US2067080A - Method and apparatus for purifying wet steam - Google Patents

Description

Jar 5, 1937. I E. M. FRANKEL METHOD AND APIAIiATUS FOR PURIFYING WET STEAM Filed Dec. 7, ,1935 2 Sheets-Sheet l |NVENTOR [DIM/f0 /7 fawn 1 ATTORNEY 5, 1937. E. M. FRANKEL METHOD AND APPARATUS FOR PURIFYING WET STEAM 1935 2 Sheets-Sheet 2 Filed Dec. 7

lam v INVENTOR ATTOFKNEY Patented .Fan. 5, 1937 WET STE

Edward M. Frankel, New York, N. Y.

Application December 7, 1935, Serial No. 53,318

7 Claims.

My present invention relates to improvements in methods and apparatus for purifying wet steam. Steam as it leaves the steam releasing drum of the boiler offers a problem in purification chiefly for two reasons: (1) because it ontrains droplets of relatively impure water especially that collecting in the steam releasing drum which often has a distillate solid content of 3,000 or more parts per million and, (2) because of entrained solid matter picked up from the foam or other material on the surface of the water in the drum. Wet steam thus obtained is commonly passed through mechanical separators which remove a large portion although not all of the entrained droplets and rather little of the entrained solid matter. When the steam is superheated, droplets remaining are vaporizedand the residue which they yield upon evaporation is thus added to the solid matter entrained by the steam when it entered the superheater. The foreign matter thus entrained in the superheated steam exerts a cumulative deleterous effect upon the various apparatus in which the steam is utilized particularly upon the blades and guide passages of the steam turbines.

It has been proposed to wash the steam with waterof greater purity than that entrained in the steam. This washing is partially effective in that it removes the solid materials and some of the impurities carried by the entrained water. As heretofore proposed, it is only partially effective however, because the wash water itself becomes contaminated by the materials washed out and is itself entrained in the steam so that while the steam is partially purified, it is not fully so by such previously proposed treatments and the amount of impurities left in the steam is suflicient to adversely affect the steam utilizing apparatus.

My present invention seeks to overcome the drawbacks mentioned first by providing for an improved more or less automatically regulatable supply of distilled water for washing and further by providing for an improved method and means of washing and subsequent purification treatment of the steam. Further according to my invention, this supply of distilled water is obtained by passing the steam through a condenser in which'the steam is used to heat the feed water and is thereby condensed to give a distillate of great purity since the steam has been previously washed before being admitted to the condenser. The distillate obtained is then passed to the washer. In this manner a supply of pure distilled water is obtainedwithout the sacrifice of boiler efiiciency since heat lost by the steam is acquired by the feed water which, moreover, being at a temperature more nearly that of the water within the boiler creates less disturbance when admitted thereto. By my improved system of washing in which a countercurrent of wash water to steam is set up, the steam is washed free of entrained solid particles while any particles of water ultimately entrained by the steam are composed almost entirely of fresh distillate. Then by leading the wet steam over a series of condenser tubes, also preferably arranged to give a countercurrent flow ofsteam to cooling (feed) water, further purification and substantial elimination of the then entrained distillate occur since one action of the condensertubes is to provide focal points upon which the water particles collect .and

coalesce. Droplets remaining in the steam leaving the separator are of such purity as when evaporated in the superheater, leave but a negligible trace of solid matter.

It is desirable thatmeans be provided for insuring'the proper flow of wash water from the washer, and for this purpose I have provided an improved arrangement of partswhereby the used wash water is removed by being inspirated into the stream of boiler feed water leaving the purifier.

Further objects of the invention and the advantages thereof will be evident as the description proceeds and the features of novelty will be pointed out in the claims. For a full understanding of the invention, reference may now be had to the drawings in which Fig. 1 shows an illustrative embodiment of my invention in conjunction with a water tube boiler.

Fig. 2 shows the improved device in longitudinal section, the same being taken on line 2-2 of Fig. 3.

Fig. 3 shows the device in vertical cross section taken on line 3-3 of Fig. 2.

Fig. 4 is an enlarged detailed view partly in section taken along line 4-4 of Fig. 3.

Referring to Fig. 1, wet steam from the drum l0 leaves the boiler through pipe II and passes through branch pipes l3 and M to the purifier denoted generally by l2. The steam leaves the purifier by means of pipe I6 through which it passes to the superheater H. The superheated steam leaves through pipe l8 and passes therethrough to a prime mover I9. The feed water enters the system through the purifier l2 being admitted thereto by pipe 2| and leaving through pipe 22 by means of which it is conveyed to drum III of the boiler.

Referring now to Figures 2, 3, and 4 showing details of construction of the purifier, the shell 25 thereof desirably of cylindrical shape is divided by partitions 26, 26 into an upper compartment in which is located condenser A and into a lower compartment in which is located the washer B. The washer consists preferably of a plurality of wash chambers in cascade i. e. a, b, c, d and a, b, c, 11' formed by vertically extending partitions 28, 29, 30 on one side and 28', 29' and 30' on the other side, the number of partitions and of chambers formed thereby being susceptible to variation. In order to fix the water level in each chamber the same are each provided with a plurality of educt pipes 3| (Figs. 3 and 4) which lead from the position of the water level of one chamber to the adjacent bottom of the next adjoining chamber in the direction of water flow. The wash water is removed from the system in the lowermost chambers 32, 32 by. means of educt pipes 33 at spaced intervals (see Fig. 2) which pipes terminate in a collector pipe 34, a similar arrangement of educt pipes 33 and a collector 34 being provided for the right hand side of the device as seen in Fig. 3. As shown, the partitions 26 each have a downwardly extending portion 26a which provide a central well for liquid through the device and also serve as baiiies for the steam. Other baflies depend from the partitions 26 to beneath the water level of their respective chambers and are indicated at 3! to 39 and 31' to 39'.

Bafiles 31 to 39 and 31' to 39' preferably are provided with pear shaped openings 40, Fig. 4

which are normally below the liquid level, such openings facilitating passage of the steam through the washer and making for a constant velocity thereof at all ratings.

The condenser is formed preferably of tubes 45 which extend from a header 46 at the left of Fig. 2 to header 41 at the right thereof. The space between the header 46 and the end 48 of the shell is preferably divided into chambers by partitions 49 and 50 while the corresponding space enclosed by the opposite shell end 5| is divided by partition 52. This arrangement causes the water to make a plurality of passes, in this case three, through the condenser counter current to the passage of the steam whereby the hottest steam first contacts with the hottest tubes. The heated water is finally collected in the space 54 and passes out through a pair of outlets 55, 55 (see also Fig. 1), such outlets being disposed opposite the ends of pipes 34 and 34 respectively in such a manner as to form an ejector with the ends of the feed pipes and thus carry out of the washer the condensate collected by said pipes.

The condenser is also provided preferably with steam bailies 51, 58, 58' and 59 so as to aid-circulation of the steam over the tubes, the steam finally leaving the device through outlet 66. The impure steam enters the device through the distributer pipes 62, 62, such pipes joining compartments 32 and 32' by a plurality of nipples 63 spaced longitudinally of the device, Figs. 2 and 3.

In the operation of my improved device, the wet impure steam from the boiler drum [0 is caused to enter the washer through the distributer 62, 62 and the nipples 63, one part passing through the wash chambers d to a in series and the other part through chambers 11' to a in series, the streams uniting in the central well and thence passing through the vapor space of the condenser. In traversing the wash compartments steam is caused to pass beneath the wash water through the pear shaped openings 40 whose shape causes greater area of passage as the volume of steam is increased. In passing thus from one chamber to the next the droplets of entrained water from the boiler are replaced by the water in the several compartments. However, since the water in these compartments is successively purer, the steam emerging from the compartment a, a will have entrained in it only droplets of substantially pure distillate. Also the entrained solid particles are completely removed. The steam now passes through the vapor space of the condenser A wherein the steam first impinges upon the hottest tubes 45 which are wet with condensate and which cause the droplets of already substantially pure water to coalesce and to be replaced with those of even greater purity as the steam ascends through vapor space. Finally the completely purified steam containing some moisture passes out of the device through the opening 60 and thence into the pipe I 6 by means of which it is conveyed to superheater H as already mentioned.

The condensate which forms on the tubes 45 is caused to collect in the well formed by the members 26a and flows therefrom through the educt pipes 3| successively through the compartments a, b, c, d, on one side and a, b, c, and d on the other side acquiring more and more impurities from the steam until finally it reaches the chambers d and d and leaves the system through the pipes 34 and 34' by uniting with the heated feed water as previously described. The mixture of feed and wash water is now passed to the boiler through pipe 22.

If desired, the wash water can be kept separate from the feed water and another disposition made of it using a modified arrangement not shown.

One important advantage of my invention is that the amount of condensate furnished for washing purposes varies substantially automatically with the amount of steam produced since if the boiler is operated at excess rating for example, the amount of feed water will be proportionately greater, a greater quantity of heat will be exchanged and hence a greater quantity of condensate will be produced. 0n the other hand, when the boiler is operated at less than the full rating, the reverse situation will occur and a correspondingly smaller quan tity of condensate will be produced. The water fed to the boiler may be preheated in the usual economizers or other heat saving devices as in ordinary practice, such further heating as occurs in the purifier serving to bring the feed water to more nearly the boiler temperature. This is an advantage especially in modern high pressure practice where the metal parts are made extremely heavy and equalization of temperature among difierent parts is correspondingly made more diflicult. The hotter feed water accordingly produces less shock and sets up fewer strains in the boiler.

It will be understood that various changes may be made in the described embodiment without departing from the spirit of my invention or the scope of the appended claims. For example, if desired, only a portion rather than all of the boiler feed may be passed through the purifier and the remaining portion passed to the boiler directly.

I claim:

1. The method of purifying wet steam and of boiler operation which consists in first washing the steam, then condensing a portion of same to form a condensate by passing said steam in indirect thermal contact with the boiler feed water, then using said distillate as the washing medium in said washing step and feeding the thus heated boiler feed water to the boiler.

2. The method of purifying wet steam and of boiler operation which consists in first washing the steam, then condensing a portion of same to form a condensate by passing said steam in indirect thermal contact with the boiler feed water, then using said distillate as the washing medium in said washing step, and passing the thus heated boiler feed water and the washing medium to the boiler.

3. In a device for purifying wet steam, in combination, a washer for the steam and a surface condenser, means for passing the boiler feed water throughsaid condenser, means for passing the steam to be purified first through the washer and then through the condenser, means for passing the condensate from said condenser to said washer and means for adding the used wash water to the feed water which has passed through the condenser by causing saidwash water to be inspirated by a stream of said feed water.

4. In a device for purifying wet steam, a horizontally disposed cylinder longitudinally divided into an upper condensing compartment and a lower washing compartment, means for passing steam to be purified through the washing compartment and then through the condenser compartment, means for collecting the condensate formed and passing it through the washer in countercurrent to the flow of steam, means for a dividing said washer into compartments. a

plurality of longitudinally spaced eduction pipes in said compartments determining the water level therein and a plurality of longitudinally spaced eduction pipes for withdrawing the'water from said washing compartment.

5. The method of purifying wet steam prior to using the same for power or heating purposes, which consists in passing the steam from the boiler to a washing zone and there washing same with a washing medium, passing the washed steam directly to a condensing zone, there condensing a portion of said steam to form a condensate by passing same in indirect thermal contact with water of appreciably lower temperature, then passing the condensate so formed to the washing zone to constitute said washing medium, and then passing the washed steam. from said purifying system.

6. In a steam purifying system adapted to receive steam of relatively low purity from a boiler and deliver steam of relatively high purity to a superheater in combination with said boiler, a washer having means providing a liquid and vapor contact, a surface condenser including means for passing a cooling fiuid therethrough, means for conducting the washed steam directly to said condenser, whereby to condense a portion of same, and means for feeding the condensate so formed to said washer to constitute the washing medium therein.

7. In a steam purifying system adapted to receive steam of relatively low purity from a boiler and deliver steam of relatively high purity to a superheater in combination with said boiler, a washer having means providing a liquid and vapor contact, a surface condenser including means for passing a cooling fluid therethrough, means for conducting the washed steam directly to said condenser, whereby to condense a portion of same, means for feeding the condensate

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