US2276055A - Method of and apparatus for desuperheating - Google Patents

Description

March 10, 1942. H MASTENBROOK 2,276,055

METHOD OF AND APPARATUS FOR DE-SUPERHEATING Fil ed June 1:5, 19 39 2 Sheets-Sheetl INVENTOR. Hi/WP) I NA STE/VBIPOOK A BY I ATTORNEYS March 10, 1942. J. VMASTENBROOK 2,276,055

METHOD OF AND APPARATUS FOR DE-SUPERHEATING Filed June 13, 1939 2 Sheets-Sheet 2 a; w w t l (y wn M x INVENTOR H-VVE) IMASTFNBIPOO/f ATTORNEYS Patented Mar. 10, 1942 METHOD OF AND APPARATUS FOR DESUPERHEATING Henry J. Mastenbrook, Cleveland, Ohio, assignor to The Swartwout Company, Cleveland,

a corporation of Ohio Application June 13, 1939, Serial No. 278,925

20 Claims.

This invention relates to desuperheating steam and is more particularly addressed to t e problem of emciently desuperheating imndbr those conditions where the rate of flow steam is relatively small.

One of the most efiectiveprocedures in the art of desuperheating. steam, as it is known and practiced today, comprises injecting water into the path of superheated steam under conditions of velocity and/or change of direction with appropriate jets, nozzles, baflies and the like, which will cause the water to be evaporated and trans formed into steam, thereby consuming all or part of the superheat or reducing the quality of the steam more or less as may be desired. Obviously, it is desirable and very often imperative that the water which is added to the superheated steam be quickly and efficiently evaporated, so that the desuperheated steam will be of the desired quality and/or reduced degree of superheat as well as free from independent droplets or streams of unevaporated water, all within a limited length of piping, so that a consumer of the desuperheated steam may be certain that raw water will not be contained in the desuperheated steam at the point of use thereof.

A number of satisfactory designs of desuperheaters for the general purposes indicated are known to me, but all of them of necessity are designed on a sufiiciently large scale to carry'the maximum load expected of them, i. e. the sizes of the steam orifices and passageways, being large enough to permit sufiicient flow for maxi- -mum requirements, are necessarily such that there comes a point Where lesser flows lack sufficient velocity to agitate the water input sufficiently to bring about complete evaporation of the water within the desired or permissible limits of the device. In other words, a desuperheater having sufiicient capacity to meet the maximum requirements for which it is designed will tend to have insuiiicient steam velocity somewhere tcward the'lower limits of steam flow to function efficiently with respect to atomizing or breaking up and evaporating the cooling water input.

The foregoing assumes, of course, that the water input is efiiciently controlled with relation to the steam input and the degree of superheat thereof, so that for normal operating conditions the desired amount of desuperheating is efiected. The. same control operating in the same way tends to over-supply water at the lower steam velocities with the result that raw water tends to be carried along in the desuperheated steam.

Ohio,

The primary object of my invention is to provide a method and means whereby to extend the lower limits of efiicient operation of a-desuperheater to embrace the lower velocities of steam flow and the lighter loads to be handled. Other objects include the. carrying out of the foregoing objects with simple and economical means; and the provision of an automatic control for bringing my method .and means into play at appropriate times, and for and during the conditions of their intended use. Other objects will appear from the following description of preferred embodiments of my invention, reference being had to the accompanying drawings in which:

Figure 1 is a more or less diagramma ic layout of a desuperheating installation in which one "form of apparatus embodying the particular features of my invention is shown in relation to the other elements of the system.

Figure 2 a vertical cross-sectional view of one form of desuperheating chamber having a water inlet in which a form of the instant invention is associated.

Figure 3 is a vertical cross-sectional view showing another form of desuperheating chamber of the Venturi type having a water inlet incorporating a slightly modified form of apparatus embodying the precepts of the instant invention.

Figure 4 shows a further modification of ap-' ratus adapted for use in carrying out the instant invention, more particularly adapted for application to existing installations.

Referring to Figure l to show the general environment in which my invention may be practiced, there is disclosed an illustrative desuperheating layout comprising the steam main 1 in which high pressure superheated steam enters at the left ,as shown at 2, passing through the reducing valve 3 and the desuperheater unit 4, where water is introduced through the pipe 5, after which the desuperheated steam at reduced pressure flows to the right through the main passing within a limited distance of travel, a thermostatic control T, thermometer T, and pressure outlet conduit 6. v

. In the form of desuperheater illustrated, the thermostat T, by reflecting the temperature of the desuperheated steam, causes a fluid pressure to be raised or lowered in a conduit I, which in turn controls the movement of a valve 8 in the water line 5, whereby to increase or decrease the flow of water to give the desired resulting temperature to the desuperheated steam. It will,

of course, be appreciated that, if the desuperheated steam passing the thermostat T is not homogeneous, i. e. free from drops of raw water or free from streams of raw water, the desired results will not be obtainable. Hence the function of the main desuperheater 4 is essentially to bring about the intimate mixing of the steam and water and to so enhance the ultimate evaporation of the water in a limited length of time, and perhaps also a limited travel in the lowpressure steam main, that the whole function of evaporating and mixing the water and steam will be accomplished before the steam passes the thermostat T. The control of the reducing valve is appropriately managed by the imposition of steam pressure through the conduit 6 on a master control M, which controls the reducing valve 3. All the foregoing is, of course, illustrative of that which is practiced in the art prior to my invention.

The desuperheater housing or mixing chamber 4 may conveniently take the form illustrated in Figure 2 in whichthe incoming steam is diverted downwardly through: a tapering conduit through a reduced orifice l0, thereby passing the water ..jet ..or.. noz 1e,.. .,T esteam is given an increasing velocity toward and through the restricted orifice l0, and is then caused toreverse its fiow through 180 to the outlet orifice l2. The lower portion of the body of the desuperheater 4 may be tapped OfirtO a steam trap 9, see Figure 1, so that excess water will not accumulate in the bottom of the desuperheater housing.

Considering ,-particularly Figures 1 and 2, it will be appreciated that as the load on the whole installation is reduced, there will come a point where the velocity through the desuperheater 4 is so low that the velocity through the orifice III and adjacent the water jet II, and elsewhere in the device, will be incapable of giving suflicient mechanical atomization or agitation to the water to bring about enough evaporation thereof to ac-, complish the desired desuperheating. The re sult of such low load operation may be that the water will either accumulate in the bottom of the desuperheater or be carried along in drops or streams in the low pressure main.

To correct this situation my invention provide the introduction of steam into the water line through such means as the: branch conduit l3, shown in Figure l as leading from the high pressure side through appropriate control valves 14 and I5, to the water main as at 16. Referring particularly to Figure 2 the high pressure steam enters the housing I 6 through which the water line 5 passes, and the water line 5 is so constructed as to provide within the housing 16 a substantially annular and inclined orifice ll, through which the steam may enter the water conduit 5 and pass along with the water therein through the jet I I into the infiowing steam in the body of the desuperheater 4. Although I have shown steam being led from the particular point in the high pressure line indicated in Figure 1, it is, of course, only essential that steam be introduced through the orifice I! at a higher. pressure than tent of steam and water in the pipe 5 between the orifice l1 and the jet H is greatly increased in volume, and hence greatly increased in velocity. Thus the velocity of the mixture emanating from the jet II is increased so that the relative speed relationship of the drops or streams of raw water with respect to the adjacent steam in and around the jet II and theorifice I0 in the desuperheater is raised to a point where mechanical atomization and spreading of the liquid particles is enhanced to facilitate greatly the evaporation of the water. In like manner, where the flow of water through the pipe 5 is still less, the flow of steam beglnningat the orifice I] may be as high as desired, i. e. high enough in its flow, particularly through the orifice l1 and the remaining portion of the water pipe 5 and out through the jet ll, so that, within this length of the pipe I the mechanical breaking up and mixing of the water may be largely, if not wholly, accomplished. This results in a wet steam or mist being forced through the jet ll into the adjacent superheated steam and the relatively slowly moving superheated steam is not called upon to perform the function of atomizing or mechanically breaking up raw water. perheated steam is desuperheated by the addition to it of wet steam from the jet II or a mixture of wet steam and water vapor or mist or the like, as distinguished from the ordinary injection of raw water into the superheated steam.

I have found it feasible to control the flow of steam into the water line by such a simple means as .a hand valve (not shown) set to give suflicient steam flow through the pipe I! for the minimum desired output of desuperheated steam, and then permitting this quantity of high pressure steam to flow into the water pipe 5 throughout all periods of greater load, since under the conditions of greater load and greater flow of water through the pipe 5, the addition of the relatively small amount of steam has little effect except perhaps to warm the water somewhat in its fiow from the orifice I! to the jet ll.

put out of operation.

the water pressure in the pipe 5 and the source of steam supply is immaterial.

The operation which results is that when the load on the desuperheater .is small, the fiow of both steam and water is small, hence the flow of water through the pipe 5 is relatively slow or sluggish. With, however, the introduction of steam through the orifice I], the mixed fluid con- To make the whole operation automatic, I provide as shown in Figure 1 a pair of valves l4 and IS in the high pressure auxiliary steam line II, which may conveniently be controlled by the same source of pressure that controls the reducing valve 3. Thus where I have shown a reducing valve 3 to be opened in response to increasing control pressures in the diaphragm chamber thereof, I provide that the valve l4 be similarly arranged and that the valve l5 be oppositely arranged. Each of the valves 3, l4 and I5 may appropriately have adjustable springs S operating on the valve stems, tending to close the valves 8 and i4 and tending to open the valve II as against the actuating pressure imposed upon the diaphragms thereof from the master control M. When the load on the whole system is normal or high, the pressure from the master control will of course be high .enough to hold the reducing valve 3 in a well opened position, and the same pressure will hold the valve I4 well opened, but

In this manner the su- Where high pressure superheated steam is thus introduced into the pipe will shut or tend to shut the valve l whereby to shut off the flow of steam through the auxiliary line l3, thus permitting the whole installation to work in the manner known prior to my invention. As, however, the load on the whole installation decreases and the steam velocity in the pipe I begins to get down to the point where my invention comes into play, the pressure from the master control M will necessarily become less, permitting the spring S to throttle the reducing valve 3 and open the valve 15. The springs in the valve l4 are then appropriately adjusted, so that the valve I4 stays open, permitting steam to flow through the auxiliary line l3 into the mixer IB thrQugh the orifice l1 intothe water line 5, where it performs the function of increasing the velocity from the orifice l1 to the jet H and yaporizing, agitating or evaporating the water therein prior to its introduction into the desuperheater 4 as above described.

The springs S in the valves 3 and I4 are so set, however, that whenever the valve 3 closes the valve l4 will thereupon also close, whereby to shut off all flow of steam from the high pressure side. When this occurs the temperature in the low pressureside-of. pipe l, will fall to a point where the thermostat T will also shut offthe water valve w'jana the system will automatically have come to rest, the whole shutting down sequence being initiated by a reduction in consumption of steam at the point of consumption beyond the low pressure end of line I in the apparatus illustrated in Figure 1.

From my prior observations, it will also be understood that the automatic operation above described may profitably be carried out without the use of the valve l5, since the additional flow of steam through the line l3 and into the dewhere the steam, flowing as shown by the arrow,

passes the jet. The restricted orifice 25 receives the water from the jet 24 under normal'loads and evaporates and atomizes the same at the point of high velocity adjacent the orifice '25. In this form, the auxiliary steam enters through the inlet 20 into the chamber 26 surrounding the conduit 22, and passes into the water conduit 23 through the confined annular orifice 21, thereafter functioning in its eflect upon and with the incoming water as above described.

The details of construction which I have found advantageous are illustrated in one desirable form in Figure 3, in which the chamber 26 is shown to be formed in a flanged housing 30 into which is preferably internally threaded the conduit 22, the lower end of which, as shown, is externally chamfered, preferably about at the angle shown, whereby to lie a spaced distance from the internally chamfered end of the conduit 23. The conduit 23 in turn is preferably grooved as at 3!, and brazed or welded to the collar 32, which is clamped between the flanges 30 and 33 by bolts 33', thereby also closing the extension of the Venturi chamber through which the water conduit 23 enters. By this construction any desired size and shape of the orifice 21 may be obtained by the removal of the upper flanged housing 30 and the substitution of longer or shorter conduits 22 with varying degrees of chamfer to give the character to the orifice 21 that is found most appropriate in use. The annular inclined configuration of the orifice 21 has been found by me to be practical and eilicient, particularly in that the inflowing high pressure steam tends to tear away water that is flowing along the walls of the conduit 22 directly above the orifice and to agitate this water very vigorously in its passage in the mixture of fluids between the orifice 21 and the jet 24.

Referring back to Figure 2, it will be seen that thedetails of construction of the jet are modifled slightly in that the water conduit 5 is brazed or welded directly to the housing l6, terminating in an externally chamfered end in the central portion thereof adjacent the orifice l1, and that a separate length of pipe or conduit 5 is sepa-.

'-rately brazed or welded to the lower portion of the housing l6, having its upper end internally chamfered and spaced from the externally chamfered end of the pipe 5. The lower portion of the pipe 5' is shown to be externally threaded into the adjacent flange through which the whole assembly is bolted with the other appropriate elements of the flange joint on the top of the desuperheater body 4 as shown.

In Figure 4 a further modification of the details of an alternative form of mixer construction is illustrated. This form may be particularly convenient for use with existing installations and comprises essentially a standard pipe T at 40 in the upper end of which the incoming water may flow in a pipe 4|, which has its lower end externally chamfered at 42. The pipe 4! may conveniently be threaded into the T as shown and brazed or welded in a selected position as seen at 43. Similarly, the outflowing' connection may comprise the pipe 44, internally chamfered at 45, threaded into the lower connection or the T and brazed or welded at 46 in the desired position, whereby to give an inclined annular orifice 41 of the size desired. In assembling the parts the sizeof the orifice 41 may be observed through the middle opening 5030f the T prior to the welding of one or both'of the welded joints 43 and 46. The steam line may thereafter be connected' to the opening 50 as shown, whereby the annular steam chamber 5| will surround the orifice 41. In this form I have shownan internal restriction 48 in'the pipe 4| immediately preceding the orifice 41, whereby'to increase the water velocity at this point as well as to concentrate the water stream and subject it to an ex tra mechanical agitation from the steam entering the orifice 41 adjacent thereto. The whole assembly just described may be appropriately joined to the body of the. desuperheater by. threaded engagement with an appropriate flange joint attached to the water or fluid conduit 49 which may continue in the manner of the denduit 23 shown in Figure 3, or otherwise embrace a suflicient length of conduit to permit the agitation of the fluid therein prior to its delivery to the body of the desuperheater for the purposes above described.

While I have referred to that portion of the apparatus in which I introduced the high pres sure steam to the water of the desuperheater as a mixer, I use the term only for convenience here thereof, and have illustrated a practical embodiment of means through which my invention may be practiced, various modifications and changes thereof will occur to those skilled in the art without departing from the precepts of my invention, and I do not care to be limited to the particular forms herein illustrated and described or in any manner other than by the claims appended hereto when construed to have that range of equivation of said conduit including spaced beveled end portions forming an annular inclined steam inlet opening through the wall of said conduit.

8. The method of de-superheating steam which consists in reducing the pressure of one part of the superheated steam, supplying water thereto, injecting said water into said steam with another par. of said superheated steam at a greater pressure than said reduced pressure, and throttling said other part of said superheated steamwhen the flow of said one part of said superheated steam exceeds a predetermined amount.

9. The method of de-superheating steam which consists in reducing the pressure of one part of the superheated steam, supplying water thereto, injecting said 'water into said steam with another part of said superheated steam at a greaterpres- 2. The method of.desuperheating steam which includes the steps of adding, to superheated steam, water in amounts controlled with respect to the character of desuperheated steam and increasing the temperature of such water as the rate of flow of superheated steam decreases, such temperature increases being effected prior to adding said water to said superheated steam.

3. The method of desuperheating steam which includes the steps of adding water to. flowing steam to be desuperheated when the flow of said steam exceeds a predetermined amount, and adding a mixture of water and steam to the steam to be desuperheated when the flow of said steam becomes less than said predetermined amount.

4. The method of desuperheating steam which consists in reducing the pressure of one part of the superheated steam, supplying water thereto, injecting said water into said steam with another part of said superheated steam at a greater pressure than said reduced pressure, and varying the amount of said other part of said superheated steam in inverse proportion to the pressure of the de-superheated steam.

5. Desuperheating apparatus of the type described including a desuperheater unit having asteam inlet and a steam outlet, a conduit extending into said unit and having a discharge outlet disposed in the path of steam flowing through said desuperheater unit, means for supplying water to said conduit, and means for in-' chamber surrounding a section of said conduit and having a steam inlet opening into said chamber, said section of said conduit having an opening in the wall thereof whereby steam from said steam chamber may enter said conduit.

7. A desuperheater comprising a casing having a steam inlet and a steam outlet, a conduit extending into said casing and having a discharge outlet therein between said steam inlet and steam outlet, and walls defining a steam chamber surrounding a section of said conduit and having a steam inlet opening into said chamber, said secsure than said reduced pressure, and throttling the fiow of said other part of said superheated steam when the flow of desuperheated steam reaches a predetermined minimum.

10. The method of desuperheating superheated steam which consists in dividing the flow thereof into two separate parallel paths, throttling the fiow in one path to maintain a desired aggregate flow through both paths while maintained a higher velocity flow in the other path at least when the said desired aggregate flow is small, adding water to the steam flowing at the higher velocity in said other path in amounts suflicient to bring about the desired amount of desuperheating of the aggregate contents of both paths, causing said water andsteam to contact in an initial mixing zone and then flow together in a part of said other path which is long relative to said zone and mix and commingle therein while tending to over-desuperheat the steam therein, and thereafter joining said paths and mixing the said mixtureand/or over-desuperheated steam from the second path with the superheated steam fiowing from the first path.

11. The method of desuperheating superheated steam which consists in dividing the flow thereof into two separate parallel paths, throttling the flow in one path to maintain a desired aggregate flow through both paths while maintaining a higher velocity fiow'in the other path at least when the said desired aggregate flow is small, adding water, to the steam flowing at the higher velocity in said other path in amounts suflicient to bring about the desired amount of desuperheating of the aggregate contents of both paths. causing said water and steam to flow together in said other path and mix and commingle therein while tending to over-desuperheat the steam therein, and thereafter increasing the velocity oi! the whole fluid contents of the second path and projecting the same at said increased velocity into said first path.

12. The method of claim 11 which includes 13. The method of desuperheating superheated steam which is flowing in the first of .two separate parallel paths which consists in causing steam to flow in the second path, throttling the flow in said first path to maintain a desired aggregate flow through both paths while maintaining a higher velocity in the second path at least when the said desired aggregate flow is small, adding water to the steam flowing at the higher velociy in said second path in amounts sumcient to bring about the desired amount of desuperheatlng of the aggregate contents of both paths, causing said water and steam to contact in an initial mixing zone and then flow together in a part of said second path which is long relative to said zone and tornix and commingle therein while tending to wet the steam and vaporize the water therein, and thereafter joining said paths and mixing the contents thereof. I

14. The method of claim 13 which also includes the step of increasing the velocity of the whole fluid mass flowing in said second path when it 'joins the first path and projecting said mass at said increased velocity into the superheated steamflowing in said first path.

15. The method of claim 13 in which said second path is restricted in area adjacent the point where water is added thereto and thereby accelerating the movement of steam where the valve in said steam inlet, a steam conduit leadwater is first added to it to break up the water particles preliminary to the mixing thereof with the steam' in said second path.

16. The method oi desuperheating superheated steam which consists in moving superheated steam in a confined space past a nozzle from which desuperheatlng fluid is introduced to the superheated steam, introducing water in amounts controlled with respect to the condition of desuperheated steam into a second confined space separated from said flrst space which communi-' cates therewith only through said nozzle, introducing steam into said second space in amounts which maintain an atomizing velocity through said nozzle at least when the rate of water input would be too small tocause substantial atomiza-- tion at said nozzle if flowing therethrough alone, mixing said steam and water in said second space to form a desuperheatlng fluid, and ejecting said fluid through said nozzle with an accompanying drop in pressure 01 saidfluid into the superheated steam in said first space.

17. A desuperheater having an inlet for superheated steam, an outlet for desuperheated steam, and a water inlet conduit terminating in the desuperheater in a restricted discharge orifice disposed in the path of superheated steam, means responsive. to the condition of desuperheated steam for feeding water into said conduit at rates suflicient to maintain the desired condition of desuperheat, and means for feeding steam into said conduit at a point spaced away from and ahead of said oriflce at pressures in excess of the pressure in' said desuperheater and in amounts which tend to agitate and accelerate the movement of water from said point to said orifice at least when the rate or water input is small, the portion of said conduit 'betweenvsaid point ing from said steam'inlet ahead of said reducing valve to said water inlet conduit at a point ahead of said discharge oriflce, means controlling the supply of water responsive to the condition of desuperheated steam for increasing the flow of water when the amount of desuperheatlng is less than desired, and means including said reducing valve for maintaining a reduced pressure in said desuperheater compared with. superheated steam pressure ahead of said valve whereby to force steam through said steam and water conduits, the portion of said water conduit between said point and said oriflce comprising a chamber communicating with said desuperheater only through said orifice in which steam and water are mixed and fluid pressure is maintained to cause higher velocity through said orifice than would result from the flow of water alone at least when the amount of water required for desuperheating is small. I

19. The combination of a desuperheater having a steam inlet, a water inlet and a steam outlet. a conduit leading from a supply of water under pressure to said water inlet, valve means responsive to outlet steam pressure for restricting the flow of steam through said steam inlet when the outlet steam pressure exceeds a predetermined amount, valve means in said conduit responsive ing the water flow as outlet steam temperature tends to exceed. a predetermined value, a steam conduit leading to said water conduit between said water valve means and said water inlet, and valve means in said steam conduit responsive to outlet steam pressure for restricting the flow of steam therethrough when the outlet steam pressure. exceeds a predetermined amount.

20. The combination of claim 19 with valve means in said steam conduit responsive to outlet steam pressure for restricting the flow there-.

through when the outlet steam pressure becomes less than a different predetermined amount.

HENRY J. MAS ENBROOK.

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