US3411485A - Steam producing plant and method of operating same - Google Patents

Description

W. KRAUS STEAM PRODUCING PLANT AND Nov. 19, 1968 METHOD OF OPERATING SAME 3 Sheets-Sheet 1 Filed March 5, 1967 7 r m/ W 7 a w a x mm m .E a a mm mm m w... 8

INVENTOH 44///za// fr Nov. 19, 1968' w. KRAUS 3,411,485

STEAM PRODUCING PLANT AND METHOD OF OPERATING SAME Filed March ,3, 1967 5 Sheets-Sheet 2 I/V-YENTOR 274%Za/d fiw'ur Nov. 19, 1968 w. KRAUS STEAM PRODUCING PLANT AND METHOD OF OPERATING SAME 3 Sheets-Sheet 5 Filed March 5, 1967 MM mm mw an United States Patent 3,411,485 STEAM PRODUCING PLANT AND METHOD OF OPERATING SAME Willibald Kraus, Gummersbach, Germany, assignor to L. & C. Steinmiiller G.m.b.H., Gummersbach, Germany Filed Mar. 3, 1967, Ser. No. 620,434 Claims priority, application Germany, Mar. 4, 1966, St 25,064 9 Claims. (Cl. 122-406) ABSTRACT OF THE DISCLOSURE Steam generating installation and method of operation in which working medium is branched off from the exit side of the wall pipe system ahead of the superheater and returned to the inlet side of the pipe system downstream from the preheater and admixed at that point with the supply of working medium from the preheater to the pipe system, with the flow of working medium so branched ofl being induced by the supply of working medium from the preheater to the pipe system.

The present invention relates to a steam producing plant and a method of operating the same according to which a branch flow of the working medium, when viewed in flowing direction, is branched off behind the wall pipe system and in the form of a backfiow is superimposed upon a feed water steam flow in conformity with the steam output. When building boiler installations, the wall-less boiler is preferred to the walled-in boiler because the latter has a higher operational readiness and also permits a reduction in construction costs. The increase in the operational readiness of the wall-less boiler is due to the fact that operational disturbances caused by defects in the wall are avoided and that in certain cases of occurring damage, for instance when pipes tear, such damage can be remedied much faster. The decrease in the costs obtained by designing the boiler as a wall-less boiler is due to the reduction in the assembly work because the wall-less boiler permits a far more economic assembly. Moreover, the saving in weight is considerable which in turn results in a lighter supporting structure.

A further important aspects in connection with the construction of wall-less boilers is the endeavor to obtain a gas-tight boiler which can be operated also at superpressure in the fire-box.

The general requirements involved in connection with the design of a wall-less boiler consist primarily in that at the respective joints of the wall pipes, only moderate admissible heat tensions will occur which can be absorbed by the wall without difficulties.

Very well suitable for the construction of wall-less boilers is the so-called drum boiler (natural and forced circulation boiler). With these boiler systems, all confining wallswall pipes-are incorporated in the natural or forced circulation system. Thus, at all points the same temperature prevails, namely the saturation temperature which belongs to the pressure of operation. The greatest disadvantage inherent to a drum boiler operated with natural or forced circulation consists in that it can be employed only within the subcritical range. A further essential disadvantage is due to the end vaporation point fixed in the drum. As a result thereof it is not possible without ditficulties to maintain the steam exit temperature constant in conformity with the load. Moreover, with increasing pressures and with dropping heat of vaporization, a double pipe system is unavoidable (superheater ahead of the boiler pipes). Sliding pressure operation is not possible with these boiler systems.

With wall-less forced circulation boilers it is customary to build-up the fire-box wall of helical pipes so that a flow through these wall surfaces will be possible in one direction only. Consequently at one level (horizontal section) of the chamber there will prevail the same steam condition in all pipes and thus also the same temperature. These helical windings, however, have structural drawbacks. Thus, for instance, separate suspension irons with elastic intermediate members are required. Only with large unit outputs will it be possible to provide vertical wall pipes.

The so-called combined circulation system avoids the drawbacks of the helical pipe system to a great extent. This system, however, is employable only within the supercritical range.

It is, therefore, an object of the present invention to provide a steam producer plant and method of operating the same which will permit a highly flexible operation and will be independent of the various operational possibilities, such as subcritical operation, supercritical operation, sliding pressure operation, and sliding end vaporation point.

It is another object of this invention to provide an improved steam producing plant as set forth in the preceding paragraph, which will be relatively simple but highly reliable in operation.

These and other objects and advantages of the invention will appear more clearly from the following specification in connection with the accompanying drawings, in which:

FIG. 1 illustrates the fundamental principle of the present invention.

FIG. 2 diagrammatically illustrates a first possibility of realizing the method according to the invention.

FIG. 3 represents a further embodiment of a plant for carrying out the method according to the invention.

FIG. 4 represents a combination :of the systems illustrated in FIGS. 2 and 3.

FIG. 5 illustrates another embodiment of an arrangement for carrying out the method according to the invention.

FIG. 6 is still another embodiment of the present invention which is particularly suitable for subcritical operational range.

The present invention is characterized primarily in that, when viewing in the direction of flow, the branch flow of the working medium branched off behind the wall pipe system is in the form of a backflow applicable individually or in combined form for the various above mentioned operational possibilities and is admixed to the feed water flow within an injector (Strahlapparat).

Instead of a single return flow, also according to a preferred embodiment of the invention, a plurality of parallelly arranged return flows may be provided which in the injectors associated with the individual branch return flows are admixed to the corresponding feed water driving flows.

In order to be able to control the quantity of water of the driving jet and thus to be able to control the re.- turn flow, it is suggested in accordance with a further deyelopment of the present invention ahead of the injector to branch off feed water and to admix this feed water branch flow through a bypass with control valve means behind the injector to the flow of the working medium, whereas the residual branch quantity is conveyed through the injector for the jet return (Strahlriickftirderung).

The operation of a valve equipped bypass for controlling the return flow is also applicable when employing a plurality of parallelly arranged injectors in which instance each injector has associated therewith such valve equipped bypass.

In order to assure that the driving jet glow ahead of the injector has the pressure necessary for drawing in the return flow, it is suggested according to a further development of the invention, by means of a pump, to impart upon the feed water flow required as driving jet, the necessary pressure ahead of the nozzle, whereas the remaining residual feed water flow is behind the injector fed into the pipe system or mixing areas.

In such a circuit, it is possible in conformity with the invention, especially for controlling the starting operation at the starting point, to branch off a portion of the return flow directly ahead of the injector and to feed the same into the suction line of the pressure increasing pump.

According to a further feature of the present invention, the return fiow and the feed water flow may be subdivided into as many branch flows as there are wall pipes and to intermix these individual flows in each injector associated with the respective wall pipe, and then to convey these fiows. The feed water flow required as driving jet may by means of one or more pumps be elevated to the required pressure ahead of the individual injectors,

whereas the residual portion of the feed water flow is behind the injectors introduced into the wall pipes.

Referring now to the drawings in detail, FIG. 1 illustrates the fundamental principle of the present invention.

More specifically, the circuit of FIG. 1 shows a line 1 through which the feed water is conveyed to the preheater 2 and through the intervention of the jet apparatus or injector 3 is fed into the wall pipe system 4. Behind the wall pipe system 4, at 5 there is branched off a branch line for the working medium, the so-called return flow which through line 6 and an interposed check valve 7 is conveyed back to the jet apparatus or injector 3. The steam flow corresponding to the feed water flow is at the branch point 5 conveyed to the superheater groups 8 and 9. The principle of the invention consists in that during all possibilities of operation in a circuit formed by the jet apparatus 3, wall pipes 4, return line 6 and check valve 7 with the required inner connecting lines there is maintained a return flow which is dependent on the load and is superimposed upon the feed water feed.

FIG. 2 is a diagrammatic representation of an apparatus for carrying out the method according to the present invention. More specifically, the feed water which is intro duced through feeding line 1 is at the branch point 10 subdivided into a plurality of parallelly arranged branch fiows and is through lines 11, 12 and 13 respectively equipped with control valves 14, 15 and 16 conveyed to the jet apparatuses 17, 18 and 19.

In said apparatuses 17, 18 and 19, the likewise parallelly arranged return flows are through the lines 20, 21 and 22 with check valves 23, 24 and 25 subjected to a suction effect and are combined at the mixing station 26 and conveyed to the wall pipes 4. With this system, the principle illustrated in FIG. 1 is employed in so far as at the branch point 5 a branch flow of the working medium, the so-called return flow, is branched off and in the form of parallel branch flows is respectively conveyed to the individual jet apparatuses. The purpose of such parallel arrangement consists in that it is possible by throttling and switching on and switching off individual jet apparatuses in conformity with the load, to adapt the return flow to the respective requirements.

FIG. 3 shows a possibility of controlling the return flow by branching off a line 28 at 27 ahead of the jet apparatus 3. Line 28 contains a control valve 29 by means of which the driving jet conveyed via line 30 through the jet apparatus 3 and thus the return flow through line 6 can be controlled as to its magnitude. Line 28 leads at 31 into the line 32 located between the jet apparatus 3 and the wall pipe system 4.

The possibilities of carrying out the method according to the invention as illustrated in FIGS. 2 and 3 may also be combined with each other. In such an instance, as shown in FIG. 4, the individual jet apparatuses 17, 18 and 19 will have associated therewith bypasses 33, 34 and 35 4 which in their turn are respectively equipped with control valves 36, 37 and 38.

FIG. 5 shows a further possibility of practicing the method according to the invention. More specifically, according to FIG. 5, the working medium introduced through the line 1 and the preheater 2 is behind the preheater 2 at 39 divided into branch flows of which one branch flow in the form of a driving jet passes through line 40 to pump 41 and from there to the jet apparatus 42. In the jet apparatus 42, the return flow fed through line 43 is subjected to a suction effect and is intermixed with the driving jet conveyed through line 44 to the wall pipes 4. The feed water branch flow branched off at 39 is through line 45 passed directly through a check valve 46 at the feeding-in point 47 combined with the jet-return flow mixture flowing through connecting line 44 and is then conveyed to the wall pipes 4.

In order to be able during the starting period at a time when no feeding-in is effected, to permit a circulating operation, at the branch point 5 behind the wall pipes 4 which are filled with water, a water flow is branched 011 and passed through conduit 43 and conduit 48, check valve 49 and shut-off valve 50 drawn by circulating pump 41 into the conduit 40. In the circulating pump 41 the pressure of this circulating flow is increased so that in the jet apparatus 42 by means of a circulating flow in the form of a driving jet, an additional return flow is drawn in through conduit 43 and conveyed to wall pipes 4 through conduits 44. The return flow and the feed water fiow may, as illustrated in FIG. 6, with another possible embodiment of the method according to the invention which is particularly suitable for subcritical operation, be divided in such a way that each individual wall pipe 51 has associated therewith a separate jet apparatus 52.

While making use of the method shown in FIG. 5, it is possible additionally to provide a pump 53 by means of which it will be safeguarded that the driving jet branched off at 54 for drawing in the return flow will receive the necessary pressure in the individual pipes 57 from the jet apparatuses 52. In the jet apparatuses 52 the return stroke passing through conduit 62 with check valve 63 to the collector 64 is drawn through the individual pipes 65. The remaining portion of the feed water flow which remains at the branch line 54 is through line 58 with check valve 59 conveyed to the collector 60 from where it passes through as many individual pipes 61 as there are wall pipes 51 behind the jet apparatuses 52 into the wall pipes 51. From the return flow line 62, it is possible at 66 to provide a branch line 67 with closing valve 68 and return valve 69 which, as illustrated in FIG. 5 and described further above, are adapted to be employed for starting the installation.

There will now be advanced the advantages of the invention-throughflow boiler with jet return feedin distinction to the heretofore known steam producing methods.

When building wall-less suspended boilers, vertical wall pipes are particularly advantageous. They are able to absorb additional forces in the longitudinal direction and are thus self-supporting and able to support the cold horizontal bandages for receiving vaporizations, the insulation, the burners and other loads on the boiler walls. Thus, no separate suspending irons outside the wall pipe system are necessary as is the case with horizontal meander path pipes and for carrying a helical coil. Such suspending irons have the drawback that they cause additional costs and during stationary operation, especially when starting, lag behind the temperature of the wall pipes. A welding of the supspending irons to the wall pipes is not permissible for this reason over any greater length because the temporarily different temperatures also cause different expansions. Consequently, elastic intermediate members with blocks, joints, levers and springs are required which cause a further increase in the costs.

A further very important drawback of the gas-tight welded helical winding consists with regard to the manufacturing process. Particularly where the helical winding merges from the fire-box funnel to the prismatic fire-box, additional manufacturing difficulties occur because a fiat helical winding as wall surface cannot easily be chamfered.

The same applies for constrictions with the range of the gas jet chamber.

In order, when vertically arranged wall pipes are acted upon in a parallel arrangement, to make sure that the speed required for cooling these pipes will be realized, it is depending on the steam output and the firing time frequently necessary already at maximum permanent output to provide a circulation which in conformity with the present invention is eifected with jet returned feed.

As has been mentioned in the opening paragraphs to the specification, the heretofore known steam producing methods are limited as to their field of application (drum boiler and combined circulation) or, with wall-less construction, they require the helical winding (forced circulation passage). The present invention-throughfiow boiler with jet return feed-combines the advantages of the drum boiler and of the combined circulation system, namely vertical wall pipes, with the advantages of the forced circulation boiler, namely suitability for the supercritical and subcritical range as well as for sliding pressure operation and sliding end vaporization point.

It is, of course, to be understood that the present invention is, by no means, limited to the particular embodiments shown in the drawings but also comprises any modifications within the scope of the appended claims.

What is claimed is:

1. The method of operating a steam generating installation having forced circulation of the working medium through preheater means, a wall pipe system, and preheater means in succession for the conversion of the working medium from liquid phase to vapor phase, said method comprising: establishing a flow path for the working medium from the exit side of said pipe system back to the inlet side thereof, inducing flow along said path by the supply of working medium from the preheater means to said pipe system and admixing the thus induced flow with said supply, and varying the rate of said induced flow in conformity with the conditions of operation of said installation by by-passing a portion of said supply around the region of induction of flow along said path.

2. The method according to claim 1 in which said path is divided into a plurality of parallel branches, said supply to said pipe system being divided into a plurality of parallel supply branches, and inducing flow in one of the branches of said path by the flow in one of said supply branches while simultaneously admixing the flow from each branch of the path with the flow in the pertaining supply branch.

3. The method of operating a steam generating installation having forced circulation of the working medium through preheater means, a wall pipe system, and preheater means in succession for the conversion of the working medium from liquid phase to vapor phase, said method comprising: establishing a flow path for the Working medium from the exit side of said pipe system back to the inlet side thereof, inducing flow along said path by the supply of working medium from the preheater means to said pipe system and admixing the thus induced flow with said supply, varying the rate of said induced flow in conformity with the conditions of operation of said installation dividing said path into a plurality of parallel branches, dividing said supply to said pipe system into a plurality of parallel supply branches, inducing flow in one of the branches of said path by the flow in one of said supply branches while simultaneously admixing the flow 6 from each branch of the path with the flow in the pertaining supply branch, and by-passing a portion of said supply around each said region of induction of flow along said flow path to thereby control the rate of flow along said flow path.

4. The method according to claim 1 in which the portion of the supply to said pipe system which is passed through said region of induction is increased in pressure ahead of said region.

5. The method according to claim 2 in which working medium is conveyed from the exit side of said pipe system to a point ahead of the point where the pressure of the said portion of working medium is increased to provide for circulation through said pipe system in the absence of a supply of working medium from said preheater means.

6. The method of operating a steam generating installation having forced circulation of the working medium through preheater means, a wall pipe system, and preheater means in succession for the conversion of the working medium from liquid phase to vapor phase, said method comprising: establishing a flow path for the working medium from the exit side of said pipe system back to the inlet side thereof, inducing flow along said path by the supply of working medium from the preheater means to said pipe system and admixing the thus induced flow with said supply, varying the rate of said induced flow in conformity with the conditions of operation of said installation, the flow from the exit end of each pipe being induced by a respective supply of working medium to the said pipe through an induction region preceding the inlet end of the pipe, and controlling the rate of flow from the exit end of each pipe to the respective induction region by-passing a portion of the supply of working medium to the pipe around the induction region pertaining thereto.

7. In a forced circulation steam generating installation having serially connected preheater means, a wall pipe system, and superheater means, the improvement comprising; interposing inductor means between said preheater means and said pipe system through which the supply of working medium passes in flowing from said preheater means to said pipe system, said inductor means having port means which is reduced in pressure in conformity with the rate of flow of working medium through the inductor means, conduit means leading from the exit side of said pipe system to said port means for the induction of flow of working medium from the exit side of said pipe system back to the inlet side thereof, said induced flow admixing with the supply of working medium passing through said inductor means from the preheater means to said pipe system, by-passing means being provided for the supply of working medium extending from one side of said inductor means to the other side thereof, and flow control valve means in said by-pass means.

8. An installation according to claim 7 which includes pressure intensifying pump means in the connection between the preheater means and the inductor means and located downstream from the inlet end of said bypass means.

9. An installation according to claim 8 in which branch conduit means is provided leading from the exit side of said pipe system to the inlet side of said pump means.

References Cited UNITED STATES PATENTS 2,255,612 9/1941 Dickey. 3,225,748 12/ 1965 Schuetzenduebel 122406 XR KENNETH W. SPRAGUE, Primary Examiner.

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