US2430344A - Preheater for oil for refinery crackers - Google Patents

Description

w. w. KEMP 2,430,344

PREHEATER FOR OIL FOR REFINERY CRACKERS Nov. 4, 1947.

Filed Sept. 8, 1944 2 Sheets-Sheet l I v Q Q Q I Nov. 4, 1947.

w.'w. KEMP PREHEATEH FOR OIL FOR REFINERY CRACKERS Filed Sept. 8, 1944 2 Sheets-Sheet 2 Patented Nov. 4, 1947 PREHEATER FOR OIL FOR REFINERY CRACKERS William Wallace Kemp, Baltimore, Md., assignor to The C. M. Kemp Manufacturing Company, Baltimore, Md., a corporation of Maryland Application September 8, 1944, Serial No. 553,173

8 Claims.

Oil heaters for petroleum crackers have the common disadvantage of being so constructed and operated that the heat application is at times localized and the temperature excessive, there beingactual flame contact with the oil pipes resulting in over-heating of the pipes, carbonizing of the oil and actual blistering of the pipes. These blisters finally break away permitting the oil to leak into the furnace or combustion chamber where it burns, due to the excess of air pulled through the furnace by the stack. The oil pipes burning out cause frequent failure and shutdown of the oil heater and consequently of the cracker.

The oil should be pro-heated to a temperature of about 850 degrees Fahrenheit. The flame of combustion of natural gas, still gas or fuel oil, when mixed with the proper amount of air, will have temperatures which will approach if not exceed 3000 degrees Fahrenheit; hence, the danger of flame contact with the oil pipes is apparent. Thirty percent excess air is usually provided; this forms zones of high oxygen content and promotes deterioration and pipe oxidation.

Purposes of this invention, among others not specifically mentioned, are to use as a fuel a complete air-gas mixture such as can be produced by the proportioning air and gas mixing machines described in U. S. Letters Patent to W. W. Kemp et al.: 1,771,223, July 22, 1930, and. 1,880,141, September 27, 1932, which complete air-gas mixture produces a short, stiff blast flame which when directed within a tube or cylinder at a central point, produces a discharge or blast of combustion gases at the discharge end of the tube while entraining combustion gases at the bottom or inlet end. In this invention there are a number of these tubes placed preferably in vertical position and in rows, each entraining combustion gases from the floor of the heater and discharging toward the ceiling, thus setting up a circulation of the atmosphere within the heater chamber.

The greater the pressure at which the air-gas mixture is fed to the several burners, the stiffer the blast flame, the more rapid the circulation, consequently, the more uniform the heat distribution. The exhaust openings and pipes are at the bottom of the chamber so that the chamber will fill with gas, and thus maintain a uniform temperature in the whole chamber. Because the air-gas ratio is about complete or correct for complete combustion, no air is drawn in by inspiration or aspiration, and the flame is short,

entirely confined within the tubes and cannot contact any of the oil pipes, and subject to close control, the differential between the temperature of the gases and oil is kept low, to prevent over heating and damage to the heater. The oil pipes are heated by the rapid passage and circulation of the combustion gases among them. A thermostat placed within the heater and in the passage of the circulating gases is adjusted to limit the temperature of these gases. A second thermostat placed in an oil duct outlet will vary the volume of fuel burned to control the temperature of the oil.

With the furnace of this invention, there is no stack, chimney or exhaust fan. The pressure at which the combustion gas and air mixture is fed to the burners controls the circulation of the combustion gases, and the pressures at which these gases exhaust from the heater. There is very slight pressure drop of gases through the heater, the combustion gases exhaust through openings in the floor of the heater and are carried through a duct to a convection heater for preliminary heating of the oil and finally through heat exchangers or coolers and dryers.

Another purpose of this invention is to supply inert gas, the device serving the double purpose of an oil heater and an inert gas generator. The inert gas is required in the oil refinery for purging. producing inert blanketing atmosphere and, when compressed and dried, can be used for instrument operation.

The complete air-gas mixture above referred to produces the highest and most uniform flame temperature. It is common practice to so adjust the Kemp air and gas proportioning machine, patent numbers previously referred to, to obtain a combustion gas having one-half per cent or less of oxygen and no monoxide, or one-half per cent or less of monoxide and no oxygen, either of which is an ideal inert gas for refinery purposes, especially when the water vapor content is reduced to the desired extent by the heat exchanger or desiccant towers. Under present operating conditions, a broken or leaky oil pipe within the heater can result in a bad fire, flame occurring within the heater and. extending to the top of the stack, the atmosphere in the entire system being such as to support combustion. With the apparatus of the present invention, the atmosphere is inert and should an oil leak occur, the petroleum actually playing on the gas flames, the oil and the'oil vapor actually could not ignite or combust, as there is no oxygen present to support combustion.

The heater is under a pressure of inert gas of from a few ounces to one pound or more; therefore, it is not possible for atmospheric air to leak in. Should the air and gas mixture flame contact a combustion blast tube, oil piping or any other surface after the mixture is ignited at the face oi the; burner, the combustion would. be retarded, theflame cooled somewhat. and monoxide gas produced. Flame contact with any surface is studiously avoided in the construction of this invention.

An apparatus by which the objects of this invention may be carried out is shown in the accompanying drawings, forming; a part-hereof, and. in which Figure 1 is a vertical: sectional. View on line l-I of Figure 2. Figure2ii's a sectional view on line 2-2 of Figure 1. Figure 3. is. a partial sectional view on line 33 of Figure 2 in reduced scale. Figure 4 is an e1evation,.partl-y' in section of an oil pre-heater, shown in reduced scale.

Similar numerals refer tosimilar partsin the. several'views.

A- large chamber l is supported. on. uprights 2, and, it. has in it. two. opposed side headers 3-3,. having; inlet 4- and outlet 5, cold; oilcoming in the; inlet 4 and. Oil; heated to a temperature: of approximately-850 Fahrenheit comingoutof the outlet 5. Between the headers are oil-carryin pipes ortubes 6 arrangedvery much, like. the tubes of a steam boiler. These-tubes 6. are=closelygrouped at: the; top. of the.- chamber l and downs wardly near the center of the chamber they arearrangedin vertical rows so. that the lines I may be. nlacedin rows between, the/ tubes; These flues; are supported: by; bands 8; and, rest upon the. floor of the; chamber on stands 9.. These stands. allowfree circulation of; air: up through. the fines from; the base; of the-chamber.

Passing through openings; in; the bottom of. the; chamber are! a plurality of'burner-s: Ii], one: for each flue. 'I-hese burnersI are connected inrows fed. fromz pipes; H which; haverbackrfirer prezventers I-2=, in; them; prion to their; connection with. the manifold I 3) a: fillbstantially'completely. combustiblemixturemf fluid. 11811 such; asgas; or oil and air., It. may be; fed; by: an; industrial. carburetor: such as is illus-- tnated in. theyK'emp; et; a1; patentsrabove referred: to:vv Valves. |:4- a-nd1. I-5;irr thespipe I I-, om each side: of; the: fire preventers may be turned to. accu.-- rately control the amount of the: mixture enter-- ing: the pipes. Hr, andvalves I6. on: each; burner may be: used: to: facilitate thelighting of, onea burner or a' group. of burners turned, on: at; once.

The; burnersare lit by an igniter-insertedrthrou gh: openings. inthe: chamber; walls: covered; by flaps lt'|-.

A thermostat l:&=se.1tv.es.to. operate; a.valye on; manifold; In: to limit; the. fuel; fed at times. when: the oil temperature. is low;so; that too m ch heat: may not suddenly be applied. Another therm0.-- stat,.not'. shown; is;in; thaoir exhaust. pipe. 5; op, cratinganother valve:- om manifold l3) to; regulate: theflow of. fuel to give. an evem accurate predestermined; temperatureztothe: oil inztheiheaterz;

After: the; air; has been. forced them; the cham.- ber: l1,. the chamber; fiils.:wi17h-. the: heated inert; sasesproducedibythecombustiom and these gas s constantly: circmate: around the tubes; 6. and hl'fillghl'thfi, flues. 1;. going; out.- at the; top and. being; drawn. in; again; at? the bottom; in. a. constant flow. oi inert; gas; which. is constantlyheated; by theflame and; is; constantly. circulated; uppnthe tubes 6 to heat them to the desiredde iee'of Thema-niiold I 3 has; fed to it' l.

approximately 850 Fahrenheit. The contacting of the tubes solely by inert ga gives them the temperature required without over-heating and without blistering, and should a break occur in any of the tubes by any chance, the inert gas will not support combustion and there will be no burning of the oil possibly leaking from the tubes. The. inert. gases under their own pressure flow from the chamber I through openings I9 in the chamber bottom, passing to the pipes 20 and to manifold 2|. From the manifold 2| the inert gases may be led by pipe 22 through an oil preheater 23 having bafiles 24 therein, the gases passing out at pipe 25. Oil, prior to its entrance to header 3 may be passed through this preheater 23, entering at 26, passing through pipe 21 in thepre-heater, and then passin from the pipe at 28 to the header 3. From pipe 25 the gases be passed to a heat exchanger and towers of desiccants, not shown, for use in the refinery for purging, producing inert. blanketing. atmosphere. and when compressed and dried: itcan be used for instrument operation.

From the. oil heater above described the oil will.

pass. directly to the. reaction chamber of the cracker,

What is claimed. asnew. and desired to besecured by Letters-Patentis:

1. A fluid heater comprising a. plurality oi closely spaced. substantially horizontally, extending, fluid carrying tubes, connections at the endsof said tubes to allow for the. passing. of. fluid. constantly through the tubes, a plurality ofheat? ing flues extending upwardly between certain and. under other of said. tubes, a chamber enclosing said tubesand.fiues-,.said flues bei-ngiree. oi obstruction and spaced. from. the. bottom. and top. of. the. chamber. to.allow the free flow of. gas from. the chamber. therethrough, burners. beneath the bottom of. the lines and: means to feed: a combustible. mixture. of air and fluid. fuel. to said. burners, said flues. enclosing. the flame from. the burners. and Promoting circulation of gases. to. and from. the flame, the'fiame from. the burners. setting up a continuous flow of heated gases vertically around said tubes.

2.. Afluid heater comprising. aplurality of rowsv of substantially. vertical. heating. flues, substantially. horizontally. extending. fluid. carrying tubes,. some. extending between and. others over said. flues, connections atv the ends: of. said. tubes toallow for. the passage of fluid. constantly through. the tubes, achamber enclosing said flues. and.

tubes, the fines. being. free of. obstruction. and.

spaced from the bottom. and top. of thechamber. to allow the free flow of gas from the chamber. therethrough, burnersbeneath.the-bottom of the. flues, and meansto feedacombustible mixture. oi air and, fluid fuel to, said burners, said. fiues.

enclosing the flame from the burners, the flames setting up, a continuous. circulation. of. gases.

thrcughthe fiuesand around the tubes.

3; A; fluid heater comprisinga plurality of rows. of substantially vertical heating flues, substantially. horizontally extending fluid carrying tubes,

some extending between and others. over said flues, connections at. the ends of said tubes to.-

allow for thepassageoi fluid constantly through. the. tubes, a chamber enclosing said flues. and

tubes, the. fines being free of obstruction. and.

spaced; from the bottom andtop. of. the chamber. toallowthe freeflow. of gas from the chamber therethrough, rows of burners one beneath the. bottom of eachflue, acombustible. mixture. inlet.

piperfor; each rowof burners, amanifold. for the.

group of inlet pipes, and means to feed a combustible mixture of air and fluid fuel to said manifold, said flues enclosing the flame from the burners, the flames setting up a continuous circulation of combusted gases through the flues and around the tubes.

4. A fluid heater and inert gas generator comprising a plurality of closely spaced substantially horizontally extending fluid carrying tubes, connections at the ends of said tubes to allow for the passing of fluid constantly through the tubes, a plurality of heating flues extending upwardly between certain and under other of said tubes, a chamber enclosing said tubes and flues, said flues being free of obstruction and spaced from the bottom and top of the chamber to allow the free flow of gas fram the chamber therethrough, burners beneath the bottom of the flues and means to feed a combustible mixture of air and fluid fuel to said burners, said flues enclosing the flame from the burners and promoting circulation of gases to and from the flame, the flame from the burners setting up a continuous flow of heated substantially inert gases vertically around said tubes and outlets from the bottom of said chamber for the inert gases.

5. A fluid heater and inert gas generator comprising a plurality of rows of substantially vertical heating flues, substantially horizontally extending fluid carrying tubes, some extending between and others over said flues, connections at the ends of said tubes to allow for the passage of fluid constantly through the tubes, a chamber enclosing said flues and tubes, the flues being free of obstruction and spaced from the bottom and top of the chamber to allow the free flow of gas from the chamber therethrough, burners beneath the bottom of the flues, and means to feed a combustible mixture of air and fluid fuel to said burners, said flues enclosing the flame from the burners, the flames setting up a continuous circulation of substantially inert gases through the flues and around the tubes and outlets from the bottom of the chamber for the inert gas.

6. A fluid heater and inert gas generator comprising a plurality of rows of substantially vertical heating flues, substantially horizontally extending fluid carryin tubes, some extending between and others over said flues, connections at the ends of said tubes to allow for the passage of fluid constantly through the tubes, a chamber enclosing said flues and tubes, the flues being free of obstruction and spaced from the bottom and top of the chamber to allow the free flow of gas from the chamber therethrough, rows of burners one beneath the bottom of each flue, a combustible mixture inlet pipe for each row of burners, a manifold for the group of inlet pipes, and means to feed a combustible mixture of air and fluid fuel to said manifold, said flues enclosing the flame from the burners, the flames setting up a continuous circulation of combusted substantially inert gases through the flues and around the tubes, and outlets from the bottom of the chamber for the inert gas.

7. An oil heater for petroleum refining comprising a heating walled chamber, a series of substantially vertical open flues therein spaced from the top and bottom of the chamber to allow a free flow of gas from the chamber therethrough, each flue having a burner adjacent the bottom thereof to blast a flame within each flue, said walled chamber having exhaust openings adjacent the bottom of the flues, and the walls of the chamber directing combustion gases toward said openings, the burning flame blasting combustion gases from the upper end of each flue and drawing part of the combustion gases into the lower end of each flue and setting up paths of circulation in the heater atmosphere, a plurality of oil carrying tubes within said chamber arranged adjacent said flues and spaced from the tops thereof, and being within the paths set up by the circulating heat from the flues.

8. The process of heating oil for petroleum crackers comprising passing oil through pipes in a chamber, feeding to a burner within the chamber a completely combustible fuel mixture to produce a flame within the chamber, shielding the flame of combustion from contact with the oil carrying pipes, the complete combustion of the fuel producing inert gases substantially free from oxygen and carbon monoxide and setting up a rapid circulation of the heated inert gases around the pipes, the burning fuel mixture drawing the combusted inert gases into contact with the flame of combustion and recirculating the gases around the pipes, and maintaining the chamber under pressure of the inert gases greater than atmospheric pressure.

WILLIAM WALLACE KEMP.

, REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,297,589 Pavlon Mar. 18, 1919 1,717,115 McCann June 11, 1929 1,980,301 Stewart Nov. 13, 1934 1,756,407 Vobach Apr. 29, 1930 2,206,378 Wilson July 2, 1940 2,288,368 Parsons June 30, 1942 2,335,317 Sherman Nov. 30, 1943 2,067,864 Stirling Jan. 12, 1937 2,192,238 Ocon Mar, 5, 1940

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