US3534726A - Gas-fired heater - Google Patents

Description

United States Patent [72] Inventor Jacob P. Frelick Jr.,

Great Falls, Montana [21 Appl. No. 755,036 [22] Filed Aug. 26, 1968 Oct. 20, 1970 Phillips Petroleum Company a corporation of Delaware [45] Patented [73] Assignee [54] GAS-FIRED HEATER 8 Claims, 2 Drawing Figs.

52 u.s.c| 126/343.5, 126/360, 165/108 1511 1111.0 F24h 1/20 [50] Field ofSearch 126/360. 343.5(A). 366: l65/l(l8((0nsulted) 1 3,446,939 5/1969 Morgan et al 165/108X FOREIGN PATENTS 1,186,969 2/1965 Germany l26/343.5(A)UX Primary ExaminerFrederick L. Matteson, .lrr Assistant ExaminerRobert A. Dua Attorney- Young and Quigg ABSTRACT: Gas heated, internally combusted heating tubes are disposed in an enclosure within a space or tank containing fluid, the enclosure being partitioned by parallel baffles. Hot gas flow through tubes is preferably countercurrent to flow of fluid to be heated through the enclosure. Pumps. piping valving and temperature control means are provided to heat within said enclosure only a small portion of the medium in the space or tank and to heat that portion which is withdrawn from the tank into said enclosure to a desired higher temperature than that of the portion remaining in the space or tank but outside said enclosure I Patented Oct. 20., 1970 FIG. 2

R m m E|- VL NL 1E. R F P In FIG.

A T TORNEYS cAs-rrnun nEArun This invention relates to an improved gas-fired heater. it also relates to an improved heated storage tank facility from which there can be delivered a heated medium or material, e.g., a material viscous at ordinary temperature such as asphalt or heavy oil.

in one of its concepts the invention provides a structure in cluding a container or tank adapted to confine within a space therein a medium which is to be heated before it is removed from the tank, a heater arrangement within said tank, an enclosure substantially but not completely enclosing said heater, at least one port permitting material or fluid in said tank to enter said enclosure and to come into contact with the heater element therein, at least one outlet from said enclosure to out side of said tank, means for circulating medium from within said tank through said enclosure to without said tank and for delivery as to a loading facility, means for continuously returning, during circulation, heated medium or fluid to said tank substantially adjacent to the point at which said port is located, and means for generating heat within said heater. in

another of its concepts, the invention provides a heater ele ment as here described including means for gas-firing the same, said gas-firing means being responsive to the temperature and, therefore, controlled by the temperature of the medium within said enclosure surrounding the heater element. in a still further concept of the invention, it provides a method for heating a medium or fluid within a tank or container which comprises circulating material in said tank to an enclosure located within a relatively small portion of said tank, in said enclosure heating said medium, removing heated medium from said enclosure to a point without the tank, delivering heated medium as to a loading facility, and recirculating undelivered heated medium to a point in said tank such that the recirculated heating medium will be in or enter into said enclosure without having to traverse a substantial portion or distance within said tank without said enclosure. in a further concept still, the invention provides a method as here described wherein the temperature of the heated medium within said enclosure is sensed and heat is supplied to the heater element within said enclosure responsive to said temperature.

it is a standard practice in the petroleum and other industries to provide stock or storage tanks or containers with individual heating units for warming liquids therein, i.e., to reduce the viscosity of the liquids or fluids, e.g., hydrocarbon oils and asphalt. Usually the tank heating means is disposed in the lower portion of the tank to facilitate the circulation of stored liquid within the tank by convection currents as the stored liquid is heated. The heating means comprise in part some type of burner often located externally of the tank. U.S. Pat. No. 3,212,493, issued Oct. 19, 1965, Miles L. Lacey, discloses a gas-fired heater with remote air and exhaust gases inlets and outlets, respectively. According to that disclosure, there is provided a gas-fired heating apparatus for heating a liquid contained in a tank, the apparatus comprising heater means external to said tank adapted to take air for combustion of fuel gas from outside atmosphere at a point remote from the explosive vapors around the base of said tank, the burner being adapted to pass the hot combustion gases produced therein in one end of a tubular heating means disposed within a lower portion of the tank, the other end of said heating means passing through the tank wall and connecting with a vent conduit communicating with the outside atmosphere. As shown in the patent drawing, the heating element or coil is located in the bottom of the tank and the material within the tank has free access directly to said coil. Heated fluid will rise by convection to the top of the tank or at ieast to the surface of the fluid therein.

1 have now conceived a method and an arrangement corresponding to it for executing the same which comprises confining the fluid to be heated, e.g., asphalt or other viscous fluid in proximity to the heater coil or element, thus heating only a small portion of the asphalt, that is to say, that portion of asphalt which is adjacent the heater element within the confinement. In one form or embodiment of the invention, the heating coil is surrounded substantially by an enclosure or box, into, through and from which the asphalt to be heated is circulated by means of a pump. Heated asphalt which is not delivered as to a loading facility and taken from said facility as into a truck for delivery to a point of utilization is recirculated substantially to a point in and/or adjacent said enclosure, usually tojust about the point at which an opening provided in said enclosure for drawing asphalt from the tank thereinto is located. Thus, the asphalt entering from the tank admixes with the already heated asphalt being recirculated. This facilitates the entry of the viscous asphalt into and its passage through the initial portion of the enclosure due to the dilution of the relatively cold asphalt with an already heated asphalt. By providing one or more temperaturesensing elements within the enclosure, it is possible to so regulate the heat supplying means, for example, a gas-fired burner as to accomplish the desired heating of the asphalt and the maintaining of it within the enclosure at a desired temperature. The enclosure and the operation of it according to the invention permits confining the asphalt in a rather small portion relative to the contents of the tank adjacent the heater coil or coils. To further improve the heating, saving fuel, by this arrangement, the enclosure can be partitioned to cause a fairly thin layer of asphalt to flow surrounding the coil. Preferably, the flow of hot gases within the heater tubes or coil is countercurrent to the flow of the asphalt surrounding the exterior thereof. As a safety measure, each cell within the partitioned box or enclosure can be provided with a relief valve in the event that, as the operation is started up or for other reason, some blockage occurs and pressure within the enclosure momentarily rises beyond that which it is designed to withstand. There can be more than one port within the enclosure and there can be several enclosures as herein described.

it is an object of this invention to provide an improved heating means for heating a fluid within a container or tank. it is another object of this invention to provide a method for heating a material within a tank and removing it from said tank in heated condition. it is a further object of this invention to provide a more economical means and method for heating a medium within a tank and removing said medium from said tank for delivery as to a loading facility. lt is a further object of the invention to provide means and method for heating only a very small portion, or relatively small portion of the fluid in a tank in which it is stored so that only a small amount of heat relative to that which has been heretofore employed will be used. it is a further object of the invention still to provide heat ing means and method which automatically will heat and deliver from a small portion of heated material within a tank material from said tank.

Other aspects, concepts and objects of the invention are apparent from a study of this disclosure, the drawing and the appended claims.

According to the present invention, there is provided a method for heating a medium in a tank which comprises drawing medium within said tank to within an enclosure within said tank, said enclosure being relatively smaller than the space enclosed by said tank, in said enclosure heating the medium or fluid, and then withdrawing the heated fluid from said enclosure to a point without said tank as to a loading facility. Further, according to the invention is provided a method wherein the fluid drawn into said enclosure and passed to without said tank but not delivered as to a loading facility is recirculated ultimately to within said enclosure without traversing any substantial portion of or distance in said tank so that the recirculated earlier heated fluid will not yield up any substantial portion of its heat to the contents of the tank before it has reentered said enclosed portion. Still further, according to the invention an inlet and the conduit for returning earlier heated, recirculated liquid are arranged to be adjacent one another so as to cause the recirculated heated fluid to admix with the fluid from the tank entering into the enclosure so as to preheat the fluid entering the enclosure from within the tank to facilitate movement of the fluid within said enclosure.

Also according to the invention there is provided an improved heating means within a tank, adapted to heat a medium or fluid within said tank as to reduce its viscosity, said heating means comprising an enclosure containing a heating element, at least one inlet port from a point from within said tank to a point within said enclosure, said enclosure being arranged to cause material from within said tank to he confined against the heater element and means for removing thus heated material from a point within said enclosure to a point without said tank. Also, according to the invention, means are provided for circulating back to the enclosure heated medium or fluid which has been removed from said enclosure. Preferably, the means for recirculating the earlier heated fluid is adjacent the port in said enclosure through which the medium in said tank enters said enclosure. Still further, the means for heating or heater element which can be gas'fired or otherwise heated as by circulating a heating medium other than combustion gases or even by electricity is provided with a temperature control adapted to be responsive to the temperature of the medium heated within said enclosure. The'eirculating means, usually a pump, is provided and so piped and valved as to preferably, continuously circulate medium being heated within the enclosure from the enclosure back to the enclosure so as to maintain the relatively small amount of heated material at a desired temperature for instantaneous delivery as to a loading facility, said temperature being substantially higher than the temperature of the remainder of the contents of the tank.

Referring now to the drawing, FIG. 1 is an elevational crosssectional view showing a gas-fired heating unit within an enclosure within the tank according to the invention. FIG. 2 is a plan cross-sectional view taken through the tank and heater of the invention at a level along the axis of the heater tubes.

Referring now to the drawing, there is shown in FIG. I a tank 1, having a gas burner heated heating element tube enclosed within an enclosure 3. As shown in the drawing, air for the gas burner is mixed with gas supplied to the burner by pipe 4. The gas is combusted and passes through the burner into the coil 2 and from coil 2 up through flue gas stack 5 and to the atmosphere.

Referring now to H6. 2, there are shown a plurality of coils 2 located within enclosures 3. in the drawing there are shown two enclosures, each of which has an inlet or port provided at 6. As arranged in the drawing, each segment of the coil is located within a compartment defined by partitions 7. The arrangement provides for countercurrent flow of the tank contents through the enclosure in close proximity to the tubes with the gases going through the tubes from the burners. As shown, the heated medium from each enclosure passes to a common outlet portion 8, and then by pipe 9 and pump 10 to header 11. When loading facilities are being used, a control valve 12 removes heated medium, for example, asphalt, to said facilities. When valve 12 is closed, or is only partly open, the heated medium in header 11 is recirculated through pressure controller 13 to outlet end 14 of the header for admixing heated medium with medium in the tank just prior its entry into the compartment. More than one port can be provided and various arrangements for heating elements and the compartment will be obvious to those skilled in the art having possession of this disclosure and having studied the same. A temperature sensing means 15 sends a signal to temperature recorder controller 16 for controlling gas to the burners.

it will be seen upon consideration of the foregoing arrangement that the invention provides for heating only a relatively small portion of the medium such as asphalt within the tank, all the while some of the heat perforce will heat all of the medium in the tank. it also provides for heating just prior to the entry into the compartment of the tank contents to a higher temperature than that at which the contents need to be stored and thus there is a neat coaction between the return of the recirculated heated medium to the compartment and the tank contents. This is an important feature of the preferred form of the invention.

Although countercurrent flow to the hot gases of the medium to be heated has been shown, different flow arrangements will be obvious to those skilled in the art having possession of this disclosure and having studied the same.

it is evident that the asphalt or other medium in the tank to be heated is heated more effectively and also that there is effected a considerable savings in that a minimum of fuel is used. This is especially understood when the prior practice which included heating the entire tank contents is considered.

The use of a smaller tank located within the main storage tank and into which heating coils are placed is not satisfactory because only the amount of asphalt contained within the smaller tank is heated and this does not allow for continuous delivery of heated asphalt which can be neatly accomplished with the present invention and its arrangement.

EXAMPLE The invention has been installed in a large cone roof storage tank. The following is a description of this installation:

1. Tank size 120ft. diamcter 40 ft. height cone roof. Capacity: 80,000 bbl. 14 inch nominal diameter.

6. Temperature of asphalt inside enclosure. 300 F. 7. Tern eraturo of asphalt inside tank but 200 F.

outsi o of enclosure. 8. 'llemperature rise of asphalt through en- F.

c osure. 9. Heat input to 4burncrs at 4,000,000B.t.u. 16,000,000 l3.t.u. per hour.

per hour each. 10. Net heat absorbed by asphalt 8,000,000 B.t.u. per hour.

300 g.p.m.

1 B.t.u. per lb.

11. Flow rate through heater enclosure.

12. Heat absorbed by asphalt 13. Final temperature of asphalt delivered 800 F.

to leading facilities.

14. Calculated heat; loss through uninsu- 2,755,080B.t.u. per hour.

lated tank shall when asphalt delivery temperature is 300 F., without enclosure.

15. Calculated heat loss through uninsulated tank shall when asphalt delivery tom eruture is 300 F., with enclosure.

16. D erence in heat loss because of inven- 515,730 B.t.n. per hour.

tion (item 14 minus item 15).

17. Fuel saving, using natural gas at 45 per 1' 5 'a d' 24 h x 45 r 18. Futlal saving: $11.14X240 heating days $2,075 per season.

equo s.

2,239,350 B.t.u. per hour.

Reasonable variation and modification are possible within the scope of the foregoing disclosure, the drawing and the appended claims to the invention, the essence of which is that there have been provided method and means for delivering from a tank its contents heated to a desired temperature wherein only a relatively small portion of the tank contents is heated at any time, preferably is recirculated to the zone of heating and wherein the zone of heating is partitioned from the rest of the tank contents with controls substantially as described herein to operate a heating section enclosed within an enclosure into which there will flow from therearound contents of the tank for heating and for pumping as to a loading facility and for recirculation into the heating zone to there admix with the tank contents, preferably adjacent the inlet port to said zone.

lclaim:

l. A method for heating and delivering therefrom as to a loading facility the contents of a tank which comprises substantially completely enclosing a portion within said tank, said portion being a relatively small portion of the overall tank, positioning a heating means within said enclosed portion, providing said enclosed portion with at least one port through which tank contents can enter into said enclosure, heating contents entering said enclosure therein, removing contents from said enclosure in heated condition to a point without the tank, recirculating at least a portion of the tank contents removed to a point without the tank into said tank in a manner that the recirculated portion enters said enclosure for further heating without traversing a substantial portion or distance within said tank in contact with its contents not within said enclosure.

2. A method according to claim 1 wherein the recirculated heated portion is discharged into the tank at a point adjacent said port there to intermingle with the portion of the tank contents entering through said port, thus to increase mobility and, therefore, the movement of said contents into and through said enclosed portion.

3. A method according to claim 2 wherein a temperature sensing element is located within said enclosed portion to sense the temperature of the heated tank contents and the heater within said portion is operated responsive thereto.

4. A method according to claim 3 wherein there is maintained a predetermined rate of circulation into, out from and back into said enclosure of the contents of the tank heated therein, thus to maintain for instantaneous discharge a suitable quantity of suitably heated tank contents at a temperature relatively higher than that of the overall contents of the tank.

5. An apparatus for carrying out the method of claim i comprising a tank, an enclosed relatively small portion within said tank, a port communicating with said enclosed portion and the interior of said tank, a heating means within said enclosed portion, means for discharging contents of said tank which have entered through said port into said enclosure and have been heated therein, means for removing discharged contents from said enclosure as to a loading facility. means for recirculating into said enclosed portion in said tank a removed portion of the heated fluid so as to maintain a circulation through said enclosure of said heated fluid, said means for recirculating being located adjacent to said port so as to permit intermingling ofa portion of the tank contents and recirculated heated fluid, thus to facilitate the entry ofa fluid from the tank to said enclosure by, in effect, preheating same by its dilution with the recirculated, heated contents.

6. An apparatus according to claim 5 wherein there is provided a temperature sensing element within said enclosure and a temperature control on the heating element and said sensing element and temperature are operatively connected to heat the contents of the enclosure to a desired temperature,

7. An apparatus according to claim 5 wherein said enclosure is partitioned and there is within the partition a continu ous heating coil and the enclosure and the partition coact to cause the tank contents to flow in close proximity to said coil, thus to heat tank contents while flowing through said enclosure thus partitioned.

d. An apparatus according to claim 5 wherein the heating element in said enclosure is a tubular heater through which are passed combustion gases from a burner operating responsive to the temperature of the heating contents of said enclosure.

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