AU723076B2 - Package boiler of unitary construction - Google Patents

Description

WO 96/39594 PCT/US96/07600 PACKAGE BOILER OF UNITARY CONSTRUCTION BACKGROUND OF THE INVENTION This invention relates to steam generators, and more specifically, to package boilers of the type that embody a unitary construction.

S It has long been known in the prior art to provide package boilers. A characteristic of package boilers is that they are often shipped from the place of fabrication as assembled units. It is, therefore, necessary that the assembled unit, the package boiler, be structurally l0 rigid so that when the assembled unit is being handled and moved about there will be no appreciable relative movement between the elements of the assembled unit since this would cause cracking or destruction of the assembled unit and possible leakage of the connection of the tubes of the package boiler with the steam drum and water drum thereof. Furthermore, in order to ensure a long life for such a package boiler, it is desirable that the package boiler require minimum maintenance.

One prior art form of steam generator that is designed to be shipped from the place of fabrication as an assembled unit is depicted in U.S. Patent No. 2,763,243 entitled "Package Boiler," which issued on September 18, 1956 and which was assigned to the same assignee as the present patent application. In accordance with the teachings of U.S.

Patent No. 2,763,243, there is provided a steam generator that has a generally elongated horizontal furnace, which is provided with opposed N 1, WO 96/39594 PCT/US96/07600 2 side walls and opposed front and rear walls. One of the side walls is composed of tubes that are positioned in side-by-side relation with adjacent tubes being in contact. This wall terminates a short distance from the rear wall of the furnace and also forms the side wall of a horizontal gas pass positioned along the furnace, and which is in communication with the furnace through the passage formed between the end of the side wall and rear wall. The opposite ends of the aforementioned side-by-side tubes are connected to upper and lower drums, respectively, which extend longitudinally of the gas pass and are io interconnected by a convection tube bank positioned within the gas pass.

Also, interconnecting these drums are tubes that extend along the roof of the furnace down the other side wall and along or within the bottom of the furnace. The front and rear walls of the furnace are similarly lined with tubes and these latter tubes interconnect the two drums by extending diagonally from the upper and lower ends of the respective front and rear walls to a point immediately adjacent the respective upper and lower drums and thence into these drums. The furnace is fired through a suitable opening in the front wall and the combustion gases generated by the burning of fuel within the furnace pass around the rear end of the side wall that separates the furnace and the gas pass, and then flow through the gas pass and into a suitable chimney or stack. Heat generated by this burning of fuel is absorbed by the various tubes, and steam is thus generated in the known manner.

One prior art form of a steam generator that is designed to be shipped disassembled and to be assembled at the user's site is depicted in U.S. Patent No. 3,212,481 entitled "Integral Box Construction For Steam Generators," which issued on October 17, 1965 and which was assigned to the same assignee as the present patent application. In accordance with the teachings of U.S. Patent No. 3,212,481, there is provided a compact high capacity steam generator, which utilizes standardized, shop-assembled components to the maximum extent 1. 11 WO 96/39594 PCT/US96/07600 3 possible so as to substantially reduce the time and effort normally required to assemble such a unit at the user's site and to reduce the material costs of such units. Another characteristic of the subject high capacity steam generator is that it is bottom supported in such a manner as to require a minimum amount of supporting members. While, yet another characteristic of the subject high capacity steam generator is that it is self-encasing to the extent that the need for heavy skin casing or other pressure sealing material is substantially eliminated.

Yet another prior art form of a steam generator that is designed to be shipped disassembled and to be assembled at the user's site is depicted in U.S. Patent No. 3,971,345 entitled "Coal Fired Package Boiler," which issued on July 27, 1976. In accordance with the teachings of U.S. Patent No. 3,971,345, there is provided a coal fired steam generator that embodies a radiant heating section and a convective heating section. The radiant heating section and the convective heating section are independently fabricated and are shop assembled into units small enough in size to be shipped by conventional carriers to the user's site where they are assembled and are tied together by connecting mating pipe and duct portions.

Yet still another prior art form of a similar type of steam generator is that depicted in U.S. Patent No. 5,050,542 entitled "Boiler," which issued on September 24, 1991. In accordance with the teachings of U.S. Patent No. 5,050,542, there is provided a steam generator, which comprises a housing having a top provided with a gas outlet, which can be positioned either at the front or the rear of the housing to suit individual site conditions, a bottom, left and right sides, and a front and back. Within the housing, an upper manifold and a lower manifold extend substantially parallel to the top, bottom and side walls; between these two manifolds, two sets of tubes are displayed. Each set of tubes is identical, the tubes being bent serpentinely so as to form a plurality of superimposed gas WO 96/39594 PCT/US96/07600 4 passages; at least two tubes of each set are bent differently so as to form access openings to the passages above and below.

Although steam generators constructed in accordance with the teachings of the four issued U.S. patents to which reference has been made heretofore have been demonstrated to be operative for the purpose for which they have been designed, there has nevertheless been evidenced in the prior art a need for such steam generators to be further improved. More specifically, there has been evidenced in the prior art a need for a new and improved package boiler of unitary construction, 1o which in particular is characterized by the fact that such a package boiler requires less auxiliary power, provides drier steam, reduces maintenance and field installation time, and can be inexpensively tailored to meet the user's specific needs.

To this end, there has been evidenced in the prior art a need is for such a new and improved package boiler of unitary construction that would further be characterized in a number of additional respects. One such additional characteristic that such a new and improved package boiler of unitary construction would desirably possess is the capability of producing steam at 20,000 to 180,000 pound per hour, with design pressires to 1050 psig and design superheater outlet temperatures to 750 degrees F. Another such additional characteristic that such a new and improved package boiler of unitary construction would desirably possess is the capability of being supplied in any of three profiles, which collectively span the aforereferenced range of design pressures and design temperatures. A third such additional characteristic that such a new and improved package boiler of unitary construction would desirably possess is the capability whereby any one of the three standard profiles thereof can be customized as can the boiler length and the number of tubes wide in the boiler bank in order to thereby meet the user's specific steam flow requirement as well as the user's specific pressure and temperature requirements. A fourth such additional characteristic that WO 96/39594 PCT/US96/07600 such a new and improved package boiler of unitary construction would desirably possess is the capability of embodying any one of the following options, rigidized ceramic fiber furnace front walls for light oil or natural gas firing or heavy duty castable refractory front walls for heavy oil and other special fuels, or a fully water cooled front wall. A fifth such additional characteristic that such a new and improved package boiler of unitary construction would desirably possess is the capability of embodying fin-welded furnace tubes and rear walls in order to thereby ensure a gas-tight combustion zone and uniform heat distribution to the 1o tubes and fins, and with the fin spacing between adjacent furnace tubes being a maximum of one inch in order to thereby eliminate overheating and cracking problems associated with designs having wider tube spacing in the furnace area. A sixth such additional characteristic that such a new and improved package boiler of unitary construction would desirably possess is the capability of embodying unheated downcomers in order to thereby assure positive circulation for faster transient response time and increased water level stability. A seventh such additional characteristic that such a new and improved package boiler of unitary construction would desirably possess is the capability of embodying improved steam drum internals in order to thereby provide final polishing of the steam to maximum dryness and reduce carryover of boiler chemicals to the absolute minimum when used in conjunction with a proper boiler feedwate" conditioning program. An eighth such additional characteristic that such a new and improved package boiler of unitary construction would desirably possess is the capability of embodying large diameter/capacity upper drums in order to thereby enhance response to normal feedwater flow fluctuations associated with plant transients and other short term feed flow interruptions. A ninth such additional characteristic that such a new and improved package boiler of unitary construction would desirably possess is the capability of embodying selfsupporting, fully drainable superheaters that are located behind a row of screen tubes such as to thereby provide a balanced ratio of radiant and convective heat input in order to thereby produce a relatively stable steam temperature characteristic over a wide load range as well as reduced superheater metal temperature.

It is, therefore, an object of the present invention to provide a new and improved steam generator in the form of a package boiler that is of unitary construction, It is a preferred object of the present invention to provide such a new and improved package boiler of unitary construction that is characterized in that vis-a-vis prior art forms of steam generators it requires less auxiliary power, provides drier steam, and reduces maintenance and field installation time, while yet being capable of being inexpensively tailored to meet the.user's specific needs.

It is another preferred object of the present invention to provide such a 15 new and improved package boiler of unitary construction that is characterized in that it possesses the capability of producing steam at 20,000 to 180,000 pounds per hour, with design pressures to 1050 psig and design superheater outlet temperatures to 750 degrees F.

It is still another preferred object of the present invention to provide 20 such a new and improved package boiler of unitary construction that is characterized in that it possesses the capability of being supplied in any one of three standard profiles, which collectively span a range of steam production at 20,000 to 180,000 pounds per hour as well as a range of design pressures to 1050 psig and a range of design superheater outlet 25 temperatures to 750 degrees F.

Another preferred object of the present invention is to provide such a new and improved package boiler of unitary construction that is characterized in that it possesses the capability whereby any one of the three standard profiles thereof can be customized as can the boiler length and the number of tubes wide in the boiler bank in order to thereby meet the user's specific steam flow requirements as well as the user's specific pressure and temperature requirements.

A still another preferred object of the present invention is to provide such a new and improved package boiler of unitary construction that is characterized in that it possesses the capability of embodying any one of the following options, rigidized ceramic fiber furnace front walls for light oil or natural gas firing, or heavy duty castable refractory front walls for heavy oil and other special fuels, or a fully water cooled front wall.

A further preferred object of the present invention is to provide such a new and improved package boiler of unitary construction that is characterized in that it possesses the capability of embodying fin-welded tubes, baffle wall tubes and rear walls in order to thereby ensure a gas-tight combustion zone and uniform heat distribution to the tubes and fins, and with the fin spacing between furnace tubes being a maximum of 5I one inch in order to thereby eliminate overheating and cracking problems associated with designs having wider tube spacing in the furnace area.

A still further preferred object of the present invention is to provide such a new and improved package boiler of unitary construction that is characterized in that it possesses the capability of embodying unheated 20 downcomers in order to thereby assure positive circulation for faster transient response time and increased water level stability.

Yet a preferred object of the present invention is to provide such a new and improved package boiler of unitary construction that is characterized in that it possesses the capability of embodying improved steam drum intemals in order to thereby provide final polishing of the steam to maximum dryness and reduce carryover of boiler chemicals to the absolute minimum when used in conjunction with a proper boiler feedwater conditioning program.

Yet a further preferred object of the present invention is to provide such a new and improved package boiler of unitary construction that is characterized in that it possesses the capability of embodying large 8 diameter/capacity upper drums in order to thereby enhance response to normal feedwater flow fluctuations associated with plant transients and other short term feed flow interruptions.

Yet another preferred object of the present invention is to provide such a new and improved package boiler of unitary construction that is characterized in that it possesses the capability of embodying self-supporting fully drainable superheaters that are located behind a row of screen tubes such as to thereby provide a balanced ratio of radiant and convective heat input in order to thereby produce a relatively stable steam temperature characteristic over a wide load range as well as reduced superheater metal temperature.

SUMMARY OF THE PRESENT INVENTION According to the present invention, there is provided a package boiler Si.. of unitary construction, including: a) furnace means having a gas-tight combustion zone located therewithin, said furnace means including a front wall, a pair of side walls, and a rear wall collectively forming a gas-tight enclosure, said rear wall including a first plurality of tubes interconnected in gas-tight relation one to another by fins such that adjacent ones of said first plurality of tubes are spaced a maximum 20 of one inch apart in order to eliminate overheating and cracking problems, said front wall including a modular portion and a second plurality of tubes interconnected in gas-tight relation one to another by fins such that adjacent ones of said second plurality of tubes are spaced a maximum of one inch apart in order to eliminate overheating and cracking problems, one end of said second plurality of tubes being interconnected to one of said pair of side walls and the other end of said second plurality of tubes extending only partially toward the other one of said pair of side walls, said modular portion of said front wall being devoid of fluid carrying tubes and extending from said other end of said second plurality of tubes to said other one of said pair of side walls, and said furnace means further including a partially extending interior wall having one end interconnected in gas-tight relation to said front wall at the juncture of said second plurality of tubes and said modular portion, said partially extending interior wall extending interiorly from said front wall toward said rear wall to terminate at its other end at a spacing from said rear wall whereby gases are made to flow along the length of said partially extending interior wall and thereafter through said spacing between said other end of said partially extending interior wall and said rear wall, and said furnace means further including a third plurality of tubes disposed relative to the gases flowing through said spacing between said other end of said partially extending interior wall and said rear wall for heat exchange therewith such that the gases give up heat to fluid flowing through said second plurality of tubes, at least some of said third plurality of tubes forming spaces between each other so as to permit the flow therethrough of the gases; 0..i b) a steam drum supported in mounted relation on said furnace too: 15 means and so as to be connected in fluid flow relation with said furnace o means; and c) support means for supporting said furnace means on a floor-like S: surface.

The package boiler as set forth in claim 1 wherein said furnace means too.

20 embodying a standard profile selected from a plurality of standard profiles collectively capable of providing within a predetermined range of design pressures and a predetermined range of design temperatures steam production within a predetermined range.

0The package boiler as set forth in claim 2 wherein said predetermined range of pressures is up to 1050 psig.

The package boiler as set forth in either claim 2 or 3 wherein said predetermined range of design superheater outlet temperatures is up to 750 degrees F.

The package boiler as set forth in any one of claims 2 to 4 wherein said predetermined range of steam production is from 20,000 to 180,000 pounds per hour.

In an exemplary embodiment, the package boiler of unitary construction includes a furnace, unheated downcomers, a large diameter steam drum, water drum, improved steam drum internals and as an option a self-supporting fully drainable superheater. The furnace based on the particular pressure and temperature conditions required thereof embodies a predetermined standard profile selected from a plurality of standard profiles collectively capable of providing within a range of design pressures up to 1050 psig and a range of design superheater outlet temperatures up to 750 degrees F, steam production within a range of 20,000 to 180,000 pounds per hour, and based on the nature of the fuel to be fired therewith embodies a front wall of predetermined construction selected from front walls of rigidized ceramic fiber for use when the fuel being fired therewith is light oil and natural gas, front walls of heavy duty castable refractory for use when the fuel being fired therewith is heavy oil and other special fuels, and front walls that are fully water cooled. In addition, the furnace is comprised of fin-welded furnace S tubes and rear walls in order to thereby ensure a gas-tight combustion zone and uniform heat distribution to the furnace tubes and fins. Moreover, the fin spacing between adjacent tubes is a maximum of one inch in order to thereby eliminate overheating and cracking problems associated with designs having wider tube spacing in the furnace area. The unheated downcomers are a designed to be operative to assure positive circulation in order to thereby achieve faster transient response time and increased water level stability. The large diameter steam drum is designed to be operative to thereby enhance a..

response to normal feedwater flow fluctuations associated with plant transients and other short term feed flow interruptions. The improved steam drum internals are designed to be operative to thereby provide final polishing of the steam to maximum dryness and to reduce carryover of boiler chemicals to the absolute minimum when used in conjunction with a proper boiler feedwater conditioning program. The self-supporting fully drainable superheater is located behind a row of screen tubes such as to thereby 11 provide a balanced ratio of radiant and convective heat input in order to thereby produce a relatively stable steam temperature characteristic over a wide load range as well as reduced superheater metal temperature.

BRIEF DESCRIPTION OF THE DRAWING In order that the invention might be more fully understood, embodiments of the invention will be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a plan view, partially in section, of a package boiler of unitary construction, constructed in accordance with an embodiment of the present invention; Figure 2 is a cross-sectional view of the front wall of the package boiler of unitary construction of Figure 1 constructed in accordance with an embodiment of the present invention, taken substantially along the line 2-2 in Figure 1; 15 Figure 3 is a cross-sectional view of a first portion of the front wall of the package boiler of unitary construction of Figure 2 constructed in accordance with an embodiment of the present invention, taken substantially along the line 3-3 in Figure 2; Figure 4 is a cross-sectional view of a second portion of the front wall of 20 the package boiler of unitary construction of Figure 2 constructed in eeo.

accordance with an embodiment of the present invention, taken substantially along the line 4-4 in Figure 2; Figure 5 is a cross-sectional view of a third portion of the front wall of the package boiler of unitary construction of Figure 2 constructed in accordance with an embodiment of the present invention, taken substantially along the line 5-5 in Figure 2; Figure 6 is a cross-sectional view of the package boiler of unitary construction of Figure 1 constructed in accordance with an embodiment of present invention, taken substantially along the line 6-6 in Figure 1; Figure 7 is a cross-sectional view of the rear wall of the package boiler of unitary constriction of Figure 1 constructed in accordance with an embodiment of the present invention, taken substantially along the line 7-7 in Figure 1; Figure 8 is a cross-sectional view of another embodiment of a front wall employable in the package boiler of unitary construction of Figure 1 constructed in accordance with an embodiment of the present invention; Figure 9 is a side elevational view, partially in section, of the upper steam drum of a package boiler of unitary construction, constructed in accordance with an embodiment of the present invention; Figure 10 is a cross-sectional view of the upper steam drum of Figure 9 of a package boiler of unitary construction, constructed in accordance with an embodiment of the present invention, taken substantially along the line 10-10 in Figure 9; i 15 Figure 11 is a cross-sectional view of the upper steam drum of Figure 9 of a package boiler of unitary construction, constructed in accordance with an embodiment of the present invention, taken substantially along the line 11-11 in Figure 9; and Figure 12 is a plan viewv of a portion of a package boiler of unitary 20 construction, constructed in accordance with an embodiment of the present invention, illustrating a superheater therewithin.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing, and more particularly to Figures 1, 2, 6 a0 and 7 thereof, there is depicted therein a package boiler, generally designated by reference numeral 10, constructed in accordance with an embodiment of the present invention. As best understood with reference to the aforesaid figures of the drawing and as will be described more fully hereinafter, the package boiler 10 embodies a unitary construction, is designed so as to be capable of being assembled into an integral unit at the place of manufacture and so as to be capable thereafter of being transported as an 11b integral unit from the place of manufacture to the location whereat it is desired to utilize the package boiler 10. In this regard, package boilers 10 constructed in accordance with an embodiment of the present invention that are capable of steam production from 60,000 pounds per hour up to 180,000 pounds per hour are designed so as to be shippable as an integral unit by rail whereas package boilers 10 constructed in accordance with embodiments of the present invention that are capable of steam production up to 60,000 pounds per hour are designed so as to be shippable as an integral unit by truck. To this end, it is necessary that the package boilers 10 embody sufficient structural rigidity such that when the package boilers 10, after being assembled into an integral unit, are being handled and moved about there will be no appreciable relative movement between the various elements that collectively comprise a package boiler 10. Otherwise, such relative movement between the various elements C 4 WO 96/39594 PCT/US96/07600 12 that collectively comprise a package boiler 10 could occasion cracking or destruction of the package boiler 10, possible leakage at the connection between the tubes and the steam drum and/or water drum of the package boiler 10, etc.

Continuing with a description of the nature of the construction thereof, the package boiler 10 as best understood with reference to Figures 2, 6 and 7 of the drawing embodies essentially a Dshaped configuration. To this end, the package boiler 10, as best understood with reference to Figure 1 of the drawing, embodies a furnace portion, generally designated in Figure 1 by the reference numeral 12.

More specifically, the furnace portion 12, for purposes of ease of description, will be deemed to comprise that portion of the package boiler residing within the four walls, generally designated by the reference numerals 14, 16, 18 and 20, respectively, within the front wall 14, the two side walls 16 and 18, and the rear wall 20. The walls 14, 16, 18 and as will be described more fully hereinafter, are suitably interconnected one with another in such a manner as to thereby create a gas-tight enclosure therewithin. In accordance with the best mode embodiment of the invention, the four walls 14, 16, 18 and 20 of the package boiler are themselves preferably encased, as best seen with reference to Figure 1 of the drawing, within casing members denoted in Figure 1 by the reference numerals 22, 24, 26 and 28, respectively. Moreover, further in accordance with the best mode embodiment of the invention a mineral fiber blanket, generally designated by the reference numeral 30, of suitable thickness is preferably selectively interposed between the four walls 14, 16, 18 and 20 and the casing members 22, 24, 26 and 28 at specified locations therebetween. To this end, the mineral fiber blanket is intended to function as insulation, to effectuate the insulation of the casing members 22, 24, 26 and 28 from the four walls 14, 16, 18 and 20 in order to thereby ensure that insofar as the temperature thereof is concerned the casing members 22, 24, 26 and 28 do not pose a danger to 13 anyone that might accidentally come in contact therewith while the package boiler 10 is being operated.

Referring again to the four walls 14, 16, 18 and 20 of the package boiler 10, as best understood with reference to Figure 1 of the drawing, the side walls 16 and 18 and the rear wall 20 of the package boiler 10 are each comprised of a multiplicity of tubes, denoted in Figure 1 by the reference numeral 32, that are interconnected by fins, denoted in Figure 1 by the reference numeral 34. In the case of the front wall 14 of the package boiler 10, only a portion thereof, as can be seen from Figure to 1 of the drawing, is comprised of a multiplicity of tubes 32 that are interconnected by fins 34. More specifically, each of the tubes 32, be it the tubes 32 of the side walls 16 and 18 or the tubes 32 of the rear wall or the tubes 32 of the front wall 14, has fins 34 that project outwardly therefrom on two opposite sides thereof such that the fins of adjoining 15 tubes 32 can be welded together and/or fins welded to adjacent tubes in :11: order to thereby create a gas-tight combustion zone therewithin and also in order to thereby concomitantly ensure that uniform heat distribution is provided to the tubes 32 and fins 34. To this end, in accordance with the present embodiment in the furnace portion 12 the fins 34 are suitably dimensioned such that when the fins 34 of adjoining tubes 32 are welded together the spacing between adjoining tubes 32 created by the existence therebetween of the fins 34 is a maximum of one inch. The fin spacing between adjoining tubes 32 is made to be a maximum of one inch in order to ensure that the overheating and cracking problems, which are known to a disadvantageously characterize prior art forms of package boilers, that in their furnace area have wider spacing between the tubes thereof, are eliminated in the case of the package boiler 10 that is the subject of the present invention. Note is also made here of the fact that for a purpose.

which will become more readily apparent subsequently, the package boiler 10 embodies in the interior thereof a partially extending wall, generally designated by the reference numeral 36 in Figure 1 of the drawing, comprised Of a multiplicity of the tubes 32 that in the same manner as that which has been described hereinibefore in connection with the discussion of the nature of the construction of the walls 14, 16, 15 and of the package boiler 10 are interconnected one to another by means of the welding together of the fins 34 with which for this purpose each of the tubes 32 is suitably provided.

A more detailed description of the nature of the construction of the front wall 14 of the package boiler 10 of the present embodiment will now be set forth herein. For this purpose, reference will be had in particular to Figures 2-5 and 8 of the drawing. As has been set forth herein previously one of the features that serves to advantageously characterize the package boiler 10 of the present embodiment vis-A-vis prior art forms of package boilers is the fact that the package boiler 10 in e~g. accordance with the present embodiment is capable, insofar as the front wall thereof is concerned, of selectively embodying without necessitating any substantial modification of the construction of any of the remaining D, portions of the package boiler 10 of the present embodiment, any one of the following options, a ceramic fiber furnace front wall for applications wherein it is contemplated that light oil or natural gas will be fired in the package boiler 10 of the present embodiment, or a heavy duty castable *Deb refractory furnace front wall for applications wherein it is contemplated that heavy oil and other special fuels will be fired in the package boiler Deb* of the present invention, or a fully water cooled furnace front wall should such be desired.

Inasmuch as the nature of the construction of a ceramic fiber furnace front wall employable in the package boiler 10 of the present embodiment and the nature of the construction of a heavy duty refractory front wall employable in the package boiler 10 of the present embodiment are very similar, except for the fact that in one case the furnace front wall 3o embodies ceramic fiber and in the other case the furnace' front wall embodies heavy duty refractory, it is deemed to be sufficient to simply refer to the same figure, Figure 2, of the drawing for purposes of setting forth herein a description of a ceramic fiber furnace front wall suitable for utilization in the package boiler 10 of the present embodiment as well as a description of a heavy duty refractory furnace front wall suitable s for utilization in the package boiler 10 of the present embodiment. On the other hanrid, inasmuch as the nature of the construction of a fully water cooled furnace front wall is considerably different than the nature of the construction of either a ceramic fiber furnace front wall or a heavy duty refractory furnace front wall, reference will be had to Figure 8 of the drawing for purposes of setting forth herein a description of a fully water cooled furnace front wall suitable for utilization in the package boiler 10 of the present embodiment.

Therefore, with reference to Figure 2 of the drawing, as will be readily apparent therefrom, there is to be found illustrated therein aspects of the package boiler 10 constructed in accordance with the o:'o present embodiment other than the front wall 14 thereof. To this end, there :can be found illustrated in Figure 2 of the drawing other aspects, which the package boiler 10 in accordance with the present embodiment embodies and to which reference has been had herein previously, such as, for 20 example, portions of the mineral fiber blanket 30, the side casing members 24 and 26 associated with the side walls 16 and 18, respectively, etc. In addition, there is also to be found illustrated in Figure see 2 of the drawing the top section, generally designated therein by the reference numeral 37, of the package boiler 10 constructed in accordance with the present embodiment as well as the bottom section, generally designated therein by the reference numeral 38, of the package boiler constructed in accordance with the present embodiment.

Associated with the top section 36, in suitably supported relation thereto, of the package boiler 10 constructed in accordance with the present embodiment, as best understood with reference to Figure 2 of the drawing, is an upper stream drum, generally designated in Figure 2 by the reference numeral 40, to which further reference will be had hereinafter, and associated with the bottom section 38, in suitably supported relation thereto, of the package boiler 10 constructed in accordance with the present embodiment, as best understood with reference to Figure 2 of the drawing, is a water drum, generally designated in Figure 2 by the reference numeral 42, to which further reference will be had subsequently.

For purposes of the description thereof herein, the top section 36 of the package boiler 10, apart from the upper steam drum 40 that is associated therewith, in accordance with the present embodiment is deemed to encompass a wall-like surface, denoted generally in Figure 2 by the reference numeral 44, which in the same manner as, for instance, the side walls 16 and 18 to which reference has been had hereinbefore is comprised of a multiplicity of tubes 32 that are interconnected by fins 34, the latter not being shown in Figure 2 in the interest of maintaining clarity of illustration therein; a casing member, denoted in Figure 2 by the reference numeral 46, which in terms both of its construction and mode of operation is like the casing members 22,24, 26 and 28 to which reference has been had hereinbefore, is suitably positioned in surrounding relation to the wall-like surface 44; and the portion of the mineral fiber blanket which is suitably interposed between the wall-like surface 44 and the casing member 46. On the other hand, for purposes of the description thereof herein, the bottom section 38 of the package boiler 10, apart from the water drum 42 that is associated therewith, in accordance with the present embodiment is deemed to encompass a wall-like surface, denoted 25 generally in Figure 2 by the reference numeral 48, which in the same manner as, for instance, the side walls 16 and 18 to which reference has been had hereinbefore is comprised of a multiplicity of tubes 32 that are interconnected by fins 34, the latter not being shown in Figure 2 in the interest of maintaining clarity of illustration therein; a support structure, denoted generally in Figure 2 by the reference numeral 50, to which further reference will be had hereinafter; and the portion of the mineral fiber blanket 30, which is suitably interposed between the wall-like surface 48 and the support structure 50. As regards the support structure 50, the support structure 50 is intended to function as a support for the package boiler 10 of the present embodiment as well as a means of providing the bottom section 38 of the package boiler 10 with a horizontally extending surface in order to thereby facilitate the placement of the package boiler on a floor-like surface in resting relation thereon.

To this end, the support structure 50 in accordance with the illustrated embodiment thereof as depicted in Figure 2 of the drawing io includes a plurality of structural members denoted for ease of identification by the reference numerals 52 and 52a, respectively, which are suitably configured so as to be operative to convert the vertically extending inclination of the wall-like surface 48 into a horizontally extending surface as depicted in Figure 2, and which are designed so as to embody sufficient structural rigidity in order that the weight of the package boiler 10 is capable of being supported therewith. In accordance with the best mode embodiment of the invention, the structural member 52a, as best understood with reference to Figure 2 of the drawing, preferably embodies a flange-like surface 54, which is designed to cooperatively engage an L-shaped member 56, which is suitably positioned in mounted relation on the wall-like surface 48 in order to thereby be operative to effect a locking relationship between the L-shaped :member 56 and the flange-like surface 54.

As best understood with reference to Figures 2 and 8 of the drawing, the front wall, which for ease of reference is identified by the reference numeral 14 in Figure 2 and by the reference numeral 14' in Figure 8, of the package boiler 10 constructed in accordance with the present embodiment, regardless of whether the front wall 14 comprises as depicted in Figure 2 of the drawing a ceramic fiber furnace front wall or a heavy duty refractory front wall, or comprises a fully water cooled furnace front wall 14' as depicted in Figure 8 of the drawing, has formed 18 therewithin an opening, denoted generally by the reference numeral 58 in both Figures 2 and 8. The opening 58 is suitably dimensioned such that a burner, not shown in the interest of maintaining clarity of illustration in the drawing, may be supported in mounted relation therewithin. Although not shown, to those skilled in this art it is well-known that such a burner, which may take the form of any commercially available burner of conventional construction that is suitable for use in a package boiler, is designed so as to be operative to effectuate therewith the introduction and thereafter subsequent combustion of the fuel, light oil, natural gas, heavy oil, etc., which the package boiler 10 is designed to have fired therewithin.

Referring again to the opening 58, in accordance with the illustrated embodiment of the package boiler 10 as depicted in Figures 2 and 8 of the drawing, the opening 58 is suitably provided within a windbox, the latter being generally denoted by the reference numeral 60 in both is Figures 2 and 8 of the drawing. The windbox 60 is itself in turn suitably supported in mounted relation within the front wall 14 in the case of Figure 2 and within the front wall 14' in the case of Figure 8.

An understanding may be had, through reference in particular to Figures 1 and 3 of the drawing, of the manner in which, by way of exemplification, the windbox is suitably supported in mounted relation within the front wall 14. Namely, as best understood by reference to Figures 1 and 3 of the drawing, a refractory material, denoted by the reference numeral 62, of a suitable thickness is employed in accordance 9 *with the illustrated embodiment of the package boiler 10 of the present 25 embodiment, in adjoining relation to the opening 58 such that the refractory material 62 in effect serves to define the circumference of the opening 58.

In addition, as best seen with reference to Figure 1 of the drawing, modules, denoted by the reference numeral 64, of either ceramic fiber in the case of the ceramic fiber furnace front wall 14 or of heavy duty refractory in the case of the heavy duty refractory furnace front wall 14, are in accordance with the illustrated embodiment of the package boiler 19 of the present embodiment interposted between the outer surface of the refractory material 62 and on one hand the first tube 32 of the multiplicity of tubes 32 that collectively serve to comprise the side wall 18 and on the other hand the first tube 32 of the multiplicity of tubes 32 that collectively serve to comprise the partially extending wall 36.

For purposes of completing the description of the nature of the construction of the front wall 14 of the package boiler 10 of the present embodiment, reference will once again be had to Figure 2 of the drawing. To this end, as can be seen with reference to Figure 2 of the drawing, the modules 64, be they composed of ceramic fiber in the case of the ceramic fiber furnace front wall 14 or composed of heavy duty refractory in the case of the heavy duty refractory furnace front wall 14, are designed so as to be capable of being supported in mounted relation adjoining one another whereby the modules 64 comprise the major portion of the front wall 14. In this regard, a plurality of members, each denoted by the reference numeral 66 in Figure 2, are preferably interspersed among the modules 64 at suitable locations relative thereto. The interrelationship that exists between one of the modules 64 and the upper steam drum 40 is shown in Figure 4 of the drawing.

20 Continuing, the remainder of the front wall 14, as will be readily apparent from Figure 2 of the drawing, is comprised of a multiplicity of tubes, denoted in Figure 2 by the reference numeral 68, Seach having one end thereof affixed to the upper steam drum 40 and the other end thereof affixed to the water drum 42 such that the multiplicity of tubes 68 extend between the upper steam drum 40 and the lower steam drum 42 so as to thereby function as an interconnection therebetween.

Furthermore, adjoining ones of the multiplicity of tubes 68 are interconnected one to another by fins, the latter being denoted in Figure 2 by the reference numeral 70. The interrelationship that exists between one of the multiplicity of tubes 68 and the upper steam drum 40 is shown in Figure 5 of the drawing.

II I A description will next be had herein of the fully water cooled furnace front wall 14' of the package boiler 10 of the present embodiment.

Reference will be had for this purpose to Figure 8 of the drawing. For ease of identification those components depicted in Figure 8 which are s the same as components that are depicted in Figure 2 are identified in Figure 8 by the same reference numerals as have been utilized in Figure 2 for these same components. Moreover, it is deemed to be unnecessary for purposes of acquiring an understanding of the nature of the construction of the fully water cooled furnace front wall 14' that those io components thereof that are the same as components, which have been described hereinbefore in connection with the description of the front wall 14 depicted in Figure 2 be described herein once again.

Thus, continuing with the description of the fully water cooled furnace front wall 14', the principal difference between the front wall 14', which is illustrated in Figure 8 of the drawing, and the front wall 14, which is illustrated in Figure 2 of the drawing, resides in the fact that whereas the modules 64, be they formed of ceramic fiber or of heavy duty refractory, constitute the major portion of the front wall 14 illustrated in Figure 2 of the drawing, the major portion of the front wall 14' illustrated in 20 Figure 8 of the drawing is comprised of the multiplicity of tubes, which are denoted generally in Figure 8 by the reference numeral 72. As best understood with reference to Figure 8, adjoining ones of the multiplicity of tubes 72 are suitably interconnected by means of fins, the latter being denoted generally by the reference numeral 74 in Figure 8 such that 25 ccllectively the multiplicity of tubes 72 and fins 74 combine to provide the front wall 14' with a gas-tight, wall-like front surface.

Moreover, as will be readily apparent from reference to Figure 8 of the drawing the multiplicity of tubes 72 and fins 74 have suitably formed therewithin the opening 58, which as has been described herein previously in connection with the description of the front wall 14 depicted in Figure 2 of the drawing is suitably dimensioned such that a 21 burner, not shown in the interest of maintaining clarity of illustration In thle drawing, may be supported in mounted relation therewithin. Furthermore, as in the case of the front wall 14 of Figure 2, the opening 58 is suitably provided within a windbox 60. and the .windbox 60 is itself in turn supported in mounted relation within the front wall 14' of Figure 8. Finally, as in the case of the front wall 14 of Figure 2, refractory material 62 of a suitable thickness is employed in adjoining relation to the opening 58 such that the refractory material 62 in effect serves to define the circumference of the opening 58.

A brief description will next be had herein of the nature of the construction of the rear wall 20 of the package. boiler 10 of the present embodiment. For this purpose, reference will be had in particular to Figure 7 of the drawing. As best understood with reference to Figure 7, the nature of the construction of the rear wall 20 is similar to that of the fully water cooled furnace front wall 14, which is dep icted in Figure 8 of the drawing and the nature of the construction of which has been described hereinabove. Namely, the major portion of the rear wall 20 illustrated in Figure 7 of the drawing is comprised of the multiplicity of tubes, which are denoted generally in Figure 7 by the reference numeral 108. Adjoining ones of the multiplicity of tubes 108, as best understood with reference to Figure 7, are suitably interconnected by means of fins, the latter being denoted generally by the reference numeral 110 in Figure 7 such that collectively the multiplicity of tubes 108 and fins 110 combine to provide the rear wall 20 with a gas-tight, wall-like rear surface. The spacing of the fins 110 between adjacent tubes 108 of the rear wall 20, as in the case of the spacing of the fins 74 between adjacent tubes 72 of the fully water cooled furnace front wall 14', is made to be a maximum of one inch in order to thereby eliminate overheating and cracking problems associated with designs having wider tube spacing in the furnace area. In io accordance with the embodiment of the rear Wall 20 illustrated in Figure 7 of the drawing, the multiplicity of tubes 108 and fins .110 have suitably 22 formed therewithin an opening, denoted generally in Figure 7 by the reference numeral 112. The opening 112 is suitably dimensioned such that in accordance with conventional industry practice a sootblower, denoted generally at 114 in Figure 7, may be suitably supported in mounted relation therewithin. As is known to those in the industry, the function of the sootblower 114 is to enable cleaning of the tubes 108 to be effected therewith. To this end, although as illustrated in Figure 7 of the drawing, the rear wall 20 is shown to be provided with a single opening 112 and a single sootblower 114, it is to be understood that the rear wall 20 could, without departing from the essence of the present invention, be provided with additional openings 112 and additional' sootblowers 114, with the additional sootblowers 114 being mounted one to an opening 112. Moreover, although not shown in the drawings, it is also to be understood that one or more sootblowers 114 could also be located in the front wall 14 or 14' and/or the side wall 16 and/or the top, roof, section 37 without departing from the essence of the present invention.

With reference next to Figures 9, 10 and 11 of the drawing, a description will now be had of the upper steam drum 40, to which reference has been had herein previously, of a package boiler constructed in accordance with the present invention. In accordance with il! tthe construction of the package boiler 10 of the present embodiment, the upper steam drum 40, as best understood with reference to Figure 9, extends the full length of the package boiler 10. More specifically, the 25 upper steam drum 40 includes a front end portion, denoted by the reference numeral 76, which projects outwardly of the front wall, be it the front wall 14 of Figure 2 or the front wall 14' of Figure 8, a rear end portion, denoted by the reference numeral 78, which projects outwardly of the rear wall 20, and a housing portion, denoted by the reference numeral 80, that extends between the front end portion 76 and the rear end portion 78. Continuing with the description of the upper steam drum 40, therein WO 96/39594 PCT/US96/07600 23 suitably supported in mounted relation at preestablished locations within the housing portion 80 mesh dryer units, denoted in Figure 10 by the reference numeral 82, perforated plate means, denoted in Figure 10 by the reference numeral 84, and plate means, denoted in Figure 10 by the reference numeral 86.

In accordance with the mode of operation of the upper steam drum 40, a normal water level, a high water level, a low water level and a low water cutoff are established for the upper steam drum 40. For ease of reference in connection with the discussion thereof, the normal water level io is denoted by the dotted line identified in Figure 11 by the reference numeral 88, the high water level is denoted by the dotted line identified in Figure 11 by the reference numeral 90, the lower water level is denoted by the dotted line identified in Figure 11 by the reference numeral 92, and the low water cutoff is denoted by the dotted line identified in Figure 11 by the reference numeral 94. As best understood with reference to Figure 11 of the drawing, preferably the normal water level 88 is established at essentially the horizontally extending centerline of the upper steam drum In turn, as seen with reference to Figure 11, the high water level preferably is established at a predetermined distance above the normal water level 88, and the low water level 92 preferably is established at a predetermined distance below the normal water level 88. .Moreover, the high water level 90 and the low water level 92 preferably are each spaced the same distance from the normal water level 88. Finally, as depicted in Figure 11 the low water cutoff 94 preferably is established at a predetermined distance below the low water level 92.

Although not specifically depicted in the drawing in the interest of maintaining clarity of illustration therewithin, it is to be understood that suitably associated in known fashion with the normal water level 88, the high water level 90, the low water level 92 and the low water cutoff 94 is a conventional form of alarm means. Such alarm means is designed to be operative to provide a suitable alarm, which may be in 24 the form of an electrical, visual or audible signal, whenever the water level in the upper steam drum 40 is sensed to no longer be at the normal water level 88. More specifically, whenever the water level in the upper steam drum 40 is sensed to have reached the high water level 90 or the low water level 92 or the low water cutoff 94 such an alarm means is designed to be operative to provide an alarm signal such that appropriate action may then in response-to such alarm signal be initiated in order to thereby effect the return of the water level within the upper steam drum 40 to the desired normal water level 88. In the case of the signal generated from io the low water cutoff 94 such signal would normally also effect, in accordance with conventional practice, a shutdown of the package boiler As mentioned herein previously, the upper steam drum is characterized particularly by the fact that improvements in the internals thereof, mesh dryer units 82, the perforated plate means 84 and the plate means 86, result in final polishing of the steam, which flows therethrough, to maximize dryness and also in a reduction in carry-over of boiler chemicals to the absolute minimum when used in conjunction with a proper feedwater conditioning program. Further, the large diameter/capacity of the upper steam drum 40 enhances the ability of the package boiler 10, constructed in accordance with the present embodiment, to respond to typical feedwater flow fluctuations associated with transients that occur within the plant in which the package boiler 10 is being employed and other short term feed flow interruptions.

25 The nature of the package boiler 10 constructed in accordance with the present embodiment is such that the package boiler may be made to embody, if so desired, a superheater. To this end, reference will be had to Figure 12 of the drawing wherein a superheater, generally designated by the reference numeral 96, is depicted embodied in the package boiler 10 of the present embodiment. As best understood with reference to Figures 1 and 12 of the drawings, when employed in the package boiler 10 of the present embodiment the superheater 96 preferably is suitably supported in mounted relation therewithin such as to be located in adjoining relation to the rear wall 20 of the package boiler 10. More specifically, the location of the superheater 96 within the package boiler 10 of the present embodiment when the package boiler 10 is so equipped therewith is such that the superheater 96 essentially extends from the free end of the partially extending wall 36 to the rear wall 20. In this regard, the tubes 32 of the package boiler 10, which would otherwise be present in the area within the package boiler 10 that the superheater 96 is to intended to occupy, must of necessity obviously be moved in order to permit the superheater 96 to be located thereat.

Preferably, the superheater 96 is suitably supported on support piers, the latter being depicted at 98 in Figure 12. In addition, the tubes, denoted by the reference numeral 100, that collectively comprise the heat transfer surface of the superheater 96, are suitably interconnected at one end to the header, identified in Figure 12 by the reference.numeral 102, and at the other end to the header, identified in Figure 12 by the reference numeral 104. Although not illustrated in the drawing in the interest of maintaining clarity of illustration therewithin, it is 20 to be understood that through the headers 102 and 104 the superheater 96 is suitably interconnected within the fluid flow path of the package boiler 10 of the present invention.

To thus summarize, the superheater 96, which is selfsupporting and fully drainable when employed in the package boiler 10 of the present embodiment is located, as best understood with reference to Figure 12 of the drawing, behind a plurality of spaced tubes 32, which when arranged in this manner relative to the superheater 96 are commonly referred to by those in the industry as screen tubes. Such an arrangement of the superheater 96 within the package boiler 10, as has been mentioned herein previously, results in a balanced ratio of radiant and convective heat input, which produces a relatively stable steam temperature characteristic over a wide load range as well as reduced superheater metal temperature.

As will be best understood with reference to Figure 1 of the drawing, the burner that is designed to be mounted within the opening 58 s that is suitably provided for this purpose in the front wall, be it the front wall 14 or the front wall 14', is operative to effect the combustion of fuel within the furnace portion 12 of the package boiler 10. The gases that are generated as a consequence of this combustion of fuel in the furnace portion 12 of the package boiler 10 flow along the following path in the io course of traversing the interior of the package boiler 10. That is, these gases are made to flow along the length of the partially extending wall 36 of tubes 32 towards the rear wall 20 of the package boiler 10. As they proceed past the free end of the partially extending wall 36 of tubes 32, the gases are made to flow parallel to the rear wall 20 in the direction of the side wall 16 such that the gases pass between the tubes 32 in the spaces provided therebetween. In doing so, the gases give up heat to the fluid flowing through the tubes 32. After entering the area of the spaced tubes 32, the gases are made to flow parallel to the side wall 16 and eventually exit from the package boiler 10 through the gas outlet, denoted 20 generally by the reference numeral 106 in Figure 1. Although in accordance with the illustrated embodiment of the invention the gas outlet 106 is depicted as being located in the side wall 16, it is to be understood that the gas outlet 106 could also be located in the front wall 14 or 14', if such were to be desired by the purchaser of the package boiler without departing from the essence of the present invention.

Thus, in accordance with the present embodiment there has been provided a new and improved steam generator in the form of a package boiler that is of unitary construction. Plus, there has been provided in accord with the present embodiment such a new and improved package boiler of unitary construction that is characterized in that vis-a-vis prior art forms of steam generators it requires less auxiliary power, 27 provides drier steam and reduces maintenance and field installation time.

while yet being capable of being inexpensively tailored to meet the user's specific needs. Besides, in accordance with the present embodiment there has been provided such a new and improved package boiler of unitary construction that is characterized in that it possesses the capability of producing steam at 20,000 to 180,000 pounds per hour, with design pressures to 1050 psig and design temperatures to 750 degrees F. As well, there has been provided in accord with the present embodiment such a new and improved package boiler of unitary construction that is characterized in that it possesses the capability of being supplied in any one of three standard profiles, which collectively span a range of steam production at 20,000 to 180,000 pounds per hour as well as a range of design pressures to 1050 psig and a range of design temperatures to 750 degrees F. Moreover, in accordance with the present embodiment there has been provided such a new and improved package boiler of unitary construction that is characterized in that it possesses the capability *i whereby any one of the three standard profiles thereof can be customized as can the boiler length and the number of tubes wide in the boiler bank in order to thereby meet the user's specific pressure and temperature 20 requirements. Further, there has been provided in accord with the present embodiment such a new and improved package boiler of unitary ::construction that is characterized in that it possesses the capability of embodying any one of the following options, rigidized ceramic fiber furnace front walls for light oil or natural gas firing, or heavy duty castable 25 refractory front walls for heavy oil and other special fuels, or a fully water cooled front wall. Furthermore, in accordance with the present embodiment there has been provided such a new and improved package boiler of unitary construction that is characterized in that it possesses the capability of embodying fin-welded furnace tubes, baffle wall tubes 3o and rear walls in order to thereby ensure a gas-tight combustion zone and uniform heat distribution to the tubes and fins, and with the fin spacing 28 between adjacent furnace tubes being a maximum of one inch in order to thereby eliminate overheating and cracking problems associated with designs having wider tube spacing in the furnace area. Also, there has been provided in accord with the present embodiment such a new and improved package boiler of unitary construction that is characterized in that it possesses the capability of embodying unheated downcomers in order to thereby assure positive circulation for faster transient response time and increased water level stability. Additionally, in accordance with the present embodiment there has been provided such a new and improved package boiler of unitary construction that is characterized in that it possesses the capability of embodying improved steam drum internals in order to thereby provide final polishing of the steam to maximum dryness and reduce carryover of boiler chemicals to the absolute minimum when used in conjunction with a proper boiler feedwater conditioning program.

Penultimately, there has been provided in accord with the present embodiment such a new and improved package boiler of unitary construction o. that is characterized in that it possesses the capability of embodying large/diameter capacity upper drums in order to thereby enhance response to normal feedwater flow fluctuations associated with plant 20 transients and other short term feed flow interruptions. Finally, in accordance with the present embodiment there has been provided such a new and improved package boiler of unitary construction that is characterized in that it possesses the capability of embodying selfsupporting fully drainable superheaters that are located behind a row of screen tubes such as to thereby provide a balanced ratio of radiant and convective heat input in order to thereby produce a relatively stable steam temperature characteristic over a wide load range as well as reduced superheater metal temperature.

While several embodiments of our invention have been shown, it will be appreciated that modifications thereof, some of which have been alluded to hereinabove, may still be readily made thereto by WO 96/39594 29 PCT/US96/0 76 0 0 those skilled in the art. We, therefore, intend by the appended claims to cover the modifications alluded to herein as well as all the other modifications which fall within the true spirit and scope of our invention.

Claims (17)

1. A package boiler of unitary construction, including: a) furnace means having a gas-tight combustion zone located therewithin, said furnace meansincluding a front wall, a pair of side walls, and a rear wall collectively forming a gas-tight enclosure, said rear wall including a first plurality of tubes interconnected in gas-tight relation one to another by fins such that adjacent ones of said first plurality of tubes are spaced a maximum of one inch apart in order to eliminate overheating and cracking problems, said front wall including a modular portion and a second plurality of tubes interconnected in gas-tight relation one to another by fins such that adjacent ones of said second plurality of tubes are spaced a maximum of one inch apart in order to eliminate overheating and cracking problems, one end of said second plurality of tubes being interconnected to one of said pair of side walls and the other end of said second plurality of tubes extending only partially *toward the other one of said pair of side walls, said modular portion of said front wall being devoid of fluid carrying tubes and extending from said other end of said second plurality of tubes to said other one of said pair of side 0walls, and said furnace means further including a partially extending interior wall having one end interconnected in gas-tight relation to said front wall at the juncture of said second plurality of tubes and said modular portion, said partially extending interior wall extending interiorly from said front wall toward said rear wall to terminate at its other end at a spacing from said rear wall whereby gases are made to flow along the length of said partially extending interior wall and thereafter through said spacing between said other end of said partially extending interior wall and said rear wall, and said furnace means further including a third plurality of tubes disposed relative to the gases flowing through said spacing between said other end of said partially extending interior wall and said rear wall for heat exchange therewith such that the gases give up heat to fluid flowing through said second plurality of tubes, at least some of said third plurality of tubes forming spaces between each other so as to permit the flow therethrough of the gases; b) a steam drum supported in mounted relation on said furnace means and so as to be connected in fluid flow relation with said furnace means; and c) support means for supporting said furnace means on a floor-like surface.

2. The package boiler as set forth in claim-l wherein said furnace means embodying a standard profile selected from a plurality of standard profiles collectively capable of providing within a predetermined range of design pressures and a predetermined range of design temperatures steam production within a predetermined range.

3. The package boiler as set forth in claim 2 wherein said predetermined range of pressures is up to 1050 psig.

4. The package boiler as set forth in either claim 2 or 3 wherein said predetermined range of design superheater outlet temperatures is up to 750 degrees F. The package boiler as set forth in any one of claims 2 to 4 wherein said predetermined range of steam production is from 20,000 to 180,000 pounds per hour. S

6. The package boiler as set forth in claim 1 wherein said front wall has an opening formed therewithin.

7. The package boiler as set forth in claim 6 wherein said front wall further includes a windbox supported in mounted relation within the opening formed therewithin, and said windbox being suitable for receiving a burner in mounted FA elation therewithin.

8. The package boiler as set forth in claim 7 wherein when light oil and natural gas are being burned within the package boiler said front wall embodies a rigidized ceramic fiber construction.

9. The package boiler as set forth in claim 7 wherein when heavy oil and other special fuels are being burned within the package boiler said front wall embodies a heavy duty castable refractory construction. The package boiler as set forth in claim 7 wherein said front wall embodies a fully water cooled construction.

11. The package boiler as set forth in claim 1 wherein said rear wall has an opening formed therewithin, and said rear wall includes a sootblower supported in mounted relation within the opening formed therewithin.

12. The package boiler as set forth in claim 1 wherein said steam drum means includes a water drum supported in mounted relation at a first location on said furnace means.

13. The package boiler as set forth in claim 12 wherein said steam drum means further includes an upper steam drum supported in mounted relation at a second location on said furnace means. tee

14. The package boiler as set forth in claim 13 wherein said upper steam drum includes mesh dryer units. 0 The package boiler as set forth in claim 14 wherein said upper steam drum further includes perforated plate means.

16. The package boiler as set forth in claim 15 wherein said upper steam drum further includes plate means.

17. The package boiler as set forth in claim 1 wherein said package boiler further includes superheater means supported in mounted relation within said furnace means.

18. The package boiler as set forth in claim 17 wherein screen means is located in front of said superheater means.

19. The package boiler as set forth in claim 17 wherein said superheater means includes tube means and header means, said tube means having a first end and a second end, said first end and said second end of said tube means each being connected in fluid flow relation with said header means. The package boiler as set forth in claim 19 wherein said superheater means further includes support piers, said tube means being supported in mounted relation on said support piers. i:

21. A package boiler of unitary construction substantially as hereinbefore described and illustrated with reference to the accompanying drawings. .DATED this 15" day of May, 2000 COMBUSTION ENGINEERING, INC. WATERMARK PATENT TRADEMARK ATTORNEYS 290 BURWOOD ROAD HAWTHORN VICTORIA 3122 AUSTRALIA SKP/RJS/MEH P10480AUOO.DOC