US2187708A - Apparatus for inhibiting tar polymerization - Google Patents

Description

Jan 16, 1940.a

A. CIBULKA El AL APPARATUS FOR INHIBITING TAR POLYMERIZATION Filed Jan. 31, 1936 rqn. uns E; E; Z5 magali 27 44 J JTIA M INA Patented Jan. 16, 1940 time rarest ries APPARATUS FOR INHEBTING TAR ?GLYMERZATKN Alois Cibulla; Highlands, and Maurice W. Mayer,

Baytown, Tex., assignors to 'Standard @il Development Company, a corporation of Delaware Application .lanuary 3l, 1936, .Serial No. 61,776

1 illaim.

This invention relates to improvements in the heat `treatment of hydrocarbon oils in which polymerization of the separated from the oil during vaporization is inhibited.

"" It has been customary in the cracking ci petroleum oil to subject the oil :in a coniined zone to elevated temperatures and pressures, after which it has been passed to a digestion zone where thermo-decomposition oi' the oil has oc- 1D curred. The thus treated oil has been conducted from the 'digestion zone to a tar separator in which the oil is maintained quiescent to permit separation iromthe oil of tar formed during `decomposition of the oil. The tar has lbeen mainili tained exposed to the full heat oi the' main body of oil in the tar separator throughout `the period of separation, with a result that a high rate of polymerization of 'the tar to form coke has occurred.

'20 It is an object of this invention to minimize form, used for example in the tube and tank method 'of cracking petroleum oil. Tar formed by the pyrogenetic decomposition of the oil settles in the separator i. The tar as it settles is conducted directly to a tar pot t lconnected directly to the bottom wall of the separator l.

In the embodiment illustrated, the Atar pot 3 comprises a container the upper portion i of which is provided with a radially extending liange 5, which is secured to a similar iiange t carried by a tubular extension i dependent from the bottom wall of the separator i. The tubular extension l can be approximately 2li inches in diameter. The base I!) of the container i? is provided with a bottom closure l2 secured to a flange li on the hase of the container. The container 3 is provided with a tubular member i5 protruding outwardly from an intermediate portion of the container 3. The tubular member i5 is closed by a tubular extension il. Member l5 and extension Il are provided with radially extended ilanges i3 and I9 respectively, whereby they are secured to gether. into the container. The container 3 is of lesser diameterthan the tar separator l. l

The level of tar is maintained at `an intermediate postion in the tar pot 3 through they Tar as it separates in separator l falls,

(C1. Mii-58) following arrangement of parts. Discharge line 25 leads from the bottom Wall i2 lof the tar pot 5. The discharge line is provided with =a fluid pressure valve 2l. Valve 2l is a diaphragm control valve compri-sing a diaphragm 29 which extends f5 transversely across a fluid tight casingll. The valve 2l is connected by means of a piston 3l with the `diaphragm 29. The valve 2l is normally maintained closed by means 'of a helical spring 32. The valve 2 is actuated by means of l0 compressed air, Aor other iiuid, in a Way to be later described.

The level of tar in the tar pot 3 is controlled by a float 37, which rests upon the surface 33 oi' theta-r. The lloat 3l is attached to one end of a -16 rod itil, the opposite 'end of which carries .arm ti which is pivotally mounted in the extension il.

Rise or fall of 'the float 3l with rise or fall of the level of tar in the tar pot 3, therefore, causes rotary movement ofthe arm it. This rotary move- 20 ment of the arm M is caused to control the lsupply of air to actuate the valve 2l, as follows; An air line 44 leading to the casing it of the vdiaplfuagrn valve 2l is connected to la pilot valve 46. The pilot valve Mi, which is of well known 25 construction, is provided with a trigger Eil mounted for reciprocaticn longitudinally to open or close the pilot valve. Rotation of the arm di iscaused to eiect longitudinal reciprocation of the trigger-5t, as follows.' A crank arm 52 is 30 radially connected to the arm Ill. An adjustable linkli is connected at one end to the crank arm 52 in spaced relation to the arm lll. The opposite end of' the link et is pivotally connected to a lever 5S, an intermediate portion of which is 35 pivotally supported at 5l. The lever 55 carries a head mounted for engagement with the trigger 5B to effect longitudinall reciprocation of the trigger 5B with change in level of the tar 38. Thevtar is maintained at the low level desig- 4Q nated 38 in the tar pot-in order that the interfacial surface Will be relatively small, and any given surface quantity oi liquid tar may be maintained in direct Contact with the vapors in the separator E for a very small length of time. 45 This feature permits of considerable cooling of the tar without appreciable condensation of cycle fractions which are in the vapor state. It will be notedk that as the liquid level 38 rises the diaphragm valve 2l is caused to be open to allow 50 the tar to iiow out through the line 25.

The polymerization inhibiting pot is provided with a plurality of vertically spaced valve sample lines 63, 64, t5 and 66, which connect with a manifold 51. A valve line 68 leads from the 55' manifold 6T, whereby samples of the contents of the polymerization inhibiting pot can be withdrawn for inspection. A valved line 99 and a valved line 69a are provided to admit cold iuX to the tar pot for flushing purposes when necessary. The iiux may be admitted to the tar pot at a temperature of '700 F. or lower, to aid in inhibiting polymerization of the tar and, therefore, minimize the formation of coke. The valved line 69a specifically performs the function of cooling the pivot 4I in order to minimize the formation of coke at this point as well as aiding in reducing the temperature of the tar within the pot 3.

By the procedure described, the tar level is maintained in a relatively small tar pot of, for example, 20 inches diameter, and the tar falls directly as formed into the pot. A cylindrical screen l2 protrudes into the ta-r separator I from the tar pot 3, to prevent coke, concrete or the like, from falling from the separator I into the pot 3. The upper end of the tubular screen 'l2 is preferably open. The time that the tar must remain at the high temperature in the separator equipment is reduced and, therefore, the amount of polymerization of the tar to form cols-.e is decreased. Coke formation at the bottom of the separator I is almost completely eliminated.

By holding the liquid within the pct 3 and exteriorly of the separator I, the surface of liquid tar in direct contact with the vapors in the separator I is very small. In View of the small interfacial surface, the cooling of the liquid with cold tar iiux reduces the polymerization rate without appreciable condensation of the heavier fractions in the vapor, and the tar gravity remains unchanged. The use of the particular form of tar pot illustrated provides an economical method of improving the operation of cracking coil tar separator, since it is necessary only that a tubular extension 1, or nozzle, be driven into the bottom of the existing separator drum and the tar pot attached thereto. Furthermore, the float device 3l can be easily installed and repaired through the lateral extension of the tar pot. The addition of the tar pot to an existing separator and the maintenance of the control level in the pot itself provides additional effective separator height, since the tar level is moved farther away from the vapor outlet nozzle leading from the separator I. While the device has been described as applied to a separator used in the pyrogenetic decomposition of oil, it will be understood that it can be used in connection with any process for the heat treatment of oil in which tar is formed as a result of the treatment, and some of the advantages of the invention will be retained.

Various changes and alternate arrangements may be made within the scope of the appended claim, in which it is our intention to claim all novelty inherent in the art as broadly as the prior art permits.

We claim:

An apparatus of the character described including a tar separating chamber adapted to receive cracked hydrocarbon products, a separate smaller tar pot secured to the bottom of said tar separating zone and in communication with said tar separating chamber for receiving tar from said tar separating chamber, said tar pot at its upper portion having a smaller cross sectional area than said tar separating chamber so that a smaller surface of the tar in said tar pot is exposed to the high temperature in said tar separating chamber, said tar pot having a hollow lateral extension, means for maintaining the level of the tar substantially constant at a relatively low level in said tar pot and at a substantial distance below said tar separating chamber, said means including a discharge valve for withdrawing tar from said tar pot, said discharge valve being operated by means responsive to the changes in the level of the tar in said tar pot, level responsive means including a float arm pivoted in said lateral extension at a point removed from said upper portion of said tar pot, and means whereby a cool fluxing agent is introduced into said lateral extension of said tar pot adjacent said noat arm pivot for cooling and iushing said pivot and for cooling the tar without appreciable condensation of the vapors above the tar in said tar pot. said smaller tar pot providing means whereby the time of contact between the tar in said tar pot and hot vapors in said tar separating chamber is relatively short and the rate of polymerization of the tar is reduced.

ALOIS CIBULKA. MAURICE W. MAYER.

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