Measurements in a kitchen exhaust duct

Transcription

1 RAPPORT Measurements in a kitchen exhaust duct For Interzon AB Kjell Peterson Arkivnummer:U 2270 Box 21060, SE Stockholm Box 5302, SE Göteborg Valhallavägen 81, Stockholm Aschebergsgatan 44, Göteborg Tel: +46 (0) Tel: +46 (0) Fax: +46(0) Fax: + 46 (0)

2 Contents 1. Introduction Purpose of the measurements Measurement method General Measurement techniques and parameters Installation of the instruments Particle sampling technique Results Results (AirMaid running) Results (AirMaid switched off) Comments on the results...6 Appendix 1 Appendix 2 Instrument data for measurements (graph) Instrument data for measurements (graph) 1

3 1. Introduction IVL Swedish Environmental Research Institute has been commissioned by Interzon AB to undertake measurements in a kitchen exhaust duct that ventilates a McDonald`s restaurant in the Fältöversten shopping complex in Stockholm, Sweden. The measurements were undertaken on the 12 th February The contact at Interzon AB was Mika Lindfors. 2. Purpose of the measurements The two main purposes of the measurements in a kitchen exhaust duct were as follows: A. Study the cleaning efficiency of the installed AirMaid ozone generator for kitchen ventilation. B. Study any possible formation of air pollutants due to the installed ozone generator. 3. Measurement method 3.1 General Measurements were undertaken in the ventilation shaft on the 12 th February 2008 during two busy periods for the restaurant. Measurements were made during the period with the AirMaid unit running and during the period with the unit switched off. 2

4 Figure 1 shows the location of the sampling probe attached to the kitchen exhaust duct (after the fan unit). Figure Position of the sampling probe in the kitchen exhaust duct (after the fan unit). Measurement techniques and parameters The following table (Table 1) shows the parameters measured and the monitoring techniques used. Table 1. Monitoring parameters and techniques Parameter measured NOx (NO + NO2) O2 CO2 O3 Total hydrocarbons (THC) Particles Humidity 3.3 Technique Spot test Spot test Instrument Horiba, chemiluminescence Horiba, paramagnetic sensor Riken Keiki, IR TH49C, UV-absorption Bernad Atomic, FID Filter holder with glassfiber filter Vaisala PTB101B Installation of the instruments Figure 2 shows how the instruments were installed in the monitoring location. From left to right in the picture: gas preparation system, total hydrocarbon detector, oxides of nitrogen detector, ozone detector, pc with carbon dioxide detector behind. The sampled gas was drawn from the kitchen exhaust duct after exiting the fan via a gas preparation system to the instruments for analysis of oxides of nitrogen (NOx), carbon dioxide (CO2) and oxygen (O2). The sampled gas analysed for total hydrocarbons (THC) was drawn from a sampling line immediately preceding the gas preparation system. 3

5 A rotameter was located at the end of the sampling system in order to verify that there was always an excess of sampled gas in the system. The ozone detector had a separate sampling tube made of teflon which was coupled in parallel with the sampling tube to the gas preparation system. Figure Position of monitoring equipment Particle sampling technique The concentration of particles was sampled in the kitchen exhaust duct both when the ozoneproducing unit (AirMaid) was running and when it was switched off. The particle sampling was undertaken in isokinetic conditions, i.e. the sampled air passed through the nozzle of the filter holder at the same velocity as the surrounding medium. The particles were collected on a preweighed glass fiber filter that was then weighed at IVL s laboratory in Göteborg. 4

6 4. Results 4.1 Results (AirMaid running) Table 2 shows the measured temperature, humidity and particles in the the kitchen exhaust duct when AirMaid was running. Table 3 shows the levels of total hydrocarbons, oxides of nitrogen, carbon dioxide, ozone and oxygen as an average over the monitoring period. Appendix 1 shows a graph of all measurements during the measurement period ( ) Table 2 Temperature, humidity and particle concentrations in the kitchen exhaust duct Date Time Temperature oc Relative humidity RH% Particles mg/nm 3 Air flow m3/h*) *) Data from the fan Table 3 Concentration of total hydrocarbons, oxides of nitrogen, carbon dioxide, ozone and oxygen (average over the monitoring period). Date Time Total hydrocarbon ppm*) Oxides of nitrogen Ppm Ozone ppb Carbon dioxide ppm Oxygen % < *) ppm propane equivalents 4.2 Results (AirMaid switched off) Table 4 shows the measured temperature, humidity and particles in the the kitchen exhaust duct when AirMaid was switched off. Table 5 shows the levels of total hydrocarbons, oxides of nitrogen, carbon dioxide, ozone and oxygen as an average over the monitoring period. Appendix 2 shows a graph of all measurements during the measurement period ( ) Table 4 Temperature, humidity and particle concentrations in the kitchen exhaust duct Date Time Temperature oc Relative humidity RH% Particles mg/nm 3 Air flow m3/h*)

7 Tabell 5 Concentration of total hydrocarbons, oxides of nitrogen, carbon dioxide, ozone and oxygen (average over the monitoring period). Date Time Total hydrocarbon ppm*) Oxides of nitrogen Ppm Ozone ppb Carbon dioxide ppm Oxygen % < *) ppm propane equivalents **) Somewhat uncertain value 5. Comments on the results Measurements of the air emitted from the McDonald`s restaurant through the kitchen exhaust duct shows that the concentration of oxygen, total hydrocarbons and oxides of nitrogen are not affected by ozone generation. The concentration of carbon dioxide in the air in the kitchen exhaust duct is most likely affected more by the number of customers in the restaurant than by the ozone generation. The relative humidity was approximately % higher during ozone generation. The temperature did not vary noticeably. Concentrations of particles in the kitchen exhaust duct increased marginally with ozone generation, from to mg/m 3. However, ozone generation does create considerably more small particles ( nanoparticles ) of low mass. Ozone generation resulted in an excess of ozone in the kitchen exhaust duct of approximately 700 ppb. This air is emitted above roof level. According to dispersion modelling previously undertaken by IVL, such an emission of ozone results in a contribution to the local air quality 100 m from the source of <10 ppb. The contribution of ozone to the local air quality from the AirMaid unit is judged to have little effect on the surroundings. 6

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