US2020359A - Corrosion preventing system and process - Google Patents

Description

Nov. 12, 1935. R L, OLME 2,020,359

CORROSION PREVENTING SYSTEM AND PROCESS Filed March 17,1934 2 Sheets-Sheet 1 ATOM/Z/IVG 7 CDNDE/VSATf N LINE BOILER WATER L/NE F550 WATER TANK Sl/CT/O/V END OF PUMP dwy wl/f Nov.. 12, 1935. R. HOLMES 2,020,359,

CORROSION PREVENTING SYSTEM AND PROCESS Filed March 17, 1934 2 Sheets-Sheet 2 fi ICHUSTIC I 26 I so u 7'10 4 H29 f2 INJECTOR 4 6 7 80am STEAM /9 WA TER ,23 um H 0 mg cozvafi/vsam REF/HIV u/ve' SUPPY LINE A, my/g Patent ed Nov. 12, 1935'- PATE'N r 'oFFicE' CORROSION PREVENTING SYSTEM AND rnocnss Robert Leslie Holmes, Dallas, Tex.

Application March 17,

process for preventing corrosion in the return,

lines of steam heating systems, irrespective as to whether they operate under pressure or vac- The prime object of this invention is to utilize the concentrated chemicals normally produced in a boiler by evaporation, to neutralize the acidity of corrosive waters, and thereby avoid the preparation and introduction, by other methods in common use, of chemicals or chemical compounds for that purpose.

One of the objects of the invention is to overcome the acidity of the condensed water that is returned to the steam boiler from a heating system, by introducing into the lines through which the returning water passes a sufficient quantity of the concentrated boiler water itself so as to overcome the acidity of the returning condensate water.

A further object of the invention concerns itself with the process of neutralizing the carbonic acid acidity of condensate water by neutralizing the same with alkaline boiler water and returning the mixed fluids either directly to the boiler or to a feed water tank from which the said boiler is fed.

In its simplest embodiment, the invention comprises forcing or pumping a certain quantity of boiler water from just below the normal low-water line in the boiler into the return lines which lead from the various radiating means so that the alkalinity of the boiler water will combine and neutralize with the carbonic acid contained in the condensate water. This may be accomplished 35 either by employing the natural pressure of the boiler or by a suitable pump. a

The general system is illustrated in diagrammatic form on the two drawings submitted with the present application, in which drawings:

40 Figure l is a diagrammatic view of an installation of applicant's system for carrying out his process,in which steam is forced through a vertical pipe to the top of the building to be heated and is then passed into a downwardly directed 45 pipe, leads being taken off each of these pipes to the individual radiators; while in Fig. 2 a system is illustrated in which the steam rises through a verticalpipe and is directly distributed therefrom 55 the building which is to be heated and is then di- 1934, Serial No. 716,027

rected into a vertical pipe downwardly, this pipe being provided with branch lines'leading to the individual radiators. These radiatorsare valvecontrolled both as to inlet-and outlet, the outlet being of 'an automatic type so that only'water 5 will pass through the said outlet valve while steam or vapor will be keptin the radiator. The radiator of course acts as a condenser, condensing the steam to the liquid state, forming an aqueous condensate. Because of the fact that, almost univerl0 sally, boilers are fed with water that contains carbonates, carbon dioxide is also liberated in the boiler as a result of the temperature and pressure conditions therein existing. This liberation. of carbon dioxide is even more true when using 15 natural waters containing bicarbonates, because these break down toflform carbonate and hydroxide, with the concomitant liberation of carbon dioxide gas.

When boilers are fed with the usual softened 20 water, there is also thereby introduced into the boiler some form of carbonate, usu al1y sodium carbonate which, under the usual temperature and pressure existing in the boiler, breaks down, at least partially, into sodium hydroxide, thereby liberating carbon dioxide. This carbon dioxide, being gaseous, leaves the boiler together with the steam; but, when the carbon dioxide and the steam get into the radiators, the steam condenses, forming distilled water. Such water is an excellent solvent for carbon dioxide, so that the said gas dissolves in this distilled water, thereby forming carbonic acid, H2003, which raises the hydrogen-ion concentration of the water so that it will be on the acid side of neutrality. In other words, it will have a hydrogen-ion concentration which may be as high as pH 5.8 to 6.0. Inasmuch I as the water also dissolves oxygen, this may get into the lines from leaks. Such water is very corrosive and will attack the iron parts of the pipes, with the formation of rust, this reaction then proceeding until the pipes are virtually completely filled up with rust or destroyed and have to be removed or renewed in order to render the system again operative. 45

Ordinarily, when such acid distillate gets back into the boiler, its acidity is immediately overcome by the alkalinity of the boiler water. In other words, the cycle is completed in the boiler. 'This, however, affords no protection to the return 50 lines.

In accordance with the present invention, therefore, a sufficient amount of boiler water is positively supplied to either the return lines or the steam lines at the point near where it leaves 55 or enters theindividual radiators, although, for most purposes, it will sufllce to introduce it merely into the lines close to the point where the condensate leaves the radiators and enters the re- 5 turn pipe system. A sufficient amount of the boiler water' -should be used to bring the hydrogen-ion concentration of the combined return to =about pH 9 to 11, for, at such agdegreeof alkw tj'linity, the water will be non-corrosive.

m system'cdmprises a boiler I, a-steam.,linel,land

-13 downwardly directed steamdistributi '5, from which .therehre a plurality lines t which lead to thflylldigfil" radiators are, in turn, l l'ovidedwith 'orfmanually operated dischargedischarge the condensate through'th ipples 9 into the distillate or condensatereturn line It. The return line lli-is usually ,connectedto the '2 suction end of a condensate pump H, which J 1 pumps the condensed waterthrough the .pipe l2 Y '.\into the feed water tank i3.- From the'tank l3 water is drawn through pipe H and injected into the boiler either by an injector or by a pump 25 I5, entering the boiler through the line l6 below the water level ll. There is also provided a steam return line .l8 connected with the trap l9, which returns any condensate formed in the steam return line into the boiler through the 30 pipe 20. A supply line of softened water or supply water 2| is also shown located above the feed water tank.

In order to carry out applicants invention. there is further provided a suction line 22 which 35 is connected a short distance below the low-water level I! of the boiler. This pipe 22 has an extension 23 and branches 24, 25, and 26, suitable valves 21, 28, and 29 being provided inthis pipe. If there is not suilicient steam pressure used, as 40 in the case of a vacuum heating system, a pump 22 may be inserted in the lines 22 and 23 so as to pump the boiler water to the desired elevation. Referringfor the moment to the branch pipes 24 and 25, these may be provided with 45 atomizing injectors 30 in order to spray a small quantity of the boiler water directly into the steam line 4 or 5. The boiler water rising through pipes 22, pump 22', and line 23, passes through the valve 29 into the condensate return line Ill, 50 where it mixes with the condensate flowing through the nipples 9 into the pipe 10. At this point the desired neutralization of the acid reacting condensate water is effected and such condensate, conjointly with the boiler water fed into 55 line HI, returns to the feed water tank l3 through the pump H and the pipe I 2, thus completing its cycle.

Referring to Fig. 2, the same numbers are applied to all parts which are of the same function 60 as in Figure 1, except that in Fig. 2 there is no downwardly directed steam line 5, the steam being distributed on the contrary merely through the vertical line 4 which, at its uppermost end, is closed ofl with the cap l. In such a system 65 it is usually unnecessary to provide for means for injecting the boiler water into the steam line before it gets to the radiators, as the temperature 70 water may condense on the sides of the line and which refiurns immediately to the boiler by gravity. In Fig. 2 the mixing, therefore, takes place at the point where the distillate leaves through the nipple 9 and meets the boiler water flowing 7 through the condensate return line l0.

required alkalinity.

Referring'fto Figure 1, it will-ebeifseenithatithe of the steam line is great enough to prevent anysubstantial solution of carbon dioxide in whatever If for any reason, such as the recent addition of fresh water, the normal alkalinity of the contents of the boiler should be too low, it will be within the intent and scope of the present invention to add to the water, either in the boiler 5 or at any other point, a suflicient amount of a, substance yielding hydroxyl-ions to give it the Thus, for example some, alkali might be addedv to the wateras it flows.

from the boiler towardits distributing 'poirit-ft'yrw introduction into the ,return'lines. Suitable pro.-

vision may be made for'locating a tank holding f a concentrated alkaline solution, as at 35, c'o n-' 1 nected with the steam-line 4 and the boilerwater-line 23, respectively, by the pipes II and 31. A suitable injection device (as a pump,-in-

. Jector, etc.) 38 may serve to'inject arequired 'amount of the alkaline solution into thewater.

Obviously, the alkaline solution may, however, be added at any point between the boiler and where the boiler water mixes with the condenser water.

The present invention is applicable to all heating systems, large or small, but is particularly applicable to the heating of tall buildings, such as hotels, apartment houses, and omce buildings, where the very long return lines and the amount of cooling that takes place therein produces a serious corrosion problem. It has been found that, when operating in accordance with applicants invention, all corrosion problems in the retum lines are overcome and that these remain clean and unrusted for a long period of time.

It is usual in commercial boiler practice to soften the water that is fed into a steam boiler by means of lime and soda ash and sometimes, additionally, by the use of sodium aluminate.

.But, in any case, the water will contain dissolved carbonates and these will give rise to the production of carbon dioxide, which then causes the dimculties which applicant solves. 40

The amount of boiler water which is to be fed into the return lines represents only a small amount of the volume of the condensate water and must be gauged in each case by the particular conditions of the boiler. In other words, if 5 there is much carbonate in a boiler, there will be a relatively large amount of carbon dioxide, but then also the boiler water will be quite alkaline so that it will not require as much as would otherwise be the case. No hard and fast criterion can be given for the amount of boiler water to be fed into the return lines, for this can readily be tested by the operator by titrating the condenser water with an alkali until he has obtained a reaction alkaline to phenolphthalein. In other words, it is desired to bring the condensate water to a hydrogen-ion concentration which shows alkaline with phenolphthalein indicator; and hat is around pH 9 to 11.

Applicant does not wish to be limited to the precise construction shown in his drawings, as these are purely diagrammatic and illustrative. Known equivalents for the means for feeding the water, etc., and-for distributing the steam and for returning the condensate water to the boiler. are to be construed as within the scope of his invention, for which the following claims are made:

1. The process of preventing corrosion of condensate-return lines of a steam-heating system having a boiler, radiators, and steam-supply and condensate-return pipes, which comprises directing a portion of the water contained in the boiler into said condensate-return line near a point where said condensate water enters said return line. 16

which comprises adding to said condensed water at about the point where it enters said return line a suflicient. amount of hydroxyl-ion containing Water drawn from the boiler used in said heating system to bring the hydrogen-ion concentration of the resulting mixture to an alkalinity of at least pH 9.

3. The process of preventing corrosion of radiator equipment and condensate-retum lines of a steam-heating system which comprises admitting to said radiators, in conjunction with the steam derived from a steam boiler, a suflicient amount of the water from said boiler to overcome the acidity of carbon dioxide contained in said steam.

4. In a steam-heating system involving the use a of a steam boiler, radiators, and condensate-return lines, all operatively interconnected, the improvement which comprises connections for injecting water contained in said boiler into said radiators and condensate-return lines.

5. A steam-heating system comprising, in combination, a steam boiler, a steam-supply line connected therewith, radiators connected with said supply line, condensate-return hues connected with said radiators, and a pipe-line connecting said boiler with said steam-supply line and said condensate-return line in such a manner that water from said boiler may be introduced into said steam-supply line and condensate-return line.

6. A steam heating system comprising, in combination, a steam boiler, a steam-supply line therewith connected, radiators fed by said steam line, a condensate-return line, means connecting said radiators with: said return line, means for taking water from said boiler, and means ior directing water thus taken into said return line at a point near where the radiators are connected with said return line.

7. Theprocess of preventing corrosion of condensate-return lines of steam-heating systems in 8. A steam-heating system comprising, in combination, a steam boiler, vertical steam-supply lines therewith connected, radiators fed by said steam lines, means for taklng'water from said boiler, means for increasing the alkalinity of the water thus withdrawn, and means for spraying the thus alkalinized water into said steam lines.

9. The process of protecting a steam-heating plant against internal corrosion by carbon-dioxide-containing steam, which comprises sombbing the carbon dioxide from the steam by means of an alkaline liquid. 4

10. The process of protecting a steam-heating plant against internal corrosion, which comprises passing the steam as it comes from the boiler 15 through a spray of water withdrawn from the boiler that generates the steam.

11. The process of protecting a steam-heating plant against internal corrosion by carbon dioxide which comprises scrubbing the steam before it go enters the radiator equipment of the plant with a spray of water. withdrawn from the boiler that furnishes the steam.

12. A steam-heating system comprising in combination a steam boiler, a vertical steam conducting pipe leading therefrom, a horizontal steam conducting pipe and a second vertical steam conducting pipe through which steam passes downwardly, the latter pipe being connected with the boiler below the water line thereof, branch pipes leading from said downwardly directed steam pipe, radiators attached to said branch pipes, and a connection frombelow the water line of said boiler with said downwardly directed steam pipe so as to spray boiler water into said downwardly directed pipe to scrub the carbon dioxide from the steam but without ad-" mitting water tosaid radiators, the water being permitted to return to the boiler.

13. The method of protecting the radiator and condensate-return line system of a steam-heating plant comprising a boiler, which comprises directing steam from the boiler to said radiator, withdrawing water from the boiler and spraying the same into the steam on its'way to the radiator 45 so as to scrub the carbon dioxide contained in the steam therefrom, without permitting the water thus introduced into the steam from entering thev radiator.

ROBERT LESLIE HOLMES. g

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