US2393822A - Cooled boiler casing - Google Patents

Description

Jan. 29, 1946.

D. M. SCHOENFELD COOLED BOILER CASING Filed Jan. 1, 1942 l2 Sheets-Sheet 2 1 INVENTOR.

TTOPNEY WSW.

Patented Jan. 29, 1946 cooLEn oILER cAsING David M. Schoenfeld, New York, N. Y., assigner to Combustion Engineering Company, Inc., NewY York, N. Y.

Application January 1, 1942, Serial No. 425,281

(o1. 11o-56) This invention relates to improvements i-n 7 Claims.

steam boiler casings yand particularly to casings for boilers operating under forced draft, such as marine boilers.

In marine boilers, especially those in ships that may encounter poisonous or noxious gases,

it has been found desirable where air is drawn from outside the ship for combustion within the boiler furnace to isolate it from the air within the boiler room. Ordinarily the boiler has been surrounded by a gas tight casing separated from the setting to provide space into which the combustion air is delivered to circulate around the setting and then pass via the burner openings into the furnace. Where the air has been heated by uegases in an air heater, it has heretofore been usual to pass heated air from the heater through the space between casing and boiler. Because of the arrangement of the connection between the air' preheater and the casing this air took the path of least resistance to the burners, thereby short-circuiting some portions of the setting so that air under pressure Was not present to seal all parts of the boiler setting where gases might flow outwardly into the fire room. Because of its temperature this concentration of preheated air has required the outside of the casing to be heavily insulated so as to maintain its outer wall at a satisfactory temperature.

An object of this invention is to provide an improved gas tight casing spaced froml a boiler setting in combination with an air heater. This and other objects will be best understood upon consideration of the following description of an embodiment of the invention when read in conjunction with the accompanying drawings, illustrating the invention applied to a marine boiler.

Figure 1 is a horizontal sectional View through a marine boiler on line I--I of Fig. 2;

Figure 2 is a diagrammatic elevation on line 2 2 of Fig. 1;

Figure 3 is a diagrammatic elevation on line 3-3 of Fig. 1;

Figure 4 is a sectional elevation of a portion of the boiler unit on line 4 4 of Fig. 1 showing a cross section through the air heater.

Referring to Fig. 1, the boiler comprises a furnace I having openings II to mount burners projecting through one side wall 33 for introducing fuel and air. 'Ihe products of combustion pass over banks I2, I3 of steamV generating tubes and an intervening superheater I4 to the boiler offtake I5 at one end of the boiler. Located in the .offtake is an air heater I6 (Fig. 4), comprising tubes 20 connected into upper and lower tube sheets 2h22 and mounted vertically -so that gases from oitake I5 pass through the tubes into the boiler 'flue 23. A baffleV 24 intermediate the tube sheets ZI, 22 servesto divide the usual transverse air passsage into an upper pass '25 and a lower pass 26 connected serially at one end by a conduit 21. The ai-r for combustion is delivered to the air inlet chamber 28 by a fan, not showmand the greaterpart passes through the passes 25, 26 to the 'air outlet chamber 29 and thence via a conduit 38 l(Fig. 2) to the burner openings II.

As shown in Fig. 1 the boiler is enclosed in a composite wall 3i extending from `the offtak-e where the air preheater I6 is located across the front or burner side, around the end 'opposite the offtake and back thereto across the rear wall and also over the top of the boiler. The Acomposite wall 'is kmade up of an inner refractory lining 32 backed by insulation 33 and a steel casing 34. Spaced outwardly from the wall 3l is a second or outer wall casing 35 lined with insulation and also extending around the three sidesv and also over the top of the boiler. The casings 3l, 35 and `particularly the latter which forms the outer wall, are made gas-tight so that no gas that may be between them can enter the boiler room.

A5 may be seen in Fig. 2 the space 39u between the inner and outer walls on the burner side of thel boiler is subdivided into several conduit-like channels by partitions 40, 4I extending yalong and between these walls 3i, 35 from the offtake I5 at the vertical location of the baffle plate 24 and lower tube sheetl 22, respectively, of' preheater I6. These partitions terminate short of the end walls opposite the olitake and are inter connected by a plate 42 thereby forming a vertical channel43 placing the upper conduit 44 in communication with they lower conduit 45, the intervening conduit 30 being connected at one end with the preheater outlet '29 for directing y heated air to the burner openings II as previously mentioned. The upper channel 44 receives cool air from inlet lchamber 28 of thev air preheater I6 through an opening 46 (Figs. 2 and 4) at the lower corner of the inner side Wall-41 (Fig. 2) of the preheater. The bottom of the heated air outlet chamber 29 overlies one end of conduit 45 and has holes 48 for air to flow from conduit 45 into chamber 29 and thence to the burner openings II via yconduit 30.'

Some air from the channels 44, 45 and their intermediate branch 43 ows through the space 50 between the inner and outer endY walls that extends across the top and end of the boiler to o,

the side wall opposite the burner openings I I. At

the side opposite burner openings II a partitionV 49, extending horizontally (Fig. 3) from the end of the boiler opposite the oiftake I5 ata vertical location intermediate the baie 24 and lower tube 'sheet 22 and a parallel partition 5I below this air into the furnace, and a gas offtake at one end of the furnace; a casing around and spaced Y from said boiler along the front and rear walls and extending overthe top and across the end wall opposite said offtake whereby an air chamber is formed; a multi-pass air preheater so arranged Y in said Yofftake that its air inlet and outlet are tube sheet form .three conduit channels 52, 53,54.

Each ofthe channels `52, 53, 54 A tively, with conduit 2'I which directs theeair from the first to the second passl 26` of the'airheater. In operation cool air is delivered to inlet chamber 28 of the preheater I6, the major part pass- Y ingV through to the outlet chamber 29 and/thence via conduit 30 directly to the air registers of Vburner openings I I. Because of the relatively vhigh temperature of thispreheated air, the insulation on the outer casing adjacent conduit 30 will be relatively thick. Arr'minor. part of the air passes from-inlet chamberV 28 through opening 46 (Figs. 2 and 4) intofthe upper channel 44 of the front wall, thence via channels 43 and 45 and throughv holes 48 into the outlet chamber 29. Some of this air passes from channels 44, and

Y branch channel 43 through the space across thetop and end wall (Figs. 2 and 3) into the three channels 52, 53, 54 ofthewall opposite burner openings II and thence through the respective holes 55, 56, and 5I,Y into the conduit 2'I connecting the rst and second passesfof the heater.

Since the part of the air passing around the boiler between the inner and outer walls is heated only to the extent that it absorbs heat as it cools the setting, the insulation onthe outer casing adjacent the channels throughA which this air circulates need not be as thick as that adjacent the hot'airconduit 30 which receives preheated air. The circulation of air Athrough the channels is caused by the differences in pressure existing be-Y tween the inlet chamber` 28 and the conduit 2'I at lthe end of the first pass andtheoutlet cham- Y ber 29. TheV amount of air iiowing to seal and cool the setting may be determined by the area of the holes 48, 756, 51 .y between the respective channels andthe air heater chambersZ'I, 29, or by other known means'such as dampers 60, 6|at opening 46vand in conduit Y21. Because of this control over the distribution of the air around the setting and the use ofv coldvair, the space between outer casing and settingV wall may be reduced in depth and less outer insulation utilized thereby effecting a saving in space and weight. WhatIclaim is: U Y e Y 1. Ina steam boiler having a furnace including a front wall formed with openings for'introducing tition means in said casing extendingalong said Vfront wall to form aconduit/leading through said air chamber from the outletY of said preheater to said front wall openings; and means closing said conduit adjacent therend'wall oppositersaidxofftake- 1 --f g i Y I i i Y. ,2.4In'a steam boiler having a furnace including a' front-.wall formed with openings for introducing located adjacent the front wall of said boiler and communicate with the portion of said air chamber along said front wall at the oiftake end thereof and so that an interpass duct of said preheater is located adjacent said rear wall and communicates with the portion of said air chamber along the rear wall at the oiitake end thereof; partition Vmeans extending along said front wall in said Yair chamber 'tof form a conduit leading through said airY chamber from the outlet of said preheater to said front 'wall openings; and means closing said conduit adjacent the end wall opposite said offtake. Y g f `3,.In a steam boiler having a furnace including a front wall iormedrwith openings for introducing air into the furnace, and a gas ,oiftake atgone end of the furnace; a hollow wall extending along the front of the boiler to form an air chamber; a multi-pass air preheater so arranged vin said cfftake that its, air inlet'and outlet are located adjacent the front wall of said boiler andcommunicate directly with the V,portion of said air chamber along saidfront wall at the oitake end thereof; partition means in said rcasing-extending along said front wall to form a conduit leading centrally through said air chamber from the outlet-of said preheater to said front Wall openings;

a partition closing said conduit adjacent the end wall opposite said offtake, said partitionbeing spaced from said endv wall to ,form a channel for airto flow from the part of said air chamber above said, conduit tothe part therebelow.

4. vIn a steam boiler having aV` furnace including a front wall formed with openings for introducing air into;the furnaceand a gas-oiftake atione end of the furnace; -a vcasing around and spaced from said boiler along the front and rear walls and extending over thetop vand across'the end wallopposite said otake whereby an air chamber is formed; a multi-pass'airpreheater so arranged in said oiftake that its Aair inlet Vand outlet are located adjacent the front wallv of ksaid boiler chamber along said front/'wall above Asaid conduit` in communicationwith'the said preheater inlet; a partition in said air chamber spaced fromrthe endV wall opposite said offtakeclosingsaidconduit and forming a passage from the portion'of said air chamber along said front wall'above said conduit in communication with the portion thereofrlcelow-said conduit;V and means placing the said last portion of said air chamberin communication with said conduit in advance` of said front wall openings;

. 5. In--a steam boiler. having a furnace including a front wall-formedwith openings for introducing Y air` into the furnace, agas offtake duct communi- Y enveloping said furnace and "said elements;

outer wall spaced from said inner wally to form an air chamber; partitions dividing said chamber into channels for circulating cool air about the setting and into a conduit arranged to convey heated air from said heater outlet to said front wall openings; means delivering cool air to said air heater and to said channels; and means connecting said channels to the air passages of said air heater at locations beyond its air inlet in the direction of air flow therethrough; and means for controlling the iiow of air through said respective channels into said air heater.

6l In a steam Iboiler having a furnace including a front Wall formed with openings for introducing air into the furnace, and a gas offtake at one end of the furnace; means forming a casing around and spaced from the boiler along the front and rear side walls and extending over` the top and across the end Wall opposite said oitake whereby an air chamber is formed; a multi-pass air heater so located in said ofltake that its cold air inlet and hot air outlet are disposed adjacent the front Wall in communication with the air chamber therealong; partitions in said casings along said front wall in said air chamber dividing said chamber into a conduit in said front wall for conveying hot air :from said heater outlet to said burners and channels for conveying cold air around said conduit to the outlet of said air heater thence to said front Wall openings. 7. In a steam boiler having a furnace including a front wall formed with openings for introducing air into the furnace, and a gas oiftake at one end of the furnace; a multi-pass air heater in said oii'take having a cold air inlet and a hot air outlet adjacent said front wall and an interpass duct adjacent the rear boiler Wall; means forming an air chamber encasing said boiler along the front and rear walls and extending over the top and across the end wall opposite said oitake; partitions dividing said chamber to form front wall channels and communicating roof, end and rear wall channels for circulating air therethrough; means closing the end of a channel on said front Wall to form a conduit leading through said chamber conveying hot air from said heater outlet to said front wall openings; means delivering cold air to the inlet of said air heater and another channel in the front wall; means connecting the roof, end and rear wall channels to said inter-pass duct of said air heater and said front wall channel to said air heater outlet,

DAVID M. SCHOENFELD.

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