Ductile Iron Pipe Fittings: A Pillar in Thermal Power Generation

Abstract

Thermal power generation, as a core pillar of China's power supply, requires high reliability of pipeline components due to the high-temperature, high-pressure, and highly corrosive working conditions during production. Cast iron pipe fittings, after being optimized through customized technology, have become indispensable core pipeline components in thermal power generation due to their advantages of high-temperature resistance, corrosion and wear resistance, pressure stability, and ease of operation and maintenance. They are deeply integrated into all key links of thermal power generation, precisely meeting the working conditions from the boiler system to auxiliary equipment, ensuring the continuous and stable operation of the units, reducing operation and maintenance costs.

Table of content

1. Boiler System: Core Bearing and Adaptation
2. Desulfurization and Denitrification: Anti-corrosion Breakthroughs Provide Support
3. Circulating Water System: Efficient and Stable Empowerment
4. Auxiliary Equipment Matching: Convenient Operation and Maintenance Support
5. Summary

1. Boiler System: Core Bearing and Adaptation

The boiler is the core equipment in thermal power generation. Cast iron pipe fittings play a crucial role in transporting high-temperature media and bearing pressure. For the working conditions of boiler feedwater and steam transportation, thick-walled alloy ductile iron pipe fittings are adopted. The spheroidization process and matrix composition are optimized, and nickel and chromium alloy elements are added. The tensile strength is increased to over 500 MPa, capable of withstanding temperatures up to 150°C and pressures up to 3.0 MPa. This effectively resists the erosion of high-temperature steam and water quality. In the lower header pipeline of the boiler, the flexible joint design can adapt to the thermal expansion and contraction during boiler start-up and shutdown, preventing pipeline cracking. At the same time, the smooth inner wall reduces scaling and enhances heat exchange efficiency. In a large-scale thermal power plant's boiler renovation project, the usage rate of this type of pipe fitting reached 85%, ensuring continuous boiler operation without faults and extending the maintenance cycle of the unit.

2. Desulfurization and Denitrification: Anti-corrosion Breakthroughs Provide Support

The desulfurization and denitrification system is crucial for achieving environmental compliance in thermal power plants. Cast iron pipe fittings precisely address the strong corrosion issues in this process. During desulfurization, the acidic wastewater (pH 3-5) produced by the condensation of flue gas is highly corrosive to pipelines. Traditional carbon steel pipe fittings have a lifespan of less than five years, while cast iron pipe fittings treated with graphene composite anti-corrosion can withstand acid corrosion for over 8,000 hours and have a lifespan of more than 30 years. In the ammonia injection pipelines for denitrification, customized cast iron pipe fittings offer excellent sealing and impact resistance, ensuring stable ammonia gas transportation and preventing leakage that could affect denitrification efficiency. They also adapt well to the low-temperature conditions of the denitrification system without the risk of brittle fracture. Currently, cast iron pipe fittings have comprehensively replaced traditional ones in the desulfurization and denitrification systems of most domestic thermal power plants, significantly reducing environmental operation and maintenance costs.

3. Circulating Water System: Efficient and Stable Empowerment

The circulating water system is crucial for cooling down and ensuring the continuous operation of thermal power units. Cast iron pipe fittings, with their outstanding performance, achieve efficient compatibility. In response to the characteristics of circulating water, such as containing impurities, being prone to scaling, and having strong corrosiveness, cast iron pipe fittings adopt a dual composite anti-corrosion process of "zinc-aluminum coating + epoxy resin", significantly enhancing their corrosion and wear resistance. The annual corrosion rate is reduced to below 0.02mm, preventing pipeline damage and subsequent leakage of circulating water. Their standardized interface design facilitates batch installation, and the smooth inner wall reduces water flow resistance, lowering the energy consumption of water pumps. A single unit can save up to 2,000 kilowatt-hours of electricity annually. In closed circulating water systems, cast iron pipe fittings can withstand water temperature fluctuations of 80-100°C, adapting to the operational changes during unit start-up and shutdown, ensuring the stable and efficient operation of the circulating water system.

4. Auxiliary Equipment Matching: Convenient Operation and Maintenance Support

For the auxiliary equipment of thermal power plants (such as pumps, fans, dust collectors, etc.), the pipelines require high compatibility and convenience in operation and maintenance. Cast iron pipe fittings can perfectly meet these demands. In the inlet and outlet pipelines of pumps, the pressure resistance of cast iron pipe fittings can match the pressure shock during the start and stop of the pump, preventing interface loosening and leakage. At the same time, they have good vibration damping effects, reducing the noise of equipment operation. In the drainage pipelines of dust collectors, their wear resistance can withstand the erosion of dust, avoiding pipeline wear and damage.  

5. Summary

Cast iron pipe fittings have demonstrated strong adaptability and practical value in the four core links of the boiler system, desulfurization and denitrification, circulating water, and auxiliary equipment matching in thermal power production. They have not only solved the problems of high temperature, high pressure, and strong corrosion, but also taken into account economic efficiency and operational convenience, providing a solid support for the continuous, stable, environmentally friendly and efficient operation of thermal power units. In the future, with the green and intelligent transformation of the thermal power industry, cast iron pipe fittings will further optimize their technology, enhance their high-temperature and corrosion resistance, adapt to more stringent thermal power production conditions, and continue to play a core supporting role, contributing to the high-quality development of the thermal power industry.