US512348A - Process of refining asphalt - Google Patents

Description

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s. WILKINSON. PROCESS or REFINING ASIVIHALT; No. 512,348.?- Patented Jan. 9, 1894.

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PROCESS OF REPINING ASPHALT. No. 512,348. Patented Jan. 9, 1894.

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'W. WILKINSON; PROUESS 0P REFINING ASPHALT.

No. 512,348. Patented Jan. 9, 1894. r

WITNESSES: I INYENTOR UNITED STATES PATEN 'WALTER S. WILKINSON, OF BALTIMORE, MARYLAND.

PROCESS OF REFINING ASPHALT.

SPECIFICATION forming part of Letters Patent No. 512,348, dated January 9, 1894.

Application filed June 6, 1893. Serial No. 476,726. (No specimens.)

To aZZ whom it may concern:

Be it known that I, WALTER S. WILKINSON, a citizen of the United States, residing in the city of Baltimore and State of Maryland, have invented a new and useful Process of Refining Asphalt,of which the following is a specification.

My invention is applicable to all natural asphalts, but particularly to the asphalt obtained from the so-called Pitch Lake of the Island of Trinidad.

In order that my invention may be both understood and distinguished from operations heretofore practiced with other hydro-carbons, it is necessary to explain the composition of naturalasphalt, the nature and character of the operations heretofore resorted to for refining it, and the conditions which exist to be complied with by the operation to which I resort. Asphalt in its crude state is a combination composed essentially of hydrocarbon or bitumen, earthy matter, Water, and a small percentage of organic matter. These materials as existent in nature are so intimately mixed mechanically, and the water and hydro-carbon so thoroughly combined, that the crude Trinidad lake asphalt has been denominated an emulsion. Lake pitch contains, in addition to a small percentage of organic and non-bituminous matter, about twenty-six to twenty-eight per cent. of water, about thirty-eight to forty-two per cent. of hydrocarbon or bitumen, and about twenty-six to twenty-eight per cent. of inorganic or earthy matter. The average composition of lake (Trinidad) asphalt, according to the analysis of Professor Clifford Richardson, is as follows:

Water 27.85 Inorganic 26.38 Organic, not bitumen 7.63 Bitumen .1 38.14.

The mineral matter is chiefi silica, alumina,

oxide of iron, and lime; and the water is thermal water which contains a large percentage of salts of sodium, &;c.

Refining, as applied to asphalt, is the process of eliminating, or driving off from it all of its water, and a small percentage of its lighter oils, which are detrimental to its employrnent as a paving cement. To effect refining, by processes heretofore known, the' mass must be heated to, and maintained at, a temperature ranging from 340 to 380 Fahrenheit, until the emulsion has been broken down and all the water evaporated. A higher temperature than 380 is injurious to the asphalt, as it drives off oils which are essential to its toughness and plasticity, and it is more and more seriously impaired as the temperature to which it is subjected is increased, and

the period during which it is exposed is prolonged. Upon the other hand, asphalt subjected for a long time to heat of much less temperature than 380, is also injured in the same way by the driving off of some of the valuable oils. These injurious conditions have, however, been inseparable from the methods heretofore employed. Under existing processes, asphalt has been refined in a large vat or kettle, adapted to contain from twenty-five to thirty tons of the crude material, and suspended or supported above a fire, the heat from which passes along its bottom and through a central longitudinally-extend ing axial flue to a stack. To lessen the danger of injuring the asphalt by over heating, the bottom of this vat or kettle has usually been placed about seven feet above the fire. To maintain the asphalt agitated during the heating operation, revolving paddles have been mounted within the tank, and jets of compressed air have also been employed. Under this practice it has been possible to refine about twenty-five tons of crude asphalt in about sixty hours. The methods referred to have been defective in that they have been Wastefulof heat, the hot gases of combustion in great measure escaping up the stack, without imparting their heat to the stubborn mass of asphalt; and it has also proved injuriousto the product,the bottom of the kettle having become very hot by direct radiation from the fire, and the flue having been exposed to the heat from the gases of combustion,-the asphalt coming in contact both with the overheated bottom, and. with the surface of the flue, having either been too much dried out, a large percentage of the oils being driven ofi, or having even been burned. These pro cesses, moreover, are wasteful of asphalt, because aconsiderable percentage of the asphalt settles, adheres to, and is coked upon the bottom of thekettle,becoming not onlyatotal loss, but also entailing expense in its removal. This coke, in fact, represents a quantity of asphalt destroyed much greater than its own weight or bulk. They are, finally, destructive of the plant, because the fire heat is applied continuously to the iron of the kettle, which has no water in contact with it to carry olf the heat and thereby save the metal. These various defects have been partially remedied by increasing the number and length of the fines, and passing the gases of combustion several times through the mass of asphalt, and also by protecting the bottom of the vat from direct fire by means of fire brick. Although, by these means, greater economy in fuel has been secured, yet the time required for the refining has been greatly increased, so that tanks containing from fifty to one hundred tons of crude asphalt, have required constant care for from five to six days, with the result even then that a portion of the asphalt has been destroyed and other portions more less injured by direct contact with the overheated surfaces. Careless firing has also produced serious loss and damage, and the long time required for the operation has been a serious objection.

The problem of successfully preparing from crude asphalt material for use as a basis for paving cement and for other purposes, may be stated as follows: Given a mass of material, which is a very poor conductor of heat, and which is therefore a difficult substance through which to diffuse heat,which can be stirred or agitated only with great difficulty,-which contains a large percentage of water, which must be eliminated, and when the mass has become liquid, about twentysix per cent. of inorganic matter in suspension which it is desirable to retain evenly distributed throughout the mass;Qucere.=-In what manner, with what least amount of fuel, and in what shortest possible time,-may this water be driven off, and the inorganic matter retained in suspension, without injury to the desiccated mass by excessive heat? To satisfy the foregoing conditions, a greater area of heating surface to a given quantity of asphalt than has heretofore been used is, first of all, required. This greater area I have dis covered can be readily provided by the use of gangsof steam pipes, passing through thebod y of asphalt to be refined, contained, together with the pipes, in an open vessel which may be of any desired dimensions, the number of gangs and the consequent heating surfaces being proportionately increased. The steam employed is generated in a boiler of suitable form, preferably conducted through jacketed pipes to the heating gangs, and, after passing through them and in its passage radiating and distributing its heat thoroughly and evenly through the mass of asphalt, is condensed and returned to the boiler in the form of water. During and throughout this operation the mass of asphalt is subjected to agitation conveniently byjets of compressed air discharged at the bottom of the mass, or by mechanical or other suitable means. My operation brings almost every portion of the asphalt into contact with the heated surfaces of the steam pipes, thereby breaking down the emulsion, setting free and producing a rapid evaporation of the water from the asphalt, and at the same time keeping the mass so mixed as to prevent the inorganic matter from settling, and carrying down with it, valuable asphalt. The safety valve of the boiler being set for a pressure which will afiord the desired temperature, the surfaces of the steam pipes are never heated to a temperature which will injure asphalt in the time required to prepare it for use by this process, and therefore no coke is formed. By the use of steam and the employment of a sufficient amount of heating surface, the time required to refine at any one time a given amount of asphalt, can be reduced to not over twelve hours.

In the accompanyingdrawings I have illustrated a type of apparatus adapted to conveniently carry into practice the process described and in which alone my invention resides.

Of these drawings, Figure l is a view in side elevation of the entire apparatus. Fig. 2 is a transverse,.vertical, sectional, side elevation, through the tank or kettle represented in Fig. 1, section being supposed in the plane of the dotted line x-x of Fig. 3. Fig. 3 is a longitudinal view otherwise similar to Fig. 2, of the said tank, section being supposed in the plane of the dotted line yy of Fig. 2; and Fig. 4 is a fragmentary or perspective detail of one of the perforated injection pipes and its feeder.

Referring to the drawings,-A represents a boiler of any preferred character employed for the generation of, preferably, high pressure steam, and B a furnace operative in connection with said boiler.

O is an iron tank or kettle within which the crude asphalt is subjected to the action of the steam from the boiler. This tank may be of any preferred construction, but is conveniently of that represented in Figs. 2 and 3, in which it is assumed to be incased in brick, the walls being formed with an inclosed air space 0, and the upper opening of the tank (for it is necessarily an open tank) being conveniently surmounted and inclosed by a splash board 0*. The tank as an entirety is supported in any preferred manner, conveniently upon framework or upon brickwork sueh as D, Fig. 1.

E are gangs of steam pipes of any preferred character and arrangement, placed within the tank, and disposed therein at such preferred distances apart as to admit of the introduction between and among them of the crude asphalt. Through these pipes steam is caused to circulate, they being preferably continuously supplied with high pressure steam from the boiler A, conveniently through a steam conduit or, which leads from said boiler and is conveniently in connection with the said various gangs of transverse feed pipes e, or other preferred connection. All of the gangs connect preferably through transverse discharge pipes e with an outlet pipe 6 for the water of condensation, which conveniently leads to a chamber F from which the condensed water mayby means of a pump G, be returned to the boiler through the return pipe g. Other means for returning this water may, of course, be resorted to.

H is a series of suitably perforated injection pipes located in the bottom of the tank, preferably below the steam gangs, and in communication through a series of feeders h with an air supply pipe I, conveniently leading from a pumping air supply cylinder J, being shown as a member of the blowing engine K, which together with the force pump G is conveniently supplied through the pipe is with low pressure steam from a boiler, which, for clearness, is not represented.

It will be observed from a comparison of Fig. 1 with Figs. 2 and 3 that the arrangement of the various pipes in the region where they lead into the tank is not the same in all the figures; the difference, however, is one of mere detail,and resorted to for clearer general illustration.

The gangs of steam pipes represented are typical merely of an arrangement of steam pipes within the tank through which steam may be caused to circulate, and among or around which the lumps of crude asphalt are introduced and subjected to the heating action of the circulating steam. The perforated injection pipes and their feeders are also typical merely of a convenient agitating device through the instrumentality of which the mass of asphalt may be agitated during the period of its subjection to the heating action of the steam.

I make no claim upon the apparatus, as such, and the details of the apparatus shown may be varied at the will of the constructor.

Having now described the process in which my invention resides, and an apparatus conveniently adapted to effectuate it, it is proper for me to add, that, although apparatus of kindredcharacter has been employed in operations of rendering and refining oilsffats, and similar substances, yet my process is confined to the treatment of natural asphalt, a substance in its nature and uses dissimilar to any substance heretofore treated by kindred operations, and, that as applied to asphalt the purpose of my treatment, the effect of it upon the material, and the resulting product, are all essentially new in the art, and the result of continued and protracted experiments. In a word, natural asphalt being a, so to speak, mechanically produced emulsion composite of thermal water containing a large percentage of various salts, and of various hydro-carbons, earthy matter, and non-bituminous carbonaceous organic matter,-the methods heretofore universally adopted for refining or preparing it for use as a base for asphaltic paving cements have been by fire applied, either directly or through partially protecting surfaces of fire brick, to the vessel containing it, and the material thereby invariably produced has been one inferior in all essential qualities requisite for every purpose to which it is put, to that produced by my process.

Having thus described my invention, I claim and desire to secure by Letters Patent The process of refining natural asphalt, which consists in subjecting it in anopen tank orvessel, in its crude state and under agitation, to the action of steam heat disseminated throughout it, substantially as and for the purposes set forth.

In testimony that I claim the foregoing as my. invention I have hereunto signed my name this 31st day of May, A. D. 1893.

WALTER S. WILKINSON.

In presence of- F. NORMAN DIXON, JAMES LOUGHRAN.

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