US 3004714 A
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Description (OCR text may contain errors)
-. 1961 J. E. FEARON 3,004,714
HEATING SYSTEM Filed Jan. 14, 1958 VENT s2 SUPERHEATED g? I8 24 2o consensus:
' MAKEUP AIR FORGED 74 DRA FT FAN 64 INVENTOR.
JOHN E. FEARON a, M; ZZ
ATTORNEYS U it d sm siB 1" 3,004,714 HEATING SYSTEM I John E. Fear-on, Atlanta, Ga., assignor to Cochrane Corpolratitgn, Philadelphia, Pa, a corporation of Pennsy van a Filed Jan. 14, 1958, Ser. No. 708,898 1 Claim. (Cl. 237--67) This invention relates to a heating system and has particular reference to a steam heating system in which the heating steam originates as high temperature superheated steam.
While the invention is applicable to other uses, the problem involved may be beSt discussed as it is presented in a steam turbine power system in which it is desired to heat air supplied for combustion in a boiler.
It has been customary to heat'the air to be used for combustion by passing it in-heat exchange relationship with steam heated coils trapped to a vented receiver, condensate being then pumped back into the feedwater system. The steam most economically available for this use is turbine extraction steam which is superheated and, with a pressure in the range of 50 to 55 pounds per square inch gauge, the temperature of the steam may be typically around 520 F. At this temperature expensive equipment is required.
3,004,714 Patented Oct. 17, 1961 being respectively controlled by check valves 24 and 26.
More recently there has been a trend away from the I use of steam for air heating and toward the use of hot water recirculated from and back to a deaerator. The water is passed through finned heaters to preheat the air. For effective heating, and since the latent heat of vaporization is not available, the quantities of water which must be handled are quite high involving the use of costly water pumps and power for driving them. The advantage of the use of water is that low pressure steam may be used in the deaerator to reheat the water.
The present invention relates to a system, which as applied to this problem, involves introduction of superheated turbine extraction steam into a deaerator wherein the steam is reduced to saturation temperature. Saturated steam having, typically, a temperature of 302 F.
at 55 pounds per square inch gauge is introduced into the air heating coils wherein the latent heat of vaporization becomes available for the air heating, and the condensate may be returned to the deaerator. Through the use of this arrangement the air heating coil arrangement may be relatively inexpensive and the return pumping arrangement far less expensive. from the standpoint of both installation costs and operation than in the case of the water system.
The general objects of the invention relate to the provision of a system of the'type just indicated, and will become apparent from the following description, read in conjunction with the accompanying drawing in which the figure is a diagram showing the elements involved in a preferred embodiment of the invention.
In the drawing a boiler is indicated at 2 and a steam turbine at 4. A superheated steam extraction conduit is indicated at 6. A forced draft fan 8 supplies combustion air through conduit 10 to the boiler and there is indicated at 12 an air preheater including a heating coil 14. This heater is conventionalized in the drawing but it will be understood that it may have any suitable form known in the art. In accordance with the prior art a heater such as 12 was either arranged to receive hot water or superheated steam and its construction had to correspond to the heating medium; In particular, the heater was expensive if superheated steam was used.
A generally conventional deaerator is indicated at 16. Water is fed to this deaerator through connection 18, which receives makeup and condensate from the turbine condenser at 20 and heater condensate at 22, these lines Theconduit 18 inside the heater communicates with a distributing head 28 having spray openings to provide a spray of the water. The water passes downwardly through passages 30 in heat exchange with the enteringsuperheated steam which flows into a chamber 32 from conduit 6 and then passes into a chamber 34 surrounding the passages 30, thence flowing downwardly at 36 to meet the water in the water box 38 from which the admixed steam and water flow downwardly over the distributing trays 40 and the air separating trays 42. The deaerated water flows through connection 44 to a receiver 46 from which the boiler feed pump 48 introduces it into the boiler 2. Steam passes outwardly at 50 from the region below the trays 42 and then through connection 52 where it meets the water spray, condensation being there effected. Air and other fixed gases escape through vent 54.
The deaerator arrangement just described is essentially conventional both in its construction and in its association with the boiler and turbine. For purposes of the present invention steam is extracted at 56, passing through the valve 58 to the air heater coil 14. The steam at the point of withdrawal has been desuperheated by reason of its attaining equilibrium with the water in the passage through the trays 40 and 42 and is in essentially saturated condition at a temperature corresponding to the pressure involved in the deaerator. In the form of saturated steam it may be used most effectively for air heating since its latent heat of vaporization is available and it is at a relatively low temperature compared with the superheated extraction steam constituting its source. The heater 12 may accordingly be of relatively inexpensive type. The entrance of steam to the heater is controlled by the valve 58, in turn controlled by controller 60 responsive to a thermostat 62 located in the air stream. This single control alone is required to maintain proper operation. Only so much steam as is required for temperature maintenance is withdrawn from the deaerator, the remaining steam in the latter being condensed by the water spray.
Flow of steam and removal of condensate is desirably effected through the conduit 64 by the jet and centrifugal pump arrangement illustrated at 66. The system here involved is that described in the patent of John G. Williams, 2,612,112, dated September 30, 1952. While various arrangements may be used, that specifically illustrated herein involves a loop 68 provided with cooling fins 70 through which water is recirculated by a centrifugal pump 72 providing at 74 a jet in an eductor producing suction through the conduit 64 with advantages such as are described in said patent. Outflow of condensate is provided at 76 to the connection 22.
As will be evident from the foregoing, a system is provided by which heating may be effected by saturated steam eliminating the disadvantages of utilizing superheated steam or hot water, and this is carried out by taking advantage of the saturated steam condition existing in a deaerator which is involved in the system to perform its usual functions.
While reference has been particularly made to the preheating of air for combustion in the power plant in which the invention is incorporated, it will be evident that the invention may be applied to the economic heating of materials, spaces, or the like utilizing as a source of heat that available in superheated steam. It is accordingly to be understood that the invention is not to be regarded as limited except as required by the following claim.
What is claimed is:
A system comprising a deaerator having means for the mixing of superheated steam and water in hea t exchange relationship and producing substantially saturated Referenees Cited in the file of this patent UNITED STAIl-ES PATENTS Gibsen July 5, 1927 Arrowsmith Nov. 8, 1955 FOREIGN PATENTS 10, 1950 Great Britain May