US2330559A - Vapor generator or boiler - Google Patents

Description

' SeptA 28, 1943 G. DECKER ETAL A 2,330,559

VAPOR GENERATOR OR BOILER Filed July 13, 1939 5 Sheets-$1166.12

Sept. 28, 1943, A G. DECKER ETAL 2,330,559

VAPOR GE'NERATOR OR BOILER Filed July 13, 195,9 5 Sheets-Sheet 3 Patented Sept. 28, 1943 untreu STATES rTENT QFFICE N Gustav Decker and Fercilinandl Riedel, Berln, Germany; vested in `the Alien Ifroperty Custodian Application m5113113, 193e, sriaLNO. 284,318.,

In Germany April 6,1938 o' 7 Cairns. (o1. 1224451) The present invention relates to vapor'generators or boilers and more especially to those of the once-through type, and is particularly concerned with regulating apparatus for such generators or boilers. l if It has been proposed in connection with oncethrough boilers to regulate the supply of feed Water automatically and in accordance with the steam consumption. It has been found, however, that for still partially unexplained reasons.

the effect of an increase or decrease of the feed Water supply to the boiler is felt in the steam generatingzone only after a relatively long time lag of the order of about ten minutes. Thus, there is .an insuiicient rate or feedy Water to ythe boiler during this period, While an increased quantity of steam is Withdrawn.v This' results in a shifting of the evaporation zone and thereby changes the effective length of the superheater section .of `the boiler. nomena referred to make it almost impossible to keep the temperature of the steam constant, especially in case of rapid load changes.

It has also 'been proposed to providein connection with once-through boilers, in addition to the main feed line connected to the boiler inlet, an auxiliary feed line bymeans of which a part of the feed Water is introduced directly into the vaporizing or into the superheating section of the boiler. In this prior proposal a loaded Valve Was to be mounted in the auxiliary feed line and Was adapted to be kept closed b y the pressure in the boiler. Thus, with this arrangement, a supply of auxiliary water to-the -`boiler only occurs When the pressure in tne latter has fallen by ak considerable degree. Furthermore, the valve only shuts off the auxiliary supply of feed Water again when the pressure in the Vvboiler resumes its original value. Since, however, there is a lapse of time, Viz. the vaporization period, f between the'admission. of the auxiliary-,Water supply and the rise in pressure caused thereby, the valve in the auxiliary feed line will not close early enough, and it will thus be impossible to avoid 'very considerable uctuations in the pressure. In addition, the lvalve is in no Way responsive .to pressure increases in the boiler due to a reduction in the load. f

It is an object of this invention to v*arrange the regulation of the feed, Where use is vmade of an auxiliaryboiler feed, such that both in the case of positive and lin theicase of negative variations in the load, the pressure inthe boiler lrelznains constant and without fluctuations.

Furthermore, the phe-v Thus, the present invention Yprovides regulating .apparatusfor once-throughgboilers or vapor generators wherein an auxiliary feed Water con duit is. connectedto.' the .vaporizer or superheater section of the boiler .or generatorfand is usedin addition to a main feed Water .conduit connected 4to the inlet. The `amountA oi' auxiliary feed Water `is proportioned to the' variation in load, andv to the rate or" .variationin lload by means ora valve (in the auxiliary feed line) which is controlled by a regulator that receives corresponding impulses 'from'. .pressure means connected to the boiler, and` a 'suitable counter- .balancing kimpulse from pressure means in the `auxiliary feed Water line. u

It is also known to spray cooling Water into` the steam line or the superheater `or aboiler for the purpose of regulating the steam temperature. 1n the known arrangements utilizing this lprinciplethe cooling Water was regulated" in response to the temperature, Whereas therfeed Water Wasregulated in accordance with the load. In accordance with a further feature of the present. invention, h0WeVer,--the Ysupply of reed Waterat the inletof the boiler is set to a predetermined basicload, land the injectedwater relation to the basic loadare to be anticipated,

the supply of ileed Water at the inletof the boiler Vmust 'be regulated'- in" response to the loadv in the conventional manner. "nisu'ch instances-,to

.compensatethe delayl caused by the l phenomena referred. to above, the injected Water `mayg in accordance with another feature oi'` `iis' invention, beqcontrolled in the auxiliaryreed line by the ratepfzvariation of the load.- '1*hus, ir there is alsudden'increase in `the'load at rthe inlet of the boiler, a correspondingly increased volume.

of feed Water will berallowedto passat the inlet, although vthis will become effective in the boiler afterlalapse oi' time.n During the change vlinlload,"however, there Will'- be simultaneously passed through the auxiliary vfeed line,1 and directly to? the Vaporization zoneof the' boiler, a quantity of Water Whichv is 'greater according .as the variation in the load is morer sudden. @,Itfissalsoof advantage. to control the l.supply lof 'fuelA to .the boiler. furnace ras a function of .the rate'of variation-of vthe load, so .thatLthe by a constriction, e. g., a nozzle or capillary tube.

If the effective surfaces of the pressure devicesv are chosen of the same size, the relay will receive an impulse which is independent of the absolute value of the load and only dependent upon the rate at which the load varies, and which will thus only be effective during a variation in the load. If, on the other hand, the surface of the pressure device which receives the impulse directly is larger than the surface of the other device, as long as the same pressure obtains in the two devices, the difference in the forces exerted by the two devices will be exerted on the relay. This difference in the force is, however, a function of the absolute value of the pressure, i. e., of the load. Thus, if in a system of this kind the load is increased, the force exerted by the larger pressure device will temporarily become smaller, that is until a balance in pressure is set up between the two devices through the constriction. I'he impulse which acts on the relay is therefore dependent both on the absolute value of the load and the rate of variation thereof. In this way it is possible to distribute the regulation of the feed water in accordance with the load to both regulations, viz. to 'the main feed water conduit and the auxiliary feed water conduit.

, Embodiments of the invention are illustrated by way of example in the accompanying draw.

ings, in which Fig. l is a diagrammatic illustration of a boiler plant conforming to this invention;

Fig. 2 is a diagram of the variation of the feed water supply in the plant of Fig. 1;

Fig. 3 is adiagrammatic illustration of a second embodiment of a boiler plant according to the invention;

Figs. Lla-ld are diagrams which willV be used hereafter to explain the operation of the plant of Fig, 3;

Fig. 5 illustrates another embodiment of the invention; and

Fig. 6 shows diagrams related to the operation of the plant illustrated in Fig. 3.

In Fig. 1 the reference I designates the tubular system of a once-through boiler which is supplied with water through a feed water line 2. At the inlet to the boiler isa feed water valve 3 which is controlled by a servomotor 4 operated by an equalizing regulator 5. The quantity of feed water passing through the valve 3 is measured by the difference in pressure between two sides of a constriction 6 in the line 2, and is kept constant by the regulatorl 5 at a value corresponding to a fundamental value determined by an adjustable spring I whichalso acts on the regulator 5. The regulator is preferably of the well known,Askania type.V Y

In the diagramshown in Fig. 42, the quantity of feed water passing through valve 3 is represented by the curve a.

An auxiliary feed water conduit 8 is branched oi the feed water conduit 2 and communicates with the vaporizing and/or superheater section assassin 9 of the boiler tube I. Arranged in the conduit 8 is a regulable valve I0 and a measuring constriction II.

The valve I is controlled by a regulator I2 through the intermediary of a servo-motor I3, in such manner that the quantity of water meas ured at I I is dependent upon the pressure fluctuations in the steam delivery line I4. To this end, the pressure in the line I4 is transmitted through a measuring pressure conduit I5 to a bellows operated lever system IG forming part of the regulator I2 and dependent on the variations in pressure in the line I4. The system I6 is provided with a counterweight I'I which is so designed that it allows for a quantity of water which is already regulated by the regulator 5 and corresponds to a basic load. In Fig. 2 the quantity of additional water which is controlled by the regulator I2 is indicated by the hatched area b, and the total quantity of feed water is represented by the curve c.

The spring 1 bears against and is supported by a safety device comprising a lever I8 controlled by a bellows I9 acted upon by the pressure in the conduit I5, and by a weight 2D, the lever I8 being mounted for pivotal movement on a knife-edge 2 I. When a predetermined basic load is exceeded, the lever I8 is adapted to abut against a stop 22.

The plant described above operates as follows:

The lever I8 bears against the abutment 22 as long as the load on the boiler exceeds apredetermined basic load, and the valve 3 feeds to the boiler a quantity of water corresponding to the basic load which is set by the spring I. If the load drops below this set basic value,\the regulator 5 acts as a normal feed water regulator since the lever I8 will then be raised from the abutment 22 by the bellows I9 and the value to which the spring 'I is automatically set is varied in accordance with the load. This prevents the boiler from being overfed when the load is small.

Owing to the fact that the regulation of the feed water bythe valve 3 is not perceptible in the vaporizer section until after a large time elapses, as explained above, additional water is injected into the vaporizer or superheater section 9, through the auxiliary line 8, and, in fact, the quantity of additional water is regulated in response to the load by the regulator I2. Thus, it is impossible for an insufliciency of water to occur in the vaporizing section due to the feed water lag. i Y

In the embodiment illustrated in Fig. 3, a load-responsive regulator 5 of conventional construction is utilized for regulating the valve 3', and is so set that, for every load, the boiler is underfed by a predeterminedramount.

The diagram in Fig. 4b shows the quantity of feed water controlled by the regulator 5', as `the curve d and the desired quantity of water as the curve e running parallel to curve d.

In the embodiment of Fig. 3 the regulable valve I0 in the auxiliary conduit 8 is controlled by a regulator I2 which, when the load is con stant permits the passage of the underfed quantity of water. Thisquantity of water is represented at the regulator I2' by the weight IV'I'.

The measuring pressure conduit I5' communicates in this embodiment, with a bellows 23. A

-second bellows 24 of the same dimensions as the ione 23 and which is arranged to oppose its action, also communicates with the measuring pressure conduit I5' .through aconduit 26 which The measuring pressure conduit I' 'and .the

bellows 23 and 24are of course lled with condensate and the water also partly fills the air chamber 28. If the pressure in the conduit I5' increases, the level of the water in the air chamber will rise and the air which is still present will be compressed. This causes fluid to pass through the constriction 21 so as to set up a delayed balance in pressure between the bellows 23 and 2t.

So long as there is no change in the load, the pressures on the bellows 23 and 24 remain balanced via the conduit 26, and the regulator therefore receives an impulse from the weight Il only. As soon, however, `as the load increases the pressure on the bellows 24 is temporarily greater and the regulator I2 receives an impulse which is greater according as the rate of change in the load is greater. Thus, during an increase or decrease of the load, the quantity of extra feed water is increased or decreased by the regulator l2 proportionately to the rate of variation of the load.

The curve f in Fig. 4c represents the additional quantity of water admitted bythe regulator l2 when the load follows the course indicated by the curve g. In the Fig. 4d, the curve h represents the total quantity of feed water for which the regulators 5' and l2' are set. The supplementary amount of water which is brought into use when the load increases or decreases, but, due to the filling-up phenomena, only with a time lag, is here compensated by controlling the feed of additional Water.

Fig. 5 illustrates a modification in which the bellows 23" has a larger effective surface than the bellows 26V'. The differential pressure which acts through the lever system on the regulator l2" is dependent upon the load. The additional quantity of water passing through the auxiliary conduit 8" and controlled by the regulator l2 thus follows the curve z' in the associated diagram of Fig. 6, and it will be seen that the quantity of this water is a function of the load and also of the rate of variation of the load. If two bellows of the same size were used the impulses transmitted by them would be a function of the diiferential pressure across the restriction Il and thus of the rate of pressure change in the line l. This pressure, however, is a direct function of the rate of steam ow and therefore the differential pressureis a function of the rate of load change. When the size of the upper bellows 23 is increased in size relative to the lower bellows an yadditional force is added which is directly proportional to the line pressure and thus of the load. The total force transmitted is therefore load rate change plus load change. The impulse representing the quantity of liquid is the one taken across restriction Il.

It will be appreciated that an additional quantity of fuel can be supplied to the boiler furnace in response to variations in the load, and this extra supply can be controlled in an analogous manner to the control of the feed water as described above.

Having now particularly described and ascertained the nature of said invention and in whatl manner the same is to be performed, we declare that what we claim is:

rf""'l. Apparatus for automatically vcontrolling'the operation of avalporgenerator having aloncethrough duid passage receiving. liquid at oneend land delivering vapor at-thenother end, comprising'a main feed conduit communicatingwith the inlet endof saidv passage, an auxiliary Afeed ccn- -duit leading to the vapor part of said passage, first .impulse means .responsive .tothe generator load variations, second impulse means responsive to the quantity of liquid ilowing through the auxiliary conduit, and a control valve in said auxiliary conduit connected to be controlled by said first and said second impulse means.

2. Apparatus for automatically controlling the operation of a vapor generator having a oncethrough fluid passage receiving liquid at one end and delivering vapor at the other end, comprisinga `main feed conduit communicating with the inlet end of ksaid passage, an auxiliary feed conduit leading to the vapor part of said passage, impulse means responsive to the quantity of liquid flowing through said main feed conduit, a relay acted upon by said impulse means, a servo-motor actuated by said relay, a control valve in said main feed conduit to be controlled by said servo-motor, means for exerting on said relay a counterforce in accordance with a predetermined generator basic load including means for decreasing said counter-force in response to the actual load in the region in which the actual load is smaller than said predetermined basic load, load impulse means responsive to the generator load variations, feed impulse means responsive to the quantity of liquid owing through said auxiliary conduit, a control` valve in said auxiliary conduit connected to be controlled by said load impulse means and said feed impulse means.

3. Apparatus as claimed in claim 1 in which said first impulse means are responsive also to the -actual load.

4. Apparatus for automatically controlling the' operation of a vapor generator having a oncethrough fluid passage receiving liquid at one end and delivering vapor at the other end, comprising a main feed conduit communicating with the inlet end of said passage, an auxiliary feed conduit leading to the vapor part of said passage, first impulse means responsive to the rate of generator load variations, second impulse means responsive to the quantity` of liquid owing ythrough said auxiliary conduit, a control valve in said auxiliary conduit connected to be controlled by said rst and said second impulse means, third impulse means responsive to the generator load variations, a control valve in said main feed conduit connected to be controlled by said third impulse means.

5. Apparatus in accordance with claim l in which said iirst impulse means comprise two pressure sensitive means acting in opposition to each other, one of said two pressure sensitive means communicating directly with a pressure which is responsive to the generator load, the other pressure sensitive means communicating with said pressure by means of a constriction.

i6. Apparatus in accordance with claim 1 in which said first impulse means comprise two pressure sensitive means acting in opposition to each other, one of said two pressure sensitive means communicating directly with a pressure which is responsive to the generator load, the

other pressure Asensitive means having a smaller eiective surface than the counter-acting pressure sensitive means and communicating .with said load pressure via a constriction.

'7. Apparatus in accordance with claim 1 in which said first impulse means comprise two pressure sensitive means acting in opposition to each other, one of said two pressure sensitive means communicating directly with a pressure which is responsive to the generator load, the

other' pressure sensitive means communicating with said pressure by means of a constriction, a buier chamber filled with compressible pressure uid, said chamber communicating A with said 5 otherrpressure sensitive means.

GUSTAV DECKER. FERDmAND RIEDEL.

Images