US2986128A - Steam generator - Google Patents

Description

May 30, 1961 Filed April 15, 1958 H. G. NEHRBAS STEAM GENERATOR 4 Sheets-Sheet 1 INVENTOR. Howard G. Nehrbus (sum/)4 of ATTORNEY y 1961 H. G. NEHRBAS 2,986,128

STEAM GENERATOR Filed April 15, 958 4 Sheets-Sheet 2 ATTORNEY H. G. NEHRBAS STEAM GENERATOR May 30, 1961 4 Sheets-Sheet 3 Filed April 15, 1958 INVENTOR Howard G. Nehrbus ATTORN EY May 30, 1961 H. G. NEHRBAS STEAM GENERAT 4 Sheets-Sheet 4 Filed April 15, 1958 INVENTOR Howard G. Nehrbas ATTORNEY United States Patent STEAM GENERATOR Howard G. Nehrbas, Chicago, Ill., assignor to Combustion Engineering, Inc., New York, N.Y., a corporation of Delaware Filed Apr. 15, 1958, Ser. No. 728,742

3 Claims. (Cl. 122-406) This invention relates to high capacity vapor generators and particularly to such generators employing vapor heating elements which extend into and across a stream of hot gases which are generated in a furnace.

In modern high capacity steam generators it is necessary to employ a large amount of steam heating surface, either superheater or reheater surface, in the form of tubular panels, elements or bundles which are subjected to and traverse the stream of hot gases generated in the furnace of the unit and which gases pass through the various passages of the unit on their way to being exhausted through a suitable stack. This gas stream passing through the unit does not have a uniform heat distribution across it. Traversely of the stream, either from front to rear or side to side, a varying amount of heat will be imparted to heat exchange surface contacted by the stream with this resulting from several factors that include variation across the gas stream of flow velocity, mass flow and/or temperature. Throughout this application the term heating characteristics is employed to generically designate the many factors that attribute to this variation in heat transfer across the gas stream. This variation causes the steam heating surface over which these gases flow to be subjected to absorb more heat in one location than in another and accordingly may result in overheating the heat exchange elements in the zone of high heat absorption.

In order to offset this efiect of the transverse variation of heat absorption the present invention provides for substantially reversing the flow pattern or location of the steam from one side of the gas stream to the other during the serial flow of the steam through the steam heating surface. With the invention this result is accomplished in a simple and expeditious manner and in accordance therewith the steam heater is formed of two sections which are in serial flow relation and which are spaced from each other in the direction of the gas flow. The downstream section relative to the gas flow is disposed in the vertical gas pass of a conventionally shaped steam generator organization which has a configuration generally in the form of an inverted U. This section is comprised of numerous sinuously bent tubular elements which are disposed in vertical planes spaced across the width of the gas pass. The inlets of these tubes areconnected with suitable inlet header while the outlets are connected with a header that is located between this gas pass and the furnace. Located vertically above this outlet header is another header that supplies the other section of the steam heater which is formed of tubular panels that extend down into the furnace and which are spaced across the width of the furnace. The inlets of these panels communicate with this other header and the two headers are connected together by vertically extending conduits which straddle the horizontal gas pass that extendsfrom the upper end of the furnace with these conduits interconnecting the corresponding ends of these headers. Within the header to which the outlets of the ice tubes of the first-mentioned section of the steam heater are connected is a baffle or partition which is constructed in such a manner as to divide the interior of the header into two separate chambers with these chambers being so arranged that the steam which enters the header from the tubes connected to one longitudinal half of the header leaves the header through the vertically extending conduit at the far end of the other half and the steam entering the header through the tubes connect to said other half leaves through the vertically extending conduit connected with the far end of said one half. Through this organization the respective transverse location of the steam flowing through the two sections of the steam heater is reversed with this reversal offsetting to a substantial extent the eflect of the transverse variation in heating characteristics of the gas stream upon the steam heater.

It is the object of this invention to provide an improved vapor generator organization which is efiective to diminish the eifect that transverse variations in heating characteristics of the combustion gas has on the steam heating surface over which it flows.

Other and further objects of the invention will become apparent to those skilled in the art as the description proceeds.

With the aforementioned objects in view, the invention comprises an arrangement, construction and combination of the elements of the inventive organization in such a manner as to attain the results desired as hereinafter more particularly set forth in the following detailed description of an illustrative embodiment, said embodiment being shown by the accompanying drawing wherein:

Fig. 1 is a vertical sectional view of a high capacity vapor generator that embodies the present invention with the lower portion of the furnace being eliminated for the sake of simplicity;

Fig. 2 is a sectional view taken from line 22 of Fig. l

and shows the disposition of the low temperature section of the steam heater with the front wall of the gas pass within which this steam heater section is disposed being removed in order to show the elements of the heater;

Fig. 3 is a sectional view taken along line 3-6 of Fig. l and shows the relative positioning of the panels of the high temperature section of the steam heater and the connection of these panels with the inlet header;

Fig. 4 is a detailed perspective view partially broken away showing the interior construction of the outlet header of the low temperature section of the steam heater.

Referring now to the drawings, wherein like reference characters are used throughout to designate like elements, the illustrative embodiment of the invention depicted therein comprises furnace 10 in the lower portion of which fuel is introduced and burned with the combustion gases passing upwardly through the furnace and out the lateral outlet 12. This outlet is formed in the upper end of the rear wall 14 of'the furnace and opposite front wall 16, with horizontal gas pass 18 extending from this outlet and leading to the upper end of the gas pass 20 which extends downwardly alongside of the furnace in spaced relation with the furnace. The combustion gases leaving outlet 12 pass through a gas pass 18 and down gas pass 20 with the gases being discharged from the bottom of this gas pass and then being directed to a suitable'air heater (not shown) from which they are conveyed to a stack or other point of discharge. The flow of the coinbustion gases is indicated by arrows 22.

At the lower end of vertical gas pass 20 is economizer 2'4 and extending through the upper end of furnace 10 are superheater elements 26 with these elements being connected with additional superheater elements 28 in gas pass 18 and with these elements 18 being connected with header 30 which conveys the superheated steam to a desired point of use.

After a portion of the energy of the superheated steam has been utilized it is brought back to the steam generator to have its energy level raised with the steam being reheated to a desired temperature by passing it through a reheater heat exchanger. This reheater is formed of a low temperature section 30 and a high temperature section 32 with these sections being in serial flow relation. The steam to be reheated enters header 34, passes through the. tubular elements of low temperature section 30 and into outlet header 36. From this outlet header the steam passes upwardly to header 38 which serves as the inlet to high temperature reheater section 32. The steam is heated to its final desired temperature in this high temperature reheater section and is then conveyed to the desired point of use.

Low temperature reheater section 30 is in the form of a tube bundle that is made up of a large number of tubes 35 that are in parallel flow relation and that are sinuously bent as shown in Fig. l. A number of individual tubes 35 are disposed in successive common planes across gas pass 20 and internested, with there being four such tubes internested in each such plane in the Fig. 1 organization. The internested tubes may be said to define an element, identified as 40 in Fig. 2, with this element being disposed in vertical planes that are spaced across the gas pass 20 from side wall 42 to side wall 44. The tubes of these spaced elements 40 have their outlets connected with outlet header 36 as shown in Figs. 1 and 2 with the tubes as connected to this header occupying the same relative position that they occupy within gas pass 20 and with the tube connections being in the lower portion of the drum.

Drums 36 and 38 are interconnected by the rather large conduits 46 and 47 which connect the corresponding ends of the headers and which straddle horizontal gas pass 18 with the headers being sufficiently long for this purpose.

The high temperature reheater section 32 is comprised of a number of tubular panels 48 that extend downwardly into the upper end offurnace and which are spaced as shown in Fig. 3 across the width of the furnace from side wall 50 to side wall 52. The tubes of panels 48 have their inlets connected to one of the stub headers 54 and the outlets to one of the headers 56. Steam is supplied to inlet headers 54 through the connecting or supply-tubes 58 that extend from header 38 to the headers 54 as shown in Fig. l and with there being six such supply tubes 58 for each of the headers 54. These several supply tubes 58 for each of the headers 54 are circumferentially spaced in their connection with drum 38 and are disposed in a common transverse plane and the connection of these groups of supply tubes is such that the groups have the same relative position as the panels 40 which they supply. In other words, supply tubes 58 which supply the outermost panels 48 are connected at the outermost portion of the header 38 while those that are connected with progressively inwardly positioned panelsare connected at progressivcly inward locations on header 38.-

With this reheater construction, if there were no means to prevent it, the steam which passes through the elements 40 of low temperature section 30 would pass through panels 48 of high temperature section 32 which are in the. same general location transversely of the streamof hot gases, i.e., the steam passing through the elements 40 at the left of gas pass 20 as viewed in Fig. 2 would pass through the panels 48 at the left of furnace 10 as viewed in Fig. 3 while the steam passing through the right hand element 40 would pass through the righthand panels 48. If this were the case the same steam wouldbe passing through the elements in the high and low temperature sections of the reheater which were located. in the high heat absorption zone or region of the combustion gas stream that results from this stream of gases having nonuniform transverse heating characteristics as explained hereinbefore. This would cause the metal temperature in the high temperature section 32 to become substantially higher in these locations of high heat absorption than in other locations which may result in overheating and damaging these elements. In order to offset to a substantial extent the effect of this variation in heat absorption transversely of the combustion gas stream, outlet header 36 is provided with an internal construction which is effective to generally reverse the steam flow from one side of the unit to the other in passing from the low temperature section 30 to the high temperature section 32 of the reheater so that the steam flowing through low temperature section 30 will have an opposite transverse location upon its passage through high temperature section 32.

This internal construction comprises a bafile plate 60 which extends between the connections of conduits 46 and 47 to header 36 and which comprises an upper fiat portion 62 that extends throughout the distance between the connection of these conduits with the upper edge of this portion engaging the inner drum surface and being connected to it as by tack welding. The plate is bent on the line 64 with the portion to the left of center in Fig. 4, identified as 66, being bent in one direction and having itsedge secured to the drum wall, while the portion on the other side of the center and identified as 68, is bent in the opposite direction and has its edge secured to the drum wall. At the center of the bafile plate a transverse pic-shaped piece or element 70 is secured as shown and the sector end pieces or plates 72 and 74 are secured to opposite ends of the baffle plate and cooperate with the baffle so that separate chambers 76 and 78 are formed in the header.

The steam from the tubes of elements 40 that are located left of the center of gas pass 20 (Fig. 2) and are accordingly connected with header 36 to the left of center (Fig, 4) enters chamber 76 and passes to the right as indicated by the arrows and out conduit 47 while the steam from the remaining elements 40, the tubes of which are connected to the right of the center of header 36 as viewed in Fig. 4, enters chamber 78 and passes, as indicated by the arrows, to the left through header 36 and out conduit 46.

The engagement of plate 62 with the inner wall surface of header 36 as well as the engagement of plates 70, 72 and 74, with this header need not be a perfect fluid tight juncture since a limited steam flow from either of the chambers 72 or 74 to the other chamber will have no effect upon the overall effective operation of the invention. However, if it is desired, a tight wall juncture may be provided although tack welding to hold the baffle plate and end plates in the proper position will be sufiicient. The bafile plate has been described as fabricated of a single plate bent along the line 64. However, if desired, the plate 60 may be built up of three sections 62, 66 and 68 that are joined by welding along the line 64.

It will be appreciated that in Fig. 3 only a few of the elements 4t} have been shown with this being desirable in order that an uncomplicated illustration and showing may be had and that a better understanding of the invention produced.

While the invention has been described as applied to a reheater of a steam generator since the problem is more acute in a reheater as a result of the lower heat transfer rate as compared with a superheater resulting from the lower steam pressure in the reheater, it will be understood that the invention is also applicable to superheaters or other vapor heaters to elimniate the deleterious effect of unequal heat absorption transversely across the gas stream caused by the heating characteristic of the combustion gas.

While I have illustrated and described a preferred embodiment of my invention it is to be understood that such is merely illustrative and not restrictive and that variations and modifications may be made therein without departing from the spirit and scope of the invention. I therefore do not wish to be limited to the precise details set forth but desire to avail myself of such changes as fall within the purview of my invention.

What I claim is:

1. In a vapor generator wherein two groups of parallel fiow vapor heating tubes are positioned in a stream of hot combustion gases with the tubes of each group being positioned in spaced parallel planes across the gas stream and the two groups being spaced in the direction of the gas fiow, with the tubes of the two groups being similarly oriented with relation to the stream of combustion gases, means interconnecting the two groups for serial vapor flow and in such a manner that the vapor serially passes through tubes of the two groups located in different relative positions in the gas stream, said means including a pair of parallel, laterally spaced headers that have their axes generally normal to said planes and to one of which headers is connected the tubes of one group and to the other of which is connected the tubes of the other group with these tubes being connected to the headers in spaced relation therealong and in their same relative positions they occupy in the gas stream, a pair of spaced parallel conduits interconnecting the ends of one of said headers with the corresponding ends of the other, elongated plate means disposed within one of said headers and comprising a longitudinally extending plate having a straight flat portion extending throughout the length of the plate means with said portion being of substantial width but substantially less than the full width of the plate, the opposed halves with respect to the center and extending longitudinally toward each end of the remaining portion being angularly disposed with relation to each other at a substantial angle, with the longitudinal edges of the straight fiat portion and said remaining portion engaging the inner wall surface of the header, a transverse sector plate interposed between said angularly disposed portions and bridging the opening therebetween and transverse end plates at each end of said plate means, said sector and end plates engaging the inner wall surface of the header, said plate means being disposed within the header and cooperating with the walls of the header to form a first chamber that prevents communication of the conduit and the tubes connected to the same half of the header with respect to the center and extend longitudinally therefrom toward the end as the conduit while permitting communication with the other tubes and a second chamber which has the same efiect with regard to the other conduit.

2. A vapor generator comprising an upright elongated furnace having a front and rear wall interconnected by a pair of spaced side walls with the furnace having a lateral outlet at its upper end in the rear wall for egress of combustion gases, a lateral otftake extending from said outlet and a gas passageway extending down from the end of said ofitake and alongside said furnace in spaced relation therewith, steam heating tubular panels extending down into the furnace and disposed in vertical planes which planes extend from front to rear of the furnace and are spaced across the furnace, a steam heater in the gas passageway in the form of a tube bundle comprised of numerous sinuously bent tubes in parallel flow relation and in spaced planes disposed similar to those of said panels, a header for these latter tubes, said header being normal to said planes and positioned below said ofiftake, and intermediate said gas passageways and said furnace With the header extending beyond the side of said ofitake, the tubes of said bundle being connected to said header in spaced relation therealong corresponding with their relative location in the passageway, another header parallel with the first mentioned header and positioned above said oiftake, this latter header also extending beyond the sides of said ofitake, said panels communicating with this latter header in spaced relation therealong and in the same relative relation they occupy in the furnace, generally vertical conduits interconnecting the corresponding ends of said header and disposed o'n opposite sides of the oiftake, plate means in one of said headers effective to prevent communication of the conduit and the tubes communicating with the same longitudinal half of the header while permitting communication of the conduit and the tubes communicating with opposite longitudinal halves of the header whereby a transfer of steam flow is effected across the unit, said plate means comprising a longitudinally extending plate having a straight flat portion extending throughout its length with said portion being of substantial width but substantially less than the full width of the plate, the opposed longitudinal halves of the remaining portion being angularly disposed with relation to each other at a substantial angle, with the longitudinal edges of the straight fiat portion and said remaining portion engaging the inner wall surface of the header, a transverse sector plate interposed between said angularly disposed portions and bridging the opening therebetween and transverse end plates at each end of said plate with the sector and end plates engaging the inner wall surface of the header.

3. In a vapor generator wherein a hot stream of combustion gases is generated by burning fuel in a furnace, the combination of a first group of vapor heating tubes disposed in said gas streamin parallel planes extending longitudinally of the gas flow and spaced across the gas stream, a second group of vapor heating tubes in another location in the gas stream and in series vapor flow relation with the first group, said second group being oriented similar to said first group, means interconnecting the two groups for serial vapor flow, said means including a header disposed transversely of the gas stream and said planes within which the tubes of the groups lie and having any internal construction operative to provide a cross over flow of vapor such that the vapor flowing through the tubes of one group at one side of the group and comprising generally half of the tubes of the group flow through tubes of the other group located in the oppositely oriented half thereof, said header internal construction comprising a plate bafiie that includes a generally flat plate section extending longitudinally of the header throughout at least substantially the entire length of the header, the width of this section being substantially less than the diameter of the header with one edge being in engagement with the header wall, another plate section extending angularly from the first mentioned sectio'n throughout one longitudinal half of the other edge of the first mentioned section and into engagement with the wall of the header, a third plate section extending from the other longitudinal half of the first mentioned section in angular relation with the first mentioned plate section and generally oppositely of said other plate section and into engagement with the header wall, lateral partition means associated with the several plate sections and operative together with said sections and said header to divide the header into two separate chambers each of which extends at least sub-" of each of said groups communicating with the respective longitudinal halves of the header that correspond generally with their location in the group and such that a reversal of a vapor flow with relation to the respective halves of the two groups is bad.

References Cited in the file of this patent UNITED STATES PATENTS Bird Mar. 14, 1 92 2 Robinson ........V--....-- Mar. 31, 1936'

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