US2902010A - Radiant tubular heat exchanger - Google Patents

Description

Sept. 1, 1959 G. STEINERT 2,902,010

RADIANT TUBULAR HEAT EXCHANGER Filed Aug. 19, 1957 FIG. I FIG. 2 v

' INVENTOR.

GERHARD STEINERT ATTORNEY United States Patent TUBULAR HEAT EXCHANGER Gerhard Steinert, Stuttgart, Germany, assignor to Kohlenscheidungs-Gesellschaft, m.b.H., a corporation of Germany Application August 19, 1957, Serial No. 679,048

Claims. (Cl. 122-23i5) The invention relates to a tubular heat exchanger of, the cyclonic type and is particularly concerned with a steam generator having one or several combustion or slagging chambers and a radiant heat absorbing chamber arranged immediately thereabove and having a gas outlet duct leading from the combustion chamber 'into the radiation chamber said duct extending downwardly into the combustion chamber in the form of a sleeve; and wherein the combustion chamber, radiation chamher and gas outlet duct are lined with steam generating tubes.

In conventional designs of cyclonic steam generators of this type considerable difficulties have been experi- "enced in accommodating the tubes lining the combustion chamber and tubes of which the gas outlet duct is formed, within the available wall space of the radiation chamber. These diificulties have made it necessary in 'the past to employ tube designs of great complexity and of high manufacturing and installation costs.

The present invention provides a simple water wall construction aifording important advantages in the design of the tubular wall linings for cyclonic radiant steam generators. Such improvements include the provision of an intermediate horizontal header located at an elevation intermediate the combustion chamber and the radiation chamber for receiving the wall tubes of the combustion chamber and from which header any desired number of tubes can originate to supplement the tubular lining of the walls of the radiation chamber, a

'gas outlet duct leading from the combustion chamber to the radiation chamber.

The inventive design provides for greater flexibility and independence in the number of tubes employed for each furnace component, thereby avoiding the possible forming of bottle necks in the circulation system and preventing the creation of hot spots and the resulting failure of tubes due to inadequate circulation of water.

In addition the present invention makes it possible to considerably simplify the construction of the furnace. 'It permits prefabricati'on of portions of the furnace in the shops and thus facilitates speed of erection of the steam generator in the field.

A further advantage of this design resides in the use of the above named intermediate header for supplying platen type heating surfaces suspended within the radiation chamber with the working fluid such as steam or water. In this manner it is possible to enlarge to a considerable extent the eflective heating surface in the radiation chamber without the use of additional special headers and supply tubes. A substantial reduction in overall size of the heat exchanger can thereby be achieved.

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Additional objects and advantages of the invention will become apparent from the following description of an illustrative embodiment thereof when taken in conjunction with the accompanying drawing showing in Fig. -1 anel'eavtionalsection through a steam generator'equipped with my inventive improvement and in Fig. 2 a plan cross section taken on line 2-2 of Fig. 1.

The steam generator illustrated is provided "with a cyclonic combustion chamber or slagging chamber 1 having a coaxially arranged gas outlet 2 leading into an adjacent radiation chamber 3 disposed above said gas butlet. Both the slagging chamber 1 as well as the gas outlet 2 are of circular cross section. The radiation chamher '3, however, "has a rectangular cross section, as shown in Fig. 2, to accommodate the width of the gas passages which follow-the radiation chamber 3 with respect to gas flow. The wall of'slagging chamber 1 is lined on the inside with steam generating tubes 4. These tubes originate in water headers 5 and terminate in an intermediate header '6 located at an elevation directly above the combustion chamber 1.

The gas outlet duct 2 is formed of steam generating tubes 7 which originate in a lower water wall header 8 and which are extended upwardly to serve as a partial lining for the radiation chamber 3. Because of the rectangular cross sectional configuration of radiation chamber 3 in contrast to the circular cross section of duct 2, more tubes are needed to cover the walls of chamber 3 than can be supplied by the extensions of tubes 7 from duct 2. Tubes 7 therefore in serving as'a .partial lining for chamber 3 must be widely spaced. The spaces between the tubes are filled by tubes 9 originating in the intermediate header 6. Thus tubes 9 receiving the working fluid from tubes 4 of the combustion chamber 1 provide an additional lining for the walls of the radiation chamber 3. 7

There are also tubes 10 leading from intermediate header 6 to a vertical header 11. This header 11 serves as an inlet header for'tube panels or partition Walls 12 which are disposed within and extend transversely across the width of "radiation chamber 3, as shown in Fig. 2,

and upwardly to the roof thereof. In the upper portion of radiation chamber 3 there are disposed in between panels 12 additional tubular walls 13 which serve as the :lower end of gas passage 15 to conduct the combustion gases to additional heating surfaces such as an air heater (not shown) and/or to a stack (not shown).

Feed water enters the steam generator by way of valves 19 and flows'through feed tubes 20 into economizer inlet header 21 and thence through economizer 17. Tubes 20 also function as hanger supports for'economizer 17. The upper ends of the economizer tubes are extended 'to form wall tubes 22 lining the rear wall of gas passage 15. These tubes continue to line and support the 'roof 23 of the steam generator and terminate in steam and water drum 24. The preheated water thus entering drum 24 passes downwardly through downtake tubes 25 into distributing headers 5 and '8. The water rises from these headers and under constant evaporation passes through tubes 4, 7, 9, 10 and 12, to be discharged from these tubes into drum 24 as a mixture of Water and steam. The steam thereupon is separated from the water within the drum 24 by means well known in the art and passes through connecting tubes 27 into convection superheater 16, the tubes of which terminate in outlet header 28. From this header the partially heated steam passes into radiant superheater 13 which is provided with an outlet valve 29 through which the steam is conducted by way of steam pipe 3% to a point of use such as a turbine (not shown). Downtake tubes 26 are provided between headers 6 and to drain off water separated from the steam in header 6.

The furnace and gas passages of the steam generator are surrounded by a refractory wall 31 and a layer of insulation 32 which in turn is lined with a metallic cas- The fuel and combustion air is introduced into combustion chamber 1 by Way of burner nozzles 33 and 34 respectively which are directed tangentially towards an imaginary firing circle located coaxially within slagging chamber 1. The fuel is consumed while following a spiral path downwardly and then upwardly into the mouth of the sleeve-like gas duct 2 as indicated by the arrows. The temperatures attained by combustion of the fuel are maintained above the ash fusion point, thereby permitting the ash to be discharged in a fluid condition through a centrally located slag outlet 35. Due to centrifugal force created by the whirling of the gases most of the liquid ash is deposited on the walls of slagging chamber 1, flows down these walls due to gravity and out through slag outlet 35 to drop into a water filled ash pit (not shown). Suitable ash conveying apparatus (not shown) serve to remove the chilled slag from the ash pit. In order to increase the heat retaining capacity of the tubes 4 lining the slagging chamber 1, these tubes are provided with studs for the purpose of supporting a refractory filler lining. A similar lining is provided for the outside surface of the gas outlet duct 2.

The combustion gases after having been separated from the liquid ash pass through gas outlet duct 2 into radiation chamber 3 and after having given off most of their heat to the heating surfaces over which they flow, are withdrawn from the steam generator by way of duct 18 and by means of an induced draft fan (not shown) and are discharged into the atmosphere.

Although the herein disclosed invention has been described in connection with a natural circulation steam generator of the radiant type, being fired preferably with pulverized coal, this invention can with equally beneficial results be used in connection with a controlled ciri 1 culation unit or with a once-through type steam generator. Furthermore, the invention could also be applied to a heat exchanger in which other fluids besides water and steam are heated, such as air or gases. Also, the

invention could be employed in connection with furnaces burning such fuels as black liquor or other comminuted fuels. Furthermore the invention can also be practiced with equally beneficial results in a heat exchanger apparatus operating under pressurized firing.

Although the invention as herein above described is used in connection with a steam generator having but one combustion chamber discharging combustion gases into a radiation chamber, several of such combustion chambers can be employed, discharging their gases into one or more radiation chambers.

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

I claim:

1. In a steam generator arranged for cyclonic burning of a comminuated fuel, having a combustion chamber and a radiation chamber disposed immediately thereabove, a gas outlet leading from said combustion chamber into said radiation chamber and including a sleevelike gas duct extending downwardly into said combustion chamber, the combination of a first set of vertical water wall tubes comprising the walls of said gas duct, said first tubes extending upwardly to form the inner lining for a portion of the wall of said radiation chamber; a second set of water wall tubes extending upwardly said second tubes comprising the wall of said combustion chamber, a header for receiving and communicating with the upper ends of said second tubes; and a third set of water wall tubes extending from said header and communicating therewith, said third tubes forming an inner lining for a remaining portion of the wall of said radiation chamber; additional heating surface being provided in said radiation chamber, said heating surface taking the form of a vertical tubular partition wall extending transversely across said radiation chamber and subdividing said radiation chamber into a plurality of gas flow channels; and a fourth set of tubes connecting the lower end of said tubular partition wall with said header for fluid flow therethrough; means for circulating water through said first, second, third and fourth set of tubes and said header; and means for discharging streams of fuel and air into said combustion chamber for burning therein.

2. An apparatus as defined in claim 1 wherein a first distributing header is provided to which the lower ends of said first water wall tubes are connected, a second distributing header to which said second water wall tubes are connected and means for feeding water to each of said first and second distributing headers.

3. An apparatus according to claim 2 wherein a plurality of downtake tubes are provided connecting said intermediate header with said first header.

4. In a steam generator arranged for cyclonic burning of a comminuted fuel, having a combustion chamber and a radiation chamber arranged for serial gas flow in the order named; a gas outlet leading from said combustion chamber into said radiation chamber, said gas outlet including a sleeve-like gas duct extending downwardly into said combustion chamber, the combination of a plurality of first vertical water wall tubes comprising the walls of said gas duct, said first tubes extending upwardly to form the inner lining for a portion of the wall of said radiation chamber; a second plurality of vertical water wall tubes comprising the wall of said combustion chamber, an intermediate header for operatively communicating with the upper ends of said second tubes; and a third plurality of water wall tubes extending from said header for operative communication therewith, said third tubes forming an inner lining for a remaining portion of the wall of said radiation chamber; a vertical tubular panel disposed within said combustion chamber for absorption of heat, said tube panel taking the form of a partition wall extending transversely across said radiant chamber and subdividing said radiant chamber into a plurality of gas flow channels; a fourth set of tubes establishing communication with the lower end of said tubular panel and with said intermediate header for fluid flow therethrough; a first distributing header operatively connected for fluid flow to the lower end of said first tubes; a second distributing header operatively connected to the lower ends of said second tubes for fluid flow; a steam and water drum operatively connected to the upper ends of said vertical tubular panel, and the upper ends of said first and third set of water wall tubes for discharging steam and water into said drum; a first downtake pipe connecting said drum with said first distributing header for feeding water thereto; a second downtake pipe connecting said drum to said second distributing header for feeding water thereto; means for establishing separate circulation of water through said first downtake tube, first distributing heater, first water wall tubes and back to said drum and through said second downtake tubes, second distributing header, second water wall tubes, intertional conduit means are provided for returning water from said intermediate header to said first header.

References Cited in the file of this patent FOREIGN PATENTS Belgium Oct. 15, 1952 France Oct. 26, 1955

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