US1860322A - Resistance element for hydrocarbon cracking processes - Google Patents

Description

May 1932- R, ER

RESISTANCE ELEMENT FOR HYDROCARBON CRACKING PROCESSES Filed Feb. 12, 1929 glwum M01,

Patented May 24, 1932 1,860,322

UNITED STATES PATENT OFFICE RUSSELL CARTER, OF WASHINGTON, DISTRICT OF COLUMBIA RESISTANCE ELEMENT FOR HYDROCABBON CRACKING PROCESSES Application filed February 12, 1929. Serial No. 339,462.

This invention relates to improvements in cracking temperature. In this connection, it the art of recovering hydrocarbon values, and has been proposed more or less successfully more particularly to the electrical recovery to employ a tubular casing surrounding the of hydrogeneous and carbonaceous values resistance unit comprising the electrical heatfrom hydrocarbonsources. ing unit to prevent direct contact and re- The primary object in view is the maxisulting injury, but such proposed manner of mum efliciency in heat conservation and (lisheating has not become popular because of tribution. uncompensated and preclusive heat losses.

A more detailed object is the preservation The present invention obviates the difiiculm of the resistance of the heating unit conties thus presented by providing for the imstantly at high efficiency while permitting mediate contact of the oil or other hydrocar direct contact of the hydrocarbon sources hon source with the electrical resistance unit, with such unit. and in greater detail includes 'l1 sthel1 at ng unitre iOuS attempts attaining and maintaining such efficiency to accomplish this result have not been suc- 15 while the hydrocarbon sources are approachcessful commercially because carbonization ing and at cracking temperature under the of oil has inevitably occurred along those influence of the heat. from the heating unit. S rf s of th h a ing n t in Conta t With A still further object in view is the provithe oil, and the resistance of the heatin unit sion for the readily detachable mounting of has thus been lowered to an extent ren ering 13 a heatin unit in such location as to receive the Unit iIlCH lflble 0f affordin i the re uisite h direct contact of the hydrocarbon sources eflt- The CarlJoIliZat On referred to haS 00- while providing etfectivc electrical contact u d I t m rely p rficially but 011 the with the h atin unit, surfaces within the interstices of the heating lVith these and other objects in view as nit, so as to form Within the heating unit will in part hereinafter become apparent and self a path of relatively low resistance for in part be stated the invention comprises the eleetrlc e both the art or process of treatment for prep h P e t iI e iOI1 obviates such difaration of electrical resistance units, the imficlllties by protecting the heating unit proved mode of recovering hydrocarbon g s a Condition enabling formation of values, and also the apparatus produced e h r occ uded or surface carbon Within the thereby and utilized th r i substance or interstices of the resistance unit. In the accompanying (lra\vings, To this end, the present invention includes Figure 1 is a fragmentary, sectional plan providing a resistance bar formed of carboof a structure embodying the features of the nduln crystals located in the shape of a bar 33 present invention. and caused to adhere either byrecrystalliza- Figure 2 is an enlarged, detailed similar tion or by the use of a binder. The'recrystalsection. lization is preferably effected by electrical Figure 3 is a transverse section taken on fusing. Care should be exercised to employ the plane indicated by line 3-3 of Figure such uniformity of pulverized carborundum,

"- 2, and looking in the direction indicated by the original 'cr vstals,that the recrystallization the arrows. will afford substantially uniform electrical In the recovery of hydrocarbon values resistance at all points throughout the length from such hydrocarbon sources as heavy oils, of the bar and not provide a spot or area H it is common practice to raise the oil to crackhaving a higher or lower resistance than any ing temperature, recover the escaping volaother part which would result in localization tiles. and condense the same for the producof intensified heat during action. The same tion of the lighter hydrocarbon fuels; and precaution must be taken When a binder is it has been heretofore proposed to move a employed, so that the resistance will be unir column of such fuel past an electrical heatform throughout the length of the barand ing unit to bring the fuel to the requisite in all parts thereof. The thus produced carborundum bar is preferably constructed to offer a resistance of approximately fifty ohms per cubic centimeter at a temperature of 25 Such a completed bar is'indicated at 1 in the accompanying drawings, and to mount such a bar effectively in circuit while detachably arranged within a stream. of fluid sources of hydrocarbon values may be successfully effected only with the exercise of care and precision, first, to insure electrical contact at the respective ends of the bar in a manner to avoid arcing, and, second, to so provide such contact as to enable ready assemblage and dismantling while preserving the bar out of electrical contact with the surrounding casing or tube during use. To this end, the details illustrated in the accompanying drawings are preferably utilized by me, including the providing of a metal cap 2 for each end of the bar which is preferably cemented to the bar by appropriate contact producing means of sufficiently lower re sistance than the bar to avoid injury to the cement during use. The cement is indicated at 3 and preferably consists of a moist paste applied within the cap 2 or on the end of the bar 1 just before the assemblage of the cap on the bar. The paste or cement 3 may be of Various acceptable substances, and I have found a putty-like consistency of a mixture of litharge, glycerine, and pulverized carbon (lamp black or the likeyrquite effective. Just before applying the cap 2 to the end of the bar 1, a sleeve 1 is extended through an aperture 5 in the cap 2, and the end of the sleeve 4 within the cap is burred or swaged out at 6 to form a retaining head. The terminal portion of sleeve 4 may be slit to facilitate the formation of the head 6. The cap 2 is preferably provided with internal threads v7, and when applied with the sleeve 4 in place and the paste 3 already applied, the cap and the bar 1 are rotated relative to each other so that partial screw threads are formed on the bar by the thread 7, and the cap is brought to an effectively seated posi tion with an especially successful electrical non-arcing contact between the sleeve 4 and the bar 1. I

In Figure 2 of the drawings is seen a somewhat idealized condition of the thread 7 and its formed threads in bar 1 with the contactimproving, low-resistance paste or cement 3, therebetween. While it is understood that such clearcut threaded connection as shown in Figure 2 is quite desirable, nevertheless it frequently happens that the threads on bar 1 will not be entirely perfect and may be far from perfect while, at the same time. affording rigid and effective anchorage and mechanical connection sufficiently sturdy for withstanding application and operation stresses and shock. The threads or partial threads on bar 1 will also add to the efficacy When the bar 1 has been thus completed with its terminals provided, it is ready to be conditioned to enable it to avoid resistancechanging carbonization during use. To obtain this result, the bar 1 and its terminals,

including caps 2 and sleeves 4;, are covered with a coating 20 of an especially provided coating material. Such coating material preferably consists of a mixture of fire clay, silica, and sodium silicate. The silica is preferably of a very fine gauge of comminuted particles, and the fire clay is preferably of the kind containing magnesium chloride. The proportions preferred, by weight, are from 1 to 3 per cent. sodium silicate, ap proximately 40 per cent. powdered fire clay, and from 57 per cent. to 59 per cent. finely comminuted silica. The object in mind is the production of a coating on the bar 1 that will have a particularly high modicum of stability under thermic variations. The silicate of sodium causes the formation on the finished coating of asubstantially impervious surface,

and the proportions of fire clay and silica are varied, according to the magnesium chloride content of the fire clay. less silica being used in the absence or reduction in the quantity of magnesium chloride present. The amount of silica employed is varied to provide the requisite balance for causing the finished coating to possess maximum stability at high temperatures and to resist bulk variations expansions and contractions) under the influence of heat variations. Also, in the preparation of the mixture, the fire clay is used in proportions to provide a close texture of the finished coating especially adapted to resist erosion and to insure interfillingaccessible interstices at or near the surface of the bar 1. The mixture is moistened with water and thoroughly triturated to reduce it to a creamy consistency so as to provide as nearly impervious and smooth coating as possible, and is then flowed onto the bar 1 and its connections 2 and 4. This may be done by a brush or by dipping the bar in a bath of the creamy mix ture. After the first application to the bar 1. the bar is dried in an oven, or otherwise slowly baked to avoid cracking or disruption of the superficial finished or smooth surface from ebullitions or escaping steam. As soon as the first application has been dried, a second coat of the same material is applied and the bar again baked: and it is preferable to then apply a third coat so that the finished coating is in fact made up of a series of layers. After the last layer has been applied and baked the whole bar and its coating are subjected to a temperature of approximately 2,000 F. This may be done in any conlit) '9 and venient manner, as, for example, hooking .the bar into the requisite electrical circuit to electrically raise the bar to the required temperature. This high temperature causes the material of the coating to penetrate the barsufi'iciently to effectively resist subsequent penetration thereof by carbon deposits in the oil stream. Since the regular use of the bar does not require any such high temperature as 2,000 F. the fixing of the coating by this temperature insures capacity of the completed article to withstand all the regular operating temperatures.

Also, it should be noted that the coating made up of the mixture set forth, or appropriate variations thereof, after having been subjected to the high temperature, will not crack or spall, and the selection of materials for the coating mixture is made with this in mind.

In applying the bar 1 as the unit of resistance in actual practice for cracking hydrocarbon oils, a series of tube sections 8 is provided, one for each bar 1, and the several tube sections 8 are arranged horizontally and coupled preferably in multiple by cross nipples 9, 9, connecting the end of one section 8 at one side to the end of the adjacent section 8 and connecting the opposite end of the same section 8 at the other side to the corresponding opposite end of the next section at that side, so that the through a section 8 will pass across the nipple move in the opposite direction through the next section 8 from the direction of its flow in the former, and thus throughout a. series of such sections sufficient in number to insure the requisite raising and maintenance of cracking temperature of the oil. As a matter-of convenience and facility of assemblage, each section 8 may consist of a length of pipe having at each end an ordinary T-fitting 10, one end of which engages the section 8, the shank of which receives the nipple 9, and the other end of which receives the threaded end 11 of a plug 12. As a matter of mechanical expediency and convenience, a bushing 13 may be interposed between the threaded end 11 of plug 12 and the engaged end of the T-fitting 10. The plug 12 is quite similar in mechanical construction to the ordinary spark plug employed in internal combustion engines except that the metallic casing indicated in the drawingsas 12 forms no part of the circuit, and there is, of course, provision against rather than provision for an arc or jump spark. -Within the plug 12 is arranged an insulator or porcelain 13 through which extends a contact rod 14. The porcelain 13 at its inner terminal portion is provided with a tubular enlargement 15. The rod 14 is provided with a head 16 at the outer end of the recess 15 to sealthe passageway through which the rod extends to the exterior so as stream of oil flowing distance beyond the inner end of the porcelain 13, and the section 8 is proportioned in length to the length of the respective bar 1 to lie. between the inner ends of the two contact rods 14 for the respective section 8 without contact therewith. However, the sleeves 4 are proportioned and located to snugly receive the inwardly extending end portions of rods 14 and to extend into the respective recesses 15. The contact betwen the sleeves 4 and inner terminal portions 14 is sufficiently close to provide effective electrical contact and also to provide sufficient mechanical connection and support to sustain the bar 1 in its proper relation in section 8.

Assemblage is effected by positioning the extended inner end portion of a rod 14 Withinthe sleeve 4 of a complete bar assemblage 1, and then inserting the said bar assemblage endwise through the section 8 until the plug 12 carrying the last-named rod 14 is threaded into the bushing 13. hen this has been done, the operator starts to insert a plug in the remaining open end of the opposite T- fitting 10, but in doing so first causes the inner end of the rod 14 to find its Way into the exposed end of the exposed sleeve 4. As soonv as this coupled connection is started, the operator may screw both plugs 12 to their finally seated position with assurance that the parts are properly assembled and will remain in proper relation during operation.

When the parts have been thus assembled, the outer ends of rods 14 are clamped or otherwise effectively hooked to the bus wires 18. 18, or other appropriate source of current, as byclamping nuts 19, 19, or otherwise as preferred.

It will be observed that the parts thus assembled are well adapted for easy and quick disassembling, replacement, and reassembling.

\Vhen all of the several units have been assembled as stated, electric current will be supplied to bars 1, and oil under the requisite pressure directed through sections 8 and their connections. A column of oil will thus move continuously along the several resistance bars 1 until raised to the cracking temperature and will then be discharged into the usual expansion chamber, not illustrated, for further treatment. The plant may be left on stream practically indefinitely, so far as the units 1 are concerned, and a very high degree of efficiency in heat conservation and distribution is obtained, because notwithstanding the direct contact of the oil with the several resistance bars 1 the said bars maintain their standard high resistance. Carbon particles which are precipitated dura ing cracking and mingled with the stream present invention.

will not find lodgment or effect a condition of the several resistance bars 1 "tending to reduce the resistance thereof or of any portion thereof.

Among the many objects of the present invention is included demonstrable thermal efficiency when the heating units are properly heat insulated, which efiiciency compares favorably with other forms of fuel heating of cracking oils, and at the same time by the present improved electrical apparatus the dangers attending heating of liquid hydrocarbon to high temperatures under high pressure with an open fire are eliminated.

While a specific embodiment is illustrated and specified herein in detail, it will be readily understood thatmodifications in detail may be made almost without limit while incorpo- .;\.rating and adhering to the substance of the For instance. though 'a -multip1e arrangement of tubing is illustrated, it is quite obvious that other arrangements may be employed while affording the advantages of the present invention. Subject to those limitations of available space and other controlling factors and specific requirements of a given or individual instance, other arrangements of details than those illustrated and described may well be utilized advantageously and in some instances preferably to the specific form set forth.

It will be observed that each bar 1 is proportioned in length with respect to the length of the respective section 8 such that the sleeves 4 extend across the greater part of the cross current of oil to or from the nipples 9, and, accordingly, provide ample area to avoid contact of any possible deposits of carbon at the places of change in the direction of flow of the oil What is claimed is 1. In apparatus for heating hydrocarbon material, an electrical resistance adapted for direct contact with hydrocarbon sources during heating and maintenance thereof to and at a relatively high temperature comprising a member of electrical resistance material and a carbon-deposit resisting coating on said member, of fire-clay, silica, and sodium silicate.

2. The art of producing an electrical heating unit adapted for remaining substantially constant in its resistance capacity while in direct contact with hydrocarbon sources during heating of said sources to cracking temperature comprising forming an electrical resistance member, and coating the member with a silicious covering and raising the member and covering to a temperature higher than the maximum temperature employed in the heating of the hydrocarbon sources.

8. The art of producing an electrical heating unit adapted for remaining substantially constant in its resistance capacity while in direct contact with hydrocarbon sources during heating of said sources to cracking temperature comprising forming a member of electrical resistance material, and coating the member with a mixture of fire-clay, silica, and sodium silicate sufliciently for preserving the member against deterioration in its resistance at cracking temperature.

4. The art of producing an electrical heating unit adapted for remaining substantially constant in its resistance capacity while in direct contact with hydrocarbon sourcesduring heating of said sources to cracking temperature comprising forming a bar of carbonaceous crystals, covering the bar with a carbon deposit-resisting coating, baking the coating on the bar at a temperature and rate sufficiently low and slow to avoid disruption and deformation of parts of the coating, and thereafter raising the temperature of the coating temporarily to a temperature exceeding the maximum temperature of the bar during regular use.

5. In the art of producing an electrical heating unit, the steps of flowing a creamy consistency of sodium silicate, fire-clay, and silica onto an electrical resistance bar, drying the coating on the bar while avoiding cracking or disruption thereof, applying a second coating on the first coating, and baking the bar and its coatings at a temperature in excess of cracking temperature of hydrocarbon materials.

In testimony whereof I alfix my signature.

RUSSELL CARTER.

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