US2211724A - Forced flow generator and method of operating same - Google Patents

Description

Au 13, 1940. K R 2,211,724

FORCED FLOW GENERATOR AND METHOD OF OPERATING SAME Original Filed July 22, 1932 2 Sheets-Sheet l INVENTOR Howard J. K57

ATTO RNEY Aug 13, 1940. H. J. KERR 2,211,724

FORCED FLOW GENERATOR AND METHOD OF OPERATING SAME Original Filed July 22, 1952 ZSheets-Sheet 2 f 4 o 3 2 #5 J I8 25 I? L INVENTOR ATTORNEY Patented Aug. 13, 1940 UNETED STATES FORCED FLOW GENERATOR AND METHOD OF OPERATING SAME- Howard J. Kerr, Westfield, N. J., assignor to The Babcock & Wilcox Company, Bayonne, N. J., a corporation of New Jersey 6 Claims.

This invention relates to a forced flow vapor generator and method of operating the same for generating superheated vapor, and in which type of vapor, generator liquid enters at one end of a tube and emerges from the other end as a vapor or gas; this application being a division of my pending application filed July 22, 1932, Serial No. 623,983, and which is a continuation of my original application filed May 7, 1930, Serial No,

The present invention, however, is distinguished from the well known flash or semi-v flash generator methods in that it comprises utilizing a path, or paths, of extreme length and small bore into which liquid distributed at one end, extends therethrough for a preponderance of the length of such path and at regulated locations therein, dependent upon controlled conditions of water feed and combustion, is preheated, vaporized and superheated in the quantity and quality required to meet specific load conditions, all of which is accomplished without interposition of any separation of liquid and vapor in a drum or the like. 9 Also, a feature of the present invention is. the distribution, for the equalization of flow and temperature, of the fluid at one or several points along the flow path as, for instance, bringing the flow from several paths together in a mixing or 3 equalizing header and the redistributing to a multiplicity of paths, such mixing and distribution preferably being carried out at locations where there is no change in the physical state of the fluid, thereby avoiding the difficulties which would be encountered in endeavoring to mix fluids of unlike physical properties as, for instance, steam and water.

In a preferred form of the generator in which the method of the present invention is performed is typified by a multiplicity of long small-bore fluid-flow conduits arranged in parallel and presenting an uninterrupted state of flow from liquid inlet at one end of vapor outlet at the other, with means incorporated in the flow path intermediate the inlet and outlet for mixing the fluid of the several paths to establish an equilibrium of physical condition, and to then re-apportion the fluid flow through several paths. The invention particularly relates to a"once through steam boiler method of operation that can be practiced at very high pressures, up to, or above, the critical pressure of steam. By a once through boiler is meant a boiler into which feed water enters and is entirely evapo- 5525 rated to generate steam without any of the water returning to the inlet of the boiler before it is evaporated and the steam passed to a place of use. In this type of boiler the fluid is formed through the various sections by means: of the feed pump The boiler is provided with an economizer section where the feed water is heated while it flows in a counter-current direction to the direction of flow of the heating gases to a point beyond which steam is generated. The heated water then passes to the generating section where all of it is vaporized, the steam generated passing to a superheater wherein it is superheated before being delivered to the place of use.

In order to permit the use of Very high pres- 15 sures, e. g. up to the critical pressure of steam, it is necessary to dispense with cast iron parts in a boiler and to usesmall tubes, preferably made of seamless wrought steel with the connections between the tubes welded. In order to prevent the frictional resistance through the boiler from becoming too high with the small tubes which are connected in series, it is sometimes necessary to use two or more tubes grouped in parallel, the groups being connected in series. 2%

Also since the demand for steam may vary rapidly, requiring a corresponding rapid variation in the amount of water fed to the boiler and heat transferred to the water, it is desirable to obviate the presence of large masses of mate- 30 rial, such as thick refractory furnace walls, for example, where large quantities of heat might become stored and be transmitted to the water when it is not required. For this reason it is desirable to surround the furnace, or a substantial portion thereof, with steam generating tubes of the boiler to absorb the radiant heat of the furnace and prevent the storage of too much heat in parts where it would interfere with the desired change in the rate of steam generation. 40

In the boiler described in this application the amount of feed water is varied in accordance with the .demand for the steam and the firing of the boiler is to be varied so as to keep the outlet temperature of the steam at the desired point. 5

The desired pressure of the steam is maintained by the proper variation of the amount of feed Water and fuel.

In the accompanying drawings:

Figure 1 is a vertical sectional view, somewhat Fig. 3 is a transverse section of a modified arrangenient of tubes in the plane represented by the line 33 of Fig. l; and

Fig. 4 is a somewhat diagrammatic view, similar to Fig. 1, showing the vaporizer partially in section, and with the controls for water input and elements of combustion.

In the drawings reference character l indicates a furnace that may be fired by one or more burners 2 that are shown located at the bottom of the furnace. A flue 3 extends from the upper portion of the furnace to the stack l.

The feed water pipe 5 enters a distributing and equalizing header 8 near the upper portion of the flue 3. One or more long small bore tubes lead from the header 8 to the economizer section I of the boiler that is located in the upper portion of the flue 3. The economizer 7 may consist of coils of small seamless, wrought steel tubes in parallel, or may be made up of parallel tubes sub-divided by headers into small groups, the groups being connected in series, and the total series connected groups then joined to the header 6; the coils or groups of tubes constituting the economizer are connected so that the water passes through them counter-current to the gases in the flue 3 and the outlet ends of the economizer coils or groups of tubes are connected to a header 8 outside of the flue. The header 8 is connected by means of the pipe 9 to a header lil located outside of the wall of the furnace i.

One or more tubes extend from the header It] to the steam generating tubes or boiler section ll. This section preferably comprises coils or tubes surrounding the furnace l to shield the walls thereof from the radiant heat of the furnace and prevent a large amount of heat from being stored in walls of the furnace. In addition to the coils or tubes of the steam generating section which shield the furnace walls from the intense heat, the steam generating or boiler section may comprise additional tubes which extend across the furnace, these tubes also being connected in series or in groups in parallel with the tubes in each group connected in series. The tubes referred to in the steam generating section, in addition to the coils heated by radiant heat, may be arranged across the furnace in the manner shown in Fig. 3, which is representative of a section in any location in the steam generating section similar to the plane represented by the line 33 of Fig. 1 from the lowermost portion of the steam generating section l l to the uppermost portion thereof, if desired, it being obvious that in the case of such an arrangement the lowermost of these transverse coils would be subjected to radiant heat. The vapor or steam generating section II is comprised of a plurality of tubes coiled in parallel and each connected at its fluid entrance end to the header Ill. The steam and water in the section H are shown to flow parallel to the direction of the hot gases, so that if the steaming temperature of the water has not been reached in the economizer section I, the coolest portions of these tubes are exposed to the hottest gases. This steam generating section is so constructed that there is an upflow of water and steam to obviate any danger of steam pockets forming which might be the case if water and steam were made to flow downwardly.

The outlet ends of the tubes of the steam generating or boiler section H are connected in series to coils or groups of tubes constituting the superheater l2 which is constructed in a manner similar to that described above in connection with the economizer I. The superheater I2 is located in the flue 3 between the economizer I and boiler II. The steam to be heated in the superheater l2 flows in the same direction as the gases which heat the economizer. The out let ends of the superheater coils of groups of tubes !2 are connected to the header l3 from which a pipe l4 provided with a valve I5 leads to a steam main or place of steam consumption. In connection with Fig. 2 and the section line 2-2 of Fig. 1, it is to be understood that, if desirable, all of the coils in this superheater section may be of the type represented in this figure, or that such coils may be located at any suitable zones therein, and it is to be noted that the actual superheating may take place only in the uppermost portion of this section l2 and after the steam becomes dried in the section I 2.

A feed water pipe [6 leads from a condenser or hot well (not shown) to the inlet of a feed pump 11 which is preferably a triplex plunger pump driven in any convenient way. The pipe 5 leads from the outlet side of the pump H to the header '6 of the economizer 'l.

A by-pass it? having a regulating valve l9 may be provided around the pump H, and a make up feed water pipe 26 having a valve 2! may be connected to the pipe 56.

Portions of the coils H are extended as shown at 22 to enter the setting of the steam generator and thereby form supports.

In Fig. 4 an orifice or similar element is located between the flanges 22o, creating a pressure differential bearing a known relation to rate of vapor outflow. Such pressure dillerential is effective, through pipes 23; to continuously position a regulating valve ill in the by-pass l8, thereby automatically regulating liquid supply in accordance with the demand upon the generator. A bulb 2 t, sensitive to vapor outflow temperature, forms part of a thermostat system of which 25 indicates the connecting capillary continuously positioning the fuel regulating valve 26 to maintain desired vapor outflow temperature. Should vapor outflow pressure depart from desired value, a readjustment of liquid inflow and of fuel supply rate is automatically accomplished in the desired direction and amount, through the agency of regulating valves 2i and 21, both positioned directly by such pressure effective through the pipe 28.

When the demand upon the generator increases, the increased rate of vapor outflow causes a throttling of valve l9, with consequent increase in rate of liquid inflow. Should the temperature of the vapor fall below desired value, the valve 26 will be opened proportionately to increase the heating; while if vapor pressure at the same time decreases below desired value the auxiliary fuel supply valve 2'! will be positioned in an opening direction and the supplementary liquid supply valve 2! will be positioned in necessary direction and amount to cause the feed water supply to be adequate for the pressure to return to normal. These various regulations are quite independent in action and may act in sequence or simultaneously, to correct the variables under control.

While a specific construction of a once-through boiler has been illustrated and described in connection with the method of the present invention, it will be understood that other constructions employing the same method of operations come within the scope of this invention. Also while different portions of the boiler have been described as economizer, boiler, and superheater sections, it will be clear that the lines of demarcation between these various sections are not definitely fixed, but will vary depending upon the operation of the boiler, but in all cases the feed water will enter the economizer and after passing through the once-through sections in series will leave the last, or superheater section, as superheated steam.

I claim:

1. The method of operating a vapor generator having small liquid storage and a high rate of evaporation and receiving fuel from more than one supply, which includes, regulating one supply from an indication of vapor outflow pressure, and regulating another supply from an indication of vapor outflow temperature.

2. The combination with a vapor generator having small liquid storage and a high rate of evaporation, a liquid supply pump having a bypass, a valve in said .by-pass, means responsive to vapor outflow rate for variably adjusting said valve, an auxiliary supply of liquid for said pump, and regulating means of said auxiliary supply controlled by vapor outflow pressure.

3. The-combination with a vapor generator of the drumless forced flow type receiving liquid under pressure at one end and delivering superheated vapor at the other, a divided fuel supply for the generator, a regulating valve in each fuel supply path, means responsive to vapor outflow pressure continuously positioning one of said valves, and means responsible to vapor outflow temperature continuously positioning the other of said valves.

4. The combination with a vapor generator of the drumless forced flow type receiving liquid under pressure at one end and delivering superheated vapor at the other, vapor outflow responsive apparatus normally regulating liquid supply, vapor outflow temperature responsive apparatus normally regulating fuel supply, and vapor outflow pressure responsive apparatus adapted to readjust liquid inflow and fuel supply.

5. The combination with a high pressure vapor generator of the forced flow type, of a positive displacement feed pump for supplying a vaporizable liquid thereto continuously during normal operation thereof, means forming a regulable bypass around said pump, and control means responsive to variations in vapor outflow from said vapor generator for regulating the quantity of liquid passing through said by-pass in accordance with the variations in vapor outflow from said vapor generator.

6. The combination with a high pressure vapor generator of the forced flow type having a plurality of long small-bore liquid flow conduit portions arranged for flow in parallel and having an extremely large ratio of heat absorbing surface to cross-section, of a feed pump for supplying a vaporizable liquid thereto continuously during normal operation thereof, means forming a regula-ble by-pass around said pump, and control means responsible to variations in vapor outflow from said vapor generator for regulating the quantity of liquid discharged by said pump passing through said by-pass in accordance with variations in vapor outflow from said vapor generator.

HOWARD J. KERR.

CERTIFICATE OF CORRECTION.

Patent Nb. 2,211,72L. August 15, 191m.

HOWARD J. KERR.

It is hereby certified that error appears in the printed p cification of the above numbered patent requiring correction asfollows: Page 1, first column, line #5, for "of" read -to--; and second column, line 5, for "formed" read --forced-; page 2, second column, line 72, for "operations" read --operation--; page 5, second column, line 22, c im 6, for "liquid" read -fluid--; line 29,- same claim, for "responsible" read --responsive--; and

that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this Zhth day of December, A. D. 191m.

Henry Van Arsdale (Seal) Acting Commissioner of Patents.

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