US3130714A - Tube furnace - Google Patents

Description

April 28, 1964 J. c. KOEL 5 3,130,714

TUBE FURNACE Filed May 3. 1962 INVENTOR:

JAN C. KOEL Hls ATTORNEY United States Patent O 3,130,714 TUBE FURNACE Jan C. Koel, The Hague, Netherlands, assignor to Shell Gil Company, New York, N.Y., a corporation of Delaware Filed May 3, 1962, Ser. No. 192,106 Claims priority, application Netherlands May 1S, 1961 4 Claims. (Cl. 122-240) The invention relates to an installation for heating media which are to be passed through heater tubes, especially to an industrial furnace for heating liquid hydrocarbons in which a heating chamber is subdivided into a plurality of radiant heating sections by a plurality of rows of vertical heater tubes, each section being provided with at least one centrally positioned, vertical burner.

In a known installation the sections are divided by double rows of tubes; the side walls of the heating chamber are not provided with heater tubes. The tubes in one row are preferably staggered with respect to the tubes in the other row. In this case these tubes are loaded on two sides, i.e. heat is transferred both from the section which is laterally bounded by this tube as well as from the section adjoining this side.

The present invention now aims at providing an installation with a number of important advantages over the known installations, viz. rstly by reducing the wall surface required compared to the surface area of tubes housed in the heating chamber, and secondly by increasing the possibility of combining separate tubes into coils of tubing.

The invention therefore aims at providing an improvement in the said known installation by making better use of the available heating space and also providing a uniform heat load of the tubes in each section.

To this end the invention consists of an installation of the above type characterized in that a single row of tubes is arranged against the side-walls of the heating chamber, one or more double rows of tubes being arranged inside the said chamber in such a way as to form a plurality of sections which are rectangular in horizontal crosssection and laterally bounded by heater tubes, the double rows of tubes being arranged in such a relation to each other that the separate tubes of diferent rows are located diametrically opposite, i.e. back-to-back, and spaced so that the distance between center line and center line is double or almost double the distance between the center line of a tube of a single row and the wall.

As the result of such a provision, the burners are laterally encompassed by tubes and during operation the said tubes are very uniformly in an upward direction loaded which, as is known, is an important advantage of a vertical arrangement. Since the tubes disposed inside the heating chamber are placed back-to-back, the heat load of these tubes is substantially equal to that of the tubes arranged against the side walls. Since this arrangement erects a kind of imaginary wall inside the heating chamber, one row of tubes screening the back of the other row and vice versa. Hence this back-to-back arrangement of the double rows f tubes is of direct importance to the distribution of heat over the tubes as a result of which each section can be substantially equally loaded, which is very favorable from the point of view of heat economy.

The required heating chamber wall surface is considerably smaller than in known installations housing the same quantity of tube surface, and this results in a considerable economy in construction and maintenance costs.

The neat, uniform arrangement of the tubes relative to the heating apparatus opens up a wide range of possible methods of combining the separate tubes into coils of tubing, so that in practice a degree of freedom is, so to FPice A speak, added to existing possibilities, viz. owing to the substantially equal load on the separate tubes during operation.

The invention will now be further elucidated with reference to the drawing which shows by way of example a horizontal cross-section of a part of an industrial furnace for heating liquid hydrocarbons.

The furnace comprises a metal side-wall 1 which is profiled in transverse cross-section in order to increase resistance to buckling and bending. A layer of refractory material 2, for instance refractory concrete, is arranged against the said wall for instance being poured against the wall 1. A single row of vertical tubes 3 is arranged along the periphery of the wall which is closed upon itself and has a refractory lining, the said tubes being at a distance apart from the refractory wall which is almost equal to the outside diameter of the tubes calculated from the center line thereof. Two rows of tubes 4 and 5 are also arranged inside the space in such a way that the separate tubes of each row are diametrically opposite, namely, back-to-back. Two similar rows of tubes 4 and 5 are also arranged inside the said space. The rows of tubes 3, 4, 5, 4 and 5 together form four sections 6, 7, 8 and 9, each having a rectangular crosssection and being laterally bounded by a row of tubes. The bottom of each section is provided with a central opening 10, 11, 12, 13 in which may be arranged a suitable combustion apparatus.

The shortest distance of the tubes through the burner opening is such that during operation the largest lateral flame spread is not more than 2/a of the shortest distance between two diametrically opposed tubes; hence thus is approximately equal to the length of the shortest side of rectangle forming the lateral boundary of the section in question, or in other Words, the shortest distance from the center line of a burner in one section to the center line of a heater tube of the said section should be at least one and a half times the distance corresponding to the largest lateral flame spread during operation with respect to the center line of the burner in question.

In the example described, a firing method is adopted in which the burner installations are arranged in the bottom of each section. It is, however, also possible for the burner installations to be arrangtd in the top of each section so that the llame is downwardly directed during operation. It is also possible for several burners to be arranged in one section instead of one burner. If, for instance, the rows of tubes 4 and 5 are omitted, two sections are formed of a more oblong cross-section each of which is provided with two burners. The shape of the separate sections andthe number of burners depends on all manner of operating conditions, e.g. the type of medium to be heated, the desired degree of heating, the capacity, the throughput envisaged, and the like. It is, however, essential for each section to be laterally encompassed by rows of tubes.

The burner installations are of the type usual for such furnaces. They may consist, for example, of a central straight-pressure-type mechanical atomizer using liquid hydrocarbon as fuel, which is surrounded by suitable air supply elements and, if required, by means for mixing and conveying the media maintaining combustion.

The tube arrangement described is in principle very suitable for use in a furnace composed of a plurality of pre-fabricated elements closed upon themselves and so superposed that all the elements, the roof and the tubes are supported by the bottom element. With such a construction there is no need for the proile-stcel-support structure used in many known industrial furnaces and this results in a considerable savings in construction costs.

In the construction described, the heat is chiefly transferred by radiation; the still hot combustion gases Withdra'wn via the top still have a sufcient caloric value to permit their use for further heat transfer, so that they can be transferred direct to the following heating chamber, in which banks of heater tubes are also provided and heat is mainly given oi by convection. In this way it is, for instance, possible to connect a steam generator behind thel furnace described. Such an arrangement may be particularly advantageous in oil refineries. In principle it is also possible to connect in parallel a plurality of installations of the type described and to transfer the still hot combustion gases to a common chamber adapted for the transfer of heat by convection.

It is, of course, also possible to use an installation according to the invention solely for the generation of steam.

The installation described provides very attractive possibilities of flexible control, both as regards throughput and the degree of heating, and also provides a wide choice of media for treatment. When a plurality of the said installations are connected in parallel a compact unit may be obtained which is suitable for heating various media and can be simultaneously used for generative steam.

Example In an existing installation the heating chamber had the following dimensions:

Meters Length 6 Width 1 1 Height 19 This installation is used for heating crude oil from about 230 C. to about 350 C. at a pressure of 2 atms. The capacity of this installation is 50,000 ton calories.

l claim as my invention:

1. An industrial furnace installation for heating liquid hydrocarbons, comprising:

(a) a rectangular heating chamber having walls provided with refractory linings defining their inner surfaces, said chamber having a horizontal area divided into at least 4 equal rectangular radiant heating sections which are arranged around a central pointin the chamber;

(b) a row of vertical heater tubes extending through said chamber in close parallel relationship with respect to the linings of each of said walls to dene the outer boundaries of veach of said sections;

(c) at least two pairs of immediately adjacent parallel rows of vertical heater tubes extending through said chamber, the tubes in each of said rows being aligned with the tubes in the row immediately adjacent thereto along lines passing normal to said row and said pairs of parallel rows being normal to each other and arranged Within the chamlber to dene the inner boundaries of said sections; and,

(d) at least one centrally positioned burner in each of said sections.

2. An installation as claimed in claim 1, characterized in that the distance between the linings of the walls and the center lines of the rows of tubes extending parallel thereto is substantially equal to the outside diameter of the tubes in said rows.

3. An installation as claimed in claim 1, characterized in that at least one vertical burner is arranged on the bottom of each section.

4. An installation as claimed in claim 1, characterized in that the shortest distance from the center line of a burner in one section to the center line of a heater tube of the said section is at least equal tol one and a half times the largest lateral flame spread during operation with respect to the center line of the burner in question.

References Cited in the le of this patent UNITED STATES PATENTS 1,930,330 Gard et al NOV. 13, 1934 2,211,903 McCarthy Aug. 20, 1940 2,348,513 Barnes May 9, 1944 2,396,200 Praeger Mar. 5, 1946 2,625,918 Lurnby Jan. 20, 1953 2,965,080 Wallis et al Dec. 20, 1960 FOREIGN PATENTS 871,418 GreatBritain June 28, 1961

Claims (1)

1. AN INDUSTRIAL FURNACE INSTALLATION FOR HEATING LIQUID HYDROCARBONS, COMPRISING: (A) A RECTANGULAR HEATING CHAMBER HAVING WALLS PROVIDED WITH REFRACTORY LINING S DEFINING THEIR INNER SURFACES, SAID CHAMBER HAVING A HORIZONTAL AREA DIVIDED INTO AT LEAST 4 EQUAL RECTANGULAR RADIANT HEATING SECTIONS WHICH ARE ARRANGED AROUND A CENTRAL POINT IN THE CHAMBER; (B) A ROW OF VERTICAL HEATER TUBES EXTENDING THROUGH SAID CHAMBER IN CLOSE PARALLEL RELATIONSHIP WITH RESPECT TO THE LININGS OF EACH OF SAID WALLS TO DEFINE THE OUTER BOUNDARIES OF EACH OF SAID SECTIONS;

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