US2091421A - Apparatus for cleaning steam - Google Patents

Description

Aug. 31, 1937. w. T. SHERMAN ,09 2

APPARATUS FOR CLEANING STEAM Original File d June 25. 19:54

iNVENTOR BY .ATTORNEY Patented Aug. 31, 1937 UNITED STATES PATENT OFFICE APPARATUS FOR CLEANING STEAM William T. Sherman, Woodbury, N. 1., assignor to Sunny- Vacuum Oil Company, New York, N. Y., a corporation of New York Original application June 23, 1934, Serial No. 732,078. Divided and this application July 2, 1936, Serial No. 88,600

/ v 2 Claims- 5 material capable of forming solid deposits. The general field of this invention is the provision of apparatus capable of removing entrained liquids and/or solid material from steam,

and the more specific fleld'in which it is particu-v larly concerned is removing such materials from i I high pressure steam.

The entrainment of liquid and/or solid materials in steam gives rise to considerable difli; culties in the operation of power plants. The

15 liquids and/or solids may be entrained in the steam from a number of causes, such as foaming, priming and similar difflculties of boiler operation, and it'is frequently possible for serious amounts of such impurities to be present without foaming or priming, probably from certain causes later discussed. These impurities in the steam give rise to considerable difliculties, especially noticeable when the steam from the boiler is passed to a superheater, or when it is used in a 25 turbine. In a superheater, solid materials present in the steam fed to the superheater, are deposited upon the interior of the superheater tubes, forming a dense and compact scale which rapidly causes marked decreases in the heat transfer 30 capacity of the superheater, and frequently shutdowns are required for cleaning. This solid material gives rise to considerable dificulties in pipes and fittings used for distributing and controlling the steam, as it rapidly erodes the inner 5 walls of bends, etc., cuts the seats and discs of partially opened valves, and generally causes the flowing stream of steam to be of what might be termed an abrasive nature. If steam carrying a considerable amount of entrained materials is 40 used for driving a steam turbine, it is found to be particularly damaging, either because of erosion of the turbine blades or because of the solids being deposited upon the blades of the turbine in such a manner that the steam passages of the 45 turbine are eventually clogged and rendered inoperative to a great degree.

I have found that dry steam may frequently contain relatively high percentages of'solid ma- I terial capable of causing erosion, etc., or of being 50 deposited insuperheaters or upon turbine blades, that I can remove such solid material by an actual washing of the steam with a water of relatively low concentration of solids, and that the cleaning is not complete unless the wetting of 55 the otherwise dry steam is complete. It is important that the cleaning be relatively complete for, while the weight percentage of solids present may be minute, the potential cost and damage therefrom may be enormous, becoming especially aggravated with increases of system pressure, and the problem of their substantially complete removal is therefore acute and pressing. It is with a method for the solution of such a problem of steam cleaning that this application has to do.

Prior methods of cleaning steam which attempt to solve this problem have consisted of various arrangements ofbafliing devices interposed within the steam space of the boiler in such a way that the steam must pass through these bailies before it leaves the boiler, coupled with a spray oi. boiler makeup water which is distributed somewhat in the form of a curtain upon the entering side of the baiiles. These devices have been found to be subject to serious disadvantages, the greatest being that it is quite diificult to arrange the baflies and sprays so that there is at all times an assurance of positive contact between the steam to be scrubbed and ..the scrubbing spray. A further disadvantage is that the impurities in the spraying water itself may be relatively concentrated, and, while such-water functions to remove some of the impurities, it may do so by replacing them with other impurities. Frequently also, the interaction of the spray and the baflles is such as to cause deposit of the entrained solid material after wetting upon the surfaces of the battles, which quickly results in clogged baflies and failure of means for removing steam from the boiler. A further serious disadvantage is that the requirements of space within the boiler call for high steam velocity through the battles, and the spraying water, after taking up material from the steam, frequently may be swept off the baliies by the action of the stream of vapors and returned to ,the steam as an impurity. It may be seen fiom the above that the ordinary type of moisture removing constructions are inadequate for the solution of the problem, and that for a number of reasons, the preferable location for steam cleaning equipment to meet this problem is not within the boiler drum.

It is an object of this invention to provide apparatus in which steam may be thoroughly and efliciently scrubbed withwater of low solids concentration. A further object is the provision of apparatus wherein the scrubbing may-be performed by parallel flow of steam and water drops lets together in a confined, turbulently flowing stream. Other objects and advantages will appear in the following specification.

The process of this invention may be briefly described as that of vigorously scrubbing steam with water of low solid concentration, in a man- In order that my process of steam cleaning and the apparatus therefor may be more thoroughly understood, reference is now made to the drawing attached to and forming a part of this specification. In the drawing, Figure 1 is a diagrammatic representation of the preferred form of my invention, while Figure 2 is a diagrammatic showlng'of a variation in which the scrubbing device is placed inthe steaming space of the boiler.

In Figure 1 of the drawing, I indicates the steaming drum of a high pressure boiler, the tubes and other drums of the boiler not being shown.-

2 indicates the steam main leading from steam drum I to scrubber 3. This pipe 2 enters scrubber 3 below a partition 4. In this partition 4 there is placed a cylindrical tube 5. Thistube 5 is open at both ends and extends upwardly a short distance above partition 4. It extends a suflicient distance below partition 4 so that its end is close enough to the water level 6 for the flow of steam to pick up wash'water therefrom. A drain tube 1 extends from the space above partition 4 to a point well below water level 6. Other than for the openings through tube 5 and tube 1, the partition 4 is imperforate. The liquid storage space in the bottom of the scrubber 3 is supplied with water through line 8, and this water is removed from the storage space through line 9 controlled by liquid level valve l0, through the agency of pump ii and introduced into the boiler by means of line l2, with auxiliary feed introduced and controlled by some form of boiler water level and feed control as indicated at l3. In the upper portion of the scrubber 3 there is placed a moisture separator, of any efiicient type, such as one of the numerous forms of labyrinth bailie separators, and steam passing through this moisture separator is taken from the sembber through line l5 to the superheater or to a point of use. The water entering through line 8 may be the feed water normally charged to the boiler, or it may preferably be mixed with increasing proportions of returning condensate. For reasons later discussed it is desirable at times to feed nothing but returning condensate through line 8, so this line 8 must be understood to be connected to sources of feed water, treated or raw, condensate, and/orother source of water low in solid-forming impurities.

The action of the scrubber is as follows: the steam entering the vapor space between water level 6 and partition 4 can escape only by passing under the lower edge of tube 5 and vertically through that tube into thespace above partition 4. In so passing into tube 5, it entrains liquid from the storage space, the whole passing through tube 5 in a highly commingled and extremely actively contacting condition whereby. each and every portion of the steam is positively and forcibly contacted with scrubbing medium.

Above the partition 4, after exit from the tube 5,

J in the relatively enlarged space provided, the

water separates from the steam. Inasmuch as this water is not introduced to the steam under actively steaming conditions in the form of a fine .spray, and is usually and preferably at a temperature somewhat less than that of the steam, there is very little tendency for the steam to mm with it particles of water of a size greater than those which may be separated by an ordinarily good moisture separator placed in loca- 5 tion l4.

Figure 2 is a diagrammatic representation of.

how the apparatus accomplishing this process may be installed within the steamdrum of a boiler. In this figure the function of like parts 1 is the same as in Figure 1, and such like parts have been given'identical numbers in the two figures. A

Due to the reasons pointed out above, the

water carried out of the contacting tube is not 1.

diflicult to separate from the steam, and consequently the installation shown. in Figure 2 is frequently practicable. It may be modified somewhat by installing the moisture remover in an adjacent body, with the contacting tube in the steam drum.

The eflicacy of this process or steam cleaning is centered around the ability to attain positive and complete scrubbing contact of all of the particles of steam with a scrubbing medium. (101- 25 laterally, it is important that this scrubbing action be permitted to take place with water relatively free from impurities .which may be converted to solids upon evaporation of the water.

The requirement of relatively solid-free scrubbing water may be met by scrubbing with condensate obtained from subsequent portions of the system, or by use of the feed if that be suificlently solid-free, or by combinations of feed and condensate return in various proportions, or by adjusting temperature and amount of feedso that sufiicient condensate is formed within the 1 scrubber itself to reduce the scrubbing water to the desired solid-free degree.

In the diagrammatic drawing attached hereto, the contacting of steam and water'is shown as being performed in a single tube. As a matter of actual practice, it will be preferred to use a plurality of tubes, since requirements of space and eilicient contacting may be more easily met with several tubes 5 oi. a convenient size rather than with one large tube of equivalent'periphery or of equivalent cross sectional area. Increases of capacity can consequently be made by increasing the number oi tubes.

I do not claim, as original with me, the association of the contacting tube 5, the pm'tition 4, and the drain I, nor the general method of their operation, except in connection with the additional means set forth, and for the purpose and. in the manner described in the following claims,

In the previous discussion and the appended claims solids" is intended to mean not only solids actually present within the steam as such, but also is intended to include any material capable of appearing as solids at some subsequent point in the steam system. such as droplets of highly concentrated solution, and. the like.

This application is a division .of my copending application Serial No. 732,078, filed June 23, 1934.

I claim:

. 1. Apparatus for the scrubbing of substantially saturated steam with water of low solid-forming content to reduce the solid-forming content of the steam comprising an enclosure divided internally 10 by a horizontal imperi'orate partition into an upper and a lower chamber, a body of water within" said lower chamber, a cylindrical tube passing vertically through said partition, terminating in proximity to the level of the body of water, means for conducting steam to be cleaned from the steaming space of a boiler to the space between said body of water and said partition, an

5 exit means to remove steam from the chamber above the partition, a moisture separator cooperating with said steam exit means, means to return water collecting above said partition to the body of water below said partition, feeding means 10 whereby water of low solid-forming content may be introduced to said body of water, and exit means whereby water from said body may be passed to a boiler in which the steam is being generated, said exit means including level control 5 means whereby the body of Wateris maintained at a predetermined level spaced below the partition between the upper and lower chambers.

2. Apparatus for the production of steam relatively low in solid-forming content comprising a 20 boiler, feeding means therefor, a conduit through which steam may be removed from the steaming space thereof, an enclosure having a horizontal imperforate partition dividing it into an upper and a lower chamber, a body of water in said lower chamber having a level spaced below said partition, the above mentioned steam conduit discharging into the lower chamber above said water level, a vertical cylindrical tube extending through said horizontal partition, depending into proximity with said water body and terminating in the upper chamber, an exit conduit whereby 10 steam may leave the upper chamber, a moisture separator for steam cooperating with said exit means, means for returning water from the said upper chamber to the said body of water, means for introducing water purer than boiler water 5 to said body of water, and means for removing water therefrom, said last-named means communicating with the feeding means for the boiler, and including control means for maintaining the level of the body of water in the lower chamber. 20

WILLIAM T. SHERMAN.

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