US1959286A - Method of storing and using heat and means therefor - Google Patents

Description

May 15, 1934. J. J. GREBE 1,959,236

b lETHOD OF STORING AND USING HEAT AND MEANS THEREFOR Filed July 7, 1930 Ale 1' Rarg mg to? Condznsu' INVENTOR .M F Wm (A ATTORNEY Patented May 15,1934

UNITED STATES METHOD or STORING'AND usmonna'r AND MEANS 'rmmeroa John J. Grebe, Midland, Mien, assignor m The Dow Chemical Company, Midland, Mich a corporation of Michigan.

Application July 7, 1930, Serial No. 465,826

.8 Claims. (Cl. 122-45) 0 ployment of diphenyl oxide or other high boiling fluid stable at high temperatures asthefluid medium for storing and/or transferring heat to storage preferably in a suitable solid material such as cast iron.

heat of steam is stored as sensible heat of water under pressure isoid, as is the reuseof the so stored heat in the form of steam. In order togenerate steam from the heat so stored in water, thepressure thereon must be reduced materially and the steam so generated will have a 'lower' pressure and the heat content thereof will'have a lower availability than the same heat in the higher pressure boiler steam.

The use of accumulators employing a high boiling fluid such as phenanthrene is not new per se,

it having been proposed to boil phenanthrene in a boiler employing fuel and to vaporize water in a steam generating element exposed to the phenanthrene vapor over a body of hot phenanthrene. In this proposal the steam produced during excess demands will have a lower temperature than the steam normally produced, and, as in the previous instance employing a steam accumulator, the availability of the stored heat will be progressively lowered as used.

It has been further proposed to store heat in a large body of boiler feed water outside of the boiler proper and upon. the occasion of excess demands for steam to use such stored high temperature-high pressure water as boiler feed.

, This proposal has advantage over the previously mentioned steam accumulator method, 'but requires that there shall be suflicient steam liberating and separating capacity in the boiler to care for the extra steam produced, suilicient excess superheater capacity to superheat the extra steam, the inclusion of which in the boiler adds to the investment and reduces the economy otherwise obtainable .from theuse of an accumulator in ironing out peak loads.

It is accordingly highly desirable to provide a method and means, costing less than the equivalent additional capacityin boilers, etc., to absorb heat in an accumulator system duringoiiE-peak and operating charges for, the accumulator sys-'- The use of steam accumulators in which th steam loads and to deliver to the power mover therefrom steam at substantially full boiler pressure and temperature at the time of demand for excess steam. If in doing this the investment in,

tem are less than for the excess boiler capacity, economic limitations will have been met, and it is the object of this invention to afford such a method and means whereby the heat of fuel, preferably waste heat, going to the stack shall be stored in a high boiling fluid and shall be reusable to produce steam therefrom at full boiler pressure and temperature, insuring ,a constant pressure heat storage system which will produce high pressure superheated steam "and preheated boiler feed water 'dfuringpeak lo .1 v

Tmthe o plishment of theioregoing d :related' ends,-'- thefinvention,' then, consists of the steps and, meanshereinaiter fully described and particularly ,--pointed out in the claims, the annexeddrawing and the following description setting forth in detail certain means and modes of carrying out the invention, such disclosed means and modes illustrating, however, but

PATENTT ojFrlcE several of the various ways in which the principle 30 ofthe invention may be used;

In said annexed drawing:- Fi

1 represents in partly diagrammatic fashion a storage system and Fig. 2 represents one type of tubular heating unit employed therein.

-I- have found that diphenyl oxide, which has become recently available in quantity ata reasonable'price, has peculiarly advantageous properties for use in a heat storage system.- Its melting practical immunity from freezing in pipes, valves,

etc.,'under conditions obtaining in operation of heat storage systems. It is stable under prolonged heating at 700 F., and subject to only slight decomposition above 725 F. Its specific heat, liquid, is in the neighborhood of .45., At 700 F. the vapor pressure is approximately pounds absolute or 85 poundsgauge which low pressure at high temperature permits the'storage under pressure of a large volume of diphenyl oxide in containers of moderate thickness, whereas when heat is stored in water at high temperature the pressure rises'to boiler pressure and even limited volumes require heavy expensive storage vessels. Diphenyl oxide further possesses the property of high fluidity. It does not act upon iron at the temperatures involved and has a high rate of heat transfer to and from an iron surface. Although Ipreter to. employ diphenyl oxide be point is low,approximately 80.6 F., which insures 90 cause of its unique properties, making it admithere may be substituted and employed therefor other high boiling point substances or admixtures of other ingredients with the same or with.

diphenyl oxide without departing from the spirit of my invention.

In order to increase the heat storage capacity of a given body of diphenyl oxide, I employ a solid material of relatively high specific heat, such as cast iron, which may be in the form of pigs or other convenient economic shape which I submerge in the diphenyl oxide in the storage tank therefor. Such iron or equivalent takes on the same temperature as the diphenyl oxide which is in contact with it, the heat coming into the storage tank with the diphenyl oxide being ,shared with the iron automatically upon contact therewith. In order to store the heat in the diphenyl oxide, I prefer to install inthe path of the stack gases, after the boiler proper, either before or after an economizer, or before an air the storage tank. In this way the contents ofv the storage tank, including the iron therein, may.

preheater, .or in a by-pass around an air preheater, a suitable amount of heating surface which maybe of iron tubes and to circulate continuously a current of the diphenyl oxide through .such .a heater in countercurrent relation to the stack gases. a I prefer to draw the diphenyl oxide.

fromthe bottom or cold portion of the storage tank and to discharge the heated diphenyl oxide from the heater into the upper or hot portion of be eventually brought up to a uniform high tom-- perature accomplishing the storage therein of a large amount of heat at a high temperature level.

" Since the hot diphenyl oxide entering the storage tank will divide its sensible heat with the iron,

storage tank to a temperature above boiler temperature. In order now to return the so stored heat to the power system,I pass a current of water through a water heating and steam generating element in heat transfer relation with the diphenyl oxide whereby such water is heated and vaporized; In order. that steam shall be made f in that was, having a pressure and temperature substantially that of the boiler steam, I prefer to circulate the stored heated diphenyl oxide in countercurrent heat exchange relation with the i current of 'waterfrom which the steam is to be In this way the last pass ofthe water "'throughthe generating element will be exposed :to the .hottest' diphenyl oxide whereby sii'perheatedsteam of full boiler pressure may beobta'ined, and by providing a proper. circulatory heat exchange system between the so cooled diphenyl oxide and the hot iron in the storage tank substantially all of the heat stored in the iron as well as that in the diphenyl oxide may h-be transferred to the water for the production T of. such superheated high pressure steam, until scribed.

ilnally the temperature of the diphenyl oxide and the iron has been reduced to a temperature ap- --proximating that of the waterentering the steam generating element. A preferred arrangement of the circulatory system will be hereinafter de- I ilnd that my inventionmay be economically introduced into existing or contemplated steam -cated by the arrows. In this pass 18, I install -1,ese,ase

rably suited for the purpose inhand, invention is not restricted to the use of diphenyl oxide, but' power plants or central heating systems and the like at a total investment charge less than required ifthe initial capacity of the boiler plant I be figured-for the peak load and that my improved system may be operated at alower cost. Referring to the drawing, 1 is a closed storage tank" charged with diphenyl oxide to the level '2- 2' leaving a vapor space 3 to allow for expansion. A vapor space outlet 4 leads to a purging condenser 5 provided with a valve vent 6. 11m condenser is here shown as an air cooled chamber in which diphenyl oxide vapor will c and run back into tank 1 permitting the venting of non-condensible gases, such as air. when desirable, without venting a material amount of diphenyl oxide vapor.

Withinthe tankl isanlnnertankorshell 7.

-forming with tank 1 an annular chamber or compartment 8 and an inner chamber or compartment 9. Openings 10 in the lower portion of shell '7 communicate between the inner compartment 9 and the outer compartment 8. The upper end of the inner tank or shell '7 is provided with a cover 11 in which is a draft tube 12 enclosing a propeller type circulating pump 13, which may be drivenby the shaft 14 passing through a stufllng box 15 in the cover 16 of tank 1. The diphenyl oxide illls both the inner and outer compartments of the storage tank, but in the outer compartment 8 there is introduced.

preferably in as compact manneras practicable, a quantity of solid material such as pig iron 17, which pig iron has a greater heat capacity per unit volume than diphenyl oxide and is also cheaper per unit volume. I

18 represents a pass in the path of stack gases from a boiler, such gases being introduced at the top thereof and drawn 011 at the bottom as indisuitable tubular heating surface 19 here shown diagrammatically as spiral pancake-like coils in heat exchange relation with the stack gases flowing through the pass. A suitable pump 20 draws diphenyl oxide from the bottom of the tank 1 via the pipe 21 and delivers it via pipe 22 to the tubular heating system 19 from which it is led via pipe 23 back to the top of tank 1. Under normal conditions of heat storage, pump 20 will be in operation and the relatively colddiphenyl oxide from thebottornof the tank 1 will be passed 125 through the heater 19, therein heated in countercurrent heat exchange relation with the stack gases to a-temperature approximating stack gas temperature, and be delivered into the upper por-' tion of the storage tank 1 in such heated condition.. The so heated diphenyl oxide entering tank 1 will, because of its temperature, remain superimposed upon the colder diphenyl .oxide below, but as the circulation proceeds the line of separation between the heated and unheated diphenyl 35 oxide in the tank will, while-remaining substantially horizontal at like level in both compartments of tank 1, gradually occupy a lower and lower level therein. That portion of the diphenyl oxide above the separating or dividing plane will have delivered a portion of its heat to the iron whereas that in the upper-most levels will be at the full temperature of introduction. Eventually the line of separation will reach the bottom of the tank and a recirculation of the charge will then occur through the heater 19, and such recirculation will then proceed until a reuse of the heat is put into efiect. By adjusting the capacity for heat storage, thesurface of the heater 1!), and the rate of circulation to the conditions in hand, pariso I 1,959,286- ticularly where well defined peaks regularly occur in the'steam load, the entire charge of diphenyl oxide and the iron submerged therein may be brought to the approximate temperature of the stack gases before a reuse period starts or if a reuse period starts before such an event,'there pressure and temperature, I install within the inner shell 7 a suitable amount of water heating and steam generatingsurface submerged in the diphenyl oxide. Such surface is shown in the drawing in the form of pancake spiral coil assemblies Hand 25, the upper and lower runs only of' such coils being shown for the sake of clearness, it being understood that substantially the entire cubic content of the shell 7 may be filled with such coils. A plan view of a preferred element of such a'coil is shown in Fig. 2. By-

interconnectmg the superimposed pancake coils, a continuous coil is obtained. I then introduce water under boiler pressure to the lower-most section of the pancake coil assembly 24 via the inlet pipe 26, the water rising therein from coil peraturelat' which the said water is introduced at 26. .With 700 F. initial diphenyl oxide tom perature and feed water at 200 F., there will be available approximately 500 of temperature head in the diphenyl oxide and iron at the 700 7 level of temperature, this being accomplished by the countercurrent heat transfer relation established betweenthe diphenyl oxide and the steam generating .element and the progressive absorption ofv heat in the iron by a rising. flow of the diphenyl oxide at increasing temperature therethrough from the cooler to the hotter iron. g Although I have shown the steam generating and'water heating coils as divided into two porvtions or assemblies 24 and 25, such division is to coil-in spiral zigzag vertical course. By suitably relating the surface areas of coil assemblies 24 and 25, the water may be brought to the boilin separating-the steam from the unvaporizedwater. The latter is then led off ,at boiler pressure, at about boiler temperature, through the drain pipe 29 to the steam boiler not hereinshown. The surviving steam is then led via pipe 30 to the coil assembly 25, and the steam therein superheated in the supernatant layers of the diphenyl oxide in the shell '7 of tank 1 emerging via pipe 31 for use in a power cycle to augment that produced by the steam boiler or otherwise as desired. Coincident to the introduction of water into coil assembly 24, I start the propeller pump 13 and so adjust the rate of pumping that the charge of diphenyl oxide in the tank 1 is forced down throughthe shell 7, around, through, and past the coil assemblies 25 and 24 in sequence and out through the openings 10 in the bottom-of the shell into the outerannular compartment wherein it rises. The diphenyl oxide so passed by the pump 13 over the heating elements 25 and 24, countercurrent to the water passing therethrough, is cooled to approximately the temperature of the water entering at 26. Upon entering the outer compartment the so cooled diphenyl oxide comes into contact, either immediately or shortly thereafter (depending upon the amount of heat which has been'stored or is still available) with the pig iron therein and takes up heat therefrom, being of heat may be high pressure steam or any other not essential to my invention, but one coil may be used to produce steam, or more than two coils may be so used. Employing the arrangement illustrated, however, the largest possible proportion of the stored heat is'made available at 1 the high heat head and there is also furnished to the steam boiler, preheated boiler-feed water at boiler temperature. It will be permissible during peak loads to suspend bleeder heating of said water, thereby increasing the output capacthe normal supply of boiler steam. The steam generated from the stored heat leaving by pipe 31 may be introduced into the power mover along with the. boiler steam or used otherwise as desired, and during the final period of heat recovery when there is no longer a temperature headavailable to produce superheated steam at high pressure such steam of lower temperature may be used for any purpose available, such as ina water evaporator. when little or no more steam may be generated from the stored heat, the heating of the boiler feed water may be continued until no further stored heat may be eco-.

nomically so extracted and returned to the heat 11' cycle. Although I have illustrated the storing of heat from stack gases it is obvious that the source suitable high temperature source, and it is evident that generating unit 24-25 may be employed as the heating element when storing heat, during which period high pressure steam would be passed through in the reversed direction to that when steam is generated.

Employing the construction shown in the drawing, it will be preferable to provide baffles between adjacent pancake coils to direct the diphenyl oxide flowback and forth in a-zig-zag or serpentine path, whereby both longer contact and higher velocity relations are established.

The type of heating surface and its arrangement and other structural features are nonessential to the method of my invention, al-

scribed herein. M

If storing the heat contained in boilersteam, the steam obtainable from the heat so stored will have a temperature below that of the steam used as the sourceof heat, but the reused heat will produce steam at a substantially uniform temperature level somewhat below that of the initial steam until the exhaustion of the stored heat; By combining, however, the heating of the accumulator fluid with boiler steam and stack gases, the 1 temperature level of the stored heat may be raised above that of the boiler steam, An arrangement for combining steam and stack gas heating may be easily made, the steam heater preceding the 150 roo ity of the turbine or other power mover from though preferred forms thereof have been\de-.

i cumulatorfluid therethrough.

stack, gas hate.- relative t5 the now or the ac- Other modes of applying the principle of my -invention may be employed instead of those explained, change being made as regards the means and the steps'jherein disclosed, provided those stated by anypf the following claims or their equivalent be employed.

I therefore'pa'rticularly point out and distinctly claim as my invention:

Lln'an accumulator apparatus for storing heat, the combination of a reservoir containing aheat storing high boiling point liquid, a heating device to heat said liquid, means to circulate said liquid. through said heating'device, an elongated tubular container .vertically disposed in said reservoir, tubular meanswithin' saidwc'ontainer for conducting a low boiling point heat receiving material therethrough, propeller means inconnection with said container for circulating the heat' carrying high boiling point liquid therethrough over the surfaces of the tubular container for the low boiling point material, and a separator for,- removing' unvaporized liquid from the fluid products of the low boilingpoint material delivered from the tubular heating means therefor.

2. In an accumulator apparatus for storing heat, the combination of a reservoir containing a heat storing high boiling point liquid, a heating. device to heat said liquid, meansto circulate said liquid through said heating device, an elongated tubular container vertically disposed in said'reservoir, tubular means within said container for conducting a low boiling point heat receiving fluid therethrough, propeller meansih connection with said container for circulating the heat carrying high boiling point liquid therethrough over the surfaces of the tubular container for the low boiling point material andin countercurrent direction to the flow of the low boiling point material, a separator for removing unvaporized liquid from the fluid products of the low boiling poJnt material delivered from the tubular heating means therefor, a tubular superheater in said container receiving vapor from said separator and an outlet "connection for delivering vapor from said tubular superheater.

3. In an accumulator apparatus for storing heat, the combination of a reservoir containing diphenyl oxide, a heating device to heat said' diphenyl oxide, means to circulate said diphenyl oxide through said heating device, an elongated.

perheater for delivering superheated steam therefrom, and ahigh specific heat material piled for delivering-said separated water to a point of use, a tubular steam superheater receiving steam from said separator and located in the upper part of said container, a connection to said suin the annular space between the walls of said receptacle and said container for augmenting the heat storage capacity of the diphenyl oxide.

,4. In a steam generating system, the method of compensating a fluctuating demand for steam which comprises absorbing and storing heat from the main boiler plant in a body of a high boiling point liquid during periods of low demand, passing water at at least the pressure of the main boiler in countercurrent heat exchange relation with said heated body of high boiling point liquid in an auxiliary boiler during periods of higher steam demand, whereby to heat the water to the vaporizing temperature thereof at the existing pressure, separating the so generated steam from the water, forwarding the hot water as feed water to the main boiler and forwarding the steam to sis - a point of use.

5. In a steam generating system, the method of compensating a fluctuating demand for steam which comprises absorbing and storing heat from the main boiler plant in a body of a high boiling point liquid during periods oi low demand, passing water at at least the pressure of the main boiler in countercurrent heat exchange relation with said heated body of high boiling point liquid in an auxiliary boiler during periods of higher steam demand; whereby to heat the water to the vaporizing temperatureth'ereoi at the existing pressure, separating the so generated steam from the water, forwarding the hot water as feed water to the main boiler superheatihgthe so separated steam by passing the same inheat exchange relation with the hottest portion or the body 01' high boiling point liquid and forwarding the superheated steam to a point of use.

6. Ina steam generating system, themethod of compensating a fluctuating demand for steam which comprises circulating-a body of a high boiling point heat-storing liquid in heat exchange relation with the hot stack gases from the main boiler plant to'absorb heat therefrom, passing water at at least the pressure of the main boiler in countercurrentkheat exchange relation-with Jorm J. GREBE.

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