US2169935A - Forced circulation steam generator - Google Patents

Description

Aug. 15, 1939. H. VORKA UF 2,

FORCED CIRCULATION STEAM GENERATOR Filed. Feb. 14, 1959 ATTORNEY Patented Aug. 15, 1939 FORCED CIRCULATION STEAM GENERATOR- Heinrich Vorkauf, Berlin, Germany, asslgnorto La Mont Corporatio New York, N. Y., a corporation of New York I Application February 14, 1939, Serial No.

In Germany October 20, 1936 7 Claims. (01. 122-411) This invention relates to forced circulation and through contact steam generators and particularly to c'onstru'citself the feed water with the saturated steam tions and arrangements intended to insure conthis is done the effect of the feed water in prostancy of the circulation insteam generators of I this type.

In forced circulation steam generators, the circulating pump has usually a suction conduit connected to the water containing part of a drum in which the steam and water. separation takes place or in which the separated water accumu lates and the pump forces the water thus taken from thedrum through the steam generating heat'exchange elements of the steam generator and then back into the drum. The water thus received by the pump, through the suction conduit which connects it with the drum, is usuallyatsuch a temperature that any sudden reduction in pressure will cause at least a part of it to flash intosteam, an occurrence whichnecessarily would materially affect the operation of the pump and whichmust; therefore, be guarded against. i p

Among the methods heretofore employed for preventing, as far as possible, the formation of steam in the suction conduit to the circulating pump is to'cause feed water to flow into the intake to the pump. The feed water being colder than the drum water reduces the temperature of the water flowing into the pump and thus both prevents the tendency of the intake water to flash into steam on any slight pressure change and at the same time tends to condense steam bubbles which-may have started to form. If the feed water has passed through an economizer, however, and has been subjected to comparatively high preheating, even though the feedwater be considerably colder than the water in the drum, it may carry with it entrained steam generated in the economizer and also air bubbles which have not had an opportunity to separate from thefeed water. If, therefore, the feed water be introduced immediately into the suction conduit, both steam and air may be carried directly into the conduit with the feed water and thuscreate a condition interfering with the efficient operation of the pump.

It is, of course, common to introduce the feed water, after it has passed through the economizer, into the steam and water separating drum, in order to permit the steam and air in the feed water to separate therefrom, but when viding cooling of the water entering the suction conduit does not take place, since through steam bubbles rising through the water in the drum such manner that there bles to take place.

. mizer. To effect this result the feed water can be introduced into the drum wholly or partly in the neighborhood of the pump intake connection thereto and at such a point with respect to the movement of the water in the drum toward theintake that the velocity thereof is still so small as to permit separation of the air or steam bub On the other hand, this point will not be so far from the intake but that the feed water will be drawn into the suction connection to the pump and thus cannot be heated up morev by the steam present in the drum.

It is also proposed, in accordance with the invention, to conduct the feed waterinto a space separated from the drum water, where a more definite separation of the feed water from the drum water is desirable, while at the same time permitting air and gas bubbles to escape from .the feed water wholly or partly into a space which is connected with the steam space of the boiler, this separate feed water space having a connection to the suction conduit of the circulatis brought almost immedi ing pump. This modified embodiment of the invention has not. only the advantage that any steam or any air can freely separate itself from the water in the separate feed water-receiving compartment, but that also a certain reserve of cold water exists so that, if at any time the feed water regulator closes, there will still be a flow of cold water into the suction conduit.

Other objects and important features of the invention will appear from the following description and'claims when considered in connection with the accompanying drawing, in which Figure 1 is a diagrammatic illustration of a forced circulation steam the present invention; v

Figure 2'is a section through the boiler drum showing one embodiment of the invention, and Figure 3 is a similar section through thedrum showing another embodiment oi the invention generator embodying the circulating pump 5 is connected to a distributor or distributors B for water wall tubes l0 and to a distributor l2 for convection tubes l4, the water wall tubes Ill and the convection tubes 84 discharging into the drum 2. Above the convection tubes H are economizer tubes i6 receiving the feed water through a distributor l8 connected to a source of feed water supply 20. The

feed water from the tubes i6 is either wholly or partly collected in a collecting tube 2i and then discharged into the drum 2.

In accordance with the present invention, as illustrated more fully in Figure 2, at least a part of the feed water, either before or after it has gone through the economizer, is introduced into the drum 2 in the immediate vicinity of the connection of the suction pipe 4 thereto. The discharge end of the conduit 22, which thus introduces a part or all of the feed water into the drum 2 in the neighborhood of the intake end of the pipe 4, is suflipiently spaced from said intake end so that, as above suggested, the velocity of the water flowing to the intake end of the pipe 4 is yetso small that steam or air bubbles, if any are contained in the feed water, may rise up through the drum water and thus escape being carried into the suction pipe 4. -'-This discharge end of the conduit 22 is, however, so close to the intake end of the pipe 4 that the feed water will flow immediately thereinto without contact with the steam present in the drum sufficient to increase its temperature materially.

In the embodiment of the invention illustrated more particularly in Figure 3, a separate container 24 for the feed water is arranged within the drum 2, this container being open at the top so that air and steam bubbles may escape through the feed water into the steam space of the drum 2, the top of the container 24 being, as shown, above the normal water level of the water in the drum.

From the lower end of the container 24 a discharge tube 25 leads into the opening into the intake pipe 4 so that feed water from the container 24 can enter the suction conduit 4 to the circulating pump 5 without mixing with the drum water before it enters the conduit.

The diameter of the tube 28 is such, with re-' spect to the tube 28 which introduces the feed water into the container 24, that not all of the feed water can directly flow oif through the tube 26, the excess overflowing the container 24 into the mass of water in the drum 2. This excess, therefore, provides a reserve of relatively cool feed water in the container 24 which can continue to flow into the intake opening into the suction pipe 4 when the supply through the pipev 28 is temporarily cut, off by the action of the usual automatic feed control valve.

What is claimed as new is:

1. A forced circulation steam generator comprising, in combination, a drum in which the liquid separated from the vapor is collected, a

circulating pump having an intake connection to said drum and means for introducing feed water into said drum in such manner as to provide for the escape of air and steam bubbles from, said and means for introducing feed water before entering said. intake but to prevent substantial heating of said feed water from contact with it enters said intake, said means comprising a feed water conduit arranged to introduce the feed water into said drum at a point in the stream entering said intake sufiiciently close to the intake opening to partake in the flow thereto but sufliciently far from the intake opening to permit air and steambubbles to escape therefrom before entering said intake.

3. A forced circulation steam generator comprising, in combination, a drum in which the water separated from the steam is collected for recirculation, a circulating pump having an'intake connection to the water space in said drum, feed water into the stream of water flowing into said intake, comprising a feed water conduit arranged to discharge a portion of the feed'water into the stream entering said opening and having therein an enlargement, communicating with the steam space in the drum, in which the air and steam bubbles in the feed water, may escape, through the thus retarded water, into the drum before entering said intake.

4. A forced circulation steam generator comprising, in combination, a'drum in which the water separated from the steam is collected for recirculation, a circulating pump having an intake connection with the water space in said drum, a separate feed water compartment within said drum communicating at its steam space in said drum and having a. discharge at its lower end communicating with the intake to said pump, and means for conducting at least a portion of the feed water into said compartment. 5. A forced circulation steam generator comprising, in combination, a drum in which the water separated from the steamis collected for recirculation, a circulating pump having an intake connection with the'water space in said drum, a separate feed water compartment within said drum communicating at its upper end with the steam space in said drum and having a discharge at its lower end communicating with the intake to said pump, and means for conducting at least a portion of the feed water into said compartment, the upper end of said feed water compartment being above the normal level of the boiler water in said drum.

6. A forced circulation steam generator comprising, in combination, a drum in which the water separated from the steam is collected for recirculation, a circulating pump having an intake conduit connected with the water-containing space in said drum, a separate container for feed water to be used in cooling the stream entering said suction conduit, said containercommunicating at its' upper end with the steam space in said drum and having a discharge conduit communicating with the said intakaand means for introducing feed water into said container in a the steam and water of the upper end with the quantity in excess of that which can flow away 17. A forced circulation steam generator comprising, in combination, a drum in which the water separated from the steam is collected for recirculation, a circulating pump having an intake conduit connected with the water containing space in said drum, a separate container for feed water to be used in cooling the stream entering said suction conduit, said container communi-.

eating at its upper end with the steam space in said drum and having a discharge conduit communicating with the said intake, and means for

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