Method Of And Device For Conditioning Steam

Abstract

Steam is conditioned, to reduce its temperature and pressure, by introducing cooling water into the steam and thereafter reducing the steam pressure.

Description

This invention relates to conditioning temperature and pressure of fluids and is more particularly concerned with simultaneously reducing the temperature and pressure of superheated steam.

Heretofore it has been customary to subject superheated steam first to pressure drop and then to inject desuperheating water. That is, the temperature-reducing water is introduced into the steam downstream from the usual steam pressure-reducing valve. This has required a long extent of pipe downstream wherein cold water is sprayed through a temperature controlled valve and spray nozzle structure. It has also been proposed to spray water into the throat area of the pressure-reducing valve and mixing occuring downstream in a straight run portion of pipe. In addition to the disadvantage of the necessity for a relatively long section or run of pipe downstream from the pressure-reducing valve, the prior arrangements have further had the disadvantage of difficulty in attaining uniform mixing of the cooling water with the steam, inefficient heat transfer, tendency toward noisy operation, requirement for interstage pressure taps on the feedwater pump, difficulty in controlling the turndown ratio, requirement for desuperheaters, high alloy steel downstream pipelines, bypass valves, etc., all of which have required costly equipment and have left much to be desired in function and results.

An important object of the present invention is to overcome the foregoing and other disadvantages, defects, inefficiencies, shortcomings and problems in prior methods and structures and to attain important improvements and advantages through the new method of and device for conditioning steam to simultaneously reduce its temperature and pressure, as will hereinafter be more particularly described.

Another object of the invention is to provide a new and improved method of and device for conditioning steam to reduce its temperature and pressure attaining numerous advantages not only in proportioning the cooling water flow rate to steam flow rate but also in attaining maximum heat transfer efficiency with the cooling water.

A further object of the invention is to provide a new and improved method of and device for reducing steam temperature and pressure attaining improved mixing of the cooling water with the steam.

Still another object of the invention is to provide a new and improved method of and device for reducing steam temperature and pressure economically and without apparatus heretofore deemed necessary for the purpose.

Yet another object of the invention is to provide a new and improved method of and device for conditioning steam by reduction in temperature and pressure attaining high efficiency at low cost.

Other objects, features and advantages of the invention will be readily apparent from the following description of a preferred embodiment thereof, taken in conjunction with the accompanying drawing, although variations and modifications may be effected without departing from the spirit and scope of the novel concepts embodied in the disclosure, and in which:

FIG. 1 is a vertical sectional detail view through a typical example of a device for practicing the present invention; and

FIG. 2 is an enlarged fragmentary detail view taken substantially along the line II--II of FIG. 1.

According to the present invention steam is conditioned to reduce its temperature and pressure by introducing cooling water into the steam and thereafter reducing the steam pressure. This is accomplished with high efficiency and economy in a device representatively depicted in the drawings and comprising a high energy loss fluid control valve 5 wherein steam entering a housing 7 by way of an inlet 8 is subdivided and confined in a plurality of individual streams extending throughout a substantial length of travel through an annular control disk stack 9, thence passing into an encompassing chamber 10 within the housing and thence out through an outlet 11. It is understood, of course, that suitable piping will be connected to the inlet 8 and the outlet 11. In passing through the control disk stack 9, the steam is greatly subdivided in a generally labyrinth arrangement of flow control passages exemplified in FIG. 2, wherein each of numerous individual disks 12 in the stack has at least on one face thereof a plurality of flow-subdividing and confining control passageways 13 providing a large number of angular turns between the inner perimeter of the annular stack and the outer perimeter thereof so that as the plurality of subdivided streams travel therealong high frictional resistance losses are imparted to the flowing fluid, in accordance with the teachings in my U.S. Pat. No. 3,514,074 issued May 26, 1970. As a result highly efficient control of both velocity and pressure of the fluid are attained in a substantially erosion-free, quiet and vibration-free manner in minimum operating space.

Steam flow rate through the pressure-reducing disk stack 9 is adapted to be controlled by means of a valve plug 14 which is reciprocably slidably mounted within the central bore defined by the tubular arrangement of the stack whereby entry of the steam from the inlet 8 into the entrance openings into the pressure-reducing passages 13 is regulated. Operation of the plug 14 is effected by means of a valve stem 15 projecting from one end of the housing and provided with an actuating head 17 which may be in the form of a follower or cam yoke adapted to be operated by suitable cam device responsive to steam pressure at or adjacent to the inlet 8, thereby maintaining through the action of the valve plug 14 uniform steam pressure-responsive flow rate or volume through the pressure-reducing disk stack 9.

According to the present invention, highly efficient, economical steam temperature reduction is attained by introducing cooling water into the steam before the steam passes through the pressure-reducing disk stack 9. To best advantage, introduction of the cooling water to the steam is effected in the region of the valve end face of the plug 14. To this end, cooling water is introduced into the steam, preferably under suitable injection pressure through an axially extending passageway 18 in the valve plug and opening through an orifice 19 in the valve end face of the plug. Desirably the passage 18 is located coaxially in the plug, and one or more, and in this instance a plurality of supply ducts 20 lead from the backface of the plug to and communicate with the inner end of the passage 18 which is in the form of a blind end bore with its inner end short of the bore into which the stem 15 is secured. Water under suitable pressure is supplied to the ducts 20 from a water supply chamber 21 within the housing at the back of the plug 14 and to which water is delivered through a port 22 by means such as a duct 23 connected to any suitable source of water under the desired pressure such as a pressurized tank, pump, or the like. Through this arrangement, the water is, in effect, injected into the steam on the upstream side of the valve at the point of maximum steam temperature and heat content for most efficient heat transfer. Further, the water and steam are subjected to turbulent mixing and expansion for complete vaporization and effective temperature control by the time the steam leaves the disk stack 9 and passes to the discharge or outlet 11.

Another important advantage gained from introducing the cooling water through the plug 14 is the ability to control accurately the water flow rate proportional to steam flow rate by direct relationship of valve plug lift or position as related to steam pressure. In a simple and efficient structure, a cooling water metering pin 24 extends through the orifice 19 into the passage 18. This pin is of such length and taper that when the valve plug 14 is in minimum opening or passage relation to the pressure-reducing disk stack 9, the water supply is proportionately throttled and as the valve plug 14 lifts to increase the steam volume to the disk stack, the volume of cooling water is proportionately released through the passage 18 and the orifice 19 by corresponding reduction in the throttling effect of the pin in the passage 18. In addition, the pin by a centered spaced relation to the wall of the passage 18 and the orifice 19 effects desirable 360.degree. distribution of the cooling water into the steam which has 360.degree. access to the pressure-reducing valve disk stack 9, thereby enhancing mixing efficiency and cooling effect of the water.

Mounting of the throttling or metering pin 24 is desirably effected fixedly within the assembly of the control valve device 5. For this purpose, the pin is provided with base means in the form of an integral mounting spider disk 25 of larger diameter than the inlet 8 to seat uniformly thereabout and provided with a plurality of openings 27 therethrough to enable substantially unrestricted flow of steam toward the valve disk assembly 9. In a preferred construction, the base disk 25 is of substantially the same diameter as the outside diameter of the disk stack 9 and is clamped against a base in the housing 7 at the bottom of the chamber 10 by means of a ring member 28 which also provides a valve seat 29 engageable with the valve end of the plug 14 when it is desired to close the passage through the device. On the ring 28 the valve disk assembly 9 is concentrically seated and thrust into a rigid unit as by means of a spacer ring member 30 pressed into assembly by a thrusting ring rim 31 of a separate housing head or bonnet 32 extending into an upwardly opening assembly bore 33 in the main part of the housing 7. In addition, the rim 31 serves to maintain a packing gland 34 about the plug 14. Thrusting retention of the rim 31 within the bore 33 is effected by means comprising a retaining ring 35 secured as by means of bolts 37 to thrust against a compression ring 38 toward the rim 31 and effecting a pressure seal by means of a sealing ring 39.

From the foregoing it will be apparent that the present invention enables the simultaneous reduction of steam pressure and temperature of desired limits. The device greatly minimizes and practically eliminates noise, vibration and erosion. Typical uses for the method and device are in auxiliary steam start-up systems, turbine bypasses, plant heating systems, compressor drives, fan drives, and the like.

It will be understood that variations and modifications may be effected without departing from the spirit and scope of the novel concepts of this invention.

Claims

I claim as my invention:

1. A device for conditioning steam to reduce its temperature and pressure, comprising:

means operative to introduce cooling water into the steam;

means operative thereafter to reduce the steam pressure;

a housing having an inlet and an outlet and said means for reducing the steam pressure comprising a stack of annular disks having numerous multi-angular passages between the disks;

a valve plug controlling entry of the steam into said passages; and

said means to introduce cooling water comprising a passage through said plug.

2. A device according to claim 4, in which said passage is located axially in said plug, said plug is reciprocably mounted within a bore defined by the disk stack, said plug has a valve face, and said passage opens through an orifice in said valve face.

3. A device according to claim 2, including a metering pin mounted fixedly relative to said disk stack and extending into said passage through said orifice.

4. A device according to claim 3, in which said device comprises a housing, said metering pin has a spider disk base, a valve seat ring clamping said base to said housing, said disk stack engaged upon said valve seat ring, a bonnet engaged upon said disk stack ring and having means retaining the parts in assembly, said bonnet providing a chamber at the end of said plug opposite to said valve face end, means for delivering water supply to said chamber, said water passage in the plug communicating with said chamber, a valve stem extending from said bonnet, and means carried by said valve stem for controlling the position of said plug relative to said disk stack through said valve stem.

5. A device for conditioning steam to reduce its temperature and pressure, comprising:

means operative to introduce cooling water into the steam; and

means to receive the steam and cooling water and provided with a plurality of multi-angular passages subdividing the water and steam into individual streams each of which is subjected to a substantial number of angular turns in the passages effecting high frictional resistance losses, completely mixing the water and steam and controlling the velocity and pressure of the streams.

6. A device according to claim 5, comprising an annular pressure reducing control disk stack providing said passages and having a space therein, means for directing steam to be conditioned into said space, said means for introducing cooling water communicating with said space.

7. A device according to claim 6, including a plug valve operating in said space to control flow of steam and water to said passages, and said means for introducing cooling water including a passage through said plug communicating with said space.

8. A method of conditioning steam to reduce its temperature and pressure, comprising:

introducing cooling water into the steam; and

after the cooling water has been introduced into the steam subdividing and confining the steam and water in a plurality of individual streams in confining and control passages; and

in said passages subjecting the streams to a substantial number of angular turns effecting high frictional resistance losses;

whereby to cool the steam, completely mix and vaporize the water and control the velocity and pressure of the steam.

9. A method according to claim 8, wherein the passages are provided by an annular pressure reducing control disks stack having a space therein with inlets into the passages communicating with the space, and effecting said introducing of cooling water into the steam in said space.

10. A method according to claim 9, including controlling the inlet ends of said passageways by a plug valve in said space, and introducing the cooling water through a passage in said plug valve.