Background: For 20 consecutive years, China has ranked first in the world in cement production. The cement industry is not only a major consumer of energy but also a significant contributor to energy waste. Even with advanced new dry process technology, approximately 35% of the total heat consumption of the cement clinker calcination system, which is below 350°C, remains unutilized and directly emitted as low-temperature exhaust gas waste heat. In order to achieve an energy-saving, emission-reducing, and sustainable development strategy, it is of great practical significance and engineering value to fully utilize the mid-low temperature waste heat in cement production, reduce energy consumption in cement manufacturing, and develop and research systems for utilizing this waste heat in cement production lines. Therefore, Xi'an Jiaotong University cooperated with relevant units to undertake the National Key Science and Technology Project in 1991 and the National High-Tech '863' Program project in 2007, conducting research on the mid-low temperature waste heat power generation process and system in cement kilns. For cement production lines with capacities of 5000T/D and 2500T/D, a series of pure low-temperature waste heat power generation systems with independent intellectual property rights have been developed and researched using the dual-pressure technology. The BN7.5MW and BN9MW dual-pressure pure low-temperature waste heat power generation systems matched with 5000T/D cement kilns have been put into practical engineering use, and subsequent BN5, BN10, BN14.5, and BN20 power generation systems have also been completed. On September 27, 2006, the BN7.5MW dual-pressure pure low-temperature waste heat power generation system was completed and put into operation at the Liaoyuan Jinguang Cement Group. On August 27, 2007, the BN9MW unit was connected to the grid at Yulong Tongli Cement Company in Zhumadian City, Henan Province. During the implementation of the project, cooperating units were mainly responsible for industrialization, equipment manufacturing, installation, commissioning, and debugging of the project. The key technologies are researched and developed by Xi'an Jiaotong University. The main contents include the development of a dual-pressure steam injection supplementary steam turbine with new high-efficiency blades, anti-erosion characteristics, and digital electro-hydraulic control system; the research and development of new high-efficiency heat exchange components; the key technology research on anti-wear, anti-corrosion, and ash prevention for boiler heat exchangers; the research and development of a DCS control system centered on microprocessors; the study of a dual-pressure waste heat power generation process combined with cement production and power generation, and the optimization of system parameters. Through systematic analysis and in-depth research, a theoretical foundation and experimental data were provided for the construction of a pure low-temperature dual-pressure waste heat power generation system, which has been promoted and applied in engineering practice. Economic benefits: The general contracting unit for the project construction is a 5000T/D cement line that has added new sales revenue of 53 million yuan to the enterprise, with taxes and profits totaling 7.5 million yuan. Driving local economy by 30 million yuan. In 2005, the project cooperation unit, China National Heavy Machinery Corporation (CNH), undertook the general contracting construction of three 5000T/D waste heat power generation projects; in 2006, it contracted for nine more such projects. In 2007, the company formed an annual capacity of sixteen lines, adding new sales revenue of 1.48 billion yuan to the enterprise, with tax profits of 207 million yuan, and driving local economy by 840 million yuan. To date, CNH has undertaken waste heat power generation projects for 107 cement production lines, achieving significant economic benefits. For the construction unit: a pure low-temperature waste heat power generation project is built in conjunction with a 5000T/D dry process cement production line, with a installed capacity of 9MW, operating for 7000 hours per year, generating 63 million kWh of electricity annually. The generated electricity can basically meet one-third of the power consumption for cement production, reducing the cost of cement clinker by 20 yuan and saving 28.8 million yuan per year, resulting in significant economic benefits. To date, the total installed capacity of the cooperating units that have been built and put into use has reached 706MW. Calculated based on an annual operation of 7,000 hours, the annual electricity generation is 49.42 million KWH, saving 247 million yuan (with a power price of 0.5 yuan/kW·H). Social benefits: This technology mainly recycles the low-temperature flue gas waste heat resources from cement production lines. Taking a 5,000t/d cement clinker production line as an example, with an installed capacity of 9MW, the annual electricity generation is about 6.48 million KWH, reducing production costs by 10-15 yuan/ton, saving more than 20 million yuan per year; it also saves 22,600 tons of standard coal per year. A financial reward of 4 to 5.25 million yuan for energy conservation can be obtained; due to the utilization of low-temperature waste heat, the corresponding thermal power generation can be reduced each year by 65,000 tons of carbon dioxide, which is equivalent to $650,000 according to international carbon emission trading standards; at the same time, the exhaust gas emission temperature of the cement line is reduced from 250°C to around 90°C, significantly reducing the pollution of waste gas to the environment and contributing to environmental protection. Promotion prospects: By the end of 2008, there were 934 new dry process cement production lines in operation nationwide, and more than 80 dry process cement production lines are expected to be added each year, with a market for low-temperature waste heat power generation on cement production lines exceeding 3 billion yuan. The pure low-temperature waste heat power generation dual-pressure technology for cement lines is an essential path for cement enterprises to save energy, reduce consumption, achieve clean production, comprehensive resource utilization, and sustainable development. It is a concrete practice of implementing the scientific development concept and promoting circular economy, which is conducive to enhancing the competitiveness of enterprises. At the same time, this technology can also be widely applied in industries such as glass, steel, building materials furnaces, etc. With the support of the Ministry of Science and Technology's 863 project, the research team is currently developing a new type of waste heat recovery system that meets the lower limit of waste heat temperature at 80°C. In Guangdong, there are a large number of building materials furnaces with huge amounts of waste heat emissions, making low-temperature waste heat recovery and utilization have broad market prospects. Pure low-temperature waste heat power generation technology conforms to national industrial policies and development trends, and has important market promotion prospects and energy saving and emission reduction benefits. Working principle: Set up a kiln head AQC waste heat boiler and a kiln tail SP waste heat boiler. The kiln tail SP waste heat boiler produces high-pressure steam, while the kiln head AQC furnace produces both high-pressure and low-pressure steam and hot water. The mixed high-pressure steam from the two sources is then used to drive the turbine. A portion of the low-pressure steam generated at the kiln head is utilized for boiler feedwater deaeration, while another part enters the turbine through a supplementary steam inlet to perform work. The hot water produced is used to heat the condensate, and the exhaust gas leaving the boiler is cooled to below 90°C. Generating electricity using the waste heat of the exhaust gas plays a role in energy saving, consumption reduction, and emission reduction.