US1871862A - Dehydrated and charred lump lignite and process of producing the same - Google Patents

Description

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Patented Aug; 16, 1932 UNITED- STATES EUGENE r. SCHOCH,

PATENT OFFICE OF' AUSTIN, TEXASi This invention relates to dehydrated and charred lump lignite and process ofproducing the same, and has for its object to pro- 1 vide a procedure which will be comparatively inexpensive to carry out, and more eflicient in practice than those heretofore proposed, while at the same tim producing a superior product. I

With these and other objects in view, the invention consists in the novel stepsand. combinations of steps constituting the process and in the novel dehydrated and charred lump lignite fuel constituting the product,

7 all as will be more fully hereinafter disclosed and particularly pointed out in the claims, 7

This invention constitutes an improvement over that disclosed in my U. S. Patent No.

- 1,574,174., dated Feb. 23, 1926, entitled Dehydrated lignite and process of producing same in that, among other things, 1t enables one not only to remove and substantially recover all the oil absorbed by the lignite during the dehydrating operation but also its natural content of volatile condensible hydrocarbons, and to produce still harder'lumps than by the prior inventions, which lumps are almost free from volatiles and hence may be fired like coke. anthracite coal, and similar fuels without the production of appreciable amounts of soot. or odor, all as will presently appear.

In order that the precise invention may be the more clearly understood it is said Fresh lignite as obtained in the mines frequently contains say from 25% to 35% of moisture, which it loses when heated at 110 C. to constant weight. Heated above this temperature, to 300 C. it gives up. still more moisture, and some carbon. dioxide; and heated still higher it begins to yield tar, and combustible gases; the deep-seated decomposition which it then undergoes in volves an exothermic reaction so that the heating power of the products when used as a fuel is less than that of the original material and the decomposition thus entails an actual loss of heating power.

en exposed tothe air, rawlignite gives Application filed August 9, 1929. Serial No.,384,812.

up a large fraction of its moisture and disintegrates so extensively as to become mostly, dust or fine particles. This same disintegration takes place in the fire when lignite is used as a fuel,,and' hence, unless special grates are provided, muchoi the lignitedrops unburned intothe ash pit. When heated in reto-rtsor dryers to expel the moisture, lignite disintegrates entirely, producing dust or very small fragments.

he large amount of water in ligniteand the fact that it disintegrates whenever it loses its water either. in storage 01' during combustion, naturally aifects its commercial value greatly, and'hence improved processes for making a. better form of fuel out of lige nite have been and arebeing actively sought, The only process known to me or proposed prior, to my invention for producing a better form of lump fuel from lignite consists in retorting the material and briquetting the resulting powder. This requires 10% or more of a first class asphalt, coal tar pitch, or other suitable carbonaceous binder, a mixingoperati'on to impregnatethepowder with the binder, and then briquetting the material With strongpresses. The diihculty of doing this economically and thehigh cost of the initial installation has retarded capitalists from entering into this business. It results that the proper machinery, as well; as the details of the whole procedure are today still in their experimental stages. I I' have discovered, on. the other hand, that When fresh lump lignite is heated in astill while immersed in thin petroleum oil, such as gas oil or engine distillate, it gives up its moisture without forming any appreciable amount of powder or small fragments. In fact, the original lumps remain intact, although they may have formed some cracks. Most of these cracks are very fine, while large parts ofthe pieces are entirely free from cracks. This invention however, is not limited to the use of the speciiic oil mentioned, for oils having a paraflin base, and oilsham ing an asphaltic base of all degrees of thickness can be used so long as they are capable of coating the lignite, but I prefer athin oil to a thick one for most purposes.

In carrying out this present improved process, I cover the lignite with a hydrocarbon oil, such as ordinary petroleum fuel oil, and warm the mixture gradually through such a range of temperature as will suffice to expel, in the form of steam, a large part or all of the moisture in the lignite. In U. S. Patents No. 1,508,617 and No. 1,57 L17 1 I have stated that the temperature of this mixture in the still could be raised to 250 C. in two hours, and this is true with most of the lignites found in Texas; but I have discovered since then that some lignites such as those found in and around North Dakota and Saskatchewan which contain a greater amount of moisturethan most of those found in Texas, must be heated up much more slowlye. g. about one-third as fast-since, otherwise, the rapid formation of the steam shat ters the lumps extensively into very small pieces. Even with this slow heating, some of the lumps of such lignites crack into fragments, with diameters less than 1 inch but most of the dehydrated material will be found to be in lump-s ranging from 1 inch to 5 inches in diameter, and there will be no dust or fines in the product obtained.

The essential part of this improvement over the processes described in the above patents is based upon my discovery that when such lumps of dehydrated lignite (drained free from all the oil that will readily drain off) are heated up slowly, in an oven or retort, to a suitable temperature range, (which range may vary slightly with lignites from different fields, and which temperature ranges so far have been found to be within 350 and 750 C.) the lumps remain essentially intact and attain a hardness and toughness not attained at temperatures below or above such optimum ranges. Their final consistency is intermedi ate between wood charcoal and coke from bituminous coal, and their hardness and toughness is much greater than that of any products produced by my previously patented methods.

To illustrate with a specific trial: Lignite obtained near Minot, North Dakota, was placed in a cylindrical vessel with a wirescreen bottom, and this was submerged in a small tank full of ordinary fuel oil. By means of a steamcoil the oil was warmed up gradually in six hours to a final tem perature of 165 (1, in which operation the lignite lost Sti of water. The container with the lignite was then lifted out of the oil, and placed in an iron retort in whichit was heated gradually in five hours until there was attained a temperature of 670 C. at the bottom of the retort (inside) and a temperature of 500 C. at the top of the lignite (18 inches above the bottom of the retort). The product thus obtained was free from dust or fines, and consisted mainly of lumps with diameters rangingfrom 1 to 5 inches, and only a small part with diameters ranging from 1 to inch.

Other samples of the same lignite were then dehydrated in the same way and to the same extent; and then they were heated in the retort to temperatures differing from those above,-some to lower, others to higher temperatures, and the products of all these trials were then subjected to the same amount of shaking or tumbling in a rotating cylindrical vessel; and it was found that the prodnot obtained by retorting this lignite to a bottom temperature of 670 C. and a top temperature of 500 C. broke up to a much smaller extent than the product heated to different temperatures. Similar optimum retorting temperatures were found with lignites from other sources.

These lumps are composed essentially of fixed carbon and ash, with only a negligible amount of volatiles. They have a heating power corresponding practically to their carbon content thus an 85% carbon product has a heating power slightly, above 12000 B. t. u. per lb.

Naturally, during the retorting operation, the volatile components are gradually expelled, to an extent depending upon the final temperature. By means of suitable condensers, I have recovered from these vapors essentially all of the fuel oil absorbed by the lumps during dehydration and also the socalled lignite tar. The latter is of a composition and consistency similar to fuel oil, and is even suitable for the dehydration op eration, hence the process produces an actual gain of fuel oil in contrast to the loss of fuel oil in previous .processes.

The above illustration shows another essential fact embodied in this improved process, namely, that by this combination of oil dehydration with subsequent retorting it is possible to obtain a product composed of relatively large lumps, free from dust, not obtained by anyother procedure now known. This is due first to the fact that oil dehydration yields a dehydrated product composed of larger lumps, free from dust, than any other known procedure, and second that, by proper mechanical handling, this product can be retorted without involving any appreciable mechanical disintegration of this large lump product. Such handling is illustrated in the example above: namely, the raw lignite is placed in a container with a wire-screen bottom, in a layer about 18 inches deep, and this container is first placed in the oil vat for dehydration and then transferred to the retort, and the material within is not moved or jarred or disturbed mechanically until it is in its final, hardest form. This exact procedure may not have to be used with some lignites which, in the intermediate stages of this process, are hard enough to withstand some mechanical disturbance without undergoing mechanical disintegration, but the fact is that this procedure can be used when necessary, as with North Dakota lignites, and thus the advantage gained by oil dehydration maintained through the rest of the process.

It is obvious that those skilled in the art may vary the foregoing procedure as well as the product produced thereby without departing from the spirit of the invention, and therefore I do not wish to be limited to the above disclosure except as may be required by the claims.

lVhat is claimed is 1. The process of treating lignite which comprises heating the same in contact with a hydrocarbon oil sutticiently to drive off the moisture present and to cause a portion of said oil to enter the lignite; removing the oil not absorbed by the material; and then heating the dehydrated material to a temperature between 350 and 750 C. by applying heat to the outside 01'": its container whereby there is expelled practically all the absorbed oil .plus a substantial portion of the volatile combustible components of the lignite.

2. The process of treating lignite which comprises coating the same with a hydrocarbon oil; heating the coated lignite to a temperature suificient to drive oil a substantial portion of the moisture present; removing any oil not absorbed by the lignite; and then heating the dehydrated material to a temperature between 350 and 750 C. by applying heat to the outside of its container whereby there is expelled practically all the absorbed oil plus a substantial portion of the volatile combustible components of the lignite.

3. The process of treating lignite which comprises coating the same in the form of lumps with a hydrocarbon oil; heating the coated lignite to a temperature sufiicient to drive oil" a substantial portion of the moisture present but insufficient to destroy its lumplike form; removing any oil not absorbed by the lignite; and removing substantially all the absorbed oil and lignite tar plus a large part oi the gasifiable constituents of lignite by applying heat to the outside of the container for the material at a temperature between 350 and 7 degrees centigrade.

4. The process of treating lignite which consists in coating lumps of the raw material with a hydrocarbon oil by immersing said lumps in said oil; heating the coated lumps to a temperature sutficient to dehydrate the same; draining off any oil not absorbed by said lumps; removing the surplus oil: and removing substantially all the absorbed oil and lignite tar plus a large part of the gasifiable constituents of lignite by further heating the material to a temperature between 350 and 750 degrees centigrade by application of heat to the outside of its container.

7 treatment in a retort at a temperature range of 350 to 750 C.

6. The process of treating lignite which consists in covering lumps of the raw material with a hydrocarbon oil; heating the covered lumps and oil to a temperature sutficient to drive 01? a substantial portion of the water present, and thus to dehydrate the lumps, the heating accomplished by raising the temperature slowly to avoid extensive disrup-' tion of the lumps; removing any oil not absorbed by the lignite; and heating the dehy drated material to a temperature between 350 and 7 50 C. by applying heat to the outside of its container, thus expeling not onl all volatile portions of the absorbed oil but also a substantial portion of volatile constituents of the lignite.

In testimony whereof I aifix my signature.

EUGENE P. SCHOCH.