Recovery of sulphur dioxide from gas mixtures
It should, by now, go without our saying so that elemental, molecular Hydrogen, H2, is darned-handy stuff to have a little bit of.
As seen in:
WVU Hydrogenates Coal Tar | Research & Development; concerning: "Hydrogenation of Naphthalene and Coal Tar Distillate; West Virginia University; 2009; Abstract: The hydrogenation of naphthalene and coal-tar distillates ... in the presence of hydrogen ... for the hydrogenated product, tetralin ... (which can be used to produce) liquid fuel from solid coal";
and, in:
NASA Rocket Fuel from CO2 | Research & Development; wherein we're told that: "methane can be manufactured ... via the Sabatier process: Mix some carbon dioxide (CO2) with hydrogen (H), then heat the mixture to produce CH4 and H20 -- methane and water";
we can do some pretty interesting things with elemental Hydrogen.
And, in a recent report, as accessible via:
USDOE Makes Hydrogen by Using Sulfur Dioxide | Research & Development; concerning: "United States Patent 4,244,794 - Hydrogen Production by the Decomposition of Water; 1981; Assignee: The United States of America; Abstract: How to produce hydrogen from water was a problem addressed by this invention. The solution employs a combined electrolytical-thermochemical sulfuric acid process. Additionally, high purity sulfuric acid can be produced in the process. Water and SO2 react in (an) electrolyzer ... so that hydrogen is produced at the cathode and sulfuric acid is produced at the anode";
we learned that we can produce elemental Hydrogen in a very economical, reduced-energy way, along with a co-product of commercial value, by utilizing what might otherwise be seen as a troublesome pollutant that can sometime arise from our productive uses of Coal.
Since Sulfur Dioxide can be used to such good effect in the production of the desired Hydrogen, as in the process of "United States Patent 4,244,794"; and, since most folks have been propagandized into believing that it should, in any case, be removed from gases discharged into the atmosphere, we wanted, herein, to demonstrate that there are some effective and economical ways to recover that, as viewed especially in the context of USP 4,244,794, valuable raw material resource.
Comment follows relatively brief excerpts from the initial link in this dispatch to:
"United States Patent 2,031,802 - Recovery of Sulfur Dioxide from Gas Mixtures
Date: February, 1936
Inventor: Daniel Tyrer, England
Assignee: Imperial Chemical Industries Limited, a corporation of Great Britain
Abstract: This invention relates to processes of the kind in which gases containing sulphur dioxide ... are treated with a suitable solvent from which the sulphur dioxide is subsequently expelled by heating and/or reduction of pressure, the regenerated solvent being used again for dissolving further quantities of sulphur dioxide.
These processes are hereinafter referred to as regenerative absorption processes for the recovery of SO2.
It has previously been proposed to employ various non-aqueous solvents for this purpose, but such solvents are expensive in use and losses are difficult to avoid. It has also been proposed to use water as a solvent, but in this case the solubility is too small for economic working and large volumes of water have to be circulated and heated.
I have now found that excellent solvents for carrying out the above process are afforded by aqueous solutions containing one or more salts of substantially non-volatile acids ... .
Suitable non-volatile acids for the purpose of this invention are lactic acid, glycollic acid (and) citric acid ... .
(When) the absorption is carried out in an ordinary tower scrubber, it is preferable to choose a salt of a metal which is soluble and forms soluble sulphites and bisulphites.
Claims: A process for the regenerative absorption of sulphur dioxide which includes the step of washing an SO2-containing gas with an aqueous solution containing a soluble mono-basic phosphate and sodium citrate."
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To be clear:
Sodium Citrate is made from Citric Acid. Our understanding from available references is that Citric Acid is a commodity chemical of nearly-vast utility; and, huge amounts of it are manufactured around the world.
China is the largest single source of Citric Acid, and, although, as a bulk commodity, it's relatively cheap, the price does fluctuate.
Our further understanding is that there is as yet no commercially-viable route to the fully-synthetic manufacture of Citric Acid. Most of it seems to be industrially-produced by the action of specific microbes on organic wastes, primarily crop residues - which suggests an element of Carbon-recycling and sustainability.
However, it is nonetheless a widely-available industrial commodity, and arrangements could certainly be made to make more of it and keep prices down, should rising demand, perhaps for SO2 recovery, dictate.
The same generalizations are true of the chemicals which could be labeled as "a soluble mono-basic phosphate". They have broad, bulk-commodity applications in such things as fertilizers and detergents, and we could make a bunch more of them, cheaply, if the need arose.
And, those chemicals could thus lead to the efficient recovery and recycling of a supposed Coal industry pollutant, through the process herein of our subject "United States Patent 2,031,802", which supposed pollutant could then serve in a process such as that disclosed, as referenced above, in "United States Patent 4,244,794", to make economical Hydrogen from Water; and, which Hydrogen could then be used in the Sabatier process, as being further developed by NASA, to make Methane out of Carbon Dioxide; or, as in the "West Virginia" process, as cited above, to help make "liquid fuel from solid coal".