Waste heat recovery (WHR) power generation in the cement industry is a mature energy-saving technology that utilizes the thermal energy carried by the high-temperature exhaust gases from the kiln head (AQC) and kiln tail (SP/PH) during the cement clinker production process. This heat is used to generate low-pressure superheated steam in a waste heat boiler, which then drives a steam turbine to generate electricity.
This type of project is a typical example of comprehensive utilization of industrial waste heat and pressure, characterized by stable operation, high energy utilization efficiency, and clear economic returns. It has been widely applied in several overseas cement production regions. This case study is based on actual operating data from an overseas cement plant and has strong industry representativeness and reference value.
Project Background
This project is based on a new dry-process cement clinker production line. The production system features mature technology and stable, continuous operation, providing a solid foundation for the long-term reliable operation of the waste heat power generation system. The cement production line consists of two 2500 t/d clinker lines, with a total clinker production capacity of approximately 5000 t/d. This is a fairly typical medium-scale production line configuration in the current cement industry, possessing significant potential for waste heat recovery.
| Item | Parameter Description |
|---|---|
| Cement Production Line Type | New dry-process cement clinker production line |
| Clinker Production Capacity | 2 × 2,500 t/d (Total: 5,000 t/d) |
| Main Waste Heat Sources | Kiln tail exhaust gas (SP / PH) and kiln head grate cooler exhaust gas (AQC) |
| Kiln Tail Waste Heat Characteristics | Exhaust gas temperature at waste heat boiler outlet: approx. 230 °C |
| Kiln Head Waste Heat Characteristics | Exhaust gas temperature at waste heat boiler outlet: approx. 100 °C |
During the calcination and cooling process of cement clinker, the production line continuously generates a stable supply of medium-to-low temperature waste gas resources. The main sources include waste gas from the kiln tail preheating system (PH) and waste gas from the kiln head grate cooler (AQC). The kiln tail waste gas has a higher temperature and concentrated heat, making it one of the main heat sources for waste heat power generation systems; the kiln head grate cooler waste gas has a relatively lower temperature, but its volume is stable, and it also has high potential for recovery and utilization.
Based on the project’s operating conditions and design parameters, the waste gas temperature at the outlet of the kiln tail waste heat boiler is approximately 230℃, which can stably generate low-pressure superheated steam to provide continuous thermal energy input to the steam turbine; the waste gas temperature at the outlet of the kiln head grate cooler waste heat boiler is approximately 100℃, which is mainly used to supplement the heat in the steam system and improve the overall waste heat utilization rate. These two types of waste gases are utilized synergistically in the system, achieving comprehensive recovery of waste heat resources at different temperature levels.
Technical Configuration
Overview of the system's technical architecture
This project adopts the single-pressure pure low-temperature waste heat recovery (WHR) power generation technology. This technology is characterized by its simple system structure, stable operation, and high level of engineering maturity, and is widely used in waste heat recovery power generation projects for medium-scale cement clinker production lines (2 × 2500 t/d class).
Main equipment configuration
| Item | Configuration Description |
|---|---|
| Technical Scheme | Single-pressure pure low-temperature waste heat recovery power generation system |
| Number of Waste Heat Boilers | Total of 4 units |
| Kiln Tail Boilers | 2 × SP / PH Boilers |
| Kiln Head Boilers | 2 × AQC Boilers |
| Steam Turbine Type | Condensing steam turbine generator set |
| Steam Turbine Quantity | 1 set |
| Control System | DCS centralized control system |
| Operation Mode | Continuous operation integrated with the cement production line |
Waste heat boiler system configuration description
The waste heat boiler system consists of two kiln-end PH boilers and two kiln-head AQC boilers, corresponding to the two main sources of waste heat in the cement production process.
PH Boiler
Located in the preheater system at the kiln outlet, it primarily recovers medium-temperature waste gas discharged from the decomposition kiln. This waste gas has a stable temperature and concentrated heat, making it the main heat source for the waste heat power generation system, continuously producing low-pressure superheated steam.
AQC Boiler
Located at the grate cooler outlet, it is used to recover low-temperature, high-flow waste gas generated during the clinker cooling process. Through a reasonable wear-resistant structure and heat exchange arrangement, it achieves effective utilization of low-grade waste heat, complementing the kiln outlet boiler.
Steam turbine generator system configuration
This project is configured with one condensing steam turbine generator set, specifically designed for low-temperature waste heat conditions. It is suitable for industrial waste heat power generation scenarios with relatively low steam parameters and certain fluctuations in flow rate. The condensing system allows the steam to expand fully in the turbine, achieving higher power generation efficiency and output under existing waste heat conditions. This solution is ideal for cement plant waste heat power generation projects primarily aiming for “self-consumption and grid connection.”
Control and operating modes
The entire waste heat power generation system uses a DCS (Distributed Control System) for centralized control, enabling unified monitoring and coordinated scheduling of the boiler, turbine, and auxiliary systems. The system’s operating logic is deeply interlocked with the main cement production line, allowing it to automatically adjust its operating status based on changes in the kiln system load.
Installed Capacity & Power Generation Performance
| Item | Performance Value |
|---|---|
| Rated Installed Capacity of Steam Turbine | 9 MW |
| Average Operating Power Output | Approx. 8.7 MW |
| Annual Power Generation | Approx. 66.88 million kWh (66.88 GWh) |
| Power Generation per Ton of Clinker | Approx. 38 kWh / t clinker |
| Operation Mode | Continuous operation with grid-connected power generation |
Project Benefits & Economic Performance
As a typical waste heat power generation project in the cement industry, all the revenue of this project comes from the recovery and utilization of waste heat from the production process. Its energy-saving benefits are directly reflected in a stable and sustainable power output. After the project is put into operation, the average operating power of the waste heat power generation system is approximately 8.7 MW, with an annual power generation of approximately 62–67 million kWh, most of which is used for in-plant consumption, effectively replacing purchased electricity.
Compared to before the project’s construction, the cement plant’s annual purchased electricity decreased by approximately 60 million kWh, significantly improving its self-sufficiency in electricity and resulting in an overall electricity saving of approximately 30%. Based on conventional thermal power energy consumption calculations, the project can save approximately 22,000 tons of standard coal annually and achieve an annual reduction of approximately 64,500 tons of CO₂, demonstrating significant economic and environmental benefits.
Investment & Payback Overview
This waste heat power generation project is based on technological upgrades to existing cement production lines. The system design is mature and relatively simple, achieving high energy recovery efficiency while keeping investment costs under control. The overall investment level of the project is reasonable, and the power generation revenue is stable. Based on actual operating data, the simple payback period of the project is approximately 4.3 years, making it highly economically attractive among waste heat power generation projects in the cement industry.
In summary, this project fully validates the technical maturity and investment return potential of the single-pressure, pure low-temperature waste heat power generation technology in medium-scale cement clinker production lines. Based on a deep understanding of cement process characteristics, waste heat resource distribution, and system operational stability, AGICO CEMENT possesses solid professional experience in the technical scheme design, system configuration, and overall engineering implementation of such waste heat power generation projects. The relevant technical approach and economic performance can provide valuable reference for similar cement plants undertaking energy-saving renovations and waste heat power generation projects. If you are evaluating or planning a similar project, please feel free to contact the AGICO CEMENT team for further discussion.