US2291118A - Steam generator - Google Patents

Description

July 28, 1942- F. s. THOMAS 2,291,118

' STEAM GENERATOR Filed May 13, 1940 3 Sheets-Sheet l INVENTOR www ATTORN'EY F. s. THOMAS 2,291,118

STEAM GENERATOR Filed May l3, 1940 July 28, 1942.

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F. s. THOMAS STEAM GENERATOR Filed May 13, 1940 3 Sheets-Sheet 3 A TORNEY Patente-c1 July 28, 1942 UNITED STATES PATENT OFFICE STEAM GENERATOR Frank S. Thomas, Topeka, Kans., assignor of onehalf to Fred P. Martin, Topeka, Kans.

Application May 13, 1940, Serial No. 334,811

7 Claims.

This invention relates to steam generators, particularly those known as flash boilers designed for rapid generation of high pressure Ysteam responsive to demand therefor, and has for its principal object to provide a generator of this character whereby the temperature of the steam is held closely within a predetermined temperature range.

Other objects of the invention are to provide a generator having higher eiiiciency and capacity for a given sized unit; to provide for circulation of steam from a high temperature zone of the boiler in heat exchange relation with a cooler zone; to provide for temperature stabilization in a manner to eliminate shock or molecular disturbance in the metal parts of the boiler thereby prolonging the life of the boiler and reducing boiler failures; and to provide for steady and uniform steam generation during times of high demand.

In accomplishing these and other objects of the invention, I have provided improved details of structure, the preferred form of which is illustrated in the accompanying drawings, wherein:

Fig. l is a vertical section through a steam generator embodying the features of the present invention.

Fig. 2 is an enlarged section through a. portion of the generator illustrating the temperature responsive control mechanism and the steam bypass valve actuated thereby.

Fig. 3 is a schematic diagram of the generator and controls therefor.

Referring more in detail to the drawings:

While my improved temperature control is 3 adapted to various flash boiler systems, I have illustrated it in connection with a steam generating system of the character illustrated in my copending application Serial No. 256,920, filed February 17, 1939, which system includes a generator I having a casing 2 providing an upper heat generating chamber 3 and a lower steam generating section 4. The heat generating chamber has a burner supplied with primary fuel from a tank 6 through a pipe 1 under pressure of a pump 8. The burner is also supplied with a pilot or secondary fuel from a tank 9 through a pipe I0 under pressure of a pump II, the pumps 8 and II being initially operated by an electric motor I2 which its supplanted, when the system is in operation, by a steam turbine I3. Interposed in the pilot fuel supply line is an injector pump I4 for controlling volume and pressure at which the pilot fuel is delivered to the burner, the injector pump I4 being actuated along with the pumps 8 and I I.

Mounted in the steam generating section is a steam generating coil I5 comprising a series of spirally wound tubes I6 arranged in superimposed relation and interconnected by headers I'I (Fig.v 1) to form a continuous passageway from the bottom of the steam generating chamber to the top thereof, wherein feed Water admitted through a pipe I8 is converted into steam and discharged by way of a tubular thermostat I9 through a pipe 20 to a steam consuming appliance, for example an engine 2|. Feed water is supplied from'a tank 22 under pressure of a feed water pump 23 operated by an interconnected engine` 24which is supplied with-steam from the pipe 20 through a branch line 25. The exhaust steam from the engine is discharged through a pipe 26 which connects with the exhaust steam line 2I leading from the engine 2I to a condenser 28 wherein the exhaust steam is condensed and returned as water to the tank 22 through a pipe 29. The turbine I3 is also supplied with steam from the pipe 20 through a branch pipe 30, and the exhaust steam is delivered to the condenser through a pipe 3| connected with the pipe 21.

As disclosed in the above mentioned application, the pilot or secondary fuel is utilized as an actuating medium for controlling a valve 32 in the primary fuel supply line, a feed water pump control valve 33 and a steam by-pass valve 34 which constitutes an important part of the present invention. The elective supply of pressure medium to the valves'32, 33 and 34 is under control of the boiler temperature and pressure through the thermostat I9 and a pressure actuated device 35. Connected in the secondary fuel supply pipe I0, on the low pressure side of the injector pump I4, are valves 3B, 3'I and 38, all of which have inlets connected with the pipe I0. The outlet of the valve 36 is connected with a continuation of the pipe I0, and therefore this valve directly controls ow of secondary or pilot fuel to the burner and operates the valve 32 through pressure of the uid-acting through a pipe 39 against a spring pressed piston 40 to normally retain the valve 32 open. l The spring is arranged to close the valve 32, when the valve 35 is seated to shut off the pilot fuel, and the pressure acting on the piston is reduced by the injector pump which continues to supply fuel to the burner until The valve 36 is actuated through a series 'of-.

compound levers 4l, having connection with the thermostat as disclosed in the above mentioned application. The valve 3l is likewise actuated responsive to operation of the thermostat and also when a predetermined high temperature is reached in the boiler to control a by-pass line 42 whereby the pilot fuel is by-passed back to the tank 9 when the valve 36 is closed. The valve 38 is normally seated but is unseated to by-pass the pilot fuel back to the tank through a by-pass connection 43 with the line 42 when the thermostat is operated, and when a predetermined high pressure occurs in the boiler, the boiler pressure acting responsive to hydrostatic head through a pipe 44 which is connected with the feed water supply pipe I8 and toa pressure chamber 45 containing a fiuid which acts ona piston 46 to effect opening of the valve 38 and closing of the valve 36 through lever connections 41 Iand 48 respectively.

The pump Il has a by-pass 49, having a pressure regulating valve'i) that is set at a differ'- ent pressure than a regulating valve l in thev by-pass line 42. With the system thus far described, operation of the pump Il will buildup pressure in the pipe l0 to supply pilot fuel to the injector I4, which in turn delivers the pilot fuel to the burner, the pilot fuel being ignited by a suitable sparking device designated 52, and which is operated whenever the pump actuators H andY 8 are placed in operation. The pressure of the pilot fuel also acts through the pipe 39 to open the valve 32, whereupon the pump 8 is effective in supplying primary fuel to the burner which is ignited and maintained in co-mbustion by burning of the secondary or pilot fuel.

The products resulting from combustion of the fuels pass downwardly in heat exchange relation with the generating coils to heat the water contained therein and convert it into steam which is discharged through the pipe in Contact with the thermostat. The temperature `of the steam acting on the thermostat modifiesl the effect of the heat of combustion, which also acts on the thermostat to control fuel supply to the burner, consequently when the thermostat reaches la predetermined temperature the valveV 36 will bev closed, thereby shutting oi the pilot fuel to the injector which then acts to drain the line 39 and elect a shut oif of the primary fuel supply responsive to closing of the valve `32.

The valve 33 is set to open at a higher pressure than the regulating valves 50 and 5I, therefore, if the pressure in the boiler is not sufficient to effect opening of the valve 38, closing of the valve 3l will build up pressure in the line 53 to open the valve 33. Steam is then supplied to the feed water pump so that feed water: is delivered to the boiler. When the initial pressure is built up in the generatorv the valve 38 opens to drop pressure in the line 53 suciently to effect opening of the valve 33, shutting down the feed water supply to the boiler.

The system thus far described, with exception of the boiler coil, is identical with the system disclosed in the above mentioned application and such a system operates satisfactorily except at times when heavy demands occur on the boiler. Boilers of the character described have tubes of great length and consequently the feed water is relatively slowly converted into steam. The conversionV point or exact region wherein the water passes from the fluid to the vapor state varies considerably due principallyV to variable loads imposed on the boiler and the amount of heat released within the combustion chamber. The cooling or stabilizing eect upon the temperature of the steam is slow to respond and is, therefore, inadequate to maintain a stabilized temperature in the zone of the thermostat. When heavy demands are put on the boiler, at such times the temperature of the issuing steam will rise suddenly to effect the thermostat to bring about an increase in the water supply. The vapor point, or points of water conversion in the tube, is pushed ahead quite rapidly in response to the predetermined temperature limit having been reached in the thermostat and, as above explained, the water cannot ordinarily reach the thermostat in time to normally bring about a gradual or stabilizing condition of temperature and the temperature of the issuinfg steam will persist in rising until the fuel supply is suspended. Due to the maximum temperature having been reached, the water supply in normal response to the feed pump, will cause the water columnl or point of vaporization to beV accelerated within the boiler tube in the thermostat at a greater rate than under normal conditions. The temperature of the issuing steam underk these conditions will remain practically unchanged until the vaporization point or column of water has practically reached the zone of the thermostat, at which time the tempera ture will drop suddenly and the generator is flooded. The fuel supply will instantly be started, but the fire or heat released is so unbalanced with the large amount of water contained in the boiler tube that the burner is inadequate to maintain a desired temperature when these conditions are brought about.

In overcoming the above disadvantages, I provide for by-passing steam from the steaming portion of the coil in heat exchange relation with a cooler section in the boiler to reduce the temperature of the by-passed steam and to return the cooled steam for mixture with steam in the coil,v thereby normalizing the temperature of the steam passing in contact with the thermostat. This interchange of heat with the cooler section of the boiler conservesthe heat in the boiler and more quickly raises the temperature of thecooler section of the boiler to the steaming point. In carrying out this feature of the invention, one of the convolutions near the' upper end of the coil is interrupted and extended through the wall of the boiler asindicated at 54 to' connect by way of the valve 34 with the next upper coil through a connection 55v asV clearly shown' in Fig. 2. When the boilerl isoperating under normal conditions, the steam risinginl the'coil merely passes through the connections 541 and 55 by Way' of the valve to continuefl'ow through the upper portion of the coil. However, when the temperature at the thermostat reaches the point where the thermostat is actuated, the steam discharged through the connection- 54 is by-passed through a pipe 56 that connects with a coil 5l contained within one of the coils located in a cooler section of the boiler and returned from a continuation of the coil 5l in an adjacent coilby a pipe 58 to the connection 55. The preheated steam in the high temperature part Vof the boiler which approaches the temperature at which'the thermostat operates is thus' circulated in heat exchange relation with the coolersection of the boiler to give up a portion of itsV heat to the water or cooler steam'. After being reduced in temperature, theV bypassed steam is returnedv for mixture with the -steam remaining in the upper part of the coil, reducing the temperature to the point where the thermostat is not effective in closing the fuel control valve.

The steam circulation thus described is effected by the valve 34 which includes a valve body 59, having a valve chamber 60 connected with a passageway 6I through a port 62, the passageway 6| connecting the pipes 55 and 58, while the chamber 60 is connected with the pipe 54 through a port 63. The port 62 has a seat 64 on the valve chamber side for engagement by the seating face 65 of a valve member 66. The opposite end of the valving member also has a seat contacting face 61 adapted to engage a seat 68 encircling a port 69 that is coaxial with the port E2 and connects with the pipe 56.

The valving member includes a stem 18 slidable through a stuii'ing box 1I, the stem being guided in a nut 12 that is threaded in a collar 13, the collar 13 having lateral arms 14 spaced from the valve body by sleeves 15, the parts being retained by means of bolts 16 having their Shanks 11 extending through openings in the arms, through the sleeves, and into threaded sockets 11' formed in the end of the valve body. Also carried by the collar 13 are arms 18 carrying a diaphragm housing 19. The diaphragm housing includes an upper section 88 to which the arms are attached, and a lower section 8| connected to the upper section by fastening devices such as screws 82. Engaged between the sections is a flexible diaphragm 83 that is rigidly connected with the valve stem by jam-nuts 84 and 85 threaded on a reduced extension 86 of the stem and clampingly engaging the respective sides of the diaphragm.

The diaphragm is normally urged in a direction to cause engagement of the valve face 61 with the seat 68 by means of a coil spring 81, having one end bearing against the diaphragm and the other end against the adjusting nut 12 so that the port 62 is normally in open position to permit movement of steam rising in the coil to pass directly through the valve and be returned through the connection to the upper portion of the steam coil, so that in normal operation no steam is byi passed through the cooler section of the boiler. The diaphragm is operated in the opposite direction by fluid pressure built up in the line 53 when the valves 36 and 31 are closed. This is effected by providing the lower section of the diaphragm housing with a pressure chamber 88 that is connected by a pipe 89 with the pipe 53.

With the structure just described it is obvious that when temperature rises in the zone of the thermostat and the valve 36 closes, the pressure is built up in the line 53 to exert pressure on the diaphragm and cause seating of the valve 66 on the seat 64. Therefore steam passing from the pipe 54 is diverted through the port 69 and pipe 56 through the coil 51 in heat exchange relation with the water or steam in the cooler section of the boiler to reduce the temperature of the steam and raise the temperature of the water or steam so that it more quickly approaches the Vaporizing temperature. The cooled steam is then passed through the pipe 58 and returned through the passageway 6l and connection 55 to the steaming space of the boiler to cool the steam in the zone of the thermostat and maintain a normalized temperature thereof. When the valve 36 opens and pressure drops in the line 53, the spring 81 moves the valve 66 in the opposite direction to close the port 69 and reestablish direct ow of steam from the connection 54 through the port 62 and passageway 6l to the connection 55.

From the foregoing it is obvious that I have provided a simple and eii'icient method of normalizing the temperature in the steaming space of a boiler so as to automatically maintain a steadier, even discharge of steam especially at the times of high demand.

What I claim and desire to secure by Letters Patent is:

l. A boiler, including a steaming zone and a water heating zone, a burner, means supplying fuel to the burner to heatthe boiler, `a thermostat responsive to tem-perature of the steam, fuel supply control means, an operating connection between the fuel supply control means and the thermostat, a heat exchanger in the water heating zone of the boiler, means conducting steam from the steaming zone of the boiler to the heat exchanger and returning the steam to the steaming zone, control means in said steam conducting means, and an operating connection between said last named control means and the thermostat to effect flow of steam through the heat exchanger when the thermostat functions to shut olf the fuel supply.

2. A boiler of the character described, including a steam generating tube having a water inlet and a steam outlet, a by-pass valve connected with the tube near the steam outlet end, means yconnected with said by-pass valve and located in heat exchange relation with the water inlet end of the tube for by-passing steam in heat exchange relation with a section of the tube, temperature responsive means for controlling a fuel supply to the boiler, means responsive to boiler pressure for controlling lfeed Water supply to the tube and having governing control by said temperature responsive means, and an operative connection between the by-pass valve and the temperature responsive means.

3. In a boiler, a heat exchanger in the water containing portion of the boiler, a by-pass connected with the boiler and said heat exchanger for circulating steam in heat exchange relation with said water, control means for said by-pass, fuel and water supplies for said boiler, control means for said fuel and Water supplies, a thermostat connected `with the boiler, a hydraulic connection between all of said control means, and means responsive to said thermostat for controlling hydraulic :pressure acting on said control means to maintain normalization of temper-ature in the boiler through control of vsaid water and fuel supplies in conjunction with said steam bypass.

4. In a boiler having high and lo-w temperature zones, a heat exchanger in the low temperature zone of the boiler, a lby-pass connected with the boiler and said heat exchanger for circulating steam in Yheat-exchange relation with said loW temperature zone, control means for said by-pass, fuel and water Asupplies for said boiler, control means for said fuel and water supplies, a thermostat connected with the boiler, a hydraulic connection between all of said control means, and means responsive to said thermostat lfor controlling hydraulic pressure acting on said control means to maintain normalization of temperature in the Iboiler through control of said water and fuel supplies in conjunction with said steam Joy-pass.

5. In a boiler having high and low temperature sections, a by-pass valve connected with the high temperature section, means connected with said by-pass valve and located in heat exchange relation with the low temperature section for and a cooler zone, means for conducting steam from the high temperature zone in heat exchange relation with the cooler zone of the boiler, means for returning the steam to the high temperature zone of the boiler, means for supplying heat to the boiler, and means associated with said heat supply means for controlling conduction of steam from the high temperature zone to the cooler temperature zone.

7. A boiler having a high temperature zone and a cooler temperature zone, a burner, means supplying fuel to the burner to heat the boiler, a thermostat responsive to temperature of steam in the high temperature zone, fuel supply control means, an operating connection between the fuel Ysupply control means and the thermostat, means for conducting steam from the high temperature zone of the boiler to the cooler zone of the Aboiler and returning the steam from the cooler zone of the boiler to the high temperature zone, control means vin said conducting means, and an operating connection between said last named control means and the thermostat to effect flow of steam to and from the cooler zone when the thermostat functions to shut 01T the fuel supply.

. FRANK S. THOMAS.

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