US1676202A - Circulatory cracking still and pump therefor - Google Patents

Description

r Y 1,676,202.. E, w. [$0M ETAL. j CIRCULATORY CRACKING STILL AND PUMP THERE F OB Julyf:3,"1928.

Fil y" 1 2 sheeiis-sheet l I 5 July, 3, 1928. 1,676,202

,E.w. ISOM E'i'AL QIRCULATQRY CRACKING STILL AND PUMP THEREFOR Fil May 12.. 1921 2 sneak-sh et 2 Jar/677557 CORPORATION OF MAINE.

TUES PATENT o' FicE.

CIBCULATORY cnacxme s'rrnr'. um rumr rnnnnron.

Application filed May 12,

Our invention relates more particularly to circulatory pressure stills for cracking petroleum and other heavy hydrocarbons." An example 'of such form of still is to be 6 seen in Patent N 0. 1,285,200 granted N ovember 19, 1918, to Sinclair Refining Company. On reference to the drawing of that application it will be seen that the bulk of the oil being procexed is contained in a tank exlo'terior to the furnace by which the heat is supplied thereto and circulated from said tank through a series of heating tubes in the furnace and back to the tank. For the most efiicient operation of a still of this ,15 character it is necessary that the oil being treated be quite rapidly circulated and preferably some positive liquid forcing means such as a pump is employed. As the temperature of the oil is far above its ignition point and it is'commonly under a pressure of 4 or 5 atmospheres or even higher, the matter of preventing leakage of the hot inflammable oil presents a serious problem particularly in view of the wide range of temperatures to which the liquid forcing means is subjected.

It is the object of the present invention to provide in such a circulatory pressure still a pump which will satisfactorilymeet the conditions referred to above and properly handle the circulation of the hot oil without leakage.

In the accompanying drawings we have shown and in the following specification de- 36 scribed a cracking still with a preferred form of pump embodying our invention. It is to be understood, however, that the specific disclosure is for the purpose of exemplification.

only and that the scope of the invention is 40 defined in the following claims in which we have endeavored to distinguish it from the prior art so faras known to us without however relinquishing or abandoning any portion or feature thereof. 46 In the drawings accompanying and forming part of this application Fig. 1 is a vertical section of the preferred form of the pump of the invention on the line 11 of Fig. 2; Fig. 2 a transverse section thereof 50 on plane of line 2-2 of Fig. 1 looking in the direction of the, arrow; Fig. 3 a similar section on the line 33 of Fig. 1 looking 1921. Serial No. 469,036.

the arrows; Fig. 4 an of pumps whether of the rotary or reciproeating type. In the particular form of pump shown in the drawings the pump body comprises a body casting 5 containing the pump chamber 6, the inlet connection 9 and the outlet connection 10. Said piston chamber is closed at its ends by the'end castings 11 and 12. The pump chamber is oblong as shown in Fig. 2 and formed with semi-cylindrical ends, and the istons .7 and 8 are arranged to rotatetherem, in such close relation with each other and with the walls of the body casting as to constantly form a seal be" tween the inlet and the outlet sides respectively of the pump chamber. The pistons turn oppositely in the directions indicated by the arrows, each piston at each half r'evolution shutting off a charge of liquid received from the inlet side of the pump be tween the body of said piston and the corresponding end of the housing and transferrin it to the outlet side of the latter.

The s afts 15 and 16 onkwhich the pistons are mounted are journalled in end castings 11 and 12 and provided with gears 13 and 14 respectively, which intermesh so that they are driven in unison. One of said shafts extends beyond the casing at 17 and is coupled with any suitable source of power to drive the pump. As thus far described the pump chosen for exemplification of the invention and its operation are well known, the pump being in common use.

Our invention relates to a circulatory pressure crackin bination a circu ating pump particularly adapted for handling hot oil under pressure undergoing cracking, for preventing the escape of the hot oil about the driving shaft and for lubricating the moving parts. As the pump is necessarily subjected to exstill including in com-.

. 25, to which the treme variations in temperature the bearings of the shafts must be quite free to avoid binding when heated to the maximum temperature employed and this further complicates the problem. In the apparatus of our invention, the shafts of the circulating pump are fitted loosely in their bearings and provision is made to force relatively cool oil, for example, oil at ordinary temperature, preferably of the .kind being processed, through the bearings against the pressure of the hot oil within the pump chamber, thus not only preventing the escape of the hot oil, but thoroughly lubricating theb'earingsa in the present instance being shown as made the circulating and preventing them from becoming unduly heated. a I

In the form of circulating pump construction which we have chosen for exemplification, the end castings 11 and 12 are similar and therefore a description of one will suffice for both. Each of these end castings comprises a main body portion 18,. see dotted lines Fig. 1, of suitable dimensions toprovide for the bearings of the shafts 15 and 16 which are formed therein, and end flanges 19 and 20 arranged at the respective ends of the body portion of the casting and connect.- ed by webs 21 certain of which are shown in section in Fig. 1. The main. or body casting of the pump is formed with flangesfianges 19 of the. end castings are respectively bolted. The body portions of the end castings are respectively.- formed with suitably spaced bores 22 which receive bushings 23 in which are formed the bearings for the respective shafts 15 and 16 upon which the rotary pistons are.

keyed. The fit ofthe shafts in the bushings is sufiiciently freeto avoid binding at all times, notwithstanding the high temperature to whichthe pump is subjected by the circulating hot oil and to permit the passage of a. thin film of oil about the shafts. The gears 13 and 14 are mounted on the respective shafts beyondone of the-end castings and are enclosed in a housing 28, the flange of which is bolted at '29'to'the outer flange of said end casting. The shaft by which the pump is driven extends through said housing at 39 where there is formed a packing box -40 containing packing 41 and receiving the gland 42. Openings 35 and 36 are formed in the ends of said. housing and receive, respectively, an inlet pipe 3 andan outlet. pipe 38 by which cold oil under. pressure is supplied to the housing and escapes therefrom.- Theother end casting is provided with a cap or co er plate which 1 s bolted thereto at 27 and said cover plate 1S recessed or chambered at 30 and formed with passages 31 and 32 which receive, respectively inlet and outlet pipes 33 and 34 by m'eansof which relatively cold oil is circulated through chamber 30.

As shown diagrammatically in Fig. 5.,

which; illustrates the circulatory ressure still of the invention, the inlets33. or supplying oil respectively to the hollow cap plate and the gear housing, are connected to a small pump 44 capable of developing a.

pressure in excess of that within the main pump chamber. Said pump is connected by pipe 45 to a. supply of oil 46 which may be and preferably is main body of oil in the still and its connections is supplied. The outlet pipes 34 and- 38 may be connected to the main circulating system of the still, 'the connection to the outlet pipe 47 from r p- During the operation of the pressure cracking still of the invention the main pump is operatedto circulate the oil from the still proper or vaporizingtank 48 to and through the heating pipes in the furnace the source from which the from which the oil returns to tank 48 through pipe 49. The small pump 44 is continuously operated to force a-circulation of cold oil from supply-tank '46 through chamber 30 in the capplate 26 and through the gearing housing, the bulk of which oil passes through pipes pipe 47 of the main pump where it mingles with the hot oil. A limited amount of the \cold oil, however,.is forced through the bearings of the shafts from the chamber in the cap plate and the gear housing respectively,

34, 38 to-the exhaust into the main pump chamberv where it mingles with the circulating hot oil under pressure after, having served to prevent the escapie of the hot oil through said bearings an is no difiiculty in suitably packing thegear housing against the. escape of the oil'Jcontained therein since the oil therein is relatively cool and the ordinary packing device described suffices for this purpose.

damage would result as it is far below the temperature of ignition. If desired-a suflicient amount of cold oil can be circulated through the chamber 30 and the gear housing to substantially lower the temperature of the bearings of the pump. In -a circulatory pressure crackin circulating pump of the rotary piston type, in which 2000., gallons per minute of hot at a temperature between about 700 F. and 800 F; for example, the main pump, a per minute of cool nary temperatures,

But even in the event of the escape of the cold oil, no

still embodying the invention and inciu ing 'a.

are circulated through" fiow oiI-about .3 gallons IOU thoroughly lubricated the latter. There oil there is a clearance between al moving parts and the moving and stationary parts. When first installed in a circulator cracking still a pump with such clearness 1s inefiicient on account of the great amount of leakage but we have discovered that by operating it, pumping .centa e of carbon, the carbon will deposit and i the pump is kept in continuous operation, the carbon so deposited on two surfaces moving relative to each other is ground until it effects a satisfactory seal. As there is acontinual grinding action durin all the time the pump is in operation the t ickness of this. carbon deposit determines the resistance or friction of the pump due to this form of seal. When the carbon layer is very thin the shearing action necessary for grinding off the fresh precipitate is excessive and is reduced by increasing the thickness. We generally prefer to allow a clearance of A" to more or less between the pump pistons and the side of the pump casing and a clearance somewhat less between the pistons and the ends of the casing.

We claim: 1 v

1. In a pump for operation on cracked oil containing carbon released during cracking, and in combination with the casing, a pump piston having a clearance of approximately three-eighths inch within the casing whereb the carbon which accumulates. on the w ls of the casing forms a packing therefor.

2. In a circulatoryoil cracking still having a still proper,

heating pipes in a furnace be done in a very simple.

ump so that hot oil containing a large per- I ting bearings and connections'beltween said still and hieating pipes, a circu ator um arrange to circulate hot oil fron i s aid still to and through said heating pipes and back to the still, said pump having loosely fitting bearings and means for forcing relatively cool oil through said bearings into said pump and circulatory system.

3. In a circulatory oil cracking system a rotary pump having two impellers or pistons, the shafts of said impellers having loosely fitting bearings, gears on one endof each of said shafts 'within the pump casing beyond the bearings, a compartment for sai gears, and means for forcing relatively .cool' 011 into said com through the loosely the shaft into the hot oil.

4. In the circulatory system of an oil cracking still a rotary pump handling hot oil, said impellers with a clearance therebetwee'n and between the pistons or impellers and the casing, whereby binding of the impellers is prevented and the formation of a carbon deposit permitted vfor sealing the action of the impellers in the pump.

5. In the circulatory system of anoil cracking still a rotary pump having opposed pistons or impellers with a clearance therebetween and between and the casing, and a carbon layer on said impellers and easing forming a seal therefor.

6. In a. circulatory oil cracking still system having a vaporizing drum, a heater and a connection between said heater and vaporizin drum, means for discharging hot oil pro ucts from said including a pump for returning hot oil products discharged from said vaporizing drum to the heater, said pump having loosely fitand means for forcing relativeartment and thence tting bearings around pump and circulating pump having opposed pistons orthe pistons or impellers.

vaporizing drum, means 1y cool oil through said bearings into said pump and circulatory system, and means for maintaining superatmospheric pressure on the hot oil products throughout the system.

EDWARD W. ISOM. JOHN E. BELL.

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