US3791351A

US3791351A - Desuperheater

Info

Publication number: US3791351A
Application number: US00267765A
Authority: US
Inventors: H Kent
Original assignee: Rohm and Haas Co
Current assignee: Rohm and Haas Co
Priority date: 1972-06-30
Filing date: 1972-06-30
Publication date: 1974-02-12
Anticipated expiration: 1991-02-12

Abstract

A fluid desuperheater including a housing for a heat-exchanger having a tube, conduit or pipe for the passage of superheated fluid, such as steam, therethrough, an air inlet duct, air feeding means, and air outlet duct and a by-pass duct, the amount of air being bypassed from the outlet to recycle being controlled by interconnected valves controlled by outlet fluid temperature.

Description

waited States terrt [1 1 Kent [4 1 Feb. R2, 1974 1 DESUPERHEATER [75] Inventor:

[73] Assignee: Rohm and Haas Company,

Philadelphia, Pa.

[22] Filed: June 30, 1972 [21] Appl. No.: 267,765

Harry S. Kent, Levittown, Pa.

[52] 11.5. C1 122/479 D, 122/480, 165/34, 165/39, 165/108 [51] Int. Cl. F22g 5/00 [58] Field of Search... 122/459, 479 R, 479 D, 480; 165/34, 35, 39, 108

[56] References Cited UNITED STATES PATENTS 2,445,199 7/1948 Williams 165/34 X 1,231,894 7/1917 Jacobus 165/39 X 2,104,333 1/1938 Rosenblad 165/34 X 2,665,840 l/l954 Powell 165/108 X 2,671,643 3/1954 Gordon, Jr 165/108 X Primary ExaminerWilliam F. ODea Assistant Examiner-Peter D. Ferguson [5 7] ABSTRACT A fluid desuperheater including a housing for a heatexchanger having a tube, conduit or pipe for the passage of superheated fluid, such as steam, therethrough, an air inlet duct, air feeding means, and air outlet duct and a by-pass duct, the amount of air being bypassed from the outlet to recycle being controlled by interconnected valves controlled by outlet fluid temperature.

5 Claims, 2 Drawing Figures DESUPERHEATER The present invention is directed to a desuperheater. More particularly, the present invention is directed to a steam desuperheater utilizing ambient air and a bypass system which is useful for dependable, small to moderate-sized units serving chemical and industrial process industries.

Many industrial processes requiring heating may operate with superheated steam, since they usually can tolerate superheat which would dissipate rapidly in the heat exchanger or steam-jacketed kettle. When a process requires steam and can tolerate only a limited degree of superheat or none in the steam, for example, due to reaction control or degradation problems, desuperheaters must be applied to reduce or eliminate the superheat in a portion of the boiler output when another portion of the steam produced can tolerate, or requires, superheat or a higher degree of superheat than the first-mentioned portion. Standard desuperheaters utilizing water for desuperheating require almost pure water, such as condensate or demineralized water, which may or may not be available. When condensate or demineralized water is not available or is inadequately available and a conventional water injection-type desuperheater is necessary, a demineralizing unit, a desuperheater pump and a desuperheater unit are required. Thus, significant expenses are incurred in installation, labor, and maintenance to provide desuperheated steam when needed in small or moderate amounts by the use of standard equipment.

Further, in the past, small desuperheating installations have often had inherent maintenance and operating requirements and problems. For a continuously operating system, the desuperheater must be on-line at all times and utmost reliability is required. Systems wherein frequent cleaning or other maintenance are required are often unsatisfactory.

In the prior art, both water and combustion air for the boiler have been utilized to control the superheat of the steam exiting a boiler. For example, in Pat. No. 2,063,441 a desuperheater is disclosed which utilizes finned tubes for cooling water and passes superheated steam around the tubes. This type of system, however, in utilizing steam and water has both corrosion and scaling problems.'

Numerous other systems, such as those dislosed in Pat. Nos. 3,095,864 and 3,150,643 use relatively complex equipment to provide for the desuperheating at the boiler. However, when the temperature of the steam provided is of great importance, the amount of time required for the transmission of the steam in the superheated state to the point of use can be very important. Thus, when desuperheated steam is needed at a point remote from the boiler or other source of steam generation, some means of controlling the steam superheat is frequently needed at the point of use.

The present invention overcomes these problems by the provision of a simple, reliable and easily controlled desuperheating apparatus which is self-contained so that it may be located in close proximity to the ultimate use of the desuperheated fluid and does not require structural modification of the boiler or evaporator which serves to generate the superheated fluid. The present system may utilize superheated steam or other fluid from a normal in-plant conduit, such as a steam line, pass it directly through the desuperheating unit,

and then directly into the equipment wherein it is utilized. Thus, the apparatus of the present invention avoids problems with regard to long distance transmission of desuperheated fluids, does not require the ex pensive and complex boiler attachments, and by means of the use of ambient air is reliable and inexpensive to operate.

Therefore, the present invention has as one of its objects the provision of a desuperheater which is continuously dependable and not severely demanding in regard to maintenance.

A further provision of the invention is a desuperheating device which can be located in close proximity to the equipment which ultimately utilizes the desuperheated fluid.

These and other objects will become obvious from the remainder of the present disclosure.

In the drawings, FIG. 1 is an overall schematic diagram of the apparatus of the present invention.

FIG. 2 shows the valving or baffle arrangement that may be utilized in an embodiment of the present invention in which the discharge and bypass ducts have a modified arrangement as compared to that in FIG. 1.

In FIG. ll, ambient air enters through conduit 1 and is pumped by means of, e.g., a fan 2 which is arranged to discharge through inlet conduit (air-supply duct) 4 to the desuperheater, the housing of which is indicated generally as 5. As shown, air-supply duct 4 is at, and is connected to, the lower end of housing 5 and the fan 2 is arranged to discharge into the duct 4 to force air through the duct into a lower part of the housing 5. The amount of ambient air entering through conduit 1 and thereby the amount of ambient air that is passed through housing 5 is further controlled by the amount of air forced to be recycled through bypass conduit 3. The air in the desuperheater housing 5 passes around heated exchange tubes 12 through which the superheated fluid is passed and which are shown as finned. The tubes may be of any desired design in order to meet the heat transfer requirements expected. The heated air then passes upwardly through conduit 6 and either out through conduit 7 or is bypassed back to inlet conduit 4 by means of bypass conduit 3. As shown, air-discharge conduit 7 is at, and connected to, an upper part of the housing 5 and the bypass duct 3 communicates at its upper end with duct 7 and extends downwardly to its lower end which communicates with the suction side of fan 2. The housing 5 and the

ducts

1, 3, 4, 5, 6, and 7 are preferably provided on their exterior surfaces with suitable heat-insulation. The sections of conduits 11 and 13 that are outside the superheater housing 5 are also preferably provided with suitable heat-insulating jackets.

The relative amounts of air exhausted through 7 or bypassed through 3 and returned to the desuperheater is controlled by interconnected butterfly valves or

dampers

8 and 9 which are controlled by the temperature controller 14 which senses the temperature in conduit 13 through which the desuperheated steam is passed as more particularly discussed below. The but terfly valves or plates shown may be dampers or damper plates mounted pivotally on axes extending transversely of the respective air-discharge and bypass ducts. Instead of a single damper plate, there may be used a plurality of louvres, each being individually mounted on pivotal motion on parallel axes extending transversely of the respective ducts. The controller may be a temperature recorder controller which records the temperature or any other flow-controlling system which may be interlocked so as to operate jointly.

superheated fluid, such as steam, enters the desuperheater through conduit 11, preferably at the pressure and flow rate desired for the ultimate use, including an allowance for pressure loss through the desuperheater and flow rate loss due to fluid removal. The superheated fluid passes through the inside of a heatexchanger comprising one or more intercommunicating finned tubes 12 and exits from desuperheater 5 via conduit 13. A temperature recorder controller is provided on conduit 13 to sense the desuperheated fluid temperature and to actuate in response to the temperature, interconnected

valves

8 and 9 via control line or wire and actuator 17 which may be a pneumatic motor, piston or diaphragm or an electrically driven motor. The desuperheated fluid also passes by steam trap 16 which removes any condensate which may have formed in the lines and is then directed to the equipment to be served via conduit 13.

FIG. 2 illustrates an interconnecting linkage for actuating the

dampers

8 and 9. The line 15 from temperature recorder controller 14 passes into actuator mechanism 17 which controls the position of primary linkage 18 and thus the relative positions of the dampers. In the embodiment shown, wherein the bypass damper 9 is closed and the exhaust damper 8 is fully open, primary linkage 18 is pivotally connected to bypass control] arm 19 which is fixed to bypass damper 9.

Dampers

8 and 9 are fixedly secured to central pins or trunnions 23 which serve to provide horizontal axes of rotation transverse to the ducts 3 and 7. Arm 19 is fixedly secured to intermediate arm 20. Intermediate arm 20 is further pivotally connected to connecting arm 21 which is pivotally connected to exhaust control arm 22. The exhaust control arm is fixedly attached to exhaust damper 8, shown in the open position. However, other control means may be utilized so long as means are provided to control the relative amounts of air being exhausted and bypassed. This control is responsive to the temperature sensed in the desuperheated fluid.

By way of an example, an extended surface area heat transfer tube system, e.g. having a ratio of extended surface (fins) to tube surface of about 4011, or any other ratio depending on requirements, can be utilized for the tubes of the present invention and placed inside an

insulated duct system

3, 4, 5, 6, and 7 having an air inlet and an air circulating fan. A temperature controller 14 is provided for controlling the

dampers

8 and 9 and is connected to the outlet pipe 13 of the desuperheater 5. The temperature sensing device 14 may be set for a temperature variation of, for example, i 3 to 5F. of the effluent fluid in line 13.

The desuperheating device of the present invention is quite simple. Economical use may be made of the system since the heated air discharged through duct 7 may be utilized as part of a forced-air heating system in the winter time. Further, modifications or changes within the spirit and scope of the present invention may be utilized in the apparatus of the present invention. For example, different bypass and exhaust valving systems may be utilized, various blower systems may be utilized, and various types of tubes may be utilized to control the heat transfer.

What is claimed is:

1. A self-contained unit of apparatus for desuperheating vaporized fluids utilizing ambient air as the cooling agent and adapted to be located in close proximity'to the ultimate use of the desuperheated fluid comprising a housing, a heat exhange device therein having a tube for the passage of superheated fluid therethrough, inlet and outlet pipes extending outside the housing and communicating with the tube, an airsupply duct, at and connected to, a lower part of the housing, fan means arranged to discharge into the duct to force air therethrough into a lower part of the housing in heat-exchange relationship with the heat exchanger, an air-discharge duct, at and connected to, an upper part of the housing to receive the air from the heat exchanger in the housing and having a section through which air may pass to be exhausted from the unit, an air bypass duct communicating at its upper end with the air-discharge duct and extending downwardly to its lower end in direct communication with the suction side of the fan means, and air-flow proportioning means for controlling the relative volumes of air exhausted and recycled through said bypass duct, the latter proportioning means having interconnected valve means in the air-exhaust duct and the bypass duct.

2. The apparatus of claim 1 wherein said proportioning means includes means for sensing the temperature of the superheated fluid discharged from the unit.

3. The apparatus of claim 2 wherein said proportioning means further includes means in said air exhaust duct for varying its internal cross-sectional area effective to permit air flow therethrough, means in said bypass duct for varying its internal cross-sectional area to permit air flow therethrough, and means interconnecting said means in the air exhaust duct withsaid means in the bypass duct to vary the effective cross-sectional area in one of the ducts in inverse relation to the other.

4. The apparatus of claim 3 wherein said crosssectional area varying means are plates mounted pivotally on axes transverse of the ducts in which they are disposed.

5. The apparatus according to claim 1 in which the air-supply duct is connected to the bottom part of the housing and the air-discharge duct is connected to the top of the housing.

Claims

1. A self-contained unit of apparatus for desuperheating vaporized fluids utilizing ambient air as the cooling agent and adapted to be located in close proximity to the ultimate use of the desuperheated fluid comprising a housing, a heat exhange device therein having a tube for the passage of superheated fluid therethrough, inlet and outlet pipes extending outside the housing and communicating with the tube, an air-supply duct, at and connected to, a lower part of the housing, fan means arranged to discharge into the duct to force air therethrough into a lower part of the housing in heat-exchange relationship with the heat exchanger, an air-discharge duct, at and connected to, an upper part of the housing to receive the air from the heat exchanger in the housing and having a sectiOn through which air may pass to be exhausted from the unit, an air bypass duct communicating at its upper end with the air-discharge duct and extending downwardly to its lower end in direct communication with the suction side of the fan means, and air-flow proportioning means for controlling the relative volumes of air exhausted and recycled through said bypass duct, the latter proportioning means having interconnected valve means in the air-exhaust duct and the bypass duct.

3. The apparatus of claim 2 wherein said proportioning means further includes means in said air exhaust duct for varying its internal cross-sectional area effective to permit air flow therethrough, means in said bypass duct for varying its internal cross-sectional area to permit air flow therethrough, and means interconnecting said means in the air exhaust duct with said means in the bypass duct to vary the effective cross-sectional area in one of the ducts in inverse relation to the other.

4. The apparatus of claim 3 wherein said cross-sectional area varying means are plates mounted pivotally on axes transverse of the ducts in which they are disposed.