US 2421761 A
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Description (OCR text may contain errors)
June 10, 1947. w. H. ROWAND VETYAL 2,421,761 I ATTEMPERATOR Filed Oct. 10, 1941 4 Sheets-Sheet 2 Fig. 4
INVEN'IORS Will H. Rowand BY Lyle B- Schueler f Paul R. Zoughin Attorney J 1947- Q wfH. RowAND ELI'AL 2,421,761
Filed Oct. 10. 1941 4 Sheets-Shapi- 4 Will H. Rowand I. I8 BSehue/er BY aulfi-tou bin A omey i; i Tl Fatented J 10. 1947 ATTEMPERATOR Will H..Rowand, Madison, and Lyle B. Sclmeler and Paul R. Loughin, Westfield, N. J., assignors to The Babcock & Wilcox Company, Newark, N. J., a corporation of New Jersey 1 Our invention relates to a method of, and apparatus for, eflecting fluid heat exchange.
More specifically, our invention relates to steam generation and superheating and is concerned with thecontrol of superheat by direct contact desuperheating.
In this method of superheat control it is advantageous to spray a cooling liquid into superheated steam when cooling of the steam is desired for superheat control. It is, however, important that the spraying action be such as to result in a fairly complete and quick atomization of the liquid and a quick and thorough mixing of the atomized liquid with the steam.
Our invention solves this problem by providing a plurality of successively arranged spray nozzles which are successively cut in or cut out in response to changes in demand for desuperheating effect, the operation of the nozzles being limited to difierential pressures within an effective atomizing range. We provide one noz-= zle of such atomizing capacity that it alone can take care of the lowest boiler loads and yet be Application October 10, 1941, Serial No. 414,446
11 Claims. (Cl. 261-116) Fig. 6 is partiallya side elevation and partially 2. section of an illustrative spray nozzle;
Fig. '1 is a vertical section through the nozzle I head, on the line -l-'l of Fig. 6; Fig. 8 is a diagram illustrating a system by which the desired sequential operation of the,
spray nozzles is eflected; and
c Fig. 9 is a diagrammatic view illustrating the pressure differential control for the nozzle valves.
The Fig. 1 steam generator installation includes a water Wall furnace I8 fired by burners ing the headers 28 and 30. Parts of these tubes operated at such a differential pressure that the butes and objects of the invention will appear as the description proceeds.
In the drawings:
Fig. 1 is a diagrammatic view in the nature of a vertical section showing a steam generator installation with which an embodiment of the invention is associated; Fig. 2 is a vertical longitudinal section through the illustrative attemperator;
Fig. 3 is a horizontal section of the attemperator on the line 3-3 of Fig. 2:
Fig. 4 is a section through an attemperator nozzle and the associated temperature gradient construction;
Fig.5 is a'plan of one of the spray nozzles;
are shown as forming a screen 34 extending across the gas inlet of the convection section 36. Steam from the drum 20 passes through the tubular connections 40 to the superheater inlet header 52 and thence to a convection superheater including the banks of tubes 58-52 extending across the path of the gases in the convection section. Successive tubes of these sections are in series as to steam flow, all the tubes being connected to the super-heater outlet header .54.
From the header 54, the vertically extending attemperator pipe 56 leads to the-inlet header 58 of a second superheater. The tubes Bil of this superheater have their inlet ends connected to chamber. As the steam temperature rises above a desired value water is atomized by one or more of the spray nozzles Ill-ll disposed within the chamber. If the steam flow increases concomitantly with such a steam temperature rise, more v water is atomized by increasing the water flow 75-79 which control the flow through the lines 838'| supplying the respective nozzles. Preferably the water flow is regulated automatically by devices which respond to changes in steam flow and to changes in steam temperature. I
As shown in the drawings (Figs. 2 and 3) the nozzles, or their tubular connections 9090 extend through openings (such as 96 and 98) in a liner I-the main body of which is spaced from the pipe '56 and is provided for the purpose of preventing the water spray from contacting the pipe. Otherwise, undesirable local stresses would be developed in the heavy-walled pipe by contact of the relatively low temperature water spray with the pipe metal the temperature of which may be considerably higher.
The liner has end portions I02 and I04 so tapered that the extreme ends of'the liner contact the inner pipe surface beyond the zone of water spray. The liner is secured to the pipe 56 in such a manner that there will be no damage as a result of expansion changes due to temperature.
By way of example, and not of limitation, reference will be made to an installation of the invention for the purpose of indicating the temperature differential problem which is solved by the internal protector sleeve and the thermal gradient connections for conducting spray water to the nozzles. The latter, as elsewhere explained herein, include the radiant fins to dissipate the heat from a connection when its individual nozzle is inoperative and there is no. water flow through the connection. In the installation,
I and at a boiler output of 300,000 pounds of steam per hour, the expanded steam temperature at the inlet to the attemperator is of the order of 825 F. the temperature of the feed water under these conditions being 470 This means that at this capacity, the temperature of the water that is sprayed into the attemperator chamber may have a temperature lower than the temperature of the metal of the attemperator by more than 300 F. In the same installation, at a maximum load of 550,000 lbs. of steam perhour, the expanded steam temperature is 875 F. at the inlet of the attemperator, while the feed water temperature is 487 F., these conditions presenting to the attemperator a greater temperature differential.
Notches I08 and H0 permit steam to enter the space (or chamber) II2 between the liner and the pipe. Steam may flow from that space through the openings I I4 and H6 at the other end of the liner. These openings, as well as those at 96 and 98 may be considered as means for equalizing pressures internally and externally of the liner.
The relative arrangement ofthe liner I00, wall of the attemperator pipe 56, and a spray nozzle is indicated on an enlarged scale in Fig. 4. This figure also shows a thermal gradient connection minimizing the development of undesirable temperature created stresses in the metal of the attemperator pipe due to the admission of water at I the outer end of the tubular nozzle connection 90.
An annular sealing member 0, somewhat conically shaped, as shown, is fitted over the tubular connection 90 and welded thereto as indicated at I62--I45. The outer portion I50 of said member is preferably in tightly fitted relationship to the sleeve I20 as indicated. The elements described immediately above form an annular insulating chamber I60, which may be closed, or provided with one or more openings for the ingress or egress of a fluid. In either case, the effect of this construction is to prevent lower temperatures of water in the tubular connections I34 and 90 from exercising an excessive cooling eifect upon the metal of the pipe 56. The metal temperature of the outer tubular end I62 of the fitting I32 is substantially the same as that of the temperature of the water passing through the fitting, and from that position to a position in the sleeve I20 adjacent the outer portion I50 of the annular member I40 there is a temperature gradient the upper limit of which is of the order of the temperature of the metal of the pipe 56. This thermal gradient condition is promoted by the heat transfer effect of the extended surface fins I'I0II6 which are welded to the exterior of the fitting I32. These fins are preferably exposed'to the atmosphere, and act to transfer heat thereto from the metal of the fitting I32. keep the metal of the'extension (as at I32"), from attaining a high temperature due to conduction of heat from the walls of pipe 56 when The Fig. 4 thermal gradient construction is such that the fitting I32 with its nozzle I2, tubular nozzle connection 90 and annular sealing member I40 may be fabricated as a unit and thereafter brought into operative position relative to the sleeve I20. The outer annular member I30 of this unit is then aligned with the outer end of the sleeve I20 by the welding ring I80 and the unit is then united with the sleeve by the circumferential weld I82. Thereafter, the outer portion I62 of the unit is similarly welded to the pipe 85, as indicated at I84 and I86.
It is understood, of course, that the thermal gradient construction above described is representative of similar constructions between the attemperator pipe 56 and the other spray water lines 83, 84, 86, and 81, the radial arrangement of which with reference to the attemperator pipe is indicated in Figs. 2 and 3 of the drawings.'
The preferred construction of spray nozzle is indicated in Figs. 5, 6, and '7, wherein the cylindrical atomizing chamber of the nozzle receives Water through a tangential inlet I92 communicating with the bore I94 of the tubular connection 90. The atomizing orifice construction I96 at the top of the chamber I is particularly indicated in Fig. 7.
At low capacities only one of the spray nozzles, such as the nozzle I0. may be needed for the purpose of controlling the super heat, but the capacity and atomizing characteristics of this nozzle are such that it may be operated with a minimum differential pressure sufficient to effect the substantially complete atomization of the water. If this nozzle or any of the other nozzles are operated at a lower differential pressure, the water will not be quickly or thoroughly atomized, and, under extreme conditions, such unatomized water may be carried alongin the steam to such an extent that very undesirable effects are produced.
This construction is necessary to' By way of example-rather than limitation, the
following table is given as illustrating the diflerent capacities of the nozzles which may be employed in an installation involving the invention:
If while onlyone of the spray nozzles is in 3 operation the steam flow through the attemperator is suddenly increased, one or more of the other spray nozzles, dependent upon thesteani cooling effect desired, may be automatically brought into operation by controlmeans which is responsive to steam flow. All of the flow of water to the ease;
of 135, 140, and 145 p. s. i. respectively, until all spray nozzles is-undercontrol of such means,
and it is also within the purview of the invention that suchmeans, and such control, is efiect'ed by means responsive to changes in temperature of l the steam at a position beyond the second superheater section which includes the tubes 60, as
well as responsive to changes in steam flow.
In the superheat control system indicated in Fig. 8 of the drawings the source of spray water for the nozzles is the boiler feed water line 20a leading from the feed pump Ella and through the economizer tilt-to the steam and water drum 2t. A single spray water line 206 supplies water for all of the sequentially operated nozzle valves rev-- i, and the flow through the line 2% is regulated in accordance with a demand for desuperheatlng efiect. The means for producing this result includes a steam flow meter 2 it and steam temperature responsive means 2W5 which are indicated as associated with the outlet header $2. of the secondary superheater fill. The flow meter and the temperature responsive means ME are effective upon the flow control valve lit through the valve operator 220 and, a relay 222, connected by the line 2253.
Beyond the main control valve tilt the sequential flow of spray water to the nozzle lines til-til is controlled by the nozzle shutwfi valves 2tl'l-2H which are opened and closed by means responsive to the difierences between the pressure P4 of the spray water at a position beyond the valve tit, and the pressure P1 of the superheated steam in the attemperator chamber as.
Assuming the superheaters 561i and St to be in operation and that an increase in steam how or increase in steam temperature (or both) in the superheater outlet header 62 has caused the main control valve 2M3 to be opened; the pressure differential (P-P1) will be built up until it reaches a value at which the valve 2971 will open-125 p. s. i. is chosen as this pressure.
The nozzle line 83 will then have communication with the line 206 and, thereupon, the nozzle ill will operate at a pressure well above the lower limit of its efiective atomizing range. If, then the demand for superheating efir'ect still increases,
.the valve zit will 'be further opened to cause similarly cause the valves m, m, and m to be cut in in that order, at pressure diflerentials nozzles are in simultaneousoperation,
' Now, if the demand for desuperheatlng eflect decreases, the valveZlO will'be operated to restrict water flow from the line 206, and the differential pressure (Pi-P1) will drop. The valve 2&8 is set to close when the pressure difierential reaches 40 p. s. 1. Upon closure or this valve the diiferential pressure may vary between 40 p. s. i. and 140 p. s. 1. without opening or closingv any of the valves, but further closing of the valve 2 i8 to reduce the pressure differential to 35 psi. will then cause the valve 209 to be closed and the nozzle 13 to be cut out.
' Similarly, the valves till, an and Bill and their nozzles 12, II, and It will be successively cut out at differential pressures of so, 25, and 2c 1 I p. s. 1., respectively. Suchoperation oi the nozzle valves is co-ordinated with the different capacities of the nozzle sizes to give smooth control characteristics with a desirable minimum of cutting in and cutting out of the nozzles and to stay within the. available pressure dlfierential.
The illustrative control of the sequential operation of the nozzles thus substantially prevents nozzle operation at differential pressures beyond the range of eflectlve atomization.
Fig. 8-shows the motor operated valve 2%, provided for controlof flow'ln the by-pass tilt around At the opposite end of the cylinder the pressure P1 is communicated from the attemperator chamber within the pike by the connection 355.
The head. 25 'is fixed to a stem 255i slidable through the end walls of cylinder 2% and the movement of the stem toward 'thePr end of the cylinder is adjustably' resisted by a spring 2556i which may be confined between a fixed step 282 and a co-acting abutmentmember carried by the stem 25%.
The lower end of the stem. carries an electrical conduictor in the' form of a bridge piece 26% adapted to close an electrical circuit by engaging the contacts 25% and tilt.
Assuming that the Fig. 9 hook-up applied for the operation of the nozzleshut-ofi valve 26?, the contacts 268 and 21s are connected by the bridge piece 266 when the pressure dlfierential (P4-P1) is p. s. i. Then, assuming that the panel board push button has been operated. to close the switch 212, current flows from. the line conductor" 21% through the lead 2%, the coil Q18, connection 286 and elements ltd and 292 to the other conductor 283 of the current supply being connected to the opposite line wire 2%,.
current then flows through the coil 2% and causes the valve Zlll and its valve stem. 2% to move to the right against the spring tilt. The valve is thus opened and spray water is admitted to the line 83 and its spray nozzle ill.
With the nozzles 10 and It in operation the The latterleads to the coil 2% whichis difierential pressure (Pr-P1) may drop to such a value that the connection between the contacts 201 to close because itsactuating coil 296 is still energized by the flow of current through the circuit including the contact or switch 288, the connections 200, 292, and 284 and the switch 212. This circuit is still held closed by the energization of the coil 218 through the circuit including the lead 3l0, contacts 3| l-3M, element 3", contacts 320324, element 320, the coil, and the lead 216, it being noted that the contacts 320 and 324 were connected by the member 322 when the coil 218 was originally energized by connection of the contacts'208 and 210, and its armature 286 moved to the right.
The spring 260. is so adjusted that the valve 201 will not close until the differential pressure reaches 20 p. s. i. 7 When this differential pres- 'sure is reached the stem 258 has moved upwardly so that the contacts 330 and 332 are connected by the bridge piece 330 and its contacts 333 and 338. Current then flows through the coil-340 from the lead 342 and around through elements 343, 332, 338, 334, 336, 330' and 346 back to the supply line 284. The coil 340, thus energized, pulls back the armature 350 which carries the contacts M2 and M3. This action breaks the flow of current through the coil 210 and permits the armature 286 to be withdrawn by its spring 352. Thus, connection between the elements 290 and 292 is broken and the valve coil 296 de-energized, permitting the spring 300 to close the nozzle valve 201. When this occurs, parts of the described system will be reset, the resetting to original positions being completed when the diflerential pressure rises above 25 p. s. i. to cause contacts 330 and 332 to be disconnected and the coil 340 deenergized, the latter action permitting the spring of the armature 350 to establish connection between the contacts 3 and 3| 4.
Manual operation of the valve 201 may be independently effected by the switch 400 connected to the lines 214 and 204 by leads 302 and 204.
It will be understood that the above description of the mode of operation of the spray nozzle valve 201 is by way of example, and that the F operation, the respective valves are caused to cut-in at and cut out at different differential pressures. For example, the valves 201 may cut in at 125 p. s. i., the valve 2l0 at 135 p. s. i., the valve 209 at 140 p. s. i., and the valve 208 at 145 p, s. i. If, when all nozzles are in operation, the 'difierential pressure drops to 40 p. s. i. the valve 208 and its nozzle 14 only will be cut out. Thereupon-the differential pressure may vary between 35 p. s. i. and 140 p. s. i. without the cutting in or out of any nozzle. When, however, the decrease in demand for desuperheating effect causes such a reduction of spray water flow through valve 2|8 as to reduce the diiferential pressure to 35 p. s. i. the valve 209 and its nozzle posed at successive positions along the flow of the steam in the attemperator pipe 58, it will be noted from inspection of Fig. 1 of the drawings that all of the nozzles are located within an attemperator zone which is relatively short. Ihus, when a plurality of the nozzles are in operation, the spraying actions of the nozzles will involve additional mixing effects, permitting a quick and thorough mixing of the atomized water with the steam.
It is particularly desirable in a spray type attemperator that the spray be arranged symmetrically relative to the section of the steam and in such a manner that any atomized particles of water not immediately evaporated and absorbed into the steam stream will be prevented from accumulating. The arrangement of the spray nozzle in a vertical pipe with the steam flow in an upward direction in opposition of the tendency for water particles to pass downward due to gravity is particularly important in a unit of this type where high efllciency of operation is required.
By the utilization of the feed water line as a source of supply of the desuperheating (or attemperating) liquid, an important safety factor is provided. It resides in the substantial assurance, that, whenever steam is being generated, there will be a supply of desuperheating liquid for the attemperator.
Also,-by this provision there is assurance that, when no steam is being generated, no liquid will be atomized in the attemperator.
' What is claimed is:
1. A spray type desuperheater including an attemperator chamber receiving superheated steam, atubular liner spaced from the wall of the chamber, a plurality of spray nozzles of'differing water atomizing capacities disposed within,
the chamber, and meansconnecting the spray nozzles to a source of water under a pressure higher than the pressure of the steam, the nozzles being disposed interiorly of the liner 50 that contact of water with a wall of the chamber will be limited, the arrangement being such that additional nozzles can be cut in as the need for a steam cooling agent increases.
2. In combination; a direct contact desuperheater comprising an attemperator pipe through which superheated steam flows at high pressure, a liner fixed inside said pipe and having tis main portion spaced inwardly of the pipe in the desuperheating zone, a plurality of water spray nozzles disposed within said pipe and connected by nipples through the liner and the pipe with a source of water under pressure, and temperature gradient constructions associatin the nipples and I the pipe to prevent excessive local stresses which might otherwise be created by the temperature differential between the incoming water and the steam in the pipe, the liner being I provided with openings permitting substantially the cutting out of their free steam communication therethrough while substantially preventing contact of the atomizing water with the pipe in the spray or desuperheatmg zone.
3. In combination an attemperator pipe subject to the flow of superheated steam, a tubular liner secured within the pipe and having its main body spaced from the pipe, a plurality'of fluid atomizing nozzles disposed within the liner and spaced longitudinally thereof, tubular connections extending through openings in the liner and connected to supply water to the nozzles, and means whereby the nozzles may be selectively cut into or out of operation as the steam flow varies 9 through the attemperator pipe, the space between the liner and the attemperator pipe being in communication with the atomizing chamber through openings in the liner.
4. In an attemperator of the spray type, means forming an attemperator chamber, means providing for the flow of the superheated vapor through the said chamber, a plurality of indetype; outer metallic structure acting as a pres- 1 sure part; a thermal shield disposed inwardly of and the pressure 01' the superheated vapor in said chamber to render additional nozzle operative or inoperative, said last named means maintaining on any operating nozzle 9, diii'erential pressure suflicient to effectively atomize all of the liquid passing through the nozzle.
5. In combination, means forming an attemperator chamber receiving steam from a superheater, a pluraltiy of independently operable spray nozzles disposed within said chamber for atomizing water at a temperature considerably lower than the temperature of the steam entering said chamber, water supply means, a tubular connector through which water may flow to any of said nozzles, means including a valve through which water may flow from said supply means to 'said connector, means operable from one or to control the flow of water to said connector,
separate feed water supply lines leading to the separate nozzles. and separate pressure difierential operative valves in said last named lines for effecting sequential operation of the nozzles and cutting successive nozzles into operation at different pressure diilerentials all of which are within effective atomizing rangesof the nozzles, th pertinent pressure differentials accruing ,between the superheated steam and the water at a position on the outlet side of the main flow control valve.
8. In a heat exchanger of the direct contact the outer structure to define a fluid mixing zone through which a vapor flows; and means atomizing into said vapor flow a. liquid at a temperature materially difiering from the vapor temperature; said shield-lining saidouter' structure in the mixing zone and causing a heat flow barrier to be presented between the outerstructure and the mixing zone.
9. In fluid heat exchange apparatus of the direct contact type, means providing for the flow of the heated vapor through a heat exchange zone, a plurality of independently operable spray more factors measuring the demand for atomized water in the attemperator chamber for acting upon said valve to control the flow of water to said connector, separate water supply lines leading from said connector to the separate nozzles, and a pressure controlled valve in each of said last named lines for efifecting selective op eration of the nozzles and cutting successive nozzles into operation at difierent pressures which are within an efiective atomizing range.
6. In an attemperator of the spray type, means forming an attemperator chamber, means pro-- viding for the flow of the superheated vapor through the said chamber, a plurality oi" inde= pendent operable spray nozzles efiective to atomize into said chamber a liquid with a temperature lower than the superheatedvapor, means responsive to the temperature of thesuperheated vapor beyond said chamber to control the supply of atomizing liquid for one or more of said nozzles, and means responsive-to the pressure differential between the pressure ofthe atomizable liquid at the inlets of the nozzles and the pressure of the superheated vapor to render additional nozzles operative or inoperative, said last named means rendering any nozzle operative only when said difierential pressure is well above a value sufllcient to atomize all of the liquid which will pass through the nozzle.
7. In a fluid heat exchange installation, means perheated steam, a, plurality of independently operable spray nozzles disposed within said chamber for atomizing water at a temperature considerably lower than the temperature of the steam entering said chamber, water supply means, a tubular connector through which water may flow to any of said nozzles, means including a, main flow control valve through which water may flow from said supply means to said connector, means responsive to one or more factors indicating desuperheating demand for acting upon said valve nozzles efi'ective to atomize into said zone a liquid at a temperature lower than the temperature of the vapor, means responsive to changesln the temperature of the vapor from a. predetermined value to control the supply and pressure of atomizing liquid to the inlet sides of said nozzles, and means responsive to the pressure difierentials be tween the atomizabl liquid on the inlet sides of the nozzles and the pressure of the vapor to render the nozzles successively operative or inoperative upon the occurrence of pressure differentials of difierent values, said last named means rendering any nozzle operative only while said diflerential pressure is of a value suficlent to atomize substantially all of the liquid which passes through the nozzle.
ll). In a, spray type attemperator, an attemapen ator pipe, means providing for the flow of superheated steam through said pipe, steam desuperheating means including a plurality of spray nozzles of diflerentatomizing capacitydisposed within the pipe, means connecting the nozzles with a source or water under a pressure greater than the pressure of the superheated steam, and means responsive to the temperature of the desuperheated steam to cut in successive nozzles as informing an attemperator chamber receiving sucreasing amounts of cooling iiuid are necessary to reduce the temperature of the steam to a desired value, said last named means including a separate mechanism for each nozzle responsive to the diiierential between the pressure of the steam and the pressure of the Water to limit the initiation of the operation of each nozzle to periods during which a predetermined pressure differential obtains.
11. In a spray type attemperator, means forming an attemperator chamber, means providing The following references are of record in the file ofthls patent:
Number flow for a. substantial distance on the downstream side of the nozzle.
REFERENCES CITED UNITED STATES PATENTS Name Date Noble Mar. 23, 1937 Fleisher July 19, 1938 ,Gorrie Nov. 19, 1940 v Number