Liquid heaters and vaporizers – Heat transmitter
Patent
1994-08-30
1996-09-24
McMahon, Marguerite
Liquid heaters and vaporizers
Heat transmitter
F22B 712, F22B 3706
Patent
active
055580467
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a fire-tube boiler.
Fire-tube boilers are generally known. They consist of a horizontal cylindrical boiler drum having one or more fire tubes therein, into each of which a burner introduces hot gases at one end. At the other end, the flue gases which are already cooled and have temperatures of generally 700.degree. C. to 1000.degree. C. leave the fire tube and enter a reversing chamber where they are deflected and fed to a flue line which consists of a bundle of parallel flue tubes which extend through the boiler drum below the fire tube.
These drums are used for firing with oil and gas for the production of steam, hot water, etc. They operate satisfactorily when said fuels are used.
When firing with powdered solid ash-containing fuels, however, serious problems due to dirtying of the boiler occur with such fire-tube boilers. Since, in particular, larger particles of fuel are in a pasty state for a long time during the combustion process, they can, when impinging upon cool walls adhere to them, solidify and build up slag deposits the elimination of which is difficult. As a general rule, for this purpose, the feed water must be removed from the boiler so that the boiler cools rapidly, which means a considerable loss of feed water and long standstill periods. Fire-tube boilers fired with ash-containing powdered fuels have therefore not been able to gain substantial acceptance.
The object of the present invention is to provide a fire-tube boiler of the aforementioned type which is suitable for firing with ash-containing powdered solid fuels without danger of dirtying.
The object of the invention is achieved by providing a fire-tube boiler operated with ash-containing flue gases and containing, in a boiler drum, at least one horizontally arranged fire tube which is provided at one end with an extension for the connecting of the burner, a reversing chamber at one end of the boiler drum into which an outlet of the fire tube debouches at the other end thereof, and a plurality of flue tubes which have an inside diameter 2R and extend, starting from the reversing chamber, below the fire tube through the boiler drum, wherein diameter (2) in the direction towards the reversing chamber into which it debouches, in trumpet-like manner with a radius of curvature r over an axial distance of approximately r, r/R being >0.3, capacity and the desired temperature of the boiler water, are so selected that, in operation, the temperature of the flue gases at the outlet end of the fire tube lies a safety margin below the ash-softening temperature of the corresponding fuel, and that the dynamic pressure in the flue tubes at a point directly behind the trumpet-shaped widening is greater than 40 Pa.
Three groups of features contribute to the success achieved by the invention, namely: special manner so as to obtain favorable conditions of flow there which substantially exclude the formation of shadows, emergence from the fire tube are cooled, with a safety margin, below the ash-softening point, and there are present in the cylindrical portion of the tube inlet predetermined dynamic pressures which are necessary in order to avoid the depositing of ash in the flue tubes.
The dimensions of the fire tube which are necessary in order to obtain said sufficient cooling of the flue gases to below the ash softening point can be calculated from the heat transfer by radiation and convection, with due consideration of the wall temperature and the laws of fluid mechanics. In this connection, reference is had to the VDI Heat Atlas from which corresponding information can be obtained. The number of tubes and their cross section determines, for a given boiler capacity, the velocity of flow and thus the dynamic pressure of the flue gases in the flue tubes. From the boiler capacity, the total amount of air can namely be calculated via the amount of fuel and the air excess for complying with the provisions of the TA Air, the total amount of air and, from this, the amount of offgas which, in its turn, with a predeterm
REFERENCES:
patent: 3618572 (1971-11-01), Nauert
patent: 3672839 (1972-06-01), Moore
patent: 3857367 (1974-12-01), Giesen
patent: 4055152 (1977-10-01), Vidalenq
patent: 4109614 (1978-08-01), Viessmann
patent: 4327672 (1982-05-01), Viessmann
patent: 4398848 (1983-07-01), Siebelt
patent: 4499859 (1985-02-01), Nishiguchi et al.
patent: 4720263 (1988-01-01), Green
patent: 5273002 (1993-12-01), Balint et al.
M. Ledinegg, Dampferzeugungs-Dampfkessel, Feurerungen Dec. 1966, pp. 5, 6.
Prostler Josef
Schoppe Fritz
Dr.-Ing. Fritz Schoppe
McMahon Marguerite
LandOfFree
Fire-tube boiler does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Fire-tube boiler, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Fire-tube boiler will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1922132