Cryogenic CO2 could end rail delays caused by leaves on the line
sheffield.ac.uk
sheffield.ac.uk
That is most likely not the reason it is cleaner as releasing captured carbon dioxide back into the atmosphere is kind of polluting isn’t it! I think it’s supposedly cleaner because the alternatives like blasting the tracks with additives and sand is worse but they don’t really say why.
And they mention it's better than the sand approach since they're not leaving a contaminate around afterwards, since the CO2 will just sublimate back into gas, both which improves the cleaning and makes it more consistent when done repeatedly.
The movie is still borderline sales-pitch, so I'd take it with a grain of salt, but it adds some detail.
By any chance, does money change hands? "Carbon credits"?
Guess what! I'll start a brewery and brew billions of tons of CO2 unless you pay me!
The carbon credit industry is a scam, and it does not actually affect the CO2 concentration in the atmosphere.
Cap and trade worked very well for CFCs. In your example, why doesn't the brewery need to pay a tax for the CO2 released both in manufacture and as part of product-use?
They needed something solid that can sublimate and be relatively safe. Media blasting with CO2 is really a super common thing everywhere in industry. I could drive over to Grainger and buy a CO2 blasting machine today.
Far too many people worry about the 100lbs of CO2 emitted because of rail cleaning while ignoring the fact that a diesel train is spewing (literally) tons of CO2 in the atmosphere. And the trains are one of the best options for low carbon shipping!
Applying this to rail seems like a great idea, since the weight and mass of the apparatus is not really a problem in that situation.
Cool stuff!
The jets may also mix in some chemical solution to help with adhesion but I don't know.
Explanation of the problem and the solutions: https://www.youtube.com/watch?v=zL21bWhNsv0
https://new.mta.info/LIRR-Industry-Leading-Leaf-Fighting-Tec...
https://getpocket.com/explore/item/choo-choo-pew-pew-how-a-n...
The use is novel, the tech is decades old.
LN2 might also then be too cold and affect the temper of the steel, or it might evaporate too quickly, requiring a lot more mass than co2. Or maybe it could be a perfectly fine alternative but the co2 pellet systems have market advantage.
Sand density: 1520-1680 kg/m^3
LN2: 806 kg/m^3
CO2 is just disappearing sand as far as these systems are concerned. They probably use the same equipment that they use for sand.
Plus LN2 is way colder and harder to handle and also it's a liquid.
Nitrogen will also kill you silently, while you will definitely know when CO2 levels are getting high (because it really really hurts).
I suspect they're also taking advantage of the fact that dry ice is solid, so they're effectively sand-blasting the track (rather than merely pressure-washing it), but they're using sand that helpfully sublimates into the atmosphere without leaving residue (or poisoning anyone).
I imagine blasting sand or chemicals has the downside of leaving residue that can build up, meaning regular cleanup is required, and care required to use enough but not too much, with this you can spray as much as you can afford to buy/carry on the train and you don't have to worry about over-doing it.
Dry ice blasting is already a thing, so I guess they just realised it was a particularly promising technology for this application.
I really really don't understand how leaves are an issue with trains.
Anyone know why they can't just use a cowcatcher like device?
If a simple mechanical solution worked they'd have implemented it a century ago.
[1] https://www.railengineer.co.uk/cleaning-the-rail-head/
[2] Non-native speaker, not sure if that is the proper term.
And that's a fine term for it.
Which makes me wonder why no one bothered to try something like that, are pressure washers common in the UK? Mine is hardly the highest PSI, and it frequently needs to be turned down because at that pressure it can actually etch soft concrete. And at 2.5GPM its not using a lot of water either.
There are existing solutions for this, of course. For example, the Dutch railways deploy a mush of sand, potato fibers and iron particles on top of the mush to give trains the necessary grip when they brake while they take the caked on goop with them at the same time. This solution can be applied by separate trains running at relatively high speeds.
This approach, like the novel CO2 approach, has advantages and disadvantages, but it should be clear that "just attach a fan and a brush to the front" isn't going to cut it. You'd need a hell of a fan to blow sticky mush off the tracks at 60-65mph (average UK train speeds).
That sounds like Sandite, which is definitively in use on the UK rail network. But I think the cleaning effect of that is still relatively limited, and the adhesion improvement only lasts a certain number of trains, after which the material needs to be re-applied again to the track.
Or would the trains have just stopped at their normal stop instead waiting for leaves to be cleared?
The lasers were never meant to heat the rails. Heating a shiny metal is very difficult. The leaf-cleaning laser system works specifically because it doesn't heat the metal. It bounces off the metal surface, heating only the non-shiny gunk on the rail.
Rail corridors are some of the last vestiges of semi-wild connected space in the UK, since they stopped spraying herbicide. This in turn was responsible for the extent of what londoners call "fire weed" into northern britain -Rose Bay Willowherb: it was a southern plant, carried by wind borne dispersal of seed due to trains passing along the lines.
This sounds unbelievable to me. Has there really never been a single occurrence of a passenger train clearing the tracks in history?
I'm not sure if it was ever used while the train was also moving passengers, but I'm aware of at least a special cleaning wagon nicknamed "Schrubbi" operated by the S-Bahn Hamburg[1]. It's a repurposed passenger wagon that contains a large water tank and uses pressurized water to clean tracks. In theory you could add that to a regular passenger train, subject to some speed limits (like the tech in the article), but in practice I don't know whether that ever happened.
Because of the speed limit required to get decent results, I have doubts any such tech will be used outside of special cleaning trains...
Also I suppose there's snow plows on passenger trains, though nowadays that's probably also (mainly) done by specialized trains. Does this[2] count as cleaning?
[1]: https://s-bahn.hamburg/magazin/s-bahn/betrieb-und-technik/de...
There's no point running it through long tunnels, but it does need to clean junctions and so on in an order that is unlikely to follow a passenger train's path.