
China builds ‘world’s biggest air purifier’ and it seems to be working - cesis
https://www.scmp.com/news/china/society/article/2128355/china-builds-worlds-biggest-air-purifier-and-it-seems-be-working
======
jhugg
So... to drop the PM2.5 amount by 15%, this tower must be removing many many
tons of particulate matter every day. How is it removed from the filters they
speak of? How expensive is that to do? I have some questions about the
practicality.

On the other hand, I wonder if anyone's ever built a 100m placebo before. It
could be a _really_ interesting university study on the placebo effect in
disguise.

~~~
LeifCarrotson
> many many tons of particulate matter every day

Let's do the math.

Guidelines state that the limit on PM2.5 particulates is approximately 10
micrograms per cubic meter for an annual average. Xian, where the tower was
installed, is currently
([http://aqicn.org/city/xian/](http://aqicn.org/city/xian/)) under 231 ug/m^3
of pollution. The tower is supposed to process 10 million cubic meters of air
per day.

    
    
        10^7 m^3 x 231 x 10^-6 g/m^3 x 10^-3 g/kg x 0.15 = 231 x 0.15 x 10^-2 =>
    

0.34 kg of particulate contamination removed per day. Not many tons. But
someone check my math, please - that seems impossibly low, unless combustion
is cleaner and generates lower quantities of PM2.5 particulates than I'm
imagining. I did assume that it only removes PM2.5 contaminants, ignoring
larger dust particles and PM10 pollution.

Let's also check the amount of air it should be processing. It's about 100
meters tall, and intended to cover 10 square kilometers. We'll conservatively
assume that this volume represents the total quantity of air it needs to
process. Ihe volume is:

    
    
       10 km^2 x 10^3 m/km x 10^3 m/km x 10 ^ 2 m = 10^8 m^3
    

or 100 million cubic meters, so it's intended to process one tenth of that
volume per day.

The math still seems low. Micrograms per cubic meter are hard to intuit.

~~~
kragen
0.35 kg of particulate contamination removed per day; you rounded incorrectly,
but the rest of your math is right.

There's the issue that it's probably removing nearly all of the particulates
from the air it actually processes, say over 90%, which works out to 2.1 kg.
It doesn't reduce the PM2.5 level in the area by 90%, but only by 15%, because
it's only able to process some 16% of the air in its area during whatever the
relevant time interval is, which seems like a good match to your 10%-per-day.

However, you got the volume of that area wrong: it's 10⁹ m³, not 10⁸ m³. That
suggests that the natural lifetime of PM2.5 particulates is closer to a week
than a day.

As for jhugg's question about how the filters are cleaned, a common way to
remove particulates from flue gas or indoor spaces is using electrostatic
precipitators, which are flat plates at a high voltage. The voltage sticks the
particulates to the plates, and when the coating is thick enough, you close
the valves to stop the gas flow and vibrate the plates to unstick the dust,
and it falls out the bottom of the filter into a bucket (or, say, a truck).
Other systems clean the plates with water (either spray or immersion) and
possibly soap or lye.

~~~
nullbyte
I love HN comment like this. Seems like there's an expert in everything here!

~~~
kragen
I am not an expert in air pollution control systems, or even an amateur. I
don't even have an air filter installed in my house. I read some Wikipedia
articles over the last couple of years, Googled, and watched some videos on
YouTube (including "how-to" videos on the care and feeding of electronic air
cleaners.) That doesn't make me an expert. That makes me some sort of
approximation of a journalist — and if you've ever read those people writing
about something you know about, you know how much they get wrong.

------
gressquel
Please refrain from using AMP links. We need to take a stance against Googles
abuse of monopoly.

~~~
captainmuon
Devil's advocate: Google is generous by caching AMP sites on their own
servers. The only thing you can't do is to include your own invasive third
party tracking (ok, you can use Google's of course), which is bad anyway. But
you can still include your ad just as a <img> in the page, no JS and tracking.
Like a dumb print ad. I don't really have a problem with that.

~~~
Hello71
"Google is generous by storing your email on their own servers."

"Facebook is generous by storing your posts and friend lists on their own
servers."

~~~
send_computers
I agree

~~~
acct1771
With the nonsensical sarcastic point? Or the real point?

------
makethetick
More readable non-mobile link:
[http://www.scmp.com/news/china/society/article/2128355/china...](http://www.scmp.com/news/china/society/article/2128355/china-
builds-worlds-biggest-air-purifier-and-it-seems-be-working)

------
SurrealSoul
I wish there was more than anecdotal evidence for this. China has very strong
statistics for their pollution levels that are often recorded in their weather
reports.

For a project this big, they should be able to quantify the results instead of
just relying on what people say about the air :/

EDIT: I'm a dummy, although the article leaves with an anecdotal, there are
some nuggets of stats "The average reduction in PM2.5 – the fine particles in
smog deemed most harmful to health – fell 15 per cent during heavy pollution."
& "Cao said the results were preliminary because the experiment is still
ongoing. The team plans to release more detailed data in March with a full
scientific assessment of the facility’s overall performance."

~~~
amelius
> I wish there was more than anecdotal evidence for this.

Perhaps this will help:

[http://www.esa.int/Our_Activities/Observing_the_Earth/Copern...](http://www.esa.int/Our_Activities/Observing_the_Earth/Copernicus/Sentinel-5P/Sentinel-5P_brings_air_pollution_into_focus)

------
radarsat1
I really like how simple this solution is. Just using the sun to heat up air
and have it go up through a bunch of filters, no moving parts. It strikes me
as the right way to go about it. I wonder if you could use the greenhouses for
growing plants, and the rising air to run small turbines..

~~~
IanDrake
As far as running turbines go...

[https://en.m.wikipedia.org/wiki/Solar_updraft_tower](https://en.m.wikipedia.org/wiki/Solar_updraft_tower)

------
xkcd-sucks
Such a mainland solution... The air's dirty, install an air filter. There's
lots of air and it's really dirty? Build a bigger air filter!

...especially if my uncle manufactures air filter membranes and needs to get
rid of some extra inventory

------
quadcore
Side node: is China doing ok in terms of innovation? If yes, how come in such
a regime? I would expect everything to be stuck in bureaucracy.

~~~
stelonix
If anything, it goes to show representative democracy plus unrestrained
capitalism is not the only way to run a modern, advanced civilization.

~~~
briandear
China a "modern, advanced civilization?" You've clearly never lived in China.
China is all about the façade. And a MODERN, advanced civilization wouldn't be
polluting their entire country like it was a tannery in 1758.

Taihu lake, near Suzhou, is practically radioactive. Fish in pretty much any
freshwater within the entire country is toxic. I lived in China for 3 years or
so and as soon as my son was born, we got the hell out -- it's a fun place,
but no "modern, advanced" civilization operates like China. It's a country of
mostly uneducated, superstitious peasants who suddenly got a lot of money and
are kept in line with the threat of "re-education" or death. Even an artist
has to fear for his life. [http://aiweiwei.com](http://aiweiwei.com)

Then there's Lui Xiaobo.

Remember, this "modern, advanced" civilization still has Traditional Chinese
Medicine as a "thing." It's a complete fraud with zero scientific basis:
[https://sciencebasedmedicine.org/retconning-traditional-
chin...](https://sciencebasedmedicine.org/retconning-traditional-chinese-
medicine/)

This "modern, advanced" civilization is responsible for massive worldwide
poaching to satisfy demand for quack TCM remedies:
[https://www.forbes.com/sites/jamesconca/2014/08/08/extinctio...](https://www.forbes.com/sites/jamesconca/2014/08/08/extinction-
by-traditional-chinese-medicine-an-environmental-disaster/#c42db405bd31)

Really, powdered rhino horn? That's has the chemical composition of human
fingernails -- and works just as "effectively."

They still do "postpartum confinement"
[http://edition.cnn.com/2015/08/11/china/chinese-
postpartum-c...](http://edition.cnn.com/2015/08/11/china/chinese-postpartum-
confinement/index.html) \-- based on pretty much nothing but old wives tales
and dangerous superstition.

Then there's the atrocious human rights record: [https://www.hrw.org/world-
report/2017/country-chapters/china...](https://www.hrw.org/world-
report/2017/country-chapters/china-and-tibet)

I actually like China -- but the CCP isn't running a "modern, advanced
civilization." They're the Beverly Hillbillies.

~~~
com2kid
> They still do "postpartum confinement"
> [http://edition.cnn.com/2015/08/11/china/chinese-
> postpartum-c...](http://edition.cnn.com/2015/08/11/china/chinese-
> postpartum-c..). -- based on pretty much nothing but old wives tales and
> dangerous superstition.

And a short time ago Americans were electro-shocking homosexuals to try and
make them straight.

> Remember, this "modern, advanced" civilization still has Traditional Chinese
> Medicine as a "thing." It's a complete fraud with zero scientific basis:
> [https://sciencebasedmedicine.org/retconning-traditional-
> chin...](https://sciencebasedmedicine.org/retconning-traditional-chin..).

America has chiropractors covered under insurance, people who believe in
homeopathy, and a growing culture of vaccine denial.

No culture is perfect. Not too long ago we had horribly polluted waters, and
in a lot of places we still do. Have you seen the impact of pollution from pig
farms[0][1]?

I'm not trying to play what-about-ism here, I am just saying that "modern,
advanced civilizations" do all the things you listed.

The Chinese government is capable of undertaking massive infrastructure
projects, and they do an incredible job of picking industries for government
protectionism, allowing for growth of local talent. Multiple areas of
technology and advanced automation are both areas where China has invested
heavily in education and building a huge local talent pool. Pulling off multi-
decade economic growth plans is impressive, they plotted a path from basic
industry all the way to an advanced technology sector, and then executed on
that plan.

That more than qualifies them as an advanced modern society.

[0][http://observer.com/2017/05/pig-waste-factory-farming-
north-...](http://observer.com/2017/05/pig-waste-factory-farming-north-
carolina/) [1][http://www.businessinsider.com/mishka-henners-photos-of-
amer...](http://www.businessinsider.com/mishka-henners-photos-of-american-
feedlots-2014-8)

------
ChuckMcM
Seems like a reasonable way to pump air through a filter. It will be
interesting to see long term effects and maintenance costs (eventually the
filters need to be replaced as efficiency would go down with increased air
resistance in the tower).

This FastCompany article from 2013
([https://www.fastcompany.com/2682151/5-imaginative-
buildings-...](https://www.fastcompany.com/2682151/5-imaginative-buildings-
that-breathe-pollution-and-clean-the-air)) had some additional concepts that
could be added.

------
Kayou
>Xian can experience heavy pollution in winter, with much of the city’s
heating relying on coal.

Have they tried to filter directly the air at the source of pollution? For
instance, placing filters on the coal heating facilities. It should be more
efficient, as you wouldn't release as many particles in the air in the first
place.

~~~
chapium
Article mentions coal based heating being a big culprit, which is most likely
used residentially in homes and small businesses.

~~~
Kayou
I thought it was a central source of coal heating, but if it's in every home,
it's probably too difficult to filter then.

~~~
seanmcdirmid
In city heating is typically central, in then countryside it is by home. When
I visited Tianjin in 1999, however, the apartment I was staying at had a coal
furnace.

------
alex_duf
Edit: as pointed bellow it's using filters. Sorry didn't see that

If I understand correctly this "air purifier" is just shooting polluted air
up, bringing cleaner air from above.

That sounds like a very short term solution, but it's interesting

~~~
radarsat1
"The hot air then rises through the tower and passes through multiple layers
of cleaning filters."

------
whoiskevin
I couldn’t help but think of the book “The Water Knife”. In the book it is the
the Chinese that build massive liveable spaces that recycle the water and
purify the air. Just a small step in that direction.

~~~
jefurii
Or the Two Rivers solar updraft tower in Suarez' "Freedom TM".

------
jostmey
I don't see Humanity becoming less destructive on the environment, so this
represents our future. It would be nice if an outside source could verify its
effectiveness

~~~
anon151516888
It'll be much better when/if the third world poor countries enact similar
pollution policies as the Western developed world has. Have faith.

~~~
jcbrand
The "Western developed" world uses more energy per capita than most developed
countries (the gulf states being an exception), with the US having one of the
highest energy consumption per capita ratings.

[https://en.wikipedia.org/wiki/List_of_countries_by_energy_co...](https://en.wikipedia.org/wiki/List_of_countries_by_energy_consumption_per_capita)

------
_salmon
Has it not been completely built? The article features a few pictures of it
under construction and then an artist's impression of how it would look.

~~~
SurrealSoul
They are building several towers, the project should be completed in march

------
darethas
This may sound like a naive question, but how does this compare to say, trees?

~~~
seanmcdirmid
Trees don’t do much for PM2.5. They are a reasonable solution for dust storms,
which do generate lots of (but not all) PM10.

~~~
darethas
Follow up, can you define much here? I am just interested in this, I read this
paper as a primer to my own question, and it seems that with proper city and
road planning combined with the effect trees have locally on the air quality
it seems we could have noticeable improvement, especially during the leafy
seasons.

[https://www.sciencedirect.com/science/article/pii/S135223101...](https://www.sciencedirect.com/science/article/pii/S1352231016307336)

~~~
seanmcdirmid
Trees can help with carbon, but we are talking about small particles here. I
guess they could trap them or something, but not on the scale of a typical
polluted day in say Beijing. Anyways, in northern china, this wouldn’t be very
workable as the pollution season corresponds to leafless tree season (and the
trees turn a dreary brownish grey due to dust).

~~~
darethas
Correct my understanding here where I am wrong - In my mind, if a leaf of a
tree or any vegetation photosynthesizes, it is pulling in air (dirty air by
your account which is why those leaves are brown) By the very virtue of that
fact, it would be pulling in those small particles as well. The paper I
referenced states that this happens to an extent, which is why trees during
the leafy season are more effective at reducing PM2.5 than when they are bare.

~~~
seanmcdirmid
You are probably right, but a better solution would be to create breeze ways
that would allow wind to blow out the pollution more easily. These could be
coupled with forests, of course. These cities have plenty of trees, but they
aren’t newrly enough and anyways winter is the worst season.

------
reacharavindh
I wish there was some technical background of what such a "purification tower"
does. If they found a genuinely innovative way of purifying air and dumping
the toxins and by products sensibly, that is mazing for all of us kudos to
them! However, if they tried to push the problem away by shooting polluted air
away and sucking in fresher air, then it sucks.

~~~
Knufen
It says in the article that

>"The hot air then rises through the tower and passes through multiple layers
of cleaning filters."

Meaning you just have to clean the filters

~~~
ocardoso
I think we should find a better way to heat ourselves without burning coal,
because this air purifier will reach a limit in the future and we will be back
on step one.

~~~
tqkxzugoaupvwqr
To reduce air pollution the Chinese government forbad heating with coal in
some regions and installed gas pipes there. It turned out they severely
underestimated the spike in demand in winter and the rising gas prices.
Residents illegally switched back to coal heating because heating with gas was
2-3x more expensive. Later, the government officially sanctioned coal heating
for the time being. So the Chinese government tries to get away from coal but
it’s not as easy.

------
golem14
Maybe also an attempt to test solar updraft power generation ?

