What Is This?

This is my invention of an electrostaticly augmented cyclonic wet scrubber. It is a device that purifies the air by using water and electricity, without the use of a fabric filter. My vision is to leverage this technology to solve a variety of common household air quality problems. It would be awesome to use this technology to build centralized air cleaning units in homes, or stand alone air purifiers, or counter top kitchen range hoods, or laboratory recirculating fume hoods/extractors, or appliances that allow people to smoke indoors comfortably. Perhaps even a generic air-cleaning unit with multiple attachments that can do it all!

This invention is of vital importance to households as the air quality in households are not regulated by the EPA. More often than not, air quality inside a home is much worse than outside air due to trapped dust and allergens, smoke from cooking, chemicals from cleaning, and volatile organic compounds (VOC's) that leach from common building materials like carpet and paint. Serious chronic health conditions, ranging from asthma and bronchitis to lung cancer, can arise because of poor indoor air quality. Children and the elderly are most susceptible to developing these respiratory problems because of the amount of time they spend indoors.

My invention would be very valuable in the average household during the winter, when there is very little natural ventilation in the home to flush out indoor pollutants. It is also especially useful in areas like Beijing, where smog and PM2.5 air particles are constantly at high levels. Being an asthmatic myself and having a non-smoker friend recently being diagnosed with lung cancer, this invention is quite personal to me and I find indoor air quality a very pressing issue to address. Current wet scrubber technology is generally used in industrial settings to clean heavily polluted air, such as the exhaust of coal fired power plants and garbage incinerators. However, I strongly believe they need to be implemented into homes in one or more ways. My invention improves upon current wet scrubbing technology and makes it more accessible to the average household in both size and cost.

For the DIY enthusiast, my invention would be particularly useful in the workshop. Many DIY workshops produce dust, smoke, and harmful VOC's from activities ranging from soldering, welding, grinding, painting, cutting and staining wood, laser cutting, 3d printing, to chemistry experiments. The equipment required to clean such pollutants can get very pricey very fast. One of my goals is to make everything about my invention DIY, cheap, and yet have excellent results so the DIY enthusiast can make their own air cleaning device on a low budget. I built all of my prototypes as cheaply as possible and used second hand goods from Good Will and salvaged parts from electronic waste. Anyone on a tight budget can build one of these with parts sourced from a second hand store or a local hardware store.

Why Not Use A HEPA?

I chose wet scrubber technology over typical HEPA fabric filters for three reasons. One, because you can theoretically get the same results as a HEPA but don’t have to keep buying expensive filters - all you need is water and electricity. Second, wet scrubber technology can be used for applications where humid or oily particulates need to be removed, such as from cooking exhaust in the kitchen. HEPA fabric filters cannot handle humid or oil-laden air as it will get clogged and deteriorate. And third, wet scrubbers can absorb volatile organic compounds or gases that are soluble in water.

How Does It Work?

The key to my invention lies in the geometry of the wet scrubber and the use of electricity to boost its scrubbing power. My design is very scalable and can be implemented in a small form factor, providing good performance from a device the size of a counter top appliance.

It first ionizes the incoming particulate laden air via a high voltage pre-charger. This pre-charger can either be a pool of high voltage conductive liquid manipulated to form an electrospray, or simply a metal charge grid that emits a corona discharge. The charged particulate laden air is then directed into a highly turbulent spiral path, impacting a scrubbing liquid that is either held to ground potential or charged to the opposite polarity. The large particulates will separate from the air as it impacts the scrubbing liquid. Fine particles are attached to the scrubbing liquid through means of electrostatic attraction. Some VOC’s will dissolve into the scrubbing liquid. The rest of the VOC’s are scrubbed in the next stage, where the air is passed through an adsorbent bed of activated carbon.

How Does It Perform?

The wet scrubber alone can filter out particles above 2um at nearly 100%. Below that threshold, the wet scrubber's filtering ability drops and relies on the electrostatic stage to capture the finest particles. The electrostatic section alone can filter the smaller particulates below 2um down to sub-micron ranges.

I'm seeing a bit of penetration for the smallest sub-micron particles for a dense smoke source at about 100cfm air flow. The electrostatic precipitation is not at the 99% collection as I'd like it to be but maybe at about 80%-90% collection for sub micron particles depending on speed of air flow. I believe this is due to my high voltage circuit not being able to supply enough current & voltage. I'm sure with a little more tweaking it can easily attain 99% collection efficiency.

Using a fog machine I can accurately test that a majority of the sub-micron particles are being filtered.

Concerning VOC's, from what I can smell, the VOC’s are effectively being filtered out by the DIY activated carbon stage filters.

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