US20130036737A1 - Power generation from low-temperature heat - Google Patents

Power generation from low-temperature heat Download PDF

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Publication number
US20130036737A1
US20130036737A1 US13/569,592 US201213569592A US2013036737A1 US 20130036737 A1 US20130036737 A1 US 20130036737A1 US 201213569592 A US201213569592 A US 201213569592A US 2013036737 A1 US2013036737 A1 US 2013036737A1
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US
United States
Prior art keywords
working fluid
expander
pressure
regard
flow rate
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
US13/569,592
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English (en)
Inventor
Heinz Bauer
Rainer Sapper
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Linde GmbH
Original Assignee
Linde GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Linde GmbH filed Critical Linde GmbH
Assigned to LINDE AKTIENGESELLSCHAFT reassignment LINDE AKTIENGESELLSCHAFT ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: SAPPER, RAINER, BAUER, HEINZ
Publication of US20130036737A1 publication Critical patent/US20130036737A1/en
Abandoned legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
    • F01K13/00—General layout or general methods of operation of complete plants
    • F01K13/02—Controlling, e.g. stopping or starting
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
    • F01K25/00—Plants or engines characterised by use of special working fluids, not otherwise provided for; Plants operating in closed cycles and not otherwise provided for
    • F01K25/08—Plants or engines characterised by use of special working fluids, not otherwise provided for; Plants operating in closed cycles and not otherwise provided for using special vapours
    • F01K25/10—Plants or engines characterised by use of special working fluids, not otherwise provided for; Plants operating in closed cycles and not otherwise provided for using special vapours the vapours being cold, e.g. ammonia, carbon dioxide, ether

Definitions

  • the invention relates to a method for converting heat energy into mechanical energy by means of a Rankine cycle.
  • the invention relates to a method wherein: a working fluid circulating in a Rankine cycle is pumped to a pressure above its critical pressure prior to heat exchange with an external medium; and the working fluid is then heated during heat exchange with the external medium to a temperature above its critical temperature, the temperature being at least sufficiently high for the working fluid to expand without partial condensation.
  • the working fluid is then expanded; and the expanded working fluid is condensed.
  • the working fluid preferably water or ammonia
  • the working fluid is brought to a pressure beyond critical pressure by means of the pump P 10 and fed via line 10 to the heat exchanger E 10 .
  • An external medium for example hot water, is fed to the heat exchanger via line A.
  • the heat energy of the external medium is converted into mechanical or electrical energy by means of the Rankine cycle.
  • This external medium, cooled in the heat exchanger E 10 against the working fluid, is then drawn off via line B.
  • the heat exchanger E 10 and the composition of the working fluid should be respectively designed or selected such that the working fluid 10 is heated in the heat exchanger E 10 up to a temperature above its critical temperature.
  • the sensible heat fed to the heat exchanger E 10 by the medium A may be particularly well utilized. If the temperature of the working fluid 11 downstream of the heat exchanger E 10 is sufficiently far, typically at least 30 K, above its critical temperature, the expander X 10 may be operated in the gas phase and undesired partial condensation of the working fluid in the expander X 10 may thus be avoided.
  • the expander X 10 is connected to a generator G.
  • the valve V 10 serves to keep the pressure of the working fluid in the heat exchanger E 10 above critical pressure.
  • the expanded working fluid 12 is not only completely condensed in the heat exchanger E 20 but rather is additionally subcooled and then fed to the storage or surge tank D 10 . From there it passes via line 13 back to the pump P 10 .
  • An aspect of the present invention is to provide a method of the above type for converting heat energy into mechanical energy by means of a Rankine cycle, which method avoids the above-stated disadvantages, and in particular makes possible the achievement of higher efficiency.
  • a method for converting heat energy into mechanical energy by means of a Rankine cycle wherein the maximum pressure of the working fluid is controlled by means of an expander controllable with regard to the mass flow rate of the working fluid and/or a pump controllable with regard to the mass flow rate of the working fluid.
  • the maximum pressure of the working fluid is not controlled by means of a valve, but rather by means of an expander controllable with regard to the mass flow rate of the working fluid and/or a pump controllable with regard to the mass flow rate of the working fluid.
  • the expander controllable with regard to the mass flow rate of the working fluid preferably comprises an adjustable inlet guide vane (see, e.g., US 2009/0238681), which preferably comprises a nozzle ring at the inlet of the expander.
  • the desired operating pressure of the working fluid may be established at the inlet of the heat exchanger, in which heat exchange takes place between the working fluid and the external medium.
  • the working fluid is additionally heated in particular during the start-up procedure and/or part load operation.
  • This configuration of the method according to the invention requires an additional heat exchanger and an (additional) media stream, which is able to provide a sufficiently high level of heat.
  • This additional heating of the working fluid advantageously ensures that the temperature of the working fluid is at least 30° C., preferably 40 to 60° C., above the critical temperature even during the start-up procedure and/or part load operation.
  • this configuration makes it possible to keep the inlet temperature of the expander substantially constant even during the start-up procedure and/or part load operation.
  • the expanded working fluid is used to preheat the pumped working fluid, before the latter undergoes heat exchange with the external medium.
  • This configuration of the method according to the invention is especially meaningful when the outlet temperature of the working fluid on leaving the expander is higher than the condensation temperature in the heat exchanger downstream of the expander. In this case the heat from the temperature interval between the outlet temperature and the condensation temperature may be used to preheat the working fluid.
  • the expanded working fluid As a further development of the method according to the invention, it is proposed for the expanded working fluid to be condensed, but not subcooled. Subcooling of the working fluid may in particular be omitted when the storage tank to be provided is positioned sufficiently high above the pump to prevent undesired cavitation in the pump.
  • the latter two configurations of the method according to the invention lead to an improvement in the efficiency of the method according to the invention.
  • the pressure of the working fluid at the inlet of the expander is at least 30%, preferably between 40 and 50%, above the critical pressure of the working fluid.
  • propane, propylene or any desired mixture of propane and propylene circulates in the Rankine cycle as the working fluid.
  • This configuration is particularly advantageous when the temperature of the external medium A amounts to between 120 and 200° C., preferably between 130 and 160° C.
  • FIG. 1 shows Rankine cycle system in accordance with the prior art
  • FIG. 2 illustrates an exemplary embodiment of a Rankine cycle system according to the invention.
  • the working fluid circulating in the Rankine cycle is brought to the desired operating pressure by means of the pump P 1 and preheated in the heat exchanger E 3 against the expanded working fluid 5 .
  • a pump P 1 is provided which may be controlled with regard to the mass flow rate of the working fluid 1 .
  • the working fluid is pumped by means of the pump P 1 to a pressure such that it may be ensured that the pressure of the heated working fluid 4 at the inlet to the expander X 1 is at least 30%, preferably between 40 and 50%, above the critical pressure of the working fluid.
  • the working fluid is preheated in the heat exchanger E 3 and fed via line 2 to the heat exchanger E 1 , to which an external medium, for example hot water, is fed via line A.
  • This external medium is cooled in the heat exchanger E 1 against the working fluid and drawn off from the heat exchanger E 1 via line B.
  • the working fluid drawn off from the heat exchanger E 1 via line 3 is preferably heated to a temperature at least 30 K, preferably 40 to 60 K, above its critical temperature.
  • the heat exchanger E 4 serves to heat the working fluid by a suitable (additional) external medium, preferably during the start-up procedure and/or during part load operation. When the Rankine cycle is in normal operation, this heat exchanger is not required.
  • the working fluid is fed to the expander X 1 via line 4 .
  • the expander X 1 is an expander controllable with regard to the mass flow rate of the working fluid.
  • the expander X 1 preferably comprises an adjustable inlet guide vane Y, which preferably is a nozzle ring at the inlet of the expander.
  • the expanded working fluid is fed via line 5 to the heat exchanger E 3 .
  • the preheating of the pumped working fluid 1 carried out in the heat exchanger E 3 is particularly convenient when the outlet temperature of the working fluid 5 on leaving the expander X 1 is higher than the condensation temperature in the heat exchanger E 2 downstream of the expander X 1 .
  • the heat from the temperature interval between the outlet temperature and the condensation temperature in the heat exchanger E 3 may be used to preheat the working fluid 1 .
  • the expanded working fluid is fed to the heat exchanger E 2 via line 6 and is condensed and subcooled therein against a suitable external medium.
  • the subcooled working fluid is then fed via line 7 to the storage or surge tank D 1 . From there it passes via line 8 back to the pump P 1 .
  • Subcooling of the working fluid 6 in the heat exchanger E 2 may be dispensed with if the storage tank D 1 is positioned sufficiently high above the pump P 1 to prevent undesired cavitation in the pump P 1 .
  • the temperature of the external medium A fed to the heat exchanger E1 is between 120 and 200° C., preferably between 130 and 160° C.
  • propane, propylene or any desired mixture of propane and propylene is preferably used as the working fluid.
  • the method according to the invention for converting heat energy into mechanical energy allows stabilization of the inlet state of the expander X 1 , which results in improved operation of the Rankine refrigeration cycle.
  • the method according to the invention additionally exhibits greater efficiency than the above-described, prior art method.

Landscapes

  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Engine Equipment That Uses Special Cycles (AREA)
US13/569,592 2011-08-09 2012-08-08 Power generation from low-temperature heat Abandoned US20130036737A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE102011109777A DE102011109777A1 (de) 2011-08-09 2011-08-09 Energiegewinnung aus Niedertemperaturwärme
DE102011109777.9 2011-08-09

Publications (1)

Publication Number Publication Date
US20130036737A1 true US20130036737A1 (en) 2013-02-14

Family

ID=46633988

Family Applications (1)

Application Number Title Priority Date Filing Date
US13/569,592 Abandoned US20130036737A1 (en) 2011-08-09 2012-08-08 Power generation from low-temperature heat

Country Status (4)

Country Link
US (1) US20130036737A1 (fr)
EP (1) EP2557279A3 (fr)
DE (1) DE102011109777A1 (fr)
ZA (1) ZA201205994B (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN107905864A (zh) * 2017-11-13 2018-04-13 清华大学 一种储能发电系统及其控制方法

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ITCO20110063A1 (it) * 2011-12-14 2013-06-15 Nuovo Pignone Spa Sistema a ciclo chiuso per recuperare calore disperso
DE102014017802A1 (de) 2014-12-02 2016-06-02 Linde Aktiengesellschaft Effektivere Arbeitsgewinnung bei der Erwärmung kryogener Flüssigkeiten

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4109469A (en) * 1977-02-18 1978-08-29 Uop Inc. Power generation from refinery waste heat streams
US6751959B1 (en) * 2002-12-09 2004-06-22 Tennessee Valley Authority Simple and compact low-temperature power cycle
US20090238681A1 (en) * 2008-03-19 2009-09-24 Snecma Control device of variable pitch vanes in a turbomachine

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4358930A (en) * 1980-06-23 1982-11-16 The United States Of America As Represented By The United States Department Of Energy Method of optimizing performance of Rankine cycle power plants
JP4935935B2 (ja) * 2008-12-18 2012-05-23 三菱電機株式会社 排熱回生システム
US20100319346A1 (en) * 2009-06-23 2010-12-23 General Electric Company System for recovering waste heat
US8096128B2 (en) * 2009-09-17 2012-01-17 Echogen Power Systems Heat engine and heat to electricity systems and methods

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4109469A (en) * 1977-02-18 1978-08-29 Uop Inc. Power generation from refinery waste heat streams
US6751959B1 (en) * 2002-12-09 2004-06-22 Tennessee Valley Authority Simple and compact low-temperature power cycle
US20090238681A1 (en) * 2008-03-19 2009-09-24 Snecma Control device of variable pitch vanes in a turbomachine

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN107905864A (zh) * 2017-11-13 2018-04-13 清华大学 一种储能发电系统及其控制方法

Also Published As

Publication number Publication date
DE102011109777A1 (de) 2013-02-14
EP2557279A3 (fr) 2013-11-06
ZA201205994B (en) 2013-05-29
EP2557279A2 (fr) 2013-02-13

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Owner name: LINDE AKTIENGESELLSCHAFT, GERMANY

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:BAUER, HEINZ;SAPPER, RAINER;SIGNING DATES FROM 20120824 TO 20120827;REEL/FRAME:029152/0840

STCB Information on status: application discontinuation

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