EP-4740035-A1 - METHOD FOR DETERMINING A FLUX OF AERIAL PARTICULATES AND ASSOCIATE ELECTRONIC DEVICE

Abstract

A method for determining a flux of aerial particulates, the method comprising: - s1) controlling a steerable lidar device (2) so that the lidar device (2) scans a control surface (S), by emitting several laser pulses directed along different emission axis and acquiring corresponding back-scattered optical signals; - s2) processing the back-scattered optical signals to determine, along each emission axis, values of a particulate density and of a colinear wind speed at different distances from the lidar device, - s3) computing a particulates flux through the control surface (S) based on said values of the particulate density and of the colinear wind speed.

Inventors

• CORROCHANO DIAZ, Pablo
• GONZALEZ FERNANDEZ, Beatriz
• PEREZ ORDIERES, Jaime

Assignees

• ArcelorMittal

Dates

Publication Date

20260513

Application Date

20240702

Claims (1)

1. CLAIMS 1. A method for determining a flux ( ^) of aerial particulates, the method comprising: - s1) controlling a steerable lidar device (2) so that the lidar device (2) scans a control surface (S), by emitting several laser pulses directed along different emission axis (X j,k ) and acquiring corresponding back-scattered optical signals; - s2) processing the back-scattered optical signals to determine, along each emission axis, values of a particulate density (PM) and of a colinear wind speed ( ^ m ) at different distances (d i ) from the lidar device (2), - s3) computing a particulates flux ( ^) through the control surface (S) based on said values of the particulate density (PM) and of the colinear wind speed ( ^m). 2. A method according to claim 1 wherein the control surface (S) extends over, or around, or over and around an open-air operation area (Zo), an aerial particulates emission from the open-air operation area (Zo) being determined by computing said flux ( ^). 3. A method according to claim 1 or 2 wherein the control surface (S) and the open-air operation area (Zo) form together a closed or mainly closed surface delineating a volume of air (V) that extends over the open-air operation area (Zo). 4. A method according to claim 2 or 3, wherein the control surface (S) comprises of a top surface (ST) which is horizontal and a lateral surface (SL) which surrounds said area (Zo) and which is vertical. 5. A method according to anyone of the preceding claims, wherein the lidar device is controlled, in step s1, so that at least some of the laser pulses emitted form a set of laser pulses emitted with respective azimuths ( ^1, ^2, ^i) that are different from one another. 6. A method according to claim 5, wherein: - said set of laser pulses is called first set of laser pulses, the laser pulses of the first set being emitted with a same, first elevation (β1), - some others of the laser pulses emitted form a second set of laser pulses that are emitted with a same, second elevation (β2) which is different from the first elevation (β1), the lasers pulses of the second set being emitted with respective azimuths ( ^1, ^2, ^i) that are different from one another. 7. A method according to claim 6, wherein step s3 comprises computing a value of a vertical component (u) of the wind speed ( ^^ ) from at least: a first value ( ^m,1) and a second value ( ^ m,2 ) of the colinear wind speed ( ^ m ), obtained respectively for the first elevation (β1) and for the second elevation (β2). 8. A method according to claim 7, wherein the value of the vertical component (u) of the wind speed ( ^^ ) is computed by dividing: - the difference between the second value ( ^m,2) and the first value ( ^m,1) of the colinear wind speed ( ^m), - by the difference between the second elevation (β 2 ) and the first elevation (β 1 ). 9. A method according to claims 4 and 7, or according to claims 4 and 8, wherein step s3 comprises computing a top particulate flux, which is a flux through the top surface (S T ) of the control surface (S), the top particulate flux being computed from said values of the particulate density (PM), and from values of the vertical component (u) of the wind speed ( ^^ ) determined according to the method of claim 7 or 8. 10. A method according to any of claims 5 to 9, wherein step s3 comprises computing an amplitude (v) and/or a direction of a horizontal component ( ^^ ) of the wind speed ( ^^ ), from two or more values of the colinear wind speed ( ^ m ) obtained respectively for two or more of said azimuths ( ^1, ^2). 11. A method according to claims 4 and 10, wherein step s3 comprises computing a lateral particulate flux, which is a flux through the lateral surface (SL) of the control surface (S), the lateral particulate flux being computed from said values of particulate density (PM) and from values of the amplitude (v) and/or of the direction of the horizontal component ( ^^ ) of the wind speed ( ^^ ) determined according to the method of claim 8. 12. A method according to any one of the preceding claims wherein step s3 comprises the following steps: - building numerically a grid (G) comprising of cells (Ci,j,k) centered on the different emission axis (Xj,k) and located at the different distances (di) from the lidar device (2), - identifying frontier cells (Co,l), which are the cells (Ci,j,k) of the grid (G) that intersect the control surface (S), - computing an elemental flux ( ^l) for each frontier cell (Co,l), the elemental flux being a particulate flux through a portion (A) of control surface (S) intersected by the frontier cell considered, - computing the particulate flux ( ^) through the control surface (S) by summing the elemental particulate fluxes ( ^ l ) together. 13. Method according to claims 4 and 12 wherein, for the frontier cells (Co,l) intersecting the lateral surface (S L ), each elemental flux, noted ^ l , is computed according to equation eqn 1 below: ^^ ^^ = ^^ ^^ ^^ . ^^. ^^ ^^ . cos( ^^ ^^ ) ( ^^ ^^ ^^ 1) Where: - PM l is the value of the particulate density in the frontier cell (C o,l ) considered, - A is the area of the portion of the lateral surface (S L ) that is intersected by the frontier cell (C o,l ) considered, - v l is the amplitude of the horizontal component of the wind speed at the frontier cell (C o,l ) considered, - ^l is the angle between: a vector ( ^^ ) perpendicular to the lateral surface (SL) at the frontier cell (C o,l ) considered, and the horizontal component ( ^^ ) of the wind speed ( ^^ ). 14. A method according to anyone of the preceding claims, further comprising a preliminary calibration step which comprises: - Controlling the lidar device (2) to acquire a calibration back-scattered optical signal, for a given fixed emission axis passing at a fixed measurement position, several times successively at different instants, and acquiring jointly values of the particulate density, at said position, measured by a particulate sensor, - Processing each calibration back-scattered optical signal, to determine a value of a back-scattered coefficient βopt, at said measurement position, - Temporally aligning the set of values of βopt at said instants, with the set of values of the particulate density measured by the particulate sensor, - Determining a numerical relationship relating βopt to the particulate density, by correlating the set of values of βopt and the set of values of the particulate density. 15. A method according to anyone of the preceding claims, wherein the open-air operation area (Zo) includes or is part of an industrial facility (1). 16. A method according to anyone of the preceding claims, wherein the open-air operation area (Zo) encompasses a mineral yard (3) or an open pit mine. 17. Electronic device (10) configured to execute the following steps: - s1) controlling a steerable lidar device (2) so that the lidar device (2) scans a control surface (S), by emitting several laser pulses directed along different emission axis (X j,k ) and acquiring corresponding back-scattered optical signals; - s2’) receiving, from the lidar device: o values, along each emission axis, of a particulate density (PM) and of a colinear wind speed ( ^m) at different distances (di) from the lidar device (2), determined by the lidar device from said back-scattered optical signals; or o data, comprising the back-scattered optical signals or derived from the back-scattered optical signals, suitable to determine values of the particulate density (PM) and of the colinear wind speed ( ^m), along each emission axis, at different distances (di) from the lidar device (2), - s3) computing a particulate flux ( ^) through the control surface (S) based on said values of the particulate density (PM) and of the colinear wind speed ( ^ m ). 18. System (4) comprising a steerable lidar device (2) and a processing device (10), configured to execute the following steps: s10) scanning, by the steerable lidar device (2), a control surface (S), by emitting several laser pulses directed along different emission axis (Xj,k) and acquiring corresponding back-scattered optical signals; s2) processing the back-scattered optical signals, by the processing device (10) and/or the steerable lidar device (2), to determine, along each emission axis, values of a particulate density (PM) and of a colinear wind speed ( ^ m ) at different distances (d i ) from the lidar device (2), s3) computing a particulates flux ( ^) through the control surface (S) based on said values of the particulate density (PM) and of the colinear wind speed ( ^m). 19. Computer program comprising instructions, whose execution on a computer device (10) connected to a steerable lidar device (2) makes the computer device to execute the following steps: - s1) controlling the steerable lidar device (2) so that the lidar device (2) scans a control surface (S), by emitting several laser pulses directed along different emission axis (X j,k ) and acquiring corresponding back-scattered optical signals; - s2’) receiving, from the lidar device: o values, along each emission axis, of a particulate density (PM) and of a colinear wind speed ( ^m) at different distances (di) from the lidar device (2), determined by the lidar device from said back-scattered optical signals; or o data, comprising the back-scattered optical signals or derived from the back-scattered optical signals, suitable to determine values of the particulate density (PM) and of the colinear wind speed ( ^m) along each emission axis, at different distances (d i ) from the lidar device (2), - s3) computing a particulate flux ( ^) through the control surface (S) based on said values of the particulate density (PM) and of the colinear wind speed ( ^ m ).

Description

Method for determining a flux of aerial particulates and associate electronic device [001] The technical field is that of measuring and monitoring atmospheric aerosol particles emissions. Technical background [002] Monitoring aerial particulates emissions from an operation area, such as an agricultural or an industrial area, is very useful for air-quality monitoring and/or to monitor processes taking place in such an area. [003] Video monitoring with automatic image analysis is sometime employed to monitor industrial chimney exhaust plumes. But this technique is limited to such localised, buoyant sources, and generally does not provide a quantitative estimation of the mass of particulates emitted. [004] Lidar scans have also been used to provide maps of particulate density over an open- air operation area, to image the quantity of particulates present in air, above that area. Though useful, such maps provide no information, or at least very indirect information regarding a quantity of particulates emitted by that area, that is regarding the emissions themselves. Summary of the invention [005] In this context, a method for determining a flux of aerial according to claim 1, is provided. [006] Basing this particulate flux determination upon wind speed values, that are derived from the lidar acquisitions, enables an accurate estimation of this flux. Indeed, wind direction and speed typically varies with time, and also possibly from one point to the other, above an open- air operation area, and so, it is beneficial to use concomitant, and co-localised measurements of the particulate density and of the wind speed (or of a component thereof), at different positions on the control surface. In particular, using local measurements of the wind speed, rather than a single-point or an average wind measurement, carried on with a cup anemometer or the like, is favourable in terms of accuracy. [007] [008] Still, it is noted that computing a flux through a control surface, from data obtained during a lidar scan, is not immediate. Indeed, a back-scattered optical signal acquired by a lidar enables to determine values of the colinear wind speed ^m, but not directly values of the amplitude or of the direction of the wind speed itself, ^^ , which are however necessary to compute a through-surface flux of particulates carried away by air movements. The colinear wind speed in question, ^m, is the component of the wind speed ^^ parallel to the axis of emission of the laser pulse emitted by the lidar. It is sometimes called “radial wind speed” in the technical field of lidars.The control surface in question may extend over, or around, or over and around an open-air operation area. An aerial particulates emission from this open-air operation area can then be determined by computing said flux. [009] The control surface and the open-air operation area may in particular form together a closed or mainly closed surface (in other words, the control surface may enclose the open-air operation area). This closed or mainly closed surface delineates a volume of air that extends over the open-air operation area (volume of air which is scanned by the lidar, when it scans said control surface). [0010] When the control surface encloses the open-air area, somehow covers up that area (i.e.: the open-air area, together with the control surface, forms a closed surface), it is necessary, for some parts of the control surface, to know the value of the vertical component of the wind speed in order to compute the particulate flux in question. And determining the vertical component of the wind speed in many different points, from lidar scans, required specific developments, as explained in the detailed description. [0011] The method according to the invention may comprise one or several additional features, defined in claims 2 to 16, considered alone or in combination. [0012] The invention also concerns an electronic device, to be connected to a lidar device or integrated therein, as defined by claim 17. The electronic device has for instance the structure of a computer. The additional features of claims 2 to 14, presented in terms of method, may also apply to this electronic device. [0013] The invention also concerns a system comprising a steerable lidar device and a processing device, as defined by claim 18. [0014] The invention also concerns a computer program, as defined by claim 17. The additional features of claims 2 to 14, presented in terms of method, may also apply to this computer program. [0015] In this document, the lidar device (which stand for “LIght Detection And Ranging” device) is called indifferently “lidar device” or “lidar”. Detailed description [0016] The invention will now be described in more detail and illustrated by examples without introducing limitations, with reference to the appended figures. [0017] Figure 1 is a top view of tan area monitored using the instant method. [0018] Figure 2 represents schematically this area, in pe