Analysis And Application Of High And Low Temperature Technology For Steam Generator

1, Core definition and thermodynamic basis of high and low temperature parameters

The high and low temperature division of steam generators is not an absolute value, but an industry consensus formed based on thermodynamic principles and engineering practice. Its core basis is the Carnot cycle theory - the highest efficiency of a heat engine is determined by the temperature difference between the heat source and the cold source. The larger the temperature difference, the higher the efficiency of converting thermal energy into electrical energy.

(1) Definition and Characteristics of High Temperature Parameters

In the industrial field, the main steam temperature of high-temperature steam generators is usually defined as 500 ℃ or above, and the supporting pressure is mostly in the range of 10MPa-30MPa. Some ultra supercritical units can even reach above 600 ℃ or 25MPa. The core goal of this parameter range is to maximize the temperature difference and promote thermal efficiency to exceed 40%, or even reach over 45%. The implementation of high-temperature parameters relies on the combustion of high-grade energy sources (such as coal and natural gas) or nuclear reactions. Water is heated to high-temperature and high-pressure steam through boilers or reactors, and then driven to rotate at high speed to generate electricity.

(2) Definition and Characteristics of Low Temperature Parameters

The main steam temperature of low-temperature steam generators is usually below 300 ℃, and some waste heat recovery systems can even lower it to 80 ℃ -250 ℃, with pressures often below 2.5MPa. The core logic of such systems is not to pursue ultimate efficiency, but to use low-grade thermal energy (such as industrial waste heat, solar energy, geothermal energy) to achieve "turning waste into treasure". Although their thermal efficiency is generally between 10% -25%, they can convert the originally wasted heat into electrical energy, which has both energy-saving and environmental value. The implementation of low-temperature parameters does not rely on high-intensity energy consumption, but rather adapts to the temperature characteristics of low-grade heat sources through special working fluids or circulation technologies.

2, Differences in Technical Paths of High and Low Temperature Steam Generators

The difference in temperature parameters directly leads to significant differences in the core components, cycle modes, and system design of steam generators, forming two completely different technical paths.

(1) High temperature steam generator: technological pursuit of ultimate efficiency

High temperature steam generators, represented by traditional thermal and nuclear power plants, have the technical core of "high temperature resistance and high pressure resistance", and achieve efficient power generation through material upgrades and system optimization. On the core components, key equipment such as turbine blades and boiler pipelines need to use special materials such as nickel based alloys and heat-resistant steel to resist oxidation, corrosion, and fatigue in high temperature and high pressure environments; In terms of circulation, the Rankine cycle is commonly used, which generates high-temperature and high-pressure steam through a boiler. After the steam turbine does work, the exhaust steam is cooled into water by a condenser, and then pressurized by a feed pump and sent back to the boiler to form a closed cycle; In system design, complex temperature control and pressure reduction devices are required to ensure stable steam parameters and avoid equipment damage due to temperature fluctuations.

3, Panoramic application scenarios of high and low temperature steam generators

The characteristics of temperature parameters determine that the application scenarios of two types of steam generators have clear boundaries, covering two major fields: large-scale centralized power supply and distributed waste heat recovery.

(1) High temperature steam generator: the main force for large-scale centralized power supply

High temperature steam generators, with their advantages of high power and efficiency, have become the core choice for large-scale centralized power supply. In terms of application scenarios, large thermal power plants are mainly distributed in coal rich areas or load centers, meeting the electricity needs of regional industrial production and residential life through thermal power generation, with a single unit capacity of up to one million kilowatts; Nuclear power plants rely on the high energy density of nuclear fuel and are located in areas with high energy demand and environmental requirements, providing stable base load electricity for the region and approaching zero carbon emissions.

In addition, high-temperature steam generators are also suitable for large industrial self owned power plants, such as large enterprises in the steel, chemical and other industries. They generate electricity by burning self-produced fuels or utilizing process waste heat (high-temperature section) to meet their own production electricity needs and reduce dependence on external power purchases.

4, Industry Development Trend: Collaborative Evolution of High and Low Temperature Paths

Driven by the energy transition and the "dual carbon" goal, high-temperature and low-temperature steam generators are not mutually substitutable, but are showing a coordinated development trend of "high-end upgrading and low-end expansion".

(1) High temperature pathway: upgrading towards ultra supercritical and clean processes

High temperature steam generators will continue to develop towards ultra supercritical and near zero emissions. On the one hand, through breakthroughs in material technology, the main steam temperature and pressure can be further increased, promoting continuous improvement in thermal efficiency and reducing energy consumption and carbon emissions per unit of electricity generation; On the other hand, by combining carbon capture, utilization, and storage (CCUS) technology, near zero emissions from thermal power can be achieved, enabling it to still play a stabilizing role in the base load electricity in the energy structure with an increasing proportion of new energy.

(2) Low temperature pathway: expanding towards scale and high adaptability

Low temperature steam generators will usher in a dual opportunity of large-scale application and technological upgrading. In terms of application scale, with the tightening of industrial energy-saving policies and the increasing awareness of waste heat recovery, ORC low-temperature generators will be popularized in more industries, forming a large-scale waste heat power generation market; In terms of technological upgrading, we will focus on the research and development of new and efficient working fluids, the improvement of heat exchange efficiency, and the intelligent control of systems, reducing the cost of low-temperature waste heat power generation, improving the adaptability to waste heat resources of different temperatures and scales, and expanding the utilization boundary of ultra-low temperature waste heat (60 ℃ -80 ℃).