WO2019013669A1

WO2019013669A1 - Method for increasing energy conversion efficiency of thermal power plant and device for carrying out said method

Info

Publication number: WO2019013669A1
Application number: PCT/RU2018/000031
Authority: WO
Inventors: Владимир Алексеевич ФЕДОТОВ
Original assignee: Владимир Алексеевич ФЕДОТОВ
Priority date: 2017-07-12
Filing date: 2018-01-25
Publication date: 2019-01-17
Also published as: DE112018003573T5; RU2017124840A3; RU2017124840A

Abstract

Proposed is a method for increasing the energy conversion efficiency of a thermal power plant that provides for directing steam into a condenser after said steam has been fully processed in all turbine cylinders and subsequently converting the steam to a liquid phase by increasing the pressure of the steam to be higher than saturation pressure through the use of a fan, stopping the circulation of cooling water, and preserving the condensation heat of the steam in the cycle. Described is a sequence of actions for converting a power plant to a recommended mode of operation. The method is implemented by equipping the last ring on a turbine shaft of all low-pressure cylinders with blades of a fan having the requisite configuration and a nozzle, driven by its own electric engine, and disposed on the inlet pipe of the condenser or integrated into the last turbine stage. The use of the invention allows for increasing the energy conversion efficiency of a power plant by 42.5% and decreasing the amount of harmful emissions released into the environment.

Description

The way to increase the efficiency of a thermal power plant

and device for its implementation

Technical field

The invention relates to the field of power engineering and can be used in thermal, nuclear and combined gas turbine power plants.

Prior art

The classic cycle of electricity generation at thermal power plants is carried out as follows.

Water, with a feed pump (hereinafter PN) (101) under pressure P1 (113) and temperature T1 (114), is supplied to the steam boiler (hereinafter PC) (102). The pressure in the power plants of Russia at the entrance to the steam boiler is usually 3.4 MPa, 8.8 MPa, 12.75 MPa, 23.5 MPa or, respectively, 35 kg / cm2, 90 kg / cm2, 130 kg / cm2, 240 kg / cm2. These values are standard. In the steam boiler PC, the water is heated (heat Q 1 is supplied) and evaporates (heat is supplied (Q 2), saturated water vapor is sent to the PP superheater (103), where the steam overheats to temperature T 2 ~ 545 ° C (heat Q 3 is supplied). Superheated steam is sent to the turbine, high-pressure cylinder of the HPC (104), exhaust steam, at a temperature above the saturation temperature, with a reduced pressure is sent to the intermediate superheater PP1 (105). In the intermediate superheater, the steam is heated to a temperature of ~ 545 ° C (heat Q 4 ) and directed etsya to the next stage of the turbine, the cylinder medium pressure The exhaust steam in the CCD (106) at a temperature above the saturation temperature with an even lower pressure is sent to the intermediate superheater PP2 (107). In PGT2, steam again overheats to a temperature of - 540 ° C (heat Q5 is supplied) and is sent to the next stages of the turbine, low pressure cylinders of low-pressure cylinder (108). Low pressure cylinders are usually from 2 to 6, depending on the capacity of the plants.

Intermediate superheating of steam allows to increase the average temperature of heat supply and the process of expansion of steam in the turbine ends in the region of a higher degree of dryness of steam, therefore, the operating conditions of the flow part of the turbine are easier.

Carnot's cycle without intermediate superheating of steam, Rankine cycle with intermediate superheating of steam are applied.

The steam worked in the turbine, at Р2 (109) from 1.7 kPa to 4.2 kPa, the temperature of the technical specification (PO) from 15 ° C to 30 ° C at this pressure and temperature has a specific volume Vn from 77.97 m3 / kg to 32 93 m3 / kg. and the heat of condensation g from 2465 kJ / kg to 2430 kJ / kg (further these values will be needed for calculations), is sent to the condenser K (111), where it is completely condensed when passing into the liquid phase giving back g (heat of condensation g from 2465 kJ / kg up to 2430 kJ / kg, heat -Q6) cooling water. Per 1 kg of steam accounts for 50 to 80 kg of cooling water, which heat the atmosphere. Up to 45% of the heat supplied in the cycle is permanently lost in the condenser.

Condensate pump KN (1 12) pumps out water from the condenser, which is sent to the feed pump PN, which raises the pressure to P1 (3.4 MPa, 8.8 MPa, 12.75 MPa, 23.5 MPa, the higher the pressure, the above the boiling point of water), while T1 () is almost equal to the TK, the cycle repeats. The real scheme is more complicated, only the main equipment is described.

Water is practically non-compressible liquid, so the energy costs of increasing pressure are insignificant, the equipment is quite compact. Mechanical work that must be done to increase the pressure of water can be calculated by the formula:

A = P * dV where

A - mechanical work. Р is the working pressure of water created by the feed pump (PN) at the inlet to the steam boiler (PC 3.4 MPa, 8.8 MPa, 12.75 MPa, 23.5 MPa). dV - the change in the volume of water is practically = 0, so work A is not significant.

According to the second law of thermodynamics, all mechanical work A can be transformed into thermal Q, and thermal into mechanical only with irreversible losses, therefore A and Q are identical concepts and unit of measure, one J, different types of the same energy.

The disadvantage of this cycle is irretrievably lost heat, up to 45% in condenser K, along with cooling water. The graph of the considered cycle in T - S coordinates is shown in Fig.2.

1 - 2 Increase of water pressure with feed pump PN to operating. (3.4 MPa, 8.8 MPa, 12.75 MPa, 23.5 MPa). s The distance between points 1 and 2 is very small due to the non-compressibility of water, they practically coincide.

In the diagram, the distance between the points is specifically increased to show that there is such a process. 2 - 3 Heating the water to the boiling point at the operating pressure in the steam boiler PC. The heat input Q 1, the boiling point of water depends on the operating pressure.

3 - 4 Evaporation of water in the PC, saturated water vapor zone, boiling process. Heat supply Q2. 34 Point 34 shows in the diagram the point of water transition into steam without the process of boiling water, for direct-flow units operating at a critical pressure Pc = 22.1145 MPa.

4 - 5 Overheating of dry steam in a superheater of submarines.

Heat supply Q3. 34 - 5 Dry steam overheated for direct flow units.

5 - 6 Work of steam in the high-pressure cylinder of a high-pressure turbine turbine.

Reducing the vapor pressure and temperature above the saturation temperature.

6 - 7 Overheating of dry steam in PP1.

Heat supply Q4.

7 - 8 The work of steam in the cylinder of medium pressure turbine CCD.

Reducing the vapor pressure and temperature above the saturation temperature.

8 - 9 Overheating of dry steam at 11112.

Heat supply Q5. 9 - 10 Steam work in low-pressure cylinders of a low-pressure turbine turbine.

Reducing the vapor pressure and temperature to saturation temperature.

10 - 1 Condensation of steam in the condenser K with cooling water, transition to the liquid phase. Heat removal - Q6 = g from 2465 kJ / kg to 2430 kJ / kg. Irretrievable loss of heat from the cooling water that transfers heat to the atmosphere.

Then the cycle repeats again.

The work that can be obtained in a cycle is proportional to the area of the figure bounded by lines 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 - 9 - 10 - 1.

From patent GB 0002528830 February 10, 2016, a method is known for increasing the pressure of waste steam that is not yet saturated at the outlet of the turbine, using accelerator nozzles used in conjunction with a compressor, with subsequent overheating, without transferring steam to the liquid phase and re-directing it to the turbine to perform useful work.

The disadvantage of this method is the large energy consumption for increasing the pressure of unsaturated steam.

Patent US 6357235 03/19/2002, proposes to use pre-compressed atmospheric air to increase the pressure of unsaturated steam without transferring to the liquid phase with subsequent overheating and direct steam to the turbine.

The disadvantage of this method is the large energy consumption for increasing the pressure of unsaturated steam, which will be shown below. On the T - S diagram, the cycle will be limited to 4-5-6-4 lines, and the cycle itself will include:

6-4 Increasing the pressure of unsaturated steam.

4-5 Steam overheating. 5-6 Steam work in the turbine.

Then the cycle repeats.

The area of the figure bounded by lines 4–5–6–4 is much smaller than the area bounded by lines 1–2–4–4–6–7–9–9–10–1 (cycles used), which means that to get a lot of work is impossible.

Work is proportional to the area bounded by the cycle lines.

Consider what work must be done to compress 1 kg of steam in accordance with the patents GB 000252883010.02.2016, US 635723519.03.2002. PI = 3.4 MPa (3400 kPa) The lowest working pressure used in cycles.

V2 ~ 0.005 m3 / kg Specific volume of steam at 1545 ° C

V 1 = 32.93 m3 / kg Specific volume of steam at t 30 ° C

A = P1 * (V2-V1) Work that needs to be done to compress steam in any way.

A = PI * (V2 - VI) = 3400 kPa * (0.005 m3 / kg - 32.93 m3 / kg) = - 111945

to d l / kg

Work and warmth are identical concepts. Work on the vapor compression in any way (irretrievably lost energy), A = 1,11945 kJ / kg g from 2465 kJ / kg to 2430 kJ / kg, much more than the heat of condensation, irreversibly lost in the condenser of classic cycles. Consequently, the efficiency of the cycles proposed in the above mentioned patents will be lower than the existing ones.

Disclosure of technical solutions

The aim of the proposed technical solution is a significant increase in the efficiency of the cycle of electricity production at thermal, nuclear and combined gas turbine power plants working on the cycles of Carnot, Rankine, by significantly reducing the irretrievably lost heat in the condenser, changing part of the existing cycles to the proposed new cycle.

This goal is achieved through a fundamentally different way to solve the technical problem of reducing heat loss in the condenser and a significant increase in the efficiency of the heat cycle.

It has been established in particular that saturated water vapor begins to condense, if its pressure is slightly increased, higher than the saturation pressure. In this case, the supersaturated vapor enters the liquid phase. In accordance with the idea of the invention it is proposed

carry out the heat cycle on the existing equipment with

existing parameters up to point 10 on the T - S diagram, when the steam has fully worked in all cylinders of the turbine to direct the steam to

a condenser in which to increase the pressure above the saturation pressure and smoothly stop the circulation of cooling water through the condenser.

The transition of steam into the liquid phase will occur due to the fact that the pressure in the condenser will be higher than the saturation pressure. The heat of condensation of the steam will remain in the cycle.

The parameters of exhaust steam at the turbine outlet will be at P2 from 1.7 kPa to 4.2 kPa, the temperature of the technical specification from 15 ° C to 30 ° C and the heat of condensation g from 2465 kJ / kg to 2430 kD / kg.

The pressure boosting device can be external, driven by its own electric motor, mounted on the inlet of the condenser, and integrated with the last stages of the turbine. When designing new models of turbines, this device can be envisaged in the design, it is desirable to use an ionizer.

One option would be a device operating on the fan principle. The configuration of the blades can be very diverse, the configuration will be optimal, made on the basis of the continuity of the steam flow, as well as turbine blades. It is proposed during the scheduled preventive maintenance of the turbine to replace the blades on the last crown of the turbine of all low-pressure cylinders on the fan blade, the required configuration and, accordingly, the nozzle. Corresponding parts must be prepared in advance.

After this modification, the last rims of the rotating turbine. The low-pressure cylinder will create an overpressure in the condenser, the turbine power will slightly decrease, but the cycle efficiency will increase significantly, as will be shown below.

A schematic diagram of a modified power plant with increased efficiency; fan blades are used on the last turbine crown in order to increase the pressure in the condenser. one.

The implementation of the invention To implement the proposed technical solution, before moving to work on the proposed cycle, you must first start the existing classic cycle, as described above. With the condenser on and irretrievably losing heat with cooling water. When the turbine rotates at the operating frequency and in the condenser the nominal parameters of exhaust steam P2 from 1.7 kPa to 4.2 kPa, temperature TK from 15 ° C to 30 ° C and heat of condensation g from 2465 kJ / kg to 2430 kJ / kg are achieved , you can go to the proposed cycle.

Let P22 denote the pressure in front of the fan (see the block diagram), P2 is the pressure in the condenser. A working fan will have little effect on the condensation process, since the main vacuum will be created by cooling water and P2 ~ P22.

When reaching the operating parameters, it is necessary to smoothly reduce the flow of cooling water through the condenser K and completely stop its circulation.

The process of condensation of steam due to cooling water will stop. This will cause the P2 pressure in the condenser to increase due to the operation of the fan. When reaching the pressure P2 slightly exceeding the saturation pressure at the operating temperature, the steam condensation process will resume.

The condensation process will be self-regulating. If condensation increases, pressure P2 decreases, the process slows down, which leads to an increase in pressure, the process will resume.

This is due to the fact that at a pressure of P2 from 1.7 kPa to 4.2 kPa and a temperature of TZ from 15 ° C to 30 ° C, the specific volume of steam Vn from 77.79 m3 / kg to 32.93 m3 / kg, and the specific volume of water (vapor condensate) VB ~ 0.001 m3 / kg. This process is very sensitive to unbalanced flow because a small deviation of the process speed from the balance leads to a change in volume from 77790 to 32930 times

There will be no heat loss in the condenser with cooling water (the circulation of cooling water through the condenser is stopped), therefore, the heat will remain in the cycle.

Thermodynamic aspects of the proposed invention follow from the mathematical proof by Lars Onzager, Nobel laureate, founder of the fourth law of thermodynamics, described in the work “Thermodynamics of phase transitions” and the fact that the specific heat capacity of the components during phase transitions tends to infinity. This means that the specific heat capacity of the condensate during the phase transition will be sufficient for the kinetic energy of the vapor to transfer to the internal energy without a significant increase in temperature. A feed pump GSH significantly raise the water pressure which will lead to an increase in the boiling point of water.

With a stable, single liquid phase, the heat capacity of water will return to empirical values, and the internal energy of water will be much higher than in the classical cycle, since the heat in the condenser is not lost.

Indicator of the internal energy of water is the temperature, which in the proposed cycle (denoted by T32 (115), see the block diagram of the described cycle of Fig. 1.) at the entrance to the steam boiler PC will be significantly higher than T32 T1 ~ TZ, which will be shown below. In the steam boiler PC, for heating and evaporation of water, you need significantly less heat than in the classical cycle, this allows you to significantly increase the efficiency of the proposed cycle. Consider the proposed cycle in T - S coordinates.

As mentioned above, you must first start the above classic cycle. When switching to the proposed cycle, the process will be completely repeated to point 10, then it will go to the following points:

10 - 1 1 a slight increase in pressure above the saturation pressure, in the diagram the distance between the points is specifically increased to show that there is such a process.

11 - 12 phase transition from the vapor state to the liquid phase, points 1 and 12 almost completely coincide due to the non-compressibility of water (points 1 - 2). Heat removal - Q6 = g from 2465 kJ / kg to 2430 kJ / kg will not.

12 - 2 Increase of water pressure with feed pump PN up to operating. (3.4 MPa, 8.8 MPa, 12.75 MPa, 23.5 MPa).

The distance between points 1, 12 and 2 is very small due to the non-compressibility of water, they almost coincide.

2 - 3 Heating the water to the boiling point at the operating pressure in the steam boiler PC. Supply of heat Q1 is not needed, since the internal energy of the condensate is T32 »T1, the calculation is given below, the boiling point of water depends on the operating pressure.

3 - 44 Partial evaporation of water in the PC, saturated water vapor zone, heat supply Q2 to point 44 is not needed, since the internal energy of the condensate is T32 »T1, the calculation is given below. 44 - 4 Complete evaporation of water in PC, saturated water vapor zone, boiling process. Heat supply Q22 “Q2, the calculation is given below. 34 Point 34 shows in the diagram the point of water transition into steam without the process of boiling water, for direct-flow units operating at a critical pressure Pc = 22.1145 MPa.

4- 5 Overheating of dry steam in the GSH superheater.

Heat supply Q3.

34-5 Dry steam overheated for straight flow units.

5- 6 Work of steam in the high-pressure cylinder of a high-pressure turbine turbine.

Reducing the vapor pressure and temperature above the saturation temperature. 6-7 Dry steam overheated in PP1.

Heat supply Q4.

7-8 Steam operation in a cylinder of medium pressure of a turbine of the CCD.

Reducing the vapor pressure and temperature above the saturation temperature. 8-9 Dry steam overheating in PP2.

Heat supply Q5.

9-10 Steam work in low-pressure cylinders of a low-pressure turbine turbine.

Reducing the vapor pressure and temperature to saturation temperature. 10-11 a slight increase in pressure above the saturation pressure, on the diagram the distance between the points is specifically increased to show that there is such a process.

Then the cycle repeats again.

The area bounded by lines 12 (1) - 2- 3- 44–4–5– 6–7–8–9–10 - 11–12 (1) almost completely coincides with the classical cycle, which means the work ^ at such same The area bounded by lines 1 - 12 - 11 - 10 - 1 is proportional to the work that needs to be spent on the phase transition of steam into water, irretrievably lost energy.

An example of calculation for 1 kg of steam is shown below.

The work that needs to be done for the vapor-condensate phase transition.

The process occurs at a constant temperature t from 15 oC

30 ° C

Vapor saturation pressure P from 1.7 kPa 4.2

kPa

The specific volume of steam Vn from 77.97 m3 / kg32.93 m3 / kg

Specific volume of water (condensate) VB from 0.001 m3 / kg 0.001 m3 / kg

Specific heat of condensation g 2465 kJ / kg

2430 kJ / kg

Permanently lost work A = P * dV = P * (VB - Vn)

A = 1.7 kPa * (0.001 m3 / kg - 77.97 m3 / kg) = -133 to D W / kg

A = 4.2 kPa * (0.001 m3 / kg - 32.93 m3 / kg) = -138 kJ / kg

The heat remaining in the cycle Qn = g - A = 2465 kJ / kg - 133 kJ / kg = 2332 kJ / kg

Qn = g - A = 2430 kJ / kg - 138 kJ / kg = 2292 kJ / kg The heat lost in the condenser of the classical cycle g is ~ 45%, in the proposed cycle the lost work A is ~ 2.5%.

Thus, the efficiency of the proposed cycle will be ~ 42.5% (45% - 2.5%) higher than the classical cycle.

Additionally, below is the calculation for point 44 on the T - S diagram for a pressure of P1 = 3.4 MPa (for a higher pressure the boiling point of water will be higher) and the temperature of the exhaust steam t 30 ° C.

Operating pressure P1 3.4 MPa

The boiling point of water at a given pressure Tk 241 oC

Heat of vaporization Q2 Qn 1759 kJ / kg

Water temperature at the inlet to the steam boiler PK T1 30 ° C

Heat capacity of water average St 4,2 kJ (kg * K)

The heat required for heating 1 kg of water to Q1 = Sv * (Tk - T1) boiling point Q1 does not need to be brought Qi = 4.2 kJ / (kg * K) * (241 - 30) = 886 kJ / kg as is enough the heat remaining in the T32 cycle will correspond to TC

Heat remaining in the Qu cycle, 2292 kJ / kg

Heat remaining for partial evaporation QH = Qu, - Q 1

corresponds to point 44 on T - S diagram. QH = 2292

Heat required for complete evaporation Q22 = Qn - QH

1 kg of water in the proposed cycle. Q22 = 1759 kJ / kg -

1406 kJ / kg = 353 kJ / kg Q22 = 353 kJ kg "Q2 = 1759 kJ / kg

The remaining heat Q3, Q4, Q5 required for steam overheating is supplied in the same way as in the classical cycle.

From the above calculations it can be seen that in the classical cycle, the condensation heat g from -2465 kJ / kg to -2430 kJ / kg is lost permanently in the condenser, which is approximately - 45% of irrecoverable losses.

In the proposed cycle, the irretrievable losses A from -133 kJ / kg to -138 kJ / kg are significantly less, which will be approximately from -2.4% to -2.6% of irretrievable losses, since the process proceeds at a very low pressure in the condenser , practically in a vacuum that was previously created in the classic cycle.

Thus, the proposed cycle increases the power plant efficiency by 42.5%.

The cycle does not conflict with the first law of thermodynamics, since heat is supplied, there is no contradiction with the second, since part of the energy is irretrievably lost when thermal energy is converted into mechanical energy, does not contradict the third, since absolute zero temperatures are not reached, runs according to the fourth law of thermodynamics.

Before switching to a new cycle, it is necessary to pre-calculate the heat balance of the steam boiler, based on the elevated water temperature at its inlet, especially for direct-flow units and nuclear power plants. In this case, only one turbine can be transferred to the proposed cycle, the next turbine can be transferred to a cycle only after the completion of the previous transition process, when calculating the transfer function affecting the reduction of fuel supply to the steam boiler, it is necessary to take into account the transport delay. Performing these requirements will ensure productive and trouble-free operation of the power plant.

Practical implementation of the proposed cycle does not require significant costs, all the necessary elements can be manufactured in advance, using technology and materials, just like turbine blades, fastening to the turbine shaft will remain the same, modernization can be carried out during scheduled preventive maintenance, all other equipment and communications will remain unchanged. Since routine preventive maintenance and replacement of turbine blades are carried out constantly at all thermal power plants in the world, the transition to a new cycle of the power plant will be quite simple.

The estimated cycle reduces fuel consumption by almost 2 times, therefore, the same amount will be less emissions of combustion products and heating of the atmosphere, which will positively affect the environment and climate. At nuclear power plants will be almost 2 times less radioactive waste.

Claims

Claim

1. A method of increasing the efficiency of a thermal power plant by increasing the pressure of unsaturated steam followed by its overheating and direction to the turbine, characterized in that after full development in all cylinders of the turbine, steam is sent to a condenser, in which the fan increases the pressure above the saturation pressure and stops circulation cooling water due to which steam is transferred to the liquid phase with preservation of the heat of condensation of steam in the cycle.

2. A method according to claim 1, characterized in that after starting the existing cycle and achieving rotation of the turbine with an operating frequency ensuring the nominal parameters of the exhaust steam smoothly reduce the flow of cooling water until its circulation is completely stopped while increasing the pressure in the condenser by means of a fan and obtaining the effect self-regulating process of condensation.

3. The method according to p. 1, characterized in that the calculation of the configuration of the fan blades is the same as for turbine blades, based on the continuity of the steam flow, based on the calculation of the heat balance of the steam boiler, taking into account the elevated water temperature at its inlet.

4. The method according to p. 1, characterized in that the calculation of the transfer function affecting the reduction of fuel supply to the steam boiler is carried out taking into account the transport delay.

5. The method according to p. 1, characterized in that the modernization of existing thermal power plants to replace the blades on the fan blade at the last crown of the turbine is carried out in the period of preventive maintenance.

6. Thermal power plant, including a device for increasing the pressure of unsaturated steam with its subsequent overheating and direction to the turbine, characterized in that at the last rim instead of blades on the turbine shaft of all low pressure cylinders installed fan blades, the required configuration and the nozzle.

7. Thermal power plant under item 6, characterized in that the fan is driven by its own electric motor, located on the inlet of the condenser.

8. Thermal power plant under item 6, characterized in that the fan is integrated with the latest turbine stages.

9. Thermal power plant under item 6, characterized in that the structural elements of the fan blades are made by technology and from materials, as well as for turbine blades.