WO2015032369A2

WO2015032369A2 - Thermal energy equipment comprising a steam turbine and an operation method of the thermal energy equipment

Info

Publication number: WO2015032369A2
Application number: PCT/CZ2014/000096
Authority: WO
Inventors: Frantisek ROSECKY
Original assignee: Natural Power And Energy S.R.O.
Priority date: 2013-09-04
Filing date: 2014-09-02
Publication date: 2015-03-12
Also published as: CZ2013679A3; WO2015032369A3

Abstract

The thermal energy equipment comprises a steam turbine (4) for expansion of inlet steam and work transfer, a cooling means (8) for withdrawal of heat from the outlet steam of the steam turbine (4), a water tank or steam boiler (1) for production of steam and steam superheater (2) to supply steam with heat steam enters the steam turbine (4). The equipment further comprises a compression means (7) arranged for withdrawal of at least a part of the inlet steam from the steam turbine (4) and/or at least a part of steam cooled in the cooling means (8), its compression to the value of pressure that corresponds to the steam pressure before the turbine (4) and supply of compressed steam to the steam boiler (1) and/or superheater (2). According to an operation method of the thermal energy equipment comprising a steam turbine (4) for inlet steam expansion and work transfer, a cooling means (8) for extraction of heat from the outlet steam of the turbine (4), water tank or steam boiler (1) for production of steam and steam superheater (2) for supply of heat to steam before its entry to the steam turbine (4), before the supply of steam to the steam boiler (1) or superheater (2) at least a part of- the total amount of outlet steam that passed through the turbine (4) after expansion is compressed in the compression means (7) to the value of pressure that corresponds to the steam pressure before the turbine (4) and the steam compressed this way is supplied to the steam boiler (1) and/or superheater (2).

Description

Thermal energy equipment comprising a steam turbine and an operation method of the thermal energy equipment

Field of the invention

The invention relates to thermal energy equipment comprising a steam turbine for expansion of inlet steam and work transfer, a condenser or cooler for withdrawal of heat from the outlet steam of the steam turbine, a water tank or steam boiler for production of steam and a steam superheater to supply steam with heat before steam enters the steam turbine. The invention further relates to an operation method of the thermal energy equipment.

Background information

Work is obtained from thermal energy in thermal machines. The working medium performs work by passing through purposefully arranged changes so it returns to the original state along a different path than it took in the first part of the process. These changes form a thermal circuit. A steam circuit has some characteristic features. First of all it uses a working medium that occurs in two phases in the course of its state changes and the design of such a circuit is more complex than that of a heat circuit where^' the working medium only occurs in one phase.

Another characteristic feature is that it' is just the steam circuit with only one working medium (water) that is used to convert the absolute majority of thermal energy (in power plants) to electric energy. A simple steam circuit can be described as follows. Feeding water is injected into an exchanger (boiler) where the operation pressure is maintained and where it is heated to the boiling point at the given operation pressure and then is evaporated and superheated to the working temperature. Then, heat enters the turbine where it transfers useful work and leaves for the condenser where it transfers the condensation heat .

What is important from the thermodynamic point of view is that heat is extracted from the circuit quite ideally, speaking about a thermal circuit at the ambient temperature, which is increased by the temperature gradient of the exchanger. Heat is supplied in an isobaric manner in the whole temperature range of wet steam where the isobaric line equals the isothermal line. The share of isobaric and isothermal supply of heat depends on the maximum selected pressure of the circuit. There is a general rule that in all steam circuits the supply of heat is less favourable than its extraction from the thermodynamic point of view. The rate of this difference depends on the selected working medium.

Another important fact is that in steam circuits it is always the liquid that is compressed. As a consequence, the compression work is low as compared to the turbine work, sometimes even almost negligible. Therefore, the useful work is nearly equal to the steam turbine work, which together with high expansion ratios results in the specific output of the working medium is very high compared to all the other cycles. For all the above mentioned reasons the thermal efficiency of the circuit is also relatively high. Similarly to a gas turbine circuit the optimum pressure of a steam turbine is a function of the inlet steam temperature while the optimum pressure level is considerably high; the optimum pressure quickly rises with the rising temperature. A real circuit differs from the ideal circuit in that due to pressure losses the feeding pump overcomes a higher pressure difference than the theoretical one. Due to irreversible compression the required feeding work is higher than adiabatic work. Due to irreversible expansion the useful work of the turbine is lower than adiabatic work and due to the irreversibility of heat exchange during condensation the lower temperature of the circuit exceeds the ambient temperature. In spite of the generally advantageous features of the basic circuit its thermodynamic indicators can be further improved by using carnotization modifications out of which regenerative heating of feeding water and naturally also their combinations are especially applied.

The principle of regenerative heating is that part of steam is withdrawn from the turbine and is used to heat the feeding water. This way, thermodynamically inconvenient supply of heat at low temperatures is avoided, so the average temperature of heat supply to the steam circuit is increased. Regenerative heating of feeding water is very important and therefore it is principally used in modern steam circuits.

Steam reheating is used in such a way that heat is supplied to the working medium after partial expansion, which increases both the total heat efficiency and especially the specific output of the working medium. Besides, the expansion end is shifted to the higher dryness range, which is very convenient with regard to corrosion of blades of the last turbine stages.

Steam turbines represent the basic drive type in heat as well as nuclear power plants as part of the thermal energy equipment. As shown in fig. 1, prior art thermal energy equipment of power plants consists of a closed circuit of a steam turbine 4_, condenser 8, feeding pump 10, steam boiler 1 and steam superheater 2_r working in a closed thermal cycle where in the turbine _4 the inlet steam expands in an isenthropic way and transfers work, the outlet steam of the turbine flows into the condenser _8, in the condenser j3, heat is extracted from the outlet steam of the turbine _4 to the cooling water of the condenser _8 and steam condenses, condensate is suctioned by the feeding pump _10_, is transported to the steam boiler 1, in the steam boiler 1 water is heated to the boiling point at a constant pressure until evaporation, steam continues to the superheater 2, in the superheater 2 more heat is supplied to steam at a constant pressure and then, by injection of steam to the turbine ^4 and isenthropic expansion of steam in the turbine _4 the circulation of steam in the thermal energy equipment is completed.

The thermal efficiency of thermal energy equipment, considered without losses in the turbine ("ideal thermal energy equipment") is determined by the ratio of work that can be obtained in one cycle from 1 kg of steam and the amount of heat that is supplied to water and steam in the course of one cycle .

The effort to increase the heat efficiency of the ideal energy equipment is concentrated on increasing the temperature difference in the ideal thermal cycle, i.e. on increasing the difference between the mean temperature value at which heat is supplied to water and steam in the steam boiler and superheater and the temperature at which heat is extracted from the outlet steam of the steam turbine in the condenser. Besides, effort is also concentrated on increasing the thermodynamic efficiency of the entire steam turbine, especially on maximum possible reduction of all losses in the steam turbine. Hitherto effort has achieved the thermal efficiency of the cycle of thermal energy equipment in the range of 45 - 52 % and the possibilities of further increasing are being looked for especially in the area of thermodynamic efficiency and the design of the entire steam turbines.

A disadvantage of equipment according to the prior art generally appears to be its unsatisfactory efficiency and therefore increasing this efficiency remains to be a permanent goal.

The object of the invention is to significantly increase the thermal efficiency of thermal energy equipment and to enable increasing of thermal efficiency of existing thermal energy equipment.

Principle of the invention

Disadvantages of the prior art are substantially eliminated and the object of the invention is fulfilled by thermal energy equipment in accordance with the present invention comprising a steam turbine for inlet steam expansion and work transfer, a cooling means for extraction of heat from the outlet steam of the turbine, water tank or steam boiler for production of steam and steam superheater for supply of heat to steam before its entry to the steam turbine the principle of which is that it comprises a compression means designed for withdrawal of at least a part of outlet steam from the steam turbine and/or at least a part of steam cooled in the cooling means, its compression to the value of pressure corresponding to the steam pressure before the turbine and supply of compressed steam to the steam boiler and/or superheater.

According to one of the convenient embodiments the compression means is a compressor while the outlet of the generator turbine is connected to the compressor inlet via a mixer, the compressor outlet is connected to the superheater inlet and the superheater outlet is connected to the turbine inlet via a distributor to withdraw a part of inlet steam leaving the superheater to the inlet of the compressor turbine mechanically connected to the compressor and the outlet of the compressor turbine is connected to one of the mixer inlets. Between the mixer outlet and the compressor inlet a cooler may be arranged or there may be a distributor whose one outlet is connected to the compressor inlet and another outlet is connected to the inlet of the condenser for heat extraction whose outlet is connected to the inlet of the feeding pump whose outlet is connected to the inlet of the steam boiler.

According to one of the convenient embodiments the outlet from the compressor may also be connected to the inlet of the steam boiler and/or connected to the internal spiral of the steam boiler and the outlet of the feeding pump may also be connected to the superheater inlet and/or connected to the internal spiral of the steam boiler. According to another convenient embodiment the thermal energy equipment contains a condenser and a compression means comprising at least two compressors or compression stages while a part of the total amount of outlet steam that left the turbine after the expansion is supplied to the condenser and the remaining part of this total amount is supplied to the first compressor or compression stage while the compressors or compression stages are arranged for gradual compression of steam in such a way that steam compressed in the upstream compressor or stage to a certain pressure value is compressed in the downstream compressor or stage from this pressure value to a higher pressure while at least a part of condensate produced in the condenser is supplied to the steam compressed in the upstream compressor or stage before it is supplied to the downstream compressor or stage.

The thermal energy equipment may further contain a condensate tank for storage of condensate produced in the condenser and a pump to supply at least a part of condensate from the condensate tank to steam compressed in the upstream compressor before it enters the downstream compressor.

The thermal energy equipment may further contain a pump to supply a part of condensate from the condensate tank to the steam boiler.

According to one of the convenient embodiments the thermal energy equipment comprises the first generator turbine arranged at the steam boiler outlet the outlet of which is connected, via the superheater, to the inlet of the other generator turbine whose outlet is connected, via a cooler and distributor, to the condenser inlet while the other outlet of the distributor is connected to the inlet of the first compressor followed by the second compressor and subsequently the third compressor while the third compressor releases steam compressed to the pressure value that corresponds to the pressure of the inlet steam of the turbine to the steam boiler and/or superheater.

It is convenient for the outlet steam leaving the turbine to have a higher humidity value than 0.32 and for the steam before the beginning of compression in the compression means to have a higher humidity value than 0.18.

Another object of the invention is an operation method of the thermal energy equipment in accordance with the invention.

The above mentioned disadvantages of the prior art are eliminated and the objects of the invention are also fulfilled by an operation method of thermal energy equipment comprising a steam turbine for inlet steam expansion and work transfer, a cooling means for extraction of heat from the outlet steam of the turbine, water tank or steam boiler for production of steam and steam superheater for supply of heat to steam before its entry to the steam turbine where the principle of the method in accordance with the invention is that before the supply of steam to the steam boiler or superheater at least a part of the total amount of outlet steam that passed through the turbine after expansion is compressed in the compression means to the value of pressure that corresponds to the steam pres sure before the turbine and the steam compressed this way is supplied to the steam boiler and/or superheater. According to a convenient embodiment the thermal energy equipment contains ^' a condenser and the compression means comprises at least two compressors or compression stages while a part of the total amount of outlet steam that left the turbine after the expansion is supplied to the condenser and the remaining part of this total amount of outlet steam is supplied to the first compressor or compression stage, where the steam is compressed to a certain pressure value while further movement of this steam is that before the steam compressed in the upstream compressor or compression stage is supplied to the next compressor or compression stage at least a part of the condensate produced by condensation of steam that was supplied to the above mentioned condenser is injected to the steam compressed this way and the steam thus enriched is fed to the said next compressor or compression stage where it is compressed to a pressure that is higher than the pressure to which it was compressed in the previous compressor or compression stage while in the last compressor or compression stage the steam is compressed to the pressure value corresponding to the pressure of the inlet steam before its entry to the turbine and the steam is supplied to the steam boiler and/or superheater at this pressure.

A part of condensate produced in the condenser can be directly supplied to the steam boiler within the control function.

In accordance with another convenient embodiment steam is cooled in a cooler before it is supplied to the condenser and to the first compressor or compression stage. In accordance with another convenient embodiment the thermal energy equipment comprises at least two turbines arranged in series in such a way that steam from the steam boiler or superheater is introduced in the first turbine from where it is directed to the next turbine via another superheater while after expansion of steam in the last turbine a part of the steam is withdrawn to the first compressor of compression stage and the remaining part of the steam is routed to the condenser.

An advantage of the thermal energy equipment with a steam turbine in accordance with the invention consists in a substantial increase of the thermal efficiency of the cycle up to the level of 60% without any change of the temperature of inlet steam before the turbine and to the level of 65% if the temperature of inlet steam before the turbine is increased to the level of 610 °C and the pressure is reduced to the level of 50 bar. If multi-stage compression with a variable amount of the working medium during compression is used, thermal efficiency of over 70% can be achieved.

Overview of figures in the drawings

The present invention will be clarified in more detail with reference to drawings where:

- fig. 1 shows a schematic layout of thermal energy equipment in accordance with the prior art

- fig. 2 shows the first example of an embodiment of the thermal energy equipment in accordance with the invention with a compressor designed for withdrawal of steam cooled in the condenser, - fig. 3 shows the temperature - entropy (T-s) diagram of the ideal cycle of the prior-art thermal energy equipment of fig. 1 compared to the thermal energy equipment in accordance with the first embodiment example illustrated schematically in fig. 2,

- fig. 4 shows the temperature - enthalpy (log p-h) diagram of the ideal cycle of the prior-art thermal energy equipment of fig. 1 compared to the thermal energy equipment in accordance with the first embodiment example illustrated schematically in fig. 2,

- fig. 5 shows the second example of an embodiment of the thermal energy equipment in accordance with the invention,

- fig. 6 shows the third example of an embodiment of the thermal energy equipment in accordance with the invention,

- fig. 7 shows the fourth example of an embodiment of the thermal energy equipment in accordance with the invention,

- fig. 8 shows the pressure - enthalpy (log ρ-h) diagram of the ideal cycle of the thermal energy equipment of fig. 7.

Examples of embodiments

Fig. 1 schematically shows the layout of the prior-art thermal energy equipment that was described in the paragraph ^Background information".

Fig. 2 schematically shows the first example of an embodiment of the thermal energy equipment in accordance with the invention. A simple, closed ideal steam circuit is used where the working medium is water. The simplest thermal steam circuit can be described as follows :

1) The compressor 1_ aspirates wet, saturated or superheated steam. The dryness of the wet steam must be higher than x=0.18. The steam pressure at the compressor 1_ inlet corresponds to the pressure after the condenser _8. The outlet pressure equals to the working pressure before the turbine _4.

2) In the steam boiler 1 or exchanger heat is supplied. It the range of wet steam with a dryness value higher than x=0.18 this is done in the isothermal and isobaric manner. The heat supply is stopped in the superheater 2 by reaching of the working temperature before the turbine .

3) Steam expands from the working pressure before the turbine _4 to the pressure after the turbine 4_, which corresponds to the pressure in the condenser 8_.

4) In the condenser 8_ heat is extracted and transferred to the ambient environment. Heat extraction is stopped and limited by dryness of steam, which must be higher than x=0.18.

5) Expansion in the turbine 4_ is stopped at a steam dryness higher than 0,32.

As the above mentioned description indicates, in the thermal energy equipment in accordance with the invention of fig. 2 steam is injected into the steam boiler _1 (unlike the prior art where only water is injected into the steam boiler) . The feeding pump J10 may or may not assume the control function.

Fig. 3 illustrates the influence of parameters to thermal efficiency in a temperature - entropy (T-s) diagram of the ideal cycle of the prior-art thermal energy equipment in accordance with fig. 1 compared to the first embodiment example of the thermal energy equipment in accordance with the present invention the layout of which is shown in fig. 2. Description of the cycle of the thermal energy equipment of fig. 1 (reference marks used below - see fig. 1 and 3) .

In the thermal energy equipment of fig. 1 the supply of heat in the ideal cycle comprises three stages. According to fig. 3 as indicated by the T-s diagram the feeding water is heated to the saturation temperature at a constant pressure according to line ab and the water evaporates at a constant temperature according to line be in the steam boiler 1 and heat is supplied in the superheated steam range in the superheater 2 at a constant pressure according to line cd.

In a turbine working without losses and without heat exchange with the ambient environment the expansion has an isenthropic course. The expansion is indicated in fig. 3 in the T-s diagram by the course of line de. Steam that expanded in the turbine 4_ leaves the turbine as outlet steam and continues to the condenser 8^ There, at a constant pressure heat is transferred from the steam to cooling water (ambient environment) , the steam condenses, condensate is aspirated by the feeding pump JLO and transported to the steam boiler _1.

In the steam boiler 1 and superheater 2 heat is supplied at a constant pressure so the amount of heat supplied to water and steam is exclusively consumed to increase the enthalpy of steam. Heat transferred to steam in the steam boiler and in the superheater 2 is indicated in fig. 3 by the area 1 ' " abcd2 "1" in the T-s diagram.

Description of the cycle of the thermal energy equipment of fig. 2 (reference marks used below - see fig. 2 and 3) According to the first example of an embodiment of the example, schematically shown in fig. 2 thermal energy is converted to mechanical energy in accordance with the diagram in fig. 3. The T-s diagram contains an area delimited by the cdef line. Compression of steam in the compressor 1_ follows the fc line, heat supply in the superheater 2 follows the cd line, expansion in the turbine follows the de line and heat extraction in the condenser _8 follows the ef line.

The dcef area shows the work that can be obtained for 1 kg of steam (isenthropic work) . Heat transferred to steam in accordance with the invention is indicated by the cd2 "3" area in the diagram.

Heat efficiency of the ideal circuit of thermal energy equipment is calculated as the ratio of work that can be obtained from 1 kg of steam and the heat transferred to steam.

The ratio of the size of the dcef area (work) and the cd2 ' "3' ' area (transferred heat) in accordance with the invention is higher than the ratio of the size of the abcdea area and the 1 ' " abcd2 ' ' \' ' area.

Thus, the thermal efficiency of the ideal circuit in accordance with the invention is higher than the thermal efficiency of the ideal circuit in accordance with the prior art .

Fig. 4 compares the working cycles of _ the prior-art thermal energy equipment of fig. 1 and the thermal energy equipment in accordance with the invention of fig. 2 using the dependence of pressure p on enthalpy. In the diagram of fig. 4 the pressure unit is bar and the enthalpy unit is kJ/kg.

Description of the cycle of the thermal energy equipment of fig. 1 (reference marks used below - see fig. 1 and 4)

The cycle of the prior-art thermal energy equipment is indicated with a dashed line in the diagram. Expansion in the turbine _4 starts at the pressure of 120 bar and temperature before the turbine of 540°C. The start of expansion is indicated by point B, where enthalpy at this point is 3395 kJ/kg. The expansion has an adiabatic course, i.e. without any heat supply or extraction. The end of expansion is indicated by point C with the enthalpy of 1953 kJ/kg. The difference at the beginning and end of the expansion is the expansion useful work of the turbine 4. This means that the useful work of the turbine 4 is 3395-1953=1442 kJ/kg.

From point C with the enthalpy of 1953 kJ/kg to point A with the enthalpy of 163 kJ/kg heat is transferred to cooling water in the condenser 8_ and steam condenses to water. This means that the extracted heat is the difference of 1953-163= 1790 kJ/kg.

Condensed water is injected into the steam boiler by the feeding pump at point A with the enthalpy of 163 kJ/kg. Heat is supplied from point A to point B with the enthalpy of 3395 kj/kg. This means that the supplied heat is the difference of 3395-163= 3232 kJ/kg.

Useful work is calculated as the difference of the supplied heat and the extracted heat 3232-1790= 1442 kJ/kg. Thermal efficiency is determined as the ratio of the useful work and supplied heat, i.e. 1442/3232= 0.446. This result says that 44.6% of supplied heat is converted to useful work.

Description of the cycle of the thermal energy equipment of fig. 2 (reference marks used below - see fig. 2 and 4)

The cycle of the thermal energy equipment in accordance with the invention is indicated with a full line. In this case the parameters of turbine 4_ are the same both in the prior-art steam circuit and in the thermal steam circuit in accordance with the invention and thus the useful work is 1442 kj/kg. From point with the enthalpy of 1953 kJ/kg to point A_ with the enthalpy of 1232 kJ/kg. This means that the extracted heat is the difference of 1953-1232= 721 kj/kg. Heat is extracted at a constant pressure in the range of wet steam and at a constant temperature.

From point with the enthalpy of 1232 to point 1J_ with the enthalpy of 1813 kJ/kg adiabatic compression goes on, where wet steam is compressed to the operation pressure of the turbine 4_. So the compression work is 1232-1813= -581 kJ/kg. This means that the compression work is negative and must be deducted from the useful work. Compression work must start in the range where the humidity x is higher than 0.18. This guarantees that the end of compression will be in the range where water separated from wet steam will not hinder the course of the compression. From point l_ with the enthalpy of 1813 kJ/kg to point 2_ with the enthalpy of 3395 kJ/kg heat is supplied 3395- 1813=1582 kJ/kg at a constant pressure in wet and later in superheated steam.

Useful work is the difference between the supplied and extracted heat 1582-721= 861 kJ/kg, naturally it is also the difference of the useful work of the turbine 4_ and work of the compressor 8 1442-581= 861 kJ/ g.

The thermal efficiency of the steam circuit in accordance with the invention is the share of useful work and supplied heat ETA = 861/1582 =0.544, which means that 54.4% of supplied heat is converted into useful work. After optimization of the working field and with the use of new materials for steam turbines a comparable thermal efficiency of the steam circuit in accordance with the invention of up to 70% can be achieved.

The use of the thermal energy equipment in accordance with the invention reduced fuel consumption by at least one third.

With the use of the usual temperature before the turbine i_ of 600 °C and reheating of steam the thermal energy equipment in accordance with the invention achieves the thermal efficiency of 64.2% at a working pressure lower than 5 MPa. The use of state-of-the-art materials for the turbine _4 blades is expected to bring a thermal efficiency of about 70% and a steam-gas thermal circuit will approximate 80%.

Fig. 5 shows the second example of an embodiment of the thermal energy equipment in accordance with the invention. From the water tank la water is refilled to the superheater 2. In the superheater 2 heat is supplied to steam. In the distributor 3 steam is divided to the turbine of the generator and turbine 5_ of the compressor · ^{In tne} mixer 6 steam is mixed after expansion in the turbine 4 of the generator and turbine 5 of the compressor 7. The compressor 1_ compresses steam to the working pressure before the turbines _4, _5. Heat is extracted in the cooler _16. This arrangement represents the first option. An alternative - second option is that the compressor is directly mechanically connected to the steam turbine of the generator. The above mentioned first arrangement option can be conveniently used for the implementation of supplementary equipment that will be introduced in existing - already used thermal energy equipment known from the prior art without the necessity of principal conversion of this existing thermal energy equipment.

Fig. 6 shows the third example of an embodiment of the thermal energy equipment in accordance with the invention. The thermal heat circuit contains two steam flow circuits. The first circuit is the power circuit where superheated water steam flows from the steam boiler 1 through the superheater 2. In the distributor 3_ of superheated steam steam is divided to the flow through the steam turbine 4 of the generator and to the flow through the steam turbine _5 of the compressor 1_ to the mixer 6 and subsequently to the distributor 3a, where the respective control quantity of steam is separated. In the compressor 1_ of the turbo-compressor steam is compressed from the pressure after the steam turbine 4 of the generator and the same pressure after the turbine 5 of the turbo-compressor to the working pressure in the steam boiler _1. Compressed water steam from the compressor 1_ of the turbo-compressor enters the pipeline before the steam boiler _1, to the steam boiler _1 and after the steam boiler 1 before the superheater 2. Thus, the power circuit is completed.

The other circuit is a control circuit. From the control distributor ^3a a control quantity of steam flows to the control condenser 8_^ and then condensate is transported by the feeding pump 10 before the steam boiler 1 to the steam boiler 1_ and after the steam boiler _1.

The description of the process of the thermal energy equipment in accordance with this third embodiment example is as follows. In the steam boiler 1 water {condensate and compressed steam) is heated at a constant pressure and temperature up to the saturation limit. Then, it flows to the superheater 2, where it is superheated to the working temperature before the turbines _4 and 5. In the turbines _4, 5 it expands to the initial pressure. In the turbine it converts useful work usually to the production of electric power. The turbine _5 of the turbo-compressor compresses steam that leaves the turbine _ of the generator and the turbine _5 of the turbo-compressor to the working pressure of the steam boiler 1. The control amount of steam that is separated in the control distributor 3a condenses in the condenser _8 and through the feeding pump 1_0 it is injected by the working pressure of the turbines 4_, 5 to the steam boiler 1 and the superheater 2. The control circuit automatically maintains the thermal energy equipment in operation. Fig. 7 shows the fourth example of an embodiment of the thermal energy equipment in accordance with the invention. In this embodiment the thermal energy equipment implements a thermal steam circuit with a variable filling mass with the following course.

In the steam boiler lb, which conveniently also contains a superheater, heat is supplied that heats steam to the working temperature before the start of expansion in the first steam turbine 4a. In the first steam turbine 4a useful work is performed. In the superheater 2a. more heat is introduced in the steam. In the second steam turbine 4b steam expands up to the pressure in the condenser 8_. The compression means used in the thermal energy equipment comprises 3 compressors: the first compressor T_a, the second compressor 7b and the third compressor 7c. In the distributor 3_^ cooled steam is divided into the part that flows into the first compressor 7a while the other part flows to the condenser _8. Steam flowing to the first compressor 7a_: continues to the first mixer 6a, where it is mixed with condensate supplied by the first feeding pump 10a . Then, it is compressed in the second compressor 7b and continues to the second mixer 6b, where it is mixed with condensate supplied by the second feeding pump 10b and then steam continues to the third compressor ]_c, which injects steam to the steam boiler lb and compresses it to the inlet pressure before the first turbine 4a.

Steam that flows to the condenser 8_ is cooled and in the form of condensate it is transported to the condensate tank From the condensate tank _^9 condensate is transported by the first feeding pump 10a to the first mixer 6a, where it is mixed with compressed steam that leaves the first compressor 7a. The second feeding pump 10b transports condensate from the condensate tank 9_ to the second mixer 6b, where it is mixed with steam that leaves the second compressor 7b. The third feeding pump 10c transports condensate to the steam boiler lb. Thus, the entire cycle is completed.

Fig. 8 shows the pressure - enthalpy (log p-h) diagram of the ideal cycle of the thermal energy equipment of fig. 7 or the fourth embodiment example of the invention described above, respectively. The figure described the cycle - thermal circulation of steam in the coordinates of enthalpy h (kJ/kg) depending on the pressure log(p) in bar. In the particular example steam is divided in the distributor 3· into equal halves while one half flows to the first compressor 7a_ and the other half to the condenser 8, where one part of heat is transferred. Steam leaving the boiler _lb containing a superheater expands in the first turbine ^a from point 21 to point 2_2 and performs the expansion work Lei of 330 kJ/kg. In the superheater 2a heat is supplied from point 2/2 to point 23. From point .23 to point 2 _ steam expands in the second turbine 4b and performs useful work. Between point 2_4 and point 2_5 the other part of heat is transferred. The first compressor 7a compresses steam from point 25 to point 2_6 and consumes the compression work of 134 kJ/kg. 1/2 of the working filling participates in this first compression. In the first mixer 6a between point 2_6 and 2_ 1/4 of cold condensate is injected to proportionally reduce the humidity of steam. From point 21_ to point 2j3 the second compression is carried out with 3/4 of the steam filling and the compression work of 278 kJ/kg is consumed. Between points 2_8 and 2_9 the second 1/4 of cold condensate is injected and humidity drops proportionally again. Between points 2_9 and _30 the third compression part is executed with the complete filling quantity.

Thermal efficiency is the share of useful work and supplied heat. Useful work is the difference of expansion work and compression work.

In our example expansion work is Lel=330 kJ/kg, Le2=1215 kJ/kg, compression work Lkl=134 kJ/kg, Lk2=278 kJ/kg, Lk3=247 kJ/kg, supplied heat Qp=1340 kJ/kg. The total expansion work is 1545 kJ/kg and the total compression work is 659 kJ/kg. So the useful work is 886 kJ/kg. The result is the thermal efficiency of 66%.

List of reference marks

1, lb - steam boiler la - water tank

2, 2a - superheater

3, 3a - distributor

4, 4a, 4b, 5 - turbine

6 - mixer

6a - first mixer

6b - second mixer

7 - compressor

7a - first compressor 7b - second compressor 7c - third compressor

8 - condenser

9 - condenser tank

10 - water pump

10a - first water pump 10b - second water pump 10c - third water pump 16 - cooler

Claims

Patent claims

1. Thermal energy equipment comprising a steam turbine (4, 4a, 4b) for inlet steam expansion and work transfer, a cooling means (8, 16) for extraction of heat from the outlet steam of the turbine (4, 4a, 4b) , water tank (la) or steam boiler (1, lb) for production of steam and steam superheater (2, 2a) for supply of heat to steam before its entry to the steam turbine (4, 4a, 4b) , characterized in that it comprises a compression means (7, 7c) designed for withdrawal of at least a part of outlet steam from the steam turbine (4, 4b) and/or at least a part of steam cooled in the cooling means (8, 16), its compression to the value of pressure corresponding to the steam pressure before the turbine (4, 4a) and supply of compressed steam to the steam boiler (1, lb) and/or superheater (2, 2a) .

2. The thermal energy equipment in accordance with claim 1, characterized in that the compression means is a compressor (7) while the outlet of the generator turbine (4) is connected to the compressor (7) inlet via a mixer (6), the compressor (7) outlet is connected to the superheater (2) inlet and the superheater (2) outlet is connected to the turbine (4) inlet via a distributor (3) to withdraw a part of inlet steam leaving the superheater (2) to the inlet of the compressor (7) turbine (5) mechanically connected to the compressor (7) and the outlet of the compressor (7) turbine (5) is connected to one of the mixer (6) inlets.

3. The thermal energy equipment in accordance with claim 2, characterized in that between the outlet of the mixer (6) and compressor (7} inlet there is a cooler (16) .

4. The thermal energy equipment in accordance with claim 2, characterized in that between the mixer (6) outlet and the compressor (7) inlet there is a distributor (3a) whose one outlet is connected to the compressor (7) inlet and another outlet is connected to the inlet of the condenser (8) for heat extraction whose outlet is connected to the inlet of the feeding pump (10) whose outlet is connected to the inlet of the steam boiler (1) .

5. The thermal energy equipment in accordance with claim 4, characterized in that the outlet from the compressor (7) is also connected to the inlet of the steam boiler (1) and/or connected to the internal spiral of the steam boiler (1) and the outlet of the feeding pump (10) is also connected to the inlet of the superheater (2) and/or connected to the internal spiral of the steam boiler (1) .

6. The thermal energy equipment in accordance with claim 1, characterized in that it contains a condenser (8) and a compression means comprising at least two compressors (7a, 7b, 7c) or compression stages while a part of the total amount of outlet steam that left the turbine (4b) after the expansion is supplied to the condenser (8) and the remaining part of this total amount is supplied to the first compressor (7a) or compression stage while the compressors (7a, 7b, 7c) or compression stages are arranged for gradual compression of steam in such a way that steam compressed in the upstream compressor (7a, 7b) or stage to a certain pressure value is compressed in the downstream compressor (7b, 7c) or stage from this pressure value to a higher pressure while at least a part of condensate produced in the condenser (8) is supplied to the steam compressed in the upstream compressor (7a, 7b) or stage before it is supplied to the downstream compressor (7b, 7c) or stage .

7. The thermal energy equipment in accordance with claim 6, characterized in that it contains a condensate tank (9) for storage of condensate produced in the condenser (8) and a pump (10a, 10b) to supply at least a part of condensate from the condensate tank (9) to steam compressed in the upstream compressor (7a, 7b) before it enters the downstream compressor (7b, 7c) .

8. The thermal energy equipment in accordance with claim 7, characterized in that it contains a pump (10c) for extraction of a part of condensate from the condensate tank (9) to the steam boiler (lb) .

9. The thermal energy equipment in accordance with any of claims 6 to 8, characterized in that it comprises the first generator turbine (4a) arranged at the steam boiler (lb) outlet the outlet of which is connected, via the superheater (2a) , to the inlet of the other generator turbine (4b) whose outlet is connected, via a cooler (16) and distributor (3), to the condenser (8) inlet while the other outlet of the distributor (3) is connected to the inlet of the first compressor (7a) followed by the second compressor (7b) and subsequently the third compressor (7c) while the third compressor (7c) releases steam compressed to the pressure value that corresponds to the pressure of the inlet steam of the turbine (4a) to the steam boiler (lb) and/or superheater.

10. The thermal energy equipment in accordance with any of the previous claims, characterized in that it is arranged so that the outlet steam leaving the turbine (4, 4b) has the humidity value higher than 0.32 and the steam before the start of compression in the compression means (7, 7a) has the humidity value higher than 0.18.

11. An operation method of thermal energy equipment comprising a steam turbine (4, 4a, 4b) for inlet steam expansion and work transfer, a cooling means (8, 16) for extraction of heat from the outlet steam of the turbine (4, 4a, 4b), water tank (la) or steam boiler (1, lb) for production of steam and steam superheater (2, 2a) for supply of heat to steam before its entry to the steam turbine (4, 4a, 4b), characterized in that before the supply of steam to the steam boiler (1, lb) or superheater (2, 2a) at least a part of the total amount of outlet steam that passed through the turbine (4, 4b) after expansion is compressed in the compression means (7, 7c) to the value of pressure that corresponds to the steam pressure before the turbine (4, 4a) and the steam compressed this way is supplied to the steam boiler (1, lb) and/or superheater (2, 2a) .

12. The operation method of the thermal energy equipment in accordance with claim 11, characterized in that the thermal energy equipment contains a condenser (8) and the compression means comprises at least two compressors (7a, 7b, 7c) or compression stages while a part of the total amount of outlet steam that left the turbine (4b) after the expansion is supplied to the condenser (8) and the remaining part of this total amount of outlet steam is supplied to the first compressor (7a) or compression stage, where the steam is compressed to a certain pressure value while further movement of this steam is that before the steam compressed in the upstream compressor (7a, 7b) or compression stage is supplied to the next compressor (7b, 7c) or compression stage at least a part of the condensate produced by condensation of steam that was supplied to the above mentioned condenser (8) is injected to the steam compressed this way and the steam thus enriched is fed to the said next compressor (7b, 7c) or compression stage where it is compressed to a pressure that is higher than the pressure to which it was compressed in the previous compressor (7a, 7b) or compression stage while in the last compressor (7c) or compression stage the steam is compressed to the pressure value corresponding to the pressure of the inlet steam before its entry to the turbine (4, 4a) and the steam is supplied to the steam boiler (lb) and/or superheater at this pressure.

13. The operation method of the thermal energy equipment in accordance with claim 12, characterized in that a part of condensate produced in the condenser is directly fed to the steam boiler (lb) .

14. The operation method of the thermal energy equipment in accordance with any of claims 12 and 13, characterized in that before steam is supplied to the condenser (8) and to the first compressor (7a) or compression stage the steam is cooled in a cooler (16) .

15. The operation method of the thermal energy equipment in accordance with any of claims 12 to 14, characterized in that it comprises at least two turbines (4a, 4b) arranged in series in such a way that steam from the steam boiler (lb) or superheater is introduced in the first turbine from where it is directed to the next turbine (4b) via another superheater (2a) while after expansion of steam in the last turbine a part of the steam is withdrawn to the first compressor (7a) of compression stage and the remaining part of the steam is routed to the condenser (8) .