US1795743A - Evaporator - Google Patents

Description

March 10, 193 B. c. SPRAGUE EVAPORATOR 5W a?! W Filed July 27 192 WITNESS .vlili ll! Patented 'Mar. 10, 1931 UNITED STATES PATENT OFFICE BEN C. SPBAGUE, OF SPBINGDALE, PENNSYLVANIA, ASSIGNOR TOQLEWIS E. HANK]:-

.SON, OF DOBMONI, PENNSYLVANIA nvarona'ron Application filed July 27,

This invention relates in general to a steam generating method but more particularly to a method of treatment to be employed in making up feed water where the source of water supply is of such character that it is not desirable to deliver it to the boilers of steam generators. Water from natural sources usually bontainssalts in solution. Insofar-as these, salts occasion difficulty in connection with'steam generation, they may be broadly classed as salts which precipitate from solution on increase in temperature and those which produce adherent scale formations and which become less soluble as the temperature increases but do not precipitate out until after a definite concentration is reached. Such salts occasion scale formation and give difliculty where water,

carrying them in solution, is employed as feed water for boilers.

Where such salts are present in appreciable amounts in the water, it is desirable to employ evaporators for. the purpose of making up the feed water for the boilers. Waters containing such scale forming salts, however, cause difliculty in connection with evaporators, since it occasions the formation of scale on the heating elements of the evaporators and consequently reduces their effectiveness and the efliciency of the evaporator.

An object is to produce a new andimproved method of generating steam or of evaporating water which minimizes the detrimental effect of scale forming salts carried in solution by the water to be evaporated. This and other objects will be made more apparent throughout the further descript on of the apparatus herein disclosed as forming a part of my invention and as emplo ed for carrying out the process herein setorth.

In the'drawings formin a part hereof, I have illustrated more or ess diagrammatically a longitudinal section of an evaporator or steam generating evaporator capable of being employed in carrying out the method of treatment or the process hereinafter -more fully set forth.

As illustrated, the evaporator consistspf a shell or casing 2 which is provided w1th a vapor or steam outlet port 3 and a water 1926; Serial no. 125,217.

inlet port 4. As shown, the interior of the casing is divided into a series of compart- I ments by means of baflle 5-5 which extend understood that any number of baflies may be employed and that, while I have illustrated two such baflies, dividing the, interior of the shell into compartments A, B and C, I employ the term series in its broad sense so that it may include two or more compartments within its meaning. As illustrated, the com artment A communicates with the water inlet port 4 and its separating bafile 5 is of such height with relation to other baflies that the water contained within that compartment will rise to a higher level than in any of the other compartments. Where more than two battles are employed, they may be made progressively shorter, and I also provide means which will control the delivery of the water to the evaporator in such a way that the waterv level in the final compartment-of the series is lower than the water level in the next preceding compartment.

From the above, it will be apparent that all the water is delivered to the evaporator through the port 4 and thatthe compartment B receives water which overflows the baffle 5 between it and the compartment A.

In like manner, the compartment C receives water only from the compartment B, and only such water as overflows the bafile 5. A float 6 is located in the compartment C and controls the level of the water in that compartment by controlling the delivery of water through the inlet port 4 of the evaporator. As diagrammatically shown, the float 6 actuates a valve 7 located in a water line 8 which communicates with the inlet port 4. As shown, the float is operatively connected to a rotatable shaft 10 and operates the valve 7 through the agency of a float lever 11 secured to that shaft and operatively connected to the stem of the valve by means of a link 12.

Heat may be applied to the water con-.

tained in the separate compartments in any suitable manner but, as diagrammatically illustrated,-I have shown separate heating elements, in the form of steam coils 13, in each of the compartments. As shown, all of the heating coils receive steam from a common header 14 which is connected to a steam inlet pipe- 15 projecting through the casing 2. The lower ends of the coils 13 also commuicate with a common header 16 which preferably communicates with a steam trap (not shown) through an outlet port 17 and a flanged outlet port 18 with which the casing 2 is provided. A similar construction may and preferably will be employed in connection with the pipe 15 of the steam header.

Each of the compartments of the series is provided with a blowofl port 19 which, of course, communicates with suitable piping (not shown) controlled by an ordinary form of blowofi valve or cock 19'.

As previously stated, all of the water to be evaporated is introduced first into the comartment A. This'water is subjected to the lieat of the heating elements 13 located in that compartment, its temperature is raised and consequently a certain amount of evaporation takes place within the compartment A. The apparatus is preferably so operated that a constant fiow of water is introduced into the compartment A and, under such conditions, the amount of water delivered to the next succeeding compartment or the amount of water flowing over the baflle 5 into the compartment B will equal the difference between the amount of water introduced into the compartment A and the amount of water evaporated in that compartment. This will also be true in connection with the water introduced into the final compartment of the series, since it will equal the amount of water introduced into the next preceding compartment less the amount of water evaporated in that compartment; or it will equal the difference between the amount of water introduced into the initial compartments of the evaporator and the amount of water evaporated in all preceding compartments. Under normal operatin conditions, the float 6 controls the flow 0 water into the initial compartment A and consequently the flow through all the compartments in such a way as to prevent the water level in the last compartment C from rising above the bafile which separates that compartment from the next preceding compartment of the series.

salts is usually recipitated as a sludge. The evaporation ta 'ng place within the compartment A increases the concentration of the scale-forming salts, since these salts do not precipitate until a certain concentration is reached. Further precipitation of the nonscale-forming salts takes place within the intermediate compartment B of the series and further concentration of the scale-forming salts also takes place in that compartment, with the result that the concentration of scale forming salts is considerably in creased in the compartment B over that existin in compartment A. This results from the fact that less water is delivered to the compartment B than to the compartment A, and that the water so delivered is partially concentrated insofar as its content of scale forming salts is concerned. All the water delivered to the final compartment of the series is evaporated therein. Consequently, the concentration of scale-forming salts increases very rapidly in that compartment. It will however, be apparent that little, if any of the non-scale-forming salts enters the final compartment since they are precipitated in preceding compartments by the ncreasing tem erature and increasing concentration of t e water.

Two results flow from this method of operation, viz., the water delivered to the final compartment is substantially free of non-scale-forming salts and little or no scale forms in the earlier compartments of the serles. I

In order to ensure this last-mentioned result, it is desirable to proportion the initial compartments of the series, with relation to the heating surface in each compartment and the amount of evaporation taking place therein, so as to keep the concentration of the scale-forming salts below the point at which they will deposit in the form of scale on the heating elements. It will, of course, be apparent to anyone skilled in the art that, after the concentration of such salts has reached a certain degree of concentration, the formation of scale on 'the heating elements cannot be prevented, since the major portion of the evaporation takes place at the heating elements and there is, therefore, a greater degree of concentration of the scale-forming salts in the water immediately adjacent to the heating elements, with the result thatscale forms on these elements. In order to ensure that hard scale is formed only in the last compartment of the series, it is desirable to proportion the heating elements of the various compartments, with relation to the rate of water flow through the evaporator, so as to ensure a sufliciently rapid flow of water through the initial compartments as to prevent undue concentration of the objectionable salts in those compartments. It will, of course, be apparent that the rate of flow into the final compartment will depend upon the rate of steam generation or evaporation in that compartment and that this, to some extent, will control the rate of water fiow through all the compartments. It is, therefore, desirable to make the last compartment relatively small. This is also desirable because, if the scale formation can be limited to the final compartment,

heating elements of all the other compartments will operate continually with maxi-. mum efiiciency, and for that reason, scale formation in the final compartment, which cuts down the effectiveness of the heating elements in that compartment, will not greatly decrease the overall efliciency of the steam generating evaporator. Another advanta e in limiting the concentration of the scaleorming salts in the initial compartments and in making the final compartment small, with relation to the capacity of the entire evaporator, is that the major portion of the steam generated in the evaporator is generated in'the initial compartments and is, therefore, cleaner steam and freer from scale-forming salts even though some priming may take place or some salt contaminated water may be entrained with the steam issuing from the evaporator.

This lower concentration in the initial sections, however, not only decreases the liability of priming in those sections but any water thrown oil with the vapor will contain a lower amount of solids.

I have found in practice that two compartments give materially improved results insofar as feed water conditions are concerned. Results are improved where the final com artment of such a series is a relatively sma l compartment. Under such conditions, maximum concentration of the scale-formingsalts is confined to the last compartment with the result that little or no scale is formed in the first compartment, whereas the major portion of the steam is generated in that compartment.

In ordinary operation, the sludge or nonscale-forming salts precipitated in the various com artments and settling to the bottom of tl iose compartments is blown out periodically through the blowoff ports coinmunicating with those compartments. It will, of course, be apparent that a certainamount of this sludge will collect in the final compartment, but that the non-scale-forming salts will not be present in that compartment in suflicient quantities to affect the character of the scale forming therein on the heating elements. In other words, .the heating elements will be covered by a hard scale formation which will respond to the usual scale cracking processes and consequently may be removed from the heating elements without the necessity of closingdown 'the evaporator and resortingtochippingtools elements can be blown out and, as a matter of fact, the final compartment can be periodically drained, for the pur ose of avoiding undue concentration 0 scale-forming salts, without material loss in either heat or water.

In the drawings, I have in efiect shown two modifications of the apparatus in that the bafile between compartments A and B extends well above the water level and water is delivered from compartment A to B through orts 24 which are formed near the top of the fiafiles and which are provided with check valves 25. \Vith this arrangement, there is less opportunity for surging and consequently less opportunity for water from the final or intermediate stages to surge back into the initial stages than with the form of bafile shown between compartments B and C. The possibility of surging can, of course, be prevented to a large extent by so arranging such .bafiies that a relatively great difi'erence in forming salts in the water treated, it will be,

apparent to those skilled in the art that various changes and modifications may be made in the procedure herein set forth without departing from the spirit and scope of the invention as defined by the appended claims.

What I claim is 1. A method of generating steam from water containing scale forming salts, which consists in successively passing the water through a plurality of steam generating chambers, limiting the concentration of scale forming salts in the initial chamber by delivering less water therefrom to the next successive chamber than the water formin a lessv concentrated solution of said salts de ivered thereto, and in generating the greatest volume of steam from chambers containing less concentrated solutions of said salts.

A method of generating steam from through a series of steam through a series of steam water containing scale forming salts in solution, which consists in passing the Water through successive heat impartin chambers, increasing the concentration 0% the scale forming salts in successive chambers, but in limiting the concentration of saidsalts in the initial chamber by delivering more water of less concentration to said chamber than the water of greater concentration delivered from said 'chamber to the next successive chamber, and in controlling the rate of delivery of water to the initial chamber in response to the rate of evaporation in the final chamber.

3. The method of generating stem, which consists in successively passing water generating chambers, controlling the concentration and temperature of the water in the initial chambers so as to substantially free the water entering the last chamber of non-scale forming salts and at the same time perventing such concentration of the scale forming salts in the initial chambers as scale therein.

4. The method of generating steam, which consists in successively passing water generating chambers, maintaining the concentration of scale forming salts in the water in the initial chambers below the point at which scale is deposited and increasing the concentration of said salts so as to deposit scale only in the last of said chambers.

5. The method of generatingsteam from water containing scaleforming salts, which consists in passing such water through a series of steam generating chambers, controlling the concentration and temperature oi f less concentration 'of to cause formation of and concentration of the water in the initial chamber or chambers to precipitate non-scale forming salts therein and 'to substantially prevent the formation of scale therein and to render the Water entering the last chamber of the series substantially free from nonscale forming salts, and mixing the steam generated in the chambers of the series.

I 8. The method of generating steam from water containing scale forming salts, which consists in successively passing such Water through a plurality of steam generating chambers, promoting a concentration of the non-scale forming salts in the initial chambers so as to precipitate the same at the temperatures therein encountered While limiting the concentration of the scale forming salts therein by deliverin less water therefrom to the next chamber 0 the series than water of scale forming salts delivered thereto, and in mixing the steam generated in all said chambers.

In testimony whereof, I have hereunto subscribed my name this 24th day of Jul 1926.

BEN C.'SPRA UE.

the water in the initial chambers of the series-j".

so as to render the water entering the last chamber substantially free from non-scale forming salts and controlling the delivery of water to the first chamber in response to the rate of steam generation in the last chamber.

6. The method of generating steam from water containing scale forming salts, which consists in successively passing such Water through a series hers, controlling, the temperature and the concentration of the water in the initial chamber, so as to substantially prevent the formation of scale therein, and so as to render the water entering the last chamber substantially free from non-scale forming salts, controlling the delivery of water to the first chamber in proportion to the rate of steam generation in the last chamber, and in mixing the steam issuing from the chambers of the series.

7. The method of generating steam from water containing scale forming salts, which of steam generating chamconsists in successively passing such water through a-series-ofi' ste'am generating chamlbers while subjecting itto a steam generating temperature,

controlling the temperature

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