actuators, filtration and rinsing means known per se. Was.

Analyzer A is a means for taking a sample of the pickling solution from tank V; according to the specific conductivity and potentiometer methodology, the preset parameters (not only those of trivalent and divalent iron, but also of sulfuric acid, for example) Means for analyzing the concentration of the strong acid and hydrofluoric acid), the oxidation-reduction potential and the temperature of the diluted sample, the correction chemicals to be sent from the vessel S to the tank V to adjust the parameters, It comprises means for calculating the amount and means for operating the device at the output of the container S for sending the calculated amount of said correction chemical into the pickling tank (FIG. 2).

[0028] Hereinafter, "sulfuric acid" will mean any strong mineral acid.

Since the time required to measure the concentrations of sulfuric acid and hydrofluoric acid is shorter than that required to measure the iron ion concentration (just several minutes to about 30 minutes), the analyzers (A1, A2)
Preferably, each is divided, preferably each of which is specialized to only one of the analyses (the respective measurements of sulfuric acid, hydrofluoric acid, and iron ion concentration).

The analyzers (A1, A2) are connected to each other via a bidirectional transmission means known per se.
A1, A2) and can be operated by a higher level logic unit, not shown, which can be installed in loco or at a remote location.

Alternatively, said analyzers (A1, A2) are of the same type and comprise analytical means suitable for measuring the concentration of both acids (sulfuric acid and hydrofluoric acid) and iron ions. Can be done.

In such a case, the device according to the invention was able to work even if one of the analyzers (A1, A2) failed.

FIG. 2 shows a simplified diagram of the analyzer A (A1, A2) of FIG. 1, consisting of a combination of the following items: a sampling module C, its sampling input I (I1 ,..., In) are in turn connected to a permanent recirculation line between the pickling tank V (V1,..., Vn; FIG. 1) and the analyzer A; at least the sample of the tank to be analyzed is contained. One container (not shown) is provided inside the sampling module C; a reagent reservoir DR containing the chemicals for analysis; Dosing means D (D1, D2) suitable for transferring the same drug into, and a part of the dosing means D is suitable for withdrawing a large amount of drug with low accuracy (from about 2 to about 5%). , The remaining dosing means is accurate Suitable for withdrawing in degrees (approximately 0.1%); in FIG. 2 the dosing means D with low and high accuracy are each divided into two different functional units (D1, D2); (Generally referred to as EM in FIG. 2), from the sampling module C to the sample of the tank to be analyzed, from the dosing means D to the chemicals required for the analysis and to the container W (not shown). Analytical vessel CA that receives the water (preferably having a conductivity of less than 100 microsiemens) necessary to dilute the sample to the desired dilution rate; FIG. 2 is not part of the invention , Analysis container C
Further elements present in A (such as a stirrer) have been omitted; control and control of the analysis procedure, obtain information from the measuring electrode EM, elaborate and process the vessel S (fig. A logic operation unit UL for activating means for sending the solution of the correction chemical contained in 1) into the pickling tank.

In a preferred, but non-limiting embodiment, the dosing means of functional unit D1 is a peristaltic pump with a constant delivery, while the dosing means of functional unit D2 is an antacid material operated by an electric stepper motor (Eg, PES) syringe.

In the preferred embodiment again, the analyzer is also provided with an analytical vessel CA and a measuring electrode EM with water after each measurement (hereinafter described with reference to FIGS. 3 and 4) after a given number of measurements. Is a chemical solution (preferably not necessarily 10-20% hydrochloric acid)
Means to enable rinsing with, thus keeping the measuring electrode EM in an optimal state,
It has reliable analytical data and allows for minimal maintenance interruptions and increased electrode life.

[0036] In order to ensure a final product of constant quality, each type or family of material to be pickled is subject to specifications and characteristic parameters (hydrofluoric acid and sulfuric acid concentrations, trivalent and divalent iron ion concentrations, Must be processed according to the ratio between divalent and divalent iron ions, the concentration of hydrogen peroxide, the temperature of the sample to be analyzed, etc .; in a preferred embodiment of the invention, all The parameters that characterize each working step, as well as those relating to the operation of Analyzer A, which enable a separate analysis to be performed on the pickling tank, can be divided into the material itself and two uniquely correlated operating procedures. When necessary, it is stored in the logical operation unit UL called according to the material to be pickled.

The operating procedure comprises, but preferably not necessarily, at least the following information: the sequence and type of analysis to be performed; the predefined values of the parameters for the pickling bath; The magnitude of the deviation which is permissible with regard to which, the logic unit UL activates said means for feeding the solution of the correction chemical contained in the container S into the pickling tank;
The dilution ratio of the sample of the pickling tank to be analyzed with water in the analysis container CA.

[0038] Proper operation of the analyzer A can be effectively and periodically checked automatically; for this purpose a preferred embodiment of the invention provides a further effective auto-calibration procedure for a given number of times. Withdrawing an aliquot of a standard solution having a known composition from a container (preferably but not necessarily located in the reagent storage DR) which is stored in the logic operation unit UL which is activated after the analysis. Then, it is transferred into an analysis container CA, analyzed, and the obtained analysis result is compared with a known composition. If the difference between the obtained analysis result and the known concentration is desired, If it is greater, it comprises functional steps for issuing a warning signal.

According to an embodiment of the invention not shown in the figures, the logic unit UL can be connected to a central control unit and / or a higher-level logic unit so that control and management can be performed. As noted above, this higher level logic unit may be located "on the fly" or at a remote location.

In particular, at each change of work activity, the central operator can modify the operating procedure performed by one or more logic units UL and activate those relating to the activity to be started The operator also invokes the operating procedure from one or more of the logic units UL, modifies it and has it to be executed by the logic unit UL and / or sends it to the logic unit UL. You can also enter new operating procedures to be saved.

The analytical method used for the analysis of the pickling bath is part of the present invention and will now be described for a better understanding of the details already set forth.

A ) A method for determining the conductivity of hydrofluoric acid and sulfuric acid (or strong acids other than those related to hydrofluoric acid) . This method of determination is that in aqueous solutions formed by a mixture of a weak acid such as hydrofluoric acid and a strong acid such as sulfuric acid, the conductivity of the solution is practically equivalent to that of a strong acid at the same concentration; It also utilizes the high affinity of hydrofluoric acid for metal cations present in solution as a salt of known concentration (in a step subsequent to the first conductivity measurement on a sufficiently diluted bath sample to measure sulfuric acid concentration). Most of the anions in the salt are derived from strong acids (eg, nitric acid or hydrochloric acid), so the reaction to form the fluorine complex of the metal cation and hydrofluoric acid was determined by a second conductivity measurement, which was fully dissociated. Will cause a significant increase in conductivity due to the formation of an equivalent amount of strong acid.

For example: nHF + Fe (NO ₃ ) ₃ → FeF _n ^(3-n) ++ nHNO ₃ Therefore, such an increase in conductivity is proportional to the concentration of hydrofluoric acid which can be measured quantitatively after proper calibration. . Such salts can be, for example, ferric nitrate, ferric chloride, aluminum nitrate, aluminum chloride; in a preferred embodiment of the invention, ferric nitrate.9H ₂ O is used at a concentration of 750 g / l. .

In order to ensure a sufficiently linear dependence of the conductivity from fluctuations in the acid concentration, the dilution of the sample must be carefully evaluated as a function of the concentration of the acid present in the vessel to be analyzed; By way of example, sulfuric acid concentrations up to 200 g / l and hydrofluoric acid concentrations up to 60 g / l, dilution ratios from 1: 100 to 5: 100 and preferably 4: 100 are considered to be acceptable.

Another variable essential for obtaining reliable results (which must be managed by the logic unit UL of analyzer A) is the temperature of the sample after dilution with water; The temperature can have a considerable variation (usually between +5 and + 40 ° C.) according to the weather, the water source and the holding time in the container W.

It is clear that conductivity measurements are greatly affected by temperature, and this problem is usually overcome by an automatic compensation system built into the measurement device; in the present case, automatic compensation is the first It can only be adjusted precisely with the effect on the conductivity measurement (determination of the sulfuric acid concentration) and not on the second one (determination of the hydrofluoric acid concentration) performed after the addition of ferric nitrate as the solution composition changes And, in fact, its dependence on temperature is different before and after ferric nitrate addition.

This significant problem is solved by the analyzer A according to the invention, in which the logic unit UL changes the conductivity due to the addition of the volume v3 of the ferric nitrate solution which is dependent on the sample temperature. Consider.

The amount of ferric nitrate used during the titration must ensure complete complexation of hydrofluoric acid; in the system under consideration, for nitric acid concentrations of less than 60 g / l, ferric · 9H ₂ O in 750 g / l volume of the sample volume v3 and bath solutions v1
The ratio between must be higher than 0.5 and preferably 1 is better.

As a non-limiting example, the following procedure was followed by a sample volume dilution of 4: 100.
Filling the analytical vessel CA with the dosing means D2 a given water volume v2 having a conductivity of less than 100 microSiemens to obtain a dilution of 4: 100; Pumping a given volume v1 of the sample of the pickling tank to be analyzed from the sampling module C (by the dosing means D2); starting stirring of the solution; first conductivity measurement (L ₁ ); Addition of a given volume v3 = v1 of a 750 g / l solution of ferric nitrate 9H ₂ O; stirring of the solution and measurement of its temperature T; second conductivity measurement (L ₂ ).

The logical operation unit UL data L _1, L _2, to get the T automatically find the concentration of the acid by the following calculation: Sulfuric acid concentration (g / l): a · L 1 2 + b · L ₁ -c · hydrofluoric acid concentration _{(g / l): a 1} · δ 2 + b 1 · δ-c 1 where: a, b, c, coefficients a _1, b _1, c ₁ is quadratic Δ = L ₂ −L ₁ −φ; φ = c ₂ + (c ₃ · T); where c ₂ and c ₃ are nitric acid added to the diluted sample before the second conductivity measurement. Nitetsu 9
It is a constant depending on the amount of H ₂ O.

[0051] In this embodiment: a = 0.0066; b = 5.015 ; c = 6.98; a 1 = 0.0120; b 1 = 2.881; c 1 = 3.81; c 2 = 9.632; c ₃ = 0.297.

FIG. 3 shows the characteristics of the conductivity cell CC that allows the special morphology to minimize the negative effects due to the high viscosity of the solution and to facilitate the rinsing of the measuring platinum plate.

The conductivity cell CC is made of glass and has a substantially cylindrical shape and consists of a hollow body B containing two platinum black plates EL; Has holes (F1, F2) for circulating the sample to be analyzed inside the hollow body B.

Preferably, the hollow body B has a diameter of about 20 mm (and comprises anyway between about 17 and 23 mm) and a height of about 40 mm (and comprises anyway between about 35 and 45 mm); The dimensions are about 10 x 5 mm (and about 8 x 12
mm and about 3 × 7 mm) and the distance to each other is about 15 mm (and between about 12 and 18 mm anyway).

In order to avoid polarization of the electrode EL, a measuring electric circuit (
(Not shown) must operate at high frequencies (between 25 and 40 kHz).

B) Method for determination of divalent iron The method for determination of divalent iron was determined by potassium permanganate titration according to classical methodology.
This can be done through potentiometric analysis.

The operating procedure requires the following: • Inject the volume v2 of the water provided through the overflow TP into the analytical vessel CA to obtain a dilution ratio ≧ 1: 50; Pump a given volume v1 of the sample in the pickling bath from the sampling module C (by the dosing means D2) and add the sample into the analysis vessel CA; a solution of a strong acid, eg 1: 1 by weight Acidification of the diluted pickling bath sample by addition of a given approximate amount of sulfuric acid solution into the analytical vessel CA (by the dosing means D1);-added into the analytical vessel CA by the dosing means D2 Potentiometric titration with 0.1 N potassium permanganate solution with preset end point or by automatic exploration of end point;-Empty and rinse analytical vessel CA.

C) Determination of trivalent iron Trivalent iron is measured by iodometric titration, but some special measures are required to allow the use of automated equipment and the acquisition of reliable and reproducible results. Is to pay attention.

The method of determination requires the following operating procedure: Inject the volume v2 of the given water through the overflow TP into the analytical vessel CA in order to obtain a dilution ratio ≧ 1: 50; Pump a given volume v1 of the sample of the pickling tank to be analyzed from the sampling module C (by the dosing means D2) and add the sample into the analysis vessel CA; start of agitation; known concentration Of a predetermined approximate amount of the lanthanum nitrate solution having the following formula (by the dosing means D1) into the analytical vessel CA: wait for 30 seconds without stirring; default definition of the hydrochloric acid solution with a volume ratio of 1: 1 Quantity of analytical container CA (by dosing means D1)
A predetermined approximate amount of potassium iodide solution, for example at a concentration of 1 kg / l (dosing means D
1) Addition into analysis vessel CA; 5 minutes without stirring; start of solution stirring; iodine released by reaction of trivalent iron with potassium iodide (by dosing means D2) Potentiometric titration with 0.1 N sodium thiosulfate (added);-Empty the analysis vessel CA and rinse with water.

For this automated analysis, the most striking aspect is the use of lanthanum nitrate; in fact, the addition of salts containing cations capable of complexing with fluorine linked to iron ions involves the addition of ferric ions by iodometric analysis. It is essential for quantitative analysis.

This analysis can be performed manually using a solution of calcium chloride; however, it has been proven that calcium chloride cannot be used for automatic titration of trivalent iron, since it is necessary to continuously analyze the analytical vessel CA. The subsequent precipitation of calcium fluoride and calcium sulphate tends to adhere to the inner electrode and cause serious errors and complex repairs. Conversely, lanthanum salts produce lanthanum fluoride, which does not adhere in powder form, and can quantitatively release ferric ions, thus enabling automatic control of the process with high reliability and very limited repair costs To

The same result can be achieved in any way by adding a complexing agent for iron ions to the system, which can quantitatively release it during the subsequent reaction with potassium iodide; EDTA Complexing agents such as (ethylenediaminetetraacetic acid) are suitable for this purpose.

The potentiometer system schematically illustrated in FIG. 4 comprises a measuring electrode (inactive in the working environment) immersed in an analytical container CA and a small plastic A reference electrode (which is in contact with the solution under measurement through a saline bridge consisting of an electrolyte (contained in a tank SR) that can be passed continuously through a porous partition SP located at the end of the tube T Preferably made of glass, Ag /
AgCl type).

The continuous passage of the electrolyte through the partition SP is intended to coincide with the electrical conduction in order to avoid contact between the partition SP and hydrofluoric acid and to continuously renew the electrolyte.

In a preferred embodiment, the measuring electrode E is made at its end from a body made of an antacid material supporting a platinum plate P whose one surface, the lower surface, has been mirror-finished, thus the plate P
To prevent salts derived from the reaction product settling on the measuring surface of the sample from fouling it.

Advantageously, the electrolyte (preferably 3 moles of potassium chloride) has glycerin (viscosity at 20 ° C. 1.15 and 1.45 centipoise) to increase viscosity and reduce flow rate. , A 10% solution of another stable product that is inert and functionally equivalent to the working environment, allowing better autonomy of the potentiometer system for a given volume of tank SR.

D) Method for Determining Hydrogen Peroxide Determination of free hydrogen peroxide during a nitric acid-free pickling process, such as those described herein, is commonly used in the treatment of ferritic and martensitic steels prior to final rinsing. Necessary for control of the finishing / passivation bath used during the last operation; usually the bath solution is sulfuric acid (20-60 g / l), hydrogen peroxide (3-10 g / l) and sometimes hydrofluoric acid. Consists of hydrofluoric acid.

The analytical methodology and operating procedures used for the determination of hydrogen peroxide are the same as those used for the determination of divalent iron in the pickling tank.

E) Method of Determining the Redox Potential The device according to the invention measures the redox potential of the solution on the diluted pickling tank sample used in the potentiometer system described before the determination of the divalent iron. The value thus obtained is very close to the oxidation-reduction potential measured in the tank before its dilution (± 20
mV). The value obtained is compared to a range of values (usually consisting of between 200 and 550 mV) stored in the logic unit UL to be used as the first signal of the correction operation of the system: If the value is out of the range, the logical operation unit UL of the analyzer A stops the analysis procedure and sends an alarm. Calibration of the potentiometer system is performed at a predetermined frequency (eg, once a week) by measuring the redox potential of a standard solution of known potential (typically 468 mV).

As described above, the logical operation unit UL of the analyzer A according to the present invention measures the desired parameter relating to the sample in the pickling tank under analysis, and then corrects the known concentration correction chemical ( Sulfuric acid, hydrofluoric acid and oxidizing agent) to calculate the amount of each of the solutions,
The chemical is added from time to time to the pickling tank to restore the desired composition value, and addition means (e.g., Activate the dosing pump or solenoid valve).

In order to have the correction amount of the correction chemical added to the pickling tank, the characteristic value of the facility (tank V
, The amount of delivery of each addition means, the preset concentration value of the correction medicine, the concentration of the medicine, etc.) are known, and the logical operation unit UL has to calculate exactly the operating time of the addition means. .

The applicant's research and experiments have shown that, in order to restore the concentrations of sulfuric acid, hydrofluoric acid, trivalent iron ions and oxidizing agent in the pickling tank to desired values, the logical operation unit UL It has been shown that for a period of time s (seconds) given by the expression, each of the addition means for controlling the addition of sulfuric acid, hydrofluoric acid and oxidant solution into the pickling tank must be activated: s = K · (v ₀ −v _m ) · v _b / p where: s = operating time (seconds); K = factor (l / g) inversely proportional to the concentration of the correction chemical; v ₀ = given the specific correction chemical V _m = concentration of the specific correction chemical obtained as a result of the analysis (g / l); v _b = volume of the tank; p = amount delivered by the addition means (l / s) .

In order to return the ratio R between the concentration of trivalent and divalent iron ions to a desired value, the logical operation unit UL operates the addition time s ₁ (to supply the oxidizing solution into the pickling tank). Calculate (in seconds) by the following operation: Calculate B ₁ = A · R where A is the divalent iron ion concentration (g / l) resulting from titration with permanganate and R Is the desired ratio between the concentrations of trivalent and divalent iron ions, respectively, and B1 is the theoretical concentration of trivalent iron ions; B ₁ and the measured concentration of trivalent iron ions B (g / L); if B ≧ B ₁ (the measured concentration of trivalent iron ions is larger than that of divalent iron), the logic operation unit UL does not operate; if B <B ₁ ( If the trivalent iron ion concentration is lower than the measured value), the logical operation unit UL adjusts the addition of the oxidizing agent solution to the pickling tank. That the operating time s ₁ of adding means for calculating the following _{formula: s 1 = K · K 1} · C / p where: s ₁ = actuating time (seconds); K = factor inversely proportional to the concentration of the correction chemicals (l K ₁ = factor proportional to tank volume V (l); C = (B ₁ -B) / R = second to be oxidized to restore the desired value for iron ion concentration (g / l) The amount of ferrous ions; p = the delivery amount of the addition means (l / s).

Alternatively, the vessel can be managed as a function of the ratio R between trivalent and divalent iron according to the following formula: Calculation of total iron ions T = A + B where A is the permanganate titration analysis a and B is the concentration of Fe ²⁺ obtained is the concentration of Fe ³⁺ obtained from iodometric analysis from; - calculating R = B / a; - R (present ratio) with R ₁ (default ratio) comparison; • If R> if R _1, logical operation unit UL does not perform any addition of an oxidizing agent; - if if R <R _1, pickling bath of the oxidizing agent solution in accordance with the logic operation unit UL by the following equation Calculate the operating time s ₁ (second) of the addition means for adjusting the addition into the medium: s ₁ = K · K ₁ · C / p where C = A-[(A + B) / (R ₁ +1)] = amount of bivalent iron to oxidize to restore the present ratio R to the default R _1; s ₁ = actuating time (seconds); K = coefficient, the tank Inversely proportional to the amount V (l); p = delivery of the addition means (l / s).

FIG. 3 schematically shows an exploded view of the analytical vessel CA of FIG. 2, comprising a preferred embodiment of a conductivity-type measuring system and rinsing means for the analytical vessel CA and the measuring cell CC.

In FIG. 3, it is possible to see: a conductivity cell CC used for conductivity measurement; an analysis container CA; a liquid level in the analysis container CA, and An overflow pipe TP whose position (controlled by the logic operation unit UL) can be moved as it is emptied; rinsing means (F, U) controlled by the logic operation unit UL, the analysis container CA and the conductivity Rinsing of the measuring cell CC is possible.

FIG. 4 schematically shows an exploded view of the analysis vessel CA of FIG. 2, which, like that of FIG. 3, comprises not only a preferred embodiment of the rinsing means for the analysis vessel CA and the measuring electrode but also a potential difference measuring system. I have.

In FIG. 4, it can be seen that: The measuring electrode E, the reference electrode R positioned outside the analytical vessel CA, and the porous partition SP installed at one end of a small plastic tube T are continuously connected. A potentiometer system consisting of a saline bridge containing the electrolyte passed through and contained in a tank SR; an analysis vessel CA; setting the liquid level in the analysis vessel CA and emptying the same analysis vessel. An overflow pipe TP whose position (controlled by the logical operation unit UL) can be moved in accordance with the following: rinsing means (F, U) controlled by the logical operation unit UL, the analysis container CA, the electrode E
And the porous partition SP can be rinsed.

In the preferred embodiment shown in FIGS. 3 and 4, such rinsing means comprises a plurality of slits F and measuring electrodes E and a porous septum SP arranged along the upper edge of the analytical vessel CA, a conductivity measurement. The end of each cell CC consists of a nozzle U suitable for rinsing with a water spray; in FIGS. 3 and 4, a lid CP for the analytical vessel CA and an electrode E of the potentiometer system, a small tube T, a conductivity measurement. The means MS supporting the cell CC and the dosing means D (D1, D
One can also see a small tube (not explicitly shown in FIGS. 3 and 4) linking 2) to the analysis vessel CA; the lid CP and the support means MS are well known per se, and the invention is not limited thereto. Has nothing to do with it and will not be described.

Preferably, the analysis container CA, the measurement electrode E, and the porous partition wall SP (each of the analysis container C
A and the conductivity measuring cell CC) are rinsed with water after each analysis and washed with a chemical solution after a predetermined number of analyses.

To rinse the parts with water after each analysis, the logic unit UL performs the following steps one after the other: completely empty the analysis vessel (CA); a large amount of water through the slit (F). Is poured into the analysis container (CA);-Fill the analysis container (CA) with water until the tip of the electrode E, the porous partition wall SP, and the conductivity measurement cell CC are immersed;-Empty the analysis container (CA). Rinse the tip of the electrode E, the porous partition wall SP, and the conductivity measurement cell CC by spraying a certain amount of water onto them through the nozzle (U); and empty the analysis container (CA). Prepare for the next analysis.

After the predetermined number of analyses, the analytical container CA, the tip of the electrode E and the porous partition wall SP (the analytical container CA and the conductivity measuring cell CC, respectively) are washed with a chemical solution (preferably 10-20% hydrochloric acid). The logical operation unit UL fills the analysis container CA with water through the slit F until the tip of the electrode E, the porous partition wall SP, and the conductivity measurement cell CC are immersed, and the amount of the product necessary for the chemical cleaning (as much as possible) Then, hydrochloric acid) is pumped from a tank (preferably not necessarily placed inside the reagent storage unit DR) and sent to the analysis container CA; after a predetermined time, the logical operation unit UL Analysis container CA
It is rinsed with water in order to empty and erase any traces of the chemical solution.

Furthermore, when not in operation, the analytical vessel CA is filled with water through the slit F and the nozzle U in order to avoid any dirt and / or scratches on the tip of the electrode E, the porous partition SP and the conductivity measuring cell CC. It is.

According to the present description, as suggested by routine experience and by natural technological evolution, modifying and improving the control of the pickling tank, which still remains within the scope of the present invention, is to the expert. Is possible.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing equipment comprising an analyzer according to the present invention.

FIG. 2 is a simplified diagram of an analyzer according to the invention.

FIG. 3 schematically shows the analysis container CA of FIG. 2 comprising a preferred embodiment of the conductivity measuring system and the container itself and the rinsing means of the measuring electrode.

FIG. 4 schematically shows the analysis container CA of FIG. 2 comprising a preferred embodiment of a potentiometric measurement system and a rinsing means for the container itself and the measuring electrode.

[Procedural Amendment] Submission of translation of Article 34 Amendment of the Patent Cooperation Treaty

[Submission date] November 13, 2000 (2001.11.13)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction contents]

Apparatus and method for controlling the pickling process of steel

[Claims]

DETAILED DESCRIPTION OF THE INVENTION

[0001] The present invention resides in an apparatus and method for controlling the pickling process for carbon steel, austenitic, ferritic and martensitic stainless steels, duplex stainless steels and special alloys, wherein the apparatus comprises: The pickling bath sampling and the analysis of said sample are automatically operated to define precise process parameters (according to specific conductivity and potentiometric methodology) and to restore the desired concentration of essential chemicals in the pickling bath.

[0002] The present invention also specializes in the processing of steel through the clarification of remotely operable operating procedures that automatically retrieve and implement the most appropriate operating conditions for pickling of a particular type of material during processing. It is also possible to control the pickling conditions.

BACKGROUND OF THE INVENTION In the rolling, drawing, extrusion and heat treatment of steel products (such as plates, strips, tubes, bars), not only passivation and corrosion resistance but also a fine finished appearance and further work are required. An oxide layer is formed on the surface which must be removed both to allow for

The oxide layer on the surface, usually at an appropriate dilution and temperature, comprises one or more acids containing inorganic mineral acids (sulfuric, hydrochloric, nitric, hydrofluoric) alone or in a mixture with one another. The action of the bath is followed by a chemical treatment (pickling) based on at least one finishing rinse with water.

[0005] For stainless steel, the usual pickling process (either dipping, spraying or turbulent)
Requires a mixture of nitric acid and hydrofluoric acid; the process is not only due to the problem of large amounts of nitrates in the wastewater, but also due to the release of reaction by-products (extremely toxic nitrogen oxides) into the atmosphere. Dragging serious ecological problems.

[0006] Therefore, a number of "ecological" alternative processes have recently been devised that feature nitric acid elimination.

Among such processes, those particularly effective on an industrial scale are those that use a mixture of sulfuric acid or hydrochloric acid, hydrofluoric acid and ferric ions, where the mixture in a pickling tank is used. The proper concentration of such ions is maintained by the addition of hydrogen dioxide. Such several steps (corresponding to U.S. Patent US-A-5345383) Italian patent No. 1,245,594 and No. 1,255,655 and European Patent Application No. EP-A- 0769575 It is noted.

[0008] In traditional pickling techniques, the control of the process is usually performed by manual titration of the acidity or by measuring the conductivity of the solution and its iron content (or total metal by measuring solution density). Includes ad hoc control; it also allows for the measurement of hydrofluoric acid content by specific ion selective electrodes.

[0009] Some of these techniques have been used to automate the single operation of a pickling process based on nitric acid in stainless steel.

US Pat. No. 4,060,717 (LECO) measures the concentration of nitric acid (or other strong acid) and hydrofluoric acid in a pickling bath containing nitric acid and hydrofluoric acid. Discloses the use of ion-selective electrodes for fluorine and hydrogen ions; the voltage data collected by the control circuit is carefully processed by a microprocessor to calculate the concentrations of the two acids and adjust the relevant concentrations. Is done.

[0011] Japanese Patent No. 55040908 (Nippon Steel) discloses that to adjust the concentration of acid, hydrofluoric acid and another hydrofluoric acid are determined through ion-selective electrode determination of the relevant anions after the solution has passed through the ion-exchange membrane. A method for determining one strong acid (nitric acid, hydrochloric acid, sulfuric acid) is disclosed.

US Pat. No. 5,286,368 (Foxboro) discloses nitric acid and hydrogen fluoride through the ability to complex ferric ions towards fluoride ions, which allows the determination of the concentration of acid in the mixture. The concentration of hydrofluoric acid in the acid mixture is measured. Japanese Patent No. 072944509 (Kawasaki Steel) is the free acid concentration of iron ion by absorptiometry of salicylic acid iron complex, the concentration of Yu away hydrofluoric acid by discoloration spectrophotometry of iron acetylacetone complex and by neutralization titration method Measure the concentration of free hydrofluoric acid and nitric acid and iron ions in the pickling solution by measuring the total concentration of free nitric acid. The concentration of free nitric acid is calculated by subtracting the concentration of free hydrofluoric acid from the total concentration of free acid. It is more determined to. Japanese Patent No. 081660003 (Mitsubishi Heavy Industries) relates to a method for continuously measuring the iron ion concentration in a pickling solution .

[0013] The continuous automatic control of such pickling processes based on nitric acid is better than, for example, manual or automatic control sometimes performed two or three times a day, but for processes relating to the quality of the material to be treated. Is not essential, since the functional properties of such tanks, especially in pickling stainless steel, such tanks usually have a high nitric acid concentration (about 12-15%) and about 2-5% hydrofluoric acid. This is because it has a concentration. The high nitric acid concentration simultaneously ensures both high acidity and almost constant oxidizing power, making it possible to operate the process through the occasional addition of chemicals. Moreover, the determination of the acid concentration is sufficient to have adequate control of the pickling capacity of the bath.

On the contrary, the nitric acid-free pickling system as cited above has a ferric ion (F
e ³⁺ ) concentration measurements, or better, the oxidation properties of the system with respect to the Fe ³⁺ / Fe ²⁺ ratio.

In this case, 2Fe ³⁺ + FeO → 3Fe ²⁺ (1) trivalent due to the pickling reaction (1) in a continuous process for producing stainless steel strip or an automatic, high-productivity facility for pickling bars. The iron ion concentration, the Fe ³⁺ / Fe ²⁺ ratio and therefore the oxidizing capacity of the solution tend to decrease rapidly and change the behavior of the vessel continuously and intensely.

Therefore, the optimum conditions must be continuously adjusted with an oxidizing agent such as hydrogen peroxide.

Furthermore, fluctuations in the concentration of trivalent iron also indirectly affect the concentration of free acid present in the tank.

For example, in a pickling system based on a mixture of sulfuric acid, hydrofluoric acid and ferric salt, this effect is related to the following preferred equilibrium equation: Fe ³⁺ + nF ⁻ → FeF _n ^{(3 -n) +} Fe ²⁺ + SO ₄ ^2- → FeSO ₄ Therefore, during the oxidation / reduction reaction of a pair of Fe ³⁺ / Fe ²⁺ , from the complex salts involved in the release of sulfuric acid and hydrofluoric acid respectively. Occurs, thus altering the composition of the bath.

The occasional process control by analytical measurements, followed by the large addition of chemicals to restore the best pickling conditions, is therefore too great to have opposite conclusions regarding product quality and process cost. Causes changes in tank parameters.

On the other hand, adjusting the composition associated with frequent manual control is time consuming and costly.
Therefore, this requires a lot of manpower to ensure a sufficient control frequency (e.g., one control per hour).

The criticality of the nitric acid-free pickling process is the total amount of iron dissolved per unit time, the number of pickling tanks to be controlled, the number of substances requiring different operating conditions and the It is clearly related to the performance required to frequently add the acid manually.

[0022] Control of the stainless steel pickling process as previously cited for stainless steel strip continuous pickling equipment or high productivity automated equipment for the bar process has proven critical to the quality of the final product; It can also be uneconomical without the use of automated systems for reactant sampling, control and dosing.

The control apparatus and method according to the present invention require the use of unique techniques and analytical methods for proper management of such steps.

DISCLOSURE OF THE INVENTION It is an object of the present invention to provide a means for collecting a sample of a tank to be analyzed; not only measuring the oxidation-reduction potential value of the sample and its temperature , but also the specific conductivity methodology (hydrofluoric acid) Means for analyzing said sample to determine a number of parameters according to a method for finding the concentration of sulfuric acid or another inorganic strong acid) and potentiometric methodology (for finding the concentration of trivalent and divalent iron); Appropriately calculate the amount of correction chemicals (preferably hydrofluoric acid, sulfuric acid and oxidizing agent) to be added to the pickling tank in order to restore the value of said parameter to the desired level, and A control device for a nitric acid-free pickling tank comprising recovery means for activating at least one device for adding an amount into said pickling tank. If possible, the parameters to be measured is their concentration, hydrofluoric acid it及 beauty divalent and trivalent iron ions of sulfuric acid. A further object of the invention is a control method for controlling a nitric acid-free pickling bath, which comprises at least the following steps: -taking a sample of the pickling bath solution; -acids, divalent Measuring the concentration of iron and trivalent iron in the sample in the pickling tank ; measuring the oxidation-reduction potential and temperature of the sample in the pickling tank ; adding the calculated amount of correction chemical to the pickling tank By doing so, the value of the measured concentration in the pickling tank is restored to a preset level.

FIG. 1 schematically shows a facility comprising an analyzer according to the invention, comprising: a plurality of pickling tanks V; (V1,..., Vn); In the embodiment described here, the analyzer A (comprising a simplified schematic diagram of FIG. 2) comprising a set of analyzers (A1, A2) working simultaneously on different parameters A plurality of containers S (S1, S2, S3) each of which is a correction chemical (strong acid, preferably sulfuric acid, hydrofluoric acid and oxidizing agent) to be added into one of the tanks V; (Preferably not necessarily hydrogen peroxide) at a given concentration. A plurality of permanent recirculation pipes connecting the tank V to the sampling inlet I of the analyzer A (FIG. 2); a plurality of pipes connecting the container S to the tank V, supplying correction chemicals; An adding means for allowing the analyzer A to add the correction chemical contained in the container S into the tank V;

For the sake of simplicity, FIG. 1 omits not only other circuit parts but also parts not relevant to the invention, such as valves, pumps, actuators, filtration and rinsing means known per se. Was.

Analyzer A is a means for taking a sample of the pickling solution from tank V; according to the specific conductivity and potentiometer methodology, the preset parameters (not only those of trivalent and divalent iron, but also of sulfuric acid, for example) Means for analyzing the concentration of the strong acid and hydrofluoric acid), the oxidation-reduction potential and the temperature of the diluted sample, the correction chemicals to be sent from the vessel S to the tank V to adjust the parameters, It comprises means for calculating the amount and means for operating the device at the output of the container S for sending the calculated amount of said correction chemical into the pickling tank (FIG. 2).

[0028] Hereinafter, "sulfuric acid" will mean any strong mineral acid.

Since the time required to measure the concentrations of sulfuric acid and hydrofluoric acid is shorter than that required to measure the iron ion concentration (just several minutes to about 30 minutes), the analyzers (A1, A2)
Preferably, each is divided, preferably each of which is specialized to only one of the analyses (the respective measurements of sulfuric acid, hydrofluoric acid, and iron ion concentration).

The analyzers (A1, A2) are connected to each other via a bidirectional transmission means known per se.
A1, A2) and can be operated by a higher level logic unit, not shown, which can be installed "in loco" or at a remote location.

Alternatively, said analyzers (A1, A2) are of the same type and comprise analytical means suitable for measuring the concentration of both acids (sulfuric acid and hydrofluoric acid) and iron ions. Can be done.

In such a case, the device according to the invention was able to work even if one of the analyzers (A1, A2) failed.

FIG. 2 shows a simplified diagram of the analyzer A (A1, A2) of FIG. 1, consisting of a combination of the following items: a sampling module C, its sampling input I (I1 ,..., In) are in turn connected to a permanent recirculation line between the pickling tank V (V1,..., Vn; FIG. 1) and the analyzer A; at least the sample of the tank to be analyzed is contained. One container (not shown) is provided inside the sampling module C; a reagent reservoir DR containing the chemicals for analysis; Dosing means D (D1, D2) suitable for transferring the same drug into, and a part of the dosing means D is suitable for withdrawing a large amount of drug with low accuracy (from about 2 to about 5%). , The remaining dosing means is accurate Suitable for withdrawing in degrees (approximately 0.1%); in FIG. 2 the dosing means D with low and high accuracy are each divided into two different functional units (D1, D2); (Generally referred to as EM in FIG. 2), from the sampling module C to the sample of the tank to be analyzed, from the dosing means D to the chemicals required for the analysis and to the container W (not shown). Analytical vessel CA that receives the water (preferably having a conductivity of less than 100 microsiemens) necessary to dilute the sample to the desired dilution rate; FIG. 2 is not part of the invention , Analysis container C
Further elements present in A (such as a stirrer) have been omitted; control and control of the analysis procedure, obtain information from the measuring electrode EM, elaborate and process the vessel S (fig. A logic operation unit UL for activating means for sending the solution of the correction chemical contained in 1) into the pickling tank.

In a preferred, but non-limiting embodiment, the dosing means of functional unit D1 is a peristaltic pump with a constant delivery, while the dosing means of functional unit D2 is an antacid material operated by an electric stepper motor (Eg, PES) syringe.

In the preferred embodiment again, the analyzer is also provided with an analytical vessel CA and a measuring electrode EM with water after each measurement (hereinafter described with reference to FIGS. 3 and 4) after a given number of measurements. Is a chemical solution (preferably not necessarily 10-20% hydrochloric acid)
Means to enable rinsing with, thus keeping the measuring electrode EM in an optimal state,
It has reliable analytical data and allows for minimal maintenance interruptions and increased electrode life.

[0036] In order to ensure a final product of constant quality, each type or family of material to be pickled is subject to specifications and characteristic parameters (hydrofluoric acid and sulfuric acid concentrations, trivalent and divalent iron ion concentrations, Must be processed according to the ratio between divalent and divalent iron ions, the concentration of hydrogen peroxide, the temperature of the sample to be analyzed, etc .; in a preferred embodiment of the invention, all The parameters that characterize each working step, as well as those relating to the operation of Analyzer A, which enable a separate analysis to be performed on the pickling tank, can be divided into the material itself and two uniquely correlated operating procedures. When necessary, it is stored in the logical operation unit UL called according to the material to be pickled.

The operating procedure comprises, but preferably not necessarily, at least the following information: the sequence and type of analysis to be performed; the predefined values of the parameters for the pickling bath; The magnitude of the deviation which is permissible with regard to which, the logic unit UL activates said means for feeding the solution of the correction chemical contained in the container S into the pickling tank;
The dilution ratio of the sample of the pickling tank to be analyzed with water in the analysis container CA.

[0038] Proper operation of the analyzer A can be effectively and periodically checked automatically; for this purpose a preferred embodiment of the invention provides a further effective auto-calibration procedure for a given number of times. Withdrawing an aliquot of a standard solution having a known composition from a container (preferably but not necessarily located in the reagent storage DR) which is stored in the logic operation unit UL which is activated after the analysis. Then, it is transferred into an analysis container CA, analyzed, and the obtained analysis result is compared with a known composition. If the difference between the obtained analysis result and the known concentration is desired, If it is greater, it comprises functional steps for issuing a warning signal.

According to an embodiment of the invention not shown in the figures, the logic unit UL can be connected to a central control unit and / or a higher-level logic unit so that control and management can be performed. As noted above, this higher level logic unit may be located "on the fly" or at a remote location.

In particular, at each change of work activity, the central operator can modify the operating procedure performed by one or more logic units UL and activate those relating to the activity to be started The operator also invokes the operating procedure from one or more of the logic units UL, modifies it and has it to be executed by the logic unit UL and / or sends it to the logic unit UL. You can also enter new operating procedures to be saved.

The analytical method used for the analysis of the pickling bath is part of the present invention and will now be described for a better understanding of the details already set forth.

A ) A method for determining the conductivity of hydrofluoric acid and sulfuric acid (or strong acids other than those related to hydrofluoric acid) . This method of determination is that in aqueous solutions formed by a mixture of a weak acid such as hydrofluoric acid and a strong acid such as sulfuric acid, the conductivity of the solution is practically equivalent to that of a strong acid at the same concentration; It also utilizes the high affinity of hydrofluoric acid for metal cations present in solution as a salt of known concentration (in a step subsequent to the first conductivity measurement on a sufficiently diluted bath sample to measure sulfuric acid concentration). Most of the anions in the salt are derived from strong acids (eg, nitric acid or hydrochloric acid), so the reaction to form the fluorine complex of the metal cation and hydrofluoric acid was determined by a second conductivity measurement, which was fully dissociated. Will cause a significant increase in conductivity due to the formation of an equivalent amount of strong acid.

For example: nHF + Fe (NO ₃ ) ₃ → FeF _n ^(3-n) ++ nHNO ₃ Therefore, such an increase in conductivity is proportional to the concentration of hydrofluoric acid which can be measured quantitatively after proper calibration. . Such salts can be, for example, ferric nitrate, ferric chloride, aluminum nitrate, aluminum chloride; in a preferred embodiment of the invention, ferric nitrate.9H ₂ O
Are used at a concentration of 750 g / l.

In order to ensure a sufficiently linear dependence of the conductivity from fluctuations in the acid concentration, the dilution of the sample must be carefully evaluated as a function of the concentration of the acid present in the vessel to be analyzed; By way of example, sulfuric acid concentrations up to 200 g / l and hydrofluoric acid concentrations up to 60 g / l, dilution ratios from 1: 100 to 5: 100 and preferably 4: 100 are considered to be acceptable.

Another variable essential for obtaining reliable results (which must be managed by the logic unit UL of analyzer A) is the temperature of the sample after dilution with water; The temperature can have a considerable variation (usually between +5 and + 40 ° C.) according to the weather, the water source and the holding time in the container W.

It is clear that conductivity measurements are greatly affected by temperature, and this problem is usually overcome by an automatic compensation system built into the measurement device; in the present case, automatic compensation is the first It can only be adjusted precisely with the effect on the conductivity measurement (determination of the sulfuric acid concentration) and not on the second one (determination of the hydrofluoric acid concentration) performed after the addition of ferric nitrate as the solution composition changes And, in fact, its dependence on temperature is different before and after ferric nitrate addition.

This significant problem is solved by the analyzer A according to the invention, in which the logic unit UL changes the conductivity due to the addition of the volume v3 of the ferric nitrate solution which is dependent on the sample temperature. Consider.

The amount of ferric nitrate used during the titration must ensure complete complexation of hydrofluoric acid; in the system under consideration, for nitric acid concentrations of less than 60 g / l, ferric · 9H ₂ O in 750 g / l volume of the sample volume v3 and bath solutions v1
The ratio between must be higher than 0.5 and preferably 1 is better.

As a non-limiting example, the following procedure was followed by a sample volume dilution of 4: 100.
Filling the analytical vessel CA with the dosing means D2 a given water volume v2 having a conductivity of less than 100 microSiemens to obtain a dilution of 4: 100; Pumping a given volume v1 of the sample of the pickling tank to be analyzed from the sampling module C (by the dosing means D2); starting stirring of the solution; first conductivity measurement (L ₁ ); Addition of a given volume v3 = v1 of a 750 g / l solution of ferric nitrate 9H ₂ O; stirring of the solution and measurement of its temperature T; second conductivity measurement (L ₂ ).

The logical operation unit UL data L _1, L _2, to get the T automatically find the concentration of the acid by the following calculation: Sulfuric acid concentration (g / l): a · L 1 2 + b · L ₁ -c · hydrofluoric acid concentration _{(g / l): a 1} · δ 2 + b 1 · δ-c 1 where: a, b, c, coefficients a _1, b _1, c ₁ is quadratic Δ = L ₂ −L ₁ −φ; φ = c ₂ + (c ₃ · T); where c ₂ and c ₃ are nitric acid added to the diluted sample before the second conductivity measurement. Nitetsu 9
It is a constant depending on the amount of H ₂ O.

[0051] In this embodiment: a = 0.0066; b = 5.015 ; c = 6.98; a 1 = 0.0120; b 1 = 2.881; c 1 = 3.81; c 2 = 9.632; c ₃ = 0.297.

FIG. 3 shows the characteristics of the conductivity cell CC that allows the special morphology to minimize the negative effects due to the high viscosity of the solution and to facilitate the rinsing of the measuring platinum plate.

The conductivity cell CC is made of glass and has a substantially cylindrical shape and consists of a hollow body B containing two platinum black plates EL; Has holes (F1, F2) for circulating the sample to be analyzed inside the hollow body B.

Preferably, the hollow body B has a diameter of about 20 mm (and comprises anyway between about 17 and 23 mm) and a height of about 40 mm (and comprises anyway between about 35 and 45 mm); The dimensions are about 10 x 5 mm (and about 8 x 12
mm and about 3 × 7 mm) and the distance to each other is about 15 mm (and between about 12 and 18 mm anyway).

In order to avoid polarization of the electrode EL, a measuring electric circuit (
(Not shown) must operate at high frequencies (between 25 and 40 kHz).

B) Method for determination of divalent iron The method for determination of divalent iron was determined by potassium permanganate titration according to classical methodology.
This can be done through potentiometric analysis.

The operating procedure requires the following: • Inject the volume v2 of the water provided through the overflow TP into the analytical vessel CA to obtain a dilution ratio ≧ 1: 50; Pump a given volume v1 of the sample in the pickling bath from the sampling module C (by the dosing means D2) and add the sample into the analysis vessel CA; a solution of a strong acid, eg 1: 1 by weight Acidification of the diluted pickling bath sample by addition of a given approximate amount of sulfuric acid solution into the analytical vessel CA (by the dosing means D1);-added into the analytical vessel CA by the dosing means D2 Potentiometric titration with 0.1 N potassium permanganate solution with preset end point or by automatic exploration of end point;-Empty and rinse analytical vessel CA.

C) Determination of trivalent iron Trivalent iron is measured by iodometric titration, but some special measures are required to allow the use of automated equipment and the acquisition of reliable and reproducible results. Is to pay attention.

The method of determination requires the following operating procedure: Inject the volume v2 of the given water through the overflow TP into the analytical vessel CA in order to obtain a dilution ratio ≧ 1: 50; Pump a given volume v1 of the sample of the pickling tank to be analyzed from the sampling module C (by the dosing means D2) and add the sample into the analysis vessel CA; start of agitation; known concentration Of a predetermined approximate amount of the lanthanum nitrate solution having the following formula (by the dosing means D1) into the analytical vessel CA: wait for 30 seconds without stirring; default definition of the hydrochloric acid solution with a volume ratio of 1: 1 Quantity of analytical container CA (by dosing means D1)
A predetermined approximate amount of potassium iodide solution, for example at a concentration of 1 kg / l (dosing means D
1) Addition into analysis vessel CA; 5 minutes without stirring; start of solution stirring; iodine released by reaction of trivalent iron with potassium iodide (by dosing means D2) Potentiometric titration with 0.1 N sodium thiosulfate (added);-Empty the analysis vessel CA and rinse with water.

For this automated analysis, the most striking aspect is the use of lanthanum nitrate; in fact, the addition of salts containing cations capable of complexing with fluorine linked to iron ions involves the addition of ferric ions by iodometric analysis. It is essential for quantitative analysis.

This analysis can be performed manually using a solution of calcium chloride; however, it has been proven that calcium chloride cannot be used for automatic titration of trivalent iron, since it is necessary to continuously analyze the analytical vessel CA. The subsequent precipitation of calcium fluoride and calcium sulphate tends to adhere to the inner electrode and cause serious errors and complex repairs. Conversely, lanthanum salts produce lanthanum fluoride, which does not adhere in powder form, and can quantitatively release ferric ions, thus enabling automatic control of the process with high reliability and very limited repair costs To

The same result can be achieved in any way by adding a complexing agent for iron ions to the system, which can quantitatively release it during the subsequent reaction with potassium iodide; EDTA Complexing agents such as (ethylenediaminetetraacetic acid) are suitable for this purpose.

The potentiometer system schematically illustrated in FIG. 4 comprises a measuring electrode (inactive in the working environment) immersed in an analytical container CA and a small plastic A reference electrode (which is in contact with the solution under measurement through a saline bridge consisting of an electrolyte (contained in a tank SR) that can be passed continuously through a porous partition SP located at the end of the tube T Preferably made of glass, Ag /
AgCl type).

The continuous passage of the electrolyte through the partition SP is intended to coincide with the electrical conduction in order to avoid contact between the partition SP and hydrofluoric acid and to continuously renew the electrolyte.

In a preferred embodiment, the measuring electrode E is made at its end from a body made of an antacid material supporting a platinum plate P whose one surface, the lower surface, has been mirror-finished, thus the plate P
To prevent salts derived from the reaction product settling on the measuring surface of the sample from fouling it.

Advantageously, the electrolyte (preferably 3 moles of potassium chloride) has glycerin (viscosity at 20 ° C. 1.15 and 1.45 centipoise) to increase viscosity and reduce flow rate. , A 10% solution of another stable product that is inert and functionally equivalent to the working environment, allowing better autonomy of the potentiometer system for a given volume of tank SR.

D) Method for Determining Hydrogen Peroxide Determination of free hydrogen peroxide during a nitric acid-free pickling process, such as those described herein, is commonly used in the treatment of ferritic and martensitic steels prior to final rinsing. Necessary for control of the finishing / passivation bath used during the last operation; usually the bath solution is sulfuric acid (20-60 g / l), hydrogen peroxide (3-10 g / l) and sometimes hydrofluoric acid. Consists of hydrofluoric acid.

The analytical methodology and operating procedures used for the determination of hydrogen peroxide are the same as those used for the determination of divalent iron in the pickling tank.

E) Method of Determining the Redox Potential The device according to the invention measures the redox potential of the solution on the diluted pickling tank sample used in the potentiometer system described before the determination of the divalent iron. The value thus obtained is very close to the oxidation-reduction potential measured in the tank before its dilution (± 20
mV). The value obtained is compared to a range of values (usually consisting of between 200 and 550 mV) stored in the logic unit UL to be used as the first signal of the correction operation of the system: If the value is out of the range, the logical operation unit UL of the analyzer A stops the analysis procedure and sends an alarm. Calibration of the potentiometer system is performed at a predetermined frequency (eg, once a week) by measuring the redox potential of a standard solution of known potential (typically 468 mV).

As described above, the logical operation unit UL of the analyzer A according to the present invention measures the desired parameter relating to the sample in the pickling tank under analysis, and then corrects the known concentration correction chemical ( Sulfuric acid, hydrofluoric acid and oxidizing agent) to calculate the amount of each of the solutions,
The chemical is added from time to time to the pickling tank to restore the desired composition value, and addition means (e.g., Activate the dosing pump or solenoid valve).

In order to have the correction amount of the correction chemical added to the pickling tank, the characteristic value of the facility (tank V
, The amount of delivery of each addition means, the preset concentration value of the correction medicine, the concentration of the medicine, etc.) are known, and the logical operation unit UL has to calculate exactly the operating time of the addition means. .

The applicant's research and experiments have shown that, in order to restore the concentrations of sulfuric acid, hydrofluoric acid, trivalent iron ions and oxidizing agent in the pickling tank to desired values, the logical operation unit UL It has been shown that for a period of time s (seconds) given by the expression, each of the addition means for controlling the addition of sulfuric acid, hydrofluoric acid and oxidant solution into the pickling tank must be activated: s = K · (v ₀ −v _m ) · v _b / p where: s = operating time (seconds); K = factor (l / g) inversely proportional to the concentration of the correction chemical; v ₀ = given the specific correction chemical V _m = concentration of the specific correction chemical obtained as a result of the analysis (g / l); v _b = volume of the tank; p = amount delivered by the addition means (l / s) .

In order to return the ratio R between the concentration of trivalent and divalent iron ions to a desired value, the logical operation unit UL operates the addition time s ₁ (to supply the oxidizing solution into the pickling tank). Calculate (in seconds) by the following operation: Calculate B ₁ = A · R where A is the divalent iron ion concentration (g / l) resulting from titration with permanganate and R Is the desired ratio between the concentrations of trivalent and divalent iron ions, respectively, and B ₁ is the theoretical concentration of trivalent iron ions; the measured concentration of B ₁ and trivalent iron ions B ( If & If B ≧ B ₁ (the measured concentration of the trivalent iron ions is greater than that of divalent), the logical operation unit UL does not operate;; g / l) and comparing the & If B <B ₁ If the trivalent iron ion concentration is lower than the measured value, the logical operation unit UL adjusts the addition of the oxidizing agent solution to the pickling tank. The operating time s ₁ of the addition means is calculated by the following equation: s ₁ = K · K ₁ · C / p where: s ₁ = operating time (seconds); K = a factor (l K ₁ = factor proportional to tank volume V (l); C = (B ₁ -B) / R = second to be oxidized to restore the desired value for iron ion concentration (g / l) The amount of ferrous ions; p = the delivery amount of the addition means (l / s).

Alternatively, the vessel can be managed as a function of the ratio R between trivalent and divalent iron according to the following formula: Calculation of total iron ions T = A + B where A is the permanganate titration analysis a and B is the concentration of Fe ²⁺ obtained is the concentration of Fe ³⁺ obtained from iodometric analysis from; - calculating R = B / a; - R (present ratio) with R ₁ (default ratio) comparison; • If R> if R _1, logical operation unit UL does not perform any addition of an oxidizing agent; - if if R <R _1, pickling bath of the oxidizing agent solution in accordance with the logic operation unit UL by the following equation Calculate the operating time s ¹ (second) of the addition means for adjusting the addition into the medium: s ₁ = K · K ₁ · C / p where C = A-[(A + B) / (R ₁ +1)] = amount of bivalent iron to oxidize to restore the present ratio R to the default R _1; s ₁ = actuating time (seconds); K = coefficient, the tank Inversely proportional to the amount V (l); p = delivery of the addition means (l / s).

FIG. 3 schematically shows an exploded view of the analytical vessel CA of FIG. 2, comprising a preferred embodiment of a conductivity-type measuring system and rinsing means for the analytical vessel CA and the measuring cell CC.

In FIG. 3, it is possible to see: a conductivity cell CC used for conductivity measurement; an analysis container CA; a liquid level in the analysis container CA, and An overflow pipe TP whose position (controlled by the logic operation unit UL) can be moved as it is emptied; rinsing means (F, U) controlled by the logic operation unit UL, the analysis container CA and the conductivity Rinsing of the measuring cell CC is possible.

FIG. 4 schematically shows an exploded view of the analysis vessel CA of FIG. 2, which, like that of FIG. 3, comprises not only a preferred embodiment of the rinsing means for the analysis vessel CA and the measuring electrode but also a potential difference measuring system. I have.

In FIG. 4, it can be seen that: The measuring electrode E, the reference electrode R positioned outside the analytical vessel CA, and the porous partition SP installed at one end of a small plastic tube T are continuously connected. A potentiometer system consisting of a saline bridge containing the electrolyte passed through and contained in a tank SR; an analysis vessel CA; setting the liquid level in the analysis vessel CA and emptying the same analysis vessel. An overflow pipe TP whose position (controlled by the logical operation unit UL) can be moved in accordance with the following: rinsing means (F, U) controlled by the logical operation unit UL, the analysis container CA, the electrode E
And the porous partition SP can be rinsed.

In the preferred embodiment shown in FIGS. 3 and 4, such rinsing means comprises a plurality of slits F and measuring electrodes E and a porous septum SP arranged along the upper edge of the analytical vessel CA, a conductivity measurement. The end of each cell CC consists of a nozzle U suitable for rinsing with a water spray; in FIGS. 3 and 4, a lid CP for the analytical vessel CA and an electrode E of the potentiometer system, a small tube T, a conductivity measurement. The means MS supporting the cell CC and the dosing means D (D1, D
One can also see a small tube (not explicitly shown in FIGS. 3 and 4) linking 2) to the analysis vessel CA; the lid CP and the support means MS are well known per se, and the invention is not limited thereto. Has nothing to do with it and will not be described.

Preferably, the analysis container CA, the measurement electrode E, and the porous partition wall SP (each of the analysis container C
A and the conductivity measuring cell CC) are rinsed with water after each analysis and washed with a chemical solution after a predetermined number of analyses.

To rinse the parts with water after each analysis, the logic unit UL performs the following steps one after the other: completely empty the analysis vessel (CA); a large amount of water through the slit (F). Is poured into the analysis container (CA);-Fill the analysis container (CA) with water until the tip of the electrode E, the porous partition wall SP, and the conductivity measurement cell CC are immersed;-Empty the analysis container (CA). Rinse the tip of the electrode E, the porous partition wall SP, and the conductivity measurement cell CC by spraying a certain amount of water onto them through the nozzle (U); and empty the analysis container (CA). Prepare for the next analysis.

After the predetermined number of analyses, the analytical container CA, the tip of the electrode E and the porous partition wall SP (the analytical container CA and the conductivity measuring cell CC, respectively) are washed with a chemical solution (preferably 10-20% hydrochloric acid). The logical operation unit UL fills the analysis container CA with water through the slit F until the tip of the electrode E, the porous partition wall SP, and the conductivity measurement cell CC are immersed, and the amount of the product necessary for the chemical cleaning (as much as possible) Then, hydrochloric acid) is pumped from a tank (preferably not necessarily placed inside the reagent storage unit DR) and sent to the analysis container CA; after a predetermined time, the logical operation unit UL Analysis container CA
It is rinsed with water in order to empty and erase any traces of the chemical solution.

Furthermore, when not in operation, the analytical vessel CA is filled with water through the slit F and the nozzle U in order to avoid any dirt and / or scratches on the tip of the electrode E, the porous partition SP and the conductivity measuring cell CC. It is.

According to the present description, as suggested by routine experience and by natural technological evolution, modifying and improving the control of the pickling tank, which still remains within the scope of the present invention, is to the expert. Is possible.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G01N 27/30 G01N 27/30 F 311 311C 27/401 313A (72) Inventor Muscianni Fabio Italy, 48024 Massa Lombarda, Via Botte 9 (72) Inventor Demartis Ioannis Italy, 20137 Milan, Via Ga Divona 18 (72) Inventor Forznazi Sandro Italy, 05100 Terni, Viale Benedetto Brin 218 Atchia I Spettiettiari Terni Societa (72) Inventor Manchia Franco Italy, 00129 Rome, Via di Castel Romano 100/102 St. Lo Civilruppo, Materiali Societe Tapel Within Thioni (72) Inventor Novaro Ezio Italy, 00129 Via di Castel Romano, Rome 100/102 Centro Civilruppo, Materiali Societe Inside Felme Terme d'Azioni (reference) 2G060 AA06 AC04 AC05 AE17 AF08 AF15 FA15 HC10 HD03 4K053 PA02 PA03 PA07 QA01 RA15 RA17 RA29 SA06 XA24 YA03 YA05 YA14

Claims (49)

[Claims] Means for taking a sample of the vessel to be analyzed; analyzing said sample to determine a number of parameters according to the specific conductivity and potentiometric methodology as well as the redox potential value and temperature of said sample. Means for appropriately calculating, in accordance with said measurements, the amount of correction chemical to be added to the pickling tank in order to restore the value of said parameter to a desired level, and said amount of correction chemical to the pickling tank A control device for a nitric acid-free pickling tank, characterized by comprising a recovery means for operating at least one device added therein. 2. The control device according to claim 1, wherein the parameters are various concentrations of sulfuric acid, hydrofluoric acid, and divalent and trivalent iron ions. 3. The control device according to claim 1, wherein the recovery means introduces a calculated amount of the solution of the correction chemical having a known concentration into the pickling tank. 4. The control device according to claim 3, wherein the correction chemicals are sulfuric acid, hydrofluoric acid and an oxidizing agent. 5. The method according to claim 4, wherein the oxidizing agent is hydrogen peroxide.
The control device according to claim 1. 6. The control device according to claim 1, wherein it comprises at least one analyzer (A). 7. Control device according to claim 6, characterized in that it consists of two analyzers (A1, A2) operating simultaneously on different parameters. 8. One of the analyzers (A1, A2) measures the concentrations of sulfuric acid and hydrofluoric acid in the pickling tank and returns sulfuric acid and hydrogen fluoride to the pickling tank in order to restore the concentration to an appropriate predetermined concentration level. During the addition of hydrofluoric acid, other analyzers (A2, A1 respectively) measure the concentration of iron ions in the pickling tank and determine the trivalent iron ion concentration and / or trivalent and divalent iron ions. Control device according to claims 2, 4 and 7, characterized in that an oxidizing agent is added to the pickling bath in order to restore a predetermined value of the ratio between. 9. An analyzing device (A) comprising: a pickling tank (V) for sequentially sending a sample of a pickling tank to be analyzed to at least one container placed inside a sampling module (C); A sampling module (C) with a connected sampling input (I); a reagent storage (DR) containing at least a tank of reagents used for the analysis of the pickling tank sample; a reagent storage (DR) Dosing means (D) for appropriately withdrawing a predetermined amount of chemicals from the tank in the container and transferring the same to the analysis container (CA); a measuring electrode (EM) used for analyzing a pickling tank sample; An analysis vessel (CA) containing and receiving the bath sample to be analyzed from the sampling module (C) and also the medication required for the analysis from the dosing means (D); controlling and operating the analysis procedure; Measuring power A logic operation unit (UL) that obtains and processes information from the pole (EM) and activates means for sending a solution containing a correction chemical into the pickling tank.
The control device according to claim 6, wherein the control device comprises a combination of: 10. A portion of the dosing means (D) withdraws a large amount of the drug properly with low accuracy (from about 2% to about 5%), and the other means of dispensing a small amount of the drug with high accuracy (about 0%).
. 10. The control device according to claim 9, wherein the control device is appropriately drawn at 1%). 11. The device according to claim 1, wherein the dispensing means having a low accuracy and a high accuracy are respectively divided into two different parts (D1, D2).
The control device according to 0. 12. It is used for rinsing the container (CA) and the measuring electrode (EM) in the analytical container (CA), and for diluting the pickling tank sample contained in the analytical container (CA) with a desired dilution ratio. Characterized in that it also comprises means for sending water for dilution into
The control device according to claim 9. 13. The control device according to claim 12, wherein the water for rinsing and dilution has a conductivity of less than 100 microsiemens. 14. The logic unit according to claim 9, wherein each logic unit is connected to a central control unit and / or a higher-level logic unit which can be controlled and managed by it. Control device. 15. The means for performing a conductivity measurement comprises a hollow glass body (B) at one end and has a substantially cylindrical shape and a pair of platinum black plates (EL).
And holes (F1, F2) through which a sample to be analyzed flows are provided at the lower and upper portions of the hollow body (B), and an analysis container ( Control device according to claim 1, characterized in that it comprises a conductivity measuring cell (CC) contained in CA). 16. The (EL) plate wherein the hollow body (B) has a diameter between about 17 and 23 mm and a height between about 35 and 45 mm, between about 8 × 12 mm and about 3 × 7 mm, about Control device according to claim 15, characterized in that it has a mutual distance between 12 and 18 mm. 17. The hollow body (B) having a diameter of about 20 mm, a height of about 40 mm, a plate (EL) size of about 10 × 5 mm, and a distance from each other of about 15 mm. The control device according to claim 1. 18. The means for performing a potentiometric measurement is connected to a measuring electrode (E) immersed in an analytical vessel (CA) and a porous partition (SP) placed at one end of a small plastic tube (T). Characterized in that it comprises a reference electrode (R) arranged outside the analysis vessel (CA), which is connected to the solution under measurement by a saline bridge constituted by an electrolytic solution passing through it. Item 2. The control device according to Item 1. 19. The control device according to claim 18, wherein the electrolyte comprises a product having a viscosity at 20 ° C. between 1.15 and 1.45 centipoise. 20. The control device according to claim 19, wherein the electrolyte contains 10% glycerin. 21. A measuring electrode (E) comprising a body made of an antacid material supporting a platinum plate (P) having a mirror-polished surface on one side at one end thereof. The control device according to claim 18, wherein: 22. An analyzer (A) comprising an analysis container (CA), a measurement electrode (E) and a porous partition wall (SP) of a saline solution bridge, an analysis container (CA) and a conductivity measurement cell (CC), respectively. It also comprises means for chemical washing and water rinsing, said means being a container (1) for direct water flow to the end of the measuring electrode (E), the porous partition (SP) and the conductivity measuring cell (CC) respectively. 19. Control device according to claim 9, 15 and 18, characterized in that it comprises a small slit (F) and a nozzle (U) arranged along the upper edge of CA). 23. It comprises at least the following steps: measurement of the concentration of acid in the pickling tank; measurement of the concentration of divalent iron ions in the pickling tank; trivalent iron ions in the pickling tank. A method for controlling a nitric acid-free pickling tank, comprising: measuring the oxidation-reduction potential of a pickling tank solution. 24. Measuring the concentration of free hydrogen peroxide in a finishing / passivation bath where it is used as a final operation prior to a final rinse in the treatment of ferritic and martensitic steels. A method according to claim 23, characterized in that: 25. The method for measuring the concentration of acids in a pickling tank comprises the following steps:
By means of a precise dosing means (D2), to fill the analytical vessel (CA) with a given volume of water having a conductivity of less than 100 microsiemens in order to obtain a defined dilution rate; By means (D2) pump a predetermined volume of the pickling tank sample to be analyzed from the sampling module (C) and insert it into the analysis vessel (CA); agitate the solution; Conductivity measurement (L ₁ ); add a defined volume of ferric nitrate 9H ₂ O solution into the analytical vessel (CA); stir the solution to reduce its temperature (T). measurements are; - second time measurement of conductivity (L ₂₎ is carried out; empty-analysis vessel (CA), characterized in that it further consists, the method of claim 23. 26. The method according to claim 25, wherein a 750 g / l ferric nitrate solution having the same volume as the pickling tank sample to be analyzed is added to the analysis vessel (CA). The described method. 27. Concentration of pickling bath of sulfuric acid (as) the following ^{_{equation: as = a · L 1 2}} + b · L 1 -c where a, b and c are calculated in accordance with the coefficient of the quadratic equation, 26. The method of claim 25, wherein: 28. The concentration (af) of hydrofluoric acid in the pickling tank is represented by the following formula: af = a₁・ Δ^Two+ B₁・ Δ-c₁ Where a₁, B₁, C₁Is the coefficient of the quadratic equation; δ = L_Two-L₁-Φ; φ = c_Two+ (C _Three · T); c_Two, C_ThreeIs ferric nitrate 9H added to the analytical vessel (CA)_TwoO's
26. The method according to claim 25, characterized in that it is calculated according to a quantity-dependent constant.
Method. 29. The method according to claim 23, wherein the determination of the concentration of ferrous ions in the pickling tank is performed by a permanganate titration method. 30. The determination of the concentration of divalent iron ions in the pickling tank is at least the following operations: Filling the analytical vessel (CA) with a predetermined volume of water to obtain a predetermined dilution; Pumping a predetermined volume of the pickling tank sample to be analyzed from the sampling module (C) by means of the dosing means (D2) and adding it into the analytical vessel (CA); (D1) acidifying a diluted pickling bath sample by adding a predefined approximate amount of a strong acid solution having a known concentration to an analytical vessel (CA);
-Potentiometric titration with a known concentration of potassium permanganate added into the analytical vessel (CA) by means of high precision dosing means (D2), the potentiometric titration has an end point to show or an automatic search for the end point 30. The method according to claim 29, comprising: emptying the analysis vessel (CA). 31. The method according to claim 23, wherein the determination of the trivalent iron ion concentration in the pickling tank is performed by an iodometric method. 32. The determination of the concentration of trivalent iron ions in the pickling tank is at least the following operations: • Filling the analytical vessel (CA) with a predetermined volume of water to obtain a predetermined dilution rate; Pumping a predetermined volume of the pickling tank sample to be analyzed from the sampling module (C) by means of the dosing means (D2) and adding said tank sample into the analysis vessel (CA); Start; a solution of a known approximate concentration of a known concentration of an element which reacts with sulfuric acid and hydrofluoric acid by low precision dosing means (D1) to form soluble salts or easily removable precipitates Into the analytical vessel (CA); wait for the given period without agitation; and, by means of a low-precision dosing means (D1), add a predefined approximate amount of hydrochloric acid solution of known concentration to the analytical vessel (CA). • Low-precision dosing means (D1) Add a known approximate concentration of potassium iodide solution with known concentration into the analytical vessel (CA); wait for a given period without agitation; agitate the solution; high-precision dosing means (D2 ), Potentiometric titration of iodine liberated by reaction of ferric ion with potassium iodide with sodium thiosulfate of known concentration;-emptying the analytical vessel (CA) The method according to claim 31, characterized in that: 33. The salt of an element which reacts with sulfuric acid and hydrofluoric acid to form soluble salts and easily removable precipitates is lanthanum nitrate,
33. The method according to claim 32. 34. The analysis container (CA) according to claim 30, wherein the volume of water is filled into the analysis container (CA) through an overflow tube incorporated in the analysis container (CA). Method. 35. The determination of the oxidation-reduction potential of the pickling tank is made before the determination of the divalent iron concentration, and the value of the oxidation-reduction potential thus obtained is compared with a predetermined range. 24. The method according to claim 23, wherein if the measured value is outside the range, the analysis procedure is stopped and an alarm signal is issued. 36. The procedure for determining the free hydrogen peroxide is at least the following: Filling the analytical vessel (CA) with a predetermined volume of water to obtain a predetermined dilution rate; High precision dosing means (D2) Withdraws a predetermined volume of the pickling tank sample to be analyzed from the sampling module (C) and adds it into the analysis vessel (CA) by means of a low-precision dosing means (D1) Acidify the diluted pickling tank sample by adding a defined approximate amount of strong acid to the analytical vessel (CA); a known dose added into the analytical vessel (CA) by precision dosing means (D2) Potentiometric titration with potassium permanganate at a concentration, said potentiometric titration has a visible endpoint or an automatic search for endpoint; emptying the analytical vessel (CA). Method according to 24 . 37. After each analysis, of the analytical vessel (CA), of the means for measuring the potential difference and of the conductivity measuring cell; ie, the analytical vessel (CA), of the means for measuring the potential difference, the conductivity measuring cell and the predetermined 24. The method according to claim 23, further comprising a water rinsing operation of the conductivity measuring cell that has been chemically cleaned after the analysis of the number of times. 38. The water rinse comprises at least the following operations:-completely emptying the analytical vessel (CA);-plenty of water through a slit (F) arranged along the upper edge of the analytical vessel (CA). Is poured into the analytical vessel (CA); the means for measuring the potential difference and the tip of the conductivity measuring cell are filled with water until the analytical vessel (CA) is immersed; Rinsing the tip of the conductivity measuring cell and the means for measuring the potential difference,
38. Spraying some water onto them through a nozzle (U) located in CA);-Emptying the analysis vessel (CA) for the next analysis; the method of. 39. The chemical washing comprises at least the following operations: the means for measuring the potential difference and the analysis container until the tip of the conductivity measuring cell is immersed.
Fill the analytical vessel (CA) with water through a slit (F) arranged around the upper edge of the CA); pump the required quantity of product from the tank to obtain a chemical cleaning solution and remove it from the analytical vessel (CA); rinsing the analytical vessel (CA) after a predetermined period of time and rinsing with water to eliminate any traces of the cleaning chemical solution. 38. The method of claim 38. 40. The method of claim 39, wherein said chemical cleaning is performed with 10-20% hydrochloric acid. 41. The amount of product required to make the chemical cleaning solution is in the reagent reservoir (D).
40. The method according to claim 39, wherein the method is withdrawn from a tank located in R). 42. A slit (F) in which the analytical container (CA) is arranged along the upper edge of the analytical container (CA) and a nozzle (U) installed in the container when not operating.
24. The method according to claim 23, characterized by being filled with water through. 43. A sulfuric acid, hydrofluoric acid, trivalent iron ion and the concentration of pickling bath of the oxidizing agent is the following _{formula: s = K · (v 0} -v m) · v b / p where: s = actuating time; the concentration of resulting the particular correction chemicals were of v _m = analysis;; K = correction factor is inversely proportional to the concentration of the drug; v ₀ = specific correction chemicals given concentration v _b = tank P = amount delivered by the dosing means; p = amount delivered by the means for adjusting the dosing of the corresponding correction chemical into the pickling bath for a period of time (s) given by 24. The method of claim 23, wherein the method is characterized. 44. The ratio, R, between the concentration of trivalent iron ions and divalent iron ions in the pickling tank is calculated as follows: B ₁ = A · R where A is permanganese Is the divalent iron ion concentration resulting from titration with an acid salt, R is the desired ratio between the trivalent and divalent iron ion concentrations, respectively, and B ₁ is the theoretical concentration of trivalent iron ion Comparing B ₁ with the measured concentration B of trivalent iron ions; and if B ≧ B ₁ , a dosing means (D) that regulates the charging of the oxidizing agent into the pickling bath.
2) not operate the; - if if B <B _1, actuating the time represented by the following formula (s ₁₎ dispensing means for regulating the introduction of into the pickling bath of the oxidizing agent (D2): s _{1 = K · K 1 · C} / p where: s ₁ = actuating time; factor proportional to K ₁ = tank volume;; K = factor inversely proportional to the concentration of the correction chemicals _{C = (B 1 -B) /} R 24. The method according to claim 23, characterized in that: = the amount of ferrous ions to be oxidized to restore the desired value for the iron ion concentration; p = the delivery of the addition means; . 45. The ratio R between the concentration of trivalent iron ions and the concentration of divalent iron ions in the pickling tank is as follows: Calculation of total iron ions T = A + B where A is the permanganate titration The concentration of Fe ²⁺ obtained from the analysis and B is the concentration of Fe ³⁺ obtained from the iodometric titration analysis. ・ Calculation R = B / A; ・ R (current ratio) is R ₁ (predetermined ratio) compared with; - if R> if R _1, logical operation unit UL does not perform any addition of an oxidizing agent; - if if R <R _1, pickling of the oxidizing agent solution in accordance with the logic unit operation UL the following formula Calculate the operating time s ₁ (second) of the adding means for adjusting the addition into the tank: s ₁ = K · K ₁ · C / p where C = A − [(A + B) / (R ₁ +1) ] = amount of bivalent iron to oxidize to restore the present ratio R to the default R _1; s ₁ = actuating time (seconds); K = coefficient, the capacity of the tank V ( Is inversely proportional to); p = delivery of the addition means (l / s), characterized in that it is returned to the desired value by the method of claim 23. 46. A logic unit (UL) manages the pickling bath by one of the operating procedures loaded into its memory and associates a plurality of parameters characterizing the particular operation with the particular operation. 24. The method according to claim 23, comprising operating parameters of the analyzer for analyzing the pickling bath. 47. Each of the operating procedures has at least the following information: • the order and type of analysis to be performed; • the default values of the parameters to be examined in the pickling bath; , The logical operation unit (U
47. The method according to claim 46, characterized in that L) activates a dosing means (D) for delivering the corrective chemical into the pickling bath; diluting the pickling bath sample to be analyzed with water. Method. 48. The logic unit (UL) pumps a given amount of a solution having a known composition from a container and analyzes it, comprising the steps of: (CA); • Compare the value obtained from the analysis with the expected value; • Raise an alarm if the deviation between the measured value and the expected value is greater than a given amount; 47. The method of claim 46, further comprising performing an automatic calibration procedure that operates after the analysis of the number. 49. The method according to claim 48, wherein a solution having a known composition is pumped from a container located in the reagent reservoir (DR).