Design, development and application of a particulate matter control technology with special consideration for indoor air quality management

Design, development and application of a particulate matter control technology with special consideration for indoor air quality management

Aiswarya Kumar¹, Manoranjan Sahu^1*

¹Environmental science and engineering, Indian Institute of Technology Bombay (IITB), India

^*Corresponding email: mrsahu@iitb.ac.in

ABSTRACT

Indoor air quality is a major concern in the modern environment since people especially those in urban areas spend 80-90% of their time in living, workspaces as well as in different means of transportation and also due to construction of tightly sealed buildings because of space constraints in developing and populated countries like Indian subcontinent. Among different indoor pollutants, particles are major concern for health due to their smaller size and easy attachment to different species. Particle exposure indoors depends on the characteristics of indoor sources, activities causing resuspension of particles and infiltration from an outdoor polluted environment. Conventional particle cleaning technologies such as filtration and ionisers have lot of draw backs such as high energy consumption, maintenance difficulties and reduced efficiency with time. Electrostatic precipitation (ESP) is a promising emerging technology in indoor environments due to benefits like high efficiency removal, minimal pressure drop, flexibility of keeping as standalone/induct, lesser energy consumption and low maintenance requirements. Therefore current study designed and developed a miniature wire-plate ESP for capture of indoor particles. Designed ESP was operated at a voltage of 6 kV considering voltage-current characteristics, different empirical formulas, visualization of corona and based on number of ions generated. Flow rate was kept at 8 LPM considering migration-residence times as well as uniform velocity distribution obtained from computational fluid dynamics (CFD) modelling. Characteristics of discharge wire were selected such as keeping by-product emission and power consumption minimal which are required optimal conditions for an indoor application. Designed ESP provided high capture efficiency for standard laboratory aerosols such as sodium chloride, ammonium chloride and magnesium chloride achieving promising results with a total removal efficiency of 95-99% for wide particles sizes from 10 nm to 10 µm as measured by sophisticated instruments like scanning mobility particle sizer (SMPS) and optical particle sizer (OPS). To simulate performance in a real scenario experiments were also carried out with major indoor particle sources like incense sticks, burning candles, mosquito coils and bio-aerosols such as Mycobacterium smegmatis as well as  Escherichia coli having varied particle number distributions and obtained total particle capture efficiency 99.99, 99.97, 99.98 and 95% respectively. Designed ESP also removed particles from ambient as well as infiltrated particles at a total capture efficiency of 99.8%. Nonthermal plasma (NTP) ionisation process happening inside the ESP has provided bioaerosol deactivation efficiency and volatile organic compound (VOC) degradation efficiency of 70 and 85% respectively. Additionally, this multipollutant removal technology  has an  lower energy consumption/Clean air delivery rate (CADR) (0.32 W/m³/hr) and emission of by-products like ozone and ultrafine particles compared to best commercial purifiers thereby suggesting its possible applicability as a product for air quality management