V4 Fume Extraction
Hey community, I’m Suvda, chemical engineer working on PP V4 fume extraction. In this post, I will include information about the amount and contents of the fumes created. I found out which respirators are suitable to protect ourselves. Now, I am finding out which filters and ventilation design is suitable for us. In July, me and @pauldufour will build the fume extraction system. From August, we will test its efficiency with a fume detector and document the results. If you have any questions or recommendations, feel free to comment on this thread or send a message to me.
Fumes are created usually due to thermal, mechanical and oxidative degradation. The fumes are mainly made up of Volatile Organic Compounds (VOCs). VOCs are organic compounds that have boiling points roughly in the range of 50 to 250 °C. VOCs might be produced at 150-300C, due to the aging, long thermal exposure, intrinsic sensitivity and the interactions between additives and polymers.
Fume content and amount
In V4, we are working with HDPE, PP and PS. PS creates 8 times more fumes than PP and 17 times more fumes than PE. PP and PE are essentially refined wax, that’s why it has less fumes. PS fume contains mostly styrene and other similar aromatics. PP and HDPE mostly emit some alkane vapors. HDPE is the safest material in terms of fume creation. (picture below)
PS fume = 470 ± 100 mg/m3
PP fume = 59 ± 14 mg/m3
HDPE fume = 2.8 ± 2.4 mg/m3 
The maximum 3-hour concentration of hydrocarbon content is 0.24 ppm, not to be exceeded for more than a year . In conclusion, our biggest threat is styrene vapor formed from PS melting.
We need ABEK1 6059 3M filters for filtering organic vapors which have boiling points above 65C, ammonia, acid and inorganic gases, this includes our fumes from melting plastic. These filters can be used for 6 hours continuously in one go, overall maximum of 50 hours and should be stored in airtight container while not in use. We used simple circles to indicate how many hours we have used the mask. Mask side is needed for particulate filter for preventing fine dust to enter the filter of the respirator.
VOC detector is needed to check efficiency of filter and ventilation. Photo-Ionization detector (PID) is the most commonly used technology to detect VOC content in the air. When air enters the end of a VOC meter, a UV light interacts with the molecules in the air. Organic compounds release positively charged ions when they pass through the light, which are then captured by a negatively charged plate producing measurable electrical current. For us UV lamp of 10.6eV is suitable.
At V4, we are planning to rent a PID detector for a week. Their primary use is for monitoring possible worker exposure to volatile VOCs.
Gas detection tubes are useful for detecting the presence of specific gases such as styrene.
LEV is Local Exhaust Ventilation which is a standard for industry to ventilate the toxic air efficiently.
Hood: contaminant cloud enters the LEV
Ducting: Conducts air and the contaminant from the hood to the discharge point.
Air cleaner: filters or cleans the extracted air.
Discharge: releases extracted air to a safe place
For temporary measure, we are using fume caddie for fume extraction of sheet press (pics below).
For VOCs the cleanest, easiest cleaning method is via activated carbon filter (ACF) especially granular ACF and fibrous ACF. Activated carbon has big surface area due to a lot of pores where VOC molecules can get trapped, thus filtered. ACF remove following VOCs very well: toluene, xylene, styrene, alcohol, benzene, decane, ethylbenzene, heptane and octane. And the following gases well: pentane, acetone, hexane . Porosity is the most determining feature of activated carbons.
This week, we would like to find the suitable ACF to install above the extrusion machine. If you have any recommendations and suggestions, do not hesitate to send me a message 🙂
Hi Suvda @irismongolia
Somewhat disturbing topic, but hey lets indeed not be naïve about the dangers of working with plastic(s)!
I have a question: Do you have ant data about using water filtration?
Simply said: blowing the exhaust air through a body of water. Pretty low-tech, but I heard some good things about it, if only for the dust particles…
They can, indeed, be very simple (and cheap) to make – and can be very effective at particulate removal. I don’t know about VOC removal, though, as the scrubbing fluid has to be capable of absorbing the chemicals – and mustn’t create its own pollution by sending nasty vapours out of the chimney. 😉
Edit: Been looking for suitable (cheap and non-toxic) fluids that could take VOCs out of the air in a wet scrubber – and some suggestions are:
– Vegetable Oil (any oil of low volatility)
– A water / surfactant solution (e.g. soap or detergent)
– An aqueous caustic solution (e.g. sodium hydroxide)
Of course, you are then faced with having to dispose of a liquid contaminated by VOCs…
I’m sure @irismongolia will be able to correct any of this, and offer some sensible advce 😉
…and here I was just thinking I could solve world polution by dunking the exhaust pipe into a bucket of water! 😉
Thank you for confirming it’s a valid idea.
@irismongolia so what about the VOC in wet scrubbers?
And I love this follow up question: “and/or what could be the best ‘solution’?”
Even if vinegar would only be a 75% improvement, not everybody can affort £1 an hour gas mask, so knowing this could already make a big difference.
@donald I was going to mention acetic acid (vinegar) in the list, above, but could only find one reference (that was rather vague).
At least it isn’t as bad as the stuff I was having to mess about with 35 years ago – where the end result was inevitably a large tank of radioactive liquid 🙁
For anyone faced with having to make an air extractor, instead of just buying one, this article (and video) is quite handy. Actually, I think it is interesting for its own sake (I’ve been in awe of this guy’s workshop experiments for a few years).
@irismongolia thank you for looking into this. I’m looking forward to your results.
The mg/m3 and ppm values may be a little misleading in that they apply to the workshop configurations tested in the referenced study. I expect that when you test the air near the extrusion machine in the large work volume in the Eindhoven workspace and compare it to the PP container workspace the results will be different. The relative comparison between the plastics should hold.
@donald , looks like the filters can be found a bit cheaper. https://www.zoro.co.uk/shop/personal-protection-and-clothing/respirator-spares/6059-abek1-gas-and-vapour-cartridges-filters-pk-2/p/ZT1178484X .The Amazon price was for 4 pairs
@donald @frogfall Thanks for the inputs. I have looked at wet scrubbers (also called absorption) and found that it is possible to use wet scrubbers (pic below), only concern is that the VOCs need to be at least slightly soluble in the scrubbing liquid (also called absorbent). Main VOC we want to filter, styrene, is not soluble in water. Water wet scrubbing work for dust, mold and pollens size of 2 micrometers.
One study I looked at, was scrubbing PS fumes with 2 stage scrubbing method. Sodium Hypochlorite was used for oxidizing the VOCs and to neutralize chlorine hydrogen peroxide was added. Secondary pollution control done by Sodium hydroxide. Thus, 90% of hot melt VOCs removed, except benzene compounds. Scrubbing solution cost USD 0.32 for 1000m3 gas. VOCs in hot melt exhaust consists of acrolein, acetone, benzene, ethyl benzene, styrene and alpha methyl styrene.
In my point of view, using a lot of chemicals is not a very environmentally friendly option, but wet scrubbing still needs to be explored more.
This guy made a DIY air filter using cyclonic wet scrubber for dust filtration, electrostatic precipitator for ultra fine particles like smoke and mist filtration and activated carbon for VOCs.
In my point of view, having a pre-filter for dust and activated carbon filter for VOCs seem to be the simplest solution. Buying bulk activated carbon and renewing it yourself is quite easy compared to wet scrubbers. But I might test both activated carbon and wet scrubbers. My main focus now is to find the most suitable activated carbon by considering the main properties: pore size, density, particle size
@donald in terms of VOCs in the liquid, distillation could be used for VOC recovery, but I don’t think it will be economical. There isn’t much commercial systems that recover VOCs from the scrubbing liquid.
@s2019 Thanks for your input. Yeah, that is why we want to rent a PID sensor for VOCs to detect it in real life.
@irismongolia do you have a link for an easy DIY carbon reactivation process? The process described on the wiki page https://en.wikipedia.org/wiki/Activated_carbon#Reactivation_and_regeneration is high temperature and not DIY friendly. Is there a way to monitor carbon’s remaining effectiveness other than cumulative hours?
@s2019 As you have mentioned one way to recover activated carbon is heat desorption and the other way is vacuum desorption at a sufficiently low vacuum pressure. Another reason why heat desorption is not suitable for us is that styrene monomers are highly temperature sensitive and will polymerize.
Spent carbon should be disposed when it contains 2% organics by weight, can be placed in a US municipal landfill (at $0.10/kg), based on current Federal regulations. If, instead, the spent carbon were classified as hazardous, this disposal cost (including transport) would increase to about $5.60/kg (disposal contractor quote). But our workshop are quite small so for sure it will be best if we regenerate in a DIY way. I will look into that.
Yeah, I was going to mention that one of the problems of desorption is having somewhere to send the nasty stuff once it comes back out of the filter 😉
@frogfall that’s a great idea of wheat bran, we can test with it once the fume detector arrives in late July. I am not sure if it will be as effective as carbon as it is not as porous as carbon, but we should try testing.
About the spent carbon, I was also thinking of feeding to the worms or the right strain of bacteria or fungi to make the spent activated carbon not chemically nasty. That would solve our problem in a very environmentally friendly way 🙂
@irismongolia Great – I look forward to seeing the results 😉
I guess it would also be possible to partly pyrolyse the bran to make it more active, if it could be done without using a lot of non-renewable energy in the process (e.g. maybe by using a solar oven). But who knows, maybe raw wheat bran will be enough, if the air flow through the filter is handled sufficiently well.
@irismongolia , There may be workshops that limit themselves to PE and PP. As you are coming up with a fume management approach, if you could identify what is needed just for those two and then the step up to PS.
I wonder how much the PE PP environment is different from a candle making shop for example. I guess the higher temperatures generate more VOC but on the other hand the candle makers have open pots of hot wax.
On a side note:
I know it’s not ‘fumes’, but it is a harmfull matter stream into which you might have an insight.
Could the microplastics created by washing the plastic be filtered out of the waste water using an sand filtration system?
This sand, once spend, could then be used to make bricks…
@irismongolia – regarding the bran, I see that the composition includes some oil, which might help with VOC retention. Whether that would mean that rice bran would work better than wheat or rye bran, I don’t know.
@donald – the V4 washing project already includes sand bed filtration. So they will eventually need to do something with the contaminated sand. Anything that locks it up, along with the contaminants/microplastics, has to be better than landfill. I guess it could be mixed into conventional concrete – unless the microplastics just float to the surface… 😉
Hi, a simple design for a wet scrubber I read about a few years ago, sounds similar to the ones mentioned:
Large plastic barrel; 100mm plastic pipe fume inlet cut through the side at the bottom, with a 90degree bend pointing down on the inside at the mid point of the barrel; 100mm outlet pipe of your choice cut into the lid, with inline fan to draw air upwards through the barrel.
Hose with garden sprinkler atatchment fitted upside-down on inside of lid. Outlet for waste water at bottom to separate sand and charcoal filter.
Fill barrel almost full with ping-pong balls or other small plastic items. This creates a huge surface area for fume gasses to be collected or neutralized.
In the example I read, they used a Lye solution through the sprinkler, but this may not be appropriate for plastic fumes.
Hi @timberstar – there are lots of cheap ways to build wet scrubbers. For the chemicals we are talking about here, PVC drainpipe & other fittings available in a typical DIY store would work fine. Upcycled PE drums – as you mentioned – would be fine too.
For random packing, the traditional method is to use Raschig Rings. These could be made by chopping up lengths of pipe. (Way back, when I worked in the nuclear industry, we used borosilcate glass Raschig rings in off-gas scrubbers – just as mentioned in the wikipedia article).
I suspect ‘Lye’ (sodium hydroxide) could work for at least some of the VOCs, as they might create a “soap reaction” (although that might not work at the low temperatures involved). I guess it depends on how reactive the volatile hydrocarbons are.
I’ve even read one article that reckoned that the newly created soap can help to emulsify more VOCs than are involved in the original reaction. Hence, you could possibly use a soap solution from the start (safer than the hydroxide), and just rely on forming an emulsion, rather than a solution.
Here, I would like to share some tests we have done:
– Date: 11 July 2019
– Fan: Nederman1998, 2800-3400min-1, 200-240’, 380-420V 3~, 50Hz, 0.37kW, Serial number 521, Art N. 510521, 9840-00
– No pre-filter
Test 1: Attach in the sucking end of the centrifugal fan.
Result: very low flow at 130mm AC, 75mm AC, 37.5mm AC
Summary: don’t attach in the sucking end of fan.
Test 2: Attach in the blowing end of the centrifugal fan
Result: Activated carbon was moving too much when there was low amount of carbon, 75mm activated carbon pulling seemed to be enough, much better than Test 1. Could be suitable for extrusion but not enough for sheet press.
To make another filter that has another geometry of carbon bed shown in picture below.
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