US3179709A - Process of heating olefin feed to dehydrogenation process - Google Patents

Description

April 20, 1965 G. P. BAUMANN PROCESS OF HEATING OLEFINFEED TO DEHYDROGENATION PROCESS Filed May 27, 1960 WATER LIQUID BUTENES George P. Boumcmn Inventor Pcnenf Attorney United States Patent 3,170,709 PROCESS OF HEA'HNG @LEIFW FREE) TO DEHYDROGENATION PROUESS George I. Baumann, Sparta, NHL assignor to Esso Research and Engineering Company, a corporation of Delaware Filed May 27, 1900, Ser. No. 32,3115 6 Claims. (Cl. 200-680) This invention relates to a novel and improved process and apparatus for vaporizing and heating C to C olefins to high temperatures in the range of 600 to 1100 F. More particularly this invention relates to vaporizing these feed stocks by contacting them countercurrently with steam in a distillation tower. Thus, according to this invention steam is condensed and provides a liquid wash on the stripper trays which washes any deposits formed off the trays. Yet more particularly, in a preferred embodiment, this invention relates to vaporizing and heating C -C olefinic feed stocks in such a tower pnlor to their being supplied to the dehydrogenation furnace and reactors where these feed stocks are converted to dioleiins. Most particularly, in a preferred embodiment this invention relates to supplying a C -C olefin-containing liquid stream to the top of a distillation column, supplying at least a sufiicient amount of steam to a lower section of said column to obtain substantially complete vaporization of the olefin stream, removing vaporized olefins overhead from the top of said column, the said vaporized olefins being at a temperature in the range of 100 to 300 F., and removing condensed water from the bottom of the column. The resultant C -C olefin-containing stream comprising 5 to 15 volume percent of C -C hydrocarbons intermixed with 85 to 95 volume percent of steam is then heated to 1000 to 1350 F. and passed over a calcium nickel phosphate catalyst to effect the conversion of said C to C olefins to the corresponding diolefins.

According to the present invention it has now been discovered that the vaporization and heating of C -C olefinic feeds can be much more efficiently and cheaply obtained with less formation of undesirable degradation byproducts by vaporizing the feeds with steam (preferably countercurrently in a tower). Prior to the present the vaporization of streams of this type in conventional heat exchangers or furnaces has resulted in excessive fouling of the equipment. This fouling required either frequent shutdowns for cleaning or preferably the design of spare equipment to allow cleaning of one of the units while the other was on stream. According to the present invention an extremely efficient vaporization of these olefin streams is obtained at any pressure with essentially no fouling and less degradation of the feed stream.

For economy purposes it is preferable to supply substantially saturated steam to the vaporizer. Thus, the latent heat evolved upon condensation of the steam supplies the majority of the heat required for vaporization of the hydrocarbon stream. However, it is of course contemplated that if desired superheated steam may be utilized.

This invention will beparticularly advantageously applied in dehydrogenation processes for converting C -C olefins to diolefins. In these processes fouling of conventional heat exchangers or furnaces used for preheating and vaporizing the feed prior to its being supplied to the main dehydrogenation furnace have been particularly se- Vere. The temperatures and composition of the feed streams to be supplied to the vaporizer in these processes along with the general reaction conditions are described below.

hydrogenation of n-butenes to butadiene.

Butene dehydrogenation to bumdiene Range Preferred Specific Feed Composition:

n-Butylene, Wt. Percent 20-100 40-85 75. 0 Isobutylenc, Wt. Percent. 0-30 0-3 1. 5 Butanes, Wt. Percent 0-60 10-60 24. 5 Pressure in Vaporizer, p.s.1.a 20-300 -140 Steam/f; Feed in Effluent Supplied to Furnace 0.1-1.0 0. 1-0. 5 0; 23 Furance Inlet Temperature, F 100-400 -250 200 Range Specific Reaction Conditions:

Space Velocity of n64", v./v./hr. 75-170 120 Space Velocity of Steam, v./v./hr. 1, 400-10, 000 2, 300 Reactor Inlet Temperature, F.-. 000-1, 350 1, Reactor Outlet Pressure, p.s.i.a 15-30 20 n-Butylene Conversion, percent per pass 30-75 40 Selectivity to Butadiene, percent 75-95 85 Catalyst:

1 V./v./hr.=volume of gas at S.I.P./volume catalyst/boon Isopentene dehydrogenation to isoprene Feed Composition Range Pericrred Specific Z-mcthyl Butcnes, Wt. Percent 20400 40-85 75.0 Other 0 Olcfins, Wt. Percent- 0-30 0-3 1. 5 C Paratfins, Wt. Percent 0-60 10-60 24. 5

Same vaporizer pressures. f Same dehydrogenation finance teed temperatures and steam proporions.

Same reaction conditions as in dehydrogenation of butenes.

Dehydrogenation of 2,3-dimethyl butene to 2,3-dimethyl butadi ne Same vaporizer pressures. noSgismc dehydrogenation furnace feed temperatures and steam propor- Same reaction conditions as in dehydrogenation of butcnes.

The present invention will be more clearly understood from a consideration of a particular process for the de- In this process the butene-butane feed mixture is vaporized and heated to about 200 F. prior to its being passed to the cracking furnace. In the prior art processes vaporization of thisfeecl stream was obtained in commercial heat exchange equipment (tube and shell exchangers) with low level heat. In commercial operations using this process the vaporization of the butenes has resulted in excessive fouling so that ordinarily a 100% spare bundle of tubes has been necessary to allow cleaning without disrupting the operation. This spare bundle and piping involved, of course adds to the capital investment and the frequent cleaning required increases operating costs.

According to the present invention referring to the figure, the liquid butene-butane feed stream is. supplied after some preheating if desired through line I to tower 2, containing a series of bubble plates, 3, d, 5, and 6 with associated downcomers. The feed stream is supplied in a preferred embodiment above plate 6 and steam is supplied through line 8 to the tower below plate 3. The liquid butene-butane stream descending through the tower is countercurrently contacted with the steam, thus obtaining essentially complete vaporization of the liquid butene-butane stream overhead. The vaporized butenebutane stream is taken from the top of the tower through line 9 and condensed water is taken from the bottom of the tower through line 10. It should be noted that the condensation of the steam on each plate continuously provides the heat to vaporize the butenes and also provides a liquid wash on the stripper trays which Washes deposits off the trays. It is, of course, contemplated that other types of plates in the tower rather than bubble plates may be used and that also less desirably a packed column rather than a plate column may be used.

An additional advantage of this process results from the periodic need to remove feed for emergency repairs or accidental loss of feed to the butene dehydrogenation plant due to maloperation of catalyst reactor equipment such as automatic cycle timer and motor operated valves. During this period extra steam over that required for vaporization of butenes is required to adjust the furnace tube mass velocity so that the amount of hydrocarbon cracking occurring in the butene furnace is minimized. This addition of steam may be extremely advantageously supplied from the present type vaporizer since when hydrocarbon feed is withdrawn an automatic increase in steam evolved occurs due to the reduction in the steam condensed by the hydrocarbon. It should be noted that without the availability of additional steam the cracking furnace must be quickly shut down whenever a loss of feed occurs. Thus, without a feed stream the furnace will quickly burn out with failure of the furnace tubes and/or brickwork and structural steel.

It is estimated that the inherently improved operations resulting from this invention will provide large savings. Thus, for example investment savings alone have been estimated to be in the order of $20,000 for a small unit producing 35 tons of butadiene per day.

The foregoing description contains a limited number of embodiments of the present invention. It will be understood that this invention is not limited thereto since numerous variations are possible without departing from the scope of the following claims.

What is claimed is:

1. An improved process for vaporizing and heating a liquid hydrocarbon feed stream containing at least 20 Wt. percent of C -C olefins, the major proportion of the remainder of said feed stream consisting of C -C hydrocarbons which comprises supplying said feed stream to the top of a distillation column and supplying at least a suflicient amount of steam to a lower section of said column to obtain substantially complete vaporization of C -C the olefin content of said feed stream and steam essentially no fouling of the heat exchange surfaces of the dehydrogenation furnace and less degradation of the feed stream.

2. The process of claim 1 wherein said steam is saturated steam.

3. In a process for dehydrogcnating a C -C olefin containing stream wherein said olefin stream is passed with to volumn percent of steam based on the total stream supplied at temperatures of 1000 to 1350" F. over a calcium nickel phosphate catalyst, the improvement which comprises vaporizing and heating a liquid hydrocarbon feed stream containing at least 20 wt. percent of C -C olefins, the major proportion of the remainder of said feed stream consisting of C -C hydrocarbons prior to its being supplied to the dehydrogenation reactor by contacting said feed stream in a distillation column with at least that amount of steam to obtain substantially complete vaporization and heating of the C -C olefin content of said feed stream removing steam and vaporized olefins overhead from the top of said column and condensed water from the bottom of the column, charging the vaporized olefins and steam to a dehydrogenation furnace and heating the same to temperatures of about 1000l350 F. whereby said olefin feed is heated to active dehydrogenation temperatures with essentially no fouling of the heat exchange surfaces of the dehydrogenation furnace and less degradation of the feed stream.

4. The process of claim 3 in which the olefin stream is a C stream containing 20 to wt. percent n-butylene, 030 wt. percent isobutylene and 060 wt. percent butanes.

5. The process of claim 3 in which the olefin stream is a C stream containing 20100 wt. percent 2-methyl butenes, 0-30 wt. percent other C olefins and 0-60 wt. percent C parafins.

6. The process of claim 3 in which the olefin stream is a C stream containing 20 100 wt. percent 2,3-dimethyl butenes, 0-30 wt. percent other C olefins and 0-60 wt. percent C parafiins.

References Cited by the Examiner UNITED STATES PATENTS 2,297,004 9/42 Lee 202-46 2,367,623 1/45 Schulze et al 260--680 2,411,808 11/46 Rupp et a1 260--677 2,459,449 1/ 49 Oliver et al 260-680 2,509,900 5/50 Wormith 260680 2,733,285 1/56 Hammer 260683.15 2,918,508 12/59 Coopersmith et a1. 260683.l5 2,957,928 10/60 Cann 260-680 FOREIGN PATENTS 591,209 1/60 Canada.

OTHER REFERENCES Faradays Encyclopedia of Hydrocarbon Compounds, by J. E. Faraday and A. S. Freeb'orn, page 060160801 (1960, received July 18, 1961) pages 060550091 and 060930091 (1953, received January 26, 1954); volume 2a, Chemindex Limited, London, 1960.

ALPHONSO D. SULLIVAN, Primary Examiner.

MILTON STERMAN, Examiner.

Claims (1)

1. AN IMPROVED PROCESS FOR VAPORIZING AND HEATING A LIQUID HYDROCARBON FEED STREAM CONTAINING AT LEAST 20 WT. PERCENT OF C4-C6 OLEFINS, THE MAJOR PROPORTION OF THE REMAINDER OF SAID FEED STREAM CONSISTING OF C3-C6 HYDROCARBONS WHICH COMPRISES SUPPLYING SAID FEED STREAM TO THE TOP OF A DISTILLATION COLUMN AND SUPPLYING AT LEAST A SUFFICIENT AMOUNT OF STEAM TO A LOWER SECTION OF SAID COLUMN TO OBTAIN SUBSTANTIALLY COMPLETE VAPORIZATION OF C4-C6 THE OLEFIN CONTENT OF SAID FEED STREAM AND STEAM AND VAPORIZED OLEFINS OVERHEAD FROM THE TOP OF SAID COLUMN AND CONDENSED WATER FROM THE BOTTOM OF THE COLUMN, AND CHARGING VAPORIZED OLEFINS AND STEAM TO A DEHYDROGENATION FURNACE AND HEATING THE SAME TO TEMPERATURES OF ABOUT 1000-1350*F. WHEREBY SAID OLEFIN FEED IS HEATED TO ACTIVE DEHYDROGENATION TEMPERATURES WITH ESSENTIALLY NO FOULING OF THE HEAT EXCHANGE SURFACES OF THE DEHYDROGENATION FURNACE AND LESS DEGRADATION OF THE FEED STREAM.

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