I am asking how one can chemically convert small pieces of coal into larger ones.
Good question - I think there is a great market for such technology in coal mining.
You may be well aware, in coal mining, one is left with large chunks of coal, as well as many fines. The lower CV fines are washed, but sometimes blended with better quality coal to achieve a specific CV coal. The problem with blending is that the blended coal is not always compatible with the current arrangement of coal fired plants, as the fines tends to clog the hoppers and pulverizing mills and requires mechanical intervention.
The commercial process I know of, which is closest, is the sintering of coal and iron ore for the direct reduction of iron, but it's a thermal process - the problem of course, the coal is changed to coke in the process. (this is well described in the Iron and steel processing literature)
To answer your question, I think one will have to get a good mixture of course- and fine coal (to take up most of the voids; grading and mixing) and bond it with a little organic based adhesive - perhaps something like crude oil, pitch or tar, which may require moderate pressure- and heat, to complete the bonding.
If I have not just redesigned the wheel, I think this may well be a great research topic, with commercial application - have fun !
In extraction experiments we've seen very fine coal powder to coagulate under solvent pressure and elevated temperatures. We use a variety of solvents to successively extract leechables from german lignite, including water... My guess is, that hydrophobic "pressure" induced by the water extraction process at 100 bar and 150°C forces to the particles to rebond to a certain degree.
Hi, using the term coagulate to me suggests you want to treat coal 'fines'. If this is the case and there are run of mine and sufficient quantities - froth flotation is the technique you should look at.
Thanks to all answers, but I want to ask about the froth flotation technique
Briquetting techniques and processes will provide information about binders. The problem is cost; fines are a continuing problem.
Flotation is a standard coal preparation technique.
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