The "Improved" Siemans Process for Producing Polysilicon for Solar Cells.
I keep hearing over and over and over, year after year, decade after decade, that the world will be saved from climate change by solar cells and batteries. None of this endless talk has prevented the atmospheric concentrations of the dangerous fossil fuel waste carbon dioxide from being over 420 ppm for the last 14 weeks of this year, 2022, less than 10 years after it first went over 400 ppm in 2013.
Of course, one cannot read any scientific journal without hearing about improving batteries, recycling them, and how wonderful the solar nirvana will be some day, "some day" having not come, is not here, and I think, won't come.
The environmental implications of this scheme have escaped much attention in the popular press, but increasingly one sees more and more questions about this topic in the scientific press.
I don't really follow the chemistry of solar cells all that much, since I find the issue to be of low value but occasionally I'll take a peek.
Tonight I came across this paper: A SiCl4-Assisted Roasting Approach for Recovering Spent LiCoO2 Cathode
Mengting Li, Beilei Zhang, Xin Qu, Muya Cai, Dongxu Liu, Fengyin Zhou, Hongwei Xie, Shuaibo Gao, and Huayi Yin
ACS Sustainable Chemistry & Engineering 2022 10 (26), 8305-8313.
It contains this text about the production of polysilicon, the most popular component of solar cells, citing an "improved" process:
Ten to fifteen tons of a highly toxic compound per ton of polysilicon, an "improvement..."
You don't say?
I imagine a few Bhopal type events in there with a leak, which were solar energy to become a significant form of energy - I think it won't - would increase in probability. This won't excite many scare stories over at the Union of Concerned "Scientists" of the ilk that the moron Ed Lyman produces daily about nuclear energy, without a single whimper about the hundreds of millions of deaths from air pollution that took place during his career in insipid whining, but I suspect over all, because of the extremely low energy to mass ratio of solar energy, it would become inevitable were the industry to matter, which it doesn't.
In order for the SiCl4 treatment of LiCoO2 cathodes to treat all of the SiCl4 waste generated, the masses of these products would need to be perfectly balanced, but that won't happen either.
Have a nice day tomorrow.
= new reply since forum marked as read
or reaction with Si back to HSiCl3, the most useful intermediate. Recycling within the Siemens process should keep the amount of SiCl4 down, with most of it ultimately being converted to silicon. I was under the impression this is basically the same way silicon for ICs is produced, so you'd sort of think they had this problem in hand after all this time, wouldn't you ?
SiCl4 is also used to produce optical fibers, so I wonder if there really is such a great need for means of "getting rid of" SiCl4.
Unfortunately, it appears that the whole process is run in batches (horrors!) so this may complicate logistics pretty badly.
