1 Scope
This document specifies the system components and parameters of the heat exchange system for solar thermal power plants, the environmental conditions for normal use. Technical requirements and test and inspection etc.
This document applies to heat exchange systems for water/steam, molten salt and heat transfer oil media.
2 Normative references
The contents of the following documents constitute the essential provisions of this document through the normative references in the text. Among them, note the date of the reference document, only the date of the corresponding version applies to this document; not note the date of the reference document, its latest version (including all the revision of the list) applies to this document.
GB/T 150 Pressure vessels
GB/T 151 Heat exchangers
GB/T 5657 Technical conditions for centrifugal pumps (Class III)
GB/T 12145 Quality of water vapour for thermal power generating units and steam power equipment
GB 12158 General guidelines for the prevention of electrostatic accidents
GB/T 17116(all parts)Pipeline support hanger
GB/T 19518(all parts) Resistance heat tracers for explosive environments
GB/T 20801 (all parts) Code for pressure piping Industrial piping
3 Terminology and definitions
The following terms and definitions apply to this document.
3.1
Heat exchange systemheat exchange system
Consists of a series of equipment for heat exchange between the heat transfer medium and the workpiece or heat storage medium and its ancillary components.
Note: Mainly includes steam generation systems and oil and salt heat exchange systems.
3.2
Oil-salt heat exchanger
A device for heat exchange between a molten salt medium and a heat-conducting oil medium.
3.3
Preheater preheater
A device for pre-heating the feed water with a heat transfer medium in order to increase the temperature of the feed water.
3.4
Evaporator
Heat transfer medium with water heat exchange to produce high-pressure saturated steam device.
3.5
Superheater superheater
A device for heating saturated steam with a heat transfer medium to produce superheated steam.
3.6
Reheater reheater
Heat transfer medium to heat the turbine high pressure cylinder exhaust steam to produce high temperature reheat steam device.
3.7
Heat transfer oilthermal oil
A type of special heat carrier used for indirect heat transfer and good thermal stability.
Note: Divided into mineral oil type and synthetic organic heat carrier, including phenyl aromatic type synthetic heat transfer oil and siloxane type heat transfer oil, etc.
3.8
System thermal efficiency
The ratio between the output thermal power of the heat exchange system and the input thermal power.
3.9
Steam generation system
A system that uses molten salt or heat transfer oil to heat feed water to produce steam for turbine operation.
3.10
oil-salt heat exchanger system
A system that uses molten salt media to exchange heat with heat-conducting oil media.
4 System components and parameters
4.1 System components
The heat exchange system of the solar thermal power station is mainly composed of the following systems: steam generation system, oil-salt heat exchanger system.
According to the different heat transfer media, steam generation system can be divided into molten salt steam generation system and heat transfer oil steam generation system. In the heat exchange system, the definition of the range of each medium side is as follows:
4.2 basic parameters
4.2.1 The basic parameters of the design input mainly include the following:
a) operating parameters, including flow, temperature. pressure. Heat load, etc;
b) physical parameters, including media components, density, specific heat capacity or baking value, partial pressure of steam, viscosity, thermal conductivity, etc.;
c) allowable pressure drop;
d) system operation, including the number of starts and stops and the frequency of load changes under various operating conditions in power stations, etc;
e) other.
4.2.2 System and equipment life should not be less than 25 years.
4.2.3 The design pressure of the system shall not be lower than the highest possible operating pressure during operation.
4.2.4 The design temperature of the system is not lower than the maximum operating temperature that may be reached during operation.
4.2.5 The number of starts and stops of the solar thermal power generation heat exchanger system may be as follows, the specific number shall be determined in accordance with the operating characteristics of the power station:
a) Cold start (stopping for more than 72 h) 10 times/year (24 times/year during the commissioning period);
b) Warm start (shutdown between 10 h and 72 h) 250 times/year (320 times/year during the commissioning period);
c) Hot start (downtime between 1 h and 10 h) 300 times/year (commissioning period 400 times/year);
d) Very hot start (unit shutdown within 1 h) 50 times/year (100 times/year during the commissioning period);
e) load step (load change value ≥10% of nameplate power per minute) 15,750 times/25 years.
4.2.6 The temperature rise rate of the solar thermal power generation heat exchange system should meet the operating requirements of the power station. On the premise of ensuring the safety of the operation of the system and equipment, the temperature rise rate of the heat exchange system of the tower-type solar thermal power generation station should be no less than 6 ℃/min, and the temperature rise rate of the heat exchange system of the trough-type solar thermal power generation station should be no less than 8 ℃ / min.
5 Normal use of environmental conditions
5.1 Ambient temperature: -50 ℃ ~ 60 ℃.
5.2 Ambient humidity should not be higher than 95%.
5.3 The maximum wind speed should not be higher than 30 m/s.
6 Technical requirements
6.1 General requirements
6.1.1 The rated evaporation capacity of the steam generation system should be matched with the rated working condition of the turbine, and the maximum continuous evaporation capacity should be matched with the fully open working condition of the turbine valve, while the variable working condition characteristics of the system should be considered.
6.1.2 The rated working condition of the oil salt heat exchange system should be matched with the rated working condition of the turbine.
6.1.3 The thermal efficiency of the system under the design conditions of the heat exchange system shall be not less than 98%.
6.1.4 The main steam temperature of the steam generation system shall meet the requirements of the rated working condition of the turbine.
6.1.5 The total pressure drop of the heat exchange system under the rated working condition of the turbine shall meet the requirements of Table 1.
6.1.6 The heat exchange system shall meet the requirements for daily start-up and shutdown of the power station, and consider the impact of the resulting temperature difference stress on the system and equipment.
6.1.7 Equipment should take measures to prevent fatigue damage caused by frequent alternating thermal stresses.
6.1.8 The system should be hydrostatically tested and comply with GB/T 20801 (all parts) or GB 50764.
6.1.9 The system shall be provided with a complete evacuation system.
6.1.10 The materials used in the system and equipment should have corrosion resistance.
6.2 Steam generation system
6.2.1 Vapour side
6.2.1.1 The steam quality should be in accordance with the provisions of GB/T 12145.
6.2.1.2 The evaporator equipment should be in the form of steam ladle or kettle type structure.
6.2.1.3 Evaporation system can be divided into natural circulation and forced circulation. When using natural circulation, the design working condition circulation multiplier should be 4 ~ ~ 10.
6.2.1.4 The capacity of the heat exchanger on the steam side should be optimally allocated according to the operating conditions.
6.2.1.5: Preheater outlet water temperature should be at least below its saturation temperature minus 1.5 ℃.
6.2.1.6 The feed water temperature into the vapour system should not be lower than the melt precipitation temperature plus 10 °C.
6.2.1.7 The technical requirements of the steam package should be in accordance with the provisions of TSG G0001 and GB/T 150.
6.2.1.8 The water storage capacity of the ladle under rated working conditions should be not less than 3 min.
6.2.1.9 The steam ladle should have good steam-water separation capability, and the dryness of the separated saturated steam should be not less than 98% under the design working condition. 6.2.1.10 The steam ladle should be able to withstand the load changes in the system operation.
6.2.1.11 steam package should have the ability to withstand heat shock.
6.2.1.12 The system design shall take into account the cyclic stability under start-up and low load conditions.
6.2.1.13 Piping and equipment shall be provided with reasonable drainage and venting systems.
6.2.2 Molten salt side
6.2.2.1 The molten salt shall comply with the provisions of GB/T 36376.
6.2.2.2 The design of molten salt equipment and piping should be designed with a certain inclination angle for self-flow evacuation.
6.2.2.3 - When designing the system, a certain height difference should be set between the molten salt heat exchangers.
6.2.2.4 ﹑ Under all operating conditions, the final salt return temperature in the system should not be lower than the molten salt precipitation temperature plus 15°C.
6.2.2.5 The sealing gasket on the molten salt side should not be made of graphite.
6.2.2.6 The design of the system should take into account the drainage and exhaust of the piping and equipment.
6.2.2.7 The system shall be designed with a complete salt evacuation system.
6.2.3 Heat-conducting oil side
6.2.3.1 The heat-conducting oil should comply with the provisions of GB 23971.
6.2.3.2 The final return oil temperature in the system should not be lower than the crystallisation point temperature of the heat transfer oil plus 50°C.
7 Testing content
The main test contents of the heat exchange system are as follows:
a) Evaporation volume;
b) Thermal efficiency;
c) flow rate, inlet and outlet temperature and pressure drop of the steam and water system
d) Heat transfer oil and molten salt system flow rate, import and export temperature, pressure drop
e) steam quality.
8 Technical documentation and drawings
The following technical documents and drawings should be included as a minimum:
a) management information documents
b) Quality documentation;
c) Installation, operation. maintenance. drawings and technical documentation required for inspection;
d) Design, installation, operation, maintenance and overhaul instructions;
e) other relevant technical documents.
Foreword
1 Scope
2 Normative references
3 Terminology and definitions
4 System components and parameters
4.2 basic parameters
5 Normal use of environmental conditions
6 Technical requirements
7 Testing content
8 Technical documentation and drawings
