US2025667A - Method of protecting selected parts of heating units - Google Patents

Description

Dec. 24, 1935.

P. C. KEITH, JR

Filed Dec. 6, 193s ////////H/ f f f 1/ INVENTOR R., J H .J E K C. m C R E P ATTORNEY Patented Dec. 24, 1935 UNITED STATES PATENT OFFICE METHOD OF PROTECTING SELECTED PARTS OF HEATING UNITS Percival C. Keith, Jr., Peapack, N. J., assignor to Gasoline Products Company, Inc., Newark, N. J., a corporation of Delaware This inventiion relates to a method of protecting selected parts of heating units from excessive heat and has reference particularly toa method of protecting certain portions of heating units which are normallyexposed to radiant heat, in which some of the intense radiant heat is caused to be reflected from the surface of the tubes rather than being absorbed thereby.

As an illustration, the invention is of advantage in protecting certain parts of tubular heating coils exposed to excessive radiant heat such as, for example, in protecting parts of heating coils mounted in the radiant heat sections of furnaces such as are employed in the treatment of hydrocarbon oils.'

As a further illustration, the invention is of particular merit when applied to furnaces for the treatment of hydrocarbon oils in which a plurality of separate streams of oil are heated in independent tubular heating units or coils mounted in a single furnace setting.

In the latter case the separate streams of oil in the independent heating coils ordinarily require different temperature treatment. It has been customary when different temperatures are required to control the firing of the furnace so as to bring the oil in all of the coils to the desired temperatures. Generally the temperatures of one or more streams may be controlled byV regulating the firing of the furnace In some instances When one or more of the streams pass through a convection heating zone and then through radiant heating zones, the temperatures of these streams are controlled by regulating the volume of oil passing through the various coils as well as regulating the firing of the furnace in the radiant heating Zones. The quantity of oil being passed through the various zones depends on the pressure employed. However, since the treatment to which these oils are subjected ordinarily requires that they be maintained Within pre-determined pressure ranges, the regulation of the pressure to control the temperature is limited and it may often happen that a portion or all of the individual coils becomes overheated necessitating replacements or repairs.

Also it may be desired to reduce the temperature to which the oil is heated, in one or more of the heating coils, below that to which it was intended to be heated at the time the heating coils were installed While maintaining original temperature conditions for the oils in the remaining coils.

Furthermore, certain portions of the heating coil or other heating unit may become overheated during normal operating conditions. My invention is particularly adapted to protect such overheated parts.

One of the primary objects of the invention is to protect selected parts of a heating unit against excessive heat.

A further object of the invention is to cover ycertain selected parts of a heating unit with a radiant heat reflecting surface capable of being readily applied thereto.

A further and more specific object of the invention is to cover certainselected parts of a tubular heating coil employed for heating hydrocarbon oils with .a uid of paint-like consistency capable of reflecting radiant heat.

I shall now describe suitable materials that may be used in accordance with my invention for protecting certain parts of a heating unit with a radiant heat reflecting surface. The radiant heat reflecting surfaceto be. applied to the part or parts to be protected is preferably made up as a paint-like mass of paint-like consistency that is capable of being applied by a paint brush or the like, or if desired, by any suitable spraying or dipping method. Wherever the expression paint-like mass or paint-like consistency is used in the specication and claims, it is to be understood that the expression includes any material capable of reflecting radiant heat and applied, as desired, to provide a closely adhering surface to the part or parts to be protected. The paintlike mass may be prepared as a freely owing iiuid, the thickness thereof Varying from a freely owing fluid to a mass of paste-like consistency which may be applied as a thin film or layer of closely adhering material. Y In accordance with the preferred embodiment of the invention, the part'to be protected from excessive radiant heat is provided With a thin coating or covering of white pigment suspended in a suitable vehicle such as, for example, sodium silicate to form a paint-like mass which, after being applied and dried, forms a hard and impervious coating.

While sodium silicate is mentioned as being particularly suitable as a vehicle because of its refractory characteristics and because it produces a hard and impervious coating, it is to be understood that other types of vehicles may also be employed. It has been found, for example, that a White pigment such as finely divided calcium oxide in an oil suspension is entirely suitable for the purpose intended. A

As a pigment it is preferred to use an inorganic oxide or salt rather than an organic material because of the latters tendency to decompose at higher temperatures. Among the pigments which may be used to advantage ,are white metallic oxides such as calcium or lead oxides and salts such as barium sulphate or zincl sulphide or a mixture of these latter two, commonly called lithopone.

It is preferred, however, to use a white metallic oxide or salt which does not react with sulphur gases normally present in a furnace atmosphere so as to form a resulting compound of difierent heat reflecting characteristics. Lead oxide, for example, reacts with sulphur to form a black sulphide and consequently would not ordinarily be desirable as a pigment for fired tubes when the combustion gases contain substantial amounts of sulphur.

As an example of a suitable composition to be applied to the selected part to be protected I may mix lithopone, which as before stated consists of a mixture of zinc sulphide and barium sulphate with hydrated sodium silicate, sometimes referred to as water glass, and add to the mixture sufficient water to make a paint-like mass capable of being applied in any desired manner on the portion of the tubes or other parts desired to be protected. The sodium silicate, upon drying, forms a hard glass-like surface and causes the pigment to firmly adhere to the surface of the tube.

As another example, I may suspend a pigment such as barium sulphate, calcium oxide or zinc sulphide in a light oil medium which may be sprayed or brushed on the parts to be protected. The oil upon being subjected to the temperature of the furnace will decompose leaving the. white pigment on the surface of the parts.

As a further example, a plurality of coats of colloidal lime in aqueous suspension may be applied to the part or parts to be protected.

While my invention is particularly directed to covering the parts to be protected with a paintlike mass, other radiant heat reflecting surfaces may be used. For example, the parts may be provided with an electrolytic deposit of metal such as chromium or chromium alloys, or a sprayed metal coating Aof chromium, aluminum or other similar metals or alloys having a high luster. As a further example, the tubes or heating unit to be protected may be covered with a white procelain or vitreous glazed enamel.

The accompanying drawing illustrates a conventional box type furnace having banks of tubes for heating hydrocarbon oils in which the tubes located adjacent the roof directly above the fire chamber and the tubes in the rst two rows in the convection zone may be protected as hereinbefore described. It is undertood, however, that the invention is also of advantage in other types of furnaces and for protecting tubes or other selected parts located in zones other than that illustrated.

Referring to the drawing the furnace chamber I is divided by a fire wall 2 into a combustion chamber 3 and `a convection chamber 4. The combustion chamber 3 is red by any suitable means such as a burner 5 and the products of combustion after passing through the combustion chamber flow over the iire wall 2 and down through the convection zone 4 in which they impinge directly upon tubes 6. rIlhe combustion gases are withdrawn from the convection chamber 4 through the flue 'I which may ycommunicate with a stack (not shown) As illustrated, banks of heating tubes 8 and 9 which may be suitably interconnected to extend around the four walls of the combustion chamber are adapted to be heated by radiant heat from the products of combustion produced by the burner 5. The furnace may also be provided 5 with banks of heating tubes III adjacent the roof which may be in communication with the tubes 8 and 9 located in the combustion zone. If desired, the roof tubes I0 may communicate with tubes I2 mounted in the upper portion of the 10 convection Zone, such for example as the two top rows of tubes in the convection zone. While I have shown tubes 8 'and 9 within the radiant heating zone to form two coils, it is to be understood that only a single coil may be used. It 15 is also to be understood that the two upper rows of tubes I2 in the convection heating zone 4 may be dispensed with.

In heating hydrocarbon oils in a furnace of the type described, a stream of oil may be introduced 20 into the lower row of tubes 6 and passed countercurrent to the combustion gases therein to be preheated. The thus preheated oil may then be conducted through the tubes 8 and 9 which are subjected to radiant heat in the combustion 2:5l chamber 3 from which the oil passes to the two upper rows of convection tubes I2. The oil leaving the convection tubes I 2 may be conducted to any apparatus suitable for carrying out the desired separation of the constituents of the oil. 30 While the heating of one stream of oil has been described, it should be understood that two streams of oil may be heated in a similar manner, one stream thereof passing through certain of the tubes in each of the heating sections and 35 the other stream through the remaining tubes in these heating sections.

It has been found that the roof tubes I0 directly above the combustion chamber are subjected to intense radiant heat with the result 40 that the oil passing through them may be too intensely heated and the tubes may become damaged. In addition to the roof tubes, experience has also shown that the first rows of tubes in the convection zone, such as tubes I2, may also be 45 subjected to severe conditions due to the radiant heat from the roof of the furnace directly above, in addition to the intense convection heat from direct impingement of the combustion gases. In

accordance with my invention, overheating of the 50 oil and possible damage to the tubes subjected to the intense heat may be avoided. These tubes, such as the tubes I0 and I2 may be provided with a protective covering I I of a composition such as hereinbefore described which when applied forms 55 a protective film or layer of material, capable, when dry, of reflecting intense heat and particularly intense radiant heat.

If desired, the oil may be progressively heated during its passage through the tubes 6, 8, 9 and 60 I and maintained at the desired conversion temperature in the two upper rows of tubes l2, which in this instance, may function as a soaking section for the oil. When the two upper rows of tubes I2 are to be dispensed with, the roof tubes 65 Il] may function as a soaking section for the oil.

In operating the furnace in such a manner as to accomplish the desired soaking of the oil in either of the `above described soaking sections, it may only be necessary to impart sufficient heat 70 to the oil passing through these tubes to counterreact the heat lost by the heat of cracking. These tubes being subjected to the intense heat in the furnace may be provided with the protective covering II of the composition and in the manner 75 hereinbefore described. By providing a reecting heat surface for these tubes, it Will be clear that some of the heat that would normally be imparted to the oil passing therethrough is reflected therefrom thereby permitting only the neecssary heat to reach the oil as is required to maintain it at the desired conversion tempera.- ture, or if desired, to slightly raise it in temperature.

While I have described applying my invention to certain parts of the heat absorbing surfaces Within the furnace, it is to be clearly understood that it may be applied to other parts, the application thereof depending upon the parts that are subjected to the intense heat and should be protected.

Animportant advantage of the invention is that the coating may be applied in situ and can be applied to any parts of the tubes subject to overheating.

While the invention has many specic advantages in connection with tubular heating coils, particularly coils used for the treatment of hydrocarbon oils, it will -be apparent that the invention is also applicable to other types of heating units in which it is desired to protect a portion of the unit from excessive heat.

Having thus described some of the preferred embodiments of the invention, it is understood 5 that other modifications and variations come Within the scope and spirit thereof, and that the invention is not to be limited except as necessary to distinguish from prior art.

I claim: 10

'I'he method of increasing the heat reflecting capacity of selected parts of a tubular heating coil exposed to radiant heat that comprises painting the selected parts with a paint comprising a White pigment capable of being subjected to nor- 15 mal furnace conditions Without material discoloration and a vaporizable vehicle and applying heat to the heating coil to eiect vaporization of the vehicle and x the pigment on the painted surfaces as a relatively thin closely adherent 20 light colored layer of material capable of reflecting radiant heat. 4

PERCIVAL C. KEITH, JR.

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