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@s2019 sorry for late reply! Yeah you can compare my results to the US regulation I mentioned in my first post. But there are many regulations present and it was quite hard to discern which one is of use. Right now, I am writing the download kit information, so you can read from download kit. It may be more elaborate 🙂
@s2019 Yes you can use this regulation: The maximum 3-hour concentration of hydrocarbon content is 0.24 ppm, not to be exceeded for more than a year .
And yes we should post the summary here on the forum. I am also working on the download kit information atm. Progress could be slow because I am doing it part time as I am not at Precious Plastic V4 office anymore. But I will most definitely post a summary here on this thread 🙂
@s2019 unfortunately my time at Precious Plastic V4 has ended. However you can check out a document of my fume tests with the PID detector I hope it is of use: https://docs.google.com/document/d/1Da_O60i6RFD4qfRhTQ7ApYcHpC08p_HAb3fRNehLI3c/edit
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.
@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 🙂
@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.
@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.
From my research about the fumes, mostly PS has the most issues concerning with toxic fume production, because melting can create styrene and similar aromatic compounds in the air. PE and PP creates much less fume when heated because it is essentially a refined wax. Fortunately, we have some masks available commercially which is 3M ABEK filter respirator which filters organic vapours above 65C, inorganic gases, acid gases and ammonia. These filters need to be changed after 40 hours of use (around 15USD for a pair).
Hi, I’m Suvda from Mongolia, studying my MSc Chemical Engineering in Budapest. I will be helping out in V4 in the summer and a little bit remotely from here as well.
I have found some interesting research papers on solvents oriented to PE and PP. The papers are usually about dissolving the polymers completely and the dissolving processes usually required heated solvents at high temperatures. I believe we can use lower temperatures than the required dissolution temperatures for our use of joining, welding, melting and finishing.
Dissolution of polymers in solvents SUMMARY:
1. LDPE can be dissolved at 85C in Toluene, xylene and trichloroethylene (5ml toluene dissolved 0.3g LDPE in 2.5 min, xylene and trichloroethylene dissolved it in 3 min) (Source #1)
2. HDPE can be dissolved above 130C in Decaline with 99% purity (Source #2). PE can be dissolved in 1,2,4-trichlorobenzene+0.015% Butylated Hydroxytoluene at 160C (Source #3).
3. PP can be dissolved at above 165C in Decaline with 99% purity (Source #2). PP can be dissolved in 1,2,4-trichlorobenzene+0.015% Butylated Hydroxytoluene at 160C (Source #3).
Source #1: Study on Dissolution of Low Density Polyethylene (LDPE)
This paper was about solving the problem of pipelines clogged by molten plastic feed during pyrolysis process. They experimented with LDPE powder, pellet and sheet forms, but the difference between their solubility was quite low. The solvents needed to heated to 85C except for the trichloroethylene (due to its boiling point of 86.7C), it was heated to 80C to avoid boiling of solvent.
Solvents experimented were benzene (banned in EU), toluene, chlorobenzene, isooctane, xylene and trichloroethylene. They used 5ml of each solvent and 0.3g of LDPE powder (This amount is only for experiment of dissolution rather than the required amount). When LDPE powders dissolve in solvents they swell and change their color to colorless, before they dissolve into solution.
The result of the paper: Toluene (2.5 min needed to dissolve 0.3g LDPE), xylene (3 min) and trichloroethylene (3 min) were more preferable to be used, as they have similar performance to benzene, as well as less hazardous compared to benzene.
This paper was also interesting, because it mentioned about dissolution/precipitation method, which is dissolving and precipitating the plastic with high recovery and purity. The method can be helpful to separate mixed plastic waste according to their difference in solubility and different heating temperature. Also, in the pyrolysis process, the dissolved LDPE solution can be directly cracked without precipitating it.
Source #2: Preparation of Ultra Thin PS, PP and PE Films on Si Substrate Using Spin Coating Technology
The polymers used in this study were PS, PE and PP were supplied in pellet form. Because of the amorphous structure of polystyrene, dissolving PS is relatively easy. Toluene anhydrous 99.8 % (Sigma Aldrich) was chosen as a solvent for polystyrene. Heating of the PS solution in toluene to 50 °C for 2 hours was sufficient to completely dissolve the polymer.
Polyethylene and polypropylene have high crystallinity degree structures, which means that to ensure dissolving of polymer pellets in solvent, the solution should be heated above the polymer melting temperature. These are 120-130 °C for PE and 160-165 °C for PP. To ensure fast polymer dissolving, the solvent must have a boiling point that is higher or comparable with the above mentioned temperatures and so decaline, anhydrous 99 % purity (Sigma Aldrich, mixture of cis and trans) was used (boiling point range of 189-191 °C).
Solutions of PE and PP in tetrahydrofuran (THF) and toluene are possible but require more than 6 hours to be obtained. When decaline was used as a solvent and the temperature was above 160 °C, complete polymer dissolving in both PE and PP cases were obtained in less than 3 hours. After the solution has been obtained, great care must be taken with its handling.
Source #3: Polymer-to-Solvent Reference Table
This table is for the Gel Permeation Chromatography where they use polymers in their appropriate solvent. From the tables, PS can be dissolved in Tetrahydrofuran (THF) at 25C, PP and PE can be dissolved in 1,2,4-trichlorobenzene+0.015% Butylated Hydroxytoluene at 160C. This method can be better than the Source #2 method since the PE, PP can be dissolved at low T.
Safety: Before working with any substance we need to read the MSDS of the substance. In the solvents case we need powerful fume extractor, goggles, sleeve length lab gloves and masks.
I will add on this forum topic whenever I have something substantial to share 🙂