US2206378A - Apparatus for heating fluids - Google Patents

Description

y 1 0 L WILSON E1- AL 2,206,378

APPARATU S FOR HEATING FLUIDS Fi10d Aug. 11, 1958 2 Sheets-Sheet 2 Patented July 2, 1940 UNiTED STATES 2,206,378 APPARATUS FOR HEATING FLUIDS Lee Wilson and James 0.

Ohio, assignors Woodson, Cleveland,

to Lee Wilson Engineering 00.,

Cleveland, Ohio, a corporation of Ohio Application August 11, 1938, Serial No. 224,325

2 Claims.

This invention relates generally to the heating of fluids. It will be described herein as applied to oil'cracking stills but it will be understood that it may likewise be applied to other processes wherein the heating of fluids is involved.

It has been the practice heretofore in cracking hydrocarbon oils, to pass the oil through banks of heat absorbing tubes and to supply heat to the tubes by the combustion of fuel in the immediate neighborhood thereof. This practice has prevailed for many years even though there are serious objections thereto. In the first place, the direct impingement on the tube banks of the flames resulting from the combustion of fuel in the immediate neighborhood exerts an eroding action on the tubes which renders them unfit for further service after a relatively short time. A further objection is the coking of the oil on the interior of the tubes which results from localized hot spots. These are occasioned by the inability of the still operator to control the temperature of various portions of the still. When the hot combustion gases have been formed, their subsequent course is determined solely by the draft through the furnace and it has proved impossible even with the aid of baflles, dampers, etc., to maintain the desired temperature in different portions of the still.

We have invented an apparatus for heating fluids which overcomes the aforementioned objections to the previous practice in the construction and operation of oil stills and is characterized by further features of advantage which are of value in other fields. In a preferred form and practice, the invention consists in passing the fluid to be heated through banks of heat absorbing tubes and heating such tubes substantially exclusively or at least principally by direct radiation. As a source of radiant heat, We prefer to employ heat-radiating tubes disposed adjacent the banks of heat exchange tubes, and

having burners mounted to discharge hot combustion gases therethrough. The heat-radiating tubes are thus heated to radiant temperature and radiate heat directly to the still tubes. We also utilize heating of the still tubes by direct contact of combustion gases therewith by limiting direct contact of the gases with the tubes to. zones-in which the velocity and temperature of the gases have been reduced somewhat from their initial maximum values. We also employ the countercurrent principle by introducing the oil to :be heated to the minimum temperature zones of the still and then passing it through the zone .of maximum temperature.

A few typical "forms of stills embodying our invention are illustrated diagrammatically in the accompanying drawings and the following detailed description should thereto. In the drawings:

1:Fig. l is a transverse sectional view through a s ill;

Fig. 2 is a partial sectional View taken substan tially along the line II-II of Fig. 1; line I-I of Fig. 2 indicates generally the plane on which the sectionof Fig. l-is taken; and

Fig. 3 is a view similar to Fig. 1 showing a modified form of still.

Referring now in detail for the present, to Figs. 1 bodiment of our apparatus chamber to of any desired illustrated embodiment, the compartments I I, I2 and and 2, a typical emincludes an enclosed construction. In the chamber It includes l3 defined by bafile walls M. Banks of heat-absorbing, still tubes indicated generally at it are mounted on the sides, bottom and top of the compartment H by any suitable mounting means (not shown). Burners it are mounted in an end wall thereof charge hot combustion gases into the compartment for heating fluid circulating through the banks l5.

Banks ll of heat-absorbing tubes are disposed in the compartment l2, being supported thereon by any convenient known structure. Heatradiating tubes l8 are positioned in rows between the banks l7 and extend upwardly from a hearth or the like l9 carried on structural members 26. A burner 2| is mounted in the lower end of each of the tubes l8 and pipe connections '22 extend therefrom to a supply of a suitable fuel. The upper ends of the tubes I8 are preferably open sothat combustion gases are discharged therefrom after passing the length of the tubes, into the upper portion of the compartment l2.

The compartment I 3 is provided with a heata'bsorbing tube bank 23 and communicates with a stack (not shown) by means of a passage 24. The combustion gases discharged by the burner l6 and tubes 18 will thus pass through the compartment I3 in direct 'co tact with the tubesof the'bank 23.

The tubes of the several banks I5, I! and 213 are so connected that the fluid traversing them follows the course indicated by the arrows 25. Suitable means such as'pumps and the like are provided for circulating fluid through the tubes and the necessary control valves installed at the proper points. These details are not shown on the drawings (w-h-ic'h are "largely diagrammatic) be read with reference to the drawings and,

and disbecause they represent merely conventional practice.

As will be noted by tracing the arrows 25, the oil or other fluid to be heated enters the bank 23 at the bottom thereof and then flows through the banks I5. From the latter, it passes through the banks successively. Gases and vapors resulting from the heating of the oil are taken off by suitable means and delivered to appropriate apparatus for further processing. By this arrangement, the entering oil is subjected to the heating action of the combustion gases on their way to the stack after giving up most .of. their heat to the banks I1 and I5. The banks |5 are heated by the combustion gases delivered by the;

burners l6. The banks l5 need not be heated on at high velocity, the life of the tubes forming the banks I5 is not seriously shortened by the direct contact of the gases therewith. In the zone of the maximum temperature, the compartment l2, the tubes of banks H are protected from the impingement of maximum temperature gases thereon at high velocity and are heated substantially exclusively by direct radiation. This arrangement effectively solves the problem of short tube life which has heretofore been experienced, particularly in the maximum temperature zones wherein the heat-absorbing tubes were subjected to the impingement of combustion gases at high temperatures and considerable velocities. 1

Fig. 3 illustrates a modified structure which is similar in principle to that shown in Figs. 1 and 2. In Fig. 3, a still 30 includescompartments 3|, 32, 33 and 34 defined by baffles 35 and across wall 36, An opening 31 in the latter connects the compartments 33 and 34. Heat-absorbing tube banks 38 are disposed in the compartment 3| alongside the bafile 35 and adjacent the top or roof of the still. The compartment 32 isproe vided with heat-absorbing tube banks 39 and compartment 34 with heat-absorbing tube banks 40. All these banks are supported by known means, Banks 4| of heat-absorbing tubes are disposed in the compartment 34 in spaced relation. Heat-radiating tubes 42 are disposed 'in rows on opposite sides of the banks 4|. The tubes 42 project downwardly from the top of the compartment 34 and each of them is provided with a burner 43. v The combustion gases passing through the tubes 42 heat them to radiant temperature. The ends of the tubes are open and the combustion gases discharged therefrom pass through-the opening 31 into the compartment 33 and thence around the tubes of banks 40. Thegases then pass upwardly around the right hand bafiie 35 and downward through the banks 39 to a stack port 44. I A burner 45 is mounted in a suitable opening 46 in the side wall of compartment 3| and de livers hot combustion gases against-the tubes of. banks 38. As indicated. by the arrows, the fluid to be heated is first passed through the tubes of banks 39 then through the tubes of banks 40. From the latter, the fluid passes through a connection 41 to the banks 38 and after traversing the latter it passes through a connection 48 into the banks 4|, From the latter, the products formed in the cracking process are taken off through an outlet 49. The combustion gases discharged in the compartment 3| pass upwardly around the left hand :bafile .35

well as other products formed by the combustion of fuel flowing from a burner.

' The connections and control valves mentioned above include, of course, valves for controlling theamount of fuel supplied to each burner. By

manipulating such valves it is possible to control the temperatures-at various points throughout the still in a manner appropriate to the nature of the cracking operation being carried on. If the temperature of any one portion of the still becomes excessive, it is a simple matter to reduce the amount of fuel delivered to the in.. dividual burners in a manner such as to correct the abnormal temperature condition.

Further advantages of the invention include the fact that in the zones of maximum temperature the tubes through which the fluid circulates are not subjected to direct impingement of the combustion gases at high velocity. The oil tubes in the zones at highest temperature are heated indirectly or, in other words, by radiation substantially exclusively and it is only in the lower temperature zones in which the temperature and velocity of combustion gases are considerably reduced from their maximum values, that direct contact of the gases with the heat exchange tubeis permitted. This, prevents the useful life of the heat exchange tubes in the zones of maximum temperature from being shortened by the eroding efiect of combustiongases at high temperatures and velocities. Atfthe same time the use of convection heating in the zones of lower temperature raises the overall thermal efficiency of the cracking operation. The indirect heating of the tubes in the zones of maximum temperature has the further advantage that localized hot spots are largely avoided, together with the highly objectionable result usually accompanying such conditions, viz., coking of the oil on the interior of the heat exchange tubes. It will be readily apparent that the inventionthus effects a material reduction in the cost of maintaining a fluid heating apparatus such as a still in efficient operating con-, dition.

While we have illustrated and described but a few embodiments of the invention and a preferred practice thereof, it will be understood that changes in the embodiments and practice described may be made without departing from the spirit of the invention or the scope of the appended claims,

. We claim:

1. In a cracking still, a radiant heating chamber and a convection heating chamber communicating therewith, a plurality of spaced banks of superposed heat-absorbing tubes in said radiant heating chamber, a plurality of substantially vertical' heat radiating tubes between adjacent banks. and 'a-burn'er in one end of each heatradiating tube, the other end of each heatradiating tube being open todischarge combustion products into said convection heating chamber. P I

2. In a cracking still, a radiant heating chamber and a convection heating chamber disposed side by side and communicating with each other, a bank of superposed heat-absorbing tubes in said radiant heating chamber, a plurality of substantially vertical heat-radiating tubes adjacent said bank, and a burner in one end of each heat-radiating tube, the other end of each heatradiating tube being open to discharge combustion products into said convection heating chamber, a second radiant heating chamber, heatabsorbing tubes therein, burners for heating it, said second radiant heating chamber communicating with said convection heating chamber, and a stack flue leading from said convection heating chamber.

' LEE WILSON.

JAMES C. WOODSON.

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