US2676575A - Steam superheat control - Google Patents

Description

April 27, 1954 A. J. ROSENBERGER STEAM SUPERHEAT CONTROL 7 Filed July 8, 1950 ATTORNEYS Patented Apr. 27, 1954 STEAM SUPERHEAT CONTROL Albert J. Rosenberger, Chicago, 111., assignor to Republic Flow Meters Company, Chicago, 111., a corporation of Illinois Application July 8, 1950, Serial No. 172,700

3 Claims.

This invention relates to a steam superheat control and particularly to a control to maintain a uniform superheat temperature under varying loads.

In boiler equipped with superheaters, the superheat temperature tends to be higher at high loads than at low loads. It has been the usual practice to design and adjust the superheater to produce the desired superheat at approximately half load and to desuperheat at higher loads. At lower loads the steam has been used at reduced superheat.

It is one of the objects of the present invention to provide a steam superheat control which will maintain a uniform superheat temperature under varying load conditions.

Another object is to provide a steam superheat control in which steam is recirculated through the superheater at lower loads.

Still another object is to provide a steam superheat control in which the amount of steam recirculation is controlled in response to a function, preferably the temperature, of the steam at the outlet side of the superheater. Preferably an adjustable injector is employed to produce the recirculation and is adjusted in response to variations in the selected steam function.

A further object is to provide an adjustable steam injector.

The above and other objects and advantages of the invention will be more readily apparent from the following description when read in connection with the accompanying drawing, in which Figure 1 is a diagrammatic view of a steam superheat control embodying the invention; and

Figure 2 is a sectional View through the adjustable injector.

As shown in Figure l, the invention is applied to a steam generator or boiler having a. steam drum I0. Steam from the drum flows through a superheater H to a header 12 from which the steam is withdrawn for any desired use. These parts represent a conventional boiler construction except that the superheater, according to the present invention, is designed and adjusted to produce the desired superheat of the steam in the header 12 at some predetermined high load approaching maximum load, that is, when the maximum quantity of steam is flowing from the boiler and the header in the normal operating range. With the superheater so designed and adjusted, the superheat temperature of the steam will be lower than the designed temperature at all load conditions other than maximum load.

To correct for the lower temperature at the lower load conditions, a recirculating connection 13 is provided from the header [2 at the outlet side of the superheater to the inlet side of the superheater between the superheater and the boiler drum I8. The recirculating connection l3 leads to an injector I4 which functions in response to flow of steam from the boiler drum to the superheater to induce a flow of steam through the recirculating connection.

The injector is constructed as best seen in Fig ure 2 with a hollow body l5 providing an enlarged chamber it having an inlet connection at I! for connection to the boiler drum and an outlet 18 for connection to the superheater inlet. The inlet connection ll preferably opens into the side of the chamber, and the chamber tapers toward the outlet connection as indicated at 19.

An inlet chamber 2! i provided at one end of the chamber it and is separated therefrom by a wall 22 having a circular central opening therethrough opposite to the outlet 18. An injector nozzle 23 extends slidably through this opening in alignment with the outlet [8 and is shiftable axially toward and away from the opening it. With this construction the area of the passage around the nozzle 23 and within the tapered portion is can be varied to vary the injector effect and the quantity of steam circulating through the recirculating connection. The nozzle is formed with lateral inlet openings 24 communieating with the inlet chamber to receive steam from the bypass H3.

The nozzle is adapted to be shifted by an operating rod 25 extending through the outer end of the inlet chamber and sealed by means of a packing 26. The rod 25 is moved by a control device indicated generally at 26 which may be any de sired type of regulator or controller capable of shifting the rod in response to a controlling force.

The regulator 25 is preferably responsive to a function of the steam in the header I2 such, for example, as the rate of flow of steam through the header, the pressure in the header, or the temperature in the header. As shown, the regulator is responsive to the header steam temperature, and for this purpose a bulb 21 is mounted in the header and is connected by a tube 28 to the regulator 26. As the temperature in the header increases, the regulator will move the nozzle 23 to the left, as seen in Figure 2, and as the temperature decreases, the regulator will move the nozzle to the right.

In operation, when the apparatus is operating at full load, the temperature in the header will be high at the desired superheat value, and the 3 nozzle 23 will be shifted fully to the left. At this time the injector provides a minimum degree of suction on the nozzle so that there will be a minimum or zero return flow of steam through the recirculating connection. At lower loads the temperature in the header tends to drop so that the nozzle 23 will be shifted to the right. This increases the injector effect causing a circulation of steam from the header through the recirculating connection to recirculate through the superheater. As the steam recirculates through the heater, its temperature will be increased and by properly adjusting the regulator the correct amount of steam can be recirculated to maintain the desired superheat temperature in the header under all load conditions.

While one embodiment of the invention has been shown and described in detail herein, it will be understood that this is illustrative only and is not to be taken as a definition of the scope of the invention, reference being had for this purpose to the ap ended claims.

What is claimed is:

1. In a steam generator including combustion means for steam generation and a convection superheater heated by said combustion means and having a steam inlet connected to said generator and a steam outlet and designed to produce the desired superheat at a predetermined high load, a superheater control comprising, a direct recirculating connection from the steam outlet to the steam inlet, control means to control the quantity of steam flowing through the recirculating connection, and a control device including a sensing element responsive to the temperature of the superheated steam to regulate the control means to maintain a uniform superheat temperature at said steam outlet under varying load conditions by increasing the quantity of steam flowing through said recirculating connection when said temperature decreases and decreasing said quantity when said temperature increases.

2. In a steam generator including combustion means for steam generation and a convection superheater heated by said combustion means and having a steam inlet connected to said generator and a steam outlet and designed to produce the desired superheat at a predetermined high load, a superheater control comprising, a

direct recirculating connection from the steam outlet to the steam inlet, an injector connected to the steam inlet and the recirculating connection to draw steam from the steam outlet through the recirculating connection into the steam inlet, adjustable means to control the quantity of steam flowing through the recirculating connection, and a control device including a sensing element responsive to the temperature of the superheated steam to adjust said adjustable means to maintain a uniform superheat temperature at said steam outlet under varying load conditions by increasing the quantity of steam flowing through said recirculating connection when said temperature decreases and decreasing said quantity when said temperature increases.

3. In combination, a steam generator including combustion means for steam generation, a convection superheater connected to the generator and heated by said combustion means and designed to produce the desired superheat at a predetermined high load, a steam header connected to the superheater, a direct recirculating connection from the steam header around the superheater, and means responsive to the temperature of the steam flowing from said superheater to said header to maintain a uniform superheat temperature at said header under varying load conditions by increasing the quantity of steam flowing through said recirculating connection when said temperature decreases and decreasing said quantity when said temperature increases.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 123,264 Korting Jan. 30, 1872 395,456 Sauer Jan. 1, 1889 1,014,919 Sweeny et a1. Jan. 16, 1912 1,449,228 Hasegawa et a1. Mar. 20, 1923 1,661,106 Broido Feb. 28, 1928 1,934,724 Lucke Nov. 14, 1933 1,973,517 Armacost Sept. 11, 1934 1,992,115 Belohlavek Feb. 19, 1935 2,257,805 Kolling Oct. '7, 1941 2,594,818 Sprague et al Apr. 29, 1952 2,594,962 McDonald Apr. 29, 1952

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