Liquid heaters and vaporizers – Stand boiler – Fluid fuel burner
Patent
1992-11-09
1994-06-14
Favors, Edward G.
Liquid heaters and vaporizers
Stand boiler
Fluid fuel burner
122 19, 122250R, 1223671, 1223673, 165182, F22B 502
Patent
active
053200713
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is directed to a device for indirectly heating fluids, particularly for high temperature processes. The device includes a heating space in which at least one tube coil is arranged. The tube coil is constructed in a planar member and the fluid to be heated can be conducted through the tube coil. Radiation heat of a heat radiator may act from the outside on the tube coil.
2. Description of the Related Art
Such devices are required particularly for carrying out high temperature processes which occur frequently in oil refining and petrochemistry. The fluid to be heated, e.g. liquid or gaseous hydrocarbons or a mixture of hydrocarbons and steam, is conventionally guided through a heating space in heat exchanger tubes and heated by the tube wall of the heat exchanger tubes without coming into direct contact with the heating medium. The transfer of heat to the tube wall is usually primarily effected by heat radiation which proceeds from an open flame of a combustible material burned in the heating space and to a small extent by the hot combustion gases by way of convection. The heat exchanger tubes run through the heating space in the form of tube coils.
The great disadvantage of open flames is that it is very difficult to adjust a desired geometric form of the flame and a temperature distribution which is as uniform as possible. Uniform heating ratios are therefore very difficult to achieve particularly under variable operating conditions. The boundaries for corresponding intervention for purposes of control are very narrow in practice. Changes in the flame geometry are equivalent to changes in the distance of individual locations of the heat exchanger tubes from the "flame surface". This means that the flow of heat through the heat exchanger tubes always fluctuates considerably not only along the tube coil. In particular, a nonuniform flow of heat can also be determined along the circumference of the heat exchanger tubes, since the individual partial pieces of the tube surface differ in their alignment with respect to the flame in a compulsory manner and are sometimes even remote from the flame and accordingly irradiated at different intensities. This can lead to localized overheating at isolated points of the heat exchanger tubes and simultaneously to a considerable drop below the desired tube wall temperature at other locations. Accordingly, thermal damage to the heat exchanger tubes can occur proceeding from the outside on the one hand and undesirable effects can also be triggered with respect to the fluid to be heated (e.g. coking of the inner surface of the tubes) on the other hand. In conventional furnaces for high temperature processes, the differences are often so great that the ratio of the maximum to mean heat flow in the walls of the heat exchanger tubes can lie in the range of 3:1 to 4:1.
It is known in practice to burn gaseous combustibles (gas or evaporated liquid combustibles) without flame formation in a burner with a heat radiation surface in that the gaseous combustible which is mixed with an oxygen containing gas (e.g. air) is guided through a porous radiation body and ignited and burned on its outer surface. The ignition is effected by the glowing of this outer surface (heat radiation surface). Corresponding to the geometric form of the radiation body, the heat radiation surface has a regular shape which, in contrast to an open flame, does not change when the supply of combustible material changes. Moreover, the temperature distribution within the heat radiation surface is very uniform.
Such a burner with heat radiation surface (heat radiator) is known e.g. from U.S. Pat. No. 4,722,681. Its radiation body is formed from a ceramic fiber matrix and has great length and width compared to the physical depth of the burner, resulting in a large heat radiation surface. This burner is provided for thermally treating long webs of paper or woven materials.
Further, it is known from U.S. Pat. No. 4,865,543 to use a burner with a heat
REFERENCES:
patent: 2578136 (1951-12-01), Huet
patent: 4886018 (1989-12-01), Ferroli
Bezzeccheri Maurizio
Giacobbe Francesco
Valenti Quintiliano
Villante Raffaele
Favors Edward G.
Mannesmann Aktiengesellschaft
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