US1732395A - Method of superheating steam - Google Patents

Description

Oct. 22, 1929. J, E, BELL 1,732,395

METHOD 0F SUPERHEATING STEAM Original Filed April 26, 1925 III I l J li @ffm E ATrRNEY Patented Oct. 22, 1929 UNITED STATES PATENT OFFICE JOHN E. BELL, DECEASED, LATE OF BROOKLYN, NEW YORK, BY LOLA. R. BELL, EXECU- TRIX, OF BROOKLYN, NEW YORK, ASSIGNOR TO FOSTER WHEELER CORPORATION,

OF NEW YORK, N. Y., A CORPORATION OF NEW YORK METHOD OF SUPERHEATING STEAM v Original application filed April 26, 1923, Serial No. 23, 1925.

l`he general object of the present invention 1s to provide an lmproved method of regulating thc heat absorbing capacity ot' radiant tion, advantage is taken of the tact that fur nace dust tends continually7 to accumulate on the heat. absorbing face of the radiant heat superheater, and that such accumulations rcduce the heat absorbing capacity of the superheater; and the superheat obtained is regulated by providing means for removing such dust accumulations in a regulable manner and by operating such dust removing means to vary the furnace dust accumulations on the superheater and thereby the heat absorbing capacity of the superheatcr, at different times and under different conditions, as required to give the degree ot superheat desi red.

The various features ot novelty which characterize the invention are pointed out with particularity in the claims annexed to, and forming a part ot this specification. For a better understanding of the invention, however, lits advantages and specific objects at tained with its use, reference should be had to the accompanying drawings and descriptive mattei' in which there is illustrated and described a preferred form of apparatus for use in carryingyout the invention claimed herein.

Of the drawings:

Fig. 1 is an elevation in section of a portion of the Wall of a combustion chamber in which a radiant heat superheater is incorporated;

Fig. 2 is an elevation of a portion of the inner Wall of the combustion chamber shown 634,712. Divided and this application led January Serial No. 4,181.

in Fig. tion;

Fig. 3 is a partial section on the line 3-3 of ug.

Fig. 4 is a longitudinal section of a portion of one ot the superheater elements of Figs. l, 2, and 3; and

Fig. 5 is a section on the line 5-5 of Fig. 4.

In the apparatus shown in the drawings, A represents a boiler furnace combustion chamber Wall incorporating a radiant heat superheater provided with one form of soot blowing provisions suitable for use in accordance with the present invention. The superheater shown comprises a plurality of elements B which are shown as vertically disposed, though they may be horizontal. Each element B is connected at its ends by horizontal pipes C to inlet and outlet headers D and DA.. Each superheater element B is formed of hollow sections connected at their ends by threaded nipples or sleeves E. The joints between the section ends thus connected are advantageously sealed by welding the scctions together as indicated at F. The sections, as shown, are formed of cast metal, such as ordinary cast steel or more refractory steel alloys. 4,ach of the elements B has a plane heat absorbing face exposed to the interior of the combustion chamber, and has side faces perpendicular to its inner face, and in the assembled superheater, the inner faces of the various elements unite to form a substantially smooth or plane heat absorbing surface.

The super-heater elements B are formed at their rear sides With bosses B for connecting the elements to suitable supports. These supports, as shown, in Figs. l to 3, comprise angle bars g arranged parallel to, and one immediately behind each element B. These angle bars are formed with holes to receive bolts g tapped into the bosses B. To accommodate relative longitudinal expansion of each element B and the corresponding support g, each element may be rigidly clamped adjacent its center, to its support g, by the corresponding bolt g', While the holes in that element g through which the other bolts (1 pass may be longitudinally slotted. The angle bars g may, or may not be connected to,

1, With parts broken away and in secand form a part of a structural metal framework G back of the superheater, which assists in carrying lthe weight of the masonry furnace wall above the superheater. If so connected, the angle -bars g form means for carrying the weight of the superheater ele` are supported.'

i the superheater.

In the operation of such a superheater as is shown in the drawings, soot, ashes and other furnace dust tend to, continuously deposit on the heat absorbing'face of the superheater, and such deposits diminish the heat absorption capacity of theY superheater. To remove such deposits, when and as required, provisions are made for sweeping the deposited dust, ashes or other furnace dust from the heat absorbing face of the superheater, with jets of ajsuitab'le cleaning fluid. These provisions, as shown, comprise nozzles mounted in the superheater and protected against overheating Aby the transfer of heat from the metallic structure of the superheater to the steam superheated in the -circulating channels thereof, and supplied with cleaning fluid through passages for the latter formed in Each nozzle, in the particular construction shown, is formed by the closed end of a tubular member H which traverses the steam thoroughfare By of the corresponding superheater element B, and is threaded into the latter at opposite sides of said thoroughfare. yTo seal the joints between each member H and the superheater element into which it is threaded, the parts are advantageously welded together as indicated at H. The nozzle end of each member H is enlarged to form a head H2 which abuts against the heat absorbing face of the superheater element proper, and in which are formed a series of angularly displaced radial discharge orifices H3, through which a suitable cleaning fluid, supplied under proper pressure to the interior of each member H, is discharged in jets parallel to, and closely adjacent to the heat absorbing surface of the superheater. The inner end of each member H may advantageously be polygonal in outline to facilitate the application of a wrench for screwing the member into and out of place. To provide sufficient flow space for the steam fiowing past the members H, the superheater element thoroughfares B may advantageously be enlarged, as indicated at B3 adjacent each member H The variousmembers H are so disposed t that the ,jets discharged by them will sweep the entire heat absorbing face of the superheater. As shown in Figs. 1 to 4, the members H are arranged in transverse rows spaced a couple of feet or so apart, a portion only of the various superheater elements B having members H mounted in them. The means shown for supplying cleaning fluid to the members H comprises supply piping I connected to each of the members H and including a colnmon branch supply pipe I for each member H in each horizontal row of such members. Each pipe I is connected by yan individual control valve I2 to a cleaning fluid supply main I3. The cleaning fluid supplied to the main I3 may well be superheated steam, though other cleaning fluids supplied under suitable pressure may be employed.

With the cleaning provisions described, the heat absorbing face of the superheater can be kept as free as may be desired of deposited soot, ashes or other furnace dust. The cleaning fluid lnay be supplied intermittently or constantly to the members H. lWhen supplied intermittently, the sections of the superheater at different levels may be successively cleaned, each section being swept with the proper amount of cleaning fluid. While I contemplate supplying cleaning fluid to the nozzles intermittently in ordinary practice, it may sometimes be desirable to supply cleaning fluid continuously and this is possible as the cleaning fluid jets discharged over the heat absorbing surface do not materially affect the absorption of radiant heat by said surface. lVhether the cleaning fluid is supplied intermittently or continuously, the independent control of the amount of cleaning fluid supplied for cleaning different sections of the superheater facilitates the regulation of the heat absorbing capacity of the superheater which diminishes rapidly as the accumul-ation of furnace dust on its heat absorbing surface increases.

In accordance with the present invention, the superheating effect obtained is regulated by operating the soot blowing provisions in such fashion as to maintain a minimum average thickness of deposit when a. high superheating effect is desired, and to maintain a deposit of greater average thickness when a lesser superheating effect is desired. For instance, in the normal operation of a superheater boiler having a radiant heat superheater there is a tendency for the degree of superheat to decrease as the rate at which steam is generated increases. When the rate at which steam is generated varies more or less gradually and uniformly during various periods in each day, as is the case in most large central power stations, it is possible to obtain an approximately constant superheat by keeping the heat absorbing face of the entire superheater, or portions thereof, comparative- IBO ly clean during heavy boiler load periods, and allowing dust. deposits to remain on said face or portions thereof, during periods in which the load is lighter. The soot blowing provisions may also be operated without regard to the degree to permit dust deposits to accumulate and protect the superheater against overheating during very light and no load periods in which the superheater elements might otherwise become overheated.

lil/*ith the described provisions for separately cleaning diderent sections of the 4heat ab sorbing surface of the superheater it is possible to readily regulate the heat absorbing capacity of the apparatus in many cases, withn out paying close attention to the thickness of the character of de posit on any particular section of said face, by successively cleaning different sections both With respect to the frequency of the cleaning operations and with respect to the ext-ent or number of sections cleaned. and the degree of cleaning, as required to maintain the desired heat absorbing effect. For example. in the case of a superheater boiler operatingr under fairly steady load conditions, the frequency with which successive sections of the superheater are cleaned may well be made dependent upon the reading of the thermometer showing the superheat obtainedfwthe cleaning provisions being operated whenever the degree of superheat begins to fall off', and being then operated to the extent necessary to restore the superheat to its desired value.

While the invention was primarily devised for, and is especially adapted for use in controlling the superheating effect obtained with a radiant heat superheat-er, the invention may be used, of course, With other forms of radiant heat absorbing apparatus in which a regulated heat absorbing effect is desirable. The novel soot blowing provisions disclosed, but not claimed herein, are claimed in the prior application, Serial No. 634.712, filed April 26, 1923, of which this application is a division.

Having now described the invention, what is claimed as new and described to be secured by Letters Patent, is:

l. The method of operating fluid heating apparatus comprisinga metallic structure having one face exposed to the interior of a furnace chamber and channels parallel to said face for the fluid to be heated, which consists in regulating the accumulation of furnace dust on said face to thereby vary the heat absorption capacity of said face.

2. The method of operating a radiant heat superheater which consists in cleaning the heat absorbing surface of the superheater in accordance with variations in thc superheater load7 so as to make the heat absorption capacity of the superheater relatively higher at heavy loads than at 10W loads.

3. The method of operating fluid heating apparatus haring a surface absorbing heat by radiation which consists in successively removlng furnace dust from diderent sections of sa1d surface when and as required to maintain a desired rate of heat absorption, which is normally less than the maximum rate of heat absorption.

4. The method of operating a radiant heat superheater which consists in removing furnace dust accumulations from different sections ofthe radiant heat absorbing face of the superheater in accordance with changes in the degree of superheat from a desired degree of superheat. y

5. ln the art of operating a boiler furnace having an enclosing Wall including a metallic fluid conduit structure having one face exposed to the interior of the furnace chamber and absorbing radiant heat therefrom and on which furnace ashes normally accumulate, the method of regulating the rate of heat absorption of said fluid conduit structure which comprises allowing a greater accumulation of furnace ashes on said face at light loads than at heavy loads.

G. In the art of operating a steam boiler burning fuel in a furnace chamber having an enclosing wall including a fiuid cooled wall surface exposed to heat radiation from the combustion chamber and on which furnace dust tends to accumulate. the method of regulating the rate of heat absorption of said surface which comprises removing the dust from one portion of said surface while permitting dust to accumulate on another portion of said surface.

Signed in the county of New York and State of New York, this 20th day of January, A. D. 1925.

LOLA R. BELL, E @recur/Z111 of the Last Will and Testa-ment 0f J afm E. Bell, Deceased.

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