Method and device for producing energy in thermodynamic cycles

Abstract

The present solution consists in producing high-pressure high-temperature steam in a first boiler unit, feeding the steam to a steam turbine, feeding the spent steam to a condenser and feeding the condensate to the first boiler unit by means of a condensate pump, wherein the condensate is first fed to a second boiler unit in order to be heated to the effective temperature of feedwater for the first boiler unit. The condensate is first fed to a low-temperature part of said second boiler unit, where it is heated, and is then fed to a deaerator. After the deaerator, the pressure of the feedwater is increased and the feedwater is fed to a high-temperature part of the second boiler unit, which heats the feedwater to a set temperature without bringing about a phase transition. The heated feedwater is then fed to the first boiler unit.

Description

[0001] Method and device for obtaining energy in thermodynamic cycles

[0002] The present invention relates to the field of generating electric and thermal energy during the energy utilization of waste or fuel from waste, biomass, the use of solar energy and geothermal energy (hereinafter RES) in thermodynamic cycles using a heat carrier.

[0003] In particular, the invention relates to a method for obtaining energy from the combined combustion of municipal solid waste (MSW) or fuel from them (SRF), as well as geothermal or solar energy in a separate boiler plant, for heating condensate (feedwater) to a temperature of no higher than 330° C at an appropriate pressure that eliminates the phase transition of feedwater into steam, to an effective temperature of boiler plants with high pressure and high steam temperature - no lower than 400° C, using fossil solid, liquid, gaseous and nuclear fuel, as well as heat from exhaust gases of gas turbines, with further expansion of this steam on powerful steam turbines and with the possible replacement of regenerative steam extraction from these steam turbines.

[0004] State of the art

[0005] Currently, energy recovery or the use of renewable energy sources such as waste and biomass, solar energy in solar concentrators and geothermal energy consists of a cycle that is usually carried out in heat exchangers that convert heat from flue gases obtained from the combustion of waste, biomass or fuels made from them, as well as using the heat of solar energy and geothermal energy with the production of superheated steam for its subsequent expansion in a condensing turbine, which is usually connected to an electric generator.

[0006] This process is based on the Rankine cycle, the energy efficiency of which is determined by the parameters of the steam: the higher the parameters (pressure and temperature), the higher the efficiency of the thermodynamic cycle.

[0007] However, in boiler plants currently in use with combustion devices for burning waste and some biomasses, especially in the case of boilers for municipal solid waste (MSW) or fuels thereof, the maximum temperature reached is above 350°C, usually above 400°C. The results of numerous studies and practical operation show that at temperatures above 350°C, the heat exchange surfaces of boiler plants experience excessive corrosion caused by flue gases from the combustion of waste and biomass.

[0008] The presence of hydrogen chloride during combustion of chlorine-containing products stands out among the factors causing the above-mentioned corrosion effects in the case of solid municipal waste or fuels made from them. In addition, in biomass such as wood or agricultural plant waste such as straw, husks of grain crops, etc., it is necessary to take into account the corrosion effects caused by the content of alkali metals present in the waste, which, as part of the fly ash deposited in superheaters, cause slagging of heat-exchange surfaces, reducing the efficiency of the boiler plant, and when removed from the heat-exchange surfaces, corrosive and erosive wear of the heat-exchange surfaces accelerates, which leads to a decrease in the coefficient of the used power of the equipment due to more frequent maintenance and repairs.

[0009] The existing conventional boiler plants operate mainly with steam parameters at a pressure of at least 40 bar and a temperature of at least 400°C, so that the corrosion rate on the outside of the tube bundles is several times greater than that which occurs when the steam temperature is below 350°C. However, a decrease in steam parameters sharply reduces the efficiency of steam turbines and the power plant as a whole.

[0010] In order to overcome the above-mentioned problems of corrosion of steam superheater tube bundles, methods have been developed in which steam is generated in a waste incineration boiler at a high pressure exceeding 70 bar and usually from a value of about 100 bar, which is slightly superheated or not superheated, i.e. at temperatures of about 330 ° C, and in which the corrosion effects are not very significant. However, the reduction in steam parameters sharply reduces the efficiency of steam turbines and the electrical efficiency of the power plant as a whole does not exceed 18%.

[0011] To increase the efficiency of the steam turbine in installations using these methods, the high-pressure, moderate-temperature steam produced is superheated in a waste heat boiler section with a separate gas path, in which flue gases from fossil clean fuel (usually natural gas) are not mixed with flue gases from waste incineration or SRF, which does not cause corrosion, achieving high steam parameters - pressure, about 70-110 bar, and temperature, about 450-540 ° C with high efficiency of electrical energy production.

[0012] Similar methods to this type are described in Spanish patents ES-2006059-A6 and ES-2010890-A6, which describe methods in which high-pressure steam generated in a solid waste boiler, at a temperature below the temperature at which the effects of corrosion begin to be significant, is superheated in the boiler to recover heat from the combustion gases of clean fuel or from the exhaust gases of a gas turbine. With these systems, the effects of corrosion are avoided, while the production of electrical energy is increased with high energy efficiency using both types of fuel.

[0013] Similarly, US Patent No. 5,724,807 also describes a method of superheating steam at pressures above 68 bar generated in a waste heat boiler using gas turbine exhaust gases, which in addition generates low pressure steam that is used for services such as cooling gas turbine air or preheating combustion air for furnace exhaust and condensates.

[0014] However, the effective industrial application of the above methods has not been very successful, so conventional installations operate with steam at pressures below 60 bar and temperatures above 350°C, which is due to the complexity of boiler equipment with separate gas paths for flue gases from different types of fuel, the lack of availability of clean and cost-effective fuel in the immediate vicinity of the incineration plant, and also the fact that the increase in energy efficiency associated with the above methods does not allow economic compensation for the need for higher investments and additional costs for auxiliary fuel.

[0015] On the other hand, one of the most common ways of using solar energy is to concentrate direct solar radiation, using mirrors, on a concentrator in which a non-aqueous organic heat carrier circulates. This method is used in thermal power plants, where the maximum temperature level is limited by the decomposition temperature of the heat carrier, about 400° C.

[0016] Due to this technical limitation, boilers of solar concentrating plants with an intermediate heat carrier are designed to generate steam at temperatures of about 380°C, which means that the thermal cycles that occur in these solar plants also have low energy efficiency.

[0017] In order to improve the energy efficiency of thermal cycles based on the exploitation of solar energy, several methods have been considered, including the French patent No. FR-2450363-B1, which describes a thermal power plant for the production of electricity from solar energy by superheating steam at 50 bar pressure, generated by an intermediate organic liquid from solar collectors, by means of a mixture of molten salts heated at high temperature in a solar collector with a central tower and heliostats.

[0018] Similarly, US Patent Application No. US-2006260314 describes a method and system in which low temperature steam generated by intermediate organic fluids from solar collectors is superheated by high temperature steam from solar collectors, a combined cycle that can also be implemented with tail exhaust gases of combined cycle gas turbines, as described in International Patent Application PCT WO-9511371.

[0019] On the other hand, international patent applications PCT WO-2007093464 and WO-2007093474 describe the use of external heat supply in a Rankine cycle, for which a turbine with intermediate reheat and the use of non-renewable fuel is used.

[0020] However, in practice, all these installations and methods for increasing the efficiency of generating electric energy using solar heat energy have expensive and complex industrial applications, since they require the participation of a complex, for example, systems such as combining with combined cycles, using non-renewable fuels and using molten salts at high temperatures, and also, in the case of MSW or SRF, a large amount of them per installation, since it is necessary to spend heat from them on vaporization.

[0021] Analysis of the current state shows that to obtain electrical energy with moderate steam temperature, as in waste heat boilers that convert renewable energy into high-parameter steam to obtain electrical energy, simpler and more efficient thermal cycles are required to prevent the effects of corrosion, as well as in solar thermal power plants to prevent the decomposition of organic heat carriers by replacing the regenerative cycle of steam turbines to heat the condensate to the effective temperature of boiler plants using fossil solid, liquid, gaseous and nuclear fuel, as well as the heat of exhaust gases from gas turbines.

[0022] Disclosure of invention.

[0023] What is needed now is more efficient thermal cycles for boilers operating on heat from renewable energy sources, at low coolant parameters, without phase transitions, which are built into thermodynamic cycles using high-pressure and high-temperature steam in steam power cycles of power plants operating on fossil fuels such as natural gas, coal, fuel oil, and nuclear fuel, as well as using waste heat from gas turbines.Thus, increasing energy efficiency when using heat from renewable energy sources compensates for energy losses in a steam turbine both due to regenerative extractions and due to increasing the overall efficiency of thermodynamic cycles, increasing the cost-effective feedwater temperature to the theoretically most effective feedwater temperature of a boiler plant operating on fossil fuels such as natural gas, coal, fuel oil, and nuclear fuel, as well as using the heat of exhaust gases of gas turbines, reducing specific capital and operating costs for the production of electrical energy from renewable thermal energy sources.

[0024] The proposed invention serves the following purposes:

[0025] - reduction of energy costs in intermediate, regenerative extraction of steam turbines of power plants,

[0026] - reducing the risk of thermal corrosion of a boiler unit that extracts energy from waste,

[0027] - reduction of capital expenditures for the conversion of energy from renewable energy sources into mechanical and electrical energy, since the energy obtained is converted in the thermal cycles of regenerative extractions of high-power steam turbines, which will increase energy and operational efficiency by reducing intermediate - regenerative extractions of steam for heating condensate and (or) feedwater, with a coolant temperature in the liquid aggregate state below 330°C and the corresponding pressure in the thermal cycle of using energy from renewable energy sources, excluding phase transitions of the coolant, combined with thermal cycles of regenerative extractions of high-power steam turbines.The present invention relates to a method for obtaining energy with the combined use of energy from renewable energy sources in a cycle that ensures the absence of a phase transition of the coolant from a liquid to a gaseous state, replacing the energy of regenerative extractions of steam turbines operating on steam obtained from the use of heat from fossil fuels, such as natural gas, coal, fuel oil, as well as nuclear fuel and using the heat of exhaust gases of gas turbines, making it possible to increase the energy, operational and investment efficiency of the conversion of thermal energy from renewable sources of thermal energy or fuel and to achieve an effective temperature of feedwater that is maximally close to, or coincides with, the theoretically most effective temperature.

[0028] The objective of the present invention is to increase the energy efficiency of Rankine cycles using heat from fossil fuels such as natural gas, coal, fuel oil, as well as nuclear fuel and gas turbines using waste heat using renewable energy sources, to reduce steam consumption in regenerative extractions and to increase the feedwater temperature as close as possible to the theoretically most efficient feedwater temperature, in which the coolant temperature is limited to moderate values ​​not exceeding values ​​of about 330° C, which is associated with corrosion processes in steam boilers using heat from the combustion of biomass and solid municipal waste or due to the decomposition of organic coolants for other types of renewable energy sources, as indicated above.

[0029] It is obvious that the invention is also applicable to any method of obtaining energy in which the temperature of the coolant is limited by some technical or economic reason other than those indicated above.

[0030] The invention solves several problems, which are described below.

[0031] The first objective of the present invention is to achieve a thermal cycle that uses high temperature steam above 400°C, using energy from renewable sources to superheat said steam in boiler plants using fossil solid, liquid, gaseous and nuclear fuel, as well as waste heat from gas turbines, and which at the same time has better energy and operational efficiency than those offered by the above-mentioned methods with regenerative steam extraction from a steam turbine.Similarly, the aim of the invention is to achieve higher efficiency of operation of boiler plants for burning MSW and other waste, including biomass, and fuel from them, reducing the rate of corrosion of heat exchange surfaces, resulting in a reduction in downtime of the plant for repair work, with associated costs, which in turn makes it possible to increase the annual tonnage of waste burned in the plant using the method of the invention, as well as an increase in the generated electrical energy.

[0032] The technical result is a reduction in high-temperature corrosion of a renewable energy source boiler unit and an increase in the energy efficiency of the thermal cycle as a whole, a reduction in investment and operating costs when using renewable energy sources to generate electrical energy, which is achieved by using the method and system implemented by this method.

[0033] The technical result is achieved in that the method for obtaining energy in thermodynamic cycles consists of obtaining high-parameter steam in the first boiler unit using fossil solid, liquid, gaseous and atomic fuel, as well as heat from exhaust gases of gas turbines, supplying high-parameter steam to at least one steam turbine, supplying exhaust steam from the steam turbine to a condenser, heating condensate to the effective temperature of feedwater and supplying it by condensation and feed pumps to the first boiler unit.In this case, the condensate is first supplied by the condensation pump to the second boiler unit using renewable energy sources for heating it to the effective temperature of the feedwater of the first boiler unit, wherein the condensate is first supplied by the condensation pump to the low-temperature part of the second boiler unit, where the condensate is heated to a temperature of no more than 170°C, then, if necessary, the condensate is supplied to the deaerator, then after the deaerator the feedwater pressure is increased on the feedwater pump, and the feedwater is supplied to the high-temperature part of the second boiler unit, which heats it to a temperature of no more than 330°C without performing a phase transition, after which the heated feedwater returns to the first boiler unit.

[0034] A device for obtaining energy in thermodynamic cycles includes a first boiler unit using fossil solid, liquid, gaseous and atomic fuel, as well as heat from exhaust gases of gas turbines, supplying steam to a steam turbine, a steam turbine, a condenser converting exhaust steam by the turbine to condensate and a condensation pump and, if necessary, a deaerator and a feed pump supplying condensate to the first boiler unit, characterized in that the device additionally includes a second boiler unit using renewable energy sources, including a first circuit for heating condensate to a temperature of no more than 170 °C and a second circuit for heating feed water to a temperature of no more than 330 °C without performing a phase transition, wherein the condensation pump supplies condensate to the first circuit of the second boiler unit for heating condensate, after which the condensate goes to the deaerator,from where the feed water is fed by a feed pump into the second circuit of the second boiler unit and then returned to the first boiler unit.

[0035] The claimed method and device are illustrated by a figure, where the following elements are designated by positions.

[0036] 1 - the first boiler plant using fossil solid, liquid, gaseous and nuclear fuel, as well as the heat of exhaust gases from gas turbines.

[0037] 2 - the second boiler plant using renewable energy sources, including, if necessary, a combustion device, a gas tract, and a flue gas cleaning system.

[0038] 2a - the first circuit for heating the condensate to a temperature of no more than 170°C

[0039] 26 - the second circuit for heating feedwater to the effective temperature of a boiler plant using fossil solid, liquid, gaseous and nuclear fuel, as well as heat from exhaust gases of gas turbines, but not more than 330°C,

[0040] 3 - deaerator,

[0041] 4 - feed pump,

[0042] 5 - condensation pump

[0043] 6 - steam turbine,

[0044] 7 - steam turbine condenser

[0045] According to the invention, see Fig., the method for producing energy in thermodynamic cycles with high-pressure steam includes the following stages: a) producing steam at a temperature above 400° C in the first boiler unit 1, b) expanding the steam formed in stage a) in at least one steam turbine 6, c) feeding the exhaust steam from the steam turbine 6 to the condenser 7 with the supply of water in a liquid aggregate state (condensate) to the condensation pump 5, d) feeding water in a liquid aggregate state by the condensation pump 5 to the second boiler unit 2, d) heating the water in the first circuit to heat the condensate 2.a to a temperature of no more than 170° C of the second boiler unit 2, e) feeding the heated water from the first circuit to heat the condensate 2.a) to deaerator 3, g) deaerating heated water with possible secondary superheated steam by deaerator 3 and feeding deaerated feedwater to feed pump 4, h) feeding deaerated feedwater under pressure from feed pump 4 to the second circuit 2.6 for heating feedwater to the effective temperature of the first boiler plant using fossil solid, liquid, gaseous and nuclear fuel, as well as heat from exhaust gases of gas turbines, but not more than 330°C for subsequent steam generation at stage a).

[0046] The device for obtaining energy in thermodynamic cycles includes the first boiler unit 1, which supplies steam to the steam turbine 6, the steam turbine 6 itself, a condenser 7, which converts the exhaust steam of the turbine into water, and a condensation pump 5.

[0047] The device also includes the following installed in series at the outlet of the condensation pump 5:

[0048] - the first heat exchanger 2.a, heating water from the condensation pump 5,

[0049] - deaerator 3,

[0050] - feed pump 4,

[0051] - the second heat exchanger 2.6, which heats the deaerated water from the feed pump 4 and directs it to the first boiler unit 1.

[0052] Depending on the specific parameters of the system described above and the required parameters of the theoretically most efficient temperature of the feedwater of a boiler plant using fossil solid, liquid, gaseous and nuclear fuel, as well as the heat of exhaust gases of gas turbines, a single-stage scheme for implementing a boiler plant 2 using renewable energy sources can be used - only a condensing pump 5 and a low-temperature heat exchanger 2. and with a feedwater heating temperature of no more than 170°C, without a feed pump 4 and a high-temperature circuit 2.6.

[0053] 9

[0054] SUBSTITUTE SHEET (RULE 26) Thus, a water-steam thermal cycle is achieved that allows increasing the productivity of a steam turbine plant by up to 10% (according to TsKTI) without capital-intensive reconstruction, and with capital-intensive reconstruction up to 25% (according to UTZ), and more - with a new steam turbine, which increases the energy efficiency of the combined boiler plant as a whole when using thermal energy from renewable energy sources for heating feedwater and a boiler plant with high-parameter steam for a steam turbine when using heat from fossil fuels such as natural gas, coal, fuel oil, as well as nuclear fuel and gas turbines using waste gas heat.

[0055] In the proposed method and device, steam generation in the RES boiler 2 is not carried out, but the condensate (water) is first heated at the pressure of the condensation pump 4 to a temperature of no higher than 170°C, and then, if necessary to achieve a theoretically effective temperature, water deaeration, at the pressure of the feed pump 2, the water is heated to a temperature of no higher than 330°C.

[0056] Advantages of the invention: compared to previous steam cycles using renewable energy heat with high capital and operating costs associated with the need to provide infrastructure (electricity generating equipment, power distribution schemes, water treatment, etc.)d) separately for each power unit of the corresponding RES station at low steam parameters and low efficiency, including the fact that the method of the invention has a higher regenerative capacity, energy efficiency and that corrosion of heat exchange surfaces is not significant, which reduces the costs and time required for technical maintenance of the installation due to its shutdowns, as well as its cost, and the absence of phase transitions in the RES boiler plant allows using RES in the reconstruction of existing power plants or in the construction and design of new ones using fossil solid, liquid, gaseous and nuclear fuel, as well as using the heat of exhaust gases of gas turbines, with minimal costs. Thus, with a significant reduction in specific capital and operating costs, the utilization factor of the installed capacity per year increases, the efficiency of using renewable energy sources increases.

[0057] The absence of a phase transition of the coolant in a renewable energy boiler plant allows the use of this invention for the reconstruction of existing power plants with a steam power cycle to replace the regeneration cycle of steam turbines with minimal costs for reconstruction and increasing the capacity of steam turbines with more efficient use of energy from renewable energy sources.

[0058] For example, one of the most common power units based on the PT-100-130 steam turbine:

[0059] Electric power 100 MW three cylinders, high, medium and low pressure, regenerative extraction from high and medium pressure cylinders for heating feedwater from 35 to 229° C. Steam temperature 555° C, condensate temperature after condenser 34° C, before deaerator 152° C, feedwater flow rate on feedwater heater 493 t / h, feedwater temperature 229° C.

[0060] Replacing regenerative extractions from the turbine for heating condensate and feedwater with heating condensate and feedwater in a boiler plant using renewable energy sources using the example of burning fuel from municipal solid waste (SRF) with a calorific value of 10 MJ / kg allows achieving an increase in turbine capacity by 10% to 110 MW. With the efficiency of a boiler plant using renewable energy sources (fuel from waste) of 80%, 17.5 tons / hour of such fuel is required at a capacity utilization factor of 6500 h / year. A standard steam power unit with the consumption of such fuel from waste of 17.5 tons / hour and a steam temperature of 430°C has a capacity of no more than 8 MW electrical (WtE technology) with capital costs for the construction of a full technological cycle of the power plant, a power distribution scheme, infrastructure, water treatment, the need for personnel, etc.

[0061] As can be seen from the given example, the efficiency of using renewable energy for the production of electrical energy is more than 20% higher due to the high parameters of steam in the steam turbine and a significantly lower rate of corrosion of heat exchange surfaces, and in the case of using organic heat carriers, a significant slowdown in their decomposition.

[0062] For example, to replace the regenerative extraction of the PT 100-130 turbine of the steam power unit, a hot water boiler plant using the energy of fuel from municipal solid waste (RES) can consist of a furnace device with heat shields as an element of the low-temperature part of the boiler plant for heating the condensate under the pressure of the condensate pump, the fuel is burned on a roller grate under oxidation by primary air heated in the air heater of the boiler plant to 180 ° C and then the flue gases are burned with secondary air to a temperature above 1100 ° C and their combustion in the afterburning chamber of the furnace for at least 2 seconds to decompose dioxins and furans at a flue gas velocity of no more than 6.5 m / s, with further heating of the feedwater after deaeration under the pressure of the feed pump on convective heat exchange tube packages of the high-temperature part of the RES boiler plant to the feedwater temperature 270° C for boiler installation,using heat from fossil fuels such as natural gas, coal, fuel oil, as well as nuclear fuel or using heat from exhaust gases of gas turbines to generate high-parameter steam for the PT 100-130 turbine.

Claims

Invention formula 1. A method for producing energy in thermodynamic cycles, which consists of producing high-parameter steam in a first boiler unit using fossil solid, liquid, gaseous and atomic fuel, as well as heat from exhaust gases of gas turbines, feeding high-parameter steam to at least one steam turbine, feeding exhaust steam from the steam turbine to a condenser, feeding condensate by a condensation pump to the first boiler unit, characterized in that the condensate is fed by the condensation pump to a second boiler unit using renewable energy sources, for heating it to the effective temperature of the feedwater of the first boiler unit, wherein the condensate is first fed by the condensation pump to the low-temperature part of the second boiler unit, in which the condensate is heated to a temperature of no more than 170°C, then the condensate is fed to a deaerator,then, after the deaerator, the feedwater pressure increases on the feedwater pump, and the feedwater is supplied to the high-temperature section of the second boiler unit, which heats it to a temperature of no more than 330°C without a phase transition, after which the heated feedwater returns to the first boiler unit.

2. A device for generating energy in thermodynamic cycles, including a first boiler unit using fossil solid, liquid, gaseous and atomic fuel, as well as heat from exhaust gases of gas turbines, supplying steam to a steam turbine, a steam turbine, a condenser that converts exhaust steam from the turbine to condensate and a condensation pump that supplies condensate to the first boiler unit, characterized in that the device further includes a second boiler unit using renewable energy sources, including a first circuit for heating condensate to a temperature of no more than 170°C and a second circuit for heating feedwater to a temperature of no more than 330°C without performing a phase transition, wherein the condensation pump supplies condensate to the first circuit of the second boiler unit for heating the condensate, after which the condensate enters a deaerator, from where feedwater is supplied by a feed pump to the second circuit of the second boiler unit and then returns to the first boiler unit.

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