WO2012069963A1 - Capteur pour évaluer la pollution de l'air - Google Patents

Capteur pour évaluer la pollution de l'air Download PDF

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Publication number
WO2012069963A1
WO2012069963A1 PCT/IB2011/055120 IB2011055120W WO2012069963A1 WO 2012069963 A1 WO2012069963 A1 WO 2012069963A1 IB 2011055120 W IB2011055120 W IB 2011055120W WO 2012069963 A1 WO2012069963 A1 WO 2012069963A1
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WO
WIPO (PCT)
Prior art keywords
sensor
conduit
air
unit
electrode
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PCT/IB2011/055120
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English (en)
Inventor
Johan Marra
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Koninklijke Philips Electronics N.V.
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Application filed by Koninklijke Philips Electronics N.V. filed Critical Koninklijke Philips Electronics N.V.
Publication of WO2012069963A1 publication Critical patent/WO2012069963A1/fr

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/62—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode
    • G01N27/64—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode using wave or particle radiation to ionise a gas, e.g. in an ionisation chamber
    • G01N27/66—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode using wave or particle radiation to ionise a gas, e.g. in an ionisation chamber and measuring current or voltage
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C3/00—Separating dispersed particles from gases or vapour, e.g. air, by electrostatic effect
    • B03C3/017—Combinations of electrostatic separation with other processes, not otherwise provided for
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C3/00—Separating dispersed particles from gases or vapour, e.g. air, by electrostatic effect
    • B03C3/02—Plant or installations having external electricity supply
    • B03C3/04—Plant or installations having external electricity supply dry type
    • B03C3/08—Plant or installations having external electricity supply dry type characterised by presence of stationary flat electrodes arranged with their flat surfaces parallel to the gas stream
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C3/00—Separating dispersed particles from gases or vapour, e.g. air, by electrostatic effect
    • B03C3/02—Plant or installations having external electricity supply
    • B03C3/04—Plant or installations having external electricity supply dry type
    • B03C3/12—Plant or installations having external electricity supply dry type characterised by separation of ionising and collecting stations
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C3/00—Separating dispersed particles from gases or vapour, e.g. air, by electrostatic effect
    • B03C3/34—Constructional details or accessories or operation thereof
    • B03C3/36—Controlling flow of gases or vapour
    • B03C3/368—Controlling flow of gases or vapour by other than static mechanical means, e.g. internal ventilator or recycler
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C3/00—Separating dispersed particles from gases or vapour, e.g. air, by electrostatic effect
    • B03C3/34—Constructional details or accessories or operation thereof
    • B03C3/38—Particle charging or ionising stations, e.g. using electric discharge, radioactive radiation or flames
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C3/00—Separating dispersed particles from gases or vapour, e.g. air, by electrostatic effect
    • B03C3/34—Constructional details or accessories or operation thereof
    • B03C3/40—Electrode constructions
    • B03C3/41—Ionising-electrodes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C3/00—Separating dispersed particles from gases or vapour, e.g. air, by electrostatic effect
    • B03C3/34—Constructional details or accessories or operation thereof
    • B03C3/40—Electrode constructions
    • B03C3/45—Collecting-electrodes
    • B03C3/47—Collecting-electrodes flat, e.g. plates, discs, gratings
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
    • G01N15/06—Investigating concentration of particle suspensions
    • G01N15/0656—Investigating concentration of particle suspensions using electric, e.g. electrostatic methods or magnetic methods
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N1/00—Sampling; Preparing specimens for investigation
    • G01N1/02—Devices for withdrawing samples
    • G01N1/22—Devices for withdrawing samples in the gaseous state
    • G01N1/2273—Atmospheric sampling

Definitions

  • the present invention relates to a sensor for assessing air pollution. More specifically, the present invention relates to a sensor comprising a volatile organic compound (VOC) sensing section for sensing airborne VOCs and an ultrafme particle (UFP) sensing section for sensing airborne UFPs.
  • VOC volatile organic compound
  • UFP ultrafme particle
  • Health- hazardous air pollutants comprise airborne particles, sized between 10 nm and 10 ⁇ , and a broad range of gases comprising mostly inorganic combustion-related gases (CO, NO x , S0 2 ) and many other volatile organic compound (VOC) gases, together usually referred to in terms of the total volatile organic compound (TVOC) concentration.
  • CO, NO x , S0 2 inorganic combustion-related gases
  • VOC volatile organic compound
  • TVOC total volatile organic compound
  • the sources of particulate and gaseous pollutants may be found outdoors and indoors.
  • outdoor sources of particulate and gaseous pollutants comprise automobile traffic, industrial emissions and heating installations for buildings.
  • Most outdoor combustion sources are easily recognized through their emission of ultrafme particles (UFPs) with a size between about 10 nm and 300 nm.
  • UFPs ultrafme particles
  • outdoor combustion sources give often rise to the emission of variable amounts of gases like CO, NO x , and S0 2 .
  • outdoor VOC sources are relatively less common and are generally not associated with combustion or heating processes.
  • indoor air pollution is of particular importance because most exposure occurs indoors.
  • Indoor spaces comprise homes, buildings, work places, and car cabins.
  • Common indoor sources of air pollution also comprise processes and human activities that involve combustion or heating such as, e.g., cooking, smoking, candle burning and ironing. Again, these sources are readily recognized through their emission of UFPs. Examples of indoor sources of air pollution that do not involve combustion may be paints, building materials, decoration materials, hobby activities, deodorant spraying, cleaning, cosmetics, animals, and humans themselves, wherein few of these sources betray themselves trough the emission of UFPs but almost all of them emit VOCs, which may or may not be odorous.
  • a sensor for assessing air pollution comprises a volatile organic compound (VOC) sensing section and an ultrafine particle (UFP) sensing section.
  • VOC sensing section includes an ionizing unit for ionizing at least part of airborne VOCs in air passing through a first conduit.
  • the VOC sensing section further includes a first electrode arranged, in the first conduit, downstream of the ionizing unit. The first electrode is arranged in proximity to a second electrode on which a bias voltage is applicable for enabling precipitation of at least part of the ionized airborne VOCs on the first electrode.
  • the UFP sensing section includes a charging unit for charging at least part of airborne particles in air passing through a second conduit.
  • the UFP sensing section further includes a capturing element arranged, in the second conduit, downstream of the charging unit.
  • the capturing element is capable of capturing charged airborne particles.
  • the sensor comprises an evaluation unit being connected to both the first electrode and the capturing element for obtaining a signal representative of the air pollution.
  • the present invention is based on an understanding that a VOC sensing section and a UFP sensing section may be integrated on a single sensing technology platform and share a common evaluation unit for obtaining a signal representative of the air pollution. Indeed, as such, the presence of gaseous VOCs in air is rather unrelated to the presence of UFPs or larger particles in air. Further, their presence is generally not related to the indoor C0 2 concentration. Thus, UFPs and VOCs correspond to different classes of air pollutants and information about the UFP concentration level is therefore complementary to information about the VOC concentration level.
  • the present invention is therefore advantageous in that it provides an integrated sensor capable of sensing both the UFP concentration and the TVOC (the total volatile organic compound/hydrocarbon)
  • the signal obtained by the evaluation unit is preferably an electrical signal such as an electrical current representative of, for the UFP sensing section, the amount of particles captured per unit time at (i.e. in or on) the capturing element and, for the VOC sensing section, the amount of ionized airborne VOCs precipitated per unit time on the first electrode.
  • the sensor of the present invention is therefore capable of providing a signal indicative of either one of the concentration level of UFPs in the air passing through the second conduit and the concentration level of VOCs in the air passing through the first conduit.
  • the sensor has the dual capability of measuring, on the one hand, the VOC concentration level and, on the other hand, the UFP concentration level.
  • the sensor of the present invention is capable of quantifying the ambient air pollution with respect to both UFPs and VOC gases (TVOC). Such a sensor provides therefore a more detailed insight in the overall state of the ambient air pollution when compared to the situation wherein only a single UFP sensor or a single VOC sensor is present.
  • the senor may alternatively (or sequentially) activate the VOC sensing section and the UFP sensing section in order to separately monitor the VOC concentration and the UFP concentration, respectively.
  • the present invention is also advantageous in that it provides for an integration of a TVOC gas sensor into an existing (electrical) UFP sensor platform with which the concentration levels of UFPs and the TVOC can be separately measured.
  • existing UFP sensors may be upgraded with a VOC sensing section such that, in addition to the concentration of UFPs, the concentration level of TVOC can also be measured.
  • the present invention is also advantageous in that the integration of a VOC sensing section and a UFP sensing section into a single sensor with a shared evaluation unit is less expensive, less voluminous and more convenient for the user than the use of a plurality of individual sensors, as done in the prior art.
  • the present invention is advantageous in that the first electrode is arranged downstream of the ionizing unit in the first conduit, thereby providing a more robust and reliable measurement of the VOC concentration via the evaluation unit since the first electrode itself can be positioned at a "safe" distance away from the ionizing unit.
  • the first electrode can be shielded from direct exposure to the ionizing effect of the ionizing unit, thereby remaining largely insensitive to the ionizing effect of the ionizing unit, while still having exposure to ionized VOC in the air passing through the first conduit.
  • the first electrode may be shielded from direct exposure to the radiation emitted from a source of ionization, the radiation being of sufficiently high energy to induce photo -ionization of airborne VOCs.
  • the present invention is advantageous in that it provides a more reliable sensor for the quantitative indoor measurement of the concentration of volatile organic compounds (the TVOC concentration), such as hydrocarbon gases, which is often independent of the indoor UFP concentration.
  • the TVOC concentration volatile organic compounds
  • the ionizing unit and/or the charging unit may be configured to be intermittently activated, which is advantageous in that the respective lifetimes of the ionizing unit and/or the charging unit may be further increased.
  • the present embodiment by periodically activating the ionizing unit and the charging unit during predetermined time intervals, any build-up of contaminants within the ionizing unit (e.g. on an optical window of a radiation source) and/or within the charging unit is retarded.
  • the senor may be configured to simultaneously activate the ionizing unit and deactivate the charging unit for obtaining a (current) signal indicative of the TVOC concentration in the air passing through the first conduit, and to simultaneously deactivate the ionizing unit and activate the charging unit for obtaining a (current) signal indicative of the UFP concentration in the air passing through the second conduit.
  • the sensor may alternatively (or sequentially) infer the TVOC concentration and the UFP concentration from the corresponding signals obtained by the evaluation unit.
  • the sensor may comprise a UFP charging unit comprising a high- voltage corona electrode, a VOC ionizing unit comprising a photo -ionization (PI) lamp, and a shared evaluation unit comprising a current meter.
  • the shared evaluation unit may then serially measure (in time) at least part of the particle-bound charge in air passing through the second conduit of the UFP sensing section (PI lamp “off, corona electrode “on”) and at least part of the charge associated with ionized gases in air passing through the first conduit of the VOC sensing section (PI lamp “on”, corona electrode "off) with the current meter.
  • the capturing element may be a particle filter arranged inside a Faraday cage, the first electrode being electrically connected to the Faraday cage, the (current meter in the) evaluation unit being connected to the Faraday cage for producing a signal representative of the air pollution.
  • the capturing element may comprise a set of
  • (substantially parallel) electrodes comprising a precipitation electrode and a counter electrode.
  • the counter electrode is supplied with a voltage for creating an electric field between the counter electrode and the precipitation electrode which enables the precipitation of at least part of the charged particles from the air passing through the second conduit onto the precipitation electrode.
  • the precipitation electrode is electrically connected to the first electrode, and the evaluation unit is connected to the precipitation electrode for obtaining a signal representative of the air pollution.
  • At least part of an inner wall of the first conduit may form the second electrode, which is a convenient way of implementing the present invention.
  • the first conduit may then preferably be made of an electrically-conductive material, such as metal, so that a bias voltage can be applied on it.
  • the ionizing unit may comprise a radiation source arranged to irradiate the air passing through the first conduit for inducing photo- ionization of airborne VOCs.
  • the present embodiment is advantageous in that the degree of photo -ionization may be controlled by regulating the intensity level of the radiation provided by the radiation source.
  • the first electrode is arranged downstream of the radiation source and substantially shielded from direct exposure to the emitted radiation, photo- emission of electrons from the first electrode is avoided, or at least reduced, thereby nullifying or at least reducing the contribution of electron emission to the measured current signal, which provides a more reliable sensor.
  • the senor may further comprise a photo- detector facing the radiation source for measuring the intensity of emitted radiation from the radiation source, thereby enabling feedback-control of the radiation source with regard to its emitted radiation intensity.
  • the photo-detector may be a ultra-violet (UV) sensor for measuring the UV intensity emitted from the radiation source (even if the radiation source itself is not dedicated to UV emission only).
  • UV ultra-violet
  • the present embodiment is advantageous in that, via a feedback loop, the driving voltage of the radiation source may be adjusted such that a constant radiation emission (e.g. UV emission) is obtained in the course of time, thereby enabling compensation for possible aging effects affecting the emission from the radiation source.
  • the ionizing unit may be arranged in a recess of the first conduit, which is advantageous in that the ionizing unit is then protected from direct exposure to the air passing through the conduit (also referred to as the "airflow" in the following).
  • the ionizing unit comprises a radiation source equipped with an optical window through which radiation irradiates the air passing through the first conduit
  • the optical window inside the recess is largely protected from the deposition of polymeric organic substances, gases, ions and particles from the airflow.
  • the arrangement of the ionizing unit in the recess also allows for a build-up of an elevated ozone gas concentration directly adjacent to the optical window which helps to continuously clean the optical window through oxidation.
  • the ionizing unit is then less subject to contamination and maintenance of the sensor is less often required. Further, the lifetime of the ionizing unit, and thereby the sensor, is increased.
  • the senor may further comprise an air filter arranged upstream of the ionizing unit for removing particulate material from the air passing through the first conduit, which is advantageous in that all air passing the ionizing unit is ensured to first pass a particle filter which removes at least a substantial part of the particulate material from the airflow.
  • the air filter may be arranged to filter VOCs of a certain molecular weight, for instance of lower molecular weight (i.e. below a predetermined molecular weight threshold), thereby providing a sensor sensitive to only VOCs of a somewhat higher molecular weight (i.e. above the predetermined molecular weight threshold) which are the most health-hazardous species.
  • the senor may further comprise at least one of a temperature sensor, a relative humidity sensor and a C0 2 sensor, which is for instance advantageous in that it provides additional air quality parameters that may be of interest for feedback control in, e.g., air handling units.
  • information about temperature and relative humidity may be used for the correct interpretation of the electrical current signal obtained from the current meter in the evaluation unit in terms of the concentration levels of UFPs and/or TVOC in air.
  • the output of the temperature and relative humidity sensors may be used to account and compensate for any loss of radiation intensity from the radiation source comprised in the ionizing unit due to radiation absorption by moisture in the air.
  • Such a loss is generally related to the absolute humidity (AH) and could be accounted for through an arithmetic exponential factor (via the Lambert-Beer law).
  • the absolute humidity can be derived when the relative humidity and the temperature are known. Correcting for such a loss enables for a correction of the proportionality factor between the measured current signal from the current meter and the inferred TVOC concentration in the air so that the inferred TVOC concentration level becomes independent of the humidity concentration in the air.
  • the senor may further comprise at least one air displacement unit (such as a ventilator, a ventilation arrangement, a fan, or a pump), configured to provide (draw) a first airflow through the first conduit (of the VOC sensing section) and a second airflow through the second conduit (of the UFP sensing section).
  • at least one air displacement unit such as a ventilator, a ventilation arrangement, a fan, or a pump
  • the magnitude and sign of the bias voltage may be selected such that the value of the obtained (current) signal is substantially nullified or minimized when air that is substantially free of VOCs is passed through the first conduit.
  • a zero-VOC concentration can be obtained by passing the air through an activated carbon filter located upstream of the first conduit.
  • the selected bias voltage is chosen such as to compensate for the influence on the measurement signal (normally a measured electrical current) of any other charged species (other than photo-ionized VOCs) in the airflow such as photo-emitted electrons or ions emitted from surfaces directly or indirectly irradiated by the radiation source.
  • the bias voltage furthermore serves to create the electric field between the first electrode and the second electrode that enables the precipitation of at least part of the ionized VOCs from air onto the first electrode.
  • the present embodiment is advantageous in that the chosen bias voltage provides for a more reliable zero signal value for the VOC sensing section of the sensor.
  • the bias voltage obtained according to this procedure only needs to be established during the first sensor calibration immediately after sensor manufacture and requires re- calibration only during infrequently applied periodic sensor servicing.
  • the present embodiment is particularly advantageous over prior art sensors in which frequent separate calibrations with substantially VOC-free air and with air having a specific known VOC concentration are normally required due to the presence of a non-optimized bias voltage, aging of the lamp, internal contamination, and spurious signal drifts.
  • the present embodiment can easily account and correct for a possible electronic offset current through an additional internal calibration procedure that involves the zeroing of the airflow through the first conduit (i.e. blocking the airflow), e.g. by switching-off the air displacement unit (such as a ventilator).
  • a zero airflow through the first conduit effectively stops the transport of charged airborne species to the sensing electrode, also when VOCs are present in the air, hence any remaining measured current signal will then be an electronic offset current which can subsequently be compensated for internally by the evaluation unit.
  • the existence of an electronic offset current is independent of the chosen value for the bias voltage and the VOC concentration in the air. This internal compensation calibration for an electronic offset current is therefore independent of the first calibration for establishing an optimized value for the bias voltage on the second electrode.
  • the correction for an internal electronic offset current at any arbitrary VOC concentration may be carried out automatically at any frequency and may involve the de-activation of the air displacement unit (such as a ventilator) and the simultaneous measurement of the remaining current signal, which then corresponds to the internal offset current signal for which a correction can be made.
  • Free air convection through the first conduit during the de-activation of the air displacement unit (such as a ventilator) may be avoided (or at least very significantly reduced) due to the presence of a fibrous particle filter at the entrance of the first conduit and inside the Faraday cage, thereby blocking free airflow.
  • the measured net current signal that is corrected for the internal electronic offset current corresponds to the zero signal level.
  • the same zero signal level is obtained in substantially VOC-free air when the second electrode is supplied with the aforementioned improved (and preferably optimized) bias voltage.
  • the senor may be configured to periodically deactivate the air displacement unit (such as a ventilator) for resetting the obtained signal to zero under conditions of zero airflows through the first conduit and the second conduit.
  • the air displacement unit such as a ventilator
  • an air handling unit comprising a sensor as defined in any one of the preceding embodiments and a control unit configured to control the air handling unit as a function of a VOC concentration and/or a UFP concentration obtainable by the sensor.
  • minimization or reduction of indoor exposure to air pollutants occurs mostly through ventilation with outdoor air.
  • Air ventilation in buildings is usually carried out by means of mechanical air handling units which take care of air transport, heating, cooling, and air cleaning requirements. Higher ventilation levels normally incur higher expenditures of energy. To reduce (and preferably minimize) the energy demand while maintaining the indoor air quality at an optimum level (thereby safeguarding human health, well-being, and productivity), active feedback to air handling units is desirable.
  • Feedback information advantageously comprises information about air quality parameters such as the temperature, the relative humidity, the C0 2 concentration, and the local indoor air pollution level by UFPs and VOCs.
  • such feedback may be provided by the sensor of the present invention.
  • the feedback may be useful for enabling demand-controlled ventilation, demand-controlled air cleaning, and demand-controlled air heating/cooling.
  • the air handling unit may for example be an air ventilation unit, an air cleaning unit, a heating or cooling unit or even an automatically- controlled air ventilation unit.
  • Fig. 1 is a schematic illustration of a sensor in accordance with a first embodiment of the present invention.
  • Fig. 2 is a schematic illustration of a sensor in accordance with a second embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS
  • Fig. 1 is a schematic illustration of a sensor 1 comprising a first sensing section 100 for sensing airborne VOCs and a second sensing section 200 for sensing airborne UFPs.
  • the first sensing section 100 comprises an ionizing unit 120 for ionizing at least part of airborne VOCs in the air passing through a first conduit 110.
  • the first conduit 110 may comprise an air inlet 112 for receiving air and an air outlet 114 for releasing air from the inside of the first conduit 110.
  • the VOC sensing section 100 further includes a first electrode 130 arranged, in the first conduit 110, downstream of the ionizing unit 120.
  • the first electrode 130 is also arranged in proximity to a second electrode 140 onto which a bias voltage "VpiD prec" is applicable for enabling precipitation of at least part of the ionized airborne VOCs from air on the first electrode 130.
  • the second sensing section 200 hereinafter referred to as UFP sensing section
  • the 200 includes a charging unit 220 for charging at least part of airborne particles in the air passing through a second conduit 210.
  • the second conduit 210 may comprise an air inlet 212 for receiving air and an air outlet 214 for releasing air from the inside of the second conduit 210.
  • the air outlet 114 of the first conduit 110 corresponds with the air outlet 214 of the second conduit 210.
  • the UFP sensing section 200 further includes a capturing element 230 arranged, in the second conduit 210, downstream of the charging unit 220 and capable of capturing charged airborne particles.
  • the sensor 1 further comprises an evaluation unit 300 including an electrical current meter 160 being connected to both the first electrode 130 and the capturing element 230 for obtaining a signal representative of the air pollution.
  • the evaluation unit 300 may for instance also comprise processing means (not shown) for processing the signal obtained by the current meter 160.
  • the ionizing unit 120 may be a photo -ionization radiation source (or PI lamp) 122 capable of emitting radiation that is sufficiently energetic to ionize at least part of the airborne VOCs in the air passing through the first conduit 110.
  • the radiation source 122 may be equipped with an optical window 126 arranged to enable the irradiation of the airflow passing by the optical window 126 of the radiation source 122 through the first conduit 110.
  • the PI lamp 122 may for example be a 10.6 eV Krypton gas-filled radiation source that can be excited or powered by means of either internal or external electrodes 124 (e.g.
  • the optical window 126 of the PI lamp 122 may for example be a MgF 2 optical window.
  • the PI lamp 122 may be controlled by the application of a high- frequency (100 kHz) voltage V PID lamp between two external electrodes 124 around the PI lamp 122.
  • a 10.6 eV lamp is used, at least part of those airborne VOCs that have an ionization potential less than 10.6 eV can be ionized, which normally corresponds to VOCs with a molecular mass larger than about 40 to 50 dalton.
  • the airborne charged gaseous species can be at least partly precipitated from the airflow onto the first electrode 130 by means of an externally-applied electric field.
  • the electric field corresponds to the field generated between the first (sensing) electrode 130 and the second electrode 140 arranged in proximity to the first electrode 130.
  • an inner wall of the first conduit 110 may form the second electrode 140, such as illustrated in Fig. 1.
  • the first (sensing) electrode 130 is in electrical contact with a Faraday cage 240 which itself is connected to the evaluation unit 300 comprising the electrical current meter 160.
  • the first electrode 130 may be directly connected to the (current meter of the) evaluation unit 300.
  • the sensor 1 may further comprise an air displacement unit such as a ventilator 400 or pump arranged to provide or draw a first airflow through the UFP sensing section, i.e. through the second conduit 210, and a second airflow through the TVOC sensing section, i.e. through the first conduit 110.
  • the charging unit 200 Referring now in particular to the UFP sensing section 200, the charging unit
  • the charging unit 220 comprises a corona electrode 222 set at a potential V cor which is sufficiently high to locally ionize the air, thereby emitting ions.
  • the corona electrode 222 is surrounded by a porous screen electrode 221 set at a much lower potential V scr . Ions transmitted through the porous screen electrode 221 enable the electrical diffusion charging of particles in the air passing through the annulus between the screen electrode 221 and the inner wall of the second conduit 210.
  • the charging unit 220 is located downstream of the capturing element 230, which is embodied as a Faraday cage 240 comprising a particle filter for capturing the charged airborne particles.
  • the Faraday cage is connected to the evaluation unit 300 comprising the sensitive current meter 160 which is capable of measuring the amount of precipitated charge per unit time on the first electrode 130 and/or the amount of captured charged particles per unit time in the filter of the Faraday cage 240 as an electrical current I sensor-
  • the particle capturing element 230 is embodied as a set of substantially parallel electrodes comprising a counter electrode 232, to which a voltage V pa rt prec is applied, and a precipitation electrode 234 whereupon at least part of the charged particles precipitate from the air passing through the second conduit 210 under the influence of the electric field between the counter electrode 232 and the precipitation electrode 234.
  • the precipitation electrode 234 is connected to the evaluation unit 300 comprising the sensitive current meter 160 which is capable of measuring the amount of precipitated charges per unit time on the first electrode 130 and/or the amount of precipitated charged particles per unit time on the precipitation electrode 234 as an electrical current I sen sor.
  • the sensor 2 depicted in Figure 2 is identical to the sensor 1 described with reference to Figure 1 except for the realization of the capturing unit 230.
  • the electrical current I sen sor corresponds to the signal of the sensor 1.
  • the magnitude of the signal I sen sor reflects the TVOC pollution level in the air when the ionizing unit 120 (i.e. the PI lamp 122 used to ionize the airborne VOCs) is "on” and the charging unit 220 (i.e. the corona electrode 222 used to charge airborne particles) is "off.
  • the magnitude of the signal reflects the UFP pollution level in the air when the PI lamp 122 is "off and the corona electrode 222 used to charge airborne particles is "on”. In the latter situation, the particle filter in the Faraday cage in Fig. 1 or the precipitation electrode in Fig.
  • the sensors 1 and 2 captures charged UFPs from air and the captured amount of particle charges per unit time is recorded as the signal I sen sor.
  • the corona electrode 222 and the PI lamp 122 or sequentially activating the charging unit 220 and the ionizing unit 120
  • a series of I sen sor recordings may be obtained in the course of time, such recordings alternatively reflecting the UFP concentration level and the TVOC concentration level, respectively.
  • the sensors 1 and 2 are therefore capable of providing information about both the UFP concentration and the TVOC concentration, thereby assessing the overall severity of the air pollution level.
  • the UFP sensing section may be identical to the sensor described in e.g. US20100043527 by the same applicant and inventor.
  • the details of the UFP sensor described in US20100043527 are therefore incorporated herein by reference.
  • the obtained signal I sen sor is proportional to the product of N and d p , av wherein N is the particle number concentration and d p,av is the average particle diameter.
  • I sen sor can be derived from charged UFPs when the corona electrode 222 is activated (i.e. capable of emitting ions in the airflow in the second conduit 210) and UFPs are present in the airflow while, at the same time, the PI lamp 122 is switched off to prevent the sensor signal to become affected by the presence of charged VOCs.
  • the air displacement unit may be periodically switched off and the subsequently measured signal I sen sor is internally set to zero.
  • the air displacement unit may be periodically switched off and the subsequently measured signal I sen sor is internally set to zero.
  • the sensors 1 and 2 may further comprise a separate temperature (T) sensing element and a relative humidity (RH) sensing element (not shown).
  • T temperature
  • RH relative humidity
  • the outputs of the T and RH sensing elements may for instance be used to deduce the absolute humidity in the air, the value of which is necessary to be able to compensate for the loss of radiation intensity from the PI lamp 122 due to radiation absorption by moisture in the air. Such a loss is proportional with the absolute humidity and can be accounted for through an arithmetic exponential factor (the Lambert-Beer law).
  • the sensor 1 may further comprise an air filter 180 arranged upstream of the ionizing unit 120.
  • the air filter is advantageous in that any particulate material is first removed from the air passing through the first conduit 110 before the air reaches the ionizing unit 120.
  • the selection of the PI lamp is related to the type of VOCs (depending on the molecular weight) that can be ionized and thus measured.
  • the extent to which different VOCs are charged or ionized depends on the particular VOC.
  • a widely used reference VOC gas for this purpose is isobutylene, which is considered to be "an average VOC" with regard to its sensitivity to photo-ionization.
  • the measured current I sen sor obtained when the PI lamp is activated and the corona electrode is deactivated is normally the result of the contribution of many different kinds of VOCs.
  • the contribution of each individual VOC to I se nsor is dependent on its concentration and on the fraction of its molecules that are ionized.
  • This charged fraction can have quite different values for different kinds of VOCs. Even when they would all have the same concentration, the various VOCs would therefore contribute differently to the measured total current I sen sor.
  • the (total) signal obtained from the VOC sensing part 100 of the sensor comes from isobutylene and the relationship between I sen sor and the airborne isobutylene mass concentration can be calibrated for.
  • the TVOC concentration inferred from I sen sor denotes an isobutylene-equivalent TVOC concentration.
  • isobutylene other gases such as toluene may be used as the reference gas.
  • the ionized charged gaseous species may be at least partly precipitated from air onto the first electrode 130 that is connected to the Faraday cage 240 by applying a voltage VpiD prec to the first conduit 110, thereby creating an electric field between the first conduit 110 and the first electrode 130.
  • the electric field may also be created between the first electrode 130 and a second electrode 140 (not necessarily formed by the conduit 110) arranged in proximity to the first electrode 130.
  • the voltage bias V PID P rec applied to the second electrode may advantageously be chosen such that, when no VOCs are present in the first conduit 110 while the PI lamp 122 and the pump 400 are activated (the corona electrode 222 being deactivated), the signal I sen sor, corrected for a possibly existing internal electronic offset current, becomes zero.
  • an activated PI lamp normally generates photo-emitted electrons (and some positive ions as well) from the various internal surfaces, such as the portion of the inner wall of the first conduit 110 facing the PI lamp 122, that become irradiated.
  • the bias voltage V PID prec is normally a modestly high voltage and has a positive value with respect to the reference voltage on the sensing electrode.
  • the selection of the bias voltage V PID prec is preferably performed when the ventilator 400 is activated and when the air drawn through the first conduit 110 is free from VOCs. Elimination of VOCs from air is, for instance, possible by passing the air through an activated carbon filter.
  • This calibration for the bias voltage V PID prec provides a reliable zero sensor signal obtained at zero TVOC concentration, which is very stable in the course of time and needs checking and/or adjustment only during infrequently applied periodic instrument servicing.
  • a “span-calibration” may be performed to derive the proportionality factor between the TVOC mass concentration in air and the measured sensor signal I sen sor. This can, for instance, be done with a known concentration of the reference gas isobutylene in the air passing through the first conduit (PI lamp and air displacement unit both activated, corona electrode de-activated). Using the then obtained proportionality factor enables the deduction of an isobutylene-equivalent TVOC mass concentration from the sensor signal I sen sor.
  • a “span calibration” wherein the current signal due to a known
  • VOC concentration in air is measured, is not performed too frequently.
  • the need for less frequent "span calibrations" is the result of various measures that reduce internal
  • These measures include the intermittent operation of the air displacement unit (such as a ventilator ) and the PI source, the shielding of the optical window of the PI source from direct exposure to flowing air by positioning the PI source and its optical window in the recess 116, the maintenance of a low radiation emission intensity from the PI source, the use of a particle filter at the entrance of the first conduit, and the maintenance of a constant radiation emission strength from the PI source through feedback control by a UV photo-detector facing the optical window of the PI source.
  • the air displacement unit such as a ventilator
  • both the corona electrode 222 and the PI lamp 122 may be preferably operated according to an intermittent mode of operation wherein they are only activated during, at most, a few percent of the total time of an operation cycle. Indeed, activation of the air pollution sensor during only a few percent of the total time of an operation cycle is normally sufficient for most practical applications with respect to the air handling strategy in e.g. buildings wherein the concentrations of the various air pollutants do not normally exhibit rapid fluctuations in the course of time.
  • the sensor of the present invention may be part of an air handling unit used for e.g. air cleaning.
  • the present invention is therefore applicable for controlling the air handling strategy in buildings and homes, specifically with respect to "green" buildings wherein the control of any air ventilation system is then performed in an energy- efficient way.
  • the present invention is also applicable for the monitoring and control of air pollution in buildings, homes and cars (providing awareness about the level of air pollution and, preferably, control of an air cleaner for filtering such pollution) and industrial facilities (for air pollution assessment and control in workplaces for the protection of workers' health).

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Abstract

L'invention concerne un capteur (1) pour évaluer la pollution de l'air. Le capteur comprend une section détection des composés organiques volatils (COV) (100) et une section détection des particules ultrafines (PUF) (200). La section de détection des COV comprend une unité d'ionisation (120) servant à ioniser au moins une partie des COV en suspension dans l'air passant à travers le premier conduit (110). La section détection des COV comprend en outre une première électrode (130) placée, dans le premier conduit, en aval de l'unité d'ionisation. La première électrode est placée à proximité d'une seconde électrode (140) à laquelle une tension de polarisation est applicable pour permettre la précipitation sur la première électrode d'au moins une partie des COV ionisées en suspension dans l'air. La section détection des PUF comprend une unité de chargement (220) servant à charger au moins une partie des particules en suspension dans l'air passant à travers un second conduit (210). La section détection des PUF comprend en outre un élément de capture (230) placé, dans le second conduit, en aval de l'unité de chargement. L'élément de capture est capable de capturer les particules chargées en suspension dans l'air. En outre, le capteur comprend une unité d'évaluation (300) connecté à la fois à la première électrode et à l'élément de capture pour obtenir un signal représentatif de la pollution de l'air.
PCT/IB2011/055120 2010-11-26 2011-11-16 Capteur pour évaluer la pollution de l'air WO2012069963A1 (fr)

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Cited By (10)

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WO2016193246A1 (fr) * 2015-06-05 2016-12-08 Koninklijke Philips N.V. Capteur de particules et procédé de détection
WO2017157987A1 (fr) * 2016-03-16 2017-09-21 Koninklijke Philips N.V. Purificateur d'air et procédé de purification d'air
WO2018115531A1 (fr) * 2016-12-23 2018-06-28 Koninklijke Philips N.V. Système et procédé de mesure de concentration de polluant dans un gaz
CN108426810A (zh) * 2018-03-16 2018-08-21 天津大学 一种空气中颗粒物平均浓度的测量装置
JP2018528400A (ja) * 2015-07-03 2018-09-27 コーニンクレッカ フィリップス エヌ ヴェＫｏｎｉｎｋｌｉｊｋｅ Ｐｈｉｌｉｐｓ Ｎ．Ｖ． 粒子センサ及び粒子感知方法
US10813570B2 (en) 2015-06-05 2020-10-27 Koninklijke Philips N.V. Device and method for monitoring a subject
US20210008570A1 (en) * 2018-03-26 2021-01-14 Lg Electronics Inc. Window-type dust collecting apparatus on basis of artificial intelligence
US11027038B1 (en) 2020-05-22 2021-06-08 Delta T, Llc Fan for improving air quality
CN112986086A (zh) * 2021-04-16 2021-06-18 北京英视睿达科技有限公司 细颗粒物的一次排放监控方法、装置、存储介质及设备
US11400177B2 (en) 2020-05-18 2022-08-02 Wangs Alliance Corporation Germicidal lighting

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Cited By (21)

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Publication number Priority date Publication date Assignee Title
WO2016193246A1 (fr) * 2015-06-05 2016-12-08 Koninklijke Philips N.V. Capteur de particules et procédé de détection
CN107709965A (zh) * 2015-06-05 2018-02-16 皇家飞利浦有限公司 颗粒传感器和感测方法
US10859485B2 (en) 2015-06-05 2020-12-08 Koninklijke Philips N.V. Particle sensor and sensing method
US10813570B2 (en) 2015-06-05 2020-10-27 Koninklijke Philips N.V. Device and method for monitoring a subject
JP2018528400A (ja) * 2015-07-03 2018-09-27 コーニンクレッカ フィリップス エヌ ヴェＫｏｎｉｎｋｌｉｊｋｅ Ｐｈｉｌｉｐｓ Ｎ．Ｖ． 粒子センサ及び粒子感知方法
CN108779926B (zh) * 2016-03-16 2021-02-05 皇家飞利浦有限公司 空气净化器以及用于检测气体过滤器的状况的方法
WO2017157987A1 (fr) * 2016-03-16 2017-09-21 Koninklijke Philips N.V. Purificateur d'air et procédé de purification d'air
US10948207B2 (en) 2016-03-16 2021-03-16 Koninklijke Philips N.V. Air purifier and air purification method
CN108779926A (zh) * 2016-03-16 2018-11-09 皇家飞利浦有限公司 空气净化器及空气净化方法
US11280705B2 (en) 2016-12-23 2022-03-22 Koninklijke Philips N.V. System and method for measuring a concentration of a pollutant within a gas
WO2018115531A1 (fr) * 2016-12-23 2018-06-28 Koninklijke Philips N.V. Système et procédé de mesure de concentration de polluant dans un gaz
CN108426810A (zh) * 2018-03-16 2018-08-21 天津大学 一种空气中颗粒物平均浓度的测量装置
US20210008570A1 (en) * 2018-03-26 2021-01-14 Lg Electronics Inc. Window-type dust collecting apparatus on basis of artificial intelligence
US11806727B2 (en) * 2018-03-26 2023-11-07 Lg Electronics Inc. Window-type dust collecting apparatus on basis of artificial intelligence
US11400177B2 (en) 2020-05-18 2022-08-02 Wangs Alliance Corporation Germicidal lighting
US11433154B2 (en) 2020-05-18 2022-09-06 Wangs Alliance Corporation Germicidal lighting
US11612670B2 (en) 2020-05-18 2023-03-28 Wangs Alliance Corporation Germicidal lighting
US11696970B2 (en) 2020-05-18 2023-07-11 Wangs Alliance Corporation Germicidal lighting
US12109338B2 (en) 2020-05-18 2024-10-08 Wangs Alliance Corporation Germicidal lighting
US11027038B1 (en) 2020-05-22 2021-06-08 Delta T, Llc Fan for improving air quality
CN112986086A (zh) * 2021-04-16 2021-06-18 北京英视睿达科技有限公司 细颗粒物的一次排放监控方法、装置、存储介质及设备

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