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OPERATION OF THE HEAT AND POWER COMPLEX ALATYR TO POWER RUSSIAN OIL AND GAS FACILITIES
Boris Boltyanskiy
Master of Science thesis TRITA-ITM-EX 2018:728
KTH Royal Institute of Technology School of Industrial Engineering and Management
Energy Technology 2017 SEE-100 44 STOCKHOLM
2017
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Mater of Science Thesis TRITA-ITM-EX 2018:728 Operation of the heat and power complex Alatyr to
power Russian oil and gas facilities Boltyanskiy Boris
Examiner
Andrew Martin
Supervisor
Vladimir Kutcherov Valery Bessel
Approved
02.11.2016
Commissioner
KTH Royal Institute of Technology
Gubkin Russian State University of Oil and Gas
Contact person
Alexey Lopatin
ABSTRACT
B. Boltyansky Operation of the heat and power complex Alatyr to power Russian oil and gas facilities, Master's Dissertation, 2017 - 102 pages, 26 tables, 30 figures Supervisor Prof. V. G. Kucherov, Doctor of Sciences, Department of Energy Technology.
The work includes the following. A calculation of the main thermodynamic cycle of the heat and power complex Alatyr heat and power complex. A consideration of various schemes of using the Rankine organic cycle WERE integrated in the Alatyr heat and power complex with the aim of increasing energy efficiency. Conclusions about the feasibility of using the heat and power complex Alatyr. Conclusions about the feasibility of integration of the organic Rankine cycle. Economic comparison of the heat and power complex Alatyr with similar facilities on the distributed power generation market. Economic analysis of the comparison of energy blocks of HPC Alatyr with similar designs from other countries.
Keywords: energy efficiency, petroleum industry, remote oil fields, organic Rankine cycle
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Schlumberger-Private
Mater of Science ThesisTRITA-ITM-EX 2018:728 Operation of the heat and power complex Alatyr to
power Russian oil and gas facilities Boltyanskiy Boris
Examiner
Andrew Martin
Supervisor
Vladimir Kutcherov Valery Bessel
Approved
02.11.2016
Commissioner
KTH Royal Institute of Technology
Gubkin Russian State University of Oil and Gas
Contact person
Alexey Lopatin
SAMMANFATTNING
B. Boltyansky Drift av värme- och kraftkomplexet Alatyr till makten Ryska olje- och gasanläggningar, Masters uppläggning, 2017 - 102 sidor, 26 tabeller, 30 figurer Handledare Prof. VG Kucherov, doktorsexamen, kandidatexamen för teknisk vetenskap, institutionen för termodynamik och termisk motorer.
Arbetet innehåller följande. En beräkning av värmekraftkomplexets värme- och kraftkomplex Alatyrs värmekomplex. En övervägning av olika system för användning av Rankine organiska cykeln var integrerad i Alatyr värme- och kraftkomplexet i syfte att öka energieffektiviteten. Slutsatser om möjligheten att använda värme- och kraftkomplexet Alatyr. Slutsatser om möjligheten att integrera den organiska Rankine-cykeln. Ekonomisk jämförelse av värme- och kraftkomplexet Alatyr med liknande anläggningar på den distribuerade kraftproduktionsmarknaden. Ekonomisk analys av jämförelsen av energiblock av HPC Alatyr med liknande konstruktioner från andra länder.
Nyckelord: energieffektivitet, petroleumindustrin, avlägsna oljefält, organisk Rankine-cykel
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TABLE OF CONTENTS
INTRODUCTION... 6
CHAPTER 1 Heat and power complex Alatyr (HPC Altayr) ... 8
1.1 Description of HPC Alatyr ... 8
1.2 Principle of operation HPC Alatyr ... 8
1.3 Special features of HPC Alatyr ... 9
1.4 HPC Alatyr 1-5 ... 10
1.5 HPC Alatyr 1/0 ... 19
CHAPTER 2. CALCULATION OF THE MAIN THERMODYNAMIC CYCLE OF HPC ALATYR ... 26
2.1 Determination of thermodynamic parameters of the state at characteristic points of the cycle ... 27
2.2 Determination of the state functions at characteristic points of the cycle ... 31
2.3 Determination of the specific operation of the cycle (lc) and thermal efficiency (ηtP) ... 32
CHAPTER 3. ORGANIC RANKINE CYCLE ... 34
3.1 Description of the Organic Rankine Cycle ... 34
3.2. Potential areas of application for ORC ... 35
3.3 Selection of the working fluid for the organic Rankine cycle ... 37
3.4 Refrigerants ... 37
3.5 R245fa ... 38
CHAPTER 4. USE OF EXCESS HEAT AT HPC ALATYR ... 42
4.1. Utilization of heat from exhaust gases ... 42
4.2 Use of excess heat from outgoing steam after the turbines ... 43
CHAPTER 5. ORGANIC RENQUIN CYCLE CALCULATION ... 49
5.1 Determination of parameters and functions of the state at characteristic points of the cycle ... 49
5.2 Determination of the specific operation of the cycle (lc) and thermal efficiency (ηtP) ... 52
CHAPTER 6. ANALYSIS OF USING THE ORGANIC RANKINE CYCLE ... 54
CHAPTER 7. ECONOMIC COMPARISON OF THE HPC ALATYR .... 58
7.1 Comparison of HPC Alatyr 1/0 with foreign counterparts ... 58
Main conclusions from the calculation results ... 65
7.2 Comparison of HPC Alatyr 1-5 with Russian counterparts ... 65
CONCLUSION ... 73
REFERENCES ... 75
ANNEX A. ECONOMIC CALCULATION DATA ... 80
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ANNEX B. DIAGRAMS OF THE BASIC CYCLE OF HPC ALATYR .. 87
ANNEX B. DESCRIPTION OF THE TYPE K-0.6-1.4 / 0.25 TURBINE 89
APPENDIX D. COMPARISON OF HPC ALATYR ... 102
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INTRODUCTION
Russian Federation has a territory of 17.1 million [1] square kilometers.
Russia is a country richly in hydrocarbon fuels of varying composition and quality.
Throughout the country, the number of hydrocarbon production facilities is rapidly growing. Due to the remote location of some deposits, there is a problem of providing the mining areas with electricity, both during construction and during operation.
Furthermore, the oil and gas industry facilities are often located in the severe climates of the northern regions. This creates a realistic possibility of power equipment failures, cutting power from the oil and gas facilities in the area. The main sources of uninterrupted electricity supply to the oil and gas industry are electrical networks of distribution grid companies or own autonomous power plants, which also support the household energy needs of the personnel.
The locations of new deposits may lack the necessary technical infrastructures, or a blatant physical possibility of connecting the oil or gas field to electric grids due to insufficient reserve of capacity in the power system or if such connection is economically unjustified due to the remoteness of the electric power source and the capital investments associated with the laying of such networks.
Under these conditions, it is difficult to ensure reliable and uninterrupted power supply to oil production fields.
The reliable and efficient operation of technological facilities [35] of the oil and gas industry is largely determined by the operation of the energy equipment used. In the Russian Federation, the majority of low-power generation facilities operate on diesel and gas [36], and power is supplied by stationary and mobile diesel power plants or steam-turbine units.
The equipment supplies, and the tackling of associated reliability issues, usually falls with the energy market giants such as General Electric, Siemens and others. In the conditions of the modern market, both domestic and foreign manufacturers of power equipment supply products of different quality levels, with
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different technical parameters, in a wide range of prices. That is why there is an evident demand for an objective assessment of technical parameters, reliability and efficiency of various power equipment, their compliance with operating conditions at oil and gas production facilities and with the Russian Federal industrial safety standards [34].
In the light of the current active policy of substituting imported technologies with domestic (Russian) equivalents, there is a live demand for the creation and support of Russian-made heat an power complexes [2].
The heat and power complex Alatyr ("HPC Altayr") [3] is intended for the powering of industrial enterprises, oil, coal and gas facilities, and the housing and communal services sector, wherever a reliable source of distributed low-power generation is needed. It is a steam heat power plant that generates electric and thermal energy, as well as, if necessary, process steam with the desired parameters.
The uniqueness of HPC Alatyr is its ability to work with different types of fuel:
• natural gas;
• associated petroleum gas (crude);
• crude oil (including high-viscosity and extra-viscous, with a sulfur content of up to 5%); - fuel oil of any brand, including non-compliant with GOSTs;
• oil refining waste (requires customisation);
• diesel fuel;
• methane (released during degassing of seams in the coal mining industry);
• bioethanol;
• aggressive combustible gases emitted in the chemical industry, with a calorific value of 4000 kcal / nm3 (requires customisation).
In addition, HPC Alatyr is able to operate simultaneously on a mixture of fuels in the gaseous and liquid aggregate state.
Due to its ability to work at critically low temperatures (as low as -65°C), HPC can be used at special facilities in the Far North and Arctic regions.
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The complex can also be equipped for operation in hot climatic conditions.
The purpose of this dissertation is to investigate the possibility of using HPC Alatyr to power various oil and gas facilities in Russia.
The work posed the following tasks:
1. Thermodynamic calculations of the main cycle of the heat and power complex Alatyr.
2. Feasibility assessment of the integration of organic Rankine cycle in order to use the emitted excess heat and increase the effectiveness of the HPC.
3. Comparative calculation of technical and economic indicators of HPC Alatyr.
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CHAPTER 1 Heat and power complex Alatyr (HPC Altayr)
1.1 Description of HPC Alatyr
The heat and power complex Alatyr ("HPC Altayr") [3] is intended for the powering of industrial enterprises, oil, coal and gas facilities, and the housing and communal services sector, wherever a reliable source of distributed low-power generation is needed. It is a steam-heat power plant that generates electric and thermal energy, as well as, if necessary, process steam with the desired parameters.
Due to its ability to work at critically low temperatures (as low as -65°C), HPC can be used at special facilities in the Far North and Arctic regions.
The complex can also be equipped for operation in hot climatic conditions.
The complex was designed and created to provide cheap electricity and heat generation at any facilities located at a great distance from the central electric systems of the Russian Federation; it is based on combustion of liquid and gaseous hydrocarbons of any quality, as well as of their mixtures with varying chemical composition and percentage. The cost reduction in oil production, as well as the use of associated petroleum gas (increased energy efficiency of subsoil operations) and greater power supply to remote regions, while reducing the electricity supply from the single power system of the country.
1.2 Principle of operation HPC Alatyr
The principle of operation is basically similar to that of a large thermal power plant .
The fuel burned in the boilers generates thermal energy, which is used to change the water circulating in the pipes from the liquid state to steam. This steam then enters the steam turbine generator, which generates the electric energy supplied to the consumer. The exhausted steam is fed to the condenser, where it
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condenses, and the resulting condensate is pumped to the deaerator, then back to the boiler, and the cycle is repeated.
1.3 Special features of HPC Alatyr .
1. The ability of the heat and power complex Alatyr to operate using any gaseous and liquid fuel (as well as their mixtures), including cheap refinery waste, which can significantly reduce the cost of fuel. The complex is able to operate on crude oil with a high sulfur content (up to 5%), super-viscous crude oil, and aggressive associated gas.
2. Low cost of generated electricity, due to low operating costs, and the possibility of using cheap fuels.
3. Short payback period.
4. The effective redistribution of deposit's energy balance between heat and electricity significantly reduces the consumption of electrical energy (eliminating, for example, the need for oil heaters, heating cables, etc).
5. The variability of HPC Alatyr, which allows selecting from a range of possible power generation solution, as well as the production of process steam, which will significantly reduce consumer's spending on procurement from third-party sources. There is no need for additional steam sources for cleaning oil pipelines and dewaxing wells (steam can be taken both from the boilers and the turbines).
6. Easy maintenance and fast scheduled maintenance.
7. Reliability and long service life (25 years and more). TPP are reliable, time- tested technologies.
8. HPC also features a self-cleaning system for boilers, which allows maintaining the required quality and quantity of steam for the operation of the turbine.
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9. Adjustment of the supplied electric and thermal energy from 15% to 100%.
The ability to quickly deploy and load - the equipment of the complex is supplied in transportable modules.
When used in the oil industry, it is facilitated by the implementation of Decree No. 7 of the Government of the Russian Federation of January 8, 2009 "On Measures to Promote Reduction of Air Pollution by Combustion Products of Associated Petroleum Gas on Flare Facilities".
The design of HPC Alatyr relied on materials about the small and medium production fields, their infrastructure and their energy balance. The manufacturer offers different versions of HPC Alatyr. This dissertation looks at HPC Alatyr 1-5 HPC Alatyr 1/0. The HPC Alatyr 1-5 version was considered when researching integration of the Rankin organic cycle; HPC Alatyr 1/0 was taken for the comparison with Russian and foreign counterparts.
1.4 HPC Alatyr 1-5
HPC Alatyr 1-5 is a multifunctional, universal, autonomous (no need to supply electricity for its own needs), transportable energy complex capable of autonomous operation in remote, inaccessible, isolated regions, generating 1 MW of electric power and 8 MW of thermal energy [3].
The proposed fuel is associated petroleum gas and crude oil (with a sulfur content of up to 5%), as well as their mixtures (with APG deficiency).
The equipment includes heat exchangers designed to heat the watered oil to strictly specified parameters (regulated by the automation of the complex).
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Figure 1.1 - 3D model of HPC Alatyr 1-5 [3]
As a result, thanks to the redistribution of the energy balance of the deposit between thermal and electric energy, the consumption of electric energy has been significantly reduced. HPC eliminates the use of oil heaters and heating cables.
Equipment composition of HPC Alatyr 1-5
1. Boiler unit
consists of a boiler and ancillary equipment, namely: gas and oil fuel ramps, a burner, a top purging system of the drum, a lower purge system, a system for cleaning internal surfaces of the boiler, air pipes, water, steam and fuel pipelines, fittings, mountings, automation, appliances and control and protection devices, a chimney.
Boiler
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Water-tube boiler with a horizontal water-cooled combustion chamber, designed to burn fuel with a high sulfur content in the compounds, with a steam system for the cleaning of soot formation. The flue gas temperature is not lower than 175 ° C, in order to prevent the formation of flue gases acidic dew point on thermal surfaces.
Figure 1.2 - Appearance of the boiler [3]
The characteristics of the boiler are presented in Table 1.1.
Table 1.1 - Features of the HPC Alatyr 1-5 boiler [3]
Burner device
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Industrial burner device for separate and joint combustion of APG and oil with a high sulfur content in the compounds. Power control - modulating. Fuel / air ratio control - electronic.
Figure 1.3 - Appearance of the burner device [3]
Gas fuel rail.
It is designed to adjust the pressure of the incoming gas flow and ensure its uniform supply to the burner.
Figure 1.4 - Appearance of the gas fuel rail [3]
Oil fuel rail.
It is designed for preheating and pumping fuel, providing the constant temperature pressure necessary for feeding the burner.
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Figure 1.5 - Appearance of the oil fuel rail [3]
2. Turbogenerator
Designed for the generationof electrical energy. Guaranteed electric power 650 kW. a) a steam turbine with back pressure (BP) is a single-stage turbine with a working wheel equipped and a single row of rotor blades. b) generator - three- phase, synchronous. The appearance of the turbogenerator is shown in Figure 1.6.
Figure 1.6 - Appearance of the turbogenerator [3]
Table 1.2. - Turbogenerator features [3]
3. Switchgear set [3]
Alatyr 1-5 includes two sets of 6.3 kV switchgears, which together with
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turbine generators can be connected to an autonomous network, and can synchronise and transmit 1.0 MW of electricity to the consumer.
Software and hardware set for the automatic control system
The automated process control system of HPC Alatyr 1-5 is comprises devices and automation means from renowned international manufacturers:
• Metran measuring converters by EMERSON;
• actuating control valves by AUMA;
• duplicated controller and other controller equipment by SIEMENS.
The measuring transducers and drive fittings control units applied are certified by the level of functional safety completeness SIL 3 according to GOST R MEK 61508-1-2007 "Functional safety of electrical, electronic, programmable electronic systems related to safety".
Each parameter involved in the ESS (emergency shutdown system) is measured using three transducers (sensors) and relying on the "2 out of 3" trigger logic. This approach ensures reliable protection and interlocking and prevents false triggering.
The process control system is supplied with well-adjusted programs for collecting, processing, presenting and transmitting information, automatic control and protection. This ensures the security integrity of the hardware used in control loops, protections, locks, and SIL3.
The equipment is operated without the constant presence of maintenance personnel in the main building. Equipment operation is started, stopped, directed and controlled from the operator's room, the control module, which features an automatic workstations (AWS).
HPC is equipped with: energy consumption units (water, fuel); energy resources metering units (steam, electricity, heat to the consumer). The process control system also features a modem for remote viewing of the operating modes of technological equipment and the state of the premises, via the Internet.
It is possible to connect the automated process control system of Alatyr 1-5
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to the high-level automated process control system and connect to the engineering systems monitoring and control system of the Russian Civil Defense Ministry [30]. The automated process control system of HPC Alatyr 1-5 has the following integrated components:
• Local radio system:
• Access control and management system;
• Video surveillance for process equipment and control points, for example to check for oil leaks;
• A security and fire alarm system, and a fire extinguishing system with smoke detectors and flame detectors. The system has automatic fire extinguishing elements. There are back-up fire-fighting elements with manual operation (covering 100% of the demand).
4. Atmospheric deaerator
This device is designed to remove corrosive gases (oxygen and free carbon dioxide) from the feed water of steam boilers.
It is intended for the transfer of thermal energy to the consumer and, if necessary, if the heat energy is not required, for disposal through dry cooling towers. The system is closed and requires only recharges during operation.
Composition: dry cooling tower, heat exchangers working as a condenser, network heat exchangers, pumps, and other auxiliary equipment.
5. Dry cooling tower
Cools the circulating fluid-coolant by passing the outside air through the plate heat exchanger.
6. Heat transfer equipment
From Russian manufacturers and suppliers: ZAO Hydrolex and OOO ATIS, St. Petersburg - bellows-tube heat exchangers, small weight, compact. Standard plate heat exchangers.
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7. Pumping equipment
OOO Grundfos, Moscow Region.
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1.5 HPC Alatyr 1/0
It is designed to generate electricity, and consists of the same basic components of the system as other modifications of the heat and power complex . Figure 1.7 shows the enlarged scheme of HPC Alatyr 1/0.
Figure 1.7 - Enlarged technological scheme of HPC Alatyr 1/0.
The main difference from other modifications of HPC Alatyr is the use of a normal condensing turbine (other versions of the HPC Alatyr use backpressure turbines, or condensing with steam collection).
The principle of operation of HPC Alatyr is similar to other major condensing power plant - the fuel burnt in the boilers emits heat energy that is used to turn the water circulating in the pipes from liquid to vapor state. This vapor (steam) then enters the steam turbine generator, which generates the electric energy
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supplied to the consumer. The exhausted steam is fed to the condenser, where it condenses, and the resulting condensate is pumped to the deaerator, then back to the boiler, and the cycle is repeated.
All equipment of the plant is placed in containers (blocks) of full factory readiness, assembled into a single building volume directly at the site.
Main equipment:
1. Boiler
Water tube, with a horizontal water-cooled combustion chamber, designed to burn fuel with a high sulfur content in the compounds, with a steam system for cleaning the soot formation. The flue gas temperature is not lower than 175 ° C, in order to prevent the formation of flue gases acidic dew point on thermal surfaces. Appearance of the boiler - figure 1.3.
Table 1.3 - Basic features of the boiler [3]
2. Burner
Industrial burner for separate and combined incineration of APG and oil with high sulfur content in the compounds. Power control - modulating. Fuel / air ratio control - electronic. Appearance of the burner device - figure 1.9.
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Table 1.4 - Key features of the burner [2]
3. Gas fuel rail.
It is designed to adjust the pressure of the incoming gas flow and ensure its uniform supply to the burner.
4. Oil fuel rail
It is designed for preheating and pumping fuel, providing the constant temperature pressure necessary for feeding the burner.
5. Turbine generator (with condensation turbine)
Designed for the production of electrical energy. Guaranteed electrical power (at generator terminals) 1 250 kW. Appearance of the turbogenerator -
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Figure (1.6.).
Table 1.6 - Key features of the turbogenerator [3]
6. Switchgear set
Includes one set of 6.3 kV switchgear, which together with the turbogenerator equipment can be linked to the autonomous network, can be synchronized and transmit 1.1 MW of electricity to the consumer.
7. Water treatment
The main water treatment equipment is a block-modular water treatment unit, factory-made. The water treatment equipment is produced serially according to TU 489-001-80586333-2011 and guarantees fulfillment of the initial data requirements. Equipment features ensure the quality of the treated water at outlet, which meets the requirements of GOST 20995-75, PB 10-574-03, para. 8.2.3, subject to the operation and the maintenance conditions specified in the equipment certificate.
Table 1.6 (continued)
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8. Atmospheric deaerator
This device is designed to remove corrosive gases (oxygen and free carbon dioxide) from the feed water of steam boilers. The key features are presented in Table 1.7.
Table 1.7- Key features of the air deaerator [3]
Manufacturer: Russian
Key features DA 10/4
Capacity G: 10.0 m3/ h
Pressure Pwork: 12bar (abs.)
Volume V: 4 m3
Temperature Twork: 104.25 ° C
9. Equipment for the utilization of thermal energy
Intended for utilization of heat released during the condensation of water vapor in the condenser. Composition: dry cooling towers, condenser, pumps for pumping ethylene glycol liquid and other auxiliary equipment.
10. Dry cooling tower
Cools the circulating fluid-coolant by passing the outside air through the plate heat exchanger. The key features are presented in Table 1.8.
Table 1.8 - Key features of a dry cooling tower [3]
Manufacturer: OOO TERRAFRIGO FACTORY
Key features of TF 916.6.22.GR
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Power: 1.8kW
Hydraulic resistance 0.53 bar
Number of fans: 6
Pressure Pwork: 12 bar (abs.)
Air temperature output: 66.4 ° C
Air Consumption: 135000 m3 / h
Dimensions:
L/W/H 5.80 m / 2.376 m / 2.40 m
Water treatment
The main water treatment equipment is a block-modular water treatment unit, factory-made.
The water treatment equipment is produced serially according to TU 4859- 001- 80586333-2011 and guarantees fulfillment of the initial data requirements.
Equipment features ensure the quality of the treated water at outlet, which meets the requirements of GOST 20995-75, PB 10-574-03, para. 8.2.3, subject to the operation and the maintenance conditions specified in the equipment certificate.
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CHAPTER 2. CALCULATION OF THE MAIN THERMODYNAMIC CYCLE OF HPC ALATYR
The calculation is made for a single turbine with a unit capacity of 650 kW.
The steam-powered unit operates on the Rankine cycle. The thermodynamic cycle of the steam power plant is calculated using the tables of thermodynamic properties of water and steam and the h-s diagram for water steam. Figures 2.1 and 2.2 show the diagram and the cycle of the steam power plant, respectively.
Steam power plant diagram:
Figure 2.2 - Rankin cycle at a steam power plant in coordinates
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4
3
2 1
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Figure 2.1. - Steam power plant diagram:
1 - steam turbine, 2 - condenser, 3 - pump, 4 - steam boiler, 5 - superheater,
6 - consumer (for example, power generator) [4]
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P-V [4]
Temperature t1= 430 ◦C and pressure P1= 9 MPa of superheated steam before the turbine, pressure in the condenser P2= 98 kPa, installation power N = 10.5 MW, steam pressure at the outlet of the high-pressure turbine P1= 2.5 MPa, steam temperature at the outlet of the high pressure turbine t1= 410 ◦C.
Determine:
1. Parameters and functions of states at the characteristic points of the cycle P, V, T, t, x, u, h, s.
2. Specific work of the cycle (lc), thermal efficiency (ηtP).
3. Specific consumption of steam (d) and heat (q).
4. Steam (D) and heat (Q) for a given capacity of the steam power plant N.
Calculations
Determination of parameters and functions of the state at characteristic points of the cycle
2.1 Determination of thermodynamic parameters of the state at characteristic points of the cycle
Determination of thermodynamic processes:
• process 1-2 - adiabatic (q = 0);
• process 2-3 - isobaric (P - const);
• process 3-4 - isochoric (V - const);
• process 4-5 - isobaric (P - const, x = 0, x - degree of saturation);
• process 5-6 - isobaric (P - const, x = 1, x - degree of saturation).
• process 6-1 - isobaric (P - const).
To determine the parameters at each point, we can use the h-s diagram (Fig.
2.3) for water steam and the tables for the thermodynamic properties of water and steam, and the diagram.
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Figure 2.3 - h-s diagram of the state of water and water steam
The figure shows a diagram of the state of water and water steam, along which the working points of the main cycle of HPC Alatyr were determined.
Pressure (P [MPa]), temperature (t [C]), enthalpy (h [kJ / kg]), entropy (s [kJ / (kg * K)]), dryness degree (x) is determined by the program, setting the mode and input parameters. The value of the volume (V [m3/ kg]) can be obtained both from the program and by calculation using the formula:
𝐕𝐧 =𝐑∗𝐓𝐧
𝐏𝐧 (2.1)
where
• 𝐕𝐧 - density, m3/ kg
• R- universal gas constant, m3/ kg
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• 𝐏𝐧 - process pressure, MPa
• 𝐓𝐧 - temperature, C
The value of the internal energy for water steam (as a simple body) is calculated:
𝐮𝐧 = 𝐡𝐧 − 𝐏𝐧 ∗ 𝐕𝐧 (2.2)
where
• 𝐮𝐧 - internal energy of the process, kJ / kg
• 𝐡𝐧 - enthalpy of the process, kJ / kg
Point 1:
Set the input parameters of the working fluid at the inlet to the turbine P1= 9 MPa and t1= 430 ◦C to obtain the other parameters listed below:
P1= 3.1 MPa, t1= 440 C, V1= 0.102 m3/ kg, h1 = 3325 kJ / kg, s1 = 7.07 kJ / (kg * K), x = -.
u1 = h1− P1∗ V1 = 3325 - 3.1 * 103* 0.102 = 3008.8 kJ / kg Point 2.
The steam expansion process in the turbine is adiabatic. We set the values of s1 and P2 and get the values of the other parameters at point 2:
P2 = 0.098 MPa, t2= 45.84 C, V2= 15.1 m3/ kg,
h2 = 2232 kJ / kg, s1 = s2 = 7.07 kJ / (kg * K), x2 = 0.88,
u2 = h2− P2 ∗ V2 = 2232 - 0.098 * 103 * 15.1 = 752.2 kJ / kg
At the second point we have saturated saturated steam, with dryness at 0.88 Point 3.
The spent steam with the parameters of point 2 is completely condensed, therefore at point 3 we will have a condensate with temperature t3 = t2. All parameters are determined for boiling water.
P3 = P2 = 0.098 MPa, t3= 45.84 C, V3= 0.001 m3/ kg, h3 = 191.9 kJ / kg, s3 = 0.65 kJ / (kg * K), x = 0,
u3 = h3− P3 ∗ V3 = 191.9 - 0.098 * 103 * 0.001 = 191.8 kJ / kg
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Point 4.
After that, the water enters the pump. The pressure rises to the original value, P4= P1. The volume is preserved, i.e. V4= V3.
P4 = P1 = 3.1 MPa, t4 = 107.96 C, V4 = V3 = 0.001 m3/ kg, h4 = 195.1 kJ / kg, s4 = 0.65 kJ / (kg * K), x = -,
u4 = h4− P4 ∗ V4 = 195.1-3.1 * 103 * 0.001 = 192 kJ / kg Point 5.
After an isobar supply of heat, the water in the boiler boils, P5= P4 and the degree of dryness x = 0.
P5 = P4 = 3.1 MPa, t5 = 303.35 C, V5 = 0.00122 m3/ kg, h5 = 1015 kJ / kg, s5 = 2.66 kJ / (kg * K), x = 0,
u5 = h5− P5 ∗ V5 = 1015 - 3.1 * 103 * 0.00122 = 1011.23 kJ / kg Point 6.
Then it turns into dry saturated steam, boiling under isobaric process and with a degree of steam dryness = 1.
P6 = P5 = 3.1 MPa, t6th = 303.35C, V6 = 0.0666 m3/ kg, h6 = 2803.9 kJ / kg, s6 = 6.17 kJ / (kg * K), x = 1,
u6 = h6− P6 ∗ V6 = 2803.9 - 3.1 * 103 * 0,0666 = 2597.44 kJ / kg Calculation results are listed in Table 2.1.
Table 2.1 - Values of parameters and state functions at characteristic points of the Rankine cycle
Values of parameters and state functions at characteristic points of the Rankine cycle Point
No
Р,
MPa T, K t, C V, m3/
kg x u, kJ / kg
h, kJ / kg
s, kJ / (kg * K) 1 3.10 713.00 440.00 0.10 - 3 008.80 3 325.00 7.07 2 0.10 318.84 45.84 15.10 0.88 752.20 2 232.00 7.07 3 0.10 318.84 45.84 0.001 0 191.80 191.90 0.65 4 3.10 318.84 45.84 0.001 - 192.00 195.10 0.65 5 3.10 513.00 240.00 0.00122 0 1 011.23 1 015.00 2.66 6 3.10 513.00 240.00 0.066660 1 2 597.44 2 803.90 6.17 1 3.10 713.00 440.00 0.10 - 3 008.80 3 325.00 7.07
31
2.2 Determination of the state functions at characteristic points of the cycle The change in the state functions in each process of the cycle Δu, Δh, Δs is defined as the difference between the values of these functions in the final (j) and initial (i) process points.
ΔZi-j = Zi – Zj. [5] (2.3)
To determine the thermodynamic (l) and potential (w) work, heat transfer q in all the processes of the cycle, we use:
• in the adiabatic process (1-2):
o li−j = −Δui−j [kJ / kg]; (2.4)
o wi−j = −Δhi−j [kJ / kg]; (2.6)
o q = 0 [kJ / kg]; (2.7)
• in the isobar process (2-3, 4-5, 5-6, 6-1):
o li−j = Pi∗ (Vj− Vi) [kJ / kg]; (2.8)
o wi−j = 0 [kJ / kg]; (2.9)
o qi−j = Δhi−j [kJ / kg]; (2.10)
• in the isochoric process (3-4):
o li−j = 0 [kJ / kg]; (2.11)
o wi−j = −Vi ∗ (Pj− Pi) [kJ / kg]; (2.12)
o qi−j = Δui−j [kJ / kg]. (2.13)
Checking the results obtained from the first law of thermodynamics for each process and the cycle as a whole:
qi−j = li−j + Δui−j = wi−j + Δhi−j. (2.14)
The relative error in the calculations, the presence of which is due to rounding, is small, which is permissible for approximate thermodynamic calculations.
Calculation results are listed in Table 2.2.
Table 2.2 - Process status and function changes
32
Process status and function changes process Δu, kJ /
kg
Δh, kJ / kg
Δs, J / (kg
* K) l, kJ / kg w, kJ / kg q, kJ / kg
1-2 -2
256.60
-1
093.00 0.00 2256.60 1093.00 0
2-3 -560.40 -2
040.10 -6.42 -
1479.70 0 -2040.10
3-4 0 3.20 0 0 -3.20 0
4-5 819.23 819.90 2.01 0.67 0 819.90
5-6 1 586.21 1 788.90 3.51 202.69 0 1788.90
6-1 411.36 521 1 109.74 0 521.10
Sum by
column 0 0 0 1090 1090 1090
2.3 Determination of the specific operation of the cycle (lc) and thermal efficiency (ηtP)
When calculating the operation of a cycle, engineering calculations usually neglect the operation of the pump lн due to the fact that it is less than 1% of the turbine's operation lt. Therefore, the work of the cycle is equal to the work received in the turbine.
Due to the fact that the process of water steam expansion in the turbine is adiabatic, the operation of the steam power plant cycle is calculated by the formula:
lц = lт = h1− h2 [kJ / kg] (2.15)
lц = 3325 − 2232 = 1093 [kJ / kg]
Let us calculate the amount of heat supplied in the isobar process 4-5-6-1:
q1 = h1− h4 [kJ / kg] (2.16)
q1 = 3325 − 195 = 3130 [kJ / kg]
The degree of perfection of the heat conversion into mechanical work in the thermodynamic cycle of the engine is estimated by the thermal efficiency ηt
Thermal efficiency of the steam power plant:
ηt = lц
q1 (2.17)
ηt =1093
3130 = 0,349 or ≈ 35%
Determination of specific consumption of steam and heat
33
Determine the specific consumption of steam:
d = 3600
h1−h2 [kg / kJ] (2.18)
d = 3600
3325−2232 = 3600
1093 = 3,29 [kg / kWh]
Calculate the specific heat consumption:
q = q1∗ d = (h1− h4) ∗ d (2.19)
q = 3130 ∗ 3,29 = 10308,91 [kJ / kWh]
The calculation of steam and heat costs for a given power of 10.5 MW Calculate hourly heat consumption:
D = q ∗ N [kg / h] (2.20)
Q = 10297,7 ∗ 650 ∗ 103 = 6,69 ∗ 106 [kJ / h]
Annex B shows diagrams of the cycle processes in different coordinates.
34
CHAPTER 3. ORGANIC RANKINE CYCLE
3.1 Description of the Organic Rankine Cycle
For the utilization of low-potential thermal energy, we can use the organic Rankine cycle. In this cycle, the coolant is made up of alternative working bodies, which are usually organic substances with a lower boiling point than water. For the cycle, it is customary to use a class of compounds containing carbon, with the exception of carbides, carbonates, carbon oxides and cyanides. Such heat transfer helps make advantageous use of low-potential thermal energy, if the temperature does not exceed 500-570K (230-300C). [6]
Figure 3.1 - ORC principle of operation [19]
The figure shows the scheme of the principle of the action of the organic Rankine cycle (ORC). In the boiler (heat exchanger), the source of thermal energy heats the heat exchanger (2) and heats the chosen heat carrier through the means of heat exchange. The working body, which decomposes at 100% and is not toxic, begins to boil and expand, when heated to a certain temperature (depending on the composition of the selected working fluid), but below the boiling point of water.
The liquid passes into a gaseous state and under pressure transfers mechanical energy to the turbine (3) that generates electricity. At the turbine outlet, the liquid
35
condenses in the heat exchanger (4), where it gives off excess heat and returns to the liquid phase. Through the pipe (1), the coolant in the liquid state enters the pump, which increases the pressure and allows the heat carrier to return to the boiler.
A wide range of temperatures and pressures, depending on the working medium in the cycle, allows adapting the ORC to various sources of thermal energy.
3.2. Potential areas of application for ORC Solar power
Solar energy is a resource that is the main source of energy on our planet. At the moment, there is a growing popularity trend of solar energy concentration by using mirrors. The energy of solar rays refraction from the surface of mirrors is capable of providing heating and phase transition of the ORC working body.
ORC can be used for the desalination of sea water. In this case, the turbine drives the reverse osmosis plant, and solar energy provides the heating of the working fluid in the ORC [17].
Biofuel
The cost of fuel obtained from biomass is much lower than the cost of fossil fuels. Since biomass has a low density, its combustion generates thermal energy, which is then converted into thermal or electric power. This principle should be used at the site of biofuel production, for example at agricultural and some industrial enterprises [21].
The capacity of biomass combustion plants does not usually exceed 10 MW [23], and the electricity accounts for 10-20%. For such small capacities, the use of the traditional steam turbine Rankine cycle is technically and economically impractical [22].
Geothermal energy
36
Geothermal steam at geothermal stations can be used as a working fluid for a turbine, but most often the temperature of the water from the bowels is too low.
But the introduction of the ORC allows the use of underground water to generate electricity without additional heating. Figure 3.2 shows a diagram of an installation with an ORC using geothermal energy [20].
Figure 3.2 - Diagram of an installation with ORC using geothermal energy [20]
Ground water from the source is pumped into the heat exchanger-evaporator, where the heating and evaporation of the working fluid occurs. After that, the water is pumped back into the ground.
At the moment, there are several hydrothermal power plants that use the energy of low-enthalpy hydrothermal sources, in which the ORC is implemented.
Utilization of heat waste
In order to increase the overall efficiency and reduce the amount of unused energy in the energy sector, it is possible to use excess heat energy [21]. This can be the heat of exhaust gases or the heat released during coolant condensation after the turbine. The temperature of the exhaust gases varies depending on the purpose of the enterprise itself. Starting at 175 C, and at the gas turbine plant outlet usually exceeding 500C [6].
37
Only about 37% of the energy of the fuel is efficiently used in heat and power plants [6], and consequently 63% of this energy is released into the
environment through exhaust gas and cooling towers. This has a negative impact on the environment.
3.3 Selection of the working fluid for the organic Rankine cycle
When choosing a coolant for the organic Rankine cycle, various factors and criteria must be taken into account. At the moment it is difficult to determine exactly which qualities of the working fluid maximize the efficiency of the cycle, but there are common parameters that must be taken into account to ensure the safe and efficient operation of the thermodynamic cycle. [19]
Factors determining the composition of the working fluid.
Calculation of the operating temperature range at which the specific operation of the cycle will reach a maximum. Additionally, the substance should not freeze over throughout the entire operating temperature range.
The working body must:
• have a sufficiently low viscosity.
• cause no corrosion
• possess high thermal conductivity; this will help provide its effective heating and cooling in heat exchangers.
• be thermally stable at high temperatures.
• be inexpensive and easily procurable.
The working body should not be toxic or flammable, and should not cause pollution when emitted into the environment. These factors correspond to refrigeration agents or refrigerants. [6]
3.4 Refrigerants
38
A refrigerant has a low boiling point at atmospheric pressure, which means the phase transition from liquid to gaseous state occurs at low temperatures. In comparison with water at equal pressure, the coolant passes to the gaseous state at lower temperatures. The English letter "R" at the beginning of the symbol for refrigerant corresponds to the first letter in the word "Refrigerant".
The figures and letters after the letter "R" in the name of the refrigerant indicate the chemical composition. Similarly, refrigerants are classified according to the severity of the environmental impact. The considerations take into: ozone safety (ODP), low global warming potential (GWP), incombustibility and non-toxicity [7].
In general, from the rich variety of different types of refrigerants used in refrigeration plants, the most attractive options for the use in the ORC are: R134a, octamethyltrisiloxane, toluene, azeotropic solution and R245fa. These substances are used in existing commercial installations operated on the basis of ORC.
This paper uses the example of R245fa refrigerant. This refrigerant has a high enough level of global warming potential (GWP) and the high cost, but due to the high volume of production of the refrigerant and the availability of materials in the public domain, it was decided to use it for the present calculations. If necessary, it can be replaced with analogues.
3.5 R245fa
The American Society of Heating Engineers assigned this refrigerant a
"propane" number. The name is indicative of the composition of this refrigerant.
R245fa contains 3 carbon atoms, 3 hydrogen atoms, 5 fluorine atoms, and the suffix "a" or "fa" indicates growing unbalanced isomers. [7] Table 3.1. offers a brief description of the main parameters of R245fa refrigerant.
Table 3.1 - R245fa refrigerant is regulated by the Kyoto Protocol [8]
Type R-
number
Chemical formula /
common name Safety group Status
HFCs R-245fa ГФУ- B1 K
39
245fa/CHF2CH2CF3
The abbreviation "ГФУ" is used to refer to hydrofluorocarbons. Safety group B indicates the presence of toxicity at concentrations below 400 ppm. The number 1 means that at a standard temperature (20-21 ° C) and atmospheric pressure, the flame does not spread when it is released into the air. The letter "K" indicates that the refrigerant is regulated by the Kyoto Protocol. [8] Figure 3.3. shows a diagram of the pressure dependence on enthalpy.
Figure 3.3 - Ph diagram of refrigerant R245fa [9]
42
CHAPTER 4. USE OF EXCESS HEAT AT HPC ALATYR
The use of excess heat is an opportunity to increase the efficiency of the entire HPC. There are various technical and economic problems associated with the integration of additional equipment into the existing energy system, but solving these problems will increase the overall efficiency of HPC Alatyr.
4.1. Utilization of heat from exhaust gases
The flue gas temperature is not lower than 175 ° C, in order to prevent the formation of flue gases acidic dew point on thermal surfaces. The exhaust gases heat of HPC Alatyr can be used as fuel for heat exchange and heating of the working body of the organic Rankine cycle.
The main problem of using the exhaust gases heat is the collection of heat from the exhaust gases, and, consequently, the decrease in their temperature.
Reducing the temperature of the exhaust gas will cause the appearance of sulfur formations [31]. The appearance of sulfur and sulfur-containing substances has a number of negative consequences:
1. To prevent emissions containing sulfur compounds, it is necessary to increase the height of the exhaust pipes, which will lead to a number of costly changes, both in the design and in a number of further coordination procedures with the environmental authorities.
2. It is necessary to make changes in the design of the exhaust pipe in order to ensure the possibility of sulfur recovery, since it will accumulate on the pipe (chimney) walls or flow down under the force of gravity.
3. The design of the heat exchanger, which will collect the heat from the exhaust gases and return it to the refrigerant line, must
43
consist of strong materials that will not be affected by the negative effects of sulfur. Using these materials will significantly increase the design costs.
4.2 Use of excess heat from outgoing steam after the turbines
The second and most attractive option is the use of excess heat from the outgoing steam after the turbines.
A calculation of the amount of energy that is lost in this process is given below.
Input parameters of the Rankine organic cycle for HPC Alatyr 1.5 Working body: Water
m1= 13400 [kg / h] = 3.72 [kg / s]
where m1 - mass use of water, Turbine efficiency is 97.8%, h189= 2847.85 [kJ / kg]
where
h189 - enthalpy of steam at 189 [° C],
(The data were obtained with the help of the program for calculating the thermophysical properties of water and water steam. Figure 4.1.
44
Figure 4.1 - Steam enthalpy at 189 ° C.
h95 = 398 [kJ / kg]
where
h95 - steam enthalpy at 95 [° C],
at a pressure of P = 0.15 [MPa] = 1.5 [bar],
(The data were obtained with the help of the program for calculating the thermophysical properties of water and water steam. Figure 4.2.
Figure 4.2. - Enthalpy of water at 95 ° C.
Qsteam = (h189- h95) * m1(4.1)
where
Qsteam - input heat to the ORC
Qsteam= 0.978 * 3.72(2847.85-398) = 8920 [kJ / s]
The conversion factor kJ / s in kW is 3600; therefore, per hour the plant produces 8920 kW of energy, which is utilized by means of dry cooling towers.
Utilization of waste steam is most attractive to consider in periods of maximum load of dry cooling towers, since the energy spent on the use of cooling towers can be reduced. For the sake of clarity of calculation I used the ambient temperature equal to the approximate maximum temperature of the summer period throughout Russia.
Figure 4.3 shows the condensation scheme of the exhaust steam. Steam temperature reaches 189° C by means of heat exchangers and gives warmth to the line with ethylene glycol in such a way that ethylene glycol is supplied to a dry
45
cooling tower at 110° C. After cooling, the ethylene glycol is back in the heat exchanger at a temperature of 80° C. Thus after the turbine the steam condenses, and at the condenser outlet the boiler gets water at a temperature of 95° C.
Figure 4.3 - Scheme of exhaust steam condensation
Having examined the drawings, I was decided to use ethylene glycol as a source of thermal energy, since the temperature of the steam after the turbine (189)
C) exceeds the critical temperature of the refrigerant
Figure 4.4 - Application of ORC to the condensation of the exhaust steam In Figure 4.4, it can be seen that the mass flow on the ethylene glycol line can be regulated by a valve before the ORC boiler inlet. This makes it possible to regulate the amount of heat supplied to the ORC, as well as the temperature of ethylene glycol at the ORC outlet. The temperature of ethylene glycol at the exit from the cooling tower is 80 C. Actuating the ORC permits to lower this temperature. Similarly, the heat given off by ethylene glycol into cycle can vary depending on the number of cooling towers.
46
It was decided to reduce the refrigerant flow temperature at the inlet to 105
C, as there would be a loss of temperature on heat transfer and heating up to a temperature of 110 C, taking into account that the heating agent (ethylene glycol from the condenser) is also at 110 C. Since the ORC is planned to be used in the summer period (at the outside air temperature of +40 C), and heat release by means of a dry cooling tower (with the condensation of the agent). Coolant temperature before heating + 40 C
It is possible to consider the different modes of connecting ORC to the cooling towers:
1. The use of𝟏
𝟑 heat diverted to the heat recovery system.
Qethylene glycol = 𝟏
𝟑 Qsteam (4.2)
where
Qethylene glycol - heat removed to the line of ethylene glycol [kJ / s], Qcond= 8920 kW Qethylene glycol = 2973.3 kW
Working body: R245fa T1 = 105 C
where
T1 - boiling point at pressure P1= 1.41 [MPa], T0 = 40 C
where T0 - temperature of the refrigerant before the start of heating, mR245fa= Qethylene glycol / h1-h0 (4.3)
where
mR245fa - mass use of refrigerant, h1= 477.09 kJ / kg
where
h1 - refrigerant enthalpy at the turbine inlet, h0= 252.57 kJ / kg
where
h1 - refrigerant enthalpy at the turbine outlet,
47
mR245fa = 2973.3 / (477.09 -252.57) = 13.92 kg / s
2. The use of𝟏
𝟐 heat diverted to the heat recovery system.
Qethylene glycol= 𝟏
𝟐 Qcond
Qcond= 8920 kW Qethylene glycol= 4460 kW Working body: R245fa
T1=105 C
where T1 - temperature of the refrigerant at P1= 1.41 MPa, Т0=40 C
where T0 - temperature of the refrigerant before the start of heating, mR245fa= Qethylene glycol / h1-h0
where
mR245fa - mass use of refrigerant, h1= 477.09 kJ / kg
where
h1 - refrigerant enthalpy at the turbine inlet, h0= 252.57 kJ / kg
where
h1 - refrigerant enthalpy at the turbine outlet, mR245fa = 4460 / (477.09 - 252.57) = 20.8 kg / s.
The mass flow for calculating the turbine for ORC is taken as 20.8 kg / s using half the heat energy of the exhaust steam. HPC Alatyr 1-5 uses two turbo generators with 650 kW each, but useful electricity generated is only 1 mW, which means that 300 kW got to serve own needs, and 200 kW of them are spent on powering the dry coolers. Reducing the number of cooling towers by 50% will increase the amount of useful generated electricity by 100 kW. Using the maximum number of cooling towers starts from 10 C ambient air temperature.
49
CHAPTER 5. ORGANIC RENQUIN CYCLE CALCULATION
5.1 Determination of parameters and functions of the state at characteristic points of the cycle
Determination of thermodynamic parameters of the state at characteristic points of the cycle
Determination of thermodynamic processes:
• process 1-2 - adiabatic (q = 0);
• process 2-3 - isobaric (P - const);
• process 3-4 - isochoric (V - const);
• process 4-1 - isobaric (P - const);
Pressure (P [MPa]), temperature (t [C]), enthalpy (h [kJ / kg]), setting the mode and the input parameters [23]. The value of the volume (V [m3/ kg]) can be obtained both from the program and by calculation using the formula:𝐕𝐧 = 𝐑∗𝐓𝐧
𝐏𝐧
(5.1)
where
• 𝐕𝐧 - density, m3/ kg
• R- universal gas constant, m3/ kg
• 𝐏𝐧 - process pressure, MPa
• 𝐓𝐧 - temperature, C
The value of the internal energy for water steam (as a simple body) is calculated:
𝐮𝐧 = 𝐡𝐧 − 𝐏𝐧 ∗ 𝐕𝐧: (5.2)
where
• 𝐮𝐧 - internal energy of the process, kJ / kg
• 𝐡𝐧 - enthalpy of the process, kJ / kg
50
The temperature at the turbine outlet was calculated by the power equipment specialists of OOO InnoTechMash. After processing the information, the temperature at the turbine outlet was determined to be 58.6 C. The figure shows the h-s diagram of R245fa refrigerant in this ORC.
Figure 5.1. - h-s diagram for R245fa refrigerant
To determine the parameters at each point, we can use the p-h diagram for the refrigerant steam and thermodynamic properties tables.
51
Figure 5.2 - p-h diagram of refrigerant R245fa [9]
Point 1:
Set the input parameters of the working fluid at the inlet to the turbine P1= 1.41 MPa and t1= 105◦C to obtain the other parameters listed below:
P1= 1.41 MPa, t1= 105 C, V1= 0.0122 m3/ kg, h1= 477.09 kJ / kg
𝐮𝟏 = 𝐡𝟏− 𝐏𝟏 ∗ 𝐕𝟏 = 477.09 - 1.14 * 103 * 0.0122 = 459.96 kJ / kg Point 2.
The steam expansion process in the turbine is adiabatic. The values of the other parameters at point 2:
P2 = 0.25 MPa, t2= 58 C, V2= 0.04122 m3/ kg, h2 = 446.62 kJ / kg,
𝐮𝟐 = 𝐡𝟐− 𝐏𝟐 ∗ 𝐕𝟐 = 446.62 - 0.25 * 103 * 0.04122 = 436.31 kJ / kg Point 3.
The spent steam with the parameters of point 2 is completely condensed and cooled. Therefore at point 3 we will have a condensate with temperature t3 = 26◦C.
P3 = P2 = 0.25 MPa, t3= 40 C, V3= 0.0708 m3/ kg, h3 = 255.57 kJ / kg,
52
𝐮𝟑 = 𝐡𝟑− 𝐏𝟑 ∗ 𝐕𝟑 = 255.57 - 0.25 * 103 * 0.0708 = 237.87 kJ / kg Point 4.
After that, R245fa enters the pump. The pressure rises to the original value, P4= P1. The volume is preserved, i.e. V4= V3.
P4 = P1 = 1.41 MPa, t4 = 40C, V4 = V3 = 0.0708 m3/ kg, h4 = 255.57 kJ / kg,
𝐮𝟒 = 𝐡𝟒− 𝐏𝟒 ∗ 𝐕𝟒 = 255.57 - 1.41 * 103 * 0.0708 = 155.74 kJ / kg Calculation results are listed in Table 5.1.
Table 5.1. - Values of parameters and state functions at characteristic points of the organic Rankine cycle
Values of parameters and state functions at characteristic points of the Rankine cycle
Point No Р, MPa T, K t, ◦С V, m3/
kg u, kJ / kg h, kJ / kg 1 1.41 378.00 105.00 0.0122 459.96 477.09
2 0.25 331.00 58.00 0.0587 436.31 446.62
3 0.25 313.00 40.00 0.0708 237.87 255.57
4 1.41 313.00 40.00 0.0708 155.74 255.57
5.2 Determination of the specific operation of the cycle (lc) and thermal efficiency (ηtP)
When calculating the operation of a cycle, engineering calculations usually neglect the operation of the pump lн due to the fact that it is less than 1% of the turbine's operation lt. Therefore, the work of the cycle is equal to the work received in the turbine [24].
Due to the fact that the process of refrigerant steam expansion in the turbine is adiabatic, the operation of the steam power plant cycle is calculated by the formula (5.3):
𝐥ц = 𝐡𝟏 − 𝐡𝟐 [kJ / kg] (5.3)
𝐥ц = 𝟒𝟕𝟕, 𝟎𝟗 − 𝟒𝟒𝟔, 𝟔𝟐 = 𝟑𝟎, 𝟒𝟕 [kJ / kg]
53
Below is a calculation of the heat amount in the isobaric process 𝐪𝟏 = 𝐡𝟏 − 𝐡𝟒 [kJ / kg] (5.4)
𝐪𝟏 = 𝟒𝟕𝟕, 𝟕𝟖 − 𝟐𝟓𝟓, 𝟓𝟕 = 221,52[kJ / kg]
The degree of perfection of the heat conversion into mechanical work in the thermodynamic cycle of the engine is estimated by the thermal efficiency ηt [25]
Thermal efficiency of the steam power plant:
ηt = lц
q1 (5.5)
ηt = 30,47
221,52 = 0,137 or ≈ 14%
