Mineral oils: processes and products – Chemical conversion of hydrocarbons – With prevention or removal of deleterious carbon...
Patent
1996-07-22
1999-07-13
Yildirim, Bekir L.
Mineral oils: processes and products
Chemical conversion of hydrocarbons
With prevention or removal of deleterious carbon...
208 48AA, 208130, 208131, 208132, 585648, 585650, 585950, 422198, C10G 916
Patent
active
059221925
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention is directed to heat exchange surfaces in reactors and tubular heat exchangers in installations for converting hydrocarbons and other organic compounds in relation to the problem of coke formation on these exchange surfaces.
BACKGROUND OF THE INVENTION
In order to produce ethylene and other lower olefins, hydrocarbons or mixtures of hydrocarbons are thermally cracked, for example in externally heated reactors formed of metallic materials and the hot cracked products obtained thereby are cooled after leaving the cracking furnace in heat exchanger apparatuses which are operated externally with water under pressure serving as coolant.
The cracking furnaces are preferably formed of high-temperature steels containing chromium and nickel. The tubular heat exchangers are preferably formed of low-alloy steels or boiler construction steel. This apparatus can also be used to produce other organic products, e.g., as in the production of vinyl chloride by pyrolysis of 1,2-dichloroethane.
The operating efficiency of such apparatus formed of metallic materials is highly dependent on the extent of carbon-rich deposits forming at their inner surfaces during operation. Such deposits can not only impede the desired heat transfer, but can also reduce the free cross section of the employed tubes which is important for maintaining throughput. This is true of currently used apparatus 25. FIG. 1 shows a typical curve A for the dependence of the quantity of deposited coke-like products m on the reaction time t.
After a certain period of operation, the deposits formed on the sides of the apparatus coming into contact with the organic compounds reach a permissible coke layer thickness S, as shown in FIG. 1, which causes reductions in output and necessitates the shutdown of operations and costly cleaning procedures. The coke-like deposits are usually removed by gasification using a mixture of hot steam and air which uncovers the metallic surfaces and ensures the desired heat flow.
In spite of thorough removal of the deposited coke, the newly forming deposits can again lead to compulsory shutdown and coke removal procedures already after a relatively short period of operation (e.g., 20 to 60 days). Since the applied oxidative decoking procedures simultaneously bring about a change in the material surfaces, such decoking procedures always involve an increase in the catalytic activity of the material surfaces which promotes unwanted surface coking. This catalytic activity increases with the number of decoking procedures to which the respective heat exchange surface is subjected and the operating periods between decoking procedures decline steadily. This is undesirable for technical reasons as well as from an economic viewpoint because it not only prevents maximum periods of stationary operating states, but also reduces the effective use of the installation and results in increasingly frequent cleaning costs. For these reasons, efforts have been made for years to find solutions for preventing rapid coking of the inner surfaces of such apparatus. In order to achieve this objective, it has been suggested, among other things, to prevent the formation of catalytically active centers or to inhibit such formation on the inner surfaces of tubes of the respective apparatus by developing passivating oxide coats, as described in U.S. Pat. No. 3,919,073; to coat the inner walls of the tubes with thin coats of low-alloy or nickel-free steels, as described in German patent publication DE-A 3 2476 568, to generate supporting layers or diffusion layers of chromium, as described in the publication by Brown, S. M. and Albright, L. F. ACS Symp. Ser. 32 (1976) 296, aluminum, as described in the publication by Frech, K. J., Hopstock, F. H. and Hutchings, D. A. ACS Symp. Ser. 32 (1976) 197, or silicon, as described in the publications by Brown, D. E., Clark, J. T. K., Foster, A. J., McCaroll, J. J. and Simms, M. L. ACS Symp. Ser. New York 202 (1982) 23; Bach, G., Zychlinski, W., Zimmermann, G., Kopinke, F. D. and Ande
REFERENCES:
patent: 4692234 (1987-09-01), Porter et al.
patent: 5208069 (1993-05-01), Clark et al.
patent: 5358626 (1994-10-01), Gandman et al.
patent: 5413700 (1995-05-01), Heyse et al.
patent: 5616236 (1997-04-01), Brown et al.
patent: 5656150 (1997-08-01), Reed et al.
Zimmermann Gerhard
Zychlinski Wolfgang
Mannesmann Aktiengesellschaft
Yildirim Bekir L.
LandOfFree
Apparatus and process for reducing coking of heat exchange surfa does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Apparatus and process for reducing coking of heat exchange surfa, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus and process for reducing coking of heat exchange surfa will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2272798