AU2016327141A1

AU2016327141A1 - Device, method and system for in-line monitoring of the concentration of acid mist

Info

Publication number: AU2016327141A1
Application number: AU2016327141A
Authority: AU
Inventors: Claudio Abraham Acuña Pérez; Felipe Ignacio Antonio AVILA GALAZ; Pablo Stephanno Campos Bracamonte; Maria Cristina CARMONA RAMOS; Rodrigo Antonio Duarte Olavarria; Gerardo Erasmo Fuentes Cáceres; Mijali Janacok KARAPAS DIAZ; Claudio Andres LEIVA HURTUBIA
Original assignee: Universidad Catolica del Norte
Current assignee: Universidad Catolica del Norte
Priority date: 2015-09-25
Filing date: 2016-09-15
Publication date: 2018-04-26
Anticipated expiration: 2036-09-15
Also published as: WO2017051290A1; PE20170994A1; CL2015002882A1; AU2016327141B2

Abstract

The invention relates to a device for the real-time monitoring of the concentration of acid mist generated in hydrometallurgy processes that use sulphuric acid. The device comprises means for aspirating atmospheric air disposed to establish a negative pressure difference with the environment, causing a sample of the atmospheric air to pass through an arrangement of communicating vessels that includes an air inlet pipe (20) and an acid absorption reactor (2) containing a siphon tube (3). The device further comprises: a sensor (31) for measuring the pH of the flow of the solution of air in water, which is connected with means (40) that can record and transmit the measurements of the sensor (31); and means for neutralising the solution (10) by means of the dosed input of a water-soluble alkali compound.

Description

(57) Resumen: Dispositivo para la monitorizacion en tiempo real de la concentracion de neblina acida generada en procesos de hidrometalurgia que emplean acido sulfurico. Comprende unos medios de aspiracion de aire atmosferico dispuestos para establecer una diferencia de presion negativa con el ambiente, que provoca el paso de una muestra de dicho aire atmosferico por una disposicion de vasos comunicantes que [Contimia en la p/tgina siguiente] wo 2017/051290 Al lllllllllllllllllllllllllllllllllllll^ (84) Estados designados (a menos que se indique otra cosa, para toda clase de protection regional admisible): ARIPO (BW, GH, GM, KE, LR, LS, MW, MZ, NA, RW, SD, SL, ST, SZ, TZ, UG, ZM, ZW), euroasiatica (AM,

AZ, BY, KG, KZ, RU, TJ, TM), europea (AL, AT, BE, BG, CH, CY, CZ, DE, DK, EE, ES, FI, FR, GB, GR, HR, HU, IE, IS, IT, LT, LU, LV, MC, MK, MT, NL, NO, PL, PT, RO, RS, SE, SI, SK, SM, TR), OAPI (BF, BJ, CF,

CG, CI, CM, GA, GN, GQ, GW, KM, ML, MR, NE, SN, TD, TG).

Declaraciones segiin la Regia 4.17:

— sobre la identidad del inventor (Regia 4.17(i)) — sobre el derecho del solicitante para solicitar y que le sea concedida una patente (Regia 4.17(H)) — sobre el derecho del solicitante a reivindicar la prioridad de la solicitud anterior (Regia 4.17(iii)) — sobre la calidad de inventor (Regia 4.17(iv))

Publicada:

— con informe de bdsqueda international (Art. 21(3)) — antes de la expiration del plazo para modificar las reivindicaciones y para ser republicada si se reciben modificaciones (Regia 48.2(h)) incluye un conducto (20) de entrada de aire y un reactor (2) de absorcion de acido, en cuyo interior hay un tubo sifon (3). Asimismo comprende un sensor (31) para medicion de pH del flujo de la disolucion del aire en agua, en comunicacion con unos medios (40) capaces de registrar y transmitir las mediciones del sensor (31); e incluye medios para neutralizar la solucion (10) mediante el aporte dosificado de un compuesto alcali soluble en agua.

DEVICE, METHOD AND SYSTEM FOR ONLINE MONITORING OF ACID MIST

CONCENTRATION

SPECIFICATION

The invention is directed to the measurement of acid mist, typically generated in processes of electrodeposition (plating, electrowinning) involving the use of sulfuric acid and an electrochemical process where micro bubbles of gas are generated, which break and generate micro-drops of sulfuric acid in the form of aerosol when ascending to the surface (acid mist).

Particularly, the invention aims to provide a device for on-line monitoring of the concentration of acid mist, in copper electro-winning processes.

The object is to have a positive impact on the working conditions of the operating personnel, the useful life of the equipment, and the costs for maintenance of structures and equipment. It will also provide operational management tools to control the concentration of mist under the permissible limits, thereby increasing the capacity of the process (production of cathodes).

STATE OF THE ART

In electro-winning copper plants, as an undesired condition, acid mist is generated, which corresponds to an aerosol of sulfuric acid, harmful to the health of the workers, the infrastructure and the environment. The concentration is subject to regulations according to each country. In Chile, for example, a maximum of 3 mg/m³ is established and is currently measured by off-line sampling (punctual measurement with subsequent chemical analysis with OSHA standard 113 or 121). This measurement methodology limits the effective control of the working environment and puts at risk the health of the people, the infrastructure and the compliance with national and international regulations.

Among the effects of the punctual measurement of the concentration of acid mist, is to delay the mitigation actions that may be implemented. In this way, actions such as the use of extraction hoods and the dosing of reagents, at present, have an outdated or reactive application with respect to events exceeding the permissible limit, becoming late actions.

Only in Chile there are at least 17 plants of EW (electro deposition, electrowinning) of large size, with an estimated amount of 7500 cells of EW, which do not have technology for online measurement of acid mist. In addition, it is projected that the environmental regulations in terms of control will be more demanding.

To date, the measurement of acid mist is made by punctual sampling and chemical analysis in the laboratory with a delay of days. Alternatives for its measurement are the optical devices that were originally developed for particles, therefore the measurements are biased by dust.

Currently in Chile there are no commercial devices for continuous measurement. While in the field of research relating to acid mist the focus has been installed in the way of reducing acid mist (for example through: surfactants, spheres, extraction hoods, spray showers), without considering that for its monitoring and automatic control it is essential to measure on line the concentration of acid mist.

Regarding the patents or applications in this technical field, reference will be made to documents US 3915646 and DE 2851761. The first document refers to a technique specific for a facility for punctual measurement and the second document teaches an arrangement for on line gas analysis.

In US 3915646 a method and means for the quantitative analysis of gases containing sulfuric acid in aerosol form are described. The gas sample is contacted with the exposed surface of an aqueous medium to collect the sulfuric acid component. The resulting solution is diluted with additional water and the electrical conductivity thereof is subsequently measured for the quantification of the acid component.

In DE 2851761 a trace detector of volatile substances in a carrier gas is disclosed, comprising sections for absorbing, for separating phases and a measuring cell. With this detector, the gas and a liquid (for example water) are mixed to dissolve the ion forming substances, the mixture flowing through a tube 1 to the phase separator comprising a jacket tube 4 with a connection 7 for the outlet of gases and a rod 8 for draining after the tube 1. In consequence, the separation of the gas bubbles contained in the gas-water mixture is carried out at the lower end 6 of the tube 1, where it has a diagonal cut. Then the liquid to be measured drops from the end of the rod 8 to an opening 12 of a capillary tube 10 leading to the measuring cell 13, in which this configuration is directed to avoid the entry of bubbles into the measuring cell. It also comprises a liquid barrier formed from the same overflow of the capillary tube 10 to separate the environment in the separator from the outside atmosphere.

As in the previous example, many of the devices of the state of the art use conductivity measurement to evaluate acid content. However, it has been found that the conductivity measurement is not selective; in the laboratory, the results are adjusted, but in the field the results are not, because there are other ions present in the electro-winning (EW) environment and the results show deviations that are difficult to adjust.

In this context, a technological development associated with an on line sensor of acid mist is presented, which allows to enable a continuous control over the mitigation actions in electro3 winning (EW) plants. A device providing this technology will positively impact the security conditions, the continuity of operations, and the health of the workers, among others.

An additional requirement is to improve the frequency, usually a day with conventional methods, at a measurement frequency of 10 to 20 minutes between measurements, in order to provide sufficient information for an on-line control of the acid mist.

The equipment operates autonomously for 2 to 3 months, after which time the containers with reagents must be maintained and replaced. The power consumption does not exceed 2 kW.

GENERAL DESCRIPTION

The solution proposed for the online monitoring of the concentration of acid mist is based on the direct measurement of hydronium ions (pH) of a descending flow substantially free of gas bubbles inside a siphon tube. The measured descending flow corresponds to a liquid solution generated in a reactor in which the bubbling of atmospheric air, which contains acid mist, allows a volume of water to absorb the sulfuric acid originally contained in the form of acid mist in the atmospheric air. The configuration of the siphon tube inside the reactor is such that the upper opening of the siphon tube is submerged below the level of the water in the reactor and the lower hole of the siphon tube too, being in communication with the fluid inside the reactor. In operation, a means that produce the air bubbles from the base of the reactor enable an ascendant flow in the reactor and outwardly to the siphon tube, which in turn by the laws of the fluids induces a descendant flow into the siphon tube. The effect required for the correct pH measurement, that the flow inside the siphon tube to be free of bubbles, is achieved by the appropriate relative dimensions between the upper opening and the lower hole of the siphon tube. As described in the preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings represent the properties of the invention from its main embodiments. The following figures are included:

Figure 1: Schematic representation of the device for online monitoring of the concentration of acid mist of the present invention.

Figure 2: Schematic representation in section of the acid absorption reactor and the interior of the siphon tube, of the device of figure 1, during the mixing operation.

Figure 3: Schematic representation in section of a portion of the acid absorption reactor with the siphon tube during the pH measurement, in the device of figure 1.

Figure 4: Schematic representation in section of the acid absorption reactor and the siphon tube during neutralization, in the device of figure 1.

Figure 5: Schematic representation in section of the acid absorption reactor and the siphon tube during the restoration of level, in the device of figure 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description is referred to the preferred embodiment shown in the figures, without thereby limiting the scope of the invention, defined in the set of claims. Therefore, alternative embodiments that arise from simplifications of the same or from the application of the same concepts and essential elements, are also included.

Figure 1 shows a general view of the components of the device for online monitoring of the concentration of acid mist. The extension to a system of continuous control of the process environment is obtained by considering at least one device in wired or wireless communication with a receiving node, with computing capacity, which is the user of the information obtained by each device. Regarding the location of the devices in a copper electro-winning plant or other in which acid mist occurs, places that allow an effective control of the working environment would be preferred, following for example the indications of the regulations regarding the realization of punctual measurements with subsequent chemical analysis. Thus, by means of the available information, the system will be able, for example, to facilitate the taking of timely actions in order to control the levels of acid mist.

Specifically, the device operates generating a solution (10), figures 2 and 3, from the mixture of a certain volume of water and the sulfuric acid contained in a sample of atmospheric air in the form of an acid mist. For this purpose it has mixing means that are operatively connected to an atmospheric air suction means.

The suction means are arranged to establish a negative pressure difference with the external environment, which causes or induces the passage of the atmospheric air sample through an arrangement of communicating vessels that includes an air inlet duct (20) and an acid absorption reactor (2), being inside the latter where the mixture is made. In figure 1 the dotted line OO' indicates the level of water in the duct (20), while the water level corresponding to the reactor (2) can be seen more clearly in figure 2, in which both levels are establish by communicating vessels.

The reactor (2) has means for dispersing in a bubble form the sample of atmospheric air in the volume of water from a lower portion of the reactor (2). In Figure 2 the means for dispersing are shown as a mesh or screen (4) disposed in the lower entrance (8), however, any other apparatus for bubbling the sample of atmospheric air can be employed. For example, the screen (4) may correspond to a polyester mesh, to a stainless steel mesh, etc.

We emphasize herein the relevance in the effectiveness of the mixing that has the size of the bubbles that are formed when passing through the means for dispersing. A desirable bubble size is between 0.5 mm to 1.5 mm, which can be achieved, for example, with the use of a permeability filter fabric 20-80 L/dm²*min at 20 mm w.c.

The device also includes gas separation means comprising a siphon tube (3), arranged vertically inside the reactor (2). The siphon tube (3) has an upper opening (6) and a lower hole (7) located below the water level inside the reactor (2). The separation between the opening (6) and the hole (7) is of a distance L.

The objective of the gas separation means is to generate a flow of the solution (10) free of bubbles, a necessary condition for the acidity measurement methodology that is used. For this, the ratio between the diameter DA of the upper opening (6) and the diameter DO of the lower hole (7) is such that it allows an ascendant flow of the solution (10) outward the siphon tube (3) as a product of the ascent of the air bubbles to induce a descendant flow into the interior of siphon tube (3), without generating bubbles entrainment inside the siphon tube (3). Based on the drawings, arrows A and B in figure 2 indicate the passing direction of the air; while in figure 3, the black arrows pointing up indicate the flow direction outside the siphon tube (3) and the black arrow pointing down indicates the flow direction inside the siphon tube (3).

The preferred dimensional characteristics for the siphon tube (3) include that the diameter DA is related to the diameter DO such that DA/DO is in the range of 9:1 to 11:1; and with better observed results when DA/DO is equal to 10:1. Additionally, the distance L, of separation between the opening (6) and the lower hole (7), is related to the diameter DA of the upper opening (6) such that L/DA is in the range of 4.5:1 at 5.5:1; and with better observed results when L/DA is equal to 5:1.

In another relevant aspect of the present device, the generation of the negative pressure difference, or vacuum level, or depression with respect to the atmospheric pressure is necessary in order to obtain the air sample and the suction means are arranged to achieve it. Specifically, the negative pressure difference is established within an auxiliary volume or buffer tank (22) from which the vacuum pump (23) can draw air when the valve (42) is in an open position. In addition, the buffer tank (22) is in permanent communication via the conduit (21) with the inner volume (11) within the reactor (2). Wherein, said inner volume (11) is defined over the level of water in the reactor (2). Therefore, the accumulated pressure difference will only act when the valve (41) that is arranged in the duct (20) to control the passage of air to the reactor (2), is open.

The elements described so far allow to support the operation of the present device in the stages of: a) mixing and b) generating a flow of the solution (10) free of bubbles. Both stages follow one another continuously or without interventions after a means (40) generate control signals for the opening of the valves (41) and (42) and for closing the valves (25) and (28), allowing passage of the air sample through the duct (20) that feeds the reactor (2). It is emphasized that both stages are not dissociable, or in other words, they are part of a continuity in the development of the flows established within the reactor (2) and the siphon tube (3). With respect to the air that passes in the form of bubbles through the reactor (2), it yields most of its acid content when the solution is produced (10); therefore, it comes with a low or null content of acid to the inner portion or volume (11) in the upper part of the reactor (2), to the interior of the buffer tank (22), and eventually to the atmosphere expelled by the vacuum pump (23) as outlined by arrow B in figure 1.

Regarding to the determination of the acid content in the acid mist, the sensor (31) for the direct measurement of hydronium ions is used for the pH measurement. In addition, said determination of the acid content is carried out on the basis of the pH change between measurements. Therefore, the device has means (40) in communication with the sensor (31) capable of performing an estimation of the content of acid at a given time based on pairs of measurements that are made before and after the absorption of acid by the solution (10). Consequently, the first measurement of the device must be made directly to the volume of water inside the reactor, before starting normal operation.

In step c), the pH measurement is performed from the sensor (31) practically at the same time as step b), since said measurement is applied to the flow of the solution (10) that descends into the siphon tube (3).

Regarding the arrangement of the pH sensor, the siphon tube and the reactor, the following is proposed. To provide support to the siphon tube (3) within the reactor (2) there is an elongated element that passes from the external environment into the reactor (2) and also into the siphon tube (3). The elongate element is connected in a hermetic or airtight manner to the passage of fluid or gas both with the reactor (2) and with the siphon tube (3). Preferably, said elongated element is a tubular element (32), with the advantage of further serving to install the sensor (31) at its distal end - inside the siphon tube -, allowing to guide a connection (33) from the sensor (31) towards the means (40) inside the tubular element (32). To comply with the operating conditions of the sensor (31) the distal end of the tubular element (32) must be located between the upper opening (6) and the lower hole (7), and is preferably arranged in the lower third with respect to the longitudinal dimension of the siphon tube (3).

For reasons of simplicity and symmetry of the flow of fluids in a preferred embodiment the reactor (2) has a cylindrical geometry, and the siphon tube (3) is located concentrically therein; being both components with coincident longitudinal axes. Also for simplicity and symmetry, it is preferable that the distal end of the element holding the sensor (31) is located at a position along the longitudinal axis of the siphon tube (3).

In order to maintain the device in appropriate conditions for subsequent measurements, ina an autonomous manner and free of maintenance for prolonged periods, once a predefined level of pH has been reached inside the reactor (2) the method includes the steps of:

e) neutralizing the solution (10) by providing a water-soluble alkaline compound in a dosed manner; and

f) restoring the determined volume of water inside the reactor (2).

Wherein the determined volume is a fixed volume, and each time it is neutralized, a greater amount of water is added and by the overflow it is ensured that inside the reactor (2) the amount of water is constant.

Due to the pH modification of the water in the reactor, and provided that the determination of the acid content that occurs after step c) is relative, the following pH measurement can be considered as loss and resume monitoring in the subsequent pH measurement. Considering the above, steps e) and f) can be omitted or postponed until a predefined pH acidity level is reached inside the reactor (2).

An alternative to the above would be to consider a step g) of pH measurement of the neutralized water, by means of the sensor (31). The value obtained here is recorded by part of the means (40) so that the next pH measurement for determining the acid content in the atmosphere considers a corrected value corresponding to the determined volume of water inside the reactor (2), after neutralizing.

To carry out the previous steps, the device comprises, respectively, means for neutralizing the solution (10) and means for restoring the determined volume of water inside the reactor (2).

The means for neutralizing the solution (10) comprise: a container (26) for storing the watersoluble alkaline compound, a pumping or dosing means (27) and a valve (28) arranged in a duct (29) that connects an outlet in the container (26) with the reactor (2), see Figures 1 and 4. The associated method comprises in step e) the opening of a valve (28) and the actuation of the dosing means (27) allows introducing an amount of alkaline compound from the container (26) in the solution (10) to the interior of the reactor (2). Furthermore, during step e) the valves (41) and (42) are kept closed, preventing the flow of air from the atmosphere during the operation of the means for neutralizing the solution (10).

The means for restoring the determined volume of water inside the reactor (2) comprise a lateral outlet (15) for the overflow of the reactor (2) with the opening being regulated by a valve (25), wherein the position of the lateral outlet (15) establishes the minimum level of water inside the reactor (2), see figures 1 and 5. Preferably a duct (24) communicates the lateral outlet (15) for overflow with the container (26). Thus in step f) by the opening of the valve (25) that regulates the overflow from the lateral outlet (15), the water level inside the reactor (2) can be restored to the minimum level, and in addition, by adding the overflow from the reactor (2) to the water-soluble alkaline compound in the container (26) a closed cycle is established for the flows associated with the neutralization and restoration of the water level in the reactor (2). Eventually the flow of overflow water will ostensibly decrease the effectiveness of the alkaline compound for neutralizing the acidity of the solution (10). The tests carried out indicate that for a container of a volume in the order of a quarter of the volume of water in the reactor (2) a service life of three months is obtained. In figure 5 the overflow flow is diagrammed by arrow A, while the remaining inputs and/or outputs to the reactor are closed (crosses B, C, D).

In a further aspect of step e), to neutralize the solution (10), the closure of the valve (25) is further included so that the container (26) does not receive overflow from the reactor (2). In figure 4 the dosage of the alkali compound is schematized by the arrow A, while the remaining inputs and/or outputs to the reactor are closed (crosses B, C, D).

In an alternative embodiment, the neutralization can be carried out cyclically until reaching a parameter value or pH target (pH7 - pH8) in the fluid inside the siphon tube and the reactor (2). This is achieved by the step g) described above, and a step h) in which the means (40) determine if is necessary an additional provision of alkaline compound to the reactor (2). If affirmative, steps e) of neutralization, f) of restoring the determined volume of water inside the reactor (2), and step g) of pH measurement are repeated, thus defining a cycle directed to reach the target value of pH.

The means (40) are available in relation to the control, recording and transmission processes, which in figure 1 are represented in communication with the valves and with the pH sensor by dotted lines. The graphic representation of other relations such as those existing with the vacuum pump (23) and the dosing pump (27) have been omitted.

Thus the means (40), which are in communication with the sensor (31) via the connection (33), are arranged to process the data of the pH measurements, before and after the absorption of acid, to determine the change of pH between measurements which allows an estimation of the acid content present at that moment in the atmosphere. The means (40) are also responsible for determining whether it is necessary to provide alkaline compound to the reactor (2) from the container (26), by comparison with a minimum pH value or in a preestablished manner every certain number of measurements of acid content. The information that the means (40) register, either the pH change values obtained or pairs of data obtained from consecutive pH measurements, is transmitted via wired or wireless means (43) -in step

d) of the method- to be received and used by the processing node or system of the user. In addition, the means (40) are arranged to generate control signals for the valves (25, 28, 41, 42) and to control the operation of the vacuum pump (23) and the dosing means (27).

Means (40) also provide context information for the measurements and others related to maintenance. In the first case the data of the pH measurements include the date and time of the measurement, and an identification of the monitoring device. In the second case the means (40) are arranged to generate information of the cycles necessary to neutralize the acidity of the solution (10), or of the amount of neutralizations performed. Thus, the device is capable of delivering a guide for its maintenance that includes recharging or changing of the fluids, to return to standard operating conditions.

EXAMPLE OF APPLICATION

The parameters of the siphon tube (3) are: DA/DO = 10 and L/DA = 5.

The operation starts with 1.4 liters of water in the reactor (2) and the equipment is used until it registers below pH 5, proceeding to a neutralization with diluted NaOH solution. Alternatively, the water is neutralized every certain amount of measurements (pH), previously defined.

The autonomy of the device described herein has three months of use, without intervention or calibration. The equipment is programmed in such a manner that it works based on differences and not on punctual values, focusing on the increments and not on the punctual values. Regarding the provision of supplies such as NaOH, a three-month autonomy is considered before adding an amount in the order of 0.5 ml of diluted solution.

The estimated water consumption for a system as the one proposed herein is 0.5 liters every three months. Therefore, besides the possible water saving, a relevant aspect is the nondependence of a continuous source for water supply.

There are multiple ways to carry out the neutralization process. For example, in an alternative embodiment it is neutralized with a dilute solution of Caustic Soda, or with a diluted solution of Sodium Bicarbonate. The minimum criterion that the chosen compound must fulfill is to be a base (alkali).

The supply of electric power can be provided by autonomous power sources or from the electricity grid. The above means that the total consumption of the prototype equipment is 6A with a voltage of 220 VAC.

Claims

1. A device for online monitoring of the concentration of acid mist generated in processes of hydrometallurgy using sulfuric acid, to provide useful information to the continuous control of the process environment, which includes mixing means, gas separation means, a sensor (31), CHARACTERIZED in that:

the mixing means are operatively connected to atmospheric air suction means, in which the suction means are arranged to establish a negative pressure difference with the external environment, causing a sample of atmospheric air to pass through an arrangement of communicating vessels that includes an air intake duct (20) and an acid absorption reactor (2), wherein the reactor (2) has means to disperse in the form of bubbles the atmospheric air sample in a determined volume of water from a lower portion of the reactor (2), to generate a solution (10) from the determined volume of water and the sulfuric acid contained in the sample of atmospheric air in the form of an acid mist;

the gas separation means include a siphon tube (3), arranged vertically inside the reactor (2), in which the siphon tube (3) has an upper opening (6) and a lower hole (7) both located below a water level of the reactor (2) and separated by a distance L, wherein the ratio between a diameter DA of the upper opening (6) and a diameter DO of the lower hole (7) allows an ascendant flow of the solution (10) to the outside of the siphon tube (3), as a consequence of the rise of the air bubbles, to induce a descendant flow of the solution (10) into the siphon tube (3) without generating bubble entrainment;

the sensor (31) for the pH measurement of the flow of the bubble-free solution (10) is in communication with means (40) capable of recording and transmitting the measurements of the sensor (31); and the device includes means for neutralizing the solution (10), by a dosed supply of a water-soluble alkaline compound, and means for restoring the determined volume of water to the interior of the reactor (2).

2. The device according to claim 1, CHARACTERIZED in that the siphon tube (3) has a length L that is related to the diameter DA of the upper opening (6) such that L/DA is in the range of 4.5:1 to 5.5:1.

3. The device according to claim 1, CHARACTERIZED in that the diameter DA of the upper opening (6) is related to the diameter DO of the lower hole (7) such that DA/DO is in the range of 9:1 to 11:1.

4. The device according to claim 1, CHARACTERIZED in that the sensor (31) is able to measure directly hydronium ions, and is arranged to measure the bubble-free descendant flow into the siphon tube (3).

5. The device according to claim 1, CHARACTERIZED in that an elongate element is arranged to pass from the external environment to the interior of the reactor (2) and also to pass into the siphon tube (3), establishing a hermetic connections to the passage of fluid or gas with both the reactor (2) and the siphon tube (3), in which the elongate element supports the siphon tube (3) inside the reactor (2).

6. The device according to claim 5, CHARACTERIZED in that the elongate element is a tubular element (32) and has a distal end arranged between the upper opening (6) and the lower hole (7).

7. The device according to claim 6, CHARACTERIZED in that the distal end of the tubular element (32) is preferably arranged in the lower third with respect to the longitudinal dimension of the siphon tube (3).

8. The device according to claim 7, CHARACTERIZED in that the sensor (31) is arranged at the distal end of the tubular element (32), establishing a hermetic connection to the passage of fluid or gas between them, wherein also a connection (33) from the sensor (31) to the means (40) is guided inside the tubular element (32).

9. The device according to claim 1, CHARACTERIZED in that the suction means comprise an auxiliary volume or buffer tank (22) which is arranged in communication with a vacuum pump (23) with a valve (42) to control the passage of air, in which the difference of negative pressure with the external environment is established both in the buffer tank (22) and in the interior volume (11) within the reactor (2) defined over the water level in the reactor (2).

10. The device according to claim 1, CHARACTERIZED in that the means for dispersing the air sample, arranged in the lower portion of the reactor (2), include: a screen (4) arranged so that the air form bubbles when it passes through the same.

11. The device according to claim 10, CHARACTERIZED in that the bubbles formed have a size between 0.5 mm and 1.5 mm, for a permeability filter fabric of 20-80 l_/dm²*min at 20 mm w.c.

12. The device according to claim 1, CHARACTERIZED in that a valve (41) is arranged in the duct (20) to control the passage of air to the reactor (2).

13. The device according to claim 1, CHARACTERIZED in that the means for neutralizing the solution (10) comprise a container (26) for storing the water-soluble alkali compound, a pumping or dosing means (27) and a valve (28) arranged in a duct (29) that connects an outlet in the container (26) with the reactor (2).

14. The device according to claim 1, CHARACTERIZED in that the means for restoring the determined volume of water in the interior of the reactor (2) comprise a lateral outlet (15) for overflow of the reactor (2) with an opening regulated by a valve (25), wherein the position of the lateral outlet (15) establishes the minimum level of water inside the reactor (2).

15. The device according to claims 13 and 14, CHARACTERIZED in that a duct (24) communicates the lateral outlet (15) for overflow with the container (26).

16. The device according to claim 1, CHARACTERIZED in that the means (40), in communication with the sensor (31), are arranged to transmit data of the pH measurements via wired or wireless means (43).

17. The device according to the preceding claims, CHARACTERIZED in that the means (40) are further arranged to process the data of the pH measurements, to determine whether is necessary to provide an alkaline compound to the reactor (2) from the container (26), to generate control signals for the valves (25, 28, 41, 42) and to control the operation of the vacuum pump (23) and the dosing means (27).

18. Method for operating a device for online monitoring of the concentration of acid mist generated in processes of hydrometallurgy using sulfuric acid, to provide useful information for the continuous control of the process environment, wherein the device includes a mixing means, a gas separation means, a sensor (31), and the method is CHARACTERIZED in that it comprises the steps of:

a) mixing a determined volume of water and the sulfuric acid contained in a sample of atmospheric air in the form of acid mist to generate a solution (10), by passing the sample of atmospheric air through an arrangement of communicating vessels that includes an air intake duct (20) and an acid absorption reactor (2), caused by a negative pressure difference with the external environment, established by suction means operatively connected to the mixing means; wherein the passage of the sample of atmospheric air through the determined volume of water is in the form of bubbles, produced in a means for dispersing from a lower portion of the reactor (2);

b) generating a flow of the solution (10) free of bubbles, by entering a flow of the solution (10) to a siphon tube (3) arranged vertically inside the reactor (2), through an upper opening (6) and exiting through a lower hole (7) both located below a water level of the reactor (2) and separated by a distance L, in which the ratio between a diameter DA of the upper opening (6) and a diameter DO of the lower hole (7) allows an ascendant flow of the solution (10) to the outside of the siphon tube (3), as a consequence of the rise of the air bubbles, to induce a descendant flow of the solution (10) into the interior of the siphon tube (3) without generating bubble entrainment;

c) measuring the pH of the flow of the bubble-free solution (10) by means of a sensor (31) in communication with a means (40);

d) recording and transmitting the sensor measurements (31), by the means (40);

wherein when reaching a predefined level of pH inside the reactor (2) the method comprises the steps of:

e) neutralizing the solution (10) by the dosed supply of a water-soluble alkali compound; and

f) restoring the determined volume of water inside the reactor (2).

19. The method according to claim 18, CHARACTERIZED in that in step c) the sensor (31) performs a direct measurement of hydronium ions from the descendant flow into the siphon tube (3).

20. The method according to claim 18, CHARACTERIZED in that in step a) the negative pressure difference necessary to obtain the air sample is established inside an auxiliary volume or buffer tank (22) from which a vacuum pump (23) extracts air that passes through a valve (42) in an open position, while a valve (41) disposed in the duct (20) is kept in the closed position.

21. The method according to claim 20, CHARACTERIZED in that the negative pressure difference with the external environment is also established in an interior volume (11) within the reactor (2) that is in communication with the buffer tank (22) via the conduit (21).

22. The method according to claim 18, CHARACTERIZED in that steps e) and f) are perform every amount predefined by the user of pH measurements associated with step c).

23. The method according to the preceding claims, CHARACTERIZED in that the step e), in order to neutralize the solution (10), includes the opening of a valve (28) and the actuation of a dosing means (27), to introduce an amount of alkali compound from the container (26) in the solution (10) to the interior of the reactor (2) through a duct (29) that connects them.

24. The method according to claim 23, CHARACTERIZED in that it includes maintaining the valves (41) and (42) closed, avoiding the flow of air from the atmosphere during the operation of the means for neutralizing the solution (10).

25. The method according to claim 18, CHARACTERIZED in that step f), in order to restore the determined volume of water within the reactor (2), includes the opening of a valve (25) that regulates the overflow from a lateral outlet (15) in the reactor (2), wherein the position of the lateral outlet (15) establishes the minimum level of water inside the reactor (2).

26. The method according to claims 24 and 25, CHARACTERIZED in that the overflow from the reactor (2) passes through a duct (24) that communicates the lateral outlet (15) with the container (26).

27. The method according to claim 26, CHARACTERIZED in that step e), of neutralizing the solution (10), further includes closing the valve (25) so that the container (26) does not receive overflow from the reactor (2).

28. The method according to claim 26, CHARACTERIZED in that it further comprises step

g) of pH measurement of the water in the reactor (2) after neutralization, performed by the sensor (31).

29. The method according to claim 27, CHARACTERIZED in that it further comprises step

h) , in which the means (40) determine based on the pH measurement of step g) whether an additional supply of alkaline compound to the reactor is necessary (2), and if affirmative, steps e), f), and g) are repeated, defining a cycle directed to achieve a target value of pH in the volume of water in the reactor (2).

30. The method according to the preceding claims, CHARACTERIZED in that steps a) and b) follow each other after the means (40) generate control signals for the opening of the valves (41) and (42) and the closing of the valves (25) and (28), allowing passage of the air sample through the duct (20) that feeds the reactor (2).

31. The method according to claim 18, CHARACTERIZED in that in step d), the sensor measurements (31) recorded by the means (40) are processed to transmit the pH measurement data via wired or wireless means (43).

32. The method according to claim 31, CHARACTERIZED in that, along with the data of the pH measurements, the date and time of the measurement are included, and an identification of the monitoring device.

33. A system of continuous control of the process environment, for online monitoring of the concentration of acid mist generated in processes of hydrometallurgy using sulfuric acid, CHARACTERIZED in that it comprises at least one device in wired or wireless communication with a receiver node, wherein said at least one device comprises:

mixing means operatively connected to atmospheric air suction means, wherein the suction means are arranged to establish a negative pressure difference with the external environment, which causes the passage of a sample of atmospheric air through an arrangement of communicating vessels that includes an air intake duct (20) and an acid absorption reactor (2), wherein the reactor (2) has means for dispersing in a bubble form the sample of atmospheric air in a determined volume of water from a lower portion of the reactor (2), to generate a solution (10) from the determined volume of water and the sulfuric acid contained in the sample of atmospheric air in the form of an acid mist;

gas separation means including a siphon tube (3), arranged vertically inside the reactor (2), wherein the siphon tube (3) has an upper opening (6) and a lower hole (7) both located below a water level of the reactor (2) and separated by a distance L, in which the ratio between a diameter DA of the upper opening (6) and a diameter DO of the lower hole (7) allows an ascendant flow of the solution (10) to the outside of the siphon tube (3), as a consequence of the rise of the air bubbles, to induce a descendant flow of the solution (10) into the siphon tube (3) without generating bubble entrainment;

a sensor (31) for the measurement of pH in the flow of the bubble-free solution (10), which is in communication with a means (40) capable of recording and transmitting the measurements of the sensor (31); and the device including means for neutralizing the solution (10), by a dosed supply of a 5 water-soluble alkaline compound, and means for restoring the determined volume of water within the reactor (2).

34. The system according to claim 33, CHARACTERIZED in that the at least one device is located in a facility in which acid mist is produced, in a place that allows an effective control of the working environment.

WO 2017/051290

PCT/IB2016/055502

1/3

FIG.l

WO 2017/051290

PCT/IB2016/055502

2/3