Exchange Rate Temodynamics - GTU Calculation

Contents

Contents

Introduction

1. "Heat engine" subsystem

1.1Describing System Description

1.2 Calculation of compressor air compression process

1.3 Calculation of fuel compression process in "booster" compressor

1.4 Calculation of combustion chamber

1.5 Calculation of process of expansion of working medium in gas turbine (GT)

1.6 Calculation of GTU energy characteristics

1.7 Mode change: 90%, 80%, 70%, 60%, 50% of nominal fuel consumption

2 Subsystem "Heat Exchange Group"

2.1 Subsystem Description

2.2 Calculation of flue gas energy utilization processes: generation of superheated steam and heating of network water

2.2.1 Parameters of characteristic points

2.2.2 Calculation of media flow rates and heat of flue gas cooling, steam generation, CB heating

2.2.3 Energy balance of heat exchange group

2.2.4 Heat balance of heat exchange group

3 Utility subsystem

3.1 Subsystem Description

3.2 Calculation of purge expansion process

3.3 Calculation of heating process of mains water makeup

3.4 Calculation of feed water heating process in deaerator

4. Exergetic balance

4.1 Exergetic balance of "booster" compressor (DC)

4.2 Gas Turbine Unit (GTU) Exergetic Balance

4.3 Electric Generator (EG) Exergetic Balance

4.4 Recovery Boiler (CU) Exergetic Balance

4.5 Exergetic Balance of Blowdown Separator-Expander (C)

4.7 Exergetic balance of feedwater deaerator

List of literature used

Introduction

Currently, in the generation of electricity, technologies are widely used in which the thermal energy of the fuel to be accumulated is converted into the mechanical energy of the generator drive, and then the mechanical energy is converted into electric (steam and gas turbines, piston engines). The main disadvantage of these technologies is that electric energy is converted from 2040% of the thermal energy of the fuel combustion reaction, the rest of the energy is carried away by the working medium of the unit (exhaust steam of a steam turbine, exhaust flue gases of a gas turbine plant, etc.). To improve the quality of use of fuel combustion heat, combined production of thermal and electrical energy is used - cogeneration. The essence of cogeneration is as follows. The energy carried out from the unit by the spent working medium is used to meet the needs of the heat consumer, i.e., it is used to obtain hot water and steam. Gas turbines have a significant advantage because the energy carried from the gas turbine by the flue gases has a high temperature potential, which allows it to be used in a wide range, allowing the generation of superheated steam of high parameters and further heating the network water without reducing electric power. In steam turbines, this is possible with the organization of steam extraction of high parameters, which significantly affects power generation. In piston units, a significant part of the energy is carried away in the form of low-potential energy of cooling water, which significantly reduces the scope of their use in combined production.

"Heat engine" subsystem

1.1A description of the system under investigation.

It consists of a "booster" compressor and a gas turbine plant (GTU).

Gas turbine plant consists in its turn of air compressor, combustion chamber, gas turbine and electric generator.

"Booster" compressor (DC) is a device designed to raise the pressure of fuel gas from the gas pipeline to the working pressure in the combustion chamber of the gas turbine plant.

Gas turbine plant is a device designed to convert chemical energy of fuel (natural gas) into electric energy.

The principle of GTU operation is as follows. Fuel after compression in the "booster" compressor and air after compression in the air compressor are supplied to the combustion chamber, where the oxidation (combustion) reaction of natural gas occurs. The flue gases generated as a result of the reaction enter the gas turbine, where, expanding from the pressure in the combustion chamber to the pressure on the turbine exhaust, the rotor rotates. Thereby, part of the energy of the flue gases is converted into the mechanical energy of rotation of the rotor. Mechanical energy is mostly used to drive the air compressor, the rest goes to the electric generator drive.

In the thermodynamic diagram, the GTU cycle is shown in Fig. 1.1.2.

1-2- process of adiabatic compression of working medium in compressor;

1-2-process of irreversible compression of working medium in compressor;

2-3 (2d3) -process of isobaric heat supply to working medium;

3-4-process of adiabatic expansion of working medium in gas turbine;

3-4-process of irreversible expansion of working medium in gas turbine;

4-1-process of heat removal from working medium.

Calculation of GTU characteristics at change of mode: 80%, 70%, 60%, 50% of nominal fuel consumption is given in Table 1.7.2.2.

Subsystem "Heat Exchange Group"

2.1 Subsystem description.

As a result of expansion in the gas turbine, most of the chemical energy of the fuel is carried away by smoke gases. For further use of this energy, flue gases are cooled in units of the heat exchange group. The heat of the cooling process is used to obtain superheated steam and heat the network water.

The flue gases immediately enter the recovery boiler (FP), which consists of the following heat exchange surfaces along the flue gases:

superheater, evaporation surface, economizer and network heater.

Changes of flow temperatures (flue gases, water and steam) in heat exchange surfaces are shown in Fig.2.1.1.

We determine the specific isobaric heat capacity of flue gases before the KU economizer taking into account the temperature according to the formula (1.3.4). The calculation is summarized in Table 2.2.1.1.

The approximate temperature of flue gases downstream the recovery boiler is taken equal to saturation temperature in the boiler drum ().

We determine specific isobaric heat capacity of flue gases downstream the recovery boiler taking into account temperature by formula (3.4). The calculation is summarized in Table 2.2.2.1.

load.

We determine the specific isobaric heat capacity of flue gases downstream the recovery boiler taking into account the temperature according to the formula (1.3.4). The calculation is summarized in Table 2.2.2.2.

We determine the specific isobaric heat capacity of flue gases after the network water heater taking into account the temperature according to the formula (3.4). The calculation is summarized in Table 2.2.2.3.

Utility Subsystem

3.1 Subsystem description.

The engineering subsystem is designed to ensure proper operation of the heat exchange group. It consists of a separator expander, feed water deaerators and by-feed water of heat networks.

During operation of the boiler, salts accumulate in the drum. To remove them, drum is purged, lower layer of drum water is partially drained. A separator-expander is used to partially recover the energy carried away with the purge water. In it, the pressure of the drum water is reduced to the pressure of the separator, and part of the water boils. Formed steam is fed into feed water deaerator, and remaining water is drained into drain.

To compensate for losses of network water in heat networks, chemically purified water is used. Removal of gases from make-up water and its heating is performed by saturated steam of boiler in deaerator of network water.

To compensate for losses of feed water with blowing, condensate losses at the consumer, chemically purified water is also used. Gases are removed from make-up water and heated by saturated steam of boiler in feed water deaerator.

The approximate flue gas temperature behind the recovery boiler economizer is assumed (approximation).

We determine the specific isobaric heat capacity of flue gases downstream the recovery boiler taking into account the temperature according to the formula (1.3.4). The calculation is summarized in Table 3.3.2.

4. Exergetic balance.

Exergy is a property of a thermodynamic system or energy flow determined by the amount of work that can be obtained by an external energy receiver during their reversible interaction with the environment until full equilibrium is established.

If there is a complete equilibrium between the system (energy flow) and the environment, then this state is called zero, and the state is characterized by zero exergy.

Due to the presence or absence of a material carrier, excersion is divided into two types:

excersion of substance flow;

energy flow exergy;

The exergy of the substance flow consists of three components: mechanical, thermal, chemical.

For ease of calculation, we combine mechanical and thermal components.

Internal losses are determined by irreversibility of processes occurring in the unit. D=E’E’’. [1]

List of literature used

1.B.M. Khrustalev, A.P. Nesenchuk, V.N. Romanyuk "Technical thermodynamics," t.1. UP "Technoprint," Minsk 2004.

2. B.M. Khrustalev, A.P. Nesenchuk, V.N. Romanyuk "Technical thermodynamics," vol. 2. UP "Technoprint," Minsk 2004.

3.M.P. Vulkalovich, S.L. Rivkin, A.A. Alexandrov "Tables of heat and physical properties of water and water vapor." Standards Publishing House, Moscow, 1969

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