FR3042423A1 - SYSTEM AND METHOD FOR DIAGNOSING A GASEOUS EFFLUENT FILTRATION DEVICE CONTAINING PCBS - Google Patents

Abstract

System for the diagnosis of a filtration device (2) for gaseous effluents containing polychlorinated biphenyls (PCBs) in gaseous and / or particulate form, comprising an upstream intake pipe (5a) stitched on an inlet pipe (3) of the filtration device, a downstream intake pipe (5b) stitched onto an outlet pipe (4) of the filtration device, a first trapping system (6a) connected to the upstream inlet pipe (5a) and a means gas flow rate regulator (7), a second trap system (6b) connected to the downstream intake pipe (5b) and a gas flow control means (7), the trapping systems (6a, 6b) being capable of trapping the PCBs in a liquid (10) for subsequent analysis, and the gas flow control means (7) being adapted to admit equal volumes of gas through the upstream intake pipe (5a) and by the downstream intake pipe (5b).

Description

System and method for diagnosing a gaseous effluent filtration device containing PCBs. The technical field of the invention is the systems for diagnosing filtration devices, and more particularly the systems for diagnosing gaseous effluent filtration devices containing polychlorinated biphenyls in gaseous and particulate form.

PCBs (Polychlorinated Biphenyls) are stable, non-flammable molecules that have been used for more than 80 years in a variety of industrial applications, primarily as dielectric fluids in electrical transformers and capacitors. They are currently considered major pollutants given their high persistence, potential toxicity, and their impact on health and the environment. In France, the manufacture and use of PCBs has been banned since 1987. In 2003 a national plan called "plan PCB" was established and set as objective the total elimination of PCBs held by all industrialists and national authorities . In 2004, PCBs were included in the Stockholm Convention on Persistent Organic Pollutants (POPs), and have become a global environmental priority. The PCB plan in France provided for the elimination of PCBs in the national territory in highly contaminated matrices until the end of 2010 (containing more than 500 ppm), and by 2022 for the least contaminated (less than 500 ppm). ). The underestimation of stocks and the scarcity of those involved in processing have inexorably lengthened these deadlines.

Decontamination of transformers and capacitors containing PCBs meets stringent environmental discharge standards and implements complex industrial processes limiting the number of companies in the field. Three technologies are used for the decontamination of contaminated devices or matrices: - Draining and baking for "retrofilling" (English term to define the replacement of the oil polluted by an uncontaminated oil) or elimination; - Autoclaving with solvent; - Vacuum autoclaving without solvent.

The processes involving autoclaving require a treatment of the gaseous effluents by a set of condensation and filtration devices, sized to capture the quasi-totality of the PCBs in particulate and gaseous forms; the effectiveness of each device conditioning the overall efficiency of performance and compliance with environmental discharge standards. Currently, the measurement of PCBs in gaseous releases, which requires a 4 to 5 week analysis time, is carried out at the end of the decontamination process at the chimney outlet, for example, which results, in the event of exceeding the standards, questioning of all the unitary filtration operations, the shutdown of the installations and the replacement of all the filters in a curative way without knowing which one is failing. This generates a very significant financial cost with a loss of production due to the shutdown of the facilities. The analysis at the end of the process, which requires a processing time of the order of 5 weeks, therefore does not identify the weakest link in the chain of capture of the pollutant. This compromises any preventive intervention by partially replacing the defective device (s) by limiting costs and avoiding the environmental impact.

There is currently no technique for selective, continuous and real-time analysis of PCBs.

This is due to the extremely low doses to be measured (ppm, ppb), the complexity of PCB molecules with more than 209 congeners, only 12 of which are toxic (DL-PCBs, for Dioxin-like) and the potential presence of other contaminants at least as complex to detect (dioxins, furans ...). This requires a high performance chromatographic analysis, performed by gas chromatography (GC) coupled or not with mass spectrometry, to determine the concentration of total PCBs in the effluents and the proportion of each congener.

In addition, each device for capturing or filtering gaseous effluents must provide a part of the elimination of PCBs, the effectiveness of which is expressed by a percentage of specific abatement. The addition of the abatement percentages of each device must approach the end of the process by 100%. In this case, we reach the conditions of "zero rejection".

Industrialists responsible for PCB removal would like techniques to monitor the performance of potentially contaminated waste gas capture and filtration systems, allowing preventive interventions and reducing costs and accidental or uncontrolled releases in the event of a failure. The invention relates to a system for diagnosing a gaseous effluent filtration device containing polychlorinated biphenyls (PCBs) in gaseous and / or particulate form. The system comprises: an upstream intake pipe stitched onto an inlet pipe of the filtration device, an inlet pipe downstream stitched onto an outlet pipe of the filtration device, a first trapping system connected to the pipe of the filtration device, upstream inlet and a first gas flow control means, a second trapping system connected to the downstream intake pipe and a second gas flow control means, the trapping systems being able to trap the PCBs in a liquid for subsequent analysis, and the gas flow control means being able to take equal volumes of gas through the upstream intake pipe and the downstream intake pipe.

The first and second means for regulating gas flow rates may be identical or different.

The entrapment system may comprise an outer receptacle receiving entrapment fluid, a cannula connected to the intake conduit and inserted into the outer container and the trapping liquid, and a capturing member connected to the flow control means, able to collect the gases admitted by the intake pipe and the cannula.

The entrapment system may comprise solid balls disposed in the entrapment fluid so as to increase the contact time between the gas and the trapping liquid and limit the trapping liquid volume to reach a predefined and optimal level of system filling. trapping.

The solid balls may have diameters of between 1 and 10 mm.

Preferably, the solid balls may have a diameter of 4 mm.

The solid balls may be glass.

The trapping liquid may be chosen from an organic solvent, an aqueous phase, a virgin organic oil or a mineral oil. The invention also relates to a method for diagnosing a gaseous effluent filtration device containing polychlorinated biphenyls (PCBs) in gaseous and / or particulate form. The method comprises the following steps.

Equal quantities of gas are taken upstream and downstream of the filtration device during a predefined measurement period.

The gases taken upstream of the filtration device are bubbled into a first trapping liquid,

The gases taken downstream of the filtration device are bubbled into a second trapping liquid,

The first trapping liquid is analyzed so as to know the amount of PCB passing upstream of the filtration device during the measurement period, and

The second trapping liquid is analyzed so as to know the amount of PCB passing downstream of the filtration device during the measurement period,

The percentage of reduction of the PCB concentration downstream of the filtration device with respect to the concentration of PCB upstream of the filtration device is determined,

It is determined whether the abatement percentage is greater than the predefined threshold,

If this is not the case, it is considered that the filtration device must be changed.

The measurement time can range from a few hours to several days depending on the gas flow rate and the PCB concentration of the gases passing through the filtration device. Other objects, features and advantages of the invention will become apparent on reading the following description, given solely by way of nonlimiting example and with reference to the appended drawings in which: FIG. 1 illustrates the main elements of a diagnostic system for a PCB filtering device; - Figure 2 illustrates the main elements of a system for trapping a diagnostic system; and - Figure 3 illustrates the main steps of a diagnostic process of a diagnostic system. a filtering device for PCBs.

The diagnostic system makes it possible to capture, for their analysis, the gaseous effluents, upstream and downstream of a gas filtration device containing PCBs in gaseous and / or particulate form. The diagnostic system, called FIPMO (Filter Performance Monitoring), requires taps in the gas pipes upstream and downstream of each filter device. These connections allow to deflect an equivalent part of the gas, at the inlet and outlet of each filtration device and are provided by any instrument that allows the regulation and control of gas flow. The fraction of the gases diverted upstream and downstream of the filtration device is then fed separately to trapping systems comprising any solid or liquid product capable of trapping PCBs which can then be easily and quickly analyzed.

Ideally, this trapping system includes a liquid that effectively dissolves PCBs, including a virgin organic oil. The oil is preferred to organic solvents to limit evaporation during use and to ensure the safety of the device and the operators.

In order to achieve measurable concentrations of PCBs, the volume of oil is minimized by the addition of glass beads which allow a homogeneous distribution of gases in the oil and an optimal contact time.

After an optimum "bubbling" time for each capture or filtration device, determined beforehand on a test bench, the oil is recovered and analyzed by gas chromatography to determine on the one hand the concentration of total PCBs and on the other hand the proportion of each congener The percentage of abatement of the PCB concentration downstream of the capture or filtration device must reach the expected performances If there is a significant decrease in the abatement percentage, the monitoring is increased and beyond an alert level, calculated for each capture or filtration device, it will be changed preventively to avoid compromising the performance of downstream devices, and to avoid any exceedance of discharge standards.

FIG. 1 diagrammatically shows a diagnostic system 1 at the terminals of a device 2 for filtering gaseous and particulate effluents containing PCBs.

The filtration device 2 comprises an inlet pipe 3 and an outlet pipe 4. During normal operation of the filtration device 2, the amount of PCBs in the gases flowing in the outlet pipe 4 is practically zero regardless of the amount of PCB in the gases flowing in the inlet pipe 3.

In case of saturation of the capture capacity of the filtration device 2, the amount of PCBs in the gases flowing in the outlet pipe 4 increases gradually over time.

The diagnostic system 1 makes it possible to check the capture efficiency of the filtration device 2 by confirming that PCBs are present in the gases upstream of the filtration device 2, by measuring the amount of PCBs present in the gases downstream of the filtration device 2. filtration device 2, and determining the efficiency of capture PCBs according to these two quantities.

The diagnostic system 1 comprises an upstream intake pipe 5a upstream of the filtration device 2, connected to the inlet of a first trapping system 6a, a downstream intake pipe 5b downstream of the filtration device 2, connected to the inlet of a second trapping system 6b, a first gas flow regulating means 7a connected to the output of the first trapping system by a first pipe 8a and a second regulating means 7b of gas flows connected to the output of the second trapping system 6b by a second pipe 8b. The regulation means 7a, 7b of gas flow rates are connected at the outlet to a venting, possibly via a filtration means, not shown, to prevent accidental release of PCBs during the diagnostic.

The upstream intake pipe 5a is stitched on an inlet pipe 3 of the filtration device 2. Similarly, the downstream intake pipe 5b is stitched onto an outlet pipe 4 of the filtration device 2. In both cases , the pipes are pricked preferably in a sealed manner so as not to expose users to the PCBs.

The gas flow control means 7a, 7b make it possible to regulate, separately or together, the flow rate of the gases taken upstream downstream of the filtration device.

An equal flow rate is preferred in the intake pipes 5a and 5b so that the quantities of PCBs measured can be directly compared. The regulation means 7a, 7b of gas flow rates may be any gas suction means. These include a set of two separate adjustable flow pumps or a pump with two heads separately adjustable.

The trapping systems 6a and 6b are capable of trapping the PCBs in trapping liquid 10 for subsequent analysis.

In Figure 2, it can be seen that a trapping system 6 is a bubbler type system in which the admitted gases are forced to pass through a liquid phase before being collected and discharged from the system.

More specifically, it can be seen that the trapping system 6 comprises three elements, an outer container 9, a cannula 11 and a collection and / or collection element 12.

The outer container 9 comprises a trapping liquid 10 into which is inserted a cannula 11 connected to the intake pipe 5. The cannula 11 makes it possible to force the passage of the gases admitted into the trapping liquid 10. The admitted gases are then collected by the collecting element and / or capturing 12 which, connected to a pipe 8, allows their suction via the gas flow control means 7.

The outer container 9, the cannula 11 and the collection and / or collection element 12 are connected in a sealed manner so that only the flow circuit described above can be borrowed by the admitted gases.

The outer container 9, the cannula 11 and the collecting and / or capturing element 12 may be of metal, plastic or glass. However, glass is preferred in order to provide an inert surface to the admitted gas and the trapping liquid 10 in order to avoid any interaction that may distort the measurement.

The trapping liquid may be any liquid, aqueous or organic capable of solubilizing the molecules to be detected (PCB). Very low volatility liquids, especially oils, are preferred, preferably a mineral oil without additives or contaminants.

The outer container 9 may also comprise solid balls 13 which promote the time of contact of the gas with the liquid and limit the amount of trapping liquid 10 required for a predetermined level of filling of the trapping system 6. Thus, the admitted gases flowing by the cannula 11 see a path at least as long to reach the collection element and / or capture 12 that they would see in a trapping system 6 without full beads 13. However, the amount of liquid in such a trapping system 6 being less than the amount of liquid in a trapping system 6 without full beads 13, the concentration of PCBs in the trapping liquid 10 increases, for the same gas flow, faster than in the trapping liquid 10 a trapping system 6 devoid of solid balls 13.

Like the outer container 9, the cannula 11 and the collection and / or collection element 12, the solid balls 13 may be made of metal, plastic or glass. However, glass is preferred in order to provide an inert surface to the admitted gas and the trapping liquid 10 in order to avoid any interaction which may distort the measurements.

Alternatively, a compact version of the diagnostic system has no control means 7 for gas flow rates. Such a version comprises a common output, connected to the first pipe 8a and the second pipe 8b, intended to be connected to external control means 7 gas flow rates.

In Figure 3, we can see the main steps of an associated diagnostic process.

During a first step 20, equal amounts of gas are taken upstream and downstream of the filtration device 2, during a predefined measuring period. The measurement time can vary from a few hours to several days depending on the sampling rates and concentrations of PCBs to be measured in the effluents.

During a second step 21, the gases taken upstream of the filtration device 2 are bubbled into a first trapping liquid.

During a third step 22, the gases taken downstream of the filtration device 2 are bubbled into a second trapping liquid.

During a fourth step 23, the first trapping liquid is analyzed so as to know the amount of PCB transiting upstream of the filtration device 2 during the measurement period. The analysis may for example be carried out by gas chromatography.

Similarly, during a fifth step 24, the second trapping liquid is analyzed so as to know the amount of PCB passing downstream of the filtration device 2 during the measurement period.

During a sixth step 25, the percentage reduction of the PCB concentration downstream of the filtration device 2 with respect to the PCB concentration upstream of the filtration device 2 is calculated,

During a seventh step 26, it is determined whether the abatement percentage is below the predefined threshold. If this is the case, it is considered that the filtration device must be changed.

Claims (9)

1. A system for diagnosing a device for filtering (2) gaseous effluents containing polychlorinated biphenyls (PCBs) in gaseous and / or particulate form, characterized in that it comprises: an upstream inlet pipe (Sa) piqued on an inlet pipe (3) of the filtration device, a downstream intake pipe (Sb) stitched onto an outlet pipe (4) of the filtration device, a first trapping system (6a) connected to the pipe of an upstream inlet (5a) and a first gas flow control means (7a), a second trapping system (6b) connected to the downstream intake pipe (Sb) and a second flow control means gas (7b), the trapping systems (6a, 6b) being able to trap the PCBs in a liquid (10) for subsequent analysis, and the gas flow control means (7a, 7b) being able to admit volumes gas equalities through the upstream intake duct (Sa) and the duct e downstream intake (Sb). 2. System according to claim 1, wherein a trapping system (6a, 6b) comprises an outer container (9) receiving a trapping liquid (10), a cannula (11) connected to the intake pipe (S). and inserted in the outer container (9) and in the trapping liquid (10), and a collection and / or collection element (12) connected to a regulating means (7a, 7b), capable of collecting the admitted gases through the intake pipe (5) and the cannula (11). 3. System according to claim 2, wherein the trapping system (6a, 6b) comprises solid balls (13) arranged in the trapping liquid (10) so as to limit the trapping liquid volume to reach a predefined level. filling the trapping system (6a, 6b). 4. System according to claim 3, wherein the solid balls (13) have diameters of between 1 and 10 mm. 5. System according to claim 3, wherein the solid balls (13) have diameters of 4 mm. 6. System according to any one of claims 3 to S, wherein the solid balls (13) are made of glass. 7. System according to any one of claims 2 to 6, wherein the trapping liquid (10) is selected from an organic solvent, an aqueous phase, a virgin organic oil or a mineral oil. 8. A method of diagnosis of a filtration device polychlorohniphenyls (PCBs) in gaseous form or particles, characterized in that it comprises the following steps is taken equal amounts of gas upstream and downstream of the filtration device during a predefined measurement period, the gases taken upstream of the filtration device are bubbled into a first trapping liquid. The gases taken downstream of the filtration device are bubbled into a second trapping liquid. the first trapping liquid so as to know the amount of PCB transiting upstream of the filtration device during the duration of the measurement, and the second trapping liquid is analyzed so as to know the amount of PCB passing downstream of the filtration device during the duration of the measurement, the percentage reduction of the PCB concentration downstream of the filt device is calculated ration relative to the concentration of PCB upstream of the filtration device, it is determined whether the percentage of abatement is below a predefined threshold, If this is the case, it is considered that the filtration device must be changed. 9. The method of claim 8, wherein the measurement time is between a few hours and several days depending on the gas sampling rate and the PCB concentration of the gas passing through the filter device.