US2201618A - Steam generator - Google Patents

Description

y 1940-. w. D. LA MQNT 2,201,618

' STEAK GENERATOR Til-d Nov. 1a, 1953 2 Sheets-Sheet 1' INVENTOR .1 th main working fluid in ini u period of the tube with a pressure drop at the outlet Patented May 21 1940 PATENT OFFICE 2,201,818. I

GENERATOR Walter Douglas La Mont, North Colebrook, Conn. asslgnor to W. D. La Montv 1110., Wilmington, Del, a corporation of Delaware Application November 18, 1933, Serial No. 697,788

2c (oi. 122 -250) This invention relates to high speed steam and 288, filed August 22, 1933, in which I disclosed power producing apparatus and high speed methhow to obtain unidirectional flow, the inlet end ods of operating the same, of the tube is open, and a largernuantity of It deals with supercharged steam boilers and Water would normally be used for operation of 5 high speed, light weight, power plants using such he Steam g nerating tubes n hi il-P n .l n especially 11 bummg fl id fuels, application than would be used if the water were in which all fluids; namely, the fuel, the air metered into the tube in the desired quantity (for supporting combustion) and the main workat orlnear the entrance of the tube. Also, while ing fluid in the tubes of the boiler, eachflow at y degree of compactness the Steam a d extremely high velocities in the performance 0 water 11mm in the tube can be obtained to inw their several duti sure unidirectional flow inthe above co-pending It further concerns the coordination at all c io there'is no means w ri speeds, of the velocities of all flowing fluids, to inm f Steam and .water can be made more elassure the maximum and constant evaporation of 1310 and 18 5 C p than results from Operation 15 of time. and an open inlet end with'forced circulation.

It makes possible controlled and positive water Under certain low load conditions with lower input into each tube of the steam generator with heats then at full power. the col mn of steam controlled unidirectional flow or controlled nonand Water can be m ry elastic Without unidirectional flow of the main working fluid rin ing an undue sing r k an forth in my steam generating m t as desired travel of steam and water in sufficient degree to under conditions of high temperature radiant interfere Seriously With the P p Operation of heat transfer at high rates of heat release. the steam generation w y E v n maximum A main object of my invention is to reduce heat load for which the unit is designed, a

the size. Weight and cost of high speed steam tain degree of compactness of the steam and n ators and high speed steam power plants, water column in the tube isnecessary for proper I do this by increasing their speed of oper- Operation f th Steam ze w anon. the designed heatloads of the steam generator It is vital that the main working fluid espey be of such d e that this necessary decially, flow at least with some control of surging. gree f compactness of tho steam d w te or travel back and forth of steam and water in 0011111111111 y caseslmflybe 1858 than that whi h the steam generating tube at all times, under would be obta-lnedflom Operating the tubes w h all steam making loads and speeds, substantially an open inlet end with forced circulation and a regardless of firebox temperatures or rates of P r p at h let end. heat release. It is also vital that a controlled in e h e r e f compactness of the steam quantity of water be positively put into each tube and water column in the tube is mainly conto assist with other means in controlling surging trolled by the pressure drop device at the outlet of working fluid in the steam generating tube. oo-o dl ated with t e quant ty of wa e ou to I have found that by placing a pressure drop the tube y given heat n 11 the column device at or near the inlet end of the tube and Of water and Steam in the tube is more compact n vco-ordinaiaing it with the quantity of water used than is necessary or is not as elastic in character in forced circulation, a positive input of water s it can be allowed to Wi interfering into each tube can be obtained in any desired with the proper op at n f th r; t n more quantity with a minimum of pressure drop, at Water is required than is e ssa y with the any desired time, to meet any heatload ondiforced and positive water circulation input into tion imposed on the tube and by co-ordinating each tube and/or more pres ur r p n the Pr the quantity of water put into the tube with a sure d op devices is used than is S ypressure drop device at or near the outlet end of y in a Prossuro r p device at or near the the tube, the hydraulic column of steam and inlet into each tube in combination with a preswater in the tube can be madeas compact a sure drop device at or near the outlet of each desired to control surging or travel back and tube. and coordinating each pressure drop device forth of the steam water in the tube or to entirely with the quantity of water used in the forced eliminate this surging as found necessary to incirculation; adjustments can be made as follows:

sure proper operation at the steam generator. The pressure drop device at or near the inlet In my co-pendlng application, serial No'. 686, end of the tube can be djusted o positively put ,5

column oi. steam and water in the tube, the back pressures and pressure drops acting therein and/or the'degree of heat load imposed on the tubes.

The pressure drop device at or near the outlet end can be adjusted to give any desired degree of compactness of the column 01 steam and water in the tube irrespective of the back pressureand pressure drops acting therein and/or the degree 01' heat load imposed on said tube.

By adjusting the degree of compactness of the steam and water column any degree of surging, or travel back and forth 01' water in the tube, can be controlled regardless of the back pressures and pressure drops acting therein and/or the degree of heat load imposed on each tube, and a minimum of water can be used with forced circulation with a minimum of pressure drop in the system.

In my co-pending application, Serial No. 692,- 236, filed October 5, 1933, I disclosed how to obtain semi-unidirectional flow. In the present invention, by moving the pressure drop device from near the outlet end of the tube to another position toward the inlet end, any degree of semiunidirectional fiow can be obtained, and by using another pressure drop device at or near the inlet end of the tube, or at or near the point where steam is formed, all of the advantages of the invention in the above co-pending application can be obtained with semi-unidirectional flow together with added advantages of the present in-' vention.

In this present invention, in referring to a pressure drop device it is not intended to confine the use of the pressure drop feature to a single device. An equivalent to the pressure drop features called for in this invention, can be obtained by other means, such as a combination of devices in various forms substituted for each single pressure drop device referred to.

Other objects of my' present invention include; use of a minimum pressure drop in the steam generating tubes and positive and controlled and minimum necessary supply of water to each of the steam generating tubes or elements conveying working fluid through the water wall surrounding.

the combustion zone; and through the water pa'ssages or tubes of the water wall boiler; and steam generating elements exposed to convection heat to provide for the proper and adequate flow 0! water through the different parts of the steam generating apparatus and in such relation to the steam generated therein that an adequate flow of water may be maintained through each part and in suitable relation in one part relative to the other. It is a still further object of the invention to provide for the positive control of the amount of water delivered to or flowing through the different parts and to control the conditions under which it flows so as to accomplish the proper delivery to and fiow through the diflerent parts of the steam generating apparatus to suit conditions of steam generation in said parts.

-A still further object is to increase the amount of water circulated and therefore the speed 01' the circulation of steam and water in the tube onlywhen and as necessary with the increase in the rate of heat release, in order to increase the rate of heat transfer from the metal or the tubes to the water and steam by moving the forming bubbles of steam away from their point of formation faster, thus protecting the water wall tube from the increasing heat to which it is exposed with every increase in the rate of heat release in the combustion chamber.

In accordance with my invention, the placing of pressure drop devices at or near the water inlet end oi! the tubes, or in that part 01' the tube exposed to radiant and/or convection heat, and the placing of pressure drop devices at or near the outlet ends of said tubes is a preferred position for these pressure drop devices, or orifices, if orifices are used as pressure drop devices.

Also in'accordance with my invention, the pressure drop devices for use at or near the inlet end of each tube which are used in combination with pressure drop devices used at or near the outlet of each tube are placed preferably at any point in the tube beyond the point where steam begins to form, at the designed rate of heat release for the steam generator, thus insuring under the proper load conditions, the passing through the pressure drop devices of at least some steam with the water.

This immediately gives the advantage of a larger area for steam and water passage through the pressure drop device for a given pressure drop, and a given quantity of water, than would be possible if water alone were passed through th pressure drop device.

Andalso in accordance with my invention the pressure drop devices may be used in multiple and placed at different points along the steam generating elements, provided the object of preventing undue surging or travel oi. steam and water back and forth in a necessary portion of the length of the tubes is accomplished, and provided a minimum quantity of water can be used to accomplish the abovepurpose.

A steam generating apparatus operating in the manner set forth in this invention has certain advantages over my previous inventions because of the opportunity given to control the quantity of water put into each tube whether operating in the full condition, or less than sufficient to fill condition, and at the same time to control the degree of compactness or elasticity in the steam and water column in the steam generating portion, regardless of the rate oi! heat release, together with the opportunity to operate the tubes as full tubes and/or less than sufiicient to fill, as desired, at difierent heat loads of the steam generator.

With a single orifice in .the tube at the inlet end, practically the whole length of the tube is subject to a surging action as the rate of heat releaseincreases especially if the tube is operated with the less than enough water to fill the tube condition. The tube has a non-compact, elastic column of steam and water throughout its length and sudden'high heat eflects on a local section or the tube will cause sudden local increase in pressure acting both ways, causing a compression oi. the column toward the inlet end as well as toward the outlet end resulting in a back and forth how or steam and water in the tube past the orithe which may become violent enough to interiere with the proper operation of the boiler.

By adding an orifice toward the outlet end of the tube, the steam and water column in the length or the tube between the orifices can be.

made as compact as desired or given any desired degree of elasticity, thereby controlling the degree of interference to proper operation from back and forth fiow within the tube. The tube under this condition has a controlled flow for that part of its length between the orifices, while quantity of water circulated.

the part of the length from the orifice to the outlet end may have some degree of surging or non-unidirectional flow, ii. the orifice is placed in some degree away from the outlet end toward the inletend. This results in the tube as a whole giving what is termed semi-unidirectional flow, and these results can be accomplished with the minimum use oi" pressure drops and minim As the rate of heat release increases, the need of advancing the orifice nearest the outlet end and along the tube, toward the end of the tube,

likewise increases, until the exit end of the tube is finally reached. V

The selection of the point along the length of the tube where the orifices can best be used is a matter of the general duty for which the apparatus is designed-and for which it is to be put in use. The main factors to be considered are:

1. The rate of heat release in the combustion zone.

2. The degree of fluid compactness required to prevent surging in the hydraulic column from behind the orifice to the inlet endof thesteam ordinated with the quantity of water circulated,

to insure one path flow and/or unidirectional flow and/or semi-unidirectional flow of the work i fluid.

7. The size of orifice, or pressure drop device desirable to avoid clogging.

8. Mechanical and cleaning considerations.

9. The question as to whether it is better to operate a portion of the steam generating section with the so-called full tube condition, or with less than sumcient to fill the tubes condition.

I have found that with steam generator units, designed for certain load conditions, using an economizer that gives considerable steam generation at full load, or with-an economizer which steams; the art of placing the orifices or pressure drop devices at the proper positions along the length of the economizer tube, to insure proper operation of the economizer tubes may be used in the same way as previously outlined for waterwall and convection generating tubes. 'The placing of the orifice or pressure drop device past the point where steam may form is especially advantageous in the economizer. to permit the use of larger orifices or pressure drop devices than would be possible if feed water only passed through such devices with sufilcient'pressure drop to insure one path flow under full load conditions, and by adding an oriflceat'or near the outlet end, the portion of the tube which may steam is made to operate properlv.

In one of its aspects my invention is a high speed steam generator, whose water walls in the radiant heat releasing and receiving area, namely the combustion zone, and whose steam generat-' ing tubes and economizer tubes exposed to convection heat transfer in the convection heat zone, will not give an undue amount of surging of' steam and water travelling back and forth in the'tubes, but will have positive unidirectional,

semi-directional, and/or controlled non-directional (i. e., controlled surging) fiow of water in each tube, at all times, as found desirable or necessary, regardless of combustion conditions in the fireboxthe temperature of the gases entering the convection heat zone and the size or movement of large steam bubbles shifting from side to side in individual tubes, or groups of tubes, up to the maximum rate of combustion which the steam generator is designed to operate.

In its further aspectQmy invention seeks to take this steam made at high speeds, then by means of a high speed steam engine, (preferably a steam turbine operating under high temperatures and pressures), convert this steam into power in a rapidly operating steam power plant where all auxiliaries are functioning at maximum speeds, and are closely co-ordinated and controlledto produce power in large quantities with the minimum in size, weight and cost of power producing equipment.

Boilers in general use may be divided roughly into three main classes: (1) mass boilers; (2) James boilers; and (3) flash boilers.

A mass boiler is a boiler which boils water in a mass, maintaining at all times avisually indicated water level in the boiler. It may either be a closed receptacle, a fire tube, or a water tube boiler, with or without forced circulation of water.

James boiler (see British Patent- No. 7,854, dated A. D. 1838, to William Henry James, inventor), are water tube boilers, having forced delivery of water to their steam making elements, and a complete and rapidly moving continuous circuit of water through the tubes of the boiler,

with a wat'er'level apart from the boiler, but in circuit therewith, and with constant forced water circulation to the tubes. Such boilers might also be fire tube boilers.

Flash boilers are practically instantaneousboilers, having water-steam-superheated-steam tubes, using no closed water circuit, and without any return circulation of water, but operating on a forced feed delivery of water to its steamgenerating-superheating tubes.

This present invention is particularly concerned with the improvement of high speed steam boilers, and power plants embodying the same, and methods of operating saidboilersand said power plants. Where my invention, and/or any of its features, applies to flash boilers or mass boiling boilers and to high speed power plants using said flash boilers or mass boiling boilers, such improvements are well within the scope of my invention as herein described.

While my invention has been described herein as relating to steam generating apparatus is intended especially for the generation of steam from water, it will be understood that the terms "steam and water" as used in the specificationsand claims, are intended to include as equivalents, any liquids which might be handled by the novel process and/or apparatus herein described, resulting in the generation of any vapors which might be handled by, or be useful in connection with my process and/or apparatus, and it will also be understood that many. of the novel features of this invention are applicable in other specifically illustrated and described is particularly intended.

An important object of this invention is to co-ordinate the quantity of liquid used in forced circulation in order to obtain positive input of water into each tube in suflicient quantity to protect each tube regardless of how rapid rates of heat release are obtained in the combustion chamber, up to the maximum heat effects for' which said (combustion chamber) is designed to withstand.

Other objects and features will be particularly pointed out and disclosed hereinafter in the illustrations, descriptions, specification and claims of this present patent application.

In the drawings:

Fig. 1 shows a diagrammatic layout of my supercharged high speed steam generating power unit with a cross-sectional view oi the high speed steam boiler forming a part thereof,

Fig. 2 is a detailed sectional view, with certain parts broken away, of a high speed steam boiler,

Fig. 3 is a sectional view of one formoi' working fluid distributor device used asa part of my high speed steam boiler,

Fig. 4 is a sectional view taken in Fig. 3,

Fig. 5 shows a preferred form of pressure drop device for tube outlets, and i Fig. 6 illustrates another form of pressure device. In my present invention, I preferably locate a pressure drop device 353 at the outlet end of each working fluid tube of my steam generator along line 4-4 and a second pressure drop device A, is 10.-

cated at the inlet end of each working fluid tube of my steam generator for all designed heat loads and for high efflciency.

In my fluid heater apparatus as shown in my present invention, the apparatus is built and operated as follows: when preferably used with a means for forced circulation on the boiler.

Heating surface in the form of several tubes 53, is placed in the flow of the convection gases. The feed water connection is arranged to deliver water directly from the feed pump into each of these tubes of the fluid heater, via the feed stop and check valves.

The ends of the tubes 53. of the fluid heater are arranged in a compact group parallel to each other and secured in a disc 623, which in turn,

flts directly into the feed line discharge l8.

Feed flowing in this line I8, will be driven by the pump directly into each fluid heater tube, but said flow striking the flat disc where it enters the fluid heater tubes would be disrupted. To prevent this, stream lining at the entrance of the tubes is resorted to, by placing a hollow cone shaped chamber 63A, in the feed line with its apex in the center of the feed line pointing away from flow of the feed approaching it, and its base equal to the diameter of the disc in which the fluid heater tubes are secured and said base resting on, and is secured to said disc 623 also the diameter of the base of the cone equals the inside diameter of the feed line. Thecone has holes in it from its apex to its base, said holes being of inside diameter equal to the inside diameter of each fluid heater 'tube 53, and leading directly thereto.

With this arrangement the feed flow strikes the apex point of the hollow cone 63A, and is evenly distributed in a smooth fluid flow down each tube 53, of the fluid heater.

The feed pump I1, is connected-directly to the auxiliary turbine i, which also drives the air supply and oil supply. The speed of this auxiliary turbine is controlled by the automatic combustion control 10, to give the proper air supply for combustion for any given load, but the sire and speed of the feed pump i1, when directly connected to this auxiliary turbine B, is designed to make available at least, ample feed water for protection and proper operation of the fluid .heater tube. 53, at each load or rate of speed required for delivering proper air for the given combustion condition of said load. The amount of water actually delivered however, by the feed pump l1, into the fluid heater tube 53, is controlled by a by-pass arrangement on the feed pump II, said by-pass ISA, being controlled by a valve l9, operated by the water level regulation device 24. A cross connection II, controlled by automatievalve' 15, and II, is made from the discharge of the steam generator circulating pump 28, to the inlet of the fluid heater.

The cross connection 13, connects to the inlet of the fluid heater tubes 63, beyond the feed stop and check valve 20, discharge on the fluid heater inlet side or before said discharge. The cross connection has two automatic valves, II and 18, on a by-pass around the other automatic valve.

The fluid heater tubes 53, discharge directly into the water level cylinder 8, above the water level of the steam generator apparatus.

When the water and/or steam discharge from the fluid heater tubes they pass the pressure drop device 353, and a separator device 86, at the outlet end of each of said tubes. The pressure drop device 35B,and the separator device 86, for each individual tube are very effective in obtaining a preliminary separation of the small volume of steam and water coming from each tube.

This new method of a mechanical means for separation of steam and water from each individualtube, as it is discharged therefrom is important. By immediate separation action on the volume of steam and water coming from a single tube, the volume and resulting velocities to be handled by the separating device, is much smaller than when attempting to separate the output of a group of tubes and the separation device can be designed to act more effectively if there is one for each tube instead of one for a group of tubes. Further, in the case of'the present invention, the pressure drop devices at the outlet of each tube 353, are so designed that with the pressure drop eflect, they give a preliminary breaking up of steam bubbles and separation of steam and water as they discharge from the tubeand this preliminary separating action is immediately augmented by the individual separating device 66, for each tube 53, just beyond the outlet pressure drop device.

Additional meansfor separation of steam and water discharged from all the fluid heater tubes 53, is further provided at their points of discharge said separation means 61, and 68, acting as a common device for each group of tubes as distinct from the individual separating device in each tube. A still further separation of any steam mixed with water from the fluid heater occurs when steam from the fluid heater passes through the main'separator 69, in the water level cylinder 8, to go to the superheater ll.

When the steam generating system is not to be used for extreme heat loads a pressure drop device 35A, is added'to or near the inlet end of each tube 53, in addition to the pressure ,drop

I moderate length superheater tubes Ii. At the device 268, already placed at the outlet end of tube for proper operation 01' that tubeat various each tube. v In the superheater I use four small diameter,

steam inlet end these four tubes are secured to the water level cylinder 2, above the main steam separator 69.v The four tubes then lead. to the top of the combustion chamber metal casing covering or combustion chamber inlet end wall 22L- entering into the combustion chamber through the metal covering at four diametrically opposite points, where they are spiralled on a circumference which will bring theminto the combustion chamber I06, tangent to the combustion chamber side walls 220, as the spirals extend downwards on the diameter of said circumference.

If the four tubes entered the combustion chamber I, together or nearly together, and they were then wound in the form a spiral they would leave a considerable part of the combustion chamber wall exposed at the'top, beginning at the spiral when the first turn is complete and at the bottom of the combustion chamber when the last turn is completed.

By entering the tour tubes at diametrically opposite points on the circ'umference,- or at widely separated points on the circumference the rise of each spiral as each tube passes above the tube starting a spiral just ahead of it, is gradualand the section of combustion chamber wall left exposed is small, especially if the tube passing above the tube ahead or it is brought tangent or nearly tangent, to the tube ahead of it before the spacing of the spirals between. the two tubes is started. This brings the maximum width of the space of the combustion chamber wall not covered by a tube down to the width 01' the tubes diameter used.

When the four spiralled superheater tubes reach the bottom of the combustion chamber they pass through the bottom casing or combustion chamber outlet end wall 222, at four diametrically opposite points in a manner similar to that described for the top, so that all parts of the combustion chamber casing are properly, protected. 1

The four tubes are then lead to a common point where they are secured in a compact manner to a disc62A, with ends parallel to each other and arranged to discharge directly into thesteam lead to the turbine. At this point, each tube has a properly adjusted pressure drop device in its outlet end.

Saturated steam enters the tubes trom, the

water level cylinder I, at the top and superheated steam leaves the tubes at the bottom of the boiler.

' I have found that with supercharged combustion and high rates 01 heat transfer with high velocities of steam fiow, the column of steam in the superheatertubes, should be kept compact and the flow of steam in each superheater tube regulated to protect and insure proper operation of each superheater tube.

In the embodiment of the present'invention, 1

heat loads. However, it is within the scope of this invention to use pressure drop devices and locate same in my superheater tubes as disclosed in my co-pending applications: 686,268, of Aug. 22, 1933, covering my waterwall controlled unidirectional working fluidflow type of high speed generator; and 692,236, of October 5, 1938, covering my controlled semi-unidirectional working fluid type of high speed steam generator; or I may for certain designs, omit the useoi' any pressure'dropdevices in my superheater tubes.

It is not-intended to limit the scope of this invention to any particular form or use of pressure drop devices if any pressure drop devices are used in my superheater tubes.

I accomplish this purpose by using pressure drop devicesin each superheater tube, as disclosedmainly for steam generating tubes in my.

'co-pending applications: 686,268, of Aug. 22,

1933, covering my waterwall controlled unidirectional working fiuidfiow typeoi high speed steam generator; and 692,236, of Oct. 5, 1933, covering,

operation. 3

The waterwall tubing is spiralled in a manner similar to the superheater tubing except the spirals are arranged to cover the bottom and top ends of the combustion chamber as; well as assisting in protecting the side walls and, sup rheater tubing. The main diameter of the waterwall spiral tubes is arranged so that the waterwall spiral coil as a whole fits inside oi the superheater coil and just clears the superheater spiral coil making it'possible to separate and replace or repair either coil.

.The waterwall tubing is made up or four small diameter tubes 34, of moderate length. The

ends of the fourtubes are arranged parallel to 'each other in a.- compact group secured into a disc 62, which in turn is'secureddirectly into the discharge lead 22, from the steam generator circulating; pump at the bottom of thesteam generator so that'the circulating water discharges directly into each tube. A cone distributer ll, with its apex pointed toward the oncoming circulating water is placed'in iront oi said disc 62,

with holes leading to each tube as previously described for my fluid heater. r

If the generator is tobe exposed to extreme heat loads apressure drop device is not placed in the inlet end 01 each tube;

Ifthe generatoris. not to be exposed to extreme heat loadsa pressure dropdevice 36A, is addedto the inlet end [of each tube for certain designs.

The four tubes 34; lead from the discharge end of'the circulating pump to four diametrically opposite points, at the bottom =otthe combustion chamber where they enter the bottom casing 222, and spiral around in amanner similar to that described for the superheater tubing Ii, the waterwall spirals at first being adjacent to and protecting the bottom casing 222, then travelling up along the sides of the combustion chamber,

not adjacent to the casing 226, but on an inside diameter which fits the spiral coil inside of the superheater coil 5!. This diameter is held by the waterwall tubes 34, until they reach and become adjacent to the top casing 22!. They now spiral inwards following the curve at the top casing HI and being adjacent thereto until they reach the central portion at the burner 2 where each spiral tube turns up through the top casing 22!, at diametrically opposite points, through stufling boxes, and then lead to the water level cylinder 8.

The spiral coils of the waterwali tubing 34, are so spaced relative to the spacing of the superheater coils ii, that the superheater coils receive radiant and/or semi-radiant and convection heat as previously described for'the superheater in this invention.

Each waterwall tube 34, at its outlet end has a pressure drop device 353, adjusted in it of proper size, relative to the quantity of water circulated in it, and relative to the heat load imposed on it.

In addition, just beyond the pressure drop device 35B, which in itself is a separator or steam and water, and helps to break up steam bubbles; there is placed a mechanical separating device 66, to assist in the separation of the steam and water output from said tube only.

The circulating pump 25, takes water from the water level cylinder 8, drives it into each individ ual waterwall tube 34, and the steam with excess water, if there is any excess water, not evaporated from the tube is discharged back into the water level cylinder 8. Separation of steam and water occurring at the pressure drop device 35B, at the individual mechanical separator 6, for each tube, at the separator for the group of waterwall tubes 64, and in the main separator leading to the superheater II.

The saturated steam enters the superheater 5|, as described, and the excess water from the various points of separation of steam and water, it there is any excess water over that evaporated in the waterwall tubes 34; falls to the'water level in the water level cylinder 8, and is again picked up with water from the fluid heater for forced circulation into the waterwali tubes 34.

In my present invention when I add the use of a convection steam generating gas passage I21, with its convection steam generating tubing 52,

' to the use of waterwall steam generating tubing 34, and superheating tubing 5|, in combustion chamber I06, and fluid heater tubing 53, in tapered gas passage H5; I arrange for spiral cross flow of the gases in the convectionsteam generator tapered gas passage i2'l.

The convection steam generator gas passage I21, containing the convection steam generator tubing 52, is tapered with the passage decreasing in cross section as the gases pass through it from inlet to outlet, said taper being arranged to give the proper velocity of the gas throughout its travel through the passage as the gas is cooled decreasing in volume and changing its density.

In my convection steam generator tapered passage i2'l, in some designs, I use three tubes 'although any number of tubes may be used to meet the proper requirements for a given design. At the bottom of the steam generating apparatus these three tubes are arranged in a compact group parallel to each other and secured to a disc 628. This disc with a cone distributor 63B. is secured to the discharge lead from the boiler circulating pump 26, so that the circulating pump discharges directly into each convection generator tube 52, as described for the fluid heater tubes 53.

' tion steam generating tubes '2, and by the main separator before any steam can reach the superheater tubes. The water from the convection generator tubes, it any, goes to the water level chamber and is later picked up by the steam generator circulating pump to be used in re circulation and for evaporation.

In operation, feed water and/or circulation water enters the fluid heater tubes at the bottom of the steamgenerating apparatus under the controls as previously described and after travelling up the fluid heater tubes in counter flow to the gases, the fluid water and/or steam is discharged into the water level cylinder where the steam, if any, is separated from the water by the pressure drop device and mechanical separator in the outlet of each fluid heater tube, by the separator for the outlet of all fluid heater tubes and by the main separator before any steam can reach the superheater tubes. The water from the fluid heater goes to the waterlevel vessel and is later picked up by the steam generator circulating pump to be used in circulation and for evaporation.

I have found that, with multiple tubes and high pressure it is advisable to use as few joints as possible. However, it is desirable to be able to at least, disassemble the main parts of the steam generating apparatus and separate theair preheater spiral tubing from the fluid heater, the fluid heater from the superheater and the superheater from the waterwall.

To facilitate such disassembly I make joints in the metal casings oi' the steam generating apparatus at the necessary places and single Joints at each group of tubes at the bottom of the steam generating apparatus such as one joint for the fluid heater tubes, one joint for the superheater tubes and one joint for the waterwall tubes.

The joints for the waterwall tubes and the superheater tubes are at that point on the diameter oi the bottom casing so that both superheater tubes and waterwali tubes can be withdrawn from the combustion chamber without interierence from said joints in their passage up through the combustion chamber. At the top the leads of all tubing go directly to the water level cylinder, all superheater tubes being at the' highest level each with a joint, the waterwali tubes at a level just below without joints and the fluid heater tubes at the lowest level without joints. The water level cylinder has a Joint at each one of these levels said joints being all 542- cured together by a single means so that disassembly of waterwall spirals, superheater spirals and generator spirals can be made without putting joints in all of the individual tubes at the top.

The water level cylinder has the usual equipment of safety valve, main stop drain, water level indicator, and connection to circulating pump.

It also has a water level regulator and the combustion of. the steam generating apparatus is controlled by an automatic combustion control.

Method of operation A preferred embodiment of this invention is shown in Figure 1, which consists of a power unit bustion chamber I96, my fluid heater tubes .53, 9

in convection gas passage H5, and my spiral cross flow air preheater with burnt gas tubes 65, and air passage II5, also my convection generating tubes 52 in tapered gas passages I21.

All piping, valves, auxiliaries and controls are shown for proper operation of my heat transfer surfaces together with the steam generator water level cylinder 8, for maintaining a water level in the system, a suction head for the circulation pump and a source of reserve power.

The main steam turbine I8, receives steam from the steam generator I, exhausting to main condenser I I. The auxiliary turbine 6, drives on its shaft the air supercharger 5, condensate pump I6, feed pump II, circulating pump 26, and oil pump 21.

A master combustion controller I9, operates all main controls to maintain a constant boiler pressure and to supply the boiler I, with the nec-, essary quantities of air, oil, feed water and circulating water for the proper operation of its heat transfer surfaces and to meet the various load demands.

The speed of the auxiliary turbine 6, is controlled by the master controller I0, to deliver the proper quantity of air. 1

The oil pump 21, and boiler circulating pump 26, have by-passes with control valves, operated by the master controller 10, to deliver the proper quantity of oil and circulating water as the auxiliary turbine speed is changed to meet the requirements for combustion.

The condensate pump I6, and feed pump II, have a by-pass I9A, with control valve I9, operated by a water level regulator 24, on the water level cylinder 8, to maintain a water level in the system.

The boiler circulating pump 26, has a cross connection I3, to the feed inlet with control valve I6, op ,rated by the master controller I8, to augment the supply of water for the fluid heater as the heat load increases.

The opening and closing of cross connection control valve I6, is modified by the opening and closing of the feed water level regulator by-pass valve I9, so that when one valve is closing the other valve is closing. This eliminates the use of unnecessary quantities of heated water for recirculation in the fluid heater as changes in load occur.

The control valve I6, on cross connection 13, has a by-pass 14, with thermostat operated control valve I5. Thermostat control valve I5, is operated bya thermostat device 11, on the outlet end of a fluid heater tube53. Whenever said tube 53, or the steam therein goes above the saturated temperature of the steam in the boiler thermostat element II, opens valve I5, in by-pass I4, to protect the fluidheater tubes 53.

The general operation of the power unit is as follows:

Starting with a. water level in the water level cylinder 8, water is sent by the circulating pump 26, to the waterwall tubes 34, and convection generating tubes 52, of the boiler I. Water and steam discharges from waterwall tubes 34, and convection generating tubes 52, into the water level cylinder 8, where the steam and water are separated. steam going to the superheater tubes and excess water going to the water level cylinder 8, where it is picked up by the circulating pump 26, with make up feed and re-circulated in the system.

Thesteam in the superheater tubes 5I, becomes highly superheated and passes to the main turbine I6, to main condenser II; also to auxiliary turbine 6, and then 'to main condenser II.-

Condensate from main condenser II, goes to feed water tank I5.

Starting with the feed water in feed water tank I5, this water is picked up by condensate pump I8, and sent to feed pump IT. The feed pump I I, by means of the by-pass I 9A, and control valve I9, supplies water to the fluid heater tubes 53, this supply being in accordance with the demands of the water level regulator 24, maintaining a water level in water level cylinder 8.

The'circulating pump 26, by means of the bypass I4, and thermostat valve 15, actuated by the thermostat 11, on fluidheater tube 53, and by means of the cross connection I3, and control valve I6, actuated by the master combustion control 18, supply water for re-circulation in the fluid heater tubes 53, when necessary for protection and proper operation of the fluid heater tubes, independent of the water level at different load demands. 1

The feed water and re-circulation waterln-the fluid heater tube 53, together with any steam formed, is discharged into the water levelcylinder 8, where the water and steam, if any, is

separated. The steam going to the superheater tube 5|, and the water going to the water level in water level cylinder 8, to be used for main.- taining a water level, for re-oirculation and for formation of more steam.

The more detailed method of operation of my power unit is as follows:

Starting To start the boiler I, after a shut down of the boilerand power unit, it is necessary after filling the system with water to a low water level in water level cylinder 8, to insure a supply of oil under pressure to the burner 2', to insure some degree of atomization of the oil and mixing of the air for combustion.

With a slow fire, natural air draft can be used, until steam is formed to turn over the auxiliaries. In this case a hand oil pump is employed to force oil through line SIC, past opened valve 6ID, to the burner, valve BIE being closed. Only a small quantity of oil is used and when ignited through burner door 2I2,there is suflicient air from the opening I05, through door 2I2, and from the air passages to carry on slow combustion until steam forms and the resulting pressure causes flow of steam under pressure from the superheater tubes 5|, through the main hausts through exhaust lead 28, to exhaust lead,

IOA, of the main turbine to main condenser II, to condensate line I4, to feed tank I5. Valve GIE, is then opened'and valve SID is closed, combustion then being carried on by the auxiliaries on the shaft of turbine 6.

When electrical power is available or when a motor-generator storage battery system is used for starting, a motor on auxiliary turbine 6, drives the auxiliaries supplying all the air, oil and water for quick starting and operation of the power unit.

However, it is within the scope of this invention to use any known method of starting the steam generator.

From the time that auxiliary turbine 6, starts driving all the auxiliaries, the operation is as follows:

Feed water Feed water, whenever it is necessary before and during the operation of the power unit, is put into feed tank I5, from the reserve feed tanks through filling line 46, past filling line valve 43, to maintain a supply of feed water in this tank for operation of the water in the system. Vent 41, in feed tank I5, is open to the atmosphere.

Feed water is picked up by condensate pump l5 through condensate suction line 29, from feed tank l5, and delivered to the suction of the feed pump ll, through connection passage in the casings of the two pumps, as long as the two pumps are being driven by auxiliary turbine 5, and there is water in feed tank [5.

Feed water is received from condensate pump I8, by feed pump I1, and discharged through feed pump discharge line l8, past feed stop and check valve 20, past feed water hollow cone distributor 63A, past fluid heater tube disc 62B, and into the fluid heater tubes 53; and/or the feed water from pump IT in discharge line i8, is by-passed through by-pass line l9A, past water level regulator control valve I 9, back to condensate pump suction line 29.

Water level regulator valve I9, is ope ated by water level regulator element 24A, through pipe line 25.

The water level regulator element 24A, is attached with the gauge glass 23, to a point above and below the water level, in water level cylinder 8.

As the water level rises and falls in water level cylinder 8, the water level regulator element 24A, through pipe lead 25, opens or closes the water level regulator valve IS, in varying degrees depending on the height of the water in the water level cylinder 8. The water level regulator bypass valve l9, closing or decreasing its opening with a fall in the water level and opening or increasing the degree of its opening with rise in the water level. I

This opening and closing of the Water level regulator valve 19, opens or closes in varying degrees the by-pass line lQA, from the feed pump discharge line l8, to the condensate pump suction line 29, thereby decreasing or increasing the amount of make up feed water delivered into the fluid heater tubes 53, in accordance with the demands for maintaining a water level in the water level cylinder 8, independent of the speed of auxiliary turbine 6, driving condensate pump l6. and feed pump ll, and also independent of the requirements of the fluid heater tubes 53, for their proper protection and operation against the heat loads imposed on them. In general, the feed input into the fluid heater tubes from the action of the water level regulator valve I9, will be normally increased with increase in heat load, requiring more make up 'feed and thereby causing a fall in water level, but often the water level may be rising or may be at too high a level or the water level may be raised by steam bubble formation at a time of sudden increase in heat load and the water level regulator l9, may fail to close on the by-pass line ISA, or may remain open or may not move for some time from its partially opened position at the time of sudden change in heat load thereby not increasing the input of feed water into the fluid heater tubes with increase of heat load. The action of the water level regulator valve I9, is always entirely dependent on the action of the water level.

Water forced into the fluid heater tubes 53, by the feed pump l1, and the action of the water level regulator valve IS, on by-pass line ISA, passes through the fluid heater tubes 53, in the convection burnt gas heat transfer zone passage H5, and discharges with steam, it any is formed, into water level cylinder 8, at the top, above the water level.

The feed input, as it discharges from feed pump discharge line 18, just before it enters the fluid heater tubes 53, enters and passes through the apex of the hollow feed cone distributor 83A, which smoothly spreads and directs the flow into the holes in the hollow cone leading to each tube. This action gives a minimum disruption of the flow of water to each tube and results in a more direct drive of the water into each tube. After the feed input passes the hollow cone distributor it enters a pressure drop device or Venturi shaped orifice 35A in each tube in the design used for Fig. 1, which gives it a pressure drop delivery into the tube, which co-ordinated with the pressure drop device 353 at the outlet of each fluid heater tube 53, and the quantity of water put into each tube, gives full control of the degree of compactness of the steam and'water column in each tube I for each heat load imposed on the tubes.

to co-ordinate with the inlet pressure drop device 35A, of the design shown in Fig. 1, and the quantity of water circulated to give full control of the compactness of the steam and water column in each tube and to insure unidirectional or controlled flow of steam and water in each tube.

At the outlet end of each Venturl shaped pressure drop device 353, in each fluid heater tube. there is placed a twisted strip of metal 65, (see Fig. 17) in this design shown in Fig. 5, which whirls the water and/or steam, issuing from the pressure drop device throwing the water outward, in the form of a cone shaped spray or film with the main part of the steam in the central portion of the cone. Division walls or double bafiles 51, are placed in front of each tube with a central opening in the inner wall pointing toward each tube which takes the steam through this opening and causes the water to strike the bafile wall resulting in considerable separation of steam and water at this point. The preliminary centrifugal separation of steam and water from the output of each tube is obtained. by means of the individual separator device 66 for that tube only.

After the discharging water and/or steam from each fluid heater tube has a preliminary breaking up of its steam bubbles and separation of the steam and water from the Venturi shaped presaaoneie sure drop device 353, then a further augmentation oi. the separation action by addingcentrifugal force from both the twisted metal strips 56, at the outlet of each tube, and the still further separation and collection of the steam and water with the battles 61, having openings for steam in them, the water separated from the steam dis-- charges to the water level for maintaining a water level, for-re-circulation in the system and for replacing steam generated, and the steam passes the oil pump 21, the speed of the auxiliary turbine 6, being controlled by the master combustion control 10, to deliver the required amount of air for combustion, although the speed of the auxiliary turbine might be used to control the amount of oil, feed water, and/or circulating water used, and it is intended to be within the scope of this invention to use any of these'control means.

The circulating pump 26, picks up the water from the'water level cylinder 8, through suction lead 3|, discharging it through discharge lead 32, past waterwall hollow cone distributor .63, and past convection generator hollow cone distributor 633, which acts on the circulatingwater in the same way as described for the feed hollow cone.

distributor 83A, past waterwall tube holding disc 62, and past convection generator holding disc 62C, and into each tube, pasta Venturi shaped pressure drop device 35A, at the inlet into each waterwall tube 34, and convection generator tube 52.

The pressure drop device 35A, is used in each waterwall tube 34, and in each convection steam generating tube 52, in the same manner and for the same purpose as the pressure drop device 35A, described in this invention for the fluid heater tubes.

In Fig. 2 is also shown the location of pressure drop devices 350 at intermediate points of the tubes 34 which maybe used in conjunction with the pressure drop devices at the inlets of the tubes or the outlets of the tubes for the purposes described above, relating to alternative locations of a plurality of pressure drop devices in the fluid conveying tube elements.

Water and/or steam discharges from the waterwall tubes 34, and convection steam generating tubes 52, at the outlet end,. past a Venturi shaped pressure drop device 353, past a twisted metal separator strip 56, and into the water level cylinder 8. Said pressure drop devices 353 and twisted metal separator strips 65, foreach individual tube actingin the same manner on the water and steam coming from the waterwall tubes 34, and convection steam generating tube 52, as described in this invention for'the fluid heater tubes .53.

As the water and steam from the waterwall tubes 34, and the convection generating tubes 52 enters the water level cylinder 8, the cone shaped .water spray with steam in the center, strikes baffle walls 68, and A similar to the bailie walls 61, described, for the fluid heater tubes. The resulting separated steam goes through the main up again for re-circulation, by the circulatin8 pump 26, with the make up feed water from the fluid heater tubes. where it is sent again as previously described, to the waterwall tubes 34', convection steam generating tubes 52, and/or the fluid heater tubes 53.

. The discharge lead 32, of -the circulating pump connecting it to the circulating pump suction 25, has by-pass line 45, with control valve 44, line 3|. r

The control valve 44, is operated by the moving rod 12, of the moving arm II, of the master combustion control III, which in turn is operated by change in boiler pressure.

Since the master combustion control rod 12,

moves with change in heat load demand, its

movement can be used to operate the by-pass line 45, of'the circulating pump 26, opening said valve 44, when load demands decrease, and closing said valve 44, when load demands increase, thereby given heat load and setting of the valve.

The discharge lead 32, of the circulating pump 26, has a cross connected line I3, connecting to the discharge lead l8, of the feed pump ll, be-

- tween the feed stop and check valve 20, of line I8, and the fluid heater tubes 53..

' This cross connecting line 13, has a. control valve 15, and a check valve 20, also a by-pass line I4, around valve 13, with a thermostatic operated valve I5.

- When the valve or valves of the cross connecting line I3, are open, the circulating pump 26, delivers water positively into each fluid heater tube 53, for circulation and re-circulation in any quantity desired, at any time, independent of the water level in water level cylinder 8'.

Thermostatic valve I5, in by-pass line '14, is opened or closed by the action of a thermostat said thermostatic device becomes heated, as the steam formed within the tubes becomes super-j heated, causing the thermostat element 11, to

. open control valve 15, on by-pass line 14, on cross connecting line 13, opening cross connectingline I3, and thereby discharging circulating water from circulating pump 25, into the fluid' heater tubes 53.

Thermostat element 11., is set to cause the opening of valve 15, at any time the temperaturein the fluid heater tubes goes above that of the The action of the thermostat element 11, and valve I5, is independent of the water level and also independent of the heat load except indirect-' ly, when lack of water with the heat load might I cause rise in temperature in the fluid heater above that at the temperature of the saturated steam.

Control valve I6, is operated by the master combustion control arm II, moving rod I2, with change in heat load. This rod 12, is connected to the lever valve 16, from a lever point over on the water level regulator valve stem of water levelregulator valve [9. The connecting arm between rod I2, valve I6, and the lever point on'valve stem |9, together with the location of both valves l9, and I5, are so arranged at the different heat load settings, that if the water level regulator valve stem is in the open position, the rod 12, will have opened valve I6, but if the water level valve closes, it will close valve I6, 'or close it to any degree desired, as made with the valve and arm setting.

When valve 16, is open, cross connection I3, is open, thereby discharging circulating water from circulating pump 26, into the fluid heater in any quantity desired.

The cross connection I3, with its valves'and controls is mainly for the purpose of supplying water to the fluid heater in any desired quantity for co-ordination with the pressure drop devices in the tubes to protect said tubes and insure their proper operation, at any time, only when and if,.

the supply of feed water coming into the fluid heater is insufficient to accomplish this purpose due to the. water level condition and action of the water level regulation valve on the feed line.

Steam The saturated steam from the waterwall tubes 34, convection generating tubes 52, and/or the fluid heater tubes 53, passing through the main separator 69, and into the superheater tubes inlet ends SI, at the top of the water level cylinder 8, as previously described; becomes highly superheated as it passes through the superheater tubing At the outlet of each superheater tube ii, I place a Venturi shaped pressure drop device 353, adjusted to insure proper distribution of steam flow in each tube and compactness of the steam column in the coiled tubes 5|.-

The highly superheated steam dischargesi'rom the outlet ends of the superheated tubes 5|, past the superheater tube holding disc 82A. into main steam line 9, where a second safety valve is generally located (not shown).

The superheated steam in main steam line 9. passes through main throttle stop valve Bl, to main steam turbine I0, exhausting through exhaust lead IDA, to main condenser ll where it is cooled and condensed back to water by cooling water entering inlet I2, and leaving by exit I3, in main condenser I I.

The superheated steam from main steam line 9, also passes through auxiliary steam line I, past auxiliary control valve 42, to auxiliary turbine 8, which drives all of the main auxiliaries. The exhaust steam from auxiliary turbine 6, passes through auxiliary turbine exhaust line 28, to main exhaust line IDA, to main condenser II, where it is condensed with the exhaust steam from main turbine Ill. The condensate then passes through line l4, to feed tank II, where it mixes with any feed water from the reserve feed tanks, put into the feed tank l5. through filling line 4i, past valve 43. The resulting water mixture then passes through condensate suction line 2!, of condensate pump IE, to pass through the system as previously described.

Fuel

The feed oil tank It, is filled when necessary from the reserve fuel tanks through filling line 48, past stop valve 49. Vent ll, connects the fuel Y oil tank 38, with the atmosphere.

The fuel oil pump 21, picks up fuel oil from fuel oil tank 38, through fuel oil pump suction line 39, discharging it to the burner 2, through discharge line 40.

Fuel oil under pressure from the fuel oil pump 21, issues from the burner, in a finely divided or atomized spray Where it mixes with the air, and

after ignition keeps continually forming the gases of combustion in combustion chamber I", at a rate of heat release proportional to the amount of air and oil mixture made available in the combustion chamber by input from the fuel oil pump 21, with its controls and the air supercharger 5, with its controls.

The fuel oil pump discharge line 40, has a. lead I G, going to the control valve 8 IH, on the master combustion control II, for power operation of its moving arm II, and motion of its valve operating rod I2.

Oil passing through control valve GIH, on master combustion control Iii, discharges through line F, to the suction line 39. of oil pump 27.

The fuel oil burner has a centrifugal atomizing chamber with by-pass opening at its rear through which oil from the fuel oil pump, not issuing from the burner opening into the combustion chamber is by-passed back to the suction of the fuel oil pump suction line 39.

The fuel oil by-pass line IA, has a lever control valve filB, which controls the quantity of oil sent to the burner.

The master combustion control, In, through its moving arm II; and moving rod 12, operates the fuel oil by-pass lever valve SIB, so that if the boiler pressure is lowered from load demand the rod I2, moves, closing the bypass valve MB, and increasing, the oil output of the burner. If the boiler pressure is raised from decrease in load demand, the master combustion control rod 12, is moved so that the by-pass valve SIB, is opened. decreasing the pressure in the centrifugal chamber of the burner and the input of oil into the combustion chamber. In this manner a sufficient quantity of oil is automatically forced in the combustion chamber in proportion to the load demands maintaining a fairly constant boiler pressure throughout the system, at all load conditions.

Air

The air supercharger I, driven by auxiliary turbine 5, picks up air from the atmosphere through its suction inlet 4|, and by high speed rotation with centrifugal action compresses and drives the air throughout the boiler air and gas passage system with the combustion gases against any pressure drop conditions occurring in the system. i

The air leaves the air supercharger 5, through the supercharger air discharge line H9, which enters the circular air entrance dome passage I 20, tangentially, giving the entering air a whirling motion in said passage.

Air from the circular air entrance dome passage still whirling, enters through and into the stream lined air passages "I, of the tapered spiral cross flow air preheater. The air, as it is forced at high velocity into said air preheater air passage I 2|, past the spiral tapered air preheater burnt gas tubes I, meets with more resistance to cross flow than to spiral flow along the tapered spiral coiled air preheater burnt gas tubes II, which result in a combination of spiral flow and cross flow of the air in its air passages I2i, giving spiral cross flow of the air along the heat transfer surfaces. The spiral tubes I, of the air preheater are wound around the circular tapered iiuid heater outer casing 22!, so that the air original direction, enters the circular air inlet passage I25, and then the circular air inlet bumer chamber I22, to the burner guide vanes at the burner entrance I23.

The burner guide vanes augment the whirling of the air, leaving the circular air inlet chamber I22, without change of direction of-the whirl. guiding the air into the burner throat passage I24, and on into the combustion chamber I06, where it mixes with the atomized fuel oil from the burner to form the combustion gases.

,Combustion gases Thecombustion gases formed in the combusence and thereby guided smoothly into the combustion chamber circular burnt gas passage 1, and then into'the convection generating spiral tapered burnt ga's passage I21. As the combustion gases pass down the sides of the spiral coiled waterwall tubes 36, and superheater tubes 5i, in

the combustion chamber I06, these tubes tend to whirl the air in the same direction it had when leaving the throat I24, and this air with the combustion gases, continues to whirl as it enters the convection generating spiral tapered burnt gas passage I21. a Since the spiralled convection generating coils 53, inthe spiral tapered convection generating passage I21, are coiled in the opposite direction to the waterwall coiled tubes 34, and superheater coiled tubes 5i, in the combustion chamber I06, the combustion gases continue to whirl in ,the same direction they had when leaving the combustion chamber, as they travel through the convection generating passage I21, the circular outlet convection generating passage I26, and into the spiral tapered fluid heater passage I I5.

Since the fluid heater tubes 53 are coiled in the opposite direction to the'convection steam generating tubes 52, the gases continue to whirl in the same direction while passing through the fluid heater tapered spiral cross flow passage I I5, as they whirled when passing through the convection steam generating gas passage I21,

The combustion gases" travelling through the spiral tapered fluid heater passage H5, at high 1 Velocity, strike the coiled fluid heater tubes 53, meeting with more resistance to cross flow than spiral flow and resulting in a combination of spiral flow along the fluid heater tubes 53, and

r. by the streamlined entrance into the spiral tathe inlets and outlets of said steam generating "means and to said vessel in a space therein unoccupied by water, said positive circulating means steam generated thereirom'comprising a vessel in which a water level is maintained, positive water circulating means connected in circuit with said vessel, a steam generating tube connected in circuit with said positive circulating meansand 5 to said vessel in a space therein unnoccupied by water, said positive circulating means circulating water from said vessel through said steamgenerating tube, and fluid flowcontrolling means at the inlet and outlet of said steam generating tube 10 to control the flow of water and steam within said tube, said steam generating tube receiving water in quantity greater than is evaporated.

. 2. In a steam generator, a circuit for water and steam generated therefrom comprising a vessel in v which a water level is maintained, positive water,

circulating means connected in circuit with said vessel, steam generating tubes connected in circuit with said positive circulating means and to said vessel in a space therein unoccupied. by wa- 2 ter, said positive circulating means circulating water from said vessel through said steam generating tubes, and fluid flow controlling means near tubes to control the flow of water and steam within said tubes, said steam generating tubes receiving water in quantity greater than is evaporated.

3. The combination set forth in claim 2 wherein said fluid flow controlling means comprise 30 pressure drop devices.

,4. The combination set forth in claim 2 wherein a steam and water separator is disposed in said vessel.

5. The combination set forth in claim 2 wherein means for separating steam and water is disposed in said circuit operatively associated with said vessel and the steam generating'tubes discharging thereinto.

6. The combination set forth in claim 2 where- '4 in means for separating steam and water are disposed in said steam generating tubes adjacent the outlets thereof.

7. Ina steam generator, a circuit for water and steam generated therefrom comprising a. vessel in which a water level is maintained, positive water circulating means connected in circuit with said vessel, steam generating tubes connected in circuit with said positive circulating circulatin'g'water from said vessel through said steam generating tubes and fluid flow controlling means for controlling the flow of water and steam within said tubes comprising pressure drop devices near the inlets of the tubes and at points intermediate the inlets and outlets thereof, said steam generating tubes receiving water in quantity greater than is evaporated.

8.-In a, steam generator, a circuit forwater 60 and steam generated therefrom comprising a vessel in which a water level is maintained, positive water circulating means connected in circuit with said vessel, steam generating tubes connected in circuit with said positive circulating means and to said vessel in a space therein unoccupied by water, said positive circulating means circulating water from said vessel through said steam generating tubes and fluid flow controlling means for controlling the flow of water and steam within said tubes comprising pressure drop devices at the outlets of the tubes and at points intermediate the inlets and the outlets thereof, said steam generating tubes receiving water in quantity greater than is evaporated.

9. In a vapor generating circuit, the combination including a vapor liquid separation device,

positive liquid circulating means operatively connectedto said separation device, liquid conveying tubes operatively connected to said circulating means and tosaid separation device in a space therein unoccupied by liquid, said positive circulating means circulating liquid from said separation device into and through said liquid conveying tubes and pressure drop devices at the inlets and outlets of said tubes for controlling the flow of vapor and liquid mixtures passing therethrough, said liquid conveying tubes receiving liquid in quantity greater than is vaporized.

10. In a steam generator, a circuit for water and steam generated therefrom comprising a vessel in which a water level is maintained, positive water circulating means connected in circuit with said vessel, water wall tubes connected in circuit with said positive circulating means and to said vessel in a space therein unoccupied by water, additional steam generating tubes connected in circuit with said positive circulating means and to said vessel in a space therein unoccupied by water, said positive circulating means circulating water from said vessel through said water wall tubes and said steam generating tubes, and pressure drop devices near the inlets and outlets of said water wall tubes to control the flow of water and steam within said tubes, said water wall tubes and. said steam generating tubes receiving water in quantity greater than is evaporated.

11. The combination set forth in claim 10 wherein a plurality of pressure drop devices are disposed in each of said additional steam generating tubes.

12. The combination set forth in claim 10 wherein said steam generating tubes are disposed in a convection passage of the steam generator' and each of said tubes is provided with pressure drop devices near the inlets and outlets thereof.

13. In a steam generator, a circuit for water and steam generated therefrom comprising a vessel in which a water level is maintained, positive water circulating means connected in circuit with said vessel, water wall tubes connected in circuit with said positive circulating means and to said vessel in a space therein unoccupied by water, additional steam generating tubes connected in circuit with said positive circulating means and to said vessel in a space therein unoccupied by water, feed water preheater tubes connected in circuit with said positive circulating means and to said vessel in a space therein unoccupied by water. said positive circulating means adapted to circulate water from said ves sel through said water wall tubes, steam generating tubes and feed water preheater tubes, and a plurality of pressure drop devices in each of said water wall, steam generating and feed water preheater tubes for controlling the flow of water and steam within said tubes, said water wall tubes, steam generating tubes and feed water preheater tubes receiving water in quantity greater than is evaporated.

14. The combination set forth in claim 2 where in a superheater tube is connected with the space in said vessel unoccupied by water, and a pressure drop device in said superheater tube.

15. The combination set forth in claim 2 wherein a superheater tube is connected with the space in said vessel unoccupied by water, and a plurality of pressure drop devices in said superheater tube.

16. The combination set forth in claim 2 wherein a superheater tube is connected with the space in said vessel unoccupied by water, and pressure drop devices in said superheater tubes at the inlet and outlet thereof.

- 17. The combination set forth in claim 2 wherein the fluid flow controlling means near the out lets oi said steam generating tubes comprise pressure drop devices operating to separate water from the steam.

18. The combination set forth in claim 2 wherein means for separating steam and water are dis-' posed in said steam generating tubes adjacent the outlets thereof and operating in conjunction with the pressure drop devices at the outlets of said tubes.

19. In a vapor generating circuit as set forth in claim 9. wherein said pressure drop devices are of proper size in relation to said liquid conveying tubes to obtain the desired flow conditions of the fluids therein.

20. In a steam generator as set forth in claim 13 wherein said pressure drop devices in each of said water wall, steam generating and feed water preheater tubes are of proper size in relation to the tubes in which they are disposed to obtain the desired flow conditions of the fluids therein.

21. The combination set forth in claim 2 wherein a superheater tube is connected with the space in said vessel unoccupied by water, a plurality of pressure drop devices in said superheater tube and said fluid flow controlling means in said steam generating tubes being in the form of pressure drop devices, all of said pressure drop devices being of proper size in relation to the tubes in which they are disposed to obtain the r desired flow conditions of the fluids therein.

22. In a steam generator, a plurality of tubes adapted to conduct a fluid, means for imposing a forced circulation of water through said tubes, a plurality of pressure drop devices in each tube adapted to control the passage of the fluids therethrough, a water level chamber connected with said tubes, and means near the junction 01 the discharge ends of said tubes with said chamber above the water level therein for separating the generated steam from the water collected in said.

chamber for recirculation through said tubes.

WALTER DOUGLAS LA MONT.

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