RU2078950C1 - Rankine-cycle power plant and its operation - Google Patents

Abstract

FIELD: power engineering. SUBSTANCE: Rankine-cycle power plant has evaporating element responding to heat introduced for evaporating working medium and forming evaporated working medium, turbogenerator responding to evaporated working medium to generate energy and to form working medium releasing heat, condenser element responding to working medium releasing heat for its condensation and producing condensate, as well as associated piping to return condensate to evaporator. Working medium is liquid containing great number of fractions at least one of which is distilled from mentioned liquid to form distilled medium which is supplied to power plant as working medium. EFFECT: improved reliability, provision for using fossil medium. 8 cl, 1 dwg

Description

 The invention relates to a power plant operating according to the Rankin cycle and using an organic medium, as well as to a method of using such a plant.

Well-known power plants operating on the Rankine cycle and using an organic medium. In such installations, the organic medium is evaporated in an evaporator or boiler using heat from fuel combustion, a geothermal source or industrial processes, and the evaporated working medium is expanded in a pipe generator to generate energy and generate a heat-transfer medium that condenses in a condenser cooled by air or water, to obtain a liquid working medium that is returned by the pump to the evaporator [1]
The working medium is selected so that it has the proper thermodynamic properties for the cycle, such as heat capacity, stability at operating temperatures, etc. and was also compatible with metals used in conventional turbine plants. In addition, the working medium must have good lubricating properties, since, as a rule, the turbine and the generator connected to it are in a hermetically sealed housing, inside of which the liquid medium from the condenser is used as a lubricant.

 Generally speaking, the working medium will be a hydrocarbon, for example, pentane or hexane, or an isomer thereof, for example, isopentane or isohexane. Other well-known chemicals are also used. But in any case, the working environment is a commercially available, commercially pure material that has well-defined known properties that are used in the construction of power plant equipment. Mixtures of hydrocarbon fluids are sometimes used in order to take advantage of the special properties of the mixtures described in US Pat. No. 3,842,593, where a special hydrocarbon mixture allows the power plant to operate in ambient conditions that would prevent the use of clean material.

 Since the manufacturer of a power plant operating according to the Rankin cycle on an organic medium must ensure that it will provide a given output electronic power from a source that generates a given amount of heat per unit time, the selected working medium, or a mixture of media, must have well-defined physical properties. The fact that the selected medium or media will have these properties is guaranteed by the use of commercially pure media that meet international standards. These media are easily accessible in most parts of the world, but there are many places in the world where acceptable clean media are excessively expensive, or when their use in an energy installation creates problems of state regulation due to insufficient historical precedent for their use in such conditions.

 Some organic media that can theoretically be used in a power plant are significantly less expensive or more affordable than those commonly used in power plants, but these media are usually mixtures whose characteristics regarding pressure-volume-temperature are unknown, either vary widely from place to place and in time. As a result, the designer of a power plant can never be sure that such media will work in a power plant in the same specified ways as a pure liquid whose properties are established. For example, motor fuel gasoline is one of the most common environments in the world from the most developed industrial countries to the poorest countries of the third world. In some countries, gas is more accessible than water, while the public’s favorable attitude to the storage and use of gas and government regulations on this subject are clearly defined compared to many that non-professionals consider exotic organic environments that are offered for power plants operating on 0rankin cycle. However, the use of gasoline or another hydrocarbon containing a large number of fractions is not the best choice for a power plant operating on the Rankin cycle on an organic liquid, due to the uncertainty in the thermodynamic properties of a particular batch of gasoline in a certain place in the world at a certain time. The designer may not know in advance the thermodynamic properties of gasoline, which will be supplied to the unit at startup or later as a replenishing working medium; therefore, the design developed by him cannot take into account possible changes that may occur. As a result, the designer rejects gasoline.

 An object of the present invention is to provide a method and means for using well-known, readily available acceptable commercial organic media, such as gasoline, in power plants operating on the Rankin cycle, regardless of possible changes in thermodynamic properties from place to place and time .

 The present invention relates to the operation of a Rankine cycle power plant of a type that has an evaporation element responsive to input heat to vaporize a working fluid and form a vaporized working fluid, a turbine generator responsive to a vaporized working fluid to generate energy and generate a heat transfer fluid , a condenser element that responds to the heat medium that has provided heat to condense and form condensate, and also means for returning condensate to the evaporator. The working medium is in the form of a liquid having a large number of fractions; the present invention provides distillation of at least one fraction of said liquid to create a distilled medium. This is the distilled medium that is supplied to the power plant as a working medium.

 A distilled medium is a liquid that is introduced into the power plant and acts together with it, at least one element of the power plant is an evaporation element or a condenser element, or both of them are used to distill the fraction from the liquid to create a distilled medium. In this case, the last fraction mentioned is removed from the power plant, the operation of which is then continued using a distilled medium. As a result, the working medium intended for stable operation is the main fraction of the liquid, the thermodynamic properties of which are well known and reproducible.

 Preferably, the working fluid is gasoline. The removal of fractions with a low boiling point by means of an evaporation element, as well as fractions with a high boiling point by a condenser element, will result in a medium whose properties are well known. Alternatively, fractions with a high boiling point can be removed by means of an evaporation element, and fractions with a low boiling point can be removed by means of a condenser. Therefore, even if the properties of the liquid before starting work, the power plant is unknown, or only slightly known, after distillation processes are carried out using the evaporation element and the condenser element as fraction columns, and after fractions with a larger and smaller points are removed boiling, the remaining working environment will operate in a predetermined manner, which allows the power plant to generate the required energy.

 In a modification of the invention, the temperature and pressure in the elements are controlled, and the amount of said fractions in the distillate is controlled according to the controlled temperature and pressure in the said elements, so that the flow rate through the power plant is actually kept constant.

An embodiment of the present invention is shown by way of example in the accompanying drawings, in which:
In FIG. 1 is a block diagram of a power plant operating according to the invention, operating according to the Rankin cycle on an organic medium; in FIG. 2 is a diagram of a method according to the present invention for maintaining the installed output power of a power plant according to FIG. 1 by providing adjustment of the flow rate of the working environment; in FIG. 3 is a diagram of another method according to the present invention for maintaining the installed output power of the power plant of FIG. 1 by providing adjustment of the flow rate of the working medium.

 Reference numeral 10 denotes a power plant operating according to the present invention and operating according to the Rankine cycle on an organic liquid. The power plant 10 comprises an evaporation element 12 that receives the heat generated by the burner 14 to vaporize the organic working medium 16 and is formed by the evaporated working medium in the outlet pipe 18, connected via a node 19 to the pipe 20, which is connected to the inlet stage of the turbine generator 21. The evaporated working medium expands in the turbine 21 with the formation of heat-transferring working medium, which is supplied to the condenser element 24, where the condensation of the working medium, which gave off heat, occurs. The condenser may be air or water cooled, the condensate 25 in the condenser being returned via the pump 26 to the evaporator to complete the cycle with the organic medium. A generator 23 connected to the turbine 21 is thereby driven and an expansion of the working medium in the turbine generates electricity.

 The components described above and their operation are generally common, with the exception of the nature of the work environment. Prior to the present invention, the working medium could be a pure organic medium, for example, pentane or isopentane, having certain thermodynamic properties that allow the designer to design a power plant having a selected output power for a given heat input that will provide the selected steam flow through the turbine. According to the present invention, the working medium may be a hydrocarbon having a large number of fractions, for example gasoline, whose properties and in fact whose components vary in time and from place to place due to changes in various fractions present in gasoline.

 In order to use a hydrocarbon, such as gasoline, a refill tank 30 is used, this tank is filled with a sufficient amount of hydrocarbon liquid to provide loading of the power plant of the working medium at start-up. To this end, a valve 5 is introduced between the tank 30 and the pump 26. Therefore, to load the power plant with a working medium at the start of startup, when there is no working medium in the evaporator or somewhere else, the valve 5 opens and the pump 26 is actuated to draw the evaporator 12, which is in a cold state, the amount of liquid sufficient to fully load the installation.

 Then, valve 6 opens to supply heat to the evaporator. The fractions with a low boiling point in the liquid of the evaporator are first boiled by keeping, if it is preferable, the temperature in the evaporator at a lower level than the projected level until all fractions with lower boiling point. During this time, valve 1 is open and most of the fractions with a lower boiling point are piped to the collection tank 32. An additional valve (not shown) may block the entry of these fractions into the turbine.

 To detect the evaporation of fractions with a lower boiling point and to be able to control such evaporation, temperature and pressure sensors indicated by 33 can be installed in the evaporator. When the temperature and pressure detected by the sensor 33 reach a level that indicates that the fractions with a low boiling point removal from the liquid in the evaporator, the valve 1 closes and the vapors that then form are supplied through the pipeline to the condenser 24 by opening the valve 7.

 The steam that enters the condenser has a temperature and pressure that are almost equal to the temperature and pressure of the steam leaving the evaporator. The condenser 24 carries out the condensation of the evaporated working medium with its transition into a liquid state. The first part of the liquid that condenses will be fractions with a higher boiling point, and they are fed to the collection tank 34 through an open valve 3. To control the temperature and pressure with the sensors indicated at 35, a shut-off valve 3 can be installed. installation can be powered. That is, valves 1, 2, 3, 4, 5, and 7 are closed and the working medium that passes through the evaporator, turbine, and condenser in a cycle is fractions with an average boiling point from the initial hydrocarbon in the additional tank 30.

 In order for the installation to work efficiently and provide the required power, the temperature and pressure in the evaporator and condenser can be adjusted to create the desired flow rate. These parameters are taken in places 33 and 35 and their obtained values are supplied to the control unit 36, which may be a computer controlled to control various valves in the system. The fluid from the collection tanks 32 and 34 is supplied through the valves to the system, so that it works to control the temperature and pressure in order to optimize the electrical power developed by the power plant. Such operations can be carried out during summer or winter conditions, for example, the ambient temperature changes, which changes the cooling temperature of the cooling medium of the condenser, such as water or air. These operations are similar to the operations carried out in US patent N 3842593, the essence of which is introduced here by reference to it. Consequently, if, for example, in the summer, when the ambient temperature rises, with increasing temperature of the cooling medium of the condenser, fractions with a higher boiling point can be introduced into the system. On the other hand, for example, in winter, when the ambient temperature drops, which causes a decrease in the temperature of the cooling medium of the condenser, fractions with a lower boiling point can be introduced into the system.

 Alternatively or in addition to the above, the device shown in FIG. 2. In this case, the inlet stage of the turbine is provided with a large number of separate groups of nozzles 51, 52, 53, washed from the evaporator through individually controlled valves a, b, c. These valves are controlled by the control unit 36, so that the flow rate to the turbine is adjusted in such a way as to optimize the output of the installation.

 In addition, the device shown in FIG. 3. Here, the turbine inlet stage 22B is configured with a group of nozzles 51B powered by steam generated by the evaporator 12. The steam exiting the stage 22B passes through the group of nozzles 51C to an additional degree 22C of turbine. The steam that enters from the last mentioned stage flows to stage 22 through a group of nozzles 51. The exit angles of the group of nozzles 51B, 51C and 51 can be adjusted, while the angles are set by control devices 36B, 36C and 36, respectively, to control the pressure drop, and therefore mass flow rate in various steps.

 Although a conventional burner for burning fuel is shown as a heat source for a power plant, other types of heat sources, such as geothermal media, can be used with the present invention.

 The advantages and improved results provided by the method and apparatus of the present invention are apparent from the above description of preferred embodiments of the invention. Without deviating from the scope and spirit of the invention, various changes and modifications described in the appended claims can be made.

Claims (8)

 1. The method of operation of a power plant with a Rankin cycle, including the evaporation of the working fluid in the evaporator of the installation under the influence of heat supplied to the latter, the generation of energy by means of a turbogenerator, the evaporated working fluid to produce the heat combined by the working fluid, condensation of the latter in the condenser and the return of the condensate to the evaporator pipeline with a pump, characterized in that as the working fluid using a composite fluid, including high and low boiling fractions and at least one fraction is separated from the composite fluid and stored, and the remainder of the composite fluid is used in the turbogenerator to generate energy.  2. The method according to claim 1, characterized in that gasoline is used as the composite fluid.  3. The method according to claim 1, characterized in that the temperature and pressure in the evaporator and condenser are additionally controlled, while maintaining a constant volume flow of the working fluid through the turbogenerator by replenishing the working fluid of the appropriate fraction from the first or second storage tank, depending on the values of the above controlled parameters.  4. The method according to claim 1, characterized in that the temperature and pressure in the evaporator and condenser are additionally controlled, while a turbogenerator with adjustable parameters is used, and the volumetric flow rate of the working fluid through the turbogenerator is kept constant by changing the adjustable parameters of the latter.  5. A power plant operating according to the Rankin cycle, comprising an evaporator with heat supply to evaporate the working fluid, a turbogenerator connected to it to generate energy and a heat-depleted working fluid, a condenser for producing condensate from the latter, connected to the output of the turbogenerator, and a pipeline with a pump connected to the condenser and evaporator for supplying the condensate to the evaporator, characterized in that it is equipped with an additional reservoir with a composite liquid, including high co- and low-boiling fractions, two reservoirs for storing high- and low-boiling fractions, respectively, as well as pipelines with shut-off and regulating bodies, while the executive tank, through one of the additional pipelines, is connected by its outlet to the pipeline connecting the condenser to the evaporator, up to the one installed in it pump, and tanks for storing high- and low-boiling fractions by means of additional pipelines with shut-off-regulating bodies are connected respectively to condensate and at the evaporator.  6. The installation according to claim 5, characterized in that it contains means for monitoring temperature and pressure installed in the evaporator and condenser and connected to the shut-off and regulating organs of additional pipelines connecting the storage tanks for high and low boiling fractions with a condenser and evaporator, for creating a working fluid corresponding to maintaining the output power of the turbogenerator depending on the controlled temperature.  7. Installation according to claim 6, characterized in that a hydrocarbon is used as a working fluid.  8. Installation according to claim 6, characterized in that gasoline is used as the working fluid.

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