Liquid heaters and vaporizers – Water tube – Headers
Patent
1987-10-06
1989-05-23
Favors, Edward G.
Liquid heaters and vaporizers
Water tube
Headers
122 32, F22B 3722
Patent
active
048319686
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a naturally circulating reboiler.
Conventional water tube boilers comprise a plurality of tubes connected between two drums or tube sheets such that each tube communicates between two headers. It is common practice to contain the pressurized boiling liquid inside unobstructed tubes and to heat these tubes by passing hot gases over the outer tubes surface. Natural circulation of the liquid is achieved by installing unheated tubes between the two headers to provide a return liquid passage.
The above described arrangement has major disadvantages when used with small boilers due to differential expansions between the boiler tubes and the casing which can lead to tube failure and leakages. Tubes and baffles are difficult to clean due to limited access and the relatively large space requirements used to accommodate liquid and liquid vapor headers.
In a naturally circulating reboiler, the first stage separation of one of the compounds from a mixture of two or more chemicals is accomplished by the application of heat. This heat provides latent heat of vaporization as well as the energy to break the chemical bonding between compounds. The resultant separated fluid, in vapor form, contains a higher concentration of the required chemical compound than the liquid from which the vapor has derived. A double rectifying column connected to the reboiler further purifies the liberated vapor. This column forms an integral part of the reboiler as it feeds liquid to the vaporizing section that is relatively more concentrated than the liquid circulating in the heated vessel. This reboiler differs from conventional units by being directly fired as most are heated indirectly by a heat exchanger. The form of construction described below has major advantages when used in small scale systems. Differential expansion between vaporizing tube and casings which can lead to high stresses, distortion and eventual leakage are avoided. Cleaning outer surface of tubes and baffles is also simplified as access is greatly improved.
The present invention provides an improved reboiler construction.
According to the present invention there is provided a reboiler comprising a rectifying section and an evaporating section in which the evaporating section comprises a plurality of upright evaporator tubes connected at their upper ends to a tube sheet, means for supplying a mixture of chemicals in liquid form to the evaporator tubes and means for heating the surface of evaporator tubes, the lower ends of the evaporator tubes being sealed and each evaporator tube being provided with a concentrically positioned inner tube extending from the upper end of each evaporator tube to a position above the sealed end of each evaporator tube, and in which the rectifying section comprises a series of trays containing liquid and means for directing vapor generated in the evaporating section through the trays.
The reboiler of the invention has an evaporator section of simple effective construction. In operation, mixture of chemicals in liquid is introduced into the header above the evaporator tubes formed by the tube sheet and each of the evaporator tubes are completely filled with liquid due to the level of liquid in the header. Heat is applied to the outer surface of the evaporator tubes which causes boiling of the liquid to occur in the annulus formed between the evaporator tube and its concentrically mounted inner tube. The vapor rises through the liquid contained in the annulus towards the liquid surface in the header creating a difference in bulk density between fluids in the inner tube and the annulus. This density difference creates a natural circulation of liquid which is drawn down the inner tube from the body of liquid contained in the header, around the gap between the inner tube and the sealed end of the evaporator tube, to pass into the annulus between the evaporator and inner tubes where boiling occurs.
The concept of the invention allows increased constructional flexibility compared with the arrangements of the prior art. It i
REFERENCES:
patent: 743316 (1903-11-01), McKechnie
patent: 825649 (1906-07-01), Henry
patent: 1154194 (1915-09-01), Meier
patent: 1450838 (1923-04-01), Bussac
Holmes Paul
Houghton Fred
Fallow Charles W.
Favors Edward G.
Foster Wheeler Energy Corporation
Naigur Marvin A.
Seman Robert J.
LandOfFree
Reboiler does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Reboiler, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Reboiler will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1722981