Method of producing energy in hybrid power plant using renewable resources

Abstract

FIELD: hybrid energy.SUBSTANCE: invention relates to the field of hybrid energy based on renewable energy sources (RES), in particular to methods for the integrated generation of electrical energy with the simultaneous utilization of biomass. The method includes generating electric power using generator (7) connected to steam turbine (4). Superheated steam enters the turbine from closed circuit II, formed by multi-stage heat exchange system (3), condenser (5), deaerator (9) and feed pump (10). The production of superheated steam in heat exchange system (3), consisting of a sequential heater, evaporator and superheater in counter-current, is achieved through interaction with synthetic oil of closed circuit I. The synthetic oil is preheated by solar radiation in the field of parabolic collectors (1) and is further heated in biofuel boiler (2). The exhaust steam condensate is cooled in condenser (5) with water from circuit III with fan cooling tower (6) and circulation pump (8). Part of the steam exhausted from the turbine is fed into deaerator (9). The invention is distinguished by the fact that biofuel pellets prepared directly at the power plant are fed into boiler furnace (2). For this purpose, the plant material from bin (11) is crushed in mill (12), moistened with exhaust steam from steam turbine (4), mixed in mixer (13) with a binder and formed in extruder (14). From the extruder to storage bin (15) the granules are transported with natural drying.EFFECT: increasing the energy efficiency and autonomy of a hybrid power plant by eliminating the cost of external energy for heating and moistening plant materials by using exhaust steam from a steam turbine to prepare the raw materials for forming granules.1 cl, 1 dwg

Description

[0001] The invention relates to the field of energy, namely to hybrid power plants designed for the production of electrical and thermal energy and autonomous energy supply using renewable energy sources through the combined use of solar energy and solid biofuel.

[0002] Hybrid power plants are combined heat and power plants powered by renewable energy sources and solid fuels. Steam production can be performed separately in a solar steam generator and a fuel-fired boiler, while all other equipment is shared. Furthermore, hybrid power plants have the ability to maintain a constant load on the fuel-fired steam generator, thereby eliminating fuel overburning during startup and transient conditions. The fuel for a small-capacity hybrid thermal power plant can be solid plant-based biofuel, which undergoes specific preparation before combustion in the boiler's combustion chamber.

[0003] Currently, there are various schemes of hybrid power plants based on renewable resources.

[0004] A diagram of a combined solar-fuel power plant is known (Akhmedov, R.B. Solar Power Plants / R.B. Akhmedov, I.V. Baum, V.A. Pozharnov, V.M. Chakhovsky / / Series "Helioenergetics". - Vol. 1. - M .: VINITI, 1986. - 121 p.), where the boiler unit of the solar-fuel power plant consists of a gas-oil steam boiler and a strip-type solar steam generator, the heating surface of which is included only in the primary steam path of the boiler after exiting the wall screens. The steam generated by the fuel steam generator and heated in the solar steam generator passes through a steam-steam heat exchanger installed directly at the boiler, in which it transfers part of its heat to the secondary steam, then enters the platen superheater and then passes through the subsequent convective packages of the primary superheater, in which it is heated to the nominal temperature.Before entering the boiler, the secondary steam passes through a steam-steam heat exchanger, where it is partially heated by solar heat absorbed by the primary steam in the solar heat receiver. It is then fed to the boiler's secondary superheater, where it is superheated to the nominal temperature. The main drawback of this design is the complexity of the thermal engineering implementation and increased heat losses due to the multi-stage heat exchange process, which leads to additional heat losses and hydraulic resistance in the secondary steam path, as well as increased boiler system costs. This design can be applied to high-capacity power plants with a fossil-fuel boiler and a multi-stage turboplant.

[0005] A well-known scheme of a hybrid solar energy production system is (Ghazi, M.K.A. Prospects for the Use of Solar Power Plants in Iraq / M.K.A. Ghazi, N.N. Efimov / / News of Higher Educational Institutions. North Caucasus Region. Technical Sciences. - 2013. - No. 6. - Pp. 57-61.), which uses an additional heating device for the coolant, running on natural gas, connected in parallel with the solar field, or an additional combined-cycle boiler connected in parallel with the solar heat exchanger. Parabolic trough collectors are used to heat synthetic oil, which transfers energy through a heat exchanger to a traditional steam turbine cycle consuming gas for conversion into electricity. The disadvantage of this scheme is the parallel connection of a gas turbine unit to the steam cycle, which leads to an increase in capital investments and does not ensure autonomous operation.

[0006] The prototype chosen is a hybrid configuration of concentrated solar power and biomass energy (Srinivas T., Reddy BV Hybrid solar-biomass power plant without energy storage / / Case Studies in Thermal Engineering. 2014. Vol. 2. P. 75-81.), in which the natural gas boiler is replaced by a biomass boiler, where the biomass boiler is designed to heat synthetic oil coming from a solar field instead of water.

[0007] The disadvantage of the prototype is the additional use of natural gas to make the biomass boiler have a more efficient dynamic characteristic to adapt its operating point to the variability of solar radiation conditions.

[0008] The technical result, which the invention is aimed at achieving, is the elimination of the listed disadvantages: uninterrupted operation of the boiler plant due to the inclusion in the fuel preparation system of the briquetting of fuel from agricultural plant waste, as well as an increase in the efficiency of energy conversion with an increase in the reliability of heat and electricity supply to autonomous facilities, saving energy resources and protecting the environment.

[0009] The technical result is achieved in that the method of producing energy at a hybrid power plant through the use of renewable resources is characterized by the fact that:

[0010] a) electric power is generated by an electric generator 7 connected to a steam turbine 4, into which superheated steam is supplied from a closed circuit II formed by a multi-stage heat exchange system 3, a condenser 5, a deaerator 9 and a feed pump 10;

[0011] b) the production of superheated steam in a multi-stage heat exchange system 3 is carried out through interaction with synthetic oil circulating in a closed circuit I, including a biofuel boiler 2;

[0012] c) steam production occurs in a multi-stage heat exchange system 3, consisting of a heater, evaporator and superheater, located sequentially in counter-current to the incoming synthetic oil;

[0013] d) synthetic oil is heated to 300°C in the field of solar parabolic collectors 1 due to solar radiation;

[0014] d) the synthetic oil heated in the field of parabolic solar collectors 1 is sent to the biofuel boiler 2 for additional heating up to 400°C, forming a closed circuit I, due to which the synthetic oil is returned to the field of solar collectors 1 after passing through the multi-stage heat exchange system 3;

[0015] e) the process of deaeration of the condensate of the steam exhausted in the turbine occurs in the deaerator 9 by feeding part of the exhaust steam (up to 10%) into the steam turbine 4;

[0016] g) exhaust steam condensate is formed in condenser 5 due to cooling by circulating water, which is cooled in fan cooling tower 6 and pumped into condenser 5 by circulation pump 8, forming closed circuit III,

[0017] according to the present invention

[0018] z) biofuel boiler 2 heats synthetic oil by burning fuel granules, the preparation of which is carried out by grinding plant material coming from raw material bin 11 to 1-2 mm in mill 12, moistening with exhaust steam from steam turbine 4, mixing in mixer 13 with a binder - molasses and forming granules in extruder 14;

[0019] i) biofuel granules transported from the extruder 14 to the storage bin 15 with natural drying are fed into the furnace of the biofuel boiler 2.

[0020] The figure shows a circuit diagram for generating heat and electricity from solid biofuel using solar energy.

[0021] The numbers in the diagram indicate a field of solar parabolic collectors 1, a biofuel boiler 2 for heating synthetic oil, a multi-stage heat exchange system 3 consisting of a heater, evaporator and superheater, a steam turbine 4, an electric generator 7, a condenser 5, a fan cooling tower 6, a circulation pump 8, a deaerator 9, a feed pump 10. The fuel preparation unit consists of a raw material bin 11, a mill 12, a mixer 13, an extruder 14, a storage bin 15 for biofuel pellets.

[0022] The method is as follows: in the field of solar parabolic collectors 1, synthetic oil is heated to 300°C by solar radiation. Then, the heated oil is sent to the biofuel boiler for additional heating to 400°C. The thermal energy of the synthetic oil is transferred to water to produce superheated steam in the multi-stage heat exchange system 3. The field of solar parabolic collectors 1, the biofuel boiler 2, and the multi-stage heat exchange system 3 form a closed circuit of synthetic oil I. The synthetic oil, having given up heat during the vaporization of water in the multi-stage heat exchange system 3, returns to the field of solar collectors 1. The water vapor formed in the superheater is sent to the steam turbine 4 to generate electrical energy.The exhaust steam from the steam turbine 4 enters the condenser 5, then is fed to the deaerator 9, where, using the steam extracted at the outlet of the steam turbine, both the feedwater is deaerated and heated to the condensation temperature of the extracted steam. The steam turbine 4, condenser 5, and deaerator 9 form a closed steam-water circuit II. Exhaust steam condensate is formed in the condenser 5 due to cooling with circulating water, which is cooled in a fan cooling tower 6 and pumped to the condenser 5 by a circulation pump 8, forming a closed circuit III. The fuel preparation unit operates as follows: raw material from the hopper 11 is fed to the mill 12, then the raw material, crushed to 1-2 mm, is fed to the mixer 13, into which, together with the crushed biofuel, a portion of the exhaust steam from the steam turbine is fed for fuel moistening and a binding agent - molasses. The mixture, ready for molding, enters the extruder 14, where the biofuel is granulated.During the transportation of biofuel pellets from the extruder 14 to the storage bin 15, they are naturally dried.

[0023] Thus, the method of generating thermal and electrical energy using solar energy can be applied in agricultural facilities, logging sites and small industrial enterprises operating in autonomous mode, and makes it possible to produce electricity and steam for the needs of the facility.

[0024] The method of producing energy at a hybrid power plant through the use of renewable resources is carried out by heating synthetic oil in a multi-stage system of parabolic solar collectors and additionally heating synthetic oil in a biofuel boiler, the fuel for which is prepared in a mill, then fed to a mixer together with exhaust steam from a turbine to moisten the raw material and a binder - molasses, the finished fuel mixture is fed to an extruder to form fuel pellets, which are dried during transportation to the fuel feed bin of the boiler.

[0025] An example of a similar system is provided on the website of the Renewable Energy Development Center of the Ministry of Higher Education and Scientific Research of the People's Democratic Republic of Algeria [1]. The prototype, using an organic Rankine cycle, is a hybrid system combining solar thermal collectors with an auxiliary biomass unit for the production of electricity and heat. Solar collectors, which heat synthetic oil, are connected in a single closed loop to a heat exchanger in which the heated medium is water, which enters a biomass boiler for steam generation by burning agricultural waste. The prototype is designed for a power of 6 kW and will be classified as a decentralized system.

[0026] Another example of such a scheme is the hybrid plant in Brennerslev, North Jutland, Denmark, the world's first plant using concentrated solar power and biomass for waste heat recovery [2]. The combined heat and power plant consists of a 16.6 MW parabolic trough collector array, two 10 MW biomass boilers, and a 4 MW organic Rankine Cycle (ORC) system. The solar collectors and biomass boilers are hydraulically connected and feed heat into the ORC system in parallel. A multi-stage heat recovery process ensures that the waste heat is fed into the local district heating system. The solar power plant can be operated independently of the biomass plant, feeding heat directly into the district heating system.The hybrid power plant was designed to meet 90% of the city's district heating needs. The remaining heat is generated by the existing natural gas-fired combined heat and power plant.

[0027] List of references:

[0028] 1. REELCOOP: cooperation in the field of renewable energy sources. Available at https: / / www.cder.dz / spip.php?article2074. Link active as of 03.03.2026.

[0029] 2. Adam R. Jensen, loannis Sifhaios, Bengt Perers, Jan Hoist Rothmann, Soren D. Morch, Poul V. Jensen, Janne Dragsted, Simon Furbo. Demonstration of a concentrated solar power and biomass plant for combined heat and power / / Energy Conversion and Management, Vol.271, 2022, 116207, ISSN 0196-8904, https: / / doi.org / 10.1016 / j.enconman.2022.116207.

Claims

A method for producing energy at a hybrid power plant using renewable resources, characterized in that electric power is produced by an electric generator (7) connected to a steam turbine (4), superheated steam which is supplied from a closed circuit II formed by a multi-stage heat exchange system (3), a condenser (5), a deaerator (9) and a feed pump (10), the production of superheated steam in the multi-stage heat exchange system (3) is carried out due to interaction with synthetic oil circulating in a closed circuit including a biofuel boiler (2), the production of steam occurs in a multi-stage heat exchange system (3) consisting of a heater, an evaporator and a superheater, arranged sequentially in countercurrent to the incoming synthetic oil, the synthetic oil is heated to 300°C in the field of solar parabolic collectors (1) due to solar radiation,the synthetic oil heated in the field of parabolic solar collectors (1) is sent to the biofuel boiler (2) for additional heating to 400°C, forming a closed circuit I, due to which the synthetic oil is returned to the field of solar collectors (1) after passing through a multi-stage heat exchange system (3), the process of deaeration of the condensate of the exhaust steam in the turbine occurs in the deaerator (9) due to the supply of a portion of the exhaust steam (up to 10%) in the steam turbine (4), the condensate of the exhaust steam is formed in the condenser (5) due to cooling with circulating water, which is cooled in a fan cooling tower (6) and pumped into the condenser (5) by a circulation pump (8), forming a closed circuit III, characterized in that the biofuel boiler (2) heats the synthetic oil due to the combustion of fuel pellets, the preparation of which is carried out by grinding plant material coming from the raw material bin (11) to 1-2 mm in mill (12),humidification with exhaust steam from a steam turbine (4), mixing in a mixer (13) with a binder – molasses and forming granules in an extruder (14), biofuel granules, transported from the extruder (14) to the storage bunker (15) with natural drying, enter the furnace of the biofuel boiler (2).,

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