US1909488A - Method of and apparatus for control of a heat energy system employing two fluids of different boiling points in heat exchange relation - Google Patents

Description

H. H. DOW TUS FOR CONTROL OF A HEAT ENERGY SYSTEM EMPLOYING TWO FLUIDS OF DIFFERENT BOIL IN HEAT EXCHANGE RELATION 22, 1928 2 Sheets-Sheet 1 ING POINTS Filed Dec May 16, 1933.

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May 16, 1933. H, Dow 1,909,488 METHOD OF AND APPARATUS FOR CONTROL OF A HEAT ENERGY SYSTEM EMPLOYING TWO POINTS IN HEAT EXCHANGE RELATION FLUIDS OF DIFFERENT BOILING v Filed Dec. 22, 1928 2 Sheets-Sheet 2 1 N VEN TOR.

ATTORN Y6 Patented May 16, 1933 UNITED STATES PATENT OFFICE HERBERT H. DOW, OF MIDLAND, MICHIGAN, ASSIGN OR TO COMPANY, OF MIDLAND, MICHIGAN, A CORPORATION THE DOW CHEMICAL OF MICHIGAN METHOD OF AND APPARATUS FOR CONTROL OF A HEAT ENERGY SYSTEM EMILOYING TWO FLUIDS OF DIFFERENT BOILING POINTS IN HEAT EXCHANGE RELATION Application filed December 22, 1928. Serial No. 328,027.

The present invention relates to power generation by means of the expansion of a vapor, such as steam, in combination with superheating of said steam and reheating same between expansions in the power generation cycle by means of a relatively lower pressure vapor of a higher boiling point substance, specifically to methods of control of the supply or feed of fuel and water to the system and the maintenance of the two fluids Within a closed system in working balance.

Such a method of vapor generation is dis closed in copending application, Serial No. 163,609, filed January 26, 1927, in the name of JohnJ. Grebe and the present invention relates specifically to methods of control as above indicated.

Although the control methods herein disclosed are applicable, in general, to employment of various power and superheating fluids, they are particularly applicable to the control of a power system, such as herein described employing water and diphenyl oxide, where the steam pressure is relatively high, e. g., 1200 pounds absolute, or more,

at which pressure it is desirable to dispense with drums and headers in the steam boiler construction and employ only tubes ofrelatively small diameter. Such a boiler provides but little opportunity for vapor and liquid separation of the character occurring in the drum type boiler and it becomes important that means be provided to insure a satisfactory degree of coordination between the rates of firing, boiler feed and steam demand which it is the object of the present invention to meet.

My invention comprises, briefly, of a method and means directed to the employment conjointly of the changes in Vapor pressures of the two fluids employed to effect thereby control of the rates of supply of.fuel and low boiling point liquid tothe boiler and further to the use of the excess heat absorbed by the high boiling point substance to preheat the low boiling point liquid before entering the boiler whereby, respectively, the fuel input and the supply of low boiling point liquid to the boiler is regulated to meet the demands for heat and/or power and further the heat inputs and outputs, respectively, to and from the two fluids are maintained in balance. i

To the accomplishment of the foregoing and related ends, the invention, then, consists of the steps and means hereinafter fully described and particularly pointed out in the claims, the annexed drawings and the following description setting forth in detail certain means and one mode of carrying out the invention, such disclosed means and mode illustrating, however, but one of the various ways in which the principle of the invention may be used.

In the drawings accompanying this application the single figure appearing thereon illustrates in a diagrammatic fashion a power system of the character with which this invention is concerned employing water and diphenyl oxide, and illustrates also diagrammatically the application of the controls which are the subject of the present invention.

The boiler furnace 1 is fitted for the combustion of powdered coal which is fed to the boiler furnace through the conduit 2 by means of any integral, or other coal pulverizer, and feeding device illustratedat 3. 4 is an air preheater adapted to absorb heat from the waste products of combustion and return it to the furnace. The products of combustion reach the preheater through the 'breeching flue 7 and are exhausted by the fan 5 after passing through the air preheater. The air for combustion is forced through the air preheater 4 by the blast fan 6 from which it is carried in the flue or duct 8 to the furnace 1, as indicated, it being permissible to use a part of it through the branch flue 10 to suspend the powdered fuel, the balance entering the furnace by way of branch flue 11 and tuyeres 12.

The Water boiler is comprised of a series of tubes 13 placed in the path of the products of combustion of the fuel, the feed water entering at 14 taking up heat in the back-passes 15, 16 and 17, and further heat in the front pass 19 exposed to both radiation and convection. The tubes 13 then rise through a closed drum 20 containing the high boiling point liquid, specifically diphenyl oxide, or the vapor thereof, or both liquid and vapor, from which they emerge at the top thereof, i. e., at 21 and then are led as steam supply pipes 22 to the high pressure turbine 23. The boiler feed water is derived from the hot well 24 from which it is drawn and forwarded through pipe 14 by the feed pump 46.

llncluded within the boiler setting is the high boiling point substance heater comprised of the tubes 25 and drums 26 and 28, the u per drum 28 being connected to the super eating drum 20, the latter having a return connection 27 to the drum 26 in which is included a circulating pump 29 if desired to insure or assist in securing a suficiently rapid circulation of the fluid in the system. From the top of the superheater drum 20 a vapor pipe 30 leads the high boiling point vapor to the reheating and heating elements of the steam and water system, such vapor being condensed therein and returned to the hot well 31 from which it is drawn by the feed pump 32 and returned by pipe 33 to the drum 26 of the boiler. The power system illustrated in the drawings provides for expansion of the steam in three power units, i. e., turbines 23, 34 and 35, the steam being finally condensed in a surface condenser 36 from which it is drawn ed by the condensate pump 37 and discharged into the hot well 24. Reheaters 38 and 39 are interposed respectively between turbines 2334 and 34-35 for the purpose of reheating the exhaust steam therein. These reheaters may be of the tubular type and are shown with the steam passing through the tubes and thefluid high boiling point substance surrounding same. As

illustrated in the drawings, the flow of they reheating vapor is in series entering the reheater 38 by way ot pipe 30, then flowing by way of pipe 40 to a jacket 41 of the turbine 34 from which it passes by pipe 42' to the reheater 39. The condensed reheating vapor is collected and forwarded by the traps 43 and 44 to the collecting well 31. Included in the feed pipe14 is a stabilizing heater 47 employing excess vapor of the high boiling point substance passing the reheaters 38 and 39 for heating the low boilin point liquid before it enters the boiler, relief or backpressure valve in the vapor and/or'condensate discharge pipe 77 is set to maintain the desired pressure in the heater so as to utilize the vapor heat at the maximum temperature level for heating the low bpiling point liquid in the stabilizing heater Pressure reliefvalves 45A and 4518 may be inserted, as shown, to still further control the back pressure in the reheaters 38 and 39, if desired. I

A water cooled condenser 49 may be connected with the vapor space in the collecting well 31 for the purpose of condensing any reoaeee excess vapor of high boiling point substance which would otherwise escape in case of supply thereof in excess of the heater and reheater requirements, thus acting to conserve same in such emergency.

The-rate of supply of fuel to the furnace is controlled by a device indicated at 53 which may be of any standard or known character suited to the method of drive used for the feeder, pulverizer or other equipment preparing and delivering the fuel to the furnace. This control device 53 is connected either electrically, mechanically or otherwise, to the vapor pressure actuated controller 54 comprising a series of electrical contact points swept by a contact arm 55 tulcrumed at 56 and counterweighted at 57. The arm 55 is linked through members 58, 59, 60 and 61 to power vapor and reheating vapor pressureresponsive elements 62 and 63 connected respectively with the power vapor and reheating vapor systems, as indicated, the steam connection being preferably taken from a point near the turbine 23 where fluctuations in steam pressure due to load changes will be' most marked, the connection to the reheating vapor being taken from a convenient point, such as the reheating vapor main 30.-

The pressure- responsive elements 62 and 63 may be constructed on the diaphragm or piston principle, the effect of pressure therein being to cause the contact end of the arm 55 to move downwardly whereas the efiect of the counterweight 57 is to cause the contact end of the arm 55 to move upwardly. The connection 64 between the controllers 54 and 53 is such that when the contact end of the arm 55 is moved downwardly 54 suggests to 53 "to reduce the rate of fuel input and conversely when the contact end of the arm 55 moves u wardly 54 suggests to 53 that the rate of uel supply be increased. The mass and position of the counterweight 57 will then be chosen and adjusted so that it will balance in the desired contact position the combined pressures of low boiling fluid vapor, such as for instance steam, and reheating vapor exerted in the counter direction through the pressure- responsive devices 62 and 63, respectively.

It will be seen from the above description that consequent upon a drop in pressure of the power vapor at the turbine 23 following an increased demand for power there will be a decreased efi'ort of the said power vapor pressure-responsive device 62 upon the controller connected therewith, permitting the counterweight 57 to raise the contact end of the arm 55, suggesting through connection 64 to the controller 53 to increase the rate of fuel supply. In the same manner consequent upon a return or rise of power vapor pressure at the turbine following a reduced demand for power, the greater efiort exerted by the connected pressure-responsive device 62 upon the controller will cause the contact end of the arm 55 to move downwardly and suggest to the controller 53 that the rate of fuel supply be reduced. The arm 55 of the controller will, therefore, be caused to move in response to power vapor pressure changes consequent upon load changes and such movement acting through the controller 54 and connection 64 to the controller 53 will sug gest to the fuel feeder the proper change in the rate of fuel supply.

The pressure-responsive device 63 connected with the reheating vapor pressure will act in the same manner, in co-operation with the power vapor pressure upon the connected controller, augmenting its action to lower the contact arm when the reheating vapor pressure rises and conversely decreasing that action when the reheating vapor pressure falls. The pressure of the reheating vapor willfall consequent upon increased requirements for reheating and will rise responsive to decreased requirements therefor, such action being in agreement with the power vapor pressure in that respect. In the extreme case of entire loss of load both the power vapor pressure and the reheating vapor pressure will rise sharply and the combined effect of the increased pressure exerted upon the pressure- responsive devices 62 and 63 will act to suggest to the controller 53 to stop the supply of fuel entirely or to reduce it very substantially as may be desired, which effect can be obtained by suitable adjustments of co-ordinating relations. Similarly, with extreme increase in load requirements the pressure of the reheating vapor will drop markedly consequent upon the increased requirement therefor and such decreased pressure will cooperate with the coincident decreased power vapor pressure to suggest in the same manner a commensurate increase in the rate of fuel supply.

In case the reheating vapor be at full pressure, a sudden demand for more power vapor will call for increased fuel supply through the action of the connected pressure-responsive device 62 but will not increase said fuel supply to the extent necessitated by a prolon ed demand for more power vapor in which latter case the reduced reheating vapor pressure will co-act through pressureresponsive device 63 to effect the still further increased fuel supply rate required. This action will reduce the liability of blowing reheater vapor from the safety valve 52 shown connected to the drum 20. 4

It remains to provide for the control of the rate of supply of power fluid, specifically water to the boiler. This I accomplish by means of control of the rate of delivery from the feed pump 46, either by control of the valve 65 in the delivery line, or of the rate of revolution of the motor 66 shown as driving the pump 46, effecting thereby change in delivery rate of the pump 46, or by control of both elements 65 and 66. This is done through the controller 67 actuated by the control suggesting elements 68 and 69 connected respectively to the power vapor pres-. sure at the high pressure turbine 23 and the reheating vapor in pipe 30. The duty of device 68 will be to suggest to the control device 67, change in operation of the motor 66 or change in opening of the valve 65, or both, consequent upon change in steam pressure at the turbine 23. The effect will be to increase speed and /or increase the opening of the valve 65 as the pressure is lowered and/or decrease speed and the valve-opening as the pressure rises. The province of device 69 will be to supersede the action of device 68 when the pressure of the reheating vapor falls to a low value when it will either reduce the speed of pump 46 to a point at which it will deliver a desired minimum flow of feed water to the boiler and/or will limit the opening of valve 65 for the same purpose. Such a reduction of vapor pressure in the reheating system may be caused by the overfeeding of the boiler with water and the absorption of a large amount of heat of vaporization thereof from the reheating fluid in the drum 20.

I have indicated at 70 and 71 the usual bleeder feed water heaters and at 47 a final stabilizing feed water heater using the reheating vapor as source of heat. It is not to be expected that the character of boiler herein described can be either designed or operated so as to deliver steam at some certa-in pressure and superheat and to deliver also a desired steam reheating duty and remain in balance at all loads or during load changes, due in part to inevitable chan e in ratio of heat inputs from fuel to the uids. The oflice of the stabilizer reheater 47 is to assist in maintaining a balance between the heat delivered by the reheating vapor and that absorbed by the reheating fluid from the fuel. When the heat delivered to the reheating fluid in the boiler rise-s beyond that required in the reheaters 38 and 39 and the jacket 41 of the turbine 34 for reheating water vapor, the excess of reheating vapor will pass to the stabilizer feed Water heater 47 where the heat will be absorbed by the feed water, thus effecting a balance of duty between the two fluids and the fuel heat absorbed by them.

The balance between heat inputs and outputs in a two fluid boiler of the character described is, accordingly, secured or insured in my method by using the heat of one fluid to superheat the other before use in a power cycle, reheat it between expansions and heat it before return to the boiler, whereby the heat absorbed by the said one fluid in excess of that required to balance the system is transferred to the said other fluid. The

amount of heat, if any, which will be transferred'at times from one fluid to the other in the stabilizer heater 47 will vary as will the heat transferred in the reheaters 38 and 39, but it is obvious that the arrangement disclosed will act automatically to maintain a balance otherwise not to be expected.

lit remains to provide for control of the rate of feed of the reheating fluid to the boiler drum 26. This may be accomplished in several ways, one of whichqis illustrated and has been found practicable particularly when diphenyl oxide is used as the high boiling point reheating agent, since it eliminates the use of packing in the level indicator. A closed container 72 is connectedzby vapor pipe 73 and liquid pipe 74: to the superheating drum 20 at points respectively above and below the liquid level therein, the pipes 7 3 and 74 being flexible and having suflicient length that the change in weight of the contents of the container 72 will cause said chamber to rise and fall with change of level of the fluid therein. Such rise and fall of the container 72 .may then be connected, as by electrical means, indicated in the drawings at 76, to act upon the pump control 7 5 connected to feed pump 32 in manner well known to the art to regulate the rate of feed of the reheating fluid to the drum 26 and thereby the liquid level thereof in the system.

lln the practical application of a power generation system of the character herein described, it is convenient to use water for the low boiling point liquid and diphenyl oxide for the high boiling point superheating and reheating system. Tn such a system, if the boiler pressure be chosen at 1500 pounds, the diphenyl oxide pressure may be chosen at 83 pounds gauge. The temperature of the saturated steam will be in the neighborhood of 600 F. and the temperature of the saturated diphenyl oxide vapor will be in the neighborhood of 700 F, insuring an efl'ective superheatingofthesteamleavingthediphenyl .oxide heating and superheating drum 20. The volume of superheater drum 20, together with the drums 26 and 28 and tubes 25, will preferably be chosen to contain a considerable quantity of diphenyl oxide, in fact, a suflicient quantity to store up therein a heat content usable for flattening out fluctuations in superheating temperature otherwise marked due to changing demands for steam, and the area of steam heating surface supplied within the drum 20 will also be chosen suflicicntly large to utilize fully the heat supplied and available therein to make sure that the steam leaving the boiler will be suitably superheated .at all times and at all the rates of supply.

lit will be seen that my invention as herein disclosed provides a practical method and means of control of a two fluid heat energy system of the character described, said method comprising control of the rate of fuel supaeoaeee ply to the furnace and the rate of fluid supply to the boiler commensurate with the rate of demand for the heat carrying fluids heated therein, and provides further a method and means for maintainingv a. balance between the heat outputs from the two fluids and the heat inputs thereto whereby the heat energy liberated at the heat source is automatically controlled to meet the requirements therefor and the inequalities consequent upon inevitable variations in ratio of heat inputs to the two heat carrying fluids respectively consequent upon changing operating conditions are automatically equalized and the heat energy system stabilized.

, Although I have described the application of my invention somewhat specifically to a power generation system in diphenyl oxide are respectively employed as power and reheating fluids, it is to be understood that the invention is equally applicable to power or heat generating systems in which there are two fluids of suitably diflering boiling points employed and in which it is desired to maintain a substantial balance as hereinbefore set forth. Many such fluids having properties fitting them in greater or less degree for use in such systems may be mentioned among which are alcohol, acetone, halogen-organic compounds, organic hydrocarbons, diphenyl, and the like, or mixtures of same, or other fluids having suitable physical characteristics.

l[ have shown a power cycle employing three turbines but the method disclosed is applicable to the employment of a power cycle employing reciprocating power units or a combination and is also applicable to expansion in two stages or even in one. With two expansions, but one reheater would be used; with but one expansion, no reheater. In either case, the heat to be delivered to and by the high boiling point substance is reduced and the ratios of heating surface to be provided in the boiler for the respective fluids will be changed, but in any case the employment of the temperature balancing heat transfer element 20 will be advantageous and the use of the feed water heater 4? will perrnit balancing the system automatically as to heat inputs and outputs to and from the respective power and heating fluids.

Although it is intended that normally, the reheating fluid shall deliver heat to the power fluid not only in the reheaters and feed heater, but in the equalizing or temperature balancing heat transfer element 20, the reheating fluid in the latter serves to insure dry power vapor or suitably superheated power vapor. It should be pointed out that under certain circumstances the power fluid may deliver heat to the reheating fluid in the ele ment 20, such reheating fluid acting as an equalizing heat reservoir to deliver heat to the power fluid or to take up heat therefrom.

which water and The two fluids are placed in temperature balancing heat transfer relation in the element 20, but such relation is extended in the reheaters and feed water heater, the latter particularly functioning to complete the said heat balancing transfer relation for the purpose of balancing heat inputs and outputs to and from two fluids.

Other modes of applying the principle of my invention may be employed instead of the one explained, change being made as regards the means and the steps herein disclosed, provided those stated by any of the following claims or their equivalent be employed.

I therefore particularly point out and distinctly claim as my invention 1. In methods of control applicable to bifiuid heat energy systems of the character described, the steps which consist in employing pressure changes in the vapor systems to effect jointly changes in the rates of heat supply and fluid supply to the heating zone to oppose such pressure changes.

2. In methods of control of a water boiler employing also a higher boiling point substance for superheating the steam generated therein,- the steps which consist in causing pressure changes in the steam and vaporized superheating substance to effect jointly changes in the rate of supply of fuel and feed water to overcome at least in part such changes in pressure.

3. In methods of control of a water boiler employing also an at least partially vaporized higher boiling point substance for superheating the steam generated therein, the steps which consist in causing a drop in pressure in the water and superheating fluid systems, below the average operating pressures, to efl'ect jointly an increase in the rates of fuel and water supply and conversely causing an in crease in said average pressures to jointly effect a decrease in said supply.

4. In methods of control of a water boiler employing also an at least partially vaporized higher boiling point substance for superheating the steam generated therein, the steps which consist in causing changes in the pressure of the water and superheating fluid systems to effect jointly a change in the rate of fuel supply to the boiler to overcome at least in part such changes in, pressure.

5. In methods of control of a water boiler employing also an at least partially vaporized higher boiling point substance for superheating the steam generated therein, the steps which consist in causing changes in the pressure of the water and superheating fluid systems to effect jointly a change in the rate of water supply to the boiler to overcome at least in part such changes in pressure.

6. In methods of control of a water boiler employing an at least partially vaporized higher boiling point substance-as an auxiliary heat carrier, wherein both are in heat receiving relation with the same source of heat, the steps which consist in using the vapor of the higher boiling point substance to reheat steam in a power cycle connected with the boiler, separating the condensate of the high boiling point substance so used, returning it to the boiler, and further using the vapor of the high boiling point substance to heat the boiler feed Water.

7. In methods of control applicable to power generation systems in which the heat of the fuel is used to generate vapor from two liquids of different boiling points, the

so-generated fluid products next being brought into heat exchange relation prior to the vapor of the lower boiling point liquid being used in a power generation cycle, the step which consists in transferring excess heat received by the higher boiling point liquid to the feed of lower boiling point liquid entering the boiler.

8. In methods of control of a boiler of the character described for the purpose of balancing the heat inputs and outputs, the steps which consist in using the heat of one fluid to superheat another and supply heat to it at the point of use and before return to the boiler in the form of condensate from such point of use, whereby the heat absorbed by the said one fluid in excess of that required to be delivered by it to the other vapor for initial heating and subsequent reheating is transferred to the condensate of said other vapor.

9. In methods of control of a boiler of the character described for the purpose of balancing the heat inputs and outputs, the steps which consist in using the heat of either fluid substance to heat the other, and absorbing in the condensate of the lower boiling point substance the heat delivered to the higher boiling point substance in excess of that required for the said output therefrom.

10. In methods of control of bi-fluid power systems of the character described, the steps which consist in causing vapor pressure changes to eflect balancing changes in rates of supply to the boiler of heat and lower boiling point substance and transferring to said lower boiling point substance heat absorbed by the higher boiling point liquid, such heat being supplied as vapor heat and liquid heat to the lower boiling point sub stance before it enters the boiler.

11. The combination with a boiler in which two fluids are heated in separate circulatory systems, one of which fluids is employed to deliver heat to the other fluid, of two pressure devices responsive to change in pressure of said fluids respectively, coupled to act in conjunction upon the boiler fuel supply element for the purpose of changing the rate at which fuel is supplied by same to the boiler @3- Leoaees to overcome at least in partfthe change in pressure of said fluids.

12. The combination with ahbiler in which two fluids are heated in separate circulatory 5 systems, one of which fluidsis employed to deliver heat to the other fluid, out two pressure devices responsive to change in pressure of said fluids respectively, arranged to act in conjunction upon the element controlling the supply of the relatively lower-"boiling point fluid to the boiler for the purpose of changing the rate of said supply to overcome at least in part the change in pressure of said 13. The combination with alooiler in which two fluids are heated in separate circulatory systems, one of which fluids is employed to Q deliver heat to the other fluid, of two-pressure devices responsive to change inpressure of said fluids respectively, arranged to act con- Tointly upon the elements controlling respec tively the rates of supply of heat and relatively low boiling point fluid irt liquid form to the boiler for the purpose of changing said rates of supply to overcome at least in part the change in pressure of said fluids.

14. The combination with a boiler in which two fluids are heated in separate circulatory systems in heat exchange relation, or two pressure devices responsive to change in pressure of said fluids respectively, coupled to act in conjunction upon the boiler fuel supply element for the purpose of changing the rate at which fuel is supplied by same to the boiler whereby any change in pressure of said fluids is overcome at least in part.

15. The combination with a boiler in which two fluids are heated in separate circulatory systems in heat exchange relation, of two pressure devices responsive to change in pressure of said fluids respectively coupled, to act in conjunction upon the element controlling the supply of the relatively lower boiling point fluid to the boiler for the purpose of changing the rate of said supply to overcome at least in part any change in pressure of said relatively lower boiling point fluid. M

16. The combination with a boiler in which two fluids are heated in separate circulatory systems in heat exchange relation, of two pressure devices responsive to change in pressure of said fluids respectively, coupled to act conjointly upon the elements controllin respectively the rates of supply of fuel and relatively low boiling point fluid in liquid form to the boiler for the purpose of changing said rates of supply to overcome at least in art any change in pressure of said fluids.

igned by me this 10 day of December HERBERT. H. DOW.

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