Heat exchange – With protector or protective agent
Patent
1996-07-31
1998-10-27
Leo, Leonard R.
Heat exchange
With protector or protective agent
16510421, 165154, 165158, F28F 1900, F28D 710, F28D 1502
Patent
active
058266470
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a heat exchanger of the type for cooling process gases containing finely-dispersed solid components at high temperatures, preferably between 800.degree. and 1200.degree. C., particularly for carbon black production.
BACKGROUND OF THE INVENTION
Heat exchangers of this type are known from, for example, German Published, Non-Examined Patent Application DE-OS 27 25 045, German Patent DE-PS 29 48 201 and U.S. Pat. No. 3,364,983. These heat exchangers, which are used in systems for carbon black production, are the point of departure for the invention. The bulk of the carbon black serves as a filler in the tire industry. It is obtained by means of substoichiometric combustion of a heavy oil residue (feed stock). The process gas that forms during combustion carries along the carbon black, in finely-dispersed form, and is conveyed through the pipes of the heat exchanger. The temperature of the process gas as it enters the heat exchanger is in a range of approximately 800.degree. C. to 1200.degree. C., typically in a range of 800.degree. to 1050.degree. C. As it passes through the pipes, the process gas is cooled to temperatures in an order of magnitude of 550.degree. to 650.degree. C. as heat exchange occurs. The exchange medium, generally cooling air (process air), flows along the outer circumference of the pipes, in the opposite direction of the process gas, and is warmed during the process from, for example, between 40.degree. and 60.degree. C. to between 700.degree. and 800.degree. C. Air heated in this way can be used as preheated combustion air.
Some types of carbon black carried along by the process gas have the tendency to deposit on and clog the surrounding surfaces. This is particularly the case for the flow supply pipes; consequently, they are equipped with a cleaning apparatus, by means of which a blast of steam or other compressed gas can be sent through the pipes at regular intervals to loosen the deposited carbon black from the wall and entrain it. Cleaning apparatuses of this type are known from the three cited publications.
In practice, the pipes, and thus the entire heat exchanger, have a considerable length of approximately 8 to 12 meters, and are combined to form a pipe bundle of approximately 50 to 100 in a boiler-type housing, which is generally cylindrical. The assemblies can be arranged vertically or horizontally.
While carbon black production was the starting point for the invention, similar problems can also occur in other chemical and combustion processes in which process gases are formed that contain finely-dispersed solid components and are to be cooled.
A critical feature of heat exchangers of this type are the pipe headers arranged on the side of the process gas intake chamber, which are in a high temperature range and must endure a temperature difference of several 100.degree. C. on their two sides. In addition, the geometrical shape of the pipe headers as a plate provided with multiple perforations is unsuitable for continuous thermal exposure. In the past, therefore, cracks appeared repeatedly in the pipe headers. This led to the formation of air on the one hand and carbon-containing gas on the other hand, as well as the presence of high temperatures and excessive combustion inside the heat exchanger, resulting in a breakdown of the same within a short time. When this occurs, of course, the entire upstream and downstream production line must be halted. The resulting damage extends well beyond merely replacing the heat exchanger, which already represents a large unit associated with a corresponding investment.
From DE-OS 22 23 805, it is already known to reduce the temperature stress of the pipe header disposed on the side of the process gas intake chamber by configuring the pipe header as a double pipe header flowed through by a cooling medium. No details are disclosed regarding the cooling medium and its conduction. If the cooling medium is flowing water, the cooling performance is limited in the region of the double header, because the cooling performa
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Colombo Massimo
Engelhardt Wolfgang
Engelhardt Wolfgang
Leo Leonard R.
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