US1393800A - Process for conserving heat in steam-power plants - Google Patents

Description

S. IVI. LILLIE.

PROCESS FOR CONSEHVI NG HEAT TAI STEAM POWER PLANTS.

APPLICATION FILED APR.23, Ism.

. f WEZ W AI UNITED STATE PATENT OFFICE.

PROCESS FOR CONSERVINGHEAT IN STEAM-POWER PLANTS.

Specification of Letters Patent.

Patented Oct. 18, 1921.

Application filed April 23, 1918. Serial No. 230,255.

To all whom 'it' may concern.' Y

Be it known that l, SAMUEL MORRIS LILLIE, a citizen o-f the United States, residing at Philadelphia, in the county of Philadelphia and State of Pennsylvania, have invented a new and useful Process for Conserving Heat in Steam-Power Plants, Notably in Those of Public Utilties Companies, which process and apparatus are set forth in the following specification, in which reference is had to the accompanying draw- 1n s.

n the operationl of power plants in which the heat agent is steam furnished by steam boilers it is the practice to blow down or away water from the boilers at intervals to remove impurities which become 'concentrated in the boilers due to the evaporation of the feed water with which the boilers are supplied to replace that leaving the boilers as steam, as blow down waters or as other escaping water. The blow down water leaves the boilers at boiler temperature and the feed water is initially much below the boiler water temperature. As a. rule the feed waten. before being passed into the boilers is heated partway to boiler temperature by various means; exhaust steam from steam motors, and flue gases from the boilers are among those commonly used. y

An object of my invention is to return to the steam producing system the heat taken from the boilers with the blow down water and in any water taken from the boiler in addition which the practising of my process may make desirable, Another object of my invention is to return to the boilers practically all of the blow down7 water, but in the purer form of -distilled water. Still another object is to deliver back into the system heat from auxiliary exhaust steam after the heat has been first employed for a useful purpose.

The first object is attained by leading the blow down water, as it leaves the boilers, into an inclosed space in which a pressure is'maintained less than that corresponding to the temperature at which the water comes to the'space, in virtue of which a portion of the blow down water flashes into steam, and by delivering the heat in the flash steam into the feed water for the boilers, either by condensing the flash steam in the feed water, or by intermediate means, such as a surface heater through which the feed water flows and in which the flash steam agent. Incidentally to this proceeding is the employmenty of the heat in the flash steam for some useful purpose which does not prevent the heat from continuing on to the feed water. The highest point, at which, 1n the course of the heating of the feed water, this flash heat may be delivered to the feed. water will depend upon the pressure maintained in the said inclosed space. If this pressure be above that corresponding to the temperature at which the feed water leaves the last of the other means for heatmg 1t', some at least of the heat in the flash is the heating steam may be the last heat put into the feed' waten before it enters the boilers.

In this application, an example of the use ful employment of the flash steam heat o n its way to the feed water, is the evaporation ofi water by the heat to produce make up feed for the boilers, and to realize another object of my invention the blow down water is the wat-er evaporated by the heat in the flash steam which has come from itself; the vapors from this evaporation are condensed by the feed water and its heat passes into the latter and also the distilled water resulting from the condensation. Therefore with the exception of a trifle of the blow down water which is not evaporated, all of it 'and all of the heat it contained is delivered into the feed water and thereby returned to the boilers. The auxiliary exhaust steam heat is also used to evaporate water and in the resulting vapors it is used for heating feed water.

Referring to the drawings A, A, A, indicate three of a set of boilers; the Babcock and Wilcox water tube type are shown. The casing at the rear or down flow end of one of the boilers is removed to expose to view the steam drum B above, the mud drum C below and also the down flow pipes o, and headers L of the evaporating tubes, which together connect the steam drum to the mud drum. Each of the boilers has a blow down pipe a, which pipe has ya valve fitted branch c, to the mud drum C, and a similar branch b to the steam drum B, which enters the latter through its underside near the down flow pipes 0. Each blow down pipe a, discharges through a graduated control valve d, into a T D, through one of its run ends, the opposite end of which is closed by a removable and replaceable blank flange c.'

The branch of each T D, connects through a valve e, with a branch of the manifold iash main E, that'leads to the branch of the vertical run T which connects from the upper end by e pipe 1, with the reduced pressure tank F through its top side, and the T from its lower end by the pipe 2 connects through one end of the said tank near the bottom of the latter.

A steam motor represented by the turbine T, receives operating steam from the boilers A, through a steam main U, having branches u, one to each of the boilers A: this main and its branches are provided with proper control valves. An exhaust steam line X y leads from the turbine T through the casing of a surface condenser W, through whose tubes a cooling water is passed to condense the exhaust steam on the outer surfaces of the tubes. The case of the condenser opens below into a well V, into which the condensate falls and from which a boiler feed pump P, draws through the connecting pipe d. The condensate which falls into this well is somewhat cooler than urated steam at the pressure maintained on the condensate side of the condenser tubes. This pump P delivers by the pipe 'v' to and through an auxiliary surface condenser N and the'n through feed water heaters (not shown)" into the boilers A, by connecting branches to the several boilers.

From the top of the reduced pressure tank F leads a vapor main G, iitted with a safety valve 3. `The main G connects through the branch H fitted withvalve 4 to an evaporator I', which is indicated as the hottest effect of a'triple-eifect I", I2, I, and it connects through its continuation J fitted with the valve 9 with the cross 22 and through the branchesL and M of the cross, fitted with stop valves 11 and 12 respectively, the main G may be connected with either the main condenser W or the anxiliary condenser N or. with both. The cross 22 also is connected with the evaporatiug chamber of the effect I3 through the vapor main K fitted with the stop valve 10. The bodies or effects of this tripleeiect are all of similar construction. This construction and the connections between the eects of the tripleeifect are such that when in Service the steam, for evaporation, enters the steam end P of the hottest effect and` thence paes f into slightly upward inclined tubes, each closed at .its far end, which project through a separating tbe plate into an evaporating chamber in which the tubes are surrounded by water from which water evaporation is eected by theesteam in the tubes. The vapor of eva ration passes from the evaporating cham r of effect I by the main 5 into the steam end I2 of the intermediate 65 e'ect and causes evaporation in its' evapo the temperature which corresponds to sat? rating chamber from water inthe latter. The vapor from .the intermediate eect passes through the main 6 into the steam end E3 of the third and coolest edect, in which this vapor causes evaporation from water in its evaporating chamber. The condensate in the case 'of each eiect flows from its tubes into the steam chamber of the eil'ect. The vapor from the evaporating chamber of the third eiect passes through the vapor main K either through the main L into the main condenser W, or into the auxiliary condenser through the branch main M, or through both of these branch mains partly into each of the two condensers. A pipe m leads from the bottom'of the auxiliary condenser N into the main condenser well V, which pipe serves to pass the condensate of the condenser N into the well V, and also to pass any incondensible gases into the well V, any vapors which may pass with the gases assist in heating the eenden/sate from condenser A vacuum pump VP connected with the Well V of the condenser W by the pipe 23 serves to draw the incondensible gases from the condenser to maintain the vacuum in the same. The contlensates from the steaml ends, l', I2, I3, of the effects are delivered into the well V, of the condenser, W, and forms a part of the boiler feed as through the pipes 7, 8, m and e an', for example. A pipe g, fitted withstop ifalve 19, connects to the vapor main system at the cross H, and affords means of delivery to the system steam from other sources than the boiler blow down waters, auxiliary exhaust steam as from a pump R, for example.4

Methods of operating the illustrative apparatus of the drawings to obtain the pur- 105 poses o my invention are as follows:

Water is drawn from each boiler concerned in the operation through its blow udown pipe a, as re ated by its indexed Hvalve d, into its T The water may be 110 drawn from the mud drum C alone through the pipe c, or from the steam drum B alone, through the pipe d, in which latter case it 1s impossible to lower the water in the boiler suiclently to uncover any of its tube surv faces. in the water may be drawn simultaneously from both drums. .The water and vapor from all Ts D pass through the open valves e, into the flash main E, and thence into the reduced pressure tank F via the T f, in which a lower pressure `than that in the boilers is'maintained by the condensation of flash steam in the evaporator I, or in the condensers N or W as hereinafter described.

The reduced pressure in tank F is communicated back into the main E, and also into the Ts D, in the last to degrees which may be controlled severally by the valves d.' There is some flash steam formed in these 13p Ts. The main E and T f, are assumed to be large enough so that the flashing of the water into steam, due to the lower pressure, i

face of the water in the tank.- The plate 7',

and the space in the upper part of the tank F, free the vapors passing throughvof any yundue amount of entrained water; r1`he pressures in the Ts D, by'means of the valves e, are kept about equal and enough lower than the pressures in the boilers so that slight differences in pressure between the several boilers will have practically no ef-` fect on the relative flows of water from the boilers into the Ts D, when the system is operating with continuous flows from the ',boilers.

A preferred way of operating this apparatus is one which transfers into the feed water for the boilers nearly all the heat contained in the blow down water taken from the boilers, and nearly all the water` itself, but in form of distilled water. Operatmg for these purposes waters are taken continuously from the boilers through lthe indexed valves a3, respectively set so that the flow of water from the different boilers will be about proportionate to their rates of evaporation. The vapor from 'the reduced pressure tank F is passed into evaporator I and is employed in the triple effect to evaporate the blow down water which passes from the tank F` into the evaporator I by the pipes s, as controlled by the valve 20, unless the How is automatically controlled by the evaporator, in which case the valve 2O is kept wide open. This multlple eHect is supposed to befitted with the customary inter-connecting pipes and valves between the effects, so -that each effect, save the hottest one, receives its supply of water to be evaporated from the next hotter effect, from which it follows that the impurities concentrated by evaporation collect in the water in the coolest effect I3, which water may be kept below any desired degree of concentration .by venting the impure water from the effect constantly or occasionally through the vent pipe e. Apart from radiation losses this f vented water contains all the heat of the boiler blow down water, or for that matter of any other heat that may be used for evaporation, that is lost.

This loss is small in amount but might be mostly saved by using it in a heat transferrer of any kind for heating the make-up water, if colder, which comes to the system from an exterior source.

The vapors from the coolest effect I3 may pass throughI the mains K and M into the auxiliary condenser N, or through the main L into the well V of the main condenser W. In either case its heat is transferred to the feed water from the boiler. With respect to the vapor which may be sent into the well V should not be more than sufficient to heat the condensate falling from the condenser tubes, of the condenser, W, higher than a little below the temperature corresponding to the pressure carried in the condenser, for if the amount of vapor passed exceeds this,

some of it is likely topbe condensed on the surfaces of the tubes and the heat of this portion be carried away in the cooling water of the condenser. he amount of feed water make up is, of course, greater than the blow down water, and consequently some water from an extraneous source has to be added to the blow down water to permit of sufficient distilled water being' obtained to furnish the entire make up feed water needed. This extraneous water `may be added to the blow down water in the reduced pressure tank F, through the pipe n, leading into the tank: this pipe is fitted with a stop valve 13 and also a balanced valve 14: which is automatically operated by a float resting on the surface of the water in the tank F by which the inflow of the said water is made to keep pace with the extra evaporation needed to furnish the make up, this added water might be introduced directly into evaporator I though the pipe z', fitted to the stop valve 16. With a sufficient number of effects in the multiple effect, the flash steam from the 'blow down waters may be made alone sufficient to not only evaporate itself, but also the added water. In case of a smaller number of effects, the deficiency in the flash steam may be made up by auxiliary exhaust steam taken into the multiple effect through the pipe g asn controlled by the stop valve 19.

By the method of operating just described all of the heat and all of the water leaving the boilers in the blow down waters is with but slight loss transferred to the boiler feed water and returned to the boilers, and this is also the case with any heat which enters the multiple effect with the auxiliary exhaust steam. It is apparent that by the transfer of all the blow down water into the feed water in the boilers, a considerable saving in water is effected, which may be of consequence in arid regions.

In cases where it may not be necessary' steam by the feed water itself without the intervention of an evaporator. For example, in the apparatus of the drawings the triple eH'ect Il, l2, 13 could be cut out b y closing the valves in the connections to 1t and opening the valve 9 in the main J and either one or both of the valves 11 and 12 in the mains L and M, leading respectively to the main condenser W and to the auxiliary condenser il, in which the Hash steam would be condensed by the feed water and its heat imparted to the latter, and its condensate would be added to the feed water by the pipe M', in the case of the latter condenser. lit all ot the Hash steam may be condensed in the well of the condenser W, without raising the temperature of the water above that corresponding to the pressure in` transferred to the extraneous make up feed water, if the latter befcooler than the former. l

It is often the case in a power plant that there are a number of'imain turbines each supplied with steam from its own battery boilers. ln such a power plant there might, of course, be an evaporating outfit similar to this described herein, for each unit of turbine and boilers, but one large evaporator unit might be made to serve for all the boilers of the plant by having the Hash down system for each set of boilers and conveying the Hash steam .from each to the evaporators, for example, if the power unit and boilers shown in' the drawings were one of a number, the Hash steam from the other power units might be brought to the triple eH'ect Il, l2, 13 through the pme g to whlch Hash steam connections would bring the Hash steam from the other units. The blow down waters from the reduced pressure tanks F of the other units could be brought to the triple etl'ect by pipe Connections Z, leading to the pipes 1.

In the foregoing a continuous How of the blow-down waters from the yboilers is assumed, but with intermittent blowfdowns Howing as they come into the Hashing down means, a recovery of heat and of water may be obtained. With intermittent blowdowns a continuous How of the blow-down waters may still be had t0 the flashing down system by sending the blow-down waters into a closed storage tank located below the boilers in which a suiiciently lower presmaestro sure, than boiler pressure, is maintained to permit the blow-down waters to discharge into it.

ln the drawings the condensate and vincondensible gases of the auxiliary condenser N, pass through the pipe m into the main condenser well V, in which the pressure is lower. This condensate and these incondensible gases might of course be taken away :from the condenser N, by independent suitable pumps, as it is customarily done for surface condensers.

`plhe heat in the blow-down waters might be used in a modified way for evaporating while on its way to the feed water, z'. e. by sending the hot blow down waters through the tubes of an evaporator, arranged with an inlet and outlet for the blow-down waters similar, for example, to the arrangement of the tubes in the condenser W of the drawings, with the water to be evaporated covering the exteriors of' the tubes. If the evaporation in the evaporator were proceeding under atmospheric pressure, the blowdown water might be cooled nearly to the corresponding temperature of 212 F.; the cooled blow-down waters could be delivered back into the evaporator as the water to be evaporated.

By waste steam heat where employed in the following claims, is to be understood as heat which had been imparted to the water in the boilers, and which would'` be discharged away from the system to waste, un-

less employed for some useful purpose, or returned by. some means to the boiler system. Examples of such heat are found in the blowdown waters and in the exhaust steam from auxiliaries in power plants.

ll claim as my invention:

1. The process of utilizing heat in hot water in steam power plants consisting in leading it into a space in which is'maintained a lower pressure than the pressure corresponding to the temperature of the water, in employing the resulting Hash vapors in an evaporating plant to evaporate water for the production of vapor and distilled water, and

in using the vapors for heating the feed water for the boilers.

2,I The process ofutilizing the heat in hot Water drawn from steam boilers consisting in leading it into a space in which is maintained a lower pressure than, the pressure corresponding to the temperature of the -water, in employing the resulting Hash vapors in an evaporating plant to evaporate water for the production of vapor and distilled water, and in delivering the distilled water into the boilers.^

l 3. The process of utilizing the heat in hot water drawn from steam`boilers consisting in leading it into a space in which is maintained a lower pressure than the pressure corresponding.. to the temperature of the Water, in employing the resulting ash vapors in an evaporating plant to evaporate Water for the production of vapor and distilled Water, in using the vapors for heating the feed Water for the boilers, and in delivering the distilled Water into the boilers.

4. The process of utilizing the heat in hot Water taken from steam boilers, such as blowdown Waters, consisting in employing a portion of its heat in a suitable evaporator for evaporating Water to produce vapor, in using the partially cooled Water drawn from the boilers as the said Water evaporated, andfin using the vapor formed for heating feed Water for the boilers.

5. The process of returning heat and Water contained in heated Water obtained from the steam boilers of steam power plants back into the steam boilers consisting, first, in evaporating the heated Water into vapor,

second, in cooling and condensing the said` vapor by the feed Water for the steam boilers1 third, in adding to the said feed Water the condensate obtained by the said cooling and condensing the vapor, and, fourth, in delivering the feed Water thus heated and added to into the steam boilers.

6: The process of utilizingA heat in hot Water drawn from the boilers, consisting in drawing the said Water from the boilers, ina continuous and practically uniform stream, and in employing the heat for evaporating water for the productionV of distilled Water, and in delivering the distilled Water into the boilers'.

S. MORRIS LILLIE.

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