US2063441A

US2063441A - Superheated steam cooling device

Info

Publication number: US2063441A
Application number: US469657A
Authority: US
Inventors: Howard J Kerr
Original assignee: Babcock and Wilcox Co
Current assignee: Babcock and Wilcox Co
Priority date: 1930-07-22
Filing date: 1930-07-22
Publication date: 1936-12-08
Anticipated expiration: 1953-12-08

Description

H. J. KERR SUPERHEATED STEAM COOLING DEVICE Dec. 8,

s sheets-sheet 1 Filed July 22, 1930 1936- 'H. J.' KERR I SUPERHEATED STEAM COOLING DEVIGE Filed July 22, 1930 3 sneet-sh et 2 INVENTOR Dec. 8, 1936. H. 'J. KERR SUPERHEATED STEAM COOLING DEVICE Filed July 32, 1939 s sheets-sheet 3 Patented Dec. 8, 1936 SUPEBHEATED STEAIVI COOLING DEVICE Howard J. Kerr, Westfield, N. J., assignor to The Babcock 8; Wilcox Company, Bayonne, N. J., a corporation ol-Ncw Jersey Application July 22, 1930, Serial No. 469,657

11 Claims.

This invention relates to steam. superheaters and more particularly to a device for regulating the temperature of superheated steam delivered from a superheater of a steam boiler.

An obect of the invention is to provide a device to regulate the temperature of superheated steam and avoid overheating of the metal of the superheater.

Another object the invention is-to provide a boiler which will deliver superheated steam at constant temperature independent of the quantity without damage to the superheater itself.

Other objects will be apparent to those skilled in this particular art from the description in the specification in connection with the drawings, in which- Fig. 1 is a side view of a portion of a boiler and its setting illustrating the invention with one arrangement of superheaters;

Fig, 2 is a side view of a portion of a boilerand its setting illustrating the invention with a second superheater arrangement;

Fig. 3 is a sectional plan view of the temperature regulating part of the superheater in section;

Fig. 4 is a sectional end view of the temperature regulating part of the superheater taken along the section line 4-4 of Fig. 3;

Fig. 5 is a sectional side view of a portion of the temperature regulating part of the superheater taken at right angles to Fig. 3;

Fig. 6 is a sectional end view of a modified form. of the temperature regulating part of the superheater; and

Fig. 7 is a somewhat diagrammatic view of the superheat regulator control system.

In the arrangement shown in Fig. 1 hot gases of combustion from a furnace (not shown) pass first through aset of steam generating tubes i and then over the tubes of a secondary superheater 2. The tubes I serve a multiple purpose, for in addition to their generating function they limit the radiant heat received by the superheater and act as a slag screen to prevent the closing of passages between the superheater tubes by slag. After passing through the secondary superheater tubes the hot gases of combustion pass over the tubes of a primary superheater 3 and finally, by virtue of the several bafiiing arrangements 4, the hot gases of combustion are directed across the tubes 5 and 6 of the water tube boiler.

The front and middle steam and water drums are connected along their lengths by water circulators 9 and steam circulators ll while the middle and rear drums l are directly connected by steam circulators 8 only. The steam generated in the boiler collects in the rear steam and water drum and is conducted to a saturated steam header [0 by means of delivery pipes II. The saturated steam from the header I0 is delivered 5 to the bank of looped tubes in the upper portion of the first gas pass of the boiler constituting the primary superheater section 3 through tube' portions l2 bent to pass between the circulators 9 and 9 and steam generating tubes 5. Each of 10 the primary superheater tubes is arranged in a' series of vertical legs connected at their upper and lowerends to the adjacent tube legs for a v series steam 'fiow therethrough. The primary superheater section is positioned in the upper part of the first gas pass oi. the boilerwithin the space between the rowsof generating tubes I and 5. The steam will flow in parallel through the bank of primary superheater tubes and be superheated by the heat absorbed from the combustion gases contacting with the tubes after the gases have been partly cooled. by their passage across the row of boiler tubes l and the secondary superheater tubes. The superheated steam is conducted from the primary superheater section through tube portions I 4 to a cooler or superheat regulator l3. The primary superheater tubes being arranged above the generating tubes I and the secondary superheater tubes will receive substantially all of their heat from the combustion gases. The superheat temperature of the steam entering the regulator It will thus be dependent uponthe amount and temperature of the combustion gases flowing across the primary superheater tubes, and will normally vary over a substantial range with changes in the rate of operation of the boiler.

The superheat regulator l3 comprises a cylindrical casing 2i having heads'22 and 23 secured to opposite ends thereof. A pair of longitudinally extending side partitions 34 and an intermediate 40 center baffle 35 unite with circular

transverse partitions

23 and 23 to define a pair of side-by-side compartments extending longitudinally of the casing 2| and connected for a serial flow of steam therethrough over the upper end of the center baiile 3'5. A bank of nested U-shaped tubes 8% having spaced tube legs I5 and it are arranged longitudinally of the casing 2 [with the tube legs l5 arranged in horizontal and vertical rows in one compartment and the tube legs I6 similarly arranged in the other compartment. The tube portions M open along the bottom of the compartment containing the tube legs l5 so that the superheated steam will flow upwardly across the tube legs l5, over the battle 3'5, and downwardly subjacent tubes I.

across the tube legs I 8. to the secondary superheater section 2 open along the length of the chamber containing the tube legs I similar to the arrangement of the tube portions I4, 50 that flow paths of uniform length having substantially similar heat transfer relations with the regulator tubes are formed between corresponding tube portions I 4 and I1.

The tube legs iii are connected to a common inlet header 29 between the partition 23 and the head 23, while the tube legs ii are connected to a common outlet header 3| adjacent the header 29. A water inlet pipe 24 and an outlet pipe 25 are mounted in the head 23 by means of steam tight expansion sleeves 2i welded thereto. The regulator steam cooling water entering the pipe 24 passes into the header 29, through the tube legs I! and I5 successively to the outlet header 3| and outlet pipe 25, with the steam to be desuperheated passing through the regulator counter-current to and out of contact with the cooling water. Metallic fins 32 are mounted on the regulator tube legs l5 and I6 in good thermal contact therewith to add to the effectiveness of heat transfer from thesuperheated steam to the cooling water.

The regulator cooling water may be derived from any convenient source,@.nd water from one of the steam and water drums lrnay be used. In the latter case, the regulator water will enter at the saturated steam temperature, and the heat absorbed in desuperheating will result in the evaporation of some or all of the regulator water, depending upon the amounts of water introduced and heat absorbed. Saturated steam or a mixture of steam and water will then be discharged from the outlet pipe 25.

The desuperheating effect of the regulator on the superheated steam from the primary superheater section will depend upon the amount of water supplied to the inlet pipe 24. A suitable flow regulating means, such as a control valve 21, is incorporated in the inlet pipe 24. By means of the control device 21, the supply of cooling water to the regulator may be-regulated even to zero.

The desuperheated steam leaves the regulator through the tube portions H to the bank of looped tubes constituting the secondary superheater section 2. These tubes have a series of horizontally inclined superposed parallel tube legs connected by loops for a series fiow therethrough and arranged across the lower part of the tapering first gas pass between the single row'of boiler tubes l and the generating tubes 5, and in operation absorb heat from the high temperature combustion gases leaving the furnace and by radiation from the furnace. The secondary superheater tubes are arranged in pairs with their looped portions nested as shown in Fig. 1. While the lower portions of the tubes I restrict the amount of radiant heat from the furnace to the secondary superheater tubes to prevent overheating, these superheater tubes will receive a substantial amount of radiant heat through the spaces between the The steam is superheated to the desired final temperature in the secondary section and is conducted by tube portions I 8 to an external steam outlet header is. Due to the relatively large amount of radiant heat received by the secondary superheater tubes from the furnace, fluctuations in boiler load will have relatively little effect on the amount of superheat obtained in the secondary section as compared with the variations in superheat temperature in the Tube portions l'l leading primary section. The tube portions l4, l1 and i8 are bent similarly to the tube portions 12 to pass between the generating tubes 5 and circulators 9.

Fig. 2 shows a modified steam boiler having-the same general construction and arrangement'of the steam generating and superheating parts as the boiler shown in Fig. 1, differing therefrom mainly in the particular formation of the tubes forming the primary and secondary superheater sections. In Fig.2 the secondary superheater tube legs below the primary superheater are more horizontal than in Fig. 1 and have the tube portions connected to the superheat regulator casing this device it is obviously possible to control the temperature of the steam independently of the quantity used.

The steam from the boiler is superheated in two stages-first, in the primary superheater 3, then in the secondary superheater 2, with a regulator between these two stages and in its passage through the regulator it is normally cooled to an extent sufficient to maintain the outlet steam temperature constant, the amount of interstage cooling being regulated by the water supply through the control valve 21. when the conditions of boiler operation are such as to make the superheated steam deliveryto be at too high a temperature more water is admitted to the regulator so as to lower the temperature of the steam entering the secondary superheater. Contrariwise, a decreased supply of water is used when the superheated steam temperature is too low. It will be clear that with this method of regulating the temperature of the delivered steam there is a corresponding regulation of the temperature of the metal of the superheater which obviously cannot become so hot as to be damaged so long as the outlet of temperature of the superheated steam emerging from it is kept within the desired limits. While water is a convenient and delet steam temperature it is to be understood that automatic thermostatic control of the water supply may be used and actuated by outlet temperature of the superheated steam leaving the secondary superheater section. Suitable automatic thermo-responsive control means adapted for such use are well known and, as somewhat diagrammatically illustrated -in Fig. 7, comprise a thermostatically controlled valve 21' in the inlet pipe 24, the position of which valve is controlled by a thermostat 40 installed in the steam outlet header l9 and directly actuating the valve 21 through the volumetric changes of the volatile liquid in the thermostat and flexible pipe connection 4| to the valve 21' in response to steam outlet temperature changes.

Although certain features of the present invention have been described in more or less detail, it will be apparent that various changes, additicns, omissions, and substitutions can be made therein without departing from the spirit of this invention and the scope or the appended claims.

I claim:

1. A steam generator having a combustion chamber, a multiplicity of steam generating,

elements arranged above said combustion chamber, a steam andwater drum connected to said steam generating elements, a plurality of primary superheating tubes arranged to receive all ofthe steam to be superheated from said steam and water drum, a. plurality of secondary superheating 'tubes in series with said primary superheat ing tubes and arranged for exposure in operation to heating gases at a temperature different from the temperature of the heating gases contactingwith said primary superheating tubes, a regulable desuperheater arranged to receive the steam from said primary superheating tubes and comprising cooling tubes for cooling the steam before delivery to said secondary superheating tubes, corresponding primary and secondary superheating tubes being similarly connected to said'desuperheater and so arranged relative to said desuperheater cooling tubes as to form substantially individual flow paths of uniform length in said desuperheater having substantially similar heat transfer relations with said cooling tubes, whereby all of the steam will be subjected to substantially uniform cooling in said desuperheater and the metal temperature conditions in said secondary superheating tubes will be substantially uniform in operatiom 2. In asteam generator having a combustion chamber, a multiplicity of steam generating elements arranged to absorb heat from the heating gases leaving said combustion chamber, and a steam and water drum connected to the steam 'generating elements, the combination with a nected to said outlet header at points substantially throughout the length thereof and equispaced from the points of connection of the corresponding primary superheating tubes and so forming steam flow paths therein .ofuniform length between corresponding primary and secondary super-heating tubes, and cooling fluid] conduits extending longitudinally in said outlet header and transversely of said steam flow paths for substantially uniformly cooling all of the steam passing to the tubes of said secondary superheater, whereby the steam superheating capacity of all of the tubes of said secondary superheater may be fully utilized without exceeding the permissible metal temperatures therein.

prising, in combination, a boiler, a first superheater section located in the boiler so-as to absorb heat substantially by convection, a second superheater section located in a zone of intense heat and so as to absorb heat substantially by 3. Apparatus of the character described com-- radiation, a conduit for conducting saturated steam from the boiler to said first section, a controllable superheat regulator arranged to receive steam from said first section and to deliver to said secondsection all the steam to be superheated therein, said regulator comprising means providing a substantially uniform path oi! flow for steam passing through the regulator and a space for cooling water out of contact with, but

a in heat exchange relation to, the steam flowing through said path, and means responsive to the temperature of steam whichhas received additional superheatin said second section ror cdntrolling said regulator.

' '4. Inthe art of superheating steam to high temperatures, the improved method which consists in initially superheating saturated steam by convection in a zone of relatively low temperature,'regulating the temperature of the initially superheated steam by uniformly subjecting said initially superheated steam to the cooling eflfect of water out of contact therewith,*subsequentlysuperheati'ng the steam-to desired final temperature in a zone of intense radiant heat and govern- V ing the regulated temperature of the initially superheated steam in response to variations in temperature ofsteam which has been superheated in said second mentioned zone.

5. Apparatus of the character described comprising, in combination, a-boiler, a first superheater section, a second superheater section, said sections being located in different heating zones in the boiler and said first section being located in a zone in which the variation in the amount of superheat obtained during normal operation of the boiler is greater than in the zone in which said second section is located, a superheat regulator, .a conduit for conducting saturated steam from the boiler to said first section, a conduitfor conducting steam from said first section to said regulator, a conduit for conducting from said regulator to said second section all of the steam to be superheated therein, said regulator comprising meansproviding a path of flow for steam through the regulator and a space for water to be evaporated 'by steam flowing through said path out of contact with the water, and means responsive. to the temperature of steam on the discharge side of said regulator for controlling operation of the regulator.

6. Apparatus or the character described comprising, in combination, a boiler, a first superheater section, a second superheatersection, said sections being serially arranged with respect to gas flow through the boiler and said .second section being located in a zone of intense gas temperature where the difference in the amount of superheat obtained is less at different rates of boiler operation than is the difference in the amount of superheat obtained in said first secsuperheat regulator, a conduit for conducting saturated steam from the boiler to said first section, a conduit for conducting steam from said first section to said regulator, a conduit for conducting from said regulator to said second section 'all of the steam to be superheated therein, said regulator comprising means providing a. path of flow for steam through the regulator and a space for ,water to be evaporated by steam flowing through said path out of. contact with the water, and means responsive to the temperature of steam on the discharge side ofsaid regulator for controlling. operation of the regulator.

60 tion at different rates of boiler operation, a.

7. Apparatus of the character described comprising, in combinat on, a boiler, a first superheater section located in the boiler so as to absorb heat substantially by convection, a'second superheater section located in a zone of intense heat and so as to absorb heat substantially by radiation, a superheat regulator, a conduit for conducting saturated steam from the boiler to said first section, a conduit for conducting steam from said first section to said regulator, a conduit for conducting from said regulator to said secondsection all of the steam to be superheated therein, said regulator'comprisingmeans providing a substantially uniform path of fiow for steam passing through the regulator and a space for water to be evaporated by steam flowing through said path out of contact with the water, and means responsive to the temperature of steam which has received additional superheat in said second section for controlling said regulator.

8. Apparatus of the character described comprising, in combination, a boiler, a first superheater section, a second superheater section, said sections being located in difierent heating zones in the boiler and said first section being located in a zone in which the variation in the amount 01' superheat obtained during normal operation of the boiler is g'reater'than in the zone in which said second section is located, a superheat regulator, a conduit jor conducting saturated steam from the boiler to said first section, a conduit for conducting steam from said first section to said regulator, a conduit for conducting from said regulator to said second section all of the steam to be superheated therein, said regulator comprising means provi g a path of fiow for steam through the regulator and a space for water to be evaporated by steam flowing through saturated steam by convection in a zone of relatively low temperatures, whereby the temperature of the initially superheated steam tends to vary with variations in rate of operation of the boiler, regulating the temperature of the initially superheated steam by evaporating water out of contact therewith, subsequently superheating the steam to desired final temperature in a zone of intense radiant heat and governing the regulated temperature of the initially superheated steam in response to variations in temperature of steam which has been superheated in said second mentioned zone.

10. In the art of superheating steam to high temperatures, the improved method which consists in initially superheating saturated steam in a .first zone, regulating the temperature of the initially superheated steam by passing the same in heat exchange relation and out 01' contact with water at substantially the vaporizing temperature corresponding to the pressure or the water, whereby to desuperheat the steam by evaporating water, subsequently superheating the steam in a second zone'of materially higher temperature than said first mentioned zone and tending to impart tothe steam a relatively constant amount of superheat as compared with the amount of superheat imparted in said first mentioned zone and regulating the amount of desuperheating in response to variation in temperature. of steam leaving said second zone to provide a supply of superheated steam'oi substantially constant temperature entering said second zone.

11. The improved method or operating a superheating boiler to provide superheated steam at high temperature which consists in initially superheating saturated steam in a first zone in the boiler, withdrawing water from the boiler and passing the same in heat exchange relation and out of contact with the initially superheated steam to regulate the temperature of the initially superheated steam by causing the steam to evaporate some of said water and subsequently adding additional superheat to the desuperheated steam in a second zone of intense heat in said boiler in advance oi? said first mentioned zone with respect to fiow of combustion gases through the boiler and tending to impart to the steam a relatively constant amount of superheat as compared with the amount of superheat imparted in said first mentioned zone.

' HOWARD J. KERR.