US1942861A - Producing high-pressure steam - Google Patents

Description

Jan. 9, 1934. A. HUSTER 1,942,861

PRODUCING HIGH PRESSURE STEAM V Filed Oct. 24, 1931 ZSheets-Sheet 2 if A Fig. 2.'

3f LE 60 67 Patented Jan. 9, 1934 PATENT OFFICE 1,942,861 l PRODUCING HIGH-PRESSURE STEAM Alfred Huster, Kronshagen, near Kiel, Germany,

assigner to Fried.

Krupp Germaniawerft Aktiengesellschaft, Kiel-Gaarden, Prussia, Germany Application @ctober 24,

1931, Serial No. 570,937,

and in Germany November 7, 1930 2'? Claims.

The present invention relates to a process for the production of particularly clean high pressure steam which is free of water, dust and gas, by means of a series steam generator comprising 5 a system of tubes into which the Water is forced at one end and is converted to steam without circulation and without being superheated and subsequently expanded. ln known steam boilers of this class, which is remarkable for its simplicity and for the fact that there is no danger of explosion, certain serious drawbacks exist which hitherto were a hindrance to a wide use of these boilers. The salts and other substance unavoidably contained in the feed water which make it hard, remain in the steam in the form of dust and injure the engines driven by the steam. Besides they are deposited in the tubes and destroy them very soon. The temperature of the hot steam varies considerably, since at times more and at times less water is carried into the superheater and frequently even to the hot steam piping. For, due to periodical superheating of the tube walls and occurrence of the Leidenfrost phenomenon the vaporization takes place impulsive and is frequently accompanied by violent water hammers. The Leidenfrost phenomenon is a condition which occurs sometimes when water comes in contact with a hot surface. It consists in the formation of spheroidal drops separated from the hot surface by Vapor. When this occurs in a steam generator it interferes with the heat exchange and the cooling of the tubes. These drawbacks are to be observed in a particularly high degree with reduced load on the boiler. Consequently, a regulation of the pressure as required in modern steam plants and a regulation of the temperature of the hot steam and of the water supply to the boiler is rendered impossible owing to the drawbacks indicated and owing to the fact that no measurable water level exists in these boilers. These drawbacks, however, could not be overcome hitherto in their totality neither by a careful purification of the feed water nor by producing the steam at over-critical pressure nor by the provision of spiral or other arrangements within the tubes, on the contrary, these brought additional disadvantages with them.

By the present invention all these drawbacks are overcome simultaneously. It consists of the combination of a series of features known per se but in suitable novel modification.

According to the invention somewhat more water than that to be evaporated, about 10 percent, is fed to the series steam generator of the class described by the feed pump and this water when passing the tube system is evaporated except for the water in excess, the latter when leaving the tube system being separated from the steam in a suitable separator, by the watered sur faces of which at the same time the dust con- ,60 tained in the steam is retained, whilst the purified drysteam passes through the superheater to the place of consumption. The excess water, which contains the dissolved substances of the feed water and the dust deposited from the steam, is carried out of the installation; on board ship for instance it is delivered to the sea. It may first be made to deliver the greater part of its heat to the feed water by means of a suitable heat exchanger.

The amount of the non-evaporated water excess delivered by the separator is so determined that the capacity for holding the impurities contained in the water in solution is not exceeded during the vaporization. In case the feed water contains many bi-carbonates and similar substances, which would separate previous to the commencement of the vaporization, the solubility of these substances is increased, by adding to the feed water in a known manner small amounts of 8@ acid to such an extent that thelimit of the dissolving capacity of the excess water to be carried away is not exceeded. The result is that there is no place in the entire installation where highly concentrated solutions may exist which might cause formation of scale deposits and destruction of the boiler material. On the other hand, however, it will be impossible to maintain in this way a determined minimum alkalinity which is usually provided for in the known boiler designs and which serves to weaken the oxygen'attack. Therefore, an arrangement, known per se, for the expulsion of the gases from the feed water is provided in front of the new steam generator and combined in a suitable manner with the whole installation. By the combination of the described means the seam generator not only is protected from the noxious influences of impurities in the feed water and is rendered independent of the quality of the latter, but also a chemically pure 10o hot steam, a noble steam, so to speakis produced although no expensive appliances for the purification `of the feed water are provided and a1- though the design of the boiler is a very simple one.

According to the invention the quantity of water to be run off to waste is regulated automati-j cally in dependence on the quantity supplied or, which comes to the same thing, on the quantity of steam produced. This regulation is effected 110 in such a manner that with decreasing load on the boiler an increased amount of the feed water supplied is run off to waste. In this way even with a small boiler load a sufficient watering and scavenging of the tube coils is obtained.

By the new process in combination with a sieam generator adapted to this new process all abovementioned drawbacks are overcome. By the regulated slight water excess both the superheating of portions of the evaporating surface and formation of scale deposits in the tubes are prevented. This excess is further great enough to take up and carry away the dust etc. separated from the steam. Owing to the separation of the water excess being effected between the evaporating surface and the superheating surface any carrying of water into the superheater is avoided even with suddenly increased loads and a constant temperature of the hot steam obtained. The water level forming in the separator or any vessel communicating therewith may be used to survey and regulate the water feed like in a normal steam boiler. The problem of water feeding which hitherto was a very difficult one, is thus solved in a very simple manner. Assuming for instance, 100 kg. of steam are generated in a marine boiler plant according to the invention within a determined period of time, then at the same time 110 kg. of feed water, composed of 95 kg. of recovered condensed water and 15 kg. of sea water, are fed to the boiler and 10 kg. of water having a salt concentration 11/2 fold that of the sea water are delivered to the sea. The increase of concentration is so small that salt deposits in the boiler or separator cannot occur.

Owing to its insensitivity to impurity of the feed water the steam generator operating according to the new process may even serve for the production of the make up Water with steam plants where normal boilers are used.

The construction of the steam producing plants suited for carrying the new process into effect is madeA according to determined rules, in order to assist in the performance of the process, 'these rules also forming a part of the present invention.

In order that the invention may be more readily understood and easily carried into effect, an embodiment of the same is illustrated schematically in the accompanying drawings, by way of example. In these drawings Fig. 1 is a section of the new steam generating plant, and

Fig. 2 is an illustration thereof, partly in a section normal to that of Figure 1 and partly in elevation.

Referring to these drawings, 1 denotes the fire chamber of the plant which is heated by oil burners 2. The nre chamber 1 is prolonged upwardly to form a smoke gas flue which tapers,

v partly in steps and partly gradually, and to which an air preheater 4 is attached from which the smoke gases are sucked at 5. A fan 6 pumps the air of combustion through the air preheater 4 and through hot air conduits 7 provided on both sides, to the oil burners 2.

The condensed water re-gained from the engine plant (not shown) arrives through a pipe 8 in a collecting tank 9. In case the condensed water should not suffice to feed the boiler,V crude water is added thereto through pipe 10 from a tank 11, in turn fed with crude water by pipe 12. In case the crude water contains a large amount of bi-carbonates and other substances precipitating upon heating of the water, a regulated amount of acid may be added to it from a tank -of inclined tube coils fixed 13, in order to increase the solubility of these substances. A pump 14 delivers the feed water mixture from tank 9 through a pipe 15 to a gas expeller and mixer-preheater 16 to which exhaust steam is supplied by a pipe 17 including a regulating valve 18. Another regulating valve 19 provided in pipe 15 and controlled by the water levelv in the gas expeller 16, as illustrated by fioat 20 and dotted axial line 21, ,regulates the quantity delivered by pump 14. A heat exchanger 22 is arranged in pipe 15 by means of which the excess water flowing off from the boiler gives off the remainder of its heat to the feed water mixture before escaping through pipe 23.

The gasless feed water mixture is pumped from the gas expeller and mixer-preheater by the feed pump 24 at a pressure of say 120 atmospheres through the pipes 25 and 26 to the feed Water preheater 27 mounted in the top portion of the smoke ue 3. The feed pipe 25 is provided with a feed check valve 28, a feed regulating valve 29, and a regulating valve 30 which maintains a constant difference of the feed water pressures in front of and behind the feed regulating valve 29. This latter valve 29 is controlled by the level in a vessel 31 in any suitable known manner, as indicated by the float 32 and dotted axial line 33. The vessel 31 is designed advantageously as an expansible pipe, the variations in length of which actuate the feed regulating valve 29. The feed pipe 25 opens into a high pressure heat exchanger 34 in which the excess water coming from the boiler gives off the greater part of its heat through heat exchange surfaces to the feed water. The feed water preheater 27 consists of collecting boxes 35, 36 and tube tables 37 composed to one another. From this preheater the feed water preheated to about 200 C. enters a collector 39 mounted above the rear wall 38 of the fire chamber and forming the entry of the radiation heating surface of the steam generator. This radiation heating surface is formed by tubes 40 suspended as flat looped bundles in front of the walls 38, 41, 42 of the fire chamber 1. After one or several loops the bundles 40 open into collecting boxes 43, the number or cross section of tubes connected in each bundle increasing. Two groups of tube.

bundles 40 go out tcward both sides from the collector 39 disposed above the middle of the rear wall 38 of the flre chamber, which bundles protect the rear wall 38, lateral walls 41 and partly also the front wall 42 of the re chamber. The tubes of the last bundle of each group open each into one of the two collecting boxes 44 disposed on both sides laterally above the front wall 42. The bundles 40 are freely suspended by their tube ends from the collecting boxes 39, 43, 44 and with the intermediate loops from special suspension members 45 made from a heat-resisting material. Beneath the loop-shaped tube bundles 40 are'provided recesses 47 in the floor 46 of the flre chamber to facilitate removal of the bundles, which recesses are filled with loose refractory material, such as sand. The fire chamber is provided on all four sides with projections 48 whereon rest the collecting boxes 39, 43, 44, and the abutments of the supporting members 45. In these screening tubes 40 the feed water is merely heated from the preheater exit temperature of say 200 C. to the vaporization temperature, and it is only in the last section of the heating surface formed by the tubes 40, namely the section protecting the front portion of the fire chamber, that vaporization begins to occur. The steam-water mixture arriving in the collecting boxes 44 from this last section passes therefrom into the tubes of the lateral groups 49 of the rst tube bundle of the contact heating surface, from there through the collecting boxes 50 to the tubes of the medium groups 51and from these to the collecting box 52 disposed above the middle of the front wall 42 on the wall projection 48. With each passage of the-steamwater mixture to a new group of tubes the passage area at disposal for the mixture increases. The individual tubes of the groups 49 and 51 are bent in the form of differently shaped superposed coils interconnected by Welding or the like in such a manner as to form tube tables like lattice girders which are thus reliably protected from bending down under their own weight. Each of the tube tables of the bundles 49, 51 contains several horizontal tubes staggered to one another and a zig-zag tube that forms a diagonal strengthening member. These tubes are connected in series in such a manner that the zigzag tube lies in the vicinity of the entrance of the tube table, this being of advantage with respect to the resistance and continuity of the flow.

The tube tables are freely suspended from the collecting boxes 44, 50,52 so that they may easily be exchanged through the re chamber 1.

` The bundles 49, 51 are situated at a certain distance from the wall projection 48, to compensate for the ow of the smoke gases.

From the collecting box 52 the steam-water mixture which now is already rather rich in steam, passes through the pipe 53 to the lower collecting box 54 of the rst tube bundle of the secondary heating surface which is formed by tube tables 55. Each table 55 is formed by a tube bent so as to form two oppositely inclined coils fixed to one another. These coils stiffen one another so that the tables are protected from bending in their plane. Due to the in-` clined disposition of these coils the lower peripheral portions of the coils which are exposed to the heating gases, are* in good contact with the water of the steam-water mixture. The tube tables are narrower at top than at bottom so that the passage area for the smoke gases continually decreases in upward direction. The tubes of the tab'es 55 open into a collecting box 56 from which the steam-water mixture passes through similar tube tables 57 of the second bundle of the secondary heating surface to a collecting box 58. The tube tables 57 are suspended at their rear ends by heat-resisting supporting members 59 which are fixed to a bar 6l supported by heatresisting projections 60. The tube tables 55 are suspended at their rear ends from the tables 57 by :means of similar heat-resisting suspension members 62, a heat-resisting supporting bar 63 being interposed. All these suspensions are flexible so as to follo'rty the heat expansion of the tube tables.

By the location of the plane of the tube tables in parallel with the direction of the flow of the smoke gases not only a favorable mountingv but also auniform heating of the tube tables connected in parallel is obtained. The superposed groups of adjacent tube tables are separated from one another by comparatively large free spaces which allow inspection of the tablesand provision of soot blowers to clean the individual groups of tube tables.'

The steam water mixture is evaporated in the two tube bundles 55 and 57 of the secondary heating surface to such an extent that merely the water fed in excess remains. The steam and this excess water then pass from the collecting box 58 through a pipe 64 to a separator 65 the upper portion of which contains numerous coils of a -spiral steam passage 66, which are xed to the removable cover 67 of the separator 65. The large wall surfaces of passage 66 are mois'- tened by the excess water sothat the dust car'- ried along by the steam adheres thereto and is taken up and carried away by the excess water. The lowermost spires of passage 66 are surrounded externally by an annular space 68 and communicate with this space by a plurality of apertures 69, the excess water flowing off through this annular space into the lower portion of the separator which forms a collecting chamber 70 for the water. Between this collecting space and the helical passage 66 is disposed the steam chamber' 71 of the separator said annular space'68 extending through this steam chamber 71 down to the water space 70, but communicating with' chamber 71 by apertures 72 which are protected from entrance of water by suitably projecting edges 73. The separator 65 is fitted with a means for surveying the water level therei nsxuch as a water gauge 74. j

The dry, dustless, saturated steamgis deflected in the separator in upward direction above the Water level in the bottom space 70 `and supplied through a central pipe 126 extending through the spires of passages 66 to a pipe 75 and to the receiving collecting box 76 of the superheater composed of tube tables 77. These tables 77 are designed like those of the secondary heating surface and of the preheater and open into the hot steam collecting box 78 from which the hot steam is fed to the engine plant (not shown) through the hot steam pipe 79. The tube tables 77 are suspended at their rear ends by heat-resisting suspension members 80 which in turn are fixed to a wall projection 81. In front of the tube tables 77 there is a by-passv passage 82 formed by heat-resisting sheet metal which can be closed more or less by means of a heat-resisting damper 83 in order to regulate the temperature of the hot steam. The portions 84, 85, 86 of the rear wall of the smoke gas flue which are situated, respectively, behind the superheater, the secondary heating surface and the water preheater are easily removable in order to secure convenient exchange of individual tube tables. It is only this rear wall of the iiue which is partly gradually and partly stepwise narrowed in the direction of the smoke gas flow, whereby a simple scaffoldlike structure of the steam generator and nue is obtained. The excess water is carried off from' lthe collecting chamber 70 of the separator 65 through the tube system 87 of the heat exchanger 34, conducts 88 and 89 and tube system 90 of the heat exchanger 22, from which it is discharged at 23. In this way the highest possible recovery of the heat contained in the excess water is obtained.

A series of essential rules are to be seen from the above-described construction of the steam generator. The water preheated in the economizer 27 is conducted through the vaporizer in a current of the same direction as the smoke gases so that the pipes' which lead the Water to be preheated to vaporization tempera-ture and those leading the mixture richest in water are heated to the highest extent and those leading the mixture poorest in water to the lowest extent. In this way occurrence of the Leidenfrost phenomenon in the last portion, poorest in water, of

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the vaporization heating surface and the undesirable generation of superheated water-mixed steam instead of water-containing saturated steam is prevented. The production of superheated water-containing steam would render very difficult the regulation of the feed of the excess" water and of the temperature of the hot steam as well as the separation of the dust from the steam. By virtue of the conduction of the water and the smoke gases in the same direction a sufficient cooling of the radiating heating surfaces is achieved even with small loads of the plant. A uniform steam generation without impacts is secured chiey by the speed of flow and cooling action of the steam-water mixturel being adapted to the heating intensity in such a manner that the inner surface of the tubes cannot acquire at any place the temperature above vaporization temperature that causes occurrence of the Leidenfrost phenomenon. To this end the tubes of the steam generator have so small an internal diameter that the length of the way to be travelled by the water to be evaporated in the tube system (Without the feed Water preheater and superheater) amounts to more than 3000- fold and less than 9000-fo1d of the average internal diameter of the individual tube coils. Within those limits a sufficiently high speed and sufficient cooling is obtained in the first section of the heating surface, without an unnecessarily high loss of pressure being caused. Owing to the water excess increasing with decreasing load of lthe boiler, this speed remains great enough even with small loads. The area of flow of the tube system increases in the direction of the ow of the steam-water mixture, but not in accordance with `the increase in volume of the mixture, so that therefore the speed of liow increases in the direction of flow. The area increases to such an extent that the dynamic'pressure, that is the product ofthe square of the speed and specific weight, decreases in the direction of ow from tube group to tube group. The area for the smoke gases within the contact heating surfaces decrease in such a manner in the direction of the flow of the gases that the speed of the latter increases in spite of the gases cooling.

The embodiment of the new steam generator. illustrated in the drawings and showing the generator designed a vertical single draught boiler secures the lowest manufacturing costs, smallest space and best accessibility of all parts. The air preheater 4 situated at the exit of the smoke gas flue 3 is so arranged in order to best utilize the ground area at disposal and to save structural height, that the smoke gases pass through it horizontally. Where only a small space in height is at disposal, as for instance in certain types of vessels. the boiler may also be designed as a horizontal single draught boiler. VIn this case the tube tables rest on their collecting boxes disposed below the smoke flue and can easily be vremoved upwardly, the air preheater may be disposed accordingly perpendicularly to the direction of the smoke gas flue.

The regulation .of the excess water leaving the separa'or 65 through the heat exchangers 34 and 22 is effected by an automatic regulating valve 91 built into pipe 88 which regulates the delivered quantity of water in accordance with the quantity of feed water flowing through pipe 25. This valve 91 is designed as a balanced valve. A controlling piston 94 is connected to the valve discs 92 by means of the valve stem 93 on the two sides of which piston act the pressures existing before and behind a throttling disc 95 or the like disposed in pipe 88. The throttling disc 95 is disposed in the direction of the flow in front of valve 91 so that its action cannot be influenced by steam formation by the excess water. The valve 91 is further so designed that the admission pressure which represents also the pressure behind the throttling disc 95, lls the valve case and acts upon the upper side of 'piston 94. Through a by-pass 96 the pressure prevailing in front of throttling disc 95 acts upon the lower side of piston 94. Piston 94 has a deep annular recess 97 into which projects a partition 98 provided on the valve case and extending close up to the central portionof piston 94. The spaces situated on both sides of partition 98 communicate by two pipes 99 and 100 with pipe l25 in front 'of and behind a measuring disc 101 disposed therein. As can easily be seen, the regulating valve 91 always releases such a quantity of excess water that the differential pressure of disc 95 is equal to the total of the differential pressure of disc 101 and the weight of piston 94, valve stem 93 and valve discs 92. By suitable determination of the discs 95 and 101, the deplh of the recess 97 on piston 94. and piston weight it is easily to be attained that the escaping excess water is automaiically adjusted so as to form a determined percentage of the quantity of the feed water, which percentage increases with decreasing load of thev boiler. By having the feed water differential pressure communicate with the recess 9'7 of piston 94 the advantage is obtened that the valve 91 is self-cleaning, since impurities carried by the excess water are removed by the slight quantities of feed water passing between piston 94 and the valve case wall. A valve 102 which can be operated by hand is disposed in parallel with the automatic regulating valve 91. According to the open passage area of the valve 102 the perceniage of the excess water increases more or less with 'decreasing load of the boiler, since the wider the opening of valve 102, the smaller will be 'the portion of the excess water controlled by the feed water. Thus even when steam is no longer taken from the boiler,

an adjustable minimum quantity of water flows through the boiler. The heating of the radiation heating surface decreases more slowly than the load on the boiler decreases, and the regulation of the quantity of excess water in the manner described results in the speed of flow in the pipes of the radiation heating surface decreasing more slowly than the load on the boiler decreases, thus prevening excessive heating of the pipes as the load drops. In determining the regulation` the further fact must be taken into consideration. that owing to the proportion of excess water to feed water increasing with decreasing load, the excess water will have a greater heating effect on the feed water with decreasing load. In other words, more 0f the heat of the re goes into the excess water instead of the steam as the load decreases, and is returned by the excess water to the feed water at the heat exchangers. In addition, owing to a minimum flow in the pipes any deposition of sludge in the pipes is prevented. A sludge removing valve 103, however, is disposed in parallel with the valves 91 and 102 by which valve the quan'ity of escaping excess water and the speed of ow in the tubes can be increased temporarily to such an extent that the tubes of the boiler are satisfactorily cleaned.

A safety outlet valve 104 is mounted in communlcation with the water collecting space of the separator which valve, as indicated by the float 105 and dotted axial line 106 is actuated in dependence upon the water level in space and is opened automatically when the Water level surpasses an upper limit. The water escaping.

through this valve arrives through an expansion pot 107, a iiow throttling disc 108 and a check valve 109 in the pipe 89. The steam developed in pot 107 escapes'through a whistle and calls the attention of the crew to the disturbance occurring.

Furthermore, with the water collecting space 70 of separator 65 is connected the water space 111 of the vessel 31 already mentioned. The steam space 112 of this vessel through a pipe 113 ,includinga regulating valve 114 communicates with the steam space I1 of separator 65 and through a pipe 115 including a regulating valve 116 with the steam supply pipe 64 and the space in front of the helical passage 66 below cover- 67. It is essentialto provide a fiow-throttling member in the path of the steam between the places of connection of the pipes 113, 115, this member being formed in the embodiment illustrated by the helical passage 66. As already mentioned, thefeed regulating valve 29 is automatically controlled in any suitable manner in dependence upon the water level in vessel 31. This arrangement operates as follows: Owing to the fact that the excess of pressure at the place of connection of pipe 115 with separator 65 over the pressure prevailing in the steam space of the separator varies in accordance with the steam consumption, the water level in vessel 31 sinks more or less relatively7 to the level in the separator 65 in accordance with the drawing oif of steam, and the sensitiveness of the device 31 to changes in load can be controlled by regulating valves 114, 116. Consequently the feed water regulating valve is opened according to this drawing on and the boiler is fed correspondingly. Since the water level in vessel 31 depends also upon that in the separator 65, the feed is controlled additionally at the same time by the water level in separator 65. The boiler thus never will be fed too much nor too little. On the other hand the feeding follows atonce all variations of the steam consumption, even before those variations have exerted any effect upon the pipe system of the boiler and upon the steam pressure. By a determined adjustment'of the valves 114, 116 the dependence of the variations of the level in vessel 3l and thus also the dependence of the opening of the feed regulating valve 29 upon the steam consumption can easily be tuned. In order to prevent injury of the boilerl by the pipes becoming red-hot in case of any disturbance of the feeding arrangement, the feed regulating valve 29 has an adjustable minimum passage area.

The described regulation of the feed of the boiler in accordance with the steam consumption would be disturbed by the variations of the pressure of the feed water in front of the regulating valve 29 relatively to the pressure prevailing behind this valve and in the boiler,' if it were not vfor the regulating valve 30, already mentioned, disposed in front of the feedvregulating valve 29 which valve 30 is actuated by a controlling piston 117 lodged in the valve case.

The lower side of this piston 117 is acted upon by the feed water pressure in front of the feed regulating valve whilst the upper side thereof is acted upon through a connecting pipe 118 by the feed Water pressure behind said valve. The drop of pressure in the latter thus tends to lift piston 117 and to close valve 30, whilst the weight of the particularly loaded piston 117 tends to open the valve. As can easily be seen, the valve adjusts automatically the desired difference of pressure since with a slight increase or decrease of this difference it is closed or opened to a further extent. The regulating valve 30 is preferably tted with an alarming device (not shown) which comes to act when the valve is completely opened that is when the feed water pressure inadmissiblyv sinks for any reason. As a matter of course, the regulating valve 30 is equipped with a suitable damping member, like valve 91.

An automatic valve 119 is provided in pipe 64 which, as indicated by the dotted axial line 120 is opened with increasing pressure in front of it and becomes operative only when the boiler is fired up. It is opened completely even with a pressure which is considerably lower than the normal pressure of service of the boiler. During operation of the boiler this valve is therefore always completely open and inoperative but when the boiler is started it maintains in the tube system of the boiler a minimum pressure until also.

in the steam space 71 of the separator 65 this minimum pressure gradually is established. In

the same manner this` valve becomes operative when owing to an excess steam consumption, for instance upon breakage of a pipe, the pressure in the separator 65 sinks below the minimum value.

The oil burners 2 are regulated by a governor 123, as marked by a dotted line 122, which governor regulates the heating "power about in proportional dependence uponthe quantity of the feed water and, additionally, in dependence upon the load of the boiler, for instance upon the steam pressure. The dependence upon the quantity of feed water, as marked by a dotted line 124 leading to the feed water measuring disc 101, is operative primarily. The dependence upon` the*` load of the boiler, marked by a dotted line 125 leading to the hot steam pipe 79 has merely a tuning effect ,on the factor of proportionality of the rst dependence, in order to compensate for variations `of the efciency and the quantity of excess water. Consequently the boiler never can be heated more strongly than is admissible with regard to the extent of feeding. By this means any danger of the tubes of the boiler becoming red-hot is excluded in case the water feed fails to act.

Instead of being .designed as a single draught boiler the new steam generator can also be constructed as a multi-draught boiler, if required with regard to the space at disposal.

I claim:

1. The method of operating a series steam boiler plant with feed water containing harmful constituents, which comprises continuously feeding to the boiler a quantity of feed water substantially equal to that required to supply the instantaneous steam demand, plus a predetermined and substantial excess for holding said harmful constituents; vaporizing a said first mentioned quantity of water; separating from the steam so produced the unvaporized excess water; and running to waste all of said excess water with said harmful constituents therein.

2. The method of operating a series steam boiler plant, which comprises positively feeding to the boiler a sufficient quantity of water to produce the steam demanded, plus an excess of feed water sufficient to hold in solution substantially all of the harmful constituents in the feed water; evaporating said first mentioned quantity of feed water in the boiler; separating said excess water from the steam so produced; and removing from the boiler plant said excess water containing said harmful constituents.

3. The method as described in claim 1, wherein the feed water is controlled in accordance with the steam demand in such ratio that the proportion of the excess water to the total feed water increases as the steam demand decreases.

4. 'Ihe method of generating steam in a series boiler, which comprises continuously feeding to said boiler a quantity of water which is regulated in dependence upon the load, evaporating in said boiler somewhat less than the full amount of the feed water, separating the excess unvaporized water from the steam, and continuously running off to waste a quantity of excess water regulated in dependence upon the supply of feed water.

5. The method of generating steam in a series boiler which comprises continuously pumping feed Water into said boiler, evaporating in said boiler somewhat less than the full amount of the feed water, separating the excess water fromthe steam, accumulating said excess water and continuously running off to waste from said accumu? lation an amount of water regulated in accordance with the flow of feed water, and controlling the supply of feed water in accordance with the load and the level of accumulated excess water.

6. The method of generating steam in a series boiler, which comprises continuously feeding to said boiler a quantity of water which is regulated in dependence upon the load, evaporating in said boiler somewhat less than the full amount of the feed water, separating the excess unvaporized water from the steam, and continuously running off to waste a fixed main quantity `of excess water plus a variable quantity regulated in accordance with the amount of feed water.

7. The method as described in claim 1, in which the heating power for the vaporization is varied in dependence upon the quantity of feed water and additionally in dependence upon the ratio of steam delivery to steam consumption.

8. The method as described in claim 1. in which the heating power for the vaporization is varied in dependence upon the quantity of feed water and the factor of proportionality of this dependence is modified in accordance with the ratio of steam delivery to steam consumption, whereby each of Said regulating influences can reduce the heating power to its minimum value independently of the other.

9. Apparatus for the production-of steam, comprising a series boiler, means for feeding water to said boiler somewhat inexcess of'its vaporizing capacity, means for separating unvaporized excess water from the steam including a receptacle for the collection of said water, an excess water outlet leading from said receptacle, a regulating device in said outlet, and means for controlling said regulating device in accordance with the quantity of feed water.

10. Apparatus for the production of steam,A

comprising a series boiler, means for feeding Water to said boiler somewhat in excess of its vaporizing capacity, means for separating unvaporized excess water from the steam including a receptacle for the collection of said water, an excess water outlet leading from said receptacle, regulating means in said outlet adapted to pass a constant primary quantity of excess Water and a variable secondary quantity of excess water controlled in flow of feed Water.

11. Apparatus for the production of steam, comprising a series boiler, means for feeding water to said boiler somewhat in excess of its vaporizing capacity, means for separating unvaporized excess water from the steam including a receptacle for the collection of said water, an excess water outlet leading from said receptacle, a regulating device in said outlet, means for controlling said regulating device in accordance with the quantity of feed Water, and means for controlling the quantity of feed water in dependence upon the steam demand and the level of the Water in said receptacle.

12. Apparatus for the production of steam, comprising a series boiler, means for feeding dependence upon the water to said boiler somewhat in excess of its vaporizing capacity, means for separating unvaporized excess water from the steam including areceptacle for the collection of said water, an excess water outlet leading from said receptacle, a regulating device in said outlet, and means for automatically setting said regulating device in dependence upon the flow of feed water and the flow of excess Water through said outlet. 13. Apparatus as described in claim 12, in

.which the means for setting said regulating device in dependence upon the flow of excess Water through said outlet comprises a throttle in said outlet in advance of said regulating device.

14. Apparatus for the production of steam, comprising a series boiler, means for feeding water to said boiler somewhat in excess of its vaporizing capacity, means for separating unvaporized excess Water from the steam including a .receptacle for the collection of said water, an excess water outlet leading from said receptacle, a regulating device in said outlet, comprising a valve. a casing therefor, a piston connected to said valve, a throttle in said outlet in ad- Vance of said valve, means whereby the pressures prevailing before and behind said throttle are brought to act upon the opposite ends of said piston, an annular recess in said piston, a sta-I tionary partition dividing said recess, a throttle in said water feeding means, and means for bringing the pressures prevailing before and behind said last mentioned throttle into the spaces of said recess on opposite sides of said partition.

15. Apparatus as described in claim 14, in which the weight of said valve and piston and the pressure difference at said throttle in said water feeding means tend to open said valve, while the pressure difference at said throttle in said outlet tends to close said valve.

16. Apparatus as described in claim 9, in combination with a by-pass having a manually controlled valve arranged in parallel to said regulating device.

17. Apparatus as described in claim 9, in combination with a heat exchanger for cooling the discharged excess water located in said outlet in advance of said regulating device;

18. A steam generating plant, adapted to use feed water containing harmful constituents, comprising a series boiler; means for feeding water to said boiler in quantity sufficient to produce the steam demanded, plus an excess of water sufficient to hold in solution substantially all of the harmful constituents in the feed Water; a separator connected to said boiler for separating said excess water from the steam; a conduit for leading off the steam from said separator; means for continuously leading olf a controlled flow of said excess water from said separator and discharging it outside of the plant, and means for controlling said water feeding means in dependence upon the level of said excess water in said separator and upon the quantity of steam used. 19. Apparatus for the production of steam, comprising a series boiler, means for feeding water to said boiler somewhat in excess of its vaporizing capacity, means for separating unvaporized excess water from the steam including a receptacle for the collection of said water, means for continuously discharging a controlled amount of excess water from said receptacle, and means for controlling said water feeding means in dependence upon the level of water in said receptacle and the quantity of steam used, said last-mentioned means comprising a vessel having a water chamber in communication with the water chamber of said receptacle, throttling means between said boiler and the steam space of said separating means, means connecting the steam space of said vessel in advance of said throttling means, and a regulating device for the feed water controlled by the water level in said vessel.

20.- Apparatus for the production of steam, comprising a series boiler, means for fee-ding water to said boiler somewhat in excess of its vaporizing capacity, means for separating unvaporized excess water from the steam including a receptacle for the collection of said water, means for continuously discharging a controlled amount of excess water from said receptacle, and means for controlling said water feeding means in dependence upon the level of water in said receptacle and the quantity of steam used, said last mentioned means comprising a vessel having a water chamber in communication with the water chamber of said receptacle, throttling means between sai-d boiler and the steam space of said separating means, two conduits respectively connecting the steam space of said vessel to a point in the steam line in advance of said throttling means and to the'steam space of said receptacle behind said throttling means, adjustable valves in said conduits, and a regulating device for the feed water controlled by the water level in said vessel. 2l. Apparatus for the production of steam, comprising a series boiler, means for feeding water to said boiler somewhat in excess of its vaporizing capacity, a steam conduit leading from said boiler, a separator in said conduit comprising means for whirling the steam and throttling its flow, and a receptacle to receive the separated water and steam, means for continuously discharging a controlled amountl of excess water from said receptacle., a vessel communicating with the water chamber of said receptacle and having a steam chamber above its water level, a bypass.con.

necting the steam chamber of said vessel with said separator adjacent the inlet end of said whirling and throttling means, and means operated in accordance with the water level in said vessel for controlling said water feeding means.

22. Apparatus' as described in claim 2l, in combination with a second by-pass connecting the steam chamber of said vessel with the steam chamber of said separator behind said whirling and throttling means, and means for adjustably closing at least one of said by-passes.

23. Apparatus as described in claim 9, in combination with an overflow device for said'receptacle adapted to open automatically when the water level exceeds a maximum limit.

24. Apparatus as described in claim 9, in combination with an overflow device for said receptacle adapted to open automatically when the water level exceeds a maximum limit, said overflow device comprising a conduit, an expansion chamber in said conduit, a whistle on said expansion chamber, and a throttle in said conduit on the outlet side of said expansion chamber.

25. Apparatus for generating steam comprising a series boiler, means for feeding water to said boiler somewhat in excess of its vaporizing capacity, a separatorl for separating the excess water from the steam, a discharge conduit for leading oi excess water from said separator, an automatic regulating device in said discharge conduit for controlling the amount of excess water discharged, two heat exchangers wherein the heat in said excess water is transferred to the water in said water feeding means in counter current, and an overflow device connected with the water chamber of said separator and adapted to open automatically when the water level in said separator exceeds an upper limit, said overflow device delivering into said discharge conduit between said heat exchangers and behind said regulating device.

26. Apparatus as described in claim 9, in combination with means for automatically controlling the heating power of said boiler in dependence upon the quantity of feed water supplied and additionally upon-the ratioof steam delivery to steam consumption.

27. Apparatus as described in claim 9, in combination with means for automatically controlling the heating power of said boiler in dependence upon the quantity of feed water supplied, and means for modifying the proportionality factor of said automatic control of .the heating power to make it additionally dependent upon the ratio of steam delivery to steam consumption, said controlling and modifying means each being adapted to reduce the heating power of said boiler to its minimum value independently of the other;

ALFRED HUSTER.

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