US2741327A - Water deaerating apparatus - Google Patents

Description

o. H. HEDRICH EI'AL 2,741,327

WATER DEAERATING APPARATUS April 10, 1956 Filed Oct. 2, 1952 OTTO H. HEDRlCH AND' CHADWELL O'CONNOR JNVENTORS ATTORNEY United States Patent WATER DEAERATING APPARATUS Otto H. Hedrich and Chadwell OConnor, Pasadena, Calif., assignors to The Permutit Company, New York, N. Y., a corporation of Delaware Application October 2, 1952, Serial No. 312,808

1 Claim. (Cl. 183-.2.5)

This invention relates to improvements in water deaerating apparatus as more fully hereinafter set forth and as claimed.

In the operation of modern boiler plants in power stations it is general practice to obtain steam for heating and deaerating the feed water from a stage of a steam turbine. The pressure at any given stage of a steam turbine is subject to increases and decreases with increases and decreases of the load.

When a water deaerator is in operation it contains a relatively large amount of water at a temperature and pressure which closely correspond to the temperature and pressure of the steam supplied to it. If the load suddenly decreases, the pressure of the steam available from the turbine stage to the deaerator also decreases. Because of such reduction in pressure the Water in the deaerator begins to boil and give up steam without any immediate substantial reduction in pressure within the deaera-tor tank. It is apparent therefore that the 1636mtor will not, under these circumstances, receive any heating steam from the turbine; on the contrary, there is a-tendency for flashed steam to flow from the deaerator into the turbine. Under these conditions the incoming water is, of course, not being properly .deaerated.

It is an object of our invention to provide an arrangement of deaerator and deaerated water storage in which a supply of steam for heating and deaerating the incoming feed water is assured at periods of diminishing load; and more particularly an arrangement in which the deaerated water storage tank serves as a steam accumulator during :periods .of diminishing load.

Another object of this invention is to provide an arrangement in which steam flashed in the deaerated water storage tank is used for deaerating the incoming boiler feed water without being able to bypass the deaerating zone.

Other objects will become apparent from the following description and from the appended drawings in which:

Fig. 1 is a diagrammatic showing, partly in cross-section, of an apparatus embodying our invention; and

Fig. 2 is a modification of the apparatus shown in Fig. 1.

The deaerating apparatus shown and described is of the general basic type disclosed in Yoder U. S. Patent 2,241,873 dated May 13, 1941, on which this invention is an improvement.

Referring now to Fig. l, the apparatus comprises an enclosed deaerator tank and a deaerated water storage tank 11. Water to be deaerated is admitted to the upper portion of tank 10 through a connection 12 leading to an inlet compartment 13 provided with spray valves 14 (only one being shown) which spray the water into the upper portion 16 of the tank. The tank 10 is divided by a plate 15 into an upper section 16 and a lower section 17 which communicate with each other through a vent passage 18. A bafl'le 19 prevents water discharged by the spray valves 14 from entering the vent passage 18.

A vertical passage 20 provided with vortex breaking pounds per square inch absolute.

2,741,327 Patented Apr. 10, 1956 2 bellies :21 leads from the upper section 16 to a horizontal passage 22 and thence to a scrubbing section 23 which has a perforated wall 24 in common with a steam chest 25. The steam chest 25 is connected by a pipe 26 through a check valve 27 with a source of steam such as the stag of a steam turbine (not shown). The lower sec.- tion 17 is provided with an overflow 28 leading through vaive (not shown) to a point of disposal for excess water. The upper section 16 is provided with a vent 29.

The storage tank 11 is provided with a deaerated water outlet 30 in its lower portion. A passage 31 leads from the lower portion of the lower section 17 ,to a point in storage tank 11 adjacent to and directly above the outlet 30. A vertical cylindrical wall 32 is fastened to the bottom of tank 11 in such fashion as to surround the outlet 30 and the lower end of passage 31. The wall 32 is provided with one or several notches or openings 33 to permit complete draining of tank 11 through outlet 30. A steam pipe 35 interconnects the top or" tank 11 with the steam chest 25. In the modification shown in Fig. 2, a pipe 36 connects the top of storage tank 11 with the steam pipe 26. jPipes 35 (Fig. l) and 36 (Fig. 2) are obviously equivalent in "function.

In operation, steam supplied through pipe 26 to steam chest 25 flows through the perforated wall 24 into the scrubbing section 23 where it mixes with and effectively deaerates the Water therein. Thence the steam passes, as indicated by dotted arrows, through vent passage 1%; into the upper section 16 where it preheats the water that is admitted through the spray valves 14. Uncondensed gases escape through the vent 29. The preheated water flows, as indicated by solid arrows, through vertical passage 20 and horizontal passage 22 to the scrubbing section 23 where it is being deaerated, thence through the lower section 17 and passage 31 into the deaerated water storage tank 111. From the tank 11 the water is withdrawn by a boiler feed pump (not shown) through the outlet 30,

Let it be assumed that steam is being supplied to pipe 26 from a stage in the turbine where the pressure is 120 pounds per square inch absolute while the turbine is operating at full load. Let it further be .assumed that the load now suddenly drops to 25% of full load accompanied by a drop in pressure in .pipe 26 from 120 to 20 With steam under pressure no longer flowing through pipe 26 to the steam chest 25 the incoming water discharged by spray valves 14 quickly condenses the steam in the upper section 16 and the pressure therein drops. When the pressure in tank 10 has dropped just a small amount, such reduction in pressure is communicated through pipe 35 (or pipe 36 in Fig. 2) to the storage tank 11 with the result that some of the water in the storage tank 11 flashes into steam which flows through pipe 35 into the steam chest 25, thus supplying steam for deaerating the water in the scrubbing section 23 and for preheating it in the upper section 16. Thus operation continues with the pressure in the deaerator tank 10 and the storage tank 11 gradually diminishing as steam is being flashed from the deaerated water storage. Eventually, the pressure in tanks 10 and 11 will have diminished to a point where it equals the pressure in the turbine stage connected to pipe 26 and from that point on the deaerator will again operate with steam supplied from the turbine.

A typical size of deaerator is one that is capable of deaerating 500,000 pounds of steam per hour at full load, and that is provided with a storage capacity of 100,000 pounds which can thus provide boiler feed water at per cent rating for 12 minutes. water entering chamber 13 at 60 F., 284 B. t. u. are required to heat one pound of water to a temperature of 341 F. corresponding to p. s. i. abs, or 168 With the feed B. t. u. to heat it to 228 F. corresponding to 20 p. s. i. abs. Thus, during the gradual reduction in pressure from 120 to 20 p. s. i. abs. an average of about 226 B. t. u. is required to heat and deaerate one pound of water.

Each pound of water in the storage tank 11 is able to give up 116 B. t. u. as the pressure drops from 120 to 20 p. s. i. abs. Thus the storage tank, containing 100,000 pounds, can supply 11,600,000 B. t. it. which will be contained in flashed steam passing through pipe 35 into the steam chest 25. This steam is capable of heating and deaerating approximately 51,000 pounds of water. In other words, upon such sudden drop in load from 100% to 25% satisfactory deaeration will be provided by steam from storage tank 11 acting as accumulator for a period of about 25 minutes While the presence gradually drops in the system; then the operation will continue with steam supplied by the turbine to V pipe 26.

U or pipe 36 of Fig. 2 any steam flashed in the deaerator during or after a drop in load would serve to heat the water discharged by the spray valves 14 and so be condensed, but no such steam would reach the scrubber section 23 so that complete deaeration would not be attained.

The check valve 27 is, of course, provided to prevent any back flow of flashed steam to the turbine which might otherwise occur during periods of diminishing load.

The arrangement of the lower end of pipe 31 adjacent to outlet 30 with the wall 32 surrounding them provides two important features: first, even with the storage tank 11 empty or nearly empty, the water within wall 32 forms a seal preventing steam from rising through pipe 31; any such steam would by-pass the scrubbing section 23 and would, therefore, not be useful in effective deaeration. Secondly, this arrangement supplies freshly deaerated water to the outlet 30 with the water stored in tank 11 floating on the line, and during periods of may be made without departing from its spirit, and refencc is, therefore, made to the appended claim for a definition of the scope of our invention.

What we claim is:

Water deaerating apparatus comprising an enclosed deaerator tank, a primary deaeration stage in the upper portion of said tank and a secondary scrubbing section in saidtank below said primary deaeration stage, means for admitting water to said primary deaeration stage and a pipe conducting such water from said primary stage to said secondary scrubbing section, a steam chest adjacent to said secondary scrubbing section, means for admitting steam from said steam chest to the lower portion of said secondary scrubbing section, means for connecting said steam chest with a source of steam, steam passage means for conducting steam from said secondary scrubbing section to said primary deaeration stage, means connected with said primary deaeration stage for removing uncondensed gases, a deaerated water storage tank below said secondary scrubbing section, water passage means for conducting water from 'said secondary scrubbing section to said storage tank and terminating adjacent to the bottom of said storage tank, a deaerated water outlet in the bottom of said storage tank, said water passage means terminating adjacent to said deaerated water outlet, a vertical wall surrounding said deaerated water outlet and the lower end of said water passage means, a flow passage between the lower portion of said vertical wall and the bottom of said storage tank, and a steam passage for establishing communication between the top of said storage tank and said steam chest.

References Cited in the file of this patent UNITED STATES PATENTS 1,914,166 Rohlin June 13, 1933 2,078,288 Sherman Apr. 27, 1937 2,204,062 Applebaum June 11, 1940 2,223,237 Cooke Nov. 26, 1940 2,241,873 Yoder May 13, 1941 2,277,368 Rohlin Mar. 24, 1942 2,308,719 Seabald et a1 Jan. 19, 1943 2,559,129 Miller July 3, 1951 2,564,584 Seabald Aug. 14, 1951 2,580,791 Kahn Jan. 1, 1952 2,671,524 Gilwood Mar. 9, 1954 FOREIGN PATENTS 638,198 Great Britain May 31, 1950

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